7.1 Introduction

Concrete undergoes volume changes due to temperature and moisture changes. If these volume changes are not controlled properly, excessive stresses will develop, resulting in uncontrolled cracks. These cracks can be sources of distress that could be avoided if properly controlled. Joints can be considered as intentional cracks and are provided where the cracking is most likely. These joints relieve stresses, thus preventing uncontrolled cracks. Provisions are made at the joints to provide wheel load transfer.
In CRCP, however, the concrete volume changes are controlled by random cracks, which are held tightly closed by longitudinal reinforcing steel. Figure 9-68 shows an example of random cracks in CRCP. These random cracks do not cause distress.
Random cracks in CRCP. (click in image to see full-size image)
Figure 9-68. Random cracks in CRCP.
There are three types of joints in rigid pavements:
  1. Contraction joint,
  2. Construction joint,
  3. Expansion joint.