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Патент USA US2406757

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IUUI
UUI'I' UUI l IUIIV,
.35
COATING 0R PLASTIC
89
2,406,757
Patented Sept. 3, 1946
UNITED STATES PATENT OFFICE
2,406,757
SET STABILIZED PLASTER
Harry F. Gardner, Highland Park, Ill., assignor
to Certain-teed Products Corporation, New
York, N. Y., a corporation of Delaware
No Drawing. Application October 23, 1942,
Serial No. 463,068
5 Claims.
(Cl. 106-89)
2
1
This invention relates to (Wigs
mortar under different atmosphere and tempera
ture conditions. This stabilization of the set
ters particularl ~thosemir?itende % o bemused with
or asgreeatessigristrilciilraLpwposesi, against temperature change is important because
it makes unnecessary changes in the amount of
The invention particularly vrelates to calcined
gypsum plasters with which sand and water are 5 retarder incorporated in the plaster at the manu
facturing plant in order to meet variations in the
mixed to form mortar for application to a plaster
seasonal changes or to reduce the degree of change
base in the construction of walls and ceilings.
which may be required in some cases.
A problem which arises in the use of such plas
It has been proposed heretofore to accomplish
ters is that a given plaster as manufactured is
shipped to and used in diiierent localities where 10 one or more of these objects and overcome some
of the di?iculties above referred to by admixture
different sands are available having different
characteristics as to their sharpness and con
with calcined gypsum ogj'pmindnement and the
usual commercia‘i‘fétar ~er. As a modi?cation of
tamination with loam and clay and other impuri
this proposa
a 0 has been proposed to incor
ties which actively affect the setting time of the
calcined gypsum. In general admixture of sand 15 porate with calcined gypsum both Pqrtlanu;
ment and lime, especially in the form of hydrated
or aggregates with gypsum plaster tends to ace 1
ime, oge her with the usual commercial retarder.
erate the
‘n relative to the t e of
Such a composition is described in the patent to
settin f
ster. Moreover, it is a
Hann, 2212,811, Aug. 27, 1940. It has also been
well known characteristic of most gypsum plasters
that in general the setting time becomes longer 20 proposed to stabilize plasters against variations
occurring for the above described reasons by ad
as the plaster stands following manufacture. In
mixing with the plaster reground set calcined
addition to variations caused by the above men
gypsum. Such a composition is described in the
tioned qualities of the plaster and of the aggre
patent to Gallagher No. 1,683,539, Sept. 4, 1928.
gates there is experienced also variation in the
setting time because of the different conditions 25 The further proposal has been made in the patent
to King No. 2,078,198, April 20, 1937, of incor
of the mortar boxes and mechanical mixers used
porating ?nely ground raw gypsum with the cal
making mortars by mixing water with the plaster.
cined gypsum containing the usual commercial
The amount of set plaster left in the mixing box
or in the mixer and the cleanliness of these con
tainers a?ect materially the setting time of ordi
nary plaster.
It is an object of the invention to overcome
these di?iculties and to provide a plaster which
will have a stable set with varying conditions of
use.
It is also an object of the invention to provide
a plaster which may be used at a longer or a
retarder.
In this proposal the raw gypsum is
30 ground to a ?neness such that the particle size
of the raw gypsum is between 10 and 25 microns.
Other proposals to secure set stabilization have
been made in the art which have involved the
incorporation in the mix of other ingredients
which are described as tending to form in situ
seed crystals of hydrated calcium sulphate,
CaSO4.2H2O.
The invention proposes a simple composition
shorter period of time after its manufacture with
for a manufactured plaster containing relatively
its set determined and stabilized within limits
which make it suitable for the use to which it is 40 small amounts of auxiliary ingredients in addi
tion to the calcined gypsum stucco and usual com
to be applied.
mercial retarder in order to secure the desired
It is a further object of the invention to pro
set stabi‘ization. Tneinlentioncutillzesiqrhthcse
vide a composite plaster which may be made at
auxiliary setstabilizinaagents an hydraulic ce
the manufacturing plant and in which the time
of set will be fairly constant with different types 45 ment of the type represented by Portland. cement
and natural cement, together with calcium sul
and with different amounts of the aggregates
phate containing two molecules of water of crys
which are used and regardless of the adventitious
tallization, CaSO42H2O. Calcium sulphate dihy
admixture of foreign materials. and a plaster the
drate in the form of raw gypsum or land plaster
setting time of which as so determined at the
manufacturing plant is maintained over a long 50 is preferred, but calcined gypsum set to the di
hydrate may be used. "'The hydraulic cements are
period of timeso that the plaster may be stored
those which possess their setting properties due
for a long time and used without substantial
entirely or largely to the formation of silicates
modi?cation of its setting time.
during the process of manufacture or use, these
It is a further object of the invention to secure
stabilization of set in plaster to be applied as a. 55 setting properties developing when the cement is
2,406,757
3
mixed with water.
4
The properties of Portland
cement are well known.
cement in this and the following formulae. Some
variations may be made in the amounts of these
ingredients beyond the range indicated in the
Natural cement is a
product obtained by ?nely pulverizing calcined
argillaceous limestone to which not to exceed 5%
of non-deleterious materials may be added sub
sequent to calcination. The temperature of cal
cination shal1 be no higher than necessary to
drive oif carbon dioxide (CO2).
By land plaster is meant for the purposes of
above tabulation. Preferably, however, the pro
portions of these ingredients of the composite
stucco for purpose of the invention is as follows:
Pounds
the invention, raw gypsum or gypsum as it is 10 Tube calcined gypsum stucco_._._
mined, or in a state before it is calcined, ground
to suitable size. It may be mixed dry with the
calcined gypsum, the hydraulic cement and the
retarder in the manufacturing plant.
Per cent
1985 —1969
4
2
——
12
8
.20.10—-
.60
.40
Oommeroialretarder ____________ __
6%—-
10
.33-
.50
100.00—l00.00
‘The de- -
gree of ?neness of the land plaster for most pur
poses for which the invention is used may be rep
15
resented as follows:
Typical of the results to be obtained by the
invention a plaster utilizing Portland cement and
of the composition
Per cent
Through 50 mesh ____________________ __ 98-100
Through 100 mesh ___________________ __ 90- 98
99.37—98.50
Portland cement ______________ __
Land plaster _______ -_
_._
Formula B
F
20 Tubed stucco manta/mi
____________ -- 2000
Through 200 mesh ___________________ __ 68- 86
Portland cement ______ -7"? ___________ __
10
Through 325 mesh ____ "approximately-.. 50
Land plaster ____ _(_'L,2_(_Z;§_/_Qf_Q/: _______ _._
4
These screen tests may be taken as representative
Commercial retarder ___________________ __
8
of the standard grinds in plaster plants for or 25 was tested for stabilization and aging. Table I
dlnary purposes.
below shows the setting time for the fresh plaster,
In general it has been considered that the basis
the setting time for plaster after ?ve days aging
on which set stabilization has been effected in
in a small paper bag and the setting time after
the past has been that an accelerator is added
aging for 5 weeks.
to the plaster to hasten the formation of the 30
Table I
gypsum crystals. This over-acceleration of the
set is then offset by incorporating the retarder to i
the proper degree for securing the desired set
of the plaster. The incorporation of Portland
cement alone with the usual commercial retarder
as proposed in the Patent 2,212,811 accomplishes
Item
Type of sand
Standard Ottawa testing sand.
Buffalo sand.
Pittsburgh sand.
It should be
noted, however, that a very large amount of Port
land cement must be used in order to secure the
' set stabilization to a certain degree.
0.
Pittsburgh sand plus 0.1% ?ne ground fresh
results. . Moreover, the Portland cement even
raw gypsum.
Bridgeport
sand.
0.
when used in proportions indicated in the patent
will not suiliciently stabilize the plaster against
Bridgeport sand plus 0.1% ?ne ground fresh
raw gypsum.
adventitious changes or against the effects of
different sand and aggregates. The proposal of
the Patent 2,078,198, requiring mixture with the
plaster of land plaster, raw gypsum, ground to a
particle size of 10 to 25 microns, involves costly
Item
grinding operations, necessitates careful control
and is believed not to prevent marked slowing
down of setting time upon aging even though
invention
accomplishes
stabilization
against all such variations and causes of varia
tions above referred to by the simple composition
of an hydraulic cement of the type of Portland
cement or natural cement, land plaster and com
mercial retarder with a normal calcined gypsum
plaster or stucco capable of setting with water.
Preferably the stucco is tube milled but the in
vention is not limited to “tubed” stuccos. With
in the scope of the invention the ingredients may
be used in the proportions as follows:
Stabilized
aged 5 days
Hours
3:15
2:48
4:00
2:56
4:11
4:29
4:09
3:07
4:22
2:50
2:05
3:33
3:31
2:00
2:18
3:26
3:14
1. 47
Stabilized
- -
aged 5 weeks Unstabmzed
Hours
4:29
‘3:22
3:55
4:31
Hours
‘
30:00
24:00
4:55
181!)
3:16
9:2l
2:24
3:27
4:05
2:03
239
18:00
8:22
2:25
55
shown in this table these tests were made
with a number of different sands as well as with
the neat plaster.
Also, wit
me of the sands
there was mixed an additional amount of ac
celerator, raw gypsum, representing a condition
which may occur in the use of dirty mixing boxes
and mixers contaminated with set gypsum plaster
or other foreign material.
For comparison in the right-hand column is
65 given the setting time for an ordinary unstabilized
Formula A
Pounds
Tube milled stucco ______________ __
Portland cement ________________ _.
Land plaster ____________________ __
Commercial retarder ____________ _.
fresh
Hours
there may accrue some set stabilization with vari
ous proportions of sand or aggregate in a given
mix.
The
Stabilized
Per cent
199l-—l928
2- 40
1—- 20
6- 12
99 .55-—96.40
.10- 2.00
.05- 1.00
.30- .60
2000-2000
100. Oil-100.00
wall plaster containing commercial retarder. Al
though with some plasters of the prior art it may
have been possible to obtain stabilized set for
various types of sand and aggregates when the
plaster is fresh such stabilization is not always
maintained when the plaster has aged. Com
parison of the ?rst column with the second and
third columns of the above table shows that the
stabilization not only is obtained with a consider
Natural cement may be used in place of Portland 75 able variety of aggregates but that the degree of
comma 0R PLASHU
2,406,757
this stabilization is maintained after the plaster
is aged so as to be almost the same as when it is
fresh or with little slowing, and for all the dif
Item
ferent aggregates.
Not only has the set been stabilized by the
present invention as above described and indi
cated in the table but it is found that the com
position plaster of the invention is strongly sta
bilized against the effect of changes in tempera
ture of the atmosphere. This makes it possible
to avoid marked changes in the amount of re
tarder which is added to the plaster in the winter
Similar results may be obtained with natural
cement substituted for the Portland cement of
Moreover, it makes it possible to ship the plaster
Formula B. The following Table IV of setting
into different territories having di?erent condi 15 times shows the comparison of Portland and nattions of climate without risk of difficulties arising
ural cements for a di?erent formula, Formula C,
in the use of the plaster after a period of time
but within the range of composition of the gen
and with different aggregates.
eral formula, that is, Formula A above. The set
Indicative of the results which may be ob
ting times are those for the fresh stabilized
tained with the above composition of the inven 20 product.
tion utilizing Portland cement under varying
Formula 9
conditions of temperature the following table is
season as compared with the summer season.
given:
Pounds
Table II
,
Ratio
Item
31332;:
25 Tube
{ort‘lianld
millctement
stucco .... __
811
Neat
Type of sand
3/1
Standard Ottawa testing sand.
3/l
Buffalo sand.
D BS
er _ . . . .
2,000
3(3)
10
Table IV
'
2/1 Pittsburgh sand plus 0.1% and ground fresh
Item
raw gypsum.
Bridgeport sand.
D0.
35
Bridgeport sand plus 0.1% ?ne ground fresh
1
Paw gypsum.
5213131320
Type “sand
Plaster
Neat
""" "
3/1
3/1
Standard Ottawa.
Bu?alo.
Pittslgurgh.
0.
Item
2,000
33 / ’ 5, .64 I
‘
10
2;: Pittiburgh
sand.
0.
2/1
3%[1
2/1
Tube mill stucoo.-_._
. ._
Regal-(1e; __________ __
'30
Pounds
Set at 42° F. Set at 70° F. Set at 90° F.
Hours
3:21
2:34
4.02
3:30
3.00
2:05
2:54
3:00
Hours
4:29
3:22
3:55
4:31
3:16
2:24
3:27
4:05
1:45
2:03
2/1
v
Pittsburgh Dill-5 J70 ?ne raw gypsum‘
Hours
me
5:15
6.08
5:11
3:14
3:02
5:50
4:3
2:26
I
Portland
cement
Natural
cement
Hours
7.3
4.58
5. 56
4. 24
Hours
9.55
6.38
7. 51
5. 51
2 52
3.32
45
.
It will be noted that the variation in setting 50
3-20
“0
e as shown in Table II, while somewhat great
with some sands than the variations shown
The item numbers in Table IV correspond re
in Table I, nevertheless is quite limited for a sub
spectively to the like numbered items in Tables
stantial change in atmospheric temperature,
I and II. As will be seen the data is secured
namely, between 42° F. and 90° F. which may be 55 for the same sands. While natural cement shows
co sidered to correspond to differences between
somewhat slower setting time than the Portland
cement for certain sands and for the neat stucco,
' ter and summer job conditions. In compari
marked stabilization is secured as compared with
so with the setting times indicated in Table II
to plaster set stabilized according to the inven
the unstabilized plaster indicated in the right
tion, the following table shows for unstabilized 60 hand column of Table I. In general the results
obtained with natural cement and with Portland
plaster and for a variety of sands a wide varia
tion in the setting time at different temperatures.
cement are closely similar. These two among
the hydraulic cements are preferred for the pur
Table III
poses of the invention.
65
Type of sand
1
Standard Ottawa testing sand.
Cleveland sand.
1
York sand.
Philgdelphia
sand.
0.
Philadelphia sand plus 0.125% line ground
fresh land plaster.
The composition plaster of the invention
utilizes these ingredients and such amounts of
these ingredients as make possible a reduction
in the cost of plasters of this type known as set
stabilized plasters. The land plaster or raw, un
70 calcined gypsum utilized in the composition of the
invention is a cheap, intermediate product in the
process of manufacture of calcined gypsum. It
is produced by grinding the broken gypsum rock
at a relatively early stage of the manufacturing
75 process. Portland cement and natural cement
l
l
2,406,757
8
also are relatively cheap materials. The amounts
of these ingredients as may be seen from the
above tables are small percentages. In the
preferred range of the materials of the composi
tion these ingredients are of fractional percen
tage. The amount of retarder necessary for the
composite plaster corresponds in a general way to
that amount which is required for set stabilized
plasters of the prior art.
mercial retarder, the amount of the Portland ce
ment being not substantially less than the amount
of the raw gypsum.
2. Calcined gypsum plaster comprising as a dry
mixture for gauging with water calcined gypsum
capable of setting with water and in predominant
amount, Portland cement in amount between .l%
and 2%, land plaster in amount between .05% to
1% and retarder in amount between .3% and
It is important for the preparation of the set 10 .6%.
stabilized plaster of the invention that the stucco
3. Calcined gypsum plaster comprising as a
following its calcination shall have been allowed
dry mixture for gauging with water calcined
to cool down to a temperature not substantially
gypsum capable of setting with water and in pre
in excess of 130° F. This removal of heat from
dominant amount, Portland cement in amount
the calcined gypsum coming from the kettle is 15 between .2% and .6%, land plaster in amount
necessary because the land plaster of the com
between .I% to .4% and retarder in amount be
position of the invention will become calcined if
tween .33% to 50%.
the stucco with which it is mixed is at too high
4. Calcined gypsum plaster comprising as a dry
a temperature. Calcination of the land plaster
mixture for gauging with water calcined gypsum
to calcined gypsum will prevent the desired ac 20 capable of setting with water and in predominant
celerating action of the land plaster so that in
amount, Portland cement, land plaster with a
combination with the Portland cement and the
?neness to pass 90% to 98% through 100 mesh,
retarder the desired interaction will not take place
and a commercial retarder, the amount of the
which is effective to secure a substantially con
Portland cement being not substantially less than
stant time of set which is signi?cant of the 25 that of the land plaster, the sum of the amounts
stabilization of the invention.
of the Portland cement, land plaster and com
This application is a continuation in part of my
mercial retarder being not substantially greater
prior application Serial No. 382,016, ?led March
than 3.6% .
6, 1941.
5. Calcined gypsum plaster comprising as a dry
Having thus described my invention, I now 30 mixture for gauging with water calcined gypsum
claim:
‘
capable of setting with water and in predominant
1. Calcined gypsum plaster comprising as a dry
amount, an hydraulic cement selected from the
mixture for gauging with water calcined gypsum
group consisting of Portland cement and natural
capable of setting with water and in predominant
cement, land plaster, and commercial retarder.
amount, Portland cement, raw gypsum and com 35
HARRY F. GARDNER.
Certi?cate of Correction
September 3, 19st.
Patent No. 2,406,757.
HARRY F. GARDNER
It is hereby certi?ed that errors appear in the above numbered patent requiring
correction as follows: In the grant, line 3, and in the heading to the speci?cation,
line 5, state of incorporation, for “Delaware” read Maryland; as shown by the record
of assignments in this Office; and that the said Letters Patent should be read with
these corrections therein that the same may conform to the record of the case in the
Patent Of?ce.
Signed and sealed this 12th day of November, A. D. 1946.
[Ml
LESLIE FRAZER.
First Assistant Commissioner of Patents.
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