MARINE AND COASTAL STRUCTURES

Cr. Photo: https://commons.wikimedia.org/wiki/File:M.V._%22Heung-A_Venus%22_(8564906074).jpg

Reinforced concrete structures in marine and tidal areas are exposed to harsh conditions and can deteriorate quickly. Concrete forms a passivating high alkalinity layer around reinforcement in its formative years ,with time this layer may be broken down and corrosion of reinforcement initiated .

Where concrete structures are exposed to salt bearing waters such as in a splash zones or tidal areas chloride and or sulphate salts may penetrate the concrete, the former acting as a catalyst to corrosion of the rebar and the latter attacking the cement paste .Intermittent wetting and drying exacerbates chloride penetration .Moisture and oxygen work together with the chlorides to create electrical conductivity leading to corrosion of the reinforcement cracking and finally spalling of the concrete surface .Even in areas where the concrete is submerged and limited oxygen present low cover to rebar may result in corrosion creating challenges for repair

Problem

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Many buildings , industrial utilities and infrastructure structures have been built close to the sea or in it the inherent harsh conditions cause corrosion due to salt in the air and salt water in splash and tidal zones constant wetting and drying . The result is spalled and cracked concrete with often severe corrosion or failure of reinforcement

Solution

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After

Reinforced concrete structures in marine and tidal areas are exposed to harsh conditions and can deteriorate quickly. Concrete forms             a passivating high alkalinity layer around reinforcement in its formative years ,with time this layer may be broken down and corrosion of reinforcement initiated .

Where concrete structures are exposed to salt bearing waters such as in a splash zones or tidal areas chloride and or sulphate salts may penetrate the concrete, the former acting as a catalyst to corrosion of the rebar and the latter attacking the cement paste .Intermittent wetting and drying excerbates chloride penetration .Moisture and oxygen work together with the chlorides to create electrical conductivity leading to corrosion of the reinforcement cracking and finally spalling of the concrete surface .

Even in areas where the concrete is submerged and limited oxygen present low cover to rebar may result in corrosion creating challenges for repair

Typical Marine Structure Repair

After removal of all damaged concrete and reinforcement clean up apply

Congard ST surface tolerant coating to reinforcement

Reinstate the concrete to profile with Conpatch 600HS high strength >70N/mm2 polymer modified repair mortar containing.

a migrating corrosion inhibitor by hand or spray

Big soffit areas can be reprofiled using spray applied Conpatch GC   shotcrete.

In tidal areas repair use Conpatch Marine very early setting repair mortar which can be  immersed is less then 2 hours

Below the water line use Congrout UWG underwater anti washout grout

All sound areas not removed spray with Conpatch NCI migrating corrosion inhibitor to provide longe life protection

Finally apply a protective crystalline waterproofing impregnation combined with a water repellant Contite HHH to all areas

Note : in areas of severely corroded reinforcement the reinforcement may require replacing .Condur CF carbon fibre structural strengthening may be also be used according to the specification to reinforce the structure  and over coated with Elastoclad anti carbonation coating .

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