Synopsis Research into in situ reinforced concrete joints has been almost exclusively restricted to the study of their behaviour under seismic loading. Different research workers in different parts of the world have used widely differing cyclic loading patterns and this has led to inconsistencies in the proposals put forward for the design of a joint for shear. Even for single-cycle (static or monotonic) loading, there is widespread disagreement on how a joint should be designed. In this paper. a method is proposed for ultimate shear strength design for joints subjected to monotonic loading which gives reliable predictions for an extensive range of test results. A proposal for predicting the serviceability limit state, or the diagonal cracking strength of a joint, which may be necessary for some designs is also given.

Use of Recycled Coarse Aggregate (RCA) in concrete can be described in terms of environmental protection and economy. This paper deals with the mechanical properties of concrete compressive strength, splitting tensile strength, modulus of elasticity, and modulus of rupture. Three kinds of concrete mixtures were tested, concrete made with Natural Coarse Aggregate (NCA) as a control concrete and two types of concrete made with recycled coarse aggregate (50% and 100% replacement level of coarse recycled aggregate). These kinds of concrete were made with different targets of compressive strength of concrete f ’c (35MPa) and (70 MPa). Fifty specimens were tested of the fresh and hardened properties of concrete. The waste concrete from laboratory test cubes was crushed to produce the Recycled Coarse Aggregate used in recycled concrete. A comparative between the experimental results of the properties for fresh and hardened concrete is presented in the paper. Recycled aggregate concrete (RCA) had a satisfactory performance despite the replacement ratios. It was found using the size of Recycled Coarse Aggregate (RCA) of (5-14) mm has quite similar in performance with the same size of Natural Coarse Aggregate (NCA), it is necessary to use high quality of recycled concrete (with low levels of impurities). Recycled aggregate as an alternative to natural aggregates -seems quite successful.

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The recycling of aggregate concrete (RAC) is the ideal solution for reducing the natural resources. The experimental works have been carried out to investigate the torsional moment behavior and the strength of RAC beams in comparison with those  beams consisting of natural aggregate concrete (NAC). Nine beams were casted with different compression strengths of concrete (25, 45, and 70 MPa), and coarse RAC of three different percentages within the full bloc of coarse aggregate in concrete mixes (0, 50, and 100%), with the same reinforcement ratio. The properties of the concrete comprised of recycled and natural aggregates were investigated. The results showed, that the difference in the torque of first crack is less than 12.5% for RAC and NAC beams, while the difference in ultimate torque is less than 7.7% for RAC and NAC. Also, it can be conclude that, the torsional moment performance of RAC beams is acceptable as compared to the conduct of NAC beams and the use of RAC is practically possible

The recycling of aggregate concrete (RAC) is the ideal solution for reducing the natural resources. The experimental works have been carried out to investigate the torsional moment behavior and the strength of RAC beams in comparison with those  beams consisting of natural aggregate concrete (NAC). Nine beams were casted with different compression strengths of concrete (25, 45, and 70 MPa), and coarse RAC of three different percentages within the full bloc of coarse aggregate in concrete mixes (0, 50, and 100%), with the same reinforcement ratio. The properties of the concrete comprised of recycled and natural aggregates were investigated. The results showed, that the difference in the torque of first crack is less than 12.5% for RAC and NAC beams, while the difference in ultimate torque is less than 7.7% for RAC and NAC. Also, it can be conclude that, the torsional moment performance of RAC beams is acceptable as compared to the conduct of NAC beams and the use of RAC is practically possible