Research Reports

The Minnesota Department of Transportation (MnDOT) investigated the use of dowel bars with various anchoring methods. This report examines the characteristics of various epoxy and grout anchorage systems at the interface between new construction and existing concrete. Twelve different anchoring materials as well as various anchoring methods were studied and compared to a control using no grout. This study did not examine the effects of the number of dowels used but instead was limited to the methods and materials used to anchor the dowels. This experiment was performed on concrete panels in-house. The tube grout method exhibited the best visual and magnetic imaging results. The evaluation methods did not clearly categorize the materials in order of performance but showed advantages of cleaning the drill-hole prior to dowel placement as well as the merits and demerits of using a retaining collar. The results generally suggested the need for an actual deployment research project on actual pavement in real-world service conditions. The field experiment was reported in a separate document.

This is the Executive Summary of the findings and recommendations to the Special Refuse Collection Vehicle Committee jointly under the auspices of the State Commissioner of Highways and the Director of the Pollution Control Agency. This Executive Summary is a condensed non-technical version of the final report. It provides a capsulized summary and acts as a guide for future decisions as they relate to the issue of overweight rear loading refuse compactor vehicles under load conditions when collecting or transporting solid waste refuse. The full and final report contains the complete findings, recorded weight datum, identification of contributing factors and suggested recommendations. Readers interested in the more detailed version should refer to the final report.

This report summarizes the approach, findings, and recommendations of the Minnesota Truck Size and Weight (TS&W) Project led by the Minnesota Department of Transportation (Mn/DOT) in cooperation with other public and private stakeholders. The purpose of the project is to assess changes to Minnesota's TS&W laws that would benefit the Minnesota economy while protecting roadway infrastructure and safety.

On May 7, 1975, one of the main girders of the Lafayette Street Bridge over the Mississippi River in St. Paul, Minnesota, was discovered to be cracked. Subsequently, on May 18, 1975, Dr. J. W. Fisher visited the site for a visual examination of the cracked girder. An agreement was made with the Department of Highways to investigate the cracked girder in order to ascertain the causes of the cracking and provide recommendations for corrective action-as may be deemed necessary for other details that may need attention.

The objective of this project was to conduct a state-of-the-art or synthesis research study on bridge design methods used in areas where low bearing capacity or unstable soils exist. Over the past 15 years, foundations of certain bridges in the Red River Valley region of Minnesota have experienced detrimental degrees of movement. Settlement or shifting of piers, abutments and approach fills are common and particularly difficult to correct. The result has been that maintenance operations to keep structures in service are frequent and costly. Three courses of action were pursued in preparing the synthesis. First, a literature search was conducted and various reports dealing with the topic were reviewed. Second, a limited field inspection was undertaken and problem sites (failure areas) were visited. Lastly, several meetings were held with persons knowledgeable about the situation and possible methods for correcting it. Through this process, the problem was more thoroughly analyzed and a better definition of the scope of the study was developed with limits established.

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.

This report is meant as a state of the art on utilization of solid waste material for road construction and maintenance. There are many waste materials, but in Minnesota three products are of prime interest because they are available in such large quantities. These are: Taconite Tailings, Fly Ash, and Boiler Slag Much study has been done on some of these large volume materials. Some of the successful uses found for these products are embankment fill, subbase, base, stabilize for soil or aggregate, paving aggregate, and bituminous mix components. This report undoubtedly is not the "last word" on the subject of solid waste utilization. Some materials or uses may have been overlooked or neglected, but it is hoped that the overall local state picture is well represented. This report has attempted to show that there are some large volume waste materials, there are bona fide uses for them, and utilization could be expanded with some effort. This also applies to lesser volume materials that sometimes aren't recognized as being usable.