Degradation progress of Portland cement mortar under the coupled effects of multiple corrosive ions and drying-wetting cycles

Shukai Cheng, Zhonghe Shui, Xu Gao, Jianxin Lu, Tao Sun, Rui Yu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

6 Citations (Scopus)

Abstract

Concrete structures serving in the marine tidal zone usually suffer the most severe degradations due to multiple ions attacks and drying-wetting cycles. This study systematically investigates the influence of multiple ions presented in the seawater on the degradation process of Portland cement mortar under drying-wetting cycles. The interactions between sulfate (SO4 2-) and magnesium (Mg2+) on the chloride diffusion and damage behaviors of cement mortar were determined. The results show that the SO4 2- and SO4 2-+ Mg2+ in composite solution firstly decrease the chloride ingress and then increase the chloride diffusion, while the presence of Mg2+ increases the chloride diffusion of mortar samples regardless of the exposure to the NaCl + MgCl2 or NaCl + MgCl2+Na2SO4 solution, and rich Mg2+ is found at the outer layer. The existence of SO4 2- and SO4 2-+ Mg2+ in multiple ions solutions accelerates the degradation progress, whereas the single Mg2+ has negligible effect on the damages of samples. The phase compositions highlight that the Mg2++SO4 2- in chloride solution increases consumption of portlandite and causes the decalcification of C–S–H, thus aggravating the degradations of mortar. Moreover, the microstructure analysis reveals that the presence of Mg2++SO4 2- coarsens pore structure of matrix and induces a higher porosity, which further accelerates the ingress of corrosive ions.

Original languageEnglish
Article number103629
JournalCement and Concrete Composites
Volume111
DOIs
Publication statusPublished - Aug 2020

Keywords

  • Degradation
  • Drying-wetting cycles
  • Microstructure
  • Multiple ions
  • Seawater

ASJC Scopus subject areas

  • Building and Construction
  • Materials Science(all)

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