The Effect of Preconditioning Temperature on Gas Permeability of Alkali-Activated Concretes

Abstract

Alkali-activated materials (AAMs) are a group of environmentally friendly binders considered alternatives to conventional cementitious binders. They utilise industrial wastes such as slag and fly ash to reduce cement production and related CO2 emissions. Despite the strong interest of researchers, the application of alkali-activated concrete (AAC) in constructions is still very limited. Given the difference in the process of producing the AAC and ordinary Portland cement concrete (OPCC), some of the testing methods need to be adjusted to a new type of binder. The increased sensitivity of AAM to high temperatures leads to discussions on the results achieved in the gas permeability tests that require the samples to be dried first. In this paper, the influence of drying temperature applied to the samples on the gas permeability will be presented. The binders’ precursors are blends of fly ash (FA) and ground granulated blast furnace slag (GGBFS) in slag proportions of 5%, 20%, and 35%, expressed by the mass of FA. Materials are denoted AAC5, AAC20, and AAC35, respectively. Measurements of the gas permeability of concretes were conducted by the RILEM–CEMBUREAU method, with lab adaptation for gas flow measurements. The comparison of results obtained shows the increase in gas permeability values with the temperature. However, the corresponding effect of temperature on permeability is driven by, on the one hand, the binder composition, and on the other hand, the aggregate’s nature.

Keywords

• gas permeability
• geopolymer concrete
• temperature impact
• drying