Advances in concrete construction

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Thermomechanical behavior of alkali-activated slag/fly ash composites with PVA fibers exposed to elevated temperatures

  • Kim, J.S. (Department of Civil and Environmental Engineering, Korean Advanced Institute of Science and Technology) ;
  • Lee, H.K. (Department of Civil and Environmental Engineering, Korean Advanced Institute of Science and Technology)
  • Received : 2020.09.23
  • Accepted : 2020.11.20
  • Published : 2021.01.25
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Abstract

The present study fabricated polyvinyl alcohol (PVA) fiber-reinforced alkali-activated slag/fly ash (AASF) composites with varying mixture ratios of slag and fly ash. The thermomechanical behaviors of the AASF composites exposed to 200, 400, 600, or 800℃ were evaluated by means of compressive strength test, visual observation, and fire resistance tests. X-ray diffractometry, mercury intrusion porosimetry, and thermogravimetry tests were performed to analyze the microstructure change of the AASF composites upon exposure to high temperatures. Specimens exhibited a gradual strength loss up to 600℃, while also showing a significant decrease in the strength above 600℃. The fire resistance test revealed the occurrence of an inflection point as indicated by an increase in the internal temperature at around 200℃. In addition, specimens showed the dehydration of C-S-H gel, the presence of åkermanite, gehlenite, and anorthite upon exposure to 800℃, which is associated with the formation of macropore population with pores having diameters of 1-3 ㎛ and 20-40 ㎛. Visual observation indicated that the PVA fibers mitigated the cracking and/or spalling of the specimens upon exposure to 800℃.

Keywords

Acknowledgement

This study was supported by a grant from the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT) (No. 2017R1A5A1014883). Furthermore, the authors would like to express our deepest gratitude to Mr. S.M. Park and Mr. J.H. Seo for their valuable comments on this manuscript.

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