About Fosroc Conbextra LC

Fosroc Conbextra LC sits within the Conbextra family of cementitious grouts, but it is purpose-built for a job that the general-purpose bedding grouts (such as Conbextra GP) are not designed for: getting a fluid, stable cement slurry deep into narrow, congested gaps around steel. It is a single-component, factory-blended dry powder based on Portland cement, graded fine fillers and chemical additives. On site it requires nothing more than the controlled addition of clean water and mechanical mixing to produce a homogeneous, free-flowing slurry. Because the mix is “all-fines” with no coarse aggregate, it can travel through long ducts and thread itself around closely spaced cables, strands and reinforcement without blocking or segregating.\n\nThe additive package is what distinguishes Conbextra LC from a site-batched cement grout. It is formulated to minimise water demand, suppress bleed and provide controlled expansion in the plastic state so that the hardened grout stays in intimate contact with the steel and the surrounding concrete or rock. That combination of fluidity plus dimensional stability is the core engineering value: a fluid grout that fills completely, then sets without slumping or leaving a bleed channel at the top of the duct that could become a corrosion path. Fosroc lists Conbextra LC for cable grouting in reinforced-concrete diaphragm walls, grouting of long bolts in rock and walls, micropiles, pumping in concrete dams, and foundation strengthening — in short, applications where a durable, high-strength, pumpable slurry is the right tool.\n\nFor Indian projects, Space Arc Engineering supplies Conbextra LC as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, with technical support on mix design, pumpability and method-statement preparation for cable, anchor and pressure-grouting works.

The technical insight

The performance of any cable or duct grout is governed less by ultimate strength than by three plastic-state properties: flowability, bleed and expansion. Conbextra LC is engineered around all three. High flow (achieved at a controlled water:powder ratio rather than by over-watering) lets the slurry fill the annular gap between strand and duct over long pumping distances. Negligible bleed prevents the formation of a water lens or void at the high points of an inclined or vertical duct — historically a primary cause of tendon corrosion in post-tensioned structures. Controlled plastic expansion compensates for settlement and keeps the grout pressing against the steel and substrate, which is what delivers the high bond/adherence Fosroc highlights. The practical lesson for engineers is that water content must be held at the specified minimum: adding water to ease pumping increases bleed, lowers strength, raises porosity and undermines the very durability the product is chosen for. Conbextra LC should therefore always be mixed by volume/weight to the published ratio using a high-shear grout mixer, screened, and kept agitated in the holding tank until pumped.

Where it is used

• Grouting of post-tensioned cable, strand and tendon ducts
• Cable grouting in reinforced-concrete diaphragm walls
• Grouting of long rock bolts, ground anchors and wall anchors
• Micropile and mini-pile annulus grouting
• Pressure (consolidation) grouting in concrete dams and tunnels
• Foundation strengthening and underpinning by injection
• Filling of narrow voids and annular gaps around steel where high-strength durable slurry is required

Key advantages

• High penetration and adherence — the fine, fluid slurry threads around closely spaced strands and bars and bonds intimately to steel and substrate
• Pumpable or gravity-poured, giving flexibility for long-duct, inclined and vertical grouting
• High early strength supports faster stressing and construction cycles
• Controlled plastic expansion with negligible bleed keeps grout in contact with steel and avoids bleed-channel voids
• Low porosity and high ultimate strength deliver durability against static and dynamic loads and chemical attack
• Factory pre-blended and single-component — only clean water is added, giving consistent, repeatable site results
• No coarse aggregate, so reduced risk of blockage and segregation in narrow ducts

Limitations & considerations

• Cementitious slurry grout — not a structural epoxy; for chemical-resistant or very high dynamic-load machine bases use an epoxy grout such as the Conbextra EP range
• Sensitive to over-watering: exceeding the specified water:powder ratio increases bleed and porosity and reduces strength and durability
• Requires high-shear mechanical mixing and continuous agitation; hand-mixing gives poor flow and uneven set
• Working/pumping time is limited once gauged and is shortened in hot Indian site conditions
• Not formulated for large-gap structural bedding under base plates (use Conbextra GP/GP2/GP3) or for very large rock-fissure consumption (use a dedicated rock/cable grout to mix design)
• Pre-grouting checks (duct integrity, vent/outlet layout, flushing) are essential; the product cannot compensate for a blocked or leaking duct

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Conbextra LC

Conbextra LC is Fosroc’s fine, high-flow cementitious slurry for getting durable grout into narrow gaps around steel — cable ducts, rock bolts, anchors, micropiles and pressure-grouting works. It sits alongside the other cable/anchor-class Conbextra products (Conbextra L, Conbextra Cable Grout, Conbextra Cable Grout HS and Cable Grout Plus); for larger structural bedding gaps under base plates, look instead at Conbextra GP/GP2/GP3, and for chemical-resistant or very high dynamic-load grouting, the epoxy-based Conbextra EP range. Against the wider Indian market, credible alternatives in the cementitious cable/anchor and pressure-grout space include Sika (SikaGrout and post-tensioning duct grouts such as the SikaGrout PT/Intraplast systems), MBS / MYK (cementitious grout ranges), Dr. Fixit (Pidilite’s grouting range) and STP (Shalimar/Choksey-type non-shrink grouts). The right choice is dictated by gap geometry, pumping distance, required early strength and the project specification — Space Arc helps engineers and consultants match the correct Conbextra grade to the duct or anchor detail and supplies it Pan-India with the official Fosroc datasheet.

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