CFB Quality Control & Inspection 3 — Questions and Answers
Question 1: Which non-destructive testing method uses high-frequency sound waves to detect internal flaws in structural steel welds?
- Magnetic particle testing (MT)
- Dye penetrant testing (PT)
- Ultrasonic testing (UT) (Correct answer)
- Visual testing (VT)
Correct answer: Ultrasonic testing (UT)
Ultrasonic testing (UT) transmits sound waves through material and detects internal discontinuities by analyzing reflected signals, making it ideal for subsurface weld defects.
Question 2: What is the minimum curing period for normal-weight concrete flatwork to achieve adequate strength gain before removing forms, according to ACI 308?
- 1 day at any temperature
- 3 days in moderate conditions
- 7 days minimum for most applications (Correct answer)
- 28 days for all applications
Correct answer: 7 days minimum for most applications
ACI 308 recommends a minimum 7-day moist curing period for most concrete flatwork using Type I/II cement to ensure adequate early-age strength development.
Question 3: During roofing installation, a field inspector observes that membrane laps are only 2 inches wide instead of the specified 3 inches. This deficiency primarily risks:
- Increased insulation R-value
- Water infiltration at the seam under wind-driven rain (Correct answer)
- Reduced fire rating of the roof assembly
- Overloading the structural deck
Correct answer: Water infiltration at the seam under wind-driven rain
Insufficient lap width reduces the seam bond length, making it prone to separation and allowing water to infiltrate the building envelope during rain events.
Question 4: A field builder reviewing reinforcing steel placement finds the bottom mat in a slab has 3/4-inch cover instead of the specified 1.5-inch clear cover. The BEST course of action is:
- Accept it since it is close enough
- Reject and require repositioning to meet specification before concrete placement (Correct answer)
- Add extra concrete thickness to compensate
- Note it in the log but allow placement to continue
Correct answer: Reject and require repositioning to meet specification before concrete placement
Insufficient cover reduces corrosion protection and fire resistance; reinforcing must be repositioned to meet the specified cover before concrete is placed.
Question 5: What does a pull-out test on a post-installed anchor evaluate?
- The chemical composition of the anchor bolt
- The installed anchor's load capacity in tension within the base material (Correct answer)
- The torque applied during anchor installation
- The alignment of the anchor relative to the plan
Correct answer: The installed anchor's load capacity in tension within the base material
A pull-out test applies a measured tensile load to a post-installed anchor to verify that it achieves the required holding strength in the substrate.
Question 6: When inspecting gypsum board (drywall) installation, which fastener condition requires rejection?
- Fastener heads set slightly below the panel surface (dimpled)
- Fastener heads flush with the panel surface
- Fastener heads that have broken through the paper face (Correct answer)
- Fasteners spaced at 12 inches o.c. in the field
Correct answer: Fastener heads that have broken through the paper face
Fasteners that break through the gypsum board paper face lose their holding capacity and must be rejected and replaced with new fasteners nearby.
Question 7: Which of the following is the correct sequence for a field quality inspection of a welded steel connection?
- Final inspection → cleaning → welding → preheat check
- Preheat check → welding → cleaning → visual inspection → NDT if required (Correct answer)
- NDT → welding → cleaning → preheat check → visual inspection
- Cleaning → NDT → preheat check → welding → visual inspection
Correct answer: Preheat check → welding → cleaning → visual inspection → NDT if required
The correct sequence ensures preheat is verified before welding, the weld is cleaned after welding, and visual inspection followed by NDT confirms weld quality.
CFB Quality Control & Inspection 3
Which non-destructive testing method uses high-frequency sound waves to detect internal flaws in structural steel welds?