Solution transportation in concrete partially exposed to Na₂SO₄ solution

Abstract

Wick action is the key factor in understanding the salt weathering of porous materials. In this study, concrete discs were partially exposed to Na₂SO₄ solution to simulate the wick action in concrete. We evaluated the effects of the relative humidity (RH), solution concentration, and pore structures (different water to cement ratios) on the solution transport mechanism based on the water evaporation rate. Interestingly, we found that lower RH and larger W/C ratio accelerated evaporation, but the higher concentration of the solution slowed it down. The micro-analyzer results of NMR and XRD confirmed that the formation of ettringite and gypsum due to chemical sulfate attack blocked the pores in the concrete, resulting in a decrease in water evaporation. Na₂SO₄ crystallization distress was not detected in the concrete. Therefore, the solution transport process in the concrete discs could not be described by wick action.

Keywords:

• concrete
• partially immersed
• wick action
• chemical attack
• salt crystallization

Disclosure statement

No potential conflict of interest was reported by the author(s).

Acknowledgments

We express our gratitude to the Central South University for providing instruments and materials. Special thanks are due to Professor Zanqun Liu for the guidance and assistance in the design of the test scheme and the process of writing this paper.

Additional information

Funding

We greatly appreciate the financial support from the National Natural Science Foundation of China (grant no. 51378508) and the Fundamental Research Funds for the Central Universities of Central South University (grant no. 2019zzts288).