Steel structure fireproof protection plate

Abstract

A fireproof protection plate for a steel structure is characterized by being prepared from the following raw materials in percentage by mass: 15%-40% of water glass, 40%-60% of modified closed-cell expanded perlite, 5%-15% of kaolin, 5%-10% of expanded vermiculite, 5%-10% of aluminum hydroxide, 10% of reinforced fibers 4 and 2% of a sodium fluosilicate early strength agent 1. The modified closed-cell expanded perlite is prepared by the following steps: (1) preheating and drying; (2) primary puffing; (3) cooling the preliminarily-expanded expanded perlite to normal temperature, spraying a certain amount of water glass solution on the surface of the expanded perlite, then spraying an aluminum sulfate solution, and continuously stirring for a period of time; and (4) carrying out secondary puffing to obtain the closed-cell expanded perlite.

Description

Technical Field

[0001] The present invention relates to a steel structure fire protection board, which uses a closed-cell expanded perlite that can be prepared by gas furnace expansion and has excellent strength and waterproofness, and has excellent waterproofness, strength and low cost. Background Art

[0002] With the development of steel structure application technology and the increasing maturity of steel structure fire protection technology, steel structures, as a form of high-rise building structures, have been widely used in the construction industry due to their high strength, good plasticity and toughness, light self-weight, good extensibility, seismic resistance and short construction period. Although steel belongs to non-combustible materials, its fire resistance is very poor. So far, four main measures have been taken for the protection of steel structures: namely, direct cladding protection method, shielding protection method, water spray and flushing cooling protection method. Among the four measures, the direct cladding method is the most commonly used in engineering due to its simplicity, good protection performance and economic cost. The direct cladding method refers to directly applying fire protection materials such as building clay bricks, pouring concrete, plastering, spraying fire retardant coatings and encapsulating fire protection boards on the surface or periphery of steel structure components to encapsulate or cover the exposed steel components, so as to achieve the purpose of improving the fire resistance of steel structures. Currently, the most commonly used for steel structure fire protection are fire retardant coatings and fire protection boards. Protecting steel structures with fire protection boards has the advantages of convenient construction, good decoration, low cost, small loss, no environmental pollution, not affected by seasons and climate, dry construction, short construction period. Compared with the spraying construction of steel structure fire retardant coatings, only half of the working hours are required to complete the fire protection construction of the same area, and at the same time, it has excellent durability and fire resistance, and has a good promotion prospect. Specifically, it is to cover the fire protection board on the surface of the steel structure through a high-temperature fire-resistant adhesive to achieve the purpose of heat insulation in case of fire, thereby preventing the temperature of the steel from rising rapidly during a fire.

[0003] In current steel structure fireproof boards, expanded perlite and expanded vermiculite can both be used as lightweight fireproof fillers, but their characteristics and application focuses are different. Expanded perlite has a better thermal conductivity than expanded vermiculite, and its price is usually lower than that of expanded vermiculite (about 30% - 400% lower). However, its water absorption rate is significantly higher than that of expanded vermiculite, which not only affects the fireproof performance of the fireproof board but also has a greater negative impact on the forming of the fireproof board. Therefore, during actual use, hydrophobic pretreatment is required. Although this improves the waterproof property, it cannot compare with expanded vermiculite, and the cost increases significantly. At the same time, expanded perlite is extremely easy to break, and the strength of the prepared fireproof board is poor. In recent years, compared with traditional expanded perlite (open-cell), closed-cell expanded perlite and vitrified microspheres have been developed, and their water absorption rate and compressive strength have been significantly improved. However, they also have obvious problems. First, both closed-cell expanded perlite and vitrified microspheres are produced by precisely controlling the gradient heating and residence time of raw material ore sand to make the product surface melt and the pores close. This requires very strict temperature control of the production process, and low-cost gas furnaces cannot meet the requirements. Since electric furnaces have higher temperature control advantages compared with gas furnaces, in current actual production, both closed-cell expanded perlite and vitrified microspheres must be produced using electric furnaces, and their cost is much higher than that of the gas furnaces used for open-cell expanded perlite. Second, the low closed-cell rate of closed-cell expanded perlite has always been a difficult problem in the industry. The closed-cell rate obtained by general processes is only close to 60%. Although some literature claims to exceed 70% or even more than 80%, in technical discussions in the industry and actual sold products, industry experts have a consensus that it is difficult for the closed-cell rate of mass-produced closed-cell expanded perlite to exceed 70%, and the performance of different batches is unstable. Relatively speaking, vitrified microspheres have a higher closed-cell rate and better performance, but the production of vitrified microspheres has high requirements for raw materials. Only pearlite in the form of obsidian can be used, the output is low, and the process is complex and the cost is high.

[0004] Therefore, in current fireproof boards or fireproof coatings, expanded vermiculite serves as the main lightweight fireproof filler. Due to factors such as strength, waterproofness, and cost, expanded perlite cannot replace expanded vermiculite and is only used as an auxiliary fireproof filler. For example, in the steel structure fireproof protection board developed by the applicant before (CN 114907090A), this steel structure fireproof protection board is prepared from raw materials with the following mass ratios: sodium silicate 20 - 40%, expanded vermiculite 50 - 60%, kaolin 5 - 15%, perlite 5 - 10%, aluminum hydroxide 5 - 10%, reinforcing fiber 4 - 10%, sodium fluosilicate early strength agent 1 - 2%. Among them, the dosage of expanded vermiculite is 5 - 12 times that of perlite. This protection board has excellent fireproof performance, but there is also the problem of high cost. The manufacturing cost is high, and it can only be used as a high-temperature special fireproof board. Currently, the transportation cost of vermiculite produced in Xinjiang is extremely high. Although the vermiculite in the Hebei region represented by Lingshou County has excellent quality, its price is high, and with continuous mining, the output shows an obvious downward trend, and the market price of expanded vermiculite continues to rise. Therefore, it has become an urgent need in the industry to develop a fireproof board that can meet the industrial performance requirements and cost control requirements and uses expanded perlite as the main lightweight fireproof filler. Summary of the Invention

[0005] The present invention provides a steel structure fireproof protection board, which is prepared from raw materials with the following mass ratios: sodium silicate 15 - 40%, modified closed-cell expanded perlite 40 - 60%, kaolin 5 - 15%, expanded vermiculite 5 - 10%, aluminum hydroxide 5 - 10%, reinforcing fiber 4 - 10%, sodium fluosilicate early strength agent 1 - 2%; The sodium silicate is modified sodium silicate, and organosilane-modified sodium silicate can be used. Its preparation method consists of the following steps: Step A: Mixing. Weigh the raw materials and mix the above raw materials evenly in a high-speed mixer to obtain a slurry; Step B: Compression molding. Use a mold to compress the slurry obtained in Step A into a blank; Step C: Microwave drying and shaping. Use a microwave kiln for microwave drying and shaping. The drying time is 20 - 40 minutes, and finally a fireproof board with a thickness of 20 - 40 mm is obtained.

[0006] The size of the fireproof board is 1.2m * 2.4m or 1.2m * 1.2m.

[0007] Among them, the preparation method of the modified closed-cell expanded perlite includes the following steps: 1. Preheating and drying Preheat and dry the perlite raw materials at a temperature of 300 - 450°C for a holding time of 5 - 30 minutes to obtain perlite raw materials with a combined water moisture content of 1.5 - 3%.

[0008] 2. Preliminary expansion Pre-expand at a temperature of 800 - 900°C for 5 - 10 seconds using a rotary kiln.

[0009] 3. Sprayed coating Cool the preliminarily expanded expanded perlite to room temperature, first spray a certain amount of sodium silicate solution on its surface, then spray aluminum sulfate solution, and continuously stir for a period of time; the continuous stirring time is 5 - 10 minutes; 4. Secondary expansion At 1100 - 1150 °C for 2 - 10 seconds to obtain closed-cell expanded perlite; use a gas jet expansion furnace or a vertical expansion furnace for secondary expansion.

[0010] For the said closed-cell expanded perlite, the bulk density (Kg / m 3 ) is 40 - 150, the thermal conductivity (25 °C) (w / (m*K)) is 0.035 - 0.048, the water absorption rate is (24h, %) 15 - 35, the cylinder compressive strength / kPa is 150 - 220, and the volume floating rate ≥ 85%; the closed-cell rate ≥ 85%.

[0011] In the preheating and drying process of step 1, further, the preheating temperature is 400 - 450 °C, and the heat preservation time is 8 - 10 minutes; further, the preheating and drying are carried out in a rotary kiln or a vertical preheater; Further, before preheating and drying, select natural perlite ore, carry out crushing and screening, divide it into coarse crushing and fine crushing, and the water content is 2 - 6%; The particle size of the finely crushed perlite is 20 - 325 mesh (45μm - 850μm), preferably 40 - 200 mesh (75μm - 425μm); The inventor also found that when applied to fireproof materials such as coatings and perlite boards, the expanded perlite prepared by grading the raw materials has better heat insulation effect. Through a large number of experimental studies, its preferred ratio is: the mass ratio of perlite ore with (40 - 60 mesh):(80 - 120 mesh):(140 - 200 mesh) is (1 - 3):(4 - 6):(2 - 4).

[0012] In the preliminary expansion process of step 2, it is preferably pre-expanded at a temperature of 850 °C, and the further time is 8 - 10 seconds In step 3 of spraying the coating, the water glass solution contains 10-20 wt% of water glass; the aluminum sulfate solution contains 10-20 wt% of aluminum sulfate; the mass ratio of water glass, aluminum sulfate and pre-expanded perlite is (4-5): (3.2-3.6): (72-152) based on the mass of the raw materials. In the theoretical reaction, the molar ratio of water glass to aluminum sulfate should be 3:1, and the mass ratio is about 107:100. In actual technical development, it is found that water glass needs to be added slightly more. This may be because part of the water glass in the first spraying of the water glass solution is adsorbed into the pores of the pre-expanded perlite and does not participate in the subsequent reaction with aluminum sulfate.

[0013] In the secondary expansion process of step 4, the expansion temperature is 1100° C. and the time is 3-5 seconds to obtain closed-cell expanded perlite; Technical Effects The present invention adopts modified closed-cell expanded perlite instead of traditional expanded vermiculite as the main lightweight fireproof filler to prepare the steel structure fireproof protection board, which overcomes the negative effect of traditional expanded perlite on the waterproofness and strength of the fireproof protection board. The waterproofness, strength and fireproofness of the fireproof protection board are close to those of the steel structure fireproof protection board using expanded vermiculite as the main lightweight fireproof filler, and the cost is greatly reduced, providing a new idea of using expanded perlite instead of expanded vermiculite.

[0014] For the modified closed-cell expanded perlite, the present invention addresses the problem that the existing closed-cell expanded perlite requires a gas furnace with low closed porosity, requires an electric heating expansion furnace with precise temperature control, and has a complex process and high cost. The present invention uses aluminum sulfate and sodium silicate to coat the pre-expanded perlite, and then performs secondary expansion. The special pre-coating process realizes the preparation of expanded perlite with high closed porosity using a gas furnace. At the same time, the special pretreatment process also reduces the expansion temperature, and the high-temperature expansion time is also greatly shortened, which greatly reduces the production cost and improves the production efficiency.

[0015] After secondary expansion, the surface of the expanded perlite is covered with a gray coating layer. The inventor speculates that its main components may be albite, nepheline, etc. This may be due to the double decomposition reaction of aluminum sulfate and sodium silicate on the surface of pre-expanded perlite, generating aluminum silicate and sodium sulfate. Among them, a small part of the aluminum silicate may also exist in the form of a composite colloid precipitate of aluminum hydroxide and silicic acid and / or a precipitate of aluminum silicate. Under the condition of 1100 - 1150 degrees Celsius, it is obtained by the reaction of aluminum silicate, sodium sulfate with SiO2, Al2O3, etc. in perlite. Among them, sodium sulfate may undergo a decomposition reaction. Relatively speaking, it takes a longer time and higher temperature for vitrified microspheres and traditional closed-cell perlite to soften and melt the surface perlite sufficiently to form a vitreous layer on the surface of perlite. Currently, the expansion temperature of the traditional process is 1250 - 1300 °C, and the time is at least 5 - 20 seconds, or up to 2 - 5 minutes.

[0016] In the expansion stage of the process of the present invention, due to the adoption of the pre-coating technology, precise temperature control and long-time expansion are not required. Therefore, gas furnaces can be used for all equipment, and there is no need for electric furnaces with high construction costs and operating costs. Since the equipment for closed-cell expanded perlite and open-cell expanded perlite of the invention can be used interchangeably, the production line for open-cell expanded perlite can be directly used to produce closed-cell expanded perlite, which not only reduces costs but also avoids the trouble of technological transformation of the production line.

[0017] Due to the adoption of the pre-coating technology, the closed-cell rate of the closed-cell expanded perlite of the present invention exceeds the mainstream closed-cell expanded perlite products with a closed-cell rate of 50 - 70% in the current market, reaching more than 90%, which is close to the closed-cell rate of vitrified microspheres, but the cost is greatly reduced compared with vitrified microspheres, and the raw material requirements are much lower than those of vitrified microspheres.

[0018] The albite, nepheline, etc. on the surface coating, due to their dense crystal structure and low surface energy, not only have high strength but also excellent waterproofness, thus significantly improving the cylinder compressive strength and waterproofness of expanded perlite.

[0019] In addition, compared with the current finished product spraying of inorganic waterproof materials such as silica sol or water glass or organic waterproof materials such as VAE emulsion, polyurethane, etc. for closed-cell or open-cell expanded perlite, the coating material of the present invention is added during the preparation process of expanded perlite and reacts in situ to form a dense coating layer of albite and nepheline. It not only has a high closed-cell rate but also high strength and excellent waterproofness. At the same time, the coating before the finished product reduces the phenomenon of the coating material being adsorbed into the pores, not only reducing the usage amount of the coating material but also avoiding the filling of the pores of expanded perlite by the coating material and reducing its heat insulation and fireproof performance.

[0020] In addition, the inventors also found that when using perlite ore raw materials with different mesh combinations in the process of spraying sodium silicate and aluminum sulfate solutions after pre-expansion, the coating effect of the above composite solution is significantly higher than that of perlite ore with a single mesh. This may be because fewer voids in the perlite are beneficial for the composite solution to coat the surface of the perlite. Secondly, the closed-cell expanded perlite products with different mesh combinations also achieved good heat insulation and fire prevention effects. This may be because the closed-cell expanded perlite with different particle sizes reduces the packing voids and prevents the formation of microscopic thermal bridges, significantly improving the heat insulation and fire prevention effects of the closed-cell expanded perlite. Example

[0021] Preparation of Closed-cell Expanded Perlite A in Example 1 Select perlite ore with mesh sizes (40 - 60 mesh): (80 - 120 mesh): (140 - 200 mesh) respectively, with a mass ratio of 2:5:3, and stir and mix them. Preheat and dry the perlite at a temperature of 400 °C for a holding time of 10 minutes to obtain perlite ore with a combined water content of less than 2%; conduct preliminary expansion at a temperature of 850 °C for 8 seconds; cool the preliminarily expanded expanded perlite to room temperature, then first spray sodium silicate with a concentration of 15 wt% on its surface, and then spray aluminum sulfate with a concentration of 10 wt%. Based on the mass of the raw materials in the reaction, the mass ratio of sodium silicate, aluminum sulfate, and pre-expanded perlite is: 4.5:3.5:92, and continuously stir for 7 minutes; conduct secondary expansion of the pre-expanded perlite with coating treatment at 1100 °C for 4 seconds to obtain closed-cell expanded perlite A.

[0022] Preparation of Closed-cell Expanded Perlite B in Example 2 Select perlite ore with a mesh size of 80 - 120 mesh, preheat and dry the perlite at a temperature of 400 °C for a holding time of 10 minutes to obtain perlite ore with a combined water content of less than 2%; conduct preliminary expansion at a temperature of 850 °C for 8 seconds; cool the preliminarily expanded expanded perlite to room temperature, then first spray sodium silicate with a concentration of 15 wt% on its surface, and then spray aluminum sulfate with a concentration of 10 wt%. Based on the mass of the raw materials in the reaction, the mass ratio of sodium silicate, aluminum sulfate, and pre-expanded perlite is: 4.5:3.5:92, and continuously stir for 7 minutes; conduct secondary expansion of the pre-expanded perlite with coating treatment at 1100 °C for 4 seconds to obtain closed-cell expanded perlite B.

[0023] Preparation of Closed-cell Expanded Perlite C in Comparative Example 3 In the process of spraying the coating, only spray sodium silicate with a concentration of 15 wt%. The mass ratio of sodium silicate to pre-expanded perlite is: 8:92. Other processes are the same as in Example 1 to obtain closed-cell expanded perlite C.

[0024] Preparation of Closed-cell Expanded Perlite D in Comparative Example 4 In the process stage of spraying the coating, only an aluminum sulfate solution with a concentration of 10 wt% is sprayed, where the mass ratio of aluminum sulfate to pre-expanded perlite is 8:92, and other processes are the same as in Example 1, obtaining closed-cell expanded perlite D.

[0025] Comparative Example 5 Preparation of Closed-Cell Expanded Perlite E The process of spraying the coating is omitted, and the pre-expanded perlite is cooled to room temperature and then subjected to secondary high-temperature expansion. Other processes are the same as in Step 1, obtaining closed-cell expanded perlite E.

[0026] Example 6 Preparation of Expanded Perlite Fire Protection Boards A-E The raw material formula of the fire protection board is by mass ratio: sodium silicate 20%, modified closed-cell expanded perlite 60%, kaolin 5%, expanded vermiculite 5%, aluminum hydroxide 5%, reinforcing fiber 4%, sodium fluorosilicate early strength agent 1%. The specific preparation method of the expanded perlite fire protection board is as follows: (1) Mixing: Weigh the raw materials and mix the above raw materials evenly in a high-speed mixer to obtain a slurry; (2) Pressing and forming: Press the slurry obtained in step (1) into a mold to obtain a slab; (3) Microwave drying and shaping: Use a microwave kiln for microwave drying and shaping. The drying time is 25 minutes, and finally a fire protection board with a thickness of 25 mm is obtained, generally sized at 1.2 m * 2.4 m. Among them, the above-mentioned modified closed-cell expanded perlite are respectively the modified closed-cell expanded perlite A-E prepared in Examples 1-6, and then the corresponding expanded perlite fire protection boards A-E are obtained.

[0027] Example F Preparation of Expanded Vermiculite Fire Protection Board F Refer to the method in Example 3 of the inventor's existing patent CN114907090A to prepare the expanded vermiculite fire protection board F. The raw material formula for fire protection is by mass ratio: sodium silicate 20%, expanded vermiculite 60%, kaolin 5%, expanded perlite 5%, aluminum hydroxide 5%, reinforcing fiber 4%, sodium fluorosilicate early strength agent 1%. Among them, the expanded perlite is traditional perlite (open-cell). Example

[0028] Performance Testing Test according to the fire protection industry standard for steel structure fire protection boards (XF / T 3012-2020), and test the water resistance, fire resistance, and dry-state flexural strength of the vermiculite fire protection boards prepared in Examples 6-7.

[0029] The water resistance is qualified. After 30 days, the board is considered qualified if there are no cracks, delamination, or peeling, and slight swelling and discoloration are allowed.

[0030] The fire resistance performance was tested using the HC hydrocarbon fire heating curve. When fabricating the test piece, a 36b hot-rolled I-beam (section modulus of 126 m-1) was used as the experimental base material, and thermocouples were set on the test piece. The fire resistance limit of the steel structure fire protection board was calculated based on the time when the average temperature reached 538 °C.

[0031] Table 1 Performance of the fire protection board Fire protection board Main light fireproof filler Water resistance (number of days with cracking, delamination, and peeling) Fire resistance limit (h) Dry state flexural strength (MPa) Fire protection board A Closed-cell expanded perlite A 33d 3.1 15.9 Fire protection board B Closed-cell expanded perlite B 32d 3.0 15.2 Fire protection board C Closed-cell expanded perlite C 28d 2.6 11.8 Fire protection board D Closed-cell expanded perlite D 25d 2.4 11.4 Fire protection board E Closed-cell expanded perlite E 22d 2.5 11.6 Fire protection board F Expanded vermiculite 35d 3.2h 16.2 As can be seen from the above table, for the fire protection board prepared using the modified closed-cell expanded perlite prepared by the present invention as the main lightweight fireproof filler, its waterproofness, strength and fire resistance are close to those of the fire protection board prepared using expanded vermiculite as the main lightweight fireproof filler, while its cost has decreased significantly.

Claims

1. A steel structure fire protection board, characterized in that, Prepared from raw materials including the following mass ratios: water glass 15-40%, modified closed-cell expanded perlite 40-60%, kaolin 5-15%, expanded vermiculite 5-10%, aluminum hydroxide 5-10%, reinforcing fiber 4-10%, sodium fluosilicate early strength agent 1-2%; The modified closed-cell expanded perlite is prepared by the following steps: (1) Preheating and drying: Preheat and dry the perlite raw materials at a temperature of 300-450°C for a holding time of 5-30 minutes to obtain perlite raw materials with a combined water moisture content of 1.5-3%; (2) Preliminary expansion: Pre-expand at a temperature of 800-900°C for 5-10 seconds; (3) Cool the preliminarily expanded expanded perlite to room temperature. First, spray a certain amount of water glass solution on its surface, then spray aluminum sulfate solution, and continuously stir for a period of time; the continuous stirring time is 5-10 minutes; (4) Secondary expansion: At 1100-1150°C for 2-10 seconds to obtain closed-cell expanded perlite.

2. The steel structure fire protection board according to claim 1, wherein The modified water glass is water glass modified with organosilane.

3. The steel structure fire protection board according to claim 1, characterized in that, The expanded perlite with closed pores has a bulk density of 40 - 150 Kg / m 3 , a thermal conductivity (at 25°C) (w / (m*K)) of 0.035 - 0.048, a water absorption rate (for 24 hours) of 15 - 35%, a cylinder compressive strength of 150 - 220 kPa, a volume floating rate of ≥85%; and a closed pore rate of ≥85%.

4. The steel structure fire protection board according to claim 1, characterized in that, Before preheating and drying, select natural perlite ore, perform crushing and screening, divide it into coarse crushing and fine crushing to obtain perlite with a moisture content of 2-6%.

5. The steel structure fire protection board according to claim 4, characterized in that, In the preheating and drying process of step (1), the preheating temperature is 400-450°C and the holding time is 8-10 minutes.

6. The steel structure fire protection board according to claim 1, wherein, In the preliminary expansion process of step (2), pre-expand at a temperature of 850°C for a further time of 8-10 seconds.

7. The steel structure fire protection board according to claim 1, characterized in that, In the process of spraying the coating in step (3), the water glass solution contains 10-20 wt% of water glass; in the aluminum sulfate solution, it contains 10-20 wt% of aluminum sulfate.

8. The steel structure fire protection board according to claim 1, wherein In the process of spraying the coating in step (3), the mass ratio of water glass, aluminum sulfate, and pre-expanded perlite is: (4-5):(3.2-3.6):(72-152).

9. The steel structure fire protection board according to claim 1, characterized in that, In the secondary expansion process of step (4), the expansion temperature is 1100°C and the time is 3-5 seconds to obtain closed-cell expanded perlite.

10. The steel structure fire protection board according to claim 1, characterized in that, The preparation method of the fire protection board consists of the following steps: Step A: Mixing, measure the raw materials and mix the above raw materials evenly in a high-speed mixer to obtain a slurry; Step B: Compression molding, use a mold to compress the slurry prepared in step A to form a board blank; Step C: Microwave drying and shaping, use a microwave kiln for microwave drying and shaping, and the drying time is 20-40 minutes to finally obtain a fire protection board with a thickness of 20-40 mm.