CN115057720A

CN115057720A - 3D printing function gradient ultrahigh-performance fiber foam concrete material and preparation method thereof

Info

Publication number: CN115057720A
Application number: CN202210650399.2A
Authority: CN
Inventors: 杨贞军; 林墨; 曾毅
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2022-06-09
Filing date: 2022-06-09
Publication date: 2022-09-16
Anticipated expiration: 2042-06-09
Also published as: CN115057720B

Abstract

The invention discloses a functionally graded ultrahigh-performance fiber foam concrete material for 3D printing and a preparation method thereof, and relates to the field of building materials. The composite material comprises 0.3-1.5 parts by mass of foam, 900 parts by mass of cement 800-. The composite material has the advantages of porous heat preservation, light weight, high strength, low heat conduction property and orientable physical property design; the addition of the fiber increases the tensile strength of the composite material, improves the brittleness of the material, expands the application range of the material, reduces the drying shrinkage value, and realizes the unification of low manufacturing cost, light weight, high strength, heat preservation, fire prevention, impact resistance and structural bearing.

Description

3D printing functional gradient ultrahigh-performance fiber foam concrete material and preparation method thereof

Technical Field

The invention relates to the field of building materials, belongs to a novel green energy-saving building functional material, and particularly relates to a 3D printing functional gradient ultrahigh-performance fiber foam concrete material and a preparation method thereof.

Background

The traditional foam concrete is a multiphase and multicomponent cement-based composite material formed by introducing a foaming agent or lightweight aggregate into common concrete. Although the traditional common foam concrete has the advantages of light weight, sound insulation and heat preservation, the mechanical property of the foam concrete is weaker due to the lower strength of the original matrix and the addition of foam, the compressive strength generally cannot meet the structural bearing requirement, the material is only limited to be used in a non-bearing structural member, namely a heat-preservation partition wall, the use function is single, although the research and the application of adding coarse aggregate to improve the mechanical property are carried out, the performances of heat preservation, sound insulation and the like are reduced while the compactness is increased, and the self weight and the material cost of the structure are increased. In addition, the building blocks of the common foam concrete have larger thickness, and correspondingly occupy the using space of the building. Based on the improvement of the material mixing ratio, although the ultra-high performance concrete or the ultra-high performance fiber has excellent mechanical properties, the manufacturing cost is 8 to 10 times that of the common concrete due to the limitation of the material manufacturing cost, the engineering application range is limited, and the ultra-high mechanical properties cannot be fully exerted in the using process.

A3D printing functional gradient fiber reinforced ultra-high performance foam concrete composite material is a novel green environment-friendly composite material which is provided based on the concept of a functional gradient material and is suitable for the extrudability and the formability of printing by adjusting the mixing proportion, the composite material can fully play the superior mechanical property of an ultra-high performance concrete matrix on the premise of reducing the material consumption, and can be combined with a 3D printing technology to realize the functional gradient distribution of an additional material, so that the material has the property of similar directional anisotropy on macroscopic and microscopic scales. Compared with common foam concrete and ultrahigh-performance fiber concrete, the composite material and the preparation method thereof can provide corresponding directional heat preservation and sound insulation physical properties and corresponding functional gradient mechanical properties. The 3D printing functional gradient fiber reinforced ultrahigh-performance foam concrete composite material can effectively reduce the section area of a component, increase the space utilization rate, provide high toughness and impact resistance, and can be combined with the design and construction of an assembled component to replace the current multi-process construction process of external thermal insulation of an external wall, so that the installation of the external wall with four-effect integration of thermal insulation, sound insulation, earthquake resistance and structural bearing is realized. In conclusion, the 3D printing functional gradient fiber reinforced ultrahigh-performance foam concrete composite material is a novel multifunctional green building material which can be used in the fields of building and protection engineering.

Patent publication nos. CN112679185A, CN112624795A and CN102561532 show preparation and application of foam concrete and functionally gradient material, but do not reach the high strength standard of the material, and do not realize functionally gradient distribution of multiple materials inside.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a functionally-graded ultrahigh-performance fiber foam concrete material for 3D printing and a preparation method thereof. The invention aims to realize the functional gradient distribution of various materials based on 3D printing equipment, endows a sample or a component with directional and anisotropic mechanical and physical properties based on the mixing proportion of ultra-high-performance fiber concrete on the premise of reducing the self weight, optimizing the distribution of the material-containing phase and reducing the manufacturing cost, and can be applied to exterior wall laying engineering by combining the construction of an assembled component.

The invention adopts the following specific technical scheme:

in a first aspect, the invention provides a 3D printing functional gradient ultrahigh-performance fiber foam concrete material, which comprises 0.3-1.5 parts by mass of foam, 900 parts by mass of cement, 90-100 parts by mass of silica fume, 440 parts by mass of fine sand, 250 parts by mass of water, 200 parts by mass of quartz powder, 3-6 parts by mass of a water reducing agent and 60-180 parts by mass of fiber.

Preferably, the foam is obtained by foaming a foaming agent in combination with a foam stabilizer, and the foaming agent can be a physical foaming agent, a chemical foaming agent or a mixture of the physical foaming agent and the chemical foaming agent.

Furthermore, in the foaming process, the foaming agent is 0.5-10 parts by mass, and the foam stabilizer is 0.01-0.12 part by mass.

Further, the physical foaming agent is sodium dodecyl sulfate or a protein foaming agent, and the protein foaming agent is one of sodium dodecyl benzene sulfonate, n-butyl alcohol, alpha-olefin sodium sulfonate, fatty acid polyoxyethylene ether sodium sulfate and dodecyl polyoxyethylene ether which are used as auxiliary materials for animal or human hair; the chemical foaming agent is one of aluminum powder, hydrogen peroxide and solid sodium percarbonate; the foam stabilizer is one of polyvinyl alcohol, modified silicone polyether emulsion, lauryl alcohol, sodium chloride, polyacrylamide, hydroxypropyl methyl cellulose, sodium polyacrylate, sodium carboxymethyl cellulose and hydroxyethyl cellulose.

Preferably, the foam is filled with lightweight porous particles calculated on a mass basis based on the same volume loading. Preferably, the lightweight porous particles are one or more of expanded perlite, polystyrene particles and porous ceramics.

Preferably, the cement is a cement having an early strength property, and is preferably a composite portland cement or ordinary portland cement.

Preferably, the specific surface area of the silica fume is 18-30m ² Per g of SiO contained ₂ The mass fraction of the component (A) is more than or equal to 90 percent.

Preferably, the fine sand has a particle size of 0.1 to 0.25mm, and is preferably quartz sand or river sand.

Preferably, the quartz powder has a particle size of 5 to 50 μm and contains SiO ₂ Mass fraction of (SiO) ₂ ≥95％。

Preferably, the water reducing agent is a polycarboxylic acid powder water reducing agent, and the water reducing efficiency is 15-20%.

Preferably, the fiber is one or more of steel fiber, carbon fiber, polyvinyl alcohol fiber, polypropylene fiber, basalt fiber, alkali-resistant glass fiber and plant fiber. The obtained fiber material can be directly purchased from commercial sources.

Further, the plant fiber comprises one or more of coconut fiber, straw fiber and stalk fiber.

Further, the steel fiber is one of a linear steel fiber, an end hook steel fiber or a spiral steel fiber; the diameter of the linear steel fiber is 0.12mm, the length of the linear steel fiber is 13mm, the length-diameter ratio is more than or equal to 30, and the tensile strength is more than or equal to 2000 MPa; the equivalent diameter of the end hook steel fiber is 0.22mm, the cross section is approximately circular, the length is 14mm, and the tensile strength is more than or equal to 2000 MPa; the equivalent diameter of the spiral steel fiber is 0.2-0.6mm, the torsion pitch is 5-15mm, the tensile strength is not less than 2000Mpa, and the cross section is in a polygonal shape including a triangle and a quadrangle.

Preferably, an inorganic mineral admixture can be added to replace part of the cement, and the replacement amount is not more than 50%; the inorganic mineral admixture includes, but is not limited to, fly ash, slag powder and other materials.

In a second aspect, the invention provides a preparation method of a functionally graded ultrahigh-performance fiber foam concrete material for 3D printing, which comprises the following specific steps:

s1: uniformly mixing 800-900 parts by mass of cement, 90-100 parts by mass of silica fume, 400-440 parts by mass of fine sand and 200-240 parts by mass of quartz powder for 2-3min to obtain a powder mixture;

s2: adding 40-80 parts by mass of water and 60-180 parts by mass of fiber into the powder mixture, and stirring for 1-2 minutes to obtain a prepared mixture in a powder-to-flow solid transition critical state;

s3: taking an aqueous solution containing 0.3-1.5 parts by mass of a foam phase as a first mixed solution, wherein the first mixed solution contains 100-160 parts by mass of water;

s4: adding 3-6 parts by mass of a water reducing agent (the water reducing agent does not participate in the reaction and only plays a dissolving role by water) into the first mixed solution to obtain a second mixed solution;

s5: gradually adding the second mixed solution into the prepared mixture, and continuously stirring for 1-2min to obtain a mixture;

s6: and adding the rest 10 parts by mass of water into the mixture, and continuously stirring for 1-2min to obtain the 3D printing functional gradient ultrahigh-performance fiber foam concrete material, wherein the aim is to ensure the humidity and slump of the mixture.

Specifically, step S3 may be performed by one of the following two methods:

1) if a blowing agent is used to introduce the foam phase:

s31: 0.5-10 parts by mass of foaming agent and 0.01-0.12 part by mass of foam stabilizer are added into 100-160 parts by mass of water and stirred to complete foaming, and a first mixed solution containing 0.3-1.5 parts by mass of foam phase is obtained.

2) If porous particles are used to introduce the foam phase

S32: 100-160 parts by mass of water is taken, 0.3-1.5 parts by mass of foam particles are soaked in water and then put into a storage box for later use, and a first mixed solution is obtained.

Compared with the prior art, the invention has the following beneficial effects:

1) the composite material prepared by the invention has high strength performance, and the functional gradient distribution of the inclusion in the composite material in the layer and outside the layer can be realized by setting the printing path and the printing speed, so that the formability and the extrudability of the 3D printing material are ensured.

2) The material has the minimum foam compression amount in the stirring and printing process, compared with a manual casting method, the actual density of the material has higher controllability, the unification of the actual density and the designed density can be ensured, the functional gradient distribution of the material in or outside a casting direction layer can also be ensured, and the strength of the printed material is far higher than the bearing requirement of a structure (35MPa) based on the matching ratio. Meanwhile, on the premise of keeping the same physical function and mechanical property, the novel composite material has the advantages of reducing the area of the cross section and releasing more usable space.

3) The invention can realize that the actual hole density and the design density approximately take into account the construction requirement of the functional gradient distribution of the contents (such as fiber and foam), and ensure the design function and the corresponding mechanical property.

Drawings

FIG. 1 is a functional gradient profile of each sample in example 1, wherein (a) is a positive gradient, (b) is a negative gradient, (c) is a concave gradient, and (d) is a convex gradient.

FIG. 2 is a functional gradient profile of each sample in example 2, wherein (a) is a forward gradient, (b) is a reverse gradient, (c) is a concave gradient, and (d) is a convex gradient.

FIG. 3 is a graph of the functional gradient distribution of each sample of example 3, wherein (a) is the foam reverse-fiber forward cross-gradient, (b) is the foam convex-fiber concave cross-gradient, and (c) is the foam concave-fiber convex cross-gradient.

FIG. 4 is a schematic diagram illustrating a gradient distribution in which (a) is a positive gradient, (b) is a negative gradient, (c) is a negative gradient, and (d) is a positive gradient.

FIG. 5 is a graph showing the mean nominal stress-strain curves of the test pieces of example 1.

FIG. 6 is a graph showing the mean nominal stress-strain curves of the test pieces of example 2.

FIG. 7 is a graph showing the mean nominal stress-strain curves of the test pieces of example 3.

Detailed Description

The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical characteristics of the embodiments of the invention can be correspondingly combined without mutual conflict.

In the following embodiments, unless otherwise specified, the reagents and materials are well known and commercially available. In the following examples, the raw materials used are specifically as follows:

the diameter of the linear steel fiber is 0.2mm, the length is 12-13mm, the length-diameter ratio is 60, and the tensile strength is 2000 MPa.

The foam can be introduced by physical foaming, chemical foaming, physical-chemical foaming, introduction of porous particles and the like. As the porous particles, for example, polystyrene particles (diameter of 4 to 5mm, density of 16.8 kg/m) are used ³ )。

The cement is ordinary portland cement. The specific surface area of the silica fume is 22m ² Per g, wherein SiO ₂ 90 percent of the fine sand, the grain diameter of the fine sand ranges from 0.1mm to 0.5mm, the grain diameter of the quartz powder ranges from 5m to 50 m, and SiO is ₂ The content is 95 percent. The high-efficiency water reducing agent is a polycarboxylic acid high-efficiency powder water reducing agent, and the water reducing efficiency is 15-20%. The water is industrial water.

As shown in fig. 4, the positive gradient example is, 1% -2% -3%; example inverse gradients are, 3% -2% -1%; concave gradient examples are, 3% -1% -2%; the convex gradient example is: 2 to 3 to 1 percent.

Taking the fiber as an example, the positive gradient distribution refers to: the variable density distribution of 1% -2% -3% of the fibers in the vertical direction of printing is realized in sequence from the lowest layer of printing; the inverse gradient distribution refers to: realizing 3% -2% -1% variable density distribution of the fibers in the vertical direction of printing in sequence from the lowest printing layer; the concave gradient distribution refers to: realizing 3% -1% -2% variable density distribution of the fibers in the vertical direction of printing in sequence from the lowest layer of printing; the convex gradient distribution refers to: the variable density distribution of the fibers in the vertical direction of printing is realized by 2% -3% -1% in sequence from the lowest layer of printing.

Example 1

In the 3D printing functional gradient ultrahigh-performance fiber foam concrete material of the embodiment, the functional gradient distribution phase is foam, and the components of the material include cement, silica fume, fine sand, water, quartz powder, a high efficiency water reducing agent, fiber (steel fiber), and foam (polystyrene particles). Designing 4 groups of composite materials with functionally graded foam content, wherein the composite materials are numbered as S1-FPOS, S1-FNEG, S1-FCCA and S1-FCEX, and in the 4 types of 3D printing functionally graded ultrahigh-performance fiber foam concrete materials, S1-FPOS represents a sample with 1% of fiber content and with positively graded foam content; S1-FNEG represents a sample with the fiber content of 1 percent and the foam reverse function gradient distribution; S1-FCCA represents a sample with a fiber content of 1% and a foam concave to functional gradient distribution; S1-FCEX represents a sample with the fiber content of 1% and the foam convex direction functionally graded; the gradient direction is the thickness direction. Fig. 1 is a schematic diagram of the gradient distribution of each sample in this embodiment. The quality of each component of each group of 3D printing functional gradient ultrahigh-performance fiber foam concrete material is shown in the following table 1, and the data in the table 1 are given according to the parts of the components by mass ratio.

Table 13D shows the mix proportion of the functionally graded ultra-high performance fiber foam concrete material

In this example, the preparation process of the 3D printing functionally graded ultra-high performance fiber foam concrete material is as follows:

1) uniformly mixing 800-900 parts by mass of cement, 90-100 parts by mass of silica fume, 400-440 parts by mass of fine sand and 200-240 parts by mass of quartz powder for 2-3min to obtain a mixture;

2) adding 40-80 parts by mass of water and 60-180 parts by mass of fiber into the dry-mixed mixture, stirring for 1-2 minutes, wherein the powder is in a critical state of transition to fluid solid, and the cementing material (cement and silica fume) is not completely reacted (aiming at uniformly distributing the fiber in a semi-flowable matrix);

3) taking 100-160 parts by mass of water, soaking 0.3-1.5 parts by mass of foam particles in water, putting the soaked foam particles into a storage box for later use, and reserving the residual water for later use;

4) adding 3-6 parts by mass of a water reducing agent into the remaining water of 3) to obtain a mixed solution containing 3-6 parts by mass of the water reducing agent.

5) Gradually adding the mixed solution obtained in the step 4) and the soaked foam particles obtained in the step 3) into the mixed material obtained in the step 2), and continuously stirring for 1-2min to obtain a mixture with better fluidity and extensibility;

6) and adding the rest 10 parts by mass of water into the mixture, and continuously stirring for 1-2min to obtain the 3D printing functional gradient ultrahigh-performance fiber foam concrete material (namely the ultrahigh-performance concrete matrix composite material), wherein the aim is to ensure the humidity and the slump of the mixture.

7) Repeating the steps to change the fiber content or the foam content to obtain the ultra-high performance concrete matrix composite material with different fiber content and foam content, and spraying and moisturizing can be properly carried out to ensure the fluidity of any layer of mixture;

8) designing a printing path, putting the ultra-high performance concrete matrix composite materials with different fiber and foam contents into a hopper of a 3D printing device according to the sequence of design gradient, and starting the device until the test piece or member is printed.

The mean nominal stress strain curve of the test pieces of this example is shown in fig. 5, from which it can be seen that the fiber phase content is the same (50) and the foam phase content is different for each printed layer in example 1. The content of a foam phase of a layer of an active pressure surface in S1-FNEG is 0.4, the internal structure is compact, although the content of a foam phase of a bottom layer is 0.6, the foam phase is extruded by an upper layer in the printing process, so that the matrix structure is more compact, and the highest nominal compressive strength of the whole is promoted; the printing process in S1-FPOS is opposite to that in S1-FNEG, and the active compression layer has high foam phase content (0.6) and is positioned at the top printing layer, and the external extrusion compaction effect is avoided, so that the compression strength is lowest, and the strength after the peak is reduced most quickly; the printing, natural compaction and maintenance processes of S1-FCCA and S1-FCEX are similar to those of S1-FPOS, the strength is slightly different, but the strength is higher than S1-FNEG and lower than S1-FPOS. The compressive strength of the four mixed materials reaches the structural load (35MPa), and 0.5 mass part of foam is approximately equal to 20% of porosity.

Example 2

In the 3D printing functional gradient ultrahigh-performance fiber foam concrete material of the embodiment, the functional gradient distribution phase is fiber, and the components of the material include cement, silica fume, fine sand, water, quartz powder, a high efficiency water reducing agent, fiber (steel fiber), and foam (polystyrene particles). Designing 4 groups of composite materials with functionally graded foam content, wherein the composite materials are numbered as F20-SPOS, F20-SNEG, F20-SCCA and F20-SCEX, and in the 4 types of 3D printing functionally graded ultrahigh-performance fiber foam concrete materials, F20-SPOS represents a sample with 20% foam content and with fiber positively graded and graded; F20-SNEG represents a sample with 20% foam content and fiber reversed functional gradient distribution; F20-SCCA represents a sample with 20% foam content and fiber concave to function gradient distribution; F20-SCEX represents a sample with 20% of foam content and fiber convex direction function gradient distribution; the gradient direction is the thickness direction. Fig. 2 is a schematic diagram of the gradient distribution of each sample in this embodiment. The quality of each component of each group of 3D printing function gradient ultrahigh-performance fiber foam concrete material is shown in the following table 2, and is given according to the parts of the components by mass ratio.

TABLE 23D mix proportion of printing functionally graded ultra-high performance fiber foam concrete material

In this embodiment, the preparation process of the 3D printing functional gradient ultrahigh-performance fiber foam concrete material is as follows:

2) adding 40-80 parts by mass of water and 60-180 parts by mass of fiber into the dry-mixed mixture, stirring for 1-2 minutes, wherein the powder is in a critical state of transition to fluidized solid, and the gelled material (cement and silica fume) is not completely reacted (aiming at uniformly distributing the fiber in a semi-flowable matrix);

4) 3-6 parts by mass of water reducing agent of the rest water in the step 3) to obtain a mixed solution containing 3-6 parts by mass of water reducing agent

6) and adding the rest 10 parts by mass of water into the mixture, and continuously stirring for 1-2min to obtain the 3D printing functional gradient ultrahigh-performance fiber foam concrete material, wherein the aim is to ensure the humidity and slump of the mixture.

8) designing a printing path, putting the ultra-high performance concrete matrix composite materials with different fiber and foam contents into a hopper of a 3D printing device according to the sequence of design gradient, and starting the device until a test piece is completed or printing is constructed.

The average nominal stress-strain curve of the test piece in the embodiment is shown in fig. 6, and it can be seen from the graph that the foam content of each printing layer in the embodiment 2 is the same, the fiber content of the active compression surface is different from that of the passive compression surface, the foam phase content of the layer of the active compression surface in the SNEG-F20 is 0.5, the fiber phase content is 40, the fiber phase content of the first layer is moderate, the structure is compact, the foam phase content of the bottom layer is 0.5, the fiber phase is 60, the layer is pressed by the upper layer in the printing process to enable the matrix structure to be more compact, and compared with the other three mixing ratios, the compressive strength is highest under the mixing ratio; the SPOS-F20 has the advantages that the fiber phase content of an active compression layer is 60, the fiber phase content of a passive compression layer is 40, the fiber mixing amount of the active compression layer is high, excessive fiber-foam phase interface air holes can be introduced due to interaction between the fiber phase and the foam phase and are positioned at the top printing layer, no external force is used for pressurization and compaction, the structure is slightly loose, the number of local defect positions is large, the integral damage is caused, and the compressive strength is slightly lower than that of SNEG-F20; SCCA-F20 printing and curing mechanism is similar to SPOS-F20; SCEA-F20 printing and curing mechanism is similar to SNEG-F20; the SCCA-F20 has smaller strength difference with SCEA-F20, and the curve change trend after peak load is similar. The compressive strength of the four mixed materials reaches the structural load (35 MPa).

Example 3

In the 3D printing functional gradient ultrahigh-performance fiber foam concrete material of the embodiment, the functional gradient distribution phase is fiber and foam (cross gradient), and the components of the material include cement, silica fume, fine sand, water, quartz powder, high efficiency water reducing agent, fiber (steel fiber), and foam (polystyrene particles). Designing 4 groups of composite materials with functionally graded foam content, wherein the materials are numbered FNEG-SPOS, FCEX-SCCA and FCCA-SCEX, and in the 3 kinds of 3D printing functionally graded ultrahigh-performance fiber foam concrete materials, the FNEG-SPOS represents samples with functionally graded foam in the reverse direction and functionally graded fiber in the forward direction; FCEX-SCCA represents a sample with foam convex functional gradient distribution and fiber concave functional gradient distribution; FCCA-SCEX represents a sample with foam in concave functional gradient distribution and fiber in convex functional gradient distribution; the gradient direction is the thickness direction. Fig. 3 is a schematic diagram of the functionally graded distribution of a two-phase material, wherein the solid lines represent foam (i.e., polyphenyl particles) and the dashed lines represent straight steel fibers. The quality of each component of each group of 3D printing function gradient ultrahigh-performance fiber foam concrete material is shown in the following table 3, and is given according to the parts of the components by mass ratio.

Table 63D printing mix proportion of functionally graded ultrahigh-performance fiber foam concrete material

6) and adding the rest 10 parts by mass of water into the mixture, and continuously stirring for 1-2min to obtain the 3D printing functional gradient ultrahigh-performance fiber foam concrete material, wherein the aim is to ensure the wet and slump of the mixture.

7) Repeating the steps to change the fiber content or the foam content to obtain the ultra-high performance concrete matrix composite material with different fiber contents and foam contents, and properly performing spray moisturizing to ensure the fluidity of any layer of mixture;

The average nominal stress-strain curve of the test piece in this example is shown in fig. 7, and it can be seen from the graph that the foam phase and the fiber phase of each printed layer in example 3 are different in content, the foam phase content of the layer of the active pressure surface in SCEX-FCCA is 0.5, the fiber phase content is 40, the fiber phase content of the first layer is moderate, the structure is dense, the foam phase content of the bottom layer is 0.6, the fiber phase content is 50, although the foam phase content is high, the matrix structure is made to be more dense by the extrusion effect of the upper layer in the printing process, and the compressive strength is highest under the mixed ratio; the foam phase content of an active compression layer in SCCA-FCEX is 0.4, the fiber phase content is 50, the fiber phase content of a passive compression layer is 60, the foam phase content is 0.5, although the fiber mixing amount is high, the matrix structure is enabled to be compact under the extrusion action of an upper layer in the printing process, the foam phase content of the active compression layer is higher than that of SCEX-FCCA under the matching ratio, a first layer is firstly destroyed when being compressed, and the peak strength is slightly lower than that of SCEX-FCCA; although the content of the foam phase of the SPOS-FNEG active compression layer is moderate, the fiber mixing amount is high, too many pores are introduced into a fiber-foam phase interface due to interaction between the fiber phase and the foam phase, the structural compactness is weakened, the integral compressive strength is slightly lower than that of SCCA-FCEX and SCEX-FCCA due to the defect position of a stress concentration point, the time point of reaching the peak load is early, and the compressive strengths of the three mixed materials meet the structural load (35 MPa).

In conclusion, the ultra-high performance concrete matrix obtained by the method has the advantages that the fiber has higher cohesive force in the ultra-high performance concrete matrix; the higher foam-matrix interface adhesion and the local gravity action of the ultra-high performance fiber concrete are balanced, so that the foam (polyphenyl granules) is approximately uniformly distributed in the space. The holes introduced into the sample or the member can reduce the dead weight of the structure, reduce the construction cost and have the performances of heat preservation and sound insulation.

The composite material has the advantages of porous heat preservation, light weight, high strength, low heat conduction property and orientable physical property design; the addition of the fiber increases the tensile strength of the composite material, improves the brittleness of the material, expands the application range of the material, reduces the drying shrinkage value, and realizes the unification of low manufacturing cost, light weight, high strength, heat preservation, fire prevention, impact resistance and structural bearing.

The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical solutions obtained by means of equivalent substitution or equivalent transformation all fall within the protection scope of the present invention.

Claims

1. A3D printing functional gradient ultrahigh-performance fiber foam concrete material is characterized by comprising 0.3-1.5 parts by mass of foam, 900 parts by mass of cement, 90-100 parts by mass of silica fume, 440 parts by mass of fine sand, 150 parts by mass of water, 240 parts by mass of quartz powder, 3-6 parts by mass of a water reducing agent and 60-180 parts by mass of fiber.

2. The 3D printing functionally graded ultra high performance fibrous foam concrete material of claim 1, wherein the foam is filled with lightweight porous particles calculated on the basis of the same volume loading in mass; preferably, the lightweight porous particles are one or more of expanded perlite, polystyrene particles and porous ceramics.

3. The 3D printed functionally graded ultra high performance fibrous foam concrete material according to claim 1, characterized in that the cement is a cement with early strength properties, preferably a composite portland cement or ordinary portland cement.

4. According to claim 1The 3D printing functional gradient ultrahigh-performance fiber foam concrete material is characterized in that the specific surface area of silica fume is 18-30m ² Per g of SiO contained ₂ The mass fraction of the component (A) is more than or equal to 90 percent.

5. The 3D printed functionally graded ultra high performance fibrous foam concrete material according to claim 1, characterized in that the fine sand has a particle size of 0.1-0.25mm, preferably quartz sand or river sand.

6. The 3D printed functionally graded ultra high performance fiber foam concrete material of claim 1, wherein the quartz powder has a particle size of 5-50 μm and contains SiO ₂ Mass fraction of (SiO) ₂ ≥95％。

7. The 3D printing functional gradient ultrahigh-performance fiber foam concrete material as claimed in claim 1, wherein the water reducing agent is a polycarboxylic acid powder water reducing agent, and the water reducing efficiency is 15-20%.

8. The 3D printed functionally graded ultra high performance fibrous foam concrete material of claim 1, wherein the fibers are one or more of steel fibers, carbon fibers, polyvinyl alcohol fibers, polypropylene fibers, basalt fibers, alkali resistant glass fibers, and plant fibers.

9. The 3D-printed functionally graded ultra high performance fibrous foam concrete material of claim 8, wherein the steel fibers are one of straight steel fibers, end-hooked steel fibers or spiral steel fibers; the diameter of the linear steel fiber is 0.12mm, the length of the linear steel fiber is 13mm, the length-diameter ratio of the linear steel fiber is more than or equal to 30, and the tensile strength of the linear steel fiber is more than or equal to 2000 MPa; the equivalent diameter of the end hook steel fiber is 0.22mm, the length is 14mm, and the tensile strength is more than or equal to 2000 MPa; the equivalent diameter of the spiral steel fiber is 0.2-0.6mm, the torsion pitch is 5-15mm, and the tensile strength is more than or equal to 2000 Mpa.

10. A preparation method of a 3D printing functional gradient ultrahigh-performance fiber foam concrete material is characterized by comprising the following steps:

s3: taking an aqueous solution containing 0.3-1.5 parts by mass of a foam phase as a first mixed solution, wherein the first mixed solution contains 160 parts by mass of water in an amount of 100 parts by mass;

s4: adding 3-6 parts by mass of a water reducing agent into the first mixed solution to obtain a second mixed solution;

s6: and adding the rest 10 parts by mass of water into the mixture, and continuously stirring for 1-2min to obtain the 3D printing functional gradient ultrahigh-performance fiber foam concrete material.