Sintered hollow batten for building and preparation method of sintered hollow batten

Abstract

The invention provides a sintered hollow batten for buildings and a preparation method, and belongs to the technical field of novel wall materials, the sintered hollow batten for buildings comprises the following raw materials: high-calcium fly ash, construction waste recycled aggregate, clay, sulphoaluminate cement, a foaming agent, reinforced fibers and an additive; wherein the particle size of the construction waste recycled aggregate is 0.5-5mm, and the construction waste recycled aggregate is subjected to plasma activation treatment; a nano TiO2 photocatalytic coating is loaded on the surface of the construction waste recycled aggregate; the reinforced fibers are composite fibers of basalt fibers and polypropylene fibers, and the mass ratio of the basalt fibers to the polypropylene fibers is (1: 1)-(1: 2). According to the sintered hollow batten for the building, the building waste recycled aggregate subjected to plasma activation treatment is adopted, and the nano titanium dioxide photocatalytic coating is loaded, so that the bonding strength of the aggregate is greatly improved, and the hollow batten is endowed with the function of degrading pollutants such as formaldehyde.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel wall materials, and in particular relates to a sintered hollow slab for construction and a preparation method thereof. Background Art

[0002] The current field of building wall materials faces the triple challenges of resource depletion, environmental pollution, and performance bottlenecks. Traditional sintered hollow slats rely primarily on natural aggregates and ordinary sulfoaluminate cement, which not only consumes non-renewable resources but also emits up to 1.2 tons of CO2 per ton of product during production. Although improved solutions using fly ash or construction waste as raw materials have emerged in recent years, key technical flaws still exist: in terms of aggregate processing, the surface activity of recycled aggregates after mechanical crushing is low, and the interface bonding with the matrix is weak, resulting in a compressive strength of the product generally below 10MPa; in terms of functional expansion, existing technologies focus on basic mechanical properties and lack the development of environmental functions of materials. Small attempts to add TiO2 powder have also not been widely used due to uneven dispersion and low loading, resulting in a single function of hollow slats; in terms of reinforcement system, traditional glass fiber has poor alkali resistance, and polypropylene fiber easily melts at high temperatures. A single fiber cannot meet the dual requirements of sintering process and service performance.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The first purpose of the present invention is to provide a sintered hollow slat for construction, which modifies the aggregate by plasma activation and combining microwave-assisted deposition to precisely load nano-titanium dioxide, thereby retaining the aggregate while imparting the function of degrading formaldehyde. At the same time, a three-dimensional network structure is formed by a composite synergistic system of reinforced fibers, thereby further improving the flexural strength of the slat.

[0005] The second purpose of the present invention is to provide a method for preparing the above-mentioned sintered hollow strip board for construction. The preparation method forms a gradient foaming effect by using a composite foaming agent of hydrogen peroxide and aluminum powder, and accurately controls the pore size by combining vacuum extrusion molding. In the sintering process, a mixed gas of nitrogen and carbon dioxide is used to create a weak oxidizing atmosphere, which not only prevents fiber oxidation but also enhances the compressive strength of the material.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0007] A sintered hollow slab for construction, comprising the following raw materials, calculated by mass percentage:

[0008] High calcium fly ash: 30-55%;

[0009] Recycled aggregate from construction waste: 20-35%;

[0010] Clay: 15-25%;

[0011] Sulphoaluminate cement: 5-12%;

[0012] Foaming agent: 0.5-1.5%;

[0013] Reinforcement fiber: 1-3%;

[0014] Admixture: 0.2-0.8%;

[0015] The particle size of the recycled aggregate from construction waste is 0.5-5 mm, and after plasma activation treatment, the specific surface area is ≥500 m 2 / g;

[0016] The surface of the construction waste recycled aggregate is loaded with a nano-TiO2 photocatalytic coating, and the loading amount of the nano-TiO2 photocatalytic coating is 0.5-1%;

[0017] The reinforcing fiber is a composite fiber of basalt fiber and polypropylene fiber, with a length of 3-12 mm, and the mass ratio of the basalt fiber to the polypropylene fiber is 1:1-1:2.

[0018] Preferably, as a further specific embodiment, the following raw materials are included:

[0019] High calcium fly ash: 40%;

[0020] Recycled aggregate from construction waste: 30%;

[0021] Clay: 15%;

[0022] Sulphoaluminate cement: 10%;

[0023] Foaming agent: 1.5%;

[0024] Reinforcement fiber: 3%;

[0025] Admixture: 0.5%;

[0026] Wherein, the particle size of the construction waste recycled aggregate is 3mm;

[0027] The loading amount of the nano-TiO2 photocatalytic coating is 0.6%;

[0028] The length of the reinforcing fiber is 10 mm, and the mass ratio of the basalt fiber to the polypropylene fiber is 1:1.5.

[0029] In the technical solution of the sintered hollow slats for construction of the present invention, a new wall material with high strength, light weight and environmental functionality is realized mainly through scientific proportioning and functionalized recycled aggregates. The core of the present invention lies in the selection and proportioning design of raw materials, as well as plasma activation and nano-TiO2 loading technology for recycled aggregates of construction waste, and the mechanical properties of the material are optimized through a composite fiber reinforcement system. From the perspective of raw material principles, high-calcium fly ash is the main gelling component, and its content is controlled between 30-55%, which can not only give full play to its active effect, but also avoid the problem of shrinkage and cracking caused by excessive use. The rich CaO in high-calcium fly ash can generate hydrated calcium silicate gel during the sintering process, thereby significantly improving the density of the matrix, and it can also activate the active surface of the recycled aggregate in an alkaline environment. properties, promoting interface bonding. Therefore, if the fly ash content exceeds 55%, the drying shrinkage rate of the pretreated material will increase. The proportion of recycled aggregate from construction waste in the present invention is 20-35%, and its particle size is controlled between 0.5-5 mm. This limitation optimizes the packing density of the recycled aggregate, so that a uniform skeleton structure can be formed inside the pretreated material. After the recycled aggregate is treated with plasma activation, the specific surface area is significantly increased, and the surface energy is significantly improved. After the high-energy particles in the plasma treatment bombard the aggregate surface, the recycled aggregate can also form a micron-nanometer rough structure, so that the nano-TiO2 coating can be firmly anchored. When the loading amount of the nano-TiO2 photocatalytic coating is 0.5-1%, it not only ensures the effectiveness of the coating in degrading pollutants, but also avoids the cost increase or degradation of aggregate surface performance caused by excessive loading.

[0030] In terms of the reinforcement system, the present invention adopts a composite fiber of basalt fiber and polypropylene fiber, with a content of 1-3%, a length controlled between 3-12 mm, and a mass ratio of 1:1-1:2, so that the prepared hollow strip has excellent performance. The basalt fiber is resistant to high temperatures and can withstand the high temperature environment during the sintering process, while the polypropylene fiber gives the material higher toughness and suppresses the brittleness of the basalt fiber. Through the synergistic effect of the two, a three-dimensional network structure is formed inside the material, which significantly improves the bending resistance of the hollow strip; when the fiber length is 10 mm and the mass ratio is 1:1.5, the bending strength of the material is excellent.

[0031] When the foaming agent hydrogen peroxide is combined with aluminum powder in a mass ratio of 2-4:1, the resulting composite foaming agent can form a gradient pore structure within the material through differential outgassing reaction rates, achieving the dual goals of lightweighting and thermal insulation. The admixture content is 0.2-0.8%, consisting of nano-silica, lignin sulfonate, a water reducer, and a retarder. Nano-silica, comprising 40-60% with a particle size of 10-50nm, has been modified with a silane coupling agent to effectively fill capillaries and increase material density. It also synergizes with the water reducer to further reduce the water-to-binder ratio and minimize the risk of shrinkage during sintering.

[0032] Preferably, as a further specific embodiment, the foaming agent is a composite foaming agent of hydrogen peroxide and aluminum powder, the foaming pore size of the composite foaming agent is 0.1-1 mm, and the porosity is ≥60%;

[0033] The mass ratio of the hydrogen peroxide to the aluminum powder is (2-4):1.

[0034] Preferably, as a further specific embodiment, the foaming pore diameter of the composite foaming agent is 0.6 mm, and the mass ratio of the hydrogen peroxide to the aluminum powder is 3:1.

[0035] In the present invention, by adopting a composite foaming agent system of hydrogen peroxide and aluminum powder, combined with precise ratios and process parameters, a gradient distribution of the pore structure inside the material is achieved, thereby achieving a breakthrough balance between lightweight, thermal insulation performance and mechanical strength. The combined use of hydrogen peroxide and aluminum powder in the foaming agent forms a unique synergistic foaming mechanism. Hydrogen peroxide decomposes under heating conditions to produce oxygen. This reaction has mild degassing characteristics and can form uniform micron-sized bubbles inside the material. Aluminum powder reacts with water in an alkaline environment to produce hydrogen. The reaction rate is relatively fast and can form pores with larger pore diameters. Therefore, it can be seen that the mass ratio between the two is particularly important. When the mass ratio is (2-4):1, the prepared hollow strip board The performance is excellent. This is because when the ratio is lower than 2:1, the rapid degassing of aluminum powder easily leads to the merging of bubbles, forming an uneven macroporous structure; when the ratio is higher than 4:1, the slow foaming of hydrogen peroxide dominates, and although the porosity is high, the pore size is too small, affecting the lightweight effect; and when the mass ratio of the two is 3:1, the gradient pore structure formed inside the material is the most ideal, the pore size distribution presents a bimodal feature, and the porosity is stable, achieving the goal of high porosity without sacrificing strength. The advantage of this gradient pore structure is that the micropores can significantly improve the sound insulation performance by increasing the sound wave refraction path, while the macropores can effectively reduce the density of the material. At the same time, the nano-TiO2 coating loaded on the inner wall of the macropores increases the exposed area, further improving the photocatalytic efficiency.

[0036] Preferably, as a further specific embodiment, the admixture includes the following raw materials:

[0037] Nano-silicon dioxide: 40-60%;

[0038] Lignin sulfonate: 20-30%;

[0039] Water reducing agent: 10-20%;

[0040] Retarder: 5-10%;

[0041] The nano-silicon dioxide has a particle size of 10-50 nm and is modified with a silane coupling agent.

[0042] Preferably, as a further specific embodiment, the admixture includes the following raw materials:

[0043] Nano-silicon dioxide: 50%;

[0044] Lignin sulfonate: 25%;

[0045] Water reducing agent: 15%;

[0046] Retarder: 10%;

[0047] The particle size of the nano-silicon dioxide is 30 nm.

[0048] Preferably, as a further specific embodiment, water is further included, and the water-to-binder ratio is 0.5:1.

[0049] The present invention also implements a refined component design for the admixture system. By compounding nano-silica, lignin sulfonate, water reducer and retarder in a specific ratio, the technical problems of single function and insufficient synergy of traditional admixtures in the sintering process are solved. From the perspective of material composition, the nano-silica in the present invention serves as the core component, its particle size is controlled at 10-50nm and is modified with a silane coupling agent. This design enables the nano-silica to produce a triple effect at the microscopic level: first, the high specific surface area of the nanoparticles enables it to effectively fill the capillary pores in the cement-fly ash matrix. When the silica particle size is 30nm, it can form a "core-shell structure" with the CSH gel, the hydration product of sulfoaluminate cement, thereby improving the density of the matrix. Thereby, the compressive strength is further improved; secondly, the introduction of silane coupling agent forms an organic-inorganic hybrid interface on the surface of nano-silica. This structure causes the pretreated material to gradually carbonize during the sintering process to form a conductive network, which synergizes with the composite fiber to produce an electrostatic shielding effect, thereby improving the material's shielding effectiveness against electromagnetic waves and expanding the intelligent functions of the wall material; at the same time, the silanol group on the surface of nano-silica forms a Si-O-Ti bond with the TiO2 coating on the surface of the recycled aggregate in an alkaline environment. This chemical bond further enhances the microhardness of the aggregate-matrix interface transition zone and improves the interface bonding strength. Therefore, when its content is less than 40%, a continuous three-dimensional network cannot be formed; exceeding 60% will cause a sharp increase in the viscosity of the system, affecting the process performance.

[0050] The amphiphilic molecular structure in lignin sulfonate can form a "molecular bridge" between nano-silica and cement particles. When the content is 25%, the thixotropic index of the slurry decreases, which makes the shear thinning effect of material flow more significant in the subsequent vacuum extrusion process and reduces the extrusion pressure. More importantly, the phenolic hydroxyl groups in lignin sulfonate will undergo pyrolysis and recombination at the sintering temperature to generate a carbon skeleton with a microporous structure. These carbon skeletons and the pores formed by the foaming agent constitute a multi-level pore system, which enhances the breathing performance of the material and effectively regulates the indoor humidity.

[0051] The selection and proportioning of the water reducer reflects the system's compatibility with the overall formulation. By selecting a polycarboxylic acid-based water reducer, the present invention not only ensures its conventional dispersing properties within the system, but also enables the carboxyl groups on its molecular chain to form coordinated bonds with plasma-activated sites on the surface of the recycled aggregate. This effect further reduces the water-to-binder ratio without causing segregation. Furthermore, in the subsequent preparation process, the water reducer, foaming agent, and water are added simultaneously during the wet mixing stage. At this stage, the water reducer preferentially adsorbs on the aluminum powder surface, slowing its reaction rate with water and better aligning the hydrogen release peak with the slurry coagulation time. This is crucial for achieving uniform pore size distribution.

[0052] In addition, the present invention uses sodium gluconate as a retarder to regulate the early pozzolanic reaction rate of high-calcium fly ash, preventing the premature formation of a rigid skeleton in the pre-foaming stage and inhibiting pore expansion; when the retarder content is 10%, the Ca content of the fly ash 2+ The release rate is optimally matched to the foaming agent gas generation, enabling the material to maintain suitable plasticity for a long period of time during the pre-curing stage before sintering. Furthermore, the hydroxyl groups in the retarder molecules undergo an esterification reaction with nano-silica at high temperatures, forming a silicate compound with internal lubrication, significantly improving the dimensional accuracy of the product.

[0053] The present invention also provides a method for preparing the above-mentioned sintered hollow slab for construction, comprising the following steps:

[0054] The construction waste recycled aggregate was treated with plasma activation and loaded with nano-TiO2 by microwave assisted deposition to obtain activated aggregate.

[0055] Then, fly ash, activated aggregate, clay, sulphoaluminate cement and reinforcing fiber are dry-mixed and then foaming agent, admixture and water are added and wet-mixed until a uniform mixture is obtained;

[0056] The mixture is then vacuum extruded to obtain a pre-strip board, which is then pre-foamed and sintered. After sintering, the pre-strip board is cooled and kept warm.

[0057] In the initial aggregate processing stage of the present invention, the surface of the recycled aggregate from construction waste is modified by a plasma activation process. The high-energy particles with an electron temperature of 10000K are bombarded to form a nano-scale concave-convex structure on the surface of the aggregate, which greatly increases the specific surface area, thereby providing an ideal anchoring point for the subsequent microwave-assisted deposition of nano-TiO2. Subsequently, during the microwave deposition process, the electromagnetic field is used to excite the hydrolysis of the TiO2 precursor, thereby constructing a coating with uniform thickness on the surface of the aggregate. The surface dangling bonds generated by the plasma activation can also react with the Ca2+ of the high-calcium fly ash. 2+ In the subsequent sintering stage, strong Ca-O-Si bonding is formed, which further improves the shear strength of the aggregate-matrix interface.

[0058] Preferably, as a further specific embodiment, a mixed gas of nitrogen and carbon dioxide is introduced during the sintering;

[0059] The volume ratio of nitrogen to carbon dioxide is 1:1-1:3, and the gas flow rate is 5-10 L / min.

[0060] In the present invention, a unique weak oxidizing sintering environment is constructed by using a mixed gas of nitrogen and carbon dioxide at a flow rate of 5-10L / min during sintering, wherein the inert property of nitrogen effectively protects the composite fiber from excessive oxidation, especially prevents the complete pyrolysis of polypropylene fiber at a sintering temperature of 600-800°C, and the introduction of carbon dioxide reacts with the free CaO in the high-calcium fly ash to carbonize, which not only compensates for the heat loss of the system but also generates nano-CaCO3, and the generated nano-calcium carbonate is preferentially deposited at the interface between the recycled aggregate and the matrix, so that the microhardness of the interface transition zone is further improved. Therefore, when the mixed gas flow rate is lower than 5L / min, the insufficient CO2 partial pressure leads to incomplete carbonization reaction; and when it is higher than 10L / min, the fiber surface will be overcooled, affecting the wrapping effect of the polypropylene melt on the basalt fiber; and the volume ratio of the mixed gas of 1:1-1:3 can produce a synergistic effect with the nano-TiO2 coating on the surface of the recycled aggregate. In a weak reducing atmosphere, part of the TiO2 in the TiO2 4+ Will be restored to Ti 3+ These trivalent titanium ions act as electron traps and can significantly enhance the photocatalytic activity. At the same time, the CO2 gas flow reacts with the inner wall of the pores formed by the foaming agent to generate a thicker CaCO3 / titanium dioxide composite film, thereby increasing the light reflectivity of the pores and indirectly enhancing the quantum efficiency of the photocatalytic reaction.

[0061] Preferably, as a further specific embodiment, the sintered hollow slats for construction are used in prefabricated building walls, wherein the hollow slats are connected by mortise and tenon structures, and the joints are filled with graphene-modified cement-based grouting material.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] (1) The present invention provides a sintered hollow slat for construction, which modifies the aggregate by plasma activation and precise loading of nano-titanium dioxide in combination with microwave-assisted deposition, thereby retaining the aggregate while imparting the function of degrading formaldehyde. At the same time, a three-dimensional network structure is formed by a composite synergistic system of reinforced fibers, thereby further improving the bending strength of the slat.

[0064] (2) The present invention provides a method for preparing the above-mentioned sintered hollow strip board for construction, which forms a gradient foaming effect by using a composite foaming agent of hydrogen peroxide and aluminum powder, and accurately controls the pore size by combining vacuum extrusion molding. In addition, a mixed gas of nitrogen and carbon dioxide is used in the sintering process to create a weak oxidizing atmosphere, which can prevent fiber oxidation and enhance the compressive strength of the material. DETAILED DESCRIPTION

[0065] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, not all of them, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0066] In order to more clearly illustrate the technical solutions of the present invention, specific embodiments are provided below for illustration.

[0067] Example 1

[0068] The preparation steps of the sintered hollow slab for construction of the present invention are as follows:

[0069] 1. The specific raw material components are as follows:

[0070] High calcium fly ash: 30g

[0071] Recycled aggregate from construction waste (particle size 0.5mm): 35g

[0072] Clay: 25g

[0073] Sulphoaluminate cement: 5g

[0074] Foaming agent (hydrogen peroxide: aluminum powder = 2:1): 1.5g

[0075] Reinforcement fiber (basalt fiber: polypropylene fiber = 1:1, length 3mm): 3g

[0076] Admixture (40% nano-silica, 30% lignin sulfonate, 20% water reducer, 10% retarder, the nano-silica has a particle size of 10 nm and is modified with KH-570 silane): 0.5 g

[0077] Water: 17.5g (water-to-binder ratio 0.5:1)

[0078] Nano-TiO2 photocatalytic coating loading: 0.5% (based on the mass of recycled aggregate);

[0079] 2. Preparation Process

[0080] 2.1 Aggregate pretreatment:

[0081] The recycled aggregates from construction waste (particle size 0.5 mm) were fed into the plasma activation equipment and treated for 30 min at a power of 5 kW and a pressure of 50 Pa.

[0082] The activated aggregate was immersed in a tetrabutyl titanate ethanol solution (concentration 0.1 mol / L) and irradiated in a microwave reactor (800 W, 2.45 GHz) for 90 seconds to achieve uniform loading of the nano-TiO2 coating to obtain the activated aggregate;

[0083] 2.2 Mixing process:

[0084] Add high calcium fly ash, activated aggregate, clay, sulphoaluminate cement and reinforcing fiber into a twin-shaft mixer according to the proportion and mix them;

[0085] Subsequently, a composite foaming agent (hydrogen peroxide and aluminum powder premixed at a ratio of 3:1), an admixture (nano-silica particles with a diameter of 30 nm, modified with KH-570 silane), and water were simultaneously added to the dry mix and mixed in a planetary mixer at 120 rpm for 8 minutes to obtain a mixture;

[0086] The mixture was then fed into a twin-screw extruder, with the screw speed set at 20 rpm and the vacuum degree at -0.08 MPa, and extruded to obtain a pre-striped board;

[0087] Finally, the pre-strip board was transferred into a tunnel heating furnace and heated to 180°C at 2°C / min and kept at this temperature for 30 minutes to form a gradient pore structure.

[0088] The sample was transferred to a sintering furnace, and a mixed gas of nitrogen and carbon dioxide with a volume ratio of 1:1 (flow rate 5 L / min) was introduced. The temperature was raised to 750°C at a rate of 5°C / min and sintered for 2 hours, followed by slow cooling to room temperature.

[0089] Example 2

[0090] The preparation steps of the sintered hollow slab for construction of the present invention are as follows:

[0091] 1. The specific raw material components are as follows:

[0092] High calcium fly ash: 55g

[0093] Recycled aggregate from construction waste (particle size 5mm): 20g

[0094] Clay: 15g

[0095] Sulphoaluminate cement: 7.7g

[0096] Foaming agent (hydrogen peroxide: aluminum powder = 4:1): 0.5g

[0097] Reinforcement fiber (basalt fiber: polypropylene fiber = 1:2, length 12mm): 1g

[0098] Admixture (nano-silica 60%, lignin sulfonate 20%, water reducer 10%, retarder 10%, the nano-silica particle size is 50nm and is modified with KH-570 silane): 0.8g

[0099] Water: 31.35g (water-to-binder ratio 0.5:1)

[0100] Nano-TiO2 photocatalytic coating loading: 1% (based on the mass of recycled aggregate);

[0101] 2. Preparation Process

[0102] 2.1 Aggregate pretreatment:

[0103] The recycled aggregates from construction waste (particle size 5 mm) were fed into the plasma activation equipment and treated for 30 min at a power of 5 kW and a pressure of 50 Pa.

[0104] The activated aggregate was immersed in a tetrabutyl titanate ethanol solution (concentration 0.1 mol / L) and irradiated in a microwave reactor (800 W, 2.45 GHz) for 90 seconds to achieve uniform loading of the nano-TiO2 coating to obtain the activated aggregate;

[0105] 2.2 Mixing process:

[0106] Add high calcium fly ash, activated aggregate, clay, sulphoaluminate cement and reinforcing fiber into a twin-shaft mixer according to the proportion and mix them;

[0107] Subsequently, a composite foaming agent (hydrogen peroxide and aluminum powder premixed at a ratio of 4:1), an admixture (nano-silica particles with a diameter of 50 nm, modified with KH-570 silane), and water were simultaneously added to the dry mix and mixed in a planetary mixer at 120 rpm for 8 minutes to obtain a mixture;

[0108] The mixture was then fed into a twin-screw extruder, with the screw speed set at 30 rpm and the vacuum degree at -0.1 MPa, and extruded to obtain a pre-striped board;

[0109] Finally, the pre-strip board was transferred into a tunnel heating furnace and heated to 180°C at 2°C / min and kept at this temperature for 30 minutes to form a gradient pore structure.

[0110] The sample was transferred to a sintering furnace, and a mixed gas of nitrogen and carbon dioxide with a volume ratio of 1:3 was introduced (flow rate 10 L / min), and the temperature was raised to 600°C at 5°C / min for 2 hours, and then slowly cooled to room temperature.

[0111] Example 3

[0112] The preparation steps of the sintered hollow slab for construction of the present invention are as follows:

[0113] 1. The specific raw material components are as follows:

[0114] High calcium fly ash: 45g

[0115] Recycled aggregate from construction waste (particle size 3mm): 20g

[0116] Clay: 20.3g

[0117] Sulphoaluminate cement: 12g

[0118] Foaming agent (hydrogen peroxide: aluminum powder = 3:1): 1.5g

[0119] Reinforcement fiber (basalt fiber: polypropylene fiber = 1:2, length 10mm): 1g

[0120] Admixture (50% nano-silica, 30% lignin sulfonate, 20% water reducer, 10% retarder, the nano-silica has a particle size of 30 nm and is modified with a silane coupling agent): 0.2 g

[0121] Water: 28.5g (water-to-glue ratio 0.5:1)

[0122] Nano-TiO2 photocatalytic coating loading: 0.8% (based on the mass of recycled aggregate);

[0123] 2. Preparation Process

[0124] 2.1 Aggregate pretreatment:

[0125] The recycled aggregates from construction waste (particle size 3 mm) were fed into the plasma activation equipment and treated for 30 min at a power of 5 kW and a pressure of 50 Pa.

[0126] The activated aggregate was immersed in a tetrabutyl titanate ethanol solution (concentration 0.1 mol / L) and irradiated in a microwave reactor (800 W, 2.45 GHz) for 90 seconds to achieve uniform loading of the nano-TiO2 coating to obtain the activated aggregate;

[0127] 2.2 Mixing process:

[0128] Add high calcium fly ash, activated aggregate, clay, sulphoaluminate cement and reinforcing fiber into a twin-shaft mixer according to the proportion and mix them;

[0129] Subsequently, a composite foaming agent (hydrogen peroxide and aluminum powder premixed at a ratio of 3:1), an admixture (nano-silica particles with a diameter of 30 nm, modified with KH-570 silane), and water were simultaneously added to the dry mix and mixed in a planetary mixer at 120 rpm for 8 minutes to obtain a mixture;

[0130] The mixture was then fed into a twin-screw extruder, with the screw speed set at 25 rpm and the vacuum degree at -0.09 MPa, and extruded to obtain a pre-striped board;

[0131] Finally, the pre-strip board was transferred into a tunnel heating furnace and heated to 180°C at 2°C / min and kept at this temperature for 30 minutes to form a gradient pore structure.

[0132] The sample was transferred to a sintering furnace, and a mixed gas of nitrogen and carbon dioxide with a volume ratio of 1:2 (flow rate 10 L / min) was introduced. The temperature was raised to 750°C at a rate of 5°C / min and sintered for 2 hours, followed by slow cooling to room temperature.

[0133] Example 4

[0134] The preparation steps of the sintered hollow slab for construction of the present invention are as follows:

[0135] 1. The specific raw material components are as follows:

[0136] High calcium fly ash: 40g

[0137] Recycled aggregate from construction waste (particle size 3mm): 30g

[0138] Clay: 15g

[0139] Sulphoaluminate cement: 10g

[0140] Foaming agent (hydrogen peroxide: aluminum powder = 3:1): 1.5g

[0141] Reinforcement fiber (basalt fiber: polypropylene fiber = 1:1.5, length 10mm): 3g

[0142] Admixture (50% nano-silica, 25% lignin sulfonate, 15% water reducer, 10% retarder, the nano-silica has a particle size of 30 nm and is modified with KH-570 silane): 0.8 g

[0143] Water: 25g (water-to-glue ratio 0.5:1)

[0144] Nano-TiO2 photocatalytic coating loading: 0.6% (based on the mass of recycled aggregate);

[0145] 2. Preparation Process

[0146] 2.1 Aggregate pretreatment:

[0147] The recycled aggregates from construction waste (particle size 3 mm) were fed into the plasma activation equipment and treated for 30 min at a power of 5 kW and a pressure of 50 Pa.

[0148] The activated aggregate was immersed in a tetrabutyl titanate ethanol solution (concentration 0.1 mol / L) and irradiated in a microwave reactor (800 W, 2.45 GHz) for 90 seconds to achieve uniform loading of the nano-TiO2 coating to obtain the activated aggregate;

[0149] 2.2 Mixing process:

[0150] Add high calcium fly ash, activated aggregate, clay, sulphoaluminate cement and reinforcing fiber into a twin-shaft mixer according to the proportion and mix them;

[0151] Subsequently, a composite foaming agent (hydrogen peroxide and aluminum powder premixed at a ratio of 3:1), an admixture (nano-silica particles with a diameter of 30 nm, modified with KH-570 silane), and water were simultaneously added to the dry mix and mixed in a planetary mixer at 120 rpm for 8 minutes to obtain a mixture;

[0152] The mixture was then fed into a twin-screw extruder, with the screw speed set at 25 rpm and the vacuum degree at -0.09 MPa, and extruded to obtain a pre-striped board;

[0153] Finally, the pre-strip board was transferred into a tunnel heating furnace and heated to 180°C at 2°C / min and kept at this temperature for 30 minutes to form a gradient pore structure.

[0154] The sample was transferred to a sintering furnace, and a mixed gas of nitrogen and carbon dioxide with a volume ratio of 1:2 (flow rate 10 L / min) was introduced. The temperature was raised to 750°C at a rate of 5°C / min and sintered for 2 hours, followed by slow cooling to room temperature.

[0155] Comparative Example 1

[0156] The specific implementation steps are the same as those in Example 4, with the only difference being that the particle size of the construction waste recycled aggregate in Example 3 is adjusted to 0.1 mm.

[0157] Comparative Example 2

[0158] The specific implementation steps are the same as those in Example 4, with the only difference being that the particle size of the construction waste recycled aggregate in Example 3 is adjusted to 10 mm.

[0159] Comparative Example 3

[0160] The specific implementation steps are consistent with those of Example 4, with the only difference being that the loading amount of the nano-TiO2 photocatalytic coating in Example 3 is adjusted to 0.1%.

[0161] Comparative Example 4

[0162] The specific implementation steps are consistent with those of Example 4, with the only difference being that the loading amount of the nano-TiO2 photocatalytic coating in Example 3 is adjusted to 5%.

[0163] Comparative Example 5

[0164] The specific implementation steps are the same as those in Example 4, with the only difference being that the length of the reinforcing fiber in Example 3 is adjusted to 1 mm.

[0165] Comparative Example 6

[0166] The specific implementation steps are the same as those in Example 4, with the only difference being that the length of the reinforcing fiber in Example 3 is adjusted to 20 mm.

[0167] Comparative Example 7

[0168] The specific implementation steps are the same as those in Example 4, except that the mass ratio of basalt fiber to polypropylene fiber in Example 3 is adjusted to 0.1:1.

[0169] Comparative Example 8

[0170] The specific implementation steps are the same as those in Example 4, except that the mass ratio of basalt fiber to polypropylene fiber in Example 3 is adjusted to 1:5.

[0171] Comparative Example 9

[0172] The specific implementation steps are consistent with those in Example 4, except that the mass ratio of hydrogen peroxide to the aluminum powder in Example 3 is adjusted to 0.5:1.

[0173] Comparative Example 10

[0174] The specific implementation steps are the same as those in Example 4, except that the mass ratio of hydrogen peroxide to the aluminum powder in Example 3 is adjusted to 10:1.

[0175] Comparative Example 11

[0176] The specific implementation steps are consistent with those in Example 4, except that the volume ratio of nitrogen to carbon dioxide in Example 3 is adjusted to 0.5:1.

[0177] Comparative Example 12

[0178] The specific implementation steps are the same as those in Example 4, except that the volume ratio of nitrogen to carbon dioxide in Example 3 is adjusted to 1:5.

[0179] Comparative Example 13

[0180] The specific implementation steps are the same as those in Example 4, the only difference being that the construction waste recycled aggregate is not subjected to plasma activation treatment.

[0181] Comparative Example 14

[0182] The specific implementation steps are the same as those in Example 4, with the only difference being that the nano-TiO2 photocatalytic coating is not loaded on the construction waste recycled aggregate.

[0183] Comparative Example 15

[0184] The specific implementation steps are the same as those in Example 4, with the only difference being that only polypropylene fibers are used as the reinforcing fibers.

[0185] Comparative Example 16

[0186] The specific implementation steps are the same as those in Example 4, with the only difference being that only aluminum powder is used as the foaming agent.

[0187] Comparative Example 17

[0188] The specific implementation steps are the same as those in Example 4, except that the nano-silica is not modified with a silane coupling agent in the admixture.

[0189] Experimental Example 1 Performance Test of Sintered Hollow Strip Board for Construction

[0190] Test method:

[0191] Compressive strength: According to GB / T 23451-2023 standard, use universal testing machine to test, loading rate 0.5MPa / s, take the average value of 3 groups of specimens;

[0192] Thermal conductivity: According to GB / T10294 standard, using Hot Disk thermal constant analyzer, ambient temperature 25℃;

[0193] Formaldehyde degradation rate: According to GB50325-2020 standard, within 1m 3 The initial formaldehyde concentration in the closed cabin is 1.0±0.1mg / m 3 , UV light (365nm, 10W / m 2 ) Determine the residual concentration after 24 hours;

[0194] Porosity: The ratio of total pore volume to apparent volume was determined by mercury intrusion porosimetry;

[0195] Drying shrinkage: According to GB / T11969 standard, the length change of the specimen is measured after 28 days of curing, where

[0196] The final test results are shown in Table 1 below:

[0197]

[0198] From the above experimental results, it can be seen that Examples 1-4 demonstrate the performance gradient improvement of the sintered hollow strip board of the present invention under the optimization of raw material ratio and process parameters. Example 4 is the best solution. Among them, Example 1 adopts the smallest particle size aggregate and the lowest fiber content. Although its compressive strength and thermal conductivity meet the basic requirements, there is still a significant gap compared with Example 4; Example 2 improves the porosity and lightweight effect by increasing the fly ash content and the proportion of the foaming agent, but the adjustment of the fiber mass ratio causes the bending strength to be slightly lower than that of Example 4; Example 3 optimizes the aggregate particle size and TiO2 loading, and the formaldehyde degradation rate reaches 90.2%, but due to insufficient bonding between the fiber length and the matrix, the compressive strength is slightly inferior to that of Example 4;

[0199] Comparative Examples 1-2 show that the particle size of the recycled aggregate has a certain influence on the performance of the hollow strip board finally prepared. When 0.1 mm ultrafine aggregate is used in Comparative Example 1, although its specific surface area is increased, the bulk density is obviously insufficient, resulting in lower compressive strength and porosity than Example 4, and the drying shrinkage rate is increased due to excessive fine particles. Comparative Example 2 uses 10 mm aggregate. Although the skeleton strength is improved, the excessive particle size leads to weakened interface bonding, increased thermal conductivity, and reduced TiO2 coating coverage, which reduces the formaldehyde degradation rate.

[0200] By comparing Comparative Examples 3 and 4, it can be seen that the TiO2 loading has a certain influence on the performance of the hollow strip board finally prepared. When the loading in Comparative Example 3 is only 0.1%, the photocatalytic activity is insufficient, but the mechanical properties are not significantly affected. When the loading in Comparative Example 4 reaches 5%, although the degradation rate is increased to 93.2%, the excessive TiO2 blocks the pores of the aggregate, resulting in an increase in thermal conductivity and a decrease in compressive strength.

[0201] Comparative Examples 5-6 investigated the effect of fiber length. When 1 mm short fibers were used in Comparative Example 5, the fibers were too short to form a continuous network, resulting in low compressive strength and porosity of the prepared hollow strips. In Comparative Example 6, the 20 mm fibers were too long, resulting in agglomeration and increased drying shrinkage.

[0202] Comparative Examples 7 and 8 adjusted the fiber ratio. In Comparative Example 7, the proportion of basalt fiber was too low, causing polypropylene to melt at high temperatures and collapse the structure, resulting in a compressive strength of only 8.9 MPa. In Comparative Example 8, the excessive amount of polypropylene reduced the heat resistance of the hollow slats, increasing the thermal conductivity to 0.134 W / (m·K).

[0203] Comparative Examples 9-10 tested the effect of the foaming agent ratio. In Comparative Example 9, excessive aluminum powder resulted in the merging of bubbles, resulting in a porosity of only 54.6%, which in turn caused a sharp drop in compressive strength. In Comparative Example 10, excessive hydrogen peroxide caused the prepared hollow strips to form too many closed cells. Although the formaldehyde degradation rate increased, the strength was limited.

[0204] In Comparative Examples 11-12, the sintering atmosphere was adjusted. In Comparative Example 11, insufficient nitrogen resulted in fiber oxidation and decreased compressive strength, while in Comparative Example 12, excessive carbon dioxide caused excessive reaction, uneven CaCO3 deposition on the interface, and increased drying shrinkage.

[0205] Among them, Comparative Example 13 did not perform plasma activation on the recycled aggregate, resulting in weak interface bonding and a 45% decrease in compressive strength compared with Example 4, which illustrates the necessity of activating the recycled aggregate; Comparative Example 14 did not have a TiO2 coating, resulting in a sharp drop in the formaldehyde degradation rate of the prepared hollow strips, but similar mechanical properties; and in Comparative Example 15, a single polypropylene fiber was used as the reinforcing fiber, resulting in its high-temperature failure and a significant decrease in strength, confirming the synergistic effect of the composite fiber; Comparative Example 16 only used aluminum powder for foaming, and the porosity was too high, resulting in insufficient strength, verifying the advantages of the composite foaming agent; Comparative Example 17 did not modify the nano-silica, and the particle agglomeration increased the thermal conductivity, illustrating the key role of silane modification.

[0206] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sintered hollow board for construction, characterized in that: Calculated by mass percentage, it includes the following raw materials: High calcium fly ash: 30-55%; Recycled aggregate from construction waste: 20-35%; Clay: 15-25%; Sulphoaluminate cement: 5-12%; Foaming agent: 0.5-1.5%; Reinforcement fiber: 1-3%; Admixture: 0.2-0.8%; The particle size of the recycled aggregate from construction waste is 0.5-5 mm, and after plasma activation treatment, the specific surface area is ≥500 m 2 / g; The surface of the construction waste recycled aggregate is loaded with a nano-TiO2 photocatalytic coating, and the loading amount of the nano-TiO2 photocatalytic coating is 0.5-1%; The reinforcing fiber is a composite fiber of basalt fiber and polypropylene fiber, with a length of 3-12 mm, and the mass ratio of the basalt fiber to the polypropylene fiber is 1:1-1:

2.

2. The sintered hollow strip for construction according to claim 1, characterized in that: Including the following ingredients: High calcium fly ash: 40%; Recycled aggregate from construction waste: 30%; Clay: 15%; Sulphoaluminate cement: 10%; Foaming agent: 1.5%; Reinforcement fiber: 3%; Admixture: 0.5%; Wherein, the particle size of the construction waste recycled aggregate is 3mm; The loading amount of the nano-TiO2 photocatalytic coating is 0.6%; The length of the reinforcing fiber is 10 mm, and the mass ratio of the basalt fiber to the polypropylene fiber is 1:1.

5.

3. The sintered hollow board for construction according to claim 1, characterized in that: The foaming agent is a composite foaming agent of hydrogen peroxide and aluminum powder, the foaming pore diameter of the composite foaming agent is 0.1-1mm, and the porosity is ≥60%; The mass ratio of the hydrogen peroxide to the aluminum powder is (2-4):

1.

4. The sintered hollow strip for construction according to claim 3, characterized in that: The foaming pore diameter of the composite foaming agent is 0.6 mm, and the mass ratio of the hydrogen peroxide to the aluminum powder is 3:

1.

5. The sintered hollow board for construction according to claim 1, characterized in that: The admixture includes the following raw materials: Nano-silicon dioxide: 40-60%; Lignin sulfonate: 20-30%; Water reducing agent: 10-20%; Retarder: 5-10%; The nano-silicon dioxide has a particle size of 10-50 nm and is modified with a silane coupling agent.

6. The sintered hollow slab for construction according to claim 5, characterized in that: The admixture includes the following raw materials: Nano-silicon dioxide: 50%; Lignin sulfonate: 25%; Water reducing agent: 15%; Retarder: 10%; The particle size of the nano-silicon dioxide is 30 nm.

7. The sintered hollow board for construction according to claim 1, characterized in that: Water is also included, and the water-to-binder ratio is 0.5:

1.

8. A method for preparing a sintered hollow slab for construction according to any one of claims 1 to 7, characterized in that: The following steps are involved: The construction waste recycled aggregate was treated with plasma activation and loaded with nano-TiO2 by microwave assisted deposition to obtain activated aggregate. Then, fly ash, activated aggregate, clay, sulphoaluminate cement and reinforcing fiber are dry-mixed and then foaming agent, admixture and water are added and wet-mixed until a uniform mixture is obtained; The mixture is then vacuum extruded to obtain a pre-strip board, which is then pre-foamed and sintered. After sintering, the pre-strip board is cooled and kept warm.

9. The preparation method according to claim 8, characterized in that During the sintering, a mixed gas of nitrogen and carbon dioxide is introduced; The volume ratio of nitrogen to carbon dioxide is 1:1-1:3, and the gas flow rate is 5-10 L / min.

10. Application of the sintered hollow slab for construction according to any one of claims 1 to 7 in prefabricated building walls, characterized in that: The hollow strips are connected by mortise and tenon structures, and the joints are filled with graphene-modified cement-based grouting material.

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