Copyright Goodheart-Willcox Co., Inc. Chapter 18 Concrete Flatwork and Formed Shapes 391 Colored Concrete Concrete can be colored using any of three methods—one-course, two-course, and dry-shake. See Figure 18-26. The first two methods are similar. In both, the concrete mix is colored by adding a mineral oxide pigment prepared especially for use in concrete. White Portland cement produces brighter colors or light pastel shades when used with light-colored sand. Normal gray cement can be used for black or dark gray colors. All materials must be accurately controlled by weight to attain a uniform color in each batch. The amount of pigment should never exceed 10% of the weight of the cement. Mix color pigments with the cement while dry. Dry mixing of cement and color pigments ensures Goodheart-Willcox Publisher Figure 18-24. These types of control joints are used in sidewalks, drives, and patios. 1/2" maximum radius t/5 minimum t t t 1/4" maximum Hand Tooled Control Joint t/5 minimum 1/2" maximum radius Sawed Control Joint 2 × 4 redwood, cedar, or cypress 16d galvanized nails, 16" O.C. from opposite sides Wood Divider Strips Goodheart-Willcox Publisher Figure 18-25. Details of a construction joint. The wood key can be made from a beveled 1″ × 2″ strip and is used for slabs 4″ to 6″ thick. The premolded key can be left in the slab permanently by tacking it lightly to the bulkhead. 3/4" minimum Metal Key Wood Key Premolded Key Break bond with oil, paint, or curing compound t t/2 Edge before removing form 2" lumber 1/8" t/4 Portland Cement Association Figure 18-26. This decorative exposed aggregate slab is further enhanced through the use of colored concrete to form a design.