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Direct Tension-Compression (DTC) test on cylindrical samples Fatigue resistance of rich bottom type asphalt mixtures that contains Aramid pulp will also be performed. This mix is used in a perpetual pavement structure as a layer meant to resist cracking because of its high binder content. Use of the Aramid pulp should allow to increase the quantity of binder in those mixes without causing bleeding.
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It is well known that asphalt materials are more resistant in compression than in tension.
When properly homogenized with the asphalt mixture, high tensile strength fibers are
supposed to carry part of the tensile strength, which results in a longer lasting material. The
goal of this research is to understand the impacts of adding Aramid pulp to as...
Citations
... Flexible pavement is the most extensively used pavement type in most jurisdictions around the world. Canada, for instance, has an extensive network of paved roads, with asphalt concrete paved roads accounting for an estimated 95% of this paved road network [1]. One key to extending the service life of these pavements, especially in regions with extremely cold weather, such as Canada, is adequate preventive maintenance plans. ...
Cracking is one of the major distresses affecting pavement’s serviceability and performance. This structural distress often observed in hot mix asphalt can be accelerated or more extensive in cold regions such as Canada. In recent decades, synthetic fibers have been commonly used to reinforce asphalt concrete. This technology has been shown to have the potential to enhance the structural properties of hot mix asphalt. However, information related to the assessment of the performance of fiber-modified asphalt mixtures at low temperatures is limited. In this study, different sizes and concentrations of three types of polymer fibers (aramids, polyethylene terephthalate, and polyacrylonitrile) are added to conventional hot asphalt mixtures to evaluate their performance at low and intermediate temperatures. A stereomicroscope is used to investigate the dispersion of fibers in the modified asphalt mixtures. The cracking resistance of fiber-reinforced and unmodified asphalt mixtures, meanwhile, is investigated using four-point beam and IDEAL-CT tests. Moreover, indirect tensile strength test results are used to evaluate the low-temperature properties of both modified and unmodified mixtures. It is found that, at the same quantity, shorter fibers have better dispersion compared to longer ones. It is also found that the type of fiber used may influence the volumetric properties of hot mix asphalt. In general, fiber-modified asphalt mixtures are found to exhibit better cracking resistance at all temperatures compared to unmodified ones; however, the improvement is observed to be more significant in modified mixtures featuring polyethylene terephthalate and a high concentration of aramid fibers.
... However, different fiber types, which are being introduced to the industry, have different characteristics such as tensile strength, melting point, bitumen absorption and moisture sensitivity, which can influence the performance of the asphalt mixtures. Therefore, it is needed to investigate their effect on the performance of asphalt mixtures (Badeli, Saliani, and Carter 2017;Sun et al. 2018). ...
In this study, polyolefin-aramid fibers were used as an additive to modify the performance properties of asphalt mixtures. For this purpose, three percentages of the fiber (i.e., 0.025%, 0.05%, and 0.075%) were added to asphalt mixtures and the rutting, fatigue and cracking performance of the mixtures were evaluated using the dynamic creep, wheel track, indirect tensile fatigue, and semi-circular bending (SCB) fracture tests. The results showed that the rutting and cracking resistance improved incrementally by increasing the fiber content, and the fatigue performance enhanced by adding up to 0.05% fiber and then leveled out by increasing the amount of fiber.
... Previous research demonstrated the importance of using Aramid Pulp Fiber (APF) in road construction (Badeli, Saliani, & Carter, 2017a, 2017bMcDaniel, 2015;Mirabdolazimi & Shafabakhsh, 2017;Mitchell et al., 2010;Park et al., 2015;Saliani et al., 2017). Kevlar® is the trademark of a para-aramid synthetic polymer fiber, which can be used in advanced composite materials since it has a very high tensile strength, modulus, and high cohesiveness. ...
... A recent study in the laboratory of LCMB at the Ecole de Technologie Superieure conducted the indirect tensile strength test (ITS) on APF mixes (Badeli et al., 2017a). It was found that the addition of the APF could increase the ductility and tensile strength even at minus temperatures (Saliani et al., 2017). ...
... The fiber used in this work is Aramid Pulp Fiber (APF) provided by DuPont production (Badeli et al., 2017a). It is known as Kevlar® brand pulp, with the product code of 1F361 ( Figure 5.1) (Badeli et al., 2017a(Badeli et al., , 2017b. ...
Asphalt mixtures are temperature sensitive and have viscoelastic characteristics, so the
performances of an asphalt mixture are often affected by nature phenomenon. In Canada, like in many other northern countries, freeze-thaw cycles are a common phenomenon. Also, it is believed that the number of freeze-thaw cycles is increasing with the influence of climate change. Because of that, the actual methods to predict the pavement distress may overestimate the pavement life.
Fatigue distress is a fracture mechanism generated by repeated applications of tensile strains that creates stresses which are less than the strength of the materials. It is initiated at the bottom of the asphalt base layer that is mostly built, in Quebec, with GB20 mix. GB20 is a rutting resistant mix with low binder content that makes it sensitive to fatigue damage. On the other hand, during the thaw period, the melting of snow induces bearing capacity loss. The loss of structural support from underlying layers creates a significant increase in tensile stresses at the bottom of the asphalt layers. In addition, there is another possibility of increased tensile stresses due to temperature variations and water expansion/contraction which causes an increase in early fatigue cracking. The effect of temperature and moisture at the bottom of the asphalt layer is totally neglected so far. The thermal variation and moisture contraction/expansion can
produce horizontal strains that induce fatigue damage. The effect of environmental freeze-thaw cycle test on the evolution of fatigue cracking has not investigated properly yet. In this research, an asphalt mixture commonly used in the province of Quebec mostly as a base course is studied (GB20). The expansion and contraction of tested specimens are generated by the environmental chamber and measured by strain gauges. Direct Tension-Compression (DTC) equipment is used for the analysis of fatigue, and complex modulus tests. Rapid freeze-thaw cycles have been implemented to the conditioned specimens in the lab to simulate the daily rapid freeze-thaw cycles.
The results demonstrated that the compaction level significantly affects the behavior of the GB20 mix after a large number of rapid freeze-thaw cycles. The effect of rapid freeze-thaw cycles on viscoelastic behavior of the mix was added to the Witczak formula to improve the prediction of the service life of this type of mix. Considering the results of the complex modulus analysis, it was found that the influence of freeze-thaw conditions on the stiffness behavior of the mix is higher with increasing the number of cycles. Regarding fatigue test results, the reference mixture (no freeze-thaw cycles) was more resistant to fatigue cracking than the conditioned mix (mix conditioned with 300 rapid freeze-thaw cycles). The results also indicated that the addition of Aramid Pulp Fiber (APF) could increase the performance and durability of the GB20 asphalt base mix.
... A recent study in the laboratory of LCMB at the Ecole de Tech- 102 nologie Superieure conducted the indirect tensile strength test 103 (ITS) on APF mixes [17]. It was found that the addition of the APF 104 could increase the ductility and tensile strength even at minus 105 temperatures [19]. ...
... Previous studies demonstrated some advan- 106 tages of using APF in asphalt mixtures such as better rutting resis- 107 tant and delay in cracking propagation [15]. The fiber used in this work is Aramid Pulp Fiber (APF) provided by DuPont pro- 140 duction [17]. It is known as Kevlar ? ...
... It is known as Kevlar ? brand pulp, with the product code of 1F361 141 ( Fig. 1) [17,18]. Fig. 1(a) indicates that the existence of micro-roots in Aramid Pulp 142 ...
The main deteriorations of asphalt pavements in cold regions are due to the effect of heavy traffics, water action, low-temperature fluctuations, freeze-thaw cycles and the combination of all these factors together. Fiber additives are mainly used as reinforcement materials in asphalt pavements to improve the tensile properties and increase the strength against low-temperature cracking and potholes. Aromatic polyamide fiber (aramid fiber) is used in advanced composite materials since it has a very high tensile strength, modulus, and high cohesiveness. Whether the addition of Aramid Pulp Fiber (APF) can effectively improve the fatigue life, thermal performance, and durability of asphalt mixture under repeated freeze-thaw cycles are also major problems needed to be investigated properly. In this regard, thermo-mechanical analyses (complex modulus, fatigue, and thermal stress restrained specimen test (TSRST)) have been conducted on the asphalt mix with a nominal maximum aggregate size of 20 mm, known as Grave Bitume (GB20) in Quebec, Canada. The improvement effect of APF incorporation is assessed to compare the stiffness variation before and after 300 rapid freeze-thaw cycles, fatigue behavior, and thermal strength. The results indicate the ability of APF to increase the durability of the GB 20 mix against freeze-thaw cycles. The TSRST and fatigue results also show that the APF additives can increase the performance of the GB 20 mix against low temperature cracking and heavy truckloads.
The application of polymer in an asphalt concrete (AC) mixture has reached wide popularity lately to deal with the increasing demand for higher quality roads with heavier traffic loading. Ethylene-vinyl acetate (EVA), classified as a thermoplastic, is currently one of the most popular polymers employed. This research attempts to evaluate the effect of adding EVA by means of the dry method, namely by pouring the additive directly into the mixture, which produces both hot and warm Polymer-Modified Asphalt Concrete (PMAC) mix. FTIR result indicates the polymer as a thermoplastic material. Moreover, the volumetric and mechanical properties of the mixture were examined through the density and semi-circular bending (SCB) tests. The outcomes show that the inclusion of the polymer could slightly modify the density and VMA of the AC mix. Meanwhile, the tensile strength, fracture energy, crack resistance index (CRI), and flexibility index (FI) results describe substantial enhancement brought by the polymer, with a generally increasing trend up 200% of the control mix. Conclusively, the application of polymer could enhance the physical and mechanical properties of hot and warm AC mixes with the optimum dosages of 5 and 6%. Additionally, the properties of warm PMA are somewhat comparable to the regular hot AC mix.
Thermal cracking of pavement is caused by contraction of the asphalt layer at low temperatures, when tensile stresses build up to a critical point at which a crack is formed. The cracks formed then propagate under traffic loading conditions. Freeze-thaw cycles accelerate crack propagation and deterioration of the asphalt layer, and can also lead to the formation of more severe distresses such as potholes. Fibers have attracted increasing attention in the asphalt industry for use as asphalt concrete modifiers. The addition of fibers to hot mix asphalt (HMA) results in a composite material that has a higher tensile strength, along with the ability to absorb greater energy during the fracture process. The fibers within the material also act as a barrier preventing the formation and propagation of cracks in the asphalt mix. This research evaluates the effectiveness of adding polymer fibers to HMA to increase both its resistance to cracking at intermediate and low temperatures, and its rutting resistance and moisture susceptibility at high temperatures. For this purpose, three different types of polymer fibers: aramids, polyethylene terephthalate (PET), and polyacrylonitrile (PAN), were added to conventional HMA mixes. The resulting samples were compacted, and their mechanical properties were compared with conventional HMA in the laboratory. At the end of the paper, a material cost comparison is provided as a reliable source of information when selecting materials to fulfill minimum industry specifications.
