A kind of agricultural and forestry waste-red mud composite self-sensing building material and preparation method thereof

Abstract

The present invention relates to an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof. The method comprises the following steps: treating a mixture of agricultural and forestry waste and red mud by high-temperature calcination; thermally cracking the agricultural and forestry waste into biochar fibers with a certain degree of conductivity under high-temperature conditions; reducing ferric oxide in the red mud into ferroferric oxide with high magnetism; and imparting electromagnetic functionality to the red mud. Finally, the pyrolyzed biochar fibers, the electromagnetically functionalized red mud, and a self-granulated conductive aggregate are used to prepare the self-sensing building material. The method not only overcomes the problems of traditional self-sensing building materials such as high cost, high environmental pollution risk, and poor stability, but also has a wide range of raw material sources, a simple preparation process, and low cost, which is conducive to industrial-scale production and realizes the resource utilization of agricultural, forestry, and industrial solid waste.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof. Background Art

[0002] Currently, traditional structural health monitoring methods add embedded, surface-coated, or externally attached sensors to cement-based materials, thereby imparting additional sensing capabilities. However, typical embedded sensors not only disrupt the concrete's original internal structure but also weaken its bearing capacity and durability. Surface-coated or externally attached sensors are susceptible to the effects of the coating, the external environment, and noise. Furthermore, these sensors also suffer from high cost and poor durability, and their installation and wiring are cumbersome, causing certain inconveniences during construction applications.

[0003] Numerous studies have proposed adding conductive fillers such as carbon fibers, carbon nanotubes, nickel powder, multilayer graphene, carbon black, and metal fibers or powders to cement-based materials to create functional, integrated materials capable of self-sensing changes in stress, strain, displacement, temperature, and humidity. These self-sensing building materials, with their lifespan comparable to cement concrete, excellent compatibility, and high sensitivity, are ideal for intelligent building materials, providing a reliable and effective approach for long-term, stable, real-time monitoring and health diagnosis of concrete structures.

[0004] Current self-sensing ultra-high-performance concrete (UHPC) uses a large amount of nanomaterials as conductive fillers, resulting in self-sensing concrete with excellent electrical conductivity. However, the production process for these nanomaterials is immature, expensive, and unstable, making them unsuitable for large-scale industrial application and posing environmental risks. Therefore, the development of low-cost, high-performance conductive fillers and their associated self-sensing building materials is urgently needed. Summary of the Invention

[0005] In view of this, it is necessary to provide an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof to solve the current problems of high prices and high environmental risks of self-sensing building materials.

[0006] The present invention provides a method for preparing an agricultural and forestry waste-red mud composite self-sensing building material, comprising the following steps:

[0007] Mixing agricultural and forestry waste with red mud to obtain a first mixed powder;

[0008] The first mixed powder is subjected to high temperature heat treatment to obtain a modified mixed powder;

[0009] Mixing the modified mixed powder, the inorganic gelling material and the activation enhancer to obtain a blended powder;

[0010] The uniformly mixed powder is granulated and sprayed with a water-based adhesive to obtain a spherical mixture;

[0011] The spherical mixture is solidified to obtain conductive fine aggregate;

[0012] The silicate cement, mineral admixture, modified mixed powder, high-performance water reducer and water are stirred and mixed, and then the conductive fine aggregate and coarse aggregate are added and continued to be stirred evenly. The mixture is cured for a period of time to obtain the agricultural and forestry waste-red mud composite self-sensing building material.

[0013] Optionally, the agricultural and forestry waste includes one or more combinations of rice straw, corn straw, wheat straw, wood chips and sugarcane bagasse; the water-based adhesive includes one or more combinations of water-based polyurethane, water-based vinyl resin and polyisocyanate.

[0014] Optionally, the inorganic cementitious material includes one or more combinations of silicate cement, aluminate cement, phosphate cement, lime, and gypsum; the activation enhancer includes one or more combinations of sodium silicate, triethanolamine, nano-silica, and triisopropanolamine.

[0015] Optionally, the mineral admixtures include one or more combinations of blast furnace slag powder, fly ash, steel slag powder, metakaolin, and silica fume; the high-performance water reducer is a polycarboxylic acid water reducer with a water reduction rate of ≥25%; the coarse aggregate is crushed stone with a particle size distribution range of 5~25mm.

[0016] Optionally, mixing agricultural and forestry waste with red mud may include:

[0017] Select agricultural and forestry waste and red mud with a mass ratio of 1:1 to 1:4;

[0018] The agricultural and forestry wastes and red mud are placed on a mixer and mixed evenly;

[0019] The mixer speed is controlled to be 40-80 r / min and the mixing time is 4-12 h to obtain a first mixed powder.

[0020] Optionally, subjecting the first mixed powder to high-temperature heat treatment specifically includes:

[0021] Adding the first mixed powder into a crucible, and then placing it in a tube furnace;

[0022] Introduce an inert or reducing protective atmosphere into the tube furnace;

[0023] Control the heating rate of the tube furnace to 5~15℃ / min;

[0024] The modified mixed powder is obtained by performing high temperature heat treatment at a calcination temperature of 300-800°C and keeping the temperature for 1-4 hours.

[0025] Optionally, the modified mixed powder, the inorganic gelling material and the activation enhancer are mixed in a ball mill mixing tank; the speed of the ball mill mixing tank is 100-200 r / min, and the mixing time is 12-36 h; and then the mixed powder is passed through a 100-200 mesh sieve to obtain the blended powder.

[0026] Optionally, the curing conditions are 20°C and 95% humidity, and the curing time is 28 to 90 days.

[0027] Optionally, the spherical mixture has a continuous particle size of 0.15 to 4.75 mm.

[0028] The present invention also provides an agricultural and forestry waste-red mud composite self-sensing building material, which is characterized by being prepared from the following raw materials in parts by weight:

[0029] 50-150 parts of Portland cement;

[0030] 40~120 parts of mineral admixture;

[0031] 240~480 pieces of agricultural and forestry waste;

[0032] 480~960 parts of red mud;

[0033] 50-200 parts of inorganic gelling material;

[0034] 10-50 parts of activation enhancer;

[0035] 80~200 parts of water-based adhesive;

[0036] 0.5~2 parts of high performance water reducer;

[0037] 100-300 parts water;

[0038] 800~1200 parts of coarse aggregate.

[0039] The beneficial effects of the present invention are:

[0040] The present invention first uses a high-temperature calcination method to treat a mixture of agricultural and forestry waste and red mud. Under high-temperature conditions, the agricultural and forestry waste is thermally cracked into biochar fibers with a certain degree of conductivity, and at the same time, the ferric oxide in the red mud is reduced to ferroferric oxide with high magnetism, thereby giving the red mud electromagnetic functionality; then the electromagnetically functionalized red mud and pyrolyzed biochar fibers are granulated together with inorganic gelling materials, activation enhancers and organic adhesives to form low-cost, high-performance conductive functional aggregates; finally, silicate cement, mineral admixtures, high-performance water reducers, water and coarse aggregates are used as the base material of building materials, and pyrolyzed biochar fibers, electromagnetically functionalized red mud and self-granulated conductive aggregates are used to prepare self-sensing building materials, and a three-dimensional cross-linked conductive network structure of magnetic red mud particles-biochar fibers-self-granulated conductive aggregates is constructed inside the self-sensing building materials, so that electrons can be transmitted on a denser effective conductive path, giving it good self-sensing sensitive properties. In addition, high-temperature calcination will also change the crystal structure of red mud, causing the inert lattice structure therein to collapse, changing from the original ordered lamellar crystal structure to a disordered structure, thereby giving it higher chemical reaction activity, allowing it to play a secondary hydration role in the subsequent preparation of conductive fillers and self-sensing building materials, further enhancing the mechanical properties and stability of the matrix. The agricultural and forestry waste-red mud composite self-sensing building material and its preparation method provided by the present invention not only overcome the problems of high cost, high environmental pollution risk, and poor stability of traditional self-sensing building materials, but also have a wide source of raw materials, a simple preparation process, and low cost, which is conducive to industrial-scale production, and realizes the resource utilization of agricultural, forestry and industrial solid wastes. The economic and ecological benefits are very significant, the market potential is huge, and the prospects for engineering applications are broad. It has effectively promoted the comprehensive green transformation of my country's economy and society, and is of great significance for accelerating the construction of a waste recycling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] FIG1 is a flow chart of the method for preparing the agricultural and forestry waste-red mud composite self-sensing building material provided by the present invention. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0044] Example 1

[0045] Combine Figure 1 As shown, the method for preparing a self-sensing building material made of agricultural and forestry waste and red mud disclosed in an embodiment of the present invention includes the following steps:

[0046] S01. Mixing agricultural and forestry waste with red mud to obtain a first mixed powder. In step S01, the agricultural and forestry waste and red mud are selected in a weight ratio of 1:1 to 1:4. Specifically, the weight ratio of the agricultural and forestry waste to the red mud is: 20-40 parts agricultural and forestry waste to 40-80 parts red mud.

[0047] In this embodiment, the agricultural and forestry waste includes a combination of rice straw, corn stalks, wheat straw, wood chips, and sugarcane bagasse. The rice straw, corn stalks, wheat straw, wood chips, sugarcane bagasse, and red mud are uniformly mixed in a mixer at a speed of 40 to 80 rpm for 4 to 12 hours to produce a first mixed powder.

[0048] S02. The first mixed powder is subjected to high-temperature heat treatment to obtain a modified mixed powder after the high-temperature heat treatment. In step S02, specifically: the first mixed powder is first added to a crucible, and then placed in a tubular furnace, and subjected to high-temperature heat treatment under different calcination systems, with a calcination temperature of 300-800°C, a holding time of 1-4 h, a heating rate of 5-15°C / min, and an inert or reducing protective atmosphere in the furnace, to obtain a modified mixed powder after the high-temperature heat treatment.

[0049] S03. Mixing a modified mixed powder, an inorganic gelling material, and an activation enhancer to produce a blended powder. In step S03, the inorganic gelling material includes one or more combinations of Portland cement, aluminate cement, phosphate cement, lime, and gypsum; and the activation enhancer includes one or more combinations of sodium silicate, triethanolamine, nanosilica, and triisopropanolamine. Furthermore, the modified mixed powder, inorganic gelling material, and activation enhancer are mixed in the following weight ratios: 100 parts modified mixed powder, 5-20 parts inorganic gelling material, and 1-5 parts activation enhancer.

[0050] After the proportioning is completed, the modified mixed powder, inorganic gelling material and activation enhancer are mixed in a ball mill mixing tank; the speed of the ball mill mixing tank is 100~200 r / min, and the mixing time is 12~36 h; then the mixed powder is passed through a 100~200 mesh sieve to obtain the blended powder.

[0051] S04. Granulate the uniformly mixed blended powder while simultaneously spraying a water-based adhesive to obtain a quasi-spherical mixture. In step S04, the water-based adhesive includes one or more combinations of water-based polyurethane, water-based vinyl resin, and polyisocyanate. The blended powder and water-based adhesive are proportioned by weight as follows: 100 parts blended powder: 8-20 parts water-based adhesive. Furthermore, the uniformly mixed blended powder is placed in a granulator for granulation. During granulation, the water-based polyurethane, water-based vinyl resin, and polyisocyanate are simultaneously sprayed to obtain a quasi-spherical mixture with a continuous particle size range of 0.15 to 4.75 mm.

[0052] S05. Curing the spherical mixture to obtain conductive fine aggregate. Curing the spherical mixture at room temperature for 7 to 28 days to obtain conductive fine aggregate that can be used to prepare self-sensing building materials.

[0053] S06. Mix the Portland cement, mineral admixtures, modified mixed powder, high-performance water reducer, and water. Then, add the conductive fine aggregate and coarse aggregate and continue mixing until uniformly mixed. Curing for a period of time produces the agricultural and forestry waste-red mud composite self-sensing building material. Specifically, the mineral admixtures include one or more combinations of blast furnace slag powder, fly ash, steel slag powder, metakaolin, and silica fume; the high-performance water reducer is a polycarboxylate water reducer with a water reduction rate of ≥25%; and the coarse aggregate is crushed stone with a particle size distribution of 5-25 mm. The Portland cement, mineral admixtures, modified mixed powder, high-performance water reducer, and water are sequentially added to a concrete mixer and mixed at a slow speed. The conductive fine aggregate and coarse aggregate are then added and mixed at a high speed. Finally, the mixture is poured into a mold of specified specifications, vibrated to compaction, and allowed to stand for 24 hours before demolding. The mixture is then cured at 20°C and 95% humidity for 28-90 days to produce the self-sensing building material.

[0054] Example 1 of the present invention also provides an agricultural and forestry waste-red mud composite self-sensing building material, which is prepared from the following raw materials in parts by weight: 50-150 parts of Portland cement; 40-120 parts of mineral admixture; 240-480 parts of agricultural and forestry waste; 480-960 parts of red mud; 50-200 parts of inorganic cementitious material; 10-50 parts of activation enhancer; 80-200 parts of water-based adhesive; 0.5-2 parts of high-performance water reducer; 100-300 parts of water; and 800-1200 parts of coarse aggregate.

[0055] Example 2

[0056] As another embodiment of the present invention, this embodiment specifically provides an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof, comprising the following steps:

[0057] S01, first, 10 parts of rice straw, 5 parts of corn stalks, 6 parts of wheat straw, 3 parts of sawdust, 10 parts of bagasse, and 75 parts of red mud were placed on a mixer and uniformly mixed at a mixer speed of 70 r / min for 6 h to obtain a first mixed powder;

[0058] S02. Adding the first mixed powder into a crucible, and then placing it in a tubular furnace, and performing high-temperature heat treatment under different calcination systems, the calcination temperature is 500°C, the holding time is 4 hours, the heating rate is 10°C / min, and an inert or reducing protective atmosphere is used in the furnace to obtain a modified mixed powder after high-temperature heat treatment;

[0059] S03, 100 parts of modified mixed powder, 2 parts of Portland cement, 5 parts of aluminate cement, 2 parts of phosphate cement, 1.2 parts of lime, 1.5 parts of gypsum, 0.8 parts of sodium silicate, 0.5 parts of triethanolamine, 0.3 parts of nano-silicon dioxide, and 0.5 parts of triisopropanolamine were added to a ball mill mixing tank at a speed of 140 r / min for 32 h, and then sieved through a 100 mesh sieve to obtain a blended powder;

[0060] S04. The uniformly mixed blended powder is then placed on a granulator for granulation. During the granulation, 5 parts of waterborne polyurethane, 4 parts of waterborne vinyl resin, and 4 parts of polyisocyanate are simultaneously sprayed to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm.

[0061] S05, curing the spherical mixture at room temperature for 14 days to obtain conductive fine aggregate that can be used to prepare self-sensing building materials;

[0062] S06. Add 100 parts of Portland cement, 30 parts of blast furnace slag powder, 10 parts of fly ash, 15 parts of steel slag powder, 10 parts of metakaolin, 5 parts of silica fume, 120 parts of modified mixed powder, 0.8 parts of polycarboxylate water reducer, and 240 parts of water into a concrete mixer in sequence, and stir at a slow speed for 5 minutes. Then, add 800 parts of conductive fine aggregate and 1100 parts of crushed stone, stir at a fast speed for 10 minutes, and then pour into a mold of specified specifications, vibrate and compact it, leave it for 24 hours, and then demold it. Then, cure it at 20°C and 95% humidity for 28 days to finally obtain a self-sensing building material.

[0063] Example 3

[0064] As another embodiment of the present invention, this embodiment specifically provides an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof, comprising the following steps:

[0065] S01, first, 15 parts of rice straw, 8 parts of corn stalks, 4 parts of wheat straw, 2 parts of sawdust, 12 parts of bagasse, and 60 parts of red mud were placed on a mixer and uniformly mixed at a mixer speed of 70 r / min for 6 h to obtain a first mixed powder;

[0066] S02. Adding the first mixed powder into a crucible, and then placing it in a tubular furnace, and performing high-temperature heat treatment under different calcination systems, the calcination temperature is 550°C, the holding time is 3 hours, the heating rate is 15°C / min, and an inert or reducing protective atmosphere is used in the furnace to obtain a modified mixed powder after high-temperature heat treatment;

[0067] S03, 100 parts of modified mixed powder, 4 parts of Portland cement, 3 parts of aluminate cement, 3 parts of phosphate cement, 0.6 parts of lime, 1.2 parts of gypsum, 1.0 parts of sodium silicate, 0.3 parts of triethanolamine, 0.8 parts of nano-silicon dioxide, and 1.0 parts of triisopropanolamine were added to a ball mill mixing tank at a speed of 120 r / min and a mixing time of 28 h, and then passed through a 100 mesh sieve to obtain a blended powder;

[0068] S04. The uniformly mixed blended powder is then placed on a granulator for granulation. During the granulation, 8 parts of waterborne polyurethane, 6 parts of waterborne vinyl resin, and 3 parts of polyisocyanate are simultaneously sprayed to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm.

[0069] S05. Curing the spherical mixture at room temperature for 14 days to obtain conductive fine aggregate that can be used to prepare self-sensing building materials;

[0070] S06. Add 80 parts of Portland cement, 35 parts of blast furnace slag powder, 15 parts of fly ash, 20 parts of steel slag powder, 10 parts of metakaolin, 8 parts of silica fume, 100 parts of modified mixed powder, 1.2 parts of polycarboxylate water reducer, and 280 parts of water into a concrete mixer in sequence, and stir at a slow speed for 5 minutes. Then, add 900 parts of conductive fine aggregate and 1200 parts of crushed stone, stir at a fast speed for 10 minutes, and then pour into a mold of specified specifications, vibrate and compact it, leave it for 24 hours, and then demold it. Then, cure it at 20°C and 95% humidity for 60 days to finally obtain a self-sensing building material.

[0071] Example 4

[0072] As another embodiment of the present invention, this embodiment specifically provides an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof, comprising the following steps:

[0073] S01, first, 8 parts of rice straw, 10 parts of corn stalks, 8 parts of wheat straw, 5 parts of sawdust, 14 parts of bagasse, and 80 parts of red mud were placed on a mixer and uniformly mixed at a mixer speed of 50 r / min for 5 h to obtain a first mixed powder;

[0074] S02. Adding the first mixed powder into a crucible, and then placing it in a tubular furnace, and performing high-temperature heat treatment under different calcination systems, the calcination temperature is 700°C, the holding time is 1.5 hours, the heating rate is 5°C / min, and an inert or reducing protective atmosphere is used in the furnace to obtain a modified mixed powder after high-temperature heat treatment;

[0075] S03, the modified mixed powder is 100 parts, Portland cement 1 part, aluminate cement 8 parts, phosphate cement 2 parts, lime 0.5 parts, gypsum 0.8 parts, sodium silicate 0.5 parts, triethanolamine 1.0 parts, nano-silicon dioxide 1.0 parts, triisopropanolamine 0.4 parts are added to the ball mill mixing tank, the ball mill mixing tank speed is 200 r / min, the mixing time is 16 h, and then passed through a 100 mesh sieve to obtain a blended powder;

[0076] S04. The uniformly mixed blended powder is then placed on a granulator for granulation. During the granulation, 3 parts of waterborne polyurethane, 11 parts of waterborne vinyl resin, and 6 parts of polyisocyanate are simultaneously sprayed to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm.

[0077] S05. Curing the spherical mixture at room temperature for 14 days to obtain conductive fine aggregate that can be used to prepare self-sensing building materials;

[0078] S06. 120 parts of Portland cement, 20 parts of blast furnace slag powder, 15 parts of fly ash, 10 parts of steel slag powder, 25 parts of metakaolin, 10 parts of silica fume, 150 parts of modified mixed powder, 1.2 parts of polycarboxylate water reducer, and 220 parts of water were added to a concrete mixer in sequence, and stirred at a slow speed for 5 minutes. Then, 750 parts of conductive fine aggregate and 950 parts of crushed stone were added, and stirred at a fast speed for 10 minutes. The mixture was then poured into a mold of specified specifications, vibrated and compacted, and then placed for 24 hours before demolding. The mixture was then cured at 20°C and 95% humidity for 90 days to finally obtain a self-sensing building material.

[0079] Example 5

[0080] As another embodiment of the present invention, this embodiment specifically provides an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof, comprising the following steps:

[0081] S01, first, 20 parts of rice straw, 2 parts of corn stalks, 7 parts of wheat straw, 2 parts of sawdust, 12 parts of bagasse, and 65 parts of red mud were placed on a mixer and uniformly mixed at a mixer speed of 40 r / min for 12 h to obtain a first mixed powder;

[0082] S02. Adding the first mixed powder into a crucible, and then placing it in a tubular furnace, and performing high-temperature heat treatment under different calcination systems, the calcination temperature is 450°C, the holding time is 3.5 hours, the heating rate is 5°C / min, and an inert or reducing protective atmosphere is used in the furnace to obtain a modified mixed powder after high-temperature heat treatment;

[0083] S03, 100 parts of modified mixed powder, 5 parts of Portland cement, 4 parts of aluminate cement, 6 parts of phosphate cement, 0.7 parts of lime, 2.0 parts of gypsum, 1.2 parts of sodium silicate, 0.4 parts of triethanolamine, 0.9 parts of nano-silicon dioxide, and 0.4 parts of triisopropanolamine were added to a ball mill mixing tank at a speed of 190 r / min and a mixing time of 18 h, and then passed through a 100 mesh sieve to obtain a blended powder;

[0084] S04. The uniformly mixed blended powder is then placed on a granulator for granulation. During the granulation, 5 parts of waterborne polyurethane, 7 parts of waterborne vinyl resin, and 3 parts of polyisocyanate are simultaneously sprayed to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm.

[0085] S05. Curing the spherical mixture at room temperature for 14 days to obtain conductive fine aggregate that can be used to prepare self-sensing building materials;

[0086] S06. Add 110 parts of Portland cement, 35 parts of blast furnace slag powder, 6 parts of fly ash, 14 parts of steel slag powder, 8 parts of metakaolin, 6 parts of silica fume, 85 parts of modified mixed powder, 0.7 parts of polycarboxylate water reducer, and 300 parts of water into a concrete mixer in sequence, and stir at a slow speed for 5 minutes. Then, add 850 parts of conductive fine aggregate and 1050 parts of crushed stone, stir at a fast speed for 10 minutes, and then pour into a mold of specified specifications, vibrate and compact it, leave it for 24 hours, and then demold it. Then, cure it at 20°C and 95% humidity for 60 days to finally obtain a self-sensing building material.

[0087] The agricultural and forestry waste-red mud composite self-sensing building materials prepared in Examples 3 to 6 were tested for mechanical properties, resistivity, and resistance change rate according to JTG3420-2020 "Testing Procedures for Cement and Cement Concrete in Highway Engineering." The comparative example was concrete with 5% carbon nanofiber added in the prior art. The test results are shown in the following table:

[0088]

[0089] As can be seen from the table, the 28-day compressive strength of the agricultural and forestry waste-red mud composite self-sensing building material samples prepared in Examples 2 to 5 is greater than 50 MPa, and the 28d flexural strength exceeds 10 MPa, which has similar mechanical strength to the comparative example, but its resistivity is less than 20Ωm, which is significantly lower than the resistivity of the comparative example (52.4Ωm), indicating that the biochar and electromagnetic functionalized red mud in the agricultural and forestry waste-red mud composite self-sensing building material can be well dispersed, and synergistically act with the self-granulated conductive aggregate to form a good three-dimensional conductive network through tunneling effect and conductivity seepage effect, so that it has excellent conductivity; in addition, the resistance change rate of the agricultural and forestry waste-red mud composite self-sensing building material samples is more than 20%, which is significantly higher than 8.7% of the comparative example, indicating that the internal conductive raw materials are more closely overlapped with each other, forming a better conductive path.

[0090] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing an agricultural and forestry waste-red mud composite self-sensing building material, characterized in that: The following steps are involved: Selecting agricultural and forestry wastes and red mud in a mass ratio of 1:1 to 1:4 and mixing them to obtain a first mixed powder; The first mixed powder is added to a crucible, and then placed in a tube furnace, an inert or reducing protective atmosphere is introduced into the tube furnace, and a high-temperature heat treatment is performed at a calcination temperature of 300 to 800° C. to obtain a modified mixed powder; Mixing the modified mixed powder, the inorganic gelling material and the activation enhancer to obtain a blended powder; The uniformly mixed powder is granulated and sprayed with a water-based adhesive to obtain a spherical mixture; curing the spherical mixture to obtain conductive fine aggregate; The silicate cement, mineral admixture, the modified mixed powder, high-performance water reducer and water are stirred and mixed, and then the conductive fine aggregate and coarse aggregate are added and continued to be stirred evenly. The mixture is cured for a period of time to obtain the agricultural and forestry waste-red mud composite self-sensing building material.

2. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: The agricultural and forestry waste includes one or more combinations of rice straw, corn straw, wheat straw, wood chips and sugarcane bagasse; the water-based adhesive includes one or more combinations of water-based polyurethane, water-based vinyl resin and polyisocyanate.

3. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: The inorganic gelling material includes one or more combinations of silicate cement, aluminate cement, phosphate cement, lime, and gypsum; the activation enhancer includes one or more combinations of sodium silicate, triethanolamine, nano-silicon dioxide, and triisopropanolamine.

4. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: The mineral admixture includes one or more combinations of blast furnace slag powder, fly ash, steel slag powder, metakaolin, and silica fume; the high-performance water reducer is a polycarboxylic acid water reducer with a water reduction rate of ≥25%; the coarse aggregate is crushed stone with a particle size distribution range of 5~25mm.

5. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: Mixing agricultural and forestry waste with red mud specifically includes: Placing the agricultural and forestry waste and the red mud on a mixer and uniformly mixing them; The mixer is controlled to have a rotation speed of 40-80 r / min and a mixing time of 4-12 h to obtain the first mixed powder.

6. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: During high temperature heat treatment, the heating rate of the tube furnace is controlled to be 5-15°C / min; After high-temperature heat treatment, the modified mixed powder is obtained by keeping the temperature for 1 to 4 hours.

7. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: The modified mixed powder, inorganic gelling material and activation enhancer are mixed in a ball mill mixing tank; the rotation speed of the ball mill mixing tank is 100-200 r / min, and the mixing time is 12-36 h; then the mixed powder is passed through a 100-200 mesh sieve to obtain a blended powder.

8. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: The curing conditions are 20℃ and 95% humidity, and the curing time is 28~90d.

9. The method for preparing the agricultural and forestry waste-red mud composite self-sensing building material according to claim 1, characterized in that: The continuous particle size of the spherical mixture is 0.15-4.75 mm.

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