【摘 要】
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Geopolymers are a new type of cement, obtained through a chemical reaction between an amorphous aluminosilicate precursor and an alkaline activator, resulting in the formation of hardened material.Now
【机 构】
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Núcleo Orientado para Inova(c)(a)o de Edifica(c)(o)es (NORIE), Universidade Federal do Rio Grande do
【出 处】
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The 14th International Congress on the Chemistry of Cement (
论文部分内容阅读
Geopolymers are a new type of cement, obtained through a chemical reaction between an amorphous aluminosilicate precursor and an alkaline activator, resulting in the formation of hardened material.Nowadays,there is particular interest in the development of these novel cements due to its lower environmental footprint when compared to ordinary Portland cement (OPC), as well as their technical advantages, including high compressive strength, low permeability and higher chemical stability under certain conditions of exposure.This paper assesses the use of two industrial wastes generated in a large volume in Brazil, which are currently disposed in landfills, and have no commercial value.A kaolinitic sludge from the mining industry (CKS) and a bottom ash (BA) generated during coal combustion in a thermal station were used as precursors.Thermal and mechanical treatments were applied to the raw materials in order to increase their reactivity.The CKS/BA blends geopolymers were synthesized with an overall SiO2/Al2O3 molar ratio between 4 and 5, an overall Na2O/SiO2 molar ratio of 0.25.The reaction products formed during the geopolymerisation were assessed up to 90 days of curing by different characterization techniques, including isothermal calorimetry, X-ray diffractometry, Fourier transformed infrared spectroscopy, and thermogravimetric analysis.Complementary,compressive strength at different ages of curing were also determined.The results show these waste are suitable precursor for the production of alternative geopolymers-based cement, with compressive strength higher than 45 MPa after 7 days of curing The content of silicates soluble in the alkali activator (through the adjustment of the SiO2/Al2O3 molar ratio) plays an important role during the geopolymerization.Increase the silicates content lead the formation of a highly dense and crosslinked Si-enriched type gel with low Al content when compared to the geopolymers produced with lower SiO2/Al2O3 molar ratio.This elucidates that geopolymerisatios can be a viable solution for the valorization of these industrial wastes.
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