Effect of fly ash content on waterproofness and shrinkage of concrete

Abstract

This paper aims to evaluate the effect of fly ash (FA) content on the strength and durability of cement concrete. In this experimental study, the properties tested were compressive strength (CĐCN), water resistance and shrinkage of concrete. For this purpose, a type F FA concrete mix was designed with five levels of FA replacing cement PCB40 (0%, 20%, 25, 30% and 35%). The test results showed that at 28 days, the CĐCN of the FA 20 - 35% concretes decreased compared to the 0% control sample, the concrete with FA dosage of 20% - 30% had higher water resistance than the control sample, but when it increased to 35%, the water resistance began to decrease compared to the control sample. At 56 days old, the 20% FA sample had a higher CĐCN than the control sample by about 1,5%, the remaining mixtures were slightly lower than the control sample by -1,1%, -3,3% and -6% respectively, but all FA concrete mixtures had better waterproofing ability than the control sample. Regarding shrinkage, the experimental results showed that at 28 and 56 days old, the concrete with increased FA content had a decrease in shrinkage compared to the control sample and decreased almost linearly.