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Geopolymer

About: Geopolymer is a research topic. Over the lifetime, 6776 publications have been published within this topic receiving 157991 citations. The topic is also known as: geopolymers.


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Journal ArticleDOI
TL;DR: In this paper, the effect of moisture content, concrete strength, heating rate and temperature level on the spalling behavior of geopolymer concrete is investigated through the measurement of residual compressive and splitting tensile strength, variation in permeability (by sorptivity test) and chemical composition (by X-ray diffraction test).
Abstract: Fire-induced spalling is a serious risk to concrete structures, especially for high strength concrete structures. This paper presents results from high temperature spalling tests on geopolymer concrete. The effect of moisture content, concrete strength, heating rate and temperature level on the spalling behavior of geopolymer concrete is studied. The temperature-induced spalling mechanism in geopolymer concrete is investigated through the measurement of residual compressive and splitting tensile strength, variation in permeability (by sorptivity test) and chemical composition (by X-ray diffraction test) of geopolymer concrete after elevated temperature exposure up to 700 °C. The test results indicate that geopolymer concrete exhibit a good spalling resistance as compared to that of OPC concrete. The lower spalling risk in geopolymer concrete under high temperature exposure is facilitated from the highly connected pore structures and lower strength degradation with temperatures. Further results indicate that the pore structure (permeability) of geopolymer concrete gets a significant evolution with the exposure temperature, especially above 500 °C range. This is related to the sintering reaction in geopolymer binders at high temperatures.

108 citations

Journal ArticleDOI
TL;DR: In this article, the durability of steel reinforced-concrete specimens made from three alkali-activated fly ash (FA) stockpiles and ordinary portland cement (OPC) in cyclic wet-dry chloride environment was evaluated over a period of 12 months.
Abstract: The durability of steel reinforced-concrete specimens made from three alkali-activated fly ash (FA) stockpiles and ordinary portland cement (OPC) in cyclic wet-dry chloride environment was evaluated over a period of 12 months. Testing methods included electrochemical methods, chloride diffusion and contents analysis, chemical and mechanical analyses, and visual examination. Geopolymer concrete (GPC) specimens made from Class F FA exhibited lower diffusion coefficients, chloride contents, and porosity compared with their GPC Class C FA and OPC counterparts. Overall, GPC specimens displayed limited signs of leaching and corrosion product formation, whereas OPC specimens exhibited the formation of multiple corrosion products along with significant leaching.

107 citations

Journal ArticleDOI
TL;DR: In this paper, the importance of mix design parameters affecting the mechanical properties of metakaolin-based geopolymers has been quantitatively assessed, and machine learning-based classifiers were employed for strength predictions.

107 citations

Journal ArticleDOI
TL;DR: In this article, the local structural correlations of metakaolin-based geopolymer gel have been elucidated using in situ neutron pair distribution function analysis, following the structural changes occurring due to dissolution and repolymerization molecular processes.
Abstract: Geopolymer cement is fast becoming a technologically important alternative to ceramics and traditional cement. However, the amorphous nature of the phases which participate in the molecular processes occurring during evolution of geopolymer gel has made nanoscale research challenging. Here, for the first time, the local structural correlations of metakaolin-based geopolymer gel have been elucidated using in situ neutron pair distribution function analysis, following the structural changes occurring due to dissolution and repolymerization molecular processes. Over the initial 17 h of reaction, the subtle structural changes observed predominantly relate to dissolution of the initial metakaolin precursor before formation of the gel. After 90 days the gel has formed and has transitioned from the initially formed geopolymer structure (gel 1) to a more stable and more ordered state (gel 2), via an increase in cross-linking within the geopolymer gel. Through analysis of precursor dissolution behavior in different activator solutions, the impact of morphology on the rate of dissolution has been postulated, with layered precursors (metakaolin) shown to behave differently than spherical precursors (fly ash) depending on the type of activator solution used. Hence, this investigation reveals the important structural changes occurring during synthesis of this new class of low-temperature ceramics.

107 citations

Journal ArticleDOI
TL;DR: In this paper, the fraction of metakaolin consumed varied from 10(8) to 75(3) wt% for geopolymers with compressive strengths varying from 3.1(2) to 67(17) MPa, respectively.
Abstract: This study presents four independent methods to determine the fraction of metakaolin dissolution in geopolymers. Two quantitative X-ray diffraction (XRD) results agreed with two independent techniques using scanning electron microscopy. The fraction of the metakaolin consumed varied from 10(8) to 75(3) wt% for geopolymers with compressive strengths varying from 3.1(2) to 67(17) MPa, respectively. It is proposed that the increase in strength with higher consumption of metakaolin is primarily due to the resultant changes in the matrix chemistry rather than changes in the quantity of matrix. Input Si/Al ratios of 1.5, 1.9, 2.5, and 3.0 resulted in matrix Si/Al ratios of 1.7, 2.3, 3.8, and 21. As anticipated the fraction of metakaolin dissolved was found to vary with OH− concentration. The area ratio method and the partial or no known crystal structure method have been identified as suitable for analysis of geopolymerization by time resolved XRD.

107 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,059
20221,744
2021990
2020891
2019752
2018658