A study on the characteristics and microstructures of GGBS/FA based geopolymer paste and concrete

•Focus on characteristics changes of geopolymer concrete after indoor/outdoor curing.•Compressive strength reach over 53 MPa after 180 days of indoor/outdoor curing.•Geopolymer concrete has excellent chloride resistance over prolonged curing time. The purpose of this study is to focus on the durability of geopolymer concrete after nine months of an indoor and outdoor curing period. The geopolymer paste was prepared with fly ash and ground granulated blast furnace slag as raw materials and sodium silicate/sodium aluminate as an alkali activator. The geopolymer concrete was prepared with a 1:2.5:2.4 geopolymer:sand:gravel ratio. The influence of sodium aluminate, wollastonite additions and NaOH concentration on the microstructure, physical and mechanical properties were evaluated. The compressive strength of the geopolymer concrete can reach 67 MPa and 53 MPa after 180 days of indoor and outdoor curing, respectively. Rapid Chloride Ion Permeability Test (RCPT) shows the geopolymer concrete has excellent chloride resistance over prolonged curing time. After 180 days of accelerated wetting-drying cycles, the continued growth of compressive strength indicates the good weathering resistance of geopolymer concrete. According to the test results obtained during this study, the geopolymer has a high potential to be a key material for civil construction.