Influence of Two Types of Nanosilica Hydrosols on Short-Term Properties of Sustainable White Portland Cement Mortar

Abstract

The present study explored the influence of two types of nanosilica hydrosols (with different specific surface areas of 1 and 3 m2/g) on short-term mechanical, durability, and microstructural properties of white portland cement mortar containing low-activity blast furnace slag (ASTM C989 Grade 8). Accordingly, various tests, including mechanical (compressive and flexural strengths), durability (electrical resistivity, chloride ion penetrability, and water absorption), and microstructural (X-ray diffraction, thermogravimetry/differential scanning calorimetry, and field emission scanning electron microscopy), were carried out on the combined performance of low-activity blast furnace slag (BFS)–nanosilica in a white cement mortar system. Based on the obtained results, substitution of a high volume of BFS for cement (3 and 5%) brought about a dramatic decrease in mechanical strength and porosity-related durability indices (e.g., water absorption). Nonetheless, electrical-based durability parameters such as resistivity and chloride ion impermeability were enhanced as the content of BFS was increased. Furthermore, the combinations of low-activity BFS and nanosilica hydrosols were synergistic in improving the mechanical and durability properties of white cement mortar. The synergistic effect of the aforementioned blends was more pronounced in electrical resistivity test results and less significant in flexural strength test results.