A sludge-based geopolymer self-melting snow-free brick and its preparation method

Abstract

The present invention discloses a sludge-based geopolymer self-melting snow-free brick and a preparation method thereof. The self-melting snow-free brick comprises a geopolymer gelling material and a salt-storing aggregate. The salt-storing aggregate is evenly distributed in the geopolymer gelling material, and the mass of the salt-storing aggregate accounts for 10% to 20% of the mass of the geopolymer gelling material. The present invention adopts the above-mentioned sludge-based geopolymer self-melting snow-free brick and a preparation method thereof, with low production cost and simple process. The self-melting snow-free brick is prepared by utilizing the excellent mechanical properties and chloride ion corrosion resistance of the geopolymer, solving the disadvantages of poor mechanical properties and short service life of the self-melting snow-free brick. The raw materials used in the present invention are all solid waste, which improves resource utilization, facilitates large-scale promotion and use, and has high engineering applicability.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to a sludge-based geopolymer self-melting snow-free brick and a preparation method thereof. Background Art

[0002] The climate in my country changes significantly in four seasons, especially in late autumn, winter and early spring, the temperature changes significantly due to the influence of cold air, bringing a lot of snowfall, making it easy for snow and ice to accumulate on brick roads in squares, communities, parks, etc., which brings great safety hazards to people's travel. How to efficiently remove ice and snow on pavement bricks is of great significance to ensure the safety of people's travel in winter. At present, the main snow removal methods are manual snow removal, mechanical snow removal, and snow melting agent snow removal, but these snow removal methods are ex post facto and cannot guarantee the timely removal of snow. The use of active, long-term, safe and environmentally friendly snow and ice removal technology will become an important solution.

[0003] At present, active snow and ice removal technologies include thermal snow melting technology, embedding high elastic material to melt snow and ice, etc. However, these active snow and ice removal technologies still have certain defects. Thermal snow melting technology has complex process, high energy consumption, high cost and large amount of subsequent maintenance work; embedding high elastic material to melt snow and ice technology uses the difference in deformation between structural materials and high elastic materials under load, which will cause the ice to fall off by itself, achieving the effect of snow melting and ice removal, but this method can easily cause damage to bricks.

[0004] In recent years, with the advancement of science and technology, the technology of melting ice and snow by adding salt-storing aggregates has become more mature. Due to its simple process and low cost, it can be widely used in practical projects. The Chinese patent with publication number CN111662057A discloses a method for preparing self-melting colored square bricks. The snow-melting bricks mix salt-storing aggregates with silicate cement, inorganic color powder, and fine river sand as a self-melting snow wear layer, and realize the self-melting snow function by reducing the freezing temperature of water and the adhesion of the square brick surface. This method concentrates the salt-storing aggregates above the bricks. During use, the friction generated by pedestrians and vehicles on the snow-melting bricks will damage and fall off the snow-melting layer, affecting its service life. In addition, silicate cement has poor resistance to chloride ion erosion, and bricks may be damaged by chloride ion erosion during use. In addition, the process of this invention is complicated and not suitable for large-scale promotion.

[0005] Sludge is a residue produced during the wastewater treatment process. It has a large output, complex composition, and high content of toxic pollutants. It is a hazardous waste. Therefore, the treatment of sludge is a very difficult and urgent environmental problem. At present, the traditional method of sanitary landfill is more commonly used, but on the one hand, landfill will occupy a lot of land, and on the other hand, sludge leachate will still spread and pollute the soil and groundwater. Sludge is also a resource. At present, there are ways to recycle sludge resources, such as preparing environmentally friendly bricks, producing cement products, and preparing adsorbents for wastewater treatment. However, these methods all have certain disadvantages. The environmentally friendly bricks prepared from sludge have low strength, which is not conducive to promotion, and heavy metal curing agents need to be added during the preparation process, which greatly increases the production cost; the sludge itself contains organic matter, and in the process of producing cement products, it will release gases such as ammonia and hydrogen sulfide, resulting in low product strength, and there are a large number of chloride ions and sulfate ions in the sludge, which will corrode cement. Therefore, it is necessary to find a better way to recycle sludge resources.

[0006] Geopolymer is an inorganic polymer material with excellent mechanical properties, and has the characteristics of acid and alkali resistance, heat resistance, and resistance to chloride ion corrosion. At the same time, geopolymer has a dense three-dimensional network structure, and can be used to seal heavy metal ions through physical and chemical methods. It is considered to be one of the most effective solidification materials for heavy metal ions. At present, the application of geopolymer is very extensive, such as in the field of building materials, road repair and other aspects. The Chinese patent with publication number CN113185200A discloses a method for preparing geopolymer pavement bricks, which uses waste FCC catalyst and F-grade low-calcium fly ash to prepare geopolymers, and the single block compressive strength is higher than 49.6MPa. However, most of the materials currently used for geopolymers are slag, fly ash, metakaolin, etc.

[0007] Sludge can also be used to prepare geopolymers, which can also seal heavy metal ions in sludge to realize the recycling of sludge resources. Due to the excellent resistance of geopolymers to chloride ion corrosion, they can be used to replace silicate cement and salt-storing aggregates to prepare self-melting snow bricks. Based on this, the present invention is proposed. Summary of the invention

[0008] The purpose of the present invention is to provide a sludge-based geopolymer self-melting snow-free brick and a preparation method thereof, so as to solve the problems of poor mechanical properties and short service life of the self-melting snow bricks prepared by combining silicate cement and salt-storing aggregate in the prior art.

[0009] To achieve the above-mentioned purpose, the first aspect of the present invention provides a sludge-based geopolymer self-melting snow-free brick, which comprises a geopolymer cementitious material and a salt-storing aggregate. The salt-storing aggregate is evenly distributed in the geopolymer cementitious material, and the mass of the salt-storing aggregate accounts for 10% to 20% of the mass of the geopolymer cementitious material.

[0010] The self-melting snow-free bricks of the invention are composed of geopolymer gelling materials and salt-storing aggregates, and realize self-melting snow by lowering the freezing temperature of water.

[0011] Preferably, the geopolymer gelling material is a three-dimensional network gelling material formed by sludge and slag in an alkaline environment, and the salt-storage aggregate is prepared from foamed ceramics, a geopolymer hydrophobic coating, and a saturated calcium chloride solution.

[0012] The present invention utilizes the adsorption property of foamed ceramics and uses it as a carrier of calcium chloride to prepare salt-storage foamed ceramics, and then coats the salt-storage foamed ceramics with a geopolymer hydrophobic coating, so that the calcium chloride and the foamed ceramics form a whole under the coating of the geopolymer hydrophobic coating, thereby achieving the stability and slow release effect of calcium chloride in the foamed ceramics, and ensuring the usability and durability of the self-melting snow-free unfired bricks.

[0013] The three-dimensional network cementitious material in the present invention has excellent mechanical properties and chloride ion corrosion resistance. Therefore, the self-melting snow-free bricks prepared by using the geopolymer cementitious material have high performance and ensure their durability.

[0014] Preferably, the mass ratio of sludge to geopolymer gelling material is 10% to 30%, and the mass ratio of slag to geopolymer gelling material is 70% to 90%.

[0015] The second aspect of the present invention provides a method for preparing sludge-based geopolymer self-melting snow-free bricks, comprising the following steps:

[0016] Step 1, preparing foamed ceramics;

[0017] Step 2: preparing salt storage aggregate;

[0018] Step 3, preparing geopolymer gelling material;

[0019] Step 4: Mix and stir the geopolymer cementitious material and salt-storage aggregate, and inject them into a mold;

[0020] Step 5: Maintain the demoulded self-melting snow-free bricks.

[0021] Preferably, the preparation method of the foamed ceramic in step 1 is to select fly ash, waste glass and albite as raw materials, add silicon carbide and stir well, place in a muffle furnace to form the foamed ceramic through calcination and heat preservation.

[0022] Preferably, the preparation method of the salt-storage aggregate in step 2 is to crush the foamed ceramic using a crushing device, screen the crushed foamed ceramic residue, select the 3-5 mm foamed ceramic residue and soak it in a saturated calcium chloride solution for one day, then remove it and dry it, and cool it naturally for use; after placing n-octyltriethoxysilane, diatomaceous earth and water in a magnetic stirrer and stirring for 4 hours, slag and water glass are added and stirred for another 20 minutes to obtain a geopolymer hydrophobic coating; the geopolymer hydrophobic coating is brushed on the foamed ceramic residue after soaking and drying, and cured at 20±5°C for 1d to obtain a salt-storage aggregate.

[0023] Preferably, the preparation method of the geopolymer gelling material in step three is to dissolve solid water glass and sodium hydroxide in water, and let it stand for one day as an alkaline activator; put the sludge and slag in a cement slurry mixer, slowly add the alkaline activator and stir and mix them thoroughly to make the geopolymer gelling material.

[0024] Preferably, the curing process in step five is to place the mold in a curing box, and cure it at 20±5°C and 95% humidity for one day to obtain self-melting snow bricks, and cure the bricks at room temperature for 7 days to obtain self-melting snow-free bricks.

[0025] Preferably, in step one, the particle size of fly ash is 5 μm, the particle size of waste glass is 38 μm, and the particle size of albite is 11 μm; in step two, the particle size of diatomaceous earth is 30 μm, and the particle size of slag is 5 μm; in step three, the particle size of sludge is 74 μm, and the particle size of slag is 5 μm.

[0026] Preferably, the water glass modulus is 1.5.

[0027] Therefore, the present invention adopts a sludge-based geopolymer self-melting snow-free brick and a preparation method thereof of the above structure, which has the following beneficial effects:

[0028] 1. The present invention achieves the purpose of snow melting through the dissolution of chloride salt in salt-storing aggregate, which can effectively avoid the time-consuming and labor-intensive manual snow removal and the damage to the brick surface and structure caused by mechanical snow removal. Compared with the self-melting snow wear layer used in the Chinese patent publication number CN111662057A, the present invention has a longer service life, a simpler preparation process, and more affordable preparation materials.

[0029] 2. The geopolymer hydrophobic coating used in the present invention has the following advantages compared with commercially available hydrophobic coatings: excellent resistance to chloride ion corrosion, excellent bonding performance, low chloride ion diffusion rate, and environmental protection. When the geopolymer coating is brushed on the salt-storage aggregate carrier, it will penetrate about 100 μm into the interior thereof, forming an interlocking structure between the two. The Ca, Si, and Al ions in the salt-storage aggregate carrier will react with the geopolymer hydrophobic coating to form a new gel, so the bonding strength is good. The pore structure and chloride ion binding ability of the geopolymer hydrophobic coating will hinder the diffusion of chloride ions, and the diffusion rate of chloride ions after entering the geopolymer is very slow. The geopolymer hydrophobic coating is prepared from solid waste and is a green hydrophobic coating. The corrosion resistance, excellent bonding performance, and chloride ion diffusion resistance of the geopolymer hydrophobic coating can effectively limit the concentration of salt precipitation and extend the service life of the salt-storage aggregate.

[0030] 3. The present invention uses foamed ceramics as a salt-storage aggregate carrier. Compared with the patent with publication number CN105461247A which uses magnesium oxychloride cement as a salt-storage aggregate, the salt-storage aggregate carrier of the present invention is prepared from pure solid waste, which is cheaper and more environmentally friendly. In addition, compared with magnesium oxychloride cement, foamed ceramics have better resistance to chloride ion corrosion, and the service life of salt-storage aggregates is longer.

[0031] 4. The present invention uses sludge as raw material to prepare geopolymer self-melting snow-free bricks. The high alkalinity and dense three-dimensional network gel structure of geopolymer cementitious materials determine its excellent resistance to chloride ion corrosion. At the same time, compared with the environmentally friendly bricks prepared from sludge in the current market, self-melting snow-free bricks have not undergone any high-temperature treatment, which greatly reduces energy consumption and carbon emissions. Sludge-based geopolymers themselves are also green and environmentally friendly building materials. Compared with cement, carbon dioxide emissions in its production process are reduced by 80% to 90%, which can effectively help enterprises save energy and reduce emissions and improve profitability.

[0032] 5. The present invention uses sludge as raw material to prepare sludge-based geopolymer self-melting snow-free bricks. Compared with the environmentally friendly bricks currently prepared from sludge in the market, the mechanical properties of geopolymer bricks are very excellent, and the 28d compressive strength can reach up to 63.41MPa. The geopolymer gelling material itself can seal the heavy metal ions in the sludge, so there is no need to add chemical reagents such as heavy metal curing agents during the preparation process.

[0033] 6. The sludge-based geopolymer self-melting snow-free bricks developed by the present invention require raw materials that are all solid waste, which is not only a rational application of resources, but also can reduce production costs.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of the geopolymer-based self-melting snow-free brick of the present invention;

[0036] Figure 2 This is a preparation flow chart of the geopolymer-based self-melting snow-free brick of the present invention;

[0037] Figure 3 This is a rendering of the self-melting snow effect of the geopolymer-based self-melting snow-free unfired brick of the present invention;

[0038] Figure 4 It is the technical roadmap of the geopolymer-based self-melting snow-free bricks of the present invention.

[0039] In the figure: 1. Salt-storing aggregate; 2. Geopolymer cementitious material. DETAILED DESCRIPTION

[0040] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment. Example 1

[0041] A method for preparing geopolymer-based self-melting snow-free bricks comprises the following steps:

[0042] Step 1: Preparation of foamed ceramics

[0043] Fly ash, albite and waste glass were selected as raw materials with a mass ratio of 7:2:1. Silicon carbide was used as a foaming agent with a dosage of 0.2% of the total mass of the raw materials. The raw materials were placed in a muffle furnace and fired at 1200°C for 50 minutes to form foamed ceramics. Fly ash, albite and waste glass were not subjected to any other treatment process.

[0044] Step 2: Preparation of salt storage aggregate

[0045] The foamed ceramics were crushed by crushing equipment, and the crushed foamed ceramic residues were screened, and the foamed ceramic residues of 3-5 mm were selected as the carrier of salt-storage aggregates; calcium chloride was dissolved in water as a chloride salt de-icing agent, and the foamed ceramic residues were soaked in a saturated calcium chloride solution at 25°C for one day, then taken out and dried, and naturally cooled for use; n-octyltriethoxysilane, diatomaceous earth and water were placed in a magnetic stirrer and stirred for 4 hours, and slag and water glass were added and stirred for 20 minutes to obtain a hydrophobic geopolymer gel, wherein the mass ratio of n-octyltriethoxysilane, diatomaceous earth, water, slag and water glass was 5:1:25:25:7; the hydrophobic geopolymer gel was brushed on the foamed ceramic residues, and cured at 20±5°C for 1 day to serve as salt-storage aggregates.

[0046] Step 3: Preparation of geopolymer cementitious materials

[0047] Water glass with a modulus of 1.5 is dissolved in water and left to stand for one day as an alkaline activator; the sludge is naturally dried and then ball-milled for 45 minutes. The sludge and slag are placed in a cement slurry mixer, and the alkaline activator is slowly added for thorough stirring and mixing to make a geopolymer cementitious material, in which the mass ratio of the precursor composed of sludge and slag, water, and water glass is 2:1:1.

[0048] Step 4: Mix and stir the geopolymer cementitious material and the salt-storage aggregate and inject them into the brick mold;

[0049] Step 5: Maintain the demoulding self-melting snow bricks

[0050] The mold was placed in a curing box and cured for one day at 20±5°C and 95% humidity, and then the self-melting snow bricks were removed from the mold and cured at room temperature for 7 days.

[0051] The prepared self-melting snow-free bricks are composed of salt-storing aggregate and geopolymer cementitious materials; the mass of the salt-storing aggregate is 10% of the mass of the geopolymer cementitious materials, the mass ratio of the sludge to the geopolymer cementitious materials is 10%, and the mass ratio of the slag to the geopolymer cementitious materials is 90%. Example 2

[0052] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 15% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 20%, and the mass ratio of the slag to the geopolymer cementitious material is 80%. The other steps and parameters are the same as those in embodiment 1. Example 3

[0053] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 20% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 30%, and the mass ratio of the slag to the geopolymer cementitious material is 70%. The other steps and parameters are the same as those in embodiment 1. Example 4

[0054] The difference between this embodiment and embodiment 1 is that the mass of the salt-storing aggregate is 15% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 10%, and the mass ratio of the slag to the geopolymer cementitious material is 90%. The other steps and parameters are the same as those in embodiment 1. Example 5

[0055] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 20% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 20%, and the mass ratio of the slag to the geopolymer cementitious material is 80%. The other steps and parameters are the same as those in embodiment 1. Example 6

[0056] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 10% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 30%, and the mass ratio of the slag to the geopolymer cementitious material is 70%. The other steps and parameters are the same as those in embodiment 1. Example 7

[0057] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 20% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 10%, and the mass ratio of the slag to the geopolymer cementitious material is 90%. The other steps and parameters are the same as those in embodiment 1. Example 8

[0058] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 10% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 20%, and the mass ratio of the slag to the geopolymer cementitious material is 80%. The other steps and parameters are the same as those in embodiment 1. Example 9

[0059] The difference between this embodiment and embodiment 1 is that the mass of the salt-storage aggregate is 15% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 30%, and the mass ratio of the slag to the geopolymer cementitious material is 70%. The other steps and parameters are the same as those in embodiment 1. Example 10

[0060] A method for preparing a Portland cement self-melting snow-free brick comprises the following steps:

[0061] Step 1: Preparation of foamed ceramics

[0062] Fly ash, albite and waste glass are selected as raw materials in a ratio of 7:2:1, silicon carbide is used as a foaming agent, and the amount of the foaming agent is 0.2% of the total mass of the raw materials. Place it in a muffle furnace and burn it to 1200℃, keep it warm for 50 minutes, and form a foamed ceramic.

[0063] Step 2: Preparation of salt storage aggregate

[0064] The foamed ceramics were crushed by crushing equipment, and the crushed foamed ceramic residues were screened, and the foamed ceramic residues of 3-5 mm were selected as the carrier of salt-storage aggregates; calcium chloride was dissolved in water as a chloride salt de-icing agent, and the foamed ceramic residues were soaked in a saturated calcium chloride solution at 25°C for one day, then taken out and dried, and naturally cooled for use; n-octyltriethoxysilane, diatomaceous earth and water were placed in a magnetic stirrer and stirred for 4 hours, and slag and water glass were added and stirred for 20 minutes to obtain a hydrophobic geopolymer gel, wherein the mass ratio of n-octyltriethoxysilane, diatomaceous earth, water, slag and water glass was 5:1:25:25:7; the hydrophobic geopolymer gel was brushed on the foamed ceramic residues, and cured at 20±5°C for 1 day to serve as salt-storage aggregates.

[0065] Step 3: Preparation of Portland Cement Material

[0066] The silicate cement powder and water are fully mixed in a ratio of 2:1 to prepare a silicate cement material.

[0067] Step 4: Mix the silicate cement material and the sludge to obtain a cementitious material, mix the cementitious material with the salt-storage aggregate, and then inject it into a brick mold.

[0068] Step 5: Maintain the demoulding self-melting snow bricks

[0069] The mold was placed in a curing box and cured for one day at 20±5°C and 95% humidity, and then the self-melting snow bricks were removed from the mold and cured at room temperature for 7 days.

[0070] The prepared self-melting snow-free unburned bricks consist of salt-storing aggregate and cementitious material, wherein the mass of the salt-storing aggregate accounts for 10% of the mass of the cementitious material, the mass ratio of the sludge to the cementitious material is 10%, and the mass ratio of the silicate cement to the cementitious material is 90%. Embodiment 11

[0071] The difference between this embodiment and embodiment 10 is that the mass of the salt-storing aggregate is 15% of the mass of the cementitious material, the mass ratio of the sludge to the cementitious material is 20%, and the mass ratio of the silicate cement to the cementitious material is 80%. The other steps and parameters are the same as those in embodiment 10. Example 12

[0072] A method for preparing geopolymer-based self-melting snow-free bricks comprises the following steps:

[0073] Step 1: Preparation of foamed ceramics

[0074] Fly ash, albite and waste glass are selected as raw materials in a ratio of 7:2:1, silicon carbide is used as a foaming agent, and the amount of the foaming agent is 0.2% of the total mass of the raw materials. Place it in a muffle furnace and burn it to 1200℃, keep it warm for 50 minutes, and form a foamed ceramic.

[0075] Step 2: Preparation of salt storage aggregate

[0076] The foamed ceramics were crushed by crushing equipment, and the crushed foamed ceramic residues were screened, and the foamed ceramic residues of 3-5 mm were selected as the carrier of salt-storage aggregates; calcium chloride was dissolved in water as a chloride salt de-icing agent, and the foamed ceramic residues were soaked in a saturated calcium chloride solution at 25°C for one day, then fished out and dried, and naturally cooled for use; DASU NANO / Da Shu S400 coating produced by Shanghai Huaxia Jiahe New Material Technology Co., Ltd. was used as a hydrophobic coating, which was brushed on the foamed ceramic residues and cured at 20±5°C for 1 day as salt-storage aggregates.

[0077] Step 3: Preparation of geopolymer cementitious materials

[0078] Water glass with a modulus of 1.5 and sodium hydroxide are dissolved in water and left to stand for one day as an alkaline activator; the sludge is naturally dried and then ball-milled for 45 minutes. The sludge and slag are placed in a cement slurry mixer, and the alkaline activator is slowly added for thorough stirring and mixing to make a geopolymer cementitious material, in which the mass ratio of the precursor composed of sludge and slag, water, and water glass is 2:1:1.

[0079] Step 4: Mix and stir the geopolymer cementitious material and salt-storage aggregate and inject them into the brick mold.

[0080] Step 5: Maintain the demoulding self-melting snow bricks

[0081] The mold was placed in a curing box and cured for one day at 20±5°C and 95% humidity, and then the self-melting snow bricks were removed from the mold and cured at room temperature for 7 days.

[0082] The prepared self-melting snow-free bricks are composed of salt-storing aggregate and geopolymer cementitious materials; the mass of the salt-storing aggregate is 10% of the mass of the geopolymer cementitious materials, the mass ratio of the sludge to the geopolymer cementitious materials is 10%, and the mass ratio of the slag to the geopolymer cementitious materials is 90%. Embodiment 13

[0083] The difference between this embodiment and embodiment 12 is that the mass of the salt-storage aggregate is 15% of the mass of the geopolymer cementitious material, the mass ratio of the sludge to the geopolymer cementitious material is 20%, and the mass ratio of the slag to the geopolymer cementitious material is 80%. The other steps and parameters are the same as those in embodiment 12.

[0084] The geopolymer-based self-melting snow-free bricks prepared in Examples 1 to 9 were tested for compression, flexural and frost resistance according to GB / T17671 "Test method for strength of cement mortar" and GB / T41060-2021 "Test method for frost resistance of cement mortar".

[0085] The compressive and flexural properties of the silicate cement self-melting snow-free bricks of Examples 10 to 11 were tested.

[0086] The adhesion test of the hydrophobic coating of the salt-storage aggregate in Examples 1, 2, 12 and 13 was carried out, specifically using a friction test, which is a method for testing the adhesion performance of a super-hydrophobic coating.

[0087] The compressive and flexural properties of geopolymer-based self-melting snow-free bricks were tested. The results are shown in Table 1:

[0088]

[0089] It can be seen from Table 1 that with the increase of sludge addition, the compressive strength and flexural strength of the prepared geopolymer-based self-melting snow-free bricks are reduced, indicating that the amount of sludge added in the present invention is not the more the better, and a specific amount of sludge needs to be added to ensure the strength of the self-melting snow-free bricks.

[0090] The compression and flexural properties of silicate cement self-melting snow-free bricks were tested, and the results are shown in Table 2:

[0091]

[0092] From Table 2, it can be seen that Example 10 uses silicate cement to replace the slag in Example 1. The compressive strength and flexural strength of Example 10 are both lower than those of Example 1, indicating that the addition of sludge and slag is essential in the process of preparing geopolymer cementitious materials in the present invention. The combination of the two can prepare a three-dimensional network cementitious material and improve the strength of self-melting snow-free bricks. Similarly, the compressive strength and flexural strength of Example 11 are also lower than those of Example 2.

[0093] The antifreeze performance test of geopolymer-based self-melting snow-free bricks is shown in Table 3:

[0094]

[0095] It can be seen from Table 3 that the sludge-based geopolymer self-melting snow-free bricks prepared in the present invention have better antifreeze performance and can be applied to cold areas.

[0096] The bonding performance test of the hydrophobic coating on salt-storage aggregates is shown in Table 4:

[0097]

[0098] It can be seen from Table 4 that the geopolymer hydrophobic coating prepared by the present invention has more friction times and better bonding performance than commercially available hydrophobic coatings. The geopolymer hydrophobic coating applied on the foamed ceramic will not fall off easily, which makes the life cycle of the salt-storage aggregate longer and the service life of the self-melting snow-free bricks longer.

[0099] Therefore, the present invention adopts a sludge-based geopolymer self-melting snow-free brick with the above-mentioned structure and a preparation method thereof. The self-melting snow-free brick prepared by using the geopolymer gelling material has high performance and ensures its durability; the production cost of the present invention is low and the process is simple. The self-melting snow-free brick prepared by using the excellent mechanical properties and chloride ion corrosion resistance of the geopolymer solves the disadvantages of poor mechanical properties and short service life of the self-melting snow-free brick; the raw materials used in the present invention are all solid waste, which improves resource utilization, facilitates large-scale promotion and use, and has high engineering applicability.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A sludge-based geopolymer self-melting snow-free brick, characterized in that: The self-melting snow-free bricks include geopolymer cementitious materials and salt-storing aggregates. The salt-storing aggregates are evenly distributed in the geopolymer cementitious materials, and the mass of the salt-storing aggregates accounts for 10% to 20% of the mass of the geopolymer cementitious materials. The preparation method of salt-storage aggregate comprises the following steps: crushing foamed ceramics by crushing equipment, screening the crushed foamed ceramic residues, selecting 3-5 mm foamed ceramic residues and soaking them in a saturated calcium chloride solution for one day, then taking them out and drying them, cooling them naturally and setting them aside; placing n-octyltriethoxysilane, diatomaceous earth and water in a magnetic stirrer and stirring them for 4 hours, adding slag and water glass and stirring them for another 20 minutes to obtain a geopolymer hydrophobic coating; brushing the geopolymer hydrophobic coating on the soaked and dried foamed ceramic residues, and curing them at 20±5°C for 1 day to obtain salt-storage aggregate.

2. The sludge-based geopolymer self-melting snow-free brick according to claim 1, characterized in that: Geopolymer cementitious materials are three-dimensional network cementitious materials formed by sludge and slag in an alkaline environment.

3. The sludge-based geopolymer self-melting snow-free brick according to claim 2, characterized in that: The mass ratio of sludge to geopolymer cementitious materials is 10% to 30%, and the mass ratio of slag to geopolymer cementitious materials is 70% to 90%.

4. The method for preparing a sludge-based geopolymer self-melting snow-free brick according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, preparing foamed ceramics; Step 2: preparing salt storage aggregate; Step 3, preparing geopolymer gelling material; Step 4: Mix and stir the geopolymer cementitious material and salt-storage aggregate, and inject them into a mold; Step 5: Maintain the demoulded self-melting snow-free bricks.

5. The method for preparing a sludge-based geopolymer self-melting snow-free brick according to claim 4, characterized in that: The preparation method of the foamed ceramic in step 1 is to select fly ash, waste glass and albite as raw materials, add silicon carbide and stir them evenly, and place them in a muffle furnace to form the foamed ceramic through calcination and heat preservation.

6. The method for preparing a sludge-based geopolymer self-melting snow-free brick according to claim 5, characterized in that: The preparation method of the geopolymer cementitious material in step three is to dissolve solid water glass and sodium hydroxide in water, and let it stand for one day as an alkaline activator; put sludge and slag in a cement slurry mixer, slowly add the alkaline activator and stir and mix them thoroughly to make the geopolymer cementitious material.

7. The method for preparing a sludge-based geopolymer self-melting snow-free brick according to claim 6, characterized in that: The curing process in step five is to place the mold in a curing box, and cure it at 20±5°C and 95% humidity for one day to obtain self-melting snow bricks, and then cure the bricks at room temperature for 7 days to obtain self-melting snow-free bricks.

8. The method for preparing a sludge-based geopolymer self-melting snow-free brick according to claim 7, characterized in that: In step one, the particle size of fly ash is 5 μm, the particle size of waste glass is 38 μm, and the particle size of albite is 11 μm; in step two, the particle size of diatomaceous earth is 30 μm, and the particle size of slag is 5 μm; in step three, the particle size of sludge is 74 μm, and the particle size of slag is 5 μm.

9. The method for preparing a sludge-based geopolymer self-melting snow-free brick according to claim 8, characterized in that: The modulus of water glass is 1.5.

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