Abstract
In this paper, the recent research progress on the corrosion of reinforced alkali-activated materials (AAMs) concrete structures is reviewed. The corrosion mechanisms induced by carbonation and chloride ingress in AAMs concrete are discussed, from the perspectives of composition, microstructure and pore solution chemistry, in comparison to ordinary Portland cement (OPC) concrete. The steel–alkali-activated concrete interface is a key to investigating corrosion initiation and propagation, which has different physical and chemical characteristics of the steel–concrete interface in OPC concrete. Moreover, the electrochemical process testing methods including half-cell potential and linear polarization resistance are critically discussed with a focus on what could be inherited from the OPC concrete and what criteria are no longer suitable for AAMs concrete due to underestimation in most cases. New data and theories are urgently needed for using AAMs in concrete structures to replace OPC. At the end of this paper, the research gaps and future research needs are summarised for the sake of widespread application of AAMs in concrete structures for sustainable and low-carbon construction.
Highlights
Ordinary Portland cement (OPC) is the most consumed construction material worldwide due to its excellent performance, such as high mechanical strength especially in compression, high durability, good fire resistance, etc
Two categories of activated materials (AAMs) are usually used by researchers to distinguish the binder type and their related microstructures [3], namely, (1) high-calcium AAMs for which the microstructure is calcium aluminium silicate hydrate (C-A-S-H); (2) low-calcium AAMs for which the microstructure is sodium aluminosilicate hydrate (N-A-S-H)
This paper aims to present a comprehensive and critical review of recent progress in understanding the corrosion mechanism of reinforced concrete structures, fully incorporated with alkali-activated materials
Summary
Ordinary Portland cement (OPC) is the most consumed construction material worldwide due to its excellent performance, such as high mechanical strength especially in compression, high durability, good fire resistance, etc. Babaee and Castel [35] systemically studied chloride diffusion and threshold of AAMs (blended fly ash and slag) through their electrochemical experiments They suggested re-defining the Tafel constant (B) value for 45~58 and 13~20 mV for active and passive specimens, respectively, to replace what has been used so far for OPC concrete, i.e., 26 and 52 mV, respectively [36]. Noushini et al [75] found a more homogenous matrix formed in AAFA concrete, which was achieved by increasing temperature; AAFA concrete has lower chloride resistance compared to OPC concrete This may be due to the polycondensation [76] of AAMs that leads to increased microcracks, which accelerates the ingress of chloride ions. The higher alkali concentration may lead to the risk of leaching in the matrix pastes [77]
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