Feasibility exploration on the geopolymerization activation of volcanic tuff, parametrical optimization, and reaction mechanisms

The potentiality on alkali activation of volcanic tuff with calcium-based materials, fly ash, and their mixtures as additives were comprehensively investigated in this study. Several characterization strategies have been employed for mechanism exploration. CaO and fly ash (FA) brought about more dramatic responses than CaSO 4 and alkaline activator on activating the volcanic tuff-based geopolymer, which was relatively stable under the wet-dry alternated conditions. The symmetrical stretching vibration of Si–O–T (T = Al or Si) was right-shifted to the band at approximately 1036 cm −1 , implying the incorporation of Ca into Si–O–T. FA accompanying with CaO enhanced the polycondensation, gelation, and hardening of geopolymer. However, too many quartz balls brought into geopolymer paste by an excessive amount of fly ash deteriorated the cementing quality and reduced the mechanical strengths. This work contributes to the module usage of volcanic tuff in the construction industries and supplies an innovative method in activating geopolymerization.