الفهرس 
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Abstract
1: -Introduction: - Ultra-High Performance Concrete (UHPC) is a new class of concrete technology and a remarkable increase in durability compared even with high-performance concrete (HPC). UHPC tends to exhibit superior properties such as advanced strength, durability and long term stability. Ultra-high performance concrete (UHPC) is made using fine, coarse aggregate, very low amounts of water and high amounts of cement. These materials are characterized by dense microstructure. Adequate workability is obtained by using superplastisizer in combination with low water demand of fresh concrete, but it is a brittle material. Fibers are added to improve durability and toughness and to change the mechanism of concrete failure from brittle failure to ductility failure. By using available materials in Egypt, a composite concrete was produced which has the properties of Ultra-High Performance, fibrous concrete, and high strength concrete. 2: - Research scope: - The scope of this research included an examination of the influence of elevated Temperatures and different exposure time with different cooling regimes on Ultra-High performance Concrete. 3:- Research Objective: The objectives of the research work to study the influence of elevated Temperatures and different exposure time with different cooling regimes on the mechanical properties of Ultra-High performance Concrete. 4:- Steps Study: - To achieve the aims of the study six specimens were produced by UHPC Mix and which exposed to elevated temperatures with different exposure times (1, 2, 4) hours and with different cooling regimes and compared with the reference specimens which is not exposed to elevated temperatures. The hardened properties measured by the compressive strength, splitting tensile strength, Mass Loss, and Water Absorption. 5: - Summary of Study:- The results showed that ability to produce UHPC by available material in Egypt is possible and elevated temperatures up 200 C used as heated curing generally, the hardened properties of the concrete revealed slightly increase in compressive strength up 200 C, while there marked increase in the splitting tensile strength. The cooling regime of quenching in water helps compression strength and hardness recovery before 200 ºC till two-hour exposure time but after that is defect the strength.