Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
Moulded concrete units have been put to differ-
ent uses because of their relative economical character.
Of particular interest are concrete units used as
security bar.riers for roads or as retaining walls on
bridges or overpasses, supporting columns for bridges,
steps, balconies, building beams and columns, septic
tanks, park benches and tables, burial vaults and the
like. Unfortunately, such concrete units have a
tendency to deteriorate when used in climates subject to
cyclical freezing and thawiny such as roads which are
frequently sprayed with chemicals such as calcium
chloride ~o cause melting of ice formed on the roads and
also deterioration due to aggressive attack of numerous
chemical agents such as acids, sulphates and other mate-
rials which are deleterious to Portland cement concrete.
In order to overcome such deterioration due to
the elements such as freezing and thawing and to contact
with chemicals, it has been proposed to protect the
exposed surfaces of concrete moulded units with a
variety of plastic resinous components. Such a method
for coating a concrete moulded unit has been proposed in
U.S.P. 3,619,457, W. Chandler, inventor, where a mould,
coated with. a parting agent coating, is coated with a
plastic resinous component. There is then applied to
the plastic resinous component an adhesive bond.ing
coating and, before the complet~ curing of the adhesive
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bonding coating, a concrete rnix is poured into the mould
whereby a chemical bond is established betw~en the
adhesive bonding coating and the cement mix whi].e curing.
Unfortunately, since there is always a certain
amount of retraction (shrinkage~ of the cement mi~ upon
setting, there is less than adequate bond be-tween the
adhesive coating w.ith the walls of the moulded units
which are not horizontal, the concrete mix and the
plastic resinous coating so that such moulded units are
not suitable for their intended purposes. A further
disadvantage of the Chandler procedure is that all units
must be moulded within the plant so that transportation
of the larger and heavier moulded units is required from
the moulding plant to the site of use. A further disad-
vantage of the Chandler procedure is that the curing of
the adhesive resinous bonding coating and of the con-
crete must take place at the same time. Finally, it has
been found that the Chandler procedure is not suitable
when vertical, inclined or curved walls are present
since the adhesive resinous bonding coating has a
tendency to run along the vertical walls in the moulding
frame and as a result there is a lack of adhesive
resinous bonding coating,resulting in th~ absence of
adequate bonding between the inner concrete layer and
the outer plastic resinous coating~
It would therefore appear desirable if a
method could be devised which would resolve the
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~2~
-- 3 ~
drawbacks of the above Chandler procedure relating to an
inadequate bond between the outer plastic resinous
coating and the inner concrete layer.
It would also appear desirable if a way could
be devised whereby moulds of resinous components could
be made in a moulding plant and then transported, when
large units are required, ~o the site where concrete can
be poured into the moulds, thus avoiding the drawbacks
of transporting large and heavy moulded concrete units.
10 SUMMARY OF T~E INVENTION
In accordance with the present invention,
there is provided a moulded shell unit comprising an
outer layer of cured epoxy resin having its correspond-
ing inner fac~ bonded to a layer of aggregates embedded
in the cured epoxy resinO
In a further aspect of the present invention,
there is provided a rigid moulded shell unit comprising
an outer layer of cured epoxy resin having a layer of
aggregates partially embedded in the inner face of the
cured epoxy resin and partially embedded in a layer of
cured fiber reinforced concrete.
Also in accordance with the present invention
the cement concrete can be poured into any of the
moulded shell units of the present invention and af~er
the concrete is cured there is provided a moulded
concrete unit having part of its outside surface pro-
tected with a rigid, cured epoxy resin shell.
The cured epoxy shell units comprising an
outer layer of cured epoxy resln and an inner layer of
aggregates embedded therein are suitable for receiving
Portland cemen~ concrete to provide epoxy resin moulded
units which can be manufactured in a concrete manu-
facturing plant and the units can then be readily trans-
ported for use to any site.
On the other hand, when the moulded units are
very large and too heavy to transport if filled with
concrete, i~ is preferable to transport the large
moulded units of the present invention to the site of
use. In this case, the shell units comprise an outer
layer of cured epoxy resin, an intermediate layer of
aggregates partially embedded in the inner surface of
the cured epoxy resin layer and partially embedded in
the inner face of a cured layer of cured fiber-
reinforced concrete thus providing a shell unit having
sufficient rigidity for transportation to the re~uired
site. Such reinforced units are suitable for repairing
concrete structural units such as security barriers for
roads, retaining walls on bridges, overpasses, support-
ing columns for bridges or for constructing building
beams or columns on site. The repair of damaged
concrete structural units involves removal o~ the
damaged concrete, cleaning of any exposed reinforcing
steel when present, placing the shell unit over
concrete structural unit and causing it to adhere
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5 -
thereto. This can be done by means of a bonding agent
when the concrete structural unit is small or by pouring
fluid concrete b~tween the shell unit and the concrete
structural unit whereby curing of the aaded concrete
will bind the shell unit to the structural unit.
The present invention also comprises a method
for moulding a shell unit which comprises applying an
epoxy resin mix to the inner wall or walls of a shaping
mould, and before the cuxing is complete, spraying or
coating the epoxy resin layer with a layer of aggre-
gates. When the ~hickness of the epoxy layer is suf-
ficient to provide sufficient rigidity, the shell can be
readily removed from the mould. On the other hand, when
the epoxy layer is so thin that the shell cannot be
removed from the mould, it is then preferable to pour
the concrete in the shell unit and after curing of the
concrete the whole unit is then removed from the shell
thus providing a moulded concrete shape having at least
one face coated and thus protected wi$h an epoxy resin.
Also, in a further aspect of the present invention, the
layer of aggregate partially embedded in the cured epoxy
resin layer can be sprayed with a thin layer of fiber
reinforced concrete which will provide the required
rigidity and after allowing the reinforced concrete to
set, the moulded shsll is removed from the shaping mould
and can then be transported to a building site so that
concxete may be poured in the moulded shell, thus
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avoiding the transportation of large moulded epoxy resin
coated concrete units.
In a further aspect, the mould~ after the
spraying or coating of the aggregate and after the epoxy
resin is cured, can be filled at any time with cement
concrete and, after allowing the unit to set/ the epoxy
coated concrete unit is removed from the shaping mould
giving a finished concrete unit having at least one face
coated with an epoxy resin and the unit can then be
transported ~o a building site for installation.
Furthermore, it has been found that the method
of the present invention is sui~able for moulding shapes
having a vertical, inclined, horizontal or curved
surface, thus providing a moulded cement concrete unit
of the desired shape and coated ox protected with an
outer rigid epoxy resin shell.
DETAILED DESCRIPTION OF THE INVENTION
-
In its broadest aspect, the moulded shell
units of the present invention are prepared by a method
2Q which comprises applying a layer of epoxy resin to at
least one inner surface of a shaping mould which is non~
bonding to epoxy resins, coating the uncured epoxy resin
surface with a layer of aggregates and, after allowing
the epoxy resin to cure, removing the moulded epoxy
resin shell having aggregates embedded in its inner
surface. The moulded shPll can then be used to prepare
finished concrete products having part of the outside
surfaces coated with epoxy resin by pouring concrete in
the shell and allowing the concrete to cure whereby said
cured concrete will be mechanically bonded with the
aygregates which are partially embedded in the cured
epoxy resin.
Where it is desired to mould larger unit, it
is necessary to provide a moulded shell having suffi-
cient rigidity for transportation to the site and suf--
ficient resistance to be used as a mould. Accordingly,
the method comprises the further step of spraying onto
the inner aggregate layer of the moulded shell previ-
ously obtained with a lay~r of fiber reinforced concrete
which mechanically binds with the layer of aggregates
and, after curing said fiber reinforced concrete layer~
the moulded shell unit, after removal from the shaping
mould, has sufficient strength and rigidity to be trans-
ported to a desired site where concrete will be poured
into the unit.
THE MOULDING SURFACE
An important feature of the present invention
is the selection of a moulding surface or a mould which
is non-bonding to epoxy resins thus avoiding the use of
a parting layer required to be applied to the moulding
surface or mould in prior art procedures.
In accordance with -the present invention, the
shaping mould is made from a material which is itself
non-bonding to epoxy resins~ Thus, the shaping mould
-- 8
can be a moulded shape of polyethylene, polypropylene or
Teflon and the like. If desired, patterns can be
present in the original mould so that moulds which are
non-bonding to epoxy resins will be obtained with corre~
sponding patterns or designs thus eventually providing
epoxy resin shellshaving the corresponding patterns or
designs on their outer surface.
It is also possible to use an ordinary mould,
such as wood, and line same with a plastic sheet of a
material which is non-bonding to epoxy resins such as
polyethylene, polypropylene, Teflon or the like. In
this case the plastic sheet can readily be peeled from
the cured epoxy resin shell after its removal from the
shaping mould.
It will now be appreciated that in previous
procedures the moulding surface was coated with a
parting or demoulding agent such as polyvinylacetate,
waxes or oils to prevent adhesion of the resin layer to
the mould surface. In practice this procedure usually
led to a mould which could not be readily reused without
prior preparation. Furthermore, the moulding surface
required elaborate preparation to insure proper and even
application of the parting layer to avoid bonding of the
epoxy resin layer to the moulding surface r~sulting
either in a damaged moulded unit or damaged moulding
surface or both. Accordingly, all the undesirable
features are eliminated by using the novel moulding
surface o~ the present invention.
THE EPOXY RES I N
The epoxy resin is applied ayainst the mould
surface which is non-binding to epoxy resin in any
suitable manner, such as, by spray, coating with a
trowel, a brush or the like.
The thickness of the epoxy resin layer in
general can vary from 0.1 mm to 10 mm but in some cases
a thick~r coating may be required such as in cases where
the epoxy resin layer will b~ subjected to severe
abrasive conditions such as road markers where the epoxy
layer may be as much as 1 to 1.5 cm in thickness. In
many cases, ~he thickness of the epoxy resin layer will
be dictated by economical factors, appreciating the cost
of epoxy resins, and the intended use of the moulded
units~
As fax as the epoxy resin, there is a vast
selection available extending from low viscosity to high
viscosity. When using a high viscosity, usually one
coat is sufficient while when usiny a low viscosity
epoxy resin, it is preferable to allow the first coat to
cure and then apply a second coat and in some cases,
when needed a third coat of low viscosity or even of
high viscosity epoxy resin.
Epoxy resins constitute a well defined class
of binding resins and are characterized by the opening
of epoxy groups in the polymerization process.
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A general description of the preparation o
these epoxy resins is presented in the Encyclopedia of
Polymer Science and Technology, page 209-271, volume 6,
Intersciences Publishers, NYC, 1967. Another reference
is "Hand~ook of Epoxy Resins" by H. Lee and K. Neville,
McGraw Hill Book Co., Inc., 1967.
The epoxy resins used in accordance with the
present invention are prepared from saturated polyhydric
alcohols and phenols which contain no carbon to carbon
unsaturation other than that which is present in the
aromatic ring.
By the epoxy equivalency, reference is made
the average number of 1,2-epoxy groups
o
(C~I2-C )
contained in the average molecule of the ether.
A preferred group of epoxy ethers for use in
the invention is prepared by reacting a dihydric phenol
with epichlorhydrin in alkaline solution. There
products are of resinous character and frequently are
solid materials at normal temperature ~20-30C~. Any of
the various dihydric phenols are used in preparing these
glycidyl ethers, including mononuclear phenols like
resorcinol, catechol, hydroquinone, etc., or polynuclear
phenols like bis-~4-hydroxyphenol)-2,2-propane ~bis-
phenol A), 4,4'-dihydroxy benzophenone, bis-(4-hydroxy-
phenyl)-l,l-ethane, bis-(4-hydroxyphenyl)-1,1-iso-
butane, bis-(4-hydroxyphenyl)-2,2-butane, bic-(hydroxy-
2-tertiary butyl phenyl)-2,2-propane, bis-(hydroxy-~-
tertiary butyl phenyl)-2,2 propane, bis-(2-hydroxy-
naphthyl~-methane, l,S-dihydroxy naphthalene~ etc. The
product may be represented by the formula:
-CH2-CH-CH2-(0-R-O-CH2-CHOH-CH2)n-0-R-O-CH2-CH-CH-
wherein n is an integer, e.g. from 1 to 7, and R repre-
sents the divalent hydrocarbon radical of the dihydric
phenol.
There can be used 1,2-epoxy-containing poly-
ethers of polyhydric alcohols, such as polyglycidyl
ethers thereof, like the diglycidyl ether of ethylene
glycol, propylene glycol, trimethylene glycol, diethyl-
ene glycol, triethylene glycol, glycerol, dipropylene
glycol and the like. Other typical ethers of this class
include glycidyl ethers of polyhydric alcohols having a
1,2-epoxy equivalency greater than one, such as the
polyglycidyl ethers of glycol, diglycerol, erythritol,
pentaglycerol, mannitol, sorbitol, and the like.
As an example of suitable epoxy resins, there
may be mentioned BAKELITE ERL-2744 of Union Carbide
Corp. for a liquid bisphenol A epoxy resin having an
- 12 -
epoxide equivalent of 185-200, BAKELITE ERL-4221 of
Union Carbide Corp. for a liquid cycloaliphatic epoxy
resin havlng an epoxide equivalent of 131-143, EPON 1002
or of Shell Oil Co. for solid bisphenol A epoxy resins
having an epoxide equivalent of 600-700, EPON 1004 of
Shell Oil Co. for solid bisphenol A epoxy resin having
an epoxide equivalent of 870-1025, EPON 828 of Shell
Oil Co. which is a diglycidyl ether of bisphenol A,
ARALDITE 6010 of Ciba-Geigy Corp. for a liquid bis-
phenol A epoxy resin having an epoxide Pquivalent of
185-196 and a product manufactured and sold by Reichold
under the trademark QT-1219. Thus there can be used,
for example, bisphenol A-epichlorhydrin resins.
If desired, dyes can ~e incorporated in the
epoxy r~sin so as to obtain a corresponding coloured
epoxy resin shell. In some cases, it may be desirable
to use a transparent epoxy resin with a coloured aggre-
gate so that the finished epoxy shell will be spotted
with the coloured aggregate.
The epoxy resin can be cured at room temper-
ature or the curing time can be accelerated by supply-
ing a small amount of heat.
The epoxy resin can be applied to the mould
with a brush or sprayed and therefore one should select
the viscosity of the epoxy resin accordinglyO :[f a
high viscosity epoxy resin is used, it will be applied
with a trowel, roller or the like.
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The epoxy resin is applied with a diluent as
is well known in the art. As an example of a suitable
diluent there may be mentioned butyl glycidyl ether sold
as EPOXIDE 8 by the Wilmington Chemical Corp.
In some instances, the epoxy resin may include
an ultraviolet absorber or ultraviolet screen such as a
mixture of a nickel complex and zinc oxide or a nickel
complex thiobisphenol light stabiliz~r with an inert
metallic oxide. A suitable ultraviolet absorber is the
product sold by Ferro Industrials Products Ltd under the
trademark UV CHECK AM 105.
To facilitate spraying or spreading of the
epoxy resin a wetting agent such as glycerine is used.
There may also be used a thixotropic agent such as fumed
silica, for example, a colloidal pyrogenic silica
pigment scld as CAB-O-SIL by Cabot Corporation.
Inert charges such as pulverized silicium such
as INSIL 1240 sold by Illinois Minerals can also be
included along with powdered pigments such as titanium
dioxide or liquid pigments for example carbon black
paste such as EP-90 sold by Duochem Co.
There will also be advantageously added
hardeners such as triethylene tetraamine or aliphatic
polyamines. The product sold under the trademark DEH-24
by Dow Chemical is an example of a suitable hardener.
Also, accelerators such as any proton donor~
for example, acids, phenols and alcohols may advanta-
geously be included. As a suitable proton donor theremay be mentioned the product sold by Texaco Chemical
under the trademark AOC~399.
AGGREGATES
The aggregates used are those readily availa-
ble on the market in various sizes and colors. As far
as the aggregates are concerned, it is preferable to use
those having angular ~dges, but even a certain amount of
round aggregates can be used. I~he size of the aggre-
gates may vary from 2 mm to 10 mm or more if desired.
The aggregates can be sprayed onto the uncured epoxy
resin with an air gun or any other suitable mechanical
means such as those readily available on the market, or
also applied manually.
GLASS REINFORCED CONCRETE
In those cases where the desired end product
is so large that it may be an advantage that the
concrete be pou~ed into the cured epoxy resin shell on
the site of its use, then it is pxeferable that suffi-
cient rigidity be provided for its transportation.
Accordingly the aggregate layer of the epoxy resin shell
is coated with a layer of glass reinforced concrete
which, upon curing, will be mechanically bonded to the
aggregates. ThR glass reinforced concrete layer is
light enough and provides sufficient rigidity to the
unit to allow its transportation to any site and for its
easy use.
~ 15 -
In general the thickness of the glass rein-
forced concrete layer will vaxy from 1/4 to 3/4" which
provides the desired flexibility and rigidity for the
intended purposes. A much thicker layer of Portland
cement concrete would have to be used to obtain the
desired rigidity but with a loss in flexibility and a
substantial increase in weight.
CONCRETE
As far as the concrete which can be poured
into the epoxy resin shell units of the present in-
vention, any of the commercially available c~ncrete can
be used such as for example Portland cement concrete,
refractory cement concrete or polymer concrete.
PROPERTIES OF EPOXY RESIN COATED CONCRETE UNITS
It has been found that epoxy resin coated
concrete units, prepared in accordance with the present
invention, are highly resistant to degradation when sub-
jected to the A.S.T.M. B-1117-73 "Standard Method of
Salt Spray (Fog~ Testing". Units prepared in accordance
with the present invention were not altered after 3~661
hours of testing while units prepared with a polyester
resin became powdery after 500 hours and showed cracking
and separation of the resin after 800 hours.
~ hen submitted to a series of cycles of
freeæing and thawing as prescribed by AoS~T~M~ C~666-77
"Resistance of Concrete to Rapid Freezing and Thawing,
procedure A", it was obs;erved that no change occurred up
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to 846 cycles while units coated with a polyester resin
started to disintegrate after 50 cycles.
EXAMPI.E I
SE~MI-CYLINDRICAL PANEL
A 1/4" board of polypropylene is used as a
mould surface because it is non-bonding to epoxy resins.
This flexible board i5 placed in a wooden frame to
provide a shape of the panel which is a semi-cylinder
having a diameter of 4 feet and a length of 8 feet. The
moulded panel to be prepared is to be used as a perma-
nent form in the repair and restoration of concrete
columns. The epoxy coated panel is prepared by the
following steps.
The polypropylene surface is coated with a
layer of about 1.5 mm in thickness of an uncured epoxy
resin manufactured by Shell Chemical and sold under the
trademark "EPON 828". The uncured epoxy resin layer is
then coated with a layer of angular calcium aggregates
having 3 to 5 mm in size which are partially embedded in
the ~ncured layer of epoxy resin. The epoxy resin is
then allowed to cure for three hours whereby there is
obtained a moulded and cured epoxy resin shell having
angular aggre~ates partially embedded therein. The
layer of aggregates is then coated with a layer of fibre
reinforced concrete to a thickness of 3/4 of an inch and
after allowing the reinforced concrete to cure there is
obtained a semi-cylindrical shell which can easily be
~ .
- 17
stripped from the wood moulding frame. Th~ shell has
sufficient rigidity and strength to be transported to a
site for use as a permanent form. The outer shell of
the same ,cylindrical form and the inner layer of the
fibre reinforced concrete are mechanically bonded
together by means of the intermediate ],ayer of aggre-
gates partially embedded in the cured epoxy resin layer
and partially embedded in the cured glass fibre rein-
forced concrete.
INSTALLATION ON JOB-SITE
_
Deteriorated concrete is removed from a
concrete column and the exposed reinforcing steel is
cleaned as is well known in the art. Then, two semi-
cylindrical panels as prepared previously are placed
around the concrete column to form the cylinder and the
two panels are held together by means of binding metal
straps while the vertical joints of the two panels are
filled and sealed with asphalt rubber joint material
well known in the art.
Fluid Portland cement concrete is poured into
the shell and completely fills the space between the
inner concrete column and the outer cylindrical shell.
After allowing the Portland cement concrete to cure and
harden, the metal straps are removed, the epoxy resin
cured cylindrical shell now constitutes an integral part
of the concrete column and provides protection against
deicing as well as freezing and thawing.
-- 18 --
XAMPLE I I
EPOXY RES IN COATED CONCRETE STEPS
A board of polyethylene having a textured
surface is used as a mould because it is non binding to
epoxy resin. The textured surface of the mould will
provide an anti-slip surface on the finished product.
The mould was 40 inches in length, 13 inches in width
and had a flange on one side of 1 1/2ll.
The inner mould surface was coatPd with a
layer of 1 mm of epoxy resin (EPON 828) and immediately
after, th~ epoxy resin layer was coated with a layer of
angular aygregates which w~re partially embedded in the
uncured layer of epoxy resin. The epoxy resin was then
allowed to cure for a period of three hours, thus
obtaining a moulded and cured epoxy resin form having
angular aggregates partially embedded therein.
Then, the cured epoxy resin shell thus obtain-
ed was filled with Portland cement concrete and after
allowing the concrete to cure, the whole unit was
stripped from the mould. The outer layer of cured epoxy
resin and the inner layer of cured Portland cement
concrete were mechanically bonded together by means of
the intermediate layer of aggregates, partially embedded
in the cured epoxy resin and partially embedded in the
cured concretP layer.
INST~LLATION OF THE STEP
_
Deteriorated concrete on the surface of
-- 19 --
existing concrete steps is removed and -the exposed
surface is then thoroughly cleaned. A layer of an
adhesive epoxy resin or other suitable bonding material
is then applied on the surface of the cleaned concrete
step. The epoxy resin coated concrete step is then
placed on the uncured material and the bonding matexial
is then allowed to harden. If necessary, the joints
between the steps can then be filled with cement mortar
or other suitable jointing material such as silicone
rubber.
EXAMPLE I I I
EPOXY RESIN CONCRET~5 SI~BS
A polypropylene mould which is not bonding to
epoxy resin in the form of an open box 12 inches by 1~
inches and 2 inches in height is used as a mould. The
inside surface of the mould was textured to immitate
slate.
The inside surface of the bottom face of the
mould is coated with a layer of epoxy resin by spraying
or manual coating to a thickness of l mm. The layer of
uncured epoxy resin is then coated with a layer of
angular aggreyates which are partially embedded in the
uncured layer of epoxy resin. The epoxy resin is then
permitted to cure and after curing the mould is Eilled
with liquid Portland cement concrete and the outer
surEace of the concrete is smoothed with a trowel.
After curing of the concrete, the epoxy resin concrete
ffl~a
unit or slab i5 stripped from the mould. Preferably
before the pouring of the concrete, the plastic mould is
inserted in a steel frame to prevent buckling of the
sides of the plastic mould because of the weight of the
fresh concrete.
The thus obtained epoxy resin coated concrete
slab is suitable for use in making patios, driveways or
walkways.
