Monitoring the Evolution of Accelerated Carbonation of Hardened Cement Pastes by X-Ray Computed Tomography

The evolution of carbonation front progress, crack spatial distribution, and pore structure parameters of hardened cement paste have been monitored in situ by three-dimensional (3D) X-ray computed tomography (XCT) at different accelerated carbonation ages of 0, 3, 7, 14, and 28 days, respectively. The gray-value histograms of cement paste are a function of carbonation time, and the carbonation degrees at different times can be estimated by the volume fractions of uncarbonated and carbonated parts. Many cracks generate along the carbonation direction because of carbonation shrinkage. With the extension of the carbonation time, the volume and surface of cracks become larger. The porosity markedly decreases when pore volume is between 0.01 and 0.1 mm3 as the carbonation time increases.