Finishing involves all processes and equipment used to create the final surface finish and texture of fresh PCC. Generally, finishing can be divided into floating and texturing:
- Floating. A flat surface is run across the PCC in order to eliminate high and low spots, embed larger aggregate particles beneath the surface, remove slight imperfections and to compact the mortar at the surface in preparation for texturing (PCA, 1988). Floating can involve a number of different tools and may involve multiple passes over the same surface.
- Texturing. After floating, fresh PCC is usually quite smooth. In order to create a slip resistant surface for traffic, a rough pattern is usually imparted by dragging a broom, rough-textured item, or tined instrument across the surface. Typically, texturing is divided into the following two categories (FHWA, 1999):
- Microtexture (Figure 1). This is achieved by dragging a section of burlap or artificial turf behind the paver. Microtexture enhances friction between vehicle tires and the pavement surface, and enhances safety at low speeds.
- Macrotexture (Figure 2). This is generally achieved by tining the pavement surface. Macrotexture permits water to escape from between tires and the pavement surface and enhances safety at high speeds. Typically, an average texture depth of 0.7 mm (0.03 in) will substantially reduce both total and wet weather accident rates. Tining practices vary by agency, but many states require transverse grooves on the order of 3 – 5 mm (0.12 – 0.20 inches) deep, 3 mm (0.12 inches) wide and spaced 12 – 20 mm (0.47 – 0.79 inches) apart (ACPA, 1995). Sometimes the area over the future joint locations is not textured in order to provide a good sawing and sealing surface. Some agencies consider microtexturing sufficient and do not macrotexture their rigid pavements.
Footnotes (↵ returns to text)
- Portland Cement Association (PCA). (1988). Design and Control of Concrete Mixtures. Portland Cement Association. Skokie, IL.↵
- Federal Highway Administration (FHWA). (1999). Concrete Pavement Design Details & Construction Practices. Course No. 131060. CD-ROM course companion including technical digest, instructor’s guide, participants workbook and visual aids. Federal Highway Administration. Washington, D.C.↵
- American Concrete Pavement Association (ACPA). (1995). Construction of Portland Cement Concrete Pavements. National Highway Institute Course No. 13133. AASHTO/FHWA/Industry joint training. Federal Highway Administration, Department of Transportation. Washington, D.C.↵