William CRAWFORD / Peter
[ Got Hemp ? ]
Telephone: 0845 680 1908
Concrete Canvas Ltd.
Unit 3, Block A22,
CF37 5SP, UK
Concrete Canvas (CC) is a flexible, concrete impregnated fabric
that hardens when hydrated to form a thin, durable, water proof
and fire resistant concrete layer. CC allows concrete construction
without the need for plant or mixing equipment. Simply position
the Canvas and just add water.
CC consists of a 3-dimensional fibre matrix containing a specially
formulated dry concrete mix. A PVC backing on one surface of the
material ensures the material is water proof. The material can be
hydrated either by spraying or by being fully immersed in water.
Once set, the fibres reinforce the concrete, preventing crack
propagation and providing a safe plastic failure mode.
CC is available in 3 thicknesses: CC5, CC8 and CC13, which are 5,
8 and 13mm thick respectively. CC is used in a variety of civil
infrastructure applications, such as ditch lining, slope
protection and capping secondary containment bunds.
Compared to traditional concrete solutions, CC is faster, easier
and, more cost effective to install and has the additional benefit
of reducing the environmental impact of concreting works by up to
Concrete Canvas Shelters
Concrete Canvas Shelters (CCS) are rapidly deployable hardened
shelters that require only water and air for construction.
CCS have two major advantages over conventional tented shelter:
- Operational: CCS enable a hardened structure from day one of an
operation. They provide much better environmental protection,
increased security and vastly improved medical capability.
- Financial: CCS have a design life of over 10 years, whereas
tents wear out rapidly and must then be replaced. CCS are a one
stop solution, saving effort and cost over the lifetime of medium
to long term operations.
The key to CCS is the use of inflation to create a surface that is
optimised for compressive loading. This allows thin walled
concrete structures to be formed which are both robust and
CCS are constructed from Concrete Canvas, bonded to the outer
surface of a plastic inner which forms a Nissen-Hut shaped
structure once inflated.
- Packaging -- CCS are supplied in polyethylene, airtight, water
proof, rot proof sacks within ISPM15 heat treated timber/ply panel
- Modularity -- CCS structures are designed as part of a modular
system; units can be docked together to create arrays of
structures to suit operational requirements.
- Inflatable Inner -- Each CCS has a flame retardant reinforced
polyethylene inflatable inner with internal hanging tabs (maximum
load 20kg/tab). Disinfecting with high chlorine concentration will
not damage the inner.
- Requirements for deployment -- Both CCS variants can be deployed
by 2 people. A CCS50 will require a vehicle or winch to aid with
the unfolding of the shelter prior to inflation. Each shelter is
provided with the ground pegs required for inflation.
CCS are deployed in four stages; Delivery, Inflation, Hydration
The invention provides a knitted spacer fabric having a tightly
knitted bottom layer, a more loosely knitted upper layer and pile
yarns extending across the space between the lower and upper
faces. Settable material, e.g. cement, is introduced into the
space between the upper and lower faces and can be caused to set
by the addition of a liquid, e.g. water. Until set, the fabric is
flexible and can be shaped but after the material in space has
set, the fabric is rigid and can be used as a structural element
in a wide range of situations, e.g. to form a cover of a
prefabricated shelter, a track-way for vehicles, pedestrians or
animals; a shelter by applying the fabric to a framework; formwork
for casting concrete; barriers, e.g. to line tunnels; to repair
structures, e.g. roofs; to form floors or damp proof structures;
to reinforce earth structures, e.g. river banks; to provide flood
defences; or to repair existing pipes, including buried water
pipes or to construct new pipes.
The present invention relates to a fabric impregnated with a
material that, when mixed with a liquid, will set. Such fabric has
WO 2005/124063 describes a shelter that includes a ground sheet
and a cover; the space between the ground sheet and the cover can
be inflated by pumping air into the space to raise the cover and
form the shelter. The cover is made of a fabric that has been
impregnated with cement; the fabric may be a type of felt known as
“wadding”, which is a loose non-woven fabric. Immediately before
the interior space is inflated, the cover is wetted with water, so
that, after inflation, the cement in the cover sets and forms a
rigid shell that acts as a self-supporting roof for the shelter,
which is particularly useful in providing temporary accommodation
in emergency areas.
Spacer fabric is a known material and comprises a top face layer,
a bottom face layer and pile yarns extending between the two
faces. It is commercially available, for example from Culzean
fabrics of Kilmarnock, United Kingdom; Scott and Fyfe of Tayport,
Fife, United Kingdom and W Bull and Son Ltd (Baltex) of Ilkestone,
United Kingdom. It is used to manufacture garments and other
articles where the fabric must be thick but light and/or where the
fabric should include an air gap, for example in cycle helmets,
boot soles, fireman's clothing, body armour; mattresses and
bandages; climate-control seating in vehicles. The pile yarns are
self-supporting to space the two faces apart by a desired distance
and to resist crushing forces, i.e. forces acting perpendicular to
the plane of the faces. The thickness of the spacer fabric is
determined during manufacture by choosing an appropriate length
for the pile yarn. The yarns used for forming the two faces can be
the same or different from each other and from the pile yarns so
that it is possible to choose the properties of the two face
layers and of the pile to provide the desired properties. Among
the fibres employed are polyethylene, polyester, Nomex, Kevlar,
polyamide and microfibre (Nomex and Kevlar are trademarks).
JP-A-04327272 discloses a woven or knitted lattice-like fibre
sheet to which is applied a composition containing all the
components of a thermosetting resin, and containing a large
proportion of plasticizer. The resin composition is cured to
provide a sheet having high flexibility, high strength, low
elongation and good shape stability. Because of the high amount of
plasticizer in the resin, the resin is flexible and so allows the
sheet to be wound up on a roll.
U.S. Pat. No. 5,461,885 describes a hardenable substrate that is
used for forming casts and splints for immobilising patients'
limbs and joints that have been fractured, broken or strained. The
substrate is formed of a fabric having two spaced-apart webs; a
hardenable liquid composition is drawn into the space between the
webs by capillary action and allowed to set. The liquid
composition may be a resin or a liquid dispersion of plaster of
Paris. The hardenable liquid sets in situ shortly after it has
been added to the fabric.
US 2003/0077965 discloses the use of a spacer fabric in a resin
infusion process or a resin transfer moulding process in which
liquid resin is introduced into the fabric and allowed to
DISCLOSURE OF INVENTION
According to the present invention, there is provided a fabric
a first face;
a second face separated from the first face by space;
self-supporting pile yarns extending between the first and second
faces that maintain the first and second face in a spaced-apart
a solid powder material, located in the space between the first
and second faces, which material is capable of setting to a rigid
or semi-rigid solid mass on the addition of a liquid or on
exposure to radiation, e.g. UV radiation.
The settable powder material may be settable on the addition of
water and in one embodiment may comprise cement, optionally
together with sand or fine aggregates and/or plasticizers and
other additives found in cement or concrete compositions, that
will set to solid cement or concrete on the addition of water or a
water-based solution. Alternatively, the settable material may be
a UV settable material or one component of a multi-part curable
resin that cures when two or more liquid components are mixed
together, e.g. an epoxy resin system.
The amount of settable material in the space in the fabric is
preferably such that, particularly when the material has set, it
occupies substantially the whole of the space between the first
and second faces.
The settable powder material can be easily loaded into the fabric
and, in the case that it is hardened by the addition of a liquid,
the liquid can rapidly penetrate between the powder particles to
form a composition that will set over time.
The settable powder material and/or the liquid can include
additives e.g. flexiblizers, foaming agents, fillers,
reinforcement materials etc. that are known in the art in
connection with the settable materials concerned.
The first and the second faces may be formed of yarns and the
yarns of the two faces may be the same as each other or different.
The settable material is preferably added to the space through
pores formed in the first face of the fabric, in which case, the
first face will have pores that are large enough to allow the
material to be placed in the fabric. However, after the material
has been placed in the fabric, it is desirable to prevent it
falling out through the first face and several techniques can be
applied to achieve this aim.
Firstly, a further layer may be bonded onto the first face after
the settable material has been introduced into the fabric. This
further layer may be permeable to the liquid used to cause the
settable material to set and, if the permeability is brought about
by the presence of pores in the bonded layer, such pores should be
sufficiently small to prevent the settable materials from falling
through the first face material. Any suitable layer may be used to
seal the first face, e.g. a PVC layer, which can be secured to the
upper face by a variety of techniques, for example by thermal
welding or by means of an adhesive. Alternatively the layer may be
formed of a curable paste which is subsequently cured, e.g. using
heat. Such a layer is preferably thin, typically less than or
equal to 0.5 mm. The layer may be flexible to maintain the
flexibility of the overall fabric prior to setting. Additional
layers may be applied to the sealing layer by a variety of
techniques, for example by thermal or chemical welding or by means
of an adhesive. One such layer could by way of example be a
damp-proof layer for applications, which could find application in
the construction industry or tunnelling.
Secondly, the first face may be made of, or include, an
elastomeric yarn so that the upper face can be stretched to
enlarge pores within the face to allow the settable material to be
introduced into the fabric but, once the material has been added
to the fabric, the stretching forces can be released, to close the
pores to a size such that the settable material cannot readily
escape through the first face.
Thirdly, the first face can be treated after the settable material
has been introduced into the fabric to close the pores of the
first face. For example, it is possible to treat the first face by
applying a sealing material such as an adhesive or to subject the
first face to solvent treatment to fully or partially close the
pores. In one example, a PVC paste may be applied (for example
using a scraper) to the first face and cured for example by heat,
e,g. by means of radiative heaters or hot air blowers.
Fourthly, the first face can be knitted from a fibres that will
shrink when heated, thereby enabling the settable materials to be
introduced through a knit having pores sufficiently open to allow
the particles to pass through; after the particles of the settable
material have been introduced into the fabric, the first face can
be heated, e.g. using heated air, and the heat will cause the
fibres to contract sufficiently to close the pores enough as to
substantially prevent the particles of settable materials from
escaping. Such fibres that shrink when heated include the majority
of thermoplastic fibres for example polypropylene. The method of
heating fibres to cause shrinkage described above may also have an
advantage in compacting the settable material especially if such
heat shrinkable fibres are also used to form the second face
and/or the pile yarns.
The second face is preferably substantially impervious to the
settable material so that the settable material does not fall
through the second face when added through the first face.
However, in order to assist in the penetration of liquid into the
space, the second face is preferably porous to the liquid applied
to set the material. Thus, the second face preferably includes
pores having a size allowing the liquid to penetrate but not
allowing material particles to pass through. If nevertheless the
second sheet has pores that are too large to retain the material
within the space, it is possible to prevent the material falling
out through the second face using any of the measures discussed
As already mentioned, the second and in some cases the first face
of the fabric may be such that the liquid can penetrate into the
space through the faces to contact the settable powder material
within the space. Such liquid penetration can take place either by
including pores within the face (as discussed above) and/or by
making the yarns of the first and second faces of a material that
can be wetted by the liquid concerned and therefore the liquid
will be wicked through the first and second faces to come into
contact with the settable material within the fabric. Furthermore,
capillary action between fibres within the first and second faces
can assist in providing liquid to the settable material.
Suitable materials for use in forming the first and second faces
polypropylene, which is the preferred material to use when the
settable material includes cement, as it has excellent chemical
resistance to alkaline conditions;
coated glass fibres, which can provide reinforcement to the set
PVC fibres, which have the advantage of being relatively easy to
bond using chemical or thermal bonding.
A mixture of fibres can be used.
The length of the pile yarns controls the spacing between the
first and second faces and, as described above, they must be
self-supporting. They should be sufficiently stiff, i.e. they
should be sufficiently resistant to bending under forces tending
to crush the fabric, to maintain the spacing between the faces
when the settable material has been loaded onto the first face to
feed the material into the fabric. The density of the pile yarns,
i.e. the number of yarns per unit area, is also an important
factor in resisting crushing forces while the material particles
are being added and so maintaining the spacing between the faces
and in restricting the movement of the material particles once
they are trapped between the upper and lower layers.
It is important, in accordance with the present invention, that
the pile yarn does not divide the space within the fabric into
individual small closed compartments since such a division would
allow cracks to propagate within the fabric and so reduce the
strength of the fabric once the material has set.
The particle size of the settable material must be sufficient to
allow it to be introduced into the fabric but it should not be so
fine as to fall out of pores in the first and/or second faces.
Especially preferred are high alumina cements since they provide
shorter setting times than other cements.
The first and second faces and the pile yarn are preferably part
of a spacer fabric, which can be formed with pores in the first
and second faces by the knitting process used to make it. The
second face is preferably more tightly knitted than the first face
so that the pores in the second face are smaller than in the first
face to allow the settable powder material to be introduced into
the space through the relatively large pores in the first face and
prevent the material falling out of the fabric through the second
The fabric of the present has the advantage that it can be
manufactured and caused to set at will any time later by the
addition of the liquid, e.g. water. The fabric can therefore be
made at one location, transported to another location, where it is
caused to set by the addition of the liquid, which can be supplied
locally, thereby reducing the bulk that must be transported. The
fabric impregnated with the solid powder will still be flexible
and can be folded or rolled up for transport.
The fabric of the present application has many applications.
Firstly, it can be used to form the cover of a prefabricated
shelter as described in WO 2005/124063. However, it has wider
applications and, for example, can be used:
to form a track-way for vehicles, pedestrians or animals;
to form a shelter by applying the fabric to a framework;
to make formwork for casting concrete;
to form barriers, e.g. to line tunnels;
to repair or reinforce structures, e.g. roofs;
to form floors or damp proof structures;
to reinforce earth structures, e.g. river banks and unstable
to provide flood defences;
to repair existing pipes, including buried water pipes or to
construct new pipes;
to fireproof elements of new or existing structures e.g. as a
fireproof covering or lining for chimneys;
to form a hard surface, reduce dust hazards and contain fuel
spills for aircraft e.g. helicopter landing sites and runways;
to reinforce sandbag structures and protect them from ultra violet
degradation and damage from the elements such as wind and ultra
to line ground works and prevent the leaching of chemical
contaminants eg. for land fill or secondary fuel containment
to form a waterproof lining for the containment of water e.g.
pond, canal lining and water storage or septic tanks;
to form permanent awnings or roof structures;
to form artistic or decorative forms, or
to form hulls and superstructure of floating vessels such as boats
If the settable material is set by the addition of water, the
water can be added deliberately or the fabric can be put in a
place where it will come into contact with water, e.g. in a
watercourse or outside where it can absorb rain. For example, it
is possible to bury the fabric in damp earth and allow it to
absorb water from the earth, thereby causing the settable material
Once the material has set, the pile yarns also provide
reinforcement to the set material and substantially increase its
A substantial advantage of the fabric is that the pile yarns and
the fibres of the first and second faces provide reinforcement to
the material once it has set and accordingly increase the physical
properties of the set material, as discussed more extensively
There is theoretically no limit to the thickness of the fabric,
although it will generally be limited by the manufacturing
techniques used to produce it. A typical thickness would be
between 2 and 70 mm, e.g. from 2 to 40 mm, and typically between 4
and 30 mm, e.g. from 4 to 20 mm. One important consideration
limiting the thickness of the material is the ability of the
liquid to penetrate through the interior of the settable material
before the outer portions of the settable material is set. A
further limitation on the thickness comes from the increased
weight of the fabric with increased thickness and if it is too
thick, the faces may not be able to support the weight of the
settable material within the fabric.
BRIEF DESCRIPTION OF DRAWINGS
There will now be described, by way of example only, a
fabric material in accordance with the present invention, by
reference to the accompanying drawings in which:
FIG. 1 is a cross sectional view through a spacer fabric;
FIG. 2 is a diagrammatic illustration of the fabric; and
FIG. 3 is a graph showing the strength of the fabric under
DETAILED DESCRIPTION OF THE BEST MODE FOR PUTTING THE
INVENTION INTO OPERATION
Referring to the accompanying drawings, FIG. 1 shows a knitted
spacer fabric having a tightly knitted bottom face layer 10, a
more loosely knitted upper face layer 12 and pile yarns 14
extending across the space 16 between the lower and upper face
layers 10, 12. The spacer fabric is made of knitted polyethylene
and is commercially available from Scott & Fyfe as 5 mm spacer
Settable material, e.g. cement, is introduced into the fabric
through pores 20 in the open-knit upper face layer 12. The pores
20 arise through the knitting process during manufacture of the
spacer fabric. The cement can be placed on the spacer fabric and
will fall through pores 20 into space 16. The penetration through
the pores 20 can be assisted through vibration. It is preferred
that the whole of the space 16 is filled with cement in this way.
Vibration also has the advantage of settling the cement within the
space 16 to prevent voids or air pockets being formed.
Additionally, the settable material can be drawn into space 16 by
resting the spacer fabric on a porous surface and applying suction
through the porous surface to form a pressure drop across the
spacer fabric, which assists in the compaction of the settable
material within the spacer fabric and reduces the instances and
size of residual voids and air pockets. Additionally, compaction
of the settable material within the space 16 may be further
increased by vibration of a heavy plate resting on the spacer
fabric containing the settable material.
The bottom face 10 has a relatively tight knitted structure and
the size of the pores in the bottom face are smaller than in the
upper face layer such that the pores are sufficiently small to
prevent substantial amounts of the cement from falling out.
After the material has been introduced into the space 16, the
upper face layer 12 is sealed by the application of a thin coat of
PVC paste which is then cured by heating the surface.
Water can penetrate into the fabric through the pores in the
bottom face 10; hydration of the cement is aided by the pile yarns
14, which can wick water into the interior of the fabric.
The fabric including the settable material within the space 16 is
flexible and can be formed to shape prior to the introduction of
liquid to set the material within the space.
The long fibres 18, together with the shorter fibres in the
fabric, provide reinforcement to the material, when set and
prevent crack propagation.
Three test pieces of fabric in accordance with the present
invention having a surface area of 725 mm<2 >were produced
by introducing high alumina cement into a spacer fabric, the
spacer fabric was a polyethylene knitted fabric manufactured by
Scott and Fyfe being 5 mm thick. The fabric was then sprayed with
water and allowed to set for 4 days. The test pieces were then
subjected to the following test: the test pieces were each placed
in an Instron—5584-52536 Universal Materials Testing Machine
having a movable anvil that can apply compressive forces to the
test piece. Each test pieces was loaded so that the anvil acts
perpendicularly to the knitted faces. A load cell measures the
compressive load and the displacement of the anvil. The
compressive load was progressively increased until the test piece
failed and the load exerted on the test piece and the displacement
of the anvil at failure were logged by a computer connected to the
machine. The procedure was repeated four times using separate
The results are shown in FIG. 2, from which can be seen that the
four test pieces of fabric material in accordance with the present
invention failed at a consistently high compressive load and that
once initial failure had occurred, when cracking could be observed
in the samples, the samples did not fail catastrophically but
continued to support a consistently high compressive load as the
displacement was increased progressively.
Other Patents :
Quick-setting and rapid-hardening cement matrix for concrete
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