Fosroc Cebex Cable Grout Plus
Pre-bagged, hydrogen-free, chloride-free expansive grout admixture engineered to protect post-tensioning tendons in bridge decks, prestressed elements and silo cable ducts.
What is it?
An all-fines, pre-bagged grout admixture containing expansive cement that is blended on site with Ordinary Portland Cement and clean water to produce a free-flowing, non-shrink cementitious grout for post-tensioning cable ducts.
Where is it used?
Inside post-tensioned bridge deck ducts, prestressed structural element tendon ducts and slip-form silo tendon ducts, wherever stressed cables must be encased and protected from corrosion.
Why use it?
It fully fills the duct, compensates for plastic shrinkage and settlement through a hydrogen-free expansion of up to 4%, and develops high early strength without chlorides, so the encased tendon is durably bonded and protected.
How is it applied?
One 12 kg bag is mixed with 200 kg OPC and 64-84 litres of clean water in a mechanical grout mixer for 5 minutes, then pumped from a single point into a pre-soaked, sealed duct within 20 minutes.
About Fosroc Cebex Cable Grout Plus
Fosroc Cebex Cable Grout Plus is a specialised admixture for the grouting of post-tensioned (PT) cable ducts, where the grout has a dual job to do: it must completely encapsulate the high-tensile prestressing strand to lock it permanently to the surrounding concrete, and it must form a dense, alkaline, corrosion-protective sheath around that strand for the design life of the structure. A duct that is only partially filled, or grout that bleeds and leaves voids at high points, exposes the tendon to moisture and chloride ingress, which is one of the most serious and difficult-to-repair durability failures in prestressed construction. Cebex Cable Grout Plus is formulated specifically to prevent that outcome.\n\nIt is not a ready-to-use mortar. It is supplied as a dry, all-fines powder containing an expansive cement system, packed in 12 kg bags. On site it is combined with a controlled quantity of Ordinary Portland Cement and clean water to produce a fluid, pumpable grout. The ‘all fines’ nature means there is no coarse aggregate to segregate, so the mix stays homogeneous as it travels through long, congested ducts. The expansive component drives a positive volumetric expansion of up to 4% while the grout is still plastic, counteracting the natural shrinkage and settlement of a cement grout and helping it stay in intimate contact with both the strand and the duct wall.\n\nTwo features matter most to specifiers in India. First, the expansion mechanism is hydrogen-free. Older aluminium-powder gassing agents liberate hydrogen, which can be problematic in a sealed duct around stressed steel; the Cebex Cable Grout Plus system avoids that gas-generation route entirely. Second, the grout develops its early and ultimate strength without the use of chlorides, so no chloride is deliberately introduced next to the very strand it is meant to protect. The hardened grout is dense and low in permeability, which underpins the long-term durability of the tendon. The product is compatible with Ordinary Portland Cements complying with BS 12 and ASTM C150, and the datasheet references compliance with BS 8110 Part 1: 1985 Section 8 and testing to the BS EN 445 family of grout test methods.
The technical insight
The engineering value of Cebex Cable Grout Plus lies in how its fresh-state behaviour is balanced against its hardened performance. Tested at a 0.36 water/cement ratio with OPC, the grout reaches roughly 25 N/mm2 at 1 day, 45 N/mm2 at 3 days and 55 N/mm2 at 7 days, exceeding the common 50 N/mm2-at-7-days performance threshold for PT grouts, before climbing to about 60 N/mm2 at 28 days. Those strengths are achieved while keeping the grout fluid enough to pump: the BS EN 445 cone fluidity stays in the 10-20 second band both initially and after 30 minutes, which tells a site engineer the mix will not stiffen prematurely inside a long duct. Just as critical, bleeding is held to less than 1% after 3 hours and the chloride content is nil to BS 5075, while the plastic-state expansion of up to 4% (BS EN 445) actively pushes grout into the highest points of the profile. The trade-off the designer must respect is the tight working window: the grout must be placed within 20 minutes of mixing, the mix design (64-84 litres of water per bag depending on the cement) must be dialled in by trial, and the annular gap should not exceed 60 mm in thickness. Get the mix, pump rate and single-point injection right and you get a fully encapsulated, void-free tendon; treat it like an ordinary cement grout and the same fluidity that makes it pumpable can become a source of bleed lensing if the rules are ignored.
Where it is used
- Grouting of post-tensioned bridge deck cable ducts after stressing
- Filling tendon ducts in prestressed structural elements such as beams, girders and transfer slabs
- Grouting slip-form silo wall tendon ducts in cement, grain and clinker storage structures
- Encapsulation and corrosion protection of high-tensile prestressing strand in sealed metal or formed ducts
- Pumped or free-flow grouting of long, profiled cable ducts where bleed and segregation must be controlled
- Annular gap filling of up to 60 mm thickness around stressed cables
Key advantages
- Hydrogen-free expansion system avoids gas generation around stressed steel inside the duct
- Positive plastic-state expansion of up to 4% compensates for shrinkage and settlement, helping eliminate voids
- Develops high early strength (approx. 25 N/mm2 at 1 day) without the use of chlorides
- High ultimate strength (approx. 60 N/mm2 at 28 days) and low permeability for durable tendon protection
- All-fines formulation resists segregation and bleeding (<1% bleed after 3 hours) in long ducts
- Chloride content nil to BS 5075, protecting rather than threatening the prestressing strand
- Stable fluidity (10-20 seconds, BS EN 445 cone) maintained for up to 30 minutes for reliable pumping
- Pre-bagged 12 kg powder gives consistent, factory-controlled dosing on site
- Compatible with BS 12 / ASTM C150 Ordinary Portland Cements widely available in India
Limitations & considerations
- Not a ready-mix grout: requires site addition of 200 kg OPC and 64-84 litres clean water per 12 kg bag, so batching discipline is essential
- Short working window: grout must be placed within 20 minutes of mixing
- Trials are recommended before use to confirm the best OPC source and final water content, as fluidity depends on cement
- Annular gap is limited to a maximum of 60 mm thickness; not intended for thick-section or bedding applications
- Requires mechanical grout mixing and a heavy-duty pump; colloidal impeller mixers must not be used if sands/aggregates are introduced
- Low-temperature working needs normal cementitious winter-working precautions; performance and set are temperature-sensitive
- Alkaline dust and wet grout demand PPE (gloves, goggles, dust mask) and careful handling
- Shelf life of 12 months is reduced if bags are stored in high-temperature, high-humidity conditions common in Indian monsoon climates
Selection & best practice
Pre-soak the duct with fresh water several hours before grouting and remove all free water immediately before injection; seal cable anchorages first. Run a site trial to fix the exact water dose (within the 64-84 litre band) for your specific OPC source, then batch by weight: accurately measure water into a mechanically powered grout mixer, add the full 12 kg bag together with 200 kg of cement and mix continuously for 5 minutes to a smooth, even consistency. Pump from a single injection point to push out air and presoak water, and ensure the grout is placed within 20 minutes of mixing, using a grout holding tank with gentle agitation if continuity demands it. Bleed and consistency should be verified against the BS EN 445 values before full-scale grouting. In Indian summer conditions, protect mixed grout from rapid temperature rise and store unopened bags in a cool, dry, sealed condition; for sample cubes, demould and water-cure per the specified intervals. Clean all equipment with clean water immediately after use, before the grout cures.
Specifications
| Product type | Pre-bagged, all-fines expansive admixture for cementitious PT cable grout |
| Chloride content | Nil to BS 5075 |
| Volume change / expansion (BS EN 445) | Positive expansion of up to 4% in the plastic state |
| Compressive strength (OPC, 0.36 w/c, BS EN 196) | approx. 25 N/mm2 @ 1 day; 45 N/mm2 @ 3 days; 55 N/mm2 @ 7 days; 60 N/mm2 @ 28 days |
| Fluidity (BS EN 445 cone method) | 10-20 seconds initial; 10-20 seconds final (after 30 minutes) |
| Bleeding (BS EN 445) | <1% after 3 hours |
| Fresh wet density | Approximately 2000 kg/m3 (depending on consistency used) |
| Mix proportions | 1 x 12 kg bag + 200 kg OPC + 64-84 litres clean water |
| Yield | approx. 136 litres when mixed with 200 kg cement and 68 litres water |
| Working / placing time | Place within 20 minutes of mixing; mix 5 minutes |
| Maximum annular gap | Up to 60 mm thickness |
| Cement compatibility | OPC complying to BS 12 and ASTM C150 |
| Standards | BS 8110 Part 1:1985 Sec.8; tested to BS EN 445 / BS EN 196; chloride nil to BS 5075 |
| Packaging | 12 kg bags |
| Shelf life | 12 months in a dry store in sealed bags (reduced in high temperature/humidity) |
Industry use cases
Bridges & Flyovers
Grouting post-tensioned deck and segmental tendon ducts on highway bridges, metro viaducts and flyovers across Delhi NCR and national highway projects, where void-free encapsulation of cables is essential for fatigue durability.
Prestressed Buildings
Filling tendon ducts in post-tensioned transfer girders, long-span beams and PT slabs in commercial towers and parking structures, restoring full bond between strand and concrete after stressing.
Industrial Silos & Storage
Grouting slip-form silo wall tendon ducts in cement, clinker and grain storage silos, where hoop prestress must be permanently protected against an aggressive stored environment.
Precast / Prestress Yards
Production grouting of cable ducts in factory-cast prestressed girders and segments, with batched trials ensuring repeatable fluidity and strength for QA documentation.
Water & Infrastructure
Tendon-duct grouting in prestressed water-retaining structures and circular tanks, where low permeability and chloride-free composition support long-term watertightness and corrosion control.
Frequently asked questions
Is Fosroc Cebex Cable Grout Plus a ready-to-use grout?
Why is the hydrogen-free expansion system important for post-tensioning?
What compressive strength does it achieve?
How long do we have to place the grout after mixing?
Does it contain chlorides that could corrode the strand?
How is it different from Fosroc Cebex Cable Grout and Cebex 100?
How we position Fosroc Cebex Cable Grout Plus
Within the Fosroc range, Cebex Cable Grout Plus sits in the post-tensioning grout family alongside Cebex Cable Grout, Cebex Cable Grout 100 and the Cebex 100 grout admixture, and is typically specified together with Fosroc duct, anchorage and Conbextra high-flow grout systems on the same prestressing package; Concure curing membranes are referenced for related cube and surface curing. It is positioned as a specialist PT cable-duct admixture rather than a general non-shrink grout, so for base-plate, anchor-bolt or bedding work the Conbextra GP / HF cementitious grouts or Conbextra EP epoxy grouts are the correct cross-references. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering supplies and supports this product against project specifications. Credible competitor equivalents that consultants may encounter for PT cable-duct grouting include Sika (Sika cable-duct / IntraPlast grout systems and SikaGrout), MBS / Mc-Bauchemie grout admixtures, BASF Master Builders Solutions (MasterFlow / MasterInject ranges), and broader Indian waterproofing and grout brands such as Dr. Fixit (Pidilite) and STP for adjacent grouting and protection scopes. The decisive selection factors remain the hydrogen-free, chloride-free chemistry, the documented BS EN 445 fluidity and bleed control, and conformance to the governing PT grouting specification, which is where Cebex Cable Grout Plus is strongest.
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