Continuous spectrum approach to evaluate the effect of binder modification and aging

Abstract

ABSTRACT The present work proposes a novel mathematical approach to directly obtain the continuous spectrum of asphalt binder from frequency domain data. Using the asymmetric sigmoidal function to obtain continuous spectrum offers advantages of flexibility and improvement in describing the spectrum well. Initially, complex modulus, storage modulus, and storage compliance master curves were constructed using experimental data. In the next stage, the continuous relaxation and retardation spectrum were constructed directly from the storage modulus and storage compliance master curves, respectively. Statistical indicators like mean, variance, and skewness were used to describe the shape of these finalised continuous spectra. To check the efficacy of the proposed approach, asphalt binders altered with modifiers (at different dosages) were aged under laboratory conditions. Critical evaluation of the results indicated that the underlying changes could be captured using the continuous spectra (which were not obvious with respective master curves or black space diagrams). Continuous spectra of binders constructed (with different dosages of modifier and under different aging conditions) were compared using the statistical indicators. Thus, the spectral shape parameters could capture the effect of aging and modifier dosage. These changes can be attributed to molecular changes, chemical reactions occurring with the addition of modifiers and aging.