Experimental Study On Mechanical Properties And Drying Shrinkage Of Machine-made Sand Concret

In order to ensure the reliable performance of C35 and C40 concrete,the thesis takes C35 and C40 concrete as the main object of study,The working performance,compressive strength at 7d,28 d and 60 d and 360 d drying shrinkage of C35 and C40 sand concrete are investigated by using orthogonal test,single factor test and variance analysis method to investigate the mechanical performance and drying shrinkage of C35 and C40 sand concrete with the mechanism of limestone powder in sand,and then optimize the performance of C35 and C40 sand concrete.This study was conducted to find out the actual performance and factors influencing the drying shrinkage of C35 and C40 sandcrete,to optimize the ratio of green lowcarbon C35 and C40 sandcrete,to improve the working and mechanical properties of sandcrete,to reduce the long-term drying shrinkage deformation of sandcrete in the real application,and to make it more suitable for the actual engineering construction,which is of great significance to the performance improvement and promotion of sandcrete.The main research findings are as follows:(1)The orthogonal test method was used to optimize the design of C35 and C40 mechanism sand concrete mixes,and the working performance performance and mechanical property change laws of four factors in the mechanism sand concrete mixes,namely water-cement ratio,sand rate,fly ash admixture and mineral powder admixture,under the action of three different levels,and the extreme difference analysis and analysis of variance were used to explore the influence of each factor on the working performance and mechanical property test indexes The order and significant level of the influence of each factor on the working performance and mechanical properties of the test indexes were investigated by using the extreme difference analysis and ANOVA methods,and the optimal ratio of the above four factors was obtained.(2)Based on the optimal combination of orthogonal test,the drying shrinkage performance of C35 and C40 concrete was studied,and the correlation between the drying shrinkage and the age of C35 and C40 concrete was further analyzed,and the drying shrinkage of C35 and C40 concrete was analyzed in conjunction with the actual project.The reference value of drying shrinkage rate of C35 and C40 concrete was determined.(3)The correlation between the content of stone powder in the mechanism sand and the performance of workability and mechanical properties of mechanism sand concrete was studied,and the correlation fitting equation was established,and at the same time,the test of colloidal strength ratio of limestone stone powder in mechanism sand was carried out,and the mechanism of the effect of stone powder in mechanism sand on workability and mechanical properties of concrete was further demonstrated by the combination of macroscopic test and microscopic analysis,and the reference values of maximum drying shrinkage of C35 and C40 mechanism sand concrete were determined.The optimum stone powder content for C35 and C40 concrete was determined.(4)After comprehensive analysis,it is concluded that the optimal combination of the hydraulic cement ratio 0.41,sand rate 44%,fly ash admixture 14%,mineral powder admixture28% and the optimal combination of the hydraulic cement ratio 0.33,sand rate 46%,fly ash admixture 10%,mineral powder admixture 23% for the C35 and C40 concrete is the optimal combination of the hydraulic cement ratio 0.33,sand rate 46%,fly ash admixture 10%,mineral powder admixture 23%;the optimal combination of the hydraulic cement ratio 0.33,sand rate46%,fly ash admixture 10%,mineral powder admixture 23% for the C35 and C40 concrete.Sand concrete in the practical application of the best stone powder content should be controlled at 12%,10%,respectively.