Fast solidification kinetics of parts of bituminous binders

Hartmut R Fischer,Bastiaan Ingenhut,Bert Dillingh

doi:10.1617/s11527-015-0723-2

Abstract

Abstract A quantification of the kinetics of formation of the micro-phases in bitumen during cooling as it occurs in applications, e.g. a road pavement will enable a better prediction of the performance of asphalt in models and an understanding of functional properties and their development in time. This microphase formation is part of the process of physical ageing (hardening) and starts almost immediately after or instantaneously during cooling. The earlier proposed process of liquid liquid demixing within bitumen upon cooling is followed by a, at the beginning homogeneously nucleated and three-dimensional crystallization, which changes in the course of crystallization to 2-dimensional crystal growth and mixed nucleation, both homogeneous and heterogeneous.

Highlights

Bituminous binders undergo changes in properties with time, even in the course of annealing, storage and/ or use at room temperature—a phenomenon longThe study of the process of physical hardening during extended storage at isothermal conditions dates back to 1936 when a report by Traxler and Schweyer [2] was published
The process of increasing viscosity during isothermal storage was explained by the structural sol–gel transition [3] according to the micellar model of bitumen structuring [4]
The term ‘‘physical hardening’’ of asphalt binders was first used by Blokker and Van Hoorn [6] who explained the process by wax crystallization and asphaltene aggregation

Summary

Introduction

Bituminous binders undergo changes in properties with time, even in the course of annealing, storage and/ or use at room temperature—a phenomenon long. Increase of the stiffness of several asphalt binders after isothermal storage was found in a later investigation by Brown et al [5] Physical hardening which may be termed as ‘‘spontaneous hardening’’ is connected with the establishment of (new) interactions between polar and apolar components leading to the formation of discrete crystalline domains as observed earlier This process takes days to weeks if bitumen is stored at room temperature [5, 7, 8] respectively at low temperatures, but still above Tg [9,10,11,12] and is basically a thermally activated process. It is certainly of interest to quantify the kinetics of the formation of the micro-phases during cooling of bitumen as it occurs in the applications of bitumen, e.g. a road pavement, to better predict performance of asphalt in models and to understand the functional properties and their development

Experimental part

Results

Conclusions