The most vital design component for long-term durable concrete flatwork is the appropriate performance-based design for joint stability.
Owners and occupiers want a flatwork design to help mitigate facility maintenance costs and downtime; and, many realtors leverage the durability and cost savings associated with joint stability/performance as a key selling factor. While some methods lower initial construction costs, they do not address joint stability. Industry frontrunners are incorporating positive load transfer at contraction joints to gain long-term joint stability.
Choosing a Design for Proper Joint Stability
- Minimizes random cracking and joint spalling
- Eliminates excessive differential deflection between slab panels that causes joint spalling
- Achieves good joint stability
Good Joint Stability
The key performance standard for joint stability is to maintain total differential deflection of less than 0.010 inch (0.25 mm) for small, hard-wheeled lift trucks and 0.020 inch (0.51) for larger, cushioned wheels. The total differential deflection of a contraction joint is comprised of three factors:
- Initial dowel looseness
- Elastic deflection due to loading
- Additional dowel looseness due to repetitive loading
The total allowable deflection is a very small value and can be very difficult to achieve without the right joint design, such as strategic reinforcement or nominal joint design. PNA offers a full range of proven plate dowel systems designed to provide true joint stability at construction and contraction joints: Diamond Dowel® System and PD3 Basket® assembly.
Key Design Factors for Joint Stability
Call your local PNA expert (see Territory Manager Locator) to discuss appropriate joint types, details such as joint spacing and joint stability criteria to best suit your design, enabling you to reliably deliver durable, cost-effective concrete flatwork that meets yours or your customer’s expectations.