For a typical above-grade veneer backup repair, the documents call for Type N mortar. What minimum 28-day compressive strength corresponds to Type N mortar?
Correct Answer
B) 750 psi
Type N mortar corresponds to 750 psi minimum average compressive strength at 28 days under the ASTM C270 property specification table. Other choices: 350 psi belongs to Type O, 1,800 psi to Type S, and 2,500 psi to Type M.
Why This Is the Correct Answer
Type N mortar corresponds to 750 psi minimum average compressive strength at 28 days under the ASTM C270 property specification table.
Why the Other Options Are Wrong
Option A: 350 psi
Choice A (350 psi) is rejected because 350 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 750 psi. The cited answer is 750 psi.
Option C: 1,800 psi
The trap in C is 1,800 psi. That selection is wrong because 1,800 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 750 psi; Type N mortar minimum average compressive strength is 750 psi.
Option D: 2,500 psi
Choice D gives 2,500 psi. Its specific error: 2,500 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 750 psi. The accepted answer is 750 psi.
Memory Technique
Treat mortar type strength like a labeled shelf; only the matching condition belongs with 750 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 Type N mortar corresponds to 750 psi minimum average compressive strength at 28 days under the ASTM C270 property specification table.
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