Experimental Study On The Influence Of Manufacture Sand Characteristics On The Properties Of Cement-based Materials

With the rapid development of infrastructure construction and the strengthening of environmental protection,natural sand resources are increasingly scarce,and the use of manufactured sand has become an inevitable trend.However,manufactured sand is significantly different from natural sand in terms of grain shape,gradation,and particle content below 0.075 mm.Therefore,it has important practical value and theoretical significance to carry out research on the influence of the above characteristics of machine-made sand on concrete performance and its action mechanism.Frist,under the condition that the gradation of manufactured sand remained unchanged,the fluidity,flexural strength,compressive strength and pore structure characteristics of cement sand mortars were tested when the content of the combined particle size of the flake particles in the manufactured sand is 10 %,20 %,and 30 %,and the particle size is 1.18 to2.36 mm,2.36 to 4.75 mm,and 4.75 to 9.5 mm,the single flake particle size is 10%.The experimental results show that with the increase of the particle size of the flake particles,the porosity of the manufactured sand increases,the porosity of the prepared cement mortar increases,and the number of harmful pores increases,which results in fluidity,flexural and compressive strength of cement mortar reduce obviously,when the content of flake particles in manufactured sand is increased or the content of flake particles is 10 %.Grey correlation analysis shows that the content of flake particles is the most critical factor affecting cement mortar,and the single particle size of 4.75 ～ 9.5mm is the second factor affecting cement mortar.In order to ensure the performance of cement sand,the total content of flake particles in the manufactured sand and the content of 4.75 ～ 9.5mm flake particles should be strictly controlled.Secondly,the influence of manufactured sand particle gradation on the fluidity,flexural and compressive strength,and pore structure characteristics of cement mortar is studied,and the manufactured sand particle gradation on concrete work performance,compressive strength,splitting tensile strength,and The influence of chloride ion permeability and microscopic pore structure.The results of the study show that the existing requirements for cumulative sieving percentages is met,but the concrete performance of manufactured sand samples with large differences in the percentage of fractional sieve residue differs significantly.The existing cumulative sieving percentage control method cannot characterize the grading of manufactured sand pros or cons and their changing trends.In contrast,the change of the fractional sieve residue has a more obvious influence on the performance of concrete,and the percentage of sieving residual can more clearly express the proportion of each particle size of manufactured sand,so it is advisable to use the percentage of fractional sieve residue to characterize and limit the particle grading of manufactured sand.Finally,for the high-absorptive granite porphyry powder,on the one hand,the influence of the content of the high-absorptive granite porphyry powder on the fluidity,flexural and compressive strength and microstructure of cement mortar is studied;on the other hand,The effect of the content of high-adsorbing granite porphyry powder on concrete working performance,early cracking performance,early shrinkage performance,compressive strength,resistance to chloride ion penetration,resistance to sulfate attack and microstructure performance was studied.The research results show,the high-absorption stone powder has the effects of "surface area","filling","nucleation","chemistry","dilution","free" and "interface defects" in cement-based materials,in front of the stone powder content in the best threshold,the granite porphyry powder is mainly used for "filling",which is beneficial to the development of the macro properties and microstructure of cement mortar and concrete;When the stone powder content exceeds the optimal critical value,the influence of granite-porphyry rock powder on concrete performance tends to be "diversified",and the influence of stone powder content on the macroscopic properties and microstructure of concrete is more complex and cannot be directly explained.