In situ determination of cement paste porosity in parallel with corrosion study of aluminium alloy 1100 in Portland cement pastes

Abstract

A quantitative characterization of the capillary porosity of cement pastes has been performed in the context of corrosion of aluminium alloy 1100 in contact with Portland cement pastes. The originality of the study is to combine an electrical equivalent circuit model identified based on electrochemical impedance spectroscopy (EIS) data and a two-phase model derived from the general effective media theory (GEM). The effective resistance of the cement paste entering the GEM is approximated by the resistance of connected capillary pores as provided by the EIS analysis to determine the evolving porosity of cement pastes. Mercury intrusion porosimetry data agree with the porosity results obtained from EIS. The porosity in the 0.36 OPC is reduced from ~ 15% to below 10% over the first 30 days and then keeps decreasing slowly, while the porosity of the 0.36 OPC + 3% LiNO₃ samples slightly decreases at the beginning and finally remains constant at ~ 10%. For the 0.50 OPC + 1.607% Li₂CO₃ composition, the porosity decreases from ~ 25% to ~ 15% over the first 30 days. The influence of the curing conditions is also studied to extract the impact on the porosity. Besides, the diffusion of corrosion products is limited to a small region near the interface and hence the corrosion process does not affect the porosity of the cement paste.