Showing papers in "Road Materials and Pavement Design in 2011"
TL;DR: In this paper, it was shown that the alcohols, which are formed concurrently with the sulfoxides from the same hydroperoxide precursors as the ketones, have a similar effect on asphalt viscosity increase as does the ketone.
Abstract: The correlation between asphalt viscosity increase on oxidative aging and the carbonyl compounds formed (almost exclusively ketones) has been well established; however, the effect of sulfoxide formation on physical properties during age hardening has received little attention. Evidence is presented in this paper that shows that the alcohols, which are formed concurrently with the sulfoxides from the same hydroperoxide precursors as the ketones, have a similar effect on asphalt viscosity increase as does the ketones. These alcohols are the main contributors to oxidative age hardening of high sulfur asphalts. Analysis of the kinetic data for ketone and sulfoxide formation during asphalt oxidation also provides additional evidence for the validity of the dual asphalt oxidation mechanism previously reported.
266 citations
TL;DR: In this article, the authors investigated the change in complex modulus (norm and phase angle) during cyclic tests on bituminous mixtures and found that the change can be explained by four phenomena: nonlinearity, heating, thixotropy and fatigue.
Abstract: This paper describes investigation into the change in complex modulus (norm and phase angle) during cyclic tests on bituminous mixtures. The change can be explained by four phenomena: nonlinearity, heating, thixotropy and fatigue. An experimental campaign has been performed at ENTPE laboratory in order to identify and quantify the first three phenomena. The analysis of the results reveals that the two reversible effects (heating and thixotropy) are very important and can not be ignored when interpreting fatigue tests. Nonlinearity, for the rather small strain level amplitudes considered in our experimental campaign (up to 122 μm/m), is also shown to be reversible. Heating is due to the viscous dissipated energy that heats the specimen. At the beginning of the test, temperature increase in the sample is shown to be proportional with the total dissipated energy. Thixotropy effect is quantified. In addition, it is shown that thixotropy effect can be modeled using an equivalent temperature increase.
197 citations
TL;DR: In this paper, the suitability of the current resilient modulus test protocol (NCHRP 1-28A) for its application to unsaturated soils was assessed, and the results allowed for the enhancement of the Universal Model for resilient Modulus prediction by incorporating suction as a stress state.
Abstract: The suitability of the current resilient modulus test protocol (NCHRP 1-28A) for its application to unsaturated soils was assessed. Modifications to the stress state conditions of the protocol are necessary due to the axis-translation needed during the test when measuring matrix suction. This study presents the modulus of unbound materials resulting from tests performed under unsaturated soil conditions. Two different materials were tested. The base material was tested under drained and undrained boundary conditions, while the subgrade was tested under drained boundary condition. The results allowed for the enhancement of the Universal Model for resilient modulus prediction by incorporating suction as a stress state. This model predicts the resilient response of unbound materials as a function of external stress state and matrix suction levels and therefore, it is independent of moisture variation.
145 citations
TL;DR: In this article, a simple method allowing approximation of a linear viscoelastic model by a generalized Kelvin Voigt or generalized Maxwell model having "n" bodies is proposed.
Abstract: A linear viscoelastic model having a continuous spectrum is difficult to implement in a finite element calculation. Then approximation of this model by a generalized Kelvin Voigt model or generalized Maxwell model is another option allowing calculation. A simple method allowing approximation of a linear viscoelastic model by a generalized Kelvin Voigt or generalized Maxwell model having “n” bodies is proposed. This method is applied to bituminous materials. The continuous spectrum 2S2P1D model developed at the “Ecole Nationale des Travaux Publics de l'Etat” (ENTPE) for bituminous materials is approximated by a generalized Kelvin Voigt and a generalized Maxwell Model having any chosen number (n) of bodies. The three-dimensional case is also considered and influence of the number of chosen bodies “n” is presented.
61 citations
TL;DR: In this paper, the shape characteristics of aggregate particles were determined by DIP technique and a control mixture containing all of aggregate shapes was used as the image analysis program, where coarse aggregate sizes of 19 to 12.5 mm were selected by hand as three categories of flat, elongated, and spherical.
Abstract: The importance of the shape of aggregate particles on their mechanical behavior of bituminous materials is well recognized. In asphalt concrete, the shape of aggregate particles affects the durability, workability, shear resistance, tensile strength, stiffness, fatigue response, and optimum binder content of the mixture. In recent years, DIP techniques are widely used to analyze the shape indexes of aggregate. In this study, the shape characteristics such as aspect ratio, elongation, flatness, form factor, roundness, shape factor, and sphericity were determined by DIP technique. The coarse aggregate was proportioned into three size fractions, namely, 19 to 12.5 mm, 12.5 to 9.5 mm, and 9.5 to 4.75 mm. Coarse Aggregate sizes of 19 to 12.5 mm and 12.5 to 9.5 mm were selected by hand as three categories of flat, elongated, and spherical. In addition, a control mixture containing all of aggregate shapes was prepared. ImageJ Java program was used as the image analysis program. This program measures a l...
60 citations
TL;DR: In this article, the influence of air void distributions on mechanical properties and response of asphalt mixtures was analyzed using the Hamburg Wheel-Tracking Test (HWTT) and a repeated tensile test.
Abstract: Air voids play an important role in influencing the performance of asphalt mixtures. This study utilized several mechanical tests to characterize the influence of air void distributions on mechanical properties and response of asphalt mixtures. The overlay tester, Hamburg Wheel-Tracking Test (HWTT), and a repeated tensile test were used to characterize the resistance to fatigue cracking, permanent deformation, and moisture damage, respectively. The overlay test results showed that specimens with more uniform air void distribution had less variability in terms of resistance to fatigue cracking compared with specimens with less uniform air void distribution. Consequently, recommendations were made to improve air void distribution and reduce the test variability. The HWTT results were found to be insensitive to the air void distribution. The repeated tensile test was used to measure material properties that were required inputs to a fracture-based model for the analysis of moisture damage. The repea...
45 citations
TL;DR: In this paper, the authors developed a research based on the fundamental dissipated energy analysis to quantify the cohesive healing in asphalt binder and evaluated the key impact factors on healing in a systematic way under different loading and environmental conditions.
Abstract: The effect of healing on asphalt material fatigue performance has been accepted as an important property which is, at least partially, responsible for the significant difference between the laboratory and field fatigue behavior. Although some studies have been conducted to characterize the asphalt healing and its mechanism, very few researches have clearly identified how different loading and climate conditions can influence the effect of healing in a quantitative way. In addition, little suggestion has been provided on the integration healing into fatigue life prediction and pavement design. Therefore, this study develops a research based on the fundamental dissipated energy analysis to quantify the cohesive healing in asphalt binder. The key impact factors on healing are evaluated in a systematic way under different loading and environmental conditions. A healing rate predictive model and fatigue life prediction model based on binder rheological properties and visco-elastic energy dissipation i...
43 citations
TL;DR: In this paper, a linear viscoelastic analysis (LVE) was used to evaluate the thermal properties of the three NMAS mixture beams for the bending beam Rheometer (BBR) test.
Abstract: The paper is presented to validate the use of asphalt mixture beams in the Bending Beam Rheometer (BBR) test. Experimental work was performed to address the concerns regarding the sources of variability of using asphalt mixture beams for the BBR tests. The dimensional differences on the accuracy of deflections of a beam are evaluated using finite element method and statistical analyses. The effect of air voids on the overall stiffness of asphalt mixtures is found to be less significant at low temperatures through the volumetric measurements on three nominal maximum aggregate sizes NMAS (i.e., 12.5 mm, 9.5 mm, and 4.75 mm) mixture beams. The homoscedasticity of variances among the 12.5 mm, 9.5 mm, and 4.75 mm NMAS mixture groups is statistically validated using the Bartlett's test, so the measurements and comparisons among these NMAS mixture groups are valid for the BBR tests. A linear viscoelastic analysis (LVE) was used to evaluate the thermal properties of the three NMAS mixture beams. The LVE ...
33 citations
TL;DR: In this article, the effects of truck tire types on near-surface pavement responses were evaluated via finite element anyalysis, and the results indicated that the Super Single (SS) tire produced the worst damage to the pavement in terms of top-down cracking and AC rutting in Asphalt Concrete (AC) layers, while New Generation Wide-Based (NGWB) tire (445/50R22.50) induced approximately the same damage as the standard dual tire assembly (11R 22.5) evaluated in this study.
Abstract: The effects of truck tire types on near-surface pavement responses were evaluated via finite element anyalysis. First, two wide-based truck radial tires (425/65R22.5 and 445/50R22.5) were modeled based on the tire geometries and specifications from the tire manufactures. Accordingly, tire-pavement interaction models were developed. These models were then calibrated to make sure models can be used for further evaluation purpose. A study on how truck tire types affect near-surface respones were investigated based on calibrated tire-pavement contact models. The results indicated that the Super Single (SS) (425/65R22.5) tire produced the worst damage to the pavement in terms of top-down cracking and AC rutting in Asphalt Concrete (AC) layers, while New Generation Wide-Based (NGWB) tire (445/50R22.50) induced approximately the same damage as the standard dual tire assembly (11R22.5) evaluated in this study.
27 citations
TL;DR: In this article, a new crack depth fracture model is proposed to predict the thermal cracking performance of asphalt concrete mixtures. But, the model is not suitable to predict low temperature cracking of asphalt rubber mixtures in the field.
Abstract: The existing Thermal Cracking Model (TCMODEL) that is currently an integral part of the Mechanistic Empirical Pavement Design Guide (MEPDG) has been shown to adequately predict low temperature cracking of asphalt concrete mixtures utilizing conventional binders. However, test results from several asphalt rubber mixtures in this research study showed that the TCMODEL in the MEPDG falls short in predicting the observed thermal cracking resistance of these mixtures in the field. This paper presents development and findings of a new method for thermal cracking potential evaluation in asphalt mixtures, with a focus on asphalt rubber mixtures. Refinements of the existing IDT test protocol are presented, and a new Crack Depth Fracture Model is proposed to include a fracture energy parameter. The new fracture energy model is evaluated with laboratory test results and rationality corresponding with field observations. The new model proved to be satisfactory in predicting the thermal cracking performance f...
23 citations
TL;DR: In this paper, the adequacy of using conventional traffic data and national default values in the absence of weigh-in-motion (WIM) data for pavement design was examined.
Abstract: This study examines the adequacy of using conventional traffic data and national default values in the absence of weigh-in-motion (WIM) data for pavement design. A comparative study was conducted on 14 unique sections in Arizona (AZ), where WIM data are available through the Long Term Pavement Performance (LTPP) program. The study consists of two parts: 1) comparisons of input traffic data and 2) comparisons of pavement distresses predicted by the Mechanistic Empirical Pavement Design Guide (MEPDG). The traffic related input parameters include average design-lane truck volumes, Vehicle Classification Percentages (VCP), Monthly Adjustment Factors (MAF), axle load distribution factors and the number of axles per truck. The truck volumes and VCPs are available through the Arizona Department of Transportation (ADOT) while only national average values are available for the other traffic inputs in the absence of WIM data. The comparisons of the input variables showed that the truck volumes for a design...
TL;DR: In this article, the effects of foaming effects on binder chemistry were investigated using two bitumens from different sources with similar grades, and infrared spectroscopy techniques were done on neat and foamed bitumen samples.
Abstract: Foaming effects on binder chemistry were investigated using two bitumens from different sources with similar grades. Infrared spectroscopy techniques were done on neat and foamed bitumen samples. A ...
TL;DR: In this article, correlations were found between the energies transferred by the two devices to reach the same density level, and the evolution of the densification processes attained with the two compaction methods.
Abstract: The Proctor method is the most widely utilized compaction method in the study of unbound granular soils that are used in road infrastructures. However, a possible drawback of the Proctor test is that material undergoes impact loads that do not have a well defined correspondence with the energy application modes in field compaction methods. For this reason, some research studies have recently focused on the use of the gyratory method, which has been successfully utilized so far in the study of bituminous mixture, for unbound materials. In the present work, the elaboration of the data allowed the authors to understand and compare the evolution of the densification processes attained with the two compaction methods. In particular, correlations were found between the energies transferred by the two devices to reach the same density level.
TL;DR: In this article, a contact model is developed in statics where the tyre tread is modelled by an elastic half-space and the road surface by several perfectly rigid asperities.
Abstract: This paper deals with the influence of road texture on normal pressure distribution for tyre/road contact in statics, within the framework of rolling noise prediction. A contact model is developed in statics where the tyre tread is modelled by an elastic half-space and the road surface by several perfectly rigid asperities. The problem is solved using a Two-scale Iterative Method (TIM) which is fast and efficient. The numerical results give high resolution contact patterns for real road surfaces. Predicted results are compared to contact pressures measured between a slick tyre and several road surfaces. The agreement is fairly acceptable by keeping in mind both the precision of the measurement device and the simplicity of the model. The best correlations are obtained for model surfaces composed of spherical punches and real road surfaces of moderated or high macro-texture. The results are less conclusive for road surfaces of fine macro-texture. The efficiency of the TIM at a tyre/road contact sca...
TL;DR: In this paper, the authors evaluated the properties of asphalt pavement materials and made recommendations for materials and test methods that can be used to build long-lasting roads that are necessary to support economic growth.
Abstract: The state of Qatar is experiencing tremendous economic growth, and traffic loading has increased rapidly as a consequence of the need to increase road transport efficiency. This study was initiated to evaluate the properties of asphalt pavement materials and make recommendations for materials and test methods that can be used to build long-lasting roads that are necessary to support economic growth. Many tests were conducted to evaluate the physical, chemical, and mechanical properties of asphalt pavement materials. Some of these results will be valuable as the state of Qatar moves toward mechanistic-empirical design. The imported aggregates referred to as gabbro were found to have better resistance to degradation under mechanical forces and better skid resistance in comparison to the local limestone aggregates. However, the surface energy results reveal that gabbro has less resistance to moisture damage than the limestone aggregate. The dynamic mechanical analysis of the mixtures demonstrates th...
TL;DR: In this article, an attempt at using X-ray computerized tomography (CT) and stereology method to estimate the gradation of asphalt mixtures is made, and a simple method of converting the gradations of spherical aggregate assumption to that of mechanical sieving is proposed.
Abstract: An attempt at using X-ray computerized tomography (CT) and stereology method to estimate the gradation of asphalt mixtures is made. Using X-ray CT which is a nondestructive test technique to obtain batch of slice images, analyzing these two-dimensional (2-D) slice images, and applying stereology method which is a probability statistical theory, the three- dimensional (3-D) volumetric gradation of coarse aggregate under the assumption of spherical aggregate can be estimated from 2-D area gradation. There is error between the gradations of spherical aggregate assumption and mechanical sieving and a simple method of converting the gradation of spherical aggregate assumption to that of mechanical sieving is proposed. Moreover, a correction factor C is used to convert the gradation of spherical aggregate assumption to that of mechanical sieving so that comparison between these two gradations can be made.
TL;DR: In this paper, the authors examined which constitutive model is the most appropriate for predicting the resilient behavior of RAP as a base layer and examined the Resilient modulus (MR) for specimens containing different ratios of Rap and aggregate.
Abstract: The use of Reclaimed Asphalt Pavement (RAP) as a base layer is a sustainable rehabilitation method and reduces local agency cost. Proper characterizations of the stress-dependent behavior of pavement layers have significant impact on the accuracy of pavement response predictions. This research examines which constitutive model is the most appropriate for predicting the resilient behavior of RAP as a base layer. The Resilient modulus (MR) was examined in the laboratory for specimens containing different ratios of RAP and aggregate. The MR of RAP/aggregate blends were higher, less sensitive to bulk stress and more sensitive to confining pressure compared to base aggregate. The MEPDG model that presented the nonlinear resilient behavior of unbound layers fitted the RAP material and was mathematically stable.
TL;DR: In this paper, the effects of Silica Fume (SF) and Fly Ash (FA) additives on the frost salt scaling resistance and flexural strength properties of pavement concrete were investigated.
Abstract: The purpose of this study is to investigate the effects of Silica Fume (SF) and Fly Ash (FA) additives on the frost salt scaling resistance and flexural strength properties of pavement concrete An attempt is also made to attain a more durable and higher strength concrete by a suitable combination of Ordinary Portland Cement (OPC), SF and FA SF and FA are used as cement replacement in proportions of 0, 5, 10% and 0, 5, 10, 15% by weight respectively Flexural strength is tested after 7, 28 and 91 days of the lime saturated water curing period The experimental results indicate that using FA only decreases while SF only slightly increases 28-days flexural strength On the other hand, using SF and FA together shows relatively more strength gain Among all those tested, maximum 28 days flexural strength of 453 MPa is obtained for the mix proportions of 85% OPC + 10% FA and 5% SF SF significantly decreases the amount of liquid absorption by capillary suction and has a significant effect on the sca
TL;DR: In this article, the influence of pavement types on water chemistry using recirculating laboratory mesocosms was studied and it was found that pavement types can act as a source of contaminants to receiving waters, not just a conduit.
Abstract: Urban pavements may influence water quality by leaching contaminants such as total hydrocarbons, nutrients and metals which can negatively influence receiving waters. We studied the influence of different pavement types on water chemistry using recirculating laboratory mesocosms. Pavement types tested were unsealed and sealed asphalt concrete pavement, recycled asphalt concrete pavement, Portland cement concrete (PCC), PCC with fly ash, PCC with ground-granulated blast furnace slag, and porous PCC. Pavement types variably influenced pH, metal, bromide, chloride, phosphate and sulfate concentrations relative to controls. Data suggest pavement types can act as a source of contaminants to receiving waters, not just a conduit.
TL;DR: In this article, a semi-analytical solution is proposed to attack the problem of viscoelastic pavement response (displacements, stresses and strains) subjected to a surface moving dynamic load.
Abstract: A semi-analytical solution is proposed to attack the problem of viscoelastic pavement response (displacements, stresses and strains) subjected to a surface moving dynamic load. The general solution, in the context of Layered Viscoelastic Theory (LVET), is formulated in terms of two convolution integrals: the implicit and the explicit convolution integrals. The implicit convolution integral is solved using the technique by Chen et al 2009, by which the explicit convolution integral is then addressed and a semi-analytical solution is generated. This semi-analytical solution is fully analytical in the time domain and involves only a single integral in the space domain. The accuracy of the proposed semi-analytical solution is verified by the commercial finite element method software Abaqus. Since the proposed semi-analytical solution is analytical in the time domain, it is computationally very efficient. Pavement response subjected to a Falling Weight Deflection (FWD) load is introduced briefly for i...
TL;DR: In this article, the authors show that using light aggregate for road surface pavements, significant energy savings in road lighting could be achieved due to significantly higher reflectance properties of the surface.
Abstract: Current road lighting standards and recommendations are based on luminance levels and luminance distributions on the road surface. The luminance of the road surface depends on the amount of light falling on it and the reflection properties of the road surface. Using light aggregate for road surface pavements, significant energy savings in road lighting could be achieved due to significantly higher reflectance properties of the surface. In this study several experimental pavement samples with light surface characteristics were manufactured and their reflection properties were measured. The results indicate that lighter pavement materials result in higher average road surface luminance values and lower average lighting energy usage costs per kilometer.
TL;DR: In this article, the effects of a warm mix asphalt additive, Sasobit, and a liquid anti-stripping agent, AD-here® HP Plus, on the rheological properties of a selected performance grade binder (PG 64-22) as per Superpave® specifications were evaluated.
Abstract: This study evaluated the effects of a warm mix asphalt (WMA) additive, Sasobit®, and a liquid anti-stripping agent, AD-here® HP Plus, onthe rheological properties of a selected performance grade binder (PG 64-22) as per Superpave® specifications. The optimum dosage (mass) of Sasobit®was found to be 1.5%, which was expected to reduce the mixing and the high PG temperatures by 9oC and 4.5oC, respectively. Sasobit® was also found to decrease the fatigue resistance and low temperature resistance of the base binder to some extent. Furthermore, a reduced rolling thin film oven (RTFO) temperature was expected to exhibit significant reduction in the rut resistance of the WMA. While anti-stripping agent was expected to reduce the rutting resistance, it was anticipated to increase low temperature resistance of the WMA. The findings of this study are expected to enhance rheological database and help in implementing WMA mixes in Oklahoma and elsewhere.
TL;DR: In this paper, a numerical tool based on the Distinct Element Method (DEM) is developed and applied to asphalt compaction studies, which is applied to three asphalt mixtures with different compactabilities.
Abstract: Asphalt mixtures compaction is considered to be one of the most important factors that influence bituminous layers durability. However, it is still not clear how compaction should be carried out. In this paper a numerical tool, based on the Distinct Element Method (DEM), is developed and applied to asphalt compaction studies. Asphalt mixtures were modelled in 2D as an assemblage of circular rigid particles that interact with each other at soft contact points. The methodology was applied to three asphalt mixtures with different compactabilities: Asphalt Concrete 0/16 and 0/5, and Porous Asphalt 0/8. It is shown a good agreement between the static compaction laboratory tests results and the results obtained with the proposed numerical model. Despite the 2D limitations, the obtained results clearly indicate the viability of the proposed numerical tool.
TL;DR: In this paper, a catalogue of test roads in Denmark, four long lasting test sections constructed in the early 80's were selected for field sampling and extensive laboratory study, which focused on characterizing the bituminous materials used in the test sections.
Abstract: Based on a catalogue of test roads in Denmark, four long lasting test sections constructed in the early 80's were selected for field sampling and extensive laboratory study. This paper focuses on characterizing the bituminous materials used in the test sections. First, asphalt cores were investigated in a non-destructive way using X-ray tomography and indirect tensile stiffness test. The field samples were further analyzed with respect to binder content, air void content, and aggregate gradation. To characterize recovered binders, both chemical and rheological tests were applied. It was found that the long lasting test sections consisted of thick asphalt layers of low air void contents. The wearing courses contained relatively high binder content except for one with a binder content of slightly below 6%. For all the test sections, no propagated cracks were observed. In achieving a long pavement lifetime, aging of bitumen was indicated as one of the key factors. Field aging of bitumen was strongly...
TL;DR: In this article, a two-phase mixing method was proposed to improve the mechanical properties of hot mix asphalt by precoating the coarse aggregate with an appropriate amount of optimum binder content.
Abstract: In this research, in order to improve the mechanical properties of hot mix asphalt, the mixing method was considered. The new method is mainly based on precoating the coarse aggregate with an appropriate amount of optimum binder content. Then the coated coarse aggregate was mixed with fine aggregate + filler and remaining optimum asphalt content. Three types of asphalt cement AC-5, AC-10 and AC-20 was used as binder. To investigate the effectiveness of two-phase mixing method on modified mixtures, the styrene-butadiene-styrene (SBS, Kraton D 1101) modified AC-10 was also used. Basalt was used as aggregate. In conclusion, two-phase mixing method increased the Marshall Quotient, stiffness, creep stiffness, fatigue life and decreased the moisture-induced damage of the hot mix asphalt. It was determined that the efficiency of two-phase mixing system on modified mixtures was greater than that of the unmodified mixtures. A mixing plant for two-phase mixing method was designed to manufacture hot mix asp...
TL;DR: In this article, an experimental investigation on the effect of the freezing-thaw cycles of bituminous materials was carried out in a laboratory environment and it was observed that the freezing expansion can be measured for high degree of saturation of the material.
Abstract: Contraction/expansion effects induced by freeze-thaw cycles are thought to be at the origin of important and sudden deteriorations of pavement surface course, observed on some road sections in North-East of France. Therefore following these events and observations, it was decided to investigate in laboratory the phenomenon of freeze-thaw on partially water saturated bituminous materials specimen. This article presents some aspects of this beginning research work. We report an experimental investigation on the effect of the freezing-thaw cycles of bituminous materials. Some specimens are subjected to laboratory freeze-thaw cycles under a freezing rate without moisture change with the environment. In addition to basic mechanical properties and pore distribution, the measurement is also performed for freezing expansion of material of the specimen in each cycle. From these results, it is observed that the freezing expansion can be measured for high degree of saturation of the material. The results in...
TL;DR: A literature study of rheological and fatigue modeling of asphalt mixtures is presented in this paper, where theoretical aspects on structural modeling, Rheological behavior and the fatigue integration in design procedures are reviewed.
Abstract: A literature study of rheological and fatigue modeling of asphalt mixtures is presented. Theoretical aspects on structural modeling, rheological behavior and the fatigue integration in design procedures are reviewed. In principle, pavement design methods can be categorized in three broad groups: empirical, semi-mechanistic and fully mechanistic methods. Pavement design is generally performed using semi-mechanistic methods comprising analytical or numerical structural response models and deterioration modeling based on transfer functions and shift factors. In the case of fatigue deterioration, several approaches have been elaborated e.g. classical models, fracture mechanics and damage mechanics. The approaches differ regarding theoretical foundation and evaluation methods used. Recognizing significant limitations concerning theoretical basis as well as lack of empirical support for current design methods, a shift in paradigm from semi-empirical methods towards more advanced fully mechanistic metho...
TL;DR: In this paper, an experimental investigation has been carried out on specimens of bituminous mixtures cored in the wearing course of 16 test sections of a motorway in Switzerland, and their thermomechanical behaviour through the Tensile Stress Restrained Specimens Test (TSRST), and their mechanical behaviour when subjected to mechanical load through a new highly precise Direct Tensile Test (DTT) were assessed.
Abstract: Temperature variations are particularly harmful to wearing courses with asphalt mixture. During wintertime, and especially, at very low temperatures, a surface cracking may appear and propagate more or less rapidly. An experimental investigation has been carried out on specimens of bituminous mixtures cored in the wearing course of 16 test sections of a motorway in Switzerland. These 16 wearing courses are composed with 16 different bitumen as pure bitumen, polymer modified bitumen and bitumen with additives. Those selected bitumen give a representation of the bitumen market in the 80's in Switzerland. 8 years after construction, bituminous mixtures specimens were cored in the driving carriageway and in the “emergency lane”, which is not driving Their thermomechanical behaviour through the Tensile Stress Restrained Specimens Test (TSRST), and their mechanical behaviour when subjected to mechanical load through a new highly precise Direct Tensile Test (DTT) were assessed. Significative behaviour, ...
TL;DR: In this paper, a life cycle inventory model was developed to evaluate three alternatives for the management of waste hot mix asphalt (HMA) including, (1) recycling as new aggregate, (2) recycling of new HMA, and (3) disposal in a landfill.
Abstract: Market based policies to reduce greenhouse gas emissions have become increasingly popular in the last decade. These policies provide economic incentives for reducing greenhouse gas emissions. A life-cycle inventory model was developed to evaluate three alternatives for the management of waste hot mix asphalt (HMA) including, (1) recycling as new aggregate, (2) recycling as new HMA, and (3) disposal in a landfill. Global warming potential, environmental emissions, and total energy use were quantified for each management alternative. The recycling of used asphalt into new HMA results in a reduction of 16 kg CO2e compared to landfilling. Recycling used HMA as aggregate reduced GHG emissions by 9 kg CO2e A Monte Carlo analysis on the alternatives showed that the range of reduction for recycling as HMA was 12 to 26 kg CO2e and for recycling as aggregate 6 to 11 kg CO2e.
TL;DR: In this article, a 4th order Runge-Kutta numerical method was developed to model the heat fluxes and energy balance using measured temperature data and other environmental factors such as solar radiation, convection and evaporation heat flux for the pavement system.
Abstract: Geothermal pavement systems are novel to the paving industry. It is the combination of ground source heat pumps and permeable pavements which treats urban runoff and utilises renewable energy for heating and cooling applications. An energy and temperature balance was developed for two experimental geothermal paving systems. The heat fluxes were analysed for a heating and cooling cycle to determine the thermogeological relationship for the systems. A 4th order Runge-Kutta numerical method was developed to model the heat fluxes and energy balance using measured temperature data and other environmental factors such as solar radiation, convection and evaporation heat fluxes for the pavement system. The model was statistically tested for its validity and it can be concluded that the Runge-Kutta technique proved to be an effective and reliable predictive tool.