Project Descriptions

Alkali-silica reaction (ASR) is a material degradation mechanism in concrete structures. ASR is a chemical reaction between the reactive aggregate particles and alkalis in cement. The reaction occurs when the alkali load concentration in the concrete mix exceeds the threshold level of the reactive siliceous ingredients. Multiple locations in Arkansas are experiencing early-age concrete deterioration, and ASR has been detected by petrographic analysis in some of those locations. However, additional research is needed to determine if ASR is contributing to the deterioration of other locations and whether the aggregates currently being used to produce concrete are susceptible to ASR.

New test methods have been developed to determine the susceptibility of aggregates to ASR and the alkali threshold of aggregate combinations. This project will examine the ASR susceptibility of aggregates, determine the alkali threshold of common aggregate combinations, and develop a mix design analysis tool to evaluate the ASR susceptibility of concrete mix designs.

TRC2402: Field Evaluation of High-Performance Cold Mix (HPCM) Products

TRC2403: Evaluation of Air in Concrete

Air content is a crucial component of hardened concrete that is directly linked to the durability and lifespan of structures. A widely known phenomenon of air loss occurs when pumping air-entrained concrete through a pump truck. ARDOT’s specifications require samples to be taken at the pump truck hose discharge for the most accurate determination of air content. This process is often difficult and somewhat dangerous.

The main objectives of this project are to determine the correct location for sampling air-entrained concrete, evaluate the theory that entrained air returns to concrete after pumping and before the initial set, assess the ability of the Super Air Meter (SAM) to predict entrained air bubble size and spacing through the petrographic analysis, evaluate the durability of current concrete mix designs, determine the optimized concrete curing methods through comparison to current methods by using test decks, test the resistivity and chloride penetration of hardened concrete to establish a baseline of current concrete mix designs, and evaluate fly ash variability in relation to air entrainment efforts through the use of the foam index test.

TRC2301: Smart Work Zone (SWZ) System Design, Specifications, Estimates, and Implementation Guidelines

The ability to manage traffic through highway work zones is rapidly improving. Portable Intelligent Transportation System (ITS) devices can detect slowing traffic, and push alerts to the contractor, Resident Engineer, Transportation Management Center, and drivers’ smartphone apps such as Waze or Google Maps. Smart arrow boards can inform stakeholders of lane closures in real time. Dynamic speed limits based on work zone conditions are being used successfully in many states. Third-party data providers that push data to consumers via smartphone apps can also detect and impute traffic conditions near work zones. This research will inform the development of an SWZ special provision that will replace the automated work zone information system (AWIS) special provision for highway contracts. Specific objectives intend to provide a process that will assist in identifying the need for an SWZ earlier in the project development process, consider when to use specific new technologies, and better design and estimate SWZ costs.

TRC2302: Development of Pedestrian and Bicyclist Flow Volumes and Risk Factors

Pedestrian and Bicyclist safety is a growing concern and priority for the U.S. Department of Transportation. Fatalities for non-motorists have increased nationwide since 2009, and this increase has also been observed in Arkansas. The first objective of this project will be to collect data on non-motorized transportation users across the state using count stations and crowdsourced data. Traffic volume data will be overlaid with historical crash data to determine crash risks. Recommended countermeasures will be determined to address high-risk areas and provide resources for future project planning to make Arkansas roads safer for all users.

TRC2303: Evaluation of Impacts Due to a Bridge Closure: A Case Study of the Mississippi River Bridges in Arkansas

The objective of the proposed research is to quantify the multi-modal impacts due to a Mississippi River bridge closure. This study will consider different scenarios/combinations of bridge closures (i.e., full and partial bridge closures that take into account one/both directions, single/multiple lanes, and day/night closures), including all the Mississippi River bridges in Arkansas (i.e., I-40, I-55, Hwy 49, and Hwy 82 bridges). A comprehensive multi-modal analysis will be performed that considers the number of vehicles, trucks, and marine vessels/barges disrupted due to the bridge closure (with all potential scenarios/combinations) and applies detailed cost conversions to monetize direct (delays) and indirect (safety, infrastructure, operations) impacts. Also, this study will develop an Excel-based tool to conduct “what-if” analyses for decision-making purposes, whether for construction, maintenance, or planning activities.

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 (N_des) 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 N_deswill 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.

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.

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.