Acid resistance of alkali-activated materials: recent advances and research needs

Abstract

Cementitious materials are frequently applied in environments in which they are exposed to acid attack, e.g., in sewer systems, biogas plants, and agricultural/food-related industries. Alkali-activated materials (AAMs) have repeatedly been shown to exhibit a remarkably high resistance against attack by organic and inorganic acids and, thus, are promising candidates for the construction and the repair of acid-exposed structures. However, the reaction mechanisms and processes affecting the acid resistance of AAMs have just recently begun to be understood in more detail. The present contribution synthesises these advances and outlines potentially fruitful avenues of research. The interaction between AAMs and acids proceeds in a multistep process wherein different aspects of deterioration extend to different depths, complicating the overall determination of acid resistance. Partly due to this indistinct definition of the ‘depth of corrosion’, the effects of the composition of AAMs on their acid resistance cannot be unambiguously identified to date. Important parallels exist between the deterioration of low-Ca AAMs and the weathering/corrosion of minerals and glasses (dissolution-reprecipitation mechanism). Additional research requirements relate to the deterioration mechanism of high-Ca AAMs; how the character of the corroded layer influences the rate of deterioration; the effects of shrinkage and the bond between AAMs and substrates.

"An In-situ Method for Assessing the Kinetics of Acid Attack on Iron-rich Alkali-activated Materials"

“…In several applications and environments, concrete and cementitious materials are exposed to acidic solutions. For example, sulfuric acid attack is the main cause of structural material degradation in sewer pipes carrying waste water, acid mine drainage areas, biogas plants, and power plant cooling towers (Gluth et al 2022). In this paper, the resistance of iron-rich AAMs to the sulfuric acid attack was investigated.…”