| Replacing natural aggregate and cement with recycled aggregate and mineral admixture has become an important feature of modern concrete[1].Recycled coarse aggregate self-compacting concrete（RCASCC）is a kind of recycled coarse aggregate（RCA）with 4.75mm to 16 mm diameter,which is processed by crushing,cleaning and sieving of solid waste from construction,and is configurated into concrete with excellent performance and no vibration[2].Fly Ash（FA）and Ground Slag（GS）are two typical mineral admixtures of pozzolanic ash,both of which are collected and processed from industrial waste residue.They can also reduce energy consumption while saving cement costs and play a role in solid waste reuse and environmental protection[3].With the rapid development of modern industry and construction industry,environmental pollution and natural aggregate depletion are becoming more and more serious.In order to solve this problem,the RCASCC technology with mineral admixtures came into being,and has been studied in various countries in the world,and has gradually been widely used.At present,it has become one of the hotspots in the development of concrete materials.In order to further promote the RCASCC technology with mineral admixtures and expand the application scope of RCASCC technology with mineral admixtures,this paper studies the working performance and mechanical properties of RCASCC cubic blocks with mineral admixtures and the flexural properties of simply supported beams[4].1.In this paper,FA,GS and RCA in Urumqi are used to make concrete blocks.On the basis of 50%RCA substitution rate,FA and GS were mixed with 20%,30%and 40%cement substitution rate separately,and on the basis of 30%cement substitution rate,FA and GS were mixed with 7:3,3:7,5:5,6:4 and 4:6 respectively.The mix ratio of RCASCC is designed,and the mix ratio is optimized properly by working performance test,so that the working performance of RCASCC can meet the working performance requirements of self-compacting concrete.2.Compressive strength and splitting tensile strength of concrete specimens were tested in 4 curing ages of 7,14,28 and 56 days.The effects of different mix ratios on the working performance and mechanical properties of concrete were compared and analyzed,and the conclusions were as follows:（1）The compressive strength and splitting tensile strength of RCAC specimens mixed with FA and GS can maintain a steady growth rate during the four curing ages when mineral admixtures are mixed with 30%cement replacement rate.（2）On the basis of 30%cement substitution rate,FA and GS are mixed at a ratio of 6:4,which can give full play to their material properties and chemical properties,and make RCASCC with mineral admixtures show better mechanical properties.3.The flexural properties of RCASCC beams and SCC beams doped with FA and GS at the ratio of 6:4 are tested.The differences between RCASCC beams and SCC beams are studied.The following conclusions are drawn:（1）The theoretical bearing capacity values of RCASCC beams and SCC beams are lower than the experimental bearing capacity values,and the theoretical bearing capacity values of RCASCC beams are similar,but the experimental bearing capacity values of RCASCC beams are slightly higher than that of SCC beams.（2）The longitudinal stress-strain curves of RCASCC and SCC flexural specimens are basically the same,and they all go through three stages in the process of loading,namely,the pre-cracking stage of concrete,the working stage with cracks and the failure stage.Both RCASCC and SCC simply supported beams satisfy the assumption of flat section.（3）The load-mid-span deflection curves of the two groups of flexural members are basically the same before the steel bar yields.After the steel bar yields,the stiffness of RCASCC and SCC beams decreases rapidly.Until the RCASCC beams are damaged,the stiffness is still slightly higher than that of SCC beams.This shows that RCASCC beams are better than SCC beams in ductility before and after steel bars reach yield load. |
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