MXPA96004745A - Compositions of air retention for cemen compositions - Google Patents

Abstract

Compositions and methods related to cementitious compositions are provided. The use of a mixture of a rosin and a tannin to retain air in the cementitious compositions is provided of course. A mixture of a rosin and a tannin in a ratio of 10: 1 to 1:10 is added a wet cementitious composition at levels of less than 1 weight percent based on the weight of the cement and the air mixed in the cement. The resulting cement will containv. gr., from 5 percent to 10 percent by volume of air that improves the strength of the cured cement to freeze damage. A method for retaining air in a cementitious composition using this mixture is also provided

Description

"COMPOSITIONS OF AIR RETENTION FOR CEMENT COMPOSITIONS" FIELD OF THE INVENTION * This invention relates to naturally derived compositions useful for retaining air in cement compositions.

ANTECEDENTS OF THE TECHNIQUE The usual practice is to add air retention agents to cement-based mixtures such as concrete and mortar, in order to retain the miscroscopic air bubbles in the mixture. This imparts certain advantages to concrete or mortar. It plasticizes the mixture, making it more manageable and, in this respect, the retention agent frequently acts as a replacement, at least in part, for lime. When the concrete or mortar is set, the retained bubbles increase its elasticity, its resistance to salt solutions and particularly its * resistance to freeze damage. Air retention agents are usually mixtures of a surfactant that produces a foam in the cement that persists so that the set cement contains many small air voids, generally spherical, e.g., measuring 10 microns at 250 micrometers in diameter. These air voids are believed to attenuate the internal stresses in the cement that are caused when moisture freezes in the pores in the cement that are inherently formed during the setting of the cement. In practice, up to about 10 percent by volume of the cement air is retained in the cement to be placed in severe environments.

COMPENDIUM OF THE INVENTION This invention relates generally to a mixing composition that is useful for retaining air in cementitious compositions. In one aspect, this invention relates to a composition useful for retaining air in a cementitious composition comprising a mixture consisting essentially of a rosin and a tannin in a weight ratio of from about 10: 1 to about 1:10. In certain embodiments, the composition is essentially a dry powder, e.g., has a moisture content of less than about 20 weight percent and preferably a moisture content low enough to make the dry powder fluent. In preferred embodiments, the mixture further contains an alkaline material in an amount sufficient to neutralize the mixture, i.e., to impart an essentially neutral or alkaline pH to a dispersion or aqueous solution of the mixture, eg, a pH from about 6 to about 13. In a related aspect, this invention relates to a dispersion or aqueous solution comprising a small amount by weight of a mixture consisting essentially of a rosin and a tannin in a weight ratio of about 10: 1 to 1:10 and a predominant amount by weight of water. The dispersion or aqueous solution will typically contain the mixture at a solids content of about 5 percent to about 50 percent, more typically from about 10 percent to about 15 percent. In the preferred embodiments, the aqueous dispersion or solution further contains an alkaline material in an amount sufficient to neutralize the mixture, i.e., to impart to an aqueous dispersion or solution of the mixture, an essentially neutral or alkaline pH, e.g. , a pH of from about 6 to about 13. Both aqueous compositions and the flowing powder are useful as additives in industrial products such as hydraulic cement mixtures.

In another aspect, this invention relates to a cementitious composition comprising a cementitious material hydratable in a predominant amount by weight and an air retention agent consisting essentially of a rosin and a small amount by weight of the cementitious composition, and a of tannin and in a small amount by weight of the cementitious composition, the weight ratio of the rosin to tannin varies from about 10: 1 to about 1:10. In the preferred compositions, from about 0.0005 percent to about 0.5 percent (dry basis) of a mixture of a rosin and a tannin based on the weight of the cement, is present to retain the air in the cementitious composition. In a related aspect, this invention relates to a method of retaining the air in a cementitious composition comprising mixing a small amount by weight of an air retention agent consisting essentially of a rosin and a tannin, in a weight ratio from about 10: 1 to about 1:10, with a predominant amount by weight of a hydratable cementitious composition comprising a cement and water, the amount of the air retention agent is effective to retain from about 1 percent to about 20 percent. one hundred in volume of air, in the cementitious composition.

DETAILED DESCRIPTION OF THE INVENTION Rosin predominantly comprises a complex mixture of monocarboxylic acids of alkylated hydrophenanthrene compounds that are isolated from pine trees. The monocarboxylic acids represent approximately 90 weight percent of most commercially available rosins. Gum rosin is sometimes also known as rosin and is derived from several species of pine trees, which when subjected to incisions yield an oleoresin product known as crude turpentine. Vacuum distillation removes the turpentine oil and leaves the rosin solid. Varying in color from a pale yellow to a dark brown, the rubber rosin is usually soft, brittle and practically transparent. It has an aromatic odor and is soluble in alcohol, acetic acid and volatile and mixed oils. Typically, the specific gravity varies from 1,045 to 1,085. The softening temperature is about 75 ° C with a melting temperature of about 120 ° C to 135 ° C. With respect to its chemistry, gum rosin consists almost entirely of abietic acid possibly in the form of isomers thereof. In addition, of the historical gum rosin, there are two other types of commercially obtainable rosin products, wood rosin and resin oil rosin. The wood rosin is a product of rosin isolated from aged pine stumps that remain either by clearing the land for cultivation or logging. The stumps are crushed and the resulting wood chips are soaked in an organic solvent under high temperature and pressure. The extract is distilled to collect the crude non-volatile rosin, the volatile extractables and the recovered solvent. Resin oil rosin is a by-product of paste formation. Raw wood chips are digested under heat and pressure with caustic soda and sodium sulfide. The soluble sodium salts are lignin, rosin and fatty acids are in a separate solution of the wood pulp. Fatty acids and rosin float to the top of the solution and foam and acidify to release the rosin and fatty acids. This mixture is known as crude resin oil and is refined by fractional distillation to produce resin oil rosin and resin oil fatty acids.

The characteristics and properties of the rosins are well known in the art. Colophonies, their properties, manufacturers and uses are described, for example, in "Resins, Natural", Encyclopedia of Polymer Science and Engineering, volume 14, pages 438 to 444 (John Wiley &Sons, Inc., NY, NY, 1988 ), the disclosure of which is incorporated herein by reference. Tannins are the polyhydroxyphenolic compounds derived from plants, characterized by their capacity to precipitate proteins. The tannin component can be obtained from various wood and vegetation materials found throughout the world. Tannins are a large group of complex, water-soluble organic compounds. Almost every tree or shrub that grows contains a certain amount of tannins in the leaves, branches, bark, wood or fruit. Examples of bark are mimosa, mangrove, oak, eucalyptus, fir, pine, larch and willow. The examples of wood are quebracho, chestnut, oak and urunday. Examples of fruits are myrobalens, walloon, divi-divi, tara and algarobilla. The examples of leaves are from sumac and gambier from India and the examples of roots are from canaigre and palmito. Specific examples of plants that can be used as a tannin source (with the main availability country or region having been shown in parentheses) include: mimosa also known as acacia or mimosa (South Africa, South America, especially Brazil); Quebracho (Argentina, Paraguay and Brazil); chestnut (France and Italy); Myrobalan (India); Mangrove (tropical cypress, such as South Florida, Colombia, Brazil, Africa); divi-divi (western coast of South America); tara (Peru); Sumac (Sicily, Albania, Yugoslavia); cypress (United States); gambier from India (Malaysia, Sumatra, Borneo) and chestnut oak (cultivated in the United States, but obtainable from numerous other sources). Tannins can be categorized into traditional "hydrolysable" tannins and "condensed" tannins. Examples of condensed tannin extracts are those made from the bark of the black mimosa tree (or trade mimosa tannin), from the wood of the quebracho tree (in Spanish: Quebra ax, ax breaker), from the bark of the fir tree, and from the bark of several commonly used pine species. The preparation of the extracts of mimosa and quebracho is a well established industrial practice and these extracts can be obtained freely in considerable quantities. Preferred tannins are in their native form as they are extracted and have not been chemically modified, eg, by oxidation or by alkaline or acid hydrolysis.

The condensed tannin extracts such as mimosa and quebracho, are composed of approximately 70 percent polyphenolic tannins, from 20 percent to 25 percent of non-tannins, sugars, mainly simple and polymeric carbohydrates (hydrocolloidal gums), the last of the which usually make up 3 percent to 6 percent of the extract and contribute heavily to the viscosity of the extract, while the rest accounts for a low percentage of moisture. Although the exact structure is not well known, it is believed that the main polyphenolic pattern in quebracho tannins is represented by flavonoid analogues based on the resorcinol A and pyrogallol B rings. The word "tannin" as used herein and in the claims, unless specified to the contrary, it refers to and includes gallotannins and flavotannins. Examples of gallotannins include: tannic acid or Chinese tannin; tannin from Turkey; Hamamelis tannin; Acer tannin, glucogalin, Sumac's tannin, Wallonia oak tannin; Tannin from tea and tannins from Tara, Miróbaleno, Divi-Divi, Algarobillo, oak and chestnut. Examples of flavotannins include Gambier tannins from India and catechu or Burma Cutch, quebracho, Tizerah, Urunday, mimosa, mangrove, spruce, larch, willow, walnut shells and Avaram. These flavotannins are tannins that are currently preferred for use in accordance with the invention. Quebracho is the preferred tannin. The quebracho is extracted from the bark and wood of the quebracho tree with water. The conventional method to prepare the quebracho is to disintegrate wood and bark, extract the bark and / or wood with water, after which the quebracho and water solution evaporates to a concentration of approximately 85 percent quebracho, and The concentrated quebracho is dried by spraying. Quebracho is the most common catechin tannin or commercial flavotannin product. The high tannin content (approximately 20 percent) of the wood of the quebracho tree produces the source of especially preferred catechol tannins. The main commercial source of gallotannins are nuts. The preferred tannin materials will contain at least about 60 weight percent of compounds identified as tannins. The weight ratio of the rosin to tannin in the mixture can vary widely. Preferred mixtures have ratios that are closer to the equal proportions of rosin and tannin eg a weight ratio of from about 3: 1 to about 1: 3, more preferably from about 1.5: 1 to about 1: 1.5 . Preferred compositions have a weight ratio of rosin to tannin greater than about 1: 2, e.g., from about 2: 1 to about 1: 1.5. Because the mixture is composed of carboxylic acids and phenols, if it is not neutralized it can have a pH on the acidic side eg, from a pH of about 3 to a pH of about 5. To be active as an agent of Air retention, a considerable amount of the carboxylic acids in the rosin must be present in the carboxylate form. Although the cemetery compositions to which the mixture will be added are typically alkaline, it may not be strictly necessary to neutralize the mixture prior to its addition to the cementitious composition. However, pre-activation of the mixture by pre-neutralization will facilitate efficient incorporation of the active air retention material in the cementitious composition. Thusif the rosin, as obtained, has not been pre-neutralized, the mixture must also contain an alkaline material in an amount sufficient to neutralize the mixture, that is, to impart to an aqueous dispersion or solution of the mixture, a Essentially neutral or alkaline pH, eg, a pH of from about 6 to about 13. Examples of useful alkaline materials include alkali or alkaline earth metal hydroxides, oxides or carbonates, e.g., sodium hydroxide, caustic soda (i.e. , a mixture of sodium hydroxide and sodium oxide), potassium hydroxide, sodium carbonate, potassium carbonate, aqueous ammonia, calcium oxide and calcium hydroxide. The mixture can be used either as a dry mix or as a dispersion or aqueous solution of the components. The efficient dispersion of the mixture in water at relatively low solids content of the mixture. e.g., from 5 percent to 25 percent solid of the mixture, facilitates the dispersion of the mixture through the cementitious composition. Therefore, the mixture is preferably added to the cementitious composition as a dispersion or aqueous solution containing a predominant amount by weight (ie, at least 50 percent by weight) of water (preferably fresh water or water that contains a chelating agent for the hardening materials, e.g., EDTA), and a small amount by weight of the rosin and tannin mixture. As discussed above, the dispersion or aqueous solution is preferably adjusted to an essentially neutral or alkaline pH with an alkaline material. The air retention agent may be added to a cementitious composition, e.g., a cement or a concrete mixture at any convenient point during its preparation after which considerable air mixing will be carried out. For example, the mixture can be added to a portland cement slag before being crushed and mixed thoroughly with the cement during the grinding. The mixture can also be combined with the ground cement. The mixture can be added to the water where the cement, sand and / or gravel are mixed. The cement can be premixed with water and then either a dry or aqueous mixture composition can be added. Generally, a mixture composition, either dry or aqueous, at any stage before final mixing with air can be added to the cement mortar or concrete mix. The cementitious compositions are cements, mortars or concrete mixtures that include concretes, mortars, net paste compositions, slurries of oil well cement, cement slurry compositions and the like. The cementitious compositions are discussed in an article in the encyclopedia "Cement" which is cited below. The cements used in the preparation of cementitious compositions, especially concrete mixtures, include Type I, II and III cements. These cements are well known and are described in "Cement", Encyclopedia of Chemical Technology, (Kirk-Othmer, editors., Jonh Wiley & amp;; Sons, Inc. N.Y., N.Y., Fifth Edition, 1993), volume 5, pages 564 to 598, the disclosure of which is incorporated by reference herein. Portland cement is, of course, the most widely used hydraulic cement. The term "hydraulic cement" as used herein includes those inorganic cements which, when mixed with water, set and harden as a result of chemical reactions between water and the compounds present in the cement. The term "Portland cements" as used herein includes those products prepared by heating a mixture of limestone and clay or shale or other calcareous and argillic materials to a molten state and grinding the molten product which is called slag with a small percentage normally. from about 4 percent to 6 percent of a retarding agent such as gypsum. The term "concrete" as used herein includes a mixture of these hydraulic cements and inert aggregates. Typical aggregates include conventional aggregates such as gravel, sand, granite, limestone, discerned from quartz. Conventional hydraulic cement concretes, eg, Portland cement concretes, employ predominant amounts, that is, more than 50 percent usually up to about 75 percent by volume of these aggregates in the set product. Pozzolanic materials such as condensed silica fume and fly ash may also be included. The cements can be used to prepare concrete mixtures containing 100 parts by weight of cement and about 140 to about 260 parts by weight of sand, from about 100 to about 200 parts by weight of gravel, from about 35 to about 60 parts by weight of water and an amount of the mixture composition of the invention effective to retain the desired amount of air in the cementitious composition upon mixing with air. Preferred concrete mixtures contain 100 parts by weight of cement, and about 160 to about 240 parts by weight of sand, from about 120 to about 180 parts by weight of gravel, from about 35 to about 60 parts by weight of water and a amount of the mixture of this invention effective to retain the amount of air desired in the composition. The concentration of the blend composition of this invention in the cementitious composition may vary, but will generally be less than about 1 percent, typically from about 0.0005 percent to about 0.5 percent, preferably from about 0.001 percent to about 0.01 percent (by weight of the cement). After preparation, these cementitious compositions are allowed to harden to obtain a hardened cement mass.

The amount of air that is to be retained in the cement will depend on the degree of resistance to damage of the desired freezing in relation to the sacrifice of physical resistance that can be tolerated. Generally, the amount of air retained will be less than about 15 volume percent of the foamed cement composition, generally from about 5 percent to about 10 percent. The amount of air retained in the cementitious composition can be determined in accordance with Method Number C-231 of the American Society for the Testing of Materials, the disclosure of which is incorporated herein by reference. Mixing techniques commonly employed to mix the solid and liquid components of the cementitious composition will typically also be sufficient to mix the desired amount of air, for techniques and / or mixers designed to add air to the mixture can be used if is desired For a more complete understanding of the nature and advantages of this invention, reference may be made to the following examples. These examples are provided solely to illustrate the invention and should not be construed in a sense of limitation. Even though the invention has been described with reference to certain specific embodiments thereof, it will be understood that it is not limited in this way since the same alterations and changes as are within the fully proposed scope of the appended claims can be made. All quantities, proportions and percentages are by weight and all references to temperature are in degrees centric (° C), unless otherwise indicated.

EXAMPLES Example 1 A solution or dispersion was prepared within the scope of this invention by mixing 7.5 parts by weight of a rosin gum (which can be obtained as M-grade from Akzo Coatings, Inc., of Baxley, Georgia, and is described as consisting mostly of abietic, levopimaric, isopimaric and mahoganic acids), 7.5 parts by weight of quebracho tannin (obtainable from Pilar River Píate Corporation, of Newark, New Jersey, and which is described as containing 65 percent tannin, 10 percent no tannin, 9.5 percent insoluble materials and 15.5 percent moisture), 5 parts by weight of a 50 percent solids solution of caustic soda and 80 parts by weight water. The mixture exhibited a pH of 12.2 and was an opaque, dark brown liquid that appeared as a reddish crystalline solution during dilution.

EXAMPLE 2 A series of concretes were prepared by loading 5.45 kilograms of Portland cement, 10.9 kilograms of sand, 8.7 kilograms of gravel and an initial amount of water (the amount was recorded) to a cement mixer and mixing began. Additional water was added until the gravel began to show wetting (the amount was recorded) and mixing was continued for about 3 minutes. The mixing was then stopped and the concrete mixture was allowed to stand in a still state for 2.5 minutes. The additives used to prepare the concrete mixtures were as follows: Additive A: a mixture of the colofin and tannin of Example 1, but at a solids content shown in the following table. Additive B: a gum rosin which can be obtained from Akzo Coatings, Inc., of Baxley, Georgia, under the designation of quality M and described as a state comprised mostly of abietic, levopimaric, isopimaric and palustric acids.

Additive C: a resin obtainable from W.R. Grace & Company, of Cambridge, Massachusets, under the factory name "Daravair" and which is believed to be derived from the stump wood of the Sudeño pine which comprises a complex mixture of high molecular weight phenolic compounds, resin acids and neutral materials ( and which is believed to be similar to the Vinsol NVX resin obtainable from Hercules Incorporated). Additive D: a neutralized tannic acid material. Additive E: industrial grade fatty acids obtainable from Henkel Corporation, from Ambler, Pennsylvania, as Aliphat 34R. An aqueous sample of each additive was prepared at a solid content shown in the following table. Each aqueous sample in the amount shown in the following table, was then emptied over the large area of the exposed surface of the mixture within 30 seconds. (As can be seen from the following table, the amount of each aqueous sample was adjusted in relation to the solids content of the aqueous sample so that 0.0055% solids of the additive would be present in the resulting concrete mixture based on the weight of the cement ( 5.45 kilograms)). Mixing of the concrete mix was resumed and additional water was added (the amount was recorded) and the mixture did not flow properly. The concrete was then mixed for two additional minutes. The weight ratio of water: cement (W: C ratio) of each sample is indicated in the following table together with the percentage by volume of the retained air as determined by Method C-231 of the American Society for Testing Materials, immediately after the mixing (initial) and 20 minutes after the mixing is finished.

TABLE 1 EFFECT OF ADDITIVES IN AIR RETENTION IN CONCRETE ADDITIVE SOLID IDENTITY QUANTITY (% IN WEIGHT) (GRAMS) (none) 6.0 A 5.0 6.0 A 2.5 12.0 5.0 6.0 2.5 12.0 B 15.0 2.0 B 30.0 1.0 B 7.5 4.0 15.0 2.0 A 5.0 6.0 5.0 6.0 D 5.0 6.0 E 5.0 6.0 TABLE 1 (CONTINUED) RETAINED AIR (% IN VOLUME) W: C INITIAL RELATION 20 MINUTES 0. 508 2.92 2.81 0. 508 7.50 6.57 0. 508 10.95 10.55 0. 508 6.66 6.96 0. 508 9.32 9.27 0. 495 6.98 6.53 0. 495 5.39 4.96 0. 495 9.10 8.30 0. 495 7.20 6.20 0. 495 7.64 7.25 0. 495 7.18 6.81 0. 495 3.26 2.63 0. 495 4.58 4.52

Claims (28)

R E I V I N D I C A C I O N E S:

1. A composition useful for retaining air in a cementitious composition comprising a mixture consisting essentially of a rosin and a tannin in a weight ratio of from about 10: 1 to about 1:10.

2. A composition according to claim 1, wherein the composition is essentially a dry powder.

3. A composition according to claim 1, wherein the composition has a moisture content of less than about 20 weight percent.

4. A composition according to claim 1, wherein the composition has a moisture content low enough so that the composition is fluent.

5. A composition according to claim 1, further containing an alkaline material in an amount sufficient to neutralize the mixture.

6. A composition according to claim 1, further comprising a predominant amount by weight of water.

7. A composition according to claim 6, wherein the composition is a dispersion or aqueous solution containing a mixture or a solids content of about 5 percent to about 50 percent by weight.

8. A composition according to claim 7, wherein the solids content is from about 10 percent to about 15 percent.

9. A composition according to claim 6, further containing an alkaline material in an amount sufficient to netralize the mixture to an essentially neutral or alkaline pH, from about pH 6 to about pH 13.

10. A composition according to claim 1, wherein the rosin predominantly comprises monocarboxylic acids.

11. A composition according to claim 1, wherein the rosin is an unmodified gum rosin.

12. A composition according to claim 1, wherein the rosin consists predominantly of monocarboxylic acids of alkylated hydroxyphenanthrene compounds.

13. A composition according to claim 1, wherein the tannin is a native tannin.

14. A composition according to claim 1, wherein the tannin is a flavotannin.

15. A composition according to claim 1, wherein the tannin is quebracho tannin.

16. A composition according to claim 1, wherein the tannin consists of at least 60 weight percent of the compounds identified as tannins.

17. A composition according to claim 1, wherein the rosin is composed of at least about 50 weight percent carboxylic acids.

18. A composition according to claim 1, wherein the rosin is composed of at least about 90 weight percent monocarboxylic acids.

19. A composition according to claim 1, wherein the weight ratio of the rosin to tannin is from about 3: 1 to about 1: 3.

20. A composition according to claim 1, wherein the weight ratio of the rosin to tannin is greater than 1: 2.

21. A composition according to claim 1, wherein the weight ratio of rosin to tannin is from about 1.5: 1 to 1: 1.5.

22. A composition useful for retaining air in a cementitious composition comprising a mixture consisting essentially of an unmodified gum rosin predominantly comprising monocarboxylic acid compounds and a tannin comprising at least 60 weight percent of the identified compounds as tannins in a weight ratio of the rosin to tannin from about 2: 1 to about 1: 1.5, the mixture yields an aqueous solution or dispersion having a pH of about pH of about pH-13.

23. One cementitious composition comprising a cementitious material hydratable in a predominantly by weight amount and an air retention agent consisting essentially of a rosin in a small amount by weight of the cementitious composition and a tannin, and in a small amount by weight of the cementitious composition, varying the weight ratio of the rosin to tannin from approximately 10: 1 to approximately e 1:10.

24. A composition according to claim 23, wherein the total of the small amount by weight of the rosin and the small amount by weight of the tannin is from about 0.0005 percent to about 0.5 percent by weight based on the weight of the cementitious material hydratable

25. A composition according to claim 23, wherein the cementitious material consists of a Portland cement.

26. A composition according to claim 23, wherein the cementitious material is a concrete formulation comprising a Portland cement of type I, II or III.

27. A method for retaining air in a cementitious composition comprising mixing a small amount by weight of an air retention agent consisting essentially of a rosin and a tannin in a weight ratio of from about 10: 1 to about 1:10. , with the predominant amount by weight of a hydratable cementitious composition comprising a cement and water.

28. A method according to claim 27, wherein the amount of the air retention agent is effective to retain from about 1 percent to about 20 volume percent of air in the cementitious composition.