Recycled Coarse Aggregate Replacement Percentage Research Articles

Mechanical characteristics of structural concrete using building rubbles as recycled coarse aggregate

Abstract The aim of this research is to investigate whether construction rubbles may be utilized as coarse aggregates in concrete. Experimentally, the slump, unit weight, compressive, tensile, and flexural strength tests were applied on concrete samples with varying percentages of recycled coarse aggregate (RCA) and compared with reference concrete produced with natural coarse aggregate. This research conducted 96 concrete samples with RCA replacement percentages of 0, 35, 65, and 100%, respectively. The control mixture produced with natural aggregate showed better results than the mixtures containing recycled aggregate; thus, compressive, tensile, and flexural strengths reduced as the amount of the recycled aggregate increased. Using 100% RCA, the compressive, tensile, and flexural strength reduction reached up to 64, 29, and 38%, respectively.

Study on mechanical properties and microcosmic morphology of polypropylene fiber reinforced recycled concrete after freeze–thaw cycles

Compressive tests, tensile tests, and scanning electron microscopy (SEM) tests were performed on polypropylene fiber recycled concrete (PFRC) after freeze–thaw cycles. The effects of the replacement percentage of recycled coarse aggregate (RCA) and the addition percentage of fiber on strength characteristics were analyzed. The variation rules of strength and failure modes after freeze–thaw cycles were described. The development of stress–strain curves and deformations were observed at different times of freeze–thaw cycles. The experimental results showed that the compressive and tensile strength both present a trend of first increasing and then decreasing with the increase addition percentage of fiber or the replacement percentage of RCA. The optimum mix proportion of RCPP30-0.1 was obtained. The tensile and compressive strength both reduced as the times of freeze–thaw cycles increased. After 75 times, the strength dropped by 6.37% and 4.52% compared with that at 0 time of cycles, respectively. Overall, freeze–thaw cycles have adverse effects on the mechanical properties of PFRC. Based on the theoretical analysis of experimental data, prediction models on macroscopic and microscopic properties were established in this study, which can help promote more extensive applications of RAC and realize persistent development strategy of building, resources, and environment to a certain extent.

Cyclic loading tests and horizontal bearing capacity of recycled concrete filled circular steel tube and profile steel composite columns

To investigate the seismic performance of recycled aggregate concrete (RAC) filled circular steel tube and profile steel composite columns, the cyclic loading tests were conducted for eleven columns. The influences of design parameters on the seismic performance of composite columns were considered and investigated in detail, including the replacement percentage of recycled coarse aggregate (RCA), diameter to thickness ratio of circular steel tube, axial compression ratio, profile steel ratio and section form of profile steel. The failure characteristics, hysteresis loops, skeleton curves, stiffness degradation, ductility and storey drift ratio of columns were presented and discussed in detail. The results show that the column base forms an obvious plastic hinge under the combined action of horizontal cyclic loads and vertical loads, which belongs to the typical compression-bending failure. The hysteresis loops of composites columns are plump and spindle-shaped, indicating good energy dissipation capacity. With the increase of RCA replacement percentage, the ductility and energy dissipation capacity of columns decrease gradually, while the bearing capacity and stiffness of columns firstly reduce and then increase. The seismic performance of columns is significantly improved by the increasing wall thickness of circular steel tube and profile steel ratio. Increasing the axial compression ratio is unfavorable to the seismic performance of columns. The greater the axial compression ratio, the worse the ductility and energy dissipation capacity of column. Based on the test analysis and relevant specifications, the modified formulas on the horizontal bearing capacity of RAC filled circular steel tube and profile steel composite columns were proposed, and the validity of formula was verified by comparing with the test results.

Eccentric compression behavior of reinforced recycled aggregate concrete columns after exposure to elevated temperatures: Experimental and numerical study

As the thermal performance of recycled aggregate concrete (RAC) is different from that of natural aggregate concrete (NAC), the mechanical properties of reinforced recycled aggregate concrete (RRAC) members after exposure to elevated temperature have been attracted great interest. However, there are little literatures about the eccentric compression behavior of the RRAC column after exposure to elevated temperature. This paper presents experimental and numerical studies on the eccentric compression behavior of RRAC columns after exposure to elevated temperatures. In this research, nine specimens were tested to study the effects of the recycled coarse aggregate (RCA) replacement percentage, elevated temperature and eccentricity ratio on eccentric compression behavior. The results showed that the temperature was the primary factor influencing the eccentric compression behavior, followed by eccentricity ratio, while RCA replacement percentage had the least effect. As temperature increased or eccentricity ratio decreased, the failure mode of eccentric columns changed from tension-controlled to compression-controlled, while the RCA replacement percentage had a little influence on it. The eccentric load bearing capacity decreased as the temperature and eccentricity ratio increased or RCA replacement percentage decreased. The parametric analysis of finite element (FE) model indicated that there was a coupling effect between design parameters of slenderness ratio, eccentricity ratio and longitudinal reinforcement ratio with temperature on the eccentric load bearing capacity. Based on the ABAQUS, the cross-sectional thermal field of RRAC columns was simulated. An equivalent model for the residual bearing capacity of RRAC columns was presented and agreed well with the results of experiment and simulation.

Bond behavior between recycled aggregate concrete and steel rebar subjected to biaxial lateral pressure

Eighty-four pull-out tests were carried out to study the bond behavior between recycled aggregate concrete (RAC) and steel rebar, considering different levels of recycled coarse aggregate (RA) substitution and biaxial lateral pressure. The effects of these two parameters on bond strength and peak slip were analyzed, the bond-slip constitutive relation between RAC and steel rebar under biaxial lateral pressure was established, and the energy of bonded interface was also analyzed. The results show that the failure patterns of specimens without lateral pressure were splitting failure, while the failure patterns of specimens with different biaxial lateral pressure can be classified as splitting-pull out failure. With an increase of lateral pressure, the relative bond strength, peak slip and bond energy gradually increased, whereas the relationship between RA replacement percentages and these parameters could not be clearly observed. In addition, the relative bond strength and peak slip approximately increased linearly with the increase of lateral pressure. Finally, based on the experimental results, a modified expression for bond-slip prediction was developed, taking into account damage, and the obtained results show that the predicted curves fit well with test data.

Experimental tests and numerical simulation of eccentrically loaded SRRC filled square steel tube columns

ABSTRACT To investigate the mechanical properties of the eccentrically loaded steel reinforced recycled concrete filled square steel tube columns, 14 specimens of the columns were designed and tested. The failure modes, load-displacement curves, bearing capacity and deformation of specimens were obtained and analyzed in detail. In addition, the numerical model of columns considering the unfavorable effects of recycled coarse aggregate (RCA) and the restraint effect of square steel tube were also established by ABAQUS software. The results show that the deflection deformation on the mid-span section of columns was obvious and the failure mode of compression-bending occurred to the eccentrically loaded columns. The replacement percentage of RCA has some adverse effect on the eccentric compression performance of columns. Compared with ordinary concrete columns, the eccentric bearing capacity of columns fully using RCA is reduced by 9.53%. As the increasing eccentricity and slenderness ratio, the maximum reduction on the eccentric bearing capacity of columns was 46.14% and 25.86%, respectively. In addition, the increasing strength of RAC or steel effectively improves the eccentric bearing capacity of columns, but the ductile deformation of columns decreased gradually. Based on the above analysis, a modified calculation formula on the eccentric bearing capacity of columns was proposed.

Carbonation Resistance in Ordinary Portland Cement Concrete with and without Recycled Coarse Aggregate in Natural and Simulated Environment

This research aims to examine the effect of carbonation on the strength properties and carbonation depth of ordinary Portland cement (OPC) concrete using two different water to cement ratios (w/c) and two different replacement percentages of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA). Two concrete mixes were prepared using w/c of 0.4 and 0.43. The two concrete mixes were subdivided into two subgroups based on the use of NCA and 30% RCA. The first concrete mix having w/c of 0.4 was contained NCA and from this concrete, 42 cylinders of 100 mm dia. and 200 mm height were cast. Six out of 42 cylinders served as control specimens and were not exposed to CO2. A total of 18 out of the remaining 36 cylinders was exposed to the simulated environment and the rest were exposed to the natural environment. The second concrete mix having a w/c of 0.4 contained 30% RCA/70% NCA, and using this concrete, 42 cylinders of similar size were cast. A similar scheme was adopted for w/c of 0.43 and, in total, 84 cylinders using four mix designs were cast. After casting and 28 days of curing, six out of 42 cylinders cast from each concrete mix design were tested for compression and splitting tensile strength, following ASTM C39 and ASTM C496 without any exposure to carbon dioxide (CO2). A total of 18 out of the remaining 36 cylinders was exposed to the simulated environment in a carbonation chamber for an equivalent time duration of 90, 180 and 365 days following CEN test guidelines and the other 18 cylinders were kept in the natural environment for a period of 90, 180 and 365 days. After the completion of simulated and natural exposure periods, these cylinders were distributed equally to test for compressive strength and splitting tensile strength to observe the effect of carbon dioxide (CO2) at each time duration (i.e., 90, 180 and 365 days), and replacement percentage of RCA (i.e., 0 and 30%), which showed that carbonation depth increases incrementally with the w/c ratio and CO2 exposure duration. In both the simulated and the natural environment, the use of RCA in concrete cast using a w/c of 0.4 increased carbonation depth up to 38% and 46%, whereas, in the case of the concrete cast using a w/c ratio of 0.43, the use of RCA increased the carbonation depth up to 16% and 25%. In general, the use of RCA in the concrete exposed to the natural environment significantly affected the compressive strength of concrete, due to multiple interfaces and the porous structure of RCA, and the variation in the temperature, humidity and content of carbon dioxide (CO2) present in the actual environment. The maximum compressive strength variation prepared from the mixes M0-0.4, M30-0.43, M0-0.43 and M30-0.43 differed by 5.88%, 7.69%, 16.67% and 20% for an exposure period up to 365 days. Similarly, the results of splitting tensile strength tests on cylinders prepared from the same mixes exposed to the natural environment differ by 7.4%, 27.6%, 25.41% and 18.2% up to 365 days of exposure, respectively, as compared to the simulated environment.

Prediction of Shear Strength of Reinforced Recycled Aggregate Concrete Beams without Stirrups

For decades, recycled coarse aggregate (RCA) has been used to make recycled aggregate concrete (RAC). Numerous studies have compared the mechanical properties and durability of recycled aggregate concrete (RAC) to those of natural aggregate concrete (NAC). However, test results on the shear strength of reinforced recycled aggregate concrete beams are still limited and sometimes contradictory. Shear failure is generally brittle and must be prevented. This article studies experimentally and analytically the shear strength of reinforced RAC beams without stirrups. Eight RAC beams and two controlled NAC beams were tested under the four-point flexural test with the shear span-to-effective depth ratio (a/d) of 3.10. The main parameters investigated were the replacement percentage of RCA (0%, 25%, 50%, 75%, and 100%) and longitudinal reinforcement ratio (ρw) of 1.16% and 1.81%. It was found that the normalized shear stresses of RAC beams with ρw = 1.81% at all levels of replacement percentage were quite similar to those of the NAC counterparts. Moreover, the normalized shear stress of the beam with 100% RCA and ρw = 1.16% was only 6% lower than that of the NAC beam. A database of 128 RAC beams without shear reinforcement from literature was analyzed to evaluate the accuracy of the ACI 318-19 shear provisions in predicting the shear strength of the beams. For an RCA replacement ratio of between 50% and 100%, it was proposed to apply a reduction factor of 0.75 to the current ACI code equation to account for the physical variations of RCA, such as replacement percentage, RCA source and quality, density, amount of residual mortar, and physical irregularity.

Mechanical properties and bearing capacity of CFRP confined steel reinforced recycled concrete columns under axial compression loading

To study the axial compression behavior of carbon fiber reinforced plastics (CFRP) confined steel reinforced recycled concrete (CSRRC) columns, 11 specimens of CSRRC columns were manufactured and tested under axial compression loading. The design variables in the experiments included the replacement percentage of recycled coarse aggregate (RCA), layers of CFRP, strength of recycled aggregate concrete (RAC), profile steel ratio and slenderness ratio. Subsequently, the failure process and modes, load-displacement curves, stress-strain curves, transverse deformation coefficient and stiffness degradation of the specimens were obtained and analyzed in detail. The experimental results showed that the profile steel yielded before the steel rebars in the columns, then the RAC was crushed, and finally the CFRP broke under axial compression loading. The axial bearing capacity of CSRRC columns decreased with the increase of replacement percentage of RCA and slenderness ratio, respectively. However, the CFRP can give full play to its high-strength confinement performance and effectively improve the axial bearing capacity and deformability of columns. Moreover, the profile steel ratio and strength of RAC have significant effects on the initial stiffness of CSRRC columns, and the stiffness degradation rate of columns decreases with the increase of these parameters. Overall, the CSRRC columns exhibit high axial bearing capacity and good ductility deformation ability. Based on ACI 440.2R-08, the modified formula on the nominal axial bearing capacity of CSRRC columns was proposed in this study. The accuracy on the modified formulae was evaluated by the comparison between the calculated values and test values.

Residual behavior of recycled aggregate concrete beam and column after elevated temperatures

This paper presents the results of an experimental study on the residual behavior of reinforced recycled aggregate concrete (RRAC) beam-columns after exposure to elevated temperatures. Two parameters were considered in this test: (a) recycled coarse aggregate (RCA) replacement percentages (i.e. 0, 30, 50, 70 and 100%); (b) high temperatures (i.e. 20, 200, 400, 600, and 800℃). A total of 25 RRAC short columns and 32 RRAC beams were conducted and subjected to different high temperatures for 1 h. After cooling down to ambient temperature, the following basic physical and mechanical properties were then tested and discussed: (a) surface change and mass loss ratio; (b) strength of recycled aggregate concrete (RAC) and steel subjected to elevated temperatures; (c) bearing capacity of beam-columns; (d) load-deformation curve. According to the test results, the law of performance degradation of RRAC beam-columns after exposure to high temperatures is analyzed. Finally, introducing the influence coefficient of RCA replacement percentage and high temperatures, respectively, to correct the calculation formulas of bearing capacity of beam-columns in Chinese Standard, and then the residual bearing capacity of RRAC beam-columns subjected elevated temperatures is calculated according to the modified formulas, the calculated results are in good agreement with the experimental results.

Behaviour of sea sand recycled concrete filled steel tube under axial compression

This paper presents the results of an experimental study of sea sand recycled concrete filled circular steel tubes (SSRCFSs) under axial compression. The mechanical behaviours of axially loaded SSRCFSs were investigated. Two different parameters were considered: sea sand chloride ion (Cl−) content and recycled coarse aggregate (RCA) replacement percentage. Typical influences of sea sand Cl− and RCA contents on the bearing capacity, deformation and load–deformation curve of SSRCFS were studied. The test results showed that the typical failure mode of the SSRCFSs was similar to that of ordinary concrete filled steel tubes. The axial load–deformation curves of the SSRCFSs could be divided into elastic, plastic growth, declining and steady stages. It was found that the bearing capacity of SSRCFSs increased with decreasing RCA replacement percentage. The effect of sea sand Cl− content on the mechanical behaviour of the SSRCFSs decreased with an increase in RCA replacement percentage. The peak strain of the specimen could be enhanced due to the low modulus of the RCA, but this improvement decreased with increasing sea sand Cl− content. Finally, numerical expressions were developed to obtain the peak load and load–deformation curve of the SSRCFSs. The calculated results were in line with the experimental data.

Impact of the properties of old mortar on creep prediction model of recycled aggregate concrete

By changing the replacement percentage of recycled coarse aggregate (RCA) (0%, 50%, 100%), the basic creep performance and total creep performance of recycled aggregate concrete (RAC) were studied. The experimental results reveal that increasing the RCA replacement percentage can both increase the basic creep deformation and total creep deformation of RAC with the RCA having a bigger impact on the basic creep of RAC. Based on the experimental research and studies on the interaction mechanism of natural coarse aggregate (NCA), old mortar and new mortar in the creep process of RAC, a calculation model of the relationship between the creep of the old mortar, new mortar and the RAC (ONRM) was established. The creep of the old mortar in the RAC was calculated by using the ONRM. Based on this, a two-dimensional random convex aggregate model of the RAC was established with ANSYS finite element software, and the creep of the RAC was calculated. The results of the calculation showed that the ONRM could well reflect the relationship between the creep of the old mortar, new mortar, and the RAC. From above analysis, with ACI 209(92) model as the benchmark, a creep prediction model reflecting the content and performance of the old mortar was built. It is proven that this model can calculate the creep of RAC well.

Eccentric compression performance of composite columns composed of RAC-filled circular steel tube and profile steel

To study the eccentric compression performance of composite columns composed of recycled aggregate concrete (RAC)-filled circular steel tube and profile steel, 17 static loading tests of the columns under eccentric compression loading were performed in this study. The design parameters of these columns were recycled coarse aggregate (RA) replacement percentage, diameter–thickness ratio of circular steel tube, profile steel ratio, eccentricity, RAC strength grade, slenderness ratio and section form of profile steel. The load–lateral displacement curves, load–strain curves, lateral deflection and bearing capacity of the columns were established and assessed in detail. The results showed that the failure of the columns began with the yield of profile steel in the middle of compression side, and then the yield strength of circular steel tube was reached at the compression side. Subsequently, the core RAC was crushed, and local buckling occurred in the middle of the circular steel tube, thereby resulting in the loss of the eccentric bearing capacity of the columns. The eccentric bearing capacity of the columns decreased with the increase in RA replacement percentage. Reducing the diameter–thickness ratio of circular steel tube and increasing the profile steel ratio can improve the eccentric bearing capacity of the columns. Meanwhile, the increase in eccentricity and slenderness ratio was disadvantageous to the eccentric bearing capacity of the columns. In summary, the columns generally show good ductile deformation capacity and high eccentric bearing capacity. On the basis of the failure mechanism and calculation model of these columns, the calculation formulas suitable for the eccentric bearing capacity of the columns were deduced, and the calculation results were verified compared with the test results.

Performance evaluation of recycled aggregate concrete under multiaxial compression

This paper presents the results of an experimental study of the failure criteria and mechanical behavior of recycled aggregate concrete (RAC) under uniaxial and triaxial compression. Three parameters: the recycled coarse aggregate (RCA) replacement percentage (γ), lateral confining pressure (σ3) and the age of concrete from which the RCA was obtained were considered in the tests. The effects of these parameters on the failure behavior of RAC and the compressive strength, elastic modulus and stress-strain curves of RAC are discussed. The results show that RCA replacement percentage has a very little effect on the compressive strength of RAC under uniaxial and triaxial compression; the lateral confinement significantly affects the failure pattern and the stress-strain behavior of RAC, with the increase of lateral confining pressure, the failure pattern changes from vertical fracturing to oblique fracturing. Based on the experimental observations and test results, the Mohr-Coulomb failure criterion, shear stress failure criterion and failure on the compression meridian plane are extended to describe the behavior of RAC under multiaxial compression. For analysis and design purposes, empirical models are proposed to predict the stress-strain relationship of RAC under multiaxial compression.

Cyclic loading tests and shear strength of composite joints with steel-reinforced recycled concrete columns and steel beams

Cyclic loading tests were conducted for eight composite joints (five interior joints and three exterior joints) with steel-reinforced recycled concrete (SRRC) columns and steel beams under cyclic loading. The axial compression ratio and recycled coarse aggregate (RCA) replacement percentage were considered as the main design parameters for the above composite joints. The failure process, failure modes, hysteresis loops, skeleton curves, stiffness degradation, storey drift ratio, bearing capacity, ductility and energy dissipation capacity of the joints were presented and analysed in detail. The influence of the design parameters on the mechanical performance of the composite joints under cyclic loading was also investigated. Results showed that the cracking loads of the joints increased with the increase of axial compression ratio. Typical shear failure was the failure mode. The spindle-shaped hysteresis loops of the joints, the ductility coefficients, the elastic-plastic storey drift ratios and the equivalent viscous damping coefficients indicated a relatively good seismic performance. The bearing capacity and stiffness of the joints decreased gradually, while the ductility and energy dissipation capacity of the joints decreased slightly with an increase in the RCA replacement percentage. Additionally, the stiffness degradation of the composite joints accelerated and the energy dissipation capacity and ductility reduced evidently with an increase in the axial compression ratio. Finally, a comparative analysis of each shear strength formula was conducted. The result showed that the formulas of ASCE, AIJ and JGJ138-2001 could predict the shear strength of the joints accurately. This validation indicated that the existing methods are applicable to this group of composite joints.

Residual properties of recycled concrete after exposure to high temperatures

This paper presents the results of an experimental study on the residual properties of recycled concrete after exposure to high temperatures. Three parameters were considered in this test: (a) high temperatures (i.e. 20, 200, 300, 400, 500, 600, 700 and 800°C); (b) recycled coarse aggregate replacement percentages (i.e. 0, 30, 50, 70 and 100%); (c) recycled coarse aggregate types (gravel and pebble). A total of 144 standard prism specimens (150 mm × 150 mm × 300 mm) of recycled concrete were prepared and subjected to different high temperatures for 1 h; after cooling down to ambient temperature, the following basic physical and mechanical properties were then tested and discussed: (a) surface change and mass loss ratio; (b) compressive strength; (c) compressive stress–strain curve; (d) elasticity modulus. Based on the mass loss ratio, a residual strength assessment method for recycled concrete after exposure to high temperatures was put forward.

Experimental research on behavior of axially circular CFRP steel tubular confined recycled aggregate concrete long columns

In order to reveal the mechanical properties of CFRP recycled aggregate concrete long columns under axial compression load, we designed 7 experimental members for the test. The specimens parameters are recycled coarse aggregate replacement percentage, slenderness ratio and layers of CFRP jackets. According to the test, the failure process and patterns were obtained, and the curve of load-displacement were measured. The influence of recycled coarse aggregate replacement ratio, slenderness ratio, layers of CFRP on the bearing performance of CFRP circular steel tubular confined recycled aggregate concrete long columns were analysed.

Analysis on Mechanical Properties of Recycled Aggregate Concrete Members after Exposure to High Temperatures

In order to study the mechanical properties of recycled aggregate concrete (RAC) specimens after exposure to high temperatures, 120 RAC prism specimens, 57 reinforced recycled aggregate concrete (RRAC) specimens, and 56 steel reinforced recycled aggregate concrete (SRRAC) specimens were designed, involving two varying parameters such as recycled coarse aggregate (RCA) replacement percentage and temperature. The performance degradation of RCA materials, RRAC members, and SRRAC members after exposure to high temperatures was analyzed in depth. The research results show that after exposure to high temperatures the surface color of members may change from cinereous to gray-white. Some cracks may appear on surface of members and the mass of members may be lighter. With the increase of the experiencing temperatures, the bearing capacity (compressive, bending, and shearing) of RAC and its members are reduced, but their ductility and energy dissipation capacity have little effect on the change of high temperature. With the increase of the RCA replacement percentage, the mass loss ratio, ultimate bearing capacity, and peak deformation of each RAC and its members increase slightly, and the displacement ductility and energy dissipation capacity of the RRAC members decrease slightly. With the increase in replacement percentage of RCA, mechanical properties of RAC and their members have little effect after exposure to elevated temperatures, and the fluctuation range is within 20%.

Dynamic behaviour and energy dissipation of reinforced recycled aggregate concrete beams under impact

Abstract In order to study the dynamic behaviour and energy dissipation of reinforced recycled aggregate concrete (RAC) beams under impact, four groups of reinforced RAC simply supported beams with various recycled coarse aggregate (RCA) replacement percentages are designed and tested under drop weight impact at the mid-span of beams and corresponding another four groups of beam specimens under static loading. The static resistance versus mid-span displacement curves are obtained from static loading test to analyse the effect of RCA replacement percentage on the beam's mechanical performance. It is concluded that the static resistance and stiffness of the RAC beam decrease slightly as the RCA replacement percentage increases and the deformation curve of reinforced RAC beam conforms to the classical bending theory of beam. In the drop weight impact test, the reinforced RAC beams failed with both global and local damage, and in bending controlled mode. The time history of impact forces, mid-span displacements and stress states of the beams are investigated. The mid-span displacement of the beams increases with the increase of RCA replacement percentage. The energy dissipation of the beams under impact is discussed based on the simplified resistance model. A concept of global damage energy dissipation is introduced and the method for calculating the global damage energy dissipation of the reinforced RAC beam under impact is proposed. The global damage energy dissipation ratio is defined and used to measure the proportion of global damage and local damage on reinforced RAC beam under impact. The experimental results presented here provide benchmark data for the further research work on the dynamic response of reinforced RAC beam under impact.

Flexural bond behavior of reinforced recycled aggregate concrete

Abstract Replacing natural aggregate concrete with recycled aggregate concrete (RAC) can effectively solve aggregate shortage problems. However, application of recycled aggregate in engineering structures requires analysis of the interaction between steel bars and RAC. The bond behavior under flexure is similar to the actual state of stress in structural members. 15 beam specimens were designed and tested to investigate the RAC-reinforcement bond behavior and the constitutive relationship at the interface between them. Test parameters include water-binder ratio, recycled coarse aggregate (RCA) replacement percentage, recycled fine aggregate (RFA) replacement percentage, bar surface shape, and anchorage length of reinforcements. The influence of the above variables on the load to slip curves, bond strength, and the bond efficiency coefficient is discussed. Bond strength between reinforcements and concrete decreases with increasing RCA replacement percentage, however, the rate of decrease is reduced for specimens with low water-binder ratio. The addition of RFA significantly degrades bond behavior. The bond strength between deformed reinforcements and RAC is approximately 2 times of that of plain reinforcements. With increasing anchorage length, the interface bond behavior between the reinforcements and RAC decreases.