The Dynamic Elastic Modulus and Microstructure Study of High Performance Concrete in Sulfate Environment

Abstract

Aimed at determining the durability of concrete in very salty regions, this paper describes a study carried out to examine the performance of various high performance fine aggregate concrete in a sulfate environment, such as high performance concrete inside a composite additive, and Portland cement concrete, and sulfate resistant cement concrete. They experienced dry-wet cycles in sodium sulfate solutions. By examining the changes of elastic moduli and analyzing the SEM of the concrete, the test results show that the salt resistances of sulfate resistant cement concrete is no better than Portland cement concrete in the extremely aggressive dry-wet cycle environment, and high performance concrete containing a composite additive has better resistance to a sulfate environment. Besides, the composite additive can create the environment for a second hydration to reduce the amount of Ca(OH)2 inside the concrete, and build additional C-S-H gel to reform the microstructure of concrete effectively. Finally, the paper offers some advice for mixing concrete in salt regions.