Study On The Preparation And Application Technology Of Recycled Aggregate In Concrete

Produced and classified the recycled concrete aggregate made use of the differentstrength grade waste concrete test blocks, using mainly pressure testing machine, Jaw Crusherand artificial broken of methods. The results show that after optimize with20%5-10mmsingle grain recycled coarse aggregate and80%5-25mm continuous graded recycled coarseaggregate, the gradient of various sieve pore accumulated retained rate of every kind ofrecycled coarse aggregate decrease, and the whole particle size distribution is more reasonable.Compare with the natural coarse aggregate, recycled coarse aggregate’s bulk density andsoundness are lower, and particle angularity, elongated or flat particle and porosity are higher.But through the optimization design of the recycled coarse aggregate’s particle sizedistribution, all performances of the recycled coarse aggregate can meet the requirements ofrecycled coarse aggregate for concrete GB/T25177-2010.This paper has designed a preparation process of recycled aggregate concrete, andprovides technology parameters for developments of the recycled aggregate. The surfacetreatment of the recycled aggregate adopted the chemical enhanced method, steeping withcement and fly ash slurry，reflecting the characteristics making use of locally availablematerials and not affecting the concrete performance. The method of mix proportion design ofrecycled aggregate concrete based on the free water avoided to effect the properties ofconcrete because of the relatively high water absorption of the recycled aggregate comparedwith the natural aggregate. Studying the mixing process of recycled concrete, workability(slumps, cohesive property, water-retaining property), mechanical properties (compressivestrength, splitting tensile strength), durability (carbonation resistance), recycled aggregatereplacement rate and free water-Binder ratio, provide the good frame of reference for thefuture study of the mix proportion design of recycled aggregate concrete.The research results show that the slump of the recycled concrete is130±30mm.Cohesive property and water-retaining property are good.28d compressive strength had passed30MPa, and met the criterion. With the increase of recycled coarse aggregatesreplacement rate, pre-wet water demand and free water-Binder ratio increase. With theincrease of the age, the compressive strength increase. When the recycled coarse aggregatereplacement rate is70%, all age compressive strength and28d splitting tensile strength ofrecycled coarse aggregate concrete made use of C60waste concrete are higher then others.7dcarbonation resistance of recycled coarse aggregate concrete made use of C60waste concreteis worse then the basic concrete, but28d carbonation resistance is better.Popularization and application of recycled aggregate and recycled concrete can solve theprocessing difficulties of waste concrete and environmental degradation, and improve people’squality of life, and reduce the depletion of natural resources. At present, the recycledaggregate concrete technology has become the world common concern project, and theengineered and academic focus of attention at home and abroad.Recycled concrete industry is a good development direction in the future, which can formeffective circulation with other industries, and accord with national strategy of sustainabledevelopment. Produce the recycled aggregate made use of waste concrete blocks to use in theproduction of recycled aggregate concrete, which can ease the shortage of natural aggregateresources，reduce environmental pollution caused by waste concrete blocks, and be of greatsignificance for the sustainable development of the industry.