Specifying Concrete
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Transcript of Specifying Concrete
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CIV2226
Specification,Ordering, and Supply of
oncre e
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Specifying Concrete
AS1379 Specification and Supply of Concrete
Site-mixed, factory mixed and truck-mixed
concretes Specification of materials
Plants and equipments
Specifying and ordering of concrete
Sampling testing for compliance
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AS3600 Concrete StructuresSection 17 Material and Construction Requirements
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Relationships Between the Australian Standards
Structural DesignAS3600 Concrete Structures
Specification of ConcreteAS1379 Supply of Concrete
Specification of
Concrete TestingAS1012 Methods of Testing Concrete
Aggregate TestingAS1141 Methods for Sampling& Testing Aggregates
Portland & BlendedCementsAS3972
Cement TestingAS2350
AdmixturesAS1478
Aggregates
AS2758
Sampling and Testing Specifications
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Two Classes of Concrete (AS1379)
Normal Class (bulk of the concrete supplied)
Special Class (special requirements for a
particular project)
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Normal Class Concrete
Applies to most concrete Strength grades: N20, N25,
N32, N40 or N50
, ,
Max size aggregate: 10, 14 or20 mm
Method of placement
whether Project Assessmentto be carried out
other requirements by
AS1379
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Special Class Concrete
Performance Specification
(i.e. particular fresh,mechanical, or durability
or
Prescription Specification
(e.g. the minimum cementcontent shall be 400 kg/m3 )
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Project Assessment
On a regular testing basis:
volume
slump strength (compressive, flexure or
tensile)
air content chloride and sulphate content
drying shrinkage
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Slump and Tolerance
Specified slump Tolerance (mm)
60 to 80 15
80 to 110 20
>110 30
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Assessment for Compliance
Tests at least 1 per 100 m3 Assess at selected production interval from
2 weeks to 3months (1 month usual)
One grade to be selected as control gradeand to have at least 10 results per productioninterval (most have many more)
Variability of production to be assessed onbasis of this grade
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Strength
Strength varies between batches
Histo ram
0
10
20
30
40
50
60
70
80
40 45 50 55 60 65 70Numberof
Specimens
Strength (MPa)
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Probability very good
StrengthTarget
Poor
fc(poor)
fc(verygood)
Good
fc(good)
k S
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Strength assessment
Production assessment
Project assessment
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specifically for a plant or a group ofplants
continuous sampling
Production assessment
one selected grade to comply
fcm > fc + 1.25 s
Supplier is obligated to provide therecords, if requested by the purchaser
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Project Assessment
assessment specified by the purchaser
fcm> fc + k s
No of Samples >15 k = 1.25
11 to 14 k = 1.4
At least 1 sample per 50 m3
Moving average of 3 to exceed fc
o = .8 k = 1.7
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Other Standard Requirements(wide basic requirements for all concrete)
Density 2100-2800kg/m (130-175lb/cu ft) Acid soluble chloride and sulphate limits
Shrinkage (max 1000 microstrain)
7 day strength 50% of grade strength (upto N50)
Cement complying with AS3972 alone or
plus one or more supplementarycementitious materials
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Chloride and Sulphate Content
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Drying Shrinkage
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Ordering Normal Class Concrete
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Ordering Special Class Concrete
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Storage of Materials
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Storage of Materials
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Manufacturing of Concrete
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Accurate Batching
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Batching Tolerances in AS1379
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Mixing Equipment Uniformity of MixingBatch Mixers are designed to:
uniformly distribute ingredients throughout the volume ofmixed concrete with the minimum mixing time or numberof revolutions necessary.
,
have a rated mixing capacity not more than 65% of thegross internal volume of the mixing chamber unlessproven otherwise
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Slump Control A sufficiently experienced operator will assess the consistency of a batch and estimate any further addition of water needed to produce the specified slump
Slump Stand at the Concrete Plant Water is added via a hose fitted with a measuring device Slump Control ensure desired level of consistence and workability is achieved Slump tests are conducted on site to confirm the consistency of concrete
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Contractual Issues .
Difficult Specifications Demonstrating the correct volume Demonstrating Strength Compliance
Special Class concrete can contain prescriptive and performance basedrequirements with the aim of obtaining the best possible concrete
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Next Week
Placement, Compaction, and Finishing Concrete Curing