Development of Shear Tester with Normal Stress (STNS) for Asphalt Concrete Mixes

Abstract

The Shear Tester with Normal Stress (STNS) is developed in this study for measuring the fundamental shear properties of asphalt mixes at a low cost. The device can shear an asphalt concrete specimen subjected to controlled normal stress of 113 kPa (16.35 Psi). A total of 72 test specimens of three asphalt mixes, produced at different daily times, were tested for the Frequency Shear Test at Normal Stress (FSNS) and Repeated Shear Test at Normal Stress (RSNS). The FSNS test was used to measure the dynamic shear modulus |G*| and shear phase angle (δ), whereas the RSNS test was conducted to measure the permanent shear deformation for asphalt mixes. The results showed that the average values of the measured |G*| and (δ) have generally the same trends over the shear load frequencies for all mixes. All sample groups have average permanent shear deformations of less than 1.1 mm at 5000 repeated shear loads. The shear phase angle had comparable variabilities to that of the dynamic shear modulus at high shear load frequencies. The measured permanent shear deformations had variabilities of less than 17% for all mixes.