Deterioration analysis and expansion behavior prediction of electric arc furnace slag as fine aggregate in mortar

Electric arc furnace slag (EAFS) possesses potential expansiveness, which may cause durability issues when replacing natural fine aggregates in mortar. In this study, mortar specimens containing EAFS from two different sources were prepared, and subjected to curing for 730 days under standard conditions. The aim was to investigate the long-term deterioration behavior and mechanisms of mortar containing EAFS as fine aggregate. Additionally, to expedite the mortar deterioration process and predict the expansion of EAFS mortar bars, an accelerated environment was proposed and validated as a feasible method. The deterioration of EAFS mortar was mainly manifested as volume expansion and surface defects, and the influence of EAFS-2 on mortar was greater than that of EAFS-1. Compared with NA mortar bars, the expansion in the volume of the two EAFS mortar bars was approximately 1.59 and 2.11 times, respectively. The volume change could be categorized into three stages: 0–30 days (cement expansion stage), 30–180 days (co-expansion stage), and beyond 180 days (EAFS sustained expansion stage). The hydration behavior of EAFS was found to primarily affect the development of the co-expansion (stage two) and the EAFS sustained expansion (stage three). The accelerated environment could condense the expansion process of EAFS mortar bars into stages: 0–1 day, 1–7 days, and 7 days onwards. Furthermore, the testing outcomes could provide more accurate predictions for the expansion behavior of EAFS mortar bars in the 30–180 day period.