Microstructure and durability of alkali-activated materials as key parameters for standardization

Abstract

Alkali-activated concrete (AAC) has been commercialized as a low-CO2 construction material, but its adoption still faces several challenges, including standardization, lack of a dedicated supply chain, limited service track record, and the question of whether laboratory durability testing can predict service life. This paper outlines how using different precursors leads to the formation of different AAC phase assemblages, and how AAC can be recognized in standards using a performance-based approach independent of binder chemistry. Microstructural assessment of pastes, strength development, water permeability, and chloride migration of two AACs (100% slag and 1:1 slag:fly ash) are presented, and compared to Portland cement concrete. Manipulation of binder chemistry leads to differences in the properties of the AACs; however, both AACs assessed exhibited technical benefits in a performance-based comparison. AACs can meet the requirements of the equivalent performance concept, independent of the binder chemistry, supporting their scale-up, regulatory acceptance, and wider adoption.