Journal Published Online: 01 December 1999
Volume 21, Issue 2

Assessing the Distribution of Sulfate in Portland Cement and Clinker and Its Influence on Expansion in Mortar



The present work is a continuation of a study previously reported on the characterization and analysis of 33 different clinkers from North American cement plants which varied widely in molar SO3/Na2Oeq, SO3 content, and mineralogical phase distribution. This research examined the distribution of sulfur in a broad range of clinkers and identified its presence as alkali sulfates, alkali calcium sulfates, and as sulfate incorporated in the silicate phases. As a key part of the work, it has been necessary to develop relevant analytical methods for measuring potentially slowly soluble sulfate in clinker phases. The selective dissolution procedures described are applicable to the evaluation of sulfate distribution of both clinker and finished portland cement.

In the current phase of the study, physical measurements are being performed to substantiate the chemical observations of the earlier work. Five cements commercially ground from clinkers characterized earlier were chosen for further evaluation based on various sulfate levels and sulfate/alkali ratios. The volume stabilities of mortar bars (25 by 25 by 255 mm) made with these five cements were determined for several curing conditions: curing and storage under water at 23°C; curing for 24 h at 23°C, with subsequent storage under water at 38°C; 4 h initial curing at 23°C, followed by a 12-h exposure to 70 or 80°C, followed by storage under water at 23°C. The rate of temperature increase or decrease was 20°C/h in all cases. These mortar bars were prepared according to European Standard EN 196-1 with German DIN Standard Sand (Normensand). After 28 weeks of storage, bars appear to have stabilized below about 0.03% expansion. More recent testing has begun using mortar bars prepared with the above cements plus two additional Type III cements commercially ground from two of the same clinkers. These mortars have been prepared with an ASTM C 109 mortar composition and graded standard sand, which will permit direct comparison of ASTM and European standard test procedures.

Author Information

Tennis, PD
Product Standards and Technology, Portland Cement Association (PCA), Skokie, IL
Bhattacharja, S
Materials Science and Consulting, Construction Technology Laboratories, Inc. (CTL), Skokie, IL
Klemm, WA
Materials Science and Consulting, Construction Technology Laboratories, Inc. (CTL), Skokie, IL
Miller, FM
Materials Science and Consulting, Construction Technology Laboratories, Inc. (CTL), Skokie, IL
Pages: 5
Price: $25.00
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Stock #: CCA10435J
ISSN: 0149-6123
DOI: 10.1520/CCA10435J