Building recycled material and preparation method thereof

Abstract

The invention relates to the field of building materials, and provides a building recycled material and a preparation method thereof.The building recycled material is prepared from, by weight, 900-1100 parts of recycled coarse aggregate, 290-310 parts of cement, 220-240 parts of natural sand, 35-45 parts of fly ash, 5-15 parts of a water reducing agent, 0.5-2 parts of a retarder, 15-25 parts of a modified polyimide-based composite material and 15-30 parts of polypropylene glycol; and 200 to 300 parts of water. The building recycled material provided by the invention is recycled concrete and has the characteristics of high compressive strength and freezing resistance.

Description

Technical Field

[0001] The invention relates to the field of building materials, and in particular to a building recycled material and a preparation method thereof. Background Art

[0002] With the rapid economic development and the accelerated pace of urbanization in China, more and more old buildings are being demolished and rebuilt because they cannot meet the requirements of urban planning. This leads to the problem of the reasonable disposal of a large amount of construction waste. In order to make full use of construction waste and reduce the damage and pollution to the environment caused by the storage of construction waste, researchers have classified, processed and treated construction waste to achieve resource reuse, and have been able to produce a variety of building recycled materials, among which recycled concrete is an important example.

[0003] Recycled concrete refers to a new type of concrete made by crushing, cleaning, grading, mixing with grades in a certain proportion, partially or completely replacing natural aggregates such as sand and gravel, and then adding cement, water and other concrete raw materials. Recycled concrete has the advantages of environmental protection, low density, heat insulation and sound insulation, but because the apparent density of recycled aggregates is lower than that of natural aggregates, its compressive strength is low and cannot meet the standards, and the frost resistance of recycled concrete is also low.

[0004] Patent CN 111087211 A discloses a recycled coarse aggregate concrete and a preparation method thereof. The recycled coarse aggregate concrete prepared in the application includes components of a coarse aggregate composition, cement, blast furnace slag, natural river sand, waste plastic, a water reducer and water. Recycled coarse aggregate, blast furnace slag and waste plastic are used as raw materials to prepare the recycled coarse aggregate concrete, which effectively utilizes waste, reduces the cost of new construction projects and can also achieve basic strength. However, the application does not modify and improve the compressive strength and frost resistance of the recycled concrete, which limits its scope of application to a certain extent.

[0005] Therefore, there is an urgent need for a recycled building material in the market, which is a recycled concrete with high compressive strength and frost resistance. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention uses recycled coarse aggregate, cement, natural sand and the like as main components, designs and adds modified polyimide-based composite materials and modified diatomaceous earth to prepare a building recycled material with high compressive strength and frost resistance.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On one hand, the present invention provides a building recycled material, which comprises the following raw materials in parts by weight: 900-1100 parts of recycled coarse aggregate, 290-310 parts of cement, 220-240 parts of natural sand, 35-45 parts of fly ash, 5-15 parts of water reducer, 0.5-2 parts of retarder, 15-25 parts of modified polyimide-based composite material, 15-30 parts of polypropylene glycol, and 200-300 parts of water.

[0009] In some embodiments of the present invention, the method for preparing the recycled coarse aggregate comprises the following steps:

[0010] The waste concrete is crushed and sieved to obtain the undersize with an average particle size of less than 4 mm, silicon nitride powder is added to the undersize, and after stirring, it is immersed in a sodium silicate aqueous solution for 0.5-3 hours, taken out, and naturally dried to obtain recycled coarse aggregate.

[0011] In some embodiments of the present invention, the water reducer is a polycarboxylate water reducer.

[0012] In some embodiments of the present invention, the retarder is lignin sulfonate.

[0013] Preferably, the retarder is sodium lignin sulfonate or calcium lignin sulfonate.

[0014] In some embodiments of the present invention, the method for preparing the modified polyimide-based composite material comprises the following steps:

[0015] (1) hydroxyethylidene diphosphonic acid, KH560, deionized water and anhydrous ethanol are mixed and stirred to obtain a mixed solution for use, basalt fibers are added to the ethanol aqueous solution, ultrasonicated, and then transferred to the mixed solution after drying, heated to 80-90° C., stirred, filtered, and dried to obtain pretreated basalt fibers for use;

[0016] (2) trimethylmethoxysilane, polyvinyl pyrrolidone, sodium dodecyl sulfate and deionized water are mixed, stirred, triethylamine is added, stirred, KH560 is added, stirred, filtered, washed, and the product is obtained for later use;

[0017] (3) under an inert atmosphere, adding the product of step (2) to a mixed solution of 4,4-diaminodiphenyl ether and N,N-dimethylacetamide, heating to 75-85° C. for reaction, cooling to room temperature, adding pyromellitic anhydride, stirring, filtering, washing, heating to 305-315° C., stirring, and obtaining a modified polyimide for standby use;

[0018] (4) The pretreated basalt fiber of step (1) and the modified polyimide of step (3) are mixed, cold-pressed, heated to 180-220° C., pressurized and kept warm and pressurized, cooled to room temperature, and dried to obtain a modified polyimide-based composite material.

[0019] Wherein, in the step (1), the ratio of basalt fiber, hydroxyethylidene diphosphonic acid, KH560, deionized water and anhydrous ethanol is 1g:(1.5-2.5)g:(0.5-1.5)ml:(2.5-3.5)ml:(5.5-6.5)ml; in the step (2), the mass ratio of trimethylmethoxysilane, polyvinylpyrrolidone and sodium dodecyl sulfate is 1:(0.015-0.04):(0.1-0.4).

[0020] In some embodiments of the present invention, in step (3), the mass ratio of the product, 4,4-diaminodiphenyl ether and pyromellitic anhydride is 1:(0.2-0.5):(0.2-0.5).

[0021] Preferably, in step (3), the mass ratio of the product, 4,4-diaminodiphenyl ether and pyromellitic anhydride is 1:0.3:0.3.

[0022] In some embodiments of the present invention, in step (4), the mass ratio of the modified polyimide to the pretreated basalt fiber is 1:(0.08-0.2).

[0023] Preferably, in step (4), the mass ratio of the modified polyimide to the pretreated basalt fiber is 1:0.11.

[0024] For recycled concrete, frost resistance is crucial, which directly affects the durability and structural integrity of recycled concrete. If the frost resistance of recycled concrete does not meet the standard, its application in cold areas will be limited, thus affecting its economic and social benefits. Polyimide has good temperature resistance, especially a very wide range of low temperature resistance. Adding it to recycled concrete can effectively improve the frost resistance of recycled concrete. However, polyimide itself is slightly more brittle and there is a risk of fracture under stress.

[0025] On the one hand, the applicant reacted trimethylmethoxysilane with polyvinyl pyrrolidone, sodium dodecyl sulfate, triethylamine and KH560 to obtain polysiloxane microspheres (product), and then obtained a modified polyimide with polysiloxane microspheres as the core and polyimide as the shell by controlling the ratio of 4,4-diaminodiphenyl ether and pyromellitic anhydride to the product, which effectively improved the toughness of the polyimide; on the other hand, the applicant used a mixed solution obtained by mixing hydroxyethylidene diphosphonic acid, KH560, deionized water and anhydrous ethanol to surface treat basalt fiber to obtain pretreated basalt fiber, and then mixed the pretreated basalt fiber with the modified polyimide. Amine composite, basalt fiber has the advantages of high strength, large modulus, good temperature resistance and high temperature dimensional stability, and surface treatment thereof can improve its compatibility with modified polyimide, thereby effectively strengthening and toughening the modified polyimide, thereby improving the compressive strength of recycled concrete. Furthermore, the applicant also added an appropriate amount of hydroxyethylidene diphosphonic acid when treating the surface of basalt fiber. The hydroxyl group contained in hydroxyethylidene diphosphonic acid enables it to play a role in making the basalt fiber and the modified polyimide closely combined. Furthermore, the phosphonic acid group in hydroxyethylidene diphosphonic acid can also react with Ca in concrete. 2+ Chelation occurs to form a chelate structure that is not easily hydrolyzed, and a coating is formed on the surface of unhydrated concrete particles, which inhibits the contact between concrete particles and water, thereby inhibiting the hydration process of concrete and enhancing the retarding effect of the water reducer to a certain extent.

[0026] In some embodiments of the present invention, 20-30 parts by weight of modified diatomaceous earth are further included.

[0027] In some embodiments of the present invention, the method for preparing the modified diatomaceous earth comprises the following steps:

[0028] 1) placing diatomaceous earth in a reaction vessel, adding sulfuric acid aqueous solution, stirring, soaking, heating to 80-90° C., stirring, washing, drying, and roasting to obtain an intermediate product for use;

[0029] 2) adding the intermediate product of step 1) into an ethanol aqueous solution, ultrasonicating, adding a silane coupling agent KH570 and sodium dodecylbenzene sulfonate, stirring, precipitating, filtering, washing, and drying to obtain modified diatomaceous earth.

[0030] In some embodiments of the present invention, in step 2), the mass ratio of the intermediate product, the silane coupling agent KH570 and sodium dodecylbenzene sulfonate is 1:(0.5-0.7):(0.7-0.9).

[0031] Preferably, in the step 2), the mass ratio of the intermediate product, the silane coupling agent KH570 and sodium dodecylbenzene sulfonate is 1:0.6:0.8.

[0032] Diatomite has a porous structure and a high specific surface area, which enables it to fill in the micro-cracks inside the recycled concrete, thereby changing the pore structure of the concrete, improving the compactness of the concrete, and thus improving the compressive strength of the concrete. The applicant first modified the diatomite with dilute sulfuric acid and controlled the roasting temperature to make the pore distribution of the diatomite uniform and the void size concentrated, and then used silane coupling agent KH570 and sodium dodecylbenzene sulfonate to synergistically modify it, so that the modified diatomite has the characteristics of large pore size and large specific surface area, and effectively improved its dispersibility, so that it can be filled in the recycled concrete to a greater extent, thereby improving the compressive strength of the recycled concrete to a certain extent.

[0033] Another aspect of the present invention further provides a method for preparing the building recycled material described in the above technical solution, comprising the following steps:

[0034] The recycled coarse aggregate, cement, natural sand, fly ash and water are mixed and stirred for 1-2 minutes, and a water reducer, a retarder, a modified polyimide-based composite material, modified diatomaceous earth and polypropylene glycol are added and stirred for 5-10 minutes to obtain the building recycled material.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention uses recycled coarse aggregate, cement, natural sand and the like as main components, and designs and adds modified polyimide-based composite materials and modified diatomaceous earth to prepare a building recycled material. Through the synergistic effect of the components, the building recycled material has high compressive strength and frost resistance.

[0037] (2) The present invention adopts a specific method to synthesize pretreated basalt fiber and modified polyimide, and compound the two to obtain a modified polyimide-based composite material, which can improve the compressive strength and frost resistance of recycled concrete.

[0038] (3) The present invention first uses dilute sulfuric acid to modify diatomite and controls the roasting temperature, and then uses silane coupling agent KH570 and sodium dodecylbenzene sulfonate to synergistically modify it, so that the modified diatomite has the characteristics of large pore size and large specific surface area, effectively improves its dispersibility, and thus improves the compressive strength of recycled concrete to a certain extent.

[0039] (4) The building recycled material prepared by the present invention is a recycled concrete with high compressive strength and frost resistance, can be widely used in the field of building materials, and has good commercial application value. DETAILED DESCRIPTION

[0040] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0041] In the following embodiments and comparative examples, except for the modified polyimide-based composite material and the modified diatomaceous earth, the other compound monomers and related reagents used can be purchased from the market, among which the polycarboxylic acid water reducer was purchased from Shandong Zhongwei High-tech Materials Co., Ltd.; polyvinyl pyrrolidone was purchased from Jinan Zhengkang Chemical Co., Ltd.; and the polypropylene glycol was polypropylene glycol 2000.

[0042] Preparation Example 1

[0043] The synthesis method of recycled coarse aggregate comprises the following steps:

[0044] The waste concrete is crushed and sieved to obtain the undersize with an average particle size of less than 4 mm. 1 g of silicon nitride powder is added to 200 g of the undersize, stirred for 30 min, and then immersed in a 25 wt% sodium silicate aqueous solution (the powder can be completely immersed in the liquid), soaked for 3 h, taken out, and dried naturally to obtain recycled coarse aggregate.

[0045] Preparation Example 2

[0046] The synthesis method of the modified polyimide-based composite material A comprises the following steps:

[0047] (1) 20 g of hydroxyethylidene diphosphonic acid, 10 ml of KH560, 30 ml of deionized water and 60 ml of anhydrous ethanol were mixed and stirred for 30 min to obtain a mixed solution for use, 10 g of basalt fiber was added to 50 ml of 75 wt% ethanol aqueous solution, ultrasonicated for 2 h, dried at 130° C. for 2 h, and then transferred to the mixed solution, heated to 85° C., stirred for 2 h, filtered, and dried at 90° C. for 2 h to obtain pretreated basalt fiber for use;

[0048] (2) 15 g of trimethylmethoxysilane, 0.5 g of polyvinylpyrrolidone, 3 g of sodium dodecylsulfonate and 200 ml of deionized water were mixed, stirred for 30 min, 20 ml of triethylamine was added, stirred for 8 h, 10 g of KH560 was added, stirred for 2 h, filtered, and washed with deionized water 3 times to obtain a product for use;

[0049] (3) Under nitrogen atmosphere, 10 g of the product of step (2) was added to a mixed solution consisting of 3 g of 4,4-diaminodiphenyl ether and 200 ml of N,N-dimethylacetamide, heated to 80° C. for reaction for 4 h, cooled to room temperature, and then 3 g of pyromellitic anhydride (divided into 6 times, 0.5 g each time, and stirred until uniform after each addition), stirred for 20 h, filtered, washed with anhydrous methanol 3 times, heated to 310° C., and stirred for 2 h to obtain a modified polyimide for use;

[0050] (4) 3 g of the pretreated basalt fiber of step (1) and 27 g of the modified polyimide of step (3) were mixed, cold-pressed at 5 MPa and maintained at this temperature for 3 min, heated to 200° C., applied 5 MPa and maintained at this temperature for 60 min, cooled to room temperature, and dried at 170° C. for 2 h to obtain a modified polyimide-based composite material A.

[0051] Preparation Example 3

[0052] The specific implementation manner of the modified polyimide-based composite material B is the same as that of the modified polyimide-based composite material A, except that in step (1), the mass of hydroxyethylidene diphosphonic acid is replaced with 14 g.

[0053] Preparation Example 4

[0054] The specific implementation manner of the modified polyimide-based composite material C is the same as that of the modified polyimide-based composite material A, except that in step (3), the mass of 4,4-diaminodiphenyl ether is replaced with 1.5 g.

[0055] Preparation Example 5

[0056] The specific implementation manner of the modified polyimide-based composite material D is the same as that of the modified polyimide-based composite material A, except that in step (3), the mass of pyromellitic anhydride is replaced with 1.5 g.

[0057] Preparation Example 6

[0058] The specific implementation manner of the modified polyimide-based composite material E is the same as that of the modified polyimide-based composite material A, except that in step (4), the mass of the pretreated basalt fiber is replaced with 1.8 g.

[0059] Preparation Example 7

[0060] The synthesis method of the polyimide-based composite material comprises the following steps:

[0061] (1) 20 g of hydroxyethylidene diphosphonic acid, 10 ml of KH560, 30 ml of deionized water and 60 ml of anhydrous ethanol were mixed and stirred for 30 min to obtain a mixed solution for use, 10 g of basalt fiber was added to 50 ml of 75 wt% ethanol aqueous solution, ultrasonicated for 2 h, dried at 130° C. for 2 h, and then transferred to the mixed solution, heated to 85° C., stirred for 2 h, filtered, and dried at 90° C. for 2 h to obtain pretreated basalt fiber for use;

[0062] (2) 3 g of the pretreated basalt fiber of step (1) and 27 g of polyimide were mixed, cold-pressed at 5 MPa and maintained at this temperature for 3 min, heated to 200° C., applied 5 MPa and maintained at this temperature for 60 min, cooled to room temperature, and dried at 170° C. for 2 h to obtain a polyimide-based composite material.

[0063] Polyimide was purchased from Dongguan Hongfu Plastic Co., Ltd.

[0064] Preparation Example 8

[0065] The synthesis method of modified diatomite A comprises the following steps:

[0066] 1) 20 g of diatomaceous earth was placed in a reaction vessel, 50 ml of 30 wt% sulfuric acid aqueous solution was added, stirred for 30 min, soaked for 24 h, heated to 85° C., stirred for 60 min, washed with deionized water until neutral, dried at 60° C. for 12 h, and calcined at 450° C. for 3 h to obtain an intermediate product for use;

[0067] 2) 10 g of the intermediate product of step 1) was added to 100 ml of 50 wt% ethanol aqueous solution, ultrasonicated for 30 min, 6 g of silane coupling agent KH570 and 8 g of sodium dodecylbenzene sulfonate were added, stirred for 30 min, precipitated, filtered, washed with deionized water 3 times, and dried at 105° C. for 4 h to obtain modified diatomite A.

[0068] Preparation Example 9

[0069] The specific implementation manner of modified diatomite B is the same as that of modified diatomite A, except that in step 2), the mass of silane coupling agent KH570 is replaced with 4.5 g.

[0070] Preparation Example 10

[0071] Modified diatomite C, the specific implementation method is the same as modified diatomite A, except that: in step 2), the mass of sodium dodecylbenzene sulfonate is replaced with 6.5 g.

[0072] Example 1

[0073] A building recycled material comprises the following raw materials, measured by weight: 1000 parts of recycled coarse aggregate, 300 parts of cement, 230 parts of natural sand, 40 parts of fly ash, 10 parts of polycarboxylic acid water reducer, 1 part of sodium lignin sulfonate, 20 parts of modified polyimide-based composite material A, 25 parts of modified diatomaceous earth A, 22 parts of polypropylene glycol, and 25 parts of water.

[0074] The preparation method of building recycled materials in this embodiment includes the following steps:

[0075] Recycled coarse aggregate, cement, natural sand, fly ash and water are mixed and stirred for 1.5 minutes, polycarboxylic acid water reducer, sodium lignin sulfonate, modified polyimide-based composite material A, modified diatomaceous earth A and polypropylene glycol are added and stirred for 7 minutes to obtain building recycled materials.

[0076] Example 2

[0077] A building recycled material comprises the following raw materials, measured by weight: 900 parts of recycled coarse aggregate, 290 parts of cement, 220 parts of natural sand, 35 parts of fly ash, 5 parts of polycarboxylic acid water reducer, 0.5 parts of calcium lignin sulfonate, 15 parts of modified polyimide-based composite material A, 20 parts of modified diatomaceous earth A, 15 parts of polypropylene glycol, and 200 parts of water.

[0078] The preparation method of building recycled materials in this embodiment includes the following steps:

[0079] Recycled coarse aggregate, cement, natural sand, fly ash and water are mixed and stirred for 1 minute, polycarboxylic acid water reducer, calcium lignin sulfonate, modified polyimide-based composite material A, modified diatomaceous earth A and polypropylene glycol are added and stirred for 5 minutes to obtain building recycled materials.

[0080] Example 3

[0081] A building recycled material comprises the following raw materials, measured by weight: 1,100 parts of recycled coarse aggregate, 310 parts of cement, 240 parts of natural sand, 45 parts of fly ash, 15 parts of polycarboxylic acid water reducer, 2 parts of sodium lignin sulfonate, 25 parts of modified polyimide-based composite material A, 30 parts of modified diatomaceous earth A, 30 parts of polypropylene glycol, and 300 parts of water.

[0082] The preparation method of building recycled materials in this embodiment includes the following steps:

[0083] Recycled coarse aggregate, cement, natural sand, fly ash and water are mixed and stirred for 2 minutes, polycarboxylic acid water reducer, sodium lignin sulfonate, modified polyimide-based composite material A, modified diatomaceous earth A and polypropylene glycol are added and stirred for 10 minutes to obtain building recycled materials.

[0084] Example 4

[0085] A building recycled material comprises the following raw materials, measured by weight: 1000 parts of recycled coarse aggregate, 300 parts of cement, 230 parts of natural sand, 40 parts of fly ash, 10 parts of polycarboxylic acid water reducer, 1 part of sodium lignin sulfonate, 20 parts of modified polyimide-based composite material A, 22 parts of polypropylene glycol, and 25 parts of water.

[0086] The preparation method of building recycled materials in this embodiment includes the following steps:

[0087] The recycled coarse aggregate, cement, natural sand, fly ash and water were mixed and stirred for 1.5 minutes, and polycarboxylic acid water reducer, sodium lignin sulfonate, modified polyimide-based composite material A and polypropylene glycol were added and stirred for 7 minutes to obtain the building recycled material.

[0088] Example 5

[0089] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified polyimide-based composite material B replaces the modified polyimide-based composite material A in equal amounts.

[0090] Example 6

[0091] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified polyimide-based composite material A is replaced by the modified polyimide-based composite material C in equal amounts.

[0092] Example 7

[0093] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified polyimide-based composite material A is replaced by the modified polyimide-based composite material D in equal amounts.

[0094] Example 8

[0095] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified polyimide-based composite material E replaces the modified polyimide-based composite material A in equal amounts.

[0096] Example 9

[0097] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified diatomaceous earth B replaces the modified diatomaceous earth A in equal amounts.

[0098] Example 10

[0099] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified diatomaceous earth A is replaced by the modified diatomaceous earth C in equal amounts.

[0100] Embodiment 11

[0101] This embodiment provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that diatomaceous earth A is replaced by diatomaceous earth in equal amounts.

[0102] Comparative Example 1

[0103] This comparative example provides a building recycled material and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the modified polyimide-based composite material A is replaced by an equal amount of modified polyimide.

[0104] The modified polyimide is the same as that in Preparation Example 2.

[0105] Comparative Example 2

[0106] This comparative example provides a building recycled material and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified polyimide-based composite material A is replaced by an equal amount of pretreated basalt fibers.

[0107] Comparative Example 3

[0108] This comparative example provides a building recycled material and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the modified polyimide-based composite material A is replaced by an equal amount of a polyimide-based composite material.

[0109] Performance Testing

[0110] The compressive strength and frost resistance of the building recycled materials of Examples 1-11 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0111] (1) Compressive strength

[0112] The compressive strength of the building recycled materials of test examples 1-11 and comparative examples 1-3 at room temperature for 28 days is recorded as P1, with reference to GB / T50081-2002 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete".

[0113] (2) Freeze resistance

[0114] The building recycled materials of the above-mentioned Examples 1-11 and Comparative Examples 1-3 were laid in a cold storage room and frozen at -50°C for 28 days. After returning to room temperature, the compressive strength was tested, recorded as P2, and the loss rate of compressive strength was calculated.

[0115] Loss rate of compressive strength = (P1-P2) / P1×100%,

[0116] The compressive strength test is the same as (1).

[0117] Table 1

[0118]

[0119] It can be seen from the data in Table 1 that the building recycled materials in Examples 1-3 have the characteristics of compressive strength and frost resistance as a whole. Among them, Examples 5-8 change the addition ratio of the main components when synthesizing the modified polyimide-based composite materials, so that the compressive strength and frost resistance of the modified polyimide-based composite materials are not well improved, which leads to a certain degree of decrease in the compressive strength of the building recycled materials at room temperature and low temperature, especially the loss rate of compressive strength is significantly increased, that is, the frost resistance of the building recycled materials is significantly reduced; Example 4 is compared with Example 1 without adding modified In the present invention, the modified diatomite is prepared by using modified polyimide, pretreated basalt fiber and polyimide-based composite material to replace the modified polyimide-based composite material A in equal amounts. The test results show that the compressive strength and frost resistance of the recycled building materials both show poor results.

[0120] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A building recycled material, characterized in that: Calculated by weight, the recycled building materials include the following raw materials: 900-1100 parts of recycled coarse aggregate, 290-310 parts of cement, 220-240 parts of natural sand, 35-45 parts of fly ash, 5-15 parts of water reducer, 0.5-2 parts of retarder, 15-25 parts of modified polyimide-based composite material, 15-30 parts of polypropylene glycol, and 200-300 parts of water.

2. The building recycled material according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer.

3. The building recycled material according to claim 1, characterized in that: The retarder is lignin sulfonate.

4. The building recycled material according to claim 1, characterized in that: The preparation method of the modified polyimide-based composite material comprises the following steps: (1) hydroxyethylidene diphosphonic acid, KH560, deionized water and anhydrous ethanol are mixed and stirred to obtain a mixed solution for use, basalt fibers are added to the ethanol aqueous solution, ultrasonicated, and then transferred to the mixed solution after drying, heated to 80-90° C., stirred, filtered, and dried to obtain pretreated basalt fibers for use; (2) trimethylmethoxysilane, polyvinyl pyrrolidone, sodium dodecyl sulfate and deionized water are mixed, stirred, triethylamine is added, stirred, KH560 is added, stirred, filtered, washed, and the product is obtained for later use; (3) under an inert atmosphere, adding the product of step (2) to a mixed solution of 4,4-diaminodiphenyl ether and N,N-dimethylacetamide, heating to 75-85° C. for reaction, cooling to room temperature, adding pyromellitic anhydride, stirring, filtering, washing, heating to 305-315° C., stirring, and obtaining a modified polyimide for standby use; (4) The pretreated basalt fiber of step (1) and the modified polyimide of step (3) are mixed, cold-pressed, heated to 180-220° C., pressurized and kept warm and pressurized, cooled to room temperature, and dried to obtain a modified polyimide-based composite material.

5. The building recycled material according to claim 4, characterized in that: In the step (3), the mass ratio of the product, 4,4-diaminodiphenyl ether and pyromellitic anhydride is 1:(0.2-0.5):(0.2-0.5).

6. The building recycled material according to claim 4, characterized in that: In the step (4), the mass ratio of the modified polyimide to the pretreated basalt fiber is 1:(0.08-0.2).

7. The building recycled material according to claim 1, characterized in that: According to weight percentage, 20-30 parts of modified diatomaceous earth are also included.

8. The building recycled material according to claim 7, characterized in that: The preparation method of the modified diatomite comprises the following steps: 1) placing diatomaceous earth in a reaction vessel, adding sulfuric acid aqueous solution, stirring, soaking, heating to 80-90° C., stirring, washing, drying, and roasting to obtain an intermediate product for use; 2) adding the intermediate product of step 1) into an ethanol aqueous solution, ultrasonicating, adding a silane coupling agent KH570 and sodium dodecylbenzene sulfonate, stirring, precipitating, filtering, washing, and drying to obtain modified diatomaceous earth.

9. The building recycled material according to claim 8, characterized in that: In the step 2), the mass ratio of the intermediate product, the silane coupling agent KH570 and sodium dodecylbenzene sulfonate is 1:(0.5-0.7):(0.7-0.9).

10. A method for preparing a building recycled material according to any one of claims 7 to 9, characterized in that: The following steps are involved: The recycled coarse aggregate, cement, natural sand, fly ash and water are mixed and stirred for 1-2 minutes, and a water reducer, a retarder, a modified polyimide-based composite material, modified diatomaceous earth and polypropylene glycol are added and stirred for 5-10 minutes to obtain the building recycled material.

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