Two-phase fibre-concrete mix for 3D construction printing

Abstract

The invention relates to a fibre-concrete composition for 3D printing. A two-phase fibre-concrete mix for 3D printing consists of two phases: a solid phase (1) comprised of a mixture of dry components; and a liquid phase (2) comprised of an aqueous solution. More specifically, phase 1 contains Portland cement, sand, basalt fibre, condensed silica fume, xanthan gum and tetrapotassium pyrophosphate, and phase 2 contains water and Master Glenium polycarboxylate ether-based plasticizer. The invention permits a judicious choice and use of fibre-concrete mix ingredients which provide increased compressive strength and enhanced watertightness, resulting in an improvement in the shape retention and strength of layers of the composite.

Description

[0001] Two-Phase Fiber-Reinforced Concrete Mixture for Construction 3D Printing

[0002] The invention relates to a fiber-reinforced concrete composition adapted to construction 3D printing conditions. The proposed two-phase mixture can be used to produce innovative materials for printing construction objects using 3D additive manufacturing.

[0003] 3D printing materials require more stringent requirements for rheological control, strength gain kinetics, adhesion between elements, and several other parameters than traditional ready-mixed concrete. Using traditional cement mixtures for 3D printing is complicated by the fact that their rheological properties are not adapted to 3D printing modes. Specifically, they lack the plasticity necessary for extrusion, the dimensional stability necessary to support loads during layer-by-layer printing without formwork, and they have late setting times and slow curing.

[0004] A Chinese patent (CN 104891891A, published on September 9, 2015) describes a type of cement-based composite material for 3D printing technology, including cement with a total weight of 33% - 40%, inorganic powder 0% - 8%, sand 32% - 38%, high-molecular polymer - 2.5% - 3%, composite coagulant - 0.2% - 1% (accelerator: lithium carbonate - 0.05% - 0.01%; retarders: sodium tetraborate - 0.05% - 0.35%, sodium gluconate - 0% - 0.05%), stabilizer - 1% - 2%, thixotropic agent - 0.5% - 1.5%, superplasticizer - 0.1% - 0.5% and mixing water - 16.7% - 20%.

[0005] Although this patent tests the characteristics of some cement-based materials, such as coagulation time, ultimate compressive strength and vertical expansion coefficient, but these characteristics are difficult to reflect in the processability of the printed material. If this material is a basic gel material with aluminosulfate cement, the material can be made to have very high early strength and fast coagulation function. The coagulation time of the material is adjustable, making its coagulation time within 10-60 min. Regarding the design of prints for extrusion casting, because the loss of fluidity of aluminosulfate cement is very fast, which may lead to a decrease in extrusion performance. Snapping easily occurs when transferring and printing the material. It can also have a strong impact on the printing performance between layers at the same time. Make between the printing layer and the intermediate layer.then many defects may arise, which threatens the safety of the building.,

[0006] The disadvantages of this technical solution include the fact that curing the alumina cement-based composite material in the air-dry conditions typical of 3D printing is accompanied by a significant loss of strength late in the curing process. Furthermore, the curing time for all variants is 18 minutes, which is insufficient for the adhesion bond between layers to develop strength.

[0007] The technical problem addressed by the present invention is the production of a fiber-reinforced concrete mixture for 3D printing, which has high performance characteristics and mechanical properties, with minimal cement consumption, as well as reducing the cost of the mixture by using screened sand and fly ash.

[0008] The technical result of solving the problem is the rational selection and consumption of the components of the fiber-reinforced concrete mixture, which ensures increased compressive strength and increased water resistance, which, as a result, increases the dimensional stability and strength of the composite layers.

[0009] Said technical result is achieved by the fact that a two-phase fiber concrete mixture for 3D printing is proposed, containing Portland cement and sand, which consists of two phases, a solid phase (1) - a mixture of dry components, and a liquid phase (2) - an aqueous solution, wherein phase 1 contains: Portland cement, sand, basalt fiber, condensed microsilica, xanthan gum and tetrapotassium pyrophosphate, in the following ratios, wt.%: Portland cement 15.00 20.00 condensed microsilica grade 1.50 2.50 basalt fiber O, 01 0, 20 sand 60.00-70.00 xanthan gum 0.10-0.15 tetrapotassium pyrophosphate 0.10-0.15 fly ash 4.50-6.00 and phase 2 consists from: water and plasticizer (Master Glenium) based on polycarboxylate esters, with the following ratio of mass components, %: plasticizer Master Glenium 0.10 0.70 water 96-97

[0010] Characteristics of the original components:

[0011] 1. Portland cement CEM 1 42.5 N was used as cement according to GOST 31108-2016 “General construction cements. Technical conditions”.

[0012] 2. Sand (fine aggregate) with a fineness modulus Mk=2.0-2.5 according to GOST 8736-2014 “Sand for construction work. Technical conditions”.

[0013] 3. Condensed microsilica grade MK-85 GOST R 58894-2020.

[0014] 4. Plasticizer Master Glenium.

[0015] 5. Micro-reinforcing basalt fiber, 20 mm long and 20 µm in diameter.

[0016] 6. Xanthan gum with a content of (C35H49O29)p of at least 91%. It is a viscosity modifier - a thickener that increases the dimensional stability of the mixture, necessary for layer-by-layer laying of the mixture without deformation of the underlying layers when printing without formwork;

[0017] 7. Tetrapotassium pyrophosphate with a K4P2O5 content of at least 98%. It is an accelerator and viscosity modifier that regulates the plasticity of the mixture, ensuring extrusion of the mixture during printing.

[0018] 8. Fly ash according to GOST 25818-2017 “Fly ash from thermal power plants for concrete”;

[0019] 9. Water - complies with GOST 23732-79 "Water for concrete and mortars. Technical conditions."

[0020] The use of microsilica in the composition increases the density of the mixture, increases strength, reduces porosity of the cement stone, and reduces cement consumption. The main active oxide of the compound consists of S1O2 and AI2O3, etc., which, at normal temperatures, can generate and form a compound with hydraulic gelling properties through a chemical reaction forming calcium hydroxide in the cement, imparting strength and making the material weather-resistant. When mixed with water, the active additive can increase the workability of fresh concrete, adhesion, water resistance, and pumpability of 3D printed material. The intensity can also improve after the material hardens, as well as its weather resistance. The plasticizer improves the rheological and technological properties of the mixture.The setting accelerator can act as a catalyst in the cement hydration process, stimulating rapid activation and anhydrous calcium sulfate aluminate forming a large amount of ettringite, rapidly shortening the cement coagulation time. Moreover, the surface of solid particles can be adsorbed by adding a retarder. A film of a single insoluble layer forms on the surface of the cement particles, delaying the rapid formation of the cement and paste structure, reducing the rate of cement hydration, enhancing the rapid condensation of cement and making the intensity relatively soft. The coagulation time of the 3D printing material is more stable and easily controlled.

[0021] When evenly distributed throughout the volume, basalt fiber allows for the production of highly durable, water-resistant, and crack-resistant products. Using such compositions for 3D printing ensures sufficient load-bearing capacity.

[0022] The introduction of tetrapotassium pyrophosphate, which is an accelerator and viscosity modifier that regulates the plasticity of the mixture, allows for an increase in the density and stability of the mixture due to interaction with the ions of the liquid phase.

[0023] Xanthan gum is used as a viscosity modifier-thickener, which is chemically inert with respect to the minerals of the mixture, but changes the density and viscosity of the mixture, increasing the structural strength of the system, which, as a result, increases the dimensional stability of the mixture, necessary for layer-by-layer laying of the mixture.

[0024] Technology for producing a two-phase mixture for construction 3D printing:

[0025] At the first stage, phase 1 is obtained, which consists of dry components: Portland cement CEM 142, 5N - 15.00 - 20.00%; microsilica -1.50-2.50; basalt fiber - 0.01 - 0.20; xanthan gum - 0.10 - 0.15; tetrapotassium pyrophosphate - 0.10 - 0.15; fly ash -4.50-6.00; sand - 60.00 - 70.00. The components of the solid phase are loaded into the mixer and mixed for 4-5 minutes until all components are uniformly distributed throughout the mixture.

[0026] The second stage involves obtaining liquid phase 2, an aqueous solution consisting of 96-97% water and Master Glenium plasticizer based on polycarboxylate esters (0.10-0.70%). The plasticizer is added to the water with vigorous stirring.

[0027] Next, a two-phase cement mixture for construction 3D printing is prepared as follows: liquid phase 2 is added to the prepared solid phase 1 and the mixture is intensively mixed for 3-5 minutes until a homogeneous mass is obtained.

[0028] We developed and tested various fiber-reinforced concrete mixes for 3D printing. The mixes that demonstrated the best physical and mechanical properties are presented in Table 1.

[0029] Table 1

[0030] Fiber-reinforced concrete mixes for 3D printing

[0031] The physical and mechanical properties of fiber concrete mixtures for 3D printing are presented in Table 2.

[0032] Table 2

[0033] Physical and mechanical properties of fiber-reinforced concrete mixtures for 3D printing

[0034] Basalt fiber increases crack resistance and compressive strength. The invention achieves the desired technical result by producing fiber-reinforced concrete mixtures for 3D printing, at specified component ratios, that provide dimensional stability, compressive strength, and water absorption. The composition is 15-20% less expensive than existing commercially available mixtures due to the use of fly ash. The introduction of a polycarboxylate ether-based plasticizer at an optimal concentration modifies the properties of the liquid phase and allows for effective control of the plasticity, structural, and ductile strength of the mixture.The achievement of the required technical result in the implementation of the invention consists in the fact that the two phases included in the composition of the cement-based mixture for 3D printing are specified in a certain ratio, with specified percentage ratios of the components in these phases, which, when interacting, provide plasticity that affects extrusion, dimensional stability necessary for layer-by-layer laying of the mixture without deformation of the layer during its subsequent loading, certain setting times necessary based on the technology of layer-by-layer 3D printing, compressive strength, tensile strength of the material during bending, water absorption, and the adhesion strength of the layers of the composite.

Claims

CLAUSES OF THE INVENTION A two-phase fiber-reinforced concrete mixture for construction 3D printing, containing Portland cement and sand, characterized in that it consists of two phases, a solid phase (1) - a mixture of dry components and a liquid phase (2) - an aqueous solution, wherein phase 1 contains Portland cement, sand, basalt fiber, condensed microsilica, xanthan gum and tetrapotassium pyrophosphate, in the following ratio, wt.%: Portland cement 15.00 20.00 condensed microsilica grade 1.50 2.50 basalt fiber O, 01 0, 20 sand 60.00-70.00 xanthan gum 0.10-0.15 tetrapotassium pyrophosphate 0.10-0.15 fly ash 4.50-6.00 and phase 2 consists of water and a plasticizer (Master Glenium) based on polycarboxylate esters, with the following ratio of mass components, %: plasticizer Master Glenium 0.10 0.70 water 96-97

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