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. © 2018 Chinese Society of Pavement Engineerin

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

Laboratory investigations on the utilization of recycled construction aggregates in asphalt mixtures

Road networks are increasingly expanding all over the world. The construction and maintenance of the road pavements require large amounts of aggregates. Considerable usage of various natural aggregates for constructing roads as well as the increasing rate at which solid waste is generated have attracted the attention of many researchers in the pavement industry 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. Creating opportunities for the application of RCA in civil and geotechnical engineering applications is an efficient way to increase the market value of RCA. 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, as a first step of a comprehensive research, aims to investigate the feasibility of the application of RCA obtained from construction and demolition wastes for the replacement of part of coarse aggregates in asphalt mixture. As the suitability of aggregates for using in asphalt mixtures is determined based on the aggregate characteristics, including physical and mechanical properties of the aggregates, an experimental program is set up to evaluate the physical and mechanical properties of RCA. This laboratory investigation included the measurement of compressive strength and workability of RCA, particle shape, water absorption, flakiness index, crushing value, deleterious materials and weak particles, wet/dry strength variation, and particle density. In addition, the comparison of RCA properties with virgin aggregates has been included as part of this investigation and this paper presents the results of these investigations on RCA, basalt, and the mix of RCA/basalt

Laboratory investigations on the utilization of recycled construction aggregates in asphalt mixtures

Road networks are increasingly expanding all over the world. The construction and maintenance of the road pavements require large amounts of aggregates. Considerable usage of various natural aggregates for constructing roads as well as the increasing rate at which solid waste is generated have attracted the attention of many researchers in the pavement industry 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. Creating opportunities for the application of RCA in civil and geotechnical engineering applications is an efficient way to increase the market value of RCA. 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, as a first step of a comprehensive research, aims to investigate the feasibility of the application of RCA obtained from construction and demolition wastes for the replacement of part of coarse aggregates in asphalt mixture. As the suitability of aggregates for using in asphalt mixtures is determined based on the aggregate characteristics, including physical and mechanical properties of the aggregates, an experimental program is set up to evaluate the physical and mechanical properties of RCA. This laboratory investigation included the measurement of compressive strength and workability of RCA, particle shape, water absorption, flakiness index, crushing value, deleterious materials and weak particles, wet/dry strength variation, and particle density. In addition, the comparison of RCA properties with virgin aggregates has been included as part of this investigation and this paper presents the results of these investigations on RCA, basalt, and the mix of RCA/basalt

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 effect of utilization of RCA on volumetric properties of asphalt mixtures

The need for sustainable asphalt mixture design is becoming a priority within pavement industry. This trend is necessitated by high rate of construction and demolition waste, pressing demand on landfill sites. Recycled Construction Aggregate (RCA) is one of the potential options for utilization in pavement construction. Therefore, the feasibility of partial substitution of virgin aggregate in hot-mix asphalt (HMA) with RCA is investigated in this research project. RCA differs from virgin aggregate because of the cement paste which is attached to the surface of the virgin aggregates as well as the variety in its composition. This highly porous cement paste and the variation in quality of RCA results in the lower particle density and higher porosity, and subsequently higher bitumen absorption and wet/dry strength variation. However, the test results demonstrate that some parameters such as flakiness Index and particle shape have a smaller value in RCA compared to virgin aggregates. These parameters are two dominant characteristics which have significant impact on asphalt mixture strength and stability. This paper presents some of the results of an investigation on the feasibility of utilization of RCA in asphalt mixtures. For this purpose, firstly, a preliminary experimental study is conducted to evaluate the properties of RCA as an alternative for natural aggregate in asphalt mixture under different combination and percentages with virgin aggregates. The aggregate properties studied in this preliminary level were flakiness index, particle shape, water absorption and particle density, wet/dry strength variation, crushing value, and weak particles. Based on the results obtained from the aggregate specification tests on unbound RCA, in the second step, different asphalt mixtures incorporating substitutions of coarse virgin aggregate with 25% and 50% RCA were prepared and evaluated through gyratory compaction method; the optimum bitumen contents were found to be 5.1%, 5.8 and 6.2% of C320 bitumen, respectively

Evaluation of structural and thermal properties of rubber and HDPE for utilization as binder modifier

Today, high-performance requirements for asphalt pavements demand enhanced properties for bitumen to withstand the environmental condition and traffic demand. On the other hand, the rapid growth in population and economy results in a continuously increased material consumption, and subsequently waste generation. Among various waste materials, rubber and plastic, including high-density polyethylene (HDPE), constitute some part of the non-biodegradable solid wastes worldwide. Because of the great difficulties in managing the non-biodegradable wastes and the required volume of bitumen, the idea of using plastic and rubber as bitumen modifier in new asphalt mixtures appears to be an effective and meaningful utilization of these materials. As binder plays an important role in the final performance of the asphalt mixture, an understanding of modified binder properties is essential in designing an asphalt mixture. To this point, since compatibility of asphalt mixture with polymer is the most important factor in the blend of polymers and asphalt, the properties of the waste polymers were evaluated in this ongoing research by means of advanced thermal analysis and scanning electron microscope (SEM). This chapter presents the results of this experimental study to evaluate the properties of polymers as potential modifier for virgin bitumen in asphalt mixture

Classification and characterization of recycled construction aggregate (RCA)

Construction projects use up large quantities of natural resources and produce tonnes 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, recycling and utilization of recycled materials in construction projects can be the most promising solution for this problem. Due to important role and high portion of aggregates in asphalt concrete, utilization of recycled materials including recycled construction aggregates (RCA) can provide enormous benefits from the viewpoint of environmental sustainability and effective use of resources. 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 about the characteristics of the RCA. The variability in behaviour and performance of RCA used in construction projects indicates the variability in their composition. This paper presents the results of a statistical study, image analysis and experimental study to evaluate the characteristics of RCA as an alternative for virgin aggregate in asphalt mixture. A series of characterization tests were conducted three times, using RCA collected at different dates

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

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