Development of Low Cost Geopolymer from Calcined Sedimentary Clay
Geopolymer, a low environmental impact material, is recently used as an alternative binder to Portland cement in concrete manufacturing because the geopolymer production is a low-energy-consuming process, and does not emit pollutants, especially carbon dioxide, which is the main cause of the global warming problem. Geopolymer is synthesized from variety kinds of raw materials/precursor such as fly ash, slag, and kaolinite clay. However, supplies of slag and fly ash are limited due to the large demand of cement. These are the driving forces for the need to seek for alternative precursor. Abundant Sedimentary Clay (SC) in Nakhon Ratchasima province, Thailand contains high amount of kaolin and is possibly used to develop a cost-effective and sustainable calcined precursor, which is the focus of this paper. The precursor was prepared by calcining SC at 600 °C for 1, 2 and 5 h. The precursor was mixed with the alkali activator solution, which is the mixture of sodium silicate (Na2SiO3) solution and sodium hydroxide (NaOH) solution to develop a SC-geopolymer binder. The ratios of Na2SiO3 to NaOH studied were 0.5, 1 and 1.5. The geopolymer pastes were cured at 60 °C for 7 days. The results show that 2 h-calcined SC and Na2SiO3 to NaOH ratio of 0.5 provides the highest strength of the SC-geopolymer paste. Its compressive strength is higher than that of the ordinary Portland cement.
KeywordsCompressive Strength Portland Cement Ordinary Portland Cement Calcination Time Kaolinite Clay
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This research was supported by the Suranaree University of Technology. The second author acknowledges the Thailand Research Fund under the TRF Senior Research Scholar program Grant No. RTA5680002.
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