SE448230B - PORTLAND-CEMENT CLINKS AND PROCEDURES FOR PRODUCING THEREOF - Google Patents

Description

u 40 448 230 2 'gypsum, the potassium sulphate can react with gypsum (CaSO4-2H2O) to form syngenite (KZSO4'CaSO4-H20), which causes air bonding after which the cement becomes clumpy, with poor flow properties.

Clumsy cement is difficult to mix with aggregates to form a homogeneous mixture and this results in poor quality Gïtmurbruk. An additional problem is "flash binding". As is well known, tricalcium aluminate (CSA, where C represents CaO and A represents the AIZOSJ component of the cement undergoes rapid reaction in contact with water. It is believed that the sulfate added to the cement clinker results in the formation of a layer of ettringite (Ca 6 Al 2 (SO 4)). (OH] 12-26H 2 O] on the C3A regions, which layer regulates the binding reaction. However, when there is insufficient sulfate to stop the hydrogenation of the C3A phase, flash bonding can occur. This is essentially irreversible in preventing It is an object of the invention to eliminate or mitigate the foregoing problems in producing clinkers with inherent bonding control. for a Portland cement to produce as hitherto - gypsum or other sulphates added to the clinker after firing, in other words the clinker introduces an inherent delay component, which provides improved bonding properties of the clinker itself a component that performs the role of a self-regulating blow to the cement produced by the clinker.

It is well known to those skilled in the art that SO 3 present in the form of calcium sulphate as a dead-burned anhydrite in the Portland cement clinker (as separated from calcium sulphate added afterwards to the clinker) is ineffective as a binding retarder due to its slow rate of dissolution in the measured water. The more readily soluble alkali metal sulphates are also known to be poor retarders and promote further elevated early concrete strengths at the expense of the latter strengths.

The present invention provides a Portland cement clinker comprising as an integral bond regulating component (a) sulfate in the presence of alkali metal in combined form and / or (b) halogen in combined form, the bond regulating component being present in an amount which is sufficient to prevent premature bonding of cement made from this tile.

The present invention also provides a process for producing such a clinker, which process comprises heating to partially melt a mixture of materials containing principally lime (CaO) and silica (SiO7) with a minor proportion of alumina (Al ) and iron oxide (Fe 2 O 3), in the presence of (a) sulfur-bearing material and alkali metal-bearing material and / or in the presence of (b) halogen-bearing material under conditions such that sufficient sulphate and alkali metal and / or halogen are retained within the clinker to prevent premature bonding of cement made therefrom.

Cement can be obtained by pulverizing or grinding clinker according to the present invention and this can be accomplished by conventional methods and using conventional apparatus. However, in order that the advantages of the invention may be fully apparent, it is preferred that the clinker be ground substantially in the absence of added sulphate, such as gypsum or anhydrite. At least some of the elements required to form the bonding control component in clinker may already be present in the cementitious raw materials or introduced into the furnace with the fuel used to fire the furnace. However, the process will normally involve the introduction into the furnace of one or more additives, which include halogen and / or sulfur and alkali metal. It will, of course, be appreciated that a reference herein to halogen or to an alkali metal normally refers to the element in a combined form such as halide ion or alkali metal ion. Similarly, a reference to sulfur to the combined form usually includes as sulfate. Additives can be introduced into the furnace either separately or together by introduction into raw cement or by some other method such as by blowing. .

The source of sulfur other than that which can be derived from the main raw materials and the fuel is preferably selected from calcium sulphate, hydrate of calcium sulphate, alkali metal sulphate, alkali metal-calcium double sulphate and mixtures of any of these. Preferably, sources of gypsum, potassium sulphate and precipitated dust from cement plants rich in potassium and sulfur are preferred. The preferred sources of alkali metal compounds are the main feedstocks or the fuel or additives of alkali metal sulfate or alkali metal calcium double sulfate referred to above. The preferred alkali metal is potassium, although sodium will usually also be present. The preferred halogen is fluorine. The source of fluorine other than that which may be in the main raw material is preferably calcium fluoride.

As can be seen from the context above, the use of sulfate as the inherent binding regulator requires the presence within the 2 alkali metal clinker; but with sufficiently high levels of sulphate, halogen Ci (in particular fluorine) need be present only in a small amount can in appropriate cases be dispensed with altogether. Conversely, when halogen (especially fluorine) is used as the bond-regulating component at sufficiently high levels, sulphate and alkali metal need be present only in small amounts and may in some cases be dispensed with altogether.

However, it is preferred that the clinker contain both halogen and sulfate in the presence of alkali metal. The halogen and sulfur introduced into the furnace exert a combined mineralizing action which allows the combination of raw materials in the furnace to take place at reduced firing temperatures, thus facilitating, especially in low heat furnaces, the desired retention of sulphate and alkali metal in the clinker at levels required for bonding. regulatory effect. The halogen, especially fluorine, also has a retarding effect that assists as a binding control.

The halogen used as a binding regulating agent is generally present in the clinker in an amount, measured as halogen, of 0.01 to 1% by weight of the clinker, preferably 0.1 to 1% by weight and in particular 0.15 to 0.30% by weight. .

The amount of alkali metal is normally measured as the oxide. In general, the alkali metal content of the clinker (expressed as Na 2 O equivalent) is from 0.1 to 3 percent and preferably from 0.4 to 2.0 percent and most preferably 0.60 to 1.0 weight percent of the clinker.

According to the purpose of the present invention, the minimum content of sulphate in the clinker is determined by the expression: minimum weight percentage of SO 3 = (equivalent Na 2 O in the clinker in weight percent x 1.29) + 0.2%. This minimum requirement of SO 3 is sufficient for all alkali metal oxides to occur as sulphates together with a small amount of calcium sulphate. This calcium sulphate and potassium sulphate will in turn combine to form the double sulphate, known as calcium langinite.

The figure calculated in each given case from the preceding expression of pure convenience is called "minimum clinker sulphate". ~ L5 40 s * 448 230 This figure is preferably_not_ less than 0.33%.

To avoid the problems of cement volume instability, the upper limit of SO3 in the clinker is normally 5.0% by weight.

The preferred range for the SO 3 content is 2.0-4.0% by weight.

When the bonding control component is wholly or partly sulphate, it has been found that the presence in the clinker of an alkali metal-calcium double sulphate especially calcium potassium sulphate (calcium langbeinite) is particularly advantageous.

The content of C3A phase in the clinker relates to two chemical parameters, namely the silica ratio and the alumina ratio (the calculations of the ratios are described below). In general, a decrease in the silica ratio at a given alumina ratio means an increase in the C3A content. Since CSA is rapidly reactive with water, it would be expected that the bonding of the cement made from clinkers with high CSA levels would be more difficult to control. Surprisingly, however, it has been found that the present invention still provides excellent bonding control even for cements made from clinkers with silica ratios of 2.80 and lower. Furthermore, good bonding control can be achieved even with tiles with CSA levels higher than 5% by weight. Appropriate selection and control of the amounts of bond-regulating components and control of the firing by methods known per se in principle to ensure that the required amounts of these components are retained in the clinker produced, in particular in the form of readily soluble sulphates, allow a cement to be obtained from the clinker which has regulated_binding properties and thereby eliminates the need for the addition of sulphate, such as gypsum to the clinker during grinding. The addition of additional sulfate may be considered unnecessary by the present invention but cannot be ruled out; such an additive can be found to be useful in effecting "fine tuning" of the bonding properties of the cement. In the absence of gypsum or the like, the grinding can be achieved hot without deteriorating effects on the cement quality and thereby eliminate the need for expensive cooling equipment.

By enabling the tile to be ground without the addition of gypsum, the problem of false bonding can thus be avoided. Furthermore, the presence of the inherent regulator component within the tile can inhibit flash binding. It should be noted that grinding in q é 448 230 in the absence of gypsum avoids the problem of air bonding due to syngenite formation. Furthermore, even if some gypsum were added to the grinding step when the readily soluble calcium long bone is formed during the clinker manufacturing process, this would reduce the amount of potassium sulfate that would presumably be available to form syngenite.

A further advantage of the invention is that low gypsum and gypsum materials obtained as a by-product are normally considered unsuitable for use as retarders when ground with Portland cement clinker used as a source of sulphate according to the present invention.

A further advantage is that the materials (excipients) such as slag, fly ash or pozzlin clay can be collected with clinker according to the present invention in a possibly hot grinding process to produce an elongated cement without a bad effect on the cement properties; such excipients can also be ground separately and then mixed with the separately ground tile. Thus, a wide range of cemented Portlands type cements can be advantageously made from clinkers made by the present invention together with a suitable extending agent. The clinker of the present invention can be ground to form a cement of any desired fineness. However, the specific surface area of the cement will not normally be less than zzs mg / kg.

In general, the amount of binding regulating component is selected so that the binding time from the beginning is less than 45 minutes (in accordance with BS (British Standard) 12: 1928, which document is hereby incorporated by reference), preferably not less than 60 minutes. The final binding time should not normally be more than 10 hours. Initial bonding times for typical production cement are usually from 90 to 220 minutes, while the final bonding times for such cements usually range from 150 to 300 minutes.

The present invention is illustrated by the following examples in which the contents, parts and ratios are by weight unless otherwise indicated. The chemical parameters of the clinker, namely the lime saturation factor (LSF), the silica ratio (S / R) and the aluminum ratio (A / F) are defined by the following expression: 'i 1' 448 230 cao - 0.7 so Lsr = 3 2, p S102 + 1.2 A1z03 + 0.65 FCZOS S102 S / R = ------- Al2O3 + Fe2O3 A1 0- A / F = __Ä_i_ Fe2O3 and the C3A content can be calculated according to the expression CSA = 2.65 AIZOS - 1, 69 Fe2O 3 wherein each chemical symbol represents the weight percent of the identified substance present in the composition taken into consideration. The percentages of the oxides are determined by the methods described in BS4550: part 2: 1970, which document is hereby incorporated by reference.

Free lime contents are determined by the hot ethylene glycol extraction method.

Specific water area (SSA) is determined by the method described in BS4550; Part 3: Section 3.3: 1978.

The division times are determined by the methods described in BS4550: part 3: sections 3.5 and 3.6: 1§78.

Settlement tests were performed in accordance with BS1881: Part 2: 1970. The settlement figures were assumed to be an indication of the workability of the composition in question; a figure of 40 mm is considered acceptable and 50 mm is considered good.

Example 1. The raw materials used were a limestone shale / sand mixture (A), which is a cement plant raw material included, together with shale clay (B) and gypsum (C), the analysis being as follows: _A_ _ë_ _§_ siozc 15,7 0 55.5 0 0.7 5 Al 2 O 3 3.8 21.2 0.19 Pezos 1.5 8.6 0.15 Cao 45.1 0.5 52.4 s (sa; 0m s03) 0.10 0, 46.4 Gloss loss 35.1 5.2 20.2 K 2 O_ 0.95 4.8 0.02 Nazo .- 0.15 0.54 0.02 448 230 (CaF 2) for general purpose reagent grade was also used.

The raw materials were mixed together in the following approximate proportions: 93.2% A, 0.2% B, 6.1% C, together with 0.5% of CaF 2. The mixture was ground until it had a residue of 9.5% on a sieve with a mesh size of 90 μm.

The resulting crude mixture was mixed with water and formed into cakes which were thoroughly dried and then fired at 140,000 to produce a clinker which was found to contain 2.6% free lime and which was found to have the following oxide composition: SiO 2 19.6% Alzos 5.6 Fezoz 2.5 cao 65.1 soz 3.6 K 2 O 1.1 Na 2 O less than 0.1 F (such as fluoride) 0.28 The LSF number was 0.99, the S / R number was 2.48 and A / The F-number was 2.43. The C3A content of the clinker was calculated as 10.9%. The equivalent Na 2 O content was 0.83% and the "minimum clinker sulfate" obtained from the above Na 2 O content was 1.27%.

The clinker was ground without any additives in a ball mill at 115 ° C to produce a cement with a specific surface area of 296 mz / kg.

The composition test on this cement gave a number of 43 mm. When the bonding times were tested, it was found that this cement had an initial bonding time of 230 minutes and a final bonding time of 290 minutes.

Example gel 2. approximate parts The raw materials described in Example 1 were mixed in 93.7% A, 0.2% B, 6.1% C and then ground to produce a raw material with a residue of 9.2% in a sieve down arnmskviàiav 90 pm. The raw material was formed into cakes which, after drying, were fired at 140006 to produce a clinker, which was found to have a free lime content of 2.8% and to have the following oxide composition: SiO 2 19.9 5 Al 2 O 3 5.5 Fezoš 2.2 cao 65, SO 3 3.4% K 2 O 1.2 Na 2 O less than 0.1 F 0.03 LSF was 0.99, S / R was 2.58 and A / F was 2.50. The C3A content was calculated to be 19.3% - the "minimum clinker sulphate" of 1.35% The equivalent NaZO content was 0.89%, from which it was calculated.

The clinker was ground without any addition in a ball mill at 115 ° C to produce a cement whose specific surface area was determined to be 331 m2 / kg.

The composite number test gave a figure of 48 mm.

When testing for bonding times, the cement was found to have an initial bonding time of 50 minutes and a final bonding time of 65 minutes.

Example 3. The raw materials described in Example 1 were mixed in approximate parts 97.3% A, 0.2% B and 2% C together with 0.5% calcium fluoride, and then ground to give a raw material with a residue of 9%. 4 0 on a screen with 90 μm muscle width. This raw material was formed into cakes, which were dried and then fired at 145 DEG C. to produce a clinker, which was found to have a free lime content of 3.0% and to have the following oxide composition: SiO2 20.6% Al2O3 5.8 Fe2O3 2.3 CaO 66.9 SO 3 1.2 K 2 O 0.9 Na 2 O less than 0.1 F 0.25 LSF was 1.00, S / R was 2.54 and A / F was 2.52. A C3A content of 11.4% was calculated. The equivalent Na 2 O content was 0.69%, from which value a "minimum clinker sulphate" content of 1.09% was calculated.

The clinker was ground without any additive in a ball mill at 11500 to produce a cement with a specific surface area of 337 m2 / kg.

A settling number test was performed on this cement and gave a figure of 52 mm. This cement was found to have an initial setting time of 50 minutes and a final setting time of 60 minutes.

Example gel 4. The raw materials used were a limestone / slate clay mixture (A), fuel ash (B) and gypsum (C), the analyzes of which were 448 230 the following: _ê_ B _E_ SiO 2 12.3% 44.0% 0.7% Al 2 O 3 3.0 29.4 0.19 Fe 2 O 3 2.5 9.2 0.15 CaO 43.2 2.6 32.4 Total S (as SO 3) 1.2 tracks 46.4 Annealing loss 35.4 9.45 20.2 Kzo 0.70 2.2 0.02 Na 2 O 0.31 0.4 0.02 Calcium fluoride for general purposes of reagent purity was also used.

The raw materials were mixed together at approximate levels of 93.5% A, 2.0% B and 4.0% C, together with 0.5% CaF 2, and then ground to give the resulting mixture a residue of 10.2% in a sieve. with 90 μm mesh size.

This raw material was mixed with water and formed into cakes, which were thoroughly dried and then fired at 1400 ° C to produce a clinker whose free lime content was found to be 2.0% and which had the following oxide composition: sioz 19.2 Al 2 O 3 5.0 Fezos 3.0 cao 05.0 SO 3 2.9 K 2 O 0.70 Nazo 0.40 P 0.31 LSF was 1.01, S / R was 2.18 and A / F was 1.32. A C3A content of 0.8% was calculated. The equivalent Na 2 O content was 0.86%, from which a "minimiclinker sulfate" content of 1.31% was calculated.

This tile was ground without any addition in a ball mill at 120 ° C to produce a cement with a specific surface area of 333 mz / kg.

The set number test was performed on this cement and gave a result of 49 mm.

The cement was found after the test to have an initial bond time of 180 minutes and a final bond time of 230 minutes.

Example 5. The raw materials described in Example 4 (with the exception of the gypsum) were mixed in the proportions of 97.5% A, 2.0 l of B and 0.5% CaF 2 and then ground to give a raw material with a residue of 10.4% on a sieve with a 90 Pm mesh size. The raw material was mixed with water and formed into cakes which after thorough drying were fired at 140 DEG C. to produce a clinker which was found to have a free lime content of 3.2% and which had the following oxide composition: SiO2 19.9% Al2O3 5.2 Pe2 O3 4.0 CaO 66.1 SO 3 1.4 K 2 O 0.7 Na 2 O 0.4 F 0.26 LSF was 1.01, S / R was 2.16 and A / F was 1.30. A CSA content of 7.0% was calculated. The equivalent Na 2 O content was 0.86%, from which a "minimum clinker sulfate" content of 1.31% was calculated.

This tile was ground, without any additives, in a ball mill at 12000 to produce a cement with a specific surface area of 337 m2 / kg.

A settling number test was performed on this cement and gave a yield of 45 mm.

When tested for bonding times, this cement was found to have an initial bonding time of 60 minutes and a final bonding time of 90 minutes.

Example gel 6. The raw material used was a chalk / clay mixture (A), gypsum (B) and fuel ash (C) whose analysis was as follows: Li_C_ SiO3 12.7% 0.7% 44.0% Al 2 O 3 4.3 0.19 29.4 Fe2O3 1.7 0.15 9.2 cao 43.1 32.4 2.6 Total S (as SO3) 0.75 46.4 tracks Annealing loss 35.4 20.2 9.45 KZO 0.80 0.02 2.2 Na 2 O 0.22 0.02 0.4 General purpose calcium fluoride with reagent purity was also used.

These feedstocks were mixed together in approximate proportions 92.65% A, 6.0% B, 1.0% C and 0.35% then to give a feedstock with a residue of 7% on a sieve CaF2, and ground with a snag width of 90 μm size.

This raw material was mixed with water and formed into cakes, which were then dried and fired at 1400 ° C to produce a clinker whose free lime content was 0.9% and which had the following oxide composition.

SiO2 18.5% Aizos 6.3 Fe2O3 2.5 Ca0 64.6 SO3 3.5 KZO 1.0 Na2O 0.26 F 0.23 LSF was 1.02, S / R was 2.10 and A / F was 2.52. The CSA content was estimated to be 12.4%.

The equivalent Na 2 O content was 0.92%, from which a "minimum clinker sulphate" content of 1.39 l was calculated.

This tile was ground without any additive in a ball mill at 120 ° C to produce a cement with a specific surface area of 326 mz / kg.

A settling test was performed on this cement and gave a result of 48 mm.

The cement was found when tested to have an initial bond time of 200 minutes and a final bond time of 230 minutes. ßxemgel 7. approximate proportions 94.65% A, 4.0% The raw materials described in Example 6 were mixed in B, 1.0% C and 0.35% CaF 2, and then ground to give a raw material with a residual ev 3.2% on a term with a meekvied ev so mm. The raw material was formed into cakes which, after thorough drying, were fired at 140 DEG C. for a preparation in a kiln with a free calyx or 0.8% and with the following oxide composition sio, 19.0% Alzö 6.5 Fezoš 2.6 Ca0 65.5 so , 2.5 Kzo 0.95 Na7O Û, 24 0.20

Claims (12)

13,448,230 Patent claims Portland cement clinker containing (a) sulphate, (b) ulkali metal and (c) halogen, characterized in that the sulphate (a) is present in an amount of 0.33 to 5% by weight of the clinker, the alkali metal (b) is present in a combined state and in an amount (expressed as the equivalent Na 2 O) from 0.1 to 3% by weight of the clinker and the halogen (c) is present in a combined state and in an amount of 0.01 to 1 weight percent of the tile and in that the silica ratio of the tile is not greater than 2.80. Tile according to claim 1, characterized in that it contains halogen in an amount of 0.1 to 1.0% by weight of the tile. Clinker according to claim 1 or 2, characterized in that the clinker contains fluorine as said halogen. Clinker according to Claims 1, 2 or 3, characterized in that it contains alkali metal in an amount (expressed as equivalent to Na 2 O] from 0.4 to 2.0% by weight of the clinker. 5. A tile according to any one of claims 1-4, characterized in that the alkali metal is essentially potassium or a mixture of potassium and sodium. Clinker according to one of Claims 1 to 5, characterized in that it contains sulphate in an amount of from 2.0 to 4.0% by weight of the clinker. Clinker according to claim 6, characterized in that it contains fluorine in an amount of 0.15 to 0.30% by weight of the clinker and contains alkali metal in an amount (expressed as the equivalent of Na 2 O) from 0.60 to 1.0 weight percent of the tile. Clinker according to one of Claims 1 to 7, characterized in that it contains calcium long bone. Clinker according to one of Claims 1 to 8, characterized in that it has a tricalcium aluminate content greater than 5% by weight. 10.. A process for producing Portland cement clinker according to any one of claims 1-10, which process comprises heating to partial melting a mixture of materials containing mainly lime and silica together with a minor proportion of alumina and iron oxide, in the presence of ( A) sulphate-containing material, (B) alkali metal-containing material, and (C) halo-containing material, characterized in that the heating is effected under conditions such that it is retained in the clinker (a) sulphate in a small amount of 0.33 to 5% by weight of the clinker, (b) alkali metal in the combined state and in an amount (expressed as the equivalent Na 2 O) of from 0.1 to 3% by weight of the clinker. ag, the clinker and (c) halogen in a combined state and in an amount of 0.01 to 1% by weight of the clinker, the silica ratio in the clinker not being more than 2.80. Characterized in that the sulphate-containing material comprises calcium sulphate, a hydrate of calcium sulphate, an alkali metal sulphate, a A process according to claim 10, alkali metal calcium double sulphate or a mixture of any of these. 12. A process according to claim 10 or 11, characterized in that calcium fluoride is used as the holding-containing material. flat