Geopolymer is an environmental friendly material, and is expected to use as the cement replacement materials. Because, the geopolymer production does not emit carbon dioxide gas, and is a low energy consuming process. Moreover, geopolymer can be synthesized from variety kinds of waste materials. The present work, the room temperature curing geopolymer has been developed by using the calcined water-treatment-sludge (WTS) and the rice husk ash (RHA) as the precursors. Mixture of sodium hydroxide solution and sodium silicate solution was used as an alkali activator solution. The results show that the RHA promotes strength of the WTS-geopolymer. By adding RHA 30 wt%, strength of geopolymer is close to the minimum required strength of the ordinary Portland cement (OPC). In addition, density of WTS-RHA geopolymer is 3 times lower than that of the OPC. Knowledge in the present work opens an opportunity to apply geopolymer for using in variety kinds of engineering applications, especially the lightweight construction materials.
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 (Na 2 SiO 3 ) solution and sodium hydroxide (NaOH) solution to develop a SC-geopolymer binder. The ratios of Na 2 SiO 3 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 Na 2 SiO 3 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.
Low‐thermal‐expansion porous ceramics are required for numerous applications. This work develops low‐thermal‐expansion porous ceramics by using SiC and ZrW2O8 as positive and negative thermal expansion materials, respectively, bonded by a glassy material. The mixture of SiC, ZrW2O8, and glassy material was sintered by the conventional method or pulsed electric current sintering (PECS, or sometimes called spark plasma sintering) at 850°C. In samples sintered by PECS with ZrW2O8, particle size 20–45 μm or 45–90 μm can preserve ZrW2O8 during the sintering process and have a low thermal expansion coefficient. Samples sintered by the conventional method have a high thermal expansion coefficient because ZrW2O8 decomposes to ZrO2 and WO3 at the sintering temperature.
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