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Minimizing Paste Content in Concrete Using Limestone Powders – Demonstration Mixtures

Published

Author(s)

Dale P. Bentz, Scott Z. Jones, Didier Lootens

Abstract

In recent years, there has been great interest in reducing the cement content of concrete, due to the high energy and carbon dioxide footprints of cement production. There are numerous (waste) materials that can be substituted for cement in the concrete mixture proportions, including fly ash, slag, silica fume, metakaolin, waste glass, etc. However, a more abundant material substitute would be limestone powder, created from the same limestone that is currently heavily employed in cement production as the primary source of calcium oxide. This technical note presents an approach to replacing not only cement powder, but effectively cement paste consisting of the cement and water, with appropriately sized limestone powder(s). Such an approach effectively extends the conventional utilization of centimeter-sized coarse aggregates (rocks) and millimeter-sized fine aggregates (sand) that occupy between 65 % and 75 % of the volume of a concrete structure to include micro-aggregates ranging between about 1 µm and 100 µm in size. Here, pastes, mortars, and concretes are each formulated with limestone powder replacement for a portion of their cement paste component. For these mixture modifications, the water-to-cement ratio (w/c) is maintained at or above 0.4 to provide sufficient water to react with all of the cement, so that none of this most costly component of cement-based materials goes to waste. Meanwhile, the water-to-solids ratio (w/s) is reduced to a value in the range of 0.22 to 0.40 in order to maximize the limestone powder replacement level, while still providing sufficient flow and rheology, by using reasonable dosages of high range water reducing admixtures. The fresh, early age, and long term performance properties of these high volume limestone powder (HVLP) mixtures are contrasted with a w/c=0.4 ordinary portland cement (OPC) paste or mortar, or a w/c=0.5 OPC concrete reference, respectively.
Citation
Technical Note (NIST TN) - 1906
Report Number
1906

Keywords

Concrete, high range water reducing admixture, high volume limestone powder, mortar, paste content, sustainability.

Citation

Bentz, D. , Jones, S. and Lootens, D. (2016), Minimizing Paste Content in Concrete Using Limestone Powders – Demonstration Mixtures, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.TN.1906 (Accessed February 29, 2024)
Created January 14, 2016, Updated November 10, 2018