RU2795274C1 - Method of 3d printing using modified concrete mix - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: used for additive manufacturing by layer-by-layer extrusion (3D printing) of construction products, structures, buildings and constructions. The method of 3D-printing using modified concrete mix includes preparing a concrete mixture, including Portland cement, quartz sand with a fineness modulus of 1.2-3 and water, squeezing it out in the form of a moulding filament through a printer dispensing head and laying it in the design position. At the same time, the modified concrete mixture for the transition layer is prepared and it is laid on the filament from the specified concrete mixture, a process break is carried out for 10, 360 or 720 minutes, followed by the resumption of laying after the process break of the specified filament, while the modified concrete mixture for the transition layer includes Portland cement, quartz sand with a fineness modulus of 1.2-3, MasterGlenium ACE 430 superplasticizer based on polycarboxylate ether, finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg/g, a grinding degree of at least 1100 m²/kg, organosilicon compound - potassium methyl siliconate and water with t a certain content of components.

EFFECT: longer process breaks (up to 12 hours) without formation of cold joints or reduction the adhesion of layers laid immediately before and after the process break, due to a transition layer from a modified concrete mixture, which ensures high quality of construction products.

1 cl, 2 tbl

Description

The invention relates to the field of construction and can be used for additive manufacturing by layer-by-layer extrusion (3D printing) of building products, structures, buildings and structures.

A method is known for erecting a concrete wall, along which a plastic solution of artificial stone material is extruded layer by layer through the nozzle of a construction 3D printer to form the outer and inner layers of the wall, the wall is reinforced and the cavity between the outer and inner layers of the wall is filled with a heat-insulating material [1]. The disadvantages of this invention are the impossibility of organizing long technological breaks due to a decrease in the adhesion of the layers laid immediately before and after the technological break. In addition, the high labor intensity of the reinforcement processes leads to an increase in the duration and cost of the work.

The closest solution to the proposed invention is a method for erecting a monolithic building, a structure using 3D printing, including the preparation of a concrete mixture, squeezing it in the form of a plastic filament through the dispensing head of the printer and layer-by-layer laying in the design position, with positioning flexible reinforcing elements in the body of the filament in the form twisted or braided reinforcing ropes made of polymeric or mineral fibers for continuous and/or discrete reinforcement of concrete mix [2].

The disadvantages of this invention are the impossibility of organizing long technological breaks, the need for which is caused by the need to gain plastic strength, ensuring the dimensional stability of the printed layers and the required geometric parameters, as a result of which the adhesion of the layers laid immediately before and after the technological break is reduced, which causes the formation of cold seams and reduces the quality of the finished product. products. In addition, the presence of processes for positioning flexible reinforcing elements in the body of the filament causes a high complexity of the invention.

The objective of the invention is to ensure high quality of construction products during long technological interruptions in construction 3D printing, by increasing the adhesion of layers, excluding the formation of cold seams, while simplifying additive manufacturing by eliminating complex technological operations associated with reinforcement.

The technical result of the proposed solution is the possibility of carrying out longer technological breaks (up to 12 hours) without the formation of cold joints and reducing the adhesion of layers laid immediately before and after the technological break, due to the device of a transition layer from a modified concrete mix, which causes high quality construction products.

The task is achieved by the fact that the method of 3D printing with a modified concrete mixture, including the preparation of a concrete mixture, including Portland cement, quartz sand with a fineness modulus of 1.2-3 and water, squeezing it out in the form of a plastic filament through the dispensing head of the printer and laying it in the design position , differs in that they prepare a modified concrete mixture for the transition layer and lay it on a filament from the specified concrete mixture, carry out a technological break for 10, 360 or 720 minutes, followed by resumption of laying after a technological break of the specified filament, while the modified concrete mixture for the transition layer includes Portland cement, quartz sand with a fineness modulus of 1.2-3, MasterGlenium ACE 430 superplasticizer based on polycarboxylate ether, finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg/g, a grinding degree of at least 1100 m ² / kg, organosilicon compound - potassium methylsiliconate and water with the following content of components, wt.%:

Portland cement
Specified sand
Superplasticizer "MasterGlenium ACE 430"
Specified finely ground pozzolanic component - biosilica
Silicone compound - potassium methyl siliconate
Water 20.0-30.0
44.4-69.8
0.2-1.2
2.0-8.0
0.1-0.8
7.9-15.9

For the manufacture of concrete mix for 3D printing, the following materials were used:

- Portland cement CEM I 42.5N produced by Asia Cement LLC (GOST 31108-2016) with the following mineralogical composition: C ₃ S - 68.1%, C ₂ S - 9.4%, C ₃ A - 7.2% , C ₄ AF - 11%;

- quartz sand of the Kamsko-Ustyinsky deposit of the Republic of Tatarstan with a fineness modulus of 1.2-3 (GOST 8736-2014). To prepare the samples, sand with a fineness modulus of 2.3 was used;

- tap drinking water that meets the requirements of GOST 23732.

The following materials were used to make a modified concrete mix for 3D printing of the transition layer:

- Portland cement CEM I 42.5N produced by Asia Cement LLC (GOST 31108-2016) with the following mineralogical composition: C ₃ S - 68.1%, C ₃ S - 9.4%, C ₃ A - 7.2% , C ₄ AF - 11%;

- quartz sand of the Kamsko-Ustyinsky deposit of the Republic of Tatarstan with a fineness modulus of 1.2-3 (GOST 8736-2014). To prepare the samples, sand with a fineness modulus of 2.3 was used;

- superplasticizer based on polycarboxylate ether "MasterGlenium ACE 430" manufactured by BASF Building Systems LLC, which is a light brown liquid with a density of 1.06 g/cm ³ at 20 °C, pH - 5.5;

- finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg/g, a grinding degree of at least 1100 m ² /kg (STO 23998461-020-2018). For the preparation of samples used biosilica with a hydraulic activity of 1400.5 mg/g, a grinding degree of 1186 m ² /kg;

- potassium methylsiliconate produced by PJSC "Khimprom", which is a dark brown liquid with a density of 1.3-1.4 g/cm ³ ;

- tap drinking water that meets the requirements of GOST 23732.

The present invention is carried out as follows:

1. The concrete mixture for 3D printing is prepared: pre-dosed dry components of the concrete mixture - Portland cement, sand are loaded into the working mixer and mixed until a homogeneous mass is obtained. Then, dosing is carried out by weight of water and added to the dry components, mixing until a homogeneous mass is obtained.

2. The 3D printer is prepared: the inner surface of the removable storage bin is moistened with tap drinking water or a release agent.

3. The storage hopper of the construction 3D printer is filled with the prepared concrete mixture and test extrusion is carried out until the resulting extrudate is homogeneous.

4. The concrete mixture is extruded by layer-by-layer extrusion (3D printing) on a construction 3D printer (for example, AMT S-6044 of SPETSAVIA LLC) and placed in the design position in accordance with a pre-prepared three-dimensional digital model.

5. The modified concrete mixture is prepared for 3D printing of the transition layer: pre-dosed dry components of the modified concrete mixture - Portland cement, sand, finely ground pozzolanic component - biosilica are loaded into the working mixer and mixed until a homogeneous mass is obtained. Then, water, superplasticizer "MasterGlenium ACE 430", organosilicon compound - potassium methyl siliconate are dosed by weight, they are mixed until a homogeneous solution is obtained and it is gradually added to the thoroughly mixed dry components, stirring the mixture until a homogeneous mass is obtained.

6. The storage bin of the construction 3D printer is filled with the prepared modified concrete mixture and test extrusion is carried out until the resulting extrudate is homogeneous.

7. The modified concrete mixture of the transition layer is extruded by the method of layer-by-layer extrusion (3D printing) on a construction 3D printer (for example, AMT S-6044 of the SPETSAVIA LLC company) and its laying in the design position in accordance with the previously prepared three-dimensional digital model.

8. A technological break is carried out for 10, 360 or 720 minutes with washing the storage bin of the construction 3D printer.

9. After the completion of the technological break, the concrete mixture is molded by layer-by-layer extrusion (3D printing) on a construction 3D printer in accordance with paragraphs 1-4.

The adhesion of the printed layers was determined after 28 days of normal hardening using the PSO-10MG4S adhesion meter using the normal tear-off method of steel disks (plates) in accordance with GOST R 58277-2018 “Dry building mixes on a cement binder. Test Methods". Test specimens were strips 100 mm long and 50 mm wide printed in two layers: 1 - concrete mixture; 2 - modified concrete mixture (transition layer).

Samples were also tested according to the prototype [1].

The compositions of the modified concrete mixes (transition layer) are shown in Table 1, the adhesion indices of the layers for various durations of technological breaks are given in Table 2.

Table 1 Components Compositions of modified concrete mixtures (transition layer), wt.% 1 2 3 4 5 6 (prototype) Portland cement 20.0 20.0 25.0 30.0 30.0 25.0 Sand 69.63 69.8 56.85 44.4 44.4 61.6 Superplasticizer - "MasterGlenium ACE 430" 0.05 0.2 0.7 1.2 1.5 Finely ground pozzolanic component - biosilica 0.5 2 5 8 10 Silicone compound - potassium methyl siliconate 0.02 0.1 0.8 0.5 0.6 Water 9.8 7.9 11.65 15.9 13.5 13.4 table 2 The duration of the technological break, min Layer adhesion, MPa 1 2 3 4 5 6 (prototype) 10 0.43 0.53 0.59 0.62 0.55 0.41 360 0.37 0.41 0.47 0.52 0.48 0.34 720 0.26 0.35 0.45 0.48 0.43 0.26

From the given data it follows that the maximum adhesion of the printed layers is achieved when the content of Portland cement in the composition of the modified concrete mix is 20.0-30.0% of the total mass of the composition, sand is 44.4-69.8%, superplasticizer "MasterGlenium ACE 430 "- 0.2-1.2%, finely ground pozzolanic component - biosilica - 2.0-8.0%, organosilicon compound - potassium methylsiliconate - 0.1-0.8%, water - 7.9-15.9 %. With the introduction of the superplasticizer "MasterGlenium ACE 430", a finely ground pozzolanic component - biosilica, an organosilicon compound - potassium methylsiliconate, in an amount less than those indicated in table 1 (composition 1), a decrease in adhesion indicators is observed compared to the claimed limits. With their introduction, in amounts greater than those indicated in Table 1 (composition 5), the adhesion indices of the layers printed on a 3D printer decrease.

The method of 3D printing with a modified concrete mix, according to the proposed invention, makes it possible to carry out longer technological breaks (up to 12 hours) without the formation of cold joints and a decrease in the adhesion of layers laid immediately before and after a technological break, due to the device of a transition layer from a modified concrete mix which determines the high quality of construction products.

The use of the MasterGlenium ACE 430 superplasticizer makes it possible to reduce the amount of mixing water, improve the plasticity of the modified concrete mixture, increase its density and the adhesion of the hardened composite during cohesive failure.

The introduction of a finely milled pozzolanic component - biosilica with a grinding degree of at least 1100 m ² /kg, a hydraulic activity of at least 1400 mg/g makes it possible to improve the uniformity and coherence of the mixture, increase the adhesive strength of composites due to denser packing of particles, interaction with portlandite and an increase in the amount of low-basic calcium hydrosilicates.

The use of an organosilicon compound - potassium methylsiliconate makes it possible to slow down the kinetics of structure formation, reduce the loss of chemically unbound water during a technological break.

The combined use of a superplasticizer - "MasterGlenium ACE 430", a finely ground pozzolanic component - biosilica, an organosilicon compound - potassium methylsiliconate makes it possible to achieve a synergistic effect, which is expressed in improving the plasticity, uniformity and cohesion of the modified concrete mixture, increasing its density and strength, slowing down the kinetics of structure formation, reducing losses chemically unbound water during the technological break, which contributes to an increase in the interfacial contact area of the layers printed before and after the technological break with the transition layer, and leads to an increase in the adhesion index of the hardened layers.

Thus, the proposed solution makes it possible to ensure high quality of construction products during long technological interruptions in construction 3D printing, by increasing the adhesion of layers, which excludes the formation of cold seams, while simplifying additive manufacturing by eliminating complex technological operations associated with reinforcement.

Information sources:

1. Patent, RU 2 725 716, E04 B 2/84, B33Y 30/00, Method for erecting a reinforced concrete wall on a 3D printer, Mukhametrakhimov R.Kh., Lukmanova L.V., patentee Federal State Budgetary Educational Institution of Higher Education "Kazan State University of Architecture and Civil Engineering" 12/23/2019, publ. 07/03/2020, bul. No. 19.

2. Patent, RU 2 683 447, E04C 5/07, C04B 7/52, A method of erecting a monolithic building, structures by 3D printing and a device for its implementation, Dzhantimirov H.A., Zvezdov A.I, Dzhantimirov P.Kh ., patentee Joint Stock Company "Research Center" Construction ", App. 12/05/2017, publ. 03/28/2019, bul. No. 10.

Claims (4)

A method for 3D printing with a modified concrete mixture, which includes the preparation of a concrete mixture, including Portland cement, quartz sand with a fineness modulus of 1.2-3 and water, squeezing it out in the form of a plastic filament through the dispensing head of the printer and laying it in the design position, characterized in that it is carried out preparation of the modified concrete mixture for the transition layer and its laying on the filament from the specified concrete mixture, a technological break is carried out for 10, 360 or 720 minutes, followed by the resumption of laying after the technological break of the specified filament, while the modified concrete mixture for the transition layer includes Portland cement, quartz sand with a fineness modulus of 1.2-3, MasterGlenium ACE 430 superplasticizer based on polycarboxylate ether, finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg / g, a grinding degree of at least 1100 m ² / kg, an organosilicon compound - methyl silicone potassium and water with the following content of components, wt.%: Portland cement 20.0-30.0 specified sand 44.4-69.8 superplasticizer "MasterGlenium ACE 430" 0.2-1.2 specified finely ground pozzolanic component - biosilica 2.0-8.0 organosilicon compound - potassium methyl siliconate 0.1-0.8 water 7.9-15.9