Hyun Hwan Kim

Recycling of aged asphalt binders with wax warm additives

Warm mix asphalt (WMA) has been used in pavement industry since 2000. While there were several studies related to WMA performances, recycling characteristics of WMA binders are not investigated in detail. Rudimentary performances of recycled binder with wax warm additives were evaluated through a series of Superpave binder tests. WMA binders were produced using two wax additives of LEADCAP and Sasobit, and then artificially short-term and long-term aged using the rolling thin film oven and pressure ageing vessel procedures. The control binder was mixed with aged binders at two recycling contents of 15% and 30%. Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer, and the bending beam rheometer. In general, the results of this study indicated that (1) the addition of warm asphalt additives considerably improves the high-temperature properties of control and recycled binders, (2) the recycling contents played a significant role in determination of the binder properties, and (3) the wax additives in recycled WMA binder were still effective to improve viscosity and rutting properties, even though those additives experienced short- and long-term ageing processes.

Micromorphology and Rheology of Warm Binders Depending on Aging

AbstractIn this paper, the micromorphology of asphalt binders with wax warm additives is investigated by atomic force microscopy (AFM) and optical microscopy before and after aging. Performance gra...

Characterization of CRM Binders with Wax Additives Using an Atomic Force Microscopy (AFM) and an Optical Microscopy

This paper investigates the change in micromorphology of two binders and their respective warm mix asphalt binders before and after aging using atomic force microscopy (AFM) and optical microscopy. The control (PG 64-22) and crumb rubber modified (CRM) binders were blended with two different types of wax additives (L, a wax-based composition including crystal controller, and S, a long chain aliphatic hydrocarbon) and then artificially short-term and long-term aged using the rolling thin film oven and pressure aging vessel procedures. L is a wax based composition including crystal controller and S is a long chain aliphatic hydrocarbon. The AFM tapping-mode imaging technique was used to analyze the microstructure and the Superpave asphalt binder test was used to measure the rheology properties. In general, the results of this study indicated that (1) a correlation was observed between the changes in micromorphology (the distribution of dispersed domains and matrix) and rheology properties regardless of the aging, binder, and wax types; (2) the addition of crumb rubber into the base binder decreased the dimension of the catana phase (“bee-like”) structure, which increased the quantity of these structures; (3) the opposite trend was found between the aged control binder and the aged CRM binder regarding the size of the bee-like structure; (4) the long-term aging seemed to have a significant effect on the microstructures of the warm control and CRM binders; and (5) the inclusion of S and L was observed to have a similar trend for both binder types in terms of increased size of the bee-like structure and no bee-like structure, respectively.

Quantifying the environmental impacts of crack sealing and filling treatment in hot mix asphalt pavement

Crack sealing and filling treatments have always been an important consideration in order to prolong the life of pavement among all the pavement maintenance programs. Crack sealing uses a router to cut the crack to provide a uniform rectangular reservoir for greater penetration of sealants in order to have good bonding whereas crack filling is simply inserting sealant without performing any modification to the crack walls. This research study is intended to compare the initial and long-term environmental burdens between crack sealing and filling treatment. The parameters related to the field implementation of crack treatment methods (length sealed per day, amount of materials, configuration techniques, and equipment data) were collected from the Abilene district database system and the inventory loadings were gathered from the industry and the literature. Each life cycle phase of crack filling and sealing treatment was quantified in eight impact categories in terms of environmental emissions. In general the results of this study indicated that the initial environmental emissions of crack sealing treatment are very high compared to filling technique. However, this environmental burdens can be compensated along with an approximately 25% reduction in emissions by implementing crack sealing treatment over a long period.

Correlation between the Properties of Superpave Binder and Engineering Properties of Recycled Aged CRM Mixtures

PURPOSES : The performance properties (indirect tensile strength, rutting resistance, and resilient modulus) of recycled aged CRM mixtures and their correlation with Superpave binder properties (viscosity, high failure temperature, G*sinδ, and stiffness) were investigated. METHODS: A series of Superpave binder tests was performed by using a rotational viscometer, DSR, and BBR to evaluate the performance properties. In addition, the CRM mixes were artificially aged through accelerated aging processes, and their properties were evaluated. The correlation between the properties of recycled aged CRM binders and the engineering properties of recycled aged CRM mixtures was experimentally determined. RESULTS : The rut depth values decreased and the ITS values increased with increasing high failure temperature. In general, the resilient modulus properties seemed to be poorly correlated with the high-temperature values, regardless of the aggregate source. CONCLUSIONS: The recycled aged CRM binders and mixtures can lead to satisfactory performance, and the properties of these binders are strongly correlated with the engineering properties of the mixtures.

Tight Budgets and Roadway Maintenance: The Need for Further Study of the Conversion/Reconversion Scenario for Low-Volume Roadways

PURPOSES : This paper presents a description of the current issues facing road managers regarding the surface-type conversion of low-volume roads for cost savings. METHODS: The paper reviews previous works conducted toward this end, acknowledges gaps in the current research, and lays out what information is needed for further studies. RESULTS : If the cost to maintain an unsurfaced road is less than the cost of maintaining a surfaced road, then there is potential for cost savings for the management agency. However, the problem is bigger than simply maintaining the roads that already exist. If unsurfaced roads prove to be more economical than surfaced roads, then the cost to convert from a surfaced to an unsurfaced roadway, and vice versa, when necessary, must also be examined. CONCLUSIONS : No other studies have addressed the un-surfacing of a road for cost savings, and it is therefore unknown whether substantial savings can be realistically obtained by converting from a surfaced to an unsurfaced road. To determine whether a conversion policy would be a viable option, additional data and research are needed.