DEF Resistance of Mortar Using Japanese Granulated Blast‐Furnace Slag

Abstract

Delayed Ettringite Formation (DEF) is a type of sulfate attacks in concrete that causes cracking accompanied by abnormal expansion over long periods of time. The direct factor of DEF is a crystal growth pressure of ettringite generated within hardened concrete. On the other hand, granulated blast‐furnace slag, a by‐product from the steel industry, possesses latent hydraulicity that contribute to the long‐term densification of the internal microstructure. This study investigated that the expansion behavior over time and changes in strength properties with the material age of mortars using ground granulated blast‐furnace slag powder (GGBS) and granulated blast‐furnace slag sand (BFS), under DEF‐promoted condition. For the BFS, two types were prepared from different steel mills in Japan. The GGBS and BFS were used as binder and fine aggregate, respectively. Although the mortars using the GGBS and/or BFS declined DEF‐induced expansion and improved decrease in flexural/compressive strengths due to DEF. However, when the mortars using only BFS, a degree of these effects slightly varied with the difference in the types of BFS. The mortars using GGBS and BFS in combination suppressed DEF deteriorations the greatest in the mortars, regardless of the types of BFS.