scholarly journals How to Achieve Efficiency and Accuracy in Discrete Element Simulation of Asphalt Mixture: A DRF-Based Equivalent Model for Asphalt Sand Mortar

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yu Liu ◽  
Peifeng Su ◽  
Miaomiao Li ◽  
Hui Yao ◽  
Junfu Liu ◽  
...  
Keyword(s):  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Wall Stress ◽  
Element Model ◽  
Discrete Element ◽  
Reduction Factor ◽  
Equivalent Model ◽  
Asphalt Binders ◽  
Volumetric Features ◽  
Diameter Reduction

The clump-based discrete element model is one of the asphalt mixture simulation methods, which has the potential to not only predict mixture performance but also simulate particle movement during compaction, transporting, and other situations. However, modelling of asphalt sand mortar in this method remains to be a problem due to computing capacity. Larger-sized balls (generally 2.0–2.36 mm) were usually used to model the smaller particles and asphalt binder, but this replacement may result in the mixture’s unrealistic volumetric features. More specifically, replacing original elements with equal volume but larger size particles will increase in buck volume and then different particle contacting states. The major objective of this research is to provide a solution to the dilemma situation through an improved equivalent model of the smaller particles and asphalt binders. The key parameter of the equivalent model is the diameter reduction factor (DRF), which was proposed in this research to minimize the effects of asphalt mortar’s particle replacement modelling. To determine DRF, the DEM-based analysis was conducted to evaluate several mixture features, including element overlap ratio, ball-wall contact number, and the average wall stress. Through this study, it was observed that when the original glued ball diameters are ranging from 2.00 mm and 2.36 mm, the diameter reduction factor changes from 0.82 to 0.86 for AC mixtures and 0.80 to 0.84 for SMA mixtures. The modelling method presented in this research is suitable not only for asphalt mixtures but also for the other particulate mix with multisize particles.

Effectiveness of Loaded Wheel Tracking Test to Ascertain Moisture Susceptibility of Asphalt Mixtures

2021 ◽  
pp. 036119812110363
Author(s):  
Moses Akentuna ◽  
Louay N. Mohammad ◽  
Sanchit Sachdeva ◽  
Samuel B. Cooper ◽  
Samuel B. Cooper
Keyword(s):  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Moisture Damage ◽  
Asphalt Mixtures ◽  
Asphalt Binders ◽  
Creep Recovery ◽  
Moisture Susceptibility ◽  
Freeze Thaw ◽  
Wheel Tracking ◽  
Mixture Samples

Moisture damage of asphalt mixtures is a major distress affecting the durability of asphalt pavements. The loaded wheel tracking (LWT) test is gaining popularity in determining moisture damage because of its ability to relate laboratory performance to field performance. However, the accuracy of LWT’s “pass/fail” criteria for screening mixtures is limited. The objective of this study was to evaluate the capability of the LWT test to identify moisture susceptibility of asphalt mixtures with different moisture conditioning protocols. Seven 12.5 mm asphalt mixtures with two asphalt binder types (unmodified PG 67-22 and modified PG 70-22), and three aggregate types (limestone, crushed gravel, and a semi-crushed gravel) were utilized. Asphalt binder and mixture samples were subjected to five conditioning levels, namely, a control; single freeze–thaw-; triple freeze–thaw-; MiST 3500 cycles; and MiST 7000 cycles. Frequency sweep at multiple temperatures and frequencies, and multiple stress creep recovery tests were performed to evaluate asphalt binders. LWT test was used to evaluate the asphalt mixture samples. Freeze–thaw and MiST conditioning resulted in an increase in stiffness in the asphalt binders as compared with the control. Further, freeze–thaw and MiST conditioning resulted in an increase in rut depth compared with the control asphalt mixture. The conditioning protocols evaluated were effective in exposing moisture-sensitive mixtures, which initially showed compliance with Louisiana asphalt mixture design specifications.

Rheological Properties of High Grade Asphalt and its Mixture

2014 ◽  
Vol 599 ◽  
pp. 244-247 ◽  
Author(s):  
Qun Shan Ye ◽  
Chang Jian Ye ◽  
Zhi Lin Sun
Keyword(s):  
Rheological Properties ◽  
Dynamic Modulus ◽  
Permanent Deformation ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Asphalt Binders ◽  
Test Results ◽  
Complex Shear Modulus ◽  
Complex Shear ◽  
Dynamic Modulus Test

Viscosity test, dynamic shear test, dynamic modulus test and creep test were conducted to investigate the rheological properties of high modulus asphalt and its mixture. Test results indicated that the viscosity of hard grade asphalt could be increased when compared with the ordinary asphalt, especially at high temperatures. The complex shear modulus and dynamic modulus of hard-grade asphalt binder and its mixture were increased, which implied that the stiffness of them was enhanced. Furthermore, the elastically portions for viscoelastic property of asphalt binders were increased, which resulted in the reduction of phase angle for hard grade asphalt binders and mixtures. The rutting parameter for hard-grade asphalt mixture was increased remarkably, which revealed that the resistance to permanent deformation could be significantly improved for hard grade asphalt mixture.

Highly Modified Asphalt Binder for Asphalt Crack Relief Mix

2017 ◽  
Vol 2630 (1) ◽  
pp. 110-117 ◽  
Author(s):  
Matheus S. Gaspar ◽  
Kamilla L. Vasconcelos ◽  
Amanda H. M. da Silva ◽  
Liedi L. B. Bernucci
Keyword(s):  
Hot Mix Asphalt ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Bending Test ◽  
Asphalt Binders ◽  
Reflective Cracking ◽  
Modified Asphalt ◽  
Asphalt Overlay ◽  
Modified Asphalt Binder ◽  
Styrene Butadiene

Reflective cracking is a common issue with respect to rehabilitated asphalt pavements, especially when the rehabilitation is done by applying a hot-mix asphalt overlay on the existing damaged pavement. Several approaches can be adopted to delay reflective cracking. They include an increase of the overlay thickness and the use of a stress relief asphalt mixture (SRAM), which is a fine-graded, flexible, and thin asphalt interlayer. Because the efficiency of a SRAM is highly related to the properties of the asphalt binder used in the mixture, it is of interest to use a highly modified asphalt (HiMA) binder. This paper describes a field test comprising three sections at BR-116 (a heavily trafficked highway in Brazil). One of the rehabilitation strategies used for a cracked asphalt pavement was a 2.5-cm SRAM (produced with a HiMA binder) and 5-cm styrene–butadiene–styrene (SBS) hot-mix asphalt (HMA). The other two strategies were to apply SBS HMA overlays of different thicknesses (7.5 cm and 10.5 cm). The aim was to evaluate and compare the capability of these solutions to control reflective cracking. Rheological properties and multiple stress creep and recovery tests were performed on the asphalt binders, and the semicircular bending test was performed on the asphalt mixtures. The surface conditions were monitored, and the results for each section were compared. After a 29-month period, the section that received the interlayer had the lowest cracked area and showed better resistance than the overlays did to reflective cracking and better maintenance of the original thickness of the pavement.

The Effect of Asphalt Binder Aging on Fatigue Performance of Evotherm WMA

2012 ◽  
Vol 535-537 ◽  
pp. 1686-1692
Author(s):  
Yong Chun Qin ◽  
Sui Yuan Wang ◽  
Wei Zeng ◽  
Xiao Pei Shi ◽  
Jian Xu ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Warm Mix Asphalt ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Asphalt Binders ◽  
Different Temperatures ◽  
Binder Aging ◽  
Lower Production

One of the main benefits advertised with the use of warm mix asphalt (WMA) is the decreasing aging of the asphalt binder resulting from the lower production temperature compared to conventional hot mix asphalt (HMA). Some tests were performed to determine the asphalt binder aging properties from WMA and HMA. Asphalt binders were recovered by extraction and distillation from asphalt mixtures premixed at different temperatures (140°C, 160°C, 180°C for HMA, 100°C and 120°C for WMA) in the mixing plant. Penetration@25°C, softening point (R&B) and rotational Brookfield viscosity tests were carried out. Results show that the aging of asphalt binder increases as the mixing temperature is elevated, and remarkably accelerates at the temperatures higher than 150°C. Warm mix asphalt (for example, mixing temperature at 100°Cor 120°C) can greatly reduce the aging of asphalt. Aging of the asphalt binder is one of the factors that would affect the mixture’s fatigue life. Four-point beam fatigue test samples were mixed and compacted at 140°C for HMA and 120°C for WMA, and fatigue tests with a frequency of 10 Hz and three constant strain levels (150 micro-strain, 300 micro-strain, 450 micro-strain, respectively) were performed. Results show that WMA’s fatigue life was higher than the control HMA, which indicates that it may reduce aging of asphalt binder and improve fatigue performance of asphalt mixture at lower production temperatures.

scholarly journals Shear Deformation Behavior of a Double-Layer Asphalt Mixture Based on the Virtual Simulation of a Uniaxial Penetration Test

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3700
Author(s):  
Changjiang Kou ◽  
Xiaohui Pan ◽  
Peng Xiao ◽  
Aihong Kang ◽  
Zhengguang Wu
Keyword(s):  
Shear Deformation ◽  
Double Layer ◽  
Deformation Behavior ◽  
Lower Layer ◽  
Asphalt Mixture ◽  
Element Model ◽  
Discrete Element ◽  
Asphalt Mixtures ◽  
Penetration Test ◽  
Coarse Aggregates

This paper aims to clarify the shear deformation behavior of double-layer asphalt mixtures using the virtual uniaxial penetration test (UPT) with a discrete element method. For this purpose, asphalt mixtures with two different nominal maximum aggregate sizes were designed for the preparation of double-layer wheel tracking test specimens. Then, the cylindrical cores were prepared from the specimens and were cut for capturing the longitudinal profile images. These images were used to reconstruct a two-dimensional discrete element model (DEM) of the uniaxial penetration test specimen. The results indicate that the shear deformation behavior of the asphalt mixtures showed corresponding changes under the virtual loading. The tensile and compressive stress were distributed unevenly within the upper layer after the test, and both coarse aggregates and asphalt mortars bore a greater shear stress. Therefore, cracks were more likely to occur in the upper layer, leading to the failure of the specimens. This process enhanced the bonding between the asphalt mortars and the mineral aggregates. The aggregate particles in the upper layer moved more vertically, while those in the lower layer generally moved more laterally under the virtual loading. This behavior reveals the rutting mechanism of asphalt pavement.

Recycled Polyethylene Modified Asphalt Binders and Mixtures: Performance Characteristics and Environmental Impact

2022 ◽  
pp. 036119812110657
Author(s):  
Ibrahim A. Abdalfattah ◽  
Walaa S. Mogawer ◽  
Kevin D. Stuart
Keyword(s):  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Asphalt Binders ◽  
Dry Process ◽  
Modified Asphalt ◽  
Wet Process ◽  
Melted Snow ◽  
Recycled Polyethylene ◽  
Asphalt Paving

This study addresses the effects of recycled polyethylene (RPE) on the performances of both asphalt binders and asphalt mixtures. Whether using RPE in an asphalt mixture might leach harmful chemicals into rainwater or melted snow was also determined. Two processes, wet and dry, were used to formulate the RPE modified asphalt binders and mixtures. In the wet process, RPE was added to asphalt binder. In the dry process, it was added to heated aggregates. RPE from two sources and PG 64-22 virgin asphalt binders from two sources were used in this study. In conclusion, RPE improved the rutting resistance of the asphalt binders and asphalt mixtures. However, it had adverse effects on their resistance to intermediate-temperature and non-load associated cracking. The dry process could produce a mixture with a higher RPE dosage compared with the wet process using one virgin asphalt binder but not the other; thus, the virgin asphalt binder source was a significant factor for the dry process. Based on an embryotoxicity test, it was found that RPE can be used by the asphalt paving industry without creating any significant environmental risks.

scholarly journals The Effect of Aging on the Cracking Resistance of Recycled Asphalt

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Mojtaba Mohammadafzali ◽  
Hesham Ali ◽  
James A. Musselman ◽  
Gregory A. Sholar ◽  
Aidin Massahi
Keyword(s):  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Fatigue Cracking ◽  
Asphalt Mixtures ◽  
Asphalt Binders ◽  
Reclaimed Asphalt Pavement ◽  
Cracking Resistance ◽  
Recycled Asphalt ◽  
Reclaimed Asphalt ◽  
Important Concern

Fatigue cracking is an important concern when a high percentage of Reclaimed Asphalt Pavement (RAP) is used in an asphalt mixture. The aging of the asphalt binder reduces its ductility and makes the pavement more susceptible to cracking. Rejuvenators are often added to high-RAP mixtures to enhance their performance. The aging of a rejuvenated binder is different from virgin asphalt. Therefore, the effect of aging on a recycled asphalt mixture can be different from its effect on a new one. This study evaluated the cracking resistance of 100% recycled asphalt binders and mixtures and investigated the effect of aging on this performance parameter. The cracking resistance of the binder samples was tested by a Bending Beam Rheometer. An accelerated pavement weathering system was used to age the asphalt mixtures and their cracking resistance was evaluated by the Texas Overlay Test. The results from binder and mixture tests mutually indicated that rejuvenated asphalt has a significantly better cracking resistance than virgin asphalt. Rejuvenated mixtures generally aged more rapidly, and the rate of aging was different for different rejuvenators.

scholarly journals Properties of Direct Coal Liquefaction Residue Modified Asphalt Mixture

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Jie Ji ◽  
Hui Yao ◽  
Di Wang ◽  
Zhi Suo ◽  
Luhou Liu ◽  
...  
Keyword(s):  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Coal Liquefaction ◽  
Asphalt Binders ◽  
Modified Asphalt ◽  
Viscoelastic Parameters ◽  
Direct Coal Liquefaction ◽  
Coal Liquefaction Residue ◽  
Sbs Modified Asphalt

The objectives of this paper are to use Direct Coal Liquefaction Residue (DLCR) to modify the asphalt binders and mixtures and to evaluate the performance of modified asphalt mixtures. The dynamic modulus and phase angle of DCLR and DCLR-composite modified asphalt mixture were analyzed, and the viscoelastic properties of these modified asphalt mixtures were compared to the base asphalt binder SK-90 and Styrene-Butadiene-Styrene (SBS) modified asphalt mixtures. The master curves of the asphalt mixtures were shown, and dynamic and viscoelastic behaviors of asphalt mixtures were described using the Christensen-Anderson-Marasteanu (CAM) model. The test results show that the dynamic moduli of DCLR and DCLR-composite asphalt mixtures are higher than those of the SK-90 and SBS modified asphalt mixtures. Based on the viscoelastic parameters of CAM models of the asphalt mixtures, the high- and low-temperature performance of DLCR and DCLR-composite modified asphalt mixtures are obviously better than the SK-90 and SBS modified asphalt mixtures. In addition, the DCLR and DCLR-composite modified asphalt mixtures are more insensitive to the frequency compared to SK-90 and SBS modified asphalt mixtures.

scholarly journals Effect of PolyPhosphoric Acid on Rutting Resistance of Asphalt Concrete Mixture

2019 ◽  
Vol 5 (9) ◽  
pp. 1929-1940
Author(s):  
Hussein Burhan Raof ◽  
Mohammed Qadir Ismael
Keyword(s):  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Evaluation Process ◽  
Asphalt Binders ◽  
Rutting Resistance ◽  
Ambient Temperatures ◽  
Modified Asphalt ◽  
Modified Asphalt Binder ◽  
Tracking Device ◽  
Wheel Tracking

The action of high repeated trucks load associated with dramatically elevated ambient temperatures leads to the most harmful distress in asphalt pavements occurred in Iraq known as rutting. Essentially, it is produced from the accumulation of irrecoverable strains, which mainly occurred in the asphalt layers. That visually demonstrated as a longitudinal depression in the wheel paths as well as small upheavals to the sides. Poly Phosphoric Acid (PPA) has been used as a means of producing modified asphalt binders and the interest to use it has increased in recent years. The PPA provides modified asphalt binder, which is relatively cheaply produced compared to polymer-modified asphalt. In this paper, PPA was used by three-percentages 1, 2 and 3 % of the weight of asphalt binder. Two asphalt binder grades were used in this study, 40-50 and 60 -70.  The evaluation process based on conducting Marshall Test, Compressive strength test and the Wheel Tracking test. The optimum asphalt content was determined for eight asphalt mixture. The results of the index of retained strength of modified asphalt were slightly increased compared with conventional mixtures. The rut depth was determined by using wheel tracking device at different temperature (45 and 55 ºC) for each asphalt mixture under 10000 cycles and the results showed that modified asphalt with PPA produced mixtures with more rutting resistance than conventional asphalt mixture. Moreover, the effect of PPA on rutting resistance for asphalt grade 60-70 was higher than asphalt grade 40-50.

Relating Adhesion and Cohesion of Asphalts to the Effect of Moisture on Laboratory Performance of Asphalt Mixtures

2005 ◽  
Vol 1901 (1) ◽  
pp. 33-43 ◽  
Author(s):  
Kunnawee Kanitpong ◽  
Hussain Bahia
Keyword(s):  
Permanent Deformation ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Asphalt Binders ◽  
Fundamental Properties ◽  
Water Conditioning ◽  
Before And After ◽  
Indirect Tensile ◽  
Wheel Tracking

Antistripping additives and polymer modifications are two common modifiers used to improve the fundamental properties of asphalt binders as those properties relate to the performance of asphalt mixtures. Adhesion and cohesion are two important related properties of asphalt binders that can affect asphalt mixture performance before and after water conditioning. The purpose of this study was to quantify the effects of antistripping additives and polymers on the adhesion and cohesion of binders and to relate these effects to the performance of mixtures as measured in the laboratory before and after water conditioning. The performance tests of asphalt mixtures included indirect tensile strength, uniaxial compression permanent deformation, and Hamburg wheel tracking. Asphalt mixtures were produced with different modified binders and with two aggregate types. The binders were modified with antistripping additives and polymers and by chemical treatment and oxidization methods. Granite and limestone were selected as two types of aggregate sources. The results indicate that the performance of asphalt mixtures is highly dependent on modification techniques and water conditioning. The overall performance of polymer-modified mixtures is more desirable than those of unmodified mixtures and of mixtures modified with antistripping additives. Polymers are found to improve rutting performance, adhesion, and cohesion of an asphalt binder. In contrast, the antistripping additive can improve only the adhesion without changing other properties. The results of this study also illustrate that the adhesion and cohesion of an asphalt binder are good indicators of the performance of asphalt mixtures in the laboratory when they are conditioned with water.

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