Deformation characteristics and prediction of unbound volcanic ash pavement based on the mechanistic-empirical design guide

•Loads and water content are correlated to the permanent deformation behavior of volcanic ash.•The permanent deformation of volcanic ash are predicted by prediction models.•The accuracy of the prediction models is validated using 10 sets of experiments.•Improved methods of volcanic ash are proposed. The objective of this study is to determine the deformation characteristics and prediction methods of volcanic ash in pavement ME design. For this purpose, the chemical composition, physical properties and mechanical properties of volcanic ash have been investigated. The results show that volcanic ash is an unbound fine-grained material with a maximum particle size of