Pavement Layer Properties Research Articles

Evaluating Cumulative Damage Factor (CDF) of 20 Brazilian Airfield Pavement structures using FAARFIELD and BAKFAA

There is a growing concern regarding the structural integrity of Brazilian airport pavements. This concern arises from the fact that they were originally designed to accommodate lighter aircraft during an era of lower traffic. However, with the substantial increase in air traffic and the introduction of heavier aircraft, compounded by the aging infrastructure predominantly built between the 1950s and 1970s, these pavements are now confronted with significant challenges. This research involves collecting data on aircraft characteristics, traffic patterns, and pavement layer properties to update information on the pavement life service of existing Brazilian airfield pavements. Research involves the analysis of determine the Cumulative Damage Factor (CDF) of 20 Brazilian airport runways pavement. Backanalysis of deflection basins obtained from Heavy Weight Deflectometer (HWD) tests is conducted using the BAKFAA software. The FAARFIELD software is then employed to calculate the CDF, incorporating the latest information on aircraft mix and pavement conditions. The study reveals that 65% of the analyzed airport pavements consist of 4 structural layers, with 50% of the structures composed of cement-treated base course layers. Notably, 11 airports exhibit a CDF less than 0.01, suggesting potential overdesigned of pavements for existing aircraft movement. Boa Vista Airport/RR (SBBV) stands out with a CDF of 1.5, prompting recommendations for actions to mitigate pavement degradation. The findings offer valuable insights for future actions, maintenance strategies, and recommendations for the construction of new airports.

Impact of cement content in cement bound materials on the reflection cracking performance of asphalt pavements

This study investigates the impact of cement contents in cement bound material (CBM) on asphalt pavement reflection cracking, considering two levels: 4.5 % (CBM1) and 5.4 % (CBM2). Mechanical properties of CBMs, including elastic modulus, rupture modulus, and thermal expansion, were evaluated. Simultaneously, properties of asphalt pavement layers (wearing course and base course) underwent assessment through dynamic modulus, flow number, and overlay tests. Resilient modulus tests were conducted for subbase and subgrade layers. Laboratory test outcomes served as inputs for a AASHTOWare Pavement ME Design program. The results indicated that despite CBM2's higher elastic modulus and rupture modulus, CBM1 outperformed in pavement design. Based on the outcomes from pavement design program CBM1 exhibited lower total transverse cracking (400.19 m/km) compared to CBM2 (403.38 m/km) after 6 years of service. The higher cement content in CBM2 was identified as a potential contributor to increased cracking, attributed to shrinkage during cement hydration process. Moreover, the higher cement content showed a higher coefficient of thermal expansion (CTE), where CBM1 displayed a CTE of 70 µm/°C, while CBM2 material had a CTE of 40 µm/°C. These findings emphasize the intricate relationship between cement content in CBM and pavement performance, crucial for effective design considerations.

Thermal Diffusivity of Concrete Samples Assessment Using a Solar Simulator.

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from 0.16×10-6m2s to 0.52×10-6m2s and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete.

Development of a temperature prediction model for flexible pavement structures

This study focuses on developing a temperature prediction model for the flexible pavement structure using an analytical approach based on local conditions. Flexible pavement layer samples were taken to determine the pavement layer properties. Temperature data-logger with four thermo-couple inputs was embedded in the pavement to record temperature values at pavement surface, 6 cm, 11 cm, 20 cm, and 40 cm depths to validate the prediction model. The temperature profiles were established for the pre-defined pavement depths. The temperature prediction model of this study was developed based on the assumption of treating the whole pavement structure as a full-depth asphalt layer in terms of the thermal properties. The initial conditions were determined using the measured temperature values. The external heat transfer modes including radiation and heat convection effect were applied to the pavement surface by simulating the surface temperature profile. The field temperature values were used to study and adjust the model behavior with the input parameters. MATLAB software was used to generate the temperature profiles. The study results indicated that the prediction model predicted the field temperature profiles of the pavement structure fairly well. The maximum relative error was 7.02% (0.83 °C) and 6.68% (1.92 °C) at 11 cm and 6 cm depths, respectively.

Effect of thermal variances on flexible pavements

This article presents recent findings on the effect of thermal variances on pavements. It covers temperature measurement in asphalt pavement; the history of asphalt pavement temperature prediction models, determination of asphalt layer depth temperature; main factors contributing to temperature variations in the asphaltic pavement; energy balance in flexible pavements; asphalt pavement design incorporating the temperature factor; the effect of temperature on the structural performance of asphalt pavement; and environmental factors. The study concluded that temperature substantially affects the asphalt pavement layer's mechanical and physical material characteristics. This study has taken a close look at how pavement temperatures are measured and the models used to predict future temperatures. The research shows that temperature significantly affects the mechanical and physical properties of asphalt pavement layers.

Microstructural evaluation of the cement stabilization of hematite-rich red soil

Red soil, composed of a clayey bed containing hematite, is used as pavement material in southern Iran. As an effective and economical technique, soil improvement with cement is common practice for improving the engineering properties of different soil and pavement layers. The formation of nanostructured calcium silicate hydrate (C-S-H) is the primary factor contributing to this improvement. On the other hand, the presence and dissolution of hematite in the soil structure can also influence C-S-H formation. The present study investigates the effects of cement on the engineering properties of the hematite-rich red soil from a microstructural point of view, with particular emphasis on changes in the C-S-H nanostructure. For this purpose, red soil specimens were stabilized with 2, 4, 6, 8 and 10 wt% cement for different curing times. The soil's engineering properties were evaluated by macrostructural testing, namely by soil particle size analysis and slake durability, water absorption, Unconfined Compressive Strength (UCS), and Ultrasonic Pulse Velocity (UPV) tests. Furthermore, the soil stabilization process and the effects of hematite on the C-S-H microstructure were evaluated by pH and Electrical Conductivity (EC) tests, X-Ray Diffraction (XRD), energy-dispersive X-ray analysis (EDX), and Scanning Electron Microscope (SEM) imaging. It was shown that adding cement to hematite-rich soil promotes Calcium Ferrite Hydrate (C-F-H) and ilavite (C-F-S-H) formation and, consequently, improves the red soil's stability and compressive strength. In fact, using 6 wt% cement, the presence of hematite, and the formation of Fe-containing nanostructures helped the red soil specimen develop a compressive strength of 2.04 MPa (17 times that of the natural soil) in seven days.

Effect of Polymer on the Properties of Bitumen and Pavement Layers, Case Study: Expressway No.1, Republic of Iraq

Increasing attention has been paid to use polymer as a modifier in bituminous mixtures manufacturing. Unmodified bituminous mixtures are highly affected by the undesirable environmental conditions at which such mixtures present brittle behaviour and crack at cold weather, whereas present soft behaviour at elevated temperatures resulting in rutting and surface deformation. As a result of bituminous mixtures modification using polymers, more elastic and durable bituminous materials that show developed stability at high temperatures can be obtained. In this present study, using 4% polymer with bitumen grade of 40/50 leads to improve bitumen properties such as viscosity, penetration, flash point, softening point, dynamic shear and creep stiffness. The results of investigation samples which were cutting from pavement show improvement of these pavement properties according to results of tests at site lab and independent lab. The use of polymer in design mixture of asphalt help in improving pavement properties which lead to the successful road and increases the age of pavements and become more resistant to hard conditions such as high temperature in the middle east region.

Evaluating the mechanical properties of thin asphalt overlay incorporating reed ash

Thin Asphalt Overlay (TAO) is a preservation maintenance technique that has been shown to overcome shortcomings in the functional properties of surface pavement layers. Although TAO is not a structural layer, its application sustains the pavement’s structural strength and increases its lifespan, which is a valuable effect for the paving industry. Due to recent realisation of the limits of natural resources and the high cost of raw materials, the paving industry has also developed a secondary target of incorporating waste materials as an alternative to conventional raw materials, both to reduce environmental pollution and minimise costs, in such applications. This study focuses on evaluating the effect of using reed ash (RA) in this manner on the mechanical properties of TAO. The control TAO mixture was densely graded, with a 9.5 mm nominal maximum aggregate size (NMAS) utilising a 40/50 asphalt binder grade. Three percentages of RA were incorporated, 6%, 12% and 18%, to produce modified asphalt binder. To verify the effect of this material on cracking behaviours, resistance to permanent deformation of TAO, indirect tensile strength, creep compliance, and wheel track tests were carried out on both control and modified asphalt mixtures. The results showed a significant enhancement in the performance of TAO modified with 6% RA as compared to the control mixture, although the very high dosage of 18% reduced the performance of the relevant TAO mixtures. This study thus indicates that using this waste material can offer an alternative solution for asphalt cement modification, increasing sustainability, if dosages are carefully controlled.

WITHDRAWN: Effect of cement on cement stabilized low plastic graded gravel soils

Gravel soil stabilization with cement materials has been widely used to improve the mechanical properties of road pavement layers, which consequently result in better performance, both in paved and unpaved roads. The strength in component layers of a pavement mainly explained by materials, mixing and method of curing especially in stabilized soils. The present study concentrated the influence of the type of curing in improving the CBR characteristics of a gravel soil stabilized with cement OPC of 53 grades. The method of curing influences in improving CBR values by considering the moisture required for development of cementation and pozzalanic activity during curing period. The present study involves moist curing achieved high values than water curing moist curing strengthen the formation of gel compounds compared to water curing.

A review of chemical stabilisation in road construction

This paper presents a literature review of the application of cement, lime and polymer emulsion in road construction. The focus is mainly on the soil candidates, binding mechanism, the reported strengths and weaknesses for each chemical stabiliser used in soil stabilisation. While it is generally agreed that cement is best suited for sand-sized to gravel-sized soil mixtures (well-graded), lime is mainly used for wet heavy-clay soil mixtures. Polymer emulsion is more suitable for silt-sized to fine gravel-sized soil mixtures (well-graded). Organic soils are the most difficult soil type to stabilise, and for any kind of chemical stabiliser used, the strength gain is relatively minimal. Cement undergoes hydration reaction which is rapid, and results in high compressive strength, while lime undergoes a slower pozzolanic reaction is slower, and provide lower compressive strength. Polymer emulsion depends on the rate of evaporation for the film formation to complete, and results in ductile polymer-soil matrix. Like lime, polymer does not provide significant compressive strength but does provide great flexural strength that prevents crack propagations. The outcomes from this paper provide an insight into recent and upcoming research trend using chemical soil stabilisers on local soil mixtures to improve the engineering properties of pavement layers made of these soil mixtures.

Field Characterization of Pavement Materials using Falling Weight Deflectometer and Sensor Data from an Instrumented Pavement Section

This study deals with the backcalculation of the mechanical properties of pavement layers using not only the falling weight deflectometer (FWD) sensor data but also pavement response under that FWD load from the embedded sensors in an instrumentation section. To perform the backcalculation, a layered viscoelastic pavement model incorporating asphalt concrete (AC) cross-anisotropy is developed as the forward model. Field degree of cross-anisotropy in AC is determined at the maximum magnitude frequency obtained through continuous wavelet transform of the material response signal. The material response signal is obtained from the deconvolution between the loading signal and the signal registered at the embedded sensors. An inverse analysis methodology is also developed to calculate the gross vehicle weight (GVW) of any vehicle passing through the instrumentation section using only the backcalculated material properties and pavement responses. From the results, it is observed that inclusion of the AC cross-anisotropy reduces the error norm, and a good agreement is observed with the laboratory dynamic modulus in both horizontal and vertical directions. It is also observed that the maximum magnitude frequency of material response and degree of cross-anisotropy in AC both decrease with an increase in average AC temperature. Furthermore, using the backcalculated material properties and pavement responses, it is possible to determine the GVW with 95% accuracy.

Asphalt concrete master curve using dynamic backcalculation

ABSTRACT The dynamic backcalculation of pavement layer properties, and more specifically the ability to determine the asphalt concrete master curve, using Falling Weight Deflectometer (FWD) data has caught the attention of many researchers for years. The damaged or aged master curve of existing pavement structures allows the accurate prediction of the pavement structural capacity and remaining life – a goal that cannot be achieved through laboratory testing. To address this need, the authors developed a dynamic backcalculation application that employs the ABAQUS software for forward calculation using implicit dynamic analyses, and the Newton-Raphson’s root-solving algorithm for optimisation. The capabilities of the application were demonstrated for three simulated flexible pavement structures and two asphalt concrete mixes using 40 combinations. The asphalt concrete moduli at the FWD most dominant frequencies around 17 Hz, and the variables of unbound layers converged to the exact values in few iterations for all combinations. The master curves, and mainly the maximum moduli, were reliably determined to less than 1% and 4% error for about 60% and 85% of the combinations, respectively. The potential for determining the master curve and maximum modulus was shown to be dependent on the asphalt concrete mix, asphalt concrete temperature and pavement structure.

Determining field bearing resistance of subgrade soils using physical characteristics

In highway design, subgrade strength is mostly affected in pavement layers’ thickness. California Bearing Ratio (CBR) is one of the simple testing methods that is commonly used to determine the strength of unbounded paving materials; i.e., subgrade, subbase, and base course materials of highways and airfield pavement. In-situ CBR test is intended to determine the static properties of unbound pavement layers represented by bearing capacity of subgrade soils without requiring the digging of test pits. The in-situ CBR test is laborious, time-consuming, and relatively expensive, therefore an alternative methodology is proposed for correlating CBR value with physical properties of subgrade soils such as field density and moisture content. Three testing methods were used: in-situ CBR test, sand replacement method for determining the field density and moisture content of granular soils and clayey soils, respectively. Selected types of soils were nominated from the local area having soil’s type of A-l-b, A-3, and A-6-7. Statistical analyses were performed to evaluate bearing resistance of subgrade soils depending on water content and dry density obtained from field density tests. The results of two statistical models indicated that both field density and water content correlate well with the bearing ratio for various subgrade soils.

Alternate Method of Pavement Assessment Using Geophones and Accelerometers for Measuring the Pavement Response

Pavement instrumentation with embeddable in-situ sensors has been a feasible approach to determine pavement deteriorations. Determining pavement deflections during the passage of the load is a promising strategy to determine the overall performance of the pavement. There are different devices that apply loads to the pavements and measure the deflection basin, these include static, vibratory, or impulse loadings. Most commonly used are the static loading like Benkelman beam and impulse loading like the Falling Weight Deflectometer (FWD). However, these techniques are costly and the measurements are recorded infrequently, i.e., once per year or two years. This study focuses on the use of geophones and accelerometers to measure the surface deflections under traffic loading. To develop a method to measure pavement deflections, the sensors were submitted first to laboratory tests, and then tested in situ, in a full scale accelerated pavement test. In the laboratory, the sensors were submitted to different types of loading using a vibrating table. These tests were used to determine the noise and sensitivity of the sensors, and then to evaluate their response to signals simulating pavement deflections under heavy vehicles. The sensor response was compared with measurements of a reference displacement sensor. Different processing techniques were proposed to correct the measurements from geophones and accelerometers, in order to obtain reliable deflection values. Then, the sensors were evaluated in a full scale accelerated test, under real heavy axle loads. Tests were performed at different loads and speeds, and the deflection measurements were compared with a reference anchored deflection sensor. The main advantage of using accelerometers or geophones embedded in the pavement is to enable continuous pavement monitoring, under real traffic. The sensor measurements could also be used to determine the type of vehicles and their corresponding speeds. The study describes in detail the signal analysis needed to measure the pavement deflections accurately. The measurements of pavement deflection can be then used to analyze the pavement behavior in the field, and its evolution with time, and to back-calculate pavement layer properties.

Comparative analysis of strain-pulse-based loading frequencies for three types of asphalt pavements via field tests with moving truck axle loading

The asphalt-based pavement performance evaluation includes the derivation of the dynamic moduli and loading frequencies of pavement layers under various traffic- and climatic-induced loading conditions. The traffic-induced strain pulses and loading frequencies of commonly used (semi-rigid, flexible, and steel deck) asphalt pavements were experimentally determined by vehicular loading field tests with embedded strain gauges for different axle loads, motion speeds, and temperatures. It was found that the axle load values had no noticeable effect on the pavement loading frequency, which was mainly controlled by the vehicular motion speed. The transverse frequencies were found to be higher than longitudinal ones, while the distributions of loading frequencies by pavement depth differed for three pavements under study. The frequency values at temperatures over 35 °C exceeded those at lower temperatures, while in the temperature range from 4 to 31 °C, the motion speed vs. loading frequency relations for three pavements were nearly identical. The loading frequency f increased approximately linearly with the motion speed V, according to the unified fitting equation for three types of pavements under study, namely f = 0.127 × V. This unified equation was further proved valid to predict the dynamic modulus properties of field asphalt pavement layers. Moreover, several previous prediction models for loading frequency, including the Brown model, Ullidtz model, MEPDG procedure and Ulloa model, were compared to the results in this study. These previous models were found to overestimate the loading frequencies within the asphalt layer. The prediction errors of the Brown model and the Ullidtz model were pronounced. The loading frequencies calculated by the MEPDG procedure and the Ulloa model need to be modified by dividing 2.8 and 1.7, respectively.

Simulation of Temperature Regime of Pavement Layers in Transition Periods of Road Climatic Zone IV

Pavement icing during short-term night temperature drops leads to deterioration of highway performances and increase in road traffic accidents (RTA) in Krasnodar Krai. Peculiar features of temperature regime in road climatic zone (RCZ) IV are analyzed. The considered climatic zone is characterized by frequent zero crossing temperatures of air and road pavement, sharp short-term temperature drops in nighttime, frequent icing of road pavement. Main factors are highlighted which effect temperature regime of road structures. Mathematical model is presented for prediction of road pavement temperature based on weather forecasts. Possibility to decrease the volume of pavement icing by means of thermophysical properties of pavement layers is analyzed.

Validation of the subgrade shear strength parameters estimation methodology using light weight deflectometer: Numerical simulation and measured testing data

Abstract Shear strength parameters (angle of internal friction, ϕ, and cohesion, c) of a soil medium are the key properties for the bearing capacity and stability analyses. The strength parameters have been recognized as one of the most reliable mechanical properties of pavement subgrade that can be used to estimate its permanent deformation behavior under repeated loading. In addition, when a pavement structure is subjected to a non-standard superheavy vehicle load (i.e., gross vehicle weight in excess of a few million pounds), investigation of instantaneous shear failure or onset of yielding in the pavement subgrade layer requires the knowledge of the strength parameters. Light Weight Deflectometer (LWD) has been commonly used as a Non-Destructive Test (NDT) method for in-situ determination of stiffness properties of pavement layers, unpaved roads, and subgrade layer during the construction process. In this study, the validity of a recently developed LWD-based methodology for estimating the in-situ shear strength parameters of the pavement subgrade layer has been further investigated. In this methodology, the commonly accepted hyperbolic stress-strain constitutive soil model along with the consideration of stress dependency of subgrade materials under multiple LWD load levels have been incorporated. The methodology was validated using numerically simulated LWD testing at multiple load levels for two different subgrade materials. In addition, the LWD data collected from large-scale experiments conducted at University of Nevada, Reno testing facility and National Airport Pavement Test Facility were also utilized to verify the methodology. It was found that the proposed LWD-based methodology provides a reasonable estimate for the in-situ shear strength parameters of the compacted soil subgrade.

Impact of pavement layer properties on the structural performance of inundated flexible pavements

Abstract The assessment of the structural performance of flooded pavements remains complicated due to the lack of structural data in the aftermath of flooding and the fact that information about the pavement structure and materials is not always readily available. The objective of this study is to acquire a better understanding of the structural response of pavements that have been inundated and the foreseen changes in capacity using two approaches: a mechanistic approach using layer elastic analysis and the AASHTO empirical approach to determine the structural number. The relative impact of parameters such as unbound material type, layer thickness, traffic loads, and interlayer bond conditions on the reduction in expected strain values at critical locations were evaluated. The results show increases of 15–80% in vertical strains at the top of subgrade layer for low volume and interstate sections and 6–15% increase in horizontal strain at the bottom of asphalt layer for low volume sections and 3–8% for interstate sections. Accurate information on the layer thicknesses, traffic type, and interlayer bond condition were found to be most important for the evaluation of the change in expected horizontal strain. The types of base and subgrade materials are the most important factors for evaluating the change in expected vertical strain. The results of this study provide guidance on the type of information that is most important to collect for the assessment of the structural capacity of a pavement following inundation.

Application of System Dynamics to Integrate Pavement Preservation in Flexible Pavement Design Process

Abstract The performance of a pavement depends on factors like the characteristics of the materials in different pavement layers, traffic, climates, environments, construction quality, etc. Though a pavement is designed for 15 years, conventionally, the pavement reaches the threshold level of performance before the design life, warranting minor and major rehabilitation treatments because of factors beyond the control of the designer. However, the maintenance and rehabilitation treatments during the design life of a pavement are not considered in the design process. The performance of a pavement is defined in terms of the various distresses, i.e., cracking, rutting, roughness, potholes, etc. The performance of the pavement also depends on the strength properties of different pavement layers and their thicknesses, quality of construction, traffic, climate, etc. The level of influence of these parameters on each of the distresses is different. In this study, the Mechanistic Empirical Pavement Design Guideline design tool AASHTOWare is used to simulate the data for cracking (percentage of bottom up fatigue cracking), rutting (total rutting), and roughness in terms of the International Roughness Index. A sensitivity analysis is carried out to study the influence of the design parameters on the distresses. From the results of AASHTOWare simulations, a relationship is established between design input parameters and distress growth using multiple linear regression. While this model gives the estimate of distress over time with respect to the design parameters, the year at which the first preservation activity has to be carried out is to be determined. Considering the pavement as a system, the system dynamics concept could be well suited to study the influence of various factors on the performance of the pavement. A system dynamic model is formulated and implemented using system dynamic software POWERSIM. This study identifies the optimal intervention year for the pavement preservation strategies that depend on traffic level, design layer thicknesses, and modulus (strength) of the pavement layers.

Effects of Asphalt Mixture Type on Asphalt Pavement Interlayer Shear Properties

AbstractThis study compares the interlayer shear properties of pavement layers composed of different asphalt mixture types. Two dense asphalt mixtures (one surface mixture with Tennessee designatio...