CN114436578A

CN114436578A - Controlled-release quick-setting functional particles and application thereof in 3D printing of cement-based materials

Info

Publication number: CN114436578A
Application number: CN202210209043.5A
Authority: CN
Inventors: 冯攀; 邵丽静; 刘琪; 王浩川; 刘钊龙
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2022-05-06

Abstract

The invention provides a controlled-release quick-setting functional particle and application thereof in 3D printing of a cement-based material, wherein the controlled-release quick-setting functional particle comprises a core material and a wall material, and the weight part ratio of the core material to the wall material is 2: (1-2); the functional particles are spheroidal and the contact angle of the functional particles with water is greater than 90 degrees. The 3D printing cement-based material comprises cement, water, functional particles and other common additives. When the functional particles are applied to the preparation process of the cement-based material with high fluidity, the contact angle between the functional particles and water is larger than 90 degrees due to the fact that the functional particles are not dissolved in water or subjected to hydrophobic treatment, and the particles are guaranteed not to be dissolved in advance to release internal core materials, so that the cement-based material has good fluidity at the initial preparation stage; heat release or microwave heating or other ways are provided along with the hydration process of the cement-based material, so that the wall material is melted and the core material is released, and the short-time regulation and control of the fluidity of the cement-based material are realized through the core material.

Description

Controlled-release quick-setting functional particles and application thereof in 3D printing of cement-based materials

Technical Field

The invention relates to the technical field of concrete admixtures, in particular to controlled-release quick-setting functional particles and application thereof in 3D printing of cement-based materials.

Background

As a novel template-free construction technology, the 3D printing cement-based material has higher requirements on the flow performance of cement concrete, needs to have larger fluidity before extrusion to meet the requirement of conveying, and simultaneously needs to meet the requirement of no collapse and deformation under the self weight and the weight of the next printing layer after extrusion, so that contradictory requirements on the fluidity are met.

At present, the printing requirement is met mainly by the self rheological property of cement concrete, namely, slurry has lower dynamic yield stress in a stirring state before printing, the conveying can be met, and after printing, due to the thixotropy of the slurry and high static yield stress during standing, the requirement of layer-by-layer stacking and obvious deformation is met. The excellent thixotropy can be achieved by matching a series of additives such as a water reducing agent, a thickening agent, an accelerating agent, a thixotropic agent and the like, but in the preparation process of concrete, the phenomena of incompatibility or incomplete adaptation exist among a plurality of additives and between the additives and cement, so that the using effect of the additives is influenced to a certain extent. For example, when the machine-made sand is used for mixing concrete, mud powder in the machine-made sand can adsorb the additive, so that the use efficiency of the additive is greatly reduced. However, the rheological property of the material changes along with the change of time, and if the printing is interrupted accidentally, the slurry with good thixotropy can not be printed any more, so that the material is lost and wasted, and therefore, the material is required to have a certain open time while the edge forming property is met, so that the material can be extruded and printed for a long time after being mixed. However, the thixotropy of the material itself is limited, and only the reversible thixotropy of the material is relied on, so that the risk of large deformation or collapse of a printing high layer is easily caused. Therefore, the fluidity of the cement paste needs to be actively controlled by means of external signals, the fluidity of the cement concrete is reduced by controlling the release of the additive, the irreversible change of the fluidity is achieved, and the pumping performance and the constructability of the concrete are improved. Controlled release of the additive by the capsule is a suitable means.

Patent application CN202010294070.8 discloses an additive microcapsule based on microwave controlled release and a preparation method thereof, which can realize microwave response through a PDVF material, so that the active controlled release of an additive in concrete can be realized, and the problem of performance loss caused by the advance release of the additive is effectively solved. However, the carrier used in the method is the hollow fiber, PVDF still exists in the cement matrix after the release, the loaded material is the liquid admixture, the controlled release method is to control the melting of the capsule by controlling the melting of the paraffin phase-change material, and the fibrous capsule is easy to damage in the mixing process to cause the advance release of the admixture.

Patent application CN202010382083.0, a microwave responsive additive active release capsule and a preparation method thereof, using Fe in the packaging material₃O₄The capsule can be triggered to respond by applying an external microwave signal to actively release the additive, so that the problems of low utilization efficiency, even possible negative effect and the like caused by the direct doping of the additive into the building material are effectively solved, and the active control on the performance of the building material is further realized. However, the method mainly adopts porous aggregate load and the wave absorbing performance of ferroferric oxide, so that the amount of the loaded additive is limited, and the additive loaded in porous aggregate can not be completely released. The single-grain preparation method is adopted, the preparation speed is low, the capsule grains are more than 10mm, the grain size is large, the porous aggregate carrier still exists in a cement matrix after being released, certain defects can be introduced, and the single-grain preparation method is mainly used for releasing the rust inhibitor after concrete is hardened to improve the durability.

Disclosure of Invention

The invention provides a controlled-release quick-setting functional particle and application thereof in 3D printing cement-based materials, aiming at solving the defects that the existing high-fluidity cement-based materials cannot be applied to a 3D printing process, and the use efficiency of an additive is greatly reduced due to the fact that the additive is easily adsorbed by mud powder in machine-made sand in the using process, the fluidity of slurry is too low when the additive is directly added and the slurry is hardened in a short time when the slurry is sprayed out from a nozzle or extruded out from a printing nozzle, and the like.

A controlled release quick-setting functional particle comprises a core material and a wall material, wherein the content of a powdery quick-setting agent in the core material is not lower than 50%, the wall material is a phase-change material with a melting point of 40-70 ℃, and the weight part ratio of the core material to the wall material is 2: (1-2); the functional particles are spheroidal and the contact angle between the functional particles and water is larger than 90 degrees.

The core material is at least one of powdery thickener, powdery early strength additive and retarder.

The admixture in the field of cement-based materials can be used as a core material.

The particle size of the functional material is 0.5mm-5 mm.

The phase change material is at least one of polyethylene glycol, paraffin and stearic acid, and the weight average molecular weight of the polyethylene glycol is 1500-10000. Wherein, when the phase-change material is a water-soluble material, the effect is better.

The weight part ratio of the core material to the wall material is 2: (1-2), when the weight part of the core material is too high to exceed the proportion range, the mixed suspension is too thick and is not easy to stir uniformly; when the weight portion of the core material is too low and is not in the proportion range, the influence on the fluidity of the cement paste is not obvious under the same mixing amount.

Firstly, after a phase-change material is melted, adding a core material into the melted phase-change material, and stirring to form a suspension; then pouring the mixture into a mold for cooling and molding, and crushing and screening the mixture to obtain small particles; and (3) carrying out hydrophobic coating treatment on the small particles, and then filtering and drying to obtain the functional particles.

The particle size of the small particles is 0.5mm to 5 mm.

Firstly, after a phase-change material is melted, adding a core material into the melted phase-change material, and stirring to form a suspension; dripping the suspension into the condensate by a dripping pill method to form pills; and (3) carrying out hydrophobic coating treatment on the pills, and then filtering and drying to obtain the functional particles.

The pill has a particle size of 1-4 mm.

The hydrophobic coating treatment comprises the following steps of firstly soaking the small particles in a normal hexane solution of 2-10% perfluorooctyl trichlorosilane for 2-4h, filtering and drying, then soaking the dried small particles in a 4% paraffin-cyclohexane solution for 4h, and filtering and drying.

In the preparation process of the controlled-release quick-setting functional particles, if the contact angle between the wall material and water is more than 90 degrees, the surface of the wall material does not need to be subjected to hydrophobic modification.

The application of the controlled-release quick-setting functional particles is applied to the construction process of concrete spraying and 3D printing of cement-based materials.

The utility model provides a 3D prints cement-based material, above-mentioned 3D prints cement-based material and includes that 3D prints cement, mineral admixture, grit, water, additive, functional granule, above-mentioned 3D prints cement, mineral admixture, grit, water, additive, functional granule's weight ratio is 1: (0-0.05): (0-2): (0.3-0.5): (0-0.01): (0.02-0.08); the functional particles are the functional particles according to claim 1 or the functional particles prepared by the preparation method according to claim 5.

Compared with the prior art, the invention has the following advantages:

1. the functional particles are applied to the preparation process of the cement-based material with high fluidity, and because the functional particles are subjected to hydrophobic treatment, the contact angle between the functional particles and water is larger than 90 degrees, so that the cement-based material is ensured to have better fluidity at the initial preparation stage; the wall material is melted and the core material is released along with heat release or microwave heating in the hydration process of the cement-based material or heat sources are provided in other modes, the short-time regulation and control of the fluidity of the cement-based material are realized through the core material, namely, the core material powder accelerator plays a role, and the cement-based material is rapidly solidified.

2. The 3D of this application prints cement-based material and is used for 3D to print, has better mobility in printing earlier stage, can not lead to 3D to print the jam of shower nozzle because mobility undersize in pumping process, and can solidify in the short time after the blowout, guarantees that the building layer after printing can stand rapidly and do not slump, but increases 3D and prints pumpability and the printable nature of cement-based material.

3. Utilize 3D to print cement-based material of this application to be expected to use microwave heating device to couple together cement concrete pumping and 3D printer in the future, increase convenience and the practical application nature that 3D printed, realize that cement concrete material still can realize printing after longer distance, longer time's transport.

4. Utilize the 3D of this application to print cement-based material can satisfy under the regulation and control of fluidity, and does not influence the intensity that 3D printed cement-based material.

Drawings

FIG. 1 shows the release of functional particles 1 under the condition of microwave power of 600W;

FIG. 2 shows the fluidity of the functional particles 1 when they are incorporated into a cement paste for 30 seconds;

FIG. 3 is a graph showing the fluidity of comparative example 1 in which the powdery admixture was incorporated into a cement paste for 30 seconds;

FIG. 4 shows extrusion stacking properties obtained by adding the functional particles 1 to a cement paste, extruding the cement paste through an injector, and applying a microwave signal to an extrusion port;

fig. 5a shows that functional particles 4 are doped into cement mortar, and the obtained 3D printing cement-based material is subjected to constructability test before microwave;

fig. 5b shows that the functional particles 4 are doped into cement mortar, and the obtained 3D printing cement-based material is subjected to a building property test after microwave irradiation;

fig. 5c shows that the functional particles 4 are doped into cement mortar, and the obtained 3D printed cement-based material is subjected to post-microwave printing test;

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

10g of polyethylene glycol 2000(CP) was weighed in a small beaker, melted at a water bath temperature of 75-80 ℃, and 9g of a powdery quick-setting admixture (SBT-N (III) which is a sodium metaaluminate powdery quick-setting admixture from Jiangsu Subot New materials GmbH) and 1g of cellulose ether were weighed, added to a polyethylene glycol liquid, and stirred at 200rpm for 5 minutes to form a uniform suspension. Dropping the obtained suspension into liquid paraffin in a cold water bath to form uniform spherical pill particles, soaking the particles in a normal hexane solution of perfluorooctyl trichlorosilane with the concentration of 4% for 4h, taking out and drying to obtain the functional particles 1, wherein the contact angle is 151 degrees.

Example 2

Weighing 10g of polyethylene glycol 2000(CP) in a small beaker, melting at the water bath temperature of 75-80 ℃, weighing 10g of aluminum sulfate (the main component of the alkali-free accelerator), grinding through a 0.3mm square-hole sieve, gradually adding into the polyethylene glycol liquid, and continuously stirring to form a uniform and thick substance. And pouring the obtained thick substance into an iron pan for cooling and solidification, grinding and sieving the obtained solid, taking particles with the particle size of 0.6-2.36 mm, soaking the particles in a normal hexane solution of perfluorooctyl trichlorosilane with the concentration of 4% for 3 hours, filtering and drying the particles, soaking the particles in 4% paraffin-cyclohexane for 4 hours, taking out the particles and drying the particles to obtain the functional particles 2, wherein the contact angle is 114 degrees.

Example 3

15g of polyethylene glycol 4000(CP) is weighed by using a small beaker, melted at the water bath temperature of 75-80 ℃, 10g of aluminum sulfate (the main component of the alkali-free accelerator) is weighed, ground through a 0.3mm square-hole sieve, added into polyethylene glycol liquid, and stirred at 200rpm for 5min to form uniform suspension. And pouring the obtained suspension into an iron pan for cooling and solidification, grinding and sieving the obtained solid, taking particles with the particle size of 1.18-2.36 mm, soaking the particles in a normal hexane solution of perfluorooctyl trichlorosilane with the concentration of 4% for 2 hours, filtering, drying, soaking the particles in 4% paraffin-cyclohexane for 4 hours, taking out the particles, and drying to obtain the functional particles 3 with the contact angle of 112 degrees.

Example 4

20g of polyethylene glycol 4000(AR) is weighed by a small beaker, the mixture is melted at the water bath temperature of 75-80 ℃, 10g of aluminum sulfate (the main component of the alkali-free accelerator) is weighed and added into the polyethylene glycol molten liquid, the mixture is uniformly stirred to obtain suspension, the obtained suspension is dripped into liquid paraffin in a cold water bath to form uniform spherical pill particles, the particles are soaked in a normal hexane solution of perfluorooctyl trichlorosilane with the concentration of 4 percent for 4 hours, and then the particles are taken out and dried to obtain functional particles 4, wherein the contact angle is 117 degrees.

Example 5

Weighing 20g of polyethylene glycol 4000(AR) in a small beaker, melting at the water bath temperature of 75-80 ℃, weighing 20g of sodium metaaluminate (containing an alkali accelerator as a main component), adding into the polyethylene glycol molten liquid, and manually stirring to obtain a uniform and thick substance. And pouring the obtained thick substance into an iron pan for cooling and solidification, grinding and sieving the obtained solid, taking particles with the particle size of 0.6-2.36 mm, soaking the particles in a normal hexane solution of perfluorooctyl trichlorosilane with the concentration of 4% for 4 hours, filtering, drying, soaking the particles in 4% paraffin-cyclohexane for 4 hours, taking out and drying to obtain the functional particles 5, wherein the contact angle is 111 degrees.

Example 6

Weighing 10g of paraffin by using a small beaker, melting at the water bath temperature of 80-90 ℃, weighing 10g of aluminum sulfate (the main component of the alkali-free accelerator), adding the aluminum sulfate into paraffin melting liquid, uniformly stirring to obtain suspension, pouring the obtained suspension into an iron plate for cooling and solidifying, crushing and sieving the cooled solid, and taking particles with the particle size of 0.6-4.75mm, wherein the functional particles 6 are obtained without any treatment because the paraffin is insoluble in water, and the contact angle is 108 degrees.

Example 7

Weighing 10g of stearic acid by using a small beaker, melting at the water bath temperature of 80-90 ℃, weighing 10g of aluminum sulfate (the main component of the alkali-free accelerator), adding the aluminum sulfate into stearic acid melting liquid, uniformly stirring to obtain suspension, pouring the obtained suspension into an iron disc for cooling and solidifying, crushing and sieving the cooled solid, and taking particles with the particle size of 0.6-4.75mm, wherein the stearic acid is insoluble in water, so that no treatment is needed, and the functional particles 7 are obtained, and the contact angle is 123 degrees.

Comparative example 1

As the functional particles 8, 10g of aluminum sulfate (alkali-free accelerator main component) was used.

Comparative example 2

As the functional particles 9, 9g of a powdery quick-setting admixture (SBT-N (III) which is a sodium metaaluminate type powdery quick-setting admixture from Jiangsu Subo New Material Co., Ltd.) and 1g of cellulose ether were used.

Comparative example 3

Weighing 10g of polyethylene glycol 2000(CP) in a small beaker, melting at the water bath temperature of 75-80 ℃, weighing 10g of aluminum sulfate (the main component of the alkali-free accelerator), grinding through a 0.3mm square-hole sieve, gradually adding into the polyethylene glycol liquid, and continuously stirring to form a uniform and thick substance. Pouring the obtained thick substance into an iron pan for cooling and solidification, grinding and sieving the obtained solid, and taking particles with the particle size of 0.6mm-2.36mm to obtain the functional particles 10, wherein the contact angle is 19 degrees.

Test example 1: functional particle functional material release result graph under microwave action

Using the functional particles 1 obtained in example 1 as an example, the release under the microwave power of 600W was measured. After the phase change material polyethylene glycol is placed under the microwave power of 600W for one minute, the phase change material polyethylene glycol is completely melted, and an internal functional material is released, so that the microwave regulation and control functional material release scheme is feasible, and the result is shown in figure 1.

Test example 2: study on flowability of 3D printing cement paste material before and after application of microwave signal

The functional particles prepared in examples 1 to 7 and the functional particles 8 of comparative example 1 (the same mass of the functional particles as used in example 3) and the functional particles 9 of comparative example 2 (the same mass of the additives as used in example 1) were mixed into cement paste to test the fluidity of the paste, respectively, and the test time was 3min after mixing with water for initial fluidity test, 5min after stirring for second test, and 1min after applying microwave signals for third test after stirring for 1 min. The water-cement ratio is 0.5, the mixing amount of the functional particles is 5 percent, and no other functional particles are used. The net slurry fluidity was measured before and after application of the microwave signal and the results are given in table 1 below:

TABLE 1

Numbering	Initial fluidity	Fluidity after 5min	Fluidity at 1min after microwave
				Example 1	150mm	150mm	60mm (loss of fluidity)
Example 2	155mm	140mm	60mm (loss of fluidity)
				Example 3	155mm	145mm	75mm
Example 4	155mm	145mm	100mm
				Example 5	150mm	145mm	60mm (loss of fluidity)
Example 6	150mm	145mm	60mm (loss of fluidity)
				Example 7	150mm	145mm	60mm (loss of fluidity)
Comparative example 1	145mm	95mm	70mm
				Comparative example 2	60mm (loss of fluidity)	——	——
Comparative example 3	145mm	100mm	70mm
				Blank group
1	160mm	160mm	145mm

As can be seen from the test results of Table 1, the fluidity of the functional particles 1 when incorporated into a cement paste is 30 seconds, as shown in FIG. 2; the functional particles 1 to 7 are doped into the cement paste, mixed with water and stirred for at least 8 minutes, the fluidity is basically kept unchanged, and the concrete can be quickly solidified after a microwave signal is applied, so that the pumping problem of the 3D printing cement-based material is solved, the spraying quick solidification performance of the 3D printing cement-based material is met, and the pumping performance and the printing performance are better; comparative example 2 due to the quick setting effect of the powdery admixture, the slurry lost fluidity already when the initial fluidity test was performed, that is, the slurry lost fluidity already within 3min of being mixed with water, and at this time the slurry lost pumpability and extrudability, which did not meet the basic requirements as a 3D printing cement-based material, as shown in fig. 3. While comparative example 1 and example 3 have the same effect of reducing fluidity after the capsule is released and directly mixed with the same admixture, the coated admixture can maintain the constant fluidity of the slurry before the release compared with the uncoated admixture. Comparison of comparative example 3 with example 2 shows that the fluidity of the functional particles before hydrophobicity treatment is relatively lowered, and the effect of maintaining the fluidity of the slurry before no signal is applied cannot be achieved.

Test example 3: performance comparison of 3D printing mortar before printing and after printing

And (2) doping the sodium metaaluminate quick-setting type capsule prepared in the example 4 into cement mortar to prepare a 3D printing cement-based material, wherein the water-to-gel ratio is 0.45, the capsule doping amount is 3%, and the gel-to-sand ratio is 1: 1, stirring the mixture by using a mortar stirrer without using any other additive, performing a constructability test on the mortar by using a cylindrical mould of 80mm multiplied by 80mm, performing the constructability test again after 1min by using microwaves, and performing a 3D printing test by using a desktop-level 3D printer, wherein the diameter of a nozzle is 10 mm. The result is shown in fig. 5, the cement mortar has no construction stacking performance without applying the micro-wave front (fig. 5a) and the expansibility reaches about 170mm, and at the moment, the fluidity is good, the fluidity is high, and the pumping and the transportation are convenient. However, after microwave response (fig. 5b), sodium metaaluminate is released due to melting of the phase change material polyethylene glycol, so that the fluidity is rapidly reduced, the requirement of building accumulation is initially met, and no deformation is generated at a low layer number (fig. 5 c). The functional particles can actively regulate and control the fluidity of the cement concrete by applying microwave signals from the outside so as to meet the requirement of printability of 3D printing cement-based materials. In later application, the concrete pump truck and the 3D printer can be connected by using the microwave reactor, so that the aims of long-distance conveying and anytime and anywhere extrusion printing of the 3D printed cement-based material are fulfilled.

Test example 4: influence of released functional particles on cement mortar strength

The functional particles 3 obtained in example 3 and the functional particles 8 obtained in comparative example 1 were mixed with 3% of cement mortar, respectively, and the compressive and flexural strength of the mortar was tested. According to GB/T17671-: 1. the results are shown in Table 2 for the flexural strength values of the cement mortars.

TABLE 2

The data results in table 2 show that the incorporation of the phase change material slightly reduced the compressive flexural strength of 3D and 7D compared to the blank control, comparative example functional particle 8 group, but did not affect its use as a 3D printing material.

And (4) conclusion: the functional particles obtained by the method are doped into the cement paste, microwaves are not applied or external heat sources are not provided, the 3D printing paste basically keeps good fluidity, the functional materials can be released to play a solidification role after the microwaves are applied, and microwave signals can be applied at any time according to engineering requirements to realize paste condensation; the 3D printing cement base material is used for 3D printing, has better mobility in printing earlier stage, can not lead to the jam of 3D printing shower nozzle because mobility undersize in the pumping process, and can solidify in the short time after the blowout, guarantees that the concrete building layer after printing can stand rapidly and do not slump, increases 3D and prints pumpability and the printable nature of cement base material.

Claims

1. A controlled release fast setting functional granule is characterized in that: the functional particles comprise a core material and a wall material, wherein the content of a powdery accelerator in the core material is not less than 50%, the wall material is a phase-change material with a melting point of 40-70 ℃, and the weight part ratio of the core material to the wall material is 2: (1-2); the functional particles are spheroidal and the contact angle between the functional particles and water is greater than 90 degrees.

2. The controlled-release fast-setting functional granule according to claim 1, wherein: the core material is at least one of powdery thickener, powdery early strength admixture and retarder.

3. The controlled-release fast-setting functional granule according to claim 1, wherein: the particle size range of the functional material is 0.5mm-5 mm.

4. The controlled-release fast-setting functional granule according to claim 1, wherein: the phase change material is at least one of polyethylene glycol, paraffin and stearic acid, and the weight average molecular weight of the polyethylene glycol is 1500-10000.

5. The method for preparing controlled-release fast-setting functional granules according to claim 1, wherein: firstly, after a phase-change material is melted, adding a core material into the melted phase-change material, and stirring to form a suspension; then pouring the mixture into a mould for cooling and forming, and crushing and screening the mixture to obtain small particles; and (3) carrying out hydrophobic modification on the small particles, and then filtering and drying to obtain the functional particles.

6. The method of claim 5, wherein: the particle size of the small particles is 0.5mm-5 mm.

7. The production method according to claim 5, characterized in that: the hydrophobic modification is hydrophobic coating treatment, and comprises the following steps of firstly soaking small particles in a normal hexane solution of 2-10% perfluorooctyl trichlorosilane for 2-4h, filtering and drying, then soaking the dried small particles in a 4% paraffin-cyclohexane solution for 4h, and filtering and drying.

8. Use of the controlled-release fast-setting functional granules according to any one of claims 1 to 4, characterized in that: the functional particles are applied to the construction process of concrete spraying and 3D printing of cement-based materials.

9. The utility model provides a 3D prints cement-based material which characterized in that: the 3D printing cement-based material comprises 3D printing cement, mineral admixture, sand, water, additive and functional particles, wherein the weight ratio of the 3D printing cement to the mineral admixture to the sand to the water to the additive to the functional particles is 1: (0-0.05): (0-2): (0.3-0.5): (0-0.01): (0.02-0.08); the functional particles are the functional particles according to claim 1 or the functional particles prepared by the preparation method according to claim 5.