The binder content of hot mix asphalt (HMA) is most commonly determined either by solvent extraction or ignition oven (IO) methods. Generally, the IO method has worked well with various HMA mixtures except those containing certain types of high mass loss (decomposing) aggregates, especially dolomite. For these aggregates, the high temperatures experienced during the ignition process initiate chemical changes within the aggregate particles, which result in variable mass losses. This, in turn, causes difficulties in calculating a consistent correction factor and determining a repeatable binder content. This paper presents a modified IO binder content determination method, which involves lowering the test temperature to 427°C and reducing the sample mass by half. In addition, only the bottom material basket of the typical IO test setup is used to avoid errors in the results due to temperature differentials that develop when, upon ignition, mixture from the lower basket starts heating the mixture in the upper basket. The proposed method was successfully verified by using six different plant-produced mixtures.

Accurate determination of asphalt content (AC) in hot mix asphalt (HMA) is essential to evaluate the performance characteristics of HMA pavements. The standard test methods for determining the AC, currently used by the Oklahoma Department of Transportation (ODOT) and other DOTs and asphalt industries, are time-consuming, environmentally unsuitable, and not applicable to several absorptive and dolomitic aggregates. This study has developed a systematic method for the determination of AC using volumetric properties of aggregate, asphalt, and HMA mix. The developed method employed the theoretical maximum specific gravity (Gmm) of an HMA mix, the bulk and apparent specific gravity of the aggregate (Gsb and Gsa), and the specific gravity of the asphalt binder (Gb). The CoreLokTM device is used to determine the volumetric properties of the aggregate and HMA mix. This developed method is easy to use, environmentally safe, time efficient, and accurate. Three different aggregates were selected for the study based on varying gradation, absorption, and ignition oven correction (IOC) factor. HMA mixes were prepared with each of these aggregates using 5.0 %, 5.5 %, and 6.0 % AC. For each of the mixes, AC was calculated using the proposed method and compared with the actual AC value. The predicted AC values were compared with AC values from the ignition oven method (AASHTO T 308) and the solvent extraction method (AASHTO T 164). Results showed that the proposed method predicted the AC of HMA mix accurately. The method introduces a correction factor (Cv), which needs to be determined during the design stage and specified on the mix design information. The Cv value is used to calculate AC by the proposed method during quality assurance and quality control at the production and service life of HMA.

This book presents new studies dealing with the attempts made by the scientists and practitioners to address contemporary issues in geotechnical engineering such as characterization of soil, geomaterials, soil stability and some other geomechanics issues that are becoming quite relevant in today's world. Papers were selected from the 5th GeoChina International Conference on Civil Infrastructures Confronting Severe Weathers and Climate Changes: From Failure to Sustainability, held on July 23-25, 2018 in HangZhou, China.

The Materials and Tests Division's Bituminous Section evaluated the ignition method as an alternative to the solvent method for determining asphalt content. Three ovens (the Gilson Asphalt Binder Ignition Furnace, Model HM 378; the NCAT Asphalt Content Tester; and the Troxler Asphalt Quality Analyzer) were evaluated for accuracy, precision, and performance. Ignition was proven to be an appropriate method of determining asphalt content. The test procedure resulting from this work is Tex-236-F, which is included in Appendix A.

"Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method," requires determination of asphalt and aggregate correction factors for asphalt mix designs for each ignition furnace used to test a design. In some cases, where there are numerous asphalt mix designs or numerous ignition furnaces testing a particular mix design, correction factors may be shared between ignition furnaces, though this practice is not strictly permitted by AASHTO T 308 without supporting evidence. The objectives of this research were to (1) determine the significant influences that affect the variability of asphalt and aggregate correction factors for ignition furnaces; (2) develop guidelines for the installation, operation, and maintenance of ignition furnaces to minimize the variability in correction factors between furnaces; and (3) develop and document a statistically valid correction factor verification procedure to identify and troubleshoot causes for non-comparing, statistically different, or biased results of AASHTO T 308. The research was conducted in three parts: (1) a study of the sensitivity of asphalt and aggregate correction factors to variation in experimental factors such as furnace type, test temperature, asphalt content, and sample mass; (2) a round-robin study to identify correction factor outliers and determine the contributory cause(s); and (3) troubleshooting of outliers from the round-robin study. The research found that the primary factors affecting asphalt and aggregate correction factors determined by AASHTO T 308 are furnace type and test temperature. Conducting the test at 800°F appears to substantially reduce the magnitude and standard deviation of the correction factors for asphalt mixtures that do not contain lime. Sharing correction factors among different ignition furnaces appears acceptable for low correction factor aggregates (0.1% or less) but is problematic for aggregates with correction factors of 1.0% or greater. The current precision estimates in AASHTO T 308 appear applicable only to mixtures with low correction factor aggregates. The key product of this research is a Proposed Standard Practice for Installation, Operation, and Maintenance of Ignition Furnaces (Appendix I). Development of a verification procedure to identify causes for non-comparing, statistically different, or biased test results from ignition furnaces was found to be premature and further research is planned.

TRB's National Cooperative Highway Research Program (NCHRP) Report 714: Special Mixture Design Considerations and Methods for Warm-Mix Asphalt: A Supplement to NCHRP Report 673: A Manual for Design of Hot-Mix Asphalt with Commentary presents special mixture design considerations and methods used with warm-mix asphalt. NCHRP Report 714 is a supplement to NCHRP Report 673: A Manual for Design of Hot-Mix Asphalt. All references to chapters in NCHRP Report 714 refer to the corresponding chapters in NCHRP Report 673.