High-strength lightweight water permeable brick as well as preparation method and application thereof

Abstract

The invention provides a high-strength lightweight water permeable brick as well as a preparation method and application thereof, and relates to the technical field of building materials. According to the method, the iron tailings are ground and calcined and activated in the presence of the limestone, silica, aluminate and other mineral substances in the iron tailings are combined with calcium to generate phase change and are converted into a mineral phase with high pozzolanic activity, and therefore the hydration reaction activity of the iron tailings is enhanced. The aluminum ash is ground and subjected to calcination denitrification modification in the presence of the quick lime, the aluminum ash and the quick lime react to generate calcium aluminate, dicalcium aluminate and an amorphous silicon-aluminum phase, high hydration reaction activity is achieved, and the early strength of the material can be improved; the modified aluminum ash is uniformly and stably foamed, so that the micro-pore structure of the prepared water permeable brick is relatively high in homogeneity; meanwhile, the Portland cement, the sulphoaluminate cement and the auxiliary additive are adopted, so that the water permeable brick has early strength, long-term strength and durability, and the comprehensive performance of mechanical property and water permeability is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a high-strength lightweight permeable brick and a preparation method and application thereof. Background Art

[0002] In the current global context of environmental pollution and resource shortages, the development of new environmentally friendly building materials is particularly important. Permeable bricks, as a building material with excellent permeability, can not only alleviate urban flooding but also promote the recycling and reuse of water resources, with significant ecological benefits.

[0003] Traditional permeable brick materials fall into two categories: ceramic permeable bricks, made primarily from solid industrial waste and construction waste, are crushed, formed, and then fired at high temperatures. The other type of permeable brick, made primarily from inorganic non-metallic materials, uses organic or inorganic binders to bind aggregates without requiring firing. However, existing ceramic permeable bricks made primarily from solid industrial waste and construction waste lack sufficient early strength. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a high-strength lightweight permeable brick and its preparation method and application. The high-strength lightweight permeable brick prepared by the present invention has high early strength.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing high-strength lightweight permeable bricks, comprising the following steps:

[0007] The iron tailings are first ground, the ground iron tailings are mixed with limestone, and calcined and activated to obtain modified iron tailings;

[0008] The aluminum ash is subjected to a second grinding, the obtained ground aluminum ash is mixed with quicklime, and calcined for denitrification modification to obtain modified aluminum ash;

[0009] The dry material, auxiliary additives and water are mixed, and the obtained slurry is foamed, pressed and cured in sequence to obtain high-strength lightweight permeable bricks; the dry material includes the modified iron tailings, the modified aluminum ash and a cementitious material; the cementitious material includes silicate cement and sulphoaluminate cement.

[0010] Preferably, the parameters of the first grinding include: a ball-to-material ratio of 1.9 to 2.1:1, a ball mill speed of 250 to 300 r / min, and a grinding time of 50 to 70 min;

[0011] The ultrafine particles with a particle size of less than 20 μm in the ground iron tailings account for ≥50 wt%;

[0012] The mass ratio of the ground iron tailings to limestone is 0.9-1.1:1.

[0013] Preferably, the calcination activation temperature is 950-1050° C., and the holding time is 90-110 minutes.

[0014] Preferably, the parameters of the second grinding include: a ball-to-material ratio of 1.9 to 2.1:1, a ball mill speed of 250 to 300 r / min, and a grinding time of 50 to 70 min;

[0015] The average particle size of the ground aluminum ash is less than 10 μm;

[0016] The mass ratio of the ground aluminum ash to quicklime is 2.8-3.2:1.

[0017] Preferably, the temperature of the calcination denitrification modification is 900-950° C., and the holding time is 50-80 minutes.

[0018] Preferably, the mass ratio of the modified iron tailings to the modified aluminum ash is 1.9 to 2.1:1;

[0019] The mass ratio of the silicate cement to the sulphoaluminate cement is 0.9-1.1:1;

[0020] The ratio of the total mass of the modified iron tailings and modified aluminum ash to the mass of the cementitious material is 0.9 to 1.1:2;

[0021] The ratio of the mass of the water to the mass of the dry material is 0.35 to 0.4.

[0022] Preferably, the auxiliary additives include a water reducer and a retarder; the mass of the water reducer is 0.2-0.3% of the mass of the dry material; the mass of the retarder is 0.1-0.2% of the mass of the dry material.

[0023] Preferably, the foaming time is 30 to 40 minutes;

[0024] The compression molding pressure is 15-20 MPa and the time is 30-60 seconds;

[0025] The curing temperature is 18-20° C., the relative humidity is 88-92%, and the curing time is 13-15 days.

[0026] The present invention also provides high-strength lightweight permeable bricks prepared by the preparation method described in the above technical solution. The high-strength lightweight permeable bricks have a compressive strength of ≥24MPa, a water permeability of >0.021m / s, and a porosity of 24-32%.

[0027] The present invention also provides the use of the high-strength lightweight permeable bricks described in the above technical solution in building materials.

[0028] The present invention provides a preparation method of high-strength lightweight permeable bricks, comprising the following steps: performing a first grinding on iron tailings, mixing the obtained ground iron tailings with limestone, and calcining and activating the mixture to obtain modified iron tailings; performing a second grinding on aluminum ash, mixing the obtained ground aluminum ash with quicklime, and calcining and denitrifying the mixture to obtain modified aluminum ash; performing a third grinding on the modified iron tailings and the modified aluminum ash to obtain active solid waste foamed aggregate; mixing the active solid waste foamed aggregate, a cementitious material, an auxiliary additive, and water, pressing and molding the mixture, and then curing the mixture to obtain high-strength lightweight permeable bricks; the cementitious material comprises silicate cement and sulphoaluminate cement.

[0029] The present invention increases the specific surface area and improves the calcination modification effect by first grinding the iron tailings, and then performs calcination activation in the presence of limestone. Minerals such as silicon dioxide (SiO2) and aluminates in the iron tailings combine with calcium to undergo phase change and are converted into a mineral phase with high volcanic ash activity, thereby enhancing the hydration reaction activity of the iron tailings.

[0030] The present invention increases the specific surface area and improves the calcination modification effect by performing a second grinding on the aluminum ash, and then performs calcination denitrification modification in the presence of quicklime. The aluminum ash reacts with the quicklime to generate calcium aluminate (CA), dicalcium aluminate (CA2) and an amorphous silicon-aluminum phase. These mineral components have strong hydration reaction activity and can improve the early strength of the material.

[0031] The technical invention utilizes modified iron tailings and modified aluminum ash. Due to the presence of a large amount of calcium aluminate (CA), dicalcium aluminate (CA2) and amorphous silicon-aluminum phase, a large amount of hydration products such as CSH and calcium aluminoferrite are produced in the initial hydration stage, and the compressive strength increases rapidly within 15 days; and because the modified aluminum ash foams evenly and steadily, the microscopic pore structure of the prepared permeable bricks is more homogeneous, and the strength and other mechanical properties are better than those of the existing permeable bricks prepared with solid waste as raw materials under the same curing time (15 days).

[0032] The present invention adopts Portland cement and sulphoaluminate cement as cementing materials, wherein the sulphoaluminate cement can provide higher early strength, while ordinary Portland cement can ensure long-term strength and durability.

[0033] The present invention uses iron tailings, aluminum ash, and cement as raw materials. By efficiently utilizing these industrial by-products, it significantly improves the resource utilization rate of waste, thereby reducing environmental pollution and reducing the dependence on natural resources in traditional production processes. After high-temperature activation treatment, iron tailings and aluminum ash can release mineral components that are beneficial to cement hardening, thereby enhancing the performance of permeable bricks. At the same time, the production process of permeable bricks is low-carbon and energy-saving, which helps achieve the energy conservation and emission reduction goals of the construction industry. It not only meets environmental protection needs, but also can promote the industrial application of green building materials by improving the recycling of industrial solid waste, reducing landfill and pollution.

[0034] The high-strength lightweight permeable bricks prepared by the present invention have a compressive strength of ≥24 MPa, which is significantly higher than the minimum requirement (≥20 MPa) of C30 permeable bricks specified in the "Technical Standard for Permeable Bricks" (JG / T 503-2016); the water permeability is >0.021 m / s, which is better than the national standard requirement (≥0.01 m / s), meeting the permeability requirements of ecological city construction; the porosity is 24-32%, which is in line with the appropriate range of 20-30% in the national standard, ensuring a balance between permeability and mechanical properties, and having excellent comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 SEM image of the high-strength lightweight permeable brick prepared in Example 1 (×5000 times) DETAILED DESCRIPTION

[0036] The present invention provides a method for preparing high-strength lightweight permeable bricks, comprising the following steps:

[0037] The iron tailings are first ground, the ground iron tailings are mixed with limestone, and calcined and activated to obtain modified iron tailings;

[0038] The aluminum ash is subjected to a second grinding, the obtained ground aluminum ash is mixed with quicklime, and calcined for denitrification modification to obtain modified aluminum ash;

[0039] The dry material, auxiliary additives and water are mixed, and the obtained slurry is foamed, pressed and cured in sequence to obtain high-strength lightweight permeable bricks; the dry material includes the modified iron tailings, the modified aluminum ash and a cementitious material; the cementitious material includes silicate cement and sulphoaluminate cement.

[0040] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0041] The present invention performs a first grinding on the iron tailings, mixes the obtained ground iron tailings with limestone (referred to as the first mixing), and performs calcination and activation to obtain modified iron tailings.

[0042] In the present invention, the parameters of the first grinding preferably include: a ball-to-material ratio of 1.9 to 2.1:1, which may be 1.9:1, 2:1 or 2.1:1 in a specific embodiment; a ball mill speed of 250 to 300 r / min, which may be 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min or 300 r / min in a specific embodiment; and a grinding time of 50 to 70 min, which may be 50 min, 55 min, 60 min, 65 min or 70 min in a specific embodiment.

[0043] In the present invention, the proportion of ultrafine particles with a particle size of less than 20 μm in the ground iron tailings is preferably ≥50wt%, more preferably 50-60wt%, and in specific embodiments, can be 50wt%, 52wt%, 55wt%, 58wt%, or 60wt%. The present invention helps increase the specific surface area of ​​the ground iron tailings by controlling the particle size, thereby improving the calcination modification effect.

[0044] The present invention has no particular limitation on the first mixing, as long as the raw materials can be dispersed and mixed uniformly.

[0045] In the present invention, the mass ratio of the ground iron tailings to limestone is preferably 0.9 to 1.1:1, and in specific embodiments may be 0.9:1, 0.95:1, 1:1, 1.05:1 or 1.1:1.

[0046] In the present invention, the calcination activation temperature is preferably 950-1050°C, and in specific embodiments it can be 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C or 1050°C; the calcination activation holding time is preferably 90-110 min, and in specific embodiments it can be 90 min, 95 min, 100 min, 105 min or 110 min.

[0047] The activity of iron tailings is relatively low. The present invention increases its specific surface area and improves its calcination modification effect by first grinding the iron tailings, and then calcining and activating it in the presence of limestone. Minerals such as silica (SiO2) and aluminates in the iron tailings combine with calcium to undergo phase change and are converted into a mineral phase with higher volcanic ash activity, thereby enhancing the hydration reaction activity of the iron tailings.

[0048] The present invention performs a second grinding on the aluminum ash, mixes the obtained ground aluminum ash with quicklime (referred to as the second mixing), and performs calcination and denitrification modification to obtain modified aluminum ash.

[0049] In the present invention, the parameters of the second grinding preferably include: a ball-to-material ratio of 1.9 to 2.1:1, which may be 1.9:1, 2:1 or 2.1:1 in a specific embodiment; a ball mill speed of 250 to 300 r / min, which may be 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min or 300 r / min in a specific embodiment; and a grinding time of 50 to 70 min, which may be 50 min, 55 min, 60 min, 65 min or 70 min in a specific embodiment.

[0050] In the present invention, the average particle size of the ground aluminum ash is preferably less than 10 μm. The present invention helps to increase its specific surface area and improve its calcination modification effect by controlling the particle size of the ground aluminum ash.

[0051] In the present invention, the mass ratio of the ground aluminum ash to quicklime is preferably 2.8 to 3.2:1, and in specific embodiments can be 2.8:1, 2.85:1, 2.9:1, 2.95:1, 3:1, 3.15:1 or 3.2:1.

[0052] The present invention has no particular limitation on the second mixing, as long as the raw materials can be dispersed and mixed uniformly.

[0053] In the present invention, the temperature of the calcination denitrification modification is preferably 900-950°C, and in specific embodiments it can be 900°C, 910°C, 920°C, 930°C, 940°C or 950°C; the holding time of the calcination denitrification modification is preferably 50-80min, and in specific embodiments it can be 50min, 55min, 60min, 65min, 70min, 75min or 80min.

[0054] The present invention increases the specific surface area and improves the calcination modification effect by performing a second grinding on the aluminum ash, and then performs calcination denitrification modification in the presence of quicklime. The aluminum ash reacts with the quicklime to generate calcium aluminate (CA), dicalcium aluminate (CA2) and an amorphous silicon-aluminum phase. These mineral components have strong hydration reaction activity and can improve the early strength of the material.

[0055] The present invention mixes dry materials, auxiliary additives and water, and sequentially foams, presses and cures the obtained slurry to obtain high-strength lightweight permeable bricks; the dry materials include the modified iron tailings, the modified aluminum ash and a cementitious material; the cementitious material includes silicate cement and sulphoaluminate cement.

[0056] In the present invention, the mass ratio of the modified iron tailings to the modified aluminum ash is preferably 1.9 to 2.1:1, and in specific embodiments, can be 1.9:1, 1.95:1, 2:1, 2.05:1, or 2.1:1. By controlling the usage ratio of the modified iron tailings to the modified aluminum ash within the above range, the present invention can maximize the utilization of the mineral components of both, thereby optimizing the mechanical properties such as strength and the water permeability of the permeable brick.

[0057] By using industrial solids such as iron tailings and aluminum ash as the main raw materials, the present invention reduces the production cost of permeable bricks. The use of industrial solids avoids large-scale landfill or pollution, while improving its resource utilization efficiency and having good economic value.

[0058] Compared to traditional cement production processes, the preparation method of this invention saves a significant amount of raw materials and reduces carbon dioxide emissions. In particular, the high-temperature calcination and activation process of iron tailings and aluminum ash not only improves material performance but also reduces cement usage, achieving energy conservation and emission reduction. Carbon emissions per ton of permeable bricks are approximately 15% lower than those of traditional cement bricks, offering significant environmental advantages.

[0059] In the present invention, the mass ratio of the Portland cement to the sulphoaluminate cement is preferably 0.9 to 1.1:1, and in specific embodiments, can be 0.9:1, 0.95:1, 1:1, 1.05:1, or 1.1:1. By controlling the ratio of the Portland cement to the sulphoaluminate cement, the present invention helps improve the early strength, long-term strength, and durability of the material.

[0060] In the present invention, the ratio of the total mass of the modified iron tailings and modified aluminum ash to the mass of the cementitious material is preferably 0.9-1.1:2, and in specific embodiments can be 0.9:2, 0.95:2, 1:2, 1.05:2 or 1.1:2.

[0061] In the present invention, the ratio of the mass of water to the mass of dry materials (ie, the water-cement ratio) is 0.35 to 0.4, and in specific embodiments can be 0.35, 0.36, 0.37, 0.38, 0.39 or 0.4.

[0062] In the present invention, the auxiliary additives preferably include a water reducer and a retarder. In the present invention, the water reducer preferably includes a polycarboxylate water reducer; the mass of the water reducer is preferably 0.2-0.3% of the dry material mass, and in specific embodiments, it can be 0.2%, 0.22%, 0.25%, 0.28%, or 0.3%. In the present invention, the retarder preferably includes a lignin sulfonate, and in specific embodiments, it can be one or more of sodium lignin sulfonate, potassium lignin sulfonate, calcium lignin sulfonate, and magnesium lignin sulfonate; the mass of the retarder is preferably 0.1-0.2% of the dry material mass, and in specific embodiments, it can be 0.1%, 0.12%, 0.15%, 0.18%, or 0.2%.

[0063] The present invention can improve the foaming effect of the modified aluminum ash in the initial hydration stage by controlling the water-cement ratio, the addition amount of the polycarboxylic acid water reducer and the retarder, thereby improving the mechanical properties such as strength and the water permeability of the permeable brick.

[0064] In the present invention, the mixing of dry material, auxiliary additives and water preferably includes: a third mixing of the modified iron tailings and modified aluminum ash to obtain active solid waste foamed aggregate; a fourth mixing of the active solid waste foamed aggregate and a cementitious material to obtain dry material; and a fifth mixing of the cementitious material by silicate cement and sulphoaluminate cement.

[0065] In the present invention, the third mixing step preferably includes grinding (referred to as the third grinding step). The parameters of the third grinding step preferably include: a ball-to-material ratio of 1.9 to 2.1:1, and in specific embodiments, it may be 1.9:1, 2:1, or 2.1:1; a ball mill speed of 250 to 300 r / min, and in specific embodiments, it may be 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, or 300 r / min; and a grinding time of 10 to 40 min, and in specific embodiments, it may be 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, or 40 min. In the present invention, the average particle size of the activated solid waste foamed aggregate is preferably less than 20 μm.

[0066] The present invention has no particular limitation on the fourth mixing and the fifth mixing, as long as the raw materials can be dispersed and mixed uniformly.

[0067] In the present invention, the foaming temperature is preferably 15-30° C. (room temperature); the foaming time is preferably 30-40 min, and in specific embodiments can be 30 min, 32 min, 35 min, 38 min or 40 min.

[0068] In the present invention, the temperature of the press molding is preferably 15 to 30°C (room temperature); the pressure of the press molding is 15 to 20 MPa, and in specific embodiments, it can be 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, or 20 MPa; the time of the press molding is preferably 30 to 60 seconds, and in specific embodiments, it can be 30 seconds, 40 seconds, 50 seconds, or 60 seconds; and the press molding is preferably performed in a mold. The present invention performs press molding under the above conditions, especially controlling the pressure conditions of the press molding, which helps to improve the mechanical properties such as strength and the water permeability of the permeable brick.

[0069] In the present invention, the curing temperature is preferably 18-20°C, and in specific embodiments, it can be 18°C, 19°C, or 20°C; the curing relative humidity is preferably 88-92%, and in specific embodiments, it can be 88%, 89%, 90%, 91%, or 92%; and the curing time is preferably 13-15 days, and in specific embodiments, it can be 13 days, 13.5 days, 14 days, 14.5 days, or 15 days. Curing under the above conditions helps to fully hydrate the raw materials, thereby improving the strength and other mechanical properties and water permeability of the permeable bricks.

[0070] The activity of iron tailings is relatively low. The present invention grinds the iron tailings and calcines them in the presence of limestone to increase calcium, which is beneficial to the formation of active silicate minerals, improves the hydration reaction activity of the modified iron tailings, and thus increases the strength performance of permeable bricks to a certain extent. The raw material aluminum ash contains a large amount of AlN. When used as a raw material to prepare permeable bricks, it reacts violently with the alkaline environment and releases a large amount of ammonia, which not only causes certain harm to the human body, but also makes it easy for bubbles to accumulate inside the permeable bricks, seriously affecting the mechanical properties of the permeable bricks; and the activity of the raw material aluminum ash is relatively low, and more cementitious materials need to be consumed when preparing permeable bricks. After the present invention grinds the aluminum ash and calcines it in the presence of quicklime to modify it, its hydration activity is greatly improved; the AlN content is greatly reduced, and it reacts smoothly in an alkaline environment, releasing a small amount of ammonia, most of which can exist in the permeable bricks in the form of uniform bubbles, which is beneficial to the preparation of high-strength and lightweight permeable bricks and the improvement of their strength and other properties.

[0071] The present invention also provides high-strength lightweight permeable bricks produced by the preparation method described in the above technical solution. In the present invention, the compressive strength of the high-strength lightweight permeable brick is ≥24MPa, preferably 24-30MPa, and in specific embodiments, it can be 24MPa, 24.2MPa, 25MPa, 26MPa, 27MPa, 27.3MPa, 28MPa, 29MPa, 29.6MPa or 30MPa; the flexural strength of the high-strength lightweight permeable brick is preferably ≥4.8MPa, preferably 4.8-5.2MPa, and in specific embodiments, it can be 4.8MPa, 4.81MPa, 4.9MPa, 4.92MPa, 5MPa, 5.1MPa, 5.12MPa or 5.2MPa; the tensile strength of the high-strength lightweight permeable brick is preferably ≥2.8MPa, preferably 2.8-3.2MPa, and in specific embodiments, it can be 2.8MPa, 2.81MPa, 2.83MPa, 2.9 MPa, 3MPa, 3.01MPa, 3.09MPa, 3.1MPa or 3.2MPa; the porosity of the high-strength lightweight permeable brick is 24-32%, and in specific embodiments it can be 24%, 25%, 25.1%, 26%, 27%, 27.5%, 28%, 29%, 29.4%, 30%, 31% or 32%; the water permeability of the high-strength lightweight permeable brick is ≥0.021m / s , preferably 0.021~0.03m / s, in specific embodiments it can be 0.021m / s, 0.022m / s, 0.023m / s, 0.024m / s, 0.025m / s, 0.026m / s, 0.027m / s, 0.028m / s, 0.029m / s or 0.03m / s. The high-strength lightweight permeable brick provided by the present invention can meet the permeability requirements of ecological city construction. The high-strength lightweight permeable brick provided by the present invention has a compressive strength of ≥24 MPa, which is significantly higher than the minimum requirement (≥20 MPa) of C30 permeable bricks specified in the "Technical Standard for Permeable Bricks" (JG / T 503-2016); the water permeability is >0.021 m / s, which is better than the national standard requirement (≥0.01 m / s), meeting the permeability requirements of ecological city construction; the porosity is 24-32%, which is in line with the appropriate range of 20-30% in the national standard, ensuring a balance between permeability and mechanical properties, and having excellent comprehensive performance.

[0072] The present invention also provides the use of the high-strength, lightweight, permeable bricks described in the above technical solution in building materials. In the present invention, the building materials preferably include building materials for urban pavement.

[0073] Compared with the prior art, the high-strength lightweight permeable bricks prepared by the present invention have the following advantages:

[0074] 1.Excellent performance:

[0075] (1) Compressive strength: The compressive strength is ≥24MPa, which is significantly higher than the minimum requirement of C30 permeable bricks (≥20MPa) specified in the Technical Standard for Permeable Bricks (JG / T503-2016).

[0076] (2) Water permeability: Water permeability > 0.021m / s, which is better than the national standard requirement (≥0.01m / s) and meets the high water permeability requirements.

[0077] (3) Porosity: 24-32%, which is in line with the appropriate range of 20%-30% in the national standard, ensuring the balance between water permeability and mechanical properties.

[0078] 2. Innovative material formula and preparation method:

[0079] (1) The present invention efficiently utilizes iron tailings and aluminum ash, activates them through grinding and high-temperature calcination, enhances the reactivity of the minerals, makes the hydration products uniformly distributed, and improves the mechanical properties.

[0080] (2) By adding sulphoaluminate cement, the early strength is improved, and at the same time, the water-cement ratio and the proportion of additives (such as polycarboxylic acid water reducer and retarder) are optimized to further improve the performance of the brick.

[0081] 3. Low-cost raw materials:

[0082] (1) By using industrial waste such as iron tailings and aluminum ash to replace some natural raw materials (such as sand and cement), the cost per ton of permeable bricks is reduced by about 10-20% compared with traditional cement bricks. Based on an annual output of 100,000 tons, the cost can be saved by about 500,000 yuan.

[0083] (2) Reduce waste disposal costs: The recycling and reuse of industrial by-products (such as iron tailings and aluminum ash) reduces the disposal costs of waste landfill or incineration and avoids additional costs for environmental governance.

[0084] 4. Standardized production:

[0085] The pressure (15-20 MPa) and curing conditions (18-20°C, humidity 90±2%) during the preparation process of high-strength lightweight permeable bricks meet the preparation process specifications of permeable bricks, ensuring the comprehensive performance of high-strength lightweight permeable brick products.

[0086] 5. Long-term market competitiveness

[0087] The high-strength, lightweight, permeable bricks produced by this method offer excellent overall performance and are suitable for green projects such as eco-cities and sponge cities, generating widespread market demand. Under current green building material subsidy policies, products that meet these standards are expected to receive additional financial incentives.

[0088] 6. Environmental advantages

[0089] (1) The use of modified iron tailings and modified aluminum ash significantly reduces cement usage during the activation process. Carbon emissions from cement production are approximately 0.85 tons of CO2 per ton. The preparation method provided by the present invention reduces cement usage by approximately 20% per ton of permeable bricks, and carbon emissions drop by approximately 15%.

[0090] (2) Use waste materials instead of natural sand and gravel raw materials to reduce the damage of mining to the ecological environment and extend the life of the mine.

[0091] (3) The high-strength, lightweight, permeable bricks prepared can achieve rapid rainwater infiltration, alleviate urban waterlogging, and replenish groundwater resources, meeting the requirements of sponge city construction. Compared with traditional cement bricks, the high-strength, lightweight, permeable bricks prepared by the present invention are more environmentally friendly in urban pavement applications.

[0092] In order to further illustrate the present invention, the high-strength lightweight permeable bricks provided by the present invention, their preparation method and applications are described in detail below in conjunction with embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0093] The chemical compositions of the aluminum ash and iron tailings used in the following examples are shown in Table 1:

[0094] Table 1 Chemical composition of aluminum ash and iron tailings (wt%)

[0095]

[0096] Example 1

[0097] (1) Iron tailings were ground at a ball-to-material ratio of 2:1 and a speed of 300 r / min for 70 min. The ground iron tailings were mixed with limestone at a mass ratio of 1:1, and calcined at 1000°C for 110 min to obtain modified iron tailings. Ultrafine particles with a particle size of less than 20 μm accounted for more than 50 wt% of the ground iron tailings.

[0098] (2) Aluminum ash was ground at a ball-to-material ratio of 2:1 and a speed of 300 rpm for 70 minutes. The ground aluminum ash was then mixed with limestone at a mass ratio of 3:1 and calcined at 950°C for 50 minutes for denitrification to obtain modified iron tailings. The average particle size of the ground aluminum ash was less than 10 μm.

[0099] (3) The modified iron tailings and modified aluminum ash were mixed in a mass ratio of 2:1, and ground for 20 minutes at a ball-to-material ratio of 2:1 and 300 r / min until the average particle size was less than 20 μm to obtain active solid waste foamed aggregate.

[0100] 425 Portland cement and sulphoaluminate cement are mixed in a mass ratio of 1:1 to obtain a cementitious material.

[0101] The active solid waste foamed aggregate and the cementitious material are uniformly mixed in a mass ratio of 1:2 to obtain a dry material. Water, 0.3% of the dry material mass of a polycarboxylic acid water reducer, and 0.2% of the dry material mass of a retarder calcium lignin sulfonate are added to the dry material at a water-cement ratio of 0.4. The obtained slurry is foamed at room temperature for 40 minutes and then placed in a mold. It is pressed into shape at room temperature and 15 MPa for 45 seconds, and then placed in a curing box for curing for 15 days at a temperature of 20°C and a relative humidity of 90±2%. High-strength lightweight permeable bricks are obtained.

[0102] Through testing, the high-strength lightweight permeable bricks prepared in this embodiment have a strength of 24.2 MPa, a flexural strength of 4.81 MPa, a tensile strength of 2.83 MPa, a porosity of 29.4%, and a water permeability of 0.029 m / s.

[0103] By scanning electron microscopy (SEM) analysis, Figure 1 This is the SEM image of the high-strength lightweight permeable brick (×5000 times). It can be seen that the high-strength lightweight permeable brick has a uniform pore distribution, moderate porosity, and dense pore wall, which helps to improve the overall mechanical properties and permeability of the material.

[0104] Example 2

[0105] (1) Iron tailings were ground at a ball-to-material ratio of 2:1 and a speed of 300 r / min for 70 min. The ground iron tailings were mixed with limestone at a mass ratio of 1:1, and calcined at 1000°C for 110 min to obtain modified iron tailings. Ultrafine particles with a particle size of less than 20 μm accounted for more than 50 wt% of the ground iron tailings.

[0106] (2) Aluminum ash was ground at a pellet-to-material ratio of 2:1 and 300 rpm for 70 minutes. The ground aluminum ash was then mixed with limestone at a mass ratio of 3:1 and calcined at 950°C for 70 minutes for denitrification to obtain modified iron tailings. The average particle size of the ground aluminum ash was less than 10 μm.

[0107] (3) The modified iron tailings and modified aluminum ash were mixed in a mass ratio of 2:1, and ground for 20 minutes at a ball-to-material ratio of 2:1 and 300 r / min until the average particle size was less than 20 μm to obtain active solid waste foamed aggregate.

[0108] 425 Portland cement and sulphoaluminate cement are mixed in a mass ratio of 1:1 to obtain a cementitious material.

[0109] The active solid waste foamed aggregate and the cementitious material are uniformly mixed in a mass ratio of 0.9:2 to obtain a dry material. Water, 0.3% of the dry material mass of a polycarboxylic acid water reducer and 0.2% of the dry material mass of a retarder calcium lignin sulfonate are added to the dry material at a water-cement ratio of 0.4. The obtained slurry is foamed at room temperature for 35 minutes and then placed in a mold. It is pressed and formed at room temperature and 18 MPa for 45 seconds, and then placed in a curing box for curing for 15 days at a temperature of 20°C and a relative humidity of 90±2%. High-strength lightweight permeable bricks are obtained.

[0110] Through testing, the high-strength lightweight permeable bricks prepared in this embodiment have a strength of 27.3 MPa, a flexural strength of 4.92 MPa, a tensile strength of 3.01 MPa, a porosity of 27.5%, and a water permeability of 0.027 m / s after curing for 15 days.

[0111] Example 3

[0112] (1) Iron tailings were ground at a ball-to-material ratio of 2:1 and a speed of 300 r / min for 70 min. The ground iron tailings were mixed with limestone at a mass ratio of 1:1, and calcined at 1000°C for 110 min to obtain modified iron tailings. Ultrafine particles with a particle size of less than 20 μm accounted for more than 50 wt% of the ground iron tailings.

[0113] (2) Aluminum ash was ground at a ball-to-material ratio of 2:1 and 300 rpm for 70 minutes. The ground aluminum ash was then mixed with limestone at a mass ratio of 3:1 and calcined at 950°C for 80 minutes for denitrification to obtain modified iron tailings. The average particle size of the ground aluminum ash was less than 10 μm.

[0114] (3) The modified iron tailings and modified aluminum ash were mixed in a mass ratio of 2:1, and ground for 20 minutes at a ball-to-material ratio of 2:1 and 300 r / min until the average particle size was less than 20 μm to obtain active solid waste foamed aggregate.

[0115] 425 Portland cement and sulphoaluminate cement were mixed in a mass ratio of 1:1 to obtain a cementitious material. High-activity solid waste foamed aggregate and cementitious material were mixed in a mass ratio of 0.9:2 to obtain a dry material.

[0116] Water, 0.3% polycarboxylate water reducer by weight of dry material and 0.2% retarder calcium lignin sulfonate by weight of dry material were added to the dry material at a water-cement ratio of 0.38. The obtained slurry was foamed at room temperature for 30 minutes and then placed in a mold. It was pressed into shape at room temperature and 20 MPa for 45 seconds, and then placed in a curing box for curing for 15 days at a temperature of 20°C and a relative humidity of 90±2%. High-strength lightweight permeable bricks were obtained.

[0117] Through testing, the high-strength lightweight permeable bricks prepared in this embodiment have a strength of 29.6 MPa, a flexural strength of 5.12 MPa, a tensile strength of 3.09 MPa, a porosity of 25.1%, and a water permeability of 0.022 m / s after 15 days of curing.

[0118] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength lightweight permeable bricks, characterized in that: The following steps are involved: The iron tailings are first ground, the ground iron tailings are mixed with limestone, and calcined and activated to obtain modified iron tailings; The aluminum ash is subjected to a second grinding, the obtained ground aluminum ash is mixed with quicklime, and calcined for denitrification modification to obtain modified aluminum ash; The dry material, auxiliary additives and water are mixed, and the obtained slurry is foamed, pressed and cured in sequence to obtain high-strength lightweight permeable bricks; the dry material includes the modified iron tailings, the modified aluminum ash and a cementitious material; the cementitious material includes silicate cement and sulphoaluminate cement.

2. The preparation method according to claim 1, characterized in that The parameters of the first grinding include: a ball-to-material ratio of 1.9 to 2.1:1, a ball mill speed of 250 to 300 r / min, and a grinding time of 50 to 70 min; The ultrafine particles with a particle size of less than 20 μm in the ground iron tailings account for ≥50 wt%; The mass ratio of the ground iron tailings to limestone is 0.9-1.1:

1.

3. The preparation method according to claim 1 or 2, characterized in that The calcination activation temperature is 950-1050° C., and the heat preservation time is 90-110 minutes.

4. The preparation method according to claim 1, characterized in that The parameters of the second grinding include: a ball-to-material ratio of 1.9 to 2.1:1, a ball mill speed of 250 to 300 r / min, and a grinding time of 50 to 70 min; The average particle size of the ground aluminum ash is less than 10 μm; The mass ratio of the ground aluminum ash to quicklime is 2.8-3.2:

1.

5. The preparation method according to claim 1 or 4, characterized in that The temperature of the calcination denitrification modification is 900-950° C., and the heat preservation time is 50-80 minutes.

6. The preparation method according to claim 1, characterized in that The mass ratio of the modified iron tailings to the modified aluminum ash is 1.9 to 2.1:1; The mass ratio of the silicate cement to the sulphoaluminate cement is 0.9-1.1:1; The ratio of the total mass of the modified iron tailings and modified aluminum ash to the mass of the cementitious material is 0.9 to 1.1:2; The ratio of the mass of the water to the mass of the dry material is 0.35 to 0.

4.

7. The preparation method according to claim 1, characterized in that The auxiliary additives include a water reducer and a retarder; the mass of the water reducer is 0.2-0.3% of the mass of the dry material; the mass of the retarder is 0.1-0.2% of the mass of the dry material.

8. The preparation method according to claim 1, 6 or 7, characterized in that: The foaming time is 30 to 40 minutes; The compression molding pressure is 15-20 MPa and the time is 30-60 seconds; The curing temperature is 18-20° C., the relative humidity is 88-92%, and the curing time is 13-15 days.

9. The high-strength lightweight permeable brick prepared according to the preparation method according to any one of claims 1 to 8, wherein the high-strength lightweight permeable brick has a compressive strength of ≥24 MPa, a water permeability of >0.021 m / s, and a porosity of 24-32%.

10. Use of the high-strength, lightweight, permeable bricks according to claim 9 in building materials.

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