Brittleness progression for short- and long-term aged asphalt binders with various levels of recycled binders

It is generally believed that an asphalt paving mixture should have an adequate asphalt film thickness around the aggregate particles to ensure reasonable durability (resistance to aging) of the mixture. The minimum asphalt film thickness generally recommended ranges from 6 to 8 μm. However, no significant background research data are available in the literature to support these recommended minimum asphalt film thicknesses. Some states specify minimum asphalt film thickness for mix designs. This study was undertaken to quantify the relationship between various asphalt film thicknesses and the aging characteristics of the asphalt paving mix so that an optimum film thickness desirable for satisfactory mix durability could be established. Mixes prepared with asphalt binder film thickness ranging from about 4 to 13 μm were subjected to accelerated aging using Strategic Highway Research Program (SHRP) procedures to simulate both short- and long-term aging. Both the aggregate (RD) and the asphalt cement (AAM-1) used in this study were obtained from the SHRP Materials Reference Library. The aged, compacted mix was tested for tensile strength, tensile strain at failure, and resilient modulus. The aged asphalt cement was recovered and tested for penetration, viscosity, complex modulus, and phase angle. Aging indexes were obtained from these tests, and the relationship between film thickness and the aged mix/aged asphalt cement properties were determined using regression analysis. For the particular aggregate/asphalt cement combination used in this study, it was found that accelerated aging would occur if the asphalt binder film thickness was less than 9 to 10 μm in an asphalt paving mixture compacted to 8 percent air void content.

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Rheological and chemical characteristics of warm mix asphalt binders at intermediate and low performance temperatures

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2012-0363 ◽

2013 ◽

Vol 40 (9) ◽

pp. 861-868 ◽

Cited By ~ 12

Author(s):

Feipeng Xiao ◽

V.S. Punith ◽

Serji N. Amirkhanian ◽

Bradley J. Putman

Keyword(s):

Rheological Properties ◽

Warm Mix Asphalt ◽

Environmental Benefits ◽

Asphalt Binders ◽

Testing Procedures ◽

Binder Type ◽

Creep Stiffness ◽

Short And Long Term ◽

Low Performance

Warm asphalt has been gaining increasing popularity in recent years around the world due to many reasons including the energy reductions and environmental benefits. In the present study, the objective was to conduct a laboratory investigation of rheological properties of eight binders with four non-foaming warm mix asphalt (WMA) additives at intermediate and low performance temperatures in terms of Superpave low temperature test criteria. The conventional testing procedures such as dynamic shear rheometer (DSR), bending beam rheometer (BBR) test as well as specific Fourier transform infrared spectroscopy (FTIR) were performed to determine the influences of non-foaming additives on asphalt binders after a long-term aging procedure. The test results indicated that the binder type and source play key roles in determining the G*sin δ values of WMA binders with the non-foaming WMA additive. All eight binders containing Sasobit generally have higher creep stiffness values compared to the binders with other WMA additives. The FTIR tests illustrated that the absorbance of the C-O stretch and C-H bend regions of the WMA binders after a short and long-term aging procedure can be considered similar. Moreover, the WMA binders generally exhibit better performance properties than control binders at intermediate and low temperatures after a long-term aging procedure. Furthermore, FTIR analysis results indicate that the binder type and source play important roles in determining the rheological properties of WMA binders.

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