FI63735C - PULVERFORMED COMPOSITION FOR ANALYZING SOM EXPANDERMEDEL FOR CEMENT COMPOSITION FOERFARANDE FOER DESS FRAMSTAELLNIN AND CH DESS - Google Patents

Description

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Patent and Registration Office of the United States of America and the Republic of Germany published 29 · 04. 83 (32) (33) (31) Pnr4 «tty privilege -Begird priorltet 19.09-77 USA (US) 83I + 539 (71) A / S Norcem, N-3950 Brevik, Norway-Norge (NO) (72) Wendell William Moyer, Jr., Atherton, California,

Robert Smith-Johannsen, Portola Valley, California, USA. (7I +) Berggren Oy Ab (5I +) Powder mixture for use as an expansion additive in cement mixtures, method for its preparation and use - Powder formulation account and its use in cement mixtures.

Mixtures containing hydratable cements (usually Port-land cement) tend to shrink as they dry. It is known to counteract this undesirable tendency by including in the mixture an expansion additive which expands at the correct stage during the drying of the mixture. e.g., Gen. Civ. 109, 285 (1936, H. Lossier), U.C. SESM Report No. 72-13 (1973, G. Komendant et al.), Pian,

Bau 2, 351 (1951, H. Bickenbach), Concrete Technology and Practice, 3rd Edition, 359 (1969, WH Taylor) and U.S. Patent Nos. 3,519,449, 3,649,317, 3,801,339, 3,883,361 , 3,884,710, 3,947,288 and 4,002,483 /. In many known expansion additives, the active ingredient is free lime (CaO), also called quicklime, which, when hydrated, expands by about 100% by volume, and other ingredients are involved in preventing hydration from occurring before the desired step in drying the cement mixture is achieved. Burnt lime is one of the ingredients in Portland cement, but too much of it is normally considered harmful, and the addition of free 63735 2 lime to cement mixes is avoided. Free lime does not act as an expansion additive because it hydrates inherently rapidly and thus expands far too early in the curing process to be effective. It is also known (see e.g. U.S. Pat. No. 3,146,453 and DE Pat. No. 1,216,753) to carry out certain special treatments on free lime with water and / or CCl 4 to obtain a lime which hydrates more slowly, but the products obtained are ineffective as an expansion additive. Similarly, products obtained by exposing lime to the atmosphere and containing Ca (OH) 2 and CaCO2 are ineffective as blowing additives.

U.S. Patent No. 1,732,409 relates to a process for preparing a lime-containing product by treating granular quicklime with CCl 4 at a temperature of 500 to 850 ° C until it has absorbed 3 to 40% by weight of CCl 2. The patent states that the particle size of quicklime may vary, but that substantially all particles should be smaller than 500 microns. The example uses quicklime as the starting material, which has been ground so that substantially the entire batch can pass through a 50 mesh screen (i.e., a particle size of less than 300 microns). The patent mentions that the product has a sand uptake capacity corresponding to the sand uptake capacity of gypsum mortar made from quicklime and at the same time shrinks less after coating. It is also mentioned that Portland cement may be added to products containing quicklime consisting of ordinary quicklime and semi-carbonated lime. The U.S. patent does not mention steam treatment.

DE-A-370 018 relates to a process for the production of dry concrete, which process provides a suitable mixture of cement and dry aggregates which can be mixed with water at the place of use. The concrete mix has very good resistance to the effects of moisture even when cement sacks are stored in humid conditions. In the cement mixture, quicklime is used as a desiccant because quicklime reacts with water to form calcium hydroxide even at low relative humidities. This DE patent (claim 3) also mentions that quicklime partially pretreated with moist carbonic acid can be used.

DE 538 069 relates to a process for preparing a water-repellent additive for use in mortar from lime and 3 63735 beef slabs by immersing the non-extinguishing tower in the water for a short time and then immediately introducing them together with the beef slab into a sealable rotating drum. Quicklime is used here both to provide the amount of heat needed to melt the added fat so that it can be better mixed as a chemical reagent.

It has now been found that excellent expansion additives for cement mixtures can be made by heating particles containing CaO 2 in the presence of water vapor and / or CO 2, or simply by heating particles containing CaO and a sufficient amount of calcium hydroxide formed by absorbing absorb water vapor.

The invention relates to a powder mixture which is useful as a blowing agent for hydratable cementitious mixtures and which contains calcium oxide and other ingredients which delay the hydration of the calcium oxide. The invention is characterized in that this mixture consists essentially of particles of less than 100 microns in size comprising a calcium oxide core and a protective coating of calcium hydroxide or calcium carbonate surrounding the core or both, that it contains 36-95% by weight of calcium oxide and that it contains defined below) is at least 0.06%. Such mixtures can be prepared by a method comprising heating particles (a) consisting essentially of particles less than 100 microns in size and (b) containing at least 36% by weight of CaO so as to maintain the particles at a temperature of at least 100 ° C. , and if the particles initially contain less than 8% by weight of Ca (OH) 2, the particles are kept at a temperature of 100 to 400 ° C in an atmosphere comprising water vapor or at a temperature of 350 to 850 ° C in an atmosphere comprising carbon dioxide, heating under conditions such that the product will contain 36-95% by weight of CaO and that its coefficient of expansion (defined below) is at least 0.06%.

The invention also encompasses the use of such lime-containing mixtures as blowing agents in hydratable cement mixtures, in particular in cement mixtures containing Portland cement, water and a lime-containing mixture as defined above, less than 30% by weight of the cement-lime mixture.

Unless otherwise indicated, parts and percentages in this specification are by weight. The coefficient of expansion of the lime-containing mixture is defined here as the percentage increase in the length of the test prism (test rod) which has been cured in water for 7 days. After being cast in accordance with ASTM C490-70 and C 157-69 T, a mortar made in accordance with ASTM C405-65 and containing 0,1 parts of a calcareous mixture, 0,9 parts of Portland cement type III, 2 parts washed sand No. 20 and 0.4 parts water. The coefficient of expansion of the treated lime according to the invention is at least 0.06%, generally 0.07-2.5%, preferably 0.07-0.4%. The coefficient of expansion is a measure of how effective the protective coating is in delaying the entry of water into the calcium oxide core, and also a measure of the calcium oxide content of the mixture.

The larger the particle size of the treated lime, the higher its calcium oxide content at a given thickness of the protective layer. For this reason, the particle size is usually at least 1 micron. On the other hand, if particles larger than 250 microns are used, they will cause a detrimental deterioration in strength. Larger particle sizes also make it more difficult to make the treated lime evenly distributed in the cement mix. The particle size of the treated lime is preferably 1-100 microns, especially 5-60 microns.

The starting materials according to the invention comprise at least 36% CaO, the remainder consisting essentially of CaCO 2 and / or CaCO 2. The phrase "consisting essentially" is used to indicate that the starting material may contain minor amounts, generally less than 10%, of other ingredients which do not prevent the formation of an effective protective coating, for example impurities such as iron, magnesium and aluminum silicates and oxides. When the treated lime is prepared by heating the starting material in the presence of steam and / or carbon dioxide, the starting material preferably contains at least 80%, in particular at least 90%, CaO. Thus, dolomitic lime containing small amounts of CaO are not suitable starting materials.

When the atmosphere comprises water vapor but not carbon dioxide, the temperature should be 100-400 ° C, preferably 150-400 ° C, more preferably 150-250 ° C.

When the residual CaO content is certain, the higher the treatment temperature, the better the swelling activity of the product. At temperatures below 100 ° C, the lime hydrates, but no effective protective coating is formed. At temperatures above 400 ° C, no calcium hydroxide is formed, or if it is initially present, it is at least partially decomposed. In order to ensure a suitable protective coating, the heating in an atmosphere comprising water vapor should preferably be continued until the weight of the particles has increased by at least 2%, for example 2-16%, especially 4-12%, preferably 5-11% by weight of the starting material. With a starting material consisting essentially of CaO, these weight increases result in a product containing up to 92%, for example 92-36%, in particular 84-59% residual active lime as core and a protective coating consisting essentially of calcium hydroxide.

When the atmosphere comprises carbon dioxide, a temperature between 350 and 850 ° C is required to convert CaO to CaCO 3. At temperatures below 350 ° C, the reaction between CaO and CCl 3 is inherently slow and no effective protective coating is formed, at temperatures of 850 ° C no CaCO 3 is formed, or if it is initially present, it decomposes. In order to ensure a suitable protective coating, heating in a CO2-containing atmosphere should preferably be continued until the weight of the particles has increased by at least 2%, for example 2-28%, especially 4-16% and especially 5-16% by weight of the starting material. With a starting material consisting essentially of CaO, these weight increases give a product containing up to 95%, for example 36-95%, in particular 64-91%, in particular 64-89% of residual active lime as core and a protective coating consisting essentially of calcium carbonate. a.

The head also forms a protective coating comprising both CaCO 3 <63735 6 and Ca (OH) 2 by heating the starting material in an atmosphere comprising (Χ> 2 and water), preferably at a temperature of 350-400 ° C. Under these conditions, heating should preferably be continued until the particles the weight is increased by 4-14%, in particular 5-12%, which weight gains correspond (with the starting material consisting essentially of CaO) to the final products containing 91-40, in particular 80-50% of residual active lime.

As mentioned above, limes that are partially hydrated and / or carbonized at temperatures below 100 ° C do not have an effective protective coating and are not useful as expansion additives. Useful blowing agents can be obtained from such partially hydrated and / or carbonated limes by using them as starting materials in the processes described above, which is known to be heated in an atmosphere comprising water vapor and / or CC> 2, provided that the product has a sufficient residual CaO content. However, it has been found that partially hydrated limes can also be converted into useful blowing additives by heating them to a temperature of at least 100 ° C, preferably below 500 ° C, for example 200-400 ° C, in an atmosphere free of water vapor and carbon dioxide; in this embodiment of the invention, the starting material may comprise 8-64%, preferably 16-50% Ca (OH) 2, the remainder preferably consisting of CaO. Once the CaO content is given, the higher the treatment temperature and the longer its duration, the better the swelling activity of the product.

The treated lime, which already has some swelling activity, can be further treated by one of the methods described above to improve their activity. It should be noted, however, that such further treatment, if carried out in an atmosphere comprising water vapor at relatively low temperatures, for example below 200 ° C, in particular below 150 ° C, can reduce the residual CaO content of the treated lime to such an extent that its activity is reduced.

The heat treatments described above can be performed in any suitable manner that does not involve grinding of the particles which would break the protective coating. In the case of small amounts of product, the starting material can simply be applied to the sheet metal. In the case of larger amounts, fluidized bed methods can be used.

These new types of blowing agents can be incorporated into hydratable cementitious mixtures in any paste-like manner, but we have found that optimum swelling activity is obtained if the additive is added to a mixture containing at least a portion of cement and at least a portion of water. , but more the presence of CaO, slaked lime or carbonate lime is preferably avoided. The delayed reactivity of these new additives with respect to water, as measured by ASTM test C110-71, Section 9, is up to 100 minutes, but this is not sufficient to explain that they have a much higher delayed reactivity in cement mixtures. It is likely that this unexpectedly delayed reactivity is due to some kind of interaction between the protective coating and the components present in the cement slurry. The amount of additive used depends, inter alia, on the CaO content and the desired strength and expansion of the final product, and is generally from 3 to 30%, preferably from 3 to 10%, in particular from 5 to 7%, based on the total weight of the hydratable cement and additive. In particular, when the treated lime has been thoroughly treated, its presence has little or no detrimental effect on important properties of the cement mix, such as water demand, consistency, "opening time" and "false cure" tendency.

The invention is illustrated by the following examples. The expansion activities of the various samples prepared in Examples 1-7 are shown in Table 1, which shows the percentage increase in length of test prisms (i.e., test bars) that were cured (except where otherwise noted) in water after casting to ASTM standards C490-70 and C157- According to 69T, mortars prepared according to ASTM C305-65 containing 1 part of a mixture of treated lime sample and Type III Portland cement (Norcem Rapid), 2 parts of washed Monterey sand No. 20 and 0.4 parts of water. The amount of treated lime sample in the test prism and the number of days of curing are shown in parentheses after each expansion percentage value. Samples with a "C" after the sample number in Table 1 are comparative examples and not in accordance with the invention.

Example 1

CaCO 2 particles with a particle size of less than 44 microns were heated in a muffle furnace at 1000 ° C for the time required 8 63735 100% (Sample 1), 93.6% (Sample 2), 90.2% (Sample 3) and 72.3% (sample 4) to obtain samples containing CaO, and portions of sample 1 were heated in a muffle furnace at 580 ° C under a CO 2 atmosphere until the CaO content was 94.5% (sample 5), 89.8% (sample 6) or 80.5% (Sample 7). Aliquots of commercially available lime (Flintkote) with a particle size of less than 4 microns were heated in a muffle furnace at 580 ° C under a CO 2 atmosphere until the CaO content was 94.8% (Sample 8), 87.5% (Sample 9), or 74.8% (sample 10).

Example 2

Batches of commercially available lime (Flintkote) containing about 95% CaO with a residual Ca (OH) 2 and a trace amount of CaCO 2 and a particle size of less than 44 microns were kept exposed to water vapor at 22 ° C (Sample 11), 60 ° C (Sample 12), 100 ° C (Sample 13), 150 ° C (Sample 14), or 200 ° C (Sample 15) until the CaO content had decreased to the level shown in Table 1.

Example 3 Treated lime with swelling activity containing 60% CaO, 27% Ca (OH) 2 and 13% CaCO 2 and having a particle size of less than 100 microns (Sample 16) was kept exposed to water vapor at 22 ° C (Sample 17). ), At 60 ° C (sample 18), at 100 ° C (sample 19), at 150 ° C (sample 20) or at 200 ° C (sample 21) until the CaO content was 31% (sample 17) or 40% (samples 18-21).

Example 4 Treated lime with swelling activity containing 85% CaO, 5% Ca (OH) 2 and 10% CaCO 2 and a particle size of less than 100 microns was kept exposed to water vapor at 110 ° C until the CaO content had decreased. % (sample 22). Aliquots of sample 22 were heated at 110 ° C for 180 minutes (sample 23), at 200 ° C for 15 minutes (sample 24), at 200 ° C for 60 minutes (sample 25), at 300 ° C for 15 minutes (sample 26). ), At 340 ° C for 30 minutes (sample 27), at 340 ° C for 50 minutes (sample 28), at 400 ° C for 90 minutes (sample 29) and at 455 ° C for 15 minutes (sample 30). Samples 29 and 30 lost 2 and 3% of their weight during the heat treatment, respectively, due to the decomposition of calcium hydroxide. The same treated lime was kept exposed to water vapor at 200 ° C until the CaO content had decreased to 64% (Sample 31). Commercially available lime (Diamond Springs) consisting essentially of CaO and having a particle size of less than 100 microns was kept exposed to water vapor at 25 ° C until the CaO content was 64% (Sample 32). A portion of Sample 32 was heated at 340 ° C for 60 minutes (Sample 33). Another sample of the same commercially available lime was kept exposed to water vapor at 200 ° C until the CaO content had decreased to 58% (sample 34).

Example 5

Portions of the commercial lime used in Example 2 (Flintkote) were kept exposed to water vapor at 220 ° C until the CaO content was 85% (Sample 35) or 58% (Sample 36). These samples were made into mortars as described above except that cement (Kaiser Permanente) was used and the amount of water was 0.36 parts. A reference mortar to which no lime was added was also prepared. The prisms cast from these mortars were cured in both water and moist air with a relative humidity of 50%.

Example 6 Treated lime with swelling activity containing 84.5% CaO, 6.2% Ca (OH) 2 and 9.3% CaCO 2 and having a particle size of less than 100 microns was used to make mortars containing 0.9 parts of type 1-2 cement (Kaiser Permanente), 0.1 parts of treated lime, 2 parts of washed Monterey sand No. 20 and 0.36 parts of water. Mortars were prepared by three different methods.

Method 1 (ASTM C305-65) - A. The treated lime and cement were mixed dry. B. Water was added and stirred at a slow speed for 30 seconds. C. Sand was added and slow stirring was continued for another 30 seconds. D. The stirrer was accelerated to average speed for 30 seconds. E. Pause for 30 seconds. F. Stir at medium speed for 1 minute.

Method 2 - A. The cement and water were mixed for 30 seconds. B. The treated lime was added, and mixed for 30 seconds. C-F. Same as method 1.

Method 3 - A. Treatment with lime and water was mixed for 30 seconds. Cement was then added and mixed for 30 seconds. D-F. Same as in method 1.

10 63735 The percentage expansions of the prisms cast from these mortars are shown in Table 1 for Samples 37, 38 and 39 (Methods 1, 2 and 3, respectively).

Example 7

Commercially available lime (Flintkote) was screened into a first fraction with a particle size of 45-425 and a second fraction with a particle size of less than 45 microns. Both fractions were heated at 950 ° C for one hour and then treated with steam at 200 ° C until the CaO content was 65.9% (first fraction, sample 40) and 73% (second fraction, sample 41).

table 1

Eg Sample n: is: o% CaO Expansion (parts of sample in mortar; days) 1 1 (C) 100 0.042 (0.1; 7) 2 (C) 93.6 0.031 (") 3 (C) 90.2 0.031 (") 4 (C) 72.3 0.029 (") 5 94.5 0.234 (") 6 89.8 0.188 (") 7 80.5 2.3 (") 8 94.8 0.077 (") 9 87.5 0.150 (") 10 74.8 0.757 (") 2 11 (C) 49 0.037 (") 12 (C) 53 0.043 (") 13 53 0.125 (") 14 57 0.212 (") 15 53 0.347 ( ") 3 16 60 0.61 (0.1 *, 14) 0.067 (0.04, * 16) 17 (C) 31 0.134 (") 0.046 (") 18 40 0.186 (") 0.045 (") 19 40 0.330 (") 0.044 (") 20 40 0.413 (") 0.058 (") 21 40 2.8 (") 0.092 (") 63735 11 o ro oo

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Example G

Commercially available lime (Cementa) was treated with steam at 250 ° C until the CaO content was 80% and then partitioned into a first fraction with a particle size of less than 74 microns and a second fraction with a particle size of 75-120 microns. The first fraction was used to make a mortar containing 0.954 parts of type 1 cement (Norcem PC 300), 0.046 parts of treated lime, 3 parts of washed Monterey sand No. 20 and 0.5 parts of water. The second fraction was used to make mortars in the same way except that 0.96 parts of cement and 0.04 parts of treated lime were used. The compressive strength of the test prisms cast from these mortars was measured after curing in water for the number of days indicated in the table, and these strength values are shown in Table 2.

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Particle size Compressive strength (kg / cm) after 1 day 3 days and 7 days 0.74 105.5 240 300 75-125 103.5 195 248

Example 9

Aliquots of the same industrially available lime (Flintkote) used in Example 2 were treated with steam at 200 ° C until the CaO content was 91% (sample 42), 70% (sample 43) or 49.5% (sample 44), or CO 2 at 580 ° C until the CaO content was 88% (Sample 45) or 68% (Sample 46). A portion of Sample 45 was treated with steam at 200 ° C until the CaO content was 54% (Sample 47). Cement mortars were made by dry mixing 0.1 part of the sample and 0.9 parts of type 1-2 cement (Kaiser Permanente); water (0.36 parts) was then added and the mixture was stirred in a Hobart mixer for 20 seconds at slow speed and then for 20 seconds at medium speed. The mortars were placed in a Halliburton Consisto meter and their densities, expressed in Halliburton consistency units, are shown in Table 3 below (which also shows the results of a mortar containing the 1-2 types of cement mentioned in Part 1 and no treated lime at all).

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Claims (11)

A powdery composition which can be used as an expanding agent for hydrable cement compositions and comprising calcium oxide and other constituents which delay the hydration of the calcium oxide, characterized in that it consists essentially of particles having a size less than 100 microns and containing core of calcium oxide and a protective casing around the core of calcium hydroxide or calcium carbonate or both, contain 36-95% by weight of calcium oxide and have an expansion factor of at least 0.06%. Composition according to claim 1, characterized in that the calcium oxide content is 36-92% by weight and that the protective casing is essentially composed of calcium hydroxide. Composition according to claim 1, characterized in that the calcium oxide content is 64-91% by weight and that the protective casing is essentially composed of calcium carbonate. Composition according to any of the preceding claims, characterized in that it has an expansion factor of 0.07-0.4%. A process for preparing a powdery composition which can be used as an expanding agent for hydratable cement compositions and comprising calcium oxide and other ingredients which delay the hydration of the calcium oxide, characterized in that particles are heated (a) which are essentially made up of particles of a large size. less than 100 microns and (b) containing at least 36% by weight of CaO, the particles being poured at a temperature of at least 100 ° C and, the cm temperature of 100-400 ° C in an atmosphere containing water vapor or at a temperature of 350-850 ° C in an atmosphere comprising carbon dioxide, the heating being carried out under such conditions that the product contains 36-95% by weight CaO and has an expansion factor (as defined above) of at least 0.06%. 6. A process according to claim 5, characterized in that the particles initially comprise at least 80% by weight CaO and are heated at a temperature of 100-400 ° C in an atmosphere containing water vapor for so long that the weight of the particles increases by 4-12. %. Process according to claim 5, characterized in that the particles initially contain at least 80% by weight CaO and are heated at a temperature of 350-850 ° C in an atmosphere containing CO2 for a sufficient period of time for the weight of the particles to increase by 4-16 %.