Characteristics of CRM Binders and Mixtures Used in Nevada

The use of crumb rubber modified binders to improve the performance characteristics of hot mixed asphalt (HMA) mixtures have shown mixed results throughout the U.S. Some studies showed improved performance properties such as added resistance to rutting, fatigue, and low temperature cracking while some field performances have shown problems with raveling bleeding and aging of the CRM HMA mixtures. Before the Nevada Department of Transportation (NDOT) can assess the merit of using CRM HMA mixtures, it must have the following: 1-A system to evaluate the CRM binders in order to assign the binder most suitable for the environmental and traffi.c loading conditions of a particular pavement segment; 2-A procedure for mix design to select the most appropriate proportioning of binder and aggregate; 3-A mixture analysis system to predict the long-term performance of CRM mixtures under the combined action of environment and traffic loadings. It is necessary to develop a system that enables NDOT to predict the performance of CRM pavements before construction (as is done for traditional HMA mixes) and to select better pavement alternatives. In 1994, NDOT initiated a multi-year research project to develop a system for the evaluation of CRM binders and mixtures under Nevada's environmental and traffic conditions. The project started on January 1, 1994 and was completed on August 31, 1997

Laboratory Evaluation of Thin Asphalt Concrete Overlays for Pavement Preservation

A significant percentage of the existing lane miles of roadways in the United States, and in particular in Nevada, consists of rural roads. Thus, using a cost-effective pavement surface treatment becomes critical and essential in reducing maintenance and preservation costs on rural and low volume roads. The overall objective of this study was to assess the use of locally available materials in Nevada for the development of a durable fine-graded thin hot-mix asphalt (HMA) overlay mixture for pavement preservation. Accordingly, a comprehensive laboratory evaluation was conducted. The investigation considered establishing two mix designs using typical local materials for the northern and southern part of the state. For each mixture, the determined optimal binder content based on volumetric properties was varied within the allowable tolerances to simulate the potential variation in asphalt binder content during plant production. The performance of the two thin HMA mixtures were then evaluated at the various asphalt binder contents in terms of their resistance to moisture damage, resistance to surface raveling and abrasion, dynamic modulus property, resistance to rutting, and resistance to reflective cracking. Furthermore, the workability of the designed thin HMA overlay mixtures using the locking point concept in addition to the developed interlayer bond strength using the Louisiana Interlayer Shear Strength Tester were evaluated. Overall, both designed fine-graded mixtures showed a very good performance and are expected to perform well when used as a thin HMA overlay in Nevada. In particular, good stability, very good resistance to surface raveling and abrasion, and excellent resistance to reflective cracking were observed for both thin HMA overlay mixtures at all evaluated asphalt binder contents. A cost analysis was also conducted between the thin HMA overlay and a typically used pavement surface treatment. Based on the findings from this study, it was recommended to construct field test sections in various parts of the state to evaluate the field performance of the developed thin HMA overlay mixtures in Nevada

Evaluation of Rutting Resistance of Superpave and Hveem Mixtures: Volume III - Impact of Gyratory Compaction

This report represents the third in a series of four reports documenting the overall evaluation of rutting resistance of Superpave and Hveem mixtures. Specifically this report documents the evaluation of the impact of the gyratory compaction on the permanent deformation performance of HMA mixtures using the RSCH test

Use Of Reclaimed Asphalt Pavements (RAP) In Airfields HMA Pavements

This report documents the results and findings of the AAPTP Project No. 05-06: Use of Reclaimed Asphalt Pavements (RAP) in Airfields HMA Pavements. The report includes a review of current technology in RAP pavements and its application in highway and airfield pavements. Additionally, the report includes the current highway specifications on the use of RAP and a mechanistically based method to transfer the RAP technology that has been successfully used on highway pavements into the design and specification systems for RAP on airport pavements. Review of in-service airfield pavements was conducted as part of this study. Furthermore, the report includes an evaluation of the impact of RAP on the performance life of HMA airfield pavements under three actual airport traffic mixes of a large hub, small hub, and general aviation. The Life cycle cost analysis used the characteristics and mechanical properties of HMA mixtures in the LEDFAA1.3 airfield pavement design software to compare the estimated performance life of HMA pavements with and without RAP materials. Finally, sections 401-3.3 and 403-3.3 of FAA’s P-401 and P-403 specifications, respectively, on RAP were reviewed and recommendations were made based on the findings of the research effort conducted in this project

Evaluation of Low Temperature Properties of HMA Mixtures

The deterioration of flexible pavements due to low temperature cracking is a significant and costly problem in the State of Nevada. The Nevada Department of Transportation initiated several research efforts aimed at exploring Nevada's problem with this distress. The research evaluated several newly developed low temperature performance tests under Nevada's conditions. The goal of the research was to determine the applicability of the tests for characterizing the low temperature response of Nevada's asphalt binders and HMA mixtures. This paper summarizes Nevada's experience with the SHRP low temperature tests and specifications; highlighting the effectiveness of the Superpave PG binder grading system and Thermal Stress Restrained Specimen Test. The contribution of asphalt aging to Nevada's cracking problem is also included in the paper. An investigation of the Superpave Performance Graded Binder tests has determined that the bending beam rheometer and the direct tension test correlate very well and it may not be necessary to run both tests as they are set up in the current Superpave specifications. The TSRST appears to provide the greatest value for evaluating low temperature properties of HMA mixtures. Findings from the research indicate that there are some significant correlations between the low temperature properties of asphalt binders and HMA mixtures if the mixtures are aged appropriately. This emphasizes the need to implement the appropriate conditioning procedure when low temperature cracking is used as part of the mix design and evaluation process. On the other hand, the research showed that when using polymer-modified asphalt binders, the low temperature grade of the asphalt binder maybe conservative enough where testing ofthe HMA mix may not be necessary

Variability Of The Moisture Sensitivity Of Field HMA Mixes

The objective of this study is to evaluate the variability in moisture sensitivity of lime treated HMA mixes that were sampled during construction from three projects located in the Truckee Meadows region

Laboratory Evaluation Of HMA Mixes Manufactured With Pg64-28nv And Pg64-28pm Polymer-modified Asphalt Binders

The purpose of this study was to evaluate and compare the mechanical properties of asphalt mixtures manufactured with PG64-28PM to those manufactured with PG64-28NV. Additionally, a mechanistic-empirical analysis was conducted to evaluate the impact of the two polymer-modified HMA mixtures on predicted pavement performance

Pavement Design and Materials Research 2003-2005 Activities

This report documents the workthat has been completed under the NDOT-UNR cooperative agreement for Pavement Design and Materials Research for the 2003-2005 time period

Structural Coefficient for High Polymer Modified Asphalt Mixes [Summary]

BE321University of Nevada, Reno (UNR), researchers determined the structural coefficient for asphalt concrete mixes manufactured with a high polymer (HP) modified asphalt binder that contains approximately 7.5% Styrene-Butadiene-Styrene (SBS) polymer

Instrumentation for Flexible Pavements

DTFH61-88-R00052This report documents the findings of the literature search on instrumentation used in flexible pavements. The search covered areas such as strain, stress, deflection, temperature, moisture, load location, load magnitude, performance models, and backcalculation techniques. Each group of instrumentation was evaluated in terms of the design feasibility, cost, availability, and field performance