Application Of Recycled Concrete Aggregates Research Articles

Recycled Concrete Aggregates: A Promising and Sustainable Option for the Construction Industry

The recycling of locally collected concrete waste is being promoted toward reducing the carbon footprint. In the preparation of concrete, recycled concrete aggregates (RCA) are encouraged instead of natural aggregates (NA), as they can help reduce the consumption of virgin materials, the extraction and transportation of which can be costly and environmentally damaging. In this context, we conducted an experimental study on various concrete mixes to evaluate the effect of using RCA instead of NA on the physical and mechanical properties of fresh and hardened concrete. The main novelty of our study lies in meeting one of the principles of circular economy, i.e., reducing the carbon footprint, by recycling concrete waste collected locally. We prepared and investigated test specimens containing 0%, 20%, 40%, and 60% of fine and coarse recycled concrete aggregates. Results for fresh concrete were determined for temperature, consistency, air content, and density, while on the other side, in hardened concrete, results were determined for compressive strength, tensile splitting strength, and density. All results were determined experimentally and then compared. Our results showed that, with the use of RCA in the concrete mix, construction companies can significantly reduce their carbon footprints and help conserve natural resources. RCA can help create a more sustainable and affordable construction industry and is better suited to meet future challenges. Our study can serve as a basis for advancing the application of RCA in the preparation of concrete for sustainable construction. Doi: 10.28991/HEF-2023-04-02-03 Full Text: PDF

Performance Improvement of Recycled Concrete Aggregates and Their Potential Applications in Infrastructure: A Review

In the construction industry, natural aggregates (NA) can be replaced by recycled concrete aggregates (RCA), which can address the issue of construction-waste disposal and resolve the dilemma between demand and supply. This paper aims to systematically review the modification of RCA techniques and their application in producing recycled aggregate concrete (RAC). First, the pretreatment approaches for enhancing the properties of RCA are introduced. Next, the improved efficiency of these approaches and their influences on the workability, mechanical strengths, and permeability of RAC are analyzed and discussed. Subsequently, the effectiveness of different techniques and their cost/environmental impact are compared. Finally, some case studies of the application of RCA in infrastructure are presented, and the remaining challenges and perspectives are discussed. The results of this review work can extend the knowledge of RCA and RAC, as well as serving as a source of inspiration for further studies.

Perspective on the Application of Machine Learning Algorithms for Flow Parameter Estimation in Recycled Concrete Aggregate

The constantly expanding civilization and construction industry pose new challenges for a sustainable development economy. Aiming to protect the environment is often associated with waste management, thereby reducing the number of landfills. The management of recycled concrete aggregate (RCA) from building demolition and its reuse in construction perfectly fits into this trend. The characteristics of post-industrial and recycled materials are not homogeneous as is usually the case with natural materials. This leads to a search for solutions to determine the parameters in the simplest possible manner and with as few resources as possible, while eliminating estimation risks. This task can be solved using machine learning, whose algorithms are increasingly used and developed in many areas of life and industry. The research in this study is aimed at comparing the effectiveness of k-Nearest Neighbors (k-NN) and Artificial Neural Network (ANN) algorithms in determining the permeability coefficient to a linear regression model. This parameter has an important role from the perspective of the application of RCA in civil engineering, particularly in earth construction. Two different RCA materials with different origins and properties were used in the study. The filtration test for each sample was pre-prepared using different compaction energies of 0.17 and 0.59 J/cm3 and for loosely packed samples. Differences in the structures of the test results are presented for both materials. The lowest prediction errors were obtained for the k-NN model. This algorithm obtained for the training sample a coefficient of determination (R2) equal to 0.947 and for the test sample an R2 equal to 0.980. In the case of ANN, the coefficient of determination was in the range of 0.877-0.936. An important part of the study was the interpretation with SHAP of the obtained models, allowing insight into which parameters influenced the predictions. That is significant and novel, considering the heterogeneity of the materials studied, and provides a rationale for further research in this area.

Application of recycled concrete aggregates for stabilization of clay reinforced with recycled tire polymer fibers and glass fibers

The application of recycled materials for soil improvement is advantageous from the viewpoint of lowering construction costs, preventing depletion of natural resources, and reducing environmental pollutions. This experimental study investigates the application of recycled concrete aggregates to enhance the strength properties of clay soil reinforced with recycled tire polymer fibers and glass fibers. Unconfined compression and indirect tensile tests were performed on composite soils comprising clay reinforced with 0.5 % fibers and stabilized with 5 %, 10 % and 15 % recycled concrete aggregates. Laboratory findings elaborated that the increase in the RCA content and curing time would significantly improve the unconfined compressive and tensile strengths as compared to the clay. Moreover, the approximate ratio of tensile to compressive strength is a constant value for the composite soils, irrespective of fiber type, RCA amount and curing duration. Concerning the practical implications, the clay reinforced with 0.5 % fibers and stabilized with 10 % recycled concrete aggregates is strong enough after 28 days of curing to fulfill the strength requirements of subbase layers in both flexible and rigid pavements.

Recycled Aggregates Production Through Economic Perspectives

Construction and Demolition Waste (CDW), especially laboratory waste and concrete debris from construction, manufacturing errors, and demolition of existing structures, is posing challenges to the urbanization. As nowadays the aforementioned waste is disposed in landfills, this diminishes the development opportunity of cities. Although there are standards and research pointing out the application of recycled concrete aggregates in proper proportion, the theory has never been put into practice. This research aims to present feasibility of applying recycled aggregates through Bangkok’s economic perspectives. It is found that the investment in recycled aggregate plants takes nine years of payback period. Besides, the sensitivity analysis suggests that implementing certain strategies, such as imposing a landfill tax increase and applying dumping fee will significantly shorten the payback period of recycling business.

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.

Sustainable Materials: A Review of Recycled Concrete Aggregate Utilization as Pavement Material

In this paper, a comprehensive literature review was conducted on the utilization of recycled concrete aggregate (RCA), which is the dominant construction and demolition waste material, in base and subbase layers and its comparison with natural aggregate (NA). The effects of crushing on the particles as a result of the compaction on the resilient modulus, permanent deformation, and California Bearing Ratio are analyzed. The paper also contains the NA consumption and waste disposal policies of different countries, RCA standards, and the environmental-economic reasons for its use. This literature review mainly focuses on pavement layers as this is the main application of RCA in the use of recycled materials. Developing integrated construction and demolition waste management will help achieve the primary goal of preventing and reducing the generation of these wastes, both locally and globally. In this way, not only is the main purpose of preventing the increase in the production of construction and demolition waste achieved, but also the reuse and recycling of the waste materials produced are encouraged. Results show that RCA has equivalent or better performance than virgin aggregate for almost any application with proper care and process control, and can be used in unbound pavement layers or other applications requiring compaction. But it is always recommended that its mechanical properties and durability performance be evaluated with full-scale tests before use. The information provided will be useful for contractors and engineers to evaluate alternative solutions and to explore the rational use of such sustainable materials in applications.

Enhanced workability, durability, and thermal properties of cement-based composites with aerogel and paraffin coated recycled aggregates

The use of construction and demolition (C&D) wastes in building materials is a key step toward a sustainable construction industry. In this context, the application of recycled concrete aggregates (RCAs) in cement composite mixtures has been investigated by various researchers. The results available in the literature indicate that cement mortar adhered to the surface of RCAs leads to high water absorption and large porosity in cementitious mixtures. As a result, lower workability, durability, and mechanical properties in comparison to conventional aggregates are often known as the main attributes of mixtures containing RCAs. Additionally, improving the thermal energy storage capability of RCAs by using high-performance thermal insulation materials, such as phase change materials (PCMs) and aerogel can assist in minimizing the energy consumption in buildings. Accordingly, this paper aims at characterizing RCA mixtures with enhanced workability, durability, and thermal properties. The effect of using paraffin coated recycled concrete aggregates (PCRAs) and aerogel aggregates on the mechanical, thermal, and durability properties of cement composites are investigated in this paper. Results of dry density, compressive strength, water absorption content, permeable voids, thermal conductivity, rapid chloride migration test (RCMT), capillary water absorption, and scanning electron microscopy (SEM) tests along with energy-dispersive X-ray spectroscopy (EDX) are reported to evaluate the effect of several variables on the investigated concrete mixtures. Results of the conducted tests indicate that using PCRA significantly improves the durability characteristics of mixtures such as water absorption content, permeable voids, and RCMT, while it slightly decreases the compressive strength of mixtures with respect to the control mixture. In addition, aerogel aggregates significantly improve the thermal conductivity of mixtures while reduced the mechanical and durability characteristics.

Potential of Natural and Recycled Concrete Aggregate Mixtures for Use in Pavement Structures

This study investigates the feasibility of using recycled concrete aggregate (RCA) as a partial substitution of natural aggregate in pavement engineering. Despite RCA’s good properties, such as polishing value and freeze-thaw resistance, its use is limited by low resistance to fragmentation and high-water absorption. This paper parent the experimental results of mineralogical-petrographic and physical-mechanical properties of RCA, natural stone (dolerite) and their combination (RCA content—15%, 30%, 45%, and 60%). The tested granular mixtures showed good resistance to fragmentation and wear (LA 22–27%, MDE 14–15%), as well as satisfactory Polished Stone Value of 55–57, which means they can be used in different layers of pavement structures. According to the obtained testing results, the application of RCA is possible in different flexible and rigid pavement layers and for various traffic loads.

Recycled aggregate concrete from large-scale production to sustainable field application

Concrete waste is the most prominent construction and demolition waste generated by the construction industry, which is mainly disposed to landfills. Recycling this waste in the form of recycled concrete aggregates (RCA) and substituting it for natural aggregates in the production of concrete could lead to environmental conservation. A growing body of literature in lab settings has already recognized the importance of utilizing RCA in the production of new concrete. However, intense utilization of RCA in the large-scale industrial production of new concrete (structural and non-structural) is not widely accepted by international standards due to its high porosity, a disparity of source concrete and lack of territorial field studies. In this paper, two full-scale field studies of the foundation system and municipal sidewalk constructed with recycled aggregate concrete (RAC) are presented. In addition to this, the long-term performance of RAC examined for 5 years in terms of in-place compressive strength is reported. Moreover, strength correlations developed specifically for RAC for the estimation of compressive strength based on rebound numbers are discussed. This study shows that RCA has significant potential of using as substitution of natural aggregate in the production of concrete of 25 and 32 MPa compressive strength. Furthermore, RAC shows a higher rate of compressive strength development after 28 days of curing and results in comparable long-term compressive strength to conventional concrete. By providing an insight into the sustainable application of RCA in the production of new concrete, the results of this study can serve as a basis for updating the current standards in Canada.

Effect of different aggregate treatment techniques on the freeze-thaw and sulfate resistance of recycled aggregate concrete

The inferior durability of recycled aggregate concrete (RAC) is causing hindrance in the application of recycled concrete aggregates (RCA) in structural concrete. This research focuses on the influence of different treatment methods of RCA on the freeze-thaw and sulfate resistance of resulting concrete. For this reason, freeze-thaw and sulfate resistance tests were conducted on carbonated RAC (C-RAC), lime carbonated RAC (LC-RAC), acetic acid immersed RAC (A-RAC), acetic acid immersed and rubbed RAC (AR-RAC) and acetic acid immersed and carbonated RAC (AC-RAC). Furthermore, mechanical properties and porosity of all the specimens were also explored. The results of this study showed improved mechanical performance and porosity of treated RAC. Enhanced frost and sulfate resistance was also observed for the treated RAC specimens. For example, 23, 17, and 21% reduction in the weight loss was noticed for LC-RAC, AR-RAC, and C-RAC after the freeze-thaw test than RAC specimens, respectively. Similarly, 24 and 19% less reduction in compressive strength was observed after sulfate exposure for LC-RAC and AR-RAC than RAC specimens, respectively. Scanning electron microscopic images of specimens after freeze-thaw test also showed lesser microcracks and denser interfacial transition zone for AR-RAC and LC-RAC than RAC supporting the improved frost resistance due to RCA treatment. Based on the results obtained in this study, LC-RAC and AR-RAC may be used in colder and sulfate-rich environments leading towards sustainable construction. Furthermore, regression models developed in this study show that the durability performance of concrete can be estimated through the physical properties of aggregates leading towards the durable and eco-friendly design of concrete structures.

Effects of waterproofing admixture on the compressive strength and permeability of recycled aggregate concrete

The recycling and reuse of demolished concrete aims to preserve the environment by reducing the waste disposal areas. Moreover, the replacement of virgin aggregates with aggregates obtained by crushing concrete waste can decrease the new quarries development rate. However, the application of recycled concrete aggregates (RCA) in new concretes is generally hindered by the loss of properties of produced concretes. Indeed, the addition of RCA normally affects the concrete properties due to their porosity and weakness. The effectiveness of waterproofing admixtures to improve the durability performance and increase the physical and mechanical properties of natural aggregate concrete (NAC) is well documented in the literature. Yet, the effect of this type of admixture on the properties of concrete incorporating recycled aggregates is not sufficiently studied. This paper investigates some properties of recycled aggregate concrete (RAC) containing waterproofing admixture. Concrete mixes with and without waterproofing admixture are tested in order to examine the slump, temperature, density, and air content of concrete at fresh state, and the compressive strength and permeability of concrete at hardened state. The permeability of concrete is assessed by determining its chloride ion penetration resistance using the rapid chloride permeability test and by measuring the depth of penetration of water under pressure. Test results have shown an improvement of the properties of RAC when waterproofing admixture is added; an improved compressive strength and a decreased permeability of RAC are tangible.

РАЗРАБОТКА СОСТАВОВ САМОУПЛОТНЯЮЩЕГОСЯ БЕТОНА НА ОСНОВЕ БЕТОННОГО ЛОМА С ИСПОЛЬЗОВАНИЕМ СТРУКТУРНЫХ ХАРАКТЕРИСТИК

Abstract. Huge amount of recycled concrete is formed when dismantling of buildings. The paper describes an efficient application of recycled concrete aggregates and concrete grinding fines to obtain technological, economic and ecological benefits. The possibility of effective application as materials for self-compacting concrete with the use of crushed concrete and recycled concrete fines is shown. The use of filler in self-compacting concrete mixtures obtained by activation of concrete grinding fines with polycarboxylate-based superplasticizer is shown. This paper presents the results of research of self-compacting concrete produced with recycled concrete aggregates and activated filler. The physical and mechanical characteristics of coarse aggregate, grain distribution of aggregates and sand proportion in aggregate mix, design of self-compacting concrete mixture and its structure properties with use mathematical experiment planning method were carried out. This method applies in the design of the self-compacting concrete mixture by solving the system of equations. The equations obtained by corresponding mathematical models. The obtained mathematical models include argumentative characteristics defined by the end of structure formation. The optimal content of filler in self-compacting concrete mixture is determined. The optimal grinding mode of the equipment with specified specific surface area of the filler is obtained. The grain-size composition of mixture consisting of quartz sand and crushed concrete aggregate with fraction of 5-10 mm based on term of maximum approximation to the Fuller ideal gradation curve is designed.

Application of recycled concrete aggregates and crushed bricks on permeable concrete road base

Application of recycled concrete aggregates (RCA) and crushed bricks (CB) into pavement materials is an ideal waste management solution. By appropriate material design, the RCA and CB could be used in permeable concrete as the pavement base which meets the principle of ‘sponge city’. This study aims to evaluate the performance of cement treated permeable concrete containing RCA and CB as the road base. Because of high-water absorption of RCA and CB leads to greater design deviations and resulted in leakage of cement slurry, the optimised volume method was used in mixture design. The compressive strength test, shrinkage test and water permeability test were performed. Results showed that the cement treated permeable concrete containing CB was an ideal fast-drying and low shrinkage due to drying material. Although CB had certain weakening effect on concrete strength, the strength of the permeable concrete was found acceptable according to the available specification. In addition, satisfied permeable performance was observed. It was recommended that concrete containing 15% of CB in weight (CB-15) was suitable to road base with moderate traffic level, and the concrete without CB (CB-0) to high traffic level, respectively. As the concept of environmental protection was being recognised by most countries in the world. This study suggested a potential direction for the large-scale application of RCA and CB.

Potential of recycled concrete aggregate pretreated with waste cooking oil residue for hot mix asphalt

Application of recycled concrete aggregate (RCA) in hot mix asphalt (HMA) is a sustainable alternative to natural aggregate. However, the increased asphalt consumption and decreased mechanical properties induced by the incorporation of RCA limit the extensive substitution of natural aggregates with RCA in HMA. In this paper, an experimental program was carried out to investigate the potential of recycled concrete aggregate pretreated with waste cooking oil residue (WCOR) with the expectation of reducing asphalt consumption and enhancing performance of HMA. The optimum pretreatment process for coarse and fine RCA in terms of content of WCOR, curing time and curing temperature was determined by an orthogonal design method and the grey correlation analysis. Subsequently, a laboratory characterization of HMA incorporating 40% coarse RCA, 40% coarse RCW (RCA pretreated with WCOR), 20% fine RCA and 20% fine RCW was further conducted in terms of optimum asphalt content, resistance to permanent deformation, cracking resistance at low temperature, fatigue performance, moisture sensitivity and dynamic modulus. Finally, scanning electron microscopy (SEM) test and fluorescence microscope (FM) test were performed to provide insight into the mechanism of WCOR-induced performance alteration. The experimental results showed that the pretreatment of RCA with WCOR decreased the optimum asphalt content from 5.4% to 4.5% for HMA incorporating 40% coarse RCA, from 5% to 4.5% for HMA incorporating 20% fine RCA. Moreover, RCA pretreated with WCOR enhanced significantly fatigue life and low temperature performance of HMA, while had a slight adverse effect on moisture sensitivity, permanent deformation resistance and dynamic modulus. Based on the SEM and FM tests, WCOR was observed to penetrate into tiny voids of cement mortar attached on RCA, which contributed to the reduction of optimum asphalt content and enhancement of fatigue life and low temperature performance of HMA.

The Friction and Dilatancy Angle of Recycled Concrete Aggregate

Recycled Concrete Aggregate (RCA) is a construction and demolition material, which in unbound state can be placed as subbase in road structures. Over last decades there was many investigations which highlighted physical and mechanical properties of this material. Nevertheless, successful application of RCA still needs more tests. For sustainable development of road engineering, utilization of recycled material is essential. In this article direct shear tests were performed to characterize mechanical properties of RCA. Direct shear tests were conducted with and without modification by adding metal frames to shear cubic shaped box with length of side equal 250mm. Material used in this paper was RCA in gradation with lead to recognize it as sandy gravel. Tests were performed for various moisture content material compacted with to respect of normal energy in Proctor method. Tests shows differences between direct shear with and without metal frames. For RCA tested in standard test conditions friction angle differs between 32.4° to 65.1°. Modification of test equipment results in friction angle equal 38.7° to 41.5°. Both tests indicated impact of moisture conditions during compaction. In this study, dilation angle analysis was also performed. Dilation angle values were in range from 5° to 10°. Brittle nature of RCA results in low value of the dilatancy index.

Application of recycled concrete aggregate in mineral-cement-emulsion mixtures

The article presents selected problems connected with the accomplishment of the research grant ‘Application of reclaimed materials’ as part of the joint project Development of Road Innovations (RID) co-financed by the National Centre of Research and Development as well as the General Directorate for National Roads and Motorways. The main aim of the project was to analyse possibilities of application of reclaimed concrete obtained from the demolition waste from the existing roads to produce new layers of road pavements. The article presents selected test results which show the influence of the reclaimed concrete content on the strength parameters of the MCE mixtures. Significant variation of the tested MCE mixtures properties depending on the percentage of the reclaimed material has been indicated. It has been suggested that new tests should be implemented in the process of MCE mixtures design process. An optimal content of reclaimed concrete has been determined in order to obtain required values of the analysed parameters. The application of reclaimed concrete in conventional MCE mixtures made it possible to achieve positive economical and environmental effects.

Quality Evaluation System for Description of Recycled Concrete Aggregates and Verification of its Functionality

Article presents quality evaluation system for description of recycled concrete aggregates (RCA), verification of RCA properties and subsequent application in to concrete mixtures as a partial or total replacement of natural aggregates (NA). Modernization and rehabilitation of constructions is accompanied by creation of demolition waste from old buildings and structures. The necessity of recycling is unavoidable, because volume of construction and demolition waste (C&DW) is increasing and the landfills are reaching their maximum capacity. Nowadays, there are numerous research teams focused on analysis of characteristics and application of RCA into new concrete as a replacement of NA. Test samples of RCA have always different source, grain composition and other physical and mechanical properties, which are variously described in each different paper. Up to now, there is no any uniform quality evaluation system for description of recycled concrete aggregates, which can easily describe their source and assumed properties. Our aim is to set up rules for description of RCA and simplify the evaluation of properties of various RCA. Qualification system will be applied on three different samples of RCA and verified by the selected properties tests. Tested samples of RCA will be than used as a replacement of natural aggregates in concrete mixtures. The replacement amount was set up on 20%, 40% and 100% according to the reviewed literature, to have a comparable replacement amount and valuable results for discussion. The results of RCA testing and testing of concrete with partial and total replacement of NA showed that the evaluation system is working properly. It can be concluded, that accuracy of the quality evaluation system for description of recycled concrete aggregates is sufficient, but more tests on RCA should be done to prove all connections in between description of RCA and their properties.

Thirty Years Researches on Development for Sustainable Concrete Technology

The enormous amount of concrete production has a serious impact on energy, resources, environment and ecosystem. Therefore, the issue of development of sustainable concrete technology with little impact on the environment is becoming a major issue. In this paper, researches related with sustainable development of concrete are presented in last three decades. FRP has high corrosion resistance and lightweight, thus it can be potential solution for sustainable development of concrete structures as strengthening material or reinforcement instead of steel. Researches and techniques are presented on performance of concrete beam with FRP rebar and enhancing performance of existing concrete structure using FRP strengthening methods. The application of recycled concrete aggregate (RCA) has sometimes been limited in the practice and remained in the low-valued purposes only such as road base materials. In past 10 years, a great improvement in the recycling technique to produce RCA of which quality is close to natural aggregate, hence the applicability and evaluation of RCA are presented in this paper. This paper includes experimental studies for application of waste glass which could decrease CO 2 emission from cement producing. The achievements of these studies are presented in this paper to contribute for sustainable development of concrete infrastructures.

Influence of polymer treatment on strength and water absorption capacity of recycled aggregate concrete

Dearth of natural coarse and fine aggregate has severely affected the construction industries worldwide. Recycled Concrete Aggregate (RCA) may be a compatible substitute to fresh aggregate, provided they are treated prior to their applications in concrete. Overall quality of the RCA depends on the aggregate parent material and present condition of the old concrete from which RCA was extracted. Experiments were performed on M20 and M25 concrete mix designs prepared using RCA in various combination. Influences of polymeric treatment on recycled aggregate concrete (RCA) and its water absorption capacity was analysed thoroughly. Results indicate that in polymeric treatment, compositions of the polymers, their concentration and duration of treatment directly or indirectly affects the strength and water absorption capacity of RCA. Good improvement in compressive strength and water absorption capacity of RCA was obtained after treatment, which proves the significance of polymeric treatment methods. This study will be very useful for promoting the application of RCA in road and building construction and preventing its disposal as a waste.