Pavement Design and Components

Joints are placed in concrete pavements transversely at regular intervals to release tensile stresses induced by temperature decreases.
- These are called Contraction Joints.
Joints are also placed transversely across the pavement width to provide a transition between concrete placed at different times/days.
- These are called Construction Joints.

The layer that finally carries the load from the road is the sub-grade.
The component that receives the traffic load and transfers it to the subgrade is the base.
Soil stabilized roads with cement/lime cannot be used as a wearing surface.

Bitumen stabilization is suitable for sandy soils.
A prime coat over a road surface consists of a thin film of low viscosity cutback.
One or more layers of crushed aggregate, bonded by bituminous materials with a seal coat on top, is called surface dressing.
A 20 mm thick premix bitumen layer with a seal coat is called bitumen carpet.

A properly designed mix of coarse aggregate, fine aggregate, filler, and a bituminous binder is called asphaltic concrete.
A mixture of bitumen, fine aggregate, and filler in suitable proportion heated to about 200 degrees Celsius and laid is called mastic asphalt.

The layered structure placed over a soil sub-grade for forming a road is called a pavement.
A pavement with negligible flexural strength is called flexible.
The layer of natural soil over which the pavement is laid is called the sub-grade.
The layer providing resistance to wear and tear due to traffic is called the wearing coarse.
The part immediately above the sub-grade, composed of stone boulders or superior soil, is called the sub-base.
The top surface of a road structure is termed the base.

A road made of coarse aggregate mechanically interlocked by rolling and bonded with screening dust is called water bound macadam.
An application of hot bitumen material given to the old surface to provide adhesion to the old and new road surface is called a tack coat.
A layer of stone chippings coat laid over a hot to make the surface water-proof is called a prime coat.
The application of one or two layers of bituminous material over a prepared base, each layer covered with cover material and rolled, is called surface dressing.
A very thin surface applied over a bituminous pavement to make it impervious is called a seal coat.

The time for mixing ingredients for a concrete cement road should be at least 1.5 minutes.
Final curing for a concrete cement pavement is done for 14 days.
Joints provided at right angles to the center line are called transverse joints.
Joints provided when construction is suspended are called construction joints.

Plain concrete pavement has no temperature steel or dowels for load transfer and is used on low volume highways or with cement stabilized soil sub-bases.
Simply reinforced concrete pavement has no dowels, joints spaced from $10$ m to $30$ m, and temperature steel throughout the slab.
Continuously reinforced concrete pavements have no transverse joints (except construction/expansion joints) and are used on high volume, high speed roadways.

The measurement of the deviation of a road surface from the plane is called pavement roughness.
The condition of a pavement in terms of its general appearance is pavement distress.
The structural adequacy of the pavement section is pavement deflection.
The effectiveness of a pavement to prevent skid-related crashes is skid resistance.

Stresses developed in rigid pavements are induced by traffic loads, temperature changes, and bending.

No Passing Zone is defined as any section of the road with a passing sight distance of $460$ m or less.
Capacity for two-lane highways ranges from $2000$ to $2800$ passenger car equivalents per hour.
Factors affecting capacity and service volumes on freeways and multilane highways: Roadway factor, traffic factor, control factor.
Vehicles attempting to make a left turn and caught within the intersection at the end of the signal phase are expected to discharge at headways of $2.5$ seconds and delay the cross traffic accordingly.