Evaluation of the Effects of Asphalt Additives on Properties of Class A Surface Mixtures

Various modified asphalt mixture systems were selected for laboratory and field testing. These systems included the following asphalt mixtures: Class A mix, as the control mixture; Class N, which is a coarse mixture; polymerized Class A; polyester fiber; polypropylene fiber; and Vestoplast. Laboratory testing included: Marshall stability, resilient modulus, moisture susceptibility, tensile strength, and freeze-thaw. A field trial section was constructed for long-term performance monitoring

Rubberized Asphalt Membrane

This document reports findings of a study involving the use of scrap tire chips in an asphaltic membrane. The research project was designed with two objectives in mind. First, to investigate the effectiveness of an asphaltic membrane on top of a subgrade for maintaining moisture equilibrium in subgrade, and second, to study the potential use of scrap tire chips in asphaltic membranes. The effectiveness of the membrane as a moisture barrier needs to be evaluated over a long period of time (i.e. several years). However, the method proved to be a feasible alternative for recycling waste tires in pavements. It is hoped that this study will contribute to various efforts in the area of cost effective and sound utilization of waste materials in construction

Large-Stone Mixes for Reducing Rutting

Large-stone mixes are becoming a very popular means for reducing rutting in flexible pavements. Aggregate interlock in large-stone mixes provides for very efficient dissipation of compressive and shear stresses that are known to be responsible for rutting and shoving in flexible pavements. This report documents mix design procedures and laboratory testing for characterization of rutting potential of large-stone asphalt mixes (LSAM) in Kentucky and particularly the Louisa Bypass project. A series of large-stone aggregate gradations were studied. A promising aggregate gradation was selected in cooperation with Kentucky Department of Highway officials and representatives of the asphalt industry. Based upon the findings of this study, several test sections were constructed on coal-haul corridors throughout the Commonwealth of Kentucky. LSAM sections have been in service for less than one year, and conclusions on the performance of these mixes would be premature. It is important, however, to note that conventional asphalt mixtures on pavements subjected to heavy tTuck traffic in Kentucky usually exhibit severe rutting after only a few months in service. In this respect, one may conclude that LSAM projects have performed well. Performance-oriented laboratory test results indicate that higher levels of structural capacity and rutting resistance, as compared to conventional hot mix asphalt, may be achieved by using the LSAM in flexible pavements. A field trial followed the laboratory investigations. Construction of the Louisa Bypass, which is located in the mountainous region of eastern Kentucky, was studied. Recommendations presented in this report for construction of Large-stone mixes in heavy haul roads are based upon information obtained from the Louisa Bypass

Evaluation of Modified Asphalt Mixtures

The primary objective of this study was to conduct a comparative analysis on various modified asphalt mixture systems in order to determine their suitability for conditions that are commonly encountered in Kentucky. Several modified asphalt mixture systems were selected for laboratory and field testing (one-mile long field test section on KY 80, Pulaski County). These systems included the following asphalt mixtures: Control, Vestoplast, Polypropylene Fiber, Gilsonite, PMAC #1, Polyester Fiber, and PMAC #2. Laboratory testing included: Marshall stability and flow, mixture air voids and density, indirect tensile strength, moisture damage susceptibility, freeze-thaw damage susceptibility, resilient modulus, and repeated load permanent deformation. Statistically based comparative analyses were conducted in order to determine any significant relative differences in the performance potential of different modified systems. All statistical analyses were conducted at 90% level of significance (i.e., alpha error rate = 10%)

Louisa Bypass Experimental Project

In an effort to reduce rutting in the new Louisa Bypass in Lawrence County, Kentucky, a large-stone asphaltic base mix (Class K) was used in the base layer. A one-inch surface wearing course was used in this project, a polymer-modified asphalt was used in the surface course on half of the project. In order to facilitate subsurface drainage, a free draining subbase (No. 57\u27s) was placed between the large-stone base and a dense-graded aggregate (DGA) layer. The drainage design was further enhanced by edge and median drains. Construction processes were monitored and photographed. Laboratory and field studies were conducted to determine the performance characteristics of individual pavement components. Performance of the Louisa Bypass project has been and will be monitored

A User’s Guide for By Product and Discarded Material Utilization in Highway Construction and Maintenance

This report presents a user\u27s guide for an expert decision-making system that utilizes findings of an extensive literature search and review conducted as part of this study. The literature search and review were conducted to determine current attitudes and document available technical data relative to the use of recyclable and recoverable materials in highway construction and maintenance activities. Specifically, the literature search focused upon the engineering, economic, and performance aspects of using recyclable and recoverable materials in highway construction and maintenance projects. The effort centered upon asphalt and Portland cement concrete pavement recycling, discarded tire recycling, reuse of paint removal wastes, fly ash, glass, alternative fuels, and other miscellaneous recycled and recovered materials as related to construction and maintenance of highways. Additionally, regulatory and policy matters associated with the use of recyclable and recoverable materials in the transportation area were investigated during the review of pertinent literature. The user\u27s guide was developed for use by Kentucky Transportation Cabinet officials to address a large number of multi-disciplinary issues. These issues may include, but not be limited to, environmental impact legal or legislative mandates, performance, cost and implementation. Since the aforementioned variables change with time, there is a user-friendly updating feature for the expert decision-making system. This feature of the expert system format presentation represents a major advantage over the familiar report format. An expert system has three major parts: a user interface, an inference engine, and stored expertise. When consulting the expert system, the user states a problem and interacts with the system. An expert system\u27s inference engine is software that actually carries out the reasoning needed to solve a problem. This software draws upon the stored expertise in order to reach its conclusions

Development of Guidelines and Performance for Asphalt Concrete Containing Recycled Rubber

The primary objective of this study was to investigate the feasibility of implementation of the crumb rubber technology in Kentucky. The impetus for this study was provided by the Intermodal Surface Transportation Efficiency Act of 1991 (lSTEA). This study included an overview of existing literature on the subject from an implementation point of view for Kentucky\u27s conditions. Upon completion of this phase of the study, guidelines were developed by the KTC research team and were submitted to the Transportation Cabinet for field implementation of the crumb rubber modifier (CRM) technology in Kentucky. From the ease of implementation point of view, the Cabinet opted to construct a field trial section using the wet process\u27 which utilized a fine ground rubber (80 mesh} material. The rationale for this decision was based upon the fact that the fine ground CRM mix closely resembles the polymer modified HMA, and that both the Cabinet and Kentucky contractors have an extensive amount of experience with polymer modified asphalt. In July 1993, a field trial project was constructed on a portion of the US 421, Franklin County, Kentucky. The project involved milling of nominally one inch of the wearing surface followed up by a nominally one-inch overlay. The four-lane trial project (two lanes in each direction) was divided into two approximately half-mile sections. This allowed for a comparison of performance between the CRM hot mix asphalt (HMA) and the conventional HMA. In summary, the trial implementation of the CRM technology in Kentucky proved to be a success. The 177-micron (80-mesh) fine ground rubber at 7.5% by weight of asphalt cement provided a material similar to polymer modified asphalt. Construction of the field project was possible with existing specifications and practices in Kentucky. The non-intrusive nature of the fine ground technology was most desirable from the ease of implementation point of view

Development of Guidelines and Performance for Asphalt Pavements Containing Rubber -- Review of State-of-the-Practice

This interim report provides a summary of key points that are important to successful implementation of the asphalt rubber technology in Kentucky in accordance with ISTEA. Various asphalt rubber technologies are presented in this report along with their advantages and disadvantages. Issues related to structural design and construction are discussed. A variety of environmental issues such as: emissions, leachate and issues related to future recyclability are presented. Finally, criteria are recommended to be used for selection of future asphalt rubber projects in Kentucky

Effects of Hinged Dowel System on the Performance of Concrete Pavement Joints

Concrete joint failure is a major distress mode in rigid pavements. Improving the joint performance in concrete pavements could yield substantial savings in terms of reduced maintenance and rehabilitation costs. The newly developed Hinged Dowel System (HDS) is a means for transferring loads across the concrete pavement joints. The HDS was patented as a new invention by the United States Patent and Trademark Office, and it is envisioned that it could significantly reduce the potential for joint failure in concrete pavements. The HDS assembly comprises a number of dowel bars and a collective hinge provided at the mid-length of the dowel bars. A finite element analysis showed that the application of HDS reduces the shear stress in concrete pavement joints by approximately 15% when compared to the conventional dowel bars. This amount of reduction in shear stress could translate into a significant reduction in shear-induced failures in concrete pavements. The HDS includes mechanisms which would allow a horizontal slip condition for the dowel bars imbedded in concrete. Moreover, these mechanisms eliminate the punching stress at the dowel tip, which is often induced by thermal expansion of the concrete slabs. The hinge in the HDS gives the concrete slab joints a degree of flexibility to reduce the stresses caused by daily curling and warping of slabs, and seasonal expansion and contraction. In addition to installation in new concrete pavements, the HDS could be utilized in retrofit of old concrete pavements. Finally, the HDS eliminates most construction-related issues associated with the installation of dowel bars, such as dowel bar misalignment and full-depth joint cut

Load Transfer Assembly

A load transfer apparatus accommodates movement between adjacent concrete slabs. The load transfer apparatus includes a spine in a form of an elongated hinge having a longitudinal axis A. A first dowel and a second dowel project radially from the spine and are located at two spaced points along said longitudinal axis A