Note: Descriptions are shown in the official language in which they were submitted.
2192733
CEMENTITIOUS GYPSUM-CONTAINING COMPOSITIONS
AND MATERIALS MADE THEREFROM
i0 BaCsGRO~'~1D OF THE Ii~tVENTION
Field of the Invention
The invention relates to cementitious
compositions and in particular to cementitious
construction materials such as floor underlayments,
backer boards, floor and road patching materials,
fiberboard, fire-proofing sprays, and fire-stopping
materials made from a composition comprising gypsum,
Portland cement and silica fume.
Description of Related Technoloay
Construction materials, such as backer
boards for showers and floor underlayments,
typically do not contain gypsum because gypsum-
containing materials are usually not water
resistant. However, gypsum is a desirable component
in construction materials due to its rapid cure and
early strength characteristics. Attempts to improve
the water-resistance of gypsum boards by mi:~cing
Portland cement and gypsum (calcium sulfate
hemihydrate) have met with limited success i~ecause
such a mixture can result in the formation of
ettringite, which causes expansion of the
gypsum/Portland cement product and thus leads to its
deterioration. Ettringites are formed when
2192733
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tricalcium aluminate (3CaO~Al2O3) in the Portland
cement reacts with sulfate.
A cementitious composition useful as a
pavement patching compound which contains Portland
cement and alpha gypsum is disclosed in Harris, U.S.
Patent No. 4,494,990. The composition also includes
a pozzolan source, such as, for example, silica
fume, fly ash or blast furnace slag. The Harris
patent discloses that the pozzolan blocks the
interaction between the tricalcium aluminate and the
sulfate from gypsum. The Harris patent discloses
mixing a three-component blend of Type I Portland
cement, alpha gypsum and silica fume with a fine
aggregate to prepare a mortar used to cast mortar
cubes for evaluating the strength of the resulting
composition.
Ortega et al., U.S. Patent No. 4,661,159
discloses a floor underlayment composition that
includes alpha gypsum, beta gypsum, fly ash and
Portland cement. The patent also discloses that the
floor underlayment material can be used with water
and sand or other aggregate to produce a fluid
mixture which may be applied to a substrate.
SUMMARY OF THE INVENTION
It is an object of the invention to
overcome one or more of the problems described
above.
According to the invention, a cementitious
composition includes about 20 wt.o to about 75 wt.o
calcium sulfate beta-hemihydrate, about 10 wt.o to
about 50 wt.o Portland cement, about 4 wt.% to about
20 wt.o silica fume and about 1 wt.o to about 50
wt.o pozzolanic aggregate. The Portland cement
component may also be a blend of Portland cement
~T 9273.
- 3 -
with fly ash and/or ground blast slag. The
invention further includes construction compositions
and materials made from the inventive cementitious
composition.
Other objects and advantages of the
invention will be apparent to those skilled in the
art from the following detailed description taken in
conjunction with the drawings and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional view of a
covered board according to the invention.
Fig. 2 is a graph depicting compressive
strength vs. curing time for a composition #1
according to the invention and a comparative
composition #2.
Fig. 3 is a scanning electron microscope
(SEM) micrograph (500x) of a board made from a
composition according to the invention disclosed in
Example 3.
Fig. 4 is an SEM micrograph (100x) of the
board shown in Fig. 3.
Fig. 5 is an SEM micrograph (1000x) of the
board shown in Fig. 3.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, a composition
for use in construction materials is provided which
is particularly useful in areas where water
resistance is an important consideration, such as
for backer boards for baths and showers, floor
underlay applications and exterior sheathing boards.
Further uses of the inventive composition include
materials such as self-leveling floors and road
2192733
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patching materials, fire-proofing sprays, fire
stopping materials, and fiberboard.
Compositions according to the invention
include about 20 wt.o to about 75 wt.% calcium
sulfate beta-hemihydrate (i.e., beta-gypsum), about
wt.% to about 50 wt.o Portland cement (Type III
is preferred), about 4 wt.o to about 20 wt.% silica
fume, and about 1 wt.% to about 50 wt.o pozzolanic
aggregate as filler.
10 The beta-gypsum component of the inventive
composition is calcium sulfate beta hemihydrate,
commonly referred to as stucco. Beta-gypsum is
traditionally less expensive than alpha-gypsum.
Alpha-hemihydrate powder has a higher apparent
density and Smaller related surface area than beta-
hemihydrate, resulting in a lower water requirement
for the same workability and a higher compressive
strength of the set material. However, boards made
from the inventive composition have exhibited more
than adequate strength for interior applications
such as backer boards and floor underlayments and
exterior applications, such as exterior sheeting and
eaves.
The Portland cement component of the
composition according to the invention may be any of
Types I, II, III, IV, or IV (or mixtures thereof) as
set forth according to ASTM standards. However,
Type III Portland cement is preferred. Type III
Portland cement cures faster than Type I and Type II
Portland cement and exhibits an early high strength.
Blended cements also may be used in
compositions according to the invention. Blended
cements are blends of Portland cement with one or
more pozzolanic materials such as fly ash and blast-
furnace slag. The pozzolanic materials that are
2192733
added to produce a "blend" with Portland cement are
distinguished from the pozzolanic aggregate filler
component according to the invention of the
application in that the components of the cement
"blend" have a particle size which is in the same
range as the particle size range of Portland cement.
Portland cement particle size may be defined as
having approximately 15s of the particles retained
on a 325 mesh screen. In other words, at least 85s
'_0 of the Portland cement particles p asj through a X23
mesh screen (allows particles having a diameter of
up to 45 microns to pass through). Thus, for
example, blast furnace slag and certain fly ash must
be ground prior to mixing with Portland cement to
result in a ''blend" for use in the invention.
The silica fume component of compositions
according to the invention is an extremely active
pozzolan and prevents the formation of ettringite.
Silica fume is very fine (particle average diameter
of between about 0.1 microns and about 0.3 microns),
has a high surface area (between about 20 meter=!gram
and about 30 meter'/gram), and is highly amorphous
(between about 98 wt.o and about 100 wt.o amorphous
SiO, (glassy material)).
The pozzolanic aggregate filler component
of compositions according to the invention may be a
natural or man-made filler that contains a high
percentage cf amorphous silica. Natural pozzolanic
aggregates are of volcanic origin and include trass,
pumice, and perlite. Man-made pozzolanic aggregate
fillers include fly ash and FILLITE ~ (hollow silicate)
spheres which may be made from fly ash; produced by
Fiilite Division of Boliden Intertrade, Inc.
Atlanta, :~eorgia). As compared to cement "blend"
components cf the invention, pozzolanic aggregates
2192 X33
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used as fillers according to the invention are
defined herein as having an average particle size
larger than that of Portland cement (i.e., average
particle size larger than 45 microns).
Pozzolanic aggregate fillers contain a
high percentage of amorphous silica which possesses
little or no cementitious prcperties. However, in
the presence of moisture, pozzolanic aggregates have
surfaces that are chemically reactive with calcium
hydroxide at standard temperatures to form hydrated
calcium silicate (CSH) which, in compositions and
methods according to the invention, are believed to
become a homogeneous part of a cementitious system
due also to the presence of the finely divided
pozzolan of the invention, silica fume.
Compositions according to the invention which
include both a pozzolanic aggregate and a finely
divided pozzolan result in cementitious materials
wherein the transition zone between the aggregate
and a cement paste is densified and thus produces a
cured product of higher compressive strength than
compositions which utilize a pozzolanic aggregate
alone or a finely divided pozzolan alone. It is
believed that the mechanism which causes changes in
the microstructure of compositions according to the
invention to result in higher compressive strengths
is associated with two effects: a pozzolanic effect
and a micro-filler effect (due to the fine size and
spherical shape of the silica fume).
Compositions for construction materials
such as backer boards and floor underlays according
to the invention preferably include about 20 wt.o to
about 75 wt.% calcium sulfate beta-hemihydrate
(about 30 wt.% to about 50 wt.% is preferred), about
10 wt.o to about 50 wt.% Portland cement (about 6
2~ 92133
wt.o to about 35 wt.% is preferred), about 4 wt.% to
about 20 wt.o silica fume (about 4 wt.o to about
wt.o is preferred), and about 10 wt.% to about 50
wt.% a pozzolanic aggregate filler (about 25 wt.o to
5 about 35 wt.o is preferred). A preferred aggregate
filler for use in such construction materials is
pumice. Pumice is desirable as it is relatively
light weight and can be sized to result in a product
of desirable strength and physical properties. For
10 example, Hess Pumice Products Inc. manufactures a
size No. 10 pumice aggregate that measures about 93%
greater than 1400 microns, while the size No. 5
pumice aggregate has a particle size measurement of
about 23o greater than 1400 microns.
Although fillers such as calcium
carbonate, crystalline silica and different types of
clay could be included in the composition, it has
been found that the use of a pozzolanic aggregate
filler results in a product according to the
invention having superior properties. As explained
above, this is believed to occur because the
surfaces of the pozzolanic aggregate filler react
with free lime to form hydrated calcium silicate
(pozzolanic reaction) which becomes part of the
product matrix. Such a reaction is only possible
with pozzolanic aggregate fillers.
The composition according to the invention
produces building materials which set up quickly,
exhibit high strength and durability, and are water
resistant. Gypsum boards produced from compositions
according to the invention may be produced on a
continuous line. Because the composition according
to the invention sets up quickly (typically in three
minutes or less), building materials made from the
composition can be handled (e.g. sheets can be cut
219733
g _
into smaller sheets or boards) much faster than
products made from Portland cement alone. Unlike
traditional gypsum board, boards or other products
made from a composition according to the invention
do not require kiln drying, and in fact, kiln drying
should be avoided.
With reference to Figure 1, a backer board
1 according to the invention comprises a core 3 made
from a cementitious composition according to the
invention and adjacent cover sheets 5 and 7 disposed
at either side thereof. Such a board may be
manufactured by the following process:
Raw gypsum may be calcined at about 160°C
(320°F) to about 175°C (347°F) to form calcium
1~ sulfate hemihydrate. The calcined gypsum can be
post-ground to a finer particle size if, for
example, certain strengths, water requirements, and
working properties are desired. The gypsum powder
is fed to a mixer and blended with Portland cement,
silica fume and a pozzolanic aggregate filler. The
pozzolanic filler may be pumice, perlite, trass, or
fly ash or a mixture thereof. Other ingredients
that may be included in the composition are set
control additives (e. g. accelerators), water
reducing agents, water repellent additives and latex
or polymer modifiers. The resulting blend is
combined with a slight stoichiometric excess of
water to produce a slurry. The slurry, which forms
the core 3 of the board, is poured onto a lower,
continuous cover sheet 5 which is disposed on a
conveyor. Then, an upper continuous cover sheet 7
is placed on the core as it moves on the conveyor.
The cover sheets 5 and 7 are preferably made from
fiberglass matt, fiberglass scrim, or a composite of
both. The cover sheets may also be made from
219'133
_ g _
polyethylene, polypropylene or nylon; however, such
materials are not as desirable as fiberglass as they
are more expensive. As the slurry sets, scrim and
mat are imbedded into the slurry matrix during the
forming process. As the covered board moves along
the conveyor line in a continuous sheet, the board
gains sufficient strength so that it can be handled.
The board is then cut into sections, (for backer
boards, usually either 3 ft. x 5 ft. or 3 ft. x 4
ft. sheets) and transferred to pallets. The board
thickness preferably ranges between about 1/8 inch
and about 5/8 inch. The boards are then preferably
stacked and cured from one to seven days
(particularly preferred about. three days) at a
temperature of about 16°C (60°F) to about 27"C (80°F)
(i.e. room temperature) and a humidity ~f about 40%
to about 7Go, after which the boards may be sent to
a customer. The snacking of the boards
advantageously provides a moist environment for
curing. The boards Tray be cured at temperatures and
humidities outside of the above-stated ranges
resulting in an acceptable product. However, this
may extend the curing time. A board according to
the invention usually substantially reaches its full
strength about fourteen to about twenty-eight days
after formation.
When preparing a board or other product
according to the invention, the forced drying
required for gypsum board should be avoided. An
alternative curing procedure is to cover or wrap the
boards in plastic wrapping for about three days to
retain moisture for continuous curing. Such covered
boards have exhibited about 50o higher strength than
normal gypsum boards of the same density. Also, the
2~9213~
- 10 -
covered boards develop about 70o to about 800 of
their ultimate strength in three days.
When a board or other product having a
thickness of about 1/8 inch is desired, the
cementitious composition thereof preferably includes
about 20 wt.% to about 75 wt.o calcium sulfate beta-
hemihydrate, about 10 wt.o to about 50 wt.o Portland
cement, about 4 wt.% to about 20 wt.o silica fume,
and about 1 wt.% to about 50 wt.o pozzolanic
aggregate filler, resulting in a very strong thin
product, especially useful, for example, for floor
underlayments. A preferred cementitious composition
for use in very thin boards (i.e. about 1/8 inch)
and floor underlayments includes about 70 wt.o to
about 75 wt.o calcium sulfate beta hemihydrate
(about 74 wt.% is particularly preferred), about 15
wt.% to about 40 wt.o Portland cement (about 35 wt.o
is particularly preferre3), about 4 wt.o to about 10
wt.o silica fume (about 10 wt.o is particularly
preferred), and about 1 wt.% to about 25 wt.b
pozzolanic filler.
Compositions according to the invention
may also be used to prepare self-leveling floor
compositions and road patching materials. In such
materials, a master blend composition according to
the invention is prepared which includes about 20
wt.% to about 75 wt.% calcium sulfate beta-
hemihydrate (i.e. beta-gypsum) (about 30 wt.o to
about 50 wt.o is preferred), about 10 wt.% to about
50 wt.o Portland cement (about 6 wt.o to about 25
wt.o is preferred), about 4 wt.o to about 20 wt.o
silica fume (about 4 wt.o to about 8 wt.o is
preferred), and about 1 wt.% to about 50 wt.a a
pozzolanic aggregate filler (about 1 wt.a to about
15 wt.o is preferred; about 1 wt.o to about 5 wt.o
2.192733
- 11 -
particularly preferred). The master blend is then
mixed with silica aggregates (i.e., predominately
quartz local sand) to form the floor or road
patching material.
Preferably, a self-leveling floor
composition according to the invention includes (i)
about 25 wt.~ to about 75 wt.o of the master blend;
and (ii) about 75 wt.o to about 25 wt.o sand. Most
preferably, a self-leveling floor composition master
blend includes abcut 71 wt.% calcium sulfate ~beta-
hemihydrate, about 20 wt.o Portland cement, about 6
wt.% silica fume and about 2 wt.% FILLITE ~ pozzolanic
filler. Because of its low density, FILLITE
addition of amounts as low as about 1 wt.o of the
composition provide a considerable volume of filler
(see Example 2, Table II for FILLITE ~ physical
properties).
A road patching composition according to
the invention includes (i) about 25 wt.o to about
100 wt.o~ of the master blend described herein with
respect to the self-leveling floor compositions of
the invention; and (ii) about 75 wt.% ~o about 0
wt.o sand.
Compositions according to the invention
may also be used in fiberboards according to the
invention. Such fiberboards include ii) about 70
wt.o to about 90 wt.o of the master blend described
herein with respect to the self-leveling floor
compositions and road patching compositions of the
invention; and ~;ii) about 30 wt.o to about 10 wt.o
of a fiber component. The fiber component is
preferably selected from the following: wood
fibers, paper fibers, glass fibers, polyethylene
fibers, polypropylene Fibers, nylon 'fibers, and
other plastic fibers.
2192733
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Most preferably, a master blend according
to the invention for use in such a fiberboard
includes about 74 wt.o calcium sulfate beta-
hemihydrate, about 20 wt.o Portland cement, and
about 6 wt.% silica fume.
Fire-proofing sprays and fire-stopping
materials mall also be prepared utilizing
compositions according to the invention. Such fire-
proofing and fire-stopping materials include about
20 wt.o to about 75 wt.o calcium sulfate beta-
hemihydrate (about 30 wt.a to about 50 wt.o is
preferred), about 10 wt.% to about 50 wt.o Portland
cement (about 10 wt.o to about 25 wt.o is
preferred), about 4 wt.o to about 20 wt.o silica
fume (about 4 wt.o to abut 10 wt.o is preferred),
and about 1 cvt.a to about 50 wt.o a pozzolanic
aggregate filler (about 1 wt.o to about 10 wt.% is
preferred). Preferably, the pozzolanic filler is
FILLITE or perlite or mixtures thereof. FirF-
proofing sprays and fire-stopping materials
according to the invention also preferably include
about 1 wt.o to about 30 wt.o unexpanded vermiculite
filler. Such fire-proofing and fire-stopping
materials may also include up to about 2 wt.o glass
fibers and up to about 2 wt.% of a thickening agent.
The thickening agent is preferably selected from the
following: cellulose derivatives, acrylic resins
and mixtures
thereof .
EXAMPLE 1
A cementitious composition according to
the invention was prepared with components set forth
in the amounts stated in Table I below:
21927
- 13 -
TABLE I
Material Weight Percent
Beta-gypsum (Stucco) 45.1
Type III Portland Cement 19.2
Silica Fume 9.5
Pumice Filler 24.6
Perlite 1.47
W.R.A.1 0.87
Water Repellent Agent2 0.11
Accelerator 0.042
(ball-mil:~ed CaSo4~2H20
gypsum diazydrate3)
Water reducing agent or wetting agent inci_uding
lic~nosulfonates and/or naphthalene sulfonates
manufactured b~: Georgia Pacific Cord. and Henkel
Corp., respectively.
A silicone pro3uct or like material, e.g.,
VeQceal 2100 and Veoceal 1311 (both TM desianations
of products.manufacturcd by blacker Silicone Corp.)
See U.S. Patent Ncs. 3,920,465, 3,8'70,538
and 4,019,920
The materials identified in Table I were
mixed and 100 grams thereof was mixed with 35.6
grams of water. About 1 wt.o to about 5 wt.~ cf a
polymer latex (acrylic or SBR) was added to the
mixture to improve flexibility. The mixture was
then formed into boards according to the invention
using a glass matt/scrim composite. The boards were
tested for water absorption, nail holding
properties, deflection, compression strength (wet
and dry), water wicking characteristics and other
ASTM specification requirements. The boards met the
ASTM specifications with respect to each test.
2192733
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EXAMPLE 2
A self-leveling floor composition #1
according to the invention was prepared with the
components set forth in the amounts stated in Table
II below. A cementitious composition #2 with
components also set forth in the amounts stated in
Table II below (which did not include a pozzolanic
filler) was also prepared.
219213.:
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TABLE II
Composition #1 Composition #2
Material (weight percent) ~weight~ercent)
Beta-Gypsum
(Stucco) 36.1 40.0
Type III
Portland Cement 9.8 10.8
Silica Fume 2.96 3.24
FILLITE ~ 500
Pozzolanic
Fillers 0.0 ,.35
Sand (quartz;
crystallized
silica) 49.4 43.26
W.R.A.2 0.82 0.9
Retarder3 0.06 0.06
Anti-foaming
agents 0.33 0.26
s Fillite Division of Boliden Intertrade, Inc.,
Atlanta Georgia. Hollow silicate spheres with the
fo7_lowing physical properties: average particle
density of 0.6-0.8 g/cc; average bulk density of
0.35-0.45 g/cc; and typical particle size of 5-300
microns. The shell composition includes 27 wt.o to
33 wt.o A12C~, 55 wt.o to 65 wt.o Si0-" and maximum
of 4 wt . o FezO~.
Water reducing agent or wetting agent including
lignosulfonates and/or naphthalene sulfonates
manufactured by Georgia Pacific Corp. and Henkel
Corp., respectively.
A natural protein-based material.
A vegetable oil-based dry powder.
In order to form a floor composition of a
smooth consistency, composition #1 was mixed with
about 26 wt.~ water and composition #2 was mixed
with about 24 wt.~ water. The density of
composition #1 was 107 _! bs . ;'f t~. The density of
composition ~'2 was 111.62 ibs. ft's
~ ~ 9 X733
- 16 -
Both compositions were allowed to dry at
about 21°C (70°F) and a relative humidity of about
500. The compressive strengths of samples (2 inch
by 2 inch by 2 inch cubes) of each of the
compositions were tested after 2 hours of drying,
and after 1, 3, 7 and 28 days by pressing in an
Instron press according to ASTM C472-9A.
The results of the compressive strength
tests are shown in Fig. 2. Composition #1 according
to the invention exhibited a greater compressive
strength than Composition #2 for all samples tested.
Although the compressive strengths of both
compositions were similar after curing for 28 days,
the advantage of a composition according to the
invention is evident when the densities of the two
compositions are taken into consideration.
Typically, a composition having a higher density
should also exhibit a higher compressive strength.
However, in this instance, Composition #1 according
to the invention had a lower density than
Composition #2, and yet exhibited a slightly higher
compressive strength.
EXAMPLE 3
A cementitious composition according to
the invention was prepared with components set forth
in the amounts stated in Table III below:
219273
- 17 -
TABLE III
Material Weight Percent
Beta-gypsum (Stucco) 35.9
Type III Portland Cement 15.6
Silica Fume 7.g
Pumice F'illEr 39.5
W.R.A.1 0.87
Water Repellent Agent2 0.11
Accelerator 0.058
(ball-milled CaSo4~2H20
gypsum ~ihydrate3)
Mater rr~ducing agent or wetting agent including
ligr~osulfona~es and/or naphthalene sulfonates
manufactured by Georgia Pacific Corp. and Henkel
Corp., respectively.
A silicone product or ll.ke material, e.g.,
Ver~ceal 2100 and Veoceal 1311 (both TM designations
of products manufactured by blacker Silicone Corp.)
j See U.S. Patent Nos. 3,920,65, 3,870,538
and 4,019,920
The materials identified in Table III were
mixed and 100 grams thereof was mixed with 35.6
grams of water. About 1 wt.% to about 5 wt.o of a
polymer latex (acrylic or SBR) was added to the
mixture to iTnprove flexibility. The mixture was
then formed into boards according to the invention
using a glass matt/scrim composite. The boards were
tested fcr water absorption, nail holding
properties, deflection, compression strength (wet
and dry), water wicking characteristics and other
ASTM specification requirements. The boards met the
ASTM specifications with respect to each test.
The scanning electron microscope (SEM)
micrographs shown in Figs. 3, 4, and 5 were made of
a cured sample of Example 3. An arrow 30 points to
~ ~ 9z~3~
- 18 -
pumice in the sample, illustrating that in a
composition according to the invention, the pumice
becomes part of the hydrated calcium silicate (CSH)
matrix, substantially eliminating any transition
zone 32 between the pumice filler and the cement
paste.
EXAMPLE 4
A cementitious master blend binder
according to the invention was prepared with the
components set forth in the amounts stated in Table
IV below:
TABLE IV
Material A~~r_ox. Weight Per<~ent
Beta-gypsum (Stucco) 40
'Type IIT Portland Cement 46
Silica Fume 14
Acce7.eratorl 0.35
BMA (board milling accelerator, a fine-ground
gypsum produced by Nationa?_ Vypsum Company).
The materials identified in Table IV were
mixed to form the master blend binder. Then, about
75 wt.% of the binder was mixed with about 25 wt.%
pumice aggregate (Hess Products, Inc., Malard City,
Idaho) and 100 grams thereof was mixed with 43 grams
of water. To improve the workability of the
mixture, a water reducing agent (lignosulfonates
and/or naphthalene sulfonates manufactured by
Georgia Pacific Corp. and Henkel Corp.,
2192733
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respectively) was added. The mixture was then
formed into two-inch by two-inch (2" x 2") cubes to
evaluate strength gain over the time lapse of
twenty-eight days. The cubes were sealed in a
plastic bag and kept at room temperature (about
25°C) .
For the purpose of comparison, about 75
wt.o of the master blend binc.~er of Table IV was
mixed with about 25 wt.o of CaC02, a non-pozzolanic
aggregate having about the same particle size as the
pumice, and 100 grams thereof was mixed with 44
grams of water. This mixture also was formed into
two-inch by two-inch (2" x 2") cubes tc evaluate
strength gain over the time lapse of twenty-eight
days. The cubes were sealed in a plastic bag and
kept at room temperature (about 25'C)
The density and wet compressive strengths
for the samples made according to the invention and
the comparative samples made with CaCO3 were measured
and are shown in Table V below:
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TABLE V
Time Sample Sample
Elapsed Made With Made With
Pozzolanic Non-
Aggregate Pozzolanic
Aggregate
Wet Wet
Days Densityl Compressive Densityl Compressive
Strength2 Strength2
1 79.8 1151. 87.0 725
3 83.3 1779 88.9 1329
7 83.3 2646 92.6 2155
28 84.8 I 4267 I 92.8 I 3983
1 Poundsjr_ubic foot.
Pounds/square inch.
Table V illustrates the acceptable weight
strength development of the samples made 2rom a
composition according to the invention.
A second test was performed on the
composition made from 75 wt.o master blend binder of
Table IV and the pumice aggregate to study
durability. A four and one-half inch (4 1/2")
diameter, one-half inch (1/2") thick patty of the
composition was placed under running water for a
period of two months. No deterioration of the patty
was visible and the total weight loss of the patty
after the two-month test was 0.5%.
In other tests, the master blend binder
disclosed in Table IV was blended with up to about
50 wt.o pozzolanic aggregate filler (pumice or
perlite), with and without foaming agent, to produce
2 ~ 9273.
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boards according to the invention. Such boards
exhibited acceptable physical properties.
The foregoing detailed description is
given for clearness of understanding only, and no
unnecessary limitations should be understood
therefrom, as modifications within the scope of the
invention will be apparent ~~o those skilled in the
art.
