New Experimental and Modelling Tools for Multiscale Characterization of Asphalt Mastic
Time: Thu 2020-05-28 10.00
Location: Via Zoom - https://kth-se.zoom.us/j/68519700863, Du som saknar dator/datorvana kan kontakta email@example.com för information / Use the e-mail address if you need technical assistance, Stockholm (English)
Subject area: Civil and Architectural Engineering, Building Materials
Doctoral student: Hassan Fadil , Byggnadsmaterial
Opponent: Dr Robert Ingemar Karlsson, Trafikverket, Linköping
Supervisor: Docent Denis Jelagin, Byggnadsmaterial
Asphalt mastics act as a binding phase in asphalt mixtures and their rheological properties strongly affect the performance of asphalt mixtures with respect to virtually all damage modes. In order to measure mastics properties, relevant for field performance, testing should be performed at size-scales representative for the morphology and material inhomogeneity of asphalt mixtures. This thesis aims to contribute to solving these important issues by developing new experimental and modelling tools for the multi-scale characterization of asphalt mastics.
An instrumented indentation test for viscoelastic characterization of asphalt mastics is proposed as a new alternative to existing techniques. A methodology for spherical indentation testing of bituminous materials is developed allowing measuring their viscoelastic properties at arbitrary non-decreasing loading. The potential of indentation tests for multi-scale measurements of viscoelastic properties of binder-aggregate composites is investigated for the special case of asphalt mortar, composed of mastic and aggregates smaller than 2.36 mm. The effect of the test parameters on the measured apparent shear relaxation modulus of asphalt mortar is evaluated. Experimental and modelling results indicate that the measurement scale in the indentation tests can be controlled efficiently by testing with different indenter-specimen contact areas. Accordingly, indentation tests may be used for reliable viscoelastic characterization of binder-aggregate composites on macro-scale as well as on the mastic phase level. It may thus potentially provide a relatively simple tool for measuring viscoelastic properties of mastics in situ in asphalt mixtures.
In order to establish a quantitative link between material design parameters of mastics and its rheology, a new finite element (FE) micromechanical modelling approach has been developed. It allows predicting the viscoelastic properties of bitumen-filler mastic from its volumetric, mechanical and geometrical design parameters. The influence of modelling parameters on the model’s accuracy is evaluated and optimal parameter combinations are identified. The model is validated with the measurements performed on several mastics and for a range of volumetric concentration of filler. It is shown that the proposed model can capture the measured viscoelastic behaviour of mastics for the examined range of loading, temperature and material parameters. Accordingly, it may be a useful tool for optimizing mastics material design for the target viscoelastic properties.