INFULUENCE OF ANHYDRITE AND FINENESS ON THE REACTIVITY OF LOW-BASICITY BLAST FURNACE SLAG

Abstract

This study examined changes in BFS reactivity with varying powder degree and anhydrite additions in a blast furnace cement Class B（BB）system with blast furnace slag fine powder（BFS）of lower basicity than the current system. The reactivity of the low-basicity BFS at the early 7 days of age could be improved to the same level as that of the current BFS by controlling both the fineness of the BFS and the amount of anhydrite added, as well as by increasing only the powder content of the BFS and the amount of anhydrite added. The reactivity index of BFS with low basicity was also improved to the same or higher than that of the current BB by controlling both the powder degree and the amount of anhydrite added, indicating that not only the reactivity of BFS was improved by controlling the powder degree of anhydrite and BFS, but also the reactivity of BFS was improved by adding It is suggested that this is due to the formation of ettringite（Ett）by the addition of anhydrite. The addition of anhydrite also decreased the amount of CH in the BB paste, which was presumably due to the fact that the amount of CH consumed by the BFS also increased as the amount of anhydrite was increased.