METHOD OF PLACING A FLOWABLE CONSTRUCTION MATERIAL
A method of placing a flowable construction material including a hydraulic cement for building structural components layer-by-layer, such as for 3D concrete printing, the method including conveying the flowable construction material to a deposition head, placing the construction material through an outlet of the deposition head in order to form a layer of construction material, before placing the construction material, adding a thickening agent to the construction material so that the placed material has an increased yield stress before setting occurs when compared to the material during the conveying procedure, wherein successive layers of construction materials are placed on top of each other, wherein the thickening agent is added in the form of a colloidal dispersion of mineral particles dispersed in a liquid, the colloidal dispersion having a pH value of ≥7.
1 . A method of placing a flowable construction material comprising a hydraulic cement for building structural and architectural components layer-by-layer, said method comprising:
conveying the flowable construction material to a deposition head,
placing the construction material through an outlet of the deposition head in order to form a layer of construction material,
before placing the construction material, adding a thickening agent to the construction material so that the placed material has an increased yield stress before setting occurs when compared to the material during the conveying step,
wherein successive layers of construction materials are placed on top of each other,
wherein the thickening agent is added in the form of a colloidal dispersion of mineral particles dispersed in a liquid.
2 . The method according to claim 1 , wherein water is used as a dispersion medium of the colloidal dispersion.
3 . The method according to claim 1 , wherein the mineral particles have a particle size distribution characterized by a D10 of ≥2 nm and a D90 of ≤200 nm.
4 . The method according to claim 1 , wherein the mineral particles have a BET specific surface area of 100-500 m 2 /g, measured according to the standard ISO 9277:2010.
5 . The method according to claim 1 , wherein the colloidal dispersion has a solid content of 20-55 wt.-%.
6 . The method according to claim 1 , wherein the thickening agent comprises at least one member selected from the group consisting of a pozzolanic material and a phyllosilicate.
7 . The method according to claim 1 , wherein the thickening agent comprises at least one member selected from the group consisting of amorphous silica, fumed aluminum oxide and phyllosilicate clay.
8 . The method according to claim 1 , wherein the step of placing the construction material comprises extruding the construction material in a pasty form through a nozzle of the deposition head.
9 . The method according to claim 1 , wherein after the placement of a first layer of construction material, at least one subsequent layer of construction material is placed onto the first layer, wherein the amount of thickening agent added to the construction material is selected so as to increase the yield stress so that the first layer does not collapse under the load of said at least one subsequent layer.
10 . The method according to claim 1 , wherein the yield stress of the freshly placed construction material is 500-2000 Pa measured 30-60 sec. after its placement.
11 . The method according to claim 1 , wherein the construction material is concrete, a cement mortar, or a cement micro-mortar.
12 . The method according to claim 1 , wherein the thickening agent is amorphous silica and/or fumed aluminum oxide and is added to the construction material in an amount of 8-18 g/l defined as weight of the solid content of the thickening agent per volume of the construction material.
13 . The method according to claim 1 , wherein the thickening agent is a phyllosilicate clay and is added to the construction material in an amount of 2-5 g/l, defined as weight of the solid content of the thickening agent per volume of the construction material.
14 . The method according to claim 1 , wherein the hydraulic cement comprises at least 30 wt.-% Portland clinker.
15 . The method according to claim 1 , wherein the hydraulic cement comprises at least 10 wt.-% of a supplementary cementing material.
16 . The method according to claim 1 , wherein a water reducer is added to the construction material before the conveying step, wherein the conveying of the construction material is performed by pumping.
17 . A kit of components for building structural components layer-by-layer for performing a method according to claim 1 , comprising:
a flowable construction material comprising a hydraulic cement,
a thickening agent for increasing the yield stress of the flowable construction material before setting occurs, the thickening agent being in the form of a colloidal dispersion of mineral particles dispersed in a liquid.
18 . The method according to claim 1 , wherein the method for building structural and architectural components layer-by-layer is a 3D concrete printing method.
19 . The method according to claim 1 , wherein the colloidal dispersion has a pH value of ≥7.
20 . The method according to claim 3 , wherein the mineral particles have a particle size distribution characterized by a D10 of ≥5 nm, and a D90 of ≤100 nm.