This document discusses two main types of pavement: flexible and rigid. Flexible pavement, like bituminous roads, acts like a flexible sheet and wheel loads are transferred through the sub-grade soil. Rigid pavement, like cement concrete roads, acts like a rigid plate with wheel loads transferred through the pavement's own flexural strength. It also outlines some of the key differences and failures that can occur in each type of pavement such as cracking, edge cracking, and failures in design, construction, materials or maintenance.
4. FLEXIBLE PAVEMENT
โข The flexible pavement, having less flexural strength, acts like
a flexible sheet (e.g. bituminous road). On the contrary, in
rigid pavements, wheel loads are transferred to sub-grade soil by
flexural strength of the pavement and the pavement acts like a rigid
plate (e.g. cement concrete roads)
6. RIGID PAVEMENT
โข A rigid pavement is constructed from cement concrete or reinforced
concrete slabs. Grouted concrete roads are in the category of semi-
rigid pavements.
โข The design of rigid pavement is based on providing a structural
cement concrete slab of sufficient strength to resists the loads from
traffic
9. FAILURES IN PAVEMENT
โข FAILURES IN DESIGN
โข FAILURES IN CONSTRUCTION
โข FAILURES IN MATERIALS
โข FAILURES IN MAINTENANCE
10. LONGITUDINAL CRACKS
โข Longitudinal cracks are long cracks that run parallel to the canter line
of the roadway.
โข These may be caused by frost heaving or joint failures, or they may be
load induced.
โข Understanding the cause is critical to selecting the proper repair.
11. FATIGUE CRACKING
โข Fatigue cracking is an asphalt pavement distress most often
instigated by failure of the surface due to traffic loading.
However, fatigue cracking can be greatly influenced by environmental
and other effects while traffic loading remains the direct cause.
12. TRANSVERSE CRACKING
โข The reflection of a crack or joint in an underlying pavement layer;
โข A construction joint of shrinkage crack (due to low temperature or
bitumen hardening) in an asphalt surface
โข The structural failure of a concrete base course.
13. EDGE CRACKING
โข Edge cracking is the formation of crescent-shaped cracks near
the edge of a road.
โข It is caused by lack of support of the road edge, sometimes due to
poorly drained or weak shoulders.
โข If left untreated, additional cracks will form until it resembles
fatigue cracking.
14. MERITS AND DEMERITS
ADVANTAGES OF RIGID PAVEMENT
โข ยป Low maintenance costs
โข ยป Long life with extreme durability
โข ยป High value as a base for future resurfacing with asphalt
โข ยป Load distribution over a wide area, decreasing base and sub grade
requirements
โข ยป Ability to be placed directly on poor soils
โข ยป No damage from oils and greases.
โข ยป Strong edges
15. DISADVANTAGES OF RIGID PAVEMENT
The disadvantages of rigid pavements include -
โข ยป High initial costs
โข ยป Joints required for contraction and expansion
โข ยป Generally rough riding quality
โข ยป High repair costs
16. MERITS OF FLEXIBLE PAVEMENTS
The advantages of flexible pavements include -
โข ยป Adaptability to stage construction
โข ยป Availability of low-cost types that can be easily built
โข ยป Ability to be easily opened and patched
โข ยป Easy to repair frost heave and settlement
โข ยป Resistance to the formation of ice glaze
17. DEMERITS OF FLEXIBLE PAVEMENTS
The disadvantages include -
โข ยป Higher maintenance costs
โข ยป Shorter life span under heavy use
โข ยป Damage by oils and certain chemicals
โข ยป Weak edges that may require curbs or edge devices
