Rut Depth Research Articles

Assessing the Impact of Various Industrial Wastes on the Volumetric and Mechanical Properties of Warm Mix Asphalt (WMA)

In recent decades, sustainable practices in pavement construction have been studied to promote circular economy principles and protect the environment. This research seeks to determine the potential benefits of using three different industrial waste materials in formulating warm mix asphalt (WMA). WMA mixes were prepared using ground granulated blast furnace slag (GGBFS) from steel production and biomass fly ash (FA) from the paper industry as virgin filler replacement, and an industrial waste rich in lignin biopolymer (LB) from the hardboard industry as a partial substitute for binder. The study analyzed their volumetric and mechanical properties, including moisture damage resistance, resilient modulus, fatigue resistance, permanent deformation, and abrasion resistance, which were compared with those of a control WMA mix (without any waste). The findings provide insights into an important gap in the literature on the use of GGBFS and LB in WMA. GGBFS-2 mix (75% GGBFS) exhibited the best fatigue performance but the highest axial deformation and rut depth. LB-1 mix (5% LB) performed slightly worse than the optimum control WMA in all tests.

Comprehensive Study on Dynamic Modulus and Road Performance of High-Performance Asphalt Mixture

Asphalt pavement durability significantly impacts the service life of roads, and hence, understanding the performance of high-performance asphalt mixtures is crucial. This study investigates the performance of four high-performance asphalt mixtures: heavy-load AC-20, high-viscosity AC-20, heavy-load SMA-13, and heavy-load SMA-10. Linear Amplitude Sweep (LAS) tests revealed that heavy-load asphalt mixtures exhibit superior fatigue resistances, with the fatigue life of heavy-load SMA-13 exceeding 1.5 times that of high-viscosity AC-20 under similar stress levels. Bending Beam Rheometer (BBR) tests at −6 °C, −12 °C, and −18 °C demonstrated that both heavy-load and high-viscosity asphalts had comparable low-temperature crack resistance, with heavy-load SMA-13 showing a stiffness modulus of 627 MPa at −18 °C. Marshall tests indicated that heavy-load AC-20 had the highest stability (14.3 kN) among the tested mixtures, while heavy-load SMA-13 exhibited the highest density (2.603 g/cm3). Dynamic modulus tests spanning a frequency range of 10−4 Hz to 105 Hz at various temperatures showed that heavy-load SMA-13 had a higher dynamic modulus than heavy-load SMA-10, particularly at lower frequencies (higher temperatures). Rutting tests at 60 °C indicated that heavy-load SMA-13 had the lowest rut depth (18.5 mm), outperforming other mixtures by up to 25%. The heavy-load SMA-13 asphalt mixture demonstrated the best overall performance, especially in terms of high-temperature stability, fatigue resistance, and rutting resistance. This study provides essential material performance parameters for the development of durable high-performance asphalt pavement structures.

Traction Assistance of a Forwarder in Flat Terrain

Traction assistance of forest machines via traction aid winches has gained widespread application in steep-terrain forest operations as it can mitigate soil disturbance by reducing wheel or track slip of the assisted machine. Since slip affects machine operations in flat terrain as well, especially on fine-grained and moist soils, the effectiveness of traction assistance under such conditions was evaluated. At a forest site, a forwarder with a total mass of 28.6 t was driven over two plots in 15 passes. The machine travelled unassisted over one plot, while on the second plot traction assistance was manually adjusted to keep slip close to 0%. Wheel slip and winch tractive force were recorded during each pass, and rut depth was measured after each pass. Soil density was measured pre-impact and at three times after different traffic increments. Although the mean wheel slip was low even during unassisted travel, traction assistance was found to cause a significant reduction. While both a decrease in rut depth and soil compaction were observed with traction assistance, only the latter was significant after three machine passes. A potential influence of inhomogeneous soil reinforcement due to roots suggests repeating the experiment on a more homogenous soil.

Characterization and prediction of hydraulic properties of traffic-compacted forest soils based on soil information and traffic treatments

Key messageThe hydraulic properties of compacted and rutted soils were evaluated through in-situ infiltration experiments and predicted based on soil texture class and traffic treatments. A significant decrease in saturated soil water content and soil hydraulic conductivity at saturation was observed. The resulting soil hydraulic parameters, when integrated into a soil water transfer model, effectively simulated water dynamics in these impacted forest soils, providing a crucial first step toward developing decision support tools for real-time trafficability. This approach can assist forest managers in minimizing the extent of soil compaction.ContextTo overcome trafficability issues of forest soils induced by heavy logging machinery, planning support tools are needed to determine suitable soil moisture conditions for traffic.AimsThis study aimed to identify the soil properties that differ significantly between undisturbed and compacted soils and to provide several estimation tools to predict the hydraulic properties of compacted soils beneath the skid trails.MethodsFour hundred seventeen water infiltration tests were conducted on 19 forest sites, mostly in North-eastern France, and analysed with the BEST method to estimate the hydraulic properties of the skid trails and undisturbed soils. The hydraulic properties of the skid trails were predicted thanks to linear mixed effect models using a bulk treatment effect, a site effect, or a skid trail degradation score. The predicted hydraulic properties were tested using a water flow model to assess their relevance regarding the prediction of water dynamics in skid trails.ResultsThe compaction effect was only significant for the logarithm of the hydraulic conductivity at saturation (log10(Ksat)) and the soil water content at saturation (θsat). For the skid trails, θsat was reduced by - 0.02 and − 0.11 m3m−3 in the 0 − 10 cm and 15 − 25 cm layers respectively, compared to undisturbed topsoil (0 − 10 cm). log10(Ksat) was reduced by − 0.38 and − 0.85 for skid trails in the 0 − 10 and 15 − 25 cm soil layers respectively, compared to undisturbed topsoil. The use of a pedotransfer function, in replacement of water infiltration tests, and their combination with the same correction coefficients proved to efficiently simulate the difference in water dynamics between skid trails and undisturbed forest soils.ConclusionEstimation of soil hydraulic properties based on in situ water infiltration experiments proved efficient to simulate water dynamics in compacted and rutted forest soils. Yet, further studies are needed to identify the most adapted pedotransfer function to forest soils and to test the generalisation of our findings in different conditions, especially deeply rutted soils (rut depths > 12 cm).

Influence of direct coal liquefaction residue (DCLR) on the rutting behavior of asphalt mixture with the discrete element method

The research explores the influence of direct coal liquefaction residue (DCLR) as a fine aggregate on the rutting behavior of asphalt mixtures (AMs). Four AMs were prepared and modeled, namely AM (AM-0), AM with 2.36 mm DCLR (AM-2.36), AM with 1.18 mm DCLR (AM-1.18), and AM with 0.6 mm DCLR (AM-0.6). Firstly, the rutting depth and uplift height of AMs were analyzed. Results indicated that the rutting depth and uplift height of AMs increased with rising temperatures and loads. The order of rutting depth and uplift height of AMs at different temperatures and loads was: AM-0＞AM-2.36＞AM-1.18＞AM-0.6. This suggests that DCLR replacing fine aggregates improved the high-temperature performance of AMs, and DCLR replacing 0.6 mm fine aggregate was the best alternative. Moreover, the influence mechanism of DCLR on the rutting behavior was investigated by the force chain distribution and particle movement. The results showed that the rutting deformation was caused by the movement of 0.6–2.36 mm particles. Compared with AM-0, the chain distribution of AM-2.36 was uniform and sparse, and the movement of 0.6–2.36 mm particles in AM-2.36 was small. This was due to the composite modification effect of DCLR within the AM, which increased the bonding degree of asphalt mastics. This enhancement improved connectivity between aggregates, strengthened their load transfer capacity, and raised the AM's overall self-organizing adaptability. Finally, it was also found that DCLR as fine aggregates served dual roles within the AM, acting both as a skeleton and a filler.

Pavement performance analysis considering the influence of suction and temperature on subgrade soil modulus

Subgrade soils can experience varying suction (equivalent to moisture) and temperature, which could affect the modulus of subgrade soil and the response of flexible pavements. The influence of these two factors on pavement performance has not been explored on purpose despite their importance in a changing climate. In this study, a simple approach was proposed for analyzing pavement performance with consideration of suction and temperature effects on soil modulus. Modulus values at different conditions of suction and temperature are calculated using a semi-empirical equation. Then, they are utilized in the numerical software KENLAYER to evaluate the stress and strain distributions in pavements composed of an asphalt layer, base layer, and subgrade layer based on linear elastic theory. The computed results are used to predict the rutting and fatigue cracking using some field-calibrated semi-empirical equations. In parametric studies using this method, the suction and temperature-dependent modulus of a clayey soil determined from laboratory experiments was applied. The results reveal that an increase in subgrade soil modulus due to drying and cooling can reduce the total rut depth mainly due to a reduction of the vertical compressive strain in the subgrade layer. For instance, a change in suction from 0 to 150 kPa (equivalent to optimum moisture content of the clayey soil) can lead to a 34 % decrease in the total rut depth. However, the effects of an increase in soil subgrade modulus on fatigue cracking are influenced by the asphalt thickness. A reduced subgrade modulus because of wetting and heating decreases horizontal tensile strain (more susceptible to fatigue cracking) at the lowest section of relatively thinner asphalt but increases horizontal tensile strain for thicker asphalt.

Development and Validation of Asphalt Pavement Rutting Prediction Model with Transient Temperature Field Considered

This study developed a transient rutting analysis program based on the principles of heat transfer and the viscoelastic–viscoplastic theory of asphalt mixtures. Using the finite element model (FEM) model corresponding to the multi-layer pavement structure and the subprogram interface of ABAQUS software, along with Python programming, the program was designed to estimate rutting under transient temperature field conditions with climate conditions, traffic flow, and structure layer constitutive parameters of pavement considered. Subsequently, the program was used to validate the efficiency of the solution and analyze the influencing factors of internal temperature field and rutting depth within the asphalt pavement structure. Results showed that, based on meteorological data and recommended values of material thermal properties, the FEM of transient temperature field can accurately simulate the temperature field distribution of pavement structure. Based on loading information and dynamic modulus test, the transient temperature variable rutting with FEM proposed in this paper can simulate and calculate the rutting of pavement structure layer with some errors for different pavement conditions from 5% to 40%. Through parametric analysis of the influence factors of temperature field and rutting, the modified transient temperature field rutting prediction program can effectively simulate rutting of pavement structure, and the minor errors were less than 20%.

The impact of climate change on variations in rutting resilience of asphalt pavement across the climate zones in China

This study aims to investigate resilience differences of asphalt pavements across China's climate zones in response to climate change. The impacts of climate change on rutting depth (RD), influence degree on rutting resilience, and Greenhouse Gas emissions in various climate zones were evaluated, and adaptation measures were proposed. The findings indicate that the warmer climate zones will be significantly affected. Freeways in these zones, serving for 10 years under projected climate conditions 40 years ahead, are expected to have RD increments exceeding 2 mm. Carbon dioxide equivalent emissions could increase by 23.1 million tons (a 39.4% increase) compared to current conditions. The degree of influence of climate change on rutting resilience will significantly differentiate among the climate zones. Four potential adaptation measures have been proposed to urgently enhance rutting resilience in response to climate change.

Machine learning modelling the rut depth of WMA mixtures with variable reclaimed asphalt pavement (RAP) and foamed bitumen content

ntroduction. Rutting of flexible, super flexible and semi-rigid pavement structures is a typical and frequently decisive condition parameter, form of pavement deterioration. That is why, any research result in the field can have of high importance for the road engineers. Problem Statement Rutting poses a significant challenge to asphalt pavements, causing permanent deformation under heavy loads, particularly in warm and wet conditions. Purpose. This pavement distress type has — in addition to riding comfort challenges — important traffic safety consequences (e.g. aquaplaning), as well. The research work concentrates on the influence of the use of warm mix asphalt, reclaimed asphalt material and foamed bitumen binder on the rut depth of asphalt pavements.

Impact of winch-assisted logging machinery on soil disturbance in the mountainous forests of Western Carpathians

IntroductionTimber harvesting on steep terrain is a challenge in terms of economic viability, safety, and environmental performance. Felling with chainsaws and use of yarders seems optimal in this environment. However, using mobile traction winches allows for the safe work of ground-based technologies even in these challenging conditions.MethodsOur study assessed the impact of winch-assisted cut-to-length harvesting on soil disturbance in young forest stands (up to 40 years old) across slopes of 14.9°-27.4° (27–52%). Utilizing 78 measurement points (i.e., 234 measurements), we analyzed soil samples from trail ruts, between ruts, and undisturbed areas for soil bulk density (g.cm−3) and soil moisture content (%), simultaneously measuring penetration resistance (MPa), penetration depth (cm) and rut depth (cm).ResultsThe results highlighted that areas without winch assistance experienced the most significant increases in soil bulk density (up to 22.35%) and penetration resistance (up to 26.8%), though these differences were not statistically significant. Linear mixed effects models did not confirm a significant effect (p > 0.05) of a traction winch on the soil bulk density (g cm−3) and penetration resistance (MPa) in the ruts of the forwarding trails. Mean forwarding trail profile depths ranged from 4.63 to 7.28 cm, with the maximum depths between 10.86 and 17.25 cm, showing deeper ruts in non-assisted areas. Moreover, the presence of the traction winch (p < 0.05) significantly affected the maximal depth of the forwarding trail rut.ConclusionThe findings suggest that winch-assisted harvesting may mitigate soil disturbance (rut depths) on steep slopes, offering a sustainable option for utilizing ground-based machinery with reduced environmental impact.

Experimental Study on Pavement Performance of Warm High Modulus Mixture WHMM-13

In order to solve the dusting and rutting problems of hot mix asphalt mixture during construction and operation, rutting test, bending test, Marshall stability test, freeze-thaw splitting test, uniaxial compression dynamic modulus test, overlay test, and four-point bending fatigue life test are applied on WHMM-13 to study the high-temperature stability, low-temperature cracking resistance, water stability, anti-reflection crack performance and fatigue durability in comparison with HMM-13. The results show that, compared to HMM-13, the dynamic stability and dynamic modulus (45 ℃, 10 Hz) of WHMM- 13 are improved by 10.0% and 47% respectively, and the rutting depth is reduced by 27.3%, indicating that the high temperature stability of WHMM-13 has been greatly improved. As for low temperature cracking resistance, the bending failure strain, stiffness modulus, flexural tensile strength and rupture energy of WHMM-13 are slightly lower than those of HMM-13. As for water stability, the residual stability of WHMM-13 in immersion Marshall test is 87.5%, and the splitting strength is 82.3%, both higher than that of HMM-13. As for anti-reflection crack performance, the total tensile rupture energy of WHMM-13 is 2.32 times that of HMM-13, with cracking resistance index (CRI) increased by 25%, which shows that WHMM-13 has better strength, can effectively prevent the crack from spreading and effectively improve the cracking resistance capacity of asphalt pavement. As for fatigue durability, the fatigue life of WHMM-13 is 5.4% lower than that of HMM-13, with bending stiffness modulus and cumulative dissipation energy reduced by 11.3% and 2.8% respectively, indicating that the fatigue durability of WHMM-13 is slightly reduced.

Study on Fatigue Performance and Rutting Prediction Model of Steel Slag Asphalt Mixture

Steel slag, a significant industrial waste, poses environmental and land issues due to its accumulation. This research explores using steel slag to replace natural aggregates in steel slag asphalt mixture (SSAM) at varying levels by weight: 25%, 50%, 75%, and 100%. The research evaluated the pavement and fatigue performance of SSAM, noting that dynamic stability (DS) peaked at a 75% slag content. Although low-temperature flexibility decreased, it remained within acceptable limits. The mixture met or exceeded Chinese specifications for resistance to water and traffic stress. Fatigue life varied with slag content, decreasing at high levels due to increased stiffness and stress. A rutting prediction model for SSAM was developed, utilizing a back propagation neural network for accurate rut depth forecasts, demonstrating the model's precision with a fit of 0.99744. This study suggests optimized slag content enhances SSAM performance, offering a sustainable approach to managing steel slag.

Pavement performance and model studies with modified bitumen binder

Flexible pavements experience premature deterioration due to several factors, such as high volumes of traffic, repeated wheel loads, overloading, adverse weather conditions, inferior quality of materials, and other related issues. One of the most commonly found types of distress is rutting, which severely affects pavement performance; hence, the prediction of rutting behaviour is crucial. Research has been done by adding various industrial wastes, chemicals, additives, and modifiers such as rubber, natural rubber, polymers, and waste plastic into the bitumen. These materials are expected to have a substantial impact on enhancing the strength, durability, and performance of pavement while simultaneously reducing the cost of construction. The present research deals with a laboratory investigation of bituminous mixes using both Marshall stability and rutting tests. The performance tests were carried out by Roller Compactor cum Rut Analyzer (RCRA) equipment and Finite Element (FE) analysis in ABAQUS. The experimental findings show that the modified bitumen exhibits 48% greater strength and 20% more resistance to rutting than the conventional bituminous mixes. The model analysis was successfully validated by experimental results. The findings of the research resulted in the development of a mathematical equation that helps to calculate in-service pavement rut depth.

MECHANICAL AND PERFORMANCE CHARACTERISTICS OF SEMI-RIGID MIX DESIGN WITH RECYCLED MATERIALS AND STANDARDIZATION OF RUT DEPTH MEASUREMENTS

Pavement industry requires substantial modifications in terms of materials. Stakeholders are in need to opt the solutions of semi-rigid design mix with recycled materials. Necessary evaluations in terms of experimental measures are initially required to represent characteristics properties. Moreover, the behavior to be assessed is rut depth measurements through the implications of wheel tracker apparatus and in accordance with prescribed standards. The mix with specified curing days is being differentiated through subsequent directions focusing choice of recycled materials. The paper presents a model to excel distinguished properties inclusive of the analysis for maintaining air voids, induction of grouting material and stability. The output-oriented data is justified within the enumerations of rut depths for grouted samples. It is analyzed for 25%, 30% and 35% air voids in conditioned to fresh and recycled aggregates. The deliberations are meant with 91 and 13 sample combinations of aggregates and hot mix asphalt respectively followed by the significant tests on bitumen and grouting material. It is observed that critical samples are passed in the configurations of rut depths when processed with reclaimed and construction waste materials at 35% voids. The research data entails its affectivity due to the uniqueness in superior model of current scenario.

Experimental assessment of strength characteristics of anthropogenic soils in a given mining area for justification of tractor propulsion type

BACKGROUND: In mining, there is a need to develop tractors as special robotic vehicles of the robotic mining facility that can efficiently move and work on soils with low bearing capacity, in waterlogged areas and in the underwater position. A preliminary evaluation of the strength characteristics of such a heterogeneous surface of the exploitation area helps to choose an effective concept and technical characteristics of the propulsor of the tractor. AIM: Formation of the database of the physical condition and mechanical properties of the environment in which the tractor will move and operate. METHODS: In order to achieve the aim, preliminary experiments were conducted on the terrain. Typical kinds of soil sites and watered areas, including those of anthropogenic origin, of a given mining area were identified. Full-scale instrumental tests were conducted to determine: granulometric composition of soils; physical and mechanical parameters of these soils at the selected sites using the developed original types of a penetrometer and a shear rig. RESULTS: The database of numerical values of measured strength characteristics of one of the soil types (as an example) as a possible supporting surface for vehicle motion in the area of mining facility operation is presented in a graphical form. The basis of this database is the graphs according to the results of experiments on free settlement and shear with the help of dies of two types of configuration (the round die and the original caterpillar track respectively); the granulometric composition of the selected soils has been evaluated. CONCLUSION: The methodology of preliminary assessment of the soil condition by two indicators of soil strength (the rut depth z depending on the average pressure under the die) and shear (average tangential stresses τ in the contact patch on the motion of the die relative to the soil, depending on the ratio of the normal force and the traction force in the contact plane) has been developed. The 3D model of the coastal and bottom area of the technogenic mining zone has been developed. Design variants of highly efficient types of tractor propulsors are selected on the basis of prediction of maximum allowable stresses in the contact patch with the ground for the bearing surface areas of the considered area of operation.

On the Influencing Factors of Non-asphalt Originated Rutting in Flexible Pavements

Rutting can substantially impact pavement serviceability and driving safety. Since most of the permanent deformation develops in the unbound layers beneath the asphalt course, the focus should be on these layers. In this research, rut depths were calculated and analyzed using the high-cycle accumulation model, where the resilient response and cyclic strain amplitude were determined through finite element analysis. Consequently, settlement depression curves were described for various subgrades and cross-sections. It was observed that grain size distribution, particularly the uniformity coefficient, plays a decisive role in rutting depth. Analysis of the relationship between settlements and axle loads indicates that the calculated settlements demonstrate a linear increase relative to the axle load. For various axle loads, the number of axle passes required to induce an equivalent settlement to the standard axle was established. The possibility to reduce the depth of ruts by increasing the thickness of the subbase was also investigated. It was found that the predicted rutting is highly influenced by the particle shape (angular, rounded, or mixed material) of the subbase. It was found that the primary portion of permanent deformations occurs within the subgrade.

Modeling and design optimization of the performance of stone matrix asphalt mixtures containing low-density polyethylene and waste engine oil using the response surface methodology

In recent years, the use of waste plastic materials such as low-density polyethylene (LDPE) to modify asphalt binders and enhance mixture performance has garnered significant attention. One major concern with using such materials is the higher production temperature required, which necessitates the use of a bitumen extender agent, such as waste engine oil (WEO), to reduce the viscosity and mixing temperature. Therefore, using these stabilizing additives can reduce the consumption of virgin binder, especially for Stone Matrix Asphalt (SMA) mixtures, which require higher asphalt content. This study aimed to optimize the design of SMA modified by LDPE and WEO to minimize the optimum asphalt content (OAC) and mixing temperature while maximizing SMA performance. To achieve this, Response Surface Methodology (RSM) was utilized to develop the necessary models for optimizing design and predicting performance. The selected independent variables (factors) for the design include LDPE content, WEO content, OAC, and mixing temperature. Meanwhile, the responses (dependent variables) consist of Marshall stability, rut depth, tensile strength ratio, and resilient modulus, which were used to determine the best mix design. The findings demonstrated that the suggested models for the output variables can predict performance with a higher level of confidence. The Analysis of variance (ANOVA) demonstrated that predictive models were significant and well-fitted, with a coefficient of determination (R2) of higher than 0.80, an adequate precision value of greater than 4, and a low p-value (less than 0.05). The error percentage between the RSM-predicted and actual values was less than 5 %, indicating that RSM-established models can accurately and efficiently predict the SMA performance. The best mix design of the SMA mixture modified by LDPE and WEO was found to be 10 % LDPE, 3.91 % WEO, 5.92 % OAC, and mixing temperature of 152.24°C with a combined desirability of 82.8 %.

Enhancing High-Temperature Performance of Flexible Pavement with Plastic-Modified Asphalt.

Previous studies indicate that traditional asphalt mixtures lack the ability to withstand the stresses caused by heavy traffic volumes under high temperatures. To enhance the rutting resistance of flexible pavement under high levels of temperature and loading, extensive laboratory experiments were carried out. A 60/70 grade bitumen was used as a neat sample for comparison. The study introduced three distinct polymers, polypropylene (PP), low-density polyethylene (LDPE), and acrylonitrile butadiene styrene (ABS), at varying concentrations by weight into the neat bitumen. Initially, conventional tests were performed to evaluate the conventional properties of both the neat and modified bitumen, while aggregate tests assessed the mechanical properties of the aggregates. Subsequently, a Marshall mix design was performed to determine the optimum bitumen content (OBC) in the asphalt mixture. Finally, wheel-tracking tests were performed under a specific load and temperature to investigate the rutting behavior of the modified asphalt mixtures. The results of this comprehensive study revealed that the modified asphalt mixtures displayed improved resistance to rutting compared to the neat asphalt mixture. Furthermore, it was also observed that the LDPE exhibited a superior performance against rutting, followed by the PP and ABS. At polymer contents of 3%, 5%, and 7%, the LDPE achieved reductions in rut depth of 13%, 24%, and 33%, respectively, outperforming both PP- and ABS-modified asphalt. These findings not only enhance our understanding of asphalt behavior under diverse conditions but also highlight the potential of plastic-modified asphalt as an effective solution for mitigating rutting problems in road pavements. By incorporating plastic modifiers into asphalt mixtures, this approach aligns with the principles of sustainable construction by reducing plastic waste while improving pavement durability and performance.

One-year results of the first road surface with the addition of sunflower oil porous capsules

This paper presents findings from the first surface course in the UK employing sunflower oil-filled porous capsules as a self-healing additive. The capsules, designed to mitigate ravelling, were tested on a road constructed at an asphalt plant and subjected to a year of traffic in temperatures ranging from below 0°C to 35°C. Spherical in shape with a diameter of about 1.5 mm, the capsules possess a porous structure filled with sunflower oil. Each tonne of asphalt contained 5 kgs of capsules. The material used was Stone Mastic Asphalt (SMA), one of the UK's most utilised surface course materials. Eight sections were built, with four varying binder contents (6.4 %, 5.9 %, 5.5 % and 5.2 %), each with and without capsules. The road performance was evaluated by measuring two indicators: rut depth and surface macrotexture. Results show that the capsules delay fretting progression in wearing courses. Fretting could have resulted from the complex interaction between early life wearing and asphalt compaction by traffic that caused the mastic to move to the road surface. In addition, no considerable difference in rutting was observed between the different materials. Moreover, core samples were extracted from the road before and after traffic and age exposure for further laboratory analysis to assess the long-term performance. Results showed that stone loss resistance in asphalt-containing capsules was 30.02 % lower before ageing and 25.92 % lower after ageing. Furthermore, the stiffness ageing factor was 15–20 % lower in materials with capsules, while the fatigue life remained consistent across all materials.

Enhancing Hamburg Wheel Tracking Test Analysis: A Novel Energy-Based Performance Index

Rutting and moisture damage are the most common distress types in the pavement; therefore, agencies have adopted performance tests such as the Hamburg wheel tracking test (HWTT) to specify and screen the asphalt concrete rutting performance, following the AASHTO T324 standard. Many studies have shown that the AASHTO parameters can be used to characterize and rank the performance of asphalt mixes. Additionally, researchers proposed new analysis methods and performance parameters to provide a more systematic approach to analyzing the HWTT results. However, some of these performance parameters are determined subjectively by the operator, which may result in ambiguous values, preventing agencies from adopting them in the specification. On top of that, it is also unclear whether each analysis method or the performance parameters can universally distinguish the rutting performance when applied to various HWTT results. Thus, this study investigates the feasibility of different HWTT analysis methods among the performance parameters. 61 HWTT results from various material combinations were analyzed using three different data analysis approaches and calculating the performance parameters. The result showed that the current analysis methods and parameters have certain limitations in analyzing HWTT results. Therefore, a performance parameter, namely the Hamburg performance index (HPI), was introduced, incorporating the number of passes, maximum rut depth, and rut path history into one parameter. It was found that the HPI can resolve the limitation encountered by other analysis approaches and significantly improve the accuracy of distinguishing a mix's rutting and moisture resistance.