Compressive strength and hydration process of wet-grinded granulated blast-furnace slag activated by sodium sulfate and sodium carbonate

Abstract

In this study, the super-fine ground granulated blast furnace slag was obtained by wet grinding (i.e. WGBBS), and an attempt to activate the super-fine ground granulated blast furnace slag by sodium sulfate (SS) and sodium carbonate (SC) was made. SS/SC-activated WGGBS samples were prepared and cured at the room temperature. The compressive strength at the age of 3 d, 7 d, 28 d, and 56 d was tested. Hydration heat was assessed, and micro structure and hydrates were also characterized with XRD, TG-DTG, SEM-EDS, and NMR; the pore structure was assessed with MIP. The results showed that SS and SC efficiently activated the hydration of WGGBS with D50 = 3.87 μm at the room temperature, and such high activating efficiency of SS and SC under room temperature was seldom reported in the literature. The mechanism behind was mainly because of the super-fine particles of slag with greater amounts of hydration points, which were produced in the process of wet grinding. Difference in activating efficiency between SS and SC was mainly because the anionic groups acted as different roles in hydration process: SS could induce the formation of ettringite while SC could induce the formation of calcite. Such results were expected to provide guidance on designing weak base-activated slag system.