Performance Of Hot Mix Asphalt Research Articles

Determining meso-parameters of hot mix asphalt with reclaimed asphalt pavement based on workability

The flowability and compaction behaviors of hot mix asphalt (HMA) are critical for the mechanical performance and durability of HMA. When reclaimed asphalt pavement (RAP) is incorporated into HMA, the flowability and compaction would be significantly affected. Since the recycled asphalt mixture consists of virgin aggregate, virgin asphalt, aged asphalt, and RAP, the contact parameters and the related contact relations cannot be directly defined during discrete element modeling. Therefore, this study employed the slump test to measure the flowability of two types of HMAs, HMA with 0 % and 100 % RAP. The angle of repose (AoR) was used to characterize the macroscopic flowability and to determine the mesoscopic parameters used in the discrete element modeling (DEM). The contact parameters inside the asphalt mixture were determined by comparing the actual AoR with the virtual AoR at different asphalt contents. The results of the study showed that the contact relations between particles in the mixtures were directly affected by the RAP and the asphalt content, which leads to the variation of flow behaviors of the uncompacted asphalt mixtures. The macroscopic flow behaviors could be qualitatively explained as a coupling effect of friction and bonding. The friction between particles and the bonding provided by asphalt binder were determined when different binder content was added. By trial calculation, the friction coefficient of the RAP surface was 0.37, which was lower than that of the virgin aggregate. When AoRs reached the maximum values, the bond strength inside the HMA without RAP was 7.5 × 104 Pa. Due to the compatibility of the aged and virgin asphalt, the bond strength inside the HMA with 100 % RAP was only 6.2 × 104 Pa. Then, virtual compaction tests were conducted for HMAs with 0 % and 100 % RAP. Under the same compaction effort, HMA with 100 % RAP presented larger porosity, which was consistent with the actual situation, indicating the parameter calibration method is feasible to characterize the flowability of HMA with or without RAP. In conclusion, this study indirectly realizes the calibration of internal parameters in recycled asphalt mixtures based on the flowability and provide a microscopic mechanism to explain the macroscopic performance variations of recycled asphalt mixtures.

Aggregate Gradation Variation on the Properties of Asphalt Mixtures

National highway projects present a crucial role in economic growth, as they have a great influence on the national income. Therefore, the decision makers plan to construct these projects at a rapid rate. To achieve the just aforesaid, the utilization of asphalt of adequate quality and gradation is essential. The key problem which lies in recent decades is that many types of asphalt mixtures are rejected and reconstructed in the site due to the gradation variation of aggregates in the asphalt mixture which waste raw materials, cost and time. Thus, this research seeks to assess the possibility of accepting asphalt mixes with aggregates gradation variation (within the range from +4% above the upper specification limit to −2% below the lower specification limit). A wearing surface mix with gradation 3B was prepared according to the Egyptian code. The gradation variation was presented as the aggregate gradation is out of the specification limits during Hot Mix Asphalt (HMA) production. The aggregate gradations lie above and below the upper and lower specification limits, respectively, by ±2%, ±4% and ±6%. The design gradation of the control mix was included as a reference case. The different mix properties were measured using the Marshall Mix design method. Then, the performance of HMA mixes was evaluated under the effects of high temperature and water cycles through applying wheel loading tracking and Indirect Tensile Strength (ITS) tests. The results show that the 3B mixes with a gradation within a range of +4% to −2% of the upper and lower specification limits recorded the lowest rutting depth and the highest water damage resistance in hot regions compared to ordinary asphalt mixes. In summary, the new aggregate gradation limits will provide a reference for the design of asphalt mixture in hot climate regions.

Evaluation of fracture performance of Polyvinyl Alcohol fiber reinforced hot mix asphalt

• Fracture performance of reinforced HMA was significantly affected by Gradation type, binder grade, and PVA fiber dosage. • Coarse graded reinforced HMA exhibited 25% higher strength than fine graded HMA at 0.3% fiber content. • FE and FI doubled for lower grade asphalt reinforced HMA than control. • Coarse graded HMA showed higher fracture growth rate. • SEM and DIC analyses revealed effective crack bridging and enhanced strain distribution due to fiber reinforcement. Several studies have been conducted over the past two decades to evaluate the fracture and fatigue performance of hot mix asphalt (HMA) reinforced with different fiber types, dosages, and aspect ratio. However, a few studies focused on the impact of aggregate gradation and binder grades on the fracture performance of fiber reinforced mixtures. This study adopted a systematic approach to evaluate the impact of three different coarse and fine aggregate gradations with different nominal maximum sizes using three different binder grades and varying Polyvinyl Alcohol (PVA) fiber content. Semicircular bending beam (SCB) test was performed to evaluate several fracture characteristics of PVA fiber reinforced HMA. Experimental results revealed that binder grades and gradation significantly affect the fracture performance of such mixtures. Total fracture energy, flexibility index, and stiffness of 0.3% PVA reinforced PG 58-22 mixtures were doubled relative to control ones. However, fiber reinforced PG76-22 mixtures exhibited up to 50% improvements. The fracture growth rate reduced by 250% at 0.3% fiber content in coarse graded mixture while cumulative energy per unit crack length increased by 190% in fine graded mixture. Digital Imaging Correlation analyses revealed more twisted and convoluted fracture path and higher strain distribution in lower grade asphalt reinforced mixtures with lower nominal maximum size gradation. Scanning electron microscopy micrographs showed proper fiber coating of asphalt and effective fiber bridging across the cracks indicating enhanced resistance to post-peak deformation under load.

A novel approach to determine mode II fracture toughness of hot mix asphalt

Fracture behaviors of hot mix asphalt (HMA) are critical to the durability of asphalt pavement, especially at low temperatures. This study proposed a method to test the mode II fracture behaviors of HMA, which is inspired by the mode II test of cement concrete. In this method, compressive tests were conducted on two types of specimens, including the double-edged notch specimen and the cubic specimen. The shear action resulting in the mode II fracture was extracted from the energy difference between the load–displacement curves of the two types of specimens. The stress intensity factor (KII) and fracture energy (GF) were calculated from the theory of energy consumption. On the other hand, the effects of reclaimed asphalt pavement (RAP) and rejuvenator were examined on the mode II fracture performance of HMA. Meanwhile, asymmetric semi-circular bending (SCB) tests were also conducted to obtain the mode II KII and GF, which were used to verify the feasibility of the method proposed in this study. Results indicated that with the increase of RAP, KII and GF both decreased remarkably. When RAP content was 100%, KII and GF were reduced by 42.8% and 55.8%, respectively. When the rejuvenator and 75% RAP were added, the fracture performance was enhanced compared to HMA with 75% RAP only, indicating rejuvenator benefited the mode II fracture resistance. The result comparison between the double-edge notched specimens and the SCB specimens verified the feasibility of the method proposed in this study.

Evaluating the effects of using reclaimed asphalt pavement and recycled concrete aggregate on the behavior of hot mix asphalts

In this research, the performance of hot mix asphalts mixes (HMA) with RAP and RCA was evaluated, in terms of their Marshall stability, flow, and volumetric properties, to verify their applicability as a replacement for the natural aggregate in the flexible pavement surface layers of HMA mixtures. The experimental work was divided into two phases; the first phase investigated the crushed limestone, white hard-rock, and basalt aggregate materials with a nominal maximum aggregate size of 19 mm. The second phase studied the replacement of crushed limestone, by weight, with the RAP and RCA at different asphalt cement contents. The coarse and fine aggregate of the recycled materials were used at four percentages of 25%, 50%, 75%, and 100%, respectively. The experimental test results showed that replacing limestone with recycled aggregate materials affected the mechanical characteristics, mainly the volumetric properties of the HMA. Using RCA in the hot asphalt mixes violated the upper limit of 5% for the air voids property and increased the optimum asphalt content (OAC) up to 5.96% for mixes prepared with 50% RCA. The results also revealed that adding RAP aggregate to the limestone in the HMA improved their Marshall stability, and the highest value of 29.32 kN was recorded for the asphalt mixes prepared with 75% RAP at 3% asphalt content. The combination of RAP and RCA aggregates indicated that as the RCA proportion in the mix increased, lower load capacity was observed and higher OAC compared to the other asphalt mixes.

Influence of unserviceable tires’ rubber on the mechanical performance of hot mix asphalt

This work aimed to optimize the production of hot mix asphalt (HMA) from the use of asphalt-rubber. For that, the mechanical performance of asphalt mixtures produced with different binders was evaluated: commercial asphalt-rubber (AR08), asphalt crumb rubber 10% (AR10) and 15% (AR15), and conventional asphalt (PEN 50-70). For the composition of these mixtures, the optimum asphalt contents were defined by the Marshall design. To carry out the mechanical tests, specimens molded with Marshall and Superpave compactors were tested. From the results obtained, it was verified that AR08 and AR10 asphaltic mixtures, compacted with Superpave, carried out the best mechanical performance. However, the AR08 binder is already available on the market, which facilitates its usage in paving works

Evaluation of Moisture Damage Potential in Hot Mix Asphalt Using Polymeric Aggregate Treatment.

To enhance the moisture damage performance of hot mix asphalt (HMA), treating the aggregate surface with a suitable additive was a more convenient approach. In this research, two types of aggregate modifiers were used to study the effect of moisture damage on HMA. Three different aggregate sources were selected based on their abundance of use in HMA. To study the impact of these aggregate modifiers on moisture susceptibility of HMA, the indirect tensile strength test and indirect tensile modulus test were used as the performance tests. Moisture conditioning of specimens was carried out to simulate the effect of moisture on HMA. The prepared samples’ tensile strength ratio (TSR) and stiffness modulus (Sm) results indicated a decrease in the strength of the HMA after moisture conditioning. After treating the aggregate surface with additives, an improvement was seen in dry and wet strength and stiffness. Moreover, an increasing trend was observed for both additives. The correlation between TSR and strength loss reveals a strong correlation (R2 = 0.7219). Also, the two additives indicate increased wettability of asphalt binder over aggregate, thus improving the adhesion between aggregate and asphalt binder.

Investigation of Waste Electrical Power Plant Oil as a Rejuvenating Agent for Reclaimed Asphalt Binders and Mixtures.

One of the main difficulties with employing recycled asphalt pavement (RAP) in hot mix asphalt (HMA) is bitumen aging; hence, the percentage of RAP in the HMA is limited. This research evaluates the rheological properties of the RAP binder and the performance of HMA containing high RAP content using waste engine oil (WEO) from an Electrical Power Plant as a rejuvenator. The rheological and microstructural properties of the RAP binder and rejuvenated RAP binder were determined in the laboratory. Both the recycled and rejuvenated recycled mixes were tested for Marshall stability, indirect tensile strength, dynamic modulus (E*), and flow number tests. The RAP binder was recovered using two different processes: rotavapor distillation followed by centrifugation (RCRD) and column distillation without centrifugation (RNCCD). The optimal WEO percentages for the RCRD and RNCCD recovery procedures were 0.5% and 3%, respectively. The Marshall test results revealed that adding WEO to the recycled mix enhanced its stability and flow compared to the control mix. The rejuvenated mix containing recovered binder from the RCRD recovery process was found to be better than the rejuvenated mix containing recovered binder from the RNCCD recovery process. The rejuvenated recycled mixes outperformed the recycled mix in terms of moisture resistance, which was evidenced by tensile strength ratio values of 0.88, 0.90, and 0.91 for the control and 0.5% and 3% WEO modified mixes, respectively. Finally, the results of dynamic modulus and flow number testing revealed that the rejuvenated mixes had a modest drop in both the dynamic modulus and flow number compared to the non-rejuvenated mix.

Laboratory investigation on the moisture susceptibility and fatigue resistance of hot mix asphalt modified with high- and low-density polyethylene plastic wastes

The demand for better management of plastic wastes all over the world is increasing. Polymers such as high-density polyethylene (HDPE) and low-density polyethylene (LDPE) are examples of these wastes. Studies showed that these could be used as polymer modifiers that could improve asphalt pavement performance. Although several studies had been conducted to evaluate the performance of asphalt mixtures with HDPE and LDPE, conflicting results had been seen. Additional research is still needed to find out the true effect of plastic on the performance of asphalt mixtures. Hence, this study assessed the performance of hot mix asphalt (HMA) modified with HDPE and LDPE pellets. The Marshall mix design was used to prepare, evaluate HMA mixtures and determine the optimum percentage of HDPE and LDPE that can be added to HMA. Moreover, wheel-tracking, and immersion-compression tests were used to evaluate rutting resistance and compressive strength of HMA mixtures, respectively. Results showed that the addition of 8% HDPE and 8% LDPE by weight of bitumen are the optimum contents. The performance of the HMA mixtures with HDPE and LDPE in terms of fatigue resistance and moisture susceptibility shows improved results. This proves the potential use of the materials as polymer modifiers in HMA. Moreover, HMA with HDPE when compared to the HMA with LDPE shows better results in reducing the moisture susceptibility and improving the fatigue resistance of HMA.

Experimental study of the tensile strength of hot asphalt mixtures measured with indirect tensile and semi-circular bending tests

This paper examines the tensile strength performance of hot mix asphalt without and with reclaimed asphalt pavement (RAP), different gradations, asphalt content, and test temperatures applying the Indirect Tensile Test (IDT) and the Semi-Circular Bending Test (SCB). Laboratory test results indicated the dependence of the tensile strength on the study variables, with evident trends for the type of test and the test temperature. A reasonable correlation between IDT and SCB tensile strength was verified. There is also a good correlation between IDT and SCB when data reported in previous research is incorporated.

Using recycled plastic waste to improve the performance of hot-mix asphalt

The use of recycled plastics in asphalt mixtures has become a major interest for the pavement and plastics industries due to the potential environmental benefits. An investigation was carried out into the use of three recycled plastic waste materials to modify asphalt binders and influence the performance of the resulting hot-mix asphalt (HMA). Asphalt binders were modified with three different types of recycled plastics: high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polypropylene (PP). Marshall stability and flow were determined for 12 control mixtures using unmodified binders and 72 mixtures modified by different percentages of recycled plastic. The results revealed that, in general, recycled plastic enhanced the stability of HMA. Both recycled HDPE and PP resulted in higher mixture stability than LDPE. Optimum stability for all recycled plastic types was achieved at 8% plastic content by weight of asphalt. Mixes with 8% HDPE increased stability over the unmodified mixture by almost 17% and reduced flow by 7%. This type of plastic waste also had the highest Marshall quotient value, which suggests a better performance than the other two.

Laboratory Investigation of Microwave Healing Characteristic of Hot Mix Asphalt Incorporating Steel Slag and Fly Ash

Abstract: This research aims to analyze the usage of fly ash (FA) as filler and Steel slag as coarse aggregate in hot mix asphalt concrete to monitor its healing characteristic under microwave heat. Both fly ash and steel slag are the industrial by-products. Using Marshall, Hot mix asphalt (HMA) mixtures were prepared for control and three different modified specimens having 10%, 20% and 30% steel slag as coarse aggregate, and 75% optimum fly ash content (OFC) as filler. Then thermal distribution and optimum healing time of test specimens were recorded using infrared thermometer. A three-point bending (TPB) tests were applied to the samples before and after the microwave healing procedures. Test results demonstrated that adding steel slag and fly ash in asphalt concrete mixtures increases the heating rates and improve the healing performance of hot mix asphalt using microwave heat. The replacement of natural coarse aggregate by 30% steel aggregate is extremely promising since it has not only improved healing results but also enhance the load-displacement relationship of the HMA mixtures with more ductile behavior. Overall, the use of steel slag and fly ash in hot mix asphalt is a significant option that helps to the sustainable pavement construction as it improves healing and cracking resistance. Keywords: Fly ash, Steel slag, Hot mix asphalt, Microwave heating, Three-point Bending

Predicting fatigue service life reductions of asphalt pavements due to deficiency in design-level values of effective binder content

The focus of this study is the evaluation of the effects of deficiencies in design-level values of effective binder content (Δ Vbe) on the top-down (TD) and bottom-up (BU) fatigue cracking performance of hot-mix asphalt (HMA) mixtures using AASHTOWare Pavement ME Design structural simulation program. Using an analytical–mathematical-based methodology, this study also aims to predict the reduction in fatigue service life (i.e., TD, and BU fatigue cracking) of asphalt pavements that are most sensitive to the variation (Δ Vbe). Two types of mixes with varying levels of Vbe are used to simulate the fatigue cracking performance of a full-depth (FD) pavement structure. For each of the three studied cases, one asphalt course has a variable value of Vbe, while the two other courses have a fixed value of Vbe. Results indicate that the Δ Vbe of 3% reduced 50%–70% of fatigue cracking service life. Additionally, Pavement ME shows a limitation to account for the effect of Vbe in the intermediate course on the BU fatigue cracking.

Re-using Ladle Furnace Steel slags as filler in asphalt mixtures

In the last few years, the deployment of the natural sources has been leading to re-use and recycle several materials that have been considered as “waste” so far. The proposed study analyses the possible re-employment of the Ladle Furnace Steel (LFS) slags as filler in Hot Mix Asphalt (HMA). The main aim of the research is the evaluation of both the chemical composition of LFS and the performance level of HMAs. The analysis of chemical composition involved three different hydration methods. The HMA performance level was evaluated at different scales (mixture and mastic), performing mechanical tests. Three different conventional fillers and one type of LFS were investigated in combination with two different asphalt binders. The results showed that the presence of LFS leads to an increase in brittleness in terms of mechanical response, while not significantly modifying chemical and mineral composition.

Effects of Iron Ore Tailing on Performance of Hot-Mix Asphalt

In Brazil, large quantities of iron ore tailings (IOT) are produced as a result of iron mining, which may affect the environment negatively. This work evaluated the use of IOT in hot mix asphalt type C (HMA-C). For this purpose, IOT was incorporated as a filler (at 1% in relation to the total mass of HMA-C). The hot asphalt mix with IOT (called HMA-IOT) was designed and compared with a control HMA-C. The behavior of the mixtures under monotonic (indirect tensile strength, ITS, and the Marshall stability test), under dynamic (fatigue and resilient modulus tests), and static (static creep test) loading conditions was evaluated. Also, the resistance to induced moisture damage (tensile strength ratio, TSR) was calculated. As a general conclusion, it was shown that the use of IOT in HMA improves its mechanical response without increasing mixing and compaction temperatures and using less effective asphalt binder content. This could provide a new form of environmentally safe disposal of IOTs.

Microscopy-Based Approach for Measuring Asphalt Film Thickness and its Impact on Hot-Mix Asphalt Performance

Microscopy-Based Approach for Measuring Asphalt Film Thickness and its Impact on Hot-Mix Asphalt Performance

Biochar effects on the performance of conventional and rubberized HMA

Biogenic carbon made from biomass waste (referred to as Biochar here) has shown to enhance rheological and mechanical properties of asphalt binder. This paper presents the results of using biochar as an additive in Hot Mix Asphalt (HMA). The Semi-Circular Bend (SCB) test and the Hamburg Wheel Tracking (HWT) test were selected to analyze the resistance to fracture and rutting, respectively. Also, the resistance to colour degradation of HMA was evaluated using the Xenon Arc Test. The SCB test results suggested that biochar's presence led to an increase of strain energy and subsequently higher resistance to fracture. HWT test results showed that biochar's presence reduced total permanent deformation after 20,000 cycles and subsequently enhanced resistance to rutting. As for the resistance to colour degradation, biochar's addition helped preserve colour and decrease the surface degradation of the asphalt mixture exposed to solar radiation compared to the control mixture.

Rutting Performance of Hot Mix Asphalt Using Bagasse Ash as Filler

Transportation plays an important role in the development of a country. Due to the increase in the population, the demand for good transportation and passengers increased. For this purpose, new highways are built up every year. The demand for material for the construction is increasing and the researchers are in the race to find out materials which not only used as a replacer but also increase the strength parameters and decrease destresses in Hot Mix Asphalt pavement. In the present study Sugarcane, Bagasse Ash which is an agricultural waste was used as a filler material. At Optimum Binder Content 4.55 maximum stability of 7.03 KN was achieved while for the samples having stone dust as a filler material give maximum stability at 4.33 percent of 7.37 KN. Bagasse ash used as a filler in Wheel tracker test has given the best result at temperature 300C and the average rut depth was recorded as 2.065mm while stone dust samples showed average rut depth 2.235mm at 30 0Cand the number of passes was recorded as 14000. On the other hand, the samples which are subjected to a temperature of 600C BA samples showed greater rut of the average value of 6.81mm whereas the average value of stone dust samples showed 6.615mm rut depth. From the above results, the author concluded that bagasse is the best modifier material for the areas having low temperature such as 30 0C or below.

Influence of Asphalt Concrete Internal Structure on their Packing and Mixture Properties

Hot Mix Asphalt (HMA) pavement is most used in road construction in Iraq due to its economic benefits and ease of maintenance. Several factors are affecting the performance of HMA in the field. One of the major factors is aggregate gradation. The Universal Specification for Roads and Bridges in Iraq (SCRB) specifies limits for the different types of asphalt layers and allows tolerance for the designed aggregate gradation. In the current asphalt industries, it quite difficult for contractors to achieve the required job mix due to difficulties in sieves control. This study concentrates on the effect of aggregate gradation deviations on the required specification performance. A mid gradation of the binder asphalt mixture was selected as a reference mix and more than 20 deviated mixtures were then prepared. Typical Marshall routine trials were performed on the prepared admixtures to evaluate the mixture properties. Bailey packing theory for mixture evaluation (Coarse Aggregate Ratio CA, Coarse Portion of Fine Aggregate FAc ratio) was also used to understand the impact of these deviations on the particle arrangement and mixture performance. Results showed that minor aggregate deviations do not greatly affect the mixture performance, however, a large deviation in coarse aggregate results in a drop in Marshall properties. Results showed that the Bailey method for performance evaluation is a good tool to understand the mixture performance. This paper aims to study the influence of aggregate gradation deviations on the mixture performance.

Correlating the Asphalt-Binder BBR Test Data to the HMA (ML-OT) Fracture Properties

AbstractAn asphalt-binder is one of the key constituent elements that significantly influences and controls the fracture behavior and cracking performance of hot-mix asphalt (HMA). In particular, t...