Reliability study on fracture and fatigue behavior of pavement materials using SCB specimen

Reliability of semi-circular bending (SCB) specimen for measuring the fracture behaviour of pavement materials under static and cyclic loadings has been examined. This study is divided into three phases. In the first phase a comparison between different equations suggested by several specifications and by researchers has been made. Three different SCB specimen types used for predicting mixed mode fracture behaviour of pavement materials have been evaluated in the second phase. In the third phase the applicability of using SCB specimen in predicting fatigue crack growth rate in pavement materials under mode I has been examined. 3-D finite element analysis (FEA) has been adopted.Although there is conformity of the specimen dimensions there is no unique equation to measure the fracture parameters. The prediction of the fracture behaviour of pavement materials obtained by the present FEA is acceptable. The value of KIC predicted from each specimen type has been examined for its reliability by using the concept of maximum size of non-damaged defect (dmax). Mode I fracture toughness predicted by SCB-1 (standard specimen) is the only consistent value, while SCB-2 and SCB-3 (specimens with shifted crack) failed in this reliability test. To check the reliability of SCB specimen for measuring the fatigue behaviour of pavement materials, the relation between the stress intensity factor range (ΔK) and the crack mouth opening displacement (CMOD) through the whole life of the specimen has been examined. A good relation is found between the CMOD and the ΔK through the whole life of SCB specimen.