Stiffness Modulus Of Asphalt Mixture Research Articles

Decay Characteristics of Mechanical Properties of Asphalt Mixtures under Sizeable Wet Temperature Cycle

Asphalt mixtures will inevitably be affected by rainwater and the effect of the wet temperature cycle during a pavement’s life span. Especially in coastal areas such as Guangdong and Hainan in China, asphalt pavement is particularly susceptible to the sizeable wet temperature cycle formed by the high temperature and sudden temperature drop of rainstorms in summer. For this study, we used a homemade sizeable wet temperature cycle environment simulation device to analyze the decay characteristics and the mechanical properties of asphalt pavements in this environment; modified bending and tensile strength and shear strength tests were used to study the decay patterns of shear strength, bending, and tensile strength, and the stiffness modulus of asphalt mixtures with different air voids and different pavement depths under the action of a sizeable wet temperature cycle. In addition, the Grey correlation method was used to analyze the significance of each influencing factor on the decay of mechanical properties, and mathematical fitting was used to establish the prediction equation of the mechanical properties of asphalt mixtures. The results show that with the increase in the number of sizeable wet temperature cycles, the asphalt mixture’s shear strength, flexural tensile strength, and flexural tensile modulus decrease, the degree of decay increases, and the rate of decay gradually slows down. In the case of the same number of sizeable wet temperature cycles, the degree of decay of the asphalt mixtures gradually decreases with increasing depth or decreasing void ratio. After 100 sizeable wet temperature cycles, the maximum values of the decay of shear strength, modulus of strength, and flexural tensile strength were 22.30%, 23.29%, and 32.01%. The importance of the influence of each factor on the decay of the mechanical properties is as follows: the number of sizeable wet temperature cycles > void rate > depth. The prediction equations of the established mechanical properties have a good prediction effect, and the correlation between predicted values and actual values can be up to 0.925. The prediction equations can effectively predict the mechanical properties of asphalt mixtures with different air voids and depths under the action of sizeable wet temperature cycles.

Performance Prediction of Fine-Grained Asphalt Concretes with Different Quarry Fillers by Machine Learning Approaches

In general terms, an artificial neural network is a distributed processor that consists of elementary computational units interconnected. Such structure is inspired by the functioning principles of the biological nervous system and has proven to be effective in identifying complex relationships between an assigned input features vector and an experimental- investigated target vector for any scientific problem. The current paper represents a forward feasibility study on predicting the mechanical response of asphalt concretes prepared with different quarry fillers used as alternatives for traditional limestone filler or portland cement by Machine Learning approaches which consider the chemical properties of the selected fillers and the quarry aggregate types as input variables. In fact, the case study involved several fillers and stone aggregates that were used to produce Marshall specimens of a specific fine-grained asphalt concretes designed originally for the assessment of filler suitability in terms of adhesion phenomenon. The asphalt concrete variants had the same material composition and mix design: all specimens were compacted by 2x50 blows using impact compactor, filler content was fixed at 10% by mass of the mix, the grading curve is roughly the same, the employed bitumen has a 160/220 penetration grade and is about 6% by mass of the mix. The mineralogical composition was investigated by X-ray fluorescence spectrophotometry tests. It represents a non-destructive laboratory analysis that allowed to specify and compare the main oxides composition associated with the employed natural fillers to be identified. Based on the results thus obtained and applying a categorical variable that distinguishes the stone aggregate type, a neural model has been developed that can predict the stiffness modulus of asphalt mixtures: therefore, this study presents a possible procedure for the development of predictive models that can help or improve the mix design process, when different fillers and stone aggregates are available.

Evaluation of measured and predicted resilient modulus of rubberized Stone Mastic Asphalt (SMA) modified with truck tire rubber powder

Rubberized asphalt is known for its elastic deformation recovery and good resilience in response to loads owing to the elastic characteristics of tire rubber powder. There are several methods for the prediction of the stiffness modulus of asphalt mixtures. However, there are limited studies on predicting the stiffness modulus incorporating both wet and dry rubberization methods based on the available methods of Asphalt Institute (AI) and IDOT (Illinois department of transportation). In this research, Stone Mastic Asphalt (SMA) mixtures were modified with truck tire rubber powder (TRP) with two different processes: SMA-WP (SMA mixtures modified in the wet process) and SMA-DP (SMA mixtures modified in the dry process). In both methods, 3%, 6%, and 9% of TRP were used for modification, and the performance of the control and modified mixtures was evaluated under indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM) tests. Finally, the results of ITSM were compared to predicted resilient modulus based on the Asphalt Institute (AI) and Illinois Department of Transportation (IDOT). The experiments revealed that SMA-DP mixes have higher ITS than SMA-WP. At the same time, both methods showed a decrease in ITS as TRP content increases. Furthermore, the SMA-WP samples showed a lower phase angle than SMA-DP samples, indicating higher elasticity for the mixtures. In addition, SMA-WP showed lower horizontal deformation than SMA-DP, which helps reduce rutting on the surface layer. Finally, the prediction results showed that the IDOT method could not predict the Stiffness Modulus, while the AI method was more accurate and can be used for prediction.

Impact of Aging and Moisture on Fatigue Life of Asphalt Mixture

Abstract In this study, the mechanical behavior of a dense-graded asphalt mixture subjected to unaged, short-term, and extended aged conditions along with one freeze-thaw moisture conditioning cycle was evaluated at two temperatures and three stress magnitudes. A stress-controlled repeated indirect tensile loading fatigue test with 0.1-s loading and a 0.4-s rest period was used for determining the fatigue life of asphalt mixture. Aging, moisture conditioning, and an increase in the test temperature adversely affected the tensile strength of the asphalt mixture. The reduction in stiffness modulus of asphalt mixture that was due to moisture conditioning increased with the increase in the level of aging. The ratio of conditioned to unconditioned stiffness modulus (stiffness modulus ratio) was noticed to be more sensitive to different aging conditions compared with the ratio of conditioned to unconditioned tensile strength (tensile strength ratio). The effect of aging on fatigue life of asphalt mixture reduced with the increase in stress from 450 kPa to 550 kPa and 650 kPa. Further, the fatigue life of asphalt mixture reduced with the increase in test temperature and moisture conditioning. The short-term and extended aged mixture had higher damage value at failure compared with the unaged mixture. The mean fatigue life represented by the scale parameter of Weibull distribution reduced with the increase in aging and moisture conditioning. Further, the reliability of fatigue life of short-term aged and extended aged asphalt mixture was lower than the unaged asphalt mixture. The fatigue model based on plateau value and fatigue life was found to be more accurate compared with other regression models considered. Statistical analysis showed that the critical combinations of factors that influenced the mechanical behavior of asphalt mixture were also dependent on the test type, which included the tensile strength test, stiffness test, and fatigue test.

Research into effect of asphalt mixture aging on stiffness

The paper focuses on the research of the stiffness of asphalt mixtures exposed to short-term and long-term aging. Asphalt mixtures are exposed to this type of ageing during their production, laying and compaction and subsequently during service. The research was carried out on test samples of asphalt mixtures AC11 50/70 and AC11 PMB 45/80-75 for wearing course of asphalt pavements. The asphalt samples have been exposed to the effects of short-term and long-term ageing by the conditioning of loose mixture method. Subsequently, the stiffness modulus of asphalt mixtures at temperature 20 °C was determined by the IT-CY method according to EN 12697-26. The obtained results showed higher values of stiffness modulus for the mixture with paving grade bitumen 50/70. The largest difference in the stiffness modulus was recorded for origin asphalt mixtures. Furthermore, an increase in the mixture stiffness due to ageing was observed, more pronounced in the case of the mixture with the polymer modified bitumen PMB 45/80-75. Gradual ageing changes the properties of asphalt mixtures, which are essential for the durability of the road.

Probabilistic modeling of fatigue damage in asphalt mixture

Fatigue cracking is considered as one of the major distress in asphalt pavements. Environmental factors like aging and moisture intrusion further complicate the cracking process. In this study, the effect of two levels of aging and three levels of moisture conditioning on the fatigue damage of asphalt mixtures was determined using a probabilistic approach. The fracture energy, the stiffness modulus, and the fatigue life of four different asphalt mixtures were determined at 15 °C and 25 °C. It was noticed that the stiffness modulus and fatigue life of asphalt mixtures increased with an increase in the level of aging and reduced with an increase in moisture conditioning cycles. At three freeze–thaw cycles, the reduction in fatigue life of asphalt mixtures was much higher compared to the stiffness modulus of the asphalt mixtures. It was noticed that moisture had a higher negative impact on the fatigue life of asphalt mixtures at 15 °C as compared to 25 °C. Both stiffness modulus and fatigue life of asphalt mixtures reduced with the increase in test temperature. The fatigue damage of unconditioned and moisture conditioned asphalt mixtures followed a lognormal distribution. The lognormal distribution parameters were used to determine the probability of fatigue damage at each loading cycle. It was noticed that a moisture conditioned asphalt mixture had a higher probability of fatigue damage compared to unconditioned asphalt mixture at different aging condition and test temperature. Asphalt mixtures subjected to three freeze thaw cycles had a higher probability of fatigue damage compared to one freeze thaw cycle. Further, the probability of fatigue damage was higher in the case of long term aged asphalt mixtures when compared to short term aged asphalt mixtures at a lower temperature of 15 °C. The damage based fatigue life prediction model had a good coefficient of determination for different conditions evaluated in this study. A Monte Carlo simulation with one million iterations was used to simulate the fatigue life of the damage based fatigue life prediction model. It was observed that a moisture susceptible asphalt mixture might not show an increase in fatigue life with an increase in the aging level.

Consideration of dynamic loads in the determination of axle load spectra for pavement design

Axle load spectra constitute a crucial part of the data for pavement design and pavement distress analysis. Typically, axle load spectra represent static load from vehicles and do not include dynamic loads generated by vehicles in motion. While dynamic loads can significantly contribute to faster pavement distress, this fact is mostly omitted in pavement design methods. The paper presents a methodology for consideration of dynamic loads in axle load spectra for mechanistic-empirical pavement design. Calculations of dynamic axle load spectra for pavements of various evenness (expressed by IRI) and various vehicle speeds were performed and discussed. The effect of dynamic axle load spectra on pavement performance was analysed. M-EPDG calculations performed for three selected flexible pavements show that dynamic loads have a minor effect on pavement performance if the pavement is smooth and IRI is close to 1.0 mm/m. The detrimental effects of dynamic axle loads increase rapidly with the pavement evenness deterioration, resulting in faster (up to 25%) development of pavement distresses for IRI = 4.0 mm/m and a vehicle speed of 60 km/h. The analysis proved that thinner pavement structures are more sensitive to dynamic loads than thicker pavement structures. The investigation of vehicle speed impact on vehicle dynamic loads and pavement performance showed that at low vehicle speed (30 km/h) dynamic loads have a minor effect and pavement distress results mostly from a decrease in stiffness modulus of asphalt mixture and increase in permanent deformations, while for vehicle speeds higher than 90 km/h dynamic loads significantly contribute to pavement distress and adverse dynamic effects are not compensated by an increase in stiffness modulus of asphalt mixtures. The results also emphasise the significance of proper pavement evenness maintenance, especially on high speed motorways.

Laboratory investigation of fatigue parameters characteristics of aging asphalt mixtures: A dissipated energy approach

The objective of this paper is to reveal the effects of aging on the fatigue performance of asphalt mixture based on variation patterns of fatigue parameters with aging degrees. Specimens with different aging degrees were prepared by modified SHRP’s Long-Term-Oven Aging (LTOA) test method, in which five different aging durations, included 0, 1, 3, 5, 7 days, were adopted to substitute the fixed 5 days. The fatigue parameters, including stiffness modulus, fatigue life, phase angle, Plateau Value (PV), and cumulative dissipation energy of specimens with different aging degrees under different stress ratios were obtained by the tensile fatigue test. The relationship of fatigue parameters with aging degrees and stress ratios were established. It could be observed from the results that the aging degree and stress ratio had dramatic influences on the fatigue performance of asphalt mixture. Sensitivity analysis showed that aging had the most significant effect on the initial stiffness modulus of asphalt mixture, and should be used as a control index in fatigue design. Statistical models of the relation between (PV) and fatigue life (Nf) established by the Rate of Dissipated Energy Change (RDEC) approach has an effective correlation. The Plateau Value model eliminated the effects of aging degrees and reflected the uniqueness of material parameters. Also, it could provide novel ideas for effective prediction of the fatigue life of asphalt mixtures with different aging degrees based on plateau value.

INFLUENCE OF FINE RECYCLED CONCRETE AGGREGATE ON THE PROPERTIES OF ASPHALT MIXTURES

The objective of this paper was to assess the possibility of using fine recycled concrete aggregate (RCA) in asphalt mixtures. The experimental research included four asphalt mixtures with partial natural aggregate substitution by fine RCA (0/4 mm), in the amount of 0% (control mixture), 15%, 30% and 45%, by mass. All asphalt mixtures were designed for the base course. The stiffness modulus of asphalt mixtures with RCA was lower compared with the control mixture. The use of fine RCA had no significant influence on the water sensitivity and ranged from -2.4% to +1.7% relative to the control mixture. Resistance to permanent deformation increases with the addition of up to 30% fine RCA.

Effect of mixing and ageing on the mechanical and self-healing properties of asphalt mixtures containing polymeric capsules

In this paper, polymeric capsules with sunflower oil as the encapsulated rejuvenator were manufactured and added to asphalt mixtures to improve their self-healing properties. A capsule content of 0.5% by total mass of mixture was added to the asphalt samples. Physical, thermal and mechanical properties of the capsules were evaluated. Additionally, the effect of the mixing order and the ageing time on the mechanical stability and self-healing properties of asphalt mixtures with, and without, capsules were evaluated through stiffness modulus and flexural strength tests. Self-healing properties of asphalt mixtures were evaluated through three-point bending tests on cracked asphalt beams with, and without, capsules. In addition, capsules’ distribution and their integrity inside the asphalt mixtures were analysed using X-ray computed tomography. The main results proved that the capsules can resist the mixing and compaction conditions and break inside the mixture releasing the encapsulated oil in small volumes. In addition, it was observed that the addition of capsules did not improve the stiffness modulus of asphalt mixtures compared to mixtures without capsules, and that the mixing order and the ageing time did not have a significant influence on the flexural strength of the mixtures. Moreover, the healing levels obtained by the mixtures varied depending on the order of addition of capsules, and mixtures with capsules showed higher healing levels than mixtures without capsules. Finally, the levels of healing for the mixtures without ageing were greater than those of mixtures after the ageing process.

Effects of recycled concrete aggregate on stiffness and rutting resistance of asphalt concrete

The objective of this research was to assess the possibility of using recycled concrete aggregate (RCA) in asphalt mixtures. The experimental research included 10 asphalt mixtures with partial natural aggregate substitution by RCA, which ranged from 15% to 45% of fine (⩽4mm), coarse (4/22.4mm) and both fine and coarse aggregate. The optimum bitumen content increased with increasing RCA content. The use of RCA had no significant influence on the permanent deformation, while the stiffness modulus of asphalt mixtures with RCA was lower compared with the control mixture, especially at high frequencies. The results indicate that RCA can be successfully used in asphalt mixtures.

Calculation of Measurement Uncertainty for Stiffness Modulus of Asphalt Mixture

Asphalt mixture is a highly heterogeneous material, which is one of the reasons for high measurements uncertainty when subjected to tests. The results of such tests are often unreliable, which may lead to making bad professional judgments. They can be avoided by carrying out reliable analyses of measurement uncertainty adequate for the research methods used and conducted before the actual research is done. This paper presents the calculation of measurements uncertainty using as an example—the determination of the stiffness modulus of the asphalt mixture, which, in turn, was accomplished using the indirect tension method. The paper also shows the employment of the basic methods of statistical analysis, such as testing two mean values and conformity tests. Essential concepts in measurements uncertainty have been compiled and the determination of the stiffness module parameters are discussed. It has been demonstrated that the biggest source of error in the stiffness modulus measuring process is the displacement measure. The aim of the research was to find the measurement uncertainty for stiffness modulus by an indirect tensile test and the presentation of examples of the used statistical methods.

Studies and analysis on interlayer bonding in asphalt pavements

The paper describes research works of interlayer bonding of asphalt layers conducted at Gdansk University of Technology. The studies included laboratory and field tests, and calculation of pavement structures with different interlayer bonding models. Laboratory tests included interlayer bonding tests using the direct shear method which evaluated the influence of selected factors on interlayer bonding: the type and the amount of the emulsion, the method and the effectiveness of compaction, vulnerability to dirt, water and repeated shear loads. Field works were focused on the impact of interlayer bonding of asphalt layers on the deflection of pavement structure and the back-calculated stiffness modulus of asphalt mixtures. The analyses of the field tests also included the impact of the asphalt layers compaction ratio on interlayer bonding. Computational analyses of asphalt pavement structures consisted of the simulation of different interlayer bonding in a multi-layered elastic half-space. Calculations were also made by using the finite element method within cohesion and friction models to simulate interlayer bonding.

Laboratory evaluation on performance of diatomite and glass fiber compound modified asphalt mixture

The purpose of this paper is to investigate the compound effects of diatomite and glass fiber on asphalt mixture. The diatomite and glass fiber compound modified asphalt mixture (DGFMAM) was prepared in laboratory. Performances of DGFMAM were investigated by experimental method. Wheel tracking test, low temperature indirect tensile test, indirect tensile fatigue test (ITFT) and indirect tensile stiffness modulus test (ITSM) were carried out. The statistical analysis of variance (ANOVA) method and statistical regression method were used to evaluate the effects of diatomite and glass fiber on properties of asphalt mixture. Results indicate that diatomite and glass fiber improve the rutting resistance and fatigue properties of control asphalt mixture. Diatomite has a significant effect on the stiffness modulus of asphalt mixture. Disadvantage of diatomite on low temperature deformation property of asphalt mixture is solved by glass fiber. DGFMAM has better travelling performances than the control mixture. It will provide a reference for the design of compound modified asphalt mixture.

Stress and Strain Analysis of Asphalt Pavement Impacted by Temperature and Load

Temperature and load are the major factors of road surface deformation. This paper studies how the temperature causes the road surface deformation and what the deformation trend is. A simplified model of the pavement structure and double round load loading mode were adopted respectively to analyze the stress and strain changes of road surface result of the load and the coupling effect of temperature and load. The major conclusions drew on this study are: stiffness modulus of asphalt mixture attenuates rapidly as the temperature increases, and thereby results in a significant shear deformation of asphalt pavement. At the same temperature, compressive stress decreases with the increasing of load and the deepening of the pavement structure. The influence of coupling effect of temperature and load is more significant than a single temperature or load factor. Under different coupling effect of temperature and load circumstances, the pavement structure influenced mostly by the shear stress is located 3-9cm underneath the surface.

Investigation of the properties of epoxy resin‐modified asphalt mixtures for application to orthotropic bridge decks

AbstractCompared with the general pavement, the steel bridge deck pavement endure much larger deform and higher temperature. Epoxy asphalts were used to prepare modified asphalt concrete for steel bridge deck paving. The effects of epoxy resin contents on the fatigue life and creep properties of epoxy asphalt mixture were investigated in this study. The fatigue properties of epoxy asphalt mixtures were studied by the indirect tension fatigue test at different stress. A static creep test with a loading and recovery period was conducted on the asphalt mixture. The results showed that the fatigue life and recovery elasticity of asphalt mixtures with epoxy resins was large, which indicated that the fatigue property could be improved by epoxy resin. Compared with control asphalt, epoxy asphalt showed better resistance to deformation and recovery performance. Epoxy resin has caused a dramatic ascent in the creep stiffness modulus of asphalt mixture. And Burgers model can describe the creep performance of epoxy asphalt. Based on the obtained results, epoxy asphalt mixtures had decrease in permanent deformation and increase in fatigue life. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Study on Dynamic Indirect Tension Test of Hard Asphalt Mixture

AbstractThe index of asphalt mixture verified by the dynamic measurement can really reflect the response of asphalt mixture to the vehicle loading, and have the advantage to correctly show the visco-elastic nature of asphalt mixture. Employing multi-functional asphalt materials test machine imported from England, the dynamic indirect tension stiffness modulus of hard asphalt mixture No. 30 was measured, the test data were studied by two variance analysis and nonlinear regression, and the influence of gradation, asphalt aggregate ratio, asphalt type and test temperature on the dynamic indirect tensile test were analyzed. The results show that (1) hard asphalt mixture No. 30 has very high dynamic indirect tension stiffness modulus, using it in the lower layer of asphalt pavement can reduce the tensile strain; (2) gradation, asphalt aggregate ratio, temperature and penetration of asphalt all has notable influence on the dynamic indirect tension stiffness modulus of asphalt mixture.

Evaluation of Semicircular Bending Test for Determining Tensile Strength and Stiffness Modulus of Asphalt Mixtures

Abstract The semicircular bending (SCB) test has been shown to possess several advantages over other tests in characterizing asphalt mixtures in previous studies. This research study evaluates the SCB test for determining the tensile strength and stiffness modulus of the paving material with numerical simulation and laboratory experimentation. An analytical model describing the tensile stress at the middle point of the lower surface of the specimen in the SCB test was developed based on the plane assumption in mechanics of materials. Analysis using the finite element method indicated that the error induced by the model was within 2 %. Laboratory experiment carried out on three types of asphalt mixtures at various temperatures showed that the strength of the material by the SCB test was nearly 50 % higher on average than that by the flexural beam bending (FBB) test due to such factors as complexities in stress and strain states as well as nonlinearity and viscoelasticity of the material. Laboratory experiment also showed that the stiffness moduli for 10–40 % of maximum load from the FBB test and from the SCB test were in a well-defined linear relationship with differences less than 10 %. In addition, based on finite element analysis, a practical approach for determining stiffness modulus of asphalt mixtures using deflection at the middle point of the lower surface of the specimen in the SCB test was established.