CN108147753B - Recycled concrete, assembled composite wallboard and preparation method thereof - Google Patents

Abstract

The invention provides a recycled concrete, an assembled composite wallboard and a preparation method thereof. A recycled concrete is mainly made of the following materials: by weight, 70-90 parts of cement, 3-6 parts of fly ash, 10-15 parts of slag, 200-250 parts of construction waste, and 0.6-1 part of water reducing agent , 0.08-0.12 part of defoamer, 0.06-0.1 part of water-retaining agent, 0.2-0.4 part of retarder and 30-50 parts of water. Compared with the existing powder concrete, the compressive strength of the recycled concrete of the present invention is improved, and the properties such as density and thermal conductivity can reach at least the same level as the existing recycled concrete, and the self-weight of the wallboard can also be reduced, and various decorations can be displayed. Effect.

Description

A kind of recycled concrete, assembled composite wall panel and preparation method thereof

technical field

The invention relates to the technical field of building materials, in particular to a recycled concrete, an assembled composite wallboard and a preparation method thereof.

Background technique

At present, building energy consumption has been tied with industrial energy consumption and transportation energy consumption, becoming the three major "energy consumers" in my country's energy consumption. Building energy consumption (including construction energy consumption, living energy consumption, heating and air conditioning, etc.) 30% of the total social energy consumption, the most important of which is heating and air conditioning, accounting for 20%. Therefore, the construction technology of building wall thermal insulation came into being. However, in recent years, fire accidents caused by the poor flame retardant performance of wall thermal insulation materials have continued, causing serious losses to the life and property of the country and the people. , and flame-retardant wall insulation materials are particularly important.

Prefabricated concrete structure is the main structure assembled by concrete components through reliable connection, including fully assembled concrete structure, assembled monolithic concrete structure, etc. All or part of its structural components are prefabricated in factories and installed on site. It has the advantages of fast construction speed, low labor intensity, less noise pollution and wet work, and easy quality control. The promotion of prefabricated concrete structures will greatly reduce the energy consumption in the construction process, and the thermal insulation treatment of the envelope structure is of great significance to the reduction of building operating energy consumption. In the process of advancing the prefabricated concrete building, a large number of "sandwich" thermal insulation integrated wall panels will be used. The "sandwich" sandwich panel consists of inner leaf wall panels, thermal insulation panels and leaf wall panels. Between the inner and wall panels, the corresponding thickness of insulation layer is designed according to the energy-saving standard, and the inner and leaf walls are connected through special connectors.

Recycled concrete means that after crushing, cleaning, and grading waste concrete blocks, they are mixed with grading in a certain proportion, partially or completely replacing natural aggregates such as sand and gravel (mainly coarse aggregates), and then adding cement, water, etc. new concrete. Because recycled concrete can recycle part of waste industrial products or garbage, the cost is low, so it is considered to be one of the best choices for making prefabricated composite wall panels. However, the existing recycled concrete has insufficient compressive strength, which limits its application range. . For example, the strength level of recycled concrete used in patent application CN103541462A can only reach C35.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a recycled concrete, the compressive strength of the recycled concrete is improved compared with the existing powder concrete, and the properties such as density and thermal conductivity can at least reach the same level as the existing recycled concrete, and can also Reduce the self-weight of the wall panel and show colorful decorative effects.

The second object of the present invention is to provide a prefabricated composite wallboard made of the above recycled concrete.

The third object of the present invention is to provide a preparation method of the above-mentioned prefabricated composite wallboard, the preparation method has a simple process, low technical requirements, and is easier to industrialize production.

In order to achieve the above purpose, the present invention provides the following technical solutions:

A recycled concrete mainly made of the following materials:

By weight, 70-90 parts of cement, 3-6 parts of fly ash, 10-15 parts of slag, 200-250 parts of construction waste, 0.6-1 part of water reducing agent, 0.08-0.12 part of defoamer, 0.06 part of water-retaining agent ~0.1 part, 0.2-0.4 part of retarder and 30-50 parts of water.

Compared with the prior art, the compressive strength of the recycled concrete of the present invention is improved, and the 28-day compressive strength can reach more than 46.6 MPa, and the density does not increase and remains below 1980 kg/cm ³ .

The formulation of the above recycled concrete can be further improved, as follows.

Preferably, the cement is ordinary Portland cement, and the strength grade is one of 42.5 or 42.5R or a mixture of both;

Preferably, the fly ash grade is one of grade I or grade II or a mixture of both;

Preferably, the slag grade is one of S95 grade or S105 grade or a mixture of both;

Preferably, the construction waste is one or a mixture of waste concrete or waste brick, and the particle size is less than or equal to 20 mm;

Preferably, the superplasticizer is a polycarboxylate superplasticizer;

Preferably, the defoamer is one of silicone oil or ether defoamer or a mixture of both;

Preferably, the water-retaining agent is one of hydroxypropyl methyl cellulose ether or methyl cellulose ether or a mixture of both;

Preferably, the retarder is one or a mixture of sodium gluconate, tartaric acid and boric acid.

All of the above recycled concrete of the present invention can be used in any part of any building, as long as its performance meets preset requirements. The present invention now enumerates one of the purposes of recycled concrete—as the decorative protective layer of the prefabricated composite wallboard, and the concrete structure of this prefabricated composite wallboard is as follows:

The assembled composite wall panel sequentially includes a first decorative protective layer, a reinforcing layer, a second decorative protective layer, a vacuum insulation panel layer and a structural layer;

The first decorative protective layer and the second decorative protective layer are both made of the recycled concrete.

In addition to utilizing the advantages of the recycled concrete, the composite wallboard also has the following advantages:

1. Integrate the five-layer structure of the first decorative protective layer, the reinforcement layer, the second decorative protective layer, the vacuum insulation board layer and the structural layer. The effect of integrating thermal properties and other characteristics.

2. A reinforcing layer is inserted into the decorative protective layer, and the reinforcing layer has the characteristics of high strength and lightness, so the present invention does not need to increase the thickness of the decorative protective layer to increase the load-bearing capacity of the wall panel, and also avoids excessively thick decorative layer. Easy to crack, seepage and other phenomena. In addition, the reinforcing layer also effectively blocks the unexpected sharp stab force from the outside, so as to avoid damage to the vacuum insulation panel caused by the stab force.

3. The vacuum insulation board is used as the insulation layer, which has the advantages of fire prevention, low thermal conductivity, and no toxicity. Specifically, the vacuum insulation panel is a new type of energy-saving insulation material. On the one hand, the principle of vacuum insulation can be used to effectively eliminate the convection effect; Heat radiation. Due to the combination of vacuum insulation and microporous insulation, the vacuum insulation panel ideally achieves the insulation effect and purpose of heat preservation and energy saving. On the other hand, under the same thermal insulation performance, compared with other thermal insulation materials, the thickness of the thermal insulation layer of the present invention can be saved by at least 60%.

The following materials should be used for each layer of the above composite wall panels.

Preferably, the reinforcing layer is a high-strength fiber mesh cloth or a steel mesh sheet.

The high-strength fiber mesh cloth of the present invention includes materials such as alkali-resistant glass fiber mesh cloth, basalt fiber mesh cloth and the like.

Preferably, the structural layer is a reinforced concrete layer.

Preferably, the vacuum insulation panel layer is formed by staggered splicing of a plurality of vacuum insulation panels.

Staggered paving can avoid the formation of thermal bridges, leading to problems such as easy water seepage and shortening the service life of the building.

In addition, the thermal insulation layer of the present invention is formed by splicing a plurality of small vacuum thermal insulation panels, which can avoid the problem that the large vacuum thermal insulation panels need to be cut and the thermal insulation effect is reduced.

Preferably, the staggered stitching distance of the staggered stitching is more than 150mm.

A long enough staggered seam distance can effectively avoid the thermal bridge problem.

Preferably, the width of each slit in the staggered stitching is less than 10 mm.

When the gap is too wide, the thermal insulation effect will drop sharply. Therefore, it is recommended that the gap width should not exceed 10mm.

Preferably, a connecting piece is arranged in the gap in the vacuum insulation panel layer, and the connecting piece connects the first decorative protective layer, the reinforcing layer, the second decorative protective layer and the structural layer.

The connector connects the layers of the wall panel together, increases the firmness of the wall panel, and increases its bearing capacity at the same time.

Preferably, the gaps between the vacuum insulation panels are filled with polyester foam or thermal insulation mortar.

Polyester foam or thermal insulation mortar has low thermal conductivity and good thermal insulation effect. Of course, other materials with better thermal insulation effect can also be used.

Preferably, the thicknesses of the first decorative protective layer and the second decorative protective layer are respectively 25-40 mm and 25-40 mm, the thickness of the vacuum insulation board layer is 10-20 mm, and the thickness of the structural layer is 160-220 mm .

If each layer of the wallboard adopts the above thickness, the thermal performance and load-bearing performance of the wallboard will be well balanced, that is, the wallboard can be used as a load-bearing wall and has good thermal insulation.

Preferably, the second decorative protective layer and the vacuum insulation board layer are bonded through an interface mortar layer, and the vacuum insulation board layer and the structural layer are bonded through an interface mortar layer.

The interface mortar has stronger cohesion, and spraying the interface mortar on both sides of the vacuum insulation board layer can effectively ensure the bonding strength between the vacuum insulation board and the decorative protective layer and the structural layer.

Preferably, the strength grade of the reinforced concrete layer is above C30, and the density is preferably 1500-1700 kg/m ³ .

Reinforced concrete that meets this level has good load-bearing capacity, can transfer the load of the decorative protective layer to the main structure, and has a lower density than traditional concrete, which can reduce the weight by at least 30%, and has the advantage of light weight.

Specifically, the following formula can be used:

Preferably, the reinforced concrete layer is mainly made of the following materials: by weight, 50-60 parts of cement, 3-10 parts of fly ash, 10-20 parts of slag, 60-80 parts of steel slag, and 50-60 parts of ceramsite parts, 0.05-0.15 parts of water-retaining agent, 0.1-0.2 parts of water-reducing agent, and 20-25 parts of water;

Preferably, the reinforced concrete layer is mainly made of the following materials: by weight, 50-55 parts of cement, 5-10 parts of fly ash, 10-15 parts of slag, 70-80 parts of steel slag, and 50-55 parts of ceramsite parts, 0.1-0.15 parts of water-retaining agent, 0.1-0.15 parts of water-reducing agent, and 22-25 parts of water;

Preferably, the cement is ordinary Portland cement, and the strength grade is one of 42.5 or 42.5R or a mixture of both;

Preferably, the fly ash grade is one of grade I or grade II or a mixture of both;

Preferably, the slag grade is one of S95 grade or S105 grade or a mixture of both;

Preferably, the fineness modulus of the steel slag is 3.0-3.3, and the bulk density is 1020-1080 kg/m ³ ;

Preferably, the ceramsite is fly ash ceramsite, preferably, the particle size of the ceramsite is 5-15 mm, the bulk density is 840-870 kg/m ³ , and the cylinder compressive strength is ≥5.0 MPa.

Preferably, the water reducing agent is one of polycarboxylate water reducing agent, naphthalene water reducing agent and melamine water reducing agent.

Preferably, the water-retaining agent is hydroxypropyl methylcellulose.

All the above-mentioned prefabricated composite wallboards of the present invention can adopt the following preparation methods:

Step A: in the mold sprayed with the release agent, pour a layer of the recycled concrete, then spread the reinforcement layer, and then spray another layer of recycled concrete above the reinforcement layer to form a second decorative protective layer;

Step B: before the initial setting of the recycled concrete of the second decorative protective layer, lay a plurality of vacuum insulation panels on the upper staggered joints, flatten them, and fill the gaps to form a thermal insulation layer;

Step C: pouring reinforced concrete above the thermal insulation layer to form a structural layer.

The above method first makes the decorative protective layer, and then finally lays it on the structural layer in a layer-by-layer order. No conflict, high production efficiency, and less interference between layers, higher product qualification rate, and more stable wallboard structure.

If the above factors are not considered, the wallboard can also be prepared in the reverse order of the above method.

laying connecting pieces in the gaps created when laying a plurality of vacuum insulation panels;

Preferably, lifting rings, embedded parts, pipelines, electrical boxes and reserved holes are pre-embedded between the thermal insulation layer and the structural layer.

In addition, some preprocessing work can be done before step A, such as cleaning the platform, setting up side molds, and leaving door and window openings. When spraying recycled concrete, vibrate while spraying to ensure uniform thickness.

If the vacuum insulation panel is to be laid before the initial setting of the recycled concrete, it needs to be placed for 15 to 20 minutes.

The anchoring length of the connector in the single-sided wall panel should not be less than 15mm. Fix anti-corrosion wood bricks and vacuum insulation boards around the door and window openings for bridge breaking treatment; set up pads, hoist steel cages, pre-embedded rings, pre-embedded parts, pipelines, Electrical box, reserved holes, etc.

After pouring the structural layer, it is necessary to vibrate, burn out, natural curing or steam curing, grinding, polishing, demoulding, lifting and stacking.

To sum up, compared with the prior art, the present invention achieves the following technical effects:

(1) The recycled concrete of the present invention has improved compressive strength, is suitable for making shear walls, and can still maintain a relatively low density without increasing the self-weight of the wall; it can also enrich the decorative effect by adding inorganic pigments of different textures and colors. ;

(2) The wallboard of the present invention can integrate the characteristics of fire prevention, heat preservation, lightness, thinness and load-bearing, especially outstanding load-bearing performance, better comprehensive performance, and wider application range; it avoids the traditional sandwich assembly wallboard which is easy to crack, seepage, etc. Thermal bridges, etc.;

(3) The wallboard preparation method of the present invention has a simple process and high production efficiency.

Description of drawings

In order to illustrate the specific embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the specific embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an assembled composite wall panel provided in Embodiment 1 of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, rather than all of the embodiments, It is only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market.

Example 1

Fabrication of prefabricated composite wall panels

(1) Clean the platform, build side molds, leave door and window openings, and spray mold release agent.

(2) Evenly spray 25mm thick recycled concrete, and lay the reinforcement layer; the formula of recycled concrete is: 70 grams of cement, 6 grams of fly ash, 10 grams of slag, 250 grams of construction waste, 0.6 grams of water reducer, 0.12 grams of defoamer gram, water retention agent 0.06 grams, retarder 0.4 grams and water 30 grams, the cement is ordinary Portland cement, the strength grade is 42.5, the fly ash grade is I grade, the slag grade is S95 grade, the construction waste is waste concrete, The particle size is less than or equal to 20mm, the water reducing agent is polycarboxylate superplasticizer, the defoaming agent is silicone oil, the water retaining agent is hydroxypropyl methyl cellulose ether, and the retarder is sodium gluconate. The reinforcement layer is made of alkali-resistant glass fiber mesh.

(3) Then spray 40mm thick recycled concrete on the reinforcement layer again (the same formula as the second step), after vibrating the decorative protective layer to a uniform thickness, immediately place a vacuum insulation panel coated with a 0.5mm thick interface agent on both sides (Thickness is 10mm). The placement time should be controlled within the range of 15 to 20 minutes to ensure that the recycled concrete does not reach the initial setting state.

(4) When laying the vacuum insulation panels, the gaps between the panels should be staggered, and the minimum local staggered seam should not be less than 150mm. The vacuum insulation panels at the outside corners should be staggered or special matching panels should be used, and the width of the panels should not exceed 10mm. .

(5) After placing the vacuum insulation panels, the gaps between the insulation panels are filled with polyurethane foam or thermal insulation recycled concrete to prevent the infiltration of reinforced ceramsite concrete, and the connectors are embedded in advance. The anchorage length of the connectors in the single-sided wall panel is not suitable If it is less than 20mm, fix anti-corrosion wood bricks and vacuum insulation boards around the door and window openings for bridge breaking treatment.

(6) Set up pads, hoist steel cages, pre-embed lifting rings, pre-embedded parts, pipelines, electrical boxes, reserved holes, etc.

(7) Pour the ceramsite concrete structure layer with a thickness of not less than 160mm (according to JGJ3-2010 "Technical Specifications for Concrete Structures of High-rise Buildings", the section thickness of the shear wall should meet the following requirements: first and second-level shear walls: bottom reinforcement part should not be less than 200mm, and other parts should not be less than 160mm; the reinforcement part at the bottom of the in-line independent shear wall should not be less than 220mm, and other parts should not be less than 180mm), vibrate and burn out; the formula of ceramsite concrete used is: cement 50 grams, 10 grams of fly ash, 10 grams of slag, 80 grams of steel slag, 50 grams of ceramsite, 0.15 grams of water retention agent, 0.1 grams of water reducing agent, and 25 grams of water; the cement is ordinary Portland cement with a strength grade of 42.5 powder The coal ash grade is I; the slag grade is S95; the fineness modulus of the steel slag is 3.0-3.3, and the bulk density is 1020-1080kg/m ³ ; the ceramsite is fly ash ceramsite, and the particle size of the ceramsite is 5 ～15mm, bulk density is 840～870kg/m ³ , cylinder compressive strength is ≥5.0MPa; water-retaining agent is hydroxypropyl methylcellulose, and water-reducing agent is polycarboxylate water-reducing agent.

(8) Natural curing or steam curing, grinding, polishing, demoulding, lifting and palletizing.

The structure of the wall panel produced in this embodiment is shown in Figure 1, which is consistent with the above method, including the first layer of decorative protection layer 1 (completed by the second step), the reinforcement layer 2, and the second layer of decorative protection layer that are laminated in sequence Layer 3 (completed by the third step), vacuum insulation panel layer 4 and structural layer 7; connecting pieces 6 are arranged in the caulking 5 of the vacuum insulation panel layer.

Example 2

The difference from Example 1 is that the used recycled concrete formula for the decorative protective layer is different, and the used recycled concrete formula is:

90 grams of cement, 3 grams of fly ash, 15 grams of slag, 200 grams of construction waste, 1 gram of water reducing agent, 0.08 grams of defoamer, 0.1 grams of water retention agent, 0.2 grams of retarder and 50 grams of water, the cement is ordinary silicon Acid cement, strength grade is 42.5R or a mixture of both, fly ash grade is II, slag grade is S105, construction waste is waste brick, particle size ≤ 20mm, water reducing agent is polycarboxylic acid High-efficiency water-reducing agent, defoamer is ether defoamer, water-retaining agent is methyl cellulose ether, and retarder is boric acid.

The other steps and the structure of the wall panel are the same as those in Example 1.

Example 3

The difference from Example 1 is that the formula of the ceramsite reinforced concrete used in the structural layer is different, which is:

60 grams of cement, 3 grams of fly ash, 20 grams of slag, 60 grams of steel slag, 60 grams of ceramsite, 0.05 grams of water retention agent, 0.2 grams of water reducing agent, and 20 grams of water; the cement is ordinary Portland cement with a strength grade of 42.5 R; fly ash grade is II; slag grade is S105; steel slag has a fineness modulus of 3.0 to 3.3, and a bulk density of 1020 to 1080 kg/m ³ ; ceramsite is fly ash ceramsite, and ceramsite particles The diameter is 5-15mm, the bulk density is 840-870kg/m ³ , the cylinder pressure strength is ≥5.0MPa; the water-retaining agent is hydroxypropyl methylcellulose, and the water-reducing agent is a naphthalene-based water-reducing agent.

The other steps and the structure of the wall panel are the same as those in Example 1.

Example 4

The difference from Example 1 is that the thickness of each layer is different, specifically:

The thicknesses of the first decorative protective layer and the second decorative protective layer are 30mm and 30mm respectively, the thickness of the vacuum insulation board layer is 20mm, and the thickness of the structural layer is 160mm.

The other steps and the structure of the wall panel are the same as those in Example 1.

The present invention also tested the density, compressive strength, thermal performance and other indicators of the recycled concrete used in Examples 1 and 2. The results are shown in Table 1.

Table 1 Properties of recycled concrete

The present invention also tests the density, compressive strength, thermal performance and other indicators of the ceramsite concrete used in Examples 1 and 3 (that is, the material used for the structural layer), and the results are shown in Table 2.

Table 2 Properties of concrete

The present invention also tested the load-bearing and thermal insulation properties of the wallboards of Examples 1 and 4, and the results are shown in Table 3.

Table 3 Properties of Wall Panels

Example 1 Example 4 Heat transfer coefficient (W/(m²·K) 0.46 0.38

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (5)

1. A prefabricated composite wallboard, characterized in that, the prefabricated composite wallboard comprises a first decorative protective layer, a reinforcing layer, a second decorative protective layer, a vacuum insulation panel layer and a structural layer in turn; The first decorative protective layer and the second decorative protective layer are both made of recycled concrete; The recycled concrete is mainly made of the following materials: by weight, 70-90 parts of cement, 3-6 parts of fly ash, 10-15 parts of slag, 200-250 parts of construction waste, 0.6-1 part of water reducing agent, 0.08-0.12 part of defoamer, 0.06-0.1 part of water retention agent, 0.2-0.4 part of retarder and 30-50 parts of water; The cement is ordinary Portland cement, and the strength grade is one of 42.5 or 42.5R or a mixture of both; The fly ash grade is one of grade I or grade II or a mixture of both; The slag grade is one of S95 grade or S105 grade or a mixture of both; The construction waste is one or a mixture of waste concrete or waste brick, and the particle size is less than or equal to 20mm; The water-reducing agent is a high-efficiency water-reducing agent of polycarboxylate; The defoamer is one of silicone oil or ether defoamer or a mixture of both; The water-retaining agent is one of hydroxypropyl methyl cellulose ether or methyl cellulose ether or a mixture of both; Described retarder is one or more mixtures in sodium gluconate, tartaric acid and boric acid; The reinforcing layer is a high-strength fiber mesh cloth, and the high-strength fiber mesh cloth is an alkali-resistant glass fiber mesh cloth or a basalt fiber mesh cloth; The vacuum insulation panel layer is formed by staggered splicing of a plurality of vacuum insulation panels, The staggered distance of the staggered stitching is more than 150mm; The width of each gap in the staggered stitching is less than 10mm; A connecting piece is arranged in the gap in the vacuum insulation panel layer, and the connecting piece connects the first decorative protective layer, the reinforcing layer, the second decorative protective layer and the structural layer; The gaps between the vacuum insulation panels are filled with polyester foam or thermal insulation mortar; The structural layer is a reinforced concrete layer, the strength grade of the reinforced concrete layer is above C30, and the density is 1500-1700 kg/m ³ ; The reinforced concrete layer is mainly made of the following materials: by weight, 50-60 parts of cement, 3-10 parts of fly ash, 10-20 parts of slag, 60-80 parts of steel slag, 50-60 parts of ceramsite, and water-retaining agent 0.05-0.15 parts, water reducing agent 0.1-0.2 parts, water 20-25 parts; The cement is ordinary Portland cement, and the strength grade is one of 42.5 or 42.5R or a mixture of both; The fly ash grade is one of grade I or grade II or a mixture of both; The slag grade is one of S95 grade or S105 grade or a mixture of both; The fineness modulus of the steel slag is 3.0-3.3, and the bulk density is 1020-1080 kg/m ³ ; The ceramsite is fly ash ceramsite; The particle size of the ceramsite is 5-15 mm, the bulk density is 840-870 kg/m ³ , and the cylinder compressive strength is greater than or equal to 5.0 MPa; The water-reducing agent is one of a polycarboxylate water-reducing agent, a naphthalene-series water-reducing agent and a melamine-series water-reducing agent; The water-retaining agent is hydroxypropyl methylcellulose. 2. The prefabricated composite wallboard according to claim 1, wherein the recycled concrete is mainly made of the following materials: by weight, 80-90 parts of cement, 3-5 parts of fly ash, and 12 parts of slag ~15 parts, 200-230 parts of construction waste, 0.8-1 part of water reducing agent, 0.08-0.1 part of defoamer, 0.08-0.1 part of water retention agent, 0.2-0.3 part of retarder and 40-50 parts of water. 3. The prefabricated composite wallboard according to claim 1 or 2, wherein the thicknesses of the first decorative protective layer and the second decorative protective layer are respectively 25-40 mm and 25-40 mm, and the vacuum heat insulation The thickness of the board layer is 10-20mm, and the thickness of the structural layer is 160-220mm; The second decorative protection layer and the vacuum insulation board layer are bonded by an interface mortar layer, and the vacuum insulation board layer and the structural layer are bonded by an interface mortar layer. 4. a preparation method of the prefabricated composite wallboard according to any one of claims 1-3, is characterized in that, comprises the following steps: Step A: in the mold sprayed with the release agent, pour one layer of the regenerated concrete, then spread the reinforcement layer, and then spray another layer of regenerated concrete above the reinforcement layer to form a second decorative protective layer; Step B: before the initial setting of the recycled concrete of the second decorative protective layer, lay a plurality of vacuum insulation panels on the upper staggered joints, flatten them, and fill the gaps to form a thermal insulation layer; Step C: pouring reinforced concrete above the thermal insulation layer to form a structural layer. 5. The preparation method according to claim 4, characterized in that, connecting pieces are laid in the gaps generated when laying a plurality of vacuum insulation panels; Lifting rings, embedded parts, pipelines, electrical boxes and reserved holes are pre-embedded between the thermal insulation layer and the structural layer.

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