TRC2201 – Update to ARDOT Superpave Gyratory Compaction (SGC) Specification to Increase Pavement Durability
The overall objective of the proposed research is to increase the durability of asphalt pavements. This study will evaluate current mix designs for surface asphalt concrete hot-mix (ACHM) used around the state when reducing the number of design gyrations (Ndes) and examine its effect(s) on change in mixture durability (rutting and cracking performance). The key is to assure that the mixtures produced with reduced Ndes will have sufficient asphalt binder content to provide enhanced long-term cracking performance while maintaining adequate aggregate structure to resist the permanent deformation (rutting) in the field for a given traffic level. Increasing the durability of asphalt pavements will result in a reduction in necessary maintenance, preservation, and rehabilitation efforts/ costs, and in a longer pavement life which will significantly reduce life-cycle costs. Also, the proposed study is the next logical step in fully implementing a performance engineered mixture design (PEMD) system for Arkansas. This project is expected to last 18 months.
TRC2202 – Updating ArDOT Liquefaction Evaluation and Mitigation Procedures
When designing bridge pile foundations in liquefiable soil, engineers at ARDOT use a Standard Penetration Test-based spreadsheet that was developed 10 years ago. Since then, more information has been published regarding liquefaction triggering procedures, skin friction, as well as end-bearing of piles in liquefiable soils, generating the need to create a more up-to-date version. This project aims to update ARDOT’s spreadsheet and liquefaction triggering evaluation methodology as well as incorporate additional means of evaluation and procedures. This project is expected to last 24 months.
TRC2203 – Low Shrinkage Concrete Mixtures For Arkansas
Early age cracking has been identified as a common cause for Arkansas bridge decks not meeting their design life. It is suspected that dimensional changes in the concrete during the curing phase, known as shrinkage, are the culprit behind early age cracking. A possible solution to this issue revolves around concrete mixtures and curing procedures. This project is focused on evaluating the relationship that local aggregate and cement combinations have with shrinkage and early age cracking, finding optimal mix designs to prevent shrinkage cracking using locally available materials, and determining the curing methods required to best prevent shrinkage issues. This project is expected to last 36 months.
TRC2204 – Materials and Testing Specifications for Drilled Shaft Concrete
This project will study drilled shaft concrete and attempt to create a new mix design for self-consolidating concrete. Drilled shafts are common in bridge foundations used across the state, and due to the amount of rebar in drilled shafts, self-consolidating concrete is needed to ensure full cement coverage and correct aggregate displacement. Research has been conducted in the past to create a self-consolidating mix design, but not specifically for drilled shafts. Additionally, this research project will review the testing procedures for self-consolidating concrete and recommend new QA/QC testing. This project is expected to last 24 months.
TRC2101 – Update of the ARDOT Workforce Forecasting System
To replace the current outdated system, TRC2101 – Update of ARDOT Workforce Forecasting System will re-estimate and expand the capabilities of the workforce prediction model and software. The project will develop new equations for the Construction Division’s Workforce Forecasting System and find or write new software with the possibility of integrating artificial intelligence (AI) in a future interface. The project will also explore the possibility of using this workforce forecasting system for more than Construction office crews.
TRC2102 – Effect of Aggregate-Binder Compatibility on Performance of Asphalt Mixtures in Arkansas
The primary objective of this study is to develop a draft specification including the implementable test protocols that ensure the use of durable and compatible aggregate-binder systems in the mix design phase for enhanced asphalt mixture performance in the field. This study will require comprehensive laboratory and field investigations that consider the multiple factors involved, including a range of aggregate and binder types used in Arkansas. The successful implementation of research findings obtained from TRC2102 could lead to potential cost savings for ARDOT due to increased longevity and constructability, and reduced premature failures for asphalt mixtures placed in the field.
TRC2103 – Developing Guidelines for Evaluating Weathering Steel Bridges
The objectives of TRC2103 are to identify, develop, and implement a framework for evaluating weathering steel bridges in Arkansas. Doing so will allow ARDOT to identify if weathering steel bridges have any future potential for oxide film degradation. Also, the project will take into consideration the location (proximity to water, characteristics of the body of water, etc.) and function (overpass, hydraulic structure, etc.) of the bridges.
Weathering steel has improved corrosion-resistant behavior over conventional steel. However, it is not maintenance-free and will corrode if not used in the proper ambient conditions. While weathering steel retards corrosion, it may require future restoration thorough cleaning and painting. ARDOT inspects 1192 weathering steel bridges yearly. Of those, 908 structures are state-owned and have an element level inspection per the AASHTO Manual for Bridge Element Inspection, 2nd Edition. Approximately 23% of those 908 are documented to have oxide film degradation of the steel protective coating, otherwise known as patina.
The proposed research will provide ARDOT with a final report and implementation plan. This plan will discuss how to incorporate inspection guidelines on evaluating patina corrosion conditions of weathering steel bridges either by a workforce training or developing a Technology Transfer Program course.
TRC2104 – Maintanence Guidelines for Mechanically Stabilized Earth (MSE) Walls
The objective of this research project is to determine Best Management Practices (BMP) for MSE walls, and the primary deliverable is to develop a maintenance inspector’s guidebook, which could provide assistance to address potential signs of distress. A part of this guidebook is to include a Grading Level (A – F) scale to be applied per ARDOT Maintenance guidelines and provide appropriate repair options. The details for BMP would include routine inspections and frequency of inspections, the Level of Effort needed to repair or reconstruct problematic issues, and emergency inspections after significant weather events or accidents that may have compromised MSE walls.
Another deliverable is to expand on an ArcGIS database to be provided by ARDOT Maintenance Division. This inventory would include all MSE and other specified wall types currently maintained by ARDOT. Within the database system, the metrics will be outlined and categorized for each wall type to include System/Type, Design Specifications, Materials, Performance, and Maintenance History. Having these metrics outlined in a formal layout will provide clearer guidance for all maintenance personnel when inspections are conducted.
TRC2105 – Innovative Countermeasures to Deter Wrong-Way Driving
TRC2105 Innovative Countermeasures to Deter Wrong-Way Driving is being developed to research technologies to prevent wrong-way vehicle entry onto interstates and freeways. Wrong-way driving has been of concern since divided highways were first opened to traffic. Drivers traveling in the correct direction encounter wrong-way vehicles head-on, and crashes are often severe.
Since 2011, annual reports of wrong-way driving crashes in Arkansas have been prepared, per Act 641 of the 87th Arkansas General Assembly, and applicable countermeasures have been implemented. In 2017, a statewide traffic safety job added signs and markings and upgraded devices at freeway entrance ramp intersections with surface streets.
This research will expand the toolbox of available countermeasures. Steps will include analyzing wrong-way crash data, reviewing emerging technologies and devices to deter wrong-way drivers, and testing the most promising countermeasures.
TRC2106 – Applying UAS LiDAR for Developing Small Project Terrain Models
The goal of this project is to take small size bridge projects and produce a 3D model using an Unmanned Aircraft System (UAS) mounted with a LiDAR sensor in order to extrapolate quantities and get precision surveys with literally millions of points accurate down to mere inches! To get a model with this many data points and to this accuracy using conventional surveying would take a lifetime, but with aerial LiDAR it could be done in as little as an evening! Results from this method will then be compared to current techniques to produce a cost/benefit analysis to illustrate the many advantages it could potentially provide to the Department.
TRC2107 – Non-Nuclear Moisture Content and Density Determination
TRC2107 is a project investigating Non-Nuclear Density measurement techniques for moisture content and density of soil. Currently, ARDOT utilizes nuclear density gauges for QA/QC for embankment and subgrade material compaction. The cost associated with these gauges includes annual maintenance, dosimeter badges, training for radioactive materials, as well as secondary costs associated with transporting and storing radioactive devices. TRC2107 will investigate any available technology that can accurately and quickly determine the density and moisture of materials, and only devices comparable to the nuclear gauge will be considered. The anticipated outcome of the project will be to find a feasible replacement for the nuclear density gauge.
TRC2001 – Determining Costs Attributable to Overweight Axle Loads
Arkansas currently has no ability to assess fines for axle load limit violations. About 8,100 load shift tickets were issued in 2017 for overweight axle load limit violations. TRC2001 will determine if there is a significant amount of damage on Arkansas roadways due to overweight axle loads. The research would determine pavement and bridge repair life-cycle costs attributed to overweight axle loads. A literature review and a survey to other State DOTs will identify various methodological approaches. Falling Weight Deflectometer (FWH) training will support pavement conditions assessment. The research team will then develop a methodology to quantify damages caused by overweight axle loads. The survey results, load shift citations, and data from FWD tests will be collected and analyzed.
TRC2002 – Investigating Calcium Sulfoaluminate (CSA) Cement and Sacrificial Anodes
Calcium Sulfoaluminate (CSA) Cement is a rapid setting hydraulic cement similar to Portland cement with a very fast strength gain. If a typical Portland cement concrete mixture can reach 4,500 psi in 28 days, the complementary CSA cement mixture would reach 4,500 psi in 4 hours. Because of this extremely fast strength gain, CSA cement is an ideal material for repairs. ARDOT currently utilizes CSA cement for bridge deck repair, but corrosion issues tend to arise in the patched area due to several factors. One objective of this project is to evaluate the effectiveness of using sacrificial anodes when patching bridge decks with CSA cement mixtures in regards to corrosion inhibition and repair longevity. This will be accomplished by patching sections of a bridge deck with the anodes included and monitoring the corrosion and wear of the patch compared to other patches that were placed without anodes. The other objectives include evaluating the feasibility of ARDOT using CSA cement for full depth repairs of roadways and determining an appropriate mix design for ARDOT to use CSA cement for full-depth repairs of roadways.
TRC2003 – Data Driven Methods to Assess Transportation System Resilience in Arkansas
The goal of this study is to develop and implement a framework for measuring the resilience of Arkansas’s highway transportation system. Tasks will include: synthesizing existing studies and practices to define resiliency assessment methods and resiliency indices as well as evaluating current state of practices within ARDOT; applying the most relevant methodology to perform a resiliency assessment of the Arkansas highway network; providing recommendations for improving system resiliency; and implementation. Key deliverables include development of a criticality map for the ARDOT highway system, development of case studies to demonstrate the application of risk and resilience analyses for ARDOT critical assets, and review of ARDOT policies and practices to determine appropriate locations for inclusion of risk and resilience analysis findings and procedures.
TRC1902 – Capillary Pressure Sensor Testing to Identify Curing Regimen in Freshly Placed Bridge Decks
The overall performance of concrete in bridge decks can be affected by the curing regimen. With the advent of new testing equipment for freshly placed concrete, Capillary Pressure Sensor System (CPSS), the evaporation effects can be measured. By measuring the capillary pressure during the initial set period after finishing, shrinkage cracks can be avoided by adding moisture and/or curing compound to the concrete surface when the alarm is triggered by threshold pressure limit. Additional curing compound and/or moisture can be added to reduce or mitigate the effects of the evaporation. This project would use the CPSS to evaluate the different curing regimens the contractor uses and determine which product and/or method works best. This project aims to investigate the use of a CPSS to monitor the development of capillary pressures in the surface of fresh concrete bridge decks. This capillary pressure can be used to determine if plastic shrinkage cracking is likely to occur and alert the user when moisture should be added to the surface to prevent cracking. The sensor will be tested in the lab to verify its ability to measure plastic shrinkage pressures, then lab testing will be performed to compare curing techniques. A field study will help determine if the sensor is useful in practice to ARDOT and to contractors. With the success of the sensors, training workshops can be developed for sensor usage for ARDOT employees and contractors.
TRC1903 – Investigating Concrete Deck Cracking in Continuous Steel Bridges
Concrete bridge deck cracking creates serious serviceability issues during a bridge design’s life, and can compromise a bridge’s structural strength. This project aims to identify the primary causes of deck cracking, as well as determining the stresses in the due to concrete slab movement during shrinkage. After determining the cause for bridge deck cracking, long-term corrective measures will be recommended to prevent future cases of bridge deck cracking. The current objective in this project is to review documents about bridge deck cracking in Arkansas and look for correlations between projects. After reviewing the procedures contractors go through when pouring a bridge deck, examine previously constructed bridges and determine the best mapping of strain gauges for examining the stresses inside of a freshly poured concrete bridge deck.
TRC1905 – Implementing CPT Procedures in ARDOT Geotechnical Designs
The overarching objective of this research effort is to examine the applicability of using CPT to reduce uncertainties associated with geotechnical subsurface investigations. The main goal of this project is to review and implement comprehensive CPT-based geotechnical design procedures for site exploration, interpretation of soil behavior, and design of shallow/deep foundations and embankments in Arkansas. Work Plan will include conducting a literature search, collecting field testing procedures, conducting the field tests (six sites), analyzing resulting CPT data, and applying results to specific geotechnical design. Tasks will be performed by Research Section personnel with the help of Materials Division. The research project is broken into two phases. Phase 1 will mostly cover Year 1 of the project and will introduce CPT rig and its in-field operations to ARDOT personnel involved with this study. Phase 2 will cover Year 2 of the project and will deal with developing best practice for CPT field testing and CPT Geotechnical designs.
TRC1802 – Performance-Based Asphalt Mixture Design (PBD) for Arkansas
Historically asphalt mixture design has been based on component specifications and volumetric properties. With volumetric based design, engineering properties of asphalt mixtures are controlled only indirectly — influenced by properties of the components and proportions of each component. Superpave was intended to include performance-based tests — that is, tests that measure engineering properties directly related to performance, but these tests proved to be non-implementable. As a result, Superpave is based solely on volumetric properties. Performance-Based Mixture Design (PBD) includes performance tests to evaluate rutting potential, cracking potential and moisture resistance during the mixture design process. Performance tests provide a more direct evaluation of expected performance than volumetric properties. Such tests can better characterize the effect of new materials and processes (e.g. RAP, RAS, Warm-Mix) as well as changes to mix design criteria.
Recent surveys (NCHRP Synthesis 492; FHWA Expert Task Group; LTRC; Arkansas Asphalt Pavement Association) have indicated concern that current mixture design procedures do not ensure adequate field performance. Of prime concern is early-age cracking in asphalt pavements. In addition, the AAPA survey suggests differences in the cracking performance of mixtures with different aggregates (e.g. sandstone versus limestone) in Arkansas. TRC 1404 identified mixture design related issues as a significant contributor to early-age pavement distress. A key item to note is that many agencies have implemented a ‘rutting test’ to accompany the Superpave volumetric design process (AASHTO M323, R35) — however, only a few have implemented a cracking test into routine mix design (although surveys indicate the number is growing).
Research is needed to develop/adapt and implement a ‘cracking test’ for asphalt mixture design – and to use this test in conjunction with the current APA rutting test (AHTD Test Method 480) to shift mixture design in Arkansas to a performance basis, rather than a volumetric basis. In addition, the research should re-evaluate the effectiveness of the current method for estimating resistance to moisture damage (AHTD Test Method 455A) – and develop/adapt alternate methods as appropriate. A performance-based mixture design system will provide a much higher degree of confidence that Arkansas roadways will not experience materials-related premature distresses and failures.
TRC1803 – Mapping Subsurface Conditions for Transportation Applications
Each year AHTD spends millions of dollars to deal with troublesome soil and rock layers, which cause slope stability issues along roadways or require removal of rock layers. The remediation of slopes or removal of bedrock can be both time consuming and expensive. While slope stability and shallow bedrock issues may be unavoidable or even expected on certain projects, unexpected subsurface conditions during construction can lead to significant cost overruns, change orders, and construction delays. If a more accurate/complete 3D understanding of the subsurface conditions was available during the design phase, some problems could be avoided or at least budgeted for during construction. Currently subsurface conditions are assessed on transportation projects using drilling and sampling along the project alignment. While this provides an acceptable level of accuracy for projects where problematic soil and rock layers depth and thickness are consistent, significant errors can exist when conditions are variable both inline and crossline to the alignment. To provide a more complete picture of the subsurface layering where conditions are quite variable, a continuous 3D subsurface profile can be developed rapidly using Capacitively Coupled Resistivity (CCR). CCR is a drag along array resistivity system that measures the electrical resistance of soil and rock formations. This system can be used to provide continuous 3D models of the subsurface and has been shown to be effective at identifying weak clay seams, which exhibit higher moisture levels (due to high PI) and bedrock location (due to lack of moisture). Knowledge regarding the location of these layers can be used in slope stability analysis and used for developing better estimates of rock cut quantities on transportation projects.
TRC1805 – Access Management Implementation
Access management concepts were well in place by the 1970s, and state departments of transportation begin to implement access management programs in the 1980s. Since then, research and experience has contributed to the evolution of the concepts and the implementation mechanisms. Even though access management improves both traffic flow and safety, the extent to which state and local agencies have adopted it varies widely. Adoption and implementation of access management is challenging because it cuts across organizational lines and involves a number of interrelated practices. Before an agency embarks upon an access management program, it should examine current organizational structure and practices within the agency, and then develop a plan that presents a detailed strategy for adoption and implementation.
TRC1703: – School Bus Stops and Safety
Transporting students safely is the main priority for school transportation directors, bus drivers, and other essential personnel involved in getting students to school. The primary task for school transportation directors is planning bus routes, which can impact student safety. These bus stop placements not only dictate the routes students travel between home and the stop, but also environmental conditions in which students are subjected while waiting for the bus. According to a 2015 FHWA/NHTSA study, from 2004 to 2013, 327 school-age children died in school-transportation related crashes with highest numbers during the hours of 7AM to 8AM and 3PM to 4PM. Beginning in October 2012, Safe Routes to School (SRTS) activities was eligible to compete for funding alongside other programs under MAP-21. The current SRTS legislation provides $612 million to the states to distribute to communities for providing safer child travel to school by bike or on foot. The intent of the funding is primarily (70 to 90 %) for infrastructure improvements, but is also intended to provide 10 to 30% for safety education and enforcement. Possible suggestions by working with school transportation directors could be: 1) Providing safer “Student Pickup Zones,” installing raised sidewalks and loading/unloading areas within ROWs. 2) Install centralized bus stops in the ROW to reduce the number of vehicle stops. 3) Install flashing signs for areas with high potential for accidents, such as multiple curves.
TRC1601 – Determining the Feasibility of an AHTD Mobile LiDAR System
TRC1601 deals with Mobile LiDAR Systems. Mobile LIDAR combines 3-D laser scanning, GPS, inertial measurement and video technologies to collect highly accurate data quickly, efficiently and cost effectively. The objectives of this research project are to determine the Districts/Divisions/Sections within the Department that could benefit from the data produced by a mobile LiDAR system as well as investigate the economic feasibility of purchasing a mobile LiDAR system by AHTD to be used in-house rather than contracting mobile LiDAR consultants’ services. TRC 1601 will also aim to determine the additional resources required to facilitate the use of an in-house mobile LiDAR system.
TRC1605 – Evaluating the Usage of Culverts and Bridges by Wildlife in Arkansas
TRC1605 will evaluate the Usage of Culverts and Bridges by Wildlife. This project’s research will survey surrounding states to determine their policies on wildlife shelves and other wildlife crossing tools and establish baseline data by monitoring wildlife movements in selected areas in order to determine major crossing areas, behaviors and crossing frequencies. Part of TRC 1605’s research will require the installation of game cameras in or near select culverts and bridges to determine the extent that wildlife are utilizing these structures for road crossings. Other objectives of this research project include Collect crash data associated with wildlife crashes within the monitored areas, Collect road kill data before and after wildlife walkway installations and develop a plan to utilize wildlife shelves and other wildlife crossing tools based on data collected.