TRANSFORMATION OF LUMP SLAG INTO SUPPLEMENTARY CEMENTITIOUS MATERIAL BY CARBONATIZATION

Abstract

The present invention relates to a supplementary cementitious material, a method for producing the supplementary cementitious material, the use of the supplementary cementitious material, a binder comprising the supplementary cementitious material, a method for the preparation of the binder and use of the binder to make hydraulic building materials like concrete.

Claims

1-15. (canceled)

16. A supplementary cementitious material comprising Si, Ca, Mg, Al, Fe, wherein an X-ray amorphous portion is at least 15% by weight based on a total weight of the supplementary cementitious material and wherein a sum of an amount of carbonated calcium and magnesium is at least 15% by weight based on the total weight of the supplementary cementitious material, obtained by carbonatization of a precursor material, wherein the precursor material is a lump slag, having a basicity B.sub.1 $B_1=\frac{m\left(\mathrm{CaO}\right)}{m\left({\mathrm{SiO}}_2\right)}$ in arrange from 0.60 to 1.25, and a weight ratio CaO/Fe.sub.2O.sub.3 from 20 to 350 determined from amounts of the oxides measured by X-ray fluorescence (XRF).

17. The supplementary cementitious material according to claim 16, having a particle size distribution with a D.sub.90 of ≤500 μm determined by laser granulometry.

18. The supplementary cementitious material according to claim 16, wherein the precursor material is an air-cooled blast-furnace slag.

19. The supplementary cementitious material according to claim 18 having a particle size distribution with a D.sub.90 of ≤200 μm determined by laser granulometry.

20. A method for producing a supplementary cementitious material comprising the steps of: i) providing a precursor material comprising Si, Ca, Mg, Al, Fe, having basicity B.sub.1 defined as weight ratio of CaO to SiO.sub.2 in a range from 0.60 to 1.25, having an X-ray amorphous portion of less than 66%, and having a particle size distribution with a D.sub.90 of ≤500 μm determined by laser granulometry, wherein the precursor material is a lump slag, and ii) carbonatization of the precursor material of step i) to provide the supplementary cementitious material.

21. The method according to claim 20, wherein the carbonatization in step ii) is carried out at a temperature in a range from 20° C. to 200° C. or at a pressure in a range from 1 bar to 100 bar.

22. The method according to claim 20, wherein the carbonatization in step ii) is carried out at a temperature in a range from 20° C. to 200° C. and at a pressure in a range from 1 bar to 100 bar and a carbonatization time is in a range from 4 to 24 hours and a concentration of CO.sub.2 is in a range of 20 to 80 Vol.-%.

23. The method according to claim 20, wherein the carbonatization time in step ii) is in a range of 1 to 48 hours.

24. The method according to claim 20, wherein the concentration of CO.sub.2 in step ii) is in a range of 10 to 100 Vol.-%.

25. The method according to claim 20, wherein the precursor material has a weight ratio CaO/Fe.sub.2O.sub.3 from 30 to 350.

26. The method according to claim 20, wherein the precursor material has an X-ray amorphous portion of less than 55% by weight, or a basicity B.sub.2 $B_2=\frac{m\left(\mathrm{CaO}\right)+k_{1}m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)}$ in a range from 0.7 to 1.6, or a basicity B.sub.3 $B_3=\frac{m\left(\mathrm{CaO}\right)+k_{1}m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)+k_{2}m\left({\mathrm{Al}}_2{O}_3\right)}$ in a range from 0.6 to 1.2.

27. The method according to claim 26, wherein the precursor material has a weight ratio CaO/Fe.sub.2O.sub.3 from 50 to 350.

28. The method according to claim 27, wherein the carbonatization in step ii) is carried out at a temperature in a range from 20° C. to 200° C. and at a pressure in a range from 1 bar to 100 bar and the carbonatization time is in a range from 4 to 24 hours and the concentration of CO.sub.2 is in a range of 20 to 80 Vol.-%.

29. A hydraulic binder comprising the supplementary cementitious material as defined in claim 16 and a cement selected from the group consisting of Portland cement, calcium sulfoaluminate cement and calcium aluminate cement.

30. The binder according to claim 29, comprising, based on a total weight of the binder, 1 to 88% by weight supplementary cementitious material and 22 to 99% by weight cement.

31. The binder according to claim 29, wherein the supplementary cementitious material has a particle size distribution with a D.sub.90 of ≤500 μm determined by laser granulometry.

32. The binder according to claim 29, wherein the supplementary cementitious material is obtained from a precursor material having an X-ray amorphous portion of less than 55% by weight, or a basicity B.sub.2 $B_2=\frac{m\left(\mathrm{CaO}\right)+k_{1}m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)}$ in a range from 0.7 to 1.6, or a basicity B.sub.3 $B_3=\frac{m\left(\mathrm{CaO}\right)+k_{1}m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)+k_{2}m\left({\mathrm{Al}}_2{O}_3\right)}$ in a range from 0.6 to 1.2.

33. A method for the manufacturing of a hydraulic binder comprising the steps of a) providing the supplementary cementitious material obtained by the method as defined in claim 20, and b) blending the supplementary cementitious material of a) with at least one cement selected from the group consisting of Portland cement, calcium sulfoaluminate cement and calcium aluminate cement, to provide the binder.

34. The method according to claim 33, comprising the additional step of blending the binder of b) with at least one admixture and/or at least one additive.

35. The method according to claim 33, wherein the supplementary cementitious material is obtained by carbonatization of a precursor material at a temperature in the range from 20° C. to 200° C. and at a pressure in the range from 1 bar to 100 bar and the carbonatization time is in the range from 4 to 24 hours and the concentration of CO.sub.2 is in a range of 20 to 80 Vol.-%.

36. The method according to claim 33, wherein the supplementary cementitious material is obtained from a precursor material having an X-ray amorphous portion of less than 55% by weight, or a basicity B.sub.2 $B_2=\frac{m\left(\mathrm{CaO}\right)+k_{1}m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)}$ in a range from 0.7 to 1.6, or a basicity B.sub.3 $B_3=\frac{m\left(\mathrm{CaO}\right)+k_{1}m\left(\mathrm{MgO}\right)}{m\left({\mathrm{SiO}}_2\right)+k_{2}m\left({\mathrm{Al}}_2{O}_3\right)}$ in a range from 0.6 to 1.2.

Description

EXAMPLE 1

[0093] To obtain a lump slag for testing a glassy blast-furnace slag with the composition determined by X-ray fluorescence spectroscopy (XRF) as given in Table 1 was heated in a laboratory furnace to 1200° C. and then slowly cooled in the switched-off furnace.

TABLE-US-00001 TABLE 1 Composition of slag constituent amount [% by weight] SiO.sub.2 34.84 Al.sub.2O.sub.3 11.12 TiO.sub.2 1.05 MnO 0.2 Fe.sub.2O.sub.3 0.27 CaO 41.51 MgO 5.93 K.sub.2O 0.61 Na.sub.2O 0.22 SO.sub.3 2.79 P.sub.2O.sub.5 0.01 LOI 950° C. (+0.49) Glass content 96.4

[0094] The obtained lump slag was ground in a ball mill obtaining a specific surface according to Blaine of about 5000 cm.sup.2/g and a D.sub.90 of ˜28 μm. The ground lump slag was then carbonated in an autoclave (Pilotclav Type 3E/31 Liter, Büchi AG) as follows. 200 g of lump slag were mixed with water (water/solid ratio of 0.5) and placed in porcelain bowls in the autoclave. After closing the autoclave, the temperature was increased to 80° C. Subsequently, CO.sub.2 was introduced up to a pressure of 40 bar. This temperature and pressure were kept constant for 24 hours. After opening the autoclave, the sample was taken out and dried at 105° C. until the weight was constant.

[0095] The phases in the lump slag and in the carbonated slag were determined with QXRD. The QXRD was taken using a diffractometer from Bruker with Cu anode in reflection geometry from 2Θ=4°-35° with increments of 0.02 at 25° C. Table 2 lists the phases identified with QXRD and their amount in % by weight.

TABLE-US-00002 TABLE 2 phases in carbonated slag amount in non- amount in Phase carbonated slag carbonated slag Aragonite CaCO.sub.3 10% Calcite CaCO.sub.3 18% Quartz SiO.sub.2 Akermanite Ca.sub.2MgSi.sub.2O.sub.7 41%  34% Gehlenite Ca.sub.2Al.sub.2SiO.sub.7 37%  20% Rankinite (Mg, Fe).sub.6(Si, Al).sub.4O.sub.10(OH).sub.8 12%  Belite Ca.sub.2SiO.sub.4 5% Perovskite CaTiO.sub.3 1%  1% Rutile TiO.sub.2 1%  1% X-ray amorphous 3% 16%

[0096] Thermogravimetric/differential thermal analyses (TG/DTA) were carried out. The samples (8 to 22 mg) were placed in a platinum sample cup for measurement. A temperature program from 50 to 1000° C. at 10° C./min and nitrogen gas flow was used. FIG. 1 shows the TGA thermogram of non-carbonated and carbonated lump slag. The comparison proves that lump slag has a potential for CO.sub.2 absorption. An increase in carbonate content of 24 wt. % relative to the untreated sample is found.

EXAMPLE 2

[0097] To measure the activity all carbonated and non-carbonated samples from example 1 were mixed with Portland cement. The evaluation is based on EN 450, a standard describing the method for determining the contribution of a fly ash to the strength development. Accordingly, 100% Portland cement was measured as reference and for the tests 25% Portland cement were replaced by the test substance (lump slag or carbonated lump slag). Measurements of strength and mortar composition were carried out in accordance with EN 196-1. The results are shown in table 3 wherein the first two lines indicate the sample composition and the following lines list the measured strength and activity index calculated therefrom. The last column indicates the difference between carbonated and not carbonated slag.

TABLE-US-00003 TABLE 3 amount of cement 100% 75% 75% change from CEM I 42.5R non-carbonated to carbonated amount of slag none 25% 25% carbonated compressive slag slag strength [MPa] after 2 days 38 28 27 −1 MPa 7 days 47 36 40 +4 MPa 28 days 57 44 55 +11 MPa 90 days 62 50 63 +13 MPa activity index 0 according to EN450 after 2 days 100% 74% 71% −3 pp 7 days 100% 77% 85% +8 pp 28 days 100% 77% 96% +19 pp 90 days 100% 81% 102%  +21 pp

[0098] The activity of the lump slag is increased by carbonatization. EN 450 specifies a minimum level of activity. The activity index after 28 days for a fly ash according to standard should be at least 75%, after 90 days at least 85%. Lump slag reached these targets after carbonatization. In contrast, not carbonated lump slag shows insufficient reactivity for use as SCM in composite binders, confirming general wisdom in the art.

EXAMPLE 3

[0099] To examine different carbonatization conditions the lump slag from example 1 was carbonated in an autoclave (Pilotclav Type 3E/31 liter, Büchi AG) as follows. 50 g lump slag were mixed with water (water/solid ratio of 2.0) and placed in porcelain bowls in the autoclave and treated according to method A or method B described below. After opening the autoclave, the sample was taken out and dried at 105° C. until constant weight was achieved.

[0100] Method A: After closing the autoclave, the pressure in the autoclave was increased to 40 bar by introducing N.sub.2 and then heated to 160° C. When the temperature was reached, the pressure in the autoclave was increased to 100 bar by introducing CO.sub.2. This temperature and pressure were kept constant for 24 hours.

[0101] Method B: After closing the autoclave, the pressure in the autoclave was increased to 40 bar by introducing N.sub.2 and then heated to 160° C. The temperature and pressure were kept constant. After 24 hours the pressure in the autoclave was increased to 100 bar by introducing CO.sub.2. This temperature and pressure were kept constant for another 24 hours.

[0102] Table 4 lists the phases and their amount in % by weight as determined with QXRD.

TABLE-US-00004 TABLE 4 amount in lump slag carbonated carbonated Phase method A method B Aragonite CaCO.sub.3 21% 18% Calcite CaCO.sub.3  7%  9% Calcite magnesian (Ca, Mg)CO.sub.3 10% 13% Quartz SiO.sub.2 Akermanite Ca.sub.2MgSi.sub.2O.sub.7 20% 17% Gehlenite Ca.sub.2Al.sub.2SiO.sub.7 13% 11% Rankinite (Mg, Fe).sub.6(Si, Al).sub.4O.sub.10(OH).sub.8 Belite Ca.sub.2SiO.sub.4 Perovskite CaTiO.sub.3  1%  1% Rutile TiO.sub.2  1%  1% X-ray amorphous 27% 30%

[0103] Table 5 shows the amount of CO.sub.2 absorbed per dry mass of the unreacted sample in % by weight, determined with TG.

TABLE-US-00005 TABLE 5 lump slag sample carbonated method A carbonated method B CO.sub.2 absorption 18% 19%

[0104] These results show that both methods A as well as B yielded sufficiently carbonated products useful as SCM as apparent from the phase composition.