Tunnel fireproof coating is composed of binders, fireproof fillers, flame retardants, and additives. (1) Adhesive: Mainly composed of high alumina cement, compounded with an appropriate amount of redispersible latex powder and fly ash, can greatly improve the bonding strength and water resistance of the coating. (2) Fireproof filling: expanded vermiculite, expanded perlite, mica powder

Tunnel fireproof coating is composed of binders, fireproof fillers, flame retardants, and additives.

(1) Adhesive: Mainly composed of high alumina cement, compounded with an appropriate amount of redispersible latex powder and fly ash, can greatly improve the bonding strength and water resistance of the coating.

(2) Fireproof filling material: Expanded vermiculite, expanded perlite, and mica powder are mixed in a 16:13:1 ratio to form a fireproof filling material. This fireproof filling material has the characteristics of high temperature resistance, low thermal conductivity, and low density.

(3) Flame retardants: Aluminum hydroxide and magnesium hydroxide are both halogen-free flame retardants that absorb heat and decompose at high temperatures, causing the system temperature to decrease. In addition, the water generated during the decomposition process also needs to absorb heat to become water vapor at high temperatures, which can suppress the production of smoke.

(4) Additives: In order to meet the needs of use, chemical additives such as air entraining agents and anti-seepage agents need to be added to the coating. Silane based powder, polypropylene fiber, and hydroxymethyl cellulose ether are selected as coating additives

The most important performance indicators of tunnel fireproof coatings are fire resistance and bonding performance. After determining the composition of the raw materials for Guizhou tunnel fireproof coating, the influence of three factors, high alumina cement, fireproof filler, and flame retardant, on the fire resistance limit and bonding performance of the coating was determined by changing the proportion of the raw materials.

Fireproof fillers have the greatest impact on the fire resistance limit, while flame retardants and high alumina cement not only have bonding properties, but also have high temperature resistance.

The bonding strength is most affected by high alumina cement, followed by fire-resistant fillers. The use of redispersible latex powder and high alumina cement as a binder can improve the bonding strength of coatings. This is because the liquid phase of redispersible latex powder and high alumina cement suspension permeates into the pores and capillaries of the matrix, and the polymer forms a film in the pores and capillaries and firmly adsorbs on the surface of the matrix, thereby ensuring good bonding strength between the binder and the matrix.

The influence of main components on the fire resistance and bonding strength of tunnel fireproof coatings 

1. The influence of high alumina cement on the fire resistance and bonding strength of tunnel fireproof coatings

As the amount of high alumina cement added increases, the bonding strength of the fireproof coating increases while the fire resistance limit decreases. This is because increasing the amount of high alumina cement leads to an increase in the content of binders per unit area of the coating, while the content of fire-resistant fillers, flame retardants, etc. is relatively reduced. On the one hand, this makes the substrate and coating more tightly bonded, improving the bonding strength. On the other hand, the relative reduction of flame retardants and fire-resistant fillers reduces the fire resistance performance of the coating. 

2. The influence of fireproof fillers on the fireproof performance and bonding strength of tunnel fireproof coatings

With the increase of fireproof filler, the fire resistance limit of the coating is increasing, and the bonding strength is decreasing. The content of fire-resistant coating and filler in Guizhou tunnels should be appropriate. If the content is too high, the adhesive content per unit area will be relatively low, which will reduce the bonding strength of the coating. 

3. The influence of flame retardant dosage on the fire resistance and bonding strength of tunnel fireproof coatings 

With the increase of flame retardant dosage, the bonding strength of fireproof coating decreases and the fire resistance limit increases. The impact of flame retardants on the fire resistance limit is significant. With the increase of flame retardant dosage, the increase in fire resistance limit is greater, and the impact on bond strength is relatively small. Jiangsu Tunnel Fireproof Coating