Institute for Transportation

About the research

The lack of a national standard for winter weather road condition indices has led to inconsistencies in assessing road conditions and providing accurate information to drivers across the United States. This research aims to develop a national standard for winter weather road condition indices that is consistent, accurate, and reliable, enhancing driver safety and winter weather response effectiveness. The project involves conducting a comprehensive literature review, data analysis, and case study analysis, as well as engaging key stakeholders from public and private organizations. The anticipated outcomes include a national standard framework, implementation guide, training materials, monitoring and evaluation toolkit, best practices repository, communication templates, and an interactive map/dashboard for road conditions. The implementation of a national standard for winter weather road condition indices is expected to improve driver safety, reduce traffic crashes and congestion, and optimize winter weather response strategies by transportation agencies.

About the research

This research will support the Iowa Department of Transportation through ad hoc implementation of the methods developed in a previous draft report entitled, “A Transportation Agency Data Collection Practice for Use with In-Service Performance Evaluations (ISPEs).” This will include analysis of data related to traffic barrier elements and roadside hardware such as crash cushions, steel beam, cable, concrete barriers, breakaway signs, breakaway light poles, etc. Research will include both a review of the data and optional implementation.

About the research

This research aims to develop, test, and implement a cost-effective ultra-high performance concrete (UHPC) mixture design tailored to equip new bridge decks with a protective layer against environmental and mechanical stressors. For this purpose, utilizing the ingredients available from local resources and regional suppliers in Iowa, the non proprietary UHPC mixture design developed for Iowa bridges will be further optimized, especially to achieve the expected balance between flow and viscosity. With completing a set of laboratory investigations, the outcome will provide a UHPC mixture design enabled with thixotropic properties required for bridge deck and overlay applications. In the next step, laboratory trials will be performed to determine the most optimal surface preparation and curing regime. This will directly assist contractors with the field implementation of non proprietary UHPC for target applications. In the proposed project, the developed thixotropic non-proprietary UHPC will be used (as overtop) to construct the deck of a new bridge structure identified by the Iowa Department of Transportation’s Bridges and Structures Bureau. This candidate bridge deck will provide a unique testbed to apply and further evaluate the performance of the developed UHPC mixture in a real field setting. The scope of field work will involve both short- and long-term studies. The short-term investigations will cover the practical aspects and considerations that must be figured out to successfully add a layer of non-proprietary UHPC to the normal concrete substrate. On the other hand, the long-term investigations will closely monitor the integrity and overall condition of this new bridge deck system over time. For this purpose, a dense array of instrumentation will be utilized, while regular inspections will be performed in parallel. The outcome is expected to benefit from the superior strength and durability of UHPC to address the long-standing issues associated with the deterioration of bridge decks.

About the research

The project aligns with the Iowa Department of Transportation’s (DOT’s) focus areas of sustainability and technology. Maintenance and rehabilitation of granular-surfaced roads consumes significant portions of counties’ annual budgets, as well as large amounts of natural resources in the form of virgin aggregates. By assessing the performance of different test sections constructed with and without the Perma-Zyme stabilization product through two winter-spring cycles, the Iowa DOT and county engineers will better understand the life-cycle costs and relative advantages of using the enzymatic stabilizer as well as the different construction methods (i.e., compaction by sheepsfoot vs. smooth-drum roller during construction).

Most importantly, the project would establish a new Granular Surfaced Roads Test Facility comprising several miles of granular-surfaced roads at Camp Dodge, through a cooperative relationship with the Iowa Army National Guard. The facility would enable long-term research on unpaved roads with great efficiency by reducing travel time compared to locating test sections in several counties around the state and by enabling many different projects on an ongoing basis in one central location. Overall, the long-term benefits of the project will be to improve the quality, longevity, and state of good repair of Iowa roadways, which constitute a vital component of Iowa’s infrastructure.

About the research

In recent years, various proprietary bio–based fog sealers or rejuvenators have been introduced and marketed as potentially cost–effective and environmentally friendly alternatives to traditional petroleum–based sealers for preserving asphalt roads. The RePLAY Agricultural Oil Seal and Preservation Agent, as one such bio–based fog sealer, and its performance, has been evaluated on a 3.3–mile pilot testing section located in Clinton County, Iowa, for five consecutive years (i.e., summer 2016 through summer 2021). This study has important insights about RePLAY and its first–level field implementation in Iowa. However, further research is needed to identify the frequencies and benefits of the reapplication of RePLAY and further evaluate and validate its cost effectiveness. In addition, Clinton County has interested in evaluating the reapplication of RePLAY at the same project site for extending its use on other project sites. This research will be performed in response to such a research need and interest and will be achieved through the execution of the following primary tasks: (1) developing and executing a detailed field experimental plan, (2) evaluating and validating cost effectiveness, (3) executing subsequent technology transfer and information dissemination activities and developing implementation plans with recommendations, and (4) publishing final research project documents.

This research project will be highly helpful to the Iowa Department of Transportation and Iowa counties in better understanding the benefits of the reapplication of RePLAY while facilitating their decision making in selecting cost–effective application frequency options.

About the research

The VKelly test was developed to provide agencies and contractors a tool that reports how a slipform paving mixture responds to vibration. In the past, the slump test was useful but did not provide a complete picture of the workability of a mixture.

Initial evaluation showed that the test provided useful, numerical, and repeatable data on how a mixture will perform in a paving machine and that it could distinguish between the workability of mixtures with similar slumps. It was used to develop mixture proportions that were reported to be successful in the field. So, a number of rigs were sent to agencies around the country for them to evaluate. Feedback indicated that while seemingly technically sound, the test was still challenging to operate.

The aim of this project is threefold:

• Make the test more user-friendly
• Understand the science behind the method to guide mixture proportioning and field operations based on test results
• Broaden the applicability to include structural mixtures

The long–term vision of this work is to develop an understanding of how mixtures can be proportionated that are relatively insensitive to vibration abuse or are ideal for the vibration
system planned to be used on a given site. In addition, it is desirable that a real-time test be available on a site so that as a mixture is delivered, it can be tested for workability variances due to batching or transport, thus providing the operator with guidance on how to tune the placing equipment for that particular truckload.

About the research

Curling and warping behavior due to temperature and moisture variation has been widely considered an influential factor affecting the smoothness of jointed plain concrete pavement (JPCP). In recent decades, while extensive efforts have been made to quantify the impact of curling and warping-related deflections on the smoothness of JPCP, a standardized method for characterizing the effects of environmental factors on JPCP smoothness is still unavailable. A Phase I study examined curling and warping conditions at six sites using a stationary light detection and ranging (LiDAR) system and developed recommendations to minimize curling and warping based on literature review findings. However, the data collection effort in the Phase I study was limited and was insufficient to validate the recommendations derived from the literature review.

The Phase II study described in this report aimed to evaluate and quantify the impact of curling and warping on Iowa concrete pavements and determine the factors that most influence curling and warping behavior. A high-speed profilometer and a LiDAR device were utilized to execute a large-scale field data collection plan for JPCP sites in Iowa, including Long-Term Pavement Performance (LTPP) Program highways, non-LTPP highways, and county roads and city streets. The variables evaluated in this study included temperature and moisture gradients, seasonal and diurnal effects, slab geometry, pavement structural design, mix design, and construction conditions. A validated MATLAB-based algorithm with two different curve-fitting models was coded to evaluate the degrees of curling and warping in multiple ways. This study also used statistical analyses to select the variables that significantly affect curling and warping behavior. The proposed actionable pavement design and construction recommendations will help minimize curling and warping and correct curling and warping-related performance issues.

About the research

This Performance-Engineered Concrete Paving Mixtures Transportation Pooled Fund—TPF-5(368)—brought newer concrete pavement technologies to state agencies and assisted states in the adoption of specifications and test methods that will help them deliver on the promise of concrete durability.

The Federal Highway Administration (FHWA), 19 state transportation agencies, and 4 national associations representing the concrete paving industry came together to fund this project, which was dedicated to maximizing pavement performance. The focus of the work was to address mixtures up to the point of leaving the batch plant.

The objective was the deployment of performance-engineered mixtures (PEM), which involved building off the foundational work that the FHWA and PEM champion states have done. The emphasis was on implementation, education and training, adoption of specification language to increase the likelihood of achieving durable pavement performance in the field, and continued development relating early-age concrete properties to pavement performance.

This project covers the efforts, results, and accomplishments of this TPF. While progress was made, more work needs to be done. With PEM approaches, concrete pavement should perform better and last longer with a lower environmental impact. This will enable agencies to lower costs by minimizing maintenance operations, keeping the flow of traffic undisturbed for longer periods of time and increasing safety for the traveling public.

About the research

Iowa has three classes of public roads: state primary highways, county (secondary) roads, and city streets. Among these, Iowa county roads serve rural Iowa transport needs by assuring a public road connection (i.e., to local access roads) for serving as conduits that channel the flow of people and commodities to and from towns and terminals (i.e., farm-to-market roads). Many Iowa county pavement systems are multilayered structures that have experienced multiple cycles of construction and renewal that make it more complex to estimate pavement structures’ current structural capacities.

This study developed a Microsoft Excel macro and Visual Basic for Applications (VBA)-based automated Pavement Structural Analysis Tool (PSAT) with three analyzing options—asphalt concrete (AC) pavement systems with 1 to 10 layers on a (1) stabilized base, (2) granular base, and (3) stabilized base and granular base—to estimate the current structural capacities of in-service pavement systems by following consecutive sections within the user-friendly platform. To address this aim, a systematic approach to develop a highly realistic annotated synthetic database was created for use in artificial neural network (ANN)-based pavement response prediction models that required inputs of pavement materials and structural features and outputs of pavement responses, deflections, and strains at critical locations within the pavement structure. In addition, the equivalent layer theory (ELT) concept was integrated into the PSAT to simplify multilayered pavement systems into three-layered systems—an asphalt layer, a base layer, and a subgrade layer. Thus, it could make it easier for an Iowa county engineer to understand the current structural capacities of in-service county pavements. Mechanistic- and empirical-based approaches were also integrated into the tool to estimate the remaining service life (RSL) associated with two types of major failures for flexible pavements, namely fatigue and rutting failures, by relating pavement responses predicted by the ANN models through transfer functions. The PSAT is expected to be used as part of routine pavement analysis, design, and asset management practices for better prioritization and allocation of resources, as well as to support effective communication related to pavement needs both with the public and with elected officials.

About the research

Improving the accuracy of work zone data is a multi-layered problem of which a number of agencies have been working to address over the last several years. Connected temporary traffic control devices (cTTCDs) such as smart arrow boards and other connected devices have the capabilities to improve the accuracy of work zone data without a contractor or agency employee having to manually enter the information. As the number and types of devices have increased, little guidance has been developed on how to use information from these devices within an agency. This project will document and evaluate how cTTCDs can be used by an agency for both historical and real-time applications. The approach starts with an agency state-of-the-practice review to summarize how the data are currently being utilized. A number of integration methods will be evaluated with the goal of highlighting noteworthy practices and documenting agency considerations when integrating the data into their systems.