About MC-Bauchemie MC-Crete 615

MC-Crete 615 is MC-Bauchemie’s calcium-nitrite corrosion inhibitor for steel-reinforced concrete, supplied as a concentrated aqueous solution that is added at the mixing stage rather than applied to the finished surface. In a durable structure the biggest long-term threat to reinforcement is not the concrete cracking but chlorides from seawater, spray or de-icing salts slowly diffusing to the rebar and breaking down its natural passive film. Once that film fails, the steel corrodes, expands and spalls the cover concrete. MC-Crete 615 tackles the problem at the source by putting a protective, corrosion-fighting chemistry into the pore solution of the concrete itself, present from day one and distributed uniformly through the section.

For engineers and consultants specifying coastal and marine work in India, the appeal is that it works with the mix rather than against it. It is compatible with OPC, PPC, PSC and blended cements incorporating fly ash, GGBFS and silica fume, so it can sit alongside the low-permeability, supplementary-cementitious mixes that are already standard practice for XS and XD exposure. It does not replace good cover, a sound water-cement ratio or a well-graded durable mix; it is a complementary line of defence that extends the time-to-corrosion for a given chloride ingress rate. That makes it a considered choice for structures where repair access is difficult or shutdown costs are high, such as bridges, jetties and elevated marine decks.

The technical insight

Reinforcing steel in fresh concrete is naturally protected by a thin passive oxide film that forms in the high-alkalinity pore water. Chloride ions attack that film locally, initiating pitting corrosion once their concentration at the steel surface crosses a critical threshold, commonly taken as roughly 0.4% chloride by mass of cement. MC-Crete 615 works by anodic passivation: the nitrite ions compete with chlorides at the anodic sites on the steel, reacting with ferrous ions to reinforce and stabilise a protective ferric-oxide film. In practical terms the nitrite does not stop chlorides arriving, it raises the amount of chloride the steel can tolerate before pitting starts, effectively doubling that critical threshold. Because protection depends on maintaining a sufficient nitrite-to-chloride ratio at the rebar, dosage is engineered to the expected chloride load rather than set as a single fixed figure, which is why the range spans 10 to 30 litres per cubic metre.

Where it is used

• Bridge deck and substructure concrete in coastal and de-icing-salt environments
• Marine pile caps, jetty substructures and other splash-zone marine concrete
• Multilevel and rooftop parking decks exposed to carried-in road salts
• Foundations and plinths for coastal residential and commercial buildings
• Precast concrete elements destined for coastal and marine infrastructure
• Industrial floors and structures in chloride-laden chemical-processing settings
• Water-retaining and tidal-zone structures where rebar protection is critical
• New RCC designed to a specified extended service life in EN 206 XD/XS classes

Key advantages

• Raises the critical chloride threshold for corrosion initiation, roughly doubling it from the ~0.4% by mass of cement baseline
• Distributed uniformly through the concrete from the moment of casting, protecting the full section, not just a coating
• Dosed on a nitrite-to-chloride ratio, so protection can be tuned to the actual exposure severity
• Compatible with OPC, PPC, PSC and blended mixes using fly ash, GGBFS and silica fume
• Adds a durability line of defence without forcing a change to the base mix design
• Only a marginal effect on compressive strength at standard dosages
• Batched as a liquid at the mixer, so no extra site application step or curing coat is needed
• Long shelf life of at least 12 months when stored correctly, easing project logistics

Limitations & considerations

• It is an anodic inhibitor: under-dosing relative to the chloride load can be counterproductive, so the nitrite-to-chloride ratio must be engineered, not guessed
• It does not stop chloride ingress or reduce permeability; it must be paired with adequate cover, low w/c ratio and a durable mix
• It protects new concrete dosed at the mixer and is not a remedial treatment for existing corroding structures
• As a liquid its added water must be accounted for in the total water content of the mix
• It must be protected from freezing and stored below 40 degrees C to remain effective
• Set and early-strength behaviour can shift with dosage and cement type, so trial mixes are advisable before large pours

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie MC-Crete 615

MC-Crete 615 sits in the durability admixture line of the MC-Bauchemie range as the dedicated corrosion-inhibiting solution for chloride-exposed reinforced concrete; on a marine or coastal project it is normally specified together with MC-Bauchemie superplasticisers and permeability-reducing admixtures that deliver the low water-cement ratio and dense matrix the inhibitor is designed to complement, plus MC-Bauchemie surface protection and repair systems for the finished structure. Where a client’s specification is written around Fosroc, the equivalent role is filled by Fosroc’s corrosion-inhibiting admixture (the Conplast corrosion-inhibitor line) alongside Fosroc superplasticisers and Nitobond/Renderoc repair products; as an authorised distributor for both, Space Arc can match the durability package to whichever brand the project standardises on. For remedial corrosion control on existing structures rather than new pours, ask us about migrating corrosion-inhibitor and repair-mortar systems, which address a different scenario from this mixing-stage admixture.

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