RU2817919C1 - Method of additive manufacturing in construction with controlled duration of technological break - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction and can be used for additive production by layer-by-layer extrusion (3D printing) of construction products, structures and buildings. Method of additive manufacturing in construction with controlled duration of technological break includes preparation of concrete mixture, including portland cement, quartz sand and water, extrusion thereof in form of plastic filament through printer dispensing head and laying into design position. Method comprises preparing a modified concrete mixture for the transition layer, which includes, wt.%: portland cement 20–30, quartz sand 44.4–69.8, superplasticiser "MasterRheobuild 183" based on naphthalenesulphonates 0.1–0.6, bio-silica with hydraulic activity of not less than 1,400 mg/g, degree of grinding of not less than 1,100 m²/kg 2–8, potassium methyl siliconate 0.1–0.8, water 8–16.5, and its laying on a filament from said concrete mixture. Technological break is carried out with subsequent resumption of laying of said filament. Before laying the transition layer, steel electrodes are laid on top of the previously laid layer. During the technological break, the laid layers are exposed with the electric field created by passing alternating electric current through modified concrete mixture by connecting electrodes to power source – single-phase portable welding transformer “Blue Weld Gamma 4.181”. Duration of exposure by electric field is 0.1–3 hours.

EFFECT: provision of possibility to control duration of technological break by method of layer-by-layer extrusion at implementation of long technological breaks due to increase in the average rate of gaining critical plastic strength of the concrete of the transition layer while ensuring high quality of construction products with long technological breaks of construction 3D printing, due to provision of high adhesion of layers (0.5–1.5 MPa), excluding formation of cold seams.

1 cl, 1 tbl

Description

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

There is a known method for constructing a monolithic building or structure using the 3D printing method, which includes preparing a concrete mixture, extruding it in the form of a plastic filament through the dispensing head of a printer and layer-by-layer laying in the design position, with the positioning of flexible reinforcing elements in the body of the filament in the form of twisted or braided reinforcing ropes made of polymer or mineral fibers for continuous and/or discrete reinforcement of concrete mixtures [1]. 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, ensure the dimensional stability of the printed layers and the required geometric parameters, as a result of which the adhesion of 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 into the filament body makes the implementation of the invention highly complex.

The closest solution to the proposed invention is a method of additive manufacturing in construction, including the preparation of a concrete mixture including Portland cement, quartz sand with a fineness modulus of 1.2-3 and water, extruding it in the form of a plastic filament through the dispensing head of the printer and laying it in the design position, preparing a modified concrete mixture for the transition layer and laying it on a filament from the specified concrete mixture, implementing a technological break 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 (20 ,0-30.0 wt.%), quartz sand with a particle size modulus of 1.2-3 (44.4-69.8 wt.%), superplasticizer "MasterRheobuild 183" based on naphthalene sulfonates (0.1-0.6 wt.%), finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg/g, degree of grinding of at least 1100 m ² /kg (2.0-8.0 wt.%), organosilicon compound - potassium methyl siliconate (0. 1-0.8 wt.%) and water (8.0-16.5 wt.%) [2].

The disadvantages of this invention are the impossibility of regulating the technological break, namely, reducing its duration, which depends on the rate at which the concrete transition layer gains the required plastic strength, which leads to a slowdown in the rate of layer build-up during additive construction production and an increase in the duration of construction of construction products.

The objective of the present invention is to provide the ability to regulate the duration of a technological break using the layer-by-layer extrusion method when carrying out long technological breaks by increasing the average rate of gain of the critical plastic strength of concrete in the transition layer while simultaneously ensuring high quality construction products during long technological breaks of construction 3D printing, by ensuring high layer adhesion indicator (0.5-1.5 MPa), eliminating the formation of cold seams.

The technical result of the proposed solution is to provide the ability to regulate the duration of a technological break using the layer-by-layer extrusion method when carrying out long technological breaks by increasing the average rate of gain of the critical plastic strength of the transition layer concrete while simultaneously ensuring high quality construction products during long technological breaks of construction 3D printing, by ensuring high layer adhesion rate (0.5-1.5 MPa), eliminating the formation of cold seams.

The task is achieved by the fact that the method of additive manufacturing in construction with an adjustable duration of the technological break, including the preparation of a concrete mixture including Portland cement, quartz sand and water, squeezing it in the form of a plastic filament through the dispensing head of the printer, laying it in the design position, preparing a modified concrete mixture for a transition layer, including Portland cement 20-30 wt.%, quartz sand 44.4-69.8 wt.%, superplasticizer "MasterRheobuild 183" based on naphthalene sulfonates 0.1-0.6 wt.%, finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg/g, degree of grinding of at least 1100 m ² /kg 2-8 wt.%, organosilicon compound - potassium methyl siliconate 0.1-0.8 wt.% and water 8-16.5 wt. %, and its laying on a filament from the specified concrete mixture, the implementation of a technological break with the subsequent resumption of laying of the specified filament, differs in that before laying the transition layer on top of the previously laid layer, steel electrodes are laid; during the technological break, the laid layers are exposed to electrical field created by passing an alternating electric current through a modified concrete mixture by connecting the electrodes to a power source - a single-phase portable welding transformer “Blue Weld Gamma 4.181”, while the duration of exposure to the electric field is 0.1-3 hours.

The following materials were used to produce the concrete mixture for 3D printing:

- 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 from the Kamsko-Ustinsky deposit of the Republic of Tatarstan with a fineness modulus of 2.3 (GOST 8736-2014);

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

To produce a modified concrete mixture for 3D printing of the transition layer, 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 from the Kamsko-Ustinsky deposit of the Republic of Tatarstan with a fineness modulus of 2.3 (GOST 8736-2014);

- superplasticizer based on naphthalene sulfonates “MasterRheobuild 183” produced by BASF Construction Systems LLC, which is a dark brown liquid without chloride content, density at 20°C 1.12 g/cm ³ , pH – 5;

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

- potassium methyl siliconate 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.

A single-phase portable air-cooled AC welding transformer “Blue Weld Gamma 4.181” with the following technical characteristics was used as a power source to influence the laid layers of the electric field: voltage – 220 V, maximum power – 2.5 kW, maximum current – 160 A , minimum current – 55 A, number of posts – 1, net weight – 15.8 kg, dimensions – 370×250×310 mm. Steel rods with a diameter of 6 mm were used as electrodes, which were laid in increments of 100 mm - 300 mm on the layer laid earlier than the transition layer.

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 a running mixer and mixed until a homogeneous mass is obtained. Then dispense water by weight and add it to the dry ingredients, mixing until a homogeneous mass is obtained.

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

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

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

5. Steel electrodes are laid on top of the layer preceding the transition layer.

6. 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 operating mixer and mixed until a homogeneous mass is obtained. Then dosage by weight of water, superplasticizer “MasterRheobuild 183”, organosilicon compound - potassium methyl siliconate, mix them until a homogeneous solution is obtained and gradually add it to the thoroughly mixed dry components, stirring the mixture until a homogeneous mass is obtained.

7. Fill the storage hopper of the construction 3D printer with the prepared modified concrete mixture and carry out test extrusion until the resulting extrudate is homogeneous.

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

9. A technological break is carried out with washing of the storage hopper of the construction 3D printer.

10. During a technological break, connect the electrodes to a power source and pass an alternating electric current through the modified concrete mixture for 0.1-3 hours.

11. The concrete mixture is formed by layer-by-layer extrusion (3D printing) on a construction 3D printer in accordance with paragraphs. 1-4.

The plastic strength of the concrete mixture was determined in accordance with the requirements of ASTM C403 “Standard Test Method for Time of Setting of Concrete Mixtures by Penetration Resistance” based on the resistance of the raw mixture to penetration of the plunger of a C194 pocket penetrometer with a cross-sectional diameter of 6.35 mm at regular time intervals.

The adhesion of the printed layers was determined after 28 days of normal hardening using a PSO-10MG4S adhesion meter using the normal tear-off method of steel disks (plates) in accordance with GOST R 58277-2018 “Dry building mixtures with a cement binder. Test methods". The test samples were strips 100 mm long and 50 mm wide, printed in three layers: 1 – concrete mixture; 2 – transition layer of modified concrete mixture, through which an alternating electric current was passed by connecting electrodes; 3 – concrete mixture.

The average rate of gain of critical plastic strength of concrete in the transition layer was determined by the ratio of its value equal to 3000 kPa, which ensures the ability to withstand the weight of overlying layers without the formation of defects, to the duration of its gain from the moment the influence of the electric field begins.

Tests of prototype samples were also carried out [2].

Indicators of the average rate of gain of critical plastic strength of concrete in the transition layer, adhesion of printed layers from the concrete mixture, and the possibility of regulating the duration of the technological break are given in Table 1.

Table 1

Properties Indicators for methods 1 2 (prototype) Average rate of gain of critical plastic strength of transition layer concrete, kPa/min 65.5 3.7 Adhesion of printed layers of concrete mixture and modified concrete mixture during a technological break of 360 minutes, MPa 0.55 0.53 Possibility of adjusting the duration of a technological break Yes No

From the data presented it follows that the average rate of gain of critical plastic strength of concrete in the transition layer increases by 17.7 times, it is possible to regulate the duration of the technological break in comparison with the prototype, and also ensures a high rate of layer adhesion, eliminating the formation of cold joints.

The method of additive manufacturing in construction according to the present invention leads to the possibility of regulating the duration of a technological break during long technological breaks by increasing the average rate of gain of the critical plastic strength of concrete in the transition layer while simultaneously ensuring high quality construction products during long technological breaks of construction 3D printing, due to ensuring a high rate of layer adhesion, eliminating the formation of cold seams.

The effect on the laid layers of the electric field created by passing an alternating electric current through the concrete mixture by connecting electrodes makes it possible to increase the average rate of gain of the critical plastic strength of the transition layer concrete, which leads to the possibility of regulating the duration of the technological break during additive manufacturing in construction.

As the temperature of the modified concrete mixture increases under the influence of an electric field, the chemical reactions that occur during the hydration of clinker minerals are accelerated, the processes of formation of the coagulation and crystallization structure of concrete are intensified, and the adhesion of layers is ensured.

Thus, the proposed solution makes it possible to obtain high-quality construction products molded by layer-by-layer extrusion (3D printing) with adjustable duration of technological breaks.

Information sources

1. Patent, RU 2683447, E04C 5/07, C04B 7/52, Method for erecting a monolithic building, structure using 3D printing and a device for its implementation, Dzhantimirov H.A., Zvezdov A.I., Dzhantimirov P.Kh., patent holder Joint Stock Company "Research Center "Construction", appl. 12/05/2017, publ. 03/28/2019, bulletin. No. 10.

2. Patent, RU 2789220, E04G 21/04, B33Y 10/00, C04B 28/04, C04B 111/20, Method of additive manufacturing in construction, Mukhametrakhimov R.Kh., Ziganshina L.V., patent holder Federal State Budgetary Educational institution of higher education "Kazan State University of Architecture and Civil Engineering", appl. 01.11.2022, publ. 01/31/2023, bulletin. No. 4.

Claims (1)

A method of additive manufacturing in construction with an adjustable duration of a technological break, including preparing a concrete mixture including Portland cement, quartz sand and water, extruding it in the form of a plastic filament through the dispensing head of a printer, laying it in the design position, preparing a modified concrete mixture for the transition layer, including Portland cement 20-30 wt.%, quartz sand 44.4-69.8 wt.%, superplasticizer "MasterRheobuild 183" based on naphthalene sulfonates 0.1-0.6 wt.%, finely ground pozzolanic component - biosilica with a hydraulic activity of at least 1400 mg/g, grinding degree of at least 1100 m ² /kg 2-8 wt.%, organosilicon compound - potassium methyl siliconate 0.1-0.8 wt.% and water 8-16.5 wt.%, and its placement on filament from the specified concrete mixture, implementation of a technological break with the subsequent resumption of laying of the specified filament, characterized in that before laying the transition layer on top of the previously laid layer, steel electrodes are laid; during the technological break, the laid layers are exposed to an electric field created by passing an alternating electric current through the modified concrete mixture by connecting the electrodes to a power source - a single-phase portable welding transformer “Blue Weld Gamma 4.181”, while the duration of exposure to the electric field is 0.1-3 hours.