Permeability Reduction of Restrained Concrete in a Chloride-Rich Environment – Phase I

The Mississippi Department of Transportation (MDOT) is currently requiring that permeability reducing admixtures be included in concrete mixtures used for bridge deck overlays through Special Provision No. 907-804-1 in an effort to improve the long-term performance of bridges. These admixtures are also included in section 713.02.4 of the 2017 edition of “Mississippi Standard Specifications for Road and Bridge Construction” where these materials are referenced as “waterproofing admixtures.” Hydrostatic permeability reducing admixtures (PRAHs) typically contain hydrophilic crystalline materials that react with water and byproducts of hydration to form non-water-soluble deposits that reportedly seal pores, capillary tracts, and hairline cracks in hardened concrete. This makes hardened concrete less permeable and more resistant to ingress of chloride ions that corrode reinforcing steel and create costly repairs. This study evaluates two hydrostatic permeability reducing admixtures for their effectiveness in reducing permeability and sealing hairline cracks in hardened concrete. Three concrete mixtures were evaluated including one with no permeability reducing admixture (control mixture) and two mixtures each using a hydrostatic permeability reducing admixture. Hardened concrete properties used in this evaluation included; compressive strength, rapid chloride permeability, surface resistivity, cracking tendency, and chloride ion content. While all data developed for this study did not ascertain the benefit of the current practice of requiring permeability reducing admixtures in portland cement concrete for bridge deck overlays, one product did reduce chloride ion intrusion through hairline cracks when compared to the control mixture


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Filing Info

  • Accession Number: 01784435
  • Record Type: Research project
  • Source Agency: Mississippi Department of Transportation
  • Files: RIP, STATEDOT
  • Created Date: Oct 8 2021 9:01AM