Maintenance

The Program Evaluation Division was established by the Legislature in 1975 as a center for management and policy research within the Office of the Legislative Auditor. The division's mission, as set forth in statute, is to determine the degree to which activities and programs entered into or funded by the state are accomplishing their goals and objectives and utilizing resources efficiently. Reports published by the division describe state programs, analyze management problems, evaluate outcomes, and recommend alternative means of reaching program goals. A list of past reports appears at the end of this document. Topics for study are approved by the Legislative Audit Commission (LAC), a 16- member bipartisan oversight committee. The division's reports, however, are solely the responsibility of the Legislative Auditor and his staff. Findings, conclusions, and recommendations do not necessarily reflect the views of the LAC or any of its members.

This Research Summary is part of the final deliverable for Report 2024-28, "Bridge Pile Repair Using Underwater Fiberglass Reinforced Plastic (FRP) Jacket and Steel Reinforced Grout, published in February 2025.

This study explored the feasibility and acceptability of using stay in-place fiberglass reinforced plastic (FRP) jackets and underwater steel reinforced grout for timely bridge piling repairs in Minnesota without dewatering. One of the goals of the project was to determine the current state of practice to this corrosion repair and inspection by researching other projects using similar repairs and to develop a survey to other departments of transportation to gather their experience with this type of repair. Another goal was to document the entire repair process on bridge 9462. Two different products, Five Star PileForm F Jacket and grout system and Denso SeaShield FX-70 and grout system, were installed, and contractor feedback was collected during the installation. This type of repair had a very limited impact to the surrounding area compared to a cofferdam-type repair. In fact, the repair was practically invisible to the drivers on the bridge and boaters were able to pass under the bridge while repairs were taking place. The contractor preferred the Denso product due to the jacket being stiffer, which made the jacket want to shut, since visibility in the water was zero. The jacket’s seam was easier to line up. Both products had identical installation steps, and both seemed to be a viable alternative to bridge pile repairs based on the performances from other projects found during the research.

Managing MnDOT’s network of roadways to a satisfactory level of performance requires pavement investment selection methods and activities that consider performing the “right fix” at the “right place” at the “right time” and the “right way.” Although these investment selections consider a broad assortment of investment methods and activities beyond traditional maintenance, maintenance investments and activities play a significant role in roadway pavement performance, often affected by the availability of localized and regionalized resources. To optimize roadway pavement maintenance investment methods and activities, MNDOT Maintenance has determined that the Smooth Roads Project Management Team should be re-established to address this topic.

Many Minnesota bridges have older barriers or parapets that met the design code at the time of construction in the 1950s. Many of these bridge barriers no longer meet current strength and performance requirements of NCHRP Report 350 or the Manual for Assessing Safety Hardware (MASH). As the Minnesota Department of Transportation (MnDOT) begins to rehabilitate older existing bridges; a determination needs to be made as to whether the existing older type of barrier can remain in place or if it should be rehabilitated or replaced with a newer style barrier. This research documented the number of bridges in Minnesota that have One-Line Rails and type G; J; and F barriers and when they were built. Evaluations were then performed for both the structural strength and crashworthiness of each type of barrier and recommended guidance and evaluation criteria were developed to determine when an existing barrier should be upgraded or replaced.

One of the most serious and costly problems presently facing highway agencies is premature bridge deck deterioration. In many cases decks designed to last forty years have required major surface repairs after only ten years of service due to spalling. This spalling has been determined to be related to deicing chemical "chloride" induced corrosion of the rebars. In response to this problem, Mn/DOT initiated a comprehensive program to restore damaged decks and protect new decks. At present, the two basic approaches to solving the problem are: 1. Prevent the penetration of chloride ions and moisture into the deck through the use of protective membranes, special concrete overlays and deck sealers. 2. Coat the rebars with epoxy to prevent chloride Ions from reaching the steel once the surrounding concrete has become contaminated. Bridge decks were constructed or reconstructed using protective membranes, special concrete overlays and coated rebars. Testing and evaluation consist of visual observations, delamination detection, determining depth of concrete cover over rebars, electrical potential measurements and electrical resistance measurements.

This report represents data obtained through a comprehensive field study encompassing some 70 bridge decks with a variety of protection systems in place and subject to varying traffic volumes and conditions of exposure. Decks repaired also exhibited varying initial condition and extents of concrete removal prior to rehabilitation. The basic categories of protection systems under study are as follows: 1. Membrane and bituminous overlay. 2. Special concrete overlays. 3. Coated rebar systems. Primary testing of these systems consisted of: 1. Delamination/debonding surveys. 2. Clear cover measurement. 3. Half cell potential testing. 4. Chloride penetration testing. 5. Visual surveys. The criteria followed for evaluation of system performance were separated into two elements: 1. System effectiveness (how well i.t does its job). 2. System durability (how., long it performs under service conditions

In August of 1976 a special study was undertaken by the Mn/DOT Research and Development Section under the existing Investigation 639 program (Bridge Deck Deterioration and Restoration). The objective of the special study was to identify sealers which would reduce chloride penetration into concrete decks and hopefully slow the corrosion process. This would in turn slow the corrosion induced spalling of the deck surface.

One of the most serious and costly problems presently facing highway agencies is premature deterioration of concrete bridge decks. The cause has now been linked to deicing chemical "chloride" induced corrosion of the reinforcement. In some cases bridge decks designed to last 40 years have required major repairs after only 10 years of service due to corrosion related "chuckholing" or spalling. Mn/DOT has become increasingly aware of this problem during the last 5 years and has initiated a comprehensive program to resolve it. The two basic approaches to solving the problem are to: 1. Keep the salt and moisture out of the decks with protective overlays and membranes, modified concretes or sealers. 2. Protect the steel from corrosion once the concrete's protective nature has been destroyed by chloride contamination, using epoxy and zinc coatings. Bridge decks were constructed or reconstructed using protective membranes, modified concretes and coated bars. Testing and evaluation consists of visual observations, delamination detection, chloride content testing, depth of concrete cover over rebars and electrical potential measurement.

New bridge decks will be designed to standards which insure a reasonably long maintenance free life. The new bridges have been grouped into three categories with a deck protective system designed to be cost effective for the anticipated exposure to de-icing chemicals in each of these categories.