Machine base grouting fills the gap between a concrete foundation and the steel base of a pump, compressor, generator or crane rail. It looks like a small item on the drawings. Yet a poor grout layer leaves voids under the plate, loose anchor bolts and a machine that slowly loses alignment. In Egyptian factories, pump stations and workshops, we often meet these problems on older plinths. This guide explains how to choose the grout, prepare the base and pour it properly.
Contents
- What Machine Base Grouting Has to Do
- Choosing the Material for Machine Base Grouting
- Preparing the Foundation and Base Plate
- Formwork and Pouring Steps
- Hot Weather and Curing
- Common Mistakes
- FAQ
- Conclusion
What Machine Base Grouting Has to Do
The grout is not a filler for appearance. It carries the load from the base plate into the foundation, so it must touch the steel over the whole bearing area. Air pockets or shrinkage gaps concentrate the load on a few points instead.
For that reason, specifications ask for a non-shrink material. ASTM C1107, for example, covers packaged non-shrink cement grouts for use under applied load, such as under a machine. The grout also has to flow into every corner, then gain strength quickly so the equipment can return to service.
In practice, a good result needs:
- a sound, clean concrete foundation;
- the right material for the gap thickness;
- formwork that holds the grout without leaking;
- a pour method that pushes air out instead of trapping it.
Choosing the Material for Machine Base Grouting
The gap size usually decides the product. Two materials from the data sheets cover the common cases.
| Item | Sikacrete-114 (Sika) | MasterProtect 2020 (Master Builders Solutions) |
|---|---|---|
| Type | One-component, free-flowing cement micro-concrete, 10 mm maximum aggregate | Three-pack, non-slump epoxy bedding and repair mortar |
| Uses listed | Machine bases, bridge bearing plates, anchor bolts, crane rails, mechanical bridge joints | Gap filling, grouting, bedding fixtures, securing bolts, dowel anchoring, filling bolt pockets |
| Thickness | 50 mm minimum, 500 mm maximum per pour; base plate grouting where thickness exceeds 50 mm | Applied by trowel or knife; deep recesses built up in layers |
| Strength stated | 60–70 N/mm² compressive at 28 days (EN 196-1); about 3 N/mm² pull-off | 75 N/mm² compressive at 7 days (ASTM D695); bond greater than the concrete |
| Working notes | 1.9–2.1 litres water per 20 kg bag; mortar kept below 30 °C | Pot life 40 minutes at 20 °C; full cure 5 days at 25 °C |
Where each one fits
Sikacrete-114 suits deep pours under base plates and crane rails, where the grout must flow. Its sheet limits it to gaps over 50 mm. MasterProtect 2020 behaves differently. It is stiff and does not slump, so it suits bolt pockets, small bedding pads and edge repairs rather than flowing under a wide plate.
For gaps under 50 mm, neither sheet gives a solution. In that case, the specification calls for a flowable grout rated for thin sections, chosen with the equipment supplier.
Preparing the Foundation and Base Plate
For machine base grouting, both sheets start with the substrate. The concrete must be clean and sound, and free from oil, grease, laitance and loose particles. Machine plinths in workshops are often soaked in oil, so we cut back contaminated concrete until clean material shows.
Steel needs the same care. The Sikacrete-114 sheet asks for metal surfaces free from scale, rust, oil and grease. Then, before pouring, absorbent concrete must be saturated thoroughly with clean water. However, standing water is removed, so the surface is wet but not flooded.
Our typical preparation steps are:
- Agree levels, shims and bolt positions with the equipment supplier.
- Break out weak or oil-soaked concrete and roughen the top of the plinth.
- Clean the underside of the base plate and the anchor bolts.
- Fill bolt pockets where the design calls for epoxy, for example with MasterProtect 2020.
- Soak the concrete, ideally for several hours, then remove free water.
Formwork and Pouring Steps
Formwork is where many grout jobs fail. The Sikacrete-114 sheet asks for formwork that is secure and watertight, so the grout does not move or leak during placing and curing. It also asks for channels that let air escape.
Target crews then follow this sequence for flowable machine base grouting:
- Fix tight formwork around the plate, with a head box on the pouring side.
- Leave the opposite side slightly higher, with vents for air.
- Dry-mix the full Sikacrete-114 bag for 3 minutes, then add 1.5–1.6 litres of water.
- Mix for at least 3 minutes with a slow-speed drill or forced-action mixer, never by hand.
- Add the remaining water and mix for 2 more minutes.
- Let the mix stand 2–3 minutes so trapped air escapes.
- Pour from one side only, keeping enough head to keep the grout flowing.
- Continue until grout rises evenly on the far side, then protect it from rain until it sets.
Using epoxy mortar on small pads and pockets
MasterProtect 2020 is supplied in pre-weighed packs and mixed by trowel. For more than one pack, its sheet suggests a portable mixer. It is then knifed or trowelled into place. Deep recesses are built up in layers, and the sheet says no bonding agent or primer is needed.
Hot Weather and Curing
Heat is the main risk to machine base grouting on Egyptian sites. The Sikacrete-114 sheet advises chilled mixing water to keep the mortar below 30 °C. It also asks to shade base plates and foundations from direct sunlight, and to condition the bags before use.
After the pour, curing starts at once. The sheet recommends a curing compound, polythene sheeting or wet hessian on exposed surfaces. Meanwhile, MasterProtect 2020 cures more slowly when it is cold. Its sheet gives a tack-free time of 7 hours at 20 °C and full cure in 5 days at 25 °C. Therefore, the machine should only be loaded when the supplier and the specification allow it.
Checking the grout after it hardens
The job does not end with the pour. Once the formwork comes off, we trim the edges and look for cracks or gaps. Next, we tap the exposed grout lightly with a hammer, because a hollow sound usually means a void below. The equipment supplier then checks alignment and bolt torque before start-up.
Common Mistakes
- Pouring onto oily, dusty or dry concrete.
- Using a flowable grout in a gap thinner than its sheet allows.
- Leaky formwork that drains the grout from under the plate.
- Pouring from two sides and trapping air in the middle.
- Mixing by hand or using part bags.
- Skipping shading and curing in summer.
FAQ
How thick should machine base grouting be?
It depends on the design and the product. Sikacrete-114, for instance, is for pours of 50 mm to 500 mm. Thinner gaps need a grout rated for them.
Can epoxy mortar replace cement grout under the whole plate?
Not with a non-slump mortar like MasterProtect 2020. It suits pockets, pads and edges. Full-area epoxy grouting needs a flowable epoxy grout, chosen with the equipment supplier.
When can the machine start running?
The specification and the equipment supplier set that time. Strength figures such as 30–35 N/mm² at one day for Sikacrete-114 help them decide.
Is the grout resistant to oil spills?
The MasterProtect 2020 sheet lists resistance to oils, greases and petroleum. The Sikacrete-114 sheet does not list oil resistance, so exposed cement grout may need a protective coating.
Conclusion
Machine base grouting works when the gap, the material and the pour method match. A clean, saturated plinth, tight formwork and a one-side pour give full contact under the plate. Then shading and curing protect the grout while it gains strength.
Target carries out grouting and concrete repair work for industrial and infrastructure sites in Egypt. See our fixing and implanting anchors service, our repair and rehabilitation works and the guide to concrete spalling repair. Contact Target to inspect your machine foundations before the next shutdown.
For epoxy mortars, MasterProtect 2020 states compliance with ASTM C881, the specification for epoxy-resin bonding systems for concrete.
No comment