Study On Mechanical Properties And Micro Analysis Of Aeolian Sand Self Compacting Concrete

With the coming of 2020,China will build a well-off society in an all-round way,complete the first centenary goal,and start to build a socialist modernization.As one of the indispensable materials in the modernization project,the output of concrete will continue to increase,so the demand for sand and stone aggregate will increase day by day.China is one of the countries with serious desertification.The desertification area accounts for about 18.1% of the land area.There is abundant desert sand in the desert.If it can replace part of river sand,the use of self compacting concrete in practical projects can not only turn waste into treasure,but also protect the environment,save resources,reflect the concept of national green development and realize green production.Therefore,aeolian sand self compacting concrete(aeolian sand self compacting Concrete),the optimum mix proportion,basic mechanical properties and microstructure are studied by means of orthogonal test,single factor test and micro test analysis.The specific research contents are as follows: the replacement rate of aeolian sand,water cement ratio,cement replacement rate of fly ash,aeolian sand and its mixing and mixing sand ratio are considered by orthogonal test,and five factors of aeolian sand self compaction are also considered Based on the influence of mechanical properties and working performance of concrete and the influence order of various factors,the best mix proportion is finally determined;based on the best mix proportion,the single factor test is designed,and the influence rule of three factors with greater influence on the mechanical and working performance of aeolian sand self compacting concrete is considered separately;finally,the micro analysis is carried out after the concrete fragments of single factor test are sampled,and the analysis results are analyzed Compared with the macro mechanical index,the results show that:(1)Using aeolian sand to replace part of fine aggregate can prepare self compacting concrete whose mechanical properties and working performance meet the requirements of the specification.Under the condition of 28 d age,the influence of various factors on the compressive strength of aeolian sand self compacting concrete can be sorted from large to small: particle gradation > aeolian sand replacement rate > fly ash replacement rate > sand rate > water cement ratio;the order of influence on working performance is Water cement ratio > cement replacement ratio of fly ash > sand ratio > particle size distribution > sand replacement ratio of aeolian sand.In order to ensure better strength and durability,it is suggested that the replacement rate of aeolian sand should not exceed 30%,the replacement rate of fly ash should not exceed 40%,and the increase and decrease of particles in the range of 0.075-0.15 mm and 0.15-0.3mm of graded aeolian sand should not exceed 30%.(2)The failure process and failure mode of aeolian sand self compacting concrete are similar to that of ordinary concrete.Adding appropriate aeolian sand can reduce the plasticity of self compacting concrete.With the increase of replacement rate of aeolian sand and coarse particles in grading,the basic mechanical properties of aeolian sand self compacting concrete show a trend of increasing first and then decreasing,and the working performance becomes worse.With the increase of the replacement rate of fly ash for cement,the basic mechanical properties of concrete show a decreasing trend,and the working performance becomes better.(3)the filling effect of aeolian sand.The main body aeolian sand particles are the filling of pores in the interfacial transition zone and the filling of pores in the cement matrix.The activation effect is that the aeolian sand contains a large amount of acidic oxides Si O2 and Al2O3 active substances,while promoting hydration of the hydration products Ca(OH)2 of the cement,and promoting the formation of higher strength C-S-H gels and C4A4 S hydrates.It not only improves the compactness of cement matrix,but also improves the bond strength of the interface between cement matrix and aggregate.(4)The macro mechanical index and micro index of aeolian sand self compacting concrete can be used to establish a binary quadratic curve model.The parameters a0 ～ a5 in the curve model are 73.199,2.805,-7.528,0.105,0.501,0.457,respectively.