- May 3, 2021
- Posted by: qbit-adm20
- Category: Bitumen
Bitumen is a black thick and sticky mixture of long chain hydrocarbons. It’s obtained from the distillation of crude oil or sometimes occurs in nature. It has various properties and advantages over other road construction materials.
In this article the author addresses:
(A) The unique properties of Bitumen
(B) The Flexibility of Bitumen
(C) Basic steps in bituminous road construction.
(A) The Unique Properties of Bitumen:
Bitumen boasts of certain unique properties that are inbuilt during its manufacture.
Bitumen is the Bottom of the Barrel in Crude oil Distillation
Bitumen is a by-product of the crude oil distillation process so it can survive for a long period in the open. It is optimal as a construction material, without going for alternatives.
The Melting Point of Bitumen is low
Bitumen has a suitable melting point. This helps in both surface dressing and wearing resistance. The property also makes it suitable for use across a wide range of climatic conditions.
Bitumen is recyclable
As the melting point of bitumen is favourable it is meltable back to its original state over and over.
Bitumen’s Adhesive Nature
Bitumen has an adhesive nature. This keeps the materials in the road mix bound together under strong bonds. For Example, the mix of bitumen and crushed stones.
Bitumen is Durable
Bitumen takes long-term resistance to oxidative hardening of the material in the field.
(B) The Flexibility of Bitumen
Bitumen as a raw material in flexible. In a premix, as used in road construction, it serves certain advantages which include:
A smooth Ride Surface
A bitumen road surface is smooth to ride or drive on. The ride emits less sound with less wear and tear. There are less costs in maintaining the smoothness.
The roads can’t melt in hot weather conditions. They are inert de-icing materials in cold climates.
Bituminous road services are quick and fast to repair. They don’t consume time in reverting the road back for traffic as they set fast.
(C) Steps In Bituminous Road Construction
Bitumen road construction consists of various steps. The steps start from preparation of the road base or the ground layer. Then follows a priming and/or tack coating phase. Preparation and placing of premix preceeds rolling. At the tail end is quality control of bituminous concrete on the finished surface.
Step 1: Preparation Of Existing Road Base Ground Layer.
Fill the any existing pot holes with a premix before priming. After about a week lay the surface course. Lay a bituminous levelling course of adequate thickness on the on the binder course.
Step 2: Application of Tuck Coat
A tack coat is a thin bituminous liquid asphalt or cutback layer. It’s applied on the prepared surface to promote bonding. Thus, the completed pavement structure behaves as a single unit with adequate strength. Each road design specifies the spray rate of the tuck coat.
Step 3: Preparation And Placing Of Premix
Preparation of a premix involves mixing heated bitumen and crushed stones called aggregates. This mix is spread on the road surface using a mechanical paver. The drainage of water and the thickness of the layer are critical factors in the road surface.
Step 4: Rolling
A tandem roller, moves at about 5km per hour on the road surface. The number of passes depends on the thickness of the laid layer. If the surface is thick then, more passes and vice versa.
Step 5: Quality Control
It is very important to check the quality at all stages. Check the grade of the bitumen, temperature ranges and the grade of the aggregates. The composition of the premix and the final road surface are also checked.
Step 6: Finished Surface
Check the finished surface to be hard, tough, durable, and well drained.