Evaluation of the degradation of fine asphalt-aggregate mixtures containing high reclaimed asphalt pavement contents

Abstract

This paper evaluates the mechanical properties and performance of the Fine Aggregate Matrix (FAM) existing within full RAP asphalt mixtures, in terms of their rheological and fatigue deterioration properties. The RAP material was produced in the laboratory to control its properties and to reduce the effects of variability associated with these materials. Four FAM mixtures were analysed, including a virgin HMA, a 100%RAP and two mixtures containing 50% RAP in combination with virgin materials using different penetration grade virgin binders.The analysis of the deterioration properties was based on the application of a fracture model that incorporates the viscoelastic properties of the material, the quality of the adhesive bonds developed between the aggregates and the corresponding bitumen present in each mixture, and the rate at which the material dissipates energy when subjected to cycling loading. The input parameters for this model include the results obtained from Dynamic Mechanical Analysis (DMA) and Surface Free Energy (SFE) tests. In general, the results showed that the incorporation of 50%RAP content increased the stiffness of the final mixtures, as expected. However, this hardening effect did not result in mixtures with inferior fatigue performance of the FAM present in the full mixtures, at the applied strain level.

Effect of foaming technique and mixing temperature on the rheological characteristics of fine RAP-foamed bitumen mixtures

“…The Dynamic Mechanical Analyser (DMA) testing procedure was then performed on the prepared cylindrical FAM specimens for each mixture to determine their linear viscoelastic properties. DMA is a non-standardised method that has been previously used by various researchers to characterise linear and nonlinear viscoelastic properties, and deterioration processes of these materials (Masad et al, 2006(Masad et al, , 2008Caro et al, 2008, Sánchez et al, 2017b. The experimental procedure consists of using a rheometer with a solid geometry to conduct frequency and temperature sweep tests using a sinusoidal strain-control torsional loading scheme to measure the corresponding shear stress response.…”

“…Characterising bituminous materials at this level is important since the fine matrix is responsible for holding the structure together under loading of the asphalt mixture, and because it has been recognised that several fracture processes initiate and propagate through this matrix (Montepara et al, 2011). In addition, a main advantage of FAM materials in comparison with the full mixtures is that they have a more uniform internal structure, which contributes to the control of the experimental variability associated with the heterogeneity of the mixtures (Masad et al, 2008, Caro et al, 2008 It is noteworthy to mention that limited studies related to RAP mixtures have been conducted by testing these FAM materials (He et al, 2016, Sánchez et al, 2017b, and only one study has evaluated fine mixtures with FBM and RAP materials (Sánchez et al, 2017a). Thus, the evaluation of RAP-FBMs at this scale is useful to obtain novel information about the effect of different foaming techniques in combination with RAP material and plant production variations, such as different mixing temperatures, on their rheological response.…”

Environmental effects on the rheological properties of fine warm RAP-foamed bitumen mixtures using SATS conditioning protocol

“…Initially, one cylindrical specimen for each FAM mixture with dimensions of 100 mm in diameter by 60 mm in height was compacted in the laboratory using the Superpave gyratory compactor (SGC) following the BS EN 12697-31:2007 (Figure 2a), following the procedure proposed by Masad et al, 2016. For this study, the specimens were compacted targeting a density of 2056 kg/m 3 , which corresponds to a target air void content of the compacted FAM specimens of 10%; a typical value used in existing studies that focus on this material (Masad et al, 2008, Sánchez et al, 2017. It should be noted that all the fine mixtures reached the targeted values and were workable at the various production temperatures.…”

“…For the FAM samples, their rheological properties were measured by means of the DMA testing technique, which has been widely used to characterise the linear and non-linear viscoelastic properties of these materials, as well as mechanical deterioration processes under cyclic loading (Masad et al, 2006(Masad et al, , 2008Caro et al, , 2012Caro, Sánchez, & Caicedo, 2015;Gudipudi & Underwood, 2015;Tong et al, 2013, 2015, Sánchez et al 2017, Klug et al, 2018, Sánchez et al, 2019. The procedure consists of using a rheometer with a fixture configuration for solid materials, to apply oscillation loading to the small FAM cylindrical specimens (i.e.…”

Multi-Scale Rheo-Mechanical Study of SMA Mixtures Containing Fine Crumb Rubber in a New Dry-Hybrid Technology

“…Indeed, all the aforementioned phenomena occur largely between the coarsest aggregate particles. Thus, FAM should provide direct indications of how it affects the ACs [20]. However, a specific analysis of FAM is not enough to have a complete picture of the behavior of ACs.…”