6  Rigid Pavement Types

  Major Topics on this Page
  6.1 Jointed Plain Concrete Pavement
  6.2 Jointed Reinforced Concrete Pavement
  6.3 Continuously Reinforced Concrete Pavement

Almost all rigid pavement is made with PCC, thus this Guide only discusses PCC pavement.  Rigid pavements are differentiated into three major categories by their means of crack control:

Figure 2.38: Rigid Pavement Type Usage in the U.S.
(information on state practices taken from ERES, 1998 and ACPA, 2001)

 

6.1  Jointed Plain Concrete Pavement (JPCP)

Jointed plain concrete pavement (JPCP, see Figure 2.39) uses contraction joints to control cracking and does not use any reinforcing steel.  Transverse joint spacing is selected such that temperature and moisture stresses do not produce intermediate cracking between joints.  This typically results in a spacing no longer than about 6.1 m (20 ft.).  Dowel bars are typically used at transverse joints to assist in load transfer.  Tie bars are typically used at longitudinal joints.

 

Figure 2.39: Jointed Plain Concrete Pavement (JPCP)

Crack Control: Contraction joints, both transverse and longitudinal
Joint Spacing: Typically between 3.7 m (12 ft.) and 6.1 m (20 ft.).  Due to the nature of concrete, slabs longer than about 6.1 m (20 ft.) will usually crack in the middle.  Depending upon environment and materials slabs shorter than this may also crack in the middle.
       
  Reinforcing Steel:   None.
       
  Load Transfer:   Aggregate interlock and dowel bars.  For low-volume roads aggregate interlock is often adequate.  However, high-volume roads generally require dowel bars in each transverse joint to prevent excessive faulting.
       
  Other Info:   A majority of U.S. State DOTs build JPCP because of its simplicity and proven performance.
 

Washington State JPCP Information

WSDOT builds only JPCP.  Links to further WSDOT JPCP design practices are listed below: 

 

6.2  Jointed Reinforced Concrete Pavement (JRCP)

Jointed reinforced concrete pavement (JRCP, see Figure 2.40) uses contraction joints and reinforcing steel to control cracking.  Transverse joint spacing is longer than that for JPCP and typically ranges from about 7.6 m (25 ft.) to 15.2 m (50 ft.).  Temperature and moisture stresses are expected to cause cracking between joints, hence reinforcing steel or a steel mesh is used to hold these cracks tightly together.  Dowel bars are typically used at transverse joints to assist in load transfer while the reinforcing steel/wire mesh assists in load transfer across cracks.

 

Figure 2.40: Jointed Reinforced Concrete Pavement (JRCP)

Crack Control: Contraction joints as well as reinforcing steel.
Joint Spacing: Longer than JPCP and up to a maximum of about 15 m (50 ft.).  Due to the nature of concrete, the longer slabs associated with JRCP will crack.
       
  Reinforcing Steel:   A minimal amount is included mid-slab to hold cracks tightly together.  This can be in the form of deformed reinforcing bars or a thick wire mesh.
       
  Load Transfer:   Dowel bars and reinforcing steel.  Dowel bars assist in load transfer across transverse joints while reinforcing steel assists in load transfer across mid-panel cracks.
       
  Other Info:   During construction of the interstate system, most agencies in the Eastern and Midwestern U.S. built JRCP.  Today only a handful of agencies employ this design (ACPA, 2001).

In general, JRCP has fallen out of favor because of inferior performance when compared to JPCP and CRCP.
 

WSDOT does not build JRCP

 

6.3  Continuously Reinforced Concrete Pavement (CRCP)

Continuously reinforced concrete pavement (CRCP, see Figure 2.41) does not require any contraction joints.  Transverse cracks are allowed to form but are held tightly together with continuous reinforcing steel.  Research has shown that the maximum allowable design crack width is about 0.5 mm (0.02 inches) to protect against spalling and water penetration (CRSI, 1996).  Cracks typically form at intervals of 1.1 - 2.4 m (3.5 - 8 ft.).  Reinforcing steel usually constitutes about 0.6 - 0.7 percent of the cross-sectional pavement area and is located near mid-depth in the slab.  Typically, No. 5 and No. 6 deformed reinforcing bars are used.

During the 1970's and early 1980's, CRCP design thickness was typically about 80 percent of the thickness of JPCP.  However, a substantial number of these thinner pavements developed distress sooner than anticipated and as a consequence, the current trend is to make CRCP the same thickness as JPCP (FHWA, June 1990).  The reinforcing steel is assumed to only handle nonload-related stresses and any structural contribution to resisting loads is ignored.

 

Figure 2.41: Continuously Reinforced Concrete Pavement (CRCP)

Crack Control: Reinforcing steel
Joint Spacing: Not applicable.  No transverse contraction joints are used.
       
  Reinforcing Steel:   Typically about 0.6 - 0.7 percent by cross-sectional area (ACPA, 2001).
       
Load Transfer: Reinforcing steel, typically No. 5 or 6 bars, grade 60.
       
  Other Info:   CRCP generally costs more than JPCP or JRCP  initially due to increased quantities of steel.  Further, it is generally less forgiving of construction errors and provides fewer and more difficult rehabilitation options.  However, CRCP may demonstrate superior long-term performance and cost-effectiveness.  Some agencies choose to use CRCP designs in their heavy urban traffic corridors (ACPA, 2001).

WSDOT does not build CRCP
 

WSDOT Rigid Pavement Intersections

In 1995, WSDOT began replacing flexible pavement with rigid pavement at selected intersections.  These intersections were severely rutted and distressed due to loads from slow moving vehicles and warm temperatures.  Statewide, ruts of 50 mm (2 inches) or more occasionally have occurred and resurfacing to restore the intersection to an acceptable level recurred at intervals of eight years or less.  Though WSDOT has numerous rigid pavement intersections, the unique feature with these particular intersections was the replacement of existing flexible with rigid pavement only at intersections. 

A major advantage with rigid pavement replacement is that once the rigid pavement is placed rehabilitation should not be necessary for 40 years.  The major disadvantage with rigid pavement  intersections is the initial construction cost; however, these costs appear to be coming down, particularly as contractors become familiar with this type of construction.  Rigid pavement intersections in the Tri-Cities area completed in 2000 showed that an entire intersection can be paved in a single weekend closure. 

The following WSDOT report discusses rigid pavement intersection design and construction in detail:

The following is a overview of some considerations for rigid pavement intersection design:

  • The area of pavement rutting or distress must be well defined.  The major arterial approach legs to intersections may require rigid pavement sections reaching as long as 60 - 150 m (200 - 500 ft.) back from the crosswalk.  The approach legs on the minor arterial typically require 60 m (200 ft.) or less but may extend farther.  It is desirable to extend the leave legs as far as the adjacent approach legs but, at a minimum, the leave leg should extend at least 30 m (50 ft.) from the crosswalk.
  • Rigid pavement intersection plans should include intersection joint layout detail.  In 1996, the American Concrete Pavement Association (ACPA) prepared a useful step by step procedure entitled “Concrete Information - Intersection Joint Layout.”
  • Dowel bars should be used for all joints with cross traffic.  For slabs without cross traffic, use dowel bars on the transverse joints and tie bars on the longitudinal joints.  Dowel bars and tie bars should not be placed within 0.61 m (2 ft.) of new signal detection loops.  Tie bars should not be placed within 0.46 m (1.5 ft.) of dowel bars.
  • If a transverse or longitudinal joint is within 1.22 meters of a valve, utility hole, or catch basin, the joint should be skewed to pass through the center of the valve, manhole or catch basin. Care should be taken in the jointing detail to place joints across valves, manholes, or catch basins wherever possible.
  • Transverse joints, as much as possible, should line up with existing curb jointing. A lightweight roofing paper should be used between the curbing and the PCC slab.