Hydration Mechanisms, Microstructure, and Mechanical Properties of Mortars Prepared with Mixed Binder Cement Slurry-Asphalt Emulsion

Abstract

Nowadays, deep cold recycling techniques are increasingly considered an effective method for the preventive and corrective maintenance of existing pavements. Not only are these techniques quickly performed and cost effective, but they also allow one to recycle in-place materials, thus limiting the cost of transportation. Various binders can be used for the cold recycling process, including asphalt emulsion, asphalt foam, hydraulic binders, or mixed binders. Of the latter, asphalt emulsion is most often used with the addition of a small quantity of cement (less than 2% with respect to the total mass of aggregates) to accelerate the breaking of the emulsion. This paper aims at understanding the hydration process, the microstructure, and the mechanical properties of mortars prepared with a new mixed binder made of a cement slurry and a small quantity of asphalt emulsion (SS-1 and CSS-1). Conduction calorimetry data reveal that the cement hydration process is nominally influenced by the presence of a small quantity of emulsion. Scanning electron microscope observations show the good dispersion of the asphalt droplets inside the hydrated cement paste. A cationic emulsion tends to entrain less air than anionic emulsion. Test results also indicate that the introduction of asphalt droplets inside a cement mortar matrix leads to a significant reduction in compressive strength and elastic modulus as well as a slight decrease in flexural strength. Mortars made with the cationic emulsion (CSS-1) show higher strengths and elastic modulus than mortars made with anionic emulsion (SS-1).