Influence of Hydration Time Prior to Carbonation in Portland Cement Admixed with CaO Expansive Additive

抄録

Portland cement slurries have undergone degradation due to carbonation-induced corrosion in contact with a CO₂-rich environment. Many studies have observed degradation such as a decrease in the mechanical strength and an increase of permeability and porosity. When utilized in wells as a zonal isolation material in the CO₂-rich environment, such degradation can be worsen by hydration shrinkage of Portland cement, in which micro-annuli are formed and, thus, effective permeability is increased. In this work, CaO was employed as an expansive additive admixed with Portland cement. The samples were hydrated for 1 and 7 days prior to carbonation for 14 days in an autoclave to simulate shorter and longer hydration times before contacted with a CO₂-rich environment. Before carbonated in the autoclave, the samples were analyzed by X-ray diffraction. The expansion of the hydrated slurries was also observed for the first 24 h of hydration. After carbonation, the percentage of the corroded area was calculated, and a three-point bending test was conducted. The result shows that the CaO additive below 15% by weight of cement in the Portland cement slurry can enhance the slurry resistance against corrosion encroachment induced by the carbonation process. The presence of the CaO additive in the Portland cement slurry can mitigate the severe detrimental effect induced by carbonation.