how silica fume improves concrete performance
Silica fume is an excellent material with broad application prospects in high-tech fields at home and abroad. Silica fume can be widely used in chemical, metallurgical and other industries. Micro silica fume is used in cement or concrete to improve the performance of cement or concrete. And special concrete or composite cement with super high strength, wear resistance, erosion resistance, corrosion resistance, penetration resistance, frost resistance and early strength to adapt to oil field solids. Special requirements for wells, offshore oilfield drilling platforms, seaport terminals, railway bridge highways, airport runways, tunnels and urban high-rise buildings; Silica fume is used in rubber to improve the ductility, tear resistance and tensile strength of rubber; In addition, silica fume is used in refractory materials and ceramic products to improve the strength and durability of the product effectively.
Micro silica fume for concrete can improve the resistance to penetration and salt corrosion and protect steel bars. In underwater engineering, chloride ions penetrate into concrete, causing rapid corrosion of steel bars, delamination of concrete, short life and serious destructiveness. Underwater concrete pouring is generally carried out by a duct method. Due to the loss of the cement slurry, it does not bond well with the base layer and reduces the strength of the portion in contact with water. While these problems can be significantly improved after the incorporation of micro silica fume in underwater concrete.
Concrete is a permeable material whose permeability is related to its porosity, pore distribution and pore connectivity. The smaller the water-cement ratio of the vibrating compact concrete, the longer the curing age, the smaller the permeability. Adding air entraining agents into concrete also reduces permeability. Generally, concrete with a water cement ration of less than 0.5 can have a permeability coefficient of 1×10-11m/s.
The permeability of concrete in seawater is the most important factor determining the durability of concrete works. Concrete with high permeability is easily damaged in seawater. Since the micro silica fume particles are small, 20-100 times smaller than the cement particles, they can be filled into the gaps between the cement particles to make the concrete dense, meanwhile, the secondary hydration of the silica fume, the new product blocks the permeation channel in the concrete. Therefore, the micro silica fume concrete has a strong impermeability and the permeability of the concrete increases with the increase to the water to binder ratio, the water cement is relatively inferior to the concrete.