Properties Of Recycled Aggregate Concrete Research Articles

Calcium dissolution behaviors of recycled coarse aggregate concrete with the initial stress damage

The accelerated calcium dissolution tests of concrete with different replacement rates of recycled coarse aggregate (RCA) and different initial damage degrees D0 were carried out by using ammonium chloride solution. The results show that the dissolution resistance of recycled aggregate concrete (RAC) is negatively correlated with the replacement rate of RCA and the D0. The mass loss, dissolution depth, the attenuation of ultrasonic wave velocity, and the degradation of mechanical properties (compressive strength and splitting tensile strength) of RAC after calcium dissolution increase with the increasing replacement rate of RCA. When the D0 is less than 0.2, the dissolution resistance of RAC is not obviously affected by the initial stress damage; however, when the D0 is greater than 0.2, the mass loss, dissolution depth, the attenuation of ultrasonic wave velocity, and the deterioration of mechanical properties of RAC increase linearly with the increasing of D0. Compared with the compressive strength, the splitting tensile strength is more sensitive to the calcium dissolution and the initial stress damage of concrete. An obvious pH gradient is formed in the concrete after dissolution, and the pH value in a certain depth of the concrete decreases with the increasing of the replacement rate of RCA and the D0. Finally, the prediction model for compressive strength and splitting tensile strength of RAC after calcium dissolution is established.

Mechanical properties and microstructure of nano-strengthened recycled aggregate concrete

Abstract The surface adhesion mortar of recycled coarse aggregate (RCA) is the main factor leading to poor aggregate quality, and it also affects the internal structure and mechanical properties of recycled aggregate concrete (RAC). To improve the quality of RCA and mechanical properties of RAC, self-developed mortar removal equipment was used to strengthen the RCA. Then, the RCA was soaked in 1, 2, and 3% nano-silica solutions, and the vibration-mixing process was used to improve the quality of RAC. In addition, the microstructure of the RAC was examined via scanning electron microscopy to observe its improvement effect on the microstructure of the RAC. The results indicated that the quality of the RCA was improved by mechanical and physical strengthening, and the water-absorption rate and crushing value decreased by 32.9 and 23.9%, respectively. The improvement effect of nano-immersion on the RAC was obvious. The optimal condition was a combination of physical strengthening, 2 days of immersion in 2% NS solution, and vibration stirring. The 28 day compressive strength increased by 31.3%, the splitting tensile strength increased by 23%, and the flexural strength increased by 49%. The proposed strengthening method improves the mechanical properties and microstructure of RAC. The results of this study provided a technical reference for the mechanical strengthening of RAC and promotion of the application and popularization of RAC.

Study on compressive mechanical properties of recycled aggregate concrete with silica fume at different strain rates

Treating waste concrete to produce recycled aggregate concrete (RAC) is an important measure to save resources and protect environment. Studies have shown that adding silica fume to RAC can improve the mechanical properties of RAC. Based on the experiment, the uniaxial compressive mechanical properties of RAC specimens with silica fume content (S) for 0%, 5% and 9% at strain rates of 10−5/s, 10−4/s, 10−3/s and 10−2/s were studied. From the mesoscopic point of view, the damage and failure mechanisms of RAC were analyzed based on the statistical damage constitutive model. The results showed that with the increase of strain rate, the peak stress, elastic modulus and brittleness of RAC were on the rise. In addition, the peak stress and elastic modulus of RAC with high silica fume content were higher than those of RAC with low silica fume content. Considering two damage evolution modes of mesoscopic fracture and yield, the variation characteristics of mesoscopic damage parameters were obtained. From the perspective of effective stress, the whole process of damage evolution and accumulation induced catastrophe of concrete was expounded. The critical state and peak nominal stress state were distinguished, and it is considered that the critical state should be the limit state of the stress process of concrete material. These results were evaluated and analyzed by acoustic emission (AE), scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) tests.

Influence of modified two-stage mixing approaches on recycled aggregate treated with a hybrid method of treatment

ABSTRACT The depletion of natural resources occurs at a rapidly decreasing rate due to the growing demand for concrete. Therefore, the current research study uses recycled aggregate (RA) in concrete as a replacement for natural aggregate (NA) after proper treatment. The fresh, hardened, and durability properties have been examined in the current work. The adherent mortar over recycled aggregate (RA) makes it lower grade due to increased water absorption and lower strength. Based on Literature, natural aggregate concrete (NAC) has better strength and durability properties than recycled aggregate concrete (RAC). While making concrete using RA, using a two-stage mixing approach (TSMA) improves RAC properties better than the normal mixing approach (NMA). This study examines the influence of different mixing methods on concrete made from treated recycled aggregate(TRA). Four different mixing variants (viz. NMA, TSMA, TSMA1, TSMA2) were used in this work. The natural aggregate (NA) was replaced with TRA at various replacement levels in all variants, including 0%, 25%, 50%, 75%, and 100% in a control mix of M40. Based on the experimental results, the mixing method TSMA2 improved the various properties like strength and interfacial transition zone (ITZ) of TRA concrete compared to all other mixing techniques considered.

Development and strength assessment of eco-friendly geopolymer concrete made with natural and recycled aggregates

Purpose This study aims to develop geopolymer concrete (GPC) using manufactured sand (M-sand) and recycled concrete aggregate (RCA) under different curing conditions. GPC is a sustainable construction material developed with industrial waste products such as fly ash to eliminate the use of cement in the production of concrete. GPC requires heat curing for the attainment of early age strength. The development of GPC under heat curing conditions is a hard process in practice. To overcome such circumstances, an attempt was made to develop the GPC under different curing conditions with the aid of coarse aggregate (CA) and RCA. The influence of different curing conditions on strength gain and microstructural characteristics of GPC is investigated. Mechanical properties of GPC such as compressive strength, tensile strength, flexural strength and elastic modulus are reported and discussed. Design/methodology/approach This study focuses on the assessment of mechanical and microstructure characterization of eco-efficient GPC developed with natural CA and RCAs. The required optimum quantity of binder, alkali activator, alkaline liquid to binder ratio and aggregates was determined by appropriate trials. Three types of curing methods, namely, ambient, oven and water, were used for the development of GPC mixes. Following the properties of RCA, it is realistic to substitute up to 40% of coarser aggregates as the resulting aggregate mix falls within the requirements of the analyzed mix. Findings Special attention is required for the mix with RCA because the mix’s consistency is affected by the high water absorption of the RCA mix. GPC specimens cured at ambient and water conditions exhibited marginal variation in the compressive strength for both CA and RCA. The compressive strength of GPC mixes prepared with RCA was marginally higher than that of the GPC made with CA under different curing regimes. RCA can be used as a sustainable material in lieu of CA in GPC. Originality/value The main significance of this research work is to develop the optimal mix design with appropriate mix proportion. The present study proposes a satisfactory methodology that enhances the mechanical strength of GPC as the guidelines are not available in the standards to address this problem. Effective use of waste materials such as fly ash and recycled aggregate for the development of GPC is another major research focus in the proposed investigation.

Bond properties of basalt fiber reinforced polymer (BFRP) bars in recycled aggregate thermal insulation concrete under freeze–thaw cycles

In this study, recycled aggregate thermal insulation concrete (RATIC) with good frost resistance and basalt fiber reinforced ploymer (BFRP) bars were used to overcome the corrosion of recycled aggregate concrete (RAC). First, the influence of recycled coarse aggregate (RCA) and glazed hollow beads (GHBs) on the basic mechanical properties of concrete under freeze–thaw (FT) cycles was studied. Second, through FT cycle tests, the freeze–thaw resistance of four kinds of concrete (normal concrete, RAC, GHB thermal insulation concrete, and RATIC) was determined and the apparent morphology, mass loss rate, relative dynamic elastic modulus, and durability coefficient were obtained and analyzed. Finally, the bond performance between BFRP bars and four kinds of concrete under different FT cycles was investigated by center pull-out tests. The effects of RCA and GHBs on the failure mode, ultimate bond strength, peak slip, and bond slip curve of concrete were analyzed. The research results show that RCA has adverse effects on the mechanical properties, freeze–thaw resistance, and bond properties of RAC. The reasonable addition of GHB can compensate for the adverse effects of RCA and significantly improve the freeze–thaw resistance of concrete. GHB can also improve the bond properties between BFRP bars and RAC under freeze–thaw cycles. The combined use of BFRP bars and recycled aggregate thermal insulation concrete is an important way to effectively solve the problem of steel bar corrosion in structural engineering in severely cold areas.

Potential use of recycled concrete aggregate (RCA) for sustainable asphalt pavements of the future: A state-of-the-art review

With the continuous paving of roads around the world, the huge consumption of natural aggregate (NA) obtained through widespread excavation and extraction is now an inevitable part of highway construction. To alleviate this phenomenon, the use of recycled concrete aggregates (RCA) is considered beneficial to potentially substitute these aggregates in asphalt mixtures while concurrently providing secondary environmental, economic, and societal benefits. Nevertheless, engineering asphalt mixtures containing RCA to meet desired performance properties still poses several challenges and uncertainties for practitioners. Based on this, the present work reviews the previous relevant literature on this topic and summarizes the potential use of RCA for asphalt pavement related applications. An important characteristic of RCA is that it consists of various interfacial transition zones (ITZs) and voids caused by adhered mortar which leads to higher water-absorption and crushing characteristics as compared to NA. The treating methods used such as mechanical processing, calcium carbonate bio-deposition, and pozzolanic materials incorporation have been shown to be effective to improve the quality of RCA. The structural and material durability of RCA-asphalt pavement is closely dependent on its mix design, moisture-induced damage, and high and low temperature properties, which is in direct relation to the overall properties of RCA. Moreover, the shape variability of RCA during mixture preparation leads to the change in design gradation and its influence on the properties of RCA-asphalt mixtures should be carefully considered. The total substitution of coarse NA by RCA in asphalt pavement can be reached as long as the engineering properties, particularly the moisture susceptibility, are satisfactorily addressed. Overall, the potential application of RCA is a promising candidate to replace the excessive use of NA for the construction of high quality and sustainable asphalt pavements of the future.

Effect of crystallizer treatment on chloride diffusion and microstructure of recycled aggregate concrete

The crystallizer (CA) treatment on recycled concrete aggregate (RCA) can improve its quality and further benefit the utilisation of RCA in manufacturing recycled aggregate concrete (RAC). Unfortunately, the long-term properties of RAC with CA treated RCA have not been fully explored yet. Therefore, this paper is aim to evaluate the performance of CA treatment on RCA and the durability and permeability of corresponding RAC. To achieve the goal, the permeability of RAC with different RCA replacement ratios was investigated by capillary water absorption test and rapid chloride migration test, and the effects of CA on the interfacial transition zone (ITZ) and pore structure were determined through mercury intrusion porosimetry and scanning electron microscope. The results showed that CA treatment significantly improved the chloride diffusion resistance of RAC due to the calcium silicate hydrate (C-S-H) formed by the reaction between CA treatment and calcium-rich hydrates. The formed C-S-H can partially fill the pores and micro-cracks in adhesive mortar and ITZ, compact the microstructure and reduce the pore size, thus improving the permeability of RAC.

Partially fly ash and nano-silica incorporated recycled coarse aggregate based concrete: Constitutive model and enhancement mechanism

The single use of nano-silica (NS) or fly ash (FA) can improve the strength of recycled aggregate concrete (RAC). However, the studies on NS-FA-modified RAC (NFRAC) are limited, and further research is required to understand the mechanical behaviors of NFRAC over different curing ages. In this study, to further improve the properties of RAC, these two supplementary cementitious materials (SCMs) were utilized in RAC together: NFRAC. The workability as well as the compressive and split tensile properties were determined by an orthogonal test along with the effects of various factors, including curing age, recycled coarse aggregate (RCA) replacement rate, and SCM content on the performance of NFRAC. NFRAC was found to have adequate mechanical properties, both in the early and later curing ages. Based on NFRAC with 100% RCA replacement rate as the main research object, the strain ductility, energy consumption, and constitutive model were further explored. Scanning electron microscopy was performed to explore the modified mechanism owing to the incorporation of NS and FA. Both the SCMs can successfully accelerate the pozzolanic reaction, thereby improving the mechanical properties. In addition, NS can also fill the micropores in RCAs and react with the CH of mortar to form C–S–H gels, thereby improving the properties of ITZ. However, NS weakens the workability that can be compensated by incorporating spherical FA. Finally, 10% FA and 2% or 3% NS are recommended as SCMs for RAC.

Effect of utilization of rice husk ash on hardened properties of recycled concrete aggregate

The manufacturing of Portland cement accounts for more than 5 percent of worldwide carbon dioxide emissions. The rising expense of conventional building materials, as well as the need to ensure long-term growth in the construction industry, have encouraged designers and developers to investigate alternate materials for use in civil engineering constructions. An excellent way to accomplish this is to make use of agricultural byproducts. They can be employed as cementing materials because of their pozzolanic tendency, which would otherwise necessitate the usage of enormous areas of land for the dumping of these agricultural byproducts. As a result of the existence of these components within concrete not only helps to minimize carbon dioxide emissions, but it also contributes to the major enhancement in the workability, and durability of the concrete. Goal of this research is to discover whether or not it is feasible to use rice husk ash as a concrete addition., as well as efforts were undertaken to determine the parameter affecting concrete's strength (Compressive strength). The IS technique of mix design was used to control concrete, and a mix design for replacement approach was created using this as a foundation. In terms of replacement approach, five distinct replacement levels of rice husk ash (RHA) have been selected for the study: 5%, 7.5%, 10%, 12.5%, and 15%. A 25% of recycled coarse aggregate (RCA) has been selected as a partial replacement of virgin coarse aggregate in the mix. The present study takes into account a wide duration of time needed for cure ranging from 7 days to 14 days to 28 days. According to the findings, the compressive strength gradually improves from 7 days to 14 days after the experiment, and additionally, there is a considerable improvement in strength (compressive) from 7 days to 28 days.

Effect of compression casting technique on the water absorption properties of concrete made using 100% recycled aggregates

Effect of compression casting technique on the water absorption characteristics of low grade 100% Recycled Aggregate Concrete (RAC) of target strength range 11 to 15 MPa to be used in the manufacturing of masonry units is investigated. Water absorption characteristics were determined by performing sorptivity test. Recycled aggregates were produced by crushing laboratory-tested concrete samples of strength ranging from 21 MPa to 28 MPa. Two different ratios of recycled coarse aggregate and recycled fine aggregates were investigated using two different cement contents. For comparison, natural aggregate concrete mixes were also tested. The study parameter included effect of aggregates type, casting pressure, casting technique and cement content on the water absorption properties of RAC. Further, depth of penetration of salt was observed using silver nitrate solution after 3-month immersion in 10% NaCl solution. The results of sorptivity test showed positive impact of compression casting technique on water absorption properties of low grade 100% RAC. Further, results showed that RAC mixes exhibited inferior water absorption properties compared to natural aggregates concrete mixes. Various equations were proposed to predict water absorption of 100% RAC under different conditions of casting pressure and cement content based on initial and secondary rate of water absorption.

Investigation on mechanical, durability and time-dependent properties of standard grade recycled aggregate concrete with pozzolanic material

Sustainable development is the development that meets the needs of the present without compromise the availability for future generations to meet their own needs. Sustainability goals concentrate on the global challenges, including poverty, inequality, environmental degradation and climate change. Sustainable Construction is the utilization of materials and products in buildings and construction that will require less use of natural resources and boost the reusability of such materials and products for the same or similar purpose, thus reducing waste as well. In this research paper, experimental investigation were carried out to study the strength and durability properties of standard grade recycled aggregate concrete (RAC), namely M40 with constantly replacing 30% cement by fly ash throughout each sample, keeping all the materials quality and composition same and only replacing the different percentage of natural aggregate (NA) by recycled aggregate (RA) to study the properties of RAC. Concrete prepared by natural aggregate concrete (NAC), recycled aggregate concrete made with 25% replacement of NA by RA (R25),50% replacement of NA by RA (R50), 75% replacement of NA by RA (R75) & 100% replacement of NA by RA (R100) were tested. The present work results show that the replacement of RA by NA up to 100 percent does not affect the strength and durability of concrete significantly.

Performance enhancement of the recycled aggregate concrete properties using blended sand

Massive consumption of River sand in construction activities around the world led to the depletion of natural resources. Demolition waste was gaining popularity as a substitute for sand, but recycled fine aggregate(RFA) exhibits poor performance in concrete in terms of strength and workability. Therefore, the current study is a small attempt to improve the properties of RAC (Recycled aggregate concrete) by applying blending of RFA with copper slag (CS) to form blended sand. The study investigates the use of recycled fine aggregate (RFA) and blended sand (RFA + CS) separately in M−40 grade of concrete at 20%, 40%, 60%, 80% and 100% replacement levels of natural sand. Then concrete mixes are checked for workability (slump value) and compressive strength at 7, 14 and 28 days of curing. Results show that RFA concrete presents poor properties. In contrast, improved results were obtained in the case of blended sand concrete, which performed even better than reference samples prepared with river sand at 20% replacement of natural sand. Therefore, the study concluded that the enhancement in properties of recycled aggregate concrete(RAC) was achieved by using proper blending material in the required proportion with RFA. Further, the finding reveals that blended sand can use to enhance the strength and workability of concrete and have the potential as a sustainable alternative to river sand that brings sustainability to the construction sector.

Various recycled steel fiber effect on mechanical properties of recycled aggregate concrete

PurposeThe current study mainly focuses on the effect of varying diameter recycled steel fibers (RSF) on mechanical properties of concrete prepared with 25 and 50% of recycled coarse aggregate (RCA) as well as 100% natural aggregate (NA). Two types of RSF with 0.84 mm and 1.24 mm diameter having 30 mm length were incorporated into normal and recycled aggregate concrete (RAC).Design/methodology/approachThe fresh behavior, compressive, splitting tensile, flexural strengths and modulus of elasticity of all the mixes were investigated to evaluate the mechanical properties of RACs. In addition, specimen crack and testing co-relation were analyzed to evaluate fiber response in the RAC.FindingsAccording to the experimental results, it was observed that mechanical properties decreased with the increment replacement of NA by RCA. However, the RSF greatly improves the mechanical properties of both normal concrete and RACs. Moreover, mixes containing 1.24 mm diameter RSF had a more significant positive impact on mechanical properties than mixes containing 0.84 mm diameter RSF. The 0.84 mm and 1.24 mm RSF addition improved the mixes' compressive, splitting tensile and flexural strength by 10%–19%, 19%–30% and 3%–11%, respectively when compared to the null fiber mix. Therefore, based on the mechanical properties, the 1.24 mm diameter of RSF with 25% replacement of RCA was obtained as an optimum solution in terms of performance improvement, environmental benefit and economic cost.Practical implicationsThe practice of RCA in construction is a long-term strategy for reducing natural resource extraction and the negative ecological impact of waste concrete.Originality/valueThis is the first study on the effects of varying size (0.84 mm and 1.24 mm diameter) RSF on the mechanical properties of RAC. Additionally, varying sizes of RSF and silica fume added a new dimension to the RAC.

Characterization of compaction and CBR properties of recycled concrete aggregates for unbound road base and subbase materials in Vietnam

Characterization of compaction and CBR properties of recycled concrete aggregates for unbound road base and subbase materials in Vietnam

Utilization of construction and demolition waste and synthetic aggregates

Construction and demolition (C&D) waste are generated during the creation of structure or building or when renewing or demolishing a current structure. C&D waste exhibits many environmental problems including diminishing landfill, increasing wastage areas, landfill contamination, and increasing energy required for waste disposal and transportation. The re-using C&D waste as an aggregate in concrete making have reduced extraction demanding and landfill pressure. The utilization of C&D as recycled concrete aggregate (RCA) alternative to natural one not only decreases environmental problems but also leads to the conservation of naturally occurring resources. On the other hand, the synthesis of an aggregate from powdered industrial solid waste was also found to have a good alternative to natural aggregate with lower specific gravity and high thermal insulation . This work have reviewed the application of C&D and synthetic aggregates for making structural and non-structural concrete. Owing to the contaminants attached on the surface of RCA, the replacement of natural aggregate with this aggregate has resulted in a significant reduction in the performance of cement concrete . Therefore, many approaches have been done to enhance the quality of RCA. Among these different methods, the carbonation and pozzolan slurry are regarded as the best methods for enhancing the properties of RCA. Synthetic aggregate could be prepared by different methods including sintering, cold bonding, and autoclaving. Lightweight aggregate synthesized by the cold-bonding method could be successfully applied to fabricate a moderate strength lightweight concrete. More research is required to evaluate the resistivity of lightweight concrete containing autoclaved lightweight aggregate. • The construction and demolition waste aggregate could be reused in concrete mixes. • Different methods were used to improve the performance of recycled aggregate. • Carbonation is the best method for improving the performance of this aggregate. • The synthetic aggregate could be also used in some types of concrete pastes.

Evaluating the combined effect of recycled aggregate and rice husk ash on concrete properties

This paper evaluates the synergistic influence of utilizing agricultural wastes i.e. rice husk ash (RHA) and coarse recycled concrete aggregates (CRCA) on the properties of recycled aggregate concrete (RAC). The RAC mixes were made with 0%, and 100% substitution of coarse natural aggregates by CRCA. Cement is further substituted by RHA at 0%, 5%, 10%, 15%, 20%, 25% and 30% to understand the influence of RHA on the fresh and hardened properties of RAC. The mechanical properties were investigated through compression, tension and flexure test at various ages such as 7, 28 and 56 days and other hardened properties like the water penetration resistance and the dry density were also studied. The various properties of the RAC were found to be improved as the RHA quantity is raised till 25% and further decreased when RHA content is increased to 30%. The use of RHA has proved to be very effective as the compressive strength improved by about 26% at 25% RHA. The correlation among the different strength parameters in the RAC mixes has also been established. The water permeability of the concrete mixes got reduced and the dry density increased with the increase in RHA content due to the reduced porosity. This was possible because of the pozzolanic reaction of amorphous silica present in RHA. Hence, the short comings of RAC can be overcome with the use of low end pozzolanic materials like RHA and can be used for retaining the performance of concrete containing 100% RCA.

Efficiencies of carbonation and nano silica treatment methods in enhancing the performance of recycled aggregate concrete

This study compared the efficiencies of five recycled aggregate treatment methods (pressurized gas–solid carbonation (PC), flow-through gas–solid carbonation (FC), wet carbonation (WC), nano-silica (NS) spraying and combined PC with NS spraying (PCNS)) in enhancing the performance of recycled aggregate concrete (RAC). Mechanical properties, durability and microhardness of RACs were evaluated. The results showed that PC method recorded higher enhancing efficiency than both FC and WC method. NS spraying method caused higher improvement in mechanical properties of RAC than three carbonation methods. Because of the synergistic effect of enhanced old mortar and new ITZ, PCNS method recorded the highest efficiency.

The effects of surface treatment methods on properties of recycled concrete aggregates

In developing countries like India, a large quantity of construction and demolition waste is generated every year. Hence the disposal of this waste in large quantity has become a serious problem as it requires huge space for dumping. Considering the state of our country's infrastructure, it will be required to discover new sources of aggregate for the manufacture of concrete in the future due to rising demand and a relatively limited quantity of natural aggregate. One good solution is to obtain Recycled concrete aggregate (RCA) from the material that have been previously used in construction. Natural aggregates have different characteristics than RCA. The existence of mortars in RCA is one of the primary reasonsfor RCA's lower quality when compared to natural aggregates. In this paper various treatments like water washing, heating and acid soaking are used for removal of attached mortar and enhance the properties of RCA. Following the RCA treatment, mix designs for M35 and M40 concrete grades were created, and the characteristics of the concrete were evaluated and compared to natural aggregate concrete. Concrete mixes are prepared using recycled aggregate, recycled aggregate treated with HCL, recycled aggregate obtained after heating treatment and natural aggregate. These aggregates physical and mechanical characteristics, as well as their strength and performanceare determined. However, results show that there is improvement in properties such as workability, split tensile strength and compressive strength when treated aggregates were used.

Shear Characteristics of the Interface between Recycled Concrete Aggregates and Various Geosynthetics

To investigate the interface shear characteristics between various geosynthetics and recycled concrete aggregate (RCA), 30 large-scale monotonic direct shear tests were conducted. The main work was to analyse the effect of a biaxial polypropylene geogrid, a glass fiber geogrid, a warp-knitted polyester geogrid, a woven geotextile, and geonet on the interface shear properties of RCA. The test results show that adding a biaxial polypropylene geogrid or a geonet to RCA can improve its interface shear strength. The inclusion of glass fiber geogrids, warp-knitted polyester geogrids, and woven geotextiles decrease the interface shear strength of RCA. The reinforcing RCA with geosynthetics can effectively suppress its shear dilation, and the change in internal friction angle is consistent with the change law of the material interface enhancement coefficient. Finally, the aperture size of a geogrid has a significant effect on the mechanical properties of the geogrid-RCA interface. The interface shear strength increases first and then decreases with an increase in the ratio between aperture size and median particle diameter. It is concluded that there is an optimal range of aperture ratio between a geogrid and RCA.