Laboratory Studies and Evaluations of Concrete Containing Dead-Burned Dolomite

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Title: Laboratory Studies and Evaluations of Concrete Containing Dead-Burned Dolomite

Author(s): J. M. Scanlon and J. D. Conolly

Publication: Special Publication

Volume: 145

Issue:

Appears on pages(s): 1115-1134

Keywords: calcium oxides; concrete panels; concretes; contamination; differential thermal analysis; dolomite; durability; hydration; magnesium oxides; popouts; repairs; samples; volume fraction; wetting and drying tests; x-ray diffraction; Materials Research

Date: 5/1/1994

Abstract:
In 1980, dead-burned dolomite particles removed from a cement kiln were inadvertently distributed in aggregates that were later used in concrete. These particles were of coarse aggregate size (38 mm) and contained approximately 55 percent calcium oxide (CaO) and 35 percent magnesium oxide (MgO). When this contaminated aggregate was used to make concrete in 1980, it caused some relatively large popouts (up to possibly 230-mm-diameter). Subsequent periodic visual evaluations of this contaminated concrete were performed to verify the acceptability of the concrete and the durability of popout repairs. To the authors' knowledge, only one structure was removed and repaired. In 1989, another such incidence occurred, but this time the portland cement was contaminated with smaller (<9.5-mm) dead-burned dolomite particles with approximately the same proportions of CaO and MgO. Paper reports on how data developed from the 1980 incident was extended for use in evaluating the concrete contaminated in 1989, and how instrumentation was used to effectively determine the actual volume of dead-burned dolomite in the contaminated concrete and degree of hydration of the particles. Such information is being used to predict the long-term effects of the contamination.