An integrated life cycle assessment and life cycle analysis model for pavement overlay systems

Pavement systems have significant impacts on the environment and economy due to large material consumption, energy input, and capital investment. To evaluate the sustainability of rigid pavement overlay designs, an integrated life cycle assessment and life cycle cost analysis model was developed to calculate the environmental impacts and costs of overlay systems resulting from material production and distribution, overlay construction and maintenance, construction-related traffic congestion, overlay usage, and end of life management. An unbonded concrete overlay system, a hot mix asphalt overlay system, and an alternative engineered cementitious composite (ECC) overlay system are examined. Model results indicate that the ECC overlay system reduces total life cycle energy by 15% and 72%, greenhouse gas (GHG) emissions by 32% and 37%, and costs by 40% and 58% compared to the concrete overlay system and the HMA overlay system, respectively, over the entire 40 year life cycle. These advantages are derived from the enhanced material properties of ECC which prevent reflective cracking failures (discussed in a complementary paper). Material consumption, traffic congestion caused by construction activities, and roughness effects caused by overlay deterioration are identified as three dominant factors that influence the environmental impacts and costs of overlay systems.