CPII Materials & Testing 5 — Questions and Answers
Question 1: What does 'specific gravity' of an aggregate indicate to an inspector?
- The aggregate's resistance to freeze-thaw cycles
- The ratio of aggregate density to the density of water, used in mix design calculations (Correct answer)
- The percentage of voids in the aggregate
- The aggregate's hardness on the Mohs scale
Correct answer: The ratio of aggregate density to the density of water, used in mix design calculations
Specific gravity is the ratio of aggregate mass to the mass of an equal volume of water and is used to calculate volumes in concrete and asphalt mix designs.
Question 2: Which type of pipe joint is most commonly used for ductile iron water main installations to allow slight angular deflection?
- Welded joint
- Push-on (bell and spigot) joint with elastomeric gasket (Correct answer)
- Threaded joint
- Flanged joint
Correct answer: Push-on (bell and spigot) joint with elastomeric gasket
Push-on joints with rubber gaskets provide a watertight seal while allowing small angular deflections to accommodate ground movement and alignment changes.
Question 3: What does 'aggregate absorption' measure, and why is it important for concrete mix design?
- How much water the aggregate absorbs during curing, affecting shrinkage
- The percentage of water aggregate can absorb into its pores, affecting effective water-cement ratio (Correct answer)
- How quickly aggregate dries after batching
- The resistance of aggregate to water infiltration
Correct answer: The percentage of water aggregate can absorb into its pores, affecting effective water-cement ratio
Absorption capacity determines how much water aggregate will draw from the mix, so it must be accounted for to maintain the target water-cement ratio.
Question 4: During pile driving inspection, what does the pile driving analyzer (PDA) measure?
- Soil bearing capacity at the pile tip only
- Force and velocity waves during driving to estimate capacity, stress, and hammer energy (Correct answer)
- Pile alignment and plumbness
- Soil type along the pile shaft
Correct answer: Force and velocity waves during driving to estimate capacity, stress, and hammer energy
The PDA uses sensors attached to the pile to record stress wave data during each hammer blow, allowing estimation of pile capacity and integrity.
Question 5: What is the purpose of a pentrometer test in soil inspection?
- Determine soil gradation
- Quickly estimate in-place shear strength or consistency of cohesive soils (Correct answer)
- Measure soil permeability
- Assess frost depth
Correct answer: Quickly estimate in-place shear strength or consistency of cohesive soils
A pocket penetrometer provides a rapid estimate of unconfined compressive strength of cohesive (clay) soils at the point of testing.
Question 6: What ASTM test method is used to determine the flash point of asphalt binder, which governs safe handling temperatures?
- ASTM D92 (Cleveland Open Cup) (Correct answer)
- ASTM D5 (Penetration)
- ASTM D2170 (Kinematic Viscosity)
- ASTM D113 (Ductility)
Correct answer: ASTM D92 (Cleveland Open Cup)
ASTM D92 (Cleveland Open Cup test) determines the flash and fire points of asphalt binder to establish safe mixing and storage temperature limits.
Question 7: When reviewing a certified material test report (CMTR) for structural steel, which property confirms the steel meets the minimum yield strength requirement?
- Elongation at break
- Yield point or 0.2% offset yield strength (Correct answer)
- Brinell hardness number
- Charpy absorbed energy
Correct answer: Yield point or 0.2% offset yield strength
The CMTR must show a measured yield strength at or above the specified minimum (e.g., 36 ksi for A36 steel) to confirm compliance.
CPII Materials & Testing 5
What does 'specific gravity' of an aggregate indicate to an inspector?