Institute for Transportation

About the research

Speeding contributes to around 31% of fatal crashes. As a result, agencies rely on speed management countermeasures to reduce crashes and improve quality of life for residents around facilities where speeding is an issue. Several speed management toolboxes exist. However, most are focused on countermeasures for lower speed urban facilities. Iowa is characterized by a much wider range of speed issues, including rural communities, rural roadways, suburban, and high-to-low speed transition areas. A number of studies have been conducted to assess the impact of different countermeasures for these facilities (including a number conducted in Iowa). However, the information is not summarized in a format that is easily accessed. As a result, a toolbox is needed which provides a “one stop shop” for Iowa agencies interested in conducting speed management.

About the research

The Iowa Work Zone Safety Workshops have provided an opportunity for operations personnel from various cities in Iowa to improve their work zone safety and setups when conducting routine street maintenance. Many participants come from cities with a population of less than 10,000 residents and small city budgets for this type of work can sometimes lead to a lack of funding for temporary traffic control devices and the use of signs, barricades, cones, and vests that are deteriorated and may be out of compliance with the 2009 Manual on Uniform Traffic Control Devices (MUTCD).

This project was developed to assist smaller cities with the introduction or upgrade of their temporary traffic control devices and vests to meet current standards for compliance and to make their work zones safer for workers and motorists. The program has grown from 10 applications in 2017, the initial year of the project, to 91 applications in 2021–2022 and over 100 in 2022–2023.

The goal of this project is to provide an avenue for smaller cities to be able to obtain a basic work zone sign package that is in compliance with the 2009 MUTCD and to make their work zones safer for operations personnel and motorists. It is currently proposed that the materials to be included in the package will be the following:

• One Lane Road Ahead Signs
• Road Work Ahead Signs with “CLOSED” snap on
• Be Prepared to Stop Signs
• Type III Barricades
• 28” Traffic Cones
• Class 2 Safety Vests
• Sign Stands
• 42 inch Channelizers

About the research

Water intrusion on bridge decks leads to degradation of the concrete and reinforcement at an accelerated rate when compared to other concrete bridge components. As an example, freeze/thaw effects can result in delamination or spalling, and chloride ion penetration can result in the material degradation of the concrete and steel reinforcement. Eliminating or reducing water intrusion into the bridge deck concrete has the potential to greatly increase the service life of the bridge deck and,
subsequently, the overall bridge.

An admixture product and surface sealer are proposed for use on a bridge construction project in Appanoose County, Iowa. The bridge superstructure will consist of concrete prestressed, precast girders topped by a concrete, steel-reinforced deck. The project presents an opportunity to observe and document the construction and performance of the deck with the inclusion of the moisture prevention products.

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.