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Pay for Performance (PFP) is a statistical-based quality assurance specification used to evaluate asphalt concrete construction for projects having mix quantities greater than 7,260 t (8,000 US tons). The contractor pay is adjusted based on mix field density, air voids, and voids in mineral aggregate. In this study, data were analyzed from the 2015 to 2017 highway construction seasons in Illinois to determine variability trends. Density was the major factor driving contractor pay disincentives in PFP, followed by air voids. To identify the impact of construction field density consistency on the final pay factor, a sensitivity analysis was performed to determine the changes in the contractor pay with respect to variability, which is measured by standard deviation. In addition, an econometric analysis based on sensitivity analysis using linear regression was conducted. The results showed that a 1% reduction in density standard deviation led to a 0.066 increase in density pay factor. Based on the 79 projects analyzed, if the density standard deviation had been reduced from 1.67 to 1.0, the average increase in pay per project would be $38,000. [ABSTRACT FROM AUTHOR]

Delivering durable asphalt concrete within a reasonable cost is one of the great ambitions of pavement material engineers. This state-of-the-art review article documents the efforts spent in the past two decades to ensure the durability and performance of asphalt mixtures in mix design and production. A perspective with the attempt to integrate laboratory mix design, plant production quality assurance, and field place acceptance is applied in the review. The development of the performance specification and performance mix design is summarized. The paper categorizes performance specification into index-based performance specification and predictive performance specification that include performance-related specification and performance-based specification. The approaches to developing index-based performance mix design/balanced mix design and predictive performance mix design are also compared in the review. The challenges and solutions in incorporating performance tests in asphalt productions are documented and discussed. The challenges include selecting performance testing methods, determining index threshold limits, estimating and incorporating testing variability and uncertainty, determining sampling position and testing frequency, and so forth. The paper also provides suggested areas of future research and implementation activities. [ABSTRACT FROM AUTHOR]

Fatigue cracking due to repeated truck traffic loads is the leading cause of failure of asphalt concrete pavement in many locations. Rest periods, referring to the time intervals between successive trucks, may allow for partial or full recovery from fatigue damage and in turn extend pavement fatigue life. This paper delves into the characteristics of rest periods between highway truck traffic loads using traffic data from 40 weigh-in-motion (WIM) stations installed on California state highways and evaluates their effects on pavement performance using mechanistic-empirical incremental-recursive damage and cracking simulation (CalME software). Toward this purpose, truck traffic data were extracted from these WIM stations at selected periods throughout the year 2015 to calculate rest periods. The probability distribution of rest periods and quantiles of cumulative rest periods were calculated, respectively. Regression and statistical analysis for 0.5 quantiles (median) of cumulative rest periods were also performed for different spectra groups and seasons. It was found that rest periods are strongly correlated with the truck traffic volume regardless of the WIM station location and seasons of the year. The actual rest periods based on the nonuniform truck traffic measured from the WIM data were found to be slightly shorter than the corresponding theoretical average rest periods for uniform traffic (ARP-UT) currently assumed in CalME, likely due to truck-following. This theoretical value assumes an equal time interval between trucks all the time. After comparing pavement performance with and without rest periods, it was found that rest periods have a significant influence (30% in difference) on pavement cracking performance in the modeling. Based on this preliminary analysis, the difference in pavement performance caused by the difference between the actual rest periods and ARP-UT is minimal. It is therefore recommended to continue to use ARP-UT to account for the effect of rest periods in pavement design. [ABSTRACT FROM AUTHOR]

Although high-friction surface treatments (HFSTs) are a proven efficient countermeasure for the reduction of roadway departure crashes, their long-term pavement performance has yet not been fully understood with large-scale field monitoring. This paper presented and analyzed 3 years of monitoring results on 36 HFST sites located in 12 states in the US ranging from 0 to 11 years in treatment age. Taking the traffic directions and number of lanes at each site into consideration, a total of 65 HFST segments were measured. Onsite data were collected by a Grip Tester for pavement friction, the PaveVision3D laser imaging system for condition evaluation and high-resolution pavement images, and the AMES high-speed profiler for surface texture and roughness. The evolutions of HFST surface characteristics and field performance were evaluated. It was found that most HFST sites continued providing superior friction values compared with the neighboring nontreated surfaces. Cracking and surface delamination were observed as the major failure types on a few sites. The delaminated area exhibited higher roughness values and lower friction numbers. Subsequently, a multivariant friction prediction model was developed to assist in understanding its influencing factors and deterioration trends. Furthermore, a safety performance function was built for crash frequency estimation on HFST sites, through which the benefit of HFST in reducing roadway departure crashes could be further quantified. [ABSTRACT FROM AUTHOR]

Phase change material is a high thermal storage substance, which can reduce temperature-related diseases of asphalt pavement when mixed with asphalt mixture. In this paper, NiTi alloy phase change heat-storage asphalt mixture (NiTi APCHAM) are prepared by using equal volume parts to replace fine asphalt aggregates partially with the NiTi alloy phase change energy-storage particles (NiTi APCEP). As the temperature increases, the specific heat capacity of NiTi APCHAM will increase first and then decrease due to the heat-storage effect of NiTi APCEP. The thermal conductivity coefficient of NiTi APCHAM shows a linear increasing trend with the increase in the substitution rate of NiTi APCEP. Adding NiTi APCEP in asphalt mixture can reduce its daily maximum temperature. Increasing admixture of NiTi APCEP in asphalt mixture can help to improve the phase change heat-storage thermoregulation capacity of the mixture. However, at a 6 wt% substitution rate of NiTi APCEP, the latent heat thermoregulation efficiency of NiTi APCEP reaches to maximum. With the increase in the content of NiTi APCEP, the Marshall stability of asphalt mixture gradually increases, and flexural-tensile strain at low temperature decreases gradually. By contrast, the water stability of the asphalt mixture is unaffected by the addition of NiTi APCEP. • NiTi alloy phase change heat-storage asphalt mixture were prepared. • Adding NiTi APCEP in asphalt mixture can reduce its daily maximum temperature. • The optimal substitution rate of NiTi APCEP was recommended in this paper. [ABSTRACT FROM AUTHOR]

• Rheological properties were tested for asphalt aged under different situations. • Chemical methods (FT-IR and GPC) were tested for asphalt aged under different situations. • The characteristics of rheological properties under different aging conditions were analyzed. • A time-temperature equivalent model of short-term aging was constructed. • Relationships between rheological properties and chemical composition were obtained. The degradation of asphalt pavement performance is severely affected by the aging of asphalt. In order to improve the anti-aging performance of asphalt, it is necessary to study the aging mechanism of asphalt first. The objective of this paper was to systematically study the characteristics and mechanism of short-term aging of neat asphalt based on rheological indexes and chemical indexes, including complex modulus (G *), phase angle (δ), stiffness (S), m -value, fatigue performance parameter (N f), carbonyl index (I C O) and polydispersity (PDI). The short-term aging of asphalt was performed by the rolling thin film oven test (RTFOT) at different temperatures and durations, the rheological properties were evaluated by the dynamic shear rheometer (DSR) and bending beam rheometer (BBR), the chemical indexes were got by the Fourier transform infrared (FT-IR) and the gel permeation chromatography (GPC). Meanwhile, the time-temperature equivalent effects based on the high/low-temperature performance of asphalt were analyzed. The relationships between asphalt rheological properties and chemical indexes were discussed. The results showed that the fatigue resistance was most sensitive to aging while compared with the high/low-temperature performance of asphalt. The indexes including G *, S , and N f tended to increase as the aging degree increased, whereas other rheological indexes had opposite trends. According to the changing characteristics of the high/low-temperature performance of asphalt, a time-temperature equivalent effect model of asphalt aging was constructed. Moreover, both the oxidation and volatilization of asphalt components were accelerated as the aging temperature increased, but the volatilization was more sensitive to temperature than the oxidation. Based on the correlation analysis, both I C O and PDI exhibited a strong correlation to rheological properties. Therefore, prediction models based on I C O and PDI were constructed to predict the rheological properties of aged asphalt. [ABSTRACT FROM AUTHOR]

Waste recycling is becoming one of the most concerned issues in the field of environmental conservation. This study developed environmental friendly alternative binders for permeable asphalt concrete suitable for Low Impact Development by recycling engineering wastes including crumb rubber powder and recycled oil to prepare high-viscosity asphalt binders. Firstly, three waste-based high-viscosity asphalt binders (WHABs, including D-Ⅰ, D-Ⅱ and F) and TAFPACK-SUPER (TPS) modified asphalt (TMA, control sample) were prepared. Then four binders' characterization were detected by FT-IR, SEM-EDS and TG-DSC. Finally, the pavement performance including viscosity, viscoelasticity, high-temperature, low-temperature and storage stability performance were investigated. Chemical structure and micro morphology illustrated that WHABs had better chemical stability and aging resistance than TMA, and thermal stability indicated that the four binders were similar. Analyses on pavement performance revealed that WHABs had similar pavement performance to TMA, especially the D-Ⅰ and F, which had obvious advantages in aging resistance, temperature sensitivity in the range of 30–80 °C, high-temperature performance, low-temperature performance and storage stability. This study demonstrates that crumb rubber powder, recycled oil and appropriate additives can contribute to well-performance high-viscosity asphalt binder, which will be one of mainstreams for the future development in high-viscosity asphalt binder area. Keywords: High-viscosity asphalt binder; Crumb rubber powder; Recycled oil; Viscosity; Pavement performance. Image 1 • Engineering wastes were used to prepare well-performance high-viscosity asphalt binder. • Micro structure and pavement performance of WHABs and TMA were studied. • Micro performance before and after aging were analyzed by FT-IR and SEM-EDS. [ABSTRACT FROM AUTHOR]

The effectiveness of porous pavement (PP) and bio-retention cells (BCs) under the influence of potential climate change was investigated based on representative concentration pathways (RCPs). A case study of a test catchment in Guangzhou illustrated changes of peak runoff under various climate scenarios. There were distinct increases in runoff volume and peak discharge in response to RCP8.5 but only marginal increases in response to RCP2.6 (compared with present conditions). The performance of PP and BCs in terms of percentage reduction of runoff volume and peak discharge was examined for 1-, 10-, and 100-year return period and 1- and 6-h-duration storms under various climate scenarios. The effectiveness of PP and BCs varied non-linearly with the extent of PP and BCs adopted. In general, the fluctuation of hydrological performance of PP is greater than that of BCs in RCP2.6 and RCP8.5 (e.g., peak flow reductions range from −60% to 69% and from −22% to 9%, for 5% area of PP and BCs, respectively). And PP is more cost-effective for frequent storms using life cycle costing analysis. We find that PP and BCs could significantly reduce runoff volume and peak discharge in response to rainfall events with short return period, but not for heavy storms with longer return period. Image 1 • Hydrological responses investigated under climate scenarios. • Cost-effectiveness of PP and BC analyzed based on LCC and hydrological indices. • PPs and BCs could be more effective in response to small storms. • Optimizing PP and BC proposed for adapting potential climate change. [ABSTRACT FROM AUTHOR]

The performance of asphalt pavement is highly affected by climate factors, such as temperature and precipitation. Different temperature and moisture conditions change the paving material properties, which consequently influence pavement performance. Considerable research has been conducted to study the effect of climate factors on pavement performance; however, there are no focused studies that have investigated the performance of asphalt pavements in cold regions. In this research, the effect of different design factors on asphalt pavement performance in cold regions is investigated utilising data extracted from the Long-Term Pavement Performance database. Only control sections with no historical maintenance or rehabilitation records were considered. The International Roughness Index (IRI) was adopted as the pavement performance measure. The IRI value is expected to increase gradually over time due to pavement deterioration. Initial screening of the data showed that most of the pavement sections experienced remarkable IRI increase followed by an unexpected decrease. An in-depth investigation revealed that frost heave was the main reason of this unexpected IRI trend as it was correlated in most of the cases to sudden monthly freezing index increases, especially for sections with no subsurface drainage and less layers thicknesses. An Artificial Neural Network with a Forward Sequential Feature Selection algorithm and regression analysis were employed to model pavement performance in cold regions and determine the most significant design factors prevailing in cold climate conditions. Moreover, a sensitivity analysis was performed to investigate the interrelation between the considered features and the IRI. As a result, several climate-related factors were found to have a significant impact on the performance of asphalt pavements in cold regions such as average temperature, freezing index, freeze/thaw, wind velocity and relative humidity. [ABSTRACT FROM AUTHOR]

The assessment of the structural performance of inundated pavements is crucial to reduce the induced damage in the aftermath of flooding. The objective of this study is to present a simplified approach to investigate the impact of different subsurface water levels on the performance of pavement structures. The flooded conditions and subsequent water recession were simulated by slowly lowering the subsurface water from the pavement surface down in depth. A hydrostatic water pressure distribution was assigned above and below the water level for different cross sections with different subgrade types. Layer Elastic Analysis was performed to predict the surface deflection, stresses and strains at the bottom of asphalt layer and at the top of subgrade layer to evaluate the impact of saturated and unsaturated pavements. Finally, the influence depth for subsurface water level at which the road can withstand traffic with zero to minimum deterioration was discussed given the pavement structure and soil type. The results showed that the pavement structural capacity decreases significantly when the base and subgrade layers are fully saturated. The pavement starts to regain its strength once the subsurface water level dropped below the base course layer. [ABSTRACT FROM AUTHOR]

This study was initiated with the aim of evaluating the impact of stabilised and untreated base layers on the performance (i.e. fatigue and rutting) of flexible pavements. Four field sections constructed using stabilised base layers (i.e. bituminous (asphalt emulsion), calcium chloride (CaCl2), Portland cement and geogrid stabilised base layers) and a control section constructed using untreated recycled asphalt pavement (RAP) aggregates were analysed in this study. Falling weight deflectometer tests were conducted on all field sections and the collected data was used to back-calculate the elastic moduli for all layers. The influence of the stabilised bases and the untreated (RAP) base on the mechanical responses (stresses and strains) of the overall pavement structure was also evaluated by conducting layered elastic analyses. In addition, pavement ME design simulations were conducted to determine which of the four stabilised base types enhanced the overall predicted performance of flexible pavements the most. A service life of 20 years was used for pavement ME analysis. Based on the results, it was concluded that the Portland cement-treated base seemed to be more effective than the other stabilised bases at improving the resistance of the pavement sections to fatigue cracking followed by the CaCl2 and bituminous stabilised bases. The geogrid stabilised base appeared to have the least impact on improving fatigue cracking resistance. It was also determined that base layer stabilisation appeared to have little effect on the rutting resistance of the pavement sections. [ABSTRACT FROM AUTHOR]

A significant number of agencies allocate low funding levels for their low-volume roads (LVRs) as part of their pavement management system (PMS) funding strategies. Although agencies have been applying a number of low-cost treatments, the effectiveness of the applied treatments towards improving pavement performance is not well understood or documented. The application of low-cost treatments on roads has different levels of impact on the pavement performance depending on the initial pavement condition. This study introduces a methodology of evaluating in-practice surface treatments on LVRs. The methodology can be implemented by different transportation agencies using historical data of pavement condition and treatment records. A case study of managing LVRs in Colorado was investigated using the historical PMS data of Colorado Department of Transportation (CDOT). The performance of pavement in the context of fatigue, longitudinal, and transverse cracking was analysed and the results show different trends of common treatment options applied to LVRs. It was concluded that some surface maintenance strategies are effective long-term treatments for fatigue, longitudinal, and transverse cracking. However, the effectiveness of these treatments depends mainly on the initial condition index. The findings of this study permits increased understanding of selected maintenance treatments. An appropriate maintenance strategy was developed including all effective treatments. The comprehensive long-term analysis of road maintenance and costs shows that the proposed maintenance strategy is more cost-effective compared to the current policy followed by CDOT. [ABSTRACT FROM AUTHOR]

Due to the special characteristics of nanoparticles, pavement engineers have used nanoparticles as an additive in asphalt pavement to improve pavement performance. This study focuses on characterizing modified asphalt performance using nanoclay particles compared to the unmodified asphalt binder. For this evaluation, 3% of nanoclay particles were added to a neat binder to prepare the nanomodified binder. Then, the modified and unmodified binders underwent a short- and long-term aging process using the Rolling Thin Film Oven (RTFO) and two cycles of Pressure Aging Vessel (PAV). Finally, the Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Fourier-Transform Infrared Spectroscopy - Attenuated Total Reflection (FTIR-ATR) tests were carried out in each aging step to assess and monitor the rutting, fatigue, low-temperature performance, durability, and chemical changes of binders during the aging process. The results of this study proved the enhanced properties and performances of the nanomodified binder compared to the unmodified binder. These results can pave the path with the use of nanomodified binders in the recycling of aged pavement and construction of roads that experience poor weather conditions and high traffic loads. [ABSTRACT FROM AUTHOR]

Concrete pavement recycling has become a common practice for many states in the U.S. While material properties and structural performance of pavements with virgin concrete aggregates replaced by recycled concrete aggregate (RCA) have been extensively characterized, very little effort has been made to assess potential sustainability benefits of this application. A life cycle assessment to compare an RCA based portland cement concrete (RCA-PCC) pavement and a plain PCC pavement (i.e., without RCA) from all three aspects of sustainability (i.e., economic impact, social impact, and environmental impact) was carried out using an economic input-output life cycle assessment (EIO-LCA) approach. An inventory of stressors during materials production and construction, use, and end-of-life phases of pavement life cycle was obtained, followed by a life cycle impact analysis using the Tool for Reduction and Assessment of Chemicals and other Environmental Impacts (TRACI). Based on the results, the benefits of using RCA during the materials production and construction phase are invariably achieved for all the sustainability categories, but the RCA-PCC pavement would pose higher negative impacts during the use phase of pavement life. Still, the pavement made with RCA-PCC was found to be generally more environmentally and socially friendly compared to the pavement made with virgin aggregates, especially for the TRACI categories of ecotoxicity, human health cancer, and human health non-cancer. The sustainability benefits of using RCA for concrete pavement application will only be magnified with a growing level of environmental awareness, further diminishment of local virgin aggregate sources, and a rapid increase of landfill tipping costs for construction demolition debris in the future. • Compare RCA-PCC pavement with plain PCC pavement from all three aspects of sustainability. • Conduct an economic input-output life cycle assessment case study for concrete pavements with and without RCA. • Assess the environmental and social benefits of using RCA in PCC pavement via the TRACI. [ABSTRACT FROM AUTHOR]

Transportation agencies should have the capacity to evaluate the damage caused by oversize and overweight (OS/OW) vehicles in order to develop effective infrastructure management and rehabilitation strategies. In this paper, we discussed how to combine different paradigms that influence pavement performance into a single evaluation methodology by integrating the most available historical data with respect to the characteristics of OS/OW vehicles (i.e. dimension and weight), their origin and destination, permitted routes, frequency of the routes, pavement condition data, and climatic effects. The proposed methodology is then implemented into three case studies to indicate its applicability and practicality. In the case studies, we evaluate the impacts of OS/OW loads on pavements under different scenarios and combinations of the related factors. The corresponding relationships between pavement conditions and passing OS/OW loads are quantified with a well-accepted sigmoidal function. The results also indicate that, at the early age of the road, higher OS/OW loading would bring a faster deterioration rate (e.g. about 6% of the reduction in service life for extreme high OS/OW loading, while only 2.35% for low OS/OW loading). At the end of road life, the reduction trend slows down, nearly above 2% for all OS/OW loading levels. [ABSTRACT FROM AUTHOR]

Pavement management systems employ pavement performance models to plan the most effective allocation of public funds. The most used models are the deterministic and the probabilistic or stochastic ones. Among stochastic models, the Markov Chains are receiving considerable research attention. In this paper, transition probability matrices (TPMs) are presented for Portland Cement Concrete (PCC) pavement road network in the Republic of Moldova with available International Roughness Index (IRI) data collected in spring and in autumn from 2013 to 2015. Although one-year cycle time is usually employed, half-year cycle time was defined to handle a bigger amount of transitions. The aim of this paper is to prove that TPMs for rigid pavements can be developed using IRI values from a short period, with a half-year step time, for a road network where the time since last major rehabilitation varies in each section and where maintenance and rehabilitation activities are carried out simultaneously. In order to consider all these aspects, some assumptions must be made. Roughness seasonal variations can arise in PCC pavements due to the effect of curl and warp. Hence, a threshold of 0.40 m/km was defined as the maximum improvement on a section after half-year step for not being considered as maintenance work or spurious data. When the IRI value improves more than 4 m/km after one step, a rehabilitation activity is considered. That rehabilitation is not used in the matrix calculation, but the subsequent deterioration contributes. Results demonstrate that rigid road sections can jump two condition states in one transition, instead of only remaining in the same condition state or shifting to the next one. Obtained matrices give an overview of deterioration tendencies of rigid pavements, and they fit better to real data if a large proportion of no rehabilitated or maintained sections are compared to predicted values. [ABSTRACT FROM AUTHOR]

The deterioration of asphalt binders rheological behaviors in different aging stages were investigated by using self-developed indoor aging equipment SAT (simple aging test), and the corresponding relationship between indoor simulated aging and field asphalt aging was established. It was found that SAT equipment can better simulate the aging process of asphalt on site, with asphalt film thickness of 2 mm, short-term aging temperature at 150 °C, long-term aging temperature at 95 °C. [ABSTRACT FROM AUTHOR]

Highlights • The effect of both organic and inorganic fiber on the performance of concrete was investigated. • Three indexes for evaluating the anti-wheel impact performance of airport pavement were established and the attenuation law of which was investigated. • Scanning electron microscopy (SEM) was used to analyze the improvement mechanism of fiber to the micro state of the interfacial transition zone. • The optimum volume of both organic fiber and inorganic fiber in airport pavement concrete was obtained. Abstract In this paper, the poly-acrylonitrile synthetic fiber concrete (PSC) (the representative of organic fiber concrete) and alkali resistant glass fiber concrete (ARGC) (the representative of inorganic fiber concrete) were studied and compared. The test were carried out by the IMYD-X single side freeze-thaw machine of concrete and the modified wheel impact test machine which was pressurized and accelerated. The dynamic deformation and toughness performance of fiber concrete have been comparatively analyzed, and the effect of fiber on the performance of concrete has been investigated. Three concrete performance indexes were selected to evaluate the anti-wheel impact performance of the airport pavement concrete in freeze-thaw environment, namely relative mass ratio, relative compressive strength ratio, and relative dynamic modulus ratio. The results showed that adding fiber in the concrete can significantly improve these indexes. Four indexes of concretes decreased when the test durations increased, and the relationship between various indexes and test durations can be described as an exponential function. Moreover, all the indexes of fiber concrete increase with the increasing fiber volume content. The optimal content of both organic fiber concrete and inorganic fiber concrete were 1.6 kg/m3. From the overall trend, the relationship among fiber concretes by the anti-wheel impact performance in freeze-thaw environment can be listed as follow: ordinary concrete < inorganic fiber concrete < organic fiber concrete. Combined with the SEM analysis of fiber concrete, it was found that fiber can obviously improve the dense state of the concrete transition zone, and the improvement of organic fiber is more obvious. Judging from the comprehensive analysis, the addition of organic fiber with the 1.6 kg/m3 can improve the anti-wheel impact performance in freeze-thaw circumstance. [ABSTRACT FROM AUTHOR]

Highlights • ITS of modified asphalt is higher than conventional asphalt. • Model values showed a very good regression with the experimental results. • Performance of HMA modified with silica is improved. • Nano-silica can improve moisture sensitivity of asphalt Mixtures. • Use of nano silica resulted in a significant increase in compressive strength. Abstract The primary objectives of the design and implementation of asphalt pavement on road and road surfaces are to achieve the best performance in different climatic conditions. Asphalt pavement performance depends on the adhesion and bonding of binder and aggregates that the moisture causes it to disappear and it results in bleeding and stripping. Although the moisture susceptibility mechanism is not fully known, factors such as binder properties, aggregates properties, asphalt mixture properties, quality control during congestion, the dynamic effect of traffic load and the type of anti-stripping additive play a significant role in creating a moisture susceptibility and aggravation of failures. In this paper, Group Method of Data Handling (GMDH)-type neural networks have been used for modeling and prediction of moisture susceptibility of nano silica-modified asphalt concrete. To achieve this goal, 5 types of mixtures with different percentage of nano-silica (0, 0.2, 0.4, 0.7 & 0.9%) were prepared and the moisture susceptibility of modified mixtures was evaluated. Results showed that nano-silica can improve the moisture susceptibility of asphalt mixtures. For modeling, the experimental data were divided into train and test sections (70% for training and 30% for testing). The predicted values were compared with those of experimental values in order to estimate the performance of the GMDH-neural network. The model values showed a very good regression with the experimental results. [ABSTRACT FROM AUTHOR]

Mine haul road pavements are often designed with informal methods. This approach means the energy consumption in haulage is not quantified and so pavement operating costs are not able to be defined. The energy consumption of haul trucks operating on unbound and cementitiously modified haul road pavement basecourse and wearing courses were estimated with variable traffic, climate and maintenance inputs. Energy consumption estimates showed that significant benefits may arise through the use of superior gravels that contain a suitable fines content with low to medium plasticity in the pavement wearing course. Similarly, it was shown that the pavement structural class significantly impacts haul truck energy consumption. Structural class is determined by pavement design and may be improved by increasing the pavement depth or utilizing stiffer materials. Estimating the energy consumption of haul trucks as part of the pavement design process would allow optimization of capital and operating costs over the life of a haul road. [ABSTRACT FROM AUTHOR]

• We proposed four lateral control modes for autonomous trucks of different proportions. • The effects of four modes on pavement rutting and fatigue damage were assessed by finite element simulation. • The two-section uniform distribution is suggested as the proper lateral control mode. With ongoing massive investment in the field of autonomous vehicles, fully autonomous self-driving vehicles are set to become a reality soon. Despite the benefits in traffic safety and economy, the potential effects of autonomous vehicles, especially autonomous trucks, on transportation infrastructure remain to be determined. In this study, a finite element model was developed based on a typical flexible pavement structure. The effects of autonomous trucks' lateral distribution within the lane with respect to rutting depth and fatigue damage were estimated by finite element analysis under certain environmental condition. Characteristics of the pavement structure and environmental condition have been collected and presented in this paper. Four possible lateral control modes on managing autonomous trucks' lateral distribution were proposed, listed as zero-wander mode, uniform mode, double peak Gaussian mode, two-section uniform mode. Considering the difference between autonomous trucks and human-driven trucks, the ratio of autonomous trucks was also evaluated. Based on the simulation results, it has been confirmed that, if controlled appropriately, autonomous trucks could be highly beneficial to asphalt pavements for wider using of pavement. Conversely, if without appropriate lateral control, the effect of autonomous trucks on the typical flexible pavement life could be negative, owing to repeated single point load caused by lane centering and keeping. For example, the uniform mode, double peak Gaussian mode and two-section uniform mode all throw positive effect on the pavement. On the contrary, under the zero wander mode, the time when the rutting depth of the proposed pavement reaches 15 mm (defined as maintenance year) may advance by 1.56 years and fatigue damage at the bottom of asphalt layer increases by 146%. Compared with the normal situation nowadays, the two-section uniform distribution of autonomous trucks, the best performing control mode, delays the maintenance year by 2.3 years. From the aspect of fatigue, a much uniform distribution curve of fatigue within the lane can also be found under this mode. When all trucks' lateral positions were in control, the two-section uniform mode could reduce the fatigue damage by up to 35% under repeated standard axle load on the flexible pavement. Finally, a framework of dealing with the lateral control was proposed as a reference for different conditions, such as asphalt pavement structures and materials. [ABSTRACT FROM AUTHOR]

Inverted base pavements involve a well-compacted granular aggregate base built between a thin asphalt concrete layer and a cement-treated base. Inverted base pavements can be constructed using conventional equipment and procedures but require proper quality control. This study reviews the extensive South African experience and case histories in the USA. Accumulating evidence suggests that inverted base pavements are a viable alternative and can outperform conventional pavements at a lower cost. Inverted base pavements rely on the complementary interaction between layers. The cement-treated base provides a stiff foundation for efficient compaction and constrains the deformation of the stress-sensitive granular aggregate base. The thin asphalt surface layer deforms as a membrane and develops low tensile stress. Additional large-scale field tests should be conducted to assess the performance of inverted base pavement designs in a wide range of conditions relevant to the USA. [ABSTRACT FROM AUTHOR]

• Bio-modification of Recycled Asphalt Shingles (RAS) could facilitate their application in pavement construction. • Bio-modification of RAS modified asphalt delays its physical hardening. • Bio-modification of RAS modified asphalt increases its crossover modulus and frequency. • Bio-modification of RAS modified asphalt increase its fracture energy and strain at failure. • Bio-modification of RAS modified asphalt increases its fatigue resistance. The use of recycled asphalt shingles (RAS) in pavement construction has received significant attention due to its economic and environmental advantages. However, asphalt binder in RAS is significantly aged and requires modification before application to ensure it does not compromise pavement performance. The paper introduces a novel approach to modify RAS to facilitate its application in new construction while examining the feasibility of rejuvenating RAS via bio-modification. In addition, this study investigates the durability of the modified RAS, referred to as bio-modified shingles (BMS), by exposing BMS to both severe oxidation aging and sub-zero extended conditioning followed by a comprehensive thermo-mechanical characterization. Study results showed the performance of RAS was significantly improved after bio-modification. The performance improvement was reflected in BMS having lower viscosities, stiffnesses, shear susceptibilities, crossover temperatures, while having higher m-values and failure strains compared to RAS asphalt. It was further observed that the enhancement lasted even after BMS was exposed to severe oxidation aging and 72 hr conditioning at −18 °C indicating an enhanced durability of BMS. The latter can be attributed to molecular interactions between the bio-modifier and aged asphalt disturbing the molecular packing of asphaltene and wax molecules. Such molecular packing is known as a dominant mechanism for hardening at sub-zero temperatures. This paper contributes to the body of knowledge and practice by providing insights on the merits of revitalizing recycled asphalt shingles to enhance its durability and facilitate its application in construction to promote sustainable construction practices. [ABSTRACT FROM AUTHOR]

• WMA produced at lower temperatures than HMA exhibited enhanced workability. • Specimens subjected to simultaneous LTA and water damage recorded the highest percentage adhesive failure and lowest ITS. • Polymer modified binder mixtures demonstrated superior moisture damage resistance than unmodified binder mixtures, regardless of conditioning method. The destructive effects of moisture remain to be the main distress adversely influencing pavement performance. Warm mix asphalt (WMA) compacted at lower temperatures than Hot Mix Asphalt (HMA) is more vulnerable to moisture infiltration and subsequent stripping at the asphalt-aggregate interface. To evaluate the potential mechanisms, the failure severity was computed in indirect tension. Two binder types and various compaction temperatures were used for sample fabrications. The gyratory compaction data were used to quantify the mixtures Workability Index (WI) and Compaction Energy Index (CEI). Six long-term conditioning methods were used namely, Long-Term Aged (LTA), Long-Term Aged + 1 Freeze-Thaw (F-T), LTA + 3 F-T, LTA + 1 F-T (Accelerated Laboratory Vacuum Saturation (ALVS)), simultaneous LTA + Moisture-Induced Damage and simultaneous LTA + Water Damage. The ALVS was used to subject asphalt mixtures to the combined effects of pore pressure and high temperature. As aging and moisture damage occur concurrently during the pavement service life, a new moisture conditioning chamber was fabricated to simulate the simultaneous effects of LTA and moisture/water damage. The effects of conditioning on the indirect tensile strength (ITS), fracture energy, resilient modulus and percentage adhesive failure were investigated. The percentage adhesive failure and broken aggregates were quantified using the advanced 3-D imaging technique. WMA compacted at lower temperatures exhibited improved workability in terms of lower CEI and higher WI than HMA. The mixtures percentage adhesive failure increased, while ITS reduced with F-T cycles. Asphalt mixtures subjected to simultaneous LTA and water damage exhibited the highest percentage adhesive failure and lowest ITS compared to other conditioning methods. ALVS conditioned specimens showed slightly higher percentage adhesive failure than LTA + 1 F-T specimens. The test results also demonstrated that polymer modified binder mixtures exhibited superior moisture resistance than unmodified binder mixtures, regardless of compaction temperature and conditioning level. [ABSTRACT FROM AUTHOR]

• The method of coating refractory bauxite in an organosilicon solvent. • The surface coating effects of different organosilicon solvents on high-alumina refractory bauxite. • The fundamental properties of different organosilicon–refractory bauxite materials. • The comprehensive performance evaluation of organosilicon–refractory bauxite based on the grey target decision-making method. The aim of this study is to improve the fundamental properties of refractory bauxite to promote its further application in the heat-resistant asphalt pavement technology. A method of coating refractory bauxite in an organosilicon solvent is proposed. The surface coating effects of different organosilicon solvents on high-alumina refractory bauxite are compared and evaluated using the macropore structure and the microsurface morphology. Based on the optimal treatment process and material proportion, the fundamental properties of different organosilicon–refractory bauxite materials are analyzed systematically. Based on the grey target decision-making method, the comprehensive performance of different organosilicon–refractory bauxite is evaluated. On this basis, the organosilicon–refractory bauxite material with better comprehensive performance was added into the asphalt mixture and its pavement performances were identified. The results show that a large number of pores of refractory bauxite are sealed by using organosilicon solvents. Moreover, the coating effect is good. In addition, the heat resistance is improved. The mechanical property and adhesion of refractory bauxite are increased by 30.66% and 66.67%, respectively. [ABSTRACT FROM AUTHOR]

We report, the first of its kind, modified AFM probe tip of mineral particles could effectively measure the adhesion differences between mineral particle and asphalt binders which provide a new approach to investigate adhesion properties of asphalt binder in microscale. • Microspheres of mineral particle were prepared to modify AFM tips. • Adhesion differences between mineral-asphalt interfaces could be measured by modified mineral probe tips. • Adhesive force strength enhances as the content of SiO 2 increases. • Physical adsorption plays a greater role in interfaciale adhesion than chemical adsorption. Adhesion between asphalt binders and aggregates is important to the performance of pavement. Atomic force microscopy is commonly used to measure the adhesive forces of asphalt binders. In this paper, AFM probe tips were modified with four types of spherical mineral particles: limestone, basalt, granite and sandstone. These were prepared by planetary ball mill grinding and their compositions investigated by X-ray diffraction. The modified tips were used to investigate the adhesive forces at mineral particle-asphalt substrate interfaces. Adhesive forces increased obviously with SiO 2 content. This indicates that physical adsorption plays a greater role in interfaciale adhesion than chemical adsorption. Linear model, single-factor analysis of variance, and interquartile analyses were also applied to investigatinge the distributions of adhesive force. It was found that different degrees of distributions might be attributable to the different microstructures of the mineral particle surfaces. [ABSTRACT FROM AUTHOR]

• New test for bond strength of bitumen and mastics. • This compression approach is useful than direct tension test. • A new gap assembly is developed for film thickness of binder. • CPOT is successful in evaluation of relevant testing parameters. The quantification of moisture susceptibility has been a major concern for researchers as it adversely affects the performance of asphalt pavements. Several methods have been developed to assess bond strength using asphalt mixtures in loose and compacted state. These tests lack in their ability to study fundamental properties that affect the bond between bitumen and aggregate. In this context, more fundamental techniques have been developed such as pull-off stub tests and direct tension tests. The first group only measures the maximum pull-off strength and second group has problems related to use of consistent binder film thickness and operational difficulties in test itself. This paper presents a new test to evaluate bond strength, in an attempt, to solve problems associated with traditional direct tension tests. The aim is achieved through a review of existing techniques, development of a gap assembly, fabrication of direct tension test moulds, development of Compression Pull-Off Test (CPOT) and evaluation of its results. The key parameters for bitumen and mastics were evaluated. The CPOT shows promising results for use of this technique to study cohesive as well as adhesive bond strength of binder. [ABSTRACT FROM AUTHOR]

Abstract Many different test methods are used in practice to evaluate the surface infiltration performance of permeable pavements. This has led to inconsistency in reporting of test results. This study recognizes the differences in nature between a soil infiltration study and the surface infiltration evaluation of permeable pavements, and identifies the main issues associated with the current practice of surface infiltration testing. It proposes that hydraulic conductivity be adopted as the flow property for measurement and reporting instead of the commonly used infiltration rate. The advantages of measuring hydraulic conductivity are elaborated from both theoretical and practical implementation points of view. The theoretical merits of providing a consistent and integrated treatment of surface infiltration performance of a permeable pavement during the design, construction and maintenance phases are presented. The practical benefits are addressed from the following aspects: consistency between laboratory and field testing, uniformity in reporting of test measurements, rationality in construction quality control and acceptance checking, effectiveness in surface infiltration performance monitoring, and enhanced ability in implementing effective maintenance management. It is emphasized that the techniques and methods needed for measuring hydraulic conductivity of permeable pavement materials, for laboratory testing as well as on-site field testing, are already readily available and have been used by researchers and some practitioners for surface infiltration testing. Two falling-head test methods are recommended: one applies Darcy's law and determines hydraulic conductivity in the conventional way; another measures the time history of falling head and calculates hydraulic conductivity using a modified Darcy equation. It is also highlighted that the measurement of hydraulic conductivity offers a convenient platform for assessing the durability of a permeable pavement against clogging. Highlights • Permeable pavement surface infiltration capacity governs stormwater management. • Conventional infiltration rate inadequately addresses stormwater management needs. • Consistent laboratory and field test methods of surface infiltration is proposed. • Proposed test methods measure hydraulic conductivity instead of infiltration rate. • Proposed tests permit integrated framework of design, construction and maintenance. [ABSTRACT FROM AUTHOR]

In recent years, nanomaterials have led to promising developments in the improvement of pavement performance. In this study, characterisation of nanocomposite-modified binders using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and dynamic shear rheometer was investigated. The study investigates the application of response surface methodology (RSM) to develop models and determine optimum proportions for higher linear viscoelastic properties. FT-IR spectroscopy confirms chemical reaction between nanosilica- and polypropylene-modified bitumens, which resulted in a reduction in oxidative hardening of the modified binders. FE-SEM analysis for the modified binders shows a good dispersion of polypropylene and nanosilica within the modified binder matrix. RSM statistical analysis shows a high correlation coefficient (R 2) of 0.9959, 0.9972, and 0.9964 for the responses complex modulus, phase angle, and viscosity. This indicates that the experimental values analysed are in real agreement with the developed models. Analysis of the individual effects of the independent variables temperature and nanosilica content reveals that all the responses are influenced by the interaction of both the two independent variables, but temperature shows a strong influence in the complex modulus and complex viscosity responses than nanosilica content. Numerical optimisation results using the models developed show that an optimum mix can be achieved with 1% nanosilica at a temperature of 30 ∘ C . [ABSTRACT FROM AUTHOR]

Traffic constitutes a fundamental parameter in the analysis, design and performance prediction of pavement structures. Although the current mechanistic empirical pavement design guide uses axle load spectra to characterize the traffic variable for pavement design purposes, pavements around the world continue to be designed using the equivalency single axle load concept, which is based on the static load of the vehicles (dead weight). However, the dynamic loads induced by roughness can be considerably higher than the static load in specific locations of a pavement section, causing an unexpected adverse impact on the performance of pavement structures. In the present investigation, the effects of both pavement roughness and vehicle speed on the dynamic loads developed at the tire pavement interface are evaluated along with their effects on the performance of pavement structures. In order to achieve the above objective, 787 pavement profiles were analyzed, combining rural and urban environments, as well as rigid and flexible pavement sections. The dynamic load produced at the tire pavement interface for all pavement profiles was modeled. Two roughness indices, The International Roughness Index (IRI) and the Dynamic Load Index (DLI), were determined for each profile. A correlation model between the IRI and the DLI was developed. Additionally, a Traffic Correction Factor (TCF) was proposed to account for the dynamic load effects induced by roughness and vehicle speed. The proposed TCF could be used to modify the estimation of traffic damage on road sections with high roughness levels, therefore improving future performance prediction processes. Finally, a methodology to calculate the reduction of the remaining life of a pavement structure due to the surface roughness was proposed. [ABSTRACT FROM AUTHOR]

Pavement surface deflection has been used by researchers and highway agencies to assess the structural condition of the pavement structure. None of the currently available approaches provides an acceptable evaluation method for the rigid pavement structural capacity at the network level. In this research, pavement structural ratio (PSR) and overall pavement structural index (OPSI) were derived from deflection bowls generated from finite element simulations and validated by actual field deflection data measured by falling weight deflectometer and performance data extracted from long-term pavement performance database. The PSR parameter provides structural evaluation of the rigid pavement slab and the base course above the subgrade only. Whereas, OPSI parameter provides an overall evaluation of the pavement structure and the subgrade. [ABSTRACT FROM AUTHOR]

Highlights • Employed relative importance measure inherent in the random forests to determine critical variables. • Alligator cracking was found sensitive to mixture gradation and specific gravity of asphalt binder. • IDT of mixture significantly affected transverse cracking, wheelpath longitudinal cracking, and rutting. • Stiffness of asphalt binder considerably impacts rutting and IRI. Abstract Numerous laboratory studies have demonstrated that the properties of hot-mix asphalt (HMA) play a crucial role in the performance of the HMA. However, few studies have directly correlated HMA properties to field pavement performance. The present study addressed this issue with data obtained from the database of the Long-Term Pavement Performance (LTPP) program through the relative importance score inherent in the random forests. The data from 78 sections with a relatively complete record of mixture properties were used to develop the random forests models and determine the relative importance of exploratory variables. A total of seventeen variables representing the physical properties of the HMA and the pavement were incorporated, including the aggregate gradation, mixture volumetric parameters such as bulk specific gravity and air voids, asphalt binder properties such as viscosity and content, the section service age, and the thickness of the pavement. The pavement performance considered was represented by three types of cracking (alligator cracking, wheelpath longitudinal cracking, and transverse cracking), the rutting, and the roughness (IRI). The results showed that the gradation of aggregates has close association with the alligator cracking; the viscosity and stiffness of asphalt binder were strongly correlated with the longitudinal cracking; and the density and indirect tensile (IDT) strength of the mixture significantly affected the transverse cracking. The air voids and binder stiffness played a critical role in the rutting performance. The percentage passing the No. 200 sieve was found a determinant of the evolution of the IRI. [ABSTRACT FROM AUTHOR]

In pavement design, traditional empirical catalog methods leave their place to next generation mechanisticempirical (M-E) design methods that utilize cracking, faulting and roughness as pavement performance parameters. Within the scope of this study, the effects of different traffic, subgrade and concrete strength classes for 20 and 40 year's service periods on the thickness and joint spacing of JPCP are determined by M-E design method for ten regions representing different climatic classes. A total of 360 rigid pavement designs are made for three traffic volumes, three subgrade types and two concrete strength classes for each region. As a result, the effects of subgrade type, traffic volume and concrete strength class on slab thickness and joint spacing is clearly identified for different climatic conditions. In addition, the joint spacing, which is predicted based on experience and observations in the in AASHTO 93 empirical method, can be successfully determined by M-E design method. This is especially advantageous for countries without rigid pavement experience like our country. Another output of this study is that M-E method makes it possible to use more innovative materials in the construction of rigid pavements since the material properties of the concrete slab have significant effects on the design. [ABSTRACT FROM AUTHOR]

This paper investigates dynamic response, rutting resistance, and fatigue behavior of three stone mastic asphalt (SMA) concrete mixtures selected on basis of nominal maximum aggregate size (NMAS): 25 mm, 19 mm, and 12.5 mm using cellulose fiber added as 0.3% of the total weight of aggregate. Superpave gyratory specimens were fabricated and subjected to the dynamic modulus (E∗) and flow tests (flow number and flow time) using an asphalt mixture performance tester. The E∗ test results were employed to develop stress-dependent master curves for each mixture, indicating that the mixture with the NMAS of 25 mm is relatively stiffer than other tested mixtures; this mixture also exhibits excellent strength against rutting failure. In addition, fatigue parameter, which is derived from dynamic response and phase angle, is determined, and results reveal that 12.5 mm NMAS mix has relatively better resistance to fatigue than other selected mixtures. Furthermore, nonlinear regression model specifications were utilized to predict accumulated strains as a function of loading cycles. Also, a flow number model is developed that predicts the rutting behavior of mixtures, and results suggest that model predicted and observed outputs of 25 mm SMA mix are found to be very close. The results of this study help in understanding the performance and behavior of cellulose fiber-added stone mastic asphalt concrete mixtures under varying simulated temperature and stress levels, which can be used in areas where the premature failure of flexible pavements is often observed. The testing protocol employed in this study will also help in evaluating pavement performance using Mechanistic-Empirical Pavement Design Guide. [ABSTRACT FROM AUTHOR]

The temperature and precipitation meteorological data for near 60 years in six regions along the Qinghai-Tibet highway were statistically analyzed, and four temperature ranges were proposed to show the environment impacts on pavement performance. The freeze-thaw intensity classification criterion was proposed based on the temperature influence on asphalt pavement structure, and freeze temperature and thaw temperature were simultaneously considered in the freeze-thaw intensity classification criterion. The freeze-thaw intensity was classified as weak freeze-thaw and strong freeze-thaw. The site freeze-thaw cycles in six regions were analyzed. and the statistical characteristics were obtained. The annual field freeze-thaw cycles in six regions were almost more than 150 times. The results show that the freeze-thaw cycles in six regions are different, and the freeze-thaw cycles present seasonal concentration trends. The freeze-thaw mainly happens in rapid cooling temperature range, fast warming temperature range and continual low temperature range. The influence of freeze-thaw cycles is the critical environment factor on highway engineering. [ABSTRACT FROM AUTHOR]

Highlights • The effect of materials contents on pavement performance of cold recycled mixture were studied. • Optimal materials content combination was determined by multi-index weighted grey target method. • Fatigue Crack characteristic and resistance mechanism was revealed by SEM test. • Cement-emulsified asphalt mortar improved the microstructure and the interfacial deformation. Abstract To enhance the selection of material content for a cold recycled mixture of emulsified asphalt in hot and rainy areas, the effect of emulsified asphalt content, cement content and Reclaimed Asphalt Pavement (RAP) content on high temperature properties, moisture stability and the fatigue properties of cold recycled mixture were investigated. Based on multi-index weighted grey target theory, the performance of cold recycled mixture were analyzed and the material content were optimized. Then, the crack resistance mechanism of the cement-emulsified asphalt mortar was revealed via a scanning electron microscopy test. The results showed that emulsified asphalt content and cement content mainly affected the high temperature properties, while the effect of the RAP content on water stability was the most significant, and the fatigue performance was significantly affected by various factors under different the stress ratio. The proportions of 3.8% emulsified asphalt, 2% cement and 80% RAP were recommended by grey target optimization. Plentiful hydration products were found positioned in the interfacial crack between the asphalt and aggregate, enhancing the interfacial strength and improving the micro-interface deformation of the cold recycled mixture. [ABSTRACT FROM AUTHOR]

Every day, roads are submitted to greater stresses. Thereby, additives have been incorporated to asphalt mixtures to enhance pavements performance. The purpose of this experimental study is to characterize for the first time, to date, the viscoelastic properties of asphalt samples modified with recycled rubber --from used vehicles tires-- and asphaltite in the same mixture, at different temperatures and frequencies. All with the aim of optimizing the material properties and coming up with a proposal to an environmental issue: discarded vehicles tires and their after-service use. The stiffness of briquettes was analyzed by axial compression test. The results were principally represented in Black Space and Cole-Cole plot and indicate a substantial increase in stiffness and elasticity of the modified asphalt throughout the whole temperature range. This shows that the simultaneous addition of these two ingredients to the bitumen is a favorable alternative in road construction using asphalt pavements. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Studying pavement thermal cracking through large-scale data analysis. • Mining multiple association rules among indicators of the asphalt mixture, asphalt binder, climate, pavement structure, service age, and traffic loading. • Providing constructive recommendations to pavement engineers based on the findings. Abstract Thermal cracking is one of the most noteworthy distresses in asphalt concrete (AC) pavements. It is caused by the thermal stress in pavement layers, when air temperatures are extremely low or change rapidly. This paper aims to mine multiple association rules for thermal cracking in seasonal freezing zones. Relevant data on thermal cracking, including 36 potential influence factors, were collected from 339 samples from 46 Long-Term Pavement Performance (LTPP) sections in 6 US states and 3 Canadian provinces. Grey Relational Analysis was used to identify the most significant elements among these 36 factors as inputs for an Apriori algorithm, which was implemented to explore the association rules among the key influence factors. Results showed that the asphalt binder percentage, measured stiffness (PG + 4 240s) from BBR testing, monthly freezing index, AC layer thickness, service age and Annual Average Daily Traffic (AADT) all exhibited significant influences on thermal cracking, and the proposed indicator, the thermal cracking development rate (TCDR), had different levels of strong associations with these significant influence factors. All six factors were taken into account for mining association rules. Based on these association rules, recommendations for pavement design, construction and management are provided to prolong the service life of pavements. [ABSTRACT FROM AUTHOR]

In determination of flexible pavement layers moduli using Falling Weight Deflectometer (FWD), the pavement depth temperature should be determined and then the moduli should be corrected into a reference temperature. As direct measurement of pavement temperature is time consuming and is difficult to be determined in trafficked roads, some models are developed to predict temperature of asphalt layers through pavement depth, including BELLS model. The objective of this research is to determine correlation between actual measurement and prediction of temperature variations through asphalt layers with applying BELLS model. Ten new and rehabilitated pavement sites were selected in hot climate regions in Khuzestan and Kerman provinces in southern part of Iran. In typical hot summer days, pavement temperatures were measured at half and at one-third of the depth of asphalt layers and FWD testing were performed. Results indicated that a linear regression analysis of BELLS predicted temperatures versus measured values, provides very good correlation with actual field measurements of temperatures through the asphalt layers. Furthermore, predictions were more precise in rehabilitated pavements rather than in newly constructed pavements. Finally, using multi parametric linear fitting analysis, a new model was developed to accurately predict the temperature of asphalt layers in new pavements. [ABSTRACT FROM AUTHOR]

Highlights • The pavement performance and thermal properties of CAM with different ceramsite ratio are studied. • Effects of ceramsite replacement on pavement cooling of HMA are evaluated. • Using ceramsite in HMA is an effective way to reduce pavement temperature and enhance dynamic stability. • The optimal ceramsite ratio in HMA is given through considering pavement performance and cooling effect. Abstract The aim of this paper is to explore hot asphalt mixture (HMA) with potential cooling capacity through adding ceramsite. Ceramsite asphalt mixtures (CAM) are prepared by adding ceramsite to replace fine aggregate with different ratio. Marshall and pavement performance tests were performed to test the pavement performance of CAM. Indoor radiation and outdoor radiation tests are carried out to evaluate the thermal properties of CAM. Results indicate that the Marshall Stability and dynamic stability of CAM increase with the increasing ceramsite ratio from 0% to 60%. The retained MS and low temperature performance of CAM nearly do not change with ceramsite ratio, but the tensile strength ratio decreases with ceramsite ratio. However, all values of the tensile strength ratio are above the requirements of specification. In the aspect of the thermal properties of CAM, the addition of ceramsite can effectively reduce the thermal conductivity of asphalt mixtures. Also, ceramsite is helpful in reducing the temperature of pavement and enhancing the ability of heat resistance, and the optimal effect can reduce the bottom surface temperature about 2.6 °C when ceramsite ratio is 60%. Because of the improvement in the dynamic stability and the thermal conductivity, CAM can have a good rutting resistance and the recommended ceramsite ratio is 60%. [ABSTRACT FROM AUTHOR]

Rutting is one of the most common distresses in flexible pavements and can affect vehicle controlling features. Although asphalt binder constitutes a small percentage of the asphalt mixture, its properties play a crucial role in pavement performance and its rutting resistance. One way of improving binder properties and rutting resistance is to use additives. In this research, nanoclay and SBR polymer have been simultaneously used to modify 60–70 penetration binder to study rutting resistance of binder and asphalt mixture. To this end, the storage stability, rotational viscosity, DSR, and RCR tests on binder and marshal stability were performed, and dynamic creep and wheel track tests on asphalt mix were performed to assess rutting performance. The test and statistical analysis results indicated that nanoclay has considerably positive impact on rutting and elastic deformation of neat and SBR-modified asphalt binder and mixture. [ABSTRACT FROM AUTHOR]

By means of curing agent hardening technology applied for lime-fly ash road surface, the performance of unconfined compressive strength, water stability and freezing stability of hardened fly ash mixture has been tested, and the feasibility of the technology has been verified. At the same time, combined with the indoor test results, the test road has been paved which achieved good results, and the construction technology is simple, economical and reasonable, so it has a good value of popularization and application. [ABSTRACT FROM AUTHOR]

Rapid growth of populations and extension of societies leads to the production of waste by-products, which puts a burden on landfills. To address this issue, tire derived aggregates (TDA) from scrap tires have been used as road embankments in several projects. Three different test sections using different TDA, and TDA and soil mixtures, were constructed at the Integrated Road Research Facility test road in Edmonton, Alberta, Canada. Based on falling weight deflectometer tests in different months, the fatigue life performance of the TDA embankments was evaluated against that of a conventional control section using the measured horizontal strains at the bottom of the asphalt layer and the Asphalt Institute’s fatigue model. The results showed satisfactory performance of all three TDA test sections and significantly longer fatigue lives as opposed to the fatigue life of the control section. This analysis showed compelling evidence regarding the long-term performance of TDA material as road embankments in construction projects. [ABSTRACT FROM AUTHOR]

For the design of new jointed plain concrete pavements (JPCPs), three national calibrations of the AASHTOWare Pavement ME Design have been necessary due to model and database updates. Local calibration is also recommended to better match a state’s experience. To date, 8 states have changed the calibration coefficients to local values, while 11 states have implemented national coefficients. This study presents a review of the national and local calibrations and a comparison in terms of, (1) pavement performance prediction and (2) thickness design. It was found that the difference between the local and national calibrations was significant in terms of predicted pavement performance, but much less with respect to thickness design. Furthermore, a full factorial was conducted to study the impact of various design features on the local calibrations. The results showed that the difference between the national and local calibrations decreased as optimum design features such as short joint spacing were used. [ABSTRACT FROM AUTHOR]

In order to improve the performance of semi-flexible pavement material, Carboxyl Latex is tried to be added into cement mortar as additives, in this study. Then, the degree of cement mortar performance improvement is evaluated, and the appropriate proportion of Carboxyl Latex added is determined. The improved cement mortar performance evaluation indicators used include fluidity, compressive strength, flexural strength, and drying shrinkage. Then the influence of the Carboxyl Latex on semi-flexible pavement material performance (high-temperature rutting, low temperature crack, water damage and fatigue) with warm mixed open-graded asphalt mixture matrix of varied air void contents is tested. Study results show that the addition of Carboxyl Latex reduces the rutting depth of pavement material by 30% or more, increases the dynamic stability by more than 40% and the strain energy density to 1.6 times, and the freeze–thaw splitting tensile strength is also increase by over 93%. Furthermore, the value of K increases by more than 6%, and the n value decreases by 12% or more, in where, the two parameters, K and n, represent the fatigue resistance of semi-flexible pavement material that can be obtained from the regression equation of loading numbers vs. stress levels of fatigue test. The larger K value or the smaller n, the better the fatigue resistance. Overall, after adding the Carboxyl Latex into cement mortar, the high-temperature rutting resistance, low-temperature crack resistance, water damage resistance, and fatigue resistance of semi-flexible pavement materials have been significantly enhanced. [ABSTRACT FROM AUTHOR]

The dynamic effects exerted by the vehicles on the road pavement have been thoroughly investigated over years. The main reason for this investigation is the major influence on the propagation and worsening of the pavement damages exerted by the dynamic loads rather than the static ones. To date, the modelling theories of systems have evolved, along with the computational capability of the modern calculators. To this effect, threedimensional simulations of the tire-surface interaction are commonly used. These simulations take into account the dynamics of the load and the consequent deformation of the pavement. However, previous studies aimed at analyzing the above interaction for the optimisation strategies of the maintenance activities within the context of effective road asset management. On the contrary, this work focuses on the safety-related issues linked with the dynamic effects suffered by the vehicle, when passing on different road defects. The goal of this study is to analyse numerically the kinematic and the dynamic effects of the pavement degradations (and in particular rutting) on the driving safety. The simulation of the main characteristics and the evolution of the pavement damages over the time (e.g., the simulation of the tire-pavement contacts and the dynamic response on the vehicles) is a useful method for the development of safe and comprehensive rehabilitation programs. These are of paramount importance to limit the accident rates. The effects on the driving safety were analysed using a simulation model for the behaviour of the vehicle in the case of damaged pavements. Different road geometries and vehicle types were considered to evaluate the rutting effects on safety, as a function of the evolution stage of this type of pavement damage. In more detail, the performance characteristics of the vehicles, the dynamic and kinematic parameters (e.g., the vehicle trajectory and the vertical acceleration), were collected for pavement conditions with progressively high levels of rutting. The study proposes a theoretical model of qualitative relationships between differing stages and location of rutting, and the consequent effects on driving safety for different types of vehicles (passenger cars and powered two wheelers). It is worth to emphasize the relevance of this research for maintenance prioritization purposes at the road network level. Priority is based on the level of risk associated with the pavement degradations and with different types of vehicle. [ABSTRACT FROM AUTHOR]

In cold climates, pavement surface and foundation layers are subjected to seasonal temperature variation and freeze-thaw cycles. The number and duration of freeze-thaw cycles in the foundation layers can significantly influence the pavement performance. Seasonal variation in foundation layers is accounted for in pavement design by empirically adjusting the foundation layer moduli values. This paper presents results from in situ falling weight deflectometer (FWD) and dynamic cone penetrometer (DCP) tests conducted over a two-year period at five sites in Iowa; at one of these sites, temperatures of the foundation layers were continuously monitored during the testing period. FWD testing was conducted to determine the modulus of subgrade reaction (k) values. DCP testing was conducted to estimate California bearing ratio (CBR) values of the subbase and subgrade. Temperature data was analyzed to determine freezing and thawing periods and frost penetrations. Seasonal variations observed in the foundation mechanistic properties were compared with the assumed design values. Empirical relationships between the different mechanistic properties are explored. [ABSTRACT FROM AUTHOR]

This paper proposes an Analytic Hierarchical Process (AHP) theory based method to determine the weight of the decision-making influence factors, considering their relative significance and generating an overall ranking for each road section. A case study on the highway network maintenance priority was conducted to illustrate the proposed procedure. A total of five pavement maintenance decision-making related factors were considered in the study, including pavement performance, pavement structure strength, traffic loads, pavement age and road grade. The weightings of the five factors were quantified through AHP method. Then, the comprehensive ranking index value Ui was determined, which indicated the maintenance priority of a road section in network level decision-making. From the aspect of maintenance cost, the sensitivity analysis results were in accordance with the weightings of different maintenance decision-making factors. The pavement maintenance cost was significantly sensitive to the change of pavement performance. The case study clearly demonstrated the applicability and rationality of the AHP theory based decision-making method and it can be used as a guideline for pavement maintenance agencies. [ABSTRACT FROM AUTHOR]

This paper provides a brief description of the technological developments involved in the development and use of the Heavy Vehicle Simulator (HVS) accelerated pavement testing equipment. This covers the period from concept in the late 1960's, to the current state-ofthe art HVS Mk-VI and highlights the development and improvements being built into the Mk VI. It also provides a brief overview of the research performed by the various accelerated testing programs currently using the HVS as their accelerated testing tool, which include the Gauteng Provincial Department of Transportation and the CSIR (South Africa), the UC Pavement Research Center (California), the U.S Army Corps of Engineers Engineering Research and Development Center (CRREL and WES), the Florida DOT HVS test program, the US Federal Aviation Administration (FAA), the HVS programs of the University of Costa Rica and the Mexico Institute of Transportation amongst others. Brief descriptions of HVS research and summaries of key results from these programs are provided. Planned research is covered where available. [ABSTRACT FROM AUTHOR]

The properties of foamed asphalt cold recycling mixture (FACRM) will seriously affect the application performances of pavement structure made from FACRM. The results from this study suggest that FACRM has a high modulus and small temperature shrinkage stress, reducing early damage caused by pavement cracks. FACRM has good water stability but poor stability at high temperatures. The strength of the old subgrade, thickness of the FACRM and environmental temperature have significant effects on the performance of pavement structure. FACRM is ideally used as pavement material for light traffic, but not suitable for use as a surface layer for heavy traffic. [ABSTRACT FROM AUTHOR]