Fosroc Patchroc GP
A rapid-setting, single-component patching mortar that puts damaged concrete floors, ramps and pavements back into service within hours, not days.
What is it?
A pre-bagged, single-component, fast-setting cementitious patching mortar for horizontal concrete repairs, conforming to BS EN 1504-3 Class R4.
Where is it used?
Concrete floors, industrial pavements, access ramps, loading bays, airport aprons and any trafficked slab where downtime must be kept to a minimum.
Why use it?
It reaches around 20 MPa in 2 hours and takes traffic the same shift, so a repair started in the morning is running by lunch instead of closing the area for days.
How is it applied?
Mix the dry powder with clean water, work into a primed, saturated-surface-dry pothole or spall in lifts of 12 to 100 mm, compact, and finish before the short working window closes.
About Fosroc Patchroc GP
Patchroc GP is Fosroc’s answer to a problem every plant engineer and facilities manager knows well: a spalled floor joint, a broken ramp edge or a pothole in a busy pavement that cannot be shut down for a conventional 28-day repair. It arrives as a ready-blended bag of cement, graded aggregates and performance additives that needs nothing on site but clean water and a bucket. Because the binder chemistry is chloride-free and does not rely on calcium chloride accelerators, it develops early strength without the corrosion risk that dogs older quick-set patching compounds, making it safe to use around embedded reinforcement.
What sets it apart in day-to-day use is the speed-to-service. The mortar takes an initial set in roughly 40 minutes and a final set at about 60 minutes, and it will generally accept traffic within two hours of placement. For a distribution warehouse, a factory gangway or an access road, that means the crew patches during a shift changeover and the forklifts are back over the repair before the next shift starts. It is a horizontal-repair specialist though, engineered for floors and pavements rather than walls or soffits, and that focus is exactly why it performs so well within its lane.
The technical insight
The performance comes from a rapid-hardening binder system that drives an accelerated but controlled hydration reaction. Instead of the slow calcium-silicate-hydrate development of ordinary Portland cement, the modified binder generates load-bearing hydrates within the first couple of hours, which is why compressive strength climbs to around 20 MPa at 2 hours, 50 MPa at 1 day and 65 MPa at 28 days. Critically this early strength is achieved without added chlorides, so the pore solution stays alkaline and passivating rather than aggressive toward steel. The graded aggregate skeleton keeps the mix dimensionally stable through that fast cure, resisting the plastic cracking that a neat rapid cement would suffer, and the dense hardened matrix gives good abrasion and impact resistance under wheeled traffic. The trade-off engineers must respect is the short working window, roughly 30 minutes at 20 degrees C, because the same chemistry that gives early strength also stiffens the mix quickly in the pan.
Where it is used
- Emergency and permanent repair of potholes and spalls in concrete floor slabs
- Reinstating broken joint arrises and edges on trafficked floors
- Repairing damaged access ramps, loading docks and vehicle approach slabs
- Patching industrial and warehouse pavements between operational shifts
- Restoring airport aprons, taxiways and hard-standing where rapid reopening is required
- Filling voids, honeycombing and cast-in defects in horizontal concrete
- Localised repair of car park decks and service yards
- First-fix reinstatement of concrete road surfaces before a wearing course
Key advantages
- Traffic-ready in about 2 hours, minimising downtime on operational floors and roads
- Single-component: only clean water is added on site, removing batching errors
- Chloride-free and free of calcium chloride accelerators, safe around reinforcement
- High ultimate strength of around 65 MPa at 28 days, exceeding most host concrete
- Conforms to BS EN 1504-3 Class R4, the highest structural repair class
- Builds up to 100 mm in a single lift for deep repairs
- Dense, abrasion-resistant surface suited to wheeled and forklift traffic
- Consistent factory-blended quality bag after bag
Limitations & considerations
- Very short working time, roughly 30 minutes at 20 degrees C, so mix only what can be placed and finished quickly
- Formulated for horizontal repairs; not intended for vertical or overhead patching where a thixotropic mortar such as Renderoc is more suitable
- Minimum thickness of 12 mm means it is not a feather-edge or skim product
- Rapid set makes it unforgiving in high ambient temperatures, where working time shortens further
- Requires a properly prepared, saturated-surface-dry and primed substrate for a durable bond
- Not a decorative topping; it is a structural patch that usually receives a separate wearing or coating system
Selection & best practice
Success with Patchroc GP is mostly about preparation and pace. Break out all loose and weak concrete to a sound, square-edged perimeter at least 12 mm deep, avoiding feather edges, and expose clean substrate. Pre-soak the area to a saturated-surface-dry condition and apply the recommended primer while it is still tacky. Add only the specified quantity of clean water and mix mechanically for a uniform, lump-free consistency; do not over-water to extend workability, as this cuts strength. Place and compact firmly into the prepared pocket in lifts up to 100 mm, keeping individual bay sizes within about 4 square metres so a fresh batch can be finished inside the working window. In warm conditions, chill the mix water, work in smaller batches and protect the fresh repair from direct sun and drying wind. Because the material self-cures rapidly, extended curing is minimal, but avoid trafficking until the two-hour strength has developed.
Specifications
| Product type | Single-component, fast-setting cementitious patching mortar |
| Standard / class | BS EN 1504-3, Class R4 (structural repair) |
| Initial set | Approx. 40 minutes |
| Final set | Approx. 60 minutes |
| Working time | Approx. 30 minutes at 20°C (60 minutes at 10°C) |
| Compressive strength | ~20 MPa at 2 h, 50 MPa at 1 day, 55 MPa at 7 days, 65 MPa at 28 days |
| Application thickness | 12 mm minimum to 100 mm maximum per lift |
| Coverage / yield | Approx. 12 litres per 25 kg bag (about 1.0 m² at 12 mm) |
| Chloride content | Nil (no calcium chloride accelerators) |
| Pack size | 25 kg bag |
Industry use cases
Warehousing & Logistics
Patching spalled floor joints and forklift-worn slabs during a shift change so material handling resumes the same day.
Roads & Highways
Emergency reinstatement of potholes and broken concrete pavement sections where lane closure time is strictly limited.
Aviation
Rapid repair of airport aprons, taxiways and hard-standings that must be returned to aircraft or vehicle traffic within hours.
Manufacturing Plants
Reinstating damaged ramps, dock edges and gangway slabs between production runs without a prolonged shutdown.
Commercial Car Parks
Localised repair of deck slabs and approach ramps where keeping bays open to traffic is a commercial priority.
Frequently asked questions
How soon can traffic run over a Patchroc GP repair?
Can I use Patchroc GP on walls or overhead soffits?
How much water do I add, and can I add more to make it easier to work?
What is the minimum and maximum repair depth?
Is it safe to use near steel reinforcement?
How much area does one 25 kg bag cover?
How we position Fosroc Patchroc GP
Patchroc GP is the right call when the job is a horizontal concrete floor, ramp or pavement and speed of reopening is the priority. If the same defect is on a wall, column, beam or soffit, or if you have time for a conventional cure and want a trowel-friendly reprofiling mortar, Fosroc Renderoc GP is the better-suited product from the same family. Where the failure is an active water leak rather than a dry structural patch, reach for Fosroc Renderoc Plug to stop the flow first, then reinstate. For repairs that need a bonding bridge or reinforcement primer, pair Patchroc GP with the appropriate Fosroc primer and, on Space Arc, you will also find complementary systems from our other brands, including Sika and Dr. Fixit repair mortars, so specifiers can match the exact class, cure time and substrate their project demands.
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