Influence of the environmental relative humidity on carbonation behavior of cracked PC, FA and GGBS concretes

Abstract

In this study, based on the accelerated carbonation test results on unloaded 100-mm cubes and loaded RC beams, where test specimens were made with three types of concretes, i.e., Portland cement (PC) concrete, PC with 30% of fly ash (FA) and PC with 50% of ground granulated blast-furnace slag (GGBS), an analytical model was proposed to predict the carbonation depth of the in-service RC elements made from concretes similar to those in the accelerated tests. It is concluded that, in general, for those real RC elements with different types and water-binder ratios (w/b), the trend of the predicted carbonation depths first increases and then decreases with the increase of the relative humidity (RH) in typical design working life of 50 years. Under different environmental relative humidity, for loaded RC elements, only Portland cement concrete and concrete GGBS with lower w/b meet the durability requirements of the different exposure environments in 50-year design working life. The maximum predicted carbonation depths of various types of concretes are observed in the range of 50-70% relative humidity and the ‘green’ FA and GGBS concretes with larger w/b can not meet the durability requirements of the exposure environments in this relative humidity range when they were subjected to in-service loads.