About Fosroc Cebex Cable Grout 100

Fosroc Cebex Cable Grout 100 belongs to Fosroc’s Cebex family of cable-duct grouting admixtures, the products used to fill the ducts around post-tensioning tendons once they have been stressed. Unlike a ready-mixed bagged grout, Cebex Cable Grout 100 is supplied as a dry, all-fines powder that the contractor combines on site with ordinary Portland cement and a controlled quantity of clean water. The result is a fluid, cohesive, non-shrink cementitious grout that flows the full length of the duct, surrounds every wire and strand of the tendon, and then sets to a dense, low-permeability solid that bonds the tendon to the surrounding concrete and protects it for the life of the structure. Two features define the product. First, it is iron-free and chloride-free: there are no metallic aggregates that could rust and stain, and no chloride accelerators that could pit the high-tensile steel of the prestressing strand. Second, it carries a controlled gaseous/expansive system that produces a positive volumetric expansion of up to 4% while the grout is still plastic. That expansion counteracts the natural plastic settlement and bleed of a neat cement grout, keeping the grout in intimate contact with the top of the duct and the anchorage zone, where voids are most damaging. For Indian contractors and consultants, the product is relevant wherever post-tensioning is specified, from PSC girder bridges and flyovers on highway packages to metro viaducts, elevated water tanks and circular prestressed silos. Space Arc Engineering supplies Cebex Cable Grout 100 and the wider Fosroc cable-grouting range, including Conbextra cable grouts, across Delhi NCR and on a Pan-India basis, with technical support on dosage, trial mixes and site procedure.

The technical insight

Cable-duct grouting is a durability operation disguised as a filling operation: the grout is the last line of corrosion protection for a tendon that may be carrying hundreds of tonnes of permanent prestress. Cebex Cable Grout 100 addresses the three classic failure modes of neat cement grout. Bleeding and plastic settlement, which leave water lenses and voids at high points and anchorages, are controlled by the all-fines, low-water-demand formulation that holds bleed below 1% and by the up-to-4% positive expansion that pushes grout back into those high points. Corrosion of the strand is prevented by eliminating chlorides and metallic iron and by maintaining a high-alkalinity (pH > 12.5) passivating environment around the steel. Loss of bond and incomplete filling are countered by the high, sustained fluidity, measured at roughly 10-20 seconds through the BS EN 445 flow cone both initially and after 30 minutes, which lets the grout be pumped continuously from a single inlet through long, congested ducts without segregating. The reference performance figures, achieved with OPC at a 0.36 water/cement ratio, are roughly 25 N/mm2 at 1 day, 45 N/mm2 at 3 days, 55 N/mm2 at 7 days and 60 N/mm2 at 28 days, comfortably exceeding the common specification floor of 50 N/mm2 at 7 days for prestressing grout. Because the reactive expansive agents are sensitive to mixing and handling, Fosroc requires that compressive-strength samples be batched from a sealed bag in a temperature-controlled laboratory using restrained, stacked 50 mm cubes rather than site-mixed samples, a point worth flagging to QA engineers who expect to cast cubes at the duct mouth.

Where it is used

• Grouting post-tensioned bridge and flyover deck ducts on NHAI and state highway packages
• Filling cable ducts in precast and cast-in-situ PSC box and I-girders
• Grouting tendon ducts in metro and elevated-corridor viaduct segments
• Slip-form silo and circular prestressed tank tendon ducts
• Cable ducts in prestressed roof beams, transfer girders and long-span floors
• Anchorage-zone and high-point grouting where plastic settlement voids must be eliminated

Key advantages

• Iron-free and chloride-free, so there is no metallic staining and no chloride attack on high-tensile prestressing steel
• Controlled positive expansion of up to 4% in the plastic state compensates for settlement and bleed and keeps ducts fully filled
• Low water demand gives high early and ultimate strength (about 55 N/mm2 at 7 days, 60 N/mm2 at 28 days) and low permeability
• High, sustained fluidity allows continuous single-point pumping through long, congested ducts
• Bleeding held below 1% after 3 hours, minimising water lenses and voids at high points and anchorages
• Simple site logistics: one pre-bagged admixture combined with locally available OPC and water, no separate aggregates
• Develops high early strength without chlorides, supporting faster construction cycles

Limitations & considerations

• Not a ready-to-use grout; it must be batched with OPC and accurately measured water, so mix discipline and a mechanical grout mixer are essential
• Working time is short, the grout must be placed within about 20 minutes of mixing
• Compressive-strength sampling must be done from a sealed bag in a temperature-controlled lab using restrained 50 mm cubes; conventional site cube sampling is not valid
• Performance depends on the OPC source, so trial mixes to select a suitable cement are recommended before production grouting
• Single-pass placement is limited to annular gaps of around 60 mm; larger voids need a reviewed procedure
• Cold-weather working below 10 C needs extended formwork/cure time and, below 5 C, warm mixing water; hot weather above 35 C needs cooled materials and equipment
• Alkaline dust and wet grout; gloves, goggles and a dust mask are required and trapped air must be vented during pumping

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Cebex Cable Grout 100

Within Fosroc’s own range, Cebex Cable Grout 100 sits alongside the closely related Cebex Cable Grout and Cebex Cable Grout Plus (the hydrogen-free variant) as the dedicated cable-duct grouting solution, while Cebex 100 is the more general expanding-and-plasticising grout admixture used for bed grouting, duct grouting and non-shrink infilling. Where a contractor prefers a fully pre-formulated bagged cable grout rather than a site-batched admixture system, Fosroc’s Conbextra cable-grout products (such as Conbextra Cable Grout and Cable Grout HS) are the natural cross-reference. It is normally paired on site with a Fosroc Concure curing membrane and Fosroc Acid Etch for cleaning, and complemented by Conbextra GP2 or HF for general structural and anchorage grouting. Among credible alternatives that Indian specifiers may evaluate, Sika offers SikaGrout cable and duct-grouting systems, while BASF/Master Builders Solutions (MBS) markets MasterFlow prestressing duct grouts; Dr. Fixit and STP (Pidilite) are strong in the broader waterproofing and general-grout space but are less commonly specified for post-tensioning duct grouting, where dedicated, code-compliant prestressing grouts are the norm. The honest positioning is that Cebex Cable Grout 100 is a proven, long-established choice for post-tensioning duct grouting where chloride-free, non-shrink performance and reliable corrosion protection of the tendon are the priorities; the right pick on any given project depends on the specified standard, the available cement source and whether the site wants an admixture-plus-OPC system or a single pre-bagged grout.

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