Compatibility of different fibres with red mud-based geopolymer grouts.

• A new strength enhancement method for red mud-based grout was proposed. • Workability of red mud-based grout was investigated. • Mechanism of fibres on the properties of red mud-based grouts was analyzed. Grouting materials are subjected to high stress during underground engineering construction and are easily damaged. To overcome the shortcomings of red mud-based geopolymer grout, systematic experiments were conducted to analyse the workability, mechanical properties and failure mode of red mud-based grouts reinforced with polypropylene, glass and basalt fibres. Micro-structural analysis was conducted to reveal the mechanism of the effects of fibres on the geopolymer grouts, and the results show that the yield stress of the red mud-based grouts increased with the fibre content. The addition of polypropylene, glass and basalt fibres increased the mechanical strength of the grouts by 27.5%, 32.6% and 27.3% and increased the flexural strength by 16.07%, 30.35% and 35.36%, respectively. Moreover, all fibre-reinforced red mud-based grouts exhibited higher elastic modulus and low porosity, as revealed by the longitudinal wave velocity performance and mercury intrusion porosimetry. Micro-structural analysis of the grouts revealed an effective interfacial bonding between the fibres and the geopolymeric binder. The obtained grouts overcome the shortcomings of red mud-based geopolymer grouts and exhibit an improved utilisation rate of red mud in geotechnical engineering. [ABSTRACT FROM AUTHOR]