The carbonation of concrete structures in the tropical environment of Singapore and a comparison with published data for temperate climates

Abstract

The carbonation depths and compressive strengths of four reinforced concrete buildings which ranged in age from 7 to 59 years were measured in the tropical environment of Singapore. The average carbonation depths, d, were related to the age of the building by the relationship d = K√age, where the carbonation constant. K, was approximately 7 mm/(year)1/2. For any given structure the ratio of the maximum to average carbonation depth varied from 2.1 to 2.8. The carbonation depth and K value were also dependent on the quality (compressive strength) of the concrete, concrete with compressive strengths > 20 MPa showing lower carbonation depths and K-values than concrete with compressive strengths < 20 MPa. The K-values measured in this study. 5.5-8.6 mm/ (year)1/2, were generally higher than those reported for temperate climates (1-3 mm/(year)1/2). The differences are attributed to (i) the generally lower grade (compressive strength) of the concrete used in the construction of the buildings and (ii) the significantly higher mean daily temperature in Singapore, 27°C, compared to the temperate climates, 8° to 9°C.