Experimental Study on the Effects of Carbonated Steel Slag Fine Aggregate on the Expansion Rate, Mechanical Properties and Carbonation Depth of Mortar

Abstract

Steel slag is the main by-product of the steel industry and can be used to produce steel slag fine aggregate (SSFA). SSFA can be used as a fine aggregate in mortar or concrete. However, SSFA contains f-CaO, which is the main reason for the expansion damage of mortar and concrete. In this study, the carbonation treatment of SSFA was adopted to reduce the f-CaO content; the influence of the carbonation time on the content of f-CaO in the SSFA was studied; and the effects of the carbonated SSFA replacement ratio on the expansion rate, mechanical properties and carbonation depth of mortar were investigated through tests. The results showed that as the carbonation time increased, the content of f-CaO in the SSFA gradually decreased. Compared to the mortar specimens with carbonated SSFA, the specimens with uncarbonated SSFA showed faster and more severe damage and a higher expansion rate. When the replacement ratio of carbonated SSFA was less than 45%, the carbonated SSFA had an inhibitory effect on the expansion development of the specimens. The compressive strengths of the specimens with a carbonated SSFA replacement ratio of 60% and 45% were 1.29% and 6.81% higher than those of the specimens with an uncarbonated SSFA replacement ratio of 60% and 45%, respectively. Carbonation treatment could improve the replacement ratio of SSFA while ensuring the compressive strength of specimens. Compared with mortar specimens with uncarbonated SSFA, the anti-carbonation performance of mortar specimens with carbonated SSFA was reduced.