SUPPLEMENTARY CEMENTITOUS MATERIAL MADE OF ALUMINIUM SILICATE AND DOLOMITE

Abstract

A method for producing a supplementary cementitious material (SCM) that includes providing a starting material containing dolomite and aluminium silicate, converting the starting material to the supplementary cementitious material by burning in the temperature range of >800 to 1100° C. or by burning in the temperature range of 725 to 950° C. in the presence of a mineralizer and cooling the supplementary cementitious material.

Claims

1. A method for producing a supplementary cementitious material (SCM), comprising the steps: providing a starting material containing an aluminium silicate constituent and a dolomite constituent, wherein a weight ratio of Al.sub.2O.sub.3+SiO.sub.2 to MgO+CaO of the starting material is in a range of 0.7 to 6, and converting the starting material to the supplementary cementitious material by burning the starting material to a sintered product in a temperature range of >800° C. to 1100° C. if no mineralizers are contained, and in a temperature range of 725° C. to 950° C. if mineralizers are contained.

2. The method according to claim 1, wherein the step of providing includes mixing and combined grinding of the dolomite constituent and the aluminium silicate constituent.

3. The method according to claim 2, wherein before or during the grinding, one or several grinding aids are added.

4. The method according to claim 1, wherein a mixture containing 40 to 80 wt % aluminium silicate constituent and 20 to 60 wt % dolomite constituent is used as the starting material.

5. The method according to claim 1, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 10 wt % MgO, occurring as carbonate.

6. The method according to claim 1, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 15 wt % Al.sub.2O.sub.3.

7. The method according to claim 1, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 15 wt % SiO.sub.2.

8. The method according to claim 1, wherein the starting material is burned for 5 to 240 minutes.

9. The method according to claim 1, wherein the starting material is burned in a fluidized-bed reactor or in a flash calciner for 5 to 300 seconds.

10. The method according to claim 1, wherein the supplementary cementitious material is ground to a fineness of 2000 to 10,000 cm.sup.2/g according to Blaine.

11. The method according to claim 10, wherein before or during grinding, one or several grinding aids are added, which are chosen from the group consisting of glycols, alkanolamines, alkyl dialkanolamines and mixtures thereof.

12. The method according to claim 1, wherein the starting material does not contain any mineralizers and is burned at 825° C. to 1000° C.

13. The method according to claim 1, wherein the starting material contains one or several mineralizers and is burned at 725° C. to 950° C.

14. The method according to claim 13, wherein the mineralizer or mineralizers is/are chosen from the group consisting of borax, waste glass, iron salts alkaline salts and/or alkaline earth salts.

15. A binder comprising: at least one cement selected from the group consisting of Portland cement, calcium sulphoaluminate cement, and calcium aluminate cement, and a ground supplementary cementitious material (SCM) produced according to the method of claim 1.

16. The binder according to claim 15, wherein an amount of cement is from 1 to 90 wt %, and an amount of supplementary cementitious material (SCM) is from 10 to 99 wt %.

17. The binder according to claim 15, further comprising an additional sulphate carrier.

18. The binder according to claim 17, wherein the sulphate carrier comprises from 0.1 to 10 wt % calcium sulphate or a mixture of calcium sulphates.

19. The binder according to claim 1, further comprising one or several setting accelerators, hardening accelerators, or both, chosen from the group consisting of aluminium salts and aluminium hydroxides, calcium (sulpho)aluminates, lithium salts and lithium hydroxides, other alkaline salts and alkaline hydroxides, alkaline silicates and mixtures thereof.

20. The binder according to claim 15, further comprising at least one activator to 19, characterized in that one or several activators are contained, preferably in an amount of 0.1 to 5 wt % based on the amount of the supplementary cementitious material (SCM).

21. The binder according to claim 15, further comprising one or more of the group consisting of concrete plasticizers, water reducing agents and retarders, and wherein the concrete plasticizers, reducing agents and retarders are based on lignin sulphonates; sulphonated naphthalene, melamine, or phenol formaldehyde condensate; or based on acrylic acid-acryl amide mixtures or polycarboxylate ethers, or based on phosphated polycondensates; phosphated alkyl carboxylic acids and salts thereof; (hydroxy-) carboxylic acids and carboxylates; borax, boric acid and borates, oxalates; sulphanilic acid; amino-carbonic acids; salicylic acid, and acetylsalicylic acid; dialdehydes and mixtures thereof.

22. The binder according to claim 15, further comprising additives selected from the group consisting of rock flour, precipitated (nano) CaCO.sub.3, pigments, fibers, and mixtures of two or more thereof in an amount of up to 40 wt %.

23. The binder according to claim 15, further comprising one or more of the group consisting of granulated blast furnace slag, fly ash, SiO.sub.2 in a form of silica fume, microsilica, and pyrogenic silica in an amount of up to 40 wt %.

24. The method according to claim 3, wherein the grinding aids are chosen from the group consisting of glycols, alkanolamines, alkyl dialkanolamines and mixtures thereof.

25. The method according to claim 4, wherein the mixture used as the starting material contains 50 to 70 wt % aluminium silicate constituent and 30 to 50 wt % dolomite constituent.

26. The method according to claim 4, wherein the mixture used as the starting material contains 55 to 65 wt % aluminium silicate constituent and 35 to 45 wt % dolomite constituent.

27. The method according to claim 5, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 12 wt % MgO as carbonate.

28. The method according to claim 6, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 20 wt % Al.sub.2O.sub.3.

29. The method according to claim 7, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 25 wt % SiO.sub.2.

30. The method according to claim 26, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 10 wt % MgO as carbonate, at least 15 wt % Al.sub.2O.sub.3 and at least 15 wt % SiO.sub.2.

31. The method according to claim 8, wherein the starting material is burned in a range of 25 to 120 minutes.

32. The method according to claim 10, wherein the supplementary cementitious material (SCM) is ground to a fineness according to Blaine of 3500 to 8000 cm.sup.2/g.

33. The method according to claim 12, wherein the starting material is burned in a temperature range of 850° C. to 975° C.

34. The method according to claim 13, wherein the starting material is burned at a temperature range of 775° C. to 900° C.

35. The method according to claim 26, wherein the starting material does not contain any mineralizers and is burned in a temperature range of 825° C. to 1000° C.

36. The method according to claim 26, wherein the starting material contains one or several mineralizers and is burned in a temperature range of 725° C. to 950° C.

37. The binder according to claim 15, comprising from 10 to 70 wt % cement and from 30 to 90 wt % supplementary cementitious material (SCM).

38. The binder according to claim 15, wherein the binder contains from 20 to 50 wt % cement and from 50 to 80 wt % supplementary cementitious material (SCM).

39. The binder according to claim 19, wherein the one or several setting accelerators, hardening accelerators or both, is/are chosen from the group consisting of Al.sub.2(SO).sub.3, AlOOH, Al(OH).sub.3, Al(NO.sub.3).sub.3, CaAl.sub.2O.sub.4, Ca.sub.12Al.sub.14O.sub.33, Ca.sub.3Al.sub.2O.sub.6, Ca.sub.4Al.sub.6O.sub.12(SO.sub.4), LiOH, Li.sub.2CO.sub.3, LiCl, NaOH, Na.sub.2CO.sub.3, K.sub.2Ca.sub.2(SO.sub.4).sub.3, K.sub.3Na(SO.sub.4).sub.2, Na.sub.2Ca(SO.sub.4).sub.3, K.sub.3Na(SO.sub.4).sub.2, K.sub.2Ca(SO.sub.4).sub.2*H.sub.2O, Li.sub.2SO.sub.4, Na.sub.2SO.sub.4, K.sub.2SO.sub.4, KOH, nanosilica and microsilica, water glass and mixtures thereof.

40. The binder according to claim 20, wherein the one or several accelerators is/are contained in an amount of 0.5 to 3 wt %, based on the amount of the supplementary cementitious material (SCM).

41. The binder according to claim 22, further comprising additives in an amount of 5 to 30 wt %.

42. The binder according to claim 23, further comprising one or more of the group consisting of granulated blast furnace slag, fly ash, SiO.sub.2 in the form of silica fume, microsilica and pyrogenic silica, in an amount of 5 to 30 wt %.

Description

EXAMPLE 1

[0084] As a low quality aluminium silicate constituent (very complex mixture of phases that are destroyed in substantially different temperature ranges (600 to 1000° C.)), use was made of Clay 1, which was burned at 825° C. Table 3 lists the supplementary cementitious materials tested and the results.

TABLE-US-00003 TABLE 3 Compressive strength [MPa] after supplementary cementitious material 7 d 2d 100% limestone (unburned) 25.1 31.1  50% clay + 50% limestone (only clay burned) 25.1 29.2  50% clay + 50% dolomite (burned together) 22.6 34.5  66% clay + 34% dolomite (burned together) 26.4 38.6  66% clay + 34% dolomite (burned separately) 22.3 35.5  50% clay + 50% dolomite + alkali (burned together) 27.5 39.4  66% clay + 34% dolomite + alkali (burned together) 27.1 42.3  66% clay + 34% dolomite (burned separately) + 22.4 31.6 alkali in the mixing water

[0085] It is apparent that the method according to the invention provides a reactive supplementary cementitious material from a very poor quality clay; Clay 1 contains large quantities of mica and quartz, but hardly any kaolinite. In spite of the unsuitable composition (50:50) of the starting material, a 10% higher compressive strength was achieved compared to the comparison standard with limestone. With regard to the combination of limestone and separately burned clay proposed in the prior art, the supplementary cementitious material according to the invention is significantly more reactive (9 to 32% greater compressive strength). The addition of 1 wt % NaHCO.sub.3 as a mineraliser during burning further optimizes the reactivity. This effect is not achieved if the alkalis are added to the mixing water instead. The comparison to clay and dolomite burned separately from each other illustrates the synergistic effect of burning them in combination. Also evident is the substantial improvement compared to the use of so-called Roman cement. It is evident that increasing contents of Clay 1 (see 50:50 to 66:34 comparison) lead to a substantial increase in strength development and that strength development is therefore not attributable (or at least only partially) to the reaction of burned lime or dolomite (as in the case with Roman cement). Instead the strength development is attributable to the contribution of reactive clinker phases (e.g., C.sub.3A, CA, C.sub.12A.sub.7, C.sub.2S and C.sub.4A.sub.3$), occurring partially in x-ray amorphous form, obtained by the method of the invention, as well as to a pozzolanic reaction. A clay:dolomite weight ratio of 2:1 proved to be particularly favourable for Clay 1. With an ideal starting material mixture and mineralisers, according to the invention a clay that is otherwise unusable as an SCM can be used in a very advantageous manner.

EXAMPLE 2

[0086] The influence of burning temperature was investigated, wherein in each case 1:1 mixtures of Clay 1 and dolomite were compared to the mixtures of Clay 1 and limestone as the prior art standard. The results are summarized in Table 4.

TABLE-US-00004 TABLE 4 Compressive strength Burning [MPa] after supplementary cementitious material temperature 7 d 28 d 100% limestone (unburned) ./. 25.1 31.1  50% clay + 50% limestone 825° C. 25.1 29.2 (only clay burned)  50% clay + 50% dolomite 825° C. 24.6 34.5 (burned together)  50% clay + 50% limestone 950° C. 23.7 32.4 (only clay burned)  50% clay + 50% dolomite 950° C. 25.4 39.1 (burned together)

[0087] These results confirm that in contrast to the prior art, with the method according to the invention the higher burning temperature is not critical and even leads to better results. Furthermore, a substantial reduction of the water demand is to be expected with higher burning temperatures (see Example 5).

EXAMPLE 3

[0088] Clay 2, which has calcite and quartz as crystalline main phases, was investigated. On the basis of the clay(s) that it contains (almost exclusively palygorskite and kaolin (dehydroxylation or decomposition in comparable temperature ranges)), this material is deemed high quality. Owing to the high CaCO.sub.3 fraction, Clay 2 should actually be classified as marl. The burning temperature was also varied in this example. The supplementary cementitious materials studied and the results are presented in Table 5.

TABLE-US-00005 TABLE 5 Compressive strength Burning [MPa] after supplementary cementitious material temperature 7 d 28 d 100% clay (burned) 825° C. 26.8 46.1  50% clay + 50% limestone 825° C. 26.6 45.0 (only clay burned)  50% clay + 50% dolomite 825° C. 33.9 53.5 (burned together)  50% clay + 50% dolomite 825° C. 25.3 41.2 (burned separately) 100% clay (burned) 950° C. 19.6 27.7  50% clay + 50% limestone 950° C. 22.8 32.9 (only clay burned)  50% clay + 50% dolomite 950° C. 31.0 47.3 (burned together)  50% clay + 50% dolomite 950° C. 23.1 34.6 (burned separately)

[0089] The experiments demonstrate the lack of sensitivity of the method according to the invention to different burning temperatures, in contrast to the burning of pure Clay 2 (prior art). It was furthermore confirmed that an increased reactivity was achieved compared to the clay-limestone mixtures as described in, e.g., Danner, “Reactivity of Calcined Clays”. Also worth mentioning is the accelerated reaction of the composite binder for the SCM according to the invention, which is quite evident from the 7 d compressive strengths. It turns out that compared to the prior art, even a material that is already high quality per se can be further improved.

EXAMPLE 4

[0090] Clay 3 was studied, which has kaolin and quartz as crystalline main phases. On the basis of the clay(s) that it contains (almost exclusively kaolin and only a little illite and montmorillonite), this material is deemed high quality. The burning temperature was also varied in this example. The supplementary cementitious materials studied and the results are presented in Table 6.

TABLE-US-00006 TABLE 6 Compressive strength Burning [MPa] after supplementary cementitious material temperature 7 d 28 d 100% clay (burned) 825° C. 30.5 45.0  50% clay + 50% limestone 825° C. 38.5 51.8 (only clay burned)  50% clay + 50% dolomite 825° C. 48.2 55.5 (burned together) 100% clay (burned) 950° C. 21.8 39.6  50% clay + 50% dolomite 950° C. 41.7 56.1 (burned together)

[0091] The experiments demonstrate the lack of sensitivity of the method of the invention to different burning temperatures, in contrast to the burning of pure Clay 3 (prior art). Also worth mentioning is the accelerated reaction of the composite binder for the SCM according to the invention, which is quite evident from the 7 d compressive strengths. It turns out that compared to the prior art, even a material that is already high quality per se can be further improved.

EXAMPLE 5

[0092] The effect of the method according to the invention on a low quality pozzolanic material unsuitable as a supplementary cementitious material was studied. The pozzolan (pozzo.) has a very complex mixture of phases that are destroyed in substantially different temperature ranges and is therefore deemed an inferior quality material. The burning temperature was varied here as well. The results are shown in Table 7.

TABLE-US-00007 TABLE 7 Compressive strength Burning [MPa] after supplementary cementitious material temperature 7 d 28 d 50 wt % pozzolan + 50 wt % limestone ./. 23.7 31.8 50% pozzo. + 50% limestone 825° C. 26.5 39.7 (only pozzo. burned) 100 wt % pozzo. (burned) 825° C. 23.4 39.6 50% pozzo. + 50% dolomite 825° C. 32.0 45.0 (burned together) 66% pozzo. + 34% dolomite 825° C. 33.4 49.9 (burned together) 66% pozzo. + 34% dolomite 825° C. 32.1 43.8 (burned separately) 50% pozzo. + 50% limestone 950° C. 24.4 34.9 (only pozzo. burned) 100 wt % pozzo. (burned) 950° C. 20.2 32.9 50% pozzo. + 50% dolomite 950° C. 27.1 38.4 (burned together) 50% pozzo. + 50% dolomite 950° C. 24.8 34.7 (burned separately)

[0093] The unburned pozzolan does not contribute to the development of compressive strength after 28 d. Furthermore, the pozzolan alone reacts very clearly to the degree of the burning temperature. If the temperature is increased from 825° C. to 950° C., the material makes nearly the same strength contribution as the untreated pozzolan (comparable to the 100% limestone reference standard). However, high temperatures are needed in order to convert all of the material present and in order to achieve the least possible surface area and thus a low water demand, as well as the destruction of all unwanted phases (e.g., swellable clays such as montmorillonite) in the binder. The supplementary cementitious material according to the invention is more reactive than the comparable prior art pozzolan-limestone mixture in each case, and a reactive SCM is obtained with the method according to the invention even at high temperatures. The comparison to pozzolan and dolomite burned separately from each other clearly shows the synergistic effect of burning them in combination.

EXAMPLE 6

[0094] In order to show the influence of the burning temperature on the surface area of different clays, the specific surface area was determined before and after burning by means of gas absorption and desorption (BET). The results summarized in Table 8 were achieved for the clayey, pozzolanic starting materials:

TABLE-US-00008 TABLE 8 BET surface area in m.sup.2/g Before Clay burning 525° C. 700° C. 825° C. 950° C. Pozzolan 24.9 — 15.6 13.5 7.1 Clay 1 15.3 14.6 14.5 6.4 1.8 Clay 2 38.6 29.3 26.2 9.4 1.9 Clay 3 42.1 41.4 41.8 31.5 24.1

[0095] In order to achieve the least possible surface area, the burning temperature should clearly be as high as possible. A small surface area is advantageous because the water demand becomes less as a result and the absorption of admixtures is also prevented or at least reduced. According to the prior art, however, a high burning temperature results in a material that has only limited use as an SCM, as can be inferred from Examples 1 through 4. As shown in the preceding examples, according to the invention it is possible to increase the burning temperature without sacrificing the reactivity as an SCM. By doing so the surface area can be reduced to a greater extent than in the prior art, and with some clays a greater fraction can be converted, with the reactivity increasing as a result.

EXAMPLE 7

[0096] The conversion of clay with dolomite was compared to that of clay with Ca(OH).sub.2+Mg(OH).sub.2 as individual constituents. To this end, 1 part dolomite and as much of a mixture of Ca(OH).sub.2 and Mg(OH).sub.2 as needed in order to obtain the same chemical composition after the burning process as for the conversion with dolomite were added in each case to 2 parts by weight of a pozzolanic material. Again, burning was carried out at two different temperatures. Table 9 summarizes the results.

TABLE-US-00009 TABLE 9 Compressive strength Burning [MPa] after supplementary cementitious material temperature 7 d 28 d Pozzo. + dolomite 825° C. 33.4 49.9 Pozzo. + Ca(OH).sub.2 + Mg(OH).sub.2 825° C. 28.8 42.3 Pozzo. + dolomite 950° C. 28.8 43.6 Pozzo. + Ca(OH).sub.2 + Mg(OH).sub.2 950° C. 22.8 32.8

[0097] The form in which the MgO was bound before burning is clearly a decisive factor. In both cases the supplementary cementitious material produced according to the invention with dolomite as the MgO source is more reactive than the one with calcium hydroxide and magnesium hydroxide as the MgO source.