Geopolymer pervious concrete modified with granulated blast furnace slag: Microscale characterization and mechanical strength

Geopolymer is green cementitious material that can be produced from industry waste or abundant earth materials through alkali-activated reaction. This study aims to conduct microscale characterization of geopolymer paste and mechanical properties of pervious concrete. Metakaolin (MK) and fly ash (FA) were used to synthesize geopolymer with granulated blast furnace slag (GBFS) as admixture. The experimental results showed that the room temperature curing was sufficient for strength formation of MK based geopolymer paste as compared to high temperature. The microscale characterization indicated that GBFS had introduced new crystal phases and better surface integrity was realized with the optimum content of GBFS. The GBFS had prominent effect on mechanical strength enhancement, and the optimum content was 10% and 30% for MK and FA based geopolymer paste and pervious concrete, respectively. In addition, mechanical strength of geopolymer pervious concrete was inversely proportional to the porosity caused by different aggregate gradations. However, when the porosity was similar, the smaller aggregate size induced the higher compressive but the lower splitting tensile strength.