Method and composition for preventing volume change of rapid curing flowable impermeable cement specific tissue

(24) Race day (11) Publics88-10-10 number 456 501

82-11-12

82-05-06 „_ _ _„ _ Application received as:

82-05-06 (62) Tribal application number

Q Swedish patent application (86) International filing day (86) Filing date for European patent application (30) Priority information □ Completed international patent application with number □ European patent application converted with number

5/11/11 US 262175 (71) Applicant International Construction Products Research Inc,

Fairfield Conn US (72) Inventor W K. Babcock, Stamford Conn (74) Agent H Albihns Patent Office AB (54) Designation Cement-containing composition which, when mixed with water, can bind to hard pulp with inhibited wet expansion in hardened state (56) Publications: SE 426 164 (C04B 13/22) DE 2 914 215 (C04B 22/00)

US 4,216,022 (106-104) (57) Summary:

A cementitious composition which, when mixed with water, can bind to a hardened mass inhibited wet curing compound comprising 60-90% by weight of aluminate cement, 10-40% by weight of gypsum, 0.1-25% by weight of drying shrinkage inhibitor, calculated on the aluminate cement and gypsum, and 0.01-0.5% by weight of a lithium salt based on the amount of aluminate cement and gypsum. Additional components such as viscosity control agents, surfactants, retardants, accelerators, gas generators or gas release agents, fly ash, plasticizers, pumping aids, water retention additives, fillers and ballast may be used.

OB 705293 ALLF 139 β Οββ

Figures in brackets indicate international identification code, INID code Letters in clamps indicate international document code

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The present invention relates to a cementitious composition which, upon admixture with water, can bind to a hard mass with inhibited wet blending in the hardened state.

The term cementitious composition here refers to compositions which generally exhibit the characteristic of hardening underwater, including cementitious sealing materials, abrasive layers, protective coatings and the like, and mixtures with ballast and water, such as concrete, mortar, grouting and products made therefrom.

As used herein, the term aluminum-containing cement is intended to include the cementitious materials which are normally implied in the art as the principal cementitious constituent of monocalcium aluminate (CaO 2 A 2 O 2) such as high alumina content and calcium aluminate cement.

Examples of commercially available aluminum containing cements suitable for use in the invention are Lumnit from Lehigh Portland Cement Company and the high alumina cement Fundu or Secar cement from LoneStar LaFarge Aluminous Cement Company, Ltd.

The term gypsum is intended herein to mean gypsum as commonly understood in the art, including calcium sulphate (CaSO 4) and its various forms, calcium sulphate anhydrate, calcium sulphate hemihydrate, calcium sulphate dihydrate and burnt gypsum, pressurized gypsum and plastics of Paris. Examples of commercially available gypsum suitable for use in the invention are the pressure burners

456 The 501 plaster sold under the trade name K-5 of the Georgia Pacific Corporation or the trade name Hydrostone of the United States Gypsum Company.

The term portland cement is intended herein to include those cements which are normally understood in the art by portland cement as described in Specification ASTM C 150, with Type I and Type III being particularly preferred for use in the invention, although other forms of Portland cement are suitable. The Portland cement works to reduce the drying shrinkage and increase the wet expansion of the composition of the present invention. Thus, other types of cement which function as drying shrinkage inhibitors, although not specifically designated as Portland cement, are also suitable for use herein and the term is understood to include such types of cement. Such other drying shrinkage inhibitors may include, for example, expansion promoters, such as expansive cement types, which are compatible with the other components of the system.

By the term wet expansion is meant herein the extension of a cementitious system in a hardened state, i.e.^:is the final bond, under humid conditions, as generally determined in accordance with the standard test method ASTM C 157-75 for Length Change of Hardened Cement, Mortar and Concrete.

The term wet expansion inhibitor and wet expansion counterpart is used herein interchangeably to describe, as a minimum, a decrease in the wet expansion of the cementitious system in a hardened state and / or suitably maintaining an equal volume or greater than the volume of the system in execution and includes similar expression .

In the prior art, various attempts have been made to provide cementitious systems that meet the needs of the construction industry, especially with regard to protecting, sealing and repairing concrete structures. Such systems are suitably non-flammable, non-toxic and, within a relatively short period of time, bind to a hard pulp or coating of sufficient strength, abrasion resistance and corrosion resistance.

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They should also exhibit fluid impermeability, especially liquid impermeability. At the same time, such systems should not exhibit excessive volume changes in the hardened state, neither under wet or dry conditions. For commercial use, these types of cementitious systems must also exhibit good bonding characteristics to damp or dry surfaces, strength as well as bi. Jan who for a long time and practical carry-on lever in the field. They must be able to withstand freezing and thawing and the action of salts, solvents and other corrosive substances.

Although there are cementitious system compositions which exhibit one or more of the above-mentioned properties, previous attempts to achieve all of these properties in one composition have had only limited success. Many mixed cement compositions exhibit wet expansion. Other compositions, which include the addition of certain accelerators to reduce the binding time, exhibit excessive drying shrinkage. Thus, previous attempts to provide cementitious compositions of commercial value in the construction industry have generally specified or emphasized certain properties without regard to or in some cases to the detriment of other desired properties.

U.S. Patent 3,861,929 discusses the inherent shrinkage characteristics of concrete produced with conventional cement, resulting in cracking during curing and drying. The patent describes an expansive cement, which during and after bonding and curing appreciably increases in volume. The expansive cement disclosed comprises a mixture consisting mainly of Portland cement and calcium aluminate cement and an amount of calcium sulphate which may be in the form of gypsum.

U.S. Patent No. 3,775,143 discloses a stress cement comprising Portland cement and an expanding component consisting of calcium sulfate, calcium oxide, and an aluminate-containing material such as aluminum-containing cement or highly alkaline calcium hydroaluminate. The cement is said to exhibit water resistance as well as resistance to gasoline and gas.

U.S. Patent 3,147,129 discusses some of the problems in the basic processes of making

456 501 sulfoaluminate cement, extensive difficulty in controlling the properties. The patent then describes a sulfoaluminate cement composition which is said to have uniform properties and which can be used as an expansive cement after incorporation of suitable additives such as zinc sulfate and sodium bisulfate. The patent states that certain constituents may be added as retardants which do not cause appreciable expansion and even tend to neutralize the expansive action of the additives, such as zinc sulfate and sodium bisulfate. Such constituents may include sucrose; quenched lime and silica mixtures.

Compositions containing high alumina cement and Portland cement for use as a quick-setting blend are known. For example, U.S. Patent No. 4,012,264 discloses that it is known that very quickly bonding and hardening cement can be prepared by mixing Portland cement and high alumina cement and / or by using various accelerators and disclosing a calcium aluminate and Portland cement composition containing retardant and / or accelerators. Cement with high alumina content has also been added to burnt plaster or anhydrite plaster - to produce stronger molds or castings. TD Robson, High Alumina Cements and Concretes, John Wiley & Sons, NY, 1962, p. 126-127, disclose that lithium salts have been proposed as accelerators for high alumina cement cement. However, compositions containing alumina cement, gypsum and lithium salts as the sole accelerator have been found to exhibit excessive drying shrinkage in the hardened state. In addition, compositions containing aluminum-containing cement and gypsum exhibit only excessive wet expansion in the hardened state.

U.S. Patent 2,339,163 discloses a composition for a protective cement coating comprising calcium aluminate cement and an inorganic additive consisting of calcium chloride, calcium sulfate, magnesium sulfate, iron (III) sulfate, aluminum sulfate or alkali metal carbonates, and acceleration of alkaline metal for limiting the water removal rate to prevent excessive drying and shrinkage. It is said that the material provides a coating which does not crack after.

456 501 that it is bound and hardened, which is obviously intended to reduce drying shrinkage.

U.S. Patents 4,045,237 and 4,157,263 disclose a cementitious composition exhibiting a high degree of impermeability to liquids and vapors and reduced long-term shrinkage, which is composed of a particulate mixture of Portland cement, a burnt plaster, and a high alumina cement. . Alternatively, the composition may be composed of a particulate mixture of a high alumina cement and a pressurized plaster.

The present invention relates to a cementitious composition which, when mixed with water, can bond rapidly to a high mass of high compressive strength without substantial shrinkage during bonding, the composition exhibiting reduced wet and dry volume changes in the hardened state, while exhibiting a high degree of impermeability to fluid and abrasion, erosion and chemical resistance and similar characteristics, which are desirable in a composition with commercial utility in the construction industry. This is achieved according to the invention by a cementitious composition of the kind mentioned above, characterized in that it comprises 60-90% by weight of aluminate cement, 10-40% by weight of gypsum, 0.1-25% by weight, based on the amount of aluminate cement and gypsum, drying. shrinkage inhibitor and 0.01-0.5% by weight, based on the amount of alumina cement and plaster, of a salt of lithium.

An object of the invention is thus to provide a cementitious composition which, when mixed with water, binds for a relatively short period of time to a hard mass without excessive wet or dry volume changes in the hardened state.

Preferred embodiments are apparent from the subclaims.

The wet expansion inhibiting lithium salt can be added in an effective amount ranging from 0.01 to 0.5% by weight, calculated

456 501 on the aluminum-containing cement and plaster, and preferably between 0.1 and 0.3% by weight. It is suitable to use between 60 and 90% by weight of aluminate cement and between 10 and 40% by weight of gypsum.

The Portland cement, which constitutes the drying-shrinkage inhibitor in the hardened state, is added in an amount of between 0.1 and 25% by weight, calculated on aluminate cement and gypsum, preferably between 1 and 20% by weight.

In addition to the above-mentioned essential ingredients of the cementitious composition of the invention, additional components such as viscosity regulating additives, surfactants, retardants, accelerators, gas generators or gas releasing agents, fly ash, plasticizers, pumping aids, water retention additives, fillers and fillers can be used.

It is a further object of the invention to provide a method and composition for inhibiting wet expansion in cementitious systems, while these systems can still bind for a relatively short period of time to form a hard pulp with high compressive strength, high abrasion resistance and high erosion resistance. and corrosion resistance, without significant shrinkage during bonding and without excessive dry volume changes in the hardened state, while the composition exhibits a high degree of impermeability to fluids.

The above and other objects, features and advantages of the invention will become more apparent from the following detailed description thereof and the appended claims.

The invention is best illustrated by the following examples, which illustrate that the addition of lithium salts to cementitious compositions containing aluminate cement, gypsum and portland cement such as a hardened state drying shrinkage inhibitor surprisingly inhibits wet expansion of the composition in the hardened state. In the examples, the ingredients were mixed in the form of

456 501 dry powder and then mixed with tap water to obtain a loosely workable consistency. In general, the ratio of constituents to sand or ballast was 1: 1 or 1: 2. The homogeneous mixture was then placed in 25 cm steel rod molds according to the standard specification of Apparatus for Use in Measurement of Length Change of Hardened Cement Paste, Mortar, and Concrete, ASTM C 490. The molds were heavily coated on the inside with a resin-based release agent and a thin sheet of polyethylene to facilitate removal from the mold of brittle hardened samples. The samples were taken out of the mold as soon as possible after curing without causing damage to the test hardened samples, usually 0.5 2 hours after final binding.

The first measurements of length change for the specimens were made immediately after removal from the mold to best determine the actual length change in the hardened state. Two samples of each mixture were tested. One test piece was used to determine the wet length change and the other to dry length change. The wet test pieces were completely immersed in water for the duration of the test, while the dry samples were air cured for the duration of the test. 25 cm bar samples were measured to the nearest 2.5 / 1000. of a centimeter when using a length change comparator corresponding to the requirements of the aforementioned ASTM C 490. The length change measures were made essentially in accordance with the standard test method for Length Change of Hardened Cement, Mortar and Concrete, ASTM C-157. All length change results were based on a mixture of some cement and some sand or adjusted to this base. Wear resistance was determined on a coating of the mixture stretched on a cement block. The following examples are representative of the results obtained in carrying out the invention.

Example 1

A control sample was prepared as described above using 80 wt% aluminate cement (Lumnite) and 20 wt% gypsum (Densite K-5) · After four days of aging, the percent length change in the hardened state was measured and found to be 0.321 percent wet expansion and 0.012 percent dry shrinkage. The abrasion resistance was measured on a scale of 1 to 10, with 10 being

456 50.1 the hardest. The abrasion resistance turned out to be 4.

Example 2

The composition and process of Example 1 was followed, except that 0.2% by weight, based on the aluminate cement and plaster (which is hereinafter the base, unless otherwise stated) wet expansion inhibitor comprising lithium carbonate was added to the composition. The percent length change in the hardened condition after four days was 0.065 percent wet expansion and 0.179 percent dry shrinkage, with the abrasion resistance being 6.

Example 3

The composition and process of Example 1 was followed except that a Portland type III cement was added as a drying shrinkage inhibitor in an amount of 19% by weight based on the combined amount of aluminate cement and gypsum. The percentage change in length was measured after two hours, when the wet expansion was so large that the sample burst. At the end of the two-hour period, wet expansion was 1.33 percent. No dry shrinkage occurred, but rather a dry shrinkage of 0.084 percent. The abrasion resistance was 7.

Example 4

The composition and process of Example 2 was followed, with the addition of Type III Portland Cement, as a drying shrinkage inhibitor in an amount of 10% by weight. After four days, the percent change in length was measured such as 0.188 percent wet expansion and 0.100 percent dry shrinkage. The abrasion resistance was 10.

Examples 1-4 show that the lithium salts are effective wet expansion inhibitors for aluminate cement gypsum preparations, while compositions containing aluminate cement, gypsum and lithium salts with the additional addition of Portland cement such as drying shrinkage inhibitor provide a composition which exhibits favorable longitudinal change in length. In addition to the addition of lithium carbonate, other lithium salts are useful as wet expansion inhibitors. Examples of such lithium salts which have been found to be satisfactory include lithium citrate, lithium hydroxide and

456 501 lithium acetate.

Example 5

The composition and procedure of Example 4 was followed except that the Portland cement was added in an amount of 11 percent and a curing agent was added after the curing. After 30 days, the percent length change in the dry state was measured and found to be 0. The abrasion resistance was 10.

Example 5 illustrates that by selecting the composition of the composition, the net length can be adjusted to a net zero shrinkage or expansion. It has also been found that cementitious compositions of the present invention can be prepared by varying combinations of inhibitors or cement in such a way that the net length change is regulated in a particular environment such as wet, dry or alternating wet and dry.

Example 6

To the composition of Example 5 was added 1 wt.% Surfactant available under the commercial designation Lomar D, and 0.1 wt.% Anhydrous citric acid powder and the ingredients were mixed into an intermediate dry mixture. This cement mixture was mixed with abrasion resistant ballast in a ratio of 3: 7. The resulting mixture was then mixed with water to obtain a self-filling consistency and then applied to a concrete block. The composition bonded for 20 minutes and developed a compressive strength of 41 k Pascal over 24 hours when tested according to ASTM C 109. The composition exhibited very good bonding properties and was very hard and abrasion resistant within 24 hours. In addition, the composition exhibited good freeze / thaw resistance and resistance to corrosive substances. The composition bonded without any noticeable shrinkage, surface cracks or dust formation without the need for moisture curing or a curing agent. In addition, the surface of the coated block was exposed to a 172 Pa fine jet of water for a period of 1 week without noticeable erosion.

Example 7

According to the procedure described above with respect to Examples 1-4

456 In 501, a further control sample was prepared from a composition containing 80% by weight based on aluminate cement and gypsum Portland Type III cement such as a drying shrinkage inhibitor. The percent change in length was measured after two days and was found to be 0.383 percent wet expansion and no dry shrinkage or dry expansion at all.

Example 8

To the composition described in Example 7 was added 0.2 wt% sodium carbonate, a known accelerator, to determine its effectiveness as a wet expansion inhibitor. After two days, the percentage change in length was 0.366 percent wet expansion and 0.026 percent dry expansion. Thus, the expansion in the dry state was greater than that obtained in the control sample of Example 7, while the expansion in the wet state was practically as large as that of the control and unacceptable.

Example 9

To the composition of Example 7, 0.2 wt% aluminum sulfate, a known accelerator, was added to determine its effectiveness as a wet expansion inhibitor. After two days, the percent change in length was measured and it was 0.415 percent wet expansion and 0.017 percent dry expansion, which showed that the aluminum sulfate, like the sodium carbonate, was not effective in satisfactorily inhibiting wet expansion in alumina cement gypsum cement flooring systems.

Example 10

To the composition of Example 7, 0.2 wt% lithium citrate was added to determine its effectiveness as a wet expansion inhibitor. After two days, the length change was only 0.186 percent wet expansion, less than half that of the control sample, and 0.006 percent dry shrinkage. This shows that lithium salts are outstanding with respect to this cementitious system such as wet expansion inhibitors. Lithium salts do not adversely affect the fluid impermeability properties of the cementitious system to any appreciable degree and thus the system remains one which exhibits excellent waterproofing properties.

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In the cementitious composition of the invention, which contains aluminate cement, gypsum and dry and wet volume change inhibitors, it is convenient to use 60-90 percent aluminate cement and 10-40 percent gypsum. In general, the cured drying shrinkage inhibitor, namely Portland cement, can be added to the total weight of aluminate cement and gypsum in an amount of between 0.1 and 25 percent, and preferably in an amount of between 1 and 20 percent. In general, the lithium salts should be added in an amount between 0.01 and 0.5% by weight, based on the weight of aluminate cement and gypsum, and preferably in an amount of 0.1 - 0.3 percent.

In addition to the above-mentioned essential constituents of the present cementitious compositions, other additives for controlling the properties can generally be incorporated without loss of the benefits of wet expansion inhibition obtained, if the additives are otherwise compatible with the essential constituents. Such other additives include viscosity regulating agents, expansive agents, surfactants, retardants, accelerators, gas generating or gas releasing agents, fly ash, fillers, pumping aids, water retention agents and ballast to provide selective enhancement of particular properties. Other additives normally used in the cementitious systems industry may also be used, provided that their use is compatible with the results desired or described herein.

The lithium salts can be mixed with the other constituents in the dry state or added at the time of adding the water or to the water added or after the addition of water. It is not necessarily important when respective materials are added to the mixture as long as they are all incorporated therewith to form a homogeneous mixture in the slurry. Known methods for preparing cementitious compositions can be used for the present composition, comprising process for blending to perform the process steps, such as firing, as well as intermediate grinding or mixing of final ingredients, provided that the steps are not harmful to any of the components.

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