Study On Properties And Microstructure Of Hydraulic Concrete Based On 0 ~ 80μm Granite Powder Content

Granite powder is an unavoidable powdery waste that is unavoidably produced during the cutting and polishing of granite.It is estimated that more than 10 million tons of waste granite powder are generated each year.The massive accumulation of granite powder is likely to cause serious pollution to air,water and land,and it is a waste of granite resources.In order to solve the problems of environmental pollution and waste of resources caused by the accumulation of granite powder,many scholars have used granite powder to replace some cement to prepare ordinary concrete,and found that the appropriate amount of granite powder can improve many properties of the concrete,especially the durability.Therefore,in view of the characteristics that granite powder can significantly improve the durability of concrete,this article uses granite powder to replace part of cement to prepare hydraulic concrete,which not only realizes the resource utilization of waste granite powder,reduces the cost of hydraulic concrete,but also improves the performance of concrete helps to extend the useful life of water conservancy projects,and has significant economic,ecological and social benefits.Earlier,the research group conducted a systematic study on the use of granite stone powder from 0 ~ 150μm,and found in the study of the effect of fineness of granite stone powder on concrete properties that the finer the granite stone powder,the better the performance of concrete.Therefore,in this study,without using grinding equipment and taking into account the sieving balance of granite stone powder,a finer 0 ~ 80μm granite stone powder was selected to replace part of the cement by incorporation,and the content of granite stone powder was studied.The effect on the hydraulic concrete’s working performance,mechanical properties,and durability.The changes in microscopic pore structure and hydration products of the hydraulic concrete were analyzed by mercury intrusion method(MIP)and X-ray diffraction(XRD).Research results show that:(1)With the increase of the content of granite stone powder,the slump of hydraulic concrete gradually increases,but the increase rate gradually decreases.When the content of granite stone powder is small,the cohesion and water retention are not obvious changes,when the content of the internal content reaches 30%,both the cohesiveness and water retention become worse.(2)The compressive strength and flexural strength of hydraulic concrete at different ages increase first and then decrease with the increase of the content of granite powder.When the content of granite powder is 7.5%,the compressive strength and flexural strength are the highest.Granite powder can increase the early strength of concrete significantly,but the degree of improvement of the later strength is lower.(3)The four types of durability,impermeability,frost resistance,carbonization resistance,and chloride ion corrosion resistance,all increase first and then decrease with the increase of the amount of granite powder.The durability of hydraulic concrete is the strongest when the content of granite powder is 7.5%.However,granite powder has different degrees of improvement in different durability indicators,and the effect of improving the permeability resistance is the best,followed by the resistance to chloride ion permeability,and the improvement effect of the resistance to freezing and carbonization is slightly weaker.(4)A small amount of granite powder can reduce the porosity and specific pore volume of hydraulic concrete,optimize the micro-pore size distribution,and make the hydraulic concrete denser.In addition,the addition of granite stone powder does not change the crystal phase of the cement hardened slurry the type of hydration products,but will change the content of hydration products such as C-S-H,CH,ettringite which affect the performance of concrete.Based on the above test results,it was finally determined that when using 0 ~ 80μm granite stone powder instead of cement,the optimal blending amount of granite stone powder to improve the performance of hydraulic concrete is about 7.5%,and without reducing the performance of hydraulic concrete,the maximum amount of granite powder is about 15%.