When installing CMU blocks, which mortar type provides the highest compressive strength?
Correct Answer
C) Type M
Type M mortar has the highest compressive strength at 2500 psi minimum, making it suitable for high-strength masonry applications and below-grade construction.
Why This Is the Correct Answer
Type M mortar is specifically formulated for high-strength applications and has the highest compressive strength requirement of all mortar types at a minimum of 2500 psi. This makes it ideal for structural masonry work, below-grade construction, and applications where maximum strength is required. Type M's high cement content provides superior compressive strength compared to other mortar types.
Why the Other Options Are Wrong
Option A: Type N
Type N mortar has a compressive strength of only 750 psi minimum, which is significantly lower than Type M and is designed for general-purpose above-grade applications rather than high-strength requirements.
Option B: Type S
Type S mortar has a compressive strength of 1800 psi minimum, which is lower than Type M and is typically used for below-grade applications where moderate strength is needed but not maximum strength.
Option D: Type O
Type O mortar has the lowest compressive strength at only 350 psi minimum and is used for non-load bearing applications and interior work where strength is not a primary concern.
Memory Technique
Use 'Most Strong' for Type M - it has the Most compressive Strength. Or remember 'M-S-N-O' decreases in strength like going down a mountain slope.
Reference Hint
Florida Building Code Chapter 21 - Masonry, or ACI 530 Building Code Requirements for Masonry Structures for mortar specifications and strength requirements
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