About Fosroc Renderoc RG

Renderoc RG is Fosroc’s general-purpose repair microconcrete for situations where an ordinary hand-applied mortar simply cannot do the job. When steel congestion, restricted access or an awkward overhead pour rules out conventional placing and compaction, this material lets you flow repair concrete into the void and let it consolidate under its own weight. It arrives as a factory-blended dry powder, so the only site variable is the water you add, which removes the batching inconsistency that plagues site-mixed repair concrete. The blend is built on Portland cement, closely graded aggregates and fillers, with additives that trigger a controlled gaseous expansion while the mix is still plastic. That expansion offsets the natural shrinkage and settlement of the pour, so the hardened repair stays in intimate contact with the parent concrete and the reinforcement it surrounds.

For Indian contractors and consultants, the appeal is practical. A low water demand at a water:powder ratio around 0.16 gives you both high early strength and long-term durability without sacrificing flow. The cured microconcrete carries no chlorides and no metallic aggregate, and independent testing shows very low alkali-silica reactivity, which matters on infrastructure with a long design life. Because it can be pumped over distance and poured from a single feed point, Renderoc RG suits the jacketing and encasement work that dominates structural rehabilitation of bridges, industrial frames and older RCC buildings across the country. Where a section runs deeper than 100 mm, the mix accepts graded 5-12 mm aggregate to bulk it out and keep the heat of hydration in check.

The technical insight

The engineering that sets Renderoc RG apart is its plastic-state expansion. Most repair concretes shrink as they set and cure, which opens a hairline debond at the repair-to-substrate interface, exactly where you least want it in a load-sharing jacket. Renderoc RG counters this with additives that generate a small, controlled gas evolution while the mix is still workable, producing an unrestrained expansion in the region of 0 to 2 percent (ASTM C827). That gentle push keeps the pour pressed against the formwork and the old concrete during the critical stiffening window, so the interface stays tight and the repair behaves monolithically. The deliberately low water:powder ratio does the rest: less mix water means a denser, less permeable matrix, which is what carries the strength up to 50 N/mm2 at 28 days and slows the ingress of chloride and moisture that drives future corrosion. The result is a flowable material that behaves less like a patch and more like a structural extension of the member it repairs.

Where it is used

• Column and beam jacketing where reinforcement congestion prevents effective poker vibration
• Encasement and cross-section build-ups to structural strengthening designs
• Pile-top encapsulation, including as part of a waterproofing system
• Reinstatement of damaged reinforced-concrete elements in restricted or confined locations
• Repairs to bridge substructures, piers and abutments requiring a flowable pour
• Rehabilitation of industrial frames, silos and support structures
• Underpinning and machine-base reinstatement where access is tight
• Deeper section repairs extended on site with graded 5-12 mm aggregate

Key advantages

• Flows and self-compacts around congested steel, eliminating the need for vibration
• Gaseous expansion system compensates for plastic shrinkage and settlement, keeping the interface tight
• Factory pre-blended, so site batching variation is removed and only water is added
• Reaches high ultimate strength of 50 N/mm2 at 28 days with low permeability
• Can be gravity-poured or pumped into restricted and overhead locations
• Contains no chloride admixture and no metallic aggregate
• Very low alkali-silica reactivity (<0.1% expansion, ASTM C1260) for long-life infrastructure
• Accepts graded coarse aggregate for economical placement of deeper sections

Limitations & considerations

• Requires slurry-tight, well-braced formwork able to resist hydraulic pressure, so it is not a quick trowel-on patch
• Placed in lifts up to 100 mm; deeper sections need site-added aggregate to control heat of hydration
• Water is capped at 4.0 litres per 25 kg bag and the water:powder ratio must never be increased, or strength and expansion suffer
• Substrate must be saturated, primed and, on exposed rebar, treated with Nitozinc Primer before placing
• Cement-based, so it must be cured immediately after formwork stripping and protected in harsh drying conditions
• Shelf life is only 6 months in dry, unopened storage and shortens in high heat or humidity

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Renderoc RG

Renderoc RG sits in the flowable end of Fosroc’s Renderoc concrete-repair family. Where the repair is shallow, vertical or overhead and better suited to a hand-applied mortar, look at Renderoc GP for patch and reprofiling work, or the higher-build hand-placed grades. For pours that need finer control of flow or restricted-section placement, the modified Renderoc RG(M) variant is the natural sibling. Round out the system with the correct ancillaries we also stock: Nitobond EP as the substrate bond aid, Nitozinc Primer and Galvashield anodes for reinforcement protection, Reebol mould-release for the formwork, and the Concure range for curing. For structural crack injection or anchoring alongside a jacketing job, pair with Fosroc’s Conbextra grouts. Space Arc supplies these across Delhi NCR and Pan-India, and our team can help you match the right microconcrete grade to the section geometry and access on your project.

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