Key CRCP Design and Construction Details
Some States, including Illinois and Texas, have fine-tuned their CRCP design and construction techniques, resulting in lower life-cycle costs and increased public satisfaction.
Following is a brief list of key practices that help ensure successful CRCP projects:
- Design, mix, and construction decisions and practices should maximize load-transfer efficiency and minimize flexural stresses.
- Cracks that are closely spaced (3-4 ft [0.9-1.2 m] maximum is optimum) and tight (0.02 in. [0.5 mm] at the depth of the reinforcement) help maximize load-transfer efficiency and minimize flexural stresses, maintaining steel stress well below the yield strength.
- Closely spaced, tight cracks result when the project includes:
- Adequate longitudinal steel content (0.6 to 0.8 percent of the slab cross-section area).
- Optimum reinforcement diameter.
- Adequate lapping of reinforcement splices.
- Appropriate depth of reinforcement placement.
- Thorough consolidation of concrete around the reinforcement.
- Reinforcement design has to consider possible fracture and/or excessive plastic deformation. Stress in the reinforcement is usually limited to a reasonable percentage of the ultimate tensile strength to avoid fracture and limit the amount of plastic deformation.
- Large, abrasion-resistant aggregates promote good aggregate interlock and thus enhance load-transfer efficiency.
- Sufficient slab thickness is required to manage transverse tensile stresses due to truck traffic and curling and warping.
- The foundation must be uniform and stable, provide good drainage, and extend beyond the slab edge through the shoulder area and through transitions at bridge approaches, cuts, and fills.
- Longitudinal construction joints must be tied to adjacent pavement at centerline or shoulder.
- Longitudinal contraction joints at shoulders should be sawed directly over the transverse reinforcement.
- Curing should be thorough and appropriate to each CRCP application, weather conditions, etc.
Ongoing research, field monitoring, and materials innovations will likely result in additional refinements to these practices into the future.