Rejuvenator is not a commonly used softening agent to be used in recycling of reclaimed asphalt pavement (RAP). In this study, Superpave mixtures containing RAP were designed using rejuvenating agents, including a rejuvenator and a softer binder, and subsequently evaluated in terms of the volumetric results, obtained the indirect tensile strength (ITS) of samples as well as evaluating the mixtures for rutting using the asphalt pavement analyzer (APA). The content of the rejuvenator used for those mixtures containing the rejuvenator was determined from the blending charts of RAP binders containing the rejuvenator. A total of 12 Superpave mixtures including 10 containing RAP and two virgin were designed. The results indicated, for the mixtures tested for this project, that: (1) properties of the recycled mixtures using the rejuvenator, such as ITS and APA, were better than those containing the softer binder; (2) 10% more RAP could be incorporated in the Superpave mixtures by using the rejuvenator than using...

Many physical and chemical factors affect the rheological properties of crumb rubber modifier (CRM) binders. This study is aimed at understanding the influence of CRM microstructure on one of the rheological properties, the high temperature properties of the CRM binders. To this end, the high temperature properties of the binders that were modified by two types of CRM with different microstructures, three different sizes, two percentages as well as three different mixing times, were evaluated by dynamic shear rheometer (DSR) test on samples before and after RTFO aging. A series of scanning electron microscope (SEM) were taken on the two types of CRM of three different mesh sizes. Results from this study showed that: (1) ambient CRM has porous surfaces and cryogenic CRM has angular with smooth cracked surfaces; (2) an addition of 10–15% of CRM in the binder can increase one and two PG grades at high temperature for either ambient or cryogenic CRM regardless of the microstructure of CRM; (3) when a high percentage and coarser CRM is mixed, the microstructures of CRM have significant influence on the high failure temperature and (4) change in mixing time from 15 to 45 min did not alter much in the failure temperature, suggesting that a mixing time of 15 min interact completely for 15% CRM with the binder.

Moisture-induced damage has long been recognized as one of the major concerns for asphalt pavements. To mitigate potential moisture damage, one general method is to add mineral antistripping additives or liquid antistripping agents into hot-mix asphalt (HMA) mixtures. In this study, a comparative laboratory experiment was conducted to investigate the effectiveness of cementitious fillers on moisture susceptibility of HMA mixtures. Five types of cementitious fillers were considered: fly ash, cement kiln dust, and three types of hydrated lime with different finenesses. The laboratory performance of HMA mixtures subjected to moisture conditioning was evaluated through the following tests: dynamic modulus test; superpave indirect tensile tests; and tensile strength ratio test. The test results indicate that the cementitious fillers were generally effective in reducing the moisture susceptibility of HMA mixtures. The finer the hydrated lime particle, the more resistant the asphalt mixtures. In addition, dynami...

This research investigated the size effect of hydrated lime on the moisture susceptibility of warm-mix-asphalt (WMA) mixtures with selected additives. A superfine hydrated lime used in the study was produced from regular hydrated lime (RHL) by a Los Angeles abrasion machine. The superfine lime was measured to be 660 nm, approximately half of the RHL size of 1.3 µm, a sub-nano-sized hydrated lime (SNHL). Scanning electron microscope (SEM) pictures were taken to observe the difference of the crushed lime in size, shape, and texture. Experiments for antistripping properties, such as indirect tensile strength (ITS), tensile strength ratio (TSR), flow, and toughness were conducted on WMA mixtures containing SNHL and RHL as control samples. A total of 18 mixtures and 108 specimens were prepared from three types of aggregate, three WMA additives, and two types of lime. The results indicated that the microstructures of the SNHL and RHL are irregular: the lime particles have fractured and rough surfaces with sharp...