Fresh Concrete Field Testing Flashcards
6 cards from real ACI Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Fresh Concrete Field Testing flashcards as text
After a concrete truck arrives on site and the inspector observes that the drum has been rotating for more than 90 minutes from batching, what should the inspector do?
Answer: Reject the load if the time since batching exceeds the project specification limit (typically 90 minutes per ASTM C94) and document the rejection
ASTM C94 limits concrete delivery to 90 minutes or 300 revolutions from batching to discharge, whichever comes first; concrete exceeding this limit must be rejected regardless of slump.
What action is required if a concrete test specimen is accidentally dropped or jarred during transport from the field to the laboratory?
Answer: Discard the damaged specimen, document the incident, and note that one fewer cylinder was received at the lab; do not use the dropped specimen for acceptance testing
A dropped or jarred specimen may have micro-cracks that reduce measured compressive strength; ASTM C31 prohibits using specimens that have been subjected to excessive shock or vibration during transport.
Per ASTM C1064, how long must a thermometer be immersed in fresh concrete before the temperature reading is recorded?
Answer: A minimum of 2 minutes or until the reading stabilizes
ASTM C1064 requires the thermometer to be immersed at least 3 inches for a minimum of 2 minutes or until the reading stabilizes, whichever is longer, to ensure thermal equilibrium is reached.
What is the purpose of 'field-cured' test cylinders made in addition to standard laboratory-cured cylinders at a construction site?
Answer: To evaluate the actual in-place concrete strength under the temperature and curing conditions that the structure experienced, which may justify earlier form removal or loading
Field-cured cylinders represent the actual curing history (temperature, moisture) of the in-place concrete and are used to evaluate structural maturity for decisions like form stripping, post-tensioning, and traffic loading.
What is the 'unit weight' of fresh concrete also known as, and how is it measured per ASTM C138?
Answer: Density; measured by filling a calibrated rigid container in three layers, rodding each layer 25 times and tapping 10–15 times, striking off the top, and dividing the net weight by container volume
Unit weight (density) per ASTM C138 is determined by filling a calibrated measure in three layers with standard rodding, weighing the filled measure, subtracting tare weight, and dividing by the known container volume.
How many rod insertions are required per layer when filling a 6×12-inch cylinder per ASTM C31?
Answer: 25 rod insertions uniformly distributed over the cross section of each layer
ASTM C31 requires exactly 25 rod insertions per layer for both 4×8-inch and 6×12-inch cylinders when concrete has slump greater than 1 inch.