The Windsor Probe Test and Its Reliability

The Windsor Probe Test And Its Reliability 4229 Lafayette Center Drive. Suite 1300C Chantilly, VA 20151

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The Windsor Probe concrete test was developed in the mid-1960s in a joint effort between the New York Port Authority and the Windsor Machine Company. It is a penetration resistance test based on the surface hardness of a concrete element. Once established, the surface hardness is used to estimate concrete strength.

The test propels a ¼-inch diameter steel probe into a concrete element using a precision powder 0.32caliber cartridge. The penetration resistance is a measure of the exposed length of the probe.

Is The Windsor Probe Test Reliable?

Short answer…yes and no. Let’s start with yes.

The American Society for Testing and Materials (ASTM) and the American Concrete Institute (ACI) recognize Windsor Probe testing as an acceptable method to estimate in-situ concrete strength.

However, Windsor Probe test results must be correlated with known compressive strength values from concrete cores or cylinders obtained from the specific concrete mix being tested. Regression analysis is used to determine a “best-fit” relationship between the penetration resistance and compressive strength.

The Windsor Probe test is considered a ‘surface test.’ Therefore, harmful effects such as carbonation (affecting surface hardness) can inaccurately high test values. Other parameters that affect test results include the type, size, and distribution of coarse aggregate and the location of embedded reinforcing steel. The photos below demonstrate core samples obtained from two different concrete columns in the same structure.

Compressive strength test results varied between 440 psi and 1,920 psi.

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