Abstract
Abstract The use of geopolymer has been studied as a potential substitute for Portland cement due to lower CO2 emission and improvements on structural properties. Some of the major raw materials used in the manufacture of the geopolymer are: steel slag, fly ash and metakaolinite. Due to the impurities contained in these raw materials, the present study uses high purity synthetic aluminosilicates made from the sol gel process for production of geopolymers. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). The results showed that the synthetic aluminosilicates have similar behavior to metakaolinite (reference). It was found that the coordination of Al in the synthetic aluminosilicate changed from VI to IV and V from 300 °C, with the highest intensity at 900 °C. Temperature at which the highest mechanical strength of the geopolymer was also observed.
Highlights
Portland cement concrete is a versatile material with relatively low costs, becoming one of the world’s most consumed materials
X-ray diffraction (XRD) diffractograms (Figure 1) show that the peaks attributed to the synthetic aluminosilicate (S-AS) samples range from 22° to 25°, while the peak of the geopolymer sample cured at 60 °C occurs at approximately 28°
The samples show peaks in the region within 15° and 35°, similar to observed in the XRD spectrum of metakaolinite 2
Summary
Portland cement concrete is a versatile material with relatively low costs, becoming one of the world’s most consumed materials. The concrete lifespan is another inconvenience due to limitations concerning its porous nature. These restrictions foster the need of alternative materials to Portland cement such as geopolymers. In a pioneer study by Joseph Davidovits in 1970 2, this term was introduced to describe a class of solid materials synthesized by the reaction of powdered aluminum silicate with an alkaline solution, forming an inorganic polymer 3,4.The application of geopolymers is not limited to the use in civil construction, having potential to be used as: fireproof material, refractory, composites for repair of toxic and radioactive waste reservoir, decorative artifacts 2, electrical conductors 5, biomaterials 6, storage and gas capture 7 and others. The geopolymer is a hydrated aluminosilicate mineral with a polymeric structure. It consists of materials with activated Si and Al in solutions with medium to high alkalinity. The chaotic spatial configuration obtained between the sialates make the structure predominantly amorphous 2
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