A concrete bucket is a funnel-shaped container used to place concrete into formwork. It is moved by crane and discharged from the bottom, usually through a gate or slide operated by a lever. It is mainly attractive where hiring a concrete pump is not economic for the size of the pour. In Dutch site language it is called a kubel.
Sizes
The smallest standard versions hold around 750 litres. The largest buckets in general site use today go up to roughly 3 m³.
When choosing a size, always work back to weight rather than volume. Concrete weighs about 2,400 kg per m³. A 1 m³ bucket therefore hangs on the hook at some 2.4 tonnes, plus its own weight. That load must fit within the crane’s rated capacity at the radius concerned — and at long radius the permitted load drops sharply.
Bucket or pump?
| Concrete bucket | Concrete pump | |
|---|---|---|
| Suited to | Smaller pours, awkward locations, sites with a crane already standing | Large volumes, floor slabs, continuous pouring |
| Speed | Low: fill, lift, discharge, return | High and continuous |
| Cost | Bucket hire only, provided the crane is there anyway | Mobilisation plus hourly rate |
| Knock-on effect | Crane is tied up during the pour | Crane stays free for other work |
Working with a bucket
- Place in layers. Do not let the bucket empty in one go on a single spot; spread the concrete and compact each layer with a poker vibrator.
- Limit the drop height. Concrete falling several metres segregates: the coarse aggregate drops out and the mortar stays behind. Use a discharge hose or trunking on the bucket.
- Operate from the side. Never stand under a suspended bucket, and open the gate from the side.
- Check gate and seal. A leaking gate spatters concrete along the whole route and fouls the works.
- Wash out immediately. Hardened concrete inside the bucket costs both time and capacity on the next pour.
Related terms
- Concrete
- Concrete pump
- Ready-mixed concrete
- Fresh concrete
- Formwork
- Consistence class
- Segregation
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