Behavior Of Flexible Pavements Research Articles

Evaluation of Moisture Susceptibility of Asphalt Mixtures: Influence of Aggregates, Visual Analysis, and Mechanical Tests

Asphalt pavement failure is directly related to the traffic and climate effects. Temperature and moisture severely impact pavement service life. It is known that moisture changes the stiffness and stress–strain distribution and all the mechanical behaviors of the mixture/structure. There is a huge interest in studying the impact of water on the behavior of flexible pavements, mainly on freeze–thaw regions under tropical climates with high rainfall levels. The scope of the present paper was to check the susceptibility to moisture-induced damage of dense asphalt mixes produced and applied on highways in Brazil’s southernmost region using different laboratory tests: visual adhesion of coarse aggregate; tensile strength ratio (TSR), and dynamic modulus ratio (DMR). Thus, this study evaluated the morphological, chemical, and mineralogical properties of aggregates from 11 quarries, as well as the interaction between aggregates and the respective bituminous binders. Rocks with high Si contents performed worse in visual adhesiveness tests; chemical ratios such as Fe/Si above 1 and Ca/K above 5, as well as the rougher texture of aggregates, considerably improved the coating, reducing the failures in adhesion. Results of TSR and DMR, after applying the induced moisture damage cycle, indicated greater susceptibility to conventional binders than mixtures containing modified binders in their composition. The action of moisture damage for most mixtures caused a reduction in strength and stiffness, warning of a decrease in the binder’s ability within the mixture, completely changing the distribution of efforts within the structure. Therefore, from this study, it is possible to suggest using DMR instead of TSR to assess susceptibility to moisture damage.

The influence of truck speed on pavement defects

ABSTRACT The response of asphalt material depends on the rate of loading and varies from elastic to plastic. Therefore, the behaviour of flexible pavement would also be different along the entire length of a road because of truck speed changes due to the existence of police checkpoints, bus stations, speed bumps, intersections, horizontal and vertical curves, and climbing lanes. The objective of this study is to investigate the effect of truck speed on the performance of flexible pavement. Thus, analyses were conducted for various truck speeds (1–75 km/hr) on three different pavement structures and three traffic levels using AASHTOWare Pavement ME Design 2.5.5 for the local conditions of Izmir, Turkey. The analysis results of the study manifested that a reduction in traffic speed (75–1 km/hr) on a road resulted in higher pavement distress. According to the results, reducing truck speed from 25 to 1 km/hr resulted in a rapid increase in AC rutting, alligator cracking and top-down cracking by 13.3 mm, 10.6% and 1473.8 m/km, respectively. It is expected that the outcomes of this study would promote the local calibration of the mechanistic-empirical pavement design guide (MEPDG) and pavement design in Turkey and the region.

Behavior of Flexible Pavements by the Addition of Plastic Waste

Plastic trash production and disposal pose a serious threat to the environment, causing pollution and global warming. The characteristics and strength of plastic trash used in bituminous roads and pavements are improved. Also, it will be beneficial for India as a way to handle plastic waste disposal and numerous road/pavement flaws including ruts, potholes, corrugation, etc. Polythene, polystyrene, and polypropylene are the types of plastic trash that are used. The waste plastic is crushed, covered with gravel, and combined with hot bitumen to create a mixture that is used to build roads and pavement. The pavement will be strengthened and become more durable as a result. Its ground-breaking technology will also work in India's hot, humid climate. Both environmentally sustainable and cost-effective.

Structural Responses Data Measured in an Instrumented Flexible Pavement

This study presents and analyses the stress-strain responses data measured under real traffic conditions measured between Oct. 2012 to Oct. 2013 on an instrumented flexible pavement section on Interstate 40 (I-40) in the state of New Mexico, USA. Some weather variations data such as moisture and temperature variations at different depths of the pavement over the entire year are also discussed. The moduli of different layers determined using laboratory and field tests are also presented. It is expected that results of this study will be greatly useful to understand the behaviour of flexible pavement. The data presented in this study can be used to validate any constitutive or numerical model developed by readers.

Performance Evaluation of Flexible Pavement for Critical Parameters Causing Premature Failure

The present study focusses on the performance of flexible pavement at a different temperature. The analysis is carried out using 2D axisymmetric finite element model for a combination of varying thicknesses of a bituminous layer with base and sub-base. The study is very much useful to know the behaviour of flexible pavement under varying climatic conditions along with loading and material properties. The critical parameters are examined to know the cause of failure of the existing pavement structure. The study evaluates different pavement distresses in terms of rutting and fatigue life

Performance Evaluation of Flexible Pavements Using a New Field Cyclic Plate Load Test

Abstract This study presents a new field cyclic plate load test for characterization of the permanent and dynamic deformation behavior of flexible pavements as a function of load and number of loading cycles. Specifically, in this study a Vibroseis was used to apply thousands of loading cycles to pavement sections with a peak dynamic force of 62 kN (a ±22 kN dynamic force superimposed on a static hold-down force of 40 kN), which is approximately equivalent to [3/4] of an ESAL. These vertical loads were applied to a dual wheel-sized loading footprint resting on the pavement surface at a rate of 50 Hz. During loading, the permanent and dynamic surface deformations were recorded every 500 cycles at incremental distances from the loading footprint. The cyclic plate load test was performed for two pavement sections having similar asphalt, subgrade, and base course characteristics, but different base course thicknesses. The results from the pavement sections at two different times of the year (summer and winter) indicate improved performance with increasing base course thickness, and a stiffer response in the winter months due to temperature effects on the asphalt elastic modulus, as expected. The measured permanent deformation basins were interpreted using inverse analysis of an analytical Timoshenko-Winkler beam solution to identify softening of the Young’s moduli of the asphalt and combined base and subgrade layers after application of different numbers of loading cycles. The beam solution provides a good fit to the measured deformation profiles and the inverse analysis shows a clear decrease in Young’s moduli of the pavement layers during cyclic loading.

Evaluation of Measured and Estimated Dynamic Moduli for Selected Asphalt Mixes

Abstract An accurate measurement or estimation of dynamic modulus (|E*|) of a hot mix asphalt (HMA) mix is important to understand stress–strain behavior of flexible pavements under loading and unloading conditions. The Mechanistic Empirical Pavement Design Guide (MEPDG) (Transportation Research Board, Washington, D.C., 2004) recommends that |E*| be used in all three levels of design (i.e., Level 1, Level 2, and Level 3). For Level 1, |E*| is measured in the laboratory, while it is estimated using the Witczak models for Level 2 and Level 3 designs. The measurement of |E*| in the laboratory is not always feasible because it requires costly equipment and skilled personnel. Consequently, use of empirical models seems to be a reasonable approach to estimate |E*|. Several researchers have reported that the accuracy of the Witczak models varies with local materials and volumetric properties. The present study was undertaken to compare the measured and the estimated |E*| for some commonly used mixes in Oklahoma. Specifically, |E*| of five different HMA mixes, comprised of aggregates from several sources and sizes, binder grades, and air voids, were measured in the laboratory. The Witczak 1999 model (Andrei et al., 1999) was used to estimate |E*| for each of these mixes. A comparison was made between the measured and the estimated |E*| at four different levels of air voids, namely, 6%, 8%, 10%, and 12%. It was observed that the Witczak 1999 model overestimates |E*| at all four levels of air voids. To address these overestimates, the Witczak 1999 model was calibrated. The calibrated model was similar in form to the Witczak 1999 model but having different numerical coefficients. Verification of this model was done using a mix that was not used in the calibration process. Furthermore, two full depth field cores were obtained to further verify the accuracy of the calibrated model. Three different criteria, namely, goodness-of-fit statistics, matching the measured and the estimated |E*|, and average relative error (%), revealed that the calibrated model exhibits much better performance compared to the Witczak 1999 model. It is expected that the calibrated model would be useful in estimating |E*| for the Level 2 and Level 3 designs for the implementation of the MEPDG in Oklahoma.

Comportamento mecânico de pavimentos flexíveis submetidos a gradientes térmicos

Palavras-chave: pavimento flexivel, analise mecanistica, gradiente termico. ABSTRACT. Mechanical behavior of flexible pavements undergoing thermal gradients. The proper structural understanding of a pavement should consider, according to the pavement mechanics, the aspects related to the traffic load, the environment and material properties. When asphaltic materials are used, the stress/strain relationships and the dependencies of load-time and temperature are key parameters for understanding flexible pavement performance. In this study, we employed the finite elements method to calculate stress/strain in flexible pavements structures considering temperature variation. The input data includes material stiffness, which is function of temperature and changes with position and time. The pavement temperature is obtained through the heat transfer differential equation, applying the Laplace transform and its numerical inversion. The finite elements grid was generated by the software ANSYS ® and imported by the software MATLAB ® . In order to determine the stiffness of the first layer (asphalt concrete) we used the average of four nodes, depending on the each node temperature. The result evidences the importance of thermal gradients for the pavement analysis, both for the fatigue cracking and the accumulation of plastic deformations. The use of unique modulus for asphalt concrete layer generates results far from reality.

Damage Theory Applied to Flexural Fatigue Tests on Conventional and Asphalt Rubber Hot Mixes

ABSTRACT Application of the Continuum Damage Theory (CDT) to evaluate the evolution of internal damage in Hot Mix Asphalt (HMA) is investigated in this paper. The CDT leads to the formulation of a characteristic curve relating normalized pseudo-stiffness and the internal damage variable, and this curve is supposed to be unique for each material. The uniqueness of the characteristic curve was investigated in this paper by performing fatigue tests in which prismatic samples of HMA were subjected to cyclic bending loads under strain controlled tests. Asphalt mixtures with dense, open and gap gradation using conventional and rubber modified binders were tested. The results of all the tests showed the existence of unique curves independent of loading mode, amplitude or frequency within the studied range. This property may be implemented in numerical codes to simulate the behavior of flexible pavements under a variety of field conditions, using a well formulated mechanistic approach.

Elasto-viscoplastic Finite Element Analysis of the Long-term Behavior of Flexible Pavements

ABSTRACT This paper includes analysis of the flexible pavements rutting using an elastoviscoplastic constitutive relation for the asphalt concrete, which takes into account the influence of the temperature. The latter is considered using the time-temperature superposition principle. The loading is modeled as a uniform pressure applied during the vehicle pass. The superposition principle is used for modeling the traffic with a high number of vehicle passes. The numerical model is first calibrated on full scale tests conducted at different values of the temperature. Then, it is used for the analysis of the influence of the temperature and traffic condition on the pavement rutting. Analyses show that the increase in the temperature leads to an import augmentation in pavement rutting. They also show that the tire type and the traffic speed influence significantly the pavement rutting.