Studying the strength and drying shrinkage of high strength mortar contaminated with different contents of sulfate

Sulfates are among the aggressive agents that attack concrete and mortar and cause partial or complete damage as a result of the formation of large-sized compounds that exert internal pressure that ultimately leads to concrete failure. On the other hand, dry shrinkage is one of the problems facing concrete, which causes cracking when appropriate conditions are provided, such as hot and dry weather. Therefore, this research aims to study the effect of adding different levels of sulfate (ranged from 0% to 0.9% for sand) on the strength and drying shrinkage of a high-strength mortar. Compressive and flexural strength, drying shrinkage and crack width were investigated during the ages of 7, 28, 60 and 90 days. The results showed that the effect of sulfate on strength was more obvious at the later ages (60 and 90 days), as it increased with increasing sulfate content. On the other hand, at the early ages, the shrinkage of drying was compensated by the expansion that occurred as a result of the sulfate reaction, but at the later ages, the 0.9% SO3 mixture recorded a strain of 590 compared to 380 for the reference mixture. Furthermore, the crack width increased with the increase of SO3 content.