In hollow CMU walls, what is the purpose of filling cores around vertical reinforcement with grout?

• A. To anchor reinforcement within the wall.
• B. To provide load transfer, lateral strength, and to anchor reinforcement within the wall.
• C. To increase air leakage.
• D. To reduce wall height.

Answer: (B)

Filling the cores around vertical reinforcement with grout creates a continuous, composite element inside the hollow CMU wall. The grout bonds to the rebar and to the surrounding masonry, so the wall, grout, and steel work together to transfer loads. This increases stiffness and shear capacity, improving resistance to lateral forces such as wind or seismic loads, and it securely anchors the reinforcement in place within the wall. In short, grout-filled cores provide load transfer, enhance lateral strength, and keep the reinforcement anchored. It’s not about increasing air leakage or changing wall height, which aren’t the purposes of grout infill.