To ensure long-term protection against corrosion and enhance the durability of metallic reinforcement in concrete structures Cortec provided the corrosion inhibiting admixture MCI(r)-2005 for the construction of the Kinnet Tunnel in Israel.
To inhibit corrosion at the level of the rebar, reduce autogenous, plastic, and thermal cracking, and withstand sulfate attack throughout the Kinnet Tunnel's service life a combination of corrosion inhibiting admixture MCI®-2005 by Cortec, used with C35/45 concrete comprising CEM-III/B sulfate-resistant cement (according to Table-One of EN-197-1 and its Israeli equivalent Table-One of IS-1) was specified.
The challenges
The Kinnet tunnel is being constructed to collect flood wa¬ter from the entire Arava region and the city of Eilat, Israel. The environment in which the tunnel is located is a very harsh one, with sulfate-rich ground and extremely hot weather conditions. Moreover, the regions' flood water is considered soft water, which contains very few minerals and is very aggressive toward concrete.
The aggressive environment where the Kinnet tunnel is located poses two significant challenges: a physi¬cal challenge from drift-rich water erosion (since the tunnel is not covered and can collect debris in the water) and a chemical challenge from aggressive soil without and soft water within. The casting of thick concrete elements in a severe environment while seeking to achieve a 100-year service life posed a special con¬struction challenge. The project needed to meet re¬quirements for an exposure level set to XA-3 (harsh soil aggressiveness) according to Table One of EN-206-1 (Exposure Level 11 according to the equivalent Israeli standard IS-118).
The solution
To respond to the challenges posed by the construction of the Kinnet Tunnel, Cortec provided MCI®-2005, a
water-based, organic, corrosion inhibiting admixture for protection of metallic reinforcement in concrete structures, which can enhance the durability and extend the service life of reinforced concrete exposed to corrosive environments.
MCI®-2005 contains a blend of amine salts of carboxylic acids which, when incorporated into concrete, form a protective layer on embedded reinforcement, delaying the onset of corrosion as well as reducing existing corrosion rates.
MCI®-2005 protects both anodic and cathodic areas within a corrosion cell and has lower toxicity and environmental impact than traditional corrosion inhibiting admixtures, and a low dosage rate with minimal effect on concrete.
The performance-based method was chosen instead of the alternative "Limiting Values Design Method" because it offered better durability (demonstrated by LIFE-365 software analysis predictions) without adding to project costs.
This method also took away the need to add extra reinforcement steel to minimize dynamic cracking (maximal crack width, 0.1 mm, according to IS-466-1), which would have otherwise been required under the limiting values method.
It also reduced the likelihood of autogenous, plastic, and thermal cracking from using excess cement to achieve the required C50/60 concrete strength under the limiting values method.
Use of CEM-III/B sulfate-resistant cement provided chemical durability for the site's harsh environment and, by enabling slower strength development, was an additional way to reduce thermal cracking.
The performance-based method also provided a built-in solution for non-constructive application errors (e.g., insufficient rebar cover, surface cracking, or non-constructive segregation) that could significantly reduce long-term structural service life by allowing early corrosion initiation. The presence of MCI®-2005 will help protect against corrosion should these problems arise, while the limiting values method would have included no protection after corrosion started.
MCI®-2005 contains 67% USDA certified biobased content and meets all requirements of ASTM C1582. It is ANSI/NSF Standard 61 certified for use in structures holding potable water and complies with CSA S413, Section C1.2, for corrosion inhibiting. It is field and lab tested worldwide.