Our present study aims to investigate the optimal use of waste tire rubber as a fine aggregate in concrete and their sensitivity to high temperature effect. Five different concrete compositions were prepared: a reference concrete (RC) made with natural fine aggregate (sand) and coarse aggregate (dolomite) and four concrete mixes with replacement rates of 4%, 8%, 12% and 16% of sand by crumb rubber from waste tires. For the effect of elevated temperature: Similar specimens were exposed to a period of 4 hours to temperature of 70°C, to study the effect of high daily temperature, and a period of 2 hours for both temperatures 200° C and 400° C to study the effect of fire. After cooling down to ambient temperature, the compressive strength, flexural strength and the splitting tensile strength were measured and compared with the values that obtained before fire exposure. The inhand study indicates a gradual decrease in compressive, splitting and flexural strengths of concrete for partial substitution of crumb rubber aggregate in concrete. In addition, more decrease in these strength values are resulted after exposing the similar specimens to high temperature. While the inclusion of rubber particles reduces the rate of compressive strength loss at high temperature.

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During the past few decades, composite beams (steel I beam and concrete slab) have had a wide range of uses, particularly in bridge construction. This is due to its relatively low economic cost compared to individual steel structures or reinforced concrete structures. This type of bridges in particular and many similar industrial structures in general are repeatedly subjected to fatigue loads, and that is frequently, as a result of the vehicles passing on these bridges or the vibrations caused by the machines in the industrial facilities. It has been observed during the successive studies that they have been interested in studying this problem that it is concerned with the external structural behavior of these beams  such as a load –deflection relation, observing the cracks appearing during the failure stage and the strain in the steel and concrete flanges. Hence, in this study we have focused on several factors affecting mode of failure of these beams under the fatigue loads, and the common element in all stages of failure was the shear stud, specifically the welding collar at the base of this stud as it is a structurally weak region.

This study aims to assess the effect of high temperature on the bond strength of Concrete Filled Steel Tubular (CFST) sections incorporating crumb rubber particles as partial replacement of fine aggregates in concrete core. High daily temperatures; as in hot countries; was considered as well. Push out tests were conducted on 72 CFST specimens with five different concrete mixes. Prior to these tests, 210 concrete specimens were tested to obtain the mechanical properties of rubberized concrete under high temperature gradients. Some of the tests; on CFST sections or concrete specimens; were tested at the desired high temperature, and some others were tested after cooling down. The main variables considered were the crumb rubber replacement ratio, shape of CFST section (circular or square) and temperature gradient. The test results indicated that high temperature reduces the bond strength between steel tube and rubberized concrete core with small percentage of rubber replacement. Recovery in bond strength was observed when the specimens were cooled down. Circular sections showed higher bond strength and ductility on its square counterpart.