Geopolymerization is a low-cost, low-energy-demanding, green technology that can transform a variety of silicate and aluminosilicate raw materials and industrial by-products into useful, high-added-value products. Because of their excellent mechanical properties, the use of geopolymeric materials for the replacement of traditional construction materials is gaining ground. The most commonly used raw materials for geopolymer synthesis include metakaolin, fly ash, ground granulated blast furnace slag, and their mixtures. In this work, an amorphous aluminosilicate rock (perlite) was selected as a raw material in order to determine its utility in the synthesis of new Portland cementless binders for concrete. The effect of the following synthesis parameters on the development of the mechanical properties of the geopolymeric formulations were studied: the curing conditions (t=24, 48, 72 h; T=50°C, 70°C, 90°C); the water/solid mass ratio (mw/ms=0.28 to 0.37); the Si/Al molar ratio (5.6 to 6.5); and the alkali content and type of alkali ion (R/Al molar ratio=0.65 to 1.05; R=Na or K). The structural changes were identified by means of x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), and the mechanical properties were evaluated through compressive strength measurements. The most promising formulations were used for the synthesis of mortars using standard silica sand, according to ASTM C109/109C. Also in this case, compressive strength measurements were carried out while the structure was observed using XRD, FTIR, and SEM. The present study shows that perlite is a promising raw material for geopolymer synthesis, resulting in geopolymeric pastes with compressive strengths greater than 30MPa. In contrast to the other raw materials currently used for geopolymerization, the geopolymerization of perlite requires a prolonged curing time of a total duration of 5 days at 70°C.
Author Information
Taxiarchou, M.
National Technical University of Athens, School of Mining and Metallurgical Engineering, Athens, GR
Panias, D.
National Technical University of Athens, School of Mining and Metallurgical Engineering, Athens, GR
Panagiotopoulou, Ch.
National Technical University of Athens, School of Mining and Metallurgical Engineering, Athens, GR
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