Study On The Impacts Of Weight Fractions Of Limestone Powder On The Properties Of Concrete

Large quantities of limestone powder are generated which polluted the environment and made waste of natural resource. Otherwise, definite mass of limestone flour are mingled with limestone spall and machine-made sand during production. The effects of this limestone flour on concrete are seldom realized and little approach is finished. The settlements of these problems will bring good economic and environmental benefits.This paper researched the effacement and improvement of limestone flour as concrete admixtures on workability, mechanical property durability , dry-shinkage and creep of concrete. The studies show that :(1) Limestone flour as admixture can improve workability of concrete.(2) The degree of influence of limestone powder on concrete is different according to the age of concrete .While additional mixing quantity is getting 20%, the growth of early stage strength is obvious: 3d,7d and 28d compression strength of concrete was improved 30.4%,19.1%,15.7% respectively.(3) The effect of limestone power contained in concrete on anti-flex strength,compression modulus elasticity,elastic modulus of bending is change according to the content of powder. And this influence is same as it to compression strength. When the additional mixing quantity is below 20%, The performance of concrete was improve along with the increase of the powder .When the additional mixing quantity is higher than 20% of cement's , The performance of concrete become worse when the content get higher. When replacing cement with limestone flour, the performance of the concrete become worse along with the content become higher.(4) The effect of limestone powder on durability of concrete is similar as it on mechanical properties of concrete.(5) The influence of limestone flour mixed into concrete on the dry shrink is different according to the age of the concrete , this effects is accomplish by the acceleration effect combined with stuff effect of the powder. When the additional mixing quantity is below 15%, the acceleration effect play a significant role, and when the content become higher, it recoup the shrinkage of concrete. When replacing cement with limestone flour, the dry shrink of concrete become greater along with the content become higher. (6) While additional mixing quantity is getting 30% of cement's, it can recoup the creep of the concrete. This effect change with time : 30d,90d and 180d creep of concrete is 92%,86% and 89% of that without powder, we could conclude that ,it can recoup the creep with time increasing.