A method for recycling concrete slabs from building demolition

Abstract

This invention provides a method for recycling concrete slabs from building demolition, relating to the technical field of concrete recycling from building demolition. The method includes the following steps: sequentially cutting the reinforced concrete slab obtained from building demolition, performing rust removal and rust inhibition treatment on the reinforcing steel, vacuum pressure impregnation treatment, and surface treatment; wherein the vacuum pressure impregnation treatment includes sequentially performing degassing, injecting impregnating material and allowing the impregnating material to penetrate the internal pores of the reinforced concrete slab, and curing treatment. The concrete slabs from building demolition treated by this method possess the comprehensive advantages of maintaining structural integrity, long-term stability of the reinforcing steel-concrete interface, dense and strengthened matrix, and integration of the decorative surface with the structural body.

Description

Technical Field

[0001] This invention relates to the field of building demolition concrete recycling technology, and in particular to a method for recycling building demolition concrete slabs. Background Technology

[0002] Currently, the industry generally adopts a "whole-body crushing-screening-recycling" technical approach for reinforced concrete slabs (such as floor slabs, wall panels, and road slabs) obtained from building demolition. This method mechanically breaks down high-quality concrete components, which originally had a complete and dense structure, high strength, and low impurity content, into recycled aggregates with particle sizes of 0-10 mm and 10-31.5 mm. This disposal method requires the pre-removal of reinforcing steel bars, which are then subjected to destructive treatment during the process and cannot be further utilized, resulting in a waste of steel bar resources. Furthermore, the process of crushing hard concrete slabs into millimeter-sized aggregates consumes a large amount of energy, resulting in high economic and environmental costs.

[0003] As an improvement to the crushing path, existing technologies include direct cutting into blocks. For example, Chinese patent application number CN201210411133.9 discloses a method for recycling and reusing waste concrete pavement. Although this patent abandons crushing and adopts size-adaptive cutting, supplemented by applying a fair-faced concrete protective agent to the surface, it still has the following limitations and disadvantages: (1) Unresolved risk of internal steel reinforcement corrosion: This patent mainly targets the recycling of concrete pavement. Concrete pavement usually has little or no reinforcement, so this method does not address or can not solve the problem of steel reinforcement corrosion in concrete.

[0004] (2) The surface treatment method is relatively simple, and the adhesion and durability may be insufficient: This patent uses the method of applying a fair-faced concrete protective agent for surface treatment. The coating formed by this method is usually thin, and its main function is surface protection and decoration. It has limited ability to improve the adhesion of the porous and rough surface of the recycled concrete block itself and to withstand long-term wear and impact. The reason is that the protective agent focuses more on sealing and aesthetics, rather than forming a strong mechanical interlocking and chemical bond with the substrate.

[0005] (3) Limited improvement in product performance and limited application scenarios: Due to the failure to address the hidden danger of steel corrosion and the relatively basic surface treatment method, the long-term durability and decorative properties of the product obtained by this patent may not meet the requirements of higher-demand scenarios (such as indoor and outdoor decorative surfaces that require long-term safety and aesthetics, and frequently used flooring materials). The reason is that this technical solution does not fundamentally improve the structural stability and surface physical properties of the recycled blocks.

[0006] Therefore, existing technologies have consistently failed to solve the technical problems of steel reinforcement corrosion and weak matrix properties.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] One of the objectives of this invention is to provide a method for recycling concrete slabs from building demolition, so as to at least solve one of the technical problems existing in the prior art.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The present invention provides a method for recycling concrete slabs from building demolition, comprising the following steps: cutting the reinforced concrete slabs obtained from building demolition, performing rust removal and rust prevention treatment on the reinforcing bars, vacuum pressure impregnation treatment, and surface treatment in sequence; The vacuum pressure impregnation process includes degassing, injecting impregnation material and allowing the impregnation material to penetrate the internal pores of the reinforced concrete slab, and curing.

[0010] Furthermore, the length of the cut reinforced concrete slab is 200-1000mm and the width is 100-500mm.

[0011] Furthermore, the rust removal and rust prevention treatment of the reinforcing bars includes sequentially performing rust removal and rust prevention treatment on the exposed ends of the reinforcing bars on the cut surface.

[0012] Furthermore, the rust removal process includes removing the oxide layer on the surface of the steel bar end using mechanical or chemical methods.

[0013] Furthermore, the rust-inhibiting treatment includes: applying a cement-based penetrating crystalline rust inhibitor or a migrating organic rust inhibitor to the ends of the rust-removed reinforcing bars.

[0014] Furthermore, the degassing includes: placing the reinforced concrete slab in a sealed container, evacuating it to an absolute pressure of 40 kPa to 80 kPa, and maintaining the vacuum for 20 to 30 minutes; Furthermore, after the rust removal and rust inhibition treatment of the reinforcing bars and before the degassing, drying is also included; the drying temperature is 100-110℃.

[0015] Furthermore, the process of injecting the impregnating material and allowing it to penetrate the internal pores of the reinforced concrete slab includes: injecting a low-viscosity impregnating material into a sealed container while maintaining the vacuum level after degassing, and applying a pressure difference of 0 MPa to 0.3 MPa between the liquid surface of the impregnating material and the pore outlet of the concrete slab, and maintaining the pressure difference for 4 hours to 24 hours. Preferably, the impregnation material includes one or more of modified epoxy resin and silicone resin; Preferably, the dynamic viscosity of the impregnating material at 25°C is 100-500 mPa·s.

[0016] Furthermore, the curing process includes heating and curing the impregnated reinforced concrete slab at a temperature of 50-100°C for 6-12 hours, or curing it at room temperature at a temperature of 20-30°C for 24-48 hours.

[0017] Furthermore, the surface treatment includes one or more of grinding and polishing, sandblasting, and cleaning; Preferably, after cleaning, the process further includes applying a penetrating fluorocarbon or silane protective agent to the reinforced concrete slab.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for recycling demolished concrete slabs. This method employs a four-step synergistic process: cutting, rebar rust removal and inhibition, vacuum pressure impregnation, and surface treatment. This process preserves the structural value of the demolished concrete slab, eradicates the root causes of rust, and achieves in-situ restoration of surface decorative properties. The cutting step maximizes the preservation of the slab's integrity and original mechanical framework. The rebar rust removal and inhibition treatment seals the exposed rebar ends at the cut surface, cutting off rust channels. Vacuum pressure impregnation drives the impregnating material to deeply penetrate the concrete's capillaries and micro-cracks, solidifying to form a dense, high-strength, and highly impermeable concrete-resin composite matrix, fundamentally eliminating weak interfaces. Finally, surface treatment directly acts on this strengthened matrix, revealing the true aggregate, resin coloring layers, and processing texture through physical means, making the decorative surface completely integrated with the load-bearing structure. Therefore, the demolished concrete slabs treated by this method possess the comprehensive advantages of maintaining structural integrity, long-term stability of the rebar-concrete interface, dense and strengthened matrix, and integration of the decorative surface with the structural body. Detailed Implementation

[0019] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a method for recycling concrete slabs from building demolition, comprising the following steps: sequentially cutting the reinforced concrete slab obtained from building demolition, performing rust removal and rust prevention treatment on the reinforcing bars, vacuum pressure impregnation treatment, and surface treatment; wherein, the vacuum pressure impregnation treatment includes sequentially performing degassing, injecting impregnation material and allowing the impregnation material to penetrate into the internal pores of the reinforced concrete slab, and curing treatment.

[0022] The core of the recycling method for demolished concrete slabs provided by this invention lies in breaking through the traditional linear resource recovery path of "crushing—screening—reprocessing," and instead designing a technical solution of "overall modification, endogenous enhancement, interface symbiosis, and original texture." This method constructs a short-chain, high-value, and highly durable integrated recycling path through four organically linked process stages—cutting, rebar rust removal and rust inhibition treatment, vacuum pressure impregnation treatment, and surface treatment. The technical content, mechanism of action, and key control elements of each step are systematically explained below.

[0023] The method for recycling concrete slabs from building demolition provided by this invention includes: Step 1: Cutting and processing of concrete floor slabs (1) Dimensions of the reinforced concrete floor slabs and wall slabs produced after the demolition of the building shall be measured, including length, width, and thickness, and the thickness of the concrete protective layer of the upper and lower layers of steel reinforcement shall also be measured. The cut dimensions of the concrete floor slabs include lengths of 200-1000 mm and widths of 100-500 mm; Preferably, when designing the cutting, the length and width of the cut can be designed according to the thickness.

[0024] (2) Use a cutting machine or circular saw to cut the concrete slab into small concrete blocks of predetermined specifications (e.g., 200mm×100mm×60mm, 300mm×300mm×80mm) along the length and width of the concrete slab.

[0025] (3) Cleaning and drying: Use running water to clean the cut concrete blocks to remove dust and particles generated during cutting and grinding. If the exposed steel bars on the sides are rusted, remove the rust. Then dry the concrete blocks.

[0026] Step 2: Rust removal and rust prevention treatment of reinforcing bars (1) Rust removal of reinforcing bars. Identify the exposed ends of the reinforcing bars on the longitudinal section. Thoroughly remove rust using mechanical methods (such as an angle grinder with a wire brush wheel or a sandblasting machine) or chemical methods (such as applying pickling rust remover).

[0027] (2) Rust Inhibition Treatment. Apply cement-based penetrating crystalline rust inhibitor or migratory organic rust inhibitor to the ends of the reinforcing bars. These rust inhibitors not only form a film, but also penetrate into the tiny gaps between the reinforcing bars and concrete, providing a deeper level of protection.

[0028] Step 3: Vacuum impregnation of the matrix for overall strengthening. This invention repairs concrete defects at the microscopic level by impregnating resin under vacuum pressure, transforming it into a high-performance composite material and solving the problems of insufficient strength and impermeability of the matrix itself.

[0029] (1) Matrix drying The concrete blocks are thoroughly dried before impregnation to completely remove moisture and dampness from the pores. The drying temperature is 100-110℃, for example, 100℃, 105℃, 110℃, etc. This step is fundamental to ensuring effective resin penetration and adhesion.

[0030] (2) Vacuuming After drying, the concrete blocks are placed in a sealed pressure vessel and subjected to vacuum treatment. The goal is to remove air from the capillaries and microcracks of the concrete.

[0031] Specifically, maintain the system vacuum level within the range of 40 kPa to 80 kPa, for example, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, etc., to effectively remove internal air. Continuously evacuate until the system vacuum level reaches the set value and remains stable for 20-30 minutes, for example, 20 minutes, 25 minutes, 30 minutes, etc., to ensure that air is fully removed. The specific duration needs to be determined through testing based on the equipment power and load capacity.

[0032] (3) Pressure impregnation: Under pressure, inject low-viscosity, transparent or colored modified epoxy resin or silicone resin. Optionally, the resin can be preset to black, gray, white or other colors to unify or change the base color of the matrix.

[0033] Specifically, under the condition of maintaining a vacuum negative pressure, a prepared low-viscosity impregnation resin (such as modified epoxy resin or silicone resin) is injected into the tank, and optionally a certain positive pressure is applied to further drive penetration. The resin viscosity should be low (generally recommended to be below 500 mPa·s) to ensure excellent flowability and deep penetration capability. A pressure difference of 0 MPa to 0.3 MPa (more preferably 0.1 MPa to 0.3 MPa) can be applied between the impregnation material liquid surface and the pore outlet of the concrete slab; the pressure difference is provided by a pressurization device independent of the vacuum system, and the vacuum system continues to operate during the application of the pressure difference to maintain the pore outlet side in a low-pressure state after degassing. To ensure that the resin fully fills the pores, the impregnation liquid should be maintained under pressure for at least 4 hours, which can be extended to 24 hours depending on the block thickness and density. Specific times can be, for example, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0034] To further explain, the present invention describes injecting a prepared low-viscosity impregnation resin into a tank under vacuum negative pressure conditions, and optionally applying a certain positive pressure to further drive penetration. Physically, this means that the entire impregnation process maintains an absolute pressure environment (i.e., vacuum state, preferably 40-80 kPa) lower than the local atmospheric pressure within a sealed container. This vacuum environment acts on the pore outlet side of the concrete block to continuously expel residual gas from the pores and keep the channels unobstructed. Simultaneously, a directional pressure difference is applied to the impregnation resin liquid phase through an independent pressurization system (such as a nitrogen source or hydraulic pump). This pressure difference is the aforementioned "positive pressure," defined as the difference between the static pressure of the resin liquid surface and the static pressure at the concrete pore outlet, with a value range of 0-0.3 MPa (preferably 0.1-0.3 MPa). This pressure difference is established independently by the pressurization system and does not alter the continuous effect of the vacuum environment on the pore outlet. Driven by this pressure difference, the resin stably and controllably penetrates into the concrete pore network along the pressure gradient direction, achieving deep filling. It is important to emphasize that this "positive pressure" does not refer to the container as a whole rising to a state higher than atmospheric pressure, but specifically refers to the net driving pressure gradient between the resin liquid surface and the concrete pore outlet. Therefore, the gas phase space inside the container is always maintained in a vacuum (negative pressure), and the resin is stably and controllably forced into the degassed concrete pores by this pressure gradient. The statement that "the impregnating liquid should be maintained under pressure for at least 4 hours, which can be extended to 24 hours depending on the thickness and density of the block" means that under this combined pressure state of "vacuum substrate + controllable pressure difference," the resin has sufficient time to complete capillary penetration, interface wetting, and micro-filling, ensuring that the impregnation depth and saturation meet the performance requirements.

[0035] Preferably, the dynamic viscosity of the resin at 25°C is 100-500 mPa·s.

[0036] (4) Curing: Curing by heating or at room temperature. After impregnation, allow the resin to cure inside the block.

[0037] Preferably, curing is performed by heating or at room temperature. An initiator can be added to the resin beforehand, and the curing reaction is triggered by heating to a temperature of 50°C to 100°C and maintained for 6 to 12 hours. Alternatively, curing can be performed at room temperature for 24 to 48 hours. After curing, the old concrete block is transformed into a single block of "concrete-resin composite material" that is dense, high-strength, highly impermeable, and has a uniform base color.

[0038] Step 4: Surface Texture Discovery and Activation. This invention eliminates all external mortar or coating finishes, directly optimizing and showcasing the true texture of the reinforced substrate through physical processing. This ensures that the "decorative surface" is 100% integrated with the substrate and will never peel off, while also achieving a natural and high-end aesthetic effect, completely resolving the contradiction between beauty and durability, and between authenticity and performance.

[0039] Perform one of the following treatment steps on the surface of the reinforced composite material block: (1) Multi-stage grinding and polishing: diamond grinding discs are used to grind from coarse to fine. By controlling the depth, natural aggregates of different sizes inside can be exposed, forming a variety of effects from a rough exposed aggregate matte surface to a smooth stone surface.

[0040] (2) Controllable sandblasting: Sandblasting is performed using glass beads or fine steel shot to form a uniform rough surface or uniform exposed aggregate effect, thus achieving an industrial texture.

[0041] (3) Cleaning and final protection: After cleaning the surface, apply a penetrating fluorocarbon or silane protectant. This protectant does not form a thick film on the surface, but only enhances the water-repellent, stain-resistant, and UV-resistant properties, fully maintaining and highlighting its true texture and grain.

[0042] Therefore, this invention solves three core problems existing in current methods of recycling concrete from building demolition: (1) High energy consumption and low value of resource utilization: Most existing technologies crush waste concrete into recycled aggregates, and then process the aggregates into inorganic materials and cement products. The resource utilization path is long, the disposal process is energy-intensive, and the value of recycled products is low.

[0043] (2) The hidden danger of steel bar corrosion has not been eradicated: Whether it is separation before crushing or crushing together, the long-term corrosion problem of internal steel bars has not been effectively addressed, resulting in durability defects in recycled products.

[0044] (3) The contradiction between aesthetics and performance of recycled materials: simply covering them with a finishing layer is easy to peel off, while retaining the rough appearance cannot meet the decorative requirements. Existing technology lacks a method that can simultaneously retain the real texture of concrete and give it high durability and high decorativeness.

[0045] Specifically, the present invention solves the above problems in the following ways: (1) Replace crushing with cutting: precisely modify the concrete slab into regular blocks to maximize the preservation of its original structural value and integrity.

[0046] (2) "Root cause" protection of the steel bar ends: After cutting, the exposed steel bar ends are protected by "sandblasting and rust removal + composite coating" for long-term protection, which permanently eliminates the rust channel from a physical and chemical perspective.

[0047] (3) Strengthening the matrix: The innovative vacuum pressure impregnation process is used to inject high-performance resin into the concrete, so that it combines with the concrete to form a high-strength and high-density "concrete-resin composite material", which fundamentally improves the performance of the matrix.

[0048] (4) Surface treatment: Through physical means such as grinding, polishing, and sandblasting, the surface of the reinforced substrate is directly treated artistically to reveal the real aggregate, texture and resin coloring effect inside, creating a unique decorative texture.

[0049] To further explain, the advantages of this invention include: (1) Significant economic and environmental benefits have been achieved, realizing the high added value upgrading and recycling of construction waste, and producing building materials that can be directly used in gardens, squares, and interior and exterior decoration.

[0050] (2) A fundamental breakthrough has been achieved in product durability: Double protection to eliminate corrosion: The composite coating on the steel bar ends and the reinforcement of the base resin work together to provide protection throughout the entire product life cycle, solving the most critical safety hazard of recycled products.

[0051] Integrated structure, superior performance: The decorative surface is the structure itself, completely eliminating the risk of the decorative layer peeling off or becoming hollow. The resin-reinforced matrix significantly improves compressive strength, impermeability, and toughness.

[0052] (3) Achieving the integration of decoration and structure: The exposed aggregate morphology, texture direction and gloss characteristics of the block surface are not from the added finishing layer, but are the result of selective exposure of the heterogeneous structure of the reinforced matrix, which is determined by the aggregate distribution, resin pore filling state and cement-resin interface bonding characteristics during physical processing such as grinding and sandblasting; the surface morphology and matrix structure performance evolve synchronously, fundamentally eliminating the risk of debonding, hollowing and peeling between the finishing layer and the matrix, and ensuring the structural stability and surface function reliability under long-term service.

[0053] (4) High-end application scenarios: Due to its excellent durability and unique artistic appearance, the product can be directly used in high-end indoor and outdoor walls, floors, landscape construction, art installations and other fields with extremely high requirements for material performance and aesthetics.

[0054] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0055] Example 1 This embodiment provides a method for recycling concrete slabs from building demolition, the steps of which are as follows: Step 1: Cutting Process The dismantled C30 concrete slab (120mm thick) was cut into regular blocks of 600mm×300mm×120mm using a cutting machine, and then cleaned and dried.

[0056] Step 2, Reinforcing bar protection: Rust removal and rust prevention treatment of reinforcing bars. The exposed ends of the HRB400 steel bars were sandblasted to remove rust, and then coated with epoxy zinc-rich primer and gray fluorocarbon topcoat.

[0057] Step 3, Matrix Strengthening: Step 3.1, Matrix drying: Dry the block at 105℃; Step 3.2: Place the block in a vacuum pressure vessel and continuously evacuate to an absolute pressure of 50 kPa, maintaining this pressure for 30 minutes. While maintaining negative pressure, inject dark gray modified epoxy resin (25℃ dynamic viscosity: 350 mPa·s). A dicyandiamide-based curing agent is pre-mixed into the modified epoxy resin; this curing agent is stable at room temperature but activated at temperatures above 60℃. Close the valve connected to the vacuum pump to keep the system sealed. Subsequently, high-purity nitrogen gas is introduced into the top space of the vessel through a separate pressurization line, applying a directional driving pressure to the resin surface that is higher than the residual gas phase pressure inside the vessel. This driving pressure (gauge pressure) is controlled at 0.15 MPa. Maintain this pressure at 0.15 MPa for 6 hours, then slowly depressurize and remove the block. Transfer the block to a curing chamber at 60℃ and maintain the temperature for 8 hours to allow the resin to fully cure, forming a monolithically reinforced composite material.

[0058] Step 4, Surface Treatment Step 4.1: Use diamond grinding discs to gradually grind and polish from 80 grit to 3000 grit, and finally obtain a mirror-like effect that is as smooth as an inkstone and has the internal aggregate faintly visible. Step 4.2, Final Protection: Clean and dry the surface of the block, apply a penetrating silane protective agent, and the high-end interior decorative panel is obtained after final treatment.

[0059] Product features and uses: Luxurious texture and unified color scheme, suitable for interior walls or countertops in high-end hotels, clubs, and commercial spaces.

[0060] Example 2 This embodiment provides a method for recycling concrete slabs from building demolition. The difference from Embodiment 1 is that in step 3.2, a vacuum is drawn to an absolute pressure of 40 kPa and maintained for 20 minutes. Under this negative pressure condition, the same modified epoxy resin as in Embodiment 1 is injected. Following the same procedure as in Embodiment 1, a directional driving pressure higher than the residual pressure of the gas phase inside the tank is applied to the resin liquid surface. This driving pressure (gauge pressure) is controlled at 0.1 MPa and maintained at 0.1 MPa for 24 hours.

[0061] Example 3 This embodiment provides a method for recycling concrete slabs from building demolition. The difference from Embodiment 1 is that in step 3.2, a vacuum is drawn to an absolute pressure of 80 kPa and maintained for 30 minutes. Under this negative pressure condition, the same modified epoxy resin as in Embodiment 1 is injected. Following the same procedure as in Embodiment 1, a directional driving pressure higher than the residual pressure of the gas phase inside the tank is applied to the resin liquid surface. This driving pressure (gauge pressure) is controlled at 0.3 MPa and maintained at 0.3 MPa for 4 hours.

[0062] Example 4 This embodiment provides a method for recycling concrete slabs from building demolition. The difference from Embodiment 1 is that no positive pressure is applied in step 3.2.

[0063] Example 5 This embodiment provides a method for recycling concrete slabs from building demolition. The difference from Embodiment 1 is that in step 3.2, the directional driving pressure is 0.4 MPa and is maintained at 0.4 MPa pressure for 6 hours.

[0064] Example 6 This embodiment provides a method for recycling concrete slabs from building demolition, which differs from Embodiment 1 in that: Cutting process: Cut the concrete pavement slab into small blocks of 200mm×100mm×80mm.

[0065] Rebar protection: Rust removal and application of epoxy zinc-rich primer and gray fluorocarbon topcoat to the ends of a small number of rebars.

[0066] Matrix reinforcement: A vacuum of 50 kPa is continuously applied and maintained for 30 minutes. Low-viscosity transparent silicone resin is then injected under this pressure, with a directional driving pressure of 0.15 MPa, maintained for 6 hours, and cured at room temperature for 48 hours. The resin primarily serves a reinforcing function and does not significantly alter the original color.

[0067] Surface treatment: Sandblasting (using glass beads with a particle size of 0.5-1.0mm) is used to uniformly remove about 2mm of cement paste from the surface, fully revealing the colorful natural pebbles and sand inside, forming a uniform rough texture.

[0068] Final protection: A water-based fluorocarbon protective agent is applied, and the resulting landscape paving bricks are then produced after final treatment.

[0069] Product features and uses: Good water permeability and breathability, non-slip, natural color, suitable for garden paths and plaza paving.

[0070] Example 7 This embodiment provides a method for recycling concrete slabs from building demolition, which differs from Embodiment 1 in that: Cutting process: Cut out irregular polygonal blocks (maximum side length approximately 400mm, thickness 100mm).

[0071] Reinforcing bar protection: Same as in Example 1.

[0072] Matrix strengthening: Continuously evacuate to 50 kPa and maintain for 30 minutes. Under this pressure, inject light brown epoxy resin mixed with iron oxide red and ochre mineral pigments to simulate sandstone effect. The directional driving pressure is 0.15 MPa, and it is maintained for 6 hours. Then, it is cured at room temperature for 48 hours.

[0073] Surface treatment: First, medium sandblasting is performed to form a basic texture. Then, a handheld angle grinder with louvered grinding discs is used for localized and focused polishing to create a natural weathered sandstone texture with varying shades and strong texture contrasts.

[0074] Final protection: Apply a matte penetrating protective agent and the device mounting plate is obtained after final treatment.

[0075] Product features and uses: Highly artistic, each piece has a unique texture, suitable for building facade decoration, interior art background walls, and sculptural structures.

[0076] Example 8 This embodiment provides a method for recycling concrete slabs from building demolition, which differs from Embodiment 1 in that: Cutting process: Cut the wall panel into blocks of 400mm×200mm×200mm.

[0077] Reinforcing bar protection: Same as in Example 1.

[0078] Matrix strengthening: Continuously vacuum to 50 kPa and maintain for 30 minutes, inject colorless and transparent epoxy resin to preserve the original appearance of concrete to the maximum extent, directional driving pressure is 0.15 MPa, maintain for 6 hours, and then cure at room temperature for 36 hours.

[0079] Surface treatment: Using a chisel or special roughening tool, the surface of the block is manually or mechanically chiseled to create a rough texture of varying depths and powerful dots or stripes. The aggregate falls off randomly, resulting in a rugged effect.

[0080] Final protection: Apply a solvent-based fluorocarbon protective agent and then perform final treatment to obtain wall blocks.

[0081] Product features and uses: It retains a strong sense of originality and industrial style, and is suitable for interior and exterior wall construction or decorative cladding in creative parks and loft-style spaces.

[0082] Example 9 This embodiment provides a method for recycling concrete slabs from building demolition, which differs from Embodiment 1 in that: Cutting process: Cut the lightweight concrete wall panels into predetermined specifications.

[0083] Rebar protection: Exposed rebar ends on the cut surface are mechanically ground (or sandblasted) to remove plating damage caused by cutting and activate the surface. Subsequently, a high-performance epoxy sealant coating is applied to seal and protect the ends.

[0084] Matrix reinforcement: Due to the high porosity of the matrix, a two-stage vacuum impregnation method is employed. First, a vacuum of 50 kPa is applied and maintained for 20 minutes, followed by the injection of low-viscosity resin to fill the large pores. A second vacuum of 50 kPa is applied and maintained for 30 minutes, followed by the injection of a slightly higher viscosity resin to ensure complete saturation. The resin can be colored. The directional driving pressure is 0.15 MPa, maintained for 6 hours, and then cured at room temperature for 48 hours.

[0085] Surface treatment: Finely polish until the surface is smooth to obtain a uniform and dense slate texture.

[0086] Final protection: Apply an enhanced penetrating protective agent and then perform a final treatment to obtain a composite lightweight siding.

[0087] Product features and uses: While retaining its lightweight characteristics, it greatly improves surface hardness and decorative properties, making it suitable for dry-hanging systems on interior and exterior walls of buildings.

[0088] Comparative Example 1 This comparative example provides a method for preparing ordinary permeable bricks using traditional recycled aggregates, including: Waste concrete slabs from the same source are crushed using a jaw crusher and screened to obtain 5-10mm recycled aggregate. The recycled aggregate, cement, and water are mixed and pressed into permeable bricks, which are then cured according to standard procedures.

[0089] Comparison results: The product surface is rough, the color is dull and old, and the wear resistance is poor.

[0090] Comparative Example 2 This comparative example provides a simple cutting and brushing method using the approach described in patent CN201210411133.9: Method: The concrete slab was directly cut into blocks of the same size as in Example 1. After cleaning the surface, two coats of fair-faced concrete protective agent were directly applied by roller.

[0091] Comparison results: Existing cracks and holes on the block surface are still visible, giving it a cheap feel. The protective film wore off rapidly in the abrasion resistance test, and peeled and discolored after one year of outdoor exposure. The coating bulged and cracked at the ends of the reinforcing bars due to rust expansion.

[0092] Comparative Example 3 This comparative example provides a method for recycling concrete slabs from building demolition. The difference from Example 1 is that the matrix is ​​strengthened but the texture is not explored (only an interface agent and a thin layer of finish are applied). Method: Steps 1-3 are the same as in Example 1, except that the fourth step of grinding / sandblasting is not performed. Instead, an interface agent is applied, and then a 5mm thick layer of colored polymer cement mortar is applied.

[0093] Comparison results: The product's appearance was improved, but it lost its natural texture and became indistinguishable from ordinary artificial quartz slabs. After freeze-thaw cycles and hot rain tests, interfacial delamination occurred between the added finishing layer and the reinforced substrate, demonstrating the fundamental difference in durability between the "added layer" and the "integrated body".

[0094] Comparative Example 4 This comparative example provides a method for recycling concrete slabs from building demolition. The difference from Example 1 is that only surface grinding is performed, and no vacuum impregnation reinforcement of the substrate is carried out. Method: The concrete block is cut and the ends of the reinforcing bars are protected (same as in Example 1), and then it is directly ground and polished with a high grit.

[0095] Comparison results: After polishing, the surface can briefly show a certain gloss, but due to the porous and uneven strength of the substrate, the polishing effect is poor, and the gloss is only about 30% of that of Example 1. The product has a high water absorption rate, is easily contaminated, and the internal microcracks will expand under stress or freeze-thaw conditions, making its durability far inferior to that of the product of the example that was strengthened by vacuum impregnation.

[0096] Comparative Example 5 This comparative example provides a method for recycling concrete slabs from building demolition, in which the slabs are crushed, mixed with resin, and molded into "recycled stone". Method: Waste concrete is crushed into fine aggregate (<5mm), mixed with unsaturated polyester resin, and molded into "artificial stone".

[0097] Comparison results: The product completely loses the structure and texture of the original concrete and is a typical man-made material. The production process involves large amounts of resin and high energy consumption. Its mechanical properties (especially impact resistance) are lower than the integrated reinforced block of Example 1, and it fails to exhibit any true aggregate aesthetics.

[0098] Test case Test samples: The products prepared in Examples 1-9 and Comparative Examples 1-5 were tested.

[0099] Test method: 1. Compressive strength test Implementation standard: GB / T 28635-2012 "Concrete Paving Bricks".

[0100] Testing Methods and Indicators: The purpose of the compressive strength test is to quantitatively verify the fundamental strengthening effect of vacuum pressure impregnation on the concrete matrix. Five specimens were selected, dried to constant weight at (105±5)℃, and cooled to room temperature. They were placed at the center of the bearing plate under a compression testing machine and continuously and uniformly loaded at a loading rate of (0.4~0.6) MPa / s until the specimen failed. The maximum failure load was recorded. The average value of the five specimens was taken, accurate to 0.1 MPa.

[0101] Core evaluation index: The compressive strength of the specimens after pressure impregnation strengthening treatment is expected to reach more than 40 MPa, which is much higher than that of the unstrengthened control specimens (usually <40 MPa).

[0102] 2. Water absorption test Implementation standard: GB / T 28635-2012 "Concrete Paving Bricks".

[0103] Test methods and indicators: The water absorption rate test is used to compare the densification degree of the matrix after pressure impregnation treatment. Three specimens were selected and dried at (105±5)℃ to constant weight, and their mass (M0) was measured. Then, the specimens were immersed in water at (20±5)℃ for (24±0.5) hours. After removal, the surface water was wiped off with a damp towel, and the specimens were weighed immediately (M1). Water absorption rate (%) = [(M1-M0) / M0]×100%, and the arithmetic mean of the five specimens was taken, with an accuracy of 0.1%.

[0104] Core evaluation indicator: After pressure impregnation, the internal pores of the specimen are effectively sealed, and the water absorption rate should be less than 1.0%.

[0105] 3. Abrasion resistance test Implementation standard: GB / T 28635-2012 "Concrete Paving Bricks".

[0106] Testing methods and indicators: To verify the long-term reliability of the integrated "decorative surface" formed after physical processing and the reinforced substrate. Three specimens were selected. Using a concrete abrasion testing machine, the specimens were fixed, and a standard steel wheel was rolled and rubbed on the surface of the specimen (150 revolutions) to form a pit. The length (L) of the midpoint of the pit edge was measured, and the average value of the three specimens was taken, accurate to 0.1 mm. Average pit length (mm).

[0107] Core evaluation indicator: This value directly reflects the surface's wear resistance. Because the surface of the product of this invention is a resin-reinforced integrated substrate, the length of the grinding pit should be ≤30mm, meeting the requirements of high-quality flooring materials; while the comparative example with only surface coating or an unreinforced substrate may have a grinding pit length ≥35mm.

[0108] 4. Gloss test Implementation standard: GB / T 13891-2008 "Method for determination of specular gloss of building veneer materials".

[0109] Test methods and indicators: The purpose of the gloss test is to evaluate the controllable surface decorative texture achievable by the process of this invention. A calibrated 60° specular gloss meter is used. The instrument probe is placed in close contact with the clean, dry surface of the specimen, and at least three points are evenly selected on the surface of each specimen for measurement, and the gloss value (GU) is read.

[0110] Key evaluation indicators: For polished mirror finish, gloss should be ≥80 GU; for matte or rough finish, the expected gloss should be between 5-15 GU; for untreated rough concrete surfaces, gloss is usually extremely low, close to 0 GU.

[0111] The test results are shown in Table 1.

[0112]

[0113] As shown in Table 1, the recycled concrete slabs prepared using the method of this invention (Examples 1-9) exhibit comprehensive performance that is significantly superior to traditional technical approaches (Comparative Examples 1-5). Specifically, while effectively preserving the original structure, the compressive strength of this invention is more than 50% higher than that of traditional recycled products (Comparative Example 1) and simply treated products (Comparative Examples 2 and 4), demonstrating fundamental strengthening of the matrix; the water absorption rate is reduced by an order of magnitude compared to unimpregnated reinforced products (Comparative Examples 2, 3, and 4), reaching below 1%, fundamentally improving impermeability and durability; it exhibits excellent wear resistance, with pit lengths all less than 32 mm, and no risk of surface layer peeling (comparative Example 3 showed peeling), verifying the long-term reliability of "integration of decorative surface and structural body"; the gloss level can be precisely controlled within a wide range of 6-92 GU, achieving diversified and high-end decorative effects from natural roughness to high-gloss mirror finish, which is fundamentally different from the original rough surface (Comparative Examples 1 and 4) and the fragile coating texture (Comparative Example 2). These data fully demonstrate that the present invention systematically solves three major technical problems—steel corrosion, weak matrix performance, and easy peeling of decorative layer—through a synergistic process of "cutting-steel protection-vacuum pressure impregnation-surface treatment," successfully transforming demolished concrete into high-performance building decoration materials.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 method for recycling concrete slabs from building demolition, characterized in that, Includes the following steps: The reinforced concrete slabs obtained from the demolition of the building are sequentially cut, treated to remove and inhibit rust on the reinforcing bars, vacuum pressure impregnated, and surface treated. The vacuum pressure impregnation process includes degassing, injecting impregnation material and allowing the impregnation material to penetrate the internal pores of the reinforced concrete slab, and curing.

2. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, The length of the cut reinforced concrete slab is 200-1000mm and the width is 100-500mm.

3. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, The rust removal and rust prevention treatment of the reinforcing bars includes sequentially removing rust and preventing rust on the exposed ends of the reinforcing bars on the cut surface.

4. The method for recycling concrete slabs from building demolition according to claim 3, characterized in that, The rust removal process includes removing the oxide layer on the surface of the steel bar ends using mechanical or chemical methods.

5. The method for recycling concrete slabs from building demolition according to claim 3, characterized in that, The rust-inhibiting treatment includes: applying a cement-based penetrating crystalline rust inhibitor or a migrating organic rust inhibitor to the ends of the rust-removed reinforcing bars.

6. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, The degassing process includes: placing the reinforced concrete slab in a sealed container, evacuating it to an absolute pressure of 40 kPa to 80 kPa, and maintaining the vacuum for 20 to 30 minutes.

7. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, After the rust removal and rust inhibition treatment of the reinforcing steel bars and before the degassing, the process also includes drying; the drying temperature is 100-110℃.

8. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, The process of injecting the impregnating material and allowing it to penetrate the internal pores of the reinforced concrete slab includes: injecting a low-viscosity impregnating material into a sealed container while maintaining the vacuum level after degassing, and applying a pressure difference of 0 MPa to 0.3 MPa between the liquid surface of the impregnating material and the pore outlet of the concrete slab, and maintaining the pressure difference for 4 to 24 hours. Preferably, the impregnation material includes one or more of modified epoxy resin and silicone resin; Preferably, the dynamic viscosity of the impregnating material at 25°C is 100-500 mPa·s.

9. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, The curing process includes heating and curing the impregnated reinforced concrete slab at a temperature of 50-100°C for 6-12 hours, or curing it at room temperature at a temperature of 20-30°C for 24-48 hours.

10. The method for recycling concrete slabs from building demolition according to claim 1, characterized in that, The surface treatment includes one or more of grinding and polishing, sandblasting, and cleaning; Preferably, after cleaning, the process further includes applying a penetrating fluorocarbon or silane protective agent to the reinforced concrete slab.

Images