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.

The durability of cementitious materials is significant concerning long-term performance. Nanomaterials are promising candidates for deep refinement of cement durability. Hydrophobic calcium carbonate is a widely applied and easily accessible nanomaterial. However, its hydrophobicity and poor dispersity in water prohibit its direct application in cementitious materials. In this study, hydrophobic calcium carbonate nanoparticles (HbCC) were modified using a novel amphiphilic comb-shaped dispersant that is capable of laurinol release. The modification was conducted to improve the dispersity of HbCC and their compatibility with hydration products. The dispersion-improved calcium carbonate particles (AmphCC) were characterized and tested for cement durability improvement performance. According to the results, the AmphCC particles showed a pronounced effect on improving permeation resistance of cement mortars, with water absorption and chloride penetration considerably lowered. Moreover, the introduction of AmphCC in cement did not show significant adverse effects on strength development. Compared with AmphCC, a single addition of the unmodified HbCC and the dispersant cannot achieve equivalent effects. The superior effect of AmphCC is due to the synergistic effect of good particle dispersion and controlled release of the hydrophobic molecules, which is achieved by dispersion of HbCC with binding of the dispersant.

In this work, a novel total non-ionic polystyrene-polyurethane (PS-PU) composite latex was synthesized with polymerizable polyethylene glycol ether. Contrary to traditional styrene-butyl acrylate latex (St-BA), PS-PU has a smaller size and superior dispersion stability, and it is stable in saturated Ca(OH)2 even after 72 h. In fresh-mixed mortars, PS-PU showed a little adverse effect on workability and insignificant air entrainment, with little defoamer consumption. The retardation effect of PS-PU is also much milder than traditional St-BA. As for strength, PS-PU showed a less adverse effect on early and late age compressive strength, but its effect on flexural strength is not as pronounced as St-BA at high dosages (4% and 6%). The different behavior in cementitious materials between PS-PU and St-BA can be reasoned from their different adsorption behavior and surface charge properties, as the results from characterizations suggest. The non-ionic nature of PS-PU made it less prone to destabilization and adsorption, which turned out as the aforementioned behavior in cementitious systems. The difference can further be ascribed to the difference in their polymeric structure and properties.