Fosroc Conbextra BB92 O
Ultra-high-performance, non-shrink cementitious precision grout engineered for wind turbine foundations, segmental towers and heavily loaded structural connections.
What is it?
A factory-blended, ultra-high-strength non-shrink cementitious grout built for structural grouted connections that carry severe static, dynamic and fatigue loads.
Where is it used?
Onshore wind turbine foundation base frames, joints of segmental precast concrete towers, and heavy machinery and equipment bases where 90-100 MPa class strength is specified.
Why use it?
It reaches very high early and ultimate strength, expands positively to fill voids, resists fatigue, and flows or pumps without bleeding or segregation.
How is it applied?
Mix at a controlled 0.10-0.12 water/powder ratio, pre-soak and form the substrate, then pour or pump from one side in a continuous head up to 150 mm thick.
About Fosroc Conbextra BB92 O
Conbextra BB92 O sits at the top of Fosroc’s precision-grout range. Where a general-purpose grout is asked to bed a pump or a stanchion, BB92 O is specified where the connection itself is structural and cyclically loaded, most commonly the base frame of an onshore wind turbine tower or the horizontal and vertical joints of a segmental precast concrete tower. It arrives as a ready-to-use dry powder, a blend of Portland cement, graded fillers and chemical additives, that needs only clean water on site to produce a free-flowing, non-shrink grout with strength figures well beyond ordinary machine-base products.
For engineers in India specifying renewable-energy and heavy-industrial foundations, that positioning matters. The grout is designed to develop high strength quickly so temporary supports and shims can be released early, and to keep performing under the fatigue regime a rotating turbine imposes on its footing. Space Arc Engineering supplies BB92 O as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, so specifiers get the genuine material together with placement guidance for the gap depths, ambient conditions and pumping distances a real site throws up.
The technical insight
The performance rests on two linked mechanisms. First, a tightly graded, low water-demand powder lets the grout run at a water/powder ratio of just 0.10 to 0.12, roughly half the water an old-style bridge-bearing grout needs. Less mixing water means a denser matrix, and that is what pushes 75 mm cube strength past 70 MPa in a single day and beyond 100 MPa at 28 days on the pumpable mix. Second, chemical additives drive a controlled 0 to 1 percent expansion in the plastic state, so as the grout stiffens it presses outward against the baseplate and formwork rather than pulling away. The result is full, positive contact across the bearing area with no shrinkage gap, which is exactly what a fatigue-loaded connection needs to transfer load without hammering. Because the mix carries no fibres, it still slump-flows past 700 mm and can be pumped over distance without the segregation or bleed that would otherwise leave weak, water-rich zones under the plate.
Where it is used
- Grouting the base frames of onshore steel wind turbine tower foundations
- Filling horizontal and vertical joints in segmental precast concrete wind towers
- High-load structural grouted connections carrying dynamic and fatigue loading
- Precision bedding of heavy machinery and equipment baseplates
- Anchoring holding-down bolts and dowels in pockets ahead of plate grouting
- Grouting where long-distance pumping is required without bleed or segregation
- Foundations needing sulphate resistance in aggressive ground conditions
- Early-return-to-service bases where temporary supports must be struck quickly
Key advantages
- Ultra-high strength, exceeding 100 MPa at 28 days on the pumpable mix
- Very high early strength, over 70 MPa at one day, allowing quick load transfer
- Non-shrink with positive 0 to 1 percent plastic expansion for full contact
- High fatigue resistance suited to cyclically loaded turbine connections
- High flexural strength and modulus without any added fibres
- Free-flowing, slump flow above 700 mm, and readily pumpable over distance
- No bleeding or segregation, giving consistent strength across the bed
- Factory pre-packed, removing on-site batching variation and error
Limitations & considerations
- Not for use below -5 degrees C or above 40 degrees C ambient
- Single-pour thickness is capped at 150 mm; deeper gaps need Fosroc technical advice
- Cementitious only; for chemical attack or oil exposure an epoxy grout is more suitable
- Must not be exposed to moving water or rainfall before final set
- Requires disciplined water control; over-watering sharply reduces strength
- Twelve-month shelf life, reduced by high heat and humidity in storage
Selection & best practice
Cut back any laitance or defective concrete to a sound base and blow bolt pockets clean, then flood the cleaned foundation with fresh water for several hours and remove all free water immediately before grouting. Build leak-proof formwork, since this is a free-flowing grout. Measure clean water accurately, using 2.5 to 3.0 litres per 25 kg bag, add powder slowly into a mechanically powered shear mixer, and mix for five minutes to a smooth consistency. Place within the working time, pouring or pumping from one side only to drive air and surplus water ahead of a continuous grout front, and keep the head maintained throughout. In hot Indian summers store mixed grout in shade and use cool water below 20 degrees C; in cold conditions use warm water at 30 to 40 degrees C to aid strength gain. Cure exposed surfaces at once with Fosroc Concure membrane, wet hessian or continuous water.
Specifications
| Material type | Ultra-high-performance non-shrink cementitious grout |
| Compressive strength (pumpable, 0.10 w/p) | >70 MPa @ 1 day, >90 MPa @ 7 days, >100 MPa @ 28 days |
| Compressive strength (flowable, 0.12 w/p) | >60 MPa @ 1 day, >80 MPa @ 7 days, >90 MPa @ 28 days |
| Flexural strength (EN 196-1) | >7.5 MPa @ 1 day, >13 MPa @ 7 days, >15 MPa @ 28 days |
| Static modulus of elasticity | Greater than or equal to 41 GPa (EN 13412) |
| Expansion | 0 to 1 percent, positive, in the plastic state |
| Water / powder ratio | 0.10 to 0.12 (2.5 to 3.0 litres per 25 kg bag) |
| Gap depth / yield | 10 to 150 mm per pour; approx. 12 litres yield per 25 kg bag |
| Standard & supply | EN 1504-6:2006 (anchoring products); 25 kg bags and 1 tonne bulk bags |
Industry use cases
Renewable Energy
Grouting the base-frame connection of onshore wind turbine tower foundations, where the fatigue and dynamic loads from a rotating turbine demand a 90-100 MPa class non-shrink grout.
Precast Concrete Towers
Filling the horizontal and vertical joints of segmental precast concrete wind towers so each ring transfers load uniformly without a shrinkage gap.
Heavy Industry & Power
Bedding large compressor, turbine and generator baseplates in plants where high early strength lets equipment return to service quickly.
Infrastructure
High-load structural connections and heavy bearing beds on bridges and viaducts that require strength and fatigue resistance beyond standard grouts.
Aggressive Ground
Foundations in sulphate-bearing soils where the grout’s sulphate resistance protects the connection over the structure’s design life.
Frequently asked questions
How is Conbextra BB92 O different from a standard machine-base grout like GP2 or GP3?
What water quantity should be used per 25 kg bag?
What thickness can be grouted in a single pour?
How soon can equipment or supports be loaded?
Can it be pumped over long distances on site?
Is BB92 O suitable where there is chemical or oil exposure?
How we position Fosroc Conbextra BB92 O
Conbextra BB92 O is Fosroc’s top-tier structural grout, so it is worth matching to the load case rather than defaulting to it. For everyday machine bases, stanchion feet and anchor-bolt pockets, the more economical cementitious Conbextra GP2 or the high-strength Conbextra GP3 usually do the job. Where the environment involves chemical attack, vibration on oil-wetted plant or crack injection, step across to the epoxy Conbextra EP10. Space Arc also carries equivalent precision and epoxy grouts from Sika, MC-Bauchemie and Dr. Fixit, so if a project standard calls for a specific brand we can cross-reference a like-for-like grade and confirm it meets the same strength, expansion and standards requirements as BB92 O.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.