Testing the bond strength between cold bitumen emulsion composites and aggregate substrate

Bitumen emulsion mixtures derive their mechanical properties from the cohesion provided by the bituminous mastic formed by bitumen and filler, and from its adhesion to the aggregate particles. In cold bitumen emulsion mixtures, the mastic film is produced upon emulsion breaking and the bond strength between mastic and aggregate must be evaluated considering the evolutive nature of the material, and thus the curing process. In this study, the binder bond strength (BBS) test was used to evaluate the bond strength between a bitumen emulsion, a cold mastic prepared using limestone filler and two aggregate substrates (limestone and basalt). A 2k factorial experiment was conducted also considering the influence of substrate moisture (dry and wet), curing time (24 and 72 h), curing temperature (25 and 40 °C) and moisture damage on the bond strength. The results demonstrated that, although both emulsion and mastic showed good affinity with the aggregate substrates, the adhesion bond between emulsion and basalt substrate was the most durable and that the use of a limestone filler penalised the moisture sensitivity of the systems. The BBS test was also able to show the positive effect of curing time and temperature on the bond strength.