American Concrete Institute (ACI) Practice Exam

In a two-layer concrete application, you must choose depths that both provide a good bond between the layers and meet the required final thickness. The first layer serves as a base to level irregularities and establish a solid surface for bonding the second layer. It needs enough thickness to carry the weight of the second layer during placement and to develop a good key.

The pairing with a first layer of 2 5/8 inches gives a substantial base that supports bonding and fills surface defects, while the second layer of 6 1/8 inches supplies the remaining thickness to reach the target overall depth. The combined thickness (8 3/4 inches) aligns with common practice for thicker two-layer toppings or repairs, ensuring workable placement and proper curing. The other options either fall short on the base’s ability to provide bonding or produce an overall depth that doesn’t meet the intended design.