Durability of Alkali-activated Slag/Pumice Mortars in Mineral Acid Environments: Effects of Pumice Powder and Activator Type

Nowadays, one of the most desirable alternatives to cement-based composites is the alkali-activated blends which can be towards achieving more durable materials. In alkali-activated slag/pumice (AASP) mortars, ground granulated blast-furnace slag (GGBFS) could be replaced partially with Volcanic pumice powder (VPP) as a natural pozzolan; however, its performance in alkali-activated slag/pumice (AASP) mortars against mineral acid environments are currently missing in the literature. In this paper, the durability of AASP mortars containing ۰ or ۱۰% VPP activated by the combination of sodium silicate with NaOH or KOH exposed to a high concentration of sulphuric and nitric acids were investigated. In addition to flowability, capillary water absorption, and mercury intrusion porosimetry tests, deterioration due to the mineral acid attack was examined using visual condition assessment, mass loss, compressive strength change, and X-ray diffraction analysis (XRD). A comparison was also performed with ordinary Portland cement (OPC) mortar specimens as a reference mixture. It was found that the AASP mortars are more durable than a corresponding OPC mortar in terms of mass and compressive strength changes in sulphuric and nitric acid solutions. Generally, employing ۱۰% VPP exhibited no significant effect on the durability of AASP mortars against mineral acid attack. In addition, utilizing NaOH alkali activator could be a better choice in exposure to sulphuric acid, but in nitric acid solution, KOH-activated samples revealed better durability in terms of mass and compressive strength change.

Keywords:

Alkali activated blends , sulphuric acid , Nitric acid , Volcanic pumice powder , Slag , XRD