Chandra K. Akisetty

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...

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.

Laboratory characterization of recycled crumb-rubber-modified asphalt mixture after extended aging

This paper presents a limited study that characterizes the recycling of artificially aged crumb-rubber modified (CRM) mixtures depending on their recycling percentage and aggregate type. Eight mixtures [six recycled mixtures containing rubberized reclaimed asphalt pavement (RAP) and two control virgin mixtures] were designed and tested. Two types of aggregates were used in this research project. The rubberized RAP used in the study was artificially aged in the laboratory using an accelerated aging processes. The percentages of the RAP, by total weight of the mix, incorporated into the recycled mixtures were 15%, 25%, and 35%. Evaluation of all mixtures included the following testing procedures: tensile strength ratio (TSR), asphalt pavement analyzer (APA), resilient modulus, and indirect tensile strength (ITS) after long-term oven aging. The results from this study showed that (i) the recycled aged CRM mixtures (with 15%, 25%, and 35% rubberized RAP) can satisfy the current Superpave mixture requirements,...