Effects of adding nano-TiO2 on compressive strength, drying shrinkage, carbonation and microstructure of fluidized bed fly ash based geopolymer paste

• A geopolymer is proposed based on fluidized bed fly ash.
• Nano-TiO2 enhances both the early and later compressive strength of geopolymer.
• Nano-TiO2 accelerates the formation of geopolymer and refines the microstructure.
• Nano-TiO2 improves the carbonation resistance of geopolymer.
• Nano-TiO2 reduces the drying shrinkage of geopolymer.

This study aims to investigate the effects of nano-TiO2 addition on properties of fluidized bed fly ash based geopolymer. Compressive strength, drying shrinkage, carbonation and microstructure of fluidized bed fly ash based geopolymer incorporating nano-TiO2 were reported. Geopolymer specimens were prepared by alkali activation of fluidized bed fly ash in sodium silicate and sodium hydroxide solutions and were cured in microwave radiation environment plus a heat curing period. Properties for geopolymer with and without nano-TiO2 were assessed and compared. The experimental results reveal that the addition of TiO2 enhances both the early and later age compressive strength of geopolymer with the increasing content of nano-TiO2. The strength enhancement effect of nano-TiO2 on geopolymer is more obviously when 5% nano-TiO2 is introduced at 28-day. Microstructure analysis uncovers that the addition of nano-TiO2 promotes the formation of geopolymer and results in compact microstructure with less cracks. The incorporation of nano-TiO2 particles improves the carbonation resistance and reduces the drying shrinkage of geopolymer.

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