Why crane rails are grouted
The rail of an overhead travelling, gantry or portal crane is supported on a concrete beam, a foundation or a steel crane girder. If voids remain between the rail (or its baseplate) and the concrete, the rail deflects under every wheel pass, the fixings work loose, the concrete under the rail crumbles and the runway geometry drifts out of tolerance. Grout provides continuous or distributed support, brings the bearing surface up to the design level and transfers the vertical and horizontal wheel loads into the structure.
Loads on a crane runway are dynamic and impact loads: acceleration and braking of the trolley, skewing, impacts at rail joints. That is why the requirements for grout here are stricter than under static equipment, and the choice of material is almost always made and justified by the designer.
Support arrangements
Continuous support
The rail is laid on a continuous strip of grout, sometimes with a continuous elastomeric pad in between. The load is distributed along the entire length, which reduces stresses in the concrete. This arrangement is common in ports and on heavy gantry cranes.
Discrete support
The rail is fixed to individual soleplates installed at the spacing specified in the design. Each soleplate is grouted underneath, and the rail itself bears on the soleplates — either directly or via a pad. This arrangement makes alignment easier: the soleplates are set to level with screws and then grouted.
Elastomeric pads
Elastomeric pads are often placed between the rail and the bearing surface. They absorb impact, reduce noise, accommodate minor irregularities and protect the grout from point loading. The pad type, its stiffness and the permissible loads are determined by the rail system supplier, and the grout is selected to meet the supplier’s requirements.
Which material to choose
| Grout type | Where used | Features |
|---|---|---|
| Epoxy | heavy cranes, impact loads, frequent cycles, refurbishment of damaged runways, short downtime | high strength and adhesion, fast return to service; limits on layer thickness and application temperature; requires a dry substrate and expansion joints |
| Non-shrink cementitious | new construction, moderate loads, large volumes and thicknesses | lower cost, easier to handle in large volumes; needs moist curing, longer time to loading |
| Elastomeric (polyurethane and similar) | systems with continuous resilient rail support | works as part of the rail system; the grade and parameters are specified by the system supplier |
Crane rails are explicitly listed among the applications of many epoxy grouts — for example, Sikadur-42, Chockfast Orange and Chockfast Red SG, Planigrout 300 and Planigrout 310, Conbextra EP65 Plus and EP120 Plus, MasterFlow 648, Five Star HP Epoxy Grout. Among cementitious grouts, they are listed for Conbextra HS, MasterFlow 928, PAGEL V1/10 and V1/50.
Expansion joints and pour sections
A long strip of epoxy grout under a rail undergoes thermal movements that differ from those of the concrete, and without joints it can crack. Manufacturers limit the length of a continuous pour and require joints. For instance, for crane rail grouting with Chockfast Red SG, ITW specifies expansion joints at intervals of no more than 3 m, while Pagel limits the length of sections under the rail to three metres for EH196R and to seven metres for the slower-curing EH196S. It is convenient to locate the joints at soleplates or rail joints, but the spacing is determined by the technical data sheet of the selected material and by the design.
Geometric limits also apply to each pour section: Pagel, for example, recommends an aspect ratio for the pour area of no more than 1:3. Joints are formed with inserts of polyethylene foam or another compressible material, so that the grout cannot flow past them.
Work sequence
- Concrete preparation. Damaged and weak concrete is removed down to a sound substrate, together with laitance, oil and rust from old fixings.
- Anchor pockets. Anchor pockets are cleaned and dried: in its Sikadur-42 data sheet, Sika specifically requires anchor pockets and sleeves to be free of water. For epoxy grout, the substrate must be dry; for cementitious grout, saturated with water but free of standing water.
- Alignment. The soleplates or the rail are set to line and level using levelling screws or wedges. Tolerances on rail position, gauge, levels and straightness are set by the design and the rail system supplier — they must be obtained before work starts.
- Steel preparation. The undersides of the plates in contact with epoxy grout are cleaned to bare metal; levelling screws are greased, and anchor bolts are debonded along their free length.
- Formwork. Narrow grout-tight formwork along the rail or around the plates, with a head side and an air outlet. For epoxy, with a release coating.
- Pouring. From one side, continuously, maintaining a head, in pour sections between joints. Material and substrate temperatures within the limits given in the technical data sheet.
- Curing and tightening. Protection from water and overheating or, for cementitious grout, moist curing; anchors are tightened and the crane is put into service only after the grout has reached the strength given in the data sheet.
Crane runway refurbishment
At operating plants, crane rail grout is more often repaired than built new: the old cementitious grout under the rail has broken up and the fixings have worked loose. The task is to complete the work within a short shutdown. Fast-curing epoxy grouts are the usual choice here, since they gain strength in hours rather than days. Before the repair, it is worth establishing the cause of failure — the wrong material, a lack of joints, rigid support without a pad, or overloading — otherwise the defect will recur.
See also: grouts — overview, epoxy grouts, cementitious grouts, anchoring.
Materials from leading manufacturers
- Sikadur-42 — Sika — epoxy grout; crane rails are listed as the first application in the data sheet (au version).
- Chockfast Orange — ITW Performance Polymers — chocking compound, also used for crane rails.
- Chockfast Red SG — ITW Performance Polymers — fast-curing epoxy grout with joint recommendations for crane runways.
- Planigrout 300, Planigrout 300 SP, Planigrout 310, Planigrout 350 — Mapei — epoxy grouts for overhead crane rails and baseplates.
- Conbextra EP65 Plus, Conbextra EP120 Plus — Fosroc — epoxy grouts for crane rails with medium and large gaps.
- Conbextra HS — Fosroc — ultra-high-strength cementitious grout, also used for crane rails.
- MasterFlow 648 — Master Builders Solutions (now SikaFlow-648) — epoxy grout for crane rails and dynamic loads.
- MasterFlow 928 — Master Builders Solutions (now SikaGrout-928) — non-shrink cementitious grout; crane rails are listed among its applications.
- Five Star HP Epoxy Grout — Five Star Products — epoxy grout for crane rails and dynamic loads.
- PAGEL EH196R, EH196S — Pagel Spezial-Beton — epoxy grouts for rails and ribbed baseplates.
- PAGEL V1/10, V1/50 — Pagel Spezial-Beton — pourable cementitious grouts, also used for crane rails.
- Mapefix VE SF — Mapei — chemical anchor; fixing crane rails is listed among its applications.
- Five Star LC Epoxy Grout — Five Star Products — high-flow epoxy grout for crane rails and clearances from 10 mm.
- Five Star Elastomeric Grout — Five Star Products — elastomeric polyurethane rail grout that dampens vibration and noise.
- PAGEL V1/50SF — Pagel — steel-fibre grout for rail supports and heavy foundations.
- Fosroc Conbextra EP40 — Fosroc — free-flowing epoxy grout for 5–40 mm gaps under machinery and rails.
- Sikadur-42 Grout Pak LE — Sika — low-exotherm epoxy grout kit for baseplates, machinery and crane rails.
- Fosroc Conbextra EPR — Fosroc — epoxy grout for 10–120 mm gaps under crane rails and machinery.
- Fosroc Conbextra EP80E — Fosroc — free-flow epoxy grout for 10–80 mm gaps under crane rails and machinery.
- Sikadur-42 LP — Sika — multi-purpose epoxy grout for crane tracks, baseplates and anchors, 6–60 mm.
Frequently asked questions
What are the tolerances for laying a crane rail?
They are set by the design, the crane runway standards and the rail system supplier. Grout merely fixes the aligned position, so the tolerances must be obtained and checked before pouring, and verified afterwards by survey.
Are joints needed in the grout under a rail?
For epoxy grouts, yes — manufacturers limit the length of a continuous pour. For example, ITW requires joints at intervals of no more than 3 m for Chockfast Red SG. Take the joint spacing for a specific project from the technical data sheet and the design.
Can a rail be laid directly on the grout without a pad?
That depends on the rail system and the loads. Many modern systems have an elastomeric pad between the rail and its support, which protects the grout from impact. The decision is made by the designer together with the system supplier.
What should be used to repair a runway over a weekend?
As a rule, a fast-curing epoxy grout suited to the gap thickness and the temperature. The time to loading is taken from the technical data sheet for the actual substrate temperature.