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    Alkali-activated and geopolymer materials developed using innovative manufacturing techniques: A critical review
    (Elsevier Sci Ltd, 2021) Gokce, H. S.; Tuyan, M.; Nehdi, M. L.
    The manufacturing of geopolymers and alkali-activated materials for precast and cast in-situ construction applications could be achieved using suitable production techniques, such as one-part production, pre-setting pressure and hot pressing, two-stage concreting, and 3-dimensional printing. Adequate selection and tailoring of the manufacturing methodology are imperative for overcoming characteristic application problems of these materials and achieving eco-efficiency and superior engineering properties. With distinctive benefits including rapid solidification, lower cost, saving natural resources, less energy consumption, and reduced carbon footprint, alkali-activated and geopolymer composites have emerged as a strong contender for replacing conventional concrete in diverse construction applications. Critical analysis of the literature on innovative production methods indicates that the one-part production technique is promising for the eliminating design complexity of these mixtures. The pre-setting pressure and hot pressing applications would allow the achievement of superior physical and mechanical characteristics in a short period of time, especially for the precast industry. The workability and setting problems of alkali-activated materials could be overcome using the two-stage concreting methodology. To be used in 3D printing of alkali-activated and geopolymer materials, remarkable development is required in terms of rheological aspects. Accordingly, this paper surveys pertinent and recent literature and critically reviews the state-of-the-art of alternative production techniques of alkali-activated and geopolymeric materials, along with its use in recent applications, identifies pertinent knowledge gaps, and defines future research directions.
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    Development of Eco-Efficient Fly Ash-Based Alkali-Activated and Geopolymer Composites with Reduced Alkaline Activator Dosage
    (Asce-Amer Soc Civil Engineers, 2020) Gokce, H. S.; Tuyan, M.; Ramyar, K.; Nehdi, M. L.
    The eco-efficiency and economy of geopolymer composites largely depend on their alkaline activator dosage. In this study, the effect of applying a pre-setting pressure and variation of the aggregate-to-fly ash ratio on the alkaline solution dosage and mechanical strength of fly ash-based geopolymer composites was explored. It is shown that through control of the aggregate-to-ash ratio and application of pre-setting pressure, compressive strength could be increased by 102% and 86% for Class F fly ash-based geopolymer and alkali-activated Class C fly ash-based mixture, respectively. The total alkaline solution consumption could be reduced from 718 to 188 kg/m(3) and from 769 to 262 kg/m3 for Class F fly ash-based geopolymer and alkali-activated Class C fly ash-based mixture, respectively. The proposed method reduced the alkaline solution consumption per compressive strength (6.2 kg.m(-3).MPa-1) by up to 85% compared to that of the reference manually consolidated control geopolymer. The findings demonstrate that fly ash-based geopolymers could be made more sustainable and eco-efficient through tailored production techniques. (C) 2019 American Society of Civil Engineers.