Dynamic Modulus Master Curves Research Articles

Fast falling weight deflectometer as new tool to perform accelerated pavement testing

The development of the falling weight deflectometer (FWD) in the late 1970s made it possible to determine quickly the in situ modulus and critical stresses/strains in pavement structures, which are generally considered the most important input for the ‘mechanistic’ part of the mechanistic–empirical pavement design method. In 2015, the newly designed FastFWD was released and provided the opportunity to speed up the testing procedure and overall productivity significantly. The increased rate of loading prompted the current study into the possibility of performing in situ accelerated pavement testing to predict pavement deterioration, and to fill the gap between the heavy vehicle simulator and small-scale laboratory test methods. Numerous experimental sequences and test sites have been initiated since the start of the research; in the last of these, 1·6 million load applications were applied and the dynamic modulus master curve was back-calculated and used to filter out the viscoelastic response of the asphalt layer caused by temperature changes within the material from the repeated loading. Based on the findings of this research, an incremental-recursive fatigue model has been used to predict accurately the reduction in asphalt modulus as a function of any combination of loads and temperatures for a known material.

Laboratory investigation on chemical and rheological properties of bio-asphalt binders incorporating waste cooking oil

Recent efforts are being conducted to develop alternative asphalt binders from various bio-mass resources for future flexible pavements construction due to their renewability and the increasing costs of conventional petroleum-based asphalt. The objective of this paper is to investigate the potential of using the waste cooking oil (WCO) based bio-oil as a modifier for petroleum based neat asphalt binder and Styrene-Butadiene-Styrene (SBS) modified binder by means of chemical and rheological approaches. A series of tests were conducted for such purpose, including the infrared spectroscopy test, frequency sweep rheological test, multiple stress creep recovery test, and linear amplitude sweep test. The infrared spectroscopy results indicate identical chemical functional groups between the bio-oil and the petroleum asphalt binder though acid, ether, ester and alcohol compounds were also observed within the bio-oil. The bio-oil modified binders display increased carbonyl index with increasing the bio-oil percent weight whereas the sulfoxide index almost exhibits the same level as that of the control asphalt. Frequency sweep tests show that the bio-oil addition obviously decreased the binder stiffness according to the dynamic shear modulus master curve. Due to this softening effect from the bio-oil modifier, the weakened rutting resistance of bio-binders are demonstrated for both neat and SBS binders at the high temperature range. The fatigue life of bio-binders at intermediate temperature under cyclic fatigue loading are found to be significantly improved by increasing bio-oil content but the binder yield energy simultaneously decreased. It can be preliminarily concluded that the WCO based bio-oil tested in this study could be used as a potential bio-modifier to produce a sustainable asphalt binder.

Time-temperature-aging-depth shift functions for dynamic modulus master curves of asphalt mixtures

Oxidative aging is one of the significant environmental effects on asphalt pavement performance. This study aims to characterize the aging viscoelastic property of asphalt mixtures such as dynamic modulus at different aging times and pavement depths, then develops two aging shift functions to account for the effects of long-term aging and non-uniform field aging in the pavement depth. Tensile creep test and direct tension test are conducted on 12 laboratory-mixed-laboratory-compacted (LMLC) asphalt mixtures with three laboratory aging times and 16 field-aged asphalt mixtures with four field aging times, respectively. The dynamic modulus of LMLC mixtures is determined from the tensile creep test and the elastic–viscoelastic correspondence principle is utilized to obtain the dynamic modulus of field-aged asphalt mixtures from the direct tension test. The dynamic modulus master curves of the asphalt mixtures at different aging times and pavement depths are constructed using the modified Christensen-Anderson-Marasteanu (CAM) model. It is shown that both of the rheological index and glassy modulus increase with aging time and the crossover frequency decreases with aging time. The long-term aging shift function is determined as a function of aging time, acceleration factor, activation energy, and aging temperature. The depth shift function is determined as a function of pavement depth. With the aid of the two aging shift functions, it becomes possible to construct a single dynamic modulus master curve after taking into account the effects of temperature, long-term aging, and non-uniform aging with pavement depth below the surface.

Development of dynamic modulus master curves of in-service asphalt layers using MEPDG models

The new mechanistic-empirical pavement design guide (MEPDG) uses a combination of field and laboratory tests for structural analysis of in-service pavements. In this guide, asphalt dynamic modulus (|E*|) is one of the most important parameters used in flexible pavement design and rehabilitation approaches. This paper evaluates the validity of dynamic modulus models used in MEPDG for in-service asphalt pavements. For this purpose, nine asphalt pavement sites with various structural, ages and conditions were selected in Khuzestan and Kerman provinces in southern regions in Iran. At each site, falling weight deflectometer data, resilient modulus (determined from the cored samples) and surface condition data were collected. These three sets of data are necessary to compute damages at input levels of 1, 2 and 3 in MEPDG, respectively. Core samples were extracted, and mix volumetric properties as well as their binder characteristics were determined. Viscosity-based NCHRP 1-37A (Witczak) and G*-based NCHRP 1-40D (Modified Witczak) dynamic modulus predictive models were incorporated into these three input levels and six combinations of in situ |E*| master curves were developed. Analysis of the results indicates a weak correlation between field backcalculated moduli and those measured in laboratory. Hence, application of both field and laboratory moduli is not necessarily a good approach to determine damages, and the MEPDG proposed method would better be modified. Validation of MEPDG models showed that the NCHRP 1-37A model predicts dynamic modulus master curves with lower errors rather than the NCHRP 1-40D model. In addition, using the NCHRP 1-37A model at input level 1 would be a better approach among the others to evaluate both new and rehabilitated asphalt layers. Results will also be useful for local agencies in implementation of American Association of State Highway and Transportation Officials (AASHTO)mechanistic-empirical pavement design procedure in various climatic conditions.

Experimental study on rheological characteristics and performance of high modulus asphalt binder with different modifiers

The fundamental material for production of high-modulus asphalt (HMAC) is high modulus asphalt binder (HMAB), which is normally manufactured from hard-grade asphalt, rock asphalt modification, and polyolefin modification. This paper investigated rheological properties and performance of HMAB as compared to Styrene-Butadiene-Styrene (SBS) modified binder and neat binder using comprehensive laboratory performance tests. Specifically, the performance of HMAB modified with two different high modulus additives, rock asphalt (RA) and polyolefin (PR), were compared. The performance indicators include linear viscoelasticity characterized by temperature sweep and frequency sweep tests, rutting resistance by multiple-stress creep recovery (MSCR) test, and fatigue resistance by linear amplitude sweep (LAS) test. The effects of high-modulus modifier on master curve of dynamic shear modulus of HMAB were found identical. The temperature dependencies of asphalt binder were found to be significantly dependent on the material source of neat binder. However, the rutting resistance of HMAB modified by rock asphalt and polyolefin is better than that of SBS modified binder and neat binder. The polyolefin modified HMAB showed better rutting resistance than rock asphalt modified HMAB; while the comparison results was opposite for fatigue resistance. The simplified viscoelastic continuum damage (S-VECD) theory was employed to interpret the LAS test results for fatigue life prediction of asphalt binder. The SBS binder showed the best fatigue performance followed by HMAB and neat binder.

Erratum for “Improving the Accuracy of Dynamic Modulus Master Curves of Asphalt Mixtures Constructed Using Uniaxial Compressive Creep Tests” by Rong Luo and Hanqi Liu

Erratum for “Improving the Accuracy of Dynamic Modulus Master Curves of Asphalt Mixtures Constructed Using Uniaxial Compressive Creep Tests” by Rong Luo and Hanqi Liu

Dynamic modulus test and master curve analysis of asphalt mix with trapezoid beam method

In order to study dynamic mechanical properties of asphalt mix under two-point bend load, and the impact of load level to dynamic modulus, trapezoid beam method is employed to conduct dynamic modulus tests on asphalt mix SAC13 (Stone Asphalt Concrete with nominal maximum aggregate size 13 mm). Impacts of temperature, frequency and asphalt material on dynamic modulus and phase angle are analysed: dynamic modulus decreases as temperature increases or frequency decreases, while phase angle increases as temperature increases or frequency decreases. SBS polymer modifier can improve mechanical property of asphalt material, as a result, improve pavement performance of asphalt mix. Master curve of dynamic modulus is plotted based on temperature–time superposition principle, using non-linear least square fitting method. Shifting factor lg(αT) is calculated, and master curve of phase angle is also plotted. Influence of load level to dynamic modulus is investigated, two components regressed equation of dynamic modulus is conducted and master surface of dynamic modulus is constructed. The dynamic mechanical and viscoelastic property of asphalt mix is analysed.

Application of FWD data in developing dynamic modulus master curves of in-service asphalt layers

This paper presents a simple method to determine dynamic modulus master curve of asphalt layers by con­ducting Falling Weight Deflectometer (FWD) for use in mechanistic-empirical rehabilitation. Ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in Khuzestan and Kerman provinces in south of Iran. FWD testing was conducted on these pavements and core samples were taken. Witczak prediction model was used to predict dynamic modulus master curves from mix volumetric properties as well as the bitumen viscosity characteristics. Adjustments were made using FWD results and the in-situ dynamic modulus master curves were ob­tained. In order to evaluate the efficiency of the proposed method, the results were compared with those obtained by us­ing the developed procedure of the state-of-the-practice, Mechanistic-Empirical Pavement Design Guide (MEPDG). Re­sults showed the proposed method has several advantages over MEPDG including: (1) simplicity in directly constructing in-situ dynamic modulus master curve; (2) developing in-situ master curve in the same trend with the main predicted one; (3) covering the large differences between in-situ and predicted master curve in high frequencies; and (4) the value obtained for the in-situ dynamic modulus is the same as the value measured by the FWD for a corresponding frequency.

The advantages of using impact resonance test in dynamic modulus master curve construction through the abbreviated test protocol

Asphalt concrete behavior is heavily dependent on temperature and loading rate. Hence, the material is typically tested at a range of temperatures and loading frequencies to capture its properties. Results are then used to develop a master curve exhibiting material behavior at the full spectrum of loading frequencies. An abbreviated testing protocol, under AASHTO PP 61-13, proposes a practical approach for development of this master curve. In this practice, the low temperature asymptote of the master curve is dominated by the limiting maximum modulus estimated through the Hirsch model. In this study, the dynamic modulus (DM) testing coupled with impact resonance (IR) test was used to evaluate the effect of this limiting maximum modulus on construction of the asphalt concrete master curve. Three different asphalt mixtures prepared with the same gradation and binder content, but different grades of stiffness were tested. The DM testing was performed at multiple temperatures and loading frequencies. The IR tests were conducted on the same specimens at the same temperatures. Two sigmoid functions (MEPDG and Richards models), and three shift factors (Arrhenius, Williams–Landel–Ferry, and polynomial) were utilized in the analysis. Richards sigmoid function coupled with polynomial shift factor provided the best fitting accuracy to the measured data. It was observed that the limiting maximum modulus obtained from experimental data was underpredicted by that obtained from the Hirsch model. The results indicated potential benefits of the IR test as a complementary testing tool to the abbreviated DM testing protocol to reliably characterize asphalt concrete.

Unique liquid-to-solid transition of carbon filler filled polystyrene melts

Nanoparticle reinforcement beyond the hydrodynamics regime has been predominantly assigned to filler networking effect. Herein a unique hydrodynamics-to-nonhydrodynamics transition has been disclosed by creating master curves of relative dynamic modulus as a function of scaled frequency. Such conclusion is drawn for polystyrene filled with four different carbon fillers, i.e., carbon black, fullerene, multi-walled carbon nanotubes and graphite nanoplatelets. Additional rheological contribution of the filler phase beyond the hydrodynamics regime disclosed is sensitive to the filler type. The study may provide guidance for fundamental researches on the simultaneous reinforcement and dissipation of composites varying with filler topology.

Improving the Accuracy of Dynamic Modulus Master Curves of Asphalt Mixtures Constructed Using Uniaxial Compressive Creep Tests

Uniaxial monotonic or constant loading tests have been used to efficiently construct master curves of the magnitude and phase angle of the complex modulus of asphalt mixtures. However, when using monotonic or constant tests, the test data fitting model and time-temperature shift factor equation were usually arbitrarily chosen to construct the master curves, which were not validated at all or were validated using only a couple of data points. This study developed a composite test protocol consisting of uniaxial compressive creep tests to construct the master curves and dynamic modulus tests to validate the constructed master curves of the magnitudes of the complex moduli of asphalt mixtures. The loading force and duration were carefully chosen for each test segment to assure that the test specimen was retained in the linear viscoelastic stage during the entire test protocol. Commonly used data fitting models and time-temperature shift factor equations were compared, respectively, when constructing and validating the master curves. The Prony series model was determined to be the best fitting model for the creep strains because it not only provided satisfactory modeling accuracy but also complied with the actual material properties of asphalt mixtures. The Williams–Landel–Ferry (WLF) equation was demonstrated to be the most appropriate time-temperature shift factor equation because the master curve constructed with the WLF equation made the most accurate predictions in a fairly wide range of frequencies. This study refined the master curve construction method for asphalt mixtures using uniaxial monotonic or constant loading tests. With properly selected and validated data fitting model and time-temperature shift factor equation, the constructed master curve had the capability of accurately predicting the magnitude of the complex modulus in a wide range of loading frequencies with an R2 value of approximately 0.97 or higher.

Evaluation of fundamental viscoelastic functions by a nonlinear viscoelastic model

In this work, a new constitutive equation for the description of the nonlinear viscoelastic response of polymeric materials is presented, by proposing modifications on a model developed in previous works. This time‐dependent equation has been derived on the basis of transient model, and a new assumption regarding the kinetics of active molecular chains due to the imposed deformation. The present treatment was proved to be more flexible, given that it contains a relaxation function that has been derived by considering, instead of first‐order kinetics, a fractional derivative that controls the rate of molecular chain detachment from their junctions. It has been further explored that the potential of this equation to be employed for the evaluation of the dynamic modulus master curve, once the experimental data of the compliance modulus of a polymeric structure have been matched. POLYM. ENG. SCI., 57:1389–1395, 2017. © 2017 Society of Plastics Engineers

Study on the Change Laws of Dynamic Modulus of Asphalt Mastic with Different Framework Types

In order to study the change laws of dynamic modulus with different framework types under different frequencies and temperatures and obtain the dynamic moduli with wider frequency ranges and temperature ranges, asphalt mastic specimens through removing coarse aggregates in AC-13, SMA-13 and OGFC-13 asphalt mixture were prepared. The dynamic moduli with different frequencies and temperatures were measured by simple performance tests, and the master curves of dynamic modulus of asphalt mastics were acquired by the time-temperature equivalence principle. The results show that the dynamic moduli of asphalt mastic increase with the increase of load frequencies under the same temperature, and the dynamic modulus order is AC- 13>SMA-13>OGFC-13. In addition, the dynamic moduli of asphalt mastic decrease when the temperatures rise. The dynamic moduli with wider frequency and temperature ranges are obtained from the master curves of dynamic modulus of asphalt mastic.

Individual temperature based models for nondestructive evaluation of complex moduli in asphalt concrete

The rheological properties of bituminous materials play important roles in the selection of paving materials, and analysis and design of asphalt pavements. The series of models developed in this study are composed of five formulations for the creation of the dynamic modulus mastercurve at a wide range of testing temperatures. The predictability of these models is assessed by comparing the predicted dynamic modulus mastercurves of different mixtures with measured ones from a nondestructive impact resonance (IR) test. This assessment shows that the predictions match the dynamic modulus values measured from different techniques with a good level of accuracy.

Effect of Polymer Fibres Reinforcement on Selected Properties of Asphalt Mixtures

The paper presents selected results of the research program concerning fibre reinforced asphalt concrete. Aramid-polyalphaolefin fibres was used in this study. Selected properties responsible for low temperature cracking and resistance to permanent deformation are presented in this paper. Low temperature cracking susceptibility was evaluated with the results obtained from bending test of rectangular beams with constant rate of deformation and semi-circular bending test based on fracture mechanics theory. Performance in high temperatures was assessed by master curves of dynamic modulus. Obtained results indicated that evaluated fibres can improve low temperature pavement performance.

Evaluation of Small Specimen Geometries for Asphalt Mixture Performance Testing and Pavement Performance Prediction

The use of small specimen geometries in asphalt mixture performance testing to enable the testing of as-built pavement layers has been gaining attention in recent years. Small specimens could also improve the testing efficiency of laboratory-fabricated specimens by allowing the extraction of multiple test specimens per gyratory-compacted sample. Rigorous assessment of the small specimen geometries is required before the use of such geometries is standardized. In this study, small specimens were evaluated for dynamic modulus and simplified viscoelastic continuum damage fatigue. Three specimen geometries (100-mm- and 38-mm-diameter cylindrical specimens and 25- × 50-mm prismatic specimens) were compared by using five mixtures with a nominal maximum aggregate size (NMAS) ranging from 9.5 to 25.0 mm. The results show that the dynamic modulus and phase angle master curves agreed at low and intermediate temperatures, regardless of the NMAS values of the mixture. At the high temperature, the small specimen dynamic modulus values were slightly higher and the phase angle values were slightly lower than those of the large specimens. The specimen-to-specimen variability for the large and small specimens was comparable. The fatigue test results for the mixtures evaluated were comparable, except for the 25-mm mixture, which proved problematic in the testing of both small and large specimens. Pavement performance was predicted by the layered viscoelastic analysis for critical distresses program by using the test results for the small and large specimens. These results suggest that specimen geometry had a minimal effect on pavement fatigue damage predictions, which indicates promise for the use of small specimen geometries in practice.

Effect of SBS and HDPH polymer on rheological properties of asphalt

ABSTRACTThe present work discusses the combined effect of High Density Polyethylene Homo polymer and Styrene-Butadiene-Styrene on properties of Viscosity Grade 30 asphalt commonly used in India. Six blends of binders were prepared using varying percentages of both polymers and were evaluated for rheological properties. Use of both polymers leads to higher viscosity, while blending with HDPH polymer only leads to marginal increase in viscosity when compared to unmodified binder. Comparison of dynamic modulus and phase angle master curves indicated, significant differences were found among master curves obtained with different aging conditions when compared to unaged condition especially at lower reduced frequencies.

Performance evaluation of stone matrix asphalt using indonesian natural rock asphalt as stabilizer

One type of road pavement material which is developed to be more resistant to permanent deformation is the SMA (Stone Matrix Asphalt). Utilization of the SMA mix in Indonesia has constraints in gain stabilizer and also difficulty to comply the gradations, mainly because it needs a relatively large amount of filler. Alternative of local materials that can be used is asbuton (natural rock asphalt from Buton Island). Asbuton is expected to act as a stabilizer and simultaneously provides an additional filler. The objective of this research is to evaluate the performance of the SMA that uses the asbuton. The methodology used in this research is the experimental method, its starts from material testing, design mix and performance testing that includes dynamic modulus, permanent deformation and fatigue resistance. The results obtained showed asbuton can prevent asphalt draindown as well as increase the proportion of filler. Draindown asphalt can be prevented by using binder absorbers with fiber cellulose and viscosity boosters with asbuton. Asbuton (LGA 50/25) can behave as a stabilizer as well as cellulose fiber. Addition of asbuton also improves the performance of the SMA mix, as shown with increase in the value of dynamic stability. In terms of resistance to fatigue, SMA with cellulosa as stabilizer and SMA with asbuton as stabilizer, relatively have the same performance. Master curve of dynamic modulus indicates SMA with asbuton as stabilizer is relatively stiffer at high temperatures (more than 4.4°C), but relatively less stiff (less brittle) at low temperatures.

Maneuvering MEPDG Input Variables to Improve Level-3 and Level-2 Mastercurve Predictions to the Accuracy of Level-1 Input Hierarchy

Abstract In this study, mix and binder input variables were optimized to investigate the problems related to the accuracy of mastercurves developed using Mechanistic Empirical Pavement Design Guide (MEPDG). Dynamic modulus testing over a wide temperature and frequency range was performed on Superpave mixes typically used for structural and surface coarse pavement construction by New Mexico Department of Transportation (NMDOT). Dynamic modulus mastercurves were produced using the MEPDG software and using Microsoft Excel for the actual test data. Mastercurves developed using actual test results were compared with mastercurves produced using MEPDG software at level-1, level-2, and level-3 input hierarchies. Finally, mix and binder input variables were optimized to determine appropriate shift factors to improve accuracy of mastercurves developed at level-2 and level-3 input hierarchies. The results show that mastercurves developed using level-1 input hierarchy accurately represent the test results. However, all predicted mastercurves at level-2 and level-3 input hierarchies underpredict actual test results and level-3 prediction results showed better accuracy than level-2 outputs for all mixes in this study. The MEPDG software was also re-run to predict mix mastercurves using optimized (shifted) input values and the resulting mastercurves from level-3 and level-2 MEPDG input hierarchies were found to overlap with mastercurves produced using level-1 MEPDG input hierarchy. Optimized mix input values suggest that aggregate variables can be eliminated from the E* model.

Mechanistic-Empirical Analysis of Asphalt Dynamic Modulus for Rehabilitation Projects in Iran

In the Mechanistic–Empirical Pavement Design Guide (MEPDG), dynamic modulus of asphalt mixes is used as one of the input parameters in pavement analysis and design. For in-service pavements, MEPDG method uses a combination of some field and laboratory tests for structural evaluation of asphalt layers in rehabilitation projects. In this study, ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in provinces of Khuzestan and Kerman in the south of Iran. These provinces are known as hot climate areas and have severe climatic conditions. At each site, Falling Weight Deflectometer (FWD) testing was conducted and core samples were taken. These samples were extracted and mix volumetric properties and binder characteristics were determined. Results of these tests were used as input parameters in Witczak dynamic modulus prediction model for determination of MEPDG undamaged dynamic modulus master curves. Finally, the damaged (in-situ) dynamic modulus master curves were developed upon modifying the undamaged master curves with the damage factors determined from back calculation analysis of FWD data. It was found that with the above mechanistic-empirical procedure, it would be possible to successfully evaluate in-service asphalt layers located in severe climatic areas.