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

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

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

Comparisons of the resilient moduli of asphalt mixes containing recycled materials through empirical and experimental methods

The stiffness of asphalt mixes is a fundamental property that plays an important role in determining the performance of asphaltpavement under traffic loading. The resilient modulus (stiffness) of asphalt mixes can be either determined using laboratory experiments orpredicted through empirical methods based on asphalt components’properties. This paper characterized the effect of recycled materialsincluding recycled construction aggregate (RCA) and glass on the resilient modulus of asphalt mixes using both an empirical methodand a series of laboratory experiments. In addition, the resilient moduli obtained from different methods for different asphalt mixes werecompared, and the accuracy and reliability of different empirical methods were discussed accordingly. The outcomes indicated that in cases inwhich the value of resilient modulus cannot be obtained experimentally, empirical equations cannot well predict the actual resilient modulus.Furthermore, the addition of RCA and glass at a certain amount was shown to improve the resilient modulus of the asphalt mix. This may beattributed to the basic properties of RCA due to its smaller flakiness index and particle shape compared with virgin aggregates. These twoparameters significantly affected the final performance of asphalt mixes

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

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

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

Life cycle assessment of hot mix asphalt containing recycled materials: Case study in Australia

Application of recycled materials has considerable advantages in reduction of virgin materials consumption and greenhouse gas emissions. In spite of these encouraging benefits, the utilization of recycled materials, based on limited factors such as emissions reduction or material consumption reduction, may not be advisable to key decision makers since the recycled materials promotion requires a thorough evaluation of this technology as well as the consideration of all critical environmental factors. This paper presents a comparative life cycle assessment (LCA) and cost analysis for asphalt mixtures containing recycled materials including glass and recycled construction aggregate (RCA). The composition of asphalt mixtures selected for this study are determined through a comprehensive laboratory investigation. In order to obtain more realistic results in this LCA, it is assumed that asphalt mixtures are produced in two different asphalt plants located in NSW, Australia which are the largest asphalt plants in Australia. Accordingly, the process parameters and the transport distances are considered as close as possible to real situation. The results of these analyses indicate that the replacement of glass and RCA in asphalt mixtures at optimum content results in a significant reduction in adverse environmental impacts as well as a substantial cost saving in asphalt mixture production