CN113480263A - 3D printing concrete prepared from recycled aggregate and preparation method thereof - Google Patents

Abstract

The application relates to the field of recycled concrete, and particularly discloses 3D printed concrete prepared by using recycled aggregate and a preparation method thereof, wherein the 3D printed concrete prepared by using the recycled aggregate and the preparation method thereof comprise 140 parts of cement 110-90 parts, 70-90 parts of sand, 150-170 parts of recycled aggregate, 1-1.5 parts of a water reducing agent, 0.5-1 part of an accelerating agent and 10-15 parts of an admixture, wherein the admixture with the weight of 5-20% is coated by using a temperature sensitive film, and 70-80 parts of water. The 3D printing concrete prepared by utilizing the recycled aggregate and the preparation method thereof have the advantages of low hydration heat temperature and high concrete strength; in addition, the preparation method has the advantage of reducing the unsmooth possibility of the concrete in the 3D printing process.

Description

3D printing concrete prepared from recycled aggregate and preparation method thereof

Technical Field

The invention relates to the field of recycled concrete, in particular to 3D printing concrete prepared by using recycled aggregate and a preparation method thereof.

Background

At present, the 3D printing concrete technology is one of the concrete development directions, the 3D printing concrete technology is a novel application technology generated by combining the 3D printing technology with the technology in the commercial concrete field, the main principle of the 3D printing concrete technology is that a concrete member is subjected to 3D modeling and division by a computer to produce three-dimensional information, then the prepared concrete mixture is extruded by a nozzle to be printed through an extruding device according to a set program through mechanical control, and finally the concrete member is obtained.

In the related art, a concrete material for 3D printing and a preparation method thereof are disclosed in a chinese invention application document with an application number of 201810913908.X, and the concrete material comprises a gelled material: 1.0 part; natural fine aggregate: 0.2-4.0 parts; nano silicon dioxide: 0.001-0.03 part; high modulus polyethylene fiber: 0.005-0.05 part; redispersible latex powder: 0.001-0.05 part; cellulose: 0.0001 to 0.002 portion; water: 0.2-0.6 part; thickening water reducing agent: 0.003 to 0.02 portion.

In view of the above-mentioned related technologies, the inventor believes that, when 3D printed concrete is prepared, in order to ensure that the concrete has good mechanical properties, the water cement ratio is low, but the low water cement ratio generates high hydration heat, easily causes large temperature stress, and seriously affects the strength of the concrete.

Disclosure of Invention

In order to enhance the strength of concrete, the application provides 3D printing concrete prepared by utilizing recycled aggregate and a preparation method thereof.

In a first aspect, the application provides a 3D printing concrete prepared by using recycled aggregate, which adopts the following technical scheme:

the 3D printing concrete prepared by utilizing the recycled aggregate is prepared from the following raw materials in parts by weight: 140 parts of cement 110-90 parts, sand 70-90 parts, 170 parts of recycled aggregate 150-170 parts, 1-1.5 parts of water reducing agent, 0.5-1 part of accelerating agent and 10-15 parts of admixture, wherein 5-20% of the admixture is coated by a temperature sensitive film pre-preparation agent and 70-80 parts of water.

Through adopting above-mentioned technical scheme, because adopt higher water cement ratio to lead to higher plastic viscosity, once stir the concrete rapid rheology, suitable as 3D and print the use, reduce the concrete and be difficult to extrude, the concrete of different layers is difficult to the adhesive possibility in 3D printing process, and admixture active ingredient can improve the intensity of member and the density of structure by a wide margin simultaneously, improves the durability of member and the life of structure. The method has the advantages that part of admixture is coated, so that the water-cement ratio in the whole system can be ensured to be in a reasonable range, the water-cement ratio in the initial stage is improved, the possibility that a large amount of heat is released by water and ash at one time is reduced, after the water-cement is combined with the ash in the initial stage to release part of heat, a channel on the temperature sensitive film is opened, the water enters the temperature sensitive film, the water reacts with the admixture, the temperature sensitive film is broken, the admixture in the temperature sensitive film is released, and the water-cement ratio in the whole system is ensured to be in a reasonable range.

Optionally, the admixture is a mixture of fly ash and ceramic polished brick powder.

Through adopting above-mentioned technical scheme, the packing effect of fly ash can multiplicable 3D prints the inside closely knit degree of concrete, and simultaneously, its cistern effect can provide sufficient hydrated internal environment for the no mould maintenance of printing the concrete later stage, has reduced the possibility of printing the fracture that the structure caused owing to printing the concrete loss of water inflation to make its improvement that is showing, the polishing brick powder has good cohesiveness and the water retention nature intensity early simultaneously better. The fly ash and the ceramic polished brick powder are compounded and added, so that the advantages of the fly ash and the ceramic polished brick powder can be favorably exerted, the cohesiveness and the water-retaining property of the printed concrete are improved, and the fluidity and the early strength are better.

Optionally, the weight ratio of the fly ash to the ceramic polished brick powder is (0.5-1.5): 1.

Through adopting above-mentioned technical scheme, fly ash and ceramic polishing brick powder use as the admixture complex with similar quantity, and fly ash and the compound doping of ceramic polishing brick powder can be favorable to exerting both advantages, do not influence when printing concrete cohesiveness and water retention, have better mobility and early strength again, and the 3D of being convenient for prints the concrete and extrudes from the machine, guarantees simultaneously that lower floor's concrete has better intensity and can support when printing the upper strata.

Optionally, the coating method of the admixture comprises:

(A) taking out the admixture to be coated;

(B) and spraying the temperature-sensitive film pre-preparation agent into part of the admixture, oscillating and drying to obtain the coating admixture.

By adopting the technical scheme, the temperature sensitive film pre-preparation is coated on part of the admixture by the method, so that part of the admixture can not participate in the reaction of water and ash at the beginning, and after part of hydration heat is released, the admixture coated by the temperature sensitive film is exposed, and the water-ash ratio of the whole system is ensured to be in a reasonable range.

Optionally, the preparation method of the temperature-sensitive film pre-formulation comprises:

the mixture of poly-N-isopropylacrylamide and polyethylene terephthalate or the mixture of poly-N-isopropylacrylamide and polypropylene is irradiated by gamma rays, so that the poly-N-isopropylacrylamide is grafted on the polyethylene terephthalate or the polypropylene to prepare the temperature-sensitive film pre-preparation.

By adopting the technical scheme, when T is less than 32 ℃, the grafted poly-N-isopropylacrylamide chain is in an extended state, the membrane is closed, and when T is greater than 32 ℃, the membrane grafted with poly-N-isopropylacrylamide is opened to form a channel, and water enters and reacts with the admixture through the channel.

Optionally, the temperature-sensitive film pre-formulation is grafted onto polyethylene terephthalate using poly N-isopropylacrylamide.

By adopting the technical scheme, the polyethylene terephthalate graft polymer has the function of enhancing anti-cracking when added into the concrete, and can further increase the strength of the concrete.

In a second aspect, the application provides a preparation method of 3D printing concrete prepared by using recycled aggregate, which adopts the following technical scheme:

(A) preparing recycled aggregate;

(B) coating part of the admixture;

(B) weighing cement, gravel and sand, recycled aggregate and admixture according to the formula proportion of the concrete material, and stirring for the first time to obtain a ready-mixed compound;

(C) according to the formula proportion of the concrete material, measuring water, a water reducing agent and an accelerating agent, and stirring and mixing to obtain a mixture;

(D) and mixing the pre-mixed compound and the mixture for the second stirring to obtain the 3D printing concrete prepared by utilizing the recycled aggregate.

Optionally, the preparation method of the recycled aggregate comprises the following steps:

(A) placing the concrete waste blocks into a phosphoric acid solution with the mass concentration of 5-8% to be soaked for 15-24h, and washing the soaked concrete waste blocks with clear water to obtain acid-treated concrete waste blocks;

(B) fully wetting the waste concrete blocks with a dodecafluoroheptyl-propyl polyhedral oligomeric silsesquioxane solution, and airing to obtain recycled aggregate blocks;

(C) vibrating the large blocks of the recycled aggregate to make the large blocks mutually impact and rub to obtain broken blocks of the recycled aggregate;

(D) and screening the fragments of the recycled aggregate by using a circular hole sieve with the hole diameter of 6mm to obtain the recycled aggregate.

Through adopting above-mentioned technical scheme, 3D prints the concrete and is the process of printing the mouth through rear end pipeline with the material transport to the front end. Firstly, the material in the agitator tank is mixed evenly, gets into pipeline through rotatory link, and the size of aggregate particle diameter can influence getting of rotatory link this moment, and too big particle diameter will cause to get the material difficulty, hinders the normal operating of rotatory link even. Secondly, the viscosity of 3D printing concrete is much greater than that of pumping concrete, if the diameter of a pipeline is almost fully piled up in the cross-cut area formed in the conveying process of the aggregate in an output path, and when the friction resistance among aggregate particles becomes a main factor influencing the pumping distance, the conveying process of the printing material is slow or even interrupted, so that a blocking accident can be caused, and the probability of concrete blocking is reduced after screening.

In summary, the present application has the following beneficial effects:

1. as 5-20% of the admixture is coated by the temperature sensitive film pre-preparation, and part of the admixture is coated, the water-cement ratio in the whole system can be ensured to be in a reasonable range, the water-cement ratio at the initial stage is improved, the possibility that a large amount of heat is emitted by water and ash at one time is reduced, after part of heat is emitted by combining water and ash at the initial stage, the admixture in the temperature sensitive film is released, the water-cement ratio in the whole system is ensured to be in a reasonable range, and a good concrete strength effect is obtained.

2. Preferentially adopt fly ash in this application, ceramic polishing brick powder is as the admixture, because the inside closely knit degree of 3D printing concrete of the filling effect of fly ash, and simultaneously, its cistern effect can provide sufficient hydrated internal environment for the no mould maintenance of printing the concrete later stage, avoided printing the structure owing to print the fracture that the concrete dehydration inflation caused, and make it obtain the improvement that is showing, polishing brick powder has good cohesiveness and the simultaneously early intensity of water retention nature is better, when promoting to print concrete cohesiveness and water retention nature, better mobility and early intensity have again.

3. According to the method, the recycled aggregate is obtained by screening the recycled aggregate fragments by using the circular hole sieve with the aperture of 6mm, so that the particle size of the recycled aggregate is limited, and the possibility that the aggregate blocks equipment in the printing process is reduced.

Detailed Description

The cement is purchased from conch cement with the model of P.C32.5R, the sandstone is purchased from Guangdong wave sand-washing novel material company Limited, the recycled aggregate is purchased from City building waste disposal (Guangzhou) company Limited, the water reducing agent is purchased from Jiangsu province Haian petrochemical plant with the model of HPEG-2400, and the accelerating agent is purchased from Jinnan Fubaokang chemical company Limited, the product model is J85, the fly ash is purchased from Baofeng mica processing Co.Ltd, the ceramic polished brick powder is purchased from Baofeng mica processing Co.Ltd, the poly N-isopropylacrylamide CAS number is 25189-55-3, the polyethylene terephthalate CAS number is 5870-38-2, the polypropylene CAS number is 9003-07-0, the phosphoric acid solution CAS number is 7664-38-2, and the dodecafluoroheptyl propyl polyhedral oligomeric silsesquioxane CAS number is 7664-38-2.

Preparation example

Preparation example 1

A mixture of 0.025kg of poly-N-isopropylacrylamide and 0.025kg of vinylidene fluoride was irradiated with gamma rays for 3 minutes to graft the poly-N-isopropylacrylamide onto the vinylidene fluoride, thereby preparing a temperature-sensitive film pre-formulation.

Preparation example 2

A mixture of 0.025kg of poly (N-isopropylacrylamide) and 0.025kg of polyethylene terephthalate was irradiated with gamma rays for 3 minutes to graft the poly (N-isopropylacrylamide) to the polyethylene terephthalate to prepare a temperature-sensitive film pre-formulation.

Preparation example 3

A mixture of 0.025kg of poly-N-isopropylacrylamide and 0.025kg of polypropylene was irradiated with gamma rays for 3 minutes to graft the poly-N-isopropylacrylamide onto the polypropylene, thereby preparing a temperature-sensitive film pre-formulation.

Examples

Example 1

A3D printing concrete prepared by recycled aggregate and a preparation method thereof are prepared from raw materials with the weight shown in Table 1, and the specific preparation method comprises the following steps:

(1) placing the concrete waste blocks into a phosphoric acid solution with the mass concentration of 7% to be soaked for 20 hours, and washing the soaked concrete waste blocks with clear water to obtain acid-treated concrete waste blocks;

(2) fully wetting the waste concrete blocks with a dodecafluoroheptyl-propyl polyhedral oligomeric silsesquioxane solution, and airing to obtain recycled aggregate blocks;

(3) vibrating the large blocks of the recycled aggregate to make the large blocks mutually impact and rub to obtain broken blocks of the recycled aggregate;

(4) screening the fragments of the recycled aggregate by using a circular hole sieve with the hole diameter of 6mm to obtain recycled aggregate;

(5) taking out the admixture to be coated;

(6) spraying the temperature-sensitive film pre-preparation prepared in the preparation example 1 into part of the admixture, vibrating and drying to obtain a coating admixture;

(7) weighing cement, gravel and sand, recycled aggregate and admixture according to the formula proportion of the concrete material, and stirring for the first time to obtain a ready-mixed compound;

(8) according to the formula proportion of the concrete material, measuring water, a water reducing agent and an accelerating agent, and stirring and mixing to obtain a mixture;

(9) and mixing the pre-mixed compound and the mixture for the second stirring to obtain the 3D printing concrete prepared by utilizing the recycled aggregate.

Examples 2 to 7

The difference between 3D printing concrete prepared by recycled aggregate and the preparation method thereof and example 1 is that the raw materials and the weight of examples 2-3 are shown in Table 1.

TABLE 1 materials and weights (kg) in examples 1-7

TABLE 2 raw materials and weights in examples 1-7

Example 8

The difference between the 3D printing concrete prepared by utilizing recycled aggregate and the preparation method thereof in the embodiment 6 is that the admixture is the fly ash and the ceramic polished brick powder in a ratio of 0.5: 1.

Example 9

The difference between the 3D printing concrete prepared by utilizing the recycled aggregate and the preparation method thereof in the embodiment 6 is that the admixture is the fly ash and the ceramic polished brick powder in the ratio of 1: 1.

Example 10

The difference between the 3D printing concrete prepared by utilizing recycled aggregate and the preparation method thereof in the embodiment 6 is that the admixture is fly ash and ceramic polished brick powder in a ratio of 1.5: 1.

Example 11

A 3D printed concrete prepared using recycled aggregate and a method for preparing the same, which are different from example 9 in that a coating material uses preparation example 2.

Example 12

A 3D printed concrete prepared using recycled aggregate and a method for preparing the same, which are different from example 9 in that a coating material uses preparation example 3.

Example 13

A 3D printed concrete prepared using recycled aggregate and a method for preparing the same, which are different from example 11 in that the step (4) is eliminated.

Comparative example

Comparative example 1

A 3D printed concrete prepared using recycled aggregate and a method for preparing the same, which are different from example 6 in that no admixture is used.

Comparative example 2

The difference between the 3D printing concrete prepared by using recycled aggregate and the preparation method thereof and the embodiment 6 is that the admixture is not coated.

Comparative example 3

The difference between the 3D printing concrete prepared by utilizing recycled aggregate and the preparation method thereof in comparison with the embodiment 6 is that the coating proportion of the admixture is 1%.

Comparative example 4

The difference between the 3D printing concrete prepared by utilizing recycled aggregate and the preparation method thereof in comparison with the embodiment 6 is that the coating proportion of the admixture is 40%.

Performance test

The test adopts a ZL60 type gravity type stirrer for mechanical stirring, the molding size of the compressive strength test piece is 150mm multiplied by 150mm, meanwhile, manual vibration is used, the age is 60d, and standard maintenance is carried out on the test piece after the compressive test piece is molded.

Detection method

Examples 1-13 and comparative examples 1-4 each prepared 5 samples.

The test piece was subjected to a compression strength test in accordance with Standard test methods for mechanical Properties of ordinary concrete (GB/T50081-2016).

TABLE 3 compression Strength (MPa) for examples 1-13 and comparative examples 1-4

Combining example 6, comparative example 1 and table 3, it can be seen that when the formulation is within reasonable limits, the average strength of example 6 is 56.7MPa, which is higher than 28.9MPa of comparative example 1, and the use of partially coated admixtures instead of part of the cement helps to increase the strength of the concrete.

When the formulation is in a reasonable range, the average strength of example 6 is 56.7MPa, which is higher than 29.1MPa of comparative example 2, and the admixture is not coated, it can be seen from the combination of example 6, comparative example 2 and Table 3 that a large amount of hydration heat is generated in the concrete, resulting in a decrease in the strength of the concrete.

When the concrete is combined with the example 6 and the comparative example 3 and the table 3, the average strength of the example 6 is 56.7MPa which is higher than 35.4MPa of the comparative example 3 when the ingredients are in a reasonable range, the admixture is coated less, the effect of improving the water cement ratio in the initial stage is difficult to achieve, and the strength of the concrete is poor.

When the ingredients are in a reasonable range, the average strength of example 6 is 56.7MPa and is higher than 26.1MPa of comparative example 4, the admixture is completely coated, the water cement ratio is unbalanced, and the concrete strength is lower as can be seen by combining example 6, comparative example 4 and table 3.

By combining the examples 1-7 and the table 3, a part of the admixture is coated under a reasonable raw material ratio, so that higher concrete strength can be achieved.

With reference to example 6, example 8 and table 3, the average strength of example 6 is 56.7MPa, which is significantly lower than 62.3MPa of example 8, and the strength of concrete is better when the admixture is fly ash and ceramic polished brick powder in a ratio of 0.5: 1.

With reference to examples 6, 7, 8, 9, 10, 11 and Table 3, the average strength of example 6 was 56.7MPa, 59.4MPa of example 7 was significantly lower than the average strength of 62.3MPa, 63.0MPa of example 9, 63.7MPa of example 10 and 64.8MPa of example 11 in example 8, and the strength of the concrete was better when the admixture was fly ash and ceramic tile powder at a ratio of (0.5-1.5): 1.

With reference to example 11, example 12 and table 3, the strength of example 11 was 64.8MPa stronger than the strength of example 12, i.e., 63.5MPa, and the use of polyethylene terephthalate as a coating material contributes to the improvement of the strength of concrete.

Combining example 11, example 13 and table 3, the strength of example 11 is 64.8MPa stronger than the strength of example 13 is 49.7MPa, and the regenerated aggregate is sieved during the treatment process, so that the regenerated aggregate is not easy to block.

By combining examples 1-13, comparative examples 1-5 and table 3, it can be seen that the strength of the concrete can be effectively improved by coating part of the admixture within a reasonable range of basic raw materials, and meanwhile, the types of the admixture, the addition ratio of the admixture, the coating material and the treatment process of recycled aggregate all affect the strength of the concrete.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims (8)

1. The 3D printing concrete prepared by utilizing recycled aggregate and the preparation method thereof are characterized by being prepared from the following raw materials in parts by weight:

110 portions and 140 portions of cement;

70-90 parts of sandstone;

150 portions and 170 portions of recycled aggregate;

1-1.5 parts of a water reducing agent;

0.5-1 part of accelerator;

10-15 parts of admixture, wherein 5-20% of the admixture by weight is coated with a temperature sensitive film pre-preparation;

70-80 parts of water.

2. The 3D printing concrete prepared by recycled aggregate and the preparation method thereof according to claim 1, wherein the admixture is a mixture of fly ash and ceramic polished brick powder.

3. The 3D printing concrete prepared by recycled aggregate and the preparation method thereof according to claim 2, wherein the weight ratio of the fly ash to the ceramic polished brick powder is (0.5-1.5): 1.

4. The 3D printing concrete prepared by recycled aggregate and the preparation method thereof according to claim 1, wherein the coating method of the admixture is as follows:

(A) taking out the admixture to be coated;

(B) and spraying the temperature sensitive film pre-preparation agent into the admixture, oscillating and drying to obtain the coating admixture.

5. The 3D printing concrete prepared by recycled aggregate and the preparation method thereof according to claim 1 are characterized in that the preparation method of the temperature-sensitive film pre-formulation comprises the following steps:

the mixture of poly-N-isopropylacrylamide and polyethylene terephthalate or the mixture of poly-N-isopropylacrylamide and polypropylene is irradiated by gamma rays, so that the poly-N-isopropylacrylamide is grafted on the polyethylene terephthalate or the polypropylene to prepare the temperature-sensitive film pre-preparation.

6. The 3D printed concrete prepared by recycled aggregate and the preparation method thereof according to claim 5, wherein the temperature-sensitive film pre-formulation is a temperature-sensitive film pre-formulation grafted to polyethylene terephthalate by using poly N-isopropylacrylamide.

7. The preparation method of the 3D printing concrete prepared by using the recycled aggregate and the preparation method thereof according to any one of claims 1 to 6, is characterized in that: the method comprises the following steps:

(A) preparing recycled aggregate;

(B) coating part of the admixture;

(B) weighing cement, gravel and sand, recycled aggregate and admixture according to the formula proportion of the concrete material, and stirring for the first time to obtain a ready-mixed compound;

(C) according to the formula proportion of the concrete material, measuring water, a water reducing agent and an accelerating agent, and stirring and mixing to obtain a mixture;

(D) and mixing the pre-mixed compound with the mixture, and stirring for the second time to obtain the 3D printing concrete prepared by using the recycled aggregate.

8. The preparation method of the 3D printing concrete prepared by using the recycled aggregate and the preparation method thereof according to claim 7 are characterized in that the preparation method of the recycled aggregate is as follows:

(A) placing the concrete waste blocks into a phosphoric acid solution with the mass concentration of 5-8% to be soaked for 15-24h, and washing the soaked concrete waste blocks with clear water to obtain acid-treated concrete waste blocks;

(B) fully wetting the waste concrete blocks with a dodecafluoroheptyl-propyl polyhedral oligomeric silsesquioxane solution, and airing to obtain recycled aggregate blocks;

(C) vibrating the large blocks of the recycled aggregate to make the large blocks mutually impact and rub to obtain broken blocks of the recycled aggregate;

(D) and screening the regenerated aggregate fragments by using a circular hole sieve with the hole diameter of 6mm, and removing the regenerated aggregate fragments larger than 6mm to obtain the regenerated aggregate.