CN112608119A

CN112608119A - Foam concrete doped with light silica microspheres through 3D printing and preparation method thereof

Info

Publication number: CN112608119A
Application number: CN202011539138.0A
Authority: CN
Inventors: 黄健; 赵雨婷; 江奇; 王新; 杨正才; 段斌
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2020-12-23
Filing date: 2020-12-23
Publication date: 2021-04-06

Abstract

The invention provides 3D printing light-weight silica microsphere-doped foam concrete and a preparation method thereof, the 3D printing light-weight silica microsphere-doped foam concrete is prepared by extrusion type 3D printing, and the used matrix material is phosphogypsum slag concrete, so that the resource utilization of phosphogypsum is effectively realized. In order to solve the problems of foam merging and cracking easily caused in the process of extruding foam concrete by 3D printing preparation, the invention effectively prevents the cracking, drainage and aggregation of bubbles by introducing light silica microspheres as foam stabilizers to be adsorbed on the surface of the foam, and the light silica microspheres have a supporting effect on the structure of the foam concrete. The invention adopts simulation software to simulate the optimal printing path, thereby effectively reducing the economic and labor consumption.

Description

Foam concrete doped with light silica microspheres through 3D printing and preparation method thereof

Technical Field

The invention relates to the technical field of building materials, in particular to foam concrete doped with light silica microspheres through 3D printing and a preparation method thereof.

Background

The phosphogypsum is used as a byproduct in the phosphate fertilizer industry, has huge yield and low utilization rate, occupies a large amount of land resources after long-term stacking, and contains radioactive elements which cause certain harm to the environment, and the improvement of the utilization rate of the phosphogypsum is an effective method for solving the problem. The foam concrete is a new heat-insulating material, and compared with organic heat-insulating materials such as foamed polyphenyl heat-insulating boards and polyurethane foam heat-insulating materials, the foam concrete has the characteristics of good heat insulation, fire prevention, waste utilization and the like, and has certain strength, so that the application of the phosphogypsum to the foam concrete has great research value for solving the utilization problem of the phosphogypsum. With the rise of 3D printing technology, the application of the ardealite slag foam concrete in the field of buildings is widely concerned by people, and the 3D printing of building materials has the advantages of no-mold forming, environment-friendly process and the like, so that the ardealite slag foam concrete is supposed to be applied to 3D printing, but the foam structure inside the ardealite slag foam concrete is easy to break when being subjected to extrusion force of a 3D printing system, so that the performance of the ardealite slag foam concrete is affected, and therefore a method needs to be provided for reinforcing the strength of foam inside concrete.

Disclosure of Invention

In view of this, the invention aims to provide foam concrete doped with light silica microspheres for 3D printing, so as to solve the problem that when the existing foam concrete is applied to 3D printing, the foam structure inside the existing foam concrete is easily broken by the extrusion force of a 3D printing system, so that the performance of the existing foam concrete is affected.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

A3D printing light silica microsphere doped foam concrete is prepared by mixing the following components according to a water-to-gel ratio of 0.3-0.5 and then adopting a 3D printing technology: cementing materials, water reducing agents, foaming agents, light silicon dioxide and fibers; the cementing material comprises the following components in parts by weight: alkali activator: 2-15 parts of an accelerator: 2-4 parts, phosphogypsum: 35-50 parts of slag: 40-60 parts; the amount of the water reducing agent is 0.3-0.5% of the mass of the cementing material; the foaming agent consists of a surfactant, a thickening agent and water; the dosage of the surfactant is 0.3-1.0% of the mass of the gelled material, the dosage of the thickener is 0.15-0.5% of the mass of the gelled material, and the dosage of the water is 40-60% of the total mixing water of the foam concrete; the using amount of the light silica is 1-7% of the mass of the cementing material; the volume mixing amount of the fiber is 0.05-1%.

Optionally, the alkali-activator is one or more of steel slag and clinker.

Optionally, when the alkali-activator is a mixture of steel slag and clinker, the mass ratio of the steel slag to the clinker is (5-15) to (2-4).

Optionally, the setting accelerator is a quick-hardening sulphoaluminate cement, in the invention, the main mineral components in the quick-hardening sulphoaluminate cement are anhydrous calcium sulphoaluminate and dicalcium silicate, which are quickly hydrated and react with phosphogypsum to provide early strength, consumed Ca (OH)₂Reducing the alkalinity of the system promotes the hydration of tricalcium silicate and dicalcium silicate.

Optionally, the water reducing agent is one of a polycarboxylate water reducing agent and a polyphosphate water reducing agent.

Optionally, the surfactant is one of sodium dodecyl sulfate, dodecyl dimethyl betaine, dodecyl polyoxyethylene ether and sodium alpha-olefin sulfonate; the thickening agent is one or more of dodecanol, sodium chloride, sodium carboxymethylcellulose, sodium polyacrylate and hydroxypropyl methyl cellulose.

Optionally, the light silica is one or more of hydrophobic fumed silica, silica fume and nano-scale surface hydrophobic silica aerogel microspheres prepared by a Stober method, in the invention, 1-5% of silica fume and 1-3% of nano-scale surface hydrophobic silica aerogel microspheres prepared by the Stober method are used in a composite manner to realize a better foam stabilizing effect, the silica fume plays a role of a ball bearing on one hand and enables air holes of concrete to be more approximate to a spherical shape, and on the other hand, the silica fume and the nano-scale surface hydrophobic silica aerogel microspheres prepared by the Stober method are attached to the surfaces of air bubbles to slow down the rupture, drainage and aggregation of foams; in addition, the particle size of the nano-scale surface hydrophobic silica aerogel microspheres prepared by the Stober method is controlled to be 50-150nm, the particle size of silica fume is controlled to be 30-40nm, the microspheres form a close-packed structure, and the silica fume fills the close-packed gaps to form a close-packed pore wall structure, so that a certain strength is provided for a foam concrete system.

Optionally, the silicon source in the nano-scale surface hydrophobic silica aerogel microspheres prepared by the Stober method is one or more of tetraethoxysilane, water glass, silica sol, siloxane and polyethoxy siloxane; the volume ratio of the silicon source to the deionized water is 1: 2-4; the solvent is ethanol, and the volume ratio of the silicon source to the ethanol is 1: 8-15; the catalyst is ammonia water, the mass fraction of the ammonia water is 25-28%, and the volume ratio of the silicon source to the ammonia water is 1: 1-1.5; the hydrophobic modifier is one of hexamethyldisilazane, n-octyltriethoxysilane, phenyltrimethoxysilane and methyltriethoxysilane, and the molar ratio of the silicon source to the hydrophobic modifier is 10-20.

Optionally, the fibers are one or more of polypropylene fibers, basalt fibers, alkali-resistant glass fibers; the diameter of the polypropylene fiber is 30-80 μm, the cross section is rectangular, and the length-diameter ratio is 150-300; the basalt fiber has the average diameter of 13 mu m, the cross section of the basalt fiber is circular, and the length-diameter ratio of the basalt fiber is 350-1500; the diameter of the alkali-resistant glass fiber is 10-20 μm, the cross section is circular, and the length-diameter ratio is 300-1200.

The second purpose of the invention is to provide a method for preparing the above 3D printing foamed concrete doped with light silica microspheres, which comprises the following steps:

1) uniformly mixing the phosphogypsum, the slag, the alkali activator, the accelerator and the water reducer, adding water accounting for 40-60% of the total mixing water amount of the foam concrete, stirring to obtain slurry, adding the fibers, and continuously stirring to obtain slurry A;

2) uniformly mixing the surfactant, the thickening agent and the light silica, adding the residual water, stirring and foaming to obtain foam B; the residual water amount is the difference value between the total mixing water amount of the foam concrete and 40-60% of the total mixing water amount of the foam concrete;

3) comparing the performances of different printing paths by using simulation software, and screening the optimal printing path according to different performance requirements (such as higher bending strength or better heat preservation performance) in practical application;

4) and uniformly mixing the slurry A and the foam B, and printing according to a determined printing path to obtain the 3D printing light silica microsphere-doped foam concrete.

In the invention, a printing path is determined by a method combining experiments and simulation, the mechanical and thermodynamic properties of a test piece can be changed by different printing paths, the experiment process is simplified by simulating the printing paths by using simulation software, and the specific process is to simulate different printing paths of the test piece by using slice software and introduce numerical simulation software to carry out multi-physical-field simulation; in comparison to conventional printing paths such as a straight path (path a, as shown in fig. 3), a concentric path (path B, as shown in fig. 4) and a honeycomb-shaped printing path (path C, as shown in fig. 5), the paths a and B have less ability to limit deformation in the lateral direction when subjected to pressure in the Z direction, and therefore have similar compressive strengths; when the test piece bears tensile stress along the X/Y direction, most of the weak surfaces of the path A and the tensile stress direction form a certain angle, and most of the weak surfaces of the path B are parallel to the tensile stress direction, so that the flexural strength of the test piece of the path B is greater than that of the test piece of the path A; the structure of the C-path test piece in the heat transfer direction is more complex than that of the A, B-path test piece, so that the C-path test piece has the lowest heat loss and the best heat preservation performance.

The principle of the invention is as follows:

the main component of the phosphogypsum is dihydrate gypsum which has no gelling property, but can generate a stable hydration product with some industrial waste residue with latent hydraulicity under a proper condition, so the phosphogypsum and slag are compounded to prepare the phosphogypsum slag concrete and are applied to the preparation of foam concrete to solve the utilization problem of the phosphogypsum; in consideration of the unique advantages of 3D printing in the preparation of building materials, the phosphogypsum slag foam concrete is prepared by using the 3D printing technology, light silica is introduced as a foam stabilizer to solve the problem that foam is easy to break in the printing process, and the gas-liquid interface is changed by using the coupling effect between the light silica and a surfactant, so that the breaking, drainage and aggregation of the foam are effectively prevented. Meanwhile, in order to simplify the printing process, simulation software is introduced to analyze the influence of different printing paths on the performance of the concrete, so that the time and the cost are saved.

Compared with the prior art, the foam concrete doped with the light silica microspheres by 3D printing has the following advantages:

1. the invention applies the phosphogypsum to the foam concrete and provides a new direction for the application of the phosphogypsum.

2. In order to solve the problem that foam is easy to break when 3D printing phosphogypsum slag foam concrete is extruded, light silicon dioxide is introduced as a foam stabilizer, and a gas-liquid interface is changed and the strength of the foam is improved by utilizing the coupling effect between the light silicon dioxide and a surfactant.

3. The invention uses the method of combining the simulation software and the actual printing, and plans the printing path with better performance on the basis of not printing, thereby saving time and cost.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a diagram showing defoaming of extruded foam concrete without silica fume and nano-scale surface hydrophobic silica aerogel microspheres according to the present invention;

FIG. 2 is a diagram showing defoaming of extruded foam concrete doped with silica fume and nano-scale surface hydrophobic silica aerogel microspheres in example 1 of the present invention;

FIG. 3 is a schematic view of a linear path (A path) according to the present invention, wherein FIG. 3(a) shows an odd layer and FIG. 3(b) shows an even layer;

FIG. 4 is a schematic diagram of a concentric path (B path) according to the present invention, wherein FIG. 4(a) shows an odd layer and FIG. 4(B) shows an even layer;

FIG. 5 is a schematic diagram of a honeycomb print path (C path) of the present invention, wherein FIG. 5(a) shows an odd layer and FIG. 5(b) shows an even layer.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The present invention will be described in detail with reference to examples.

A preparation method of 3D printing light silica microsphere-doped foam concrete specifically comprises the following steps:

1) preparing the nano-scale surface hydrophobic silica aerogel microspheres by a Stober method: mixing 1000ml of absolute ethyl alcohol, 300ml of deionized water and 100ml of ammonia water, pouring the mixture into a reaction kettle, wherein the temperature of a constant-temperature water bath heating pot is 30 ℃, the stirring speed of a stirrer is 300rpm, and the concentration of the ammonia water is 25-28%; weighing 100mL of tetraethyl orthosilicate, putting the tetraethyl orthosilicate into a beaker, dropwise adding the tetraethyl orthosilicate into a middle kettle at the speed of 10mL/min through a peristaltic pump for 10min, and reacting for 4 h; weighing 4.65g of hexamethyldisilazane, dissolving in 50ml of absolute ethanol, and dropwise adding into a kettle by a peristaltic pump at a speed of 5ml/min under the reaction conditions of 65 ℃, stirring at a speed of 300r/min and reaction time of about 6 hours; after the reaction is finished, putting the product into a centrifuge, centrifuging for 6min at the speed of 8000r/min, and pouring out supernatant; washing the product with absolute ethyl alcohol, centrifuging again, and repeating for three times; putting the washed product into a blast oven, setting the temperature to be 80 ℃, and drying for 24 hours to obtain spherical nano-scale surface hydrophobic silica aerogel microspheres;

2) preparation of cement paste (paste A): mixing 40g of phosphogypsum, 50g of slag, 7g of steel slag, 3g of quick-hardening sulphoaluminate cement and 0.3g of polycarboxylate water reducer, adding 20g of water after uniform mixing, stirring to obtain slurry, adding basalt fibers, wherein the volume mixing amount of the basalt fibers is 0.05 percent, the average diameter of the basalt fibers is 13 mu m, the cross section shape is circular, the length-diameter ratio is 350-1500, and continuously stirring uniformly to obtain slurry A;

3) preparation of foam B: mixing 0.35g of sodium dodecyl sulfate, 0.21g of sodium chloride, 1g of silica fume and 1g of the nano-scale surface hydrophobic silica aerogel microspheres obtained in the step 1), adding 20g of water after uniformly mixing, and beating out foam by using a beater to obtain foam B;

4) using simulation software to compare thermodynamic performances of different printing paths (the schematic diagrams of all paths are shown in figures 3-5), and selecting a honeycomb printing path with better heat preservation performance, namely the printing path shown in figure 5;

5) and (3) uniformly mixing the slurry A and the foam B, and then printing according to the printing path determined in the step 4), wherein the extrusion rate is 5mm/S, so as to obtain the 3D printing light silica microsphere-doped foam concrete.

The seven-day strength of the foam concrete before and after the silica fume and the nano-scale surface hydrophobic silica aerogel microspheres are added is measured, and the 7d compressive strength is respectively as follows: 20.8MPa and 24.3 MPa.

The defoaming conditions of the extruded foam concrete before and after the silica fume and the nano-scale surface hydrophobic silica aerogel microspheres are added are tested, and the test results are respectively shown in fig. 1 and fig. 2.

As can be seen from fig. 1 and 2, fig. 1 shows that the foam concrete without silica fume and aerogel microspheres has severe defoaming phenomenon, and the pore size distribution is not uniform as seen from the holes after defoaming. Fig. 2 shows that the defoaming condition of the foam concrete using the mixture of silica fume and aerogel microspheres as the foam stabilizer is greatly reduced, and the foam concrete has smaller holes and more uniform size, which indicates that the pore size of the foam inside the foam concrete is smaller and the size of the foam concrete is uniformly distributed, and the silica fume and the aerogel microspheres play a good role in stabilizing the foam and generate a certain role in regulating and controlling the size of the foam.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The 3D printing light silica microsphere-doped foam concrete is characterized by being prepared by mixing the following components according to a water-to-gel ratio of 0.3-0.5 and then adopting a 3D printing technology: cementing materials, water reducing agents, foaming agents, light silicon dioxide and fibers; the cementing material comprises the following components in parts by weight: alkali activator: 2-15 parts of an accelerator: 2-4 parts, phosphogypsum: 35-50 parts of slag: 40-60 parts; the amount of the water reducing agent is 0.3-0.5% of the mass of the cementing material; the foaming agent consists of a surfactant, a thickening agent and water; the dosage of the surfactant is 0.3-1.0% of the mass of the gelled material, the dosage of the thickener is 0.15-0.5% of the mass of the gelled material, and the dosage of the water is 40-60% of the total mixing water of the foam concrete; the using amount of the light silica is 1-7% of the mass of the cementing material; the volume mixing amount of the fiber is 0.05-1%.

2. The 3D printed lightweight silica microsphere doped foam concrete according to claim 1, wherein the alkali-activator is one or more of steel slag and clinker.

3. The 3D printed foamed concrete doped with lightweight silica microspheres according to claim 1, wherein when the alkali-activator is a mixture of steel slag and clinker, the mass ratio of the steel slag to the clinker is (5-15) to (2-4).

4. The 3D printed lightweight silica microsphere doped foam concrete according to claim 1, wherein the accelerator is a fast hardening sulphoaluminate cement.

5. The 3D printing foamed concrete doped with light silica microspheres of claim 1, wherein the water reducing agent is one of a polycarboxylate water reducing agent and a polyphosphate water reducing agent.

6. The 3D printing foamed concrete doped with light silica microspheres of claim 1, wherein the surfactant is one of sodium dodecyl sulfate, dodecyl dimethyl betaine, dodecyl polyoxyethylene ether and sodium alpha-olefin sulfonate; the thickening agent is one or more of dodecanol, sodium chloride, sodium carboxymethylcellulose, sodium polyacrylate and hydroxypropyl methyl cellulose.

7. The 3D printed foamed concrete doped with lightweight silica microspheres according to claim 1, wherein the lightweight silica is one or more of hydrophobic fumed silica, silica fume, nanoscale surface hydrophobic silica aerogel microspheres prepared by Stober method.

8. The 3D printing foamed concrete doped with light silica microspheres of claim 7, wherein the silicon source in the nanoscale surface hydrophobic silica aerogel microspheres prepared by the Stober method is one or more of tetraethoxysilane, water glass, silica sol, siloxane and polyethoxy siloxane; the volume ratio of the silicon source to the deionized water is 1: 2-4; the solvent is ethanol, and the volume ratio of the silicon source to the ethanol is 1: 8-15; the catalyst is ammonia water, the mass fraction of the ammonia water is 25-28%, and the volume ratio of the silicon source to the ammonia water is 1: 1-1.5; the hydrophobic modifier is one of hexamethyldisilazane, n-octyltriethoxysilane, phenyltrimethoxysilane and methyltriethoxysilane, and the molar ratio of the silicon source to the hydrophobic modifier is 10-20.

9. The 3D printing foamed concrete doped with light silica microspheres according to claim 1, wherein the fibers are one or more of polypropylene fibers, basalt fibers and alkali-resistant glass fibers; the diameter of the polypropylene fiber is 30-80 μm, the cross section is rectangular, and the length-diameter ratio is 150-300; the basalt fiber has the average diameter of 13 mu m, the cross section of the basalt fiber is circular, and the length-diameter ratio of the basalt fiber is 350-1500; the diameter of the alkali-resistant glass fiber is 10-20 μm, the cross section is circular, and the length-diameter ratio is 300-1200.

10. A method of preparing the 3D printed foamed concrete doped with light silica microspheres according to any one of claims 1 to 9, characterized in that it comprises the following steps:

3) comparing the performances of different printing paths by using simulation software, and screening an optimal printing path according to different demand ratios of the performances in practical application;