LABORATORY EVALUATION OF THE ADDITION OF LIME TREATED SAND TO HOT-MIX ASPHALT

Moisture damage to hot-mix asphalt (HMA) is a major problem. Hydrated lime has been shown to be an effective additive for reducing moisture damage susceptibility of HMA. Among the currently used methods for addition of hydrated lime to HMA aggregate, the one most often used is to add the lime to the entire aggregate stream. A recent field trial has shown that it is feasible to add hydrated lime to only the sand fraction in amounts that are equivalent to the desired concentration on the total aggregate basis. This would allow set up of a central facility for adding lime to the sand fraction of an HMA aggregate. The lime/fine aggregate mixtures could then be transported to an HMA plant and mixed with the remaining aggregate fraction. This concept is investigated in the laboratory using three aggregate combinations, two methods of conditioning specimens for moisture susceptibility testing (AASHTO T283 and ASTM D4867), two methods of lime addition, and three lime concentration levels. A statistical analysis of the data indicates that the two methods of lime addition (lime to fine aggregate and lime to total aggregate) produce asphalt mixtures that are equivalent in reduced moisture damage susceptibility. Other statistical comparisons indicate that (a) the greatest reduction in moisture susceptibility of the mixtures studied occurred from increasing the lime content from 0.5 to 1.0% (total dry aggregate basis), with less effect resulting from a 1.0 to 1.5% increase; (b) both the AASHTO T283 and ASTM D4867 procedures can be used to evaluate moisture susceptibility, but it appears that the specific aggregate combination will determine which procedure is most severe for a particular mixture; and (c) the addition of lime in the form of a slurry was in most cases better than the addition of lime to a moist aggregate. On the basis of recent field trials and the data obtained in the investigation, it appears that the addition of lime to the fine aggregate fraction of HMA aggregates, followed by subsequent mixing with the remainder of the aggregate stream, is an innovative process that has the potential for reducing capital costs sometimes associated with lime addition, without compromising the beneficial effects of lime addition for reduced moisture damage susceptibility of HMA.

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Supplemental Notes:
- This paper appears in Transportation Research Record No. 1469, Flexible Pavement Construction Issues. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
Authors:
- Hanson, Douglas I
- Graves, Robin E
- Brown, Elton Ray
Publication Date: 1994

Language

English

Media Info

Features: Figures; References; Tables;
Pagination: p. 34-42
Monograph Title: Flexible Pavement Construction Issues
Serial:
- Transportation Research Record
- Issue Number: 1469
- Publisher: Transportation Research Board
- ISSN: 0361-1981

Subject/Index Terms

TRT Terms: Calcium hydroxide; Calcium oxide; Cost effectiveness; Hot mix asphalt; Innovation; Laboratory tests; Loss and damage; Moisture content; Moisture damage; Slurry; Statistical analysis; Water
Identifier Terms: American Association of State Highway Officials
Uncontrolled Terms: Lime content; Lime slurry; Moisture susceptibility
Old TRIS Terms: Aashto t283; Astm d4867; Methods of lime addition; Test results
Subject Areas: Data and Information Technology; Highways; Materials; I31: Bituminous Binders and Materials;

Filing Info

Accession Number: 00677639
Record Type: Publication
ISBN: 0309061059
Files: TRIS, TRB
Created Date: May 9 1995 12:00AM