26. Type of Pavement Flashcards
What are the 3 purposes of pavement?
Load support: stiffer than the material underneath it, so better at resisting loads
Smoothness: can be placed and maintained smoother, improving comfort and costs
Drainage: quick and efficient drainage which prevents mud and ponding
What are the 3 types of pavement?
Flexible (asphalt), composite, rigid (concrete)
Flexible pavement:
Surface and Binder courses
Top layer, and layer that comes into contact with traffic. Composed of 1 or several HMA sublayers
Flexible pavement:
Base course
Layer directly below surface course, generally consists of aggregate
Flexible pavement:
Subbase course
Layer or layers under base layer
Prime coat
Liquid asphalt applied to absorbent surface, used to bind granular base to HMA, must penetrate into granular layer to plug voids
Tack coat
Very light application of liquid asphalt, used to ensure bond between layers
Requirements: thin, uniform cover, allowed to cure before HMA placed
Advantages to flexible pavements
Adjusts to limited differential settlement, easily repaired, can always add additional thickness, quieter, smoother, great range of temperature, non-skid properties
Disadvantages to flexible pavement
Loses flexibility and cohesion with time, and needs resurfacing more often
Flexible pavement applications
Traffic lanes, auxiliary lanes, ramps, parking areas, frontage roads, shoulders
Rigid pavement applications
High volume traffic lanes, freeway, freeway connections, exit ramps, bus stops, high volume intersections
Rigid pavement:
Surface course
Top layer, consists of PCC slab
Rigid pavement:
Base course
Layer directly below PCC, generally aggregate or stabilized subgrade
Rigid pavement:
Subbase course
Layer or layers under base course (not always needed)
Rigid pavement:
Reinforcements
Reinforcing steel
Dowel bars: used at transverse joints
Tie bars: hold slabs at longitudinal joints
Rigid pavement:
Joints
Purposefully placed discontinuities
Contraction, construction, expansion
Either sawed in after PCC placed or by formwork beforehand
Rigid pavement:
Contraction joints
Control cracking from shrinkage, thermal contraction, and moisture or thermal variation
Either transverse or longitudinal direction
Rigid pavement:
Construction joints
Separate successive construction activities, can be planned to coincide with other joints
Rigid pavement:
Expansion/Isolation joints
Expansion - permits thermal expansion without damaging adjacent slabs or structures
Isolation - permits independent movement without causing any damage
Load transfer (LT)
Distribution of load across discontinuities
LT = unloaded/loaded
Done using aggregate interlock, dowel bars, reinforcing steel
JPCP
Jointed plain concrete pavement
No steel mesh, use tie bars, granular or stabilized base, most common rigid pavement
JRCP
Jointed reinforced concrete pavement
Steel mesh (0.1-0.2% cross-sectional area), contraction joints with dowels, granular or stabilized base
CRCP
Continuously reinforced concrete pavement
Reinforcement (0.5-0.8% cross-sectional area), granular or stabilized base
Advantages of rigid pavement
Good durability, long service life, withstand flooding and subsurface water
Disadvantages of rigid pavement
May lose non-skid surface, needs even subgrade with uniform settling, may fault at transverse joints
Composite pavements
Made from HMA and PCC, PCC provides string base while HMA provides smooth and non reflective surface, very expensive
What type of pavement does NS mostly consist of?
Flexible pavement (asphalt)
What is lean concrete?
Recycled old concrete
