Micro-structural characterization of the hydration products of bauxite-calcination-method red mud-coal gangue based cementitious materials.
In this research, the micro-structural characterization of the hydration products of red mud-coal gangue based cementitious materials has been investigated through SEM-EDS, (27)Al MAS NMR and (29)Si MAS NMR techniques, in which the used red mud was derived from the bauxite calcination method. The results show that the red mud-coal gangue based cementitious materials mainly form fibrous C-A-S-H gel, needle-shaped/rod-like AFt in the early hydration period. With increasing of the hydration period, densification of the pastes were promoted resulting in the development of strength. EDS analysis shows that with the Ca/Si of red mud-coal gangue based cementitious materials increases, the average Ca/Si and Ca/(Si+Al) atomic ratio of C-A-S-H gel increases, while the average Al/Si atomic ratio of C-A-S-H gel decreases. MAS NMR analysis reveals that Al in the hydration products of red mud-coal gangue based cementitious materials exists in the forms of Al(IV) and Al(VI), but mainly in the form of Al(VI). Increasing the Ca/Si ratio of raw material promotes the conversion of [AlO4] to [AlO6] and inhibits the combination between [AlO4] and [SiO4] to form C-A-S-H gel. Meanwhile, the polymerization degree of [SiO4] in the hydration products declines.
State Key Laboratory of Advanced Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Xiaoming
X
Liu
Na
N
Zhang
Yuan
Y
Yao
Henghu
H
Sun
Huan
H
Feng
D000535:Aluminum / Q000737:chemistry; D000537:Aluminum Oxide / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D003031:Coal; D007220:Industrial Waste; D009682:Magnetic Resonance Spectroscopy; D012825:Silicon / Q000737:chemistry; D018505:Waste Management / Q000379:methods*
D003031:Coal; D007220:Industrial Waste; D000535:Aluminum; D000537:Aluminum Oxide; D002118:Calcium; D012825:Silicon
Bauxite calcination method; Cementitous materials; Coal gangue; Micro-structural characterization; Red mud