Fosroc Sprayset HBP
A chloride-free, non-caustic powder set accelerator that lets sprayed concrete, shotcrete and gunite build thicker in a single pass while cutting rebound and material waste.
What is it?
A dry powder set-accelerating admixture that is blended into the shotcrete or gunite mix to give it high-build and low-rebound behaviour without chlorides or caustic alkalis.
Where is it used?
Dry-mix and wet-mix sprayed concrete on tunnels, mine walls, rock slopes, retaining walls, canal linings and vertical or overhead repair sections.
Why use it?
It stiffens the mix quickly on impact so a nozzleman can lay down more thickness per pass, keep material on the surface and reduce the rebound that would otherwise be swept up as waste.
How is it applied?
Dosed at 2 to 5 kg per 100 kg of total cementitious content and thoroughly dry-blended into the mix before spraying through a shotcrete gun or gunite machine.
About Fosroc Sprayset HBP
Fosroc Sprayset HBP is a set-accelerating admixture supplied as a dry, free-flowing powder and designed specifically for sprayed concrete work. When it is blended into a shotcrete, gunite or wet-mix spray, it speeds up the early stiffening of the mix at the moment it hits the substrate. That quick grab is what allows a crew to build up a genuinely thick section in fewer passes, hold fresh material against vertical faces and soffits, and get on with the next lift instead of waiting out slow sets. It is chloride-free and non-caustic, which matters both for the durability of the reinforcement embedded in the concrete and for the safety of the spraying crew.
For engineers and contractors working in tunnelling, mining, slope stabilisation and heavy repair, the practical appeal is simple: less concrete bounces off and ends up on the floor. Rebound is one of the biggest hidden costs of sprayed concrete, and a well-dosed high-build accelerator like Sprayset HBP keeps more of every batch on the wall where it belongs. Because it is a factory-produced powder added by weight of cement, dosing is straightforward to control and to record for QA, and the product does not compromise the ultimate strength of the hardened concrete when used within the recommended range.
The technical insight
The performance of Sprayset HBP comes down to how it manipulates the early hydration of the cement. Freshly sprayed concrete needs two things that normally pull against each other: it must be fluid enough to pump and atomise through the nozzle, yet stiff enough on arrival to resist sagging and to build thickness. Sprayset HBP resolves that tension by accelerating the initial set the instant the material is placed. As the powder disperses through the cementitious paste and the mix leaves the nozzle, it triggers a rapid gain in early stiffness so the shotcrete grabs the substrate and each successive layer keys onto the last rather than sliding off. That controlled, fast set is also what suppresses rebound, because material that stiffens quickly on impact is far less likely to bounce back. Crucially, the acceleration is a front-end effect on placement and early strength development; used at the correct dosage it does not rob the concrete of long-term strength, and because the formulation carries no chlorides it introduces no corrosion risk to embedded steel or rock bolts.
Where it is used
- Primary and secondary tunnel lining by dry-mix or wet-mix shotcrete
- Rock slope and cut-face stabilisation with sprayed concrete
- Mine wall and underground excavation support
- Retaining wall, embankment and soil-nailing face coats
- Canal, reservoir and channel lining where thick sprayed sections are needed
- Vertical and overhead concrete repair by gunite
- Building of thick single-pass sections on irregular or profiled surfaces
- Structural repair layers requiring quick grab on steep faces
Key advantages
- Enables a high build-up per pass, so thick sections are reached in fewer applications
- Sharply reduces rebound, keeping more material on the surface and cutting waste
- Chloride-free, so it poses no corrosion threat to reinforcement or rock bolts
- Non-caustic and safe for crews to handle compared with aggressive liquid accelerators
- Provides controlled set acceleration without adverse effect on ultimate strength
- Dry powder dosed by weight of cement, giving simple, repeatable, auditable control
- Complies with ACI 506 recommended practice and Concrete Society sprayed-concrete specifications
- Factory-blended for consistent, reliable performance batch to batch
Limitations & considerations
- It is an admixture, not a coating or render, and must be batched into a properly designed shotcrete or gunite mix
- Performance depends on correct dosage; over-dosing to force faster set can compromise ultimate strength
- As a powder accelerator for the dry/wet spray process, it is not a substitute for liquid alkali-free accelerators dosed at the nozzle where those are specified
- It does not replace the need for a sound substrate, adequate reinforcement and correct nozzle technique
- Rebound and build-up results still depend on mix design, water content and operator skill, not the admixture alone
Selection & best practice
Dose Sprayset HBP at 2 to 5 kg per 100 kg of total cementitious material and fix the exact rate through site trials that reflect your actual mix, substrate and spraying equipment, rather than defaulting to the top of the range. Add the powder to the dry components and blend thoroughly so it disperses evenly before water and spraying; uneven distribution gives patchy set and inconsistent build. Keep water content disciplined, because excess water works directly against the high-build behaviour you are trying to achieve. Have an experienced nozzleman control angle, distance and thickness per pass to get the full rebound benefit. Store the bags sealed in dry, covered conditions off the ground, and use full bags to keep dosing accurate. On repairs and linings that will be finished or protected, allow the sprayed concrete to cure properly before applying any subsequent protective or decorative Fosroc coating.
Specifications
| Product type | Powder set-accelerating admixture for sprayed concrete |
| Function | High build-up and low rebound in shotcrete and gunite |
| Form | Free-flowing powder |
| Chloride content | Chloride-free |
| Chemical nature | Non-caustic |
| Dosage | 2 to 5 kg per 100 kg of total cementitious material |
| Standards | Meets ACI 506 recommended practice for shotcreting and Concrete Society specification for sprayed concrete |
| Application method | Dry-blended into the mix, then applied by shotcrete gun or gunite machine |
| Effect on strength | No adverse effect on ultimate strength at recommended dosage |
Industry use cases
Tunnelling & Underground
Lets shotcrete crews build the required lining thickness on tunnel crowns and walls in fewer passes while wasting far less concrete to rebound.
Mining & Rock Support
Provides fast-grabbing, thick sprayed support to mine walls and excavation faces without introducing chlorides that would attack rock bolts and mesh.
Slope Stabilisation
Holds sprayed concrete on steep cut faces and rock slopes so a stabilising layer can be built up efficiently on irregular ground.
Water-Retaining Infrastructure
Supports thick, low-rebound sprayed linings for canals, channels and reservoirs where build-up per pass and material economy both matter.
Structural Repair
Enables gunite repairs to vertical and overhead sections to be built up quickly with minimal fall-off and no corrosion risk to existing steel.
Frequently asked questions
Is Sprayset HBP a render or coating I apply to a wall?
What dosage of Sprayset HBP should I use?
Does it contain chlorides that could corrode reinforcement?
Will accelerating the set reduce the final strength of the concrete?
Which standards does Sprayset HBP comply with?
How does it actually reduce rebound and save material?
How we position Fosroc Sprayset HBP
Sprayset HBP is the powder member of Fosroc’s sprayed-concrete admixture family, chosen when the priority is building thick, low-rebound sections economically in dry-mix and wet-mix shotcrete. Where a project specifies a liquid alkali-free accelerator dosed at the nozzle, the Fosroc Sprayset HBL liquid is the natural counterpart from the same family. For the hardened concrete itself, pair Sprayset HBP with Fosroc’s Conplast range of water-reducing and workability admixtures to control the base mix, and once sprayed sections have cured, protect and finish exposed faces with Fosroc Dekguard anti-carbonation and Nitocote protective coatings. For structural repair contexts we also supply Fosroc’s Renderoc and Nitomortar repair mortars alongside the Sprayset accelerators. Across brands, Space Arc can advise where a Sika, MC-Bauchemie or Master Builders Solutions shotcrete admixture is the specified alternative, so the accelerator matches the mix design and project specification rather than the other way round.
Related Concrete Repair products
Source Fosroc Sprayset HBP for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.