Evaluating the role of feldspar on the resistivity of alkali-activated slag towards seawater attack

In this study, the effect of K-feldspar on the behavior of alkali-activated slag pastes (AAS) before and after exposure to seawater was evaluated by measuring the compressive strength and the microstructure. To achieve this objective, the mixtures were prepared upon partial replacement of ground granulated-blast furnace slag (GGBFS) with calcined and un-calcined feldspar fine particles (termed as FS and CFS) at levels ranging from 5 to 20%, by mass. Under processing conditions, the solidified specimens were immersed for 1, 7, 14, and 28 days in 100% RH at 40 ± 2 °C. After 28 days, a group of samples having the same composition were soaked in seawater solution for 1, 3, and 6 months. The new phases were evaluated using X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG), and scanning electron microscopy (SEM). The inclusion of FS and/or CFS in AAS enhances the performance of the pastes in normal and harsh conditions in relation to their reference counterparts. Among all the mixtures that were tested, alkali-activated composite comprising 15% CFS indicated more durable properties in terms of increased compressive strength and dense morphological structure after exposure to an aggressive environment.