The critical element for sustainable growth in the construction industry is the development of alternative cements. A new technological process called geopolymerization provides an innovative solution, and the presence of aluminum and silicon oxides in pozzolans has encouraged its use as a source material. The present study investigated the material’s properties, practices and bonding properties between geopolymeric repair material (mortar) and concrete substrate. An experimental program was executed to establish a connection between the alkaline activator composition and the properties of geopolymer mortar and concrete in fresh and hardened states. Concentrations of sodium hydroxide and sodium silicate were ascertained that are advantageous for constructability and physical properties. Also, the influence of the properties of the repair materials itself and also the surface preparations of concrete substrate on bond strength was evaluated. The factors affecting the bond strength was studied through slant shear tests made on 72 specimens. The initial and final setting time in 50%CPA/50%MK, 100%CPA/0%MK geopolymer repair mortar is considerably shorter than cement-based mortar, which can be in most cases beneficial for using this type of mortar in repairing concrete structures. 100%CPA/0%MK geopolymer mix delays the initial setting time to 25 minutes, and the final setting time to 60 minutes. Substituting 50%CPA and 50%MK by weight of binder (precursor) in geopolymer mortar is the optimum amount to achieve the good compressive strength and enhanced slant shear bond strength. Grooved surface treatment method gave the highest slant shear bond strength with 7.31 N/mm2 value. The interfacial transition zone through Scanning Electron Microstructure (SEM) showed that geopolymer made from CPA and MK is chemically bonded to the concrete substrate. The increase in Ca++ ion balanced the negative charge of Al3+ ions, which lead to a dense interface zone. All the test results indicate that there is potential for the concrete industry to utilize alkaline activated blended Cassava Peel Ash and Metakaolin as an alternative to Portland cement in repair of concrete.
Wuna et al. (Wed,) studied this question.