Abstract
Bitumen emulsion asphalts, especially those incorporating marginal and secondary aggregates, are energy efficient, environment friendly, and sustainable alternatives to hot-mix asphalts. This study set out to compare engineering properties of a bitumen emulsion asphalt composed entirely of virgin aggregates with another composed of 55% reclaimed asphalt and 45% virgin aggregates. The aggregates were bound with a slow setting cationic bitumen emulsion composed of 65% base bitumen and 35% water. Marshall specimens molded at varying pre-mix water and bitumen emulsion contents were cured in molds for 24 h before being de-molded and cured for a further 72 h at 40 °C. Dry densities, porosities, and indirect tensile strengths for the cured specimens were determined in dry and soaked states. Virgin aggregate mix, at an optimum binder content of 6.1%, had a tensile strength ratio of 1.3 with corresponding air voids and moisture absorption values of 10.1% and 0.92%, respectively. Similarly, reclaimed asphalt mix at an optimum binder content of 6.2% had a tensile strength ratio of 1.03, with corresponding air voids and moisture absorption values of 7.9% and 0.38%, respectively. Compared to virgin mix, reclaimed asphalt mix had lower air voids and lower moisture absorption values with the overall benefit of enhanced resistance to moisture damage.
Highlights
A bituminous mixture is a three-phase composite material composed of a coarse aggregate skeleton, a viscous-elastic bituminous mortar, and air in the voids between the aggregates
The bitumen mortar is a blend of a filler and penetration-grade bitumen, whose viscosity has been reduced by heating, foaming, or emulsification
Hot-mix asphalts are produced by blending aggregates with penetration-grade bitumen at elevated temperatures, while cold-mix asphalts are produced by blending aggregates with either emulsified or foamed bitumen at ambient temperatures
Summary
A bituminous mixture is a three-phase composite material composed of a coarse aggregate skeleton, a viscous-elastic bituminous mortar, and air in the voids between the aggregates. The bitumen mortar is a blend of a filler (particles passing 75-micron sieve) and penetration-grade bitumen, whose viscosity has been reduced by heating, foaming, or emulsification. Emulsification of bitumen is achieved by mechanically dispersing minute globules of hot penetration-grade bitumen in water with the aid of negatively or positively charged emulsifiers. The emulsifiers impart positive (cationic), negative (anionic), or neutral (nonionic) charges on bitumen globules, which help to keep them continuously suspended in water [1]. On the other hand, is produced by injecting super-heated steam into hot penetration-grade bitumen. Hot-mix asphalts are produced by blending aggregates with penetration-grade bitumen at elevated temperatures, while cold-mix asphalts are produced by blending aggregates with either emulsified or foamed bitumen at ambient temperatures.
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