Constructed wetlands (CWs) are widely used as nature-based solutions for domestic wastewater treatment; however, long-term exposure of concrete infrastructure to saturated and chemically active environments may compromise its durability. This study evaluates the mechanical performance and carbonation progression of concrete specimens exposed for one year in a full-scale CW system. Cylindrical specimens (10 × 20 cm) with design compressive strengths of 150, 200, and 250 kg/cm2 were placed in three hydraulic zones (inlet, middle, and outlet). A full factorial design (33) was implemented to assess the effects of exposure zone, concrete strength, and immersion time on compressive strength and carbonation depth. Compressive strength exhibited moderate reductions (8–15%) and remained primarily governed by the initial design strength, with significant main effects and non-significant interaction effects (p > 0.05). In contrast, carbonation depth increased progressively over time and showed clear spatial variability, reaching approximately 8–12 mm under lower exposure conditions and up to ~15 mm in outlet-zone specimens after one year, with a significant interaction between exposure zone and concrete strength (p < 0.001). These findings indicate that chemical degradation processes may advance even when mechanical performance remains relatively stable, highlighting the importance of incorporating durability considerations and spatial exposure conditions into the design and monitoring of concrete infrastructure in CW systems.
Sangabriel-Lomelí et al. (Mon,) studied this question.