The invention discloses composite fireproof
coating for a tunnel. The composite fireproof
coating for the tunnel is prepared by adding nano silica
sol and ultrafine
magnesium hydroxide powder, a largenumber of
silicon hydroxyls exist on the surface of the silica
sol and are easily bonded with certain groups in the
coating, and the
thermal stability of a coating film can be improved; due to the vacancy of coordination on the surfaces of
sol particles, the coating has
high surface activity, and has a certain
adsorption effect on macroparticles such as pigments and filler, and pulverization of the coating film can be reduced; silica particles in the silica sol are dispersed to form a
network structure of Si-O-Si, so that the properties such as air permeability and
aging resistance of the coating film are improved; when heated and decomposed, an ultrafine
magnesium hydroxide flame retardant releases
moisture to absorb heat, the actual temperature of a
flame on the surface of the coating film is decreased, and thus the speed of degradation of a
polymer into low molecules is decreased; and the concentration of
oxygen on the surface of the coating film can be decreased by uniformly-released
water vapor, so that
combustion on the surface of the coating film cannot be continued, and the
fire resistance of the coating film can be improved.