Use phase assessment of photocatalytic cool pavements

Pavement Life Cycle Assessment (LCA) can be used to evaluate the environmental benefits of photocatalytic, cool concrete overlays. The use phase assessment of concrete overlays made of gray and white cement incorporating titanium dioxide (TiO2) was investigated to quantify their environmental impact on vehicular pollutant removal, Urban Heat Island (UHI) effect, and building energy consumption. Pollutant removal was estimated, with a higher decrease in NOx removal for white cement than gray cement. The UHI effect was quantified through a microscale thermal model with white cement concrete overlays resulting in five times less Global Warming Potential (GWP) than gray cement. Building energy consumption was evaluated using air temperature obtained from the ENVI-met model and empirically-derived relationships. White cement significantly decreased the cooling load in summer but increased the heating load in winter as compared to gray cement, with a net decrease in energy consumption of 9.5 kWh per capita per year. These impacts were then converted into ten Normalized Environmental Impact Parameters (NEIPs) and a single-score Net Environmental Impact (NEI) for comparison. As compared to gray cement without TiO2, the application of white cement with TiO2 led to a decrease in all NEIPs and NEIs. The largest reduction in NEI was for white cement with TiO2 at −1.16×10−2 and the least reduction in NEI was for gray cement with TiO2 at −5.35×10−4.