| The increasing costs of construction materials along with environmental conditions have given great impetus to current interests in recycling. In recent years, reuse or recycling of existing pavement materials has emerged as a viable rehabilitation and maintenance alternative as it offers several advantages over the use of conventional materials and techniques. Among the major benefits are lower costs, conservation of aggregates, binders and energy as well as the preservation of the environment and existing highway geometries.; Although the equipment and technology of recycling have been developed, there still has not been a standarized or widely accepted method for testing recycled mixtures. The practice of using a small amount of recycling agent is coupled with the problem of quality control. There is no suitable methods exists that permits detecting how well the recycling agent mixes with the aged pavement materials.; This dissertation covers an extensive evaluation of a wide range of ideas for measuring the extent of mixing during a recycling operation. A number of test methods including the resilient modulus (M(,R)), dye chemistry, fluorescence spectroscopy, ultrasonic scanning, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), X-ray image analysis, electron microscopy, and chromatography were evaluated. The study was primarily aimed at the development of a test method that could be conducted in the field with a minimum of equipment and training. It is a pioneering effort with regard to the mixing efficiency of the recycling process.; The dye chemistry technique appears conclusively to be a straightforward, rapid and inexpensive test method. The resulting dye prints were evaluated either by visual examination or by densitometric scanning. Differences of various mixing patterns in terms of dye dispersion can be measured qualitatively and quantitatively.; Ten field projects were conducted to demonstrate the application of such technique to full-scale constuction conditions. The overall mixing efficiency of a specific operation can be appraised by statistically analyzing the resulting dye distributions. Consequently, optimization of the mixing process or the plant design may be achieved through such knowledge. |
