Articles, Guides & Reports

This article reports on the mechanisms that allow portland limestone cement (PLC) mixtures to maintain the same levels of strength as portland cement (PC) mixtures. Mechanisms discussed include the filler effect, increased cement paste volume, heterogeneous nucleation, faster kinetics of hydration, and production of calcium carboaluminates. The performance of two PLCs produced on two different milling circuits are compared against a control PC produced on one of the same circuits.

The authors discuss the development of ternary concrete mixtures with performance characteristics that are equivalent or superior to those for a conventional concrete mixture produced with portland cement only. Mixtures included combinations of ordinary or high-early strength cement, Class C or Class F fly ash, and limestone powder. The developed ternary mixtures had about the same setting times as the conventional concrete mixture and they exhibited significantly improved measured compressive strengths and transport properties.

Extensive research and testing have shown that several types of ground glass can perform well as a pozzolanic material in concrete. Supported by these results, a new specification ASTM C1866/C1866M, “Standard Specification for Ground-Glass Pozzolan for Use in Concrete,” was published earlier this year. This article provides much of the background information and industry context that accompanied the balloting of this new document.