The behaviour of a recycled road base aggregate and quartz sand with bender/extender element tests under variable stress states

The paper focuses on laboratory testing investigating the small strain dynamic properties of a recycled road base material of a single fraction. A widely examined quartz sand was also used in the study for comparison purposes. The shear wave velocities (Vs) and primary wave velocities (Vp) were measured in both isotropic and anisotropic stress states with bender/extender element inserts implemented in a stress path triaxial apparatus. Subsequently, the small strain constrained modulus (Mmax), Young’s modulus (Emax) and Poisson’s ratio (ν) were derived and further analysed. For the measurement of sample volumetric strains, particularly under the application of stress anisotropy, local strain gauges were used to capture the changes of their radius while the deviatoric compressive load was gradually increased. The responses of the two materials during isotropic compression and swelling as well as under the application of stress anisotropy were thoroughly stated and quantified.