A study of wave velocities and poisson ratio of recycled concrete aggregate

The dynamic properties of two uniform recycled concrete aggregates (RCA) were investigated with a focus on shear wave velocities (Vs), primary wave velocities (Vp) and Poisson ratio (ν). The geotechnical characterization of these materials, one RCA with a fraction of 1.18-2.36 mm and the other with a fraction of 0.60-1.18 mm, was implemented through the quantification of particle shape descriptors, monotonic drained triaxial tests and one-dimensional compression tests. The grain damage of the RCA was quantified by examining the grading curves of the samples before and after the performance of the one-dimensional compression tests. Bender and extender element tests were carried out on dry samples under isotropic conditions of the confining pressure in order to investigate the dynamic properties of the RCA and comparisons were implemented between bender/extender elements and resonant column tests in torsional and flexural modes. The laboratory test results indicated that during the isotropic compression of the samples, Vs showed slightly higher sensitivity to pressure than Vp and the Poisson ratio was found to be dependent on pressure. However, during the isotropic unloading stage, Vs and Vp showed similar sensitivity to pressure and the Poisson ratio was found almost to be independent of pressure change. An empirical-type model proposed in the literature for crushed rock of irregular-shaped grains predicted within satisfactory limits the small-strain shear modulus of the RCA. The small-strain material damping in shear and the strain-dependent modulus and material damping were investigated and are discussed for a limited number of tests.