MODELLING OF CRACK PROPAGATION IN FLEXIBLE PAVEMENTS

In pavement design, the pavement life in terms of cracking is usually determined by means of calculating the tensile strain due to the design traffic load at the bottom of the asphalt layer. This strain value is then used together with a fatigue relation to determine the number of load repetitions to failure. Quite often correction factors are applied on this number to cater for the effects of lateral wander and healing and sometimes a factor that is related to the thickness of the asphalt layer is used as well. This approach might be useful for the design of new pavements with an unbound base but is insufficient when the pavement has a cement treated base, that exhibits cracks due to shrinkage as a result of hardening and temperature changes, and in case an overlay has to be designed on top of a cracked pavement. In those particular cases, one has to evaluate the presence of existing cracks on the performance of the asphalt layers that are placed on top of the cracked layers. This paper describes how the resistance to cracking of asphalt materials can be determined, and how this information can be used for pavement design purposes. For the covering abstract see ITRD E119486.