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Dune sand is a very abundant material in south of Algeria. Its high silica content gives a partial pozzolanic reactivity due to its crystalline state. This paper investigates the evolution of cement hydration based on a binary addition particularly the reactivity of dune sand finely ground in the presence of an amorphous addition: silica fume or blast furnace slag. Thus, four combinations of binary additions by substitution have been chosen. The X-ray diffraction analyses performed on cement pastes containing additions have shown the importance of the mineralogy and silica content of additions on their pozzolanic reactivity. Dune sand becomes reactive at long term, especially when associated up to 10% of amorphous addition (blast furnace slag or silica fume). It results an increasing in mechanical strength of Ultra High Performance Concrete (UHPC) and an improvement of the microstructure

The new requirements for strength and durability have led to the development of Ultra High Performance concrete (UHPC) with outstanding mechanical properties and durability. However, the application of this type of concrete is exceptional, because of the high dosage of cement and the incorporation of expensive materials, such as silica fume (SF) whose dosage can reach 30% by weight of cement. This type of concrete is formulated on two bases: A fine granular skeleton (max diameter 630μm) and high cementitious materials content. The search for local materials to exploit them in the formulation of UHPC is the current trend. It is therefore necessary to control their effect on the behavior and evolution of cement hydration.The objective of this study is to highlight the influence of blast furnace (BFS) on hydration kinetics, linear endogenous shrinkage and chemical shrinkage at very early age (before 72h), drying shrinkage after hardening, as well as, the evolution of mechanical compressive strengths as a function of time. In addition, the exploitation of dune sand in the granular skeleton is an alternative to reduce the crushing energy and avoid microcracks possibly induced.The analysis of the results showed the interest of the use of the dune sand and the partial substitution of the cement by the BFS on the properties of the UHPCs in the fresh state and in the hardened state.In addition to the high performance achieved by UHPCs, their use, in Algeria, will meet both economic and ecological requirements given the abundance of very fine dune sand (southern Algeria) and complex blast furnace BFS of EL-Hadjar (Eastern Algeria).