CA1213619A

CA1213619A - Polymer cement mortar composition

Info

Publication number: CA1213619A
Application number: CA000447975A
Authority: CA
Inventors: Hisayasu Kanayama; Naoki Furuno; Yoshitaka Sasaoka; Tatsue Saito; Yoshiaki Sasaki
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1983-02-24
Filing date: 1984-02-21
Publication date: 1986-11-04
Also published as: JPS59156949A; AU558299B2; GB8403808D0; ZA841208B; GB2135665A; FR2541672A1; GB2135665B; DE3405917A1; KR910002573B1; FR2541672B1; KR840007549A; AU2465584A; JPH0122215B2; DE3405917C2

Abstract

Abstract of the Disclosure A polymer cement mortar composition comprising a cement, an aggregate and a polymer and suitable for use as a coating applied to steel structures, metal roofs, external walls, civil engineering structures, etc.
The composition is made by incorporating an aggregate or granulated blast furnace slag (S) having a glass content of 95% or over and a polymer or styrene-butadiene polmer (P) in a cement (C) and the ratios C/S and P/C by weight are respectively selected from 0.4 to 0.65 and from 0.2 to 0.5.
The composition is excellent in adhesion to ground or prime coating, abrasion resistance, waterproofing effect, weather-ing resistance, impact resistance, chemical resistance, anti-corrosive property, elongation,damping property, thermal shock resistance, etc., and suitable for use in a wide range of applications.

Description

~Z~361~3 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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1;213~9 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 ~' .i~
- la -12~11 3619 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 ~ - 3 ~r _ _ ___ :: .

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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 l , ~2~361~
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 .... ~

1~3619 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

X X X X X

1 287 13~ 238 186 82 (~) O X X X

(~) X X X

O X X X

~1 : 1 nitrlte type, 2 metaborate type, 3 amlne type.

~2 : A(St-Bd) acryllc ester modlfled styrene-butadiene polymer _ 9 _, . .

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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 ~ .. . _ _ _ _ _ _ , .. . _ _ _ . _ _ . ... _ _ _ , .. ... , _ .. _ ... _ _ .. . . . _ . _ . _ _ 12~36i'~

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 . _ . ~ _ _ , .. .. _ _ _ , .. . _ ~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 _ 14 lZ~36-~ 9 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 ~2~3gi~9 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 L3~

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.

... , _ . _ . _ .. . . . . .. . _ lZ~3~1g 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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A polymer cement mortar composition including a cement (C), an aggregate (S) and a polymer (P), wherein said aggregate comprises a granulated blast furnace slag having a glass content of 95% by weight or over, wherein said polymer is a styrene-butadiene polymer, and wherein the ratios C/S and P/C by weight are respectfully selected from 0.4 to 0.65 and from 0.2 to 0.5.

2. The composition according to claim 1, wherein said aggregate comprises a granulated blast furnace slag having a glass content of 99% by weight.

3. The composition according to claim 1, wherein said styrene-butadiene polymer comprises a polymer selected from the group consisting of styrene-butadiene polymers and acrylic modified styrene-butadiene polymers.

4. The composition according to claim 1, further incor-porating an anti-corrosive agent in an amount corres-ponding to from 0.1 to 3% by weight of said composition.