Prediction of fatigue cracking in cement treated base courses

Stabilizing materials with cement is an attractive option to allow less suitable materials to be used as base-course or subbase. This is especially the case when good quality natural materials are not available or scarce. The problem with cement treated materials however is that they are brittle in nature and are sensitive to overloading. Pavements can only be designed properly when appropriate transfer functions, e.g. fatigue relationships, are available. Unfortunately the amount of information that is available on the fatigue performance of cement treated materials is much less than that is available for asphalt mixtures. Furthermore the information that is available is often not applicable to the specific condition. This paper describes the development of a field fatigue relationship for sand cement treated bases which are often used in the Netherlands. The relationship is based on an extensive analysis of the SHRP-NL data base which contained performance data of a number of pavements with a cement treated base. Furthermore the results will be presented of extensive finite element analyses which have been made to analyze the stress conditions near cracks and to determine the effect of load transfer. Combining all these results, an endurance limit for cement treated bases could be developed that can be used for the design of long life pavements.