The performance of micropore-foamed geopolymers produced from industrial wastes

Abstract

The characteristics of strong alkalinity and concentrated heavy metals make it difficult to dispose and re-utilize Bayer red mud (RM). As for another industrial waste, ZSM-5 (Zeolite Socony Mobil-5) waste is deactivated ZSM-5 catalysts that was formed from the industrial cycles. Herein, a new kind of foamed geopolymer composite (containing various ratios of RM/FA) with micropores was fabricated at elevated temperature from three industrial wastes: Bayer red mud (RM), fly ash (FA) and ZSM-5 waste. The final geopolymer products were characterized by compressive strength tests, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, FT-IR spectral analysis, and mercury intrusion porosimetry to evaluate the relationship between their microstructure, geopolymerization reactions and mechanical properties. ZSM-5 waste has the strong ability to foam because it contains ZSM-5 that possesses numerous mesoporous. The addition of ZSM-5 waste generates a microporous structure. Higher RM/FA ratios generally result in a lower compressive strength owing to the lower reactivity of the RM; however, excessive RM particles may cause the negative effect. The compressive strength in overall decreases from 10.7 to 8.0 MPa and the bulk density increases from 1.04 to 1.26 g/cm−1 with the increased RM/FA ratios of 0.4–1.0, respectively. Microscopic morphology analysis demonstrates that the final products are composites consisting of geopolymer gels and unreacted phases, such as mullite and hematite phases, as fillers. This research can shed light on the utilization and mechanisms of industrial RM and ZSM-5 waste into the construction and building materials.