Study On The Equal Strength Mechanism And Early Crack Resistance Of High-volume Fly Ash Mortar

As a kind of industrial waste,the large amount of fly ash discharged has caused tremendous pressure on the environment,while fly ash concrete can consume a lot of fly ash,so as to solve the problem of fly ash on environmental pollution and ecological damage.In addition,after the replacement of cement,fly ash can reduce the hydration heat of concrete,improve its crack resistance and long-term mechanical properties,and can reduce the eost.However,this also makes the early strength of eonerete low,which limits the popularity of fly ash concrete,especially the large amount of fly ash concrete in the application of engineering.This paper is devoted to exploring the mix design method and mechanical properties of high-volume fly ash concrete.The influence of coarse aggregate was excluded and took the mechanism of equal strength of mortar as object.In the study,the total amount of cementing materials remains unchanged.In the substitution level of fly ash is 0,30%and 50%,three equal strength mixing ratios of 60MPa strength grade are obtained by changing the water-binder ratio(0.31-0.41)and adding an activator.Similarly,three equal strength mixing ratios of 90MPa are achieved by changing the water-binder ratio(0.16-0.24)and adding an activator.Taking the two equal strength groups as research objects,the splitting tensile strength and bending strength of mortar are studied,and the equal strength mechanism of mortar is analyzed from the microstructure by combining SEM and pore structure test.At last,the difference of mortar crack resistance in early stage under the same strong condition is studied through the mechanical properties test of adiabatic temperature rise and dry shrinkage.The results show that under the same compressive strength,the error range of bending strength and splitting tensile strength of mortar with different mixing ratio is within 15%.The addition of fly ash increases the porosity of mortar,but the pore diameter is refined,and the addition of activator plays a significant role in improving the pore structure of mortar.In this paper,new explorations have been made in the design of mixing ratio,mechanical properties and early crack resistance of fly ash mortar with large content,which has accumulated certain achievements for the application of fly ash mortar with large content.