This study provides a fundamental understanding on the deterioration of concrete due to physical sulfate/salt attack (PSA), including local cracking and pore structure development. The results show that sulfate salt crystals in a partially immersed concrete specimen preferred to precipitate in relatively large pores (DP-III, from 1 to 100 µm in diameter) in the concrete at the early stage of exposure. The persistent formation of small pores (DP-I and DP-II) and pore throats (PT-I and PT-II) occurred at the late stage of exposure. The gel pores, transition pores and even small capillary pores played an important role in providing space for crystal growth. The pore filling during the early stage resulted in a transient gain of specimen mass due to the capacity of pre-existing voids to accumulate the precipitated crystals (buffer effect). The later cracking degeneration induced by the pressure from the crystals was found to be limited to the subflorescence zone. This cracking degeneration was a time-dependent process that primarily developed along with relatively unsubstantial zones in the concrete, such as the interfacial transition zone (ITZ), until the extensive coalescence of these pressure-induced cracks.

中文翻译：

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物理攻击引起的混凝土开裂特征和孔隙发展

该研究提供了对物理硫酸盐/盐侵蚀 (PSA) 引起的混凝土劣化的基本认识，包括局部开裂和孔隙结构发展。结果表明，在暴露早期，部分浸渍混凝土试件中的硫酸盐晶体更倾向于在混凝土中相对较大的孔隙（DP-III，直径为 1 至 100 µm）中沉淀。小孔隙（DP-I和DP-II）和孔喉（PT-I和PT-II）持续形成发生在暴露后期。凝胶孔、过渡孔甚至细小的毛细孔在为晶体生长提供空间方面发挥了重要作用。由于预先存在的空隙能够积累沉淀的晶体（缓冲效应），早期的孔隙填充导致样品质量的瞬时增加。发现由来自晶体的压力引起的后期开裂退化仅限于亚荧光区。这种开裂退化是一个与时间相关的过程，主要是随着混凝土中相对非实质性区域（例如界面过渡区 (ITZ)）发展而来，直到这些压力引起的裂缝广泛合并。