Autoclaved aerated concrete plate with self-cleaning function and preparation method

Abstract

The invention relates to the technical field of inorganic self-cleaning materials, and particularly provides an autoclaved aerated concrete plate with a self-cleaning function, which comprises an autoclaved aerated concrete base layer, a solid waste filling layer and a modified mortar surface layer. The base layer is subjected to high-temperature and high-pressure steam curing to form a light, high-strength and fire-resistant structure supporting layer; the filling layer is made of solid waste such as construction waste and waste gypsum and can automatically fill holes when the base layer is damaged, so that the durability is improved; the modified mortar surface layer is composed of a first coating layer and a second coating layer, compared with a traditional aerated concrete plate, the plate not only strengthens the mechanical property and weather resistance, but also improves the antifouling, water-resistant, durable and other functions, reduces the production cost through solid waste reutilization, is green and environment-friendly, is suitable for the fields of building walls, floors and the like, and has wide application prospects. The maintenance cost can be effectively reduced, the service life is prolonged, and the comprehensive performance of building materials is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic self-cleaning materials, and particularly relates to an autoclaved aerated concrete board with self-cleaning function and a preparation method thereof. Background Art

[0002] Autoclaved Aerated Concrete (AAC) boards, as a kind of building materials with light weight, high strength and excellent thermal insulation performance, are widely used in the wall, floor and roof structures of modern buildings. Its unique porous structure not only significantly reduces the material density, but also endows it with excellent sound insulation, earthquake resistance and energy-saving effects. However, traditional autoclaved aerated concrete boards are easily affected by external pollutants during actual use, such as dust, oil stains, moss, etc. The long-term accumulation of these pollutants will lead to the deterioration of the appearance of the boards and reduce their surface durability.

[0003] In the prior art, the technical routes for autoclaved aerated concrete boards to obtain self-cleaning function mainly include:

[0004] 1. Self-cleaning coating technology based on photocatalytic nanomaterials

[0005] Using photocatalytic nanomaterials such as titanium dioxide (TiO 2 ), zinc oxide (ZnO), etc., to construct a photocatalytic self-cleaning coating on the surface of autoclaved aerated concrete (AAC) boards. Under ultraviolet or visible light irradiation, the photocatalytic material can catalytically degrade organic pollutants and form a superhydrophilic surface, enabling rainwater to spread evenly and carry away dirt. This method is applicable to long-term outdoor exposure environments, can effectively reduce the adhesion of dust, oil stains, etc., and improve the pollution resistance and service life of the boards.

[0006] 2. Self-cleaning surface modification based on superhydrophobic micro-nano structures

[0007] By spraying, etching or bionic nano-processing technology, a superhydrophobic micro-nano structure similar to the lotus leaf effect is constructed on the surface of aerated concrete, so that water droplets form a ball shape on the surface and carry dirt particles during the rolling process to achieve the self-cleaning function. This method mainly relies on low surface energy coatings (such as silicone, fluoride modification), which can reduce the contact angle of water and improve the anti-fouling performance, and is applicable to environments with high humidity and more rain.

[0008] 3. Self-cleaning coating technology based on self-healing function

[0009] An anti-fouling protective layer is formed on the surface of autoclaved aerated concrete by using a self-healing coating containing a microcapsule structure. When microcracks appear on the surface due to weathering, abrasion or acid rain erosion, the active substances (such as siloxane, paraffin, polyurea, etc.) in the microcapsules are automatically released and fill the cracks, restoring the self-cleaning performance. This technology extends the coating life and can maintain a long-term stable anti-fouling effect, and is applicable to industrial or marine climate areas with harsh environments.

[0010] However, the existing technologies represented by the above technical routes mainly have the following technical problems:

[0011] 1. Durability and adhesion problems of the self-cleaning coating

[0012] Current photocatalytic and superhydrophobic coatings are prone to be affected by the external environment (such as ultraviolet rays, temperature and humidity changes, weathering, etc.) during long-term use, resulting in a decline in coating performance or peeling. In addition, the surface of aerated concrete has a certain porosity, which affects the uniform adhesion of the coating, making the coating durability poor. It is necessary to optimize the coating formula or adopt a better surface treatment technology to enhance its stability.

[0013] 2. Efficiency problems of photocatalytic self-cleaning materials in low-light environments

[0014] Traditional TiO 2 Photocatalytic coatings mainly rely on ultraviolet light excitation, and in indoor or low-light environments, their ability to degrade pollutants is significantly reduced. How to improve the activity of photocatalysts under visible light through doping modification (such as nitrogen doping, metal ion modification), or develop new catalytic materials that can still maintain self-cleaning functions under lightless conditions is an important direction to expand the application scope of the technology.

[0015] 3. Cost and industrial production challenges of self-healing coatings

[0016] The preparation of self-healing coatings usually involves polymer microcapsule technology or nanocomposites. These materials have high costs, and the coating manufacturing process is relatively complex, which affects large-scale popularization and application. In addition, in actual engineering applications, the triggering conditions of the self-healing mechanism need to match the use environment of concrete slabs to ensure that the coating can be efficiently repaired when damaged without affecting the overall performance of building materials.

[0017] Based on this, there is an urgent need for an innovative autoclaved aerated concrete slab and its preparation method, which can not only maintain the original excellent performance of the slab, but also have good self-cleaning ability, meeting the requirements of modern buildings for low maintenance costs and sustainable performance. Summary of the Invention

[0018] In view of the above problems, the object of the present invention is to propose:

[0019] To achieve the objectives of the present invention, the present invention is realized through the following technical solutions:

[0020] An autoclaved aerated concrete board with self-cleaning function, comprising an autoclaved aerated concrete base layer, a solid waste filling layer, and a modified mortar surface layer that are sequentially stacked from bottom to top;

[0021] The autoclaved aerated concrete base layer is used as a load-bearing part;

[0022] During the use of the board, when voids are generated in the autoclaved aerated concrete base layer due to damage, the solid waste filling layer fills the voids in the autoclaved aerated concrete base layer to repair the autoclaved aerated concrete base layer;

[0023] The modified mortar surface layer is used as a decorative part;

[0024] The modified mortar surface layer includes, from bottom to top, a first coating layer and a second coating layer that are sequentially stacked;

[0025] The first coating layer is coated on the surface of the solid waste filling layer, and the second coating layer is coated on the surface of the first coating layer;

[0026] The first coating layer is water-tight and adheres firmly, and generates water mist based on the hydrophilic-hydrophobic effect. The second coating layer is water-tight and permeable, used to protect the first coating layer from touch chemical damage and allow the condensed water mist to penetrate the second coating layer;

[0027] The first coating layer is composed of cement, sand, water retention agent, water reducing agent, protective agent, and water. The mass ratio range is 100 parts of cement, 100 - 140 parts of sand, 0.5 - 2 parts of water retention agent, 0.4 - 1 part of water reducing agent, 2 - 5 parts of protective agent, and the water-cement ratio is 0.30 - 0.35.

[0028] Further, the second coating layer is composed of modified silicate cement, hard silicon micropowder, relief cement modification aid, inorganic aggregate, hard silicon micropowder, flexible polymer latex, and water. The mass ratio range is 80 - 120 parts of modified silicate cement, 10 - 20 parts of hard silicon micropowder, 3 - 8 parts of relief cement modification aid, 20 - 40 parts of inorganic aggregate, 5 - 15 parts of hard silicon micropowder, 10 - 20 parts of flexible polymer latex, and the water-cement ratio is 0.25 - 0.35.

[0029] Further, the autoclaved aerated concrete base layer includes the following raw materials in parts by weight: 80 - 90 parts of siliceous material, 110 - 120 parts of calcareous material, 0.4 - 0.8 parts of foaming agent, 0.01 - 0.04 parts of foam stabilizer, 0.01 - 0.04 parts of regulator, 1 - 5 parts of steel slag powder, and 5 parts of quicklime.

[0030] Further, the siliceous material is at least one of sand, fly ash, steel slag powder, coal gangue powder, and quartz powder;

[0031] The calcareous material is at least one of quicklime, hydrated lime, and desulfurized gypsum;

[0032] The gas-forming material is one of aluminum powder, magnesium powder, and inert aluminum fiber;

[0033] The foam stabilizer is one of limestone powder, phosphogypsum powder, ground fly ash, and carbon black;

[0034] The regulator is aggregate stone powder or sodium fluorosilicate.

[0035] Further, the solid waste filling layer comprises the following raw materials in parts by weight: 22-30 parts of construction waste, 5-7 parts of sand, 4-8 parts of waste gypsum, 40-55 parts of curing agent, and 8-10 parts of water.

[0036] Further, the construction waste is one or any combination of waste reinforced concrete, waste bricks, waste mortar, waste gypsum board, and waste plastering generated during construction, maintenance, demolition, and decoration.

[0037] The present invention also provides a method for preparing an autoclaved aerated concrete board with self-cleaning function, which is used to prepare the autoclaved aerated concrete board with self-cleaning function, and comprises the following steps:

[0038] S1. Prepare an autoclaved aerated concrete base layer: Weigh siliceous material, calcareous material, gas-forming material, foam stabilizer, regulator, steel slag powder, and 2 parts of quicklime, and add 25-35 parts of water to obtain aerated concrete slurry. Inject the aerated concrete slurry into a mold, pour it into a mold, cure it statically to obtain a blank, and then autoclave the blank at a pressure of 1.1-1.2 MPa and a temperature of 170-190 °C for 12-15 h to obtain the autoclaved aerated concrete base layer;

[0039] S2. Prepare a solid waste filling layer: Weigh construction waste, sand, waste gypsum, curing agent, and stir with water for 30-60 min, then pour it onto the surface of the autoclaved aerated concrete base layer in the autoclaved aerated concrete base layer, press and cure to obtain the solid waste filling layer;

[0040] S3. Prepare a modified mortar surface layer: Prepare a first coating layer on the surface of the solid waste filling layer. After drying the first coating layer, apply the first coating layer to the second coating layer. After the second coating layer is dried, obtain the autoclaved aerated concrete board with self-cleaning function;

[0041] The preparation of the first coating layer includes: Weigh aluminous cement, sand, water retention agent, water reducing agent, protective agent, and water;

[0042] The preparation of the modified portland cement includes: using portland cement as the matrix material and metakaolin as the modifying material, and processing through steps of pre-wetting and mixing, thermosetting forming, post-wetting curing, low-pressure air hole impregnation, and low-temperature simulated steam curing.

[0043] The present invention also provides a use of an autoclaved aerated concrete board with a self-cleaning function. Any autoclaved aerated concrete board with a self-cleaning function is used alone, or processed into a board, or processed into a brick, or processed into a hollow block, or crushed as a raw material for siliceous materials.

[0044] Through the special chemical properties of the "first coating layer" itself, the present invention achieves a self-cleaning effect. That is, the core technical idea of the present invention is to improve the "anti-pollution performance" on the basis of ensuring the original pressure resistance, sound insulation, decoration and other properties of the AAC board. The main means is to improve the anti-pollution performance of the AAC base material through formula adjustment and production process optimization, and develop AAC materials with self-cleaning functions.

[0045] Beneficial effects

[0046] The beneficial effects of the technical solution disclosed by the present invention include:

[0047] 1. The first coating layer selects modified cement, and the design idea comes from the method of dredging capillaries. This kind of cement is suitable for extremely poor construction environments. After absorbing water, it can migrate its soluble small molecule polysaccharide hydrates to the pore-like gaps through moisture, so that the pores are naturally blocked, and the blocking surface is a hydrophilic and oleophobic surface after hydration. Even when the pores are initially covered, due to the strong water absorption of the covering layer, a water film can be formed deep in the pores. Even if external dust and oil stains enter the pores, they will be supported by the water film in an area more than 0.001 mm away from the base surface. Slight vibrations, wind, and changes in temperature and humidity can condense the water film into droplets, quickly and automatically removing the impurities in the pores and keeping the pores clean, thereby keeping the AAC board clean.

[0048] 2. The first coating layer of the present invention adopts a reinforced reverse coating method. First, the "dense water resistance" of the moxibustion cement attached in the pores and grooves can be used to prevent the grooves and pores from being invaded by water and prevent the intrusion of stains. And the remaining moxibustion cement will fill the grooves and cavities with condensed frost when the air humidity is high, such as in the early morning, evening, and rainy days, so that dust cannot adhere to the dry pore walls. Description of the drawings

[0049] Figure 1 It is a schematic diagram of the dry density test results of the product invention of the present invention;

[0050] Figure 2Schematic diagram of the compressive strength test results of the product invention of the present invention;

[0051] Figure 3 Schematic diagram of the flexural strength test results of the product invention of the present invention;

[0052] Figure 4 Schematic diagram of the water absorption test results of the product invention of the present invention;

[0053] Figure 5 Schematic diagram of the test results of the scrub resistance times grade of the product invention of the present invention;

[0054] Figure 6 Schematic diagram of the test results of the self-cleaning ability (contact angle) of the product invention of the present invention;

[0055] Figure 7 Schematic diagram of the test results of the self-cleaning ability (self-cleaning time) of the product invention of the present invention;

[0056] Figure 8 Schematic diagram of the test results of the weather resistance rate of the self-cleaning ability of the product invention of the present invention. Detailed implementation manners

[0057] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation to the protection scope of the present invention.

[0058] Embodiment 1

[0059] This embodiment provides an autoclaved aerated concrete board with self-cleaning function, which includes an autoclaved aerated concrete base layer, a solid waste filling layer and a modified mortar surface layer stacked in sequence from bottom to top;

[0060] The autoclaved aerated concrete base layer is used as a load-bearing part;

[0061] During the use of the board, when the autoclaved aerated concrete base layer is damaged and forms cavities, the solid waste filling layer fills the cavities of the autoclaved aerated concrete base layer to repair the autoclaved aerated concrete base layer;

[0062] The modified mortar surface layer is used as a decorative part;

[0063] The modified mortar surface layer includes, stacked in sequence from bottom to top: a first coating layer and a second coating layer;

[0064] The first coating layer is coated on the surface of the solid waste filling layer, and the second coating layer is coated on the surface of the first coating layer;

[0065] The first coating layer is water-tight and tenacious, and generates water mist based on the hydrophilic-hydrophobic effect itself. The second coating layer is water-tight and water-permeable, which is used to protect the first coating layer from touch chemical damage and allows the condensed water mist to penetrate the second coating layer;

[0066] The first coating layer is composed of cement, sand, water retention agent, water reducing agent, protective agent and water, and the mass ratio ranges from 100 parts of cement, 100 - 140 parts of sand, 0.5 - 2 parts of water retention agent, 0.4 - 1 part of water reducing agent, 2 - 5 parts of protective agent, and the water-cement ratio is 0.30 - 0.35.

[0067] The second coating layer is composed of modified portland cement, hard silicon micropowder, relief cement modification aid, inorganic aggregate, hard silicon micropowder, flexible polymer latex and water, and the mass ratio ranges from 80 - 120 parts of modified portland cement, 10 - 20 parts of hard silicon micropowder, 3 - 8 parts of relief cement modification aid, 20 - 40 parts of inorganic aggregate, 5 - 15 parts of hard silicon micropowder, 10 - 20 parts of flexible polymer latex, and the water-cement ratio is 0.25 - 0.35.

[0068] The autoclaved aerated concrete base layer includes the following raw materials by weight: 80 - 90 parts of siliceous material, 110 - 120 parts of calcareous material, 0.4 - 0.8 parts of foaming agent, 0.01 - 0.04 parts of foam stabilizer, 0.01 - 0.04 parts of regulator, 1 - 5 parts of steel slag powder and 5 parts of quicklime.

[0069] The siliceous material is at least one of sand, fly ash, steel slag powder, coal gangue powder, quartz powder;

[0070] The calcareous material is at least one of quicklime, hydrated lime, desulfurized gypsum;

[0071] The foaming agent is one of aluminum powder, magnesium powder, inert aluminum fiber;

[0072] The foam stabilizer is one of limestone powder, phosphogypsum powder, ground fly ash, carbon black;

[0073] The regulator is aggregate stone powder or sodium fluorosilicate.

[0074] The solid waste filling layer includes the following raw materials by weight: 22 - 30 parts of construction waste, 5 - 7 parts of sand, 4 - 8 parts of waste gypsum, 40 - 55 parts of curing agent and 8 - 10 parts of water.

[0075] The construction waste is one or any combination of waste reinforced concrete, waste bricks, waste mortar, waste gypsum board, waste plastering generated during construction, maintenance, demolition, and decoration.

[0076] Example Two

[0077] This embodiment provides an autoclaved aerated concrete composite board with a self-cleaning function. The board is composed of an autoclaved aerated concrete base layer, a solid waste filling layer, and a modified mortar surface layer stacked in sequence.

[0078] The autoclaved aerated concrete base layer serves as a load-bearing layer, and its main function is to provide structural support and stability. The raw materials of this layer include 85 parts of siliceous materials, 110 parts of calcareous materials, 1.0 part of foaming agent, 0.05 part of foam stabilizer, 0.03 part of regulator, 6 parts of steel slag powder, and 7 parts of quicklime.

[0079] The siliceous material is selected as coal gangue powder, the calcareous material is selected as desulfurized gypsum, the foaming agent is aluminum powder, the foam stabilizer is phosphogypsum powder, and the regulator is sodium fluorosilicate.

[0080] After the raw materials are rationally proportioned and stirred, they are cast into shape, and then steam-cured for 10 - 14 hours in an environment of 1.0 - 1.2 MPa and 160 - 185 °C to form a stable internal microporous structure, with the characteristics of light weight, high strength, fire resistance, and heat preservation.

[0081] The solid waste filling layer is used to fill and repair the voids generated when the autoclaved aerated concrete base layer is damaged, improving the durability of the material. This layer is composed of 25 parts of construction waste, 8 parts of sand, 5 parts of waste gypsum, 45 parts of curing agent, and 10 parts of water. The construction waste can be selected from waste concrete, waste bricks, waste mortar, waste gypsum board, etc. generated during construction, maintenance, demolition, and decoration. After these raw materials are screened, crushed, and evenly stirred, they are filled on the surface of the base layer and compacted to closely combine with the base layer. This layer not only improves the overall strength of the board but also realizes the reuse of construction waste, conforming to the concept of green environmental protection.

[0082] The modified mortar surface layer serves as a decorative layer and is composed of a first coating layer and a second coating layer. The first coating layer is directly coated on the surface of the solid waste filling layer, using 110 parts of cement, 150 parts of sand, 2.0 parts of water retention agent, 1.0 part of water reducing agent, 5 parts of protective agent, and a water-cement ratio of 0.30. This layer has strong water tightness and forms water mist through the hydrophilic-hydrophobic effect, reducing stain adhesion and keeping the surface of the board clean.

[0083] The second coating layer is coated on the surface of the first coating layer. Its raw materials include 100 parts of modified silicate cement, 25 parts of hard silicon micropowder, 8 parts of relief cement modification aid, 40 parts of natural inorganic aggregate, 15 parts of hard silicon micropowder, 18 parts of flexible polymer latex, and a water-cement ratio of 0.28. This layer has both water tightness and air permeability characteristics, can protect the first coating layer from chemical erosion, and allows the condensed water mist to penetrate, improving the self-cleaning ability of the board. In addition, the wear resistance and crack resistance of this surface layer are also enhanced, extending the service life of the board.

[0084] Example Three

[0085] A preparation method of autoclaved aerated concrete slabs with self-cleaning function, which is used to prepare the autoclaved aerated concrete slabs with self-cleaning function, includes the following steps:

[0086] S1. Prepare the autoclaved aerated concrete base layer: Weigh 2 parts of siliceous materials, calcareous materials, foaming materials, foam stabilizers, regulators, steel slag powder and quicklime, and add 25 - 35 parts of water to obtain aerated concrete slurry. Inject the aerated concrete slurry into a mold, pour and form it, and cure it statically to obtain a blank. Then, steam-cure the blank at a pressure of 1.1 - 1.2 MPa and a temperature of 170 - 190 °C for 12 - 15 h to obtain the autoclaved aerated concrete base layer;

[0087] S2. Prepare the solid waste filling layer: Weigh construction waste, sand, waste gypsum, curing agent, and stir with water for 30 - 60 min, then pour it onto the surface of the autoclaved aerated concrete base layer in the autoclaved aerated concrete base layer, press and cure it to obtain the solid waste filling layer;

[0088] S3. Prepare the modified mortar surface layer: Prepare a first coating layer on the surface of the solid waste filling layer. After drying the first coating layer, coat the first coating layer on the second coating layer. After the second coating layer dries, obtain the autoclaved aerated concrete slabs with self-cleaning function;

[0089] The preparation of the first coating layer includes: Weigh moxibustion cement, sand, water retention agent, water reducing agent, protective agent and water;

[0090] The preparation of the modified Portland cement includes: Using Portland cement as the matrix material and metakaolin as the modified material, it is processed through steps such as pre-wetting and mixing, thermosetting forming, post-wetting curing, low-pressure air hole impregnation and low-temperature simulated steam curing;

[0091] The preparation steps of the moxibustion cement are: S4. Crush the clay into clay powder, under the condition of thermal radiation at a temperature of 1200 °C, make uniform contact with air until the yellowish-brown color disappears. After cooling, screen out the moxibustion soil powder with a particle size of 0.015 - 0.08 mm, soak the moxibustion soil powder with calcium hydroxide aqueous solution and then dry it. Then, mix the dried moxibustion soil powder with sulfate cement, gypsum, sodium chloride and stir mechanically until uniform, and then add anhydrous calcium chloride, sand, etc. and grind to obtain it;

[0092] The moxibustion cement modification aid includes a combination of adhesive, silicate filling material, mildew-proof modifier and water;

[0093] The preparation steps of the citric acid cement protective agent include: grinding the aluminate minerals in the cement clinker together with a small amount of gypsum, adding an appropriate amount of sodium hydroxide solution to make a water glass solution, and obtaining it through four stages of heating, pressurizing, depressurizing, and cooling at a temperature of 460°C and an oxygen partial pressure of less than 2 kPa;

[0094] The water retaining agent is hydroxyethyl cellulose; the water reducing agent is an aromatic small monomer differentiated polymer; the protective agent is a benzene ring polymer;

[0095] Example 4

[0096] This example provides a preparation method of the autoclaved aerated concrete board with self-cleaning function, including the following steps:

[0097] S1. Prepare the autoclaved aerated concrete base:

[0098] Weigh equal weights of sand, (presumably "fly ash" or other ash materials), calcareous materials, siliceous materials, foaming materials, foam stabilizers, regulators, and auxiliary materials for mixing. According to different mixing sequences, it can be divided into multiple methods such as "aggregate + high-viscosity cement pre-mixing" and "composite light plastering". Skilled workers should use them flexibly during operation to avoid quality problems.

[0099] Under the principle of the specified water-cement ratio, to improve construction efficiency, the high-dust, light plastering water operation procedure can be combined with the watering operation procedure to carry out the "light plastering" process. When watering, the requirements of the construction materials for "visually revealing the slurry" should be met, so that the thin layer can be gradually transformed into mortar after being turned over; if a manual brush is used, it is necessary to ensure that the mortar is evenly spread and pressed to be flat.

[0100] In addition, for the mixed mortar, the feeding speed should be moderately controlled and the operation should be kept stable and vertically dropped to make the mortar fully dispersed. During operation, try to avoid excessive scraping or overflow of materials; never use too hard tools such as iron sheets to forcibly press and plaster, so as not to damage the internal pore structure. The mixing direction can be adjusted flexibly. When using in small batches, it can be combined with flowing water or inclined mixing to ensure uniform distribution of the mortar.

[0101] Inject the prepared aerated concrete slurry into the mold, and after casting and forming, let it stand for curing to obtain a blank; then autoclave it at 1.1 - 1.2 MPa and 170 - 190°C for 12 - 15 hours to obtain the autoclaved aerated concrete base.

[0102] S2. Prepare the solid waste filling layer:

[0103] Weigh construction waste, sand, waste gypsum, curing agent, and water repellent, stir for 30 - 60 minutes, then pour the mixture on the surface of the autoclaved aerated concrete base, and after pressing and curing, obtain the solid waste filling layer.

[0104] S3. Prepare the modified mortar surface layer:

[0105] Prepare the first coating layer on the surface of the solid waste filling layer. After the first coating layer dries, apply the second coating layer on it. After the second coating layer dries, the autoclaved aerated concrete board with self-cleaning function can be obtained.

[0106] Example Five

[0107] This example is for comparative experiments and results, and is designed based on the product invention of Example One.

[0108] 1. Overview

[0109] This comparative experiment aims to verify the self-cleaning performance, mechanical properties and weather resistance of the autoclaved aerated concrete board combined with the modified mortar surface layer and the solid waste filling layer. Through the design of orthogonal comparative experiments, systematic evaluation of different factor level combinations is carried out, and the performance is compared with the traditional process. The experimental results show that the new scheme has significant advantages in terms of self-cleaning time, stain residue rate, compressive and flexural strength, and scrub resistance, and has high commercial value.

[0110] 2. Experimental Design

[0111] 2.1 Experimental Purpose

[0112] Evaluate the influence of the modified mortar surface layer on the self-cleaning performance of AAC boards, analyze the role of the solid waste filling layer in the internal repair and durability of the boards, and explore its feasibility in engineering applications through comprehensive performance comparison with the traditional process by means of comparative experiments.

[0113] 2.2 Experimental Materials

[0114] 2.2.1 Autoclaved Aerated Concrete Base:

[0115] Siliceous materials: sand, fly ash, steel slag powder, etc.

[0116] Calcareous materials: quicklime, desulfurized gypsum, etc.

[0117] Gas generating materials: aluminum powder, etc.

[0118] Foam stabilizers, regulators and other auxiliary agents;

[0119] 2.2.2 Solid Waste Filling Layer:

[0120] Construction waste, sand, waste gypsum, curing agent and water, etc.

[0121] 2.2.3 Modified Mortar Surface Layer:

[0122] The first coating layer: cement, sand, water retention agent, water reducing agent, protective agent, water

[0123] The second coating layer: modified portland cement, hard silicon micropowder, relief cement modification aids, flexible polymer latex, natural inorganic aggregates, water, etc.

[0124] 3. Comparative experiment plan

[0125] 3.1 Comparative experiment design

[0126] To systematically investigate the combination method and process conditions of the modified mortar, the control group and experimental groups of this experiment include:

[0127] Control group C0:

[0128] The addition amount of each aid is at the lower limit of the interval, the water-cement ratio is low, the overall performance of the surface layer is weak, and the expected self-cleaning effect is limited.

[0129] Experimental group T1:

[0130] Both the first coating layer and the second coating layer are between the lower limit and the median of the interval, which can meet the basic construction and performance requirements, and are slightly improved compared to C0.

[0131] Experimental group T4:

[0132] Compared with T1, the content of key aids such as water retention agent and hard silicon micropowder is increased, and obvious improvements are expected in terms of crack resistance, adhesion and self-cleaning onset time.

[0133] Experimental group T7:

[0134] Higher sand dosage and aid ratio may bring better wear resistance and hydrophobicity, while maintaining good water permeability and air permeability.

[0135] Experimental group T9:

[0136] All key indicators adopt the maximum or nearly maximum values, and the expected self-cleaning effect, mechanical properties and durability are the best, but the material cost and construction difficulty also increase accordingly, which can be used as a reference for the "optimal configuration". The specific parameters are shown in Table 1 and Table 2:

[0137] Table 1 Parameters of the control group and each experimental group of the first coating layer

[0138]

[0139]

[0140] Table 2 Parameters of the control group and each experimental group of the second coating layer

[0141]

[0142] Other parameters:

[0143] To eliminate the influence of differences in the base layer or filling layer on the final performance, all experimental groups (including C0, T1, T4, T7, T9) in the examples adopted a consistent formulation method:

[0144] Autoclaved aerated concrete base layer: 80 - 90 parts of siliceous materials; 110 - 120 parts of calcareous materials; 0.4 - 0.8 parts of foaming materials; 0.01 - 0.04 parts of foam stabilizers; 0.01 - 0.04 parts of regulators; 1 - 5 parts of steel slag powder; 5 parts of quicklime; autoclaved for 12 - 15 h under the conditions of 1.1 - 1.2 MPa and 170 - 190 °C.

[0145] Solid waste filling layer: 22 - 30 parts of construction waste; 5 - 7 parts of sand; 4 - 8 parts of waste gypsum; 40 - 55 parts of curing agent; 8 - 10 parts of water; mixed at room temperature for 30 - 60 min and then pressed into shape and cured.

[0146] 3.2 Detection items and indicators

[0147] 3.2.1 Mechanical and physical properties:

[0148] Dry density (kg / m 3 ); Compressive strength (MPa); Flexural strength (MPa); Water absorption (%); Number of scrub resistance times (times).

[0149] 3.2.2 Self - cleaning related indicators: Contact angle (°); Self - cleaning time (the time required to start becoming round and detaching after injecting diesel or other polluting liquids).

[0150] 3.3 Specimen preparation and curing

[0151] Weigh the raw materials according to the designed formula, stir evenly and then pour and mold; after standing at room temperature for 2 - 4 hours, place them in a curing environment with different temperatures and durations; after the curing is completed, let the specimens cool naturally and place them in the same environmental conditions for 24 hours to ensure the balance of internal moisture and temperature.

[0152] 4. Experimental results and analysis

[0153] 4.1 Experimental methods for mechanical and physical properties

[0154] 4.1.1 Dry density (kg / m 3 )

[0155] Sampling and preparation: Cut regular cubic blocks with standard size (100 mm × 100 mm × 100 mm) from autoclaved aerated concrete plates, and the number of specimens is not less than 3 pieces.

[0156] Drying treatment: Place the specimens in an oven at 105 ± 5 °C and dry to constant weight (the difference between two weighings does not exceed 0.2% is regarded as constant weight), and record the mass M of the specimens after drying.d .

[0157] Volume measurement: Measure the external dimensions (length L, width W, height H) of the test specimen to an accuracy of 0.1 mm, and calculate the volume of the test specimen.

[0158] Calculate the dry density: Take the average value of the dry densities of 3 test specimens as the final result.

[0159] 4.1.2 Compressive strength (MPa)

[0160] Specimen preparation and curing: Prepare standard-sized cubic specimens (100 mm × 100 mm × 100 mm) using the same process as the board. The specimens are cured under specified conditions (temperature, humidity) or naturally cured to the age period according to the standard method (corresponding time still needs to be placed after coating).

[0161] Testing device: Use a compression testing machine that complies with relevant standards (GB / T 11969 or similar specifications), and the measuring range and loading speed meet the test requirements.

[0162] Operation process: Place the specimen in the center of the pressure plate, and control the loading speed within the standard requirements (such as 2 ± 0.2 kN / s or 0.5 MPa / s, etc.) until the specimen fails.

[0163] Calculate the compressive strength: Satisfy: Compressive strength = failure load / cross-sectional area; Take the average value of the test results of not less than 3 specimens. If the dispersion is too large, abnormal values can be excluded or additional tests can be conducted.

[0164] 4.1.3 Flexural strength (MPa)

[0165] Specimen preparation: Use standard-sized prismatic specimens (40 mm × 40 mm × 160 mm).

[0166] Testing device: Use a three-point or four-point bending testing machine (a universal material testing machine can also be used, equipped with a bending fixture), which meets the corresponding standard requirements.

[0167] Operation process: Place the specimen on the support rollers, and determine the span according to the standard regulations or in combination with the actual thickness of the board. Apply a uniform load and record the maximum bending load F when the specimen breaks. b .

[0168] Calculation: For a three-point bending test and the specimen cross-section is rectangular, then the flexural strength σ f is calculated according to the following formula:

[0169]

[0170] where L is the span between supports, b and h are the width and height of the specimen respectively. There are not less than 3 specimens in the same group, and the average value is taken as the final result.

[0171] 4.1.4 Water Absorption Rate (%)

[0172] Specimen Preparation: Cut specimens of the same size (the same size as the dry density) from the cured boards or specimens, with the number not less than 3 pieces.

[0173] Dry Mass: Put the specimens into an oven at 105 ± 5 °C and dry them to a constant weight, then record the mass after drying.

[0174] Water Absorption Saturation: Immerse the specimens completely in clean water at room temperature for 24 h. Take out the specimens, wipe the surface dry, and weigh them immediately; Water Absorption Rate = (Wet Mass - Dry Mass) / Dry Mass * 100%. Take the average value of 3 or more specimens as the final water absorption rate.

[0175] 4.1.5 Number of Scrub Resistance Times (times)

[0176] It is mainly used to test the scrub resistance or brush resistance performance of the modified mortar surface layer (coating), and can also be applied to the ordinary painting surface layer.

[0177] Specimen Preparation: Coat the surface layer on the substrate with the specified size (160 mm × 80 mm × board thickness) according to the actual construction method, and it can be tested only after being completely dried or cured.

[0178] Testing Instrument: Use a coating scrub resistance tester or a paint scrub resistance testing machine (such as the equipment specified in GB / T 9266, GB / T 9755 or ASTM D2486); Fix the sample on the machine table and scrub it with a standard brush (or abrasive) under a constant load and reciprocating stroke.

[0179] Operation Process: Pour the cleaning liquid or water with the specified concentration on the brush, and scrub back and forth at the specified speed. Check or count the number of reciprocating scrubbing times regularly until obvious damage occurs (such as exposing the base layer or the coating thickness thinning to the specified limit).

[0180] Result Evaluation: Record the total number of scrubbing times (round trips) before the failure of the specimen, which is the number of scrub resistance times. Conduct multiple groups of tests under the same batch conditions with the same parameters and the same instrument, and take the average value.

[0181] 4.1.6 Reference or Optional Standards

[0182] Dry Density and Water Absorption Rate: Refer to GB / T 11969 "Autoclaved Aerated Concrete Blocks" or related material testing methods, or ASTM C642 "Test Method for Water Absorption of Concrete".

[0183] Compressive Strength and Flexural Strength: Refer to GB / T 17671 (mortar), GB / T 11969 or related JC / T specifications, or ASTM C349, C348.

[0184] Scrub resistance: Refer to the commonly used domestic standards, including GB / T 9755 "Exterior Wall Coatings of Synthetic Resin Emulsion", GB / T 9266 "Putty for Interior Use in Buildings", and GB / T 17799.3, etc.

[0185] 4.2 Mechanical Property Tests

[0186] The test results of mechanical properties are shown in Table 3 with specific parameters as follows:

[0187] Table 3 Test Results of Mechanical Properties

[0188]

[0189] Groups T7 and T9 are relatively optimal in terms of compressive strength, flexural strength, water absorption and other indicators, indicating that high-temperature rapid stirring combined with modified silicate cement and appropriate addition of protective agents can significantly improve the coating density and mechanical properties.

[0190] 4.3 Self-Cleaning Performance Test Method

[0191] 4.3.1 Contact Angle (°):

[0192] Meaning: Used to quantitatively characterize the hydrophobic / hydrophilic degree of the surface of the board surface layer (or coating), and the contact angle between a water droplet or other liquid droplet and the solid surface can be measured.

[0193] Test Instrument and Conditions: Use a contact angle measuring instrument (optical contact angle tester); the environmental temperature is preferably 25 ± 2°C, and the relative humidity is 50 ± 5%; the droplet volume can be 3 - 5 μL (or as required by the standard) to ensure relatively stable shape.

[0194] Operation Steps:

[0195] Place the specimen in the specified environment for at least 24 hours to ensure that the surface is dry, clean, and undamaged;

[0196] Place the specimen on the tester platform, adjust the level and focus;

[0197] Use a micro syringe to drop the specified liquid (such as deionized water) on the surface, and record the real-time image collected by the contact angle measurement software;

[0198] Read the contact angle value after standing for 5 s or a specific time; multiple measurements can be taken and the average value can be obtained.

[0199] Result Evaluation: If the data dispersion of multiple measurement points is large, statistical analysis methods (such as removing the maximum / minimum value and then taking the average) can be used, and compared with the judgment grades in the corresponding standard (GB / T 30693), or the values can be directly recorded.

[0200] 4.3.2 Self-Cleaning Time:

[0201] Meaning: The time required for the droplet to start becoming round and detaching after dripping diesel, which is used to evaluate the self-cleaning efficiency of materials in polluted environments such as oil stains. By observing the time it takes for the polluting liquid to become round, roll, or detach on the coating surface, the surface hydrophobic / lipophilic characteristics are measured.

[0202] Test preparation: The surface of the specimen should be complete, flat, without scratches or chalking; the test temperature is 25 ± 2°C, and the relative humidity is 50 ± 5%; the diesel needs to be stored at a constant temperature in advance to ensure consistent fluidity.

[0203] Operation steps: Place the specimen horizontally, record the start time, use a syringe to drop a fixed volume of diesel (0.03 - 0.05 mL) on the surface, observe the deformation of the oil droplet, and record the time when an obvious "rounding" or "detaching" action occurs. If the oil droplet cannot completely roll off naturally, methods such as vibration or flushing with a small amount of water droplets can be used to simulate the actual environment, and then record the time point when it starts to move and detach as the end time.

[0204] Self-cleaning time = end time - start time; it is usually expressed in seconds or minutes:seconds. Multiple tests can be carried out at different dripping points on the same specimen and the average value can be taken.

[0205] 4.3.3 Weather resistance retention rate (%)

[0206] Meaning: The contact angle is measured after 500 h and 1000 h of exposure to ultraviolet lamps or outdoor exposure, which is used to evaluate the retention degree of the self-cleaning function of the coating or board under the long-term action of ultraviolet rays, heat, oxygen, water vapor, etc. Combining artificial accelerated aging or natural outdoor exposure, the attenuation amplitude of the physical and chemical properties of the coating is measured.

[0207] Test conditions: Artificial accelerated aging: Use an ultraviolet aging chamber (such as UVA-340 lamp tube or UVB-313) or xenon lamp aging chamber (compliant with GB / T 16422, ASTM G154, etc.), and the temperature, humidity, and light cycle are set according to the standard.

[0208] Test process: The prepared and cured specimens are placed in the exposure environment of the aging chamber (500 h, 1000 h), taken out or sampled at fixed points after reaching the set time, and the relevant indicators (contact angle) of their self-cleaning performance are measured.

[0209] Weather resistance retention rate = contact angle after exposure / contact angle before exposure * 100%. If the retention rate ≥ 80%, it is usually considered that the weather resistance performance is good; if the retention rate is less than 50%, it indicates that the performance has seriously declined.

[0210] 5 Experimental results and analysis

[0211] 5.1 Experimental results of mechanical and physical properties

[0212] 5.1.1 Dry density (kg / m3 ), as Figure 1 shown below:

[0213] Group C0: Since both the sand content and the additive ratio are lower than the lower limit of the range, the overall densification degree of the first coating layer and the second coating layer is insufficient, and the dry density is relatively small.

[0214] T1, T4, T7: As the sand dosage, the addition amounts of water retention agent and protective agent gradually increase, the dry density increases successively; T7 is slightly higher than T4, indicating that a relatively high coating dosage is beneficial to filling pores.

[0215] T9: When the contents of each key additive and silica fume are close to the upper limit, the dry density is the highest and the interfacial bonding is the tightest; however, too high a density may also increase the surface layer weight and construction difficulty.

[0216] 5.1.2 Compressive strength (MPa), as Figure 2 shown below:

[0217] Group C0: Since the coating with a low-strength formula has a weak bonding force with the base layer, the overall compressive strength performance is the worst.

[0218] T1: Under the conditions of a small amount of protective agent and medium curing conditions, the strength is better than that of C0, but the improvement is not significant.

[0219] T4: After moderately increasing the protective agent, water reducing agent and the addition amount of hard silica fume, the coating density is significantly improved and the compressive strength rises steadily.

[0220] T7, T9: The formula is close to the high-end configuration, and the strength is greatly improved; T9 is closer to the upper limit value, showing better coating toughness and bearing capacity, providing more safety margin for later use.

[0221] 5.1.3 Flexural strength (MPa), as Figure 3 shown below:

[0222] Group C0: Low protective agent, low sand and low water-cement ratio result in relatively obvious brittleness of the surface layer, and the specimen is prone to cracking and damage under bending load.

[0223] T1: There is a preliminary improvement, indicating that the toughness has been improved to a certain extent under the conditions of a low to medium level of water retention agent and water reducing agent.

[0224] T4: With the medium sand dosage and higher protective agent addition, the bending resistance of the board continues to improve and the apparent cracks are few.

[0225] T7, T9: The contents of components such as water retention agent and flexible latex are higher, the pore distribution inside the coating is more uniform, and more energy can be absorbed under bending load, so the flexural strength is the highest. T9 further increases the aggregate and additive dosage compared with T7 and shows the best performance.

[0226] 5.1.4 Water absorption rate (%), as Figure 4 shown below:

[0227] Group C0: Due to insufficient surface protection and densification, the surface porosity is relatively large, resulting in the highest water absorption rate. After long-term immersion, surface deformation or performance degradation is likely to occur.

[0228] T1: By starting to use a reasonable amount of water retention agent and water reducing agent, the water absorption rate is significantly reduced, indicating that the coating has a certain sealing effect.

[0229] T4, T7: Further improve the coating density by means of high-temperature or vacuum stirring process, increasing protective agent, etc. The difficulty of water penetration increases, and the water absorption rate is further reduced compared to C0 and T1.

[0230] T9: Optimize the dosage of key additives and water-cement ratio to the high-quality range, so that the pores are fully filled and the water absorption rate is the lowest. After long-term soaking in water, its self-cleaning function and surface integrity can be better maintained.

[0231] 5.1.5 Scrub resistance (times), as Figure 5 shown below:

[0232] Group C0: Insufficient additive content leads to weak coating hardness and adhesion, resulting in significant wear or damage relatively quickly during reciprocating brushing in the scrubbing instrument.

[0233] T1: There is a certain improvement, and it can withstand more reciprocating scrubs, but there is still a gap compared with the subsequent groups.

[0234] T4: Through the combination of medium-level hard silicon micro powder, relief modification additive and flexible polymer latex, the scrub resistance is significantly enhanced.

[0235] T7, T9: The coating has both high strength and toughness, and the internal bonding is firm; T9 reaches the upper limit in the dosage of latex and modified Portland cement, and generally shows the highest wear resistance life.

[0236] 5.2 Self-cleaning performance test results

[0237] The self-cleaning performance test results are shown in Table 4 as follows:

[0238] Table 4 Self-cleaning performance test results

[0239]

[0240] 5.2.1 Contact angle (°), as Figure 6 shown below:

[0241] Group C0 only has 82°, indicating poor surface hydrophobic performance; T9 reaches 121°, showing a significant "lotus effect", which easily makes oil droplets condense into spherical shapes and roll off.

[0242] 5.2.2 Self-cleaning time (s), as Figure 7 shown:

[0243] From C0 to T9, the time when the oil droplet begins to become round and detach gradually shortens. C0 requires about 924 seconds, and T9 only requires about 531 seconds to become significantly round and roll towards the periphery.

[0244] 5.2.3 Weather resistance rate of self-cleaning performance (%), as Figure 8 shown:

[0245] The weather resistance rate of self-cleaning performance refers to the ratio obtained by dripping oil stains again after 500h and 1000h of ultraviolet aging and measuring the comparison with the initial value (characterized by the contact angle); the C0 group drops to 55% after 1000h of aging; T7 and T9 can still maintain self-cleaning capabilities of 80% and 85%, indicating that the high-grade modified coating has more advantages in terms of weather resistance.

[0246] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. The autoclaved aerated concrete board with self-cleaning function is characterized by: It includes an autoclaved aerated concrete base layer, a solid waste filling layer and a modified mortar surface layer which are stacked in sequence from bottom to top; The autoclaved aerated concrete base is used as a load-bearing part; During the use of the board, the solid waste filling layer fills the cavities of the autoclaved aerated concrete base layer when the autoclaved aerated concrete base layer is damaged to repair the autoclaved aerated concrete base layer; The modified mortar surface layer is used as a decorative part; The modified mortar surface layer comprises: a first coating layer and a second coating layer which are stacked in sequence from bottom to top; The first coating layer is coated on the surface of the solid waste filling layer, and the second coating layer is coated on the surface of the first coating layer; The first coating layer is watertight and solid, and generates water mist based on the hydrophilic-hydrophobic effect. The second coating layer is watertight and water-permeable, and is used to protect the first coating layer from contact chemical damage and allow condensed water mist to penetrate the second coating layer. The first coating layer is composed of cement, sand, water retaining agent, water reducing agent, protective agent and water, and the mass ratio range is 100 parts of cement, 100-140 parts of sand, 0.5-2 parts of water retaining agent, 0.4-1 part of water reducing agent, 2-5 parts of protective agent, and the water-cement ratio is 0.30-0.

35.

2. The autoclaved aerated concrete board with self-cleaning function according to claim 1, characterized in that: The second coating layer is composed of modified silicate cement, hard silica powder, relief cement modification additive, inorganic aggregate, hard silica powder, flexible polymer latex and water, and its mass ratio range is 80-120 parts of modified silicate cement, 10-20 parts of hard silica powder, 3-8 parts of relief cement modification additive, 20-40 parts of inorganic aggregate, 5-15 parts of hard silica powder, 10-20 parts of flexible polymer latex, and the water-cement ratio is 0.25-0.

35.

3. The autoclaved aerated concrete board with self-cleaning function according to claim 1, characterized in that: The autoclaved aerated concrete base comprises the following raw materials in parts by weight: 80-90 parts of siliceous materials, 110-120 parts of calcareous materials, 0.4-0.8 parts of gas-generating materials, 0.01-0.04 parts of foam stabilizers, 0.01-0.04 parts of regulators, 1-5 parts of steel slag powder and 5 parts of quicklime.

4. The autoclaved aerated concrete board with self-cleaning function according to claim 3, characterized in that: The siliceous material is at least one of sand, fly ash, steel slag powder, coal gangue powder and quartz powder; The calcium material is at least one of quicklime, slaked lime and desulfurized gypsum; The gas-generating material is one of aluminum powder, magnesium powder, and inert aluminum fiber; The foam stabilizer is one of limestone powder, phosphogypsum powder, ground fly ash and carbon black; The regulator is aggregate stone powder or sodium fluorosilicate.

5. The autoclaved aerated concrete board with self-cleaning function according to claim 1, characterized in that: The solid waste filling layer comprises the following raw materials in parts by weight: 22-30 parts of construction waste, 5-7 parts of sand, 4-8 parts of waste gypsum, 40-55 parts of curing agent and 8-10 parts of water.

6. The autoclaved aerated concrete board with self-cleaning function according to claim 5, characterized in that: The construction waste is one or any combination of waste reinforced concrete, waste bricks, waste mortar, waste gypsum board, and waste plaster generated during construction, maintenance, demolition, and decoration.

7. A method for preparing an autoclaved aerated concrete board with a self-cleaning function, for preparing the autoclaved aerated concrete board with a self-cleaning function as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Preparing an autoclaved aerated concrete base: weighing siliceous material, calcareous material, gas-generating material, foam stabilizer, regulator, steel slag powder and 2 parts of quicklime, and adding 25-35 parts of water to obtain an aerated concrete slurry, injecting the aerated concrete slurry into a mold, casting and molding, standing and curing to obtain a green body, and then autoclaving the green body at a pressure of 1.1-1.2 MPa and a temperature of 170-190° C. for 12-15 hours to obtain the autoclaved aerated concrete base; S2. Preparing a solid waste filling layer: weighing construction waste, sand, waste gypsum, curing agent, and water, stirring for 30-60 minutes, pouring the mixture into the surface of the autoclaved aerated concrete base in the autoclaved aerated concrete base, pressing and curing the mixture to obtain the solid waste filling layer; S3, preparing a modified mortar surface layer: preparing a first coating layer on the surface of the solid waste filling layer, drying the first coating layer, coating the first coating layer on the second coating layer, and after the second coating layer is dried, obtaining the autoclaved aerated concrete board with a self-cleaning function; The preparation of the first coating layer comprises: weighing moxibustion cement, sand, water retaining agent, water reducing agent, protective agent and water; The preparation of the modified silicate cement comprises: using silicate cement as a matrix material and metakaolin as a modified material, and processing the cement through pre-wetting mixing, thermosetting molding, post-wetting curing, low-pressure pore impregnation and low-temperature simulated steam curing steps.

8. Use of an autoclaved aerated concrete board with self-cleaning function, characterized in that: Any one of the autoclaved aerated concrete panels with self-cleaning function as described in any one of claims 1 to 6 is used alone, or processed into a panel, or processed into a brick, or processed into a hollow block, or crushed as a raw material for siliceous material.

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