NZ189514A - Method of moulding employing a thin layer of a fibre reinforced plaster with a polymer additive - Google Patents

Description

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Patents Form No. 5 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No. 189514 dated 31st January 1979 "A METHOD OF BUILDING CONSTRUCTION AND MANUFACTURE" I, WILLIAM GEORGE BRAINE t of 7 Brodie Street, Christchurch 4, Neu Zealand, a British subject and New Zealand citizen, hereby declare the invention for ubich I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the follouing statement:- 189514 The invention relates to building construction and manufacture and more particularly to a method of changing the properties of a basic building material to overcome disadvantages causing a restriction of use. The term basic building material as used in this specification includes references to all settable materials for example, cement mixtures and gypsum mixtures. The basic building material as herein defined is modified with both a film forming water soluble dispersed polymer which sets to a water impervious film at room temperature and a fibrs reinforcement to form a modified building material in which a change in the properties of the basic building material has occurred, however it is envisaged that further additives can be included and that numerous additives can be premixed to achieve quality control and ease of mixing the total ingredients to produce the modified building material.

Cement and gypsum mixtures are well established basic building materials and their use with a restricted number of fibre types as reinforcement has also been well established; however most such known methods of manufacture and construction of fibre reinforced concrete and fibre reinforced gypsum suffer from various disadvantages causing a restriction of use, a restriction of fibre types and some of these disadvantages are set out below.

The unmodified cement or concrete matrix has a 189514 relatively poor bond to the fibre reinforcement and its high elastic modulus does not make it very compatable with many fibre types* Another disadvantage of fibre reinforced concrete uhen manufactured as a thin sheet or constructed as a thin layer is the problem of retaining a uet surface to maintain the moisture content required during the curing stage, particularly uhen used on site* Another disadvantage of the concrete matrix is the lou tensile strength to compressive strength ratio* Fibre reinforced concrete consists of a matrix uith a relatively lou tensile failure strain uhich results in the disadvantage of, a heavily cracked matrix by the time the fibres develop a significant stress.

Another disadvantage of thin layers of fibre reinforced concrete is the relatively high cement to sand ratio uhich causes considerable movement uhen subjected to changing temperature and moisture conditions.

Another disadvantage of thin layers of fibre reinforced concrete uhen used to sanduich a foam plastic insulation foam is the high stresses caused by differential temperature and moisture conditions betueen the internal and external sanduiching layers caused by a relatively high cement to sand ratio and the brittle nature of the unmodified concrete matrix.

The gypsum matrix also has a relatively poor bond to the fibre reinforcement and the disadvantage of a long fibre length and the uet gypsum slurry 189514 setting quickly makes the mixing of fibre reinforced gypsum folloued by trouelling difficult.

Another disadvantage of the fibre reinforced gypsum is the temporary loss of strength caused by uetting and its poor resistance to uater and uater vapour permeability.

Another disadvantage of unmodified fibre reinforced concrete and gypsum is the relatively poor bond to a foam plastic insulation material such as polystyrene and polyurethane and especially the dense skin of sprayed polyurethane foam. The bonding of a layer of fibre reinforced concrete to a previous hardened layer of fibre reinforced concrete is relatively poor.

Another disadvantage of fibre reinforced concrete and gypsum is that the long fibres that are required to develop sufficient bond to the unmodified matrix makes it difficult to hand trowel the mix especially to vertical and overhead surfaces.

Another disadvantage of applying the required thickness of concrete or gypsum in a single layer uhen applied to a relatively flexible former is that the ueight causes movement of the former uhich restricts the shape to a limited variety of inflated dome or arch shapes and unless very thin layers are applied it is very difficult to hand trouel the mix to vertical and overhead surfaces.

Accordingly an object of the present invention is to overcome at least in part the disadvantages 19851 stated above and provide an improved method of manufacture and construction using, a modified building material to form a constructional unit, sandwich panel or shell in a variety of structural shapes and usable for a variety of different purposes.

It is an object of the present invention to provide a simple and economical layer of a modified cementitious building material to form a sheet, panel, shell, layer or layers of any desired shape usable for a variety of different purposes.

It is a further object of the present invention to provide a simple and economical method of reducing the curing problems associated With a thin sheet or thin layer of a modified cementitious building material. 198514 Further objects and advantages of the present invention will become apparent from the following description which is given by way of example only.

According to the present invention there is provided a simple and economical method of constructing 5 a very thin layer or layers of modified building material both sides of a light weight core material to form a lightweight sandwich panel of any desired shape suitable for a variety of different purposes.

According to the present invention there is provided a method of constructing a very thin layer of modified building material as a stiffening and strengthening layer to a flexible former and if required for further strength an extra layer or layers of modified building material may be applied to form a building unit or shell.

According to the present invention there is provided a method of increasing the flexibility of modified building material particularly while it is setting when placed over a relatively flexible former.

According to the present invention there is 189514 provided a method of improving the resistance of modified building material to vapour permeability.

According to the present invention there is provided a method of improving the impact resistance of the modified building material layer uhich protects a lightweight insulation material.

According to the present invention there is provided a method of improving the workability and application of the modified building material mix particularly under site conditions.

According to the present invention there is provided a method of reducing or eliminating the sand content without causing differential shrinkage stress cracks.

According to the present invention there is provided a method of constructing a panel or building shell of sandwich construction which has improved resistence to cracking due to differential temperature conditions.

According to the present invention there is provided a method of spraying, trowelling or extruding a very thin layer or layers of modified building material to vertical, topside or underside sufaces.

According to the present invention there is provided a method of applying a very thin layer of modified building material by spraying or trowelling to vertical and overhead surfaces of a relatively flexible former of foamed plastic insulation. 189514 The building material may be modified by a liquid that can be diluted uith uater or mixed uith the wet cement matrix such as latex or synthetic latex uhich louers the elastic modulus of the brittle concrete matrix* Other additives may include uater soluble epoxy, uater soluble adhesives such as P.V.A., polymer dispersions, expansion additives, uater reducing additives and additives to improve uorkability.

The modified building material matrix may be reinforced uith a variety of fibres or combination of fibres such as uire fibres, asbestos fibres, alkali resistant glass fibres, polypropylene fibres, hemp fibres, vegetable fibres or polymer fibres.

The most uidely used fibre reinforced concrete is asbestosrcement produced under carefully controlled factory conditions. Because of health problems uith asbestos fibre, alkali resistant glass fibres and uire fibres are gaining wider use along uith polypropylene fibres for impact resistance. Latex modified cement and concrete has a louer elastic modulus and a higher bonding property than the unmodified matrix and hence improves the mechanical compatibility uith polypropylene fibres that have a louer elastic modulus and poorer bonding surface than asbestos or glass fibres. Latex modified polyproplene reinforced concrete (L 1*1 P R C ) is a very impact resistant material uith a chemically inert fibre reinforcement in the highly alkaline environment of hydrating cements, and may be applied as a thin layer or layers to protect 189514 and sandwich polystyrene or polyurethane foam to form a building shell of sandwich construction* Alternatively, other fibres may be used with latex modified concrete and the improved bonding properties 5 reduce the tendancy of the fibres to pull out the matrix and therefore improve the properties of glass fibre reinforced concrete or steel fibre reinforced concrete* The improved bonding properties of latex modified fibre reinforced concrete enables a shorter fibre length 10 to be used as reinforcement without a reduction in tensile strength and hence improves the workability of fibre reinforced concrete.

Other aspects of the present invention uhich should be considered in all its novel aspects will become 15 apparent from the follouing descriptions which are given by way of example only.

The present invention is preferably utilised for constructing a wide variety of different lightweight shell and panel shapes for a number of different purposes, 20 however, it is particularly suitable for sandwiching a light weight core material of any shape with a thin layer or layers of modified fibre reinforced concrete may be used as a thin protective layer over a foamed plastic insulation material such as sprayed rigid polyurethane 25 foam.

Examples of cross sections through building shells or panels in accordance with the present invention are shown in the accompanying drawings in which: 189514 Figure 1 is a cross section through part of a flat lightweight building panel.

Figure 2 is a cross section through part of a flat lightweight extruded or trowelled building unit. 5 Figure 3 is a cross section through part of a single or double curvature lightweight building panel or shell.

Figure 4 is an example of a lightweight double curvature dome shaped building shell.

Figure 5 is a cross section through part of a lightweight double curvature building shell with flaring protruding shapes.

Figure 6 is an example of a building shell formed in accordance with the present invention showing 15 a pattern of embedded reinforcing wires around each flaring protruding shape incorporating an opening in the dome shaped building shell.

Figure 7 is an alternative example of a double curvature building shell formed in accordance with 20 the present invention showing a pattern of embedded reinforcing wires around each flaring protruding shape.

Figure 8 is another alternative example of a building shell in accordance uith the present invention. The present invention is preferably utilised 25 for constructing a lightweight sanduich construction usable as an insulated outer building shell uhich can be used for a number of different purposes. The outer building shell can utilise the stiffness of sanduich construction and/or double curvature shape and can be insitu or a combination of insitu and precast construction, however it is to be appreciated that a variety of different lightweight structural shapes can be formed and are to be 5 construed as included in the present invention.

Initially, after the shape of the building panel or shell has been decided upon a lightweight relatively flexible former material, for example, polystyrene or , polyurethane foam is formed and controlled so that it can 10 support a very thin layer of modified building material.

The modified building material mixture consists of I numerous ingredients and to achieve quality control and ease of mixing particularly on site some ingredients are premixed for example a selected mix weight of dry silica 15 sand can be bagged and to this sand can be added the required amount of fibre reinforcement.

The modified building material has been applied as a very thin layer or layers 1 to 9mm thick and has been particularly used as two 3mm thick layers or one 6mm layer 20 both sides of a relatively flexible former consisting of polystyrene or rigid polyurethanefoam. However a thin layer of 9 mm and greater is also envisaged particularly if adequate control has been established and other lightweight relatively flexible formers such as thin elastic sheet, 25 galvanised steel sheeting, cloth, netting or reinforcement mesh can be used.

The modified building material mixture consists of numerous ingredients and each solids percentage by weight of the total solids can vary considerably to achieve the. - 11 - ft 189514- desired properties. For example the film forming water dispersed polymer which sets to a water impervious film at room temperature is usually in a water solution with the solids and water content in approximately equal 5 proportions in its concentrated liquid form so that the dispersed polymer solids can be between 1 and 20% by weight of the total solids. Similarly the fibre weight » can be varied considerably with the fibre weight between 0.2 and 10% by weight of total solids. Very small 10 percentages of other ingredients can be added to the cementitious mixture such as a plasticizer and/or other ingredients to improve the performance of the modified building material.

The modified building material can include the 15 following: (1) Cement between 10% and 70% by weight. (2) Water between 5% and 35% by weight; and (3) Filler, for example, sand, expanded polystyrene, perlite and the like between 0 to 80% by weight.

A very thin layer of modified building material can be trowelled onto the internal surface of a relatively flexible building shell former of any desired shape constructed of sprayed rigid polyurethane foam to # stiffen and strengthen the lightweight former. Similarly - m - 189514 a very thin layer of modified building material can be applied to more simple shapes and used to cover polystyrene foam to form numerous lightweight building panel shapes. These building shells and panels can be combined and further layers of modified building material can be applied to form a variety of building shell shapes of lightweight sandwich construction. If required selected areas of a double curvature building shell can be reinforced with small diameter galvanised high tensile wires which are tensioned over the building shell and around openings in the shell and fixed to the shell foundation. These wires are embedded and covered by modified building material to form a wire reinforced building shell that if required can be further finished and protected by a light coloured water based paint containing a film forming water soluble dispersed polymer which sets to a water impervious film at room temperature.

An example of a flat lightweight building panel of sandwich construction is shown in Figure 1 of the accompanying drawings and includes polystyrene as a 189514 lightueight core material 1 uhich is sanduiched by modified building material 2. This lightueight panel construction can be precast^or the core material can be cut and fitted on site for example betueen 5 prefabricated internal partitions and the double curvature building shell and a thin layer of modified building material 2 trowelled to both sides of the polystyrene core 1 to form a lightweight sanduich panel.

An example.of a lightueight frame cross section is shoun in Figure 2 and includes a thin layer of modified building material 3 extruded or trouelled over a lightueight polystyrene core 4.

Other lightueight polystyrene or polyurethane 15 former shapes can be formed such as the single curvature shapes or double curvature dome shapes, for example, as shoun in Figure 3 a curved lightueight core material 5 can be sanduiched with a modified building material 6 to form a lightweight single curvature shape or double 20 curvature dome shape of lightweight sandwich construction.

The dome building shell 7 as shown in Figure 4 shows small diameter high tensile galvanised uires 8 placed around arched shaped shell openings 9* These uires 8 are tensioned and fixed to the shell foundation 25 10 to reduce tension stress or to compression stress th8 building shell particularly around tops of openings uhich should be arched shape to minimise stress in the shell. These arched shaped openings are ueather 189514 protected by protruding construction of any shape (not shoun) that can include a uindou or door* The building shell shoun in Figure 5 consists of an insulstion core of rigid polyurethane foam 11 uhich uas formed by spraying the foam material in thin layers onto an inflated and propped 8heet material (not shoun) uhich is peeled off uhen the foam has sufficiently hardened to establish a polyurethane foam former of any desired double curvature shape uhich can embed opening frames 12 and be trimmed and shaped as required*The polyurethane former 11 is relatively flexible and it is inflated and the opening frames 12 can be propped by temporary screu adjustable props 13 acting in compression to tension the foam 11 to maintain the required shape uhile a very thin layer of high bonding, self curing, modified building material 14 is applied to the internal surface. Uhen the modified building material has hardened the temporary supporting air pressure can be reduced or removed and the screu adjustable props 13 adjusted to act in tension so that the hardened modified building material 14 is placed in compression to avoid the risk of tension cracking. To further stiffen and strengthen the building shell a second very thin layer of modified building material is applied to the internal surface to establish the required internal thickness of modified building material 14. To sanduich and protect the polyurethane foam 11 an outer layer of modified building material 15 189514 incorporating uhita silica sand and white cement is applied and when hardened a pattern of high tensile galvanised wires 16 are tensioned over the external double curvature surface to compression stress the 5 previous modified building material layers particularly around protruding shaped openings 17 as shown in Figures 6, 7 and 8. The galvanised wires are then covered with a layer of modified building material 15 incorporating white silica sand and white cement and 10 the complete external surface is finished to give sufficient modified building material 15 cover protection to the small diameter high tensile galvanised wires 16 and give the required surface finish. The surface can be further protected by a very light coloured 15 (preferably white) solution containing a film forming water soluble dispersed polymer which sets to a water impervious film at room temperature such as a white acrylic paint.

In use the present invention provides for an 20 inexpensive and simple building construction and manufacture which can be constructed in situ wherever required or partly premixed to simplify mixing on site or precast if required. The shape of the building shell construction is preferably of double curvature and 25 and sandwich construction to allow very thin layers of modified building material to be used and achieve a sufficiently stiff lightweight construction, however it is envisaged that other shapes particularly for 189514 building panels and units can be flat or of single curvature to construct or manufacture a lightweight building panel or unit.

Thus by this invention there is provided a 5 method of constructing lightweight buildings by using very thin layers of modified building material which is inexpensive and which enables a building to be built in situ or precast with a minimum of formwork, materials and labour.

Particular forms of the invention have been described by way of example and it is envisaged that modifications to and variations of the invention can take place without departing from the scope of the appended claims.

The applicant is also the inventor of New Zealand patent specification Nos. 184184, 199180 and 199181 which describe and claim methods of constructing constructional shells for a building or a roof of a structure. The use of the present 20 invention may infringe at least claim 1 of these New Zealand patent specifications . i j iyl/i •/

Claims (16)

189514 What I claim is:

1. A method of building construction and manufacture, the method comprising the steps of: establishing and controlling a lightweight per surface area relatively flexible permanent former for a building shell, panel or unit, which can support a thin layer of a settable modified building material; mo'difying a cementitious building material as herein defined by adding thereto both an aqueous solution or emulsion of film forming polymer material which sets to a water impervious film at room temperature and a fibrous reinforcing material, and mixing the materials to form a modified building material; applying the modified building material in a thin layer or layers by trowel, spray or extrusion, to at least one surface of the former and allowing the layer or layers to harden which establishes the building shell, panel or unit.

2. A method of building contruction and manufacture as claimed in claim 1 which additionally includes the step of: adding further additives to improve properties of the modified building material.

3. A method of building construction and manufacture as claimed in claim 1 or claim 2 which additionally includes the step of: applying a thin layer of modified building material to both internal and external surfaces of the permanent former which further layers can be finished smooth, textured or with exposed aggregate. 18?5f4

4. A method of building construction and manufacture as claimed in claim 3 comprising sandwiching the former which is formed from a foam plastics insulation foam between thin layers of the modified building material to reduce the differential 5 temperatures and moisture stresses in the sandwiching layers.

5. A method of building construction and manufacture as claimed in any one of the preceding claims which additionaly includes the steps of: applying a further thin layer of the modified building 10 material, over a previously hardened thin layer of modified building material and controlling the former to avoid damage to the previously hardened layer of modified building material while the further layer is applied. r

6. A method of building construction and manufacture as 15 claimed in any one of the preceding claims which includes the steps of: establishing the former from a lightweight insulation foam, with good tension properties, into a double curvature shell; 20 controlling the foam shell by temporary internal air pressure and/or by temporary props or screw adjustable props acting in compression to prop prefabricated shapes, window frames or door frames so that the shape of foam shell is maintained during the application of a first internal thin layer 25 of modified building material; and after hardening of the first layer of the modified building material removing the temporary props or adjusting the screw adjustable props to act in tension; and/or removing or reducing the internal air pressure so that If'V ^ 'J I 89514- the hardened modified building material is compression stressed to reduce the risk of subsequent tension stress damage ;• ; subsequently applying a further external layer or layers 5 to either protect and/or sandwich the foam shell with the modified building material.

7. ^ method of building construction and manufacture as claimed in claim 6 wherein the lightweight former is a rigid 10 polyurethane foam formed by spraying layers onto an inflated and/or propped elastic sheet material such as butyl rubber or nylon sheeting and trimming any surplus set foam from the former before applying the modified building material.

8. A method of building construction and manufacture as 15 claimed in any one of the preceding claims wherein the modified building material can have embedded therein or bonded thereto galvanised steel additional reinforcement or other suitable additional reinforcement such as nylon fishing net, nylon cloth or other suitable cloth. 20

9, A method of building construction and manufacture as claimed in any one of the preceding claims wherein the aqueous solution or emulsion of the film forming polymer material includes any one of a latex, svnthetic latex, acrylic material, P.V.A., water soluble epoxy material, 25 or other polymer dispersions.

10. A method of building construction and manufacture as claimed in claim 9 wherein the aqueous solution or emulson of the film forming polymer material includes a w - "la - [H w If sV 189514 latex or synthetic latex, the cementitious building material is formed from a sand or fine aggregate and cement mixture and the fibrous reinforcing is any one of an alkali resistant glass fibre, a polypropylene fibre or a nylon fibre. 5

11. A method of building construction and manufacture as claimed in any one of the preceding claims wherein the * cementitious building material contains white portland cement and white silica:; sand and the modified building 10 material is applied to external surfaces of the permanent former to reduce the absorption of heat when exposed to sunlight. '

12. A method of building construction and manufacture as claimed in any one of claims 3 to 11 when dependant on claim 3 15 wherein the cementitious material which is modified and applied to an internal surface of the former includes gypsum.

13. A method of building construction and manufacture as claimed in any one of the preceding claims wherein the dry materials are premixed and/or the liquid materials are 20 premixed to improve quality control and simplicity of mixing particularly for on site use.

14. A method of building construction and manufacture as claimed in any one of the preceding claims including quickly hardening and sealing the surface of the modified 25 building material by drying with a current of air.

15. A method of building construction and manufacture substantially as herein described with reference to the accompanying drawings. ifci ; - 2i - • Y ' -y I r ; ' \ 189514- \

16. A method of building as herein described incorporating \ the shell construction as shown in any one of Figure=4, Figure 6, Figure 7 or Figure 8 of the accompanying drawings. WILLIAM GEORGE BRAINE By His Attorneys: BALDWIN, SON & CAREY Per - 21£- M ' &'/