Effect of an alkali activators on the compressive strength and reaction mechanism of coal gangue-slag-fly ash geopolymer grouting materials.

To enable effective raw coal gangue use, the effects of various alkali activators on coal gangue-slag-fly ash geopolymer grouting material (CSFGM) were investigated. Results showed that for sodium silicate modulus at 1.4, sodium silicate content at 12% and Na 2 O content at 6%, CSFGM showed the highest compressive. The compressive strength of CSFGM was related to the porosity and the proportion of 0.01–1 μm pores, and the main reaction product was C-(N)-A-S-H gel. The sodium silicate modulus had no significant effect on the reaction products. An increased sodium silicate content caused ordering of the C-(A)-S-H gel, but the consumption of Na 2 O reduced muscovite depolymerization. The higher Na 2 O content increased the C-(N)-A-S-H gel, leading to a further refined microstructure with reduced porosity. At 4% sodium silicate incorporating, the increase of Na 2 O content mainly promotes the depolymerization and polycondensation reaction of precursors. At 12% of sodium silicate incorporating, the increase of Na 2 O content promotes the better participation of sodium silicate in the polycondensation reaction of precursors. • CG can be used as a precursor to prepare geopolymer grouting materials. • The main reaction product of CSFGM is C-(N)-A-S-H gel. • Adapting the alkali activator enhances kaolinite and muscovite reactions in CG. • High sodium silicate system requires increased alkalinity for polycondensation. [ABSTRACT FROM AUTHOR]