Evaluation of Rehabilitation Techniques for Flexible Pavements in Nevada
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The Nevada Department of Transportation (NDOT) is responsible for the maintenance and rehabilitation of a large number of highway miles which fit within the categories of medium to low traffic volumes. The majority of these roads are remotely located throughout the state connecting small communities to larger metropolitan areas. Therefore, , the cond~ion of these roads is highly critical to the welfare of the state. Cold in place recycling (CIR) was used in Nevada during the 1970s and had proved to be an effective rehabilitation alternative for medium -low volume roads. Since the 1970s, significant changes have occurred in the equipment, materials, and methods of design. This research effort has investigated the effectiveness of Cl R technology in rehabilitating Nevada's roads. The main objectives ofthe research were to develop a practical mix design procedure and to assess the need for an additive. The mix design process was developed using the Hveem mix design with some modifications to account for the need to evaluate the optimum moisture content and the evaluation of the rate of strength gain. Three different projects were designed and evaluated through the newly developed mix design procedure. The data from these projects indicated that the optimum moisture content can be safely assumed to be 3 and 4 percent for CIR mixtures without and with lime, respectively. Therefore, the development of the moisture-density curve for each CIR mixture is not necessary. The research also investigated the effectiveness of using lime as an additive to improve the early strength gain and the resistance of CIR mixtures to moisture damage. The data generated in this research showed that the addition of lime improves the early strength of CIR mixtures while significantly improving their resistance to moisture damage. Therefore, it is recommended that lime be used in all CIR mixtures in Nevada. Finally, the three field projects are currently being monitored through the evaluation of field cores and the comparison of the cores properties with the laboratory prepared CIR mixtures to ensure that the curing process used at the mix design stage is representative of actual field curing.