Service life of buildings subject to carbonation-induced corrosion in Hong Kong: field investigation, case studies and recommendations

This paper investigates the service life modelling of Hong Kong buildings subject to carbonation-induced corrosion. The provisions on the design parameters of carbonation-induced corrosion in Hong Kong standards at different periods are summarised. Data from field investigations concerning carbonation-induced corrosion are presented, including in relation to cover thickness, cement content, chloride content, carbonation coefficient and deterioration state. Two case studies concerning residual service life modelling and performance-based service life design are presented using practical equations proposed by a novel service life model, CECP-SAM. To achieve service lives of 50 years and 75 years, deemed-to-satisfy limitations on design parameters, considering the partial replacement of ordinary Portland cement with supplementary cementitious materials (SCMs), are provided. The results indicate a decreasing year-on-year trend in the carbonation coefficients of existing buildings. It is unnecessary to consider the chloride effect for the internal components of buildings constructed after 1965. Rather, additional attention should be paid to carbonation-induced corrosion, especially in old buildings with a high water/cementitious ratio and new buildings with PFA and GGBS substitutions.