AMAJOR PROJECT REPORT

ON

STUDY OF MATERIAL TESTING AND MIX DESIGN PROCEDURE OF READY MIX CONCRETE

BY

C SANDEEP REDDY

CONTENTS:• INTRODUCTION

•MATERIALS FOR RMC

• EQUIPMENTS REQUIRED

•MIXING PROCESS

• TESTS ON MATERIALS

•MIX DESIGN

•MERITS AND DEMERITS

•OPERATIONAL ASPECT

• CONCLUSION

INTRODUCTION:• Ready Mix Concrete (RMC) is a specialized material in which the cement aggregates and other

ingredients are weigh-batched at a plant in a central mixer or truck mixer, before delivery to the

construction site in a condition ready for placing by the builder.

• Thus, `fresh' concrete is manufactured in a plant away from the construction site and transported within

the requisite journey time. The RMC supplier provides two services, firstly one of processing the

materials for making fresh concrete and secondly, of transporting a product within a short time.

• It is delivered to the worksite, often in transit mixers capable of mixing the ingredients of the concrete

just before the delivery of batch.

• The second option available is to mix the concrete at the batching plant and deliver the mixed concrete

to the site in an agitator truck, which keeps the mixed concrete in correct form.

• The use of the RMC is facilitated through a truck-mounted 'boom placer' that can pump the product for

ready use at multi-storied construction sites. A boom placer can pump the concrete up 80 meters.

OBJECTIVE:

• The main objective to choose this topic is that an engineer should have the

knowledge of advantages of RMC and disadvantages of Site mixed concrete.

• As RMC is being widely used in bigger and medium size of projects today,

Engineer should be aware of the technicality of the RMC and the operational

work, to ensure the quality of work and the Site Engineer should know what are

the steps to be taken to check the concrete in RMC, what is required to be

specified for RMC, what is the information required to be supplied by the RMC

supplier, what checks are necessary by the consumer before ordering RMC, what

are the checks needed at site prior and after to receipt of RMC.

NECESSITY:

Normally the concrete operation carried out in India, is of site mixed, which is having some disadvantages which are shown

below:

• Quality Assurance not guaranteed.

• Constant control on aggregates for size, shape & grading not exercised on site.

• Arbitrary batching and mixing by volume. Strict water-cement ratio not exercised.

• Wastage of materials.

• Retarded speed.

• Concreting operations prolonged beyond day light without proper lighting.

• Manual operation.

• Speed restricted depending on mixers.

• Restricted spaces.

• Storages of aggregates and cement.

• Blocking of roads / approaches

• Dust pollution

HISTORY:• The Idea of Ready Mix Concrete (RMC) was first introduced by Architect Jurgen Heinrich

Magens, he got his patent of RMC in Germany in 1903.

• In 1907, he discovered that the available time for transportation could be prolonged not only

by cooling fresh concrete but also by vibrating it during transportation. So this gave rise to a

concrete which is made in the off site.

•  The first concrete mixed off site and delivered to a construction site was effectively done in

Baltimore, United States in 1913, just before the First World War.

• The first concept of transit mixer was also born in 1926 in the United States.

• Between the years 1950 and 1980 considerable growth of RMC took place in the United

States with the maximum supply of 31 million cubic meters in the year 1974.

RMC IN INDIA:

• In India RMC was first initially was used in 1950 during the construction sites of Dams like

Bhakra Nangal, Koyna.

• At the construction the transportation of concrete is done by either manually or mechanically

using ropeways & buckets or conveyor systems.

• RMC at Pune in the year 1991. However, due to various pit falls and problems this plant did

not survive for long and was closed.

• Within a couple of months in the year 1993, two RMC plant were set up in Mumbai to

commercially sell RMC to the projects where they were installed.

• These plants were later allowed to sell RMC to other projects also.

• Thus RMC was successfully established sometime after 1994 in India.

MATERIALS REQUIRED FOR RMC:

• AGGREGATE

a) Coarse aggregate

b) Fine aggregate

CEMENT

ADMIXTURE

ROLE OF ADMIXTURE IN RMC

FLYASH

WATER

I. Effect of mixing sea water in concrete

II. Quality of water for curing concrete members

III. Quality of water for curing concrete cubes

EQUIPMENTS REQUIRED:

• BATCHING PLANT

a) Storage of materials - Silos, containers and

bins

b) Batching arrangement

c) Measuring and recording equipment

d) Mixing equipment

e) Control systems

f) Electrical, hydraulic and pneumatic drives

g) Conveying systems (belt / screw conveyors)

TRANSPORTATION EQUIPMENT:

TRANSIT MIXER

MIXING PROCESS:• Transit Mixed (or "truck-mixed")

Concrete

• Shrink Mixed Concrete

• Central Mixed Concrete

JHTRANSIT MIXED (OR "TRUCK-MIXED") CONCRETE

• While ready mixed concrete can be delivered to the point of placement in a variety of ways,

the overwhelming majority of it is brought to the construction site in truck-mounted, rotating

drum mixers.

SHRINK MIXED CONCRETE

• Concrete that is partially mixed in a plant mixer and then discharged into the drum of the

truck mixer for completion of the mixing is called shrink mixed concrete.

CENTRAL MIXED CONCRETE

• Central-mixing concrete batch plants include a stationary, plant-mounted mixer that mixes the

concrete before it is discharged into a truck mixer. Central-mix plants are sometimes referred

to as wet batch or pre-mix plants. The truck mixer is used primarily as an agitating haul unit

at a central mix operation.

TESTS ON MATERIALS:• TESTS ON FINE AGGREGATE

a) Sieve analysis

b) Specific Gravity Test

c) Bulk Density Test

d) Water Absorption Test

TESTS ON COARSE AGGREGATES

a) Sieve Analysis

b) Specific Gravity Test

c) Aggregate Impact Value Test

d) Bulk Density Test

e) Water Absorption Test

f) Flakiness Index and Elongation Index Test

TESTS ON FRESH CONCRETE

a) Slump Test

b) Tests on Water

c) Tests on Hardened Concrete

MIX DESIGN:

• DESIGN STIPULATIONS FOR PROPORTIONING

a) Grade designation: M50

b) Type of cement: Ultra Tech 53 grade

c) Max. Nominal size of aggregate. : 20 mm

d) Minimum cement content: 350 kg/m3

e) Maximum water cement ratio: 0.45

f) Exposure condition: Extreme

g) Degree of supervision: Very Good

h) Type of aggregate: Crushed angular aggregate

i) Maximum cement content: 480 kg/m3

j) Chemical admixture: Glenium,BASF

TEST DATA FOR MATERIALS:• Cement used: OPC 53 grade

• Specific gravity of cement : 3.15

• Specific gravity of

a. Coarse aggregate: 2.60

b. Fine aggregate: 2.59

• Water absorption

a. Coarse aggregate: 0.28 %

b. Fine aggregate: 0.59 %

• Free (surface) moisture

a. Coarse aggregate: Nil

b. Fine aggregate: 2.0 % 57

• Sieve analysis

a. Coarse aggregate: Conforming to Table 2 of IS 383

MIX DESIGN FOR M50 GRADE:

STEP 1:

Target mean strength for mix proportioning

• fm= fck +1.65*standard deviation

• From Table 1 of IS 10262:2009 standard deviation, s = 6.4 N/mm2

(For very good control)

• Therefore target strength = 50+1.65 x6.4 = 60.56 N/mm2

STEP 2:

Selection of w/ c ratio• Water - cement ratio (from Fig. 2) = 0.35 (using data from above).

• Maximum water - cement ratio specified for durability condition = 0.45 (fromTable-6.5).

• Water cement ratio to be adopted for concrete = 0.45 (Lower of 4.5).

• Water content from Table -6.8 = 180 (for a workability of 0.80 C F).

• Sand as percentage of total aggregate by absolute volume from Table-6.8 = 25% For W/C ratio of 0.35. 

• Adjustment of water content (using table-6.9) (For C F of 0.90) = 180 + .03 x 180 = 185.4 kg/m3. 

• Adjustment for sand content (using Table -6.9) 25% - 3.0% = 22% (for W/C of 0.45) 

• Modified water content = 185.4 liters

• Modified sand content = 22% 

• Cement content = 185.4/0.45=412 kg/m3

• Minimum Cement content = 350 kg/m3 (from Table-6.5 specified for durability Condition).

• Required Cement content = 412 kg/m3 (Higher of above value).

• Entrapped air, as percentage of volume of concrete = 2%.

• From Table 5 of IS 456, minimum cement content for Extreme exposure condition = 360 kg/m3, Hence ok.

STEP 3&4 : DETERMINATION OF COARSE AND FINE AGGREGATE CONTENT:

• V= [W + C/SC + 1/P*Fagg/SFine] x 1/1000

• V= [W + C/SC + 1/ (1-P)*Cagg/SCoarse] x 1/1000

For the Specified Max. Size of aggregate of 20 mm, the amount of entrapped air in the wet concrete is 2%.

Amount of Fine aggregate, Fa required

• 1 m3 = [185.4 + 412/3.15 + 1/0.315* Fagg/2.59] x 1/1000

•  Fa =630 kg/m3.

Amount of Coarse aggregate, Ca required  

• 1 m3 = [185.4 + 412/3.15 + 1/ (1-0.315)* Cagg/2.60] x 1/1000

• Ca = 1377 kg/m3.

JK HThe Mix Proportion then becomes  

• Water = 185.4 kg/m3

• Cement = 412 Kg/m3

• Fine Aggregate = 630 Kg/m3

• Coarse Aggregate = 1377 Kg/m3

• Mix proportions for making 1 cu.m of concrete:

Water Cement Fine aggregate Coarse aggregate

185.4 kg/m3 412 Kg/m3 630 Kg/m3 1377 Kg/m3

MERITS AND DEMERITS:

MERITS OF RMC• Better quality concrete is produced.

• Elimination of storage space for basic materials at site.

• Elimination of Procurement / Hiring of plant and machinery.

• Wastage of basic materials is avoided.

• Labour associated with production of concrete is eliminated.

• Time required is greatly reduced.

• Noise and dust pollution at site is reduced.

• Organization at site is more streamlined.

• Durable & Affordable

• No storage space required either for raw materials or for the mix.

• Lower labour and supervisory cost.

• No wastage at site.

• Environment friendly.

• Availability of concrete of any grade.

DEMERITS OF RMC:

• Need huge initial investment.

• Not affordable for small projects (small quantity of concrete)

• Needs effective transportation system from R.M.C to site.

• Traffic jam or failure of vehicle creates problem if proper dose of

retarder is not given.

OPERATIONAL ASPECT:

• NEEDS TO BE SPECIFIED BY CONSUMER FOR RMC.

• INFORMATION TO BE SUPPLIED BY THE PRODUCER.

• CHECKS BY CONSUMER BEFORE ORDERING THE RMC.

• CHECKS NEEDED AT SITE PRIOR TO RECEIPT OF RMC.

• CHECKS NEEDED AT SITE DURING CONCRETING.

• THE UNNECESSARY RESTRICTIONS ON SUPPLIERS OF RMC BY

PURCHASER.

• THE CONSTRAINTS FACED BY RMC PRODUCERS AT PRESENT.

CONCLUSION:• The concrete quality produced in RMC plant is highly consistent with low deviation order.

• It provides a high degree of overall strength of hardened concrete and the performance of the structure at a later date.

• RMC operations are highly mechanized and fully controlled through electronic controls and hence reduce the probability of

errors in various operations.

• It is also environment friendly and brings down pollution due to dust at construction can also be accelerate with the use of

RMC.

• The use RMC in civil construction is widely adopted throughout the world.

• The beginning made in India is in tune with the developments outside and RMC uses provide numerous benefits to the

consumers.

• Conventional approach to durable concrete structures, namely specifying maximum water cement ratio, minimum cement

content and cement type, is now always satisfactory, especially under aggressive environmental condition.

• Site manufactured concrete cannot assure the same quality of concrete and that from controlled ready mix batching plant

backed by advanced technology and project management.

• The advantages of RMC are particularly evident in construction projects with aggressive exposure conditions.

REFERENCES:

• Concrete Technology Theory and Practice, M.S SHETTY, S. Chand- New Delhi.

• “RMC in India” (June 2001), Civil Engineering & Construction Review

• IS 4926-2003, Standard on Ready mixed concrete – Code of Practice, BIS, New Delhi.

• IS 383, Indian Standard specification for coarse and fine aggregates from natural sources for

concrete (Second Revision)

• IS 10262-2009, Indian Standard Concrete Mix Proportioning- guidelines (First Revision)

• IS 456-2000, Indian Standard Plain and Reinforced Concrete - Code of Practice (Fourth

Revision)

• “RMC on the move” (Oct. 2003), Ambuja Technical Literature, Vol. No. 90

• “Mechanisations of concreting, Part I- Batching, Mixing & Transporting” (Dec. 1996),

Ambuja Technical Literature, Vol. No. 12

THANK YOU