Abstract
The paper presents results regarding the possibility and effectiveness of carrying out the internal hydrophobization in cement-based materials with mineral additives such as granulated blast furnace slag, silica dust and silica fly ash. The obtained results indicate that effective internal hydrophobization by using triethoxyoctylsilane is achievable and provides protection against water by decreasing the capillary absorption of water in the material. However, it also affects the hydration process of the binder, which results in a reduction in the compressive strength of the material.