Design of green engineered cementitious composites for pavement overlay applications

The construction, repair and rehabilitation of concrete pavements relies on the production and flow of large quantities of concrete and its constituents. Within the US, nearly 43 megatons of cement are used annually for the construction, repair and rehabilitation of concrete pavements, accounting for over 39 megatons of CO2 emissions. To reduce environmental impact and improve the sustainability of pavement overlay systems, a class of materials called Engineered Cementitious Composites (ECC) has been designed for durable rigid pavement overlays. ECC overlays are designed to enhance sustainability in two ways. First, ‘‘greener’’ ECC materials incorporate high volumes of industrial wastes including fly ash, ground granulated blast furnace slag (GGBFS), and waste foundry sands and carbon residue to reduce the environmental impacts of material production. Fundamental micromechanics carefully guide the green material design to maintain pseudo-strain hardening material behavior under tension. This ductile behavior is critical to the second mechanism for sustainability enhancement. Through a distinct fracture phenomenon, the ductility of ECC effectively eliminates reflective cracking, a major cause of premature overlay failure, thereby increasing durability and reducing life-cycle maintenance. Experimental and theoretical analyses verify the green material and durable overlay design approaches. Incorporating industrial wastes, over 70% of ECC virgin constituents have been replaced without reducing critical mechanical performance characteristics. The combination of green raw materials, a 50% reduction in overlay thickness, and a doubling of service life as compared to concrete overlays, leads to significant sustainability improvements have been achieved. This paper presents the methodology and results of incorporating green cementitious materials design into rigid pavement overlay systems.