REPORT OF CONCRETE CORROSION INHIBITOR TESTING

PROJECT: REPORTED TO:

COMPARATIVE STUDY CORTEC CORPORATION

4119 WHITE BEAR PARKWAY

ST. PAUL MN 55110

ATTN: BORIS MIKSIC

AET JOB NO: 05-00021 DATE: DECEMBER 22, 2000

INTRODUCTION

This report presents the results of our testing of Cortec’s MCI 2005, MCI 2006, and competing products. We understand the admixture was developed to provide corrosion protection to steel embedded in concrete. Mr. Boris Miksic of Cortec Corporation requested we evaluate the material’s effectiveness. The scope of our work consists of batching concrete; testing plastic concrete for properties; casting, curing and testing cylinders for compressive strength; and casting beams containing steel and testing for corrosion.

CONCLUSIONS

Base on the results of our work and experience, it is our opinion the following conclusions are appropriate:

1. Cortec’s MCI 2005 and 2006 provide valuable corrosion protection for steel embedded in concrete. The products delayed the onset of corrosion. When corrosion developed, the products reduced the corrosion current.

2. Cortec’s MCI 2005 and 2006 generally doubled the time to the onset of corrosion. The control concrete developed corrosion in the 9^th test cycle. MCI 2005 developed corrosion in the 17^th test cycle and 2006 in the 28^th test cycle.

3. Cortec’s MCI 2005 and 2006 reduced the corrosion current more than 5 fold once corrosion began. The control concrete corrosion current generally increased over the 47 cycles observed with an average corrosion current of 120 µA. MCI 2005 average corrosion current was 26 µA and MCI 2006 9 µA.

4. Cortec’s MCI 2005 and 2006 reduced the total corrosion experienced during the test 5 to 16 fold, respectively. The average total current passed by the control concrete was 12, 749 coulombs. MCI 2005 passed only 2803 coulombs during the test and MCI 2006 passed only 773 coulombs.

5. Cortec’s MCI 2005 and 2006 extend the time to cracking of concrete from rebar corrosion at least two times. The control concrete cracked at an age of 1_ years. One beam containing MCI 2005 cracked at about 3 years. The remaining MCI 2005 beams and all MCI 2006 beams are uncracked.

6. DCI and Rheocrete 222 dramatically impact set time of the concrete. The DCI accelerated initial set about 1 hour at 2 gallons and 2 hours at 4 gallons. Rheocrete 222 delayed initial set 30 minutes and final set more than 1 hour.

7. DCI delayed the onset of corrosion. The admixture extended the initiation time more than four times. Corrosion began in the forth-third cycle in the concrete with 4 gallons of DCI. Also, the corrosion rate once established is 20% greater than the control.

8. Rheocrete delayed the onset of corrosion. In the forty-sixth cycle the corrosion current was above 10 µA in all three beams.
9. At current rates of corrosion we expect the total charge passed in the DCI @ 4 gcy to exceed the MCI 2006 samples at the 62^nd cycle.

TESTING METHODS AND RESULTS

On July 17, 1996, and the subsequent dates, six test batches of concrete were made at our laboratory. The batches were 2_ cubic feet proportioned to the following mix designs:

The plastic concrete was tested for slump, air content, temperature, and unit weight immediately after discharge into a wheelbarrow. The following data was obtained:

Three concrete beams were cast from each concrete batch for corrosion testing per ASTM:G109. The beams were 4.5" x 6" x 11". Three steel reinforcing bars were set in the form in a triangular pattern prior to casting. The bars were taped tightly with electroplater’s tape to prevent rusting during curing. At one day the beams were stripped and moist cured for 27 days. Upon removal from the moist room, the concrete surface was wire brushed. The four vertical sides were sealed with a concrete epoxy sealer. A plastic dam was positioned on top of the beam. Silicon caulk was used to seal the dam to the beam. A 3% NaCl solution was poured into the dam for two weeks. After two weeks of ponding, samples were dried for two weeks. This cycle was repeated with the corrosion potential and current measured during the middle of the ponding interval. Corrosion is considered to occur when the macrocell current is at least 10 µA. Tables 1-6 contain the test data.

Report Prepared by:

_________________________________

Tim Suess Richard D. Stehly, P.E.

Concrete Engineer MN Reg. No. 12856