Effective Structural Concrete Repair, Volume 1 of 3, Repair of Impact Damaged Prestressed Concrete Beams with CFRP, March 2004

Structural concrete is one of the most commonly used construction materials in the United States. However, due to changes in design specifications, aging, vehicle impact, etc. – there is a need for new procedures for repairing concrete (reinforced or pretressed) superstructures and substructures. Thus, the overall objective of this investigation was to develop innovative cost effective repair methods for various concrete elements. In consultation with the project advisory committee, it was decided to evaluate the following three repair methods: • Carbon fiber reinforced polymers (CFRPs) for use in repairing damaged prestressed concrete bridges • Fiber reinforced polymers (FRPs) for preventing chloride penetration of bridge columns • Various patch materials The initial results of these evaluations are presented in this three volume final report. Each evaluation is briefly described in the following paragraphs. A more detailed abstract of each evaluation accompanies the volume on that particular investigation.

Effective Structural Concrete Repair, Volume 2 of 3, Use of FRP to Prevent Chloride Penetration in Bridge Columns, March 2004

Structural concrete is one of the most commonly used construction materials in the United States. However, due to changes in design specifications, aging, vehicle impact, etc. – there is a need for new procedures for repairing concrete (reinforced or pretressed) superstructures and substructures. Thus, the overall objective of this investigation was to develop innovative cost effective repair methods for various concrete elements. In consultation with the project advisory committee, it was decided to evaluate the following three repair methods: • Carbon fiber reinforced polymers (CFRPs) for use in repairing damaged prestressed concrete bridges • Fiber reinforced polymers (FRPs) for preventing chloride penetration of bridge columns • Various patch materials The initial results of these evaluations are presented in this three volume final report. Each evaluation is briefly described in the following paragraphs. A more detailed abstract of each evaluation accompanies the volume on that particular investigation.

Effective Structural Concrete Repair, Volume 3 of 3, Evaluation of Repair Materials for Use in Patching Damaged Concrete, March 2004

Structural concrete is one of the most commonly used construction materials in the United States. However, due to changes in design specifications, aging, vehicle impact, etc. – there is a need for new procedures for repairing concrete (reinforced or pretressed) superstructures and substructures. Thus, the overall objective of this investigation was to develop innovative cost effective repair methods for various concrete elements. In consultation with the project advisory committee, it was decided to evaluate the following three repair methods: • Carbon fiber reinforced polymers (CFRPs) for use in repairing damaged prestressed concrete bridges • Fiber reinforced polymers (FRPs) for preventing chloride penetration of bridge columns • Various patch materials The initial results of these evaluations are presented in this three volume final report. Each evaluation is briefly described in the following paragraphs. A more detailed abstract of each evaluation accompanies the volume on that particular investigation.

Laboratory Study of Structural Behavior of Alternative Dowel Bars, April 2006

Load transfer across transverse joints has always been a factor contributing to the useful life of concrete pavements. For many years, round steel dowels have been the conventional load transfer mechanism. Many problems have been associated with the round steel dowels. The most detrimental effect of the steel dowel is corrosion. Repeated loading over time also damages joints. When a dowel is repeatedly loaded over a long period of time, the high bearing stresses found at the top and bottom edge of a bar erode the surrounding concrete. This oblonging creates multiple problems in the joint. Over the past decade, Iowa State University has performed extensive research on new dowel shapes and materials to mitigate the effects of oblonging and corrosion. This report evaluates the bearing stress performance of six different dowel bar types subjected to two different shear load laboratory test methods. The first load test is the AASHTO T253 method. The second procedure is an experimental cantilevered dowel test. The major objective was to investigate and improve the current AASHTO T253 test method for determining the modulus of dowel support, k0. The modified AASHTO test procedure was examined alongside an experimental cantilever dowel test. The modified AASHTO specimens were also subjected to a small-scale fatigue test in order to simulate long-term dowel behavior with respect to concrete joint damage. Loss on ignition tests were also performed on the GFRP dowel specimens to determine the resin content percentage. The study concluded that all of the tested dowel bar shapes and materials were adequate with respect to performance under shear loading. The modified AASHTO method yielded more desirable results than the ones obtained from the cantilever test. The investigators determined that the experimental cantilever test was not a satisfactory test method to replace or verify the AASHTO T253 method.

Protection of Structural Concrete Substructures, HR-220, December 1992

In the past, many pier columns were deteriorating due to attack by chlorides. The chloride (from deicers) has attacked the substructures by drainage from the superstructure. Piers supporting grade separation bridges are also subject to chlorides contained in the direct splash from lower level traffic. Repairs of these piers are both difficult and costly. In this project, four different sealants were applied to piers to evaluate their use in the protection of the concrete against chloride-ions. One pier was left untreated to use as a control pier with which to compare the protected piers. This project began in 1980 and was to be completed in 1985, but at that time it was determined further testing was needed to make a more conclusive evaluation.

Effects of Heat Straightening Structural Steel, MLR-91-3, 1992

Heat straightening of steel beams on bridges struck by over height trucks has become common practice in recent years in Iowa. A study of the effects of this heat straightening on the steel beams thus straightened is needed. Appropriate samples for mechanical and metallurgical tests were cut from the same rolled beam from the end which was heated and the end which was not heated and the test results were compared. The test results showed beyond doubt that the steel was being heated beyond the permitted temperature and that the impact properties are being drastically reduced by the current method of heat straightening.

Field Measurement of Bridges for Long-term Structural Movement, HR-295, 1988

This report describes the field application of the tilt sensing method for monitoring movement of the Black Hawk and Karl King Bridges. The study objectives were: to design a data acquisition system for tilt sensing equipment utilizing a telephone telemetry system; to monitor possible movement of the main span pier, Pier No. 2, on the Black Hawk Bridge in Lansing and the possible long-term movement of Pier No. 4 on the Karl King Bridge in Fort Dodge; and to assess the feasibility, reliability, and accuracy of the instrumentation system used in this study.

Lightweight Aggregate Use in Structural Concrete, MLR-69-1 and R-229, 1969

The Iowa State Highway Commission has adopted a number of rigid safety requirements that the Bureau of Public Roads has set forth as standards for road construction. One of these safety requirements is the elimination of two piers on Interstate grade separations, thus leaving two long spans. These longer spans lower the ability of prestressed concrete beams to compete economically with steel beams. In an effort to be more competitive, the prestressing companies have been studying the use of lightweight aggregate in structural concrete.

Long-Term Structural Movement, HR-275, 1986

This report describes the field application of the tilt sensing method for monitoring movement of the Black Hawk and Karl King Bridges. The study objectives were: to design a data acquisition system for tilt sensing equipment utilizing a telephone telemetry system; to monitor possible movement of the main span pier, Pier No. 2, on the Black Hawk Bridge in Lansing and the possible long-term movement of Pier No. 4 on the Karl King Bridge in Fort Dodge; and to assess the feasibility, reliability, and accuracy of the instrumentation system used in this study.

Structural Analysis of Aggregate Blends Using the SHRP Gyratory Compactor, MLR-95-8, 1996

The Iowa Department of Transportation (IDOT) received a Strategic Highway Research Program (SHRP) gyratory compactor in December 1994. Since then IDOT has been studying the ability of the compactor to analyze fundamental properties of aggregates such as shape, texture, and gradation by studying the volumetrics of the aggregate blends under a standard load using the SHRP gyratory compactor. This method of analyzing the volumetrics of aggregate blends is similar to SHRP's fine aggregate angularity procedure, which analyzes void levels in noncompacted aggregate blends, which in turn can be used to evaluate the texture or shape of aggregates, what SHRP refers to as angularity. Research is showing that by splitting the aggregate blend on the 2.36-mm (#8) sieve and analyzing the volumetrics or angularity of the separated blend, important fundamental properties can be determined. Most important is structure (the degree and location of aggregate interlock). In addition, analysis of the volumes of the coarse and fine portions can predict the voids in the mineral aggregate and the desired asphalt content. By predicting these properties, it can be determined whether the combined aggregate blend, when mixed with asphalt cement, will produce a mix with structural adequacy to carry the designed traffic load.

Asphalt Resurfacing Structural Research, HR-556, Construction Report, 1995

Discarded tires present major disposal and environmental problems. One method of recycling tires is to use finely ground rubber from tires in asphalt cement concrete (ACC). This process has been researched in Iowa since 1991. There are currently eight projects being researched. This project involved using crumb rubber modifier (CRM) in ACC using a dry process. This project is located on US 63 in Howard County. It involved 17 test sections. There were five test sections using 20 lb of CRM per ton, four test sections using 10 lb of CRM per ton and eight test sections using a conventional mix. Not only were different mixes used, but the overlay was also placed in various thicknesses ranging from 2 in. to 8 in. (5 cm to 20 cm). The project was completed in August 1994. The project construction went well with only minor problems. This report contains information about procedures and tests that were completed and those that will be completed. Evaluation on the project will continue for five years.

Protection of Structural Concrete Substructures, HR-220, Progress Report, 1984

The corrosion of reinforcing steel within concrete has always been a problem in construction of bridge decks. With low slump concrete and epoxy rebar, progress has been made in controlling the corrosion. There is concern, however, that the chloride also attacks the substructures, specifically the pier columns. They are subject to chloride attack by chemical deicers in the drainage from the bridge deck. Piers supporting grade separation bridges are also subject to chlorides contained in the direct splash from the lower level traffic. In this project, a field evaluation was conducted to evaluate the effectiveness of commercially available products in preventing chloride intrusion.

Dynamic Deflections for Determining Structural Rating of Flexible Pavements, HR-178, 1979

The Road Rater is a dynamic deflection measuring apparatus for flexible base pavements. The Road Rater replaces the Benkelman Beam which was last used by the Iowa DOT in 1977. Road Rater test results correlate reasonably well (correlation coefficient = 0.83) with Benkelman Beam test data. The basic differences between the Road Rater and Benkelman Beam are as follows: 1. The Benkelman Beam uses a static 18,000 lb. load while the Road Rater uses a dynamic 800 to 2,000 lb. loading. 2. The Road Rater tests much faster and more economically than the Benkelman Beam. 3. The Road Rater better simulates a moving truck than the Benkelman Beam. The basic operating principle of the Road Rater is to impart a dynamic loading and measure the resultant movement of the pavement with velocity sensors. This data, when properly adjusted for temperature by use of a nomograph included in this report, can be used to determine pavement life expectancy and estimate overlay thickness required. Road Rater testing will be conducted in the spring, when pavements are in their weakest condition, until seasonal correction factors can be developed. The Road Rater does not have sufficient ram weight to effectively evaluate load carrying capacity of rigid pavements. All rigid pavements react similarly to Road Rater testing and generally deflect from 0.65 to 1.30 mils. Research will be contined to evaluate rigid pavements with the Road Rater, however. The Road Rater has proven to be a reliable, troublefree pavement evaluation machine. The deflection apparatus was originally front-mounted,but was rear-mounted during the winter of 1977-78. Since that time, van handling has greatly improved, and front suspension parts are no longer overstressed due to improper weight distribution.

Structural Analysis and Overlay Design of Pavements Using the Road Rater, MLR-84-3, 1986

In recent years the Iowa DOT has shifted emphasis from the construction of new roads to the maintenance and preservation of existing highways. A need has developed for analyzing pavements structurally to select the correct rehabilitation strategy and to properly design a pavement overlay if necessary. This need has been fulfilled by Road Rater testing which has been used successfully on all types of pavements to evaluate pavement and subgrade conditions and to design asphaltic concrete overlays. The Iowa Road Rater Design Method has been simplified so that it may be easily understood and used by the widely diverse groups of individuals which may be involved in pavement restoration and management. Road Rater analysis techniques have worked well to date and have been verified by pavement coring, soils sampling and testing, and pavement removal by block sampling. Void detection testing has also been performed experimentally in Iowa, and results indicate that the Road Rater can be used to locate pavement voids and that Road Rater analysis techniques are reasonably accurate. The success of Road Rater research and development has made deflection test data one of the most important pavement management inputs.

Structural Characterization of UHPC Waffle Bridge Deck and Connections, TR-614, 2014

The AASHTO strategic plan in 2005 for bridge engineering identified extending the service life of bridges and accelerating bridge construction as two of the grand challenges in bridge engineering. These challenges have the objective of producing safer and more economical bridges at a faster rate with a minimum service life of 75 years and reduced maintenance cost to serve the country’s infrastructure needs. Previous studies have shown that a prefabricated full-depth precast concrete deck system is an innovative technique that accelerates the rehabilitation process of a bridge deck, extending its service life with reduced user delays and community disruptions and lowering its life-cycle costs. Previous use of ultra-high performance concrete (UHPC) for bridge applications in the United States has been considered to be efficient and economical because of its superior structural characteristics and durability properties. Full-depth UHPC waffle deck panel systems have been developed over the past three years in Europe and the United States. Subsequently, a single span, 60-ft long and 33-ft wide prototype bridge with full-depth prefabricated UHPC waffle deck panels has been designed and built for a replacement bridge in Wapello County, Iowa. The structural performance characteristics and the constructability of the UHPC waffle deck system and its critical connections were studied through an experimental program at the structural laboratory of Iowa State University (ISU). Two prefabricated full-depth UHPC waffle deck (8 feet by 9 feet 9 inches by 8 inches) panels were connected to 24-ft long precast girders, and the system was tested under service, fatigue, overload, and ultimate loads. Three months after the completion of the bridge with waffle deck system, it was load tested under live loads in February 2012. The measured strain and deflection values were within the acceptable limits, validating the structural performance of the bridge deck. Based on the laboratory test results, observations, field testing of the prototype bridge, and experience gained from the sequence of construction events such as panel fabrication and casting of transverse and longitudinal joints, a prefabricated UHPC waffle deck system is found to be a viable option to achieve the goals of the AASHTO strategic plan.