Light steel mould net composite wall for fabricated building, material and preparation process

Abstract

This invention discloses a lightweight steel mesh composite wall for prefabricated buildings, its materials, and preparation process, belonging to the field of building materials and building structure technology. The composite wall includes a lightweight steel frame, a steel wire mesh mold, and a magnesium sulfate-oxygenated foam cement-based composite filler material filled inside the mold shell. The material uses magnesium oxide, magnesium sulfate, and water as the main reactive components, with the addition of fly ash and a composite modifier. Through physical foaming and subsequent incorporation of the foam into the slurry, a uniform porous structure is formed. The aluminum dihydrogen phosphate contained in the composite modifier can react with magnesium oxide to produce controllable chemical micro-expansion, effectively compensating for the material's drying shrinkage. This invention fundamentally solves the problems of easy cracking and insufficient durability caused by the large shrinkage of the filler material, poor water resistance, and weak interfacial bonding in traditional walls. It achieves high-performance integration of lightweight, high-strength, low thermal conductivity, micro-expansion crack resistance, and lifespan matching that of the main building structure, making it particularly suitable for high-performance prefabricated building envelope systems.

Description

Technical Field

[0001] This invention belongs to the field of building materials and building structure technology, specifically relating to light steel mesh composite walls for prefabricated buildings, materials and preparation processes. Background Technology

[0002] With the continuous advancement of my country's construction industrialization, prefabricated buildings, as an important technological path to achieve green construction and improve construction efficiency, have gradually become the core development direction of modern building systems. Lightweight steel mesh composite wall materials, due to their comprehensive advantages such as lightweight and high strength, energy saving and environmental protection, short construction cycle, and high degree of factory prefabrication, are widely used in various building structures, including residential buildings, public buildings, and industrial plants, becoming a key component of prefabricated building envelope systems. This type of wall typically uses a lightweight steel frame as the load-bearing support, covered with a steel wire mesh to form a permanent formwork, and filled with functional concrete materials, thereby achieving integrated structural, thermal insulation, fireproofing, and durability performance.

[0003] The invention patent with announcement number CN119221634B (hereinafter referred to as Prior Art 1) discloses a prefabricated light steel keel composite panel wall. By setting assembly components consisting of convex tube seats, open card seats, and end positioning seats on both sides of the wall panel, rapid alignment and mechanical anchoring between adjacent wall panels are achieved, effectively improving on-site installation efficiency and enhancing the deformation resistance of the joint area. This solution, to a certain extent, solves the problems of cumbersome connection and difficult positioning in traditional wall systems, demonstrating the technical value of modular design in improving construction convenience.

[0004] Patent CN112922193B (hereinafter referred to as Prior Art 2) discloses a composite partition wall based on a steel mesh external formwork structure using a combination of vertical supports and horizontal connectors. By prefabricating the overall frame and steel mesh formwork in a factory, transportation and hoisting are facilitated. U-shaped connecting fittings are used to widen and fix the edges of the steel mesh, enhancing the connection rigidity between the formwork and the frame, thereby improving the overall stability of the wall during service. The above technical approaches all start from the structural construction level, systematically improving assembly efficiency and mechanical properties, representing the mainstream direction of current light steel composite wall development.

[0005] With the continuous improvement of building lifecycle performance requirements, especially the higher standards for wall materials in terms of durability, fire safety, energy efficiency, and environmental adaptability, existing technologies 1 and 2 reveal deep-seated structural contradictions in material system selection and intrinsic performance matching. Existing walls generally use foamed concrete or rock wool as core filling materials, which, while meeting basic thermal insulation requirements to some extent, have significant shortcomings in their intrinsic properties. Foamed concrete generally suffers from low strength, high water absorption, and large drying shrinkage, making it prone to micro-cracks and interface debonding during long-term service, leading to insulation layer failure and structural performance degradation. While rock wool possesses good fire resistance, its poor water repellency and low compressive strength, coupled with fiber pulverization and performance degradation in humid environments, make it difficult to meet the long-term stability requirements of external wall systems under complex climatic conditions.

[0006] Such filling materials have poor interfacial compatibility with light steel frames and steel mesh molds, and their coefficients of thermal expansion are mismatched. Under the influence of temperature cycling and humidity changes, they are prone to forming stress concentration areas, which can lead to wall cracking, hollowing, and even overall failure. Traditional cement-based foam materials generally suffer from defects such as uneven pore structure and weak pore walls during the preparation process, which restricts the synergistic improvement of their mechanical and durability properties.

[0007] Existing material systems exhibit a significant mismatch between their design lifespan and that of the main building structure. Traditional exterior wall insulation systems are typically designed for a service life of around 25 years, while the design lifespan of the main building structure is usually 50 years or even longer. This "weakest link" effect directly leads to large-scale repairs or replacements of the building envelope during its mid-life, increasing overall life-cycle maintenance costs and contradicting the fundamental principles of sustainable development in green building. While conventional silicate cement-based foamed concrete can achieve Class A fire resistance, it is prone to cracking and delamination at high temperatures, making it difficult to meet the higher requirements for fire-resistant exterior wall construction in high-rise buildings.

[0008] How to construct a new filling material system with high strength, low water absorption, low thermal conductivity, high durability and excellent fire resistance without sacrificing thermal insulation performance, and to achieve efficient synergy and interface stability between it and the light steel mesh structure, has become a key technical problem restricting the development of light steel mesh composite walls towards high performance and long service life. Summary of the Invention

[0009] This invention discloses a lightweight steel mesh composite wall for prefabricated buildings, its materials, and its preparation process. It solves the core technical problems of traditional lightweight steel mesh composite walls, which are prone to cracking, thermal insulation failure, interface debonding, and mismatch between the design life and the building structure due to the inherent performance defects of the filling materials (low strength, high water absorption, large shrinkage, and poor durability).

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A prefabricated light steel mesh composite wall for buildings comprises a light steel frame, a wire mesh shell, and a sulfur-oxygen-magnesium foam cement-based composite filler material inside the shell. The light steel frame is constructed of cold-formed thin-walled steel with a C- or U-shaped cross-section, a wall thickness of 1.2mm to 2.0mm, and a yield strength of not less than 235MPa. A vertical main keel is installed every 600mm along the longitudinal direction and is spatially constrained by transverse through-core tie rods connecting it to the wire mesh on both sides. The wire mesh is woven from cold-drawn low-carbon steel wire with a diameter of 2.0mm and a mesh size of 20mm × 20mm. The surface is hot-dip galvanized with a zinc coating of not less than 275g / m². The wire mesh is welded to the outside of the light steel frame, forming a closed permanent template structure. It is mechanically anchored to the light steel frame using self-tapping screws spaced 150mm apart to enhance overall load-bearing capacity.

[0012] The magnesium sulfate-oxygenated foamed cement-based composite filler material uses magnesium oxide (MgO), magnesium sulfate (MgSO4), and water (H2O) as the main reaction components, with a molar ratio of 7:1:20. The magnesium oxide used is light-calcined active magnesium oxide, with an active magnesium oxide content of not less than 85%, a loss on ignition of less than 6%, and a fineness of less than 5% residue on a 325-mesh sieve. The magnesium sulfate used is magnesium sulfate heptahydrate (MgSO4·7H2O), with a purity of not less than 98%, prepared as a solution with a Baume degree of 28° as the reaction liquid phase. The filler material also contains a composite modifier, which is added at 0.3% of the total amount of cementitious material. The composite modifier is uniformly mixed from polycarboxylate superplasticizer, silane coupling agent KH-560, nano silica and aluminum dihydrogen phosphate in a mass ratio of 3:1:1:0.5. The polycarboxylate superplasticizer has a solid content of 40% and a water reduction rate of not less than 25%. The nano silica has an average particle size of 15nm and a specific surface area of ​​200m² / g. The aluminum dihydrogen phosphate is in anhydrous state and the P / Al molar ratio is 1.0.

[0013] The filler material is further mixed with fly ash as a mineral admixture, with an admixture amount of 40% of the total mass of the cementitious material. The fly ash is Class F, Grade II fly ash, with a fineness (45μm sieve residue) of no more than 25%, a loss on ignition of less than 8%, a sulfur trioxide content of less than 3.5%, and a water requirement ratio of no more than 105%. The total mass of the cementitious material is composed of magnesium oxide, magnesium sulfate, and fly ash. Calculated on a dry basis, magnesium oxide accounts for 62.5% of the total cementitious material, magnesium sulfate accounts for 8.9%, and fly ash accounts for 28.6%. The water-cement ratio is controlled between 0.48 and 0.52. The total water consumption includes free water in the magnesium sulfate solution and a portion of the added water. The added water is deionized water with a conductivity of less than 100μS / cm.

[0014] The total amount of the cementitious material consists of magnesium oxide, magnesium sulfate and fly ash. Calculated on a dry basis, magnesium sulfate is calculated as the solid mass of magnesium sulfate heptahydrate, magnesium oxide accounts for 60%-65%, magnesium sulfate accounts for 8%-10%, and fly ash accounts for 27%-30%, with the sum of the percentages of each component being 100%.

[0015] The magnesium oxysulfate foam cement-based composite filler material introduces a porous structure through physical foaming. The foaming agent used is a protein-based foaming agent with a dilution ratio of 30 times, a foaming ratio controlled between 18 and 22, and a foam stabilization time of more than 60 minutes. The foaming process is completed in an independent foaming machine with a foaming pressure set at 0.6 MPa and a foam flow rate controlled at 8 L / min. The generated foam density is 40 kg / m³ ± 2 kg / m³, which is transported to the main mixer through a metering pump and mixed with the slurry at a volume ratio of 1:3.5. The main mixer is a twin-shaft forced mixer with a mixing speed set at 45 r / min and a mixing time of 180 seconds to ensure uniform foam dispersion and prevent foam breakage.

[0016] The preparation process of the filler material includes the following steps:

[0017] Magnesium oxide, fly ash, and composite modifier are added to a dry powder mixer according to the specified ratio and premixed for 120 seconds to form a uniform dry mixture.

[0018] Meanwhile, magnesium sulfate heptahydrate was dissolved in deionized water to prepare a solution with a Baumé degree of 28°, and the temperature was controlled at 25±2℃.

[0019] Inject the magnesium sulfate solution into the main mixer, start the mixer, then slowly add the dry mix and continue mixing for 90 seconds to form the matrix slurry;

[0020] Then, the pre-prepared foam is injected into the slurry at a constant flow rate, and stirring is continued for 90 seconds to obtain a magnesium oxysulfate foam cement slurry with good fluidity and no obvious bleeding or segregation.

[0021] After the slurry is discharged, it is immediately pumped into the mold with the light steel frame and wire mesh installed. The pouring process adopts a layered material distribution method, with the thickness of each layer controlled at 150mm and the interval between adjacent layers not exceeding 20 minutes to prevent the formation of cold joints.

[0022] The mold is a steel template with a polished inner surface coated with a water-based release agent. The release agent is made of paraffin emulsion and polyethylene glycol in a mass ratio of 4:1, and the coating thickness is 0.05 mm. After casting, the mold is placed in a curing kiln for early curing, which is divided into two stages.

[0023] The first stage is a static rest period, during which the ambient temperature is maintained at 30±2℃ and the relative humidity is not lower than 90%, lasting for 4 hours.

[0024] The second stage is heating and curing, where the temperature is raised to 50±2℃ at a rate of 2℃ per hour and kept constant for 12 hours, during which the relative humidity inside the kiln is controlled above 85%.

[0025] After curing, the specimens were allowed to cool naturally to room temperature. After demolding, the specimens were transferred to a standard curing room for continued curing for 28 days. The curing conditions were a temperature of 20±2℃ and a relative humidity of over 95%.

[0026] Furthermore, the interface area between the light steel frame and the wire mesh mold is provided with an interface reinforcement structure. Specifically, a 1.5mm thick interface modification coating is sprayed onto the inner side of the wire mesh. The coating is composed of water-based epoxy resin emulsion, silica fume, and chopped polypropylene fibers in a mass ratio of 6:3:1. The water-based epoxy resin emulsion has an epoxy equivalent of 190g / eq and a solid content of 45%. The silica fume has a specific surface area of ​​20000m² / kg and a SiO2 content of not less than 95%. The polypropylene fibers are 6mm long, 20μm in diameter, and are added at 0.3% of the dry basis mass of the coating. The coating is sprayed 2 hours before the filling material is poured, with a spraying pressure of 0.4MPa and a spray gun moving speed of 0.8m / s, forming a continuous and dense film layer. This effectively improves the bonding strength between the wire mesh and the magnesium sulfate foam cement. The measured interface bonding strength increased from 0.18MPa in the untreated state to 0.42MPa.

[0027] In a preferred embodiment of the present invention, a transverse reinforcing rib is provided every 1200mm along the height direction inside the light steel frame. The reinforcing rib is a 2.0mm thick Q235B steel plate with a width of 60mm. It is connected to the web plates on both sides by intermittent fillet welds with a weld length of 30mm and a spacing of 100mm, which is used to suppress local buckling caused by excessive slenderness ratio. At the same time, a folded edge structure is provided at the flange end of the light steel frame. The folded edge is 10mm wide and the fold angle is 90° to improve edge stiffness and prevent burn-through defects during the welding of the wire mesh.

[0028] Furthermore, the wire mesh mold has a flanged structure at the top and bottom edges of the wall. The flange width is 50mm, and the folding direction is towards the inside of the wall. The flanged part is fixed to the flange of the light steel frame by spot welding with a weld spacing of 100mm. This structure can effectively constrain the lateral flow of foamed cement slurry during the pouring process, reduce the risk of mold bulging, and provide an additional anchoring interface when connected with other components in the future.

[0029] To achieve efficient assembly of the wall modules, the lightweight steel mesh composite wall is pre-embedded with connectors during the factory prefabrication stage. Specifically, four sets of sleeve-type connectors are symmetrically installed at 150mm from the edge on both sides of the wall. The connectors are made of Q345 steel pipes with an outer diameter of 25mm, a wall thickness of 3mm, and a length of 120mm. The inner wall is tapped with M16 trapezoidal threads. The connectors are vertically embedded into the web of the lightweight steel frame and fixed by double-sided fillet welds with a weld leg size of 4mm. The connectors are positioned and installed before pouring, with the axial deviation controlled within ±2mm. The end face is flush with or slightly lower than the wire mesh by 1mm to avoid exposure and potential corrosion.

[0030] The wall assembly adopts dry connection technology. Adjacent wall units are connected to pre-embedded sleeves via high-strength bolts. The bolts are 8.8 grade galvanized high-strength bolts with a diameter of 16mm and a length of 200mm. The tightening torque is controlled at 180N·m. The joints are filled with flexible sealant, which is a modified silicone sealant with an elongation of not less than 400%, a tensile modulus of less than 0.4MPa at 23℃, and weather resistance that meets the requirements of GB / T14683-2017. An L-shaped metal cover plate is installed on the outside of the joint. The cover plate is made of 1.5mm thick aluminum alloy plate and is fixed to the surface of the wall on both sides with self-tapping screws. The coverage width on each side is not less than 50mm, forming a double waterproof barrier.

[0031] Furthermore, a micro-expansion mechanism is introduced into the sulfur-oxygen magnesium foam cement-based composite filler to compensate for drying shrinkage. Chemical expansion is achieved by adding aluminum dihydrogen phosphate to the composite modifier. It reacts with magnesium oxide to generate magnesium phosphate complex crystals, resulting in moderate volume expansion in the early stage of material hardening. The expansion rate is controlled between 0.05% and 0.10%.

[0032] The test method is based on the restricted expansion rate test device in GB / T23439-2017 "Concrete Expansion Agent". The specimen size is 40mm×40mm×160mm, and the constraint condition is a dial gauge with a steel frame. This micro-expansion effect effectively offsets the shrinkage stress caused by moisture evaporation in the material. The measured value of the 28-day drying shrinkage rate is 0.28mm / m, which is significantly lower than the level of more than 0.6mm / m of traditional foamed concrete, and greatly reduces the risk of wall cracking.

[0033] Scanning electron microscopy (SEM) analysis of the pore structure of the filling material revealed that the pores were spherical or nearly spherical, uniformly distributed, with pore sizes ranging from 0.1 mm to 1.0 mm, a porosity of approximately 58%, and an open porosity of less than 15%. The pore walls were dense, with numerous needle-like and plate-like hydration products of magnesium oxysulfate cement interwoven and growing, forming a three-dimensional network structure. Partial dissolution occurred on the surface of the fly ash particles, and they reacted with Mg²⁺. + and SO4² -Ionic reactions generate ettringite-like composite mineral phases, which further fill pores and improve the structure of the interfacial transition zone.

[0034] Furthermore, the silane coupling agent KH-560 in the composite modifier undergoes hydrolysis in an alkaline environment to generate silanol groups, which condense with the hydroxyl groups on the surface of magnesium oxide particles to form stable Si-O-Mg chemical bonds, thereby reducing the interfacial free energy, improving the fluidity of the slurry, and inhibiting early carbonization. At the same time, the polycarboxylate superplasticizer disperses the magnesium oxide particles through steric hindrance, preventing agglomeration, so that the initial fluidity of the slurry reaches 180 mm (measured by the slurry table method), and the expansion stabilization time is greater than 40 minutes, meeting the requirements of pumping and casting processes.

[0035] The overall thermal performance of the wall material was calculated by building thermal simulation, and the equivalent thermal conductivity was 0.21 W / (m·K). When the total wall thickness was 200 mm, the heat transfer coefficient K was 0.98 W / (m²·K), which meets the energy-saving design standard for exterior walls of residential buildings in cold regions. The fire resistance limit was determined by the standard fire resistance test (GB / T9978.1-2008) and reached 2.5 hours. During this period, the temperature rise on the unexposed surface did not exceed 140°C, and there were no through cracks, which meets the technical requirements for fire-resistant isolation strips on the exterior walls of high-rise buildings.

[0036] In another embodiment of the present invention, the filling material can partially replace the deionized water in the magnesium sulfate solution with fly ash extract, which is obtained by leaching fly ash in a sodium hydroxide solution at pH=12 for 24 hours and then filtering. This extract is rich in active Al³⁺. + With Si 4+ Ions can participate in the hydration reaction of the magnesium oxysulfate system to generate magnesium aluminosilicate gel phase, which further improves the later strength and durability of the material. The replacement ratio of this extract should be controlled within 15% of the total liquid phase. Exceeding this ratio will affect the slurry setting time and foam stability.

[0037] The wall preparation process also includes a quality monitoring stage. During the pouring process, an online density monitoring system is used. The online density monitoring system consists of a gamma ray densitometer and a PLC controller. The gamma source is a Cs-137 with an energy of 662keV. The detector is a NaI(Tl) scintillation counter. The sampling frequency is once every 10 seconds to monitor the slurry density fluctuation in real time. When it deviates from the target value by ±5%, an alarm is automatically triggered and pumping is suspended. At the same time, a wireless temperature and humidity sensor network is deployed in the curing kiln with a node spacing of 2m. The data is uploaded to the central control system to ensure that the curing procedure is strictly followed.

[0038] Furthermore, the light steel frame undergoes surface treatment before assembly, specifically by sandblasting to remove oxide scale and oil stains, achieving a surface cleanliness of Sa2.5 and a roughness of 40μm to 70μm. Subsequently, a 60μm thick layer of epoxy zinc-rich primer is sprayed, with a zinc powder content of not less than 70% and a zinc content of not less than 93% in the dry film, to enhance the bonding performance between the light steel frame and the filling material and provide long-term corrosion protection.

[0039] After welding, the wire mesh mold undergoes leveling treatment using a hydraulic leveling machine with multiple roller presses at a pressure of 8 MPa and a roller spacing of 2.2 mm to eliminate welding deformation and ensure the geometric accuracy of the mold shell. After leveling, the flatness error of the mold shell does not exceed 3 mm / m, and the diagonal difference is less than 5 mm, providing a foundation for subsequent precise casting.

[0040] The setting time of the magnesium sulfate foam cement-based composite filler is controlled by adjusting the concentration of magnesium sulfate solution and the ratio of composite modifier. The initial setting time is 110 minutes and the final setting time is 180 minutes, which meets the rhythm of industrial production line. The heat release during the setting process is mild, and the internal temperature rise peak does not exceed 45°C, effectively avoiding temperature cracks caused by excessive internal and external temperature differences.

[0041] Before leaving the factory, the wall structure undergoes structural performance testing. Non-destructive testing methods are used to evaluate the density of the filling material, specifically using an impact echo detector with an excitation frequency of 8kHz, a sensor center frequency of 15kHz, and a grid spacing of 500mm. When the wave velocity is below 3500m / s or obvious reflection anomalies occur, it is identified as a defective area, and a repair procedure is initiated. For local voids or honeycomb areas, pressure grouting is used for repair. The grouting material is low-viscosity epoxy resin with a viscosity of 250mPa·s and a curing time of 4 hours.

[0042] Furthermore, the composite filler material exhibits excellent anti-aging properties under long-term service conditions. In artificial accelerated aging tests (including 80 wet-dry cycles, 50 freeze-thaw cycles, and 120 days of ultraviolet irradiation), the compressive strength retention rate is not less than 90%, the water absorption rate increases by less than 3 percentage points, and no obvious powdering or peeling is observed, indicating that it has the potential for a 50-year design service life that matches the main building structure.

[0043] The wall material is suitable for non-load-bearing and partially load-bearing exterior walls in prefabricated concrete structures, steel structures, and hybrid structural systems, especially suitable for areas with seismic fortification intensity of 8 degrees and below; its standardized module size is 2.8m (height) × 3.0m (width) × 0.2m (thickness), and it weighs about 450kg, which is convenient for hoisting and transportation; the modules are quickly positioned and fastened through pre-embedded connectors, and the installation time of a single wall panel does not exceed 15 minutes, which significantly improves construction efficiency.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] This invention fundamentally alters the chemical composition and microstructure of the cementitious product by replacing the traditional silicate system with a magnesium oxysulfate cement-based cement. The needle-like crystals generated during hydration intertwine to form a dense three-dimensional network, providing a mechanical framework superior to amorphous gels. The introduction of a composite modifier, through the synergistic effect of its components at the molecular or nanoscale, achieves multiple objectives: particle dispersion, interfacial bonding, and pore refinement. The stable chemical bonds formed between the silane coupling agent KH-560 and the surface of magnesium oxide particles effectively reduce interfacial energy; while the controllable micro-expansion induced by aluminum dihydrogen phosphate actively counteracts the shrinkage stress caused by water evaporation.

[0046] At the structural performance level, this invention achieves synergy between the light steel frame, the wire mesh mold, and the sulfur-oxygen-magnesium foam cement-based composite filler material. The interface-modified coating in the interface-reinforced structure is not an isolated isolation layer, but rather a modulus transition zone constructed through the composite of water-based epoxy resin emulsion, silica fume, and chopped polypropylene fibers. This allows for smooth stress transfer between the wire mesh mold and the filler material, despite their significant stiffness differences. The flanged structure of the wire mesh mold and the folded structure of the light steel frame together constitute a three-dimensional spatial constraint on the filler material, transforming the composite material into a single, structurally sound composite wall unit.

[0047] From a manufacturing process perspective, this invention achieves an ideal pore structure with uniform pore size and high closed-cell rate by controlling the nucleation and growth kinetics of bubbles. The phased curing system is designed based on the hydration reaction kinetics of the magnesium oxysulfate system, guiding the stable growth of hydration products by controlling the temperature and humidity pathways within the curing kiln. This invention firmly integrates an intrinsically high-strength, low-shrinkage, high-temperature-resistant magnesium oxysulfate foam cement-based composite filler material with excellent compatibility with a metal skeleton with an optimized lightweight steel mesh structure, thereby endowing the composite wall with excellent structural efficiency, long-lasting thermal stability, reliable fire safety performance, and durability with the same lifespan as the main building structure at the system level. Attached Figure Description

[0048] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0049] Figure 1 This is a simplified flowchart of the preparation process of the composite wall material of the present invention.

[0050] Figure 2 This is a flowchart illustrating the preparation process of the composite wall material of the present invention. Detailed Implementation

[0051] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0052] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0053] Example 1: See Figure 1 and Figure 2 This embodiment discloses a lightweight steel mesh composite wall for prefabricated buildings, its materials, and preparation process. The main structure of the wall consists of three parts: a lightweight steel frame, a steel wire mesh shell, and a sulfur-oxygen-magnesium foam cement-based composite filler material. The lightweight steel frame, serving as the load-bearing frame, is formed from cold-formed thin-walled steel using specialized roller pressing equipment. Its cross-sectional shape is a standard C-shape or U-shape, with a flange width of 50mm, a web height of 198mm, and a wall thickness precisely controlled at 1.5mm. The steel used is Q235B grade carbon structural steel, with a measured yield strength of not less than 235MPa, a tensile strength between 375MPa and 500MPa, and an elongation of not less than 23%.

[0054] A vertical main keel is installed every 600mm along the longitudinal direction of the wall. This main keel runs through the entire height of the wall, typically 2.8m, with pre-reserved connection ends for anchoring to the floor slab or foundation components. Inside the light steel frame, a horizontal reinforcing rib is added every 1200mm along the height direction. This reinforcing rib is cut from 2.0mm thick Q235B steel plate, with a width of 60mm. It is welded to the web plates on both sides of the light steel frame via intermittent fillet welds. The weld length is 30mm, the center-to-center distance between adjacent welds is 100mm, and the weld leg size is 3mm, ensuring increased local stiffness without affecting overall welding deformation control. The flange ends of the light steel frame are equipped with a folded edge structure, with a fold width of 10mm and a 90° angle. After cold bending, this significantly improves the edge's resistance to local crushing and avoids burn-through caused by heat concentration during subsequent wire mesh welding.

[0055] The light steel frame requires surface pretreatment before assembly to enhance its adhesion to the filling material and provide long-term corrosion protection. The specific process is as follows:

[0056] The surface of light steel is cleaned using an automatic sandblasting device. The abrasive is cast steel shot with a particle size of 0.8mm to 1.2mm. The blasting pressure is 0.6MPa and the blasting angle is 75°. After treatment, the surface cleanliness reaches the Sa2.5 level specified in GB / T8923, which means that there is no visible grease, dirt, scale, rust and old coating on the steel surface. The residue is only manifested as slight shadows or spots.

[0057] The surface roughness, measured by a profilometer, ranged from 40μm to 70μm, meeting the coating adhesion requirements. Immediately after sandblasting, an epoxy zinc-rich primer was applied. This primer consisted of epoxy resin, zinc powder, curing agent, and thinner, with a zinc powder content of no less than 70%, a dry film zinc content of no less than 93%, and a film thickness controlled at 60μm. Airless spraying was used with a nozzle diameter of 0.48mm and a spraying pressure of 15MPa. After spraying, the film was allowed to dry naturally at room temperature for 2 hours, followed by curing in a drying oven at 80℃ for 4 hours to ensure complete cross-linking of the film.

[0058] The wire mesh is formed by bidirectional weaving of cold-drawn low-carbon steel wire with a diameter of 2.0mm. The mesh size is 20mm×20mm, the weaving method is orthogonal plain weave, the tensile strength of the steel wire is 550MPa, and the elongation is not less than 12%.

[0059] Before weaving, the steel wire undergoes hot-dip galvanizing. The zinc coating thickness is measured by weighing, with a measured value of no less than 275 g / m². The uniformity of the coating is verified by the copper salt accelerated galvanizing test (CASS), with no red rust appearing after 8 hours. The wire mesh is welded using an automated spot welding machine with a welding current of 8 kA, an energizing time of 0.2 seconds, a weld nugget diameter of 4.5 mm, and a shear strength of no less than 2.8 kN. The wire mesh is fixed to the outside of the light steel frame by spot welding, with the weld points spaced 150 mm apart in a staggered, quincunx pattern, and no fewer than 45 weld points per square meter.

[0060] Between the light steel frame and the wire mesh mold, self-tapping screws with a spacing of 150mm are used for mechanical anchoring. The screws are ST4.2×25, with a galvanized surface and a coating thickness of not less than 8μm. The screws penetrate the wire mesh and are screwed into the flange of the light steel frame. The tightening torque is controlled at 1.8N·m to ensure that a stable spatial cooperative force system is formed between the two.

[0061] The wire mesh formwork features flanged structures at the top and bottom edges of the wall. The flanges are 50mm wide and fold inwards towards the wall, bending 90° towards the infill material. These flanges are connected to the flanges of the light steel frame via spot welding, with weld points spaced 100mm apart and at least six weld points per flange. During pouring, the flanged structure effectively restricts the lateral flow of the foamed cement slurry, reducing the risk of formwork bulging. It also provides an additional anchoring interface when connecting to other structural components.

[0062] After welding, the wire mesh mold undergoes leveling. A hydraulic leveling machine is used for multiple rolling passes. The machine has 9 sets of working rollers, with the upper roller adjustable and the lower roller fixed. The leveling pressure is set to 8MPa, the roller spacing is adjusted to 2.2mm, and the feeding speed is 1.2m / min. After 5 passes of reciprocating leveling, the flatness error of the mold shell is detected by a laser flatness tester and does not exceed 3mm / m, with a diagonal difference of less than 5mm, meeting the requirements for high-precision casting.

[0063] An interface reinforcement structure is set on the inner side of the wire mesh, specifically by spraying a 1.5mm thick interface-modified coating. The interface-modified coating is composed of water-based epoxy resin emulsion, silica fume, and chopped polypropylene fibers in a mass ratio of 6:3:1. The water-based epoxy resin emulsion has an epoxy equivalent of 190g / eq, a solid content of 45%, a pH of 7.8, and a viscosity of 80mPa·s (25℃). The silica fume is metallurgical-grade microsilica powder with a specific surface area of ​​20000m² / kg, a SiO₂ content of 96.3%, and a bulk density of 220kg / m³. The polypropylene fibers are 6mm long, 20μm in diameter, have a tensile strength of 620MPa, an elastic modulus of 3.8GPa, and are added at 0.3% of the dry basis weight of the coating.

[0064] During coating preparation, the water-based epoxy resin emulsion was first diluted with deionized water at a mass ratio of 1:0.5. Then, silica fume was added and stirred for 10 minutes until no agglomeration occurred. Finally, polypropylene fibers were added and stirring continued for 5 minutes. Airless spraying equipment was used with a nozzle diameter of 1.8 mm, a spraying pressure of 0.4 MPa, a spray gun movement speed of 0.8 m / s, and an "S"-shaped cross-covering spray path to ensure a continuous and dense coating. Spraying was completed 2 hours before the filling material was poured. The ambient temperature was controlled between 20℃ and 28℃, and the relative humidity was below 70%. The surface drying time was 45 minutes, and the complete drying time was 6 hours. Actual measurements showed that the bond strength between the interface-modified coating and the wire mesh was 1.8 MPa, and the bond strength with the magnesium oxysulfate foam cement matrix increased from 0.18 MPa in the untreated state to 0.42 MPa. The microhardness of the interface transition zone increased by approximately 35%.

[0065] In this embodiment, the magnesium sulfate-oxygenated foam cement-based composite filler material uses magnesium oxide (MgO), magnesium sulfate (MgSO4), and water (H2O) as the main reaction components, with a strictly controlled molar ratio of 7:1:20. The magnesium oxide used is light-calcined active magnesium oxide, obtained from magnesite calcined at 750℃ to 900℃. The active magnesium oxide content, determined by EDTA titration, is 86.2%, the loss on ignition is 5.4%, and the fineness is 3.8% on a 325-mesh sieve. The magnesium sulfate used is industrial-grade heptahydrate magnesium sulfate (MgSO4·7H2O) with a purity of 98.5% and a total heavy metal content (Pb, As, Cd) of less than 10 mg / kg. It is prepared as a reaction liquid phase with a Baume degree of 28°. During preparation, 100 kg of heptahydrate magnesium sulfate is dissolved in 180 L of deionized water and stirred for 30 minutes until completely dissolved. The solution temperature is maintained at 25±2℃, and the conductivity is 48 mS / cm. The total amount of cementitious material consists of magnesium oxide, magnesium sulfate, and fly ash. Calculated on a dry basis, magnesium oxide accounts for 62.5% of the total cementitious material, magnesium sulfate accounts for 8.9%, and fly ash accounts for 28.6%. The fly ash selected is Class F, Grade II fly ash, sourced from the electrostatic precipitator system of a coal-fired power plant. Its fineness (45μm sieve residue) is 22.3%, loss on ignition is 6.7%, sulfur trioxide content is 2.8%, water requirement ratio is 103%, and glass content is not less than 75%.

[0066] The composite modifier, at a dosage of 0.3% of the total cementitious material, is a homogeneous mixture of polycarboxylate superplasticizer, silane coupling agent KH-560, nano-silica, and aluminum dihydrogen phosphate in a mass ratio of 3:1:1:0.5. The polycarboxylate superplasticizer is a copolymer of methacrylic acid and polyethylene glycol monomethyl ether ester, with a solid content of 40.2%, a water reduction rate of 26.5%, and a pH of 6.8. The silane coupling agent KH-560 is γ-glycidoxypropyltrimethoxysilane with a purity of not less than 97%. The nano-silica is produced by a gas-phase method, with an average particle size of 15 nm, a specific surface area of ​​202 m² / g, and a SiO₂ content of 99.8%. The aluminum dihydrogen phosphate is in anhydrous form, with a P / Al molar ratio of 1.0, a density of 2.4 g / cm³, and exhibits weak acidity when dissolved in water. Before use, the composite modifier is mixed for 30 minutes in a planetary mixer at a speed of 30 r / min to ensure that the components are evenly distributed.

[0067] The water-cement ratio is controlled between 0.48 and 0.52. The total water consumption includes free water from the magnesium sulfate solution and a portion of the added water. The added water is deionized water with a conductivity below 85 μS / cm and a pH of 6.5. In the actual formulation, the raw materials required per cubic meter of filler material are as follows: 386 kg of magnesium oxide, 55 kg of magnesium sulfate heptahydrate, 177 kg of fly ash, 1.8 kg of composite modifier, 192 kg of added water, and a foam volume of 350 L.

[0068] The foaming agent is a protein-based foaming agent made from animal keratin hydrolysate. The dilution ratio is 30 times, that is, 1 part foaming agent to 29 parts deionized water. The foaming ratio is controlled between 18 and 22. The foaming time is determined to be 68 minutes by sedimentation method.

[0069] The foaming process is completed in an independent foaming machine, which is a plunger-type high-pressure foaming machine. The foaming pressure is set to 0.6MPa, the foam flow rate is controlled at 8L / min, and the generated foam density is 40kg / m³ with a deviation of ±1.8kg / m³. The foam is then transported to the main mixer via a metering pump and mixed with the slurry at a volume ratio of 1:3.5.

[0070] The main mixer is a twin-shaft forced mixer with a nominal capacity of 1.5m³, a mixing shaft speed of 45r / min, a mixing arm linear velocity of 1.2m / s, and a mixing time of 180 seconds.

[0071] The preparation process of the filler material is as follows:

[0072] Magnesium oxide, fly ash, and composite modifier were added to a dry powder mixer according to the specified ratio. The dry powder mixer was a vertical conical ribbon mixer with a premixing time of 120 seconds and a mixing uniformity variation coefficient of less than 3%. At the same time, magnesium sulfate heptahydrate was dissolved in deionized water to prepare a solution with a Baume degree of 28° and the temperature was controlled at 25±2℃.

[0073] Magnesium sulfate solution was injected into the main mixer, and stirring was started. Dry mix was then slowly added at a rate of 0.5 m³ / min, and stirring continued for 90 seconds to form the matrix slurry. The initial flowability of the slurry was determined using the table runner method, with a measured value of 182 mm and an expansion of 310 mm. After 30 minutes, the expansion retention rate was 92%. Then, pre-prepared foam was injected into the slurry at a constant flow rate. The foam delivery pipe had an inner diameter of 50 mm, a flow rate of 1.2 m / s, and an injection time of 60 seconds. Stirring continued for another 90 seconds, resulting in a magnesium sulfate-oxygenated foamed cement slurry with good flowability and no obvious bleeding or segregation. The wet density of the slurry was 820 kg / m³, and the air content was 58.3%. After discharge, it was immediately pumped to a mold with a light steel frame and wire mesh installed.

[0074] The mold is a steel template made of Q345B steel plate with a thickness of 12mm. The inner surface is polished by CNC grinding machine with a surface roughness Ra≤1.6μm and coated with water-based release agent.

[0075] The release agent is prepared by mixing paraffin emulsion and polyethylene glycol in a mass ratio of 4:1. The solid content of the paraffin emulsion is 25%, and the molecular weight of the polyethylene glycol is 4000. After mixing, the mixture is stirred for 15 minutes. The coating is applied by an automatic spraying robot with a nozzle diameter of 1.0 mm and a spraying pressure of 0.3 MPa. The coating thickness is measured to be 0.05 mm by a coating thickness gauge. After drying, a uniform release film is formed.

[0076] The pouring process employs a layered material distribution method, with each layer controlled to a thickness of 150mm and a distribution speed of 0.8m³ / min. The interval between adjacent layers should not exceed 18 minutes to prevent cold joints from forming. After the material distribution is completed, a vibrator is used for auxiliary compaction, with a vibration frequency of 120Hz, an amplitude of 1.2mm, an insertion spacing of 500mm, and a vibration time of 15 seconds at each point.

[0077] After casting, the mold was placed in a curing kiln for early curing. The curing kiln was a sealed, temperature- and humidity-controlled space with a volume of 12m × 3m × 2.5m, equipped with a steam heating system and an ultrasonic humidifier. The curing regime consisted of two phases: the first phase was a static rest period, where the ambient temperature was maintained at 30±2℃ and the relative humidity was not lower than 90%, lasting for 4 hours, during which no temperature adjustment was performed; the second phase was a temperature-increasing curing period, where the temperature was increased to 50±2℃ at a rate of 2℃ per hour and maintained at a constant temperature for 12 hours. During this period, the relative humidity inside the kiln was controlled by a humidity sensor and remained above 85%. The temperature gradient during the heating process was verified by multiple temperature measurements, with a vertical temperature difference of less than 3℃ and a horizontal temperature difference of less than 2℃. After curing, the mold was allowed to cool naturally to room temperature at a rate controlled within 3℃ per hour. After demolding, the specimens were transferred to a standard curing room for continued curing for 28 days, under curing conditions of 20±2℃ and a relative humidity above 95%.

[0078] Full-process quality monitoring is implemented during the pouring process. An online density monitoring system is used to monitor the density fluctuation of the slurry in real time. The online density monitoring system consists of a gamma ray densitometer and a PLC controller. The gamma source is Cs-137 with an energy of 662keV and an activity of 10mCi. The detector is a NaI(Tl) scintillation counter with a measurement accuracy of ±0.5% and a sampling frequency of once every 10 seconds.

[0079] When the slurry density deviates from the target value by ±5%, the system automatically triggers an audible and visual alarm and suspends pumping. Operators must immediately check the foaming volume or mixing ratio parameters. Simultaneously, a wireless temperature and humidity sensor network is deployed inside the curing kiln, with 16 nodes spaced 2 meters apart. Data is uploaded to the central control system via the ZigBee protocol and stored for 30 days to ensure strict adherence to the curing procedures.

[0080] The wall structure undergoes structural performance testing before leaving the factory. Non-destructive testing methods are used to assess the density of the filling material, employing an impact-echo analyzer with an excitation frequency of 8kHz, a sensor center frequency of 15kHz, and a grid spacing of 500mm. The acquired signals are analyzed using FFT transformation; areas with a P-wave velocity below 3500m / s or exhibiting significant reflection anomalies are identified as defective. For localized voids or honeycomb areas, pressure grouting is used for repair. The grouting material is low-viscosity epoxy resin with a viscosity of 250mPa·s, a pot life of 90 minutes, a curing time of 4 hours, and a grouting pressure of 0.3MPa, continuing until the grout overflows from the vent holes.

[0081] The wall is prefabricated in the factory with embedded connectors. Four sets of sleeve-type embedded connectors are symmetrically installed at 150mm from the edge on both sides of the wall. The embedded connectors are made of Q345 steel pipe with an outer diameter of 25mm, a wall thickness of 3mm, a length of 120mm, and an M16 trapezoidal thread tapped on the inner wall with a pitch of 2mm and a thread angle of 30°.

[0082] The embedded parts are vertically embedded into the web of the light steel frame and fixed by double-sided fillet welds with a weld leg size of 4mm and a weld length of 50mm. Before pouring, the embedded parts are installed using a special positioning fixture, and the axial deviation is controlled within ±1.8mm by laser alignment. The end face is flush with or slightly lower than the wire mesh by 0.8mm to avoid exposure and potential corrosion.

[0083] The on-site assembly of the wall adopts dry connection technology. Adjacent wall units are connected to pre-embedded sleeves via high-strength bolts. The bolts are 8.8 grade galvanized high-strength bolts with a diameter of 16mm, a length of 200mm, a thread length of 60mm, and a galvanized layer thickness of 45μm. The tightening torque is controlled at 180N·m and is checked using a torque wrench, with one bolt randomly inspected out of every 10 bolts. The joints are filled with flexible sealant, which is a modified silicone sealant with a sag (vertical direction) of 0mm, an extrusion rate of 85mL / min, a measured elongation of 420%, and a tensile modulus of 0.38MPa at 23℃. After artificial climate aging test (1000 hours of xenon lamp irradiation), the performance retention rate is not less than 85%, meeting the requirements of GB / T14683-2017. An L-shaped metal cover plate is installed on the outside of the joint. The cover plate is made of 1.5mm thick 6063-T5 aluminum alloy plate, bent and anodized with a film thickness of 15μm. It is fixed to the surface of the wall on both sides with M6 self-tapping screws with a screw spacing of 300mm. The coverage width is not less than 52mm on each side, forming a double waterproof barrier.

[0084] To further compensate for drying shrinkage, aluminum dihydrogen phosphate in the composite modifier reacts with magnesium oxide in an alkaline environment to form magnesium phosphate complex crystals (MgHPO4·3H2O), resulting in moderate volume expansion during the initial hardening stage of the material. The expansion rate was determined using a limited expansion rate test apparatus as specified in GB / T23439-2017. The specimen dimensions were 40mm×40mm×160mm, placed in a steel frame, with dial gauges fixed at both ends. After measuring the initial length, the specimen was placed in a constant temperature and humidity chamber (20±2℃, 60%RH) for curing. The expansion rate was measured to be 0.082% on day 7 and stabilized at 0.091% after 28 days. The drying shrinkage rate measured at the same time was 0.28mm / m, significantly lower than the 0.62mm / m of traditional foamed concrete. Scanning electron microscopy (SEM) analysis of the pore structure revealed that the pores were spherical or nearly spherical, uniformly distributed, with pore sizes ranging from 0.1 mm to 1.0 mm, a porosity of approximately 58%, and an open porosity of 14.7% as determined by mercury porosimetry. The pore walls were dense, and numerous needle-like and plate-like hydration products of magnesium oxysulfate cement were observed to interweave and grow, forming a three-dimensional network structure.

[0085] To facilitate a better understanding of the present invention by those skilled in the art, a specific example and comparative example are provided below to further illustrate the present invention.

[0086] A lightweight steel mesh composite wall module measuring 2.8m × 3.0m × 0.2m was prepared. The lightweight steel frame used C-shaped steel with a wall thickness of 1.5mm, vertical main keel spacing of 600mm, and horizontal reinforcing ribs spaced 1200mm apart. The wire mesh mold had a diameter of 2.0mm, mesh size of 20mm × 20mm, and a hot-dip galvanized layer of 280g / m², which was leveled after welding. A 1.5mm thick interface-modified coating was applied. The filler material composition was as follows: magnesium oxide 386kg / m³, magnesium sulfate heptahydrate 55kg / m³, fly ash 177kg / m³, composite modifier 1.8kg / m³, added water 192kg / m³, foam density 40kg / m³, and a volume ratio of 1:3.5. The pouring was done in three layers, each 150mm thick, and the curing regime was as described above. Performance was tested after 28 days.

[0087] The composite wall constructed in this embodiment breaks through the limitations of traditional silicate cement-based systems. It applies a magnesium sulfate-oxygen foam cement system to a light steel mesh wall and solves the contradiction between strength, shrinkage, and durability through precise control of the molar ratio of magnesium oxide-magnesium sulfate-water and the synergistic effect of the composite modifier at the molecular / nanoscale. The needle-like 5Mg(OH)2·MgSO4·7H2O phase crystals generated by hydration intertwine to form a dense three-dimensional network, providing a mechanical framework that surpasses amorphous gels. The precise chemical micro-expansion (0.04%-0.12%) induced by aluminum dihydrogen phosphate actively offsets the drying shrinkage stress, reducing the 28-day shrinkage rate to below 0.28 mm / m. The silane coupling agent achieves excellent dispersion and interfacial strengthening of cementitious particles by forming strong Si-O-Mg chemical bonds.

[0088] At the structural level, an integrated system of "rigid skeleton - flexible interface - three-dimensional constraint" was designed: the light steel skeleton and transverse ribs provide the main load-bearing capacity, the folded edge of the wire mesh mold and the folded edge of the skeleton together constitute the spatial constraint on the filling material, and the water-based epoxy interface coating serves as a carefully designed modulus transition zone, smoothly transferring the stress between the wire mesh and foamed cement with huge stiffness differences.

[0089] This invention achieves a combination of lightweight and high strength, micro-expansion and crack resistance, low thermal conductivity and high durability through the deep integration of material intrinsic property innovation and structural interface co-design, thus achieving the design goal of having the same lifespan as the main building structure.

[0090] Comparative Example 1: Ordinary silicate cement foamed concrete was used as the filler material with a density of 850 kg / m³. The mix proportion was 350 kg / m³ of cement, 100 kg / m³ of fly ash, 0.8 kg / m³ of foaming agent, and a water-cement ratio of 0.50. The rest of the structure was the same.

[0091] The performance comparison data is shown in Table 1 below. Each performance indicator was tested using conventional methods in existing technologies. The specific test steps are not detailed here.

[0092] Table 1:

[0093] Performance indicators Example 1 Comparative Example 1 Dry density (kg / m³) 820 850 Compressive strength (MPa) 6.34 4.12 Thermal conductivity W / (m·K) 0.187 0.245 Volumetric water absorption rate (%) 8.7 18.3 Softening coefficient 0.89 0.72 Strength loss rate (%) after 25 freeze-thaw cycles 14.3 29.6 Drying shrinkage rate (mm / m) 0.28 0.62 Combustion performance rating A1 level A2 level Fire resistance rating (h) 2.5 1.8 28-day interfacial bond strength (MPa) 0.42 0.26

[0094] The setting time of the magnesium sulfate-oxygenated foamed cement-based composite filler is controlled by adjusting the concentration of magnesium sulfate solution and the ratio of the composite modifier. The initial setting time is 112 minutes, and the final setting time is 178 minutes, which meets the rhythm of industrial production lines. The heat release during the setting process is mild, and the peak internal temperature rise, as measured by an embedded thermocouple, is 43.6℃. The internal and external temperature difference is less than 15℃, effectively avoiding temperature cracks.

[0095] Under long-term service conditions, the wall material exhibited excellent anti-aging properties. In artificial accelerated aging tests, including 80 wet-dry cycles (immersion in water for 4 hours, drying for 8 hours), 50 freeze-thaw cycles (-20℃ to 20℃), and 120 days of ultraviolet irradiation (irradiance 0.68W / m², wavelength 290nm~400nm), the compressive strength retention rate of the specimens in the example was 91.3%, and the water absorption rate increased from 8.7% to 10.9%, an increase of 2.2 percentage points, with no obvious powdering or peeling observed. Based on the linear extrapolation method, its strength decay rate is less than 0.05MPa / year, possessing the potential for a 50-year design service life matching the main building structure.

[0096] The overall thermal performance of the wall was calculated using building thermal simulation, with an equivalent thermal conductivity of 0.21 W / (m·K). When the total wall thickness is 200 mm, the heat transfer coefficient K is 0.98 W / (m²·K), meeting the requirements for exterior walls in the "Energy-Saving Design Standard for Residential Buildings in Severe Cold and Cold Regions" (JGJ26-2018). The airborne sound insulation was measured in the laboratory to be 48 dB, meeting the sound insulation requirements for exterior walls of residential buildings.

[0097] Example 2:

[0098] This embodiment is an optional embodiment, in which the deionized water in the magnesium sulfate solution can be partially replaced by fly ash extract in the filling material. The extract is obtained by soaking fly ash in a sodium hydroxide solution (pH=12, concentration 0.5mol / L) for 24 hours and then filtering. The filtrate contains Al 3+ The concentration is 1.2 g / L, Si 4+ The concentration is 0.8 g / L. The extract is used to replace 12% of the total liquid phase, while the other proportions remain unchanged.

[0099] Tests showed that the material's 28-day compressive strength increased to 6.61 MPa under this scheme, with a later strength growth rate of about 8%. However, the setting time was extended to 135 minutes for initial setting, and the foam stability decreased slightly. Therefore, the replacement ratio should be controlled within 15%.

[0100] The wall material described is suitable for non-load-bearing and partially load-bearing exterior walls in prefabricated concrete structures, steel structures, and hybrid structural systems, especially suitable for areas with seismic fortification intensity of 8 degrees and below. The standardized module dimensions are 2.8m (height) × 3.0m (width) × 0.2m (thickness), weighing approximately 450kg. Lifting is achieved using a specialized vacuum suction cup lifting device with 8 suction cups and a negative pressure of -80kPa. The average installation time for a single wall panel is 13.5 minutes, significantly improving construction efficiency.

[0101] The sulfur-oxygen-magnesium foamed cement-based composite filler material achieved stable performance indicators at 28 days of age: dry density of 820 kg / m³, with an allowable deviation of ±30 kg / m³; measured compressive strength of 6.34 MPa, with a minimum value of not less than 5.8 MPa for a single specimen; thermal conductivity of 0.187 W / (m·K), tested according to GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method"; and volumetric water absorption of 8.7%, according to GB / T5486-2008. The softening coefficient was determined by the drying-immersion-weighing method in the "Test Methods for Inorganic Rigid Thermal Insulation Products". The mass loss rate after freeze-thaw cycles (25 times) was 2.1%, and the strength loss rate was 14.3%. The combustion performance was tested by the National Fireproof Building Materials Quality Supervision and Inspection Center and met the requirements of Class A1 non-combustible materials in GB8624-2012 "Classification of Combustion Performance of Building Materials and Products". It showed no open flame, no dripping, and no structural damage after continuous burning at 1000℃ for 180 minutes, and the high-temperature residual strength retention rate was greater than 75%.

[0102] Example 3: This example is basically the same as Example 1, except for the material ratio and specifications, as follows:

[0103] The magnesium sulfate-oxygenated foamed cement-based composite filler material uses magnesium oxide, magnesium sulfate, and water as the main reactive components, with a molar ratio of 6.5:0.9:19. The magnesium oxide used is lightly calcined active magnesium oxide, with an active magnesium oxide content of 83%, a loss on ignition of 4%, and a fineness index of 3% residue on a 325-mesh sieve.

[0104] Magnesium sulfate heptahydrate with a purity of 96% is used, prepared as a solution with a Baume degree of 27. Specifically, 100 kg of magnesium sulfate heptahydrate is dissolved in 185 liters of deionized water, and the solution temperature is controlled at 23°C. The fly ash content is 38% of the total mass of the cementitious materials. The fly ash specification is Class F, Grade II, with a fineness index of 20%, loss on ignition of 5%, sulfur trioxide content of 2.5%, and a water requirement ratio of 100%. The composition of the cementitious materials, calculated on a dry basis, consists of 60% magnesium oxide, 8% magnesium sulfate, and 27% fly ash. The water-cement ratio is controlled at 0.46.

[0105] The composite modifier, at a dosage of 0.25% of the total cementitious material, is a homogeneous mixture of polycarboxylate superplasticizer, silane coupling agent KH-560, nano-silica, and aluminum dihydrogen phosphate in a mass ratio of 2.5:0.8:0.8:0.4. The polycarboxylate superplasticizer has a solid content of 38% and a water reduction rate of 25%; the nano-silica has an average particle size of 13 nanometers and a specific surface area of ​​180 square meters per gram; and the aluminum dihydrogen phosphate has a phosphorus-to-aluminum molar ratio of 0.9.

[0106] Regarding structural parameters:

[0107] The light steel frame is constructed of cold-formed thin-walled C-shaped steel with a wall thickness of 1.1mm and a yield strength of 230MPa. The vertical main keel spacing is 550mm. The wire mesh is woven from cold-drawn low-carbon steel wire with a wire diameter of 1.8mm and a mesh size of 18mm x 18mm. It is hot-dip galvanized with a zinc coating of 270 grams per square meter. The wire mesh is fixed to the light steel frame by spot welding and self-tapping screws, with the self-tapping screws spaced 140mm apart. The flange structure is 45mm wide with a weld spacing of 90mm. The transverse reinforcing ribs are spaced 1100mm apart, with a rib thickness of 1.8mm and a width of 55mm, connected by intermittent fillet welds with a weld length of 25mm and a spacing of 90mm. The folded edge structure is 8mm wide with an 85-degree fold angle.

[0108] The interface reinforcement structure specifically involves spraying an interface-modified coating onto the inner side of the wire mesh mold. The coating thickness is 1.2 mm, and it is composed of water-based epoxy resin emulsion, silica fume, and chopped polypropylene fibers in a mass ratio of 5.5:2.5:0.8. The water-based epoxy resin emulsion has an epoxy equivalent of 185 g / kg and a solid content of 43%; the silica fume has a specific surface area of ​​18000 m² / kg and a silica content of 95%; the chopped polypropylene fibers are 5 mm long, 18 micrometers in diameter, and are added at 0.25% of the dry basis weight of the coating. The spraying operation is completed one hour before the filling material is poured, with a spraying pressure of 0.3 MPa and a spray gun movement speed of 0.7 m / s.

[0109] The preparation process includes the following steps: First, magnesium oxide, fly ash, and composite modifier are added to a dry powder mixer and premixed for 110 seconds to form a dry mixture. Then, magnesium sulfate solution is injected into a twin-shaft forced mixer, the dry mixture is added, and the mixture is stirred for 80 seconds to form a matrix slurry. A protein foaming agent is diluted 28 times and foamed in a foaming machine at a pressure of 0.5 MPa with a flow rate of 7 L / min, resulting in a foam density of 38 kg / m³. The foam is injected into the slurry at a volume ratio of 1:3.3 and stirred for another 170 seconds at a stirring speed of 40 rpm. The slurry is then pumped to a mold using a layered distribution method, with each layer being 140 mm thick and spaced 15 minutes apart.

[0110] The maintenance system is divided into two phases:

[0111] The first stage is a static curing period, with an ambient temperature of 28℃ and a relative humidity of over 90%, lasting for 3.5 hours. The second stage is a temperature-increasing curing period, with the temperature increased to 48℃ at a rate of 1.5℃ per hour, and then maintained at a constant temperature for 11 hours, during which the relative humidity inside the kiln is above 85%. After demolding, the specimens are transferred to a standard curing room for continued curing for 28 days.

[0112] Quality monitoring employs an online density monitoring system using a cesium-137 gamma source, with a sampling frequency of 5 seconds per sample, to monitor slurry density fluctuations in real time. Simultaneously, a non-destructive testing method is used with an impact echo detector, a grid spacing of 450 mm, and a wave velocity threshold of 3400 m / s.

[0113] The wall material prepared in this embodiment has the following 28-day performance indicators after testing:

[0114] It has a dry density of 800 kg / m³, a compressive strength of 5.8 MPa, a thermal conductivity of 0.195 W / (m·K), a volumetric water absorption rate of 9.5%, a drying shrinkage rate of 0.35 mm per meter, and an interfacial bond strength of 0.38 MPa. All performance indicators meet the requirements of relevant national standards and are significantly superior to traditional foamed concrete materials.

[0115] Example 4: This example is basically the same as Example 1, except for the material ratio and specifications, as follows:

[0116] Regarding material proportions and specifications:

[0117] Magnesium oxysulfate foamed cement-based composite filler material uses magnesium oxide, magnesium sulfate, and water as the main reactive components, with a molar ratio of 7.5:1.1:21. The magnesium oxide used is light-burned active magnesium oxide, with an active magnesium oxide content of 87%, a loss on ignition of 6%, and a fineness index of 7% residue on a 325-mesh sieve. The magnesium sulfate used is heptahydrate magnesium sulfate, 100% pure, prepared as a solution with a Baume degree of 29. Specifically, 100 kg of heptahydrate magnesium sulfate is dissolved in 175 liters of deionized water, and the solution temperature is controlled at 27℃. The fly ash content is 42% of the total mass of the cementitious material. The fly ash specification is Class F, Grade II, with a fineness index of 25%, a loss on ignition of 8%, a sulfur trioxide content of 3.5%, and a water requirement ratio of 105%. The cementitious material composition, calculated on a dry basis, consists of 65% magnesium oxide, 10% magnesium sulfate, and 30% fly ash. The water-cement ratio is controlled at 0.54.

[0118] The composite modifier, at a dosage of 0.35% of the total cementitious material, is a homogeneous mixture of polycarboxylate superplasticizer, silane coupling agent KH-560, nano-silica, and aluminum dihydrogen phosphate in a mass ratio of 3.5:1.2:1.2:0.6. The polycarboxylate superplasticizer has a solid content of 42% and a water reduction rate of 30%; the nano-silica has an average particle size of 17 nanometers and a specific surface area of ​​220 square meters per gram; and the aluminum dihydrogen phosphate has a phosphorus-aluminum molar ratio of 1.1.

[0119] In terms of structural parameters, the light steel frame is constructed of cold-formed thin-walled U-shaped steel with a wall thickness of 2.1mm and a yield strength of 300MPa. The vertical main keel spacing is 650mm. The wire mesh is woven from cold-drawn low-carbon steel wire with a wire diameter of 2.2mm and a mesh size of 22mm x 22mm. It is hot-dip galvanized with a zinc coating of 300 grams per square meter. The wire mesh is fixed to the light steel frame by spot welding and self-tapping screws with a self-tapping screw spacing of 160mm. The flange structure is 55mm wide with a weld point spacing of 110mm. The transverse reinforcing ribs are spaced 1300mm apart, with a rib thickness of 2.2mm and a width of 65mm, connected by intermittent fillet welds with a weld length of 35mm and a spacing of 110mm. The folded edge structure is 12mm wide with a fold angle of 95 degrees.

[0120] The interface reinforcement structure specifically involves spraying an interface-modified coating onto the inner side of the wire mesh mold. The coating thickness is 1.8 mm, and it is composed of water-based epoxy resin emulsion, silica fume, and chopped polypropylene fibers in a mass ratio of 6.5:3.5:1.2. The water-based epoxy resin emulsion has an epoxy equivalent of 195 g / kg and a solid content of 47%; the silica fume has a specific surface area of ​​22,000 m² / kg and a silica content of 97%; the chopped polypropylene fibers are 7 mm long, 22 micrometers in diameter, and are added at 0.35% of the dry basis weight of the coating. The spraying operation is completed 3 hours before the filling material is poured, with a spraying pressure of 0.5 MPa and a spray gun movement speed of 0.9 m / s.

[0121] The preparation process includes the following steps: First, magnesium oxide, fly ash, and composite modifier are added to a dry powder mixer and premixed for 130 seconds to form a dry mixture. Then, magnesium sulfate solution is injected into a twin-shaft forced mixer, the dry mixture is added, and the mixture is stirred for 100 seconds to form a matrix slurry. A protein foaming agent is diluted 32 times and foamed in a foaming machine at a pressure of 0.7 MPa, with a foam flow rate of 9 L / min, resulting in a foam density of 42 kg / m³. The foam is injected into the slurry at a volume ratio of 1:3.7, and stirring continues for 190 seconds at a stirring speed of 50 rpm. The slurry is then pumped to a mold using a layered distribution method, with each layer being 160 mm thick and spaced 25 minutes apart.

[0122] The curing process consisted of two phases: the first phase was a static curing period with an ambient temperature of 32℃ and a relative humidity of over 90%, lasting for 4.5 hours; the second phase was a temperature-increasing curing period, with the temperature increased to 52℃ at a rate of 2.5℃ per hour, and then maintained at a constant temperature for 13 hours, during which the relative humidity inside the kiln was above 85%. After demolding, the specimens were transferred to a standard curing room for continued curing for 28 days.

[0123] Quality monitoring employs an online density monitoring system using a cesium-137 gamma source, with a sampling frequency of 15 seconds per sample, to monitor slurry density fluctuations in real time. Simultaneously, a non-destructive testing method is used with an impact echo detector, a grid spacing of 550 mm, and a wave velocity threshold of 3600 m / s.

[0124] The wall material prepared in this embodiment has the following 28-day performance indicators after testing:

[0125] Dry density 840 kg / m³, compressive strength 6.8 MPa, thermal conductivity 0.179 W / (m·K), volumetric water absorption 8.0%, drying shrinkage 0.25 mm per meter, interfacial bond strength 0.45 MPa.

[0126] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lightweight steel mesh composite wall material for prefabricated buildings, characterized in that: The composite wall material is a magnesium sulfate-oxygenated foamed cement-based composite filler, comprising magnesium oxide, magnesium sulfate, and water, with a molar ratio of 6.5-7.5:0.9-1.1:19-21. The magnesium oxide is light-calcined active magnesium oxide, with an active magnesium oxide content of 83%-87%, a loss on ignition of 4%-6%, and a fineness of 325 mesh with a residue of 3%-7%. Magnesium sulfate is magnesium sulfate heptahydrate with a purity of 96%-100%, and is prepared as a reaction liquid phase with a Baumé degree of 27°-29°. The total amount of cementitious material consists of magnesium oxide, magnesium sulfate, and fly ash. Calculated by dry basis weight, magnesium oxide accounts for 60%-65%, magnesium sulfate accounts for 8%-10%, and fly ash accounts for 27%-30%. The water-cement ratio is controlled between 0.46 and 0.

54. The fly ash is classified as Class F, Grade II fly ash, with a fineness of 20%-25%, a loss on ignition of 5%-8%, a sulfur trioxide content of 2.5%-3.5%, and a water requirement ratio of 100%-105%. The magnesium oxysulfate foamed cement-based composite filler material also contains a composite modifier, with a dosage of 0.25%-0.35% of the total cementitious material. The composite modifier is uniformly mixed from polycarboxylate superplasticizer, silane coupling agent KH-560, nano silica, and aluminum dihydrogen phosphate in a mass ratio of 2.5-3.5:0.8-1.2:0.8-1.2:0.4-0.

6. The polycarboxylate superplasticizer has a solid content of 38%-42% and a water reduction rate of 25%-30%. The nano silica has an average particle size of 13-17 nm and a specific surface area of ​​180-220 m² / g. The aluminum dihydrogen phosphate is in an anhydrous state with a P / Al molar ratio of 0.9-1.

1. The sulfur-oxygen magnesium foam cement-based composite filler material introduces a porous structure through physical foaming. The foaming agent used is a protein-based foaming agent, which is diluted 28-32 times. It is foamed in an independent foaming machine at a pressure of 0.5-0.7MPa, with the foam flow rate controlled at 7-9L / min, generating foam with a density of 38-42kg / m³.

2. The prefabricated building light steel mesh composite wall material according to claim 1, characterized in that: The aluminum dihydrogen phosphate in the composite modifier reacts with magnesium oxide in the early stage of material hardening to form magnesium phosphate complex crystals, resulting in chemical micro-expansion. The expansion rate is limited to between 0.04% and 0.12% to compensate for drying shrinkage. The measured value of the drying shrinkage rate after 28 days is no higher than 0.35 mm / m.

3. A lightweight steel mesh composite wall for prefabricated buildings, characterized in that: The system includes a light steel frame, a wire mesh mold, and a magnesium oxysulfate foam cement-based composite filler material filled inside the mold shell; the magnesium oxysulfate foam cement-based composite filler material is the light steel mesh composite wall material for prefabricated buildings as described in any one of claims 1-2; wherein, the light steel frame is composed of cold-formed thin-walled steel with a C-shaped or U-shaped cross-section, and a vertical main keel is set every 550-650mm along the longitudinal direction, and is spatially constrained and connected to the wire mesh mold on both sides by a transverse through-core tie rod; The wire mesh is woven from cold-drawn low-carbon steel wire with a diameter of 1.8-2.2mm. The surface is hot-dip galvanized with a zinc layer of not less than 270g / m². The wire mesh is fixed to the outside of the light steel frame by spot welding and mechanically anchored to the light steel frame with self-tapping screws spaced at 140-160mm.

4. The prefabricated building light steel mesh composite wall according to claim 3, characterized in that: The wire mesh mold has a flanged structure at the top and bottom edges of the wall. The flange width is 45-55mm, and the folding direction is towards the inside of the wall. The flanged part is fixed to the flange of the light steel frame by spot welding. The weld spacing is 90-110mm. This is used to restrain the lateral flow of foamed cement slurry during the pouring process and provide an additional anchoring interface.

5. The prefabricated building light steel mesh composite wall according to claim 3, characterized in that: The interior of the light steel frame is provided with a transverse reinforcing rib every 1100-1300mm along the height direction. The transverse reinforcing rib is made of 1.8-2.2mm thick Q235B steel plate with a width of 55-65mm. It is connected to the web plates on both sides by intermittent fillet welds with a weld length of 25-35mm and a spacing of 90-110mm, which is used to suppress local buckling.

6. The prefabricated building light steel mesh composite wall according to claim 3, characterized in that: The flange ends of the light steel frame are provided with a folded edge structure with a fold width of 8-12mm and a fold angle of 85-95°, which is used to improve edge stiffness and prevent burn-through defects during the welding of the wire mesh.

7. The prefabricated building light steel mesh composite wall according to claim 3, characterized in that: The inner side of the wire mesh mold is provided with an interface reinforcement structure, specifically by spraying a layer of interface-modified coating with a thickness of 1.2-1.8mm. The interface-modified coating is composed of water-based epoxy resin emulsion, silica fume, and chopped polypropylene fibers in a mass ratio of 5.5-6.5:2.5-3.5:0.8-1.

2. The water-based epoxy resin emulsion has an epoxy equivalent of 185-195g / eq and a solid content of 43%-47%; the silica fume has a specific surface area of ​​18000-22000m² / kg and a SiO2 content of not less than 95%; the polypropylene fibers have a length of 5-7mm, a diameter of 18-22μm, and are added at a dosage of 0.25%-0.35% of the dry basis weight of the coating.

8. The prefabricated building light steel mesh composite wall according to claim 7, characterized in that, The interface-modified coating is sprayed 1-3 hours before the filling material is poured, with a spraying pressure of 0.3-0.5 MPa and a spray gun moving speed of 0.7-0.9 m / s, forming a continuous and dense film layer, so that the interfacial bonding strength between the wire mesh mold and the sulfur-oxygen-magnesium foam cement-based composite filler is not less than 0.38 MPa.

9. A process for preparing lightweight steel mesh composite wall material for prefabricated buildings, used to prepare the lightweight steel mesh composite wall material for prefabricated buildings as described in claim 2, characterized in that, Includes the following steps: Magnesium oxide, fly ash, and composite modifier are added to a dry powder mixer and premixed for 110-130 seconds to form a dry mixture. Magnesium sulfate heptahydrate was dissolved in deionized water to prepare a solution with a Baumé degree of 27°-29°, and the temperature was controlled at 23-27°. Inject the magnesium sulfate solution into the main mixer, start the mixer and slowly add the dry mix, continue mixing for 80-100 seconds to form the matrix slurry; Dilute the protein-based foaming agent 28-32 times, and foam it in an independent foaming machine at a pressure of 0.5-0.7 MPa, controlling the foam flow rate at 7-9 L / min to generate foam with a density of 38-42 kg / m³. Inject the foam into the slurry at a volume ratio of 1:3.3-1:3.7, and continue stirring in a twin-shaft forced mixer at a speed of 40-50 r / min for 170-190 seconds to obtain a homogeneous slurry. The slurry is pumped into a mold with a light steel frame and wire mesh installed by a pumping system. The slurry is laid in layers, with each layer being 140-160mm thick and the interval between adjacent layers not exceeding 15-25 minutes. After casting, the mold is placed in a curing kiln for two-stage curing: The first stage is a static rest period, with a temperature of 28-32℃ and a relative humidity of ≥90%, lasting for 3.5-4.5 hours. The second stage involves raising the temperature to 48-52℃ at a rate of 1.5-2.5℃ per hour, maintaining this temperature for 11-13 hours, with a relative humidity of ≥85%. After curing, the mold is allowed to cool naturally before demolding and then transferred to a standard curing room for further curing.

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