Optimized Production of Sol–Gel Nanosilica and Synergistic Effect on the Performance and Sustainability of Cement-Based Materials

The development of sustainable construction materials requires innovative strategies to optimize cement hydration and reduce clinker consumption. This study evaluates the influence of ammonia-controlled sol–gel synthesis on the physicochemical properties of nanosilica and its subsequent impact on the performance of sustainable cement pastes. Nanosilica was synthesized at pH 9 and 11, revealing that the pH 9 environment yields a superior specific surface area (655 m2/g) and enhanced colloidal stability (ζ = −42.5 mV). These properties triggered a 61% increase in compressive strength at 3 days with a low dosage (0.4 wt%), significantly accelerating the hydration kinetics. XRD analysis confirmed a 22% reduction in the portlandite content, validating a robust pozzolanic-nucleation mechanism. Furthermore, rheological modeling showed an increased yield stress (up to 31.2 Pa), consistent with a dense, interconnected percolation network. The observed 61% early-age strength increase conceptually enables clinker substitution strategies; the associated environmental benefits—including potential reductions in the carbon footprint of cementitious systems—warrant future quantification through life-cycle assessment (LCA), which is beyond the scope of the present work. These results demonstrate that tailored sol–gel synthesis provides a high-efficiency pathway for the development of eco-efficient, high-performance cementitious materials.