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This study evaluated the effects of adding waste PET fibers on the mechanical properties and chloride ion penetration of latex-modified ultra-rapid hardening cement concrete used for emergency road pavement repairs. The primary experimental variable was the content of waste PET fibers. The mechanical properties of the concrete were evaluated through compressive strength, flexural strength, and splitting tensile strength tests. Its durability was evaluated through chloride ion penetration, surface resistivity, and abrasion resistance tests. The experimental results were compared with the quality standards for emergency repair concrete set by the Korea Expressway Corporation. As a result, this study has enhanced the strength and resistance to chloride ions of latex-modified concrete by incorporating waste PET fibers. In the mixture with 3.84 kg/m3 of waste PET fibers, the compressive strength was 29.9 MPa at 4 h and 42.5 MPa at 28 curing days. The flexural strength was 6.0 MPa at 4 curing hours and 7.0 MPa at 28 days, and the splitting tensile strength was 4.5 MPa at 28 days of curing. The chloride ion permeability amount and abrasion depth were 1081C and 0.82 mm, respectively. The mixture with 3.84 kg/m3 of waste PET fibers has superior compressive strength, flexural strength, splitting tensile strength, chloride ion penetration, and surface resistivity compared to the mixture with 7.68 kg/m3. This result means that the waste PET fibers caused poor dispersion and fiber-balling within the concrete, leading to loose internal void structures when incorporated at 3.84 kg/m3. However, the abrasion resistance test showed better results for the mixture with 7.68 kg/m3 of waste PET fibers than the 3.84 kg/m3 mixture. Therefore, the test results indicated that 3.84 kg/m3 of waste PET fibers is the most effective for latex-modified concrete used in emergency road pavement repairs. [ABSTRACT FROM AUTHOR]

The behavior of airport precast concrete pavement (APCP) involving new design and construction concepts was experimentally analyzed under environmental and moving airplane loads, and the long-term performance of the APCP was evaluated using fatigue failure analysis. The strain characteristics and curling behavior of the APCP under environmental loads were comprehensively analyzed. The APCP slabs exhibited a pronounced curling phenomenon similar to conventional concrete pavement slabs. The dynamic response of the APCP subjected to impact loads was analyzed by performing heavy weight deflectometer tests. The test results confirmed that the vertical deformation of the APCP was small and within the typical range of vertical deformation of conventional concrete pavement. The dynamic strain response of the APCP under moving airplane loads was then analyzed and the strain variation during day and night times was compared. The strains during the day were found to be significantly larger than those at night under airplane loads because of the curling phenomenon of the APCP slabs. Finally, the long-term performance of the APCP was evaluated using fatigue failure analysis based on the obtained behavior. Even using the most conservative fatigue failure prediction model, the service life of the APCP was ascertained to be more than 30 years. Based on the overall results of this study, it is concluded that the APCP, which is designed to reduce slab thickness by placing reinforcing bars in the slabs via reinforced concrete structural design, exhibits typical behavior of concrete pavements and can be successfully applied to airport pavement rehabilitation. [ABSTRACT FROM AUTHOR]

This study investigated the flexural fatigue performance of pavement-grade geopolymer concrete (GPC) developed using low-carbon binders containing waste clay bricks (WCB), slag, and fly ash. Concrete was developed using two types of binders, one with a ternary blend of WCB, slag, and fly ash and one with only slag and fly ash as a full replacement for ordinary portland cement (OPC). Test specimens were subjected to flexural fatigue by four-point bending under three levels of stress which are equivalent to 75%, 80%, and 85% of the maximum static flexural strength. A two-parameter Weibull distribution was considered in the probabilistic analysis of fatigue life data, which corresponds to the number of cycles until failure. At all stress levels, GPC showed better fatigue performance compared to OPC concrete. At lower stress levels, the performance of GPC with WCB in the binder was better than the performance of conventional GPC with only slag and fly ash. However, GPC with WCB shows reduced performance at higher stress ratios. Survival probability of all concrete types (i.e., GPC and OPC concrete) decreased with increasing stress level. At a selected stress level, the fatigue life of all concrete types increased with the decrease of survival probability. The ultimate fatigue strength of GPC was higher than the OPC concrete. GPC with WCB binders showed an ultimate fatigue strength of more than 68% considering 107 repeated loading cycles. Practical Applications: Improving sustainability within the construction industry is a current major challenge, and all the while it is becoming an indispensable necessity. Transitioning from conventional materials with high negative environmental impacts such as OPC to more sustainable alternatives can significantly enhance sustainability in the construction industry. However, absence of data regarding the overall performance of newly identified low-carbon materials is a limiting factor to the industry uptake of these alternatives. The findings from this research characterize the fatigue behavior of low-carbon concrete that is developed using WCB-based binders and designed for pavement applications specifically. Understanding the fatigue performance is crucial for any material intended for use in pavement applications. The results from the current work provide valuable insights into the targeted application of these innovative materials, addressing a critical gap in information. [ABSTRACT FROM AUTHOR]

Bolivia has abundant pebbles, while the supply of crushed stone is limited and unstable. Thus, the resource utilization of local pebble as a coarse aggregate and the guarantee of concrete durability are the key scientific issues in the Sucre Highway Project. In this paper, a comparative analysis was conducted of the performance of crushed stone concrete and pebble concrete. Additionally, the impact of fly ash on the water permeability resistance of concrete was investigated. The results indicate that the apparent density, bulk density, and void ratio of pebbles are lower than those of crushed stone, and the aggregate gradation of pebbles is dispersed. The type of aggregate is the primary factor influencing the splitting tensile strength of concrete, with the main failure modes of pebble concrete being slurry cracking, aggregate crushing, and interface debonding. While aggregate and fly ash have a minor effect on compressive strength, they significantly impact flexural tensile strength; however, all concretes meet the requirements for extra-heavy, very heavy, and heavy traffic load levels. In terms of impermeability, fly ash effectively mitigates the negative impact of aggregate type on the impermeability of concrete. These findings support the application of pebble concrete in the highway project. [ABSTRACT FROM AUTHOR]

This paper focuses on the methodology for evaluating the degree of total curling in concrete pavement using machine learning. Deflection induced by falling weight deflectometer (FWD) testing is known as a direct correlation to total curling including built-in and daily curling. However, deflection measurement in the in-service road is also affected by others, such as environmental conditions, pavement geometry, subgrade stiffness, and mixture design. Thus, it is challenging to determine the level of curling from FWD data due to the complexity of influencing parameters. To navigate this complexity, prominent machine learning models are exploited to identify a non-linear relationship between curling and FWD deflections. A finite-element simulation of FWD is conducted to generate a vast data set, and a robust regression model is trained to estimate the total effective temperature difference (TETD) to quantify the effects of curling. Since input parameters for testing pavements can be measurable in the field, curling from TETD can be readily obtained using the proposed methodology. Comparative simulations highlight that the proposed models, with an MAE less than 0.5 °C significantly outperform the multiple regression performance, which registers an MAE of 3.45 °C in TETD, particularly in offering cost-effective and noise-tolerant prediction. [ABSTRACT FROM AUTHOR]

Reconfiguring practices within the construction industry through the utilization of diverse industrial byproducts is a crucial endeavor. This study was devoted to promoting sustainable construction methodologies while mitigating environmental implications. The focus of the research was the incorporation of reclaimed asphalt pavement (RAP) aggregates into GPC for application as pavement quality concrete (PQC). Leveraging fly ash (FA) and ground granulated blast furnace slag (GGBS) as viable aluminosilicate sources emerged as a judicious strategy for formulating blends that exhibit exceptional attributes at ambient temperatures, thereby circumventing the challenges posed by impractical on-site oven curing. Natural coarse aggregates were replaced with RAP at varying percentages ranging over 25% to 100% and the performance of the binders was assessed across a range of NaOH molarities (10M to 16M). The 14-M, 50% RAP mix exhibited superior strength and durability, achieving permissible compressive and flexural strength after just 7 days of ambient curing (41.80 and 4.72 MPa, respectively), in contrast to the 28 day of curing required for conventional cement concrete. This designed mix also showcased significant resistance to surface abrasion and carbonation, along with exemplary thermal stability as determined by thermogravimetric analysis (TGA). Upon exposure to a 2% H2SO4 concentration (to gauge performance in aggressive environments), higher RAP replacement levels revealed to influence mass and strength loss, but the effect of molarity remained quite moderate. Furthermore, toxicity characteristic leaching potential (TCLP) tests confirmed the immobilization of heavy metals in GPC blends with integrated RAP, thereby endorsing their environmental suitability for the construction of rigid pavements. [ABSTRACT FROM AUTHOR]

[Objective] Asphalt pavement structural layers experience stress and strain under mobile loads generated by vehicles. Exceedance of the material limit of strain or stress in a structural layer leads to fractures or damage, ultimately causing pavement cracking. Therefore, it is very important to clarify whether the strain in each structural layer can be coordinated and whether the stress remains below the limit value. This clarification is essential for ensuring the structural integrity of the pavement and prolonging its service life, making it a key issue in the design of pavement structural layer combinations. [Methods] To solve this issue, this study establishes a three-dimensional model of the pavement structure using the large-scale finite-element software ABAQUS and applies a moving rectangular load in the pavement model to simulate the dynamic response of the actual pavement under the action of moving vehicle loads. Based on the finite-element calculation results, this study analyzes the changes in stress, strain, and displacement of the upper layer, middle surface layer, lower layer, base layer, and sub-base layer of an asphalt pavement under the action of moving loads. Moreover, the effects of axle load, temperature, and vehicle speed on the vertical displacement, stress, and strain of each layer are systematically studied, providing a foundation for pavement design. [Results and Conclusions] The test results indicate that when the moving load is directly above the observation point, the vertical displacement, stress, and strain reach their peak values, which gradually decrease with increasing pavement depth. Moreover, the vertical displacements of the asphalt pavement layers under moving loads were most affected by axle loads, followed by temperature, and least affected by temperature. In addition, the slopes of the curves decrease with increasing pavement depth. Compared with vehicle speed, the effects of axle load and temperature change on the vertical displacement of the pavement are more significant. Furthermore, the vertical and shear stresses in the layers of the asphalt pavement under moving loads increase with increasing axle load, temperature, and vehicle speed and decrease with increasing pavement depth. The effect of axle load changes on stresses is more pronounced than that of vehicle speed and temperature. In addition, the trends of vertical and shear strains and stresses are similar for all layers of asphalt pavement. The stress and strain conditions within the pavement structure are complex. In the design process, controlling the most unfavorable stress and strain in each structural layer is essential to meet the design requirements. [ABSTRACT FROM AUTHOR]

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Roller-Compacted Concrete Pavements (RCCP) display a combination of attributes associated with both asphalt and conventional rigid pavements. However, their broader implementation remains constrained. One of the reasons is the discrepancy between the manner in which the RCCP mixture behaves in a laboratory setting and its performance in the field. In laboratory settings, the RCCP is blended in accordance with the modified Proctor approach. Subsequently, the Vibratory Hammer (VH) technique is employed to create specimens for strength characterization. In contrast, the actual pavement is constructed using a variety of rollers, including static, pneumatic, and vibratory types. Additionally, specimens are extracted from the actual pavements and compared to laboratory values to ensure quality control. The usage of diverse compaction mechanisms and energies throughout these procedures gives rise to discrepancies between field and laboratory behavior, necessitating a comprehensive understanding. This investigation examines the various techniques for designing RCCP, including the VH, Vibratory Table (VT), and Manufactured Roller (MR), which have been developed and utilized by previous researchers. These techniques are then compared to Field Specimens (FS). Furthermore, the RCCP is treated with three distinct curing methods: normal curing, coating the mixture with waterproof material, and spraying with water. The compressive strength of the RCCP has been sensitive to both the compaction method employed and the curing process. Additionally, research has indicated that the MR technique may be a viable option for the RCCP design. However, it is essential to optimize this technique to ensure an accurate simulation of the field conditions. [ABSTRACT FROM AUTHOR]

Ground Granulated Blast Furnace Slag (GGBS) is an effective supplementary cementitious material because of its pozzolanic properties and positive environmental impact. This research explores the flexural strength of concrete pavements by analyzing several high-volume formulations of GGBS concrete against conventional mixes. The study aims to assess the viability of incorporating high-volume GGBS mixes in pavement construction, with a particular emphasis on their flexural performance. The study employs various GGBS content levels (60%, 65%, 70%, and 75%) in concrete mixes, with the control mix containing ordinary Portland cement. Specimens are prepared according to standard procedures, and flexural testing is conducted to evaluate their performance. Statistical analysis is performed to compare the flexural strength and behavior of GGBS mixes with the control mix. The results obtained from the experiments revealed that the GGBS concrete mixes had better flexural performance than the control mix, with more strength and less cost. The results provide the performance of large-volume GGBS concrete mixes under flexural loading circumstances, which helps to understand whether these mixes are suitable for use in concrete pavements. Ultimately, this research sheds light on the possibilities of utilizing large- volume GGBS concrete mixes as long-term substitutes for traditional concrete pavements, which may help in the promotion of greener and more long-lasting infrastructure solutions. [ABSTRACT FROM AUTHOR]

Waste slag and rubber particles are commonly used to modify concrete, offering benefits such as reduced cement consumption and lower greenhouse gas emissions during cement production. In this study, these two environmentally friendly, sustainable waste materials were proposed for the preparation of mortar intended for snow-melting pavements. A series of experiments were conducted to evaluate the performance of the material and to determine whether its compressive and flexural strengths meet the requirements of pavement specifications. The mortar's suitability for snow-melting pavements was assessed based on its thermal conductivity, impermeability, and freeze–thaw resistance. The results indicate that slag, when used in different volume fractions, can enhance the compressive and flexural strength of the mortar. Slag also provides excellent thermal conductivity, impermeability, and resistance to freeze–thaw cycles, contributing to the overall performance of snow-melting pavements. When the slag content was 20%, the performance was optimal, with the compressive strength and flexural strength reaching 58.5 MPa and 8.1 MPa, respectively. The strength loss rate under freeze–thaw cycles was 8.03%, the thermal conductivity reached 2.2895 W/(m * K), and the impermeability pressure value reached 0.5 MPa. Conversely, the addition of rubber particles was found to decrease the material's mechanical and thermal properties. However, when used in small amounts, rubber particles improved the mortar's impermeability and resistance to freeze–thaw cycles. When the rubber content was 5% by volume, the impermeability pressure value reached 0.5 MPa, which was 166.7% lower than that of ordinary cement mortar. Under freeze–thaw cycles, the strength loss rate of the test block with a rubber content of 25% volume fraction was 9.83% lower than that of ordinary cement mortar. [ABSTRACT FROM AUTHOR]

This paper presents the fatigue properties of polypropylene fiber-reinforced concrete (PPFRC) in flexure at various stress ratios and the sustainability of PPFRC in terms of environmental impact and material cost for jointed concrete pavements. In this study, prism specimens with a size of 100 x 100 x 400 mm were cut from slabs with a size of 1000 x 1000 x 100 mm, considering the effects of fiber distribution and orientation. A polypropylene fiber with a size of 0.7 x 30 mm was mixed into concrete at 1.0 and 1.3 vol.%. Fatigue tests were conducted under four-point flexural loading to obtain the S-N curve for each mixture. In this study, plain concrete (PLC20) with a maximum aggregate size of 20 mm was also used, and its fatigue strength was compared with that of the PPFRCs. Based on the fatigue test results, the S-N curves called the Whöler curve were proposed. The fatigue life of the 1.3 vol.% PPFRC was longer than that of PLC20 at a lower stress ratio. Using the obtained S-N curves, a jointed concrete pavement was designed. The fatigue life of the thinner PPFRC with 1.3 vol.% pavement was enhanced significantly compared with a normal jointed concrete pavement. Consequently, despite the higher initial material cost, the 1.3 vol.% PPFRC can reduce pavement thickness and CO2 emissions. [ABSTRACT FROM AUTHOR]

Continuously reinforced concrete pavement (CRCP), crucial for the resilience of transportation infrastructure owing to its continuous steel reinforcement, confronts a critical challenge in the form of spalling—a distress phenomenon posing a threat to pavement durability and overall structural integrity. The detachment or breakage of concrete from the surface compromises CRCP's functionality and raises safety concerns and escalating maintenance costs. To address this pressing issue, our study investigates the multifaceted factors influencing spalling, employing a comprehensive approach that integrates statistical and machine learning techniques for predictive modeling. Descriptive statistics meticulously profile the dataset, emphasizing age, thickness, precipitation, temperature, and traffic parameters. Regression analysis unveils key relationships, emphasizing the significance of age, annual temperature, annual precipitation, maximum humidity, and the initial International Roughness Index (IRI) as influential factors. The correlation matrix heatmap guides feature selection, elucidating intricate interdependencies. Simultaneously, feature importance analysis identifies age, Average Annual Daily Traffic (AADT), and total pavement thickness as crucial contributors to spalling. In machine learning, adopting models, including Gaussian Process Regression and ensemble tree models, is grounded in their diverse capabilities and suitability for the complex task at hand. Their varying predictive accuracies underscore the importance of judicious model selection. This research advances pavement engineering practices by offering nuanced insights into factors influencing spalling in CRCP, refining our understanding of spalling influences. Consequently, the study not only opens avenues for developing improved predictive methodologies but also enhances the durability of CRCP infrastructure, addressing broader implications for informed decision-making in transportation infrastructure management. The selection of Gaussian Process Regression and ensemble tree models stems from their adaptability to capture intricate relationships within the dataset, and their comparative performance provides valuable insights into the diverse predictive capabilities of these models in the context of CRCP spalling. [ABSTRACT FROM AUTHOR]

The temperature response of pavement is not only crucial for assessing the internal stresses within pavement structures but is also an essential parameter in pavement design. Investigating the temperature response of rubberized concrete pavements (RCP) can support the construction of large-scale rubber concrete pavements. This study constructed a pavement monitoring system based on fiber Bragg grating technology to investigate the temperature distribution, temperature strain, temperature effects, and temperature stress of RCP. The results show that the daily temperature–time history curves of concrete pavement exhibit a significant asymmetry, with the heating phase accounting for only one-third of the curve. The temperature at the middle of RCP is 1.8 °C higher than that of ordinary concrete pavement (OCP). The temperature distribution along the thickness of the pavement follows a "spindle-shaped" pattern, with higher temperatures in the center and lower temperatures at the ends. Additionally, the addition of rubber aggregates increases the temperature strain in the pavements, makes the temperature–strain hysteresis effect more pronounced, and increases the curvature of the pavement slab. However, the daily stress range at the bottom of RCP is approximately 0.7 times that of OCP. [ABSTRACT FROM AUTHOR]

In order to further enhance the erosion resistance of cement concrete pavement materials, this study constructed an apparent rough hydrophobic structure layer by spraying a micro-nano substrate coating on the surface layer of the cement concrete pavement. This was followed by a secondary spray of a hydroxy-silicone oil-modified epoxy resin and a low surface energy-modified substance paste, which combine to form a superhydrophobic coating. The hydrophobic mechanism of the coating was then analysed. Firstly, the effects of different types and ratios of micro-nano substrates on the apparent morphology and hydrophobic performance of the rough structure layer were explored through contact angle testing and scanning electron microscopy (SEM). Subsequently, Fourier transform infrared spectroscopy and permeation gel chromatography were employed to ascertain the optimal modification ratio, temperature, and reaction mechanism of hydroxy-silicone oil with E51 type epoxy resin. Additionally, the mechanical properties of the modified epoxy resin-low surface energy-modified substance paste were evaluated through tensile tests. Finally, the erosion resistance of the superhydrophobic coating was tested under a range of conditions, including acidic, alkaline, de-icer, UV ageing, freeze-thaw cycles and wet wheel wear. The results demonstrate that relying solely on the rough structure of the concrete surface makes it challenging to achieve superhydrophobic performance. A rough structure layer constructed with diamond micropowder and hydrophobic nano-silica is less prone to cracking and can form more "air chamber" structures on the surface, with better wear resistance and hydrophobic performance. The ring-opening reaction products that occur during the preparation of modified epoxy resin will severely affect its mechanical strength after curing. Controlling the reaction temperature and reactant ratio can effectively push the modification reaction of epoxy resin through dehydration condensation, which produces more grafted polymer. It is noteworthy that the grafted polymer content is positively correlated with the hydrophobicity of the modified epoxy resin. The superhydrophobic coating exhibited enhanced erosion resistance (based on hydrochloric acid), UV ageing resistance, abrasion resistance, and freeze-thaw damage resistance to de-icers by 19.41%, 18.36%, 43.17% and 87.47%, respectively, in comparison to the conventional silane-based surface treatment. [ABSTRACT FROM AUTHOR]

Roadways are the main transportation mode in Brazil for both cargo and people. This strong dependence on road transport makes paving highways extremely important for the country's development. A common way to recover deteriorated pavement is through a superficial reinforcement called overlay. The whitetopping overlays are made of Portland cement concrete. The technique basically consists of building a concrete pavement over the existing asphalt pavement. The existing pavement acts as a sub-base for the concrete overlay. The addition of fibers to concrete has been increasingly frequent, especially for industrial floors and pavements, bringing longer performance life for same traffic, climate and concrete strength. The fibers promote the improvement of several characteristics of the concrete paste, such as the increase in post-cracking toughness, energy absorption, and fracture energy. This work evaluates the flexural response of composite beams of concrete and asphalt layers and the influence of adding fibers to the concrete. An experimental program is set and supports the development and validation of a finite element numerical model. The numerical model is then applied to a parametric study where tendifferent concrete mixes with different types of fibers and contents are analysed. Steel and synthetic fibers are used. The composite beams are simulated indicating the concrete mixes that best supported loads in the post-cracking regime, with some mixes managing to maintain around 90% of the peak load for large crack openings. [ABSTRACT FROM AUTHOR]

The 3D pavement surface images provide a great opportunity for transportation agencies to digitally and effectively assess jointed plain concrete pavement (JPCP) conditions. An automated and accurate JPCP slab joint detection algorithm, which can support slab separation and faulting evaluation, is a critical prerequisite for applying 3D pavement images on JPCP condition assessments. However, there is no existing study on automated slab joint detection except for commercial software, and the detected joints of the software require massive manual revisions due to insufficient accuracy. In this study, a novel slab joint detection algorithm is proposed, which leverages the power of deep learning to achieve accurate slab joint detection on 3D pavement images. The proposed algorithm consists of a convolutional neural network-based joint segmentation model and a joint coordinates extractor. The joint segmentation model is trained to generate pixel-wise joint segmentation masks from the pavement images, which provide preliminary localization information of the slab joints. Then, with the joint segmentation mask, the joint coordinate extractor is designed to eliminate the false positive predictions and accurately extract the joint coordinates. The proposed algorithm is evaluated on large-scale 3D pavement images collected from multiple interstate highways in the state of Georgia with diverse conditions. In the performance evaluation, the proposed algorithm achieved the highest F1 score of 0.956, which largely outperformed the commercial software with a 10% improvement. The evaluation results demonstrate the effectiveness of the proposed algorithm, which can further support effective and efficient assessments of JPCP conditions. [ABSTRACT FROM AUTHOR]

Pavement growth (PG) refers to the expansion of the integrated slab length when all the contraction joints of the concrete pavement are close within the expansion joint (EJ). It results from the complex interactions of numerous factors, such as climatic conditions (extremely high temperature and moisture levels), material, and the quantity of incompressible particles infiltrating the pavement joints structure. Currently, the methods and guidelines available for evaluating the annual PG and predictions of concrete pavement blowup are considerably limited. In this study, a mechanistic design framework was developed for estimating the PG and predicting pavement blowup potential. Moreover, a computer tool called Pavement Growth and Blowup Analysis (PGBA) was developed using MATLAB. This tool considers factors such as the pavement configuration, climatic conditions, configuration of EJs, and design reliability. It was used to evaluate the effectiveness of EJs and predict the blowup occurrence times for concrete pavements. To evaluate the PGBA tool, PG data from field measurements conducted by the Maryland DOT were compared with the results obtained using the PGBA tool. The PG predicted by the PGBA tool shows good agreement with the field measurements. However, because concrete pavement blowup data corresponding to PG measurement were not available, a comparison of the PGBA blowup results was not possible. The PGBA tool can be used to predict the service life of EJs and the blowup occurrence time according to the climatic data, pavement structure and materials, joint design, base friction characteristics, and engineering judgment. [ABSTRACT FROM AUTHOR]

The pavement texture wavelength and mean texture depth (MTD) of the pavement macrotexture significantly affect functional performance. However, owing to its higher correlation with the wavelength, the Exposed Aggregate Concrete Pavement (EACP) texture was evaluated based on the MTD and exposed aggregate number (EAN) in the same location. The MTD contributes significantly to road surface friction and tire-pavement noise and is vital for anti-sliding and noise reduction. Conventional methods for MTD measurement require considerable human effort when the sample size is large and sensitive to the operator. Furthermore, it is time-consuming to measure the MTD together with the EAN. Recently, image-based estimation has become a new trend, owing to its economy and convenience. Therefore, this study aimed to estimate the MTD of the EACP pavement surface texture at an image-based level as an alternative measurement approach simultaneously within the EAN location. Initially, the image acquisition was created based on aerial photography. Subsequently, photogrammetry was used to reconstruct a high-resolution point cloud of the pavement texture. Subsequently, the MTD was estimated analytically from image-based point clouds. Experiments were conducted at over 60 locations in three field tests of the EACP in South Korea. The MTD results showed good agreement and a higher correlation between the image-based and sand-patch test (SPT) methods. The image-based method showed results higher than the SPT with a value of 22%. Therefore, the developed method can be used to estimate the MTD using the established regression equation. [ABSTRACT FROM AUTHOR]

This document is a summary of a book that showcases the latest advancements in research on long-life road infrastructures. The book covers a wide range of topics, including materials and structures, performance evaluation, and modeling. The articles in the book discuss various innovative approaches and techniques for maintaining and managing rural road networks, evaluating pavement performance, and enhancing the durability and sustainability of road structures. The research presented in the book contributes to the development of more efficient and durable road systems that can withstand the demands of modern transportation networks. [Extracted from the article]

Model development activities are increasing in pavement research and engineering applications. At the same time, there is ambiguity and a lack of consistency with regard to checking and quantifying credibility and suitability for the intended application. Specifically, usage of the terms Verification and Validation (V&V) is seen to vary across contributions. In this context, this paper was motivated by the desire to provide a best-practice reference that underlines the significance of the V&V terms, clarifies their definition, and promotes a more unified usage. Accordingly, the objective was to offer examples that introduce the V&V jargon, demonstrate basic V&V concepts and processes, and highlight certain fine points. A total of five distinct models were introduced and discussed: (1) load-related responses in asphalt pavements, (2) load-related responses in concrete pavements, (3) crack initiation and propagation in asphalt concrete, (4) linear viscoelasticity of asphalt concrete, and (5) water flow through asphalt concrete pores. A general conclusion from this work is that successful V&V efforts are closely linked to a clear definition of the intended usage, i.e., the specific reality of interest being targeted by the model. It is also concluded that documenting V&V efforts is integral to any computational model development. Doing so communicates to potential users the region of confidence for the model alongside the expected differences with the reality of interest. [ABSTRACT FROM AUTHOR]

Numerous applications in civil and transportation engineering require concrete with high early strength and good durability properties. Limited studies have revised the performance of high early-strength concrete prepared with calcium sulfoaluminate (CSA) cement and internal curing technology. This study evaluates the strength and durability properties of four concrete mixtures designed with low and high cement contents, incorporated with and without internal curing. Compressive and split tensile strength, autogenous and drying shrinkage, and freezing and thawing resistance were evaluated. High early-strength concrete mixtures with internal curing achieved lower strength and improved durability (shrinkage and freezing and thawing resistance) in comparison with their analogous control mixtures. All concrete mixtures obtained compressive strength higher than 17 MPa (2,500 psi) within the first 4 h. Concrete mixtures with high cement content showed less contraction (<200 με) than their analogous control mixtures. The internally cured concrete mixture with low cement content exhibited slight expansion instead of shrinkage. Finally, the freezing and thawing resistance showed great improvement because no or little damage was observed in the internally cured concrete mixtures. The internally cured concrete specimens overcame 300 cycles, whereas the control mixtures reached maximum 164 cycles. The internally cured mixtures with low and high cement contents showed a final relative dynamic of elasticity of 79.7% and 99%, respectively. Based on these results, using CSA concrete for repair works could be feasible with internal curing technique. Practical Applications: Extensive damage is observed in concrete pavements due to several factors, primarily due to freeze–thaw action and shrinkage. Given that replacing the damaged pavement is expensive and time-consuming, several transportation agencies prefer to restore/repair the degraded portion of pavement using high early-strength concrete. Using high early-strength concrete ensures the pavement achieves its design strength at an early age, which ultimately allows opening the roadway to oncoming traffic in a shorter duration. The use of calcium sulfoaluminate cement instead of ordinary portland cement in high early-strength concrete helps to reduce the overall carbon footprint due to lower energy consumed during calcium sulfoaluminate's clinkering process, along with relatively faster strength development. Previously, researchers have demonstrated the effectiveness of internal curing to improve durability of high early-strength concrete by better freeze–thaw and shrinkage resistance. Overall, the given study focuses on understanding the benefits of internal curing in high early-strength concrete mixtures prepared with a low and high calcium sulfoaluminate cement content. Irrespective of the cement content, high early-strength concrete mixtures with internal curing had superior freeze–thaw and shrinkage resistance, proving that internal curing effectively improves the durability properties without compromising on its design strength. [ABSTRACT FROM AUTHOR]

The article discusses the durability and reliability of a separate element – bridge approach slab, which is justified by the need to maintain a satisfactory technical condition of Ukrainian bridges in general and traffic safety on public roads with limited funding during martial law. The scope of the research is forecasting the residual service life of bridge elements (on the example of approach slabs) using probabilistic methods. Approach slabs are designed to smoothly and safely connect the road approach embankment with the bridge to gradually equalize the elastic modulus of the carriageway from a less rigid asphalt pavement on an elastic base to a more rigid one on a reinforced concrete slab. The main defects in the destruction of approach slabs are: changes in the longitudinal profile of the road due to the collapse and subsidence of the soil under the approach slabs; longitudinal and transverse cracks in the asphalt concrete pavement on the bridge approaches; and potholes that lead to an increase in the additional dynamic load on the bridge deck. [ABSTRACT FROM AUTHOR]

Macro fibers have been extensively used in the construction of various concrete structures, including bridges, dams, tunnels, industrial floors, and pavements. However, their effectiveness in reducing crack opening widths in concrete pavements has not been fully explored. This study aims to delineate the role of fibers by identifying the optimal types and volumes for effectively controlling cracks in concrete pavement structures, particularly in thin overlays. The research investigates how different fiber types, such as synthetic and steel, and their respective volumes can mitigate crack propagation in concrete overlays. Additionally, it evaluates the performance of fiber-reinforced concrete overlays compared to conventional dowel bar systems in terms of crack width reduction and overall pavement durability. The findings aim to provide specific design criteria for incorporating macro fibers in concrete overlays to enhance structural integrity and longevity. [ABSTRACT FROM AUTHOR]

Considering the growing use of permeable pavements, the prediction of runoff passing through this pavement model is of considerable importance. The prediction of rainfall-runoff relationships can be a challenge because of several factors including data uncertainty, non-linear relationships, and high temporal and spatial variability. To deal with these challenges, intelligent algorithms are often used to predict such complex phenomena. In this research, runoff control parameters were investigated in two types of permeable pavements (permeable interlocking concrete pavement (PICP) and high strength clogging resistant permeable pavement (CRP)) using support vector machine (SVM), support vector machine-bat (SVM-BA) and support vector machine-grasshopper (SVM-GOA). Variables used in the models included percentage of coverage by permeable pavement (A), rainfall intensity (I), slope (S), and pavement type coefficient (K) as input data, and runoff coefficient (C), time to runoff (Tr), and peak discharge (Qp) as output data. In this research, from the total of 108 data extracted from the experimental results, 86 data were used in the training period, and 22 data were used in the test period. The results of the test period show that the SVM-BA model has the best performance with values of MAE = 0.010 in predicting C, MAE = 1.330 min in predicting Tr, and MAE = 0.029 lit/min in predicting Qp. The SVM-GOA model is ranked second with values of MAE = 0.051 in predicting C, MAE = 3.285 min in predicting Tr, and MAE = 0.097 lit/min in predicting Qp. Also, the SVM model is ranked third with values of MAE = 0.063 in predicting C, MAE = 4.470 min in predicting Tr, and MAE = 0.121 lit/min in predicting Qp. In summary, the SVM-BA algorithm showed the best performance and the SVM algorithm showed the weakest performance in predicting runoff characteristics in permeable pavements. [ABSTRACT FROM AUTHOR]

In the field of pavement damage analysis, long‐term damage monitoring and assessment remain a formidable challenge due to the dynamic nature of damage development and environmental changes. This study presents preliminary progress towards a system for tracking and analyzing the progression of pavement deterioration over time using image datasets of real concrete pavement. The research focuses on specific road sections, with annual data collection over three years, resulting in a time‐series dataset with detailed spatiotemporal information. The proposed methodology integrates GPS data for precise location mapping and employs advanced image analysis techniques to consistently identify and monitor pavement damages across different time frames. Image rectification and alignment processes are applied to ensure comparability in detail and orientation. The current status of the project is presented, including initial implementations of the methodology, limitations encountered, and suggestions for improvement in data collection. The goal is to establish a robust and replicable methodology that facilitates understanding the evolution of pavement damage. This spatiotemporal matching approach aims to lay the foundation for agencies to monitor the progression of issues and enable timely interventions throughout the pavement life cycle. [ABSTRACT FROM AUTHOR]

To evaluate the benefit of geocells of different geometrical configurations for pavement application, full-scale instrumented model tests were performed on pavement sections reinforced with geocells of different geometrical configurations subjected to monotonic and repeated loading. The responses studied were stress distribution in different pavement layers, induced strains in geocell walls, and settlement characteristics. The reinforced sections exhibited a significant reduction in rut depth as well as localized stress concentration compared to the unreinforced section. The reduction in rut depth was found to be influenced by the geocell height as well as weld spacing. The geocell reinforcement was found to distribute the stresses in the subgrade and subbase layers more efficiently, thus reducing the stress concentration in these layers. The strain measurements were found to be higher at the bottom of the geocell walls indicating a higher confinement effect on a lower part of the geocell. In the field, mostly geocells of 356 mm weld spacing and 150 mm height (SW356-H150) are used. However, this study suggests that a geocell of 330 mm weld spacing and 100 mm height (SW330-H100) having approximately 30% lower cost compared to SW356-H150 is as effective in reducing the rut depth and localized vertical stress distribution. • Effect of weld spacing and heights of geocell reinforcement on pavement section is evaluated through full-scale model testing. • Study highlights that the reduction in rut depth is significantly influenced by the geocell height and weld spacing. • Geocell reinforcement reduces stress concentration in the subgrade and subbase layers by distributing stresses efficiently. • Higher strain measurements at the bottom of geocell walls indicate higher confinement at the lower part of geocell wall. • Study suggests use of SW330-H100 configuration of geocell as an economic alternative to conventional SW356-H150 configuration. [ABSTRACT FROM AUTHOR]

Concrete pavements require substantial amount of water for curing process which is a challenge considering its large surface area and to mitigate this challenge, use of internal curing agents is considered in this study. The use of super-absorbent polymer (SAP) has been reported in this regard the increased porosity resulting after release of internal water is a major concern here. Alternatively, polymers such as polyvinyl alcohol (PVA) and polyethylene glycol (PEG) can be considered for self-curing. Scarce literature is available with respect to these two polymers. In this study, the workability, strength, durability, and microstructure properties of pavement-quality concrete with PVA and PEG were analyzed and compared with that of SAP and conventionally cured concrete. The results indicated that at the optimal dosage, PVA/PEG exhibited better mechanical and durability properties when compared to conventionally cured concrete; SAP exhibited a reduction in strength for dosages higher than 0.6%, due to the increased porosity and this was verified through SEM images also. The measurement of internal humidity on concrete slabs showed that internal humidity retention was better in the case of PEG. Pavement design as per IRC:58-2015 design guideline and cost analysis for the respective thickness showed that the use of certain self-curing additives results in economic advantages also. [ABSTRACT FROM AUTHOR]

This article investigates the viability of using natural rubber latex (NRL)-modified concrete with bottom ash (BA) as a partial replacement for river sand in sustainable rigid pavements. Concrete mixes with 10% and 20% BA replacement ratios and varying NRL dosages (0%, 1.0%, 1.5%, and 2.0% by weight of cement) were prepared and evaluated for their mechanical and microstructural characteristics. Results showed that BA substitution decreased the compressive strength of concrete. However, the addition of NRL at an optimal dosage of 1.0% significantly improved both the compressive and flexural strengths. The 10%BA+1.0%NRL and 20%BA+1.0%NRL mixes exhibited mechanical properties surpassing the control mix and meeting the minimum requirements for rigid pavement materials. However, excessive NRL content (1.5% and 2.0%) led to a reduction in mechanical strength. Scanning electron microscopy analysis exhibited a denser and more compact matrix in NRL-modified BA concrete, with NRL films enhancing the interfacial bonding and crack-bridging mechanism. Nonetheless, excessive NRL content resulted in the formation of abundant and thicker NRL films, which disrupted the continuity of the cement matrix and created weak zones. X-ray diffraction analysis confirmed the existence of crucial crystalline phases and their optimal balance in the 20%BA+1.0%NRL mix, contributing to its superior performance. Mixes with excessive NRL contents exhibited lower intensities of quartz, calcite, and portlandite peaks, indicating a disturbance in the proper formation and growth of essential crystalline phases. The findings demonstrated the potential of NRL-modified BA concrete as an eco-friendly and high-performance alternative for sustainable rigid pavements when using an optimal NRL dosage, promoting the employment of waste resources and reducing the environmental impact of the construction industry. [ABSTRACT FROM AUTHOR]

The current research adapts waste foundry sand (WFS) as a partial replacement to fine aggregate, which contributes to the principles of circular economy, providing economic and environmental advantages by rethinking waste as an essential resource of innovative and environmentally friendly building materials. This article mainly aims to showcase the research outcomes from the investigations carried out on the development of pavement quality slag-based conventional concretes (PQSC) and alkali-activated concrete (PQAC) using WFS as a partial substitution to conventional river sand (RS) aggregates. The mix design and the mechanical performances have been studied to comprehend the performance of WFS in concretes at various levels. Rigorous works were further carried out to fix the aggregate percentage of RS and WFS for the satisfactory mix design of the concrete mixtures. The mechanical strength parameters were studied along with volume-of-permeable-voids, density, and water absorption for durability assessments. The selected blends were sent to microstructural investigations involving scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) studies. A successful attempt was also made to develop rigid pavement design models using both the IRC method and KENPAVE software, and a comparative scrutiny was carried out. The results demonstrate that the utilization of WFS can be achieved to a maximum of 15% to 20% without significantly reducing the performance of PQSC and PQAC mixtures for road applications after ensuring satisfactory mechanical performances. The research results will pave a path for effective utilization of WFS in construction industry and provide a sustainable solution to significant waste management problems in the casting industry. Practical Applications: This research paper focuses on the fruitful utilization of industrial waste materials in the construction industry, specifically in the context of rigid pavements. Specifically, the study highlights the potential benefits of incorporating blast furnace slag and waste foundry sand (WFS), in achieving a more sustainable and circular construction economy. It compares the mechanical performances of slag-based AAC and conformist OPC concretes for pavement applications, finding that the former is superior. The study also explores the optimal percentage replacement of WFS in place of natural fine aggregates, noting that alkali-activated mixes can accommodate a higher percentage of replacement than OPC concretes. Rigid pavements, made of developed concrete, are a durable and sustainable alternative to flexible pavements. They are suitable for various highway infrastructure applications due to their load-bearing capacity, resistance to wear and tear, and ability to handle heavy vehicles and traffic volumes. They also offer improved aesthetics, walkability, reduced lifecycle costs, and sustainability through the use of industrial waste materials. Therefore to summarize, the adaptation of WFS incorporated, slag based alkali-activated concrete offers a better mechanical performance making it suitable for rigid pavement applications which in turn help in preserving the natural aggregates contributing to sustainability. [ABSTRACT FROM AUTHOR]

Supplementary cementitious materials (SCMs) are commonly introduced into the concrete mix to increase their properties, addressing the current need for durable and robust pavements. With every ton of Ordinary Portland Cement (OPC) produced through processes such as fossil fuel combustion and limestone fermentation, carbon dioxide is released into the atmosphere. Conversely, Ground Granulated Blast-furnace Slag (GGBS), being abundantly available, presents a viable more environmentally friendly alternative to cement for various concrete applications. This work studies the influence of GGBS, in combination with chemical admixtures, on M40 grade binary blended concrete mixtures. The aim of the study was to improve the strength characteristics at various stages of concrete curing. The results indicated that the GGBS-incorporated concretes (replacing 60%, 65%, and 70% of the cement) exhibited an increase in compressive strength after prolonged curing. The average density of fresh concrete mixes containing GGBS did not exhibited a noticeable increase. A marginal disparity in air content was observed in the replacement mix. Minimal length changes were observed in the drying shrinkage test after a curing duration of 360 days compared to conventional concrete mixtures. [ABSTRACT FROM AUTHOR]

The addition of macro fibers to concrete pavements has been used to improve the cracking of concrete pavement, reduce slab thickness and contribute to increasing the joint spacing. A laboratory test was carried out in the study to analyze the impact of fiber reinforced concrete (FRC) on plain cement concrete (PCC) and roller compacted concrete (RCC), determining the flexural strength by performing ASTM-1609 tests and compressive strength by ASTM C-39 tests. Two synthetic fiber types selected with different geometries and different dosages (0.25% and 0.5% by volume) were tested for both RCC and PCC. To examine the effect of fiber contents and property, statistical testing was done using strength-test data. The test result showed that flexural strength was not affected by fibers. As fiber content increased, both residual strength (F600 and F150) and specimen toughness (T150) increased for each fiber type. To the contrary, the compressive strength of specimens with higher fiber contents was lower in every case. Fiber properties including length and shape affected the residual strength of RCC more, than PCC. It is notable that the residual strength of RCC and PCC with the same fiber condition is very similar, even though the mix design and compressive and flexural strengths are different. In this paper, the strength-test data results are discussed, and the factors affecting the test results and the limitations of the testing methods are suggested. [ABSTRACT FROM AUTHOR]

Supporting sustainable development, contributing to reducing waste that causes environmental damage, and reducing the use of natural materials are part of preserving the environment and society. This is done by highlighting the manufacture of sustainable concrete pavement of acceptable quality and according to specifications. The authors previously produced a concrete pavement mixture with optimal properties by partially replacing the Portland cement with 55 wt.% of the ground granulated blast furnace slag (GGBFS) in addition to partially replacing the virgin aggregates with 30 wt.% of recycled aggregate from crushed rigid pavement. The goal of this research work is to produce a self-sensing rigid pavement mixture from wastes with high mechanical properties, that is better than regular concrete and less expensive. The new novel mixture has the ability to detect earlier the damages that occur to the concrete pavement so as to obtain a longer life by periodically maintaining the pavement on time. The previous mixture was improved by adding chopped steel shaving fibers with lengths ranging from 20-60 mm in four different volumetric ratios. These are 0.7%, 1%, 1.1%, and 1.2%. The results were compared with those of the basic mixture, and a decrease in workability and slump values were noticed. Moreover, significant improvements in the mechanical properties were obtained. The concrete's resistance to the applied loads increased by increasing the percentage of steel shaving in the mixtures, due to the increasing of cohesion forces within the mixture. The self-sensing capability for the developed mixtures was tested by measuring the changes in the electrical resistance under different types of mechanical loadings. The results showed that the direction of the applied load and the proportion of steel shavings affect the self-sensing properties in terms of the fractional variation in the electrical resistance (FVER, %), which highlights the importance of using steel shavings in producing smart concrete pavements from reused resources more efficiently and highly cost-effectiveness. [ABSTRACT FROM AUTHOR]

The continuously reinforced concrete pavement (CRCP) system grapples with challenges such as non-uniform transverse crack patterns and the need for substantial reinforcement. Field research on the Belgian CRCP sections along motorway E313 indicates that active cracking induced by partial surface saw-cuts consistently leads to transverse crack patterns. This study introduces an innovative modification to the CRCP: the actively reinforced concrete pavement design (ARCP). The ARCP leverages partial surface saw-cuts to reduce reinforcement needs by replacing continuous-length steel bars with partial-length counterparts. The main objective of the present study is to develop a 3D finite element (FE) model capturing the active cracking behavior of ARCP under realistic external temperature variations. Comparative analysis with CRCP considers early-age crack patterns, crack strain development, and the distribution of maximum steel stress for different steel ratios (0.67%, 0.75%, and 0.85%). FE simulation results align with field data, indicating that ARCP exhibits similar early-age cracking behavior to CRCP but with a significant 24 to 42% reduction in total reinforcement. This innovation presents a promising avenue for addressing CRCP challenges while optimizing material usage in pavement construction. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the tire–road-wear particles (TRWPs) and suspended dust generated based on the nominal maximum aggregate size (NMAS) of the polymer-modified stone mastic asphalt (SMA) mixtures indoors. The SMA mixtures containing styrene butadiene styrene (SBS) polymer and the NMASs of 19, 13, 10, 8, and 6 mm were used. Dust was generated from the wear of the tires and the pavement inside the indoor chamber by using the laboratory tire–road-wear particle generation and evaluation tester (LTRWP tester) developed by Korea Expressway Corporation (KEC). In this method, a cylindrical asphalt-mixture specimen rotates in the center, and a load is applied using three tires on the sides of the test specimen. During the test, a digital sensor was used to measure the concentration for each particle size. After the test was completed, the dust was collected and weighed. According to the test results, the generated TRWP emissions were reduced by approximately 0.15 g as the NMAS of the SMA mixture decreased by 1 mm. TRWP emissions decreased by 20% when using the 6 mm SMA mixture compared to the 13 mm SMA mixture. For practical application, a predicted equation of TRWP emissions estimation was developed by using the concentration of suspended dust measured by the digital sensor in the LTRWP tester. LTRWP can be used as an indoor test method to evaluate pavement and tire materials to reduce the amount of dust generated from tire and pavement wear. [ABSTRACT FROM AUTHOR]

Ultrathin whitetopping (UTW) is a rehabilitation technique that consists of pouring a thin layer of concrete on top of distressed asphalt pavement. UTW has shown satisfactory performance in the field; however, due to the brittleness of concrete, early pavement failure has been reported. Engineered cementitious composites (ECC) have been considered for UTW applications due to its superior tensile ductility, flexural performance, and fatigue resistance in order to serve as an alternative to concrete. To investigate this application, an ECC-UTW was constructed at the Pavement Research Facility (PRF) in Port Allen, Louisiana. A critical factor that contributes to the performance of UTWs is the bond strength with the existing asphalt concrete (AC) layer. Therefore, prior to loading, a series of laboratory bond tests were conducted on drilled core specimens to characterize the strength of ECC/AC and concrete/AC interfaces. Two existing AC surface conditions were considered: milled and unmilled. ECC/AC and concrete/AC specimens were prepared and subjected to direct shear in accordance with AASHTO TP 114. Furthermore, the tensile bond strength was assessed through the pull-off test by ASTM C1583. Results showed that concrete had a superior bond strength with AC compared to ECC under the direct shear condition. In addition, the pull-off tests carried out in the UTW also indicated that concrete had a superior bond in tension with the AC substrate compared to ECC. Interfaces were analyzed by scanning electron microscopy–electron dispersive X-ray spectroscopy (SEM–EDS), and findings indicated a lack of hydration products at the ECC/AC interface. [ABSTRACT FROM AUTHOR]

This research explored the denitrification potential of a submerged zone incorporated into the present permeable interlocking concrete pavement (PICP) design. The following three main factors controlling denitrification were investigated through a laboratory study: (i) detention time, (ii) inclusion of a carbon source (newspaper), and (iii) submerged zone depth. The study used 10 columns, each fully packed with 50– 63 mm washed aggregate and including a 1.5 m deep submerged zone. Columns were paired according to detention time (1, 2, 5, 10 and ‘varied’ days) with one set including newspaper, the other set not. All columns were loaded with synthetic stormwater over a 4-month period. Samples were taken from different submerged depths (0, 300, 600, 900, 1200 and 1 500 mm) and analysed for concentrations of ammonia (NH3), nitrate (NO3 −) and phosphate (PO4 3−) every 10 days. This study found that 10 – or more – days detention and the provision of a carbon source had the most significant impact on denitrification – providing an overall mean NO3 − and nitrogen removal above 41% and 59%, respectively. Moreover, a submerged depth of 300 mm was sufficient to achieve a minimum NO3 − removal of 41% in columns which included a carbon source and had 10 days detention. Generally, an increase in detention time resulted in an increase in NH3 and PO4 3− removal with overall mean values of 86% and 30%, respectively, achieved with 10-day detention periods. [ABSTRACT FROM AUTHOR]

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Superload vehicles (SLs) are typically defined as vehicles having a gross vehicle weight (GVW) greater than 890 kN. SLs often consist of unique axle configurations that may cause significant damage to pavements. Research has been mainly limited to SLs on asphalt pavements, therefore the effect of SLs on concrete pavements is not well established. In this study, fatigue stresses in concrete pavements were quantified for a database of pavement structures and SLs to identify critical conditions that contribute to fatigue damage. A series of load pulses were constructed from a database of finite element results to identify conditions and locations within the slab for peak stress development. Tensile stress greatest in thin pavements with a stiff base layer and large positive temperature gradients subjected to tandem axle SLs. Fatigue damage was calculated for the critical cases using several damage models, and significant variation was found between models based on inputs used. [ABSTRACT FROM AUTHOR]

This document discusses the advancements in road engineering, particularly in road pavements and materials. The road pavement sector is gaining attention due to the high number of roads in urban and non-urban areas and the importance of road systems in infrastructure networks. Governments, agencies, and contractors are investing more in pavement engineering, especially in eco-friendly materials and structures. The document covers various topics, including the design and testing of materials, the use of recycled materials, and the management of investments and maintenance. It also explores innovative techniques such as machine learning and artificial intelligence in pavement analysis. The goal of this special issue is to provide valuable scientific contributions and promote further advancements in road engineering. [Extracted from the article]

In China, airports predominantly utilize airport cement concrete pavement, which inevitably undergoes deterioration in service. To uphold pavement durability and functionality, and ensure aircraft operational safety, prompt repairs of affected areas are imperative. Therefore, ordinary Portland cement mortars were used as the control group to compare and analyze the bonding performances of two common airport pavement repair materials: modified Portland cement mortars and phosphate cement mortars. Meanwhile, through microscopic experiments, the microscopic characteristics of the interfacial transition zone (ITZ) were studied, and the interface bonding mechanism was analyzed. The research results indicate that the interface bonding strength between phosphate cement mortar and old concrete pavement is the highest. This was because the elements in phosphate cement penetrated the old concrete pavement through hydration reactions, forming van der Waals forces and chemical bonding forces. In addition, the research results indicated that the presence of old concrete pavement made the three repair materials produce similar sidewall effects with the old concrete pavement, leading to a low hydration degree of the repair materials. However, the chemical bonding and penetrating structure of phosphate cement compensated for the weakening effect of the ITZ in the repair materials. [ABSTRACT FROM AUTHOR]

In the structure of composite pavement, the formation of voids beneath concrete panels poses significant risks to structural integrity and operational safety. Ground-Penetrating Radar (GPR) detection serves as an effective method for identifying voids beneath concrete pavement panels. This paper focuses on analyzing the morphological features of GPR echo signals. Leveraging the GprMax numerical simulation software, a numerical simulation model for void conditions in concrete pavement is established by setting reasonable pavement structure parameters, signal parameters, and model space parameters. The reliability of the numerical simulation model is validated based on field data from full-scale test sites with pre-fabricated voids. Various void conditions, including different void thicknesses, sizes, shapes, and filling mediums, are analyzed. The main conclusions of the study are as follows: the correlation coefficient between measured and simulated signals is above 0.8; a noticeable distinction exists between echo signals from intact and voided structures; signals exhibit similar phase and time delays for different void thicknesses and sizes but significant differences are observed in the A-scan signal intensity, the signal intensity, and the width of the B-scan signal; the impact of void shape on GPR echo signals mainly manifests in the variation of void thickness at different measurement points; and the relationship between the dielectric properties of the void-filling medium and the surrounding environment dictates the phase and time delay characteristics of the echo signal. [ABSTRACT FROM AUTHOR]

Direct shear strength (DSS) of the precast concrete dry joints (PCDJs) is one of the critical issues for ensuring the structural integrity and performance of the precast segmental concrete bridges (PSCBs). However, the effects of shear key configurations, such as size, shape, spacing, and number of the PCDJs, were studied within narrow value ranges and were not well considered in the widely used AASHTO formula, resulting in unconservative predictions of the formula for multiple-keyed PCDJs. This study investigated the effect of shear key configurations within wider value ranges and incorporated a reduction factor into the AASHTO formula through a newly established parametric finite-element (FE) simulation. The simulation included an automatic procedure of model generation and calculation to derive the DSS of PCDJs based on 13 input parameters of the joint and was validated by a comprehensive database including 111 DSS results of PCDJs collected from existing literature. A parametric study was then conducted on a customized joint, which allows for exploring the PCDJs with large key sizes or numbers. Finally, a reduction factor was proposed to the AASHTO formula based on the test and simulation data considering the effects of key configurations. Results demonstrate that the proposed FE simulation is able to consider the reduction effect from the key configurations and reaches an excellent agreement in predicting the DSS of PCDJs in the database with more accurate mean values (MVs) (0.95 and 0.98), higher R2 values (0.63 and 0.69), and lower root-mean-squared error (RMSE) values (1.00 and 0.79 MPa) for both single-keyed and multiple-keyed joints compared with the results of the AASHTO formula. The parametric study revealed that the ASSHTO formula becomes increasingly unconservative with the increase of key numbers. The reduction factor needs to be included in the formula when multiple-keyed or large-size keyed joints are considered. The AASHTO formula with the reduction factor leads to a conservative prediction performance in the multiple-keyed joints, which is similar to that in the single-keyed joints. [ABSTRACT FROM AUTHOR]

The presence of an impervious cover layer inhibits the free evaporation of moisture in the soil during seasonal freeze–thaw cycles, leading to a phenomenon known as the pot cover effect. This can result in severe frost heave issues in airport runways, highway subgrades, railway subgrades, and other similar infrastructure. In this study, a disease investigation was conducted at a gas transmission station situated in an area with seasonally frozen soil. Meanwhile, the causes of moisture accumulation and frost heave in the lower part of concrete pavement slabs were analyzed. A coupled water–vapor–heat model for unsaturated frozen soil is then established to analyze the formation mechanism of the pot cover effect in the subgrade. Finally, the preventive effect of the impervious layer on moisture migration in the pot cover effect was analyzed. The results indicate that the pot cover effect causes a significant accumulation of moisture beneath the concrete pavement at the gas transmission station, resulting in a moisture content increase of 5%–35%. During the freezing period, the vapor of shallow soil migrates upward, while the liquid water remains unchanged. During the melting period, both vapor and liquid water migrate downward. The laying of the impervious layer can prevent moisture migration of the pot cover effect. When the impervious layer is placed on the freezing front (0°C), the prevention effect of the pot cover effect is the best. [ABSTRACT FROM AUTHOR]

The risk of the releasing of nanometric particles from construction materials with nanometric components might be one of the biggest threats to further development of them. One of the possible ingress routes to human organisms is the respiratory system. Therefore, it is crucial to determine the risk of emission of nanometric particles during material usage. In the presented paper, abrasion of mortar samples with nanometric TiO2 was investigated. A special abrasion test setup was developed to reflect everyday abrasion of the concrete surface of pavements. In the study, three TiO2-modifed mortar series (and respective reference series) underwent the developed test protocol and the grains were mobilized from their surface due to the applied load analyzed (granulation, morphology, and chemical composition). For a comparative analysis, an abrasion parameter was developed. Based on the obtained results, the modification of cementitious composites with nanometric TiO2 contributed to a reduction in the emission of aerosols and, therefore, confirmed the compatibility between TiO2 and cement matrix. [ABSTRACT FROM AUTHOR]

Sponge city construction is an ideal approach to mitigate the degradation of urban water environments. Among road materials, permeable concrete pavement stands out due to its unique structure that allows rainwater runoff to flow through its pores. This paper analyzes the current application status and the prospect of different permeable pavement designs in China's sponge cities, aiming to offer valuable insights for urban planning and construction. Statistical analysis summarizes the spatial-temporal distribution patterns of urban flooding disasters in China and their causes. By comparing the characteristics and advantages of pervious concrete pavement with traditional concrete pavement, the potential of permeable concrete pavement in sponge city construction is summarized through case studies. The findings highlight that by adjusting the pore size, permeable concrete pavement can collect rainwater while filtering impurities, thereby purifying surface runoff. The range of the pervious coefficient should ideally fall within the range of 4~8 mm/s. In addition, the pavement's large contact area with the air and internal water evaporation contributes to its self-regulating capability, reducing the occurrence of extreme temperatures. Related experiments have shown that from 8 am to 12 pm, pervious concrete pavement can reduce the temperature by approximately 1 °C compared to conventional concrete. From 12 pm to 8 pm, this temperature difference increases to approximately 3 °C. To meet the needs of environmental protection and resource utilization, permeable concrete pavement can serve as an ideal tool to achieve green and low-carbon development. [ABSTRACT FROM AUTHOR]