Influence of Polyphosphoric Acid on the Consistency and Composition of Formulated Bitumen: Standard Characterization and NMR Insights

Abstract

Over the recent years, bitumen modification with polymers, acids, or mineral fillers has gained relevance to adjust its performance properties. This work reports the use of polyphosphoric acid (PPA) for the modification of formulated bitumen. With this objective, an in-depth literature review on PPA modification was firstly performed. Subsequently, five individual refinery components were selected for the preparation of bitumen blends, namely, asphaltic residue, vacuum residue, and three lube oils extracts. Seven binary/ternary bitumen blends were prepared and then treated with PPA. Afterwards, the five components and the unmodified and PPA-modified bitumen were characterized by standard methods (penetration, softening point, and penetration index), SARA analysis, elemental analysis, and 31P and 1H nuclear magnetic resonance (NMR) spectroscopy. The results evidenced higher asphaltenes and lower saturates/resins contents in PPA-modified bitumen. The NMR data suggest that the paraffinic chains became longer, the content of condensed aromatics increased, more substituted aromatic structures appeared, and α-hydrogen in aromatic structures diminished. These findings disclosed the improved consistency and oxidation stability of PPA-modified bitumen blends.

High-Temperature Performance Evaluation of Asphaltenes-Modified Asphalt Binders

“…Two general methods of altering asphaltenes content in asphalt binders have been identified in the literature. The first is to use a mechanical stirrer to mix the asphalt binder with materials rich in asphaltenes [ 24 , 25 ], while the second is to add the asphaltenes separated from the asphalt binder, by n-heptane extraction, back into the binder [ 20 , 26 ]. The second method has the advantage of the asphaltenes content being adjustable, which has made this procedure more popular and has led to the emergence of the concept of artificial bitumen [ 27 ].…”

“…Previous investigations have shown that the temperature susceptibility of an asphalt binder decreases with an increase in asphaltenes content [ 8 , 25 ]. On the other hand, the addition of asphaltenes could improve the resistance of asphalt binders against aging [ 8 ].…”

Influence of PPA on the Short‐Term Antiaging Performance of Asphalt

“…Obviously, the effect of PPA on the aging performance of asphalt mainly lies in asphaltenes and aromatics. ese observed results are principally attributed to the fact that PPA improves the oxidation stability of the bitumen blends and increases the concentration of condensed structures [23] and the deflocculation of the asphaltene fraction caused by PPA addition [24]. erefore, combining with Figure 6, the addition of PPA will not play a role in antiflocculation of asphalt at the beginning but will play a role in the aging process, delaying the aging of asphalt.…”

“…Orange et al [22] believed that the variation in the asphalt component was caused by the mixing reaction of PPA with asphalt. Varanda et al [23] revealed that, in general, PPA modification increased the fraction of asphaltenes in asphalt and decreased the saturated and resin fraction abundance, which is explained as PPA is hydrolyzed back to phosphoric acid and reacts with bitumen, probably in the form of charge transfer complexes with polycondensed aromatic structures, while PPA disrupts the agglomerates of asphaltene micelles, which promotes the distribution of asphaltenes in the maltene phase, thereby increasing the content of the aromatic fraction. However, the content of the aromatic fraction hardly increased in this study, combined with the changes of other compositions, which shows that it is impossible to conclude that the addition of PPA will destroy the agglomeration of asphaltenes.…”

Investigation of Ageing in Bitumen Using Fluorescence Spectrum

“…So far, a lot of evaluation methods have been established and carried out to assess the macroscale performance, such as the three conventional properties of bitumen (penetration, softening point, ductility), rheological properties and so on [ 13 , 14 ]. Moreover, spectroscopy has been widely used in bitumen chemistry because it can provide unique fingerprints for the bitumen at molecular (even atomic) level, for example, infrared spectroscopy (IR) to determine the change of molecular functional groups [ 15 , 16 , 17 , 18 , 19 ], chromatography to determine the moving regularity of the average molecular weight and molecular weight distribution curve [ 20 , 21 , 22 ], and nuclear magnetic resonance (NMR) to analyze the molecular structure and atomic attribution of the molecular structure by hydrogen or carbon spectrum [ 23 , 24 ].…”