Viscoelastic Properties Of Asphalt Binders Research Articles

Study on Viscoelastic Properties of Various Fiber-Reinforced Asphalt Binders.

This study analyzed the viscoelastic properties of asphalt binders reinforced with various fibers, such as modified asphalt binder, modified asphalt binder reinforced with lignin fibers (LFs), polyester fibers (PFs), and polypropylene fibers (PPFs), using dynamic shear rheological (DSR) testing. Then, the experiment generated data on the dynamic modulus and phase angle, which described the dynamic rheological characteristics at varying temperatures. The generalized Maxwell model was employed to select the appropriate element, and the test curve was fitted into a discrete time spectrum based on the time-temperature equivalence principle (TTSP). The master curves of the relaxation modulus and creep compliance were established to predict the relaxation and creep properties of various asphalt binders. The analysis indicated that fiber-reinforced binders offer superior resistance to high temperatures and long-term deformation, while being less sensitive to temperature and having a more significant elastic characterization. The binders reinforced with PPFs and LFs exhibited superior performance in high-temperature settings and long-term durability, respectively. On the other hand, the binder reinforced with PFs displayed exceptional high-temperature elastic properties. Additionally, based on the experimental data and corresponding discussion, it appears that the 13-element GM model is more appropriate for fitting the data.

Fractional derivative Burgers models describing dynamic viscoelastic properties of asphalt binders

The Burgers model is ineffective in the representation of dynamic viscoelastic properties of asphalt binders; the existing fractional derivative Burgers (FDB I) model has limitations in its application and construction concept. Consequently, this study started by deriving the constitutive equations of the FDB I model and proposed a new application idea of Abel dashpot to construct the second fractional derivative Burgers (FDB II) model. Then, dynamic modulus formulas for the FDB II model were derived. On this basis, the frequency sweep tests of base and two polyphosphoric acid (PPA) modified asphalt binders were carried, and the dynamic viscoelastic properties of three different asphalt binders were described using three different models, and in-depth comparisons and analysis are carried out. The results show that both fractional derivative Burgers (FDB) models can simultaneously express the dynamic viscoelastic properties of asphalt binders with a set of parameters. Both FDB models perform better than traditional Burgers model in the representation of dynamic viscoelastic properties, and fitting results of master curves no longer exhibit oscillation properties like the traditional Burgers model. The R2 of FDB models could reach above 0.99, while R2 of traditional Burgers model was only 0.9349 at minimum. Among them, the FDB II model performs best. Five parameters of the FDB II model have relatively clear physical meanings. The new application concept of fractional dashpots was verified its theoretical feasibility and application advantages, which will provide a new idea for further application and development of fractional derivative constitutive models.

Establishment of correlation model between compositions and dynamic viscoelastic properties of asphalt binder based on machine learning

The complex behavior of asphalt binders makes it difficult to accurately predict their dynamic viscoelastic properties. However, the dynamic viscoelastic properties of asphalt binders are determined by their compositions. The main aim of this study was to model the relationship between compositions and dynamic viscoelastic properties in asphalt binders with machine learning algorithms. In this paper, the dataset of dynamic viscoelastic properties parameters was built using DSR test, and the dataset of composition parameters was established using elemental analyzer and infrared spectrometer tests. The effects of asphalt types, oil sources and aging effect on the macro and micro properties of asphalt binder were investigated. The principal component analysis (PCA) and distance correlation coefficient (DCC) methods were adopted to determine the input parameters of the model, while three machine learning algorithms, i.e., SVM, relevance vector machine (RVM) and random forest (RF) were used to predict the dynamic viscoelastic properties of asphalt binders. Results indicate that the content of element C was similar for different samples. The absorption peak at 1700 cm−1 was the most sensitive to oil sources. Nine variables were selected as input factors, namely, A1700, A870, A810, A745, A720, I1600, N, S and C/N. The modeling results show that the SVM performed better in predicting the dynamic viscoelastic properties than RVM and RF. Mean absolute percentage error (MAPE) of all fitting parameters were less than 10 % in SVM. The study enriches the prediction method of asphalt binder dynamic viscoelastic properties and provides technical support for realizing the on-demand design of asphalt material.

Introducing a stress-dependent fractional nonlinear viscoelastic model for modified asphalt binders

Asphalt binders generally behave in a linear viscoelastic manner under conventional stress and strain level. There are several researches and technical protocols consistent with linear viscoelastic theorem. However, two main reasons can affect this well-known behavior of asphalt binders: 1) modification of asphalt binder with some additives causing a change in its microstructure and 2) higher order stress and strain level induced to asphalt binder under heavy traffic or climate loading. It is important to consider non-linear viscoelastic behavior of asphalt binder and its effect on conventional characteristics of asphalt especially two constitutive functions of creep compliance and relaxation modulus. In this research, nonlinear viscoelastic properties of asphalt binders modified with crumb rubber, styrene-butadiene-styrene and polyphosphoric acid are investigated to evaluate the variation in non-linear viscoelastic parameters due to addition of these modifiers. For this purpose, a specified research program was defined to consider non-linear behavior of one neat asphalt binder as well as nine modified ones. Based on a robust literature review and some prior experiences, three different extents selected for each modifier and then specimens were made. Implementing a simple creep-recovery test with creep loading time of 1 s and 100 s and 999 s unloading to simulate traffic load by using a dynamic shear rheometer at different stress levels of 0.1, 1, 10, 20 and 30 kPa, non-linear viscoelastic behavior of neat and modified asphalt binder was captured. The generalized fractional nonlinear viscoelastic model is introduced and successfully implemented to simulate creep and recovery behavior of neat and modified asphalt binders. Addition of all modifiers to the neat asphalt binder alters its non-linear viscoelastic behavior and properties. For short time creep loading, crumb rubber and polyphosphoric acid amplify non-linear behavior while SBS control it and for long creep loading time all asphalt modifiers increases non-linearity of asphalt binder’s viscoelastic behavior.

The crossover temperature: significance and application towards engineering balanced recycled binder blends

Increased quantities of asphalt-based recycled materials can be incorporated in asphalt paving mixtures by using recycling agents. Previous studies demonstrated that restoring the required performance grade (PG) by the inclusion of recycling agents may not be sufficient to guarantee long-term durability. In this study the crossover temperature was used to characterise the viscoelastic properties of asphalt binders at the intermediate service temperature range for asphalt pavements. Durability thresholds for crossover temperature with aging were proposed on a trial basis from a correlation to the Glover–Rowe parameter. In combination with high PG, crossover temperature was used to evaluate rheological balance: resistance to early rutting and long-term embrittlement. Practical recommendations are provided in terms of appropriate materials selection (base binder, recycled, binders, and recycling agents) towards engineering long-lasting rejuvenated binder blends with increased quantities of recycled materials. Limitations and additional considerations for extending the rheological balance approach to evaluate polymer-modified materials are also summarised.

Impact of distillation temperature on the solvent residue and viscoelastic properties of asphalt binders

Asphalt used as a paving material is a mix of aggregates and bituminous binder. Due to reasons of acceptance tests after paving or for fault analysis, it is necessary to separate asphalt mixes into their components. Therefore, different organic solvents are commonly used. The European Standard defines a procedure for both, recovery of aggregates and the distillation of binder from solvent mixture. Within the distillation procedure, the applied maximum temperature and the time of its application are not defined clearly. This research is an approach to define the distillation temperature depending on the viscosity of the binder. Four different binder samples (unmodified, polymer-modified) were used to determine the impact of distillation temperature on solvent residue and the recovered binder and its rheological properties. The solvent residue was calculated by weight and the binder properties were obtained by a dynamic shear rheometer and rotational viscometer. These results show a dependence of the solvent residue on the viscosity at distillation temperature. Thus, it is possible to choose reasonable distillation temperatures with regard to binder viscosity instead of setting one temperature for all binders. It was also found that there is no impact of tetrachloroethene as solvent on the binder properties if its residue is low enough (<1% w/w).

Optimization criterion of viscoelastic response model for asphalt binders

The viscoelastic response model is widely used in characterizing the viscoelastic properties of asphalt binders. However, the viscoelastic response model parameters depend heavily on the optimization criterion. The predict ability of the models vary under different criteria. Most viscoelastic response model parameters were obtained by dynamic data or static data. The models determined by these methods can only well describe one type of viscoelastic properties of asphalt binders. In this paper, the generalized Maxwell model was employed as the viscoelastic response model for asphalt binders, and three types of optimization criteria were applied to get the model parameters. The advantages and disadvantages of these criteria were compared afterwards. Based on the results, it is concluded that the generalized Maxwell model under optimization criterion based on all data can well describe both dynamic and static behaviors of asphalt binder. Also, the rank of the optimization criteria is as follow: criterion under all data, criterion under dynamic test, and criterion under static test.

Evaluation of the impact of extended aging duration on visco-elastic properties of asphalt binders

There are variations in the haulage distance between an asphalt mixing plant and the road construction site (field) and this may cause variations in the levels of aging of the asphalt mixture produced. This study evaluates the effects of extended aging durations during mixture transport from the plant to field. The rheological properties of different binders were characterized from the complex modulus, phase angle and Superpave™ rutting parameter. In addition, binder rheological properties changes were calculated using an Arrhenius activation energy equation. A prolonged aging characterization method (PACM) and its gradient (▿PACM) were also proposed to characterize the binder rheology subjected to different aging conditions. The test results showed that the trends in aging differ and depend on binder type, test temperature and aging conditions. The smoothing spline algorithm can be a suitable parameter that can predict the effects of aging on ▿PACM trend.

Fracture and Viscoelastic Properties of Asphalt Binders During Fatigue and Rest Periods

Abstract Viscoelastic asphalt binder plays an important role in bonding individual aggregate particles and contributes to the durability and stability of asphalt pavement. When asphalt binder is subjected to cyclic loading, deformation and fracture may develop simultaneously within it, leading to the deterioration of material properties and eventually fatigue failure. Research has found that some degree of recovery may develop if rest periods are applied after fatigue deterioration. However, it is not clear whether such recovery is caused by fracture healing, viscoelastic recovery, or both. This paper presents an analysis to differentiate the contributions of fracture healing and viscoelastic recovery to the asphalt binder during rest periods. It also evaluates the damage caused by deformation and fracture during a fatigue process. It is found that viscoelastic recovery plays an important role in the instant increase in the dynamic shear modulus at the beginning of the rest period. The effect of fracture healing on dynamic shear modulus recovery is more dominant in the long term. A healing index is developed based only on the fracture healing of asphalt binder, excluding the effect of viscoelastic recovery. It can be used to evaluate the true healing properties of different asphalt binders.

Preparation and properties of conventional asphalt modified by physical mixtures of linear SBS and montmorillonite clay

The effect of additions of organically modified clay and a sulfur-based compound on the technological, as well as rheological properties of a conventional asphalt that was modified by a linear styrene–butadiene–styrene block copolymer, was studied via three factors and five levels of statistical experiment. Blends were prepared with conventional physical mixing. The linear viscoelastic properties of asphalt binders were studied in small-amplitude sinusoidal oscillations by a dynamic shear rheometer, and the low-temperature properties of the tested polymer modified asphalts were determined from their creep characteristics measured in a bending beam rheometer. In particular, it was shown that the organoclay had a positive influence on rheological properties of the studied systems, specifically on service temperatures.

Constitutive modeling of the nonlinearly viscoelastic response of asphalt binders; incorporating three-dimensional effects

A dynamic shear rheometer is again used to characterize the nonlinearly viscoelastic properties of asphalt binders at intermediate or high temperatures. In our previous work, the dynamic shear rheometer test results showed that, under certain conditions, a compressive normal force was generated in an axially constrained specimen subjected to cyclic torque histories. This normal force could not be solely attributed to the Poynting effect and was also related to the tendency of the asphalt binder to dilate when subjected to shear loads. The generated normal force changed the state of stress and interacted with the shear behavior of asphalt binder. This effect was considered to be an “interaction nonlinearity” or “three-dimensional effect.” The concept is explored further in this paper by developing a fundamental approach to modeling the observed behavior. In this approach, the octahedral shear stress is used to represent the three-dimensional stress state in Schapery’s model of nonlinearly viscoelastic behavior. The model was successfully validated for several different loading histories. These results highlight the importance of modeling the mechanical behavior of asphalt binders based on the three-dimensional stress state of the material.

Determination of Asphalt Binder Creep Compliance Using Depth-Sensing Indentation

Asphalt binders are common construction materials, however due to time- and temperature- dependence, their mechanical properties are often difficult to characterize. Several standard tests methods exist to describe their complex behavior. This paper presents an exploratory feasibility study of a flat-tip indentation testing to analyze the linear viscoelastic properties of asphalt binders. Depth-sensing indentation testing has been extensively used to characterize the properties of many engineering materials, however the applications to asphalt binders are very limited. This paper presents a simple solution for the creep compliance in tension derived for flat-tipped indenter. This solution was verified with the Finite Element Analysis and then applied to the experimental results from the indentation testing performed on one typical unmodified asphalt binder. The testing was conducted at three different low temperatures and under three different creep load levels to verity the linearity of the response, and to evaluate the robustness and applicability of the indentation method. Furthermore, the creep compliance functions determined from the indentation testing were compared with a more traditional 3-point bending experiments. The results show that there is a non-uniform discrepancy between the two testing methods, most likely due to nonlinear behavior of the asphalt binder at higher temperatures and micro-damage of the binder samples at lower temperatures. Other possible sources of error between indentation and 3-point bending are problems determining the initial tip-specimen contact surface and possible tip-specimen adhesion. It is concluded that flat-tipped indentation at low temperatures should be performed at lower load levels to avoid excessive stress concentrations that leads to micro-damage and nonlinear response of asphalt binders. Alternatively, asphalt binders at low temperatures could be evaluated using different indenter geometries, such as spherical or pyramidal, using corresponding parameter interpretation procedures.

Evaluation of thermal and viscoelastic properties of asphalt binders by compounding with polymer modifiers

AbstractA series of potentially useful asphalt blends containing polyethylene with different extents of polarity as modifiers have been prepared and characterized for asphalt pavement. The results of differential scanning calorimetry (DSC) studies show that poly(ethylene‐graft‐maleic anhydride) (MPE) exhibit more interaction with asphalt phase than low density polyethylene (LDPE) and high density polyethylene (HDPE) due to more dispersion of the amorphous content of MPE into the asphalt matrix. The phase distributions of micrographs from scanning electron microscopy (SEM) confirm that polyethylene modifiers with different extents of polarity in asphalt blends results in dispersion of polymer additive into the asphalt phase and affect the certain degree of the phase separation of asphalt blends. From rheological studies, most of asphalt blends exhibit superior performance at higher temperature with increasing the contents of modifiers such as reducing Newtonian flow response, enhancing rutting resistance as well as frequency of loading and improving creep resistance than tank asphalt. POLYM. COMPOS., 31:1738–1744, 2010. © 2010 Society of Plastics Engineers.

Effect of Mineral Fillers on Fatigue Resistance and Fundamental Material Characteristics: Mechanistic Evaluation

Complex characteristics of fatigue behavior were evaluated on the basis of test results and their mechanical analyses. The dynamic shear rheometer was used to characterize fundamental linear viscoelastic properties of asphalt binders and mastics. Various dynamic mechanical tests using cylindrical sand–asphalt samples mixed with pure binders, mastics, or both were also performed to estimate viscoelastic characteristics and fatigue behavior. To assess the filler effect, two distinctly compositionally different asphalt binders, AAD-1 and AAM-1, and two fillers, limestone and hydrated lime, were selected. Test results were analyzed using viscoelastic theory, a fatigue prediction model based on continuum damage mechanics, and a rheological composite model. The role of fillers in fatigue resistance was quantified, and induced mechanisms due to filler addition were investigated. The effect of hydrated lime, which is highly binder specific, as a filler was further discussed by comparing test results from hydrated lime filler and test results from limestone filler.

How Good Are Linear Viscoelastic Properties of Asphalt Binder to Predict Rutting and Fatigue Cracking?

This article evaluates the effects of linear viscoelastic properties of asphalt on pavement rutting and fatigue cracking. The parameters in the binder specification recently developed by the Strategic Highway Research Program (SHRP) were also compared for pavement performance. Two studies were conducted for asphalt-aggregate mixes. The first study was the wheel tracking test to evaluate the rutting of mixes containing three asphalts. The second study was a detailed field study of the effects of binder properties on the pavement performance of eight different sections. Results of both investigations indicated that SHRP parameters were not sufficient indicators for predicting the rutting and fatigue cracking of pavements. The discrepancies between performance data and existing parameters of the binder mainly resulted from the inherited assumptions made during the specification development, that is, stress- or strain-controlled mode and traffic loading frequency. In order to directly relate the linear viscoelastic properties of asphalt binders to pavement performance, calculating the dissipated energy per traffic cycle, Wd, became imperative. Fundamental derivation of Wd was developed in this study. Results indicated that Wd could predict the rutting and fatigue cracking of pavements reasonably well. This study, proposed the dissipated energy, Wd, as the single parameter for evaluating pavement rutting and fatigue cracking.

MODELING LINEAR VISCOELASTIC PROPERTIES OF ASPHALT BINDERS

The linear viscoelastic properties of asphalt binders are analyzed based upon two different methods: (1) nomograph and (2) dynamic mechanical analysis. The former one is an empirical procedure which has been used by paving technologists for a long time while the latter one is used to directly measure the dynamic response of materials. The application of viscoelasticity to asphalt cements is explained in terms of master curves. It is shown that data obtained from nomographs are inaccurate and misleading compared to measured data. Several models are further presented to predict the linear viscoelastic properties of asphalt binder and found that one of these models can be adequately used for asphalt binders.