Asphalt concrete is a heterogeneous material containing a viscoelastic bituminous matrix and elastic aggregates. When testing asphalt materials under cyclic loading, various phenomena (so-called biasing effects) can decrease the modulus. This effect has been explained by an increase in the temperature of materials due to energy dissipation (self-heating), thixotropy and damage. The aim of this study is to analyse a uniaxial cyclic tension-compression test performed on bitumen and asphalt mixes, in modelling self-heating as one of the biasing effects. To quantify the self-heating and dissipated energy (as a heat source), a heterogeneous thermomechanical approach is introduced by separating the viscoelastic bituminous matrix from the elastic aggregates. According to this approach, various processes such as energy dissipation in the matrix due to viscoelastic properties, the thermal sensitivity of the matrix as well as its capacity to develop a heat source and diffuse heat through aggregates can all be studied. Local temperature variations are calculated by considering the heterogeneous dissipated energy field as a heat source. The complex modulus variation can then be calculated by taking into account both the temperature field and thermal sensitivity of the material. Simulation results show that as opposed to bitumen, in which 100% of complex modulus variations observed during a strain sweep test are due to self-heating, the results on asphalt mixes indicate that thixotropy varies with mechanical properties to a greater extent than self-heating. This fact is probably correlated with a higher strain level in thin bituminous matrix films, a higher load velocity in thin matrix films, material heterogeneity, and the 3D characteristic of matrix loading during the tension-compression test on asphalt mixes.
This is an Accepted Manuscript of an article published by Taylor & Francis Group in Road Materials and Pavement Design on 2017, available online at: http://www.tandfonline.com/doi/abs/10.1080/14680629.2017.1305145.
The rehabilitation of deteriorated pavements has become one of the main concerns in road engineering. Thus, the development of more resistant bituminous mixtures to be used as surface layers is a priority for the sector. Gap graded bituminous mixtures manufactured with modified binders at high dosages have been used with satisfactory results. Nevertheless, these materials are susceptible to temperature, and their performance is dependent on the climatic conditions. In order to improve the design of these mixtures, this research has focused on a better understanding of their fatigue behaviour as a function of temperature. This study has been conducted at both binder and mixture levels using the EBADE (Ensayo de BArrido de DEformacioes) and University of Granada - Fatigue Asphalt Cracking Test (UGR-FACT) tests, and it involves the analysis of various types of bituminous materials. The results showed that the temperature could play an important role in the success of this type of solution for the rehabilitation of deteriorated roads. It is therefore of interest to take this parameter into account for the effective design of bituminous mixtures.
This is an Accepted Manuscript of an article published by Taylor & Francis Group in Road Materials and Pavement Design on 2015, available online at: http://www.tandfonline.com/10.1080/14680629.2015.1029676
The aim of this paper is to study the influence of crumb rubber on the improvement
of cohesion provided by bitumen. The UCL Method is a procedure for binder characterization based on the evaluation of the degree of cohesion provided by a set amount of binder to an aggregate of a set grading (standard mixture). This method can be used to evaluate both, the dry and the wet adding procedures. The results obtained show that the wet procedure presents clear advantages over the dry procedure with and without digestion, especially when the binders are manufactured by microscopic dispersion.