Method for manufacturing mortar-based elements

Abstract

A method is for manufacturing elements including hydraulic binder and aggregates. The method includes mixing a dry mortar composition including hydraulic binder and aggregates with water, to form a wet mortar. The method also includes pumping and conveying the wet mortar towards an outlet. During the conveying at least two physical properties of the wet mortar are measured on-line. The physical properties include viscosity and at least one of flow and density.

Claims

1. A 3-D printing method for manufacturing elements comprising hydraulic binder and aggregates, said method comprising: mixing with a mixing device a dry mortar composition comprising hydraulic binder and aggregates with water, to form a wet mortar, pumping and conveying said wet mortar using a pump positioned downstream of the mixing device towards a printing nozzle of a computer-controlled 3-D printer, wherein the wet mortar is conveyed from the pump to the printing nozzle using a hose, wherein one or more sensors are arranged between the pump and the printing nozzle such that during said conveying of the wet mortar in the hose towards the printing nozzle at least two physical properties of the wet mortar are measured on-line upstream of the printing nozzle before the wet mortar enters the printing nozzle and downstream of the pump after the wet mortar passes through the pump, said physical properties including viscosity and at least one of flow and density, adjusting a flow of water sent to the mixing device based on data received from the one or more sensors, and depositing, by extruding the wet mortar through the printing nozzle of the computer-controlled 3-D printer, a layer of wet mortar on a previous layer of mortar.

2. The method according to claim 1, wherein said at least two physical properties of the wet mortar are recorded on a computer-readable storage media.

3. The method according to claim 1, wherein the viscosity and at least one of flow and density of the wet mortar are simultaneously measured using a same sensor of the one or more sensors.

4. The method according to claim 3, wherein the density, the flow, the viscosity and the temperature of the wet mortar are simultaneously measured using the same sensor.

5. The method according to claim 1, wherein a ratio between the water and the dry mortar is adjusted depending on a value of at least one of said at least two physical properties.

6. The method according to claim 5, wherein the ratio between the water and the dry mortar is adjusted in real time.

7. The method according to claim 5, wherein a predetermined value, respectively a predetermined range is set for at least one of said at least two physical properties, and the ratio between the water and the dry mortar is adjusted so that the value of at least one of said at least two physical properties is equal to said predetermined value, respectively comprised within said predetermined range.

8. The method according to claim 1, wherein the dry mortar comprises additives selected from superplasticizers, thickeners, accelerators, retarders, and mixtures thereof.

9. The method according to claim 1, wherein the maximum size of the aggregates is less than or equal to 3 mm.

10. The method according to claim 1, wherein the dry mortar composition is adjusted so that the wet mortar shows a thixotropic behavior.

11. The method according to claim 1, wherein the density of the wet mortar is between 1800 and 2500 kg/m.sup.3.

12. The method according to claim 1, wherein the flow of the wet mortar during conveying is between 100 and 20000 L/h.

13. The method according to claim 1, wherein the viscosity of the wet mortar during conveying is between 400 and 3000 cP.

14. The method according to claim 1, wherein the dry mortar composition is adjusted so that a viscosity of the wet mortar increases by a factor of 50 or more 1 second after leaving the outlet.

15. The method according to claim 1, wherein the density of the wet mortar is between 2000 and 2400 kg/m.sup.3.

16. The method according to claim 1, wherein the flow of the wet mortar during conveying is between 150 and 1000 L/h.

17. The method according to claim 1, wherein the viscosity of the wet mortar during conveying is between 800 and 1600 cP.

18. The method according to claim 1, wherein a controller is configured to adjust the flow of water sent to the mixing device based on the data received from the one or more sensors.

19. The method according to claim 1, further comprising controlling a speed of the pump using a controller based on data received by the controller from the one or more sensors.

20. The method according to claim 1, wherein the pump is a screw pump.

21. The method according to claim 1, comprising controlling, with a controller using the data received from the one or more sensors, a valve or a flowmeter to adjust the flow of water sent to the mixing device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described in more detail by reference to a non-limiting example.

(2) FIG. 1 shows an example system used for implementing a method according to the invention.

DETAILED DESCRIPTION

(3) The system of FIG. 1 is a 3-D printing system comprising a printer having a printer head 20 adapted to extrude wet mortar through a nozzle so as to deposit a layer of wet mortar 11 on a previous mortar layer 12, and to manufacture a construction element 10. The printer is for example an industrial robot or a gantry and the wet mortar may be conveyed to the head through a hose.

(4) The construction element 10 can be for example a wall, a bridge element, a decorative element, a complex formwork for casting concrete etc.

(5) The wet mortar is produced by mixing a dry mortar composition with water in a mixing device 40. Mixing is done with a certain mixing ratio.

(6) The dry mortar composition is stored in a silo 80. Alternatively, the system may comprise several silos or containers containing each of the components of the dry mortar composition, as well as means for mixing the appropriate amounts of each component in order to obtain the desired dry mortar composition.

(7) The dry mortar composition comprises for example Portland cement, siliceous aggregates, limestone filler, rheology modifiers, additives and fibers.

(8) Water is stored in a water supply 71, and the dosage of water (impacting the mixing ratio) is adjusted through means 72 comprising for example a valve and a flowmeter. The wet mortar is continuously pumped through a pumping device 50, which is for example a pump, such as a screw pump. The wet mortar is pumped and conveyed towards the printer head 20, and on its way from the mixing device 40 to the printer head 20, at least one of its physical properties is measured on-line by a sensor 30. The measurement is made preferably close to the mixing device.

(9) The sensor 30 is for example a sensor of the Coriolis type, which is able to measure simultaneously the density, the flow, the viscosity and the temperature of the wet mortar. The system may also comprise another sensor 31 able to measure other properties, for example the pressure.

(10) The system shown in FIG. 1 is controlled through several controllers. These controllers preferably comprise processors for receiving instructions and/or data and for generating machine instructions executable by other controllers or by specific devices. These controllers can be programmable logic controllers (PLC).

(11) A central main controller 90 is configured to receive model data specifying a 3D model of the construction element 10 to be printed. These model data are typically stored in a computer-readable storage media 92. The central main controller 90 can be controlled by a controller 91 that may be manually controlled by a user, for example to start or stop the system or to adjust the printing speed. At least one of controllers 90 and 91 comprises an interface, such as a GUI.

(12) The central main controller 90 is also configured to control the first controller 60 and the second controller 21, for example by generating machine instructions executable by these controllers. These instructions are for example instructions to change the printing speed and/or the height or the width of the layers, according to the model data or the instructions given by the user.

(13) The second controller 21 controls the printer head 20. It is configured to receive instructions from the central main controller 90 and to generate machine instructions so as to control for example the position and the speed of the printer head 20.

(14) The first controller 60 controls the system for controlling and adjusting the physical properties of the wet mortar by adjusting the mixing ratio. It is configured to receive data from sensors 30 and 31 and adjust in consequence the flow of mixing water and therefore the mixing ratio by generating instructions executable by the means 72.

(15) The first controller 60 typically compares in real time the measured value, for example of the viscosity of the wet mortar, with a predetermined range to calculate a control deviation and if needed adjust the water dosage (and therefore the mixing ratio), by adjusting the flow of water.

(16) The first controller 60 may also generate instructions executable by the pumping device 50, in order for example to adjust the pumping speed according to the desired printing speed.

(17) The first controller 60 may also generate instructions executable by a third controller 100 that can control the dosage of the dry mortar, for example the flow of the dry mortar. The third controller 100 may also control the mixing of the individual components of the dry mortar.

(18) By using this system, high quality construction elements have been manufactured.