RU2777007C1 - Modified raw mixture for construction 3d printing in the technology of additive manufacturing - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to the field of building materials industry and can be used for the manufacture of building products and structures in the additive manufacturing technology by layer-by-layer extrusion (3D printing) of the raw mixture. Modified raw mix for construction 3D printing in additive manufacturing technology includes, wt.%: Portland cement containing, wt %: tricalcium silicate 68.1, tricalcium aluminate 7.2, 20.0-23.0, quartz sand with modulus particle size 2.2-2.4 and moisture content 1-2% 62.72-66.22, superplasticizer "MasterGlenium 115" based on polycarboxylate esters 0.20-0.23, finely ground pozzolanic component - diatomite with a hydraulic activity of at least 1500 mg/g and grinding degree not less than 1400 m2/kg 2.0-2.3, polyphenylethoxysiloxane "FES-50" 0.010-0.012, water 11.570-11.738.

EFFECT: reducing the consumption of Portland cement and superplasticizer in the modified raw mix, increasing dimensional stability and ensuring the absence of defects in the form of ruptures in printed layers from the modified raw mix with the possibility of extruding it on building 3D printers that implement the layer-by-layer extrusion method, reducing shrinkage deformations, water absorption and increasing the tensile strength at bending of hardened composites printed on a 3D printer.

1 cl, 2 tbl

Description

The invention relates to the building materials industry and can be used for the manufacture of building products and structures in the additive manufacturing technology by layer-by-layer extrusion (3D printing) of a raw mixture based on Portland cement, sand, finely ground pozzolanic component, superplasticizer and polyphenylethoxysiloxane.

Known raw material mixture based on cement for building 3D printing, including sulfoaluminate cement - 150-400 kg, ash - 0-250 kg, sand with a particle diameter of 0.075-5 mm, polypropylene fiber with a length of 3-6 mm, superplasticizer PCE manufactured by Shandong Hongyi Technology Co., Ltd - 1.5-2.5% by weight of cement, retarder sodium tetraborate and tartaric acid in a ratio of 1: (1-1.5) - 0.01-0.2% by weight of cement, while the 10-minute draft of the proposed cement-based material is 90-110 mm, the beginning of setting is 15-80 minutes, the end of setting is 30-100 minutes [1]. The disadvantages of this invention are: the presence of a large number of components of the mixture, the increased consumption of the components of the mixture and the increase in its cost caused by the use of fast-hardening sulfoaluminate cement and retarder.

A highly thixotropic raw material mixture for building 3D printing is known, including, wt %: a special thixotropic agent 1.0-3.0, cement 35-40, a superplasticizer based on polycarboxylate esters 0.1-0.4, polypropylene fiber 0 ,1-0.4, water 12.5-14.5, sand - the rest [2]. The disadvantages of this invention are the reduction of the physico-mechanical characteristics of the composite at temperatures above 140°C, caused by the melting of the polypropylene fiber.

A modified polymer-cement composite material for 3D printing is known, including, wt %: Portland cement 24.37-34.16, polyvinyl acetate dispersion 2.44-2.56, sand 50.74-61.38, liquid glass 1.70- 2.44, polypropylene fiber 0.02-0.03, phloroglucinfurfural modifier 0.05-0.07, water - the rest [3]. The disadvantages of this invention are the low setting start time - up to 45-70 minutes, which makes it difficult to transport the raw mix from the plant to the construction site, low compressive strength and bending at the age of 28 days, increased water absorption.

The closest solution to the proposed invention is a two-phase mixture based on cement for composites in building 3D printing technology, phase 1 of which contains components in the following mass ratio of the solid phase,%: Portland cement 44.1-44.5, sand 55.14-55 .4, xanthan gum 0.08-0.1, technical tetrapotassium pyrophosphate 0.08-0.1, polypropylene fiber 0.2-0.3; phase 2 contains components in the following mass ratio of the liquid phase, %: superplasticizer 4.1-4.6, water 95.4-95.9 [4].

The disadvantages of this invention are the increased consumption of Portland cement and superplasticizer (1.2-1.4% by weight of Portland cement), low dimensional stability of the printed layers from the raw mix, high shrinkage deformation of the hardened composite due to increased consumption of Portland cement and the use of sand belonging to the group "very fine » (according to GOST 8736-2014), high water absorption, low flexural strength of the hardened composite, reduction in the physico-mechanical characteristics of the composite at temperatures above 140°C, caused by the melting of polypropylene fiber, the use of tetrapotassium pyrophosphate and xanthan gum as viscosity modifiers intended for use as additives for concretes and mortars (according to GOST 24211-2008). Also, the disadvantage of the invention is the lack of data on the moisture content of the components of the raw mixture, which affect the rheological and physico-mechanical properties of the composites, as well as the lack of data on the implementation of this invention on a 3D printer that implements the method of layer-by-layer extrusion and the quality of the products obtained. In addition, the disadvantage is the method used in the invention for preparing samples, which consists in their manufacture in the forms of 70 × 70 × 70 mm, 70 × 70 × 280 mm, while the construction 3D printing technology excludes the use of forms, which leads to a change in the pore composite structure and distortion of obtaining reliable results of physical and mechanical properties (compressive and tensile strength, density, water absorption, etc.).

The objective of the invention is to reduce the consumption of Portland cement, a superplasticizer in a modified raw mix for construction 3D printing in additive manufacturing technology, increase dimensional stability and ensure the absence of defects in the form of ruptures in printed layers from a modified raw mix with the possibility of extruding it on construction 3D printers that implement the method layer-by-layer extrusion, reduction of shrinkage deformations, water absorption, increase in flexural strength of hardened composites printed on a 3D printer (without the use of molds).

The technical result of the proposed solution is to reduce the consumption of Portland cement and superplasticizer in the modified raw mix, increase dimensional stability and ensure the absence of defects in the form of ruptures in printed layers from the modified raw mix with the possibility of extruding it on building 3D printers that implement the layer-by-layer extrusion method, reducing shrinkage deformations, water absorption , increasing the flexural strength of hardened composites printed on a 3D printer (without the use of molds).

The task is achieved in that the modified raw mix for building 3D printing in additive manufacturing technology, including Portland cement, sand, superplasticizer based on polycarboxylate esters and water, characterized in that Portland cement is used, containing, wt.%: tricalcium silicate 68.1 , tricalcium aluminate 7.2, quartz sand with a particle size modulus of 2.2 - 2.4 and a moisture content of 1 - 2% is used as a sand, MasterGlenium 115 superplasticizer is used as a superplasticizer based on polycarboxylate esters, and additionally it contains finely ground pozzolanic component - diatomite with a hydraulic activity of at least 1500 mg/g, a grinding degree of at least 1400 m ² /kg and polyphenylethoxysiloxane "FES-50" with the following content of components, wt.%:

Specified Portland cement 20.0-23.0 Specified sand 62.72-66.22 Superplasticizer "MasterGlenium 115" 0.20-0.23 Specified finely ground pozzolanic component - diatomite 2.0-2.3 Polyphenylethoxysiloxane "FES-50" 0.010-0.012 Water 11.570-11.738

The following materials were used to manufacture a modified raw mix for construction 3D printing in additive manufacturing technology:

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 2.2-2.4, moisture content of 1-2% (GOST 8736-2014). To prepare the samples, sand with a fineness modulus of 2.3 and a moisture content of 1.5% was used;

Superplasticizer based on polycarboxylate esters "MasterGlenium 115" manufactured by LLC "BASF Building Systems", which is a light yellow liquid without chloride content, density at 20°C 1.05 g/cm ³ , pH - 5.5;

The finely ground pozzolanic component is diatomite with a hydraulic activity of at least 1500 mg/g, a grinding degree of at least 1400 m ² /kg (STO 23998461-020-2018). Samples were prepared using diatomaceous earth with a hydraulic activity of 1553.7 mg/g and a grinding degree of 1443 m ² /kg;

Polyphenylethoxysiloxane "FES-50" produced by PJSC "Khimprom", which is a brown liquid with a density of 0.8 g/cm ³ at 20°C;

Tap drinking water that meets the requirements of GOST 23732.

The proposed invention is carried out as follows: pre-dosed dry components of the modified raw mix - Portland cement, sand, diatomite are loaded into a working mixer and mixed until a homogeneous mass is obtained. Then, dosing by weight of water, superplasticizer "MasterGlenium 115", polyphenylethoxysiloxane, 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 with mobility Pk 2 (according to GOST 28013-98) at an immersion depth of the reference cone of 7-8 cm. At the next stage, the 3D printer is prepared: the inner surface of the removable storage bin is moistened with drinking tap water or a release agent. Next, the removable storage hopper of the construction 3D printer is filled with the prepared modified raw material mixture and test extrusion is carried out until the resulting extrudate is homogeneous. Then, the modified raw mixture is molded by layer-by-layer extrusion (3D printing) on a construction 3D printer (for example, AMT S-6044 of SPETSAVIA LLC) in accordance with a pre-prepared three-dimensional digital model. The three-dimensional digital model of the samples is a strip 40 cm long, with a single layer height of 20 mm. Printing of the modified raw mix is carried out with the following adjustable print parameters set in the Mach3 software package (Artsoft founder Art Fenerty): the spindle speed is 3000-5000 units, the feed rate is 4000-6000 units/min.

The shape stability of the printed layers from the modified raw mixture was evaluated by the ability of the mixture to maintain its position in space under the influence of technological factors, namely, by the maximum height of the printed sample without technological interruptions until it reaches a critical state - the loss of stability as a whole, characterized by its overturning or loss of stability of the sample shape with offset printed layers.

Samples were also tested according to the prototype using Portland cement CEM I 42.5N according to GOST 31108-2016, sand with a fineness modulus less than or equal to 1.25 according to GOST 8736-2014, xanthan gum containing (C ₃₅ H ₄₉ O ₂₉ ) _n not less than 91%, technical tetrapotassium pyrophosphate with a content of K ₄ P ₂ O ₅ not less than 98%, polypropylene fiber 12 mm long, superplasticizer based on polycarboxylate ethers, water.

After 28 days of normal hardening, samples were prepared for testing, molded by layer-by-layer extrusion (3D printing), by sawing them into prisms with dimensions of 40 × 40 × 160 mm. The water absorption of the hardened composite was determined according to GOST 12730.3-78 “Concrete. Method for determining water absorption. The flexural strength of the hardened composite was determined on beam specimens 40×40×160 mm in size according to GOST 5802-86. "Construction solutions. Test Methods” using the MII-100 testing machine. Shrinkage deformations were assessed by the presence of shrinkage cracks on the hardened composites, the presence of defects in the form of ruptures in the printed layers from the modified raw mix was carried out by a visual-instrumental method using a measuring metal ruler according to GOST 427-75 and a measuring magnifier with illumination according to GOST 25706-83.

The compositions of modified raw mixes for building 3D printing in additive manufacturing technology are shown in Table 1, the physical and mechanical parameters for the compositions are shown in Table 2.

Table 1

Components Compositions of modified raw mixes for building 3D printing in additive manufacturing technology, wt.%: one 2 3 four 5 6 7 8 (prototype) Portland cement 18.0 21.5 21.5 20.0 21.5 23.0 25.0 37.85 Sand 68.381 67.484 62.40 66.22 64.47 62.72 59.937 48.80 Superplasticizer "MasterGlenium 115" 0.18 0.215 0.20 0.22 0.23 0.25 diatomaceous earth 1.5 2.15 2.0 2.15 2.3 1.5 Polyphenylethoxysiloxane "FES-50" 0.009 0.011 0.010 0.011 0.012 0.013 xanthan gum 0.07 Tetrapotassium pyrophosphate technical 0.07 Polypropylene fiber 1.72 Superplasticizer based on polycarboxylate esters 0.47 Water 11.93 10.79 13.95 11,570 11.649 11.738 13.3 11.02

table 2

Properties Physico-mechanical parameters for compositions one 2 3 four 5 6 7 8 (prototype) Form stability of the printed layers from the raw mix (product height obtained by 3D printing without technological interruptions), cm 13 eleven ten twenty 22 21 eleven ten Bending strength for 28 days, MPa 5.1 6.4 5.7 6.0 6.1 6.7 5.2 4.0 Water absorption, % 10.9 8.9 11.4 7.2 7.0 6.9 7.1 7.5 Shrinkage deformations (presence of shrinkage cracks - yes/no) No Yes Yes No No No No Yes Defects in the form of gaps (yes / no) No Yes No No No No No Yes

It follows from the above data that the maximum values of the dimensional stability of the printed layers from the modified raw mix, ultimate strength in bending, water absorption of hardened composites are achieved when the content of Portland cement in the composition of the modified raw mix is 20.0-23.0% of the total mass of the composition, sand - 62.72-66.22%, MasterGlenium 115 superplasticizer - 0.20-0.23%, finely ground pozzolanic component - diatomite - 2.0-2.3%, FES-50 polyphenylethoxysiloxane - 0.010-0.012% , water - 11.570-11.738%. With the introduction of Portland cement, superplasticizer "MasterGlenium 115", finely ground pozzolanic component - diatomite, polyphenylethoxysiloxane "FES-50", in an amount less than those indicated in table 1 (composition 4), there is a decrease in the parameters of the studied properties compared to the claimed limits. With their introduction, in an amount greater than those indicated in Table 1 (composition 6), the studied properties of the compositions printed on a 3D printer are reduced. There are no shrinkage cracks in the compositions of modified raw mixes for construction 3D printing (compositions 1, 4-7), and defects in the form of gaps are absent in compositions 1, 3-7.

The modified raw mix for building 3D printing in additive manufacturing technology, obtained according to the present invention, has a reduced consumption of Portland cement and superplasticizer, increased dimensional stability and the absence of defects in the form of ruptures in printed layers from a modified raw mix with the possibility of extruding it on building 3D printers that implement layer-by-layer extrusion method, products - high strength characteristics in bending, the absence of shrinkage cracks, low water absorption.

The use of medium-sized sand with a fineness modulus of 2.2-2.4 in combination with a reduced cement-sand ratio makes it possible to reduce the development of shrinkage deformations of the composite molded by layer-by-layer extrusion (3D printing). In addition, a reduced cement-sand ratio makes it possible to reduce the consumption of Portland cement in the modified raw mix while ensuring formability on a 3D printer and physical and mechanical properties.

The use of MasterGlenium 115 superplasticizer based on polycarboxylate ethers in an amount of 0.20-0.23 wt.% allows reducing the amount of mixing water, increasing the density of the mixture and the physical and mechanical characteristics of the hardened composite while ensuring optimal rheotechnological properties of the modified raw mixture for its layer-by-layer extrusion.

The introduction of a finely ground pozzolanic component - diatomite with a grinding degree of at least 1400 m ² /kg, a hydraulic activity of at least 1500 mg / g can improve the formability of the modified raw mixture by providing cohesion, uniformity and plasticity, which contributes to the production of hardened composites printed on 3D- printer, with reduced shrinkage and the absence of defects on them.

The use of polyphenylethoxysiloxane "FES-50" in the amount of 0.010-0.012 wt.% makes it possible to reduce the water absorption of hardened composites printed on a 3D printer (without using molds), by making the walls of capillaries and pores water-repellent.

Joint use of the superplasticizer "MasterGlenium 115" in the amount of 0.20-0.23 wt.%, diatomite with a grinding degree of at least 1400 m ² /kg, hydraulic activity of at least 1500 mg/g in the amount of 2.0-2.3 wt .%, polyphenylethoxysiloxane "FES-50" in the amount of 0.010-0.012 wt.% contributes to giving the modified raw mixture optimal rheotechnological properties, increasing the dimensional stability of printed layers from the modified raw mixture, physical and mechanical indicators (increasing the flexural strength, reducing water absorption) of hardened composites printed on a 3D printer.

Thus, the proposed solution makes it possible to obtain a modified raw mix for building 3D printing in additive manufacturing technology with a reduced consumption of Portland cement and superplasticizer, which has high dimensional stability, and products based on it with high bending strength characteristics, low water absorption, reduced shrinkage deformations and the absence of defects on them.

Sources of information

1. Patent CN 105753404 A, B33Y 70/00, Cement-based material used for building 3D (three-dimensional) printing, Appl. 02/13/2016, publ. 07/13/2016.

2. Patent CN 108715531 A, C04B 28/02, A kind of high thixotropic 3D printing concrete and preparation method thereof, Appl. 06/12/2018, publ. 08/28/2020.

3. Patent RU 2661970, С04В 28/04, С04В 14/02, С04В 22/08, С04В 26/00, С04В 2111/20, С04В 2111/343, Modified polymer-cement composite material for 3D printing, Poluektova V.A. , Shapovalov N.A., Chernikov R.O., Evtushenko E.I., Patent holder Federal State Budgetary Educational Institution of Higher Education "Belgorod State Technological University", App. 07/31/2017, publ. 07/23/2018, bul. No. 21.

4. Patent RU 2729086, С04В 28/04, Two-phase mixture based on cement for composites in the technology of building 3D printing, Slavcheva G.S., Aratmonova O.V., Shvedova M.A., Britvina E.A., patentee Federal State Budgetary Educational Institution of Higher Education "Voronezh State Technical University", bid. 10/21/2019, publ. 08/04/2020, bul. No. 22.

Claims (2)

Modified raw mix for construction 3D printing in additive manufacturing technology, including Portland cement, sand, superplasticizer based on polycarboxylate esters and water, characterized in that Portland cement is used, containing, wt.%: tricalcium silicate 68.1, tricalcium aluminate 7.2 , quartz sand with a fineness modulus of 2.2-2.4 and a moisture content of 1-2% is used as sand, MasterGlenium 115 superplasticizer is used as a superplasticizer based on polycarboxylate esters, and additionally it contains a finely ground pozzolanic component - diatomite with hydraulic activity not less than 1500 mg/g, grinding degree not less than 1400 m ² /kg and polyphenylethoxysiloxane "FES-50" with the following content of components, wt.%: Specified Portland cement 20.0-23.0 Specified sand 62.72-66.22 Superplasticizer "MasterGlenium 115" 0.20-0.23 Specified finely ground pozzolanic component - diatomite 2.0-2.3 Polyphenylethoxysiloxane "FES-50" 0.010-0.012 Water 11.570-11.738