Experimental evaluation and modeling of physical hardening in asphalt binders

The research described in this paper deals with the experimental evaluation and modeling of physical hardening in asphalt binders. The term physical hardening refers to a reversible phenomenon occurring at low temperatures that causes time-dependent changes in viscoelastic properties. The experimental approach, followed to quantitatively assess physical hardening, was based on flexural creep tests carried out by means of the Bending Beam Rheometer at various temperatures and conditioning times. The results obtained confirmed that hardening phenomena have a significant influence on the creep response of asphalt binders, to an extent that can be quantitatively assessed by referring to the appropriate rheological parameters and by applying the loading time–conditioning time superposition principle. The experimental data were fitted to a mechanical model proposed in the literature (composed of a single Kelvin–Voigt element) and thereafter to an improved model (with two Kelvin–Voigt elements in series). Both models were assessed in terms of their prediction accuracy. The improved model was found to better describe physical hardening effects in the case of both short-and long-term conditioning. Practical implications of the study were finally highlighted by referring to possible ranking criteria to be introduced in acceptance procedures for the comparative evaluation of asphalt binders

Il BIM per la gestione manutentiva delle pavimentazioni stradali

Le nuove metodologie di modellazione informativa e parametrica hanno un impatto sempre più dirompente sulla progettazione, costruzione e gestione delle infrastrutture di trasporto e delle sue componenti. In questo studio si propone un approccio metodologico per la definizione di modelli BIM per la manutenzione delle pavimentazioni stradal

Evaluation and modelling of low-temperature fracture properties of asphalt binders in thin film by means of the local fracture test

The experimental investigation focuses on evaluating fracture properties of asphalt binders at low temperatures through the Local Fracture Test. The test consists in subjecting a thin film of binder to controlled tensile loads, simulating the response of the material inside the pavement. The methodology adopted combines laboratory measurements and FEM simulation. The model describes the theoretical response of the sample when a crack of variable size appears, integrating linear viscoelasticity and sample geometry. Different materials are compared, based on their fracture energy determined from the force–displacement curves. A specific criterion is proposed to determine the critical fracture temperature for each binder. Outcomes showed the effectiveness of the adopted methodology in evaluating the fracture properties of investigated materials. Moreover, a high correlation between the critical temperatures derived from the Local Fracture Test and the glass transition temperatures coming from Dynamic Mechanical Analysis was found for the unmodified binders

Use of vitrified municipal solid waste bottom ash as a filler substitute in asphalt mixtures

The experimental investigation reported in this paper focused on the use of filler obtained from vitrified municipal solid waste bottom ash (VBA) in asphalt concrete mixtures. Vitrification of municipal solid waste bottom ash results in a homogeneous, amorphous, and inert material which is characterized by negligible pollution risk during all phases of production and laying, overcoming most of the environmental concerns related to the use of untreated incinerator products. Performance characteristics of asphalt concrete mixtures prepared with a filler originated from VBA were compared with those of reference mixtures prepared with a standard mineral filler. The testing program included evaluation of compaction properties, volumetric characteristics, stiffness, and rutting potential. Experimental results indicated that VBA can be conveniently used as a filler substitute in asphalt mixtures resulting in a fully satisfactory pavement performance