Epoxy grouts for machinery: when they are needed and how to use them

How epoxy grout differs from cementitious grout

Epoxy grout is a mixture of epoxy resin, hardener and mineral filler (usually quartz), supplied in factory-proportioned kits. Water plays no part in it: the material cures through a chemical reaction between the components. This gives epoxy grout its main advantages — high compressive and tensile strength, a strong bond to steel and concrete, virtually no shrinkage, resistance to oils and many chemicals, and a fast return to service.

A separate group consists of so-called chocking compounds, originally developed for mounting ships’ engines and gearboxes on polymer chocks instead of fitted steel chocks. Today they are also used onshore — under compressors, pumps, generators and crane rails.

When epoxy grout is essential

• Dynamic loads. Reciprocating and gas engine-driven compressors, diesel and gas engine generator sets, crushers, mills, presses. Vibration and cyclic forces gradually break down cementitious grout at the interface with the baseframe; epoxy grout, being bonded to the steel and the concrete, acts together with them as a single unit.
• Precision machinery. Turbines, turbocompressors and high-power centrifugal compressors, where alignment must remain stable for years.
• Chemical exposure. Pump houses in chemical and petrochemical plants, electroplating and pickling areas, food-processing halls with acid washdowns, and areas constantly exposed to oil and fuel.
• Short downtime. Many epoxy grouts allow the anchors to be tightened and the unit to be started up much sooner than with cementitious grouts.
• Crane runways under impact loading and locations where cementitious grout has already failed.

Industry practice for machinery is set out in API RP 686 and ACI 351.1R, which cover substrate preparation, formwork and the placing of epoxy grouts under rotating and reciprocating equipment in detail. API RP 686 is also referenced in the technical data sheets of a number of manufacturers.

Key features of epoxy grouts

Exotherm and pour depth

The curing reaction gives off heat. In a thin layer, the heat dissipates into the substrate and the steel, but in a thick one it builds up: the material overheats, sets faster, contracts as it cools and may crack. That is why every technical data sheet states the minimum and maximum pour depth per lift. If the gap is larger than permitted, the grout is placed in layers with a waiting period between them, or a grade designed for deeper pours is chosen (usually one with a coarser filler or lower reactivity). For large masses, manufacturers give recommendations on expansion joints in the grout.

Temperature

Viscosity and reaction rate depend strongly on temperature. In the cold, the grout thickens, flows less readily and takes a long time to harden; below a certain temperature, curing may not be completed. In the heat, the pot life shortens and the exotherm intensifies. In Central Asian conditions, this means:

• in summer — store the kits in a cool, shaded place, shade the work area, pour in the morning or evening, and do not work on steel heated by the sun;
• in winter — condition the kits in a warm room, warm the substrate and the baseplate to the temperature given in the technical data sheet, and cover and heat the area until the grout has gained strength.

The service temperature is checked separately: some grades have a limit for long-term service at elevated temperatures, which matters for turbine casings and hot pumps.

Dry, clean substrate

Most epoxy grouts require dry concrete, free of laitance and with a sound surface layer. Steel surfaces in contact with the grout are cleaned to bare metal, usually by abrasive blast cleaning. Some grades tolerate a matt-damp substrate — this must be stated explicitly in the technical data sheet.

Mixing

The components are supplied in pre-measured proportions, and the whole kit is mixed at once. The filler is added gradually using a low-speed mixer, so as not to entrain air.

Formwork and head

Formwork is made leak-tight and coated with wax, polythene sheeting or a release agent. The grout is poured from one side while maintaining a head.

Edge cracking

Because epoxy and concrete expand differently with temperature, cracks sometimes appear at the outside corners of the grout. Manufacturers recommend rounding or chamfering the corners, limiting the grout projection beyond the edge of the baseplate and, for long pours, providing expansion joints.

Epoxy grout and epoxy “chocks”

There are two approaches. With full grouting, the material fills the entire space under the baseframe. With chocking, the equipment sits on individual polymer chocks poured in place into moulds, and the space between them may be left open or filled with another material. Chocking is widely used on ships and offshore platforms and when equipment is re-installed. Manufacturers produce separate grades for each approach, differing in viscosity, pour depth and curing time.

What to check in the technical data sheet

• compressive strength and test method (ASTM C579, EN 196, etc.), specimen age and temperature;
• minimum and maximum pour depth per lift;
• pot life at different temperatures;
• permissible application and service temperature ranges;
• modulus of elasticity, creep under load at elevated temperature (important for tensioned anchors);
• resistance to chemical exposure — confirmed for your medium by the questionnaire;
• time to anchor tightening and start-up.

See also: grouts — overview, cementitious grouts, equipment grouting, crane rails.

Materials from leading manufacturers

Sika

• SikaFlow-648 — Sika — three-component precision epoxy grout for equipment under vibration and dynamic loads, 10–150 mm (formerly MasterFlow 648).
• Sikadur-42 MP Normal — Sika — multi-purpose three-component epoxy grout for machinery, baseplates and crane rails; the technical data sheet gives a layer thickness limit that depends on temperature.
• Sikadur-42 HE — Sika — epoxy grout for medium-thickness layers, suitable for use at low temperatures.
• Sikadur-42 (regional versions, e.g. au) — Sika — grout for machinery, rails and anchor bolts; for deep pours, the manufacturer specifies the HP version.
• Sikadur-42 Grout-Pak — Sika — pre-proportioned epoxy grout kit for baseplates, machinery and crane rails.
• SikaFlow-678 — Sika — low-exotherm epoxy grout for deep pours under equipment.
• SikaFlow-647 — Sika — liquid epoxy grout for pressure injection under baseplates and into cracks.
• Sikadur-42 PC — Sika — castable epoxy grout for pile caps and structural cavity filling, 10–100 mm.
• SikaFlow-649 — Sika — high-strength high-temperature epoxy grout for machinery, rails and wind turbines.
• SikaFlow-668 — Sika — epoxy chock grout for mounting compressors, turbines and machinery.
• SikaFlow-690 — Sika — very-high-strength flowable epoxy grout for wind turbines, pumps and compressors.
• SikaFlow-400 — Sika — free-flowing epoxy grout for machinery, anchors and crane tracks, 20–80 mm.
• Sikadur-42 LP — Sika — multi-purpose epoxy grout for crane tracks, baseplates and anchors, 6–60 mm.
• Sikadur-42 Grout Pak LE — Sika — low-exotherm epoxy grout kit for baseplates, machinery and crane rails.
• Sikadur-42 T — Sika — three-component epoxy grout for baseplates, machine foundations, rails and anchors, 12–50 mm.
• Sikadur-12 Pronto — Sika — rapid-curing acrylic (not epoxy) mortar for grouting and repairs from −10 °C, 5–30 mm.

ITW Performance Polymers (Chockfast)

• Chockfast Red — ITW Performance Polymers — three-component deep-pour grout for large machinery and baseplates.
• Chockfast Orange — ITW Performance Polymers — chocking compound for marine engines, gearboxes, generators, compressors, pumps and crane rails; holds approvals from marine classification societies.
• Chockfast Black — ITW Performance Polymers — compound for hot reciprocating and rotating machinery, resistant to creep at elevated temperatures.
• Chockfast Gray — ITW Performance Polymers — for equipment without critical alignment requirements and for setting anchor bolts.
• Chockfast Red SG — ITW Performance Polymers — fast-curing grout for thin gaps, including under crane rails.
• Chockfast Red Versaflow — ITW Performance Polymers — high-flow pumpable grout.
• Escoweld 7505E/7530 — ITW Performance Polymers — flowable low-exotherm grout for dynamically loaded equipment.

Mapei

• Planigrout 300 — Mapei — flowable epoxy mortar for the foundations of presses and heavy machinery, rails and anchors.
• Planigrout 300 SP — Mapei — free-flowing epoxy grout (Mapei Far East technical data sheet) for machinery, rails and overhead crane baseplates.
• Planigrout 310 — Mapei — fast-curing medium-thickness grout for compressors, presses, and crane and tram rails.
• Planigrout 350 — Mapei — grout for thick layers under heavy machinery.

Other manufacturers

• Conbextra EP10 — Fosroc — low-viscosity grout for very thin gaps and injection.
• Conbextra EP65 Plus — Fosroc — fast-curing high-strength epoxy grout for machinery and crane rails.
• Conbextra EP120 Plus — Fosroc — low-exotherm grout for large pours.
• Five Star HP Epoxy Grout — Five Star Products — high-early-strength grout for rotating equipment.
• Five Star DP Epoxy Grout — Five Star Products — low-exotherm deep-pour grout.
• Five Star Rapid Epoxy Grout — Five Star Products — fast return to service, higher service temperature.
• Five Star XP 230 Epoxy Grout — Five Star Products — grout for wind turbine towers.
• PAGEL EH196R, EH196S — Pagel Spezial-Beton — two-component grouts for rails and precision supports: R — for cool conditions and small volumes, S — for hot conditions and large volumes.
• Five Star Epoxy Novolac Grout — Five Star Products — chemical-resistant epoxy novolac grout for pumps and process equipment.
• Euclid E3-Flowable — Euclid Chemical — high-flow epoxy grout for wide baseplates, rails and anchor bolts.
• Euclid E3-Xtreme — Euclid Chemical — ultra-high-strength epoxy grout for pumps, compressors and dynamic loads.
• Euclid E3-HCR — Euclid Chemical — chemical-resistant novolac epoxy grout for pumps and process equipment.
• Fosroc Conbextra EP120 — Fosroc — low-exotherm epoxy grout for 65–120 mm gaps.
• Fosroc Conbextra EP65 — Fosroc — low-exotherm flowable epoxy grout for 35–65 mm gaps.
• Fosroc Conbextra EP10(M) — Fosroc — moisture-insensitive epoxy for grouting and injecting 0.25–10 mm gaps.
• Fosroc Conbextra EUW — Fosroc — water-insensitive epoxy for underwater grouting and injection of narrow gaps.
• Fosroc Conbextra EPG — Fosroc — epoxy grout for 10–150 mm gaps under heavy dynamic loads.
• Fosroc Conbextra EPHT — Fosroc — heat-resistant epoxy grout for rails, turbines and machinery, service up to 160 °C.
• Fosroc Conbextra EPGP — Fosroc — general-purpose epoxy grout for 20–80 mm gaps under heavy and dynamic loads.
• Fosroc Conbextra EP75 — Fosroc — highly creep-resistant epoxy grout for 10–75 mm gaps.
• Fosroc Conbextra EP300 — Fosroc — low-exotherm epoxy grout for large volumes and gaps up to 300 mm.
• Fosroc Conbextra EP150 — Fosroc — epoxy grout with long working time for 10–150 mm gaps under heavy equipment.

Frequently asked questions

Why can’t epoxy grout be poured to a large depth in one go?

Because of the heat of reaction. In a thick layer, the temperature rises and the material sets faster, then contracts as it cools and may crack. That is why manufacturers state a maximum depth per pour and offer low-exotherm grades for large gaps — for example, Chockfast Red, Five Star DP or Planigrout 350.

Can part of a kit be mixed?

This is not recommended. The components are proportioned at the factory; splitting them “by eye” upsets the resin-to-hardener ratio and leads to incomplete curing. Sika, for example, specifically warns that components A and B must not be mixed without the filler because of excessive heat build-up.

What should be done in hot weather?

Store the kits somewhere cool, shade the work area, pour in the morning or evening, and choose a slow-reacting grade. Some manufacturers explicitly divide their range by temperature: Pagel’s EH196S is designed for higher temperatures and large volumes, and EH196R for lower temperatures.

Does the concrete have to be dry?

For most epoxy grouts, yes; data sheets often state a maximum substrate moisture content and require the temperature to be above the dew point. Some grades, such as Sikadur-42 (au), are insensitive to moisture during application, according to the manufacturer.

How does “chocking” differ from grouting?

In chocking, the unit rests on individual polymer chocks cast in place, whereas in grouting the material fills the entire space under the baseframe. Chockfast Orange was originally developed for chocking marine machinery, while Chockfast Red and Red SG are intended for full grouting.