Fosroc Renderoc LA
A free-flowing, low-alkali micro-concrete that pours and pumps into deep, congested and awkward-access repair zones where a hand-trowelled mortar simply cannot reach.
What is it?
A pre-bagged, single-component, low-alkali micro-concrete supplied as a dry blend that needs only site water. It flows under its own weight into formwork to reinstate structural concrete in thick sections.
Where is it used?
Large-area and deep structural repairs where reinforcement is congested or access is restricted: columns, beams, ground beams, pile caps, bridge substructures and encasements.
Why use it?
It reaches parts of a section a trowel-applied mortar cannot, self-compacts around dense steel, and develops micro-concrete-grade strength up to 60 MPa at 28 days.
How is it applied?
Mixed with clean water, poured or pumped into pre-fixed formwork against a saturated substrate, and placed in single lifts of 25 to 150 mm depending on the repair geometry.
About Fosroc Renderoc LA
Renderoc LA is Fosroc’s flowable answer to a problem that defeats ordinary repair mortars: how to reinstate concrete in deep sections, behind dense reinforcement, or in pockets a trowel cannot properly compact. Supplied as a factory pre-bagged dry powder, it is gauged with clean water on site to produce a free-flowing micro-concrete that finds its own level, self-compacts around bars and travels into the far corners of formwork without vibration-induced segregation. The “LA” stands for low alkali, a deliberate formulation choice that keeps the alkali contribution of the repair low and reduces the risk of alkali-silica reaction where reactive aggregates or sensitive service conditions are a concern.
For Indian sites, its real value is versatility across the difficult repairs. It places in single sections from 25 mm up to 150 mm, so a badly spalled column or a congested pile cap can often be reinstated in one continuous pour rather than a sequence of thin lifts. Strength gain is genuinely structural: around 14 MPa at one day, 42 MPa at seven days and up to 60 MPa at 28 days at 20 degrees C. Because it is designed to be compatible with parent concrete in the 30 to 60 MPa class, it behaves as a monolithic extension of the member rather than a cosmetic patch. As Fosroc’s authorised distributor and applicator across Delhi NCR and pan-India, Space Arc supplies Renderoc LA alongside the Nitobond and Nitoprime ancillaries a specification-compliant repair actually needs.
The technical insight
The engineering logic behind Renderoc LA is flow without segregation. A conventional repair mortar is stiff and thixotropic so it stays where a trowel puts it, but that same stiffness makes it useless in a 100 mm-deep, heavily reinforced pour where it would bridge and leave voids around the steel. Renderoc LA inverts that: a graded aggregate blend and cementitious matrix are engineered to stay cohesive while flowing, so the mix carries its coarse fraction into place instead of bleeding it out. That self-compacting behaviour is what lets it encase congested bars fully and develop an intimate, void-free bond to the prepared substrate. The low-alkali chemistry is the second half of the design: by limiting reactive alkali content, the repair does not become an internal source of expansive alkali-silica gel over the structure’s remaining service life. Compliance with the relevant repair principles of BS EN 1504-3 (covering methods such as 3.2, 4.4, 7.1 and 7.2) means the same material can serve structural reinstatement, increasing bearing capacity, preserving and restoring passivity around the steel.
Where it is used
- Reinstatement of spalled or delaminated reinforced concrete columns in single deep pours
- Repair of pile caps, ground beams and other congested-reinforcement sections
- Structural encasement and jacketing of degraded beams and members
- Bridge and flyover substructure repairs where access is restricted
- Deep-section repairs on water-retaining and marine structures needing low-alkali chemistry
- Reinstatement behind reinforcement too dense for trowel-applied mortar to compact
- Formwork-and-pour repairs on parapets, capping beams and plinths
- Large-volume repairs where a single flowable placement is faster than multiple hand lifts
Key advantages
- Free-flowing and self-compacting, so it fills congested and restricted-access sections a trowel mortar cannot reach
- Placeable in single lifts from 25 mm up to 150 mm, reducing the number of pours on deep repairs
- Low-alkali formulation lowers the risk of alkali-silica reaction over the repair’s service life
- Structural strength development up to 60 MPa at 28 days, compatible with 30 to 60 MPa parent concrete
- Factory pre-bagged for consistent, site-repeatable quality with only water added
- Can be poured into formwork or pumped through suitable plastering equipment for productivity on large areas
- Backed by BS EN 1504-3 compliance for genuine structural reinstatement
- Compatible with the Fosroc Nitobond and Nitoprime Zincrich systems for a complete specified repair
Limitations & considerations
- Requires formwork for most vertical and overhead placements, unlike a hand-applied trowel mortar
- Not intended for thin featheredge or shallow patch repairs below the 25 mm minimum section
- Minimum application temperature of 3 degrees C, and it must not be used in falling temperatures below that
- Free-fall drum mixers are not suitable; a forced-action mixer is needed to develop the flowable consistency
- Fresh horizontal placements must stay restrained during cure and be protected from moving water
Selection & best practice
Break out all unsound concrete to a sound, square-edged substrate and expose corroded steel fully around its circumference; clean the reinforcement to bright metal. Where the environment is aggressive, prime exposed steel with Nitoprime Zincrich Plus, and use Nitobond EP as a substrate primer only in the exceptional cases the datasheet identifies. Saturate the substrate to a saturated-surface-dry condition before placing. Fix rigid, grout-tight formwork with a head of at least 100 mm to drive the flow, and mix only in a forced-action mixer to reach a free-flowing, cohesive consistency. Pour or pump continuously from one side so the material displaces air ahead of itself and self-compacts around the steel. Do not place below 3 degrees C or in falling temperatures, cure promptly with Concure or damp hessian and polythene, and keep the placement restrained and clear of moving water until it has gained strength.
Specifications
| Product type | Free-flowing, low-alkali cementitious micro-concrete (single component) |
| Application method | Poured or pumped into formwork |
| Section thickness (single lift) | 25 mm to 150 mm |
| Compressive strength (1 day, 20 C) | approx. 14 MPa |
| Compressive strength (7 days, 20 C) | approx. 42 MPa |
| Compressive strength (28 days, 20 C) | up to 60 MPa |
| Compatible parent concrete | 30 to 60 MPa |
| Standard | BS EN 1504-3 (repair methods 3.2, 4.4, 7.1, 7.2) |
| Minimum application temperature | 3 C (not in falling temperatures below this) |
Industry use cases
Bridges & Highways
Reinstating spalled substructure elements, abutments and pier sections where reinforcement is congested and formwork can be fixed for a single deep pour.
Industrial & Power
Repairing degraded columns, plinths and equipment foundations in plants, where restricted access around machinery rules out hand-trowelled placement.
Water & Marine
Deep-section repairs to water-retaining and coastal structures, where the low-alkali chemistry limits long-term alkali-silica reaction risk.
Commercial & Infrastructure
Structural encasement of beams and columns in car parks, basements and multi-storey frames during rehabilitation of ageing concrete.
Frequently asked questions
Is Renderoc LA a trowel-applied mortar or a poured micro-concrete?
What thickness can I place in one pour?
What does the LA in the name mean?
What strength does it reach, and is it structural?
Do I need to prime the steel and substrate?
Can I use it in cold weather or in running water?
How we position Fosroc Renderoc LA
Within the Fosroc Renderoc range, Renderoc LA is the pourable, deep-section specialist. Where you need to hand-trowel shallow patch repairs, reprofiling or vertical and overhead reinstatement, Renderoc GP is the natural companion, and for fast-track repairs demanding early strength gain, Renderoc RG returns surfaces to service in hours. A complete specified repair usually pairs Renderoc LA with Fosroc’s Nitoprime Zincrich Plus for steel priming and the Nitobond bonding aids, finished with a Fosroc curing membrane or a Dekguard anti-carbonation coating for protection. Where a project instead calls for a lightweight overhead trowel mortar to control sag on soffits, that is a different material class and Space Arc can advise on the correct Fosroc grade. Across our other brands, Space Arc also supplies comparable structural repair micro-concretes and mortars from Sika and MC-Bauchemie for consultants who specify to those systems.
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