The increased incidence of alkali-aggregate reactivity in recent years makes re-examination of the proposed reaction mechanisms by Pagano and Cady very appropriate. Their discussion of the reaction mechanism, however, raises several points:
A chemical approach to the problem of alkali-reactive carbonate aggregates
β Scribed by M.A. Pagano; P.D. Cady
- Publisher
- Elsevier Science
- Year
- 1982
- Tongue
- English
- Weight
- 569 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0008-8846
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β¦ Synopsis
Refereed) (Received Jan. 22; in final form July 27, 198].)
ABSTRAC~
This paper presents the results of a laboratory investigation of postulated mechanisms and potential remedial measures involving alkali carbonate reaction in concrete. This reaction involving certain carbonate (limestone) aggregates when used with high alkali cement has resulted in distress (cracking) of concrete pavements and slabs.
The observed distress has been attributed to dedolomitization of the aggregates and osmotic pressures.
This study was conducted to determine whether a chemical approach to the problem could reduce the expansion to acceptable levels.
The results were encouraging. Expansion was reduced by as much as 50% using two common chemical substances, lithium carbonate and ferric chloride, introduced into a high alkali portland cement concrete made with a very reactive coarse aggregate, Gull River limestone from Kingston, Ontario, Canada. Another substance, dimethylsulfoxide, was tested also, with insignificant changes in measured expansion.
π SIMILAR VOLUMES
Research on the structure and bond between cement stone and aggregates shows that the structure of the contact zone clearly di#fers from that of the plain cement stone. The main constituent of the contact zone seems to becalcium hydroxide which is also mainly responsible for the cement-aggregate bon