Interaction mechanisms of polyphosphoric acid and nano clay in bituminous composites

Saba Shariati, Masoumeh Mousavi, Albert Hung, Elham H. Fini

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


It has been reported that adding polyphosphoric acid (PPA) to bitumen modified with Montmorillonite clay (MMT) makes the bituminous composite less prone to swelling and more resistant to moisture damage, thus improving two major causes of pavement distress. There has been no in-depth study on the underlying mechanism for such a synergistic effect between MMT and PPA. Here, we used laboratory experiments and computational modeling to study how PPA moderates the intermolecular interactions in bitumen modified with MMT. The results showed that PPA had notable interactions with both MMT and bitumen components (BCs); however, PPA's preferential adsorption to MMT was verified by a significantly higher binding energy (−127.3 kcal/mol) for PPA-sealed MMT than for PPA-BCs (−85.9 kcal/mol). The higher binding energy for PPA-sealed MMT caused PPA to be strongly adsorbed on the MMT surface in the first stage, causing partial intercalation into the clay gallery and blocking subsequent entry of water. PPA's affinity to interact with BCs then allowed PPA to be a bridge between MMT and BCs, leading to more intermolecular interactions and better sealing for MMT. The calculated binding energies for interactions of BC with pre-adsorbed PPA on MMT were higher than those for interactions of BC with PPA alone. In both dry and wet laboratory conditions, bitumen modified with PPA-sealed MMT had higher values of shear thinning and G*/sin(δ) than bitumen modified with MMT.

Original languageEnglish (US)
Pages (from-to)446-455
Number of pages10
JournalJournal of Colloid And Interface Science
StatePublished - Apr 15 2021


  • Bitumen
  • Moisture
  • Montmorillonite clay
  • Polyphosphoric acid
  • Swelling

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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