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• Under tie pads have become commonly used worldwide over in the last 20 years. • Under tie pads increase contact area and reduce contact pressure at crosstie-ballast interface. • Under tie pads decrease track stiffness and track settlement. • Under tie pads increase rail and crosstie acceleration and displacement, and rail bending. • Under tie pads reduce ground-borne track vibration and track resonant frequency. Under tie pads (referred to as under sleeper pads outside the United States) are elastic components that deliver a conformal resilient layer between the crosstie (sleeper) and the ballast. Track designs for heavier and faster trains have resulted in a need for more complex systems to decrease required maintenance and improve system reliability and utilization. They have demonstrated success in delivering on these requirements and have been a topic of substantial research over the past twenty years, though no standard understanding of their performance and behavior has been achieved. With this in mind, this paper provides a comprehensive review of the state of under tie pad (UTP) research and use. It introduces UTP technology, examines the physical, mechanical, and chemical properties of UTPs as well as how material selection affects in-track performance and discusses the different uses of UTPs. Based on the literature reviewed, UTPs can provide a reduction in substructure stresses, settlements, ground-borne noise and vibration, crosstie bending demands, and increase in track lateral resistance. UTPs can also result in increased rail bending stresses and track superstructure displacements. The paper also provides recommendations for future research to fill knowledge gaps currently in the literature. [ABSTRACT FROM AUTHOR]

• Implementation of Balanced Mix Design in the United State. • Comparison and selection of performance tests. • Determination of asphalt mix proportion. • Evaluation of different asphalt mix types. • The determination and adjustment of specification. The Balanced Mix Design, abbreviated as BMD, has been widely developed in the United States to overcome the drawbacks of volumetric design methods. The definition and approaches of BMD are introduced in this paper. Engineering practices have illustrated that asphalt mix designed by BMD possesses better performance and is combined with field pavement performance. The rutting and thermal cracking tests are conventional in BMD. Besides, aging protocols and fatigue cracking tests are recommended in BMD. Then the review introduces the performance test comparison and selection, determination of mix asphalt proportion, the evaluation of different asphalt mix types, specification determination and adjustment, and extended research. The key factors in selecting the performance tests are recommended. Furthermore, when designing virgin asphalt mixes and asphalt mixes containing additives, such as the reclaimed asphalt pavement(RAP), rejuvenator, and others, the BMD is a superior method to determine the asphalt mix proportion and evaluate different asphalt mixes. The performance test specification could be determined or adjusted based on the statistics analysis, field performance, control mix performance, and correlation between different performance tests. Finally, the BMD can be integrated with the correlation between different performance indices, the pavement structure design, quality control/quality assurance, adjustment of volumetric parameters, and field pavement aging, which could contribute to constructing a more economical and durable pavement. [ABSTRACT FROM AUTHOR]

• Sheltered natural carbonation can be similar between different climates. • Huge impact of curing on natural carbonation for very early age (i.e. 1 day) • Impact of curing is negligible for advanced curing age, regardless of cement type. • Strong impact of precipitation on natural carbonation. • The higher the number of rainy days, the lower the carbonation speed. This paper describes a unique international inter-laboratory study on the carbonation resistance of concrete prepared with different supplementary cementing materials. Concrete specimens – from 45 different concrete mixtures – prepared centrally in Lafarge Centre de Recherche (France) were shipped in a sealed condition to 4 other academia research laboratories (located in USA, Canada, India and China). The specimens were exposed to the ambient environments and atmospheric CO2 concentrations in the five locations, including Lafarge Centre de Recherche in France, in both sheltered and unsheltered condition for a period of 5 years. Measurements of carbonation depth were performed at periodic intervals, and the data was analyzed to assess the influence of climatic conditions on the resistance to carbonation. The results indicate that the general trend of carbonation is not much different irrespective of the macroclimate. Further, the number of rainy days seems to have a more significant influence on the progress of carbonation than the total rainfall in the region. [ABSTRACT FROM AUTHOR]

Highlights • Summary of current knowledge on recycling agents (rejuvenators) and their application. • Identification of current and future challenges that prevent utilization of recycling agents. • Evaluation of recycling agents effectiveness in binder blends and asphalt mixtures. • Characterization of rejuvenated binder blends and rejuvenated asphalt mixtures. • Cost-effectiveness associated with the use of recycling agents. Abstract Recycling agents, or rejuvenators, are products with chemical and physical characteristics designed to restore the rheological properties of aged asphalt binders to improve the performance of recycled asphalt mixtures with large quantities of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) that promote economic and environmental benefits. This paper summarizes current knowledge related to the use of recycling agents in the asphalt pavement industry, including properties of recycled and rejuvenated asphalt mixtures. This information is further used to identify current and future challenges that could prevent utilization of recycling agents and production of rejuvenated asphalt mixtures with adequate performance. [ABSTRACT FROM AUTHOR]

Abstract Ballast deterioration, under dynamic loads, remains an important issue on high-speed tracks that can lead to high maintenance costs. This ballast deterioration leads to settlements. Several studies have shown that these settlements were linked to high accelerations produced in the ballast by high-speed train (HST) passages. The solution with bituminous underlayment was used since 1980s in several countries like United States, Italy, Spain, especially on high-traffic and high-speed lines (HSL). In France, the interest in this technique is recent. Following the East European HSL satisfactory behavior, a layer of asphalt concrete was used under the ballast layer of the Bretagne-Pays de la Loire (BPL) HSL. It is intended, in addition to the schedule savings and the protection of the subgrade during the construction phase, to reduce acceleration amplitudes produced at the passage of HST, to ensure moisture stability in the subgrade and thereby to decrease the maintenance costs of the tracks. BPL HSL includes 105 km of innovative track with an asphalt concrete (GB) ballast sublayer, and 77 km with a granular layer under the ballast (UGM). Out of the instrumented sections of the BPL track, 3 sections are constructed with GB subballast layer and one with a layer of UGM as a subballast layer. A total of 127 sensors that includes accelerometers, anchored displacement sensors, temperature and humidity probes, and extensometers are used. Sensors are placed at various positions and depths in the track structures. Data were first acquired during a speed up test phase, under controlled conditions, with the same train passing at speeds ranging from 160 to 352 km/h. This paper presents the different sensors used for the instrumentation as well as the acquisition system installed to collect all measurements. Data treatment and processing is explained in details. Finally, results obtained for different speeds are presented, with a focus on accelerometer and anchored displacement sensor measurements, on two sections, allowing, among others, comparisons between the response of structures with and without asphalt concrete. The role of the GB, as a subballast layer, in damping the vertical displacement of the sub ballast structure and reducing the accelerations peaks in the ballast layer for ballasted tracks is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Studies on two novel uses of hybrid structural members consisting of commercially produced glass reinforced pultruded ribbed fiber reinforced polymer (FRP) planks and concrete are discussed in this paper. Pultruded planks are produced by all the major pultruders in the world and are utilized primarily as decking for platforms. These highly optimized panels have the potential to be used in many other infrastructure applications, but their flexural stiffnesses have generally been too low to be used in highway and pedestrian bridges due to current span requirements. However, when used “compositely” with concrete or cementitious materials in a hybrid form they have the potential to be much more widely used. Two research studies conducted on two possible hybrid systems of different structural depths are discussed in this paper. The first study describes the use of pultruded planks as permanent formwork in highway bridge decks where the plank is used with concrete to produce a solid slab of 200mm depth that is typical of slabs seen in highway bridge decks. The second study describes the use of pultruded planks in pedestrian bridge decks where the pultruded plank is used with a cement-board or a cast-in-place concrete panel to produce a hollow slab of 75mm depth that is typical of timber decking used in FRP pedestrian bridges. Tests were conducted on beam-type specimens of the hybrid slabs to investigate the load transfer mechanisms between the pultruded plank and the cementitious “overlays” for both the 75mm and 200mm depths. From analysis of the load-carrying capacity and failure mechanisms of the hybrid slabs it was concluded that such hybrid slabs are viable systems for both highway and pedestrian bridge decks. A bridge deck using the 200mm deep hybrid slab system was recently constructed on a highway in Wisconsin, USA. [Copyright &y& Elsevier]

• A data-driven framework is proposed for estimating the risk of track geometry defects. • More influencing factors are considered, such as multiple substructure conditions. • Data resampling including undersampling and oversampling are implemented to solve the imbalanced data issue. Analyzing the relationship between track geometry defect occurrence and substructure condition can provide assistance for track inspection and spot maintenance, which contributes to better train operation quality. This paper develops a data-driven approach to estimate the occurrence of track geometry defects on concrete-tie tracks on one passenger railroad in the United States, using substructure data, rail seat abrasion data, infrastructure data, traffic data, track class information, and maintenance data. Feature extraction was implemented to generate input variables for the machine learning models. Recursive feature elimination (RFE) was applied to reduce data dimensionality by recursively considering smaller sets of features. Three data treatment methods, including no resampling, undersampling, and oversampling, were incorporated to address imbalanced data issues. The developed models included logistic regression, artificial neural network, and gradient boosting. The hyperparameters of the proposed models were optimized using Bayesian optimization. The performance of the proposed methods was finally evaluated based on the test dataset generated using random data partitioning. Based on data collected from one passenger railroad, the gradient boosting method with data oversampling shows the highest performance in estimating the occurrence of geometry defects. The F1-score of the model is 0.662, with G-Mean of 0.738. Feature importance identifies that surfacing, traffic, curvature, switch, and rail replacement are the top five factors influencing the predicted probability of track geometry defect occurrence. The proposed model can be used to prioritize maintenance activities on locations prone to track geometry defects and thus further improve infrastructure safety given budgetary constraints. [ABSTRACT FROM AUTHOR]

Approximately 6–10 million tons of waste is produced annually by the ferrous and non-ferrous foundry industry in the United States and estimates have shown that only 15% of the waste produced is being recycled. The increasing scarcity of landfill space and disposal cost has fashioned a need for an alternative disposal method of this large industrial waste. Foundry waste can consist of many products such as used-foundry sand, slag, ash, refractory, coagulant, baghouse dust, pattern shop waste, and debris. Past researchers have presented an alternative disposal method by using spent sand and slag as constituents in concrete with positive results. This paper generalizes the foundry waste for use in Portland Cement Concrete (PCC) in order to increase the recycling percentage, by reducing processing time/cost and using all the waste produced by the foundry industry. This was done by partially replacing both fine aggregate and coarse aggregate of concrete with lightly processed foundry waste. Since foundry waste contains both fine and coarse materials, the as-received foundry waste was lightly processed and sieved to match the control concrete mixtures coarse and fine aggregate distribution. Both virgin coarse and fine aggregate were replaced by mass at 10%, 20%, and 30%. Two mixture groups replaced individual constituents separately (coarse and fine), and one mixture group replaced both coarse and fine in the same mixture. The compressive strength, splitting-tensile strength, flexural strength, and modulus of elasticity were measured for all groups at 7, 14, and 28 days. The results indicated that general foundry waste as either coarse, fine, or combined by mass replacement of natural aggregate has no impact on the mechanical performance of PCC up to 30% for individual replacement or 20% combined. This result not only demonstrates a possible avenue to increase the amount of foundry waste recycled annually, but it also reduces the demand for virgin aggregates for PCC. [ABSTRACT FROM AUTHOR]

Grout is widely used in bonded post-tensioned bridge construction as an anti-corrosive material for protecting the steel strands. Several occurrences of tendon failures in U.S. bridges, however, have led to an interest in unbonded tendons where a flexible filler, such as wax, grease, or gel, is injected into the tendon duct instead of cement grout. In general, the consistency of these flexible fillers in ambient temperature falls within the realm of semi-solids and, thus, they are not readily injectable without preheating. A major concern with flexible filler injection is, therefore, maintaining an adequately elevated filler temperature to keep the material’s viscosity sufficiently low for complete filling of the duct and to avoid a blockage that might result in a burst pipe or duct. This paper presents a simplified heat transfer model that computes the decrease in temperature of the moving filler front during injection as it cools while interacting with the surrounding strands and duct. The proposed model has been validated by multiple mockup experiments conducted with different filler materials and injection rates. A comprehensive parametric study has been conducted to determine the sensitivity of the filler front temperature to several practical factors, such as effective strand surface area, tendon length, injection rate, ambient temperature, injection temperature, and number of strands in a tendon system. The required minimum injection pressure for different flow velocities and tendon lengths has also been determined. The experimental results confirm the model’s applicability to a wide range of tendon lengths and strand patterns, and its usefulness in determining tendon constructability. [ABSTRACT FROM AUTHOR]

Permeable Friction Courses (PFC) are asphalt mixtures characterized by high air void contents that are used as surface layers in conventional pavements, principally to achieve safer roads and control noise pollution. This paper summarizes existing information related to the performance of PFC mixtures in the United States (US), including properties of the mixture that determine the durability and functionality of the pavement and mix design methodologies that are currently being used in the US. The objective of this work is not only to analyze this information but also to identify current and future challenges to enhance the performance of PFC mixtures and promote its responsible use. [ABSTRACT FROM AUTHOR]

• Material characterization of ABC-UTC emerging NP-UHPC mix. • Conduct flow, compression, tension, and flexure tests on five different NP-UHPC mixes. • Investigate effect of material sourcing and variability (fine aggregate types/particle gradation) • Provide full stress–strain relationships for modeling purposes. • Assess validity of existing mechanical behavior equations for NP-UHPC. Accelerated bridge construction (ABC) field joints, e.g. precast deck panels joints, are among the common structural applications of ultra-high performance concrete (UHPC). The higher cost and limited availability of commercial UHPC products have motivated researchers to develop non-proprietary UHPC (NP-UHPC) using locally available materials. One of these efforts is the recent work by the ABC University Transportation Center (ABC-UTC) in the United States to develop NP-UHPC mixes for use in ABC field joints. This paper documents the ABC-UTC mix design and proportions and has two main objectives. First, provide a full material characterization of such mix to allow for future replication and use of this material for different bridge applications as well as modeling purposes. Second, investigate the effect of material sourcing and variability, such as fine aggregate types and particle gradation, on the main mechanical properties of the material. The material characterization tests included flowability, compression, flexure, and direct tensile tests of the NP-UHPC mixes. The results from these tests are then compared with various proposed equations from the literature to verify their validity for use with the considered NP-UHPC mixes. [ABSTRACT FROM AUTHOR]

Abstract: Many transportation authorities in the United States and Canada require condition assessments of concrete bridge decks and roadways as part of scheduled rehabilitation and maintenance programs. Nondestructive test (NDT) methods and laboratory studies are commonly used by engineering consultants to perform these evaluations. Amongst typical NDT methods, ground-penetrating radar (GPR) is one of the best suited to accomplish this task. Unfortunately, reported test results are oftentimes ambiguous, due to the current numerical analysis approach to evaluate the data. This paper describes some of the shortcomings of numerical analysis of GPR profiles and it introduces an alternative method developed by the authors. Several examples of actual field investigations are described, where the computer-assisted visual interpretation of GPR profiles was used to validate and eventually improve this new analysis approach. The authors’ project experiences on several structures indicate that mapping defects by visual identification of corrosion-induced anomalies in concrete is a much more accurate way of mapping defects. The results obtained from the field applications suggest that use of the computer-assisted visual interpretation of GPR data is an efficient and reliable approach that can be used by experienced GPR analysts. [Copyright &y& Elsevier]

Abstract: Using increased proportions of Reclaimed Asphalt Pavement (RAP) in asphalt pavements construction has become a top priority due to significant economic and environmental benefits. A similar trend has also emerged in Recycled Asphalt Shingles (RAS), which represent the main roofing material in US. In this paper, the effect of adding RAP and RAS on low temperature properties of asphalt mixtures is investigated using microstructural analysis and modeling of rheological data obtained on eight asphalt mixtures. Detailed information on internal microstructure of asphalt mixtures is obtained from digital images of asphalt mixtures beams and numerical estimations of spatial correlation functions. It is found that that microstructure spatial distribution is not affected by RAP and RAS addition. Mechanical analog (Sharpe, 2008 ) and semi empirical models are used to back-calculate binder creep stiffness from mixture experimental data. Differences between back-calculated results and experimental data suggest blending between new and old binder may be only partial. [Copyright &y& Elsevier]

Abstract: The high shear capacity of ultra-high performance concrete (UHPC) AASHTO Type II girders tested at the Federal Highway Administration labs resulted in interest by state highway agencies in applying UHPC in bridge construction. UHPC superior shear capacity results from the random steel fibers incorporated in the mix. However, steel fibers significantly increase the mix material cost (fibers cost $400 per cubic yard). This paper presents a study to compare the structural efficiency and economical feasibility of replacing random steel fibers with grade 80 welded wire reinforcement meshes. Two AASHTO Type II girders were fabricated using non-proprietary UHPC mixes developed at the University of Nebraska – Lincoln and reinforced with WWR in replacement of steel fibers. The test results showed that WWR resulting shear capacity exceeds random steel fibers. The WWR cost effectiveness and ease in construction could accelerate the application of non-proprietary UHPC and WWR in bridge construction. [Copyright &y& Elsevier]

Abstract: Reclaimed asphalt pavement (RAP) comprises one of the largest recycled materials, and warm mix asphalt (WMA) technologies become more commonly used due to their promising advantages in the United States and Europe. This paper addresses the laboratory investigation of performance properties of WMA binders containing aged binders. The recycled binders with the additives were produced using two (i.e., zeolite Aspha-min® and wax Sasobit®) of the available warm asphalt processes. The recycled WMA binders were artificially short-term and then long-term aged through the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study indicated that (1) the additives and aged binders played an important role in determination of the binder properties; (2) the use of lower PG grade as a virgin binder (PG 58-28 in this study) was critical on offsetting the increase of binder stiffness caused by the addition of WMA additives and aged binders; and (3) even at the low recycling percentage of 15%, the lower PG grade was needed to get the results meeting current Superpave binder requirements. [Copyright &y& Elsevier]

Abstract: The objective of this study is to evaluate the effect of mix gradations associated with the Superpave restricted zone on rutting potential specifically for low traffic volume roadways. Although the elimination of the restricted zone requirement in Superpave mix design is highly recommended, some questions still remain unanswered as the research conclusions supporting the elimination of the restricted zone were largely made for medium to high traffic volume roadways, where aggregates are highly crushed and of good quality. The applicability of such research conclusions based on high traffic volume mixes needs to be verified for low volume mixes because many states in the US use non-crushed local aggregates for low traffic volume pavements, which might be related with aggregate gradation. This paper summarizes the research findings obtained from a systematic approach consisting of (1) statistical analyses of pre-existing data accumulated for quality assurance purposes, (2) experimental investigations based on the statistical analysis results, and (3) in-field investigation of the rutting performance of low traffic volume pavement. The comparison and analysis results indicate that similar to that for medium to high traffic volume pavements, the restricted zone is not a controlling factor affecting hot-mix asphalt rutting performance for low traffic volume local pavements. The fineness of aggregate gradation rather than the restricted zone seems to be a factor that affects rutting performance. [Copyright &y& Elsevier]

Abstract: There is currently 123 million tons of coal combustion by-products produced in US each year. Among these include fly ash, bottom ash, boiler slag, and flue gas desulphurization material. Of that approximately 40% are utilized as a construction material in cement manufacturing, roadway construction, and others. However, the utilization of some ashes such as those produced by fluidized bed combustion has been limited due to their inherent high sulfate and carbon content. This paper is aimed at the evaluation of the potential use of stockpiled circulating fluidized bed combustion ash (SCFBCA) to develop compressed earth brick (CEB). Laboratory tests were conducted to determine the physical, chemical, and mineralogical properties with respect to SCFBCA. A series of tests were carried out to evaluate the properties of the bricks related to filler and binder types on compressive strength, density, and absorption. Test results indicate that SCFBCA can be used to manufacture CEB. Subordinately, test results may provide a means to reduce a waste disposal problem while providing the brick industry with a new, useful, low cost raw material. [Copyright &y& Elsevier]

Abstract: Concrete pavement joints are cracks intentionally formed in the pavement to accommodate expansion and contraction due to temperature changes. Today, 98% of the agencies building and maintaining concrete roadways, and 100% of the agencies building and maintaining concrete airport pavements in the United States require the sealing of these joints for new pavements. There are two major reasons for sealing rigid pavement joints. The first is to reduce the amount of water infiltrating the pavement structure, which results in slab erosion and loss of support. The second reason is to minimize the entry of incompressible materials into the joint reservoir, resulting in point loading when slabs expand under hot temperatures and subsequent joint spalling damage. Another reason for sealing rigid pavement joints is to reduce the potential for dowel bar corrosion by reducing entrance of de-icing chemicals. The proper sealing and maintenance of concrete pavement joints thus seems to be essential for the overall performance of the rigid concrete pavement. This paper seeks to find out the factors that affect sealant life and performance and how to mitigate these to improve performance and reasonably extend sealant and thereby pavement life. [Copyright &y& Elsevier]

Abstract: The Northridge earthquake (near Los Angeles, CA, USA, January 17, 1994) and the Tecomán–Colima earthquake (near Manzanillo, México, January 21, 2003) have increased our knowledge of the behavior of masonry buildings in significant earthquakes, and also have led to changes or proposals for changes in US masonry design provisions. In this paper, the masonry code-development process in the US is briefly reviewed, with emphasis on the fundamental role of the Masonry Standards Joint Committee (MSJC). The Northridge and Tecomán–Colima earthquakes are discussed, with emphasis on the behavior of modern engineered masonry. Lessons learned from those earthquakes with regard to masonry are summarized, and the related evolution of MSJC design provisions for the US is discussed. [Copyright &y& Elsevier]