Neutralization evolution of concrete under acid rain and carbonation erosion: a review

Concrete structures in atmospheric environments are constantly affected by acid rain and carbon dioxide erosion, and the evolution of concrete neutralization is an important factor influencing the long-term performance of the material. To deepen our understanding of the long-term performance evolution mechanisms of concrete, this study reviews the mechanism of acid rain and carbonation neutralization, summarizes studies regarding the evolution of the macroscopic properties and microstructures of concrete, and discusses the internal and external influencing factors and prediction models for concrete neutralization evolution. A thorough analysis of existing studies reveals that the microscopic properties and microstructures of concrete undergo a process of optimization followed by decay in response to acid rain neutralization. The expansion products from acid rain can lead to the deterioration of concrete microstructure, whereas carbonation neutralization products enhance microstructural compactness. Moreover, the study found that the degree of concrete neutralization increases with an increase in the water-cement ratio (W/C). Furthermore, the maximal degree of concrete neutralization occurs within a relative humidity ranging from 45% to 65%. According to the diffusion theory, the process of concrete neutralization is an evolutionary one that operates from the outside to the inside of the material and is influenced by various factors. The aim of this review is to provide scholars with a systematic understanding of the evolution of concrete neutralization under acid rain and carbonation, and to establish a theoretical foundation for future research in this area. Potential areas for future research on concrete neutralization are also described in this review. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).