DOE OSTI2015
The main thrust of the project is to develop scalable, economical and convenient methods of delivering carbon dioxide to concrete, and to tailor the chemistry of concrete to make beneficial use of large carbon dioxide volumes towards achieving enhanced performance, economic, sustainability and energy-efficiency attributes. Concrete materials incorporating two different inorganic binders based on calcium silicate hydrate (Portland cement) and alkali aluminosilicate hydrate (geopolymer) were considered in the project. The novel method of carbon dioxide delivery developed in the project involves mechanosorption into cementitious materials during their size reduction. The mechanosorbed carbon dioxide becomes available during production of concrete to induce carbonation reactions which enhance concrete properties and also sequester carbon dioxide. Experimental evidence was produced for mechanosorption (mechanochemical binding) of carbon dioxide into iron slag and Portland cement, the amorphous and reactive nature of the carbonates formed via mechanosorption, and their contributions towards enhancement of concrete material properties by inducing carbonation reactions. It was shown that mechanosorption of carbon dioxide can be accomplished by simple modification of the existing milling step in production of cementitious materials. An alternative carbon dioxide delivery method was also considered where curing of concrete products was performed in carbon dioxide. A host of additives were considered to enhance the sorption of carbon dioxide, dissolution of cementitious minerals in aqueous media, carbonation reactions, and co-precipitation of hydrates and carbonates for concrete production. Experimental investigations were conducted to identify the additives which offer the greatest promise for enhancing the carbon dioxide sequestration and the beneficial effects of carbonation reactions on concrete materials with different binder chemistries. The results confirmed that tailoring the chemistry of inorganic binders to suit carbon dioxide mechanosorption and carbonation reactions yields significant benefits. Optimization experimental investigations were undertaken with selected additives to further enhance the economics, environmental and performance benefits of the process. The optimum concrete materials incorporating chemically bound carbon dioxide were thoroughly characterized. The test results demonstrated the potential to raise the carbon dioxide sequestration of concrete, and to pronounce the consequent gains in the mechanical, barrier and durability characteristics of concrete. Analytical chemistry and theoretical methods were employed to provide insight into the mechanochemical binding of carbon dioxide, the mechanisms through which carbonation reactions enhance concrete properties, and the impacts of additives on the process. Initial and life-cycle environmental, economic and energy analyses were undertaken. The outcomes of these analyses demonstrated the value of the approach in sequestering significant quantities of carbon dioxide can to induce carbonation reactions which improve diverse material properties of concrete, and significantly lower the energy content and cost of concrete production. The project outcomes offer commercially viable means of transforming concrete, the most widely used material of construction, from a major source of carbon dioxide emission and energy consumption into a valuable resource for large-volume carbon dioxide sequestration. The technology promises to significantly enhance the structural efficiency, service life, sustainability, economics and energy-efficiency of the concrete-based infrastructure
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗