Reinforced Asphalt Mixtures Research Articles

Providing a Prediction Model for Stress Intensity Factor of Fiber- Reinforced Asphalt Mixtures under Pure Mode III Loading Using the Edge Notched Disc Beam (ENDB)

The use of Edge Notched Disc Beam (ENDB) sample has been proposed as a suitable geometry in performing fracture tests in different loading modes. The most important features of the ENDB samples include easy making, quick and easy sampling, simple testing, and the ability to examine a wide range of pure and combined loading modes. Using a wide range of fracture tests, a statistical model is proposed to predict the stress intensity factors of asphalt mixtures in terms of the pure torsion mode (mode III) loading in this study. To this end, the experiments were carried out at different temperature conditions (-5, -15 and -25 °C), different loading conditions (0.5, 1 and 5 mm/min), and on control and modified asphalt mixtures with different percentages of polyolefin-aramid fibers. The results showed that, with increasing the fiber content and loading rate, the fracture strength increased with average 25%, while an increase in fracture toughness due to lower temperature had an effect of less than 5%. Using the Response Surface Method (RSM), the prediction model of stress intensity coefficients of asphalt mixtures was presented in the pure torsion mode. The results of the proposed models had a good correlation with the results of the conducted fracture tests.

Study and Verification of a New Method to Test the Bonding Ability between Basalt Fiber and Asphalt Mortar

The bonding ability between basalt fiber bundle and asphalt mortar has a great influence on the properties of basalt fiber reinforced asphalt mixtures, yet the studies about the bonding between them is very limited. In this paper, a new test instrument called fiber-asphalt pulling machine and a new index called the nominal bonding stress (NBS) were designed and adopted to test and reveal the bonding between basalt fiber bundle and asphalt mortar. The procedures and rationality analysis of this new experiment was specified in this paper. In order to verify the reliability of the NBS index, the NBS values derived from this new test method and the rheological property indexes values of asphalt mortar under different powder–cement ratios were adopted to analyze the correlation between them. Two kinds of basalt fibers produced by two different manufacturers were adopted to conduct the parallel experiment. The results show that the nominal bonding stress between basalt fiber and asphalt mortar derived from this new test has a great correlation with the rheological properties of asphalt mortar, which also proves the credibility of this new test method and the NBS index.

Effect of treated fibers on performance of asphalt mixture

In this study, a fiber surface treatment (coating technique) was developed using paraffin wax and warm-mix additive (WMA) to enhance fiber’s distribution throughout the asphalt mixture. Three types of fiber were examined, including WMA coated fiber, wax coated fiber, and uncoated fiber. The performance of fiber-reinforced mixtures was investigated by indirect tensile asphalt cracking test (IDEAL- CT), dynamic modulus, flow number, and overlay testing. Two mixing methods (e.g., dry and wet) were employed to determine the best mixing method. The promising results indicated the potential of incorporating warm-mix additive and fiber. Although Tukey-Kramer statistical analysis showed no significant difference between wet and dry mixing methods, the wet mixing method was recommended to mitigate the adverse mixing effects (e.g., fiber clustering, fiber sticking on the mixer). The insignificant difference between wax-coated fiber and uncoated fiber mixtures indicated the critical impact of coating materials on performance of reinforced asphalt mixture. Finally, mixtures containing 0.05% of WMA coated fiber suggest potential improvement in the performance of asphalt mixture, such as enhancing the cracking tolerance index (CTIndex), prolonging fatigue life, and exhibiting good resistance rutting.

Influence of basalt fiber on mode I and II fracture properties of asphalt mixture at medium and low temperatures

Basalt fiber could effectively improve the crack resistance of asphalt mixture. However, most cracks in asphalt pavement present complex fracture characteristics. Effect of basalt fiber on the mixed mode fracture resistance of asphalt mixture is still unknown. Thus, the asymmetric semi-circular bend test was used to study the mode I and II fracture properties of the control and basalt fiber reinforced asphalt mixtures (BFRAM) at low and medium temperatures. Influences of basalt fiber on the critical stress intensity factor and critical fracture energy of asphalt mixture were investigated. The applicability of different fracture criterions to asphalt mixture also was discussed. Results indicate that the critical stress intensity factors of BFRAM first decreases and then increases with the rise of Me (which describes different fracture modes) at medium and low temperatures. Basalt fiber soundly improves the critical fracture energy of asphalt mixture at medium and low temperature even though it reduces the critical stress intensity factor at 20 ℃. The reinforcing effect of basalt fiber is optimal for the mixed mode fracture. Generalized maximum tangential stress (GMTS) criterion is suitable for the prediction of fracture initiation angle. The linear empirical fracture criterion has good applicability to the control and basalt fiber reinforced asphalt mixtures. This work can be used to analyze the mixed modes fracture of asphalt layers.

Study on Mechanical and Viscoelastic Properties of Asphalt Mixture Modified by Diatomite and Crumb Rubber Particles

To optimize the properties of asphalt mixtures and make full use of waste rubber tires, diatomite and crumb rubber particles were applied to reinforce the asphalt mixtures in this study. The rutting tests, the three-point bending tests, the freeze-thaw splitting tests, and the uniaxial compression creep tests were performed to analyze the effects of asphalt types and aggregate gradation on the pavement properties of diatomite and crumb rubber particles reinforced asphalt mixtures (DRPAM). Subsequently, the creep and relaxation characteristics of DRPAM were analyzed by the Burgers model, the modified Burgers model, the second-order extensive Maxwell model, and the Scott–Blair model. The results show that rubber particles and diatomite can reinforce the high temperature, low temperature, and viscoelastic properties of asphalt mixtures, although the improvement effect is weaker than styrene-butadiene-styrene (SBS). Consequently, it is concluded that rubber particle and diatomite compound modified asphalt mixture with suspension dense gradation and SBS binder will have better performance.

Study on performance improvement of new geocell reinforced asphalt mixture

In this paper, a new type of geocell is used to reinforce asphalt mixture to improve its performance. For the reason, an experimental evaluation of the effect of high-temperature resistant geocell reinforcement on compressive strength, tensile strength, Shearing property, water stability and fatigue performance in asphalt mixture has been developed. So, uniaxial compressive test, splitting test, uniaxial penetration test, freeze-thaw splitting test and splitting fatigue test were carried out under different temperature conditions. The results show that after geocell reinforcing, the compressive strength and tensile strength of the asphalt mixture are enhanced, the shear performance is improved due to the high temperature flow deformation is restrained, and the strength reduction rate after freeze-thaw cycle is less than that of unreinforced asphalt mixture, the fatigue life is also increased. This indicates that the geocell obviously improves various aspects performance of the asphalt mixture.

Laboratory assessment of the performance and elastic behavior of asphalt mixtures containing steel slag aggregate and synthetic fibers

This study focused on the assessment of the performance of fiber-modified asphalt mixtures containing steel slag aggregates. The asphalt mixtures incorporating coarse steel slag aggregate were reinforced with three types of synthetic fibers polyvinyl alcohol, acrylic and polyester at the dosage of 0.3% by weight of the aggregates. The performance tests were resilient modulus, rutting resistance, moisture sensitivity and cracking resistance. The results showed that the resilient modulus of the reinforced mixtures was slightly lower than the reference mixtures at all frequencies. Additionally, the rut depth of the reinforced mixtures was lower than the reference mixtures due to the densification. Otherwise, the reinforced asphalt mixtures showed better resistance to rutting than the control mixtures after excluding the deformation caused by the densification. The indirect tensile strength and tensile strength ratio of the reinforced asphalt mixtures were higher than the mixture containing steel slag aggregate. The cracking resistance of the reinforced mixture was the best in comparison with the other mixtures at the applied load at the high frequencies. While the reinforced asphalt mixtures showed the worst resistance to cracking at the applied load with low frequency of 2.5 Hz.

Influence of the Long-Term Oven Aging on the Performance of the Reinforced Asphalt Mixtures

The long-term aging of the asphalt mixtures has become a major concern because it decreases the lifespan of the asphalt layer. In this study, the asphalt mixtures incorporating steel slag aggregates were reinforced with synthetic fibers as a novel contribution in terms of decreasing the effect of aging on the performance of the asphalt mixtures. However, different mixtures—namely, Mix0, Mix1, and Mix2—were subjected to long-term oven aging to study the effect of the aging on the performance of the asphalt mixes. Mix0 consisted of coarse and fine granite aggregates, while Mix1 was composed of coarse steel slag aggregate and fine granite aggregate. Mix2 represents the reinforced asphalt mixtures incorporating coarse steel slag aggregate and reinforced with the synthetic fibers of polyvinyl alcohol, acrylic, and polyester at the proportion of 0.3% by weight of the aggregates. The conducted performance tests were resilient modulus, rutting depth, and cracking resistance. The outputs of the performance tests for the unaged asphalt mixes displayed that the mixtures incorporating coarse steel slag aggregate exhibited better performance than the mixtures containing granite aggregate. Meanwhile, the reinforced asphalt mixtures have shown a lower resilient modulus and a higher permanent deformation than the unreinforced asphalt mixes due to the elastic behavior. Otherwise, the reinforced asphalt mixtures have shown superior resistance to cracking in comparison to the unreinforced mixtures. On the other hand, the performance of the aged asphalt mixtures demonstrated that the mixtures containing granite aggregates exhibited a lower susceptibility to aging than the mixtures incorporating steel slag aggregate. Meanwhile, the performance of the aged reinforced asphalt mixtures showed that introducing synthetic fibers has decreased the effect of the long-term oven aging.

Fatigue behaviour of macrofiber reinforced gap graded asphalt mixtures

The addition of fibres to reinforce asphalt mixtures is a prospective field for pavement engineering, where the use of glass or synthetic macrofibers could potentially help not only as reinforcement for new asphalt mixtures, but also as part of asphalt overlays applied on deteriorated pavements to diminish reflective cracking during maintenance operations. In recent studies, it has been found that the addition of macrofibres can improve the rutting and fracture resistance of asphalt mixtures. However, the response of these mixtures to fatigue has not been studied yet. In this study, a complete performance characterization of a gap graded asphalt mixture with the addition of glass and synthetic macrofibres was studied. Also, a reference asphalt mixture without macrofibres was provided for comparison. Results showed that the addition of macrofibres improves water sensibility, rutting performance and stiffness of the gap grade asphalt mixtures studied. Also, it was observed during the fatigue tests that the incorporation of both types of macrofibres greatly improved the durability of the mixtures to fatigue cracking at medium range temperatures. This improved fatigue behaviour correlates to an extended useful life for the fibre reinforced asphalt mixtures. The synthetic macrofibres showed better fatigue behaviour at lower temperatures, while glass macrofibres gave a better response at the higher temperature studied.

Effect of the Densification of the Reinforced Asphalt Mixtures on the Permanent Deformation

This study aims to provide a better understanding for evaluating the resistance of the reinforced asphalt mixtures to permanent deformation. The resistance of asphalt mixtures to permanent deformation was assessed using dynamic creep test at a temperature of 40 °C. Four mixtures namely Mix1, Mix2, Mix3, and Mix 4 were evaluated, Mix1 corresponds to the control mixture that containing coarse steel slag aggregate while Mix2, Mix3, and Mix4 represent the reinforced mixtures with polyester fiber at the proportions of 0.05, 0.15, and 0.3%, respectively. The findings of this study showed that the elastic deformation occurred at the primary stage has a negative influence regarding the permanent deformation assessment. In addition, increasing the content of the polyester fiber has a positive relationship with the elastic stage; the higher the proportion of the fiber, the higher the deformation at the elastic stage, which have a negative effect on the evaluation of the mixtures resistance to permanent deformation, if the deformation occurred at the elastic stage is not excluded. On the other hand, the mixtures containing a high content of polyester fiber exhibited better resistance to the permanent deformation at the viscoelastic stage.

Chemo-Mechanical Evaluation of Asphalt Mixtures Reinforced With Synthetic Fibers

The use of additives in asphalt mixtures has been an important option in order to prolong the durability of the road infrastructure. Several works have reported that the utilization of synthetic fibers (e.g. plastic fibers) visibly enhance the overall mechanical performance of asphalt mixtures. The objective of this experimental study is to understand the physicochemical mechanisms leading to this superior response. With this in mind, two synthetic fibers were selected in order to analyze their effect within a conventional dense asphalt mixture used in Switzerland. The mechanical performance of the experimental mixtures along with the thermal properties of the fibers were evaluated. First, it was concluded that the fiber reinforced asphalt mixtures could perform similarly to the standard mixtures prepared with polymer modified binder. In addition, it was confirmed by imaging analysis that the reinforcing effect was associated to the physical presence of the fibers within the asphalt matrix.

Investigation of the Performance of Basalt Fiber Reinforced Asphalt Mixture

This study is focused on the effect of basalt fiber on the road performance of the asphalt mixture. The road performance of asphalt mixture with different dosages of basalt fiber was comprehensively evaluated using Marshall Stability test, the wheel tracking test, the three-point bending beam test and the freezing-thaw splitting test. The road performance of lignin fiber reinforced asphalt mixture and polyester fiber reinforced asphalt mixture also were tested to compare with the road performance of basalt fiber reinforced asphalt mixture. The results showed that basalt fiber can enhance mechanical properties, the low-and high-temperature performance and water sensitivity of the asphalt mixture significantly. Considering the road performance and economic benefits, the appropriate dosage of basalt fiber is about 0.3%. Marshall Stability (MS), dynamic stability (DS), the maximum bending strain and the tensile strength ratio (TSR) of asphalt mixture with 0.3% basalt fiber were increased by 19.6%, 25.5%, 22.2% and 6.0%, respectively. Basalt fiber has certain advantages in improving the low-temperature performance of asphalt mixture by comparison with lignin fiber and polyester fiber.

Microstructure and mechanical properties of fibre reinforced asphalt mixtures

Conventional asphalt mixtures can perform satisfactorily in most flexible pavement and airfield applications. However, during recent years the trend has been towards traffic growth, severe climate conditions, and heavier loads. This allied to durability and cost effectiveness issues, has raised the demand to improve the mechanical properties of conventional asphalt materials by means of modification. Fibres may have the potential to achieve such modification and, thereby, enhance the mechanical properties of asphalt mixtures. This paper examines the relative performance of asphalt mixture modified with different fibre types and contents against the main distress types experienced by flexible pavements. Also, fibre distribution and orientation in the asphalt mixture are explored in this paper. The scanning electronic microscope images show the difference in the microstructure among fibre types. X-ray computed tomography investigation results indicate that steel fibres are present throughout the asphalt mixture specimen. The test results show that fibres have a notable impact on the stiffness modulus and fracture toughness of asphalt mixtures at 20 °C test temperature. In addition, fibres provide slightly improved fatigue life of fibre reinforced asphalt mixtures, mainly at low strain values. Furthermore, results indicate that there is no detrimental impact of fibres on either the tensile strength or the moisture damage resistance of such mixtures.

Investigation of the Performance of the Ecofriendly Fiber-Reinforced Asphalt Mixture as a Sustainable Pavement Material

This article presents a study to evaluate the performance of the ecofriendly calcium sulfate whisker fiber- (CSWF-) reinforced asphalt mixture as a sustainable pavement material. Asphalt mixtures containing 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, and 0.8 wt.% of the CSWF were designed by the Marshall method. Asphalt mixtures without fiber were also prepared as control samples. The Marshall test, wheel-tracking test, low-temperature bending test, water sensitivity test, and fatigue test were conducted to evaluate the performance of the CSWF asphalt mixture. And the mechanism of fiber reinforcement was discussed. The results showed that the CSWF could improve the high-temperature stability and low-temperature crack resistance of the asphalt mixture. Water stability of asphalt mixtures in the presence of the CSWF was also improved. When the CSWF content was 0.4 wt.% of the total mixture, the performance of the asphalt mixture is the best. Compared with the conventional asphalt mixture, the CSWF asphalt mixture not only utilized power plant waste effectively to preserve ecosystems but also improved the performance of the pavement, which is suggested to be used in sustainable pavement construction and rehabilitation.

Evaluation of temperature and loading rate effect on fracture toughness of fiber reinforced asphalt mixture using edge notched disc bend (ENDB) specimen

A number of specimen configuration and testing method have been developed till now for determining the fracture toughness of asphalt concrete. The Edge Notch Disc Bend (ENDB) specimen is among the suitable test specimens in this regard due to its some primary advantages such as simple geometry and testing procedure and also covering different combination of mode I and III fracture case. In this paper the influence of fiber, temperature and loading rate is investigated experimentally on mode I and III fracture toughness of asphalt mixtures tested with the ENDB specimen. The fracture toughness experiments were conducted on three different low temperature value, three loading rates and different fiber percentages.

Viscoelastic Properties of Asphalt Mixtures with Different Modifiers at Different Temperatures Based on Static Creep Tests

To obtain the viscoelastic parameters of asphalt mixtures and analyze the effect of temperatures and modifiers on viscoelastic properties of asphalt mixtures, the creep compliances of the neat asphalt mixture (AM), compound diatomite and basalt fibers reinforced asphalt mixture (DBFAM), and styrene-butadiene-styrene modified asphalt mixture (SBSAM) were tested and calculated by the static creep tests. And the creep compliances of the three asphalt mixtures at −20 °C, −10 °C, and 0 °C are deducted by the time–temperature equivalence principle (TTEP) and Arrhenius equation. Further, the relaxation modulus of the three asphalt mixtures from −20 °C to 50 °C at 10 °C increments are calculated by the convolution integral and Simpson method. Subsequently, the Burgers model, the generalized Kelvin model, and the generalized Maxwell model are applied to analyze the viscoelastic properties of the three asphalt mixtures at different temperatures. The results show that the generalized Kelvin model and the generalized Maxwell model are superior to the Burgers model in describing the variation of viscoelastic properties of asphalt mixtures with loading time. At low temperatures, asphalt mixtures have excellent properties in resisting permanent deformation and releasing internal stress. Besides, the addition of SBS modifier and compound diatomite and basalt fibers modifier can significantly raise the viscosity η1 and the elastic modulus E1 of the asphalt mixture, respectively.

A multi-criteria decision-making analysis for the selection of fibres aimed at reinforcing asphalt concrete mixtures

ABSTRACT In the last few years, fibers have been proposed as one of the most important additives for the development of reinforced asphalt mixtures. The optimal fiber selection is a very complex task, as an extensive range of criteria and alternatives have to be taken into account. Decision support systems have been applied in the construction sector, but not for selecting fibers for bituminous mixtures. To fill this gap, two Multi-Criteria Decision-Making Analysis methodologies for the selection of the best fiber to be used in Asphalt Concretes are presented in this paper. The Weighted Aggregate Sum Product Assessment (WASPAS) methodology and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) integrated with Fuzzy Analytic Hierarchy Process (FAHP) are used to evaluate the effect of various types of fibers on the mechanical performance of bituminous mixtures. Given the uncertainty involved, a stochastic simulation is proposed using the Monte Carlo method. A statistical analysis is carried out to verify the results obtained. Both methods of multi-criteria analysis were effective, with TOPSIS being slightly more conservative in the assignment of performance scores. Synthetic fibers proved to be a suitable option as did fibers with high tensile strength and elastic modulus.

Induction Heating and Fatigue-Damage Induction Healing of Steel Fiber–Reinforced Asphalt Mixture

AbstractAs a new noncontact method for heating asphalt pavement, electromagnetic induction heating has great prospects for application in snow melting and heating-induced crack healing. In this res...

Short- and long-term properties of glass fiber reinforced asphalt mixtures

ABSTRACT This study is aimed at investigating short- and long-term aged properties of glass fibre (GF)-reinforced asphalt mixtures using indirect tensile strength (ITS) and associated fracture energy, moisture susceptibility, creep compliance, resilient modulus, and indirect tension continuous and discontinuous (IDT) fatigue tests. Also, to portray the influence of fibre reinforcement at micro level, a micromechanical finite element model (MFEM) was built utilising representative volume element (RVE) to consider the effect of fibre dose, length, and dispersion (fully aligned or random) on the mechanical characteristics (or stress-strain curve) of the composite under unidirectional strain perturbation. Based on the study results, for the same binder, compared to shorter fibre (i.e. 6-mm length), the application of 12-mm GF to the mixtures showed unnoticeable change in the short- and long-term properties of the reinforced mixtures. On the whole, the GF can impart positive characteristics to the asphalt mixture such as increase strength, resistance to rutting, less susceptibility to moisture damage, retard fatigue cracking, enhance healing capability, and combat adverse aging changes. Unlike the effect of fibre length, the numerical model proved that the orientation and concentration of GF showed noticeable influence on the mechanical response of the composite. Overall, using the GF in asphalt mixtures can help produce durable bituminous pavements. Although the present study investigated the GF-reinforced bituminous materials from performance stand point, one can speculate that building GF-reinforced pavements is more costly initially compared to unreinforced pavements however the benefits may be received over time by extending service life and saving the maintenance cost of the bituminous pavement.

Grey relational evaluation on performance and mechanism of polyacrylonitrile fiber reinforced asphalt mixture

Aiming to improve pavement performance of polyacrylonitrile (PAN) fiber-asphalt mixture, five PAN fiber content was selected from 0% to 0.4% by 0.1% interval to evaluate the effect on the high temperature stability, crack resistance in low temperature and moisture stability of asphalt mixture. Then the enhancement mechanism of PAN fiber reinforcing asphalt mixture was revealed by SEM at the microscopic level. Based on the multi-index grey relational evaluation method, the optimum PAN fiber content is selected for the balance of both road performances and economic benefit. The results show that the PAN fiber significantly improves pavement performances of asphalt mixture, as it better infiltrates into the asphalt and forms higher interfacial strength. It also could be observed that the PAN fiber evenly distributed in the asphalt binder to form a spatial network structure, playing a significant role in bridging, reinforcement and toughening. When the amount of PAN fiber is 0.2%, the comprehensive performance of asphalt mixture is optimal on the basis of grey relational evaluation.