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 420, "Concrete Structures", 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:
Additionally, the FHWA has published a Technical Advisory that suggests that for roadway geometries consisting of a radius of curvature less than 1640 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 appropriate notes below in the General Notes and on all bridge layouts:
Special Provision 420---002 requires the contractor to provide a broom, burlap, or carpet drag finish on the bridge deck; therefore, a more specific note regarding surface texture is not required.