Search

The availability of high-quality aggregate for infrastructure development in Canada has significantly decreased. This reduction has posed significant challenges, particularly in large urban areas across Canada. Moreover, exploring the potential of incorporating innovative by-products into pavement structures has displayed potential advantages in technical, economic, and environmental aspects. The methodology presented in this paper is based on several research projects from over the past twenty years. This case study is based on the several research projects that have been conducted at the Centre for Pavement and Transportation Technology (CPATT) in Canada. The focus of this paper is developing a framework that can be used to evaluate the use of recycled materials in asphalt pavement. These include recycled concrete aggregate (RCA); recycled asphalt roof shingles (RAS); recycled crumb rubber (RCR); and recycled asphalt roof shingles (RAS) in asphalt pavement. In addition, the use of RCA in concrete pavement will also be evaluated. In addition, the use of RCA in concrete pavement will also be evaluated. A methodology and strategy for implementing these materials and designs into specifications, while also managing risk, are outlined. Finally, the work presents a life cycle assessment analysis, including the analysis of cost and sustainability. Overall, the paper illustrates the process of evaluating products, technologies, and designs from technical, economic, and environmental viewpoints, and then implementing them in a robustly engineered way. Generally, the collected data results from the lab, field performance of the test sites, and sustainability and Life Cycle Cost Assessment (LCCA) analyses are very promising. For example, the Hot Mix Asphalt (HMA) pavement design with a 40% RAP was the most environmentally friendly. Meanwhile, it was determined that the HMA mix comprising 20% RAP and 20% Crumb Rubber Modifier (CRM) was found to be the most creative and environmentally friendly option. According to another study, higher storage durations were shown to improve RAP and virgin binders' blending, thereby raising the general quality of HMA and RAP mixtures. Furthermore, the study discovered that mixtures containing various types of untreated CRCA in different amounts had higher Indirect Tensile Strength (ITS), rutting resistance, and stiffness modulus than the control mix, which contained 0% coarse recycled concrete aggregate (CRCA). This suggests that the effective utilization of recycled materials is a viable approach with the capacity to significantly enhance the adoption of recycled components in asphalt pavements. [ABSTRACT FROM AUTHOR]

The Ministry of Transportation of Ontario in Canada recently undertook a pilot study of using precast concrete inlay panels to rehabilitate high-volume asphalt highway pavements. Three different versions of this rehabilitation strategy were designed and constructed. The pilot study was constructed on a high-volume highway in Ontario in 2016 and subjected to service conditions. One of the performance measures being tracked for the project is Load-Transfer Efficiency (LTEδ), measured via Falling Weight Deflectometer (FWD) testing. Two FWD evaluations were performed on the pavement section: immediately following construction, and after one year of service. The LTEδ performances of the different design strategies are summarised and analysed, using least significant difference statistical analysis. Similarly, the potential for sub-panel voids is measured using zero-load back-calculation. Because of the limitations of LTEδ in measuring joint performance, a relative displacement measure (RD75) is developed and its use is outlined and recommended as a meaningful measure of joint performance based on FWD test results. [ABSTRACT FROM AUTHOR]

Pavement infrastructure is experiencing unanticipated climate conditions due to global warming. Extreme weather events, such as excessive precipitations, are increasing in intensity and frequency under climate change, which pose a flood risk to pavement infrastructure. The impact of flooding on pavements has become a rising concern since pavements are designed based on historical data, which do not adequately reflect current and future climate. Therefore, a comprehensive understanding of the flooding impacts on pavements is of great importance. The objective of this study is to analyse the impact of flooding on pavement performance. Damage pattern, flood characteristics, impact factor analysis and a case study were performed. The Mechanistic-Empirical Pavement Design Guide is employed to simulate the effect of 36 extreme hydrologic events on 2 typical pavement designs in Ontario, Canada. Extreme precipitation magnitude, number of event cycles and duration were loaded on typical pavement structures. Results show that there is no significant damage caused by short-duration exposure of extreme precipitation, and extreme events contribute to international roughness index changes. The increase of the number of event cycles leads to the increase of damage ratio. In addition, the loss of pavement life is unneglectable for long duration and higher cycle extreme events. [ABSTRACT FROM AUTHOR]

The Ministry of Transportation of Ontario was interested in a rehabilitation strategy that could be used to address deep-seated rutting issues encountered on its 400-series highways. A precast concrete inlay panel (PCIP) rehabilitation design was developed and constructed involving the installation of precast panels into partially-milled asphalt pavement. Sub-surface instrumentation was installed at the PCIP–asphalt interface including earth pressure cells and moisture sensors installed in six instrumentation clusters. This instrumentation has been monitored to gather information regarding the PCIP trial installation. Readings from the moisture sensors indicate that water penetrates beneath the PCIPs in precipitation events, though these moisture levels recede under dry conditions, indicating that the water can exit the sub-slab area. Static load testing using a fully-loaded gravel truck was used to determine the different support reactions caused by different loading configurations. Higher loads were generally found beneath the joints in the two loading situations studied. [ABSTRACT FROM AUTHOR]

Permanent deformation, or rutting, is one of several critical distresses in flexible pavements. This paper introduced a novel experimental method, a penetration test, for asphalt mixtures to quantify the effects of glass fibre geogrids embedded in asphalt under repeated loading. It was found that the evolution of permanent deformation (εp) and its strain rate have three clearly identifiable stages. It was also observed that the presence of the geogrid increased the flow number and the number of cycles to failure significantly compared to control samples. Some of the current εp fitting models were found to be valid for deformation prediction under penetration. In addition, a new simple FN calculation method was also proposed based on strain rate and it showed consistent results. In particular, geogrid type "Grid10", which has smaller aperture size (12.7 mm) had slightly better reinforcement performance regarding the rutting resistance due to its larger contact area. Overall, the test and data analysis method presented in this study could be an important reference for future investigations on geosynthetic-reinforced pavement materials. [ABSTRACT FROM AUTHOR]

Braking and turning by heavy vehicles can trigger shear-related distress in asphalt surfaces. The evolutionary increase in vehicle tyre pressure and wheel load will result in an increase in such surface failures in the future. Shear-related distress may result from delamination at the surface layer interface, or excessive shear creep within the asphalt surface layer itself. Both deformation and delamination distress appear visually identical at the surface. When subsequently cored, secondary (or symptomatic) debonding of the interface may result in asphalt deformation distress being misdiagnosed as a delamination failure. Regardless the mechanism, a broad range of properties may be responsible and a systematic diagnosis is required to determine the root cause. A framework for the diagnosis of shear distress in asphalt surfaces is presented. The framework contains three levels of investigation, including the location of the distress (at the surface layer interface or within the surface layer), the element within the interface/asphalt responsible and finally, the components or characteristics that resulted in a reduced shear resistance. The framework relies on the assessment of surface performance relative to comparable surfaces of adequate performance. Surface age, thermal gradient and traffic-induced shear stress states must all be comparable for a meaningful diagnosis to be made. The developed framework has been used to successfully determine the root cause of shear creep in the heavy braking zone of a runway at an Australian airport. Its application is recommended for other surface distress investigations, where the environmental and traffic factors are comparable. The framework may also be adapted to forensic investigation of other distress modes. [ABSTRACT FROM AUTHOR]

Coarse recycled concrete aggregate (RCA) is a variable material, and that variability can often make it less desirable for usage in concrete infrastructure. One consistent characteristic of RCA however, is a higher absorptive capacity when compared with natural aggregate (NA). Due to this higher absorptivity, there is potential for the RCA to provide some internal curing-like benefits when it is properly prepared prior to batching into concrete. Internal curing involves the entrainment of water in reservoirs within the concrete which is drawn from the reservoirs at a beneficial point of the cement hydration process. Internal curing in concrete has been found to have many benefits including reducing the negative effects of poor external curing. In this research, two types of saturated coarse RCA have been used to study the effects of different curing practices on the performance of the concrete. Particular emphasis has been placed on those properties that are critical for concrete pavement design. Two curing regimes are used in order to better understand the impact of curing practices on saturated RCA concretes. The two RCA sources oppositely affected the compressive strength: RCA 1 increased strength while RCA 2 caused a decrease. Saturated high absorption RCA appeared to provide some benefit in terms of compressive strength loss under poor curing conditions. Both RCA types had similar negative effects on the tensile strength and elastic modulus of the concretes in comparison to natural aggregate. [ABSTRACT FROM AUTHOR]

The durability of PCC refers to the ability of concrete to resist weathering action, chemical attack and abrasion. Freeze/thaw and scaling are extreme conditions that occur in cold climates and with the use of deicers that can affect the durability of concrete. Nanomaterials, which have a particle size under 100 nm and a large specific surface area, are able to improve the durability of concrete. In this research nanosilica was added to concrete mix, and was found to improve the compressive strength of concrete, paste density, and reduce the external damage of samples subject to freeze/thaw cycles. [ABSTRACT FROM AUTHOR]

The mechanistic–empirical pavement design guide (MEPDG) uses mechanistic–empirical models by analysing the impacts of traffic, climate, materials and pavement structure to predict performances of pavement. The MEPDG software uses a three-level hierarchical input to predict performance in terms of terminal International Roughness Index, permanent deformation, total cracking (reflective and alligator), asphalt concrete (AC) thermal fracture, AC bottom-up fatigue cracking and AC top-down fatigue cracking. However, these inputs with different levels of accuracy may have significant impact on performance prediction. This study focuses on the sensitivity of the inputs of MEPDG distresses to identify the effect of the accuracy level of inputs based on experimental design. A local sensitivity analysis is carried out to identify the main effect of inputs considering them as independent variables. Interaction effects are also analysed based on random combination of the inputs. Sensitive input variables and their combinations are evaluated through a multiple regression analysis for respective distresses. [ABSTRACT FROM PUBLISHER]

Performance prediction is a critical step towards the acceptance of a new pavement structure. This is true for both conventional and innovative designs; however, it is particularly important for innovative designs that attempt to redefine pavement design practices. One such innovative design concept is the solar road panel; a road panel with a transparent surface that generates electricity through embedded solar cells. Despite the work completed by multiple organisations towards the development of this concept, questions exist about the viability of these panels as a structural pavement surface. This paper investigates these questions through a finite element modelling approach that assesses a prototype panel's performance on a variety of structural bases. Overall, this paper finds that it is possible to design a solar road panel to withstand traffic loading and that a concrete structural base allows for substantial optimisation to the analysed prototype design. [ABSTRACT FROM AUTHOR]

This study investigated the sensitivity of the Illinois flexibility index test (I-FIT) and the disc-shaped compact tension [DC(T)] test with respect to oxidative aging and testing temperature. For this purpose, five plant-produced surface course asphalt mixtures covering a wide range of performance-graded asphalt cement (PGAC) were utilized. As for oxidative aging sensitivity, two methods of forced-draft oven aging, at 85°C for 120 h and at 95°C for 72 h, were utilized. Furthermore, to measure the temperature sensitivity, the I-FIT test was conducted at 23°C, 24°C, 25°C and PGAC intermediate temperatures, while the DC(T) test was conducted at −18°C , −24°C , and −30°C. In this study, the analysis of the I-FIT test results from oxidative aging showed that both methods of aging caused a reduction in flexibility index values of asphalt mixtures, and the flexibility index values after two methods of aging were statistically comparable. Moreover, even though oxidative aging caused a reduction in DC(T) fracture energies of asphalt mixtures containing hard PGAC, the fracture energies before and after the two methods of aging were statistically similar for asphalt mixtures. The analysis of the I-FIT test results from testing temperature sensitivity showed that the flexibility index values of asphalt mixtures containing hard PGAC at 23°C were statistically dissimilar to those at 25°C when the testing temperature dropped from 25°C to 23°C. Consequently, regarding the I-FIT test, the comparable flexibility index values from the two methods of oxidative aging suggested utilization of forced-draft oven aging at 95°C for 72 h as a less time-consuming method compared to forced-draft oven aging at 85°C for 120 h to evaluate the effect of oxidative aging. In addition, the variability in flexibility index values due to the drop in testing temperature suggested exercising caution when conducting the test on asphalt mixtures containing hard PGAC. [ABSTRACT FROM AUTHOR]

As critical infrastructures, bridges play an important role in the resilience and functionality of the transportation system. Typically, in the aftermath of an earthquake, the restoration process of the impacted region begins. It is vital for bridges to maintain their functionality and serviceability during this period in order to expedite the restoration process. In this regard, restoration functions are used to assess the functionality of bridges in a quantitative manner before an extreme event. This paper presents probabilistic resilience curve for the Chemin des Dalles Bridge (CDB) in Quebec, Canada by incorporating fragility and restoration profiles available in the literature. The CDB is designed according to older design codes, which they may lack seismic detailing, and it could therefore be susceptible to future earthquake damage. The resilience curves obtained were used to quantify the resilience of the CDB. The results indicate that the bridge has a resilient performance in a code-level earthquake. However, in order to improve resiliency in stronger events, the retrofit of vulnerable components should be considered. [ABSTRACT FROM AUTHOR]

Pavement infrastructures have become vulnerable to damage as they were not designed to withstand the aggressions of extreme weather events such as flooding, induced by climate change. In Ontario, flooding tops the list of climate change hazards having a consequential impact on pavement performance. Rigid pavements are recorded to provide resilience to flood hazard in literature but knowledge about its behavior and response to flood impact is currently scarce. The objective of this study is to investigate flood impact on concrete pavement performance examining case studies of Jointed Plain Concrete Pavement (JPCP) road classes in Ontario. The AASHTOWare Pavement ME was employed to simulate JPCP performance under climate-induced flood scenarios using a conservative Representative Concentration Pathway (RCP) of 4.5W/m2. Typical municipal JPCP collector and arterial road classes were chosen and modelled. While percentage change in faulting performance was considered, overall flood damage was based on relative change in International Roughness Index (IRI) under flood conditions. Results indicated lower damage ratios and pavement life loss in arterial JPCP than collector JPCP. Generally, minor flood damages were observed across RCP 4.5 return periods and event cycles in the collector and arterial case studies when compared to previous flooded concrete pavement investigation. [ABSTRACT FROM AUTHOR]

Previous analytical studies have demonstrated that low-density lightweight cellular concrete (LCC) subbase pavements can support up to 20 times more traffic loads than unbound granular subbase pavements while protecting the pavement subgrade from adverse freeze–thaw effects in cold regions. This study examines the possibility of providing better-performing pavements on the field through the construction, instrumentation, and monitoring of flexible pavement sections incorporating three LCC densities (400, 475, and 600 kg/m³) as subbase material compared with unbound granular material in Canada. The effects of daily and seasonal temperatures on pavement critical responses to stress and strains were evaluated. The findings showed that these LCC pavements reduced asphalt concrete tensile strain by over two times compared with unbound granular pavements, and that strain increased with a daily temperature increase. Daily subgrade pressure (stress) change was reduced by up to 68%. The study concluded that longer life pavements could be achieved with LCC subbase thicknesses ≥250 mm. [ABSTRACT FROM AUTHOR]

The use of Lightweight Cellular Concrete (LCC) as a subbase alternative to typical flexible pavement subbase material in cold regions is gaining attention. Since a setback of using LCC is its high cement content, which is a significant source of carbon dioxide (CO2) emissions, it becomes imperative to consider this aspect when proposing LCC for pavement applications. This study evaluated the environmental impact of three densities (400, 475, and 600 kg/m³) of LCC produced with two methods (wet and dry mix) and compared to two types of unbound granular material (granular A and B) as flexible pavement subbase. The pavement performance was predicted using MEPDG and WESLEA software and compared with measured field responses as a basis for maintenance strategy. The Life Cycle Assessment (LCA) results showed that lower-density LCC pavements decreased environmental costs by reducing total life CO2 emissions by up to 16% and reducing environmental impact for Carbon monoxide, Sulphur dioxide, Nitrogen oxide, Particulate Matter (PM)2.5, PM10 and total PM compared to granular A and B pavements. As LCC density increased, more emissions occurred, showing the importance of density to emissions output. This research demonstrates the potential benefits of using LCC as an alternative subbase pavement material. [ABSTRACT FROM AUTHOR]

The use of Lightweight Cellular Concrete (LCC) as a subbase alternative to typical flexible pavement subbase material in cold regions is gaining attention. Since a setback of using LCC is its high cement content, which is a significant source of carbon dioxide (CO2) emissions, it becomes imperative to consider this aspect when proposing LCC for pavement applications. This study evaluated the environmental impact of three densities (400, 475, and 600 kg/m³) of LCC produced with two methods (wet and dry mix) and compared to two types of unbound granular material (granular A and B) as flexible pavement subbase. The pavement performance was predicted using MEPDG and WESLEA software and compared with measured field responses as a basis for maintenance strategy. The Life Cycle Assessment (LCA) results showed that lower-density LCC pavements decreased environmental costs by reducing total life CO2 emissions by up to 16% and reducing environmental impact for Carbon monoxide, Sulphur dioxide, Nitrogen oxide, Particulate Matter (PM)2.5, PM10 and total PM compared to granular A and B pavements. As LCC density increased, more emissions occurred, showing the importance of density to emissions output. This research demonstrates the potential benefits of using LCC as an alternative subbase pavement material. [ABSTRACT FROM AUTHOR]

Protecting the pavement subgrade to increase the service life of road pavements is an aspect currently being explored. Several alternative pavement subbase materials are being considered, including Lightweight Cellular Concrete (LCC). Due to its lower weight, LCC incorporating industrial by-product, making it sustainable, and ease of use amongst other benefits, is seen as a potential candidate. This paper reports reviewing the potential application of LCC within the pavement structure with a specific application as a subbase. It examines the various properties such as modulus of elasticity, compressive and tensile strength, Water absorption, and freeze-thaw resistance necessary for pavement application. It also assesses its use in the field in Canada considering the design methods utilized. Some limitations and gaps for LCC application in pavements are also established and recommendations on how to further its use and performance. This review concludes that LCC possesses potential as a pavement subbase alternative; however, other mechanical properties like LCC's fatigue life is essential. A comparative field study is also recommended to monitor actual performance and various fact ors on performance. [ABSTRACT FROM AUTHOR]

The Mechanistic-Empirical Pavement Design Guide (MEPDG) has been employed by agencies as an innovative method for pavement design since the National Cooperative Highway Research Program (NCHRP) Project 1-37A was implemented in 2004. Over the years, the MEPDG has evolved into the AASHTOWare Pavement ME Design software (AASHTOWare®). Local calibration of the performance models in the AASHTOWare® is a crucial and challenging task to improve the effectiveness of its application. The accuracy of the calibration depends on efficient methods and validation processes. This paper aims at developing local calibration methods for joint faulting prediction model of Jointed Plain Concrete Pavement (JPCP). This study not only focuses on improving the prediction accuracy of the joint faulting model but also demonstrating the various optimisation procedures in detail. A total of 27 representative JPCP sections were used in the processes of calibration. Three optimisation approaches were used: (1) One-At-a-Time (OAT) through the trial-and-error procedure, (2) generalised reduced gradient (GRG) using MS Excel® Solver, and (3) Levenberg-Marquardt Algorithm (LMA) fitting the functions. The prediction accuracy of local models was improved as compared with the global ones. Average Bias (AB) reduced from 0.3083 to 0.0578, and Standard Error of the Estimate (SEE) reduced from 0.3345 to 0.1912. Among the three local calibration approaches, approach 2 and approach 3 had more significant improvement on results than approach 1. Finally, the integral procedures were provided for local calibration in Ontario. [ABSTRACT FROM AUTHOR]

In North America, highway agencies have started using Superpave as it incorporates a performance-based asphalt binder specification and a mix design analysis system. However, in a pavement management system (PMS), the performance of the pavement structure significantly influences management decisions. In this regard, accurate prediction and evaluation of performance is a very important aspect. With this in mind, this study investigates the performance of Superpave through the mechanistic–empirical (M-E) approach, field-evaluated performance, and laboratory performance tests. It considers 15 sections of highways from Ontario. The investigation found that the international roughness index (IRI) and permanent deformation are overpredicted in the M-E approach compared with field observations. Additionally, to better understand the performance, the dynamic modulus of asphalt mixtures and binder rheological testing are also performed. The master curve developed for the surface mixtures suggests a lower level of fatigue resistance that justifies the bottom-up fatigue failure in the field-observed scenarios. [ABSTRACT FROM AUTHOR]

Summary: Periodic road crack monitoring is an essential procedure for effective pavement management. Highly efficient and accurate crack measurements are key research topics in both academia and industry. Automatic methods gradually replaced traditional manual surveys for more reliable evaluation outputs and better efficiency, whereas the devices are not available to all functional classes of pavements and different departments considering the high cost versus the limited budget. Recently, the widespread use of smartphones and digital cameras made it possible to collect pavement surface crack images at an affordable price in easier ways. However, the qualities of these crack images are diversely influenced by the noises from pavement background, roadways, and so forth. Thus, traditional methods usually fail to extract accurate crack information from pavement images. Therefore, this research proposes a state‐of‐the‐art pixelwise crack detection architecture called CrackU‐net, which is featured by its utilization of advanced deep convolutional neural network technology. CrackU‐net achieved pixelwise crack detection through convolution, pooling, transpose convolution, and concatenation operations, forming the "U"‐shaped model architecture. The model is trained and validated by 3,000 pavement crack images, in which 2,400 for training and 600 for validating, using the Adam algorithm. CrackU‐net has the performance of loss = 0.025, accuracy = 0.9901, precision = 0.9856, recall = 0.9798, and F‐measure = 0.9842 with learning rate of 10−2. Meanwhile, the false‐positive crack detection problem is avoided in CrackU‐net. Therefore, CrackU‐net outperforms both traditional approaches and fully convolutional network (FCN) and U‐net for pixelwise crack detections. [ABSTRACT FROM AUTHOR]

The simulation model used in this study is based on a construction project in Taiwan. In this study, STROBOSCOPE and EZStrobe were used as discrete-event simulation software to assess the potential risk of the construction in terms of time and cost. The construction process, the unit cost of the resources, and the operation time of each activity were modelled based on the actual construction procedure. A total of 30 replications was required for each scenario. Scenarios with real-world data inputs and eight other models were simulated using the software. The best scenario with the lowest cost and competitive time was selected as the base model for a sensitivity analysis. During the Sensitivity Analysis, the best model 8-R was generated by changing the number of labourers to 13 and Excavators to 3. Compared to the real-world project, the total costs were reduced by 11% and the total time was reduced by 58%. Moreover, the result of risk analysis based on scenario 8-R demonstrated that using a number of labourers, trucks, excavators, rollers, millers, and pavers less than the quantities that were used in the real-world data, the associated risk in term of cost and time will exceed the real-world project cost. [ABSTRACT FROM AUTHOR]

The angularity of coarse aggregates significantly influences the performance of asphalt pavement. However, the research remains in the qualitative stage, and no universal evaluation standard has been proposed. This research proposes image-based methods to quantitatively analyze the angularity of coarse aggregates, thereby providing corresponding evaluation standards. First, aggregate levels of 4.75–9.5, 9.5–13.2, and 13.2–16 mm were obtained by sieving experiments, which were then abraded 0, 400, 800, and 1,200 times using a Los Angeles abrasion machine. Subsequently, the aggregate particle angularity parameters, including circumference, area, convex hull circumference, convex hull area, and total number of corner points, were calculated. Meanwhile, the aggregate imaging system (AIMS) gradient, skeleton extraction, convex hull, and uncompacted void content (UVC) methods were used to evaluate the angularities of the aggregates. Thereafter, the AC-13C-type mixture test specimens were formed using different angularity aggregates. On this basis, the angularity-related pavement skid resistance and rut resistance tests were conducted. The results show that the skeleton extraction method performs excellently for evaluating all aggregate levels, while the convex hull method is suitable for 9.5- and 13.2-mm aggregates, the AIMS gradient method is suitable for assessing 4.75- and 9.5-mm aggregates, and the UVC method is suitable for assessing 9.5- and 13.2-mm aggregates. [ABSTRACT FROM AUTHOR]

• Hydraulic road binders can replace ordinary cement in full-depth reclamation. • Hydraulic road binder mixes have equivalent strength as ordinary cement mixes. • Hydraulic road binder mixes have equivalent stiffness as ordinary cement mixes. • Higher binder content is not required for hydraulic road binder mixes. Hydraulic road binders (HRB) are factory made blends which are composed of a substantial amount of supplementary cementitious materials and portland cement. Previous studies indicated that the use of chemical stabilizers containing supplementary cementious materials is a sustainable approach that can reduce carbon dioxide (CO 2) emission by 5−25%. Thus, the use of HRB in full-depth reclamation process could make the practice more sustainable if strength, stiffness, and durability of treated materials are not compromised. The primary objective of this study is to evaluate the mechanical properties of full-depth reclaimed pavement materials treated with hydraulic road binders. The study was conducted in the form of comparative assessment by using full-depth reclaimed pavement materials treated with General Use (GU) cement as a control mix. For this study, three types of full-depth reclaimed pavement materials and four types of cementitious binders, including GU cement, were used to make eleven different types of mixes. Unconfined compressive strength, modulus of elasticity, and indirect tensile strength tests were used to assess the mechanical properties of the eleven mixes. The test results indicated that hydraulic road binders could provide equivalent strength and stiffness as GU cement. The study also revealed the HRB content, required to attain equivalent strength and stiffness as GU mixes, is the same or less than GU cement content. Based on the study findings, hydraulic road binders can be sustainable alternative binders that can replace GU cement in full-depth reclamation process without compromising the structural function of the treated layer. [ABSTRACT FROM AUTHOR]

• Various preheating levels of Hot In-place Recycling (HIR) were simulated by temperature and heating time in laboratory. • Effect of preheating to the recycled asphalt mixture was evaluated through performance tests. • Workability of recycled material was assessed by gyratory compacter attached program. • Bond strength between recycled layer and aged materials was tested through self-developed direct shear tester. Pavement preheating is of great significance for hot in-place recycling technology. In this study, different preheating temperatures (100 °C, 120 °C and 150 °C) and heating times (60 min, 120 min and 180 min) were set to simulate different preheating conditions for recycled asphalt pavement materials. Rutting tests, low-temperature bending beam tests, and freeze-thaw tests were conducted to investigate the effect of the different heating temperatures on the overall performance of recycled asphalt mixtures. Direct shear tests and gyratory compaction were used to evaluate the bond strength between the old and recycled pavement layers and the workability of the regenerated mixtures under the various heating conditions, respectively. The results showed that the performance and workability of a new pavement surface are both significantly affected by the preheating conditions and that the minimum preheating temperature of 120 °C can guarantee good performance and workability of recycled asphalt mixtures. [ABSTRACT FROM AUTHOR]

This paper presents a novel diagnostic model for evaluating the damage condition of a cement-stabilised base course using a T-S fuzzy neural network (FNN). An evaluation criterion for core damage rating, base core condition index (BCCI), was established based on the distress features observed in 369 core samples that had been collected from asphalt concrete pavements with cement-stabilised base courses. The core samples of cement-stabilised macadam (CSM) were classified into five levels according to the evaluation criterion. Ten parameters were chosen as inputs to establish non-linear mapping relationships in an FNN model. These input parameters include pavement distresses' characteristics (crack depth, breadth and lumpiness), Pavement Surface Condition Index (PCI), Riding Quality Index (RQI), Pavement Structure Strength Index (PSSI), Cumulative Equivalent Single Axle Loads (ESALs), thickness of asphalt concrete (AC) layers, annual temperature difference and average annual precipitation. Out of the 369 samples, 169 field cores were used in the FNN model for recursive training, and the parameters for the neural network structure were optimised until the errors between the network outputs and the expected outputs were minimised. The established FNN model was then used for the calculations of predicted quantitative results for remaining sections. The calculation results showed the logical reasoning capability of the T-S fuzzy system and the quantitative data processing capability of the neural network (NN). The comparisons between the objectively predicted results with the subjectively evaluated scores of the testing samples showed a prediction accuracy of 88.4%. The objectively predicted results calculated by the FNN model were also compared with the measurements taken using a Ground Penetrating Radar (GPR). The two groups of results showed reasonable similarity, which again indicated the effectiveness of the developed FNN method. [ABSTRACT FROM AUTHOR]

Pavement surface texture is critical to tire/pavement interaction. Texture characteristics of concrete containing nanosilica pavement surface has not yet been directly investigated, although researchers have found that nanosilica improved pavement friction values and durability. Specimens with various nanosilica content are tested for three-dimensional (3D) texture height maps which are decomposed using discrete wavelet transform for the calculation of 3D texture indices for macrotexture and microtexture. It is found that 3D texture indices increase correspondingly with the increment of nanosilica content. Significant relationship with R 2 values between 0.80 and 0.99 is found between various texture indices and nanosilica content. The increased texture amplitude indicates enhanced pavement friction and then safety. The increment of core material volume implies more texture in the core region, which indicates better longevity of texture. The findings of this research agree with the results of other studies that nanosilica increased the abrasion resistance and frictional property of concrete surface. [ABSTRACT FROM AUTHOR]

The rutting resistance of hot mix asphalt (HMA) Superpave™ mixes in surface course materials was investigated using asphalt material characterisation tests and a digital imaging processing (DIP) technique. The effects of the type of aggregate, the type of binder and the binder content on rutting resistance were quantified. Two types of aggregate were examined: Superpave™ SP12.5 and high friction SP12.5 FC2. Both a modified (PG Plus) and an unmodified binders were considered at the optimum binder content and the optimum content plus an additional 0.5%. To accurately identify the effect of each variable, the shear upheave of these mixes was also quantified. The DIP technique involved estimating the number of aggregate contacts, the total contact length and internal structure index of two-dimensional images of the experimentally tested samples. The results showed that both the rutting resistance and stiffness of HMA surface mixes were sensitive to aggregate type, binder type and binder content. A high friction aggregate provided a better internal structure characteristic, as well as superior rutting resistance and stiffness for HMA mixes. The use of PG Plus and the addition of 0.5% to the optimum binder content negatively affected HMA stiffness and rutting resistance. However, the levels of rutting resistance for all mixes were acceptable (rut depth < 12.5 mm), even when the shear upheave was considered. Internal structure indices measured by DIP were effective for capturing changes in the internal HMA structure with respect to aggregate type and asphalt cement content. [ABSTRACT FROM AUTHOR]

Pavement friction has been identified as crucial in traffic safety. Since the Highway Safety Manual prediction algorithm is often based on crash frequency, the crash severity distribution might be assumed unchanged before and after the countermeasure. However, pavement surface treatments can improve the friction to different levels, by which crash severity outcomes may vary greatly. To explore the implicit effects of pavement friction on vehicle crash severity, this paper first validates the extreme gradient boosting model performance and then the Shapley additive explanations interaction values are employed to interpret individual features and the nonlinear interactions among predictors. Under various scenarios, the extreme gradient boosting (XGBoost) output probability is utilized to convert into dynamic crash severity distributions. Results also indicate that friction becomes more significant when the friction number is less than 38, and immediate corrective actions are needed when the friction number is below 20. [ABSTRACT FROM AUTHOR]

This paper presents a framework for employing X-ray computed tomography (CT) for the assessment of hot mix asphalt (HMA) fatigue damage. The analyses were carried out on asphalt beams in order to quantify the damage created by four-point bending load. A new algorithm has been developed for calculating the thresholding levels of the images acquired before and after testing. The thresholding level prior to testing was estimated using laboratory air voids. To determine the post-testing thresholding level, the proposed algorithm matches 16-bit image histograms obtained before and after the test. This process is implemented only for the portion of the histogram that represents the aggregate colour intensities that remain unchanged during the testing. The results and analysis reveal that the developed technique is a valid method for successfully quantifying and evaluating HMA fatigue damage in large specimens. Because of the high degree of precision they provide, 16-bit images are recommended for this type of analysis. It was found that the distributions of air voids and damage are not uniform in asphalt beams and that they vary significantly throughout the length of a single beam as well as from beam to beam. This study also confirms the effectiveness of X-ray CT for quantifying HMA fatigue damage in asphalt beams following crack propagation. [ABSTRACT FROM AUTHOR]

The main objective of this research is to enhance the physical and morphological properties of coarse recycled concrete aggregate (CRCA) by combining different types of treatment methods. Heat treatments included various temperatures (250 °C, 350 °C, 500 °C and 750 °C). Presoaking method involved the use of strong acid HCl and weak acid C 2 H 4 O 2 , whereas short mechanical treatment included the utilization of a Micro-Deval device. In order to investigate the surface morphology and chemical composition for both treated and untreated CRCA, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analyzer (EDAX) analyses were also conducted. The obtained results indicated that the combination of heat treatment at 350 °C and short mechanical treatment led the best performance for enhancing physical properties, with more than 27% lowering of water absorption. The use of weak acid treatment is an effective, safe and more preferable may than strong acid. Heat treatment appears to have negative effects when used at higher temperatures (500 °C and 750 °C). A large microstructure enhancement was obtained that particularly includes increased density, increased surface homogeneity and a reduced Ca/Si ratio. Physical properties of CRCA including porosity and water absorption are strongly related to the durability characteristics in terms of resistance to freezing and thawing and resistance to abrasion loss under impact of heat treatment. Mineralogical characteristics in terms of Ca/Si ratio are strongly correlated with durable and mechanical properties including abrasion loss and adhered mortar loss under influence of heat treatment. [ABSTRACT FROM AUTHOR]

The sensitivity of the fatigue resistance of surface hot-mix asphalt (HMA) mixes is evaluated for three primary design variables. Aggregate type, binder type, and binder content as well as their interaction have been quantified with respect to their effects on HMA fatigue life, rutting resistance, and stiffness. The objective was to optimize the design by extending fatigue performance while reducing the confounded negative effect on rutting resistance. Two aggregate types were used in the evaluation. Two binders of the performance grading (PG) 64-28 were also employed: a modified binder that meets national specifications and an unmodified binder at two binder levels (optimum and optimum plus 0.5%). Aggregate texture was compared visually using high-resolution scanning electron microscopy (SEM) images. The results showed that the value of modifying the binder to produce softer mixes can be compromised when a high-friction aggregate is used due to the irregular shape of the texture, which produces stiffer mixes. A slight adjustment to the amount of binder (+0.5%) can decrease this effect. Superior HMA fatigue performance was exhibited by the regular 12.5 aggregate and the modified binder at the optimum binder content plus the additional 0.5%. This conclusion was reached through the integration of the positive effects of the investigated variables, which revealed only an insignificant reversible impact on rutting resistance. The findings of this study can therefore be considered a guide for designing HMA with superior fatigue performance for use in pavement design. [ABSTRACT FROM AUTHOR]

The elastic modulus of an asphalt mixture varies with temperature and frequency of load due to its visco-elastic nature, and this behaviour is represented by a master curve constructed by either laboratory tests or predictive models based on known material properties. The predictive approach is based on the material specifications and enables to estimate the modulus over a range of frequency without any laboratory tests. However, this estimated curve should be corrected with respect to a measured reference value, which can be obtained from non-destructive methods. In this study, ultrasonic surface waves (USW) and light weight deflectometer (LWD) tests are conducted on two laboratory slab specimens and an as built pavement, and the experimental results are compared with the predictive master curves. The measured dynamic moduli are found consistently higher than the predictive master curves indicating that the model underestimates the modulus of asphalt mix. Finally, the method is verified by shifting the moduli measured at different frequencies to the 25-Hz-design modulus, of which those obtained by the USW tests from the laboratory and field match very well, whereas those by the USW and the LWD tests from the as built pavement are also found highly consistent with each other. [ABSTRACT FROM AUTHOR]

Pavement crack detection has always been an important problem in pavement maintenance. With rapid development in computer vision technology, crack detection using deep learning has become one of the major tasks in automatic pavement condition detection and assessment. This paper aims to develop a method of crack grid detection based on convolutional neural network. First, an image denoising operation is conducted to improve image quality. Next, the processed images are divided into grids of different scales (10 × 10, 20 × 20, 30 × 30), and each grid is fed into a convolutional neural network for detection. The pieces of the grids with cracks are marked and then returned to the original images. Finally, on the basis of the detection results, threshold segmentation is performed only on the marked grids. Information about the crack parameters is obtained via pixel scanning and calculation, which realizes complete crack detection. The experimental results show that 30 × 30 grids perform the best with the accuracy value of 97.33%. The advantage of automatic crack grid detection is that it can avoid fracture phenomenon in crack identification and ensure the integrity of cracks. Thresholding smaller grids allows better combinations of the differences between objects and backgrounds, which makes segmentation results more accurate. [ABSTRACT FROM AUTHOR]

Extremely low temperatures and freeze-thaw cycles cause premature cracking and low pavement bearing capacity. However, insulation layers could influence the extent of the temperature on pavements. This study focused on understanding the thermal behavior of lightweight cellular concrete (LCC) as an insulating subbase layer to protect the subgrade in pavements. The thermal performance was compared to a Control with Canada's conventional unbound subbase pavement structure. Empirical statistical temperature prediction models were developed based on two years of field data obtained from an instrumented test road in Waterloo, Ontario, Canada. The regression models were based on the most important factor, ambient temperature. This was determined by using a Generalized Addictive Model assessment process. Hourly pavement temperature data across the four seasons in Canada were studied. The effect of daily cooling and heating on pavement layer temperature was also evaluated. Results revealed that a 200 mm thick LCC subbase layer with a density of 400 to 475 kg/m3 could prevent the subgrade directly beneath it from freezing during harsh winters. Thicknesses equal to or >350 mm could be even more beneficial in alleviating the possibility of a frozen subbase and subgrade. There were 70 freeze-thaw cycles recorded in the subgrade of the conventional pavement, but none in the >250 mm LCC pavement portion. When the temperature models were validated using 13 months of data, satisfactory results were obtained. This study enables the prediction of the thermal behavior of LCC subbase pavements for future applications. • The possibility of mitigating the effect of frost action on the pavement structure, especially the subgrade is investigated • An insulation subbase layer of three low-density Lightweight Cellular Concrete (LCC) is employed as subgrade protection • The temperature profile within the pavement structure and the number of freeze-thaw cycles are monitored • Prevention of freeze-thaw cycling and frost heaving by insulation is attainable and would mitigate early pavement failure • Empirical statistical temperature models are proposed for predicting LCC-insulated pavement temperature in cold regions [ABSTRACT FROM AUTHOR]

• Cement treated reclaimed materials showed the properties of viscoelastic materials. • Hydraulic road binder mixes have equivalent fatigue life as ordinary cement mixes. • Cement treated reclaimed materials possess the properties of quasi-brittle material. • There was no Zone-III in the rate of dissipated energy change vs N f plot. Fatigue is one of the most common modes of failure in both flexible and rigid pavements. Several studies have been conducted to study this phenomenon for pavement materials such as bituminous mixes, Portland cement concrete, and cement treated aggregates and soils. The fatigue behaviour of full-depth reclaimed pavement material treated with cementitious binders (FRPMC), however, has barely been studied. FRPMC are composed of reclaimed asphalt pavement (RAP) aggregates, granular base course/sub-base aggregate, fine grained soil particles and 3%–6% cementitious binders. As a result, FRPMC have different properties than bituminous mixes and Portland cement concrete. In this study, the fatigue behaviour of FRPMC was assessed using four-point bending test, which was conducted in strain-control mode. The objectives of the study were to assess the fatigue life range of FRPMC at different strain levels, identify the influence of various cementitious stabilizer on the fatigue life and investigate the response of FRPMC to cyclic loadings. Eight mixtures and forty-eight beam specimens were prepared for the study using the two types of reclaimed materials and four types of binders. The findings of the study indicated that the type of cementitious stabilizers used did not have significant effect on the fatigue life of FRPMC mixtures. It was also identified that FRPMC behaves as a quasi-brittle material while possessing some properties of viscoelastic materials. [ABSTRACT FROM AUTHOR]

The interface between asphalt and aggregate. • The adhesive properties of FAM composed of basalt, steel slag, and andesite were investigated. • The roughness of aggregate and the distribution of asphalt in the aggregate surface were estimated with qualitative and quantitative methods. • Movement rules and failure mechanisms of FAM were evaluated quantitatively. Quantitative analysis was conducted in this study using a three-dimensional field microscope, scanning electron microscope, energy dispersive spectroscopy, and molecular simulation to investigate the surface and interface adhesive properties of three fine aggregate asphalt mixtures (FAM): basalt, steel slag, and andesite. The roughness of the aggregate and the contact angle of the asphalt on the aggregate surfaces also were analyzed quantitatively. Molecular dynamics simulations were carried out to evaluate the adhesive properties, molecular diffusion, and interfacial failure mechanisms of the basalt-, steel slag-, and andesite-based FAM. The average roughness values of the basalt, steel slag, and andesite were found to be 138.2 µm, 244.0 µm, and 185.2 µm, respectively. The stripping percentages of the basalt, steel slag, and andesite were 11.3%, 3.3%, and 10.8%, respectively. The diffusion coefficients of the resins (3.32 × 10−9 m2/s) and asphaltenes (3.05 × 10−9 m2/s) were higher than the diffusion coefficient of the oils (2.98 × 10−9 m2/s). The results indicate that the surface roughness and adhesive capacity of the aggregate used in this study can be ranked in decreasing order as steel slag, andesite, and basalt. The asphaltenes and resins contributed to the asphalt's increased adhesion to the aggregate particles. Both adhesive and cohesive failure were found for the basalt-, steel slag-, and andesite-based FAM, but the steel slag FAM exhibited more cohesive failure, whereas the basalt and andesite FAM exhibited more adhesive failure. [ABSTRACT FROM AUTHOR]

• Heat transfer within asphalt pavement was simulated through Finite Element Method (FEM). • Various environmental and operational factors were considered in FEM model. • Univariate and Multivariate methods were applied to analyze the effect of different variables to the pavement pre-heating. • Three operational parameters and environmental factor were provided based on statistical analysis. Hot In-place Recycling (HIR) is an innovative pavement maintenance and rehabilitation technology that can reuse up to 100% of the material from an existing pavement as Reclaimed Asphalt Pavement (RAP). Pre-heating the pavement is the first step in the HIR process and uniformly heating distressed pavement is crucial to the quality of the recycled mixture in terms of rejuvenator diffusion, required adhesion between virgin and old material, and achieving an efficient asphalt ratio in RAP materials. The low thermal conductivity of asphalt concrete makes the transmission of heat from the top of the pavement to the scarification depth difficult. This study analyzed the impact of seven different operational parameters of recycling heating equipment on the heating efficacy by using the finite element method (FEM). The parameters include the height of heating board, equipment speed, output power, construction temperature, heating repetition, gap distance between two heaters, and area of heating board. The impact of variations in each parameter was statistically analyzed through fractional factorial experiment design. The heating board's area and heating repetitions were found to be the two dominant factors affecting pavement surface preheating, and construction temperature is the most significant factor for pavement heating at a depth of 4 cm. Finally, three reasonable combinations of equipment operational parameters were provided to guide field construction practices. [ABSTRACT FROM AUTHOR]

Accurate pavement crack detection has long been a challenging task, causing significant difficulties to the pavement management sectors in the managerial decision making. The high complexity of the crack's characteristics and the less effective of the crack analytical tools are the two crucial aspects to be accounted for. Recently, three-dimensional (3D) technology based high precision crack detection methodologies has undergone extensive developments. Nevertheless, none of those methods has taken into the errors caused by the data collection systems into consideration, resulting in a less satisfying performance. Hence, the primary objective of this research is to outline the Primary Surface Profile (PSP) optimized dual-phase computing 3D crack detection methodology. Two years ago, variations caused by the automatic 3D data collection systems were observed, so researchers proposed PSP based data filtering algorithm. Therefore, this research is the upgrade solution of the previous innovation regarding the unbiased 3D pavement crack detection. Firstly, the dual-phase computing approach is proposed in dealing with the non-variance 3D data. Then, the self-adaptive 3D PSP generation method is introduced. Finally, PSP is embedded in the dual-phase computing method for performance optimization. For performance assessment, both precisions and recalls of the proposed approach are compared with conventional method for transverse, longitudinal, and map crack detections. Even crack detection precisions are found for both methods, which are all higher than 0.9. However, the recalls of the proposed method (transverse cracks:0.973, longitudinal cracks:0.981, map cracks:0.940) are significantly outperforming non-optimized dual-phase computing method (transverse cracks: 0.682, longitudinal cracks: 0.789, map cracks:0.811). • Addressed the vehicle violation induced problem in the automatic three-dimensional (3D) pavement crack detection systems. • Proposed innovative primary surface profile (PSP)-based solution to the observed problem. • Developed integrated 3D based PSP optimized dual-phase crack detection methodology with high accuracy and robustness. [ABSTRACT FROM AUTHOR]

Crack Deep Network (CrackDN) is proposed in this research with the purpose of detecting sealed and unsealed cracks with complex road backgrounds. CrackDN is based on Faster Region Convolutional Neural Network (Fast-RCNN) architecture by embedding a sensitivity detection network parallel to the feature extraction Convolutional Neural Network (CNN), both of which are then connected to the Region Proposal Refinement Network (RPRN) for classification and regression. The state-of-the-art aspect of this research lies in the fusion of sensitivity detection network, which facilitated the CrackDN of being able to detect sealed and unsealed cracks with sever complex background. Four kinds of background conditions are considered for both sealed and unsealed crack analysis: normal and unbalanced illuminations, with markings and shadings. The raw pavement images are first processed simultaneously by the sensitivity extraction network, which is formed by a batch of line filters that each differ in angles for sensitive region extraction, and the CNN, which utilized ZF-Net. Then the extracted sensitive maps and feature maps are applied as the input of RPRN, thereby the prediction scores together with the bounding box can be obtained. The performance of CrackDN is compared with Faster-RCNN and SSD300 architectures for sealed and unsealed crack detection. Results demonstrate that CrackDN can achieve the detection mean average precision of higher than 0.90, which outperforms both Faster-RCNN and SSD300. The detection speed of CrackDN (around 6 fps) are slightly lower than SSD300 but significantly higher than Faster-RCNN. Meanwhile, the performance of sealed crack detection is better than unsealed crack detection for most background conditions. Moreover, sealed and unsealed cracks on the markings are the most difficult conditions for detection. However, CrackDN still can obtain the detection accuracy of above 0.85. Unlabelled Image • Sensitivity detection is necessary for analyzing complex images. • IOU threshold and anchors significantly influence the crack detection. • CrackDN can detect both cracks and sealed pavement cracks. • Road marking impacts the accuracy of sealed and unsealed cracks detections. • Sealed cracks are easier to detect than unsealed cracks. [ABSTRACT FROM AUTHOR]

Coal gangue, a solid waste produced in coal production, had caused serious environmental pollution due to accumulation on dumps. Embankment filling can solve the problem while significantly consuming the amount of coal waste for mining. The main purpose of this study is to investigate the mechanical properties and microscopic structure of coal gangue when it is subjected to erosion from water environment with different acidity. Using immersion testing to evaluate its stability in different hydro-chemical environments. Mechanical property parameters of coal gangue treated by solutions were investigated. The action microstructure of coal gangue was revealed through a series of X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). The results show that acidic solution behaved better improvement effect on compressive modulus and fraction of coal gangue samples owing to the generation of quartz and the reduction of aluminum, dissolving of some substances, and transforming of small scattered angular grains through soaking treatment. Alkalinity treatment can be chosen to improve cohesion of coal gangue as a result of polymeric silicon aluminum salt, with high viscosity, was produced by chemical reaction during immersion. Therefore, aqueous solution treatment contributes to engineering properties and presents great potential in both supplement road building materials and recycling of coal gangue. [ABSTRACT FROM AUTHOR]

Analytical hierarchy process (AHP) is a multicriteria decision-making tool with diverse applications. Previous studies indicated AHP can be used as a tool for infrastructure management including pavement management and pavement type selection. In this paper, the use of AHP as a dust palliative selection tool is introduced. Fugitive dust in unpaved roads is commonly controlled using various dust palliatives. There are different types of commercial dust palliatives available in the market. Selection of appropriate dust palliative that serves its function without compromising budget and environment is not an easy task. So far, several guidelines have been published for selecting appropriate dust palliative based on surface material type, traffic volume, climate condition and road geometry. However, based on these guidelines, it is likely to have more than one viable dust palliatives. These competing candidate dust palliatives should be compared among each other based on additional criteria to select the most appropriate of all. This can be done using the analytical hierarchy process. The use of AHP as a dust palliative selection tool is demonstrated in the paper using case study data and data from the literature. [ABSTRACT FROM AUTHOR]

Existing performance models developed for interurban pavements are not applicable to urban pavements due to differences in traffic demands and deterioration trends. The objective of the study was to develop performance models for the management of urban pavement networks. Markov chains and Monte Carlo simulation were applied to account for the probabilistic nature of pavements deterioration over time, using data collected in the field. One of the advantages of this methodology is that it can be used by local agencies with scarce technical resources and historical data. Eight performance models were developed and successfully validated for asphalt and concrete pavements in humid, dry and Mediterranean climates with different functional hierarchies. The resulting models evidence the impact of design, traffic demand, climate and construction standards on urban pavements performance. Predicted service life of asphalt and concrete pavements in primary networks are consistent with design standards. However, pavements in secondary and local networks present shorter and longer service life compared to design life, respectively. Climate is a relevant factor for asphalt pavements, where higher deterioration was observed compared to that expected. Opposite to this, no relevant differences between design and performance can be attributed to climate in concrete pavements. [ABSTRACT FROM AUTHOR]

Road agencies are facing the challenges of aging pavements, deteriorating networks, and insufficient maintenance budgets. This study addresses two limitations in the current state of practice in pavement management. First, because the evaluation of maintenance strategies has traditionally focused on economic and technical aspects, it neglects the environmental impact of maintenance decisions. Second, current management systems often provide a unique, optimised pavement maintenance strategy based on a specific objective(s) and constraint(s). The main objective of the study is to analyse the effect of including environmental aspects and funding availability in the design of maintenance strategies. To achieve this objective, the study followed a three-step methodology. First, this study reviews existing practices on pavement maintenance and the criteria considered to trigger the application of maintenance treatments and their effects on pavement condition. Then, maintenance strategies are optimised considering three levels of budgetary capacity and a sustainable evaluation which incorporates technical, economic, and environmental aspects over the pavement lifecycle. Finally, a case study dealing with an urban pavement network in Chile is analysed. Results obtained from this case study show that an increment of 2% in maintenance budget allows to account for more sustainable maintenance decisions, such as cold in-place recycling and full-depth slab repair, whose greenhouse gas emissions are lower than other alternatives. Results also show that functional asphalt overlay and microsurfacing are more recommended in flexible pavements when budgetary restrictions are low, whereas recommended treatments for rigid pavements exhibit small variability with budgetary restrictions. [ABSTRACT FROM AUTHOR]

This paper presents the feasibility of superhydrophobic films to create the nano-lotus leaf effect on concrete surface and their influence on sound absorption and friction properties of concrete for application in rigid pavements. The study involved an evaluation of nanomaterials at the laboratory scale to analyze the effects of microtexture modification on the friction and sound absorption of concrete pavement. A number of laboratory specimens were produced by applying different amounts of nano-lotus leaf coating on the top of the textured concrete surface. The British pendulum test was used to measure the friction number, and an impedance tube was used to determine the sound absorption coefficient. Laboratory results indicate that nano-lotus leaf coated concrete can maintain the required friction property for rigid pavement, but may not increase the noise absorption. Further research must be carried out to determine possible benefit of the lotus leaf effect for reducing hydroplaning, particularly during heavy rainfall. [ABSTRACT FROM AUTHOR]

• Organic intercalated LDHs and antioxidant were applied to modify asphalt. • The anti-aging mechanism of CA-LDHs/antioxidant composite modified asphalt was proposed. • There was a synergistic effect between antioxidant and LDHs in improving the aging resistance of modified asphalt. • The composite of antioxidant/CA-LDHs showed better improvement in the aging resistance of asphalt than single CA-LDHs. To improve the aging resistance of bitumen for the construction of durable flexible pavement, the composite of antioxidants and cinnamic acid intercalated layered double hydroxides (CA-LDHs) were applied to modify-four styrene–butadienestyrene (SBS) modified bitumens (SMBs) aiming at revealing the anti-aging mechanism of different modifiers according to the aging behaviors of SMBs which were evaluated by the physical and rheological properties, characteristic functional groups and chemical compositions of SMBs before and after thermal-oxidative and ultraviolet (UV) aging. The results show that antioxidants/CA-LDHs can simultaneously improve the thermal-oxidative and UV aging resistance of four kinds of SMBs. Compared with the composite of pentaerythritol tetrakis (3-(3,5-di- tert -butyl-4-hydroxyphenyl) propionate) (1010), tris (2,4-di- tert -butylphenyl) phosphite (1 6 8) and CA-LDHs, the composite of octadecyl-3-(3,5-di- tert -butyl-4-hydroxyphenyl)-propionate (1076), tris (2,4-di- tert -butylphenyl) phosphite (1 6 8) and CA-LDHs shows a better improvement effect on the anti-aging performance of SMB. LDHs can shield UV light and prevent oxygen from penetrating into SMB, and antioxidants can capture and decompose intermediate products generated during aging, these effects would restrain the oxidative aging. It is concluded that there is a synergistic effect between antioxidants and LDHs in improving the thermal-oxidative and UV aging resistance of SMBs. [ABSTRACT FROM AUTHOR]

• Asphalt binder properties are not sufficient to capture low-temperature cracking resistance of asphalt mixtures. • DC(T) and SCB tests are able to characterize low-temperature cracking resistance of asphalt mixtures. • Mixture-based low temperature PG can capture the effect of RAP, binder content, and physical interaction between aggregates and asphalt binders. • Mixture-based low temperature PG can capture the effect of asphalt mixture components. This research was focused to investigate the low-temperature cracking resistance of five plant produced SP12.5 surface course asphalt mixtures by conducting the Disc-Shaped Compact Tension (DC(T)), Semi-Circular Bend (SCB) and Bending Beam Rheometer (BBR) tests. The DC(T) and SCB testing were conducted at three temperatures, −18, −24 and −30℃, to characterize the cracking resistance and determine the mixture-based low-temperature Performance Grade (PG) of asphalt mixtures by using the suggested minimum threshold values of DC(T) fracture energy. Moreover, BBR testing was conducted on the recovered asphalt binders from the same asphalt mixtures. The analysis of tests results showed that the DC(T) and SCB fracture energies at three temperatures were statistically comparable and characterized the low-temperature cracking resistance similarly. Even though, the low temperature PG of the recovered asphalt binders were within the Superpave specifications, in some cases, they were mismatched with the mixture-based low-temperature PG. Dissimilar to the SCB fracture energies, the DC(T) fracture energies had better relationships with the low-temperature properties of the recovered asphalt binders. Considering the low-temperature PG of the recovered asphalt binders and the mixture-based low-temperature PG, the DC(T) and SCB tests are essentially needed to reliably evaluate the low-temperature cracking resistance of asphalt mixtures. Moreover, the relationships between the DC(T) fracture energies and the recovered asphalt binder properties revealed that there was a better correlation between the DC(T) fracture energies at three testing temperatures and the recovered asphalt binders' temperatures corresponding to the stiffness value of 300 MPa. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a new measurement device for the realistic assessment of braking capability of landing airplanes for winter runways. The conventional and current practice of runway condition monitoring has been focused on identifying the maximum tire-pavement frictional drag (µ value) and often neglected the characteristics of actual aircraft braking systems as well as the comprehensive effects coming from various factors such as deformable contaminants on the winter runway. The braking availability tester (BAT) proposed in this paper is designed to take a different approach for the realistic assessment of braking availability of landing airplanes. The main idea of the BAT is to mimic the braking operation of actual aircrafts as closely as possible by incorporating the same brake mechanism and antiskid braking system (ABS) used in existing aircrafts. In doing so, the BAT also incorporates a suite of sensors for monitoring the status of braking operation in real time. This paper details the design concepts and operation principles of the BAT. Preliminary test results are also presented to verify the main functionality of the BAT. [ABSTRACT FROM AUTHOR]

Crystallization of biochar modified bio-asphalt binder (BMBA) directly affects their intrinsic physicochemical properties, which can significantly impact their processing and application. This research aims to maximize recycling the pyrolysis products of biomass (biochar and bio-oil) and investigate the crystallization kinetics of BMBA to inhibit the second crystallization and phase separation. Specifically, the parameters of crystallization kinetics and free volume were quantified using molecular dynamic simulations (MD). Relative crystallinity was evaluated using dynamic shear rheometer (DSR). Crystallization structure was analyzed using X-ray diffraction (XRD) and Synchrotron radiation small angle scattering (SAXS), and high-temperature-induced crystallization and low-temperature-physical hardening were quantified using hot-table polarizing microscope (HTPM). Crystallization morphology was measured by environmental scanning electron microscope (ESEM) and atomic force microscope (AFM). The parameters of crystallization kinetics show that high temperature and stress could induce the crystallization of BMBA. The low-temperature-physical hardening and aggregation of molecules indicate that the shape of BMBA crystals tends to be spherical under isothermal conditions but lamellar crystals under the non-isothermal conditions. This study provides a better understanding of the mechanism of crystallization kinetics of BMBA and a theoretical basis for the application of sustainable materials in asphalt pavement. • Crystallization kinetics and morphology of BMBA were investigated. • High temperature and stress could induce the crystallization of BMBA. • Catana-phase has the smallest adhesive force and peri-phase has the biggest adhesive force. [ABSTRACT FROM AUTHOR]

Using recycled concrete aggregates (RCAs) as coarse aggregate in concrete has the potential to supplement current natural aggregate reserves, divert construction and demolition debris from landfills, and promote the adoption of sustainable civil infrastructure. As many of the design equations used to calculate structural concrete properties are based on empirical data for natural aggregate concrete, using these equations for RCA concrete may not be applicable. This study examined the bond of reinforcement in concrete produced using RCA as coarse aggregate. One natural aggregate (NA) and three RCA sources were evaluated and used as coarse aggregate in 14 separate concrete mixtures with four compressive strength levels. Various concrete mechanical properties, including compressive strength, splitting tensile strength, modulus of rupture, and fracture energy, were tested, and correlations between these properties and reinforcement bond were studied. The reinforcement bond was measured using 48 beam-end specimens incorporating several bonded lengths. The results showed that bond strength of RCA concrete was reduced by up to 21% in comparison to NA concrete, and that there was a strong correlation between bond strength and coarse aggregate crushing strength. A regression model was developed to relate bond strength to coarse aggregate strength, concrete compressive strength, and the bonded length. Using this model, experimentally predicted development lengths were calculated to be up to 9% greater for RCA concrete members in comparison to NA concrete members. Overall, this study was directed at providing guidance on the evaluation of multiple RCA sources and their respective impact on the bond of reinforcement in structural concrete. [ABSTRACT FROM AUTHOR]