SANS10100-2

SABS0100-2*

ICS 91.100.30

ISBN 0-626-10153-0

*This standard references other standardsEdition 2

1992(As amended 1994)

SOUTH AFRICAN STANDARD

Code of practice

The structural use of concrete

Part 2: Materials and execution of work

Reprint 1994Published byTHE SOUTH AFRICAN BUREAU OF STANDARDS Gr 15

Copyright protected. This standard may only be used and printed by subscribers to the SABS’ Complete Collection of Standards and Related Documents in accordance with a formal copyright agreement.

SABS 0100-2Ed. 2


ICS 91.100.30 SABS 0100-2Ed. 2

(As amended 1994)

SOUTH AFRICAN BUREAU OF STANDARDS

CODE OF PRACTICE

THE STRUCTURAL USE OF CONCRETE

PART 2: MATERIALS AND EXECUTION OF WORK

Obtainable from the

South African Bureau of StandardsPrivate Bag X191PretoriaRepublic of South Africa0001

Telephone : (012) 428-7911Fax : (012) 344-1568E-mail : [email protected] : http://www.sabs.co.za

COPYRIGHT RESERVED

Printed in the Republic of South Africa by theSouth African Bureau of Standards


SABS 0100-2Ed. 2

ii

Notice

This part of SABS 0100 was approved in accordance with SABS procedures on 20 February 1992.

NOTE 1 In terms of the Standards Act, 1993 (Act 29 of 1993), no person shall claim or declare that he or any otherperson complied with an SABS standard unless

a) such claim or declaration is true and accurate in all material respects, and

b) the identity of the person on whose authority such claim or declaration is made, is clear.

NOTE 2 It is recommended that authorities who wish to incorporate any part of this standard into any legislation in themanner intended by section 31 of the Act consult the SABS regarding the implications.

This part of SABS 0100 will be revised when necessary in order to keep abreast of progress. Commentwill be welcome and will be considered when this part of SABS 0100 is revised.

Foreword

This second edition (first revision) cancels and replaces SABS 0100-2:1980.

Annex A (Concrete subjected to wet conditions - aggressiveness of the water, and countermeasures)forms an integral part of this part of SABS 0100. Annex B (Curing), annex C (Technical data forprestressed structural elements required in a contract), annex D (Recommended specialist literatureon massive concrete) and annex E (Bibliography) are for information only.

Reprint incorporating Amendment No. 1: 12 September 1994

Attention is drawn to the normative references givenin clause 2 of this standard. These references areindispensable for the application of this standard.

ISBN 0-626-10153-0


SABS 0100-2Ed. 2

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Contents

Page

Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x

1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.2 Weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.3 Conditions of exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.4 Concrete, general characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.5 Concrete, strength characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.6 Prestressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Materials for concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1 Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.1.2 Properties of concrete made with a blend of cement and cement extenders . . . 74.2 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.3 Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.3.1 Aggregate classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.3.2 Natural aggregates covered by SABS 1083 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.3.3 Aggregates not covered by SABS 1083 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3.4 Nominal maximum size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3.5 Aggregates for high-strength concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3.6 Aggregates and fire resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3.7 Aggregates and concrete density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3.8 Use of "plums" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3.9 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.4 Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.4.2 Air-entraining agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.4.3 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.5 Deteriorated material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5 Plant for concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.2 Batching plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.3 Mixing plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.4 Vibrators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


SABS 0100-2Ed. 2(As amended 1994)

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6 Proportioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6.1 Quality of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.2 Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.3 Density of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.4 Consistence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.1.5 Workability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.1.6 Bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.1.7 Chloride content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.1.8 Sulfates in concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.1.9 Alkali-silica reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.1.10 Drying shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.2 Durability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146.2.2 Exposure to freezing and thawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146.2.3 Exposure to aggressive chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Amdt 1, 6.2.4 Exposure to salt-laden air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Sept. 1994 6.2.5 Exposure to corrosive fumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.2.6 Exposure to polluted air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.3 Mix proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.3.1 High cement content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.3.2 Concrete exposed only to mild conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 176.3.3 Deleted by Amendment No. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.3.4 Deleted by Amendment No. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7 Production of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7.1 Batching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.1.1 Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.1.2 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.1.3 Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.1.4 Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.2 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.2.1 Mixing on site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.2.2 Ready-mixed concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207.3 Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.2 Cover to reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.3 Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228.3.2 Preheating prior to bending or straightening . . . . . . . . . . . . . . . . . . . . . . . . . 228.4 Fixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228.4.1 Steel reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228.4.2 Zinc-coated (galvanized) reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248.4.3 Epoxy-coated reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248.5 Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248.5.2 Use of welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248.5.3 Types of welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248.5.4 Location of welded joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258.5.5 Strength of structural welded joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258.5.6 Welded lapped joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


SABS 0100-2Ed. 2

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9 Formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259.2 Design and construction of formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.2.1 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.2.2 Deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.2.3 Form accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.2.4 Temporary openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.3 Preparation of formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.4 Re-use of formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.5 Removal of formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279.5.2 Formwork removal time for cast-in-situ concrete . . . . . . . . . . . . . . . . . . . . . . . . . 279.5.3 Reshoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

10 Placing and protection of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2910.2 Placing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2910.3 Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3010.4 Construction joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3110.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3110.4.2 Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3110.4.3 Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3110.4.4 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3210.4.5 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3210.5 Embedded items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3310.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3310.5.2 Waterstops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3310.5.3 Pipes and conduits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3310.6 Concrete for water-retaining structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3410.7 Concrete in saturated ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3410.8 Protection and curing of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3410.8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3410.8.2 Concreting in hot weather or in windy conditions . . . . . . . . . . . . . . . . . . . . . . . . 3510.8.3 Concreting in cold weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3610.8.4 Concreting during rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3610.9 Surface finish of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3610.9.1 Upper surfaces of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3610.9.2 Concrete surfaces cast against forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3610.9.3 Repair of surface defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3710.10 Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

11 Massive concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

12 Prestressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

12.1 Prestressing tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3812.1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3812.1.2 Handling and storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3812.1.3 Surface condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3812.1.4 Straightness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3912.1.5 Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3912.1.6 Formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3912.1.7 Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39


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12.2 Tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4012.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4012.2.2 Safety precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4012.2.3 Tensioning apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4012.2.4 Pre-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4112.2.5 Post-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4112.3 Positioning of tendons and sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4212.4 Tensioning procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4312.5 Grouting of prestressing tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4412.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4412.5.2 Grouting equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4412.5.3 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4412.5.4 Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4512.5.5 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4512.5.6 Strength of grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4512.5.7 Injection of grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4512.5.8 Grouting during cold weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4612.5.9 Protection and bond of prestressing tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

13 Precast concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

13.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4713.2 Permissible deviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4713.3 Prestressed units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4813.4 Handling and erection of precast concrete units . . . . . . . . . . . . . . . . . . . . . . . . . 4813.4.1 Lifting equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4813.4.2 Handling and transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4813.4.3 Assembly and erection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4913.4.4 Temporary supports during construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4913.4.5 Forming structural connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4913.4.6 Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

14 Testing and acceptance of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

14.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5114.2 Testing services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5114.2.1 Basic testing services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5114.2.2 Testing services required by the engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5114.2.3 Additional services when required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5214.2.4 Test reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5214.2.5 Responsibilities and duties of the contractor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5214.3 Strength tests of concrete during construction . . . . . . . . . . . . . . . . . . . . . . . . . . 5214.3.1 General procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5214.3.2 Evaluation of strength test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5314.3.3 Acceptance criteria for strength test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5314.4 Strength tests of concrete in place . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5414.4.1 Non-destructive testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5414.4.2 Core tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5414.4.3 Acceptance of concrete on the basis of core strengths . . . . . . . . . . . . . . . . . . . . 54


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15 Load tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

15.1 Individual precast units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.1.2 Non-destructive test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.1.3 Destructive test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.1.4 Special test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.2 Structures and parts of structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.2.2 Age at test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5515.2.3 Test loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5615.2.4 Measurements during the tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5615.2.5 Assessment of results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

16 Procedure in the event of failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Tables

1 Limits of chloride content of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Total air content for various sizes of coarse aggregate for normal-density concrete . . . . 143 Cement/water ratio and cement content for normal-density reinforced concrete and

low-density reinforced concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Cement/water ratio and cement content for normal-density unreinforced concrete . . . . . 175 Minimum cover for various conditions of exposure and cement/water ratios for

normal-density concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 Minimum cover for various conditions of exposure and cement/water ratios for low-

density concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 Removal of formwork: minimum time in days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 Permitted tolerance in the location of tendons and sheathing . . . . . . . . . . . . . . . . . . . . . . 42

Annexes

A Concrete subjected to wet conditions - aggressiveness of the water, andcountermeasures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

A.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58A.2 Analytical tests required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58A.3 Assessment of the aggressiveness of water, using the Basson Index (BI) . . . . . . . 59A.4 Recommended anti-corrosion measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Tables

A.1 Ionic characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58A.2 Calculation of water properties indices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59A.3 Calculation of environmental indices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60A.4 Classification of water in terms of Basson Index BI . . . . . . . . . . . . . . . . . . . . 60A.5 Countermeasures against leaching corrosion . . . . . . . . . . . . . . . . . . . . . . . . . 61A.6 Countermeasures against spalling corrosion . . . . . . . . . . . . . . . . . . . . . . . . . 63A.7 Countermeasures against chloride corrosion . . . . . . . . . . . . . . . . . . . . . . . . . 63A.8 Concretes for aggressive chemical environments . . . . . . . . . . . . . . . . . . . . . 64 Amdt 1, A.9 Cements recommended for the making of concretes for aggressive waters . 65 Sept. 1994A.10 Coatings for concretes in aggressive waters . . . . . . . . . . . . . . . . . . . . . . . . . . 66


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Blank


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B Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

B.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67B.2 Strength of concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67B.3 Distortion and cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67B.4 Durability and appearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

C Technical data for prestressed structural elements required in a contract . . . . . . . . . . . . 69

C.1 Data for pre-tensioned elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69C.2 Data for post-tensioned elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

D Recommended specialist literature on massive concrete . . . . . . . . . . . . . . . . . . . . . . . . . 72

E Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72


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Committee

South African Bureau of Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VJ Woodlock(Chairman)I Jablonski(Standards writer)E Coetzee(Committee clerk)

CSIR Division of Building Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BG Lunt

Portland Cement Institute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BJ Addis

South African Federation of Civil Engineering Contractors . . . . . . . . . . . . . HH Meier

The South African Association of Consulting Engineers . . . . . . . . . . . . . . . GJ de Ridder

The South African Institute of Civil Engineers . . . . . . . . . . . . . . . . . . . . . . . AE Goldstein


1

CODE OF PRACTICE SABS 0100-2Edition 2

The structural use of concrete

Part 2:Materials and execution of work

1 Scope

1.1 This part of SABS 0100 covers the materials and execution of work related to the structural useof concrete in buildings and structures where the design of reinforced, prestressed and precastconcrete is entrusted to appropriately qualified structural or civil engineers and the execution of thework is carried out under the direction of appropriately qualified supervisors.

1.2 This part of SABS 0100 does not cover the structural use of concrete made with high-aluminacement.

2 Normative references

The following standards contain provisions which, through reference in this text, constitute provisionsof this part of SABS 0100. At the time of publication, the editions indicated were valid. All standards aresubject to revision, and parties to agreements based on this part of SABS 0100 are encouraged toinvestigate the possibility of applying the most recent editions of the standards indicated below.Information on currently valid national and international standards may be obtained from the SouthAfrican Bureau of Standards.

PCI. TM 9.28.

SABS 82:1976, Bending dimensions of bars for concrete reinforcement.

SABS 471:1971, Portland cement (ordinary, rapid-hardening and sulphate-resisting).

SABS 626:1971, Portland blastfurnace cement.

SABS 831:1971, Portland cement 15 (ordinary and rapid-hardening).

SABS 878:1983, Ready-mixed concrete.

SABS 920:1985, Steel bars for concrete reinforcement.


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SABS 1024:1974, Welded steel fabric for concrete reinforcement.

SABS 1083:1976, Aggregates from natural sources.

SABS 1200 G:1982, Standardized specification for civil engineering construction: Concrete (structural).

SABS 1466:1988, Portland fly ash cement.

SABS 1491-1:1989, Portland cement extenders - Part 1: Ground granulated blastfurnace slag.

SABS 1491-2:1989, Portland cement extenders - Part 2: Fly ash.

SABS 1491-3:1989, Portland cement extenders - Part 3: Condensed silica fume.

SABS 0100-1:1980, Structural use of concrete - Part 1: Design.

SABS 0109:1969, Floor finishes on concrete.

SABS 0144:1978, Detailing of steel reinforcement for concrete.

SABS 0155:1980, Accuracy in buildings.

SABS method 11:1990, Water - pH value.

SABS method 202:1983, Chloride content of water.

SABS method 212:1971, Sulphate content of water.

SABS method 213:1990, Water - Dissolved solids content.

SABS method 216:1990, Water - Calcium content.

SABS method 217:1990, Water - Free and saline ammonia content.

SABS method 218:1971, Albuminoid ammonia content of water.

SABS method 856:1976, Bulking of fine aggregates.

SABS method 861:1976, Sampling of freshly mixed concrete.

SABS method 862:1976, Slump of freshly mixed concrete.

SABS method 863:1976, Compressive strength of concrete (including making and curing of the testcubes).

SABS method 865:1982, The drilling, preparation, and testing of concrete cores.

SABS method 1071:1990, Water - Magnesium content.

SABS method 1085:1985, Initial drying shrinkage and wetting expansion of concrete.

3 Definitions

For the purposes of this part of SABS 0100, the following definitions apply:


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3

3.1 General

3.1.1 acceptable/approved: Acceptable to/approved by the engineer.

3.1.2 cement: Portland cement; blends of portland cement and portland cement extenders as coveredin SABS 1491.

3.1.3 concrete cover: The thickness of concrete between the face of the concrete, as cast, and theouter face of reinforcing steel, prestressing steel, steel used for binding the reinforcing, or anyembedded steel.

3.1.4 contractor: The individual who, or the organization that, has entered into an agreement to carryout the work specified.

3.1.5 engineer: The representative appointed by the owner to administer the requirements of aproject specification for specific concrete work.

3.1.6 formwork: All the temporary aids and material required to support, and to provide the shapeof, the concrete in a structure (while the concrete is in the fresh state).

3.1.7 ready-mixed concrete: Concrete that complies with the relevant requirements of the projectspecification and as further defined in SABS 878.

3.2 Weather

3.2.1 adverse weather: Cold weather or a combination of a high ambient temperature, low relativehumidity and high wind velocity, which may tend to impair the quality of fresh or hardening concrete orotherwise cause hardened concrete to have undesirable properties.

3.2.2 cold weather: Weather in which the ambient temperature is 5 °C or less.

3.2.3 cool weather: Weather in which the ambient temperature exceeds 5 °C but does not exceed15 °C.

3.2.4 hot weather: Weather in which the ambient temperature exceeds 32 °C.

3.2.5 normal weather: Weather in which the ambient temperature exceeds 15 °C but does notexceed 32 °C.

3.3 Conditions of exposure

NOTE - For the definitions of

- non-aggressive to mildly aggressive water,

- mildly to fairly aggressive water, and

- highly aggressive water,

see table A.4 of annex A, and for an explanation of wet conditions, see the commentary below.

3.3.1 mild conditions: The concrete is exposed generally to unpolluted air.

For example:


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4

- indoors (but not including industrial areas); or

- out of doors in arid rural areas (Karoo).

3.3.2 moderate conditions: The concrete is

a) sheltered from severe rain;

b) buried in non-aggressive soil; or

c) subject to polluted air (but not corrosive fumes).

For example:

- indoors in industrial areas; or

- out of doors in rural Highveld areas.

3.3.3 severe conditions: The concrete is exposed to

a) wet conditions in which the water is mildly to fairly aggressive;

b) corrosive fumes; or

c) salt-laden air.

For example:

- out of doors in industrial areas;

- out of doors in marine atmospheric conditions (i.e. up to 15 km from the sea); or

- out of doors in the Cape winter-rainfall area.

3.3.4 very severe conditions: The concrete is exposed to

a) wet conditions in which the water is mildly to fairly aggressive;

b) abrasive action under any wet conditions; or

c) highly corrosive fumes.

3.3.5 extreme conditions: The concrete is exposed to wet conditions in which the water is highlyaggressive.

COMMENTARY - Conditions are considered wet if the concrete is exposed to water continuously or intermittently. Theeffect on the concrete of exposure to water depends on the aggressiveness of the water, the period of time during whichthe concrete is wet, and the frequency of the wet-dry cycling. It is not possible to propose definite limits in this regard.However, it should be kept in mind that highly aggressive water can have a seriously detrimental effect on concrete evenif the period of time during which the concrete is exposed to such water is short.

3.4 Concrete, general characteristics

3.4.1 consistence: The extent (usually measured by the slump test) to which fresh concrete flowsor can be deformed.


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3.4.2 grade of concrete: An identifying number for a particular concrete, which is numerically equalto the characteristic strength at 28 d, expressed in megapascals.

3.4.3 high-density concrete: Concrete made of a high-density aggregate complying with SABS 1083and that usually has a density in the range 2 500 kg/m3 to 3 600 kg/m3. Amdt 1,

Sept. 19943.4.4 low-density concrete: Concrete intentionally made to have low density by the use oflow-density aggregate or a mixture of low-density and normal-density aggregates, and usually requiredto have an air-dry density not exceeding 2 000 kg/m3.

3.4.5 normal-density concrete: Concrete made with aggregates complying with SABS 1083 and thatusually has a density in the range 2 200 kg/m3 to 2 500 kg/m3.

3.4.6 precast concrete: Concrete that consists of units cast and cured in a position other than theirfinal position, and placed in position to form an integral part of the structure.

3.4.7 prescribed-mix concrete: Concrete for which the engineer has prescribed the mix proportions.

3.4.8 strength concrete: Concrete designed primarily for strength considerations and designated byits characteristic strength in conjunction with the maximum nominal size of stone used in itsmanufacture, e.g. 30 MPa/19 mm.

3.4.9 target slump: The average value for the slump of concrete aimed for to ensure compliance withthe slump required.

3.4.10 workability: The property of fresh concrete that determines the ease of placing andcompacting the concrete without segregation of its constituent materials.

3.5 Concrete, strength characteristics

3.5.1 characteristic strength: The value for the compressive strength of concrete, below which notmore than 5 % of the valid test results obtained on cubes of concrete of the same grade fall.

3.5.2 specified strength: The characteristic strength required by the engineer.

3.5.3 target strength: An average value of the strength of concrete that is higher than the specifiedstrength, and that is aimed for to ensure that the characteristic strength is attained.

3.5.4 valid test result: The average result obtained from three test cubes of concrete that have beentested in accordance with SABS method 863, with the additional requirement that curing water bemaintained at a temperature between 22 °C and 25 °C.

3.6 Prestressing

3.6.1 anchorage: A device used to anchor a tendon to the concrete member.

3.6.2 bonded tendon: A prestressing tendon that is bonded to the concrete throughout its effectivelength, either directly (by being cast into the concrete) or by grouting.

3.6.3 coating: Material applied to unbonded tendons to protect them from corrosion, or materialapplied to either bonded or unbonded tendons to lubricate them during stressing.


SABS 0100-2Ed. 2

6

3.6.4 coupler: A device designed to transfer the prestressing force from one tendon to another.

3.6.5 sheathing: An enclosure in which tendons intended to be post-tensioned are encased, toprevent bonding during concrete placement (e.g. a paper or plastics jacket for unbonded tendons, ormetal conduit for bonded tendons).

3.6.6 tendon: An assemblage of steel elements (e.g. wire, bar or strand) used to impart prestress toconcrete when the assemblage is tensioned.

3.6.7 unbonded tendon: A tendon that is not bonded to the concrete.

4 Materials for concrete

4.1 Cement

4.1.1 General

4.1.1.1 SABS specifications cover the following:

a) portland cements: these cements shall comply with SABS 471, Portland cement (ordinary,rapid-hardening, and sulphate-resisting);

b) cements containing ground granulated blastfurnace slag or fly ash: these cements shallcomply with the applicable of the following specifications:

- SABS 831, Portland cement 15 (ordinary and rapid-hardening);

- SABS 626, Portland blastfurnace cement; or

- SABS 1466, Portland fly ash cement.

NOTE - Any type of cement other than those referred to in 4.1.1.1 may be used when so required in terms of the projectspecification or when specifically authorized by the engineer.

4.1.1.2 Cement extenders shall comply with the applicable of the following specifications:

- SABS 1491-1, Ground granulated blastfurnace slag (GGBS);

- SABS 1491-2, Fly ash (FA); or

- SABS 1491-3, Condensed silica fume (CSF).

NOTE - It is recommended that users of cement extenders consult producers of the extender or appropriate publicationsof recognized institutions (Portland Cement Institute or CSIR).

4.1.1.3 Cements for sulfate-resisting concrete shall be chosen in accordance with the proceduresgiven in annex A, taking into account the factors described in 6.2.3. Sulfate-resisting cements may havea lower resistance to chloride-ion migration than other cements.

4.1.1.4 For particular regions, or where it is suspected that alkali-silica reaction may occur, it may benecessary to use cement of low alkali content (Na2O + 0,658 K2O) or aggregate of low potentialalkali-silica reactivity.

4.1.1.5 The type of cement to be used in each part of the structure shall be specified by the engineer,and the cement used in the structure shall correspond to that specified. The type and source of cementmay not be changed during the duration of a contract without the approval of the engineer.


SABS 0100-2Ed. 2

7

4.1.1.6 Separate storage facilities shall be provided on the site for each type of cement used, andcement shall be stored in weatherproof conditions. Storage of cement in bulk is permissible providedthat the cement drawn for use is measured by mass and not by volume. Provision shall be made toensure that different types of cement are stored in suitable silos. Cement shall be stored in such amanner that the oldest cement is used first.

Cement extender on its own or masonry cement shall not be used as cement for concrete works.

4.1.2 Properties of concrete made with a blend of portland cement and cementextenders

4.1.2.1 Strength

28 d strengths (under standard curing conditions) of GGBS or FA or CSF cement concretescomparable with 28 d strengths of ordinary portland cement concretes can be obtained in many cases,although adjustments in the concrete mix proportions may be necessary. Generally, as the cementextender content is increased, the early rate of strength development is reduced, particularly at lowertemperatures. At ages exceeding 28 d, water-cured GGBS, FA and CSF concretes show an increasein strength over ordinary portland cement concretes of equivalent 28 d strengths.

4.1.2.2 Other properties

Provided sufficient GGBS or FA or CSF is incorporated and the concrete is properly cured, there islikely to be increased resistance to some forms of chemical attack and reduction of early heat ofhydration.

4.2 Water

4.2.1 Water shall be clean and free from injurious amounts of acids, alkalis, chlorides, organic matterand other substances that could impair the strength or durability of concrete or metal embedded in theconcrete. (It should be noted that sea water contains injurious amounts of chlorides and alkalis.)

4.2.2 Should the suitability of water be in doubt, particularly in remote areas or where water is derivedfrom sources not normally utilized for domestic purposes, such water shall be tested.

4.3 Aggregates

4.3.1 Aggregate classification

Aggregates can be classified in terms of their density, as follows:

a) normal density: aggregates that have a particle density exceeding 2 000 kg/m3 but not exceeding3 000 kg/m3;

b) low density: aggregates that have a porous structure and a particle density not exceeding2 000 kg/m3;

c) high density: aggregates that have a particle density exceeding 3 000 kg/m3.

4.3.2 Natural aggregates covered by SABS 1083

4.3.2.1 Normally, both coarse aggregate (stone) and fine aggregate (sand) should comply with therequirements of SABS 1083.


SABS 0100-2Ed. 2

8

4.3.2.2 Acceptable variations to the requirements of SABS 1083 in the project specifications shall beclearly specified.

4.3.2.3 Appendices to SABS 1083 identify characteristics of certain fine and coarse aggregates thatare normally not acceptable but are nonetheless suitable for use in particular circumstances and maybe preferred on the grounds of economy. Such aggregates shall be clearly specified, and may only beused after tests have verified their particular characteristics and if guidance for their use is provided.

4.3.2.4 SABS 1083 specifies additional optional requirements for aggregates to be used for specificpurposes or where specific properties such as resistance to alkali-silica reaction, fire resistance, lowshrinkage, or general durability are of significant importance.

4.3.3 Aggregates not covered by SABS 1083

Where aggregates other than those covered by SABS 1083 are to be used, such aggregates andrequirements for their quality shall be clearly specified.

4.3.4 Nominal maximum size

The preferred nominal maximum sizes of coarse aggregate are 37,5 mm; 26,5 mm; 19 mm; 13,2 mmand 9,5 mm.

The nominal maximum size of coarse aggregate should not exceed

a) one-quarter of the minimum thickness of the concrete cross-section, and

b) the cover of reinforcement specified.

In elements with closely spaced reinforcement, the use of a nominal maximum size of 9,5 mm or13,2 mm should be considered.

4.3.5 Aggregates for high-strength concrete

Where high-strength concrete is required, both the source and the type of aggregate may need carefulselection, based on results of previous use or of trial mixes.

4.3.6 Aggregates and fire resistance

It may be necessary to use an aggregate that behaves satisfactorily when exposed to hightemperatures, e.g. low-density aggregates or limestone.

4.3.7 Aggregates and concrete density

The density of the aggregates used influences the density of the concrete. If a high-density concreteis required, a high-density aggregate (see 4.3.1) may need to be specified. If a low-density concrete(see 3.4.4) is required, a low-density aggregate (see 4.3.1) may need to be specified.

4.3.8 Use of "plums"

In plain concrete of thickness at least 300 mm, hard, clean, stone "plums" of mass 15 kg to 55 kg may,if approved, be used to displace concrete to a maximum of 20 % of the volume of the concrete,provided that

a) such plums have no adhering films or coatings,


SABS 0100-2Ed. 2

9

b) no plum has a dimension exceeding 300 mm or one-third of the smallest dimension of the concreteelement, whichever is less,

c) each plum is surrounded by at least 80 mm of concrete, and

d) the strength of the rock that makes up the plums (as indicated by the aggregate crushing value orthe 10 % fines aggregate crushing test) is at least that specified for coarse aggregate inSABS 1083.

4.3.9 Storage

4.3.9.1 Aggregates of different nominal sizes shall be stored separately and in such a way that

a) segregation of particles of the same size is minimized,

b) contamination by foreign matter is prevented, and

c) intermixing of aggregates is minimized.

4.3.9.2 Where aggregates of different chloride content are stockpiled on the same site, strict controlshall be exercised over their use in different classes of concrete.

4.3.9.3 Stockpiles of natural or manufactured sand shall be free-draining to ensure a relatively uniformmoisture content throughout the stockpile.

4.4 Admixtures

4.4.1 General

4.4.1.1 Admixtures are added to a concrete mix to change certain properties of concrete by theirchemical effect or physical effect (or both). In changing certain properties, an admixture cansignificantly affect other properties.

4.4.1.2 Admixtures that may impair the durability of the concrete, or combine with the ingredients toform harmful compounds, or increase the risk of corrosion of the reinforcement shall not be used. Whenan admixture is used in concrete that is made with any type of cement and that is to containprestressing tendons, reinforcement and embedded metal, the chloride content of the admixture,expressed as chloride ions (by mass), should not exceed 2 % (m/m) of the admixture or 0,03 % (m/m)of the cement.

4.4.1.3 Admixtures shall not be used without the approval of the engineer, who may require tests tobe conducted before admixtures are used. To facilitate approval, the following information should beavailable:

a) the trade name of the admixture, its source and the manufacturer's recommended method of use;

b) typical dosages and possible detrimental effects of underdosages and overdosages;

c) whether compounds likely to cause corrosion of the reinforcement or deterioration of the concrete(such as those containing chloride in any form as an active ingredient) are present and, if so, thechloride content of admixtures, expressed as chloride ions (by mass) or expressed as equivalentanhydrous calcium chloride (by mass); and

d) the average expected air content of freshly mixed concrete containing an admixture that causes airto be entrained (see 4.4.2) when the admixture is used at the manufacturer's recommended dosage.


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10

4.4.1.4 If two or more admixtures are to be used simultaneously in the same concrete mix, all availabledata should be used to assess the interaction of the admixtures and to ensure their compatibility.

4.4.1.5 Admixtures used in the work shall be of the same composition as those used in establishingthe concrete mix proportions.

4.4.1.6 The effect of an admixture can be highly specific to the combination of ingredients in the mix.It is therefore important that trial mixes be made before an admixture is used in concrete forconstruction and if any mix ingredient is changed during the course of the project.

4.4.2 Air-entraining agents

An air-entraining admixture shall be of such a type and the dosage of sufficient quantity that the aircontent (see table 2) is maintained at the point of placing. When another admixture (or cementextender) is present in the concrete mix, a different dosage of the air-entraining admixture may berequired. The entrainment of air tends to reduce the strength of concrete. Trial mixes should be madeto determine the extent of strength reduction, and mix proportions adjusted if necessary.

4.4.3 Storage

Admixtures shall be stored in a manner that will prevent contamination, evaporation or damage. Foradmixtures used in the form of suspensions or non-stable solutions, agitating equipment shall beprovided to ensure thorough distribution of the ingredients. Liquid admixtures shall be protected fromtemperature changes that would adversely affect their characteristics.

4.5 Deteriorated material

Cement or any other material that has deteriorated or that has been contaminated or otherwisedamaged shall not be used in concrete and shall be removed from the site without delay.

5 Plant for concrete

5.1 General

All plant shall be maintained in good working order.

5.2 Batching plant

5.2.1 Regular examination, calibration and tests shall be carried out at frequencies that will ensurethat the batching system functions effectively and accurately and that hoppers and cement containersare kept dry and clean.

5.2.2 The batching plant shall be such that the batching accuracy complies with 7.1.

5.2.3 In the case of an automatic plant, the mass batching scales shall be so interlocked that a newbatch of materials cannot be delivered until the hoppers have been completely emptied of the previousbatch and the scales are in balance. Where discharge of materials from the hoppers is manuallycontrolled, a method of signalling shall be employed to ensure that ingredients are not omitted, oradded more than once, when a batch of concrete is being made up.

5.3 Mixing plant

5.3.1 The type and capacity of mixing machines shall be such that the rate of output of concrete issuitable for the rate of concreting. Each machine shall be capable of producing a uniform distribution


SABS 0100-2Ed. 2

11

of the ingredients throughout the batch within the time specified by the manufacturer. Worn or bentblades and paddles shall be replaced. The inner surfaces of the mixer shall be clean and shall haveno hardened concrete adhering to them.

5.3.2 It is recommended that an agreement be reached between the contractor and the engineer ifthe mixer to be used

a) has unusual mixing characteristics, or

b) it is claimed that effective mixing can be consistently achieved in mixing periods shorter than thosespecified in 7.2.1.

5.4 Vibrators

Where compaction by vibration is specified, vibrators shall be capable of fully compacting each layerof concrete. It is recommended that at least one standby vibrator be available for every three (or lessernumber of) vibrators necessary to maintain the rate of placing.

6 Proportioning

6.1 Quality of concrete

6.1.1 General

Concrete for all parts of the work shall be of the specified quality and capable of being placed andcompacted without excessive segregation. When hardened, concrete should have developed all theproperties required by this part of SABS 0100 and by the project specification.

The engineer shall ensure that samples of the constituent materials of the concrete, together withevidence that they comply with the provisions of clause 4, are supplied for approval in good time beforeconcreting of the works commences.

Evidence shall be in the form of either

a) a statement, from an approved laboratory, of the results of tests, or

b) an authoritative and acceptable report or record of previous use of, and experience with, thematerial concerned.

6.1.2 Strength

6.1.2.1 Compressive strength

The specified compressive strength of concrete should be based on the 28 d characteristiccompressive strength fcu, unless a different test age is specified.

6.1.2.2 Maximum cement content

Cement content should normally not exceed 550 kg per cubic metre of concrete.

6.1.3 Density of concrete

For certain purposes, e.g. to provide radiation shielding, a high-density concrete may have to be specified. In other cases, e.g. to provide thermal insulation, a low-density concrete may have to bespecified. These densities are normally achieved by selecting suitable aggregates (see 4.3.7).



12

6.1.4 Consistence

Unless otherwise dictated by the general workability of the concrete, the method of transportation orconditions of placement, or unless otherwise specified by the engineer, slump values for different typesof construction should normally not exceed 150 mm for hand-placed concrete and 100 mm for vibratedconcrete.

6.1.5 Workability

The concrete shall be of such workability that it can be readily compacted into the corners of theformwork and around reinforcement without the materials in the mix segregating.

6.1.6 Bleeding

The concrete shall be so proportioned with suitable materials that bleeding (i.e. the upward migrationof water in compacted fresh concrete) is not excessive.

It is not possible to put quantitative limits to bleeding. To assess the bleeding behaviour of concrete,the consequences of bleeding should be borne in mind. Note that initially, bleeding is accompanied bythe settlement of solid particles (i.e. cement and aggregates). Where this settlement is prevented byreinforcement or by changes in cross-section, differential settlement occurs and cracks and voids areformed in the concrete. This phenomenon is especially troublesome in columns, in T and I beams, andin beams and slabs with top reinforcement.

On the other hand, a film of bleed water on the surface of an element such as a slab will prevent orretard plastic shrinkage of the concrete and is therefore beneficial.

Methods of dealing with the detrimental consequences of bleeding and settlement are discussed in10.3.8.

Amdt 1, 6.1.7 Chloride contentSept. 1994

The presence of chloride ions in concrete increases the risk of corrosion of embedded metal. Chloridescould be present in concrete as a result of inclusion in the raw materials; or they could become presentat a later stage by ingress, especially via cracks and when the concrete is highly absorbent orpermeable.

To reduce the likelihood of corrosion of embedded metal owing to the ingress of chlorides from anexternal source, it is essential to ensure adequate cover to reinforcement (see table 5), an appropriatecement/water ratio (minimum class 2 of table A.8 (see annex A)), good compaction and thorough curingof the concrete.

In particularly severe exposure conditions, alternative methods of reinforcement protection such as theuse of surface coatings or more resistant reinforcement may be necessary.


SABS 0100-2Ed. 2

(As amended 1994)

13

To minimize the chloride content in reinforced or prestressed concrete: Amdt 1, Sept. 1994

a) the chloride content of the mixing water shall not exceed 500 mg/L (sea water shall not be permittedas mixing water);

b) calcium chloride and chemical admixtures that contain chlorides shall not be permitted; and

c) the chloride content of fine aggregate obtained from river estuaries, the sea or other sources likely tobe contaminated by chlorides shall not exceed the limiting values given in SABS 1083.

Table 1 - Deleted by Amendment No. 1.

6.1.8 Sulfates in concrete

Although sulfates are present in most cements and in some aggregates, excessive amounts of sulfate inmix constituents can cause expansion and disruption of concrete. To prevent this, the total water-solublesulfate content of the concrete mix, expressed as SO3, should not exceed 4 % (m/m), of the cement in themix. The sulfate content shall be calculated as the total from the various constituents of the mix.

6.1.9 Alkali-silica reaction

6.1.9.1 Some aggregates containing particular varieties of silica may be susceptible to attack by alkalis(Na2O and K2O) originating from the cement or other sources, producing an expansive reaction that cancause cracking and disruption of concrete. This is likely to happen only when all the following are presenttogether:

a) a high moisture level within the concrete;

b) a cement that has a high alkali content, or another source of alkali; and

c) aggregate containing an alkali-reactive constituent.

6.1.9.2 When the materials are unknown and precautions based on the preceding three conditions arejudged to be necessary, these can take the following form:

a) limiting the alkali content of the concrete mix to 2,1 kg per cubic metre of Na2O equivalent; or

b) use of GGBS or FA or CSF as composite cements or replacement materials in order that at least 40 %of GGBS or 20 % of FA or 10 % of CSF, by mass, of the combined material is introduced in the mix.

6.1.10 Drying shrinkage

All concretes shrink when they dry out after the cessation of moist curing. Where this shrinkage isrestrained, tensile stresses develop and may cause cracking. Factors in the proportioning of concrete thatinfluence shrinkage are: water content, paste content, and elastic properties of aggregates.

Potential drying shrinkage may be determined by SABS method 1085.


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14

6.2 Durability

6.2.1 General

A concrete element is durable if, when subjected to potentially destructive exposure (other than wear orloading), it protects the embedded metal from corrosion and performs satisfactorily for the life-time of thestructure.

6.2.1.1 Impermeability

One of the main characteristics that enhances the durability of any concrete is its impermeability. Suitableimpermeability is achieved with normal-density aggregates if there is a sufficiently high cement/water ratio(see 6.3), complete compaction of the concrete, and sufficient hydration of the cement through propercuring methods.

6.2.1.2 Cement content

The cement in the concrete is the component most vulnerable to attack by aggressive substances andthus the cement type and the cement content of the concrete will determine the degree of resistance ofthe concrete to attack by such substances.

6.2.1.3 Detailing

Since many processes of deterioration of concrete occur only in the presence of free water, the detailsof shape and design of exposed structural elements shall be such as to promote good drainage of waterand to prevent standing pools. Minimum covers to reinforcement to meet the durability requirements fornormal-density concrete and low-density concrete are given in 8.2.

6.2.2 Exposure to freezing and thawing

6.2.2.1 Normal-density concrete that is likely to be subjected to freezing-and-thawing action under wetconditions should contain entrained air and should conform to the air-content limits given in table 2.

Table 2 - Total air content for various sizesof coarse aggregate for normal-density concrete

1 2

Nominal maximum sizeof coarse aggregate

mm

Total air content

% (V/V)

9,513,21937,5

6-105-94-83-6

The cement/water ratio shall be at least 1,9 by mass.

6.2.2.2 Low-density concrete that is likely to be subjected to such freezing-and-thawing action shallcontain 6 % ± 2 % total air when the nominal maximum size of aggregate exceeds 9,5 mm, or 7 % ± 2 %total air when the nominal maximum size is 9,5 mm or less. Proportions shall be so selected that acharacteristic strength fcu of 20 MPa or more is attained.


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15

6.2.3 Exposure to aggressive chemicals

NOTE - See annex A for additional information.

Deterioration of concrete by chemical attack can occur by contact with gases or solutions of manychemicals, but is generally the result of exposure to acidic solutions or to solutions of sulfate salts.

Concrete made with portland cement is not recommended in persistently acidic conditions (pH 5,5 orless).

Solutions of naturally occurring sulfates of sodium, potassium, calcium or magnesium, as may be presentin some soils and groundwaters, can cause expansion and disruption of concrete.

In extreme conditions, some form of lining such as those listed in table A.10 of annex A should be usedto prevent access by deleterious solutions.

Corrosive attack by water is one of the most serious conditions of exposure. All the materials found inconcrete are to some extent soluble in water. The aggregates normally used are generally more resistantto attack than is the cementitious binder, which is the most vulnerable constituent owing to its greaterchemical activity. (Steel reinforcement is also susceptible, if embedded in a pervious concrete or ifcorrosive attack on an initially impervious concrete has reached a relatively advanced stage and thecorrosive agents have penetrated to the depth where reinforcement is embedded.)

The two properties of water that contribute most towards its high corrosiveness are the following:

- water is an extremely effective solvent; and

- water is able to dissociate dissolved salts and enable them to participate in ion-exchange andion-addition reactions.

The corrosiveness of water depends on the rate of dissolution of concrete in the water, which is influencedby the factors given in 6.2.3.1 to 6.2.3.7.

6.2.3.1 The concentration gradient between the solid phase (concrete) and the liquid phase (water)

In the case of concrete wetted by water, the concentration of calcium compounds in the concrete isusually many orders of magnitude higher than that of these compounds in the water. In the case ofdistilled or very soft water, the concentration of dissolved calcium salts in the water is almost zero and theconcentration gradient becomes very large. The resultant dissolution rate can consequently be very highand rapid attack will take place. It is this mechanism that is responsible for the extremely aggressivebehaviour of distilled water and very soft water towards concrete, which can result in the rapidleaching-out of the components of the concrete, especially calcium hydroxide, the presence of which isessential for maintaining the integrity of the binder. On the other hand, where water already contains ahigh concentration of the compounds present in the concrete, the concentration gradient is lower and candisappear when saturation of the aqueous phase is achieved.

6.2.3.2 The acidity of the water

The materials normally found in concrete have a higher solubility in acidic than in alkaline water.

6.2.3.3 The temperature of the water

Warm water is usually more aggressive than cold water.



16

6.2.3.4 The movement of the water relative to the concrete

Corrosion rates proceed much more rapidly if the water is in motion and the interface layer is constantlyreplenished. (Thus wave movements in tidal zones or turbulent flow in pipelines are accelerating agentsby virtue of their effective mixing action.)

6.2.3.5 The volatility of reaction products

Ammonium compounds present in the water in contact with the concrete, become part of the reactionproducts resultant from the corrosive attack on the concrete and may, under certain conditions, volatilizeand be lost to the atmosphere as ammonia. The net result is the formation of voids in the concrete anda loss of alkalinity (rise in acidity) of the water, which then becomes even more corrosive.

6.2.3.6 The mobility of ions

The mobility of ions is an important factor in the control of the rate of penetration of the ions into theconcrete.

6.2.3.7 The presence of dissolved gases

The presence of dissolved gases is required for certain corrosion reactions to proceed and theconcentration of the gases in the water influences the corrosion rate.

In the case of many concrete structures in contact with water, the water level is variable and certain areasof the concrete are subjected to cycles of wet and dry conditions. The following factors can influence thecorrosion rate in such areas:

a) enhanced concentration of dissolved salts: if the water level drops, previously wetted areas dryoff as a result of evaporation of the surface layer of water. Any salts present in this layer become moreand more concentrated as evaporation proceeds and eventually crystallize out of solution. A coat ofvariably concentrated salts can therefore be created, with all the implications that this may hold for theconcrete;

b) exposure to gases present in the atmosphere: in heavily polluted industrial atmospheres, gasesmay be significant corrosion accelerators.

Amdt 1, 6.2.4 Exposure to salt-laden airSept. 1994

In coastal environments, concrete structures are exposed to wind-driven, salt-laden air. When a criticalconcentration of free chlorides is reached, depassivation of the reinforcement could occur, leading tocorrosion and to subsequent spalling of the concrete. Salts that enter the pore structure of the surfaceconcrete could also crystallize on drying. This process sets up expansive forces which could cause theconcrete to crack and spall, allowing the rate of chloride ingress to increase.

The degree of aggressiveness of coastal environment depends on the salt content of the air and theatmospheric relative humidity. In areas where the salt content and relative humidity of the air are high, itmay be necessary to undertake protective measures similar to those for concretes in marine environments(see table A.8 of annex A).


SABS 0100-2Ed. 2

(As amended 1994)

17

6.2.5 Exposure to corrosive fumes Amdt 1, Sept. 1994

The deterioration of concrete as a result of exposure to corrosive fumes is usually associated with a highrelative-humidity environment which presents a special case of concrete deterioration caused byaggressive water. Corrosive fumes are often characterized by a high concentration of corrodants, andspecial protection measures are usually required for the concrete.

Depending on the degree of aggressiveness of the fumes, protective measures could range from theprovision of a high-strength, low-permeability concrete to the application of a chemically resistant barrierto isolate the concrete from the aggressive fumes. A careful assessment of the degree of aggressivenessof the fumes, together with specialist advice, is essential in determining the most effective protectionmethod.

6.2.6 Exposure to polluted air Amdt 1, Sept. 1994

The deterioration of concrete in heavily polluted industrial areas is caused by a number of mechanisms,depending on the nature of the atmospheric pollutant; for example, in areas around coal-burning powerstations where emission of sulfates results in the precipitation of sulfuric acid, both acid attack and sulfateattack could cause concrete deterioration. The minimum requirements for concrete that is exposed toheavily polluted air are given in class 1 of table A.8 (see annex A).

6.3 Mix proportions

6.3.1 High cement content

A cement content in excess of 550 kg per cubic metre of concrete should normally not be used becausesuch a cement content tends to make concrete sticky and difficult to handle, place and compact.

6.3.2 Concrete exposed only to mild conditions (see 3.3)

Specified strength shall be determined by structural design considerations. If the concrete is to includeembedded metal, the characteristic strength shall not be less than 20 MPa. There is no requirement forminimum cement/water ratio or for minimum cement content.

6.3.3 Deleted by Amendment No. 1.

6.3.4 Deleted by Amendment No. 1.



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7 Production of concrete

7.1 Batching

7.1.1 Cement

The mass of cement in a standard sack is 50 kg. All cement taken from bulk storage containers and frompartially emptied bags shall be batched by mass to an accuracy of 2 % (or better) of the mass required.

7.1.2 Water

Mixing water for each batch shall be measured and the amount of water adjusted to allow for the moisturecontent of the aggregates (see 7.1.3). The true quantity shall be measured to an accuracy of 2 % (orbetter).

7.1.3 Aggregates

If batching is by mass, the mass of the aggregates of each size shall be measured and a correction madefor the moisture content of the aggregates. The true mass shall be measured to an accuracy of 3 % (orbetter). If batching is by volume, the fine and coarse aggregates shall be measured separately in suitablemeasuring boxes of known volume and of such capacity that the quantities of aggregates for each batchare suitable for direct transfer into the mixer. Bulking tests on the fine aggregate (or moisturedetermination if the relation between bulking and moisture content of the specific fine aggregate is known)shall be conducted at least daily (in accordance with SABS method 856) and the results used to adjustthe batch volume of fine aggregate to give the true volume required. Additional tests for bulking shall becarried out after rain has fallen or if there has been any other reason for variation in the moisture contentof the aggregate.

7.1.4 Admixtures

The amount of admixture to be used shall be measured to an accuracy of 2 % (or better). Daily calibrationof the measuring device is imperative, and after each day's use, the measuring device shall be uncoupledfrom the supply and cleaned. The person responsible for batching shall be fully conversant with theeffects of the admixture and the consequences of underdosage or overdosage.

Amdt 1, Sentence deleted by Amendment No. 1.Sept. 1994

7.2 Mixing

7.2.1 Mixing on site

7.2.1.1 General

7.2.1.1.1 Mixing of materials for concrete shall be conducted by an experienced operator.


SABS 0100-2Ed. 2

19

7.2.1.1.2 The total volume of material per batch shall not exceed the rated capacity of the mixer.

7.2.1.1.3 Concrete shall only be mixed in quantities required for immediate use. Concrete that has setshall be discarded. In the event of delay in the concreting operations, concrete may be retained in themixer for a maximum period of 2 h, provided that only just enough water is added to the mixer to maintainthe target slump. During this time, the mixer shall be restarted and run for about 2 min every 15 min. Theperiod of 2 h shall be reduced if the ambient temperature, or any other factor, tends to produce earlysetting.

7.2.1.1.4 At the commencement of each concrete production run and before any concrete is mixed, theinner surfaces of the mixer shall be cleaned and all hardened concrete removed. Sand, cement and water,proportioned as for the concrete to be made, shall then be introduced into the cleaned mixer in sufficientquantity to cover the entire inside surface of the mixer. The mixer shall then be operated (to mix thesematerials and to coat the interior surfaces of the mixer with the mixture) and discharged immediately priorto charging of the mixer with the first batch.

7.2.1.1.5 Instructions for the sequence of charging the particular mixer shall be given before operationscommence. Control systems shall be introduced to ensure that the batch is not discharged until therequired mixing time has elapsed. At least three-quarters of the required mixing time shall take place afterthe last of the mixing water has been added.

7.2.1.1.6 The period of mixing shall be measured from the time when all the materials are in the drumor pan, to the commencement of discharge. Subject to the exception given in 7.2.1.1.7, mixing shall takeplace for at least 1,5 min or 1 min, for drum-type and pan-type mixers respectively, for each batch of1,5 m3 or less, and the mixing time shall be increased by 20 s or 15 s respectively, for each additionalcubic metre or part of a cubic metre. During this period, the drum or pan shall be rotated at the speedrecommended by the manufacturer of the mixer. To prevent attrition, continuous mixing periods shall notexceed 10 min or 6 min per batch, for drum-type and pan-type mixers respectively, at the recommendedmixing speeds.

7.2.1.1.7 If a mixer of the type described in 5.3.2(b) is used, shorter mixing periods may be used ifapproved by the engineer.

7.2.1.1.8 The mixed concrete shall be so discharged that there is no significant segregation of thematerials in the mix.

7.2.1.2 Control of admixtures

7.2.1.2.1 Air-entraining admixtures, calcium chloride and other chemical admixtures shall be charged intothe mixer as solutions, and shall be measured by means of an acceptable mechanical dispensing device,the liquid being considered a part of the mixing water. Admixtures that cannot be added in solution maybe weighed or may be measured by volume if so recommended by the manufacturer.

7.2.1.2.2 If two or more admixtures are used in the concrete, they shall be added separately to avoidpossible interaction that could interfere with the effectiveness of either admixture or that could adverselyaffect the concrete.

7.2.1.2.3 Addition of retarding admixtures shall be completed within 1 min after addition of the water hasbeen completed, or prior to the beginning of the last three-quarters of the required mixing, whicheveroccurs first.

7.2.1.3 Tempering and control of mixing water

When concrete delivered at the place of operation has a slump below that suitable for placing, asindicated by the project specifications, water may be added, provided that the cement/water ratio is notreduced to below the minimum permissible for strength and durability and the maximum slump is not


SABS 0100-2Ed. 2

20

exceeded. The water shall be incorporated by additional mixing equal to at least half of the total mixingtime required. Any addition of water in excess of that permitted by the limitation on the cement/water ratioshall be accompanied by a quantity of cement sufficient to maintain the proper cement/water ratio. Theapproval of the engineer (or of his representative) for such addition shall be obtained before the water isadded.

7.2.1.4 Adverse weather

7.2.1.4.1 Cold weather

The required concrete temperature from the time of mixing until the concrete has hardened (see 10.8.3)may be obtained in several ways, such as by:

a) heating the mixing water and the aggregate (if water or aggregate is heated above 60 °C, combinethe water with the aggregate in the mixer before adding the cement. Cement shall not be mixed withwater or mixtures of water and aggregate of temperatures exceeding 60 °C);

b) increasing the cement content in the mix;

c) using a cement that hardens more rapidly; or

d) incorporating an accelerator. (Chloride-free accelerators should be used when the concrete containsreinforcement or other embedded metal.)

NOTE - If insulation is used, its effect on the temperature of concrete should be taken into consideration.

7.2.1.4.2 Hot weather

When the temperature of the fresh concrete is likely to exceed the permissible maximum (see 10.8.2), theconcrete can be cooled by

a) cooling the mixing water or substituting flaked or well-crushed ice for part or all of the mixing water;ice particles have to be small enough to melt completely during the mixing process;

b) cooling the aggregates, for example by shading the stockpiles and by wetting the stone to causeevaporative cooling; or

c) injecting liquid nitrogen into the mix during mixing.

7.2.2 Ready-mixed concrete

Where concrete is delivered to the site ready mixed, the requirements of SABS 878 shall apply.

7.3 Transportation

The mixed concrete shall be discharged from the mixer and transported as rapidly as practicable to itsfinal position by means that will prevent segregation, adulteration, loss of ingredients and ingress offoreign matter or water and that will maintain the required workability at the point of placing.

Concrete may only be conveyed through pipes made with materials that are non-reactive with cement.Aluminium pipes shall be suitably protected.

The capacity of conveying equipment shall be sufficient to ensure that placed concrete does not set beforeadjacent concrete of the same pour is placed.

Conveying equipment shall be cleaned at the end of each operation or work day.


SABS 0100-2Ed. 2

(As amended 1994)

21

8 Reinforcement

8.1 General

Reinforcement should comply with the relevant requirements of SABS 82, SABS 920 and SABS 1024.

NOTE - See also the relevant section of SABS 0100-1.

8.2 Cover to reinforcement

The minimum cover to reinforcement for normal-density concrete and low-density concrete is given in Amdt 1, table 5 for various conditions of exposure (see 3.3). Sept. 1994

Detailing of reinforcement shall allow for fire resistance (see SABS 0100-1), dimensional tolerances incutting, bending and fixing of reinforcement (see 4.13 and 5.1.5 of SABS 0144:1978), and permissibledeviations in dimensions of concrete work (see SABS 0155).

Table 5 — Minimum cover for normal-density and low-density concrete for various conditions of exposure Amdt 1,

Sept. 1994

1 2 3 4 5 6

Concrete

Minimum cover

mm

Conditions of exposure

Mild Moderate Severe Very severe Extreme

Normal-density concrete

20 30 40 50 60

Low-density concrete

20 40 50 60 70

NOTE - This table should be used in conjunction with table A.8 of annex A.

Table 6 — Deleted by Amendment No. 1.


SABS 0100-2Ed. 2

22

8.3 Bending

8.3.1 General

The following provisions shall apply:

a) all reinforcement shall be bent to the dimensions shown on the drawings and in accordance with therequirements of SABS 82;

b) all reinforcement shall be bent cold unless otherwise permitted (see 8.3.2);

c) bending shall be carried out slowly, using a steady, even pressure without jerk or impact;

d) it is permissible to bend grade 250 reinforcement protruding from concrete elements, provided thatcare is taken to ensure that the radius of bend is not less than that specified in SABS 82. 450 MPabars shall not be bent, rebent or straightened without the engineer's approval;

e) where it is necessary to reshape steel previously bent, this shall only be done with the engineer'sapproval and each bar shall be inspected for signs of fracture.

8.3.2 Preheating prior to bending or straightening

Provided that the bars do not depend on cold working for their strength, they may be bent or straightenedhot, in accordance with the following provisions:

a) the preheating procedure shall be such as not to harm the bar material (or to cause damage to theconcrete in the case of bars already cast-in);

b) the preheat shall be applied to a length of bar equal to at least five bar diameters in each direction fromthe centre of the bend. The temperature of the bar at the concrete interface shall not exceed 260 °C;

c) the preheat temperature shall not exceed 650 °C;

d) the preheat temperature shall be maintained until bending or straightening is complete;

e) heated bars shall be cooled slowly in air. (Hot bars shall not be quenched with water.)

8.4 Fixing

The grade of accuracy for cover over reinforcement shall comply with the requirements of SABS 1200 G.

Reinforcement shall not be subjected to mechanical damage, rough handling, dropping from a height, orshock loading.

8.4.1 Steel reinforcement

8.4.1.1 All reinforcement, at the time of placing of the concrete, shall be free from rust, scale, oil and othercoating that may reduce the bond between the steel and surrounding concrete, or initiate corrosion of thereinforcement. The reinforcement shall not be contaminated by any substance used as a release agentfor the formwork.

All reinforcement shall be well and cleanly rolled. Rust, seams, surface irregularities and mill scale shallnot be cause for rejection, provided that the mass per metre, dimensions, cross-sectional area and tensileproperties of a test specimen comply with the applicable requirements for the specified bar.


SABS 0100-2Ed. 2

23

8.4.1.2 Reinforcement shall be placed as shown on the drawings and shall be maintained in that positionwithin the specified tolerances. Reinforcement shall be tied with annealed wire of diameter 1,6 mm or1,25 mm or by acceptable clips, at sufficient intersections to avoid displacement of bars. It may alsosimilarly be secured by welding if permitted by the engineer. Reinforcement shall be supported in itscorrect position by hangers or saddles, and aligned by means of chairs and spacers of approved design.Spacers of such materials and designs shall be durable, shall not lead to corrosion of the reinforcementand shall not cause spalling of the concrete cover. Spacer blocks made from cement and sand shall bemade of the cement and sand used for the surrounding concrete. Proportions shall be 1 volume of cement(loose), 1 volume of sand (dry and loose) and sufficient water to produce a mix that can be thoroughlycompacted. Spacer blocks shall be cured in water for at least 14 d before being used. Concrete spacerblocks made on the construction site shall not be used unless they are made under strictly controlledconditions. Spacers and chairs shall be placed at the spacing recommended in 5.2.2 of SABS 0144:1978.

8.4.1.3 The clear distance between reinforcing bars shall be determined in accordance with 3.11 ofSABS 0100-1:1980.

8.4.1.4 In the detailing and dimensioning of bars (in particular bends, hooks and stirrups), the designershould take into account the diameters of all the bars intersecting at any point, the sweep or curve ofbends, the need for the use of ties to fix steel, the shuttering and reinforcement tolerances, the coverspecified for various exposure conditions and the tolerances permitted for the fabrication of reinforcementand erection of formwork. The concrete cover specified is equally applicable to the upper layer ofreinforcing steel in floors and slabs. For any slab, cognizance shall be taken of the specified concretecover, and the detail dimensions and diagrams of the reinforcing bars to which the steel is to be bent shallbe such that the specified concrete cover can be achieved.

8.4.1.5 The design of the laps and the lengths of main bars in vertical reinforcement shall be such as tosuit the position of construction joints shown on the drawings or as specified. It is particularly importantthat where a kicker or starter stub for a wall is specified or shown on the drawings or will be permitted, thatthe lap in the vertical reinforcement start above the kicker. A lap shall not start below a joint at the top ofa kicker and shall not finish above it.

8.4.1.6 Templates should be furnished for placement of all column dowels, unless otherwise permitted.

8.4.1.7 Welded wire fabric for slabs on grade shall extend to within 100 mm of the concrete edge. Weldedwire fabric shall be adequately supported during placing of concrete, to assure proper positioning in theslab.

8.4.1.8 Where exposed-aggregate, ribbed or patterned finishes are to be achieved, the detail dimensionsof reinforcing bars shall be such that the specified concrete cover can be maintained after the texture,ribbing or pattern is applied.

NOTE - The contractor cannot provide the specified cover unless the outside dimensions of reinforcement cages and thelike provide for greater cover than would be provided for plain finishes of concrete.

8.4.1.9 Supporting steel should be included in the reinforcing schedule by the engineer. The use of othersupporting materials is subject to the approval of the engineer.

8.4.1.10 Laps and joints of reinforcing bars shall be formed only as and where shown on the drawingsor as approved by the engineer. Bars left exposed for bonding of future extensions to the structure shallbe well protected from corrosion, using suitable means.


SABS 0100-2Ed. 2

24

8.4.1.11 Reinforcement in elements cast on ground shall rest on precast concrete blocks at least 100 mmsquare, and having a compressive strength at least equal to the specified compressive strength of theconcrete being placed. Other means of support may be used if approved by the engineer.

8.4.2 Zinc-coated (galvanized) reinforcement

Zinc-coated reinforcing bars supported away from formwork shall rest on zinc-coated wire bar-supportsor on wire bar-supports made of dielectric material or other acceptable materials. All other reinforcementand embedded steel items in contact with zinc-coated reinforcing bars, or within a minimum clear distanceof 50 mm from zinc-coated reinforcing bars, shall be zinc-coated, unless otherwise approved.

Zinc-coated reinforcing bars shall be fixed with zinc-coated tie wire or non-metallic-coated tie wire or otheracceptable material.

8.4.3 Epoxy-coated reinforcement

Epoxy-coated reinforcing bars supported away from formwork shall rest on epoxy-coated wirebar-supports, or on bar-supports made of dielectric material or other acceptable materials. Wire barsupports shall be coated with dielectric material for a minimum distance of 50 mm from the point of contactwith the epoxy-coated reinforcing bars. All reinforcing bars used as support bars or as spreader bars shallbe epoxy-coated or coated with dielectric material.

Epoxy-coated reinforcing bars shall be fastened with nylon-coated, epoxy-coated or plastics-coated tiewire, or with other acceptable materials.

8.5 Welding

8.5.1 General

Generally, all welding should be carried out under controlled conditions in a factory or workshop andwelding on site should be avoided if possible. Welding on site may be undertaken when required andpermitted by the engineer, provided that suitable safeguards and techniques are employed and the typesof steel (including high-yield steels to SABS 920) have the required welding properties. The competenceof the operators shall be demonstrated prior to, and periodically during, welding operations.

8.5.2 Use of welding

Welding may be used for:

a) fixing in position; for example, by welding between crossing or lapping reinforcement, or between barsand other steel elements (metal-arc welding or electric resistance welding may be used on suitablesteels); or

b) structural welds involving transfer of load between reinforcement or between bars and other steelelements.

Butt welds may be carried out by flash butt welding or metal-arc welding. For lapped joints, metal-arcwelding or electric resistance welding may be used.

8.5.3 Types of welding

8.5.3.1 Flash butt welding

Flash butt welding shall be carried out with the correct combination of flashing, heating, upsetting andannealing, and with the use of only those machines that automatically control this cycle of operations.


SABS 0100-2Ed. 2

25

8.5.3.2 Metal-arc welding

Metal-arc welding of reinforcement shall be carried out in accordance with the recommendations of thereinforcement manufacturer, as approved by the engineer.

8.5.3.3 Electric resistance welding

Electric resistance welding is done by the use of welding machines that can be adequately controlled butthat require the correct preparation of the bars to be welded.

8.5.3.4 Other methods

Other methods of welding may be used, subject to their satisfactory performance in trial joints.

8.5.4 Location of welded joints

Structural welds shall not occur at bends in reinforcement. Unless otherwise agreed by the engineer,joints in parallel bars of the principal tensile reinforcement shall be staggered in the longitudinal direction.For joints to be regarded as staggered, the distance between them shall be at least equal to the endanchorage length for the bar.

8.5.5 Strength of structural welded joints

The strength of all structural welded joints shall be assessed by means of testing trial joints.

8.5.6 Welded lapped joints

The length of run deposited in a single pass shall not exceed five times the diameter of the bar. If alonger length of weld is required, it shall be divided into sections and the space between runs shall be atleast five times the diameter of the bar.

9 Formwork

9.1 General

9.1.1 Materials that have a deleterious effect on concrete (e.g. untreated timber) shall not be used forformwork.

9.1.2 Forms shall have sufficient strength to withstand the pressure resulting from placement andcompaction of the concrete and shall have sufficient rigidity to maintain specified tolerances, the requiredshapes, finishes, positions, levels and dimensions shown on the drawings.

9.1.3 Tolerances shall comply with the relevant requirements of SABS 0155.

9.1.4 Forms shall be sufficiently tight to prevent loss of grout.

9.1.5 The formwork shall be capable of being dismantled and removed from the cast concrete withoutshock, disturbance or damage to the concrete.

9.1.6 Earth cuts shall not be used as forms for vertical surfaces, unless permitted or unless so required.

9.1.7 Shop drawings for formwork, including the location of shoring and reshoring, shall be submittedfor review as required by the contract documents.


SABS 0100-2Ed. 2

26

9.1.8 Where formwork is to be erected over a road, a street or a railway, the formwork shall be sodesigned that the full clearances required for the free movement of traffic are maintained to thesatisfaction of the authority controlling such road, street or railway. It is recommended that, prior to thecommencement of erection, the approval of such authority be obtained for the design of the formwork.

9.2 Design and construction of formwork

9.2.1 Loads

The forms shall be designed to withstand the worst combination of self-weight, wet concrete weight,concrete pressure, construction loads and wind loads, together with all incidental dynamic effects causedby placing and compacting the concrete.

9.2.2 Deflection

To maintain the specified tolerances, the formwork shall be cambered to compensate for anticipateddeflections in the formwork prior to hardening of the concrete.

9.2.3 Form accessories

NOTE - Recommendations for spacers are given in 8.4.

Form accessories such as ties and hangers shall be of a commercially manufactured type. Non-fabricatedwire shall not be used. Form ties and spacers left in situ should not impair the desired appearance ordurability of the structure, e.g. by causing spalling or rust staining or by allowing the passage of moisture.

After the ends or end fasteners of form ties have been removed, any embedded portion of the tie shallterminate at a distance of not less than the specified minimum cover from the formed surface of theconcrete.

Runways for moving equipment during concreting shall be provided with struts and legs, shall besupported directly on the formwork or structural member, and shall not rest on the reinforcing steel.

9.2.4 Temporary openings

Temporary openings shall be provided at the base of column forms and wall forms and at other pointswhere necessary to facilitate cleaning and observation immediately before concrete is placed.Subsequently, the openings shall be so closed as to provide the finish specified and to conform to theapplicable tolerances given.

9.3 Preparation of formwork

All matter that could contaminate or adulterate the concrete, including rubble and dust, shall be removedfrom the interior of the forms before the concrete is placed. Surfaces that are to be in contact with fresh(wet) concrete shall be clean and covered with an acceptable coating material that will effectively preventabsorption of moisture, will prevent bond with the concrete, and will not stain the concrete surfaces. Amineral oil or other approved material may be used.

9.4 Re-use of formwork

Before re-use, all formwork shall be reconditioned, and all form surfaces that are to be in contact with theconcrete shall be thoroughly clean.


SABS 0100-2Ed. 2

27

9.5 Removal of formwork

9.5.1 General

9.5.1.1 Forms and shoring in the formwork shall remain in place until the concrete has reached at leastthe strength (which should be specified in the contract documents) necessary to prevent plucking of thesurface during removal of the formwork and to support its own weight and any loads that may be imposedon it.

9.5.1.2 Due regard shall be given to curing methods to be employed before formwork is removed.

9.5.1.3 Formwork shall be removed carefully so that shock and damage to the concrete are avoided.Sudden removal of wedges is equivalent to an impact load on the partially hardened concrete.

9.5.1.4 The quality of formwork shall be such that the finished surface of the concrete is as shown on thedrawings or as required in terms of the project specification. Requirements for surface finishes are givenin 10.9.

9.5.2 Formwork removal time for cast-in-situ concrete

9.5.2.1 Recommended periods before removal of forms (see table 7)

Forms may not be removed within periods shorter than those specified by the designer. Table 7 shouldnot be used if accelerating curing methods or sliding forms are used or in cases such as in 9.5.2.2.

9.5.2.2 Shorter periods before removal of forms

It may be possible to remove formwork within periods shorter than normal if the early strength of theconcrete is assessed. This strength may be assessed by tests on cubes of equal maturity, and cured, asfar as possible, at the same temperature as the concrete in the element.

Formwork for columns, walls, sides of beams, and other parts not supporting the weight of the concrete,may be removed as soon as the concrete has hardened sufficiently to resist damage from removaloperations.


SABS 0100-2Ed. 2

28

Table 7 - Removal of formwork: minimum time in days1)

1 2 3 4 5 6 7 8 9 10

Type of structural member orformwork

Minimum time

d

Type of cement used

Ordinary portlandcement and portland

cement 15

Rapid-hardeningportland cement2) and

rapid-hardening portlandcement 153)

Cements containing morethan 15 % of GGBS or FA

Weather (see 3.2)

Normal Cool Cold Normal Cool Cold Normal Cool Cold

Beam sides, walls and unloadedcolumns 0,75

4) 1,5 0,5

4) 1 2

4) 4

Slabs with props left in place 44)

7 24)

4 64)

10

Beam soffits with props left in place, andribs of a ribbed floor construction 7

4)12 3

4) 5 10

4)17

Slab props ) )including cantileversBeam props )

10

14

4)

4)

17

21

5

7

4)

4)

9

12

10

14

4)

4)

17

21

1) The time of removal of formwork allowing for the surface finish is to be decided by the designer. This table should be regarded as aguide only.

2) Shorter periods may be used for sections having a thickness of 300 mm or more.

3) Only if rapid-hardening cement is used as a direct replacement for ordinary portland cement. Shorter removal times for formwork donot apply if mixes are designed with rapid-hardening cement to achieve the same 28-d strength.

4) In cool weather, stripping times are to be determined by interpolation between the periods specified for normal and cold weather.

9.5.3 Reshoring

When reshoring is permitted or required, it shall be planned in advance and shall be subject to approvalby the engineer.

The following recommendations are given as guidance:

a) floors that are supported by shores under newly placed concrete shall have their original supportingshores left in place or shall be reshored. The reshoring system shall have a capacity sufficient toresist expected loads and in all cases shall have a capacity equal to at least one-half of the capacityof the shoring above;

b) the shores shall be located directly under a shore position above, unless other locations areacceptable;

c) in a multistorey building, the reshoring shall extend over a sufficient number of storeys to distributethe weight of newly placed concrete, forms and construction live loads in such a way that the designsuperimposed loads on the shores that support floors are not exceeded.


SABS 0100-2Ed. 2

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10 Placing and protection of concrete

10.1 General

All placing and compacting should be carried out under suitable supervision; the engineer shall be givenadequate notice of the intention to place concrete.

Concrete shall be placed continuously, or in layers of such thickness that no concrete will be placed onconcrete that has so hardened as to cause planes of weakness within the section. If a section cannot beplaced continuously, construction joints (see 10.4) shall be located as indicated in the contract documentsor as permitted.

Concrete that has hardened to the extent that it no longer responds plastically to compactive effort or hasbeen contaminated by foreign matter shall not be placed.

10.2 Placing

10.2.1 The concrete shall be placed within 1 h from the time of discharge from the mixer. Re-temperingby the addition of water or other material shall not be permitted.

10.2.2 Placing shall be carried out at such a rate that the concrete that is being integrated with freshconcrete is still plastic.

10.2.3 Wherever practicable, the concrete shall be placed vertically into its final position to avoidsegregation and displacement of reinforcement and other items that are to be embedded.

10.2.4 Placed concrete shall not be so reworked (whether by means of vibrators or otherwise) as tocause it to flow laterally in such a way that segregation occurs. Where practicable, the concrete shall beplaced in horizontal layers of compacted thickness not exceeding 450 mm, to avoid "heaping".

Use of vibrators to move concrete laterally within forms shall not be allowed.

10.2.5 Where a chute is used to convey the concrete, its slope shall be such that it will not causesegregation; a suitable spout or baffles shall be provided for the discharge of the concrete. Generally, thechute should be at an angle exceeding 30° to the horizontal.

10.2.6 Unless permitted by the engineer, the concrete shall not be allowed to fall freely through a heightof more than 3 m.

10.2.7 Placing of concrete in an element that is supported shall not be commenced until the concretepreviously placed in supporting elements (columns, walls, beams) is no longer plastic and has been inplace for at least 2 h.

When elements that are supported and supporting elements are placed in one operation, the concretein the vicinity of the junction between these elements shall be revibrated shortly before it sets. Thisprocedure is necessary to eliminate defects such as cracks caused by the settlement of solids in the freshconcrete.

10.2.8 When a closed circuit is being concreted, work shall commence at one or more points in thecircuit and shall so proceed in opposite directions at the same time that, at completion of the circuit, thejunctions are formed with freshly placed concrete.

10.2.9 No concrete shall be placed in flowing water. When the placing of concrete underwater ispermitted owing to exceptional circumstances because, in the opinion of the engineer, it is not practicableto dewater before placing, it shall be placed by means of a tremie. During placing, the lower end of the



30

tremie shall be continuously so immersed in the concrete being placed that the fresh concrete enters themass of previously placed concrete from within, causing water to be displaced with minimum disturbanceat the surface of the concrete.

Amdt 1, The mix proportion of the concrete shall be adjusted to provide a concrete suitable for placing by tremie.Sept. 1994 Full details of the method proposed and of the adjusted concrete mix proportions shall be submitted for

approval before placing commences.

During and after concreting underwater, pumping or dewatering operations in the immediate vicinity shallbe suspended if there is any danger that such operations will interfere with the freshly placed concretebefore it has set and gained adequate strength.

10.2.10 In any section of the works, the placing of concrete by pumping is subject to approval. Fulldetails shall be furnished regarding the mix proportions of concrete intended to be placed by pumping.

10.2.11 The lift height to be concreted at any one time shall be agreed between the contractor and theengineer. In massive sections, it will be necessary to consider the effect of lift height on the temperaturerise because of the heat of hydration.

10.3 Compaction

10.3.1 All concrete shall be so compacted (by vibration, spading, rodding, etc.) during and immediatelyafter placing, that the concrete is thoroughly worked around the reinforcement, around embedded itemsand into corners of formwork and forms a solid void-free mass having the required surface finish.

Where compaction is only by means other than vibration, approval should be sought.

10.3.2 The concrete shall be free from honeycombing and planes of weakness. Successive layers of thesame lift shall be thoroughly worked together. To achieve this, the compaction tool shall be permitted topenetrate through the new layer into the lower layer, which shall be sufficiently plastic to permitinterknitting.

10.3.3 Vibration shall be applied continuously during the placing of each batch of concrete until theexpulsion of air has virtually ceased. Over-vibration that results in segregation, surface laitance orleakage, or any combination of these, shall be avoided.

10.3.4 Immersion vibrators shall be inserted vertically into the concrete to be compacted, at regularspacings not exceeding 0,6 m or 10 times the diameter of the vibrator, whichever is less.

Systematic spacing of insertions of the vibrator at the recommended intervals is essential to ensure thatno concrete remains outside the sphere of energy released by the vibrator.

As soon as a water sheen is visible on the surface, the vibrator shall be slowly withdrawn from theconcrete, care being taken to avoid the formation of voids.

10.3.5 When external vibrators are used, the design of formwork and the disposition of vibrators shallbe such as to ensure efficient compaction and to avoid surface blemishes.

10.3.6 The rate of concrete placing shall be commensurate with the available compaction equipment,and compaction by vibration shall be executed by skilled operators only. The number of vibrators usedshall be compatible with the rate at which concrete is placed. Standby vibrators shall also be madeavailable.


SABS 0100-2Ed. 2

31

10.3.7 Where permanent formwork is incorporated in the structure, its energy absorption should be takeninto account when the method of vibration to be used is being decided upon. Extra care is required toensure full compaction of the concrete, since this cannot be checked as usual when the formwork isremoved.

10.3.8 To overcome the detrimental effects of bleeding (see 6.1.6) and settlement, the technique of"revibration" or "recompaction" should be used. The technique consists of recompacting the concrete ata time that is as long as possible after initial compaction but while the concrete retains sufficientworkability to respond plastically to compactive energy. In practice, this energy is normally applied bymeans of immersion vibrators. Recompaction is especially necessary in upper zones of columns, formsthat have abrupt changes in cross-section (such as T and I beams and coffered slabs), elements thathave horizontal reinforcing bars placed near the top of the concrete, liquid-retaining structures, andstructures exposed to aggressive conditions.

10.4 Construction joints

NOTE - See also 3.11 of SABS 0100-1:1980.

10.4.1 General

The number of construction joints should be kept to the minimum necessary for the execution of the work.Their type and locations shall be acceptable to the engineer.

The concrete at the joint shall be bonded with that subsequently placed against it, without provision forrelative movement between the two. To ensure that the load-bearing capacity of the concrete in the areais not impaired, high quality workmanship is necessary when the joints are being formed.

10.4.2 Location

10.4.2.1 In general, joints should be located near the middle of the spans of slabs, beams and girders,unless a beam intersects a girder at this point, in which case the joint in the girder should be offset at adistance equal to twice the width of the beam. Joints in walls and columns should be at the underside offloors, slabs, beams or girders and at the tops of footings or floor slabs.

Joints should be perpendicular to the main reinforcement.

10.4.2.2 The term "unforeseen joint" is used to identify a joint formed during concreting when plant failure,inclement weather or some other unforeseen event has enforced a halt in the placing of concrete and thuscreated a situation in which a construction joint has to be made in a location that was not approved priorto the commencement of concreting.

If an unforeseen joint occurs at a critical section (e.g. at a section of maximum shear), it may be possibleto remove part of the fresh concrete in order to place the joint in a less critical section. The face of the jointshould be trimmed to a suitable shape.

10.4.3 Bonding

When so required or permitted, bonding shall be achieved by means of one of the methods given in10.4.3.1 to 10.4.3.4.

10.4.3.1 The use of an adhesive

Joints to which an adhesive is applied shall be prepared, and the adhesive applied, in accordance withthe manufacturer's recommendations, prior to the placing of fresh concrete.


SABS 0100-2Ed. 2

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10.4.3.2 The use of a retarder

Surfaces of joints that have been treated with a chemical retarder shall be prepared in accordance withthe manufacturer's recommendations, prior to the placing of fresh concrete.

10.4.3.3 Roughening and dampening the surface of the concrete

Roughening the surface of the concrete in an acceptable manner shall uniformly expose the aggregateand shall not leave laitance, loosened particles of aggregate or damaged concrete on the surface.

The hardened concrete of construction joints and of joints between footings and walls or columns,between walls or columns and beams or floors they support, and joints in other elements not mentionedabove shall be dampened (but not saturated) immediately prior to the placing of fresh concrete.

The hardened concrete of horizontal construction joints

a) in exposed work, or

b) in the middle of beams, girders, joists and slabs, or

c) in work designed to contain liquids

shall be dampened (but not saturated) and then thoroughly covered with a thin coat of cement grout ofsimilar proportions to the mortar in the concrete. Alternatively, application of a concrete layer of thicknessapproximately 250 mm, and made richer by reducing the amount of coarse aggregate by 25 %, may beconsidered. The fresh concrete shall be placed before the grout or the intermediate layer of concrete hasattained its initial set.

10.4.3.4 Alternative methods to roughening the surface of the concrete

Alternatively, mesh or expanded metal stop ends (not extending into the cover zone) may be used, ifapproved, to provide a rough face to the joint.

10.4.4 Reinforcement

All reinforcement shall be continued across construction joints. If a kicker or starter stub is used, it shallbe at least 70 mm high and carefully constructed. It is sometimes necessary and, in the case of columns,it is normally necessary, that a kicker stub be cast with the previous concrete.

10.4.5 Construction

10.4.5.1 Construction joints shall be formed in accordance with

a) the details shown on the drawings, or

b) the applicable requirements of the project specification.

10.4.5.2 In the case of an unforeseen joint (see 10.4.2.2), concrete shall be finished off at the place ofstoppage in a manner that will least impair the durability, appearance and proper functioning of theconcrete. The engineer's instructions shall then be followed.

10.4.5.3 In the case of a joint not covered by 10.4.5.1 or 10.4.5.2, one of the methods given in 10.4.5.3.1to 10.4.5.3.4 shall apply.


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10.4.5.3.1 Construction joints when concrete is less than 24 h old

The surface of the concrete shall be brushed with a steel wire brush before new mortar and concrete areplaced as specified in 10.4.5.3.2.

10.4.5.3.2 Construction joints when concrete is more than 24 h and less than 3 d old

The surface of the concrete shall be sand-blasted, or chipped with a light hammer, and swept clean. Thesurface dry concrete shall then be brushed with a thin layer of mortar composed of cement and sandmixed in the same ratio as the cement and sand in the concrete mixture, or a thin layer of cement/watermix of creamy consistence. This mortar or mix shall be freshly mixed and placed immediately before thenew concrete is placed. It shall not be allowed to dry out before new concrete is poured.

10.4.5.3.3 Construction joints when concrete is more than 3 d old

The old surface shall be cleaned as in 10.4.5.3.2 and kept continuously wet for at least 24 h and thenallowed to become surface dry before the mortar or cement/water mix (as in 10.4.5.3.2) and new concreteare placed.

10.4.5.3.4 Construction joints at tops of columns

The procedure for brushing or cleaning specified in 10.4.5.3.1 or 10.4.5.3.2, as applicable, shall befollowed before the steel reinforcement of the slab or floor to be cast on the columns is placed in position.

10.5 Embedded items

10.5.1 General

Expansion joint material, waterstops, pipes and conduits, and other embedded items shall be positionedaccurately and supported against displacement. Voids shall be filled temporarily with readily removablematerial to prevent the entry of concrete into the voids.

All contractors whose work is related to the concrete (or has to be supported by the concrete) should begiven ample notice and opportunity to introduce or furnish (or both) embedded items before the concreteis placed.

10.5.2 Waterstops

The material and design of waterstops and their location in joints shall be as indicated in the contractdocuments. Each piece of premoulded waterstop shall be of maximum practicable length in order to keepthe number of end joints to a minimum.

Joints at intersections and at ends of pieces shall be made in the manner most appropriate to the materialbeing used. Joints shall develop effective watertightness fully equal to that of the continuous waterstopmaterial, shall permanently develop at least 50 % of the mechanical strength of the parent section, andshall permanently retain their flexibility.

10.5.3 Pipes and conduits

No pipes or conduits, other than shown on the drawings, may be permanently embedded in the concretewithout prior approval.


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10.6 Concrete for water-retaining structures

10.6.1 Special care shall be taken when concrete for structures intended to retain water is being cast.The details of the drawings shall be followed meticulously, especially regarding the quality of concrete tobe used, construction joints, the making good of holes used for formwork fixing purposes, and thegrouting of pipes and other accessories.

10.6.2 For purposes of impermeability, durability, and the protection of steel, the cement/water ratio ofthe concrete mix shall be more than 2,0. (But see also clauses 6 and 7.)

10.6.3 When so required in terms of the project specification, tests for watertightness shall be carriedout to verify that the intended degree of watertightness of the structure has been achieved. Should thedegree of watertightness not be approved, an investigation should be carried out to ascertain whatremedial steps are required.

10.7 Concrete in saturated ground

Where concrete is to be placed in saturated ground, shallow drains shall be excavated in the ground, filledwith broken stone, and connected to suitably placed sumps. A concrete blinding layer the top of which willform the foundation level for the structural concrete, shall then be laid.

The layout and dimensions of the dry-stone drainage channels and the thickness of the blinding shouldhave been included in the detailed drawings. If this is not the case, or if the engineer considers the projectspecification inappropriate, the channels and blinding shall be constructed as directed by the engineer.

10.8 Protection and curing of concrete

10.8.1 General

10.8.1.1 Beginning immediately after it has been placed, concrete shall, as far as is practicable, beprotected from moisture loss and maintained at a temperature suitable for continued hydration for theperiod necessary for hydration of the cement and hardening of the concrete.

Concrete shall be so protected and so cured that it is not exposed to any of the following:

a) premature drying out, particularly as a result of solar radiation and wind;

b) excessively high or low temperatures;

c) erosion by rain and flowing water;

d) rapid cooling (during the first few days after placing);

e) high internal thermal gradients;

f) frost (see 10.8.3);

g) mechanical damage;

h) contamination; and

i) vibration and impact that could disrupt the concrete and interfere with its bond to the reinforcement.


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10.8.1.2 In the case of concrete surfaces not in contact with forms, one of the following procedures shallbe adopted as soon as practicable after completion of placement and compaction, subject to theprovisions of 10.8.2 and 10.8.3:

a) ponding or continuous sprinkling of the exposed surfaces with water;

b) covering the concrete with sand, or with mats made of a moisture-retaining material, and keeping thecovering continuously wet;

c) the continuous application of steam (not exceeding 60 °C) or mist spray;

d) covering the concrete with waterproof or plastics sheeting firmly anchored at the edges;

e) the use of an approved curing compound, applied in accordance with the manufacturer'srecommendations.

NOTE - Some curing compounds inhibit bond of finishes, such as toppings, plasters or paints, applied to the hardenedconcrete. The compound used should therefore be suitable for the intended finish.

10.8.1.3 Moisture loss from surfaces placed against wooden forms shall be minimized by keeping theforms wet until they are removed. After form removal, the concrete shall be cured by one of the methodsgiven in (a) to (e) above, for the duration of time prescribed below.

Whichever method of curing is adopted, its application shall not cause staining, contamination or marringof the surface of the concrete and the water used shall be in accordance with 4.2. When the ambienttemperature is 15 °C and higher, the curing period shall be at least 7 d for concrete made with ordinaryportland cement or portland cement 15 slag or portland cement 15 fly ash, and at least 10 d for concretemade with portland blastfurnace cement, and with blends of portland cement and more than 15 % ofGGBS or FA.

When the ambient temperature is below 5 °C, the curing periods shall be doubled.

When the ambient temperature is between 5 °C and 15 °C, the curing period shall be determined byinterpolation between the above times.

10.8.2 Concreting in hot weather or in windy conditions (see also 7.2.1.4.2)

High temperatures and loss of moisture may cause thermal and plastic shrinkage (and possible cracking)and a reduction in strength and durability.

The rate at which the concrete stiffens can be reduced slightly by the use of a retarder or of a cement witha low rate of hydration or by replacing of a part of the portland cement with GGBS or FA.

When the ambient temperature exceeds 30 °C, the temperature of the concrete, when placed, shall notexceed 30 °C. The following procedures may be adopted to reduce the placing temperature of theconcrete:

a) shielding aggregate stockpiles (and all metal surfaces in contact with aggregates) from the direct raysof the sun;

b) cooling aggregate (stone) stockpiles by spraying with water;

c) using chilled water or ice flakes for mixing water; and

d) injecting liquid nitrogen into the concrete during mixing.


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The protection of newly placed concrete against rapid drying, and consequent plastic shrinkage andpossible cracking, is especially important in hot, windy conditions.

Protection consists essentially of preventing evaporation from exposed concrete surfaces as soon asconcrete has been placed and compacted. A combination of shading the concrete and spraying it orcovering it with plastics sheeting may be used. Covers shall be such that they do not mark the surfaceof the concrete and shall be firmly anchored at the edges to prevent air movement over the concrete.

10.8.3 Concreting in cold weather (see also 7.2.1.4.1)

Concrete shall not be placed during falling temperatures when the ambient temperature is below 7 °C orduring rising temperatures when the ambient temperature is below 3 °C. When the concrete is placed atambient temperatures below 5 °C, the temperature of the concrete shall not be below 10 °C, for whichpurpose heating of the water or of the aggregate (or of both) shall be permitted. Heated water andaggregate shall first be mixed and the cement added only while the temperature of the mixture is below30 °C.

The temperature of placed concrete shall not be allowed to fall below 5 °C until the concrete has attaineda strength of at least 5 MPa.

10.8.4 Concreting during rainfall

Concrete shall not be placed during periods of heavy or prolonged rainfall unless the materials, plant andthe concreting operation are all well covered.

10.9 Surface finish of concrete

10.9.1 Upper surfaces of concrete

Refer to SABS 0109.

10.9.2 Concrete surfaces cast against forms

10.9.2.1 General

Surfaces cast against forms may be left as-cast (plain or profiled), or the initial surface may be removed(by tooling or sand-blasting), or the concrete may be covered (by painting or tiling).

When the type of external finish is being selected, consideration should be given to the viewing distance,the weather pattern at the particular location, any impurities in the air and the effect of the shape of thestructure upon the flow of water across the surface.

10.9.2.2 As-cast finishes

10.9.2.2.1 Rough form finish

No selected form facing-material shall be specified for rough form finish surfaces. Tie holes and defectsshall be patched. Fins exceeding 6 mm in height shall be chipped off or rubbed off; otherwise, surfacesshall be left with the texture imparted by the forms.

10.9.2.2.2 Smooth form finish

The form facing-material shall be such as to produce a smooth, hard, uniform texture on the concrete.Facing-material may be plywood, tempered concrete-form-grade hardboard, metal, plastics, paper, or


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other acceptable material capable of producing the required finish. Tie holes and defects shall be patched.All fins shall be completely removed.

10.9.2.3 Unspecified finish

If the finish is not designated in the project specification, the following finishes shall be used, asapplicable:

a) rough form finish: for all concrete surfaces not exposed to public view; or

b) smooth form finish: for all concrete surfaces exposed to public view.

10.9.3 Repair of surface defects

If, after removal of the forms or after finishing of concrete surfaces, the concrete shows any defect, nopatching or remedial work shall be undertaken without authorization by the engineer who will, afterthorough inspection and investigation of the quality and strength of the defective work, and after dueconsideration of the possible consequences of such defect, specify the extent and method of repair, ororder the demolition and reconstruction of the whole of the defective work to the extent that he considersnecessary. All repair, remedial and reconstruction work is subject to approval.

10.10 Records

Written records shall be maintained that provide the following information in relation to each part of theworks:

a) the date on which each element was concreted, the time taken to place the concrete, and the positionof the element in the works;

b) the weather; and

c) the nature of samples taken, the dates on which they were taken, and the means of identification bywhich the results of tests on such samples may be correlated with the section of work to which theypertain.

11 Massive concrete

11.1 General

11.1.1 Portions of the structure that are to be treated as massive concrete under the provisions of thisclause shall be stated in the project specification. Such massive concrete shall be subject to theprovisions of this clause in addition to all other applicable provisions of this part of SABS 0100.

11.1.2 Concrete is said to be massive when the size and proportions of an element placed in oneoperation are such that temperature increases (caused by heat of hydration) in the concrete are highenough to result in potentially harmful effects. High temperatures in the concrete can lead to temperaturegradients within the concrete; if these gradients are steep enough to cause differential strain that exceedsthe concrete's tensile strain capacity, the concrete will crack.

The critical dimension of an element with regard to heat of hydration is normally the least dimension.Concrete may usually be regarded as massive if the least dimension exceeds 0,5 m to 1,0 m, but thecritical value is specific to each situation.


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11.2 Construction

The construction of massive concrete elements should be done in such a way that the likelihood ofcracking due to thermal effects is minimized.

Possible steps include:

a) using aggregates that produce concrete with the lowest possible coefficient of thermal expansion;

b) using low cement contents;

c) cooling the aggregate and the mixing water, or installing cooling pipes;

d) replacing part of the portland cement with a cement extender such as FA;

e) reducing the placing temperature of the concrete; and

f) insulating the placed concrete to minimize internal temperature gradients.

The subject of massive concrete cannot be dealt with in detail in this part of SABS 0100 and referenceshould be made to specialist literature (see annex D).

12 Prestressing

NOTE - See also the appropriate clause of SABS 0100-1.

12.1 Prestressing tendons

12.1.1 General

Prestressing tendons should comply with specialist documentation.

NOTE - BS 4486 and BS 5896 may also be referred to.

12.1.2 Handling and storage

All prestressing tendons shall be stored clear of the ground and protected from the weather and fromsplashes from any other materials, and from welding sparks or electric ground currents. The sheathingshall also be protected from any physical damage.

12.1.3 Surface condition

12.1.3.1 At the time of incorporation in the structural member, all bonded prestressing tendons andinternal and external surfaces of sheathing or ducts shall be free of loose millscale, loose rust, oil, paints,grease, soap or other lubricants (except for the lubricant used in the drawing process), or other harmfulmatter. A uniform film of slight rust is not necessarily harmful and may improve the bond. It may, however,also increase the losses due to friction.

12.1.3.2 Cleaning of the tendons may be carried out by wire brushing or by passing the tendons througha pressure box containing carborundum powder. Solvent solutions shall not be used for cleaning withoutthe approval of the engineer.


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12.1.4 Straightness

12.1.4.1 Wire

Low relaxation and normal relaxation wire shall be in coils of diameter sufficiently large to ensure that thewire plays off reasonably straight.

12.1.4.2 Bars

Prestressing bars, as delivered, shall be straight.

Any small adjustments necessary for straightness shall be made on site, by hand, under the supervisionof the engineer. Bars bent in the threaded portion shall be rejected. Any straightening of bars shall becarried out at ambient temperature. If the ambient temperature is less than 5 °C, any necessary heatingshall be by means of steam or hot water to raise the temperature of the bars above 5 °C.

12.1.5 Cutting

The following points shall be taken into consideration:

a) any special requirements by the supplier of the prestressing system shall be met;

b) all cutting to length and trimming of ends shall be by means of either

1) a high-speed abrasive cutting wheel, guillotine, friction saw or any other mechanical methodapproved by the engineer; or

2) an oxyacetylene cutting flame, excess oxygen being used to ensure a cutting rather than amelting action. Care should be taken that neither the flame nor splashes come into contact witheither the anchorage or other tendons. The oxyacetylene method shall not be used on unbondedtendons;

c) in post-tensioning systems, the cutting action as in (1) and (2) above shall be at least one diameterfrom the anchor.

12.1.6 Formwork

Formwork shall not be such as to restrain any elastic shortening, deflection or camber of the structure thatresults from application of the prestressing force.

Form supports shall not be removed until sufficient prestressing force has been applied to support theself-weight load, the formwork and the anticipated construction loads, and shall be done to the engineer'sapproval.

12.1.7 Sheathing

12.1.7.1 Sheathing for bonded tendons

12.1.7.1.1 Sheathing or duct-formers shall be of a material that will not react with alkalis in cement andthat is strong enough to retain its shape and resist damage during construction. It shall prevent theintrusion of cement paste from the concrete. Sheathing material left in place shall not cause electrolyticaction or deterioration.

12.1.7.1.2 The sheathing shall have an internal cross-sectional area at least twice that of the net steelarea of the tendon.


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12.1.7.1.3 Sheathing shall have injection pipes fitted at each end and vent pipes at all high points exceptwhere curvature is small and the sheathing is relatively level, such as in continuous slabs. Drain holesshall be provided at all low points if the tendon may be subject to freezing after placing and beforegrouting.

12.1.7.2 Sheathing for unbonded tendons

The sheathing shall have sufficient tensile strength and weather resistance to prevent irreparable damageor deterioration during transportation, storage on site, and installation. The sheathing shall be acontinuous tube and shall continue over the unbonded length of the tendon. The sheathing shall preventthe intrusion of cement paste and loss of lubricant.

12.2 Tensioning

12.2.1 General

12.2.1.1 Tendons may be stressed either by pre-tensioning or by post-tensioning, according to theparticular needs of the form of construction. In each system, different procedures and types of equipmentare used and these govern the method of tensioning, the form of anchorage and, in post-tensioning, theprotection of the tendons.

12.2.1.2 Where possible, all wires or strands to be stressed in one operation shall be taken from thesame parcel of prestressing steel. Each tendon shall be tagged with its number and the coil number(s)of the steel used. Tendons shall not be kinked or twisted and individual wires and strands shall be readilyidentifiable at each end of a member. A strand that has become unravelled shall not be used.

12.2.2 Safety precautions

A tendon, when tensioned, contains a considerable amount of stored energy, which, in the event of anyfailure of a tendon, anchorage or jack, may be released violently. All possible precautions shall be taken(both during and after tensioning) to safeguard persons from injury and to safeguard equipment fromdamage that may be caused by the sudden release of this energy.

12.2.3 Tensioning apparatus

Hydraulic jacks are the normal means for tensioning tendons. The tensioning apparatus shall meet thegeneral provisions given in 12.2.3.1 to 12.2.3.4.

12.2.3.1 The means of attachment of the tendon to the jack or tensioning device shall be safe and secure.

12.2.3.2 Where two or more wires or strands are stressed simultaneously, they shall be of approximatelyequal length between anchorage points at the datum of force and extension measurement. The degreeof variation in individual extensions shall be small in comparison with the expected extension.

12.2.3.3 The tensioning apparatus shall be such that the controlled total force is imposed gradually andno dangerous secondary stresses are induced in the tendons, anchorage or concrete.

12.2.3.4 The force in the tendons during tensioning shall be measured by direct-reading load cells orobtained indirectly from gauges of minimum diameter 150 mm fitted into the hydraulic systems todetermine the pressure in the jacks. When pressure gauges are used, they shall be calibrated togetherwith the jack to allow for jack friction. Facilities shall be provided for the measurement of the extensionof the tendon and of any movement of the tendon in the gripping devices. The force measuring deviceshall be calibrated to an accuracy of ± 2 % (or better) and checked at frequent intervals. Elongation of thetendon shall be measured to an accuracy of ± 2 % (or better), or 2 mm, whichever is the more accurate.


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12.2.4 Pre-tensioning

Where pre-tensioning methods are used, positive means shall be used to maintain the full force duringthe period between tensioning and transfer. The force shall be transferred slowly to minimize shock, whichwould adversely affect the transmission length.

12.2.4.1 Straight tendons

12.2.4.1.1 In the long-line method of pre-tensioning, sufficient locator plates shall be distributed along thelength of the bed to ensure that the wires or strands are maintained in their proper position duringconcreting. Where a number of units are made in line, they shall be free to slide in the direction of theirlength and thus permit transfer of the prestressing force to the concrete along the whole line.

12.2.4.1.2 In the individual mould system, the moulds shall be made sufficiently rigid to provide thereaction to the prestressing force without distortion.

12.2.4.2 Deflected tendons

12.2.4.2.1 Where practicable, the mechanisms for holding down or holding up of tendons shall be suchthat the part in contact with the tendon is free to move in the line of the tendon in order to eliminatefrictional losses. If, however, a system is used that develops a frictional force, this force shall bedetermined by testing, and due allowance made.

12.2.4.2.2 For a single tendon, the deflector in contact with the tendon shall have a radius of at least5 times the tendon diameter for wire, or 10 times the tendon diameter for a strand, and the total angle ofdeflection shall not exceed 15°.

12.2.4.2.3 The transfer of the prestressing force to the concrete in conjunction with the release ofhold-down and hold-up forces shall be so effected that any tensile stresses in the concrete that resultduring the process, do not exceed permissible limits.

12.2.5 Post-tensioning

12.2.5.1 Arrangement of tendons

12.2.5.1.1 Where wires, bars or strands in a tendon are not stressed simultaneously, spacing membersshall be made so rigid that they are not displaced during the successive tensioning operations.

12.2.5.1.2 Tendons, whether in anchorages or elsewhere, shall be so arranged that they do not passround sharp bends or corners likely to provoke rupture when the tendons are under stress.

12.2.5.2 Anchorages

12.2.5.2.1 The adequate performance of anchorages shall be demonstrated before prestressing.

NOTE - Suitable tests for checking prestressing tendon anchorage performance are described in BS 4447 and in the FIPrecommendation for acceptance and application of post-tensioning systems (March 1981).

12.2.5.2.2 The anchorage system in general comprises the anchorage itself and the arrangement oftendons and reinforcement designed to act with the anchorage. The form of anchorage system shall besuch as to facilitate the even distribution of stress in the concrete at the end of the member and shall becapable of maintaining the prestressing force under sustained and fluctuating load and under the effectof shock.


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12.2.5.2.3 Split-wedge-and-barrel type anchors shall be of such material and construction that

a) under the forces imposed during the tensioning operation, the strain in the barrel does not allow suchmovement of the wedges that the wedges reach the limit of their travel before sufficient lateral forceis developed to grip the tendon, and

b) at or before the limit of travel, the wedges do not cause an excessive force in the tendon.

12.2.5.2.4 If a proprietary form of anchorage is used, the anchoring procedure shall be strictly inaccordance with the manufacturer's instructions and recommendations.

12.2.5.2.5 All bearing surfaces of the anchorages, of whatever form, shall be cleaned prior to thetensioning operation.

12.2.5.2.6 Any allowance for draw-in of the tendon during anchoring shall be in accordance with theengineer's instructions, and the actual slip occurring shall be recorded for each individual anchorage.

12.2.5.2.7 After the tendons have been anchored, the force exerted by the tensioning apparatus shall begradually and steadily so decreased as to avoid shock to the tendon or the anchorage.

12.2.5.2.8 Provision shall be made for the protection of the anchorage against corrosion.

12.2.5.2.9 Intermediate anchorages, if bearing against hardened concrete at a construction joint, shallhave design features permitting efficient transfer of prestressing force to the hardened concrete and shallhave adequate corrosion protection by epoxy-tar painting of anchor parts.

12.2.5.3 Deflected tendons

12.2.5.3.1 Where practicable, a deflector in contact with a tendon shall have a radius of at least 50 timesthe diameter of the tendon, and the total angle of deflection shall not exceed 15°.

12.2.5.3.2 Where the radius is less than 50 times the diameter of the tendon or the angle of deflectionexceeds 15°, the loss of strength of the tendon shall be determined by testing, and due allowance made.

12.3 Positioning of tendons and sheathing

12.3.1 The tendons and sheathing shall be accurately located and maintained in position both verticallyand horizontally as shown on the drawings. Unless otherwise shown on the drawings, the permittedtolerance in the location of the tendon or sheathing shall be as given in table 8.

Table 8 - Permitted tolerance in the locationof tendons and sheathing

Dimensions in millimetres

1 2 3 4

Depth of member

dVertical tolerance Width of beam Horizontal tolerance

< 200200 - 1 000

> 1 000

± d /40± 5

± 10

< 200200 - 1 000

> 1 000(incl. slabs)

± 5± 10

± 30


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12.3.2 The method of supporting and fixing the tendons (or the sheathing) in position shall be such thatthey will not be displaced by heavy or prolonged vibration, by pressure of the wet concrete, by workmen,or by construction traffic. The means of locating prestressing tendons shall not unnecessarily increasethe friction when they are being tensioned.

12.3.3 Sheathing should retain its correct cross-section and profile and shall be handled carefully toavoid damage.

12.3.4 Joints in sheathing shall be securely taped to prevent penetration of the duct by concrete orcement paste, and ends of ducts shall be sealed and protected after the stressing and groutingoperations. Joints in adjacent sheathing shall be staggered at least 300 mm.

12.3.5 As damage might occur during the concreting operation, and if the tendon is to be inserted later,the duct shall be protected during the concreting operation to ensure a clear passage for the tendon.

12.4 Tensioning procedure

12.4.1 All tendons shall be free to move in the ducts before being tensioned. Tensioning shall be socarried out under competent supervision that the stress in the tendons increases at a gradual and steadyrate. Tensioning shall not be carried out at a temperature below 0 °C without the approval of the engineer.

12.4.2 The supervisor in charge of stressing shall be provided with particulars of the required tendonforce and expected extensions. During stressing, allowance shall be made for the friction in the jack andin the anchorage, although allowance for the former is not necessary when load cells are used.

12.4.3 Stressing shall be continued until the required tendon force is reached. The measured extensionshall allow for any draw-in of the tendon occurring at the non-jacking end, but measurement shall notcommence until any slack in the tendon has been taken up. A comparison between the measuredextension and the calculated extension provides a check on the accuracy of the assumptions made forthe frictional losses at the design stage. If the difference exceeds 8 %, corrective action shall be taken,but only with prior approval. Full records shall be kept of all tensioning operations, including the measuredextensions, pressure-gauge or load-cell readings, and the amount of draw-in at each anchorage.

12.4.4 Where a large number of tendons or tendon elements are being tensioned and the full forcecannot be achieved in an element because of breakage, slippage or blockage of a duct, and if thereplacement of that element is not practicable, the engineer may have to determine whether a change inthe stress levels is still within the relevant limit state requirements.

12.4.5 In the case of curved tendons, or tendons made up of a number of constituent elements, ortendons loaded in stages, the engineer shall specify the order of loading and the magnitude of the forcefor each component of the tendon.

12.4.6 Tensioned tendons, anchorages, and duct forms shall be effectively protected from corrosionduring the period between stressing and covering with grout, concrete or other permanent protection.Ducts shall be plugged at their ends and at their vents.


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12.5 Grouting of prestressing tendons

12.5.1 General

12.5.1.1 The two main objectives when the ducts of post-tensioned concrete elements are grouted are

a) to protect the prestressing tendons from corrosion, and

b) to provide bond between the prestressing tendons and the concrete element in order to control thespacing of cracks at heavy overload and to increase the ultimate moment of resistance of the element.

12.5.1.2 Both of the objectives in 12.5.1.1 make it essential to ensure that the whole of the void spacewithin the ducts is filled. The success of this operation will be dependent on the production of a grout mixthat has the desired properties, together with efficient equipment for its injection, and careful workmanshipand supervision on site.

12.5.1.3 The important properties of a satisfactory grout for the injection of ducts in a post-tensionedmember are good fluidity and low sedimentation or bleeding in the plastic state, and durability and densitywith low shrinkage in the hardened state in order that the grout will bond with the steel and the sides ofthe duct and provide protection for the prestressing tendon. The methods to be adopted should be suchthat they can be carried out on site effectively and reasonably easily.

12.5.1.4 Grouting trials shall be undertaken when required by the engineer.

12.5.2 Grouting equipment

12.5.2.1 A high-pressure water supply of sufficient volume shall be provided before grouting commences.Sheathing shall be cleaned of dirt and other foreign matter by thorough flushing with water immediatelyprior to grouting.

12.5.2.2 The mixing equipment shall be of a type that is capable of producing a grout of colloidalconsistence by means of high local turbulence while imparting only a slow motion to the body of the grout.

12.5.2.3 The injection equipment shall be capable of continuous operation with little variation of pressureand shall include a system for agitating the grout while actual grouting is not in progress. Compressed airshall not be used to agitate or inject the grout.

12.5.2.4 Normally, equipment should have a delivery pressure of 1 MPa. Piping to the grout pump shallhave a minimum of bends, valves and changes in diameter, and connections shall be air-tight. All bafflesto the pump shall be fitted with sieve strainers of aperture size 3 mm. All equipment, especially piping,shall be thoroughly flushed with clean water after every series of operations and more frequently ifnecessary. Intervals between washings shall not exceed 3 h.

12.5.3 Materials

12.5.3.1 General

All materials shall be measured by mass.

12.5.3.2 Cement

Only portland cement that complies with SABS 471 or SABS 831 and that has not been stored in papersacks on site for more than 1 month, shall be used. The temperature of the cement shall be less than35 °C.


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12.5.3.3 Sand

Sand should only be used when the diameter of the duct exceeds 150 mm. Sand shall be of particle sizenot exceeding 0,6 mm.

12.5.3.4 Admixtures

Admixtures should only be used when experience has shown that their use will improve the quality of thegrout. Admixtures shall not contain chlorides, nitrates, sulfides or sulfites. When aluminium powder isused, the total expansion shall not exceed 6 % by volume.

12.5.4 Ducts

12.5.4.1 Air vents of diameter at least 10 mm shall be provided at any crests present in the duct profile,since it is important that the whole volume of the duct be filled with grout. Horizontal ducts of length notexceeding 30 m shall be grouted from one end, without intermediate vents.

12.5.4.2 Threaded entries to the duct or anchorage to permit the use of a screwed connector from thegrout pump may be used with advantage.

12.5.4.3 Before the concrete is placed, duct linings shall be inspected for continuity, correct alignment,secure fixing, dents, splits and holes, and any defects shall be rectified; particular attention should be paidto joints between ducts and anchorages and joints between adjacent precast units.

12.5.4.4 Lined ducts should be kept dry before grouting to prevent corrosion of the tendon, possible frostdamage or excess water, but they may be flushed with water immediately before grouting. If the tendonis to remain unstressed for more than 28 d from the time of tendon placement, temporary corrosionprotection should be provided. Vertical ducts shall be sealed at all times before grouting, to prevent theingress of rain and debris.

12.5.5 Mixing

12.5.5.1 The cement/water ratio of the mix shall be at least 2,3 by mass. The quantity of sand or fillerused should not exceed 30 % of the mass of the cement.

12.5.5.2 Water shall be added to the mixer first, then two-thirds of the cement. When these are thoroughlymixed, any admixture or sand and the remainder of the cement shall be added. Mixing shall continue fornot less than 2 min and not more than 5 min, until a uniform consistence is obtained. Mixing by hand isnot permissible.

12.5.6 Strength of grout

The compressive strength of 100 mm cubes of grout, made in conditions similar to those of the injectedgrout and cured in a moist atmosphere for the first 24 h and thereafter in water at 22 °C to 25 °C, shallexceed 20 MPa at 7 d.

12.5.7 Injection of grout

12.5.7.1 Grout should be used within 60 min of mixing unless it contains a retarder. Grout that haspartially set shall be discarded. Injection shall be continuous and slow enough (6 m to 12 m per minute)to avoid segregation of the grout. The method of injecting grout shall be such as to ensure complete fillingof the ducts and complete surrounding of the steel. The volume of the spaces to be filled by the injectedgrout should be compared with the quantity of grout injected. Grout shall be allowed to flow from the freeend of a duct until its consistence is equivalent to that of the grout injected. The opening shall then befirmly closed. Any vents shall be similarly closed, one after another, in the direction of the flow.


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12.5.7.2 Grouting shall be carried out as soon as is practicable but not later than 7 d after the tendonshave been stressed.

12.5.7.3 Vertical and inclined ducts should be grouted from the lowest point, the maximum length groutedin one operation being 50 m.

12.5.7.4 In the event of a blockage or an interruption of grouting, all grout shall be flushed from the ductwith water.

12.5.8 Grouting during cold weather

12.5.8.1 When the weather is cold, accurate records shall be kept of maximum and minimum airtemperatures, and the temperatures of the members to be grouted. Any materials in which snow, frostor ice is present shall not be used, and the ducts and equipment shall be completely free from frost andice.

12.5.8.2 Unless the member is so heated as to maintain the temperature of the placed grout above 5 °Cfor at least 48 h, no grout shall be placed when the temperature of the member is below 5 °C or is likelyto fall below 5 °C during the following 48 h.

12.5.8.3 Unless accompanied by general external heating of the member or structure, ducts shall not bewarmed with steam.

12.5.8.4 The grout materials shall be warmed within the limits recommended for concrete (see 7.2.1.4).

12.5.9 Protection and bond of prestressing tendons

12.5.9.1 General

It is essential to protect prestressing tendons from both mechanical damage and corrosion. Protectionmay also be required against fire damage.

12.5.9.2 Protection and bond of internal tendons

Internal tendons may be protected and bonded to the element by either cement grout or sand cementgrout in accordance with 12.5.3 and 12.5.5. Alternatively, the tendons may be protected by other materialsbased on bitumen, epoxy resins, rubber and the like, provided that the effects on bond and on fireresistance are investigated.

12.5.9.3 Protection and bond of external tendons

12.5.9.3.1 A tendon is considered to be external when, after stressing and incorporation in the work butbefore protection, it is outside the structure. It does not apply, for example, to a floor comprising a seriesof precast beams that are themselves stressed with external tendons and subsequently so concreted orgrouted that the prestressing tendons are finally contained in that filling together with adequate cover.

12.5.9.3.2 Protection of external prestressing tendons against mechanical damage and corrosion fromthe atmosphere or other environment should generally be provided by an encasement of dense concreteor dense mortar of adequate thickness. It may also be provided by other materials hard enough and stableenough for the particular environment.


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12.5.9.3.3 When the type and quality of the material to be used for the encasement are being determined,full consideration should be given to the differential movement between the structure and the appliedprotection that arises from changes of load and stress, creep, relaxation, drying shrinkage, humidity andtemperature in either. If the applied protection is dense concrete or dense mortar, and investigations showthe possibility of undesirable cracking, a primary corrosion protection that will be unimpaired by differentialmovement should be used.

12.5.9.3.4 If external prestressing tendons are to be bonded to the structure, this shall be achieved bysuitable reinforcement of the concrete encasement to the structure.

13 Precast concrete

13.1 General

Precast units, whether of plain, reinforced or prestressed concrete, shall have been designed inaccordance with the provisions of SABS 0100-1 and the quality and workmanship shall be in accordancewith the applicable provisions of this part of SABS 0100.

13.2 Permissible deviations

For permissible deviations, see SABS 0155. Allowances for construction inaccuracies are given inSABS 0100-1.

13.2.1 While dimensional variations are inevitable, precast concrete units can be manufactured tocomparatively small permissible deviations. Manufacturing to such fine tolerances, however, will materiallyincrease the cost of the units.

13.2.2 Permissible deviations shall only be specified for those dimensional characteristics that areimportant to the correct assembly, performance and appearance of the structure, and shall be as largeas is practicable. The permissible deviations for other dimensional characteristics shall be left to thediscretion of the manufacturer, but shall be reasonable for the conditions of production and use. Themanufacturer shall, when so requested, make these permissible deviations known.

13.2.3 The permissible deviations for the units shall be consistent with any variation in the position ofthe adjoining elements in the building.

13.2.4 The permissible deviations are a general guide. In exceptional cases, it may be possible to reducecertain permissible deviations even further by means of specially designed moulds, but such reductionsshould be made with considerable caution.

13.2.5 It is strongly recommended that the manufacturer's advice be obtained at the early design stageswhen very small permissible deviations are likely to be required, since those that can be achieved inpractice depend on a number of factors, including the following:

a) the shape of the unit, particularly since this affects the stiffness of the mould;

b) the mould materials and the method of assembly;

c) the number of castings from each mould; and

d) the position and shape of any projections through the moulded faces.


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13.2.6 For irregular, curved or specially shaped units, the necessary dimensions and permissibledeviations shall be clearly defined in the project specification and shown on the drawings.

13.2.7 Particular attention is drawn to the fact that deviations can be cumulative, i.e. adjoining edges oftwo floor panels nominally at the same level can differ by the sum of the positive deviations on bow andthickness on one unit, and the same negative deviations on the next unit.

13.2.8 Where appropriate, permissible deviations shall be given as both plus and minus values on aspecific dimension, rather than as a deviation from a maximum or minimum value; working drawings tobe used by the manufacturer shall give dimensions and permissible deviations as required.

13.3 Prestressed units

13.3.1 When permissible deviations for prestressed units are being specified, the creep, shrinkage andelastic shortening of the concrete, the eccentricity of the steel and other significant factors shall be takeninto account.

13.3.2 At a given age, and by the use of factors appropriate to that age applied to the methodrecommended in SABS 0100-1, a camber can be predicted. This predicted camber, the age and othercontrolling conditions (e.g. when supported at the ends and subjected to self-weight only) shall be statedon the drawings or in the project specification. The actual camber shall not exceed the predicted camberby more than 50 %.

13.3.3 Where variation in camber between closely associated units (e.g. floor panels laid side by sideand practically touching, and receiving plaster or topping, or both) is critical, it shall not exceed 6 mm forunits of up to 4,5 m in length, or 9 mm for longer units.

13.3.4 Where variation in camber is not critical (e.g. in the case of closely associated units that have afalse ceiling and thick top screed, or units not closely associated with one another), variations in camberin excess of those stated above may be acceptable to the engineer, and should be judged in relation tothe conditions the units have to fulfil.

13.4 Handling and erection of precast concrete units

13.4.1 Lifting equipment

Lifting equipment shall comply with safety regulations, and the method of support during lifting and placing shall be in accordance with approved procedures.

13.4.2 Handling and transportation

13.4.2.1 Precast units shall be designed to resist, without permanent damage, all stresses induced byhandling, storage and transport. The minimum age for handling and transporting shall be specified by theengineer or designer, and is related to the concrete strength, the type of unit and other factors.

13.4.2.2 The position of lifting and supporting points, the method of lifting, and the type of equipment andtransport to be used shall be as specified by the engineer or as agreed by him, and shall be practical andsafe to use, and such that no damage is likely to result from the lifting equipment.

13.4.2.3 Units shall be marked with indelible identity, location and orientation marks as and wherenecessary.

13.4.2.4 The engineer shall, in all cases, specify the points of support during storage, and shall ensurethat these are so chosen as to prevent unacceptable permanent distortion of the units; resilient supporting


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arrangements that permit small settlements without inducing stresses in the units are preferred. Theengineer shall also ensure that, when a stack is several units high, the units are vertically above oneanother to prevent bending stresses in any unit. Where disfigurement would be detrimental, packingpieces shall not discolour or otherwise permanently damage the units.

13.4.2.5 Trapped water and dirt shall not be allowed to accumulate in the units.

NOTE - The freezing of trapped water can cause severe damage.

13.4.2.6 Where necessary, precautions shall be taken to prevent projecting reinforcement from causingrust stains, and to minimize efflorescence.

13.4.2.7 During transportation, the following additional factors shall be considered:

a) overloading of the transporting vehicle;

b) centrifugal force resulting from cornering;

c) oscillation (a slim unit might flex (vertically or horizontally) sufficiently to cause damage); and

d) the possibility of damage due to chafing.

13.4.3 Assembly and erection

The method of assembly and erection specified as part of the design, shall be strictly adhered to on site.Immediately a unit is in position and before the lifting equipment is removed, temporary supports ortemporary connections shall be provided between units, as necessary. The final structural connectionsshall be completed as soon as is practicable.

13.4.4 Temporary supports during construction

13.4.4.1 When temporary supports are being provided, all construction loads (including wind) likely to beencountered during the completion of joints between any combination of precast units and in-situ concretestructural elements shall be taken into account. Temporary supports (when relevant) shall takemovements into account, including those caused by shrinkage of concrete and any post-tensioning. Inaddition, the arrangement and design of temporary supports shall be such that, if a unit breaks oraccidentally strikes against another during erection, the temporary supports of adjacent units will besufficient to prevent any local collapse from becoming progressive.

13.4.4.2 The supports shall be arranged in a manner that will permit the proper finishing and curing ofany in-situ concrete, mortar or grout. Temporary supports shall not be removed or released until therequired strength is attained in the in-situ portion of a construction.

NOTE - Attention is directed to the requirements of various Acts and regulations governing temporary works, stagings,scaffolding, and lifting equipment.

13.4.5 Forming structural connection

13.4.5.1 General requirements

13.4.5.1.1 The precast units shall be inspected to ensure that the design requirements of the structuralconnection are met.

13.4.5.1.2 The precast units shall be free from irregularities of such size and shape as to lead todamaging stress concentrations. When reliance is placed on bond between the precast units and in-situconcretes, the contact surface of the precast unit shall have been suitably prepared in accordance with


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SABS 0100-1. If frictional resistance is assumed to have developed at a bearing, the construction shallbe such that this resistance can be realized. Particular attention shall be given to checking the accuratelocation of reinforcement and any structural steel sections in the ends of precast units and to theintroduction of any additional reinforcement needed to complete a connection.

13.4.5.2 Packing requirements

The packing of joints shall be carried out in accordance with assembly instructions.

13.4.5.2.1 Concrete or mortar packing


a) when joints between units, particularly the horizontal joints between successive vertical lifts, areload-bearing and are to be packed with mortar or concrete, tests shall be carried out to prove that thematerial is suitable for the purpose and that the proposed method of filling results in a solid joint;

b) the composition and cement/water ratio of the in-situ concrete or mortar used in any connection shallbe as specified by the engineer; and

c) care shall be taken to ensure that in-situ material is thoroughly compacted. The use of an expandingagent may be considered advantageous.

13.4.5.2.2 Other packing materials


a) packing materials other than grout, mortar or concrete (e.g. resinous adhesives, lead, bituminouscompounds, etc.) may be used, provided that they fulfil all the necessary requirements and arecompatible in all respects with the concrete components being joined together;

b) the manufacturer's recommendations as to the methods of application shall be strictly followed; and

c) levelling devices, such as nuts and wedges, that have no load-bearing function in the completedstructure, shall be slackened, released or removed, as necessary.

13.4.5.3 Fixing by welding

Where precast units are fixed by welding, it should be noted that the expansion of cast-in plates maycause cracking of the precast section. Heat may be reduced by

a) the use of low-heat welding rods of small size,

b) the use of intermittent welds, and

c) the use of smaller welds.

Plates should not be less than 10 mm thick.

Welding should preferably not be done where connections are galvanized, unless steps are taken tore-instate the zinc layer, e.g. with zinc-rich epoxy paint.

Where galvanizing is used, consideration should be given to using a chromate passivator in the concrete,to prevent interaction of the zinc with the alkali in the cement.

Welding shall not be done near prestressing cables or anchorages.


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13.4.6 Protection

At all stages, and until completion of the work, precast concrete units and any other concrete associatedwith them shall be properly protected. The degree and extent of the protection to be provided shall besufficient for the surface finish and profile being protected, the position and importance of the units beingborne in mind. This is particularly important in the case of permanently exposed concrete surfaces,especially arrises and decorative features. The protection can be provided by timber strips, hessian, etc.,but shall be such as will not damage, mark or otherwise disfigure the concrete.

14 Testing and acceptance of concrete

14.1 General

Concrete materials and operations shall, as the work progresses, be tested and inspected in accordancewith the methods referred to in the project specification or in accordance with such other methods asspecified by the engineer. Failure to detect any defective work or material shall not in any way preventlater rejection when such defect is discovered nor shall it obligate the engineer to final acceptance. Sitetesting shall be carried out by a competent technician or by a person deemed by the engineer to besufficiently experienced.

Laboratory testing shall be carried out by a recognized testing authority or an accredited laboratory or afirm approved by the engineer.

14.2 Testing services

14.2.1 Basic testing services

The following testing services shall be performed by an approved testing authority:

a) reviewing or testing (or both) the contractor's proposed materials for compliance with the relevantspecification;

b) collecting samples of materials at plants or stockpiles during the course of the work and testing themfor compliance with the relevant specification;

c) during construction, conducting strength tests of the concrete in accordance with 14.3;

d) conducting tests to monitor mix characteristics such as cement/water ratio and cement content wherethese have been specified; and

e) conducting tests to monitor in-situ cover to reinforcement.

14.2.2 Testing services required by the engineer

The following services shall, when so required by the engineer, be performed by the approved testingauthority:

a) reviewing or testing (or both) the contractor's proposed mix design;

b) inspecting concrete batching, mixing and delivery operations to the extent deemed necessary by theengineer;

c) sampling concrete at the point of placement, and carrying out the required tests;


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d) reviewing the manufacturer's report for each shipment of cement, reinforcing steel and prestressingtendons, or conducting laboratory tests or spot checks of the materials as received (or both), forcompliance with relevant specifications; and

e) other testing or specification services as required.

14.2.3 Additional services when required

The following services shall be performed by the approved testing authority when necessary:

a) additional testing and inspecting when changes in materials or proportions are proposed by thecontractor; and

b) additional testing of materials or concrete occasioned by their failure by test or inspection to meetspecification requirements.

14.2.4 Test reports

All test reports shall include the exact location in the work where the batch of concrete represented by atest was placed. Reports of strength tests shall include detailed information on storage and curing ofspecimens prior to testing.

14.2.5 Responsibilities and duties of the contractor

14.2.5.1 The contractor shall submit to the engineer his proposals for the concrete materials and theconcrete mix designs. These shall include the results of the tests performed on the materials and the teststo establish the mix designs. No concrete should be placed in the works until the contractor hasreceived the approval of the engineer.

14.2.5.2 To facilitate testing and inspection, the contractor shall ensure that the following test equipment,in good condition, is available:

a) slump test apparatus as specified in SABS method 862;

b) moulds for compressive strength testing in accordance with the requirements of SABS method 863,and in sufficient quantity to permit the frequency of sampling and testing in terms of 14.3;

c) apparatus for curing strength specimens;

d) equipment to permit the measurement of entrained air, if air-entraining admixtures or any otheradmixtures are used (see 4.4); and

e) any other test equipment specified.

14.3 Strength tests of concrete during construction

14.3.1 General procedures

During construction, strength tests of the concrete shall be conducted in accordance with the proceduresin 14.3.1.1 to 14.3.1.5.

14.3.1.1 During the time when concrete of a particular grade is being placed, samples shall be taken inaccordance with SABS method 861 and in accordance with a predetermined programme. The programmeshall be worked out taking the following into account:


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a) each sample (one sample being sufficient for three cubes for each testing age) shall be taken froma different batch of concrete chosen on a random basis: the numbers of batches to be selected asthe test batches shall be determined before commencement of concrete placement;

b) at least one sample shall be taken from each day's placing and from at least every 50 m3 of concreteof each grade placed;

c) the frequency of sampling shall be determined by the importance of the work, e.g. a critical part of thestructure may require that additional samples be taken;

d) when the batch size is less than 2 m3, the first sample of each grade shall be taken after at least Amdt 1, three batches of this grade have been mixed and discharged. Sept. 1994

e) Deleted by Amendment No. 1.

14.3.1.2 The slump of the concrete sample shall be determined in accordance with SABS method 862for each strength test and whenever the consistence of the concrete appears to vary.

14.3.1.3 The cubes shall be cast and cured in accordance with SABS method 863. Cubes cured on Amdt 1, site shall be cured in water at a temperature between 22 °C and 25 °C. Sept. 1994

14.3.1.4 The cubes shall be tested in accordance with SABS method 863. Three cubes shall be testedfor acceptance at the age specified, which is usually 28 d. For prestressed concrete, sets of three cubesshall be tested at 3 d. Sets of three cubes may be tested at other ages for information.

14.3.1.5 In the case of low-density concrete, the air content and unit mass of a concrete sample shall bedetermined for each strength test.

14.3.2 Evaluation of strength test resultsTest results for test cubes shall be evaluated separately for each grade of concrete. Such evaluation isonly valid if tests have been conducted in accordance with procedures specified in 14.3.1.

14.3.3 Acceptance criteria for strength test resultsNOTE - The specified strength referred to below is the characteristic strength shown on the drawings or otherwise specified.

14.3.3.1 The strength test results shall meet both of the following acceptance criteria: Amdt 1, Sept. 1994

a) no individual test result shall be more than 3 MPa below the specified characteristic strength; and

b) the mean of any group of three consecutive and overlapping results shall exceed the specifiedcharacteristic strength by at least 2 MPa.

14.3.3.2 If the test results fail to meet the acceptance criteria given in 14.3.3.1, the following apply: Amdt 1, Sept. 1994

a) the mix design shall be adjusted to ensure compliance with the acceptance criteria, due cognizancebeing taken of available 7 d/projected 28 d cube results;

b) in relation to the part of the structure in which concrete represented by the test results has been used,

1) an assessment of the stress level in the structure should be carried out; or

2) tests should be carried out in accordance with 14.4 or clause 15, or both;

c) if the acceptance criterion given in 14.3.3.1(a) is not met, the amount of concrete represented by thetest should be limited to the lesser of 50 m3 and that represented by the actual testing frequency; and

d) if the acceptance criterion given in 14.3.3.1(b) is not met, it shall be assumed that the concreterepresented by the test includes the batches represented by the first and the last samples, togetherwith all intervening batches.

14.3.3.3 Should a concreting operation of the same concrete mix be of such magnitude or the sampling Amdt 1, of such frequency that 30 or more valid test results have become available within three months, the con- Sept. 1994tractor may choose to have results assessed statistically. In such a case, the average of overlapping sets



54

of 30 valid test results for a specific grade of concrete shall exceed the specified strength by at least1,7 times the standard deviation, and no individual result shall fall below the value specified in 14.3.3.1(a).In the event of strength failure, 14.3.3.2 shall apply.

14.4 Strength tests of concrete in place

NOTE - For load tests, see clause 15.

14.4.1 Non-destructive testing

Testing by rebound hammer, sonoscope or other non-destructive device may be permitted by theengineer to determine relative strengths at various locations in the structure as an aid in evaluating thestrength of concrete in place or for selecting areas to be cored. Such tests, unless properly calibrated andcorrelated with other test data, shall not be used as a basis for acceptance or rejection.

14.4.2 Core testsWhere so required, drilled cores shall be obtained and tested in accordance with SABS method 865.Cores should be drilled and tested when the age of the concrete is as close as possible to the age forstrength acceptance according to cubes. At least three representative cores shall be taken from eachmember or predetermined volume of concrete in locations that are considered potentially deficient. Thelocation of cores shall be determined by the engineer, to cause the least impairment to the strength of

Amdt 1, the structure. The lesser of the top 300 mm and top 20 % of the depth of the concrete member shall notSept. 1994 be used for core testing unless unavoidable (e.g. thin slabs). If, before testing, one or more of the cores

shows evidence of having been damaged subsequent to or during removal from the structure, it shall bereplaced with a new core.

If a core contains reinforcing steel, the measured compressive strength of the core shall be corrected inaccordance with SABS method 865.

Core holes shall be filled with low-slump concrete or mortar (see 10.9.3).

Amdt 1, 14.4.3 Acceptance of concrete on the basis of core strengthsSept. 1994

14.4.3.1 If the average core strength is at least 80 % of the specified strength (see 14.3.3), and if nosingle core strength is less than 70 % of the specified strength, the concrete shall be accepted.

14.4.3.2 If the concrete in a certain area fails to comply with 14.4.3.1 because a single core result fallsbelow 70 % of the specified strength, a further set of three cores may be taken from the same area, todetermine the extent of deficient concrete. If the new set of three cores complies with the requirementsof 14.4.3.1, the area represented by this second set of cores shall be considered acceptable. If the newset of cores fails to comply with the requirements of 14.4.3.1, 14.4.3.3 applies.

14.4.3.3 If the core strength does not meet the acceptance criteria of 14.4.3.1 or 14.4.3.2, the followingshould be considered in relation to the deficient part of the structure:

a) strength requirements for the member(s);

b) performance of a full-scale load test as in clause 15;

c) strengthening the deficient part of the structure; and

d) removal and replacement of the deficient part of the structure.


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15 Load tests

15.1 Individual precast units

15.1.1 General

The load tests described in this clause are intended as checks on the quality of the units, and are not tobe used as a substitute for normal design procedures. Where units require special testing, such specialtesting procedures shall be in accordance with the project specification. Test loads are to be applied andremoved incrementally.

15.1.2 Non-destructive test

15.1.2.1 Support the unit at its designed points of support, and load it for 5 min with a load equal to thesum of the nominal self-weight plus 1,25 times the nominal imposed load. Record the deflection. Ensurethat the maximum deflection measured after application of the load is in accordance with the requirementsdefined by the engineer.

15.1.2.2 Measure the recovery 5 min after the removal of the applied load and then re-impose the load.Ensure that the recovery after the second loading is not less than that after the first loading and not lessthan 90 % of the deflection recorded during the second loading. At no time during the test shall the unitshow any sign of weakness or faulty construction as defined by the engineer in the light of a reasonableinterpretation of relevant data.

15.1.3 Destructive test

Support the unit at its designed points of support and load it. The unit shall not fail at its ultimate loadwithin 15 min of the time when the test load (see 15.2.3) becomes operative. Regard a deflectionexceeding 1/40 of the span as failure of the unit.

15.1.4 Special test

In the case of very large units or units not readily amenable to the above tests, such as columns, theprecast parts of composite beams, and units designed for continuity of fixity, the testing arrangementsshould be agreed upon before such units are cast.

15.2 Structures and parts of structures

15.2.1 General

The tests described in this clause are intended as a check on structures other than those covered by 15.1,where there is doubt regarding serviceability or strength. Test loads are to be applied and removedincrementally.

15.2.2 Age at test

15.2.2.1 Carry out the test as soon as possible after expiry of the 28 d from the time of placing theconcrete. The test may be carried out earlier, if the test is for any reason other than uncertainty in respectof the quality of the concrete in the structure, and provided that the concrete has already reached itsspecified strength.

15.2.2.2 When testing prestressed concrete, make allowance for the effect of prestress being above itsfinal value at the time of testing.


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15.2.3 Test loads

15.2.3.1 The test loads to be applied for the limit states of deflection and for local damage are theappropriate loads, i.e. the self-weight plus the nominal imposed load. When the ultimate limit state is beingconsidered, ensure that the test load, maintained for a period of 24 h, is the greater of

a) the sum of the self-weight plus 1,25 times the nominal imposed load, or

b) 1,125 times the sum of the self-weight plus the nominal imposed load.

If any of the final self-weight loads is not in position on the structure, add compensating loads asnecessary.

15.2.3.2 Where only part of a structure is to be tested, special precautions may be necessary to ensurethat all the elements actually under test are subjected to the full test load, with proper allowance beingmade for load sharing between elements.

15.2.4 Measurements during the tests

Examine the structure before loading, and record the location and width of any cracks present. Takemeasurements of deflection and crack width as follows:

a) immediately after the application of load;

b) in the case of the 24 h sustained load test, at the end of the 24 h period of loading;

c) after removal of the load; and

d) after a 24 h recovery period.

Record ambient temperature and weather conditions during the test.

15.2.5 Assessment of results

15.2.5.1 In assessing the serviceability of a structure or part of a structure after a loading test, considerthe possible effects of variation in ambient temperature and humidity during the period of the test.

15.2.5.2 The following criteria shall apply:

a) in the case of reinforced concrete structures and class 3 prestressed concrete structures (seeSABS 0100-1), the maximum width of any crack measured immediately on application of the test loadfor local damage shall not exceed two-thirds of the value for the limit-state requirement (seeSABS 0100-1). In the case of class 1 and class 2 prestressed concrete structures, no visible cracksshall have occurred under the test load for local damage;

b) in the case of elements spanning between two supports, the deflection measured immediately afterapplication of the test load for deflection shall not exceed 1/500 of the effective span. Agreement onlimits shall be reached before cantilevered portions of structures are tested;

c) if the maximum deflection, in millimetres, occurring during a period of 24 h under load test, does notexceed 40 L 2/h (where L is the effective span, in metres, and h is the overall depth of construction, inmillimetres), the recovery need not be measured, and the criteria given in (d) and (e) below will notapply;


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d) if, within 24 h of the removal of the test load calculated in accordance with 15.2.3 for the ultimate limitstate, a reinforced concrete structure or class 3 prestressed concrete structure does not show arecovery of at least 75 % of the maximum deflection occurring during the 24 h under load, repeat theloading. Consider the structure to have failed the test if the recovery after the second loading is lessthan 75 % of the maximum deflection shown during the second loading;

e) if, within 24 h of the removal of the test load calculated in accordance with 15.2.3 for the ultimate limitstate, a class 1 or class 2 prestressed concrete structure does not show a recovery of at least 85 %of the maximum deflection occurring during the 24 h under load, repeat the loading. Consider thestructure to have failed the test if the recovery after the second loading is less than 85 % of themaximum deflection occurring during the second loading.

16 Procedure in the event of failure

Concrete work judged (by structural analysis or by results of a test) to be inadequate shall be replacedor shall be strengthened by additional construction or other means approved by the engineer. Theprocedure shall apply to

a) each section that failed or contains concrete that failed, as relevant, and

b) any other section, irrespective of strength, the functional purpose of which is affected by the sectionor concrete referred to in (a) above.


SABS 0100-2Ed. 2

1) For more information, see the Portland Cement Institute publication, Deterioration of concrete in aggressive waters -measuring aggressiveness and taking countermeasures by JJ Basson.

58

Annex A(normative)

Concrete subjected to wet conditions - aggressivenessof the water, and countermeasures1)

A.1 General

Where concrete is subjected to wet conditions, the water in contact with the concrete should be assessedfor aggressiveness, and appropriate measures taken to ensure the durability of the concrete.

A.2 Analytical tests required

Unless it is known with certainty that the water contains no more than trace quantities of any of the ioniccharacteristics listed in table A.1, all the corresponding tests (or other tests that give equivalent results)should be carried out.

Additional tests may be specified in special circumstances at the discretion of the engineer, e.g. brinesin salt pans, and water from hot mineral springs.

Table A.1 - Ionic characteristics

1 2

Ionic characteristics Test method

pH value SABS method 11

Calcium-carbonate-saturated pH value PCI TM 9.28

Calcium hardness SABS method 216

Total ammonium ion content SABS method 217SABS method 218

Magnesium ion content

Total sulfates

SABS method 1071

SABS method 212

Chloride ion content*) SABS method 202

Total dissolved solids SABS method 213

*) This determination is necessary only in the case of reinforced-concrete or prestressed-concrete structures andmay be omitted if plain concrete only is at issue.


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A.3 Assessment of the aggressiveness of water, using the BassonIndex (BI)

A.3.1 Basson Index

The Basson Index BI is a measure of the total aggressiveness of water, and is calculated as follows:

BI = Na + Nb

where

Na is a factor representing the water properties; and

Nb is a factor representing environmental factors (e.g. temperature, flow).

A.3.2 Calculations

A.3.2.1 Factors Na and Nb

A.3.2.1.1 The water properties factor Na is calculated as the sum of the indices N1 to N6, each of whichis calculated as shown in table A.2.

A.3.2.1.2 The environmental factor Nb is calculated as the sum of the indices N11 to N14 (each of whichis calculated as shown in table A.3) for whichever conditions are being taken into account.

Table A.2 - Calculation of water properties indices

1 2 3 4

Property Symbol UnitsIndex

Nx

pH value V1 1/log[H+] N1 = 200 x (9,5 - V1)

Calcium carbonate-saturated pH value V2 1/log[H+] N2 = - 2 000 x (V1 - V2)

Calcium hardness(as CaCO3) V3 mg/L N3 = 2,2 x (500 - V3)

Total ammoniumions (as NH4) V4 mg/L N4 = 10 x V4

Magnesium ions(as Mg) V5 mg/L N5 = 0,6 x V5

Total sulfates (asSO4) V6 mg/L N6 = 0,3 x V6


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60

Table A.3 - Calculation of environmental indices

1 2

PropertyIndex

Nx

Flow - turbulent N11 = 0,75

- stagnant N12 = -0,5

Temperature t, °C N 13 = 0,05 x (t - 20)

Wet-dry cycles:

d = dry time fraction c = cycles per year s = total dissolved solids, mg/L N14 = 0,16 x 10-6 x d x c x s

A.3.2.2 Other indices

The subindex for leaching corrosion LSI, and the subindex for spalling corrosion SSI, are calculated asfollows:

LSI = (N1 + N2 + N3)

3

SSI = (N4 + N5 + N6)

3

A.3.3 Classification

After the Basson Index BI has been calculated as shown in A.3.1 and A.3.2.1, the water is classified asin table A.4.

Table A.4 - Classification of water in terms of Basson Index BI

1 2 3

Basson Index BI Water aggressiveness Recommendation

Under 350 Non-aggressive to mildlyaggressive

Use concrete class as required forstructural design, but see remarks intable A.6.

350 to 750 Mildly to fairly aggressive Good concrete design andconstruction essential. See remarksin table A.6.

750 to 1 000 Highly aggressive Identify dominant corrosion sub-index and follow applicablerecommendations.

Over 1 000 Very highly aggressive Do not use in contact withunprotected concrete unlessrecommended anti-corrosionmeasures can be carried out in full.


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A.4 Recommended anti-corrosion measures

A.4.1 Identification of suitable countermeasures

A.4.1.1 Identify the dominant mode of attack by establishing which one of the leaching or spallingcorrosion subindices, as calculated, is the greater.

If leaching-corrosion subindex LSI is the greater, use table A.5.

If spalling-corrosion subindex SSI is the greater, use table A.6.

Use table A.5 or table A.6, as appropriate, to determine what anti-corrosion measures are applicable tothe case under consideration.

A.4.1.2 Repeat this procedure for the subdominant mode of attack, to ensure that all the anti-corrosionmeasures that may be required have been taken into consideration. As a result of the fortuitous andbeneficial overlap of treatments, a second or third anti-corrosion treatment will seldom be required unlessvery unusually aggressive conditions are present.

A.4.1.3 When reinforcing or prestressing steel is present in the concrete, it should be remembered thatthe degree of protection provided by the concrete to such steel is related to cover thickness. See therecommendations given in table A.7.

Table A.5 - Countermeasures against leaching corrosion

1 2 3 4 5

Limits ofleaching-corrosionsubindex

LSI

Other applicablefactors

Recommendedclass of

concrete*)

Recommendedtype of coating**) Remarks

Below 350

Spalling-corrosionsubindex SSI lessthan 300

1

None or A

High turbulence ortemperaturecorrections (or both)may necessitate extrasacrificial inorganiccoating allowance,depending onanticipated service lifeof concrete structure

Spalling-corrosionsubindex SSI 300to 500

2

350 to 750 Spalling-corrosionsubindex SSI notexceeding 500

3 or4

750 to 1 000 3 or4

BCDE

Obtain coatingmanufacturer's adviceon best coating typefor specific conditionsof exposureAbove 1 000 3 or

4BDE

*) See table A.8.

**) See table A.10.


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A.4.2 Materials to be used

A.4.2.1 Concrete

See tables A.5, A.6, A.7 and A.8.

A.4.2.2 Cement

Table A.9 lists the cements that may be used in concrete intended for exposure to aggressive waters.

A.4.2.3 Aggregates

See 4.3.

A.4.2.4 Mixing water

See 4.2.

A.4.2.5 Mix proportions

Table A.8 summarizes the classes of concrete considered suitable for use under aggressive waterconditions and indicates the proportions in which the various components should be mixed in order toachieve the desired properties.

A.4.2.6 Anti-corrosion coatings for concrete

See table A.10.


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Table A.6 - Countermeasures against spalling corrosion

1 2 3 4 5

Limits ofspalling-corrosionsubindex

SSI


Recommendedclass of

concrete*)

Recommendedtype of coating**) Remarks

Below 350 Leaching-corrosionsubindex LSI lessthan 300

1 or2

None or A

High turbulence and/ortemperature and/orwet-dry cyclingcorrections maynecessitate anadditional thicknessallowance, dependingon anticipated servicelife of concretestructure

350 to 750 Leaching-corrosionsubindex LSI 300to 500

3 or4

or5

Preferred type if attackis mainly because ofsulfates

750 to 1 000 Sulfate subindexN6 less than 800

3 or4

BCDE

Obtain coatingmanufacturer's adviceon best coating typefor specific conditionsof exposureAbove 1 000 Sulfate subindex

N6 exceeding 800or5

BDE

*) See table A.8.

**) See table A.10.

Table A.7 - Countermeasures against chloride corrosion

1 2 3 4 5

Chloride ioncontent(as Cl)


Recommendedclass of concrete

Recommendedtype of coating

Recommendedminimum cover of

concrete overreinforcement

mm

Below 350

As determined for dominant and subdominant corrosionsubindices (or for both) (see tables A.3 and A.4)

25

350 to 750 35

750 to 1 000 50

Above 1 000 75 (greater in tidalzones)

NOTE -This table is only applicable if reinforcing or prestressing steel is present.



64

Table A.8 - Concretes for aggressive chemical environments Amdt 1, Sept. 1994

1 2 3 4 5 6

Class Cement code*)

Minimumcement

content**)

kg/m3

Minimumcement/water

ratio**)

Characteristicstrength

MPa

Remarks

1

OPCRHPCPC 15 (SL)RHPC 15 (SL)PC 15 (FA)PC 45 (SL)50/50 PC/GGBSPC 30 (FA)90/10 PC/CSF

340 1,8 30 Minimum quality recommended for useunder freshwater conditions and inheavily polluted air

2

OPCRHPCPC 15 (SL)RHPC 15 (SL)PC 15 (FA)PC 45 (SL)50/50 PC/GGBSPC 30 (FA)90/10 PC/CSF

420 2,2 40 Minimum quality recommended for useunder marine or saline conditions andin salt-laden air

3 PC 45 (SL)50/50 PC/GGBS

420 2,2 40 Improved protection of steel undermarine or saline conditions, because ofchloride-binding ability

4 PC 30 (FA)90/10 PC/CSF

420 2,2 40 Improved denseness andimpermeability of concrete and alsoimproved resistance to leaching attack,because of pozzolanic pore-refinementproperties

5 SRPC***) 420 2,2 40 Moderately resistant to some sulfatesbecause of low tricalcium aluminatecontent

*) See table A.9 for explanation. Note that the cement types grouped together for any one class of concrete do not necessarilyproduce concrete of the same strength.

**) Refers to total quantity of all binders.

***) In cases where low strength is acceptable, a site blend of 20 parts of OPC and 80 parts of ground granulated blastfurnaceslag may be considered as an alternative.


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Table A.9 - Cements recommended for the making ofconcretes for aggressive waters

1 2 3

Code Applicablestandard Description

OPC SABS 471 Ordinary portland cement

RHPC SABS 471 Rapid-hardening portland cement

PC 15 (SL) SABS 831 Portland cement with not more than15 % ground granulated blastfurnaceslag

RHPC 15 (SL) SABS 831 Rapid-hardening version ofPC 15 (SL)

PC 15 (FA) SABS 831 Portland cement with not more than15 % fly ash

RHPC 15 (FA) SABS 831 Rapid-hardening version of PC 15 (FA)

PC 45 (SL)*) SABS 626 Portland cement with 45 % to 55 %ground granulated blastfurnace slag

50/50 PC/GGBS Site blend of portland cement with50 % ground granulated blastfurnaceslag

PC 30 (FA) SABS 1466 Portland cement with 30 % fly ash

90/10 PC/CSF Site blend of portland cement with10 % condensed silica fume

SRPC SABS 471 Sulfate-resistant portland cement

*) To be used in preference to portland blastfurnace cement (PBC) in whichthe slag content is allowed to vary over a wide range of 15 % to 70 % (seeSABS 626). In the case of PC 45 (SL), the manufacturer guarantees a slagcontent in the range 45 % to 55 %.


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Table A.10 - Coatings for concretes in aggressive waters

1 2 3 4 5

Type Category Some examples Minimum coatingthickness required Remarks

A Inorganic Extra thickness ofbase concrete assacrificial allowancePlaster coats

20 mm to 50 mm

Use under mild tomoderate leachingconditions only

B Preformedpolymeric liners

PolyethylenePolyvinyl chloridePolychloroprene

0,2 mm to 1 mmAvailable in light,regular and heavy-duty gauges

C Emulsion-basedwaterborne organics

PolyacrylicsPolyacrylonitriles 150 µm Tolerant of wet

surfaces

D Solvent-basedorganics

Chlorinated rubbersVinylsVinylidenes

150 µmHigh-build,thixotropic typesavailable

E Catalysed organics Epoxy tarsSolventless andwater-basedepoxies*)

Polyurethanes

150 µm to 300 µm

Accurate mixingand time-schedulingrequired

*) Aggregate-filled, solventless epoxy systems, applied in film of thicknesses 2 mm to 5 mm have provedto be very effective on surfaces of oil rigs.


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Annex B(informative)

Curing

B.1 General

The principal requirements for curing concrete are given in 10.8. The following notes are intended toamplify the factors that should be considered in complying with these requirements. Therecommendations are based on the assumption that the temperature of the concrete during the curingperiod will not fall below 5 °C. Particular precautions that have to be taken when concreting at low ambienttemperatures are given in 10.8.3.

B.2 Strength of concrete

A rough guide to the development of strength at early ages at different temperatures can be obtained byusing the concept of "maturity", which may be defined as the area under a curve of the temperature of theconcrete (in degrees Celsius), plotted against time (in hours). Once the maturity is known, thecorresponding age of concrete cured at normal temperatures can be estimated and the strength thenfound from data relating to the strength of that type of concrete to age at that temperature. Suchcalculations are only applicable if the concrete is kept constantly moist for the period under consideration.

B.3 Distortion and cracking

B.3.1 The concrete should be so cured that internal stresses within the element, whether owing todifferences in temperature or differences in moisture content within the concrete, are not sufficient tocause distortion or cracking. The disposition of reinforcement will affect the restraint to the strains andhence will also have an effect on any distortion and cracking.

B.3.2 When the likely temperature variation within the concrete is being assessed, the following factorsapply:

a) rate of heat evolution (related to rate of development of strength);

b) size and shape of element;

c) different insulation values of curing media (e.g. wooden moulds or water spray); and

d) ambient temperature.

For example, surface cracking may occur as a result of variation in temperature when cold water sprayis applied to a relatively massive element immediately after the moulds have been stripped and while theconcrete is still hot.

B.3.3 When the likely variation in moisture content within the concrete is being assessed, it should bekept in mind that the rate of evaporation from unprotected concrete will be higher in the case of

a) atmospheric conditions that encourage evaporation (e.g. low relative humidity, high wind speed,concrete surface hotter than the air) especially if the rate of migration of water through the concreteexceeds the rate of evaporation from the surface,


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68

b) members of high surface/volume ratio,

c) early age concrete, and

d) lower grades of concrete.

For example, cracking may occur as a result of varying shrinkage in elements when sudden changes insection affect the surface/volume ratio appreciably, especially if the more massive section is reinforcedand the more slender section is not.

B.3.4 If the shrinkage of precast units after they have been built into the structure is likely to causeundesirable cracking at the ends of the unit, curing aimed at preventing the loss of water from the unitshould be continued no longer than is necessary to obtain the desired durability and strength. Theconcrete should then be given the maximum opportunity of drying out to an extent consistent with thelimitation of the variation in moisture content as already outlined. For example, cracks may occur at theends of precast concrete lintels that were moist-cured but were not allowed to dry sufficiently before theywere built into the structure.

B.4 Durability and appearance

B.4.1 As deterioration is most likely to occur if the concrete provides inadequate protection for thereinforcement, all vulnerable surfaces of newly cast concrete should be protected from excessive loss ofwater by evaporation, which would result in a weak, porous surface layer. The factors given in 10.8therefore apply.

B.4.2 Where it is important that the formation of lime bloom be prevented, especially in cold weather,the atmosphere adjacent to the surface of the concrete should be maintained at a constant relativehumidity approaching 100 % for as long as is practicable. Concrete should be protected from the wettingand drying cycles produced by rain or condensation and drying winds.


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Annex C(informative)

Technical data for prestressedstructural elements required in a contract

C.1 Data for pre-tensioned elements

The following technical data in a contract in respect of pretensioned structural elements shall be given onthe construction drawings:

C.1.1 Tendon alignment

A diagrammatic layout showing the centroid of the tendons in both the horizontal and vertical planes,together with the ordinates and offset dimensions.

C.1.2 Tendons

The tendons on which the design is based, designated by the number and nominal diameter of the bars,wires or strands and the type of prestressing steel, expressed in that order, e.g. 15 x 12,5 mm 7-Hi strand.

C.1.3 Tensioning force

The maximum tensioning force and the corresponding stress level in the prestressing steel, for eachtendon or group of tendons. The forces shall be given in kilonewtons (kN) and the stress levels shall beexpressed as a percentage of the characteristic strength, the 0,2 % proof stress or the yield stress of theprestressing steel, as relevant.

C.1.4 Prestressing losses in tendons

The losses allowed for in the design shall be given as follows:

a) elastic deformation of concrete: the "elastic factor", which, when multiplied by the averagecompressive stress in the concrete adjacent to the tendon, will give the loss due to elastic deformationof the concrete;

b) creep of concrete: the "creep factor", which, when multiplied by the average compressive stress inthe concrete adjacent to the tendon, will give the loss due to the creep of the concrete;

c) shrinkage of concrete: the stress loss, in megapascals (MPa), due to shrinkage of the concrete; and

d) relaxation of prestressing steel: the stress loss, in megapascals (MPa), at a stress level of 70 % ofthe characteristic strength of the prestressing steel due to relaxation of the prestressing steel.

C.1.5 Bursting reinforcement

The bursting reinforcement for the prestressing system on which the design is based.


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70

C.1.6 Precamber

The precamber at intervals not exceeding 0,25 times the span length.

C.2 Data for post-tensioned elements

The following technical data in a contract in respect of post-tensioned structural members shall be givenon the construction drawings.

C.2.1 Tendon alignment

A diagrammatic layout showing the centroid of the tendons in both the horizontal and vertical planes,together with the ordinates, offset dimensions and curve equations of the centroid of the tendons.

C.2.2 Tendon system

The tendon system on which the design is based, designated by the number and nominal diameter of thebars, wires or strands per tendon and the type of prestressing steel, expressed in that order, e.g.12 x 12,7 mm 7-Hi strand.

C.2.3 Tensioning force

The initial jacking force and the effective force at the live anchorage(s) after transfer, as well as thecorresponding stress level in the prestressing steel, for each tendon or group of tendons. The forces shallbe given in meganewtons (MN) and the stress levels shall be expressed as a percentage of thecharacteristic strength, the 0,2 % proof stress or the yield stress of the prestressing steel, as relevant.

C.2.4 Draw-in

The draw-in or intended release (or both) of the tendons or group of tendons, in millimetres (mm).

C.2.5 Prestressing losses in tendons

The losses allowed for in the design shall be given as follows:

a) friction loss: the formula used to determine the tendon/duct friction loss together with the valuesadopted for the friction coefficient (u) due to curvature and the wobble factor (k) due to unintentionalvariation from the specified alignment;

b) elastic deformation of concrete: the "elastic factor", which, when multiplied by the averagecompressive stress in the concrete section, will give the loss due to elastic deformation of theconcrete;

c) creep of concrete: the "creep factor", which, when multiplied by the compressive stress in theconcrete adjacent to the tendon, will give the loss due to the creep of the concrete;

d) shrinkage of concrete: the stress loss, in megapascals (MPa), due to shrinkage of the concrete; and

e) relaxation of prestressing steel: the stress loss, in megapascals (MPa), at a stress level of 70 % ofthe characteristic strength of the prestressing steel due to relaxation of the prestressing steel.


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C.2.6 Anchorages

The positions where loop type or fan type dead end anchorages may be used.

C.2.7 Concrete cover

The minimum depth of concrete over the outside of the surface of the sheath or tendon support, or both.

C.2.8 Tensioning of tendons

The following tensioning requirements are allowed for in the design:

a) the minimum concrete strength required for initial tensioning;

b) requirements for partial tensioning or tensioning at a specific stage;

c) the overall sequence of tensioning; and

d) the precamber at intervals not exceeding 0,25 times the span length.


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Annex D(informative)

Recommended specialist literature on massive concrete

ADDIS, BJ (ed.). Fulton's concrete technology. 6th ed. Midrand: Portland Cement Institute, 1986.p. 710-735.

American Concrete Institute. Cooling and insulating systems for mass concrete. Rev. ed. Detroit: ACI,1986. ACI Committee Report 207.4R-80.

BAMFORTH, PB. Mass concrete. Concrete Society Digest, 1984, No. 2.

Annex E(informative)

Bibliography

BS 4447:1973 (1990), Specification for the performance of prestressing anchorages for post-tensionedconstruction.

BS 4486:1980, Specification for hot rolled and hot rolled and processed high tensile alloy steel bars forthe prestressing of concrete.

BS 5896:1980, Specification for high tensile steel wire and strand for the prestressing of concrete.

Basson, JJ. Deterioration of concrete in aggressive waters - measuring aggressiveness and takingcounter-measures. Midrand: Portland Cement Institute, 1989.

Fédération Internationale de la Précontrainte. Recommendation for acceptance and application of post-tensioning systems. Slough: FIP, 1981.

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