Dynamic Material Functions and the Structure of Asphalts

Abstract

A simple model of the complex modulus, based on the general principles for a linear response function, is presented. The model represents a generalization of the Maxwell model and it is indicated that the model well describes a relatively broad group of regular and modified asphalts. A discrete spectrum of no more than 10 relaxation times is obtained for all the asphalts studied. The spectra of modified asphalts indicate the presence of several relaxation times that can be related to the interface interactions of the base asphalt and the polymers used. It is indicated that the phase angle of the complex modulus contains valuable information about the structure of asphalts. An attempt to use this information for calculations of the molecular mass distribution is presented. A possibility to characterize asphalts by the so-called pseudospectra is also discussed.

Development of internal structure of polymer‐modified asphalts via transformations of the reduced frequency

“…In 1990s, it was shown that the parameters of the calibration equation depend not only on the method used to determine the molecular weight, but also on the type of base asphalt used. 6,13,16 Roughly speaking, K $ 3 and α $ 0.1 for conventional unmodified asphalts can be used. Here, we use the calibration equation given by Themeli et al, 19 log MWÃ ð Þ= 2:…”

“…It is known, that when conventional asphalt B with its high-penetration value (low viscosity) was modified by polymers and some additives, the graph of f(MW*) had the potential to contain at least one negative peak. 6,10,13,16 Such peaks are not artifacts that can be eliminated by a "proper" baseline. The negative peaks of f(MW*) were identified by Stastna et al 10 by the general model of the complex modulus.…”

“…This equation relates the molecular weight of asphalt to the reduced angular frequency, ω, which is the independent variable of the dynamic master curves. 6,9,13,16 As in polymers 14,15,17,18 the model of G(t) was crucial to such attempts. Calculation of MWD was promising in conventional asphalt binders; however, in polymer modified asphalt binders an unphysical (negative) peaks on MWD were obtained (8.9) and the research work in this direction was abandoned by the Chair.…”

“…where M represents the molecular weight and K and α are model parameters. 6,9,10,16 There is a variety of different methods to determine molecular weight, any of which can be used in Equation (4). For example, Zanzotto et al 16 use a molecular weight obtained by vapor pressure osmometry.…”

“…5,6 In linear viscoelasticity, the generalized response function is represented by the complex modulus G*(ω), which is a complex function of the angular frequency ω. 5,6 The complex modulus is commonly determined by dynamic experiments where the small periodic shear strain acts as an input and the resulting out-of-phase shear stress is the output. Both shear strain and shear stress are periodic, with the same frequency ω.…”