Chapter 8: Rigid Pavement DesignAnchor: #CEGEICDE
Section 1: OverviewAnchor: #i1002109
Rigid Pavement Types
Different pavement types use different types of joints and reinforcement to control the forces acting on the concrete pavement. These forces include curing shrinkage of the concrete, environment changes and traffic loads. Forces in the concrete pavement will cause cracks to form without traffic.
The designer can select the location where the joints will be placed and, consequently, where the cracks will form. Joints may be thought of as “controlled cracks” that will reduce the stresses the concrete will experience during its life and greatly increase the life of the concrete pavement. Through the use of reinforcement, the location and spacing of cracks can also be controlled.
Two types of concrete pavements commonly used in Texas are contnuously reinforced concreted pavement (CRCP) and jointed concrete pavement (JCP).
Continuously Reinforced Concrete Pavement (CRCP)
CRCP contains both longitudinal and transverse steel. CRCP does not contain transverse joints except at construction joints.
The function of the longitudinal steel is not to strengthen the concrete slab, but to control concrete volume changes due to temperature and moisture variations and to keep transverse cracks tightly closed. The function of the transverse steel is to keep longitudinal joints and cracks closed. If the steel serves its proper function and keeps cracks from widening, aggregate interlock is preserved and concrete stresses in the concrete slab due to traffic loading are reduced.
The CRCP thickness design is detailed in Section 2, “Approved Design Method,” and Section 3, “Rigid Pavement Design Process.” Steel reinforcement and other design details are governed by the CRCP standards that can be obtained from TxDOT’s internet web site at the following address: http://www.dot.state.tx.us/insdtdot/ orgchart/cmd/cserve/standard/rdwylse.htm. Some districts have district-wide CRCP standards.
Figure 8-1. Continuously Reinforced Concrete Pavement
Jointed Concrete Pavement (JCP)
JCP has transverse joints spaced at regular intervals. The transverse joints are used to control temperature induced contraction and expansion in the concrete. Smooth dowel bars are used at the transverse joints for load transfer. The transverse joints are spaced at 15 ft.
Longitudinal joints are used to control random longitudinal cracking. Longitudinal joints are tied together with tie bars.
The thickness design of JCP is same as CRCP and is detailed in Section 2, “Approved Design Method,” and Section 3, “Rigid Pavement Design Process.” Other JCP details are governed by the concrete pavement contraction design (CPCD) standards that can be obtained from TxDOT's internet web site at the following address: http://www.dot.state.tx.us/insdtdot/ orgchart/cmd/cserve/standard/rdwylse.htm.Anchor: #i1002153
Selection of Rigid Pavement Type
CRCP provides excellent long-term performance requiring very low maintenance. The Department policy is to utilize CRCP for new or reconstructed rigid pavements in Texas. There are situations where jointed pavement may be desirable. If jointed pavement is to be utilized, its use must meet one of the following criteria:
- for roadways controlled and maintained by another government entity
- for aesthetic reasons where pedestrian traffic might interpret the randomly spaced cracks of CRCP with premature failure
- for parking areas or roadways with crosswalks, adjacent parking, or sidewalks
- for railroad crossings, approaches to structures or to widen existing jointed pavement
- for intersections and approaches in flexible pavement roadways that are associated with vehicle braking and acceleration which could cause shoving and rutting of an asphalt pavement
- for other situations approved by the Administration, after submittal of request and justification to the Materials & Pavements Section of the Construction Division (CST-M&P).
Rigid pavement types other than CRCP and JCP may be appropriate for a wide variety of situations. Refer to Chapter 7, “Concrete Overlays” and Chapter 10, “Bonded Concrete Overlay” and “Unbonded Concrete Overlay” for a description of other rigid pavement applications.Anchor: #i1002195
For rigid pavements, the initial pavement structure shall be designed and analyzed for a performance period of 30 yr. A performance period other than 30 yr. may be utilized with justifications. For example, an existing pavement to be widened will be completely reconstructed within 15 yr. In this case, a selection of a 15-yr. performance period is more reasonable and justifiable for the widening.