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Journal ArticleDOI

Discrete element modelling of mechanical response of crumb rubber-modified asphalt pavements under traffic loads

27 Apr 2022-International Journal of Pavement Engineering (International Journal of Pavement Engineering)-pp 1-18
TL;DR: In this paper , the authors used 3D discrete element models to predict the mechanical response of crumb rubber-modified (CRM) asphalt pavements under traffic loads using three-dimensional (3D) discrete element method (DEM).
Abstract: This study aims to predict the mechanical response of crumb rubber-modified (CRM) asphalt pavements under traffic loads using three-dimensional (3D) discrete element method (DEM). First, irregular-shaped aggregates were generated in Python language, and discrete element models of six different asphalt layers, which considered the temperature gradient and fatigue damage, were established using 3D DEM. Then, model parameters were obtained through the uniaxial creep test for asphalt mastics at different temperatures. The fatigue damage was implemented by introducing a damage factor into the Burgers model. Finally, three mechanical response parameters (namely, permanent deformation, shear stress and transverse strain) of the six asphalt layers under traffic loads were analysed and compared. Results show that the mechanical response of CRM asphalt layers under traffic loads is significantly influenced by number of repeated loads, temperature, and asphalt layer materials. The shear stress and transverse strain at the wheel centre vary along the depth of asphalt layers, and the middle layer is the principal area of shear stresses in asphalt pavements.
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TL;DR: In this article , a new explicit three-dimensional generalised Kelvin (GK) contact model formulation for the discrete element method is proposed for asphalt materials and validated in uniaxial tension-compression sinusoidal tests for predicting the dynamic modulus (|E∗|) and phase angle (ϕ) of these composites at a frequency range of 1-10 Hz at 20∘C.
Abstract: Rigid particle models based on the discrete element method (DEM) have been adopted to model creep, fracture, and the viscoelastic behaviour of asphalt mixtures considering an irregular micro-structure and particle contacts. Within a DEM framework, the Burgers contact model, which is known to have a narrow frequency and temperature range, is usually adopted to model viscoelastic properties. In this study, a new explicit three-dimensional generalised Kelvin (GK) contact model formulation for the DEM model is proposed for asphalt materials. The model is implemented following two different methodologies (GK1 and GK2). The models are validated in uniaxial tension-compression sinusoidal tests for predicting the dynamic modulus (|E∗|) and phase angle (ϕ) of these composites at a frequency range of 1–10 Hz at 20∘C. Four mixtures are investigated based on the modelling of their mastic. The influence of the GK contact parameters on the dynamic response of mastics is assessed. Results show that κm has an important influence on both rheological properties and that ηm can be used for small adjustments focussing on the predicted phase angle. Moreover, it is shown that a viscoelastic contact model should be adopted to simulate aggregate-to-mastic contacts in mixtures. As expected, the response obtained for both GK models is the same but the simulations with the GK1 are 14% faster. In addition, the response predicted with the proposed GK contact model is compared with the response predicted with a Burgers contact model. The DEM predictions obtained for the GK model are more accurate. For mastics, the average errors for |E∗| and ϕ when adopting the GK model (Burgers) are 2.40% (3.46%) and 3.64% (4.17%), respectively. For mixtures, the average errors for |E∗| for the GK model (Burgers) are 7.00% (7.92%). The proposed contact model greatly enhances the DEM ability to simulate the viscoelasticity of asphalt materials.
References
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Journal ArticleDOI
Weidong Cao1
TL;DR: In this paper, the properties of recycled tire rubber modified asphalt mixtures using dry process were studied in laboratory, and the rubber content has a significant effect on the performance of resistance to permanent deformation at high temperature and cracking at low temperature.

222 citations

Journal ArticleDOI
TL;DR: In this article, a heterogeneous fracture model based on the discrete element method (DEM) is developed to investigate various fracture toughening mechanisms of asphalt materials using a high-resolution image processing technique.

183 citations

Journal ArticleDOI
TL;DR: In this paper, a 3D microstructure-based discrete element model of asphalt mixtures was developed to study the dynamic modulus from the stress-strain response under compressive loads.
Abstract: The main aim of this paper is to develop three-dimensional (3-D) microstructure-based discrete element models of asphalt mixtures to study the dynamic modulus from the stress-strain response under compressive loads. The 3-D microstructure of the asphalt mixture was obtained from a number of two-dimensional (2-D) images. In the 2-D discrete element model, the aggregate and mastic were simulated with the captured aggregate and mastic images. The 3-D models were reconstructed with a number of 2-D models. This stress-strain response of the 3-D model was computed under the loading cycles. The stress-strain response was used to predict the asphalt mixture's stiffness (modulus) by using the aggregate and mastic stiffness. The moduli of the 3-D models were compared with the experimental measurements. It was found that the 3-D discrete element models were able to predict the mixture moduli across a range of temperatures and loading frequencies. The 3-D model prediction was found to be better than that of the 2-D model. In addition, the effects of different air void percentages and aggregate moduli to the mixture moduli were investigated and discussed.

139 citations

Journal ArticleDOI
TL;DR: In this article, a 3D finite element (FE) model was developed to investigate the dynamic responses of thin, flexible pavement under impulsive loading similar to a falling weight deflectometer test.
Abstract: A three-dimensional (3-D) finite element (FE) model was developed to investigate the dynamic responses of thin, flexible pavement under impulsive loading similar to a falling weight deflectometer test. The FE model simulated the hot-mix asphalt (HMA) surface layer as a linear viscoelastic material and considered the cross-anisotropic stress dependent modulus for the unbound base layer. Implicit dynamic analysis was used to consider the effect of inertia on pavement structural responses. Using two thinpavement structures of different HMA layer thicknesses, 76 and 127 mm, the study analyzed the effects of cross-anisotropic stress-dependent aggregate base modulus and dynamic analysis on pavement responses, including surface deflection, tensile strain at the bottom of the HMA layer, deviator stress in the base layer, and compressive strain on top of the subgrade. Results showed that use of the cross-anisotropic stress-dependent modulus for the unbound base layer resulted in greater predicted pavement response...

111 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the discrete element method (DEM) to simulate the dynamic mechanical behavior of asphalt mastics, defined as dispersions of aggregate fillers within a medium of asphalt binder.
Abstract: This study uses the discrete element method (DEM) to simulate the dynamic mechanical behaviour of asphalt mastics. Asphalt mastics are defined as dispersions of aggregate fillers within a medium of asphalt binder. The fillers refer to the fraction of mineral aggregate passing the 200-mesh sieve, (i.e. smaller than 75 μm). Mastic measurements obtained using the dynamic shear rheometer were compared to DEM predictions and available micromechanics-based models. Three asphalt binders (ABD-1, AAM-1 and ABM-1) and four mineral fillers (glacial gravel, granite, limestone and greywacke) were used to prepare the mastics in this study. The stiffening effect of the mineral fillers was investigated at different filler volume fractions. The DEM results captured the stiffening behaviour of asphalt mastics as a function of the volumetric concentration of mineral fillers. The DEM results exhibited a high rate of stiffening that is typically observed in experimental measurements of mastics at relatively low volume concent...

109 citations