Tuning the Hydration Acceleration Efficiency of Calcium Carbonate by Pre-Seeding with Calcium Silicate Hydrate

Nanomaterials are promising candidates for refined performance optimization of cementitious materials. In recent years, numerous studies about the performance improvement of nanomaterials using polymers have been conducted, but the modification of cement-oriented nanomaterials with inorganic modifiers is seldom assessed. In this study, we explored the performance tuning and optimization of nanomaterials by inorganic modification. In this work, hydration acceleration efficiency of calcium carbonate (CaCO₃, CC) was tuned via surface deposition with calcium silicate hydrate (C-S-H) nanogel through seeding. Multiple calcium carbonate-calcium silicate hydrate (CC-CSH) samples with varying degrees of surface modification were prepared via dosage control. According to characterizations, the degree of C-S-H modification on the CaCO₃ surface has a maximum that is controlled by available surface space. Once the available space is depleted, excessive C-S-H turns into free form and causes adhesion between CC-CSH particles. The resultant CC-CSH samples in this work showed enhanced hydration acceleration efficiency that is tuned by the actual degree of C-S-H modification. Elevated C-S-H modification causes CC-CSH's acceleration behavior to shift to enhanced early-age acceleration. According to mortar strength tests, CC-CSH with 5% C-S-H modification showed the most balanced performance, while CC-CSH with higher C-S-H modification showed faster early-age strength development at the cost of lower later-age strength. The inferior later-age strength of highly C-S-H-modified CC-CSH samples may be due to the coarsening of hydration products and stiffening of their network, as well as agglomeration caused by C-S-H adhesion. This study may offer a novel route for performance tuning of cement-oriented nanomaterials.