Proceed SA of Switzerland is marking a special milestone in its history. Its widely used test hammer for fast and reliable assessment of concrete quality, the Original SCHMIDT has just turned 50 - and shows no signs of losing its popularity, a company spokesman says.

"This purely mechanical impact device, which has remained virtually unchanged for many years, is now indispensable in concrete testing and monitoring," the spokesman adds.

Elaborating on how it works, he says: "The measuring principle is very simple: position the device, press it against the concrete surface until the impact is triggered and then take a reading. The so-called rebound value 'R' can be directly related to the compressive cube strength and is, therefore, a measure of the quality, that is, the strength of the concrete.

"This non-destructive test method has been standardised for more than 30 years. Owing to its simple handling, many measurements can be made in any areas of the structure in a very short time. The detection of weak points, such as local differences in hardening, etc, is made considerably easier by the statistical evaluation of the measurements.

"The non-destructive Original Schmidt test hammer for concrete is, therefore, unbeatably economical, compared with all other methods. This has led to the creation of a whole product family with an extensive range of applications, such as the measurement of masonry mortar, thin-walled parts, fired clay and large foundations, such as dams, roads and airstrips.

"The mechanical structure of the devices appears very simple, but the secret lies in the detail. To date, only Proceq SA engineers have succeeded in mastering the complicated interplay between 'spring mechanism', hammer and plunger so that the basis for measurement has remained constant over this long period up to the present."

"Proceq's Tico ultrasonic instrument can be used to confirm measurements taken by the Original SCHMIDT test hammer for concrete, further enhancing the accuracy of the measurement of compressive cube strength," he adds.