RECOMMENDATIONS
The following recommendations are provided to continue research and developmental
work with calcium nitrite.
1.      Work should be conducted to improve the finish of calcium-nitrite concrete decks. Experimental laboratory design work should be conducted to develop an improved calcium-nitrite concrete that incorporates super water reducers. That concrete should be field tested in conjunction with a screed that will not excessively work the concrete during finishing. This work should be performed prior to constructing other bridge decks with calcium nitrite in the concrete.
2.      Additional bridge decks should be constructed incorporating the improved calcium-nitrite concrete and modified screed. Department of Highways officials should also consider using calcium nitrite in other bridge elements such as pier caps where chloride-induced corrosion can be a problem.
3.      Laboratory work should be conducted to develop a concrete mix design incorporating calcium nitrite, super water reducers, and microsilica. That concrete could be employed on decks of new or rehabilitated bridges having high traffic volumes.
REFERENCES
1.      Locke, C. E., "Corrosion of Steel in Portland Cement Concrete: Fundamental Studies", Corrosion Effect of Stray Currents and the Techniques for Evaluating Corrosion of Rebar in Concrete, ASTM STP 906. V. Chaker Ed., American Society for Testing and Materials, Philadelphia, PA, 1986, pp 5-14.
2.      Rosenberg, A. M.; Gadis, J. M.; Kossivas, T. G.; and Previte, R. W., "A Corrosion Inhibitor Formulated with Calcium Nitrite for Use in Reinforced Concrete", Chloride Corrosion of Steel in Concrete. ASTM STP 629. Tonini, P.E. and Dean, S. W. Jr., Eds., American Society for Testing and Materials, Philadelphia, PA, 1977, pp 89-99.
3.      Berke, N. S., "The Effects of Calcium Nitrite and Mix Design on the Corrosion Resistance of Steel in Concrete (Part 2, Long-Term Results)", Corrosion 87 Conference, March 9-13,1987 San Francisco, CA, Paper 132, National Association of Corrosion Engineers, Houston, TX, pp 1-11.
4.      Virmani, Y. P.; Clear, K. C.; and Pasko, T. J. Jr., "Time-to-Corrosion of Reinforcing Steel in Concrete Slabs, Volume 5: Calcium Nitrite Admixture or Epoxy-Coated Reinforcing Bars as Corrosion Protection Systems", FHWA Report No. FHWA/RD-83/012, Federal Highway Administration Office of Engineering and Highway Operations RP, Washington, DC, 1983.
5.      Hunsucker, D. Q., (KTC) Memorandum to Ted Hopwood (KTC) on Inspection of the Experimental Calcium Nitrite Bridges in Washington and Boyle Counties, December 16, 1986.
6.      Beto, A. R., (W. R. Grace) Letter to Ted Hopwood (KTC) dated August 2, 1987 on Corrosion Readings taken June 24, 1987 on the Gose Road Bridge.
7.      Berke, N. S., "Corrosion Rates of Steel In Concrete - Why Worry?", ASTM Standardization News. Washington, DC, March 1986, pp 57-61.
8.      Kolakowski, J. A. (W. R. Grace) letter to Ted Hopwood (KTC) on Strength and Permeability Tests of Microsilica Concrete, prepared at the Prestress Services of Kentucky Inc. Fabrication Shop, May 31, 1988,
9.      Smith, G. Memorandum to B. Wheat on Darex Corrosion Inhibitor (DCI) dated April 13, 1987.
ITEM         DESCRIPTION  QUANTITY
1.      Calcium Nitrite (DCI)        4 gal/yd3*
2.      Water       30 gal/yd3
3.      Cement    6.6 bags/yd3**
4.      Coarse Aggregate (60 percent)       1,914 lb/yd3
5.      Five Aggregate (40 percent)    1,287 lb/yd3
6.      Retarder (Daratard 17)   6 oz/100 lb cement
7.      Air entraining agent (Protex)  5 oz/yd3
 
*       See Special Note for calcium nitrite inhibitor in the appendix. ** Increased to 7.0 bags/yd3 for a portion of the deck placed later.
ITEM         DESCRIPTION  QUANTITY
1.      Calcium Nitrite (DCI)        4 gal/yd3
2.      Water       26 gal/yd3*
3.      Cement    6.6 bags/yd3
4.      Coarse Aggregate (60 percent)       1,817 lb/yd3
5.      Five Aggregate (40 percent)    1,177 lb/yd3
6.      Super Water Reducer (Daracem 100 Type G)14 oz/100 lb cement**
7.      Air Entraining Agent (Russtech)      8 oz/yd3
 
*       Increased between 28.1 to 28.9 gal/yd3 in subsequent batches, ** Use restricted to keep slump less than 5 inches.
TABLE 3. Reinforcing Steel Corrosion Measurements from the Gose Road Bridge over Clarks Run in Boyle County - June 24, 1987.
PROBE#   LOCATION        REBAR POTENTIAL vs 315SS (mV)*CORR. POTENTIAL CSE**(mV) SCE***(mV)    POLAR. RESISTANCE
1.      12' {Gutter Line)       25     -200-13842
2.      8’-8’ (Center of Lane)       30     -220-ISO  52
3.      12-5" (Tire Track)     14     -220-14452
4.      16’-0’ {Center of Deck)    42     -210-13755
 
*       Data furnished by W. R. Grace August 2, 1987 ** Copper Sulfate Electrode *** Saturated Calomel Electrode.
 
Figure 1. Rough Concrete Surface Texture after Initial Finishing with Spinnmg-Drum Screed KY 152 Bridge (August 28, 1986).
 
 
Figure 2. KY 152 Bridge (December 1986).
 
 
Figure 4.
 
Irregular Grooved Finish on the Gose Road Bridge Deck (December 1986).
 
SPAN 7
CORROSION POTENTIAL READINGS IN mV
 
 
Figure 7. Stainless Steel Reference Electrode Installed on a
Transverse Rebar in the Gose Road Bridge (October 1986).
 
 
Figure 8. Polarization Resistance Measurements Being Taken of the Reference Electrodes Buried in the Deck of the Gose Road Bridge (July 24, 1987).
 
 
APPENDIX
(Transportation Cabinet Special Note for Calcium Nitrite Corrosion Inhibitor Used in the KY 152 and Gose Road Bridge Decks)
2CC
SPECIAL NOTE FOR CALCIUM NITRITE CORROSION INHIBITOR (EXPERIMENTAL)
I.       DESCRIPTION
This work shall consist of furnishing and adding calcium nitrite corrosion Inhibitor to reinforced concrete in the locations designated on the plans or in
Ura proposal,
II,     MATERIALS
The corrosion inhibitor shall be an aqueous solution and shall be W. R. Sraee’s DCI Corrosion Inhibitor or approved equal. The solution shall contain 30 ± X percent calcium nitrite by weight and shall weigh 10.6 ±0.1 pounds per gal Ion.
III.    CONSTRUCTION REQUIREMENTS
The calcium nitrite solution shall be added to the concrete mixture at the rat^ of 4.0 gallons per cubic yard. Precautions shall be taken to ensure that the solution does not contact other admixtures before entering the concrete. A1r entraining, water reducing, or water reducing and retarding admixtures shall bs compatible with the calcium nitrite, solution. Calcium nitrite acts as an accelerator in addition to inhibiting corrosion of the steel, and adjustment in quantities of other admixtures to produce acceptable workability and setting time snay be required.
The calcium nitrite solution shall be added isaediately after tha other admixtures have been incorporated into the mixture. Precautions shall be taken to ansure that the solution does not contact' other admixtures before entering the concrete. The water in the calcium nitrite solution shall be considered as part of the mixing water.
The manufacturer of the calcium nitrite solution shall provide a represent tative to assist the Contractor and the Engineer when use of the material begins, ar\d to be available on request during subsequent construction.
IV.    MEASUREMENT AND PAYMENT
No seperate measurement or payment will be Bade for furnishing and Incorporating the calcium nitrite solution into the concrete mixture. The cost of furnishing and incorporating the admixture, and furnishing a manufacturer's representative for technical assistance, is considered incidental to the contract unit price for the concrete in which the admixture is used.