CCIL Advanced Aggregate Characterization 4

Question 1

Which accelerated chemical test per ASTM C1260 evaluates mortar bar expansion to assess potential alkali-silica reactivity (ASR)?

Accepted Answer

Mortar bar immersion in 1N NaOH at 80°C for 16 days

Answer

ASTM C1260 measures mortar bar expansion after immersion in 1N NaOH solution at 80°C for 16 days, providing accelerated assessment of ASR potential.

Question 2

What expansion limit at 16 days in the ASTM C1260 accelerated mortar bar test is typically classified as potentially deleteriously reactive?

Accepted Answer

Greater than 0.10%

Answer

ASTM C1260 classifies aggregates with expansion greater than 0.10% at 16 days as potentially deleteriously reactive, requiring further evaluation or mitigation.

Question 3

The concrete prism test (ASTM C1293) is considered more reliable than ASTM C1260 primarily because it:

Accepted Answer

Uses actual concrete mixtures and measures expansion over 1–2 years

Answer

ASTM C1293 uses actual concrete prisms tested over 1–2 years, better replicating field conditions and reducing false positives compared to the accelerated mortar bar method.

Question 4

Which deleterious substance in fine aggregate can interfere with cement hydration and is detected using the ASTM C40 colorimetric test?

Accepted Answer

Organic impurities

Answer

ASTM C40 uses a sodium hydroxide colorimetric test to detect organic impurities in fine aggregate that can retard or prevent normal cement hydration.

Question 5

Alkali-carbonate reaction (ACR) in concrete differs from ASR because it primarily involves:

Accepted Answer

Dedolomitization of argillaceous dolomitic limestone aggregates

Answer

ACR involves dedolomitization — the reaction of dolomite in argillaceous limestone with alkali hydroxides — producing brucite, calcite, and expansive products.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL Advanced Aggregate Characterization 4