Steel-Mortar and Flexural Mortar-Mortar Bond Strengths of Metakaolin-based Geopolymer

This research analyzes the interfacial bond strength of metakaolin-based geopolymer mortar across two key connections: flexural mortar-mortar and steel-mortar. It investigates the influence of varying interface roughness conditions and curing age on the bond behavior of metakaolin-based geopolymer mortar (GPM) and cement-based mortar (CM). For the mortar-to-mortar bond investigation, the flexural three-point bending test was performed on smooth and grooved interfaces after 28+7 and 28+28 days of curing, complementing previous slant shear and split tensile test results. For the steel-mortar investigation, push-in tests were conducted on 10 mm diameter ribbed and 8 mm diameter smooth steel reinforcing bars, with 7 and 28 days of curing for each. Additional tests included compressive strength, ultrasonic pulse velocity, slant shear, drying shrinkage, and split tensile tests. Results demonstrate that geopolymer mortar achieves superior bond strength compared to cement mortar, with bond strengths more than double that of cement mortar. Geopolymer mortar also attained faster bond strength on grooved surfaces. Similarly, the steel-mortar bond strength of metakaolin-based geopolymer mortar was approximately four times greater than that of cement mortar with ribbed rebars, although results were closer with smooth rebars. These findings highlight the potential of metakaolin-based geopolymer mortar to enhance bond performance while reducing environmental impact, presenting a promising avenue for sustainable construction practices.