THE ROLE OF HVFA CONCRETE IN THE SUSTAINABILITY OF THE URBAN BUILT ENVIRONMENT

Although fly-ash as a partial replacement for cement has been utilized for many years, its use has been almost exclusively used in low volume percentages such as 10% or 20% cement replacement. This paper looks at high volume percentage replacements from 40% to 70%. A mini-mix study revealed that 50% and 60% cement replacement percentages were the best candidates for full scale testing. The environmental benefits included a 25% reduction in smog, human health, and fossil fuel reduction compared to the same element built with 100% Portland cement mix. The economic benefits included a 15% capital cost reduction and a 20% life-cycle cost reduction when compared with a 100% Portland cement mix. Full scale testing included a complete mix design in addition to the construction of four concrete infrastructure products. The products built included an alley panel and curb and gutter sections in the City and county of Denver, a precast manhole and lid, and a twin tee prestressed girder. Although cement products are just one of many materials used in the construction of the built environment, its production has a large impact on the environment. Lowering the embodied energy of multiple types of construction materials will have a significant effect on sustainable urban development. Symbiotic recycling of waste material, such as fly ash in concrete, back into the built environment can help reduce materials on the input side and pollution on the output side of the hulk material flow of an urban city.(4)