The previous researches on the degradation process of concrete under sulfate attack mainly focus on non-damaged concrete. It may lead to an excessive evaluation of the durability of the structure, which is detrimental to the safety of the structure. In this paper, three different damage degrees of concrete specimens with non-damaged ( D 0 ) and initial damage of 10% ( D 1 ) and 20% ( D 2 ) were prefabricated and subjected to sulfate attack and wetting–drying cycles. With the increase of sulfate attack cycles (0, 30, 60, 90, 120, 150 cycles), the changes in mass loss, relative dynamic modulus of elasticity, and the stress–strain curve were studied. The results show that the mass of the D 0 specimen had been increasing continuously before 150 sulfate attack cycles. The mass of D 1 and D 2 had been increasing before 60 cycles, and decreasing after 60 cycles. At 150 cycles, the mass loss of D 0 , D 1 , D 2 were − 1.054%, 0.29% and 3.20%, respectively. The relative dynamic modulus of elasticity (RDME) of D 0 specimen increases continuously before 90 sulfate attack cycles. After 90 cycles, the RDME gradually decreases. However, for D 1 and D 2 specimens, the RDME began to decrease after 30 cycles. The damage degree has an obvious influence on the compressive strength and elastic modulus. For the D 0 specimen, the compressive strength and elastic modulus increased continuously before 90 cycles and decreased after 90 cycles. The compressive strength and elastic modulus of D 1 and D 2 specimens began to decrease after 30 cycles. The stress–strain curves of concrete with different initial damage degrees were established, and the fitting results were good. Finally, based on the analysis of experimental data, the degradation mechanism of concrete with initial damage under the sulfate wetting–drying cycle was discussed.

中文翻译：

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硫酸盐侵蚀和干湿循环下初始损伤程度对混凝土降解的影响

以往关于硫酸盐侵蚀下混凝土降解过程的研究主要集中在未损坏混凝土上。可能会导致对结构耐久性的过度评价，不利于结构的安全。在本文中，预制了三种不同损伤程度的混凝土试件，其未损坏（D 0 ）和初始损伤为10％（ D 1 ）和20％（ D 2 ），并进行硫酸盐侵蚀和干湿循环。随着硫酸盐侵蚀循环次数（0、30、60、90、120、150次循环）的增加，研究了质量损失、相对动态弹性模量和应力应变曲线的变化。结果表明，在 150 次硫酸盐侵蚀循环之前，D 0 试样的质量一直在不断增加。D 1 和 D 2 的质量在 60 次循环之前一直在增加，并在 60 个循环后下降。在 150 次循环时，D 0 、D 1 、D 2 的质量损失分别为 - 1.054%、0.29% 和 3.20%。D 0 试样的相对动态弹性模量 (RDME) 在 90 次硫酸盐侵蚀循环之前连续增加。90 个循环后，RDME 逐渐降低。然而，对于 D 1 和 D 2 试样，RDME 在 30 次循环后开始下降。损伤程度对压缩强度和弹性模量有明显影响。对于 D 0 试样，压缩强度和弹性模量在 90 次循环前持续增加，在 90 次循环后下降。D 1 和D 2 试样的压缩强度和弹性模量在30次循环后开始下降。建立了不同初始损伤程度混凝土的应力-应变曲线，拟合效果良好。最后，