Binding material suitable for three-dimensional printing formation

Abstract

A cementitious composition suitable for formation by three-dimensional printing according to the present invention is aimed at developing a cementitious composition suitable for formation by three-dimensional printing which gives good stability to the extruded material coming out of a nozzle. The workpiece obtained from the three-dimensional printing formation therefore has fewer errors and greater fineness and is easier to use. The cementitious composition comprises cement, fine aggregate, powdered limestone, expanding admixture, retarding admixture, thickener and rheology modifier.

Claims

1. A cementitious composition suitable for formation by three-dimensional printing comprising a. cement 20-30% by weight of dry binding material b. a fine aggregate 50-70% by weight of dry binding material c. powdered limestone 2-20% by weight of dry binding material d. expanding admixture 0.1-5% by weight of dry binding material e. retarding admixture 0.1-1.5% by weight of dry binding material f. thickener 0.1-2.0% by weight of dry binding material g. rheology modifier different from the thickener 0.1-4% by weight of dry binding material characterized in that the powdered limestone has an average fineness between 6,000-12,000 square centimeters per gram, and when the cementitious composition suitable for formation by three-dimensional printing is mixed with an appropriate amount of water, its flowability is between 60 and 70 centimeters, resulting in a mini slump between 75 and 100 millimeters.

2. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the cement is selected from at least one or more of Portland cement, blended cement or alumina cement, with an average surface area of the cement between 2,700 and 5,600 square centimeters per gram.

3. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the fine aggregate is selected from ground limestone, sand, recycled aggregate or a cement inert particle.

4. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the fine aggregate comprises an average particle size greater than 600 microns and is present in an amount less than 10% and comprises a fineness modulus of the fine aggregate is between 2.3-5.5.

5. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the expanding admixture comprises calcium oxide, with an average surface area of the expanding admixture between 4,000 and 7,000 square centimeters per gram.

6. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the retarding admixture is selected from a group consisting of sodium silico fluoride or sucrose.

7. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the thickener is selected from a group consisting of cellulose or starch ether.

8. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the rheology modifier is selected from a group consisting of naphthalene, melamine or polycarboxylate.

9. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the cementitious composition suitable for formation by three-dimensional printing contains any one of or both natural clay or synthetic clay as a component, the natural clay or synthetic clay is present in an amount between 0-5% by weight of dry binding material.

10. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the cementitious composition suitable for formation by three-dimensional printing contains redispersible powder made of acetate, acrylic, vinyl acetate, epoxy or ethylene vinyl acetate between 0-5% by weight of dry binding material.

11. The cementitious composition suitable for formation by three-dimensional printing according to claim 1, wherein the cementitious composition suitable for formation by three-dimensional printing contains any one of or a combination of natural fiber, synthetic fiber and metallic fiber as a component, each fiber type is present in an amount between 0-5.4% by weight of dry binding material.

12. A cementitious composition suitable for formation by three-dimensional printing comprising TABLE-US-00004 a. cement 20-30% by weight of dry binding material b. a fine aggregate 50-70% by weight of dry binding material c. powdered limestone 2-20% by weight of dry binding material d. expanding admixture .sup.0.1-5% by weight of dry binding material e. retarding admixture 0.1-1.5% by weight of dry binding material f. thickener 0.1-2.0% by weight of dry binding material g. rheology modifier .sup.0.1-4% by weight of dry binding material different from the thickener characterized in that the powdered limestone has an average fineness between 6,000 to 12,000 square centimeters per gram, and when the cementitious composition suitable for formation by three-dimensional printing is mixed with an appropriate amount of water, its flowability is between 60 and 64 centimeters, resulting in a mini slump between 75 and 105 millimeters wherein, when the composition is mixed with water, the composition comprises a weight ratio of cementitious composition to water between 1:0.018-1:0.060.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a test for determining a mini slump which is modified from the ASTM C143/C143M standard.

(2) FIG. 2 is a process for forming a workpiece using the cementitious composition with different W/D values.

DETAILED DESCRIPTION

(3) A cementitious composition suitable for formation by three-dimensional printing according to the present invention comprises:

(4) TABLE-US-00001 cement 20-30% by weight of dry binding material fine aggregate 50-70% by weight of dry binding material powdered limestone 2-20% by weight of dry binding material expanding admixture 0.1-5% by weight of dry binding material retarding admixture 0.1-1.5%.sup. by weight of dry binding material thickener 0.1-2% by weight of dry binding material rheology modifier 0.1-4% by weight of dry binding material.
By weight of dry binding material means the weight of the portions that are binding material, namely cement, fine aggregate and powdered limestone. The binding material containing supplementary cementitious materials such as fly ash, bottom ash, rice husk ash, volcanic ash, fine crushed stone, blast furnace slag, aluminium blast furnace slag or silica fume are also considered the dry binding material. According to the preparation of the cementitious composition of the present invention, the dry binding material is mixed with fresh cement modifying agents, namely expanding admixture, retarding admixture, thickener and rheology modifier. Admixtures which are minerals and chemical additives commonly used in the cement industry to adjust other properties can also be added.

(5) The fine aggregate with an average particle size greater than 600 microns is present in an amount less than 10% and the fineness modulus is between 2.3-5.5, resulting in suitable flowability of the mortar for the three-dimensional printing formation. The surface of the mortar is smooth, not rough or cracked. This improves compressive strength and increases a long-term resistance, especially in terms of the drying shrinkage.

(6) The powdered limestone used in the invented mortar for the three-dimensional printing formation has an average fineness between 7,000-13,000 square centimeters per gram. In Experiment 1, the average fineness used of approximately 11,000 square centimeters per gram gives the substance of the cementitious composition suitable flowability and good formability, optimizes the dynamic yield stress property, accelerates the hydration reaction of the cement in an early stage by accelerating the nucleation reaction to form portlandite, and strengthens the interfacial transition zone between the fine aggregate and the cement, as the calcium ion dissolved from the powdered limestone in a strong base condition of the cement paste can cause a hydration reaction in the interfacial transition zone.

(7) According to this study, the width of the line formed by the three-dimensional printing method which provides convenience in designing should not exceed 2 times the dimension of the nozzle size of the printer (W/D as in FIG. 2). Therefore, in order to achieve such property, the substance of the mortar obtained from the printing needs to be controlled so that it has good stability. The static yield stress is controlled to make it appropriate. Since it is difficult to measure the static yield stress of a mortar material directly, the mini slump is used instead in the test.

(8) The preferred property of the mortar for the three-dimensional printing formation using the extrusion printing method which makes the substance of cement paste and mortar become extrudable through the nozzle should have a flowability of the fresh mortar (as measured according to the ASTM C1437/C1437M which is modified to suit the three-dimensional mortar with only 10-time tapping) between 60-62 centimeters. From the results of Experiment 1, it can be seen that the mini slump is between 75 and 100 millimeters (as measured according to the ASTM C143/C143M, modified to suit the three-dimensional mortar according to the study of Tan Z; Bernal S A; Provis J L, 2017: Reproducible mini-slump test procedure for measuring the yield stress of cementitious pastes). The mini slump test has the same model of equipment used in the concrete slump test to make it suitable for testing the fresh mortar, except that the cone used is smaller and made of metal or plastic material according to FIG. 1. The test results from the formulae with cement expanding admixtures provide the width of the line relative to the dimension of the nozzle size (W/D) of less than 2. The different W/D values are shown in FIG. 2.

Experiment 1

(9) Experiment 1 shows a study result on a suitable mini slump which make the W/D value less than 2. Each sample has the same or similar flowability.

(10) TABLE-US-00002 Composition (% by weight) Combined fresh Calcium Quicklime-based properties Fine Powdered sulfoaluminate-based expanding modified Total Formula Cement aggregate limestone expanding admixture admixture agent (%) 1 27 56 17 0 0 0.19 100.19 2 27 56 17 1 0 0.19 101.19 3 27 56 17 3 0 0.19 103.19 4 27 56 17 0 1 0.19 101.19 5 27 56 17 0 3 0.19 103.19 6 27 56 17 0 0 0.21 100.21 7 30 54 16 0 0 0.21 100.21 8 30 68 2 0 0 0.21 100.21 9 27 71 2 3 0 0.21 103.21 10 27 66 7 3 0 0.21 103.21 11 27 61 12 3 0 0.21 103.21

(11) TABLE-US-00003 Compressive Compressive Mini slump strength of strength of Flowability value 1-day mortar 7-day mortar Formula (centimeter) (millimeter) W/D (megapascal) (megapascal) 1 62 110 2.2 18.1 0.1 36.2 1.1 2 61 105 2.0 18.6 2.0 40.5 0.4 3 61 105 2.0 17.9 0.2 41.1 0.9 4 62 100 1.9 18.4 0.3 38.5 0.8 5 60 80 1.8 17.7 0.7 39.7 0.1 6 62 112 2.3 12.8 0.5 32.9 1.0 7 64 115 2.5 43.1 0.6 62.3 1.2 8 56 68 Not formable 9 60 70 Not formable 10 62 85 1.8 17.5 1.4 40.3 2.1 11 60 93 1.9 16.9 0.1 38.1 0.5

(12) From the test result showing the mini slump of the fresh mortar for the three-dimensional printing which was combined with quicklime-based and calcium sulfoaluminate-based expanding admixtures at 1 percent and 3 percent per weight of dry binding material, respectively, it is found that an increase in the cement expanding admixture results in a decrease in mini slump value. The decreased mini slump value reflects the higher resistance to the static yield stress. The best value is the case where the calcium sulfoaluminate-based expanding admixture was added in a ratio of 3 percent per weight of the dry cement mortar, which results in a decrease of the slump from 110 to 80 millimeters, an improvement of 27.3 percent. However, when forming a sample according to the mortar formula 8, the flowability was lower than 56 centimeters and the substance of the mortar was rough, separated and not formable with the use of three-dimensional extrusion printer. Also, when forming a sample according to the mortar formula 9 using only 2 percent of powdered limestone per weight of the dry cement mortar, it is found that the flowability was suitable and the slump was 70 centimeters. However, the substance of the fresh mortar could not be used.

(13) When forming a workpiece with the mortar cement for the three-dimensional printing by a three-dimensional extrusion printer to form a workpiece with a diameter of 1.8 meters and height of 2.0 meters using a nozzle with a diameter of 3 centimeters and the same control parameters for the machine, the test result shows that the ratio of W/D of the extruded line when using the mortar cement formula 5 (the formula with an addition of calcium sulfoaluminate-based expanding admixture) in a ratio of 3 percent per weight of the dry cement mortar was decreased from 2.2 to 1.8, a decrease of 18.2 percent approximately. The lower ratio gives accuracy and better sharpness to the workpiece formed by an injection. Two advantages for the three-dimensional material for designers are: 1) increased fineness and accuracy of the formed workpiece, and 2) the problem wherein the designer cannot form the workpiece that corresponds to the design because the workpiece flows laterally more than 2 times of the line or the predetermined size of the nozzle is eliminated.

(14) From the study of the compressive strength value (as measured according to the ASTM C109/C109M standard) of the mortar for the three-dimensional printing with and without calcium sulfoaluminate-based expanding admixture (comparing formula 1 with formula 5) in a ratio of 3 percent per weight of the dry cement mortar, it is found that the values were similar.