A comparison between bending and diametral fatigue tests for bituminous materials: Fid-Bau Portal

A comparison between bending and diametral fatigue tests for bituminous materials

Khalid, H. A.

Abstract This paper presents laboratory fatigue results on five bituminous paving mixtures, including a Hot Rolled Asphalt, a Dense Bitumen Macadam and a Stone Mastic Asphalt. Centre-point bending fatigue tests were conducted on prismatic beam samples cut from laboratory prepared slabs and the strain/fatigue life relationships were achieved for the five mixtures. Cylindrical samples were produced by coring identical slabs of the five mixtures and were tested in the diametral fatigue test to establish the corresponding fatigue relationships. Also, the theoretical approach used to deduce the applicability of the diametral test as a fatigue testing tool for bituminous materials is discussed. A typical pavement model was then developed to calculate the load-induced strains in each of the five mixtures used as wearing courses. These strains, together with the developed fatigue relationships, were used to predict the fatigue lives of the five mixtures from the two techniques. The main findings of the paper are that, at low strain levels, the fatigue lines of the five mixtures obtained from the diametral test assume similar relative positions to those from bending tests. However, there is a significant difference in the estimated fatigue lives resulting from the two techniques. Fatigue equivalence ratios have been derived to emphasize this difference.