The proprietary materials used to repair concrete structures are often polymer-modified hydraulic binders. The influence of the presence of polymer on the properties of these composites has been studied, but few works have focused on the evolution of these properties when the material is applied on a structure exposed to an environment that can be aggressive to concrete. In this paper, the properties of polymer-modified mortars made in the laboratory are reported and compared to those obtained on similar commercial products but whose precise composition is unknown. Thus, the influence of the type and quantity of polymer on the consistency, the setting time, the microstructure, the porosity and the mechanical properties of the mortars are analyzed. Special attention is given to the study of the influence of the curing conditions on the final properties of the hardened material.