Creep in reactive colloidal gels: a nanomechanical study of cement hydrates

TL;DR

This study investigates the microscopic origins of creep in hydrating cement pastes, revealing that nanoparticle slippage driven by inter-particle distance governs time-dependent deformation, which can inform the design of more durable concrete.

Contribution

It provides the first detailed nanomechanical analysis linking creep behavior in cement hydrates to nanoparticle interactions and packing density changes during hydration.

Findings

Creep in cement paste is mainly controlled by inter-particle distance.

Slippage between calcium silicate hydrate nanoparticles causes creep.

Creep response evolves with hydration stage and packing density.

Abstract

From soft polymeric gels to hardened cement paste, amorphous solids under constant load exhibit a pronounced time-dependent deformation called creep. The microscopic mechanism of such a phenomenon is poorly understood in amorphous materials and constitutes an even greater challenge in densely packed and chemically reactive granular systems. Both features are prominently present in hydrating cement pastes composed of calcium silicate hydrate (C-S-H) nanoparticles, whose packing density increases as a function of time, while cement hydration is taking place. Performing nano-indentation tests and porosity measurements on a large collection of samples at various stages of hydration, we show that the creep response of hydrating cement paste is mainly controlled by the inter-particle distance and results from slippage between (C-S-H) nanoparticles. Our findings provide a unique insight into the microscopic mechanism underpinning the creep response in aging granular materials, thus paving the way for the design of concrete with improved creep resistance.