Nano C-S-H seeds prepared from ground granulated blast-furnace slag-carbide slag and its application in Portland cement

• Published in: Construction & building materials 2022-04, Vol.329, p.127204, Article 127204
• Main Authors: Gu, Xianyue, Tan, Hongbo, He, Xingyang, Zhang, Junjie, Li, Maogao, Su, Ying, Yang, Jin
• Format: Article
• Language: English
• Subjects: Early strength; Hydrates; Nano C-S-H seeds; Portland cement
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2022.127204

•Nano C-S-H seeds with D50 = 420 nm were prepared from GGBS and CS by wet grinding.•Nano C-S-H seeds notably augmented the compressive strength of PC.•Nano C-S-H seeds accelerated PC hydration and refined the pore structure.•The results provided a new approach to prepare nano C-S-H seeds. In the present study, to enhance the early mechanical properties of Portland cement (PC), ground granulated blast-furnace slag (GGBS) and carbide slag (CS) were cured and treated by wet grinding to prepare nano C-S-H seeds (NCSH). The properties of NCSH were characterized in details. NCSH-PC system was designed, and the dosage of NCSH was chosen as 0%, 0.5%, 1%, 2% and 4% of cement. Compressive strength and the setting time of NCSH-PC system were examined. The related mechanism was analyzed by XRD, hydration heat, 29Si NMR, TG-DTG and MIP. Results exhibited that NCSH slurry with D50 = 420 nm was obtained, and it notably augmented the early compressive strength of PC mortars, noting that 4% NCSH enhanced the compressive strength by 131.4% at 12 h. Moreover, the final setting time of PC pastes was shortened by 46.3% by adding 4% NCSH. The reason was that NCSH greatly accelerated PC hydration and further expedited the hydrates formation; also, the pore structure was refined owing to the filling effect offered by NCSH, noticing 4% NCSH reduced the total porosity from 22.8% to 19.7% at 12 h. Such results suggested a novel method to prepare NCSH, and it was expected to act as an accelerator in PC system.