Application of geopolymer paste for concrete repair

In this study, ground granulated blast furnace slag and coal fly ash were used as raw materials to prepare geopolymer paste as repair material for concrete structure. The functional properties, such as compressive strength, fluxural strength, and bonding strength between slag/fly ash based geopolymer paste and paste substrate were investigated. The SiO2 /Na2O molar ratio of the alkali activator plays an important role on the strength of geopolymer paste. The nature of the geopolymeric reaction product was examined using FTIR and NMR. The compressive strengths and flexural strength of the geopolymer paste were 47 MPa and 16 MPa, respectively. For concrete substrate bonded with geopolymer paste, the compressive strength test shows up to 120% repairing rate can be achieved. By comparing with Portland cement, it can be proved that the slag/fly ash based geopolymer paste has very good potential for further engineering development in the future.