CCI Concrete Testing & Evaluation 3

Question 1

The Windsor probe test is used to estimate which concrete property non-destructively?

Accepted Answer

In-place compressive strength

Answer

The Windsor probe system estimates in-place compressive strength by measuring the penetration depth of a hardened steel probe driven by a powder-actuated driver.

Question 2

According to ASTM C805, rebound hammer readings should be taken at a minimum of how many points on a test area to get a valid average?

Accepted Answer

10 readings

Answer

ASTM C805 requires a minimum of 10 rebound readings per test area, discarding any that differ from the median by more than 6 units.

Question 3

Carbonation of concrete surface affects rebound hammer readings by causing them to be:

Accepted Answer

Higher than actual strength

Answer

Surface carbonation hardens the concrete surface layer, causing the hammer to read higher than the actual bulk compressive strength of the element.

Question 4

When cores are taken to evaluate structural concrete strength per ACI 318, what is the minimum number of cores required per location of concern?

Accepted Answer

3 cores

Answer

ACI 318 requires a minimum of three cores per questionable location; the concrete is considered adequate if the average of three cores ≥ 0.85f'c and no single core < 0.75f'c.

Question 5

What correction factor is applied to a concrete core with a length-to-diameter (L/D) ratio of 1.75 when converting to the equivalent standard cylinder strength?

Accepted Answer

Multiply by a factor less than 1.0

Answer

Cores with L/D below 2.0 require a correction factor less than 1.0 per ASTM C42, as shorter specimens register higher apparent strength than standard 2:1 cylinders.

(CCI) Certified Construction Inspector Practice Test

(CCI) Certified Construction Inspector Practice Test

CCI Concrete Testing & Evaluation 3