Does concrete suffer sulfate salt weathering?

• Published in: Construction & building materials 2014-09, Vol.66, p.692-701
• Main Authors: Liu, Zanqun, Deng, Dehua, De Schutter, Geert
• Format: Article
• Language: English
• Subjects: Chemical; Chemical properties; Concrete; Mechanical properties; Physical; Salt weathering; Sulfate attack
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2014.06.011

•Sulfate salt weathering of concrete is questioned in this review paper.•The contradictions between test results and classic theory are extensively discussed.•A viewpoint that chemical sulfate attack should still be the mechanism for concrete is deduced.•Several issues needing further research are proposed to prove the above viewpoint. Due to several similarities in deterioration behavior between concrete and other porous materials, sulfate salt weathering is regularly considered to be the degradation mechanism causing the concrete deterioration in evaporation zone of partially buried concrete elements in the sulfate environment. This issue has received increasing attention in recent years. However, according to an extensive literatures review on long term field and laboratory tests in this paper, the experimental results are clearly illogical and contradict with the classic theory of salt weathering of porous materials, such as (1) the sulfate crystals cannot be identified by means of micro-analysis methods in the damaged concrete as direct evidences for sulfate crystallization in concrete; (2) concrete is susceptible to deterioration in a high RH environment; (3) a mere change of cement compositions shows significant influence on concrete damage, however concrete damage is immune to pore structure change; and (4) the damaged concrete part does not contain the highest salt content, and so on. Instead, the experimental results support that the chemical sulfate attack should be still the mechanism causing the concrete deterioration. Therefore, an adequate understanding of deterioration mechanism of concrete in the evaporation zone of partially buried concrete elements is quite urgent. In this paper, several issues aimed at the contradictions deduced from field and laboratory tests are proposed to attempt to seek the truth of sulfate salt weathering of concrete.