Effect of Calcareous Fillers on Bituminous Mix Aging

Abstract

The aim of this paper is to explain phenomena associated with bitumen aging and establish design patterns that contribute to optimizing the aging resistance of bituminous mixes based on the rational addition of calcareous fillers (hydrated lime and limestone filler).The potential benefits of using fillers to improve aging resistance are well-known. However, concepts related to the biphasic filler-bitumen system affecting some of the main characteristics of mixes are not always considered.In this paper, a new study procedure, "Universal de Caracterización de Ligantes" (UCL®), a method for characterizing both conventional and polymer-modified binders developed at the Technical University of Catalonia, has been applied. In addition, rheological tests have been performed with the dynamic shear rheometer and non-routine procedures such as macromolecular analysis (e.g. gel-permeation chromatography and infrared spectroscopy). These techniques have provided greater insight into the causes and effects of aging based on the changes undergone by the bituminous binder.The obtained results show the advantages of incorporating calcareous fillers into bituminous mixes provided that filler content does not exceed a "critical concentration" determined by the type of filler and binder to be used. Moreover, some variations on the concept of critical concentration of filler in bituminous mixes have been found, notably those resulting from the degree of mix aging and use of polymer-modified bitumens.Bianchetto, Miró, Pérez-Jiménez, Martínez 3 INTRODUCTION Aging is one of the reasons for the failure of bituminous wearing courses. The consequences of this process are a decrease in the level of comfort and safety and an increase in pavement maintenance and rehabilitation activities, which results in higher costs.Most of the research to date has focused on binders in isolation. The "aging" factor has been assessed by accelerated simulation of some of the mechanisms affecting this deterioration process.Petersen (1), Khandal and Chakraborty (2) and other researchers observed that the primary causes of aging are light fraction volatilization and oxidation resulting from a "dual mechanism" by which oxygen is combined with highly reactive elements of the hydrocarbon. This gives rise to the appearance of cyclic-aromatic compounds. A slow oxidation process of benzylic carbons, whose main final product is ketones (3), is then initiated.Classical characterization methods do not allow material behavior to be accurately predicted during service time since void content, aggregate-binder interaction and the effect of mineral filler and other additives dramatically change the characteristics of bitumen in the final mix (4). The irruption of polymer-modified binders into the road industry brought into question the validity of these processes.The past few years have witnessed the emergence of new techniques for simulating transformation processes undergone by bitumen in bituminous mixes as it ages and the way it acts. Such methodologies consid...

Evaluación del desempeño de mezclas asfálticas convencionales y con filler de cal hidratada expuestas a humedad en climas fríos

“…Los beneficios potenciales del uso de rellenos para mejorar la resistencia al envejecimiento son bien conocidos. Sin embargo, no siempre se consideran conceptos relacionados con el sistema bifásico filler-betún que afectan a algunas de las principales características de las mezclas (Bianchetto et al, 2007).…”

“…Petersen et al, 1987). Bianchetto et al (2007) muestran las ventajas de incorporar cargas calcáreas en las mezclas bituminosas, siempre que el contenido de carga no supere una concentración crítica determinada por el tipo de carga y ligante a utilizar.…”

Fillers Influence on Hot-Mix Asphalt Mixture Design and Performance Assessment

“…Filler's contribution to the properties of HMA mixtures subjected to transient loading and climatic conditions are studied based on types and concentrations [1][2][3][4][5][6][7]. Fillers tend to improve the asphalt viscous flow and delay aging process [8]. Many researchers believe that the asphalt mastic created in the asphalt mixture is due to the interaction between asphalt and fillers [9,10].…”

Reduction in the use of mineral aggregate by recycling cellulose ashes to decrease the aging of hot asphalt mixtures

“…Incorporating contribution filler generates changes in the properties of bituminous continuous medium making the bitumen a thicker with the aim of modifying its vicious flow and improving adhesion between the aggregate-binder. This provides thickening of the film that covers the aggregates, decreasing volatilization and oxidation processes and supplying increased cohesion, slowing the mixture aging process [3,20,21]. Another benefit and/or filler action that contributes to mixture aging resistance is the ''obstacle effect" established by Gubler et al (1999).…”