CEMENT COMPOUND AND A METHOD FOR THE PRODUCTION THEREOF

Abstract

The present invention relates to a cement compound. The invention also relates to a method for producing such a cement compound. More in particular, the present invention relates to a cement compound comprising at least a reactive glass compound, an alkaline activator and a filler, and optionally additives, said reactive glass compound comprising at least 35 wt % CaO, at least 25 wt % SiO.sub.2 and at least 10 wt % Al.sub.2O.sub.3, and optionally other oxides.

Claims

1. A cement compound comprising at least a reactive glass compound, an alkaline activator and a filler, and optionally additives, said reactive glass compound comprising at least 35 wt % CaO, at least 25 wt % SiO.sub.2 and at least 10 wt % Al.sub.2O.sub.3, and optionally other oxides, characterised in that the reactive glass compound is obtained from one or more secondary raw materials, the cement compound comprising: at least 10 wt % reactive glass compound; at least 10 wt % filler; at least 1 wt % alkaline activator and optionally additives, said wt % being based on the total weight of said cement compound, the alkaline activator comprising one or more parts selected from the group consisting of sodium or potassium salts of sulphate, carbonate, phosphate, silicate, oxalate, formiate, lactate, sodium hydroxide and potassium hydroxide, CEM I, Portland cement clinker, belite clinker and calcium sulphoaluminate clinker.

2. A cement compound according to claim 1, wherein the alkaline is used in a combination with at least two alkaline activators, which combinations are selected from the group consisting of Na.sub.2CO.sub.3 and Ca(OH).sub.2; Na.sub.2CO.sub.3 and CEM I; Na.sub.2CO.sub.3 and Ba(OH).sub.2; Na.sub.2CO.sub.3 and belite cement; K.sub.2CO.sub.3 and Ca(OH).sub.2; K.sub.2CO.sub.3 and CEM I; K.sub.2CO.sub.3 and Ba(OH).sub.2; K.sub.2CO.sub.3 and belite cement; Na.sub.2SO.sub.4 and Ca(OH).sub.2; Na.sub.2SO.sub.4 and CEM I; Na.sub.2SO.sub.4 and Ba(OH).sub.2; Na.sub.2SO.sub.4 and belite cement; K.sub.2SO.sub.4 and Ca(OH).sub.2; K.sub.2SO.sub.4 and CEM I; K.sub.2SO.sub.4 and Ba(OH).sub.2; K.sub.2SO.sub.4 and belite cement; NaOH and sodium silicate; KOH and sodium silicate; NaOH and potassium silicate; KOH and potassium silicate; Na.sub.3PO.sub.4 and Ca(OH).sub.2; K.sub.3PO.sub.4 and Ca(OH).sub.2; Na.sub.3PO.sub.4 and Ba(OH).sub.2; K.sub.3PO.sub.4 and Ba(OH).sub.2; sodium oxalate and Ca(OH).sub.2; potassium oxalate and Ca(OH).sub.2; sodium oxalate and Ba(OH).sub.2; potassium oxalate and Ba(OH).sub.2.

3. A cement compound according to claim 2, wherein the alkaline activator is selected from at least one of Na.sub.2CO.sub.3, K.sub.2CO.sub.3, Na.sub.2SO.sub.4 and K.sub.2SO.sub.4 in combination with at least one of Ca(OH).sub.2, CEM I, Ba(OH).sub.2 and belite cement, or the alkaline activator is selected from at least one of NaOH and KOH in combination with at least one of sodium silicate and potassium silicate.

4. A cement compound according to one or more of the preceding claims, characterised in that the cement compound comprises: 30-70 wt % reactive glass compound; 30-70 wt % filler; 3-20 wt % alkaline activator and optionally 0.5-10 wt % additives, said wt % being based on the total weight of said cement compound.

5. A cement compound according to one or more of the preceding claims, wherein the cement compound has a compressive strength of at least 30 MPa, measured according to EN197, after 28 days.

6. A cement compound according to any one of the preceding claims, wherein the reactive glass compound comprises 35-50 wt % CaO, 25-45 wt % SiO.sub.2 and 10-25 wt % Al.sub.2O.sub.3, and optionally other oxides, preferably 40-45 wt % CaO, 28-35 wt % SiO.sub.2 and 13-20 wt % Al.sub.2O.sub.3, said wt % being based on the total weight of said reactive glass compound.

7. A cement compound according to any one of the preceding claims, wherein the weight of the one or more secondary raw materials, from which the reactive glass compound is obtained, is at least half of the total mass of the glass compound.

8. A cement compound according to any one of the preceding claims, wherein the one or more secondary raw materials are selected from the group consisting of ashes, including fly ash and soil ash released in the combustion of coal, wood, biomass, rice waste, paper sludge, waste; substances released in recycling concrete and concrete products, cement-bound fibre plates, glass wool, rockwool; filter substances from rock processing, cement production or lime production; residual substances from the metal industry, in particular slag, more in particular blast-furnace slag; residual substances from the paper industry; residual substances from (drinking or sewage) water purification; thermally treated soil or sludge; residual substances from the recovery of primary raw materials such as bauxite, brick clay and corundum; or mixtures thereof.

9. A cement compound according to one or more of the preceding claims, wherein the additive is selected from the group consisting of Ca(OH).sub.2, Ba(OH).sub.2, CaCl.sub.2; BaCl.sub.2, polyphosphate and tartrate, or combinations thereof.

10. A cement compound according to any one of the preceding claims, wherein the filler is selected from the group consisting of filter substances; fly ash, in particular pulverised coal fly ash; microsilica; crushing waste and stone powder; thermally activated clay or sludge; residual substances from the metal industry, in particular slag, more in particular blast-furnace slag; and pozzolana, or a combination hereof.

11. A cement compound according to any one of the preceding claims, wherein the filler and the one or more secondary raw materials have the same source.

12. A method for producing a cement compound, which cement compound comprises at least a reactive glass compound, an alkaline activator and a filler, and optionally additives, said reactive glass compound comprising at least 35 wt % CaO, at least 25 wt % SiO.sub.2 and at least 10 wt % Al.sub.2O.sub.3, and optionally other oxides, which method comprises iii) production of the reactive glass compound from one or more raw materials, and iv) mixing of the reactive glass compound with at least a filler and an alkaline activator to obtain said cement compound, characterised in that step i) comprises a number of sub-steps: a) providing one or more raw materials, comprising predominantly secondary raw materials; b) thermally treating the one or more raw materials to obtain a reactive glass compound; c) optionally calcining the raw materials; wherein in step a) one or more corrective substances may be added to the raw materials, the alkaline activator comprising one or more parts selected from the group consisting of sodium or potassium salts of sulphate, carbonate, phosphate, silicate, oxalate, formiate, lactate, sodium hydroxide and potassium hydroxide, CEM I, Portland cement clinker, belite clinker and calcium sulphoaluminate clinker, after which step ii) is carried out.

13. A method according to claim 12, wherein the one or more corrective substances are selected from the group consisting of calcium oxides, calcium carbonates, silicon oxides and aluminium oxides.

14. A method according to claim 12 or 13, wherein solid fuel is used as the fuel for carrying out step i), in particular organic solid fuel, more in particular brown coal, pit coal or charcoal.

15. A method according to one or more of the preceding claims 12-14, wherein the thermal treatment in sub-step b) is concluded with the thermal quenching of the reactive glass compound.

16. A method according to one or more of the preceding claims 12-15, further comprising the mixing of the cement compound with water, wherein the alkaline activator is optionally added only after the mixing of the reactive glass compound, the filler and optional additives.

17. A method according to one or more of the preceding claims 12-16, wherein the alkaline activator is used in a combination of at least two alkaline activators, which combinations are selected from the group consisting of Na.sub.2CO.sub.3 and Ca(OH).sub.2; Na.sub.2CO.sub.3 and CEM I; Na.sub.2CO.sub.3 and Ba(OH).sub.2; Na.sub.2CO.sub.3 and belite cement; K.sub.2CO.sub.3 and Ca(OH).sub.2; K.sub.2CO.sub.3 and CEM I; K.sub.2CO.sub.3 and Ba(OH).sub.2; K.sub.2CO.sub.3 and belite cement; Na.sub.2SO.sub.4 and Ca(OH).sub.2; Na.sub.2SO.sub.4 and CEM I; Na.sub.2SO.sub.4 and Ba(OH).sub.2; Na.sub.2SO4 and belite cement; K.sub.2SO.sub.4 and Ca(OH).sub.2; K.sub.2SO.sub.4 and CEM I; K.sub.2SO.sub.4 and Ba(OH).sub.2; K.sub.2SO.sub.4 and belite cement; NaOH and sodium silicate; KOH and sodium silicate; NaOH and potassium silicate; KOH and potassium silicate; Na.sub.3PO4 and Ca(OH).sub.2; K.sub.3PO4 and Ca(OH).sub.2; Na.sub.3PO.sub.4 and Ba(OH).sub.2; K.sub.3PO.sub.4 and Ba(OH).sub.2; sodium oxalate and Ca(OH).sub.2; potassium oxalate and Ca(OH).sub.2; sodium oxalate and Ba(OH).sub.2; potassium oxalate and Ba(OH).sub.2.

18. A method according to one or more of the preceding claims 12-17, wherein the alkaline activator is selected from at least one of Na.sub.2CO.sub.3, K.sub.2CO.sub.3, Na.sub.2SO.sub.4 and K.sub.2SO.sub.4 in combination with at least one of Ca(OH).sub.2, CEM I, Ba(OH).sub.2 and belite cement, or the alkaline activator being selected from at least one of NaOH and KOH in combination with at least one of sodium silicate and potassium silicate.

Description

EXAMPLE 1

Production of Glass

[0058] A number of glass compounds for use in a cement compound were produced on the basis of the method described here.

TABLE-US-00001 TABLE 1 raw material compounds for the production of reactive glass Batch 1 2 fly ash 47.5% 35.3% limestone 52.5% 58.8% aluminium oxide 5.9% correction

[0059] Two different mixtures of fly ash and limestone were produced, as shown in Table 1. On the basis of the element analysis of the fly ash, 5.9 wt % aluminium oxide was added to the second batch as a corrective substance. The percentages are based on the total glass compound.

[0060] The compound was processed into glass according to the invention. The raw materials were ground into granules and mixed. In a first step the mixture was preheated and calcined to 800 C. in a preheater and calciner. In a subsequent step the mixture was further heated to 1450 C., resulting in a molten glass. The molten glass mixture was quickly cooled in water or air (quenched). X-ray diffraction showed that the reactive glass obtained had around 98% glass character. Table 2 shows the composition of the obtained glass on the basis of X-Ray Fluorescence analysis (XRF). XRF is a well-known method for the analysis of solid substances, and was used according to NEN-EN 15309:2007, Characterisation of waste and soilDetermination of elemental composition by X-ray fluorescence. The method for determining the glass content is described in for example T. Westphal, T. Fllmann, H. Pllmann, Rietveld quantification of amorphous portions an internal standardmathematical consequences of the experimental approach, Powder Diffract. 24 (2009) 239-243. The measurements were carried out using a Seifert XRD 3003 TT, with ZnO as the internal standard reference.

TABLE-US-00002 TABLE 2 reactive glass compounds Batch g1 g2 SiO.sub.2 33.6% 26.4% Al.sub.2O.sub.3 14.4% 19.0% CaO 40.0% 45.0% other oxides 12.0% 9.6%

[0061] The ratio of the mass of the secondary raw material (fly ash in this case) and the glass mass was 0.63 in the case of batch g1 and 0.50 in the case of batch g2.

[0062] The same method was used to prepare some more batches, whose results are presented in table 3. The chemical composition was determined with the aid of XRF, the average particle size with the aid of laser granulometry using an HORIBA LA-300 Particle Analyzer in water. Laser granulometry is a well-known method for determining average particle sizes.

TABLE-US-00003 TABLE 3 Composition (mass %) and average particle size of the glass (m) Batch g3 g4 g5 g6 g7 CaO 42.0 39.8 41.1 48.0 43.0 SiO.sub.2 36.3 31.5 32.4 31.0 32.0 Al.sub.2O.sub.3 14.5 18.1 18 18.9 14.3 Fe.sub.2O.sub.3 1.4 3.7 1.5 0.35 1.72 MgO 1.5 2.1 2.3 0.48 2.43 K.sub.2O 2.0 1.3 1.3 0.2 0.47 Na.sub.2O 0.6 0.8 1.5 0.03 0.11 other oxides 1.7 2.7 1.9 0.7 1.5 d50 [m] 8.5 8.0 7.6 9.0 7.5

EXAMPLE 2

Cement Compounds

[0063] The following cement compounds were prepared on the basis of the glass compounds described above.

[0064] Cement compound c1 was prepared using 44 wt % glass compound g5, 44 wt % fly ash as filler and a combination of 7% Na.sub.2CO.sub.3 and 5% Ca(OH).sub.2 as alkaline activator. Other additives could optionally be added to this compound. In 3 tests mortars were prepared using the cement in different cement/water ratios. The water/cement (w/c) ratios were 0.5, 0.45 and 0.4, respectively, with 0.05 wt % tartaric acid, based on the cement, being added to the water for the last batch. The compressive strength of the cement was then measured at different times for 28 days according to EN196, using a press suitable for that purpose. FIG. 1 shows the development of the compressive strength as measured according to EN196. After 28 days the cement with w/c=0.45 showed the greatest compressive strength, of 55 MPa. This makes this cement particularly suitable for applications demanding a cement that hardens relatively quickly, such as prefab concrete products. The testing of compressive strength is described in NEN-EN 196-1:2005 (Methods of testing cementPart 1: Determination of strength). The strength is determined using a mortar sample with a defined sand/cement ratio and wcf of 0.5 for the classification as standard strength. The compressive strength is measured using a press (Form+Test Type 506/100/10 D-S).

[0065] Cement compound c2 was prepared using 49 wt % glass compound g5, 49 wt % fly ash and 3% NaOH as the activator. Filler and other additives could optionally be added to this compound. This cement compound was mixed 1:1 with water. FIG. 2 shows the development of the compressive strength, measured according to EN196.

EXAMPLE 3

[0066] In example 3 a number of cement compounds according to NL1001242 were prepared and compared with cement compounds according to the present invention.

[0067] The following Table 4 shows the compounds of examples 1-4 according to NL1001242.

TABLE-US-00004 TABLE 4 compounds of examples 1-4 according to NL1001242 Example 1 Example 2 Example 4 Example 5 Blaine 4000 4500 5000 4000 slag oxidic analysis CaO 43.2 38.1 47.8 44.6 slag/glass SiO.sub.2 41.6 36.7 29.1 28.5 (main oxide Al.sub.2O.sub.3 9.4 11.7 14.7 13.3 in mass %) FexOy 3.4 4.2 5.9 5.8 MgO 0.6 8.3 1.1 3.6 Binder slag 80% 89% 82% 84% compound CEM I 15% cement 0% 8% 15% 12% clinker gypsum 5% 3% 3% 4% compressive 28 days 30 35 40 30 strength [MPa]

[0068] Compounds were prepared for examples 2 and 4 of NL1001242, i.e. compounds 728 and 730, so as to be able to determine the initial strength, which values in NL1001242 are not mentioned for examples 2 and 4 of NL1001242. The results are shown in Table 5.

TABLE-US-00005 TABLE 5 initial strength in examples 2 and 4 of NL1001242 and compounds 728 and 730. Example 2 Example 4 728 730 blaine slag 4500 5000 6000 5000 oxidic analysis CaO 38.1 47.8 44.2 39.2 slag/glass SiO.sub.2 36.7 29.1 33.1 32.5 (main oxide Al.sub.2O.sub.3 11.7 14.7 20.5 17.4 in mass %) Fe.sub.xO.sub.y 4.2 5.9 0.3 3.8 MgO 8.3 1.1 0.4 2.3 Binder slag/glass 89% 82% 80% 89% compound cement 8% 15% 15% 8% clinker gypsum 3% 3% 3% 3% compressive 1 day 12.8 4.1 strength of 7 days 37.7 9.7 mortar [MPa] 28 days >35 >40 50.0 21.9

[0069] Surprisingly, it was found that good compressive strengths can be obtained even with 50% of the employed slag and replacement of it with less reactive or non-reactive filler (here fly ash), as shown in Table 6.

TABLE-US-00006 TABLE 6 compressive strength in example 4 of NL1001242 and compounds 728 and 725. Example 4 728 725 blaine slag 5000 6000 6000 oxidic analysis CaO 47.8 44.2 44.2 slag/glass (main oxide SiO.sub.2 29.1 33.1 33.1 in mass %) Al.sub.2O.sub.3 14.7 20.5 20.5 Fe.sub.xO.sub.y 5.9 0.3 0.3 MgO 1.1 0.4 0.4 Binder compound slag/glass 82% 82% 41% filler: fly ash 41% cement clinker 15% 15% 15% gypsum 3% 3% 3% compressive 1 day 12.8 8.7 strength of 7 days 37.7 29.2 mortar 28 days >40 50.0 41.6

[0070] The following Table 7 shows the influence of the replacement of slag/glass by a mixture of slag/glass and fly ash.

TABLE-US-00007 TABLE 7 compressive strength in example 2 of NL1001242 and compounds 730, 726 and 727. Example 2 730 726 727 blaine slag 4500 5000 6000 5000 oxidic analysis CaO 38.1 39.2 44.2 39.2 slag/glass SiO.sub.2 36.7 32.5 33.1 32.5 (main oxide Al.sub.2O.sub.3 11.7 17.4 20.5 17.4 in mass %) Fe.sub.xO.sub.y 4.2 3.8 0.3 3.8 MgO 8.3 2.3 0.4 2.3 Binder slag/glass 89% 89% 44% 44% compound filler: fly ash 45% 45% cement clinker 8% 8% 8% 8% gypsum 3% 3% 3% 3% compressive 1 day 4.1 4.6 3.3 strength of 7 days 9.7 15.5 11.9 mortar 28 days >35 21.9 27.7 18.7

[0071] In Table 8 the present inventors find that surprising results can be obtained when sodium sulphate is used as the sulphate component instead of calcium sulphate. The initial strength can be more than doubled.

TABLE-US-00008 TABLE 8 compressive strength in example 4 of NL1001242 and compounds 724 and 725. Example 4 724 725 blaine slag 5000 6000 6000 oxidic analysis CaO 47.8 44.2 44.2 slag/glass SiO.sub.2 29.1 33.1 33.1 (main oxide in mass %) Al.sub.2O.sub.3 14.7 20.5 20.5 Fe.sub.xO.sub.y 5.9 0.3 0.3 MgO 1.1 0.4 0.4 Binder compound slag/glass 82% 41% 41% filler: fly ash 41% 41% cement clinker 15% 15% 15% (sodium) sulphate 3% (calcium) 3% sulphate 3% compressive 1 day 22.7 8.7 strength of 7 days 35.4 29.2 mortar 28 days >40 41.3 41.6

[0072] Table 9 shows that replacement of sodium sulphate by calcium sulphate lowers both the initial strength and the final strength. The compound values specified for examples 713 and 726 correspond to one another as far as the oxidic analysis is concerned. The same holds for examples 715 and 727.

TABLE-US-00009 TABLE 9 compressive strength in example 2 of NL1001242 and compounds 713, 726, 715 and 727. Example 2 713 726 715 727 blaine slag 4500 6000 5000 oxidic analysis CaO 38.1 44.2 39.2 slag/glass SiO.sub.2 36.7 33.1 32.5 (main oxide Al.sub.2O.sub.3 11.7 20.5 17.4 in mass %) Fe.sub.xO.sub.y 4.2 0.3 3.8 MgO 8.3 0.4 2.3 Binder slag/glass 89% 44% 44% 44% 44% compound filler: fly 45% 45% 45% 45% ash cement 8% 8% 8% 8% 8% clinker (sodium) sulphate 3% 3% (calcium) 3% sulphate 3% 3% compressive 1 day 14.4 4.6 5.9 3.3 strength of 7 days 27.6 15.5 24.5 11.9 mortar 28 days >35 31.6 27.7 34.4 18.7

[0073] The present inventors also concluded (see Table 10) that the strength development can be geared to the strength development required in the application by using other sulphate/clinker ratios.

TABLE-US-00010 TABLE 10 compressive strength of compounds 710, 712, 714, 711 and 715. 710 712 714 711 715 blaine slag 6000 5000 oxidic analysis CaO 44.2 39.2 slag/glass SiO.sub.2 33.1 32.5 (main oxide Al.sub.2O.sub.3 20.5 17.4 in mass %) Fe.sub.xO.sub.y 0.3 3.8 MgO 0.4 2.3 Binder slag/glass 43% 46% 44% 43% 44% compound filler: fly ash 44% 46% 44% 44% 44% cement clinker 5% 8% 8% 5% 8% sodium 8% 0% 4% 8% 4% sulphate compressive 1 day 18.3 3.6 19.0 2.7 5.9 strength of 7 days 43.8 18.0 33.9 18.8 24.5 mortar [MPa] 28 days 54.1 32.3 37.9 37.9 34.4