Study On Effect And Mechanism Of Volcanic Ash Modified Slaked Lime Cememtitious Material

Traditional lime mortar is a commonly used cementing material in ancient buildings,but its use is limited due to its slow curing speed,large dry shrinkage,low initial strength and poor water resistance.in this paper,three common pozzolanic materials(diatomite,silica fume and fly ash)and nano-silica are added to slaked lime for modification,and through tests of basic properties(curing time,volume shrinkage,water absorption,etc.),mechanical properties(deformation strength and compressive strength)and durability(water resistance,freeze-thaw resistance,salt tolerance)to obtain the best modified material formulation.Simultaneously,the modified materials were tested for composition and morphology to study the modification mechanism by using XRD,FTIR,TG,SEM,etc.The results show that:(1)When the addition amount of diatomite is less than 15wt.%,silica fume is 15%-20wt.%,and fly ash is about 20wt.%,the effect of each modified cementitious material is the best.It mainly produces hydrated calcium silicate(CSH)particles of different morphological sizes,such as needles and rods,by reacting with volcanic ash of slaked lime to improve the internal structure and composition of the mortar,thereby improving the performance of the mortar cementing material.(2)Each modified cementing material can improve the performance of the mortar.When the ratio of the cementing material to sand is 1:3,the mortar sample has the best use effect.(3)When the nano-SiO2 and pozzolanic materials were adsorbed according to 1:3,the adsorption amount was the largest,and the adsorption effects of the volcanic ash materials were as follows:the best silica fume,followed by diatomaceous earth and the worst of fly ash.(4)The composite modification of slaked lime with nano-SiO2 and pozzolanic materials can further improve the performance of mortar cementitious materials,which mainly reduces the porosity of the slurry and further CSH in the system by filling and further promoting the pozzolanic reaction.Generated to achieve the effect of further modification.