An-Najah Staff

Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation, before and/or during carbonation, may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (1) its structural and chemical simplicity, (2) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (3) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for minimizing the cost of any lamellar-hydroxide-based mineral carbonation sequestration process. This final report covers the overall progress of this grant.

Fire represents one of the most severe environmental conditions to which structures may be subjected and, hence, the provision of appropriate fire safety measures for structural members is an important aspect of design. The recent introduction of performancebased codes has increased the focus on fire resistance evaluation through computer models. One of the key components for fire resistance evaluation of reinforced concrete (RC) members is the high-temperature properties of concrete and reinforcing (prestressing) steel. Even to date, there is limited information on high-temperature constitutive relationships. This paper presents a comparative study of the high-temperature concrete constitutive relationships and illustrates the variations in the high-temperature properties of concrete. The available constitutive relationships for concrete and steel in the American and European standards are reviewed and compared to published experimental results. The different fire resistance predictions that result due to variations in the hightemperature materials properties are illustrated through case studies. Recommendations are drawn for adopting the suitable constitutive relationships for performance-based design of RC members.