Low-belite CSA cement for construction-chemical applications

Abstract

The invention relates to a calcium sulfoaluminate cement, whereby it contains at least 90% by weight % C4A3$ in crystalline or amorphous form or as a mixture of crystalline and has amorphous parts.

Claims

1. Method for manufacturing a calcium sulfoaluminate cement having at least 90% by weight C4A3$ in crystalline or amorphous form or as a mixture of crystalline and amorphous parts and a specific grinding fineness according to Blaine between 3500 cm2/g and 6250 cm2/g, wherein for manufacturing the calcium sulfoaluminate cement a mixture of raw materials is used, which contains between 41 and 50% by weight Al.sub.2O.sub.3, between 34 and 41% by weight CaO and between 11 and 19% by weight SO.sub.3, as well as between 0.1 and 3% by weight SiO.sub.2 and/or between 0.1 and 1% by weight Fe.sub.2O.sub.3 and/or between 0.05 and 2.5% by weight TiO.sub.2 and/or between 0.05 and 2.5% by weight ZnO, the method comprising the steps: pulverizing the raw materials to a mixture with a specific grinding fineness according to Blaine between 3500 cm.sup.2/g and 6000 cm.sup.2/g and calcining the mixture at a calcining temperature of at least 1150° C.

2. Method as claimed in claim 1, characterized in that the pulverizing is performed in a ball mill preferably in two steps, wherein in both steps different grinding bodies are used in the ball mill.

3. Calcium sulfoaluminate cement, characterized in that it contains at least 90% by weight C4A3$ in crystalline or amorphous form or as a mixture of crystalline and amorphous parts as well as at most 0.5% by weight free lime, calculated as CaO, and/or at most 0.5% by weight C.sub.3A and/or at most 2.0% by weight Mayenit, calculated as C.sub.12A.sub.7, and/or at most 10.0% by weight Krotit, calculated as CA, and further between 0.5 and 10.0% by weight C.sub.4AF and its mixed crystals C.sub.6A.sub.3-xF.sub.x with 1≤x≤3 and/or between 0.5% by weight and 10.0% by weight Belit, calculated as C.sub.2S, and/or at least 0.5% by weight Krotit, calculated as CA, and further has a specific grinding fineness according to Blaine between 3500 cm.sup.2/g and 6000 cm.sup.2/g.

4. Calcium sulfoaluminate cement as claimed in claim 3, characterized in that it contains one or more of the following further elements or their oxides with different oxidation numbers as well as their compounds: Si, Na, K, Mg, Sr, Ba, Ti, Zr, V, P, Cr, Mn, Zn and/or other transition metals.

Description

EXAMPLE 1

(1) By using the starting materials: calc. bauxite, limestone, calcium sulfate and calc. alumina, 7 homogenous mixtures with a specific grinding fineness according to Blaine of approx. 5000 cm.sup.2/g have been produced. Each chemical composition of the starting materials is specified in Table 4.

(2) The mixture 7 additionally contains the powdery pure substance component ZnO as a mineralizer. Each of the amounts of starting materials for manufacturing the 7 mixtures are given in Table 5. Each chemical composition of the 7 mixtures is given in Table 6.

(3) TABLE-US-00004 TABLE 4 Chemical characterization of starting substances Raw material Calc. bauxite Limestone Calcium sulfate Calc. alumina LOI 0.21 43.72 10.85 0.14 SiO.sub.2 5.13 0.19 0.27 0.02 Al.sub.2O.sub.3 88.52 0.04 0.35 99.86 TiO.sub.2 4.45 0.01 0.01 0 MnO 0.01 0.01 0.01 0.01 Fe.sub.2O.sub.3 1.12 0.04 0.07 0.03 CaO 0 55.77 40.49 0 MgO 0.29 0.43 0.11 0.03 K.sub.2O 0.54 0.03 0.03 0.01 Na.sub.2O 0.01 0 0 0.1 SO.sub.3 0.03 0.05 47.79 0.03 Total 100.31 100.29 99.98 100.23 all data in wt. %

(4) TABLE-US-00005 TABLE 5 Composition of 7 raw mixtures Mixture 1 2 3 4 5 6 7 Calc. bauxite — 30.4 39.2 20.5 — — — Limestone 34.4 38.6 40.2 36.9 33.3 33.3 34.4 Calcium sulfate 24.6 21.5 20.6 22.1 26.7 30.0 24.0 Calc. alumina 41.0 9.5 — 20.5 40.0 36.7 40.0 ZnO — — — — — — 1.6 all data in wt. %

(5) TABLE-US-00006 TABLE 6 Chemical analysis (free of loss on ignition) of the raw mixtures according to Table 5 Mixture 1 2 3 4 5 6 7 SiO.sub.2 0.2 1.9 2.5 1.3 0.2 0.2 0.1 Al.sub.2O.sub.3 49.9 44.4 42.5 46.4 47.5 45 47.2 TiO.sub.2 0.0 1.6 2.1 1.1 0.0 0.0 0.0 Fe.sub.2O.sub.3 0.1 0.5 0.6 0.4 0.1 0.1 0.1 CaO 35.5 38.3 39.5 37.2 36.3 37.1 35.7 SO.sub.3 13.9 12.9 12.5 13.0 15.6 17.4 13.8 ZnO — — — — — — 2.31 Total 99.6 99.6 99.7 99.4 99.7 99.8 99.21 all data in wt. %

(6) Pellets were pressed from partial amounts of each of the 7 mixtures and each was calcined for 1 hour at 1250° C. Then they were removed from the kiln, cooled down to room temperature and ground back to the starting fineness. These materials were analyzed by quantitative XRD analysis using the Rietveld method and then the entire sample was calcined again for one hour at the same temperature. After being cooled down and ground down again, this sample was analyzed again by XRD analysis. The results of these analyses are shown in the following Table 7.

(7) TABLE-US-00007 TABLE 7 Mineralogical analyses of mixtures 1-7 (calcining at 1250° C.) Mixture 1 2 3 4 5 6 7 Ye'elimite (C.sub.4A.sub.3$) 94.3 93.7 91.3 95.3 91.0 92.3 98.5 Anhydrite (C$) 0.8 — — 0.4 3.7 6.8 — Perovskite (CT) — 3.1 3.2 1.6 — — — Krotite (CA) 4.4 — — — 3.9 — 0.4 Mayenite (C.sub.12A.sub.7) 0.4 — 0.5 — 1.3 — — Free lime (CaO) — 0.1 — — — 0.8 — Belite (C.sub.2S .sub.α, β) 0.1 3.1 5.0 2.3 0.1 0.1 — Gehlenite (C.sub.2AS) — — — 0.4 — — — Gahnite (ZnAl.sub.2O.sub.4) — — — — — — 1.1 all data in wt. %

(8) Table 7 shows that the targeted ye′elimite content of >90 wt. % is present in all 7 mixtures under the mentioned conditions with the raw materials used.

(9) Samples 1, 5, 6 and 7 were selected from the seven clinkers obtained in this way. Each were ground for 2 minutes in a vibrating disk mill with agate insert at 700 rpm without additives to a fineness of 5000 cm.sup.2/g+/−250 cm.sup.2/g according to Blaine and then hydrated in a heat flow calorimeter at 20° C. with a water/cement of 0.50 for 50 h. The measured heat flow curves are shown in FIG. 1.

(10) FIG. 1 shows a comparison of the heat flow curves of mixtures 1, 5, 6 and 7. All the mixtures examined in the calorimeter have a long dormant period of at least 2.5 h after being mixed and show a pronounced heat flow maximum. In comparison to the heat flow curves of mixtures 1, 5 and 6, mixture 7 shows a clearly longer open time in the cement paste of approx. 7.5 h. At the same time, mixture 7 has a homogenous hydration reaction.

EXAMPLE 2

(11) For a calcining test on the semi-industrial scale, the raw mixture was selected according to the chemical composition of mixture 7 in Table 6 and manufactured from new raw materials under the designation “R-BC7.” The chemical compositions of these raw materials are shown in Table 8. The percentage composition of raw mixture R-BC7 is shown in Table 9.

(12) TABLE-US-00008 TABLE 8 Chemical characterization of the raw materials for mixture R-BC7. Raw material Anhydrite Calc. alumina Limestone Lime hydrate LOI 3.37 0.71 43.57 24.29 SiO.sub.2 0.74 0.01 0.26 1.94 Al.sub.2O.sub.3 0.05 99.03 0.09 0.57 Fe.sub.2O.sub.3 0.05 0.01 0.01 0.25 CaO 40.30 0.03 55.32 71.51 MgO 0.74 0.06 0.68 0.96 SO.sub.3 54.29 0.00 0.00 0.25 K.sub.2O 0.02 0.00 0.00 0.10 Na.sub.2O 0.06 0.16 0.03 0.04 P.sub.2O.sub.5 0.02 0.00 0.02 0.01 TiO.sub.2 0.00 0.00 0.00 0.02 Mn.sub.2O.sub.3 0.01 0.00 0.00 0.02 SrO 0.33 0.00 0.03 0.04 ZnO 0.01 0.01 0.00 0.01 Total 99.99 100.02 100.01 100.01 all data in wt. %

(13) TABLE-US-00009 TABLE 9 Percentage composition of raw mixture R-BC7 Calc. alumina 39.7 Limestone 27.8 Lime hydrate 9.5 Anhydrite 21.0 ZnO 2.0 all data in wt. %

(14) Using a granulating plate, granules of raw mixture R-BC7 having an average diameter of 10 mm. The lime hydrate part used as a raw mixture component was used to improve the ability to granulate.

(15) The granules were placed in a heavy oil-fired test rotary kiln that was 7 m long and had an inner diameter of 50 cm. The kiln was run at 1.5 rpm. The calcining temperature in the sinter zone was maintained at an average of 1270° C. The dwell time of the material to be calcined in the sinter zone was 30-40 minutes.

(16) After being cooled, the clinker K-BC7 according to the invention was ground in two stages. It was first ground in a ball mill with a ball filling and it was ground for a second time in a ball mill having cylindrical grinding bodies. The clinker was pulverized without further additives. The target fineness was 5000 cm.sup.2/g according to Blaine. In total, more than 100 kg of the CSA cement according to the invention with the designation BC7 were produced from the clinker K-BC7 according to the invention.

(17) Table 10 shows the chemical analysis of the CSA cement according to the invention with the designation BC7 from the grinding of clinker K-BC7. The chemical analyses of random samples of the two commercially available CSA cements “Alipre” (Italcementi) and “Next Base” (Buzzi Unicem) are shown as comparison data.

(18) TABLE-US-00010 TABLE 10 Chemical analyses of the CSA cement BC7 according to the invention and of two commercially available comparison products. “Alipre” “Next Base” “BC7” Cement Test parameters (Italcementi) (Buzzi Unicem) (Calucem) Chemical LOI 0.52 1.43 0.06 composition SiO.sub.2 8.83 10.52 0.59 (wt. %) Al.sub.2O.sub.3 31.23 29.43 47.20 TiO.sub.2 0.43 1.49 0.02 MnO 0.17 0.04 0.00 Fe.sub.2O.sub.3 1.50 3.00 0.05 CaO 40.18 41.68 36.90 MgO 4.28 2.51 0.49 K.sub.2O 0.50 0.39 0.01 Na.sub.2O 0.81 0.37 0.00 SO.sub.3 11.37 9.24 12.90 P.sub.2O.sub.5 0.12 0.00 0.01 ZnO 0.00 0.00 1.90 Total 99.94 100.10 100.12 Residues 90 μm 0.0 1.4 4.2 (wt. %) Fineness Blaine (cm.sup.2/g) 4700 4600 5210

(19) The mineralogical composition of the CSA cement BC7 according to the invention is shown in Table 11. These values are compared with random sample analyses of the commercially available calcium sulfoaluminate cements “Alipre” (Italcementi) and “Next Base” ((Buzzi Unicem).

(20) The two CSA cements “Alipre” and “Next Base” have a C.sub.4A.sub.3$ content of less than 90 wt. % and a belite (C.sub.2S.sub.α,β) content of 11.80 wt. % (“Alipre”) or 17.70 wt. % (“Next Base”).

(21) The CSA BC7 according to the invention has a C.sub.4A.sub.3$ content of 94.5 wt. % and a belite (C.sub.2S.sub.α,β) content of 2.0 wt. %. Rapidly setting phases, such as C.sub.12A.sub.7, are not present or only in traces.

(22) All phase contents were determined using the Rietveld software, HighScore Plus, Version 4.6a from PANalytical B. V., Almelo, The Netherlands. A PANalytical Cubix Röntgen Diffractometer with rapid Xcelerator Detector was used for analysis.

(23) TABLE-US-00011 TABLE 11 Mineralogical analyses of the CSA cement BC7 according to the invention and of two commercially available CSA cements CSA BC7 according “Alipre” “Next Base” to the invention CSA cement (Italcementi) (Buzzi Unicem) (Calucem) C.sub.4A.sub.3$ 69.2 61.9 94.5 α-C.sub.2S 4.2 11.3 0.8 β-C.sub.2S 7.6 6.4 1.2 C$ 0.7 4.4 1.0 C.sub.3MS.sub.2 2.1 5.3 — C.sub.2AS 2.3 4 — 3C.sub.2S.sub.3•C$•CaF.sub.2 5.3 — — (ellastadite-fluorine) CT 0 3.9 — C.sub.3FT 3.7 1.1 — MgO 4.1 1.7 — CA — — 1.1 C.sub.12A.sub.7 0.8 0 0.3 ZnA (gahnite) — 1.1 all data in wt. %

(24) The water demand to achieve the standard stiffness, setting time on the lime and compressive strength development on the standard mortar after 24 hours were determined in accordance with EN 14647 for the cement BC7 according to the invention and the comparison samples “Alipre” and “Next Base.”

(25) In accordance with EN 14647, the test method of EN 196-3 is used to determine the standard stiffness and the water demand required therefor. The compressive strength is determined in accordance with EN 14647 on a standard mortar which, at a standard sand content of 1350 g, contains 500 g cement and 200 g water (water/cement=0.40). The results of the tests of the water demand and the setting behavior on lime and the compressive strength tests are shown in Table 12.

(26) TABLE-US-00012 TABLE 12 Results of the setting test and the strength test. “Next CSA BC7 Base” according to “Alipre” (Buzzi the invention Test parameters (Italcementi) Unicem) (Calucem) Setting lime Water 32.0 32.0 28.0 requirement (%) SB (h:min) 0:09 0:17 1:45 SE (h:min) 0:12 0:20 2:30 Compressive 24 h (MPa) 25 6 44 strength SB = Setting begins; SE = Setting ends

(27) The commercially available comparison cements both demonstrate a quick setting on the cement lime of 9 minutes (“Alipre”) or 17 minutes (“Next Base”), with a water demand of 32%.

(28) In contrast, the calcium sulfoaluminate cement BC7 according to the invention has a significantly longer setting characteristic in the lime with a lower water requirement of 28%. The values for the water requirement and the setting characteristic in the lime can be comparable with the values of Portland and aluminous cements. The “Alipre” comparison cement shows the shortest processing time with the setting beginning at 9 minutes.

(29) After 24 h the compressive strength of the “Next Base” is at 6 MPa and that of the “Alipre” is at 25 MPa. However, the calcium sulfoaluminate cement BC7 according to the invention already has a compressive strength of 44 MPa after 24 h and therefore has a strength which is almost double the strength of the commercially available comparison sample “Alipre.”

EXAMPLE 3

(30) Using the CSA cement BC7 according to the invention, various construction-chemical mixtures were manufactured as self-levelling filler, using industry-standard binder components, additives and filing agents which are typical for products in the field of tile adhesives, levelling compounds, fillers and repair mortars.

(31) Self-levelling fillers are particularly demanding products among the construction-chemical recipes. It should have a good to very good progression over the processing time of 30 min and it must ensure high early strength and rapid accessibility. Generally, high-quality self-levelling fillers have a high content of calcium sulfoaluminate cement.

(32) The compositions of the different recipes are given in Table 13. The recipe components are divided into “binder,” “additive I and II” and “filling agent.” Each of the basic recipes was made with the calcium sulfoaluminate cement BC7 according to the invention. The two recipes with the CSA cement BC7-1 and BC7-2 according to the invention are compared with recipes with the commercially available comparison cements “Alipre” (Italcementi) and “Next Base” (Buzzi Unicem). Recipe BC7-1 contains 19.66 wt. % of the CSA cement BC7 according to the invention. The BC7 content was reduced to 14.74 wt. % in recipe BC7-2 and the recipe was made up to 100% with ground limestone (F2).

(33) The four mixtures were tested over a period of time of 30 minutes after their manufacturing by measuring slump a5, a15 and a30 for their consistency, and on standard prisms 4 cm×4 cm×16 cm for their compressive strength development after 4 h, 6 h and 24 h. The terms and abbreviations used in Table 13 are explained in the following.

(34) “Binder” is understood to mean the recipe parts: Portland cement (OPC) Milke Premium CEM|52.5 R, HeidelbergCement AG; calcium sulfoaluminate cement (CSA) and calcium sulfate (C$) anhydrite—Micro A, Casea.

(35) “Additive I” refers to the additives having a primarily retarding and accelerating effect: tartaric acid L(+) p.a. (WS), HARKE Chemicals GmbH; and lithium carbonate pure. (LiC), Merck, item no. 5670.

(36) “Additive II” comprises additives which exert primary influence on the consistency of the mixture: liquefied ViscoCrete-225 P (VF), SIKA; cellulose ether Culminal MHPC-500 PF (CE), Ashland; anti-foaming agent Agitan P 801 (ES), Munzing Chemie GmbH; and redispersible polymer powder (RPP) ELOTEX FL 2280, Akzo Nobel Chemicals AG.

(37) Filling agent (F) refers to inert materials which are not involved in the hydraulic reactions. Quartz sand F34 (F1), Quarzwerke GmbH, and ground limestone 40GU (F2), Omya GmbH, were used in the examples.

(38) In Table 13, specified percent values relate to the percentage part of a component in the total weight of the mixture.

(39) All construction-chemical mixtures were mixed with a constant water/solid value (w/s value) of 0.21.

(40) The slump was tested in such a way that 2000 g of the dry recipe mixture was weighed exactly and mixed in a mortar mixer in accordance with EN 196 with 420 g demineralized water for 30 seconds at stage I and then 90 seconds at stage II. The mixing water was placed in the mixing trough and then the dry mixture was added. The resulting pourable mixture was then distributed to 3 discharge rings, i.e. annular aluminum vessels which are 35 mm high and have an inner diameter of 68 mm, that were arranged so as to be centered on 3 dry spreading plates made of plexiglass, provided with concentric graduations and oriented exactly horizontally. 5 minutes after the start of mixing, the first ring was raised, and the diameter of the circular mass was determined using the caliper as the average value from two measurements which are perpendicular to one another, as the a5 value. In the same way, the two other rings were moved after 15 and 30 minutes and the values a15 and a30 were determined.

(41) In order to determine the compressive strength after 4, 6 and 24 h, the construction-chemical mixtures were manufactured in the same way and, after the end of mixing, the pourable materials were poured into prism molds in accordance with EN 196 without additional compaction measures. The molds were stored in accordance with EN 196 and the prisms were tested in accordance with the standards on the scheduled dates.

(42) TABLE-US-00013 TABLE 13 Self-levelling fillers with different calcium sulfoaluminate cements Cement “Alipre” “Next Base” BC7-1 BC7-2 Recipe CSA (%) 19.66 19.66 19.66 14.74 OPC (%) 4.91 4.91 4.91 4.91 C$ (%) 4.91 4.91 4.91 4.91 Total binder 29.49 29.49 29.49 24.57 Additive I WS (%) 0.13 0.13 0.13 0.13 LiC (%) 0.29 0.29 0.29 0.29 Additive II VF (%) 0.10 0.10 0.10 0.10 CE (%) 0.07 0.07 0.07 0.07 ES (%) 0.14 0.14 0.14 0.14 RPP (%) 0.98 0.98 0.98 0.98 Filling agent F1 (%) 40.54 40.54 40.54 40.54 F2 (%) 28.26 28.26 28.26 33.17 W/S value 0.21 0.21 0.21 0.21 Slump  a5 (mm) 245 232 245 242 a15 (mm) 246 232 240 245 a30 (mm) 250 236 235 245 Compressive strength  4 h (MPa) 15.3 13.9 17.8 14.3  6 h (MPa) 17.5 15.3 22.2 17.1 24 h (MPa) 26.3 21.2 33.9 27.1

(43) It is clear from Table 13 that all self-levelling fillers have a very good progression over 30 min. The filler BC7-1 having 19.66% calcium sulfoaluminate cement BC7 according to the invention shows clearly higher compressive strength after 4 h, 6 h and 24 h in comparison with the fillers having 19.66% “Alipre” and 19.66% “Next Base.” The fillers BC7-2 having only 14.74% calcium sulfoaluminate cement BC7 according to the invention is surprisingly on the level of strength of the comparative recipes “Alipre” and “Next Base” having 19.66% cement content.

(44) The calcium sulfoaluminate cement can contain in particular at most 97 wt. % C.sub.4A.sub.3$, at least 1 wt. % belite, calculated as C.sub.2S, and at least 0.5 wt. % krotite, calculated as CA.

(45) The calcium sulfoaluminate cement can contain in particular at most 97 wt. % C.sub.4A.sub.3$, at least 1 wt. % belite, calculated as C.sub.2S, and at least 0.5 wt. % krotite, calculated as CA, and at least 0.1 wt. %, at most 2.0 wt. %, in particular at most 1.0 wt. %, in particular at most 0.5 wt. %, mayenite, calculated as C12A7.

(46) The calcium sulfoaluminate cement can contain in particular at most 97 wt. % C.sub.4A.sub.3$, at least 1.5 wt. % belite, calculated as C.sub.2S, and at least 0.5 wt. % krotite, calculated as CA.

(47) The calcium sulfoaluminate cement can contain in particular at most 97 wt. % C.sub.4A.sub.3$, at least 1.5 wt. % belite, calculated as C.sub.2S, and at least 0.5 wt. % krotite, calculated as CA, and at least 0.1 wt. %, at most 2.0 wt. %, in particular at most 1.0 wt. %, in particular at most 0.5 wt. %, mayenite, calculated as C12A7.