Fabrication, structure, and mechanical properties of a high-order calcium silicate hydrate based on polymer and pH tuning

Calcium silicate hydrates (C-S-H) are the strength sources of cement-based materials. However, the arbitrary packing of C-S-H particles at the nanoscale limit the mechanical properties considerably. In this study, we achieved high-order growth and improved mechanical properties of C-S-H by polymer addition and fine-tuning of the pH value. We found that a proper initial condition contributes to a uniform dispersion of colloidal C-S-H particles, which is essential for subsequent ordered growth. On the basis of stable dispersion, an accurate control of increasing pH values can induce the high-order and dense growth of C-S-H, which obtains a significantly higher elastic modulus as twice as traditional C-S-H. Furthermore, the polymer steric hindrance effect in low pH condition and templating effect of long chain in the higher pH condition explained the well-arranged growth of C-S-H with the interaction to polymer. We hope this highly ordered C-S-H may pave the way for designing tougher and more durable cement-based materials.