U.S. patent application number 14/318816 was filed with the patent office on 2015-07-23 for polyurethane foam in foundation footings for load-bearing structures.
This patent application is currently assigned to Royal Adhesives & Sealants Canada Ltd.. The applicant listed for this patent is Royal Adhesives & Sealants Canada Ltd.. Invention is credited to Alexander Botrie, Neil Goodman.
Application Number | 20150204044 14/318816 |
Document ID | / |
Family ID | 53544312 |
Filed Date | 2015-07-23 |
United States Patent
Application |
20150204044 |
Kind Code |
A1 |
Botrie; Alexander ; et
al. |
July 23, 2015 |
Polyurethane Foam In Foundation Footings For Load-Bearing
Structures
Abstract
Foundation footing system for a load-bearing structure
comprising a hole in the ground and a post in the hole extending
above the hole. A gap present between the sides of the post and the
sides of the hole contains a cured, hydrophobic, closed-cell,
polyurethane foam to firmly hold the post in place and protect the
post from moisture. Alternatively, a foundation footing system for
a load-bearing structure comprising a hole in the ground filled
with a cured, hydrophobic, closed-cell, polyurethane foam and a
post place on and connected to the top of the foam.
Inventors: |
Botrie; Alexander; (Toronto,
CA) ; Goodman; Neil; (Brampton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Royal Adhesives & Sealants Canada Ltd. |
Toronto |
|
CA |
|
|
Assignee: |
Royal Adhesives & Sealants
Canada Ltd.
Toronto
CA
|
Family ID: |
53544312 |
Appl. No.: |
14/318816 |
Filed: |
June 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61928453 |
Jan 17, 2014 |
|
|
|
Current U.S.
Class: |
52/292 |
Current CPC
Class: |
C08G 2101/0025 20130101;
C08G 18/4804 20130101; C08G 18/4829 20130101; E04H 12/2269
20130101; E02D 27/42 20130101; E04H 12/2215 20130101 |
International
Class: |
E02D 27/42 20060101
E02D027/42 |
Claims
1. A foundation footing system for a load-bearing structure
comprising a hole in a ground, the hole having a bottom and sides,
and a post positioned in the hole and generally centered within the
hole, wherein the post extends above the hole, wherein the width of
the hole is wider than a width of the post thus forming a gap
between sides of the post and the sides of the hole; the foundation
further comprising a cured, closed-cell, polyurethane foam
surrounding the post and in direct contact with the sides of the
hole, wherein the polyurethane foam fills the gap between the post
and sides of the hole, the polyurethane foam comprising a cured
mixture of a polyurethane composition comprising polyisocyanate and
at least one active hydrogen containing compound wherein the cured
polyurethane foam has a compressive strength of greater than about
80 psi.
2. The foundation footing system of claim 1 comprising at least two
holes and at least two posts, wherein the posts have the same or
different diameters, and each hole has a diameter accommodating the
diameter of the respective post and requisite gap, wherein a load
bearing structure resides on the at least two posts.
3. The foundation footing system of claim 1 wherein the cured
polyurethane foam is prepared from mixing a polyurethane
composition, pouring the composition into the hole, and allowing
the composition to foam, wherein the polyurethane foam cures to
touch in about 1 to 10 minutes after mixing the composition.
4. (canceled)
5. The foundation footing system of claim 1 wherein the cured
polyurethane foam has a compressive strength of 100 psi.
6. The foundation footing system of claim 1 further comprising a
footing pad underneath the post positioned in the hole.
7. The foundation footing system of claim 1 wherein the
polyurethane composition is hydrophobic.
8. The foundation footing system of claim 1 wherein the
polyurethane foam further comprises at least one water-immiscible
component in an amount from 10% to 80% by weight of the total
composition.
9. The foundation footing system of claim 8 wherein the
water-immiscible component(s) comprises 30% to 60% by weight of the
total composition.
10. The foundation footing system of claim 1 wherein the
composition further comprises a hydrophobicity inducing surfactant
in an amount from 0.1% to 5% by weight of the total
composition.
11. The foundation footing system of claim 10 wherein the
surfactant is selected from polysiloxane-polyalkylene oxide
copolymers.
12. The foundation footing system of claim 1 wherein the post is
positioned at the bottom of the hole.
13. A foundation footing system for a load-bearing structure
comprising a hole in a ground, the hole having a top, bottom, and
sides; the foundation further comprising cured, polyurethane foam,
wherein the foam fills the hole and extends above the top of the
hole to form a foundation footing, the polyurethane foam comprising
a cured mixture of a polyurethane composition comprising
isocyanate, and at least one active hydrogen containing compound;
and further comprising a post placed on and attached to the top of
the foam and generally centered on the foam, wherein the cured
polyurethane foam has a compressive strength of greater than 10
psi.
14. The foundation footing system of claim 13 comprising at least
two holes and at least two posts, wherein the posts have the same
or different diameters, and each hole has a diameter accommodating
the diameter of the respective post and requisite gap.
15. The foundation footing system of claim 13 wherein the cured
polyurethane foam is prepared from mixing a polyurethane
composition, pouring the composition into the hole, and allowing
the composition to foam, wherein the polyurethane foam cures to
touch in about 1 to 10 minutes after mixing the composition.
16. The foundation footing system of claim 13 wherein the cured
polyurethane foam has a compressive strength of greater than 30
psi.
17. The foundation footing system of claim 13 wherein the cured
polyurethane foam has a compressive strength of greater than 50
psi.
18. The foundation footing system of claim 13 wherein the
polyurethane composition is hydrophobic.
19. The foundation footing system of claim 13 wherein the
polyurethane foam further comprises at least one water-immiscible
component in an amount from 10% to 80% by weight of the total
composition.
20. The foundation footing system of claim 19 wherein the
water-immiscible component(s) comprises 30% to 60% by weight of the
total composition.
21. The foundation footing system of claim 13 wherein the
composition further comprises a hydrophobicity inducing surfactant
in an amount from 0.1% to 5% by weight of the total
composition.
22. The foundation footing system of claim 21 wherein the
surfactant is selected from polysiloxane-polyalkylene oxide
copolymers.
23. The foundation system of claim 1 wherein the sides of the hole
are scarified to increase the friction between the soil and the
footing.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 61/298,453 filed Jan. 17, 2014, hereby
incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates to polyurethane foam compositions in
raised foundation footings for load-bearing structures and methods
of making foundation footings using polyurethane foams.
BACKGROUND OF THE INVENTION
[0003] A firm foundation is essential to good performance of
buildings and other load-bearing structures. The foundation
includes properly installed footings of adequate size to support a
structure and prevent excessive settling. Foundation systems are
classified as shallow and deep foundations, depending on the depth
of the load-transfer member below the super-structure and the type
of transfer load mechanism. The required foundation system depends
on several factors or conditions such as the strength and
compressibility of the site soils, the proposed loading conditions,
and the project performance criteria (i.e. total settlement and
differential settlement limitations.)
[0004] In construction sites where settlement is not a problem,
shallow foundations provide the most economical systems. Shallow
foundations are typically placed from ground level to 3 meters
below ground level or below the frost line. Shallow foundation
construction is typically utilized for most residential and light
commercial raised floor building sites. FIG. 1, building structure
10 is built on shallow foundation 12. The shallow foundation may be
of any suitable shape such as the inverted "T" shape shown. This
shape allows more stability.
[0005] Where poor soil conditions are found, deep foundations may
be needed to provide the required load-bearing capacity and to
limit settlement. In FIG. 1, building structure 14 is built on a
deep foundation 16. Examples of deep foundation systems include
driven piles (i.e. pressure-treated timber piles, concrete, or
steel), drilled shafts, or micro piles.
[0006] Foundation specifications, including footing requirements,
are covered in various building codes, and sized in accordance with
the building capacity of the soil and the weight of the building.
In areas subject to seasonal frost, the bottom of the footing must
be placed below the frost line to prevent damage to the footing and
structure due to frost heave.
[0007] A raised foundation is a foundation which is raised above
the plane of the surrounding earth. The main floor of a home or
business is built on this foundation. A post and pier foundation
system is one example of a raised system. Poured concrete footings
are often used in raised foundations. In one example, a wood,
metal, plastic, or composite post is set in the ground with
concrete and bears the weight of the structure on it. The post is
below grade.
[0008] In another example, a concrete pier extends from the footing
base to above grade. There are several variations of this footing
type. FIG. 2 and FIG. 3 depict concrete footings that extend below
the frost line to above the ground. Both footings have a wood post
20, typically a 6''.times.6'' post, attached above ground to the
concrete pier. For example, in FIG. 2, an anchor bolt 22 is used to
connect the post to a concrete footing 24. A gravel base 26 may be
used at the bottom of the concrete footing to prevent frost heave.
In FIG. 3, a concrete footing 30 is poured in fiber tube 32, a
metal post anchor 34 is placed in the concrete, and then the
concrete is allowed to set. The above ground portion of the fiber
tube is removed after the concrete is set. The metal post anchor 34
connects the post 20 to the concrete footing 24. Such concrete
footings typically extend six inches below the frost line 36 and
rest on undisturbed soil 38. The top of the footing is typically at
least 6'' above grade.
[0009] Wood posts are usually attached to the top of the concrete
footing above ground. Untreated wood posts will quickly rot if
placed below ground due to the presence of water and oxygen which
results in fungal attack, for example. Likewise, untreated metal
posts placed below ground will rust. Pressure treated wood is
available for use in ground contact applications, some having
warranties as long as 75 years, however they are expensive and
further may contaminate the ground. Galvanized metals are used for
underground applications. Because such foundations rely on anchors,
the structure can be compromised if the anchor bolt becomes loose
or breaks.
[0010] Concrete has many drawbacks. For instance, concrete takes
time to cure, is heavy, porous, and brittle, has high labor costs,
has a high carbon footprint, needs large quantities of water, and
cannot be poured below 5.degree. C. It is desirable to provide an
alternative to concrete footing systems.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention is based on three types of
polyurethane footings as herein described. In the first type, as
exemplified in FIGS. 5 and 6, the post is placed at the bottom of
the hole. In the second type, as exemplified in FIGS. 7 and 8, the
post is placed on top of the foam, above grade. In the third type
of footing, the post is placed inside the foam footing as in FIG.
10.
[0012] In a first embodiment, foundation footing system for a
load-bearing structure comprises a hole in a ground, the hole
having a bottom and sides, and a post placed on the bottom of the
hole and generally centered within the hole, wherein the post
extends above the hole, wherein the width of the hole is wider than
a width of the post thus forming a gap between sides of the post
and the sides of the hole; the foundation further comprising a
cured, closed-cell, polyurethane foam surrounding the post, wherein
the polyurethane foam fills the gap between the post and sides of
the hole, the polyurethane foam comprising a cured mixture of a
polyurethane composition comprising polyisocyanate and at least one
active hydrogen containing compound. The foundation footing system
comprises the post and foam.
[0013] In another embodiment, method of making a foundation footing
system for a load-bearing structure comprises, a) forming a hole in
a ground, the hole having a bottom and sides; b) placing a post
onto the bottom of the hole such that the post is generally
centered within the hole and a gap is formed between sides of the
post and the sides of the hole; and c) adding a polyurethane
composition into the gap, allowing the polyurethane composition to
react and form a foam, thereby filling in the gap, and then to cure
to form a cured, closed-cell, polyurethane foam, the polyurethane
foam mixture comprising polyisocyanate and at least one active
hydrogen containing compound.
[0014] In a further embodiment, foundation footing system for a
load-bearing structure comprises a hole in a ground, the hole
having a top, bottom, and sides; the foundation further comprising
cured, polyurethane foam, wherein the foam fills the hole and
extends above the top of the hole to form a foundation footing, the
polyurethane foam comprising a cured mixture of a polyurethane
composition comprising isocyanate, and at least one active hydrogen
containing compound; and further comprising a post placed on and
attached to the top of the foam and generally centered on the foam.
The foundation footing system comprises the post and foam.
[0015] In a further embodiment, method of making a foundation
footing system for a load-bearing structure comprises a) forming a
hole in a ground, the hole having a top, bottom, and sides; b)
placing a polyurethane composition into the hole, allowing the
polyurethane composition to react and form a foam, filling in the
hole and rising above the hole, and then to cure to form a cured,
polyurethane foam footing, the polyurethane foam mixture comprising
a polyurethane composition comprising isocyanate, and at least one
active hydrogen compound; and further comprising attaching a post
to the top of, and generally centered on, the foam.
[0016] In preferred embodiments of the above, the foam is a
hydrophobic, closed-cell foam that contains at least one
water-immiscible component.
[0017] These and other aspects of the invention are apparent from
the following Detailed Description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 illustrates examples of shallow and deep building
foundations.
[0019] FIG. 2 illustrates an example of a prior art concrete
footing.
[0020] FIG. 3 illustrates another example of a prior art concrete
footing.
[0021] FIG. 4 illustrates an example of a foam and post footing in
accordance with aspects of the present invention.
[0022] FIG. 5 illustrates an example of a foam and post footing in
accordance with aspects of the present invention.
[0023] FIG. 6 illustrates another example of a foam and post
footing in accordance with aspects of the present invention.
[0024] FIG. 7 illustrates an example of a foam footing having a
post attached to the top of the foam footing in accordance with
aspects of the present invention.
[0025] FIG. 8 illustrates another example of a foam footing having
a post attached to the top of the foam footing in accordance with
aspects of the present invention.
[0026] FIGS. 9a-9c illustrate concrete anchoring systems that can
be used with aspects of the present invention.
[0027] FIG. 10 illustrates an anchoring system where the post is
imbedded in the foam.
[0028] FIG. 11 illustrates the use of foam in prefabricated and
pre-molded footing forms in accordance with aspects of the
invention.
[0029] FIG. 12 illustrates a space between the footing pad on top
of the foam footing and the edge of the foam in accordance with an
aspect of the invention.
[0030] FIGS. 4-12 should be understood as illustrative of various
aspects of the invention, relating to the compositions, systems,
and methods described herein and/or the principles involved. Some
features depicted have been enlarged or distorted relative to
others, in order to facilitate explanation and understanding. FIGS.
4-12 do not limit the scope of the invention as set forth in the
appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Type A, unconfined soil, has a compressive strength from
about 21 psi to 83 psi. It can support a load of at least 3000
lb./ft.sup.2 and as high as 12,000 lb./ft.sup.2. It was discovered
that polyurethane foam with similar compressive strength, can have
similar load-bearing capacity. This allows for improvements over
conventional concrete-based raised foundation systems and footings
such as shown in FIGS. 2 and 3. The present invention is therefore
directed to the use of polyurethane as footers in foundation
systems.
[0032] It was further discovered that polyurethane provides
improved results over conventional concrete footings. (a) Concrete
takes time to cure, for example, standard concrete takes up to 28
days to cure. Polyurethane foam cures in less than five minutes and
reaches full strength in 30 minutes. (b) Labor costs are much
higher for constructing foundations with concrete than with
polyurethane. (c) Concrete is very heavy; thus transportation and
handling costs are very high. In addition, the carbon footprint
with concrete is very high. Polyurethane foam is much lighter than
concrete and hence cheaper to transport. One pound of polyurethane
foam replaces about 100 pounds of concrete. (d) Concrete needs
large quantities of water. Polyurethane foam does not need water
and can be easily used in isolated areas. (e) Concrete is porous
and allows water to travel through it. Polyurethane foam can be
made impervious to water and will protect the post from rotting or
rusting. It also blocks chemicals used to treat the wood from
contaminating the soil. (f) Concrete cannot be poured below
5.degree. C. For every 10.degree. C. reduction in concrete
temperature, the time of setting of the concrete doubles, thus
increasing the amount of time that the concrete is vulnerable to
damage due to freezing. Polyurethane foam can be poured below
freezing, as long as the foam components are maintained at about 20
to 25.degree. C. prior to mixing. (g) Concrete is very brittle and,
without reinforcement, breaks easily. The polyurethane foam
utilized in the present invention is not brittle, does not stress
the post, and will not break easily.
[0033] The present invention is directed to post and pier
foundation footings that allow for wood, metal, plastic, and
composite posts to be used both above ground and below ground for
load-bearing structures without a concern of rotting, rusting, or
deterioration. In one aspect, the foundation footings utilize
posts, such as load-bearing wood and metal posts, as well as
water-immiscible and hydrophobic, closed-cell, polyurethane foam
surrounding the posts. The closed-cell polyurethane foam bonds to a
wood post, preventing moisture from reaching the wood and thus
preventing fungal attack. The closed-cell polyurethane foam also
bonds to a metal post preventing moisture from reaching the metal
and thus preventing rust. The closed-cell polyurethane foam may
also be bonded to a plastic post to prevent moisture from reaching
the plastic, preventing deterioration or weakening of the
plastic.
[0034] The present invention further allows for posts to be used
both above and below ground for load-bearing structures without a
concern of the post moving or shifting. That is, the polyurethane
foam of the present invention will provide full support for a post
for a load-bearing structure.
[0035] A load-bearing foundation is one that supports more than its
own weight. It transmits force generally from a higher level to a
lower level.
[0036] The term post includes any suitable support structure, pole,
pier, and the like, to create a proper foundation for a
load-bearing structure. The post may be wood, metal, plastic,
composite material, or any other material capable of supporting the
load. The post may be any suitable geometric shape such as round or
square. Typical woods used for support posts are pine and fir.
Typical metals used for support posts are aluminum and galvanized
steel. Typical plastics used for support posts are PVC and ABS. An
example of a composite post is fiberglass or carbon fibers with
polyester or epoxy resin as a binder.
[0037] One aspect of the invention is shown in FIG. 4. A post hole
42 is made in the ground (aka earth) 40 to a suitable depth
depending on the required foundation specifications. The hole may
be made with any suitable device including, but not limited to, an
auger. As shown in FIG. 1, the depth will depend on whether a
shallow or a deep foundation is required and depends on the weight
of the structure and type of ground. Generally holes are round, but
other shape holes may be used if desired such as square holes.
[0038] The sides of the hole may be scarified to increase the
friction between the soil and the footing. As the foam rises it
will follow the shape of the scarified walls and go into all the
grooves. This will increase the contact area and increase the
friction between the soil and the foam. This also pushes the foam
against the soil, compacting the soil, and increasing the
compressive strength of the soil contacting the foam.
[0039] A concrete footing pad can also be placed at the bottom of
the hole and below the post. Larger diameter pads are used for
weaker soils to increase the load-bearing capacity. This is shown
in Table 1.
TABLE-US-00001 TABLE 1 Minimum Width of Concrete or Masonry
Footings (inches) Load-Bearing Value of Soil (psf) 1,500 2,000
2,500 3,000 3,500 4,000 Conventional Wood Frame Construction
1-story 16 12 10 8 7 6 2-story 19 15 12 10 8 7 3-story 22 17 14 11
10 9 4-Inch Brick Veneer Over Wood Frame or 8-Inch Hollow Concrete
Masonry 1-story 19 15 12 10 8 7 2-story 25 19 15 13 11 10 3-story
31 23 19 16 13 12 8-Inch Solid or Fully Grouted Masonry 1-story 22
17 13 11 10 9 2-story 31 23 19 16 13 12 3-story 40 30 24 20 17
15
[0040] Usually precast concrete, at least four inches thick with a
28 day compressive strength greater than 1200 psi, or
poured-in-place concrete at least six inches thick with a
compressive strength of at least 3000 psi after 28 days, is used.
For heavy loads, pads over twelve inches thick may be required. ABS
footing pads and other pads that are listed for the required load
capacity can also be used.
[0041] A post 44 is placed onto the bottom of the hole, either
directly, or on a footing pad placed on the bottom of the hole, and
generally centered within the hole 42. The post being generally
centered means that the post is placed roughly in the middle of the
hole; but the post may be slightly off center with the hole so long
as the foundation structure is not compromised. Moreover, the shape
of the hole and the shape of the post may not correspond to provide
the same distance between all sides of the post and all sides of
the hole. For instance, a square post may be used in a round
hole.
[0042] A footing pad has a very high compressive strength (greater
than 1000 psi). It will not distort when there are high loads on
the post. This ensures that the load is evenly distributed over the
entire surface of the footing pad and the soil.
[0043] A polyurethane composition is mixed, and immediately poured
into the hole around the post. The foam will rise and generally
will be tack-free in 1 to 20 minutes, more typically 2 to 10
minutes, or 4 to 6 minutes at 25.degree. C. It will be fully cured
in 25 to 180 minutes, generally approximately 60 minutes. At this
point a load can be placed on the post. The foam components can be
mixed in environments from about 30.degree. C. to temperatures well
below freezing. The components of the foam just prior to mixing can
be at any suitable temperature, but preferably between 20 and
25.degree. C. Typically component temperatures should be at least
15.degree. C. prior to mixing. At lower temperatures, the foam will
cure slower and will have a higher foam density then when cured at
higher temperatures. At higher temperatures the foam will cure
faster and will be tack-free in a shorter time but the cured
density of the foam may be much lower than required for the
application. A lower foam density will make the foam weaker. The
air temperature can be hot or cold, but soil temperature in the
hole typically should not be above 30.degree. C. The foam generates
a considerable amount of heat as it cures. This exotherm allows it
to cure quickly at low temperatures. For example, the foam when
cured at 25.degree. C. may have a foam density of 0.080 gm/cc and a
compressive strength of 100 psi. When cured at 15.degree. C., the
foam density will be 0.100 gm/cc with a compressive strength of 150
psi. When cured at higher temperatures, such as 35.degree. C., the
foam density will be around 0.050 gm/cc, with a compressive
strength around 70 psi.
[0044] Any premeasured portable mixing/dispensing system can be
used to mix and dispense small quantities of the foam. For large
holes or for filling many holes, a meter/mix dispenser can be used.
In this equipment, the two components can be dispensed and mixed
from 5 gallon pails, 55 gallon drums, or bulk dispensers. The two
components can be mixed with a dynamic or static mixer. This
equipment is well known by those familiar with the art.
[0045] Turning again to FIG. 4, the polyurethane components react
and foam 46 rises up, typically to above the ground surface, and
completely surrounds the post 44. After curing, the foam firmly
anchors the post in the ground. Any excess foam that rises above
ground level may be cut off, if desired. The polyurethane foam
allows the post to be placed directly in the hole, below the frost
line. The foam holds the post firmly in an upright position and
prevents moisture from contacting the post. Unlike concrete, the
foam does not stress the post. The foam bonds to the post. The foam
adapts to the changing climatic conditions and efficiently
transfers the load from the foundation to the soil. A building
floor 48 may be built on the post 44.
[0046] FIGS. 5 and 6 show two aspects of using a post below ground.
In FIG. 5, post hole 52 is made in the ground 50. A post 54 is
placed onto the bottom of the hole and generally centered within
the hole 52. Polyurethane components are combined and poured into
the hole. The polyurethane components react and foam 56 rises up.
In FIG. 6, post hole 62 is made in the ground 60. A footing pad 68
is placed at the bottom of the hole. A post 64 is placed onto pad
68 at the bottom of the hole and generally centered within the hole
62. Polyurethane components are combined and poured into the hole.
The polyurethane components react and foam 66 rises up. As
discussed above, pads may be made of any suitable material and
would typically be concrete or a polymer, such as ABS.
[0047] As shown in FIG. 7 and FIG. 8, the polyurethane foam can
also be used to completely fill the hole and rise above the hole.
The post can then be placed on top of the foam and anchored to it.
The foam is the foundation footing.
[0048] In FIG. 7, a post hole 72 is made in the ground 70 to a
suitable depth depending on the required foundation specifications.
Polyurethane components are combined and poured into the hole. The
polyurethane components react and foam 76 rises up, typically from
one to three feet above ground. A round cardboard forming tube, the
same diameter as the hole, such as a Sonotube, can be used to shape
the foam when it rises above ground. When the foam has cured, it
can be cut level to the ground or up to three feet above the
ground. It is usually cut above the ground to prevent the post from
degrading by contacting the wet soil.
[0049] A footing pad 73 can be placed on top of the tube so that
the foam presses up against the pad as it rises. The foam must bond
to the pad as it cures. The pad helps to distribute the load on the
post over the surface of the foam that is under the pad. The floor
of a structure can be built on top of the post 74. When the post is
on top of the footing pad, the compressive strength of the foam and
the adhesions of the foam to the soil are important factors in the
load-bearing capacity of the footing.
[0050] Post 74 may be attached to the foam footing or the plate on
top of the foam footing in any suitable manner. For example,
brackets or adhesives may be used to attach the post.
[0051] Similarly in FIG. 8, a post hole 82 is made in the ground 80
to a suitable depth. A footing pad 88 is placed at the bottom of
the hole. Polyurethane components are combined and poured into the
hole. The polyurethane components react and foam 86 rises up as
discussed above. A flat footing pad 83, as discussed above may be
used so that the foam cures flat and the pad is bonded to it. Post
84 is then attached to the pad as discussed above.
[0052] Many of the anchoring systems used with concrete footings
also can be used with foam footings. FIGS. 9a-9c illustrate
examples of concrete anchoring systems that can be used with foam
footings. The bottom of such systems may either be embedded into
the foam (FIG. 9a) and/or attached to the foam or a footing pad via
fasteners such as screws or bolts (FIGS. 9b and 9c.). Adhesives can
also be used.
[0053] FIG. 10 shows an anchoring system where the post 104 is
imbedded in the foam 106. A hole 102 is dug in soil 100. A footing
pad 103 is attached to the bottom of the post 104. Foam 104 fills
the hole 102 to the desired level. The footing pad 103 and post 104
are placed on top of the foam and leveled. Additional foam is
poured on top of the footing pad and surrounding the post and then
the foam is allowed to cure.
[0054] FIG. 11 depicts the use of a prefabricated footing form. A
hole is dug in soil 110. A prefabricated footing form 117, for
example, a prefabricated box, such as a wood box attached to a
cardboard construction tube or a pre-molded footing form, is placed
in the hole and soil is back filled outside the footing form. The
footing form 117 extends above the ground level 118. The post 114
is placed within the footing form 117. Foam 116 fills the interior
of the footing form and surrounds the pole.
[0055] FIG. 12 depicts a post 124 placed in soil 120 utilizing a
foam footing 126 and a footing pad 123. The space between the
footing pad 123 on top of the foam footing 126 and the edge of the
foam footing should be small so the load on the post will be
distributed over the largest area possible. That is, in FIG. 12,
the radius of footing pad 123 is only slightly smaller than the
radius of the foam footing 126.
[0056] The post with the footing pad attached to its bottom can be
placed at the bottom of the hole or at the top or it can be placed
anywhere in between. It is preferable to place it closer to the top
of the hole to make leveling of the foam easier.
[0057] When prefabricated footing forms are used, the post can be
placed above ground or below ground as described above. The foam
footings can also be cured inside of the prefabricated footing form
during the manufacture of the footing form or at the construction
site.
[0058] Deep foundations are greater than 3 meters below ground
level. In deep foundations driving piles have a higher load-bearing
capacity than drilling shafts. Driving the piles compress the
surrounding soil, causing greater friction against the soil next to
the pile. Injecting the polyurethane composition between the
drilling shaft and the soil will increase the friction and the
load-bearing capacity of the pile.
[0059] Depending on the load, the soil and the compressive strength
of the foam, a footing pad may need to be placed under the foam
footing. When the post is at the bottom of the hole, a concrete
footing pad can be used. When the post is not touching the soil at
the bottom of the hole, the post should be attached to a treated
wood, ABS, or any other type of footing pad that will not
substantially increase the load on the foam.
[0060] The method to determine the proper size and load-bearing
capacity required for footings is the same for foam, concrete, or
any other load-bearing footing material. First it must be
established how much total weight each footing will support. The
type of soil that will be under the footing and the load-bearing
capacity of this soil must be determined. As discussed above, the
compressive strength of the foam must also be considered. For
higher loads or weaker soils, larger footings are required. There
are standard tables available to help determine the size and design
of footing (see Table 1 above). An engineer may be required to
calculate the footing requirements for higher loads or in areas
where the load-bearing capacity of the soil is less than 1500
lb/ft.sup.2. Determining the requirements of the footing can easily
be obtained by those skilled in the art. The footing transmits the
load into the soil. The lower the bearing capacity of the soil, the
wider the footing needs to be.
[0061] Table 2 illustrates a sample load footing size chart
utilizing polyurethane foam.
TABLE-US-00002 TABLE 2 SOIL TYPE Gravel Sand Clay Compressive 3000
2000 1500 Strength of Soil (lb/ft.sup.2) Circular Footing Size
(inches) (Nominal 4'' .times. 4'' Post Maximum Allowable in Fast 2K
Load) Load/Footing (lbs.) 6'' 600 400 300 8'' 1000 700 500 10''
1600 1100 800 12'' 2300 1500 1100 13'' 2700 1800 1300 14'' 3200
2100 1600 15'' 3600 2400 1800 16'' 4100 2700 2000 17'' 4700 3100
2300 18'' 5300 3500 2600 19'' 5900 3900 2900 20'' 6500 4300 3200
21'' 7200 4800 3600 22'' 7900 5200 3900 23'' 8600 5700 4300 24''
9400 6200 4700
(A nominal 4''.times.4'' post is actually a 31/2''.times.31/2''
post)
[0062] Structures that weigh little and only put a light load on
the soil only require small footings. For example, a small pergolas
or arbor that weights 400 lbs will have a 100 lb load per footing.
A 6'' footing on the weakest soil can hold up to 300 lbs and would
be adequate for this type of project.
[0063] One can look up the recommended footing size, based on the
size and type of house and the bearing capacity of the soil. As can
be seen, heavy houses on weak soil may need footings 2 feet wide or
more. But the lightest buildings on the strongest soil may only
require footings as narrow as 7 or 8 inches.
[0064] It is very important that the foam used for this
application, in wet or damp soil is water-repellant and
hydrophobic. "Water-repellant" refers to the mixed isocyanate and
polyols composition in the liquid state and while it is curing.
"Hydrophobic" refers to the polyurethane foam when it is cured.
[0065] The hole to be filled with the polyurethane foam may contain
ground water or runoff water. Standard polyurethane foam will
absorb and react with this soil water. This will produce a footing
having low density and low strength. The foam density and strength
must be closely controlled. The present invention utilizes special
polyurethane foam forming compositions which are resistant to the
undesired side reaction with ground water. Foams that are not
water-repellant can be used when the soil is not wet and the hole
to be filled does not contain ground water or runoff water. They
can also be used to make prefabricated footings.
[0066] U.S. Pat. No. 3,564,859 first introduced the concept of
adding a non-volatile water-immiscible material to polyurethane
components so that the properties of the resultant product are not
affected excessively in the presence of groundwater. U.S. Pat. No.
4,966,497 improved on the above by removing halogenated hydrocarbon
blowing agents from the formulation. The above patents are
incorporated by reference in their entirety. It was discovered for
the present application that adding a hydrophobic surfactant to the
formulation provides the desired properties for the polyurethane
foam used for footers.
[0067] Water-Repellency
[0068] The composition of the present invention utilizes
conventional materials such as polyisocyanate and active hydrogen
containing compounds, but for wet or damp conditions, also includes
water-immiscible components. The water-immiscible components
provide the water-repellency of the polyurethane foam composition
in the liquid state, while it is curing. The water-immiscible
components can be any of a large number of materials or mixtures of
materials. Preferably the water-immiscible component is a liquid
having a low vapor pressure which is substantially non-reactive
under the usual conditions of foam formation with either the active
hydrogen or the isocyanate components used to form the polyurethane
compositions. Materials which react with either or both of the
polyurethane components may comprise part or most of the
water-immiscible component.
[0069] "Water-immiscible" means that the solubility in water at
about 70.degree. F. is less than about 5 grams per 100 grams and
preferably less than about 1 gram per 100 grams of water. In a
preferred embodiment, the water-immiscible component has no
measurable solubility in water. Among the water-immiscible
components are those described in U.S. Pat. No. 3,968,657, hereby
incorporated by reference in its entirety. Among the
water-immiscible components having a low vapor pressure are the
higher alkanes (C.sub.8 and above), crude oil, petroleum oils and
higher petroleum fractions of all kinds (both pure and crude),
asphalts, tars, petroleum refining bottom or residues. Components
that are comprised primarily of aromatic or aliphatic hydrocarbons
are water-immiscible. Also included are materials such as coal tar
pitch, wood tar pitch, tall oil, tall oil derivatives, vegetable
oil, vegetable oil derivatives, and waxes. Solid materials that are
water-insoluble and that can be dissolved in a water-immiscible
liquid. Halogenated hydrocarbons and halogen derivatives can also
be used.
[0070] Water-immiscible solvents can also be used. Suitable
water-immiscible solvents include blowing agents such as HCFC's,
pentane, and hexane as well as high boiling solvents such as high
flash aromatic naptha in amounts up to about 15% by weight of the
total composition.
[0071] Sufficient compatible water-immiscible components should be
present to inhibit the reaction with water. Excessive
water-immiscible components or incompatible water-immiscible
components may result in unacceptable deterioration of the physical
characteristics of the final foam and should be avoided. The
desired polyurethane foam can be obtained from compositions
containing 10%-80% by weight of the water-immiscible components.
Preferably, the amount of water-immiscible components is in the
range of 30% to 60% by weight of the polyurethane foam forming
compositions.
[0072] Hydrophobicity
[0073] It is preferred that the cured foam is closed-cell. Water
should not be able to pass through the foam. This is particularly
important when the post is in-ground and surrounded by the
foam.
[0074] Surfactants help to control the precise timing and the size
of the foam cells. Within each foam formulation, a minimum level of
surfactant is needed to produce commercially acceptable foam. In
the absence of a surfactant, a foaming system will normally
experience catastrophic coalescence and exhibit an event known as
boiling. With the addition of a small amount of surfactant, stable
yet imperfect foams can be produced; and, with increasing
surfactant concentration, a foam system will show improved
stability and cell-size control.
[0075] Most cured, rigid polyurethane foams contain closed cells.
Higher density rigid foams have thicker cell walls and thus have a
higher percentage of closed cells than lower density rigid foams.
The inclusion of a hydrophobic surfactant improves the uniformity
and size of the cell structure. It also increases the closed cell
content; thus, increasing the hydrophobicity of the foam. It is
important that lower density foams that require hydrophobicity have
a sufficient concentration of closed cells to make them
hydrophobic. Foams suitable for use in some footing applications
have foam densities as low as 0.035 gm/cc and a compressive
strength as low as 10 psi although generally at least 30 psi. Foams
with densities higher than 0.10 gm/cc and compressive strengths
higher than 100 psi can be used, but may be cost prohibitive in
many applications. Preferred foam densities are higher than about 4
lb/ft.sup.3. Preferred compressive strengths are higher than about
50 psi, 80 psi, and in some instances are preferably 100 psi. There
is no preferred upper limit for both the foam density and the
compressive strength. However, the cost will increase as the foam
density increases. Foams can be formulated with specific
properties, such as compressive strength and foam density for
specific applications.
[0076] Surfactants
[0077] The foams of the invention are prepared using a surfactant,
particularly a hydrophobicity inducing surfactant. Typically,
hydrophobicity inducing surfactants are polysiloxane-polyalkylene
oxide copolymers, usually the non-hydrolyzable
polysiloxane-polyalkylene oxide copolymer type. The polyoxyalkylene
(or polyol) end of the surfactant is responsible for the
emulsification effect. The silicone end of the molecule lowers the
bulk surface tension. When a hydrolyzable surfactant, which
contains Si-O linkages between the silicon and polyether groups, is
contacted with water, the molecule breaks apart to form siloxane
and glycol molecules. When this occurs, the individual molecules no
longer exhibit the proper surfactant effects. Non-hydrolyzable type
surfactants, which contain a water stable Si--C bond between the
silicon and polyether chain, are thus preferred.
[0078] Hydrophobicity inducing surfactants include: Goldschmidt
Chemical Corp. of Hopewell, Va. products sold as B8110, B8229,
B8232, B8240, B8870, B8418, B8462; Organo Silicons of Greenwich,
Conn. products sold as L6164, L600 and L626; and Air Products and
Chemicals, Inc. products sold as DC5604 and DC5598. Preferred
surfactants are B8870, B8110, B8240, B8418, B8462, L626, L6164,
DC5604 and DC5598. B8870 and B8418 from Goldschmidt Chemical Corp.
are more preferred; B8418 is most preferred.
[0079] Non-hydrophobic inducing surfactants, such as Dow Corning
DC190 and DC 193 can be used in dry, above ground and prefabricated
applications.
[0080] The surfactant is used in the range of 0.1-5% of the total
formulation. Generally, lower density foams require more surfactant
than higher density foams
[0081] Isocyantes
[0082] In principle, a wide range of isocyanates may be used to
prepare polyurethane foams of the invention such as, for example,
toluene diisocyanate (TDI), diphenylmethane diisicyanate,
polymethylenepolyphenylene polyisocyanate, hexamethylene
diisocyanate (HMDI), 1,5-naphthylene diisocyanate, xylylene
diisocyanate, hydrogenated polymethylenepolyphenylene
polyisocyanate, and mixtures thereof. Isocyanate prepolymers can
also be used. Polymeric MDI is the preferred isocyanate used in
this invention.
[0083] Polyols
[0084] Polyols useful in the preparation of the polyurethane foams
used in this invention can be either one or a combination of
polyether, polyester polyols, or polyalkyldiene polyols, or derived
from reaction of excess of such polyols, alone or in combination
with isocyanate function compounds. The polyols can be diols,
triols, tetrols or polyols with higher functionality. They can be
used alone or in combination. Representative examples of useful
polyols include polyoxypropylene polyol, polyalkylene polyol, and
polypropylene glycols. They can be amine polyols, sucrose polyols,
glycerol polyols, sorbitol polyols, or combinations. The polyols
used can be aliphatic or aromatic.
[0085] Most commercially available polyols have a polyether or
polyester backbone. They are usually hydrophilic and soluble in
water. Water-immiscible and hydrophobic polyols available include
those with hydrocarbon and polybutadiene backbones. Bio based,
water-immiscible, polyols are also available.
[0086] Catalysts
[0087] Tertiary amines and organo-tin compounds are preferably used
as catalysts. The particular tertiary amine and organo-tin catalyst
used in obtaining the hydrophobic polyurethane foams of the present
invention is not critical, and any combination of components
readily known to those skilled in the art may be used. Examples of
suitable tertiary amines include triethylenediamine, triethylamine,
N-methylmorpholine, N-ethylmorpholine and
N,N,N'N'-tetramethylbutanediamine. Suitable organo-tin catalysts
include stannous octoate and dibutyltin dilaurate.
[0088] Up to about 5% by weight of a catalyst can be used bases on
the total reaction material weight. Preferably the catalyst should
range from 0.01 to about 1.0% by weight. Tertiary amine and
organo-tin compounds are preferred.
[0089] Blowing Agents
[0090] Examples of blowing agents that can be used in the present
invention include water, low boiling alkanes such as butane and
pentane, acetone and liquid carbon dioxide. Halogenated blowing
agents (HCFC's) can also be used, even though they are not
preferred. Water is the preferred blowing agent in this invention.
Blowing agents are used between 1 and 20% by weight and more
preferably between 1 and 15% based on the total weight of the
formulation.
[0091] Additional Components
[0092] Additional components that may be used in the present
polyurethane foams include, for example, crosslinking agents;
fillers, such as carbon black and calcium carbonate; coloring dyes,
antioxidants, fungicides, pesticides and anti-bacterial additives,
flow agents, viscosity modifiers, foam control agents, plasticizing
agents, moisture scavengers, adhesion promoters, temperature
stabilizers, and ultraviolet radiation stabilizers.
[0093] Flame retardants may also be added to render the foamed
product flame retardant. Suitable flame retardants include
tris(chloroethyl) phosphate, tris(2-chloroethyl)phosphate,
tris(dichloropropyl)phosphate, chlorinated paraffins,
tris(chloropropyl)phosphate, phosphorus-containing polyols, and
brominated aromatic compounds such as pentabromodiphenyl oxide and
other brominated polyols.
[0094] The polyurethane composition has a low viscosity, typically
500 to 5000 cps when measured with a Brookfield Viscometer at
25.degree. C. temperature. The low viscosity, in part, allows the
composition to be easily poured into the hole. The composition can
be made water-repellant and hydrophobic to prevent external
moisture from becoming part of the foam structure and reducing the
compressive strength. The polyurethane will start to foam as soon
as the two components are mixed together.
[0095] The polyurethane composition is added to the hole, reacts,
and foams up. It is noted that some of the reaction may begin prior
to adding to the hole. For in-ground applications, it is preferred
that the resulting polyurethane foam is water-repellant hydrophobic
and closed-cell, to prevent water or other liquids from passing
through the foam to rot wood or corrode metal. The resulting
polyurethane foam then preferably cures to touch in about 3 to 4
minutes after mixing and is fully cured in less than 2 hours after
mixing. By changing the catalyst concentration, the gel time and
tack-free time of the foam can be made faster or slower, depending
on the working time required for a particular application. The gel
time can be as long as 20 minutes and as fast as 30 seconds.
[0096] The polyurethane foam has good adhesion to wood, metal,
plastics and composite materials, soil, clay, gravel and rocks.
This is evident from the results listed in Table 2 below.
[0097] The polyurethane foam also provides an abrasive surface to
increase friction against soil. This helps prevents movement of the
footing through the soil.
[0098] The compressive strength is also important to prevent damage
to the foam as a greater load is placed on the footing and it moves
through the soil. The compressive strength of the foam is usually
between 30 psi and 300 psi for most applications. However, it may
be higher, depending on the footing requirements. A particular
aspect utilizes foam that provides a compressive strength of 100
psi.
[0099] The foamable compositions utilized in the present invention
can vary with the requirements mentioned above. The following are
representative of water-repellant, hydrophobic closed cell foams.
All parts are by weight.
[0100] Aspects of the invention include compositions and methods as
follows:
[0101] Aspect 1: A foundation footing system for a load-bearing
structure comprising a hole in a ground, the hole having a bottom
and sides, and a post positioned in the hole and generally centered
within the hole, wherein the post extends above the hole, wherein
the width of the hole is wider than a width of the post thus
forming a gap between sides of the post and the sides of the hole;
the foundation further comprising a cured, closed-cell,
polyurethane foam surrounding the post, wherein the polyurethane
foam fills the gap between the post and sides of the hole, the
polyurethane foam comprising a cured mixture of a polyurethane
composition comprising polyisocyanate and at least one active
hydrogen containing compound wherein the cured polyurethane foam
has a compressive strength of greater than 10 psi, greater than 30,
greater than 50, greater than 80, or 100 psi.
[0102] Aspect 2: A foundation footing system for a load-bearing
structure comprising a hole in a ground, the hole having a top,
bottom, and sides; the foundation further comprising cured,
polyurethane foam, wherein the foam fills the hole and extends
above the top of the hole to form a foundation footing, the
polyurethane foam comprising a cured mixture of a polyurethane
composition comprising isocyanate, and at least one active hydrogen
containing compound; and further comprising a post placed on and
attached to the top of the foam and generally centered on the foam,
or wherein at least a portion of the post is embedded within the
foam wherein the cured polyurethane foam has a compressive strength
of greater than 10 psi, greater than 30, greater than 50, greater
than 80, or 100 psi.
[0103] Aspect 3: The foundation footing system of aspect 1 or
aspect 2 comprising at least two holes and at least two posts,
wherein the posts have the same or different diameters, and each
hole has a diameter accommodating the diameter of the respective
post and requisite gap.
[0104] Aspect 4: The foundation footing system of aspects 1-3
wherein the cured polyurethane foam is prepared from mixing a
polyurethane composition, pouring the composition into the hole,
and allowing the composition to foam, wherein the polyurethane foam
cures to touch in about 1 to 10 minutes after mixing the
composition.
[0105] Aspect 5: The foundation footing system of any of aspects
1-4 further comprising a footing pad underneath the post positioned
in the hole and/or the post is positioned at the bottom of the
hole.
[0106] Aspect 6: The foundation footing system of any of aspects
1-5 wherein the polyurethane composition is hydrophobic.
[0107] Aspect 7: The foundation footing system of any of aspects
1-6 wherein the polyurethane foam further comprises at least one
water-immiscible component in an amount from 10% to 80% by weight
or 30% to 60% by weight of the total composition.
[0108] Aspect 8: The foundation footing system of any of aspects
1-7 wherein the composition further comprises a hydrophobicity
inducing surfactant in an amount from 0.1% to 5% by weight of the
total composition, wherein the surfactant may be selected from
polysiloxane-polyalkylene oxide copolymers.
[0109] Aspect 9: A method of making a foundation footing system for
a load-bearing structure comprising a) forming a hole in a ground,
the hole having a bottom and sides; b) placing a post in the hole
such that the post is generally centered within the hole and a gap
is formed between sides of the post and the sides of the hole; and
c) adding a polyurethane composition into the gap, allowing the
polyurethane composition to react and form a foam, thereby filling
in the gap, and then to cure to form a cured, closed-cell,
polyurethane foam, the polyurethane foam mixture comprising
polyisocyanate and at least one active hydrogen containing compound
wherein the cured polyurethane foam has a compressive strength of
greater than 10 psi, greater than 30, greater than 50, greater than
80, or 100 psi.
[0110] Aspect 10: A method of making a foundation footing system
for a load-bearing structure comprising a) forming a hole in a
ground, the hole having a top, bottom, and sides; b) placing a
polyurethane composition into the hole, allowing the polyurethane
composition to react and form a foam, filling in the hole and
rising above the hole, and then to cure to form a cured,
polyurethane foam footing, the polyurethane foam mixture comprising
a polyurethane composition comprising isocyanate, and at least one
active hydrogen compound; and further comprising attaching a post
to the top of, and generally centered on, the foam, or embedding a
pole within the foam wherein the cured polyurethane foam has a
compressive strength of greater than 10 psi, greater than 30,
greater than 50, greater than 80, or 100 psi.
[0111] Aspect 11: The method of aspect 9 or aspect 10 further
comprising forming at least two holes and placing a post in each of
the holes, wherein the posts have the same or different diameters,
and each hole has a diameter accommodating the diameter of the
respective post and requisite gap; and erecting a load-bearing
structure on the foundation footing system.
[0112] Aspects 9-11 may likewise have the features of any or all of
the features of aspects 3-7 above.
EXAMPLE 1
TABLE-US-00003 [0113] Component 1 4,4'diphenylmethane diisocyanate
100% Component 2 Sucrose Based Polyether Polyol 60.8% Petroleum
Hydrocarbon 30% High Flash Naptha Solvent 5% Hydrophobic Silicone
Surfactant 2% Catalyst 0.2% Water 2%
[0114] The mixed viscosity is 1100 cps. This composition has a
cured foam density of 0.10 gm/cc and a compressive strength of 100
psi.
EXAMPLE 2
TABLE-US-00004 [0115] Component 1 4,4'diphenylmethane diisocyanate
100% Component 2 Sorbitol Polyol 47.9% Amine Polyol 20% Vegetable
Oil 20% Hydrophobic Surfactant 5% Catalyst 0.1% Water-Repellant
Blowing Agent, e.g. Pentane 7%
[0116] The mixed viscosity is 4200 cps. The foam density is 0.06
gm/cc. The compressive strength is 60 psi.
[0117] Below are formulations for non-water-repellant rigid,
polyurethane foams. They can be used above grade, in dry soils and
to make prefabricated footings.
EXAMPLE 3
TABLE-US-00005 [0118] Component 1 4,4'diphenylmethane diisocyanate
100% Component 2 Sorbitol Polyol 60% Polyether Polyol 32%
Non-Hydrophobic Surfactant 3% Catalyst 1% Water 4%
[0119] The mixed viscosity is 1800 cps. The foam density is 0.05
gm/cc. The compressive strength is 55 psi.
EXAMPLE 4
TABLE-US-00006 [0120] Component 1 4,4'diphenylmethane diisocyanate
100% Component 2 Glycerol Polyol 73.8% Polypropylene Glycol 20%
Non-Hydrophobic Surfactant 3% Catalyst 0.2% Water 3%
[0121] The mixed viscosity is 3000 cps. Foam density is 0.085
gm/cc. The compressive strength is 80 psi.
[0122] By adjusting the concentration of the various raw materials,
the physical and chemical properties of the foam can be changed.
For example, decreasing the catalyst concentration will slow down
the gel time. Increasing the water concentration will decrease the
foam density and decrease the compressive strength. Changing the
properties of the foam is easily done by those familiar with the
art.
[0123] In the Tables below, the compressive and tensile strength of
wood post/foam footings are compared to wood post/concrete
footings. Tables 2 and 3 give the compressive and tensile strength
of the footing system shown in FIG. 5 consisting of wood post 54 in
hole 52 held in place by foam 56. The soil 50 was compressed. The
100 psi foam gave values similar to concrete.
TABLE-US-00007 TABLE 2 COMPRESSIVE STRENGTH PEAK LOAD COMPRESSIVE
SOIL ON STRENGTH OF COMPRESSIVE FOOTING FOOTING FOOTING STRENGTH
SOIL 73 lb. 960 PSI 28 PSI CONCRETE 145 lb. 206 PSI 24 PSI 40 PSI
FOAM 99 lb. 141 PSI 21 PSI 100 PSI FOAM 146 lb. 208 PSI 28 PSI
TABLE-US-00008 TABLE 3 TENSILE STRENGTH TENSILE SOIL PEAK LOAD
STRENGTH COMPRESSIVE FOOTING ON FOOTING OF FOOTING STRENGTH
CONCRETE 40 lb. 57 PSI 28 PSI 40 PSI FOAM 41 lb. 59 PSI 21 PSI 100
PSI FOAM 49 lb. 70 PSI 28 PSI
[0124] Tables 4 and 5 give the compressive and tensile strength for
the footing shown in FIG. 6. Post 64 and foam 66 were placed over
rigid pad 68 in hole 62. The soil 60 was compressed. In a similar
manner, a post and concrete was placed over a rigid pad. The pad
was 2000 psi concrete or a 2000 psi polymer. Loose gravel was also
used. In this system, the 100 psi foam performed best. The concrete
performed similarly to the 40 psi foam.
TABLE-US-00009 TABLE 4 COMPRESSIVE STRENGTH PEAK COMPRESSIVE SOIL
COM- BOTTOM LOAD ON STRENGTH OF PRESSIVE FOOTING PAD FOOTING
FOOTING STRENGTH SOIL Prefab 83 lb. 1092 PSI 28 PSI Concrete
CONCRETE Prefab 225 lb. 321 PSI 35 PSI Concrete 40 PSI Prefab 234
lb. 331 PSI 28 PSI FOAM Concrete 100 PSI Prefab 297 lb. 424 PSI 35
PSI FOAM Concrete 100 PSI Polymer 296 lb. 422 PSI 35 PSI FOAM Pad
100 PSI Gravel 177 lb. 252 PSI 21 PSI FOAM 40 PSI Gravel 118 lb.
168 PSI 24 PSI FOAM
TABLE-US-00010 TABLE 5 TENSILE STRENGTH TENSILE PEAK STRENGTH SOIL
BOTTOM LOAD ON OF COMPRESSIVE FOOTING PAD FOOTING FOOTING STRENGTH
CONCRETE Prefab 44 lb. 63 PSI 28 PSI Concrete 40 PSI Polymer 59 lb.
84 PSI 28 PSI FOAM Pad 100 PSI Polymer 97 lb. 138 PSI 28 PSI FOAM
Pad
[0125] Tables 6 and 7 give the compressive and tensile strength for
the footings shown in FIG. 7. The 100 psi foam and the concrete are
the footings that have been placed in the hole and extend above
grade. The wood post is placed on top of the footing.
[0126] A footing pad was placed on top of the foam to spread the
load across the entire surface of the foam. Without the pad, the
foam would compress directly under the post when a load greater
than the compressive strength of the foam was applied. Both the
compressive and tensile strength of the 100 psi foam footing was
higher than for the concrete footing. The post was attached to the
top of the footing with an anchor bolt.
TABLE-US-00011 TABLE 6 COMPRESSIVE STRENGTH COMPRESSIVE SOIL
STRENGTH OF COMPRESSIVE FOOTING PEAK LOAD FOOTING STRENGTH 100 PSI
FOAM 514 lb. 170 PSI 28 PSI CONCRETE 426 lb. 141 PSI 25 PSI
TABLE-US-00012 TABLE 7 TENSILE STRENGTH TENSILE SOIL PEAK STRENGTH
COMPRESSIVE FOOTING LOAD OF FOOTING STRENGTH 100 PSI 78 lb. 25 PSI
25 PSI FOAM CONCRETE 69 lb. 22 PSI 41 PSI
[0127] The polyurethane foam also provides an abrasive surface to
increase friction against soil. This helps prevents movement of the
footing through the soil.
[0128] While the invention has been described with respect to
specific examples including presently preferred modes of carrying
out the invention, those skilled in the art will appreciate that
there are numerous variations and permutations of the above
described systems and techniques that fall within the spirit and
scope of the invention as set forth in the appended claims.
* * * * *