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Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders
Highlights The geopolymer foams were prepared using waste glass powders in a NaOH and Na2SiO3 activation solution and an Al foaming agent powder. The prepared slurries expanded and the temperatures of the slurries saturated at 85–88 °C at increasing Al additions. The increase of the apparent viscosity of the slurries due to the increased S/L ratio and rate of geopolymerization reaction caused the termination of slurry expansion. The release of CO2 gas due to the decomposition of thermonitrite reduced the density of sintered foams at above 700 °C. The geopolymer foams sintered at 750 °C exhibited the lowest density and the highest compressive strength.
Abstract Geopolymer foams of fine and coarse waste glass (WG) powders were prepared using an activation solution of NaOH (8 M) and Na2SiO3. The effects of WG powder particle size, solid/liquid ratio (S/L = 1, 1.5, and 2) and Al foaming agent content (2–20 wt%) on the expansion and temperature behavior of the slurries were determined in-situ using a laser sensor and a thermocouple, respectively. The geopolymer foams processed using a coarse WG powder slurry, S/L = 2, and 2 wt% Al, were further sintered at 600, 700, 725, and 750 °C. The compression strengths and thermal conductivities of the geopolymer and sintered geopolymer foams were also determined. The slurry expansions continued until about a maximum, and the temperatures of the slurries increased to a maximum, 85–88 °C. At the maximum temperature, the slurry evaporation and the resultant increase in the S/L ratio limited the slurry expansion. Increasing the Al content decreased the final density of the foams (238–555 kg m−3), while the coarse powder slurries resulted in lower densities than the fine powder slurries. Three crystal phases, muscovite, sodium aluminum silicate hydrate, and thermonitrite, were determined in the geopolymer foams. The muscovite formation was noted to be favored at high S/L ratios. During sintering, the partial melting of glass particles started after about 700 °C, while sintering above this temperature decreased the final density of the foams. The reduced density above 700 °C was ascribed to the release of CO2 due to the decomposition of thermonitrite. Both the compressive strength and thermal conductivity of the geopolymer and sintered geopolymer foams increased with increasing foam density. The highest increase in the compressive strength and reduction in the density were seen in the geopolymer foams sintered at 750 °C.
Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders
Highlights The geopolymer foams were prepared using waste glass powders in a NaOH and Na2SiO3 activation solution and an Al foaming agent powder. The prepared slurries expanded and the temperatures of the slurries saturated at 85–88 °C at increasing Al additions. The increase of the apparent viscosity of the slurries due to the increased S/L ratio and rate of geopolymerization reaction caused the termination of slurry expansion. The release of CO2 gas due to the decomposition of thermonitrite reduced the density of sintered foams at above 700 °C. The geopolymer foams sintered at 750 °C exhibited the lowest density and the highest compressive strength.
Abstract Geopolymer foams of fine and coarse waste glass (WG) powders were prepared using an activation solution of NaOH (8 M) and Na2SiO3. The effects of WG powder particle size, solid/liquid ratio (S/L = 1, 1.5, and 2) and Al foaming agent content (2–20 wt%) on the expansion and temperature behavior of the slurries were determined in-situ using a laser sensor and a thermocouple, respectively. The geopolymer foams processed using a coarse WG powder slurry, S/L = 2, and 2 wt% Al, were further sintered at 600, 700, 725, and 750 °C. The compression strengths and thermal conductivities of the geopolymer and sintered geopolymer foams were also determined. The slurry expansions continued until about a maximum, and the temperatures of the slurries increased to a maximum, 85–88 °C. At the maximum temperature, the slurry evaporation and the resultant increase in the S/L ratio limited the slurry expansion. Increasing the Al content decreased the final density of the foams (238–555 kg m−3), while the coarse powder slurries resulted in lower densities than the fine powder slurries. Three crystal phases, muscovite, sodium aluminum silicate hydrate, and thermonitrite, were determined in the geopolymer foams. The muscovite formation was noted to be favored at high S/L ratios. During sintering, the partial melting of glass particles started after about 700 °C, while sintering above this temperature decreased the final density of the foams. The reduced density above 700 °C was ascribed to the release of CO2 due to the decomposition of thermonitrite. Both the compressive strength and thermal conductivity of the geopolymer and sintered geopolymer foams increased with increasing foam density. The highest increase in the compressive strength and reduction in the density were seen in the geopolymer foams sintered at 750 °C.
Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders
Polat, Dilan (author) / Güden, Mustafa (author)
2021-07-13
Article (Journal)
Electronic Resource
English
Glass , Powder , Geopolymer , Foam , Aluminum , Sintering , Compressive strength , Thermal conductivity