A recycled facing concrete block and a method of manufacturing the same

Abstract

The application provides a recycled facing concrete block and a preparation method thereof, and relates to the technical field of recycling of waste concrete, and comprises: a base body cut from a waste reinforced concrete member, original structure steel bars being reserved in the base body, and at least one surface of the base body being exposed to end portions of the steel bars; a rust-proof coating is arranged on the exposed end portions of the steel bars; an interface transition layer and a facing layer are sequentially arranged on at least one surface of the base body in a laminated mode, and the interface transition layer is used for enhancing the bonding between new and old materials. The application not only realizes the cathodic protection and long-term rust prevention of the steel bars by using the rust-proof coating, prevents cracking and damage caused by rust expansion, but also significantly enhances the bonding performance between the base body and the facing layer by using the interface transition layer, and improves the overall structural stability and impact resistance. Meanwhile, the multilayer composite design makes the product have excellent decorative property and long-term weather resistance, and realizes the upgrading and transformation of the construction waste from low-value recycled materials to high-value and long-life facing building materials.

Description

Technical Field

[0001] This invention relates to the field of waste concrete recycling technology, and in particular to a recycled decorative concrete block and its preparation method. Background Technology

[0002] Currently, the recycling of concrete from building demolition mainly utilizes recycled aggregate technology: large pieces of waste concrete are crushed and screened to obtain recycled aggregates of different particle sizes, such as 0-5mm and 5-10mm, which are then used to formulate road materials or cement products. In this disposal model, construction waste disposal is a crucial step in the resource utilization of construction waste, determining the quality of the recycled aggregates. The disposal process includes crushing, screening, and impurity removal. The level of this process determines the impurity content, particle shape, gradation, and mud content of the recycled aggregates. Construction waste disposal lines range from over 1 million to over 10 million yuan, requiring large land areas and significant investment. The crushing and screening stages of the construction waste disposal process generate large amounts of dust and noise, posing high environmental protection requirements. The resource utilization model for construction waste is prone to a disconnect between disposal and utilization, resulting in a large amount of recycled aggregates not being utilized in a timely manner, affecting the normal operation of disposal projects. Concrete slabs, beams, and pavements are high-quality construction waste with high strength and low impurity content. Using traditional construction waste disposal methods is an over-utilization of concrete construction waste.

[0003] Existing technologies also attempt to reuse waste concrete as a whole. For example, Chinese invention patent application number CN201210411133.9 discloses a method for recycling and reusing waste concrete pavement. This method mainly includes the following steps: 1) evaluating the performance of the waste concrete pavement; 2) designing products based on the dimensions of the waste concrete pavement; 3) cutting the waste concrete pavement to obtain stone blocks; 4) surface treatment of the stone blocks; 5) coating treatment: uniformly applying a fair-faced concrete protective agent to the surface of the stone blocks, ultimately obtaining stone that can be used for construction and decoration. This technical solution aims to directly transform waste concrete pavement into building stone through simple cutting and surface coating with a protective agent, thereby achieving resource reuse.

[0004] However, this method still has the following limitations and drawbacks: (1) Unresolved risk of internal steel reinforcement corrosion: The comparative patent mainly targets the recycling of concrete pavement. Concrete pavement usually has little or no reinforcement, so the patented method does not address or can not solve the problem of steel reinforcement corrosion in concrete.

[0005] (2) The surface treatment method is relatively simple, and the adhesion and durability may be insufficient: The comparative 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 its ability to withstand long-term wear and impact.

[0006] (3) Limited improvement in product performance and limited application scenarios: Due to the lack of resolution of the steel corrosion hazard and the relatively basic surface treatment method, the long-term durability and decorative properties of the products obtained by comparison patent may not meet the requirements of higher scenarios (such as indoor and outdoor decorative surfaces that need to ensure safety and aesthetics for a long time, and flooring materials that are used frequently).

[0007] In addition, traditional recycling technologies generally have the following problems: 1. The root cause of the durability problem remains unresolved: If the recycled material contains steel bars, traditional simple rust removal or no treatment at all cannot prevent the steel bars from rusting again from the cut surface in a humid environment, ultimately causing the product to fail from the inside. 2. Obvious appearance defects: Crushed aggregates result in rough product surfaces and uneven color; 3. Product positioning limitations: Traditional technology approaches lack a systematic design for the durability of products throughout their entire life cycle. Summary of the Invention

[0008] One of the objectives of this invention is to provide a recycled finished concrete block to at least solve one of the technical problems existing in the prior art.

[0009] The second objective of this invention is to provide a method for preparing recycled decorative concrete blocks.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a recycled decorative concrete block, comprising: a matrix cut from waste reinforced concrete components, wherein the original structural steel bars are retained inside the matrix, and at least one surface has the end of the steel bars exposed. A rust-proof coating is applied to the exposed ends of the reinforcing bars; An interface transition layer and a finishing layer are sequentially stacked on at least one surface of the substrate, wherein the interface transition layer is used to enhance the adhesion between the new and old materials.

[0011] Furthermore, the substrate is a block formed by cutting a reinforced concrete slab or wall obtained through building demolition; Preferably, the length of the substrate is 300mm to 600mm, the width is 100mm to 300mm, and the height is 200mm to 300mm.

[0012] Furthermore, the thickness of the anti-rust coating is 60–100 μm; Preferably, the anti-rust coating comprises a coating formed by mixing and curing component A and component B, wherein component A comprises epoxy resin, reactive diluent and additives, and component B comprises curing agent, active anti-rust component and functional filler; Preferably, the mass ratio of component A to component B is 1:2.5 to 4; Preferably, component A comprises, by weight: 50-70 parts epoxy resin, 5-10 parts reactive diluent, and 0.5-2.5 parts additives; Preferably, the epoxy resin includes one or more of bisphenol A type epoxy resin and bisphenol F type epoxy resin; Preferably, the reactive diluent includes one or more of monofunctional, difunctional, or multifunctional epoxy reactive diluents; Preferably, the additives include one or more of wetting and dispersing agents, defoamers, and leveling agents; Preferably, component B comprises, by weight: 10-25 parts curing agent, 200-350 parts active rust inhibitor and 20-50 parts functional filler; Preferably, the curing agent includes one or more of polyamide curing agents and amine adduct curing agents; Preferably, the active rust-preventing component includes a sacrificial anode material and an optional passivating rust-preventing material; the sacrificial anode material includes zinc powder, and the content of the sacrificial anode material accounts for more than 70% of the total mass of the active rust-preventing component; Preferably, the functional filler includes one or more of sericite, talc, barium sulfate, and wollastonite.

[0013] Furthermore, the thickness of the interface transition layer is 1–2 mm; Preferably, the raw materials for preparing the interface transition layer include composite liquid and composite powder. The composite liquid includes polymer emulsion, migratory rust inhibitor and surfactant, and the composite powder includes cementitious material, aggregate, polymer powder, water-retaining agent and water-reducing agent. Preferably, the mass ratio of the composite liquid to the composite powder is 1:3 to 4; Preferably, the composite liquid agent comprises, by weight, 80-120 parts polymer emulsion, 5-15 parts migratory rust inhibitor, and 0.5-2 parts surfactant; Preferably, the polymer emulsion includes one or more of styrene-acrylic emulsion, pure acrylic emulsion, and styrene-butadiene emulsion; Preferably, the migratory rust inhibitor includes one or more of amino alcohols and fatty acid esters as migratory steel rust inhibitors; Preferably, the surfactant includes one or more of nonionic surfactants and anionic surfactants; Preferably, the composite powder comprises, by weight, 350-450 parts of cementitious material, 450-600 parts of aggregate, 15-35 parts of polymer powder, 1-3 parts of water-retaining agent and 0.5-2 parts of water-reducing agent; Preferably, the cementitious material includes one or more of silicate cement, aluminate cement, and sulfoaluminate cement; Preferably, the aggregate includes one or more of quartz sand, river sand, limestone sand and tailings sand of different particle sizes; Preferably, the polymer powder includes redispersible latex powder, which includes one or more of vinyl acetate-ethylene copolymer powder and acrylate copolymer powder; Preferably, the water-retaining agent comprises one or more of cellulose ether and starch ether; Preferably, the water-reducing agent includes one or more of polycarboxylate-based and naphthalene-based water-reducing agents.

[0014] Furthermore, the thickness of the finishing layer is 1.5 ± 0.5 mm; Preferably, the raw materials for preparing the finishing layer include: cementitious materials, aggregates, fillers, and additives; Preferably, the cementing material comprises white silicate cement; Preferably, the aggregate comprises 100-200 mesh quartz powder; Preferably, the filler comprises 200-300 mesh heavy calcium carbonate powder; Preferably, the additives include one or more of redispersible latex powder, stearate water-repellent agents, polycarboxylate water-reducing agents, and color powder; Preferably, the redispersible latex powder comprises one or more of vinyl acetate-ethylene adhesive powder and acrylate adhesive powder; Preferably, the pigment comprises alkali-resistant inorganic oxide pigments; Preferably, the raw materials of the finishing layer include, by weight: 300-400 parts of cementitious material, 200-300 parts of aggregate, 200-300 parts of filler, 25-40 parts of redispersible latex powder, 3-5 parts of stearate water-repellent agent, 0.5-2 parts of polycarboxylate water-reducing agent, and 5-20 parts of color powder.

[0015] Secondly, the present invention provides a method for preparing recycled finished concrete blocks, comprising the following steps: (a) Cutting scrap reinforced concrete components into bases of predetermined dimensions; (b) Prepare a rust-proof coating on the exposed ends of the reinforcing bars in the substrate; (c) An interface transition layer and a finishing layer are sequentially stacked on the surface of the substrate; wherein, the substrate is etched before the interface transition layer is prepared.

[0016] Furthermore, in step (b), the anti-rust coating is formed by mixing component A and component B, applying the mixture to the exposed ends of the reinforcing bars, and then curing it. Preferably, the coating method includes scraping or airless spraying.

[0017] Furthermore, in step (c), the etching process includes: chemically etching the surface of the substrate concrete using an acidic solution with a pH value of 2 to 3. Preferably, the preparation of the interface transition layer includes: after the etching treatment, rinsing and drying, and then applying a polymer-modified cement-based interface agent; Preferably, the etching process takes 3 to 5 minutes; the rinsing pressure is 0.5 to 0.8 MPa; and the drying method includes natural drying or drying in an oven at ≤50°C. Preferably, the polymer-modified cement-based interface agent is prepared by mixing a composite liquid agent and a composite powder agent; the stirring speed during the mixing process is 600-800 rpm, and the stirring time is 3-5 minutes. Preferably, the coating method includes brush coating or airless spray coating.

[0018] Furthermore, in step (c), the preparation of the finishing layer includes: forming it by applying a mixture of raw materials for the finishing layer and then sealing and curing it; Preferably, the raw materials for the finishing layer include a dry powder component and water, wherein the dry powder component includes a cementitious material, aggregate, filler and additive, and the mass ratio of the dry powder component to the water is 1:0.18 to 0.22; Preferably, the coating is applied by mechanical spraying or manual wiping.

[0019] Furthermore, the sealing and curing time is 24-48 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The recycled facing concrete block provided by this invention effectively solves key technical problems in recycled blocks, such as easy corrosion of reinforcing bars, weak bonding between old and new layers, and poor durability of the facing layer. This is achieved by applying an anti-rust coating to the exposed ends of the reinforcing bars on the substrate surface cut from waste reinforced concrete components, and sequentially applying an interface transition layer and a facing layer on the substrate. The recycled facing concrete block not only utilizes the anti-rust coating to achieve cathodic protection and long-term rust prevention for the reinforcing bars, preventing cracking damage caused by rust expansion, but also significantly enhances the bonding performance between the substrate and the facing layer through the interface transition layer, improving the overall structural stability and impact resistance. Simultaneously, the multi-layer composite design gives the product both excellent decorative properties and long-term weather resistance, realizing the upgrading and transformation of construction waste from low-value recycled materials to high-value-added, long-life facing building materials. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 A half-sectional view of the recycled finished concrete block provided by the present invention.

[0023] Illustration: 100 - Substrate; 200 - Anti-rust coating; 300 - Interface transition layer; 400 - Finishing layer. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] like Figure 1As shown, the first aspect of the present invention provides a recycled finished concrete block, comprising: a substrate 100 cut from waste reinforced concrete components, wherein the substrate 100 retains the original structural steel bars inside, and at least one surface exposes the ends of the steel bars; an anti-rust coating 200 is provided on the exposed ends of the steel bars; and an interface transition layer 300 and a finishing layer 400 are sequentially stacked on at least one surface of the substrate 100, wherein the interface transition layer is used to enhance the bonding between the new and old materials.

[0027] To address the technical challenges of the durability of recycled masonry blocks, particularly the problem of reinforcing steel corrosion prevention (if the cut reinforced concrete blocks are to be used as a whole, the exposed reinforcing steel inside and on the surface is extremely prone to corrosion in humid environments, leading to block expansion, cracking, and structural damage, which is the core bottleneck restricting its high-value utilization), weak bonding between new and old concrete (applying a new finishing layer directly to the old concrete substrate carries the risk of poor adhesion, hollowing, and easy detachment, affecting the integrity and service life of the blocks), and the finishing layer's susceptibility to cracking, efflorescence, and insufficient durability (traditional finishing materials have poor compatibility with the recycled substrate, and are prone to cracking, peeling, and surface whitening (efflorescence) in harsh environments such as freeze-thaw cycles and wet-dry cycles, affecting aesthetics and durability), this invention provides a completely new product structure, which is systematically designed from the inside out: (1) Multiple rust prevention: First layer (electrochemical protection): Apply epoxy zinc-rich primer to the exposed steel bars. Zinc will preferentially rust and protect the steel bars. Second layer (chemical protection): Add migration-type rust inhibitor to the interface agent. It can actively penetrate into the surface of the steel bars to form a protective film.

[0028] (2) Strong bonding: Add an interface transition layer by using a chemical roughening method to clean the surface of the old concrete with a weak acid to make it rough without damaging the anti-rust layer. At the same time, use a special interface agent with high polymer content to firmly bond the new and old concrete together.

[0029] (3) High weather-resistant finishing layer: The finishing layer uses inorganic decorative mortar with high polymer content, which is crack-resistant, waterproof and alkali-resistant.

[0030] This invention has the following advantages: 1. This invention realizes the high-value application of waste: the product can be used directly as a decorative block for walls and floors, realizing the transformation from "construction waste" to "high-end building materials".

[0031] 2. The structure of this invention is stable and durable: the internally retained steel bars provide core structural strength; the rust prevention treatment of the steel bar ends and the dense finishing layer together constitute a long-term protection system, which significantly improves the service life of the product.

[0032] 3. The present invention has the advantage of combining decoration and functionality: the finishing layer not only provides a beautiful surface, but its specific materials and thickness also bring excellent wear resistance, stain resistance and impact resistance.

[0033] In some preferred embodiments, the substrate is a block formed by cutting a reinforced concrete slab or wall obtained through building demolition; Preferably, the length of the substrate is 300mm to 600mm, for example, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, etc.; the width is 100mm to 300mm, for example, 100mm, 150mm, 200mm, 250mm, 300mm, etc.; and the height is 200mm to 300mm, for example, 200mm, 250mm, 300mm, etc.

[0034] In this invention, the substrate originates from reinforced concrete slabs or walls demolished from buildings. It is a block directly cut from the waste reinforced concrete slab or wall, retaining the original steel reinforcement framework intact. The substrate has a compressive strength ≥25MPa, a length of 300mm–600mm, a width of 100mm–300mm, and a height of 200mm–300mm. During substrate processing, the thickness of the reinforced concrete slab or wall is used as the height of the substrate. The upper and lower surfaces of the reinforced concrete slab or wall serve as the outer finish of the substrate. The laitance layer on the upper and lower surfaces is polished, and the thickness of the steel reinforcement protective layer on both surfaces is not less than 5mm. There is no laitance on the four sides of the substrate, and the ends of the steel reinforcement are flush with the sides.

[0035] In some preferred embodiments, the thickness of the epoxy zinc-rich anti-rust coating is 60-100 μm, for example, it can be 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc.

[0036] In this invention, a special rust-preventive agent is applied to all exposed steel reinforcement surfaces on the substrate to form an epoxy zinc-rich rust-preventive coating. The rust-preventive agent used in this invention is preferably an epoxy zinc-rich primer system. Its key feature is the introduction of a sufficient amount of sacrificial anode material (such as metallic zinc powder). This material, through the principle of electrochemical cathodic protection, can continuously provide long-lasting and active rust protection for the steel reinforcement even when the paint film of this invention experiences localized damage. This is fundamentally different from ordinary rust-preventive paints that rely solely on the shielding effect of the paint film.

[0037] Preferably, the epoxy zinc-rich anti-rust coating comprises a coating formed by mixing and curing component A (base material) and component B (curing system and pigment).

[0038] Preferably, component A includes epoxy resin, reactive diluent, and additives.

[0039] Specifically: (All portions below are by weight) The epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin, or a mixture thereof, and the addition amount is 50-70 parts, for example, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, etc.; the reactive diluent is at least one of monofunctional, difunctional, or multifunctional epoxy reactive diluents, specifically including: n-butyl glycidyl ether, allyl glycidyl ether, ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and the addition amount is 5- 10 parts, for example, can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.; the additives include one or a combination of wetting and dispersing agents, defoamers, and leveling agents, specifically including: polyether-modified polydimethylsiloxane, polyacrylate, silicone defoamer, polyether-modified silicone defoamer, acrylate leveling agent, silicone leveling agent, the total addition amount is 0.5 to 2.5 parts, for example, can be 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, etc.

[0040] Preferably, component B includes a curing agent, an active rust inhibitor, and a functional filler.

[0041] Specifically: (All portions below are by weight) The curing agent is a polyamide curing agent, an amine adduct curing agent, or a mixture thereof, and the addition amount is 10-25 parts, for example, 10 parts, 15 parts, 20 parts, 25 parts, etc.; the active rust-preventing component is a sacrificial anode material and an optional passivating rust-preventing material; wherein, the sacrificial anode material is metallic zinc powder, and its content accounts for more than 70% of the total mass of the active rust-preventing component; the total addition amount of the active rust-preventing component is 200-350 parts, for example, 200 parts, 250 parts, 300 parts, 350 parts, etc.; functional filler: the functional filler is one or a combination of several of sericite, talc, barium sulfate, and wollastonite, and the addition amount is 20-50 parts, for example, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, etc.

[0042] Preferably, the mass ratio of component A to component B is 1:2.5 to 4, for example, it can be 1:2.5, 1:3, 1:3.5, 1:4, etc.

[0043] In some preferred embodiments, the thickness of the interface transition layer is 1 to 2 mm, for example, it can be 1 mm, 1.5 mm, 2 mm, etc. Preferably, the raw materials for preparing the interface transition layer include composite liquid and composite powder. The composite liquid includes polymer emulsion, migratory rust inhibitor and surfactant, and the composite powder includes cementitious material, aggregate, polymer powder, water-retaining agent and water-reducing agent.

[0044] Specifically: (All portions below are by weight) The polymer emulsion is at least one of styrene-acrylic emulsion, pure acrylic emulsion, and styrene-butadiene emulsion, and is added in an amount of 80-120 parts, such as 80, 90, 100, 110, or 120 parts. Its function is to act as an organic binder after film formation, giving the interface layer excellent flexibility, crack resistance, and initial adhesion to the substrate. The migratory rust inhibitor is at least one of amino alcohols and fatty acid esters that are migratory steel rust inhibitors, and is added in an amount of 5-15 parts, such as 5, 10, or 15 parts. Its function is to penetrate to the microscopic defects of the rust-preventive layer, adsorb and form a film on the steel surface, provide active chemical protection, and form a synergistic rust-preventive system with the rust-preventive layer. The surfactant is at least one of nonionic surfactants and anionic surfactants, and is added in an amount of 0.5-2 parts, such as 0.5, 1, 1.5, or 2 parts. Its function is to reduce the surface tension of the system and improve the wettability and dispersion uniformity when the liquid agent and the composite powder are mixed.

[0045] The cementitious material is at least one of silicate cement, aluminate cement, and sulfoaluminate cement, added in an amount of 350-450 parts, for example, 350 parts, 400 parts, 450 parts, etc. Its function is to act as an inorganic binder phase, hydrate to form a rigid skeleton, provide main strength, and create a highly alkaline environment to stabilize the passivation film on the reinforcing steel. The aggregate is at least one of quartz sand, river sand, limestone sand, and tailings sand of different particle sizes, added in an amount of 450-600 parts, for example, 450 parts, 500 parts, 550 parts, 600 parts, etc. Its function is to form a supporting skeleton for the interface layer, achieve the densest packing through reasonable gradation, reduce shrinkage, and lower system costs. The polymer powder is a redispersible latex powder, of the type being vinyl acetate-ethylene copolymer powder or acrylate copolymer powder. At least one of the following, added in an amount of 15-35 parts, such as 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, etc., has the function of: after redispersement, intertwining with cement hydration products to form an organic-inorganic composite network, significantly enhancing bonding strength, impact resistance, and crack resistance; the water-retaining agent is at least one of cellulose ether and starch ether, added in an amount of 1-3 parts, such as 1 part, 2 parts, 3 parts, has the function of: preventing excessive water loss, ensuring sufficient hydration of the cementitious material, and improving workability; the water-reducing agent is at least one of polycarboxylate superplasticizer and naphthalene superplasticizer, added in an amount of 0.5-2 parts, such as 0.5 parts, 1 part, 1.5 parts, 2 parts, etc., has the function of: reducing water consumption while ensuring workability, thereby improving the density and final strength of the interface layer.

[0046] Preferably, the mass ratio of the composite liquid to the composite powder is 1:3 to 4, for example, it can be 1:3, 1:3.5, 1:4, etc.

[0047] In some preferred embodiments, the thickness of the finishing layer is 1.5 ± 0.5 mm, for example, it can be 1 mm, 1.5 mm, 2 mm, etc.; Preferably, the finishing layer is a high-strength, crack-resistant, weather-resistant colored inorganic decorative mortar, the composition of which, by weight, includes: Cementitious material: The cementitious material is white silicate cement, added in an amount of 300-400 parts, for example, 300 parts, 350 parts, 400 parts, etc. Its function is to provide the main strength and development of the finishing layer, and to provide a pure white base for its color expression.

[0048] Aggregate: The aggregate is 100-200 mesh quartz powder, 200-300 parts, for example, 200 parts, 250 parts, 300 parts, etc.; Filler: 200-300 mesh heavy calcium carbonate powder, with a total addition of 200-300 parts, for example, 200 parts, 250 parts, 300 parts, etc. The combination of aggregate and filler provides a fine texture, and through particle size distribution optimization, reduces porosity, providing a dense skeletal structure for the finishing layer.

[0049] The additives include: redispersible latex powder (vinyl acetate-ethylene or acrylate), added at 25-40 parts, for example, 25, 30, 35, or 40 parts, etc., its function is to form a film, impart flexibility, enhance adhesion, and block capillaries to inhibit efflorescence. Stearate-based water-repellent agents, added at 3-5 parts, for example, 3, 4, or 5 parts, etc., provide a surface hydrophobic effect to prevent water intrusion; polycarboxylate-based high-performance water-reducing agents, added at 0.5-2 parts, for example, 0.5, 1, 1.5, or 2 parts, etc., reduce the water-cement ratio and improve density and strength. Pigment is a highly alkali-resistant inorganic oxide pigment, added at 5-20 parts, for example, 5, 10, 15, or 20 parts.

[0050] This invention employs a composite treatment of "interface enhancement + finishing layer" to achieve a leap in surface performance: Instead of a simple protective coating, this invention introduces "interface enhancement treatment" to significantly improve the adhesion between the substrate and the surface layer, followed by a finishing layer. This composite approach of "physical adhesion enhancement + chemical adhesion + surface protection" far surpasses that of a single protective coating in terms of bonding strength, wear resistance, impact resistance, and decorative effect.

[0051] This invention forms a complete upgrade and remanufacturing process chain, realizing high added value of the product: Starting from cutting, through local rust prevention, interface enhancement to finishing, this invention forms a complete process chain specifically designed for the upgrade and remanufacturing of reinforced concrete slabs. The final product retains the original structural strength while possessing excellent durability and advanced decorative properties, thus successfully entering the high-end building materials market and achieving a qualitative leap from "construction waste" to "high added value product".

[0052] Therefore, this invention fundamentally solves the above problems through its unique multi-layered composite structure that includes a built-in rust-preventing system: Addressing the root cause of durability issues, a permanent rust-proofing layer is defined as a key component within the product structure. This is not merely a process, but a structural feature of the product itself, ensuring its long-term safety.

[0053] Addressing aesthetic defects: A new, high-quality decorative finish is provided through an outer fine-grained finish layer.

[0054] Regarding product positioning: This product is designed from the structural perspective to be a high-end decorative material with long-lasting durability.

[0055] A second aspect of the present invention provides a method for preparing recycled finished concrete blocks, comprising the following steps: (a) Cutting scrap reinforced concrete components into bases of predetermined dimensions; (b) Prepare an epoxy zinc-rich anti-rust coating on the exposed ends of the reinforcing bars in the substrate; (c) An interface transition layer and a finishing layer are sequentially stacked on the surface of the substrate; wherein, the substrate is etched before the interface transition layer is prepared.

[0056] In some preferred embodiments, in step (b), the epoxy zinc-rich anti-rust coating is formed by mixing component A and component B, applying the mixture to the exposed ends of the reinforcing bars, and then curing it. Preferably, the coating method includes scraping or airless spraying.

[0057] Specifically, the preparation process of the epoxy zinc-rich anti-rust coating includes: during construction, component A and component B are mixed evenly at a mass ratio of 1:(2.5-4), preferably using an airless spraying method, with the dry film thickness controlled at 60-100 μm. This coating achieves long-term rust prevention for exposed reinforcing bars through the excellent adhesion and sealing properties of epoxy resin and the cathodic protection electrochemical effect of zinc powder.

[0058] In some preferred embodiments, in step (c), firstly, use oil-free compressed air or a soft brush to thoroughly remove dust, debris, and other adhering substances from the surface of the substrate concrete. The purpose is to ensure that there is no isolation layer between the interface agent and the substrate, achieving direct and close contact. Then, roughen the base layer. On the surface of the block substrate concrete with an epoxy zinc-rich anti-rust layer already applied, apply a dilute phosphoric acid solution with a pH of 2-3 as an acidic etching agent by spraying or brushing. React for 3-5 minutes. After small bubbles are uniformly precipitated on the surface, immediately rinse thoroughly with high-pressure clean water (0.5-0.8 MPa) until the outflow is neutral. Then, allow it to dry naturally or dry it at a low temperature (≤50℃). This process can effectively remove the laitance on the concrete surface, expose fresh aggregate, form an ideal micro-roughness, and does not damage the underlying anti-rust layer. Then, apply a polymer-modified cement-based interface agent. During construction, the composite liquid agent and composite powder agent are mixed evenly at a mass ratio of 1:(3-4) before application.

[0059] Preferably, the polymer-modified cement-based interface agent is prepared by mixing a composite liquid agent and a composite powder agent; the stirring speed during the mixing process is 600-800 rpm, for example, 600 rpm, 700 rpm, 800 rpm, etc., and the stirring time is 3-5 minutes, for example, 3 minutes, 4 minutes, 5 minutes, etc. Preferably, the polymer-modified cement-based interface agent is applied by brushing or airless spraying.

[0060] Further explanation: The chemical roughening process includes: using a low-pressure sprayer or brush, evenly applying a dilute phosphoric acid solution with a pH of 2-3 to the concrete surface. Keep the surface moist and allow it to react for 3-5 minutes, during which fine bubbles will be observed to uniformly precipitate on the surface. Immediately rinse thoroughly with clean water at a pressure of 0.5-0.8 MPa until the running water is neutral (this can be tested with pH paper). Subsequently, place the blocks in a ventilated area to air dry naturally or dry them in a low-temperature oven at ≤50℃ until the surface turns white. Purpose: By reacting the acidic substance with the cement hydration products, the surface laitance is dissolved, exposing fresh aggregate and pores, forming a micro-rough surface, which greatly enhances the mechanical adhesion of subsequent interface agents without damaging the underlying anti-rust layer.

[0061] The preparation process of polymer-modified cement-based interface agent includes: weighing the composite liquid agent and composite powder according to a mass ratio of 1:(3-4). First, pour the composite liquid agent into a mixing tank, and then gradually pour in the composite powder agent while mechanically stirring at low speed. After all the powder agent has been added, increase the speed to medium (600-800 rpm) and continue stirring for 3-5 minutes until a fine paste with uniform color and no dry powder particles is formed. Purpose: To ensure that all components are fully mixed and hydrated to obtain optimal workability and final performance.

[0062] The application process of the interface agent includes: the mixed interface agent should be used within 30 minutes to prevent solidification. It can be applied by brushing or airless spraying. Brushing: Use a brush to evenly apply the interface agent to the prepared substrate, controlling the thickness to 1-2 mm. This method is easy to control the thickness and has low material waste. Spraying: Use specialized spraying equipment to evenly spray 1-2 coats to achieve the same thickness. This method is highly efficient and suitable for large-area construction.

[0063] Preferably, after applying the interface agent, the process also includes curing the interface layer: After the interface agent is applied, meticulous curing is required to ensure its full performance. After application, allow it to cure for 24 hours at an ambient temperature of 23±2℃ and a relative humidity of ≥50%. During this period, avoid wind, rain, direct sunlight, and severe vibration. After the initial curing, continue drying curing in a natural environment for a total curing time of no less than 48 hours. After curing, lightly scratch the surface with your fingernail; if there are no scratches and it feels hard, the next step of construction can proceed.

[0064] In some preferred embodiments, step (c) involves the preparation of the finishing layer by applying a mixture of raw materials for the finishing layer and then sealing and curing it. Preferably, the raw materials of the finishing layer include a dry powder component and water. The dry powder component includes a cementitious material, aggregate, filler and additive. The mass ratio of the dry powder component to the water is 1:0.18 to 0.22, for example, it can be 1:0.18, 1:0.19, 1:0.20, 1:0.21, 1:0.22, etc.

[0065] Specifically, the preparation process of the finishing layer's mixed raw materials is as follows: the dry powder components are mixed with water at a low water-cement ratio of 1:(0.18~0.22), and mechanically stirred into an extremely fine and uniform paste. The paste is then applied by mechanical spraying or manual troweling, with the thickness strictly controlled at 1.5±0.5mm.

[0066] In some preferred embodiments, the sealing and curing time is 24-48 hours, for example, 24 hours, 36 hours, 48 ​​hours, etc.

[0067] 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.

[0068] Example 1 This embodiment provides a recycled finished concrete block, the preparation process of which is as follows: Step 1: Cut the scrap reinforced concrete components into bases of predetermined dimensions, specifically as follows: The substrate originates from demolished reinforced concrete slabs, cut directly from the waste slabs, retaining the original steel reinforcement framework intact. The substrate has a compressive strength ≥25MPa, a length of 500mm, a width of 200mm, and a height of 250mm. During processing, the thickness of the reinforced concrete slab is used as the substrate height, and the upper and lower surfaces of the slab serve as the substrate's outer finish. The laitance layer on both surfaces is ground down, and the protective layer thickness for the reinforcement on both surfaces is no less than 5mm. There is no laitance on any of the four sides of the substrate, and the ends of the reinforcement are flush with the sides.

[0069] Step 2: Prepare an epoxy zinc-rich anti-rust coating on the exposed ends of the reinforcing bars in the substrate: Apply a special rust inhibitor to the surface of all exposed steel bar ends on the substrate. The inhibitor consists of two components, A and B. During application, mix components A and B at a mass ratio of 1:3 and apply using an airless spray method. The dry film thickness should be controlled at 80μm. The components, by weight, are as follows: Component A includes 60 parts epoxy resin E-51, 8 parts reactive diluent (n-butyl glycidyl ether), and 1.5 parts additives (organic silicone defoamer); Component B includes 15 parts polyamide curing agent, 250 parts active rust inhibitor (zinc powder, 5-15μm), and 35 parts functional filler (talc). Step 3: Prepare an interfacial transition layer on each surface of the substrate: (1) Surface cleaning and chemical roughening are performed sequentially before preparing the interface transition layer.

[0070] Surface cleaning: Use a soft brush to thoroughly remove dust, debris and other adhering substances from the surface of the concrete substrate.

[0071] Chemical roughening treatment: On the concrete surface of the block substrate that has been coated with an epoxy zinc-rich anti-rust layer, use a brush to evenly apply a dilute phosphoric acid solution with a pH of 2-3 to the concrete surface. Keep the surface moist and react for 3-5 minutes. You can observe small bubbles evenly precipitating on the surface. Immediately rinse thoroughly with clean water at a pressure of 0.7 MPa until the water that runs off is neutral (which can be tested with pH paper). Then, place the blocks in a ventilated place to air dry naturally until the surface turns white.

[0072] (2) Preparation of interface agent: Weigh the composite liquid agent and composite powder according to the mass ratio of 1:3.5. First, pour the composite liquid agent into the mixing tank, and then gradually pour in the composite powder agent while stirring at low speed. After all the powder agent has been added, increase the speed to medium (700 rpm) and continue stirring for 4 minutes until a fine paste with uniform color and no dry powder particles is formed.

[0073] The composite liquid agent comprises, by weight, 100 parts polymer emulsion (styrene-acrylic emulsion), 10 parts migratory rust inhibitor (diethanolaminomethoxypropylamine), and 1 part surfactant (fatty alcohol polyoxyethylene ether); the composite powder comprises, by weight, 400 parts cementitious material (PO 42.5 cement), 500 parts graded aggregate (70-140 mesh quartz sand), 25 parts polymer adhesive powder (VAE adhesive powder), 2 parts water-retaining agent (cellulose ether), and 1 part water-reducing agent (polycarboxylate superplasticizer).

[0074] (3) Application of interface agent: The mixed interface agent should be used within 30 minutes to prevent solidification. Apply by brush. Brush method: Use a brush to evenly apply the interface agent to the prepared substrate, controlling the thickness to 2 mm.

[0075] (4) Interface Layer Curing: After the interface agent is applied, it needs to be carefully cured to ensure its performance is fully utilized. After application, allow it to stand for 24 hours under ambient temperature of 23±2℃ and relative humidity ≥50%. During this period, avoid wind, rain, direct sunlight, and severe vibration. After the initial curing, continue drying curing in a natural environment for a total curing time of 72 hours. After curing, you can lightly scratch the surface with your fingernail. If there are no scratches and it feels hard, you can proceed to the next step of construction.

[0076] Step 4: Prepare the finishing layer: The mixture of finishing layer is applied to the interface transition layer by manual troweling, and the thickness of the finishing layer is controlled at 1.5 mm. After application, it is immediately covered with plastic film and sealed for curing for 36 hours, and then dried under natural conditions. The preparation process of the finishing layer mixture (i.e., high-performance inorganic mortar) is as follows: dry powder components are mixed with water at a low water-cement ratio of 1:0.2 and mechanically stirred into an extremely fine and uniform paste. The dry powder components, by weight, include: 350 parts cementitious material (white cement), 550 parts graded aggregate (40-100 mesh quartz powder), 250 parts filler (200-300 mesh heavy calcium carbonate powder), 30 parts redispersible latex powder (VAE powder), 4 parts stearate water-repellent agent, 1 part polycarboxylate superplasticizer, and 15 parts alkali-resistant inorganic oxide pigment (iron oxide red).

[0077] Example 2 This embodiment provides a recycled finished concrete block, which differs from Embodiment 1 in that: in step 3, no migration-type rust inhibitor is added to the interface agent.

[0078] Example 3 This embodiment provides a recycled decorative concrete block, which differs from Embodiment 1 in that: in step 4, the amount of VAE adhesive powder is 12 parts.

[0079] Example 4 This embodiment provides a recycled decorative concrete block, which differs from Embodiment 1 in that: in step 2, the rust inhibitor is a zinc phosphate modified epoxy primer, with zinc phosphate replacing zinc powder, and the amount of zinc phosphate is 150 parts.

[0080] Example 5 This embodiment provides a recycled finished concrete block, which differs from Embodiment 1 in that: In step 2, component A includes 70 parts epoxy resin, 10 parts reactive diluent, and 2.5 parts additives; component B includes 25 parts curing agent, 350 parts active rust inhibitor, and 50 parts functional filler.

[0081] In step 3, the composite liquid agent comprises 120 parts by weight of polymer emulsion, 15 parts by weight of migratory rust inhibitor and 2 parts by weight of surfactant; the composite powder comprises 450 parts by weight of cementitious material, 600 parts by weight of graded aggregate, 35 parts by weight of polymer powder, 3 parts by weight of water-retaining agent and 2 parts by weight of water-reducing agent.

[0082] In step 4, the dry powder components include, by weight: 400 parts of cementitious material, 300 parts of graded aggregate, 300 parts of filler, 40 parts of redispersible latex powder, 5 parts of stearate water-repellent agent, 2 parts of polycarboxylate superplasticizer and 20 parts of alkali-resistant inorganic oxide pigment.

[0083] Example 6 This embodiment provides a recycled finished concrete block, which differs from Embodiment 1 in that: In step 2, component A includes 50 parts epoxy resin, 5 parts reactive diluent, and 0.6 parts additives; component B includes 12 parts curing agent, 200 parts active rust inhibitor, and 20 parts functional filler.

[0084] In step 3, the composite liquid agent comprises 90 parts by weight of polymer emulsion, 6 parts by weight of migratory rust inhibitor and 0.6 parts by weight of surfactant; the composite powder comprises 350 parts by weight of cementitious material, 450 parts by weight of graded aggregate, 15 parts by weight of polymer powder, 1 part by weight of water-retaining agent and 0.5 parts by weight of water-reducing agent.

[0085] In step 4, the dry powder components include, by weight: 300 parts of cementitious material, 200 parts of graded aggregate, 200 parts of filler, 25 parts of redispersible latex powder, 3 parts of stearate water-repellent agent, 0.5 parts of polycarboxylate superplasticizer and 5 parts of alkali-resistant inorganic oxide pigment.

[0086] Comparative Example 1 This comparative example provides a recycled finished concrete block, which differs from Example 1 in that: Step 2 uses traditional red lead alkyd rust-preventive paint instead of a special rust-preventive agent. The components of the red lead alkyd rust-preventive paint include 60 parts alkyd resin, 200 parts red lead powder, 10 parts talc powder, 8 parts medium chrome yellow, 0.5 parts cobalt naphthenate, and 25 parts No. 200 solvent oil. In the interface agent of step 3, no migration-type rust inhibitor is added.

[0087] Comparative Example 2 This comparative example provides a recycled finished concrete block, which differs from Example 1 in that chemical roughening is not performed in step 3.

[0088] Comparative Example 3 This comparative example provides a recycled finished concrete block, which differs from Example 1 in that: in step 3, the interface agent is pure cement paste, and the components are: 100 parts of PO 42.5 cement and 20 parts of water; In step 4, the finishing layer mixture uses ordinary cement mortar (without adhesive powder), and its components are: 300 parts of PO 42.5 cement and 600 parts of standard sand.

[0089] Comparative Example 4 This comparative example provides a recycled finished concrete block, which differs from Example 1 in that: step 2 is not performed (i.e., no rust prevention treatment); and in step 3, no migration-type rust inhibitor is added to the interface agent.

[0090] Test case Test samples: Recycled finished concrete blocks prepared in Examples 1-6 and Comparative Examples 1-4 were used as samples for testing.

[0091] Test method: 1. Rust prevention performance of reinforcing steel Neutral salt spray test, standard: GB / T10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test".

[0092] Test Methods and Indicators: This test aims to accelerate the evaluation of the corrosion resistance of the anti-rust coating in the harsh marine atmospheric environment. Specimens with cross-cutting marks (deep to the reinforcing steel) are placed in a salt spray chamber and continuously sprayed with a sodium chloride solution of (5±1)% concentration and neutral pH, while maintaining a constant temperature of (35±2)℃. It is recommended to continue the test for 500 hours. After the test, the specimens are removed, rinsed clean, and the corrosion at the scratches is examined.

[0093] The core evaluation criteria are: the width of rust expansion on one side of the scratch edge should not exceed 2.0 mm, and there should be no red rust in the intact paint film area outside the scratch.

[0094] 2. Adhesion performance Tensile bond strength test, standard: JGJ / T 70-2009 "Standard for Test Methods of Basic Properties of Building Mortar"; Test methods and indicators: This test is used to quantitatively determine the bonding strength between the finishing layer and the base layer. Using a suitable tensile testing machine, the bonded specimen after standard curing is stretched at a loading rate of (5±1) mm / min until failure.

[0095] The core evaluation indicators include two parts: Strength value: The tensile bond strength (original strength) should not be less than 0.8 MPa. Failure mode: Ideally, failure should occur within the substrate, finishing layer, or interface agent, i.e., "cohesive failure". If failure occurs at the interface between two layers (bond failure), it indicates insufficient interfacial bonding.

[0096] 3. Freeze-thaw resistance test Freeze-thaw resistance test standard: JGJ / T70-2009 "Standard for Test Methods of Basic Properties of Building Mortar" (rapid freezing method); Test methods and indicators: This test is used to simulate the durability of blocks subjected to repeated freeze-thaw cycles in cold regions. Standard-cured specimens are placed in a freeze-thaw testing machine and subjected to one complete freeze-thaw cycle (e.g., freezing in a cryogenic solution at (-20±2)℃ for 4 hours, then thawing in water at (20±2)℃ for 4 hours). No fewer than 50 cycles are required.

[0097] The core evaluation indicators are: Appearance integrity: the finish layer should be free of hollow areas, peeling, and visible cracks. Quality loss: the cumulative quality loss rate of the specimen should not exceed 5%.

[0098] 4. Anti-alkali blooming properties Reference standard for wet-dry cycle test: JC / T1024-2021 "Wall Finishing Mortar"; Test Methods and Indicators: This test is used to examine the ability of the finishing layer to inhibit the migration and precipitation of alkaline substances from cement with moisture. A wet-dry cycle method is used. One standard cycle consists of immersing the specimen in water at (20±2)℃ for (24±2) hours, then removing it and drying it at (23±2)℃ and (50±5)% relative humidity for (24±2) hours. Three cycles are recommended. After the test, the surface of the finishing layer is visually observed at a distance of 1 meter under sufficient light.

[0099] The core evaluation indicator is: no obvious (i.e. imperceptible) white salt bloom or efflorescence on the surface.

[0100] The test results are shown in Tables 1-4.

[0101] Table 1. Corrosion Resistance Testing of Reinforcing Steel

[0102] Table 2. Adhesion strength (original strength) test of finishing layer

[0103] Table 3. Freeze-thaw resistance and crack resistance tests

[0104] Table 4. Anti-alkali test

[0105] As shown in Tables 1-4, the recycled finished concrete blocks prepared in each embodiment of the present invention exhibit strong adhesion between the finished layer and the waste concrete matrix, demonstrating excellent rust resistance, freeze-thaw resistance, crack resistance, and efflorescence resistance, as well as good durability. Specifically, Table 1 shows that the rust-preventive pigment used in Example 4, zinc phosphate, is a passivating type and cannot provide cathodic protection at scratches, thus reducing performance. Tables 3 and 4 show that the amount of adhesive powder in Example 3 was insufficient, resulting in a discontinuous polymer network that could not effectively resist stress. Sufficient adhesive powder is crucial for crack resistance. Furthermore, insufficient density provided channels for moisture and alkali migration, leading to slight efflorescence. Tables 3 and 4 also show that the finished layer of Comparative Example 3, lacking adhesive powder, was extremely brittle and unable to withstand the internal stress generated by freeze-thaw cycles, resulting in severe cracking and peeling. Additionally, the high porosity of Comparative Example 3 led to significant alkali precipitation, causing severe efflorescence.

[0106] Comparative Examples 1-4, due to the absence or replacement of key anti-rust components, interface treatment processes, and polymer modification materials, resulted in significant deterioration in one or more key properties of the prepared blocks, such as hollow cracking of the surface finish, spread of steel reinforcement corrosion, or severe efflorescence on the surface.

[0107] This invention integrates substrate treatment, dual rust prevention, interface strengthening, and high-performance finishing layer technologies to transform waste reinforced concrete from building demolition into wall materials that combine high durability and aesthetics. This technology achieves high-value-added resource utilization of construction waste, reduces natural stone mining and cement consumption, and its superior durability helps extend building maintenance cycles and lower total life-cycle costs, aligning with the direction of green and sustainable building development.

[0108] 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 recycled finished concrete block, characterized in that, include: The base is made by cutting up scrap reinforced concrete components, the original structural steel bars are retained inside the base, and at least one surface has the end of the steel bars exposed. A rust-proof coating is applied to the exposed ends of the reinforcing bars; An interface transition layer and a finishing layer are sequentially stacked on at least one surface of the substrate, wherein the interface transition layer is used to enhance the adhesion between the new and old materials.

2. The recycled finished concrete block according to claim 1, characterized in that, The substrate is a block formed by cutting a reinforced concrete slab or wall obtained through building demolition; Preferably, the length of the substrate is 300mm to 600mm, the width is 100mm to 300mm, and the height is 200mm to 300mm.

3. The recycled finished concrete block according to claim 1, characterized in that, The thickness of the anti-rust coating is 60–100 μm; Preferably, the anti-rust coating comprises a coating formed by mixing and curing component A and component B, wherein component A comprises epoxy resin, reactive diluent and additives, and component B comprises curing agent, active anti-rust component and functional filler; Preferably, the mass ratio of component A to component B is 1:2.5 to 4; Preferably, component A comprises, by weight: 50-70 parts epoxy resin, 5-10 parts reactive diluent, and 0.5-2.5 parts additives; Preferably, the epoxy resin includes one or more of bisphenol A type epoxy resin and bisphenol F type epoxy resin; Preferably, the reactive diluent includes one or more of monofunctional, difunctional, or multifunctional epoxy reactive diluents; Preferably, the additives include one or more of wetting and dispersing agents, defoamers, and leveling agents; Preferably, component B comprises, by weight: 10-25 parts curing agent, 200-350 parts active rust inhibitor and 20-50 parts functional filler; Preferably, the curing agent includes one or more of polyamide curing agents and amine adduct curing agents; Preferably, the active rust-preventing component includes a sacrificial anode material and an optional passivating rust-preventing material; the sacrificial anode material includes zinc powder, and the content of the sacrificial anode material accounts for more than 70% of the total mass of the active rust-preventing component; Preferably, the functional filler includes one or more of sericite, talc, barium sulfate, and wollastonite.

4. The recycled finished concrete block according to claim 1, characterized in that, The thickness of the interface transition layer is 1-2 mm; Preferably, the raw materials for preparing the interface transition layer include composite liquid and composite powder. The composite liquid includes polymer emulsion, migratory rust inhibitor and surfactant, and the composite powder includes cementitious material, aggregate, polymer powder, water-retaining agent and water-reducing agent. Preferably, the mass ratio of the composite liquid to the composite powder is 1:3 to 4; Preferably, the composite liquid agent comprises, by weight, 80-120 parts polymer emulsion, 5-15 parts migratory rust inhibitor, and 0.5-2 parts surfactant; Preferably, the polymer emulsion includes one or more of styrene-acrylic emulsion, pure acrylic emulsion, and styrene-butadiene emulsion; Preferably, the migratory rust inhibitor includes one or more of amino alcohols and fatty acid esters as migratory steel rust inhibitors; Preferably, the surfactant includes one or more of nonionic surfactants and anionic surfactants; Preferably, the composite powder comprises, by weight, 350-450 parts of cementitious material, 450-600 parts of aggregate, 15-35 parts of polymer powder, 1-3 parts of water-retaining agent and 0.5-2 parts of water-reducing agent; Preferably, the cementitious material includes one or more of silicate cement, aluminate cement, and sulfoaluminate cement; Preferably, the aggregate includes one or more of quartz sand, river sand, limestone sand and tailings sand of different particle sizes; Preferably, the polymer powder includes redispersible latex powder, which includes one or more of vinyl acetate-ethylene copolymer powder and acrylate copolymer powder; Preferably, the water-retaining agent comprises one or more of cellulose ether and starch ether; Preferably, the water-reducing agent includes one or more of polycarboxylate-based and naphthalene-based water-reducing agents.

5. The recycled finished concrete block according to claim 1, characterized in that, The thickness of the finishing layer is 1.5 ± 0.5 mm; Preferably, the raw materials for preparing the finishing layer include: cementitious materials, aggregates, fillers, and additives; Preferably, the cementing material comprises white silicate cement; Preferably, the aggregate comprises 100-200 mesh quartz powder; Preferably, the filler comprises 200-300 mesh heavy calcium carbonate powder; Preferably, the additives include one or more of redispersible latex powder, stearate water-repellent agents, polycarboxylate water-reducing agents, and color powder; Preferably, the redispersible latex powder comprises one or more of vinyl acetate-ethylene adhesive powder and acrylate adhesive powder; Preferably, the pigment comprises alkali-resistant inorganic oxide pigments; Preferably, the raw materials of the finishing layer include, by weight: 300-400 parts of cementitious material, 200-300 parts of aggregate, 200-300 parts of filler, 25-40 parts of redispersible latex powder, 3-5 parts of stearate water-repellent agent, 0.5-2 parts of polycarboxylate water-reducing agent, and 5-20 parts of color powder.

6. The method for preparing recycled finished concrete blocks according to any one of claims 1-5, characterized in that, Includes the following steps: (a) Cutting scrap reinforced concrete components into bases of predetermined dimensions; (b) Prepare a rust-proof coating on the exposed ends of the reinforcing bars in the substrate; (c) An interface transition layer and a finishing layer are sequentially stacked on the surface of the substrate; wherein, the substrate is etched before the interface transition layer is prepared.

7. The preparation method according to claim 6, characterized in that, In step (b), the anti-rust coating is formed by mixing component A and component B, applying the mixture to the exposed ends of the reinforcing bars, and then curing it. Preferably, the coating method includes scraping or airless spraying.

8. The preparation method according to claim 6, characterized in that, In step (c), the etching process includes: chemically etching the surface of the substrate concrete using an acidic solution with a pH value of 2 to 3; Preferably, the preparation of the interface transition layer includes: after the etching treatment, rinsing and drying, and then applying a polymer-modified cement-based interface agent; Preferably, the etching process takes 3 to 5 minutes; the rinsing pressure is 0.5 to 0.8 MPa; and the drying method includes natural drying or drying in an oven at ≤50°C. Preferably, the polymer-modified cement-based interface agent is prepared by mixing a composite liquid agent and a composite powder agent; the stirring speed during the mixing process is 600-800 rpm, and the stirring time is 3-5 minutes. Preferably, the coating method includes brush coating or airless spray coating.

9. The preparation method according to claim 6, characterized in that, In step (c), the preparation of the finishing layer includes: forming the finishing layer by applying a mixture of raw materials and then sealing and curing it; Preferably, the raw materials for the finishing layer include a dry powder component and water, wherein the dry powder component includes a cementitious material, aggregate, filler and additive, and the mass ratio of the dry powder component to the water is 1:0.18 to 0.22; Preferably, the coating is applied by mechanical spraying or manual wiping.

10. The preparation method according to claim 9, characterized in that, The sealing and curing time is 24-48 hours.

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