No description available.

No description available.

No description available.

Electrically conductive asphalt composites have immense potential for various multifunctional applications such as self-healing, self-sensing, snow and ice removal, and energy harvesting, and controlling asphalt conductivity is the first step to enable such applications. Previous investigators have used conductive fibers as major conductive additive for asphalt composites, and the sudden transition from the insulated phase to the conductive phase, known as the percolation threshold, is commonly observed. Since the percolation threshold hinders precise control of asphalt conductivity, it is imperative to mitigate the sudden transition in the electrical resistivity curve to enable practical applications of asphalt composites. Some recent publications showed the potential of graphite in mitigating the sudden transition. The study presented herein investigates possibility of precisely controlling the electrical conductivity of asphalt concrete only by adding filler size graphite powder. Nine different types of graphite having different particle shapes and sizes are selected to investigate their effect on conductivity control. The volume resistivity of the asphalt mastic specimens containing various concentrations of graphite is evaluated. In addition, scanning electron microscope analysis is conducted for the graphite particles to provide physical explanation for their different effects on imparting conductivity. The results show that the electrical resistivity of asphalt mastic is significantly varied with the types of graphite. The mastics containing natural flake graphite show gradual decrease in volume resistivity as the graphite content increases, and sufficiently low resistivity can be obtained in the specimens with natural flake graphite. On the other hand, amorphous graphite is not efficient in reducing volume resistivity. Graphite with high surface area presents difficulty in mixing. In the next stage of research, two best performing graphite out of the nine different types are selected to be added to asphalt concrete, and the effect of aggregates on electrical resistivity is examined. It is found that flake graphite 516 provides good electrical conductivity along with improved mechanical performance of asphalt concrete. Thus the study provides fundamental information on the selection of graphite type and amount to achieve proper electrical conductivity required for multifunctional applications.

This thesis discusses and documents the validation efforts related to two new test methods developed for the grading of asphalt cement. Asphalt cements that were recovered from a large number of regular paving contracts and trial sections in eastern and northeastern Ontario were tested according to LS-299 and LS-308 test methods. The LS-308 Extended Bending Beam Rheometer (BBR) Method involves testing of asphalt cement in a regular BBR after specific times of conditioning at –10ºC and –20ºC. The LS-299 Double-Edge-Notched Tension (DENT) Test involves testing of asphalt cement in DENT configuration at 15ºC and 50 mm/min. Both these methods improved the ranking of asphalt more than that of regular BBR protocol as in AASHTO M320 method. Pavement contracts and trial sections showing little or no distress were made with asphalt cements having low grade losses in LS-308 and high strain tolerances as measured in LS-299. Hence, future implementation of these methods should reduce thermal cracking distress in Ontario roads. Besides, a number of other properties were investigated. All recovered regular contract materials were tested at –10ºC, –20ºC, and –30ºC after various periods of conditioning. Samples were loaded for 240 s, followed by unloading for 720 s in BBR, allowing the separation of elastic and viscous creep deformations. The regular specification parameters, stiffness (S) and relaxation ability (m-value) and also other performance-related properties were determined. It was found that the confounding effect of simultaneous elastic and viscous deformations and inadequate conditioning prior to testing in the BBR protocol are the most important reasons for the observed inconsistency in grading. These findings are in general agreement to those from the earlier LS-308 tests. The main reason for the poor performance is asphalt physically age during extended periods of exposure to low temperatures. Hence, those that are graded according to the current AASHTO M320 protocol are often under-designed for thermal cracking. The slow crystallization of waxes and precipitation of asphaltenes from oily phase is the primary cause for deterioration of properties. Besides, waste engine oils with other gelling agents like PPA, increase the chemical ageing tendency of asphalts and hence, thermal cracking distress. / Thesis (Master, Chemistry) -- Queen's University, 2009-04-21 11:34:36.946

No description available.

No description available.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains viii, 73 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-54).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Reclaimed Asphalt Pavement (RAP); Wax Modified Asphalt (WMA). Includes bibliographical references (leaves 45-46 ).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 130-133). Also available via the Internet.