Bituminous mixing and laying plant

[edit] Introduction

The mixing and laying of bitumen for roads and pavements can be undertaken using a range of different types of plant. The type of plant used will be determined by the type of material that is required and the process adopted.

[edit] Heaters and boilers

Bitumen heaters and boilers range from small mobile units to large permanent plant. The most common types are:

Mobile boilers: Mounted on a steel chassis and towed from place to place. The furnace at the base of the boiler is either gas or oil-fired.
Static heating and storage tanks: These are heated by oil-fired burners and are available for high outputs as they can have capacities of up to 18,000 litres. They will usually be transported on a low loader.

[edit] Binder distributors

The most common type of binder distributor is the bulk tank sprayer. The binder is kept at the required temperature by fitted heating units. A static heating unit feeds the binder into the bulk tanker which can have a range of tank capacities. A horizontal spray bar and power-driven pump mounted at the rear of the unit is used to spray the binder over the road surface.

[edit] High speed road-surfacing units

These are commonly used in resurfacing projects. The road is sprayed with hot binder and then coated with grit from a slow-moving machine. A lorry follows behind the chip-spreader to keep it supplied with chippings. These are fed into a rear hopper and carried on a conveyor to the spreader.

[edit] Road planers and heaters

Road planers heat the bituminous road surface until soft and then make it even by using revolving blades. The blades cut away to leave a smooth surface that can then be treated as required.

Road heaters are used on road surfaces that have become too smooth. They dry, heat and burn the road surface to enable further treatment as required.

[edit] Asphalt and bitumen mixing plant

These are either permanent plant installations or small mobile units. They perform a complete sequence of operations, from drying, to aggregate heating and mixing, to coating them with binder, to delivering them ready to be laid.

Drying units: A long rotating cylindrical drum is heated internally by hot gases through which the aggregate is passed, ensuring that it is thoroughly dry before being coated with a binder.
Batch-mixing plants: These have several individual sections – aggregate feeder, drier unit, binder heater, weighing plant and mechanical mixer.
Mixing units: These are a form of paddle mixer that enables a thorough mix in a short space of time.

[edit] Spreading and finishing plant

Large machines are used for spreading and finishing the surface coating, ideally in a single pass. They are available with different laying speeds and hopper capacities. Rollers on the front of the lorry’s hopper are connected to the tyres and so push the lorry forward whilst unloading. The screed plate is hydraulically adjusted so as to control the thickness of the surface finish.

[edit] Find out more

[edit] Related articles on Designing Buildings Wiki

[edit] External references

‘Introduction to Civil Engineering Construction’ (3rd ed.), HOLMES, R., The College of Estate Management, (1995)

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Comments

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