About Fosroc Renderoc RG 45

Fosroc Renderoc RG 45 belongs to the Renderoc RG family of free-flow micro-concretes — the workhorse repair material specifiers reach for when a damaged reinforced-concrete element has to be reinstated to near-original or higher strength but the section is too congested, too deep or too inaccessible to hand-pack with a trowel mortar. It arrives on site as a ready-to-use blend of Portland cement, graded aggregates, fillers and performance additives in sealed bags; the only thing added at site is a tightly controlled quantity of clean water. That single-pack discipline removes the biggest source of variability in field repairs — operatives guessing at sand-cement-water proportions in a wheelbarrow.\n\nThe name ‘RG 45’ points to the material’s defining property: it is the free-flow (‘RG’ = repair grout/micro-concrete) grade that comfortably exceeds the 45 N/mm² strength band, reaching of the order of 50 N/mm² at 28 days. In Indian conditions this matters because most structural concrete being repaired is M25 to M40; a micro-concrete that over-matches the parent concrete restores, rather than weakens, the load path. The chemistry is deliberately ordinary Portland-cement based so the coefficient of thermal expansion stays close to that of the host concrete — a detail that prevents the repair de-bonding under day-night and seasonal temperature swings common across Delhi NCR, Rajasthan and coastal sites.\n\nWhat separates a micro-concrete like Renderoc RG 45 from ordinary site concrete is fluidity without segregation. The mix is engineered to a very low water demand yet pours like a liquid, so it can be gravity-fed or pumped into formwork and find its way around dense reinforcement cages with no poker vibration. A gaseous expansion system generates a controlled volume increase in the plastic state, which counteracts the settlement and shrinkage that would otherwise leave a gap at the top of a repair or under a soffit. The result is a dense, low-permeability, intimately-bonded repair — the qualities that govern how long the rebar inside stays protected from carbonation and chloride attack.\n\nFor Space Arc Engineering’s customers across construction-chemical projects in the National Capital Region and pan-India, Renderoc RG 45 is typically specified as part of a complete Fosroc repair system rather than in isolation: rebar primed with Nitozinc, substrate bonded with Nitobond EP, the micro-concrete placed, and the surface protected with a Dekguard or Nitocote coating. Used that way it is a durable, code-aligned solution for concrete rehabilitation.

The technical insight

The engineering value of Renderoc RG 45 lives in three coupled properties. First, low water:powder ratio — roughly 3.75–4.0 L per 25 kg bag (W/P near 0.16) — which is what simultaneously delivers high early strength (~10 N/mm² in 24 hours at 30°C) and the low permeability that protects embedded steel. Second, plastic-state gaseous expansion (unrestrained expansion in the ~0 to 2% / 1–4% band per ASTM C827) which compensates for settlement so the repair stays in full contact at the soffit and behind congested bars; this is fundamentally different from hardened-state expansive grouts and means the benefit is captured only if the material is placed and confined while still plastic. Third, a coefficient of thermal expansion of 10–12 x 10⁻⁶/°C matched to the host concrete, so the composite repair behaves monolithically under thermal cycling rather than shearing at the bond line. The material is also chloride-free and tests <0.1% expansion to ASTM C1260, giving resistance to alkali-silica/alkali-aggregate reaction — important where reactive aggregates or marine exposure are in play. Crucially, the 100 mm single-pour depth limit is a heat-of-hydration control, not a strength limit: beyond it, 5–12 mm clean SSD aggregate must be blended in to bulk the section and suppress thermal cracking.

Where it is used

• Jacketing and encasement of distressed RC columns and beams to increase section and load capacity
• Repair of spalled, honeycombed or carbonation-damaged reinforced concrete where access is restricted
• Pile-top encapsulation and cut-off-level reinstatement as part of a waterproofing system
• Filling voids, blowholes and honeycombs behind dense reinforcement without vibration
• Structural reinstatement of cover concrete after corroded-rebar cleaning and priming
• Grouting of deep or congested repair sections that cannot be hand-trowelled
• Bridge, jetty and industrial-structure rehabilitation requiring durable, low-permeability repair concrete

Key advantages

• Free-flowing and self-levelling — places into congested, restricted sections with no poker vibration
• Gaseous expansion system compensates for plastic settlement and shrinkage, ensuring full contact at soffits
• Pre-packed single component — only clean water added on site, eliminating site-batching variation
• Rapid strength gain (~10 N/mm² in 24 h) allows early reinstatement and reduced downtime
• High ultimate strength (~50 N/mm² at 28 days) over-matches most M25–M40 parent concrete
• Low water demand gives low permeability and long-term durability protection to embedded steel
• Chloride-free and resistant to alkali-silica / alkali-aggregate reaction (ASTM C1260 <0.1%)
• Coefficient of thermal expansion matched to host concrete, minimising thermal de-bonding
• Can be poured or pumped, suiting both small patch repairs and large jacketing pours
• Class A1 fire rating (EN 1504 cl 5.5) and non-flammable

Limitations & considerations

• Single-pour depth limited to 100 mm; deeper sections need 5–12 mm graded SSD aggregate blended in to control heat of hydration
• Water content is strictly capped (must not exceed ~4.0 L/25 kg bag) — over-watering destroys strength and shrinkage compensation
• Requires slurry-tight, well-vented formwork able to resist hydraulic pressure; not a trowel-applied patch mortar
• Plastic-state expansion benefit is lost if the material is not placed and confined promptly within its working time
• Cement-based and exothermic — large continuous pours risk thermal cracking without aggregate extension and good curing
• Needs full surface preparation (rebar cleaning, Nitozinc priming, substrate saturation or Nitobond EP) for the system to perform
• 6-month shelf life, reduced further by high heat/humidity — relevant for monsoon and summer storage in India
• Not intended for thin overlays, fairing coats or vertical/overhead trowel work — use a Renderoc HB/Renderoc Plug grade instead

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Renderoc RG 45

Within the Fosroc range, Renderoc RG 45 is the free-flow, pour-and-pump micro-concrete for deep and congested structural repairs — distinct from Renderoc HB (hand/trowel-applied, vertical and overhead), Renderoc Plug (rapid leak-stopping) and the Renderoc RG sub-grades RG(S), RG(M) and RG(L) which trade strength against economy. Pair it with Nitozinc Primer (rebar), Nitobond EP (substrate bond), Galvashield anodes (galvanic corrosion control) and Concure curing compounds for a complete EN 1504-aligned repair system, then protect with Dekguard or Nitocote anti-carbonation coatings. Against competitor systems it is directly comparable to Sika MonoTop / SikaGrout micro-concrete grades, MBS/MYK Schomburg repair micro-concretes, Dr. Fixit Pidicrete micro-concrete and STP structural repair micro-concretes; the honest differentiator is the specified system and local technical support rather than headline strength, since all reputable grades land in a similar 45–60 N/mm² band. Space Arc Engineering positions Renderoc RG 45 as the dependable default where the parent concrete is M25–M40 and the section is too dense or deep to vibrate, supplying it pan-India with application guidance from Delhi NCR.

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