The University of Massachusetts Amherst
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Synthesis and characterization of red mud and rice husk ash-based geopolymer composites

TitleSynthesis and characterization of red mud and rice husk ash-based geopolymer composites
Publication TypeJournal Article
Year of Publication2013
AuthorsHe J, Jie Y, Zhang J, Yu Y, Zhang G
JournalCement and Concrete Composites
Start Page108
Date Published03/2013
KeywordsComposite, compressive strength, Geopolymer, Microstructure, Red mud, Rice husk ash

A new type of geopolymer composite was synthesized from two industrial wastes, red mud (RM) and rice husk ash (RHA), at varying mixing ratios of raw materials and the resulting products characterized by mechanical compression testing, X-ray diffraction, and scanning electron microscopy to assess their mechanical properties, microstructure, and geopolymerization reactions. Prolonged curing significantly increases the compressive strength and Young’s modulus, but reduces the ductility. Higher RHA/RM ratios generally lead to higher strength, stiffness, and ductility, but excessive RHA may cause the opposite effect. The compressive strength ranges from 3.2 to 20.5 MPa for the synthesized geopolymers with nominal Si/Al ratios of 1.68–3.35. Microstructural and compositional analyses showed that the final products are mainly composed of amorphous geopolymer binder with both inherited and neoformed crystalline phases as fillers, rendering the composites very complex composition and highly variable mechanical properties. Uncertainties in the composition, microstructure, the extent of RHA dissolution, and side reactions may be potential barriers for the practical application of the RM–RHA based geopolymers as a construction material.