RU2821490C1 - Method of construction 3d printing by layer-by-layer extrusion 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, buildings and structures. Disclosed is a method for construction 3D printing by layer-by-layer extrusion with controlled duration of technological break, which includes preparation of a concrete mixture, which includes portland cement, quartz sand and water, extruding it in the form of a plastic filament through the dispensing head of the printer with laying into the design position, preparing the modified concrete mixture for the transition layer, which contains the following, wt.%: portland cement 20–30, quartz sand 44.4–69.8, superplasticiser "Polyplast BF" based on surface-active sodium salts and alkyl sulphates 0.2–0.4, finely ground pozzolanic component diatomite with hydraulic activity of not less than 1,500 mg/g, degree of grinding of not less than 1,400 m²/kg 2–6, organosilicon compound potassium methylsiliconate 0.1–0.8 and water 7.9–18.7, its laying on a filament from said concrete mixture, implementation of a technological break with subsequent resumption of laying of said filament, wherein before laying transition layer on top of previously laid layer of filament, laying steel electrodes, during the technological break, the laid layers are exposed to an electric field created by passing alternating electric current through the modified concrete mixture by connecting electrodes to a power source – a single-phase portable welding transformer "BlueWeldGamma 4.181", wherein duration of exposure to 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 by increasing the average rate of gaining the critical plastic strength of the concrete of the transition layer while ensuring high quality of construction products with long technological interruptions of construction 3D printing, due to provision of high adhesion index 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 construction 3D printing using the layer-by-layer extrusion method, which 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 plastic filament through the dispensing head of the printer and laying it in design position, preparation of a modified concrete mixture for the transition layer and its laying on a filament from the specified concrete mixture, implementation of a technological break for 10, 360 or 720 minutes with subsequent resumption of laying after a 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 "Poliplast BF" based on surface-active sodium salts and alkyl sulfates (0.2-0.4 wt.%), finely ground pozzolanic component diatomite with a hydraulic activity of at least 1500 mg/g, degree of grinding of at least 1400 m ² /kg (2-6 wt.%), organosilicon compound - methyl siliconate potassium (0.1-0.8 wt.%) and water (7.9-18.7 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 goal is achieved by the fact that the method of construction 3D printing by layer-by-layer extrusion 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 printer dispensing head with laying in the design position, preparation modified concrete mixture for the transition layer, containing in wt.%: Portland cement 20-30, quartz sand 44.4-69.8, superplasticizer "Poliplast BF" based on surface-active sodium salts and alkyl sulfates 0.2-0.4, finely ground pozzolanic component - diatomite with a hydraulic activity of at least 1500 mg/g, grinding degree of at least 1400 m ² /kg 2-6, organosilicon compound - potassium methyl siliconate 0.1-0.8 and water 7.9-18.7, 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 of filament, steel electrodes are laid; during the technological break, an electric field is applied to the laid layers, 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 “BlueWeldGamma 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 surface-active sodium salts and alkyl sulfates “Poliplast BF” produced by Poliplast Kazan LLC, which is a dark brown liquid with a density at 20°C of 1.18 g/cm ³ , pH – 8;

- finely ground pozzolanic component – diatomite with a hydraulic activity of at least 1500 mg/g, degree of grinding of at least 1400 m ² /kg (STO 23998461-020-2018). To prepare the samples, diatomaceous earth with a hydraulic activity of 1553.7 mg/g and a degree of grinding of 1443 m ² /kg was used;

- 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 – 370x250x310 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 - diatomaceous earth - are loaded into the operating mixer and mixed until a homogeneous mass is obtained. Then dosage by weight of water, superplasticizer "Poliplast BF", 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 based on 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 increase in the 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 the overlying layers without the formation of defects, to the duration of its increase 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 54.7 3.3 Adhesion of printed layers of concrete mixture and modified concrete mixture during a technological break of 360 minutes, MPa 0.58 0.54 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 16.6 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 when implementing 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", app. 12/05/2017, publ. 03/28/2019, bulletin. No. 10.

2. Patent, RU 2792455, E04B 2/84, B28B 1/00, B33Y 10/00, C04B 28/04, C04B 111/20, Method of construction 3D printing using layer-by-layer extrusion, Mukhametrakhimov R.Kh., Ziganshina L. V., patent holder Federal State Budgetary Educational Institution of Higher Education "Kazan State University of Architecture and Civil Engineering", application. 01.11.2022, publ. 03/22/2023, bulletin. No. 9.

Claims (1)

A method of construction 3D printing by layer-by-layer extrusion with an adjustable duration of a 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 with laying in the design position, preparing a modified concrete mixture for the transition layer , containing, wt.%: Portland cement 20-30, quartz sand 44.4-69.8, superplasticizer "Poliplast BF" based on surfactant sodium salts and alkyl sulfates 0.2-0.4, finely ground pozzolanic component diatomite with hydraulic activity of at least 1500 mg/g, grinding degree of at least 1400 m ² /kg 2-6, organosilicon compound potassium methyl siliconate 0.1-0.8 and water 7.9-18.7, its laying on a filament from the specified concrete mixture , carrying out a technological break with the subsequent resumption of laying the specified filament, characterized in that before laying the transition layer on top of the previously laid layer of filament, steel electrodes are laid; during the technological break, the laid layers are exposed to the 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 “BlueWeldGamma 4.181”, while the duration of exposure to the electric field is 0.1-3 hours.