SUPPLEMENTARY CEMENTITIOUS MATERIAL MADE OF ALUMINIUM SILICATE AND DOLOMITE

Abstract

This invention relates to a method for producing a supplementary cementitious material comprising the steps: providing a starting material containing dolomite and aluminium silicate, converting the starting material to the supplementary cementitious material by burning under reducing conditions in the temperature range of >700 to 1100 C. or by burning in the temperature range of 625 to 950 C. in the presence of a mineraliser, and cooling the supplementary cementitious material. The invention further relates to a binder comprising cement and to the ground supplementary cementitious material.

Claims

1. A method for producing a latent hydraulic and/or pozzolanic supplementary cementitious material, including the specific adjustment of the colour thereof, comprising the steps: Provision of a starting material containing an aluminium silicate constituent and a dolomite constituent and having a ratio (SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) from 0.7 to 6, Conversion of the starting material to the supplementary cementitious material by burning the starting material under reducing conditions in the temperature range of >700 C. to 1100 C. if no mineralisers are contained, and in the temperature range of 625 C. to 950 C. if mineralisers are contained.

2. The method according to claim 1, wherein the starting material is obtained by mixing and combination grinding of dolomite constituents and aluminium silicate constituents.

3. The method according to claim 2, wherein before or during the grinding, one or several grinding aids are added, which are preferably chosen from the group consisting of glycols, alkanolamines, alkyl dialkanolamines, and mixtures thereof.

4. The method according to claim 1, wherein a mixture containing 40 to 80 wt % aluminium silicate constituent, preferably 50 to 70 wt % aluminium silicate constituent, and in particular 55 to 65 wt % aluminium silicate constituent and 20 to 60 wt % dolomite constituent, preferably 30 to 50 wt % dolomite constituent, and in particular 35 to 45 wt % dolomite constituent is used as a starting material.

5. The method according to claim 1, wherein the starting material, calculated on a loss on ignition-free basis, contains at least 5 wt % MgO, preferably at least 7 wt % MgO, particularly preferred at least 10 wt % and in particular at least 12 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 8 wt % Al.sub.2O.sub.3, preferably at least 15 wt % Al.sub.2O.sub.3, in particular at least 20 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, preferably at least 25 wt % SiO.sub.2, in particular at least 40 wt % SiO.sub.2.

8. The method according to claim 1, wherein the starting material is burned for 5 to 240 minutes, preferably for 25 to 120 minutes, and in particular for 40 to 75 minutes, under reducing conditions.

9. The method according to claim 8, wherein the starting material is burned in a directly or indirectly fired rotary kiln, shaft kiln, or multi-deck oven.

10. 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, preferably for 10 to 150 seconds, and in particular for 20 to 100 seconds, under reducing conditions.

11. The method according to claim 1, wherein the reducing atmosphere is established by adding carbon, carbon monoxide, organic compounds, ammonia, sulphur, methane or other gases of the hydrocarbon group, and/or by process engineering, i.e. by choosing the appropriate amounts of fuel and/or by minimizing the oxygen input.

12. 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 (Blaine), preferably 3500 to 8000 cm.sup.2/g, and particularly preferred 4000 to 7000 cm.sup.2/g.

13. The method according to claim 12, wherein before or during grinding, one or several grinding aids are added, which are preferably chosen from the group consisting of glycols, alkanolamines, alkyl dialkanolamines, and mixtures thereof.

14. The method according to claim 1, wherein the starting material does not contain any mineralisers and is burned at 825 C. to 1000 C., preferably at 850 C. to 975 C.

15. The method according to claim 1, wherein the starting material contains one or several mineralisers and is burned at 625 C. to 950 C., preferably at 675 C. to 900 C., in particular at 800 C. to 875 C.

16. The method according to claim 15, wherein the mineraliser or mineralisers is/are chosen from the group consisting of borax, waste glass, iron salts (e.g., sulphates, hydroxides, carbonates, fluorides, nitrates, or mixtures thereof), alkaline salts (e.g., sulphates, hydroxides, (bi)carbonates, fluorides, or mixtures thereof) and/or alkaline earth salts (e.g., sulphates, hydroxides, (bi)carbonates, fluorides, or mixtures thereof).

17. A binder comprising a ground supplementary cementitious material, which can be obtained according to claim 1, and at least one cement, which is selected from among Portland cement, calcium sulphoaluminate cement, and calcium aluminate cement, and/or at least one activator, which releases aluminium and/or silicon in the form of ions.

18. The binder according to claim 17, wherein it contains from 1 to 90 wt %, preferably from 10 to 70 wt %, and in particular from 20 to 50 wt % cement or activator and from 10 to 99 wt %, preferably from 30 to 90 wt %, and in particular from 50 to 80 wt % supplementary cementitious material.

19. The binder according to claim 17, wherein it contains an additional sulphate carrier.

20. The binder according to claim 19, wherein it contains from 0.1 to 10 wt %, preferably from 1 to 7 wt %, and in particular from 2 to 5 wt % calcium sulphate or a mixture of calcium sulphates.

21. The binder according to claim 17, wherein one or several setting and/or hardening accelerators, preferably chosen from among aluminium salts and aluminium hydroxides, calcium (sulpho) aluminates, lithium salts and lithium hydroxides, other alkaline salts and alkali hydroxides, alkali silicates, and mixtures thereof are contained, in particular selected from among 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.2r 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, nano- and microsilica, water glass, and mixtures thereof.

22. The binder according to claim 17, wherein it contains at least one cement and that one or several activators are contained, preferably in an amount of 0.1 to 5 wt %, in particular 0.5 to 3 wt %, and particularly preferred 1 to 2 wt %, based on the amount of the supplementary cementitious material.

23. The binder according to claim 17, wherein concrete plasticizers and/or water reducing agents and/or retarders are contained, which are preferably based on lignin sulphonates; sulphonated naphthalene, melamine, or phenol formaldehyde condensate; or based on acrylic acid-acrylamide mixtures or polycarboxylate ethers or based on phosphated polycondensates phosphated alkyl carboxylic acids and salts thereof; (hydroxy-)carboxylic acids and carboxylates, in particular citric acid, citrates, tartaric acid, tartrates; borax, boric acid and borates, oxalates; sulphanilic acid; amino-carboxylic acids; salicylic acid, and acetylsalicylic acid; dialdehydes and mixtures thereof.

24. The binder according to claim 17, wherein additives, e.g., rock flour, in particular limestone and/or dolomite, precipitated (nano) CaCO.sub.3, pigments, fibres, and mixtures of two or more thereof are contained, preferably in a fraction of at most 40 wt %, particularly preferred 5 to 30 wt %, and in particular 10 to 20 wt %.

25. The binder according to claim 17, wherein in addition, granulated blast furnace slag, fly ash, SiO.sub.2 in the form of silica fume, microsilica, and/or pyrogenic silica is/are contained, preferably in an amount of at most 40 wt %, especially preferred 5 to 30 wt %, and in particular 10 to 20 wt %.

26. The binder according to claim 17, characterized in that wherein an activator is contained, which is preferably chosen from the group consisting of Al.sub.2(SO.sub.4).sub.3, Al(OH).sub.3 and calcium aluminates such as CA, C.sub.3A and C.sub.12A.sub.7, and furthermore nano- or microsilica, water glass and mixtures thereof.

Description

EXAMPLE 1

[0084] The clay 1-dolomite mixture was burned under reducing conditions and for comparison under oxidizing conditions. Three burning temperatures and two materials, namely a 66% dolomite-34% clay mixture as well as the clay alone for comparison, were tested. The two samples were each burned directly for one hour at 700 C., 800 C. or 900 C. The reducing atmosphere was established by using ground coal. To this end, the coal dust was transferred to a large (250 ml) crucible and then the sample in a small (30 ml) crucible was placed into the larger one. The container was then closed with a lid.

[0085] The burned samples underwent a subjective colour characterization. The results are given in Table 3. The corresponding values of the L*a*b* colour space and according to CMYK are given in parentheses ( ) and brackets [ ], respectively. This classification was performed subjectively.

TABLE-US-00002 TABLE 3 Material, Burning temperature [ C.] conditions 700 800 900 Clay, Red oxidizing (50 36.6 45) [7 84 92 1] Clay, Grey, slightly brownish Grey reducing (70 0 0) to (80 0 20) (30 0 0) [26 20 22 2] to [53 43 44 29] [15 15 40 1] Mixture, Red Red oxidizing (50 38.3 32.1) (50 46 38.6) [18 72 76 7] [13 78 84 3] Mixture, Grey, slightly Light grey Light grey, reducing brownish (70 0 0) slightly yellowish (60 0 0) to [26 20 22 2] (80 0 0) to (80 0 30) (60 10 17.3) [14 10 13 0] to [36 28 31 8] to [14 15 50 1] [25 39 50 15]

[0086] It is clear that the method according to the invention is suitable for systematically improving the colouration of the product that is produced. It is furthermore evident that compared to pure clay, a broader spectrum of colours can be achieved with burning under reducing conditions. It is possible to produce materials that are considerably lighter in colour. At all temperatures tested, it was possible to avoid a brown and/or red colouration. Compared to pure clay, in addition to the burning temperature the colouration can be systematically varied by the selection of the composition of the mixture, wherein the reactivity of the SCM in the final binder mix is still retained. Furthermore, the advantage arises that, compared to pure burnt clay, the combined burning of clay and dolomite leads to an increased reactivity of the SCM that is produced. This surprising positive effect manifests itself precisely at temperatures above 900 C.

EXAMPLE 2

[0087] Analogously to example 1 the following mixtures were burnt and examined:

mix 1: 50% dolomite and 50% clay 1(SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) about 1.5
mix 2: 50% limestone and 50% clay 1(SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) about 1.4
mix 3: 73% dolomite and 27% clay 1(SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) about 4.0
mix 4: 74% limestone and 26% clay 1(SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) about 4.0
mix 5: clay 2(SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) about 1.7

[0088] The colour that was determined for each mixture is summarized in table 4.

TABLE-US-00003 TABLE 4 burning temperature 825 C. 950 C. mix 1, reducing brown, slightly yellowish brown, slightly yellowish (80 13.7 37.6) [0 27 54 0] (70 0 20) [26 24 48 6] mix 2, reducing brown, slightly reddish brown, reddish (comparison) (60 20 34.6) [22 45 61 11] *(60 0 50)*[31 31 93 14] mix 3, reducing brown, slightly reddish brown, slightly yellowish (60 5 8.7) [32 35 42 15] (60 0 20) [34 31 69 14] mix 4, reducing reddish brown, slightly yellow (comparison) (50 23 19.3) [25 60 59 18] (60 0 20) [35 31 57 14] mix 5, reducing brown, slightly reddish brown to grey (60 17.1 47) [19 46 85 8] (70 0 50) [43 38 66 25] mix 5, oxidizing brown, reddish brown, slightly reddish (comparison) (60 30 52) [11 57 91 2] (70 20 34.6) [7 41 60 1]

[0089] The results reveal that all samples with dolomite show a slightly brighter colour compared to samples based on calcite. This indicates that the release of reactive MgO due to the two step decomposition of dolomite (i.e. 1st from 600 to 800 C. decomposition of dolomite and formation of secondary calcite) enables the binding/consumption of iron by its incorporation into new magnesium (+/) calcium bearing phases.

[0090] In addition, at elevated temperatures of 950 C. and even in the not optimized condition (lab furnace trial, reducing conditions were simulated by the addition of coal which is not the achievable optimum) the reddish colour was fully avoided. Based on the literature and own experiments the calcination of clays alone or blends with limestone strongly reduced the activity index of the aluminium silicate material. In contrast, mixtures with dolomite are less sensitive towards high temperatures (or even become better, depending on the used aluminium silicate), i.e. maintain an almost constant activity index. This example shows that also for a higher and a lower ratio (SiO.sub.2+Al.sub.2O.sub.3)/(CaO+MgO) of 4.0 and 1.5 as compared to the 2.8 in example 1 a significant improvement of colouration is achieved for mixtures with dolomite instead of limestone. Especially for high burning temperatures that are desired to reduce the surface area of the aluminium silicate constituent the colouration is improved as shown by mix 5.