METHODS AND MATERIALS FOR PRINTING 3-DIMENSIONAL STRUCTURES WITH LOW DENSITY AND HIGH COMPRESSIVE STRENGTH

Abstract

A method of printing a 3-dimensional object, the method including the steps of mixing a dry cementitious composition with water, conveying the mixture obtained to a print head, applying the mixture from the print head layer-by-layer to form a 3-dimensional object, curing the 3-dimensional object, wherein the dry cementitious composition includes at least one cement, at least one type of slag, at least one activator for the slag, and at least two lightweight aggregates of different particle size.

Claims

1. A method of printing a 3-dimensional object, the method comprising the steps of a) mixing a dry cementitious composition with water, b) conveying the mixture obtained under a) to a print head, c) applying the mixture obtained under a) from the print head to form a 3-dimensional object, d) curing the 3-dimensional object obtained in step c), wherein the dry cementitious composition comprises (in each case relative to the total dry weight of the composition) i) 20-75 w % of a cementitious binder which itself comprises ia) at least one cement, ib) at least one type of slag and/or calcined clay, and ic) optionally at least one activator for said slag, ii) 5-50 w % of at least two lightweight aggregates of different particle size, iii) optionally further aggregates and/or fillers, and iv) optionally further additives.

2. A method according to claim 1, wherein in step c) the mixture obtained under a) is applied layer-by-layer from the print head to form a 3-dimensional object.

3. A method according to claim 1, wherein in step c) the mixture obtained under a) is applied into a mold to form a 3-dimensional object.

4. A method according to claim 1, wherein an additional additive is admixed during conveying or in the print head.

5. A method according to claim 1, wherein the at least one cement is selected from Portland cement of the type CEM I, CEM II, or CEM IV according to standard EN 197-1, calcium aluminate cement according to standard EN 14647:2006-01, calcium sulfoaluminate cement, puzzolane, latent hydraulic binder, or mixtures thereof, with the exception of CEM II/A-S or CEM II/B-S.

6. A method according to claim 5, wherein the at least one cementitious binder comprises Portland cement and slag in a weight ratio of Portland cement to slag of 1:2 or higher.

7. A method according to claim 1, wherein the dry cementitious composition comprises two or three lightweight aggregates of different particle size.

8. A method according to claim 1, wherein the lightweight aggregates comprise or consist of glass particles, wood particles, cork, rubber particles, layered particles, plastic particles, volcanic rock such as pumice, and/or expanded slate.

9. A method according to claim 1, wherein the dry cementitious composition comprises two types of lightweight aggregate, whereby a first type of lightweight aggregate has a particle size of 1-300 m and a second type of lightweight aggregate has a particle size of 250-500 m.

10. A method according to claim 1, wherein the dry cementitious composition comprises three types of glass particles as lightweight aggregate, whereby a first type of glass particles has a particle size of 1-300 m, a second type of glass particles has a particle size of 250-500 m, and a third type of glass particles has a particle size of 500-1000 m.

11. A method according to claim 1, wherein about one third of the lightweight aggregate present in the dry cementitious composition have a particle size of below 200 m, about one third of the lightweight aggregate present in the dry cementitious composition have a particle size of between 200-500 m, and about one third of the lightweight aggregate present in the dry cementitious composition have a particle size of more than 500 m.

12. A dry cementitious composition comprising (in each case relative to the total dry weight of the composition): ia) 15-30 w % of Portland cement, ib) 3-7 w % of calcium aluminate cement and/or calcium sulfoaluminate cement, ic) 15-35 w % of slag and/or calcined clay ii) 10-33 w % of at least two lightweight aggregates of different particle size, iii) 5-30 w % of further aggregates and/or fillers, iv) 1-2 w % of further additives.

13. A method of applying a dry cementitious composition comprising (in each case relative to the total dry weight of the composition): ia) 15-30 w % of Portland cement, ib) 3-7 w % of calcium aluminate cement and/or calcium sulfoaluminate cement, ic) 15-35 w % of slag and/or calcined clay ii) 10-33 w % of at least two lightweight aggregates of different particle size, iii) 5-30 w % of further aggregates and/or fillers, iv) 1-2 w % of further additives; in a method according to claim 1.

14. A 3-dimensional object obtained by a method as claimed in claim 1.

15. A 3-dimensional object as claimed in claim 14, wherein it is a thermal and/or acoustic insulation panel or forms part of a thermal and/or acoustic insulation system.

16. A 3-dimensional object as claimed in claim 14, wherein it is used as infill for structures.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0146] The drawings used to explain the embodiments show:

[0147] FIG. 1 An exemplary system for producing a 3-dimensional object with an additive manufacturing process of the present invention.

[0148] FIG. 2 A photo showing a method of the present invention where a mixture of cementitious material with water is applied layer-by-layer from a print head to form a 3-dimensional object.

[0149] FIG. 3 A photo showing a method of the present invention where a mixture of cementitious material with water is applied into a mold to form a 3-dimensional object.

[0150] FIG. 4 A photo showing a 3-dimensional object filled with a mixture of cementitious material with water of the present invention.

SYSTEM FOR PRODUCING A 3-DIMENSIONAL OBJECT WITH AN ADDITIVE MANUFACTURING PROCESS

[0151] FIG. 1 schematically shows a system 1 for carrying out a process according to the invention.

[0152] The system 1 comprises a movement device 2 with a movable arm 2.1. A print head 3 is attached to the free end of the arm 2.1, which can be moved by the arm 2.1 in all three spatial dimensions. This allows the print head 3 to be moved to any position in the working area of the movement device 2.

[0153] Inside, the print head 3 has a tubular passage 3.1 extending from the end face facing the arm 2.1 (at the top in FIG. 1) to the opposite and free end face for the passage of mixture of cementitious material with water. At the free end, the passage 3.1 opens into a controllable outlet 4 in the form of a nozzle which may be continuously openable and closable.

[0154] An inlet nozzle 5 for adding an additive opens laterally into the passage 3.1 in a region facing the arm 2.1. Through the inlet nozzle 5, an additive, for example a rheological aid, can be added to the mixture of cementitious material with water moving through the passage 3.1 as required.

[0155] Furthermore, inside the print head 3 downstream with respect to the inlet nozzle, a static mixer 6 is arranged in the passage 3.1, which additionally mixes the mixture of cementitious material with water and the optional additive.

[0156] In the area of the controllable outlet 4, a measuring unit 8 is arranged for determining the pressure in the tubular passage 3.1. A sampling rate of the measuring unit 8 is, for example, 10 Hz.

[0157] A device 7 for deaerating the mixture of cementitious material with water is also attached to the print head 3. The device is designed as a vacuum treatment device and makes it possible to reduce the air content in the mixture of cementitious material with water. For this purpose, for example, a section of the wall of the passage 3.1 can be designed as a gas-permeable membrane, so that air is drawn out of the mixture of cementitious material with water by applying a vacuum outside the passage 3.1.

[0158] The system 1 for applying a mixture of cementitious material with water also has a feed device 9 which corresponds on the input side with containers 11.1, 11.2, and optionally 11.3 as well as 11.4. Container 11.1 contains the first component, which is a dry cementitious composition according to the present invention. The second component, which is present in the second container 11.2, consists of water. The third component is optional. If present, the third component is present in the third reservoir 11.3 and is a further additive, for example a superplasticizer in the form of a polycarboxylate ether. In the optional additive reservoir 11.4 there is optionally present, for example, a rheological aid

[0159] On the output side, the feed device 9 has at least two, optionally three separate outlets, each of which is connected to one of inlets 10.1, 10.2, and optionally 10.3 of a mixing device 10. The feed device 9 also has individually controllable metering devices (not shown in FIG. 1), so that the individual components in the individual containers 11.1, 11.2, and optionally 11.3 as well as 11.4 can be metered individually into the mixing device 10.

[0160] A further outlet of the feed device is connected to the inlet nozzle 5 (not shown in FIG. 1), so that optional additive can be fed from the additive reservoir 11.4 into the inlet nozzle 5 via a further metering device of the feed device 9.

[0161] The mixing device 10 is designed as a static mixer or as a dynamic mixer, preferably as a continuous dynamic mixer and may comprise, in addition thereto, an integrated conveying device in the form of a screw conveyor. In the mixing device, the individually metered components are mixed together and conveyed into the flexible line 12 attached to the outlet side of the mixing device. In operation, the mixing and conveying of the mixture of cementitious material with water can take place continuously.

[0162] The mixture of cementitious material with water can be conveyed into the print head 3 via the flexible line 12, which opens into the tubular passage 3.1 at the end of the print head facing the arm 2.1, and continuously applied through the controllable outlet 4.

[0163] Also part of the system 1 is a measuring unit 13, which is integrated into the delivery line 12 in the area between the mixing device 10 and the print head 3. The measuring unit includes, for example, an ultrasonic transducer which is designed to determine the flow properties of the mixture of cementitious material with water. A sampling rate of the measuring unit 13 is, for example, 10 Hz.

[0164] A central control unit 14 of the system 1 includes a processor, a memory unit, and a plurality of interfaces for receiving data and a plurality of interfaces for controlling individual components of the system 1.

[0165] In this regard, the mixing device 10 is connected to the control unit 14 via a first control line 15a, while the feeding device is connected to the control unit 14 via a second control line 15b. As a result, the individual components in the containers 11.1, 11.2, and optionally 11.3 can be metered into the mixing device 10 via the central control unit in accordance with predetermined recipes stored in the control unit and conveyed into the flexible line 12 at adjustable conveying rates.

[0166] The controllable outlet 4, the inlet nozzle 5, and the device 7 for deaerating the mixture of cementitious material with water at the print head are each connected to the control unit 14 via a separate control line 15c, 15d, 15e as well and can be controlled or monitored by the latter.

[0167] The movement device 2 is also connected to the control unit 14 via a further control line 15g. This means that the movement of the print head 3 can be controlled via the control unit 14.

[0168] The measuring unit 8 is connected to the control unit 14 by a data line 15h, so that print data recorded in the measuring unit can be transmitted to the control unit 14.

[0169] Similarly, the measuring unit 13 is connected to the control unit 14 by a data line 15f, so that data recorded in the measuring unit characterizing the flow properties can be transmitted to the control unit 14.

[0170] The control unit 14 is thereby programmed, for example, in such a way that: [0171] (i) the addition rates of the components with the feeding device 9 are controlled depending on the flow properties of the mixture of cementitious material with water in the flexible line 12 determined via the measuring unit 13; [0172] (ii) the feeding device integrated in the mixing device 10 is controlled depending on the pressure determined via the measuring unit 8 and the structure of the 3-dimensional object to be produced with the material of the present invention; [0173] (iii) the addition rate of the additive via the inlet nozzle 5 is controlled depending on the flow properties of the mixture of cementitious material with water determined via the measuring unit 13 and the structure of the 3-dimensional object to be produced; [0174] (iv) the degree of deaeration of the mixture of cementitious material with water in the apparatus 7 is controlled in accordance with the flow properties of the mixture of cementitious material with water detected via the measuring unit 13; [0175] (v) the movement device 2, and thus the position of the print head 3, is controlled in dependence on a model of the 3-dimensional object to be produced stored in the data memory of the control unit 14.

Examples

[0176] The following table 1 shows exemplary compositions E1 to E-3 according to the present invention and comparative compositions C-1 to C-3 not according to the present invention. The compositions were obtained by thoroughly mixing the individual components in a Hobart mixer until visually homogeneous.

TABLE-US-00001 TABLE 1 example composition (in g) E-1 E-2 E-3 C-1 C-2 C-3 Portland cement (CEM I 52.5N) 23 20 20 20 45 20 Calcium sulfoaluminate cement 3.5 4 4 4 6 4 Calcium aluminate cement 0 2.5 0 5 0 2.5 Ground granulated blast furnace 18 35 27 0 0 35 slag*.sup.1 Calcined clay*.sup.2 11.5 0 8 0 0 0 Activator*.sup.3 1 0 0 0 0 0 Lightweight filler 1-300 m*.sup.4 9 3 3 6 4 0 Lightweight filler 250-500 m*.sup.4 13.5 6 6 13 9 11 Lightweight filler 500-1000 m*.sup.4 11 2 2 4 3 0 Limestone filler*.sup.5 8.4 6.5 7 7 8 6.5 Calcium Carbonate filler*.sup.6 0 20 22 18 24 20 Sand (0.06-0.2 mm) 0 0 0 22 0 0 Additives*.sup.7 1.1 1 1 1 1 1 *.sup.1Blaine surface 4500 cm.sup.2/g *.sup.2<0.02 wt.-% residue on 325 mesh; Chapelle index 1,000 mgCa(OH).sub.2/g (acc. NF P18-513: 2012) *.sup.3mixture of Ca(OH).sub.2 and Na.sub.2CO.sub.3 (4:1 by weight) *.sup.4closed cell micro beads *.sup.5purity: 99.3% CaCO.sub.3; BET surface: 10 m.sup.2/g; particle size distribution: D98: 5 m, D50: 0.8 m *.sup.6purity: 99.3% CaCO.sub.3; particle size distribution: D50: 325 m *.sup.7mixture of polycarboxylate ether superplasticizer, defoamer, thickener, redispersible polymer powder

[0177] The following table 2 shows exemplary compositions E4 to E-7 according to the present invention. The compositions were obtained by thoroughly mixing the individual components in a Hobart mixer until visually homogeneous.

TABLE-US-00002 TABLE 2 example compositions (in g) E-4 E-5 E-6 E-7 Portland cement 10 20 20 20 (CEM I 52.5N) Calcium sulfoaluminate cement 4 4 4 4 Calcium aluminate cement 2.4 2.4 2.4 2.4 Ground granulated blast furnace 45 35 35 35 slag*.sup.1 Lightweight filler 1-300 m *.sup.4 3 3 5 3.6 Lightweight filler 250-500 m *.sup.4 6 6 6 3.6 Lightweight filler 500-1000 m *.sup.4 2 2 0 3.6 Limestone filler*.sup.5 6.5 6.5 6.5 6.5 Calcium Carbonate filler*.sup.6 20 17.4 20 20.2 Additives*.sup.7 1.1 1.1 1.1 1-1 *.sup.1Blaine surface 4500 cm.sup.2/g *.sup.4 closed cell micro beads *.sup.5purity: 99.3% CaCO.sub.3; BET surface: 10 m.sup.2/g; particle size distribution: D98: 5 m, D50: 0.8 m *.sup.6purity: 99.3% CaCO.sub.3; particle size distribution: D50: 325 m *.sup.7mixture of polycarboxylate ether superplasticizer, defoamer, thickener, redispersible polymer powder

[0178] The dry compositions of above tables 1 and 2 were mixed with water in a water:powder weight ratio (w/p ratio) as indicated in below table 3. Mixing was done at 23 C. on a Hobart mixer for 3 min at maximum speed. In case of example E-3, additionally 0.2 w % (relative to the total dry powder components) of an aqueous composition comprising 17 w % of aluminum sulfate were added together with the mixing water. The following table 3 gives an overview of the performance measured.

[0179] Flow was measured according to standard ASTM C1437. Initial set-time was measured according to standard ASTM 266. Linear shrinkage was measured according to standard EN 12617-4 on prisms of 4040160 mm within 5 h and 24 h of mixing with water (negative values designate shrinkage while positive values designate expansion). Compressive strength was measured according to standard ASTM C109 after 24 hours. Density was measured according to standard DIN EN 12190 on prisms of 4040160 mm after 7 days.

[0180] Printability was judged from the visual appearance of material extruded from a printing system as described in FIG. 1. Layers of material having a width of 5 cm and a height of 2 cm were applied. Material judged printable (yes in table 3) showed all of the following: individual layers show very limited sagging and do not flow, adhesion between layers is good, a minimum of three layers could be applied on top of each other.

TABLE-US-00003 TABLE 3 performance measured E-1 E-2 E-3 C-1 C-2 C-3 w/p ratio 1.0 0.22 0.22 0.22 0.3 0.22 Flow [cm] n.m. 14 14 11 15 n.m. Initial set time [min] n.m. 40 23 65 n.m. n.m. Linear shrinkage 100 n.m. n.m. n.m. n.m. n.m. @ 5 h [m/m] Linear shrinkage +60 n.m. n.m. n.m. n.m. n.m. @ 24 h [m/m] Compressive strength n.m. 20.1 16.4 15 14.8 10.1 [MPa] Density @ 7 d [kg/m.sup.3] 1100 1270 n.m. n.m. n.m. n.m. Printability yes yes yes no no no E-4 E-5 E-6 E-7 w/p ratio 0.22 0.22 0.22 0.22 Flow [cm] 16.9 15.7 17.5 18 Initial set time [min] 29 17 32 33 Compressive strength 14.8 10.8 21.4 22.3 @ 24 h [MPa] Density @ 7 d [kg/m.sup.3] 1684 1671 1699 n.m. n.m.: not measured

[0181] It can be seen from the above results that printing of materials was not possible for compositions C-1 (comprising sand but no slag or calcined clay), C-2 (comprising high cement content but no slag or calcined clay) or C-3 (comprising lightweight filler of only one particle size).