What is pavement?
The pavement is the wearing course provided over the road surface for protection of the subgrade of the road. The primary functions of the pavements are:
- To distribute the load uniformly to subgrade.
- To provide a smooth-riding surface for the vehicles.
- To regulate required friction for the tire and road surface.
- To act as an impervious layer to prevent water penetration to the base layer.
- The paved surface reduces the erosion of road material, watershed pollution.
Type of pavement for roads
Flexible pavement is a series of granular layers (sub-base and base) overlying on the subgrade with a bituminous surface on the top as a wearing course. Flexible pavements are flexible in their structural action under the load.
Also, they have low flexural strength. When the load is applied on the flexible pavement, the load is distributed to a wider area with a decrease in stress as it goes deeper by grain to grain distribution. The stability of pavement depends upon the interlocking of the particle, particle friction, and cohesion.
Deformation on the subgrade and base courses are seen on the surface course due to its flexible nature but have the self-healing property.
Typical flexible pavement comprises of sub-grade, sub-base, base course, prime coat, binder coat, tack coat, and seal coat. The basic material used in flexible pavements is aggregates and binders.
The rigid pavement is a layer of Portland cement concrete over the subsoil. Rigid pavements have high flexural strength and a life of about 30 years. Rigid pavements are constructed in the areas where,
- Soil condition is poor
- Heavy Rainfall
- Poor Drainage Condition
- Extreme climatic Condition
Rigid pavement should include longitudinal joints, traverse joints to accommodate stress produced due to temperature change. Also, these pavements do not heal as flexible, the deformation is seen to stay permanent on the road.
Materials used in pavements
Binder: Binders should have adhesive property. Bitumen is used as a binder for flexible pavements and cement in the rigid pavement. Bitumen sticky black, highly viscous, and adhesive material obtained as a byproduct of the petroleum distillation process.
The consistency of binder and thickness to be used depends upon the climatic condition of the area.
Whereas cement is obtained by burning calcium hydroxide under high temperature. Cement is mixed with fine and coarse aggregate to get the compacted layer, which will withstand vehicle loads.
Aggregates: It is the aggregation of non-metallic inert mineral to form a solid particle. The requirements of aggregates to used for pavements are. They should be hard, tough, dry, inert.
Types of pavement marking
Pavement markings are the method to convey information among road users and controlling and guiding the traffic. Marking on the road can be provided in the pavement and objects. Further, it can be classified as warning signs, informative signs, and regulatory signs. The general principle longitudinal road lines,
- A solid line represents restriction in crossing for the vehicles.
- Wide lines are generally 40-50 cm used as stop lines.
- A Broken line represents the permission of crossing lanes with safety.
- Double lines indicate maximum restriction.
- Diagonal lines indicate a nondriving zone. Also acts as a solid line.
Color and sign Code for pavement markings
Red and white: They are restrictive in nature. All the pavement markings are in while color except those indicating parking restriction
Yellow: This color is road signs that refer to be cautious. They warn users of changing conditions. Also, they indicate parking restrictions.
Alternate Black and white: They are used in object Markings, like curbstone, island.
Horizontal rectangular shape: These are informative signs placed at the entrance of town and cities.
Vertical rectangular shape: They are moreover regulatory signs for drivers like “keep Left”
Inverted triangular: They are yielding signs. Yield means to slow down, get ready to stop, and let the traffic pass.
Circular: They are used as regulatory sign like no parking, no speed over 20 and similar.
Octagon shape: They are warning signs to stop immediately.
I hope this article on “Types of pavement” remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Rukshana Shrestha