AGGREGATE TOUGHNESS / ABRASION RESISTANCE AND DURABILITY TESTS RELATED TO ASPHALT CONCRETE PERFORMANCE IN PAVEMENTS By
i DISCLAIMER The contents of this report reflect the views of the authors who are solely responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views and policies of the National Center for Asphalt Technology of Auburn University. This report does not constitute a standard, specification, or regulation. ii ABSTRACT Numerous tests have been developed to empirically characterize aggregate without, necessarily, a strong relationship with the performance of the final products incorporating these aggregates. This seems to be particularly true for aggregate " toughness and abrasion resistance " and " durability and soundness. " The purpose of this research was to identify and evaluate toughness/abrasion resistance and durability/soundness tests for characterizing aggregate used in asphalt concrete and to determine those test methods that best correlate with field performance. Based on a review of literature and specifications, laboratory tests for characterizing aggregate toughness/abrasion resistance and durability/soundness were selected. Sixteen aggregate sources with poor to good performance histories were identified for evaluation with the selected suite of tests. Performance histories of pavements containing these aggregates in asphalt concrete layers were established through personal contacts with state transportation agencies and performance evaluation questionnaires. Aggregate properties from laboratory tests were correlated with field performance. The Micro-Deval and magnesium sulfate soundness tests provide the best correlations with field performance of asphalt concrete, and are recommended for characterizing aggregate toughness/abrasion resistance and durability/soundness.
ESTABLISHMENT OF ACCEPTANCE LIMITS FOR 5-CYCLE MSS AND MODIFIED WET BALL MILL TESTS FOR AGGREGATES USED IN SEAL COATS AND HMAC SURFACES. FINAL REPORT
This research report evaluates the performance of aggregates from several sources commonly used throughout Texas. The aggregate selection was primarily based on the magnesium sulfate soundness (MSS) loss. Aggregates used in the project had a range of MSS values, with a large fraction of the total having mid-range MSS loss (more than 10.0 but less than 25.0). Included in the study were hot-mixed asphalt concrete (HMAC), seal coat, and micro-seal pavement surfacing. Pavement test sites were selected to provide a range of traffic. Other laboratory tests performed for this study include Texas degradation, Los Angeles abrasion, and polish value. Evaluation of the pavement surfaces included frictional resistance, macro-photographs, surface texture, and condition rating. Regression equations have been developed to predict performance of different aggregates in pavement surfaces. A mini-texture meter was used for surface texture measurements. Micro- and macro-textural measurements were integrated in an attempt to forecast attendant frictional resistance.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME