Volume 37, Issue 2 (March 2009)
Evaluation of Semicircular Bending Test for Determining Tensile Strength and Stiffness Modulus of Asphalt Mixtures
The semicircular bending (SCB) test has been shown to possess several advantages over other tests in characterizing asphalt mixtures in previous studies. This research study evaluates the SCB test for determining the tensile strength and stiffness modulus of the paving material with numerical simulation and laboratory experimentation. An analytical model describing the tensile stress at the middle point of the lower surface of the specimen in the SCB test was developed based on the plane assumption in mechanics of materials. Analysis using the finite element method indicated that the error induced by the model was within 2 %. Laboratory experiment carried out on three types of asphalt mixtures at various temperatures showed that the strength of the material by the SCB test was nearly 50 % higher on average than that by the flexural beam bending (FBB) test due to such factors as complexities in stress and strain states as well as nonlinearity and viscoelasticity of the material. Laboratory experiment also showed that the stiffness moduli for 10–40 % of maximum load from the FBB test and from the SCB test were in a well-defined linear relationship with differences less than 10 %. In addition, based on finite element analysis, a practical approach for determining stiffness modulus of asphalt mixtures using deflection at the middle point of the lower surface of the specimen in the SCB test was established.