Fosroc Sprayset HBL
A chloride-free liquid admixture that lets sprayed concrete build thick in a single pass, sets fast and slashes rebound waste on shotcrete and gunite works.
What is it?
A chloride-free liquid admixture, based on a blend of inorganic powders, dosed into wet or dry sprayed-concrete mixes to give high build and low rebound with controlled set acceleration.
Where is it used?
Shotcrete and gunite works: tunnel linings, slope and rock stabilisation, swimming pools, repair overlays and any spray-applied concrete on vertical faces or soffits.
Why use it?
It lets fresh concrete stay put in thick layers instead of sloughing off, so crews cover more area per pass, waste far less rebound and get an earlier set without adding chlorides.
How is it applied?
Metered into the mix at the nozzle or batch, typically starting around 5.0 litres per 100 kg of cementitious material, then fine-tuned by site trial before full production spraying.
About Fosroc Sprayset HBL
Sprayset HBL is Fosroc’s high-build, low-rebound liquid admixture for sprayed concrete. It is a chloride-free formulation based on a blend of inorganic powders that, once introduced into a shotcrete or gunite mix, changes how the fresh material behaves the instant it hits the substrate. Rather than slumping or bouncing off, the treated concrete grips and holds, which is exactly what a spraying crew needs when building thickness against a vertical rock face or overhead on a tunnel crown. For Indian contractors working on infrastructure, mining and civil-repair packages, it is the additive that turns a difficult spray application into a controlled, repeatable one.
The commercial logic is straightforward. On any sprayed-concrete job, rebound (the material that bounces off and lands on the ground) is pure waste of cement, aggregate and labour, and every extra pass to reach design thickness costs time. By raising the build achievable in a single application and cutting rebound, Sprayset HBL directly attacks both losses. It also brings set acceleration, so a freshly sprayed layer stiffens quickly enough to accept the next layer and to hold on overhead work. Because the product is chloride-free and non-caustic, it suits reinforced structures and is safer to handle on site than many older accelerating systems. It is supplied ready to meter into the mix and is intended to be dialled in by trial, since aggregate, cement type and spraying equipment all influence the optimum dose.
The technical insight
The performance comes from how the inorganic powder blend acts on the cement paste at the moment of placement. As the admixture disperses through the mix, it triggers rapid early stiffening of the paste, so the sprayed layer develops enough internal cohesion and yield strength to resist sagging under its own weight the instant it lands. That thixotropic, fast-stiffening behaviour is what allows a genuinely high build in one pass, with Fosroc quoting application up to 300 mm on vertical surfaces and up to 200 mm overhead in a single application, depending on the weight and volume of aggregate in the mix. The same early set is what keeps rebound low: material that grabs and holds is material that does not bounce back off the wall. Critically, this acceleration is engineered to firm up the fresh concrete without robbing it of long-term performance, so the 28-day strength of the mix is not adversely affected. Keeping the chemistry chloride-free avoids introducing the single biggest driver of reinforcement corrosion, which is why it is acceptable on reinforced and structurally significant shotcrete.
Where it is used
- Sprayed concrete linings for tunnels, adits and underground excavations
- Rock face and slope stabilisation by shotcrete or gunite
- Overhead and vertical spray work where fresh concrete must resist sag
- High-build repair overlays on concrete and masonry substrates
- Gunite construction of swimming pools, reservoirs and water-retaining shells
- Mining and civil ground-support applications requiring rapid early set
- Any sprayed-concrete pass where reducing rebound waste is a priority
Key advantages
- High build in a single pass, cutting the number of applications needed to reach design thickness
- Low rebound, so far less cement and aggregate is wasted off the substrate
- Set acceleration lets each layer stiffen quickly and accept the next lift, aiding overhead work
- Chloride-free, making it suitable for reinforced and structurally sensitive shotcrete
- Non-caustic formulation that is safer for spraying crews to handle than many older accelerators
- Does not adversely affect the 28-day strength of the sprayed concrete
- Liquid form meters cleanly into the mix at the batch or nozzle
- Backed in India by Fosroc technical support and Space Arc site guidance
Limitations & considerations
- It is an admixture, not a mortar or a coating; it must be dosed into a properly designed sprayed-concrete mix, not applied on its own
- The optimum dose is not fixed and must be established by site trial, because aggregate, cement type and equipment all shift the result
- Achievable build depends on the weight and volume of aggregate in the mix, so quoted maxima are not guaranteed for every mix
- As a set-accelerating admixture, it demands disciplined batching and spraying to control the fast set on site
- Being a liquid, it has a finite shelf life (minimum six months in sealed, dry storage) and is degraded by exposure to high temperatures
- It addresses build, rebound and set only; water reduction, workability and durability still depend on the base mix design
Selection & best practice
Always establish the working dose by trial before production spraying, using the same cement, aggregate, water content and spray equipment you will run in the field; take Fosroc’s guideline of around 5.0 litres per 100 kg of cementitious material (including any PFA, GGBFS or microsilica) purely as a starting point, then adjust for the build and rebound you actually achieve. Meter the admixture consistently into the mix and keep the base mix design sound, since Sprayset HBL improves spray behaviour but does not fix a poorly graded or badly proportioned mix. Build up thick sections in controlled lifts, letting each accelerated layer stiffen before the next, and pay particular attention to overhead work where the sag limit is lower. Protect fresh sprayed concrete and cure it properly. Store drums sealed, dry and out of direct heat, and use stock within its six-month shelf life. Crews should wear gloves and eye protection and rinse any splashes with water.
Specifications
| Product type | Chloride-free liquid admixture for sprayed concrete |
| Composition | Blend of inorganic powders in liquid form |
| Primary function | High build, low rebound and set acceleration |
| Max build (vertical) | Up to 300 mm in a single application, subject to aggregate weight/volume |
| Max build (overhead) | Up to 200 mm in a single application, subject to aggregate weight/volume |
| Typical starting dose | Approx. 5.0 litres per 100 kg of cementitious material (trial-adjusted) |
| Chloride content | Chloride-free |
| Effect on 28-day strength | Not adversely affected |
| Shelf life | Minimum 6 months in sealed, dry storage away from high temperatures |
Industry use cases
Tunnelling & underground
Building sprayed-concrete linings on crowns and sidewalls, where high build in one pass and low rebound keep the cycle fast and material loss down.
Slope & rock stabilisation
Shotcreting steep and vertical rock faces on highway, hydro and mining works, where the accelerated set holds thick layers against gravity.
Water-retaining structures
Gunite construction and repair of swimming pools, reservoirs and tanks that need dense, well-bonded spray-applied concrete.
Structural repair
High-build overlays that rebuild section on degraded concrete and masonry, with a chloride-free additive suited to reinforced elements.
Mining ground support
Rapid-set sprayed concrete for tunnel and stope support, where early stiffening and reduced rebound improve safety and productivity.
Frequently asked questions
Is Sprayset HBL a levelling mortar or render?
How much Sprayset HBL do I add to the mix?
What thickness can I build in one pass?
Does it contain chlorides or harm the reinforcement?
Will accelerating the set weaken the concrete later on?
How is it packed and how long does it keep?
How we position Fosroc Sprayset HBL
Sprayset HBL is the high-build, low-rebound piece of a sprayed-concrete package, and it works best when the rest of the mix is engineered alongside it. On the same job, contractors typically pair it with a Fosroc water reducer such as Conplast SP430 to control water demand and workability, and where flash or rapid set is needed at the nozzle, Fosroc’s dedicated sprayed-concrete accelerators complete the system. For structural section rebuild that is trowel- or hand-applied rather than sprayed, Fosroc’s Renderoc range of repair mortars is the correct route rather than an admixture like this one. Across our other brands, MC-Bauchemie and Sika both offer shotcrete admixture and accelerator systems that a specifier may standardise on for a particular tunnelling or ground-support framework. Space Arc can supply and advise across all of these so the admixture, water reducer, accelerator and any repair mortar are matched to one another and to the spray equipment on site.
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