A specification calls for Type M mortar by property specification. Which minimum 28-day compressive strength is associated with that mortar type?
Correct Answer
D) 2,500 psi
ASTM C270 property values list Type M mortar at 2,500 psi minimum average compressive strength at 28 days. Other choices: 750 psi is Type N, 1,800 psi is Type S, and 1,200 psi is not the standard Type M value.
Why This Is the Correct Answer
ASTM C270 property values list Type M mortar at 2,500 psi minimum average compressive strength at 28 days.
Why the Other Options Are Wrong
Option A: 750 psi
The trap in A is 750 psi. That selection is wrong because 750 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 2,500 psi; Type M mortar minimum average compressive strength is 2,500 psi.
Option B: 1,200 psi
Choice B gives 1,200 psi. Its specific error: 1,200 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 2,500 psi. The accepted answer is 2,500 psi.
Option C: 1,800 psi
Choice C (1,800 psi) is rejected because 1,800 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 2,500 psi. The cited answer is 2,500 psi.
Memory Technique
Link mortar type strength to its book condition; a different condition means a different answer than 2,500 psi.
Reference Hint
Open Modern Masonry - Brick, Block, Stone, 9th Ed., 2020; use the index entry or section for "ASTM C270 mortar property specification values" to confirm that ASTM C270 property values list Type M mortar at 2,500 psi minimum average compressive strength at 28 days.
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