Silica sol is also known as silica sol, the molecular formula is SIO2 ·xH₂O, is a colloidal solution formed by silicic acid polymolecular polymer, polymer particles are usually in 7~20nm, if the use of special processing technology can also be made larger particle size silica sol. Silica sol polymer particles can be dispersed not only in water, but also in organic solvents. Silica sol has a wide range of water loss temperature, and water loss will not only damage its bond strength, but also make its three-dimensional structure more stable and produce higher bond strength.
When silica sol is used as a refractory binder, it can give the material ceramic condensation bond after sintering, which overcomes the fatal weakness of low middle temperature strength of cement bonded refractory. The principle of silica sol as a refractory castable binder is based on sol-gel technology. Silica sol is distributed on the surface of refractory particles, forming gel around the particles. In this process, the hydroxyl group on the surface of the particles solidifies and removes water, forming Si-O-Si bond, which makes the refractory produce strength in the construction and curing process. When the construction body dries, the gel binds the aggregate together to form a skeleton that provides strength.
1, the application of silica sol in pressing mud
In order to pursue the high efficiency and long life of blast furnace ironmaking, pressing mud has been widely applied in the rapid repair technology of blast furnace body in China. However, at present, the more widely used is the use of organic resin and tar as a binder pressed into the mud, this kind of mud is difficult to cure, but also produce a large number of benzopyrene harmful gases when heated, and the material shrinkage is large, the volume stability is poor.
Therefore, in recent years, silica sol has been used as a binder for pressing materials. The experimental study confirmed that the shrinkage rate of the slurry combined with silica sol after 1200℃*3h high temperature treatment is much smaller than that of the slurry combined with resin. Moreover, the silica sol combined with the mud sample after drying at 110℃ did not crack after nearly 100 times of 1100℃ water-cooled thermal shock test, and the compressive strength at this time exceeded 80MPa, and the strength retention rate after thermal expansion exceeded 80%. This is mainly because nano SiO₂ in silica sol produces mullitization reaction in the substrate pressed into the mud, which improves the thermal shock resistance of the material.