Characterisation of Fatigue Performance of Selected Cold Bituminous Mixes

Fatigue cracking of bound pavement layers is one of the primary structural distress modes found in the flexible pavements. While the fatigue behaviour of hot-mix asphalt has extensively been studied in the past, the fatigue behaviour of cold- bituminous mixes is relatively unknown. The fatigue performance of cold mixes is influenced by interaction of both binder, mineral aggregates, moisture as well as the use of active filler. This paper discusses the results of cold mix beam test methods developed using four point beam testing apparatus. The fatigue, strain-at-break and flexural stiffness (master curves) properties of typical cold-mixes (blends of crushed limestone rock and reclaimed asphalt pavement (RAP) millings) were investigated. These mixes were treated with either bitumen emulsion or foamed bitumen. The main focus is on the characterisation of fatigue performance of these mixes by providing a understanding of the fatigue properties and the link of the strain-at-break and visco-elastic behaviour to the performance of these mixes. It was found that the cold mix fatigue relationships are linear on a log-log scale. The influence and the effect of the active filler were investigated and it was found that the addition of a small amount of active filler (1% cement) has a different effect, depending on the type of aggregate blend and binder.