Concrete Mix Design and Material
Properties 100% Correct
Aggregate grading importance - ANSWER-Better grading reduces paste demand.
ASR - ANSWER-Alkali-silica reaction causing cracking and expansion.
ASTM C1602 testing requirement - ANSWER-Strength and setting time if water source
is questionable.
Benefits of fibers in concrete - ANSWER-Reduce shrinkage cracking and improve
toughness.
Best cement for cold weather - ANSWER-Type III / HE (high early strength).
Calcium chloride limit - ANSWER-≤2% by mass of cement (ASTM D98).
Chlorides in mixing water effect - ANSWER-Corrosion of reinforcing steel.
Cold weather concreting temperature definition - ANSWER-≤40°F during placement and
risk of freezing for 24 hours.
Common concrete test for workability - ANSWER-Slump test (ASTM C143).
Compressive strength test standard - ANSWER-ASTM C39.
Designing vs proportioning a concrete mix - ANSWER-Design = requirements;
Proportioning = ingredient quantities.
Difference between hydration and curing - ANSWER-Hydration = chemical reaction;
Curing = keeping moisture/temp to allow hydration.
Downside of epoxy-coated rebar - ANSWER-Lower bond strength → longer lap splice.
Effect of accelerators - ANSWER-Faster set and early strength gain.
Effect of air on strength - ANSWER-Every 1% air ↑ → ~5% strength ↓.
Effect of set retarders - ANSWER-Slow set time.
Examples of SCMs - ANSWER-Fly ash, slag, silica fume, natural pozzolans.
Harmful materials in aggregate - ANSWER-Clay, contaminants → reduced
strength/durability.
Properties 100% Correct
Aggregate grading importance - ANSWER-Better grading reduces paste demand.
ASR - ANSWER-Alkali-silica reaction causing cracking and expansion.
ASTM C1602 testing requirement - ANSWER-Strength and setting time if water source
is questionable.
Benefits of fibers in concrete - ANSWER-Reduce shrinkage cracking and improve
toughness.
Best cement for cold weather - ANSWER-Type III / HE (high early strength).
Calcium chloride limit - ANSWER-≤2% by mass of cement (ASTM D98).
Chlorides in mixing water effect - ANSWER-Corrosion of reinforcing steel.
Cold weather concreting temperature definition - ANSWER-≤40°F during placement and
risk of freezing for 24 hours.
Common concrete test for workability - ANSWER-Slump test (ASTM C143).
Compressive strength test standard - ANSWER-ASTM C39.
Designing vs proportioning a concrete mix - ANSWER-Design = requirements;
Proportioning = ingredient quantities.
Difference between hydration and curing - ANSWER-Hydration = chemical reaction;
Curing = keeping moisture/temp to allow hydration.
Downside of epoxy-coated rebar - ANSWER-Lower bond strength → longer lap splice.
Effect of accelerators - ANSWER-Faster set and early strength gain.
Effect of air on strength - ANSWER-Every 1% air ↑ → ~5% strength ↓.
Effect of set retarders - ANSWER-Slow set time.
Examples of SCMs - ANSWER-Fly ash, slag, silica fume, natural pozzolans.
Harmful materials in aggregate - ANSWER-Clay, contaminants → reduced
strength/durability.
