Viability and Durability of Shotcrete for Repairing Bridges

Several construction projects were reviewed that had used shotcrete for unformed repair work on bridge superstructures and substructures. These repairs, usually overhead or vertical repairs, are normally done by using rapid set cement mix and the manual lay-up method. In the past contractors have asked to substitute shotcrete. There now is a Bridge Special Provision sometimes used to specify shotcrete for a particular job. The main problems seen in the field with shotcrete were shrinkage cracking and lack of bond to the existing bridge. Through observation of four projects and checking literature on best practices from other states and the AASHTO-AGC-ARTBA Task Force 37 - 1999 report on Shotcrete Repair, several conclusions were reached. If the special provisions are followed closely shotcrete is a viable repair method for highway bridges. Good surface preparation and pre-wetting before shotcreting are critical to getting a good bond. Contractors quite often use the dry-mix shotcrete method, especially for small repairs. The Missouri Department of Transportation should require pre-bagged mixes for dry-mix shotcrete because it makes a more consistent mix. The pre-bagged mix should include silica fume in order to make the mix stickier and provide better bond strength. Testing showed a good air structure in the hardened concrete and an air entraining agent should be required in a pre-bagged mix. A 7-day moist cure is needed for shotcrete, and curing compound use should be secondary to specifying wet curing to decrease shrinkage cracks. Changes to the Bridge Special Provision incorporating these conclusions have been presented in this report.

• Record URL:
  • https://spexternal.modot.mo.gov/sites/cm/CORDT/or07014.pdf
• Record URL:
  • https://ntlrepository.blob.core.windows.net/lib/30000/30700/30708/or07014.pdf
• 
• Corporate Authors:

  Missouri Department of Transportation

  P.O. Box 270
  Jefferson City, MO  United States  65102

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Wenzlick, John D
• Publication Date: 2007-6-27

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Appendices; Bibliography; Photos;
• Pagination: 27p

Subject/Index Terms

• TRT Terms: Air entraining agents; Best practices; Bond strength (Materials); Bonding; Bridge substructures; Bridge superstructures; Bridges; Cracking; Curing agents; Repairing; Shotcrete; Shrinkage; Silica fume; Surface preparation
• Uncontrolled Terms: Moist curing; Prewetting
• Subject Areas: Bridges and other structures; Highways; Maintenance and Preservation; I24: Design of Bridges and Retaining Walls; I61: Equipment and Maintenance Methods;

Filing Info

• Accession Number: 01126244
• Record Type: Publication
• Report/Paper Numbers: OR07-014, RI03-011
• Files: NTL, TRIS, USDOT, STATEDOT
• Created Date: Apr 13 2009 10:08AM