Exploring the Potential of Nonclassical Crystallization Pathways to Advance Cementitious Materials.

Area of Science:

• Materials Science
• Chemical Engineering
• Civil Engineering

Background:

• Cement production significantly contributes to global CO2 emissions.
• Calcium-silicate-hydrate (C-S-H) is the primary binding phase in ordinary Portland cement (PC).
• Increasing use of supplementary cementitious materials (SCMs) and alternative binders necessitates understanding new phase crystallization.

Purpose of the Study:

• To review crystallization pathways of cement-binding phases, focusing on nonclassical crystallization.
• To explore how understanding these pathways can lead to enhanced cement performance and reduced environmental impact.
• To highlight additive-controlled crystallization strategies for developing advanced cementitious materials.

Main Methods:

• Literature review of nonclassical crystallization in cementitious systems.
• Analysis of intermediate steps in phase formation, including solute ion associates, dense liquid phases, amorphous intermediates, and nanoparticles.
• Examination of additive-controlled crystallization, exemplified by synthetic mesocrystalline C-S-H.

Main Results:

• Nonclassical crystallization involves intermediate steps beyond simple ion-to-crystal transitions.
• Additive use can control crystallization pathways, leading to optimized cement matrices.
• Mesocrystalline C-S-H, produced via controlled subunit assembly, demonstrates superior flexural strength.

Conclusions:

• Understanding multistep crystallization pathways provides innovative strategies for cement formulation.
• Additive-controlled crystallization offers a route to advanced cement-based materials with enhanced properties.
• Fundamental insights into crystallization mechanisms are crucial for sustainable construction materials development.