METHOD FOR MANUFACTURING A SUPPLEMENTARY CEMENTITIOUS MATERIAL

Abstract

A method for manufacturing supplementary cementitious material includes the steps of: providing a starting material containing clay and fly ash or a mixture of fly ash and bottom ash, wherein at least 70 wt.-% of the starting material are clay, fly ash and bottom ash, homogenization of the starting material, thermal treatment of the starting material at a temperature from 700 to 1000 C. to provide a heat treated material, cooling the heat treated material to provide a cooled product, and grinding the cooled product to provide the supplementary cementitious material, and use of the supplementary cementitious material obtainable through the method for manufacturing hydraulic building materials, as well as supplementary cementitious material obtained.

Claims

1. A method for manufacturing a supplementary cementitious material comprising the steps of: providing a starting material containing fly ash and clay or a mixture of fly ash and bottom ash and clay, wherein at least 70 wt.-% of the starting material are clay, fly ash and bottom ash, wherein the fly ash or the mixture of fly ash and bottom ash has a water demand determined according to EN 450-1 above 105% or an activity index determined according to EN 450-1 on a sample prepared with 70 wt.-% CEM I 42,4 R at 28 days below 70% or at 90 days below 85%, either before or after heat treatment at a temperature ranging from 700 to 1000 C., homogenization of the starting material, thermal treatment of the homogenized starting material at a temperature ranging from 700 to 1000 C. to provide a heat treated material, cooling the heat treated material to provide a cooled product, and grinding the cooled product to provide the supplementary cementitious material.

2. The method according to claim 1, wherein the fly ash and/or the mixture of fly ash and bottom ash is a by-product of coal dust combustion.

3. The method according to claim 1, wherein the fly ash or the mixture of fly ash and bottom ash contains at least 25 wt.-% reactive SiO.sub.2, and one or more of: a sum of SiO.sub.2, Al.sub.2O.sub.3, and Fe.sub.2O.sub.3 of at least 65 wt.-%, less than 10 wt.-% CaO, below 2.0 wt.-% SO.sub.3, below 0.10 wt.-% Cl.sup., a loss on ignition at 950 C. below all with respect to the total weight of the fly ash or the mixture of fly ash and bottom ash.

4. The method according to claim 1, wherein the fly ash or the mixture of fly ash and bottom ash contains sum of reactive SiO.sub.2 and reactive CaO of at least 30 wt.-%, and one or more of: a sum of SiO.sub.2, Al.sub.2O.sub.3, and Fe.sub.2O.sub.3 of more than 40 wt.-%, at least 10 wt.-% CaO, below 6.0 wt.-% SO.sub.3, below 0.10 wt.-% Cl.sup., a loss on ignition at 950 C. below 10 wt.-% all with respect to the total weight of the fly ash or the mixture of fly ash and bottom ash.

5. The method according to claim 1, wherein the clay contains at least one mineral selected from the group consisting of kaolinite, dickite, halloysite, nacrite, montmorillonite, nontronite, beidelite, saponite, illite, palygorskite, and sepiolite in crystalline, semi-crystalline and/or amorphous form.

6. The method according to claim 5, wherein the clay contains at least 15 wt.-% of one or more of the minerals with respect to the total clay weight.

7. The method according to claim 1, wherein the starting material comprises at least 40 wt.-% fly ash or mixture of fly ash and bottom ash and at least 30 wt.-% raw clay.

8. The method according to claim 1, wherein the temperature during thermal treatment ranges from from 800 to 900 C.

9. The method according to claim 1, wherein the thermal treatment is carried out until the clay is dehydroxylated and partially sintered providing a heat treated product with a higher pozzolanic activity and a lower water demand than the starting material.

10. The method according to claim 1, wherein the cooled product is ground to a specific surface from 3000 cm.sup.2/g according to Blaine.

11. The method according to claim 1, wherein the clay calcined at a temperature ranging from 700 to 1000 C. absent the fly ash or mixture of fly ash and bottom ash has a water demand determined according to EN 450-1 above 105% or an activity index determined according to EN 450-1 on a sample prepared with 70 wt.-% CEM I 42,4 R at 90 days below 90%.

12-14 (canceled)

15. A supplementary cementitious material, having an activity index according to EN 450-1 after 28 days of not less than 70%, and a water demand according to EN 450-1 Annex B of not more than 110%, as well as: a loss on ignition at according to EN 196-2 of not more than 7.0 wt.-%, and/or a volume stability according to EN 196-3 for a paste made from 30 wt. % of the supplementary cementitious material and 70 wt.-% of an ordinary Portland cement, measured with the expansion value, of no more than 10 mm, wherein the supplementary cementitious material is obtained by providing a starting material containing fly ash and raw clay or a mixture of fly ash and bottom ash and raw clay, wherein at least 70 wt.-% of the starting material are clay, fly ash and bottom ash, wherein the fly ash or the mixture of fly ash and bottom ash has a water demand determined according to EN 450-1 above 105% or an activity index determined according to EN 450-1 on a sample prepared with 70 wt.-% CEM I 42,4 R at 28 days below 70% or at 90 days below 85%, either before or after heat treatment at a temperature ranging from 700 to 1000 C., homogenization of the starting material, thermal treatment of the homogenized starting material at a temperature ranging from 700 to 1000 C. to provide a heat treated material cooling the heat treated material to provide a cooled product, and grinding the cooled product to provide the supplementary cementitious material.

16. The supplementary cementitious material according to claim 15, having an activity index according to EN 450-1 after 28 days of not less than 85%, and/or a water demand according to EN 450-1 Annex B of not more than 105%, and/or: a loss on ignition at according to EN 196-2 of not more than 5.0 wt.-%, and/or a volume stability according to EN 196-3 for a paste made from 30 wt. % of the supplementary cementitious material and 70 wt.-% of an ordinary Portland cement, measured with the expansion value, of no more than 5 mm.

17. The supplementary cementitious material according to claim 15, wherein the fly ash or the mixture of fly ash and bottom ash contains at least 25 wt.-% reactive SiO.sub.2, and one or more of: a sum of SiO.sub.2, Al.sub.2O.sub.3, and Fe.sub.2O.sub.3 of at least 70 wt.-%, less than 10 wt.-% CaO, below 2.0 wt.-% SO.sub.3, below 0.10 wt.-% Cl.sup., a loss on ignition at 950 C. below 20 wt.-%, all with respect to the total weight of the fly ash or the mixture of fly ash and bottom ash.

18. The supplementary cementitious material according to claim 15, wherein the fly ash or the mixture of fly ash and bottom ash contains sum of reactive SiO.sub.2 and reactive CaO of at least 40 wt.-%, and one or more of: a sum of SiO.sub.2, Al.sub.2O.sub.3, and Fe.sub.2O.sub.3 of more than 60 wt.-%, at least 20 wt.-% CaO, below 3.0 wt.-% SO.sub.3, below 0.10 wt.-% Cl.sup., a loss on ignition at 950 C. below 10 wt.-%, all with respect to the total weight of the fly ash or the mixture of fly ash and bottom ash.

19. The supplementary cementitious material according to claim 15, wherein the raw clay contains at least 30 wt.-% of minerals selected from the group consisting of kaolinite, montmorillonite, and/or illite, in crystalline, semi-crystalline and/or amorphous form.

20. The supplementary cementitious material according to claim 15, wherein the starting material comprises from 50 to 70 wt.-% fly ash or mixture of fly ash and bottom ash, and from 30 to 50 wt.-% raw clay.

21. The method according to claim 1, wherein the fly ash and/or the mixture of fly ash and bottom ash is a by-product of coal dust combustion and wherein wherein all solid residues from the coal dust combustion are mixed.

22. The method according to claim 1, wherein the fly ash or the mixture of fly ash and bottom ash contains at least 25 wt.-% reactive SiO.sub.2, and one or more of: a sum of SiO.sub.2, Al.sub.2O.sub.3, and Fe.sub.2O.sub.3 of at least 70 wt.-%, less than 5 wt.-% CaO, below 2.0 wt.-% SO.sub.3, below 0.10 wt.-% Cl.sup., a loss on ignition at 950 C. below 15 wt.-%, all with respect to the total weight of the fly ash or the mixture of fly ash and bottom ash.

23. The method according to claim 1, wherein the fly ash or the mixture of fly ash and bottom ash contains sum of reactive SiO.sub.2 and reactive CaO of at least 40 wt.-%, and one or more of: a sum of SiO.sub.2, Al.sub.2O.sub.3, and Fe.sub.2O.sub.3 of more than 60 wt.-%, at least 20 wt.-% CaO, below 3.0 wt.-% SO.sub.3, below 0.10 wt.-% Cl.sup., a loss on ignition at 950 C. below 10 wt.-%, all with respect to the total weight of the fly ash or the mixture of fly ash and bottom ash.

24. The method according to claim 5, wherein the raw clay contains at least 30 wt.-% of one or more of the minerals with respect to the total clay weight.

25. The method according to claim 1, wherein the starting material comprises from 50 to 70 wt.-% fly ash or mixture of fly ash and bottom ash, and from 30 to 50 wt. % raw clay.

Description

EXAMPLE 1

[0067] Different SCM compositions were prepared from the mixture of fly ash and bottom ash and addition of clay 1. Materials were mixed for 5 minutes in a laboratory mixer acc. to EN 196-1, then dried for 244 hours at 105 C., then heated up to 850 C. and fired for 1 hour at 850 C. in a laboratory electric furnace. The obtained SCM was air-cooled to ambient temperature and ground in a ring mill to a specific surface of 3500500 cm.sup.2/g. Water demand was tested according to EN 450-1 as consistency of mortar with 70 wt.-% ordinary Portland Cement (CEM 42,5R) and 30 wt.-% of SCM. The activity index at 28 and 90 days was tested on samples prepared as standard mortar with 70 wt.-% ordinary Portland Cement (CEM I 42,5R) and 30 wt.-% of SCM taking into account a correction of the water content caused by water demand. Test procedure was as described in EN 450-1. The results are presented in table 3.

TABLE-US-00003 TABLE 3 Binder composition [wt.-%] CEM I 42,5R 70 70 100 SCM 30 30 0 SCM composition [wt.-%] Mixture of fly ash and bottom 100 70 50 30 0 0 0 ash Clay 1 0 30 50 70 100 0 0 Quartz sand 0 0 0 0 0 100 0 Results Fineness acc. Blaine [cm.sup.2/g] 3690 3480 3210 3640 3370 3230 3750 Loss on ignition [wt.-%] 13.4 3.4 3.0 2.8 7.1 Soundness [mm] 1.0 0.0 1.0 0.0 0.0 0.0 0.4 Water demand [%]* 108.0 100.0 100.0 104.4 103.6 100 100 Activity index at 28 days [%]* 61.2 84.9 78.4 81.4 81.9 64.1 100 Activity index at 90 days [%]* 74.3 94.7 90.5 87.4 85.3 65.5 100 *% with reference to standard mortar with only CEM I 42,5R

[0068] From the results it is apparent that the clay alone had a high water demand, although the activity index was high enough. The mixture of fly ash and bottom ash alone had a too low activity (lower than quartz sand at 28 days) and also a high water demand. But the SCM from thermally treating 50 or 30 wt.-% clay together with 50 or 70% ash mixture had normal water demand and high activity indices at 28 and at 90 days. Thus, it was possible to obtain useful SCM from ashes not suitable as such and even obtain an SCM with properties improved over the pure calcined clay for the starting materials with 50 and 70 wt.-% ashes.

EXAMPLE 2

[0069] Different SCM compositions were prepared from the mixture of fly ash and bottom ash and clay 2. Materials were mixed for 5 minutes in a laboratory mixer acc. to EN 196-1, then dried for 244 hours at 105 C., then heated up to 850 C. and fired for 1 hour at 850 C. in a laboratory electric furnace. The obtained SCM was air-cooled to ambient temperature and ground in a ring mill to a specific surface of 3500500 cm.sup.2/g. Water demand was tested according to EN 450-1 as consistency of mortar with 70 wt.-% ordinary Portland Cement (CEM I 42,5R) and 30 wt.-% of SCM. The activity index at 28 and 90 days was tested on samples prepared as standard mortar with 70 wt.-% ordinary Portland Cement (CEM I 42,5R) and 30 wt.-% of SCM taking into account a correction of the water content caused by water demand. Test procedure was as described in EN 450-1. The results are shown in table 4.

TABLE-US-00004 TABLE 4 Binder composition [wt.-%] CEM I 42.5R 70 70 100 SCM 30 30 0 SCM composition [wt.-%] Mixture of fly ash and bottom 100 70 50 30 0 0 0 ash Clay 2 0 30 50 70 100 0 0 Quartz sand 0 0 0 0 0 100 0 Results Fineness acc. Blaine [cm.sup.2/g] 3690 3430 3290 3370 3610 3230 3750 Loss on ignition [wt.-%] 13.4 3.5 3.3 3.0 3.6 Soundness [mm] 1.0 0.0 1.0 1.0 0.0 0.0 0.4 Water demand [%]* 108.0 100 101.8 108.0 104.9 100 100 Activity index at 28 days [%]* 61.2 83.6 83.5 74.7 84.1 64.1 100 Activity index at 90 days [%]* 74.3 92.3 93.2 81.8 86.0 65.5 100 *% in reference to standard mortar only with CEM I 42.5R

[0070] From the results it is apparent that the clay alone had a high water demand, even though the activity index was high enough. The mixture of fly ash and bottom ash alone had a too low activity (lower than quartz sand at 28 days) and too high water demand. But the SCM from thermally treating 50 or 30 wt.-% clay together with 50 or 70% ash mixture had normal water demand and high activity indices at 28 and at 90 days. Again, it was possible to obtain useful SCM from ashes not suitable as such and even obtain an SCM with properties improved over the pure calcined clay for the starting materials with 50 and 70 wt.-% ashes.

EXAMPLE 3

[0071] Different SCM compositions were prepared from fly ash and clay 2. Materials were mixed for 5 minutes in a laboratory mixer acc. to EN 196-1, then dried for 24 +4 hours at 105 C., then heated up to 850 C. and fired for 1 hour at 850 C. in a laboratory electric furnace. The obtained SCM was air-cooled to ambient temperature and ground in a ring mill to the specific surface 3500500 cm.sup.2/g.

[0072] Water demand was tested according to EN 450-1 as consistency of a mortar with 70 wt.-% ordinary Portland Cement (CEM I 42,5R) and 30 wt.-% of SCM. The activity index at 28 and 90 days was tested on samples prepared as standard mortar with 70 wt.-% ordinary Portland Cement (CEM I 42,5R) and 30 wt.-% of SCM taking into account a correction of the water content caused by water demand. Test procedure was as described in EN 450-1. The results are shown in table 5.

TABLE-US-00005 TABLE 5 Binder composition [wt.-%] CEM I 42,5R 70 70 100 SCM 30 30 0 SCM composition [wt.-%] Calcareous fly ash 100 70 50 30 0 0 0 Clay 2 0 30 50 70 100 0 0 Quartz sand 0 0 0 0 0 100 0 Results Fineness acc. Blaine [cm.sup.2/g] 3710 3420 3680 3550 3610 3230 3750 Loss on ignition [wt.-%] 4.1 2.6 2.6 2.4 3.6 Soundness [mm] 1.0 0.0 0.0 0.0 0.0 0.0 0.4 Water demand [%]* 118.2 104.0 102.7 106.7 104.9 100 100 Activity index at 28 days [%]* 72.5 81.2 93.2 79.3 84.1 64.1 100 Activity index at 90 days [%]* 75.6 92.3 99.8 82.8 86.0 65.5 100 *% with reference to standard mortar only with CEM I 42,5R

[0073] From the results it is apparent that thermal treatment of the clay alone gives good results on activity index after 28 days but still water demand is rather high and activity index after 90 days did not increase significantly. Similarly, thermal treatment of fly ash alone did not give satisfactory results both in terms of water demand and activity index. The treatment of the mixture containing 50 wt.-% clay and 50 wt.-% fly ash provided a reactive SCM with an acceptable water demand. Thus, it was possible to obtain useful SCM from a fly ash not suitable as such and even obtain an SCM with properties improved over the pure calcined clay for the starting materials with 50 and 70 wt.-% fly ash.

[0074] From the examples it is clear that a thermal treatment of ashes in mixture with clays provides highly reactive SCM with activity indices well above the required ones. Thereby, ashes which are unsuitable for SCM use as such-also after heating-due to e.g. high water demand, high LOI, low activity index, can be made useful as SCM. The clay component is also often more reactive and/or the water demand reduced as compared to calcination of the clay alone. Further, clays which are difficult or impossible to activate fully by calcination on their own can be used. This saves valuable resources and energy and considerably increases the possible amounts of composite cements.