Tar and Bituminous Equipments

On the works of road construction, bitumen is used for surface painting. Bituminous pavements and wearing surfaces provide a resilient and waterproof layer that projects the underlying materials from water and traffic. In case of isolated jobs, the aggregate filler and binder are heated together after being mixed dry in the required proportions. Mixing is done on a mixing platform from which the mix is carried to the site. In case of large projects, the mixing is done in a centrally placed stationary plant mixers and then the material is carried to the site either in trucks or in dumpers. The bituminous concrete is also mixed in stationary or portable plant depending upon the magnitude of the project.

There are two types of plants generally referred to as “Batch Plants” and “Continuous mix Plant”. The principle of operating both the plants is the same. The component parts of a tar and bitumen mixing plants are as follows:

1.      Bins for storage of various size aggregate:

The aggregates are fed into the plant at “Cold Feed” end. A very common method of feeding the aggregate at the cold feed is by means of storage bins and crane, to charge them from the stock. Sometimes, the aggregate are stored on the ground and bulldozer is used to push the aggregates over the feeder.


2.    Aggregate Drier:

The aggregates of various sizes are fed to the drier through a cold elevator. The drier dries off most of the moisture in the aggregate at the same time heats the material to the desired mixing temperature. Drier consists of a long rotating drum with inside lifting flights which continuously drops the aggregates through hot gases. The drum is in a tilting position.


Aggregate Drier


3.    Hopper and Screens:

After the aggregates are dried, they are transferred. Before entering into the hopper, they are screened into two or more size ranges. The screens are so selected that the gradation is split according to the specifications.

4.    Mixers:

From the hoppers the aggregates are discharged into the mixer and at the same time they are weighed. Quantity of hot bitumen is led into the mixer. After mixing bituminous the concrete is discharged into a truck. Trucks are used for transportation to the construction site. Mixer consists of a chamber containing central shaft with paddles and heating appliances. It contains a door which can be automatically opened for the discharge of mixed material into trucks.




Bitumen Sprinkler:

For surface dressing of large areas, bitumen sprinklers having a capacity of 3,000 – 15,000 litres are used. The tanks are insulated and are provided with heaters that may be used to maintain the temperature of the binder. Tanks are mounted on vehicles and a thermometer is fitted to check the temperature.



Distribution of the binder is done by a spray bar which is fixed at the rear end. The spray bar is properly nozzled. The rate of spraying bitumen is controlled by speed of vehicle which is indicated by tachometer reading. A bitumen distributor sprays bitumen efficiently and quickly.