Characterising cement carbonation curing using non-contact electrical resistivity measurement

Carbonation curing of cement paste and concrete promotes early strength gain, improves durability and recycles carbon dioxide in a beneficial manner. To examine the carbonation curing mechanism, fresh cement pastes and concretes subject to carbonation are characterised using a non-contact electrical resistivity measurement method. Resistivity measurements reveal that characteristic features of the hydration accelerated by carbonation are different from conventional hydration. The typical induction period is absent in the carbonation curing owing to the rapid precipitation of calcium carbonate. The resistivity measurement method produces a superimposed result of early hardening and multiple instances of progressive hardening by carbonation curing. The electrical resistivity is 3-6 times higher in the carbonated cement paste and about 8-16 times higher in the carbonated concretes in comparison with the hydration references. The carbonated lightweight concrete shows lower bulk resistivity than the carbonated normal-weight concrete, possibly owing to the release of internal water from the lightweight aggregates during carbonation. This is evidence of internal curing by lightweight aggregates.