Experimental Investigation on the Combined Effects of Physical Hardening and Chemical Ageing on Low Temperature Properties of Bituminous Binders

Abstract

Physical hardening is a phenomenon that takes place at low temperatures, producing time-dependent isothermal changes in the rheological properties of bituminous binders. Stiffening effects caused by physical hardening combine with those consequent to chemical ageing, thus promoting the build-up of thermally-induced stresses which may lead to premature pavement failure. The main goal of this paper was to investigate the influence of physical hardening on low temperature properties of bituminous binders tested in different ageing conditions. Moreover, reversibility of hardening phenomena was directly assessed by means of a dedicated testing protocol. The study, carried out by making use of the Bending Beam Rheometer (BBR), considered four binders of different type and origin (two neat bitumens and two commercial SBS polymer-modified binders) and three ageing conditions (original, short-term ageing and long-term ageing). Obtained results, expressed in terms of a Physical Hardening Rate (PHR), showed a significant effect of chemical ageing on low temperature hardening of binders. In particular, rate of hardening was found to vary with temperature and to decrease with degree of ageing. Reversibility of the hardening process was also verified.

Investigation on the technical performance and workability of hot-melting road marking materials using for the high-altitude area

“…However, since the road traffic marking material has undergone the high-temperature construction process during service, thermal oxygen aging under service condition is no longer the main reason for the aging of road traffic marking material [43]. Physical hardening is a reversible process, which changes the macro technical characteristics of the marking paint, manifested as hardening embrittlement, but does not change its chemical composition [44]. Volatilization of volatile components (saturated and aromatic components), which is also considered to be an mechanism, has little effect on the marking coating [29].…”

Asphalt Binder Testing at Low Temperature: Three-Point Bending Beam Test in Dynamic Shear Rheometer

“…• Depending on the specific type of the BBR instrument, tempering the liquid bath takes relatively long (total 60 min, including a stabilization time of 20 min to achieve ± 0.2 °C), and moreover, it can be challenging to ensure a homogenous temperature distribution within the bath (EN 14771, 2012;Riccardi et al, 2017). • During storage of the BBR specimen at constant low temperature, physical hardening was observed (Lu and Isacsson, 2000;Baglieri et al, 2012;Santagata et al, 2016;Wang et al, 2019b;Santosh and Kim, 2019;Zeng et al, 2020;Xu et al, 2021). The specific conditions of storage (temperature and conditioning time) may have a significant effect on BBR test results.…”

A Review on Bitumen Aging and Rejuvenation Chemistry: Processes, Materials and Analyses

“…Assuming that the material volume consists of the volume of the oscillating molecules and the free volume between the molecules [66,67], when the bitumen temperature decreases, both molecular mobility and free volume reduces, maintaining the same proportion between occupied and free volume. When the glass transition temperature is reached, the free volume decrease becomes slower than the decrease of molecule oscillation, entailing a kind of "over-hardening" for the bitumen [68].…”