Tran-SET 2020

Over the last decade, safety and sustainability issues are regarded as important elements of transportation systems. Preservation of natural resources and utilization of renewable energy resources are influential factors to sustainability and in certain cases would lead to safety improvement. Energy harvesting from roadways has demonstrated a great potential to generate electrical power for roadway networks. The electromagnetic technology is known as one of the most promising implemented technologies in field of energy harvesting. In this study, an electromagnetic energy harvesting device is introduced, which utilizes linear generator mechanism. The harvester prototype is designed to be similar to a speed bump. Laboratory experimental tests were conducted to examine the performance of the device in terms of generating power. A universal testing machine (UTM) was used to simulate the traffic loading conditions. Results demonstrate that the device can generate output power of 81 mW. Regarding the small parts employed in the device at this stage of design, the output power is considerable. The achieved output power is sufficient to operate sensors and LEDs in roadways. The resulting illumination by the LEDs will be useful for promoting safety in roadways in addition to speed control feature of the device. In addition, the embedded sensors can monitor the traffic and pavement structural condition continuously. Continues monitoring provides useful data for both pavement and traffic management and structural analysis of the pavement under environmental and traffic conditions.

Solar energy is undoubtedly recognized as an unlimited and environmentally friendly energy resource. Harvesting energy from road infrastructure is an emerging renewable energy technology that collects and utilizes the otherwise wasted energy of heated pavements. Solar radiation can be absorbed by asphalt pavement causing an increase in the temperature of asphalt pavements. This paper describes the operation, design, and performance of an efficient system installed within pavement that captures the heat energy from the temperature differential between the pavement surface and the subgrade soil. The designed prototype includes a thermoelectric generator, coolant module, heat collector, and conductor. Experiments and numerical simulations were conducted to evaluate the efficiency of the system in producing electrical power within different environments. The results revealed that the generated power from the tested asphalts can be used for long-term self-powered applications such as LED traffic lighting, wireless monitoring systems, and near-field data communications.

There is an immense amount of activity surrounding connected and automated vehicle (CAV) technology deployment. This paper briefly reviews the main research, administrative, and legislative initiatives Louisiana has taken in preparation of these technologies. To encourage wider participation in these activities, a brief electronic survey was developed and disseminated to 273 Louisiana organizations. The purpose of the survey was to initially engage these organizations under the context of CAV planning and gauge their awareness, perception, and viewed importance of planning for CAV technologies. 117 participants completed the survey. Low awareness and perception by economic development, freight, and transit organizations—coupled with low levels of perceived importance of planning by freight and transit operators—indicate areas of concern. Wide variability in which organizations are currently preparing for CAV technologies—including the low percentage reported by state agencies (21.1%), local agencies (15.8%), and nonprofits (8.3%)—is also a potential concern.

The performance and maintenance of an infrastructure asset depend on the stability of adjacent structures. In this study, rail line passing through rock cut is selected to analyze the stability of the rock slopes. Generally, two-dimensional slope analysis is used to evaluate the stability of slopes owing to its simplistic and widely used approach. Three-dimensional understanding of the slope behavior is necessary to estimate the factor of safety of slopes with complex geometry. Method of columns which is an extension of method of slices, considered for most two-dimensional analyses, was used in this study to conduct three-dimensional stability analysis which requires comprehensive slope geometry data. Limitations of present traditional methods arising out of their inability to access hard-to-reach areas on the steep rock slopes have created a need for adopting new technologies. The advancement in lightweight compact sensors complimenting the robust unmanned aerial platforms have found their applications in remotely conducting qualitative and quantitative assessments of infrastructure assets. The research presented in this study discusses an approach that involves the use of aerial platform coupled with close range photogrammetry techniques to collect comprehensive rock slope data. Three-dimensional stability analysis using commercially available software was conducted by using generalized Hoek-Brown (HK) failure criterion to represent the true failure envelope of rock mass. The global minimum factor of safety of the surfaces on the rock slope was identified using Morgenstern-Price stability analysis method. This approach has resulted in significant savings in data collection time and cost, but also provided comprehensive idea about the stability of rock slopes for a given set of material properties.

Crack sealing in asphalt concrete (AC) overlays is an important component of pavement preventive maintenance. The objectives of this study were to evaluate the cost-effectiveness of crack sealing applied on AC overlays (flexible and composite) in Louisiana considering the pre-treatment overlay conditions and to determine the optimal timing of crack sealing. To achieve these objectives, AC overlay, crack sealing, and chip seal projects in Louisiana were identified for data collection. Based on the data collected, the equivalent annual cost (EAC), life-cycle cost analysis (LCCA), and cost-effectiveness (CE) approaches were employed to identify the optimal timing of crack sealing. Additionally, a case study was considered including five different alternative strategies for which the LCCA was calculated to identify the optimal long-term strategy as well as the corresponding optimal timing of this strategy. The results of the cost-benefit analyses for the field projects and case study were compiled and analysed to provide the final recommendation for crack sealing. Results indicated that the cost-effectiveness of crack sealing is optimum when the pre-treatment overlay condition ranges between 81 and 89. When the pre-treatment overlay condition exceeds 90, crack sealing should not be applied. Based on the results of this study, a series of automated excel spreadsheets were developed to allow the user to predict the cost-effectiveness and optimal timing of crack sealing knowing the project conditions and costs without the need for additional calculations.

In Louisiana and many other states, the design pavement service life (PSL) for structural asphalt concrete (AC) overlays is typically assumed 20 years. However, research studies showed that the actual pavement service life is rarely monitored. The objective of this study was to assess the field performance of structural overlays in Louisiana and to estimate PSL under field conditions. Considering all the distresses, about 75% of the projects had a pavement service life less than 20 year and the mean PSL for all the projects was 17±6 years. This suggests that the overlay thickness designed with the 1993 ASSHTO procedure using a pavement service life (PSL) of 20 years may not last the entire design period without additional maintenance activities. Results also showed that random cracking, followed by rutting, were the primary causes of long-term failure in the evaluated projects. A methodology was developed to adjust the designed overlay thickness by the AASHTO 1993 design procedure such that the actual PSL matches the design PSL. This methodology included the development of an extreme gradient boosting (XGB) classification model to predict PSL with an acceptable level of accuracy based on sensitivity, accuracy, and specificity. This approach may be used by transportation agencies in the planning phase of future maintenance and rehabilitation activities and in the design phase of AC overlays. This would also ensure adequate allocation of maintenance and rehabilitation funds by a state agency.

A framework for estimating the damage caused by flooding on a road or street network is presented. The framework includes the development of evolution models for each road section in the network for two pavement performance indicators, the pavement condition index (PCI) and the international roughness index (IRI), using performance data recorded on the section before the flooding. Then the damage caused by flooding, directly through the increase moisture in foundation layers or indirectly due to the increase heavy traffic during the relief effort is estimated by comparing the predicted and measured condition indicators for each road section. The framework estimates the increase in pavement rehabilitation costs to the road administrating agency, the increase in fuel consumption and gas emissions for each road or street section and for the entire network. The framework can also be used to determine the pavement structural configurations and material most affected and thus more vulnerable to flooding. The framework can also be employed for quantifying the effects of natural disasters other than flooding.

Silty soils originally found onsite or borrowed can be problematic in nature particularly in its liquefied state and this may affect the service life of any pavement layer. Cement stabilized soil, using ordinary Portland cement (OPC), is traditionally utilized to stabilize such soils to enhance its strength. Clearly, several environmental issues have stemmed from the use of OPC wherein a more sustainable material with a low carbon footprint has generated lots of interest in present climes. In recent decades, fly ash has become more abundant in nature solely because of its constant disposal as a byproduct from industrial plants. However, when mixed with soil under alkali activation, it tends to form geopolymers and this has been studied to be at par or greater in strength than cement stabilized soil (CSS) and other chemical stabilizers. Therefore, this research proposes the use of fly-ash-based geopolymer with recycled concrete aggregates (RCA) as a stabilizer for sandy silt road base material. A low calcium fly ash was applied on sandy silt soil to obtain an effective mix that would enable soil to be stabilized for road base use. The fly ash-based soil geopolymer specimens were tested for unconfined compressive strength (UCS), resilient modulus (Mr), durability, and indirect tensile strengths. Results have shown geopolymer-stabilized sandy silt soil to have greater improvements in strength and durability as compared to CSS.

The moisture condition in the pavement subgrade is critical because it directly affects the strength and stiffness of the pavement structure. Subgrade soils are usually unsaturated, and the resilient modulus of the subgrade soil is highly dependent on the degree of saturation and the corresponding matric suction. Past studies showed that the equilibrium suction has a direct influence on the strength and stiffness of pavement systems. Hence, an accurate estimation of equilibrium suction underneath pavement structures is critical for determining the long-term resilient modulus of subgrade soil, which is further used to predict pavement performance. In this study, a mechanical-empirical model was developed based on the Mitchell 1980 model to predict suction variation within subgrade soil. The proposed suction variation model predicts the suction distribution throughout the soil subgrade by solving the diffusion equation and incorporates the measured suction from the Oklahoma Mesonet weather stations to estimate the diffusion coefficient. The research study resulted in a practical and implementable tool for pavement engineers in predicting site-specific moisture variations underneath the pavement within the moisture active zone in response to wetting and drying weather cycles. The proposed model was tested, and the results were compared with the predicted values from the well-established climatic model in the literature.

Sinkholes pose a severe threat to transportation infrastructure. Therefore, being able to accurately detect and map existing sinkholes is very important for transportation infrastructure risk management, and ultimately, leading to more informed planning of transportation infrastructure and public safety. Traditionally, sinkholes are primarily detected through area reconnaissance method, which is expensive, time-consuming, labor-intensive, and potentially dangerous to the inspectors. To overcome these challenges, this study explored the utility of airborne LiDAR in detecting and mapping existing sinkholes. Using airborne LiDAR point cloud as the input, digital terrain models were created and used to develop preliminary sinkhole maps. Then object-based image analysis techniques were used to delineate sinkhole boundaries to create final sinkhole maps. Additionally, auxiliary context information was used to further improve the final sinkhole maps. Results revealed that the practical workflow developed in this research can be effectively used to detect and map existing sinkholes from airborne LiDAR data.

The movement of water plays a critical role in the mechanical performance and service life of transportation infrastructure, especially for pavement subgrades and highway embankments consisting of high-plasticity, expansive soils that saturate and ultimately lead to infrastructure distress. Shallow slides along highway embankments are ubiquitous across Region 6 because long-term wetting and drying cycles considerably weaken these compacted soils. In the aftermath of heavy rains, pore-water pressures increase to a critical threshold such that a failure occurs. The implications of embankment failures range from repeated maintenance repairs to long-term road closures. A comprehensive approach to model highway embankments comprising of laboratory testing, setup, and field data collection using unmanned aerial vehicles have been proposed in this study.

Coastal bridges are prone to failure during extreme hurricane events. Engineers can prevent failures of coastal bridges during extreme hurricanes by ensuring that wave forces do not exceed the structural capacity of the bridges. To understand the performance of bridges in coastal areas during hurricanes, empirical equations have been applied to several bridge decks in Louisiana by assuming different hydrodynamic conditions. Several plots were created to illustrate and compare the uplift and horizontal forces on bridge decks provided by these three sets of equations. The analysis demonstrated that the maximum vertical force during a hurricane event could potentially cause uplift of the superstructure. The equations predict that when the superstructure is partially or fully submerged, the uplift forces can exceed seven times the weight of the superstructures and the horizontal forces could reach up to 35% of the weight of the superstructures. Further work is required to determine the accuracy of these equations when the water level is higher than the lower chord of the girders of the superstructure.

Cracks at the pole-to-base plate connection of high mast illumination poles (HMIPs) are a major source of concern to highway transportation officials. Thermally induced deformations induced during the galvanizing process are known to introduce damages to the pole-to-base plate connection. In this study, finite element analyses were performed to evaluate the effects of geometric configuration variables on the response of the HMIPs during galvanizing, particularly in determining the stress demand magnitudes. The control variables of the study were base plate thickness, pole shaft wall thickness, and number of pole sides. The numerical results indicated that the stress demands were highest at locations near the pole-to-base plate connection. Reducing the base plate-to-pole thickness ratio and using poles with round shape were identified as effective approaches to reduce stress demands in HMIPs during galvanizing.

The study of the vulnerability of coastal bridges due to wave impacts through numerical methods requires the correct generation of nonlinear, long-period waves at shallow water conditions. In this paper, waves are generated using the first-order wave theory based on the “Lagrange-plus-remap” finite element method. The free surface elevation was obtained as a function of space and time. The accuracy and the stability of the generated waves, and the boundary condition effects on the results were analyzed in this study. The generated wave has been observed to slightly deviate from the analytical solution in terms of amplitude and phase. The outlet surface has been observed to cause wave reflections that affect the profile of the incoming waves. A Fourier analysis revealed that initial disturbances dissipate as the wave progresses, making the generated wave stable.

This study examined the effect of a new generation of light-activated self-healing polyurethane prepolymer on self-healing and mechanical performance of asphalt mixtures. This new modifier was designed to enhance the performance of the asphalt pavement while increasing its crack healing rate. Modified asphalt binder was produced using an optimized reactive method. Asphalt mixtures were prepared using three different percentages of self-healing polymer (5%, 10%, and 15%). Prepared samples were tested using semi-circular bending test, loaded wheel tracking test, and crack healing test. Furthermore, asphalt binder was extracted and tested using a dynamic shear rheometer. Results obtained from self-healing tests demonstrated an enhanced crack sealing rate with the addition of SPP, however, using 15% SPP can lead to loss of cohesion and strength of the asphalt mixture. Furthermore, an increased rutting resistance at high temperature and improved cracking resistance at intermediate temperature was observed with the addition of 5% SPP. A further increase in the percentage of SPP may have negative effects on the cracking performance due to loss of strength and cohesion.

The primary objective of this study was to observe any changes in asphalt binder spectra due to modification at different aging conditions. A performance grade (PG) binder (PG 64-24) was modified with different dosages and combinations of PPA (polyphosphoric acid), styrene-butadiene-styrene (SBS), and nanoclay. This analysis was able to detect changes in certain functional groups due to aging. After simulating aging on asphalt binder samples, aromatic index ratios were observed to increase, whereas the aliphatic index ratio decreased. Moreover, reactions that occurred during the aging process caused significant increases within the aromatic index (C=C) and carbonyl index (C=O). Observations made from this analysis led to the conclusion that nanoclay modification might cause changes within the chemical fractions to enhance mechanical properties of asphalt binders, whereas the addition of PPA might have changed the polarity of one or more chemical fractions after the modification. In the case of SBS modification, the emergence of the new peak indicates the existence of a new functional group. Finally, it was evident that changes within the functional groups that occurred due to any modification or aging from the spectroscopic analysis can establish the FTIR spectroscopy as a quick tool to observe changes in the chemical fingerprint of asphalt binders.

The durability of the asphalt pavement can be seriously affected due to the aging of the asphalt binder over the service life of the pavement. The main goal of this study is to evaluate the performance of asphalt binders through nanoscale measurements under various aging conditions. Binders used in this study include two performance grade (PG) binders (PG 64-22) along with their modified counterparts. These binders were prepared from two different crude sources. The atomic force microscopy (AFM) technology was utilized to quantify the microscopic rheological and mechanical properties of the asphalt binders. To verify the test results, the macro-level dynamic shear rheometer (DSR) and the rotational viscosity (RV) tests were also conducted on these asphalt binder samples. Three different aging conditions (unaged, short-term aged, and long-term aged) of the binders were considered in this study. The AFM test results revealed that the microstructures presented on the binder’s surface were dispersed and/or reformed due to aging, which can seriously affect the mechanical properties (e.g., modulus, and adhesion). The AFM-based test results also showed that the molecular-level modulus and adhesion increased, whereas the deformation decreased due to the aging of asphalt binders, irrespective of the crude source. The DSR and RV test results supported the findings of the AFM-based test results. The findings of this study can help the pavement professionals and highway agencies to have a proper insight into aging influence on properties of the asphalt binders.

Reflective cracking is common distress when hot-mix asphalt (HMA) overlays are constructed on top of a pre-cracked base. Cracks on existing base gradually propagate upward because of traffic loading and/or temperature variation, reach surface course, and result in reflective cracking. Previous studies demonstrated that Texas Transportation Institute overlay tester (OT) could effectively simulate the effect of temperature variation, which is considered as the leading mechanism causing reflective cracking in the field. In this study, the effectiveness of using the OT test setup to mimic the field and evaluate the performance of various HMAs against reflective cracking is assessed based on various aspects found in the literature. It was concluded that OT is the most suitable equipment to study thermally induced reflective cracking in the laboratory. Additionally, potential modifications to improve the OT setup is proposed, which is expected to provide a more representative performance evaluation of mixtures against reflective cracking.

Nowadays, reclaimed asphalt pavement (RAP) is becoming more popular in producing new asphalt mixtures since it is a cost-effective and environmentally-friendly approach. However, there are some negative impacts of using RAP in new mixtures, especially with high RAP content. Previous studies show that the mixtures containing high RAP content have poor fatigue and cracking performance. Warm-mix asphalt (WMA) technologies are used to counter the negative effects of RAP on cracking resistance of asphalt mixtures. In this paper, the current specifications used in the south-central states (i.e., Arkansas, Louisiana, New Mexico, Oklahoma, and Texas) and previous regional studies conducted on the use of RAP and WMA technologies are discussed. Based on these specifications, an overview of the challenges and limitations of producing mixtures containing high RAP content and WMA technologies is presented. The objective is to identify deficiencies that currently exist in these specifications toward the implementation of these technologies.

Stripping or moisture-induced pavement distress has been recognized as one of the major problems to most state Departments of Transportation (DOTs) and highway agencies. It is believed that the poor compatibility between asphalt binder and aggregates is one of the prominent reasons behind stripping. This study aims to analyze the compatibility of selected asphalt binders and aggregates used in Arkansas. Asphalt binders used in this study include two performance grade (PG) binders (PG 64-22) from two different sources along with their modified counterparts. Additionally, the Arkansas Department of Transportation (ARDOT) approved four different types of aggregates (sandstone, limestone, gravel, and dolomite) from four different sources to be evaluated in the laboratory. The surface free energy (SFE) measurements of these binders and aggregates are being estimated by using an optical contact angle (OCA) analyzer. The SFE data are then used to determine the compatibility between the asphalt binders and aggregates. The findings of this study are expected to help pavement researchers and highway professionals to find suitable asphalt binder-aggregate combinations in constructing the durable pavements.

In this study, two commonly used emulsion recovery methods (beaker method and thin-film 2-day method) have been compared based on polymer degradation. The performance of polymer modified asphalt emulsion has been determined based on the ductilometer-based force ductility and recently introduced dynamic shear rheometer (DSR)-based extensional deformation test parameters. In the case of the force ductility test, the second peak force, F₂, indicates polymer characteristics. In the case of the extensional deformation test, the second peak force, F₂, detects the presence and quantifies the amount of elastomeric polymer in asphalt binder and emulsion. It was hypothesized that the lower the F₂ value, the higher the polymer degradation. Three polymer-modified asphalt emulsions (CRS-2P, CHFRS-2P, and PME) were tested. The thin-film 2-day residue recovery method exhibited lower F₂ value than the beaker method which, indicated the polymer network was damaged more during the thin-film 2-day residue recovery method. The findings of this study will help to understand the recovery methods of asphalt emulsion residue and select the appropriate recovery method.

Polymers, rubbers, and acids have been widely used for asphalt binder modifications. Different state and highway agencies follow different performance grade (PG) plus test techniques to characterize polymer-modified binders. The elastic recovery (ER) test method (AAHSTO T 301) is one of the most commonly used PG Plus test techniques to determine the presence of elastomeric modifiers. However, the ER test method is not suitable to determine the mechanical properties of the polymer-modified binders beyond its linear viscoelastic range and there is no uniform guideline to conduct the ER test. Thus, the main research goal of this study is to recommend alternative test method(s), which can possibly be pursued by using a commonly available device, a dynamic shear rheometer (DSR). Guidelines have been developed toward adopting the appropriate test method(s) so that neither suppliers nor users are penalized. In this study, the Arkansas Department of Transportation (ARDOT) and the Texas Department of Transportation (TXDOT) certified SBS-modified PG 70-22 and PG 76-22 binders collected from ten sources were investigated in the laboratory. Test procedures including multiple stress creep and recovery (MSCR), ER-DSR, linear amplitude sweep (LAS), and binder yield energy test (BYET) have been explored to find their effectiveness. After exploring the DSR-based tests, it is concluded that the presence of the elastomer can be identified through ER-DSR and MSCR tests. The ER-DSR test has been found to be the best alternative to the ER test method. The MSCR percent recovery (%R) parameter was also found to have a good correlation with the ER.

This study aims to evaluate the effect of the incorporation of sugarcane bagasse ash sand (BS) as a partial replacement to silica sand on the properties of engineered cementitious composite (ECC). ECC mixtures with different replacement levels of sand (including 0%, 25%, and 50% by volume) with BS were produced. To characterize the mechanical properties of all produced ECC mixtures, compressive and uniaxial tensile tests were carried out. Sugarcane bagasse ash (SCBA) utilized in this study was collected from a sugar mill in Louisiana, and further processed by drying, sieving, and burning to produce BS. The experimental characterization of BS revealed that it consists of a combination of different particle sizes and shapes (i.e., spherical, prismatic, and irregular) and a high content of silica. In the context of ECC properties, while 25% sand replacement with BS did not lead to an increase in compressive strength, the results showed that ECC mixture with 50% sand replaced with BS demonstrated higher compressive strength than control ECC. Furthermore, ECCs implementing 25% and 50% sand replacement with BS exhibited higher tensile strength and tensile strain capacity compared to the control ECC. The improvements in compressive and tensile strength were attributed to the filler effect and potential pozzolanic activity of BS. On the other hand, enhancements in tensile ductility were likely ascribed to an enhanced fiber dispersion and a reduction in the matrix fracture toughness due to the fine particle size of BS.

This study aims to evaluate the possibility of using raw sugar cane bagasse ash (SCBA) as a sand replacement in engineered cementitious composites (ECC). A total of three mixtures, i.e., 0, 25%, and 50% of sand replaced with SCBA (by volume), were produced in this study. The experimental characterization of raw SCBA revealed that SCBA collected from the sugar mill consists mainly of silica and carbon with small particle size. In terms of ECC properties, the addition of SCBA caused a loss in workability and decreased the density of fresh ECC mixtures. For proper workability, higher HRWR dosages were utilized, which altered the air content of ECC mixtures (i.e., air content increased from 1.4% to 3.5%). The compressive strength of SCBA-ECC mixtures was slightly lower than the control mix. However, the tensile strength and, more markedly, the tensile ductility were enhanced compared to control. The negative effect on compressive strength was mainly attributed to the higher air content of the SCBA-ECC mixtures. The increment in ductility observed in SCBA-ECC mixtures by increasing the contents of SCBA may be attributed to the combined effect of smaller particle size of SCBA, increased air content, and the possible carbon coating of the PVA fiber.

Engineered cementitious composites (ECC) are advanced construction materials capable of extending the useable life of asphalt pavement roadways. First introduced in the 1990s, ECC required costly fibers and micro silica for the design mix as well as high volumes of cement. The price per cubic yard of ECC far exceeded the cost of typical Portland cement concrete (PCC) for overlay projects. While research has been conducted to reduce material costs, ECC still remains more expensive than PCC. This research extends beyond the material costs to study innovative construction techniques for ECC that could result in cost savings. Conventional concrete mixing plant procedures and contractor placement, finishing, and curing procedure variations for the ECC material are studied through a case study. Preliminary findings indicate ECC construction and labor costs should be less than the equivalent PCC ultra-thin white topping. Construction costs for a newly designed ECC material are determined and analyzed from actual construction methods.

Ultra-thin whitetoppings (UTWs) are a repair alternative for deteriorated asphalt pavements. Typically, UTWs are constructed using conventional Portland cement concrete (PCC) or fiber reinforced concrete (FRC) utilizing short slab sizes, i.e., 4 feet by 4 feet, and 6 feet by 6 feet. Historically, UTWs have generally exhibited satisfactory performance; yet, due to issues related to the brittle nature of concrete and debonding with the underlaying asphalt layer, many distresses have been observed. On the other hand, engineered cementitious composites (ECC) are characterized by its superior ductility, flexural performance, and fatigue resistance, which can significantly enhance the performance of pavement structures. However, the bond strength of ECC with asphalt concrete has not been studied. This study evaluates and compares the bond of ECC and conventional PCC with asphalt concrete for UTW applications. ECC/asphalt and PCC/asphalt specimens were prepared and subjected to direct shear in accordance to AASHTO TP114 (Louisiana interlayer shear strength test). The results showed that PCC had a superior bond strength with asphalt compared to ECC under direct shear.

This research investigated the use of locally produced ultra-high-performance concrete (UHPC) as a grouting material to repair deteriorated shear keys. Shear keys are used in adjacent girder superstructures to produce monolithic behavior and load transfer across the structure. Shear key degradation can jeopardize the integrity of the structure. Transportation agencies have reported that 75% of distress in adjacent girder bridges is due to cracking and de-bonding along shear keys. Previous research has shown that locally produced UHPC has excellent mechanical and durability properties. UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material. Full-scale testing was used to evaluate load-deflection behavior of channel girder assemblages with grouted shear keys. Results showed that while UHPC grout and non-shrink grout had similar mechanical performance, the non-shrink grout began to deteriorate faster under cyclic loading. Excellent bond was achieved with all grouts, even with minimal surface preparation.

This paper assesses the potential of a locally produced ultra-high performance concrete (UHPC) mixture proposed for use as an overlay material for concrete bridge decks. In this study, early-age and longer-term shrinkage tests were performed on locally produced UHPC. Slant-shear tests were conducted to evaluate the shear strengths at the bond interface between the UHPC and substrate concrete. Thermal and shrinkage effects in normal strength concrete slabs overlaid with UHPC were also observed. Early-age shrinkage testing showed that approximately 55% of the strain occurred in the plastic state and may not contribute to bond stresses since the elastic modulus of the UHPC should be small at such early ages. Adequate shear strengths were achieved for texture depths ranging from 0.05 to 2.8 mm. Thickness of the substrate and amount of reinforcing steel were important factors for shrinkage in the slabs. The thickest slab experienced greater shrinkage than a thinner slab with the same reinforcement, indicating reinforcement ratio is more important than the area of steel. Continuing work focuses on the development of a failure criterion for the brittle bond between a UHPC overlay and a concrete bridge deck.

To facilitate research on polyester polymer concrete (PPC) by the Utah Department of Transportation, the California Department of Transportation hosted a scanning tour of PPC bridge deck overlays. The objectives of the scanning tour included observation of a PPC overlay placement, inspection of existing overlays, and discussion of selected topics related to PPC. Items related to material properties, mixture and overlay design, laboratory testing, and construction and field testing were investigated. Several recommendations relevant to Utah bridge deck preservation practice were developed based on the findings, which are expected to also be highly valuable to other state departments of transportation.

Rice husk ash (RHA) has been considered as an agricultural by-product in the United States as well as all over the world. The chemical composition of the RHA particle makes it a potential supplementary cementitious material. This study investigates the potential uses of RHA as a supplementary cementitious material (SCM) in the preparation of flowable fill concrete (FFC). Flowable fill is defined as a self-compacting material, which has been used for different aspects such as backfilling, utility trenches, bridge abutments, pile excavations, and retaining walls. In this study, two different types of RHA samples (600-RHA: 600 μm, and 150-RHA: 150 μm) with two different particle sizes were utilized to evaluate their application in producing low strength FFC. The evaluation process of RHA modified FFC mixtures includes determination of strength, flowability, unit weight, and air content of modified FFC mixtures through different laboratory experiments. Fresh FFC test result showed that RHA modified FFC mixtures required higher amounts of water to maintain a desired level of consistency. Laboratory experiments on hardened FFC mixtures prepared using coarse RHA particles resulted in lower strength properties compared to the regular FFC where medium-fine RHA particles in FFC mixers were found to be effective in increasing the strength properties. Two field demonstrations have been conducted to evaluate the workability, placement, and in-service performance of RHA modified FFC in field conditions. The findings of this study are expected to help the transportation and construction agencies in finding an alternative construction material.

In this research, the feasibility of roller compacted geopolymer concrete (RCGPC) containing 100% recycle concrete aggregate (RCA) was investigated. Mechanical characteristics of the RCA-RCGPC composite were evaluated using a compressive strength test, and semi-circular beam test. The effects of different curing conditions (time and temperature) on compressive strength were also assessed. The durability of the material was studied using the freeze-thawing test. Microstructure and morphology investigations were also performed using X-ray diffraction (XRD). Throughout the experimentation, class F (low calcium) fly ash was used. The mixture of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) was used as an alkali activator. It was observed from the test results that, RCA-RCGPC has a high optimum moisture content, which was due to the higher absorption capacity of RCA. By using 8 M concentration of NaOH, Na₂SiO₃ to NaOH ratio of 1 by mass and 15% fly ash content, 60°C accelerated curing method yielded satisfactory unconfined compressive strength (UCS), semicircular bending beam (SCB) strength and durability were also found to be promising using 100% RCA aggregate. XRD analysis had also proven the formation of new chemical bonds or geopolymeric compounds in the newly formed RCA-RCGPC composite. Based on the test results, this material could be a cost-effective and durable solution to the construction of pavement structures.

Geopolymer is an aluminosilicate network polymer that has gained interest in recent years as an eco-friendly alterative to ordinary Portland cement for transportation infrastructure. This novel material can be processed from waste and/or widely available natural materials under ambient conditions. In this study, a comprehensive set of metakaolin-based geopolymers and geopolymer mortars with construction sand were processed using different SiO₂/Al₂O₃ ratios and water/solid ratios for geopolymer binder and cured at ambient conditions for 14 days. Pure geopolymer and geopolymer mortar samples were tested for compressive strength, density, and open porosity. The results show that the composition of geopolymers strongly affects their properties especially their compressive strength. Samples with various compositions were characterized with scanning electron microscopy (SEM) to examine the morphological and structural effect from the compositional parameters.

Metal culverts are being used by the Arkansas Department of Transportation (ArDOT) on a frequent basis. The service life of these culverts mainly depends on the properties of culvert materials and surrounding environments. The selection of pipe material at any location is mostly controlled by its life cycle costs (LCC), which include construction, operation, and maintenance costs. In this study, life cycle costs of different metal pipes are evaluated based on the existing unit costs data and other construction, maintenance, and user associated costs of a culvert. Laboratory investigations were carried out to assess the properties of the soils collected from different parts of the state. The secondary soil and water quality data were collected from secondary sources. Using neural network models developed based on secondary and primary data from state agencies, the electrical resistivity of soils has been predicted for different locations within the state. Then, the service lives of three different metal pipes were estimated. Finally, based on the service life of different metal pipes, their life cycle costs were estimated, and the geographical information system (GIS) based maps were developed for all 75 counties in Arkansas. The maps show the most feasible locations of different metal pipe culverts based on the associated life cycle costs. This study will help the ArDOT engineers to select cost-effective metal culverts for any location within the state.