NASCLA Accredited Commercial General ContractorMasonryHard
A masonry project requires the use of grout to fill the cores of concrete masonry units (CMUs) containing vertical reinforcement. Which of the following is a primary characteristic distinguishing grout from mortar in this application?
- AGrout is primarily used for bonding masonry units together, while mortar fills voids.
- BGrout is typically poured or pumped, requiring a higher slump than mortar.
- CGrout contains larger aggregate particles and is always colored for aesthetics.
- DGrout has a higher cement content and less water than mortar.
Show answer & explanationAnswer & explanation
Correct answer: B. Grout is typically poured or pumped, requiring a higher slump than mortar.
Grout is designed to be highly fluid (high slump) so it can be poured or pumped into small spaces, ensuring it fully consolidates around reinforcement and fills CMU cores. Mortar, conversely, is stiffer (lower slump) for bedding and bonding masonry units.
Why the other options are wrong
- A. This statement reverses the primary uses: mortar bonds units, and grout fills voids and consolidates reinforcement.
- C. While grout can contain aggregate, its primary distinction isn't aggregate size or color, but its pourable consistency.
- D. Grout typically has more water to achieve higher fluidity, and while it has cement, its primary distinction is fluidity.
Grout vs. Mortar
Grout is a highly fluid cementitious mixture used to fill voids in masonry, encapsulate reinforcement, and bond adjacent wythes. Mortar is a stiffer mixture used to bond masonry units.
- Grout is poured/pumped (high slump).
- Mortar is trowel-applied (low slump).
- Grout fills cores, mortar forms joints.
- Both are cement-based but differ in consistency and use.
Memory trick: Grout 'goes-in' and 'flows-in', Mortar 'makes-joints'.