AAI AAI Substrate Preparation & Surface Conditions 2 — Questions and Answers
Question 1: When drilling into cracked concrete for adhesive anchors, what additional design consideration is required?
- Use of crack-rated adhesive and reduced characteristic resistance values (Correct answer)
- Simply choosing a larger diameter anchor
- Filling the crack with epoxy before drilling
- No special consideration is needed
Correct answer: Use of crack-rated adhesive and reduced characteristic resistance values
Cracked concrete reduces the confinement around the anchor, so ACI 318 requires crack-rated products and appropriately reduced capacity values in design.
Question 2: How should a diamond-cored hole be prepared differently than a hammer-drilled hole for adhesive anchors?
- Diamond-cored holes require additional roughening because the walls are smooth (Correct answer)
- Diamond-cored holes need no extra preparation because they are cleaner
- Diamond-cored holes must be filled with grout before anchoring
- No difference exists between the two preparation methods
Correct answer: Diamond-cored holes require additional roughening because the walls are smooth
Diamond coring produces a smooth, polished borehole wall that reduces mechanical keying; roughening or special adhesives are required to achieve rated bond strength.
Question 3: Which condition requires the installer to consult the adhesive manufacturer before proceeding?
- Lightweight concrete substrate (Correct answer)
- Normal-weight 4,000 psi concrete
- Standard damp concrete at 65°F
- Cleaned dry hole at room temperature
Correct answer: Lightweight concrete substrate
Lightweight concrete has different porosity, tensile strength, and bond behavior than normal-weight concrete, requiring manufacturer confirmation of product suitability and capacity values.
Question 4: What is the minimum concrete compressive strength (f'c) typically required for adhesive anchor installations per ACI 318?
- 2,500 psi (17 MPa) (Correct answer)
- 1,000 psi (7 MPa)
- 5,000 psi (35 MPa)
- 8,000 psi (55 MPa)
Correct answer: 2,500 psi (17 MPa)
ACI 318 and most ICC-ES evaluation reports specify a minimum f'c of 2,500 psi as the baseline for published adhesive anchor characteristic bond strengths.
Question 5: Why must the hole diameter for an adhesive anchor be within the manufacturer's specified tolerance?
- An oversized hole reduces bond area and an undersized hole prevents full insertion (Correct answer)
- Hole diameter only affects the anchor's appearance
- Larger holes always produce stronger anchors
- The tolerance only matters for mechanical anchors, not adhesive ones
Correct answer: An oversized hole reduces bond area and an undersized hole prevents full insertion
Adhesive anchor bond strength depends on the annular gap filled by adhesive; holes outside tolerance change adhesive volume, bond area, and anchor alignment.
Question 6: Before installing adhesive anchors, how should an installer verify that the substrate does not contain hidden rebar that would conflict with the anchor location?
- Use a rebar locator or cover meter to scan the concrete surface (Correct answer)
- Probe the hole with a steel rod after drilling
- Review only the original design drawings
- Tap the surface with a hammer to listen for rebar
Correct answer: Use a rebar locator or cover meter to scan the concrete surface
A rebar locator (cover meter or GPR scan) non-destructively maps embedded steel, allowing anchor locations to be adjusted before drilling begins.
AAI AAI Substrate Preparation & Surface Conditions 2
When drilling into cracked concrete for adhesive anchors, what additional design consideration is required?