Investigating the Effect of Hydrophobic Additives in Moisture Damage Reduction of Asphalt Mixtures

Abstract

In order to increase the life of the asphalt mixture and reduce the cost of the pavement life cycle, methods must be provided to improve the quality. Accordingly, the effects of aggregate surface coating with hydrophobic material in order to modify the aggregate mixture’s polar properties and reduce its hydrophilic properties are investigated. To this end, limestone and granite aggregates, 60-70 bitumen, and Two types of additives were used as the primary materials for the construction of asphalt mixtures. Thermodynamic concepts with cyclic loading have been used to evaluate the effects of these additives. The results obtained in this study indicate that the hydrophobic coating on the aggregate surface has increased the acidic components and decreased the alkaline components of the surface free energy for both types of aggregates. These changes will increase the bitumen-aggregate adhesion and make a better coating of bitumen on the aggregate surface. The results based on thermodynamic concepts suggest that the aggregate surface coating has reduced the system’s separation energy and the desire for stripping. The results of the dynamic modulus in wet to dry conditions also approve this outcome. The combination of thermodynamic concepts and the cyclic loading results show that the coating on the aggregate surface has reduced the aggregate’s stripping from bitumen. It is also obvious that the samples made with granite aggregates, which have acidic properties, are prone to moisture damage and have a higher tendency to strip.

Moisture Sensitivity of Hot Mix Asphalt Modified with Micronized Calcium Carbonate

“…Various factors affect the occurrence of moisture sensitivity and resistance of a mixture against it, with the structure of minerals which form aggregates being one of the most important ones. Two minerals, SiO 2 and CaO (or CaCO 3 ), induce a substantial change in the hydrophilic or hydrophobic properties of HMA. The higher the percentage of SiO 2 in aggregates, the more hydrophilic it will be.…”

“…However, the presence of water within and between bound layers, specifically asphalt layers, is a relatively recent understanding within the professional community [1]. The bond quality between bitumen-aggregates has a considerable influence on the durability of HMA against moisture sensitivity [2].…”

An Experimental Investigation into the Effect of Asphalt Binder Modified with SBR Polymer on the Moisture Susceptibility of Asphalt Mixtures

“…The primary investigation was reported in Texas Transportation Institute which revealed that Surface Free Energy (SFE) measurements could be applied as an impressive tool to predict moisture damage and fatigue cracking in asphalt mixtures. Hamedi et al [6] examined the concepts of SFE and its application in asphalt mixtures. The results of his study showed that thermodynamic changed in adhesion and cohesion of SFE were directly related to debonding in the asphalt binder aggregates contact surface and cracks in the mastic.…”

Investigating the Effect of Curing and Thermal Equilibrium Time on Rutting Potential of Hot Mix Asphalt

“…6 demonstrate the effect of curing and thermal equilibrium time on the final strains of different asphalt mixtures, mixtures constructed by limestone aggregate and 60-70 penetration grade asphalt binder, granite aggregate and 60-70 penetration grade asphalt binder, limestone aggregate and 85-100 penetration grade asphalt binder, and granite aggregate and 85-100 penetration grade asphalt binder.…”

“…environmental conditions (temperature), vehicle speed, tire contact pressure, and volume of passing traffic can contribute to the occurrence of this type of damage. Most rutting tests are performed at high temperatures as a major part of rutting occurs due to high thermo-sensitivity of asphalt binders and weakness in the stability of asphalt layers at high temperatures [5,6].…”