Test Methods For The Fracture And Fatigue Crack Growth Behavior Of Hot Mix Asphalts

The service life and mechanical properties of bituminous mixtures are greatly affected by distress problems such as fracture, thermal cracking, and fatigue cracking of the asphalt layers. The fracture and fatigue crack growth (FCG) behavior of bituminous mixtures are difficult to quantify due to material-, test-, and equipment-related uncertainties. The goal of this study is to introduce a systematic fracture and fatigue crack growth testing approach for hot mix asphalts (HMAs). The objective is to experimentally evaluate the fracture resistance and fracture toughness behavior of a dense-graded HMA material at different temperatures and varying thicknesses. The effect of thickness on the fracture tests is investigated to identify plane-stress or plane-strain conditions. The FCG behavior for a single stress ratio and frequency at 5, 25, and 40°C is also evaluated and investigated. The tensile and fracture properties are recorded using indirection tension tests (IDT) and disk-shaped compact tension (DCT) tests. Disk compact tension specimens exhibit more advantages in evaluating cracking resistance and fracture behavior. Fracture toughness tests and load-controlled fatigue tests according to ASTM standards are performed. Digital image correlation (DIC) is employed to measure the crack length, determine the stress intensity factor for crack opening, and observe the stress fields on the plastic zones of the crack. Using linear elastic fracture mechanics (LEFM) the Paris, Walker, and Forman law material constants are determined and modeled to the experimental data to predict the linear crack growth region