Mechanical Resilience of Modified Bitumen at Different Cooling Rates: A Rheological and Atomic Force Microscopy Investigation

Abstract

Due to the wide variation in geographic and climatic conditions, the search for high-performance bituminous materials is becoming more and more urgent to increase the useful life of pavements and reduce the enormous cost of road maintenance. Extensive research has been done by testing various bitumen modifiers, although most of them are petroleum-derived additives, such as polymers, rubbers and plastic, which in turn do not prevent oxidative aging of the binder. Thus, as an alternative to the most common polymeric rheological modifiers, selected binder additives falling in the categories of organosilane (P2KA), polyphosphoric acid (PPA) and food grade phospholipids (LCS) were homogeneously mixed to a base bitumen. The goal was to analyse the micro-morphology of the bitumens (neat and modified) subjected to different cooling rates and to find the corresponding correlations in the mechanical response domain. Therefore, microstructural investigations carried out by Atomic Force Microscopy (AFM) and fundamental rheological tests based on oscillatory dynamic rheology, were used to evaluate the effect of additives on the bitumen structure and compared with pristine binder as a reference. The tested bitumen additives have been shown to elicit different mechanical behaviours by varying the cooling rate. By comparing rheological data, analysed in the framework of the "weak gel" model, and AFM images, it was found that both P2KA and PPA altered the material structure in a different manner whereas LCS revealed superior performances, acting as "mechanical buffer" in the whole explored range of cooling rates.

Use of plasticizers in the production of PMB, as a tool for creating effective binders

“…Let's consider the "polymer -plasticizer" system for the most characteristic plasticizers under a microscope, Figure 2-4. The distribution, extent, and homogeneity of various phases in sistems largely depend on various factors, including plasticizer [10][11][12][13][14][15][16]. The recorded difference in the systems is obvious.…”

New Experimental Approaches to Analyse the Supramolecular Structure of Rejuvenated Aged Bitumens

“…Results and discussion. The bulk mechanical properties of bituminous materials such as, e.g., ductility and rigidity, are empirically determined by the amplitude oscillatory rheometry through the measurement of the complex modulus G * consisting in its real (elastic modulus G′) and imaginary (viscous modulus G″) components [30][31][32][33]. However, more sophisticated experimental investigations such as NMR relaxometry and X-ray scattering are being proposed as emerging methods for the comprehension of the microscopic/molecular processes underneath the observed behaviour of a bituminous material subjected to both physical and chemical treatments.…”

Effects of Natural Antioxidant Agents on the Bitumen Aging Process: An EPR and Rheological Investigation

“…In absence of additive a shift of T TR towards higher temperatures has been observed with ∆T CTRL = 6.5 • C. Then, the following sequence of ∆T values has been detected for bitumen supplemented with inhibitors of free radicals: ∆T LCS = 4.5 • C, ∆T RH = 5.8 • C and ∆T VC = 7.2 • C. Those data clearly indicate a superior performance manifested by LCS in retarding oxidative hardening compared to the other tested antioxidants. Hitherto, the use of raw mixtures of natural phospholipids has been confirmed to be a powerful method to increase both the adhesion properties of bitumen [34] and its mechanical resistance to the action of thermal shocks [41]. Here, the discover of anti-aging properties of LCS adds another advantage of using these green compounds as multi-functional additives to enhance the bitumen performances.…”