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The high temperature in the concrete destroys the hydrates of the cement paste. This destruction means the weakness of the materials caused by the deterioration of their mechanical properties. This work aims to study the behavior of high-performance fiber concrete sets at high temperatures; specifically, we used polypropylene fibers and studied their influence on deterioration behavior. This study includes high performance concrete and three types of fiber concrete, each containing a specific ratio of polypropylene fibers (0.12 %, 0.18 %, and 0.24 %). Consequently, cubic test specimens (15 cm x 15 cm x 15 cm) were subjected to the temperature of 250 °C, with a speed of 2 °C/min followed by a step of one hour at the target temperature then cooling to the ambient temperature. The results showed that fiber-reinforced concrete exhibited a better performance when exposed to the temperature studied. The mechanical properties were improved by up to 56% for compressive strength and 86% for tensile strength.

The South of Algeria is known for these immense sand dunes, which cover part of its territory (Sahara). The main objective of this study is the recovery of sands dune and wood waste (sawdust). The latter, which constitutes a potential source of several environmental and economic problems. The objective of this present work is to characterize the physico-mechanical properties at a young age of a dune sand-based mortar lightened by wood waste and to examine the suitability of using it for various applications in the construction of buildings. The improvement of the characteristics of these sands, which essentially formed of sand untapped to date and with the sole aim of enhancing this national sand wealth. The formulation of the mixtures is based on the substitution of dune sand by sawdust, at different weight contents 0, 10, 20 and 30%. The quantity of cement is fixed at 450 g. The results obtained show firstly that the introduction of sawdust improves the characteristics of the mixture (grain size tends to be spread out, reduction in densities), and secondly the physico-mechanical characteristics, especially at 30% substitution (reduction absorption by total immersion of 20.50%, porosity of 28.32%, wet density of 1.73% and dry density of 14.94% and increase in tensile strength of 61.43% and in compression of 63.87%). The effect of sawdust on the relationships between the properties of mortars was clearly noted either for the relationships between early strengths or between compressive and tensile strengths.