Net Carbon Sink Potential of Porous Vegetated Concrete: A Life-Cycle Assessment

Porous vegetated concrete has been widely used in highway slope protection because it provides both engineering stability and ecological restoration benefits. However, its life-cycle carbon emissions and long-term carbon sequestration performance have not been systematically quantified within a unified evaluation framework. In this study, 1 m³ of porous vegetated concrete was adopted as the functional unit, and a life-cycle assessment framework integrating carbon emissions and carbon sequestration was established. The results show that the material production stage is the dominant source of life-cycle carbon emissions, with cement consumption being the primary controlling factor. Under the system boundary and carbon sequestration assumptions adopted in this study, cumulative carbon sequestration over a 50-year service period was estimated to be approximately 470-475 kgCO₂eq. This exceeded the corresponding life-cycle carbon emissions of 73-124 kgCO₂eq and resulted in a net carbon sink potential of approximately 351-397 kgCO₂eq. Based on equal weighting of 28-day shear strength and material production-stage carbon emissions, the efficacy coefficient method identified M2 as the preferred mix proportion for balancing mechanical performance and low-carbon objectives within the selected evaluation framework. Monte Carlo simulation confirmed the statistical stability of the estimated mean carbon emissions during the material production stage. Sensitivity analysis further showed that cement-related emissions and the vegetation carbon sequestration factor were the two most influential parameters affecting life-cycle carbon performance. Overall, this study provides a quantitative basis for evaluating the net carbon sink potential of porous vegetated concrete and offers decision support for low-carbon mix design in highway slope ecological protection engineering.