A Comparative Study on Dynamic Modulus of Asphalt Concrete with Different Loading Mode

Abstract

Abstract Loading mode is an important but under-estimated factor for the dynamic modulus test of asphalt concrete. This article presents a comparative laboratory study of using uniaxial-compression, two-point bending and three-point bending to test dynamic modulus of 12.5 mm asphalt concrete (AC) with two asphalt materials. Dynamic moduli |E*| and phase angle φ between different tests were compared and analyzed in multiple ways. Results show that good correlations exist between |E*| and φ of different loading modes, but the values of |E*| and φ, as well as their temperature sensitivities are different. When subjected to bending, AC demonstrates a smaller |E*|, a larger φ, and is more thermal sensitive. The Black Space diagram also shows that the linear viscoelastic property and the pure elastic modulus of AC under different loading modes are different. It is indicated from master curve analysis that the loading mode has a significant influence on |E*| and φ, and the main reason is that the stress state varies with the loading mode. The influence of the loading mode becomes more significant as the temperature increases. The small size specimen of three-point bending brings in larger variation, and the inferior aggregate structure causes a smaller |E*|. However, with at least four replicates, the small size specimen in this study can still represent the overall characteristics of material. Statistical analysis shows that dynamic modulus from the three loading modes are significantly different, indicating that when choosing a test method for the dynamic modulus test, the influence of the loading mode should be taken into consideration.