Zero-Cement Concrete Resistance to External Sulfate Attack: A Critical Review and Future Needs

Abstract

The durability of zero-cement concrete or alkali-activated materials (AAMs) is a subject of controversy, especially when exposed to sulfate attacks. This can be due to the different elemental and microstructural compositions of the broad alkali-activated systems that exhibit different degradation mechanisms in sulfate-rich environments. Various parameters, such as properties of raw source materials (nature, fineness, and mineralogy), activators (type and concentration), mixture design, curing regime, types of sulfate salt and sulfate ion concentrations, and weathering conditions, are considered to have a significant impact on zero-cement concrete sulfate attack resistance. Furthermore, the adequacy of the standard sulfate immersion tests raises more concerns about the reported behavior. This paper presents a critical review of the current aging protocol associated with ordinary cement resistance and zero-cement concrete or AAMs to external sulfate attack.