00666225

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http://onlinepubs.trb.org...trr/1994/1434/1434-003.pdf

https://scholar.google.co...more&publication_year=1994

Iron and steel slags are often used as subbase materials in the construction of highways. Previous studies have suggested that the free lime (CaO) in these subbases is responsible for the deposition of calcium carbonate (tufa) in many highway drains. Clogging of these drains leads to the deterioration of highways. Previous work has shown that if the total original CaO in slags exceeds 1%, the slags will readily produce tufa. Therefore, to classify the tufa-producing potential of these slags, it is necessary to determine the total original CaO. Thermogravimetry (TG) methods were employed and most of the TG plots indicated two major changes in weight loss--dehydroxylation of Ca(OH)2 and dissociation of carbonates. From these changes in weight loss the percentage of CaO was calculated. These calculated percentages of CaO from the TG plot plus the results from the "sugar test" determine the total original percentage of CaO. Five groups are recognized according to the calculated total percentage of CaO: 0%, 3.5 to 5%, 8 to 9%, 10 to 12%, and 24 to 25%. Air-cooled blast furnace slag (0% CaO) is the only slag that should be used as a subbase in highway construction, whereas all others are considered to be harmful and could lead to the formation of tufa. TG methods and the sugar test are excellent and economical ways to characterize the original CaO in slags and the susceptibility of the slags to precipitate CaCO3 in subdrains of highways.

This paper appears in Transportation Research Record No. 1434, Subsurface Drainage, Soil-Fluid Interface Phenomena, and Management of Unpaved Surfaces. 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

01401242

English

p. 17-22

1994

Transportation Research Record

0309055113

Figures (1) ; References (12) ; Tables (6)

Calcium carbonate; Calcium oxide; Iron and steel industry; Slag; Subbase materials; Subdrains; Thermogravimetric analysis

Clogging; Tufa

Geotechnology; Highways; Materials; I33: Other Materials used in Pavement Layers; I42: Soil Mechanics

TRIS, TRB

Sep 16 1994 12:00AM

• ACCELERATED GROUNDWATER TRANSPORT STUDIES USING A GEOTECHNICAL CENTRIFUGE
• ALKALINE LEACHATE AND CALCAREOUS TUFA ORIGINATING FROM SLAG IN A HIGHWAY EMBANKMENT NEAR BALTIMORE, MARYLAND
• CHARACTERIZATION OF BASE AND SUBBASE IRON AND STEEL SLAG AGGREGATES CAUSING DEPOSITION OF CALCAREOUS TUFA IN DRAINS
• DEVELOPMENT AND COMPARISON OF PERMEABILITY MEASUREMENT TECHNIQUES FOR JOINTED CONCRETE PAVEMENT BASES
• DRAINABILITY OF GRANULAR BASES FOR HIGHWAY PAVEMENTS
• FACTORS INFLUENCING THE TRANSFERABILITY OF MAINTENANCE STANDARDS FOR LOW-VOLUME ROADS
• FIELD EVALUATION OF VARIOUS TYPES OF OPEN-GRADED DRAINAGE LAYERS
• INSTITUTIONAL ASPECTS OF ENVIRONMENTAL MANAGEMENT IN ROAD DEVELOPMENT
• MOLDING WATER CONTENT AND HYDRAULIC CONDUCTIVITY OF COMPACTED SOILS SUBJECTED TO FREEZE/THAW
• OPERATIONAL UNPAVED ROAD MANAGEMENT SYSTEM IN THE CAPE PROVINCE OF SOUTH AFRICA
• QUALITY ASSURANCE PROCEDURES RELATED TO ADMINISTRATION OF UNSURFACED ROADS
• SOME PHYSICAL FACTORS AFFECTING CONTAMINANT HYDROLOGY IN COLD ENVIRONMENTS