Novel C-F-S-H/PCE nanocomposites with high-efficiency seeding effect on the hydration of Portland cement

Novel C-F-S-H/PCE (calcium-ferrite-silicate-hydrates/polycarboxylate ether) nanocomposites were synthesized successfully by incorporating Fe3+ during the synthesis of C-S-H/PCE. The results of isothermal heat flow calorimetry and compressive strength tests indicated that C-F-S-H/PCE nanocomposites showed high-efficiency seeding effect on early cement hydration due to the higher absorption of PCE and smaller particle size of nano-seeds than those of traditional C-S-H/PCE nanocomposites. And the best seeding effect of C-F-S-H/PCE nanocomposites was identified when the Ca/Si and Fe/Si were 1.0 and 0.03 respectively. Moreover, the incorporation of Fe3+ did not affect the concentration of free calcium in the C-F-S-H/PCE suspension whose morphologies were composed of irregular globules and network gel. Additionally, the incorporated Fe3+ made the semi-crystalline C-S-H structure more amorphous though it was not a direct factor that affected the seeding effect of the nanocomposites. All in all, this study provided a new idea from modified seeding nanocomposites for low-CO2 cement and a basis for the production of nano-seeds based on Fe-rich wastes.