What is a Precast Concrete Traffic Barrier?
Precast traffic barriers are concrete structures that prevent vehicles or pedestrians from entering vulnerable or unsafe areas or colliding with dangerous obstacles.
There are three common shapes of traffic barriers: Jersey, F-Shaped, and Constant Slope. Each of these meets durability and crash test standards.
The most common length of a traffic barrier is 10 feet. 20- and 30-foot variations may be better suited for some DOT applications that require greater permanence or stability.
Greater stability can be achieved by incorporating mat and bar reinforcement. Improved anchorage to prevent lateral movement can be addressed with interlocking joints and dowels.
- Shape and length to handle the demands of an impact and leave a clear zone that meets DOT standards
- Concrete strength and bar reinforcement to meet crash test standards
- Surface finishing for uniform appearance
- Interlocking joints or hooks with hardware such as JJ Hooks® (see figure 1)
- Anchor the system with a washer or other product such as Clampcrete™ (see figure 2)
Precast Concrete Advantages – For Designers
- Unmatched durability and strength
- High quality concrete mix designs
- Documented QA/QC programs
- Easily customizable to meet project needs
Traffic Barrier Sizing
Differing lengths of traffic barriers are necessary to meet the demands of different roadways. The Federal DOT has a tool to help calculate the length that is right for each purpose.
State, City and Municipality Requirements
ASTM C825 Standard Specification for Precast Concrete Barriers
This specification covers precast concrete barriers intended for use adjacent to a roadway or as a median to redirect vehicles unintentionally leaving the roadway. The acceptance criteria for these barriers shall be based on strength properties, dimensional properties, and end results. Conformance as to materials (cement, aggregates, admixtures, and steel reinforcements), design (concrete strength, air entrainment, dimensions, steel reinforcements, concrete finish, lifting devices, anchorage, and reinforcement laps, welds, and splicing), and manufacture (mixture, accelerated curing, water curing, membrane curing, and forms) should be observed precisely. Physical requirements shall be examined by compression, curing compression, and core compression tests.
ASTM 2656 Standard Test Method for Crash Testing of Vehicle Security Barriers
This test method provides a range of vehicle impact conditions, designations, and penetration performance levels. This will allow an agency to select passive perimeter barriers and active entry point barriers appropriate for use at facilities with a defined moving vehicle threat. Agencies may adopt and specify those condition designations and performance levels in this test method that satisfy their specific needs. Agencies may also assign certification ratings for active and passive perimeter barriers based on the tests and test methodologies described herein. Many test parameters are standardized to arrive at a common vehicle type and mass, and replication, and produce uniform rating designations.