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Project Details
STATUS

In-Progress

PROJECT NUMBER

24-871, TR-829

START DATE

01/01/24

END DATE

12/31/27

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center, PROSPER
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

Co-Principal Investigator
Dan King

Research Engineer, CP Tech Center

About the research

Roller-compacted concrete (RCC) is a no-slump concrete having same basic ingredients as ordinary portland cement concrete (PCC). While RCC has been used in commercial areas and for local streets and highways, its use for paving shoulders has not been studied in Iowa. The primary objective of this project is to develop mix design, construction, and maintenance/preservation specifications for using RCC in Iowa pavement applications. This will be achieved through execution of the following primary tasks: (1) literature review; (2) comprehensive laboratory assessment; (3) field demonstration construction and evaluation; (4) life-cycle cost analysis (LCCA) for quantifying cost effectiveness of various shoulder options; (5) facilitation of three workshops on RCC maintenance and preservation, life expectancy, recycling, and potential Iowa transportation infrastructure application types; and (6) Iowa RCC specification development. The successful outcomes of this research will be of great benefit when providing justification on the proper use of RCC as an alternative durable and strengthened material for the paving of shoulders and other applicable areas in Iowa transportation systems.

Project Details
STATUS

Completed

PROJECT NUMBER

18-665, TR-753

START DATE

07/01/18

END DATE

12/13/23

RESEARCH CENTERS InTrans, CMAT, PROSPER
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Charles Jahren

About the research

Iowa has over 110,000 miles of roads, and they frequently support local residential vehicles as well as heavy trucks. Traditional bituminous surface treatments (BST) could be employed to maintain these roads properly, but these treatments typically require high-quality materials and standard construction equipment. Otta seal is a relatively new BST that allows for the use of more economical local aggregates and commonly available equipment. To evaluate the feasibility of Otta seal implementation, a Phase I study was launched to design and construct Iowa’s first Otta seal-surfaced road in Cherokee County in 2017. The successful construction of the first Otta seal road in Iowa provided valuable experience and knowledge for local public agencies, and a follow-up Phase II study was initiated in 2018. The Phase II study described in this report aimed to establish the recommended specifications through comprehensive laboratory evaluation and characterization and additional field implementation projects. In the Phase II study, more than 50 Otta seal sites constructed since 2017 were evaluated. These sites had various local aggregate and binder types, as well as various application rates. Five consecutive years of field measurements were executed in this Phase II study, including lightweight deflectometer-derived elastic modulus, International Roughness Index, dust generation, and skid resistance. The field evaluation in 2023 indicated that all Phase II Otta seal sites still exhibit satisfactory performance. A detailed laboratory investigation was conducted to establish a rational methodology for designing Otta seal road surfaces utilizing locally available materials. Four distinct aggregate types were considered in this study: limestone, recycled concrete aggregate (RCA), slag, and river aggregates. The McLeod method was modified to determine optimal rates for aggregate and binder application. The laboratory study primarily assessed Otta seal performance through a sweep test exploring the impact of material type, aggregate gradation, binder type, and application rate on aggregate loss. Key findings include the significance of aggregate gradation in reduced aggregate loss, the comparable performance of HFMS-2s and MC 3000 binders, the suitability of recycled materials (especially slag), and the effectiveness of the modified McLeod method. A life-cycle cost analysis revealed that the lowest cost was associated with Otta seal designed using the modified McLeod method. These findings contribute to a more efficient Otta seal design, enhancing road surface longevity while utilizing locally sourced materials.

Project Details
STATUS

Completed

PROJECT NUMBER

19-705, TR-777

START DATE

06/01/19

END DATE

12/13/23

SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Wensheng Zhang

About the research

Pavement roughness serves as a critical indicator of the overall ride quality of road surfaces. Elevated levels of pavement roughness can give rise to concerns regarding driving safety, fuel consumption, and exhaust gas emissions. The International Roughness Index (IRI) stands as the globally accepted standard for quantifying road surface roughness. Although one of the primary responsibilities of local public agencies (LPAs) involves monitoring and maintaining appropriate IRI levels for the local road system, existing techniques used to collect IRI data, such as using high-speed and walking profilometers, typically entail high annual costs for network-level inspection. Consequently, LPAs are in need of a cost-effective IRI data collection system that enables them to gather pavement performance data annually. Smartphones come equipped with an array of sensors, including multi-axis accelerometers and global positioning systems (GPS), that present an efficient and economical approach for collecting vehicle suspension data, specifically vertical acceleration. These data can then be harnessed to estimate pavement profiles and roughness. This study endeavored to develop a low-cost, smartphone-based, nonproprietary data collection system designed for use by LPAs to gather pavement roughness data on an annual basis. This adaptable system can be implemented on Android phones, iPhones, or custom-developed smart boxes that incorporate accelerometers and GPS units. All data gathered in this way can be seamlessly transferred to a cloud-based server and subsequently processed using a Python-based algorithm to compute the IRI. The accuracy of such a system was assessed using four distinct smartphones, one custom-developed smart box, and a Class 1 high-speed profilometer that was used to establish reference IRI values. The field data collection program encompassed 24 Story County sites selected to validate the accuracy of IRI measurements. The results demonstrate that the smartphone-based and smart box systems developed offer a dependable, low-cost, and user-friendly solution for LPAs to use in assessing local road roughness. A prototype smartphone application for detecting road surface distress through captured videos and images was also developed and evaluated.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-872, TR-830

START DATE

12/01/23

END DATE

11/30/25

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center, PROSPER
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Dan King

Research Engineer, CP Tech Center

Co-Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

About the research

Joint sawing is a critical part of concrete pavement construction, as the jointing system plays an important role in concrete pavement performance and service life. To ensure successful construction, it is important to understand the basic principles of the joint sawing process. These principles include proper timing, depth, and spacing of saw cuts, as well as the many factors related to materials, climate, and equipment that affect the sawing window. Understanding the fundamentals of joint sawing is even more important today thanks to the changing construction workforce and ongoing changes to mixtures and materials used in concrete pavements. The objectives of this research are to perform a comprehensive literature review on joint sawing of concrete pavements; to conduct a survey of agencies, contractors, and equipment providers to establish today’s typical practices and the most common problems related to joint sawing in Iowa; and to perform a field investigation that diagnoses these problems and tests out potential solutions on Iowa pavement construction projects. The results of each of these components will be combined and summarized in a guide culminating the best practices for joint sawing concrete pavements.

Project Details
STATUS

Completed

PROJECT NUMBER

17-605 TR-722

START DATE

04/01/17

END DATE

10/31/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

Integral and semi-integral abutment bridges have become increasingly popular in Iowa and across the country because they eliminate joints at the bridge ends. Expansion joints in bridge decks allow water to seep in and corrode bearings along with other structural elements in conventional bridge construction. An integral abutment connects the bridge deck and girders with the substructure in one piece to reduce maintenance and increase service life. The abutment moves with the rest of the bridge, and this movement introduces new issues with water drainage, soil settlement, soil erosion, and concrete cracking. The objective of this research was to evaluate improved bridge end details to increase service life and investigate limitations placed on the use of semi-integral abutment bridges. Research methods include a literature review, visual inspections, field monitoring, and finite element simulations.

The extensive literature review identified research relevant to improving the performance of bridge ends. Abutments, approach slabs, geotechnical aspects, drainage, and expansion joints were evaluated in detail. It was found that innovative bridge abutments allow for the elimination of conventional bearings and attempt to reduce issues associated with integral construction. Semi-integral abutment bridges and those with approach slabs attached to the abutment were inspected across the state of Iowa to assess the performance of current design methods. The condition and performance of tied joints was found to be unsatisfactory in some instances, with measured openings much larger than those built during initial construction. Joints between wingwalls and approach slabs were also found to be in poor condition. Four bridges were outfitted with a multitude of sensors, including strain gauges and displacement transducers, to measure concrete expansion and bridge displacement. Finite element models were also created to investigate the movement of approach slabs on the soil below. Simulated bridge expansion provided insights into approach slab behavior and tie bar stresses due to friction. Parametric studies were completed on various approach slab properties, including friction with soil, soil stiffness, tie bar style, and bridge skew.

Project Details
STATUS

Completed

PROJECT NUMBER

21-783, TR-800

START DATE

11/01/21

END DATE

10/30/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

ABC-UTC
Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Justin Dahlberg

Director, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

This project investigated helical pile foundation implementation for bridges, resulting in a design and construction guide. The simplicity and speed of helical pile installation, along with the ability to work within areas of limited size with smaller, more maneuverable equipment, can accelerate the construction of bridge structure foundations.

The guide provides bridge engineers and designers with direction and specifications for this substructure foundation option, which can be advantageous on any bridge project, but particularly for low-volume roads where budgetary considerations tend to be a specific priority.

The guide includes many useful design specification reference tables and also useful construction and installation documentation tools as examples and as table forms that can be used for helical pile bridge foundations.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-862

START DATE

09/01/23

END DATE

08/30/24

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE, Iowa LTAP
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Shauna Hallmark

Director, InTrans

Co-Principal Investigator
Keith Knapp

Director, Iowa LTAP

Co-Principal Investigator
Guillermo Basulto-Elias

Research Scientist, CTRE

About the research

Unpaved roads make up almost 80% of roadway miles within the State of Iowa. These unpaved roads have lower traffic volumes but still account for many of the fatal and serious injury crashes throughout the state. Since these crashes tend to be more widespread and not concentrated to a single area, low-cost systemic countermeasures would be the ideal way to improve safety on these roads. Most research and guidance materials available related to low-cost systemic countermeasures focus on applications along paved roads. This project would help to address this gap by focusing on low-cost safety improvements for unpaved roads. Additionally, local road owners desire a toolbox of strategies for improving safety on unpaved roads.

The objectives for this research project include the following:

  • Develop a toolbox of strategies for improving safety on unpaved rural roads based on
    available research and guidance
  • Identify demonstration projects for innovative (possibly untested) safety improvement
    concepts for unpaved roads
  • Identify information gaps and develop research problem statements to address those gaps
  • Identify field research needed to develop crash modification factors (CMFs) or surrogate
    safety metrics to determine the effectiveness of various rural road safety strategies on
    unpaved rural roads
Project Details
STATUS

In-Progress

PROJECT NUMBER

23-868, TR-827

START DATE

09/01/23

END DATE

08/31/24

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Peter Taylor

Director, CP Tech Center

Co-Principal Investigator
Dan King

Research Engineer, CP Tech Center

Co-Principal Investigator
Halil Ceylan

Director, PROSPER

About the research

In the past, the Iowa Department of Transportation (DOT) has had a number of pavements placed from 1986 to 1994 that exhibit vibrator trails. Many of these pavement sections exhibited cracking in the vibrator trails and investigation shown high air loss in those areas. Research was conducted on vibration in concrete pavement placements. The research found that at 12,000 vibrations per minute (vpm), aggregate distribution and air content was greatly affected. This research led to specification changes on vibration, reducing the vibration from a minimum of 7000 vpm to 5000 to 8000 vpm. Another research project led to the implementation of vibration monitoring on projects greater than 50,000 square yards. Newer paving machines have a tablet based system for inspectors to monitor vibration during the project. Older paving equipment typically have the old system of vibration monitoring, which requires occasional checks of the vibrators on the paving equipment.

This research was conducted on concrete mix designs with only coarse and fine aggregates and likely were gap graded. Since 1999, the Iowa DOT has been utilizing well graded aggregate combinations on quality management concrete (QMC) mix designs. It is not known what effect vibration has on well-graded aggregate mix designs. Perhaps, these mix designs may allow a higher tolerance on vibration or perhaps less is required. The Iowa DOT has been experimenting with reduction in cement content in QMC mixes, validated with the performance engineered mix (PEM) testing procedures.

Even with research conducted in the past, we do not have a full understanding of the vibration energy impact on durability and consolidation. Frequently, it has been noted that there are still a fair amount of voids found in concrete pavement cores. Iowa State University has conducted a small study on the effect of vibration on concrete mixtures. The study noted localized changes in w/c ratio and air movement within the concrete. It is not known if this could lead to localized durability issues. This project will investigate the impact of vibration on concrete pavement mix designs. In particular the QMC mixes and those reduced cement content mixes validated with PEM test procedures. Lab research will be validated on a concrete paving project.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-866, TR-824

START DATE

07/01/23

END DATE

02/28/26

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

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.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-859, TR-823

START DATE

07/01/23

END DATE

07/31/25

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CTRE
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Jeramy Ashlock

Faculty Affiliate, InTrans

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.

 

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