Alkali silica reactions; Alternate fuels; Carbon dioxide; Cement; Fly ash; Pollutants; Pozzolan; Sustainable development; Thermal efficiency
In 2009, the International Energy Agency and World Business Council for Sustainable Development prescribed four strategies the cement industry can utilize in order to reduce CO? emissions: (1) thermal and electric efficiency; (2) alternative fuel; (3) cement substitution; and (4) installation of carbon capture and storage devices. While cement manufacturing technology is reaching its efficiency limit, and alternative fuel and carbon capture technologies are still at infancy; cement partial substitution with Secondary Cementitious Materials (SCMs) has received the most attention with positive results, reducing demand for Portland cement by 20-25%. However, with on-going closure of coal-fired power generating plants and ash ponds across the United States (US), as well as recent changes in the Environmental Protection AgencyÛªs regulations, the production of available fly ash that is acceptable for use in concrete will be more limited in future. This supply-demand problem adversely impacts cement substitution strategy, forcing concrete industry into finding and evaluating alternative sources of SCMs. One overlooked alternative to alleviate the rapidly declining sources of SCMs in the US is natural Pozzolan as a key part of the solution to reduce environmental burden of the cement industry. The overall objective of this study is to assess effectiveness of NevadaÛªs natural pozzolans as SCMs on mitigation of alkali-silicate reactivity. This project will: (1) Assess the effectiveness of different natural Pozzolans as SCMs on resistance to alkali silica reactions (ASR) of Portland cement pastes, mortars and concretes prepared with four known NevadaÛªs reactive aggregate sources. (2) Find minimum and maximum dosages of natural Pozzolans as cement replacements based on resistance to ASR, as well as strength properties, for the selected reactive aggregate sources. (3) Compare effects of Class F fly ash and natural Pozzolans on ASR resistance of Portland cement mortars and concretes.