Advances in concrete construction

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Investigation on alkalinity of pore solution and microstructure of hardened cement-slag pastes in purified water

  • Hu, Ya-Ru (Department of Civil Engineering, Nanjing University of Science and Technology) ;
  • Zuo, Xiao-Bao (Department of Civil Engineering, Nanjing University of Science and Technology) ;
  • Li, Xiang-Nan (Department of Civil Engineering, Nanjing University of Science and Technology) ;
  • Jiang, Dong-Qi (Department of Civil Engineering, Nanjing University of Science and Technology)
  • Received : 2020.07.20
  • Accepted : 2021.12.04
  • Published : 2021.12.25
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Abstract

To evaluate the influence of slag on the alkalinity of pore solution and microstructure of concrete, this paper performs a leaching experiment on hardened cement-slag pastes (HCSP) slice specimens with different slag content in purified water. The pH value of pore solution, average porosity, morphology, phase composition and Ca/Si of HCSP specimens in the leaching process are measured by solid-liquid extraction, saturated-dried weighing, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD). Results shows that the addition of slag can mitigate an increase in porosity and a decrease in Ca/Si of HCSP in the leaching process. Besides, an appropriate slag content can improve the microstructure so as to obtain the optimum leaching resistance of HCSP, which can guarantee the suitable alkalinity of pore solution to prevent a premature corrosion of reinforced bar. The optimum slag content is 40% in HCSP with a water-binder ratio of 0.45, and an excessive slag causes a significant decrease in the alkalinity of pore solution, resulting in a loss of protection on reinforced bar in HCSP.

Keywords

Acknowledgement

The study of this paper is financially supported by the National Natural Science Foundation of China (51778297, 52078252).

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