Evaluation of carbonation depth of high calcium fly ash blended concrete

초록

High calcium fly ash (FH) is the combustion residue in electric power plants burning lignite or subbituminous coal and can be used to produce high performance concrete. For concrete incorporating FH, hydration of Portland cement and reaction of FH will proceed simultaneously. Hence the carbonation of FH blended concrete is much more complex than that of control concrete. This paper presents a numerical procedure to evaluate carbonation depth of FH blended concrete. This numerical procedure consists of a blended cement hydration model and a carbonation reaction model. First, by using the blended cement hydration model considering cement hydration, reaction of free CaO in FH, and reaction of other phases in FH except free CaO, the properties of hardening FH blended concrete, such as calcium hydroxide contents, calcium silicate hydrate contents, reaction degree of high calcium fly ash, and porosity can be determined. Second, by using the carbonation reaction model, the diffusivity of CO₂ in FH blended concrete is calculated and the carbonation depth of FH blended concrete is predicted. The proposed numerical procedure is verified using experimental results of FH blended concrete with different water to binder ratios and high calcium fly ash replacement ratios. © International Journal of Sustainable Building Technology and Urban Development.

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