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.
Highlights
Sulfate Attack: A Critical Review andThe external sulfate attack, resulting from the invasion of sulfuric ions in soils, underground, marine, or industrial wastewaters, is a significant deterioration process of concrete in-service
It showed that after 16 weeks of immersion in a 5% Na2 SO4 solution, it is possible to distinguish between the various cement types. It adopted and updated ASTM C452 and C1012 test methods to establish a more reliable and rapid test protocol. Based on these results, using the adjusted mortar bar (15 × 40 × 160 mm) that was cured for 7 days is the most convenient and practical measure for sulfate attack specified in AS 2350
Several studies have focused on developing various models that can reliably predict the performance of concrete when subjected to sulfate attack
Summary
The external sulfate attack, resulting from the invasion of sulfuric ions in soils, underground, marine, or industrial wastewaters, is a significant deterioration process of concrete in-service. The suitability of cement-based concrete standards and measures available in the literature to simulate the long-term resistance to external sulfate attack is still controversial. The inadequacy of the current standards in considering the replacement of OPC by alkali-activated materials (AAMs) has limited its expansion in the market. This review’s primary purpose is to present a critical analysis of the adequacy of classical/advanced sulfate tests in the field of alkali-activated materials to understand the underlying mechanisms governing the deterioration of those mixtures. It raises questions about the possibility of developing a new modeling approach that considers the interaction between AAMs and sulfates.
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