Soon-Jae Lee

The effects of rejuvenating agents on recycled aged CRM binders

The recycling of asphalt pavements containing crumb rubber modifier (CRM) modified binders is increasing in areas having these types of asphalt pavements more than 10 or 15 years old. The performance and physical and rheological properties of the blends of aged CRM binders containing rejuvenating agents due to the presence of CRM have not been considered in detail. In this study, two CRM binders and one control binder of PG76-22 were artificially aged and then used as recycled materials by adding different rejuvenating agents, i.e. a rejuvenator and a softer binder. The properties of the blends of the three aged binders containing various percentages of the rejuvenating agents were evaluated using Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR) as well as viscosity tests. The test involved three different aging states of the blends: original, RTFO residual and RTFO+PAV residual. Results from this study show that: (1) the aged CRM binders can be rejuvenated back to a targeted PG grade; (2) the rejuvenating agents investigated are effective in changing the properties when used with the aged CRM binders; (3) the presence of crumb rubber in the modified binders enhances their aging resistance; (4) the target grade is more easily reached by adding the rejuvenating agents to the aged CRM binders rather than the aged control PG76-22.

Recycling of Laboratory-Prepared Reclaimed Asphalt Pavement Mixtures Containing Crumb Rubber-Modified Binders in Hot-Mix Asphalt

The recycling of reclaimed asphalt pavements (RAP) containing crumb rubber—modified binder is an important issue because some of these types of pavements are more than 10 to 15 years old in some areas in the United States. In this study, a laboratory investigation was conducted on the possibility of laboratory-prepared crumb rubber—modified RAP being recycled in Superpave® mixtures according to a normal recycling practice. Six mixtures (three recycled mixtures containing laboratory-prepared crumb rubber—modified RAP and three control virgin mixtures) were designed and tested. Three types of aggregates and two types of crumb rubber—modified binders were used for the mixtures. The crumb rubber-modified RAP used in the study was artificially aged in the laboratory with an accelerated aging process. The percentage of the RAP incorporated into the recycled mixtures was 15%. Evaluation of all mixtures included the following testing procedures: indirect tensile strength, asphalt pavement analyzer, and resilient ...

Effects of warm mix asphalt additives on performance properties of polymer modified asphalt binders

This study presents an experimental evaluation for the performance properties of polymer modified asphalt (PMA) binders containing warm mix asphalt (WMA) additives. The PMA binders with the additives were produced using two of the available warm asphalt processes (i.e., Aspha-min and Sasobit) and three PMA binders graded as performance grade (PG) 76-22. The warm PMA binders were artificially short-term and then long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this research indicated that (1) the addition of the WMA additives into the PMA binders showed positive effects on increasing rutting resistance at high temperature (based on the high failure temperature values from the DSR test); (2) the PMA binders containing the additives were observed to be less resistant ...

Laboratory investigation of the influence of warm asphalt additives on long-term performance properties of CRM binders

This paper presents an experimental analysis of the long-term properties of rubberised binders containing warm asphalt additives. The rubberised binders were manufactured at 10% by binder weight using five different binder sources and the binders with the additives were produced using two (i.e. Aspha-min® and Sasobit®) of the available warm asphalt processes. The rubberised warm asphalt binders were artificially short-term and then long-term aged through the rolling thin film oven and pressure ageing vessel procedures. Superpave binder tests were carried out on the binders using the rotational viscometer, the dynamic shear rheometer (DSR) and the bending beam rheometer (BBR). In general, the results of this limited study indicated that (1) the addition of the warm asphalt additives into the rubberised binders showed positive effects on increasing rutting resistance, (2) the rubberised binders containing the additives were less resistant to fatigue cracking at intermediate temperatures than the control rubberised binders (based on the G *sin δ values at 25°C from the DSR test) and (3) the addition of Sasobit® represented a possible lower resistance to low-temperature cracking (based on the stiffness and the m-value at − 12°C from the BBR test) and the addition of Aspha-min® had a statistically insignificant effect on low-temperature properties of rubberised binders.

Analysis of rheological properties of rubberized binders containing warm asphalt additives

The main objective of using warm mix asphalt (WMA) is to reduce emissions and improve the workability by lowering the mixing and compaction temperatures of asphalt mixes through different mechanisms. Since warm asphalt is a relatively new technology, not much research has been conducted on various mix compositions. While some of the concerns about WMA have been addressed, the interaction of warm mix additives with modified binders, especially crumb rubber modified (CRM) binder, is not known in great detail. This paper presents the data on rheological tests conducted on rubberized binders containing warm asphalt additives. Binders from five different sources were modified using 10% crumb rubber by weight of the virgin binders. Two of the available warm asphalt technologies, Aspha-min® and Sasobit®, were used to produce the warm asphalt binders. From the tests, it was observed that the addition of the warm asphalt additives significantly reduce the permanent deformation of the binders, increase the viscosit...

Influence of Warm Mix Additives on PMA Mixture Properties

The objective of the study in this paper was to investigate the influence of warm mix additives on polymer-modified asphalt (PMA) mixtures in regards to engineering properties. Twelve PMA mixtures (four control PMA mixtures and eight warm PMA mixtures) were prepared by using two additives (Aspha-min and Sasobit), two binder sources, and two aggregate sources. An evaluation of all PMA mixtures included the following testing procedures: tensile strength ratio, asphalt pavement analyzer, resilient modulus, and indirect tensile strength after longterm oven aging. The results from this research generally indicated that (1) the PMA mixtures containing the additives can satisfy the current Superpave mixture requirements (including moisture susceptibility and rutting resistance) and (2) no statistical differences existed between the control and the warm PMA mixtures for the properties that the authors evaluated in this study, suggesting using of WMA technologies in PMA mixes has no negative effect on the mixture’s engineering properties.

Mechanical Properties of Fiber Reinforced Lightweight Concrete Containing Surfactant

Fiber reinforced aerated lightweight concrete (FALC) was developed to reduce concretes density and to improve its fire resistance, thermal conductivity, and energy absorption. Compression tests were performed to determine basic properties of FALC. The primary independent variables were the types and volume fraction of fibers, and the amount of air in the concrete. Polypropylene and carbon fibers were investigated at 0, 1, 2, 3, and 4% volume ratios. The lightweight aggregate used was made of expanded clay. A self-compaction agent was used to reduce the water-cement ratio and keep good workability. A surfactant was also added to introduce air into the concrete. This study provides basic information regarding the mechanical properties of FALC and compares FALC with fiber reinforced lightweight concrete. The properties investigated include the unit weight, uniaxial compressive strength, modulus of elasticity, and toughness index. Based on the properties, a stress-strain prediction model was proposed. It was demonstrated that the proposed model accurately predicts the stress-strain behavior of FALC.

Performance Evaluation of Recycled PMA Binders Containing Warm Mix Asphalt Additives

The performance properties of recycled polymer modified asphalt (PMA) binders containing warm mix asphalt (WMA) additives at high, intermediate, and low temperatures were evaluated. First, each combination of two PMA binders (performance grade (PG) 76-22 from two different sources) and two WMA additives (i.e., Aspha-min® and Sasobit®) were blended to produce warm PMA binders. They were then artificially short-term and long-term aged through the rolling thin film oven and pressure aging vessel procedures. Second, long-term aged warm PMA binders were recycled using two virgin binders (PG 76-22 and PG 70-22), and the recycled binders were artificially aged again. Lastly, Superpave binder tests were performed through the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study suggested that (1) the WMA additives and the aged PMA binders were found to have a significant influence on the performance properties of recycled binders (measured by the DSR and the BBR); (2) the use of PG 70-22 as a virgin binder was effective in offsetting the increase of binder stiffness due to the additives and the aged binders; and (3) the recycled warm PMA binders can result in satisfactory binder performance that meets current Superpave binder requirements.

Evaluation of Engineering Properties of Rubberized Laboratory Mixes Containing Warm Mix Additives

Warm mix asphalt (WMA) refers to technologies which allow a significant reduction of mixing and compaction temperatures of asphalt mixes. From previous studies, it is observed that warm mix additives work in different ways, either in reducing the viscosity of the asphalt binder or allowing better workability of the asphalt mix at lower temperatures through volume expansion in the binder. If the technologies of WMA are incorporated into rubberized asphalt mixes, which are generally produced and compacted at higher temperature than conventional mixes, it is possible to reduce the mixing and compaction temperatures of rubberized mixes to those of conventional mixes. This paper presents a limited study that characterizes the engineering properties of crumb rubber modifier (CRM) mixtures containing warm mix additives. Six CRM mixtures (two of control mixtures and four of warm mixtures) were prepared using two aggregate sources and two additives: Aspha-min® and Sasobit®. Evaluation of all mixtures included the following testing procedures: tensile strength ratio, asphalt pavement analyzer, resilient modulus, and resilient modulus after long-term oven aging. The results from this study showed that in general, there was no significant difference between the control and warm CRM mixtures for the properties evaluated in this study, indicating that the use of WMA technologies into CRM mixes is expected to have no negative effect on the mixture’s engineering properties.

30 Years of Microsurfacing: A Review

Microsurfacing has been utilized in the United States since 1980 as a maintenance treatment for pavement. This paper reviews the benefits, limitations, and factors that contribute to successful applications of microsurfacing. The history of microsurfacing, as well as a definition and process description of the treatment, is included. The body of scientific work on microsurfacing is shown to promote its use in preventative maintenance programs, and the potential for microsurfacing to meet tightening environmental and budgetary restrictions is discussed. Suggestions are given for future research to expand microsurfacing’s applications and efficacy stemming from the ability of microsurfacing to be cold-applied and utilize polymers in the bitumen.