This study investigated the chemical compatibility of recycled rubber powder "RRP" with Portland cement by hydration test. Four mixes were prepared: pure cement paste and three rubber -cement pastes included 10%, 20%, and 30% of RRP. The compatibility of rubber -cement paste was evaluated by their temperature-time curves. The results of aptness and inhibitory index have shown that RRP rates higher than 10% was strongly inhibited the hydration reaction of cement. In addition, the setting time results revealed that rubber mixes require a longer curing time than pure cement paste, so the RRP could be used with cement-based materials as a setting retarder admixture. The recycling of rubber tire waste with cement-based materials could be reduced their accumulation in landfills and protects the natural and environment facing their harmful effects.
Concrete is the most widely used material in the field of civil engineering. In order to obtain a strong and durable concrete, it is necessary to study the various parameters entering into its formulation. Mainly the elements forming the concrete skeleton, in particular the gravel content. The transfer of water into concrete directly affects its durability. This transfer is linked to the porous structure and to the continuity of the pores in the concrete. This research studies the effect of gravel content on compressive strength, porosity accessible to water, depth of water penetration and ultrasonic velocity of concrete samples. The study includes 15 types of concrete made by varying the gravel-sand ratio (G/S), 0, 1, 1.5, 2 and 2.5. The cement dosage is taken equal to 150, 250 and 350 Kg/m3. The tests are carried out on cubic samples 10x10x10 cm3 and 15x15x15 cm3 after storage in water for 28 days. The experimental results obtained show that the gravel-sand ratio (G/S) affects the mechanical strength and the porous structure of concrete. Increasing the gravel content in concrete leads to an increase in mechanical strength and ultrasonic speed. However, a high gravel content results in a reduction in the porosity accessible to water and the depth of water penetration.
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