SE434733B - CEMENT COMPOSITION, PROCEDURE FOR PREPARING THE COMPOSITION AND ANY USE OF THE COMPOSITION - Google Patents

Description

7809821-7 cases as undesirable, and the addition of free lime to cement compositions is avoided. Free lime does not act as an expander, as it hydrates very quickly and therefore expands too early during hardening to be effective; It is also known (see, for example, U.S. Pat. No. 3,106,453 and German Pat. No. 1,216,753) to subject free lime to certain specific treatments with water and / or CO2 to form a lime which hydrates at a lower rate, but they the products obtained become ineffective as expanders. Likewise, the products obtained by exposing the lime to the atmosphere, which products contain Ca (OH) 2 and CaCO3, are ineffective as expanders. It has also been proposed according to U.S. Pat. No. 1,732,409 to prepare rapidly hardening lime products which contain a large amount of lime, at least a portion of the lime being in the form of a product obtained by heating finely divided lime in an atmosphere containing CO at a temperature of 500 to 850 ° C, until the weight gain is 3 - 40%, calculated on the weight of the starting material. An expanding agent has now emerged for cement compositions of the kind initially indicated, which obviates the disadvantages of the hitherto known products. The expanding agent is characterized in that it consists essentially of particles with a size of less than 0.25 mm and containing a core of calcium oxide and a protective cover around the core of calcium hydroxide or calcium carbonate or both, which composition contains 36-95% calcium oxide. and has an expansion factor (according to the maximum definition) of at least 0.06%. Such compositions can be prepared by a process which does not involve heating particles of a size less than 0.25 mm and containing at least 36% by weight of CaO, the residue (if any preferably consisting essentially of Ca (OH22) and / or CaCO 3, the particles being kept at a temperature of at least 100 ° C and, if the particles initially contain less than 8% by weight of Ca (OH) 2, the same being kept at a temperature of 100 - 400 ° C in an atmosphere containing water vapor or at a temperature of 350 - 850 ° C in an atmosphere containing carbon dioxide, the heating being carried out under such conditions that the product contains 36 - 95% by weight of CaO and gives a expansion factor (as defined below) of at least 0.06%.

Due to the above, a cement composition of the initially stated type is characterized in that the calcareous expanding agent consists of particles of the stated type, the expanding agent being present in an amount of less than 30%, calculated on the total weight of the cement. and the calcareous expander. The invention also comprises the use of a cement composition with the above definition for the production of shaped objects.

Unless otherwise stated, parts and percentages in the present description refer to weight. The expansion factor for a calcareous composition is defined as the percentage increase in length of a test prism (test bar) cured in water for 7 days after casting, according to ASTM C490-70 and C157-69T, of a mortar prepared according to ASTM C305-65 and containing 0.1 part of the calcareous composition, 0.9 parts of Portland cement of type III, 2 parts of washed sand no. 20 and 0.4 parts of water. The expansion factor for treated lime products according to the invention is at least 0.06%, generally 0.07 to 2.5%, preferably 0.07 to 0.4%. The expansion factor is a measure of the protective cover's ability to delay the water's advancing to the calcium oxide core and, among other things, the composition's content of calcium oxide.

The larger the particle size of the treated lime, the greater the content of lime in the case of a given thickness of the protective casing. For this reason, the particle size is generally at least 0.001 mm. On the other hand, if particles larger than 0.25 mm in size are used, they give rise to an undesired decrease in strength. Larger particle sizes also make it difficult to obtain a uniform distribution of the treated lime in a cement composition. The treated lime products preferably have a particle size of 0.001 - 0.1 mm, preferably 0.005 to 0.06 mm. The starting materials used according to the invention comprise at least 36% CaO, the residue preferably consisting essentially of Ca (OH) 2 and / or CaCO 3. The term "substantially consisting of" is used to indicate that the starting material may contain minor amounts, preferably less than 10%, of other ingredients which do not prevent the formation of an effective protective casing, e.g. impurities such as silicates and oxides of iron, magnesium and aluminum. When the treated lime is prepared by heating the starting material in the presence of water vapor and / or carbon dioxide, the starting material suitably contains at least 80%, in particular at least 90%, of CaO.

Dolomitic limes containing minor amounts of CaO are not suitable as starting materials.

When the atmosphere contains water vapor, but no carbon dioxide, the temperature should be 100 - 400 ° C, preferably 150 - 40,000, in particular 150 - 250 ° C. For a given residual CaO content, the higher the temperature during the treatment, the higher the product's ability to expand. At temperatures below 100 ° C, the lime is hydrated without the formation of an effective protective cover. At temperatures above 400 ° C no calcium hydroxide is formed or if it is present from the beginning it will decompose at least partially. In order to ensure a sufficient protective cover, the heating in an atmosphere containing water vapor should suitably be completed for such a long time that the weight of the particles increases by at least 2%, e.g. 2 - 16%, in particular 4 - 12%, especially 5 - 11%, calculated on the weight of the starting material. -In the case of a starting material which essentially consists of CaO, these weight increases result in a product which contains a maximum of 92%, e.g. 92 - 36%, in particular 84 - 50%, in particular 84 - 50% residual activated lime as core and a protective coating, which consists essentially of calcium hydroxide.

As the atmosphere contains carbon dioxide, a temperature of 350 - sso ° c is needed in order to transfer cao to caco3.

At temperatures below 350 ° C, the reaction between CaO and CO 2 is very slow, and no effective protective coating is formed. At temperatures above 850 ° C no CaCO3 is formed or if CaCO3 is present from the beginning it decomposes. In order to ensure a sufficient protective cover, the heating should preferably be carried out in an atmosphere containing CO 2 for a sufficient time, in order for the particles to increase in weight by at least 2%, e.g. 2 - 28%, in particular 4 - 16%, especially 5 - 16%, calculated on the weight of the starting material. In the case of the starting material, which essentially consists of Ca0, these weight increases result in a product which contains a maximum of 95%, e.g. 36-95%, especially 64-91%, especially 64-89%, residual activated lime as core and a protective shell, which consists essentially of calcium carbonate. It is also possible to form a protective shell containing both CaCO 3 and Ca (OH) 2 by heating the starting material in an atmosphere containing CO 2 and water, preferably at a temperature of 350 - 400 ° C. Under such conditions, the heating should preferably be extended sufficiently for the particles to increase in weight by 4 - 14%, in particular 5 - 12%, the weight increases corresponding to (in the case of a starting material consisting essentially of CaO1 end products containing 91 - 40%, in particular 80 - 50% remaining activated lime.

As stated above, lime products that have been partially hydrated and / or carbonated at temperatures below 100 ° C have no effective protective coating and cannot be used as expanders. Useful expanders can be obtained from such partially hydrated and / or carbonated lime products by using them as starting materials in the processes described above, heating in an atmosphere containing water vapor and / or CO 2, provided that the product has a suitable residual calcium oxide content. However, it has been found that partially hydrated limes can also be transferred to useful expanders by heating at temperatures of at least 100 ° C, preferably less than 500 ° C, e.g. 200 - 400 ° C, in an atmosphere containing no water vapor or carbon dioxide; in this embodiment of the invention the starting material may contain 8 to 64%, preferably 16 to 50%, of Ca (OH) 2, the remainder suitably consisting essentially of CaO. For a given CaO content, the higher the temperature at which the treatment is carried out and the longer it lasts, the greater the product's ability to expand. 7899821-7 Treated limes that show a certain ability to expand in advance can be further treated by one of the methods described above to make them more active. It should be emphasized, however, that such further treatment, especially when carried out in an atmosphere containing water vapor at relatively low temperatures, e.g. below 200 ° C, especially below 150 ° C, can reduce the content of the treated lime of residual Ca0 to such a level that the activity is reduced.

The heat treatments described above can be carried out in any suitable manner which does not involve grinding the particles, thereby damaging the protective cover. In the case of small amounts of product, the starting material can simply be spread out in a container. In the case of larger quantities, fluidized bed processes can be used.

The new expanders can be incorporated with hydratable cement compositions in any suitable manner, but it has been found that optimal results in terms of expandability are obtained if the additive is added to a mixture of at least a portion of the Portland cement and at least a portion gave the water. . The cement compositions may, of course, contain sand, fillers and other customary additives, but the presence of extra quicklime, hydrated lime or carbonated lime should be suitably avoided. The new additives give a delayed reactivity with water, measured according to ASTM Test C110-71, section 9, of up to 100 minutes, but this is no guarantee that they will show a much greater delayed reactivity in cement compositions. It is believed that this unexpectedly delayed reactivity is due to some kind of interaction between the protective casing and the constituents present in the cement slurry. The amount of additive used depends, among other things, on the CaO content and the desired strength and expansion of the final product and will generally be 3 - 30%, preferably 3 - 10%, especially 5 - 7%, calculated on the combined weight of portland cement and the calcareous expander means. In particular when the limes have undergone a vigorous treatment, their presence has little or no detrimental effect on such significant properties of the cement composition as water demand, consistency, open time and propensity for so-called "false set". 9 1 L 7ßo9a21-7 The invention will be illustrated by the following examples. ' The activities of the various samples prepared according to Examples 1 - 7 in terms of expansion are shown in Table 1, which shows the percentage increase in length of test prisms (ie test rods) which (when not otherwise stated) were hardened in water after casting. according to ASTM C490-70 and C157-69T from mortar prepared according to ASTM C305-65 and containing 1 part mixture of the treated lime sample and a Portland cement of type III (Norcem Rapid), 2 parts washed sand no. 20 from Monterey and 0.4 parts water.

-The amount of treated lime sample in the test prism and the number of curing days are given in parentheses after each percentage point that indicates the expansion. The samples with a “C” after the sample number in Table 1 are comparative examples; which is not according to the invention.

Example 1 - Amounts of CaCO 3 with a particle size less than 0.44 mm were heated in a muffle furnace at 1000 ° C for the necessary time to give samples containing CaO in an amount of 100% (sample 1), 93.6 z (sample 2), 90.2 1% (sample s) or 72.3 s (sample 4).

Aliquots of Sample 1 were heated in a muffle furnace at 580 ° C in an atmosphere of CO 2 until the CaO content was 94.5% (Sample 5), 89.8% (Sample 6) and 80.5% (Sample 7). ). Amounts of technically available lime (Flintkote) with a particle size of less than 0.044 mm were heated in a muffle furnace at 580 ° C in an atmosphere of CO 2, until the CaO content was 94.8% (sample 8), 87.5% (prov 9) áler 74.8% (prov 10).

* Example 2 Quantities of technically available lime (Flintkote) containing about 95% Cao, with the residue in the form of Ca (OÉ) ¿and traces of CaCO3 and with a particle size less than (h044 mm, exposed to water vapor at 22 ° C (Sample 11), 60 ° C (Sample 12), 100 ° C (Sample 13), 100 ° C (Sample 14) or 200 ° C (Sample 15) une cec nade reduced to the level shown in Table 1.

Example 3 b A treated lime with expandability containing 60% Ca 2 O, 27% Ca (OH) 2 and 13% CaCO 3 and having a particle size of less than 0.1 mm (sample 16) was exposed to water vapor at 22 ° C _ (sample 17), 60 ° C (sample 18), 100 ° C (sample 19), 150 ° C (sample 20) and 200 ° C (sample 21), until the CaO content was 31% (sample 17) or 40% (sample 18 - 21). 1809221-7 Example 4.

A treated lime with expanding capacity containing 85% CaO, 5% Ca (OH) 2 and 10% CaCO3 and with a particle size of less than 0.1 mm, was exposed to water vapor at 110 ° C, until the CaO content had decreased to 64% (sample 22). Amounts of Sample 22 were heated at 110 ° C for 180 minutes (Sample 23), at Z00 ° C for 15 minutes (Sample 24), via .00 ° C for 50 minutes (Sample 25). via 300 ° C for 15 minutes (sample 26), at 340 ° C for 30 minutes (sample 27), at 34,000 for 50 minutes (sample .zfn, via 40 ° C for 50 minutes (sample 29) ooh via 4 ° C for 15 minutes (Sample 30): Samples 29 and 30 lost two and three% by weight during heating due to the decomposition of calcium hydroxide, the same treated lime was exposed to water vapor at 20 DEG C., while the CaO content was reduced to 64% (Sample 31). A technically available lime (Diamond Springs) consisting essentially of CaO and having a particle size of less than 0.1 mm was subjected to water vapor at 25 ° C until the CaO content became 64% (Sample 32). 340 ° C for 60 minutes (sample 33) ~ Another sample of the same technically available lime was subjected to water vapor at 200 ° C, until the content cao nade -minekat to ss- t (sample 34).

Example 5-.

Amounts of technically available lime (Flintkote) used in Example 2 were exposed to water vapor at 260 ° C until the CaO content was 85% (Sample 35) or 58% (Sample 36). These samples were transferred to mortar as described above except that a type 1-2 cement (Kaiser Permanenta) was used and the amount of water was 0.36 parts. A control mortar not containing any added lime was also added. The prisms cast from these mortars were made to harden both in water and in air with 50% 7 relative humidity.

Example 6 A treated lime with expanding ability and containing 84.5% CaO, 6.2% Ca (OH) 2 and 9.3% CaCO3 and having a particle size of less than 0.1 mm was used to prepare mortar containing 0.9 parts of a type 1 - 2 cement (Kaiser Permanente), 0.1 part of treated lime and 2 parts of washed sand No. 20 from Monterey and 0.36 parts of water. The mortars were prepared by three different methods. 7809821-7 Method 1 (ASTM C305-65) - A. The treated lime and cement were dry blended. B. The water was added and mixed at low speed for 30 seconds. C. Sandeq was added and the mixing at low speed was completed for another 30 seconds. D. The mixer was increased to medium speed for 30 seconds.

E. Pause for 90 seconds. F. Mix at medium speed for 1 min. _ _ Method 2 - A. The cement and water were mixed for 30 seconds.

B. The treated lime was added and mixing continued for 30 seconds. C - F. Same as in method 1.

Method 3 - A. The treated lime and water were mixed for 30 seconds, after which the cement was added and mixed for 30 seconds. D - F. Same as in method 1. 'The percentage expansion of the prism cast from the mortar is shown in Table 1 under samples 37, 38 and 39 (methods 1, 2 and 3 respectively).

Example 7 A technically available lime (Flintkote) was fractionated into a first fraction, in which the particles had a size between 0.045 and 0.425 mm and a second fraction, in which the particles had a size less than 0.045 mm. Both fractions were heated at 950 ° C for 1 hour and then treated with water vapor at 200 ° C until the CaO content was 69.5% (first fraction, sample 40) or 73% (second fraction, sample 41). a 7809821-7 10 TABLE '1 Example Sample No. _ No.% CaO Expansion (parts sample in mortar, days) 1 1 (C) 100 0.042 (0,1.7) z- (c) 93.6 0.031 ("") 310) 90 , 0.031 (") 4 (C) 72.3 0.029 (") 5 94.5 0.234 ("') 6 89.8 0.188 ("') 7 I 80.5 2.3 ("') 8 94, 8 0.077 ("')' 9 87.5 0.150 (") 10 _ 74.8 0.757 ("o) 2 11 (C) '49 0.037 (")' 12 (C) 53 0.043 ("') 13 53 0.125 ("')' 14 57 0,212 (") 15 53 0,347 ('"1)' 3 16 60 0,61 (0,1,1'4) ^ 0,067 (0_, 04.16) T7 (C) 31 _ 0,134 (" L ) 0.046 ("), 18 40 0.186 (" ') 0.045 (") 19 40' 0.330 (" *) 0.044 (") 20 40 0.413 (" "I) '0.058. (")> 21 40 2.8 ( "J) 0,092 (" "7809821-7 11 ^ = V m> .o A = Aæf. ~ .V vN.P Å w .Fv wN.PA = V No A = ^ mP.mo.v mF ~ o uwsm fl uxøu > fl »mHwu ^ w om wH> ^. = v Nß.o v.oP ~ o ^ oP.wo.vmww.o ^ ow.o ~ mmo ~ o | vmN0 ~ o | 0wm®Hw & ^^ ow.ßo .v ßv «o Åcw .cv No ~ o ¶. °« .M ° .v ========== NN ~ O Nmm ~ ° mm @ .o -oo m ~ wo mwm.o _ø « .o wmw.oo@mo w. ~. ° oFF ~ o wm «.0 ^« .. m ° ..wm ~. ° m ~ .Q ^ ß. °. ^>. m °.,.>. ° v>.> M .. ---_--- ~ - ----..-- n ~ -.>. M ° .. ow.o ww. ~ wo ~ o mP ~ o mmo_o | Nc.o | o mPo.o oN.o PN ~ o ßwm ~ o Nmm.o NNo ~ o mFm ~ o wmm ~ o wmm ~ o ~ mm ~ o wmm ~ o NwN ~ o Nmm ~ o voF ~ o ~ mP ~ o hvw ~ o ========== ._. m ° .v mwo_o mwo_o ßßo_O Aummmu .xøunußš w> oum um fl muv co fl wnmmww w ..muuomv _ anamma mß vw m.mm ou mh vv m ~ mm cv m ~ m ~ wæ mm m.wæ ßm .HHÛHUÉOM mm mm mm mm HH0Mv fl0 M mm .mm mm mm mm wm wm mm ww ^ UvNm vw Pm mn om Nh mm vw. wN um ßm vw mm vw mm ww vw wm MN Gm NN ONO W HC> OHm H: fl wmämxw 7809821-7 12 Example 8 A technically available lime (Cementa) was treated with water vapor at 250 ° C, until the CaO content was 80% and was then fractionated into a first fraction in which the particle size was less than 0.074 mm and a second fraction in which the particle size was between 0.075 and 0.125 mm. The first fraction was used to make mortar containing 0.954 parts of a type 1 cement (Norcem PC 300), 0.046 parts of treated lime, 3 parts of washed sand No. 20 from Monterey and 0.5 parts of water. The second fraction was used to make mortar in the same manner except that 0.96 parts of cement and 0.04 parts of treated lime were used. The compressive strength of prisms obtained from these mortars was measured after curing in water for the specified number of days, and is shown in Table 2. 'ÉQBELB 2 Particle size Compressive strength (kg / cm2) after 1 day 3 days -7 days 0 - 74 105.5 240 300 * 75 - 125 103.5 195 248 Example 9 Aliquots of commercially available lime (Flintkote) of the type used in Example 2 were treated with water vapor at 200 ° C, until the CaO content was 91% (sample 42), - 70 ~% (sample 43) or 49.5% (sample 44) or maa coz via sao ° c, until the cao-ha1- ten was.88% (sample 45) or 68% (sample 46); A portion of sample 45 was treated with water vapor at 200 ° C until the CaO content was 54% (sample 47). Cement pastes were prepared by dry mixing 0.1 part of the sample and 0.9 parts of a type 1-2 cement (Kaiser Permanente); water (0.36 parts) was then added and the mixture was mixed in a Hobart mixer for 20 seconds at low speed followed by 20 seconds at medium speed. The pastes were placed in a consistency meter from Halliburton, and the consistency expressed in Halliburton Consistency units is shown in Table 3 below (which also shows the results for a paste containing 1 part cement of type 1 - 2 and no treated lime) .

Prov nr 04 42 “1 oo, 43 40 44 32 45 * wo 46 se 4? ss Control 52 x shows s.k. 20 45 40 33 42 50 38 38 "false set". 40 45 '38 32 407 47 36 36 13 TABLE 3 7809821-7 Consistency after specified time (minutes) 60 47 38 34 42 45 36 36 80 49 40 36 42 45 36 36 100 53 42 38 43 46 36 36 120 64 43 40 47 46 38 36 140 82 45 42 52 50 40 37 160 100 48 45 58 51 41 38 180 200 52 58 50 56 63 70 53 56 43. 45 39 40 220 240 63 63 79 60 48 42 70 75 91 67 43

Claims (4)

7809821-7 14 PATENT REQUIREMENTS Cement composition containing Portland cement, water and a calcareous expander as an additive, characterized in that the calcareous expander consists essentially of particles smaller than 0.25 m in size and containing a calcium oxide core and a protective shell. around the core of calcium hydroxide or calcium carbonate or both, contains 36-95% by weight of calcium oxide and has an expansion factor of at least 0.06%, the expanding agent being present in an amount of less than 30%, calculated on the total weight of the cement and the calcareous expander. Cement composition according to claim 1, characterized in that it contains 3-10% by weight of calcareous expander, calculated on the total weight of the cement and the calcareous expander. Process for the preparation of cement, containing portland cement, water and calcareous expander as additives according to claim 1 or 2, characterized in that at least a part of the portland cement and at least a part of the water are mixed together and the calcareous substance is added. the expanding agent to the resulting mixture, the expanding agent consisting essentially of particles having a size of less than 0.25 mm and containing a core of calcium oxide and a protective shell around the core of calcium hydroxide or calcium carbonate or both, containing 36-95 wt. -% calcium oxide and has an expansion factor of at least 0.06% and is present in an amount of less than 30% based on the total weight of the cement and the calcareous expander. ' Use of the cement composition according to claim 1 or 2 for the production of shaped objects. SUMMARY The present invention relates to expandable cement compositions and expanders containing free lime intended for use in such compositions. New expanders are prepared according to the invention by heating lime with particle sizes less than 250 in an atmosphere containing water vapor at 100-400 ° C or carbon dioxide at 350-850 ° C or by heating a partially hydrated lime at a temperature of at least 100 ° C. The encapsulated lime thus prepared can be used as an expanding agent in hydratable cement compositions, the amount generally being less than 30%, preferably 3-10%, based on the weight of the cement and the additive. Cement compositions containing new expanders have a number of different uses, as one wants to avoid or prevent the shrinkage of the composition during drying.