Use of fine aggregate matrix to analyze the rheological behavior of cold recycled materials

Abstract

Nowadays, one of the main challenges to a wider application of cold recycling techniques is the lack of reliable information on the mechanical behavior of cold recycled materials (CRM). In this context, measurement and modelling of the complex modulus of CRM mixtures may give an important contribution to the design and analysis of pavements including cold recycled layers. In this study, we analyzed the rheological behavior of CRM mixtures produced using bitumen emulsion and cement through the study of their fine aggregate matrix (FAM). Starting from a fixed CRM mixture composition, we compared different FAM mortars, focusing on the effect of water and air content. Then, we selected a composition as representative of the FAM in the mixture and investigated the evolution of both materials during a fixed curing period. Next, we measured the complex modulus of the CRM mixture and FAM at two curing stages and applied a rheological model to simulate and compare their behavior. Results showed that the properties of CRM mixtures are comparable to those of FAM mortars produced using all the binding agents (bitumen emulsion and cement) and a fraction of the voids contained in the mixture. Despite the huge difference in volumetric compositions, the FAM mortar controlled the curing and the thermo-rheological behavior of the CRM mixture, while the coarse reclaimed asphalt aggregate fraction and the voids mainly affected the asymptotic properties (equilibrium and glassy moduli) and the non-viscous dissipation component.

Study on Cold Recycled Asphalt Mixtures with Emulsified/Foamed Asphalt in the Laboratory and On-Site

“…The dynamic modulus has been proved to better reflect the mechanical responses and deformation resistance of asphalt pavement structures under traffic loads. The CRM contains a certain amount of aged and newly added asphalt and also has viscoelastic properties; it is very reasonable to use dynamic modulus for evaluating the rheological behavior of the CRM [94][95][96][97].…”

Comparing the Field and Laboratory Curing Behaviour of Cold Recycled Asphalt Mixtures for Binder Courses

“…Rheological modelling was carried out using the model proposed by Graziani et al [ 10 , 11 ] that combines viscoelastic and hysteretic dissipation mechanisms. The viscoelastic part is represented by the Huet–Sayegh (HS) model [ 62 ] while the hysteretic part (HY) is represented by a time- and temperature-independent phase angle ( ).…”

“…Overall, the stiffness modulus was comprised between 9500 (B10, T = 0 °C, f = 10 Hz), and 1500 MPa (C12, T = 50 °C, f = 0.1 Hz). This range of variation is less than one order of magnitude, whereas, Rheological modelling was carried out using the model proposed by Graziani et al [10,11] that combines viscoelastic and hysteretic dissipation mechanisms. The viscoelastic part is represented by the Huet-Sayegh (HS) model [62] while the hysteretic part (HY) is represented by a time-and temperature-independent phase angle ( ).…”

“…The CRM mechanical behaviour is strictly linked to its composition [5], providing mixtures with properties ranging from those similar to unbound granular materials [6] to those of materials characterised by an intermediate behaviour between cement-bound mixtures [3,7,8] and asphalt concrete (AC). For this reason, several authors have characterised the mechanical behaviour of CRAM by using the complex modulus [9][10][11]. For CRAMs and CBTMs, the combined effect of bitumen and cement is very effective in terms of water sensitivity [7,8,[12][13][14] and high-temperature stability [12,13,15].…”

Special Issue: Characterization of Innovative Asphalt Materials for Use in Pavement Design and Analysis

“…High-performance [ 7 , 8 , 9 ] and/or innovative materials such as nanomaterials for asphalt modification [ 9 , 10 , 11 ] can be employed for investigating the possibility of achieving a longer service life of pavement structures, maximizing the material productivity. At the same time, the use of renewable materials in partial replacement of asphalt, such as bio-binders [ 12 , 13 , 14 , 15 ], and the recycling of end-of-life pavement materials with hot [ 16 , 17 ], warm [ 18 , 19 ] and cold [ 20 , 21 , 22 ] technologies is becoming more and more popular nowadays. However, these innovative/high-performance materials can be used for paving mixtures only after checking their ability to resist both traffic and environmental actions.…”