Effects of CO2 curing treatment on alkali-silica reaction of mortars containing glass aggregate

Abstract

In this study, the influence of CO2 curing treatment on the alkali-silica reaction (ASR) of mortar bars containing 100% recycled glass was investigated. The ASR expansion results according to ASTM C1260 demonstrated that a short period (3 h) of CO2 curing could fully suppress the ASR expansion. Apart from mechanical strength enhancement, reduced pH and permeability properties, it is interesting to note that the distribution of ASR gel in the CO2 cured specimen was totally different from traditional glass-induced ASR as reported in the literature. For CO2 curing treated specimen, the ASR gel which formed at the glass-cement interface instead of initiation at microcracks within the glass aggregate is identified as an important reason for the decreased expansion. With the reduction of calcium hydroxide (CH) in the cement matrix caused by CO2 curing treatment, silica could dissolve from glass surface and induced the ASR reaction. The swelling of the surface ASR gel applied inward pressure on the glass aggregate, reducing the aggregate cracking progression. In addition, these surface gels can possibly be partly accommodated by residual space in the interfacial transition zone (ITZ).