Rejuvenator seal material (RSM) is designed to revitalize an aged asphalt binder by spraying it on the surface of roads. It restores the mechanical properties of the existing pavement. This paper studied the effectiveness of RSMs containing cooking oil residue, motor oil residue, coal oil, solvent, and virgin or styrene-butadiene-styrene (SBS) modified 60/70 bitumen to improve the behavior of an in-service pavement. Three stages were followed to formulate RSMs. To achieve the effective oil, the penetration grade and softening point changes of rolling thin-film oven (RTFO) + pressure aging vessel (PAV) aged 60/70 bitumen mixing with different percentages of oils were studied. Then, the penetration depth of benzene, toluene, and xylene in hot mix asphalt (HMA) samples were measured to choose the most efficient solvent. Finally, the penetration depth of RSMs with various mixing ratios in HMA mixes was measured to determine the mix design and application values (g/m 2 ). RSM-A (5% COR + 5% MOR and 60/70 bitumen), RSM-B (5% COR + 5% CO and 60/70 bitumen), and RSM-C (5%COR + 5%CO and SBS modified 60/70 bitumen) were selected for further assessments. Other than the aforesaid RSMs, RejuvaSeal was used as a generic commercial substance. A British Pendulum Test was used to ensure sufficient skid resistance to reopen the traffic soon after distributing the RSMs. Dynamic shear rheometer and bending beam rheometer tests were used to investigate the theological properties of extracted bitumen from the upper 1.5 cm layer of the pavement with and without RSMs. Moreover, the fatigue behavior of rejuvenated asphalt mixtures was studied by the 4-point bending test. Based on the results, all RSMs had a positive effect on the softening of the aged bitumen. All RSMs regained the fatigue performance of the aged binder. However, they showed the reverse effect on the rutting resistance. RSM-C containing 5% COR + 5% CO and SBS modified 60/70 bitumen considerably modified the theological properties of the aged binder even better than those mixtures rejuvenated by RejuvaSeal.

In Sweden, during recent years, a new type of mixing protocol has been applied, in which the order of mixing is changed from the conventional method. Improved workability and diminished mixing and compaction energy needs have been important drivers for this. Considering that it is the mastic phase, which is modified by changing the mixing order, it provides an interesting case study for explaining the mechanisms of workability in connection with the mastic phase. To do so, an analytical viscosity framework was combined with a mixture morphology framework to upscale to the mixing level and tribology principles to explain the interaction between the mastic and the aggregates. From the mastic viscosity protocol, it was found that the mixing order significantly affects the resulting mastic viscosity. To analyse the effect of this on the workability and resulting mixture performance, X-ray computed tomography was used to analyse mixtures produced by the two different mixing sequences. Mechanical testing was utilised to determine the long-term mechanical performance. In this part of the study, mastic viscosity as a function of particle concentration and distribution was directly coupled to improved mixture workability and enhanced long-term performance.

In this contribution the development and results of a new test protocol for measuring the viscosity of bituminous mastics are presented. The paper describes the various considerations that need to be taken into account when dealing with mastics, gives a detailed description of the sample preparation, the test set-up and the actual test performance. A demonstration of the use of the test procedure is given by developing three types of mastics in which different filler types, but a similar bitumen base, were used. From the results it can be seen that the developed protocol is sensitive enough to allow for detailed studies of the effect of filler shape, chemistry and size distribution. In continuation of this work, more types of mastics will be investigated and the test results will be linked to additional chemical and mechanical test results to further enhance the fundamental understanding of mastics.

The successful use of additives in modified asphalt mixtures, such as warm mix asphalt, depends largely on the effect such modification has on the mastic. Previous research indicated that such modifiers do not simply change the bitumen properties, but can also change the interaction between the filler and the bitumen matrix. Understanding the effect of the properties of the fillers, the bitumen and their interaction is thus important for future asphalt mix design. In order to investigate this and to define the dominant relationships, this paper combines a numerical and experimental approach. In the experiments, the viscosities of modified and unmodified mastics with different filler concentrations and types were systematically investigated utilizing a novel testing protocol. In the numerical analyses, the Finite Element Method was utilized for a micro-mechanical analysis, in which the shape and size of the filler particles were varied in the bitumen matrix. Combining the experimental and numerical results allowed for a detailed investigation of the effect of the interface properties, with and without modifiers. The research further indicated that the effect of the shape and size of the fillers varied, depending on the interface properties. From the research relationships were established between the overall mastic viscosity and the influence of the filler-bitumen interface, considering shape and size. The conclusion of this paper can thus be useful for the effective development of modified asphalt mixtures and gives strong indications towards future research directions.

Bituminous mastics influence many other important asphalt mixture properties in addition to their own allowance for the load transfer in the aggregate skeleton. The influence of bituminous mastics extents to the overall stability of a mixture, air void distribution, bitumen draindown during transport, a mixture's workability during the laying process, and the overall in-time performance of the pavement. To understand the properties of asphalt mixtures and their resistance to environmentally induced failure mechanisms, it is paramount to study not only bitumen and the asphalt mixture but also the mastic itself. Current asphalt design procedures do not take mastic behavior into account, however; this omission leads to a significant flaw in the ability to design and predict asphalt concrete response. This paper presents the results of an ongoing research project to enhance the understanding of the mastic phase as well as to develop a new test protocol to characterize mastics. A description is given of the measurements of mastic viscosity for different types of mastics in which the bitumen source is kept as a constant but with varying fillers as well as concentrations. Environmental susceptibility was investigated by subjecting the samples to aging and moisture conditioning. Biomass fillers were included in some of the mastics, in addition to some of the traditional fillers, to show their impact on the viscosity under varying conditions. Results showed that the developed test protocol was able to identify clearly the impact of filler properties on the mastic viscosity. A critical filler concentration was identified beyond which the viscosity behavior became nonlinear. The results also showed that moisture and aging had significant effects on the viscosity of mastics.

Understanding the influence of the fundamental parameters on asphalt mastic rheology is an important step towards improving the quality of asphalt mixtures. Due to the size of fillers and the sensitivity of the rheological behaviour of mastic, it is not always possible to study the effect of all parameters at one scale. Hence in this study, a theoretical framework is established for calculating the relative viscosity of asphalt mastics as a function of its filler concentration. Furthermore, a new test protocol is introduced for measuring the viscosity of asphalt mastic at higher temperatures and different filler concentrations.  To characterize the fillers and their agglomeration and distribution inside solid mastics, X-ray tomography, laser scattering, scanning electron microscopy, BET and Helium Pycnometery were utilized. To characterize the energy dissipation potential of the mastics under cyclic loads, as a function of their fillers, the dynamic mechanical analyzer was utilized. The research shown in this paper further investigated the various dominant parameters related to fillers and bitumen in mastics and relate them to the workability and resulting mechanical properties and developed an overall framework to connect different scales. The developed characterization protocols have the potential to allow the asphalt engineers to design their hot and warm asphalt mixtures on a more fundamental and thus sustainable basis.         

Sufficient coating, easy paving and good compaction are desirable parameters, which are approachable with the optimum viscosity of the mastic. In many studies, models have been developed for calculating the viscosity for different types of suspensions at various particle-to-fluid ratios. Unfortunately, none of them are applicable to asphalt mastics, since this material has a much wider range of mineral filler concentration from dilute to very concentrate. To give an overview of the existing viscosity models and to evaluate their range of applicability to asphalt mastics, an extensive literature review was performed. A new empirical framework was developed that removes some of the stipulated limitations of the existing theories.

The rheological characteristics of mastics, or filler-bitumen mixtures, as a component of asphalt mixtures have a significant effect on the overall in-time performance of asphalt pavements such as low temperature cracking, fatigue and rutting behaviour. Viscosity is one of the rheological characteristics which is influenced by the physico-chemical filler-bitumen interaction. In this study, after reviewing some of more often used theories for calculating the viscosity of suspensions, a framework for calculating the viscosity of mastics is presented. This framework aims at covering the entire range of filler concentrations that is found in mastics. Also, a procedure for measuring viscosity mastic from dilute to high concentration mastic using a vane rotor viscometer is introduced. The paper is presenting the first experimental results and discusses the effect of the shape of the investigated fillers on the measured viscosity of the mastics.