Use Of Asphalt Mixtures Research Articles

Application of waste rice straw as fibre or filler in asphalt mixtures: materials characterisation and performance evaluation

ABSTRACT This study investigated the application of agricultural waste rice straw as fibre or filler in asphalt mixtures. Initially, the physical, chemical, mineralogical and morphological characterisation of rice straw products were analysed. Subsequently, the performance of stone matrix asphalt (SMA) mixtures containing rice straw fibre was evaluated in terms of rutting, crack resistance and moisture susceptibility, compared to cellulose fibre. Additionally, the properties of asphalt concrete (AC) mixtures incorporating rice straw filler to replace conventional mineral filler partially were examined. The findings revealed that rice straw products exhibited similar characteristics to cellulose fibre or mineral filler, indicating their suitability for use in asphalt mixtures. The appropriate addition of rice straw fibre or filler demonstrated enhancement in the high-temperature performance, low-temperature crack resistance and moisture stability of asphalt mixtures. Through experimental tests, the optimum content of rice straw fibre in SMA-13 mixtures was determined to be 0.4%, while for the rice straw filler in AC-13 mixtures, it was 20%. The mechanisms of rice straw fibre and filler added in asphalt mixtures to strengthen their road performance were binder adsorption and reinforcement effect through scanning electron microscope (SEM) images. Furthermore, rice straw filler also contributed to void filling within asphalt mixtures.

INCREASING THE DURABILITY OF PAVEMENT ON REINFORCED CONCRETE ROAD BRIDGES

Summary. Highway bridges are an important part of the transportation infrastructure, as they ensure the uninterrupted movement of vehicles and cargo. Due to the peculiarities of asphalt pavement operation on bridges with reinforced concrete roadway slabs, as well as the negative impact of weather conditions and the use of deicing materials, such pavement is more often subject to defects. In order to minimize pavement damage on road bridges and increase their durability, it is necessary to improve certain aspects of conventional asphalt mixtures, such as rutting and cracking resistance. Today, one of the methods to ensure increased durability of asphalt pavements is to modify asphalt mixtures or bituminous binders. The use of asphalt concrete pavements with increased durability is an effective method to increase the overhaul period and, as a result, reduce the cost of maintenance of road bridges. And the use of asphalt mixtures modified with rubber crumb will provide a partial solution to the environmental problem, such as the accumulation of waste from the rubber industry. Keywords: road bitumen, bitumen binder modification, asphalt concrete, asphalt mixtures.

Environmental impact of pavements formulated with bitumen modified with PE pyrolytic wax: A comparative life cycle assessment study

This study aimed to evaluate the environmental impacts of various bitumen modifiers on asphalt production, given its significant contribution to greenhouse gas emissions, waste generation, and the depletion of non-renewable resources. Four bitumen modifiers were compared, namely, recycled polyethylene (PE) pyrolytic wax, ethylene-vinyl acetate (EVA), recycled polypropylene (PP), and a combination of PE pyrolytic wax and PP, using the life cycle assessment method with one km of road as the functional unit. Results showed that the use of asphalt mixtures formulated with bitumen modified with PE pyrolytic wax had the lowest environmental impact, with a 5.9% decrease compared to traditional pavement. This reduction was attributed to the generation of environmental credits from pyrolysis and a decrease in the amount of virgin bitumen needed for asphalt mixture formulation. Conversely, binders modified with EVA and recycled PP had the highest environmental impact due to high maintenance requirements and environmental impacts in their corresponding additives, with 12% and 5% more impact than traditional pavement, respectively. The study further noted that overall environmental performance was highly sensitive to the amount of bitumen required and the yield of wax produced during pyrolysis, indicating the importance of carefully selecting bitumen modifiers. Based on the findings, the study recommends the use of asphalt mixtures formulated with bitumen modified with PE pyrolytic wax due to their favourable environmental performance.

Laboratory and numerical investigation on the behavior of reclaimed asphalt pavement (RAP) as railway track subballast layer

The use of asphalt mixtures in different places of the structure of railway tracks has been increased, given their acceptable performance and properties. Using bituminous materials in subballast layers is of great importance due to the structurally, vibrationally, and geometrically improving properties of these infrastructures. In order to enhance the mechanical behavior of railway tracks under heavy loads and high-speed trains, the tendency to use sustainable development approaches such as reuse of discarded and recycled materials has increased. The asphalt is recycled in the maintenance activities of road pavements and, in some cases, reused in the road construction and pavement industry, raising the question of whether reclaimed asphalt pavement (RAP) mixtures can be utilized in railway tracks? Has not been so extensively studied on RAP materials to be used as an interlayer in the structure of railway tracks. Accordingly, the present study seeks to investigate the behavior of these materials as the railway tracks subballast by experimental and numerical through structural approach. Given the complex behavior of these materials due to their bitumen aging, researchers are concerned about the quantity of them that can be reused. In this study, subballast layers containing RAP with percentages varying from 25 % to 100 % without any additive material and thicknesses from 5 cm to 20 cm were numerically modeled. At first, the behavioral models of the RAP materials without any additive material in a laboratory were determined for the model inputs. Using the dynamic modulus and relaxation behavior remarkably helped to identify the behavior of these materials. Numerical models were developed for RAP materials by assuming the linear elastic (LE) behavior for granular materials and linear viscoelastic (LVE) behavior for RAP materials. A conventional ballast track model with granular subballast was also simulated for validation and comparison. Eventually, by evaluating the effect of using RAP on the track settlement, the tensile strain of the bottom of the subballast layer, and compressive stress imposed on the subgrade, the subballast layer with 100 % RAP and a thickness of 20 cm was found to have the best performance, reducing the mentioned Strain and Stress parameters by 40 %. Accordingly, such a layer can be utilized as a simple permanent solution to improve the stiffness and performance of tracks.

Numerical Simulation of Moisture Diffusion in the Microstructure of Asphalt Mixtures

Laboratory tests were carried out in accordance with ASTM C664-10(2020) to measure diffusion parameters in an asphalt mixture. These diffusion parameters are effective measures for use in asphalt mixtures. However, the tests could not provide detailed images of the water vapour distribution in the asphalt mixture. To solve this problem, this study provides a method for establishing a numerical model of moisture diffusion in an asphalt mixture, and gives a more detailed picture of the water vapour movement inside the asphalt mixture. Through numerical simulation results obtained under different external conditions, it was demonstrated that water molecules were mainly concentrated in medium III after 100 days of diffusion. After 1000 days of diffusion, the water molecules gradually penetrated the asphalt film in the aggregate particles. Additionally, the water vapour concentrations in the asphalt mixture varied significantly from spot to spot, and various concentration gradients were formed at different locations. These findings revealed that water vapour concentrations in an asphalt mixture vary significantly from spot to spot, forming various concentration gradients at different locations. These findings will be helpful in revealing the mechanism of water damage caused by moisture in asphalt mixtures.

TO INCREASE THE DURABILITY OF ASPHALT PAVEMENT ON BRIDGE STRUCTURES BY USING RUBBER CRUMB

Artificial structures, which include bridges, overpasses, viaducts, overpasses and other structures, are an integral part of the transport infrastructure that meet the needs of the population in the transportation of passengers and goods. One of the main structures of a bridge structure is the bridge deck, which is the first to receive the temporary load of vehicles through the asphalt concrete pavement of the roadway. Currently, one of the methods of improving the pavement structures on bridge structures and increasing its durability is the use of the latest technologies, which involve the use of modern materials. Considering the process of construction or repair of asphalt pavement on bridge structures in the long term, special attention should be paid to the economic indicators arising from the reduction of maintenance costs, as well as significantly longer durability of the bridge deck due to the use of asphalt mixtures based on modified bitumen with rubber crumb.

A comprehensive evaluation of mixture and binder properties to explore the use of low-density polyethylene (LDPE) as an asphalt modifier and co-modifier

ABSTRACT There has been growing interest in the use of polyethylene (PE) in the asphalt industry as one way to mitigate the adverse environmental impact of waste plastics. The main goal of this study was to evaluate the potential use of low-density polyethylene (LDPE) as a modifier for use in asphalt mixtures. In addition, this study also explored the potential synergistic impact of using elastomeric polymers typically used with asphalt binders as a co-modifier along with LDPE. This study was based on a comprehensive evaluation of the rheological and performance-related properties of asphalt binder from two very different sources as well as asphalt mixtures produced using a subset of these binders. Typical methods that are standard practice in the industry and methods that are being developed to evaluate the performance metrics of asphalt binders and mixtures were used. The two chemically diverse base binders and redundancy in the evaluation process were introduced to ensure a more robust evaluation of the expected properties. Overall, results demonstrate that although the impact of LDPE on the expected performance of the binder may vary with the source of binder, LDPE can be successfully used to enhance the properties of the asphalt binder in most respects, particularly with the synergistic use of a conventional elastomeric modifier.

Use of recycled asphalt as an aggregate for asphalt mixtures: literary review

Over the years, we have seen the increase in the use of recycled asphalt in asphalt mixtures. The following article shows the review work (through database search) performed on the literature concerning the use of that type of asphalt, as it produces a great economic and ecological advantage. Nevertheless, it could mostly be found that its use in asphalt mixtures was limited to little RAP (recovered asphalt pavement) content, as it was considered that a good quality mixture with higher quantities could not be obtained. However, there is a growing trend of higher proportions of RAP in the mixtures. The objective of this review is to show through different authors and the results of their studies: performance, life and resistance to fatigue, rutting and cracking of RAP in asphalt mixtures, in different proportions and types of mixing techniques in which it can be used. The results show an increase in their properties with rejuvenating, increased resistance to fatigue, the rutting with the mixture of rap binders and virgin binders and better rap behavior if used with other green technologies such as warm asphalt mixture; allowing the implementation of increasing amounts of RAP, up to 60%, achieving higher performance of the final resulting mixture.

Preparation of shape memory epoxy resin for asphalt mixtures and its influences on the main pavement performance

Thermally induced shape memory polymers (SMPs) are stimulated by a temperature change, and in response to that change, can be restored to their initial state by adjusting the mechanical parameters, which is known as shape memory property. Thermally induced SMPs may reduce the high-temperature rutting of asphalt mixtures. Herein, a suitable shape was produced by adding a shape memory epoxy resin (SMER) by into an asphalt mixture. Four different kinds of SMERs were prepared in this study, and a fibrous shape memory epoxy resin (F-SMER) was chosen for application in asphalt mixtures. The molecular structures, thermostability, and thermal properties of the F-SMER were measured by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The high-temperature performance, low-temperature crack resistance and water stability of the asphalt mixture were measured by a rutting test, bending test, immersion Marshall test and freeze–thaw splitting test. The results show that the thermostability of the F-SMER met the requirements for use in asphalt mixtures. The dynamic stability first increased and then decreased with increasing F-SMER proportion. The low-temperature performance of the asphalt mixture mixed with F-SMER met all specification requirements. The incorporation of F-SMER was also advantageous to the water stability of the asphalt mixtures.

Incorporation of recycled concrete aggregate (RCA) fractions in semi-dense asphalt (SDA) pavements: Volumetrics, durability and mechanical properties

Recycled Concrete Aggregates (RCA) form a significant part of construction and demolition waste and its recycling is crucial for long-term construction sustainability. This study examined the incorporation of various fractions of RCA in Semi-Dense Asphalt (SDA) mixtures. The control SDA aggregates were replaced by RCA in selected fractions of 2/4 mm (coarse) and 0.125/2 mm (sand) at 100% and 50% each, and the filler at 100% of the fraction. The replacement was performed by mass with only one fraction being replaced for any single mixture. The mixtures were evaluated by their volumetrics, indirect tensile strength (ITS), water sensitivity (EN 12697-12), fracture energy and rutting resistance (EN 12697-22), in order to assess the effects of each RCA fraction on the mixture properties. The results showed that RCA coarse aggregates absorb significant amounts of binder and require more energy for compaction, which is not the case for the RCA sand or filler. The ITS results showed increased peak load for the RCA replacement samples but also increased brittleness in terms of resistance to crack initiation and propagation. RCA sand incorporation decreased the fracture energy at a higher rate than the coarse per total amount replaced. The ITSR% was similar to the control for lower amounts of RCA replacement, but significantly lower with higher replacement. The rutting resistance improved with RCA sand and especially coarse aggregate replacement. The study shows some limitations for use of RCA in asphalt mixtures, but also the potential for using them when the replacement rate is limited and replacement by volume is recommended. The RCA filler performance was very similar to the virgin filler, which makes its use in asphalt mixtures especially promising.

Special Issue on Nano-Modified Asphalt Binders and Mixtures to Enhance Pavement Performance

This Special Issue is dedicated to the use of nanomaterials for the modification of asphalt binders to support the analysis of the relevant properties and to determine if the modification indicated a more efficient use of asphalt mixtures’ fabrication or their modification in the context of asphalt mixtures’ fabrication and the improvement (or lack thereof) of these last ones to constitute effective asphalt pavement layers [...]

Properties of Asphalt Mixtures Using Reclaimed Asphalt Containing Polymer-Modified Binder and Technicoeconomical Considerations of Their Use

The article summarises findings from laboratory testing of asphalt mixtures using reclaimed asphalt containing polymer-modified binder and subsequent technicoeconomical considerations of their use in pavement management system. Tested mixtures had 0%, 15%, and 40% content of reclaimed asphalt (RA) containing polymer-modified bitumen (PMB) obtained by milling from surfacing layers of existing PA, AC11, and SMA11 pavement layers. A complete description of these mixtures is given, and testing methods used are described. The mixtures were tested for air void content, ITSR water sensitivity test, plastic deformation wheel tracking test, stiffness of the tested mixtures, and two-point bending test to ascertain fatigue. Concise and succinct conclusions from laboratory testing are derived and used as an input in the second part of the article. It is found that the addition of RA containing PMB increased stiffness modulus of the final mixture, which increases resistance to plastic deformation and leads to higher brittleness at low temperatures. It is found that virgin PMB also increases fatigue resistance as opposed to PMB content from reclaimed materials. In the second part of the article, findings from laboratory testing are addressed in the context of their practical use in pavement management. The key element identified, having a direct impact on pavement performance models, was the stiffness modulus for mixtures with different PMB-reclaimed asphalt contents. A method is described to evaluate pavement construction properties related to wearing course materials via the pavement performance model. Practical use of this method is described and applied in a case study. In this case study, the proposed method is used to evaluate the issues regarding practical use of asphalt mixtures with different ratios of reclaimed asphalt containing PMB and economic implications of their use. It is found that pavement performance of surfacing mixtures with reclaimed asphalt containing PMB is significantly better for plastic deformation at the cost of earlier initiation and progression of surface distress due to cracking and potholing. This paper suggests that due to cracking and potholing, periodic maintenance costs increase for pavements with reclaimed asphalt material containing PMB; however, they are outweighed by lower procurement cost and longer life expectancy due to slower plastic deformation of the pavement.

Effect of Different Types of Fly Ash on Properties of Asphalt Mixtures

In order to preserve natural resources, the use of waste and alternative materials in the construction and maintenance of roads is increasingly investigated. This paper presents the results of testing wearing course asphalt mixtures (AC 11s SURF 50/70) made with various percentages of fly ash, used as a partial or complete substitute for mineral filler. The properties of fly ash were determined to assess their suitability for use in asphalt mixtures. The experimental research was performed on asphalt samples containing fly ash from three different sources, with 25%, 50%, 75%, and 100% of mineral filler substitution. The control mixture was prepared with 100% of mineral filler. The paper presents the volumetric composition, stability, and flow of asphalt mixtures tested on standard Marshall’s samples, water sensitivity, and resistance to permanent deformation. The results of this study indicate that a satisfactory volumetric composition can be achieved by adding fly ash, while the bulk density and voids of the mineral and asphalt mixture generally depend on the type of fly ash and its content. The stability and flow of mixtures with fly ash are favourable compared with the control mixture. The water sensitivity of mixtures with fly ash is generally lower compared with the control mixture and depends on the type and percentage of fly ash. The resistance to permanent deformation of the asphalt mixtures depends on the fly ash type and percentage. The results obtained in this study are an important step towards broader implementation of fly ash in asphalt mixtures.

Caracterização laboratorial de resíduos de mineração como agregado alternativo para misturas asfálticas

Os processos de extração e beneficiamento do minério de ferro, ao mesmo tempo em que fomentam a economia e o desenvolvimento mundial, geram grandes quantitativos de resíduos que necessitam de destinação e/ou disposição adequada. Por sua vez, o grande apelo ambiental gerado por esse cenário, exige soluções técnicas e econômico-sustentáveis para que as mineradoras e o meio ambiente possam coexistir. O Brasil, que possui matriz de transportes pautada no modal rodoviário, com predominância dos pavimentos flexíveis à base de misturas asfálticas na camada de revestimento, insere-se no mercado mundial com uma economia diretamente associada à extração mineral e, recentemente, sofreu seu maior desastre ambiental por rompimento de barragem de resíduos dessa natureza, com perdas ambientais, materiais e humanas. No presente trabalho abordou-se a caracterização físico-química de resíduos do processo de beneficiamento do minério de ferro para utilização em misturas asfálticas, através dos ensaios de granulometria convencional e por difração a laser, Aggregate Image Measurement System (AIMS), Microscopia Eletrônica de Varredura (MEV), equivalente de areia, densidade, Espectroscopia de Energia Dispersiva (EDS), lixiviação e solubilização. A caracterização laboratorial demonstrou que o resíduo se comporta como um agregado miúdo e de enchimento, tendendo às areias finas siltosas, atendendo aos parâmetros físico-químicos, mineralógicos e geotécnicos exigidos pelas normas técnicas vigentes, ficando sua utilização em misturas asfálticas como agregado alternativo condicionada a pequenos percentuais em substituição de agregado miúdo e fíler.

Fatigue properties of crumb rubber asphalt mixtures used in railways

The use of asphalt mixtures in railway tracks provides a positive contribution to the bearing capacity, stability, durability and more importantly damping properties of the railway structure particularly for the new generation of low-vibration-railway track systems. However, one of the main concerns in the use of asphalt mixtures in railways is their fatigue cracking caused by the repeated traffic loading. The present study focused on the fatigue damage behavior of asphalt mixtures in the railways through using the viscoelastic continuum damage theory. Three experiments of creep compliance, constant crosshead rate and cyclic fatigue tests were carried out on some asphalt mixtures with different air void contents and aging conditions. Based on the results obtained, the crumb rubber modification of railways asphalt mixtures at low stress levels increases the fatigue life of asphalt up to 7.2 times while this increase is at the most 3.6 for the highway asphalt mixture. Furthermore, reducing the air void content from 4% to 2% for the crumb rubber modified asphalt mixture increases the fatigue life by 9.4 times at high stress levels and 18.2 times at low stress levels, which is a great improvement. It was shown that the lowest fatigue life is obtained in the aged crumb rubber modified mixture (i.e., 20 percent of unmodified asphalt mixture).

Mechanistic-Empirical Simulations and Life-Cycle Cost Analysis to Determine the Cost and Performance Effectiveness of Asphalt Mixtures Containing Recycled Materials

Use of reclaimed asphalt pavements (RAP) and recycled asphalt shingles (RAS) in asphalt paving, although considered as sustainable, is a practice that agencies are reluctant to employ because of the unpredictability of asphalt mixes containing recycled materials. The asphalt binder in RAP/RAS is aged and stiffened, which reduces ductility of the pavement. Consequentially, a pavement can exhibit unsatisfactory fatigue performance and have the potential for early cracking failure. Although methods exist to counteract the brittle behavior of pavements containing RAP/RAS (namely binder-grade bumping, binder-grade dumping and high binder content), they are not accounted for in mechanistic-empirical (ME) pavement design. Additionally, the cost benefits of using RAP/RAS in pavements are not easily calculated. For these reasons, characterization of fatigue performance for asphalt pavements containing RAP/RAS in ME design software needs to be accomplished and a life-cycle cost analysis (LCCA) framework for pavements containing RAP/RAS needs to be developed so that agencies can make informed decisions about RAP/RAS use in asphalt mixtures. In this study, laboratory test results for asphalt mixtures with different combinations of RAP/RAS contents, binder contents, and binder types were used to calculate ME pavement model coefficients to perform forward calculations to determine pavement performance. Using predicted performance from ME models, LCCAs were conducted to determine the cost benefits of using binder-grade bumping/dumping and high binder content in Oregon asphalt mixtures. These strategies are expected to increase RAP/RAS use in asphalt mixtures, reduce life-cycle costs, improve the cracking performance and encourage widespread use of RAP/RAS asphalt mixtures.

Asphalt mixtures with construction and demolition debris

This paper reports on research into the technical viability of the use of construction and demolition debris in hot-mix asphalt. A semi-dense and a coarse asphalt mixture were studied, both containing 50% recycled aggregate from construction and demolition debris. Two control mixtures were also studied, similar in grading but not containing recycled aggregates. It was shown that the mixtures containing recycled aggregates were more open graded and had considerable potential for stripping, a characteristic that can be related to the high water absorption level of the mortar adhered to the recycled aggregates. It was also shown that the dynamic modulus was higher in the mixtures made with recycled aggregates, particularly in the semi-dense asphalts. Whereas a deterioration of the fatigue law was observed in the semi-dense mixtures, this property did not appear to worsen in the coarse mixtures. This meant it was possible to design structural sections for flexible pavements bearing medium or low volumes of traffic with a service life comparable with that of conventional materials. Nevertheless, further research is required as, for the time being, the lack of resistance to water action casts doubt on the use of asphalt mixtures incorporating these types of recycled aggregate.