Polymer-modified cementitious systems (PMMs) are widely used in civil engineering applications for repair and waterproofing due to their specific characteristics. However, manufacturer guidelines often do not cover all real-world conditions, particularly regarding curing protocols and environmental sensitivity. This study investigates the influence of curing duration and accelerated weathering on the performance of PMMs to support the development of performance-based application guidelines. Mortars incorporating conventional polymers—styrene-butadiene rubber (SBR) and polyacrylic ester (PAE), as well as a novel silane-based emulsion (SIL), were compared with unmodified cementitious mortar (UCM). Specimens were cured for 1, 7 and 28 days, followed by exposure to alternating UV radiation and wetting cycles to simulate accelerated weathering. The mortar performance was evaluated in terms of fresh properties, pore structure, mechanical strength and durability. The results show that the performance with PMM varied significantly with curing duration and environmental exposure. The SBR and PAE systems were more sensitive to curing time, with only the 28-day curing condition ensuring strength retention after weathering. SBR-modified mortars exhibited the lowest drying shrinkage under minimal curing (1 day) but were more permeable under these conditions. In contrast, SIL-modified mortars showed better resistance to weathering, with improvement in both strength and permeability attributed to the UV stability of Si–O-Si bonds and a refined pore structure, evidenced by a 11% reduction in total porosity, compared with UCM. The SIL systems also exhibited minimal sensitivity to curing duration, and further performance gains with increased polymer dosage, which has an optimal level of 1%. These findings highlight the critical importance of aligning polymer selection and curing strategies with the environmental exposure and underscore the potential of SIL-based systems in conditions, especially where optimal curing cannot be assured or weathering could occur.
Rajendran et al. (Sat,) studied this question.