Evolution of pH and chemical composition of pore solution in carbonated concrete

An investigation of carbonation in concrete, the pH and chemical composition change of the pore solution in concrete with different degrees of carbonation, was presented. The concrete samples were manufactured using ordinary portland cement and fly ash with dimension of 100 mm diameter by 3 mm in height, and six different mix proportions. The concrete samples were exposed to the environment (CO2 5%, RH 40%) to accelerate carbonation. The suspension pH of the powdered sample, extracted from concrete, was measured for comparison. It was found that the pH values of the pore solution were mainly decreased in 15 days and the correlation between the pore solution pH and the carbonated period seemed to be almost linear in 15 days. The contents of Na+ and K+ in pore solutions were decreased mainly in first 3 days in the carbonation periods and had little change in the next carbonated periods. The pore solution pH of carbonated concrete could be inferred by suspension pH.

► The pH and chemical composition of the pore solution in concrete were presented.
► The content of K+ and Na+ reduced mostly in 3 days.
► The suspension pH and the pore solution pH had a good relationship.
► The pore solution pH was inferred by suspension pH which was more convenient.