Types Of Asphalt Mixtures Research Articles

Analysis of Nanoindentation Test Results of Asphalt Mixture with Different Gradations

Nanoindentation has been applied in the field of asphalt mixtures, but, at the nano-scale, changes in the composition of the mixture and material properties can have a significant impact on the results. Therefore, it is necessary to investigate the feasibility of nanoindentation tests on different types of asphalt mixtures with different gradations and the influence of material properties and test methods on nanoindentation results. In this paper, the nanoindentation test results on three kinds of asphalt mixture (AC-13, SMA-13, and OGFC-13) with different aggregate gradations were investigated. The load-displacement curves and moduli obtained from the nanoindentation tests were analyzed. In addition, nanoindentation tests were carried out before and after polishing with different ratios of filler and asphalt (RFA) (0.8–1.6). On this basis, the morphology of asphalt specimens with different RFAs is observed by scanning electron microscopy (SEM) imaging. The results indicate that using the nanoindentation test to characterize the mechanical behavior of asphalt mixture, the confidence level of the dense-graded mixture is low, and non-dense-graded mixtures are used as much as possible. Moreover, results illustrate that the nanoindentation modulus tends to increase as the RFA increases. and the SEM chart shows that the higher the mineral powder content in the mastic, the more complex the bitumen and mineral powder interaction surface, confirming the influence of mineral powder content on the nanoindentation test results. Furthermore, the effect of polishing is almost insignificant.

Characterization and microwave healing properties of different asphalt mixtures suffered freeze-thaw damage

Asphalt materials display the inherent ability to heal micro-cracks and the microwave heating technique can help accelerate this process thus promoting the creation of a durable asphalt pavement. The objective of this study is to investigate the difference in healing potential between two representative types of asphalt mixtures, namely dense asphalt concrete (AC-13) and open-graded friction course concrete (OGFC-13), suffered freeze-thaw (F-T) damage. In particular, OGFC concrete is especially susceptible to water damage due to its high percentage of air voids. The effect of gradation and F-T damage on the healing performance of asphalt mixtures is appraised by means of three-point bending test, freeze-thaw splitting test and X-ray computed tomography test. Results demonstrate that the gradation exerts a clear influence on the microwave healing behavior and microwave absorber content. In addition, the mechanical strength of mixtures characterized by F-T damage can be partially restored with microwave heating treatment: the healing efficiency of OGFC asphalt specimen after three cycle F-T cycles is still satisfactory. As probed with X-ray computed tomography, the proportion of micropores increases, while the amount of mesopores and macropores decrease after the microwave treatment. However, thermal heating technics are not suitable for further healing when the structural deformation of the OGFC sample occurs due to the F-T damaging process. The research outcomes can contribute to understand the microwave healing behavior for different asphalt mixture types and characterize the healing mechanism of mixtures suffered F-T damage.

Quantification of impact compaction locking point for asphalt mixture

The volumetric properties of asphalt mixture are main elements of the interaction of asphalt and aggregate. To ensure a stable structure of compacted asphalt mixture, the concept of locking point was developed to characterize the amount of compaction efforts which are needed to achieve a stable compaction state. The traditional way of defining locking point was based on the change of volume of mixtures during compaction. In this study, the locking point was defined based upon compaction curves from impact compaction. The locking point for two types of dense-graded asphalt mixtures (AC-20C and AC-13C)and one type of open graded asphalt mixture (SMA13) was evaluated by both impact compaction and gyratory compaction. The influence of compaction temperature and asphalt content on locking points was also investigated. Results showed that it was feasible to identify the locking points for impact compaction. The locking point of impact compaction could be analogically determined according to the locking point of the gyratory compaction. The size of Marshall mold may influence impact compaction curves.

Performance evaluation of asphalt mixture using polyethylene glycol polyacrylamide graft copolymer as solid–solid phase change materials

Phase change materials (PCM) have the ability to store and release thermal energy which can be used in asphalt concrete pavements to regulate the working temperature of the pavement. To ensure the stability of PCM, polyethylene glycol-polyacrylamide graft copolymer was prepared as phase change material (PPGC-PCM) by graft copolymerization. In this study, the effects of PPGC-PCM on the performance of different asphalt mixture types were discussed. Three types of asphalt mixtures (AC-10, AC-13 and AC-16) were prepared under control (without PPGC-PCM) and five modified asphalt mixtures (with different PPGC-PCM additions). The effects of PPGC-PCM on the mechanical properties, moisture resistance, high temperature performance, and low temperature crack resistance of different asphalt mixtures were analyzed. The influence of PPGC-PCM addition on the thermal properties of different asphalt mixtures types was analyzed by non-stationary thermal conductivity test. The results show that compare with the control asphalt mixture, the Marshall stability and flexural-tensile strain of AC-10, AC-13, and AC-16 asphalt mixture with PPGC-PCM were increased by 8.86%, 5.41%, 4.94% and 16.2%, 16.8%, 14.3% respectively. The addition of PPGC-PCM could improve the moisture resistance, low temperature crack resistance, and thermal insulation properties of asphalt mixture. It has negative impact on the mechanical strength and long-term high temperature stability performance. The smaller the maximum nominal particle size (MNPS) of the asphalt mixture is, the greater impact of the PPGC-PCM addition has on the mechanical properties, while, the more significant changes in thermodynamic properties of asphalt mixture. Based on comprehensive analysis of testing groups, in order to achieve the optimum balance of properties in the asphalt mixture, for the adding proportion of PPGC-PCM, 7.5% is recommended to be used in AC-10 and AC-13 and 10.0% is recommended to be applied in AC-16.

Performance prediction of asphalt mixture based on dynamic reconstruction of heterogeneous microstructure

This paper proposed an algorithm to reconstruct the microstructure of asphalt mixture considering dynamic arrangement process of aggregate particles. In this method, asphalt mixture was considered to be composed of dispersed phase including coarse aggregate and air voids, and continuous phase including fine asphalt matrix (FAM). The dispersed phase materials were characterized by high-dimensional polyhedral particles. In order to reconstruct the microstructure by 1:1 in volume fraction, three basic parameters that determine the heterogeneous structure of asphalt mixture were abided in the design of digital specimen. Then, impulse-based rigid collision response was introduced to simulate the rearrangement of aggregate particles in the compaction process of asphalt mixture. In particular, the applicability of the proposed method to typical structural types of asphalt mixture was discussed. For the asphalt mixture with high air void content, the reconstructed specimen may deviate from the real structure. Furthermore, the dynamic modulus and thermal conductivity of the generated specimens were predicted by finite element method (FEM) and compared with the experimental values. The predicted dynamic modulus and thermal conductivity coincide with the experimental results well, which indicates that the proposed method is reliable for reconstructing the heterogeneous structure of asphalt mixture with relatively low content of air voids.

Estimation of density and moisture content in asphalt mixture based on dielectric property

The density of asphalt mixture is a key quality property for in-situ pavement. And moisture within asphalt mixture easily results in various premature distresses on pavements. The basic goal of the present research is to investigate the estimation of both the density and moisture content within asphalt mixture using an electromagnetic (EM) technology. For this purpose, a generalized mixing formula was innovatively developed to predict the density of dry asphalt mixture regarding Influence coefficient v and Shape factor u based on EM mixing rules. Three types of asphalt mixture (AC-13, AC-20, and AC-25) specimens were fabricated in the laboratory with the same binder, asphalt content, and aggregate type, varying the density levels. Permittivity test of the specimens were conducted to obtain relative permittivity data. Using a nonlinear fitting method for the relationship between the bulk specific gravity and the relative permittivity of dry specimens, the optimal values of parameters v and u were determined to be 5.1 and −4.5 in the generalized mixing formula, defined as Influence and Shape Optimization (ISO) model. Moreover, considering the effect of water phase, a modified ISO (MISO) model was performed to estimate the moisture content of wet asphalt mixture. The main findings of the laboratory and field studies demonstrated that the ISO model was suitable for the density prediction of AC asphalt mixture within a reasonable error of 2%; and the MISO model predicted the moisture content with high R2 value not less than 0.74.

The aging behavior of reclaimed asphalt mixture with vegetable oil rejuvenators

In recent years, the evaluation of aging behavior of different types of asphalt mixture has become an important research field in pavement engineering. The short-term and long-term aging properties of reclaimed asphalt concrete (RAC) under the effects of vegetable/mineral oil rejuvenators are introduced in this research. Eighteen specimens of reclaimed asphalt binders classified by rejuvenator contents and types were evaluated. The viscosity of aged/unaged reclaimed asphalt binder was measured at different temperature. The results proved that the type and content of rejuvenators have significant impacts on the viscosity values of the reclaimed asphalt binder. The reclaimed asphalt binders with vegetable oil rejuvenators have lower viscosity, which also demonstrated a less increase than that with a conventional mineral rejuvenator. Less weight loss, lower complex modulus G* and lower increase rates were also found in the reclaimed binders with vegetable oil rejuvenators than that with mineral oil rejuvenators. Less weight loss, lower complex modulus G*, and lower increase rates were also found in the reclaimed binders with vegetable oil rejuvenators than that with mineral oil rejuvenators. With various RAC were determined by the Marshall design method, the results of indirect tensile strength test (ITST) displayed that the aging procedure increased the ITS of RAC. Furthermore, the results of resilient modulus test, indicated that aging did not significantly increase the resilient modulus for RAC with vegetable oil rejuvenators.

Effect of copper slag and reclaimed asphalt pavement on the skid resistance of asphalt mixes

ABSTRACT This study describes the findings of an experimental work conducted on asphalt mixtures incorporated with copper slag (CS) and reclaimed asphalt pavement (RAP). CS and RAP are considered waste materials and these waste materials create enormous environmental issues. Their use in the highway construction sector will resolve the landfill problems associated with them. In this study, nine types of asphalt mixtures were prepared with different proportions of CS (0–15%) and RAP (0–30%). These mixes were tested for frictional characteristics under various conditions. The incorporation of CS improved Marshall stability and skid resistance of asphalt pavements. Mix 3 (0%RAP, 15%CS) showed the maximum skid resistance in dry conditions. The increase in skid resistance may be attributed to the high angularity, density, and friction angle of CS particles. However, the incorporation of RAP decreased skid resistance. The CS-RAP mixes also contribute to green technology as waste materials reduce the need for virgin aggregates in the road construction sector. The statistical analysis performed showed that the results are highly significant except in icy conditions where results obtained are insignificant.

Experimental Study on the Dielectric Model of Common Asphalt Pavement Surface Materials Based on the L-R Model

The establishment of a dielectric model of the asphalt pavement surface material is the premise and key to applying the electromagnetic wave technology to asphalt pavement nondestructive testing. Asphalt pavement can be made of different materials, including various types of asphalt mixtures. Therefore, in order to study and analyze the dielectric properties of different types of asphalt mixtures and establish a dielectric model of the asphalt pavement surface material, this paper studies four types of asphalt mixtures commonly used in the asphalt pavement surface course. Based on the comparative analysis of three classical models, the complex refractive index method (CRIM), Brown, and Looyenga; based on the L-R model, the linear regression analysis was conducted on the test data. The dielectric models which are suitable for the interpretation of four types of asphalt mixtures were established, and the dielectric model database of asphalt pavement surface materials was extended, which provides theoretical and technical support for nondestructive testing of the asphalt pavement.

A molecular sensing method integrated with support vector machines to characterize asphalt mixtures

Modern and heterogeneous asphalt mixtures are usually produced using various kinds of modifiers such as rubber, polymer, and fiber. These materials are incorporated to improve sustainability and reduce the extent and severity of distresses such as rutting and low-temperature cracking. Currently, there is a lack of a robust real-time method for the identification of these additives in mixtures. In this research, a portable molecular sensing technology is integrated with machine learning (ML) to characterize asphalt binders modified with ground tire rubber (GTR) and asphalt mixtures containing different amounts of recycled materials. A database containing several near-infrared (NIR) spectra for binder and asphalt mixture samples are used to develop the ML-based detection models. The acceptable accuracy reported in this study implies that the proposed integrated NIR and ML approach can be used as a promising tool to differentiate and classify various types of asphalt binders and mixtures. This monitoring and data collection framework can contribute to improved sustainability via accelerating and optimizing the construction material detection and selection process throughout the pavement life. Furthermore, the expensive and cumbersome process of binder extraction and recovery could be avoided using the proposed method.

2D-wavelet based micro and macro texture analysis for asphalt pavement under snow or ice condition

In ice and snow weather, the surface texture characteristics of asphalt pavement change, which will significantly affect the skid resistance performance of asphalt pavement. In this study, five asphalt mixture types of AC-5, AC-13, AC-16, SMA-13, SMA-16 were prepared under three conditions of the original state, ice and snow. In this paper, a 2D-wavelet transform approach is proposed to characterize the micro and macro texture of pavement. The Normalized Energy (NE) is proposed to describe the pavement texture quantitatively. Compared with the mean texture depth (MTD), NE has the advantages of full coverage, full automation and wide analytical scale. The results show that snow increases the micro-scale texture because of its fluffiness, while the formation of the ice sheets on the surface reduces the micro-scale texture. The filling effect of snow and ice reduces the macro-scale texture of the pavement surface. In a follow-up study, the 2D-wavelet transform approach can be applied to improve the intelligent driving braking system, which can provide pavement texture information for the safe braking strategy of driverless vehicles.

Characterization of aggregate interlocking in hot mix asphalt by mechanistic performance tests

The interlocking of aggregate is critical during compaction. Nevertheless, few mix design specifications include any specific requirements for locking points, mainly because it is difficult to determine when interlocking happens during compaction precisely. This study's objectives were to validate the locking point concept by applying performance tests and evaluating aggregate interlocking influence on the rutting resistance and the fatigue cracking. Two types of asphalt mixture composed of limestone aggregates and PG 64–22 binder and designed at different Ndesign were used in this study. Two types of performance tests, the Flow Number and the IDEAL CT, were used to determine and confirm the locking point's definitions. Results showed that the locking point (LP)2-2-3 and LP3 definitions during Superpave gyratory compaction were the most reasonable to define the locking point based on the vertical axial strain from the Flow Number and the Cracking Tolerance Index (CTindex) from the IDEAL CT test..

Investigation of the Effect of Crumb Rubber Powder and Warm Additives on Moisture Resistance of SMA Mixtures

Stone matrix asphalt (SMA) mixtures are one of the most resistant types of asphalt mixtures known to date that the bulk load is borne by the aggregate skeleton. In this research, the effect of crumb rubber powder (CRP), Vestenamer polymer, and warm additives, including Sasobit, ZycoTherm, and a porous and warm mix asphalt (PAWMA), was investigated on the moisture resistance of SMA mixtures. A segregation test was performed to determine the tendency of the polymer to separate from modified polymer bitumen under storage conditions. Also, a drain down sensitivity test was conducted to explore the bleeding phenomena and drain down of SMA mixtures. Finally, a boiling water test, as well as an indirect tensile strength (ITS) test, was applied to examine the sensitivity of mixtures to moisture. The segregation test results indicated that by the use of Vestenamer polymer, a conventional (low speed) mixer can be used instead of using a high-speed mixer, and this will be very important in the cost of rubber bitumen production. The drain down test results showed that cellulose fibers prevented the bitumen bleeding of SMA mixtures. Also, the results of the boiling water test indicated that CRP samples containing ZycoTherm had the highest moisture resistance compared to the other warm additives. Among various mixtures, 8% CRP-modified samples containing ZycoTherm resulted in the lowest amount of stripping in SMA mixtures, even more than the base sample. The ITS test results illustrated that the use of CRP, Vestenamer polymer, and warm additives had a significant effect on the ITS amounts of mixtures. Moreover, the samples containing ZycoTherm had the highest tensile strength ratio (TSR) compared to the other SMA samples.

Influence of effective texture depth on pavement friction based on 3D texture area

Pavement texture significantly affects the anti-skid performance. This study applied 3D laser technology to measure the texture of asphalt pavement surfaces with an objective to explain the variation in the friction measured using a portable pendulum tester. Pavement slab samples were prepared for six different types of asphalt mixtures (SMA-Top5, AC-10, AC-13, AC-16, SMA-13, and OGFC-13). High-precision surface texture data of the samples were then collected using a portable laser scanner (LS-40), and the friction values (BPN) were measured. The 3D image reconstruction and segmentation of the pavement texture were realized through a digital image processing technology, and the texture surface area at different depths was calculated. Finally, we performed a correlation analysis between the texture surface area at different depths and the pavement friction values. The results showed that the pavement anti-skid value and the texture surface area have a significant positive correlation in the texture depth range of 0.5–2 mm, with the lowest determination coefficient value of 0.6836. Our research confirms that the effective texture depth influencing pavement friction is 2 mm and that the texture surface area can be used as an indicator of pavement friction during its service life.

Comprehensive Study about Effect of Basalt Fiber, Gradation, Nominal Maximum Aggregate Size and Asphalt on the Anti-Cracking Ability of Asphalt Mixtures

There are many parameters that could affect the properties of asphalt mixtures, such as the fiber additive, gradation type, nominal maximum aggregate size (NMAS), and asphalt. To evaluate the influence of these factors on the crack resistance of asphalt mixture, 10 different types of asphalt mixtures were prepared. The indirect tensile asphalt cracking test (IDEAL-CT) and semi-circle bending test (SCB) were adopted to test the anti-cracking ability of the test samples. The parameters of these two test results were also used to conduct the correlation analysis to find the correlation between different parameters, and scanning electron microscope (SEM) test was also used to analyze the micro cracks of asphalt mixture. The results showed that basalt fiber could further enhance the anti-cracking ability of asphalt mixture. Stone matrix asphalt (SMA) showed better anti-cracking performance than Superpave (SUP) asphalt mixtures. The increase in the nominal maximum aggregate size could decrease the anti-cracking ability of asphalt mixtures. Styrene-Butadiene-Styrene (SBS) modified asphalt could better reinforce the anti-cracking ability than pure asphalt. The CTindex of IDEAL-CT test and Flexibility index (FI) value of SCB test results showed better correlation. This paper has certain significance in guiding the design of asphalt mixtures having good crack resistance.

Application of rubber dust in modified asphalts for SMA mixtures

Abstract: The experimental investigation described in the paper refers to the properties of asphalts and asphalt mixtures with addition of rubber wastes. The influence of rubber additive, on rheological properties, viscosity, penetration, softening point of the asphalts were analyzed. An innovative technique based on the combined use of microscopic observations was developed. Tests results were compared to the conventional asphalts. Positive effects of modification were recorded. Two types of asphalt mixtures were prepared on the same mineral aggregate. For reference a Stone Matrix Asphalt (SMA) was used with polymer modified (PM) asphalt 45/80-55. Then the Stone Matrix Asphalt was prepared on the base of asphalt-rubber (45/80-55 AR). These materials were tested on rutting and water and frost resistant. The results indicated that the SMA mixtures prepared on the base of rubber modified asphalt exhibit greater resistance to permanent deformation, at elevated temperatures and greater water and frost resistance than the conventional SMA mixtures. Tests results were compared to technical requirements for SMA layers. It was found that this type of asphalt mixture can be successfully used in road surfaces, especially exposed to freezing. Keywords: Asphalt mixture; SMA mixture; rubber asphalt; Recycling; Dynamic viscosity.

A Comparison Study between Porous and Conventional Asphalt Concrete Mixtures

Asphalt concrete is the surface layer, which lay to carry the vehicles above & to transfer the loads effectively without experiencing any significant deformations. This research offers a comparison between porous and conventional asphalt mixtures in physical and service properties. Porous asphalt is an environmentally friendly mix for water runoff management, which can perform similarly to that of other pavements. It can be designed for road construction projects that can carry moderate traffic loads, while the conventional flexible pavement is designed for different projects with higher carrying ability to traffic loads. In this research, a total of 39 asphalt mixture specimens have been used to evaluate the volumetric and service properties for both types of asphalt mixtures; namely, stability, air voids, flow, and indirect tensile strength to reveal the essential differences among them. There is a considerable variation in physical and service properties of both types of asphalt concrete; in general, conventional asphalt concrete tends to have the best physical properties in the lab. The results show that conventional asphalt mixture is more efficient and durable than the porous asphalt but at the same time, porous asphalt mixture can be implemented in heavy rainfall regions regardless of traffic volume.

Evaluating the mechanical performance of asphalt mixtures in cyclic torsional shear test

In this paper, the mechanical performance of asphalt mixtures was examined in cyclic torsional shear test, in which the relationship between the averaged shear strain, γav, and the number of cyclic loading, N, was obtained by using a short, about 25mm height, specimen. In these tests, the effects of some influencing factors such as the type of asphalt mixture, the thickness of specimen and the temperature were examined. In each test, four indices; i.e., the slope of plastic flow line, the slope of stripping line, the number of load applications at the inflection point for stripping and the averaged shear strain at the inflection point for stripping, were defined for the relationship between γav and N. As a result of this study, we clarified that various performances such as rutting resistance, fatigue failure resistance and the stripping resistance of asphalt mixture can be appropriately evaluated by using the cyclic torsional shear test.

Performance of Stone Mastic Asphalt incorporating Kenaf fiber

Stone mastic asphalt (SMA) is a type of gap-graded asphalt mixture that contain large gap between big size and small size of aggregate. These criteria tend to reduce the tensile strength of mixture. To solve this, SMA usually mixed with synthetic fiber to increase tensile strength. However, synthetic fiber is costly and rarely obtained from local supplies. Thus, the aim of this study is to utilize different percentages of natural fiber which is kenaf fiber in SMA to overcome issues related to SMA. Among the test involved were LA Abrasion, Marshall Stability, Resilient Modulus, and Dynamic Creep. From the results, it shows that the addition of 0.2% fiber contributes to lowest value of abrasion. In addition, 0.2% fiber also produces the highest density of SMA20 (Stone Mastic Asphalt Grade 20). It could be seen that 0.6% of kenaf fiber producing highest value of resilient modulus. Dynamic creep also shows a significant value for 0.2% amount of kenaf fiber. Thus, it can be concluded that the existence of fiber is capable in enhancing the performance of SMA which is evident for instance, the density. The outcome of this study also contributes to the improvement of current guideline in designing SMA mixture especially for Public Work Department of Malaysia.

The effect of gradation on the mixed characteristics of HRS-WC using campurejo material

Hot Rolled Sheet (HRS) is a type of hot asphalt mixture as a layer of the road surface that will transmit traffic loads to the layer below to the subgrade. To get good results, the mixture must be designed in accordance with the provisions in the specifications with due regard to the limitations of the limits. The purpose of this study was to determine the effect of gradation on the characteristics of the HRS-WC mixture using gaps. The asphalt content used for the top gradation test was 5.50%, 6.00%, 6.50%, 7.00% and 7.50%, the middle gradation was 5.00%, 5.50%, 6.00%, 6.50% and 7.00% while the lower gradation used asphalt content 4.50%, 5.00 %, 5.50%, 6.00% and 6.50%. The results showed that the use of Campurejo aggregate as seen in the results of the aggregate characteristic test can be used as a mixture for HRS-WC, however in the use of grading it is recommended to use a gradient closer to the middle grading. Likewise, the use of asphalt content uses a percentage of asphalt content above ideal asphalt content. The use of upper and lower aggregate grading results in cavities that are close to specification limits. It is feared that if it is applied in a field with a control that is not the same as in the laboratory, it will result in a cavity outside the specification. In addition, using a middle grading can optimize stability and minimize the use of asphalt.