Soundness & Durability Testing Flashcards
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Read the first 7 Soundness & Durability Testing flashcards as text
Alkali-silica reactivity (ASR) in concrete aggregates is assessed using which ASTM test method for a rapid chemical screening?
Answer: ASTM C1260
ASTM C1260, the Accelerated Mortar Bar Test, is the primary rapid screening method for potential alkali-silica reactivity.
In ASTM C1260, mortar bars are immersed in 1N NaOH solution at what temperature?
Answer: 80°C (176°F)
ASTM C1260 requires mortar bars to be immersed in 1N NaOH solution maintained at 80°C (176°F) to accelerate the ASR reaction.
According to ASTM C1260, an expansion of greater than 0.20% at 16 days indicates:
Answer: Potentially deleterious expansion requiring further testing or mitigation
ASTM C1260 classifies expansion exceeding 0.20% at 16 days as potentially deleterious, indicating the aggregate may cause harmful ASR in service.
The concrete prism test (ASTM C1293) is considered more definitive for ASR than C1260 primarily because:
Answer: It tests actual concrete rather than mortar and uses actual cement alkali levels
ASTM C1293 uses concrete prisms with actual project materials and cement alkali levels, providing results more representative of field conditions than the accelerated mortar bar method.
Which mineral phase in aggregate is most commonly associated with deleterious alkali-silica reactivity?
Answer: Opaline silica and volcanic glass
Opaline silica, volcanic glass, and poorly crystalline silica forms are the most reactive with alkalis and are primary causes of deleterious ASR.
The freeze-thaw durability of concrete aggregates is most critically affected by the aggregate's:
Answer: Pore structure — specifically the size and connectivity of internal pores
Aggregate pore structure governs freeze-thaw durability; large, interconnected pores that fill with water and cannot accommodate ice expansion lead to hydraulic pressure and cracking.
What is the primary purpose of the alkali-carbonate reactivity test (ASTM C586)?
Answer: To measure expansion of rock cylinders in NaOH solution to identify potentially reactive carbonate rocks
ASTM C586 tests small rock cylinders in NaOH solution to screen for dedolomitization reactions in carbonate rocks that can cause expansion in concrete.