Copyright Goodheart-Willcox Co., Inc. Unit 7 Construction Materials—Types and Uses 111 strength. As the concrete hardens, it grips the steel to form a bond. The size of the bar is indicated by the bar number, which is a multiple of 1/8″. For example, a #4 ″ bar is 1/2″ in diameter (4 ″ × 1/8″ = 1/2″). ″ See Figure 7-5. Refer to Unit 10 for more information. Reinforced Concrete Concrete has great compressive strength, but very little tensile (pulling) strength. To overcome this weakness, concrete is cast around steel reinforcing bars. These bars (commonly referred to as “rebar”) have high tensile Goodheart-Willcox Publisher Figure 7-4. A ready-mix truck is typically used to transport concrete to the construction site. 1" 24 #18 3" 14 #14 3" 18 #11 1" 14 #10 1" 18 #9 1" #8 7" 8 #7 3" 4 #6 5" 8 #5 1" 2 #4 3" 8 #3 Goodheart-Willcox Publisher Figure 7-5. Reinforcing steel bars (“rebar”). Bar diameters are identified by a number that is a multiple of 1/8″. The #18 bar is 2 1/4″ in diameter the #3 bar is 3/8″. ″