Dr. Fixit Polymer Mortar HB (Repair Pro)
A high-build, EN 1504-3 Class R4 structural repair mortar engineered for vertical and overhead concrete restoration — from spalled balconies to bridge soffits.
What is it?
A ready-to-use, single-component, fibre-reinforced polymer-modified cementitious mortar that is mixed with water on site and trowel- or spray-applied to reinstate damaged reinforced concrete.
Where is it used?
RCC and pre-stressed beams, columns and slabs, bridge decks and soffits, retaining walls, tunnel linings, building facades, balconies, ceilings and any structural member needing full concrete-cover restoration.
Why use it?
It is rated to EN 1504-3 Class R4, the toughest European structural repair class, meaning it is engineered to match or exceed the strength and bond of the surrounding parent concrete, so a patched section behaves structurally rather than as a cosmetic filler that debonds within a season or two.
How is it applied?
Mixed mechanically with 4.25-4.50 litres of water per 25 kg bag to a lump-free consistency, then hand-trowelled or spray-applied onto a pre-wetted, mechanically prepared substrate in layers up to 30 mm (vertical) or 20 mm per pass overhead (max 40 mm in two layers), followed by moist curing for at least 24 hours.
About Dr. Fixit Polymer Mortar HB (Repair Pro)
Dr. Fixit Polymer Mortar HB sits in Pidilite’s Repair Pro range — the structural-grade tier of the Dr. Fixit portfolio aimed at engineers and repair contractors rather than DIY patchwork. Chloride-induced rebar corrosion is the single biggest cause of concrete spalling across Delhi NCR’s older residential towers, flyovers and commercial facades, and once cover concrete is chipped away, the repair material has to do real structural work, not just fill a hole. This mortar is formulated with cement, graded fillers, polymers and specially designed acrylic fibres so that as it hydrates and cures, it resists the shrinkage cracking that plagues ordinary site-mixed cement-sand patch repairs, while bonding tightly enough to steel and old concrete to carry load again.
For a Delhi NCR applicator, the practical value is in the detail: no formwork is needed even at 40 mm overhead thickness, high early strength (15 MPa in a single day) means a column or beam edge can be brought back into service faster, and a low chloride content protects freshly exposed rebar from re-initiating corrosion. Space Arc supplies and applies this mortar on RCC repair contracts ranging from single-flat balcony slab edges to larger structural rehabilitation works, usually pairing it with Dr. Fixit Zinc Rich Primer on exposed steel and Dr. Fixit Pidicrete MPB as a bond coat where the substrate is porous or heavily profiled.
The technical insight
The chemistry balances two competing needs. A repair mortar with too little water gains strength but becomes unworkable and prone to cold joints between layers; too much water breaks the fixed water:powder ratio (0.17-0.18 by weight here), and strength and bond both drop sharply — which defeats the entire point of specifying an R4-rated product. The specially designed acrylic fibre dosage is what Dr. Fixit calls dual shrinkage compensation: it restrains both early plastic shrinkage in the first hours and later drying shrinkage over the following weeks, which is why the mortar can be built up to 30-40 mm without the surface crazing a plain polymer-modified render would show at that thickness. EN 1504-3 Class R4 is also why the compressive strength requirement is set at a demanding 45 MPa minimum at 28 days (the tested batch reached 46.29 MPa), alongside a bond strength of at least 2 MPa and chloride content capped at 0.05% by mass — together these figures are what let a structural engineer specify the product against a load-bearing repair rather than treating it as a cosmetic filler. The low capillary absorption (≤0.31 kg/m²h½ against a 0.5 limit) is the property that most directly protects the newly exposed rebar underneath, since it limits how fast moisture and dissolved chlorides can migrate back through the patch to the steel.
Where it is used
- Structural repair of RCC and pre-stressed beams, columns and slabs damaged by rebar corrosion or spalling
- Vertical and overhead concrete reinstatement without formwork, up to 30 mm (vertical) or 40 mm in two layers (overhead)
- Repair of structural members subjected to repetitive or cyclic loading, such as industrial gantry beams and machine foundations
- Restoration of concrete cover after chipping out corroded reinforcement and re-passivating exposed rebar
- Renovation and resurfacing of bridges, flyovers, overpasses, retaining walls and tunnel linings
- Facade, chajja, balcony and ceiling concrete repair in residential and commercial towers
- Repair of RCC members in marine or coastal-exposure structures where chloride ingress is a recurring risk
- Precast and pre-stressed element patch repair on infrastructure and industrial projects
Key advantages
- Rated to EN 1504-3 Class R4, the most demanding structural repair class in the European standard, so it can be specified with confidence on load-bearing members rather than treated as a cosmetic filler
- Dual shrinkage-compensated fibre matrix controls both plastic and drying shrinkage, cutting the crazing and hairline cracking common in unmodified cement-sand patch repairs
- High early strength (15 N/mm² at just 1 day) lets contractors move faster through a repair schedule and return members to service sooner
- Can be built up to 40 mm overhead in two passes and 30 mm vertical in a single pass without formwork, reducing the number of site visits
- Single-component powder — only water is added on site, which cuts batching errors compared with multi-part or hand-proportioned repair mixes
- Low chloride content (0.01% by mass, well under the 0.05% EN 1504-3 cap) helps prevent freshly exposed rebar from re-corroding
- Documented bond strength of ≥2 N/mm² to old concrete gives a verifiable adhesion figure for consultants signing off repair works
- Backed by Space Arc’s trained applicator teams across Delhi NCR, so specification, supply and application can be handled as one accountable package
Limitations & considerations
- Performance is entirely dependent on holding the specified water:powder ratio (0.17-0.18); excess water added on site for easier troweling sharply cuts strength and bond and defeats the R4 rating
- The roughly 45-minute pot life demands disciplined batching, especially in Delhi’s summer heat, and is unforgiving of slow crews or large mixed batches
- It is a structural-grade repair mortar, not a skim coat — proper mechanical surface preparation (chipping, profiling, exposing rebar fully) is required, so it is not suited to quick cosmetic touch-ups
- Rebar with more than 20% section loss to corrosion needs a structural engineer’s involvement and possibly supplementary reinforcement; the mortar alone cannot compensate for lost steel
- It restores structural concrete sections but is not a waterproofing product; exposed roofs, terraces or retaining walls still need a separate waterproofing system over or alongside the repair
- Sold only in 25 kg bags, which is efficient for structural repair volumes but not the most economical format for a handful of very small patches
Selection & best practice
Chip out all unsound and damaged concrete back to solid substrate, expose corroded rebar around its full circumference, and mechanically profile the surface (abrasive blasting, waterjetting or an equivalent method) rather than just wire-brushing it — R4-grade bond strength depends on this key. Coat cleaned rebar with Dr. Fixit Zinc Rich Primer before patching, and where the concrete is porous, scratch-coat with Dr. Fixit Pidicrete MPB (1:1 with cement) as a bond coat. Pre-soak the substrate for at least 2 hours (ideally 24) so it is saturated surface-dry with no standing water at the time of application, and keep ambient and substrate temperature between 10°C and 35°C. Mix strictly to 4.25–4.50 litres of water per 25 kg bag — never add extra water to “loosen” the mix — using a slow-speed drill with a spiral paddle until lump-free, and place it within the roughly 45-minute pot life; in Delhi’s summer, use chilled mixing water and mix smaller batches more often. Build up in layers up to 20 mm thick (wet-on-dry) rather than one thick pour, mist-cure for the first 24 hours (or use damp burlap or an ASTM C309 water-based curing compound, never a solvent-based one), and keep the repair away from running water until it has set.
Specifications
| Compressive strength, 28 days | ≥45 N/mm² (BS 6319 Pt.2); test result 46.29 MPa per EN 12190 |
| Flexural strength, 28 days | ≥8 N/mm² (BS 6319 Part 3) |
| Tensile strength, 28 days | ≥4.5 N/mm² (BS 6319 Part 7) |
| Bond strength (to concrete), 28 days | ≥2 N/mm² (EN 1542-1999); test result 2.44 MPa without primer |
| Fresh wet density | 2200 ± 100 kg/m³ |
| Water : product ratio (by weight) | 0.17-0.18 (4.25-4.50 litres water per 25 kg bag) |
| Chloride content | ≤0.05% by mass (EN 1504-3:2005); test result 0.01% |
| Coverage | 1.4 m² per 25 kg bag at 10 mm thickness; yield approx. 14 litres at W/P 0.18 |
| Pack size / shelf life | 25 kg bag; 6 months from manufacture, unopened, stored cool and dry |
Industry use cases
Residential high-rises
Repair of chloride-corroded balcony and chajja slab edges, and RCC column spalling at parking and stilt levels, in ageing residential societies across Delhi NCR
Infrastructure and bridges
Soffit and pier repair on flyovers, overpasses and bridge decks where overhead application without formwork saves scaffolding time
Industrial facilities
Structural reinstatement of gantry beams, machine foundations and other RCC members under repetitive or cyclic loading
Commercial buildings
Cantilever slab edge, cladding support ledge and facade concrete restoration on commercial and office towers
Marine and coastal structures
Repair of RCC jetty, seawall or coastal-exposure structural members where a low-chloride, corrosion-resistant mortar reduces the risk of repeat spalling
Frequently asked questions
How thick can I apply Dr. Fixit Polymer Mortar HB in a single pass?
Do I need a primer before applying this mortar?
How much water do I mix into a 25 kg bag?
Can I use this to waterproof my terrace or a leaking wall?
What is the working time once it’s mixed?
How is this different from a regular cement-sand patch repair?
How we position Dr. Fixit Polymer Mortar HB (Repair Pro)
Within the Dr. Fixit line-up, Polymer Mortar HB is the structural workhorse of the Repair Pro range: it is typically specified alongside Dr. Fixit Zinc Rich Primer (rebar protection), Dr. Fixit Pidicrete MPB (bond coat for porous or heavily profiled concrete), and Dr. Fixit Crack-X Shrinkfree or Pidicrete URP for finer crack-injection and lighter patch work that doesn’t need a full R4-class mortar. Where the damaged section is shallow and non-structural, Space Arc would generally steer a client toward one of these lighter Dr. Fixit repair products instead, reserving Polymer Mortar HB for genuine structural reinstatement. For specifiers already committed to a different repair-system brand across a project — or wanting an alternative quote for comparison — Fosroc’s Renderoc HB40 is a genuinely comparable high-build, polymer-modified repair mortar for overhead and vertical reinstatement, and Space Arc supplies and applies both, so the choice can come down to project-level system consistency and pricing rather than any meaningful performance gap.
Fosroc Renderoc HB40 — Specifiers on projects that have already standardized on the Fosroc Renderoc/Nitobond repair system, or where Renderoc HB40 is named in an existing BOQ, may prefer it for consistency across the rest of the repair package rather than mixing brand systems on one structure.
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