THIN SHAPED STRUCTURAL ELEMENTS AND METHOD OF MAKING SAME

Disclosed is a method of fabricating a construction element. The method may include assembling a mold on a rotational casting machine; rotating the mold around at least two axes at a predetermined speed; providing a first portion of magnesium silico-phosphate cement (MSPC) mix, having an altered hardening rate, to the mold while rotating the mold until at least a portion of the mold's walls is covered by a first layer of the MSPC mix; and rotating the mold until the MSPC mix is hardened to a predetermined degree.

TECHNICAL FIELD OF THE INVENTION

The invention generally relates to methods of making shaped structural elements and more precisely to novel methods of making shaped structural elements from a magnesium silico-phosphate cement.

BACKGROUND OF THE INVENTION

Making structural elements in the construction industry has been a challenge since ancient times. The more curved and complex the structural elements is, the greater is the difficulty in producing it. Casting cements into a shaped mold, using gravitational casting methods, allows limited geometrical shapes to be fabricated, and the making of three-dimensional (3D) hollow objects in a single casting, almost impossible.

Such 3D hollow objects can be made by using rotational casting. However, this technique is limited to the use in casting polymers and metals, which have the required hardening/solidification time and the required flowing properties. Rotational casting methods use a hollow mold (usually heated to a temperature that may ensure uniform flow of the cast material) fed with a flowing material (e.g., molten metal or molten polymer or fluid polymer system which can harden at room temperature by cross-linking) while being rotated around at least two axes. During the rotation the flowing casting material disperses and sticks to the walls of the mold, forming a layer. The layer is allowed to harden while the mold continues to rotate until a desired hardness is reached and the cast object is taken out of the mold.

Commonly used inorganic cements are unsuitable for the use in rotational casting for various reasons. The hardening time of cements is usually several hours, but special formulations can be made that harden in less than an hour. Yet, their flowability is not adequate for rotational casting. Therefore, current construction methods do not utilize rotational casting. Complex hollow or heavily curved elements made from cements are usually produced by connecting simpler elements to form the more complex ones.

Accordingly, there is a need to find a way to utilize the advantages of rotational casting to be used with inorganic cements, which can provide performance superior to prefabricated rotational cast components using polymer, such as environmental stability and fire endurance.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Some aspects of the invention may be directed to method of fabricating a construction element. The method may include assembling a mold on a rotational casting machine; rotating the mold around at least two axes at a predetermined speed; providing a first portion of magnesium silico-phosphate cement (MSPC) mix, having an altered hardening rate, to the mold while rotating the mold until at least a portion of the mold's walls is covered by a first layer of the MSPC mix; and rotating the mold until the MSPC mix is hardened to a first predetermined degree.

In some embodiments, the method may further include: providing a second portion of MSPC mix to the mold while rotating the mold until at least the portion of the mold's walls is covered by a second layer of the MSPC mix; and rotating the mold until the second layer of the MSPC mix is harden to a second predetermined degree. In some embodiments, at least one of: the first hardening degree and the second hardening degree is the hardening degree which allow demolding of the MSPC construction element.

In some embodiments, the geometry of the mold may include one or more curved surfaces to be covered by the MSPC mix. In some embodiments, the layer of the MSPC mix covering at least the portion of the mold's walls may have a thickness of between 0.5 cm to 2.5 cm. In some embodiments, the layer of the MSPC mix covering at least the portion of the mold's walls may have a thickness deviation of at most 5 mm. In some embodiments, the MSPC mix may include a retarder that may allow the MSPC mix to harden to the degree for at most 30 minutes. In some embodiments, the retarder is in an amount that may allow the MSPC mix to harden to the degree for 10-20 minutes.

In some embodiments, the degree of hardening may be determined such that the extracted hardened MSPC does not undergo deformation during the demolding. In some embodiments, the MSPC mix may include: a phosphate salt or acid; an aggregate phase; fibers, for example, mono-filament or multi-filament and a retarder in an amount of between about 0.05% and about 5% by weight based upon the weight of dry cement.

In some embodiments, the method may further include: adding to the MSPC mix one or more color pigments for achieving a desired color. In some embodiments, the method may further include: adding to the MSPC mix one or more textural additives for achieving a desired texture.

Some additional aspects of the invention may be related to a construction element, that may include: one or more thin walls having a thickness of at most 2.5 cm, the thin walls may be made from a dry magnesium silico-phosphate cement (MSPC) mix. In some embodiments the MSPC mix may include: a phosphate salt or acid; an aggregate phase; fibers, for example, mono-filament or multi-filament and a retarder in an amount of between about 0.05% and about 5% by weight based upon the weight of dry cement.

In some embodiments, at least one wall of the one or more thin walls may be a curved wall. In some embodiments, the one or more walls may have a thickness of between 0.5 cm to 2.5 cm. In some embodiments, the one or more walls may have a thickness deviation of at most 5 mm.

Some aspects of the invention may be related to the use of an advanced type of a magnesium silico-phosphate cement (MSPC) that has an altered hardening rate in a casting method previously considered unsuitable for casting cements. In some embodiments, the MSPC may be cast into a mold of a rotational casting machine to form a complex, and optionally hollow, cast construction element or object.

Reference is now made toFIG.1which is a flowchart of a method of fabricating a construction element according to some embodiments of the invention. In step10, a mold may be assembled on a rotational casting machine. For example, a mold200or a mold300, illustrated inFIGS.3A and3Bmay be assembled into a rotational casting machine100illustrated inFIGS.2A-2C. Molds200or300may have any desired shape that may allow rotationally casting a construction element having any desired shape. For example, a curved shape, a hollow shape, a curved hollow shape (as illustrated inFIGS.4-6) and the like. Molds200or300may be connected to an inner frame110of rotational casting machine100using any known method, for example, clips, screws, bolts and the like. As should be understood by one skilled in the art, the design and shape of rotational casting machine100and molds200and300are given as an example only, and the invention is not limited to these specific designs. Any rotational casting machine and any molds for rotational casting machine are included in the scope of the invention.

In step20, the mold may be rotated around at least two axes at a predetermined speed. For example, Molds200or300may be rotated around two perpendicular axes X and Z illustrated inFIG.2C. The speed may be determined to allow uniform coverage of at least some of the walls of the molds. In some embodiments, the speed may be determined based on the type and composition of the cement used in the rotational casting. The speed may be determined using experimental methods or calculated based on the flowing properties of the cement.

In step30, an MSPC mix, having an altered hardening rate, may be provided to the mold while rotating the mold until at least a portion of the mold's walls is covered by a layer of the MSPC mix. The MSPC mix may include: MgO and a phosphate salt or acid selected from the group consisting of: (a) a phosphate salt or acid of the general formula MxHyPO4(1≤x≤3, y=3−x), where M is selected from the group consisting of H, Li, Na, K, Rb, Cs, NH4, and any combination of the above; (b) any other phosphate salt or acid that after mixing with water will provide a binder product characterized by the empirical chemical formula MMgPO4·6H2O, and (c) any combination of the above. In some embodiments, the mix may further include an aggregate phase selected from the group containing (a) CaSiO3, (b) SiO2, (c) fly ash, (d) sea sand, and (e) any combination thereof; fibers made of mono filaments or multiple filaments, and a fluorine-containing additive. In some embodiments, water may be added in sufficient quantity to enable hydraulic hardening of the cement as well as to provide adequate flow properties. In some embodiments, additives may be added for further control of setting and hardening time as well as flow properties.

In some embodiments, the fluorine-containing additive may be a retarder for controlling the hardening rate of the mix. In some embodiments, the retarder is selected from the group consisting of (a) alkali metal salts of [M′F6]n-, (b) alkaline earth metal salts of [M′F6]n-, and (c) HnM′F6, wherein n represents a positive integer and M′ is selected from the group consisting of (a) Ti (n=2), (b) P (n=1), (c) Zr (n=2), (d) Sb (n=1), and (e) Al (n=3). In some embodiments, the amount of retarder may be between about 0.05% and about 5% by weight based upon the weight of dry cement. In some embodiments, the retarder may be selected from the group consisting of MxTiF6where x=2 when M=alkaline metal. X=1.

In some embodiments, the MSPC mix may further include one or more color pigments for achieving a desired color. In some embodiments, the MSPC mix may further include one or more textural additives for achieving a desired texture.

In some embodiments, rotary casting machine100may rotate the mold while the MSCP mix is continuously being provided, until a layer of between 0.5 cm to 2.5 cm with a thickness deviation of at most 5 mm is formed on at least a portion of the walls of the mold. In some embodiments, the entire walls of molds200or300may be covered by a layer of the MSPC mix to form a curved hollow structural element.

In step40, the mold may be rotated until the MSPC mix is hardened to a degree which allows demolding the MSPC construction element. In some embodiments, the retarder may be selected to harden the MSPC mix to the desired degree after, at most, 30 minutes, for example after at most, 10 minutes, 15 minutes, 20 minutes or 25 minutes. In some embodiments, the degree of hardening may be determined such that the demolded MSPC does not undergo deformation during the demolding operation.

Reference is now made toFIG.1Bwhich is a flowchart of a method of fabricating a construction element according to some embodiments of the invention. Steps10and20of the method ofFIG.1Bare substantially similar to steps10and20of the method ofFIG.1A. In step50, a first portion of MSPC mix, having an altered hardening rate, may be provided to the mold while rotating the mold until at least a portion of the mold's walls is covered by a first layer of the MSPC mix. The MSPC mix may be substantially the same as the MSPC mix disclosed in step30of the method ofFIG.1. For example, a first portion of a pre-prepared MSPC mix may be provided to a rotating mold200or300as to form a first layer, having a thickness of 0.5-2.5 cm, with a thickness deviation of at most 5 mm. The mold may continue to rotate, in step60, until the first layer of the MSPC mix is hardened to a predetermined degree. For example, the degree of hardening may be determined as to allow adding a second layer of the MSPC mix on top of the first layer while avoiding mixing of the material in both layers. In some embodiments, the mold may be rotated for about 10 minutes.

In step70, a second portion of the MSPC mix may be provided to the mold while rotating the mold until at least the portion of the mold's walls may be covered by a second layer of the MSPC mix. The MSPC mix may be substantially the same as the MSPC mix disclosed in step30of the method ofFIG.1. In some embodiments, the second portion of MSPC mix may be different and may include a different composition than the first portion of the MSPC mix. For example, a second portion of a pre-prepared MSPC mix may be provided to a rotating mold200or300as to form a second layer on top of the first layer. In some embodiments, the second layer may have a thickness of 0.5-2.5 cm, with a thickness deviation of at most 5 mm. The mold may continue to rotate, in step80, until the second layer of the MSPC mix is hardened to a predetermined demolding degree. In some embodiments, the degree of hardening may be determined such that the extracted hardened MSPC does not undergo deformation during the extraction.

In some embodiments, more than two layers of the MSPC mix may be applied during the fabrication of the construction element and steps50-60and/or70-80may be repeated.

Reference is now made toFIGS.2A-2Cwhich are an isometric view, side view and front view of a rotational casting machine according to some embodiments of the invention. A rotational casting machine100may include an internal frame110, an external frame120, a first gear142configured to rotated external frame120around a first axis, a second gear144configured to rotated internal frame110around a second axis and an actuator130for providing rotational movement to gears142and144. Rotational casting machine100may further include a base150for supporting frames110,120and the mold.

Internal frame110may be configured to hold and be connected to a mold. Internal frame110may include any connectors or connecting means for connecting and holding the mold. The connectors may be bolts, screws, clamps or any other suitable connecting means. Internal frame110may be made from any suitable material, for example, wood, light metallic alloys, polymers and the like. Internal frame110may be configured to be rotated around a first axis (e.g., the Z axis illustrated inFIG.2C) due to a rotational movement provided by actuator130via second gear144.

External frame120may be configured to rotate internal frame110around a second axis (e.g., the X axis illustrated inFIG.2C) due to a rotational movement provided by actuator130via first gear142. External frame120may be made from any suitable material, for example, wood, light metallic alloys, polymers and the like.

Actuator130may include any suitable device that may provide a rotational movement. Actuator130may include a manual crank handle (illustrated inFIGS.2A-2C), an electric motor, a hydraulic motor or the like. In some embodiments, actuator130may be include at least one of: a controllable motor and a controllable gear and may further be configured to be controlled by a controller (not illustrated).

Reference is now made toFIGS.3A and3Bwhich are illustrations of molds for rotational casting of MSPC mix according to some embodiments of the invention. Each of molds200and300may include a plurality of walls210and310respectively. In some embodiments at least one of walls210and/or310may be curved. In some embodiments, all the walls included in molds200and300may be curved. In some embodiments, molds200and300may further include inlets (not illustrated) for providing the MSPC mix to the molds.

In some embodiments, the curved walls may include a flexible fabric supported on frame elements220or320. In some embodiments, the walls may include a plurality of woven threads supported on frame elements220or320. In some embodiments, walls210and310may be made from substantially rigid material, such as wood, light metals, polymers and the like. In some embodiments, walls210and310may further include protrusions230and330respectively and/or recesses240and340respectively. In some embodiments, protrusions230and330may be configured to form recesses in the cast construction element and recesses240and340may be configured to form protrusions in the cast construction element (as illustrated inFIGS.4-5). In some embodiments, a recess in a first cast construction element may be configured to accommodate a protrusion of a second cast construction element, as to allow a connection of the first casted construction element to the second casted construction element.

Reference is now made toFIGS.4A and4Bwhich are illustrations of an isomeric view and a cut in a construction element according to some embodiments of the invention. A construction element400may include one or more thin walls410having a thickness of at most 2.5 cm. In some embodiments, the thin walls are made from a dry magnesium silico-phosphate cement (MSPC) mix. In some embodiments, the MSPC mix may include MgO, a phosphate salt or acid, an aggregate phase and a retarder in an amount of between about 0.05% and about 5% by weight based upon the weight of dry cement mix. In some embodiments, the MSPC mix may include fibers and/or any one of the compounds disclosed herein above.

In some embodiments, at least one wall410of the one or more thin walls may be a curved wall. In some embodiments, all walls410of element400may be curved. In some embodiments, one or more walls410may have a thickness of between 0.5 cm to 2.5 cm. In some embodiments, one or more walls410may have a thickness deviation of at most 5 mm. In some embodiments, construction element400may be a hollow element.

In some embodiments, construction element400may further include one or more protrusions420. In some embodiments, a protrusion420of a first construction element400may be configured to be accommodated or inserted into recess520of a second construction element500, illustrated inFIGS.5A and5B, as to connect first construction element400and second construction element500, for example, by dry connection induced by an anchorage obtained between the protruding and recessed geometries on the face of the construction element (e.g.420and520) or strengthening of this connection using glues or MSPC mix, as illustrated inFIGS.6A-6B.

Reference is now made toFIGS.5A and5Bwhich are illustrations of an isomeric view and a cut in a construction element according to some embodiments of the invention. A construction element500may include one or more thin walls510having a thickness of at most 2.5 cm. In some embodiments, the thin walls are made from a dry MSPC mix that may include any of the compounds disclosed herein above.

In some embodiments, at least one wall510of the one or more thin walls may be a curved wall. In some embodiments, all walls510of element500may be curved. In some embodiments, one or more walls510may have substantially the same thickness and thickness deviation as walls410. In some embodiments, construction element500may be a hollow element.

In some embodiments, construction element500may further include one or more recesses520each being configured to accommodate a protrusion such as protrusion420of element400.

Reference is now made toFIGS.6A-6Cwhich are illustrations of assembled construction elements according to some embodiments of the invention.FIGS.6A and6Bare side view and top view and top view of a conic dome600made from a plurality of construction elements such as construction elements400and500.FIG.6Cshows an initial stage in the assembling of construction elements400and500into conical dome600. In some embodiments, alternating elements400and500may be connected together to form conical dome600, The elements may be connected by dry connection induced by an anchorage obtained between the protruding and recessed geometries on the face of the construction elements (e.g.420and520) or by strengthening of this connection using glues or MSPC mix, as illustrated inFIGS.6A-6B.