Study On The Fatigue Damage Degradation Of Mortar And Concrete Of Metakaolin-based Geopolymer

Geopolymer,as a new type of cementitious material,has the advantages of environmental protection.It has excellent performance in early strength,corrosion resistance and high temperature resistance.Its production energy consumption and carbon dioxide emission are far lower than Portland cement.During the working period,bridges,dams,sidewalks and other buildings all bear the repeated load,so it is necessary to study the degradation of mechanical properties of geopolymer mortar and concrete under the fatigue load.In this paper,the degradation of geopolymer mortar and concrete under fatigue load was studied.The main work is as follows:(1)The effects of different alkali equivalent and water-solid ratio on the damage characteristics of geopolymer mortar were studied.The deterioration differences of relative dynamic modulus of elasticity,compressive strength and micro morphology of specimens under different mix ratio,fatigue stress ratio and fatigue loading times were analyzed.The results show that under the same fatigue stress ratio,with the increase of alkali equivalent,the relative dynamic elastic modulus of the specimen decreases at first fast and then slow,the compressive strength increases first and then decreases,and the increase and decrease amplitude are gradually gentle;Under different water-solid ratio,when the water-solid ratio is low(0.6,0.65),the relative dynamic elastic modulus and compressive strength of the specimens increase first and then decrease,and the deterioration difference between different water-solid ratio is more obvious.When the water solid ratio is high(0.7,0.75,0.8),the deterioration difference of compressive strength tends to be stable.(2)The damage characteristics of polymer concrete in metakaolin base under different fatigue stress ratio and fatigue loading times were studied,including the relative dynamic elastic modulus,compressive strength,peak strain and stress-strain curve after fatigue loading.The test results show that under the same fatigue stress ratio,the decreasing rate of the relative dynamic modulus of elasticity decreases gradually,With the increase of fatigue loading times,the compressive strength first increases and then decreases,the peak strain increases,and the larger the fatigue stress ratio is,the larger the change range of corresponding test curve is.To some extent,increasing the fatigue stress ratio accelerates the damage process.(3)The difference of damage and degradation of mortar and concrete specimens prepared by geopolymer slurry with the same mix ratio under fatigue load is discussed.Without fatigue loading,there is no obvious difference in compressive strength between GPC and mortar.With the increase of fatigue loading times,the decline rate of compressive strength of GPC specimens is relatively slow,which shows that fatigue load has more significant impact on mortar specimens.