A STUDY ON SURFACE ACTIVATION AND QUICK-SETTING CHARACTERISTICS OF BLAST FURNACE SLAG

This study investigated on the early hydration and physical characteristics of blast furnace slag through pH variation. NaOH was used as a pH regulator. The pH values applied to the experiments were, 12.0 and 13.0 which are the pH values of OPC, and type 3 of pH 14.0 which is a strong alkali condition. A paste and mortar method was used to test blast furnace slag with and without 2 wt% of gypsum. It was found that CAH and CSH phases were formed as key hydrates during the early hydration of blast furnace slag, and ettringites were produced extra during the early hydration of blast furnace slag containing 2 wt% of gypsum. Furthermore, the hydration of blast furnace slag and blast furnace slag containing 2 wt% of gypsum was the most active at pH 14, and the process of early hydration was faster then OPC. At pH 14, the compressive strength of blast furnace slag on day 1 increased by approximately 30 % compared to OPC, and blast furnace slag containing 2 wt% of gypsum also increased by approximately 40% compared to OPC.