Fosroc Renderoc HF
Single-component, free-flowing, shrinkage-compensated micro-concrete for large-volume structural repairs where access is restricted or reinforcement is congested.
What is it?
A ready-to-use, single-component cementitious micro-concrete supplied as a pre-bagged dry blend of Portland cement, graded aggregates and expansion additives that needs only the site addition of clean water to produce a free-flowing, shrinkage-compensated repair concrete.
Where is it used?
Large-volume structural concrete reinstatement of beams, columns, jacketing, soffits and deep sections in bridges, jetties, water-retaining structures, industrial plants and high-rise buildings across India.
Why use it?
Its highly fluid, self-compacting nature lets it be pumped or poured into restricted, deeply formed or heavily reinforced locations without vibration, while a dual-expansion system compensates for shrinkage to maintain full bond and structural continuity.
How is it applied?
Surface is prepared, steel primed with Nitoprime Zincrich and the substrate saturated; the powder is machine-mixed with clean water at a water/powder ratio of 0.13-0.14, poured or pumped into rigid formwork in sections generally up to 500 mm, then cured with Concure curing membrane after strike.
About Fosroc Renderoc HF
Fosroc Renderoc HF (marketed in several markets as Renderoc HF Premix) is the free-flowing member of the Renderoc concrete-repair family, engineered for situations where a conventional hand- or trowel-applied repair mortar simply cannot reach. It arrives on site as a factory-controlled blend of dry powders based on Portland cement, carefully graded aggregates, fillers and performance additives. On adding only clean water, it transforms into a fluid, self-levelling micro-concrete that flows around dense reinforcement and into deep, awkward voids without any need for poker vibration or external compaction.
The defining characteristic of Renderoc HF is its rheology. Where most repair mortars are stiff and thixotropic, Renderoc HF is intentionally fluid, achieving a slump-flow in the order of 70-80 cm at a water/powder ratio of only 0.13-0.14. That combination of high fluidity and low water demand is what allows it to be poured or pumped into restricted, formed locations while still developing the high strength and low permeability expected of a structural-grade material. A dual-expansion system, acting in both the plastic and hardened states, compensates for the natural drying shrinkage of cementitious materials, so the repair stays in intimate contact with the parent concrete and the embedded steel rather than debonding at the interface.
Because it is alkaline and free of chloride admixtures, Renderoc HF re-establishes a passivating, protective environment around exposed reinforcement, making it suitable for chloride-contaminated and carbonated structures undergoing rehabilitation. It is a genuine large-section material, designed for nominal repair depths in excess of 50 mm and pours generally up to around 500 mm, which is precisely the range where flowable micro-concrete becomes more practical and economical than packing successive layers of hand-applied mortar.
For Indian contractors, consultants and asset owners, Renderoc HF sits in the middle of the Renderoc micro-concrete range alongside products such as Renderoc RG and Renderoc LA, and is typically specified hand-in-hand with the wider Fosroc repair system: Nitoprime Zincrich as a zinc-rich reinforcement primer, Concure curing membranes, and Dekguard anti-carbonation coatings to protect the surrounding structure.
The technical insight
The engineering value of Renderoc HF lies in decoupling fluidity from water content. Adding water to improve flowability normally penalises strength and durability, yet Renderoc HF reaches a 70-80 cm slump-flow at a water/powder ratio of just 0.13-0.14, so it flows like self-compacting concrete while still developing roughly 30 N/mm2 at 1 day, 50 N/mm2 at 7 days and 60 N/mm2 at 28 days (BS 1881 Part 116, ±10%). The dual-expansion system is equally important: controlled expansion in the plastic state displaces entrapped air and keeps the mix in contact with the formwork and substrate, while expansion in the hardened state offsets drying shrinkage. The practical consequences are strict but logical – the surface being repaired must be restrained by rigid, sealed formwork (the product should not be used to reinstate unrestrained horizontal areas), the substrate must be pre-saturated, and placement must be completed within about 30 minutes of mixing to capture the full benefit of both fluidity and expansion. Formwork is struck only once the material reaches about 10 N/mm2, after which immediate wet curing followed by a Concure membrane is essential.
Where it is used
- Reinstatement of large or deep structural concrete sections in beams, columns and slabs where hand-applied mortars are impractical
- Concrete jacketing and section enlargement of distressed columns and piers using formwork and a flowable pour
- Repairs to congested, heavily reinforced zones where a fluid, self-compacting material can flow around dense steel
- Rehabilitation of chloride-contaminated and carbonated reinforced concrete in marine, coastal and industrial structures
- Soffit and difficult-access repairs to bridge decks, beams and underside elements using formed, pumped placement
- Reinstatement of water-retaining and water-excluding structures such as tanks, reservoirs and treatment plants requiring low permeability
- Restoration of car park decks, jetties, wharves, cooling towers and other infrastructure subject to aggressive exposure
Key advantages
- Highly fluid and self-compacting – eliminates honeycombing and displaces air without poker vibration, even in restricted or congested locations
- Can be placed by pumping or pouring, giving access to soffits, deep sections and confined repair zones
- Dual-expansion system compensates for shrinkage in both plastic and hardened states, maintaining full bond to substrate and steel
- High strength and low permeability provide durable protection against chloride and carbon-dioxide ingress
- Single-component, pre-bagged formulation requires only clean water on site, removing batching variation
- Contains no chloride admixtures and is alkaline, helping re-passivate and protect embedded reinforcement
- Suitable for genuinely large-volume repairs at nominal depths over 50 mm, reducing the labour of multi-layer hand application
- Gains strength rapidly, allowing early formwork striking and faster repair cycles on programme-critical works
Limitations & considerations
- Requires rigid, tightly sealed formwork – it is a formed, poured material, not a trowel-applied patch repair
- Should not be used to reinstate horizontal surfaces that remain unrestrained (open-top, no formwork) during cure
- Minimum nominal application depth is around 50 mm; it is not intended for thin, feather-edged or shallow patch repairs
- Must be placed within about 30 minutes of mixing to retain full fluidity and expansion benefit, demanding good site logistics
- Should not be applied below 5 degrees C and falling, and needs shaded storage and cool mixing water above about 35 degrees C
- Part-bag mixing is not permitted and free-fall mixers must not be used – a forced-action or paddle mixer is essential
- Substrate must be pre-saturated and free of standing water, and the repair must not be exposed to moving water during application
- Demands full system discipline (steel priming, curing membrane, protective coating) to achieve the rated durability
Selection & best practice
Treat Renderoc HF as a system, not a single product. Saw-cut the repair perimeter to at least 10 mm to give a square edge and avoid feather-edging, break out to a minimum 50 mm of sound concrete, and grit-blast exposed reinforcement to a bright condition. Prime all exposed steel with Nitoprime Zincrich and allow it to dry. Build rigid, leak-tight formwork with drainage and air-venting provision, then pre-saturate the substrate by filling the formwork with clean water and removing the excess just before placing. Machine-mix using a forced-action or slow-speed paddle mixer at a water/powder ratio of 0.13-0.14, adding powder to water (never the reverse) and adding roughly two-thirds of the water first; aim for a 70-80 cm slump-flow and reduce water slightly if flow is excessive to avoid segregation. Place or pump within 30 minutes, leave formwork until the material reaches about 10 N/mm2, then cure immediately with clean water and a Concure membrane, and protect the surrounding structure with a Dekguard anti-carbonation coating.
Specifications
| Product type | Single-component, free-flowing, shrinkage-compensated cementitious micro-concrete |
| Base composition | Portland cement, graded aggregates, fillers and controlled-expansion additives (pre-bagged dry powder) |
| Compressive strength (BS 1881 Pt 116, ±10%) | 30 N/mm² @ 1 day, 50 N/mm² @ 7 days, 60 N/mm² @ 28 days (w/p 0.13, 23±3°C) |
| Water / powder ratio | 0.13 – 0.14 |
| Approx. water per bag | ~4 litres per 30 kg bag |
| Consistency / flow | Free-flowing, self-compacting; slump-flow ~70-80 cm |
| Nominal application depth | In excess of 50 mm; sections generally up to ~500 mm |
| Expansion system | Dual expansion – acts in both plastic and hardened states |
| Chloride content | Contains no chloride admixtures; alkaline (protects embedded steel) |
| Working time | Place within ~30 minutes of mixing |
| Formwork striking strength | When material reaches ~10 N/mm² |
| Yield / coverage | Approx. 14.5 litres per 30 kg bag |
| Pack size | 30 kg bag (verify current India pack with Space Arc) |
| Shelf life | 12 months in original unopened bags, stored cool and dry, out of direct sunlight |
| Associated system products | Nitoprime Zincrich (steel primer), Concure P / Concure 75 Clear (curing), Dekguard (anti-carbonation coating) |
Industry use cases
Bridges & flyovers
Pumped or poured reinstatement of distressed beams, pier caps and soffits on highway and railway structures, where congested reinforcement and overhead access rule out hand-applied mortars.
Marine & coastal infrastructure
Repair of chloride-attacked jetties, wharves, sea walls and splash-zone elements, restoring an alkaline, low-permeability cover that re-protects corroding reinforcement.
Water & wastewater
Rehabilitation of tanks, reservoirs, sumps and treatment-plant structures that need a dense, low-permeability micro-concrete placed against formwork in deep sections.
Industrial & power plants
Structural repair and column jacketing in cement, steel, fertiliser and power facilities subject to chemical and thermal exposure, using formed flowable pours.
High-rise & commercial buildings
Strengthening and section enlargement of columns and beams during structural retrofit, where a self-compacting pour speeds work in occupied or constrained buildings.
Car parks & podium decks
Reinstatement of deteriorated deck beams and downstand sections subjected to carbonation and de-icing or service-water exposure, with rapid strength gain to shorten closures.
Frequently asked questions
What exactly is Fosroc Renderoc HF?
How is Renderoc HF different from a normal repair mortar like Renderoc HB or HS Xtra?
What strength does Renderoc HF achieve?
What is the minimum and maximum thickness for Renderoc HF?
How much water do I use and how long can I work it?
Can I buy Renderoc HF in Delhi NCR and across India?
How we position Fosroc Renderoc HF
Within the Fosroc Renderoc concrete-repair range, Renderoc HF is the dedicated free-flowing micro-concrete for large, deep or congested formed pours, distinct from the thixotropic hand-applied mortars Renderoc HB and Renderoc HS Xtra and from rapid-set products like Renderoc Plug. It overlaps closely with other Fosroc micro-concretes – Renderoc RG (a gaseous-expansion micro-concrete) and Renderoc LA (a low-alkali free-flowing micro-concrete) – and the right choice depends on section size, exposure and expansion-system preference, which our team can help specify. It is normally used as part of a complete system with Nitoprime Zincrich (steel primer), Concure curing membranes and Dekguard anti-carbonation coatings. Where a project specifies an alternative brand or where availability dictates, broadly comparable flowable repair micro-concretes are offered by Sika (e.g. SikaGrout / Sika MonoTop micro-concrete grades), MBCC/Master Builders Solutions (MasterEmaco flowable repair concretes), STP Limited and Dr. Fixit (Pidilite) for general repair grouts and mortars – though exact strengths, expansion behaviour and approvals differ, so substitution should always be verified against the engineer’s specification. As an authorised Fosroc distributor and applicator, Space Arc Engineering recommends and supplies genuine Renderoc HF with full technical and application support across Delhi NCR and Pan-India.
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