Amplitude Sweep Test Research Articles

Rheological properties of plastic-modified asphalt binders using diverse plastic wastes for enhanced pavement performance in the UAE

The integration of waste plastics in asphalt mixtures has recently gained more popularity as a potential solution for repurposing waste plastics, while relieving the accumulation of plastics in landfills. This paper investigates the addition of plastic wastes from four waste products namely HDPE, PET, ABS, and LDPE, to asphalt binder at two contents of 2 % and 4 % by the weight of asphalt binder. The control and plastic-modified asphalt binders were tested for physical and rheological properties. Most of the used waste plastics increased the rutting parameter of the asphalt binder. The 4 % ABS plastic-modified asphalt binder managed to achieve the maximum Performance Grade (PG) of 82 while the 4 % PET achieved PG 76. Higher plastic content yielded higher resistance to permanent deformation. Asphalt binders modified with 2 % LDPE and 2 % HDPE yielded the best performance against low temperatures. The Linear Amplitude Sweep (LAS) test results at intermediate temperature showed that the best fatigue performance was attained using 4 % ABS at a strain level of 2.5 %, whereas at 5.0 % strain level, the 2 % PET achieved the maximum fatigue improvement (25 %) over the control. Simulated pavement performance using the AASHTOWare Pavement ME Design software showed noticeable extensions in pavement life for the plastic-modified asphalt binders against permeant deformation and fatigue cracking. The Life Cycle Cost Analysis (LCCA) displayed a reduction in the estimated LCCA cost for the plastic-modified asphalt binders by up to 50 % over the control.

Modeling Influence of Aging and Rejuvenation Mechanisms on the Recycled Asphalt Pavement (RAP) Binder Fatigue Life through the Linear Amplitude Sweep Test

Modeling Influence of Aging and Rejuvenation Mechanisms on the Recycled Asphalt Pavement (RAP) Binder Fatigue Life through the Linear Amplitude Sweep Test

Fatigue performance evaluation of epoxy-recycling technology utilising 100% reclaimed asphalt pavement (RAP): binders and mixtures

ABSTRACT In this study, a novel epoxy-recycling technology, which produces recycled mixtures using epoxy asphalt as binders, was applied to utilise 100% RAP. However, to date, the fatigue properties of epoxy-recycled asphalt mixtures (ERAM) made of 100% RAP remains unknown. The main objective of this paper is to investigate the fatigue performance of epoxy-recycled binders and mixtures. Thus, the linear amplitude sweep (LAS) tests and repeated semi-circular bending (R-SCB) fatigue tests were conducted to evaluate the fatigue resistance of binders and mixtures, respectively. The binder bond strength (BBS) tests were also performed to investigate their adhesive performance. The results show that the epoxy-recycling technology can recover the fatigue properties of ERAM to similar levels or even far superior to conventional virgin mixtures. Compared to SBS modified asphalt, the bonding strengths of epoxy-recycled binders increase by 92.38%, 110.16%, 133.33%, and 210.76% with increasing epoxy proportions. The fatigue lives between LAS tests for binders and R-SCB tests for mixtures show excellent correlations under power functions, and the fatigue performance enhancement of ERAM can be attributed to greater fatigue resistance of binders and better adhesive properties. The findings will provide evidence-based confidence in epoxy-recycling technology, thereby promoting long-life and sustainable pavement construction.

Proposal for a New Method for Evaluating Polymer-Modified Bitumen Fatigue and Self-Restoration Performances Considering the Whole Damage Characteristic Curve

Fatigue performance and self-repairing activity of asphalt binders are two properties that highly influence the fatigue cracking response of asphalt pavement. There are still numerous gaps in knowledge to fill linked with these two characteristics. For instance, current parameters fail to accommodate these two bitumen phenomena fully. This study aims to propose a new procedure to address this issue utilizing the linear amplitude sweep (LAS) test, LAS with rest period (RP) (LASH) test, and simplified viscoelastic continuum damage (S-VECD) model. This research work used four different types of asphalt binders: neat asphalt (NA), self-healing thermoplastic polyurethane (STPU)-modified bitumen (STPB), self-healing poly (dimethyl siloxane) crosslinked with urea bond (IPA1w)-modified bitumen (IPAB), and styrene–butadiene–styrene (SBS)-modified bitumen (SBSB). Before the testing process, all the materials were subjected to short-term and long-term aging. The new procedure showed a superior capacity to analyze and accommodate all bitumen fatigue performances and self-repairing activities compared to the current method. Another finding proved that asphalt binders with a higher self-restoration behavior failed to show a better fatigue performance. Moreover, the higher fatigue performance increments produced by STPU and IPA1w in NA concerning the control bitumen were 123.7% and 143.7%, respectively. Those values were obtained with 1.0% STPU and 0.5% IPA1w in NA. A breakthrough finding demonstrated that asphalt binder fatigue response is augmented when the RP was applied at a higher damage intensity (S) value. STPB and IPAB reached their highest increments of fatigue response, containing 1.0% of STPU and 0.5% of IPA1w, respectively. Those augmentations were 207.54% and 232.64%, respectively.

A novel approach for analyzing linear amplitude sweep (LAS) test data of asphalt binders

Fatigue cracking is one of the crucial distresses considered for the design of flexible pavements. The initiation of fatigue cracking occurs in the binder phase of an asphalt mixture. The linear amplitude sweep (LAS) test was developed to analyze the fatigue damage in the asphalt binder. AASHTO T391 provides a method to analyze the LAS test data by fitting a power equation between the fatigue parameter (G*sinδ) and damage intensity. This method has some inherent weaknesses of overfitting or underfitting of the data at different damage levels. This study proposes a new method where a total curve is divided into two parts that fit the data in two different equations and then sum them up. The first part comprises of the data up to cumulative damage corresponding to the maximum effective stress, and the second part consists of accumulated damage in the material till it reaches the maximum strain (30 %). This method is called the bifurcation method in this paper. LAS test data of 27 long-term aged bitumen samples having different physical properties is used to determine the number of fatigue life cycles (Nf) by these two methods, and results are compared in terms of mean absolute percentage error (MAPE), root mean square error (RMSE), and residual sum of squares (RSS). It is shown that there is a significant reduction in the errors when the data fitting was done using the proposed bifurcation method. Further, the ranking was allotted to the samples based on the number of fatigue life cycles (Nf) at three different strain levels (2.5 %, 5 %, and 10 %) at intermediate-temperature conditions estimated using two methods. The shift indicator parameter was used to analyze the variability in the ranking of the samples due to changes in the strain levels. The study concludes that the proposed bifurcation method fits the predicted values more accurately than the prescribed power law.

Effects of antioxidants on chemical and rheological properties of asphalt binders from different crude oil sources

Antioxidants can effectively mitigate or delay the oxidative aging degradation of asphalt binder, thereby improving pavement durability. While research has largely concentrated on the application of antioxidants to asphalt binders from a single source, limited studies have explored their effects on binders derived from different crude oil sources. Moreover, the relationship between the chemical and rheological properties of antioxidant-modified asphalt binders remains insufficiently understood. In this study, three antioxidants - zinc diethyldithiocarbamate (ZDC), Irganox 1010 and kraft lignin - were utilized and blended with base binders sourced from three distinct regions globally. Fourier transform infrared spectroscopy (FTIR) was utilized to analyze the impact of these antioxidants on the chemical composition of aged binders. Additionally, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were conducted to assess the high- and low-temperature performance of the antioxidant-modified binders, identifying the most effective antioxidant. The linear amplitude sweep (LAS) test further evaluated the performance of ZDC across binders from different crude oil sources. The results revealed three key findings: first, chemical functional group changes due to antioxidants are not always reflected in rheological performance; second, ZDC demonstrated superior performance across different base binders, as evidenced by improved aging indices, high-temperature rutting resistance, and enhanced fatigue and low-temperature cracking resistance; and third, asphalt binders from different crude oil sources exhibit varying sensitivities to antioxidant type and dosage. This study underscores the necessity of determining optimal antioxidant dosages for different asphalt binders, as the relationship between antioxidant dosage and effectiveness is not straightforward.

Nonlinear viscoelastic effect on the fatigue performance of wood tar-based rejuvenated asphalt

The nonlinear viscoelasticity (NLVE) effects of rejuvenated asphalt are often neglected during fatigue degradation, potentially leading to misjudgment of its true fatigue performance. To more accurately quantify the fatigue life of rejuvenated asphalt under NLVE effects, frequency sweep (FS), incremental stress sweep (ISS), and linear amplitude sweep (LAS) tests were used to study two types of rejuvenated asphalt. FS and ISS tests respectively obtained the dynamic modulus |G*|LVE and |G*|NLVE representing the linear viscoelasticity (LVE) and NLVE of rejuvenated asphalt, and incorporated them into the simplified viscoelastic continuum damage (S-VECD) model to establish the fatigue failure criterion and predict the fatigue life of rejuvenated asphalt under high strain levels in LAS tests. The findings indicate that the NLVE-based-S-VECD model quantifies fatigue damage in rejuvenated asphalt lower than the LVE model, and the fatigue life of rejuvenated asphalt increases significantly after considering the NLVE effect. Besides, the failure difference (∆GR) and failure area difference (∆A) defined during the modeling process explain the impact of NLVE on the fatigue failure criterion average pseudo strain energy release rate (GR) of rejuvenated asphalt, validating the necessity of incorporating NLVE into the fatigue performance analysis of rejuvenated asphalt. Therefore, it's necessary to account for the impact of NLVE effect on the fatigue performance of rejuvenated asphalt in engineering practice, which will contribute to the development and application of rejuvenator.

Investigating the efficacy of bio-rejuvenators in restoring aged asphalt binder properties

The asphalt binder used in pavements oxidizes quickly owing to the elevated temperatures, solar radiation, and exposure to atmospheric oxygen. In this study, epoxidized castor oil (ECO) and acrylated cashew nut shell liquid (ACNSL) were investigated as potential rejuvenators for use as aged binders. The binders were aged in the laboratory using short- and long-term aging methods. The additives and rejuvenated binders were characterized by Fourier transform infrared spectroscopy (FTIR). The properties of the rejuvenated binders were evaluated by frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS) tests. The additives improved binder performance, particularly for the sample modified with 15 % cashew nut shell liquid (CNSL). The rheological parameters indicated that both the bio-rejuvenators increased the elasticity of the binder. Regarding the rutting resistance as measured by MSCR test, the results indicated that the sample with the 7 % ACNSL rejuvenated binder exhibited the best rutting resistance at both intermediate and elevated temperatures. Additionally, the fatigue resistance of the sample with 10 % ACNSL was higher than those of the other samples. This study indicates that the bio-oils used are potentially useful as rejuvenating agents for aged binders, thus enabling the recycling of aged asphalt binders.

Tailoring pea proteins gelling properties by high-pressure homogenization for the formulation of a model spreadable plant-based product

This study investigated the impact of high-pressure homogenization (HPH) at varying intensities on the gelling properties of a commercial pea protein concentrate for the formulation of emulsion-filled gels as a model spreadable plant-based product. As a preliminary characterization, pea protein dispersions (10%-15%–20% w/w) underwent HPH treatments, 60 and 150 MPa for 5 cycles. Mechanical characteristics of heat-set gels were evaluated through rheological measurements. Emulsion-filled gels were then produced, starting from a common primary emulsion, incorporating either native or treated pea protein suspensions, and characterized with frequency and amplitude sweep tests, back extrusion, texture profile analysis (TPA) and confocal laser scanning microscopy (CLSM). Results revealed that HPH treatments had a significant influence on the aggregation state of protein suspensions reducing residue size, but inducing the formation of new, albeit smaller, agglomerates, with a direct impact on gel network formation. Treatment at 150 MPa consistently produced a stiffer, compact, and elastic gel structure, as confirmed by frequency sweep, back extrusion and TPA tests. Additionally, when this structure was disrupted, it exhibited creamy-viscous characteristics, as verified by amplitude sweep analyses. CLSM micrographs showed the formation of a more structured and compact gel matrix with the increase of the pressure applied.

Comprehensive rheological and mechanistic evaluation of an asphalt binder and mixture modified with warm mix additives.

Though warm mix asphalt (WMA) technology has been introduced for a long time, there is still reluctance in the industry to utilize it in practice. In regions like India, where WMA incorporation into road construction has been limited over the past two decades, building confidence in local binders is imperative for widespread adoption. Thus, the present study appraises the effect of three commonly used WMA additives in India, namely Sasobit®, Evotherm®, and Zycotherm®, with base binder VG-30 on the rheological and mixture performance parameters. Three dosages of each WMA additive were blended with the control binder to give ten binder combinations. Different binder evaluations such as Superpave grading and parameters, frequency sweep testing, multiple stress creep recovery test, and linear amplitude sweep test were conducted for comparative dynamic mechanical analysis. Based on the binder testing results, suitable dosages of WMA additives were established, and mixture testing was carried out using these specific additive dosages. Binder evaluations showed improvement in high-temperature characteristics with Sasobit® and better fatigue performance with Evotherm®, while Zycotherm® did not alter binder properties significantly. The asphalt mixture testing results indicated satisfactory performance with the three additives based on Marshall stability and flow testing. The WMA additives also showed enhancement in moisture susceptibility based on the modified Lottman test with Zycotherm® demonstrating the best performance. Overall, the study underscores promising effects of the three WMA additives across different parameters, signaling their potential for widespread application in real-world scenarios.

Rheological behaviour of modified binders for different loading conditions and temperatures: A case of using pig tallow and crumb rubber from end–of–life tyres

This study investigates alternatives to Styrene-Butadiene-Styrene (SBS) polymer in asphalt mixtures by evaluating End-Of-Life tire (ELT) crumb rubber (CR) and fatty acid amide wax (FAA) derived from pig tallow. The research focuses on triple modification of binders with SBS, ELT and FAA to improve performance and reuse waste and industrial by-products in an economical and environmentally responsible manner. The results show that the incorporation of ELT and FAA significantly reduces the SBS content, achieving a 73 % improvement in elastic performance according to Multiple Stress Creep Recovery (MSCR) tests. In addition, this combination improves peak stress and fatigue life in Linear Amplitude Sweep (LAS) tests, demonstrating potential benefits in asphalt mixtures. The study concludes that the combination of pig tallow and end-of-life tire materials doubles the yield energy (Yield Energy of Asphalt Binders, BYET) compared to samples with higher SBS content. In particular, a modification with 6 % CR, 3 % SBS and 2 % FAA doubles the toughness (Er) of a binder with 5 % SBS. This contributes to higher tensile strength in asphalt mixtures, promoting sustainability and efficiency in the road construction industry. This study provides a deeper understanding of how the combination of ELT, FAA and SBS can optimize the properties of asphalt mixtures, highlighting the potential of these additives to improve performance, reduce costs and minimize environmental impact.

Fatigue-Healing Performance Analysis of Warm-Mix Rubber Asphalt Mastic Using the Simplified Viscoelastic Continuum Damage Theory

As a green and low-carbon road material, warm-mix rubber asphalt (WMRA) has received extensive attention from scholars for its road performance. In the in-depth study of its properties, the fatigue characteristics of WMRA are particularly critical. However, in current studies on asphalt fatigue performance, its self-healing ability is often underestimated or neglected. Furthermore, the simplified viscoelastic continuum damage theory (S-VECD), with its accuracy, speed, and convenience, provides a powerful tool for analyzing asphalt fatigue performance. Therefore, to analyze the fatigue and self-healing performances of WMRA in practical applications, four sample materials were selected in this study: virgin asphalt mastic (VAM), rubber asphalt mastic (RAM), Sasobit rubber asphalt mastic (SRAM), and Evotherm rubber asphalt mastic (ERAM). Subsequently, the samples were subjected to a comprehensive experimental design with frequency sweep tests, linear amplitude sweep tests, and multiple intermittent loading time sweep tests under different aging conditions. The fatigue and self-healing performances of different aging degrees and different types of WMRA were evaluated based on the S-VECD theory. The results show that aging reduces the fatigue and self-healing performances of asphalt mastic to a certain extent, and at a 7% strain, the fatigue life of SRAM after long-term aging is only 30.7% of the life of the unaged sample. The greater the aging degree, the more pronounced the effect. Under different aging levels, the warm-mix agent can significantly improve the fatigue and self-healing performances of rubber asphalt mastic. After undergoing ten fatigue intermittent loading tests, the recovery rate of the complex shear modulus for the long-term aged VAM was 0.65, which is lower than that of SRAM under the same conditions, and the warm mix can further extend the fatigue life of rubber asphalt by improving the self-healing properties of the asphalt. The role of Sasobit in enhancing the fatigue and self-healing performances of rubber asphalt mastic is more significant. This study can provide a theoretical basis for the promotion and application of WMRA pavements and contribute to the sustainable development of road construction.

Effects of Adding Pectin to Milk in Varying Amounts on the Rheological Properties of Milk

Pectin, which is used as an additive in the food, cosmetics, pharmaceutical, and health sectors due to its safety, non-toxicity, low production cost, and high availability, is used as a thickener, gelling agent, brightener, stabilizer, emulsifier, and fat and sugar replacer in low-calorie foods. It is also used in milk and dairy products as a stabilizer to prevent proteins from clumping. In this study, the rheological properties of pectin and milk mixtures with pectin/milk powder (w/w) ratios of 0.1, 0.25, 0.5, 0.75, 1 and 1.5 were examined. First, a flow curve test was applied in the range of 0,01-1000 s-1 to obtain the viscosity curves and yield stress values of the samples. Then, an amplitude sweep test was performed at a fixed frequency of 10 rad/s and in the strain range of 0.01-100% to determine the linear viscoelastic range (LVR) of the samples and the solid and liquid structure of the samples. To determine the time-dependent behavior of the samples in non-destructive deformation, frequency sweep tests were performed at constant strain (0.01%) in the LVR range obtained from the amplitude sweep test and in the range of 0.1-100 rad/s. Finally, three interval thixotropy tests (3ITT) were performed to observe the structural recovery of the samples. As a result of rheological tests, it was determined that pectin-free milk showed Newtonian properties, other samples showed shear thinning properties, and viscosity values increased as the pectin rate increased. While all samples are solid at low strains, the liquid feature becomes dominant at high strains. It has been observed that as the pectin ratio in milk increases, the strain values at the yield point, where the liquid feature becomes dominant, also increase. Except for the sample with the highest pectin content, it was observed that the dominance of the storage modulus over the loss modulus was greater at low frequencies than at high frequencies. As a result of 3ITT, it was determined that the percentage of recovery at the 600th second increased as the pectin rate increased.

Improving Asphalt Binder Durability Using Sustainable Materials: A Rheological and Chemical Analysis of Polymer-, Rubber-, and Epoxy-Modified Asphalt Binders

When exposed to sun radiation and heat, asphalt binders age, resulting in reduced flexibility, cracking, and pavement failure. Given the increasing demands of traffic, environmental concerns, and resource scarcity, highway agencies and researchers are actively seeking solutions that meet performance requirements and demonstrate awareness of using non-renewable resources. Epoxy asphalt (EA) promotes sustainability concepts due to its production at significantly lower mixing and compaction temperatures, enhanced durability, improved serviceability, reduced maintenance needs, and successful recycling and reuse in hot asphalt mixtures. Crumb rubber, a widely recognized recycled waste tire material, is considered a viable option for promoting sustainability and enhancing asphalt binder properties. This study aims to enhance the durability and long-term performance of asphalt binders by utilizing sustainable materials. Six types of asphalt binders were employed: PG 67-22 base asphalt binder; styrene–butadiene–styrene (SBS)-modified PG 76-22 and PG 88-22H (3.5% and 7.0% dosage rates, respectively); a hybrid PG 76-22CS-modified asphalt binder prepared with SBS and crumb rubber modifiers; and 25EAB and 50EAB epoxy-modified asphalt binders prepared at 25 and 50% dosage rates, respectively. Results indicate that the sustainable asphalt binders PG 76-22CS, 25EAB, and 50EAB demonstrated comparable or superior performance compared to SBS-modified asphalt binders, as measured by rutting and fatigue factors. Additionally, epoxy asphalt binders had better anti-aging and cracking resistance, as shown by the outcomes of Fourier-transform infrared spectroscopy and linear amplitude sweep tests, respectively. This study contributes valuable insights into the potential of sustainable materials to enhance the overall performance and resilience of asphalt binders.

Research on Fatigue Performance of Fast-Melting SBS/Epoxy Resin Composite-Modified Asphalt

A high-performance composite modifier ER-SBS-T was prepared through the mixing of epoxy resin with a fast-melting styrene–butadiene–styrene modifier (SBS-T) to enhance material properties. This study evaluated the fatigue characteristics of ER-SBS-T-modified asphalt using a linear amplitude sweep test, and 70# base asphalt, SBS-modified asphalt, and SBS-T-modified asphalt were used as control groups. The fatigue life of ER-SBS-T-modified asphalt was determined according to viscoelastic continuous damage (VECD) theory. The findings indicated that as the ER-SBS-T modifier content increased, both the maximum value and the cumulative damage limit value increased, while the rate of change of decreased. At strain levels of 2.5% and 1%, the fatigue life of the modified asphalt improved with increasing ER-SBS-T content. However, at a strain level of 5%, the modified asphalt exhibited no significant trend in fatigue life across different ER-SBS-T contents. ER-SBS-T-modified asphalt with a modifier content of >10% demonstrated favorable fatigue performance suitable for practical engineering applications.

Fatigue performance analysis of fine aggregate matrix using a newly designed experimental strategy and viscoelastic continuum damage theory

Fine aggregate matrix (FAM), as the matrix phase in asphalt concrete (AC), significantly affects the fatigue behavior of AC. To accurately assess the mechanical properties of FAM, a newly designed experimental strategy for FAM testing was developed, and the viscoelastic continuum damage theory (VECD) theory was applied to analyze FAM’s fatigue cracking characteristics. In this study, a dumbbell-shaped geometry for dynamic shear rheometer testing was designed and verified through the FE-aided method. Subsequently, three AC mixtures’ FAM specimens with this special geometry were fabricated for the frequency sweep and linear amplitude sweep tests. Results showed that the specially designed specimens effectively capture the viscoelastic and fatigue properties of FAM with high replicability. Analyses based on the VECD theory indicated that FAM of porous asphalt (FAM(PA13)), featuring a higher asphalt content, exhibits a significant reduction in pseudo stiffness with increasing damage at the initial stage, but the reduction rate diminishes as damage progresses when compared to the other two FAMs. It was speculated that the higher aggregate content in FAM of dense-graded AC mixture (FAM(AC20) induces stress concentrations in the asphalt mastic near the protrusion areas of aggregates, thereby rendering the sample more susceptible to damage. The proposed methods will be readily extended to characterize other mechanical properties of FAM.

Effects of cellulose nanofibrils on rheological and mechanical properties of 3D printable cement composites

This study explores the effects of cellulose nanofibrils (CNF), a relatively new type of nanocellulose material, on the rheological and printability characteristics of cementitious mixtures, and the mechanical properties of 3D printed specimens. The rheology of the mortar mixtures with varying ratios of CNF is thoroughly assessed first. Two testing protocols, stress growth test and ramp test, are followed for rotational measurements using a shear rheometer with a building cell and vane motor. Stress growth tests are carried out to quantify the static yield stress of the cementitious mixtures. Ramp tests are conducted to determine dynamic yield stress and plastic viscosity of the mixes using the Bingham visco-plastic material model. As oscillatory measurements, amplitude sweep tests are carried out to determine the viscoelastic properties of the mortar mixes, including storage modulus and critical strain that are found to be essential for buildability. Thermogravimetric analysis (TGA) is conducted to assess the effects of CNF on the hydration characteristics of the mixtures. The printability and the buildability of the mortar mixtures incorporating CNF are assessed using a 3D concrete printer equipped with a 10 mm diameter nozzle and screw pump mechanism. Tensile, flexural, and compressive strength tests are conducted to determine the mechanical properties of 3D printed specimens with varying ratios of CNFs. Scanning electron microscopy (SEM) is used to conduct the microstructural analysis on fractured surfaces of the mechanically tested specimens. Results indicate that adding CNF at least 0.3 wt% of cement has a favorable effect on the rheological properties of cement composites.

Evaluating and correlating asphalt binder and mixture fatigue properties considering aging conditions

Asphalt fatigue cracking is a critical distress type for flexible pavement. This study utilized the state of practice binder and mixture cracking tests and parameters to investigate how asphalt binders’ and mixtures’ fatigue performance vary between the different mix designs and evaluate their changes with aging. The potential relationships between the measured binder properties and mixture performance were also explored. Five asphalt mixtures with disparate mix designs were evaluated and three different aging conditioning levels were conducted. The binder tests include the traditional time and frequency sweep and linear amplitude sweep test, while the mixture evaluations include the semi-circular bending and cyclic fatigue test. The results indicate that the different fatigue parameters from the tests can evaluate and rank the mixes differently. The correlation analysis using the Spearman correlation coefficient shows that the mixture cracking parameters that are more predominant by asphalt mixture’s flexibility/brittleness show strong correlations (Spearman coefficient larger than 0.8) with binder cracking indices. The LAS fatigue life-related parameters generally do not correlate well with mixture fatigue indices (Spearman coefficient smaller than 0.6). Furthermore, a prediction model to estimate asphalt mixture’s fatigue performance was developed based on linear regression and Artificial Neural Network (ANN) approach, which only requires the mix design info. and binder fatigue property as the inputs, significantly reducing the time and eliminating the effort in preparing and testing the asphalt mixture specimen for mixture fatigue performance measurement.

Asphalt binder modified with high density polyethylene: 2S2P1D rheological modelling and damage characterization

ABSTRACT The new needs in the paving industry have led to the intensification of the use of modified binders, and the use of plastics (non-biodegradable waste) can be an ally in facing both environmental and technical challenges. This study evaluated the feasibility of modifying a conventional asphalt binder with high density polyethylene (HDPE) at contents of 1, 3 and 5% for performance improvement, using rheological and performance tests. The linear viscoelastic properties were obtained by the temperature-frequency sweep test, and for the first time the 2S2P1D rheological model was used to describe these data for an HDPE-modified binder. Resistance to permanent deformation and fatigue was verified by the Multiple Stress Creep Recovery (MSCR) and Linear Amplitude Sweep (LAS) tests, respectively. The Fatigue Factor of Binder was obtained at 3 levels of strain for the first time for this material. HDPE made the material stiffer and more elastic observed by the coefficients of the 2S2P1D model. The modification resulted in better performance regarding permanent deformation and in general had an impact of less than 10% on the fatigue life of the material. Thus, it is possible to state that HDPE can be incorporated into the asphalt binder without harming its performance.

Effects of various long-term thermal aging levels on the morphology, rheology and self-healing performances of high-viscosity asphalt

Large macroporous structures of permeable asphalt pavement made high-viscosity asphalt (HVA) more susceptible to aging and failure. However, the standard pressure aging vessel (PAV) test was difficult to accurately emulate the long-term aging behavior of HVA. Hence, 1–5PAV aging levels of two HVAs (i.e. HVA-1 and HVA-2) were emulated by the simple aging test (SAT). Rheological analysis indicated that asphalt oxidation consistently dominated regardless of the long-term aging levels of HVAs. Combined with the fluorescence microscopy observation, HVA-2 with meticulous and uniform granular distribution was more resistant to aging than HVA-1 with coarse and continuously strip-like structures. Stress-strain curve analysis in linear amplitude sweep (LAS) test revealed that the accumulated strain energy (ASE) representing the overall mechanical properties of HVAs first increased and then decreased as the long-term aging level grew. The continuous repeated LAS (RLAS) test further reflected that the yield stress, yield strain and ASE of HVAs gradually decreased as the LAS loading number increased at initial long-term aging states; but as the sustained growth of aging level, the stress-strain curve of HVAs become increasingly chaotic until remarkable strain hardening occurred. Furthermore, RLAS-based self-healing (RLASSH) test was developed by introducing intermittent time into RLAS test. The variation of ratio of ASE decrease can characterize the self-healing performance of HVAs. RLASSH test showed that the self-healing performance of HVAs was unstable at 1–3PAV aging level, and the HVAs with 4 or 5PAV aging levels completely lost their self-healing performance. Overall, with the increase in long-term aging levels, significant differences were observed in the evolution characteristics of morphology, rheology and self-healing performances of different HVAs. This study helps to understand the rheology and self-healing performance evolution pattern of HVA during long-term service.