MCI-2020_Long_TermCorrosion_Test

(1994 November ̃ 1999 April)Final Test Result conducted and reported by:

GENERAL BUILDING RESEARCH CORPORATION of JAPAN

　 CORTEC CORPORATION4 119 White Bear Parkway. St. Paul. MN55110 USAPhone 651-429-1100 Fax 651-429-1122 E-mail:

info@cortecvci.com

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1. IntroductionThis is to report the test result conducted and performed by GBRC, during the period, starting from 1994 November

to 1999 April, requested by CORTEC CORPORATION(4119 White Bear Parkway, St. Paul, MN 55110 USA), onmigrating corrosion inhibitor “ MCI-2020” manufactured by Cortec Corporation in the aspect of its corrosionprotection property .According to the result obtained at the time of 8 months and also 3years and 7months, after the applying of MCI-

2020 to coat on specimens, the differences of corrosion degrees between the one repaired with MCI-2020 and un-repaired are clearly showed up with and confirmed that MCI-2020 is working to protect embodied rebar. This reportsays and leads us to the conclusion of the effectiveness of corrosion protection for rebars embodied inside of concretespecimens, which are repaired, applied and coated with MCI-2020, migrating into concrete specimens.

2. Testing MethodThe concrete specimens are prepared having 3 kg/m3 of Cl2 from the beginning and given an initial curing for 60

days and after observation they had corrosion, MCI-2020 was applied and coated on the one and left un-treated forthe others to make comparison between them.After the initial said 6o days of curing, all the specimens are put into the high temperature chamber and given furthercorrosion acceleration by repetition of dry and high humidity.

The measurements of corrosion weight loss were done at 303 days, 488 days, 1,371 days and 1,511 days on rebarsin the specimens. With these measurements and result, the effectiveness of corrosion protection repairing methodusing MCI-2020 was confirmed.

3. Condition of specimens1) Material of Specimens　 As shown below Draw _1, the specimens is in rectangular parallelepiped concrete and have embodied rebars (polishedsteel bar) at cover thickness 2 cm and 3 cm from the tops.During the course of this test, the corrosion degree of these rebars are determined the quantity.

• Test rebar 　 : φ13mm　 polished steel bar (JIS G3123 SGD-290-D)　 　 　 　 　 　 　 　 　 　 φ13mm, Cold Finished Carbon and Alloy Steel bars (JIS G3123)

• supplement rebar　 :　 D10mm deformed steel bar (JIS G3112 SD 345)　 　 　 　 　 　 　 　 　 　 　 　 　 D10mm, Steel Bars for Concrete Reinforcement (JIS G3112)

　 　 　 　25 100 10 100 25 ： Mini-sensor φ13 Polished round steel bar 20 30

30 30 150Mortar

φ3 Round bar 30 D10 Deformed bar 260 150 Unit : mm

2) Concrete MixThe materials used to make specimens are shown below in Chart-1. The specimens were made on 1994 Nov 8th.

• cement　 :　 　 Ordinary portland cement (JIS R5210)• bigger sizaggregate　 :　 Crushed stone aggregate (Maximum size:20mm)• smaller aggregate　 　:　 mixture sands :sea sands 50% crushed sands 50%

Chart-1 （ Concrete mix proportion）① Unit weight (kg/m3) ③W/C S/A water Cement Aggregate : A Chemical(%) (%) W C Fine S Coarse G Admixture (C×%)

65 47.2 190 292 831 958 0.73

■ Ordinary cement : W/C=65%

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■ Chloride ion content ■ Chemical admixture ■ Slump ■ Air content ■ Compressive strength

: 3 kg/m3

: Air entraining water reducing agent: 19.5cm: 3.8%: 29.3N/mm2 at 28days

3) Number of specimens preparedSpecimens prepared according to the above 1) and 2) specification is 17 and used for the test..

• for observation of corrosion on rebar cured initially for 60 days　 / control :　 14 piece• specimens untreated 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　- 7 pieces (three kinds of aging)

　 　 (totally untreated for all the testing period)• specimens treated after 60 days 　 　 　 　 　 　 　 　 　 　 　 - 4 pieces (three kinds of aging)

　 　 　 (treated after 60 days)• specimens treated after crack appeared　 　 　 　 　 　 　 - 5 pieces

　 　 　 (treated at 1,371 days_

4) Curing Condition　The following curing was given to the specimen under the condition of ; 1) To remold next day of molding, all the specimen were started being cured for 60 days under the temperature

at 20°C , humidity 100%RH, as the initial curing.2) Then cured in the room for 14 days at 20 °C, humidity 65%RH. During this period, at 7th day, repairing with acoat of MCI-2020 was given to specimens.

3) In order to accelerate a corrosion, cured with following drying /wetting alternation by a week.

• Drying condition : at 50°C ,　 below humidity 30%RH for one week.• Weting condition : at 40°C,　 humidity 100%Rhf for one week

5) MCI2020 coating　 During the above mentioned 2 period, MCI-2020 was coated with 333g/m2 with brush all the surface of specimens.The coating with brush was conducted in 2-3 times to achieve the standard quantity, which took one hour to coat.

6) Evaluation of corroded rebar　 To evaluate the degree of corrosion on rebars in the specimens, the weight of rebars were measured after specimenswere destructed and rebars were taken off and brushed with wire to remove corroded parts ( rust, corrosion) usingCLEAR RUST (UK, rust remover). Then the weight loss of rebars was measured after washing by clean water anddrying.　 To figure out the timing of destruction/measurement, “ Mini-Sensor” were set on the surface of rebars andembodied together to know an electrochemical behavior / change of the rebars, thus the timing were so decided.

4. RESULT　 The result of tests is shown according to the different test condition.

• Chart-2.1 :at the time of 60 days aging, corrosion level of Rebars and untreated test pieces• Chart-2.2 :test pieces having an initial treatment• Chart - 2.3 : result of test pieces treated with MCI-2020 after some cracks appeared.• Picture -2 :relative corrosion speed by each aging period.• Picture -3.1 3̃.3 :Corrosion level of rebars (ageing 60 days, 303 days, 488days)

5. About Corrosion protection of MCI-20201) Untreated rebar is getting heavy corrosion form the start and constantly for the period. At 303

days, some of the specimens had cracks (#46). During the test period, the corrosion speed is thatrebars/at 3cm depth got 73~93μ m/year, rebars/at 2 cm got 32~72μ m/year. ( refer to Chart 2.1)

2) As for untreated specimen, ageing between 1371̃ 1543days period the relative corrosion speedshows that corrosion was changed appearing dramatically. (Picture 2). In figuring out, rebar at 2cmdepth got negative one(-152μm/year), rebar at 3cm depth got big one (351μm/year). It meansthat there must be some variance in getting cracks appeared on specimens depend on its condition(

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earliest at 300 days or so) which gave some influences on the average corrosion speed between theperiod of 1371̃ 1543 days. It came from one or two specimen though. Accordingly we must say theresult of corrosion speed detected between that period would not be a proper indication andreferences came out from this experiment. In addition to say, there are also some variance withuntreated specimen showing about two times (43̃77μm/year, 1371̃ 1543 days , Chart 2.1).

3) Treated specimen with MCI-2020 at 60 days shows about 1/6 of corrosion speed compared tountreated one at the day of 428 ( Chart 3), means that MCI-2020 succeeded to protect rebarcontrolling corrosion speed well.

• A g e i n g 60̃303 d a y s p e r i o d : u n t r e a t e d specimen　 72̃73μ m/year　 　 　 corrosion speed ratio

• Ageing 60̃488 days period : treated one with MCI-2020　 12̃14μ m/year　 　 　 =0.17̃ 0.19(?1/6))

4) The result of detection of untreated specimen after 303 days and treated one after 488 days is shown inthe Chart 2 from which we could say the corrosion speed is well controlled until 1371 days having the ratio of0.53̃ 0.17 (on rebars stationed at the range of 2cm depth and at 3cm depth) and the corrosion speed isdecreased by _ 1̃/6.

1) The comparison data based on the weight loss and calculations of corrosion speed measured/obtained bybreaking specimens at 1371 days and 1543 days is shown in Chart 2.1&2.2.

In long term ageing the variance of corrosion speed appeared differently causing by specimens condition, it could beconcluded that the corrosion speed is well controlled and reduced by 1/3̃1/5. _ Ageing at 1371 days : untreated specimen　 66.0*μm/year　 　 　 corrosion speed /rate_ Ageing at 1371 days :　 treated withMCI-2020　 19.5*μm/year　 　 = about 0.30

_ Ageing at 1543 days : untreated specimen　 69.5*μm/year　 　　 corrosion speed/rate_ Ageing at 1543 days : treated withMCI-2020 15.0*μm/year　 　 = about 0.22

　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 (* averaged ones at 2cm and 3cm depth rebars)6) As for the specimens re-treated with MCI-2020 at the time when some cracks appeared, they had a bigdifferences in getting cracks needing/waiting for 1371 days to have finally each one has cracks. Then we hadonly 6 months to get the result of corrosion protection on them, which was too short to conclude clearly. As a short result for a reference, the result is shown in Chart 2.3. Remarkably said from the result, thecorrosion speed of untreated specimen got about two time quicker with 2cm rebar during the period of1371̃ 1543 days (43μm/year → 77μm/year), on the other hand, treated one had no increase of its speedeven at the days of 1543 (37μm/year). From this result it is concluded that the treatment with MCI-2020worked very well in controlling even applying on the corroded rebar and cracked specimens. However, wecould not observe the same with 3cm rebar since there was big variance among the specimens and could notcatch the corrosion tendency even on untreated specimens.

Through the corrosion test specified this time, we could conclude that coating type of corrosion inhibiter MCI-2020does control the corrosion speed of rebars embodied in the concrete having Cl2 3kg/m

3 . When MCI-2020 applied initially, the corrosion is well controlled reducing its speed by 1/6 during the period

before cracks are appeared. At medium term between 303~388 days, the corrosion control is reduced by about 1/3~1/5. In case applying MCI-2020 at cracks appeared, it is said that MCI-2020 works very well on rebar at 2cm depth

but it is too short to confirm its property in other case (cm).

In addition, there is no official coherence telling the experimental result of corrosion test corresponding to the actualprotection period, but it is so evaluated and concluded from the test that MCI-2020 could work to extend the life ofrebar reducing its corrosion rate by 6 times longer. In other words, it is considered that when MCI-2020 is appliedat rather earlier stage of corrosion, it does work so well afterwards in controlling cracks coming by 6 times longer ofperiod., which is the remarkable corrosion protection property MCI-2020 has.

6) The persons in charge of actual experiment　 　 　 　 　Material experiment room: Dr.. Masaru Nagayama　 　Ooyodo experiment room: Mr. Kazuyuki Shimozawa

Picture -1__Reinforced concrete specimen: sizing

Picture - 2_ Relative corrosion rate by each ageing period

Picture- 3.1_Corrosion of rebar: unfold(ageing 60 days)Picture- 3.2 Corrosion of rebar : unfold (ageing 303days,untreated specimen #46)Picture- 3.3 Corrosion of rebar : unfold (ageing 488days,MCI2020 treated specimen #53)