High-ductility thermoelectric functional geopolymer concrete material for building exterior wall and preparation method thereof

Abstract

The application discloses a kind of high ductility thermoelectric functional type geopolymer concrete materials for building outer wall and preparation method thereof, the concrete material includes low calcium powder material 50~60 parts, blast furnace slag powder 10~20 parts, red mud 0~30 parts, alkaline activator 50~65 parts, very fine sand 35~45 parts, functional filler 0.5~2 parts, polyvinyl alcohol fiber 1.4~2.6 parts, mixing water 19~26 parts by mass parts;The obtained concrete material has the characteristics of compressive strength higher than 40MPa, significant strain hardening, high tensile ductility, high Seebeck coefficient, thermoelectric performance stability.This application concrete material effectively realizes thermoelectric energy conversion, crack deformation control and solid waste resource utilization.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-ductility thermoelectric functional geopolymer concrete material for building exterior walls and its preparation method. Background Technology

[0002] Urban development and construction have led to greenhouse gas emissions and rising temperatures. Developing waste heat energy utilization technologies can help mitigate the urban heat island effect. Cement, as the most widely used building material, is applied in various engineering fields and has good functional compatibility; therefore, in addition to thermoelectric semiconductor materials, thermoelectric cement-based composite materials (TECC) with development potential have also emerged. TECC can utilize the Seebeck effect to convert indoor and outdoor temperature differences into electrical energy, which is of great significance for building a clean energy structure in cities.

[0003] Compared to mortar or concrete, most TECCs primarily use functional fillers incorporated into cement paste to ensure matrix homogeneity, which limits their application range. Meanwhile, among existing functional fillers containing metals and their oxides, nanoscale metal oxides introduced into the oxide / cement interface have been studied for their ability to filter low-energy charge carriers and improve the Seebeck coefficient. CN106587860A discloses a method of improving the Seebeck coefficient by adding transition metal oxides to carbon fiber cementitious composites, but the metal oxides used are 45.0-75.0 wt% of the cement mass; high dosages can lead to problems such as difficulty in uniform dispersion, high cost, and low specimen strength. CN102923984A uses Fe2O3 or Bi2O3 powder composites with carbon fibers to improve the thermoelectric properties of cement-based composites, but it does not clarify whether the thermoelectric enhancement improves or impairs the mechanical strength of the cement-based material. Furthermore, when applied to power generation in civil buildings, the external structure of urban buildings will experience eccentric forces due to uneven loads, and existing ordinary concrete has a high risk of failure due to its low tensile deformation capacity, high brittleness, and easy cracking characteristics.

[0004] Meanwhile, with global emphasis on ecological protection and carbon emission control, the use of low-carbon materials is urgently needed. Geopolymers are a new type of inorganic cementitious material formed by the activation of silica-alumina minerals or industrial byproducts by alkali activators. Their reaction mechanism, product composition, microstructure, and mechanical properties are completely different from those of silicate cement hydration systems. Geopolymers exhibit significantly lower energy consumption, lower carbon emissions, higher strength, and higher durability. The use of geopolymers to replace hardened cement as structural building components shows great promise.

[0005] Therefore, inventing and preparing a concrete material that combines high thermoelectric effect, strong tensile deformation, and low energy consumption and carbon emissions is of paramount importance for realizing the functionalization of concrete, resource utilization, and meeting engineering needs. However, there are currently no reports on concrete achieving synergistic high tensile ductility and thermoelectric functionalization. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a high-ductility thermoelectric functional geopolymer concrete material for building exterior structures. The second purpose of this invention is to provide a simple and energy-efficient method for preparing the high-ductility thermoelectric functional geopolymer concrete material for building exterior walls.

[0007] Technical solution: The high-ductility thermoelectric functional geopolymer concrete material for building exterior walls described in this invention comprises, by weight, 50-60 parts low-calcium powder, 10-20 parts blast furnace slag powder, 0-30 parts red mud, 50-65 parts alkaline activator, 35-45 parts ultra-fine sand, 0.5-2 parts functional filler, 1.4-2.6 parts polyvinyl alcohol fiber, and 19-26 parts mixing water.

[0008] Preferably, the low-calcium powder is one or more of fly ash, calcined coal gangue powder and waste brick powder, with a calcium oxide content in the range of 1%-10%; the blast furnace slag powder is of grade S95 or S105.

[0009] Preferably, the red mud is Bayer process red mud with a particle size distribution of D10 particle size of 1.1-2.3, D50 particle size of 43.2-45.6, and D90 particle size of 75.1-76.4.

[0010] Preferably, the alkaline activator is a mixture of liquid water glass and sodium hydroxide, with a modulus range of 1.5 to 2.0.

[0011] Preferably, the ultrafine sand is one or more of smooth-surfaced river sand and solid waste coal gangue sand, with a particle size of 300 mesh to 30 mesh and a fineness modulus of 1.0 to 1.2.

[0012] Preferably, the calcined fine brick particles are porous materials with an inner pore diameter in the range of 0.1 μm to 20 μm, a particle size of 100 mesh to 50 mesh, and a water absorption rate of 40.6% to 43.4%.

[0013] Preferably, the functional filler is one or more of nano zinc oxide, nano iron oxide and nano manganese oxide, with a particle size of 1-100 nm.

[0014] Preferably, the polyvinyl alcohol fiber has a length of 8-14 mm, an ultimate elongation of 5-10%, and a tensile strength of at least 1000 MPa.

[0015] Preferably, the polyvinyl alcohol fiber needs to be modified by functional filler through surface functionalization technology, and the processing steps are as follows:

[0016] (1) Unmodified polyvinyl alcohol fiber and deionized water were mixed at a ratio of 1:10 by mass, and ultrasonically vibrated for 5 to 8 minutes to remove impurities. After cleaning, the mixture was placed in a 60°C oven and dried for 6 hours.

[0017] (2) Then, the polyvinyl alcohol fiber, nano metal oxide powder, hydrotalcite, aminosilane coupling agent and dopamine solution are mixed in a mass ratio of (1.4-2.6):(0.5-2):(0.05-0.25):(0.01-0.08):(50-65) and placed in a glass beaker. The mixture is then stirred continuously for 6-12 hours on a magnetic stirrer at 50°C.

[0018] (3) After stirring, take out the fiber and mix it with deionized water at a ratio of 1:10 by mass. Then, ultrasonically vibrate for 5 to 8 minutes, wash it, and dry it in a 50°C oven for 6 hours to obtain modified polyvinyl alcohol fiber.

[0019] Preferably, in step (2), the concentration of the dopamine solution is 2 g / L.

[0020] Preferably, the water is an alkaline activator and additional water added.

[0021] The aforementioned high-ductility thermoelectric functional geopolymer concrete material for building exterior walls includes the following steps:

[0022] (1) Weighing raw materials and preparing modified polyvinyl alcohol fibers;

[0023] (2) Premix the low-calcium powder, blast furnace slag powder and red mud in a mixer at low speed for 2 minutes at a speed of 140-150 rpm.

[0024] (3) Dry-mix the powder and the ultra-fine sand in a mixer at low speed for 1 minute, with a speed of 140-150 rpm.

[0025] (4) Stir the alkaline activator and powder at a speed of 140-150 rpm until they are in a fluid state;

[0026] (5) Add modified polyvinyl alcohol fiber; stir at low speed for 2 minutes until it becomes fluid, with a speed of 140-150 rpm;

[0027] (6) Stir at low speed for 1 minute, then stir at high speed for 2 minutes, with a speed of 280-300 rpm;

[0028] (7) The sample was placed in the test mold and vibrated to compact it. After 24 hours, the sample was removed from the mold and sealed in a plastic bag. It was then cured at 20±2℃ for 14 days.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) In the research of cement-based materials, the surface modification of existing polyvinyl alcohol fibers is mainly based on inorganic nano-SiO2 materials, which are mostly used to improve the fiber / matrix bonding interface, but no obvious thermoelectric effect is generated; by grafting nano-metal oxide particles on the surface, the hydroxyl groups on the surface of non-conductive polyvinyl alcohol fibers can be directly coordinated and crosslinked with metal oxides or their ions. The metal oxides or their ions can also be first crosslinked with the modifier by shrinkage, and the modifier is then crosslinked with the polyvinyl alcohol fibers, which can improve the effectiveness and quantity of crosslinking, thereby giving polyvinyl alcohol conductive properties. Directly modifying the surface structure of fibers with nano-functional particles can achieve interface improvement, conductivity enhancement and weakening of the problem of poor particle dispersion. (2) Compared with commonly used TECC cement paste, the present invention gives concrete high ductility and thermoelectricity. The tensile deformation of high ductile concrete is prepared based on the micromechanical design theory and the key parameter criteria for strain hardening. The modification of fibers will affect their micromechanical action mechanism inside the concrete. By optimizing the processing parameters and mix proportions, the intrinsic toughening and thermoelectric power generation coupling functions of concrete under stress and temperature differences can be brought into play, thereby improving the Seebeck coefficient, electrical conductivity, and other properties. Furthermore, the material is environmentally friendly due to the utilization of waste and renewable resources, and the preparation method is simple and energy-efficient.

[0030] Figure and Table Description

[0031] Figure 1 This is a uniaxial tensile stress-strain curve of the concrete material in the example. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings.

[0033] Example 1

[0034] (1) Weigh the raw materials: 55 parts fly ash, 15 parts blast furnace slag, 30 parts red mud, 60 parts 1.6 modulus alkaline activator, 1 part nano zinc oxide, 2.6 parts fiber, 40 parts river sand in ultra-fine sand, and 24 parts water.

[0035] (2) Weigh the raw materials according to step (1);

[0036] (3) Prepare modified polyvinyl alcohol fiber according to claim 8; First, mix unmodified polyvinyl alcohol fiber with deionized water at a mass ratio of 1:10, ultrasonically vibrate for 5-8 minutes to remove impurities, and then dry in an oven at 60°C for 6 hours after cleaning; then mix polyvinyl alcohol fiber, nano zinc oxide, hydrotalcite, aminosilane coupling agent, and dopamine solution in a mass ratio of 2.6:1.5:0.15:0.05:60 in a glass beaker, and stir continuously for 10 hours on a magnetic stirrer at 50°C; finally, take out the fiber, mix it with deionized water at a mass ratio of 1:10, ultrasonically vibrate for 5-8 minutes, clean it, and then dry in an oven at 50°C for 6 hours to obtain modified polyvinyl alcohol fiber.

[0037] (4) Mix low-calcium fly ash, blast furnace slag and red mud in a mixer at low speed for 2 minutes at a speed of 140-150 rpm.

[0038] (5) Dry-mix the powder and the ultra-fine sand in a mixer at low speed for 1 minute, with a speed of 140-150 rpm.

[0039] (6) Stir the alkaline activator and powder at a speed of 140-150 rpm until they are in a fluid state;

[0040] (7) Add modified polyvinyl alcohol fiber; stir at low speed for 2 minutes until it becomes fluid, with a speed of 140-150 rpm;

[0041] (8) Stir at low speed for 1 minute, then stir at high speed for 2 minutes, with a speed of 280-300 rpm;

[0042] (9) The sample was placed in the test mold and vibrated to compact it. After 24 hours, the sample was removed from the mold and sealed in a plastic bag. It was then cured at 20±2℃ for 14 days.

[0043] Example 2

[0044] (1) Weigh the raw materials: 25 parts fly ash, 30 parts brick powder, 15 parts blast furnace slag, 30 parts red mud, 60 parts 1.6 modulus alkaline activator, 1 part nano iron oxide, 2.6 parts fiber, 40 parts solid waste coal gangue sand in ultra-fine sand, and 24 parts water.

[0045] (2) Weigh the raw materials according to step (1);

[0046] (3) Prepare modified polyvinyl alcohol fiber according to claim 8; First, mix unmodified polyvinyl alcohol fiber with deionized water at a mass ratio of 1:10, ultrasonically vibrate for 5-8 minutes to remove impurities, and then dry in an oven at 60°C for 6 hours after cleaning; then mix polyvinyl alcohol fiber: nano iron oxide: hydrotalcite: aminosilane coupling agent: dopamine solution in a mass ratio of 2.6:1.5:0.15:0.05:60 in a glass beaker, and stir continuously for 10 hours on a magnetic stirrer at 50°C; finally, take out the fiber, mix it with deionized water at a mass ratio of 1:10, ultrasonically vibrate for 5-8 minutes, clean it, and then dry in an oven at 50°C for 6 hours to obtain modified polyvinyl alcohol fiber.

[0047] (4) Mix low-calcium fly ash, brick powder, blast furnace slag and red mud in a mixer at low speed for 2 minutes at a speed of 140-150 rpm.

[0048] (5) Dry-mix the powder and the ultra-fine sand in a mixer at low speed for 1 minute, with a speed of 140-150 rpm.

[0049] (6) Stir the alkaline activator and powder at a speed of 140-150 rpm until they are in a fluid state;

[0050] (7) Add modified polyvinyl alcohol fiber; stir at low speed for 2 minutes until it becomes fluid, with a speed of 140-150 rpm;

[0051] (8) Stir at low speed for 1 minute, then stir at high speed for 2 minutes, with a speed of 280-300 rpm;

[0052] (9) The sample was placed in the test mold and vibrated to compact it. After 24 hours, the sample was removed from the mold and sealed in a plastic bag. It was then cured at 20±2℃ for 14 days.

[0053] Example 3

[0054] (1) Weigh the raw materials: 30 parts fly ash, 30 parts calcined coal gangue powder, 15 parts blast furnace slag, 25 parts red mud, 60 parts 1.8 modulus alkaline activator, 1 part nano zinc oxide, 2.6 parts fiber, 20 parts river sand in ultra-fine sand and 20 parts solid waste coal gangue sand, and 24 parts water.

[0055] (2) Weigh the raw materials according to step (1);

[0056] (3) Prepare modified polyvinyl alcohol fiber according to claim 8; First, mix unmodified polyvinyl alcohol fiber with deionized water at a mass ratio of 1:10, ultrasonically vibrate for 5-8 minutes to remove impurities, and then dry in an oven at 60°C for 6 hours after cleaning; then mix polyvinyl alcohol fiber: nano zinc oxide: nano manganese oxide: hydrotalcite: aminosilane coupling agent: dopamine solution in a mass ratio of 2:0.5:0.5:0.15:0.05:60 in a glass beaker, and stir continuously for 8 hours on a magnetic stirrer at 50°C; finally, take out the fiber, mix it with deionized water at a mass ratio of 1:10, ultrasonically vibrate for 5-8 minutes, clean it, and then dry in an oven at 50°C for 6 hours to obtain modified polyvinyl alcohol fiber.

[0057] (4) Mix low-calcium fly ash, calcined coal gangue powder, blast furnace slag and red mud in a mixer at low speed for 2 minutes at a speed of 140-150 rpm.

[0058] (5) Dry-mix the powder and the ultra-fine sand in a mixer at low speed for 1 minute, with a speed of 140-150 rpm.

[0059] (6) Stir the alkaline activator and powder at a speed of 140-150 rpm until they are in a fluid state;

[0060] (7) Add modified polyvinyl alcohol fiber; stir at low speed for 2 minutes until it becomes fluid, with a speed of 140-150 rpm;

[0061] (8) Stir at low speed for 1 minute, then stir at high speed for 2 minutes, with a speed of 280-300 rpm;

[0062] (9) The sample was placed in the test mold and vibrated to compact it. After 24 hours, the sample was removed from the mold and sealed in a plastic bag. It was then cured at 20±2℃ for 14 days.

[0063] Example 4:

[0064] (1) Weigh the raw materials: 30 parts fly ash, 30 parts calcined coal gangue powder, 15 parts blast furnace slag, 60 parts 1.8 modulus alkaline activator, 2.6 parts fiber, 20 parts river sand in ultra-fine sand and 20 parts solid waste coal gangue sand, and 24 parts water.

[0065] (2) Weigh the raw materials according to step (1);

[0066] (2) Mix low-calcium fly ash, calcined coal gangue powder, blast furnace slag and red mud in a mixer at low speed for 2 minutes at a speed of 140-150 rpm.

[0067] (3) Dry-mix the powder and the ultra-fine sand in a mixer at low speed for 1 minute, with a speed of 140-150 rpm.

[0068] (4) Stir the alkaline activator and powder at a speed of 140-150 rpm until they are in a fluid state;

[0069] (5) Add unmodified polyvinyl alcohol fiber; stir at low speed for 2 minutes until it becomes fluid, with a speed of 140-150 rpm;

[0070] (6) Stir at low speed for 1 minute, then stir at high speed for 2 minutes, with a speed of 280-300 rpm;

[0071] (7) The sample was placed in the test mold and vibrated to compact it. After 24 hours, the sample was removed from the mold and sealed in a plastic bag. It was then cured at 20±2℃ for 14 days.

[0072] The Seebeck coefficient, electrical conductivity, compressive strength, tensile strength and ductility of the above embodiments were tested, and the test results are shown in Table 1.

[0073] Table 1

[0074]

[0075] Low-calcium fly ash, calcined coal gangue powder, brick powder, and red mud provide high aluminum and silica content for constructing a three-dimensional network geopolymer gel. Simultaneously, red mud increases the alkalinity of the reaction system, aiding the geopolymerization reaction, while the calcium oxide provided by the mineral powder promotes increased matrix activity. In Seebeck tests, the alkaline ions filtered from red mud exhibit higher kinetics in transporting electrons from the hot end to the cold end, resulting in a greater negative charge at the cold end and increasing the potential. The regular and uniform microstructure of the three-dimensional network geopolymer gel, containing more low-dimensional nanomaterials and a large amount of attached zero-dimensional particles, facilitates the transfer of activated electrons from the hot end to the cold end, reducing obstacles and increasing the voltage difference between the two ends. Nanoparticles not only react with the matrix to generate more gel but also enhance thermoelectric properties. When hydrotalcite is attached to the fiber surface through coupling agents and functional groups generated by dopamine, it can fix nano-sized metal oxides due to its intercalation space. Nano-metal oxides can also be grafted onto the surface of polyvinyl alcohol fibers, promoting bonding with the matrix gel. The distribution of nanoparticles along the fibers can form rapid channels for charge carriers. Furthermore, when nano-metal oxides are grafted onto non-conductive fibers, the three-dimensional interlacing of the fibers within the matrix allows conductive phases to overlap and form interconnected conductive networks, facilitating the formation of complete conductive paths and thus improving conductivity. The large band gap and high exciton binding energy of the nanoparticles enhance the thermoelectric effect, thereby improving the Seebeck coefficient of high-ductility polymer concrete. Regarding tensile deformation, the low activity of low-calcium powder and red mud can reduce the fracture toughness and initial crack strength of the matrix, which helps to increase the bridging residual energy. Modified fibers dispersed in the geopolymer matrix still play a role in bridging, toughening, and crack prevention. Non-conductive fibers and nanoparticles work together to improve the micromechanics of the fiber / matrix interface and the construction of conductive pathways, which is beneficial to the realization of good tensile and thermoelectric properties of concrete materials.

Claims

1. A high-ductility thermoelectric functional geopolymer concrete material for building exterior walls, characterized in that: The raw materials, by weight, include the following: 50-60 parts low-calcium powder, 10-20 parts blast furnace slag powder, 25-30 parts red mud, 50-65 parts alkaline activator, 35-45 parts ultra-fine sand, 0.5-2 parts functional filler, 1.4-2.6 parts polyvinyl alcohol fiber, and 19-26 parts mixing water; wherein the red mud is Bayer process red mud with a particle size distribution D 10 Particle size is 1.1~2.3, D 50 Particle size is 43.2~45.6, D 90 The particle size is 75.1~76.4 mm; the ultrafine sand is one or two of smooth-surface river sand and solid waste coal gangue sand, with a particle size of 300 mesh to 30 mesh and a fineness modulus of 1.0~1.2; the functional filler is one or more of nano zinc oxide, nano iron oxide, and nano manganese oxide, with a particle size of 1-100 nm; the polyvinyl alcohol fiber needs to be modified by functional filler technology, and the processing steps are as follows: (1) Unmodified polyvinyl alcohol fiber and deionized water are mixed at a ratio of 1:10 by mass, ultrasonically vibrated for 5-8 minutes to remove impurities, and then dried after cleaning; (2) Then, polyvinyl alcohol fiber, functional filler, hydrotalcite, aminosilane coupling agent and dopamine solution are mixed in a mass ratio of (1.4~2.6):(0.5~2):(0.05~0.25):(0.01~0.08):(50~65) and magnetically stirred for 6~12 hours. (3) After stirring, take out the polyvinyl alcohol fiber, mix it with deionized water at a ratio of 1:10 by mass, ultrasonically vibrate for 5 to 8 minutes, wash and dry to obtain modified polyvinyl alcohol fiber.

2. The high-ductility thermoelectric functional geopolymer concrete material for building exterior walls according to claim 1, characterized in that: The low-calcium powder is one or more of fly ash, calcined coal gangue powder and waste brick powder, with a calcium oxide content in the range of 1%-10%; the blast furnace slag powder is of grade S95 or S105.

3. The high-ductility thermoelectric functional geopolymer concrete material for building exterior walls according to claim 1, characterized in that: The alkaline activator is a mixture of liquid water glass and sodium hydroxide, with a modulus ranging from 1.5 to 2.

0.

4. The high-ductility thermoelectric functional geopolymer concrete material for building exterior walls according to claim 1, characterized in that: The polyvinyl alcohol fiber has a length of 8-14 mm, an ultimate elongation of 5-10%, and a tensile strength of at least 1000 MPa.

5. The high-ductility thermoelectric functional geopolymer concrete material for building exterior walls according to claim 1, characterized in that: In step (2), the concentration of the dopamine solution is 2 g / L.

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