Day 3

Hello everyone!

On our 3^rd  day of the orientation period, Professor Prashant Garg taught us about different types of pavement.

Pavement are designed and constructed so that vehicles are able to move at designed speed without causing discomfort to users and remains stable. A pavement mainly consists different layers laying on the subgrade.

Requirements of road pavement-

• Sufficient thickness should be provided to distribute the wheel load stresses.
• Sufficient strong to withstand stresses.
• Produces less noise from moving vehicles.
• Long design life.
• Less maintenance cost.

TYPES OF PAVEMENT LAYER

• FLEXIBLE PAVEMENT – Pavements which have negligible or low flextural strength. The vertical compressive stress is maximum on the pavement surface directly under the wheel load and is equal to the contact pressure under the wheel. Flexible pavement layers distribute the compressive stresses to a larger area in the shape of truncated cone; the compressive stresses get decreased at the lower layers.
• RIGID PAVEMENT– Rigid pavement are those which possess north worthy flexural strength or flexural rigidity. High quality plain cement meant for the pavement, generally called ‘Pavement quality concrete’. The rigid pavement transfer load by ‘slab action’ and is capable of transmitting the wheel load by much wider area below pavement layer.
• SEMI RIGID – Bonded materials like the ‘pozzolanic concrete’, lean cement concrete is used in the sub base course of the pavement layer. The bonded materials have significant flexural strength but less than cc pavement.
• Interlocking cement concrete block pavement – Interlocking cement concrete block pavement (ICBP) consists of a layer of cement concrete paver blocks of specified shape, size, properly laid over a well compacted soil subgrade, sub base or base course. The gap between the paver blocks are filled with sand.

Comparison of flexible and rigid pavements

• Flexural pavement are generally designed and constructed for a design life of 15 years while cc pavement designed and constructed for a design life of 30 years or more.
• A ‘standard design wheel load’ is made use for flexible pavement design and design of CC pavement is carried out by fatigue analysis.
• The flexible pavement layers get deteriorated when exposed to stagnant water due to poor drainage while CC pavements do not get deteriorated under wet weather conditions.
• The life cycle cost of flexible pavement is costlier for flexible than rigid pavement.
• Night visibility of flexible pavement is very poor and good night visibility even in wet condition in CC pavement.
• The curing period for flexible pavement course is less and open to traffic within 24 hours and major disadvantage of of CC pavement it require long curing period and open to traffic after 28 days.