First, the physical and mechanical characteristics of the six adhesives and the concrete used were studied. The factors investigated were the viscosity and the compressive strength of the adhesives during their working life, and the variation of the compressive strength of the base and overlay concrete. Later, the specimens were sawn at a 45-degree angle. Afterwards, the shear test was used and the factors affecting the bonding interface were analyzed.

The results indicated that the compressive strength of the concrete studied, the interface roughness of the base concrete, the viscosity of the adhesives and the compressive strength of the adhesives at the time of application have important effect on the ultimate strength and on the bond strength when the mixed specimen is subjected to the slant shear stress. The Analysis of Variance (ANOVA) was used to assess the results.

The performance of commercial epoxy adhesives varies when applied to bond concrete of different strengths. The differences are smaller when applied to concrete of compressive strength in the order of 33 MPa and larger when applied to concrete of compressive strength in the order of 46 and 59 MPa, demonstrating that the concrete strength affects the performance of the epoxy adhesive. In high-strength concrete, the bonding process should be validated prior to application by studying the bonding mechanisms, the substrate roughness and the differences in compressive strength of the substrate and the overlay/repair concrete. In addition, the adhesive adopted should be previously analyzed to verify if it is compatible with the concrete strength.

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