Multiple Stress Creep Recovery Research Articles

Preparation, characterization, and properties of asphalt modified by surface-treated anhydrous calcium sulfate whiskers

In this study, anhydrous calcium sulfate whiskers (ACSW) were surface-treated with sodium carbonate and stearic acid to prepare inorganic–organic surface-co-treated ACSW modified asphalt. To investigate the mechanism, the co-treated ACSW were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), water contact angle (WCA), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). Additionally, the rough surface of the calcium stearate was examined. The effects of the co-treated ACSW on asphalt binder properties were examined using conventional tests (penetration, ductility, softening point, and storage stability) and rheological tests, such as dynamic shear rheometer (DSR) and multiple stress creep recovery (MSCR) tests. The results indicated that 2–3% of the co-treated ACSW enhanced the high-temperature stability and deformation resistance properties of asphalt but weaken the low-temperature performance to a lesser extent. Microstructural analysis showed that the co-treated ACSW were physically modified with asphalt and uniformly distributed in the modified asphalt binder. This study provides a new concept for the ACSW surface treatment for practical applications in asphalt road pavement engineering in high-temperature regions.

Investigation of the Effect of Combined Nanosilica and Iranian Natural Binder on the Rheological Behavior of Mastics and Performance of Asphalt Mixtures

The aim of this study was to evaluate the impact of nanosilica (NS) and gilsonite on the behavior of asphalt binders and stone matrix asphalt (SMA) samples. An asphalt binder with 60/70 penetration grade, 0%, 3%, 5%, and 7% gilsonite, and 0%, 2%, 4%, and 6% NS by the weight of the asphalt binder were used. The rotational viscosity (RV), linear amplitude sweep (LAS), bending beam rheometer (BBR), multiple stress creep recovery (MSCR), and dynamic shear rheometer (DSR) tests were applied to evaluate the physical and rheological behaviors of modified asphalt binders. Also, the wheel track, dynamic creep, indirect tensile strength (ITS), resilient modulus (Mr), and four-point bending (FPB) fatigue tests were utilized to examine the performance characteristics of mixtures. Moreover, a two-factor analysis of variance (ANOVA) was used to analyze the data. The rheological test results showed that gilsonite and NS enhanced the rutting and fatigue resistances of asphalt binders. Gilsonite also reduced the low-temperature resistance of asphalt binders, while NS improved that. The storage stability test showed that gilsonite enhanced the storage stability of asphalt binders. Also, adding NS led to an improvement in phase separation. MSCR test indicated an improvement in the high-temperature performance of base asphalt binder at different stress levels by the addition of gilsonite and NS. Based on the LAS test, gilsonite and NS enhanced the fatigue characteristics of asphalt binders. The sample test results also showed that gilsonite and NS improved the permanent deformation resistance, MR, ITS, fracture energy, and intermediate-temperature properties of samples.

Nonmonotonic Variation of Rutting Resistance and Fatigue Life for Polyethylene Modified Bitumen with Different Carbon Black Loading

Polyethylene (PE) and carbon black (CB) were premixed in this study for bitumen modification. The service performance of PE/CB-modified bitumen (PMB) was mainly explored by multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests to reveal the rutting resistance and fatigue life, respectively. Low-temperature properties were evaluated by glass transition temperature (Tg) measured by dynamic mechanical analysis (DMA). X-ray diffraction (XRD) results suggested that the crystalline structure of PE was almost the same regardless of different CB loading additions. It was found that the both rutting resistance and fatigue life of PMBs showed nonmonotonic variation with CB loading. The mechanism for this variation was closely related to the microstructure induced by phase separation, CB nanoparticle aggregation and PE crystallinity. As revealed by optical and atomic force microscopy, two different phase structures, network and droplet-matrix structure, can be formed in PMBs when the CB loading changes. In particular, a double percolated network structure can be formed, consisting of a PE-rich network in the bitumen-matrix and CB nanoparticle network within a PE-rich phase. With the presence of this structure, the rutting resistance and fatigue life of PMB can be significantly improved.

Characterisation of Acrylonitrile Styrene Acrylate Modified Asphalt Cement with Nano Iron Oxide and Nano Silica Particles

The current study investigated the physical properties and rheological characteristics of asphalt cement (AC) modified by nano ironoxide (Fe3O4) and nano silica (SiO2) particles. Seven different blends including base AC, Acrylete-StyreneAcrylonitrile (ASA)/ Nanosilica (Si) and ASA/ Nanoironoxide (Fe) were the subject of experimental investigations. ASA was used at 5% for all modified blends while the nanomaterials were blended in 3, 5 and 7% concentrations by the weight of AC. Temperature susceptibility, rotational viscosity (RV) and storage stability for the base and polymer nanocomposite modified asphalt cement (PNCAC) were evaluated by the physical testing procedures while the frequency sweep test and the multiple stress creep recovery (MSCR) tests were conducted using a dynamic shear rheometer. The results showed that, the viscoelastic properties of the ASA/Si and ASA/Fe modified binders were improved when subjected to a range of temperatures and loading conditions. ASA/Fe composite modified AC demonstrated superior high temperature performance characteristics while ASA/Si composite modified AC although presented less significant improvement at the high temperature conditions, it was also able to improve the intermediate temperature fatigue resistance of asphalt more than the ASA/Fe composite modified AC. The optimum concentration of additives were found to be 3 and 5% for the ASA/Fe and ASA/Si modified AC respectively. Further addition of nanomaterials beyond the abovementioned concentrations resulted in degradation of the enhancement in physical and rheological properties of PNCAC, which was associated to the occurrence of agglomeration of nanoparticles and phase separation between the polymer-nanomaterial-asphalt matrix.

Characterization of chloroprene rubber-modified asphalt binders

Despite being one of the potential candidates for a suitable elastomeric additive to modify asphalt binders, there is a lack of research on using chloroprene rubber (CR). This study evaluates the suitability of using CR to enhance asphalt binder properties, particularly rutting and fatigue performances. Two different grades of asphalt binder (60/70 and 85/100 penetration grade) were modified by 3.5% and 7% CR to meet this end. The conventional physical, high-temperature storage stability, rotational viscosity (RV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) tests were used to examine various features of the CR-modified asphalt binder. Results indicate that CR decreases penetration, ductility, and temperature susceptibility and increases softening point and viscosity of the asphalt binder. Additionally, the CR-modified binder can present acceptable pumpability and workability within the construction temperature range. However, the CR-modified binder has phase separation potential, particularly at high modification contents. Based on the results of MSCR and LAS tests, CR can effectively increase the rutting resistance, elastic recovery, and fatigue life of the asphalt binder. Nevertheless, the CR-modified asphalt binder’s rutting and fatigue behaviors depend mainly on the grade of the base asphalt binder.

Influence of Waste Toner on Asphalt Binder: Chemical and Rheological Characterization

The growing amount of waste toner (WT) has posed a significant environmental challenge. Meanwhile, researchers are interested in the feasibility of utilizing waste toner as an asphalt binder modifier because its primary chemical components (Styrene-acrylic copolymer and carbon black) are known to improve asphalt properties. The objective of this study was to evaluate the chemical and rheological properties of the waste-toner-modified asphalt binder and hence determine the suitability of integrating waste toner for asphalt modification. The waste-toner-modified asphalt (TMA) binders were produced by blending base asphalt with two types of waste toners of different gradation sizes. Microscopic tests such as x-ray fluorescence (XRF), attenuated total reflectance transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy with energy dispersive X-ray (SEM-EDS) and fluorescence microscope, as well as rheology tests such as multiple stress creep recovery (MSCR) tests, oscillation tests, and bending beam rheometer tests were performed. The FTIR results showed that there was a chemical reaction between waste toners and base asphalt binder. A fluorescence effect was observed on the binders produced with different toners used in this research. The binder modified with an optimal content of 8%WTs revealed better high and low-temperature properties. Additionally, 8%WTs used in this research could change the PG70-22 binder to PG76-22 binder. The rutting properties of asphalt material were improved for its improved elasticity. In addition, the 200-mesh TMA binders were desirable with respect to waste toner particle size. Overall, there is a benefit to using waste toner in the asphalt industry.

Characterization and assessment of aerogel-modified asphalt binders

ABSTRACT Conventional asphalt has been used along the time with relatively satisfactory performance. However better performance in terms of development, environment, and economic benefits needs to be addressed. Asphalt binder modification has been one of the most common methods to improve the performance of bitumen over time. The objective of this study is to provide insight into the modification of asphalt binders to reduce thermal cycling by introducing Aerogel. Several tests were conducted including Softening Point (SP), Rotational Viscosity (RV), Dynamic Shear Modulus (G*), Multiple Stress Creep Recovery (MSCR), Flexural Creep Stiffness (BBR), Binder Bond Strength (BBS), and Thermal Conductivity (TC) tests. The response of five aerogel products was assessed based on performance. The outcomes of this study were encouraging and promising. Thermal resistance properties and cost per kilogram of each product were used to determine the more suitable aerogel product for further utilisation. The addition of aerogel reduced the susceptibility to damaging thermal effects of bitumen, reducing the permanent deformation and thermal cracking potential. However, the implementation of aerogel in binder must be enhanced to overcome the workability and safety concerns, which restrict the feasibility of its usage.

Restoration of physical properties on an aged crumb rubber modified bitumen adding a bio-based recycling agent

Reclaimed asphalt pavement (RAP) is a popular practice in the pavement industry due to environmental and economic benefits. But, RAP must be processed and treated before being reused in new pavements for preventing premature failures. A widely adopted strategy consists of adding recycling agents, and specifically rejuvenators, to mitigate the aging of the RAP binder. From the circular economy perspective, also crumb rubber (CR) from end-of-life tyres have been used to prepare binders with enhanced properties. The actual possibility of using the RAP derived from removed and/or reprocessed pavements containing CR particles (CR-RAP) for the formulation of new suitable mixtures is still a little-explored topic. Moreover, the available rejuvenators tailored on RAP have not yet evidence of effectiveness in producing asphalt mixtures containing CR-RAP. For this purpose, unaged, aged and rejuvenated blends with and without CR were studied through a rheological characterisation to evaluate the potential restoration of their physical properties when a bio-based recycling agent is added. The results of viscosity, frequency sweep, creep-recovery and multiple stress creep recovery (MSCR) tests have highlighted on the one hand the significant contribution of CR in reducing the accelerated aging effects of the binder, on the hand the effectiveness of the rejuvenator in restoring, more clearly at low temperatures, the rheological behaviour of the binders (above all for CRMB) similar to the unaged condition.

Waste Silt as Filler in Hot Mix Asphalt: A Laboratory Characterization

Several studies aimed to improve both the performance and environmental impact of asphalt pavements using waste and recycled materials as fillers. This study focused on the effect of untreated and thermally treated silt as a filler in hot mix asphalt (HMA). The silt used in the study was a byproduct from a local aggregate production plant in Bologna, Italy. Mineral and chemical analyses revealed that the waste silt required thermal treatment at 750 °C for 2 h. The study compared the use of calcined silt, untreated silt, and a common limestone filler in the production of asphalt mastics and HMA specimens. The rheological properties of the mastics were analyzed using frequency sweep and multiple stress creep recovery tests. The physical and mechanical characteristics of the HMAs were evaluated through the air voids content, Marshall stability and indirect tensile strength tests. Additionally, the water susceptibility and thermal sensitivity of the HMAs were evaluated through the indirect tensile strength ratio and indirect tensile stiffness modulus at different testing temperatures. The results showed that the addition of calcined silt had no significant effect on the rheological properties of the mastic or the optimal binder content. However, the samples produced with thermally treated silt showed the highest stiffness and resistance to rutting compared with the other samples. On the other hand, the addition of untreated silt slightly decreased the stiffness value of the samples. In conclusion, the use of waste silt as a filler has potential as a sustainable and eco-friendly solution for HMAs.

High Temperature Performance Evaluation of High Viscosity Asphalt at Different Aging Degrees Based on Multiple Stress Creep Recovery Test

In order to investigate the effect of high temperature on the performance of three high viscous asphalt in company with various aging degrees (ADs), multiple stress creep recovery (MSCR) test was employed. CRR and irrecoverable compliance were also carried out to measure the high temperature resistance of high viscous asphalt to external loading in the presence of various aging conditions (ACs) as well as to examine the sensitivity of high viscous asphalt towards the stress. The findings of the study demonstrated that after short- and long-term aging, the high-viscosity asphalt turned harder. Also, type I high-viscosity asphalt was observed to have the greatest deformation resistance acted upon by various stress fields and ACs. Furthermore, in company with various ACs, while the average creep recovery rate (CRR) of Type I and Type II high-viscosity asphalt was found to be higher than that of the SBS modified asphalt, the average irrecoverable compliance was observed to be smaller. This indicated the significant effect of high-viscosity modifiers on the improvement of the elastic recovery performance of asphalt and its resistance to high temperature flow deformation. Contrary to the order of their CRRs, the magnitude of stress sensitivity of the three high-viscosity asphalt at various ADs was observed to be type II < type I < SBS modified asphalt, indicating a good negative correlation between stress sensitivity and average CRR. Furthermore, the obtained results revealed that, in the presence of various ACs, the high temperature viscoelastic qualities of high viscosity modified asphalt is considered by the MSCR test. Also, to comprehensively evaluate the high temperature performance of high viscosity modified asphalt at various Ads, the use of such indexes as the average CRR, average irrecoverable compliance and stress sensitivity coefficient were essential.

Rheological and physicochemical characteristics of asphalt mastics incorporating lime kiln dust and dolomite powder as sustainable fillers

The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance. However, despite numerous studies, in-depth knowledge of filler-bitumen reciprocity at a microscale level is yet to be ascertained. The goal of this research is to gain a better understanding of the filler-bitumen microscale interaction in terms of the synergy and coaction between the physicochemical and rheological performance of mastics due to filler inclusions. The rheological properties of two sustainable mastics, dolomite powder (DP) and lime kiln dust (LKD), together with a neat PEN 60/70 binder, were analysed based on a temperature sweep at elevated temperature conditions. Meanwhile, frequency sweep and multiple stress creep recovery (MSCR) tests were also conducted at pavement serviceability temperature using the dynamic shear rheometer (DSR). Physicochemical tests using a scanning electron microscope (SEM) and energy dispersive X-rays (EDX) were conducted to analyse the impact of parameters such as particle shape, grain size, texture, and chemical compositions. The DSR test results showcased how the incorporation of fillers in asphalt binder considerably improved the performance of the binder in terms of rutting and fatigue. Likewise, its strain and non-recoverable compliance parameters were substantially reduced at higher filler and binder concentrations. Physical filler attributes of low rigden voids (R.V), high fineness modulus (FM), and high specific surface area (SSA) led to greater interfacial stiffness and elasticity in LKD mastics compared to DP mastics at different loading frequencies and temperature levels. The SEM/EDX results also indicated that the elemental calcium and carbon composition of each filler component, together with its grain morphology, strongly influenced its rheological performance.

Rheological Performance of ZycoTherm/Nano-Silica Composite Modified Binders at High and Low Temperatures

This study aims to investigate the impact of control and warm mix binders modified with nano-silica on the asphalt binder functioning to resist rutting endurance and low-temperature cracking. The percentages of nano-silica employed in this research were 2%, 4%, and 6% of asphalt binder weight. The control and modified binders were evaluated by performing conventional and rheological tests. The rheological properties were examined by master curves, isochronal plots, multiple stress creep recovery (MSCR), Superpave rutting parameter, and bending beam rheometer. The outcomes implied that the performance of the asphalt binder (with or without ZycoTherm) improved when nano-silica was added concerning (G*/sin δ) parameter. The MSCR test demonstrated that the recovery (R %) of the control and warm mix binders improved whereas the non-recoverable creep compliance (Jnr) dropped, implying that nano-silica boosted the rutting potential. Moreover, it was observed at different temperatures that the values for the complex shear modulus increased when the phase angle values were reduced. Furthermore, at low temperatures, it is presumed that the performance of nano-silica modified asphalt binders will have minimal performance as opposed to the binders prepared with ZycoTherm, which prevents low-temperature cracking.

Effect of Waterborne Polyurethane on Rheological Properties of Styrene-Butadiene Rubber Emulsified Asphalt

To explore the effect of waterborne polyurethane (WPU) on the performance of styrene-butadiene rubber (SBR) emulsified asphalt and broaden the application range of polymer-modified emulsified asphalt, WPU-SBR-modified emulsified asphalt with 0%, 3%, 6%, 9%, and 12% WPU was prepared. The penetration, softening point, ductility, and storage stability tests were used to explore the effect of different contents of WPU on composite-modified emulsified asphalt. Meanwhile, the rheological properties of five modified emulsified asphalts were analyzed by temperature scanning test, multiple stress creep recovery test, and low-temperature bending creep test. The results show that the addition of WPU improved the performance of SBR emulsified asphalt, and the improvement effect varied with the addition amount. With the increase of WPU content, the penetration and unrecoverable creep compliance Jnr of WPU-SBR-modified emulsified asphalt gradually decreased, and the softening point, rutting factor G*/sinδ, and creep recovery rate R gradually increased, indicating that the high-temperature stability of modified emulsified asphalt was enhanced, and when the WPU content was 9%, the best improvement effect was obtained. However, excessive content of WPU will deteriorate the low-temperature performance of WPU-SBR-modified emulsified asphalt, and thus the content of WPU should be appropriately selected in practical engineering applications.

Applying solution of spray polyurea elastomer in asphalt binder: Feasibility analysis and DSR study based on the MSCR and LAS tests

Abstract The polyurea elastomer (PUA) powder modifier was prepared by the method of spraying–initial crushing–fine grinding, and then, the PUA-modified asphalt was produced. The typical functional structure of PUA was identified and characterized. The apparent viscosity of PUA-modified asphalt was tested at different temperatures. The impact of particle size and content of PUA on creep and recovery properties of asphalt at high temperature was investigated through the multiple stress creep recovery test. The mesothermal fatigue behavior of PUA-modified asphalt was evaluated by means of time sweep and linear amplitude sweep. Results indicated that the high elastic properties of PUA materials might depend on the spherical structure inside PUA material. The diameter of functional structure was around 20 µm and presented as 3D ball structure. The increase in PUA particle size would lead to the increase in cracks and folds in the bonding surface PUA modifier could improve by about 50% of the apparent viscosity significantly. Furthermore, PUA modifier could promote the high-temperature rutting resistance and middle-temperature fatigue property of asphalt. The improving effect on R could reach almost 28% and the 0.075 mm could be the best application size of PUA.

Rheological evolution mechanisms of asphalt binder and mastic under freeze-thaw cycles

Perennial freeze-thaw cycles have caused plenty of defects on asphalt pavements. To analyze the effect on asphalt binder and mastic under freeze-thaw cycles, the multiple stress creep recovery (MSCR) tests, frequency sweep tests, linear amplitude sweep (LAS) tests, and bending beam rheological (BBR) tests were performed first. The rheological property of asphalt binder and mastic was evaluated through the Burgers model, 2S2P1D (two springs, two parabolic elements, and one dashpot) model, Sigmoidal model, and viscoelastic continuum damage (VECD) theory. The Einstein coefficient and K.D.Ziegel−B−G∗ (K−B−G∗) model were adopted to investigate the asphalt binder-filler interaction subsequently. Finally, Fourier transform infrared spectroscopy (FTIR) test was conducted to analyze the variation of chemical composition of asphalt binder before and after freeze-thaw cycles. The results showed that as freeze-thaw cycle increased, the percent recovery of asphalt binder increased, and the non-recoverable creep compliance of asphalt binder decreased and that of asphalt mastic increased first but decreased. The rutting factor and fatigue factor of asphalt binder and mastic increased after freeze-thaw cycles. The asphalt mastic showed poorer fatigue resistance than asphalt binder at a given freeze-thaw cycle. The low-temperature stiffness of asphalt binder and mastic increased as freeze-thaw cycle increased. K−B−G∗ value showed that the asphalt binder-filler interaction damaged seriously after fifteen freeze-thaw cycles, and the Einstein coefficient decreased by 52.73% after twenty freeze-thaw cycles. The IS and IC indexes increased, and the IB index decreased after twenty freeze-thaw cycles. The design and construction of asphalt pavement in seasonal frozen regions may benefit from this study.

Moisture Susceptibility of Asphalt Mixtures: Conditioning and Testing Protocols

Moisture damage is a common distress in asphalt pavements caused by infiltrated moisture, which degrades mixture strength and affects pavement durability. Loaded wheel tracking (LWT) and modified Lottman (ML) tests are the two commonly used mechanical tests for assessing the moisture susceptibility of asphalt mixtures, but they have been reported to show limitations in consistently ascertaining the moisture sensitivity of different asphalt mixtures under field conditions. This study evaluated the effectiveness of different laboratory mechanical tests (LWT, ML, and semi-circular bend [SCB]) in ascertaining moisture sensitivity of asphalt mixtures. LWT, ML, and SCB tests were conducted on asphalt mixtures prepared with two asphalt binders (an unmodified PG 67-22 and a styrene-butadiene-styrene polymer-modified PG 70-22) and three aggregate types (limestone, crushed gravel, and semi-crushed gravel). Before testing, asphalt binder and mixture samples were exposed to five moisture conditioning levels: (1) unconditioned (dry), (2) single freeze-thaw cycle, (3) triple freeze-thaw cycle, (4) moisture induced stress tester (MiST) 3,500 cycles, and (5) MiST 7,000 cycles. A multiple stress creep recovery test was conducted on asphalt binders subjected to the five moisture conditioning levels. Results showed that the stress sensitivity of asphalt binders decreased after freeze-thaw and MiST conditioning. LWT rut depth and a new parameter which was developed as part of the study, SCB Jd ratio, were found to capture the progressive moisture damage in asphalt mixtures associated with different moisture conditioning levels. Mixtures containing PG 70-22 asphalt binder exhibited better moisture damage resistance compared with mixtures containing PG 67-22 asphalt binder.

Rheological Characterization of Ground Tire Rubber Modified Asphalt Binders with Parallel Plate and Concentric Cylinder Geometries

Recently, scrap tire rubber-modified asphalt binders and pavements have been the preferred choice of state DOTs and parties involved due to the desirable engineering, as well as economic and environmental impacts. Rheological and mechanical properties of rubber modifications have been the main focus of researchers for the last couple of decades. This paper investigates the rutting potential, fatigue cracking resistance, and continuous performance grade (CPG) changes of waste tire rubber-modified, original, and aged asphalt binders. The CPG of asphalt binders is determined at high, intermediate, and low temperatures. A Delta T Critical comparison of the binder was carried out to establish a relationship between measured parameters. Linear amplitude sweep (LAS) tests at equi-stiffness temperatures were conducted to discover the fatigue life of all binders while the multiple stress creep recovery test is performed to assess the high-temperature rutting performance of asphalt binders as per the Superpave performance grading system at accepted regional (58 °C) as well as high PG temperatures. In addition, parallel-plate geometry and concentric cylinder geometry were used with the Multiple Stress Creep Recovery (MSCR) test to discover the impact of discrete particles available in crumb/ground tire rubber-modified asphalt binders as per standards. The results show that rubber modifications improved the base binder’s rutting resistance and continuous PGs without adversely affecting the fatigue cracking resistance. Based on the mathematical expressions developed, 2.71%, 7.82%, 12.94%, and 18.05% (by weight of binder), GTR modifications improved the high PG of the modified binders one, two, three, and four grade bumps, respectively. Similar linear correlations with R2 0.872 and 0.6 were established for continuous low and intermediate PGs, respectively. MSCR test results revealed that both 9% and 20% GTR modifications were achieved to enhance the H-grade traffic level of the original binder to E-grade.

Optimized Preparation and High-Temperature Performance of Composite-Modified Asphalt Binder with CR and WEO

The main objective of this research is to develop a sustainable and environment-friendly asphalt binder based on the reutilization of waste engine oil (WEO) alongside crumb rubber (CR), two major waste materials of the automobile industry. This composite modification eliminates the limitations and the negative effects of solo application of these waste modifiers, including the poor workability and pumpability of the CR-modified binder, as well as compromised rutting resistance of the biobinder modified with WEO. Besides investigating the high-temperature properties of the composite-modified binder with CR and WEO, for the first time, a new method is presented to analyze the influence of the preparation parameters on the performance of the binder and optimize the whole production process. For this purpose, the design of experiment was conducted with the aid of the central composite design (CCD) method, and the rheological properties of the binders were evaluated by rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. Based on the results of rotational viscosity at 135°C and the unaged and RTFO-aged rutting factor values at 58°C, regression models were established and analysis of variance was carried out on the preparation parameters. Overall, test results indicated that the addition of 5%–10% blending content of WEO in the composite-modified binder could achieve a satisfactory rutting resistance while improving its workability and pumpability. On the other hand, although the content of WEO had the most significant influence on the rheological properties of the binder samples, other parameters including preparation temperature and time also had influence to some extent. Additionally, optimum values of the preparation parameters were determined, and the production process was optimized.

Rutting characteristics evaluation and prediction model development for warm mix asphalt

ABSTRACT The warm mix asphalt (WMA) technology has brought environmental sustainability into the pavement industry with its preparation at lower production temperatures than hot mix asphalt (HMA). Nevertheless, it has also raised concerns regarding the mixture’s resistance to permanent deformation as a result of its reduced aging during production. This study examines the effects of warm mix modification on the rutting potential of bituminous mixes. Two modifiers were used for WMA preparation – polyethylene wax (PEW) and waste cooking oil (WCO). Binder rutting properties were evaluated using the multiple stress creep recovery (MSCR) test. Subsequently, WMA mixtures were prepared at adequate production temperatures, and then their rutting characteristics were evaluated using the Cooper wheel tracker device. The study concluded that introducing warm mix modifiers in small amounts, approximately 1–2% by weight of bitumen, results in rutting characteristics comparable to virgin bituminous mix, whereas the characteristics deteriorate at higher modifier contents. Furthermore, a rutting prediction model based on the Weibull failure rate function (WFRF) was developed. A strong correlation was found between the measured wheel tracking data and the prediction model in all mixtures. PEW was discovered to be a superior warm mix modifier to WCO in terms of rutting resistance.

Effect of Stress Levels and Temperatures on Creep Compliance of Asphalt Binders

Abstract: Mostly, the laboratories in Pakistan use DSR (Dynamic Shear Rheometer) Test AASHTO T 315 for quality control purposes but it was designed for unmodified asphalt binders, and it gives inadequate results of modified binders. On the other hand, AASHTO T 350 called as multiple stress creep recovery (MSCR) test gives better result for modified binders. MSCR grades of mostly modified binders with additives, nano composites, viscous fluids is determined in this research paper. The effect of these modified as well as unmodified binders on the Creep Compliance factor is also evaluated. To characterize Creep Compliance factor along with Stress Sensitivity and Traffic Loading this test is now used. For evaluating the Stress Sensitivity of modified binders there is development of new factor called as JNR Slope instead of JNR Difference. Jnr Slope gives vast representation of asphalt binders and there is no congestion left between them. The binders which fail in JNR Difference might get satisfactory results from JNR Slope Which gives better results than the conventional way of testing. For determining the rutting behavior of modified as well as unmodified asphalt binders there is usage of peak strain factor at stress level of 100 Pascal, and 3200Pascal relatively. The values of JNR at the stress levels 25 Pascal to 25600 Pascal gives almost linear variation between modified as well as unmodified binders. This research paper is developed to determine Peak strain values, Creep Compliance factors, Stress Sensitivity Factors, And MSCR grading according to the Traffic Loading.