Note: Descriptions are shown in the official language in which they were submitted.
COMPOSITION AND METHOD FOR PRODUCING
GLASS REINFORCED CEMENT PRODUCTS
This invention rel~tes to the utilization of glass
as a reinforcement for cementitious articles, and more partic-
ularly to a method and composition whereby attack and degradation
of the ~lass reinforcement by the alkali content of the inorganic
cementitious binder is eliminated or greatly reduced.
Back~round of the Inventlon
The use o~ glass as a reinforcement for cementitious
materials such as concrete has been investigated for many
yearsO Consideration has been given to the use of glass fiber
rods to replace conventional steel reinforcement, as well as
to the use of glass reinforcement in the form of fibers, flakes
and woven or non-woven fabrics. Particular attention has been
given recently to the use of glass fibers as a reinforcement
for concrete and cement.
A serious obstacle in employing glass as a reinforce-
ment in cement and concrete is the alkaline environment of the
inorganic cementitious binder, which is highly deleterious to
the glass and results in significant loss of strength in the
reinforced cement or concrete products over a period of time,
or even in total destruction of the glass reinforcement.
Attack and destruction of the glass reinforcing properties is
particularly rapid under humid conditions.
Prior approaches to overcoming the problem of alkali
attack of the glass reinforcement have included the use of
low alkali t~pe cements, the use of coatings to protect the
glass from the alkali, the use of specialized alkali resistant
glass compositions, and the use of a ca~ion exchange material
to change the inorganic alkaline binder into a form which
does not attack the glass~ ~he most active areas of investi-
gation appear to be the use of protective coatings for the
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glass and the dPvelopmcllt of alkali resis~ant glass compositionas evidenced, ~or ex.-mple by several very recent patents, e.g.,
U.S. patents 4,002,48~ and 4~Q13~s78.
However, the above-mentioned prior approach~s have not
been entirely successful in prodl.~cing a practical, commercial
glass reinforced cement compositioIl. The limited availability
and expense of the speciali~ed materials required in these
approaches renders the use of these materials unfeasible for
many applications. `
Summary of the Invention
The present invention departs entirely from the
above-noted traditional areas of investigati.on and research in
protecting glass reinforcernent fibexs. Moreover, in accordance
with the present invention it has heen determined that certain
water soluble salts r when incorporated in a cement composition
containing glass reinforcing fibers, may be used most effectively
to inhibit alkali attack upon the glass reinforcement fibers in
the cement composition.
More particularly, in accordance with this invention
it has been determined that water soluble salts of a metal
selected from the group consisting of barium, lithium, a.nd
zinc, when mixed in finely divided particulate form with the
dry cementitious binder and glass reinforcement, are highly
ef~ective to inhibit alkali degradati.on of the glass reinforce-
ment when the cement mix is mixed with water and allowed tocure to form a cured glass reinforced cement product.
Thus, the method is directed to a method of making
glass reinforced cementitious material comprising the steps
of adding water to a mi~ture of inoryanic alkaline cementitious
binder and glass reinforcemen~ ~-bers, mixiny the components
and allowing the mixture to harden and cure; characterized
by inhibiting de~radation of the glass reinforcement fibers
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in the alkaline envi.ronment of the cementitious binder by
adding to the ml~ture of inorganic cementitious binder and
glass reinforcement fibers, from one-half to fifty percent
by weight based upon the weight of the glass reinforcement
5 fi.bers of finely divided parti.cles of a water soluble salt
of a metal selected from the group consisting of barium,
lithi~m and zinc.
The present invention is further directed to a method
of making a surface bonded wall comprising the steps of applying
a coatiny of a surface bonding cement over at least one surface
of an assembly of stacked concrete blocks and allowing the
cement coating to harden and cure and serve to bond the blocks
together without the necessity ofmortar between the blocks,
and wherein said coating of surface bonding cement comprises
an inorganic cementitious binder containing at ieast one
reactive alkali compound, glass reinforcement fibers distributed
throughout the binder, and fine sand aggregate also distributed
throughout the binder; characterized by inhibiting degradation
of the glass reinforcement fibers in the alkaline environment
20 of the cementitious binder by adding to the mixture of inorganic
cementitious binder, glass reinforcement fibers, and fine
sand aggregate, from one-half to fifty percent by weight
based upon the weight of the glass reinforcement fibers of
finely divided particles of a water soluble salt of a metal
selected from the group consisting of barium, lithium and
zinc.
The present invention is also directed to a cement
mix suitable for use in carrying out the above me~hodsa
It .is known that water soluble salts of certain metals,
such as bari.um and lithium for example, may be used in cement
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compositions as an inhibitor against undesixable and destructive
expansion reactions between the alkali content of the cement
binder and agyregateO
In accordance with the present invention it has been
determined that certain of these water soluble metal salts,
which were heretofore known to be e~fective to inhibit al~ali
aggregate expansion reactions in cement, may be used quite
effectively in a glass rein~orced cement composition ko protect
the glass rein~orcement from the harmful alkaline environment
of the cementitious binder.
The use of these water soluble metal salts in glass
reinforced cement compositions in accor~ance with this
invention permits the use of ordinary relatively inexpensive
E-glass reinforcing fibers instead of the more expensive and
sometimes unavailable alkali-resistant types of glass. It
will be appreciated however, tha~ the metal salts may also
be beneficially used i~ cement compositions containing alkali
resistant glass reinforcing fibers and will provide an enhanced
degree of alkali resistance thereto.
The glass reinforced cement mix compositions in accor-
dance with this invention are suita~le for numerous applications,
including use in high strength construction elements, cast or
extruded concrete articles, and for surface bonding of concrete
blocks or the like without the necessity of mortar between
the blocks.
The inorganic binders used in accordance with the
present invention may include Portland cement, masonry cement,
mixtures of Portland c~ement and rnasonry cement, and mixtures
of the foregoing with hydrated lime. The cement composition
may also include aggregate fillers such as sand, and property-
modifying additives such as piyments~ plasticizers, water
reduciny admixtures, ~aterproo~ing admixtures, shrin~age
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; compensators, set accelerators, retarders, gas forming agents,
air entraining admixtures, and water retaining admixturesO
Some of the features and advantages of the invention
having been stated, others will become apparent from the
description and examples which follow, which are lntended to
illustrate and disclose, but in no way limit, the invention.
Detailed Description of the Invention
The chemicals found effective to inhibit alkali
attack upon the glass reinforcement in a glass fiber reinforced
cement product are water soluble salts of a metal selected
; rom the group consisting of barium, lithium, and zinc, and
preferably the water soluble chloride, carbonate, nitrate,
or acetate salt of such metalu Particularly preferred are
barium chloride, zinc acetate, and lithium carbonate. The
salt is incorporated into the cement mix by uniformly blending
finely divided particles of the salt with the dry particulate
cementitious bindex and glass reinforcement.
Cement mixes for forming glass reinforced cement
products are conventionally sold pre-packaged in bags.
The water soluble salts found effective as inhibitors in
accordance with this invention may be suitably mixed with
the dry cementitious binder and ~lass reinforcement, packaged,
stored for indefinite periods of time without loss of
effectiveness as an inhibitor and without causing caking or
lumping of the cement mix. The metal salt becomes active
as an inhibitor when the cement mix is mixed with water and
the composition is allowed to cure to form a cured cement
product.
While the mechanism by which the water soluble
metal salts function to inhibit alkali degradation of the
glass reinforcement is not entirely understoGd, tests have
determined that the metallic element becomes chemically attached
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or bonded to the glass in some manner, and that tha glass is
protected from alkali attack thereby~ I t is believed that the
metal reacts with the alkali reactive silica of the glass to
produce a metal~silica complex which forms an alkali resistant
protective sheath or coating on all exposes surfaces of the
glass and thus insulates the glass from further reaction
with the alkali content of the cement binder. It will be
appreciated that since the reaction between the water soluble
metal salt and the glass reinforcement occurs ln situ while
the glass reinforcement is distributed in the alkaline
cementitious binder matrix, all alkali susceptible sur~aces
of the glass rein~orcement are protected b~ the inhibitor.
On the other hand, where a protective material is applied
as a coating to glass reinforcement fibers as is done in
accordance with many o~ the priox approaches as noted
earlier, complete coverage of the glass fiber with the
protective material cannot be achieved, since the protective
material is normally applied to the continuous glass filaments
prior ko cutting into fibers and the end surfaces of the
fibers are thus left unprotected.
In the cured glass reinforced cement product of this
invention, the metal is present not only on the surface of the
glass rein~orcement fibers but also throughout the cement matrix,
as a result of the water soluble metal salt having been blended
with the alkaline cementitious binder prior to mixing of the
cement and curingO The metal is thus a~ailable in the
cement to provide additional protection to the glass reinforce-
ment throughout the life o~ the glass reinforced cement productO
In this regard, it has been determined that under
normal environmental conditions, the greatest amount of
alkali degradation o~ the glass reinforcement occurs shortl~
after the cement is mlxedO After several months of curing,
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the alkali remaining in the cement is relatively insoluble
and non-aggressive, much of it having been neutralized by
reaction with carbon dioxide in the atmosphere or with other
materials in the cement.
However, where the cement product is used under
severe conditions of high humidity and~or high temperature,
the alkali may remain relatively active and aggressive ~or
extended periods o~ time. Similarly, if the cement product
is late~ exposed to these conditions, the relatively non-
aggressive alkali may become reactivated. The metal which isdistributed throughout the cement matrix in accordance with
this invention is available to provide additional protection
to the glass rein~orcement, if and when the severe conditions
occur.
The water soluble metal salts have been found to
be effective in concentrations as low as about one-hal~
percent by weight based upon the weight of the glass reinforce-
ment. Concentrations as high as about fifty percent by
weight may be suitably employedr although the rate of increase
in efectiveness as a function of concentration appears to level
out somewhat at concentrations exceeding about ten to fifteen
percent, and for this reason, concentrations significantly
exceeding this level are not economically attractive. The
salt is most desirably used in amounts ran~ing ~rom about one
to about ten percent by weight based upon the weight o~ the
~lass reinforcement.
The alkaline inorganic binder employed in cement
compositions in accordance with this invention may include
masonry cement, Portland cemenk, mixtures of masonry cement
and Portland cement, and mixtures of the above with hydrated
lime. Portland cement is preferred and cements having an
alkalinity as high as 1.5 percent by weight, based upon Na2O,
may be suitably employed in the compositions of this invention.
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Poxtland cements classified under ASTM specification C-150 as
Type I cements have been tested and found particularly
acceptable for the glass reinforced cement composi~ions of
this invention.
The cement mix may also include the conventional
types of fillers used in cement and concrete products such
as gravel, sand, natural or manufactured aggregates, or
crushed marble. Fine mineral aggregates (20 mesh or finer) `
are preferred in the compositions when chopped glass rein-
forcement fibers are used to obtain proper dispersion of the
glass reinforcement fibers and optimum reinforcing function
thererom. The filler may be used in amounts ranging from
0 to 300 parts per 100 parts of dry cement binder.
Property modifying additives known in the cement
and concrete industry as "admixtures" may also be included
in the cement compositions. These are compounds or materials
known to improve or alter the cement characteristics, and when
used are generally incorporated in amounts of from about one
percent up to about 20 percent by weight based upon the dry
weight of the cement binder. Products classified as admixtures
include pigments, water reducing admixtures, water retaining
admixtures, air entraining ad~ixtures, set accelerators, gas
forming additives, waterproofing admixtures, expansion producing
admixtures, shrinkage compensation admixtures, and plasticizers.
The glass reinforcement may be in the form of fibersf
chopped yarns or rovings, flakes, rods, and woven or non-woven
fabrics. Preferably however, the reinforcement is in the
form of individual glass fibers or bundles of fibers chopped
to a length of about one-fourth inch to 2 inches, most
desirably abo~-t one-half inch. Fibers shorter than about
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one-fourth inch are considerably less effective as reinforce-
ment, while fibers in excess of about 2 inches become entangled
or fo~n balls during mixing or o~herwise do not maintain
adequate dispersion throughout the cement matrix. Commer-
cially available borosilicate Type E-glass may be suitably
employed. However, other types of co~nercially available
glass, such as the various alkali resistant types of glass
may also be employed if desired. The amoùnt of glass
reinforcement employed is preferably within the range of
2 to 15 parts per 100 parts of dry cement ~nderr and most
desirably within the range of 4 to 7 parts.
The dry cement mi~ compositions in accordance with
this invention may be mixed with water and formed into
various articles, including constructlon elements for use
in applications requiring high tensile or c~npressive strength,
cast or extruded concrete articles such as decorative veneers,
concrete panels~ concrete pipes or conduits.
T~e compositions are also particularly suitable as
surface bonding CelnentS for applying to the surface of a
concrete block wall and the like for bonding the blocks
toyether without the necessity of mortar between the blocks
as has been customarily done in the past. The surface bonding
cement provides a moisture resistant, stucco appearance on
the sur~ace o~ the wall and the thus bonded concrete blocks
may be utili~ed for one or two stories, s1ngle and multi-
family dwellings, warehouses and other commercial buildings
up to two stories, below-grade basement walls, low-cost
masonry units, fann buildings, and a variety of other appli-
cations. When the composition is Qmployed as a surface
bonding cement, it should be mixed with water to a cxe~ny
consistency and applied b~ sprayiny or by trowel to the
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surface of the stacked block or brick wall, pr~ferably about one-eighth
inch thick and up to one-fourth inch thick.
Exempla~y compositions in accordance l~ith this invention are as
ollows, the preferred composition being particularly suitable for use as
a surface bonding cement: ;
parts by weight
tbroad) (preferred)
Portland cement 100 100
hydrated lime o_30 13-22
fine sand aggregate 0 300 100-160
glass reinforcement fiber 2-15 4-7
inhibitor ~Ba, Li, or
Zn soluble salt) 0.002-8.0 .5-3
admixtures 1-20 1-20
To demonstrate the effectiveness of this invention, accelerated
test methods were developed to quantitatively measure the reduction in
alkali attack on glass fibers which is achieved by the addition of water
soluble metal salts. The accelerated test specimens were subjected to
electron microscopic examination of surface defects on the glass rein-
forcement fibers as well as to chemical analysis of rate and quantity of
glass corrosion.
In most cases, the control specimen was an alkalî resistant
glass reinforcement fiber sold commercially as CEMFIL* and produced by
Pilkington Brothers, Ltd. or its licensees under IJ.S. Patent No. 3,8611926.
The CEMFIL fiber is of the following composition, in molecular weight
pe~centages:
SiO262% to 75%
Zr~27% to 11%
R 013% to 21%
R~O1% to 10%
Al 030% to 4%
B2~0% to 6%
Fe ~30% to 5%
C ~20% to 2%
TiO20% to 4%
*Trademark
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Wherein R2 represents Na2 and up to 2 mol % Li20, and R'O
is an oxide selected from the group consisting of the alkaline
earth metal oxides, zinc oxide (ZnO) and manganese oxide (MnO).
The inhibitors were evaluated in combination with
commercially available alkali susceptible E-glass fibers, which
until now have not been recommended for use in alkali binders.
Their composition is typically as follows:
SiO2 52.6~ by weight
A123 14.6
CaO 17.6
MbO 4.0
B203 6.~
Na20 1.4
K20 1. 9
Organic Sizing lo 3
100.0%
These fibers are commercially available and manufactured by
Johns Manville Company as code 308 reinforcing fibers.
Example I
The CEMFIL glass and the code 308 E-glass fibers
were exposed to an alkali solution of 1.0 N sodium hydroxide
and the level of corrosion was determined by colorometrical
quantitative analysis of the soluble silicates. In each
instance 20 grams of the glass fiber was placed in polyethylene
bottles with 200 ml of 1.0 N sodium hydroxide and maintained at
temperatures of 75 Fo and 120 F. for periods of 7 and 28 days.
Table I gives the quantity of soluble silica of these specimens
in mg/g at the specified times and temperatures.
TABLE I
soluble silica
7 days 28 davs
75~~- - 120 F. 7-5- F,cI200
(1) E-glass fiber code 308A 19.7 32.536.0 49.0
(2) E-glass fiber code 3535 8.4 41~546.0 64.0
(3) AR-glass OCF K 885 CA3.4 60.8 15,518500
(4) AR-glass CEMFIL .5 9.9 lo 533.0
It is apparent that -the alkali resistant glass fibers, while
relatively resistant to alkali attack at room temperature~ are
very susceptible to alkali attack at elevated temperature.
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Calculating Erom the known original silica content of the
fibers, the data of Table I represent a signi:Eicant amount of
glass fiher corrosion, as seen from Table II.
TABLE II
28 day exposure
to lN NaOH2 at 75F at 120F
Sample SiO2 Content% Glass attacked
5a~% 8.52% 9~07%
2 54% 6.83% 11.85%
10 3 62% 2042% 29.84%
4 69% 0.22% 4.78%
This example demonstrates that an effective inhibitor would be
desirable not only in conjunction with E-glass reinforcing fibers,
but also with the alkali resistant types of glass fibers, parti-
cularly where the alkali resistant fibers are subjected to severe
conditions such as elevated temperature.
Example II
The procedure of Example I was repeated with the
addition of small amounts of soluble salts of barium, lithium
20 and zinc to the E-glass and alkali resistant glass fibers. The
results are shown in Table TII.
TABLE III
Soluble Silicate (mg/g3
7 days 28 daYs
75F120~F 75F 120F
E-Glass Fiber JM308 no inhibitor 19.7 33.0 46.0 48.0
+19~ BaC12 8.010.7 15.0 22.3
+19~ LiC03 10.315.5 19.0 20
+1% Zn (CH3C00)2 9.8 10.2 20.0 22.8
+5% BaC12 3.35.4 5.0 14.0
AR glass Fiberno inhibitor ~ 3.3 ---- 16.0
CEMFIL +10% BaC12 ---- 0.7 ---- 1.3
E-glass Fiber Code 3535 no inhibitor ~ 25~1 ~--- 29.7
+10% BaC12 ---- 3.7 -~ 3.8
This example clearly demonstrates that bar:ium chloride, lithium
carbonate, and zinc acetate, in concentrations as low as one
percent, effectively inhibit alkali corrosion of both E-glass
fibers and alkali resistant glass fibers.
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Example III
The procedure of Example I was repeated varying the
amount of barium salt used as a percent of the weight of total
glass. ~he test was done only at 120. The results are shown
in Table IV.
TABLE IV
Soluble Silica (mg/g)
120F
7 days 28 days
E-Glass Code 308 ~o inhibitor21.622.8
~ 1~ BaC12 15~022.3
+ 5~ BaC12 5.014.0
+10% BaC12 3.04.6
+20% saC12 2.02.5
+30~ BaC12 1.61.7
+40~ BaC12 1.31~5
~50~ BaC12 1.42.0
+10% Ba(c2H3o)2 3-
+10% BaC03 22.028.0
+10% Ba(N03)2 3.8 4.2
It will be seen that the barium chloride addition is effective
at levels as low as one percent and is highly effective at levels
of ten percent or greater. It will be further noted that
barium carbonate, a water insoluble barium salt~ is ineffective -
as an inhibitor.
Example IV
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~ comparison was made of the effectiveness of various
levels of soluble barium chloride by boiling E-glass reinforcement
fibers in a Portland cement slurry with barium chloride added
thereto at levels of 0%, 1%, 5~ and 10% by weight based upon
the glass fibers. After boiling for four hours, the fibers
were removed from the slurry r washed~ dried, and examined for
corrosion and surface pitting by scanning electron microscope at
4000X magnification. The E-glass fibers exposed to the Portland
cement slurry without inhibitor showed serious surface corrosion.
However~ in those samples exposed to the slurry containing
barium chloride inhibitor, no surface defects could be observed.
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Example V
Test panels 1/8 inch thick containing E-Glass
reinforcement in a Portland cement-lime binder were prepared.
sarium chloride was incorporated in three of the panels at
concentrations of one percent, five percent and ten percent
based upon the weight of the glass. A fourth panel serving as
a control sample, contained no inhibitor. The test panels were
exposed for 1,000 hours in an atlas Weather-O-Meter. This
exposu~e simulates accelerated weathering under high ultraviolet
ligh~ and rain cycles with an intensity of one hour equals 24
hours outdoor exposure. After exposure for 1,000 hours, simulating
approximately 30 months of exposure, the glass fibers were
carefully removed and examined for possible sur~ace defects
by means of a scanning electron microscope at 5000X magnification.
No surface defects were noticed in the three samples containing
barium chloride, while the control sample without barium chloride
showed definite surface pitting.
In the specification there have been set forth
preferred details of the invention, and although specific terms
are employed, they are used in a generic and descriptive
sense only and not for purposes o limitation.
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