Dynamic Modulus Test Research Articles

Characterization and modelling of creep and recovery behaviour of waterborne epoxy resin modified bitumen emulsion

Bitumen emulsion has been widely used as the tack coat and surface treatment material for asphalt pavement. A major advantage of this material is it does not require heating during construction. However, it faces the concern of low mechanical strength, especially at high service temperatures. To improve the mechanical strength of bitumen emulsion, various research efforts have been made to use waterborne epoxy resin as a modifier to produce waterborne epoxy modified bitumen emulsion (WEB). To better understand WEB as a paving material, this study aims to investigate the microstructure and evaluate the high-temperature performance and model the creep and recovery behaviour of WEB residues. First, a confocal laser scanning microscopy was employed to investigate the fluorescence microstructure of the WEB residues. The temperature sweep dynamic shear modulus tests were then conducted to characterize the viscoelastic properties of the WEB residues within the temperature range of 4–76 °C, and multiple stress creep recovery (MSCR) tests at 50 °C, 60 °C and 70 °C were conducted to evaluate their high temperature performance. Then, the complex modulus was fitted with Arrhenius model and the activation energy was calculated; and the creep and recovery test results were modelled with both the power law model and generalized Burgers model. Finally, the average percent recovery and non-recoverable compliance were determined. It was found that the rutting resistance of bitumen emulsion can be dramatically increased by incorporating waterborne epoxy resin, and the creep and recovery behaviour of bitumen emulsion can be better fitted by the generalized Burgers model in comparison with the power law model.

Rutting Performance of Semi-Rigid Base Pavement in RIOHTrack and Laboratory Evaluation

Through a simple performance dynamic modulus test (SPT), standard rutting test, Hamburg rutting test, French rutting test and asphalt pavement analyzer rutting test, the rutting resistance of asphalt mixtures in the middle and lower courses of three semi-rigid base asphalt pavement of Beijing full-scale test track road in China was evaluated. The test results show that the rutting resistance of asphalt mixtures of the middle and lower courses can be greatly improved by using low-grade asphalt, especially 30# asphalt. The rutting resistance of SBS modified asphalt mixtures is also better. The SPT dynamic modulus test can indirectly characterize the rutting performance of the asphalt mixture. The rutting test results of a laser road detection vehicle and 3 m ruler show that the asphalt grade has a significant impact on the rutting performance of semi-rigid base asphalt pavement. Compared with 70# asphalt used in the middle and lower courses, the rutting resistance of the pavement structure can be improved by more than 20%. The result also show that the APA rutting test results can closely characterize the full-scale test track results, which is an optimal test method for evaluating the rutting performance of semi-rigid base asphalt pavement. The research results can provide a theoretical basis and reference for the rational design and rutting evaluation of semi-rigid base asphalt pavement.

Experimental Characterization of Viscoelastic Behaviors of Nano-TiO2/CaCO3 Modified Asphalt and Asphalt Mixture.

The purpose of this paper is to promote the application of nano-TiO2/CaCO3 in bituminous materials and present an experimental characterization of viscoelastic behaviors of bitumen and bituminous mixture modified by nano-TiO2/CaCO3. In this work, a series of viscoelastic behavior characterization tests were conducted, including dynamic shear rheometer (DSR) test for bitumen, uniaxial static compression creep test and dynamic modulus test for bituminous mixture. Moreover, various viscoelastic models with clear physical meanings were used to evaluate the influence of nano-TiO2/CaCO3 on the macroscopic performance of bitumen and bituminous mixture. The results show that bitumen and its mixtures are time-temperature dependent. The Christensen-Anderson-Marasteanu (CAM) model of frequency sweep based on DSR test indicated that adding nano-TiO2/CaCO3 can effectively capture the sensitivity of temperature. In addition, the incorporation of nano-TiO2/CaCO3 in bituminous mixture can significantly enhance the high-temperature anti-rutting, and slightly improve the low-temperature anti-cracking as well. At the same time, the modified Burgers model can accurately describe the viscoelastic behavior of bituminous mixtures in the first two creep stages, reflecting the consolidation effect of bituminous mixture. Also, the generalized Sigmoidal model can accurately grasp the characteristics of the relationship between dynamic modulus and reduced frequency and achieve good prediction effects in a wider frequency range.

Damage Evaluation of Poro-Elastic Road Surface with Low Polyurethane Content

Abstract This study aims to evaluate the damage evolution of poro-elastic road surface with low polyurethane content (PERS-LPC) subjected to cyclic loading with two new damage indicators. A cyclic loading test and dynamic modulus test were conducted on nine different PERS-LPC specimens to develop stress-strain hysteresis curves. The variations of curve perimeter (ΔP) and the enclosed area during the unloading period (ΔA) were proposed to evaluate damage evolution of PERS-LPC specimen as compared with the existing damage indicators. X-ray computed tomography scanning images were obtained to verify the damage evolution within PERS-LPC specimens. The results showed that damage evolution of the PERS-LPC specimen could be captured by the proposed ΔP and ΔA indicators. The PERS-LPC mixture with a low amount of rubber granule (25 %) and polyurethane (4 % by total mass of rubber and aggregate) and 20 % air void exhibited good damage resistance. The study findings can be used to optimize the composition of low-cost PERS-LPC mixtures for durable design.

Study on dynamic modulus of asphalt mixture in cold regionunder rotary accelerated loading

In order to study the evolution law of mechanical properties of asphalt pavement mixture in cold regions under long-term load, the rotary accelerated loading equipment was used to carry out a total of 500,000 accelerated loading tests on the full-scale pavement, and the dynamic modulus test of the mixture before and after wheel load was carried out respectively. The master curve of dynamic modulus and dynamic modulus ratio (dynamic modulus value after wheel load / dynamic modulus value before wheel load) of the mixture at -20ºC were established to predict the long-term mechanical response of the mixture at low temperature. The results show that: low-frequency (or high temperature) has a more significant effect on the viscoelastic properties of the asphalt mixture. In the conversion frequency range of 1.6×10–3~1.6×102 Hz, the dynamic modulus ratio decreases with the increase of frequency, and the maximum ratio is 0.62 when the frequency is 1.6×10–3 Hz, which indicates that the high frequency (low temperature) has little effect on the performance of asphalt mixture. This study can be used as a theoretical reference for the structural design and performance optimization of asphalt pavement in cold regions.

The Effect of Spent Fluid Catalytic Cracking Filler on Performance Testing of Asphalt Concrete Mixture

The spent fluid catalytic cracking (SFCC), waste from the petroleum industry, is nonstop increasing and causing environmental pollution in Vietnam. This study is an attempt to recycle SFCC in pavement construction. The study investigated the effect of SFCC, as a filler material in the hot‐mix asphalt (HMA), on the essential characteristics of the asphalt concrete mix. First, the optimum percentages of bitumen and SFCC rate were investigated based on the Marshall design method. The HMA with SFCC showed more enhanced stability, flow, and other Marshall properties than the asphalt concrete mixture with the optimum limestone filler of 5%. Besides, the effects of SFCC rates on Marshall characteristics were explored. Second, performance tests were conducted to compare the mix with the different optimum content fillers of SFCC, limestone, and Portland cement. The tests include wheel tracking, indirect tensile, fatigue, and dynamic modulus tests to evaluate the performance of HMA with SFCC. It was found that the asphalt mixture with the optimum SFCC filler content can enhance pavement performance and improve the rutting and cracking resistance of the asphalt pavement.

Effect of treated fibers on performance of asphalt mixture

In this study, a fiber surface treatment (coating technique) was developed using paraffin wax and warm-mix additive (WMA) to enhance fiber’s distribution throughout the asphalt mixture. Three types of fiber were examined, including WMA coated fiber, wax coated fiber, and uncoated fiber. The performance of fiber-reinforced mixtures was investigated by indirect tensile asphalt cracking test (IDEAL- CT), dynamic modulus, flow number, and overlay testing. Two mixing methods (e.g., dry and wet) were employed to determine the best mixing method. The promising results indicated the potential of incorporating warm-mix additive and fiber. Although Tukey-Kramer statistical analysis showed no significant difference between wet and dry mixing methods, the wet mixing method was recommended to mitigate the adverse mixing effects (e.g., fiber clustering, fiber sticking on the mixer). The insignificant difference between wax-coated fiber and uncoated fiber mixtures indicated the critical impact of coating materials on performance of reinforced asphalt mixture. Finally, mixtures containing 0.05% of WMA coated fiber suggest potential improvement in the performance of asphalt mixture, such as enhancing the cracking tolerance index (CTIndex), prolonging fatigue life, and exhibiting good resistance rutting.

Performance-based assessment of rutting resistance of asphalt mixes designed for hot climate regions

ABSTRACT In hot climate regions asphalt mixes can be designed using the classical volumetric approach supplemented by the evaluation of basic mechanical parameters. To minimize the risk of permanent deformation, composition of the mixes can be defined by selecting densely packed aggregates and low binder contents. Despite the effectiveness of such an approach, mix design systems need to be improved by including performance-based tests that focus on the evaluation of the true rutting potential of asphalt mixes. The investigation described in this paper addressed these issues by considering twelve rut-resistant asphalt mixes designed as per the requirements set in the State of Qatar. These mixes, containing neat and polymer-modified binders (PMBs), were subjected to the Hamburg Wheel-Track Test (HWTT), dynamic modulus test and flow number test. Analysis of experimental data led to tentative requirements set on the results of dry HWTTs that can be introduced in the mix design framework currently adopted in the State of Qatar. Calculation of rank correlation coefficients showed that the various tests can be employed in different conditions for the assessment of the true rutting potential of asphalt mixes.

Frequency adjustment method for in-situ seismic modulus of asphalt concrete

ABSTRACT In a mechanistic-empirical (ME) pavement design method, the modulus of asphalt concrete (AC) is essential. The in-situ AC modulus can be obtained by the surface wave method (SWM). However, the measured modulus needs to be adjusted to the design frequency values. This study aimed to propose a frequency adjustment method for the in-situ AC seismic modulus. For this purpose, coring and dynamic modulus tests, FWD (Falling Weight Deflectometer) tests, and PSPA (Portable Seismic Pavement Analyzer) tests were carried out in the accelerated pavement test (APT). The master curves generated by the dynamic modulus results correlated well with the moduli determined from the other tests. Based on this relationship, a frequency adjustment factor was developed for the seismic modulus of the undamaged AC layer. For the damaged AC layer, the proposed factor was modified by incorporating the effect of the damage. Finally, to validate the frequency adjustment factor, the measured maximum tensile strains in the APT were compared with the values determined from the adjusted seismic moduli. The results prove that the frequency adjustment factor is appropriate to obtain the design modulus from the surface wave test. The PSPA test is also recommended to obtain the in-situ AC seismic modulus.

Optimization of the pre-tension and separation distance for measurement of the dynamic elastic modulus and macromolecular orientation of a polypropylene monofilament via the sonic velocity method.

Using a fiber orientation degree measurement instrument (i.e., a dynamic modulus tester), 28 groups of averaged sonic pulse travel times in a polypropylene monofilament were measured and recorded under five pre-tensions across eight separation distances. The zero-time (or delay time) T0, sonic velocity C, sonic modulus E, Hermans orientation factor F, and orientation angle θ were calculated via two- and multi-point methods. The good agreement observed between the scatter plots of calculated data and the regression lines shows that the multi-point method provides reliable, accurate determination of the sonic modulus (or the dynamic elastic modulus) and the orientation parameters. Surprisingly, the zero-time for sonic pulse propagation depends significantly on the separation distance in practice, although it does not in theory. For easy and rapid measurement or relative comparisons using the two-point method, the optimal range of pre-tension is 0.1 gf/den-0.2 gf/den, and the optimal separation distances are 200 mm and 400 mm. The two-point method is appropriate for industrial applications, while because of its greater accuracy, the multi-point method is preferred for scientific research.

Effect of ethylene-vinyl acetate (EVA) on stone mastic asphalt (SMA) behaviour

Stone Mastic asphalt (SMA) has been of interest in research in pavement engineering. Different climates and load conditions sometimes dictate to use special products such as SMA. Due to traffic load and new developments, sometimes it is vital to develop new mixes with higher capabilities to withstand the loads. This study investigates the effect of Ethylene-Vinyl Acetate (EVA) on SMA fatigue and rutting behaviour. By application of wet techniques, EVA was blended with C320 binder and SMA mixes were prepared. EVA dosage was varied from 2% to 6%. A four-point flexural beam test, wheel rutting test, Schellenberg test, flow number test and dynamic modulus test were conducted on the mixes. The outcomes saw clear improvements in rutting resistance and the cycle to failure in four point bending test, was improved with increases in the percentage of EVA. The flow number also increased by increasing the EVA concentration. The drainage of bitumen was decreased by increasing the EVA concentration. Finally, the master curve relevant to each EVA concentration was plotted and compared. Phase angle of mixes also decreased by increasing the EVA percentage.

Investigation of the Impact of Deicer Materials on Thermodynamic Parameters and Its Relationship with Moisture Susceptibility in Modified Asphalt Mixtures by Carbon Nanotube

Road maintenance in winter is one of the road engineers’ concerns, especially asphalt specialists. As pavement frosts lead to road closures and accidents, one of the ways to prevent these events is spraying deicer materials on the pavement surface. Therefore, investigation of the impact of the deicer materials on asphalt is essential. So in this study, the effect of deicer materials on the moisture susceptibility of base asphalt mixtures and modified ones by carbon nanotube (CNT) was investigated utilizing penetration and softening point tests and surface free energy (SFE) concept and dynamic modulus (DM) test. Two common deicers CaCl2 and MgCl2 along with distilled water (DW) were used. Results indicated that using CNT increased the softening point and reduced the penetration degree of modified bitumens, which increased the penetration index amounts and improved the sensitivity of the samples against temperature variations. The SFE results showed that modifying bitumen with CNT led to an increase in adhesion free energy (AFE). The samples saturated in CaCl2 and modified with 1% CNT had the highest CFE values. The MgCl2 solution had less detachment energy, which reduced the energy of the system and stripping occurred sooner. Results of the DM test showed that CNT increased the wet-to-dry DM ratio in saturated conditions with deicer materials and DW, improving the resistance of the saturated mixtures to moisture. The GMDH model compared to the MVR method had higher accuracy and less error in prediction of stripping percentage with the R2 value of 99.46%.

Experimental investigation on the rutting resistance of permeable friction courses

This paper presents an experimental investigation on the rutting resistance of permeable friction courses (PFC). In practice, PFC are prone to permanent deformation due to heavy traffic loads and a weak mineral skeleton caused by their high air void contents. Consequently, the draining capacity of the PFC is diminished making the roads unsafe in wet conditions. Hence, the rutting mechanism of PFC is evaluated through three laboratory tests: dynamic modulus (DM), flow number (FN), and Hamburg wheel tracking test (HWTT). The samples were prepared and compacted considering four air voids (AV) contents: 18%, 20%, 22% and 25%. From the HWTT, a comparative analysis was conducted using X-ray computer tomography (X-ray CT) images obtained before and after the tests in order to investigate AV distribution due to rutting. The results show that the dynamic modulus, the flow number and the rutting response are severely affected by increasing the AV content in the PFC mixes. After increasing the AV content, the dynamic modulus and the flow number decreases significantly, while the rutting depth increases. From the analysis of the X-ray CT images, a larger AV densification was observed in the upper part of the samples beneath the developed rut, whereas in the bottom part the AV content increased further weakening the mineral skeleton.

Evaluation of glass fibres, ethylene vinyl acetate and their combination on stone mastic asphalt

ABSTRACT Glass fibre with high tensile strength and Ethylene Vinyl Acetate (EVA) polymer may change Stone Matrix Asphalt (SMA) performance significantly due to its good performance. Therefore, the study’s main objective is to evaluate these two additives’ performances and their combination on SMA. Thus, modified bitumen’s physical properties with 3, 4 and 5% of EVA and mechanical properties of SMA made by 3, 4 and 5% of EVA and 0.1%, 0.2% and 0.3% of glass fibre are investigated. For this purpose, penetration, softening point, rotational viscosity, dynamic shear rheometer, resilient modulus, dynamic creep, and fatigue tests are performed. The results demonstrate that the performance graded of modified bitumen with an optimum value of 4% EVA is improved as two classes, leading to a significant improvement in the SMA performance. However, the performance of SMA containing 0.2% and 0.3% of glass fibre decreases severely due to the fragility of the fibres. The performance of the mixture in 0.1% of the fibres is slightly improved due to the reinforcement of the bitumen mortar and the lack of effect of the fibres on the overall structure of the mixture. Also, only the combination of 4% EVA with 0.1% glass fibre gives an acceptable result.

Evaluation of effects of soybean derived oil and aggregate petrology on the performance of asphalt mixes

The realistic prediction of long term performance of hot mix asphalt (HMA) has been a challenging task for the pavement industry. This study aims to investigate the effect of soybean derived oil and aggregate petrology on the HMA performance. The properties of HMA were evaluated using Superpave gyratory compactor (SGC), indirect tensile (IDT) strength, dynamic modulus and semicircular bend (SCB) tests. The SGC results indicated that soybean derived oil has no adverse effect on compaction of HMA. The tensile strength ratio (TSR) analysis showed that the presence of quartz and feldspar in aggregates could affect the durability of HMA. The TSR results found that soybean oil improved resistance of HMA against moisture susceptibility. The SCB test results showed that the soybean oil improved the fracture resistance of asphalt mixes. The dynamic modulus results revealed that soybean derived oil decreased the stiffness of HMA.

Correlation investigation of fatigue indices of fine aggregate matrix (FAM) and asphalt mixture containing reclaimed asphalt pavement materials

Testing and evaluation of the Fine Aggregate Matrix (FAM) in terms of fatigue performance has gained popularity. However, the correlation of fatigue indices between FAM and asphalt mixture is unclear, especially for the asphaltic materials with Reclaimed Asphalt Pavement (RAP). Hence, this study aims to investigate the relationship of the fatigue performance between FAM and asphalt mixture incorporating with RAP and further validate the feasibility of optimizing the RAP mix design by FAM tests. The dynamic modulus test and direct tension cyclic test were employed to identify the viscoelastic and fatigue property of the RAP mixtures. The frequency sweep test and linear amplified sweep (LAS) test were conducted on the corresponding FAM samples. The fatigue index of the Superpave fatigue index (G*sinδ), pseudo stiffness at failure point (CF), and the LAS-based A parameter were obtained to quantify the fatigue performance of the FAM sample. Two fatigue indexes of the average reduction in pseudo stiffness up to failure (DR) and apparent damage capacity (Sapp) were used to describe the fatigue performance of the RAP mixtures. According to statistical analyses, the FAM indices exhibited relatively high discrimination. Analysis of correlation showed that strong correspondences were observed between DR or Sapp (mixture scale) and the A parameter (FAM scale). CF of the FAM showed a good agreement with the DR of the RAP mixture as well, but a fair agreement with Sapp due to different sensitivity to binder type and RAP content. The G*sinδ of the FAM presents a weak correlation with the fatigue indices of the RAP mixtures. Overall, both the CF and A parameter of FAM from the LAS test demonstrate a high potential to the prediction of the fatigue performance of asphalt mixture containing RAP at intermediate temperatures.

Laboratory investigation on thermal and road performances of asphalt mixture containing glass microsphere

To decrease the solar radiation heat entering the pavement, glass microsphere (GM) was selected as filler to replace limestone mineral filler (LMF) to improve the thermal resistance of asphalt mixture. The influence of GM on the thermal performance of asphalt pavement was studied by testing the thermal conductivity of asphalt mixture. It is found that the thermal conductivity could be reduced by 23.4%, which was beneficial to improve the cooling effect of asphalt pavement. A series of test, including dynamic repeated creep test, three-point bending test, dynamic modulus test and semi-circular bending test, were used to evaluate the influence of GM on the deformation resistance, low-temperature cracking resistance, dynamic performance and fatigue life of asphalt mixture. The results show that replacing LMF with GM negatively affected the above road performances of asphalt mixture. In further studies the actual rutting resistance of asphalt pavement with GM should be investigated by considering the cooled pavement structure and the elastic/creep performances of asphalt mixture.

Study on Morphological Parameters of Hysteretic Curve of Dynamic Resilient Modulus

The hysteresis curve of dynamic resilient modulus (DRM) is the load and deformation curve of asphalt mixture under dynamic loading, it can reflect the evolution rule of internal stress-train state with load and temperature. Based on viscoelastic theory, 3 morphological parameters could be determined: slope k of major axis, eccentricity e of ellipse, and area S of HC, which characterizes DRM, viscosity and energy dissipation capacity of asphalt mixture respectively. Thus the DRM test under various temperatures and loads are carried out. The result shows that there is a significant difference in the morphological parameters of SBS and asphalt mixture No.70 with the increase of temperature, and a inflection point exists at 15~20℃ in both hysteresis curves, the values of k and S change regularly but e keeps unchanged as load level increases. It indicates that (1) asphalt quality has more influence on the property than grade, and the viscosity is unrelated to load size; (2) between 15~20℃, the mechanical properties of asphalt mixture vary greatly, and their sensitivity to temperature are higher; (3) different values of morphological parameters of HC reflect the performance difference of asphalt mixture, and 3 morphological parameters could be used to evaluate the basic mechanical performance of asphalt mixture include viscosity, fatigue durability, etc. Finally, based on the changing rule of test curves, the stress dependence model of resilience modulus which reflects the response behaviors of asphalt mixture under various stress level conditions is established, and the prediction results are close to the real state. The variable load cumulative dissipation energy prediction equation is derived based on the Miner linear damage criterion, and the fatigue equation based on the theory of energy dissipation is established. The morphological parameters S obtained by the dynamic modulus test can be used to predict the fatigue performance of asphalt mixture.

Study on Dynamic Modulus Dependence Model for Asphalt Mixture Based on Temperature and Strain Parameters

In order to objectively characterize the nonlinear viscoelastic behavior of asphalt mixture and its dependence on temperature and load, the two-point dynamic flexural tensile modulus test of asphalt mixture at different strain levels, temperatures and loading frequencies is carried out by using French trapezoidal beam tester. By introducing the method of nonlinear operator, the dynamic modulus dependency modeling method for asphalt mixture based on temperature and strain parameters is put forward, the expression of dynamic modulus principal surface of asphalt mixture is established, and the reliability of the dynamic modulus dependent model is evaluated by correlation coefficient test and variance analysis method. The result shows that (1) for the two-point flexural tensile test of trapezoidal beam based on asphalt mixture of full-scale test track, the mean values of dynamic modulus variation coefficient at 0℃ and 45℃ are about 2.5% and 6.2% respectively, the mean values of dynamic modulus variation coefficient at 10 test temperatures is about 4%, the variation level of the test method is low, the error is small, which has a very good parallelism and reliability; (2) for the established dynamic modulus dependent model expression based on temperature and strain parameters, the decision coefficient R2 can reach more than 0.99, the P value of F test is 0, the fitting effect of the model on the test result is good, and there is a significant correlation of dynamic modulus with temperature and strain level; (3) the model can be used to describe the dynamic flexural tensile modulus of asphalt mixture, and the description model of the dynamic modulus can be transformed from principal curve to principal surface. In pavement structure analysis, this model can reflect the nonlinear response phenomenon in actual pavement more objectively, and can avoid the problems such as distortion of the calculation result caused by unreasonable modulus value in structural analysis effectively.

Study the Effect of Substitution Filler on performance of Asphalt Mixture

The major distresses in asphalt pavements are rutting, fatigue, and adhesion loss (moisture susceptibility). In this research study, two substitution fillers (Cement and Lime) were used with two different aggregate quarries (based on minerals composition) to evaluate the relatively most beneficial combination of both fillers as well as an aggregate quarry to enhance the performance life of asphalt pavements, especially in under-developed countries. Four basic tests, (Asphalt Pavement Analyzer, Four Points Bending Beam, Dynamic Modulus, and Rolling Bottle Test) that used for the most desired properties of any asphalt pavement, were utilized to access the performance properties of modified asphalt mixture. Based on all laboratory test results this research study concludes that replacement of aggregate filler with hydrated lime and cement has a beneficial effect on asphalt mix performance and to save investment by using raw material. Substitution filler improves the high-temperature rut performance and intermediate temperature fatigue performance of asphaltic concrete mixture up to 25% to that of the conventional mixture. At the same time, substitution filler has more beneficial to improve 70% adhesion properties to that of the conventional mixture.