Moisture-induced strength degradation of aggregate–asphalt mastic bonds

Abstract

A common manifestation of moisture-induced damage in asphalt mixtures is the loss of adhesion at the aggregate-asphalt mastic interface and/or cohesion within the bulk mastic. This paper investigates the effects of moisture on the aggregate-mastic interfacial adhesive strength as well as the bulk mastic cohesive strength. Physical adsorption concepts were used to characterise the thermodynamic work of adhesion and debonding of the aggregate-mastic bonds using dynamic vapour sorption and contact angle measurements. Moisture diffusion in the aggregate substrates and in the bulk mastics was determined using gravimetric techniques. Mineral composition of the aggregates was characterised by a technique based on the combination of a scanning electron microscope and multiple energy dispersive X-ray detectors. Aggregate-mastic bond strength was determined using moisture-conditioned butt-jointed tensile test specimens, while mastic cohesive strength was determined using dog bone-shaped tensile specimens. Aggregate-mastic bonds comprising granite mastics performed worse in terms of moisture resistance than limestone mastic bonds. The effect of moisture on the aggregate-mastic interfacial bond appears to be more detrimental than the effect of moisture on the bulk mastic.

Effects of Asphalt Binder Modifying with Polypropylene on Moisture Susceptibility of Asphalt Mixtures with Thermodynamically Concepts

“…This is due to the improvement in the free cohesion energy of asphalt binder and also the free adhesion energy of asphalt binder-aggregate. 4. Adding PP significantly increases resistance against moisture damage and increases the amount of the indirect tensile rate in the samples that are modified with this material in comparison with the control mixtures.…”

“…On the other hand, moisture damage occurs because moisture has less viscosity and surface tension in comparison with the asphalt binder [4]. This leads the aggregates to tend to be adjacent water rather than the asphalt binder which makes the stripping to be happened.…”

Factors affecting hydraulic conductivity of asphalt mixture

“…losing the bond between aggregates and the binder [2]. Moisture damage is associated with stripping, excessive permanent deformation and cracking [3,4]. Therefore, predicting the hydraulic conductivity and understanding the factors influencing it will help to establish a balance between deterioration and drainage performance.…”

Comparison of Wilhelmy plate and Sessile drop methods to rank moisture damage susceptibility of asphalt – Aggregates combinations

“…Further, none of these tests describe a mechanism behind bonding and debonding of aggregates-asphalt system [1,2]. Recently, researchers reported that surface free energy (SFE) of asphalt binder and aggregates can be a promising parameter in identifying a moisture resistant mix [3][4][5][6][7][8]. The SFE of aggregate and asphalt binder is used to estimate dry and wet adhesion energy and compatibility ratio (CR) to evaluate moisture susceptibility of asphalt mixes.…”