Study On Research On The Design,preparation,and Durability Damage Evolution Of Mechanized Sand Concrete

With the rapid development of infrastructure construction in China,there is an increasing demand for sand.However,natural sand resources are becoming scarce,making the use of manufactured sand an inevitable trend.The characteristics of manufactured sand,such as rock type,gradation,particle shape,and powder content,differ significantly from natural sand,which creates various problems during its usage.Therefore,it is necessary to carry out research on the design and preparation of concrete using manufactured sand,focusing on the evolution rules and mechanisms of durability performance damage of manufactured sand concrete.In this paper,based on the study of the basic characteristics of granite powder and its influence on the mechanical properties of cement mortar,the applicability of granite powder as a cementitious material was evaluated.The results showed that with an increase in grinding time,the specific surface area of granite powder increased,and the particle size decreased,indicating that grinding can increase the fineness of the powder particles.When the dosage of raw granite powder was less than 5%,the strength of the mortar was improved compared to the control group,but when the dosage exceeded 5%,the strength gradually decreased.Grey relational analysis revealed that adding 10-40 μm granite powder particles can significantly improve the strength of the mortar.To maximize the utilization of powder while ensuring the strength of the mortar,the optimal powder content should be between 5% and 10%,and the grinding time should be between 40 and 60 minutes.These research findings provide a theoretical reference for the application of granite powder as a cementitious material.Furthermore,research was conducted on the design and preparation technology of high-performance concrete using manufactured sand.Comprehensive design methods were used to optimize the mix ratio of C30,C40,C50,and C70 high-performance concrete through the combined use of chemical admixtures and mineral admixtures,and the standard mix ratios for each strength level of concrete were determined.The effects of water-to-binder ratio,sand ratio,and mineral admixtures on the workability and mechanical properties of concrete were analyzed,and an optimization design method for high-performance concrete using manufactured sand was proposed.The results showed that an appropriate water-to-binder ratio can improve the compressive strength and volume stability of concrete.Sand ratio and mineral admixtures can adjust the density of concrete to minimize the amount of cement paste used,thereby reducing water consumption and cement consumption.Finally,the effects of concrete strength grade,manufactured sand rock type,and granite powder dosage on the freeze-thaw resistance,carbonation resistance,chloride ion penetration resistance,and sulfate erosion resistance of manufactured sand concrete were studied.The results showed that,similar to ordinary concrete,the durability of manufactured sand concrete increases with an increase in strength grade.The changes in manufactured sand rock type had a slight effect on the durability performance of concrete,and the difference in impact was not significant.The durability performance of granite manufactured sand concrete was slightly better.As the dosage of granite powder increased,the air content in the granite manufactured sand concrete first decreased and then increased,and the freeze-thaw resistance,carbonation resistance,chloride ion penetration resistance,and sulfate erosion resistance of the concrete also followed a trend of increasing first and then decreasing.When the powder dosage was 5%,the minimum number of internal pores and bubbles and the most compact internal structure were observed,indicating that the durability of concrete was optimal at this point.