Overview of Construction
See FHWA’s CRCP Design and Construction Guidelines for the references included in this page. A new, more comprehensive FHWA CRCP Design, Construction, Maintenance and Rehabilitation manual is currently under development and this page will be updated upon its release in the spring of 2016.
To assure the superior performance that is commonly associated with CRCP, construction plans and specifications that properly address critical details are essential. Uniformity and consistency of concrete placement and reinforcement location along the project are also necessary. In addition, climatic conditions encountered during actual placement of the pavement can have a significant effect on future performance.
The key structural performance indicator of CRCP is the width of transverse cracks. If the transverse cracks can be held tightly together over the intended design life, the likelihood of good CRCP performance is greatly enhanced. When cracks are wide, the CRCP loses the ability to transfer shear stresses from heavy wheel loads. This loss of load transfer will quickly lead to the development of punchouts, the primary structural failure in CRCP. Punchouts lead a loss of smoothness and require full-depth repairs.
Crack width depends on several design and construction factors. These include depth of reinforcement, proper lap lengths on reinforcement bars, staggering of laps, concrete shrinkage, concrete thermal coefficient of expansion, the effects of moisture on concrete expansion and contraction, concrete consolidation, set temperature of the CRC slab (climate conditions at time of construction), and friction between the base and CRC slab. (69,70,71)
Many CRCP performance problems have been related to inconsistent or inappropriate construction practices that do not meet stated design requirements. For example, CRCP has exhibited distresses due to inadequate consolidation of the concrete at construction joints, inadequate reinforcement laps, delamination due to steel too close to the surface, and loss of ride quality due to differential subgrade settlement along the project, especially in areas where embankments are placed on heavy existing clays.
Construction quality must be consistent throughout the project. Quality construction results in both uniformity (in subgrade, base, slab, and reinforcement) and uniformly spacing and width of transverse cracks that maintain load transfer over the design life).