Cement composition for 3D printing and method of use

Abstract

A novel cement composition for 3D printing including has 90% to 99.5% by weight of one or more cements selected from a Portland cement, an aluminous cement, a sulphoaluminous cement and a prompt natural cement; and has 0.5% to 10% by weight of a silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g, as well as a method for implementing the composition.

Claims

1. A cement composition comprising: from 95% to 99.5% by weight of a Portland cement and a sulphoaluminous cement; and from 0.5% to 5% by weight of a filler selected from the group consisting of a silicoaluminous filler, silica fume, and a combination of a silicoaluminous filler and silica fume, wherein the filler has a specific surface area of at least 5 m.sup.2/g, wherein the cement composition is adapted for 3D printing, wherein the cement composition further contains a limestone filler and/or a setting retarder.

2. The cement composition according to claim 1, wherein the cement composition contains from 10% to 95% by weight relative to the total weight of cement of a Portland cement.

3. The cement composition according to claim 1, wherein the silicoaluminous filler is selected from natural pozzolans and calcined clays.

4. A 3D printing method comprising the following steps: contacting the cement composition according to claim 1 with water optionally added with superplasticizer and mixing of the whole; pumping of the composition thus obtained to a print head and optionally adding a setting trigger; printing.

5. A kit for the preparation of a cement composition for 3D printing according to claim 1, said kit comprising: a Portland cement; and a sulphoaluminous cement; wherein the filler selected from the group consisting of a silicoaluminous filler, silica fume, and a combination of a silicoaluminous filler and silica fume, is present in an element of the kit containing the Portland cement and/or in an element of the kit containing the sulphoaluminous cement, and wherein the limestone filler and/or setting retarder is present in an element of the kit containing the Portland cement and/or in an element of the kit containing the sulphoaluminous cement.

6. A 3D printing method implementing the kit according to claim 5 comprising the following steps: contacting the composition containing Portland cement optionally added with superplasticizer with water and mixing the whole and, separately, bringing the composition containing the sulphoaluminous cement into contact with water optionally added with superplasticizer and mixing of the whole; pumping each of the compositions thus obtained to a print head, bringing them into contact, optionally in the presence of a setting trigger; and printing.

7. The cement composition according to claim 1, wherein the cement composition does not contain a hardening inhibitor.

8. A cement composition consisting essentially of: from 95% to 99.5% by weight of a Portland cement and a sulphoaluminous cement; from 0.5% to 5% by weight of a filler selected from the group consisting of a silicoaluminous filler, silica fume, and a combination of a silicoaluminous filler and silica fume, wherein the filler has a specific surface area of at least 5 m.sup.2/g; and optionally, a limestone filler and/or a setting retarder, wherein the cement composition is adapted for 3D printing, wherein the cement composition further contains a limestone filler and/or a setting retarder.

9. The cement composition according to claim 8, wherein the silicoaluminous filler is selected from natural pozzolans and calcined clays.

10. The cement composition according to claim 8, wherein the cement composition does not contain a hardening inhibitor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an example of a one-component ink 3D printing device.

(2) FIG. 2 is an example of a two-component ink 3D printing device.

(3) Thus, the present invention relates to a cement composition for 3D printing comprising: from 90% to 99.5% by weight of one or more cements selected from a Portland cement, an aluminous cement, a sulphoaluminous cement and a prompt natural cement; and from 0.5% to 10% by weight of a silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g.

(4) The cement composition according to the present invention exhibits great reactivity, a very rapid or more controlled increase in strength depending on the proportions of Portland cement, aluminous cement, sulphoaluminous cement and/or prompt natural cement in the composition. Furthermore, the presence of a silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g makes it possible to significantly increase the printing speed (in particular by the generation of a threshold essential to the resistance of the printed structure) while maintaining or even improving the quality thereof.

(5) In the context of the present invention: the term cement composition for 3D printing means any composition of cement, mortar or concrete which, after adding water, is likely to be used as ink in 3D printing; the term Portland cement> means any cement based on Portland clinker classified as CEM (I, II, III, IV or V) according to standard NF EN 197-1; the term aluminous cement means any cement, amorphous or not, obtained by firing a mixture of limestone and bauxite and containing at least 5% of monocalcium aluminate CA; the term sulfoaluminous cement means any cement prepared from a sulfoaluminous clinker containing 5% to 90% of yeelimite phase C.sub.4A.sub.3$, a source of sulfate, and, optionally, a lime addition; the term prompt natural cement means any hydraulic binder with rapid setting and hardening in accordance with standard NF P 15-314:1993 in force on the date of the present invention. Preferably, prompt natural cement designates a cement prepared from a clinker comprising: from 0% to 20% of C.sub.3S; from 40% to 60% of C.sub.2S; from 7% to 12% of C.sub.4AF; from 2% to 10% of C.sub.3A; from 10% to 15% of CaCO.sub.3 (calcite); from 10% to 15% of Ca.sub.5 (SiO.sub.4).sub.2CO.sub.3 (spurrite); from 3% to 10% of sulfate phases: yeelimite C.sub.4A.sub.3$, langbeinite (K.sub.2Mg.sub.2 (SO.sub.4).sub.3, anhydrite (CaSO.sub.4); and from 10% to 20% lime, periclase, quartz and/or one or more amorphous phases; the term silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g means any mineral powder of natural origin, calcined natural, or resulting from industrial production consisting essentially of silica and/or alumina, and whose BET specific surface is greater than 5 m.sup.2/g. As examples of such fillers, mention may in particular be made of metakaolins or calcined clays in general or silica fumes with a BET specific surface greater than 5 m.sup.2/g. the term limestone filler means any finely ground limestone consisting essentially of calcium carbonate; the term hardening accelerator means any agent conventionally used as an adjuvant in concrete or mortar compositions with a view to accelerate the setting and/or hardening of the binder and to increase the mechanical performance of the concrete or the mortar. As example of a setting accelerator, mention may in particular be made of alkali metal salts such as sulphates (lithium, sodium, potassium or magnesium sulphate), nitrates (sodium, magnesium, potassium or lithium nitrates), thiocyanates (sodium, magnesium, potassium or lithium thiocyanate), carbonates (sodium, potassium, lithium, magnesium carbonate), hydroxides (sodium or potassium hydroxide), aluminates, silicates and chlorides (sodium, magnesium, potassium, or lithium chloride); the term setting retarder means any agent conventionally used as an adjuvant in concrete or mortar compositions with a view to delay the setting of concrete or fresh mortar. As an example of a setting retarder, mention may in particular be made of gluconates (sodium gluconate, potassium gluconate), carboxylic acids (citric acid, tartaric acid, etc.) and the associated bases (sodium citrate, sodium tartrate), boric acid, sodium borate and alkaline phosphates; the term setting trigger means any agent conventionally used to suddenly trigger the setting of a binder and drastically modify its rheology. As an example of a setting triggering agent, mention may in particular be made of the agents commonly used in sprayed concrete (Shotcrete) applications such as alkaline accelerators based on sodium or potassium silicate and non-alkaline accelerators based on aluminum sulphates or aluminum hydroxides; and the term superplasticizer means any synthetic polymer facilitating the placement of concrete, allowing a reduction in the required amount of the mixing water and/or increasing the strength of the hardened concrete. As examples of polymers which can be used as superplasticizers, mention may in particular be made of modified polycarboxylic ethers (PCE), polynaphthalene sulfonates (PNS), polymelamine sulfonates (PMS), calcium, sodium or ammonium lignosulfonates (LS) and polyacrylates.

(6) In the context of the present invention, the following notations are adopted to designate the mineralogical components of cement: C represents CaO; A represents Al.sub.2O.sub.3; F represents Fe.sub.2O.sub.3; S represents SiO.sub.2; and $ represents SO.sub.3.

(7) Thus, for example, the calcium aluminoferrite phase of a composition corresponding to the general formula C.sub.4AF actually corresponds to a (CaO).sub.4(Al.sub.2O.sub.3) (Fe.sub.2O.sub.3) phase.

(8) Finally, in the context of the present invention, the proportions expressed in % correspond to percentages by weight relative to the total weight of the considered entity.

(9) A subject of the present invention is therefore a cement composition for 3D printing comprising a Portland cement, an aluminous cement, a sulphoaluminous cement and/or a prompt natural cement.

(10) Preferably, the present invention relates to a cement composition for 3D printing as defined above in which the following characteristics are chosen alone or in combination: the composition contains a single cement; the cement composition contains from 95% to 99.5% of cement, preferably from 97.5% to 99.5% of cement; the cement composition contains from 10% to 95% by weight relative to the total weight of cement of a Portland cement, preferably from 20% to 95% by weight relative to the total weight of cement of a Portland cement; more preferably from 25% to 90% by weight relative to the total cement weight of a Portland cement; most preferably from 30% to 85% by weight relative to the total cement weight of a Portland cement; the cement composition contains from 5% to 90% by weight relative to the total weight of cement of an aluminous cement, of a sulphoaluminous cement and/or of a prompt natural cement; preferably from 5% to 80% by weight relative to the total weight of cement of an aluminous cement, of a sulphoaluminous cement and/or of a prompt natural cement; more preferably from 10% to 75% by weight relative to the total weight of cement of an aluminous cement, of a sulphoaluminous cement and/or of a prompt natural cement; most preferably from 15% to 70% by weight relative to the total weight of cement of an aluminous cement, of a sulphoaluminous cement and/or of a prompt natural cement; the cement composition contains a Portland cement and a sulphoaluminous cement; the cement composition contains 0.5% to 5% silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g; preferably from 0.5% to 2.5% silicoaluminous filler having a specific surface area area of at least 5 m.sup.2/g; the silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g is selected from natural pozzolans, calcined clays or silica fume; preferably the silicoaluminous filler having a specific surface area area of at least 5 m.sup.2/g is selected as being metakaolin or silica fume; the cement composition also contains a limestone filler; the cement composition also contains a setting retarder; the cement composition is in the form of a cement; the cement composition also contains sand and is in the form of a mortar; and or the cement composition also contains sand and aggregates and is in the form of concrete.

(11) The cement composition according to the present invention can therefore be used in 3D printing. Thus, the present invention also relates to a 3D printing method comprising the following steps: bringing the cement composition as defined above into contact with water optionally added with superplasticizer and mixing of the whole; pumping of the cement ink thus obtained to the print head and possible addition of a setting trigger; and printing.

(12) An example of a device allowing the implementation of the above method is described in FIG. 1.

(13) When it contains a mixture of cements, the 3D printing cement composition according to the present invention can be in the form of a single composition (or one-component) containing both Portland cement and aluminous, sulphoaluminous and/or prompt natural cement, but also in the form of two compositions (or two-components) containing Portland cement on the one hand and aluminous, sulphoaluminous and/or prompt natural cement on the other hand, the two compositions then being combined/brought into contact at the print head. Thus, the present invention also relates to a kit useful for the preparation of a cement ink for 3D printing as defined above, said kit comprising: on the one hand, a Portland cement or a composition comprising Portland cement and any additions (additives, aggregates, etc.) described above; and on the other hand an aluminous, sulphoaluminous and/or prompt natural cement or a composition comprising the aluminous, sulphoaluminous and/or prompt natural cement and any additives (additives, aggregates, etc.) described above;
the silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g which may be present in the element of the kit containing the Portland cement and/or in the element of the kit containing the aluminous, sulphoaluminous and/or prompt natural cement.

(14) Preferably, the kit according to the present invention also has the following characteristics, chosen alone or in combination: the kit contains 25% to 90% by weight relative to the total weight of cement in the kit of a Portland cement, more preferably 30% to 85% by weight relative to the total weight of cement in the kit of a Portland cement; the kit contains from 10% to 75% by weight relative to the total weight of cement in the kit of an aluminous cement, of a sulphoaluminous cement and/or of a prompt natural cement, more preferably from 15% to 70% by weight relative to the total weight of cement in the kit of an aluminous cement, a sulphoaluminous cement and/or a prompt natural cement; the kit contains a Portland cement on the one hand and a sulphoaluminous cement on the other hand; the composition containing Portland cement contains the silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g. Preferably, the filler is selected from natural pozzolans, calcined clays or silica fume; the composition containing Portland cement also contains a limestone filler; the composition containing Portland cement also contains a setting retarder; the composition containing Portland cement also contains a superplasticizer; the composition containing Portland cement also contains sand and is in the form of mortar; the composition containing Portland cement also contains sand and aggregates and is in the form of concrete; the composition containing the aluminous, sulphoaluminous and/or prompt natural cement contains the silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g. Preferably, the filler is selected from natural pozzolans, calcined clays or silica fume. More preferably, the silicoaluminous filler having a specific surface area of at least 5 m.sup.2/g is selected as being metakaolin or silica fume; the composition containing the aluminous, sulphoaluminous and/or prompt natural cement also contains a limestone filler; the composition containing the aluminous, sulphoaluminous and/or prompt natural cement also contains a setting retarder; the composition containing the aluminous, sulphoaluminous and/or prompt natural cement also contains a superplasticizer; the composition containing the aluminous, sulphoaluminous and/or prompt natural cement also contains sand and is in the form of a mortar; and or the composition containing the aluminous, sulphoaluminous and/or prompt natural cement also contains sand and aggregates and is in the form of concrete.

(15) When bringing the two compositions into contact at the print head, it may be helpful to add a setting trigger. Thus, the kit according to the present invention can also contain (in addition to the two cements or to the two compositions containing the cements) a setting trigger.

(16) The use of the kit described above makes it possible in particular to limit the quantity of adjuvants such as setting retarders or superplasticizers, or even not to use such adjuvants. Furthermore, in the case of adjuvantation, the use of the kit described above makes it possible to practice a cross adjuvantation, that is to say an adjuvant making it possible to accelerate the reactivity of the Portland cement is added to the composition containing the aluminous, sulphoaluminous and/or prompt natural cement and vice versa. So this adjuvant has no impact on the ink before the print head but reveals its effect when mixing the two compositions.

(17) The two-component cement composition described above can therefore be used in 3D printing.

(18) Thus, the present invention also relates to a 3D printing method comprising the following steps: contacting the composition containing the Portland cement as defined above with water optionally added with superplasticizer and mixing the whole and, separately, contacting the composition containing the aluminous, sulphoaluminous and/or prompt natural cement as defined above with water optionally added with superplasticizer and mixing the whole; pumping each of the compositions thus obtained to the print head, bringing them into contact, optionally in the presence of a setting trigger; and printing.

(19) An example of a device allowing the implementation of the above method is described in FIG. 2.

(20) Finally, the present invention also relates to the use of a cement composition as described above for the preparation of an ink which can be used in 3D printing.

(21) The present invention can be illustrated without limitation by the following examples.

EXAMPLE 1CEMENT INK CONTAINING A SINGLE CEMENT

(22) 1.1Composition

(23) An ink for 3D printing (E-1) whose characteristics are reported in Table 1 below was prepared from a one-component cement ink.

(24) TABLE-US-00001 TABLE 1 Ink E-1 for 3D printing Weight/ Constituent Type Volume mass % Premix Portland Cement CEM I 52.5 R 562 g 28.1 limestone Omya 663 g 33.2 filler Btocarb HP Metakaolin Argical 1000 10 g 0.5 Silica sand Sibelco HN31 765 g 38.3 Liquid Superplasticizer Chryso Optima 145 9 ml 1.6 adjuvan- (% binder) tation Setting trigger Chryso Jet 1000 Adjustable volume Water Premix 2000 g W/C = 0.48 Water 270 g
1.2Preparation and Monitoring of Rheology

(25) The ink E-1 was prepared in the laboratory in a mixer according to the following procedure: dry mixing for 45 s of all the dry constituents to homogenize the mixture; addition of water and superplasticizer in 15 s (=T.sub.0); mixing the whole for 3 minutes at low speed.

(26) The rheology of the obtained composition (without adding a setting accelerator) was monitored at T.sub.0+3 min, T.sub.0+20 min and T.sub.0+30 min and T.sub.0+60 min by spreading on an ASTM cone (without shaking table). The results are reported in Table 2 below.

(27) TABLE-US-00002 TABLE 2 Ink E-1 rheology monitoring Spreading Time (mm) T.sup.0 + 3 minutes 175 T.sup.0 + 20 minutes 180 T.sup.0 + 30 minutes 180 T.sup.0 + 60 minutes 180

(28) There is no significant change in the rheology of the ink during the first 60 minutes and before setting triggering. The obtained rheology enables the pumping and use of the ink E-1 in a 3D print head.

(29) 1.3Strengths after Triggering

(30) The properties of the ink in terms of compressive strength with or without the addition of a setting accelerator (addition at T.sub.0+10 min using a syringe) were evaluated according to the following protocol: preparation of the cement ink according to the mixing protocol described in Example 2.2; at t.sub.0+10 min, adding 5 ml of setting trigger; mixing at low speed for 15 seconds; placing in 4416 molds in a single pass (i.e. the mold is filled then undergoes 60 shocks in one minute).

(31) The results obtained in terms of compressive strength (CS) are reported in Table 3 below.

(32) TABLE-US-00003 TABLE 3 Ink E-1 compressive strength Volume of setting accelerator added (in ml) at T.sub.0 + 10 min 5 CS (MPa) 24 h 42.9 7 days 81.2 28 days 92.1

(33) The observed strengths are compatible with the use of the ink E-1 in 3D printing.

EXAMPLE 2ONE-COMPONENT CEMENT INK

(34) 2.1Composition

(35) An ink for 3D printing (E-2) whose characteristics are reported in Table 4 below was prepared from a one-component cement ink.

(36) TABLE-US-00004 TABLE 4 Ink E-2 for 3D printing Weight/ Constituent Type Volume mass % Premix Portland Cement CEM I 52.5 N 350 g 17.5 Sulphoaluminous Alpenat R.sup.2 150 g 7.5 cement Limestone filler Omya 400 g 20.0 Btocarb HP Metakaolin Argical 1000 100 g 5.0 Silica sand Sibelco HN31 1000 g 50.0 Solid Retarder Citric acid 2.5 g 0.5 adjuvan- (% binder) tation Setting trigger Lithium 2.0 g 0.4 carbonate (% binder) Liquid Superplasticizer Chryso 7.5 ml 1.5 adjuvan- Optima 145 (% binder tation Setting trigger Chryso Jet 1000 Adjustable volume Water Premix 2005.5 g W/C = 0.55 Water 276 g
2.2Preparation and Monitoring of Rheology

(37) The ink E-2 was prepared in the laboratory in a mixer according to the following procedure: dry mixing for 45 s of all the dry constituents to homogenize the mixture; addition of water and superplasticizer in 15 s (=T.sub.0); mixing the whole for 3 minutes at low speed.

(38) The rheology of the obtained composition (without adding setting accelerator) was monitored at T.sub.0+3 min, T.sub.0+15 min and T.sub.0+30 min by flow of 15 cm at the ASTM cone (without shaking table). The results are reported in Table 5 below.

(39) TABLE-US-00005 TABLE 5 Ink E-2 rheology monitoring Spreading Time (mm) T.sub.0 + 3 minutes 152.5 T.sub.0 + 15 minutes 165 T.sub.0 + 30 minutes 150

(40) There is no significant change in the rheology of the ink during the first 30 minutes and before setting triggering. The obtained rheology enables the pumping and use of the ink E-1 in a 3D print head.

(41) 2.3Strengths after Triggering

(42) The properties of the ink in terms of compressive strength with or without the addition of a setting accelerator (addition at T.sub.0+10 min using a syringe) were evaluated according to the following protocol: preparation of the cement ink according to the mixing protocol described in Example 2.2; at t0+10 min, add 0 to 15 ml of setting trigger; mixing at low speed for 15 seconds; placing in 4416 molds in a single pass (i.e. the mold is filled then undergoes 60 shocks in one minute).

(43) The results obtained in terms of compressive strength (CS) are reported in Table 6 below.

(44) TABLE-US-00006 TABLE 6 Ink E-2 compressive strength Volume of setting accelerator added (in ml) at T.sub.0 + 10 min 0 5 10 15 CS (MPa) 24 h 15.4 14.2 13.7 12.9 7 days 51.6 49.4 44.5 42.3 28 days 93.3 86.2 80.7 77.7

(45) The observed strengths are compatible with the use of the ink E-2 in 3D printing, regardless of the expiration date and or the added amount of setting accelerator. The decrease in CS due to the addition of the setting trigger was expected. However, it remains moderate.

EXAMPLE 3ONE-COMPONENT CEMENT INKS

(46) 3.1Compositions

(47) Two inks for 3D printing (E-3 and E-4) whose characteristics are reported in Tables 7 and 8 below were prepared from a one-component cement ink.

(48) TABLE-US-00007 TABLE 7 Ink E-3 for 3D printing Weight/ Constituent Type Volume mass % Premix Portland Cement CEM I 52.5 N 427.13 g 21.3 Sulphoaluminous Alpenat R.sup.2 75.38 g 3.8 cement Limestone filler Omya 402 g 20.0 Betocarb HP Metakaolin Argical 1000 100.5 g 5.0 Silica sand Sibelco HN31 1000.5 g 49.9 Solid Retarder Citric acid 3.52 g 0.7 adjuvan- (% binder) tation Hardener Lithium 2.01 g 0.4 carbonate (% binder) Liquid Superplasticizer Chryso 9.5 ml 1.9 adjuvan- Optima 145 (% binder) tation Setting trigger Chryso Jet 1000 Adjustable volume Water Premix 2010.0 g W/C = 0.54 Water 269 g

(49) TABLE-US-00008 TABLE 8 Ink E-4 for 3D printing Weight/ Constituent Type Volume mass % Premix Portland Cement CEM I 52.5 N 412.25 g 21.3 Sulphoaluminous Alpenat R.sup.2 72.75 g 3.8 cement Limestone filler Omya 630.5 g 32.5 Betocarb HP Metakaolin Argical 1000 97 g 5.0 Silica sand Sibelco HN31 727.5 g 37.5 Solid Retarder Citric acid 4.85 g 1.0 adjuvan- (% binder) tation Hardener Lithium 1.94 g 0.4 carbonate (% binder) Liquid Superplasticizer Chryso 9.5 ml 2.0 adjuvan- Optima 145 (% binder) tation Setting trigger Chryso Jet 1000 Adjustable volume Water Premix 1940 g W/C = 0.58 Water 285 g
3.2Preparation and Monitoring of Rheology

(50) The inks E-3 and E-4 were prepared in the laboratory in a mixer according to the following procedure: dry mixing for 45 s of all the dry constituents to homogenize the mixture; addition of water and superplasticizer in 15 s (=T.sub.0); mixing the whole for 3 minutes at low speed.

(51) The rheology of the obtained composition (without adding setting accelerator) was monitored at different times between T.sub.0+3 min and T.sub.0+135 min by flow of 15 cm at the ASTM cone (without shaking table). The results are reported in Table 9 below.

(52) TABLE-US-00009 TABLE 9 Inks E-3 and E-4 rheology monitoring Spreading (mm) Time E-3 E-4 T.sub.0 + 3 minutes 190 170 T.sub.0 + 15 minutes 225 215 T.sub.0 + 30 minutes 280 230 T.sub.0 + 55 minutes 285 232 T.sub.0 + 75 minutes 292 225 T.sub.0 + 95 minutes 290 222 T.sub.0 + 115 minutes 285 205 T.sub.0 + 135 minutes 272 195

(53) There is no significant change in the rheology of the inks during the first 30 minutes and before the setting triggering. An increase in spreading is observed initially and then a gradual decrease ((bell effect) characteristic of highly adjuvanted materials. However, after more than two hours, the spread is still greater than 200 mm, which allows for any risk of setting in the print head. The obtained rheology therefore allows the use of inks E-3 and E-4 in a 3D print head.

EXAMPLE 4TWO-COMPONENT CEMENT INK

(54) A two-component cement ink (E-5) whose characteristics are reported in Table 10 below was prepared.

(55) TABLE-US-00010 TABLE 10 Ink E-5 for 3D printing Component Component Constituent Type A B Premix Portland Cement CEM I 52.5 N 50 g Sulphoaluminous Alpenat R.sup.2 33 g cement Limestone filler Omya 17 g Betocarb HP Solid Retarder Citric acid 0.1 g 0.07 g adjuvan- Setting trigger Lithium 0.17 g tation carbonate Water 17.5 g 17.5 g

(56) In the example presented above, lithium carbonate has a very moderate effect on the increase in strength of Portland cement considered alone and it does not or very little disrupt its rheology. After mixing, the formed binder consists of Alpenat R.sup.2 and Portland cement CEM I in proportions of 60/40, formula setting in a few seconds, and the lithium carbonate then accelerates the increase in strength of the mixture. This cross-adjuvantation allows the introduction of adjuvants having a powerful effect on one component (A) via the other component (B), their effect only being triggered when the two components meet.

(57) Each component of the ink has been prepared separately. The dry materials were mixed for 45 seconds at low speed then water was added for 15 seconds. The cement paste is then mixed for one minute at low speed.

(58) The two components were then introduced into syringes connected to a static mixer in which they are brought into contact.

(59) At the output of this mixer, the mixture of the two components has set and the material has passed from the liquid state to that of thick paste in a few seconds without it being necessary to add liquid adjuvants such as a superplasticizer or a setting trigger.

EXAMPLE 5COMPARATIVE TESTS

(60) 5.1Tested Compositions

(61) The inks for 3D printing (E-6 to E-9) whose characteristics are reported in Tables 11 to 14 below, were prepared from a one-component cement inks.

(62) TABLE-US-00011 TABLE 11 Ink E-6 for 3D printing Constituent Type Weight/Volume Premix Portland Cement CEM I 52.5 N 425 g Sulphoaluminous Alpenat R.sup.2 75 g cement Limestone filler Omya Betocarb HP 650 g Metakaolin Argical 1000 100 g Silica sand Sibelco HN31 750 g Solid Retarder Citric acid 5 g adjuvantation Hardener Lithium carbonate 2 g Liquid Superplasticizer Chryso Optima 145 9.8 ml adjuvantation Setting trigger Chryso Jet 1000 10 ml Water Premix 2000 g W/C = 0.59 Water 293.8 ml

(63) TABLE-US-00012 TABLE 12 Ink E-7 for 3D printing Constituent Type Weight/Volume Premix Portland Cement CEM I 52.5 N 425 g Sulphoaluminous Alpenat R.sup.2 75 g cement Limestone filler Omya Betocarb HP 750 g Metakaolin Argical 1000 Silica sand Sibelco HN31 750 g Solid Retarder Citric acid 5 g adjuvantation Hardener Lithium carbonate 2 g Liquid Superplasticizer Chryso Optima 145 9.8 ml adjuvantation Setting trigger Chryso Jet 1000 10 ml Water Premix 2000 g W/C = 0.59 Water 293.8 ml

(64) TABLE-US-00013 TABLE 13 Ink E-8 for 3D printing Constituent Type Poids/Volume Premix Portland Cement CEM I 52.5 N 561.3 g Sulphoaluminous Alpenat R.sup.2 cement Limestone filler Omya Betocarb HP 663.3 g Metakaolin Argical 1000 10 g Silica sand Sibelco HN31 765.4 g Solid Retarder Citric acid adjuvantation Hardener Lithium carbonate Liquid Superplasticizer Chryso Optima 145 9 ml adjuvantation Setting trigger Chryso Jet 1000 10 ml Water Premix 2000 g W/C = 0.48 Water 270 ml

(65) TABLE-US-00014 TABLE 14 Ink E-9 for 3D printing Constituent Type Poids/Volume Premix Portland Cement CEM I 52.5 N 561.3 g Sulphoaluminous Alpenat R.sup.2 cement Limestone filler Omya Betocarb HP 673.3 g Metakaolin Argical 1000 Silica sand Sibelco HN31 765.4 g Solid Retarder Citric acid adjuvantation Hardener Lithium carbonate Liquid Superplasticizer Chryso Optima 145 9 ml adjuvantation Setting trigger Chryso Jet 1000 10 ml Water Premix 2000 g W/C = 0.48 Water 270 ml
5.2Preparation and Monitoring of Rheology

(66) Inks E-6 to E-9 were prepared in the laboratory in a mixer according to the following procedure: dry mixing for 45 s of all the dry constituents to homogenize the mixture; addition of water and superplasticizer in 15 s (=T.sub.0); mixing the whole for 3 minutes at low speed.

(67) The indicated amount of setting trigger (Chryso Jet 1000 AF) is then added and the ink is mixed again for 30 seconds.

(68) Layers of material are then stacked successively in order to validate the buildability criterion or the ability of the ink to support its own weight and that of successive layers.

(69) For this experiment, a cylindrical die of 40 mm diameter and 30 mm high is used. Successive layers are added at a rate of 1 layer every 30 seconds.

(70) This test makes it possible to study the behavior of the first deposited layer when the load applied to it increases.

(71) It is observed that for inks E-7 and E-9 (which do not contain silicoaluminous filler), the threshold generated after triggering of the setting is too low. The bottom layer begins to sag as soon as the second layer is deposited and it gives out completely after a few more layers (3 for E-7 ink and 5 for E-9 ink).

(72) On the contrary, the E-6 and E-8 inks (which contain a silicoaluminous filler) allow a stacking of layers up to at least 20 successive layers without observing deformation or sagging of the lower layer.