Moisture Damage Characteristics of Warm Mix Asphalt Mixtures

摘要

Warm Mix Asphalt (WMA) mixtures are produced and placed atrnsignificantly lower temperatures than conventional Hot Mix Asphalt (HMA)rnmixtures. WMA mixtures can be produced by means of various technologiesrnsuch as foaming (moisture-based) agents, wax-based additives, emulsionbasedrnproducts, and surfactants. The lower temperatures provide severalrnbenefits such as reduced emissions and odors, decreased energy consumptionrnfor production, and improved environmental working conditions at plants andrnpaving sites.rnA concern that arises from the use of WMA technologies is the effectrnof lower production and placement temperatures on the moisture susceptibilityrnof asphalt mixtures. This concern is primarily based on the fact that lowerrntemperatures could lead to the possibility of inadequate drying of aggregates.rnFurthermore, some WMA technologies introduce water into the mixture tornincrease its workability. Aggregates that are not sufficiently dried and/or thernintroduction of water into the mixture can adversely impact the adhesionrnbetween the aggregates and the asphalt binder and the cohesion of the mixture.rnAdhesion and cohesion failures can lead to moisture damage.rnThis study consisted of two parts. The objective of the first part wasrnto conduct an internet survey of materials and construction engineers in eachrnof the fifty state Department of Transportation (DOT) agencies to determine ifrnmoisture damage related distresses have occurred in WMA field projectsrnplaced in the United States. Based on the responses received there was nornevidence of moisture damage related distresses in the field. The second part of the study involved conducting laboratoryrnmeasurements of the resistance of various WMA mixtures to moisturerndamage. Moisture susceptibility was assessed using the Hamburg WheelrnTracking Device (HWTD); E* stiffness ratio (ESR); adhesive bond energyrnbased on surface energy measurements of asphalt binders and aggregates; andrn. s n o i t i d n o c t e w d n a y r d r e d n u d e t s e t s e r u t x i m e h t f o s c i t s i r e t c a r a h c e r u t c a r f t n e r e f f i d s s e s s a o t d e v e i l e b e r a y e h t e s u a c e b d e t c e l e s e r e w s d o h t e m e s e h Trnmechanisms of moisture damage. The tests were conducted on specimens thatrnwere aged at different times and different temperatures. In general, the resultsrnshowed that most WMA technologies have good resistance to moisturerndamage. The difference in moisture susceptibility between the WMA andrncontrol (hot mix asphalt) mixtures was dependent on the aging time. Anrnincrease in aging time decreased the difference in performance between WMArnand HMA mixtures. The HWTD results indicated that the resistance tornmoisture damage improved with the incorporation of anti-strip agentsrn(chemical and hydrated lime).