In-Place Evaluation of Concrete

The two new methods for estimating the strength of concrete in structures are: (1) The Windsor probe test; and (2) the pull-out test. The Windsor probe measures the penetration resistance of concrete. The Windsor probe consists of a power-actuated gun or driver, hardened alloy probes, loaded cartridges, a depth gage for measuring penetration, and related equipment. The probe is 0.25 in. (6.3 mm) in diameter, 3.125 in. (79.4 mm) long, and has a frusto-conical point. A pull-out test measures, with a dynamometer, the force required to pull out from concrete a specially shaped steel rod with an enlarged end that has been cast into that concrete. The pull-out force is related to compressive strength, the ratio of the pullout-compression strength being between 0.1 and 0.2. The two new pieces of equipment which are either simplified versions of equipment already available or are based upon well-established theoretical concepts are: (1) The PUNDIT; and (2) the Concrete Maturity Meter. The PUNDIT is a light-weight portable ultrasonic concrete-tester, whereas the Concrete Maturity Meter measures maturity of concrete by use of a probe.