Conventional Asphalt Pavement Research Articles

In situ mechanical response characteristics of Autonomous Rail Rapid Transit (ART) applied to semi-flexible asphalt pavements

Autonomous Rail Rapid Transit (ART), featuring multi-axles, high tire pressure, and complete channelization, leads to severe rutting on conventional asphalt pavements. Semi-flexible pavement materials (SFP) were applied to ART corridors to mitigate rutting. Mechanical response characteristics were obtained by embedding sensors to understand the interaction between ART and SFP. Results found that the damage of corridor pavement shifted from rutting to top-down transverse cracking after adopting SFP. Nonresidual longitudinal tensile strains primarily caused top-down transverse cracking. The compressive stress at the bottom of corridor pavement caused by ART is 41%, 36%, and 58% higher than that of the BUS, respectively, under the condition of constant speed, acceleration, and deceleration. The maximum strain response caused by ART under a high-temperature environment was ten times higher than that of buses. These findings can provide data support for numerical simulations, material failures, and structural damage of ART corridors. Highlights Mechanical responses of semi-flexible pavement materials influenced by Autonomous Rail Rapid Transit (ART) were first captured using sensors. ART with high tire pressure exhibits a multi-axial cumulative effect in high-temperature conditions, resulting in pavement strains that can be up to ten times those of buses. After adopting semi-flexible pavement, the damage in ART corridors shifted from rutting to top-down transverse cracking. Nonresidual longitudinal tensile strains are the underlying cause of top-down transverse cracking.

Sensor-Based Structural Health Monitoring of Asphalt Pavements with Semi-Rigid Bases Combining Accelerated Pavement Testing and a Falling Weight Deflectometer Test

The Structural Health Monitoring (SHM) of pavement infrastructures holds paramount significance in the assessment and prognostication of the remaining service life of roadways. In response to this imperative, a methodology for surveilling the surface and internal mechanical responses of pavements was devised through the amalgamation of Accelerated Pavement Testing (APT) and Falling Weight Deflectometer (FWD) examinations. An experimental road segment, characterized by a conventional asphalt pavement structure with semi-rigid bases, was meticulously established in Jiangsu, China. Considering nine distinct influencing factors, including loading speed, loading weight, and temperature, innovative buried and layout configurations for Resistive Sensors and Fiber-optic Bragg Grating (FBG) sensors were devised. These configurations facilitated the comprehensive assessment of stress and strain within the road structure across diverse APT conditions. The methodology encompassed the formulation of response baselines, the conversion of electrical signals to stress and strain signals, and the proposition of a signal processing approach involving partial filtering and noise reduction. In experimental findings, the asphalt bottom layer was observed to undergo alternate tensile strains under dynamic loads (the peak strain was ten με). Simultaneously, the horizontal transverse sensor exhibited compressive strains peaking at 66.5 με. The horizontal longitudinal strain within the base and subbase ranged between 3 and 5 με, with the base registering a higher strain value than the subbase. When subjected to FWD, the sensor indicated a diminishing peak pulse signal, with the most pronounced peak response occurring when the load plate was situated atop the sensor. In summary, a comprehensive suite of monitoring schemes for road structures has been formulated, delineating guidelines for the deployment of road sensors and facilitating sustained performance observation over extended durations.

Study on the Performance of Nano-Zinc Oxide/Basalt Fiber Composite Modified Asphalt and Mixture

In order to improve the service quality of roads and resolve the problem of defects in the conventional asphalt pavement in service, this paper uses a 5.3% aluminate coupling agent to modify the surface of nano-ZnO and prepares a composite-modified asphalt with nano-ZnO and basalt fiber (BF) as modifiers. First, the basic performance of different types of asphalt was investigated by means of a rotary film oven experiment. Then, a dynamic shear rheology experiment was carried out to analyze the high-temperature anti-rutting performance of the composite-modified asphalt at different temperatures and frequencies. Then, using a bending creep stiffness test, the low-temperature properties of the composite-modified asphalt were investigated. Finally, the microstructure and modification mechanisms of the composite-modified asphalt were analyzed with scanning electron microscopy and infrared spectroscopy. The results indicate that the anti-aging performance of the nano-ZnO/BF composite-modified asphalt is significantly improved after adding fibers to the modified asphalt. The average mass loss ratio is only 0.192%. At 46 °C, the rutting coefficient of the composite-modified asphalt was increased by 62.3%. The frequency master curve is always at the highest position and continues to rise, indicating a significant improvement in the high-temperature anti-rutting performance of the composite-modified asphalt. At 24 °C, the creep stiffness modulus S value of the composite-modified asphalt increased by 24.9%; moreover, there is no obvious effect of improving low temperature, but the variation range of creep tangent slope m of the modified asphalt after aging is decreased, which further shows that the addition of a modifier can decrease the influence of aging on asphalt. Nanoparticles are uniformly dispersed in the asphalt and form a three-dimensional interconnected structure with BF, which effectively improves the overall performance of the asphalt. Nano-ZnO and fibers have weak chemical reactions in matrix asphalt, but they are physically dispersed and compatible.

Cooling efficiency of thermochromic asphalt pavement material and its contribution to field performance enhancement of asphalt mixture

The thermochromic asphalt pavement material (TAPM) has the potential to bilaterally regulate the pavement temperature according to seasonal environment, which is beneficial to heat island effect mitigation and pavement performance enhancement. However, studies on quantifying the cooling efficiency and verifying the field performance of TAPM are still limited. This study aims to more extensively verify the cooling efficiency of TAPM in different climatic regions and to reveal its cooling mechanism in the field. The key thermophysical parameter, solar albedo, of TAPM was back-calculated using an interpolation methodology to match the numerical simulation results with the specimen temperature data monitored experimentally. The cooling efficiency of TAPM in broader climatic regions was demonstrated through the numerical simulation combined with real meteorological conditions. In view of the cooling characteristics of TAPM as well as the temperature dependency attribute of asphalt mixture, various field performance properties of TAPM were characterized. It was found that at a temperature larger than 31 ℃, the solar albedo of TAPM is 0.30, which is six times larger than that of the conventional asphalt pavement material, indicating a strong reflection ability to solar radiation. The average temperature reduction of TAPM compared with the conventional asphalt pavement material in different regions is 6.26 ℃ with a standard deviation of 0.79 ℃, demonstrating the effective, universal and stable cooling effect of TAPM in summer across China. The cooling function of TAPM contributes to the improvement of high-temperature stability, aging resistance and low-temperature cracking performance of asphalt mixture. Therefore, it is necessary to consider the unique cooling function of TAPM for a more objective evaluation of its field performance.

FARKLI DİATOMİT İÇERİĞİ İÇİN ASFALT KAPLAMA PERFORMANSININ DEĞERLENDİRİLMESİ

The majority of steel and reinforced concrete bridges are produced with asphalt pavement. The reason for this is to protect steel and concrete structures from the effects of water and degrading salt additives and to increase their durability. Asphalt bridge superstructures are mostly manufactured with four layers. These layers are the primer bonding layer, waterproofing layer, protection layer and surface asphalt wearing layers. The superstructure must protect the supporting substructure. It should protect the life of the structure and ensure the integrity of the structure against permanent deformation, aging, raveling, water damage and chemical effects. Diatomite additive is used as a performance enhancer in various aspects. It is generally preferred in the region of 5%-15% according to the bitumen mass. The granulometric size and chemical properties of the diatomite additive are other effective factors. In this study, the rutting resistance of conventional and diatomite-modified asphalt pavement for 5% and 10% ratios for selected diatomite additive gradation is investigated. The rutting resistance of the pavements is investigated by repeated creep tests for two different additive ratios on water-damaged and control mixtures. In unconditioned samples, 5% diatomite-modified mixtures; in conditioned samples, 10% diatomite-modified mixtures showed the greatest deformation resistance.

Influence of basalt fiber on performance of thin overlayer asphalt mixtures based on multiple experimental methods

Because of the fast deterioration speed of the surface function of conventional asphalt pavement, thin overlayer with many advantages has been applied to the pavement surface. However, due to problems such as insufficient stripping resistance and cracking resistance, the performance of the thin overlayer needs to be further improved. To achieve this target, basalt fiber was introduced into two types of thin overlayer asphalt mixtures (Open graded friction course, OGFC-5, and Stone matrix asphalt mixture, SMA-5). The wheel tracking test and uniaxial penetration test for high temperature deformation resistance, low temperature bending beam test and indirect tensile asphalt (IDEAL) cracking test for cracking resistance, cantabro test for stripping resistance, and friction coefficient test for skid resistance were conducted to evaluate various performance of thin overlayer asphalt mixtures, along with the dynamic modulus test for dynamic mechanical response. The results showed that adding basalt fiber could enhance the high temperature deformation resistance, low temperature cracking resistance, intermediate temperature cracking resistance and stripping resistance of the thin overlayer, while having no significant impact on skid resistance. Furthermore, adding basalt fiber could increase the modulus in the high temperature region and decrease the modulus in the low temperature region of the thin overlayer asphalt mixtures, indicating thin overlayer with basalt fiber presenting superior both high temperature and low temperature performance. In addition, the evaluation indexes of SLT and SHT proposed from dynamic modulus test exhibited good consistency with the results of the performance tests.

Damage and responses of two asphalt pavement structures under blast loads: A numerical simulation

The explosion accidents are threatening the service functionality of pavement structures, which puts forward new requirements such as multi-hazard resistance and resilience. Although the widely used asphalt pavement structure is vulnerable to blast loads, its dynamic behaviors under blast loads are still unclear. This research mainly focused on the damage and responses of two asphalt pavement structures, one of which was conventional asphalt pavement, and the other was the anti-blasting asphalt pavement structure with the reinforced concrete layer. The numerical simulation method, which was validated based on a real blast test, was proposed using Abaqus code with appropriate material models and simulation procedures. The finite element models of two pavement structures were built. Under various blast loads, the damage contours and dynamic responses of different pavement structure components were investigated. It was found that the total damage areas of two asphalt pavement structures were grew by 2.26 and 3.19 times, respectively, as the blast loads increased from 100 kg TNT to 2000 kg TNT. The slope of pavement structure was extremely sensitive to the changes in blast load. The proposed anti-blasting pavement structure could reduce the damage area by up to 20 %, but it would be invalidated under particularly destructive blast loads. These findings could be helpful for the further design of an anti-blasting pavement structure.

Molecular simulation on compatibility and mechanisms of SBS and PTW polymer modifiers in asphalt binder.

Ultrathin overlays are preventive maintenance measures; the tensile and shear stresses generated inside a structural layer under vehicle load are greater than those of conventional thickness asphalt pavement. Therefore, asphalt binders must use high-viscosity and elasticity unique cementing materials to ensure stability. To investigate the modification mechanism of styrene-butadiene-styrene (SBS)/ethylene-butyl acrylate-glycidyl methacrylate copolymer (PTW) high-viscosity modified asphalt binder suitable for ultrathin overlays, the compatibility and molecular behavior of SBS/PTW high-viscosity modified asphalt binder were analyzed by the molecular dynamics (MD) method. These research results provide a reference for preparing ultrathin overlay high-performance composite modified asphalt binder. SBS molecular models, PTW molecular models, asphalt binder molecular models, SBS/asphalt binder blend systems, and SBS/PTW/asphalt binder blend systems were sequentially constructed using Materials Studio (MS) software. The compatibility of SBS, PTW, and SBS/PTW with asphalt binder and the diffusion coefficients of SBS, PTW, and SBS/PTW in the asphalt binder were investigated separately using the MD method. The mechanical properties and molecular behavior of SBS, PTW, and SBS/PTW blended with asphalt binder were studied. The research results indicate that the compatibility of PTW with asphalt binder is better than that of SBS with asphalt binder. PTW can effectively decrease the solubility parameter of asphalt binder and improve the compatibility between SBS and asphalt binder. PTW effectively improves the diffusion coefficient and interaction energy of SBS in asphalt binder by up to 29% and 83%. In addition, SBS/PTW had a significant positive effect on the mechanical properties of the asphalt binders, increasing the elastic modulus (E), bulk modulus (K), and shear modulus (G) of the asphalt binder by 4.6%, 9.5%, and 3.5%, respectively, compared to SBS. The results indicate that the SBS/PTW modified asphalt binder composite can significantly improve the high-temperature shear resistance of asphalt binder. Meanwhile, SBS and PTW improve the self-aggregation behavior between asphalt binder component molecules. The distance between the center of mass of asphalt binder and resin system molecules is increased. PTW enhances the extensibility of the branched chains of asphalt binder component molecules and improves the interaction between asphalt binder components and the chains. This further enhances the density and stability of the asphalt binder molecular structure system, improving the physical properties of the asphalt binder.

Effect of type and aggregate gradation on the functional properties of porous asphalt (case study of Iran)

Porous asphalt mixtures are gaining popularity due to their ability to effectively drain surface water and mitigate traffic noise in regions with high rainfall. However, compared to conventional asphalt pavements, these types of pavements with high void content necessitate specific guidelines for achieving an optimal mix design. The performance characteristics of porous asphalt mixtures are notably influenced by the grading and composition of materials, especially with regards to their resistance to moisture damage. This study aimed to investigate the properties of porous asphalt mixtures using limestone and siliceous aggregates with varying gradations, while maintaining bitumen contents of 5% and 6%. In accordance with the regulations set forth by the National Center for Asphalt Technology, the findings indicate that siliceous-based aggregates exhibit improved void characteristics (increased by 3%) and permeability (increased by 11%). However, they also display reduced resistance to moisture-induced failures (decreased by 4%). On the other hand, adhering to the gradation recommendations provided by the National Asphalt Pavement Association guidelines, except for a slight decrease of 3% in moisture sensitivity, yields an overall enhancement of 25% in other performance characteristics. To analyze the data, statistical methods were employed, resulting in regression models with a minimum R2 value of 0.97. These models helped determine the optimal binder percentage for different aggregate types and gradations, providing valuable insights for practical implementation.

Design and performance evaluation of a new green pavement: 100% recycled asphalt pavement and 100% industrial solid waste

In order to achieve sustainable development of road construction while addressing the occupation of land resources and the environmental impact of recycled asphalt pavement (RAP) and industrial solid waste, as well as the problem of insufficient resistance to permanent deformation and durability of conventional asphalt pavement, this study designed a new type of green pavement, which uses 100% RAP to form a large void matrix skeleton and 100% solid waste to prepare grouting materials. Research has found that green pavement has significantly higher high-temperature stability and durability than conventional asphalt pavement. The green pavement formed with a continuous gradation RAP matrix skeleton can be 100%–1000% higher than the green pavement formed with a single particle size gradation RAP matrix skeleton under the same fatigue stress ratio and load. At the same time, it also has significantly higher low-temperature bending characteristics, strength characteristics, and crack resistance. The above indicates that the green pavement designed in this study has good pavement performance, mechanical properties, and durability, especially the green pavement formed with a continuous gradation RAP matrix skeleton.

Optimization of asphalt cold recycling containing ordinary and waste additives based on life cycle assessment considering the road traffic level- case study: Coal preparation plant

In recent years, extensive research has been conducted on the use of second-hand or waste materials in the road pavement construction layers. Most of these studies evaluated the mechanical properties of materials and emphasized the environmental benefits of using waste materials for use in road construction projects, regardless of the environmental consequences. The present study intends to compare the life cycle of waste materials with standard materials and determine the optimal conditions for the selection of waste materials based on environmental criteria by considering life cycle assessment (LCA) and several environmental indicators. The analysis considered emulsified cold recycled asphalt with different types of activator fillers including cement, coal waste+lime and coal waste ash+lime. Also, the recycled pavement was compared with that of conventional asphalt pavement in this environmental assessment. The LCA analysis was performed for pavements with design traffic of 0.1–100 million equivalent single axle loads (ESALs). In order to design the pavements structure, 96 resilient modulus tests were done for 32 recycled mixes. Environmental indicators under study included energy consumption, abiotic depletion potential (ADP), global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP). The collected data for the studied functional unit was undergone an environmental analysis in SimaPro software. Apart from a standard case, parametric study was accomplished to analyze the effect of activator additive content. Accordingly, it was concluded that for the standard case, the traffic level or in other words the highway grade is of the main importance criterion in choosing the rehabilitation method based on environmental indicators. Emulsified cold recycled pavement with waste additives can be environmentally justified only in projects with low to medium traffic levels of less than 5–10 ESALs. For projects with medium to high traffic levels, only the ordinary recycling method with cement was comparable to conventional reconstruction.

Effect of Fine Aggregates and Mineral Fillers on the Permanent Deformation of Hot Mix Asphalt

Conventional asphalt pavement is the dominant mode of passenger and freight traffic in Pakistan. As a result, asphalt pavements suffer from various failures, where rutting, corrugation, and fatigue cracking are significant. Fine aggregates and mineral fillers play a pivotal role in providing structural integrity in asphalt pavements when subjected to traffic and the environment. The current study aims to examine the effects of various locally accessible fine aggregate and mineral filler materials on the interlocking properties of asphalt mixtures in relation to internal friction angle, rutting resistance, and controlling environmental pollution as an indirect benefit, thereby reducing wastes. Four distinct asphalt samples were prepared using cinders, stone dust, natural sand, and surkhi as fine aggregates and mineral fillers, as a full replacement, as per ASTM D1559, confirming the Asphalt Institute’s gradation for asphalt wearing course. Optimum binder contents (OBC) of 4.40%, 4.1%, 6.57%, and 6.63% by weight of Marshall specimen were concluded for asphalt samples containing stone dust, natural sand, cinder, and surkhi, respectively. The results revealed that surkhi, natural sand, stone dust, and cinder all showed a diminishing tendency in developing interlocking properties in asphalt mixtures at internal friction angles of 35°, 33.7°, 32°, and 28.4°, respectively. The wheel tracking test results revealed that the asphalt samples made with surkhi as fine aggregates and fillers have the highest rut resistance, whereas samples made with cinders as fine aggregates and fillers have the lowest rut resistance. The direct shear test showed that fine aggregates with a larger angle of internal friction are significantly more stable in terms of rut resistance than fine aggregates with a smaller angle of internal friction. The current research will help to prevent pavement rutting and corrugation by adding surkhi into asphalt pavements, with the reduction in brick kiln waste providing an indirect benefit.

Load response and fatigue life of cement-stabilized macadam base structure considering dynamic and static load differences and tension-compression modulus differences

The conventional semi-rigid base asphalt pavement (SRBAP) construction is designed with the classical theory of linear elastic mechanics. There is a significant discrepancy between the calculation results of the pavement structure load response and the measured results, which leads to inaccurate structural resistance and load response calculations. For this reason, this work depended on the actual structure of the SRBAP, took the linear elasticity theory as a contrast, and considered the difference between dynamic and static loads or the difference between the compressive and tensile modulus of pavement materials. Thus, the pavement structure response to load under three conditions is calculated, and five mechanical indexes are selected for comparative analysis. Furthermore, based on the calculated mechanical response, the structural fatigue life of the cement-stabilized macadam (CSMB) was then calculated, replacing the design index in the fatigue cracking model with the underside tensile stress or equivalent stress. The results demonstrated 20–30% variations between the calculated mechanical responses to dynamic and static stresses. Additionally, there is a substantial discrepancy between the strain computed using the bimodulus theory and the traditional linear elasticity theory, with a maximum divergence of 40%. In the meantime, the fatigue life of the CSMB produced using various design indices is noticeably different, and the fatigue life achieved using equivalent stress as the design index is significantly higher than that obtained using underside course tensile stress. Following is a relationship between the CSMB's fatigue life calculated by underside course tensile stress: viscoelastic theory (dynamic load) > bimodulus theory (tension–compression modulus difference) > classical linear elastic theory; The relationship of fatigue life represented by equivalent stress is as follows: viscoelastic theory > classical linear elastic theory > bimodulus theory.

Preliminary optimization design of inverted asphalt pavement structure using response surface method

Inverted asphalt pavement (IAP) has the advantage of maintaining good performance under the condition of thin asphalt concrete (AC) layer compared with conventional flexible asphalt pavement. The stress-dependent property of unbound aggregate base (UAB) plays an important role in mechanistic responses of IAP. The focus of this paper is to quantitatively analyze the function of UAB’s stress-dependent property on the structure combinations design of IAP using response surface method (RSM). In this paper, an improved UMAT subroutine was developed to characterize the stress-dependent stiffness of UAB. The three-dimensional FE pavement model was established and validated against KENLAYER calculation and field FWD test deflection data. The critical mechanical response, maximum principal strain and bulk stress, were selected to evaluate the fatigue performance of AC layer and stress-dependent property of UAB. The significance analysis was conducted to describe the relationship between input variables (thickness and stiffness of structural layers) and the critical mechanical response variables. An optimization design method to balance the fatigue performance and stress-dependent property was proposed to obtain the optimal structure combinations of IAP. Research results demonstrate that the thickness and stiffness of the AC and UAB layers present a clearly significant impact on the maximum principal strain at the bottom of AC layer and the bulk stress in UAB, particularly during the summer season, whereas the thickness and stiffness of CTB and stiffness of subgrade have a minor impact. The responses of bulk stress and maximum principal strain can be empirically predicted by 2FI and Quadratic models. Optimal structure combinations (13.6 cm AC layer and 10 cm UAB) were recommended after quantifying the stress-dependent properties of UAB. The recommended structural combination has good fatigue resistance and can also efficiently minimize AC and UAB layer thickness.

Reconstruction of Asphalt Pavements with Crumb Rubber Modified Asphalt Mixture in Cold Region: Material Characterization, Construction, and Performance

Dry-processed rubberized asphalt mixture has recently attracted a lot of attention as an alternative to conventional asphalt mixtures. Dry-processed rubberized asphalt pavement has improved the overall performance characteristics compared to the conventional asphalt road. The objective of this research is to demonstrate the reconstruction of rubberized asphalt pavement and evaluate the pavement performance of dry-processed rubberized asphalt mixture based on laboratory and field tests. The noise mitigation effect of dry-processed rubberized asphalt pavement was evaluated at the field construction sites. A prediction of pavement distresses and long-term performance was also conducted using mechanistic-empirical pavement design. In terms of experimental evaluation, the dynamic modulus was estimated using materials test system (MTS) equipment, the low-temperature crack resistance was characterized by the fracture energy from the indirect tensile strength test (IDT), and the asphalt aging was assessed with the rolling thin-film oven (RTFO) test and the pressure aging vessel (PAV) test. The rheology properties of asphalt were estimated by a dynamic shear rheometer (DSR). Based on the test results: (1) The dry-processed rubberized asphalt mixture presented better resistance to cracking, as the fracture energy was enhanced by 29-50% compared to that of conventional hot mix asphalt (HMA); and (2) the high-temperature anti-rutting performance of the rubberized pavement increased. The dynamic modulus increased up to 19%. The findings of the noise test showed that at different vehicle speeds, the rubberized asphalt pavement greatly reduced the noise level by 2-3 dB. The pavement M-E (mechanistic-empirical) design-predicted distress illustrated that the rubberized asphalt pavement could reduce the IRI, rutting, and bottom-up fatigue-cracking distress based on a comparison of prediction results. To sum up, the dry-processed rubber-modified asphalt pavement has better pavement performance compared to the conventional asphalt pavement.

Laboratory and Field Testbed Evaluation of the Performance of Recycled Asphalt Mixture Using High-Penetration Asphalt

The application of recycled asphalt pavement (RAP) on a large scale is highly promoted to meet the current needs of carbon neutrality and sustainable development purposes. However, a majority of RAP mixture productions are currently relying on the restoring effects provided by the rejuvenators. Therefore, the study focuses on the feasibility of using high penetration asphalt binder (HPAB) in RAP mixture as a replacement for conventional rejuvenators. In this study, a recycled asphalt pavement mixture containing HPAB (RAP-H) was developed to resolve the cracking issue of RAP pavement in winter seasons owing to the rigid behavior of aged binders. To verify the applicability of the RAP-H mixture, the results of the quality standard test and mechanical performance test were compared with the reference RAP mixture having rejuvenator (RAP-R). Through the fatigue cracking test, by using Overlay Tester (OT) device, it was found that all specimens did not reach 93% load reduction after 1000 OT cycles, indicating a satisfied stress-bearing capacity. Additionally, the highest dynamic modulus of 27,275 MPa was found in the modified HPAB mixture, and this result is 4.4% higher than that of the reference mix. In the full-scale testbed, the long-term field applicability of the proposed approach was verified through field test construction. The measurement in practice reveals that the elastic modulus of RAP-H back-calculated from the FWD (Falling Weight Deflectometer) test is increased by more than 50% compared to RAP-R, which resulted in excellent performance characteristics of the HPAB pavement layer. In addition to the efficiency in the surface layer, an improved elastic modulus of the sub-base and subgrade layers in the HPAB section was found to be at 28.6% and 19.5%, respectively, compared to the RAP-R mix. In general, the performance of RAP-H satisfied all of the domestic and international quality and performance standards. The field test results confirmed the possibility of field application by showing performance higher than conventional recycled asphalt pavement.

ACOUSTIC CHARACTERISTICS OF ROAD SURFACES

The article is focused on the tyre/road noise and vibration measurements of the motorway network in the Czech Republic between 2012 and 2020. Three different surfaces were measured, namely a conventional stone mastic asphalt pavement (SMA 11S) and two cement concrete pavements with different treatments – burlap drag and exposed aggregate. A basic statistical analysis of the noise values in different years after laying was performed. Cement concrete treated by burlap drag method has lower noise values than SMA 11S. This is to be expected as burlap drag method is considered a low-noise cement concrete treatment. However, it has worse skid resistance properties and so the exposed aggregate cement concrete (EACC) began to be used. SMA 11S and EACC have very similar noise levels in all years tested, suggesting that they behave acoustically in the same way. Vibrations were investigated during field measurements with an accelerometer mounted on the CPX trailer. The noise and vibration results could thus be compared with each other. There is a positive correlation between them.

Evaluating the cost of collection, processing, and application of face masks in hot-mix asphalt (HMA) pavements

Human activities significantly contribution to the yearly generated plastic wastes. Moreover, the enormous increase in face masks and face shields caused by the emergence of the COVID-19 pandemic has doubled the generated plastic wastes. Although there is an added benefit of using plastic waste in construction, the cost associated with their application, specifically the face mask, has not been addressed. This paper presents a simplified and rapid estimation of the cost associated with the collection, processing, and application of face masks in hot-mix asphalt (HMA) pavements. Two scenarios, mask modified asphalt pavement and conventional asphalt pavement, are considered. The total cost is based on market price and prices from waste management facilities and plastic processing companies. Life Cycle Cost Analysis (LCCA) is used to evaluate the long-term costs of mask modified asphalt pavement and conventional asphalt pavement. Results show that no significant difference in initial total cost between the two scenarios for pavement sections with lengths less than 500m and the number of lanes less than 6. The difference in total cost begins with lengths greater than 500 m for 5 and 6 Lanes. Despite the higher initial costs for the mask modified asphalt pavement, the LCCA shows that there is a 29% maintenance cost reduction over the 40 years life cycle of the asphalt pavement. The use of LCCA shows the benefit of the selection of the most cost-effective strategy and how the use of mask modified asphalt pavement over the conventional asphalt pavement can save money over the life cycle of the asphalt and improve rutting and stiffens.

Numerical Investigation of the Temperature Field Effect on the Mechanical Responses of Conventional and Cool Pavements.

Conventional asphalt pavement has a deep surface color and large thermal inertia, which leads to the continuous absorption of solar thermal radiation and the sharp rise of surface temperature. This can easily lead to the permanent deformation of pavement, as well as aggravate the urban heat island (UHI) effect. Cool pavement with a reflective coating plays an important role in reducing pavement temperature and alleviating the UHI effect. It is of great significance to study the influence of temperature on the mechanical response of different types of pavement under vehicle loading. Therefore, this study examined the heat exchange theory between pavement and the external environment and utilized the representative climate data of a 24 h period in the summer. Two kinds of three-dimensional finite element models were established for the analysis of temperature distribution and the mechanical responses of conventional pavement and cool pavement. The results show that in this environmental condition, conventional pavement temperatures can exceed 50 °C under high temperatures in summer, which allows for the permanent deformation of pavement and further affects the service life of asphalt pavement. The temperature difference in a conventional pavement surface between 6 h (24.7 °C) and 22 h (30.2 °C) is much less than that between 22 h (30.2 °C) and 13 h (50.1 °C) in the summer. However, the difference in the vertical displacements of the pavement surface between 6 h and 22 h is much larger than that between 22 h and 13 h. One reason is that the difference in temperature distribution between the morning and night leads to changes in pavement structure stiffness, resulting in significant differences in vertical displacement. Cool pavement has a significant cooling effect, which can reduce the surface temperature of a road by more than 15 °C and reduce the vertical displacement of the pavement by approximately 11.3%, which improves the rutting resistance of the pavement. However, the use of cool pavement will not change the horizontal strain at the bottom of the asphalt base and will not improve the fatigue resistance of asphalt pavement. This research will lay the foundation for further clarifying the difference in the mechanical properties between the two types of pavements in the management and maintenance stage.

Building the cooling roads with high thermal conductivity pavements to relieve urban heat island effect

This study aims to propose a new highly thermally conductive pavement (HTCP) structure and evaluate the cooling effect of the structural layers and near-surface air. The HTCP consisted of coarse quartzite aggregates with high thermal conductivity instead of limestone. The HTCP and conventional asphalt pavement layers were placed in the environmental chamber. The incandescent lamp was used to simulate solar radiation to analyze the air temperature changes of the structural layers and near-surface air. The test results show that quartzite improves the thermal inertia of asphalt pavement layers. And the HTCP effectively transfers the heat accumulated in the upper layer and reduces the daily temperature of structure layers and near-surface air. However, HTCP releases more sensible heat at night, negatively impacting the urban heat island effect. This research contributes to the improvement of HTCP from an aggregate perspective and provides new ideas for mitigating the UHI effect.