In this study, the behavior of reinforced concrete deep beams containing recycled aggregates is experimentally and numerically investigated in three separate sections. In the first section, the physical and mechanical properties of concrete made with natural coarse aggregates (NCA), recycled concrete aggregates (RCA), and recycled asphalt pavement aggregates (RAP) were examined. In the second section, the behavior of RC deep beams containing NCA, RCA, and RAP was performed. Finally, numerical eva‎luation was carried out in the third section on RC deep beams containing recycled aggregates. It was concluded from the first section of this study that by adding the replacement ratio of RCA and RAP with NCA, the mechanical properties of concrete, including compressive strength and modulus of elasticity, decreased by 14 to 30% and 43 to 53% compared with NCA concrete, respectively. If a modified mix design is used, the compressive strength of RCA and RAP concretes can be reached, but the modulus of elasticity is still decreased. The results of stress-strain curves on RCA and RAP concretes indicated that the strain corresponding to the maximum compressive strength, ε0, increased up to 22 and 27% for RCA and RAP concretes, respectively. Also, the ultimate strain, εcu, decreased for RCA concrete and increased for RAP concrete nearly two times compared with NCA concrete. In the second section of this study, ten RC concrete deep beams with two length-to-depth rations of 1.6 (group: G1.6) and 2.7 (group: G2.7) were constructed. In each group, one specimen with NCA as the control specimen, two specimens containing 50 % of RCA and RAP without the use of a modified mix design, and two specimens containing RCA and RAP with the modified mix design to reach the target compressive strength were constructed. The results demonstrated that the shear strength of deep beams containing 50% of RCA and RAP decreased by 9 and 11.7% in G1.6, and 4.66 and 7.52% in G2.7 compared with NCA specimens, respectively. With 100% replacement of RCA and RAP with NCA and using a modified mix design in order to achieve the target compressive strength, the shear strength of RC deep beams was nearly identical. In addition, the absorbed energy in RAP deep beams was much higher than the NCA and RCA specimens. The cracking patterns of specimens showed that the number of flexural and diagonal cracks was less in RCA specimens and greater in RAP specimens than NCA specimens. The results of the numerical investigation in the third section indicated that the accuracy of nonlinear finite element analysis with proper introduction of material properties of concrete and steel rebars would be appropriately acceptable. Therefore, the results of the numerical analyses on 63 concrete deep beams showed that for any ratio of shear span length-to-depth (a/h) and span length-to-depth (L/h), the behavior of NCA and RCA deep beams was almost the same, whereas RAP deep beams had a completely different behavior in comparison with the corresponding specimens. NCA and RCA concrete deep beams had a brittle behavior, but RAP specimens behaved more ductile. The size effect phenomenon in NCA and RCA deep beams was approximately identical, whereas this phenomenon was less severe for RAP deep beams.

كياچهر بهفرنيا

آرمان مام عزيزي