title: Hydration mechanism and leaching behavior of bauxite-calcination-method red mud-coal gangue based cementitious materials.
abstract: A deep investigation on the hydration mechanism of bauxite-calcination-method red mud-coal gangue based cementitious materials was conducted from viewpoints of hydration products and hydration heat analysis. As a main hydration product, the microstructure of C-A-S-H gel was observed using high resolution transmission electron microscopy. It was found that the C-A-S-H gel is composed of amorphous regions and nanocrystalline regions. Most of regions in the C-A-S-H gel are amorphous with continuous distribution, and the nanocrystalline regions on scale of ∼5nm are dispersed irregularly within the amorphous regions. The hydration heat of red mud-coal gangue based cementitious materials is much lower than that of the ordinary Portland cement. A hydration model was proposed for this kind of cementitious materials, and the hydration process mainly consists of four stages which are dissolution of materials, formation of C-A-S-H gels and ettringite, cementation of hydration products, and polycondensation of C-A-S-H gels. There are no strict boundaries among these four basic stages, and they proceed crossing each other. Moreover, the leaching toxicity tests were also performed to prove that the developed red mud-coal gangue based cementitious materials are environmentally acceptable.
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Hongxu
authors.initials: H
authors.lastname: Li
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083, China. Electronic address: liuxm@ustb.edu.cn.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liu
keywords: Cementitious materials; Coal gangue; Hydration mechanism; Leaching behavior; Red mud