Durable "Green" Cement Concrete

Concrete is the most widely used man-made material, and the manufacture of portland cement – for approximately the last 150 years an active ingredient of concrete - accounts for 5 to 10 percent of all anthropogenic emissions of carbon dioxide, a leading greenhouse gas involved in global warming. Portland cement manufacture gives rise to carbon-dioxide emissions because it involves burning fuel to de-carbonate and heat a powdered mixture of limestone, clay and other raw materials to temperatures of 1,500 ºC (2,750 ºF) or more. Worldwide, the production of portland cement alone accounts for 6 to 8 percent of all human generated CO2 greenhouse gases. Because nearly 2.77 billion tonnes (3.05 billion stons) of portland and hydraulic cement was produced in 2007 and enormous amounts of water and aggregates were consumed in the production of concrete, the concrete construction sector has a responsibility to take immediate action to reduce its environmental impacts, including the generation reduction of CO2. This responsibility also brings the opportunity to develop innovative technologies. Discussed will be non-portland Green Cements, those products that are produced with reduced to no excess process energy, have a smaller to insignificant carbon footprint, are composed of recycled and/or renewable resources and which have minimal environmental impact. The scope of this paper will include discussion on permeability, corrosion and thermal resistance and comparative life cycle of portland and non-portland cements. Baseline comparisons between portland and non-portland systems will be presented to quantify reductions in CO2 generation achieved with green cements.