CA1248976A - Concrete composition for roller compacted placing method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:
According to the present invention, a concrete composition for a roller compacted placing method is provided.
The contrete composition comprises a cement, an aggregate, an organic acid and/or a salt thereof and a set accelerating inorganic salt.

Description

TITLE OF TIE INVENTIO~:
Concrete Conlposition for Roller compacted Placing Method BACKG~UND ~F T~IE I~VENTION:
Field of the Invention;
The present invention relates to a concrete composi-tion, and more particularly to a concrete composition for roller compacted placing method.
Related Art Statement, A roller compacted placin~ me-thod has been developed in Japan in recent years for placing concrete for the construction of a concrete dam. This method is entirely different from -the conven-tional concrete placing methods in which a cable crane or the like equipment is used, and has been developed to rationalize the operations for constructing a concrete dam while reconsidering systematically all operations including mixing, transportation, placing and compaction of the concrete~ More specifically, in -the roller compacted placing method, a concrete of dry consistency is transported by damp trucks, spread by bulldozers or wheel loaders, and compacted by .. . .
rollers or vibrating rollers. This method at-tracted public attention as a novel economical me-thod, as it had been increasingly used for the construction of main bodies9 water cushion roolns and aprons of dams.

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The roller compacted placing method is character;~ed in -that the thickness of a concrete layer placed by a single step is increased so large as 1.5 meters at the most ~i-th the increase in volume o the concre-te placed. The volume of concrete placed ~ithin an hour by means of the roller compac-ted placing method reaches 50 to 200 m3 which is larger than that placed by the conventional method ~hich amounts to about 30 m3 at the largest, whereby the construct:ion speed is remarkably increased. ~oreover, according to the roller compacted placing method, a concrete containing a smaller quan-tity of cement per unit volume thereof e~hibits a s-tren~th comparable to that of a concrete placed by the conventional me-thod and containing a lar~er quanti-ty of cement per unit volume. Since the content of cement in the concre-te placed by the roller compacted placing method is small the exothermic heat generated -therefrom is decreased correspondingly so that the resistance to thermal - cracking is ;II!proved. I~ccordinglys the roller compacted placing met.hod is particularly suited for the construction of a massive concrete structureO
A concrete composition containing 120 to 160 kg/m3 of cement and placed by the roller compacted placing method has a strength of 80 to 150 kgf/cm2 (af-ter aging for 3 months), ~hich is comparable to -the strength obtainable by a concrete composition conta:ining 200 kg/m3 o~ cement and placed by the . ' ":

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conven-tiorlal method. Provision of cooling means, such as cooling piPe arrangement, is not necessary ~hen a concrete containing as lo~ cement content as 120 kg/m3 is used. A
concrete composition ~hich is impoverished in cement may be used within a dam mat or the in-terior of a main body which is not an importan-t structural portion, or may be used for forming por-tions which are no-t subiected to severe abrasion, impact, repeated free~ing and thawin~ or neutrali7ation from the environment. However, since the dam apron and ~a-ter cushion room of a dam are subjected to abrasion or impact, at least the surfaces of such portions must be covered by surface layers enriched ~i-th cement to provide high strength. The surface layers should have the thicknesses so that the concrete composition enriched ~ith cement is not impaired by thermal cracking, or should be cooled by pipe cooling or o-ther proper means to avoid thermal cracking. The task of increasing the strength and the task of decreasing the exothermic heat are the conflicting tasks imposed in placing a concrete compostion to construct a massive structure.

Any~ay, in the construction of a dam, more than several hundred thousand cubic meters of concrete are placed.
If the content of cement in a unit volume of concrete can be decreased to provide a concrete having a high strength, the exotherlnic heat generated from the concre-te is decreased and .

the coolIng plpe arrangement or other coolIng means can be dls-pensed wlth. In addltlon, as the exothermlc heat generated from a unlt volume of concrete Is decreased, the volume or thlckness of concrete placeable by a slngle step Is Increased wlth signlfl-cant economlcal effect so that the constructlon speed Is~ncreased.

However, the conventlonal concrete composltlon used In the roller compacted placlng method Is prepared slmply by addlng fly ash and/or a water-reduclng agent to a mlxture of a cement and an aggregate, and does not provlde a satlsfactory strength wlthout Increaslng the exothermlc heat.

The present Inventlon provldes a concrete composltlon for the roller compacted placlng method, whlch exhlblts a suffl-clently hlgh strength wlthout the Increase In exothermlc heat generated therefrom.

The Inventlon also provldes a concrete composltlon for the roller compacted placlng method, from whlch an extremely dry concrete may be produced by decreaslng the water content wlthout the Increase In exothermlc heat generated therefrom.

The present Inventlon agaln provldes a concrete compo-sltlon for the roller compactlng placlng method, whlch can beplaced and solIdlfled wlthout the need of plpe coollng or other coollng means.

. The present Inventlon further provldes a concrete com-posltlon for the roller compacted placlng method, by the use of whlch the thlckness of the concrete placeable by a slngle step can be Increased.

Accordlng to the present Inventlon, there Is provlded a concrete composltlon for a roller compacted placlng method, com-prlslng 100 parts by welght of a cement, an aggregate, from O.OS

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to not more than 0.5 parts by welght of an organlc acld and/or a salt thereof, from 0.05 to not more than 2 parts by welght of a set acceleratlng Inorganlc salt and from 2 to not more than 15 parts by welght of a calclum sulfate when calculated In terms of CaS04, sald cement belng selected from the group conslstlng of Portland cements, mlxed cements and mlxtures thereof, sald set acceleratlng Inorganlc salt belng selected from the group con-slstlng of carbonates, slllcates, alumlnates and hydroxldes of alkall metals and mlxtures thereof, whereln sald concrete compo-sltlon has a slump of not more than 3 cm.

The present Inventlon Is characterlzed by the use of acomblnatlon of an organlc acld and/or a salt thereof wlth a set acceleratlng Inorganlc salt, whereby the quantlty of water requlred for hydratlon Is decreased to reduce the exothermlc heat generated by the hydratlon reactlon and yet to provlde a solIdl-fled mass havlng a hlgh strength.

The organlc aclds or salts thereof, whlch may be used In the present Inventlon, Include hydroxypolycarboxyllc aclds, such as mallc acld, tartarlc acld and cltrlc acld;

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hydroxymonocarboxylic acids, such as heptonic acid, gluconic acid and glycollic acid; saturated or unsaturated carboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid and heptanoic acid; salts of these organic acids, such as alkali metal salts, alkali earth metal salts,- zinc salts, copper salts, lead salts and iron salts;
polymers or carboxylic acids, such as condensation products of acrylic acid and condensation products of maleic acid anhydride;
and alkali metal salts and ammonium salts of the polymers of lo carboxylic acids. Examples of commercially available polymers of carboxyllc acids are "Work 500", a trademark of Nippon Zeon Co., Ltd. and ~Aron 6001", a trademark of Toagosei Chemical Industry Co., Ltd.

These organic acids and/or salts thereof have been well known as retarders for setting or solidification of cements, and some of them are used for retarders for rapid hardening cements.
Increase in strength cannot be expected when such an organic acid and/or a salt thereof is added singly.
The amount of the organic acid and/or a salt thereof to be added ~o the concrete composition of the invention may ran~e generally not more than 0.5 parts by weight, preferably from 0.05 to 0.3 parts by weight, based on 100 parts by weight of cement in the composition. If more than a . 5 parts by weight of the organic acid and/or a salt thereof is added, the -.~

:improvenlen-t in streng-th a-ttainable by the presen-t inven-tion is decreased.
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The set accelerating inor~anic salts, which ma~-~n~
used in combination of the organic acid and/or a salt thereof for -the preparation of the concrete composition of the in~ention, ~ re i-r~cludc carbonates, silicates, aluminates and hydroxides of alkali metals, which have been generally used as set accelerating agents for cements. Ho~ever, ~hen such a set accelerating agent is used singly, the final strength a-fter being aged for 28 days of a concrete composition added with the set accelerating agent is lo~er than that of a concrete without the addition -thereof, although the initial strength is increased by the addition thereof.
The amount of the set accelerating inorganic salt to be added to -the concrete composition of the invention may range generally not more than 2 parts by weight, preferably froM 0.~5 to l.0 parts by weight7 based on 100 par-ts by weight of cement in the co~position. Addition of more than 2 parts by welght of -the set accelerating ino}garlic salt is not preferred, since rapid or false setting may be caused or an improvement in strength may be lessened with increase in exotherMic heat by a certain set accelerating inorganic salt.
A water reducing agent may be added to the concre-te composition of the invention. By the addition of a water $~
reducing agent, handling ease of the concrete is improved and bleeding of concrete can be suppressed at the spreading s-tep. A
concrete having a sufficient workability and having a slump of zero after the lapse of 20 to 30 minutes may be prepared by the addition of a water reducing agent. It is desirous that not more than 5 parts by weight, preferably not more than 3 parts by weight, of a water reducing agent is added to lO0 parts by weight of the cement. Examples of the water reducing agent, which may be used in the composition of the invention, include those malnly composed of any of a polysaccharide, an oxycarboxylate, a polyalkylaryl sulfonate, and a polycondensation product of tri-azine modified with an alkali metal salt of sulfurous acid.

The concrete composition of the invention includes cal-cium sulfate to increase the strength. Anhydride, hemihydrate and dihydrate of calcium sulfate may be used in an amount of preferably not more than 15 parts by weight when calculated in terms of CaSO4, based on lO0 parts by weight of cement. Calcium sulfate is added more preferably in an amount of not more than lO
parts by weight, and most preferably in an amount of 2 to 8 parts by weight, based on lO0 parts by weight of cement. If the added amount of calcium sulfate exceeds 15 parts by weight, further increase in strength cannot be expected.

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The concrete composition of the invention may also include a silica powder to increase the strength. A preferable silica powder is a fine amorphous and spherical powder of silica prepared as a by-product from a furnace for producing a silicon alloy and metallic silicon. It is desirous that 30 parts by weight of such a silica powder be added to 100 parts by weight of cement. The strength of the composition may be increased theo-retically as the amount of the added silica powder is increased.
However, it is practically preferred that the silica powder be added in an amount of not more than 30 parts by weight, more preferably from 5 to 15 parts by weight, in order to avoid the increase in water content in the resultant concrete and to obvi-ate difficulty in handling the resultant concrete containing a larger amount of silica powder.

The cements, which may be used in the present inven-tion, are various Portland cements such as normal Portland cement, high early strength Portland cement, super high early strength Portland cement, moderate heat Portland cement, white Portland cement and seawater proof Portland cement (Type V); and mixed cements such as silica cement, fly ash cement and blast furnace cement.

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The concrete composition for the roller compacted plac-ing method, according to the present invention, has a slump of not more than 3 cm, preferably not more than 1 cm, and more preferably may be a composition having a vibrating compac-ting value of from 8 to 30 sec. The concrete composition of the invention has super dry consistency suited for the roller com-pacted placing method.

The concrete composition of the invention may be pre-pared by admixing an organic acid and/or a salt thereof, a setaccelerating inorganic salt, and optionally with a calcium sul-fate and a silica powder at the step of Xneading the concrete.
The concrete composition of the invention may be placed by trans-porting by a damp truck, spreading by a bulldozer or a wheel loader, and compacting by a roller or a vibrating roller.
As will be understood from the foregoing, the conflict-ing tasks of increasing the strength and decreasing the exother-mic heat can be solved by the use of the concrete composition of the invention. Although the roller compacted placing method has been developed to construct a dam by rationalized operations, it may be suited for the construction of a road and a runway for an airplane and may also be used for other wide applications.

EXAMPLES OF THE INVENTION:
The present invention will now be described more specifically with reference to some Examples thereof.

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Example Concrete mixtures shown in Table 1 were prepared while varying the kinds and used amounts of organic acids or salts thereof and set accelerating inorganic salts.

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Used ~aterials:
Cemen-t: ~ormal Portland cement produced by Denki Kagaku Kogyo Kabushiki Kaisha Sand: River sand obta;ned from Himekawa, Niigata Gravel: River gravel obtained from Himekawa, Niigata ~ater Reducing Agen-t: Produced and sold under the Trade Name ~rad~ ~r?at7~ c~ f ~' of "Selflo~ llOp"~k~ Dai-ichi Kogyo Seiyaku Co., Ltd.
Organic Acids: First-class reagents Se-t Accelerating Inorganic Salts: First-class reagents The compressive s-tren~th after being subjected to standard ageing for 9l days and temperature raise under the adiabatic condi-tion ~ere measured.
The test specimen was molded by filling a concrete in a mold frame of 15~ X 3~ cm to a height of 29.5 cm using a table vibrator and by placing a 5 cm -thick iron pla-te on the surface of the concrete and applying a load of 3 kg/cmZ while applying with'vibration using rod vibrators from both sides, the molding operation being continued for 3 minutes.
The temperature raise under the adiabatic condition was measured by the use of an adiabatic -temperature raise measuring instrument for measuring the temperature of concrete produced by Plaruto Seisakusho Co., L-td.
The results are shown in Table 2.
The test for ~neasuring the adiabatic -temperature .

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t~j raise was conducted in a room maintained at 20+2C, and the result is shown by the temperature raise.

The raised parts by weight or organic acids or salts thereof and set accelerating inorganic salts were added to 100 parts by weight of cement. Used polymers of carboxylic acids were commercially available polymers of carboxylic acids sold under the trademark of "Work 500" (produced and sold by Nippon zeon Co., Ltd.) and sold under the trademark of "Aron 6001"
~produced and sold by Toagosei Chemical Industry Co., Ltd.).
Comparative Exam~le 1 Run Nos. 1 to 3 and 5 in Table 2 were prepared simi-larly as in Example 1 except in that no organic acid and no set accelerating inorganic salt were added. The results are shown in Table 2.

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As will be seen from the results of Example 1 and Com-para-tive Example 1, although the organic acids and/or salts thereof and the set accelerating inorganic salts do not provide the aimed effect when added singly, the temperature raise due to exothermic heat by the hydration reaction is suppressed and the strength of the solidified concrete composition is increased when an appropriate amount or organic acid and/or salt thereof is used together with an appropriate amount of set accelerating inorganic salt.

For example, comparing the result of Run No. 5 (Comparative Example) with the result of Run No. 6 (Example), the temperature raise in Run No. 6 is smaller than that of Run No. 5 by 2C. In consideration of the heat capacity of entire massive concrete, decrease in temperature raise of 1C has a significant meaning when a dam is constructed by using a large volume of con-crete.

Example 2 Generally following to the procedures as described in Example 1, concrete mixtures similar to Run Nos. 5 and 8 in Table

2 were prepared except in that kind and used amount of calcium sulfate were varied and in that variant amounts of silica flour recovered from a ferrosilicon production furnace were used.

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Commercially available calcium sulfate dihydrate and calcium sulfate hemihydrate for industrial use and Type II anhy-drous calcium sulfate (Specific Surface Area: 5200 cm2/g) pro-duced as a by-product in a process Eor the preparation of fluoric acid were used as the calcium sulfate.

The added amount of each calcium sulfate is calculated in terms of CaSO4, based on lO0 parts by weight of cement.

The results are shown in Table 3. Run Nos. 41 to 43 in Table 3 are Comparative Examples.

As will be seen from the results of Example 2 and Com-parative Examples, the exothermic heats are decreased and the strength of solidified concretes is increased by the combined use of the calcium sulfate and the silica flour.

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Examp]e 3 As shown in Table 5, using citric acid, sodium silicate, Type ~ anhydrous calcium sulfate and a silica flour, concrete mix-tures having various compositions (shown in Table 4) ~ere prepared and examined similarly as in Example l. The results are shoun in Table S.
As ~mll be seen from the results of ~xample 3, the exothermic heat can be decreased and the strength o-f the solidified concretes can be increased even Yhen the quantities of cement contained in unit volume are varied. It should be understood that the quantity of cement contained in unit volume of concrete may be considerably decreased according to the present invention.
The compositions of Comparative Run No. 59 and Example Run Nos. 62 and 67 are modified such that each composition had a ~ater content per unit volume of l2 kg/m3 and a slump of lQ + 2 cm, similar to the compositions for the conventional placing method, and the thus modified compositions were molded only by using a conventional vibrator. The results were that the compressive strengths of respective modi-Fied compositions . .
were 44l kg f/cm2, ~25 kg f/cm2 and 90l kg f/cm2. By comparing the results of Comparative Run No. 59 and Example Run Nos. 62 and 67 ~ith the results of the corresponding modifed compositions, the advantageous effec-ts o~ the roller compacted '' . ~ ~.

placing method should be clearly recognized.

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' ExamPle 4 A road was actually constructed employing the roller compacted placing method. The composition of the used concretes are set forth in Table 6. Since the workabili-ties of concretes are not accurate, when the concretes have slumps of not more than 1 cm, the vibrating compacting values (VC value in sec) deter-mined by the Vee-Bees test are shown. ~he Vee-Bee test was con-ducted as follows:

Two layers of concrete were put in a vessel for the Vee-Bee (a trademark) test having an inner diameter of 24 cm and an inner height of 20 cm. After each layer was compacted 35 times using a bar, the surface of the upper layer was flattened.
A transparent disk was put on the surface of the upper layer and a weight of 20 Kg was put on the disk. The VC value was determined by vibrating the vessel at 3000 cpm (width of vibration of about 1 mm) using the Vee-Bee tester to measure seconds during which mortar in the concrete contacted the overall lower surface of the disk.
The road was separated into twelve sections, each sec-tion having a width of 5 m and a length of 10 m. Each of the sections was placed by each of the compositions including a Com-parative Example and set forth in Table 6 to form a 30 cm thickplan concrete slab. Each concrete composition was kneaded in a green concrete preparation factory and transported by a truck over a time of an hour~ and spread by workers' hands and com-pacted by using a vlbrating roller having a weight of 7 tons similar to the placing of asphalt.

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.L~ 6 The compressive strength of 10~ X 20 cm coring specimen of each of the compositions after aging for 28 days was measured, and the bending strength of a 10 cm X 10 cm X 40 cm specimen each being cut out from the road slab was measured. The results are shown in Table 7.

The same materials or the materials obtained from the same place of origin as described in Example 1 were used as the cement, sand, gravel (having a GmaX f 25 mm), water reducing agent, citric acid and potassium carbonate, and the same silica flour and the same Type II anhydrous calcium sulfate as described in Example 2 were used.

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Run No. 68 is a Comparative Example with no special aging, and the placing was effected spontaneously. The lowest temperature and the highest temperature durlng the aging period were, respectively, sC and 15C.

Since the water content in a unit volume of a concrete can be reduced to prepare and use a concrete composition of fur-ther dried condition, in the practical placing thereof as illus-trated in the foregoing Examples, the effect of the invention is extensively manifested to show extremely increased strength even when the water/cement ratio is the same as, for example, in Com-parative Example Run No. 68.

EX ample 5 Generally following to the procedures as described in Example 4, Mixture Nos. k and ~ set forth in Table 8 were placed on a road. The surfaces of the concretes were covered by panels on which a roller travelled without vibration to compact the concrete compositions, Run No. 74 is a Comparative Example.
As seen from the results shown in Table 9, Run No. 74 having a slump of 5+1.5 cm had an extremely low compressive strength of 669 kgf/cm2, and the concrete composition of Run No.
74 was flowed from both sides of the panel during the roller com-paction operation to show detrimental performance characteristics in placing operation.

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Example 6 Generally following to the procedures as described in Example 4, Mixture No. h as set forth in Table 6 was placed on a road while varying the VC value. 10~ X 20 cm test specimens were prepared by coring after aging for 28 days, and subjected to test to learn the compressive strengths and performance characteris-tics during the processing operations. The results are shown collectively in Table 10. Run No. 79 was compacted only by lo roller compaction without vibration.
Run Nos. 75 to 78 were excellent in performance charac-teristics during the processing operations. The surface of the concrete formed by Run No. 79 was undulated a little by the roller.

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v E ~ ~
h U~ ~_) Il') ¢ h ~ _ = =

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Example 7 Generally following to the procedures as descrlbed in Example 3, Mixture No. c set forth in Table 4 was added with cit-ric acid, sod.ium silicate and Type II anhydrous calcium sulfateto prepare concrete compositions shown in Table 11. The compres-sive strengths after aging for 91 days and the temperature raises during the aging period of the concrete compositions were mea-sured. The results are shown in Table 11.

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~ o ~r ~ ~ ~ ~ ~ ~

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a) ~ ~ ~ ~ o ~ ~ Ln ~ In ~ u~ ~ r~ ~ ~c> I~ oD
u lu - --~ ~ u~ In u~ u~ L~ U~ U~

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111 ~ l o Lrl o o o o s~ o o o o o o X .~ _ , _. _ ' .
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Claims (15)

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

1. A concrete composition for a roller compacted plac-ing method, comprising 100 parts by weight of a cement, an aggre-gate, from 0.05 to not more than 0.5 parts by weight of an organic acid and/or a salt thereof, from 0.05 to not more than 2 parts by weight of a set accelerating inorganic salt and from 2 to not more than 15 parts by weight of a calcium sulfate when calculated in terms of CaSO4, said cement being selected from the group consisting of Portland cements, mixed cements and mixtures thereof, said set accelerating inorganic salt being selected from the group consisting of carbonates, silicates, aluminates and hydroxides of alkali metals and mixtures thereof, wherein said concrete composition has a slump of not more than 3 cm.

2. A concrete composition according to claim 1, wherein said organic acid and/or a salt thereof is selected from the group consisting of hydroxypolycarboxlic acids, hydroxymono-carboxylic acids, saturated and unsaturated carboxylic acids, polymers of carboxylic acids, salts of said organic acids and mixtures thereof.

3. A concrete composition according to claim 2, wherein said hydroxypolycarboxylic acid is selected from the group consisting of malic acid, tartaric acid, citric acid and mixtures thereof.

4. A concrete composition according to claim 2, wherein said hydroxymoncarboxylic acid is selected from the group consisting of heptonic acid, gluconic acid, glycollic acid and mixtures thereof.

5. A concrete composition according to claim 2, wherein said saturated and unsaturated carboxylic acid is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, heptanoic acid and mixtures thereof.

6. A concrete composition according to claim 2, wherein said polymers of carboxylic acid is selected from the group consisting of condensation products of acrylic acid, con-densation products of maleic acid anhydride and mixtures thereof.

7. A concrete composition according to claim 2, wherein said salt of said organic acid is selected from the group consisting of alkali metal salts, alkali earth metal salts, ammo-nium salts, zinc salts, copper salts, lead salts and iron salts and mixtures thereof.

8. A concrete composition according to claim 1, 2 or 3, wherein said Portland cement is selected from the group con-sisting of normal Portland cement, high early strength Portland cement, super high early strength Portland cement, moderate heat Portland cement, white Portland cement, seawater proof Portland cement (Type V) and mixtures thereof.

9. A concrete composition according to claim 1, 2 or 3, wherein said mixed cement is selected from the group consist-ing of silica cement, fly ash cement, blast furnace cement and mixtures thereof.

10. A concrete composition according to claim 1, fur-ther comprising a water reducing agent.

11. A concrete composition according to claim 10, wherein 100 parts by weight of said cement is mixed with not more than 5 parts by weight of said water reducing agent.

12. A concrete composition according to claim 10 or 11, wherein said water reducing agent is selected from the group con-sisting of those composed of any of a polysaccharide, an oxycar-boxylate, a polyalkylaryl sulfonate, a polycondensation product of triazine modified with an alkali metal salt of sulfurous acid and mixtures thereof.

13. A concrete composition according to claim 1, 2 or 3, wherein said calcium sulfate is selected from the group con-sisting of calcium sulfate anhydride, calcium sulfate hemihy-drate, calcium sulfate dihydrate and mixtures thereof.

14. A concrete composition according to claim 1, fur-ther comprising a silica powder.

15. A concrete composition according to claim 14, wherein 100 parts by weight of said cement is mixed with not more than 30 parts by weight of said silica powder.