Rheological Properties Of Asphalt Mixtures Research Articles

Evaluation of rheological and mechanical properties of hot and warm mix asphalt mixtures containing Electric Arc Furnace Slag using gyratory compactor

Workability and compactability are two key rheological properties of asphalt mixtures with direct impacts on pavement construction costs. These properties can be estimated by laboratory testing using the Superpave Gyratory Compactor (SGC). The compaction curves obtained from SGC can offer a general assessment of the workability, compactability, and even mechanical properties of asphalt mixtures. The most widely used workability and compactability indicators derived from these curves are the Workability Index (WI), Compaction Energy Index (CEI), Traffic Densification Index (TDI), and the slope of the semi-logarithmic compaction curve (k). In this study, these indicators were used to examine the workability, compactability, and mechanical properties of hot and warm mix asphalt (HMA and WMA) mixtures containing different amounts of Sasobit (0, 1.5, and 3%) and Electric Arc Furnace Slag or EAFS (0, 25, 50 and 75%) with two aggregate gradations (upper limit and middle range of Iran Highway Asphalt Paving Code No. 234). The results showed a decline in workability and compactability with the increase in EAFS content and also with the introduction of 1.5% Sasobit which was respectively caused by the high surface roughness of EAFS materials and the lack of sufficient workability by 1.5% sasobit at the mixing and compaction temperatures. However, the compactability of HMA mixtures with 3% Sasobit was comparable to that of HMA mixtures. Given the correlation between TDI and rutting resistance, experiential TDI values were used to develop a regression model for Flow Number (FN) estimation. The analysis of the variance of experimental results showed the significance of changes observed in the indicators. The study's findings demonstrated that, due to the high surface roughness of EAFS materials, the amount of additive and mixing and compaction temperatures should be chosen in accordance with the mixture's required workability and compactability. The TDI index can also be used to approximate the mechanical properties of asphalt mixtures during the initial stages of preparing laboratory specimens.

Rutting prediction of asphalt pavement with semi-rigid base: Numerical modeling on laboratory to accelerated pavement testing

Rutting development and its prediction are critically important for the long-term preservation of semi-rigid pavements. A multi-scale test was developed to analyze the rutting development and its prediction model, involving triaxial, scaled loading, and full-scale loading tests. Laboratory-based triaxial tests predicted the rheological properties of asphalt mixtures at high temperatures. The flow number FN was only related to the cohesion and internal friction angle, confining pressure, and circulating pressure of the mixture. Rutting prediction models were established using a modified Burgers finite-element model and verified through scaled and full-scale loading tests. The relationship between FN of the dynamic creep test and loading times of scaled and full-scale loading test were determined through comparative analysis. Finally, the cross-scale relationship between the multi-scale tests was established by introducing correction coefficients K1 and K2. The proposed prediction model of rutting development is suggested to be computationally reasonable, which could provide a scientific reference for the treatment and maintenance of rutting on asphalt pavements.

Investigation of rheological properties of asphalt mixtures containing polymer waste.

The objective of this study was to evaluate the rheological performance of rubberised asphalt binder with varying dosages of crumb rubber (CR), and compare these modified materials with unmodified asphalt binder. It is very important to investigate the characterization of chemical structures of the asphalt binder from a closer view for useful modifications of the virgin binder by polymer waste as modifiers. The current research employed a thin layer chromatography technique (TLC) to separate and determine the different fractions in asphalt. Nuclear Magnetic Resonance (NMR) spectroscopy was also used to characterize and confirm the chemical compositions of asphalt and its fractions. Despite of NMR spectra of asphalt is difficult to be interpreted via its structural complexity, but this technique is still able to provide useful data especially with regard to asphaltene fraction. Crumb rubber is a polymer waste which used as modifier of asphalt binder via the economic benefits and improving the rheological properties of modified asphalt binder. The rubberised asphalt binders were produced by blending the virgin asphalt with CR at various contents (3%, 5%, 10%, 15% and 20%). The effects of CR contents on the rheological behaviors of modified asphalt binder have been investigated including: penetration, softening point, ductility. Furthermore, morphological analysis of rubberised asphalt was conducted via scanning electron microscopy (SEM) to assess the effect of CR on the binder morphological structure. Based on results obtained, binder with highest CR content showed improvement in rheological properties of the modified binders in terms of decreasing in penetration, increasing in softening point values and keeping the ductility higher, unlike other CR contents which exhibited poor performance of modified asphalt.

A Dynamic Semi-Circular Bending Configuration for the Rheological Characterization of Asphalt Mixtures

Many experimental procedures have been proposed for the determination of the rheological properties of asphalt mixtures. Among them, the indirect tensile test (ITT) has gained a lot of attention because of its relative simplicity and advantages. However, a biaxial state of stress is developed into the sample and then, the Poisson ratio must be estimated or measured for the calculations of the dynamic modulus. Looking for a testing configuration with the same simplicity and advantages, this paper proposes the Semi-Circular Bending (SCB) geometry with dynamic loading conditions in order to characterize the rheological properties (dynamic modulus and phase angle) of asphalt mixtures. Samples compacted in the laboratory or cored from in-service pavements can be used. A uniaxial state of stress is developed in the lower plane surface of the sample doing negligible the influence of the Poisson ratio on the dynamic modulus calculations. A specific experimental configuration was adopted and a 2D-FEM model has been used for the development of an equation for the calculation of the dynamic modulus. Two different asphalt mixtures were tested at diverse testing temperatures and loading frequencies. The obtained results have been analyzed and compared with those acquired with the more conventional testing configuration in uniaxial compression. An excellent agreement has been found for either the dynamic modulus or the phase angle with both sets of results. It could be concluded that the SCB configuration has been validated as a simple and promising methodology for the characterization of the viscoelastic response of asphalt mixtures.

Effect of Evotherm-M1 on Properties of Asphaltic Materials Used at NAPMRC Testing Facility

Abstract Rheological properties of asphalt binders significantly affect distress development and performance of asphalt concrete materials. This article presents the effect of Evotherm-M1 modifications on rheological properties of asphalt binders used in the construction of test sections at the Federal Aviation Administration’s National Airport Pavement & Materials Research Center. Four different binders (i.e., polymer styrene butadiene styrene [SBS]-modified PG 76-22, PG 64-22, SBS-modified PG 76-22 plus Evotherm-M1, and PG 64-22 plus Evotherm-M1) are studied. Multiple stress creep recovery (MSCR) and strain-controlled frequency sweep (FS) test results are analyzed to construct the master curves for the binders. Results indicate high sensitivity of SBS-modified PG 76-22 to Evotherm-M1 modifications as compared with PG 64-22. Subsequently, the results of dynamic modulus tests conducted on asphalt mixture specimens (prepared using job mix formula and different binders) are analyzed to investigate the effect of binder type and modification on rheological properties and rutting performance of asphalt mixtures. It is shown that the rutting resistance and rheological properties of asphalt mixtures can be ranked based on the results of MSCR and FS tests conducted on asphalt binders. It is shown that the rutting resistivity of traffic test sections and lab-tested asphalt mixtures can be ranked as follows: SBS-modified PG 76-22, SBS-modified PG 76-22 plus Evotherm-M1, PG 64-22, and PG 64-22 plus Evotherm-M1. This is consistent with the results obtained for tested asphalt binders.

The Evaluation of Mechanical Rheology on Rubber Asphalt Modification

Scientifically natural rubber can be used as an asphalt modifier. Natural rubber production in Indonesia is dominated by crumb rubber products. Based on the technology developed by the addition of natural rubber can improve the rheology properties of asphalt. Therefore, this research used SIR 20 crumb rubber by evaluating the mechanistic rheological properties of asphalt mixtures. The purpose of this research to analyze of effect adding crumb rubber to asphalt Pen 60/70 toward the mechanistic rheology parameters to analyze the bitumen stiffness modulus (E *) that occurs with rubber modified asphalt.In order to obtain optimum levels of addition of rubber into asphalt pen 60/70. The method of this research was carried out in two stages, the first was to make a mixture of Pen 60/70 asphalt and crumb rubber on a variation of crumb rubber content, namely 0%, 4%, 6%, 7%, 8%, 9%, 10%, and 20 % while the second is to test the mechanical rheological properties performed with a Dynamic Shear Rheometer (DSR). The results of this study indicate that the value of Bitumen Stiffness Modulus (E *) has decreased in line with the addition of SIR 20 Crumb Rubber content. The optimum level of addition of SIR 20 crumb rubber is on adding 9% of SIR 20 crumb rubber content to asphalt pen 60/70.

Experimental Study on the Phase Transition Characteristics of Asphalt Mixture for Stress Absorbing Membrane Interlayer

Asphalt mixtures used in stress absorbing membrane interlayers (SAMIs) play a significant role in improving the performance of asphalt pavement. To investigate the rheological properties and phase transition characteristics of asphalt mixtures used in SAMI with temperature changes, twenty-seven candidate mixtures with different binders, gradation types and binder contents were selected in this research. During the study, dynamic mechanical analysis method was employed to evaluate their temperature-dependent properties and a series of wide-range temperature sweep tests were conducted under a sinusoidal loading. Some critical points and key indexes from the testing curves such as glass transition temperature (Tg) can be obtained. Test results show that phase transition characteristics can better reflect the rheological properties of asphalt mixtures at different temperatures. Crumb rubber modified asphalt mixtures (AR) provide a better performance at both high and low temperatures. Additionally, the range of AR asphalt mixtures’ effective functioning temperature ΔT is wider, and the slope K value is greater than the others, which indicates that AR asphalt mixtures are less sensitive to temperature changes. Additionally, gradation type and asphalt content also influence the properties: finer gradation and more asphalt content have a good effect on the low-temperature performance of the asphalt mixtures; while mixtures with a coarser gradation and less asphalt content perform better at high temperature and they are less sensitive to temperature changes. Finally, AR asphalt mixture is more suitable to be applied in the SAMI due to its phase transition characteristics from this method.

Laboratory evaluation of the composition of nano-clay, nano-lime and SBS modifiers on rutting resistance of asphalt binder

The physical and rheological properties of asphalt mixtures affect pavement performance at high and low ambient temperatures, and thus can affect the final performance of the mixture. Adding modifiers such as polymers and nano additives to improve asphalt mixture performance has become popular in recent years. The purpose of this study is to modify the bitumen with nano-clay, nano-lime and Styrene-Butadiene-Styrene (SBS). PG 64-22 bitumen was modified using 2, 4 and 6 wt% of nano-clay and the results showed that increasing the nano-clay to the base bitumen improved the rheological properties and rutting resistance of asphalt binder. Also, it was examined the effect of adding 3% SBS to the bitumen sample, and the results indicated a positive effect of this additive, especially at lower temperatures. In the next step, bitumen was modified using 4 and 6 wt% of nano-lime and 3% SBS with 4 and 6 wt% of nano-clay in combination with the base bitumen and tested to evaluate the combined effect of these three materials. The effect of this modifier on reducing rutting failure was evaluated compared to the control sample. To this end, we evaluated the effect of these materials on the rheological properties of bitumen by performing multiple stress creep recovery (MSCR) test by Dynamic Shear Rheometer (DSR). Results showed that increasing the nano-clay to the base bitumen improved the rheological properties and rutting resistance of asphalt binder and best improvement is achieved with 6%. The effect of 3% SBS although did not produce results similar to nano-clay, but the results showed significant improvement in bitumen properties. Finally, the best combination in this study was a combination of 3% SBS, 4% nano-clay, and 6% nano-lime, which yielded good results.

Exploring master curve parameters to distinguish between mixture variables

It is well known that mixture variables such as binder grade, aging state, recycled binder ratio, and recycling agent type and dose alter the rheological properties of asphalt mixtures. The ability to understand these changes in rheological properties caused by changes in the mixture variables is beneficial to know how to change the mixture variables to impact/improve performance. Rheological evaluation can be employed through linear viscoelastic characterisation in the form of dynamic modulus and phase angle master-curves. This study investigated the ability of dynamic modulus and phase angle master-curve parameters to capture the changes in mixture properties by performing a comprehensive statistical analysis of 74 mixture variable combinations. Evaluated parameters included the mixture Glover-Rowe parameter, inflection point frequency (–β/γ), difference between the glassy modulus and the inflection point modulus (γ), –β/γ versus γ, and the lower and upper asymptotes of the sigmoidal master-curve. The effect of changes in mixture variables on master-curve parameters are qualitatively compared to expected mixture field cracking performance as well. Aging and low- and high-temperature performance grades exhibited a strong negative correlation to mixture G-Rm and –β/γ parameters whereas a strong positive relationship was exhibited to the γ parameter indicating the negative impact of increase in these parameters on cracking performance.

Impacts of Aggregate Morphological Characteristics on Asphalt-Mixture Performance During Mixing

Abstract This paper presents an experimental approach to investigate the influence of aggregate morphological characteristics on rheological properties of asphalt mixtures during mixing. Three different types of natural aggregates (limestone, gneiss, and basalt) and three types of glass aggregates (sphere, cuboid, and triangular prism shapes) were selected in the analysis. Digital image processing was applied to quantify geometrical features of aggregate, such as sieving diameter, shape index, and angularity. A mixing rheometer was developed for testing the rheological property of mixture during mixing period. The correlation between aggregate geometrical features and mixing rheological property was analyzed. Results show that the rank of average shape index value is limestone 2>basalt>limestone 1>gneiss for different types of natural aggregates with the same size, whereas the rank of average angularity value is limestone 1>basalt>limestone 2>gneiss. It was found that during the mixing period, the effect of sieving diameter or shape index of aggregate on the K value (the slope of the rotate speed-torque diagram line) is linear, which means K value increases as sieving diameter or shape index increases. For analyzing the effects of aggregate geometrical features on the rheological property of asphalt mixture during mixing, the gray relational analysis method was applied. The results show that the rheological property of asphalt mixture during mixing stage is more sensitive to sieving diameter and shape index, but less sensitive to angularity of aggregate.

Low temperature rheological properties of asphalt mixtures containing different recycled asphalt materials

Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) are valuable materials commonly reused in asphalt mixtures due to their economic and environmental benefits. However, the aged binder contained in these materials may negatively affect the low temperature performance of asphalt mixtures. In this paper, the effect of RAP and RAS on low temperature properties of asphalt mixtures is investigated through Bending Beam Rheometer (BBR) tests and rheological modeling. First, a set of fourteen asphalt mixtures containing RAP and RAS is prepared and creep stiffness and m-value are experimentally measured. Then, thermal stress is calculated and graphically and statistically compared. The Huet model and the Shift-Homothety-Shift in time-Shift (SHStS) transformation, developed at the École Nationale des Travaux Publics de l'État (ENTPE), are used to back calculate the asphalt binder creep stiffness from mixture experimental data. Finally, the model predictions are compared to the creep stiffness of the asphalt binders extracted from each mixture, and the results are analyzed and discussed. It is found that an addition of RAP and RAS beyond 15% and 3%, respectively, significantly change the low temperature properties of asphalt mixture. Differences between back-calculated results and experimental data suggest that blending between new and old binder occurs only partially. Based on the recent finding on diffusion studies, this effect may be associated to mixing and blending processes, to the effective contact between virgin and recycled materials and to the variation of the total virgin-recycled thickness of the binder film which may significantly influence the diffusion process.

Impacts of aggregate geometrical features on the rheological properties of asphalt mixtures during compaction and service stage

To study the influence of aggregates geometrical features on the rheological properties of asphalt mixtures during compaction and service stage, asphalt mixtures with partially substituted aggregates were compacted by Superpave gyratory compaction (SGC), and their properties in service were measured by creep and dynamical modulus tests. The relation between rheological properties of mixtures and aggregate geometrical features was studied by gray relational analysis method. Results show that the rheological properties of mixtures during compaction and service stage are more sensitive to sieving diameter and shape index, but are less sensitive to angularity. The results indicate potential for using these parameters for quality control and quality assurance of asphalt mixture during production.

Rheological Properties of Asphalt Mixtures for Bridge Pavements

This paper presents the laboratory test results of rheological properties of asphalt mixtures for bridge pavements. The research plan included typically used asphalt mixtures - asphalt concrete (AC) and stone mastic asphalt (SMA). A new type of mixtures, SMA-MA, were also tested. These mixtures were tested for their stiffness in different temperatures and varied frequencies. The following parameters were identified - dynamic modulus and phase angle. The results of this research proved that these types of asphalt mixtures affect the viscoelastic properties and durability of bridge pavements.

Rheological Properties of Asphalt Mixtures with Additives Based on Renewable Sources

The deformational properties and fatigue of asphalt layers are important for the design and assessment of semi-rigid and flexible pavements. The Two-point Bending Test was used for determination of deformational characteristics of asphalt mixtures on Department of Construction Management in Žilina. The results are evaluated with the KATEMS assessment software. The long-term research leads to estimation of deformational characteristics and fatigue of different types of asphalt mixtures. The tests have shown a positive impact of additives (ground rubber, hydrate lime component, recycling materials,...) on the results of these mixtures. This article is focused on assessment of deformational properties and fatigue of selected types of asphalt mixtures, there are viscoelastic materials in construction of pavement.

Rheological properties of asphalt mixtures containing various fibers

Rheological characteristics of fiber-modified asphalt mixture were investigated. Cellulous fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosages were 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using superpave simple performance tester (SPT) was adopted to study the dynamic modulus and phase angle for the control mixture and fiber-modified ones at various temperatures and frequencies. Test results show that the rheological properties can be improved significantly by the addition of various fibers. The dynamic modulus increases with the increase of frequency, and the phase angle decreases with the increase of frequency. When various fibers are used, the dynamic modulus increases and phase angle decreases at each frequency. This indicates that the stiffness and the elastic portion of fiber-modified asphalt mixtures can be enhanced when various fibers are used, which results in the change of viscoelastic properties of mixtures. The creep test results show that the total strain and the permanent strain of asphalt mixtures during load-unload cycle can be significantly reduced, which results in the improvement of resistance to permanent deformation for asphalt mixtures containing various fiber additives. The Burgers model can be employed effectively to illustrate the rheological properties of fiber modified asphalt mixtures.

Aszfaltkeverékek reológiai tulajdonságainak vizsgálata

Aszfaltkeverékek reológiai tulajdonságainak vizsgálata