Abstract
Abstract The effect of alkali concentration and curing temperature regime on fly ash-based geopolymer pastes was investigated in this study by using NaOH solutions. Prismatic specimens were molded, cured at 65 °C and 85 °C and submitted to flexural and compressive strength tests. Unreacted fly ash and geopolymers were characterized by X-ray diffraction and thermogravimetric analysis. In general, the mechanical strength was enhanced by increasing the molar concentration and the curing temperature. This trend was confirmed by thermogravimetric data. However, for a lower amount of NaOH there were no significant differences between the strength results. The mixture with the highest strength was obtained with the 16 M NaOH solution and curing temperature of 85 °C, which resulted in flexural strength of 4.20 MPa, compressive strength of 21.35 MPa and also the highest weight loss of 9.89%.
Highlights
Portland cement is the traditional binder used in the production of concretes and mortars
Industrial wastes are used as sources of aluminosilicate minerals, class F fly ash from thermoelectric plants, which has been used in the production of Portland cement since it is able to reduce the consumption of clinker and fossil fuels and the emissions of CO2
The best results were achieved with the paste prepared with the 16 M alkaline solution and a curing temperature of 85 °C, which had a flexural strength of 4.20 MPa and compressive strength of 21.35 MPa
Summary
Portland cement is the traditional binder used in the production of concretes and mortars. Industrial wastes are used as sources of aluminosilicate minerals, class F fly ash from thermoelectric plants, which has been used in the production of Portland cement since it is able to reduce the consumption of clinker and fossil fuels and the emissions of CO2. This is an environmentally friendly solution that contributes to the reduction of the carbon footprint of concrete [3]. The effect of various NaOH molarities (8 M, 12 M, 16 M) and curing temperatures (65 °C and 85 °C) on mechanical strength of fly ash geopolymer pastes were tested
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