Patent Publication Number: US-2005115185-A1

Title: Masonry block constructions with polymeric coating

Description:
FIELD OF THE INVENTION  
      THIS INVENTION is concerned with improvements in masonry block constructions.  
     BACKGROUND OF THE INVENTION  
      The invention is concerned particularly although not exclusively with reinforced mortarless block constructions.  
      Hollow structural blocks such as masonry blocks have been successfully employed for many years in the construction of load bearing and non-load bearing walls in commercial buildings, domestic dwellings and other structures such as retaining walls, fences and the like. As used herein, the expression “masonry” block is intended to embrace all manner of structural blocks.  
      Generally speaking, masonry block walls are constructed on reinforced concrete footings or a concrete floor slab as a base. Such walls include mortared joints.  
      Depending upon wind loadings for such block walls, rigidity is conferred by the formation of integral reinforced piers wherein starter bars extend into the hollow wall cavity at spaced intervals steel reinforcing bars are inserted into the wall cavities occupied by the starter bars and fluid concrete is then poured into the wall cavities occupied by the steel reinforcing bars to form spaced, steel reinforced piers in the wall structure.  
      In cyclone rated-areas it is necessary to be able to structurally tie a roof structure through steel rods to the footings or floor slab on which the masonry walls are constructed.  
      While generally satisfactory for their intended purpose, such mortar jointed structural block wall constructions suffer a number of practical disadvantages.  
      Not only are these prior art block wall construction techniques extremely labour intensive, a high level of skill is required in block laying with mortared joints. Skilled labour is expensive and frequently difficult to obtain when required.  
      The requirement for starter bars to be accurately located in a supporting base such as footings or a raft slab combined with poured concrete steel reinforced piers at required spaced intervals adds substantially to both labour and material costs, particularly in cyclone rated areas where roof tie down means must be incorporated in the wall.  
      Although mortarless masonry blocks have been proposed to reduce the level of skilled labour required, these have not found favour in building construction due to reduced structural integrity and increased reinforcing costs as well as poor weather resistance of mortarless joints.  
      Where it is required to form integral piers, it is usually necessary to hire a concrete pumping vehicle to pump a concrete slurry into the wall cavities at spaced intervals to encapsulate the reinforcing bars. This is expensive and time consuming.  
     OBJECT OF THE INVENTION  
      It is an aim of the present invention to overcome or ameliorate at least some of the shortcomings associated with prior art structural block wall constructions.  
     SUMMARY OF THE INVENTION  
      According to one aspect of the invention there is provided a method for construction of a structural block wall, said method comprising the steps of:—
          erecting on a base a wall of mortarless structural blocks; and     applying to opposite faces of said wall a fibre reinforced polymeric coating.        

      Suitably, at least some of a base course of structural blocks are anchored to said base.  
      Preferably, said at least some of a base course of structural blocks are anchored to said base by a polymeric adhesive compound.  
      If required, the structural blocks may include one or more projections engageable, in use, with complementary one or more recesses in an adjacent structural block.  
      Preferably, said structural blocks include projections and complementary recesses on opposed faces.  
      Suitably, said blocks are self-aligning when stacked.  
      Most preferably said opposed faces comprise upper and lower faces.  
      The structural blocks may include one or more apertures extending between said upper and lower faces.  
      Suitably said fibre reinforced polymeric coating extends over a portion of said base to form a bond between said wall and said base.  
      Preferably said fibre reinforced polymeric coating extends over portions of said base on opposite sides of said walls.  
      The fibre reinforced polymeric coating may extend over a top surface of said wall.  
      If required, mounting brackets may be secured to an upper course of blocks in said wall to permit, in use, connection of a roof structure to said wall.  
      Suitably, said mounting brackets are secured to respective structural blocks by a polymeric adhesive compound.  
      If required, reveal surfaces in wall openings may have applied thereto a fibre reinforced polymeric coating.  
      Preferably, said fibre reinforced polymeric coating includes a layer of fibreglass reinforcing material.  
      The layer of fibreglass material may comprise a sheet of woven or non-woven fibreglass.  
      Suitably, said fibreglass reinforcing material is an alkaline resistant grade.  
      Preferably, said fibre reinforced polymeric coating is formed by applying a base coating of a liquid curable polymeric composition to a wall surface, positioning on said base coating a layer of fibre reinforcing material, applying to an exposed surface of said layer of fibre reinforcing material a further coating of a liquid curable polymeric composition and allowing said liquid curable polymeric composition to cure.  
      The liquid curable polymeric composition may be applied to a surface of the wall and/or the exposed surface of said layer of fibre reinforcing material by any suitable means such as spraying, trowelling, squeegee application or the like.  
      Suitably, said base coating is applied to a substantially even thickness by means of guide projections extending from opposite normally exposed faces of said structural blocks.  
      Preferably, said guide projections comprise spaced substantially parallel ribs serving, in use, to guide a screeding or trowelling device to apply said base coating to a substantially even thickness.  
      If required, a decorative coating may be applied over the fibre reinforced polymeric coating.  
      Suitably, the decorative coating comprises a polymeric mineral finish sealant. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In order that the invention may be more fully understood and put into practical effect, reference will now be made to preferred embodiments illustrated in the accompanying drawings in which:— 
       FIG. 1  shows schematically a perspective view of a structural block suitable for use with the invention;  
       FIG. 2  shows a side elevational view of the block of  FIG. 1 ;  
       FIG. 3  shows a top plan view of the block of  FIGS. 1 and 2 ;  
       FIG. 4  shows an end elevational view of the block of  FIGS. 1-3 ;  
       FIG. 5  shows a cross sectional view through a wall constructed in accordance with the invention;  
       FIG. 6  shows a partial perspective view of a finished wall structure according to the invention;  
       FIG. 7  shows one form of lintel structure;  
       FIG. 8  shows a partial cross-section through a lintel structure;  
       FIG. 9  shows a truss tie-down to a lintel;  
       FIG. 10  shows an alternative lintel configuration; and  
       FIG. 11  shows an alternative block configuration. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      In  FIGS. 1-4  there is shown a masonry block suitable for building “dry-stacked” or mortarless wall structures.  
      Masonry block  1  includes opposed side walls  2 , opposed end walls  3  and intermediate webs  4  defining apertures  5   a ,  5   b  and  5   c  extending along upright axes through block  1 .  
      On the upper face of block  1  there are formed projections  6  adapted to locate in complementary recesses  7  formed in an adjacent block. Recesses  7  are formed in the lower opposite wall portions of apertures  5   a  and  5   c  whereby a channel-like recess  8  extends over the lower face of block  1  between the lower portions  2   a ,  2   b  of opposed side walls  2 .  
      The structure of the block permits quick, accurately aligned stacking of blocks in a conventional manner wherein the blocks of one course overlap the end joints between blocks of an underlying course, the end joints being located centrally of central aperture  5   b . Part blocks (not shown) are utilised for wall ends, wall openings and joints between adjacent walls.  
       FIG. 5  shows a part cross-sectional view of a wall structure according to the invention and illustrates the method of construction according to the invention.  
      A first or base course of blocks  10  is arranged in a desired configuration on a floor slab  11  and a quantity of a polymer modified cementitious mortar  12  (available under the trade mark “Quickwall Australia”) is poured into the apertures of the blocks to anchor them to the slab  11 .  
      The wall is then completed by dry-stacking the blocks of  FIGS. 1-4  to a desired height and length.  
      A fibre reinforced polymeric coating  13  is formed on both wall surfaces by applying a first or base layer of liquid curable polymeric adhesive (also available under the trade mark “Quickwall Australia”) by spraying or trowelling. The base layer extends over regions  14 ,  15  of the slab  11 .  
      A sheet of alkaline resistant fibreglass mesh of say 100-150 gm m 2  is then applied to the wetted surfaces of the slab and the opposite wall surfaces  16 ,  17  whereby the fibreglass mesh extends continuously from slab region  14 , over outer wall surface  17 , over the top of upper block course  18 , down the inner wall surface  16  and finally terminating at the outer edge of slab region  15 . The fibre reinforced coating  13  is completed by the application of a further or top layer of the same liquid polymeric adhesive.  
      Successive sheets of fibreglass are overlapped by about 200 mm whereby the finished wall structure comprises dry stacked blocks having an integrally formed high tensile fibre reinforced polymeric skin extending from the floor slab, to which the skin is bonded, up and over the top of the wall, effectively encapsulating the wall.  
      To maximise the structural integrity and weatherproofing of the joint between the base course and the reinforced wall skin, a corner bead  13   a  of wetted fibreglass rovings, a fibreglass mesh tape or the like is positioned in the corners between the wall surface and the slab surface so that a radiussed joint is formed.  
      At spaced intervals, rafter or roof truss brackets  19  are anchored to the wall structure by stuffing a block aperture with, say, newspaper  20  and then pouring in a layer  21  of cementitious mortar of the same type used to bond the base course  10  to slab  11 . Bracket  20  is anchored in the layer  21  and protrudes through the top portion  22  of fibre reinforced layer  13 .  
       FIG. 6  shows a part perspective view of a finished wall construction in accordance with the invention.  
      The wall is constructed generally in accordance with the method steps described in relation to  FIG. 5  and as such like features employ like reference numerals where appropriate but where wall openings  25  such as a window, door or the like are concerned additional steps are required.  
      While the wall is erected very quickly by dry-stacking or the like, there are several ways to form a lintel over a door or window opening.  
      In one method, a steel angle iron can be used as a lintel support and where this is done, the course of blocks forming the lintel beam are initially tied together and to the steel angle iron with a preliminary fibreglass reinforced polymer skin  26 . Once encapsulated, the wall construction can then continue as previously described. When forming the polymeric fibre reinforced skin  27  on the wall surfaces, the regions around the window reveals  28  are also coated with the integrally formed skin  27 .  
      In an alternative lintel construction, a plurality of U-shaped blocks are supported on formwork in an end to end configuration. The central channel so formed locates steel reinforcing members and concrete is poured into the cavity to form a bond beam lintel. The outer surfaces of the lintel so formed have a preliminary fibre reinforced polymeric skin formed thereon such that when the final wall structure is coated, the lintel region incorporates a double layer of fibre reinforced polymeric material. Depending upon the wind loading for the structure, the lintel may comprise two or more courses of mortar filled lintel blocks, with or without steel reinforcing therein.  
      The inner and outer wall surfaces are then given a decorative and/or protective coating of a polymeric mineral finish (once again available under the trade mark “Quickwall Australia”). This finish includes a generally spherical aggregate having a mean diameter of about 2 mm whereby the aggregate particles act as a guide to permit a trowelled coating of substantially even 2 mm thickness controlled by the aggregate particles. This permits the use of less skilled labour in the final finishing of the wall surfaces.  
      FIGS.  7  to  10  illustrates aspects of yet another lintel construction forming part of the system according to the invention.  
      In  FIG. 7 , there is shown a block wall structure  30  with a doorway aperture  31 . Above doorway aperture  31  is a lintel member  32  in the form of a steel frame  33  with void forming cores  34  located therein.  
       FIG. 8  is an enlarged partial cross-sectional view of a top rail portion  33   a  of lintel  32  as shown in  FIG. 7 .  
      Frame  33  comprises a rolled steel U-section channel  33   a  forming a top rail to the rectangular frame and a like member  33   b  (shown in  FIG. 7 ) forming a bottom rail. Similar upright channel sections  33   c ,  33   c  of slightly narrower width are nested within the outer flanges of top and bottom rails  33   a ,  33   b  respectively and are secured thereto by a suitable fastening means such as a self-piercing rivet, a self-tapping screw, welding or the like passing through overlapping channel edge flanges. A similar upright member  33   e  is located intermediate end members  33   c ,  33   d.    
      The channel like members  33   a ,  33   b ,  33   c  and  33   d  are configured with their respective recesses facing inwardly of the frame structure  33  to locate the foam styrene void forming cores  34  therein.  
      As shown in  FIG. 8 , the lintel member  32  comprises a pair of frames  33  in side by side juxtaposition with their outer edges flush with the respective opposite faces of adjacent blocks. A top course of blocks  30   a  extends over the top of lintel member  32 .  
      As with structures previously described with reference to  FIG. 5  and  FIG. 6 , the block wall structure  30  and the lintel member  32  are coated with a glass fibre reinforced polymeric skin  35  which extends over the top of the top course of blocks  30   a  and under bottom rail  33   b  to encapsulate the blocks  30   a  and lintel member  32  where it extends across opening  31  whereby the blocks  30   a  and the lintel member  32  together function as a truss member. The outer or exposed surfaces of the wall structure and lintel member can also have applied thereto a decorative and/or protective coating  36  of a polymeric mineral finish as previously described and this, when cured, serves to further reinforce that part of the wall structure and the lintel member now functioning as a truss beam.  
       FIG. 9  shows a method of attachment of a roof truss  37  to the lintel member  32  shown in  FIG. 8 .  
      Truss  37  is simply secured to the lintel member  32  by fasteners  38  extending through angle brackets  39  into the truss  37  and the top rail portions  33   a  of frames  33  forming the lintel member  32 . As the frames  33  are subsequently mechanically tied to the wall structure, on which the lintel member rests, by the fibre reinforced polymeric skin, both roof mass and wind loadings are adequately met by this tie-down method.  
       FIG. 10  shows generally a block wall structure  4   a  according to the invention with a large doorway aperture  41 .  
      To accommodate the roof and wind loading on the lintel structure  42 , the frame structures  43  are deeper and a plurality of uprights  44  are spaced along the top and bottom rail portions  43   a ,  43   b  between end members  43   c ,  43   d . Uprights  44  are suitably pairs of rolled steel channel members secured in back to back relationship such that foam core blocks  45  are secured by inwardly facing channel edge flanges extending about the peripheral edges of each core block  45 .  
      Like the composite truss beam structure described with reference to  FIGS. 7 and 8 , the lintel structure  42 , can be engineered to suit the span by altering the height of the truss beam, the gauge of the steel channel members etc. Again, like the composite lintel structures of  FIGS. 7 and 8 , the lintel structure  42  ultimately relies upon encapsulation by the fibre reinforced polymeric skin in the region where it spans aperture  41  for its structural integrity.  
       FIG. 11  shows an alternative configuration of a masonry block  50  suitable for erection of dry-stacked or mortarless wall structures.  
      Like the block of  FIGS. 1-4 , block  50  includes opposed side walls  51 , opposed end walls  52  and intermediate webs  53  defining apertures  54 ,  55 ,  56  extending along upright axes through block  50 .  
      On the upper face of block  50  there are formed projections  57  extending partly transversely of the block and having a shape and configuration to enable the projections  57  to meet in corresponding recesses  57   a  on the lower face of a corresponding adjacent block.  
      On the opposed side wall of block  50  are raised projections  58  forming a screed guide for a first layer of liquid curable polymeric adhesive. After application of the liquid adhesive by spraying or trowelling, an initial adhesive layer of even thickness is formed over a wall surface by contact of a trowel or screed bar with the raised projections which act as a thickness guiding mechanism.  
      For masonry blocks formed by the “Besser” (Trade Mark) process, the projections  58  are suitably in the form of spaced vertically extending rib-like formations  59  having any desired spacing and any desired cross-sectional shape.  
      As shown, the rib-like formations are regularly spaced and have a smooth undulating or “corrugated” shape with channel-like recesses  60  therebetween. Alternatively, the ribs may be formed with a rectangular, part circular or a tapered V-shaped cross-section with a broad spacing therebetween.  
      For extruded clay or masonry blocks, the rib-like formations  59  will also extend parallel to each other and vertically as generally shown. For blocks made in demountable moulds, the pattern of surface projections on the side walls  51  of the blocks may be regular such as spaced circular or rectangular projections or they form an irregular pattern over the side walls  51 . All that is required is that sufficient projections of a predetermined thickness are formed over the side walls of a block to permit a trowel or screed bar to contact the projections as the trowel or screed bar moves over the surface of the block wall to form an adhesive layer of even thickness thereover. This avoids waste in excessively thick layers of adhesive and otherwise serves to ensure a generally planar surface in the finished wall structure.  
      It readily will be apparent to a person skilled in the art that the wall building method according to the invention, and structures built therefrom, have substantial advantages over prior art masonry block structures requiring steel reinforcing in core filled walls.  
      The wall structures embody all of the structural insulating and fire rating qualities of conventional masonry block structure with the additional advantage of faster erection with less skilled labour and consequent cost savings.  
      Further cost savings are obtained by avoiding the need for steel reinforcing in the wall structure and the need for concrete pumping to form the spaced steel reinforced cores as with prior art structures.  
      The high tensile fibre reinforced polymeric wall skins permits use of the structures in cyclone rated geographical regions and, in addition provide a much more weatherproof and vermin resistant structure than hitherto possible with conventional masonry finishes.  
      As an alternative to woven fibreglass reinforcing, non-woven fibreglass, woven or non-woven Kevlar, carbonfibre or synthetic fibrous mats may be used. The fibrous reinforcing may also include chopped fibres distributed throughout the polymeric coating material.  
      Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.