<p>Evaluating the bond strength between geopolymer mortar (GPM) and the concrete substrate is a significant factor in ensuring the durability and effectiveness of utilizing it as a repair material. Although geopolymers are becoming more interesting due to their positive environmental impacts and perfect mechanical properties, limited studies have focused on studying the bond strength between GPM and concrete, especially the combined effect of surface treatment techniques and bonding agents on moderate/high-strength concrete substrates. This study aims to evaluate the bond strength developed between concrete substrates and a GPM made of fly ash (FA) and ground-granulated blast furnace slag (GGBS) by assessing&#xa0;the impact of surface treatment techniques and the compressive strength of the concrete substrate. In addition, the present work investigated deeply the effect of applying bonding agents on the adhesion performance between the two materials. The experimental results indicated that the bond strength between the FA/GGBS-based GPM and concrete substrate gained about 96% of its ultimate strength within the first 7 days of curing. Exposing the coarse aggregate of the concrete substrate helped to improve the bond strength by about 29%. Using a high-strength concrete substrate contributed to enhancing the developed bond by about 17%. Nevertheless, the bond strength degraded dramatically when the bonding agent was applied to the concrete substrate. The SEM and roughness analyses were valuable techniques employed for interpreting the unexpected effect of the bonding agent on the bond strength between the FA/GGBS-based geopolymer mortar and concrete substrate.</p>