CA1162951A - Cement superplasticizer - Google Patents
Cement superplasticizerInfo
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- CA1162951A CA1162951A CA000380617A CA380617A CA1162951A CA 1162951 A CA1162951 A CA 1162951A CA 000380617 A CA000380617 A CA 000380617A CA 380617 A CA380617 A CA 380617A CA 1162951 A CA1162951 A CA 1162951A
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Abstract
Ref. 5733 CEMENT SUPERPLASTICIZER
ABSTRACT
A superplasticizer admixture for hydraulic cement compositions formed from an alkali or alkaline earth metal salt of a sulfonated styrene polymer having a degree of polymerization within the range of from 150 to 675.
ABSTRACT
A superplasticizer admixture for hydraulic cement compositions formed from an alkali or alkaline earth metal salt of a sulfonated styrene polymer having a degree of polymerization within the range of from 150 to 675.
Description
9 ~ 1 Background Of The Invention The present invention is directed to a cement admixture capable of greatly increasing the fluidity of cement compositions without retarding set or causing air entrainment therein.
Hydraulic cement compositions are brought into a workable form by mixing the components with an amount of water which is greater than that required to hydrate them.
The mixed mineral binder composition is poured into a form and allowed to harden at atmospheric temperature. During the hardening, the excess water remains, leaving cavities in the formed structural unit and, thus, reduces the mechanical strength of the resultant unit. It is well known that the compressive strength of concrete structures generally bears an inverse relationship to the water-cement ratio of the unset mix. The desire to use smaller quantities of water is limited by the required workability of the uncured mixture.
Cement admixtures are known which are capable of reducing the viscosity of unset cement-water suspension to provide a suspension which is more manageable. It is desired in many structural applications to have the cement composition be of low viscosity or even self-levelling while, at the same time, to be capable o~ forming a set cement of high compressive strength (via low water-cement ratio). The flooring for buildings and industrial construction represent fields of application where considerable savings of cost and time could be obtained by using a cement composition having superior flow properties.
There are presently avail~ble, various admixtures which are known to cause the above described viscosity reducing characteristics. These materials are generally known as water-reducing agents such as lignin sulfonates and polysaccharides and superplasticizers such as sulfite ~ if ?d condensation products of melamine-formaldehyde or ~.
Hydraulic cement compositions are brought into a workable form by mixing the components with an amount of water which is greater than that required to hydrate them.
The mixed mineral binder composition is poured into a form and allowed to harden at atmospheric temperature. During the hardening, the excess water remains, leaving cavities in the formed structural unit and, thus, reduces the mechanical strength of the resultant unit. It is well known that the compressive strength of concrete structures generally bears an inverse relationship to the water-cement ratio of the unset mix. The desire to use smaller quantities of water is limited by the required workability of the uncured mixture.
Cement admixtures are known which are capable of reducing the viscosity of unset cement-water suspension to provide a suspension which is more manageable. It is desired in many structural applications to have the cement composition be of low viscosity or even self-levelling while, at the same time, to be capable o~ forming a set cement of high compressive strength (via low water-cement ratio). The flooring for buildings and industrial construction represent fields of application where considerable savings of cost and time could be obtained by using a cement composition having superior flow properties.
There are presently avail~ble, various admixtures which are known to cause the above described viscosity reducing characteristics. These materials are generally known as water-reducing agents such as lignin sulfonates and polysaccharides and superplasticizers such as sulfite ~ if ?d condensation products of melamine-formaldehyde or ~.
- 2 - ~ .
9~
naphthalene-formaldehyde. Fluidizing agents are normally categorized as water-reducing agents if they are capable of only modifying viscosity to a very limited degree. These materials normally also have the disadvantages of retarding, if not preventing, set time, increasing air content and permitting only moderate reduction in water. Fluidizing agents which have the ability to permit large water cuts in the cement mixture, while maintaining fluidity or permit large increases in fluidization for a constant water content, are known as superplasticizers. These materials should also permit increased streng~h of the cement composition after 24 hours of set and not retard set.
Japanese Patent Publication 51-525 discloses that sulfonated polystyrenes of any molecular weight can act as a fluidizing agents for cements as long as it has sufficient sulfonate groups to be hydrophilic. U.S. Patent 4,076,699 specifically directs one to use polystyrene sulfonates which are of very low molecular weight, preferably with a degree of polymerization of less than 50. Generally, the polystyrene materials have not been widely used because they are thought to impart only a low degree of fluidity to cement composition and, in addition, they may cause air entrainment in the treated cement composition.
Recently, ~. P. Preiss and H. R. Sasse compared, in Super~lasticizers in Concrete, Vol. II, Ed. by V. M. Malhotra et al. pages 733-750, the fluidity effect of various fluidizing agents. Specifically, sulfonated melamine formaldehyde condensates, sulfonated naphthalene-formaldehyde condensates, lignin-sulphonate and a dispersible polystyrene were compared. The study teaches that, of all of the materials tested, the polystyrene admixture gave the poorest performance and further concluded that very high dosages of any of the studied admixtures are needed to appreciably increase the flow of a cement composit.o It is highly desired to have a fluidizing admixture which can impart a high degree of fluidity to a cement composition, is capable of achieving this result at low dosages and is capable of achieving this result without adverse effect of increased air entrainment or set retardation.
Summary Of The Invention The present invention provides a method of providing a high degree of fluidity to cement compositions at low dosage rates. Further, the present invention is directed to a superplasticizer admixture capable of providing a high degree of fluidity to cement compositions without causing air entrainment or set retardation therein.
The present invention is directed to the utilization of a superplasticizer for cement compositions comprising an alkali or alkaline earth metal salt of a sulfonated poly-styrene having a degree of polymerization of from lS0 to 675.
Detailed Description Of The Invention It has been presently found that an unexpectedly high degree of fluidization can be imparted to cement compositions by having the composition contain small dosages of an alkali or alkaline earth metal salt of polystyrene sulfonate. The polystyrene sulfonate must have a degree Gf polymeriæation of from 150 to 675. The greatest degree of fluidization per unit dosage can be attained with polymer having a degree of ~olymerization of from 150-300.
! Cement compositions capable of being modified by the subject admixture are conventional cement based compositions formed by mixing standardized amounts of required components, i.e. a hydraulic cement, water, sand and aggregate, as is applicable for the particular material belng formed.
1 ~62`~1 The cement compositions in which the present admixture has been found useful include cement pastes, that is, mixtures composed of a hydraulic cement and water, mortars composed of hydraulic cement, water and sand in standard amounts; and concrete compositions composed of a hydraulic cement, water, sand, and aggregate, each in standard amounts and size. The present invention is of particular use in concrete composi~ion normally used to form structural units.
The cement component in the presently treated cement compositions are hydraulic cements, such as, for example, portland cement. These cements are conventionally known and are manufactured by calcininy a mixture of limestone and clay to form a clinker, and by grinding the clinker to a fine powder. The major compounds found in portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium alum:inoferrite. The tricalcium and dicalcium silicates are thought to be the principal bonding constituents in the port:land cement. Tricalcium silicate, when mixed with water, forms a calcium silicate ~0 hydrate known as tobermorite gel and calcium hydroxide. The dicalcium silicate, when contacted with water, forms similar products, but at a much slower rate of reaction. The tricalcium silicate, having the greater rate of reaction, determines to a large extent the rate of set of the cement.
To provide materials which are suitable for different uses, portland cements having a range of properties have been made commercially available. Four general types of portland cements, varying principally in the relative quantities of tricalcium silicate and dicalcium silicate present therein, are commonly produced. The proportions of the principal compounds present in three of these cements are shown in Table I.
...... .
-9 lB29~1 TABLE I
Cement Type . . . . . . . . . O . . . . . .I II III
Composition, wt. percent:
Tricalcium silicate . . . . . . . . . 53 47 58 Dicalcium silicate . . . . . . O . . 24 32 16 Tricalcium aluminate . . . . . . . . 83 8 Tetracalcium aluminoferrite . . . . . 8 12 8 ..... . . .. _ _ _ The water to cement ratio of a particular composition will determine, to a large extent, the strength of the resultant set material. As discussed above, the amount of water required to form a uniform composition is in excess of that needed to react with the cement components. Reduction of the water to cement ratio whiIe maintaining or increasing the fluidity of the mixture is highly desired. When using the presently described admixture, one has greater capability of forming a uniform mixture, of molding the cement composition into desired shapes, of causing the composition to be substantially self-leveling and of causing the cured cement composition to exhibit higher compressive strength for the same amount of cement. The term "fluidizing agent" as used herein is directed to agents capable of maintaining the fluidity oE a cement composition while reducing the water content of the composition or to increase the fluidity of a cement composition formed with a set water-cement~ ratio. The term "superplasticizer" as used herein de~ines materials capable of imparting fluidizing properties described above to a higher degree. Unlike known fluidizing agents generally, the presently described superplasticizer agents have been unexpectedly found to impart fluidity and to increase the mechanical strength and workability of a cement composition to an exceptionally high degree at very low dosages.
:
It has been presently unexpectedly found that certain specific metal salts of polystyrene sulfonate are capable of imparting a high degree of fluidity to a cement or concrete composition. These materials are alkali and alkaline earth metal salts of sulfonated polystyrene haviny a degree of polymerization of from 150 to 675. Polymeric materials whlch are outside of this D.P. range, exhibit a significantly lower effectiveness as a fluidizing agent.
The subject sulfonated styrene polymers can be formed by conventional techniques well known to the artisan. The styrene monomer is first normally polymerized to the proper degree of polymerization. The resultant polymer is sulfonated and then neutralized. ~tyrene monomer can be polymerized by conventional processes capable of forming polystyrene to a degree of polymerization of 150 to 675.
While conventional ~ree radical polymerization may be employed to form the desired polymer, it is preferred that conventional anionic polymerization techniques be used to form the polystyrene in order to provide a polymer of the proper average degree of polymerization and of a narrow range of molecular weight. Anionic polymerization of styrene monomer is performed by introducing an initiator to a monomer containing solution. The initiator ~an be any anionic initiator such as an organolithium compound, as for example, butyllithium, phenyllithium and ~he like or a Grignard reagent or other organometallic compound known to act as an anionic polymerization initiator. The styrene is normally dissolved in an organic solvent which is inert to the initiator. It is preerred that the solvent be an ether as, for example, tetrahydrofuran. The organometallic initiator, is taken up in an organic hydrocarbon solvent such as hexane or benzene, and is introduced into the polymerization zone in an amount suitable to cause the desired deg~e~e of polymerization. It is readily understood 7 ~
~ ~2~
that the degree of polymerization is inversely proportioned to the ratio of initiator to monomer. The polymerization is usually run under an inert atmosphere and at low temperatures such as ambient temperature or below with temperatures oE
from 0C to -78C being suitable. After completion of the reaction, the formed polymer is isolated by evaporating off the solvent. The polymer is washed with water to free it from the metal salt by-product. The exact amounts and concentration of monomer, initiator, etc. to form polymer 10 product required for use in the present invention are readily determined.
The resultant polystyrene having a degree of polymerization of from 150 to 675 and preferably from 150 to 300 is then sulfonated. The polystyrene can be treated in ~he reaction media used for the polymerization or it can be isolated and then redissolved in an organic solvent ?
such as a halogenated alkane. The sulfonating agent can be any conventional acid sulfonating agent such as oleum, SO3, concentrated sulfuric acid, chloxosulfonic acid and the like.
20 The degree of sulfonation should be at least suEficient to cause the polystyrene to be hyd~ophilic. Usually the degree of sulfonation should be at least 0.5 sulfonate units per styrene unit~ The sulfonated product is neutralized with an alkali metal or alkaline earth metal basic material such as sodium hydroxide, calcium hydroxide, calcium oxide, and the like. The salts of sodium and calcium are preferred.
The polystyrene can contain minor amounts of styrene derivative comonomer, such as alpha-methyl styrene, vinyl toluene, vinyl xylene and the like. The comonomer should 30 not be present in greater than 10 percent of the monomer units in the polymer.
-1 ~29~1 The formed salt of sulfonated polystyrene having a degree of polymerization of from 150 to 675 can be added to a cement or concrete composition in any manner which causes substantially uniform distribution therein. The subject agent can be added to the cement mixture in a dry state or as an aqueous solution. Small amounts of from 0.01 to 5 weight percent and preferably from 0.1 to 2 percent of the subject admixture based on dry weight of cement will increase the fluidity sufficiently for most purposes.
The use of the subject salt of sulfonated polystyrene having the particular degree of polymerization of from 150 to 675 have been found to impart an unexpected high degree of fluidity to cement and concrete compositions in comparison to equal amounts of other known fluidizing agents including sulfonated polystyrenes of low D.P. as specifically suggested by the prior art. Further, the subject has been found not to cause entrainment of air in the treated cement composition as is a problem with known fluidizing agents such as low D.P. sulfonated polystyrene.
Finally, the present material has the unexpected advantage of not causing appreciable retardation of set of the cement composition as is imparted by the use of other fluidizing agents as discussed above.
The following examples are given for illustrative purposes only and are not meant to be a limitation on the subject invention except as made in the claims appended hereto. All parts and percentages are by weight unless otherwise indicated.
EXAMPLE I
Commercially obtained sodium polystyrene sulfonates (sold as a gas permeation chromatography standard) was used. The polymer was monosulfonated to nearly lO0 percent _ g -- .
~ 1623~3 and was prepared from polystyrene of narrow molecular weight distribution (MW/Mn = 1.1) formed by anionic polymerization.
0.25 part of the above described commercially obtained sodium polystyrene sulfonate having a D.P. of 167 was mixed with 100 parts of Type II portland cement and then with sufficient water to give a water-cement ratio of 0.45. The resultant composition was tested for fluidity using a Mini-Slump Flow Test procedure as described by L. M. Mayer and W. F. Perenchio in Concrete International~ Vol. 1, No. 1, page 36ff (January 1979).
The material exhibited exceptionally high flow properties of 163+2 mm on duplicate samples.
EXAMPLE II
The process and procedures described in Example I were repeated except that the sodium polystyrene sulfonate was a commercially obtained polymer similar to that described in Example I formed from polystyrene having a D.P. of 475 (MW/Mn = 1.1).
The results of the Mini-Slump Flow Test showed that exceptionally hi9h flow properties of 153 mm can be obtained using very small dosages.
EXAMPLE III
The process and procedures described in Example I above were again repeated except that the sodium polystyrene sul~onate was formed from a commercially obtained polystyrene sulfonic acid (sold as a conductive film former and as scale inhibi~or for aqueous circulation systems) (Versa-TL 121) which has about 0.9 sulfonic acid units per styrene unit.
The acid was neutrali2ed with NaOH The D.P. of the polymer , was 650.
' .
, 1 ~29~ 1 The polymer was used as a cement admixture in the manner described in Example I and the resultant cement composition was tested for flow properties as described in Example I.
The results showed that exceptionally high flow properties of about 150 mm can be obtained with very small dosages.
EXAMPLE IV
For comparative purposes as a standard, a cement composition was formed from a Type II cement in the same manner as described in Example I above except that the cement composition was free of polystyrene sulfonate. The cement was mixed with water to give a uniform composition (water/cement = 0.45) which was tested for fluidity using the Mini-Slump Flow Test described in Example I above.
The composition exhibited a flow of 70 mm.
EXAMPLE V
For comparative purposes, a commercially available naphthalene-formaldehyde sodium sulfonate material (Daxad-15) commonly used as a cement superplasticizer was used in place of the subject polymer in the manner described in Example I. The flow properties of the ~reated cement composition was about 122 mm.
EXAMPLE VI
This example is made for comparative purpose with reference to the preferred materials of U.S. Patent 4,076,699. A commercially obtained sodium salt of a sulfonated polystyrene having a degree of polymerization of 22 (~ /Mn = 1.1) and formed in the same manner as described in Example I above was tested for fluidity.
The material had a molecular weight substantially the same as the resin of Example I of U.S. 4,076,699.
The material was mixed with Type II hydraulic cement in the same manner as Example I and tested for fluidity using the Mini Slump Test. The material exhibited a flow of only 112 mm.
A sample was formed in the same manner as described above except that the sodium sulfonate polystyrene had a D.P. of 34. The ma~erial exhibited a flow of only 123 mm.
EXAMPLE VII
This is a comparative example illustrating the fluidity 10 properties of high molecular weight material as covered by the illustrative examples of Japanese Publication 51-525.
A cement composition was prepared in the same manner as in Example I above except that the subject polystyrene sulfonate was substituted with a commercially obtained sodium polystyrene sulfonate having a D.P. of 5400 (MW = 106 based on free acid). The flow of t:he cement was only 80 mm.
While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the invention to the particular forms set forth, but, 20 on the contrary, it i5 intended to cover such alternatives, modifications and equivalents as defined by the appended claims.
9~
naphthalene-formaldehyde. Fluidizing agents are normally categorized as water-reducing agents if they are capable of only modifying viscosity to a very limited degree. These materials normally also have the disadvantages of retarding, if not preventing, set time, increasing air content and permitting only moderate reduction in water. Fluidizing agents which have the ability to permit large water cuts in the cement mixture, while maintaining fluidity or permit large increases in fluidization for a constant water content, are known as superplasticizers. These materials should also permit increased streng~h of the cement composition after 24 hours of set and not retard set.
Japanese Patent Publication 51-525 discloses that sulfonated polystyrenes of any molecular weight can act as a fluidizing agents for cements as long as it has sufficient sulfonate groups to be hydrophilic. U.S. Patent 4,076,699 specifically directs one to use polystyrene sulfonates which are of very low molecular weight, preferably with a degree of polymerization of less than 50. Generally, the polystyrene materials have not been widely used because they are thought to impart only a low degree of fluidity to cement composition and, in addition, they may cause air entrainment in the treated cement composition.
Recently, ~. P. Preiss and H. R. Sasse compared, in Super~lasticizers in Concrete, Vol. II, Ed. by V. M. Malhotra et al. pages 733-750, the fluidity effect of various fluidizing agents. Specifically, sulfonated melamine formaldehyde condensates, sulfonated naphthalene-formaldehyde condensates, lignin-sulphonate and a dispersible polystyrene were compared. The study teaches that, of all of the materials tested, the polystyrene admixture gave the poorest performance and further concluded that very high dosages of any of the studied admixtures are needed to appreciably increase the flow of a cement composit.o It is highly desired to have a fluidizing admixture which can impart a high degree of fluidity to a cement composition, is capable of achieving this result at low dosages and is capable of achieving this result without adverse effect of increased air entrainment or set retardation.
Summary Of The Invention The present invention provides a method of providing a high degree of fluidity to cement compositions at low dosage rates. Further, the present invention is directed to a superplasticizer admixture capable of providing a high degree of fluidity to cement compositions without causing air entrainment or set retardation therein.
The present invention is directed to the utilization of a superplasticizer for cement compositions comprising an alkali or alkaline earth metal salt of a sulfonated poly-styrene having a degree of polymerization of from lS0 to 675.
Detailed Description Of The Invention It has been presently found that an unexpectedly high degree of fluidization can be imparted to cement compositions by having the composition contain small dosages of an alkali or alkaline earth metal salt of polystyrene sulfonate. The polystyrene sulfonate must have a degree Gf polymeriæation of from 150 to 675. The greatest degree of fluidization per unit dosage can be attained with polymer having a degree of ~olymerization of from 150-300.
! Cement compositions capable of being modified by the subject admixture are conventional cement based compositions formed by mixing standardized amounts of required components, i.e. a hydraulic cement, water, sand and aggregate, as is applicable for the particular material belng formed.
1 ~62`~1 The cement compositions in which the present admixture has been found useful include cement pastes, that is, mixtures composed of a hydraulic cement and water, mortars composed of hydraulic cement, water and sand in standard amounts; and concrete compositions composed of a hydraulic cement, water, sand, and aggregate, each in standard amounts and size. The present invention is of particular use in concrete composi~ion normally used to form structural units.
The cement component in the presently treated cement compositions are hydraulic cements, such as, for example, portland cement. These cements are conventionally known and are manufactured by calcininy a mixture of limestone and clay to form a clinker, and by grinding the clinker to a fine powder. The major compounds found in portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium alum:inoferrite. The tricalcium and dicalcium silicates are thought to be the principal bonding constituents in the port:land cement. Tricalcium silicate, when mixed with water, forms a calcium silicate ~0 hydrate known as tobermorite gel and calcium hydroxide. The dicalcium silicate, when contacted with water, forms similar products, but at a much slower rate of reaction. The tricalcium silicate, having the greater rate of reaction, determines to a large extent the rate of set of the cement.
To provide materials which are suitable for different uses, portland cements having a range of properties have been made commercially available. Four general types of portland cements, varying principally in the relative quantities of tricalcium silicate and dicalcium silicate present therein, are commonly produced. The proportions of the principal compounds present in three of these cements are shown in Table I.
...... .
-9 lB29~1 TABLE I
Cement Type . . . . . . . . . O . . . . . .I II III
Composition, wt. percent:
Tricalcium silicate . . . . . . . . . 53 47 58 Dicalcium silicate . . . . . . O . . 24 32 16 Tricalcium aluminate . . . . . . . . 83 8 Tetracalcium aluminoferrite . . . . . 8 12 8 ..... . . .. _ _ _ The water to cement ratio of a particular composition will determine, to a large extent, the strength of the resultant set material. As discussed above, the amount of water required to form a uniform composition is in excess of that needed to react with the cement components. Reduction of the water to cement ratio whiIe maintaining or increasing the fluidity of the mixture is highly desired. When using the presently described admixture, one has greater capability of forming a uniform mixture, of molding the cement composition into desired shapes, of causing the composition to be substantially self-leveling and of causing the cured cement composition to exhibit higher compressive strength for the same amount of cement. The term "fluidizing agent" as used herein is directed to agents capable of maintaining the fluidity oE a cement composition while reducing the water content of the composition or to increase the fluidity of a cement composition formed with a set water-cement~ ratio. The term "superplasticizer" as used herein de~ines materials capable of imparting fluidizing properties described above to a higher degree. Unlike known fluidizing agents generally, the presently described superplasticizer agents have been unexpectedly found to impart fluidity and to increase the mechanical strength and workability of a cement composition to an exceptionally high degree at very low dosages.
:
It has been presently unexpectedly found that certain specific metal salts of polystyrene sulfonate are capable of imparting a high degree of fluidity to a cement or concrete composition. These materials are alkali and alkaline earth metal salts of sulfonated polystyrene haviny a degree of polymerization of from 150 to 675. Polymeric materials whlch are outside of this D.P. range, exhibit a significantly lower effectiveness as a fluidizing agent.
The subject sulfonated styrene polymers can be formed by conventional techniques well known to the artisan. The styrene monomer is first normally polymerized to the proper degree of polymerization. The resultant polymer is sulfonated and then neutralized. ~tyrene monomer can be polymerized by conventional processes capable of forming polystyrene to a degree of polymerization of 150 to 675.
While conventional ~ree radical polymerization may be employed to form the desired polymer, it is preferred that conventional anionic polymerization techniques be used to form the polystyrene in order to provide a polymer of the proper average degree of polymerization and of a narrow range of molecular weight. Anionic polymerization of styrene monomer is performed by introducing an initiator to a monomer containing solution. The initiator ~an be any anionic initiator such as an organolithium compound, as for example, butyllithium, phenyllithium and ~he like or a Grignard reagent or other organometallic compound known to act as an anionic polymerization initiator. The styrene is normally dissolved in an organic solvent which is inert to the initiator. It is preerred that the solvent be an ether as, for example, tetrahydrofuran. The organometallic initiator, is taken up in an organic hydrocarbon solvent such as hexane or benzene, and is introduced into the polymerization zone in an amount suitable to cause the desired deg~e~e of polymerization. It is readily understood 7 ~
~ ~2~
that the degree of polymerization is inversely proportioned to the ratio of initiator to monomer. The polymerization is usually run under an inert atmosphere and at low temperatures such as ambient temperature or below with temperatures oE
from 0C to -78C being suitable. After completion of the reaction, the formed polymer is isolated by evaporating off the solvent. The polymer is washed with water to free it from the metal salt by-product. The exact amounts and concentration of monomer, initiator, etc. to form polymer 10 product required for use in the present invention are readily determined.
The resultant polystyrene having a degree of polymerization of from 150 to 675 and preferably from 150 to 300 is then sulfonated. The polystyrene can be treated in ~he reaction media used for the polymerization or it can be isolated and then redissolved in an organic solvent ?
such as a halogenated alkane. The sulfonating agent can be any conventional acid sulfonating agent such as oleum, SO3, concentrated sulfuric acid, chloxosulfonic acid and the like.
20 The degree of sulfonation should be at least suEficient to cause the polystyrene to be hyd~ophilic. Usually the degree of sulfonation should be at least 0.5 sulfonate units per styrene unit~ The sulfonated product is neutralized with an alkali metal or alkaline earth metal basic material such as sodium hydroxide, calcium hydroxide, calcium oxide, and the like. The salts of sodium and calcium are preferred.
The polystyrene can contain minor amounts of styrene derivative comonomer, such as alpha-methyl styrene, vinyl toluene, vinyl xylene and the like. The comonomer should 30 not be present in greater than 10 percent of the monomer units in the polymer.
-1 ~29~1 The formed salt of sulfonated polystyrene having a degree of polymerization of from 150 to 675 can be added to a cement or concrete composition in any manner which causes substantially uniform distribution therein. The subject agent can be added to the cement mixture in a dry state or as an aqueous solution. Small amounts of from 0.01 to 5 weight percent and preferably from 0.1 to 2 percent of the subject admixture based on dry weight of cement will increase the fluidity sufficiently for most purposes.
The use of the subject salt of sulfonated polystyrene having the particular degree of polymerization of from 150 to 675 have been found to impart an unexpected high degree of fluidity to cement and concrete compositions in comparison to equal amounts of other known fluidizing agents including sulfonated polystyrenes of low D.P. as specifically suggested by the prior art. Further, the subject has been found not to cause entrainment of air in the treated cement composition as is a problem with known fluidizing agents such as low D.P. sulfonated polystyrene.
Finally, the present material has the unexpected advantage of not causing appreciable retardation of set of the cement composition as is imparted by the use of other fluidizing agents as discussed above.
The following examples are given for illustrative purposes only and are not meant to be a limitation on the subject invention except as made in the claims appended hereto. All parts and percentages are by weight unless otherwise indicated.
EXAMPLE I
Commercially obtained sodium polystyrene sulfonates (sold as a gas permeation chromatography standard) was used. The polymer was monosulfonated to nearly lO0 percent _ g -- .
~ 1623~3 and was prepared from polystyrene of narrow molecular weight distribution (MW/Mn = 1.1) formed by anionic polymerization.
0.25 part of the above described commercially obtained sodium polystyrene sulfonate having a D.P. of 167 was mixed with 100 parts of Type II portland cement and then with sufficient water to give a water-cement ratio of 0.45. The resultant composition was tested for fluidity using a Mini-Slump Flow Test procedure as described by L. M. Mayer and W. F. Perenchio in Concrete International~ Vol. 1, No. 1, page 36ff (January 1979).
The material exhibited exceptionally high flow properties of 163+2 mm on duplicate samples.
EXAMPLE II
The process and procedures described in Example I were repeated except that the sodium polystyrene sulfonate was a commercially obtained polymer similar to that described in Example I formed from polystyrene having a D.P. of 475 (MW/Mn = 1.1).
The results of the Mini-Slump Flow Test showed that exceptionally hi9h flow properties of 153 mm can be obtained using very small dosages.
EXAMPLE III
The process and procedures described in Example I above were again repeated except that the sodium polystyrene sul~onate was formed from a commercially obtained polystyrene sulfonic acid (sold as a conductive film former and as scale inhibi~or for aqueous circulation systems) (Versa-TL 121) which has about 0.9 sulfonic acid units per styrene unit.
The acid was neutrali2ed with NaOH The D.P. of the polymer , was 650.
' .
, 1 ~29~ 1 The polymer was used as a cement admixture in the manner described in Example I and the resultant cement composition was tested for flow properties as described in Example I.
The results showed that exceptionally high flow properties of about 150 mm can be obtained with very small dosages.
EXAMPLE IV
For comparative purposes as a standard, a cement composition was formed from a Type II cement in the same manner as described in Example I above except that the cement composition was free of polystyrene sulfonate. The cement was mixed with water to give a uniform composition (water/cement = 0.45) which was tested for fluidity using the Mini-Slump Flow Test described in Example I above.
The composition exhibited a flow of 70 mm.
EXAMPLE V
For comparative purposes, a commercially available naphthalene-formaldehyde sodium sulfonate material (Daxad-15) commonly used as a cement superplasticizer was used in place of the subject polymer in the manner described in Example I. The flow properties of the ~reated cement composition was about 122 mm.
EXAMPLE VI
This example is made for comparative purpose with reference to the preferred materials of U.S. Patent 4,076,699. A commercially obtained sodium salt of a sulfonated polystyrene having a degree of polymerization of 22 (~ /Mn = 1.1) and formed in the same manner as described in Example I above was tested for fluidity.
The material had a molecular weight substantially the same as the resin of Example I of U.S. 4,076,699.
The material was mixed with Type II hydraulic cement in the same manner as Example I and tested for fluidity using the Mini Slump Test. The material exhibited a flow of only 112 mm.
A sample was formed in the same manner as described above except that the sodium sulfonate polystyrene had a D.P. of 34. The ma~erial exhibited a flow of only 123 mm.
EXAMPLE VII
This is a comparative example illustrating the fluidity 10 properties of high molecular weight material as covered by the illustrative examples of Japanese Publication 51-525.
A cement composition was prepared in the same manner as in Example I above except that the subject polystyrene sulfonate was substituted with a commercially obtained sodium polystyrene sulfonate having a D.P. of 5400 (MW = 106 based on free acid). The flow of t:he cement was only 80 mm.
While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the invention to the particular forms set forth, but, 20 on the contrary, it i5 intended to cover such alternatives, modifications and equivalents as defined by the appended claims.
Claims (10)
1. A method of fluidizing a cement composition comprising incorporating into a cement composition, an alkali or alkaline earth metal salt of a polystyrene sulfonate having a degree of polymerization of from 150 to 675.
2. The method of Claim 1, wherein the polystyrene sulfonate is a sodium salt.
3. The method of Claim 1, wherein the polystyrene sulfonate is a calcium salt.
4. The method of Claim 1, wherein the polystyrene sulfonate has a degree of polymerization of from 150 to 300.
5. The method of Claim 1, wherein the polystyrene sulfonate is a sodium salt, the polystyrene is of narrow molecular weight distribution and the ratio of sulfonate to styrene units is at least 0.5.
6. In a cement composition having a fluidizing admixture therein, the improvement comprises that said admixture is an alkali or alkaline earth metal salt of a polystyrene sulfonate having a degree of polymerization of from 150 to 675.
7. The composition of Claim 6, wherein the fluidizing admixture is a sodium salt of polystyrene sulfonate having a degree of polymerization of from 150 to 675.
8. The composition of Claim 6, wherein the fluidizing admixture is a calcium salt of polystyrene sulfonate having a degree of polymerization of from 150 to 675.
9. The composition of Claim 6, wherein the polystyrene sulfonate has a degree of polymerization of from 150 to 300.
10. The composition of Claim 6, wherein the fluidizing admixture is a sodium salt of polystyrene sulfonate, the polystyrene sulfonate is of narrow molecular weight distribution and the ratio of sulfonate to styrene units is at least 0.5.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17411380A | 1980-07-31 | 1980-07-31 | |
| US174,113 | 1980-07-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162951A true CA1162951A (en) | 1984-02-28 |
Family
ID=22634886
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000380617A Expired CA1162951A (en) | 1980-07-31 | 1981-06-25 | Cement superplasticizer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1162951A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4704415A (en) * | 1986-06-13 | 1987-11-03 | The Dow Chemical Company | High efficiency superplasticizer comprising a sulfonated copolymer of styrene and alpha-mestyrene for cement compositions |
| US4786331A (en) * | 1986-07-18 | 1988-11-22 | Lion Corporation | Cement dispersion agent |
| CN106632917A (en) * | 2016-12-23 | 2017-05-10 | 卫辉市化工有限公司 | Preparation method of polymer fluid loss agent for sulphoaluminate cement |
-
1981
- 1981-06-25 CA CA000380617A patent/CA1162951A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4704415A (en) * | 1986-06-13 | 1987-11-03 | The Dow Chemical Company | High efficiency superplasticizer comprising a sulfonated copolymer of styrene and alpha-mestyrene for cement compositions |
| US4786331A (en) * | 1986-07-18 | 1988-11-22 | Lion Corporation | Cement dispersion agent |
| CN106632917A (en) * | 2016-12-23 | 2017-05-10 | 卫辉市化工有限公司 | Preparation method of polymer fluid loss agent for sulphoaluminate cement |
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