Investigation on deterioration mechanism of geopolymer cemented coal Gangue-Fly ash backfill under combined action of high temperature and salt corrosion environment

•A customized temperature-controlled corrosion chamber was used to carry out the salt-temperature coupling corrosion experiment of GCGFB.•The damage mechanism of GCGFB under combined action of high temperature and salt corrosion environment is analyzed.•The macroscopic properties of GCGFB under combined action of high temperature and salt corrosion environment are analyzed.•The microstructure of GCGFB under combined action of high temperature and salt corrosion environment is analyzed.