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South Dakota Department of Transportation
Project Synopsis
SD2001-04


Title: Alternative Sealants for Bridge Decks
Project Researcher: Ariel Soriano,
Project Manager: Dan Johnston
Research Period: 3/26/2001 - 11/30/2002
Status:
Cost: $60,000.00

Problem Statement: Transverse cracking on newly constructed bridge decks as well as shrinkage cracking on low slump concrete overlays has increased markedly in recent years. Many of these cracks run all the way through the deck and create a problem with respect to the rapid ingress of moisture and chloride ions into the deck and onto the bridge superstructure and substructure. National Cooperative Highway Research (NCHRP) Report 380 Transverse Cracking in Newly Constructed Bridge Decks looked at this problem and developed guidelines for reducing transverse deck cracking on new bridge decks, but its analysis of the problem did not provide any straightforward answer or compelling explanation as to why deck cracking has gotten so much worse. Research is underway looking into the use of F fly ash as an admixture for structural concrete that will greatly reduce concrete permeability and, hopefully, reduce transverse and shrinkage cracking. Unfortunately, the present situation with regard to cracking incidence is poor with the majority of new decks and deck overlays exhibiting extensive cracking soon after construction. Preventing water and chloride ingress into these cracks is critical and the sooner this is accomplished, the better.

Currently, the Department utilizes linseed oil/mineral spirits treatments as a penetrating deck sealer on older decks and applies epoxy treatments to random cracking, especially on overlays, where the incidence of cracking is light to moderate. For severe cracking problems we are currently employing a thin epoxy chip seal developed by SDDOT for sealing entire decks, which still allows moisture transport through the deck. Other treatments such as silanes are available as well. We have sufficient tools for sealing cracks on decks but lack guidelines as to which particular treatment strategy is appropriate for a given set of circumstances. For example, what sealing strategy should be applied to a brand new deck with widespread cracking and significant crack widths? This research project will address these questions as well as provide optimum timing strategies for maintaining serviceability and maximizing deck life.



Findings: This project investigated potential concrete bridge deck crack and surface sealers, and their optimum application timing. The purpose of this project was to determine if there were better products than what SDDOT was using (i.e. – linseed oil surface sealer and epoxy crack sealer) that can be applied by SDDOT maintenance personnel. The objectives and tasks for this project were accomplished by gathering and evaluating agency, field, laboratory, and literature data. A major portion of this research project focused on determining the optimum timing for treatment application. The results indicate the following: 1. SDDOT should discontinue use of linseed oil as a penetrating sealer. 2. SDDOT should adopt penetrating sealers such as silanes/siloxanes/siliconates for surface sealing. 3. SDDOT should continue to use crack sealers such as reactive methacrylates, modified polyurethanes, and epoxies with low viscosity (i.e. - = 15 cp)

Research Objectives:
1  Outline a series of different treatment strategies to reduce water ingress into bridge decks due to existing cracking.
2  Develop recommendations for different systems capable of providing effective sealing of bridge decks under various conditions.
3  Provide bridge deck crack sealing guidelines based on individual bridge deck characteristics.

Research Tasks:
1  Perform a literature search on crack sealing methods for bridge decks.
2  Conduct a survey of northern tier states and Canadian provinces with respect to current bridge deck crack sealing strategies.
3  Meet with the technical panel to discuss the project and scope of work.
4  Obtain detailed information with regard to bridge deck cracking in South Dakota, conduct a survey of existing crack sealing applications statewide and interview appropriate Departmental personnel.
5  Develop a listing of promising candidate sealing strategies and evaluate their effectiveness and cost.
6  Apply these sealing strategies to several structures statewide (with the aid of SDDOT maintenance forces) and evaluate their effectiveness.
7  Develop a series of protocols for crack sealing with guidelines for locating and evaluating the severity of cracks on a tined surface and any surface preparation required prior to sealing.
8  Develop stratified guidelines for crack sealing of bridge decks based on deck condition (cracking severity), deicer usage patterns, geographic and environmental considerations and age and type of structure.
9  Meet with the technical panel to discuss results and recommendations prior to drafting the final report.
10   Prepare a final report and executive summary of the literature review, research methodology, findings, conclusions, guidelines and recommendations.
11  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

Documents Available:
SD2001_04_Final_Report.pdf

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