ATT Deleterious Materials & Clay Content Flashcards
6 cards from real ATT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 ATT Deleterious Materials & Clay Content flashcards as text
What is the purpose of washing aggregate over a No. 200 (75 µm) sieve per ASTM C117?
Answer: To remove material finer than 75 µm including clay and silt coatings
ASTM C117 washing removes clay, silt, and fine dust coatings finer than 75 µm that could weaken the paste-aggregate bond.
In ASTM C117 (material finer than No. 200), after washing the aggregate is dried to constant mass at what temperature?
Answer: 110 ± 5°C
After washing, the aggregate is dried to constant mass at 110 ± 5°C in accordance with ASTM C117.
Per ASTM C33, what is the maximum allowable material finer than No. 200 sieve in fine aggregate for concrete subject to surface wear?
Answer: 3.0%
ASTM C33 limits material finer than No. 200 in fine aggregate to 3.0% for concrete subject to abrasion.
Which type of aggregate coating is most harmful to concrete strength because it prevents proper bonding with cement paste?
Answer: Clay and silt coatings
Clay and silt coatings are most harmful because they create a weak interface that prevents cement paste from bonding to aggregate surfaces.
When performing the ASTM C117 wash test, how is the mass loss reported?
Answer: As the percentage of material passing the No. 200 sieve by washing
ASTM C117 results are reported as the percentage of material passing the No. 200 sieve by mass of the original dry sample.
Soft particles in coarse aggregate are a concern primarily because they:
Answer: Can crush under load and create voids that weaken concrete
Soft particles crush under compressive loads, creating voids and weak zones that significantly reduce concrete strength and durability.