Ralph Dusseau

Rheological Properties of the Polymer Modified Bitumen with Emphasis on SBS Polymer and Its Microstructure

The rheological properties of bitumen are improved by addition of small quantities of polymers. A review of different polymers such as styrene-butadiene-styrene (SBS), styrene-butadiene-rubber (SBR), ethylene vinyl acetate (EVA) and poly phosphoric acid (PPA) with emphasis on SBS and its microstructure is presented in this paper. The polymers are divided into two groups: elastomers and plastomers. SBS, an elastomer, has shown greater potential compared to other modifiers when blended with bitumen and improves the mechanical properties and rheological behavior of conventional bitumen. SBS is made up of styrene and butadiene monomer units. It was found that maltene interacts preferentially with the polybutadiene unit of SBS, whereas asphaltene interacts predominantly with the polystyrene unit. SBR is another elastomer which also has polystyrene and polybutadiene units with a different structural make up. EVA is a plastomer which when blended with bitumen has improved the rheological properties and stability, provided the asphalt has asphaltene content below a critical level. PPA is a liquid mineral polymer. Addition of PPA to asphalt contributes to more interactions within the asphaltenes network, thus increasing the elastic behavior. A study was also conducted to determine the influence of asphaltenes and maltenes on the rheological properties of polymer modified binders.

Structural responses of transit buses : Impact of wheelchair loads

The structural responses of typical transit buses with and without wheelchair loads and the changes in these responses from one bus design to the next were investigated. To this end, finite-element computer models, with and without wheelchairs, wheelchair restraints, and wheelchair lifts, were developed for two 7.6-m transit buses designed in 1989 and 1992. These models were each analyzed under bus deceleration with seats attached to the bus floor only, and with seats attached to the bus sidewall and floor. With respect to the structural responses of these typical transit buses to bus deceleration it was concluded that (a) maximum member stresses in models with wheelchair loads versus models without wheelchair loads tended to increase in the 1989 bus models and decrease in the 1992 bus models and (b) small to moderate changes in the number, size, and location of structural members from one bus design to the next can have a substantial impact on the maximum member stresses.

Fatigue Behavior of Neat and Polymer-Modified Binders and Mastics

The purpose of the study is to determine the influence of strain amplitude and filler on long term-aged neat and polymer modified binders using two different methods of analysis. The strain amplitudes tested were 0.5% and 1.5%. The filler content for the mastic binder was 3% dust to binder by mass. The paper will compare the fatigue life of the neat and modified PAV-aged binders and mastics, and determine the influence of strain amplitude, and filler on fatigue life. The lesser the strain amplitude, the longer is the fatigue life. Adding 3% filler to neat binder shortens the fatigue life. However, adding 3% filler to a modified binder will lengthen the fatigue life. The impact of addition of dust to the binders on fatigue life is dependent on whether the binder is modified or not.

Field-Measured Natural Frequencies of Delaware Memorial Bridge

The Delaware Memorial Bridge is a major suspension bridge that is critical to the tristate region of northern Delaware, southern New Jersey, and southeastern Pennsylvania. The Delaware Memorial Bridge consists of two nearly identical suspension bridges (hence, the nickname Twin Spans) that cross the Delaware River from southern New Jersey to northern Delaware. Field ambient vibration measurements of Structures 1 and 2 of the Delaware Memorial Bridge were conducted in June 2001 and September 2003. These measurements were used to derive the natural frequencies and modes of vibration for these structures. These field-measured frequencies and modes were then compared with each other and with computer-generated natural frequencies and modes of vibration derived for Structure 2 of the Delaware Memorial Bridge in 1997. Specifically, the 2001 seismometer-generated results for Structure 1 were compared with the 2003 accelerometer-generated results for Structure 1; the 2003 field-measured results for Structure 2 we...