Patent Application
20240309660
The present invention provides a method and structure for quickly erecting, cost effective, and easily replicable structures. Particularly, this invention relates to the erecting of monolithic structures via the use of pressure supported air forms and rigid forms.
Structures built with conventional building techniques require a great deal of time, expertise, and capital expenditure to successfully erect. Furthermore, predominant methods of construction (such as timber, post-and-beam, steel, and others) are difficult and expensive to insulate effectively, due to the presence of various gaps and thermal bridges inherent to their design.
U.S. Pat. No. 5,918,438A teaches a monolithic dome constructed by creating an inflatable air form to comprise the outer surface of a building being constructed. Once inflated, workers enter the inflated structure and spray insulation (usually polyurethane) onto the interior surface of the air form. After insulation has been applied, the workers then reinforce the inner structure with rebar and apply a layer of spray-on concrete. Once the concrete has cured, the resultant structure is largely complete and exhibits excellent longevity and thermal retention characteristics. Monolithic structures, such as the one disclosed in U.S. Pat. No. 5,918,438A, present a potential solution to the insulation problems, since monolithic structures are completely constructed from one piece. This eliminates the air gaps and thermal bridging associated with other construction techniques. Monolithic domes constructed using the same or similar techniques as discussed above, such as those taught in U.S. Design Patent RE28689E, U.S. Pat. No. 4,680,901A, and U.S. Publication No. 20170321438A1, effectively meet the challenge of providing a long-lifetime, thermally regulated structure, but require a great deal of time, expertise, and most importantly, capital expenditures roughly equal to those required when constructing a traditional building. The Monolithic Dome Institute (MDI), a leader in the field of monolithic dome construction domiciled in Italy, Texas, estimates the cost of using their construction methods, disclosed in U.S. Pat. No. 5,918,438A, at “about $130 per square foot of floor area,” or roughly comparable per-square-foot to traditional construction techniques.
MDI has also developed an alternate building technique which seeks to address the relatively high cost of constructing one of their monolithic domes. The technique to construct an “Eco-Shell” is similar to that of the monolithic dome in that it uses an air form, but, unlike the monolithic dome, the air form is reusable. In erecting an Eco-Shell, the first step is to pour a foundation. The air form is then affixed to the foundation and inflated. Once inflated, workers affix rebar outside of the air form and then proceed to apply a layer of shotcrete. Once the shotcrete is cured, the air form is then deflated and removed, leaving behind a free-standing structure. The air form may then be re-used.
The Eco-Shell is cost effective to produce because one air form may be re-used. This is particularly effective for large projects, as the cost of the air form itself can be defrayed by the construction of many buildings. MDI, through their non-profit, Domes For The World, has successfully constructed large villages of Eco-Shells in various equatorial locations. MDI claims they are able to construct an Eco-Shell for as little as $1,500.00 in material costs. The Eco-Shell can be erected quite quickly with minimal expertise and is disaster resistant. However, the Eco-Shells are constructed with only a thin layer of structural concrete and do not meet the challenge of having a high insulation value. Eco-Shells are therefore an effective solution for low-cost housing, but only in tropical or sub-tropical climates where good insulation is not needed.
DomeGaia utilizes a technique that differs from those discussed above in that the structure is not monolithic. Foamed concrete has successfully been employed by DomeGaia as the primary load bearing construction material in completed buildings. In this process, foamed concrete is made by mixing cement with foamed soap, which is then poured into moulds. Once cured, the concrete blocks are removed from the forms and individually shaped with hand tools before being stacked into a domical structure. For the purposes of description, this process of stacking blocks is readily comparable to that of building an igloo. Once the blocks are in place, the structure is sealed with a layer of plaster.
The DomeGaia technique produces a structure that meets some of the challenges discussed above, such as a higher insulation value. However, this structure does not meet the constraints of being quickly erectable and is not easily erected without the labor of skilled masons. The protracted length of construction, along with the requirement for skilled labor inflates the costs associated with construction. While this technique may be more cost effective per ft2 than traditional building, it is not optimal. Further, the fact that DomeGaia domes are not monolithic leaves the potential for some thermal bridging between the blocks which comprise the final structure.
What is needed is a construction process to produce structures that avoid the drawbacks discussed above. An ideal technique would produce well insulated, long-lasting structures that can be built quickly and cheaply, with low required expertise. Despite evidence of clear, long-standing work in the field, such a construction technique has proven elusive.
The present invention provides a method for building a monolithic structure, the method including compacting and preparing a foundation on a site where the monolithic structure will reside, erecting an inner vertical structural wall on the foundation, securing the inner vertical structural wall to the foundation, connecting an inner air form to a top of the inner vertical structural wall, inflating the inner air form creating an inner mold, erecting an outer vertical structural wall around the inner vertical structural wall, wherein the distance between the inner vertical structural wall and the outer vertical structural wall is a desired thickness of the monolithic structure, securing the outer vertical structural wall to the foundation, connecting an outer air form to a top of the outer vertical structural wall, pouring a moldable mixture in a space between the inner mold and the outer mold, removing air pressure once the moldable mixture is solidified, curing the moldable mixture, detaching the outer air form from the outer vertical structural wall, and removing the outer air form and the outer vertical structural wall from the cured moldable mixture, and detaching the inner air form from the inner vertical structural wall and removing the inner air form and the inner vertical structural wall from the moldable mixture.
The present invention also provides a system for constructing a monolithic structure with a moldable mixture including one or more rigid forms connected to form an inner rigid wall, an inner inflatable air form, wherein the inner inflatable air form extends from the inner rigid wall, one or more rigid forms connected together to form an outer rigid wall, and an outer inflatable air form, wherein the outer inflatable wall extends from the outer rigid wall.
Further objects, features, and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments of the invention.
The present invention provides a novel technique which utilizes pressure supported air forms as a mould for curable mixtures (among them foam cement, cellular concrete, plastics, or other substances). Once the mixture has cured and become rigid the air forms may be removed, leaving a monolithic structure which can then be used for various purposes.
Rigid forms, reinforcement walls, may also be used in lieu of the straight and/or vertical portions of the air forms on the inside and outside of the structure to assist the air form fabrics/textiles in maintaining the appropriate shape under the considerable hydraulic forces. These rigid forms may be constructed with plywood, aluminum, steel sheets or other appropriate equipment and may be held in place with additional steel rings, ropes, or cables, for example. The air forms attach to the top of the rigid forms. The bottom of the rigid forms sit on a foundation at the site.
While this invention is agnostic as to the moldable (curable) medium used in the construction of any particular structure using the process, one possible moldable mixture utilized in the process is high porosity (foamed) cement.
Foam is mixed with the concrete or cement from a ready-mix truck to create the foamed cement (the cement and foam can also be mixed by hand, or with portable cement mixers). Foamed cement has a number of advantageous properties including compressive strength and density (approximately 100 PSI at a density of 30 pounds per ft3) sufficient to be viable as a structural, load bearing building material in low rise construction. Further, foamed concrete has a significantly higher R value (up to approx. 2.5 per inch) than that of structural concrete. These properties make it an ideal candidate as a moldable mixture.
The present invention provides a novel concept of utilizing pressure supported air forms and rigid forms to create a mould to shape curable mixtures into monolithic structures. In its simplest form, the method utilizes two “air forms” (which may be two membranes built from PVC coated nylon or other suitable fabric/textile). One or more rigid forms, are connected to one another to create a vertical structural reinforcement wall and secured to a foundation or site base. The rigid forms may be connected using any connection form, including bolts or combined with levers, for example. The rigid forms are used in addition to the air forms to create the base shape of the structure. The air forms attach to the top of the rigid forms. The air forms may also extend and attach down inside the rigid walls or outside the rigid walls. They may be attached using rope beads or bolts and plates, for example. The air forms are airtight. The air forms may be made of a single piece of fabric/textile or multiple pieces combined together that can withstand hydraulic pressure and/or air pressure. The rigid forms are secured to a foundation and the air forms are inflated to the point of being near rigid. The inner and outer air forms and rigid forms are of the same or similar shapes but are of different sizes. The inner air form and inner rigid form attach together, and the outer air form and outer rigid form connect together. Pressure is applied to the inner forms and may also be applied to the outer forms but it is not necessary. The inner form will be more highly pressurized. The pressure differential results in two freely standing air supported membranous structures with a “gap” in between. That space can then be filled with a moldable material which, upon curing, leaving a rigid, self-supporting, monolithic structure.
While concrete work has been done using air forms in the past, using them to create a large “air mould” in this fashion has not been attempted and represents an innovation that can facilitate a structure that is well insulated, long lasting, and quick and cheap to build.
For the purposes of expediency, the details of the invention provided below (a) assume (and reference) the use of foamed concrete as the moldable mixture added between the forms and (b) assumes (and references) that the structure to be constructed is a structure of revolution (such as a dome atop a cylinder). However, neither (a) nor (b) need necessarily be the case as other mixtures and shapes may be used/obtained.
where Touter is the inner radius of the outer form, Tinner is the outer radius of the inner form, and x is the thickness in units of length of the resultant wall. Once poured, x can be varied based on the size of the forms to produce a structure with sufficient strength and insulation value so as to be appropriate for the given conditions.
The air forms may be made from PVC-coated nylon or other architectural grade fabric. The rigid forms may be made be made of a rigid material, such as wood, aluminum, or steel. The rigid forms and air forms, may be used together to build a dome-on-cylinder shape, or a plurality of other shapes such as rectangular or square prisms, triangular prisms, pyramids, cones, domes, cylinders, or elliptic cylinders. Two or more shapes may also be combined, such as a rectangular square prism and a triangular prism to produce a more “traditionally” shaped structure.
A concrete entry point and air hose connection may be cut into the 3-inch reinforcement patch in the crown of the exterior shell or any other location in the exterior air form. The concrete entry point may also be on the rigid forms or through the concrete pad/foundation. A tedlar coating may be on the inside surface of the outer air form and the exterior surface of the inner shell air form.
The primary limitation on the structure's final height is a function of hydraulic pressure produced by the liquids being introduced into the system. Once the tensile strength of the air form fabrics (textile) is exceeded, they may tear open and release the mixture prior to full curing. Incorporating a series of “tourniquets” into the system can address this problem. The tourniquet effect may be achieved using ratchet straps or some other method to constrict the outer air form on the outside. On the inside the effect may be achieved via an introduction of sewn in, circumferential air pockets which can be pressurized, like a blood pressure cuff. (This method will also work on the outside). With a tourniquet system in place, the structure may be poured in “flights.” After a certain height has been reached, pouring is suspended until the mixture has cured enough to engage the tourniquets, and the next flight is then poured on top. Using this approach, the height of the structure is only bounded by the compression strength of the cured material.
The invention proposed herein seeks to combine the advantages of the various structures via an innovative new process of “air molding.” The air mould of the present invention may be deployed and utilized as follows:
Step 1: The site is compacted and prepared using any of a variety of foundation techniques. Depending on the local circumstances the foundation may be a poured concrete slab, a trench rubble foundation, a stem wall, or other appropriate techniques, for example.
Step 2: Inner form 210 (
Step 3: Outer form 220 (
Step 4: Foamed cement (or other moldable mixture) is mixed and introduced into the mould via a hole in the exterior surface of the mould 200. The hole may be located in the peak, side or bottom of the outer air form, in a portion of the exterior rigid form or through the foundation, for example, As the mixture is added to the air forms, the outer form is stretched into shape via a hydraulic pressure of the cement. Air pressure may be removed once the moldable mixture has solidified and the structure can stand on its own. Pressure can be easily removed by disconnecting the air hose. Various fibers, such as basalt fiber, acrylic fiber, fiberglass fibers, or hemp fibers, may be added to the moldable mixture to increase tensile strength. The foamed cement is subsequently allowed to cure. Other moldable mixtures may also be used or added to the foam cement, such as different concrete/cement formulations, for example, hempcrete or other formulations infused with fiberglass or polymers, epoxies, plastics, or curable liquid insulators.
Step 5: Once the cement is cured, the air forms and rigid forms may be removed from the site. The outer air form may be detached from the outer rigid form and removed from the structure. The outer rigid form reinforcement walls are then disassembled. To access the interior of the structure, a hole may be cut in the exterior of the structure or a doorway may already have been cast in the structure, Once inside the structure the inner air form is detached from the interior rigid form reinforcement wall and removed from the inside. The inner rigid forms reinforcement wall is then disassembled and removed from the interior of the structure. The air forms and rigid forms can be reused for another structure. This leaves a single, monolithic structure. The inner and outer forms, both air forms and rigid forms, may then be used to construct another structure.
Step 6: When using foamed cement, the resultant structure can be worked with hand tools. Doors, windows, and utility connections may be cast into the structure after the moldable mixture is cured, however, additional holes may be cut out easily and without a requirement for a high level of expertise.
Step 7: The structure may then be dried in by installing windows and doors and sealed appropriately for local conditions. Depending on conditions, the structure could be sealed with any of a variety of products such as paints, resins, epoxies, cement formulations, plasters, or clays, for example.
The structure produced by this process is monolithic and thus avoids thermal bridging or gaps. The walls can be made as thick as necessary to provide the insulation required for local conditions. This process requires very little expertise and can be completed in a matter of days. The monolithic nature of the structure gives it inherent longevity. Finally, the structure is extremely cost effective to produce. In the case of foamed cement, for example, the volume of the cement expands by as much as a factor of 5, and the relatively high R-value of foamed concrete (2.5 per inch) eliminates the need for other insulating materials. This structure requires only approximately 7% the amount of concrete that would be required to make a structure with a similar square footage and R-value built with non-porous, structural concrete. These factors combine to produce a structure with a cost per ft2 an order of magnitude cheaper than traditional building techniques. The resulting structure of the present invention is well insulated, long lasting and can be built quickly and cheaply.
This application claims priority to U.S. Provisional Patent Application No. 62/218,436, filed Jul. 5, 2021, entitled “Construction of Monolithic Structures with Air Forms,” which is hereby incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US22/36100 | 7/5/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63218436 | Jul 2021 | US |
