Abstract
The increase in CO2 concentrations and global warming will increase the carbonation depth of concrete. Furthermore, temperature rise will increase the rate of corrosion of steel rebar after carbonation. On the other hand, compared with normal concrete, high volume fly ash (HVFA) concrete is more vulnerable to carbonation-induced corrosion. Carbonation durability design with climate change is crucial to the rational use of HVFA concrete. This study presents a probabilistic approach that predicts the service life of HVFA concrete structures subjected to carbonation-induced corrosion resulting from increasing CO2 concentrations and temperatures. First, in the corrosion initiation stage, a hydration-carbonation integration model is used to evaluate the contents of the carbonatable material, porosity, and carbonation depth of HVFA concrete. The Monte Carlo method is adopted to determine the probability of corrosion initiation. Second, in the corrosion propagation stage, an updated model is proposed to evaluate the rate of corrosion, degree of corrosion for cover cracking of concrete, and probability of corrosion cracking. Third, the whole service life is determined considering both corrosion initiation stage and corrosion propagation stage. The analysis results show that climate change creates a significant impact on the service life of durable concrete.
Highlights
To achieve sustainable development of the modern concrete industry, high volume fly ash (HVFA) concrete, which contains more than 50% fly ash in the binder, is widely used
To address the drawbacks in the current models [3,4,5,6,7,8,9,10,11,12,13,14,15], this study presents a probabilistic approach that predicts the service life of concrete structures subjected to carbonation-induced corrosion
Ρc ρw where xc is the carbonation depth of concrete, D is the CO2 diffusivity, [CO2]0 is CO2 molar concentration at the concrete surface, [CH] is the molar concentration of calcium hydroxide, [calcium silica hydrate (CSH)]C is the molar concentration of CSH produced from cement hydration, [CSH]FA is the molar concentration of CSH produced from the fly ash reaction, ρc is the density of cement, A and a are CO2 diffusivity parameters, and RH is the environmental relative humidity. [CH] + 1.7 [CSH]C + 1.1 [CSH]FA in the denominator of Equation (6) is the content of carbonatable material
Summary
To achieve sustainable development of the modern concrete industry, high volume fly ash (HVFA) concrete, which contains more than 50% fly ash in the binder, is widely used. Jiang et al [3] proposed a mathematical model for the carbonation depth of HVFA concrete by considering mixing proportions, curing periods, and environmental conditions. Den Heede et al [9,10] proposed a model by considering the effect of global warming on the carbonation of HVFA concrete. A service life model of concrete, considering corrosion initiation, propagation period, and climate change, has been proposed [13]. Stewart et al [14,15] evaluated the effect of climate change on the service life of concrete for chloride or carbonation-induced corrosion. Because climate changes, corrosion propagation stage, and types of binders, are not taken into consideration by the current models, they cannot be used to evaluate the carbonation service life of HVFA concrete with climate change. The service life is determined considering the corrosion initiation stage and the corrosion propagation stage
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