Asphalt Layer Thickness Research Articles

Integrated and comparative Structural-LCA analysis of unbound and cement-stabilized construction and demolition waste aggregate for subbase road pavement layers formation

A more extensive use of recycled aggregate in road construction is key to meeting the ambitious targets of the EU circular economy action plan. However, scepticism among designers, contractors and road agencies remains a bottleneck. This integrated structural-environmental study demonstrates the advantages of using recycled construction and demolition waste aggregate (CDW-RA) in substitution of primary natural aggregate (NA) for the formation of subbase layers in both flexible and semi-rigid road pavements. The structural responses of different pavements with a 0.30 m subbase layer made up of four materials, i.e., two unbound and two cement-stabilized obtained including NA and CDW-RA, were compared. The environmental-related impacts were also assessed by means of a life cycle assessment (LCA).Laboratory tests and structural design led to pavement structures with the same thickness for the upper hot-mix asphalt layers, i.e., 0.26 and 0.28 m for the two unbound and the two cement-stabilized subbase materials respectively. The pavement with unbound CDW-RA subbase showed the best LCA outcomes because of the more favourable environmental performance of CDW-RA compared to NA. Although the stabilization of NA and CDW-RA reduces the thickness of the top hot-mix asphalt layers by 0.02 m, the environmental benefits are outweighed by the impact associated with the usage of cement. This study encourages the use of CDW-RA in road subbase layers with similar characteristics to those investigated here. The LCA results also support the use of alternative and more environmentally friendly binders that can enhance the environmental sustainability of stabilized materials in road construction.

Insights into permeability of rejuvenator in old asphalt based on permeation theory: Permeation behaviors and micro characteristics

Aiming to analyze the permeation behaviors and micro characteristics of rejuvenator in old asphalt, the rejuvenation fusion layer (RFL) of rejuvenator and old asphalt was first fabricated by permeation test. Then, the viscosity of RFLs was analyzed and its several influencing factors were explored via conducting the rotational viscosity test. On this basis, coupled with Fick’s law and composite material theory, the permeability coefficient (D) of rejuvenator in old asphalt was calculated and the influencing factors were investigated. Lastly, the micro-phase morphology, mechanical and chemical characteristics of RFL were analyzed via the AFM and FTIR tests. Results showed that the permeability of rejuvenator in old asphalt depended on permeation temperature, permeation time, rejuvenator type and asphalt layer thickness. The higher permeation temperature or longer time contributed to the permeation effect of rejuvenator in old asphalt. Moreover, based on the results, the mixing temperature should not be less than 150 °C and the mixing time should be about 12 s ∼ 18 s for the uniform mixing of RAP and rejuvenator in actual thermal rejuvenation engineering. The permeability of mineral oil rejuvenator in aged asphalt was stronger than that of bio-rejuvenator, and thinner aged asphalt layer made the rejuvenator more easily permeate. Further, the sampling layer exhibited the most remarkable influence on the permeability of rejuvenator in old asphalt, followed by rejuvenator type, permeation time and permeation temperature. The AFM test confirmed that the permeation effect of mineral oil rejuvenator in aged asphalt was superior to that of bio-rejuvenator from the micro perspective, and that under the permeation conditions of 130 °C and 6 h, the mineral oil rejuvenator can fully fuse with aged asphalt and show similar morphological characteristics (“bee” size and quantity) at different layers of RFLs. Further, the mineral oil rejuvenator greatly enhanced the micro mechanical properties of aged asphalt, demonstrating a favorable rejuvenation effect. FTIR test manifested that the functional group composition of the L-type rejuvenator was similar to that of the original asphalt, and that the L-type rejuvenator contained lower carbonyl contents compared to B-type and H-type rejuvenators and exhibited better permeability and rejuvenation effect.

Instrumentation response of full-scale thin airfield pavements

ABSTRACT Instrumentation response data from full-scale accelerated pavement testing have been used to inform pavement design models and enhance service life predictions to ensure long-term operating conditions. However, some aircraft, i.e. military aircraft, may have a requirement to operate under relatively short-term conditions on airfields that are constructed below optimal conditions. Accordingly, the objective of this study was to construct, traffic, and collect instrumentation data from airfield pavement test sections constructed with asphalt thicknesses below existing military standards. Three asphalt thicknesses and two base course strengths were evaluated using two different aircraft simulators each at two tire inflation pressures. Earth pressure cells, single-depth deflectometers, and asphalt strain gauges were used to collect response data. Instrumentation response data were sensitive to increases in asphalt layer thickness, i.e. an increase in asphalt layer thickness generally resulted in an improvement in measured response albeit in relatively thin asphalt layers. Instrumentation response data were more sensitive to tire inflation pressure changes at higher loading conditions when compared to lower loading conditions. Finally, a layered elastic analysis using a non-uniform tire pressure distribution was found to provide a better approximation of measured earth pressure cell response than that of a typically assumed uniform pressure distribution.

Stress-strain characteristics and service life of conventional and asphaltic underlayment track under heavy load Babaranjang trains traffic

Abstract A more durable rail track structure is fundamental in the railway industry, allowing the government to operate the train with higher speed and axle load. That means more passengers and better quality of railroads travel, thereby reducing the maintenance costs and ensuring passengers’ comfort and safety. The effect of a sub-ballast and asphalt layer thickness and freight train traffic with low operational speed on mechanical behavior and design life of conventional track and asphaltic underlayment track, are presented in this paper. One of the significant findings to emerge from this study is that an AC layer with minimum thickness of 0.20 m is required in the asphalt underlayment track application for Indonesian railway infrastructure to facilitate Babaranjang freight trains with up to 50% more tonnage. The evidence from this study also suggests that the asphalt underlayment track with 0.20 m thick of AC layer that contains grade PG70-28 binder could be beneficial to be applied in Indonesian railway system so that the rail track could be constructed with less volume of works than the regular Indonesia's conventional track with 0.40 m of sub-ballast layer.

Numerical Simulation of the Effect of Repeated Load and Waste Polypropylene on the Behavior of Asphalt Layers

Roads are utilized by many vehicle kinds and heavy vehicles among these may be seen as the most essential for cargo loading, causing paving failure and increasing expenses for rehabilitation and maintenance. In this study, in analyzing a finite element employing Abaqus 6.14, composite effects for wheel loads and temperature were addressed. The asphalt layer was designed as an elastic material, while the base and sub-bases were modeled according to the Mohr coulomb model like an elastic material. And studying the impact of wheel loads on flexible pavement settlement and the main output of analyzing pavement structure is almost represented by the vertical stresses and the surface deformation which are considered as the critical response point. A truck type 2S-2 was tried with two thicknesses of asphalt layer 140 mm and 250 mm and considering that base and subbase layer thicknesses remained constant so it does not affect the variation of displacement. It was found that the increase of asphalt layer thickness from 140 mm to 250 mm leads to a decrease in the vertical displacement of about 0.59% and studied the effect of modified asphalt with polymer and how it effect pavement vertical displacement with an obvious reduction from 0.590 mm to 0.265 mm under the repeated load of 36 ton and The vertical stress decreased from 5.036 kPa to 1.899 kPa

Research of multi-axles effects on the flexible pavement based on the viscoelastic continuum damage model

Damages caused by the multi-axles load on the pavement are more complex, due to the interaction between axles. To investigate influences of the multi-axles load on the bottom-up crack of the flexible pavement, the equivalent factor (EF) that represents damage ratios of multi-axles to single-axle based on the viscoelastic continuum damage model was proposed. Through the finite element method, influences of temperature, pavement thickness, and axle configuration on the EF were analyzed. Results suggest that the asphalt mixture with smaller m-value is more likely to have smaller EF. With the increase of temperature and asphalt layer thickness, EF of dual-axles load increases but EF of triple-axles load decreases. Besides, the wheelbase is the only factor of the axle configuration that has remarkable impacts on the EF. Making the distance between the maximum compressive and tensile stress close to the wheelbase can reduce the damage of multi-axle load.

Influence of bonding condition between layers on overlay design of flexible pavements

The interface bonding conditions between the pavement layers is one of the main factors influencing the performance of the pavement structure. The present paper analyzes the effects of the interface conditions between the layers on the process of overlay design in flexible pavements. The data were collected by deflection testing using Falling Weight Deflectometer (FWD) and by drilling cores. Simulations were performed in the software BackMeDiNa, MeDiNa and AEMC for three different conditions of interface between the layers. The data of backcalculated moduli, overlay thicknesses, cracked area and fatigue damage were compared under different bonding conditions. In most of the simulations, backcalculated moduli in the de-bonding condition were higher than ones in the full-bonding between the layers. For the overlay design, the modular sets obtained from the different interface conditions led a slight difference in the thickness of the new asphalt layer (reinforcement), but with higher percentages of cracked area for the structures with full-bonding condition. In the analysis of the fatigue damage, the results showed that the damage obtained with the full-bonding layers was higher than that one obtained with de-bonding interfaces and the bonding between the surface and base layers.

SENSIBILIDADE DE PARÂMETROS DA ESTRUTURA NA ANÁLISE DE DESEMPENHO DE PAVIMENTOS FLEXÍVEIS

The design of asphalt pavement structures is a process that involves the knowledge of variables that are difficult to predict and model.Sensitivity analysis applied to pavement performance prediction is essential to determine the most influential variables, and enable the optimization of design process. This study aimed to analyze the sensitivity of flexible pavements performance to variations in design parameters related to the thicknesses of asphalt layer, base and sub-base and resilient modulus of asphalt layer, base, sub-base and subgrade. For this purpose, a fractional factorial experiment was conducted, which had as output variables the accumulated damage in pavement structure, related to fatigue cracking and rutting in wheel wander. To obtain the accumulated damage, mechanistic-empirical design method was used, through PerRoad software. It was concluded that asphalt layer thickness isthe most sensitive parameter considering the distresses studied, having a higher sensitivity for fatigue cracking and a slightly lower sensitivity for rutting.

CZM analysis and evaluation of influencing factors on interlayer adhesion of asphalt mixture with double-layer continuous pave

The new type of double-layer continuous paving can effectively improve the interlayer adhesion of asphalt mixture and the comprehensive performance of asphalt pavement. However, in the actual process of double-layer continuous paving, the interlayer adhesion of asphalt mixture is affected by many factors (compaction function, construction temperature, process, etc). Therefore, the finite element software (ABAQUS) was used to carry on the three-dimensional modeling of the asphalt pavement, and cohesive zone model (CZM) was used to define the interlayer adhesion of the asphalt mixture to analyze the factors affecting the interlayer adhesion of continuous paving. This paper mainly discusses the influence of different underlayer compaction degree, underlayer compaction temperature, asphalt layer thickness and load action on interlayer bonding and mechanical response. Finally, the grey correlation theory was used to rate the different influencing factors. The results show that when the lower layer is compacted for 50 times, the interlayer adhesion of asphalt pavement is the best, and the ability to resist the displacement crack is the strongest. Increasing the thickness of the upper layer and the compaction temperature of the lower layer of the asphalt pavement can improve the interlayer adhesion and reduce the displacement cracks. At the same time, it is found that the number of precompaction times of lower layer and horizontal braking force are the main factors that affect the interlayer adhesion. The research results have certain theoretical and practical value for the construction technology of double-layer continuous paving of asphalt pavement.

Analysis of equivalent temperature to design of asphalt pavements in Poland using the AASHTO 2004 method

Abstract: The paper presents the analysis of the equivalent temperature on the basis of the fatigue cracking criterion of asphalt layers according to the AASHTO 2004 method and the structural deformation of subgrade criterion according to the Asphalt Institute procedure. The calculations were made with application of the KR5 pavement structure and temperature data obtained from 50 meteorological stations and from the period of 30 years from 1989 to 2019, provided by the Institute of Meteorology and Water Management. The influence of variable traffic with heavy vehicle traffic was taken into consideration, both during the day and throughout the year. It was presented how the values of the equivalent temperature change in the territory of Poland depending on the location of the meteorological station. The computational analysis showed the variability of the equivalent temperature on the territory of Poland in the range from 14.68°C (Suwalki) to 16.99°C (Tarnow).The weighted mean value of the equivalent temperature for the entire year is 16.01°C and it is higher than the value adopted in the catalogue of typical flexible and semi-rigid structures that is equal to 13,00°C. The change in the equivalent temperature value on the designed thickness of asphalt layers of the pavement structure has been also assessed in the paper. Keywords: Pavement design; Equivalent temperature; Fatigue life; AASHTO 2004 method

Spatial Representation of GPR Data—Accuracy of Asphalt Layers Thickness Mapping

Information on pavement layer thickness is very important for determining bearing capacity, estimating remaining life and strengthening planning. Ground-penetrating radar (GPR) is a nondestructive testing (NDT) method used for determining the continuous pavement layer thickness in the travel direction. The data obtained with GPR in one survey line is suitable for the needs of repair and rehabilitation planning of roads and highways, but not for wider traffic areas such as airfield pavements. Spatial representation of pavement thickness is more useful for airfield pavements but requires a 3D model. In the absence of 3D GPR, a 3D model of pavement thickness can be created by additional processing of GPR data obtained from multiple survey lines. Five 3D models of asphalt pavements were created to determine how different numbers of survey lines affect their accuracy. The distance between survey lines ranges from 1 to 5 m. The accuracy of the 3D models is determined by comparing the asphalt layer thickness on the model with the values measured on 22 cores. The results, as expected, show that the highest accuracy is achieved for the 3D model created with a distance of 1 m between survey lines, with an average relative error of up to 1.5%. The lowest accuracy was obtained for the 3D model created with a distance of 4 m between the survey lines, with an average relative error of 7.4%.

Evaluating the effect of amine-based anti-stripping agent on the fatigue life of asphalt pavements

ABSTRACT Aggregate-binder adhesiveness is a property that can affect the service life of asphalt pavements. In order to reduce the effects of the loss of adhesion between aggregates and binders over time, lime or amine-based anti-stripping agents are commonly used. The objective of this paper is to evaluate the impact of using an amine-based anti-stripping agent on the fatigue life of asphaltic pavements. Stiffness characterisation, the Simplified Viscoelastic Continuum Damage model, and the software FlexPAVE™ were used. Two different layered structures were analysed: one with a 0.10 m asphalt layer thickness, and another with a combination of two 0.05 m asphalt layers, with the same 0.10 m total asphalt layers thickness. The 10 years fatigue simulation was considered with 1,000,100 total ESALs traffic volume, single wheel loading of 40 kN, traffic speed of 60 km/h, and constant temperature of 20°C. It was concluded that mixtures with anti-stripping agent and/or granitic aggregate showed better fatigue behaviour than mixtures with neat binder and/or phonolitic aggregate. All investigated pavements showed bottom-up predicted crack initiation. It is more recommended to use the mixtures with amine-based anti-stripping agent on the bottom asphalt layer and mixtures with neat binder on the top layer.

Determination of rutting performance of asphalt pavements considering realistic tire-pavement contact area

In the conventional pavement design procedure using multilayer elastic theory, tire loading equal to tire inflation pressure and traditional circular contact area are assumed. Therefore, the area of contact is extremely overestimated and the contact stress is significantly underestimated. Rotary Compactor and Wheel Tracker (RCWT) equipment was designed and fabricated with three different functionalities. The RCWT captures the realistic contact areas of pneumatic tires, simulates the field compaction process, and conducts simulative laboratory wheel tracking test. This study was conducted to determine relative damage of realistic tire-pavement contact area with respect to the traditional contact area. Based on the obtained footprint results, 63 percent difference exists between traditional and effective contact areas. Furthermore, it was found that based on the thickness of asphalt layer, vehicle tire was 2.5 to 1.5 times more damaging than full circular contact area. Moreover, realistic contact area causes about 50 percent reduction in pavement operational life.

Structural response and sensitivity analysis of granular and asphaltic overlayment track considering linear viscoelastic behavior of asphalt

Abstract This study investigated the structural response of granular and asphaltic overlayment of rail track considering the linear viscoelastic behavior of asphalt. The calculation of the tensile strains at the bottom of the asphalt layer, the compressive stresses at the top of the subgrade layer, and the service life of the granular and the asphaltic overlayment rail track were conducted using the KENTRACK software. Furthermore, the sensitivity analysis by changing different factors was studied in this paper. The results of this study indicate that the asphaltic overlayment rail track structure has a much longer predicted service life than the granular rail track. It was also shown that the sub-grade compressive stress is more sensitive to the change in subgrade modulus than the change in ballast-sub-ballast-asphalt layer thickness and the change in binder type, respectively. In addition, the asphalt tensile strain is more sensitive to the change in asphalt layer thickness than the change in subgrade modulus and the change in binder type, respectively. These findings also enhance our understanding that subgrade compressive stress and asphalt tensile strain in the asphaltic overlayment track are more sensitive to the change in asphalt layer thickness than the change in binder type.

INVESTIGATION OF USING A BITUMINOUS SUB-BALLAST LAYER TO ENHANCE THE STRUCTURAL BEHAVIOR OF HIGH-SPEED BALLASTED TRACKS

This paper evaluates the most suitable thickness of both asphalt and ballast layers to improve the conventional high-speed ballasted tracks. The work was conducted by designing asphalt mixture using the Marshal method in the laboratory and using the ANSYS software to evaluate the best thickness of both theballast and asphalt layer to minimize vertical deformations and corresponding stresses. The results of the numerical analysis showed that the minimum deformations and stresses for a track containing a bituminous sub-ballast system are lower than the deformations and stresses for a conventional system when the thickness of the ballast layer was 250 mm. However, when the thickness of the ballast layer was 300 mm, the vertical deformation increased when the asphalt layer thickness increased. This theoretical analysis proved that a track that consists of 250 mm ballast and 120 mm bituminous sub-ballast layers enhances the structural behavior of the high-speed ballasted tracks.

Improvement of unbound granular pavement layers and subgrade with cement dust in Egypt

The main goal of this study is to assess the technical viability of using cement dust as part of the fines percentage in the unbound granular base/subbase pavement layers’ and subgrade soil as a viable sustainable solution. This study investigates the effect of adding cement dust to five types of pavement road materials which are collected from different ongoing roadway construction projects (1) Reclaimed Asphalt Pavement (RAP), (2) crushed stone base aggregates, (3) blend of crushed stone base aggregates with RAP, (4) crushed stone subbase aggregates, and (5) sandy subgrade soil. The resilient modulus (Mr) is selected as the main characteristic for evaluating the investigated materials’ stiffness. The regression parameters (k1, k2, and k3) of the universal Mr prediction model are found by fitting the experimental results of Mr testing for two replicates per each material type. The results show that using 3–5% of cement dust improves the estimated Mr of the investigated base/subbase materials and subgrades at the anticipated field stresses by 8–21%., As a result the structural layer coefficients are enhanced by 11–17%. KENLAYER nonlinear damage analysis confirms that using 3–5% of cement dust improves the predicted rutting life by up to 12% and the fatigue life up to 27%. Based on a typical pavement structure, enhancing pavement base/subbase layers and subgrade soils with 3–5% of cement dust reduces asphalt layer thickness from 11.25 to 12.50% and increases base/subbase layer thickness from 8.75 to 12.50% to maintain the same predicted rutting and fatigue lives of the typical structure. This positively affects the total construction cost in addition to the ecological benefits.

Asphalt pavement modulus backcalculation using surface deflections under moving loads

AbstractThe measurement of pavement surface deflections under moving loads can be used for evaluation of pavement structural condition. The objective of this paper is to develop an innovative backcalculation method to calculate pavement layer moduli based on traffic speed deflectometer (TSD) measurements and analyze factors influencing backcalculation results. The backcalculation method is based on 2.5D finite element method (FEM) and constrained extended Kalman filter (CEKF). Field measurements at different pavement sections were used to verify the accuracy of backcalculation results. Parametric analysis was conducted to evaluate the influences of traffic loading and pavement structure variations in the field. It was found that the backcalculation results were considerably affected by the variation of asphalt layer thickness and dynamic loading due to pavement surface roughness. A heavy truck passing the adjacent lane during TSD testing could also cause variation of backcalculation results.

A model for predicting the deterioration of the international roughness index

ABSTRACT Road pavements continuously deteriorate mainly due to the combined influence of traffic load and environmental conditions. The pavement ability to satisfy the road user demands along its designed time of service expresses its performance level. The prediction of performance deterioration curves is a basic part of any Pavement Management System (PMS). Road roughness is an important parameter in determining the performance of pavements. The International Roughness Index (IRI) is the universal standard for measuring the pavement roughness and it has become the most widely employed pavement index. This paper presents the development of a model for predicting the deterioration of the IRI and calibrating its parameters based on the pavement structural factors such as structural number, asphalt layer thickness, subgrade strength, and environmental conditions. The approach adopted for the IRI deterioration model development was based on the combination of the empirical-mechanistic approach and the regressive empirical approach. The predicted results were compared with the measurements of road sections located in various climate zones, which are embedded in the PMS of Netivei Israel (NETI), National Company for Transport Infrastructures. The comparison shows a very good correlation, and most of the predicted results are within the measurement and interpretation error range.

Review on evolution and evaluation of asphalt pavement structures and materials

Abstract The purpose of this study was to summarize the wide-range literatures on asphalt pavements, explore the evolution of road pavements, analyze typical asphalt pavement structures, highlight current trends in research and industry, and to recommend future areas of research and development. In this research, road pavement evolution was explored from the earliest roads to the modern pavements. A new method was recommended to categorize asphalt pavement materials into the three large families which may be further sub-divided according to their mechanical parameters. A unified asphalt pavement classification (UAPC) method was proposed and the worldwide asphalt pavements could be divided into six types through the new method. Based o n the UAPC method, 1087 asphalt pavement structures were classified and analyzed to explore the asphalt thickness variation. In order to evaluate asphalt pavement performance, the Chinese design specification was employed for analyzing lives of 29 high-volume pavements and 28 low-volume pavements. Through this research, it was found that: (1) in the past 100 years, asphalt pavement materials and structures had been becoming more and more strong; (2) asphalt layer thicknesses were various from 5 to 60 cm and the overall pavement thicknesses were various from 28 to 160 cm; (3) the long-life pavements in the other countries may become “shorter-life” pavements according to the prediction based on the Chinese specification.

Asphalt pavement design optimisation: a case study using viscoelastic continuum damage theory

ABSTRACT Fatigue cracking is the main type of distress in flexible pavements in Brazil. Numerical models that are based on viscoelastic continuum damage (VECD) theory can help to explain the damage evolution process in asphalt mixtures, thereby allowing the proper analysis of the fatigue phenomenon. This paper aims to characterise and verify the fatigue behaviour of four test sites constructed with dense asphalt mixtures in Santa Maria, Brazil, employing field monitoring, linear viscoelastic characterisation, uniaxial cyclic fatigue testing, the simplified VECD (S-VECD) model, and FlexPAVETM software. This study’s results are coupled with a cost/benefit analysis of the evaluated test sites. The constructed sites are compared to simulated optimal pavement designed using FlexPAVETM and fatigue damage transfer function. The results indicate that this study’s methodology can predict fatigue damage evolution by identifying early cracking in two of the test sites and capturing good fatigue resistance in the other two sites. Furthermore, in both cases of early cracking, the design requirements for fatigue resistance could be met by increasing the asphalt layer thickness (optimal pavements), which significantly reduced the US$/NFATIGUE ratio. Thus, an improved cost/benefit ratio was realised for the pavements designed using this methodology and analysed using only an established fatigue criterion.