This study was conducted to evaluate the rutting resistance of plant-produced asphalt concrete(AC) mixtures in the laboratory. Nineteen plant-produced AC mixtures containing RAPamounts ranging from 0% to 25% were used. Tests conducted on the mixtures included thedynamic modulus (∣E~*∣) test at multiple temperatures and the flow number (FN) test at 54°C tocharacterize stiffness and rutting resistance, respectively.Mixtures containing no RAP showed ∣E~*∣ values comparable to those containing 25%RAP in most cases. For the majority of the 19 mixtures tested, mixtures with lower FN eithercontained no RAP, contained 25% RAP, or had PG 64-22 as the design binder grade. In general,mixtures containing moderate amounts of RAP (10% and 15%), irrespective of design bindergrade, had higher FN than mixtures with either high or low RAP amounts. Statistical analysisshowed RAP amount was the most significant factor affecting rutting resistance in the mixturesstudied. A linear inverse relationship between RAP and FN appeared to describe the data quitewell. The results also showed that as RAP amount increased, there was a downward trend inboth effective binder content (P_be) and rutting parameter (G~*/sinδ) for the mixtures tested. Theeffect of RAP on FN in this study was unexpected and contrary to the generally expected resultsas it showed the rutting resistance to decrease with increased RAP content. The practice of usingsofter asphalt binder in mixtures containing higher RAP and the observed decrease in both P_beand G~*/sinδ with increased RAP amounts were suggested as possible reasons for the observedeffects of RAP on FN. The findings and conclusions from this study are based on 19 plant23produced mixtures and highlight the need for additional rutting-related mechanistic studies ofAC mixtures containing RAP.
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