Abstract
This paper deals with study of thermal stability of geopolymer composites enhanced by nano metakaolin materials (NMK) and exposed to high firing temperature up to 1000 °C. The main geopolymer made up of water cooled slag having various kaolin ratios. The activators used are Na2SiO3 and NaOH in the ratio of 3:3. The thermo-physical, micro-structural and mechanical properties of the geopolymers before and after the exposure to elevated temperatures of 300, 500, 600 800 and 1000 °C have been investigated. The fire shrinkage of the geopolymer specimens increased by increasing temperature up to 1000 oC. Also, the fire shrinkage increased slowly up to 500 °C. The mechanical strength of geopolymer specimens increased with temperature up to 500 oC. The good thermo-physical and mechanical properties for these geopolymer composites increase the possibility of vast application of these eco-friendly materials in construction sectors.
Highlights
The geopolymerization technology introduced as an ideal and novel environmentally-friendly process for producing supplementary materials to ordinary Portland cement (OPC) in 1980s, by professor Joseph Davidovits that possessing higher mechanical and durability properties
Geopolymers have superior resistance to thermal shrinkage when exposed to temperatures up to 1000 °C compared to Portland cements (Palomo et al, 1999; Duxson et al, 2005 ; Duxson et al, 2007; Rahier, 1996) very little attention has been given to the wider issue of ambient temperature drying shrinkage (Barbosa & MacKenzie, 2003a)
This fact, combined with the high water requirement to mix geopolymer pastes, means that there is a large excess of unbound or free water, which can evaporate from the hardened paste under low relative humidity conditions at ambient temperature (Rahier, 1996)
Summary
The geopolymerization technology introduced as an ideal and novel environmentally-friendly process for producing supplementary materials to ordinary Portland cement (OPC) in 1980s, by professor Joseph Davidovits that possessing higher mechanical and durability properties. A small percentage of the mixing water remains as interstitial water in the geopolymer gel shrinkage (Barbosa & MacKenzie, 2003-b) This fact, combined with the high water requirement to mix geopolymer pastes, means that there is a large excess of unbound or free water, which can evaporate from the hardened paste under low relative humidity conditions at ambient temperature (Rahier, 1996). The FA geopolymers in these papers were directly heated from room temperature up to the elevated temperature of 800 oC or further up to 1200 oC, without studying the changes in the geopolymer phase composition and microstructure occurred at temperatures ranged from about 600-800 oC.
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