Correlation of Small Strain Stiffness and Strength of Hot Mix Asphalt

The objective of the research was to investigate if stiffness and strength are correlated in asphalt mixtures and which stiffness/strength parameters result in similar mechanical responses. The research was limited to dynamic modulus |E*| and Simple Shear Tester (SST) shear modulus |G*| testing to obtain small strain stiffness, and strength was measured using the triaxial shear strength and indirect tensile strength tests. Generally, a good correlation of stiffness and strength properties was obtained for the dense-graded mixtures when the test specimens were fabricated using asphalt-plant-produced mixtures and were compacted with the gyratory compactor. However, for young and aged pavement cores, the correlation between stiffness and strength was poor to non-existent. Contrary to the dense-graded mixtures, some of the stiffer Stone Mastic Asphalt (SMA) mixtures had lower strength than the softer mixtures. The research suggests that due to the different loading and straining patterns caused by the test set up, the compressive modulus |E*| and SST shear modulus |G*| measure different material responses to mechanical loading.