Effects of Carbonation on Microscopic Pore Characteristics and Water Absorption Performance of Concrete

Abstract:

Capillary water absorption tests on non-carbonated and carbonated concrete specimens with different water-cement ratios were conducted to investigate the effects of carbonation on capillary water absorption performance of concrete. Mercury intrusion porosimetry （MIP）， backscattered electron microscopy （BSE） and thermogravimetric analysis （TGA） were used to identify the pore structure of concrete before and after carbonation. The results show that the water absorption performance of carbonated concrete greatly decreases， and absorption capacity declines by 20.0% to 26.5%， and the water absorption coefficient falls by 30.8% to 37.8%. Compared with non-carbonated concrete， the most probable pore diameter of the carbonated concrete decreases by 13.9 nm to 15.1 nm， with the highest reduction rate reaching 41.8%. The reduction is more significant for concrete with higher water-cement ratios. The carbonation process is found to result in the transformation of calcium hydroxide into calcium carbonate and a decrease in pore diameter. The calculation results indicate that the model proposed by Lucas-Washburn et al. is still effective for carbonated concrete water absorption， and the selection of the most probable pore diameter as the equivalent pore diameter has the best model performance.

Key words:carbonation;concrete;capillary water absorption;pore structure