Below-grade reinforced masonry is specified with Type S mortar. Which 28-day compressive strength value should be recognized for Type S under the common ASTM property table?
Correct Answer
A) 1,800 psi
Type S mortar is associated with 1,800 psi minimum average compressive strength at 28 days in the ASTM C270 property specification table. Other choices: 350 psi is Type O, 750 psi is Type N, and 2,500 psi is Type M.
Why This Is the Correct Answer
Type S mortar is associated with 1,800 psi minimum average compressive strength at 28 days in the ASTM C270 property specification table.
Why the Other Options Are Wrong
Option B: 350 psi
Choice B (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 1,800 psi. The cited answer is 1,800 psi.
Option C: 750 psi
In masonry work, 750 psi is the wrong selection for Mortar type strength: 750 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 1,800 psi.
Option D: 2,500 psi
The trap in D is 2,500 psi. That selection is wrong because 2,500 psi is a different published number than the cited Mortar type strength value; ASTM C270 mortar property specification values supports 1,800 psi; Type S mortar minimum average compressive strength is 1,800 psi.
Memory Technique
Use a dimension string memory cue for mortar type strength: the stem's condition unlocks 1,800 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 S mortar is associated with 1,800 psi minimum average compressive strength at 28 days in the ASTM C270 property specification table.
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