TTI Research Supervisor:
Roger P. Bligh, P.E., Ph.D.
Texas A&M Transportation Institute
College Station, Texas 77843-3135
(979) 845-4377 [email protected]
Pooled Fund Technical Representative:
SR 520 Bridge Replacement and HOV Program
Washington State Dept of Transportation
999 3rd Avenue, Suite 900
Seattle, WA 98104
(206) 770-3522 [email protected]
Vehicle noise is inherent in the highway environment. Increased traffic volumes on freeways have aggravated the issue of noise with surrounding businesses and residences. Departments of Transportation continue to seek cost-effective solutions for mitigating the transmission of this highway noise.
The objective of this project was to evaluate the impact performance of a single slope concrete traffic barrier with an applied acoustic coating. Test 3-11 was performed following the guidelines of the AASHTO Manual for Assessing Safety Hardware (MASH). The test installation consisted of 48 inch tall precast single slope concrete barrier segments connected together using grouted rebar connections and keyed into an adjacent concrete apron using a 3-inch asphalt overlay. A thin layer of acoustical surfacing material (Pyrok Acoustement 40) approximately ½ inch thick was field applied to the traffic face of the installed barrier.
The single slope concrete traffic barrier with Acoustement 40 coating met all applicable MASH evaluation criteria for MASH test 3-11. Upon impact, the coating disintegrated into a powdery cloud, and there were no large fragments that would pose a hazard to other traffic, pedestrians, or work zone personnel. However, the coating cloud resulting from the impact could momentarily obstruct the vision of other motorists in the area. The test results also verified that a 3-inch asphalt overlay/key is sufficient for anchorage of precast concrete median barrier with grouted rebar connections. The barrier used in the test had negligible movement and no structural damage.