The Utilisation Of Wood Ash As Alkaline Activator For Ambient Cured Geopolymer Concrete
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Date
2020-03
Authors
Samsudin, Muhammad Hasnolhadi
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
The blended hybrid geopolymer concrete utilising industrial waste ash is a new option of constituent binder material to replace ordinary Portland cement (OPC) concrete. It has a significantly reduced carbon footprint and has a positive impact on the environments. Furthermore, blended hybrid geopolymer concrete proposed to resolve the conventional geopolymer binder issues associated with a high dosage of alkaline activator and elevated curing temperature that hindered the industrial application of geopolymer binder. The study was conducted with the primary aim to hybridise industrial waste ash namely pulverised fuel ash (PFA), ground granulated blast furnace slag (GGBS), high calcium wood ash (HCWA) and silica fume (SF) with suitable alkaline activators to produce binder for concrete. The properties of the blended hybrid geopolymer concrete were assessed based on the fresh properties, mechanical, fluid transport and pore performance. Test specimens were evaluated in terms of standard consistency, setting times, compressive and flexural strength, dynamic modulus of elasticity, ultrasonic pulse velocity, water absorption, capillary absorption, porosity and microstructural performance. The inclusion of PFA at the content of 20-100% by binder weight in ternary blended hybrid geopolymer paste reduced the water demand and significantly prolonged the setting times of ternary blended hybrid geopolymer paste. Meanwhile, the addition of SF by 2-16% in quaternary blended hybrid geopolymer paste shortened the setting times instead. Enhanced compressive and flexural strengths, modulus of elasticity and ultrasonic pulse velocity were observed for ternary and quaternary blended hybrid geopolymer concrete with PFA content of 40-80% and SF of 2-12% by binder mass in comparison to Portland cement concrete, respectively. The inclusion of PFA at replacement level of 40-80 % and SF of 2-12% reduced the water absorption, capillary absorption and porosity. Besides, from SEM micrograph and EDX analysis, blended hybrid geopolymer paste matrix indicated the coexisted formation of geopolymeric hydrates of sodium aluminosilicate hydrate, calcium aluminosilicate hydrate and calcium silicate hydrate together with geopolymer framework polysialate and polysialate disiloxo that contributes to the strength development on ternary and quaternary blended hybrid geopolymer concrete. The study results indicate that ternary blended hybrid geopolymer concrete, with 80% of PFA contents (P80) and quaternary blended hybrid geopolymer concrete, with 12% of SF content (S12) exhibited significance enhanced mechanical, fluid transport and pore properties when compared with Portland cement concrete grade 30 and 50, respectively. The comprehensive body of knowledge derived from the study will lead to a broader acceptance of the blended hybrid geopolymer in various civil engineering applications.
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Keywords
Building construction