Fireproof protective layer and construction method for concrete-tube steel columns based on geopolymer mortar

Abstract

The application provides a fireproof protection layer of a steel pipe concrete column based on geopolymer mortar and a construction method, the fireproof protection layer comprises, from inside to outside, a roughened material layer, a geopolymer mortar layer and a metal wire mesh reinforcing layer embedded in the geopolymer mortar layer; wherein the geopolymer mortar comprises the following raw materials in parts by weight: sodium hydroxide 30-35 parts, water glass solution 200-210 parts, blast furnace slag 1490-1510 parts, fly ash 1490-1510 parts, silica ash 90-450 parts, natural river sand 4490-4510 parts, polypropylene fiber 5-8 parts and water 1080-1140 parts. The geopolymer-based fireproof protection layer can significantly improve the fire resistance limit of the steel pipe concrete column, so that the fire resistance limit of the steel pipe concrete column reaches more than 3-4 hours; and the compressive strength of the geopolymer mortar under high temperature is relatively high, the fireproof protection layer based on the geopolymer mortar can bear part of the vertical load under fire, so that the fireproof effect is better.

Description

Technical Field

[0001] This invention relates to the technical field of fire protection for steel-concrete composite columns, and more specifically, to a fire-resistant protective layer for steel-concrete composite columns based on geopolymer mortar and a construction method thereof. Background Technology

[0002] Concrete-filled steel tube (CFST) columns possess advantages such as high load-bearing capacity and good seismic performance, making them widely used in high-rise buildings and large-span structures. However, the strength of steel decreases sharply at high temperatures, leading to a reduction in the load-bearing capacity of the steel tube under fire and a loss of its restraining effect on the core concrete. Therefore, fire protection for CFST columns is crucial. Currently, fire-resistant coatings for CFST columns mainly include cement-based mortar, water-soluble fire-retardant coatings, solvent-based fire-retardant coatings, epoxy fire-retardant coatings, and inorganic fire-retardant coatings. However, all of these have drawbacks, such as poor durability, environmental pollution, and difficulty in achieving fire protection effects exceeding 4 hours. Summary of the Invention

[0003] This invention discloses a fireproof protective layer for steel-concrete composite columns based on geopolymer mortar and a construction method thereof, in order to solve the above-mentioned problems.

[0004] The present invention adopts the following solution:

[0005] This application provides a fireproof protective layer for steel-concrete composite columns based on geopolymer mortar. The fireproof protective layer includes, from the inside out, a roughening material layer, a geopolymer mortar layer, and a metal wire mesh reinforcement layer embedded in the geopolymer mortar layer.

[0006] The geopolymer mortar comprises the following raw materials by weight: 30-35 parts sodium hydroxide, 200-210 parts water glass solution, 1490-1510 parts blast furnace slag, 1490-1510 parts fly ash, 90-450 parts silica fume, 4490-4510 parts natural river sand, 5-8 parts polypropylene fiber, and 1080-1140 parts water.

[0007] Furthermore, the material of the textured layer is a geopolymer-based material, and its raw materials by weight are: 3000 parts textured emulsion, 3000 parts blast furnace slag, 3000 parts fly ash, 67-68 parts sodium hydroxide, 412-413 parts water glass, and 300 parts sand.

[0008] Furthermore, the water glass solution has a Baumé degree of 50, a modulus of 2.25, and a sodium hydroxide mass percentage of not less than 95%; the natural river sand has a particle size of 0.1-0.5 mm; and the polypropylene fiber has a specification of 6-19 mm.

[0009] Furthermore, when wrapping the wire mesh, it should be wrapped horizontally from top to bottom along the steel pipe column; the overlap length of all overlapping parts of the wire mesh, including the circumferential overlap of the same circle and the longitudinal overlap between adjacent circles, should not be less than 10cm, and all overlaps should be fixed with tie wire.

[0010] Furthermore, the metal wire mesh in the metal wire mesh reinforcement layer can be galvanized iron wire mesh or stainless steel wire mesh.

[0011] Furthermore, the thickness of the fireproof protective layer Calculate using the following formula:

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] ; ;

[0021] In the formula: For calculation parameters, the value is 1 if it is greater than 1, and 0 if it is less than 0; This represents the bearing capacity coefficient of the concrete-filled steel tube column. R The load ratio under fire conditions; t Expected fire resistance limit, in hours (h); C λ is the perimeter of the cross section, in mm; λ is the slenderness ratio. a For the second calculation parameter, b For the third calculation parameter, k For the fourth calculation parameter, For the fifth calculation parameter, For the sixth calculation parameter, For the seventh calculation parameter, For the eighth calculation parameter, This is the ninth calculation parameter.

[0022] Furthermore, the fireproof protective layer is applied in layers, and a metal mesh is wrapped at the interface of each layer to form the metal mesh reinforcement layer. The metal mesh can only be wrapped after the inner mortar has solidified.

[0023] Furthermore, when the thickness of the fireproof protective layer is less than 20mm, it is applied in two layers, with the second layer having a thickness of 5mm; when the thickness of the fireproof protective layer is 20mm-30mm, it is applied in two layers, with the second layer having a thickness of 10mm; when the thickness of the fireproof protective layer is 30mm-60mm, it is applied in three layers, with the inner two layers having equal thickness and the outermost layer having a thickness of 10mm.

[0024] The present invention also provides a method for constructing a fireproof protective layer, comprising the following steps:

[0025] First, the surface of the steel pipes in the steel-concrete composite column is treated for rust removal and rust prevention.

[0026] Then, a roughening material is coated on the surface of the steel pipe to form a roughening interface, thereby forming the roughening material layer;

[0027] Based on the calculated thickness of the fireproof protective layer, determine the number of layers and the thickness of each layer of polymer mortar to be applied, and then apply the mortar in layers. During the application of the mortar in layers, wrap a metal wire mesh at the interface between each layer of polymer mortar.

[0028] Finally, after all the geopolymer mortar has hardened, water spraying is performed for curing.

[0029] Furthermore, the conditions for water spraying curing are as follows: the temperature difference between the curing water and the surface temperature of the polymer mortar should not exceed 15°C, and the surface of the polymer mortar should always be kept moist during the curing process.

[0030] By adopting the above technical solution, the present invention can achieve the following technical effects:

[0031] 1. This invention utilizes solid wastes such as fly ash and blast furnace slag to create a fireproof protective layer for steel-concrete composite columns based on geopolymer mortar, thereby achieving the reuse of waste materials;

[0032] 2. Compared to traditional cement mortar fireproofing layers, this method eliminates the need for cement, significantly reducing energy consumption during cement production. Its emissions are low-carbon.

[0033] 3. The geopolymer-based roughening material of the present invention can effectively increase the surface roughness of steel pipes, making it easier to evenly apply geopolymer mortar to the surface of steel pipes and preventing the geopolymer mortar from slipping or becoming hollow.

[0034] 4. By embedding galvanized iron wire mesh or stainless steel iron wire mesh inside the fireproof mortar protective layer, the fireproof protective layer can be effectively prevented from falling off under fire. In addition, the material itself has high durability, thus avoiding the adverse effects of its own corrosion on the durability of the fireproof protective layer.

[0035] 5. The polymer fireproof mortar protective layer has the characteristics of fast setting speed and high early strength. Therefore, when applied in layers, the inner layer of mortar has a short setting time and high early strength. After the coating is completed, metal wire mesh can be wrapped around the surface of the mortar layer, which can speed up the construction process.

[0036] 6. This polymer-based fireproof protective layer can significantly improve the fire resistance limit of concrete-filled steel tube columns, enabling them to reach a fire resistance limit of 3-4 hours or more. Furthermore, the high compressive strength of the polymer mortar at high temperatures allows the fireproof protective layer based on it to bear a portion of the vertical load during a fire, thus enhancing its fire protection effect. Simultaneously, the high-temperature resistance and corrosion resistance of the polymer mortar enable it to be used in a wider range of applications. Attached Figure Description

[0037] Figure 1 This is a top view of a fireproof protective layer for a steel-concrete composite column based on geopolymer mortar, according to an embodiment of the present invention.

[0038] Figure 2 This is a curve showing the change in compressive strength of the geopolymer mortar at high temperature as a function of temperature in this invention;

[0039] Figure 3 This is a curve showing the change in compressive strength of the geopolymer mortar after high temperature as a function of temperature in this invention;

[0040] Icons: 1. Steel pipe, 2. Core concrete, 3. Textured material layer, 4. First layer of polymer mortar, 5. First layer of galvanized wire mesh, 6. Second layer of polymer mortar, 7. Second layer of galvanized wire mesh, 8. Third layer of polymer mortar. Detailed Implementation

[0041] Example

[0042] Combination Figures 1 to 3 As shown, this embodiment provides a fireproof protection layer for a steel-concrete composite column based on geopolymer mortar. The fireproof protection layer includes, from the inside out, a roughening material layer, a geopolymer mortar layer, and a metal wire mesh reinforcement layer embedded in the geopolymer mortar layer.

[0043] The following is an experimental illustration of the fireproof protective layer using specific embodiments:

[0044] The steel pipe 1 of the concrete-filled steel tube column has dimensions of 3810mm in height, 325mm in outer diameter, and 8mm in wall thickness; the core concrete 2 inside the concrete-filled steel tube column is C30 commercial concrete, and the steel pipe material is 20# steel. The fireproof protection layer consists of, from the inside out, a roughened material layer 3, a first layer of polymer mortar 4, a first layer of galvanized wire mesh 5, a second layer of polymer mortar 6, a second layer of galvanized wire mesh 7, and a third layer of polymer mortar 8.

[0045] The geopolymer mortar, by weight, mainly comprises the following materials: 33.6 parts sodium hydroxide, 206.4 parts water glass solution, 1500 parts blast furnace slag, 1500 parts fly ash, 300 parts silica fume, 4500 parts natural river sand, 6.3 parts polypropylene fiber, and 1110 parts water.

[0046] The silica fume contains more than 90% silica; the natural river sand has a particle size of 0.1-0.5 mm; and the polypropylene fiber has a length of 9 mm.

[0047] The texturing material, by weight, mainly includes the following materials: 3000 parts texturing emulsion, 3000 parts blast furnace slag, 3000 parts fly ash, 67.2 parts sodium hydroxide, 412.8 parts water glass, and 300 parts sand.

[0048] The water glass solution has a modulus of 2.25, a Baume degree of 50, and a concentration of 45%. The content is 29.99%. The content is 13.75%. The mass percentage of sodium hydroxide is 96%.

[0049] The main chemical components of the blast furnace slag, expressed as a percentage by mass, are: calcium oxide 34%, silicon dioxide 34.5%, aluminum oxide 17.7%, sulfur trioxide 1.64%, iron oxide 1.03%, and magnesium oxide 6.01%.

[0050] The main chemical components of the fly ash, expressed as a percentage by mass, are: calcium oxide 4.01%, silicon dioxide 53.99%, aluminum oxide 31.15%, sulfur trioxide 0.73%, iron oxide 4.16%, magnesium oxide 1.01%, potassium oxide 2.04%, and titanium dioxide 1.13%.

[0051] The preparation method of the geopolymer mortar is as follows: First, sodium hydroxide is added to water glass solution. After the solution is allowed to stand and cool to room temperature, it is added to a dry mixture of blast furnace slag, fly ash and silica fume. At the same time, the required amount of water is added and the mixture is stirred thoroughly until a uniform slurry is obtained. Finally, river sand premixed with polypropylene fiber is added to the slurry and the mixture is stirred until all components are evenly distributed, thus obtaining the geopolymer mortar.

[0052] The above-mentioned fireproof protective layer for steel-concrete composite columns made from solid wastes such as fly ash and blast furnace slag based on geopolymer mortar achieves the reuse of waste materials. Compared with the traditional cement mortar fireproof protective layer, it does not require cement, which can significantly reduce energy demand and CO2 emissions in the cement production process, and has low-carbon characteristics.

[0053] Wherein, the thickness of the fireproof protective layer The beneficial effect of the mortar layer on bearing capacity at high temperatures can be ignored during the design process, and the following formula can be used for calculation in a conservative manner:

[0054]

[0055] The slenderness ratio of the steel-concrete composite column is 50.1, the fire exposure time is 201 min, and the cross-sectional perimeter is 1020.5 mm.

[0056] First calculation parameter The formula for determining the value is:

[0057]

[0058] The fire load ratio is taken as 0.5. The formula for determining the value is:

[0059]

[0060] Where the second calculation parameter a Third calculation parameter b Fourth calculation parameter k Fifth calculation parameter Sixth calculation parameter Seventh calculation parameter Eighth calculation parameter Ninth Calculation Parameter The formula for determining the value is:

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] ; ;

[0067] Where: First calculation parameter If the value is greater than 1, it is taken as 1; if the value is less than 0, it is taken as 0. This represents the bearing capacity coefficient of the concrete-filled steel tube column. R The load ratio under fire conditions; t Expected fire resistance limit, in hours (h); C λ is the perimeter of the cross section, in mm; λ is the slenderness ratio.

[0068] Based on the above formula, the calculation parameters are obtained. a =24.664, b =11.8728, k =-0.2988, =0.2143, =0.3275, =2.01, =1.2525, =0.812. Bearing capacity coefficient. =-0.1541, Calculation parameter =0.7078, Design thickness of fireproof protective layer The design thickness is 55mm, and the actual thickness of the fireproof protective layer during construction is 54mm.

[0069] The following describes the construction method for the fireproof protective layer of the steel-concrete composite column, which includes the following steps:

[0070] First, use an angle grinder to remove the rust stains from the surface of steel pipe 1, and then apply anti-rust paint.

[0071] Then, the outer wall of the steel pipe 1 is roughened with the above-mentioned roughening material to form a roughening material layer 3; in order to effectively increase the roughness of the surface of the steel pipe 1, facilitate the uniform application of polymer mortar to the surface of the steel pipe 1 and prevent the polymer mortar from slipping or blistering.

[0072] After the roughened material layer 3 has sufficient strength, apply the first layer of polymer mortar 4 with a thickness of 22mm; after the first layer of polymer mortar 4 has hardened, wrap the surface with the first layer of galvanized iron wire mesh 5; after hanging the mesh, apply the second layer of polymer mortar 6 with a thickness of 22mm; after the second layer of polymer mortar 6 has hardened, wrap the surface with the second layer of galvanized iron wire mesh 7; after hanging the mesh, apply the third layer of polymer mortar 8 with a thickness of 10mm; by embedding galvanized iron wire mesh in the fireproof mortar protective layer, the fireproof protective layer can be effectively prevented from falling off under fire, and the material itself has high durability, thus avoiding the adverse effects of its own corrosion on the durability of the fireproof protective layer;

[0073] Finally, after the polymer mortar has fully hardened, wet curing should be carried out. The conditions for water curing are: the temperature difference between the curing water and the surface temperature of the polymer mortar should not exceed 15℃, and the surface of the polymer mortar should always be moist during the curing process.

[0074] After the fireproof protective layer of the steel-concrete composite column based on geopolymer mortar is poured, it is left to stand for one day, followed by a week of water spraying curing.

[0075] When wrapping galvanized wire mesh, it should be wrapped horizontally from top to bottom along the steel pipe column. All overlapping parts of the galvanized wire mesh, including circumferential overlaps within the same loop and longitudinal overlaps between adjacent loops, should have an overlap length of no less than 10cm, and all overlaps should be secured with binding wire. Stainless steel wire mesh can also be used instead of the galvanized wire mesh described above.

[0076] The steel-concrete composite columns coated with the above-mentioned geopolymer mortar and the steel-concrete composite columns coated with M5 cement mortar were tested and evaluated using the following methods:

[0077] For a steel-concrete composite column coated with a geopolymer mortar protective layer, when it reaches its fire resistance limit, assuming that the original geopolymer mortar layer is replaced with M5 cement mortar of the same thickness, calculate the vertical load that the specimen can withstand when it reaches the same fire resistance limit under this condition.

[0078] As can be seen, since M5 cement mortar basically does not bear vertical load at high temperatures, the difference between the bearing capacity of the in-situ polymer mortar specimen measured in the actual fire test and the corresponding load of the M5 cement mortar specimen under the above-mentioned assumed conditions can be approximately regarded as the vertical load borne by the polymer mortar fireproof protective layer during the fire.

[0079] The tested fire resistance limit of the steel tube concrete column with externally coated geopolymer mortar was 201 min; the bearing capacity at the fire resistance limit was 3109 kN.

[0080] When the fire resistance limit of the steel-concrete composite column coated with M5 cement mortar reaches 201 min, the applied vertical load is 2358 kN.

[0081] Therefore, it can be known that the vertical load borne by the fireproof protective layer based on the geopolymer mortar is 751kN.

[0082] This polymer-based fireproof protective layer can significantly improve the fire resistance limit of steel-concrete composite columns, enabling them to reach a fire resistance limit of 3-4 hours or more. Furthermore, the high compressive strength of the polymer mortar at high temperatures means that the fireproof protective layer based on the polymer mortar can bear a portion of the vertical load during a fire, thus providing better fire protection.

[0083] It should be understood that the above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0084] The accompanying drawings used in the above description of the embodiments only illustrate certain embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

Claims

1. A fire protection layer for a steel pipe concrete column based on geopolymer mortar, characterized in that, The fireproof protection layer comprises, from inside to outside, a layer of roughening material, a layer of geopolymer mortar, and a layer of wire mesh reinforcement embedded in the layer of geopolymer mortar. The layer of geopolymer mortar comprises, by weight, 30-35 parts of sodium hydroxide, 200-210 parts of water glass solution, 1490-1510 parts of blast furnace slag, 1490-1510 parts of fly ash, 90-450 parts of silica ash, 4490-4510 parts of natural river sand, 5-8 parts of polypropylene fiber, and 1080-1140 parts of water. The roughening material layer is made of geopolymer-based material, and the raw materials thereof comprise, by weight, 3000 parts of roughening emulsion, 3000 parts of blast furnace slag, 3000 parts of fly ash, 67-68 parts of sodium hydroxide, 412-413 parts of water glass, and 300 parts of sand. The natural river sand has a particle size of 0.1-0.5 mm, and the polypropylene fiber has a length of 6-19 mm. When wrapping the wire mesh, the steel pipe column is horizontally wrapped from top to bottom; the overlapping length of all overlapping parts of the wire mesh, including the circumferential overlapping of the same circle and the longitudinal overlapping between adjacent circles, should not be less than 10 cm, and all overlapping parts should be fixed by wire binding. The fireproof protection layer is applied in layers, and the wire mesh is wrapped at the interface of each layer to form the layer of wire mesh reinforcement, and the wire mesh should be wrapped after the inner layer of mortar solidifies.

2. Geopolymer mortar-based fireproofing layer for a concrete filled steel tubular column according to claim 1, characterized in that, The wire mesh in the layer of wire mesh reinforcement can be galvanized iron wire mesh or stainless steel wire mesh.

3. A method of applying a fire protection coating as claimed in claim 1, characterised in that, The method comprises the following steps: First, the surface of the steel pipe of the steel pipe concrete column is rusted and treated for rust prevention; Then, the surface of the steel pipe is coated with roughening material to form a roughening interface and thus the layer of roughening material; According to the calculated thickness of the fireproof protection layer, the number of layers and the thickness of each layer of the geopolymer mortar are determined, and the geopolymer mortar is applied in layers; when the geopolymer mortar is applied in layers, the wire mesh is wrapped at the interface of each layer of geopolymer mortar; Finally, after all the geopolymer mortar is hardened, water is sprayed for curing.

4. The method of applying a fire protection coating according to claim 3, wherein The temperature difference between the curing water and the surface of the geopolymer mortar should not be greater than 15℃, and the surface of the geopolymer mortar should be kept wet during the curing process.

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