Mineral Binder and Compositions Employing the Same

Portland cement has long been a standard building material. Over the years, various modifiers have been developed for Portland cement formulations to provide particular properties or advantages, such as more rapid curing, compatibility with and resistance to certain materials, varying strengths, etc. Frequently, the modified formulations have worked at cross purposes, so that a Portland cement formulation which initially cures more rapidly results in a final product with a lower strength, while the higher strength Portland cement formulations frequently cannot be demolded for substantial periods of time because there is not sufficient early strength.

In the past few years, geopolymers have been found which, though mineral in composition, provide many of the properties of molding resins, such as epoxies and polyurethanes. Such geopolymers are described and claimed, for example, in U.S. Pat. Nos. 4,349,386 and 4,472,199, each in the name of Joseph Davidovits. These geopolymers are primarily composed of silicas and aluminas, mixed and reacted in particular ways to provide the desired structure. While, in general, these geopolymers are perfectly adequate for the purposes intended, as such, they do not provide the types of strengths sought in a Portland cement composition.

The art has continued to seek a Portland cement composition which provides for utilization in standard situations, while providing both a high early strength and an ultimate, very high strength. In particular, compositions having a minimum strength of 4,000 psi at 4 hours, the release strength necessary for prestress work, have been sought.

In accordance with the present invention, a mineral binder, which can be used in conjunction with Portland cements, has been developed. In particular, this mineral binder is dry, so that it can be prepared at a manufacturing facility and shipped to the point of use without the necessity for the additional weight provided by the water required for cure, or the Portland cement with which it might be mixed. In addition to being usable as a binder with Portland cement, it can be used as a binder for a variety of other materials, such as in place of plastic for granite chips and similar materials, or, directly, as a molding material. When employed as a binder, it can be polished.

The binder composition of the present invention includes, as essential components:

From about 6 to about 25 parts by weight metakaolin

From about 3 to 30 parts by weight dry potassium hydroxide

From about 3.5 to 18 parts by weight slag

From 0 to 60 parts by weight of one or more materials selected from fly ash, calcined shale, and calcined clay

From 1 to 150 parts by weight of a finely divided silica, preferably amorphous silica

In addition to the required materials set forth, other materials can be added to the composition as, for example, retarders commonly used in cement formulations, and various substitutions are also possible for the required materials.

When the binder described is used in conjunction with Portland cement, the binder is generally supplied as a one component, dry system, which is then mixed with the Portland cement before water is added. The ratio of Portland cement to the binder can vary from, on a weight ratio basis, 40:60 to 70:30.

When the mixture of binder and Portland cement is mixed with water and placed into a mold for curing at 150.degree. F. to 195.degree. F. temperature, demolding is generally possible within about four hours. Not only is this more rapid than with Portland cement, alone, but is also generally faster than the time within which the geopolymers previously referred to can be demolded, curing of the geopolymers normally requiring one to two days before demolding is possible.

While the binder-Portland cement compositions of the present invention frequently develop strengths of 4,000 psi, the strength needed in prestress work, within the four hours allotted, and such strengths are preferable, a strength of only about 1,000 to 1,500 psi is required for demolding in other situations and the partially cured cement or concrete is generally handleable at such a strength. Because of the components of the present invention, particularly the finely divided silica, cure continues for a substantial period of time, and ultimate strengths of as much as 13,000 to 15,000 psi are obtainable employing the binders of the present invention in combination with Portland cement.

The dry, mineral binder of the present invention has, as previously indicated, the following essential components:

6 to 25 parts by weight metakaolin

3 to 30 parts by weight dry potassium hydroxide

0 to 18 parts by weight slag

0 to 60 parts by weight fly ash, calcined shale, or calcined clay, or a combination of these materials

1 to 150 parts by weight of finely divided silica, preferably amorphous silica.

The metakaolin is employed, as shown, in an amount of from approximately 6 to 25 parts by weight. Preferably, the metakaolin is employed in the higher amounts within this range, from about 15 to 25 parts by weight. The metakaolin (Al.sub.2 O.sub.3.2SiO.sub.2) is obtained by dehydroxylating kaolinite by heating at temperatures above 500.degree. C. until the characteristic crystal structure is destroyed. The optimum temperature range is 600.degree. C. to 800.degree. C.

As the mineral binder of the present invention is dry, the potassium hydroxide employed should be a dry powder, crystal, or pellet, and the final, dry binder must be protected from air prior to use. As indicated, the potassium hydroxide is employed in amounts of approximately 3 to 30 parts by weight; preferably, it is used in amounts of from about 5 to 12 parts by weight. If desired, sodium hydroxide can be substituted for the potassium hydroxide, on a weight basis. When caustic soda is used, rather than caustic potash, the freeze-thaw stability of the final material is not as good.

The slag employed in this binder, when used, can be Lone Star Miami ground sidmar slag which has the following characteristics:

The slag can be employed in amounts of from about 0 to 18 parts by weight, preferably about 10 to 15 parts by weight. The slag is one of the materials which reacts and forms a part of the cured system upon the addition of water.

The binder composition calls for from 0 to 60 parts by weight of one or more of fly ash, calcined shale, or calcined clay. Preferably, the level of this material in the binder composition does not rise to 60 parts by weight, particularly when the binder is used in combination with Portland cement, as, with such a high amount, the ultimate concrete is not as strong. Preferably, the amount of the material selected from fly ash, calcined shale, and calcined clay is in the range of from about to 50 parts by weight, and most preferably about 20 to 30 parts by weight. These materials are somewhat reactive and participate in the curing reaction in the formation of the final product.

A major distinction between the binder of the present invention and the composition of the prior art is the use of finely divided silica, preferably amorphous silica. The amount of this material, as indicated, is in the range of from 1 to 150 parts by weight, preferably from about 30 to 100 parts by weight, most preferably from about 40 to 75 parts by weight. As indicated, the preferable finely divided silica is an amorphous silica and, of the amorphous silicas, silica fume is preferred. However, other amorphous silicas such as rice hull ash, and others known in the art, can be substituted.

The finely divided or amorphous silica, to the greatest extent, is a substitute for the sodium and potassium silicates of the materials of the prior art. It has been found that the use of these silicates in combination with Portland cements should, to a great extent, be avoided, because of the possibility of flash setting of the material, preventing desired workability. Additionally, the amorphous silicas are less expensive than the silicates and allow for continuing reaction of the materials so that the ultimate strength of the binder, or concrete when used in combination with Portland cement, is higher.

In preparing the binder of the present invention, the various dry components are merely mixed together and dry blended to form a homogenous mixture. This binder can then be transported to a site for use, either as such, or in combination with Portland cement. When used in combination with Portland cement, a further dry blending is accomplished, but substantial savings are realized because only the binder need be transported substantial distances, the Portland cement with which the binder is blended generally being available near the site.

Activation of either the binder, alone, or of the binder-Portland cement mixture is accomplished by the addition of water and appropriate admixtures. The ratio of Portland cement to the binder, in accordance with the present invention should be between 40:60 and 70:30, on a weight basis. Preferably, the mixtures with Portland cement include from about 55 to 65% Portland cement and from about 45 to 35% of the binder. In addition, substantial amounts of fly ash can be included with the Portland cement component, the amount of fly ash generally comprising about 20% of the overall composition, the ratio of Portland cement and binder being essentially the same as just set forth. These blends may be produced initially, or at the site.

In addition, other materials normally added to cement compositions, such as various admixtures, can be employed in the overall compositions. These admixtures or retarders include, without limitation, such materials as borax, citric acid, sugar, and various proprietary retarders, some of which will be identified in the specific formulations, below.

The following are given as examples of the formulations of the binder and binder-Portland cement compositions of the present invention. They should be considered only as illustrative and not as limiting, in any way, the full scope of the invention as covered in the appended claims. All parts, unless otherwise indicated, are by weight.

A binder in accordance with the present invention was prepared by mixing the following components in the ratios indicated:

20.1 parts metakaolin

10.9 parts slag.

25.2 parts fly ash

34 parts silica fume

9.8 parts dry potassium hydroxide

The components listed were dry blended to a homogeneous mixture and could be employed as a binder for granite chips, such as for a terrazzo type of floor, as the binder would take a high polish after curing.

Concrete was prepared employing the binder of Example 1 and Portland cement, with other necessary materials, as indicated below:

258 parts binder of Example 1

387 parts Portland cement

1,020 parts sand

2,058 parts gravel

7 parts borax

7 parts citric acid

7 parts of a retarder sold by W. R. Grace and Co. under the name Daracem-100, a dispersion of sulfonated napthalene formaldehyde condensate, a gluconate, and a lignosulfonate

151 parts water

The various materials were dry blended and the water and liquid admixture were then added until a complete mixture was obtained. The concrete was placed into molds and steam cured for 11/2 hours. After 4 hours this concrete was found to have a compressive strength of 7,000 psi.

A binder was prepared with the following composition:

70 parts metakaolin

38.5 parts slag

63 parts of a mixture of fly ash, calcined shale, and calcined clay

154 parts silica fume

23.4 parts dry potassium hydroxide

The composition was dry blended to homogenity. lt was usable, as such, as a binder for hard, mineral materials.

The binder of Example 3 was combined with 353.8 parts Portland cement, 1,625 parts sand, and 271.2 parts water. When cured at 150.degree. F. for 4 hours, the resulting concrete had a compressive strength of 3,570 psi; continued curing for 24 hours at 73.degree. F. resulted in a compressive strength of 4,350 psi.

A binder was prepared with the following composition:

70 parts metakaolin

38.5 parts slag

63 parts of a mixture of fly ash, calcined shale, and calcined clay

142.4 parts silica fume

35 parts dry potassium hydroxide.

The binder of Example 5 was combined with 353.8 parts Portland cement, 1,625 parts sand, 7 parts borax, 7 parts citric acid, and 7 parts Daracem-100, and 206 parts water were added. When cured at 150.degree. F. for 4 hours, the resulting concrete had a compressive strength of 3,650 psi; when curing was continued for 24 hours at 73.degree. F. the resulting compressive strength was 5,630 psi.

A binder was prepared employing the same materials and amounts as in Example 5, except that 25 parts potassium hydroxide were employed rather than 35 parts, and 152.4 parts silica fume, rather than 142.4 parts.

The binder of Example 7 was employed with 353.8 parts cement, 1,625 parts sand, 7 parts borax, 7 parts citric acid, and 7 parts Daracem-100, along with 171 parts water. The composition was cured at 150.degree. F. and showed a compressive strength of 3,900 psi at 4 hours and 6,270 psi at 24 hours.

A binder was formed employing the following materials in the amounts shown:

52.8 parts metakaolin

27.7 parts slag

48.7 parts fly ash

106.5 parts silica fume

26.3 parts dry potassium hydroxide.

The binder of Example 9 was combined with 395 parts Portland cement, 1,662 parts sand, 5.3 parts citric acid and 7.9 parts Daracem-100, along with 180 parts water. When cured at 150.degree. F., a compressive strength of 2,080 psi was attained in 4 hours and 5,450 psi in 3 days.

A binder was prepared employing the same materials and amounts as in Example 9, except that 61.9 parts fly ash were employed in place of 48.7 parts, 95.9 parts silica fume were employed in place of 106.5 parts, and 23.7 parts potassium hydroxide were employed in place of 26.3 parts.

Employing the binder of Claim 11, with the additional materials as set forth in Claim 10, a compressive strength of 2,250 psi was obtained in 4 hours and 6,830 psi in 3 days.

A binder was prepared in the same manner as in Example 9, except that 75.3 parts fly ash were employed in place of 48.7 parts, 85.2 parts silica fume were employed in place of 106.5 parts, and 21 parts potassium hydroxide were employed in place of 26.3 parts.

A mortar was prepared in the same manner as in Example 10, employing the same additive, but using the binder of Example 13. When cured at 150.degree. F., a compressive strength of 2,470 psi was obtained in 4 hours and 7,100 psi in 3 days.

A binder composition was prepared with the following:

52.5 parts metakaolin

28 9 parts slag

47.2 parts fly ash

88.9 parts silica fume

30 4 parts potassium hydroxide.

A mortar formulation was prepared employing the binder of Example 15 along with 437.5 parts Portland cement, parts fly ash, 5.2 parts borax, 8.2 parts citric acid, 12.3 parts Daracem-100, 1,625 parts sand, and the compositions were blended and mixed with 221.8 parts water.

Two different batches were prepared and cured at 150.degree. F. for four hours.The first batch showed a compressive strength of 2,630 psi in 4 hours and 4,280 psi in 24 hours, while the second batch showed a compressive strength of 4,850 psi in hours and 7,650 psi in 24 hours.

A binder composition was prepared with the following components:

52.5 parts metakaolin

28.9 parts slag

47.2 parts fly ash

73.3 parts silica fume

24 parts dry potassium hydroxide.

A Portland cement composition mixture was prepared containing the following:

437.5 parts cement

175 parts fly ash

5.2 parts borax

8.2 parts citric acid

12.3 parts Daracem-100

1,625 parts sand.

Two batches were prepared employing the binder of Example 17 and the cement composition of Example 18 and employing parts water. Each was cured at 150.degree. F., the first showing a compressive strength in 4 hours of 2,530 psi and 4,200 psi in hours, while the second batch showed 3,770 psi in 4 hours and6,470 psi in 24 hours.

A binder was prepared with the following composition:

52.5 parts metakaolin

23.9 parts slag

52.2 parts fly ash

73.3 parts silica fume

24 parts dry potassium hydroxide.

The binder of Example 20 was combined with the cement composition of Example 18 and cured, with 186 parts water, at .degree. F The resulting concrete had a compressive strength of 4,550 psi in 4 hours and 6,800 psi in 24 hours.

A binder was prepared with the following components:

52.5 parts metakaolin

18.9 parts slag

57.2 parts fly ash

73.3 parts silica fume

24 parts dry potassium hydroxide.

The binder of Example 22 was combined with the cement composition of Example 18 and cured, with 186 parts water at 150.degree. F. It showed a compressive strength at 4 hours of 6,930 psi,at 24 hours of 8,080 psi. When cured at ambient temperature for 24 hours, the compressive strength was 2,750 psi.

A binder composition was prepared with the following components:

52.5 parts metakaolin

13.9 parts slag

62.2 parts fly ash

73.3 parts silica fume

24 parts dry potassium hydroxide.

The binder of Example 24 was combined with the cement composition of Example 18 and cured at 150.degree. F. with 186 parts water. After 4 hours, the concrete had a compressive strength of 5,350 psi, with a compressive strength of 6,820 psi at 24 hours.

A binder composition was prepared containing the following:

52.5 parts metakaolin

76.1 parts fly ash

73.3 parts silica fume

24 parts dry potassium hydroxide.

The binder of Example 26 was combined with the cement composition of Example 18 and cured at 150.degree. F. along with 186 parts water. The compressive strength after 4 hours was 6,280 psi, and was 7,680 psi after 24 hours.

A binder was prepared with the following components:

52.5 parts metakaolin

28.9 parts slag

35.2 parts fly ash

85.3 parts silica fume

24 parts dry potassium hydroxide.

The binder of Example 28 was combined with the cement composition of Example 18 and cured at 150.degree. F. employing 186 parts water. The resulting mortar had a compressive strength of 2,480 psi at 4 hours and 6,550 psi at 3 days.

The binder composition was prepared with the following components:

52.5 parts metakaolin

28.9 parts slag 1,

23.2 parts fly ash

97.3 parts silica fume

24 parts dry potassium hydroxide.

The binder composition of Example 30 was combined with the cement composition of Example 18 and cured at 150.degree. F. with parts water. The resulting concrete had a compressive strength of 2,970 psi at 4 hours and 7,250 psi at 3 days.

A binder composition was prepared with the following components:

52.5 parts metakaolin

28.9 parts slag

11.2 parts fly ash

109.3 parts silica fume

24 parts dry potassium hydroxide.

The binder composition of Example 32 was combined with the cement composition of Example 18 and cured at 150.degree. F. along with 186 parts water. The resulting mortar had a compressive strength of 3,050 psi at 4 hours and 7,530 psi at 3 days.

A binder composition was prepared with the following components:

52.5 parts metakaolin

28.9 parts slag

120.5 parts silica fume

24 parts dry potassium hydroxide.

The binder of Example 34 was combined with the cement composition of Example 18 and cured at 150.degree. F. along with 186 parts water. The resulting material showed a compressive strength of 7,050 psi at 4 hours and 9,220 psi at 3 days.

A binder composition was prepared containing the following components:

52.5 parts metakaolin

18.9 parts slag

126.5 parts silica fume

28 parts dry potassium hydroxide.

The binder composition of Example 36 was combined with the cement composition of Example 18 and cured at 150.degree. F. with 186 parts water. The resulting concrete had a compressive strength of 7,700 psi at 4 hours and 8,950 psi at 3 days.

A binder composition was prepared containing the following components:

52.5 parts metakaolin

18.9 parts slag

126.5 parts silica flour

28 parts dry potassium hydroxide.

The binder composition of Example 38 was combined with the cement composition of Example 18 and cured at 150.degree. F. with 196 parts water. The resulting mortar had a compressive of 3,570 psi at 4 hours and 6,200 psi at 3 days.

A binder composition was prepared containing the following components:

52 parts metakaolin

12 parts slag

46 parts fly ash

75 parts silica fume

26 parts dry potassium hydroxide.

Concrete was prepared employing the binder of Example 40 and Portland cement, fly ash, and other necessary materials, as indicated below.

211 parts binder of Example 40

353 parts Portland cement

141 parts fly ash

1102 parts sand

2046 parts gravel

5 parts borax

8 parts citric acid

10 parts Daracem-100

147 parts water.

The various dry materials were dry blended and the water and liquid admixture were then added until a complete mixture was obtained. The concrete was placed into molds and steam cured for 1 hr. to 1 1/2 hr. and then cured at ambient (73.degree. F.) temperatures. After 1 hour this concrete was found to have a compressive strength of 1670 psi., 7000 psi. at 2 hrs., 8300 psi. at 4 hrs. and 9550 psi. at 28 days. When the concrete was cured at 73.degree. F. without the initial steam curing it had a compressive strength of 2500 psi. at 24 hrs., 4480 psi. at 3 days, 7000 psi. at 7 days and 10,900 psi. at 28 days.

A binder composition was prepared containing the following components:

52.3 parts metakaolin

18.9 parts slag

57.2 parts fly ash

73.3 parts silica fume

24.0 parts dry potassium hydroxide.

Concrete was prepared employing the binder of Example 42 and Portland cement, fly ash and other necessary materials as indicated below:

211 parts binder of Example 42

353 parts Portland cement

141 parts fly ash

1102 parts sand

2046 parts gravel

5 parts borax

8 parts citric acid

10 parts Daracem-100

152 parts water.

The various dry materials were dry blended and the water and liquid admixture were then added until a complete mixture was obtained. The concrete was placed into molds and steam cured for 1 to 11/2 hrs. After 1 hour this concrete was found to have a compressive strength of 3500 psi., 6000 psi. at 2 hrs., 6700 psi. at 4 hrs. and 9400 psi. at 28 days. When the concrete was cured at 73.degree. F. it had a compressive strength of 1100 psi. at 4 hrs., 2300 psi. at 24 hrs., 4000 psi. at 3 days, 9000 psi. at 7 days and 11,000 psi. at 28 days.

Thus, in accordance with the present invention, a composition has been given for a dry, mineral binder for varying uses. The binder can be used for various mineral materials, and can be blended with Portland cement to form a concrete composition with high early strength, suitable for early demolding and early use.

The invention should not be considered as limited by the specific examples shown, but only as set forth in the appended claims.