CARBONATION SERVICE LIFE PREDICTION OF EXISTING CONCRETE VIADUCT/BRIDGE USING TIME-DEPENDENT RELIABILITY ANALYSIS

This paper examines the predicted carbonation life of an existing concrete viaduct/bridge in the atmospheric environment based on probability and reliability indices. The probability is dependent upon the carbonation rate, carbonation remainder, concrete quality, and concrete cover. The carbonation life is defined as the service life of reinforced concrete (RC) or prestressed concrete (PC) structure at the beginning of time of steel corrosion when concrete cover surfers from carbonation and loses the protection function to steel. The carbonation life is equivalent to the initiation time of corrosion of reinforcement. Both the Chorng-ching viaduct and Wann-fwu bridge were offered as illustrative examples for verifying the analytical method and carbonation life prediction. The predicted carbonation life results for the Chorng-ching viaduct and Wann-fwu bridge are 55 and 55, 40 and 17, and 18 and 0 years at beta(c) = 0, 0.5, and 1.25 reliability indices, respectively. The results show that both structures are serviceable and reliable comparing the initiation time calculated using Fick's second law, Guirguis, and AJMF methods. The results can provide a basis for repair, strengthening, and demolition of existing RC and PC viaducts or bridges.