Publication:
Thin fly ash/ ladle furnace slag geopolymer: Effect of elevated temperature exposure on flexural properties and morphological characteristics
Thin fly ash/ ladle furnace slag geopolymer: Effect of elevated temperature exposure on flexural properties and morphological characteristics
Date
2022-06-15
Authors
Yong-Sing Ng
Liew Yun Ming
Heah Cheng Yong
Mohd. Mustafa Al Bakri Abdullah
Pakawanit P.
Chan L.W.L.
Ng Hui-Teng
Ong Shee-Ween
Ooi Wan-En
Hang Yong-Jie
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Abstract
The flexural properties and thermal performance of 10 mm-thin geopolymers made from fly ash and ladle furnace slag were evaluated before and after exposure to elevated temperatures (300 °C, 600 °C, 900 °C, 1100 °C and 1150 °C). Class F fly ash was mixed with liquid sodium silicate (Na2SiO3) and 12 M sodium hydroxide (NaOH) solution using aluminosilicate/activator ratio of 1:2.5 and Na2SiO3/NaOH ratio of 1:4 to synthesise thin fly ash (FA) geopolymers. 40 wt% of ladle furnace slag was partially replacing fly ash to produce fly ash/slag-based (FAS) geopolymers. Thermal treatment enhanced the flexural strength of thin geopolymers. In comparison to the unexposed specimen, the flexural strength of FA geopolymers at 1150 °C and FAS geopolymers 1100 °C was increased by 161.3% to 16.2 MPa and 208.9% to 24.1 MPa, respectively. A more uniform heating was achieved in thin geopolymers which favoured the phase transformation at high temperatures and contributed to the substantial increase in flexural strength. The joint effect of elevated temperature exposure and the incorporation of ladle furnace slag further improved the flexural strength of thin geopolymers. The calcium-rich slag refined the pore structure and increased the crystallinity of thin geopolymers which aided in high strength development.
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Keywords
Elevated temperature | Flexural properties | Fly ash | Ladle furnace slag | Thin geopolymer