Technology, environment, resource and policy assessment of sustainable concrete in urban infrastructure

Cement production accounts for approximately one-seventh of total global CO2 emissions from all human activities. In addition, the consumption of virgin aggregates for concrete infrastructure has created virgin material scarcity issues in many areas of the United States. High Performance Green Concrete (HPGC) with fly ash and recycled aggregates can help reduce the demand for material inputs and reduce pollution outputs associated with bulk material flow of urban concrete. This thesis quantifies the sustainability of HPGC in urban infrastructure by addressing structural performance, environmental, economic and resource depletion impacts.; Structural (ASTM C 39) and durability tests (ASTM C 666, ASTM C 1012, ASTM C 1202) showed that HPGC containing fly ash and 50% recycled aggregate (100% of the coarse fraction) performed equally or better than ordinary Portland concrete (OPC---0% fly ash and 0% recycled aggregates) with the same cementitious content. Durability improvements were more significant with Class F fly ash than Class C. For both Class F and C, greater percent replacement of Portland cement with fly ash led to slower and lower strength gain, but still within acceptable strength criteria for CDOT Class B concrete. A baseline environmental life cycle assessment (LCA) of OPC (with 14% Portland cement) showed emissions of 1.21 tonne CO2equivalents/tonne of cement. Replacement of cement with fly ash reduced greenhouse gas (GHG) emissions by 21% to 36% for 20% and 40% Portland cement replacement; including fuel use for transport of fly ash and benefits of avoided landfilling. The incorporation of 50% recycled aggregates provided a further 5% reduction in GHG emissions.; A regional material flow analysis (MFA) and GHG inventory of the City and County of Denver (CCoD) showed per capita concrete and aggregate use of 3.59 tonnes and 9 tonnes, respectively, and that cement usage contributed approximately 2% to CCoD's GHG footprint. HPGC (with 20% fly ash and recycled coarse aggregates) was evaluated as a mitigation strategy with immediate cost savings, yielding annual community-wide GHG reductions of 60,000 MTCO2e (in 2005) reducing demand for virgin aggregates by approximately 790,000 tonnes, and direct cost savings of {dollar}2M to {dollar}4M per year.