About MC-Bauchemie ombran ASP

ombran ASP is the sealing layer within MC-Bauchemie’s ombran system for underground sewer and manhole rehabilitation, a range that also runs to rapid-setting patch mortars and structural repair renders sold as a coordinated build-up. ASP is a one-component, cement-bound slurry that mixes with plain water and is worked onto the substrate by hand, trowel or spray to close capillary pathways through concrete and masonry. Its C3A-free binder removes the tricalcium-aluminate phase that reacts with sulphate ions to form expansive ettringite, the mechanism behind sulphate-driven spalling in sewer lines and soil-contact structures.

That sulphate resistance matters on Indian sites. Sewer networks, STP feeder lines, effluent channels and ground-water-contact basements across the NCR and beyond often sit in sulphate- or chloride-bearing soils and high-TDS groundwater, conditions that shorten the life of ordinary cement renders within a few monsoon cycles. Space Arc stocks ombran ASP within its MC-Bauchemie repair portfolio and applies it through trained crews, since the sheet’s stated performance depends on mechanical mixing, correct coat thickness and a full 72-hour cure, not on the material alone.

The technical insight

Ordinary Portland cement contains tricalcium aluminate (C3A), which reacts with sulphate ions from soil or groundwater to form ettringite, a mineral that occupies more volume than what it replaces and so cracks the hardened matrix from within, the failure seen in untreated sewer crowns and manhole benching. Formulating ombran ASP without a C3A-bearing phase removes that reactive pathway rather than slowing it, which is why the sheet rates it for very severe, not moderate, sulphate exposure. It is also water-impermeable yet vapour-permeable, blocking liquid ingress while still letting trapped moisture vapour migrate outward, useful on old masonry where a fully vapour-tight membrane can drive salt crystallisation from behind.

Where it is used

• Sealing concrete and masonry sewer lines against groundwater and capillary ingress
• Rehabilitation coating for manholes, inspection chambers and accessible sewer structures
• Internal and external sealing of water-retaining and effluent-treatment tanks
• Waterproofing basement and retaining walls in ground contact
• Sealing brick, stone and block masonry culverts and sewer chambers
• Sulphate-attack protection in industrial belts and high-TDS groundwater zones
• Sealing coat within a full ombran sewer-rehabilitation build-up
• Rising-damp control in ground-bearing masonry walls and plinths

Key advantages

• C3A-free binder gives engineered resistance to very severe sulphate attack, not just a generic label
• Water-impermeable yet vapour-permeable, so it seals without trapping moisture inside the substrate
• Frost-resistant and built for permanent ground-contact exposure
• Bonds directly to sound mineral and cement-bound substrates, no separate bonding agent needed
• Applies by hand, trowel or spray, suited to confined manhole and chamber access
• Fast early strength gain, about 16 MPa at one day, so work progresses quickly
• Simple water-mix system, no epoxy or resin components, easy site handling and cleanup
• Documented within MC-Bauchemie’s ombran system, specified alongside compatible primers and repair mortars

Limitations & considerations

• A thin-film sealing slurry, not a structural repair mortar; spalled concrete or corroded rebar needs an ombran repair mortar first
• Maximum total build is only about 4mm, so it cannot bridge movement joints or active structural cracks
• Hand-mixing or partial-bag mixing is explicitly disallowed; it needs a mechanical mixer and a trained crew
• The mandatory 72-hour damp cure is non-negotiable; poor curing in summer heat or wind will crack or de-bond it
• Being rigid and cementitious, it tolerates less vibration or thermal movement than a flexible PU membrane
• Data is referenced to +10 to +30 degrees C, so peak-summer sites need shading and pre-wetting discipline

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie ombran ASP

ombran ASP is one layer of MC-Bauchemie’s wider ombran range for sewer and manhole rehabilitation, which also runs to rapid-setting patch mortars and repair renders used to rebuild spalled sections before ASP goes on as the final sealing coat; Space Arc specifies these as a matched system rather than mixing brands within one repair. Where a project genuinely needs a flexible, fully vapour-tight liquid membrane instead, say a slab needing crack-bridging tolerance, Fosroc’s Nitoproof 600 polyurethane coating is a credible alternative, though it is a different chemistry class (moisture-cured PU film versus cement-bound slurry) and the choice should follow substrate and exposure conditions, not brand preference.

Related Waterproofing products

View all Waterproofing products →