recycled concrete aggregate

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Introduction

Demand of aggregate on construction

What is recycled concrete aggregate (RCA)?

Benefits of RCA

Procedure of RCA

Experimental verification on various properties

→ compressive strength

→ Specific gravity & water absorption

→ Particle size distribution

→ Crushing and impact values

→ Modulus of elasticity4

Recent research of Fredonia group has found:

Global demand of aggregates

for construction

› 46 billions tones by 2011

› 49 billions tones by 2012

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No any natural aggregates

No one can construct any buildings,

industries, bridges ,dams ,roads

pavements……7

Construction and demolition wastes are generated annually in world

14.5 Million Tons (india)

13 Million Tons (France)

10-15 Million Tons (Japan)

20 Million Tons ( Hongkong)

Investigation results of Environmental resources ltd(1979) for EEC member countries found

55 Million Tons - by 1980

302 Million Tons – by 2020 8

Terrorist attack Age limit

Natural calamities 9

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The final product collected

from crushing and separated

from other contamination

obtained from construction and

demolition wastes such as

concrete wastes, broken bricks,

gravel, bridge supports, road

pavements, concrete roadbeds

etc. that has been previously

used in construction are

recycled aggregate.

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Conserve diminishing natural aggregate

resources

Use of construction wastes

Protection of environment

Save money

Create additional business opportunities

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Breaking up & removing

the old concrete

Crushing in primary

and secondary

crushers 14

Finally , stockpiling and separation of coarse and fine

aggregate

Grading and washing

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(Collecting waste concrete aggregate) (Making M20 Concrete mixture )

(Making 150 mm

cube for

comparing RCA

& NCA

properties.)

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Particle size distributionSieve analysis is done after crushing and sieving as per IS

Code 2386 to separate out coarse and fine aggregate.

Recycled aggregate meets all the standard requirements of

natural aggregate

Specific gravity & water absorptionSp. Gravity(saturated surface dry condition) of recycled

concrete aggregate(RCA) was found from 2.35 to 2.58 which

is slightly lower than natural aggregate.

Water absorption ranges 3.05 % to 7.40 % which is slightly

higher than that of natural aggregate.

Modulus of elasticity RCA has lower than NAC upto 15% only.

It can be increased if hardened cement paste adhere to

aggregate are removed well.

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The average compressive strengths cube cast are determined as per IS 516 using RCA and natural aggregate at age 1, 3, 7, 14, 28 , 56 and 90 days.

Reduction in strength of RCA as compared to NCA:2-14 % = M-20

As per IS 2386, the crushing & impact values for concrete ,

wearing surfaces should not exceed 45% and 50% resp.

RAC satisfy the BIS specifications.

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The use of recycled concrete aggregate is proved to be a valuable, buildings materials in technical, environmental & economical respects.

Recycle & reuse is an appropriate solution to problems of dumping hundred of thousands of tons of demolition wastes.

However,more research and initiation of pilot project for application of RCA is started for modifying our design codes, specifications & procedure for use of RCA.

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Hansen. T.C. (1992) , “ Recycling of Demolished

Concrete Masonry, Rilem Report NO. 6, E & FN

Sports, London , Great Britain , pp. 316

Oilonomou,N.D.(2008) “ Recycled Concrete

Aggregates,” Cement and Concrete

Composites , Vol. 27 , pp315 – 318.

Thieien, G.(2010)” Concrete Technology Reports

2001-2003,” German Cement Works Association.

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