Fosroc Conbextra EP300
Low-exotherm, free-flow epoxy resin grout built for deep pours up to 300 mm and hot-climate grouting at ambients up to 55°C — under turbines, crane rails and reciprocating machinery.
What is it?
A three-component epoxy resin grout — base resin, liquid hardener and graded inert fillers — that flows freely under baseplates and cures to around 100 N/mm² compressive strength at 7 days.
Where is it used?
Under reciprocating and rotating equipment, heavy crane and transporter rails, high-speed turbines and centrifuges, and in pours running long distances or through thick sections.
Why use it?
Its low-exotherm chemistry allows single pours up to 300 mm deep and keeps working time practical even at 40–55°C, where conventional epoxy grouts stiffen in minutes.
How is it applied?
Whole-pack mixed on site — hardener into base, then filler — and poured steadily from one side under a hydrostatic head into leakproof formwork. No part-mixing, no site additions.
About Fosroc Conbextra EP300
Fosroc Conbextra EP300 is a free-flow epoxy grout designed around a problem every Indian plant engineer recognises: heat. Any epoxy generates its own exotherm as it cures, and when you pour it deep — or place it on a 45°C afternoon — that internal heat can cut working time to minutes and lock thermal stresses into the hardened grout. EP300 is deliberately formulated as a low-exotherm system so it can be cast in sections up to 300 mm in a single operation and placed at ambient temperatures as high as 55°C without those penalties, which is why it turns up under compressors, turbines and crane rails from coastal ports to inland steel plants.
The material arrives as a factory-proportioned three-component pack — epoxy base resin, liquid hardener and specially graded inert fillers — mixed whole on site with nothing else added. Once cured it is non-shrink, so the baseplate keeps full bearing contact; it shows low creep under sustained load, stands up to repetitive dynamic loading, and resists oils, greases, fats, mild acids and alkalis, and both fresh and sea water. As an authorised Fosroc distributor and applicator, Space Arc Engineering supplies Conbextra EP300 across Delhi NCR and pan-India, with support on pour planning, formwork detailing and supervised installation.
The technical insight
Epoxy cure is an exothermic reaction that feeds on itself: heat released by the resin accelerates the reaction, which releases more heat. In a thick pour the core cannot shed that heat, so an ordinary epoxy grout flash-sets, cracks or ends up with locked-in thermal stress. Conbextra EP300 counters this two ways — a slower-reacting resin–hardener system, and a high loading of graded inert filler that dilutes the reactive mass and conducts heat outward. The practical result is unusually long usable life for an epoxy: roughly 240 minutes at 20°C, 90 minutes at 30°C, and still about 50 minutes at 40°C. The same tuned kinetics work in your favour once placed in hot service — around 75 N/mm² compressive strength in 3 days at 40°C, rising to about 110 N/mm² at 7 days when cured at 50°C — while the non-shrink matrix keeps the plate in genuine full-area bearing.
Where it is used
- Precision grouting under reciprocating compressors and rotating machinery baseplates
- Heavy crane and transporter rail grouting in ports, steel plants and heavy engineering shops
- Foundation grouting for high-speed turbines and centrifuges subject to dynamic loads
- Deep-section grouting — gaps up to 300 mm filled in a single pour
- Long-distance flow grouting under large baseplates where the grout must travel far from the pour point
- Grouting in high-ambient-temperature conditions up to 55°C — summer works, hot process areas
- Machine foundations exposed to oil, grease and chemical spillage where cementitious grout would degrade
Key advantages
- Low exotherm permits pours up to 300 mm deep without thermal cracking risk
- Long working time — about 240 minutes at 20°C, and still roughly 50 minutes at 40°C
- Non-shrink cure keeps the full baseplate area in bearing contact
- High mechanical performance: about 100 N/mm² compressive at 7 days (40°C cure), 30 N/mm² flexural
- Low creep under sustained load and proven resistance to repetitive dynamic loading
- Withstands oils, fats, most chemicals, mild acids and alkalis, fresh and sea water
- Factory-proportioned 14-litre whole packs eliminate site batching errors
Limitations & considerations
- Must be placed restrained under the plate — unrestrained shoulders or plinth extensions can crack; keep exposed grout to a minimum
- Cure slows noticeably below 25°C and effectively pauses near 5°C, resuming only when the material warms
- Optimised for hot climates — cured grout serves best at ambients of 25–55°C; cold-weather work needs warmed materials and a 72-hour hold before loading
- A free-flow grout, not a patching mortar: it demands leakproof formwork and a hydrostatic head to place properly
- Epoxy resins can sensitise skin — gloves, eye protection and covered arms are non-negotiable on site
- Costs more per litre than cementitious grouts, so reserve it for dynamic, chemical or deep-pour duty that justifies it
Selection & best practice
Get the substrate right first: concrete must be sound and free of oil, grease and laitance — cut back defective surfaces and blow bolt pockets clean. Shot-blast steel plate undersides to SA 2½; if plates will wait before setting, coat them with Nitoprime 25 to stop rust and secure bond. Build formwork leakproof (foam strip or mastic under and between boards), keeping the gap about 75 mm on the pouring side, 25 mm opposite, flank shutters tight to the plate, with air-relief holes at high spots. Mix the full pack: pour all hardener into the base container and blend with a slow-speed mixer, transfer to a 20–25 litre vessel, add all the filler and mix two minutes to a uniform colour. Pour steadily from one side only under a hydrostatic head — a hopper helps — and keep the flow continuous, pacing each pour to the next batch. In cooler weather store components warm, keep mixed material at 25°C minimum, and allow 72 hours before loading.
Specifications
| Form / composition | Three-component epoxy grout: base resin, liquid hardener, graded inert fillers |
| Gap / pour depth range | Approx. 10 mm to 300 mm in a single pour |
| Compressive strength (ASTM C579, 40°C cure) | 75 N/mm² at 3 days; 100 N/mm² at 7 days (110 N/mm² at 7 days, 50°C cure) |
| Tensile strength (BS 6319 Pt 7) | 11 N/mm² at 7 days (40°C cure) |
| Flexural strength (BS 6319 Pt 3) | 30 N/mm² at 7 days |
| Mixed density | 1.95 g/cc |
| Pot life | 240 min at 20°C; 90 min at 30°C; 50 min at 40°C |
| Pack size | 14-litre pack (whole-pack mixing) |
| Shelf life | 12 months in dry conditions at 20°C; reduced by hot storage |
Industry use cases
Power & Energy
Turbine, generator and centrifuge pedestals where low creep and resistance to sustained dynamic load keep alignment true over years of service.
Steel & Heavy Engineering
Transporter and heavy crane rail grouting, plus baseplates of large reciprocating plant, where impact and repetitive loading punish cementitious grouts.
Oil, Gas & Petrochemical
Compressor and pump foundations in process areas — chemical resistance to oils, fuels and mild acids, and placeability in hot ambient conditions.
Ports & Material Handling
Quay crane rails and handling equipment in marine environments; the cured grout tolerates fresh and sea water exposure.
Cement & Manufacturing
Deep-section and long-flow pours under mill and machine baseplates, where the low-exotherm formulation allows one continuous 300 mm placement.
Frequently asked questions
How is Conbextra EP300 different from a cementitious grout like Conbextra GP2?
What pot life should I plan for at site temperature?
What is the maximum depth I can pour in one go?
When can the machine be loaded after grouting?
Do I need a primer under the baseplate?
How do I estimate the number of packs?
How we position Fosroc Conbextra EP300
Within the Fosroc grout family, Conbextra EP300 is the deep-pour, hot-climate specialist. For thin clearances below 10 mm — skid shims, small machine bases — the low-viscosity Conbextra EP10 penetrates where EP300’s filled system cannot. For everyday static baseplates without chemical or dynamic demands, cementitious Conbextra GP2 does the job at lower cost. Pair EP300 with Nitoprime 25 for priming steel plates and Lokfix for anchor bolt fixings in the same foundation package. Where a consultant’s specification is written around another manufacturer’s epoxy grout, Space Arc can also offer comparable systems from our other principal brands — share the spec and we will match it honestly.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.