# Influence of Particle Size, Defect Density and Salts on the Dissolution and Early Hydration of a Model System (C3A + Quartz)

## TL;DR

This study explores how particle size, defects, and salts affect the early hydration of cement using a model system of tricalcium aluminate and quartz.

## Contribution

The paper introduces a novel model system (C3A + quartz) and provides mechanistic insights into hydration influenced by particle size, defect density, and salts.

## Key findings

- Product layer formation shifts C3A dissolution to diffusion-controlled regimes.
- Smaller particle size and higher defect density increase dissolution and hydration rates.
- Sulfates and chlorides alter reaction pathways, with sulfates promoting ettringite formation.

## Abstract

Understanding the hydration behavior of cementitious materials is crucial as it governs the setting, strength development and long-term durability of concrete. This study provides fundamental insights into these processes by investigating the early hydration of tricalcium aluminate (C3A) with quartz as a novel model system for multiple clinker phases. Employing a multi-technique approach combining conductivity, calorimetry and microscopy, we systematically examine the concurrent effects of product layer formation, C3A’s particle size and defect density, and salts on dissolution kinetics and early-stage reaction pathways. Results indicate that product layer formation shifted C3A’s rapid dissolution toward diffusion-controlled regimes. Reduced particle size and increased defect density accelerated the dissolution and hydration kinetics. Sulfates and chlorides differentially altered reaction pathways, with preferential sulfate reactivity driving ettringite formation. These mechanistic insights advance fundamental understanding of the hydration behavior of cementitious material.