Concrete exterior wall panel with self-cleaning function and preparation method thereof

Abstract

The application discloses a concrete outer wall plate with a self-cleaning function and a preparation method thereof, and comprises a wall body and a photocatalytic coating sprayed on the wall body; wherein the wall body comprises the following raw materials in parts by weight: cement, fly ash microbeads, silica fume, ultra-fine mineral admixture, sand, steel fiber, defoaming agent and water reducing agent. The outer wall plate of the application forms a "coating film" on the surface of the ultra-high performance concrete outer wall plate by spraying a catalyst on the surface, so that the surface is cleaned through the "self-breathing" effect of photocatalysis to realize the self-cleaning function; and the ultra-fine mineral admixture contains C-A-S-H crystal nucleus and has super-high early strength performance, and Al 3+ The application can promote the photocatalysis of nano-TiO2 in the photocatalytic coating, enhance the "breathing" effect of the ultra-high performance concrete outer wall plate, realize self-cleaning, and has better durability and longer service life.

Description

Technical Field

[0001] This invention belongs to the field of exterior wall panel preparation, and particularly relates to a concrete exterior wall panel with self-cleaning function and its preparation method. Background Technology

[0002] Concrete is widely used in various fields and is an extremely important building material. However, modern building structures rarely consider the role of sunlight. Instead, many of these basic structures exist primarily to block sunlight. To fully utilize sunlight, we need to combine its use with building components to reduce building energy consumption and environmental pollution. Ultra-high performance concrete (UHVPC) exterior wall panels, in particular, possess extremely high strength and durability and can be directly exposed to the air without the need for painting or beautification. However, long-term exposure makes them prone to accumulating dust, algae, and fungi, thus creating a new challenge: the self-cleaning problem of UHVPC exterior wall panels.

[0003] In 1967, Japanese scholar Akira Fujishima discovered the photocatalytic effect of semiconductors. Later, researchers utilized this effect to prepare self-cleaning glass. Self-cleaning glass can clean itself and also degrade organic pollutants and oxidize pollutants such as NOx and SOx in the air. Cement concrete is the most widely used material; if concrete could possess photocatalytic and self-cleaning functions, it would be of great significance in reducing air pollution and preventing urban smog.

[0004] Based on this, we now study a self-cleaning concrete exterior wall panel and its preparation method. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for achieving the self-cleaning effect of concrete exterior wall panels by attaching a photocatalyst coating to the concrete exterior wall.

[0006] Technical solution: The present invention is a self-cleaning concrete exterior wall panel, which includes a wall and a photocatalytic coating sprayed on the wall;

[0007] The wall material comprises the following raw materials by weight: 354-360 parts cement, 27-35 parts fly ash microspheres, 48-56 parts silica fume, 65-72 parts ultrafine mineral admixture, 480-492 parts sand, 6.5-7.2 parts steel fiber, 1.2-1.5 parts defoamer, and 9.5-10.2 parts water-reducing agent;

[0008] The photocatalytic coating comprises the following raw materials in parts by weight: 10-15 parts of nano titanium dioxide, 4-6 parts of silane coupling agent, and 40-60 parts of polyethylene glycol.

[0009] Furthermore, the ultrafine mineral admixture of the exterior wall panel includes, by weight, 12-17 parts of CASH crystal nuclei, 33-40 parts of fly ash, 3-4 parts of sodium benzoate, and 58-64 parts of slag.

[0010] Furthermore, the CASH crystal nuclei of the exterior wall panel are prepared by the following steps: silica fume, lime, and calcium aluminate are mixed at a Ca / (Al+Si) molar ratio of 0.8-1.0 and an Al / (Al+Si) molar ratio of 0.05-0.1. Then, gypsum accounting for 0.5-2% of the total weight of silica fume, lime, and calcium aluminate, and nano-alumina accounting for 0.5-2% of the total weight of silica fume, lime, and calcium aluminate are added. Water is added at a water-cement ratio of 0.45-0.51, the pH is adjusted to 11-13, and the mixture is subjected to hydrothermal reaction at 75-80 ℃ for 22-24 h. The CASH crystal nuclei are then obtained by spray drying.

[0011] Furthermore, the ultrafine mineral admixture for this exterior wall panel is prepared by the following steps: mixing fly ash, slag, and CASH crystal nuclei, adding sodium benzoate, and then mixing at an airflow rate of 100-120 m. 3 Grinding at a rate of 2-3 h under a specific surface area of ​​≥800 m² / min yields a product. 2 / kg, submicron-sized ultrafine mineral admixture with a particle size ≤4 μm.

[0012] Furthermore, the photocatalytic coating for the exterior wall panel is prepared by the following steps: dissolving nano-titanium dioxide in a 45-55% hydrogen peroxide solution, adjusting the pH to 9.5-10, adding a silane coupling agent and ultrasonically hydrolyzing for 20-30 min, then adding polyethylene glycol and ultrasonically reacting at 35-40 ℃ for 4-5 h to obtain the photocatalytic coating.

[0013] The method for preparing the above-mentioned concrete exterior wall panel according to the present invention includes the following steps:

[0014] (1) Preparation of concrete slurry: Cement, fly ash microspheres, silica fume, ultrafine mineral admixtures, sand, steel fibers, defoamer and water-reducing agent are mixed and stirred evenly at a water-cement ratio of 0.19-0.21 to prepare concrete slurry;

[0015] (2) Preparation of wall: Pour the slurry into the mold of the exterior wall panel, pressurize and form it at room temperature and pressure of 0.8-1.2 MPa for 6-8 h, and obtain the ultra-high performance concrete exterior wall panel after demolding;

[0016] (3) Preparation of exterior wall panels: Photocatalytic coating is applied to the wall by spraying or coating to obtain concrete exterior wall panels with self-cleaning function.

[0017] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: the exterior wall panel is made of a composite of the wall body and a photocatalyst sprayed onto the wall body, and based on the ultrafine mineral admixture, the introduction of CASH early-strength crystal nuclei greatly improves the early performance of concrete and reduces demolding time. Simultaneously, the hydrated calcium aluminum silicate produced by its hydration has a high specific surface area and high water retention capacity, and the Ca... 2+ It possesses high activity and is slowly released, reacting with sulfides in wastewater and exhaust gas to remove pollutants; furthermore, the nano-alumina added to the ultrafine mineral admixture not only promotes the formation of CASH crystal nuclei but also simultaneously... 3+ It can promote the photocatalysis of nano-TiO2 in photocatalytic coatings, enhance the "breathing" effect of ultra-high performance concrete exterior wall panels, and achieve self-cleaning.

[0018] This photocatalytic coating for exterior wall panels uses nano-titanium dioxide to form a "filter membrane" on the surface of ultra-high performance concrete exterior wall panels, playing a role in absorption and isolation. Under photocatalysis, nano-titanium dioxide can absorb nitrogen oxides and volatile harmful substances in the air. Furthermore, the silane-modified nano-titanium dioxide has extremely strong hydrophobic properties, allowing rainwater to carry away surface dust and other deposits, achieving a self-cleaning effect. Combining it with polyethylene glycol further enhances the photocatalytic effect of nano-titanium dioxide. The alcohol groups and carbon-carbon double bonds of polyethylene glycol can form hydrogen bonds with the amino groups of the silane-modified nano-titanium dioxide, improving the stability, uniform dispersion, compatibility, and binding ability of nano-titanium dioxide in the entire photocatalytic coating system. Furthermore, the combination of silane-modified nano-titanium dioxide with the alcohol groups of polyethylene glycol modifies the hydrophilicity of polyethylene glycol, weakening its hydrophilicity and improving the hydrophobic performance of the entire photocatalytic coating system.

[0019] In addition, the ultra-high performance concrete exterior wall panel was manufactured using pressure molding, which improved the strength of the ultra-high performance concrete by utilizing an extremely low water-cement ratio. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0021] It should be noted that the cement used in the preparation of the wall in this invention is preferably 525 cement; the sand is lake sand, obtained by mixing sand of three mesh sizes (20-30 mesh, 40-50 mesh, and 60-70 mesh) in a ratio of 1:1.6:0.4; the density of the fly ash microspheres is 0.7-0.8 g / cm³. 3The silica fume is semi-dense silica fume; the steel fiber is copper-plated fine straight steel fiber with a diameter of 0.22 mm and a length of 12 mm; the defoamer is an organosilicon defoamer; the water-reducing agent is a polycarboxylate high-performance water-reducing agent. Any commonly used slag in this field is acceptable. The polyethylene glycol has a molecular weight of 2000.

[0022] Example 1

[0023] The concrete exterior wall panel of Example 1 consists of a wall body and a photocatalytic coating sprayed onto the wall body. The component contents of the wall body are shown in Table 1 below. The component contents of the photocatalytic coating are shown in Table 2 below.

[0024] Table 1 Component content of the wall in Example 1

[0025]

[0026] Table 2 Component content of photocatalyst coating in Example 1

[0027]

[0028] The exterior wall panel of Embodiment 1 is obtained by the following steps:

[0029] (1) Preparation of CASH crystal nuclei: Silica fume, lime and calcium aluminate were mixed at a Ca / (Al+Si) molar ratio of 0.9 and an Al / (Al+Si) molar ratio of 0.08. Then, gypsum accounting for 1% of the total weight of silica fume, lime and calcium aluminate and nano-alumina accounting for 1% of the total weight of silica fume, lime and calcium aluminate were added. Water was added at a water-cement ratio of 0.5 and the pH was adjusted to 11-13. The mixture was subjected to hydrothermal reaction at 77 °C for 23 h and then spray-dried to obtain CASH crystal nuclei.

[0030] (2) Preparation of ultrafine mineral admixture: fly ash, slag, and CASH crystal nuclei are mixed, sodium benzoate is added, and the mixture is heated at an airflow rate of 110 m. 3 Grinding for 3 hours at a specific surface area of ​​≥800 m² / min yielded a product. 2 / kg, submicron-sized ultrafine mineral admixture with a particle size ≤4 μm.

[0031] (3) Preparation of concrete slurry: Cement, fly ash microspheres, silica fume, ultrafine mineral admixtures, sand, steel fiber, defoamer and water-reducing agent are mixed and stirred evenly at a water-cement ratio of 0.21 to obtain concrete slurry.

[0032] (4) Preparation of wall: Pour the slurry into the mold of the exterior wall panel, pressurize and form for 7 h at room temperature and pressure of 1.0 MPa, and obtain the ultra-high performance concrete exterior wall panel after demolding.

[0033] (5) Preparation of exterior wall panels: Dissolve nano-titanium dioxide in a 45% hydrogen peroxide solution, adjust the pH to 9.5-10, add silane coupling agent and sonicate for 20 min, then add polyethylene glycol and sonicate at 35 °C for 5 h to obtain the photocatalytic coating; then apply it to the wall by spraying or coating to obtain a concrete exterior wall panel with self-cleaning function.

[0034] Example 2

[0035] The concrete exterior wall panel of Example 2 consists of a wall body and a photocatalytic coating sprayed onto the wall body. The component contents of the wall body are shown in Table 3 below. The component contents of the photocatalytic coating are shown in Table 4 below.

[0036] Table 3 Component content of the wall in Example 2

[0037]

[0038] Table 4. Component content of photocatalyst coating in Example 2

[0039]

[0040] The exterior wall panel of Embodiment 2 is obtained by the following steps:

[0041] (1) Preparation of CASH crystal nuclei: Silica fume, lime and calcium aluminate were mixed at a Ca / (Al+Si) molar ratio of 0.8 and an Al / (Al+Si) molar ratio of 0.06. Gypsum accounting for 1.5% of the total weight of silica fume, lime and calcium aluminate and nano alumina accounting for 1.5% of the total weight of silica fume, lime and calcium aluminate were added. Water was added at a water-cement ratio of 0.48 and the pH was adjusted to 11-13. The mixture was subjected to hydrothermal reaction at 79 °C for 23 h and then spray-dried to obtain CASH crystal nuclei.

[0042] (2) Preparation of ultrafine mineral admixture: fly ash, slag, and CASH crystal nuclei are mixed, sodium benzoate is added, and the mixture is heated at an airflow rate of 105 m. 3 Grinding at a rate of 3 h / min yields a specific surface area ≥ 800 m². 2 / kg, submicron-sized ultrafine mineral admixture with a particle size ≤4μm.

[0043] (3) Preparation of concrete slurry: Cement, fly ash microspheres, silica fume, ultrafine mineral admixtures, sand, steel fiber, defoamer and water-reducing agent are mixed and stirred evenly at a water-cement ratio of 0.2 to obtain concrete slurry.

[0044] (4) Preparation of wall: Pour the slurry into the mold of the exterior wall panel, pressurize and form it for 7 h at room temperature and pressure of 1.1 MPa, and after demolding, the ultra-high performance concrete exterior wall panel is obtained.

[0045] (5) Preparation of exterior wall panels: Dissolve nano-titanium dioxide in a 48% hydrogen peroxide solution, adjust the pH to 9.5-10, add silane coupling agent and ultrasonically hydrolyze for 28 min, then add polyethylene glycol and ultrasonically react at 38 °C for 5 h to obtain the photocatalytic coating; then apply it to the wall by spraying or coating to obtain a concrete exterior wall panel with self-cleaning function.

[0046] Example 3

[0047] The concrete exterior wall panel of Example 3 consists of a wall body and a photocatalytic coating sprayed onto the wall body. The component contents of the wall body are shown in Table 5 below. The component contents of the photocatalytic coating are shown in Table 6 below.

[0048] Table 5 Component content of the wall in Example 3

[0049]

[0050] Table 6. Component content of photocatalyst coating in Example 3

[0051]

[0052] The exterior wall panel of Embodiment 3 is obtained by the following steps:

[0053] (1) Preparation of CASH crystal nuclei: Silica fume, lime and calcium aluminate were mixed at a Ca / (Al+Si) molar ratio of 0.8 and an Al / (Al+Si) molar ratio of 0.05. Gypsum accounting for 0.5% of the total weight of silica fume, lime and calcium aluminate and nano-alumina accounting for 0.5% of the total weight of silica fume, lime and calcium aluminate were added. Water was added at a water-cement ratio of 0.45. The pH was adjusted to 11-13. The mixture was subjected to hydrothermal reaction at 75 °C for 24 h. The CASH crystal nuclei were obtained by spray drying.

[0054] (2) Preparation of ultrafine mineral admixture: fly ash, slag, and CASH crystal nuclei are mixed, sodium benzoate is added, and the mixture is heated at an airflow rate of 100 m. 3 Grinding for 3 hours at a specific surface area of ​​≥800 m² / min yielded a product. 2 / kg, submicron-sized ultrafine mineral admixture with a particle size ≤4μm.

[0055] (3) Preparation of concrete slurry: Cement, fly ash microspheres, silica fume, ultrafine mineral admixtures, sand, steel fiber, defoamer and water-reducing agent are mixed and stirred evenly at a water-cement ratio of 0.2 to obtain concrete slurry.

[0056] (4) Preparation of wall: Pour the slurry into the mold of the exterior wall panel, pressurize and form for 8 hours at room temperature and pressure of 0.8 MPa, and obtain the ultra-high performance concrete exterior wall panel after demolding.

[0057] (5) Preparation of exterior wall panels: Dissolve nano-titanium dioxide in a 50% hydrogen peroxide solution, adjust the pH to 9.5-10, add silane coupling agent and sonicate for 25 min, then add polyethylene glycol and sonicate at 35 °C for 5 h to obtain the photocatalytic coating; then apply it to the wall by spraying or coating to obtain a concrete exterior wall panel with self-cleaning function.

[0058] Example 4

[0059] The concrete exterior wall panel of Example 4 consists of a wall body and a photocatalytic coating sprayed onto the wall body. The component contents of the wall body are shown in Table 7 below. The component contents of the photocatalytic coating are shown in Table 8 below.

[0060] Table 7 Component content of the wall in Example 4

[0061]

[0062] Table 8. Component content of photocatalyst coating in Example 4

[0063]

[0064] The exterior wall panel of Example 4 is obtained by the following steps:

[0065] (1) Preparation of CASH crystal nuclei: Silica fume, lime and calcium aluminate were mixed at a Ca / (Al+Si) molar ratio of 1.0 and an Al / (Al+Si) molar ratio of 0.1. Gypsum accounting for 2% of the total weight of silica fume, lime and calcium aluminate and nano alumina accounting for 2% of the total weight of silica fume, lime and calcium aluminate were added. Water was added at a water-cement ratio of 0.51 and the pH was adjusted to 11-13. The mixture was subjected to hydrothermal reaction at 80 °C for 22 h and then spray-dried to obtain CASH crystal nuclei.

[0066] (2) Preparation of ultrafine mineral admixture: fly ash, slag, and CASH crystal nuclei are mixed, sodium benzoate is added, and the mixture is heated at an airflow rate of 120 m. 3 Grinding at a rate of 100 m³ / min for 2 h yields a specific surface area ≥ 800 m². 2 / kg, submicron-sized ultrafine mineral admixture with a particle size ≤4 μm.

[0067] (3) Preparation of concrete slurry: Cement, fly ash microspheres, silica fume, ultrafine mineral admixtures, sand, steel fiber, defoamer and water-reducing agent are mixed and stirred evenly at a water-cement ratio of 0.19 to prepare concrete slurry.

[0068] (4) Preparation of wall: Pour the slurry into the mold of the exterior wall panel, pressurize and form for 6 hours at room temperature and pressure of 1.2 MPa, and obtain the ultra-high performance concrete exterior wall panel after demolding.

[0069] (5) Preparation of exterior wall panels: Dissolve nano-titanium dioxide in a 55% hydrogen peroxide solution, adjust the pH to 9.5-10, add silane coupling agent and sonicate for 30 min, then add polyethylene glycol and sonicate at 40 °C for 4 h to obtain the photocatalytic coating; then apply it to the wall by spraying or coating to obtain a concrete exterior wall panel with self-cleaning function.

[0070] After the photocatalytic coatings prepared in Examples 1 to 4 of this invention were left to stand for 48 hours, it was observed that no flocculent suspended particles were precipitated in the coating. This indicates that the photocatalytic coating prepared in this invention has strong stability and high compatibility.

[0071] Comparative Example 1

[0072] Compared with Example 1, the difference is that nano-alumina is not added to the ultrafine mineral admixture of the wall.

[0073] The performance of the exterior wall panels prepared in Examples 1-5 and Comparative Example 1 was tested, and the results are shown in Table 9 below.

[0074] Table 9 Performance Comparison of Ultra-High Performance Concrete Exterior Wall Panels Prepared in Examples 1-4 and Comparative Example 1

[0075]

[0076] As shown in Table 9, the ultrafine mineral admixture used in the exterior wall panel prepared by this invention contains CASH crystal nuclei, which not only greatly improves the early performance of the ultra-high performance concrete exterior wall panel (the compressive strength at 16 hours can reach more than 78 MPa, and the compressive strength at 28 days can reach more than 125 MPa); but also the photocatalytic coating can form a "filter membrane" on the surface of the ultra-high performance concrete exterior wall panel, effectively absorbing harmful substances in the air and isolating surface deposits (the nitrogen oxide absorption rate can reach more than 37%), effectively promoting environmental protection; in addition, the "filter membrane" is highly hydrophobic, and water droplets on the surface can slide off smoothly without residue.

Claims

1. A concrete exterior wall panel having a self-cleaning function, characterized by, The exterior wall panel includes the wall body and the photocatalytic coating sprayed onto the wall body; The wall material comprises the following raw materials by weight: 354-360 parts cement, 27-35 parts fly ash microspheres, 48-56 parts silica fume, 65-72 parts ultrafine mineral admixture, 480-492 parts sand, 6.5-7.2 parts steel fiber, 1.2-1.5 parts defoamer, and 9.5-10.2 parts water-reducing agent; The photocatalytic coating comprises the following raw materials in parts by weight: 10-15 parts of nano titanium dioxide, 4-6 parts of silane coupling agent, and 40-60 parts of polyethylene glycol; The ultrafine mineral admixture comprises, by weight, 12-17 parts of CASH crystal nuclei, 33-40 parts of fly ash, 3-4 parts of sodium benzoate, and 58-64 parts of slag. The CASH crystal nuclei are prepared by the following steps: silica fume, lime, and calcium aluminate are mixed at a Ca / (Al+Si) molar ratio of 0.8-1.0 and an Al / (Al+Si) molar ratio of 0.05-0.

1. Then, gypsum accounting for 0.5-2% of the total weight of silica fume, lime, and calcium aluminate, and nano-alumina accounting for 0.5-2% of the total weight of silica fume, lime, and calcium aluminate are added. Water is added at a water-cement ratio of 0.45-0.51, the pH is adjusted to 11-13, and the mixture is subjected to hydrothermal reaction at 75-80 ℃ for 22-24 h. The CASH crystal nuclei are then obtained by spray drying. The ultrafine mineral admixture is prepared by the following steps: mixing fly ash, slag, and CASH crystal nuclei, adding sodium benzoate, and then mixing at an airflow rate of 100-120 m. 3 Grinding for 2-3 hours at a constant speed to obtain a specific surface area ≥800 m² 2 / kg, submicron-sized ultrafine mineral admixture with a particle size ≤4 μm.

2. The concrete exterior wall panel having a self-cleaning function according to claim 1, wherein, The photocatalytic coating is prepared by the following steps: dissolving nano-titanium dioxide in a 45-55% hydrogen peroxide solution, adjusting the pH to 9.5-10, adding a silane coupling agent and ultrasonically hydrolyzing for 20-30 min, then adding polyethylene glycol and ultrasonically reacting at 35-40 ℃ for 4-5 h to obtain the photocatalytic coating.

3. A method of making the concrete exterior wall panel of claim 1, characterized by, Includes the following steps: (1) Preparation of concrete slurry: Cement, fly ash microspheres, silica fume, ultrafine mineral admixtures, sand, steel fibers, defoamer and water-reducing agent are mixed and stirred evenly at a water-cement ratio of 0.19-0.21 to prepare concrete slurry; (2) Preparation of wall: Pour the slurry into the mold of the exterior wall panel, pressurize and form it at room temperature and pressure of 0.8-1.2 MPa for 6-8 h, and obtain the ultra-high performance concrete exterior wall panel after demolding; (3) Preparation of exterior wall panels: Photocatalytic coating is applied to the wall by spraying or coating to obtain concrete exterior wall panels with self-cleaning function.

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