Improving cement-based materials by using silica fume: Fid-Bau Portal

Improving cement-based materials by using silica fume

Chung, D.D.L.

The use of silica fume as an admixture in cementbased materials increases the tensile strength, compressive strength, compressive modulus, flexural modulus and the tensile ductility, but decreases the compressive ductility. In addition, it enhances the freeze-thaw durability, the vibration damping capacity, the abrasion resistance, the bond strength with steel rebars, the chemical attack resistance and the corrosion resistance of reinforcing steel. Furthermore, it decreases the alkali-silica reactivity, the drying shrinkage, permeability, creep rate, coefficient of thermal expansion and dielectric constant. Moreover, it increases the specific heat and decreases the thermal conductivity, though the thermal conductivity is increased if silica fume is used with silane, another admixture. Silica fume addition also increases the air void content, decreases the density, enhances the dispersion of microfibers, and decreases the workability. In addition, the defects associated with the interface between silica fume and cement contributes to the defect dynamics during elastic deformation. The use of silane treated silica fume in place of untreated silica fume increases the consistency, tensile strength and compressive strength, but decreases the compressive ductility. Furthermore, the silane treatment increases the damping capacity and specific heat, and decreases the drying shrinkage and air void content. The use of silane and untreated silica fume as two admixtures, relative to the use of silane treated silica fume, increases the compressive modulus, but decreases the compressive ductility and damping capacity. It also decreases the air void content and increases the density, specific heat and thermal conductivity.