Abstract:
The invention relates to an insulating and structural masonry block comprising a sealed envelope of parallelepipic shape in which layers of light, dry aggregate are superposed, separated by a geotextile band placed in accordion like layers. Within the envelope is drawn a pressure lower than ambient pressure.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of fabricated materials for building construction. More precisely, the invention concerns a masonry block suitable for residential and building construction. 
     BACKGROUND OF THE INVENTION 
     Various technologies are known in the field of building construction. In the housing sector as in the construction of small apartment complexes and other buildings, masonry technologies include the use of portable prefabricated blocks such as cinder blocks and bricks. This conventional technology requires only modest material outlay and is well suited to small construction companies. The use of such materials does not require particular professional training other than that of a mason. Furthermore, the well established performance of such materials reassures the end user, generally conservative by nature. 
     Masonry blocks must generally possess several characteristics such as: 
     a light weight in order to be portable, 
     a high crush resistance, 
     low thermal conductivity, 
     mechanical and chemical compatibility with the other materials used in building construction, in particular plasters and surface coatings, 
     a pleasing surface appearance after finishing, 
     good fire resistance, 
     and the lowest possible cost per square foot or square meter of finished wall in the final structure. 
     The masonry block placed at the base of a wall must resist the permanent load of the building as well as service loads of any elevated floors. It is generally considered that the block must support, without crushing, a compression load of some 435 PSI (3 MPa) while in service in a small building having a ground floor and three elevated floors. 
     Generally known techniques for the fabrication of masonry blocks associate structural materials of which the least expensive are generally rock based, with insulating materials such as air or any material having gaseous inclusions, in order to obtain a composite material sufficiently insulating and structurally sound. Of the two components one must have binding properties in order to form a support structure. The other may generally be dispersed in the first, as the fabrication of a homogeneous medium on a structural level, having the two materials intimately bound can be a difficult procedure. 
     The most common masonry blocks, cinder blocks and bricks, most often have vertical or horizontal cavities the purpose of which is to reduce the weight and cost of the block as well as to reduce the thermal conductivity of the wall in which the block will be incorporated. Moreover, modern thermal insulation requirements make necessary the coating of the structure comprised of such blocks with one or more layers of insulating material, resulting in considerably higher cost per square foot of finished wall. 
     Various other solutions have been proposed such as building walls of families of materials of a vastly different conception such as baked cellular concretes or concrete lightened by the inclusion of polystyrene balls. Such materials, in their dry state, have low thermal conductivities, but it has been noted that their thermal conductivity increases considerably with the percentage of water contained in the concrete. To avoid water intrusion into walls, such materials must be coated with humidity inhibiters, increasing building costs without necessarily precluding the penetration of humidity into the wall in the long term. 
     It is of course possible to use wood in the construction of small buildings up to several stories high, wood having a low thermal conductivity and a high resistance to compression. However, the primary drawback in the use of wood is its high cost. 
     The object of the present invention is to provide a masonry block element which overcomes the drawbacks cited in prior art elements, and which is at the same time portable, insulating, structurally sound, chemically compatible with the other materials used in building construction such as plasters and surface coatings, which has a pleasing finished appearance, good fire resistance, and whose cost is relatively modest. 
     SUMMARY OF THE INVENTION 
     The above object is obtained according to the invention by the fact that the masonry block, particularly suitable for residential and building construction, includes; 
     an air and water tight envelope delimiting an inner cavity of generally right parallelepipedic shape, and a predetermined quantity of dry granular material completely filling the inner cavity; 
     wherein the interstitial spaces between the grains of the granular material contain dry gas at a pressure lower than ambient pressure. 
     By virtue of the foregoing structure, the block maintains its original parallelepipedic form. 
     Indeed, the low pressure existing within the sealed envelope increases the friction and cohesion of the grains of the material which fills the inner cavity of the envelope. The friction between the grains of aggregate make the assembly of the envelope and granular material under vacuum capable of resisting mechanical load. 
     Advantageously, the block further comprises continuous fibers or fibers sufficiently long to be assimulated to continuous fibers, strong in tension and placed within the predetermined quantity of granular material. 
     The continuous, long fibers are preferably provided in horizontal layers. The horizontal layers are formed of plies of a geotextile band resistant in tension and deformation, arranged in superposed layers in the cavity, and the granular material includes a plurality of superposed layers separated from one another by the layers of geotextile band. The block may also comprise, in addition to the geotextile band, long continuous fibers dispersed at random in the superposed layers of granular material. The granular material is advantageously a light aggregate. 
     The presence of the geotextile band resistant in tension and deformation, placed in an accordion like fashion in superposed plies between successive layers of aggregate such that each horizontal layer of aggregate is enveloped by a U-shaped envelope of geotextile plies, prevents the masonry block from undergoing deformation due to vertical stresses consequent with permanent loading of the final structure and with service loading. The vertical stresses consequent with loading bourne by the block bring about horizontal stresses due to the angle of contact between the grains of aggregate. These horizontal stresses result in tension forces resisted by the geotextile band. 
     The aggregate chosen should have a thermal conductivity at the most equal to 0.833 BTU-in/ft 2  h° F. (0.12 W/m° C.) and a compression strength at least equal to 435 PSI (3 MPa). 
     The aggregate as well as the air or gas filling the interstitial spaces between grains being dry, the block has a low thermal conductivity which is maintained due to the hermetically sealed envelope. 
     In order to reduce the horizontal stresses due to vertical stresses applied on the block and consequent with loading, the aggregate is made rough by crushing. This has the further advantage of reducing the average size of the interstitial spaces between grains of aggregate, thereby reducing the convection of the air or other gas within the macroporous material. 
     The aggregate used is expanded schistous or argillitic material, such base materials being very common in nature and moderately priced. 
     the geotextile band used is preferably fiberglass. Such fiberglass materials offer high tensile strength, without excessive deformation, and have good fire resistance as well as low thermal conductivity. 
     The proportion between the thickness of the geotextile band and the thickness of an aggregate layer is of the order of 0.2%. The volumetric proportion of geotextile band with respect to the volume of aggregate affords the masonry block a compression strength of the order of 435 PSI (3 MPa) without excessive deformation and without substantially altering the thermal conductivity of the block. 
     In order to maintain the low thermal conductivity of the masonry block, the envelope must be sealed against water vapour and sufficiently air and gas tight. The envelope is preferably formed from a heat fusing composite band comprising an aluminum film disposed between a polyester film and a polyethylene film, and firmly adherent to both. These three materials form a single and unique composite band allowing the envelope to resist tearing, while providing air tightness and heat fusibility. Furthermore, the polyester film placed toward the outside of the envelope allows the block to receive joint sealants and surface coverings without special preparation. 
     In order to reduce the thermal conductivity of the block, the dry air within the inner cavity can be replaced with carbon dioxide. 
     The present invention further concerns a method for fabricating a masonry block as has been described. 
     According to this method, light mineral aggregate is sorted, crushed and dried to produce a product of desired density. A sealed parallelepipedic bag is formed from a complex air and water tight band, the bag having five sides and an upwardly facing opening as well as a cover sheet for covering the opening. The bag is placed in a suitable mold having five internal faces corresponding to the sides of the bag and the end of a geotextile band having a width slightly smaller than the width of the bag is placed in the bag against the bottom side thereof. A first layer of aggregate is poured into the bag while the mold is vibrated, after which a first ply of the geotextile band is folded over the first layer of aggregate. Another layer of aggregate is then poured onto the first ply of the geotextile band while the mold is again vibrated and a second ply of the geotextile band is folded in the opposite direction of the first ply. A desired number of successive layers of aggregate are poured into the bag in a similar way while vibrating the mold with interposition of a textile band ply between the successive layers, the last layer of aggregate being covered with a ply of geotextile band. Once the parallelepipedic bag has been filled in this way the geotextile band is sectioned off, the cover sheet for the bag is placed over the last ply of geotextile band and the cover sheet is sealed by soldering the edges thereof to the upper edges of the side walls of the bag, leaving an orifice at one corner of the bag so as to form a right parallelepipedic envelope containing layers of aggregate separated by plies of geotextile band. The interior of the envelope and thus the masonry block is depressurized by drawing out air or other gases contained in the envelope through the orifice. Finally the orifice is closed by soldering. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages and characteristics of the invention will become apparent through the following description in which reference is had to the annexed drawings in which: 
     FIG. 1 shows a perspective and partially broken view of a masonry block according to the invention, 
     FIG. 2 is a transversal sectional view of the masonry block, 
     FIG. 3 is a detailed sectional view of the envelope, 
     FIG. 4 is a curve showing the deformation of the masonry block as a function of the force of loading, 
     FIG. 5 is a perspective view of a mandrel for fabricating the parallelepipedic envelope or bag with its cover sheet, 
     FIG. 6 is a horizontal sectional view of the envelope taken along the plane VI--VI of FIG. 5, and 
     FIG. 7 is a schematic view shown as a vertical section of an installation for fabricating a masonry block according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As can be seen in the drawings, the masonry block 1 comprises a sealed outer envelope 2 having the shape of a rectangular parallelepiped delimiting a cavity 3 in which layers 4a, 4b, 4c, of light mineral aggregate 5 are placed. The superposed layers 4a, 4b, 4c, are separated from one another and from the lower and upper walls of the envelope 2 by a tension and deformation resistant geotextile band 6. The geotextile band 6 has horizontal portions 6a, 6b, 6c, 6d parallel to the upper 7a and lower 7b faces of the masonry block 1, as well as vertical portions 8a, 8b and 8c alternatively contacting the inner surfaces 9a of the front 10a and rear 10b sides of the envelope 2, and respectively connecting the horizontal portions 6a and 6b, 6b and 6c, 6c and 6d of the geotextile band. The interstitial spaces 11 present between the grains of aggregate 5 within the layers 4a, 4b and 4c are filled with air or other dry gas at a pressure lower than the ambient pressure outside of the masonry block envelope 2. 
     The dimensions of the masonry block 1 are such that the weight of the block is not excessive, making the block easily workable for a mason. The height of the block may be for instance 8 inches (20 cm), its width and depth about 1 foot (30 cm). The weight of the block 1 is thus of the order of 4.5 pounds (10 kg), depending upon the density of the aggregate 5. 
     The aggregate 5, the envelope 2 and the geotextile band 6 are selected firstly, so that the masonry block 1 may have a compression strength of 435 PSI (3 MPa), substantially higher than the real compression to which the block is to be subjected, and secondly, so that the wall composed of such blocks will have a thermal conductivity lower than or equal to 0.833 BTU-in/ft 2  h° F. (0.12 W/m° C.). A large amount of empirical data exists on the thermal conductivity of light aggregate in bulk, such as expanded schistous and argillitic materials. Such materials are conventional components in light concretes and their cost is modest as they have not undergone particular refining processes. Compression strengths may also be established for such materials by crush testing. 
     The following table indicates some generally available numerical values for absolute density, bulk density, compression strength S c  and thermal conductivity K for some light, dry mineral aggregates. 
     
         __________________________________________________________________________TYPE AND DIAMETER                   KOF THE GRAINS        ABSOLUTE               BULK   S.sub.c  (BTU-in-ft.sup.2 h °F.(in.(cm))    DENSITY               DENSITY                      (PSI(MPa))                               (W/m °C.))__________________________________________________________________________Schistfine         2.09   1.02   2100                          (14.5)                               --course       1.74   1.0Clayfine         1.98   1.1    960  (6.6)                               --course       1.65   0.9Slatefine         2.20   1.2    650  (4.5)                               --course       1.29   0.65Perlite      0.86   0.15   90   (0.63)                               --Vermiculite  1.35   0.16   11.6                           (0.08)Slag         1.13   0.5    360  (2.5)                               --expandedClay(&#34;Argi 16&#34;)1.6 (4) to 4 (10) min        0.78   0.48   1130                           (7.8)                               --1.6 (4) to 8 (20) min        0.70   0.41   770  (5.3)                               --4 (10) to 10 (25) min        0.61   0.35   480  (3.3)                               --Schist(&#34;Leca&#34;)1.2 (3) to 3.2 (8) min        0.77   0.62   640  (4.4)                               --1.2 (3) to 6.3 (16) min        0.78   0.44   450  (3.1)                               --4 (10) to 10 (25) min        0.67   0.36   360   (2.5)                               --Slag         1.58   0.85   625  (4.3)                               --(&#34;Galex&#34;)1.2 (3) to 3.2 (8) minSchist       0.65   0.35   215/                           (1.5/2)                               0.625                                   (0.09)                      290        1/1.3  0.55/  1015/                           (7/9)                               1.0 (0.14)               0.7    1300__________________________________________________________________________ 
    
     The preceeding table would seem to indicate that there exists a general correlation between the light, dry aggregate bulk density, its compression strength and its thermal conductivity. The light aggregate 5 is selected from among the schists and clays having a density slightly lower than 25 lb/ft 3  (400 kg/m 3 ), corresponding to a thermal conductivity less than or equal to 0.7 BTU-in/ft 2  h° F. (0.10 W/m° C.) and a compression strength equal to or greater than 435 PSI (3 MPa). This compression strength corresponds to the crush limit of the bulk aggregate. 
     Between the geotextile plies, for example 6b and 6c, the stresses due to the weight of the building bourne by the wall in which the masonry block 1 is incorporated, diffuse as a function of the internal contact angle between the grains of aggregate 5. This angle should be as high as possible in order to reduce the deformation of the block and to avoid crushing the grains due to high stress concentrations. 
     In order to attain a suitable contact angle, rough aggregate 5 may be used, such as schistous or advantageously argillitic materials, or alternatively course aggregate may be crushed in order to obtain a product the grains of which have a maximum diameter of the order 0.8 in. (20 mm). Moreover, it is generally known to specialists in the field of paving materials that the shape and grain of aggregates play an important role in the resistance of the aggregate material to loading and consequently in the resistance to deformation. Furthermore the crushing offers the advantage of reducing the average size of the interstitial spaces 11 within the bulk and thus reduces the air convection in the macroporosity, improving the insulating ability of the block 1. 
     The envelope 2 must be sealed against water vapour and sufficiently air tight so that the block 1 maintains its low thermal conductivity as can be seen in FIG. 3. The envelope 2 is formed from a composite band 12 comprising an aluminum film 13 disposed between a polyester film 14 and a polyethylene film 15. The polyester film placed toward the outside of the block affords tear resistance, the aluminum film providing sealing, and the polyethylene film permitting soldering of the edges of the envelope during the fabrication of the masonry block 1. 
     It is very important that the envelope 2 be sealed against water vapour, for as is well known, the thermal conductivity of a material increases with its water content. 
     The geotextile band 6 is formed of as rigid a material as possible, in order to avoid strain and deformation of masonry block 1, chemical compatibility of the light aggregate, fire resistance, and low thermal conductivity, as its horizontal position makes it a potential heat transfer path between the internal face 10a and the external face 10b of the wall. 
     The following table gives the characteristics of certain organic and mineral fibers which may be used for the fabrication of the geotextile band 6. 
     
         __________________________________________________________________________ TENSILE        YOUNG&#39;S               ELONGATION STRENGTH        MODULUS               AT (KPSI  (MPSI  FRACTURE       FIRENAME  (MPa)) (GPa)) %        DENSITY                              RESISTANCE__________________________________________________________________________KELVAR 400 (2,760)        17.4           (120)               1.9      1.44  chars at29                                 800° F.                              (425° C.)GLASS 250 (1,750)        10  (69)               2.5      2.54  melts atE                                  2,300° F.                              (1,260° C.)CARBON 385 (2,650)        32.9           (229)               1.0      1.7   flame                              resistantSTEEL 375 (2,600)        29 (200)               2.0      7.85  loss of                              stiffness                              upon                              heating__________________________________________________________________________ 
    
     For the time being Kevlar and Carbon fiber are impractical due to their relatively high cost, and between steel and glass, the latter is generally preferred due to its low thermal conductivity. 
     The layers of geotextile 6a, 6b, 6c, 6d resist horizontal stresses consequent with the weight of the building structure; the thickness of geotextile corresponding to 0.2% of the thickness of the aggregate layers has been calculated, the geotextile band 6 being stretched at strain levels of the order of 72.5 kPSI (500 MPa) necessary for resolving the lateral compression of the granular mass. With such a percentage of geotextile density with respect to the density of the aggregate, the influence of the fiberglass network on the thermal conductivity of the block as a whole is negligible. 
     FIG. 4 shows an approximative curve of the vertical yield or compression of the masonry block 1. As shown in this figure, the first portion 16 of the curve corresponds to small loading forces under the influence of which the masonry block 1 undergoes only slight yield. This portion 16 of the curve corresponds to forces of between 0 and some 435 PSI (3 MPa). The next portion of the curve indicates a considerable plasticity of the block, due to crushing of the light aggregate 5 at load levels between 435 PSI (3 MPa) and about 580 PSI (4 MPa), and to the rearrangement of the aggregate under such compression as well as to sliding of the geotextile 6. A wall incorporating the masonry blocks 1 can therefore readily adapt to zones of high stress concentration such as for beam support as well as in case of load changes for instance during earthquakes. Under loads at levels higher than 580 PSI (4 MPa) the masonry block 1 becomes stiff once more due to the rigidity of the geotextile band 6, up to extreme stress levels and the eventual fracture of the geotextile band 6. 
     Some years after initial installation, or due to holes formed in the surface of the wall, the pressure within the block rises until it reaches equilibrium with the ambient atmospheric pressure. The behaviour of the block in vertical compression is thus slightly altered as is indicated in FIG. 4 by the dashed portion 17 of the curve. 
     The masonry block 1 is fabricated as follows. First the aggregate 5 received in the masonry block fabrication installation is sifted or screened and dried, after having been crushed if necessary, in order to form a dry product of desired density. 
     The envelope 2 of the masonry block 1 is pieced into the shape of a right parallelepiped from a complex, air and water tight heat fusible band. The pieced parallelepipedic envelope comprises four rectangular faces corresponding respectively to a lateral face 18a, a front face 10a, a second lateral face 18b and a rear face 10b, and two rectangular faces, an upper face 7a and lower face 7b on either side of the space enveloped by the first four faces of the envelope. 
     A bag 19 is then formed from the pieced parallelepipedic envelope by the use of a mandrel 20 of which the upper portion has the shape and dimensions of the cavity 3 of the envelope 2 of the masonry block 1, the upper face 22 of the mandrel 20 covering the face of the pieced parallelepiped corresponding to the inner face 7b of the envelope 2, and the four side faces of the pieced parallelepiped covering the four lateral faces of the upper portion 21 of the mandrel 20 respectively. 
     As can be seen in FIGS. 5 and 6 the faces of the pieced parallelepiped corresponding to the faces 18a and 10b of the envelope 2 comprise extensions on their ends 23a and 23b of which one, 23a is placed beneath the lateral face 18a while the other, 23b folds onto the rear face 10b of the bag 19. In a similar way the free edges of the faces of the pieced parallelepiped corresponding to the upper face 7a and the lower face 7b of the envelope 2 are provided respectively with extensions 24 and 25. The extension 25 is folded onto the edges of the three adjacent lateral faces 18a, 10b and 18b of the bag 19 and sealed to these faces by soldering, while the extensions 23a and 23b are also sealed to faces 18a and 10b of the bag 19, so as to form a sealed bag with a cover sheet 26 comprising the sixth face of the pieced parallelepiped corresponding to the upper face 7a of the envelope 2 and by the extension 24, the coversheet 26 being provided to cover the opening 27 of the envelope. 
     The parallelepipedic bag 19 is placed in a mold 28 comprising a parallelepipedic cavity 29 having the dimensions of the masonry block 1 and an upper opening, such that the face 7b of the bag 19 covers the bottom of the mold 28, the faces 18a, 10a, 18b and 10b of the bag 19 covering the internal lateral faces of the mold 28 and the cover sheet 26 being placed outside the mold 28. The five faces 7b, 18a, 10a, 18b and 10b of the bag 19 are held against the walls of the mold 28 by channels 30 formed in the mold wall 28, ending in a cavity 29 and connected to a vacuum pump (not shown). 
     Above the cavity 29 of the mold 28 is provided an aggregate distributor 31 which undergoes a back and forth movement between the front 10a and rear 10b vertical walls of the bag 19 placed in the mold 28. Between the upper face 22 of the mold 28 and the lower end 33 of the distributor 31 is provided a reel 34 of geotextile band 6 which is mounted moveable above the mold 28 between two outermost positions located beyond the vertical planes of the front 10a and rear 10b walls of the bag 19 in the mold 28. 
     The mold 28 rests on a base 36 with elastic elements such as springs 35 placed therebetween. The width of the geotextile band 6 is slightly smaller than the distance separating the lateral faces 18a and 18b of the bag 19. 
     The end 6a of the geotextile band 6 is placed in the bottom of the bag 19 so as to cover the bottom wall 7b of the bag by moving the reel 34 from the right to the left in FIG. 7. A first layer 4a of aggregate 5 is poured by the aggregate distributor 31 onto the end 6a of the geotextile band, and a first ply 6b is folded onto the first layer 4a of aggregate 5 by movement of the reel 34 from left to right. 
     A second layer 4b is poured onto the geotextile band, and another ply 6c of the geotextile band is formed by movement of the reel 34 from right to left. Successive layers 4c of aggregate are poured with interposition of a ply of geotextile between layers until the last layer 4c of aggregate is poured and covered with a last ply 6d of geotextile band. 
     During the pouring of aggregate 5 from the distributor 31, the mold 28 is vibrated in order to afford compaction of the various layers 4a, 4b, 4c formed in the bag 19 within the mold 28, by means of a vibrating device (not shown). 
     When the bag 19 is completely filled with layers 4a, 4b, 4c separated by plies 6b and 6c, the geotextile band is sectioned off transversally by a knife or blade (not shown), and the cover sheet 26 is placed over the upper ply 6d of geotextile band and the extension 24 of the cover sheet 26 is sealed onto the upper border 37 of the lateral walls 18a, 18b and the rear wall 10b of the filled bag 19. An orifice is left in an upper corner of the envelope 2. 
     The interior of the masonry block is depressurized by drawing out the air or gas contained in the envelope through the orifice. Finally, the orifice is closed by soldering. 
     The depth of the mold is slightly inferior to the height of the bag 19 such that the edge or extension 24 of the cover sheet 26 may be folded against the upper edge 37 of the lateral walls 10b, 18a, 18b of the bag 19 while in the mold. 
     The sealing by soldering the edges 23a, 23b, 24 and 25 onto the corresponding walls of the bag 19 is carried out by a known method such as by heat fusion or ultrasonic soldering. 
     It is to be noted that the method which has just been described yields a masonry block 1 which is ready for use, while most other conventional masonry elements require an ageing period resulting in considerable additional cost. It should also be noted that no deferred deformations occur, whereas light cement based materials exhibit shrinking upon curing due to the softness of the additive material. 
     The masonry block is used in the following manner. A block 8&#34;×12&#34;×12&#34; (20 cm×30 cm×30 cm) has a volume of approximately 0.67 ft 3  (18 l ) and weighs between 15.5 and 20 pounds (7 to 10 kg). The blocks 1 are layed and maintained in place with adhesive mortar. The roughness of the surface of the block 1 is dependent on the size of the course aggregate. The roughness is however somewhat corrected and to a certain extend smoothed by the skin formed by the envelope 2. The outer film 14 of the envelope 2 may include fibers in order to give the envelope an improved tear resistance and adherence to the mortar. The block 1 is placed in the wall such that the band portions 8a, 8b, 8c connecting the superposed plies, for example 6b and 6c of the geotextile band 6, are vertical and located adjacent the faces of the wall. 
     The mason can lay a certain number of blocks in order to complete the main part of the construction, followed by special laying work such as beam and joyce supports, frames and anchors. The technique used for thermal paths may be same as that generally used in constructions with cellular, autoclaved concrete blocks. 
     In certain types of construction, such as appartments having wooden or metal frames, in which the masonry blocks serve essentially as a filler material and thus are subjected to small loads, it is possible to use the block without the geotextile band 6 which is thus comprised of a sealed envelope 2 filled with a predetermined quantity of aggregate 5. 
     High tensile strength continuous fibers, or fibers sufficiently long to be assimilated to continuous fibers, may be disposed at random in the aggregate 5 as the aggregate is being poured into the bag 19. Such continuous or long fibers improve the cohesion between the grains of aggregate under vacuum in the external envelope 2 and are preferably glass fibers, the masonry block 1 containing approximately 0.2% of glass fibers by volume. 
     The masonry block reinforced by the geotextile band 6 laid in plies in the external envelope 2 may also include continuous or long glass fibers disposed in the layers 4a, 4b and 4c of aggregate 5.