Natural Coarse Aggregate Concrete Research Articles

Uniaxial compressive behavior and unified damage constritutive model of various types of recycled coarse aggregate concrete under freeze-thaw action

To promote the application of recycled coarse aggregates in concrete structures in cold regions, this paper focuses on the damage evolution of natural coarse aggregate concrete (NAC), recycled concrete coarse aggregate concrete (RAC) and brick-concrete mixed recycled coarse concrete (MRC) under the freeze-thaw-load coupling action. The relative dynamic modulus of elasticity is used to assess the freeze-thaw damage degree of various types of concrete after 0, 25, 50, 75, 100, 125, and 150 freeze-thaw cycles, and a freeze-thaw damage evolution model is established. Uniaxial compression tests are conducted on concretes after different freeze-thaw cycles to study the effects of freeze-thaw cycles on the failure mode, peak stress, peak strain, static elastic modulus, and toughness of the specimens. The relationship between the freeze-thaw damage variable and stress-strain characteristic parameters is analyzed, and an unified damage constitutive model for various types of concrete under the freeze-thaw-load coupling action is further established. The results show that with the increase in the number of freeze-thaw cycles, the specimens exhibit vertical splitting failure under axial compression rather than typical shear failure. The freeze-thaw cycles reduce the ability of recycled concrete to resist deformation. The peak stress and static elastic modulus decrease with the increase of freeze-thaw cycles, while the peak strain and toughness increase with the increase of freeze-thaw cycles. NAC has the best frost resistance and axial compression bearing capacity, followed by RAC and MRC. The presence of recycled brick coarse aggregate further exacerbates the freeze-thaw damage of concrete. There is an interesting finding that the water absorption of recycled aggregates is well correlated with the shape parameters of the freeze-thaw damage model and the descending section of uniaxial compression damage constitutive in recycled concrete. When the descending branch of the stress-strain curve modified by water absorption of recycled aggregates, the proposed freeze-thaw-load coupling damage constitutive model demonstrates good predictive performance for the stress-strain behavior of recycled concrete.

Experimental study on bond performance of recycled coarse aggregates concrete with circular steel tubes after freeze–thaw cycling

AbstractExtrusion tests were conducted on recycled coarse aggregate concrete with circular steel tubes (RCCST, 100% replacement of recycled coarse aggregate) to investigate the impact of freeze–thaw cycles on bond properties. RCCST samples were subjected to 0, 25, 50, 75, 100, 125 and 150 freeze–thaw cycles and their bond properties were then compared with those of natural coarse aggregate concrete with circular steel tubes (NCCST) after 0, 100 and 150 freeze–thaw cycles. The experimental results indicate that freeze–thaw cycling damages the internal structure of RCCST, causing a significant decrease in interfacial bond strength with an increase in the number of freeze–thaw cycles. Freeze–thaw RCCST exhibits lower peak load and higher peak slip compared to NCCST, with increases of 25.2%, 73.2%, and 70.3% after 0, 100, and 150 freeze–thaw cycles, respectively. Regression analysis was used to derive an exponential equation that describes the relationship between longitudinal strain and strain gauge position. Additionally, a segmented fitting method was employed to obtain an expression for the bond slip of the freeze–thaw RCCST with a circular steel pipe.

Durability life evaluation of marine infrastructures built by using carbonated recycled coarse aggregate concrete due to the chloride corrosive environment

Due to the harsh marine environment of chloride ion invasion and corrosion, the issues of long-term chloride transport and durability life evaluation for marine infrastructures constructed/maintained by recycled aggregate concrete (RAC) after enhancement remain poorly understood. For our studies, an accelerated carbonation modification method for recycled coarse aggregate (RCA) was adopted to prepare carbonated recycled coarse aggregate (CRCA) samples, and the macroproperties, i.e., apparent density and water absorption, of CRCA were enhanced by approximately 1.40-3.97% and 16.3-21.8%, respectively, compared with those of RCA. An in-door experiment for chloride transport into concrete specimens subjected to a simulated marine environment of alternating drying-wetting cycles was conducted. The chloride profiles and transport characteristics of carbonated recycled coarse aggregate concrete (CRCAC), recycled coarse aggregate concrete (RCAC), and natural coarse aggregate concrete (NCAC) were analysed and compared. The results indicated that the chloride penetration depths and concentrations of CRCAC were approximately 52.6-96.2% of those of RCAC, which highlighted the better chloride resistance of CRCAC. A chloride transport model for marine concrete structures with various coarse aggregate types in a corrosive marine environment was established. Taking a certain harbour wharf as an example, the durability life of this case considering the application of the CRCAC was evaluated based on the chloride transport model, and the durability life of the CRCAC structure was improved by approximately 28.10% compared with that of the RCAC. The CRCAC developed in this paper has improved mechanical performance and durability than those of RCAC, and it has the potential to replace the NCAC and further support the construction and maintenance of marine infrastructures.

The prediction of compressive strength for recycled coarse aggregate concrete in cold region

Concrete in cold environments may suffer from frost damage, which effects the hydration reaction and early strength development of cement. This study aims to test the early strength development of recycled coarse aggregate concrete in cold region using an assisted heating method. Based on Nurse-Saul and Hansen-Pedersen maturity calculation methods, the early strength of recycled and natural coarse aggregate concrete is fitted and predicted using exponential and logarithmic type functions. The results showed that active heating and thermal insulation can ensure early concrete hydration. The temperature of recycled coarse aggregate concrete was slightly higher than that of natural concrete, while its strength was slightly lower. The early strength development of natural and recycled coarse aggregate concrete correlated more with the logarithmic type function. The prediction error of natural and recycled coarse aggregate concrete is basically within 10% for the first 14 days of compressive strength.

Bonding properties between 3D printed coarse aggregate concrete and rebar based on interface structural characteristics

The bonding properties between 3D printed concrete and rebar are a critical factor in determining the performance and service life of 3D printed concrete building structures. Due to the difficult elimination of pores formed at the interface between the rebar and concrete during rebar placement, it becomes a key factor affecting the interfacial bonding performance. This work focuses on the structural defect characteristics of the bonding interface between 3D printed natural coarse aggregate concrete (3DPNAC) and ribbed rebar, the bonding properties of 3DPNAC-rebar with different rebar arrangement directions (parallel, vertical, 45°) were investigated through artificial placement of the rebar and compared with those of 3D printed mortar (3DPM) and cast concrete. The results showed that the bonding strength between 3DPNAC and rebar was higher than that of 3DPM, and the distribution characteristics of pore defects and natural coarse aggregate were the primary causes of the structural differences between the bonding interfaces of 3DPNAC and 3DPM with rebar. The partition distribution and geometric configuration of pore defects in the bonding interface area were identified as pivotal factors in the degradation of the bond strength between 3DPNAC and rebar. Based on the structural composition of the 3DPNAC-rebar bond interface, a bond interface-partitioning model was proposed to elucidate the bond-slip damage mechanism. Finally, a bond-slip model of 3DPNAC and rebar was established. This study can provide important guidance for the structural design and application of 3D printed concrete structures with rebar.

Service-life prediction of recycled coarse aggregate concrete under natural carbonation: A time-dependent reliability analysis

Carbonation is a phenomenon that involves several uncertainties associated with concrete properties and environmental factors. However, most existing studies have adopted a deterministic approach to deal with this phenomenon, which can lead to misinterpretations. This study aimed to carry out a probabilistic analysis of natural carbonation with data collected for over 30 months of recycled coarse aggregate (RCA) concretes and natural coarse aggregate concretes (NCA), used as reference. The probabilistic analysis showed that the cover depth collected in field presented a normal distribution behavior, in this way, random variables were generated to sample cover depth values to be used in time-dependent Monte Carlo simulations. A computational algorithm was developed in MATLAB to evaluate the probability of the carbonation depth (xc) overcoming cover depths (cd) of 15-, 20-, 25-, 30-, 35-, and 40-mm, usual values in structural design. The simulations showed that the RCA anticipated the probability of failure (xc ≥ cd) by up to 100 months compared to natural coarse aggregate (NCA) concrete. The results indicated that the total replacement of NCA by RCA requires increases of up to 1.4 in cover depth to perform equivalently to the reference concrete (with NCA). Moreover, regardless of the type of aggregate and w/c ratio, with the cover depth established in the Brazilian standard for urban environments, the evaluated concrete did not reach the minimum service life of 50 years established for structural elements of reinforced concrete. The methodology applied in this paper can be used to predict the service-life considering failure due to carbonation using the statistics response of experimental data.

Structural properties and temperature effect of sintered fly ash pellets concrete

In order to create a sustainable environment, it is essential to use industrial waste as a building construction material. For a growing nation like India, Fly Ash (FA) as a waste produced abundantly from the thermal power plants is always a significant problem. Sintered fly ash pellets produced form fly ash can be utilized as coarse aggregate in concrete, which will be considered beneficial towards sustainability of the natural resources. This current research attempts to examine the temperature effects on the structural behaviour of the concrete made from sintered fly pellets as a replacement of coarse aggregate. As sintered fly ash pellets make the concrete lighter in comparison to natural coarse aggregate concrete, the structural properties such as load deflection behaviour of beam and mechanical properties need to be investigated. In addition to structural properties, it is also essential to explore durability aspect of the same. Experimental investigation revealed that formation of shear crack is generated earlier in FA sintered pellet concrete beam in comparison to natural coarse aggregate concrete beam. However, FA pellet concrete performs better in compressive strength, split tensile strength, whereas flexural strength shows inferior strengths. Durability test that involved exposure to higher temperatures (90 °C, 180 °C & 250 °C) provides good compressive strength in case of fly ash pallet concrete. But one outstanding achievement is that the rate of gaining of strength increases from 7 days to 28 days is faster than control mix. The experimental observation recommended that FA sintered pellet concrete should be utilized in case of lighter weight concrete wherever required rather than in major structural element construction.

Mechanical Properties and Uniaxial Failure Behavior of Concrete with Different Solid Waste Coarse Aggregates.

To reveal the differences between the mechanical properties of solid waste coarse aggregate concrete and natural coarse aggregate concrete (NCAC) under equal strength, the basic mechanical properties of coarse aggregate concrete with seven different solid wastes (i.e., self-combusted coal gangue, uncombusted coal gangue, marble sheet waste, granite sheet waste, iron waste rock, recycled concrete, and self-combusted coal gangue ceramicite) were tested, and the trends in failure morphology, elastic modulus, and the stress–strain full curves of the different solid waste coarse aggregate concretes were analyzed and compared with NCAC. Finally, the interfacial structure of the concrete was characterized by SEM. The results showed that C30 strength grade concrete was prepared with different solid waste coarse aggregates; however, the 28 d compressive strength, split tensile strength, axial compression strength, flexural strength, and elastic modulus of the concrete was 35.26–47.35, 2.13–3.35, 26.43–42.70, 2.83–3.94, and 17.3–31.2, respectively. The modulus of elasticity of the solid waste coarse aggregate concrete was smaller than the NCAC under equal strength, with a maximum difference of 45%. The peak compressive strain and ultimate compressive strain were larger than the NCAC, with a maximum difference of 43%. The crushing value of the solid waste coarse aggregate affected the splitting tensile strength, flexural strength, and modulus of elasticity of the concrete to a greater extent than the compressive strength. The transition zone at the concrete interface of the coarse aggregates with different solid wastes varied widely. The porous micro-pumping effect of the self-combusted gangue and self-combusted gangue vitrified reinforced the concrete interface transition zone, and the polished surface of sheet waste, uncombusted gangue, and recycled concrete aggregate surface adhesion weakened the interface transition zone; Finally, the uniaxial compressive stress–strain curve model for concrete with different solid waste coarse aggregates was established based on the Guo Zhenhai model.

Uniaxial Compressive Stress-Strain Relation of Recycled Coarse Aggregate Concrete with Different Carbonation Depths.

Highlights Uniaxial compressive stress–strain curves of recycled aggregate concrete (RAC) with different carbonation depth were investigated.The effect of carbonation depth on peak stress, strain, elastic modulus, and the relative toughness of RAC was studied.Stress–strain models of recycled aggregate concrete with different carbonation depths were established. The stress–strain relation of recycled aggregate concrete (RAC) after carbonation is very important to the assessment of the durability of RAC. The objective of this study is to investigate the uniaxial compressive stress–strain curves of RAC after carbonation. In this study, the specimens were prepared with 70-mm diameter and 140-mm height cylinders, and the carbonation of the specimens was accelerated after curing 28 days. Then a uniaxial compressive loading test on the specimens was performed by using a mechanical testing machine. The results show that the peak stress () and elastic modulus () of all specimens increase with the increase of carbonation depth. The ratio of ultimate strain to peak strain () and relative toughness of the specimens decrease with the increase of carbonation depth. Furthermore, carbonation has a stronger effect on natural coarse aggregate concrete (NAC) than the 50% replacement rate of RAC with similar compressive strength. Stress–strain models of recycled aggregate concrete with different carbonation depths were established according to experimental results.

Influence of pore defects on the hardened properties of 3D printed concrete with coarse aggregate

In this study, 3D printed concrete was prepared with a natural coarse aggregate to investigate the mechanical properties of 3D printed natural coarse aggregate concrete (3DPNAC) after hardening, considering curing time and anisotropic mechanical strength, and the properties of 3DPNAC were compared to those of a 3D printed mortar (3DPM). The compressive and flexural strengths were measured by an electronic universal testing machine. The bond strength and damage pattern of the interlayer interface were investigated using a self-designed loading device and digital image correlation technique, and pore defects inside the printed structure were characterized using X-ray computed tomography. The results showed that the compressive and flexural strengths of 3DPNAC showed varying degrees of anisotropic characteristics and differential development patterns of mechanical strength with curing time. The filament interfacial bonding system was proposed, and the bond strength of 3DPNAC was more than twice that of 3DPM. The geometry of pore defects in 3DPNAC evolved with pore volume variations. Finally, the evolution of pore defect formation was analyzed, and the effect mechanisms of pore defects on 3DPNAC mechanical properties were revealed.

Experimental study on the effect of superplasticizer on workability and strength characteristics of recycled coarse aggregate concrete

Protecting the natural resources in every developing county like India, is one of the major problems. The vast and fast construction work deplete the natural resources and polluting the environment by emitting enormous quantity of carbon dioxide and dust as well. Therefore, reusing the structural concrete components as recycled coarse aggregate (RCA) as another source in preparation of new concrete, which can be considered advantageous to the sustainability of the virgin resources. But the RCA concrete results in lower mechanical properties than the natural coarse aggregate (NCA) concrete. This paper attempts in getting the shortcomings related to RCA use and the possible improvements of some properties in RCA concrete through the use of superplasticizers. As RCA has more water absorption property than NCA, water reducing admixtures are thus vital for RCA concrete for conserving the alike properties as that of NCA concrete. The properties of RCA concrete without plasticizers taken as control mix, were compared with the RCA concrete with plasticizers. The properties like compressive strength, split tensile strength, flexural strength and density of RCA and the fresh properties like workability in terms of slump and compaction factor were compared. Sorptivity test was conducted to examine the compactness of both the concrete mixes. The experimental outcomes demonstrate better properties of RCA concrete with plasticizers than the control mix.

Bond performance of deformed rebar embedded in recycled aggregate concrete subjected to repeated loading after freeze–thaw cycles

Freeze-thaw damage and repeated loading would degrade the performance of the concrete structures in cold regions. In this paper, 54 pull-out specimens with different recycled coarse aggregate levels (RA, i.e., 0%, 50% and 100%) were cast to exposure to freeze–thaw cycles (FTC, i.e., 0, 50, 100, 150). Next, the bond-slip curves of specimens subjected to different repeated stress ratios (0.3, 0.5 and 0.7) were tested. The effects of RA, FTC and repeated stress ratio on bond strength and peak slip were analyzed respectively. Based on damage mechanics, the bond-slip constitutive model was established, and the theoretical bond strength was calculated by using the modified cohesive-elastic ring model. The results showed that with the increase of FTCs, the bond strength of both natural coarse aggregate concrete (NAC) and recycled coarse aggregate concrete (RAC) was obviously decreased, while the peak slip exhibited an opposite law, and the RA substitution had no significant effect on bond performance due to the different cement dosages of mixtures. Furthermore, repeated loading had little effect on bond strength and slip. The damage bond-slip constitutive model was in good agreement with test results, and the bond strength calculated by the modified cohesive-elastic ring model considering stirrup pressure proposed in this paper was verified by the test data.

Static size effect of recycled coarse aggregate concrete: Experimental study, meso-scale simulation, and theoretical analysis

Although fruitful research results have been achieved on the investigation of size effect of natural coarse aggregate concrete (NAC), limited research is devoted to the study on size effect of recycled coarse aggregate concrete (RAC). Meanwhile, the feasibility of applying these results on NAC to RAC is questionable. To this end, a synthesis of experimental studies with different recycled coarse aggregate (RCA) substitute rates (0%, 30%, 50%, 70% and 100%), different prismatic sizes of 70 × 70 × 210, 100 × 100 × 300, 150 × 150 × 450 and 200 × 200 × 600 mm are carried out to investigate the size effect of RAC with consideration of the influence of substitute rate. As a powerful complement to the experimental study, the meso-scale numerical simulation is carried out. These results show that increasing the specimen size and RCA substitute rate both leads to decreasing nominal compressive strength of RAC. Furthermore, the meso-scale numerical simulation results show that the oblique concentrated damage zone is more likely to form in the specimens with higher RCA substitute rates, which exhibits more significant size effect. In addition, the size effect law of RAC is established based on the empirical formula and back-propagation neural network, respectively, both providing an accurate prediction of nominal compressive strength of RAC with consideration of specimen size and RCA substitute rate, and the results provide some references for the design specification of RAC members.

Strength and Durability Properties of Antimony Tailing Coarse Aggregate (ATCA) Concrete.

Antimony (Sb) is a trace element applied widely in modern industry. A large number of tailing solid wastes are left and accumulated in the mining area after purifying the precious antimony from the antimony ores, causing serious pollution to the environment. The major aim of this study is to investigate the feasibility of utilizing antimony tailing coarse aggregate (ATCA) as a complete substitute for natural coarse aggregate (NCA) in high-strength concrete. Concrete specimens with 25%, 50%, 75%, and 100% ATCA replacing the NCA in conventional concrete were prepared for evaluating the performance of ATCA concrete. The investigators find that ATCA concrete has good workability, and the mechanical properties and long-term behavior (shrinkage and creep) of ATCA concrete with all replacement levels are superior to those of NCA concrete. The durability indices of ATCA concrete, such as the frost-resistant, chloride permeability, and resistance to carbonation, are better than those of NCA concrete. While the alkali activity and cracking sensitivity behavior of ATCA concrete seem to be decreased, nevertheless, the difference is not significant and can be neglected. The researchers demonstrate that all of the control indices of ATCA concrete meet the requirements of the current industry standards of China. Overall, ATCA can be used in concrete to minimize environmental problems and natural resources depletion.

Coefficient of Thermal Expansion of RCA Concrete Made by Equivalent Mortar Volume

The present study was conducted to experimentally verify if the coefficient of thermal expansion (COTE) of recycled aggregate concrete is proportional to the volume of the original virgin aggregate in the total recycled aggregate concrete mix. Three types of recycled concrete aggregate (RCA) were crushed from: railroad concrete sleepers; precast (PC) culverts; commercial recycling plant. RCA concretes were mixed using two concrete mixing methods: conventional mix method and equivalent mortar volume (EMV) method. And by varying the replacement ratio, three test series were made. Test results showed that at the same RCA replacement ratio of 68%, the COTE of RCA concrete prepared by the EMV mix design was over 6–7% lower than that of RCA concrete made with the conventional mix method. It was also similar to or 1–2% lower than that of the natural coarse aggregate concrete. This may be because the conventional mix method does not take into account the residual mortar content attached to RCA. This results in a decrease in the volumetric ratio of the original virgin aggregate and a relative increase in the volumetric ratio of the mortar (or cement paste).

Properties of concrete incorporating microwave treated coarse aggregate: An experimental study

Using microwave heating technology to assist concrete recycling have great potential for improve the quality of recycled concrete aggregate. Unfortunately, there are few studies explored on the properties of concrete incorporating microwave treated coarse aggregates. This study aims to investigate the performance of coarse aggregate after microwave treatment and to evaluate the properties of the resulting concrete incorporated microwave treatment aggregate. The water absorption and crushing value tests were carried out to study the effect of microwave heating treatment on the physical properties of coarse aggregates. Concrete incorporated aggregate with various microwave heating parameters was fabricated and tested. The results indicated that physical performance of microwave treated aggregate was within the range of specification requirement and water absorption and crushing value of coarse aggregate heated under low microwave power levels (2–3 kW) is very closed to the untreated samples, while coarse aggregates treated with high power levels showed a significant increase. It was also observed that concrete made out of low microwave power levels heated aggregates are able to achieve strength on par with natural coarse aggregate concrete. In addition, in case of similar strength, the elastic modulus of microwave treated aggregate concrete is similar to natural aggregate concrete. These results indicate that using low microwave power levels to assisted aggregates recycling can reduce the damage to coarse aggregates to some extent, which provide a further understanding for the application of microwave-assisted aggregates recycling.

Comparative analysis on natural and recycled coarse aggregate concrete

Globally, in today’s world with rapid industrialization we see huge amount of waste disposed into landfills and we all know after the water, Concrete is one of the majorly used material throughout the globe. In India, construction presently generating a lot of construction and demolition debris. We should consider available options to bring the waste to production lines by recycling. In this present research work we utilized recycled coarse aggregates collected from crushed concrete. In concrete, coarse aggregate is accounts for major volume of concrete Recycling coarse aggregates (RCA) will be ideal option to reduce the amount of concrete waste goes into landfills. In this research work the main focus is to find the change in compressive strength of our required concrete combination by using Recycled coarse aggregates alternate to Virgin coarse aggregates and compare the recycled coarse aggregate concrete strength with natural coarse aggregate concrete strength.

Strength and abrasion performance of recycled aggregate based geopolymer concrete

This experimental work evaluated geopolymer concrete containing fly ash and slag by partial replacement of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) to manufacture environmental-friendly concrete. The proportion of recycled aggregates considered consists of 10%, 20%, 30%, and 40% of the total coarse aggregate amount. Also, a steel fiber ratio of 0.3% was utilized. The mechanical properties and abrasion resistance of fly ash/slag-based geopolymer concrete were then assessed. Majorly, the mechanical strength of the concrete samples decreased by the increase of RCA content. The geopolymer concrete with 40% RCA gave 28.3% lesser compressive strength and 24% lower splitting tensile strength than NCA concrete at one year. Also, the flexural strength of concrete specimens was reduced by 35% (from 5.34MPa to 3.5MPa) with the incorporation of 40% RCA. The incorporation of 30% RCA caused 23% and 22.6% reduction in compressive strength at 56 days and one year, respectively. The flexural and splitting tensile strength of the specimens was not significantly reduced (less than 10%) with the inclusion of a recycled coarse aggregate ratio of up to 30%. Furthermore, the abrasion wear thickness of every concrete sample was less than 1mm. RCA inclusion of 20% produced either insignificant reduction or better strength results compared to reference mixtures. As a result, it was considered that the combination of 0.3% steel fiber and 20% recycled coarse aggregate in fly ash/slag-based geopolymer concrete leads to an eco-friendly concrete mix with acceptable short and long-term engineering properties that would lead to sustainability in concrete production and utilization sector.

Strength and durability characteristics of binary blended recycled coarse aggregate concrete containing microsilica and metakaolin

Concrete is an important construction material. However, the consumption of natural aggregates in concrete production is responsible for depleting natural resources. Utilization of construction waste as recycled aggregate to replace natural aggregate in concrete construction is a great way to save the natural aggregate and manage the construction waste in an efficient manner. In the current study, compressive strength, water absorption and electrical resistance of concrete were investigated by replacing the natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) in the ratio of 50% and 100%. In addition, 10% cement was replaced with microsilica (MS) and metakaolin (MK) in RCA concrete mixes. Results show that RCA concrete had lower strength than NCA concrete; however, the strength of RCA concrete was improved by using binary blends of supplementary cementitious materials (SCMs). The SCM’s effect was found to be positive on water absorption and electrical resistivity of RCA concrete, water absorption was reduced, and electrical resistivity was increased. Further, the electrical resistivity results show that inclusion of SCMs reduces the chance of having corrosion in RCA concrete particularly using MK. Moreover, the microstructure investigations revealed that the incorporation of binary blends of SCMs reduces the voids in the RCA concrete and the microstructure of the concrete appears to be dense. Eventually, 100% RCA with binary blends of MS or MK can be used for the production of up to M35 grade concrete for practical concrete construction applications.

Cohesion coefficient of structural concrete made with recycled concrete coarse aggregate

The cohesion coefficient of structural concrete made with recycled concrete coarse aggregate (RCA) was evaluated independently for the first time, through push-off tests having no clamping force across the shear plane, and compared with the cohesion coefficient of structural concrete made with natural coarse aggregate (NCA). Both conventionally compacted and self-compacting concretes were made with RCA and NCA as coarse aggregates. To achieve the best structural quality, concretes made with RCA were proportioned based on the equivalent mortar volume (EMV) principle instead of percentage replacement of NCA with RCA commonly followed in most of the earlier studies. Twelve transversely unreinforced push-off specimens, three from each of the four varieties of concrete, were tested to failure. Cohesion coefficients determined from analytical and finite-element modelling of the push-off tests were found to be in close conformity with each other, and the experimentally found cohesion coefficients were reasonably close to, though not in exact conformity with, the theoretical values. Nevertheless, the experimental results clearly established that RCA concrete when proportioned by the EMV method is not inferior to NCA concrete in terms of cohesion contribution to shear strength.