Permanent Deformation Characteristics Research Articles

Prediction of resilient modulus and critical dynamic stress of recycled aggregates: Experimental study and machine learning methods

This paper aimed to investigate the feasibility of partially or completely replacing natural aggregates with recycled aggregates from construction and demolition wastes for low-carbon-emission use as coarse-grained embankment fill materials. The laboratory specimens were prepared by blending natural and recycled aggregates at varying proportions, and a series of laboratory repeated load triaxial compression tests were carried out to study the effects of material index properties and dynamic stress states on the resilient modulus and permanent strain characteristics. Based on the experimental results and by considering the main influencing parameters of the resilient modulus and permanent deformation, an artificial neural network (ANN) prediction model with optimal architecture was developed and optimized by the particle swarm optimization (PSO) algorithm, and its performance and accuracy were verified by supplementary analyses. A shakedown state classification method was proposed based on the unsupervised clustering algorithm, and a prediction model of critical dynamic stress was established based on the machine learning (ML) method and the shakedown state classification results. The research results indicate that the stress state has a greater influence on the resilient modulus and permanent deformation characteristics than other factors, and the shear stress ratio has a significant effect on the shakedown state. The resilient modulus and critical dynamic stress of such specimens vary linearly with confining pressure. The improved PSO-ANN prediction model exhibits high prediction accuracy and robustness, superior to several other commonly used ML regression prediction algorithms. The resilient modulus and critical dynamic stress prediction methods based on ML algorithms can provide technical guidance and theoretical basis for the design and in-service maintenance of similar unbound granular materials.

Experimental Study to Investigate the Performance-Related Properties of Modified Asphalt Concrete Using Nanomaterials Al2O3, SiO2, and TiO2.

The dual nature of asphalt binder necessitates improvements to mitigate rutting and fatigue since it performs as an elastic material under the regime of rapid loading or cold temperatures and as a viscous fluid at elevated temperatures. The present investigation assesses the effectiveness of Nano Alumina (NA), Nano Silica (NS), and Nano Titanium Dioxide (NT) at weight percentages of 0, 2, 4, 6, and 8% in asphalt cement to enhance both asphalt binder and mixture performance. Binder evaluations include tests for consistency, thermal susceptibility, aging, and workability, while mixture assessments focus on Marshall properties, moisture susceptibility, resilient modulus, permanent deformation, and fatigue characteristics. NS notably improves binder viscosity by about 138% and reduces penetration by approximately 40.8% at 8% nanomaterial (NM) content, significantly boosting hardness and consistency. NS also enhances Marshall stability and decreases air voids, increasing the mix's durability. For moisture resistance, NS at 8% NM content elevates the Tensile Strength Ratio (TSR) to 91.0%, substantially surpassing the 80% standard. Similarly, NA and NT also show improved TSR values at 8% NM content, with 88.0% and 84.1%, respectively. Additionally, NS, NA, and NT reduce permanent deformation by 82%, 69%, and 64% at 10,000 cycles at 8% NM content, illustrating their effectiveness in mitigating pavement distress. Notably, while higher NM content generally results in better performance across most tests, the optimal NM content for fatigue resistance is 4% for NS and 6% for both NA and NT, reflecting their peak performance against various types of pavement distresses. These results highlight the significant advantages of nanoparticles in improving asphalt's mechanical properties, workability, stability, and durability. The study recommends further field validation to confirm these laboratory findings and ensure that enhancements translate into tangible improvements in real-world pavement performance and longevity.

Investigation of the fractionalized polyethylene terephthalate (PET) on the properties of stone mastic asphalt (SMA) mixture as aggregate replacement

Polyethylene terephthalate (PET) is a widely used plastic that accounts for almost 18 % of global polymer production and is non-biodegradable, making it a major cause of environmental pollution. Innovative solutions are needed to address PET waste management and reduce its impact. This study aims to investigate the impact of adding PET, on the engineering characteristics of a Stone Mastic Asphalt (SMA-20) mixture. Laboratory tests were conducted to assess the volumetric and mechanical properties of asphalt mixes containing different proportions of PET as fine and filler (ranging from 0 % to 30 %) by volume of aggregates. The results show that the PET incorporation into the asphalt mixture has significantly improved the performance. The addition of PET (fine and filler) to asphalt mixtures significantly increases their resilient modulus (MR). The mixtures containing 10 % PET as fine and filler are 20 % and 22 % higher in MR than the control mixture. Moreover, the moisture assessment shows that the PET mixture has a higher tensile strength ratio (TSR) value of 85.9 % and 83.90 % for Fine-10 and Filler-20, thus meeting the AASHTO requirement of ≥80 %. The utilization of PET as aggregate replacement significantly improves the permanent deformation characteristics of asphalt mixtures by decreasing permanent strain. The Fine-20 and Filler-20 revealed promising results by reducing the strain to 0.92 % and 0.81 %. Also, the enhancement in the creep stiffness modulus with 216 and 244 MPa. Furthermore, the addition of PET up to a concentration of 20 % had a beneficial effect on the fatigue response of mixtures. For instance, the failure cycles of the Filler-20 and Fine-10 are 23,231 and 17,521 cycles at a load of 2250 N, whereas the control mixture only endures 8581 failure cycles. In conclusion, PET addition significantly improves SMA properties, promoting waste material utilization in the pavement industry.

Undrained permanent deformation characteristics of Yellow River silt under one-way cyclic loads

As a new type of engineering construction filler, it is particularly important to know the shakedown and permanent deformation characteristics of the Yellow River silt under cyclic load. In this study, a series of undrained cyclic triaxial tests for Yellow River silt are carried out by using GDS triaxial apparatus, the effects of relative density, loading frequency, confining pressure and cyclic stress ratio on the development curve of permanent strain are explored. Based on the shakedown theory and combined with the data of permanent strain development curve of Yellow River silt at different stress levels, a calculation model for its critical dynamic stress and limit cyclic stress ratio under shakedown state is determined. Further analysis is conducted on the development law of the permanent strain curve of Yellow River silt under shakedown state, and a prediction model for permanent strain of Yellow River silt considering different parameters was established. Then the accuracy of the model is verified. Combining with splitting summation method, the settlement of foundation can be calculated.

Permanent deformation characteristics of unsaturated subgrade soils under cyclic loading

Excess permanent deformation of subgrade may cause critical rutting in pavements, and subsurface water significantly affects the accumulation of permanent deformation. This study aims to reveal the permanent deformation behaviour of unsaturated subgrade soils. Subgrade box tests were performed at varying moisture content, stress levels and loading frequency, respectively. The test results show that the permanent deformation significantly increased with moisture content. The concept of a permitted moisture content-applied dynamic load envelope was proposed. Based on curve fitting, a prediction model of permanent deformation of subgrade soils was developed, and the effects of moisture content and loading cycles were included. The validation results show that the model exhibited reasonably good performance in modelling the deformation. This study may provide an alternative way for predicting the permanent deformation of unsaturated subgrade soils.

Feasibility of recycled concrete aggregate stabilized with one-part geopolymers as semi-rigid inclusion columns

Recycled concrete aggregate (RCA) is a voluminous solid waste material derived from the construction sector and is typically stockpiled in landfills. In recent years, the ground improvement industry has grappled with challenges stemming from the depletion of natural quarry materials, resulting in a skyrocketing of their prices and increased project costs. This research investigated the feasibility of using RCA stabilized by one-part geopolymers to produce an innovative semi-rigid inclusion column system for ground improvement of soft soils. Na2SiO3-anhydrous was used as a sole solid activator for the activation of fly ash (FA), slag (S) or a binary precursor (FA+S) in the stabilization of RCA. The unconfined compressive strength (UCS) and microstructure of the stabilized mixtures have been examined with respect to different binder formulations and curing conditions. The permanent deformation characteristics of mixtures under cyclic loading were evaluated through repeated load triaxial (RLT) tests to replicate the moving wheel loads imposed on the semi-rigid inclusion columns. In addition, the cost and environmental impacts of the optimum mixtures suggested in this research were studied. The test results indicated that stabilizing RCA with as low as 5% one-part alkali-activated FA, S or (FA+S) met the minimum strength requirement (1.034 MPa) for ground improvement work. Compared with standalone FA and S geopolymer stabilized RCA mixtures, (FA+S) geopolymer stabilized RCA mixtures were identified as preferred industrial formulations due to their prolonged setting time for ease of mixing and handling when used in stone column applications. It was found that curing temperature and duration played a pivotal role in the strength gain of the mixtures. The RLT test results demonstrated that implementing the optimum RCA + 5%(FA+S) mixture as identified in this study for semi-rigid inclusion columns, led to a reduction in permanent strain values by approximately 90% compared to conventional unbound stone columns. The comparison between the optimum mixture highlighted in this study with other stabilization methods showed that the semi-rigid inclusion columns had great potential to enable large-scale production, cost and emission reduction in future ground improvement projects.

Use of sugarcane molasses for preparation of bio-asphalt: Effect of source

Demand for asphalt binder is on rampant rise due to overpopulation and rapid urbanization. Non-renewability and fluctuating price of asphalt binder have prompted research efforts in the direction of sustainable flexible pavements using bio-asphalt. This study is aimed to evaluate the feasibility and source variability of sugarcane molasses (SM) as a partial replacement of asphalt binder. Three sources of SM were used in the study. A series of conventional, chemical, rheological, and storage tests were conducted. The optimum dosage of SM for partial replacement was found to be 30% by weight of asphalt binder. Fourier transform infrared spectroscopy (FTIR) results revealed the possibility of chemical interaction between SM and asphalt binder. Through rheological mastercurves, it was found that the addition of SM, regardless of the dosage, improved permanent deformation characteristics. The segregation test results indicated adequate thermal storage stability of bio-asphalts. Further, statistical analysis showed that the source of SM had no significant impact on the physical and rheological characteristics of the bio-asphalt. Cost analysis showed that 30% incorporation of SM could lower the cost of asphalt production by 20–30%.

The Effect of Nano-Hydrated Lime on the Durability of Hot Mix Asphalt

Recently, some of Iraq's newly constructed asphalt concrete pavements showed premature failures with significant negative impacts on roadway safety and the economy. Using Nano hydrated lime (NHL) in pavement construction could be one of the possible steps to improve pavement durability. This article discusses how NHL affects the durability of hot mix asphalt. NHL was added in two methods to the asphalt concrete mixture for the wearing course. The first is the dry method, i.e., on the aggregate, whereas the second is the wet addition method, i.e., to the bitumen. The percentages were tried for each additional method; 1, 2, and 3% by weight of aggregate for the dry method and 0.5, 1, and 1.5% by weight of asphalt concrete for the wet method. The optimum asphalt cement contents were evaluated using the Marshall procedure. Asphalt concrete mixes were prepared at their optimum asphalt content and then tested to evaluate their durability properties, including moisture damage and permanent deformation. These properties have been evaluated using indirect tensile strength and uniaxial repeated loading tests. The results show that the NHL has improved the permanent deformation characteristics and resistance to moisture susceptibility.

Effect of truck and train loading on permanent deformation and fatigue cracking behavior of asphalt concrete in flexible pavement highway and asphaltic overlayment track

Abstract This research investigated the largest magnitude of displacement and horizontal tensile strain in several critical locations within the asphalt concrete (AC) layer in both the flexible pavement highway (FPH) and asphaltic overlayment track (AOT) structure using the numerical modeling method. The role of the hauling loads, speed, and loading cycles of freight truck’s dumps and freight train’s wagons on the mechanical behavior of FPH and AOT in terms of the permanent deformation and fatigue cracking was examined. Furthermore, the performance of the FPH and AOT in terms of permanent deformation and fatigue cracking characteristics due to various magnitudes of hauling loads, speed, and loading cycles of freight truck’s dumps and freight train’s wagons was compared to determine the optimum infrastructure for the freight coal transportation, based on the hauling capacity as well as the magnitude of permanent deformation and the horizontal tensile strain of the AC layer. According to the findings of this study, it is suggested to choose the AOT structure with fourth or sixth loading systems to run the freight coal transportation with the highest magnitude of the hauling capacity of 360,000 tons, since it produces the minimum magnitude of the permanent deformation and fatigue cracking of the AC layer. Future research should be conducted to examine the potential and the characteristics of fatigue cracking due to the contact between the edge of the sleeper and the surface of the AC layer in AOT.

Permanent Deformation Characteristics of Flexible Pavement Under Palm Oil Freight Truck Loading

Most of previous studies employed dynamic stability test and Hamburg wheel tracking test to investigate permanent deformation characteristics of asphalt concrete (AC) layer. However, the permanent deformation performance only focuses on the surface course and neglected the influence of middle layer and base course. The present study investigates the permanent deformation characteristics of four (4) different configurations of flexible pavement and analyzes the contribution of AC surface and AC base course to the total permanent deformation of AC layer as the response to various truck’s speed, hauling loads, and loading cycles. Finite element modeling was performed to evaluate critical locations below the tire tread of single unit two-axles truck with the greatest magnitude of permanent deformation and to determine the optimum configuration of flexible pavement by considering the linear viscoelastic behavior of two types of AC mixtures. It can be concluded that the largest permanent deformation is measured below the right edge of the outer tire. The contribution of AC surface course on the total permanent deformation due to the increase in truck’s speed is only about 14.81% to 16.39%, while the contribution of AC surface course on the total permanent deformation due to the increase in truck’s hauling loads as well as the increase in the number of passing trucks is only around 14.76% to 16.44%. On the other hand, the contribution of AC base course on the total permanent deformation due to the increase in truck’s speed from is reaching 83.61% to 85.19%, while the contribution of AC base course on the total permanent deformation due to the increase in truck’s hauling loads as well as the increase in the number of passing trucks is achieving 83.56% to 85.24%.

Permanent deformation characteristics of expandable foam grout under cyclic loading

Expandable foam grout (EFG) is a novel flowable cementitious material for filling underground cavities. This study evaluates the permanent deformation behavior of EFGs under cyclic loading. EFG consists of cement, water, and admixture. EFG samples are mixed at a water–cement ratio of 100% and an admixture content of 5.6% to prepare cylindrical specimens cured at four different times. Sinusoidal loads with different maximum axial stresses are vertically applied. The permanent deformation of EFG increases with the number of load cycles but at a decreasing rate. A power function model is used to represent the relation between the permanent deformation and number of load cycles. The model generally matches the measured values but can overestimate the deformation at specific strain levels and curing times. The accumulated permanent deformation increases with the applied axial stress and decreases with longer curing times. The final permanent deformation decreases with the increase in the curing time, and the rate of final permanent deformation also decreases. A linear relationship is found between the final permanent deformation and unconfined compressive strength. These findings can help estimate the damage and durability of underground structures backfilled with highly flowable and expandable cementitious materials under cyclic loads.

Development of Artificial-Neural-Network-Based Permanent Deformation Prediction Model of Unbound Granular Materials Subjected to Moving Wheel Loading.

The majority of existing regression models for unbound granular materials (UGMs) consider only the effects of the number of loading cycles and stress levels on the permanent deformation characteristics and are thus unable to account for the complexity of plastic deformation accumulation behavior influenced by other factors, such as dry density, moisture content and gradation. In this study, research efforts were made to develop artificial-neural-network (ANN)-based prediction models for the permanent deformation of UGMs. A series of laboratory repeated load triaxial tests were conducted on UGM specimens with varying gradations to simulate realistic stress paths exerted by moving wheel loads and study permanent deformation characteristics. On the basis of the laboratory testing database, the ANN prediction models were established. Parametric sensitivity analyses were then performed to evaluate and rank the relative importance of each factor on permanent deformation behavior. The results indicated that the developed ANN prediction model is more accurate and reliable as compared to previously published regression models. The two major factors influencing the magnitude of accumulated plastic deformation of UGMs are the shear stress ratio (SSR) and the number of loading cycles, of which the calculated influence coefficients are 38% and 41%, respectively, while the degree of influence of gradation is twice that of the confining pressure.

Failure Analysis of Tension Clamps (SKL15) Used in Serviced Urban Railway Tracks: Numerical Analyses and Experiments.

In this study, the material properties of the damage-vulnerable parts and the residual strain of tension clamps comprising many curved parts, such as those used in urban railroads, were tested and analyzed. The effects of decreasing the strengths of the tension clamps on performance were then assessed. The permanent deformation characteristics of the tension clamps of aged specimens (6, 11, and 16 years of service) exhibited tendencies similar to the strain-hardening characteristics of the stress–strain responses reported in previous studies. As the service period increased, plastic deformation occurred in the middle bands of the tension clamps. When used for 16 years in urban railroads, the tension clamps underwent ~10% deformation compared with their initial shapes. Furthermore, based on laboratory tests, the deterioration levels of the tension clamps according to the service period were examined as functions of Young’s modulus. Stress levels close to the yield strength occurred in the middle band of the tension clamp when the clamping force was introduced. As a results, it is possible to determine whether the clamping force confirms that decrease by using the Young’s moduli of tension clamps, and the deterioration of the function and the replacement time of tension clamps that may occur during service can be predicted.

Impact of rest period on asphalt concrete permanent deformation

Truck platooning has several advantages including congestion reduction, safety, and fuel efficiency. However, there are concerns regarding its impact on pavement performance due to channelized traffic and reduced spacing. A rest period governed by the distance between each truck can have a significant impact on asphalt pavement performance due to time dependent deformation characteristics of asphalt materials. Despite numerous studies available in the literature explaining the rest period effect on fatigue cracking, the impact on permanent deformations is relatively less studied. In this paper, we present the results to characterize the impact of rest period on the permanent deformation characteristics of two asphalt concrete (AC) mixes using four different types of binders. The experimental program included repeated load permanent deformation experiments coupling rest period with various stress and temperature configurations. Increasing rest periods from 0.18 s to 2.5 s increased permanent deformations consistently for the two mixes. The results are consistent with the hardening-relaxation or hardening–softening mechanisms describing the reorientation of the aggregate structure from a more resistant to less resistant state to deformations as rest duration increases. It was also shown with the customized multiple stress creep recovery experiments that the effect of rest period on mixture level permanent deformations could not be attributed to the binders’ deformation characteristics. Rest period impact was found to be as important as temperature and stress magnitude for asphalt mixture’s permanent deformation resistance. Various truck platoon scenarios can be compared to conventional truck configuration and loading assumptions using the results presented in this paper.

Repeated Load Triaxial Testing of Recycled Excavation Materials Blended with Recycled Phyllite Materials.

Recycled Excavation Materials (REM) are becoming viable alternative construction resources due to their economic benefits. However, REM may be composed of weak rocks, e.g., phyllites, limiting the use in a base layer. The present paper attempts to further the knowledge of the mechanical performance of REM by performing Repeated Load Triaxial Tests (RLTT). REM are mixed with Recycled Phyllite Materials (RPM) in systematic blends of 0%, 25%, 50%, and 100%. The batches’ resilient modulus (MR) and permanent deformation (PD) characteristics were assessed to establish the maximum RPM allowed into REM while maintaining the required performance. Hicks and Monismith’s and Uzan’s models were used to characterize the stiffness behavior. A wide variation in the stiffness between the two materials was observed. Batches comprised of 0% RPM–100% REM and 25% RPM–75% REM showed high stiffness performance. The Coulomb model assessed the PD behavior, and the results showed a similar response for all batches. Unlike the stiffness, blended mixtures did not show sensitivity to increased RPM content in the PD. This study may help end-users to understand the performance of REM given the documented threshold on the allowable quantity of RPM in REM.

Fines content, plasticity index and dust ratio influencing the modulus and permanent deformation behavior of aggregates

Resilient modulus (Mr) and permanent deformation (PD) characteristics of unbound aggregates under repetitive traffic loads dictate the structural response and performance of pavement base and subbase layers. Aggregate material behavior is dependent on the amount of fines in particulate matrix, also referred to as fines content (percent passing number 200 sieve), as well as plasticity index, dust ratio (percent passing number 200 sieve to percent passing number 40 sieve), material type, aggregate gradation/packing and the interactions of these properties with each other. In this study, repeated load triaxial tests were conducted on crushed limestone and crushed gravel aggregates. Fines content and plasticity index were varied from 5% to 12% and 5% to 9%, respectively. Two most typical gradations of aggregates used in roadway construction in Illinois were utilized with dust ratios ranging from 0.4 to 1.0. The results of these tests were analyzed using the shakedown theory for evaluating typical base/subbase permanent deformation or rutting trends linked to practical design considerations. Charts were also established for the modulus and deformation characteristics of unbound aggregates to designate the material quality with performance trends. Such guiding charts were compared with others developed in previous studies by authors for determining aggregate behavior under monotonic loading tests such as California Bearing Ratio (CBR). The comparisons provide valuable insights on how each aggregate property influences strength, modulus and permanent deformation behavior under different loading conditions.

Effect of Emulsified Asphalt Content on Creep Behavior and Mechanical Properties of Cold Recycled Emulsified Asphalt Bases

Since the beginning of the 21st century, the rapid development of road infrastructure has facilitated enhanced mobility and accessibility that has caused environmental degradation due to the continuous extraction of natural aggregates. To address this increasing problem, recycled aggregates and Reclaimed Asphalt Pavement (RAP) materials have been utilized in road construction worldwide. The studies related to various emulsified asphalt contents on permanent deformation and other parameters are limited. This study examined the performance characteristics of cold recycled emulsified asphalt bases with RAP materials in different proportions, i.e., 25%, 50%, and 75%, and evaluated in terms of the indirect tensile strength, tensile strength ratio, density, water loss, and permanent deformation at lower and higher emulsified asphalt contents than optimum. The results demonstrated that the total residual binder content influences the permanent deformation characteristics of cold mixes. There was no significant variation in the durability and strength with the RAP at the optimum emulsified asphalt content. But, the emulsified asphalt contents other than optimum influence the strength, density, and permanent deformation. The logarithmic and power-law models are best suited to predict the first-stage permanent deformation of cold mixes.

Rutting prediction models for flexible pavement structures: A review of historical and recent developments

Rutting is the major distress mode in flexible pavements occurring due to the repeated movement of traffic loading. Deformation in the pavements comprise of both recoverable (elastic) and irrecoverable (plastic) part. Overall deformation occurring in the flexible pavement system due to continuous vehicular movement is contributed from all the components of pavement. A number of empirical models have been proposed by several researchers for analysis and prediction of accumulated rutting in different components of pavement. The accumulated permanent strain has been expressed as the function of the number of load applications and deviator stress applications in most of the models proposed; however, factors such as stress state, moisture content, material type and environmental conditions also impose a significant influence on the permanent deformation characteristics of pavement materials under cyclic loading. In this article, a comprehensive review has been carried out covering every aspect of deformation related to distress occurring in pavements. Important rut models, modeling approaches and modern concepts in the rutting analysis of pavement structures have been presented. In addition to review, fallacy existing in the current design practices related to adaptation of stiffness parameters and negligence of shear strength aspect of subgrade soil has been also presented with the support of literatures. • Permanent strain along with resilient strain must be evaluated for accurate characterization of pavement materials. • Significant rut prediction models for pavement structure and subgrade soil have been discussed. • Limitation related to the adaption of stiffness parameters ( M R , CBR) in flexible pavement design.

Performance of EME2 mixtures produced using warm asphalt technology

In order to explore the potentials of a foam-based warm-mix asphalt(WMA) technology for the production of EME2 mixtures, an extenstive laboratory study was carried out. In this study EME2 mixtures incoporating 0% and 30% reclaimed asphalt (RA) were produced at 120°C using WMA technology. As control mixtures, hot-mix variants of these mixtures were also produced at 180°C. The performances of these mixtures were determined using various methods. Among others, the water sensitivity, stiffness, fatigue and resistance to permanent deformation characteristics of the mixtures were investigated. Rheological tests were also performed on virgin and recovered binders. Results showed that using the WMA method a significant reduction in production temperature can be achieved. Despite differences in production temperatures, the WMA mixtures showed equivalent performance to their hot-mix variants. Rheological results indicate the additional benefits of WMA in preserving the bitumen by limiting oxidation during production and compaction process.

Effects of Asphalt Foaming on Damage Characteristics of Foamed Warm Mix Asphalt

In the asphalt foaming process, the foaming water content (FWC) controls the formation and characteristics of water bubbles. These water bubbles are expected to be expelled from the foamed warm mix asphalt (WMA) during mixing and compaction. However, foaming water may not be completely expelled, rather some of the microbubbles may be trapped in the foamed WMA even after compaction. These microbubbles, or undissipated water, can diffuse over time and cause damage to the foamed WMA. To this end, this study has determined the effects of foaming on the fatigue, moisture damage, and permanent deformation characteristics of foamed WMA. Foamed asphalt and mixtures were designed with varying FWCs and they were tested using linear amplitude sweep, multiple stress creep recovery, four-point flexural beam, and Hamburg wheel tracking tests. Primarily, asphalt foaming dynamics were assessed with a laser-based non-contact method. A simplified viscoelastic continuum damage concept and a three-phase permanent deformation model were used for damage evaluation. The study reveals that foaming softens the binder, which results in slightly higher rutting and moisture susceptibility, though an equivalent or slightly improved fatigue characteristic compared with the regular hot mix asphalt.