GB2469272A

GB2469272A - Slotted building block

Info

Publication number: GB2469272A
Application number: GB0905927A
Authority: GB
Inventors: Liam Clear; Hamish Corbett
Original assignee: Wembley Innovation Ltd
Current assignee: Wembley Innovation Ltd
Priority date: 2009-04-06
Filing date: 2009-04-06
Publication date: 2010-10-13
Anticipated expiration: 2029-04-06
Also published as: GB0905927D0; GB2469272B

Abstract

A cementitious block 10 comprises an aperture 12 opening into a bed joint face 14, 16 of the block, the aperture cross-section at the bed joint face being elongate and having a width dimension that allows mortar or like joint forming material 20, 24 to be squeezed up into the aperture as the block is laid or to be squeezed down into the aperture as a layer 22 of the joint forming material is applied to the upper face of the block in use and substantially without separating from the layer. Thus, the aperture provides an increased surface area available for chemical bonding between the block and the jointing material. The material 20, 24 which is squeezed up or down into the aperture 12 also cures to form a mechanical key between the layer of joint forming material and the block. Because the amount of material squeezed down into the aperture is limited, no special skill is needed to spread a layer 22 of the joint forming material such as mortar on top of the block when forming a bed joint. The aperture may be a straight or curved slot. Ties (Fig.7) for co-operation with the apertures in strengthening bed joints are also provided, the ties may have laterally extending portions for support at a bed joint.

Description

BLOCK

Field of the Invention

This invention relates to blocks made of concrete or similar cementitious materials, for use in building and construction, referred to in the following as "cement blocks".

Background of the Invention

Bricks made from fired clay have been known for millennia. They are nowadays mostly produced to more-or-less standard sizes, which vary slightly in different regions, e.g. between the USA, Australia, South Africa, continental Europe or in the UK. Other materials are now also used to form bricks, such as calcium silicate or concrete. The various sizes of brick have in common that they are of a weight and dimensions that can easily be handled by a bricklayer. Due to their relatively high density and consequent high transport costs, bricks tend to be made and used fairly locally. Some bricks are solid, but to reduce the amount of clay used to make them, many bricks have a "frog" pressed into the unfired clay, or are formed with non-penetrating holes to form a cellular structure, or with through-going holes, typically formed in an extruded clay billet, before it is cut up into individual bricks. Such apertures and indentations provide the additional benefit of increasing the available surface area to make a chemical bond with the mortar or other jointing material in which the bricks are laid. The apertures and indentations will also be at least partly filled with the jointing material to provide a mechanical key.

Cement blocks are less dense than fired clay bricks and can therefore be made in larger sizes that are still capable of being handled by the bricklayer, and which reduce the amount of labour required to form a given wall area. Block sizes are many and various, but are typically made to co-ordinate with brick sizes, e.g. 100 x 215 x 440 mm, 140 x 215 x 440 mm, to give a co-ordinating size of 225 x 450mm; or 215 x 290 x 440 mm, to give a co-ordinating size of 300 x 450 mm, in all these cases allowing for 10 mm mortar joints. (These block sizes are compatible with the UK standard brick size of 215 x 102.5 x 65 mm). Foamed cement can be used to reduce the weight of the blocks and improve thermal insulation properties. For the same reasons, cement blocks are often hollow, typically with a pair of vertical, through-going holes, separated by a central web. The holes occupy a substantial proportion of the block horizontal cross-section. Although detrimental to thermal insulation, hollow blocks of this kind can be back filled with concrete. Where necessary, steel reinforcement can be inserted through the aligned hollow block interiors prior to pouring the concrete, e.g. at corners or at the edges of openings for windows or doors. Such blocks can be regarded as permanent formwork for the concrete filling. Skill is needed to spread the mortar or other bed joint material without too much dropping into the hollow block interiors, where it is wasted, can weaken the concrete backfill, or can interfere with the insulation properties of the wall if the intention is to leave the hollow interiors unfilled. The large voids of unfiled hollow concrete blocks provide a reduced interface area which weakens the bed joints rather than providing an increased surface area for chemical bonding and a mechanical key.

Large areas of blockwork, whether hollow or solid, suffer from shrinkage and cracking e.g. as the mortar dries out, or due to thermal cycling. The blockwork can be subdivided into smaller areas by expansion joints, but these provide a discontinuity which can weaken the wall. Columns or beams may therefore have to be incorporated to ensure adequate strength.

Suitable detailing and good workmanship is needed to tie the adjacent panels together or to the beams/columns and to ensure airtightness and correct fire, thermal and acoustic insulation performance. The expansion joints can also detract from the aesthetic appearance of the wall. The bed joints can be reinforced with wire or expanded metal mesh, but as with expansion joints, this adds to costs and requires additional supervision to ensure that construction is according to plan.

An aim of the present invention is to provide an alternative means of enhancing the strength of blockwork bed joints, for example so as to reduce, distribute and control problems of shrinkage cracking over greater surface areas, enabling large, crack free blockwork panels to be constructed, as well as improving the shear strength capacity at the bed joint interfaces.

Another aim in preferred embodiments is to provide a strong light weight block that is easy to grip to enable improved manual handling.

Summary of the Invention

Accordingly, the present invention provides a cementitious block comprising an aperture opening into a bed joint face of the block, the aperture cross-section at the bed joint face being elongate and having a width dimension that allows mortar or like joint forming material to be squeezed up into the aperture as the block is laid or to be squeezed down into the aperture as a layer of the joint forming material is applied to the upper face of the block in use and substantially without separating from the layer. Thus, the aperture provides an increased surface area available for chemical bonding between the block and the jointing material. The material which is squeezed up or down into the aperture also cures to form a mechanical key between the layer of joint forming material and the block. Because the amount of material squeezed down into the aperture is limited, no special skill is needed to spread a layer of the joint forming material such as mortar on top of the block when forming abed joint.

Preferably the aperture extends through the block so as to open into opposite faces of the block. Such apertures enhance the strength of the bed joints both above and below the block. They can also be formed as the block is cast or moulded, rather than having to press or otherwise form at least one aperture into one of the faces of the block after the main block moulding operation has been completed. Because the amount of joint forming material squeezed down into the aperture is limited by its narrow width, a major portion of the aperture remains vacant and the bed joint strength is enhanced with only a modest increase in the amount of joint forming material required.

The aperture cross-section at the bed joint face preferably has a width less than approximately 20mm, more preferably less than approximately 15mm, most preferably about 10mm; although the optimum width will depend to some extent on the plasticity of the joint forming material. 10mm has been found to work well with standard mortar mixes. The optimum joint cross-sectional width can be readily determined for other jointing materials, providing sufficient penetration down into the aperture, without leading to separation of substantial quantities of the joint forming material from the layer spread on top of the block.

The width of the aperture cross-section at the bed joint face is preferably greater than about 5mm, to ensure adequate penetration of the joint forming material.

Because the apertures are relatively narrow, they will not interfere with the operation of fasteners and fixings such as expansion bolts, plug-and-screw fixings and frame fixers, even when the hole drilled into the block to receive the fastener/fixing penetrates wholly or partly into the aperture. It is therefore unnecessary to use special cavity fasteners with the blocks as described.

The aperture cross-section may be substantially straight and symmetrical, e.g. rectangular or oval; or it may be curved. A plurality of such apertures may be provided in the block, to further enhance the bed joint strength. The apertures may have the same or different cross- sectional shapes. Preferably at least one aperture is arranged with the long axis of its cross-section at the bed joint face arranged generally transverse to the width of the block. In this orientation, the nodules or ridges ofjointing material keyed and chemically bonded within the apertures tend to stop any cracks which may have developed between the layer of joint forming material and the block bed joint faces from propagating further along the bed joint.

Optionally, the blocks can be used together with one or more ties for linking adjacent courses together. The tie may have a first end insertable in a generally vertical aperture in a block in a first course and a second end insertable in an aperture in a block in an adjacent course. The tie may have a laterally extending portion between the ends, by which it may be supported on a bed joint surface between the courses as a block wall is constructed, with a lower end of the tie inserted in a block aperture and an upper end of the tie projecting freely upwardly for reception in the aperture of a block in the adjacent course as it is laid. The ends of the tie may have a generally elongate transverse cross-section, for cooperation with block apertures of slot-like form.

The laterally extending portion may be a tab or tang struck out from the material of the tie; or it may comprise a component inserted transversely through the tie; or it may comprise at least one component secured to a side of the tie. Yet alternatively, the laterally extending portion may comprise an offset formed in the tie. Where the apertures are positioned in the blocks so that they do not vertically correspond when the blocks are laid in stretcher bond (e.g. one aperture being positioned substantially midway between two apertures in the adjacent course) the offset in the tie corresponds to the offset between the apertures in adjacent courses, so that the blocks may be laid in stretcher bond with ties inserted between adjacent courses.

The tie may comprise tabs or tangs projecting from the ends insertable in the block aperture.

These may resiliently engage a wall of the aperture. Preferably the tabs or tangs are angled rearwardly and outwardly in the insertion direction of the end of the tie to which they are attached, so that they tend to bind in and resist withdrawal from the aperture into which they are inserted.

The above and further preferred features and advantages of the invention will be described below with reference to illustrative embodiments shown in the drawings.

Brief Description of the Drawings

Figure 1 is a plan view of a first cement block embodying the invention; Figure 2 is a cross-sectional view on line u-u in Figure 1; Figure 3 corresponds to Figure 2, but shows the block bedded into joint forming material above and below; Figures 4, 5 and 6 are plan views of other blocks embodying the invention, and Figures 7 and 8 are respective side and front views of a tie for linking blocks in adjacent courses together.

Description of the Preferred Embodiments

The block 10 shown in Figures 1 and 2 has a nominal with of 140mm, a nominal length of 440mm and a nominal depth of 215mm; although other sizes will be readily apparent, as dictated by particular applications. The block has six vertically extending, through-going apertures 12 formed in it. The apertures 12 are of elongate, rectangular, transverse cross-section, i.e. elongate and rectangular in section planes parallel to the block bed joint faces 14, 16. The apertures are therefore of this shape as they open into the block bed joint faces 14, 16. The long axes of the aperture cross-sections at the bed joint faces 14, 16 are arranged generally transverse to the width of the block. The apertures are positioned so that they do not come into register with each other in adjacent courses when a number of courses of blocks are laid in stretcher bond. This helps with the squeezing of the bond forming material up into the apertures 12, although it is not essential. Adequate squeezing of bonding material can still occur if the apertures are aligned end to end in adjacent courses, again due to the restricted aperture cross-sectional width. The apertures also allow insertion of ties that are used to link blocks together, e.g. as further described below.

End faces 15 of the block 10 are rebated at 17 to provide an enlarged surface area for increased chemical bonding and mechanical keying with joint forming material filling the perpends between adjacent blocks. As shown, the rebates have a flat bottom surface running parallel to the block end faces 15, and flat sides at right angles to the bottom surface, and therefore parallel to the block front and back faces. The illustrated rebates are therefore generally rectangular in horizontal cross-section. However other shapes will also serve to enhance the surface area available for chemical bonding, and to provide a mechanical key, at the perpend joints. The rebates 17 also provide an increased area to accommodate generally vertically extending reinforcing rods or brackets and projecting edges 19 which provide easily gripped "handles" for controlled manual handling.

As shown in Figure 3, as the block 10 is pressed into the layer 18 of uncured joint forming material below, some of this material is squeezed up into the lower ends of the apertures 12, forming nodules, ridges or stitch joint 20 which chemically bond on curing and mechanically key within the apertures 12. Similarly, as the next layer of uncured jointing material 22 is spread on top of the block 10, some of this material is squeezed down into the apertures 12 to form nodules or ridges 24, which likewise bond and key within the apertures 12. The narrow width of the apertures 12 prevents excessive quantities of the joint forming material from dropping into them, so that the jointing material is easily spread to form the bed joint layer 22. The central portions of the apertures 12 thus remain vacant of joint forming material.

The blocks shown in Figures 4 to 6 are similar to those described above, except for the shape of the aperture cross-sections in the planes parallel to the block bed joint faces, and their orientation and distribution across those faces. The apertures shown in Figure 4 have a mixture of elongate cross-sections 26 arranged with their long axes transverse to the width of the block 10, and other apertures of a similar cross-sectional shape 28, but with their long axes arranged longitudinally of the block 10. The aperture cross-section shapes shown in Figure 5 are a mixture of elongate, transversely extending rectangular 26, as shown in Figure 4, and X-shaped 30. The aperture cross-section shapes shown in Figure 6 are shallow 5-shaped, arranged in two groups 32 extending generally transversely of the block, and in a group 34 extending generally longitudinally of the block. It will be readily appreciated that any or all of the various cross-sectional shapes shown in the drawings can be used in other permutations, combinations and orientations not illustrated, including uniform groupings of all the same kind of cross section. Other cross sectional shapes, again not illustrated, will also be suitable for forming the desired ridges and nodules of joint forming material at the aperture ends. The apertures need not extend all the way through the block. Such apertures may be provided at one face of the block only, or in two sets at opposite bed joint faces of the block respectively.

Figures 7 and 8 show a tie 36 formed from a strip of material such as a suitable metal.

Suitable metals include for example stainless steel or zinc coated mild steel. The tie has a lower end 38 of elongate transverse cross-section for insertion into a generally vertically extending, slot-like aperture in a course of structural building blocks already laid. The tie has an upper end 40 of similar form to the lower end 38, which when the lower end is inserted in an aperture as just described, projects upwardly for reception in an aperture in the next course of blocks as they are being laid. The cross-sectional shape of the tie ends 38, 40 is adapted to conform to the cross-sectional shape and axial orientation of the block apertures with which it is to be used, e.g. adapted to (but not limited to) use with the block aperture shapes shown in Figures 1-6. The tie has a laterally extending portion 44 by which it is supported on a bed joint surface as the blocks are being laid. The laterally extending portion may be a tag or tang struck out from the material of the tie 36, or a component inserted transversely through a hole formed at a suitable location in the tie, or components attached to one or both side faces of the tie for supporting it in the desired position extending between and into adjacent courses of blocks. However, as shown, the laterally extending portion comprises an offset substantially mid-way between the ends 38, 40. The block apertures (not shown) are positioned such that when the blocks are laid in stretcher bond, the ends of the apertures at each bed joint are out of register with each other, an aperture end in one course e.g. lying substantially mid-way between the ends of two apertures in the adjacent course.

The offset 44 corresponds to this offset between aperture ends so that the ties 36 can be inserted so as to extend into and between adjacent courses of blocks in stretcher bond, so as to strengthen the bed joints. Without the reinforcing ties, the bed joints tend to be weaker than the perpend joints, as there is no interlock between the blocks along the bed joints; whereas the blocks do interlock with each other between the perpend joints. Use of the ties as described provides interlock between the bed joints too.

To allow the ties to grip the sides of the apertures into which they are inserted, the ends 38, are provided with tabs or tangs 42 struck out from the material of the tie 38. The tabs or tangs extend outwardly and rearwardly in the tie insertion direction, so that the ends of the tie are relatively easy to insert into the block apertures, but tend to bind in the apertures so as to prevent ready withdrawal.

Blocks of the present invention in preferred embodiments provide some or all of the following benefits over standard cement blocks: a. Lighter b. Stronger c. Easier to grip d. Enanced transverse and longitudinal shear capacity.

e. Prevents excessive contraction and expansion.

f. Can be used without wire reinforcement.

g. Have the ability to allow construction of walls with increased length and height.

h. Transportation savings.

i. Can accommodate all fastenings and fixings.

j. Has acoustic, fire and aesthetic advantages.

k. Construction Design Management compliant (can weigh less than 20kg, e.g. 18kg) 1. Allow ready use of bed joint reinforcing ties.

Claims

CLAIMS1. A cementitious block comprising an aperture opening into a bed joint face of the block, the aperture cross-section at the bed joint face being elongate and having a width dimension that allows mortar or like joint forming material o be squeezed up into the aperture as the block is laid or to be squeezed down into the aperture as a layer of the joint forming material is applied to the upper face of the block in use and substantially without separating from the layer.
2. A cementitious block as defined in claim 1, in which the apertures are dimensioned to allow insertion of an elongate tie so that the block is securable to a further block in an adjacent course by means of the tie.
3. A cementitious block as defined in claim 1 or 2, in which the aperture extends through the block so as to open into opposite faces of the block.
4. A cementitious block as defined in claim 1, 2, or 3 in which the aperture cross-section at the bed joint face has a width less than approximately 20mm, preferably less than approximately 15mm, most preferably about 10mm.
5. A cementitious block as defined in any preceding claim in which the width of the aperture cross-section at the bed joint face is greater than about 5mm.
6. A cementitious block as defined in any preceding claim in which the aperture cross-section at the bed joint face is substantially straight and symmetrical.
7. A cementitious block as defined in any preceding claim in which the aperture cross-section at the bed joint face is curved.
8. A cementitious block as defined in any preceding claim, comprising a plurality of such apertures.
9. A cementitious block as defined in any preceding claim in which at least one aperture is arranged with the long axis of its cross-section at the bed joint face arranged generally transverse to the width of the block.
10. A structure or a system of components for forming a structure, comprising a plurality of cementitious blocks as defined in any preceding claim and a tie having a first end insertable in the aperture in a said block in one course and a second end insertable in another said block in an adjacent course.
11. A structure or system as defined in claim 10, comprising a plurality of the ties.
12. A tie for use with generally vertically apertured structural building blocks, comprising a first end insertable in the aperture in a block in a first course and a second end insertable in the aperture in a block in an adjacent course; the tie having a laterally extending portion between the ends, by which it may be supported on a bed joint surface between the courses as a block wall is constructed, with a lower end of the tie inserted in a block aperture in the first course and an upper end of the tie projecting freely upwardly for reception in the aperture of a block in the adjacent course as it is laid.
13. A tie as defined in claim 12, or a structure or system of components as defined in claim 10 or 11, wherein the laterally extending portion comprises a tab or tang struck out from the material of the tie; or comprises a component inserted transversely through the tie; or comprises at least one component secured to a side of the tie, or comprises an offset formed in the tie.
14. A tie as defined in claim 12 or 13, or a structure or system of components as defined in claim 10, 11 or 13, in which the tie comprises tabs or tangs projecting from the ends insertable in the block aperture.
15. A tie or structure or system of components as defined in claim 14, in which the tabs or tangs are angled rearwardly and outwardly in the insertion direction of the end of the tie to which they are attached, so that they tend to bind in and resist withdrawal from the aperture into which they are inserted.
16. A cementitious block substantially as described with reference to or as shown in the drawings.