Investigation of nanoscale interfacial bonding properties in foamed asphalt cold recycled mixtures under chloride salt erosion

Salt-induced erosion from de-icing salts in Northern China and sea salt in Eastern coastal areas significantly compromises asphalt pavement integrity. A selection was made of four different types of foamed asphalt with different levels of water content, two types of aged asphalt, and three typical minerals (α-quartz, calcite, and bauxite), in addition to three chloride salt solutions (NaCl, CaCl2, MgCl2). It was found that (1) in dry conditions, the moisture level of foamed asphalt noticeably influences the adhesive performance at the juncture between asphalt and aggregates. Unlike acidic minerals, the bond strength between alkaline and neutral minerals and foamed asphalt increases as the water content of the foamed asphalt rises; (2) chloride salt solutions presence and increased levels significantly reduced the bond strength between asphalt and aggregates, particularly impacting neutral and alkaline minerals (in the presence of 10 % NaCl solution, the work of adhesion was reduced by 83.82 % and 87.48 %, respectively); (3) the influence of diverse chloride salts on the interfacial adhesive performance of asphalt mixtures varied, with the three chloride salts reducing the asphalt-aggregate interfacial adhesion work by 44.52 %, 21.90 %, and 34.94 %, respectively. (4) the investigation determined that the mineral composition considerably influences the hygroscopic sensitivity of asphalt mixtures. Minerals of an acidic nature exhibit superior moisture resistance when juxtaposed with alkaline counterparts, recommending the adoption of acidic aggregates in scenarios demanding elevated mixture stability.