Evaluation of binder grades on rutting performance

Asphalt mixes that have a good history of resisting rutting in posted speed applications may not perform well in intersections, climbing lanes, truck weigh stations, and other slow speed areas. The West Virginia Division of Highways, WVDOH, has implemented the Performance Grade binder specifications for all paving projects and Superpave for high volume road projects. The standard binder specified in the state is a PG 64-22; for high volume roads a PG 70-22 is specified. These binders appear to be working well for most projects in the state. The Superpave guidelines have provision for increasing the binder grade by one level to accommodate slow moving traffic. Prior to 2002, the WVDOH had not implemented this option. In 2002, the WVDOH elected to use a Superpave mix with a PG 76-22 binder to resolve maintenance issues at an intersection near Fort Gay, WV.;The objective of this research was to evaluate the rutting potential of the asphalt concrete mixes prepared with three binder grades. The research included mix designs for the base course and the wearing course of the pavement. The base course was a 37.5 mm mix with limestone aggregates and the wearing course was a 12.5 mm mix with predominantly blast furnace slag aggregates.;The three different binders were compared by making specimens with each of the two mix designs. The Asphalt Pavement Analyzer, APA, was used to evaluate rutting performance of the gyratory compacted samples. The statistical analysis of the rut depths provides evidence that the PG 76-22 polymer-modified binder performs better than PG 70-22 and PG 64-22 binder

Evaluation of rapid scanning techniques for inspecting concrete bridge decks with asphalt overlay

2016 Spring.Includes bibliographical references.The average age of bridges in the USA is 42 years. The life expectancy of a majority of these bridges is 50 years. At the current rates of aging and replacement, almost half of the nation’s bridges will require major structural investment in the next 15 years as stated by the Federal Highway Administration. There is a severe deficiency in both time and resources available to address this problem, and methods to increase efficiency are needed. Bridge decks are the most critical elements of a bridge structure as they are directly and continuously exposed to harsh weather conditions and cyclic loading from traffic throughout their lifespan. This thesis attempts to improve management practices for bridge decks by addressing current challenges faced by the Colorado Department of Transportation (CDOT) in estimating the extent of damage on bridge decks. The current bridge deck inspection method being employed by CDOT is sounding and chipping. This procedure involves sounding the deck with chains, hammers and rotary percussion to detect the deteriorated areas followed by chipping. The issues with this procedure include its time-consuming nature, the requirement for traffic to be diverted for extended periods and the costs associated with the inspection and traffic diversion. Additionally, sounding is not adequate to provide a rough estimation of the class of damaged area and the resulting expenses. CDOT wants to take the advantage of newer alternative techniques to evaluate bridge decks. The alternative evaluation considered by CDOT involves using Ground Penetrating Radar (GPR) and Infrared Thermography (IR) thermography together for evaluating bridge decks. The major advantage of using GPR is that it is the only available method that can estimate the deterioration in concrete decks with asphalt overlay. Additionally, GPR can estimate the deterioration in early stages, unlike sounding which detects damage in advanced stages and GPR is also capable of detecting corrosion in rebars. Thus, GPR not only has the potential to address the disadvantages of sounding it also has additional advantages which can benefit the life of the bridge deck. This study attempts to understand the limitations that this newer evaluation method comes with and possibly solve some of these limitations to take complete advantage of this technology. This study took advantage of the available as-built data of four bridge decks rebuilt after sounding and chipping and the data available from GPR and IR scanning of the respective decks to study the limitations from using GPR and IR technologies. The scanned results from GPR and IR thermography are compared to the deck condition data from sounding and chipping. In two cases the damage detected by GPR and IR thermography did not correlate well with the damage detected from sounding and chipping. The two decks with reasonable correlation are compared to the decks with poor correlation in an effort to understand the possible causes for deviation in results. It was observed that for the decks with poor correlation the GPR showed areas with higher cover as deteriorated in the estimation. An improved data processing procedure to solve such miss-interpretation issue is suggested, and a coring strategy to assist future research in the direction of eliminating the depth-amplitude effects in GPR scans

SYNTHESIS AND CHARACTERIZATION OF P-TYPE COPPER INDIUM DISELENIDE (CIS) NANOWIRES EMBEDDED IN POROUS ALUMINA TEMPLATES

This work focuses on a simple template assisted approach for fabricating I-III-VI semiconductor nanowire arrays. Vertically aligned nanowires of p-CIS of controllable diameter and thickness are electrodeposited, from an acidic electrolyte solution, inside porous aluminum templates using a three electrode set up with saturated calomel electrode as the reference. AAO template over ITO-glass was used as starting template for the device fabrication. The deposited CIS is annealed at different temperatures in a reducing environment (95% Ar+ 5% H2) for 30 minutes. X-ray diffraction of the nanowires showed nanocrystalline cubic phase structures with a strong orientation in the \u3c112\u3e direction. The effective bandgap of the deposited CIS nanowires determined using the Near Infrared (NIR) Spectrometer was found to be 1.07eV. The type of CIS electrodeposited inside the porous alumina template is determined to be p-type from the Schottky diode obtained with ITO-CIS-Au structure. Schottky diodes were characterized and analyzed at room temperature