IL26137A - Improved cement composition and method for building constructional units and the units thus prepared - Google Patents

Description

tmtpa imsi'Dn niT»r»*m man ηντπ ' Improved cement composition and method for building constructional uuaits and the units h^s? pre ared CYRIL AUBREY R1DFARN C : 24916 This invention is for improvements in or cement .compositions for use in relating to building constructional units and has for an object the provision of a unit for use in the construction of buildings which unit is a load-bearing constructional unit having internal and external cladding suitable for weather-resistance and for decorative finishes as required, together with a low-density filling in the cavity of the constructional unit to provide for both heat and sound insulation, the unit having a low degree of combustibilit .

The dimensions of the building constructional unit will, of course, be chosen so as to be of the requisite strength in order to fulfil its function as a load-bearing unit in the structure, whether this is for a "low-rise" structure, such as a dwelling-house, or a "high-rise" structure, such as a block of flats or an office building.

The building constructional units with which the invention is concerned are formed of a cementitious mixture incorporating a reinforcing aggregate such as the conventional sand, china-clay waste and other forms of finely divided silica.

According to the invention a building constructional unit comprises a preformed cavity section of a load-bearing cement composition, having the cavity containing a cellular inorganic particulate material the particles of which are bonded together with a synthetic resin binder cured in situ.

The invention also includes such a cement composition.

Preferably the synthetic resin binder forms 5 - 35 by volume of the constituents of the mix. The composition is preferably made stronger by reinforcement with mineral reinforcing fibrous materials such as asbestos fibres and glass fibres and the constructional unit is also preferably formed with reinforcing webs extending across the cavity.

The unit may be of any appropriate cross-section, for example, rectangular, circular, H-, T-, or I- sections, and in length may be straight or curved.

It is a feature of the invention that a flame-resistant synthetic resin is incorporated into the cement composition.

Such resins which may usefully be incorporated in the cement composition are flame-resistant liquid epoxy resins, particularly the liquid epoxy resins which may be mixed with the cement in the porportions of 1 part by weight of resin to 4 of cement up to 2 parts of resin to 1 part of cement. This cement-epoxy resin mixture is then mixed with the reinforcing fibres and an appropriate amount of water containing a polyamine hardener is used to effect the necessary hydration of the cement mix; in the final product so produced, there is an inter-locking inorganic crystal system and also an organic cross-linked resin system. The use of a brominated epoxy resin constituting part or the whole of the resin used assists the flame-resistant properties of the composition, whilst the effect of the resin is to give improved moisture-resistance and greater flexibility at high Young's modulus. ar3r&e-tee-ti««^-e Cavity walls, for example, in houses and other building structures, in ref igerators ,. in ships holds and railway wagons are often filled with light-weight cellular organic materials, of a density of 1 to 2 pounds per cubic foot, such as polyurethane foam and expanded polystyrene. Such cellular materials can be rendered flame-resistant by the incorporation of flame-retarding compounds therein.

However, whilst light-weight cellular organic materials that are flame-resistant can be produced, such materials are combustible in that, if they are in continuous contact with a flame, or are maintained at temperatures above 200°C , these organic materials decompose and their thermal insulating effect is thereby lost.

The object of the third aspect of the invention is the overcoming of these disadvantages.

According to this aspect of the invention a method of forming thermal insulation material for use in a cavity or in a heat shield comprises admixing a cellular inorganic particulate material with a synthetic resin binder and curing the resin in situ, the amount of resin being sufficient to form the material into a coherent mass after such curing.

The invention also includes such a thermal insulation material when used on its own in a cavity or in a heat shield and also when used to fill the cavity of a building constructional unit as referred to above. Thus the method of forming the thermal insulation material in accordance with this third aspect of the invention coupled to the method of producing a building constructional unit according to the second aspect of the invention also forms part of the invention.

For forming the building constructional unit a multi-screw plastic extruder may be used, in which owing to the low shear stresses during operation, the generation of heat is kept to a minimum and thereby premature setting of the mix is avoided. Another advantage is that the feed take-up is easy and the forward movement of material is more positive (i.e. little if any hack-slip passes the screw flights) than in a single screw extruder because the multi-screw extruder can be regarded as a laterally extended gear wheel pump. The presence of the re sir-results in quicker extrusion. The extrusion is effected through steel dies mounted at the ends of the extruder and desirably a screen is interposed between the end of the multi-screw extruder and the die in order to produce better homogenisation of the composition. The flow in the die is streamlined to prevent excessive pressure build-up, and the screw design is such that trapped air is removed from the composition in the course of its passage through the extruder. Thus the need for deaeration of the cement before extrusion is obviated.

This is particularly desirable in cases where reinforcing fibres of asbestos and glass are used since there is a considerable degree of orientation of the reinforcing fibres during extrusion which gives rise to an increased strength in the direction of extrusion of the mix., Convenient lengths of the extruded units may be cut-off and stored in a flat position to allow hardening of the composition to take place. Accelerated hardening may be attained if the extruded section is passed through a heating zone where a temperature not exceeding about 90°C. is maintained. Alternatively, autoclave treatment as conventionally used with cement compositions may be used.

It is well-known to introduce certain water soluble colloids into cement compositions in order to give smoother mixes and to prevent de-watering, that is to say sweating out of water on standing or when the composition is submitted to pressure in, for example, compression moulding or extrusion.

Thus, according to another feature of the invention, the cement composition contains a water soluble colloid additive as a water retention agent, the additive being such as to act as an emulsifier for an epoxy a—p-©ly-«= e-a-te-i* resin in a wet cement composition and such as to combine with the epoxy &r—p^iyee^-e-r resin when the cement composition is subsequently heated for the purpose of curing. This feature of the invention thus comprises a selection from the known water retention agents of those agents the chemical composition of which is such as to give them the above properties.

The following example^ illustrative of cement compositions which may be used for producing the cavity section building constructional unit, the quantities referred to being given as parts by weight Composition 1 : - Portland cement 80 Pine sand 80 Asbestos fibre 5 Liquid epoxy resin 15 Triethylene tetramine 2.1 Dibromo cresyl glycidyl ether 3 Methyl hydroxypropyl cellulose 2 Water 34 - - 26137/2 In a further form of the invention, the building constructional units are provided with holes for the insertion, after the autoclaving process, of medium or high-tensile steel rods so as to provide post-tensional structural members such as beams, girders, columns, panel-formed shapes and the like. The holes are appropriately located and the rods are anchored in accordance with established practice, so as to provide reinforced members suitable for use as major load-bearing components in "low-rise" and "high-rise" building constructions.

Where the constructional units of the present invention are required for high buildings, provision may be made in the shaping of the units to permit them to receive a primary structural reinforcement such as steel girders of, for example, hollow box section.

In forming the thermal insulation material of the third aspect of the invention, the synthetic resin is preferably used in an amount of from 5$ upwards by volume of the final admixture.' The resin and particulate material may be simultaneously sprayed into the position which is finally to be occupied by the thermal insulation material, the two streams of material being so directed that the resin is uniformly distributed throughout the particulate material. In order to ensure that the final thermal insulation is more fully flame-resistant, it is preferred to incorporate a flame-retarding agent into the said synthetic resin.

Suitable inorganic materials are pumice stone reduced to particles of about 1mm. across, exfoliated vermiculite particles, expanded perlite particles bulking about 2 to 5 pounds per cubic foot, ceramic or earthenware microballoons of substantially unbroken skin formation and microballoons or hollow beads both made of metal.

Preferred synthetic resin binders are :- 1. liquid one-stage phenol-formaldehyde resins in which a flame-retarding composition is incorporated 2. liquid polyester resins of the unsaturated type, rendered flame-resistant by the use of hexa chloro-endomethylene tetrahydrophthalic acid as part of the acid component and cured by means of styrene or methyl methacrylate monomer or diallyl phthalate or triallyl phosphate, with the appropriate peroxy catalyst. 3. liquid epoxy resins with diamine or acid anhydride curing agent with a flame-resistant agent incorporated in the system, 4. Polyurethane resin systems based on polyethers or polyesters, with a polyisocyanate as the curing agent, with a flame-resistant agent in the system. . liquid silicone polymer, essentially polydi ethyl silicone, but with some reactive hydrogen on tho molecules so that they will cure with a catalyst such as dibutyl tin dilaurate . 6. semi-inorganic resins that are thermosettable polynuclear phenolic resins which have free phenolic groups with phospho-, boro-, phosophoboro- or phospho-nitrogen linkages between the phenolic nuclei and reacted with a formaldehyde donor such as hexamethylene tetramine or paraformaldehyde, A number of flame-retarding agents for adding to synthetic resins and polymers, are readily available. These commonly are bromine containing organic compounds that are compatible with the particular resin used.

Bonding systems for cellular inorganic particles according to the invention to be used as thermal insulating materials in cavities and as layers on one or both sides of sheets of metal, asbestos board and other incombustible materials that will comply with the following requirements preferably have several advantages. For instance, there is no substantial change in the apparent density of the bonded composition and no significant amount of volatile matter is given off as the system cures. Only the minimum amount of bonding material to give a coherent mass need be used, the compositions can be cold or heat cured and the final product is flame-resistant.

A useful bond can be obtained with as little as 5$ by volume of bonding material but if improved physical strength is required as much as 35$ by volume bonding materials in the composite mass is required (the percentag being before mixing) , but in such latter products the apparent density will be higher than when using the lower percentages of the bonding material.

In one embodiment of the invention, for filling a wall cavity, the cellular inorganic material, expanded perlite particles of about -¾■ to 1 mm diameter, is blown into the cavity in conjunction with an atomised spray of polyester resin of the type described. Both streams of blown particles are metered so that the resin component amounts to about 5 by volume of the composition and the streams are mixed so that the resin particles attach themselves to the cellular particles and form a bond between them.

Such a structure is flame-resistant and of a high degree of incombustibility because of the low resin bond content. When a higher degree of heat resistance is required a silicone polymer as described is used and for still better heat resistance, a semi-inorganic resin as described above is used.

The mixed blowing method can be used for applying coatings of resin-bonded inorganic cellular materitils. V/hen the composition is to be applied by spreading and trowelling methods the resin bond content usually needs to be somewhat higher and is about 1/3 of the volume of the total mix.

In a modification of the invention, the bonding resin systems have embodied in them foaming agents for - - the purpose of expanding the resin in the manner well-known in the art. By this means the increased density effect due to the resin bond is compensated, but the structure is physically weaker than that obtained with a non-expanding resin system.

Claims (1)

1. HAVING NOW particularly described and ascertained the nature of our said invention and in what manner the same is to be we declare that what we claim i CLAIMS A cement composition comprising hydraulic mineral fibrous and epoxy resin which is insoluble in water and is liquid at room a agent for said resin and a soluble colloidal material whieh acts as a agent in the cement composition and as an emulslfier for the epoxy resin in the water of the cement composition when the composition the epoxy resin being combinable with the water soluble colloidal material when the composition is cured by A eement composition according to in which the epoxy resin ia a epoxy A eement composition according to 1 2 which contains 5 to by weight of Baid epoxy A composition according to Claim 1 or comprising the following the quantities referred to being given as parts by Portland cement 80 Fine sand 80 fibre 5 Liquid epoxy resin 15 thylene tetramine glycidyl 3 Methyl cellulose 2 Water 34 eement composition according to 2 3 wherein the fibrous material is 14 A cement composition according to any one Claims 1 to substantially as herein A construction comprising a member of a load bearing cement composition according to Claim said member a cavity therein stantially filled with a cellular inorganic particulate material particles are bonded together by a synthetic resin binder cured in A unit to Claim having steel unit according to 7 or formed reinforcing estteading across the method of forming a building constructional unit according to any of Claims 7 to comprising extruding a cement composition according to any of Claims 1 to so as to form a cavity the unit in an autoclave and filling the with a cellular inorganic particulate material the particles of which bonded together with a synthetic resin binder cured in A method according to Claim in which the cement composition is extruded by a A method according to Claim in which the extruder is a A method according to any of Claims 10 to in which the cement composition is in accordance with any of Claims 1 to A method according to any of Claims 10 to 13 in which the unit is extruded with holes in which steel reinforcing rods are inserted after the autoclaving of A method of forming a building constructional unit according to any one of Claims 10 to substantially as herein A building constructional unit according to any one of Claims 7 to substantially as herein For the Applicants insufficientOCRQuality