# Concurrent Formation of Ice Network within Mineral Colloids with Suppressed Volume Expansion

## TL;DR

Mineral particles like calcite can significantly reduce water's volume expansion when freezing, offering new insights into natural processes.

## Contribution

Discovery that mineral colloids form ice networks to suppress water expansion during freezing.

## Key findings

- Calcite colloids reduce water expansion by 69% at 243 K.
- Ice-like hydration water forms a network bound to mineral surfaces.
- Concurrent crystallization limits free water expansion.

## Abstract

The freezing behaviors
of water are one of the most critical factors
that define the formats of life and the landscapes on Earth. The current
methods for regulating the freezing behaviors mainly rely on ice-structuring
proteins or nanomaterials to hinder the conversion of water into crystalline
ice (I
h) under low temperatures. Here
we report that the presence of minuscule mineral particles can significantly
suppress the volume expansion of water upon freezing into ice. In
particular, colloidal precipitates of calcite, a primary mineral accounting
for ∼4 wt % of the Earth’s crust and the most abundant
biomineral on Earth, are able to reduce water expansion by 69% (from
8.4% to 2.6%) at 243 K. The mechanism of expansion suppression involves
the formation of a continuous network of fairly ordered “ice-like”
hydration waters that are bound to the surface of the mineral colloids
at room temperature, and their concurrent crystallization through
heterogeneous nucleation upon freezing, which confines the interstitial
free water and refrains its volume expansion. These findings reveal
the remarkable ability of common minerals to suppress a most ubiquitous
phenomenon, water volume expansion upon freezing, and offer fresh
insights into various fields such as biomineralization, hydrology,
soil science, and lithology.