Soundness & Durability Testing Flashcards
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Read the first 7 Soundness & Durability Testing flashcards as text
An aggregate has a sodium sulfate soundness loss of 8% and an LA abrasion loss of 42%. Which test result is most likely to cause rejection for use in bridge deck concrete?
Answer: The LA abrasion loss, which exceeds typical 40% limits for bridge decks
Bridge deck specifications often limit LA abrasion loss to 40%, so a 42% result would cause rejection, while 8% sodium sulfate loss is within the typical 12% coarse aggregate limit.
When a soundness test result is borderline, which supplemental test is most commonly used to confirm whether the aggregate is acceptable?
Answer: Petrographic examination (ASTM C295)
Petrographic examination (ASTM C295) identifies mineralogy and visible defects, providing the geological basis to interpret borderline durability test results.
A technician finds that a fine aggregate exceeds the maximum sodium sulfate soundness limit. The most appropriate next step is:
Answer: Request a petrographic examination and possibly the concrete prism test before final rejection
A failing soundness result warrants further investigation through petrographic examination or additional testing before final acceptance or rejection decisions.
Which of the following field conditions would most accelerate soundness-related aggregate deterioration in a concrete structure?
Answer: Repeated wetting-drying cycles combined with freeze-thaw in a deicing salt environment
Repeated wetting-drying cycles combined with freeze-thaw and deicing salt exposure creates the most severe condition for soundness-related aggregate deterioration, mimicking sulfate crystallization and frost action simultaneously.
The durability index test (California Test 229) measures fine aggregate quality by evaluating:
Answer: Resistance to degradation by agitation in water, expressed as a ratio of fine to coarse fractions
The California durability index test agitates aggregate in water and measures the ratio of settled coarse fraction to fine fraction, indicating resistance to breakdown.
For aggregates susceptible to ASR, which mitigation strategy is widely considered most effective at preventing deleterious expansion in concrete?
Answer: Using supplementary cementitious materials (SCMs) such as fly ash or slag
Supplementary cementitious materials like fly ash, slag, and silica fume dilute alkalis and alter pore solution chemistry, making them the most effective ASR mitigation strategy.
When conducting the soundness test, an aggregate sample must be separated into individual size fractions before testing primarily because:
Answer: Mixing fractions would prevent accurate calculation of weighted percent loss for each size
Separating size fractions allows calculation of percent loss for each fraction, which is then weighted by the fraction's proportion in the gradation to obtain a meaningful composite soundness value.