Percorrer por autor "Oliveira, Isaac Alves de"
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- Production and characterization of fly ash-based geopolymer concretePublication . Oliveira, Isaac Alves de; Ferreira, Débora; Gomes, Helder; Pereira, Rodrigo AllanIncreasing urbanization presents environmental, economic, and social concerns, mainly derived from the impact of carbon dioxide emissions and rapid waste generation. Geopolymer concrete (GPC) is an innovative construction material with the potential to minimize the environmental threat due to fly ash (FA) waste disposal and reduce cement consumption. In this study, cement-free GPC mixes are prepared using FA as a source of aluminosilicate material. Sodium silicate (SS) and sodium hydroxide (SH) solutions were used as alkaline activators with varying SH concentrations of 4 M, 10 M, and 16 M; sodium silicate to sodium hydroxide (SS/SH) ratios of 1.5, 2.0, and 2.5; and alkaline liquids to fly ash (AL/FA) ratios of 0.35, 0.525, and 0.70. The influence of the alkaline liquids on the mechanical properties of fly ash-based geopolymer concrete (FA-BGPC) were investigated through flexural strength and compressive strength tests in preliminary tests using prismatic molds. Additionally, water absorption tests through capillarity and immersion, and another trial of compressive strength tests were done in final tests using cubic molds. A reference composition using ordinary Portland cement (OPC) was produced to compare the results. All samples were cured at controlled temperature of 25°C. The optimum flexural strength in the initial tests (6 MPa), and optimum compressive strength in the final tests (29.4 MPa) was attained with a GPC mix using 10 M, 1.5 SS/SH ratio, and 0.70 AL/FA ratio. It was found that the mechanical behavior of GPC is similar to that of OPC concrete.