Study On The Positive Coupling Effect Of Zeolite Powder And Fly Ash Composite On The Performance Of Aeolian Sand Concrete

This thesis mainly takes zeolite powder and fly ash as main raw materials to study the influence and shortcomings of single-doped zeolite powder and fly ash on the performance of aeolian sand concrete,and further to study the positive coupling function of zeolite powder and fly ash in aeolian sand concrete.Among them,aeolian sand is prepared by replacing fine aggregates in concrete with 100%replacement rate.However,mechanical properties and durability of aeolian sand concrete have some shortcomings.Therefore,zeolite powder and fly ash are added into aeolian sand concrete separately,and the replacement rates of zeolite powder and fly ash are 0%,5%,10%,15%,20%and 0%,10%,15%,20%and 25%respectively.Subsequently,cubic compressive strength test and splitting tensile strength test are carried out on the specimens,and their macro-mechanical and micro-mechanical properties are compared to obtain the optimum content of the two.By mixing zeolite powder with fly ash according to the optimum dosage,the prepared specimens are tested for cubic compressive strength,splitting tensile strength and freeze-thaw cycle durability,and then supplemented by NMR test,TG-DTA test and SEM test.Combined with grey theory and numerical model,the mechanical properties and durability of aeolian sand concrete are comprehensively analyzed by mixing zeolite powder with fly ash.The main conclusions are as follows:（1）The compressive strength and splitting tensile strength of aeolian sand concrete with100%aeolian sand content are significantly lower than that of ordinary concrete,and the improvement effect of compressive strength and splitting tensile strength of aeolian sand concrete with zeolite powder and fly ash is not obvious.When fly ash and zeolite powder are mixed,the compressive strength and splitting tensile strength of aeolian sand concrete are improved better.Combining with SEM test,NMR test and TG-DTA test,it is shown that zeolite powder and fly ash play a positive coupling role,which improves the internal micro-structure of aeolian sand concrete and promotes the internal compactness of aeolian sand concrete.（2）The porosity of aeolian sand concrete is lower than that of ordinary concrete at all ages.When zeolite powder and fly ash are added,the best group of them is ASC-10-0 and ASC-0-20,respectively.However,it can also be seen from the best group that the porosity of aeolian sand concrete added with zeolite powder and fly ash is not significantly improved compared with that of aeolian sand concrete,In addition,ASC-10-0 group aeolian sand concrete has a significant decline in the hydration age of 3-14 days,but the rate of decline has slowed down in 28-90 days,while ASC-10-0 group of fly ash concrete of ASC-10-20group has no obvious effect on the improvement of porosity,and ASC-10-0 group of aeolian sand concrete has a slow decline in the hydration age of 3-14 days,but the rate of decline has slightly increased in 28-90 days;The spectral area of ASC-10-20 T₂ is the lowest and closest to that of ordinary concrete;At the same time,field emission scanning electron microscopy（SEM）and differential thermal gra-vimetry（TG-DTA）test correlation analysis showed that the relative content of Ca（OH）₂ in ASC-10-20 group was the lowest,and the relative content of C-S-H gel was the highest;The comprehensive analysis shows that the mechanical performance system of aeolian sand concrete mixed with zeolite powder and fly ash is better.（3）The compressive strength prediction model is established by combining the grey correlation analysis with the ANN-MEA model,and the grey correlation analysis shows that0-0.01μm,0.01-0.1μm The proportion of m pore diameter and the saturation of bound fluid are the main factors affecting the compressive strength of concrete;The regression result of the training set of the model is R²=0.920,MSE=2.2%,and the regression result of the test set is R²=0.956,MSE=2.7%,with good accuracy.（4）The durability of aeolian sand concrete is extremely poor at high salt（NaCl）concentration.When zeolite powder and fly ash are mixed only,the durability improvement effect of aeolian sand concrete is not obvious.When zeolite powder and fly ash are mixed together,the durability of aeolian sand concrete is significantly improved.Combined with Weibull distribution,it can be seen that when aeolian sand and fly ash are mixed,the predicted life of aeolian sand concrete is close to that of common concrete,which indicates that the combination of zeolite powder and fly ash plays a positive coupling role,thus greatly improving the freezing and corrosion resistance of concrete.