Copyright Goodheart-Willcox Co., Inc. Chapter 18 Concrete Flatwork and Formed Shapes 397 Another method of producing exposed aggre- gate cast-in-place walls is to preplace dry aggregate in the form and then grout under pressure with a cement-sand-water slurry. A hole near the bottom of the form is used for pumping in the grout and an external vibrator is used. The aggregate is exposed by sandblasting two to seven days after grouting. An alternate, patented method is to wrap wire mesh around the reinforcement and preplace aggre- gate between the mesh and the outside form. A special concrete mix is cast into the core of the mesh and dispensed to the outside. Cast-in-Place Window Walls Repetition of window openings makes an attrac- tive design in large structures such as the one shown in Figure 18-38. White Portland cement concrete is well suited for window walls because the color is permanent. Any coarse aggregate can be used, but it should be reasonably uniform in color. White aggre- gate is preferred if maximum whiteness is desired. Reinforced plastic forms provide a concrete surface that is smooth and hard with few air voids and defects. The plastic forms are reinforced with fiberglass and are usually from 3/16″ to 5/8″ thick. Normal thickness of wall forms is 3/8″. Column forms are usually 1/2″ thick. Sculptured Concrete Walls Sculptured concrete provides aesthetic qualities. See Figure 18-39. A wide range of materials can be used to form decorative patterns in concrete walls. KPG_Payless/Shutterstock.com Figure 18-37. Tie holes form a grid pattern in the structure and are left exposed as part of the surface texture. ASG Corporation Figure 18-38. This attractive design owes its overall effect to the use of white Portland cement. Goodheart-Willcox Publisher Figure 18-39. The fine sculptured details of these walls set them apart from the ordinary.