Study On Material Design And Properties Of Manufactured Sand High Performance Concrete

With the rapid development of China’s infrastructure construction,in the construction of various difficult projects,the requirements for the working performance and durability of concrete are higher and higher,and the high-performance concrete with excellent comprehensive performance has received more attention.For sustainable development,it has become a development trend to use manufactured sand instead of natural sand to prepare concrete.At present,the mix proportion design method of high-performance concrete mainly adopts trial and error method,which is cumbersome and time-consuming.To solve this problem,the method of gradation optimization and volume analysis is used to prepare machine-made sand highperformance concrete.The material composition of C30,C40 and C50 strength grade machine-made sand high-performance concrete is optimized from the three aspects of coarse aggregate gradation,sand rate and mineral admixture content,and its influence on the working performance,mechanical properties and durability of high-performance concrete is studied.The influence of stone powder content on the working performance and mechanical properties of machine-made sand high-performance concrete is studied by replacing cementitious materials with stone powder,and the throwing and filling aggregate process is applied to machine-made sand high-performance concrete.The research results are as follows:(1)Based on the gradation optimization method,the optimal gradation of coarse aggregate is 20 ～ 31.5mm: 10 ～ 20mm: 5 ～ 10 mm = 2:6:2.With the increase of sand ratio,the working performance and compressive strength of machine-made sand highperformance concrete first increase and then decrease.The optimum sand ratio of C30 and C40 machine-made sand high-performance concrete is 45%,while that of C50machine-made sand high-performance concrete is 40%.(2)When the content of fly ash and mineral powder is the same,and the content of fly ash is 25%,20% and 15% respectively,the working performance and mechanical properties of C30,C40 and C50 machine-made sand high-performance concrete reach the best.With the increase of the replacement amount of stone powder for cementitious materials,the compressive strength of C30 and C40 machine-made sand highperformance concrete gradually decreases,while the compressive strength of C50 concrete first increases and then decreases.When the content of stone powder is 3%,the compressive strength of each age reaches the maximum.The working performance of machine-made sand high performance concrete increases first and then decreases with the increase of stone powder substitution.(3)The process of throwing and filling aggregate improves the compressive strength of machine-made sand high-performance concrete.With the increase of coarse aggregate dumping rate,the compressive strength of C50 machine-made sand highperformance concrete first increases and then decreases.When the dumping rate is 15%,the compressive strength reaches the maximum.(4)When the content of fly ash and mineral powder is 15%,the chloride ion penetration resistance and sulfate corrosion resistance of C50 manufactured sand highperformance concrete are the best.The increase of the content of fly ash and mineral powder will increase the proportion of harmless holes of 0-20 nm and reduce the proportion of harmful holes of 100-200 nm in the concrete paste.