Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
Field of the Invention
The present invention relates to a polymer cement
mortar composition which is used by applying to steel
structures, metal roofs, external walls, civil engineering
structures, etc.
Brief Description of the Drawings
Fig. 1 is a graph showing the behaviour of the
corrosion rate of steel in pH atmospheres.
Fig. 2 is a graph showing the changes of pH value
with day when mild steels were immersed into waters having
different kinds of aggregates dispersed therein.
Fig. 3 is a graph showing in terms of maximum strain
(Smax) the resistance to bending (f) and the resistance to
compression (C) of end products due to variations in the
glass content of the aggregates incorporated in polymer
cement mortar compo~itions.
Fig. 4 is a graph showing the effect on the strength
of polymer cement mortar composition by the mixing ratio of
the cement (C) and the slag (S) in polymer cement mortar
compositions.
Fig. 5 is a graph showing the effect on the peeling
strength of polymer cement mortar composition by the mixing
ratio of the polymer (P) and the cement (C) in polymer cement
mortar compositions.
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Fig. 6 is a graph showing the peeling strength of
end product to various materials.
Fig. 7 is a perspective view showing the relation
between a peeling strength measuring jig and a test specimen.
Fig. 8 is a perspective view for explaining a test
specimen after an abrasion test.
Fig. 9 is a graph showing the behaviour of change
with time of the abrasion tests.
Fig. 10 is a graph showing the damping behaviour of
steel plates coated with polymer cement mortars.
Fig, 11 is a graph showing the stress-strain behaviour
of test specimens prepared by using polymer cement mortar
compositions.
Fig. 12 is a graph showing the dimensional changes
with time of the test specimens prepared by using polymer
cement mortar compositions and subjected to cyclic thermal
test.
Description of the Prior Art
Anti-corrosion paint is typical of coating materials
used for steel structures. While the anti-corrosion paint-
ing consists of simply applying or spraying a suitable anti-
corrosion paint to the surface of a steel structure and it
can ~e effected very easily, there have been disadvantages
that the anti-corrosive property for a steel structure
subjected to a coating treatment employing a anti-corrosive
paint is low in durability, particularly low in abrasion
durability since the coating film thickness i5 generally
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small and that it is difficult to expect that the coating
continues to exhibit the desired effect under natural and
artificial environments over a long period of time.
Under these circumstances, the method of applying
eement mortar and forming an anti-corrosive layer on steel
structures has been studied and carried out in some quarters
with a view to ensuring the desired durability. However,
the most serious disadvantage of the cement mortar application
is that the applied coating layer tends to eause cracks therein.
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ThUs, ln view of the cracking tendency of applled coat-
lng layers after hardenlng, attempts have also been made to
use cement compositlons premixed with asphalt, for example,
and these attempts have been disadvantageous in that not
only the surrounding environment such as the soil ls
contaminated by the varlous constituents exuded from the
plasticizer used but also the offensive smell emitted by
the asphalt affects seriously the operators as well as the
inhabitants in the nelghborhood.
In view of these circumstances, so-called polymer
cement mortar composltions incorporating synthetic resin
components in place of asphalt have come lnto use.
These polymer cement mortar compositiong have been used
as paving materials, waterproof materials, chemical
resistant coatings, ship's deck coverings, vehicles lining
materials since the incorporated polymers have been considered
to have the effect of increasing the cohesion of the hardened
cement and improving the adhesion to steel structures and
to be useful from the characterlstlc and antl-corroslon
effect of vlew of the composltlons as constructlon materlals.
The required characteristic properties for these
applications have included the adhesion to ground or priming,
abrasion resistance, waterproofing effect, weathering
resistance, cracking prevention, impact resistance, chemical
resistance, expansion and contraction property, anti-
corrosive property for structures to be coated, etc., and the
polymer cement mortar composltlons now ln use have been
consldered to satisfy the most of these requirements.
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However, these known compos~tions have still left
room for improvement so as to fully and satisfactorily meet
the characteristic properties required by ever divergently
increasing various applications. Some examples of these
deficiencles will be described in detail hereunder.
~1) The known polymer cement mortars mostly employ latex
or emulsion polymers of the water dispersion type whlch are
mlxed wlth hydraulic cement, aggregate, etc., and they
exhibit a rapid rusting phenomenon upon explration of a few
minutes after the coating. Such a rapid rusting phenomenon
ls called as a flush rust and the the results of experlments
have shown that this phenomenon takes place in substantially
all the polymer cement mortars to different extents.
When such a flush rust occurs, particularly-when the
steel structure i8 placed in a corrosive enrivonment after
its occurrence, thls, coupled with an expansion in the
volum~ of the rust on the steel surface, tends to cause
danger of peellng off.
This is due to the fact that no conslderation has been
given to the anti-corroslve properties of the polymer
emulslons incorporated ln the known polymer cements.
Whlle it ls generally consldered that the alkall of the
cement makes the steel to passlve state, for thls purpose
lt i8 necessary to malntaln the pH of the cement coating 12
¦ or over at the steel surface and thus lt ls dangerous to
¦ overestlmate the anti-corrosive effect of the polymer cement
! simply due to its alkaline nature. In other words, Fig. l
.j shows the relatlon between the pH and the corroslon of
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the steel according to the research works of W Whiteman and
R. Russel and lt wlll be seen that the corrosion of the
steel progresses rapldly when the pH is less than 12.
Also, the followlng Table and Fig. 2 show the results
obtalned by stlrring and mixing 100 grams of the aggregate,
cement, etc., of the samples 1 to 7 shown ln the Table wlth
900 cc of tap water, hanglng down a pollshed mlld steel
sheet lnto each of the resultlng stlll llqulds, measurlnq
the varlatlons ln the pH value of the liqulds wlth a pH
meter and observing the occurrence of rust.
.
Sample Aggregate, cement etc. Conditlon after 30 days
No. lmmerslon
1 Tap water ~blank) Unlform rust X
2 Portland cement No rust
3 Portland blast furnace No rust
cement
4 Slag Unlform rust X
Cement 30 + slag 70 Rust around speclmen O
holes
6 Cement 30 + slllca Dltto O
sand 70
7 Sand Uniform rust X
It has been found that whlle the pH values were low and
conslderable rust occurred ln the case of ths tap water
(blank), the slag and the sand, the portland cement and the
portland blast furnace cement showed hlgh pH values (12 or
over) on the average and no occurrence of ru~t and the
cement plus slag and the cement plus slllca sand showed
sllghtly lower pH values and the occurrence of sllght rust
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on the specimens.
(2) Although the known polymer cements mortars are
anti-corrosive materials, no satisfactory consideration
has been given to the surface preparation and the coating
system with the result that when the cements are placed in
corrosive emvironments (e.g., exposed places or places
subjected to the alternate wet and dry conditions in the
seaside area), rust is caused between the steel surface and
the coatin~ material in a very short period of time and
this causes deterioration of the adhesioll.
In accordance with the results of various extensive
studies made from the above-mentioned points of view, an
anti-corrosive coating composition comprising a cement, a
granulated blast furnace slag of a specified particle size
and a polymer emulsion mixed together in specified quantities
or proportions has been proposed (Japanese Patent Publication
No. 57-39661) and also a polymer cement mortar has been
developed (Japanese Patent Publication No. 58-38378) which
comprises a mixture of a hydraulic cement and a water
dispersion type polymer as a constituent of the composition
and separately incorporates an anti-corrosion agents.
However, various other properties, such as, elongation,
thermal shock resistance and abrasion resistance are also
required and cases frequently occur where the conventional
polymer cement mortar compositions are not only incapable
of full~ meeting these severe requirements but also in-
capable of coping with the requirements depending on the
applications.
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Summary of the Invention
As the result of earnest and constant research works
conducted for the purposes of developing a polymer cement
mortar composition having improved properties so as to
satisfy the requirements of such ever increasing applications
as mentioned previously, the inventors have discov~red and
invented a novel polymer cement mortar composition which
comprises a polymer, a cement and an aggregate as principal
essential components and in which the aggregate consists of
specially selected one thereby satisfactorily meeting the
previously-mentioned various required properties.
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According to an aspect of the invention there is
provided: A polymer cement mortar composition including
a cement ~C), and aggregate (S) and a polymer (P), wherein
the aggregate comprises a granulated blast furnace sla~
having a glass content of 95~ by weight or over, wherein
the. polymer is a styrene-butadiene polymer, and wherein
the ratios C/S and P/C by weight are respectively selected
from 0.4 to 0.65 and from 0.2 to O.S.
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Description of the Preferred Embodiments
The cement component used by this invention comprises
a portland cement, portland blast furnace cement or the like
and the prlncipal functions expected of this component are
the improvement of strength and durability and the mainte-
nance thereof.
Also, the polymer used comprises a styrene-butadiene
type polymer such as styrene-butadiene polymer or acrylic
modified styrene-butadiene polymer. When a polymer of any
other type than this type is used, it is difficult to
obtain the desired effects with respect to the adhesion
between the composition and an object to be coated and/or
the flush rust preventlve effect as shown by the results of
preliminary studles which will be described later.
In accordance with the invention, it is also an
essential requlrement to use an aggregate havlng a glass
content of 95~ by welght or over.
In the case of the ordlnary polymer cement mortar
compo8itlons, they are made by using aggregates comprising
silica sand such as rlver sand or pit sand, granulated blast
furnace slag or the like.
However, when the polymer cement mortar compositions
using these aggregates are used in clvll engineering appll-
catlon4, that ls, when they are applied as paving materials
or external wall materials, they have the disadvantage of
tendlng to cause cracks.
In completlng the lnventlon, prellminary studies have
been made on the varlous polymers ~P), the varlous
aggregates (S), the P/C and C/S welght ratios wlth respect
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to the cement (C) and other general tendencles and the
below-mentioned results have been obtained.
Shown in the following Table are the results obtained
by applying to steel plates polymer cement mortar composi-
tions each made by addinq to a cement component comprlsing
a portland blast furnace cement one of the following polymers
as the polymer component and one of the following anti-
corrosive agents in an amount corresponding to 0.5~ by weight
of the whole composltion to examine the effect of the
anti-corrosive agent addition and observing the subsequent
behavlor of the coatings.
Peeling strength N/cm2
=====z==========
antl-corroslve
aqent bl A(St-Bd) _ SBR A-St PAN EVA
- 335 178 262 198 84
X X X X X
1 287 13~ 238 186 82
(~) O X X X
2 317 136 173 143 76
(~) X X X
3 322 185 244 224 65
O X X X
~1 : 1 nitrlte type, 2 metaborate type, 3 amlne type.
~2 : A(St-Bd) acryllc ester modlfled styrene-butadiene
polymer
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SBR styrene butadiene rubber
A-St acrylic ester styrene copolymer
PAN polyacrylonitrile emulsion
EVA ethylene vinyl acetate copolymer
valuation ~ remarkably flush rust preventing effect
O partial rust
X no efrect or substantially no effect.
As will be seen from the results shown in the Table,
it has been found that the styrene-butadiene polymers are
the most preferred ones, the essential one of the properties
required for the polymer cement mortar, in consideration of
its balance against the rust preventing effect.
For the prevention of flush rust it is only necessary
to incorporate an anti-corrosive agent in the polymer
cement mortar composition or perform a primary treatment on
the surface of an object to be coated. Where an anti-
corrosive agent is used, it is incorporated in an amount
corresponding to about 0.1 to 3.0% by weight, preferably
about 0.3 to 1.0% by weight of the composition. Where no
anti-corrosive agent is used, it is possible to obtain a
flush rust preventive effect which is equal to or greater
than that obtained with the use of an anti-corrosive agent
by performing a primary treatment on the scale-removed
surface of an object to be coated with a material prepared
by dispersing zinc powder in an epoxy resin or silicate
compound, for example.
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In thls connection, lt is needless to say that both
of the primary treatment and the use of an anti-corrosive
agent can be employed as occasion demands.
On the other hand, studles on the aggregates in the
polymer cement mortar composltlons have resulted ln the
behavlors of Flg. 3 wlth respect to the tendency of the
bending reslstance (f~ and compression resistance (C) of the
products ln terms of the maximum straln (Smax) and the glass
content.
From these results lt has been found that the glass
content of the aggregate ln the polymer cement mortar com-
posltion has an lmportant effect on the values of f and
C and it has been ultlmately dlscovered that the use of
an aggregate havlng a glass content of about 95~ by welght
or over results ln a composltlon whlch has tlle least tendency
to crack.
The reason for thls resldes ln the fact that ln the
case of a granulated blast furnace slag havlng a hlgh glass
content, the materlal ltself exhlbits a hydraullc effect.
More speclflcally, when the granulated blast furnace
slag contacts wlth the moisture ln the mortar, minute hydrates
(CaO-S102.nH20) are flrst formed on the surface of the slag
and then a hydrated product (CaO-S102-AQ203 nH20) ls formed
under the actlon of AQ203 ln the compositlon ln the alkallne
atmosphere. It ls belleved that these hydrated products
flll tha spaces between the slag partlcles and serves as a
binder thus promotlng the hardenlng. Thls actlon is an
lmportant chemical feature whlch ls never known ln the case
of the conventlonal slllca sand and thls has the effect of
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producing a hardened substance which is dense and high in
cohesive and adhesive forces.
Wlth the aggregate meeting the thus determined require-
ments, the partlcle size of about 0.6mm or less produces
the deslred effects from the worklng property polnt of the
polymer cement mortar composition.
Whlle the aggregate havlng a glass content of 95~ by
weight or over is not limited to any partlcular type so
far as the above-mentioned requlrements are met, speciflcally
lt may be comprlsed of a granulated blast furnace slag
obtalned by qulckly cooling the molten slag dlscharged from
a blast furnace.
Wlth the polymer ~P) and the aggregate (s) selected ln
the above-mentloned ways, another lmportant matters are
the relatlon ln quantlty between the components and as
regaxds the C/S ratlo Flg. 4 shows a plot of the behavior of
the compresslon strength (C), the bendlng strength (f) and the
tenslle strength (TS) obtalned by varylng the C/S ratio and
maintalnlng the other condltions wlthln the preferred ranges
whlch are conflrmed on the above-mentloned grounds. From the
dlsclosed behaviors lt wlll be seen that a coating layer
havlng well-balanced strengths ls produced lf the C/S ratlo
ls wlthln the range of 0.40 to 0.65.
Flg. 5 ls graph wlth plots made by obtalnlng the data of
peellng strength accordlng to the P/C ratlo by means of the
slmllar technlque. In thls case, the peellng strength of a
value wlthln a glven range ls ensured when the P/C ratlo ls
wlthln a range of 0.20 to 0,50. As wlll be seen from the
behavlor ln the Figure 5, the peellng strength decreases wlth
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decrease ln the value of the P/C ratio and also any excesslve
value of the P/C ratio cannot ensure manlfestation of the
effect corresponding to the addition of the polymer.
In the actual appllcation of the polymer cement mortar,
one of the known coatlng means is selected in accordance with
the positlon, condltlon, etc., of an ob~ect to be coated so
that if, for example, the object has a wlde-spread plane
surface or the object has conslderable lrregularities or
undulatlons, it is convenienct to apply the mortor by spray
coating employlng a spray gun.
With the constltutlon described ln detall above, the
polymer cement mortar composltion according to the invention
ls a polymer cement composltlon whlch ls excellent ln
performance ln terma of the adheslon to ground or priming,
abraslon reslstance, waterproof effect, weatherlng resis-
tance, a lmpact resistance, chemical resistance, anti-
corrosive property, elongatlon, damping property, thermal
shock resistance, etc., thereby fully satisfying the func-
tions requlred for various applications.
The various properties and effects exhlblted by the
polymer cement mortar compositlon according to the lnventlon
wlll now be descrlbed by way of the followlng examples.
Note that the polymer cement mortar composltlons of the
followlng examples have the followlng proportlons as the
common proportlons.
Part by welght
Acryllc modlfled S~R latex
~solld content 48~) ................................. 20
Portland blast furnace cement .. ,................... 25
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~3~1~ Part by weight
Granulated blast furnace slag with
glass content of 99~ (0.5mm or less) .......... 55
water ......................................... 0 - 3
Example 1
Test specimens were prepared by coating blast~finished
steel plates with a zinc powder-containing epoxy resin
dispersion to a thickness of 15 to 20~m and then spraying
thereto a polymer cement mortar composition of the above-
mentioned proportions to a thickness of 5mm.
The thus prepared specimens were cured for 28 days
at a room temperature and then subjected to wet-dry cycle
test, a slurry immersion test and a natural sea water
immersion test over 1 year and a accelerated weathering test
over 1,000 hours. As will be seen from the following Table,
there was no change in the surface condition of the steel
plates.
Surface condition
Test item External aPPearance of steel ~late
wet dry cycle test Whitened surface Good
Slurry immersion test Whitened surface Good
Sea-water immersion No change Good
test
Weathering test No change Good
*wet-dry cycle condition: an alternate test with 24-hour
cycle comprising a 6-hour immersion
in 3% salt water at 40C, a 6-hour
warm-air blasting at 40C and a
12-hour left-to-stand cooling
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Slurry: a slurry essentially consisting of manures of
oxes.
Weathering test: an ultraviolet carbon arc weather-meter
was used.
Example 2
A polymer cement motar cement prepared according to
the common proportions was applied by spray coatlng to steel
plates, glass sheets, acrylic sheets, wooden plywoods and
concretes, cured for 28 days and subjected to a peeling
strength measurement. The results are shown ln Fig. 6.
As shown in Fig. 7, this peeling strength measuring
method is such that a jlg 3 ls attached wlth an epoxy
adhesive to a coatlng layer 2 applled and formed on a base
1 and a cut was made ln the portion of the coatlng layer 2
contactlng wlth the jlg 3 thereby examlnlng the peellng of
the coatlng layer 2.
From Flg. 6 lt wlll be seen that the polymer cement
mortar composltlon accordlng to the lnventlon has an
excellent adhesion.
Example 3
A comparatlve test was performed on polymer cement
mortar composltlons with respect to the wear resisting
tendency of the materlals accordlng to the following
procedure.
A tire having 12 chains wound thereon was rotated in
an atomosphere of -10C and the chains were brought lnto
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contact with the materials thereby measuring the abrasion
thereof. Each test specimen in the form of a 400x150x40mm
molded piece was reciprocated at a rate of 66 reciprocating
motions per minute with respect to the tire rotating at
3,3S . As schematically shown in Fig. 8, a specimen 4 is
abraded due to the contact with the chains and a groove 5
is formed. The determination of this abrasion test utilizes
the width (cm ) of the section S of the groove 5 as a measure
and the behaviors according to the test time are shown in
Fig. 9.
In the Figure 9, the behavior indicated by black
triangles represents the polymer cement mortar composition
using an aggregate having a glass content of 0%, and the
behavior indicated by white circles represents the polymer
cement mortar composition using an aggregate having a glass
content of 50%. The behavior indicated by black circles
represents the polymer cement ~ortar composition using an
aggregate having a glass content of 99%.
It will be seen from the Figure that the polymer cement
mortar composition of this invention has a remarkably improved
abrasion resistance than previously.
Example 4
The polymer cement ~ortar composition was applied by
spraying to steel plates (2mm thick) to different thicknesses.
With n representing the ratio of the coating thickness
to the base steel plate thickness, the specimens of n=l to
4 were caused to vibrate at 500 Hz and their damping
performances were examined thereby obtaining the behaviors
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shown in Fig. lO.
Whlle lt ls generally considered that compositlons
having loss factors of 0.1 or over in the working
temperature range can be advantageously used ln the flelds
of civil engineering and building materials, as will be
seen from the Flgure 10, where n > 2, the loss factor
becomes greater than 0.1 ln the range of 0 to 50C and
particularly the value of the loss factor becomes as high
as about 0.2 in the range of 20 to 30C.
Example 5
Molded forms of 160 x 40 x 40mm were made of the
polymer cement mortar compositiol and the relation between
the compresslon and bending stress (Ss) and the strain (Sn)
was determlned on each of the specimens cured for 28 days.
The results are shown ln Fig. 11. It wlll be seen that
the elongation is exhlblted up to the stress of about 1,100
N/cm2 and ln partlcular the relation between the straln and
the stress up to about 500 N/cm2 becomes substantlally linear
thus indlcatlng that the material of thls class is very
easlly controllable.
In the Flgure, the data of the whlte marks, O, ~ and
V relate to the compresslon stress and the data of the black
marks , and ~ relate to the bendlng stress. The
respectlve marks represent the repeatedly plotted data by the
repeated experiments and these data are consldered to have
a hlgh degree of reproduclbll~ty.
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Example 6
Molded forms of 160 x 40 x 40mm were made of the
~olymer ce~ent mortar compositions using aggregates having
glass contents of 99% and 0%, respectively, cured for 28
days and subjected to an cyclic thermal test with one cycle
comprising a 6-hour period at 80 C and 14-hour period at
5 C. The resulting dimensional changes ~ were measured and
Fig. 12 shows a plot of the program of the thermal cycle and
the dimensional changes ~.
It will be seen that the one having the glass content
of 99% is small in dimensional change or high in dimensional
stability as compared with the other (the dot-and-dash
line) having the glass content of 0%.
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