If SCM are added, it can be increased to 20 pounds per each required 100 pounds of cementitious material in excess of 550 pounds per cubic yard.

• A. 10
• B. 20
• C. 40
• D. 30

Answer: (B)

SCMs allow you to push the total cementitious content beyond a base limit while still keeping control over the mix. The rule is that when SCMs are used, you can increase the cementitious material above five hundred fifty pounds per cubic yard, but only at a fixed rate: for every additional hundred pounds of cementitious material beyond the five hundred fifty pounds, you may include twenty pounds of SCM. This creates a linear relationship between the amount of excess cementitious material and the allowed SCM addition.

For example, if the cementitious material total ends up at six hundred pounds per cubic yard, the excess is fifty pounds, which yields ten pounds of SCM allowed (half of a hundred). If it’s seven hundred pounds, you could add twenty pounds of SCM; eight hundred pounds would allow forty pounds of SCM, and so on. The consistent factor here is twenty pounds of SCM per each extra hundred pounds of cementitious material above the baseline.