MODELS FOR PREDICTING RUTTING ON ASPHALT ROADS

This paper presents the main results of a large test road programme implemented as part of the Finland Asphalt Research (ASTO) Project 1987-93, and followed up since then. The factors influencing pavement wear resistance were studied closely. Wearing decreased by 30% on average during 1991-94. Wearing is strongly influenced by weather conditions; it is 30% less in eastern Finland, which is cold and dry, than in the south west coastal area, which is warm and moist. Road wear is closely correlated with the Nordic abrasion value. A model was developed for predicting wear of different mass types. It was found that the polymer-modified binder PmB1 improves wearing properties by 10% and deformation properties by 30%, compared with bitumen B-120. For some combinations of aggregate and binder, wearing properties can be improved by adding an adhesive agent. The paper presents a new rut calculation algorithm, based on road test results, and an illustrative example of its use. The SRK value can be modified for a specific mixture type, or by binder and additives. Wear in 1997 was below average wear for 1991-94 by 30%, largely because of lighter tyre studs. The ratio of wear area to rut depth is affected by pavement width. Improved deformation models allow for mixture type, binder, and additives.