A New Insight into Concrete Impermeability: Effect of Polymer Modification of Interfacial Transition Zone

Coarse aggregates were pretreated with asphalt emulsion to concentrate asphalt film in the interfacial transition zone (ITZ) so as to improve concrete impermeability at a relatively low polymer content. Several test methods, including artificial crack samples, model aggregate concrete, and surface element scanning, were employed to characterize the contribution of modified ITZ to concrete impermeability. The results showed that incorporating hydrophobic asphalt film in ITZ could simultaneously slow down water absorption while weakening the ITZ microstructure. The water absorption of concretes decreased with an increase in the asphalt content and asphalt-coated aggregates ratio. However, the rapid chloride migration tests showed different results, which could be attributed to the different water saturation states of concretes before the tests. The hydrophobic asphalt film could retard water absorption and, consequently, chloride ion diffusion, even in the presence of cracks.