THE CARBONATION OF CONCRETE STRUCTURES IN THE TROPICAL ENVIRONMENT OFSINGAPORE AND A COMPARISON WITH PUBLISHED DATA FOR TEMPERATE CLIMATES

The carbonation depths and compressive strength of four reinforced con crete buildings which ranged in age from 7 to 59 years were measured i n the topical environment of Singapore. The average carbonation depths , d, were related to the age of the building by the relationship d = K root age, where the carbonation constant, K, was approximately 7 mm/( year)(1/2). For any given structure the ratio of the maximum to averag e carbonation depth varied from 2.1 to 2.8. The carbonation depth and K value were also dependent on the quality (compressive strength) of t he concrete, concrete with compressive strengths > 20 MPa showing lowe r carbonation depths and K-values than concrete with compressive stren gths < 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 genera lly lower grade (compressive strength) of the concrete used in the con struction of the buildings and (ii) the significantly higher mean dail y temperature in Singapore, 27 degrees C, compared to the temperate cl imates, 8 degrees to 9 degrees C.