About Fosroc Conbextra TA

Fosroc Conbextra TA sits at the specialist end of the Conbextra grout family. Where Conbextra GP and GP2 serve everyday baseplate and pocket grouting, Conbextra TA (TA = turbine application) is formulated specifically for one of the most punishing grouting jobs in civil engineering: bedding the transition piece of an onshore wind turbine onto its reinforced concrete foundation. In that joint the grout is not a passive filler. It becomes a structural element that must transfer enormous static and cyclic loads from a tower that is constantly flexed by wind and rotor forces, for a design life measured in decades.\n\nThe product is a ready-to-use, factory-blended cementitious powder; the contractor adds only clean water at a controlled ratio. What sets it apart is its fibre-free chemistry. Many high-strength grouts rely on steel or polymer fibres to lift flexural strength, but fibres reduce flowability and can cause pump blockages over the large bearing areas a turbine base demands. Conbextra TA instead achieves high flexural strength (16 N/mm2 at 28 days) and a 40 GPa static modulus of elasticity through cement chemistry alone, so it stays highly fluid and pumpable. A unique binder system also controls the heat of hydration, allowing both thin and thick sections, from 50 mm up to 250 mm gap depth, to be cast without the thermal cracking risk that plagues mass-poured cementitious grouts.\n\nFor Indian renewable-energy contractors, EPCs and OEM erection teams, Conbextra TA is the type of product specified by turbine manufacturers and consultants on wind farms across Tamil Nadu, Gujarat, Karnataka, Rajasthan, Maharashtra and Andhra Pradesh. Space Arc Engineering supplies it as an authorised Fosroc distributor with technical support on site preparation, mixing discipline and curing.

The technical insight

The performance signature of Conbextra TA is the combination of very high compressive class (C100/115) with genuine fatigue qualification. Compressive strength on 150 mm cubes (EN 12390-3) develops to 60 N/mm2 at 1 day, 85 N/mm2 at 7 days and 115 N/mm2 at 28 days; on 40x40x160 mm prisms (EN 12190) it reaches 30, 100 and 120 N/mm2 over the same ages. Crucially, the grout is fatigue-tested against the Model Code 1990 and 2010 S-N curves, the design basis for the millions of load cycles a turbine base sees in service, which ordinary structural grouts are not characterised for. Workability is equally engineered: a slump flow over 700 mm (EN 12350-8) and an initial flow over 750 mm (EN 13395-2, Class f3 to DAfStB) with retention of at least 650 mm after 30 minutes give crews time to fill large annuli in a single continuous pour. The mix is intentionally lean on water, a fixed 0.08 water/powder ratio (up to 0.085 in hot conditions), which underpins both the strength and the absence of bleed. Positive expansion after casting (0 to 1%) and a low-shrinkage classification (SKVM0) ensure the hardened grout stays in full contact with the steel base, eliminating voids that would otherwise concentrate stress.

Where it is used

• Grouting the annular gap between the steel transition piece and concrete foundation of onshore wind turbines
• Bedding of large-diameter tower base flanges and flange-mounted connections
• Filling bolt pockets and anchor-bolt cages on turbine and tall-mast foundations
• High-fatigue structural connections requiring cyclic-load-rated grout
• Wide-area, deep-section grouting (50 to 250 mm gap) where conventional grouts would segregate or block pumps
• Heavily loaded baseplates on dynamic machinery where fatigue performance is specified

Key advantages

• Fibre-free chemistry delivers high flexural strength and 40 GPa modulus while keeping the grout highly fluid and pump-friendly
• Fatigue-qualified to Model Code 1990 and 2010 S-N curves, suited to the cyclic loads of turbine towers
• Very high ultimate compressive strength, Class C100/115 (up to 115-120 N/mm2 at 28 days)
• Rapid early strength gain allows early striking of formwork and supports, even at low temperatures
• No segregation or bleeding, preventing voids and pump blockages over large areas
• Heat-of-hydration control permits both thin and thick sections (50 to 250 mm) without thermal cracking
• Positive post-cast expansion and low shrinkage (SKVM0) maintain full contact under the base plate
• Compliant with EN 1504-6:2006 and supplied as a single-component ready-to-use powder

Limitations & considerations

• Highly specialised for wind turbine and high-fatigue connections; for general baseplate or pocket grouting, Conbextra GP, GP2 or HF are more economical
• Performance depends on a strict 0.08 water/powder ratio (max 0.085 in heat); over-watering destroys strength and expansion behaviour
• Gap depths beyond 250 mm require consultation with Fosroc Technical Department before use
• Application temperature window is 2 to 35 deg C, so very hot Indian site conditions need cooling/curing measures
• Requires disciplined surface preparation and several hours of pre-soaking of the foundation before grouting
• Not an epoxy grout; for the highest chemical resistance or where oils/aggressive media are present, an epoxy grout such as Conbextra EP may be specified instead

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Conbextra TA

Within the Fosroc range, Conbextra TA is the turbine-application specialist and should be read alongside the broader Conbextra grout family rather than as a substitute for it. For routine baseplate, pocket and cable-duct grouting, Conbextra GP and Conbextra GP2 are the workhorse cementitious choices, Conbextra HF where high early flow is needed, and Conbextra EP where an epoxy grout’s chemical resistance and bond are required; for crack injection or anchoring, Fosroc’s Lokfix and Nitofill ranges are the natural companions. Conbextra TA earns its premium only where the connection is genuinely fatigue-critical and load-intensive, namely wind turbine foundations and comparable dynamic structures. Against the wider market, credible alternatives an Indian consultant might evaluate include Sika’s SikaGrout and high-performance turbine grouts such as SikaGrout-3200 HES, BASF/Master Builders Solutions MasterFlow grouts (notably the MasterFlow 9000-series turbine grouts), and STP and Dr. Fixit cementitious grouts for general work, though the latter two are not typically positioned for turbine-foundation duty. As an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, Space Arc Engineering can help specifiers confirm whether Conbextra TA is the right grade for the connection, or direct them to a more economical Conbextra option where the application does not demand fatigue-rated, C100/115 performance.

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