Influence Of Recycled Concrete Aggregates Research Articles

Study on the influence mechanism of recycled concrete aggregate on strength of asphalt mixtures

Recycled concrete aggregate (RCA) has great potential use in pavement. However, unclear characteristics of RCA and its relationship with the properties of asphalt mixture hinder severely its promotion. The objective of this study is to characterize the microscopic morphology and structure of RCA, further investigate its impact on the strength of asphalt mixture and associated mechanisms, by means of various test method. Results showed that cement mortar was the vital factor to affect the properties of RCA. Hence, the asphalt mixtures with RCA had characteristics of higher air voids (VV) and voids in the mineral aggregate (VMA), lower asphalt saturation (VFA), compared with conventional asphalt mixtures (CAM). In addition, according to the results of Micro-Scratch (MS) test, the compression depths of aggregate, interfacial transition zone (ITZ) and asphalt mortar in RAM are larger than that in CAM. Therefore, the influence of RCA on the performance of asphalt mixture is mainly in the following two aspects: reducing the strength of asphalt mortar; decreasing the skeleton strength of asphalt mixtures.

RECYCLED AGGREGATE CONCRETE (RAC): A viable solution for sustainable construction

Construction activities are booming in and around the cities with development and modernization. As a result of these constructions, natural aggregates are being extracted. Simultaneously, there is a significant amount of construction and demolition waste (CDW) generated due to the demolition of structures either due to the structure attaining service life or fashion and the ongoing trend of reconstruction. Therefore, recycling coarse aggregate from CDW in concrete is one of the sustainable solutions to prevent a serious threat to the environment due to the extraction of virgin aggregates and landfilling. This paper presents the results of a study undertaken to examine the influence of recycled concrete aggregate on the properties of new concrete and its life cycle cost (LCC) analysis. It is clear from the test that the strength of RAC is much lowered than natural aggregate concrete (NAC). In order to achieve the optimum strength, the natural aggregate is replaced by recycled aggregate within a range of 0% to 100%, in intervals of 10%. Additionally, to enhance its strength further, reinforcing RAC with new and recycled polypropylene (PP) fiber is done in percentages ranging from 0.25% to 2% by weight of cement with an interval of 0.25%. For analysis, compression, and split tensile strength tests were performed at the end of 28 days of the curing period. The result revealed that 40% replacement of natural aggregate with recycled aggregate achieves the ideal percentage replacement without compromising the strength. Moreover, incorporating 1.5% of new PP fiber or 1.25% of recycled PP fiber in the RAC provides optimum strength. For LCC analysis, the initial investment cost, operations, and maintenance cost, and salvage cost of all the alternatives are compared. Through this analysis, it was determined that the LCC of concrete manufactured using recycled aggregate as concrete ingredients is the lowest. Consequently, incorporating recycled aggregates in concrete production reduces the LCC compared to using natural aggregates.

A two-step approach for calculating chloride diffusion coefficient in concrete with both natural and recycled concrete aggregates

This paper presents an analytical approach to calculate the effective diffusion coefficient of chlorides in concrete with both natural and recycled concrete aggregates. In the approach the concrete is treated as a composite consisting of three phases, namely mortar, natural aggregate plus interfacial transition zone, and recycled concrete aggregate plus interfacial transition zone. The effective diffusion coefficient of chlorides in the composite is calculated through two steps. The first step is to calculate the effective diffusion coefficients of chlorides in the natural aggregate plus interfacial transition zone and in the recycled concrete aggregate plus interfacial transition zone by using multilayer spherical approximation, the results of which provide the information about the quality of recycled concrete aggregate in terms of chloride penetration resistance. The second step is to calculate the effective diffusion coefficient of chlorides in the three-phase concrete composite by using effective medium approximation, the results of which provide the information about the influence of recycled concrete aggregate on the diffusivity of recycled aggregate concrete. The analytical expression of the effective diffusion coefficient is derived and carefully compared with the results obtained from both the experiments and numerical simulations, which demonstrates that the present analytical model is rational and reliable. The analytical expression presented can be used to predict the service life of recycled aggregate concrete exposed to chloride environment.

Experimental study and prediction model for bond behaviour of steel-recycled aggregate concrete composite slabs

Using recycled aggregate concrete in a composite slab among the most promising solutions to effectively increase the utilisation of construction and demolition waste concrete. Longitudinal shear failure is a critical failure mode of composite slabs directly determined by the interfacial bond behaviour between concrete and profiled steel decks. However, the influence of recycled concrete aggregate (RCA) on interfacial bond behaviour remains unclear. Thus, this study conducted a pull-out test on the interfacial bond behaviour of composite slabs on 15 groups of specimens considering variables of replacement ratios of RCA (0, 50, and 100%), water-to-cement ratios (0.31, 0.45, and 0.60), steel deck thicknesses (0.8, 1.0, and 1.2 mm), and steel deck rib heights (48 and 65 mm). The bond-slip curves for all slabs were obtained, based on which the failure mechanism and influence of RCA under different parameters were discussed. Finally, an empirical prediction model for the bond-slip curve was established on the basis of the test data. The results showed that (1) the failure mode of composite slabs was independent of RCA, while the decrease in the steel deck rib heights induced more cracks in the failed slabs; (2) incorporating RCA decreased the ultimate bond stress by 4%–20% and the stiffness by 8%–14%; (3) the influence of RCA was coupled with other parameters; and (4) the proposed model exhibited a good prediction capability for the bond-slip behaviour of steel-RAC composite slabs.

Characterisation and Life Cycle Assessment of Pervious Concrete with Recycled Concrete Aggregates

The search for environmental preservation and conservation of natural resources gives rise to new concepts and viable technical solutions on the path to sustainable development. In this context, this study’s main objective is to analyse the influence of recycled concrete aggregates (RCAs) on the development of pervious concrete, whose use as a floor covering represents an excellent device to mitigate the urban soil sealing phenomena. For this, mechanical and hydraulic tests were carried out, in addition to microstructural analyses and the assessment of its environmental performance. The results obtained were compared to reference studies also involving the incorporation of recycled aggregates. A pilot-scale case study was conducted, involving a parking space lined with pervious concrete moulded “in situ”. In laboratory tests, permeability coefficients and mechanical strengths compatible with the literature and above the normative limit for light traffic were found. The case study demonstrated higher permeability than in the laboratory, but the flexural strength was lower, being indicated only for pedestrian traffic. The environmental assessment showed that the RCA represents a positive contribution to the environmental performance of pervious concrete. Still, attention should be given to the recycled aggregate transport distance between the concrete plant and the RCA treatment plant.

Influence of recycled concrete aggregates on the shear strength of reinforced concrete beams

ABSTRACT: This research evaluates the influence of the replacement of natural coarse aggregates (NCA) by recycled concrete aggregates (RCA) on the shear strength of reinforced concrete beams. Experimental tests on six reinforced concrete beams with RCA replacement ratios of 0%, 30%, and 100% are presented. Furthermore, a database with results of 170 tests on beams with RCA is used to discuss adjustments in the recommendations presented by ABNT NBR 6118 to estimate the shear strength of reinforced concrete beams. According to the Demerit Points Classification (DPC) proposed by Collins, 80% of the theoretical results obtained using models I and II from the Brazilian code fall in an appropriate safety condition range, showing that the substitution of NCA by RCA has a low impact on the shear strength reinforced concrete beams.

Effect of Recycled Concrete Aggregates on Compressive Strength and Water Permeability of Concrete

This paper discusses the effects of recycled concrete aggregates (RCA) on compressive strength and permeability of recycled aggregate concrete (RAC) by using recycled concrete aggregates as a replacement of natural coarse aggregates (NCA). Four replacement percentages were used to study the effect of replacement. Replacement percentages used were 30%, 50%, 70% and 100% with 0% replacement was used as control. Mix design of 1:1.24:2.6 was used in the study with water to cement ratio of 0.43. Influence of RCA on compressive strength was determined for all the mixes as per ASTM C39 standard. The permeability of all the mixes was determined by measuring absorption, sorptivity and Darcy’s coefficient. Results of compressive strength indicated that concrete with 30% replacement of NCA can be successfully used in structural concrete without compromising too much on strength. Whereas, the replacement of natural aggregates with RCA has a negative impact on the permeability of concrete at all replacement levels. Absorption, sorptivity and permeability of natural aggregate concrete is lower as compared to RAC with 30% replacement showing the better performance as compared to other replacement ratios.

Influence of recycled concrete aggregate on the foam stability of aerated geopolymer concrete

The effect of recycled concrete aggregates (RCA) in enhancing the foam stability and hardened properties of aerated geopolymer concrete (GFC) produced by a mechanical foaming method is investigated. The RCA was used as a partial or full replacement to fine aggregates, and approximately the same amounts of foam were used in all mixes to achieve a targeted density of 800 kg/m3. Despite the same water/binder and activator/binder ratios in all mixes, the fresh and hardened properties of GFC significantly varied between mixes. The instability of fresh geopolymer mix, caused by the collapse of air bubbles and the settlement was identified as a major issue in the control GFC mix. The use of RCA in GFC has significantly improved the foam stability with a significant reduction in settlement. The foam stability criterion was correlated to the yield stress development of base mixes, where the addition of RCA increases the initial yield stress and yield stress development over time. This has significantly influenced the stability of bubbles in GFC. On the other hand, the setting time of the geopolymer has reduced with the increasing RCA content. Nevertheless, the foam instability and corresponding settlement were stabilized well ahead of the initial setting time, indicating the setting of geopolymer has less impact on the foam instability in GFCs. The XRD and TGA analyses detect the presence of Ca(OH)2 in RCA, which increases the yield stresses of fresh geopolymer pastes. The variation in foam stability was well reflected on the hardened properties of GFC, such as porosity, pore size distribution, and thermal properties.

Influence of recycled concrete aggregates from different sources in hot mix asphalt design

The waste generated by the construction industry generally has an undesired negative impact on both human and animal life as well as the environment. Among these wastes, recycled concrete aggregate (RCA), due to its good residual physical, mechanical, mineralogical, and chemical properties, has attracted promising potential for re-use and incorporation in the construction of new infrastructural elements. These infrastructure applications include construction of sidewalks, curb and gutters, subbase/base layers, and/or as a partial replacement of natural aggregates (NA) in the production of hot mix asphalt (HMA) mixtures. In this laboratory study, experimental research work was conducted to evaluate the influence of RCA on the mechanical properties and performance of RCA modified HMA mixtures against a control HMA mixture without any RCA. RCAs were obtained from two different concrete sources, namely: (a) one from the demolition of a building (RCAB), and (b) another one from the rehabilitation of a Portland cement concrete pavement (RCAP). Both NA and RCA were characterized taking into account physical and mechanical properties. HMA mixtures were produced using the Marshall mix-design method by replacing 0.0% (control), 15%, 30%, and 45%, respectively, of the coarse NA fraction with RCA. Thereafter, laboratory testing (i.e., Scanning Electron Microscopy [SEM], resilient modulus, indirect tensile strength, etc.) including material property characterization and performance evaluation were conducted on HMA samples. Overall, the laboratory test results showed that the RCA modified mixtures exhibited a similar behavior to conventional HMA mixtures, but with greater environmental benefits and potential cost savings through the recycling and reuse of waste concrete aggregates. However, it was observed that the laboratory performance of RCA modified mixtures is strongly dependent on the RCA source and dosage, with RCAP exhibiting superior performance over RCAB. HMA mixtures produced with RCA provided higher optimum asphalt-binder content (OAC) than that of mixes with NA.

Influence of recycled concrete aggregates and blended cements on the mechanical properties of pervious concrete

The paper presents the results of an investigation conducted to study the strength properties of pervious concrete containing coarse recycled concrete aggregates (RCA). In this study, 13 pervious concrete mixes were prepared with the use of RCA replacing coarse natural aggregates (NA) by 0, 25, 50, 75 and 100%. Keeping the water–cement (w/c) ratio constant, Viscosity Modified Agent (VMA) was added at 0.8% by weight of binder content. Being environmentally advantageous, 30% Fly Ash (FA) has been added with 70% Ordinary Portland Cement (PC) in the binder of control mix. Despite being environmentally safe product, metakaolin (MK) also tends to enhance the properties of concrete containing RCA. Therefore, keeping the PC content 70% for all mixes, FA was replaced with MK at two different levels of 5% and 10% to improve the properties of pervious concrete made with RCA. Specimens in the form of cubes, cylinders and beams were prepared for studying the mechanical properties at different ages of curing. The test results showed that there was significant loss in compressive, splitting tensile and flexural strength of pervious concrete while increasing the percentage of RCA replacing NA. Addition of 5% MK compensated the decrement noticed in the strength properties after replacement of NA with RCA. The mix with 25% RCA and 5% MK was having almost same compressive strength as that of reference mix. 10% MK further enhanced the strength properties and it was concluded that loss of compressive strength in pervious concrete due to addition of 50% RCA can be compensated by the addition of 10% MK.

Influence of recycled concrete aggregates and Coal Bottom Ash on various properties of high volume fly ash-self compacting concrete

The mechanical and durability behavior of Recycled concrete aggregates (RCA) based High volume fly ash-Self compacting concrete (HVFA-SCC) has been examined through detailed experimental investigation. The article explores the overall behavior of HVFA-SCC made with 0%, 25%, 50%, 75% and 100% of RCA with alteration of Natural coarse aggregates (NCA) and in conjunction with 10% of Coal bottom ash (CBA) as alteration of Natural fine aggregates (NFA) through evaluation of several properties. Various mechanical tests (Compressive and Tensile strength) and durability tests (Accelerated carbonation, Electrical resistivity, Rapid chloride penetration-chloride permeability, Capillary suction, Initial surface absorption, Ultrasonic pulse velocity-UPV) were carried on HVFA-SCC mixes prepared with specific amounts of RCA, Fly ash (FA) and CBA. The findings confirmed the feasibility of HVFA-SCC made with alteration of NFA/NCA with CBA/RCA at specific levels respectively resulting in reasonable performance with respect to aforesaid properties. Projecting three (3) way benefits (i.e. Portland cement (PC) with HVFA; NFA with CBA and NCA with RCA) probably leads to widespread usage and recycling of by-products generated from the coal (FA and CBA) and construction industry (RCA) respectively. Such an effort assures the minimization of concerns like regulation and disposal of coal and construction industry wastes/by-products to a significant extent.

Monitoring of the rebar-concrete bond structural health through ultrasonic measurements: application to recycled aggregate concrete

The present work introduces an experimental ultrasonic method allowing for the rebar-concrete bond structural health to be assessed under loading conditions. This novel method has successfully been implemented in laboratory conditions by means of a pull-out test campaign including both conventional and recycled aggregate concretes. Two ultrasonic sensors, one emitter and one receiver were positioned on opposite side faces of the pull-out sample so that the reinforcing bar (rebar) was located in the center of the direct ultrasonic path. During the rebar pull-out, a variation of the time interval between the emitted signal and the received signal (i.e. time-of-flight) was measured. First, a potential correlation between this time-of-flight variation and the rebar-concrete bond behavior is investigated. Then, the influence of recycled concrete aggregates is discussed. In particular, a significant role of the mortar mechanical properties on the rebar-concrete bond behavior is suggested. Finally, an interpretation of this time-of-flight variation in relation to damage and fracture mechanisms occurring at the vicinity of the rebar-concrete interface is proposed. This ultrasonic-based method could likely be expanded to health monitoring applications of both conventional and recycled reinforced concrete structures, at a larger scale.

Uncertainty of shear resistance models: Influence of recycled concrete aggregate on beams with and without shear reinforcement

The model uncertainty of the shear resistance equations of three design codes {the current Eurocode 2 (2004), Model Code (2010), and the final draft of the Eurocode 2 (2020)} was investigated for coarse natural and recycled aggregate concrete beams. Databases of beams with and without shear reinforcement were made with clearly defined criteria. The statistics of the model uncertainty of natural and recycled concrete beams were compared and it was found that recycled aggregate incorporation has detrimental effects on the model uncertainty of shear design. Surprisingly, recycled concrete aggregate beams designed following the current version of Eurocode 2 (2004) are safer than those designed using the other codes. This is due to the shear resistance equations of the latter overestimating the aggregate interlock of recycled aggregate. A preliminary partial factor was proposed, offsetting the influence of recycled aggregate on the safety of beam designs. The database of beams with shear reinforcement lacks representativeness but hinted that recycled aggregate incorporation also reduces the safety of this type of shear design. The paper finishes presenting suggestions of experiments that would complement the current knowledge on this topic.

Influence of recycled concrete aggregates on alkali-activated slag mortar exposed to elevated temperatures

In this paper, the residual compressive strength behavior and the features of the alkali-activated slag (AAS) mortar made with five different replacement ratios of recycled concrete aggregates (RCA), i.e. 0, 25, 50, 75, and 100%, were investigated after being exposed to the target temperatures of 23, 200, 400, 600, and 800 °C. For this purpose, after exposure to elevated temperatures, the compressive strength and the mass loss were determined. Petrographic image analysis and scanning electron microscopy (SEM) were also used to analyze the microstructures of the specimens. The results showed that utilizing 25% RCA in the AAS mortar improved its performance at ambient and high temperatures. In addition, stronger aggregate-paste bonding was observed between RCA and AAS paste at high temperatures in the petrographic images. Overall, using these two kinds of materials (slag and RCA) seems to have a great potential for boosting the cleaner production of sustainable, environmentally friendly green mortar.

Adhesion between Asphalt and Recycled Concrete Aggregate and Its Impact on the Properties of Asphalt Mixture.

To study and evaluate the adhesion between recycled concrete aggregate and asphalt, the contact angles (CAs) between droplet (water and ethanol) and recycled concrete aggregate (RCA), natural aggregates, and solid bitumen (matrix asphalt, SBS modified asphalt) were tested via the sessile drop method with an optical microscope. The surface free energy was then calculated. The CAs between hot asphalt and RCA and natural aggregates were tested via the hanging slice method. The adhesive energy between asphalt and RCA and natural aggregates were calculated based on the test results of the surface free energy and CAs. Then, the influence of RCA on the water stability and fatigue performance of the asphalt mixture was analyzed by testing the water stability and fatigue properties of hot mix asphalts containing RCA (HMA-RCA) with different aggregates and RCA dosages. The surface energy of the various aggregates and the CAs between aggregates and asphalts were sorted as follows: Granite > RCA > serpentinite > limestone. The surface energy and CA of RCA were very close to that of serpentinite. The adhesive energy between various aggregates and asphalt were sorted as follows: Limestone > serpentinite > RCA > granite. The adhesive energy between RCA and asphalt was also very close to that of serpentinite. The residual Marshall stability, tensile strength ratio, and fatigue performance of the HMA-RCAs were gradually reduced along with the increasing RCA dosage. This effect may be attributed to the fact that the adhesive energy between the RCA and the asphalt was less than that of water and that the asphalt was easily stripped from the RCA surface. Excessive RCA content in the aggregate can lead to excessive porosity of the HMA-RCA. The CAs and adhesive energy between RCA and asphalt showed significant effects on the water stability and fatigue performance of HMA-RCA.

The influence of recycled concrete aggregate on the properties of concrete

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.

Influence of recycled concrete aggregate on volumetric properties of hot mix asphalt

Volumetric properties of hot mix asphalt (HMA) are necessary requirements to ensure good performance for asphalt mixtures. This research is conducted to evaluate the influence of coarse recycled concrete aggregate (CRCA) on the volumetric properties of HMA. Mix design of HMA mixture was performed for CRCA at various percentages 0%, 15%, 30%, and 60%, and the effects of the utilization of CRCA on HMA volumetric properties were evaluated. Additionally, various treatment methods were performed to evaluate the effect of various treatment types of CRCA on the HMA volumetric properties. To achieve this objective, presoaking, heat treatment followed by a short mechanical treatment were conducted. The obtained results showed that the use of the combination approach between different treatments appears to be very successful for enhancing physical properties of CRCA. The natural aggregate (NA) replacement by CRCA leads to increasing the optimum asphalt content (OAC) for the mixtures, whereas the property voids in mineral aggregates (VMA) is decreased. Compared to the mixture with 30% untreated CRCA, a little improvement and a slight increase in VMA and voids filled with asphalt (VFA) properties, respectively, were seen for mixtures with 30% treated CRCA with different treatment techniques. The CRCA addition with different proportions is very successful for both untreated and treated CRCA due to achieving all Ministry of Transportation Ontario (MTO) requirements for volumetric properties of HMA. However, CRCA treated with various treatment methods appears to be more successful than untreated CRCA application.

Influence of recycled concrete aggregates on the engineering and durability properties of alkali activated slag concrete

The environmental effects of production of cement have provoked to examine the growth of concrete with 100% replacement of cement with materials which are activated by alkali solutions. Alkali activated slag (AAS) concrete is eco-friendly and potentially deemed to be a division of sustainable process. As majority of the volume of concrete is consumed by aggregates, there is a necessary to decrease the utilization of natural aggregates resulting in reduction of exploiting natural resources and effective utilization of construction and demolition waste. The effect of recycled concrete aggregate (RCA) on the engineering and durability properties of alkali activated slag concrete (AASC) under ambient curing state has been investigated in this paper. Since, very few works were carried in the field of alkali activated slag concrete curing under ambient temperature state and the utilization of recycled aggregates, an investigation was performed in AASC mixes with varying RCA fraction to study their influence on strength (compressive, splitting tensile and flexural) and durability (absorption, sorptivity, chloride and sulphate exposure) properties of AASC. The outcome of the results concludes that the addition of RCA has no signification reduction in the properties of alkali activated slag concrete.

Study of pavement quality concrete mix incorporating beneficiated recycled concrete aggregates

The present study is an effort to investigate the influence of recycled concrete aggregates (RCAs) on the mechanical and durability properties of pavement quality concrete under different moisture states. Four moisture states, namely as received state (AD), saturated surface dry state (SSD), fully saturated state (FSD) and oven dried state (OD) of aggregates were considered in this study. RCAs manufactured upon processing of demolished concrete wastes were subjected to chemical beneficiation (using H2SO4) followed by abrasion prior to their incorporation in an experimental programme. In all, 24 mixes incorporating RCAs at different proportions of 10–50% with an interval of 10% for M-40 grade of concrete were prepared to investigate the properties of hardened concrete, such as compressive strength, flexural strength, water absorptions, chloride ion concentrations, sorptivity, abrasion, etc. Scanning electron microscopic analysis on thin samples collected from all 24 mixes was carried out in order to understand the surface morphology of concretes. The strength parameters of concrete mixes were found to be decreasing with increase in incorporation levels of RCAs in accordance with past studies. Among the mixes prepared with different moisture state of aggregates, SSD mixes were found to have better strength parameters, while those prepared using the FSD moisture state of aggregates showed the lowest values. The test results from chloride ion concentration and sorptivity indicate that mixes with RCA content up to 30% had test values within the specified limits, thus suggesting their potential use for pavement quality concrete.

Relationships between recycled concrete aggregates characteristics and recycled aggregates concretes properties

This research aims to analyze the quality and suitability of recycled concrete aggregates (RCA) produced by crushing concrete blocks provided from building demolition waste by comparison to natural ones in providing concretes for building structures. For each granular type, sieving, water absorption, porosity, Los Angeles and Micro-Deval tests were conducted before and after their exposure to freezing/thawing. Results show that the rules of mixtures (Voigt’s model) can be used to predict all the studied properties of granular mixes (natural gravels+recycled gravels) except for the prediction of Micro-Deval index. Relationships are established between physical and mechanical characteristics of aggregates. The analysis of the frost resistance performance show that recycled concrete gravels are less resistant to freeze/thaw than natural one but their degradation, estimated through water absorption, porosity and Micro-Deval index, is not significant. Furthermore, the influence of RCA on mechanical properties of recycled aggregates concretes (RAC) is investigated. It appears that porosity and young’s modulus of RAC are significantly affected by the porosity of the granular mixture and consequently of RCA. The compressive strength of RAC is dependent on the Los Angeles coefficient of gravels while tensile splitting strength depends on the porosity of concretes related to that of the granular mixture.