Asphalt Concrete Research Articles

Study of the Performance of Warm-Mix Asphalt Containing Recycled Concrete as a Coarse Aggregate in Egypt and the Middle East

Study of the Performance of Warm-Mix Asphalt Containing Recycled Concrete as a Coarse Aggregate in Egypt and the Middle East

Study of the Fatigue Damage Characteristics of Emulsified Asphalt Mastics

Study of the Fatigue Damage Characteristics of Emulsified Asphalt Mastics

Temporal Homogenization Modeling of Viscoelastic Asphalt Concretes and Pavement Structures under Large Numbers of Load Cycles

Temporal Homogenization Modeling of Viscoelastic Asphalt Concretes and Pavement Structures under Large Numbers of Load Cycles

Road Surface Texture Evaluation and Relation to Low-Speed Skid Resistance for Different Types of Mixtures

Pavement skid resistance is significant for driving safety. British Pendulum Number (BPN) is commonly used as a low-speed skid resistance indicator, whereas sometimes it is impractical for data collection on roads in service. Since skid resistance is greatly affected by pavement surface texture, this research aims to evaluate pavement surface texture comprehensively and estimate the low-speed friction BPN from road surface texture on macro- and micro- scale. Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA) were included. Road surface texture was evaluated from four aspects, texture depth, amplitude-related Root Means Square (RMS), elevation variances corresponding to different wavebands and texture spectral analysis. Texture depth indicators include Mean Texture Depth (MTD) and Mean Profile Depth (MPD). Elevation variances with three wavebands, from 5 mm to 50 mm, from 0.5 mm to 5 mm and from 0.024 mm to 0.5 mm respectively, were obtained. The results show that MPD is well correlated with MTD. Elevation variances with different wavebands demonstrates that the elevation variance of macro-texture with long wavelengths from 5 mm to 50 mm dominates the total variance. Spectral analysis shows that texture level is larger when the wavelength is beyond 4 mm, which is consistent with elevation variances. A linear regression between BPN and single texture index, as well as multiple linear regression analysis were conducted. The former regression result indicates that it is not feasible to estimate BPN using single index due to low correlation coefficient R2. The latter shows that the BPN can be estimated from texture levels corresponding to 64 mm and 2 mm, and the micro-texture. The R2 can be up to 0.684. This research will contribute to fast acquisition of BPN from pavement surface texture, thus improving skid resistance.

Mechanical and economical feasibility of LDPE Waste-modified asphalt mixtures: pathway to sustainable road construction

This research study evaluates the impact of low-density polyethylene (LDPE) modified asphalt binder on the mechanical performance and economical feasibility of asphalt concrete (AC) mixtures. LDPE-modified mixtures were compared with conventional mixes prepared with various binders commonly used in India, i.e., VG 30, VG 40, Polymer-Modified Binder (PMB), and Crumb Rubber Modified Binder (CRMB). LDPE-modified mixtures exhibit superior mechanical performance, increasing the stiffness of AC mixtures by 171% and 125% at 25 °C and 35 °C, respectively, compared to VG 30 base binder. Additionally, the indirect tensile strength (ITS) improved by 51% over VG 30. LDPE-modified mixtures also showed improved resistance to permanent deformation, with RTIndex values up to 133.46% higher than VG 30, and higher fatigue resistance, as indicated by increased CTIndex values compared to VG 30 and CRMB. However, the CTIndex values for LDPE-modified mixtures were 26.32% and 56% lower than those for VG 40 and PMB, respectively. Pavement analysis using 3D-Move showed lesser deflections at pavement layer interfaces, resulting in higher rutting and fatigue life for LDPE-modified pavements. Furthermore, LDPE-modified pavements showed up to 57% higher fatigue life (Nf) and up to 42.33% higher rutting life (Nr) than other pavements. The economic analysis showed that the cost of LDPE-modified pavements is comparable to VG 40 and around 10% more economical than pavements containing PMB. Using LDPE also offers environmental benefits by repurposing up to 750 kg for every kilometer of single-lane pavement section having 50mm thick surface course. Overall, LDPE-modified asphalt mixtures present a sustainable and high-performance solution for asphalt pavement construction.

Effect of nonlinear stress-dependency and cross-anisotropy on the backcalculation outputs from the TSD deflection slopes and the effect on estimated pavement performance

ABSTRACT The Traffic Speed Deflectometer (TSD) is a mobile vehicle that measures deflection slopes. Deflection slopes have been utilised in previous studies to backcalculate pavement layers’ moduli. However, the nonlinear stress-dependency and cross-anisotropy of unbound granular materials and fine-grained soils were overlooked in those studies. Utilising the Finite Element Method (FEM) based on static analysis in this study to evaluate a three-layered flexible pavement system with specific material properties and layer thicknesses revealed that neglecting the nonlinear stress-dependency of base and subgrade layers underestimated the permanent deformation life of the backcalculated pavement by more than 45%. Neglecting the cross-anisotropy of the base layer with the design anisotropy ratio of 0.5 increased the backcalculated Asphalt Concrete (AC) modulus by more than 21%, increased the estimated permanent deformation life of the pavement by more than 160%, and decreased the backcalculated base modulus by around 28%. Neglecting the cross-anisotropy of the subgrade with the design anisotropy ratio of 0.5 almost increased the estimated permanent deformation life of the pavement by 15%. The results underscore the necessity to consider the nonlinear stress-dependency and cross-anisotropy of unbound granular materials and fine-grained soils in backcalculating pavement layers’ moduli from TSD deflection slopes.

Theoretical development and validation of asphalt concrete density measurement using non-contact interdigital coplanar capacitive sensor

Asphalt concrete (AC) density serves as a critical criterion for quality control and quality assurance in asphalt pavement construction. Current non-destructive testing (NDT) approaches have shown potential for AC density measurement, but they present disadvantages such as inefficiency and unstable accuracy. This paper developed a novel NDT approach for AC density measurement based on non-contact interdigital coplanar capacitive sensor (ICCS). The feasibility of this approach was evaluated through both numerical and experimental validations. Firstly, the theoretical model of non-contact ICCS for AC density measurement was established based on conformal mapping technique, partial capacitance technique, and dielectric mixing model. Secondly, numerical simulations were performed to validate the developed theoretical model under two scenarios. Thirdly, laboratory experiments were conducted to measure capacitance data and predict density for three common types of ACs. Finally, the error of non-contact ICCS was discussed and compared with that of other NDT instruments. The results indicated that the developed theoretical model could establish the relationship between AC density and capacitance value, which provided the basis for AC density measurement using non-contact ICCS. It was also observed that the capacitance data obtained by the proposed model closely matched those computed by numerical simulations. The maximum errors between theoretical and numerical data were 4.10% and 1.08% for two cases respectively, which proved the feasibility of the theoretical model. Furthermore, experimental results indicated that the capacitance value of AC specimens increased by about 1 pF as the rolling time increases due to a decrease in the volume of air in AC, which reaffirms the validity of AC density measurement using non-contact ICCS. Additionally, the non-contact ICCS demonstrated excellent accuracy with a maximum error of 6.69%, which is comparable to the current mainstream NDT approaches. And it has the advantages of lower cost, simpler data processing and higher efficiency. The findings of this paper offer a new and reliable method and tool for non-destructive and large-scale AC density measurement.

Glass fiber waste as a potential bitumen modifier and stabilizing agent in asphalt mixture.

The deterioration of Malaysia's flexible road pavements due to rutting and moisture damage presents a critical problem. Meanwhile, disposing of glass fiber wastes from manufacturing process further worsens environmental concerns. This research explores the feasibility of using glass fiber wastes as bitumen modifiers and stabilizers in stone mastic asphalt (SMA). The performance of SMA14 incorporating glass fiber waste using wet method and dry method were compared in this study. Bitumen 60/70 PEN was modified with varying percentages of glass fiber waste namely, 0.5%, 1.0%, 1.5%, and 2.0% by weight of bitumen. The SMA14 mixture was modified with glass fiber waste at 0.3% by the weight of total mixture. The physical and rheological characteristic of modified bitumen binder were assessed using penetration, softening point, storage stability, viscosity, and dynamic shear rheometer (DSR) tests. The Marshall properties and performance of the SMA14 mixture incorporating glass fiber waste were evaluated. The findings demonstrate that glass fiber waste-modified bitumen exhibits enhanced penetration, softening point, viscosity, and rutting resistance compared to the unmodified sample. Adding glass fiber waste using dry method shows significant resistance to abrasion and rutting and demonstrates higher indirect tensile strength and TSR value.

Evaluation of asphalt mixtures modified with low-density polyethylene and high-density polyethylene using experimental results and machine learning models

The widespread use of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) plastics has resulted in a large amount of waste plastic that requires appropriate disposal or reuse. One potential solution is to use them in the modification of asphalt concrete (AC) mixtures for more sustainable highways. To study this possibility, permanent deformation and dynamic modulus (DM) of the LDPE and HDPE modified AC mixtures was investigated by conducting flow number (FN), flow time (FT) and DM tests on Superpave gyratory compacted specimens. Machine learning models; multi-layer perceptron (MLP), radial basis function neural network (RBFNN), generalized regression neural network (GRNN) and support vector machine (SVM) were used to predict the DM on the basis of frequency and temperature parameters. The model’s performance was gauged by analyzing the root mean square error, mean relative error, and coefficient of determination. The study findings revealed that the LDPE and HDPE modified AC mixtures provide 2.07 times and 1.27 times better resistance to permanent deformation, respectively, than their counterpart. It was also found that the LDPE and HDPE modified AC mixtures have 2.1 times and 1.4 times higher DM values, respectively, than the Control AC mixtures. Among the machine learning models, MLP (R2 = 0.98) showed best accuracy in predicting DM and thus is recommended to be used in similar studies due to its robustness. Additionally, the feature importance analysis revealed that frequency has the highest impact on DM predictions, followed by temperature and the inclusion of the LDPE.

A potential evolutionary trap for the extended phenotype of a nematomorph parasite

Abstract Human activities introduce new environmental cues to wild organisms, leading to maladaptive behavioural and life-history decisions known as the ‘evolutionary trap’. This trap is thought to be a major conservation concern for free-living organisms. However, it has never been studied in endosymbionts, one of the most successful and diverse life forms on Earth. Here, we examine this trap in the extended phenotype of a parasite that exploits the visual system of hosts to alter host behaviour for its benefit. Arboreal mantids infected by nematomorph parasites are drawn to horizontally polarized light, thereby inducing them to enter the water. In this study, we found that the degree of linear polarisation (DOP) of reflected light served as a reliable environmental cue for identifying perennial waters, where nematomorphs can survive in their aquatic life stage without drying out. Infected mantids exhibit attraction to horizontally polarized light with higher DOP in behavioural assays and jumped into pools reflecting light with higher DOP in field experiments. The asphalt road reflected horizontally polarized light closely resembling the polarisation levels observed in perennial waters, likely leading to a higher prevalence of mantids on asphalt roads compared to those found in natural arboreal habitats. In a field experiment, we observed infected mantids walking on asphalt roads more often than on cement roads. These findings imply that evolutionary traps can endanger endosymbionts beyond their hosts that directly perceive environmental cues.

Experimental Investigation and Statistical Analysis of Recycled Asphalt Pavement Mixtures Incorporating Nanomaterials

Reclaimed Asphalt Pavement (RAP) materials are used as substitutes for new materials in asphalt pavement construction, leveraging the engineering and commercial benefits of the aged binders and aggregate matrixes in RAP. These asphalt mixtures impart significant variations in volumetric properties and asphalt mixture characteristics. The current study investigates the Marshall properties, moisture susceptibility, and rutting behavior of 24 recycled asphalt mixtures developed with nanosilica and nanoclay. RAP material percent, nanomaterial content, binder grade, and extra binder were considered the factors influencing asphalt mixture performance. The above factors were analyzed using the Response Surface Methodology (RSM) to predict the Marshall and volumetric properties. Also, this investigation covers the moisture susceptibility and rut characteristics of recycled nanomaterial-modified Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA) mixes developed with Viscosity Grade 30 (VG-30) and Polymer-Modified Bitumen-40 (PMB-40). The chemical additive Zycotherm was used to develop WMA mixes. The test results indicate that adding RAP material at higher percentages and modifying the binder with nanomaterials affected moisture susceptibility with reduced moisture damage. Recycled nanosilica-modified HMA mixes developed with PMB-40 at higher RAP percentages reported higher tensile strength ratio (TSR) values in contrast with VG-30 mixes, indicating their greater susceptibility toward moisture-induced damage. The rutting potential of all of the recycled asphalt mixture combinations was enhanced by densely packed aggregate structures optimized with nanomaterials, total binder content, and RAP materials developed using the Marshall method. Overall, the nanosilica-modified recycled asphalt mixes developed with PMB40 at higher RAP percentages showed better performance in terms of strength and durability.

Assessing bonding and debonding properties of Evotherm modified bitumen with natural aggregates using surface free energy approach

ABSTRACT An incongruous pairing of aggregates and bitumen can result in early pavement failures such as stripping, raveling, and fatigue cracking. Surface free energy (SFE) assessments of aggregates and bitumen offer a means to evaluate the compatibility of the aggregate-bitumen system. It is important to emphasise that the SFE of both bitumen and aggregates significantly influences the determination of a compatible aggregate-bitumen combination. In this study, the moisture damage resistance of unmodified bitumen types (VG20, VG40) and modified bitumen types (PMB40, CRMB60) incorporating chemical-based warm mix asphalt (WMA) additives, specifically Evotherm, was investigated. The SFE approach was utilised to gain insights into their performance. In the laboratory, the static contact angle and SFE parameters of both unmodified and modified bitumen, with and without Evotherm, were determined using the Sessile drop method. Five different aggregate types were employed to calculate SFE performance parameters. Subsequently, the SFE performance parameter of forty combinations of aggregates and bitumen was calculated. As part of the assessment of moisture damage resistance, the compatibility ratio (CR) parameter was estimated using the dry adhesion energy, bitumen cohesion energy, wet adhesion energy, and wettability of different combinations of bitumen with aggregates. From the result, Evotherm addition to base bitumen (excluding VG20) significantly improved CR across various aggregates. Notable increases were observed for VG40, PMB40, and CRMB60 after Evotherm addition, with improvements of 66.67%, 48.48%, and 64.54% respectively for basalt aggregate. PMB40+EM with basalt aggregate exhibited the highest CR and Tensile Strength Ratio (TSR), suggesting superior moisture damage resistance compared to other bitumen combinations.

Study on the Effect of Hot and Humid Environmental Factors on the Mechanical Properties of Asphalt Concrete.

To investigate the effect of hot and humid environmental factors on the mechanical properties of asphalt mixtures research, in this paper, the dynamic modulus of asphalt mixtures under the effects of aging, dry-wet cycling, and coupled effects of aging and dry-wet cycling were measured by the simple performance tester (SPT) system, and the dynamic modulus principal curves were fitted based on the sigmoidal function. The results show that under the aging effect, the dynamic modulus of asphalt mixture increases with the aging degree; the dynamic modulus of short-term aged, medium-term aged, long-term aged, and ultra-long-term aged asphalt mixtures increased by 9.3%, 26.4%, 44.8%, and 57%, respectively, compared to unaged asphalt mixtures at 20 °C and 10 Hz; the high-temperature stability performance is enhanced, and the low temperature cracking resistance performance is enhanced; under the dry-wet cycle, the aging effect of asphalt water is more obvious in the early stage, and dynamic modulus of resilience of the mixture is slightly increased. In the long-term wet-dry cycle process, water on the asphalt and aggregate erosion increased, the structural bearing capacity attenuation, and the dynamic modulus of rebound greatly reduced at 20 °C and 10 Hz. For example, the dynamic modulus of asphalt mixtures with seven wet and dry cycles increased by 3% compared to asphalt mixtures without wet and dry cycles, and the dynamic modulus of asphalt mixtures with 14 cycles of wet and dry cycles and 21 cycles of wet and dry cycles decreased by 10.8% and 16.5%, respectively, compared to asphalt mixtures without wet and dry cycles. The main curve as a whole shifted downward; the high-temperature performance decreased significantly; in the aging wet-dry cycle coupling, the aging asphalt mixture is more susceptible to water erosion, and the first wet-dry cycle after the mix by the degree of water erosion is relatively small, along with the dynamic modulus of rebound. The dynamic modulus of resilience is relatively larger, and the high-temperature performance is relatively better, while the low-temperature performance is worse.

A Sequence-Based Hybrid Ensemble Approach for Estimating Trail Pavement Roughness Using Smartphone and Bicycle Data

Trail pavement roughness significantly impacts user experience and safety. Measuring roughness over large areas using traditional equipment is challenging and expensive. The utilization of smartphones and bicycles offers a more feasible approach to measuring trail roughness, but the current methods to capture data using these have accuracy limitations. While machine learning has the potential to improve accuracy, there have been few applications of real-time roughness evaluation. This study proposes a hybrid ensemble machine learning model that combines sequence-based modeling with support vector regression (SVR) to estimate trail roughness using smartphone sensor data mounted on bicycles. The hybrid model outperformed traditional methods like double integration and whole-body vibration in roughness estimation. For the 0.031 mi (50 m) segments, it reduced RMSE by 54–74% for asphalt concrete (AC) trails and 50–59% for Portland cement concrete (PCC) trails. For the 0.31 mi (499 m) segments, RMSE reductions of 37–60% and 49–56% for AC and PCC trails were achieved, respectively. Additionally, the hybrid model outperformed the base random forest model by 17%, highlighting the effectiveness of combining ensemble learning with sequence modeling and SVR. These results demonstrate that the hybrid model provides a cost-effective, scalable, and highly accurate alternative for large-scale trail roughness monitoring and assessment.

Study on territory-wide application of low noise road surface in Hong Kong

Hong Kong is one of the metropolitan cities in the world, with highly concentrated road network system and densely populated developments. At times, it is inevitable to build residential buildings near noisy roads, and traffic noise is one of the environmental problems affecting the locals. The Government strives to pre-empt traffic noise issue through planning new road projects or new residential developments. Concerning traffic noise from existing roads, the Government has implemented noise mitigation measures, for instance, to resurface existing roads with Low Noise Road Surface (LNRS) materials, retrofitting of noise barrier or enclosure, to alleviate traffic noise impact. Moreover, the Government is continuously developing and trialing different LNRS materials such as Polymer Modified Stone Mastic Asphalt (PMSMA6) on roads in Hong Kong, which aims for wider application of LNRS. To explore the feasibility and effectiveness of the wider application of LNRS on local roads, the Government has recently conducted a territory-wide study on the application of LNRS on local roads in Hong Kong. This paper attempts to share the common local road characteristics of applying LNRS material and the latest technical findings, such as the effect on population exposure, of the territory-wide study in Hong Kong.

Tyre/road noise frequency spectra analyses based on CPX measurement with six microphones

Road traffic noise is affected by many factors, the road surface being one of them. The CPX method (ISO 11819-2) is the method used to measure tyre/road noise, i.e. noise generated by tyre-surface contact. Up to six microphones are positioned around reference tyre (ISO 11819-3) in specified positions as the standard requires. Two microphones are mandatory; four are optional. Conventional stone mastic asphalt, low-noise pavement, exposed aggregate cement concrete and cobblestones were measured by the CPX method using six microphones at a velocity of 80 km/h. Tyre/road noise frequency spectra from each microphone will be shown in this paper. Presented results should be used to discussion about positions or necessity of mandatory and optional microphones.

Low noise pavement characterization through TCN analysis

The use of low-noise pavements is a valid solution to reduce road traffic noise at source. Further studies are needed to optimize their design and ensure their durability. In this work, low-noise pavements were characterised using innovative and traditional methods on four different pavements: two of them contained crumb rubber added by dry and wet processes, one had an optimized texture and the last one was a traditional dense asphalt concrete. Using a sensor inside the tyre, the tyre cavity noise (TCN) was recorded and analysed, putting it in relation with the Close Proximity Method (CPX) data and the pavement texture measured by a laser profilometer. This paper aims to improve the knowledge of the relationship between the vibrational components of the tyre-pavement interaction using new and old descriptors, extending the types of pavements studied in past researches.

How sustainable are low-noise pavements? Answers from a life-cycle-assessment including the use-phase and noise mitigation of typical Swiss pavements

Despite continuous efforts to reduce road noise emissions, road noise is still the dominant source of noise in Switzerland. Low-noise pavements are an effective measure for road noise mitigation, but besides their higher cost, their major drawback is a reduced service lifetime as compared to conventional pavements. How do these arguments compare in a comprehensive view? To address this question, we performed a cradle-to-grave life-cycle-analysis of four different pavement types: a conventional pavement as reference, two types of semi-dense low-noise pavements and an acoustically optimized type of asphalt concrete. Besides the needed raw materials, the construction, maintenance and demolition, this life-cycle-analysis also includes the use-phase of the road. Thus, the noise mitigation (based on latest acoustic ageing models) and changes in fuel consumption (based on rolling resistance) are included in the assessment. We evaluate the results in the dimensions of ecological scarcity, greenhouse gas emissions, primary energy consumption and life cycle costs. The impact assessment method "Swiss ecological scarcity" allows to weight noise emissions and fuel consumption directly against resource demands of the different pavement types. Our results show that in densely populated areas, the noise reduction and energy savings clearly outweigh the increased resource demand of low-noise pavements.

Comprehensive Review of Thin White Topping for Asphalt Road Enhancement

Comprehensive Review of Thin White Topping for Asphalt Road Enhancement

Development of a flow diagram for the production of asphalt concrete mixture using polyethylene waste, contaminated with oil products

Large quantities of low-pressure polyethylene containers used for transportation and storage of oil products (motor oils) entail higher environmental risks produced by their utilization or disposal. An urgent scientific task is to search for new ways for utilization of such containers, to involve them in production of new target products without thorough cleaning of waste from contaminants and residues of motor oils. The present study involved crushed containers used for storage and transportation of motor oil in order to explore the possibility of including polyethylene in the production of asphalt concrete mixture. A sample, containing 17.5% of low-pressure polyethylene (contaminated with motor oil by 8% of asphalt mass), and a control sample of asphalt concrete mixture free of polyethylene, were made in order to investigate the change of properties, occurring in the low-pressure polyethylene asphalt concrete. Results. The study assessed main physical and mechanical properties of asphalt concrete samples containing low-pressure polyethylene and motor oil. According to the assessment, a number of properties exceed the values stated in GOST 9128-2013. In addition, the study results included development of technological regulations for producing asphalt concrete mixture with polyethylene as well as the flow diagram for obtaining asphalt concrete mixture. Using polyethylene waste contaminated with motor oil in the production cycle of asphalt concrete mixtures will reduce the consumption of raw materials for asphalt concrete production and the negative impact on the environment.