Flexible Pavement Research Articles

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.

Modeling of the effect of gradation and compaction characteristics on the california bearing ratio of granular materials for subbase and landfill liner construction

The California bearing ratio (CBR) of a granular materials are influence by the soil particle distribution indices such as D10, D30, D50, and D60 and also the compaction properties such as the maximum dry density (MDD) and the optimum moisture content (OMC). For this reason, the particle packing and compactibility of the soil play a big role in the design and construction of subbases and landfills. In this research paper, experimental data entries have been collected reflecting the CBR behavior of granular soil used to construct landfill and subbase. The database was utilized in the ratio of 78–22% to predict the CBR behavior considering the artificial neural network (ANN), the evolutionary polynomial regression (EPR), the genetic programming (GP), Extreme Gradient Boosting (XGBoost), Random Forest (RF) and the response surface methodology (RSM) intelligent learning and symbolic abilities. The relative importance values for each input parameter were carried out, which indicated that the (CBR) value depends mainly on the average particle size (D30, 50 & 60). They showed a combined influence index of 66% of the considered parameters in the model exercise. This further shows the importance and structural influence of the particles within the D50 and D60 range in a granular material consistency in the design and construction purposes. Performance indices were also used to study the ability of the models. The ANN model showed the best performance with accuracy of 88%, then GP, EPR and RF with almost the same accuracies of 85% and lastly the XGBoost with accuracy of 81%. Also, the RSM produced an R2 of 0.9464 with a p-value of less than 0.0001. These values show that the ANN produced the decisive model with the superior performance indices in the forecast of CBR of granular material used as subbase and waste compacted earth liner material. The results further show that optimal performance of the CBR depended on D50 and D60 for the design of subgrade, subbase, and liner purposes and also during the performance monitoring phase of the constructed flexible pavement foundations and compacted earth liners.

Evaluating the Durability of Asphalt Mixtures for Flexible Pavement Using Different Techniques: A Review

Evaluating the Durability of Asphalt Mixtures for Flexible Pavement Using Different Techniques: A Review

Study of the Influence of the Variability of Traffic-Related Parameters on the Service Life of Flexible Pavement Structures in Senegal by a Mechanistic-Empirical Approach

The results of the study showed that exceeding the axle load and axle configuration are indisputably among the most damaging factors for flexible pavement structures in Senegal, made of local materials (Diack basalt, Sindia laterite). The regulatory axle load recommended by UEMOA for users is set at 11.5 tons and 12 tons for a single and twin axle respectively. For calculation purposes, this load is set at 13 tons. However, in Senegal, this axle load is often exceeded, and given the diversity of heavy goods vehicles in traffic, single axles, whose effects, according to several authors, are more detrimental to flexible pavement structures, are increasingly observed in road traffic. Differences in fatigue cracking and rutting damage between single and dual wheels, as well as load overruns, show the need to take axle configuration and possible overloads into account when dimensioning flexible pavement structures in Senegal, and when planning their maintenance, the costs of which are excessively high, according to Senegal's Autonomous Road Maintenance Fund (FERA). Keywords: Single wheel, dual wheel, damage, fatigue cracking, rutting, traffic

Optimizing the bituminous pavement constructions with waste plastic materials improved the road constructions performance and their future applications

The yearly production of plastic garbage is rising in the current environment as a result of the fast population rise. Recycling and reusing plastic trash is essential for sustainable development. The need of the hour is to utilize waste polythene for various supporting reasons since it is not biodegradable. These materials are made of polymers like polyethylene, polypropylene, and polystyrene. Due to the enhanced performance and elimination of the environmental issue, adding plastic waste to flexible pavement has emerged as a desirable choice. A composite material known as bituminous concrete (BC) is often utilized in construction projects such as road paving, airport terminals, and stopover areas. It includes mineral aggregate and black top or bitumen, which are combined, laid down in layers, and then compacted. The bituminous mixture in this research article was combined with plastic to use a chemical stabilizer. The ideal bitumen content is replaced by 0, 15%, 27%, and 36% plastic, as well as the bitumen's weight, stability, and Marshall value to create hypothermal. A linear scale is used to compare the flow rates to the bituminous mixture. The characterization of plastics contains bituminous materials are done by the SEM–EDX, XRD, FTIR and BET analysis. There have been several studies on the addition of trash to bituminous mixes, but this one is focused on the use of plastic waste as a modification in a bitumen binder for flexible pavement. According to research, bituminous mixes containing up to 4 percent plastic waste are excellent for sustainable development.

Permeability and Dynamic Stability in Porous Asphalt Mixtures Using Cariphalte Asphalt and Gilsonite Additives

Porous asphalt mixture is a new generation of flexible pavement that allows water to seep into the top layer (wearing course) both vertically and horizontally. This condition is possible, because the gradation used has a coarse aggregate fraction of not less than 85% of the mixture volume. This layer uses an open gradation (open graded) which is spread over a layer of waterproof asphalt to prevent seepage into the road foundation. This porous asphalt layer can effectively provide a greater level of safety, especially during rainy times to prevent aqua-planing, resulting in rougher surface roughness and can reduce noise (noise reduction). In this research, a test will be carried out on porous asphalt with a mixture using Cariphalte modified asphalt and gilsonite as the added ingredient. Variations in asphalt content used are 4%, 5%, 6%, 7%, 8%. Determination of variations in levels of variation is based on research that has been conducted. This research involves analysis of calculation results based on experimental data from laboratory scale experiments including Marshall Testing, Immersion Index, Permeability, Slip Resistance, Dynamic Stability, and Resilient Modulus. The test results show that the smallest permeability value is in the 8% gilsonite mixture but it does not meet the requirements of AAPA 2004 so the mixture with the greatest stability value is used. From the results of dynamic stability testing, it shows that the mixture of test objects with a content of 7% gilsonite has a dynamic stability value of 5250 passes/mm at a temperature of 45°C and 3150 passes/mm at a temperature of 60°C.

Impacts of Backcalculation Software Selection on Airport Flexible Pavements Using the Aircraft Classification Rating/Pavement Classification Rating Method

From November 2024, the aircraft classification rating/pavement classification rating (ACR/PCR) method will be accepted by civil aviation authorities to notify the bearing capacity of airport pavements. Structural characteristics are necessary to calculate the parameters relating to this method, such as the modulus of elasticity which, in the case of existing pavements, can be obtained by backcalculation. However, the results of this procedure may vary depending on the type of method and algorithms used to minimize adjustment errors between the deflection basins adopted in the software. Given the above, this article aims to evaluate whether the choice of backcalculation software affects the resistance classification and admissibility of aircraft on airport pavements using the ACR/PCR method based on the backcalculated elastic moduli. The elastic modulus values of the materials from two runways were backcalculated using BAKFAA, BackCAP, BackMedina, and ELMOD software, and then used to calculate the PCR. The results of the backcalculation showed differences in the elastic moduli obtained by the software, mainly in the subgrade. It was found that the backcalculation software used can limit the type of aircraft and the runway resistance. Therefore, the choice of software for backcalculation of deflection basins can influence the results of the ACR/PCR method because of divergences in determining the resistance of the pavement’s bearing capacity and the admissibility of aircraft operations in the analyzed structures.

Non-destructive compaction evaluation and comparison of different asphalt centerline longitudinal joints

Longitudinal joint quality is critical to the service life of asphalt pavements. Maintaining failed joints of asphalt pavements is a challenge for many highway agencies. Long-term performance issues of flexible pavements may result from a poorly constructed joint; the low-density joint can prematurely deteriorate an otherwise sound pavement. The longitudinal joint is built using different geometries, rolling patterns, and construction techniques, all involving risk in achieving a well-compacted joint. Conventional quality control (QC) and quality assurance (QA) testing (using cores or density gauges) provide limited coverage due to their spot-test nature. Using conventional QC/QA methods involves the risk of accepting a poorly constructed longitudinal joint at the time of construction. This study used continuous data from the non-destructive dielectric profiling system (DPS) to identify compaction ability differences between the various joint types and construction techniques. The analysis suggests avoiding constructing an unconfined joint when possible. Percent within limits (PWL) analysis shows that any joint geometry could produce minimal compaction differences between the joint and the mat. However, if an unconfined joint needs to be constructed, a portion of the unconfined joint should be cut back before paving the adjacent lane. Such a cutback technique can result in better unconfined joint compaction. Further, PWL results showed that using a smaller subsection/sublot can isolate local compaction issues; a 100 ft sublot length is preferable for PWL analysis when utilizing DPS for compaction evaluation.

A novel approach for analyzing linear amplitude sweep (LAS) test data of asphalt binders

Fatigue cracking is one of the crucial distresses considered for the design of flexible pavements. The initiation of fatigue cracking occurs in the binder phase of an asphalt mixture. The linear amplitude sweep (LAS) test was developed to analyze the fatigue damage in the asphalt binder. AASHTO T391 provides a method to analyze the LAS test data by fitting a power equation between the fatigue parameter (G*sinδ) and damage intensity. This method has some inherent weaknesses of overfitting or underfitting of the data at different damage levels. This study proposes a new method where a total curve is divided into two parts that fit the data in two different equations and then sum them up. The first part comprises of the data up to cumulative damage corresponding to the maximum effective stress, and the second part consists of accumulated damage in the material till it reaches the maximum strain (30 %). This method is called the bifurcation method in this paper. LAS test data of 27 long-term aged bitumen samples having different physical properties is used to determine the number of fatigue life cycles (Nf) by these two methods, and results are compared in terms of mean absolute percentage error (MAPE), root mean square error (RMSE), and residual sum of squares (RSS). It is shown that there is a significant reduction in the errors when the data fitting was done using the proposed bifurcation method. Further, the ranking was allotted to the samples based on the number of fatigue life cycles (Nf) at three different strain levels (2.5 %, 5 %, and 10 %) at intermediate-temperature conditions estimated using two methods. The shift indicator parameter was used to analyze the variability in the ranking of the samples due to changes in the strain levels. The study concludes that the proposed bifurcation method fits the predicted values more accurately than the prescribed power law.

Results of Using Modern Rehabilitation Techniques in Flexible Road Pavements

Results of Using Modern Rehabilitation Techniques in Flexible Road Pavements

Modelling permanent strain behaviour of soil for flexible pavement design utilizing LWD measurements

ABSTRACT This study aims to improve understanding of unbound material behavior by modeling permanent strain using Light Weight Deflectometer (LWD) measurements, as part of VTI’s broader LWD research. By comparing permanent strain modelling from LWD data with Repeated Load Triaxial (RLT) tests on silty sand soils, it validates LWD data accuracy and explores material property influences on permanent strain parameters, revealing a clear correlation with water content and stress levels. Using LWD data validated against RLT tests, the study delves into material behaviour understanding under varied conditions, focusing on comparing model parameters of permanent strain prediction derived from LWD and RLT tests. Despite minor differences, both methods produce acceptable values, affirming the modelling approach’s robustness. The findings demonstrate LWD’s potential to improve pavement design by providing insights into permanent strain behavior that supports mechanistic-empirical approaches, leading to more efficient designs and better resource use for improved performance.

Utilizing synergy of MLG and MWCNT with optimized mixing protocol to improve the high temperature stability of SBS modified bitumen

High temperature instability is the biggest problem which limits the application of Styrene-Butadiene-Styrene (SBS) modified bitumen in flexible pavements. Addition of multi-layer graphene (MLG) nanomaterial improves the performance of SBS modified bitumen, but deteriorates its thermal stability. The binary additive comprising of MLG and multi-walled carbon nanotubes (MWCNT) can be a way to improve the thermal stability through their synergistic effects, however, mixing protocol needs to be optimized simultaneously. In this present study, MLG, MWCNT and their combination have been dispersed by two different organic solvent dissolution protocols, i.e., wet and dry to prepare the SBS-nano modified binders. Thermal stability analysis and rheological characterization (small & large amplitude oscillatory shear) have been used to optimize the method and to compare the effect of sole and binary additive. Advanced tools such as Raman spectroscopy and Field emission scanning electron microscopy have been used to understand the underlying science at micro-molecular level. The synergistic effects of combined additives are prominently visible only in dry organic dissolution method and with this method, the combination of MLG-MWCNT (0.1phr-1phr) significantly eliminates the thermal instability of SBS modified binder by upto 96 %. This SBS-nano modified bitumen may serve as futuristic binder for the black top pavements.

Micro-Structure Analysis and Mechanical Behaviour of Hot Mix Asphalt Modified with Reclaimed Asphalt Pavement Using Palm Kernel Shell Ash as Mineral Filler

In pavement construction and production of hot mix asphalt HMA, the use of industrial and agricultural waste has gained much relevance because of its economic and environmental benefits. This research examined the effects of palm kernel shell ash PKSA on the physical and volumetric properties of HMA modified with reclaimed asphalt pavement RAP. All preliminary test conducted on the modified asphalt mixture in accordance with relevant standards showed adequacy for use in production of HMA. Marshall method of mix design was adopted for the HMA production. The bitumen content was varied from 4.5 to 6.5% (at intervals of 0.5%). The palm kernel shell ash was varied from 25% to 75% (at interval of 25%). A maximum stability of 7.1kN was recorded at 5.5% bitumen content which is a little increment in strength but good significance in material (virgin bitumen) when compared to the maximum stability of 6.9kN at 6% bitumen obtained from the control mix. The microstructural analysis of the hot mix asphalt done on the palm kernel shell ash PKSA showed a rough surface texture needed in flexible pavement construction and when comparison was done between the control specimen and the modified specimen, it shows an improvement in the interlocking arrangement of aggregates resulting in a denser mixture for the modified hot mix asphalt. In conclusion this study confirms that a blend of a 50% RAP and 50% virgin aggregates with 50% palm kernel shell ash PKSA as mineral filler at 5% bitumen content can improved strength performance of HMA, hence, the effect of PKSA as a mineral filler in HMA containing RAP is significant.

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.

Resilient roads in challenging terrain: a case study of Siddhartha highway in Nepal

Nepal is a country known for its diverse and challenging topography, and it relies heavily on a robust road infrastructure network to connect its remote regions and urban centers. This study addresses the critical need for enhanced road safety and infrastructure resilience on the Siddhababa road section of the Siddhartha Highway, Nepal, notorious for its high accident rates and susceptibility to landslides. Given the road's strategic importance in connecting remote regions and its challenging topographical conditions, our research aimed to identify the most suitable pavement type to mitigate these issues. Through a detailed examination incorporating eight different soil tests, alongside evaluations of traffic loads, weather conditions, and existing pavement performance, we adopted a comparative analysis methodology to assess the viability of flexible versus rigid pavements within this unique context. Results revealed that the soil composition and environmental conditions of the Siddhababa section significantly influence pavement performance, with specific gravity, moisture content, and California Bearing Ratio (CBR) tests indicating a nuanced suitability for both pavement types under varying circumstances. Our analysis concluded that, despite the economic and staged reinforcement benefits of flexible pavements, the durability, safety, and maintenance considerations favor the adoption of rigid pavement for the Siddhababa road section. However, acknowledging the economic constraints, a hybrid approach is recommended, emphasizing rigid pavements for the most vulnerable sections and flexible pavements elsewhere. This study contributes to the pavement engineering field by providing a model for pavement type selection in mountainous regions, aiming to enhance road safety and durability amidst challenging environmental conditions.

Machine learning modeling of pavement performance and IRI prediction in flexible pavement

Machine learning modeling of pavement performance and IRI prediction in flexible pavement

Hydraulic and mechanical performance of granular sub base and geo-composite drainage layers in flexible pavements: insights from laboratory experiments and field investigations

Hydraulic and mechanical performance of granular sub base and geo-composite drainage layers in flexible pavements: insights from laboratory experiments and field investigations

Influence of subgrade spatial variability on strain-alleviating ability of geogrids and rutting life in flexible pavement

This study employs the Random Field Finite Difference Analysis to assess how subgrade spatial variability impacts geogrid reinforcement’s strain-alleviating ability and the reinforced pavement’s rutting life. The geogrid’s abilities to reduce critical strains are evaluated using a strain-alleviating ratio and compared between deterministic and spatially variable scenarios. The analysis involves six geogrid reinforcement arrangements, considering two kinds of geogrid stiffness (G1 and G2) and three typical positions: top (L1), mid-depth (L1-2) and bottom (L2) of the base course. Key findings include: (a) Subgrade spatial variability significantly amplifies mean critical strains and leads to irregular strain and stress distributions, which in turn impacts the strain-alleviating ability of the geogrid reinforcements and potentially changes the optimal geogrid position. (b) The impacts of subgrade spatial variability on the geogrids’ strain-alleviating ability vary with the type of critical strains, the geogrid position, and the coefficient of variation and scale of fluctuation of subgrade modulus. When the geogrid is located at L2 (G_L2), its ability to alleviate critical subgrade strain is significantly compromised. (c) The adverse effect of subgrade spatial variability on the rutting life of G_L2 reinforced pavement is significant and can be mitigated by homogenising a very thin sublayer at the subgrade surface.

Impact of antiaging additives on the conventional properties of bituminous binder

Aging of binders is a complex phenomenon which reduces the longevity of flexible pavements. Aging involves change in physical, chemical, and morphological properties of binder which makes the binder brittle and highly susceptible to fatigue and thermal cracking. Antiaging additives enhance the service life of flexible pavements by reducing the impact of aging on the performance of binders. An iterative approach is essential to identify the optimal dosage of antiaging additive necessary to counteract the aging effects on binder. The present study aims to evaluate the mixing conditions for uniform dispersion of carbon black and hydrated lime within the binder matrix and thereby evaluate the impact of incorporating these antiaging additives on the conventional properties of binder. For this purpose, varying proportions of carbon black and hydrated lime are added to VG 30 binder and is subjected to softening point, ductility, and penetration tests. The optimal dosage of carbon black and hydrated lime is found to be 6 and 12% respectively based on their significant effects on the conventional properties of the binder. An optimal mixing duration of 60 and 75 min ensures uniform dispersion of carbon black and hydrated lime within the binder matrix at a mixing temperature of 120 °C and a speed of 1000 rpm thereby producing a homogenous binder mastic. Incorporation of antiaging additives up to the optimal dosage enhances the softening point whereas decreases the penetration and ductility of binder. The increase in softening point of binder with incorporation of carbon black and hydrated lime signifies enhanced resistance to rutting and permanent deformation of binder, whereas the reduction in ductility and penetration of binder with incorporation of carbon black and hydrated lime signifies the reduced susceptibility of binder to environmental factors such as temperature fluctuations, UV radiation, and oxidation. The surface texture of the additive influences the ability of binder adsorption, which subsequently affects the rheological properties of binder mastics. Significant improvement in conventional properties of binder with incorporation of carbon black and hydrated lime paves a viable and cost-effective solution for engineering application as it has a subsequent effect on the rheological properties of binder.

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.