University Transportation Research Center (UTRC), City College of New York
Alkali aggregate reactions, Climate change, concrete, Cracking, Energy consumption, Pollutants, Raw materials, Shrinkage, Sustainable development
Concrete is one of the most commonly used construction materials for building nationÛªs infrastructure such as roadways, bridges, tunnels, and buildings, with a per-capita consumption of more than two tons. The most energy consuming and expensive component of concrete is Portland cement, which accounts for more than 70% of the raw material cost towards producing concrete. One metric ton of Portland cement production consumes about 5,792,000 BTU of energy. In addition to the cost and vast energy consumption, cement manufacturing processes releases significant amount of into CO2 the atmosphere. The chemical reactions of raw materials during pyro-processing produce about 0.54 tons of CO2 for every ton of cement manufactured. Another 0.43 tons of per CO2 ton of cement is released from the fuel used for burning the raw materials. Thus it is not surprising that cement manufacturing process accounts for 4-5% of global CO2 emission and it touches on wide range of sustainability issues including climate change, pollution, solid waste land filling and resources depletion. A solution to address these environmental and energy challenges is to develop a sustainable alternative binding material that can replace the whole or at least part of the cement used in concrete. Significant effort has been invested in developing alternative binding materials by activating commonly available industrial by-products, such as Fly ash (FA) and Granulated blast furnace slag (GGBFS) using alkalis. The resulting concrete is called as alkali activated concrete (AAC) (also known as cement free /Geopolymer concrete).