Crane mats are materials that are put on the ground for two reasons:

1. To keep heavy machinery stable and level when travelling along the ground and working.
2. To stop the ground from churning up when the heavy machinery is travelling along it.

Where and when are crane mats used?

Crane mats are mostly used by companies in the construction industry.

These could be companies like:

• Plant-hire companies
• Crane companies
• Building companies
• Steel frame contractors
• Concrete pump contractors
• Scaffold contractors

They’re used when heavy machine needs to access areas or work in areas where there is a risk of eroding the ground because of the extreme weight of the plant.

Because of this risk of ground erosion, the heavy plant has to be kept stable by the mats. The worst-case scenario is the machinery tipping over, which could damage itself or other property, or worse, injure or kill someone.

The types of machinery that use crane mats can be things like:

• Concrete pumps
• Crawler cranes
• Mobile cranes
• Large excavators
• Piling rigs
• Concrete lorries

These are heavy-plant vehicles that have tracks, wheels, or outriggers that could sink into the ground.

Some examples of projects that need crane matts are:

• Excavation projects
• Projects where concrete needs to be pumped long distances or to high levels
• In boggy land or marshes
• Bridge construction
• Renewable energy projects, such as erecting wind turbines
• Pipeline construction
• Oil & gas works

What types of crane mats are there?

There are three styles of crane mats that are used for different reasons.

1. Liftable cranes mats that get picked up and placed into position.
2. Loose hardcore material, like crushed concrete, that is spread and compacted.
3. Concrete that gets poured as a base.

1. Liftable crane mats

Liftable crane mats have different shapes and sizes.

Timber is the most popular choice of liftable crane mat. It comes in lengths that often look like railway sleepers. They can be between 100mm-200m (4”-8”) thick.

Timber is a favourite for many reasons. It’s easily accessible, environmentally friendly, and durable.

Because timber crane mats last a few years, they often get sold on when finished with. And when they do eventually wear down, the wood naturally breaks down by decomposing.

Timber isn’t the only material used. Crane mats can also be made of composite materials, fibreglass, high-density plastics, metals, and rubber.

To summarise, liftable crane mats can be made of:

• Mixed hardwood
• Oak
• Fir
• Spruce
• Bamboo
• Rubber
• Fibreglass
• Plastic
• Composite
• Steel
• Aluminium

Liftable crane mats are either ‘handleable’ or ‘non-handleable’. Handleable crane mats are small and light enough to be picked up and carried by hand, whereas non-handleable crane mats need to be lifted in place by a machine.

2. Hardcore materials

Loose, compactible hardcore materials get used to cover large areas, or areas where liftable mat segments won’t suffice. It also gets used on top of concrete, where the concrete is either too thin or not level (i.e., on a slope).

The types of common materials used in hardcore crane mats are:

• Crushed hard rock
• Clean crushed concrete
• Well-graded natural gravels
• Graded recycled demolition material (bricks or blocks, etc)

Crushed concrete is predominately used as a crane mat for piling rigs. In this instance, the mat is generally called a ‘piling mat’. The rigs might need to cover large areas to drill the piles. These types of machines need level ground to work on, because the work involves extreme precision.

But it’s not just a case of throwing a lot of crushed concrete down and levelling it off. A lot of the time, waste material has to be taken out of the ground first.

Before that, a survey is needed to determine levels. This will tell the contractor how much muck has to be extracted and how much crushed concrete is needed to go back in.

The survey also determines what services are in the ground before digging out. When digging, contractors don’t want to damage things like drainage, cables, or gas or water pipes.

In places where a lot of water might rest, membranes are sometimes laid out under the mat to help prevent fine soils from seeping into the mat.

A Geogrid is often used under the mat. This provides stability and support for the mat. It can also be used to reduce the thickness of the crushed concrete. This is because it can be incorporated as part of the mat, increasing the mat’s strength.

The crushed concrete is then put down in Iayers and compacted.

3. Concrete base

A concrete base crane mat is useful for a crawler crane that is to stay in one position to do its lifting for a long period. It might be chosen if working on tarmac or existing concrete that is not level or too thin, and that the contractor doesn’t want to dig out.

Crushed concrete can be built up on the existing ground as a base, then concrete gets poured on top within formwork. Steel mesh gets placed withing the concrete for added strength.

When finished, the concrete can be broken up and recycled to use as crushed concrete elsewhere.

How thick do crane mats need to be?

Crane mat overall sizes are usually chosen within temporary works designs. The factors that affect the decisions are the size of and weight of the machinery, the type of ground, allowable ground bearing pressure, and outrigger load.

Also, with mats created with hardcore materials, the amount of loose material needed can vary. Again, this depends on the size and weight of the machinery, but also on how much waste needs to be extracted.

The amount of waste to be extracted can depend on the specific levels needed or if the ground is contaminated. A contamination test is often undertaken before excavation.

Are crane mats the same as outrigger pads?

Crane mats are not the same as outrigger pads. A crane pad is a single piece of material up to 1m² that gets put under outrigger legs to spread the rig’s load.

Outrigger pads are usually light enough to be put in place by hand, but are strong enough to bear the weight of any type of mobile crane. They’re usually made of high-density plastics, like ultra-high-molecular-weight polyethylene (UHMW) or high-density polyethylene (HDPE).

However, if the crane is too heavy, wooden (or other material) mats get used instead to place under the outriggers. This is because the mats cover a larger area, so will spread weight further.

Crane pads are only suitable for bearing the weight of the outriggers, so the ground still needs to be suitable to bear the weight of the whole machine. If it isn’t suitable, this is where crane mats come in. Even a 1m² soft spot can be enough to unbalance a machine.

Conclusion

Hopefully, you now have a good understanding of what crane mats are and what they’re used for. If ever you do projects where mats are needed, you shouldn’t have to provide them yourself. The contractor doing the work will provide them. They will know all the specifications of what’s needed for what machine.

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