A determination of the sonic modulus of early age concrete

The problem which the writer is analyzing in this thesis was suggested by Professor E. W. Carlton of the Civil Engineering Department. It is a determination, by use of sonic testing equipment, of the growth in the sonic modulus of early age concrete. Since 1938 when T. C. Powers published his paper, Measuring Young\u27s Modulus of Elasticity by Means of Sonic Vibrations , in the proceedings of the American Society of Testing Materials, Vol. 38, Part II, a great deal of work has been done on the applications of sonic testing of concrete. It began a new era in concrete testing, that of nondestructive testing. Prior to 1938 and still today, most tests on concrete are of a destructive nature, that is, physically breaking the specimens. Sonic testing of concrete does not damage the specimens, and they may be tested over and over again. This is a distinct advantage over destructive testing where a specimen can only be tested once. The largest practical application of sonic testing has been in concrete deterioration testing, namely freezing and thawing. Here the specimen can be tested as it progresses through accelerated freezing and thawing cycles, resulting in a large saving in time and materials. Another advantage is its simplicity, accuracy and speed. Today there are two principal methods of sonic testing. One is the pulse-velocity method, and the other is the resonant frequency method. The pulse-velocity method is a field method for testing the concrete in situ. Basically, it is the measurement of the velocity of vibration waves traveling through the concrete. The modulus of elasticity can then be calculated from the velocity of these vibrations. These vibrations can be generated by a single physical impact, by electronic devices, or by a combination of the two. This method is not too applicable to laboratory testing because the size of laboratory specimens make the measurement of the velocity wave too difficult. The resonant frequency method is a laboratory method for testing the concrete and is the method of test used in this thesis. Basically, it is the measurement of the fundamental frequency of vibration of the specimen. The specimen is supported at the nodal points and vibrations are induced in the specimen. The modulus of elasticity can then be computed from the fundamental frequency --Introduction, pages 1-2