Development of rating curves for concrete rebound hammer on concrete specimens from local aggregates

Frequently engineers find it imperative to determine the compressive strength of concrete as it exists in a structure. There are two methods of making this determination, either by a destructive or a non-destructive test. The destructive test has the disadvantage of being costly, time consuming, and detrimental to the appearance of the concrete surface. The non-destructive, pulse-velocity, sonic measuring devices used to determine the compressive strength of concrete in the field also have the disadvantage of high cost due to the large initial cost of the equipment. A relatively new non-destructive testing device has been developed which may replace the methods described above and also be an invaluable aid in other aspects of concrete control. This new piece of equipment, developed in 1948 by a Swiss Engineer, is the Concrete Test Hammer which is sometimes referred to as the Rebound Hammer . This testing device is said to have the capability of determining the compressive strength of concrete by relating this physical property to the rebound of a steel hammer from the concrete surface. The objectives of this thesis are to: Verify the accuracy of the Compressive Strength-Rebound Number rating curves provided by the manufacturer of the Rebound Hammer. Develop additional Compressive Strength-Rebound Number rating curves tor concrete containing aggregates common to Southeast Missouri. Augment the Compressive Strength-Rebound Number rating curves provided by the manufacturer by obtaining data from concrete which is 1-7 days old. Develop Compressive Strength-Rebound Number rating curves for concrete blocks aged from one to twenty eight days. Develop the proper technique for the operation of the Rebound Hammer. This subject was selected because of the author\u27s interest in concrete construction and methods of concrete control. Secondly, research in this field will be of value to the U.S. Army, Corps of Engineers, who have recently purchased several Concrete Test Hammers which have not been accepted for use in concrete control procedures at the present time. The tests included herein are for the Rebound Hammer held in the horizontal and vertically downward position. The rating curves and data for the hammer in the vertically upward position were obtained arithmetically --Introduction, pages 1-2