Alkali-activated complex binders from class C fly ash and Ca-containing admixtures |
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| Authors: | Xiaolu Guo Huisheng Shi Liming Chen Warren A. Dick |
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| Affiliation: | 1. Key Laboratory of Advanced Civil Engineering Materials (Tongji University), Ministry of Education, 1239 Siping Road, Shanghai 200092, China;2. School of Environment and Natural Resources, The Ohio State University, 1680 Madison Avenue, Wooster, OH 44691-4096, USA;1. TRC Engineering and Consulting, 215 Greenfield Parkway, Liverpool, NY, United States;2. School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-5306, United States;1. Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade, Serbia;2. Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia;1. Construction Research Center, Institute for Smart Infrastructure and Innovative Construction, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia;2. Department of Materials Science, Research Institute of Hydro-Québec, 1800 Mte Ste. Julie, Varennes, Québec J3X 1S1, Canada |
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| Abstract: | Processes that maximize utilization of industrial solid wastes are greatly needed. Sodium hydroxide and sodium silicate solution were used to create alkali-activated complex binders (AACBs) from class C fly ash (CFA) and other Ca-containing admixtures including Portland cement (PC), flue gas desulfurization gypsum (FGDG), and water treatment residual (WTR). Specimens made only from CFA (CFA100), or the same fly ash mixed with 40 wt% PC (CFA60–PC40), with 10 wt% FGDG (CFA90–FGDG10), or with 10 wt% WTR (CFA90–WTR10) had better mechanical performance compared to binders using other mix ratios. The maximum compressive strength of specimens reached 80.0 MPa. Geopolymeric gel, sodium polysilicate zeolite, and hydrated products coexist when AACB reactions occur. Ca from CFA, PC, and WTR precipitated as Ca(OH)2, bonded in geopolymers to obtain charge balance, or reacted with dissolved silicate and aluminate species to form calcium silicate hydrate (C-S-H) gel. However, Ca from FGDG probably reacted with dissolved silicate and aluminate species to form ettringite. Utilization of CFA and Ca-containing admixtures in AACB is feasible. These binders may be widely utilized in various applications such as in building materials and for solidification/stabilization of other wastes, thus making the wastes more environmentally benign. |
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