The influence of α-Al2O3 addition on microstructure, mechanical and formaldehyde adsorption properties of fly ash-based geopolymer products

► The first study to apply the geopolymer in adsorbing formaldehyde vapor. ► Appropriate α-Al2O3 addition improves the geopolymerization extent. ► Excessive α-Al2O3 addition gives rise to the dramatic decrease of compressive strength and surface area of geopolymers. ► Geopolymer exhibits better property of adsorbing formaldehyde physically and chemically.