About MC-Bauchemie Oxal VP I T flow

Oxal VP I T flow is the highly flowable member of MC-Bauchemie’s Oxal range — a dedicated line of trass-lime and trass-cement products built specifically for the repair and stabilisation of historic and natural-stone masonry, sitting apart from the company’s mainstream Emcekrete and Centrilit grouts meant for machine bases and structural anchors. Where a standard cementitious grout is designed to match the stiffness and strength of reinforced concrete, Oxal VP I T flow is designed to do the opposite: it is deliberately soft, chloride-free and low-shrinkage, so that once it has filled a void or bonded a crack inside a stone or rubble wall, it moves with the surrounding masonry rather than restraining it. That distinction sounds academic until you have seen what a rigid, high-modulus grout does to 200-year-old sandstone or lime-bedded rubble — it concentrates stress at the interface and the original material fails first, not the repair.\n\nFor Space Arc, as an authorised MC-Bauchemie distributor and applicator across Delhi NCR and pan-India, this product answers a real gap in the local repair market. India’s stock of stone and brick heritage structures — forts, stepwells, colonial-era bridges, temple plinths, riverfront ghats — is enormous, and most contractors reach for a generic non-shrink cementitious grout because that is what is stocked locally, with predictable long-term consequences for the fabric being “repaired.” Oxal VP I T flow, applied correctly with a proper injection concept and low-pressure pumping equipment, lets conservation architects and structural rehabilitation contractors specify a grout that was actually developed for this application rather than adapted from a concrete-repair catalogue. It is not a mass-market product, and specifiers should expect to order it in planned quantities rather than pick it up off a shelf.

The technical insight

The defining ingredient here is trass — a natural pozzolan (volcanic tuff) long used in German and broader European masonry conservation practice to bind lime- and cement-based grouts that need to stay chemically and physically compatible with soft natural stone. Trass reacts with lime to form additional binding phases without pushing the mix toward the high alkalinity and high stiffness of a pure Portland-cement system, which is why Oxal VP I T flow can carry a sulphate-resisting binder to EN 197 part 1 while still landing at a mortar-class strength of only M 15 to EN 998 part 2 (12 N/mm² compressive at 7 days, 16 N/mm² at 28 days) and a dynamic E-modulus of 9,600 N/mm² — roughly a third of what a typical structural repair mortar delivers. That modulus number is the one figure specifiers should not skip past: it is the mechanical reason this grout is described as “adapted to natural stone masonry in terms of construction physics.”\n\nThe “flow” designation is equally deliberate. An efflux time of approximately 139 seconds to DIN EN 14117 puts it well into pumpable, low-viscosity territory, which matters because heritage masonry voids are rarely large, clean cavities — they are hairline fissures, loose rubble cores and multi-wythe gaps that a stiffer suspension simply will not reach. A measured +0.9% volume change (DIN 4227 T5) means the grout expands very slightly rather than shrinking away from the void wall as it cures, so the fill stays in full contact with the surrounding masonry over time. The trade-off is a working time of only about 60 minutes at +20°C under constant stirring or pumping — shorter in Indian ambient conditions during peak summer — which is why the datasheet is explicit that hand-mixing and part-batching are not permitted; it has to be machine-mixed and moved with intent.

Where it is used

• Consolidation of loose or hollow natural-stone and rubble masonry in forts, temples, havelis and other heritage buildings
• Filling internal voids in multi-leaf (multi-wythe) stone or mixed masonry walls before surface conservation work
• Crack and joint injection in masonry bridges, dams, retaining walls and other civil/engineering masonry structures
• Backfilling behind loose masonry facings and veneers to restore composite action with the backing wall
• Stabilising natural stone, mixed and multi-layer masonry that is damp or non-permanently saturated with water
• Pre-consolidation grouting ahead of repointing, lime plastering or render work in restoration programmes
• Grouting of rubble-filled masonry cores in old fort and temple ramparts prior to structural strengthening works
• Injection of old masonry culverts, sewer linings and similar underground masonry structures

Key advantages

• One-component system — just add water; no resin components or complex ratios to get wrong on site
• Very low dynamic E-modulus (9,600 N/mm²) that moves with soft stone instead of stressing it against a stiffer repair
• High flowability and low viscosity (efflux ~139 seconds) that penetrate fine cracks and voids without segregating
• Pumpable at low pressure (max. 5 bar) through packers or hoses, which is gentler on fragile historic fabric
• Low-shrinkage, slightly expansive behaviour (+0.9%) that keeps the grout in full contact with the void walls long-term
• Sulphate-resisting binder to EN 197 part 1, relevant to India’s damp, saline and coastal masonry conditions
• Chloride-free formulation, so it will not corrode embedded metal cramps, dowels or reinforcement in old masonry
• Achieves EN 998-2 mortar class M 15 — enough structural consolidation without over-strengthening soft original material

Limitations & considerations

• Purely an injection/grouting product — it does not finish a wall; surface repointing or rendering needs a separate Oxal-range product
• Hand-mixing and partial-batch mixing are explicitly not permitted, so a pan or forced-action mixer must be on site
• Working time is only around 60 minutes at +20°C, tighter in Indian summer heat, which forces disciplined batch planning and pumping logistics
• Effective use depends on a proper pre-injection survey and injection concept — it is not a walk-up repair product for undiagnosed cracking
• Grey cementitious colour means it is not intended to be left visible on fair-faced stonework without separate surface treatment
• The published technical dossier is the international English datasheet; specifiers working to IS 456/IS 1200 conventions will need to cross-reference the EN 998-2 and EN 197-1 values themselves

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie Oxal VP I T flow

Oxal VP I T flow sits inside MC-Bauchemie’s dedicated Oxal restoration range alongside Oxal VP I T (its less-flowable sibling), Oxal VP III HS (a highly sulphate-resistant, limestone-powder-free grouting glue for more aggressive sulphate exposure), Oxal TKM-HS (a trass-lime masonry mortar), Oxal BS-V (a single-component injection-hole closing suspension), and the finishing-side products Oxal NHL 3 historic, Oxal SPM and the Oxal WPw restoration-render pair — together forming a full system for diagnosing, injecting, rebuilding and finishing historic masonry rather than a single standalone SKU. Space Arc typically specifies the family together on a conservation project: VP I T flow (or VP III HS where sulphate attack is severe) to consolidate the core, followed by the render and finishing products for the visible surface. There is no genuine like-for-like Fosroc equivalent for this specific heritage-masonry, low-modulus grouting chemistry — Fosroc’s flowable cementitious grouts (the Conbextra range, for example) are engineered for structural and machine-base grouting rather than for matching the stiffness of soft natural stone, so a specifier choosing between the two brands should pick Conbextra for structural/anchor grouting and stay with the Oxal system specifically for heritage and natural-stone consolidation work.

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