Abstract
This study investigates the effect of nano-SiO(2) on the mechanical properties and fracture surface morphology of cement composites. The focus was on fracture toughness (K(Ic)(S)) and compressive strength. Composites with nano-SiO(2) showed up to 63% higher fracture toughness and 68% higher compressive strength than unmodified ones. The influence of nano-SiO(2) content (0.09-2.91% by binder mass) and water-to-binder ratio (0.43-0.57) was examined using a Central Composite Design. Properties improved with higher nano-SiO(2) content and lower w/b ratio. Fractographic analysis using laser profilometry revealed a clear correlation between the fractal dimension (D) of fracture surfaces and K(Ic)(S) and fcm. Lower D values indicated smoother fracture surfaces and denser microstructures. The results clearly show that changes in the composition-particularly the nano-SiO(2) content and the water-to-binder ratio-determine the development of the microstructure, which in turn governs the mechanical properties of the material. Consequently, the study establishes a coherent, quantitative relationship between mixture composition, fracture microstructure, and the macroscopic properties of the composite.