Advanced self-healing asphalt composites in the pavement performance field: mechanisms at the nano level and new repairing methodologies.

In an effort to give a global view of this field of research, in this mini-review we highlight the most recent publications and patents focusing on modified asphalt pavements that contain certain reinforcing nanoparticles which impart desirable thermal, electrical and mechanical properties. In response to the increasing cost of asphalt binder and road maintenance, there is a need to look for alternative technologies and new asphalt composites, able to self-repair, for preserving and renewing the existing pavements. First, we will focus on the self-healing property of asphalt, the evidences that support that healing takes place immediately after the contact between the faces of a crack, and how the amount of healing can be measured in both the laboratory and the field.

In situ X-ray polymerization: from swollen lamellae to polymer-surfactant complexes.

The influence of the monomer diallyldimethylammonium chloride (D) on the lamellar liquid crystal formed by the anionic surfactant aerosol OT (AOT) and water is investigated, determining the lamellar spacings by SAXS and the quadrupolar splittings by deuterium NMR, as a function of the D or AOT concentrations. The cationic monomer D induces a destabilization of the AOT lamellar structure such that, at a critical concentration higher than 5 wt %, macroscopic phase separation takes place. When the monomer, which is dissolved in the AOT lamellae, is polymerized in situ by X-ray initiation, a new collapsed lamellar phase appears, corresponding to the complexation of the surfactant with the resulting polymer.

Copolymer-surfactant complexes obtained in a lamellar lyotropic medium.

Polymer-surfactant complexes formed between charged copolymers and oppositely charged surfactants are analyzed as a function of the charge density in the macromolecule. Copolymers of ionizable diallyldimethylammonium chloride (DADMAC) and neutral acrylamide are obtained at different comonomer ratios. When mixed with the lamellar medium formed by the anionic surfactant 1,4-bis(2-ethylhexyl)sodium sulfosuccinate (AOT) in water, they give rise to highly condensed lamellar phases in equilibrium with another lyotropic phase.

Ion pairing and anion-driven aggregation of an ionic liquid in aqueous salt solutions.

A relevant question regarding ionic liquids is whether they exist in aqueous solution as totally dissociated ions or as ionic pairs, molecularly dispersed or forming part of aggregates. Several methods were employed here to evaluate these points by comparing the results of an ionic liquid, 1-ethyl-3-methylimidazolium tosylate ([emim][TOS]) with its model compound p-toluenesulfonic acid (pTSA). Conductivity measurements of [emim][TOS] and pTSA dissolved in deionized water support the existence of small amounts of aggregates for both compounds, with a larger extent in the first case.