Effect of Dry Process Crumb Rubber Modification on the Compactibility of Warm and Hot Mix Asphalt

Description

Hande Isik Ozturk¹, Farshad Kamran²

ABSTRACT. This study focused on the association of the dry process crumb rubber (CR) modification and Warm Mix Asphalt (WMA) methods. The effects of conditioning time, mixing and compaction temperatures were analyzed to overcome the binder-CR interaction problems at lower temperatures. Three different asphalt mixes were prepared: Hot Mix Asphalt (HMA), Dry process CR modified HMA (Dry HMA) and Dry Process CR modified WMA (Dry WMA). Since the conditioning time was significant to facilitate the bond between the CR particles and binder, CR modified mixes were conditioned for four different periods, (0, 45, 90 and 120 min.) to analyze the effects on the mixture properties and to come up with the optimum duration. In addition, to investigate the effect of mixing and compaction temperatures on the compactibility and stability, Dry WMA mixes were prepared at three different temperature configurations.  Major findings of the study were: (i) Stability of all mixtures increased as conditioning time increased, (ii) 90 min conditioning time was the optimum period to gain significant strength, (iii) Strength loss was observed when the compaction temperature was lowered because of the poor interaction between CR and asphalt binder. (iv) Compaction temperature could be reduced by 15 °C without compromising the strength of Dry WMA. (v) Dry WMA allowed longer hauling distance, lower compaction effort or longer compaction frame. (vi) Lower emissions were estimated behind the paver during construction.

KEYWORDS: Dry Process, Warm Mix Asphalt, Compactibility, Volumetrics, Green Construction.