Recycled concrete aggregate
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- 4. 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 elasticity 4
- 5. Recent research of Fredonia group has found: Global demand of aggregates for construction › 46 billions tones by 2011 › 49 billions tones by 2012 5
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- 7. No any natural aggregates No one can construct any buildings, industries, bridges ,dams ,roads pavements…… 7
- 8. 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
- 9. Terrorist attack Age limit Natural calamities 9
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- 12. 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. 12
- 13. Conserve diminishing natural aggregate resources Use of construction wastes Protection of environment Save money Create additional business opportunities 13
- 14. Breaking up & removing the old concrete Crushing in primary and secondary crushers 14
- 15. Finally , stockpiling and separation of coarse and fine aggregate Grading and washing 15
- 16. (Collecting waste concrete aggregate) (Making M20 Concrete mixture ) (Making 150 mm cube for comparing RCA & NCA properties.) .) 16
- 17. Particle size distribution Sieve 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 absorption Sp. 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. 17
- 18. 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. 18
- 19. 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. 19
- 20. 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. 20
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