Work

Contact point geometry governs structural buildup at rest in Portland cement–limestone blends

Year: 2025

Type: article

Abstract: The early stiffening of fresh cement paste plays a key role in shaping and stability during casting and 3D printing. In Portland cement systems, this phenomenon arises from the formation of calcium–silicate–hydrate (), which stiffens grain‐to‐grain contacts. However, the role of powder characteristics such as particle size and morphology remains poorly understood. Here, we vary fineness and grain shape by blending Portland cement with either coarse or fine limestone, leveraging the affinity of to nucleate on limestone surfaces. By coupling calorimetry and rheometry, we relate the amount of formed hydration products to the increase in stiffness, and show that the mechanism of contact stiffening through formation remains unchanged with limestone addition. Nevertheless, the rate of stiffening varies across blends. We find that these rates correlate with a characteristic length scale that captures particle size and shape. These results demonstrate that early stiffening depends not only on the amount of hydration products formed, but also on the geometry of the contacts where these products form, offering a framework for understanding more complex systems such as limestone calcined clay cements.

Source: Journal of the American Ceramic Society

DOI: 10.1111/jace.70271

Authors: Luca Michel, Antoine Sanner, Franco Zunino, Robert J. Flatt, David S. Kammer

Institutions: ETH Zurich, Institute for Building Materials, University of California, Berkeley

Language: English

Topic: Innovations in Concrete and Construction Materials

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,070

Funder: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung