Abstract It is widely believed that the mechanical properties of concrete structures gradually deteriorate in a corrosive environment. However, it has been observed that the fracture toughness of concrete strengthens during the initial stage of sulfate attack. With the increase in the corrosion time, the fracture toughness gradually weakens. The main reasons for this contrasting response are as follows: (1) The strengthening effect is caused by the continued hydration of concrete materials; (2) sulfate ions lead to delayed ettringite formation (DEF) in the pores of mortar, which causes filling and compaction effect during the early stage of corrosion and pore swelling during the later stage that damages the concrete structure. In this paper, the effect of sulfate corrosion on the fracture toughness of mortar is investigated, and the relationship between strengthening-weakening effects of fracture toughness and corrosion time is obtained. Subsequently, the displacement and strain in the fracture process zone are analyzed by digital image correlation, which clarifies the critical influence of solution concentration and corrosion time on the mortar. Finally, based on the chemical reaction rate equations of DEF, a novel chemo-mechanical model of fracture toughness is established for mortar under sulfate attack.

中文翻译：

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硫酸盐侵蚀下砂浆断裂韧性的新型化学力学模型

摘要 人们普遍认为，混凝土结构的力学性能在腐蚀环境中会逐渐恶化。然而，已经观察到混凝土的断裂韧性在硫酸盐侵蚀的初始阶段增强。随着腐蚀时间的增加，断裂韧性逐渐减弱。产生这种反差的主要原因如下：（1）混凝土材料的持续水化作用引起的加固作用；(2)硫酸根离子导致砂浆孔隙中延迟钙矾石形成(DEF)，在腐蚀早期产生充填密实作用，在后期产生孔隙膨胀，破坏混凝土结构。本文研究了硫酸盐腐蚀对砂浆断裂韧性的影响，得到了断裂韧性的强弱效应与腐蚀时间的关系。随后，通过数字图像相关分析了断裂过程区的位移和应变，阐明了溶液浓度和腐蚀时间对砂浆的关键影响。最后，基于DEF的化学反应速率方程，建立了一种新型的硫酸盐侵蚀砂浆断裂韧性化学力学模型。