Analysis of surface deterioration of Concrete in Cold Sea Environment by Reliability Analysis

Predictions of the service life of concrete structures are an important part of maintenance，management，and durability design. One essential aspect of this is deterioration prediction. The purpose of this study is to theoretically examine the question of deterioration prediction using reliability theory. As an example， reliability theory is applied to the problem of scaling using survey data taken from exposure tests in a cold marine environment. The exposed specimens have a concrete cover of 80 mm， and the scaling deterioration limit is assumed to be 20 mm. Hazard levels are set up at 1/10 and 1/20 of this limit，corresponding to 2 mm and 1 mm， respectively. From this examination, we conclude that the Weibull distribution gives the best fit to the frequency distribution of scaling that exceeds the hazard level in depth. Covariate variables of the reliability function were extracted, and water-cement ratio and Fe_2O_3 were selected for study since their significance level was within 1％. The coefficient for water-cement ratio was found to be negative， while that for Fe_2O_3 was positive. The time taken for scaling to reach the hazard level was found to be approximately the same as required to reach the 50 ％reliability level， thus confirming the validity of this method of reliability analysi