Concrete Testing & Evaluation Flashcards
7 cards from real CCI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Concrete Testing & Evaluation flashcards as text
What does a half-cell potential reading more negative than -350 mV (vs. CSE) indicate per ASTM C876?
Answer: Greater than 90% probability that corrosion is occurring
Per ASTM C876, a half-cell potential more negative than -350 mV vs. a copper-copper sulfate electrode indicates a greater than 90% probability of active reinforcement corrosion.
Ground-penetrating radar (GPR) is primarily used during concrete inspection to:
Answer: Locate rebar and voids without drilling
GPR sends radar pulses into concrete and records reflections to non-destructively locate reinforcing steel, post-tension cables, conduits, and subsurface voids.
When evaluating concrete with impact-echo testing, what does a significant drop in the dominant frequency of the returned signal indicate?
Answer: Delamination or internal void in the concrete
In impact-echo testing, a low-frequency anomaly compared to the expected solid-slab response indicates a reflective interface such as a delamination, crack, or void.
Per ACI 308, the minimum curing period for concrete made with Type I/II cement exposed to moderate conditions is:
Answer: 7 days
ACI 308 recommends a minimum 7-day moist curing period for concrete made with Type I or II cement under moderate exposure conditions to achieve adequate hydration.
A concrete inspector notices map cracking (crazing) on a flatwork surface shortly after placement. The most likely cause is:
Answer: Rapid surface drying before finishing
Crazing or map cracking on flatwork typically results from rapid evaporation of surface moisture before or during finishing, causing the surface to shrink faster than the body.
D-cracking in concrete pavements is caused by:
Answer: Freeze-thaw deterioration of susceptible coarse aggregate
D-cracking (durability cracking) occurs when frost-susceptible coarse aggregate absorbs water, freezes, and expands, causing parallel cracks along joints and edges.
Which test method is used to determine the flexural strength (modulus of rupture) of concrete beams in the field?
Answer: ASTM C78 or C293
ASTM C78 (third-point loading) and ASTM C293 (center-point loading) both measure the modulus of rupture of concrete beams; C78 is most common for pavement work.