2. rigid highway pavements are normally constructed
of Portland cement concrete and may or may not
have a base course between the sub-grade and the
concrete surface.
When a base course is used in rigid pavement
construction, it is usually referred to as a sub-base
course
3. It is common, however, for only the concrete
surface to be referred to as the rigid pavement, even
where there is a base course.
Rigid pavements have some flexural strength that
permits them to sustain a beamlike action across
minor irregularities in the underlying material.
4. Thickness of highway concrete pavements
normally ranges from 6-13 inches. These pavement
types usually are constructed to carry heavy traffic
loads, although they have been used for residential
and local roads.
5. MATERIALS USED IN RIGID PAVEMENTS
The Portland cement concrete commonly used for
rigid pavements consists of
Portland cement,
coarse aggregate,
fine aggregate, and water.
Steel reinforcing rods may or may not be used,
6. depending on the type of pavement being
constructed. A description of the quality
requirements for each of the basic materials is
presented in the following sections
7. Different types of joints are placed in concrete
pavements to limit the stresses induced by
temperature changes and to facilitate proper
bonding of two adjacent sections of pavement
when there is a time lapse between their
construction (for example, between the end of one
day’s work and the beginning of the next). These
joints can be divided into four basic categories
8. • Expansion joints
• Contraction joints
• Hinge joints
• Construction joints
9. Expansion Joints
When concrete pavement is subjected to an
increase in temperature, it will expand, resulting in
an increase in length of the slab. When the
temperature is sufficiently high, the slab may
buckle or “blow up” if it is sufficiently long and if
no provision is made to accommodate the increased
length.
10.
11. Contraction Joints
When concrete pavement is subjected to a decrease
in temperature, the slab will contract if it is free to
move. Prevention of this contraction movement
will induce tensile stresses in the concrete
pavement
12. Hinge Joints
Hinge joints are used mainly to reduce cracking
along the center line of highway pavements.
13. Construction joints
a joint between slabs that results when
concrete is placed at different times. This type
of joint can be further broken down into
transverse and longitudinal joints.
14. TYPES OF RIGID HIGHWAY PAVEMENTS
Rigid highway pavements can be divided into three
general types: plain concrete pavements, simply
reinforced concrete pavements, and continuously
reinforced concrete pavements. The definition of
each pavement type is related to the amount of
reinforcement used.
16. Plain concrete pavement has no temperature steel
or dowels for load transfer. However, steel tie bars
often are used to provide a hinge effect at
longitudinal joints and to prevent the opening of
these joints. Plain concrete pavements are used
mainly on low-volume highways or when cement-
stabilized soils are used as sub-base. Joints are
placed at relatively shorter distances (10 to 20 ft)
than with other types of concrete pavements to
reduce the amount of cracking.
17.
18. Simply reinforced concrete pavements have dowels
for the transfer of traffic loads across joints, with
these joints spaced at larger distances, ranging from
30 to 100 ft. Temperature steel is used throughout
the slab, with the amount dependent on the length
of the slab. Tie bars also are used commonly at
longitudinal joints.
19.
20. Continuously reinforced concrete pavements have
no transverse joints, except construction joints or
expansion joints when they are necessary at
specific positions, such as at bridges. These
pavements have a relatively high percentage of
steel, with the minimum usually at 0.6 percent of
the cross section of the slab. They also contain tie
bars across the longitudinal joints.
