1 Jointed Plain Concrete Pavements—Volumetric Stability and Design

A. Introduction and Overview

Jointed plain concrete pavements (JPCP) are the most common type of pavements for roads, highways, and airports. They mainly rely on thickness and support from a stiff foundation to perform in service.

For highways, the shape of the pavement is such that the longitudinal direction (x – direction, or length) is many orders of magnitude larger than the transversal direction (y – direction, or width) (Figure 1). The longitudinal direction is sometimes called the paving direction, from the methodology of placing concrete using concrete pavers (Figure 2).

Figure 1: Typical Layout of Jointed Plain Concrete Pavements

ft = feet, m = meter.

Figure 2: Unreinforced Concrete Shrinkage

A long stretch of unreinforced concrete (in plan view) will shrink (contract) in the longest direction (blue arrows) and warp or curl in the shortest direction (red arrows).

Concrete pavement. A 5.0-meter wide newly paved airfield concrete strip 0.5-meter thick.

The main advantage of JPCP is that production is quicker and repair or removal is simpler compared to continuously reinforced concrete pavements, which are pavements where steel reinforcement is used to control cracking.

There is a common saying among professionals involved in concrete paving that a poorly designed but well-constructed pavement will last longer than a well-designed but poorly constructed one.

While the design process is a straightforward operation depending on the skills and experience of the designer, construction combines factors of influence from several sources—production, delivery, placing, compacting, curing, and repairs. Many more things can go wrong during construction than during design.

B. Dimensional Stability

When a long strip of non-reinforced concrete is laid, it will shrink in the longest direction and it will warp or curl in the shortest direction (Figures 3 and 4).

Figure 3: Transversal Cracks

Due to shrinkage, transversal cracks will appear in the longitudinal section A-A’ (top). Also, under specific climatic conditions, the strip may bend and lose support across section B-B’ (bottom).

Figure 4: Concrete Expansion and Contraction

Concrete cast in the winter will expand at first during the early stages because of heat of hydration, after which it will contract (thermal and hydraulic shrinkage). The net result is contraction. Concrete cast in the summer will expand first and it will contract afterward. The net result is expansion, because the magnitude of contraction is lower than the magnitude of