Deck Texture Requirements
The proper surface texture of a roadway will prevent vehicles from hydroplaning during wet weather. The surface texture of roadways typically consists of microtexture and macrotexture. Microtexture in concrete pavement is provided by the fine aggregates. Macrotexture is provided through broom finishing, burlap dragging, carpet dragging or saw cut grooving. The broom finish, burlap dragging, and carpet dragging all provide a texture that creates friction with the vehicles wheels. Saw cut grooving of the deck further improves upon roadway safety by improving water flow off the structure.
Item 422, "Concrete Superstructures," requires a broom, carpet drag or burlap drag finish on all bridge slabs during deck placement followed by saw cut grooving of the bridge deck once the deck has hardened. Current research indicates that saw cut grooving of bridge decks is not always necessary and is typically noisier than other methods of surface texturing. The method of macrotexture recommended is dependent on the posted speed limit and the roadway geometry.
PCC Pavements and Bridge Decks
TxDOT requirements for the surface texture for PCC pavements and bridge decks was modified in 2004 by Amadeo Saenz Jr., P.E. in his memorandum "Texture Requirements for Pavement Structures with Design Speeds of 45 Miles per Hour or Less." Saenz recommended the following:
- For roadways and structures with a posted speed limit less than or equal to 45 miles per hour, the concrete surface may be finished with a broom or carpet drag. Structures with a posted speed limit greater than 45 miles per hour require a saw cut grooving finish.
Additionally, the FHWA has published a Technical Advisory that suggests that for roadway geometries consisting of a radius of curvature less than 1,640 feet saw cut grooving should be required.
Overall, removing the saw cut grooving requirement for roadways with lower posted speed limits and greater radii will result in a cost savings and noise reduction.
Therefore, designers should include the following note below in the general notes and on all bridge layouts for bridges with design or posted speeds (whichever is greater) of 50 miles per hour and above or a radius of curvature less than 1,640 feet:
- Saw-cut grooving of the bridge deck and approach slab (if present) is required.
The following note should also be placed on the span sheets and estimated quantities sheet:
- See layout for surface texture requirements.