Patent Application
20210284575
The present invention relates to a novel cement composition for 3D printing as well as a 3D printing method using said cement composition.
The 3D printing or three-dimensional printing designates the methods for manufacturing parts in volume by adding or agglomeration of material. In the industrial environment, it is also called additive manufacturing.
The additive manufacturing can be divided into several steps:
The principle remains close to that of a conventional 2D printer except that the stacking of layers allows creating the volume.
Originally, in the early 2000s, the 3D printing began with the use of heated resins and was primarily used for rapid prototyping. Then, innovative techniques using new materials such as plastic (PLA or ABS), wax, metal (aluminum, steel, titanium, platinum), plaster of Paris, ceramics and even glass, promptly emerged. Gains in time and manufacturing precision allow the production of parts in small series.
There are many applications for 3D printing. First confined to prototyping and visualization of ergonomics for architecture or design studies, then to equipment and prosthesis, it gradually gained industrial sectors ranging from the production of car parts, airplanes, buildings, consumer goods, etc. . . . .
Depending on the type of the used material, there are two main manufacturing techniques:
The 3D printing from cement materials in order to design structures more efficiently is also booming. The used printing method is similar to the method used for plastic materials, except that extrusion and hardening are not provided by heating at the print head.
In the case of printing cement material, whether it is cement paste, mortar or concrete, the material in the fluid state is pumped to a print head where it undergoes a sudden change in its rheology that allows it to be extruded into a bead of material that does not sag and supports its own weight. The cement ink is prepared upstream of the printer in a mixer. It can be prepared by batch or via a continuous method. It is then pumped to the print head.
At the print head, the ink is mixed with an adjuvant that suddenly accelerates its setting. This mixing or mingling can be carried out using two technologies:
At the end of this mixing, the ink is extruded through a nozzle into a bead of material of size defined by the material flow rate and the displacement speed of the print head, allowing the printing of the structure following the G-Code.
To be able to be used in 3D printing, a cement ink must therefore meet three main requirements:
So far, in the majority of cases, cement inks containing essentially a Portland binder have been used. To do this, Portland cement is used as a suspension in water. However, besides the fact that upon contact with water, hydration begins to cause the cement to harden, which is not without causing difficulties in the 3D printing process, the increase in resistance of the ink thus prepared is slow, which limits the printing speed.
Alternatives to using Portland binder for preparing ink for 3D printing would therefore be useful. Chinese patent application CN 104 310 918 describes a cement ink for 3D printing comprising one or two cements, in particular a mixture of sulphoaluminous cement and Portland cement, as well as optionally a filler selected from fly ash, slag powder, silica fume, activated gangue or blast furnace slag. Again, the increase in resistance of the ink thus prepared is slow or insufficient, which limits the printing speed or makes it impossible.
Finally, international patent application WO-A-2018/083010 thus describes a multi-component mortar system comprising a component A and a component B in which component A comprises aluminous cement and at least one inhibitor preventing setting, at least one inorganic filler and water, and component B comprises an initiator system for the inhibited aluminous cement, at least one inorganic filler and water. However, this solution is expensive, especially due to the use of the inhibitor.
At the date of the present invention, it therefore remains necessary to identify cement compositions exhibiting great reactivity and a very rapid or more controlled increase in strength as required, in particular to allow faster and of at least equivalent quality printing, and which does not require the use of hardening inhibitors.
Yet, it has now been found, quite surprisingly, that the addition of a silicoaluminous filler having a specific surface area of at least 5 m2/g with compositions comprising one or more cements made it possible to obtain cement inks having particular rheological properties, particularly a high threshold which, coupled with great reactivity and a very rapid or more controlled rise in resistance as required, thus allows faster printing and of at least equivalent quality.
Thus, the present invention relates to a cement composition for 3D printing comprising:
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 m2/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.
In the context of the present invention:
In the context of the present invention, the following notations are adopted to designate the mineralogical components of cement:
Thus, for example, the calcium aluminoferrite phase of a composition corresponding to the general formula C4AF actually corresponds to a (CaO)4(Al2O3) (Fe2O3) phase.
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.
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. 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 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:
An example of a device allowing the implementation of the above method is described in
the silicoaluminous filler having a specific surface area of at least 5 m2/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.
Preferably, the kit according to the present invention also has the following characteristics, chosen alone or in combination:
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.
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.
The «two-component» cement composition described above can therefore be used in 3D printing. Thus, the present invention also relates to a 3D printing method comprising the following steps:
An example of a device allowing the implementation of the above method is described in
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.
The present invention can be illustrated without limitation by the following examples.
1.1—Composition
An ink for 3D printing (E-1) whose characteristics are reported in Table 1 below was prepared from a «one-component» cement ink.
1.2—Preparation and Monitoring of Rheology
The ink E-1 was prepared in the laboratory in a mixer according to the following procedure:
The rheology of the obtained composition (without adding a setting accelerator) was monitored at T0+3 min, T0+20 min and T0+30 min and T0+60 min by spreading on an ASTM cone (without shaking table). The results are reported in Table 2 below.
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.
1.3—Strengths after Triggering
The properties of the ink in terms of compressive strength with or without the addition of a setting accelerator (addition at T0+10 min using a syringe) were evaluated according to the following protocol:
The results obtained in terms of compressive strength (CS) are reported in Table 3 below.
The observed strengths are compatible with the use of the ink E-1 in 3D printing.
2.1—Composition
An ink for 3D printing (E-2) whose characteristics are reported in Table 4 below was prepared from a «one-component» cement ink.
2.2—Preparation and Monitoring of Rheology
The ink E-2 was prepared in the laboratory in a mixer according to the following procedure:
The rheology of the obtained composition (without adding setting accelerator) was monitored at T0+3 min, T0+15 min and T0+30 min by flow of 15 cm at the ASTM cone (without shaking table). The results are reported in Table 5 below.
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.
2.3—Strengths after Triggering
The properties of the ink in terms of compressive strength with or without the addition of a setting accelerator (addition at T0+10 min using a syringe) were evaluated according to the following protocol:
The results obtained in terms of compressive strength (CS) are reported in Table 6 below.
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.
3.1—Compositions
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.
3.2—Preparation and Monitoring of Rheology
The inks E-3 and E-4 were prepared in the laboratory in a mixer according to the following procedure:
The rheology of the obtained composition (without adding setting accelerator) was monitored at different times between T0+3 min and T0+135 min by flow of 15 cm at the ASTM cone (without shaking table). The results are reported in Table 9 below.
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.
A two-component cement ink (E-5) whose characteristics are reported in Table 10 below was prepared.
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 R2 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.
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.
The two components were then introduced into syringes connected to a static mixer in which they are brought into contact.
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.
5.1—Tested Compositions
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.
5.2—Preparation and Monitoring of Rheology
Inks E-6 to E-9 were prepared in the laboratory in a mixer according to the following procedure:
The indicated amount of setting trigger (Chryso Jet 1000 AF) is then added and the ink is mixed again for 30 seconds.
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.
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.
This test makes it possible to study the behavior of the first deposited layer when the load applied to it increases.
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).
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18/56946 | Jul 2018 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2019/051840 | 7/25/2019 | WO | 00 |
