About MC-Bauchemie MC-RIM PROTECT-H

Concrete in sewage and effluent infrastructure rarely fails from load — it fails from chemistry. Above the waterline in a sewer, wet well or scraper trackway, hydrogen sulphide gas gets converted by bacteria into biogenic sulphuric acid, pulling the surface pH down toward 3.5, while the same structure may see pH swing back up past 12–13 during alkaline CIP or lime-dosing cycles. Ordinary M25/M30 repair mortars — even ones marketed as “high strength” — are formulated to resist load and abrasion, not a daily pH swing of that magnitude. In Indian STPs, CETPs and process-industry ETPs, many running with almost no shutdown window, that mismatch shows up as spalled scraper trackways, eroded clarifier floors and the same “permanent” repair being re-tendered every three to four years.

MC-RIM PROTECT-H is MC-Bauchemie’s purpose-built answer to that specific problem, not a generic repair mortar stretched to cover it. It is applied as part of a defined system — Nafufill BC as the bonding coat, PROTECT-H built up in 15–60 mm passes to re-profile and protect the horizontal surface in a single operation, and either wet-jute curing or the companion MC-RIM PROTECT-C curing agent to lock in the dense, low-permeability matrix the product’s chemical resistance depends on. The result is independently classified to EN 13813 as a CT/C60 cement screed — a documented performance class a consulting engineer or municipal corporation can cite in a specification, rather than a manufacturer’s claim taken on faith.

The technical insight

The number worth reading twice on this datasheet is the chloride migration coefficient: 4.94 x 10-12 m2/s. That’s a very slow rate of chloride ingress, which points to a dense, low-permeability matrix — the same property that lets the product stay impermeable to water while still being open to vapour diffusion, so it doesn’t blister off a damp substrate the way a film-forming coating can. Strength development is front-loaded on purpose: 30 N/mm² compressive strength by 48 hours, climbing to 56.2 N/mm² at 28 days, paired with water resistance after just 1 day at 20°C — that’s what makes fast plant turnaround realistic. Flexural strength of 9.5 N/mm² at 28 days combined with a low shrinkage figure of 0.47 mm/m matters more than it looks: in a 15-60 mm horizontal pour, shrinkage cracking is exactly what would reopen a path for the chemical attack the product is meant to stop. And the Böhme abrasion test rating is directly relevant to scraper trackways, where a mechanical rake physically drags across the same surface thousands of times a year.

Where it is used

• STP, ETP and CETP tank floors, aeration basins and clarifier floors under continuous effluent contact
• Scraper trackways and mechanical-rake channels, where Böhme-tested abrasion resistance matters daily
• Sewage pumping station wet wells and sumps
• Distillery, sugar mill, dairy and chemical-industry effluent channels and pits
• Partial-defect and spall repair on horizontal concrete in chemically aggressive zones
• Concrete floors under EN exposure classes XA1-3 (chemical attack), XD/XS (chloride) and XF (freeze-thaw), useful reference points even where the project is specified to IS 456
• Re-profiling of degraded RCC slabs ahead of a waterproofing or protective topcoat system
• Water-retaining structure floors falling in moisture classes WO, WF and WA

Key advantages

• Rated for continuous exposure from pH 3.5 (biogenic sulphuric acid) to pH 14 (alkaline cleaning cycles) in one product, rather than needing separate acid- and alkali-resistant systems
• Factory-proportioned, one-component powder — mixing is just water addition, cutting out on-site batching error on the powder side
• Fast early strength (30 N/mm² at 48 hours) shortens the window before a scraper trackway or tank floor can be brought back into service
• Very low chloride migration coefficient (4.94 x 10-12 m2/s) gives long-term protection to any embedded reinforcement or dowels
• EN 13813 CT/C60 certification gives specifiers an auditable, third-party performance class rather than a marketing claim
• Vapour-permeable while remaining water-impermeable, so it doesn’t trap moisture and blister off a damp substrate
• Pump-applicable with standard screed pumps, which matters on large STP/ETP tank floors where hand-application alone isn’t practical
• Compatible dedicated curing agent (MC-RIM PROTECT-C) as a fallback when 5 days of continuous wet-jute curing isn’t realistic on a live plant

Limitations & considerations

• Restricted to horizontal and slightly sloped surfaces — not rated for vertical walls or soffits
• Minimum 15 mm layer thickness per pass, so it isn’t a thin skim-coat repair product
• Mandatory 5-day moist curing (or the proprietary curing agent) demands real site discipline, which is hard to enforce on a live, occupied plant
• Depends on the Nafufill BC bond coat and correct substrate preparation — shortcuts here compromise the whole system, not just the top layer
• Costs more than general-purpose repair mortars, which only makes sense where the chemical exposure is genuinely aggressive
• Not a structural strengthening product — where the problem is load-bearing capacity rather than surface chemical attack, this is the wrong tool

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie MC-RIM PROTECT-H

Within MC-Bauchemie’s own range, PROTECT-H is always specified alongside Nafufill BC (mandatory bond coat) and, where wet curing isn’t practical, MC-RIM PROTECT-C curing agent — treat these as a system, not optional add-ons. For general structural repair without the sulphate/pH-swing exposure, MC-Bauchemie’s broader Nafufill mortar range is the more economical choice; reserve PROTECT-H’s premium for genuinely aggressive wastewater and effluent environments. On the competitive side, Fosroc’s Renderoc range (e.g. Renderoc HS Xtra) is a capable general-purpose and structural repair mortar, but it’s engineered and marketed for vertical/overhead structural repair and bond stability, not for sulphate-resistant, wide-pH-range wastewater protection — a specifier defaulting to Fosroc for an STP or ETP floor would typically need to layer a separate chemical-resistant topping system rather than getting PROTECT-H’s single-pass repair-plus-protection in one product.

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