Technique for measuring the elastic properties of bitumens, tars and soils under dynamic loading

A technique is described for the measurement of the components of the complex (dynamic) Young's modulus (E*) and the complex rigidity modulus (G*) of bitumens, tars and soils under sinusoidal loading. The equipment is capable of measuring the complex Young's modulus up to about |E*| = 5 × 10 10 dyn/cm 2 (10 6 lb/in 2 ) and the complex rigidity modulus up to |G*| = 2 × 10 10 dyn/cm 2 (3 × 10 5 lb/in 2 ) over the frequency range 5 to 500 c/s and at temperatures between -20 and +30° C. To measure the complex Young's modulus, an axial sinusoidally varying force is applied to a cylindrical specimen by a moving-coil vibrator. Piezoelectric gauges are used to convert the force applied to the specimen, and the displacement of its driven end, into voltages, which are measured on a phase-sensitive voltmeter. The complex modulus is derived from a comparison of these voltages with those obtained using a steel calibration spring. For the measurement of the complex rigidity modulus, the material is sheared in the annulus between two cylinders, the inner being driven by the vibrator. The same two gauges now serve to measure the force applied to the inner cylinder, its displacement and their relative phase.