Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests

Abstract

Reliable determination of material properties is a key component for modelling and performance prediction of asphalt pavements. This paper deals with the potential use of instrumented indentation tests for viscoelastic characterisation of asphalt mortar as a new alternative to existing techniques. The main focus lies on the potential of indentation tests for multi-scale measurement of the shear relaxation modulus. A three-dimensional finite element model of a rigid spherical indenter penetrating an asphalt mortar sample is developed and used to model indentation tests performed at different material scales. The asphalt mortar is modelled as an idealised fine aggregate composite with elastic spheres, suspended within a viscoelastic bitumen mastic matrix. Based on the obtained numerical results the scale-dependency of the shear relaxation modulus measured with the indentation test is investigated. It is shown that the measurement scale is effectively controlled by the size of the indenter-specimen contact area, while the effect of indentation depth is minimal. The minimum contact area size required for obtaining representative properties, measured at the mortar scale, is determined. The viscoelastic parameters obtained from the indentation model are compared to those obtained using a representative volume element (RVE) for the asphalt mortar. In this way, the paper provides a new impulse for linking the mortar and asphalt scales in the multiscale modelling of asphalt mixtures. Feasibility of the proposed testing technique is further evaluated experimentally. Viscoelastic indentation tests are performed on asphalt mastics and mortar at two different sizes of contact areas. Experimental results indicate that indentation tests allow reliable characterisation of mortars relaxation modulus on both macro-scale as well as on individual component level.

The viscoelastic characterisation of asphalt mixtures using the indentation test

“…Mastic asphalt (MA), a material of interest for this study, has, however very low air-voids content, thus, it may be considered as a two-phase composite. In this context, indentation testing has a unique potential as it allows the characterisation of the viscoelastic properties of binder-aggregate composites on both the macro-as well as on mastic scale, as shown by Fadil et al (2019) for the case of asphalt mortar characterisation. Presently, a methodology proposed in their study is extended with an analysis procedure, based on the Gaussian mixture model, which is a technique used to identify different phases from the indentation test measurements on heterogeneous materials (Constantinides et al, 2006;Ulm et al, 2007).…”

“…In a recent study by Fadil, Jelagin, and Larsson, (2018) a new methodology for viscoelastic characterisation of bituminous material with spherical indentation test has been proposed, which allows extracting the linear viscoelastic properties at arbitrary non-decreasing loading. The technique proposed by Fadil et al has also been extended to viscoelastic characterisation of binder-aggregate composites, such as fine sand asphalt mortar, by Fadil, Jelagin, Larsson, and Partl, (2019). Based on the modelling and experimental findings, it was shown in their study that the measurement scale in indentation tests is effectively controlled by the size of the indenter-specimen contact area.…”

Effect of Material Composition on Freeze-Thaw Resistance of Asphalt Fine Aggregate Matrix at Low-Temperatures From Mesoscopic Perspective

“…The corresponding preparation process included preparation of cylindrical FAM specimens and cutting of FAM BBR beams. FAM cylindrical specimens are usually isostatic pressing (Fadil et al, 2019;Fonseca et al, 2019) and gyratory (Dong et al, 2014). To accurately simulate the role of the roller in the construction process of asphalt pavement, this paper has selected the gyratory compactor to form a cylindrical test piece (Φ150×h100 mm).…”

Utilization of Eggshells Ash as Additive in Enhancing Physical Properties of Bitumen Binder

“…Bitumen binder is used as a pavement material for the top layer of the road surface. Bitumen acts as a binder for aggregates, providing a comfortable ride and reducing noise pollution [1,2]. The issue currently facing road surfaces is that bitumen loses its ductility, ages due to oxidation, and becomes susceptible to cracking.…”