Influence of Changes in Water-to-Cement Ratio, Alkalinity, Concrete Fluidity, Voids, and Type of Reinforcing Steel on the Corrosion Potential of Steel in Concrete.

Details

• Creators:
  Sharp, Stephen R. ; Mokarem, David W.
• Corporate Creators:
  Virginia Center for Transportation Innovation and Research
• Corporate Contributors:
  Virginia. Dept. of Transportation ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Corrosion
  • Reinforced concrete pavements
  • Water cement ratio
  • Air voids
  • Alkalinity
• Publication/ Report Number:
  FHWA/VCTIR 14-R11
• Resource Type:
  Tech Report
• Geographical Coverage:
  Virginia
• Corporate Publisher:
  Virginia. Dept. of Transportation
• Abstract:
  "Research on steel corrosion has demonstrated that the concentrations of chloride and hydroxide ion at the concrete/steel ; interface influence the susceptibility of the steel to corrosive attack. This study used electrochemical means and changes in mix ; design to increase the alkalinity and improve consolidation of the concrete against the steel to determine if this would increase the ; corrosion resistance of the reinforcing steel without compromising the properties of the concrete. To understand these effects ; better, the following concrete properties were evaluated: compressive strength, splitting tensile strength, modulus of elasticity, ; and length change (shrinkage). ; The evaluation involved the casting of different types of concrete samples, all of which contained artificial voids, for ; corrosion testing. These samples were composed of one of two concrete mixtures: (1) the Virginia Department of ; Transportation’s (VDOT) Class A4 General Bridge Deck Concrete with Straight Portland Cement (A4), or (2) a selfconsolidating ; concrete (SCC). Selected A4 and SCC mixtures were electrochemically treated 135 days after samples were cast. ; Some samples were left untreated and functioned as control samples. ; There were no significant differences in the concrete properties between the short-term treatment (less than 7 hr) and ; control samples tested in this study. It was determined that alkalinity, water-to-cement ratio, and steel type all influence the ; corrosion potential of reinforcing steel when reinforced concrete is subjected to saltwater. In addition, introducing small voids ; adjacent to the steel created a greater spread between the 25th and 75th percentile of the half-cell potential measurements when ; compared to locations without voids; however, these same voids have little influence on the average value measured. A study is ; underway to perform cyclical saltwater ponding on selected samples to allow for future evaluation of corrosion resistance. ; This study showed that alkalinity, water-to-cement ratio, concrete fluidity during placement, and steel type all influence ; the corrosion potential of the reinforcing steel when reinforced concrete is subjected to saltwater. The study recommended that ; the Virginia Center for Transportation Innovation and Research (VCTIR) continue performing saltwater exposure on these ; specimens until corrosion becomes evident and then autopsy them and characterize the corrosion of the steel reinforcement. In ; addition, VCTIR should work with VDOT’s Materials Division to compare various concrete mix designs that would be ; considered acceptable to VDOT and assess how each influences the corrosion potential on embedded steel. Further, more ; emphasis should be placed on mix designs, such as SCC mixtures, that could provide VDOT with greater corrosion resistance ; and reduced labor during placement."
  More +
• Format:
  PDF
• Funding:
  99205
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/27446/dot_27446_DS1.pdf
• File Type:
  [PDF - 3.59 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:ac74169d52b52e371ce7de206fea59020e5fd69b03f91ec92132c6e6fc064451