Agricultural and forestry waste-red mud composite self-sensing building material and preparation method thereof

Abstract

The invention relates to an agricultural and forestry waste-red mud composite self-sensing building material and a preparation method thereof.The preparation method comprises the steps that a mixture of agricultural and forestry waste and red mud is treated in a high-temperature calcination mode, and the agricultural and forestry waste is subjected to thermal cracking under the high-temperature condition to form biochar fibers with certain conductivity; the preparation method comprises the following steps: reducing ferric oxide in red mud into ferroferric oxide with high magnetism, further endowing the red mud with electromagnetic functionalization, and finally preparing the self-sensing building material by adopting pyrolytic charcoal fibers, the electromagnetic functionalized red mud and self-granulation conductive aggregates together. The method not only overcomes the problems of high manufacturing cost, high environmental pollution risk, poor stability and the like of traditional self-sensing building materials, but also has the advantages of wide raw material sources, simple preparation process, low cost and facilitation of industrial large-scale production, and realizes resource utilization of agriculture, forestry and industrial solid wastes.

Description

Technical Field

[0001] The 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] At present, the traditional structural health monitoring method is to add additional embedded, surface-coated or externally attached sensors to cement-based materials, thereby giving cement-based materials additional sensing functions. However, general embedded sensors not only destroy the original internal structure of concrete, but also weaken the bearing capacity and durability of concrete to a certain extent, while surface-coated or externally attached sensors are easily affected by the coating layer, external environment and noise. At the same time, sensors also have shortcomings such as high cost and poor durability, and their installation and wiring process is relatively cumbersome, which will bring certain inconveniences to construction applications in actual use.

[0003] A large number of studies have proposed that by adding conductive fillers such as carbon fiber, carbon nanotubes, nickel powder, multilayer graphene, carbon black, metal fiber or powder into cement-based materials, functional integrated materials with the ability to self-sense stress, strain, displacement, temperature, humidity and other changes can be formed. This type of self-sensing building material can be used as an ideal intelligent building material because it has the same lifespan as cement concrete, good compatibility and high sensitivity. It can provide a reliable and effective way for long-term stable real-time monitoring and health diagnosis of concrete structures.

[0004] At present, self-sensing ultra-high performance concrete uses a large amount of nanomaterials as conductive fillers to prepare self-sensing concrete materials with good conductive properties. However, the production process of the nanomaterials used is immature, expensive, and unstable, and cannot be applied on a large scale in industry. There is also the risk of environmental pollution. Therefore, it is urgent to develop low-cost, high-performance conductive fillers and self-sensing building materials. 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 problems of high prices and high environmental risks of current 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: Mixing agricultural and forestry waste with red mud to obtain a first mixed powder; The first mixed powder is subjected to high temperature heat treatment to obtain a modified mixed powder after the high temperature heat treatment; The modified mixed powder, the inorganic gelling material and the activation enhancer are mixed to obtain a blended powder; Granulating the uniformly mixed powder and spraying the aqueous adhesive to obtain a spherical mixture; The spherical mixture is solidified to obtain conductive fine aggregate; The silicate cement, mineral admixture, modified mixed powder, high-performance water reducing agent and water are stirred and mixed, and then the conductive fine aggregate and coarse aggregate are added and stirred evenly. After curing for a period of time, the agricultural and forestry waste-red mud composite self-sensing building material is obtained.

[0007] Optionally, the agricultural and forestry waste includes one or more combinations of rice straw, corn straw, wheat straw, wood chips and bagasse; the water-based adhesive includes one or more combinations of water-based polyurethane, water-based vinyl resin and polyisocyanate.

[0008] 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-silicon dioxide, and triisopropanolamine.

[0009] 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.

[0010] Optionally, mixing agricultural and forestry waste with red mud specifically includes: Select agricultural and forestry wastes and red mud with a mass ratio of 1:1 to 1:4; The agricultural and forestry wastes and red mud are placed on a mixer and mixed evenly; 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.

[0011] Optionally, subjecting the first mixed powder to high temperature heat treatment specifically includes: Adding the first mixed powder into a crucible, and then placing it in a tube furnace; Introduce an inert or reducing protective atmosphere into the tube furnace; Control the heating rate of the tube furnace to 5~15℃ / min; The modified mixed powder is obtained by high temperature heat treatment at a calcination temperature of 300-800°C and keeping the temperature for 1-4 hours.

[0012] Optionally, 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 sieved through a 100-200 mesh sieve to obtain the mixed powder.

[0013] Optionally, the curing conditions are 20°C and 95% humidity, and the curing time is 28 to 90 days.

[0014] Optionally, the continuous particle size of the spherical mixture is 0.15-4.75 mm.

[0015] The present invention also provides an agricultural and forestry waste-red mud composite self-sensing building material, characterized in that it 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 pieces of agricultural and forestry waste; Red mud 480~960 parts; 50~200 parts of inorganic gelling material; 10~50 parts of activation enhancer; 80~200 parts of water-based adhesive; 0.5~2 parts of high performance water reducing agent; 100~300 parts of water; 800~1200 parts of coarse aggregate.

[0016] The beneficial effects of the present invention are: The present invention firstly adopts 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 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 the pyrolyzed biochar fibers are co-granulated through 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 materials 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 reactivity, allowing it to play a secondary hydration role in the subsequent preparation of conductive fillers and self-sensing building materials, and 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, with significant economic and ecological benefits, huge market potential, and broad prospects for engineering applications. It has effectively promoted the comprehensive green transformation of my country's economic and social development, and is of great significance for accelerating the construction of a waste recycling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] 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

[0019] The preferred embodiments of the present invention are 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, but are not used to limit the scope of the present invention.

[0020] Embodiment 1 CombinationFigure 1 As shown, a method for preparing an agricultural and forestry waste-red mud composite self-sensing building material disclosed in an embodiment of the present invention comprises the following steps: S01, mixing agricultural and forestry waste with red mud to obtain a first mixed powder; in step S01, agricultural and forestry waste and red mud are selected in a weight ratio of 1:1 to 1:4. Specifically, the weight ratio of agricultural and forestry waste to red mud is: 20 to 40 parts of agricultural and forestry waste and 40 to 80 parts of red mud.

[0021] The agricultural and forestry wastes of this embodiment include a combination of rice straw, corn straw, wheat straw, wood chips and bagasse. Then, the rice straw, corn straw, wheat straw, wood chips, bagasse and red mud are uniformly mixed on a mixer, and the mixer speed is 40-80 r / min, and the mixing time is 4-12 h to obtain a first mixed powder.

[0022] S02. Subjecting the first mixed powder to high-temperature heat treatment to obtain a modified mixed powder after high-temperature heat treatment; in step S02, specifically: first adding the first mixed powder to a crucible, and then placing it in a tubular furnace, subjecting it to high-temperature heat treatment under different calcination systems, the calcination temperature is 300-800°C, the insulation time is 1-4 h, the heating rate is 5-15°C / min, an inert or reducing protective atmosphere is used in the furnace, and subjecting it to high-temperature heat treatment to obtain a modified mixed powder.

[0023] S03, mixing the modified mixed powder, the inorganic gelling material and the activation enhancer to obtain a blended powder; in step S03, 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. In addition, the modified mixed powder, the inorganic gelling material and the activation enhancer are proportioned according to the following weight parts: 100 parts of the modified mixed powder, 5-20 parts of the inorganic gelling material, and 1-5 parts of the activation enhancer.

[0024] 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 mixed powder.

[0025] S04, granulating the uniformly mixed blended powder, and spraying the aqueous adhesive at the same time to obtain a spherical mixture. In step S04, the aqueous adhesive includes one or more combinations of aqueous polyurethane, aqueous vinyl resin, and polyisocyanate, and the blended powder and the aqueous adhesive are proportioned according to the following weight parts: 100 parts of blended powder and 8 to 20 parts of aqueous adhesive. In addition, the uniformly mixed blended powder is placed on a granulator for granulation, and aqueous polyurethane, aqueous vinyl resin, and polyisocyanate are sprayed synchronously during granulation to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm.

[0026] S05. The spherical mixture is cured to obtain conductive fine aggregate. The spherical mixture is cured at room temperature for 7 to 28 days to obtain conductive fine aggregate that can be used to prepare self-sensing building materials.

[0027] S06. Stir and mix silicate cement, mineral admixture, modified mixed powder, high-performance water reducer and water, then add conductive fine aggregate and coarse aggregate and continue to stir evenly, and cure for a period of time to obtain agricultural and forestry waste-red mud composite self-sensing building materials. Specifically, 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 polycarboxylate water reducer with a water reduction rate of ≥25%; the coarse aggregate is crushed stone with a particle size distribution range of 5~25mm. The above-mentioned silicate cement, mineral admixture, modified mixed powder, high-performance water reducer and water are added to the concrete mixer in sequence and stirred and mixed under slow conditions. Then add conductive fine aggregate and coarse aggregate and stir and mix under fast conditions. Finally, pour it into a mold of specified specifications, vibrate and compact it, place it for 24 hours, and then demold it, and then cure it at 20℃ and 95% humidity for 28~90d to finally obtain a self-sensing building material.

[0028] Embodiment 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 silicate 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.

[0029] Embodiment 2 As another embodiment of the present invention, in this embodiment, a self-sensing composite building material of agricultural and forestry waste-red mud and a preparation method thereof are specifically provided, comprising the following steps: 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 are placed on a mixer and uniformly mixed. The mixer speed is 70 r / min and the mixing time is 6 h to obtain a first mixed powder; 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 h, the heating rate is 10 ° C / min, and an inert or reducing protective atmosphere is used in the furnace. After high-temperature heat treatment, a modified mixed powder is obtained; S03, add 100 parts of modified mixed powder, 2 parts of silicate 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 into a ball mill mixing tank, the speed of the ball mill mixing tank is 140 r / min, the mixing time is 32 h, and then pass through a 100 mesh sieve to obtain a blended powder; S04, then placing the uniformly mixed blended powder on a granulator for granulation, and simultaneously spraying 5 parts of waterborne polyurethane, 4 parts of waterborne vinyl resin, and 4 parts of polyisocyanate during granulation, to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm; 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; S06. Add 100 parts of silicate 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, stir for 5 minutes at a slow speed, then add 800 parts of conductive fine aggregate and 1,100 parts of crushed stone, stir for 10 minutes at a fast speed, then pour into a mold of specified specifications, vibrate and compact it, place it for 24 hours, demold it, and then cure it at 20°C and 95% humidity for 28 days to finally obtain a self-sensing building material.

[0030] Embodiment 3 As another embodiment of the present invention, in this embodiment, a self-sensing composite building material of agricultural and forestry waste-red mud and a preparation method thereof are specifically provided, comprising the following steps: 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 are placed on a mixer and uniformly mixed at a mixer speed of 70 r / min for 6 h to obtain a first mixed powder; 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 h, the heating rate is 15 ° C / min, and an inert or reducing protective atmosphere is used in the furnace. After high-temperature heat treatment, a modified mixed powder is obtained; S03, add 100 parts of modified mixed powder, 4 parts of silicate 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 into a ball mill mixing tank, the speed of the ball mill mixing tank is 120 r / min, the mixing time is 28 h, and then pass through a 100 mesh sieve to obtain a blended powder; S04, then placing the uniformly mixed blended powder on a granulator for granulation, and simultaneously spraying 8 parts of waterborne polyurethane, 6 parts of waterborne vinyl resin, and 3 parts of polyisocyanate during granulation, to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm; 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; S06. Add 80 parts of silicate 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 polycarboxylic acid water reducer, and 280 parts of water into a concrete mixer in sequence, 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, then pour into a mold of specified specifications, vibrate and compact it, place it for 24 hours, demold it, and then cure it at 20°C and 95% humidity for 60 days to finally obtain a self-sensing building material.

[0031] Embodiment 4 As another embodiment of the present invention, in this embodiment, a self-sensing composite building material of agricultural and forestry waste-red mud and a preparation method thereof are specifically provided, comprising the following steps: S01, firstly, 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; 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 h, the heating rate is 5 ° C / min, and an inert or reducing protective atmosphere is used in the furnace. After high-temperature heat treatment, a modified mixed powder is obtained; S03, adding 100 parts of modified mixed powder, 1 part of silicate cement, 8 parts of aluminate cement, 2 parts of phosphate cement, 0.5 parts of lime, 0.8 parts of gypsum, 0.5 parts of sodium silicate, 1.0 parts of triethanolamine, 1.0 parts of nano-silicon dioxide, and 0.4 parts of triisopropanolamine into a ball mill mixing tank, the speed of the ball mill mixing tank is 200 r / min, the mixing time is 16 h, and then passed through a 100 mesh sieve to obtain a blended powder; S04, then placing the uniformly mixed blended powder on a granulator for granulation, and simultaneously spraying 3 parts of waterborne polyurethane, 11 parts of waterborne vinyl resin, and 6 parts of polyisocyanate during granulation, to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm; 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; S06. Add 120 parts of silicate 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 polycarboxylic acid water reducer, and 220 parts of water into a concrete mixer in sequence, stir at a slow speed for 5 minutes, then add 750 parts of conductive fine aggregate and 950 parts of crushed stone, stir at a fast speed for 10 minutes, then pour into a mold of specified specifications, vibrate and compact it, place it for 24 hours, demold it, and then cure it at 20°C and 95% humidity for 90 days to finally obtain a self-sensing building material.

[0032] Embodiment 5 As another embodiment of the present invention, in this embodiment, a self-sensing composite building material of agricultural and forestry waste-red mud and a preparation method thereof are specifically provided, comprising the following steps: S01, firstly, 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; 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 h, the heating rate is 5 ° C / min, and an inert or reducing protective atmosphere is used in the furnace. After high-temperature heat treatment, a modified mixed powder is obtained; S03, adding 100 parts of modified mixed powder, 5 parts of silicate 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 into a ball mill mixing tank, the speed of the ball mill mixing tank is 190 r / min, the mixing time is 18 h, and then passed through a 100 mesh sieve to obtain a blended powder; S04, then placing the uniformly mixed blended powder on a granulator for granulation, and simultaneously spraying 5 parts of waterborne polyurethane, 7 parts of waterborne vinyl resin, and 3 parts of polyisocyanate during granulation, to obtain a spherical mixture with a continuous particle size range of 0.15 to 4.75 mm; 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; S06. Add 110 parts of silicate 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 polycarboxylic acid water reducer and 300 parts of water into a concrete mixer in sequence, stir for 5 minutes at a slow speed, then add 850 parts of conductive fine aggregate and 1050 parts of crushed stone, stir for 10 minutes at a fast speed, then pour into a mold of specified specifications, vibrate and compact it, place it for 24 hours, demold it, and then cure it at 20°C and 95% humidity for 60 days to finally obtain a self-sensing building material.

[0033] The agricultural and forestry waste-red mud composite self-sensing building materials prepared in Examples 3 to 6 were tested for mechanical properties, resistivity, resistance change rate and other parameters of the self-sensing building materials according to JTG3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering". The comparative example is concrete in which 5% carbon nanofibers are added in the prior art. The test results are shown in the following table: 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 the tunnel effect and the 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 exceeds 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.

[0034] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope 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: Mixing agricultural and forestry waste with red mud to obtain a first mixed powder; The first mixed powder is subjected to high temperature heat treatment to obtain a modified mixed powder after the high temperature heat treatment; The modified mixed powder, the inorganic gelling material and the activation enhancer are mixed to obtain a blended powder; Granulating the uniformly mixed powder and spraying the aqueous 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 reducing agent and water are stirred and mixed, and then the conductive fine aggregate and coarse aggregate are added and stirred evenly, and the agricultural and forestry waste-red mud composite self-sensing building material is obtained after curing for a period of time.

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 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 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 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: The mixing of agricultural and forestry waste with red mud specifically includes: Selecting the agricultural and forestry waste and the red mud in a mass ratio of 1:1 to 1:4; Placing the agricultural and forestry waste and the red mud on a mixer for uniform mixing; The rotating speed of the mixer is controlled to be 40-80 r / min and the mixing time is controlled to be 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: The step of subjecting the first mixed powder to high temperature heat treatment specifically comprises: Adding the first mixed powder into a crucible, and then placing it in a tube furnace; injecting an inert or reducing protective atmosphere into the tube furnace; Controlling the heating rate of the tube furnace to be 5-15°C / min; 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.

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; and then the mixed powder is sieved through a 100-200 mesh sieve to obtain the 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° C. and 95% humidity, and the curing time is 28 to 90 days.

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.

10. A self-sensing building material made of agricultural and forestry waste and red mud, characterized in that: It 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 pieces of agricultural and forestry waste; Red mud 480~960 parts; 50~200 parts of inorganic gelling material; Activation enhancer 10~50 parts; 80~200 parts of water-based adhesive; 0.5~2 parts of high performance water reducing agent; 100~300 parts of water; 800~1200 parts of coarse aggregate.

Images