Alkali-Activated Slag Paste with Different Mixing Water: A Comparison Study of Early-Age Paste Using Electrical Resistivity

This paper reports the electrical resistivity measurements on KOH-activated ground-granulated blast-furnace slag, which was mixed with deionized water or natural seawater at three different activator-to-binder ratios (0.4, 0.45, and 0.5). Compressive strength and X-ray diffraction analyses were performed on the samples after the measurement. The type of mixing water did not affect the setting time of samples, whereas the setting time was delayed with an increase in activator-to-binder (a/b) ratio. Regardless of the mixing water type, the increasing ratio of electrical resistivity between a/b 0.45 and 0.5 was larger than that between a/b 0.4 and 0.45. For the same a/b ratio, the pastes mixed with seawater produced higher electrical resistivity and early strength than those with deionized water. The increase in the electrical resistivity in seawater-mixed pastes could be attributed to the formation of Cl-bearing phases such as Cl-hydrocalumite, AlOCl, and aluminum chloride hydrate. It is believed that the reaction products in seawater-mixed samples were helpful in preventing water percolation, and thus, the electrical resistivity increased compared with the deionized water-mixed sample.