CLOSE OVERLAY
Project Details
STATUS

Completed

PROJECT NUMBER

19-693, TR-773

START DATE

04/01/19

END DATE

09/30/21

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

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

About the research

Ultra-high performance concrete (UHPC) provides superior properties in strength and durability for the long-term performance of bridges. Despite these desirable properties and the potential to be applicable in the majority of projects, UHPC is still not widely used, mainly because of the cost associated with it.

This report details a study performed on the design of non-proprietary UHPC mixes that provide comparable strength properties to that of commercially available mixtures. A set of base mixtures were explored by varying the ratios for various constituents and investigating their durability, strength, and transport properties, including volume stability and freeze-thaw resistance.

In the later stage of the project, the selected non-proprietary mixes were evaluated for their flexural strength. The flexural strength in UHPC comes mainly from the fibers used in the mix. Bearing in mind the role of fibers, the effects of various types of steel fibers (i.e., variation in shape, size, and dosage) were evaluated. The role of fibers on strength and post-cracking behavior was carefully examined using laboratory testing and image analysis utilizing digital image correlation techniques. The efforts found that an optimal combination of micro- and macrofibers can enhance the flexural strength of UHPC mixtures.

Steel fibers contribute to more than a third of the cost of UHPC mixtures, so the possibility of utilizing less expensive and more environmentally friendly synthetic fibers—polypropylene, polyvinyl alcohol, nylon, alkali resistant glass, or carbon—to partially replace the steel fibers could reduce the cost of UHPC. The steel fibers were partially replaced by the different synthetic fibers to see their effect on the UHPC’s fresh properties and flexural strength. Utilizing digital image correlation, the synthetic fiber contribution to post-cracking behavior was evaluated, especially from the crack width control and crack propagation aspects. The replacement of steel fibers with synthetic fibers showed promise for flexural strength and post-cracking behavior.

This report provides recommendations for the preparation of cost-effective, non-proprietary UHPC mixtures that could be used for various transportation infrastructure applications. Further recommendations are also made for the optimal combination of different types of steel micro- and macrofibers to get the best flexural response. Recommendations are then extended for the use of different types of synthetic fibers and the optimum percentage of dosage replacement for steel fibers.

Project Details
STATUS

Completed

PROJECT NUMBER

15-540, TR-690

START DATE

07/01/15

END DATE

04/30/19

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Kejin Wang

PCC Engineer, CP Tech Center

Co-Principal Investigator
Scott Schlorholtz

Faculty Affiliate

Co-Principal Investigator
Sri Sritharan

Faculty Affiliate

About the research

This Phase II research project on the shrinkage behavior of high-performance concrete (HPC) used in Iowa bridge decks and overlays evaluated several concrete mixes, building off or modifying mixes developed in Phase I. Based on shrinkage behavior and mechanical properties, the mixes studied in Phase I were characterized as having either high, medium, or low cracking potential. In the Phase II study, three concrete mixes (Mixes 6, 8, and 2, characterized in Phase I as having high, medium, and low cracking potential, respectively) were selected for further investigation. The selected mixes were modified using three shrinkage control technologies: shrinkage-reducing admixtures (SRAs), cementitious materials (CM), and internal curing (IC) agents, respectively. The modification methods were first studied in a laboratory until the optimal shrinkage behavior of each concrete mix was achieved. Two pairs of the tested concrete mixes (Mixes 6 and 8 with and without modification) were then used in a field investigation on the US 20 over I-35 dual bridge. The mixes were placed side by side for the bridge overlays, which were monitored for about one year with strain gages, temperature and moisture sensors, and regular visual examinations.

The laboratory investigation confirmed positive effects for the concrete shrinkage control technologies used. The laboratory test results also provided specific details for the concrete mix modifications, ensuring optimal concrete performance and shrinkage control. The modifications included the addition of 1.0/1.25 gal/yd3 of SRA in Mix 6, the use of 10% CM reduction for Mix 8, and the use of lightweight fine aggregate as an IC material in Mix 2. The results of the field investigation suggest that environmental conditions on the casting day and the first few days of curing play an important role in the development of concrete properties. Future studies could benefit from a comprehensive stress analysis to better understand the long-term effects of the shrinkage control technologies, as well as further field tests and an extended monitoring time.

Project Details
STATUS

Completed

PROJECT NUMBER

14-511, TR-680

START DATE

07/01/14

END DATE

02/28/19

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

Co-Principal Investigator
Travis Hosteng

About the research

Buchanan County, Iowa, has been working with the National Center for Wood Transportation Structures and a timber fabricator to develop the next-generation timber bridge. The goal is to increase the structural efficiency of timber bridges and increase longevity by (1) creating a composite deck-girder system and (2) using an epoxy overlay. These design elements have the potential to increase viable bridge options for use not only on Iowa’s roadways, but nationally and internationally as well.

The bridge system developed for this research was a composite glue-laminated (glulam) girder-deck system utilizing epoxy for the connection and an epoxy overlay wearing surface on the deck. This design was investigated through small- and large-scale laboratory testing of the composite epoxy connection and a field demonstration bridge built utilizing this girder to deck connection detail and epoxy overlay.

The small-scale tests showed that the best overall joint connection is an epoxy and lag bolt connection. The joints with epoxy at least tripled the shear capacity of the lag bolt joint, and addition of mechanical fasteners to the epoxy connection marginally increased performance. The large-scale laboratory tests showed a small increase in the load capacity and movement of the neutral axis when the deck panels are affixed to the girders, both of which indicate potential composite action. Furthermore, the epoxied connection exhibited an improved composite connection over the lag bolt connection.

Three live load tests on the field demonstration bridge in 2015, 2016, and 2017 indicated that transverse load distribution for all load cases was adequate. The composite action observed was not likely substantial enough to be accounted for in design. The chip seal shows signs of cracking at the transverse deck panel joints, but because of the epoxy the joints remain sealed and show no signs of moisture intrusion on the underside of the deck. The epoxy wearing surface on the deck performed better as an impermeable joint filler than a wearing surface.

Project Details
STATUS

In-Progress

PROJECT NUMBER

19-688, TR-771

START DATE

02/01/19

END DATE

02/28/24

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC, CP Tech Center
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Kejin Wang

PCC Engineer, CP Tech Center

Co-Principal Investigator
Katelyn Freeseman

Acting Director, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

Bridge deck overlays have been adopted as an effective deck service life extension tool by the Iowa Department of Transportation (DOT) since the 1970s. High performance Concrete (HPC-O) and Type O PCC (PCC-O) are the most commonly used materials for rigid overlays. A three-day (72-hour) wet curing procedure is specified in Iowa standard specifications. Due to the high cost of traffic control for heavily traveled urban highways, it is highly desired to reduce the traffic interruption as much as possible by getting the work done at night or on weekends. To meet this need, thin epoxy overlays were tested recently with good success and it has been adopted as a bridge preservation tool for decks that are still in good or fair conditions. However, when an overlay of considerable thickness is needed and when significant patching is required, another overlay system, a high-early-strength latex-modified concrete (LMC-VE) overlay, has been proven as a better choice. LMC-VE has been used successfully when a bridge lane can be closed for 1 to 2 days, such as over a weekend, and in many situations, a lane can be closed only for 8 hours or less, necessitating only a night closure. Researchers have indicated that compared with other early strength overlays, LMC-VE overlay is more durable and less prone to shrinkage-induced problems while having higher resistance to chloride ion penetration. When LMC-VE is placed on hydro-demolition prepared bridge deck surfaces, a service life of the deck can be expected to be over 75 years, and the high initial cost of a LMC-VE can be offset by its extended service life. Thus, use of LMC-VE overlays is an ideal choice for expedited construction. Several states (e.g., Virginia, Ohio, Missouri, Kentucky) have already explored the applications of LMC-VE overlays in their bridge construction projects.

Currently, the Iowa DOT is planning to try a LMC-VE overlay at a district 2 bridge (BRFN-015-4(18) -39-32, Emmet 119, IA 15 over Black Cat Creek, letting on 11/20/18). This will be the first trial placement of LMC-VE overlay in Iowa. Documenting the construction procedure, evaluating the short term and long-term performance, and summarizing the experience and lessons learned from the project is essential for future bridge deck overlay decision making and provides design and construction guidance for future practice.

Project Details
STATUS

Completed

PROJECT NUMBER

17-613, TR-727

START DATE

06/01/17

END DATE

10/31/19

RESEARCH CENTERS InTrans, CMAT
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Hyung Seok "David" Jeong

Affiliate Researcher

Principal Investigator
Jennifer Shane

Director, CMAT

Co-Principal Investigator
Kevin Scheibe
Co-Principal Investigator
Sree Nilakanta

About the research

Determining the optimal time of equipment replacement is challenging, since the cost of maintaining road equipment increases with equipment operation, while the economic value of the equipment decreases. Accurately estimating the optimal replacement time and predicting future costs of road equipment contribute to the effective use of equipment, while avoiding expensive maintenance activities.

This research project developed a data-driven equipment life-cycle cost analysis (LCCA) model that estimates economic life, replacement time, and future costs of motor graders and trucks for Iowa counties. The current practice of equipment management in Iowa counties was studied by conducting a survey and a follow-up interview. Historical equipment management data for motor graders and trucks were explored to perform regression analysis and derive equipment cost estimation models.

A spreadsheet-based tool was also developed to capture equipment data and provide cost estimation and optimal replacement time. The tool has two modules: (1) deterministic analysis that captures single values as inputs and provides one-point estimation and (2) stochastic analysis, in which a range of values is captured and Monte Carlo simulation is used to provide a range of values as results. The stochastic analysis provides insights about the effect of uncertainties associated with variables to more realistically reflect actual practice. The tool considers both purchasing and leasing options to be applicable for counties that use each method of equipment acquisition.

The research also proposed a template for equipment data record keeping that meets LCCA requirements and allows counties to improve their data collection practices, which can enhance equipment planning over time. The output of this project not only allows Iowa county engineers to support their equipment decisions but also can be used as an example of equipment LCCA for other public agencies.

Project Details
STATUS

Completed

PROJECT NUMBER

16-584, TR-714

START DATE

08/01/16

END DATE

12/31/18

RESEARCH CENTERS InTrans, CMAT, MTC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board
Iowa State University
Midwest Transportation Center
USDOT/OST-R

Researchers
Principal Investigator
Hyung Seok "David" Jeong

Affiliate Researcher

Co-Principal Investigator
Charles Jahren

Associate Director, Construction Materials and Methods / Asset Management

Co-Principal Investigator
Jennifer Shane

Director, CMAT

Co-Principal Investigator
Kristen Cetin
Student Researcher(s)
Tuyen Le
Chau Le

About the research

Thanks to an array of advanced digital technologies, much of today’s transportation project data are available in digital format. However, due to the fragmented nature of the highway project delivery process, the growing amount of digital data is being archived and managed separately. This makes it difficult for professionals to take full advantage of the efficiencies of digitized data and information. The purpose of this research was to identify current data workflows and areas for improvement for five of the most common types of highway assets—signs, guardrails, culverts, pavements, and bridges—and offer guidance to practitioners on how to better collect, manage, and exchange asset data.

The research team conducted focus group discussions and interviews with highway professionals to capture their knowledge and practices about the data workflows. In addition, the team conducted an extensive review of the literature, manuals, project documents, and software applications regarding the exchanged information. For each type of asset, an information delivery manual (IDM) was developed. Each IDM consists of several process maps (PMs) and one exchange requirement (ER) matrix. A total of 15 PMs and 5 ER matrices were developed.

A set of limitations in current data workflows was identified and a set of recommendations to overcome those limitations was also determined and documented. The conclusion was that current data workflows were designed mostly for contract administration purposes. Thus, more efficient asset-centric data workflows need to be implemented to truly streamline the data workflows throughout an asset’s life cycle and minimize wasted resources in recreating data in the asset maintenance stage.


Funding Sources:
Iowa Department of Transportation
Iowa Highway Research Board ($50,000.00)
Iowa State University ($22,500.00)
Midwest Transportation Center
USDOT/OST-R ($80,000.00)
Total: $152,500.00

Contract Number: DTRT13-G-UTC37

Project Details
STATUS

In-Progress

PROJECT NUMBER

18-683, TR-769

START DATE

12/15/18

END DATE

03/31/22

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CTRE
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Jeramy Ashlock

Faculty Affiliate

About the research

About 74% of Iowa’s 89,000-mile road network consists of gravel roads (Iowa County Engineers Association 2018). These roads provide the fabric for rural life and livelihood in Iowa by linking agricultural producers with markets, and rural residents with their communities. The fact that these surfaces must be renewed as often as every three years imposes financial stress on county highway departments.

Coarse aggregates (CA) are a major constituent of granular surfaces and are known to undergo both physical and chemical changes due to weather and traffic that affect their properties and ultimately, their longevity. Despite the importance of these roads to the economic fabric of Iowa and their need for constant upkeep, we lack a robust understanding of not only the deterioration mechanisms that are most responsible for CA break down, but we also do not know the geological factors that make one CA perform better than another.

This study aims to characterize the changes that occur in these coarse aggregates by characterizing changes in the geological fabric and properties of coarse aggregates from both in service roads and laboratory specimens. Using this information, highway engineers and geologists can act in the fiduciary interest of taxpayers to minimize costs while providing a safe and reliable transportation network for rural communities and producers.

Project Details
STATUS

Completed

PROJECT NUMBER

InTrans Project 19-679, IHRB Project TR-767

START DATE

01/01/19

END DATE

12/31/21

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC, CP Tech Center
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

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

Student Researcher(s)
Maziar Kazemian

About the research

Concrete is made of multiple ingredients that begin in a plastic phase and become solid over time. Additionally, it is well established that concrete is exposed to various stressors from the initial hours of pouring, making it prone to cracking. The multiphase nature of concrete along with these stressors require the consideration of several factors, especially for the design of concrete bridge decks that are exposed to aggressive environmental and mechanical stressors simultaneously. Due to the low early-age strength of concrete, even small-scale tensions can result in cracking and consequently decrease the longevity of the concrete structure.

In order to address these issues, a three-stage framework was designed for this project. In Stage 1, multiple binder compositions were investigated for their performance in terms of early-age plastic shrinkage by recording capillary pressure development, monitoring crack width, and determining strain development by means of digital image correlation. After binder modification, in Stage 2 different dosages of microfibers were added to concrete mixtures to compensate for the concrete’s low tensile strength and control cracking during the life of the concrete. To measure the efficiency of the microfibers, drying shrinkage, compressive and splitting tensile strength, and rapid chloride migration tests were carried out to determine the cracking potential and mechanical and durability properties of fiber-reinforced concrete (FRC). In Stage 3, three types of macrofibers (i.e., polypropylene [PP], alkali-resistant [AR] glass, and polyvinyl alcohol [PVA]) were incorporated at multiple dosages into FRC that already contained microfibers to enhance the post-peak strength of the concrete. The compressive, splitting tensile, and flexural strengths of the concretes were recorded as the pre-peak mechanical properties, and the toughness and residual flexural strength were recorded as the post-peak mechanical properties.

The results show that Class F fly ash, as opposed to silica fume and Type K (expansive) cement, contributes most to the early-age cracking resistance of concrete. Furthermore, increasing PP microfiber content significantly reduced the cracking potential and enhanced the mechanical properties and chloride resistance of concrete. In the case of hybrid FRC (FRC containing both microfibers and macrofibers), AR glass macrofibers introduced superior performance compared to PP and PVA macrofibers, in terms of pre- and post-peak mechanical properties.

Project Details
STATUS

In-Progress

PROJECT NUMBER

18-682, TR-765

START DATE

12/15/18

END DATE

02/28/22

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
Kejin Wang

PCC Engineer, CP Tech Center

Co-Principal Investigator
Katelyn Freeseman

Acting Director, BEC

About the research

With the growing interest in use of concrete sealers, there has been an increase in the number of the manufacturers, types of sealers, and commercial products available. This has resulted in a wide range of problems, for the design engineers, contractors, and owner agencies who lack the tools to evaluate such products.

Sealers can be categorized based on the chemical structure, type and amount of the diluent used, and the mechanism of action but products from a given category may vary widely in their performance. Indeed, the parameters that define satisfactory performance are not agreed upon.

There is a need to establish a suite of performance criteria that will define acceptability of a given product, and a protocol for agencies to be able to evaluate a product that is submitted for approval. The aim of this work is to meet those needs.

Project Details
STATUS

Completed

PROJECT NUMBER

InTrans Project 18-671, IHRB Project TR-757

START DATE

09/15/18

END DATE

02/28/21

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Katelyn Freeseman

Acting Director, BEC

About the research

Recent developments in nondestructive testing technology have opened the door for innovative inspection methods for infrastructure. One such technology is ultrasound evaluation, specifically in the form of linear arrays. The objective of this project was to explore the potential ability of an ultrasound evaluation device called MIRA to assess the condition of a bridge’s superstructure. To achieve this goal, MIRA was deployed at two bridges with two different sets of objectives. On the first bridge, two concrete overlays had previously been applied, and the bridge was soon to be overlaid for the third time. The second bridge was constructed using concrete box girders, and the condition of the post-tensioning ducts was of interest. For each bridge, multiple test sections were evaluated. Based on the test results, the following conclusions were made:

  • When the overlay on the concrete deck was in good condition, MIRA could effectively detect the location and relative size of the rebar in the top layer.
  • MIRA scans could not clearly distinguish between the bottom surface of the deck and the bottom layer reinforcement at about 575 mm below the surface.
  • When cracks were present in the overlay, MIRA was able to detect these defects. However, since the substrate deck condition of one of the bridges was unknown during this project, the damage seen in the MIRA scans could not be field verified.
  • MIRA performed well in detecting voids in post-tensioning ducts.

This project hoped to capture the actual condition of the substrate of the first bridge via field evaluation during overlay placement. Unfortunately, due to delays in the letting of that work, the actual condition was not able to be captured within the timeframe of this project. As such, future research is recommended on an experimental basis to quantitatively evaluate MIRA’s performance related to validating the condition of the substrate.

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