A Study on the Carbonation Service Life and LCC Repair Evaluation of RC Structure Applied by Repair Method

Abstract

In this study, the concrete structure was carbonated with 20% CO2.Thereafter different surface carpet methods were applied to study the efficacy of repair materials . The carbonation rate of each repair material is derived and carbonation progress predicted using carbonation progress prediction formula. In order to secure reliability, we compared the carbonation depth prediction by FDM and FEM analysis. This study is to estimate the carbonation life of RC structures which have been undergoing through repair process by predicting the progress of carbonation after application of the repair method. The probabilistic carbonation repair of LCC was evaluated by using the carbonation durability evaluation method of repaired materials. Most of the existing LCC techniques are deterministic methods that consider the sum of the amounts generated at each step. However, this deterministic repair method concentrates on the cost factor rather than considering the effect of maintenance time, so it is difficult to link with the durability of concrete. Therefore, it is considered that the optimal cost considering the durability life and maintenance cost can be evaluated by using the probabilistic carbonation repair LCC model. Followings are the gist of present work: 1) The depth of accelerated carbonation of untreated specimen was measured after 5 days of exposure and the penetration was 10.3 mm thereafter repaired materials was used to measure the carbonation depth of all specimens. After 28 days of continuous carbonation, the penetration of CO2 for the inhibitive surface covering (ISC) material was 19.8 mm and it was highest among all studied specimens while the inhibiting mortar (IM) showed the lowest carbonation penetration depth and it was 13.3mm.. 2) Carbonation coefficient of WP exhibits 44.2% while IM shows 28.8% as compare to unrepaired OPC. Therefore, it is concluded that IM reduces 55% carbonation of unrepaired OPC compare to other repairing materials. 3) By using geometric carbonation prediction model, the life expectancy of WP repaired materials decreased from 72 years to 8 years when the maintenance period was 10, 15, 20, 25 and 30 years of each interval while Organic alkali Inhibitor (OAI) decreased from 89 to 9 years. On the other hand, use of inhibitor mortar (IM) decreased from 139 to 13 years which is the best repair materials compare to others. 4) Carbonation coefficient can be predicted based on initial Ca(OH)2 present in the concrete. The prediction of carbonation depth through FDM and FEM analysis was used. 5) In this study, we have used LCC evaluation model to determine the probabilistic carbonation for repair materials and it was found that the maintenance cost shows a curve which is unlike and closer to the deterministic coefficient variation. In addition, more accurate maintenance cost can be predicted by LCC than deterministic model of OPC before and after using of repair materials. This model concludes that WP is the convenient repair materials to repair the OPC in CO2 atmosphere in view of LCC.