Recycled Construction Aggregates Research Articles

Physico-mechanical and thermal properties of vibrating and self-compacting sand concrete based on recycled aggregate from concrete

This study explores the use of recycled aggregates (RA) from concrete, replacing 100% of Cruched Sand (CS) by volume. It focuses on their processing methods and their performance compared to Self-Compacting Sand Concrete (SCSC) and Vibrated Concrete (VC). Fresh properties, including workability, are affected by RA, but RA-based SCSC meets standards. While RA-based SCSC initially had lower strength than CS-based SCSC, it improved after 28 days, yielding similar mechanical properties. RA use led to lower density compared to CS in concrete. Thermal conductivity was insulating, slightly lower in RA-based SCSC. Porosity decreased with age in all mixtures, with RA-based concrete having initial higher porosity and capillary absorption. Microstructure showed finer crystal growth in RA-based concrete. RA in SCSC exhibit a superior Interfacial Transition Zone (ITZ) compared to CS concrete, enhancing homogeneity and durability. This research supports sustainable RA use in concrete, that contingent on precise mix design and method processing of waste concretes, as well-designed SCSC. RA in construction provide scalable and economic benefits, including cost savings, infrastructure investment, sustainability, and market expansion. This contributes to the provision of environmentally friendly building materials and the sustainability of the industry.

Impact of Recycled Concrete and Brick Aggregates on the Flexural and Bond Performance of Reinforced Concrete

The construction industry strongly relies on concrete and clay bricks for various applications. The escalating demand for these materials, driven by rapid population growth, has led to resource depletion and increased construction and demolition waste (CDW). Recycling CDW into construction materials, particularly in the form of recycled concrete aggregates (RCAs) and recycled brick aggregates (RBAs), has emerged as a promising solution. This study deals with the structural performance of concrete incorporating RCAs and RBAs. The experimental program encompasses material characterization, concrete mix design, and several tests to assess density, compressive strength, bond behavior, and flexural properties. The results indicate that the replacement of fine natural aggregate (NA) with fine RCAs or RBAs has a negligible impact on density, while the partial replacement of coarse NAs with RAs yields modest reductions in compressive strength. Notably, the bond strength between steel rebar and concrete is influenced by the type and content of RA, with specimens containing RCAs exhibiting a higher bond strength than those with RBAs. Empirical models used to predict bond strength generally align with experimental results, with conservative predictions by some models, such as ACI 318, and overestimation by others, such as models proposed by AS-3600 and CEB-FIB. The flexural tests of beams highlight the variation in stiffness and load-bearing capacity with the proportion of NAs replaced by RAs. While beams with 50% NA replacement demonstrate comparable performance to control beams, those with 100% RA replacement exhibit lower cracking and yielding stiffness. Cracking patterns in beams with RAs differ from control beams, with RA-containing beams showing more cracks and an altered crack distribution. The findings underscore the feasibility of using recycled aggregates in construction, with partial NA replacement offering a balance between sustainable material usage and desired structural properties.

Study of environmental impact from geosynthetic reinforced soil walls

Reinforced soil walls (RSWs) have proven to be a reliable and resilient solution in many geotechnical applications (e.g., bridge abutments, highway and railway embankments, soil retaining walls, dikes, among others). Moreover, the reduced impact of these types of structures over traditional solutions has been compared using life cycle analysis (LCA) and sustainability assessment methodologies. Nowadays, RSWs are often constructed with geosynthetic materials as reinforcement elements due to their ease of use, cost, and technical viability. The use of geosynthetic materials can assist to meet the global challenges of the United Nations global sustainability goals and to adapt to the effects of climate change. The LCA methodology allows designers to determine the environmental impact of different candidate solutions or structures for a given design life. By providing comparable score-based results, a LCA permits objective decision making. The present work describes the environmental impact assessment of idealized polymer strap geosynthetic RSWs using the LCA methodology. Case studies are focused on the use of different backfill material (granular soil from a quarry or riverbed, recycled construction aggregate, and low quality locally available soil). Analysis boundaries include cradle-to-gate considerations and a 100-year design life. Results indicate the reduced environmental impact of using on-site backfill.

An Experimental Study on Partial Replacement of GGBS with Cement and Utilizing Demolished Coarse Aggregate in Concrete

bstract: The majority of municipal solid wastes are made up of debris from construction and demolition projects, including recycled construction aggregate (RCA). This paper presents the findings of an experimental and analytical examination of the creation of environmentally friendly concrete. It is a good idea to replace natural material with aggregate from old, demolished structures to reduce debris and preserve the environment. To reduce consumption, recycled aggregate can be utilized in place of natural aggregate. To address these issues, an attempt is undertaken in the current experimental work to substitute GGBS in varied proportions for cement. The purpose of this research is to demonstrate the findings of an investigation into the applicability of GGBS in the manufacturing of concrete by using construction and demolition debris as a recycled resource. Ground granulated blast furnace slag (GGBS) and recycled concrete aggregates are the recycled materials employed in this study. A concrete mix of grade M25 was created through the mix design process. GGBS was partially replaced with wastedestroyed aggregate in the amounts of 0, 10, 20, 30, and 40% to create the mixes. Cubes of 150x150x150mm3 were poured. The compressive strength of the concrete cube specimens was measured by smashing the cube after 7, 14, 28, 60, and 90 days of curing for various curing intervals. The compression test results on the cubes show that strength increases with the amount of slag added up to the maximum value. Compressive strength was seen to grow when GGBS content increased up to 30%, but after the replacement level was above 30%, strength began to deteriorate. The outcomes of GGBS with conventional concrete and concrete made entirely of demolished aggregate without GGBS are compared to the outcomes of GGBS with concrete containing demolished aggregate

Utilization of recycled construction powder in 3D concrete printable materials through particle packing optimization

With the enhancement of awareness of environmental protection and sustainable development, reuse of industrial solid waste has gradually attracted people’s attention. The utilization of recycled construction powder (RCP) and recycled construction aggregate(RCA)in the production of 3D concrete printable material(3DPM) can not only reduce carbon emissions, but also promote the application of 3D printing technology by reducing material costs. Considering the defect of low-reactivity and inferior property of RCP, the appropriate RCP is screened out according to the modified Andreasen and Andersen model to optimize the gradation of printable materials. Influence of RCP on the fresh property is investigated by rheological experiment and the incipient failure height test. The results show that the addition of 10%RCP would increase the yield stress from 1423Pa to 1573Pa and maintain the viscosity of the material. Moreover, unconfined compressive strength test, isothermal calorimetry and mercury intrusion porosimetry test are also used to characterize the properties of 3DPM. The results show that although the addition of RCP reduces the total heat release of 3DPM, it also reduces the macropore(¿1000 nm) of 3DPM from 10.7% to 7.1%, and keep the compressive strength within an acceptable range through the gradation optimization. Finally, the results of laboratory printing or industrial printing also confirm the printing performance of 3DPM.

Properties of Concrete Made from Cupola Furnace Slag and Recycled Construction Aggregates

The replacement of traditional constituents of concrete with waste has garnered a lot of interest due to the increasing demand for natural resources used in concrete production. Hence, this study presents the outcome of an experimental investigation on the effect of partial replacement of Ordinary Portland Cement (OPC) at percentage levels of 0% to 25% in steps of 5%, partial and complete replacement of sand and granite in the percentage of 0 to 50 in steps of 10% with cupola slag and recycled construction aggregates. The fresh and hardened properties of concrete such as workability, compressive strength, and microstructural characteristics were assessed. The test results showed a decrease in workability as the percentage replacement of cupola furnace slag (CFS) and recycled construction aggregates (RCA) increases. Concrete produced at 28 days from the partial replacement of cement and sand with cupola slag has an optimum compressive strength of 20.37 N/mm2 at 10% and 22.81 N/mm2 at 20%, resulting in improved strength of 29.4% and 56.82%, respectively when compared with the control. In contrast, granite’s partial replacement with coarse cupola slag and complete replacement of sand and granite gave a lesser compressive strength when compared with the control samples at 7, 14, 28, and 56 days. The porosity of the concrete with optimum compressive strength from each mix was studied using microscopic and image analysis. The result showed that the addition of cupola slag in granulated and fine forms decreases the porosity, hence leading to higher compressive strength.

Properties of Concrete Made from Cupola Furnace Slag and Recycled Construction Aggregates

The replacement of traditional constituents of concrete with waste has garnered a lot of interest due to the increasing demand for natural resources used in concrete production. Hence, this study presents the outcome of an experimental investigation on the effect of partial replacement of Ordinary Portland Cement (OPC) at percentage levels of 0% to 25% in steps of 5%, partial and complete replacement of sand and granite in the percentage of 0 to 50 in steps of 10% with cupola slag and recycled construction aggregates. The fresh and hardened properties of concrete such as workability, compressive strength, and microstructural characteristics were assessed. The test results showed a decrease in workability as the percentage replacement of cupola furnace slag (CFS) and recycled construction aggregates (RCA) increases. Concrete produced at 28 days from the partial replacement of cement and sand with cupola slag has an optimum compressive strength of 20.37 N/mm2 at 10% and 22.81 N/mm2 at 20%, resulting in improved strength of 29.4% and 56.82%, respectively when compared with the control. In contrast, granite’s partial replacement with coarse cupola slag and complete replacement of sand and granite gave a lesser compressive strength when compared with the control samples at 7, 14, 28, and 56 days. The porosity of the concrete with optimum compressive strength from each mix was studied using microscopic and image analysis. The result showed that the addition of cupola slag in granulated and fine forms decreases the porosity, hence leading to higher compressive strength.

Evaluation of volumetric performance of asphalt mixtures containing recycled construction aggregate (RCA)

ABSTRACT High rate of construction and demolition waste materials results in a large amount of stockpiled waste materials. Pavement industry is now considering a sustainable approach for asphalt mixture design incorporating certain waste materials. This research investigates the feasibility of substitution of virgin aggregates in asphalt mixes with recycled construction aggregates (RCA) obtained from the construction and demolition sector. A preliminary experimental study including determination of flakiness index, particle shape, wet/dry strength variation, water absorption rate, particle density, crushing value, deleterious material and weak particles was conducted on blends of RCA and virgin aggregates to evaluate the engineering properties of aggregate blends. Different asphalt mixes incorporating RCA at different rates were prepared and evaluated using a gyratory compaction. The results of the regression analysis showed that the asphalt mixtures containing 20% to 22% RCA provide comparable volumetric properties as the control sample, while mixes with higher RCA substitutions achieved higher air voids, and lower voids in the mineral aggregate (VMA), voids filled with asphalt (VFA) and binder film index (BFI). The results of this study suggested a feasible use of RCA for partial aggregate replacement in hot mix asphalt (HMA).

Influence of partial replacement of RCA on properties of concrete

In the contemporary world, concrete has a vital existence, moreover is a prominent material in the construction field. Demolitions waste is also increasing due to various factors for e.g. earthquake waste, old structure waste etc. The utilization of Recycled Construction Aggregate (RCA) comes into actuality to direct the protection of natural resources, sustainable development, and environmental consciousness. This research directs towards the effect of recycled concrete aggregates in addition with fly ash on strength properties of concrete. Fine Aggregates (FA) was decided to be used as partial replacement of 20% by weight of cement, whereas RCA were used to partially replace the 20 mm natural aggregate by weight at 15%, 30%, 45% and 60%. Strength properties like Compressive strength, split tensile strength and flexural strength were analyzed after specified curing.

UTILIZING PLASTIC FOR PRETREATING RECYCLED CONSTRUCTION AGGREGATE TO ELIMINATE BINDER ABSORPTION IN ASPHALT MIXTURE

The growing quantities of waste materials, lack of natural resources and shortage of landfill spaces represent the importance of finding innovative ways of reusing and recycling waste materials. Due to the large quantities of construction and demolition waste (CDW), recycling and utilization of Recycled Construction Aggregates (RCA) obtained from CDW in construction projects, including asphalt pavement construction, can be the most promising solution to this problem. Asphalt mixtures containing RCA have the problem of high bitumen absorption. Using plastic waste in RCA-contained asphalt mixtures reduces not only bitumen absorption but also the adverse environmental impacts associated with plastic waste disposal due to the nonbiodegradability of plastic waste. In addition, the demand reduction for virgin aggregates is another advantage resulting in subsequent economic advantages. This paper characterizes the effects of different types of plastic on the bitumen absorption and properties of asphalt mixtures containing RCA through laboratory investigation. Different types of plastic including High-Density Polyethylene (HDPE) and LowDensity Polyethylene (LDPE) were investigated in this research. The test results indicate that the plastic waste can be a viable material for improving the problem of high bitumen absorption of asphalt mixtures containing RCA.

STUDY OF THE CHARACTERISTICS OF DIFFERENT COMPONENTS OF RECYCLED CONSTRUCTION AGGREGATE (RCA): STATISTICAL STUDY IN SYDNEY

The rapid economic growth of countries has led to the construction of new structures and infrastructures. Construction projects use up large quantities of natural resources and produce tones of construction and demolition waste (CDW). Because of its growth, these quantities have increased in the last few years and it has now become necessary to create a sustainable method of development in civil construction. Therefore, utilization of recycled materials in construction projects can be the most promising solution to this problem. The utilization of recycled materials including recycled construction aggregates (RCA) in the pavement industry and asphalt production is particularly very promising as 90% of asphalt is made of aggregates. However, the variability in behavior and performance of RCA used in construction projects indicates the variability in their composition. Therefore, in spite of the awareness of the importance of using RCA and much research being conducted, there is still a need for a deeper study of the composition of the RCA. This paper presents the results of the statistical study and experimental work to evaluate the characteristics of RCA as an alternative for virgin aggregate in the asphalt mixture. To this point, a series of characterization tests were conducted RCA samples collected at different dates.

The Use of Glass to Optimize Bitumen Absorption of Hot Mix Asphalt Containing Recycled Construction Aggregates.

Asphalt mixtures containing recycled construction aggregates (RCA) have the problem of high bitumen absorption. This paper characterizes the effects of glass on the bitumen absorption and volumetric properties of asphalt mixtures containing 25% and 50% RCA through laboratory investigation. The materials used in the test program include C320 bitumen, RCA and recycled glass. Three glass contents of 0%, 10%, and 20% in terms of the total weight of fine aggregates are used in the mixture designs for preparing 100 mm diameter specimens containing 0%, 25% and 50% RCA, under 120 gyration cycles. Different types of tests including aggregate specification tests and volumetric analysis tests were conducted on individual aggregates and asphalt mixtures in accordance with Australian standards. The test results indicate that the glass waste can be a viable material for improving the problem of high bitumen absorption of asphalt mixtures containing RCA.

Laboratory investigations on the utilization of RCA in asphalt mixtures

Considerable usage of natural aggregates for road construction, and at the same time, the increasing amount of solid wastes, have attracted the attention of many researchers in the pavement industry to investigate the feasibility of the application of some of the waste materials in pavement construction.Construction and demolition wastes, including Recycled Construction Aggregate (RCA) constitute a major part of the municipal solid wastes. Using RCA in asphalt mixtures generally results in significant economic and environmental benefits. However, in spite of such promising potentials, insufficient and inconclusive data and information on the engineering properties of RCA had limited the reliability and design specifications of RCA to date. In light of this, this paper aims to investigate the feasibility of the application of RCA in asphalt mixtures.As the suitability of aggregates for using in asphalt mixtures is determined based on the aggregate characteristics, an experimental program is set up to evaluate the physical and mechanical properties of RCA. This laboratory investigation included the measurement of RCA compressive strength, particle shape, water absorption, flakiness index, crushing value, weak particles, wet/dry strength variation, and particle density. Based on this research, it was observed that RCA has a lower value of flaky and misshapen particles in comparison with basalt, implying that asphalt mixtures containing the certain amount of RCA can have better workability, deformation resistance and compaction. However, the test results show higher water absorption and wet/dry strength variation for RCA compared to natural materials, emphasizing on the necessity of an appropriate mix design.

Evaluation of Mechanical Properties of Recycled Material for Utilization in Asphalt Mixtures

With an expanding world, the demand for extensive road networks is increasing. As natural resources become scarce, the necessity of finding alternative resources has led to the idea of applying recycled material to pavement construction including asphalt pavements. Amongst all asphalt components, aggregate constitutes the largest part of asphalt mixtures. Therefore, the utilization of recycled material for aggregate will represent an important opportunity to save virgin material and divert material away from landfills. Because of the large amount of construction waste generation around the world, using recycled construction aggregate (RCA) in asphalt mixtures appears to be an effective utilization of RCA. However, as aggregate plays an important role in the final performance of the asphalt mixture, an understanding of their properties is essential in designing an asphalt mixture. Therefore, in this research, the properties of RCA have been evaluated through laboratory investigations. Based on the test results, it is required that combination of RCA with some other targeted waste materials be considered in asphalt mixture. This paper presents the results of an experimental study to evaluate the RCA properties as an alternative for virgin aggregate in asphalt mixture under different percentages and combination with other aggregates, such as reclaimed asphalt pavement (RAP) and basalt.

Experimental and correlational study on the utilisation of RCA as an alternative coarse aggregate in asphalt mixtures

Over the past decades, growing population has created high demand for new road pavements. Due to considerable usage of various natural aggregates for constructing roads, these materials have started to deplete gradually. At the same time, the rate at which solid waste is generated in the society is increasing with the population growth and changes in the people life style. The management of solid wastes has become an acute problem. These challenges have attracted the attention of many to investigate the feasibility of the application of some of the waste materials as alternative materials in pavement construction. Among various waste materials, construction and demolition wastes, including Recycled Construction Aggregate (RCA), constitute a major part of the municipal solid wastes in Australia. Using RCA in asphalt mixtures results in significant economic and environmental benefits. However, in spite of such promising potentials, insufficient and inconclusive information on the engineering properties of RCA had limited the reliability and design specifications of RCA to date. In light of this, this paper aims to investigate the feasibility of RCA for the replacement of part of coarse aggregates. Accordingly, an experimental program is set up to evaluate the physical and mechanical properties of RCA. In addition, the comparison of RCA properties with virgin aggregates has been included as part of this investigation.