COMPOSITE CEMENT WITH IMPROVED REACTIVITY AND METHOD FOR MANUFACTURING IT

Abstract

Composite cement with improved reactivity and improved fresh properties comprising a hydraulic cement or a caustic activator, a hyaloclastite as pozzolan containing 45-62 wt.-% SiO.sub.2, 10-20 wt.% Al.sub.2O.sub.3, 6-15 wt.-% Fe.sub.2O.sub.3, 7-15 wt.-% CaO, 7-15 wt.-% MgO, 1.5-4 wt.% (K.sub.2O+Na.sub.2O), and having 0-5 wt.-% loss on ignition at 950° C. and ≥50 wt.-% X-ray amorphous phase, and a carbonate filler with an at least bimodal particle size distribution adapted to provide a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of ≤1.15 in a particle size distribution of the composite cement; a method for manufacturing it, as well as use of a composition comprising the hyaloclastite as pozzolan and the carbonate filler as mineral addition for composite cements comprising a hydraulic cement or a caustic activator.

Claims

1. A composite cement comprising a hydraulic cement or a caustic activator, a hyaloclastite as pozzolan containing 45-62 wt.-% SiO.sub.2, 10-20 wt.% Al.sub.2O.sub.3, 6-15 wt.-% Fe.sub.2O.sub.3, 7-15 wt.-% CaO, 7-15 wt.-% MgO, 1.5-4 wt.% (K.sub.2O+Na.sub.2O), and having 0-5 wt.-% loss on ignition at 950° C. and ≤50 wt.-% X-ray amorphous phase, and a carbonate filler with an at least bimodal particle size distribution adapted to provide a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of ≤1.15 in a particle size distribution of the composite cement.

2. The composite cement according to claim 1, wherein the particle size distribution of the composite cement has a slope n from 0.80 to 1.15, and/or the composite cement has a fineness according to Blaine from 3500 to 10000 cm.sup.2/g.

3. The composite cement according to claim 1, wherein the pozzolan contains 0.5 to 4 wt.-% other elements and/or the pozzolan contains 46-54 wt.-% SiO.sub.2, 12-17 wt.% Al.sub.2O.sub.3, 8-14 wt.-% Fe.sub.2O.sub.3, 10-13 wt.-% CaO, 10-13 wt.-% MgO, 1.5-3 wt.% (K.sub.2O+Na.sub.2O) and/or the amount of the X-ray amorphous phase in the pozzolan is ≥60 wt.-%.

4. The composite cement according to claim 1, wherein the pozzolan has a monomodal particle size distribution with a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve from 0.9 to 1.4, and/or the pozzolan has a fineness according to Blaine from 4500 to 8000 cm.sup.2/g.

5. The composite cement according to claim 1, wherein the hydraulic cement is selected from the group consisting of Portland cement, calcium aluminate cement, calcium sulfoaluminate cement, belite binder obtained by hydrothermal treatment and subsequent tempering and/or reactive grinding, and mixtures thereof, and/or the caustic activator is selected from the group consisting of free lime, portlandite, Portland cement, Portland cement clinker, alkali hydroxides, alkali carbonates, alkali sulfates and mixtures thereof.

6. The composite cement according to claim 1, wherein the hydraulic cement is a Portland cement with an Na.sub.2O Eq. from 0.3 to 2.5 wt.-%, and/or with an amount of C.sub.3S from 45 to 74 wt.-%, and/or with an amount of C.sub.3A from 1 to 18 wt.-%, all with respect to the hydraulic cement clinker.

7. The composite cement according to claim 1, wherein the hydraulic cement or caustic activator has a fineness according to Blaine from 2000 to 10000 cm.sup.2/g.

8. The composite cement according to claim 1, wherein the carbonate filler has a bimodal particle size distribution with ≥20 wt.-% particles having a D.sub.10≥30 μm, and ≥20 wt.-% particles having a D.sub.90≤30 μm, and/or the carbonate filler has a slope n below 1.0.

9. The composite cement according to claim 1, wherein the carbonate filler is selected from the group consisting of limestone; dolomite; magnesite; precipitated nanosized carbonates; poorly crystalline or X-ray amorphous carbonates; complex partly hydrated carbonates; and mixtures of two or more thereof.

10. The composite cement according to claim 1, wherein an amount of pozzolan and carbonate filler together ranges from 15 to 50 wt.-%.

11. The composite cement according to claims 1, wherein a weight ratio of pozzolan to carbonate filler ranges from 20:1 to 1:1.

12. The composite cement according to claim 2, wherein the slope n of the particle size distribution of the composite cement ranges from 0.90 to 1.05 and/or the fineness ranges from 4500 to 8000 cm.sup.2/g.

13. The composite cement according to claim 12, wherein the slope n of the particle size distribution of the composite cement ranges from 0.95 to 1.00 and/or the fineness ranges from 5000 to 6000 cm.sup.2/g.

14. The composite cement according to claim 3, wherein the amount of the X-ray amorphous phase in the pozzolan is ≥70 wt.-%.

15. The composite cement according to claim 14, wherein the amount of the X-ray amorphous phase in the pozzolan is ≥80 wt.-%.

16. The composite cement according to claim 4, wherein the slope n of the particle size distribution of the pozzolan ranges from 1.0 to 1.2 and/or the pozzolan has a fineness from 5000 to 6000 cm.sup.2/g.

17. The composite cement according to claim 6, wherein the Na.sub.2O Eq. ranges from 1.0 to 2.0 wt.-% and/or the amount of C.sub.3S ranges from 55 to 65 wt.-% and/or the amount of C.sub.3A ranges from 2 to 12 wt.-%.

18. The composite cement according to claim 17, wherein the Na.sub.2O Eq. ranges from 1.2 to 1.5 wt.-% and/or the amount of C.sub.3A ranges from 3 to 7 wt.-%.

19. The composite cement according to claim 8, wherein the particle size distribution of the carbonate filler comprises ≥30 wt.-% particles with a D.sub.10≥35 μm and/or ≥30 wt.-% particles with a D.sub.90≤20 μm and/or a slope n below 0.85.

20. The composite cement according to claim 19, wherein the particle size distribution of the carbonate filler comprises ≥40 wt.-% particles with a D.sub.10≥40 μm and/or ≥30 wt.-% particles with a D.sub.90≤10 μm and/or a slope n below 0.75.

21. The composite cement according to claim 10, wherein the amount of pozzolan and carbonate filler together ranges from 20 to 35 wt.-%.

22. The composite cement according to claim 21, wherein the amount of pozzolan and carbonate filler together ranges from 22 to 30 wt.-%.

23. The composite cement according to claim 11, wherein the weight ratio of pozzolan to carbonate filler ranges from 15:1 to 2:1.

24. The composite cement according to claim 23, wherein the weight ratio of pozzolan to carbonate filler ranges from 9:1 to 4:1.

25. The composite cement according to claim 13, wherein the amount of the X-ray amorphous phase in the pozzolan is ≥70 wt.-%.

26. The composite cement according to claim 25, wherein the slope n of the particle size distribution of the pozzolan ranges from 1.0 to 1.2 and/or the pozzolan has a fineness from 5000 to 6000 cm.sup.2/g.

27. The composite cement according to claim 25, wherein the particle size distribution of the carbonate filler comprises ≥40 wt.-% particles with a D.sub.10≥40 μm and/or ≥30 wt.-% particles with a D.sub.90≤10 μm and/or a slope n below 0.75.

28. The composite cement according to claim 26, the particle size distribution of the carbonate filler comprises ≥40 wt.-% particles with a D.sub.10≥40 μm and/or ≥30 wt.-% particles with a D.sub.90≤10 μm and/or a slope n below 0.75.

29. The composite cement according to claim 25, wherein the amount of pozzolan and carbonate filler together ranges from 22 to 30 wt.-% and/or the weight ratio of pozzolan to carbonate filler ranges from 9:1 to 4:1.

30. The composite cement according to claim 26, wherein the amount of pozzolan and carbonate filler together ranges from 22 to 30 wt.-% and/or the weight ratio of pozzolan to carbonate filler ranges from 9:1 to 4:1.

31. The composite cement according to claim 27, wherein the amount of pozzolan and carbonate filler together ranges from 22 to 30 wt.-% and/or the weight ratio of pozzolan to carbonate filler ranges from 9:1 to 4:1.

32. The composite cement according to claim 28, wherein the amount of pozzolan and carbonate filler together ranges from 22 to 30 wt.-% and/or the weight ratio of pozzolan to carbonate filler ranges from 9:1 to 4:1.

33. A method for manufacturing a composite cement according to claim 1 comprising the steps: providing a hydraulic cement or a caustic activator, providing a hyaloclastite as pozzolan containing 45-62 wt.-% SiO.sub.2, 10-20 wt.% Al.sub.2O.sub.3, 6-15 wt.-% Fe.sub.2O.sub.3, 7-15 wt.-% CaO, 7-15 wt.-% MgO, 1.5-4 wt.% (K.sub.2O+Na.sub.2O), and having 0-5 wt.-% loss on ignition at 950° C. and ≥50 wt.-% X-ray amorphous phase, providing a carbonate filler with an at least bimodal particle size distribution, ground partly or fully separately from the hydraulic cement and the pozzolan, adapted to provide a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of ≤1.15 in a particle size distribution of the composite cement, and blending the hydraulic cement or caustic activator, the pozzolan and the carbonate filler to provide the composite cement, and if needed adjusting the sulfate content of the composite cement adding a sulfate source.

34. The method according to claim 33, wherein the pozzolan is ground separately from the hydraulic cement and the carbonate filler to a monomodal particle size distribution, preferably with a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve from 0.9 to 1.4, and/or to a fineness according to Blaine from 4500 to 8000 cm.sup.2/g.

35. The method according to claim 33, wherein the carbonate filler is ground separately from the hydraulic cement and the pozzolan, or ≤20 wt.-% of the carbonate filler are ground together with the hydraulic cement, the pozzolan or a cement-pozzolan mix and the remainder is ground separately, wherein the carbonate filler is ground to a bimodal particle size distribution with ≥20 wt.-% particles having a D.sub.10≥30 μm, and ≥20 wt.-% particles having a D.sub.90≤30 μm.

36. The method according to claim 33, wherein a grinding aid is added during grinding of at least one of the hydraulic cement, the pozzolan and the carbonate filler, wherein the grinding aid is selected from the group consisting of alkanolamines; sugars and sugar derivatives; glycols; carboxylic acids and their salts; carbonic anhydrase; diols; glycerol; sulphonic acids; (ligno)sulphonates; and mixtures thereof.

37. The method according to claim 33, wherein from 15 to 50 wt.-% pozzolan and carbonate filler together are used, and/or a weight ratio of pozzolan to carbonate filler from 20:1 to 1:1.

38. The method according to claim 33, wherein the particle sizes and amounts of hydraulic cement or caustic activator, pozzolan and carbonate filler are selected such that the composite cement has a fineness according to Blaine from 3500 to 10000 cm.sup.2/g, and/or the slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of the composite cement ranges from 0.80 to 1.15.

39. The method according to claim 33, wherein the hydraulic cement has an Na.sub.2O Eq. from 0.3 to 2.5 wt.-% adjusted by addition of alkalis selected from the group consisting of alkali carbonates, alkali sulfates, alkali chlorides and process dust from clinker production when the Na.sub.2O Eq. of the used hydraulic cement is below the desired value, and/or the hydraulic cement has an amount of C.sub.3A from 1 to 18 wt.-% with respect to the hydraulic cement clinker.

40. The method according to claim 33, wherein further components are added to the composite cement, being admixtures selected from the group consisting of plasticizers, superplasticizers, water reducers, stabilizers, air entraining agents, setting accelerators, hardening accelerators, retarders, sealants, chromate reducing agents, and mixtures of two or more thereof; and/or being further SCMs selected from the group consisting of ground granulated blast furnace slag, fly ash, calcined clay or shales, trass, brick-dust, artificial glasses, waste glass, silica fume, burned organic matter residues rich in silica such as rice husk ash, carbonated recycled concrete fines, natural pozzolans other than hyaloclastite, and mixtures of two or more thereof.

41. The method according to claim 35, wherein the carbonate filler ≤10 wt.-% of the carbonate filler is ground together with the hydraulic cement, the pozzolan or the cement-pozzolan mix and the remainder is ground separately, wherein the carbonate filler is ground to a bimodal particle size distribution with ≥30 wt.-% particles having a D.sub.10≥35 μm, and ≥30 wt.-% particles having a D.sub.90≤20 μm.

42. The method according to claim 41, wherein the carbonate filler ≤5 wt.-% of the carbonate filler is ground together with the hydraulic cement, the pozzolan or the cement-pozzolan mix and the remainder is ground separately, wherein the carbonate filler is ground to a bimodal particle size distribution with ≥40 wt.-% particles having a D.sub.10≥40 μm, and ≥30 wt.-% particles having a D.sub.90≤10 μm.

43. The method according to claim 37, wherein from 20 to 35 wt.-% pozzolan and carbonate filler together are used, and/or a weight ratio of pozzolan to carbonate filler from 15:1 to 2:1.

44. The method according to claim 43, wherein from 22 to 30 wt.-% pozzolan and carbonate filler together are used, and/or a weight ratio of pozzolan to carbonate filler from 9:1 to 4:1.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0069] FIGS. 1a and 1b show the particle size distribution of three components of a composite cement according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Examples

[0070] The following materials were used: [0071] a first cement CEM I 142.5 R “Cem1” [0072] a second cement CEM I 42.5 R “Cem2” [0073] a third low-alkali cement CEM I 42.5 R NA “Cem3” [0074] a fourth cement CEM I 42.5 R “Cem4” [0075] a fifth low-alkali cement CEM I 42.5 R NA “Cem5” [0076] a sixth cement CEM I 52.5 N “Cem6” [0077] a seventh limestone cement CEM II/A 42.5 N with about 11 wt.% of limestone (co-ground) “Cem7” [0078] four different ground hyaloclastite pozzolans “P1”, “P2”, “P3”, “P4”, and [0079] a ground limestone “LL”.

[0080] Separately ground pozzolan and limestone were used if not mentioned otherwise. The chemical composition, including the loss on ignition, X-ray amorphous content of the pozzolan, and Na.sub.2O Eq. in wt.-%, the C.sub.3A content in wt.-%, and the Blaine fineness in cm.sup.2/g of the used materials is compiled in table 2 below. The sulfate content of the cements was adjusted using calcium sulfate (namely gypsum, bassanite and anhydrite). Additionally, calcium alkali and alkali sulfates from the clinker, CKD and BPD were present. High SO.sub.3 contents were chosen to bind most up to all liberated aluminium ions from the C.sub.3A dissolution into hydrates such as ettringite, and with that, enable an enhanced activation of the pozzolan.

TABLE-US-00002 TABLE 2 Cem1 Cem2 Cem3 Cem4 Cem5 Cem6 Cem7 P1 P2 P3 P4 LL loi at 950° C. 2.10 2.67 1.41 1.22 0.78 3.07 5.28 0.00 0.46 0.63 0.64 42.99 SiO.sub.2 19.70 19.90 20.46 19.71 21.51 20.16 19.60 47.64 48.07 47.40 47.51 1.04 Al.sub.2O.sub.3 5.63 5.18 4.60 4.95 3.62 4.73 4.58 14.13 14.50 13.14 13.07 0.21 TiO.sub.2 0.23 0.34 0.18 0.34 0.23 0.40 0.24 1.57 1.56 1.61 1.64 0.01 MnO 0.07 0.10 0.06 0.06 0.05 0.04 0.06 0.17 0.17 0.17 0.17 0.06 Fe.sub.2O.sub.3 2.99 3.06 3.84 3.20 5.30 2.77 2.18 12.06 11.76 12.06 12.16 0.16 CaO 60.63 61.36 63.55 62.41 63.46 63.64 62.00 11.58 11.89 11.21 11.26 54.58 MgO 2.31 2.46 1.58 2.45 1.50 1.13 2.28 10.15 9.28 11.31 11.43 0.91 K.sub.2O 1.73 1.17 0.33 1.13 0.33 0.61 0.63 0.32 0.31 0.38 0.39 0.05 Na.sub.2O 0.11 0.46 0.33 0.43 0.24 0.21 0.25 1.92 1.94 1.84 1.84 0.01 SO.sub.3 3.77 3.62 3.36 3.85 2.49 3.18 3.02 0.02 0.04 0.01 0.00 0.02 P.sub.2O.sub.5 0.14 0.08 0.11 0.12 0.21 0.05 0.12 0.17 0.16 0.18 0.19 0.01 Sum 99.41 100.40 99.81 99.72 99.88 99.99 100.31 99.73 100.14 99.94 100.30 100.05 X-ray 70.4 86.6 57.4 47.7 amorph. Na.sub.2O Eq. 1.24 1.22 0.55 1.17 0.46 0.61 0.67 2.14 2.14 2.09 2.10 0.04 Blaine 4800 5710 3800 5520 3790 3850 4480 5680 7160 7510 7130 3430 fineness

[0081] The hyaloclastite P1 had an X-ray amorphous (also referred to as glass) content of about 70 wt.-%. The crystalline phases were about 13 wt.-% pyroxene, 9 wt.-% feldspars, and 8 wt.-% olivine. The samples P2 to P4 were taken at different spots in a hyaloclastite mine, known for their differences in purity, i.e. enrichment with basalt and other crystalline rocks. P2 presents a high purity hyaloclastite source, P4 a basalt-rich one and P3 an intermediate type. The crystalline phases were the same as found in P1, namely pyroxene, feldspars, and olivine.

Example 1

[0082] The effect of the addition of limestone with a bimodal distribution was determined as follows. The particle size distribution of the three used components was measured by laser diffraction. The results are shown in FIG. 1. The PSD of the pozzolan “P1” is steep with a n value of the slope of 1.03. In contrast, the used cement “Cem1” as well as the limestone “LL” showed a much broader distribution with n values of 0.88 and 0.76, respectively. The first maximum of the derivative curve of the ground limestone was located around 9 μm and the second one around 80 μm.

[0083] The compressive strength development was measured in micro mortars. For the micro mortar tests, cubes of 2 cm×2 cm×2 cm were prepared, using a cement to sand weight ratio of 2:3. The sand used had a D.sub.10, D.sub.50 and D.sub.90 of 0.128, 0.215 and 0.355 mm, respectively. A water to cement weight ratio of 0.50 was applied. The mortar cubes were cured for 24 hours in the steel form at 20° C. and >95% RH. The cubes were stored under water after demoulding till the date of testing. The loading speed of the press for the compressive strength measurement was 0.4 kN/s and 6 cubes were tested per sample age. The deviation from the average strength of the 6 tested cubes was for all samples below 1 MPa after 24 hours and below 2 MPa at later ages. The mix design, measured compressive strengths and activity indices are shown in table 3.

TABLE-US-00003 TABLE 3 Cem1 P1 LL Compressive strength [MPa] after Activity index [%] after amount [wt.-%] 1 d 2 d 7 d 28 d 56 d 91 d 1 d 2 d 7 d 28 d 56 d 91 d Ref1 100 26.0 35.6 43.2 54.7 60.1 60.8 — — — — — — Ref2 75 25 16.0 23.0 31.2 45.1 56.7 62.7 61.5 64.6 72.2 82.4 94.3 103.1 Ref3 75 25 16.9 24.9 34.8 43.1 46.3 49.6 65.0 69.9 80.6 78.8 77.0 81.6 5LL 75 20 5 17.4 25.3 35.3 49.4 58.5 65.2 66.9 71.1 81.7 90.3 97.3 107.2 10LL 75 15 10 16.8 25.0 34.1 46.3 55.1 59.9 64.6 70.2 78.9 84.6 91.7 98.5 15LL 75 10 15 16.8 24.7 34.2 44.8 51.7 58.0 64.6 69.4 79.2 81.9 86.0 95.4 20LL 75 5 20 15.8 23.4 31.8 40.2 45.7 52.5 60.8 65.7 73.6 73.5 76.0 86.3

[0084] It is evident, that the limestone reference Ref3 outperformed the pozzolan cement reference Ref2 up to 28 days of hydration. The higher strength development linked to the pozzolanic reaction was only measureable at later hydration ages for Ref2 compared to Ref3. The replacement of 5 wt.-% of P1 by LL results in a significant increase of the compressive strength at all measured hydration ages compared to Ref2. Even a slightly better strength development up to 7 d, followed by a significant improvement at all later hydration ages was observed compared to Ref3. The replacement of 10 wt.-% improved the strength development at early ages up to 7 days of hydration compared to Ref2. The effect levelled out at later hydration ages. All pozzolan-limestone mixes outperform Ref3 after 91 days of hydration, even the mix with only 5% of pozzolan. All those results demonstrate the synergetic reaction between the hyaloclastite pozzolan and limestone in a Portland composite cement.

Example 2

[0085] Two cements, namely “Cem2” and “Cem3”, with different Na.sub.2O Eq. and fineness but similar ultimate strength at 28 and 91 days of hydration were used to investigate the impact of the reactivity of three hyaloclastite samples with different amorphous contents. “Cem2” contained about 4 wt.-% of limestone, whereas it was only about 2 wt.-% in “Cem3”. In both cases, limestone was added during the cement grinding. The particle size distribution was not measured, but is assumed to have been monomodal. The compressive strength development was measured in standard mortar cubes in accordance with EN 196-1. The composition of the mixes and the measured strength in MPa and activity indices in % are listed in table 4.

TABLE-US-00004 TABLE 4 Compressive strength Activity index [MPa] after [%] after mix composition 28 d 91 d 28 d 91 d 100% Cem2 56.1 60.7 — — 100% Cem3 58.9 63.8 — — 75% Cem2 + 25% P2 57.3 63.1 102 104 75% Cem3 + 25% P2 50.9 65.1 86 102 75% Cem2 + 25% P3 52.2 58.7 93 97 75% Cem3 + 25% P3 46.0 62.2 78 97 75% Cem2 + 25% P4 50.0 58.9 89 97 75% Cem3 + 25% P4 43.5 59.3 74 93

[0086] It can be seen that the fine, alkali-rich cement Cem2 that also contained about 4 wt.-% of limestone demonstrated the highest activation potential for all three tested pozzolans after 28 d compared to Cem3. The Cem3-based composite cements did only catch up after 91 days of hydration but still fell slightly short of the Cem2-based composite cements in case of P2 and P4. Those results demonstrate that it is possible to enhance the pozzolanic reaction and linked pozzolan dosage in composite cements by choice of the used cement type. Although this example used a carbonate filler not according to the invention, the found effect of alkali content of the hydraulic cement is expected to be the same or likely even stronger for carbonate with bimodal PSD.

Example 3

[0087] Two cements “Cem4” and “Cem5” with different Na.sub.2O Eq. and fineness but similar ultimate strength at 28 and 91 days of hydration were used to investigate the impact of Na.sub.2O Eq. on the reactivity of P1 but without limestone being present. Those cements are different batches of Cem2 and Cem3, produced in the same cement plant but without adding any limestone during grinding. The compressive strength development was measured in standard mortar cubes in accordance with EN 196-1. The composition of the mixes and the measured strength in MPa and activity indices in % are listed in table 5.

TABLE-US-00005 TABLE 5 Compressive strength Activity index [MPa] after [%] after mix composition 1 d 7 d 28 d 91 d 1 d 7 d 28 d 91 d 100% Cem2.1 35.4 50.4 57.1 61.2 100% Cem3.1 20.4 45.8 62.4 64.7 75% Cem2.1 + 25% P1 22.8 41.3 49.4 60.8 64 82 87 99 75% Cem3.1 + 25% P1 13.0 32.7 49.7 62.4 64 71 80 96

[0088] It can be seen that the fine, alkali-rich cement Cem4 demonstrated, as expected from example 2, a stronger activation potential for tested pozzolans up to 28 days of hydration compared to Cem5, also in the absence of limestone. Again, the composite cements tested are not according to the invention since no carbonate filler was used, but the effect will be the same or likely even stronger with carbonate filler used in accordance to the invention.

Example 4

[0089] The effect of blending co-ground limestone cement with separately ground pozzolan was examined. Two industrial cements were used for this trial, namely a neat CEM I 52.5 N “Cem6” with about 4 wt.-% of limestone and a CEM II/A-LL 42.5 N “Cem7” with about 11 wt.-% of limestone. Cem6 and Cem7 were produced by co-grinding with coarse limestone. The cement was further analysed by SEM-EDS analyses of polished sections to assess the particle size distribution of the individual components (also referred to as mineral liberation analysis “MLA”), namely cement and limestone, and if a monomodal or the targeted bimodal distribution of LL was achieved. The cement clinker presented a broad, monomodal distribution with particles being present in all detectable size fractions. The D.sub.50 and D.sub.90 from the MLA were about 25 μm and 50 μm, respectively. The maximum of the derivative curve was located around 35 μm. The limestone in Cem7 demonstrated a broad, bimodal distribution. The D.sub.50 and D.sub.90 from the MLA were about 7 μm and 45 μm, respectively. The first maximum of the derivative curve was located around 7 μm and the second one around 43 μm. The limestone in Cem6 had a broad, monomodal distribution with particles being present in the size fractions below 30 μm. The D.sub.50 and D.sub.90 from the MLA were about 7 μm and 22 μm, respectively. The single maximum of the derivative curve was located around 10 μm.

[0090] The compressive strength development was measured in standard mortar cubes in accordance with EN 196-1 as done for example 2. The composition of the mixes in wt.-%, the measured strength in MPa, and activity indices in % are listed in table 6.

TABLE-US-00006 TABLE 6 Compressive strength [MPa] after Activity index [%] after mix composition 1 d 2 d 7 d 28 d 56 d 91 d 1 d 2 d 7 d 28 d 56 d 91 d 100% Cem6 n.m. n.m. 48.1 60.5 n.m. n.m. — — — — — — 75% Cem6 + 25% P1 14.3 22.3 33.0 47.2 56.6 62.0 n.m. n.m. 68.6 78.0 n.m. n.m. 100% Cem7 22.4 34.5 48.7 56.9 — — — — — — 75% Cem7 + 25% P1 16.0 26.6 38.7 49.2 71.4 77.1 79.5 87.5

[0091] The strength development of the Cem7-P outperformed Cem6-P at all tested hydration ages, despite the much lower cement content, i.e. the higher limestone replacement. This again demonstrates the synergies between the bimodal limestone and the hyaloclastite pozzolan P1 in the presence of Portland cement. It further reveals the importance of the bimodal distribution of the limestone filler. Additionally, it also shows that the cement performance can be optimized by separate grinding of the pozzolan and blending with the other cement components as well as by optimizing the cement fineness. With those measures a pozzolan-limestone composite cement can be produced with high strength development and good fresh properties such water demand and workability.

Example 5

[0092] The effect of sieving on X-ray amorphous content was examined. The pozzolan P1, a sieved fraction 0-10 mm from the material as received in big bags with about 85 kg pozzolan each, was dried at 110° C. and used for the trials. The material was sieved to different size fractions and the obtained samples were analysed by X-ray diffraction coupled with Rietveld analysis to determine the X-ray amorphous content. The results for the pozzolan P1 and for the fractions made from it by sieving (sieve sizes in mm) are assembled in table 6. Further, the pozzolan from several big bags was ground together using a vertical roller press mill and the X-ray amorphous content measured. This sample is designated bulk and the result is also listed in table 7.

TABLE-US-00007 TABLE 7 sample 0-1 0-2 0-4 1-4 4-8 2-10 4-10 bulk P1 mm mm mm mm mm mm mm Crystalline 79 70 87 87 83 57 48 51 53 content [wt.-%] X-ray amorphous 21 30 13 13 17 43 52 49 47 content [wt.-%]

[0093] The results demonstrate that it is possible to separate the crystalline rock from the glassy hyaloclastite pozzolan by sieving and with that, to increase the X-ray amorphous content significantly. Consequently, the grindability as well as the reactivity in a composite cement will improve. The difference between samples P1 and bulk is likely associated with the improved material homogenisation of the several tons of material mixing during the grinding. Thus, it is expected that industrial scale grinding will provide even better results for the composite cement than found in the laboratory experiments, since the hyaloclastite pozzolan will have higher X-ray amorphous content.

[0094] The following embodiments are particularly preferred embodiments of the present invention.

[0095] Embodiment 1: Composite cement comprising [0096] a hydraulic cement or a caustic activator, [0097] a hyaloclastite as pozzolan containing 45-62 wt.-% SiO.sub.2, 10-20 wt.% Al.sub.2O.sub.3, 6-15 wt.-% Fe.sub.2O.sub.3, 7-15 wt.-% CaO, 7-15 wt.-% MgO, 1.5-4 wt.% (K.sub.2O+Na.sub.2O), and having 0-5 wt.-% loss on ignition at 950° C. and ≥50 wt.-% X-ray amorphous phase, and [0098] a carbonate filler with an at least bimodal particle size distribution adapted to provide a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of ≤1.15 in a particle size distribution of the composite cement.

[0099] Embodiment 2: Composite cement as defined in embodiment 1, wherein the particle size distribution of the composite cement has a slope n from 0.80 to 1.15, preferably from 0.90 to 1.05, most preferred from 0.95 to 1.00 and/or the composite cement has a fineness according to Blaine from 3500 to 10000 cm.sup.2/g, preferably from 4500 to 8000 cm.sup.2/g, most preferred from 5000 to 6000 cm.sup.2/g.

[0100] Embodiment 3 Composite cement as defined in embodiment 1 or 2, wherein the pozzolan contains 0.5 to 4 wt.-% other elements and/or the pozzolan contains 46-54 wt.-% SiO.sub.2, 12-17 wt.% Al.sub.2O.sub.3, 8-14 wt.-% Fe.sub.2O.sub.3, 10-13 wt.-% CaO, 10-13 wt.-% MgO, 1.5-3 wt.% (K.sub.2O+Na.sub.2O) and/or the amount of X-ray amorphous phase in the pozzolan is ≥60 wt.-%, preferably ≥70 wt.-%, more preferred ≥80 wt.-%, most preferred ≥85 wt.-%.

[0101] Embodiment 4: Composite cement as defined in at least one of embodiments 1 to 3, wherein the pozzolan has a monomodal particle size distribution, preferably with a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve from 0.9 to 1.4, more preferred from 1.0 to 1.2 and/or the pozzolan has a fineness according to Blaine from 4500 to 8000 cm.sup.2/g, preferably from 5000 to 6000 cm.sup.2/g.

[0102] Embodiment 5: Composite cement as defined in at least one of embodiments 1 to 4, wherein the hydraulic cement is selected from Portland cement, calcium aluminate cement, calcium sulfoaluminate cement, belite binder obtained by hydrothermal treatment and subsequent tempering and/or reactive grinding, and mixtures thereof, and/or the caustic activator is selected from free lime, portlandite, Portland cement, Portland cement clinker, alkali hydroxides, alkali carbonates, alkali sulfates and mixtures thereof.

[0103] Embodiment 6: Composite cement as defined in at least one of embodiments 1 to 5, wherein the hydraulic cement is a Portland cement with an Na.sub.2O Eq. from 0.3 to 2.5 wt.-%, preferably from 1.0 to 2.0 wt.-%, most preferred from 1.2 to 1.5 wt.-%, and/or with an amount of C.sub.3S from 45 to 74 wt.-%, preferably from 55 to 65 wt.-%, and/or with an amount of C.sub.3A from 1 to 18 wt.-%, preferably from 2 to 12 wt.-%, most preferred from 3 to 7 wt.-%, all with respect to the hydraulic cement clinker.

[0104] Embodiment 7: Composite cement as defined in at least one of embodiments 1 to 6, wherein the hydraulic cement or caustic activator has a fineness according to Blaine from 2000 to 10000 cm.sup.2/g, preferably from 3000 to 8000 cm.sup.2/g, most preferred of at least 4000 cm.sup.2/g.

[0105] Embodiment 8: Composite cement as defined in at least one of embodiments 1 to 7, wherein the carbonate filler has a bimodal particle size distribution with ≥20 wt.-%, preferably ≥30 wt.-%, most preferred ≥40 wt.-%, particles having a D.sub.10≥30 μm or ≥35 μm or ≥40 μm, and ≥20 wt.-% particles, preferably ≥30 wt.-%, having a D.sub.90≤30 μm or ≤20 μm or ≤10μm, and/or the carbonate filler has a slope n below 1.0, preferably below 0.85, most preferred below 0.75.

[0106] Embodiment 9: Composite cement as defined in at least one of embodiments 1 to 8, wherein the carbonate filler is selected from limestone; dolomite; magnesite; precipitated nanosized carbonates; poorly crystalline or X-ray amorphous carbonates; complex partly hydrated carbonates like monohydrocalcite, hydromagnesite, nesquehonite, dypingite; and mixtures of two or more thereof, most preferably is limestone.

[0107] Embodiment 10: Composite cement as defined in at least one of embodiments 1 to 9, wherein the amount of pozzolan and carbonate filler together ranges from 15 to 50 wt.-%, preferably from 20 to 35 wt.-%, most preferred from 22 to 30 wt.-%.

[0108] Embodiment 11: Composite cement as defined in at least one of embodiments 1 to 10, wherein the weight ratio of pozzolan to carbonate filler ranges from 20:1 to 1:1, preferably from 15:1 to 2:1, most preferred from 9:1 to 4:1.

[0109] Embodiment 12: Method for manufacturing a composite cement as defined in at least one of embodiments 1 to 11 comprising the steps: [0110] providing a hydraulic cement or a caustic activator, [0111] providing a hyaloclastite as pozzolan containing 45-62 wt.-% SiO.sub.2, 10-20 wt.% Al.sub.2O.sub.3, 6-15 wt.-% Fe.sub.2O.sub.3, 7-15 wt.-% CaO, 7-15 wt.-% MgO, 1.5-4 wt.% (K.sub.2O+Na.sub.2O), and having 0-5 wt.-% loss on ignition at 950° C. and ≥50 wt.-% X-ray amorphous phase, [0112] providing a carbonate filler with an at least bimodal particle size distribution, ground partly or fully separately from the hydraulic cement and the pozzolan, adapted to provide a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of ≤1.15 in a particle size distribution of the composite cement, and [0113] blending the hydraulic cement or caustic activator, the pozzolan and the carbonate filler to provide the composite cement, and if needed adjusting the sulfate content of the composite cement adding a sulfate source, preferably a calcium sulfate.

[0114] Embodiment 13: Method as defined in embodiment 12, wherein the pozzolan is ground, preferably separately from the hydraulic cement and the carbonate filler, to a monomodal particle size distribution, preferably with a slope n in a Rosin-Rammler-Sperling-Bennett distribution curve from 0.9 to 1.4, more preferred from 1.0 to 1.2, and/or to a fineness according to Blaine from 4500 to 8000 cm.sup.2/g, preferably from 5000 to 6000 cm.sup.2/g.

[0115] Embodiment 14: Method as defined in embodiment 12 or 13, wherein the carbonate filler is ground separately from the hydraulic cement and the pozzolan, or ≤20 wt.-%, preferably ≤10 wt.-%, most preferred ≤5 wt.-%, of the carbonate filler are ground together with the hydraulic cement, the pozzolan or a cement-pozzolan mix and the remainder is ground separately, wherein the carbonate filler is ground to a bimodal particle size distribution with ≥20 wt.-% particles, preferably ≥30 wt.-%, more preferred ≥40 wt.-%, having a D.sub.10≥30 μm or ≥35 μm or ≥40 μm, and ≥20 wt.-% particles, preferably ≥30 wt.-%, having a D.sub.90≤30 μm or ≤20 μm or ≤10 μm.

[0116] Embodiment 15: Method as defined in at least one of embodiments 12 to 14, wherein a grinding aid is added during grinding of at least one of the hydraulic cement, the pozzolan and the carbonate filler, wherein the grinding aid is preferably selected from alkanolamines; sugars and sugar derivatives; glycols like mono-, di-, triethylene glycols; carboxylic acids and their salts like oleic acid, ethylenediaminetetraacetic acid, sodium gluconate; carbonic anhydrase; diols; glycerol; sulphonic acids; (ligno)sulphonates; and mixtures thereof; more preferred from alkanolamines; most preferred from monoethanolamine, diethanolamine, diglycolamine, diisopropanolamine, triethanolamine, triisopropanolamine, and mixtures thereof.

[0117] Embodiment 16: Method as defined in at least one of embodiments 12 to 15, wherein from 15 to 50 wt.-%, preferably from 20 to 35 wt.-%, most preferred from 22 to 30 wt.-%, pozzolan and carbonate filler together are used, and/or a weight ratio of pozzolan to carbonate filler from 20:1 to 1:1, preferably from 15:1 to 2:1, most preferred from 9:1 to 4:1.

[0118] Embodiment 17: Method as defined in at least one of embodiments 12 to 16, wherein the particle sizes and amounts of hydraulic cement or caustic activator, pozzolan and carbonate filler are selected such that the composite cement has a fineness according to Blaine from 3500 to 10000 cm.sup.2/g, preferably from 4500 to 8000 cm.sup.2/g, most preferred from 5000 to 6000 cm.sup.2/g, and/or the slope n in a Rosin-Rammler-Sperling-Bennett distribution curve of the composite cement ranges from 0.80 to 1.15, preferably from 0.90 to 1.05, most preferred from 0.95 to 1.00.

[0119] Embodiment 18: Method as defined in at least one of embodiments 12 to 17, wherein the hydraulic cement has an Na.sub.2O Eq. from 0.3 to 2.5 wt.-%, preferably from 1.0 to 2.0 wt.-%, most preferred from 1.2 to 1.5 wt.-%, adjusted by addition of alkalis like carbonates, sulfates, chlorides and process dust from clinker production when the Na.sub.2O Eq. of the used hydraulic cement is below the desired value, and/or the hydraulic cement has an amount of C.sub.3A from 1 to 18 wt.-%, preferably from 2 to 12 wt.-%, most preferred from 3 to 7 wt.-%, all with respect to the hydraulic cement clinker.

[0120] Embodiment 19: Method as defined in at least one of embodiments 12 to 18, wherein further components are added to the composite cement, selected from admixtures, preferably plasticizers, superplasticizers, water reducers, stabilizers, air entraining agents, setting accelerators, hardening accelerators, retarders, sealants, chromate reducing agents, and mixtures of two or more thereof; and further SCMs, preferably ground granulated blast furnace slag, fly ash, calcined clay or shales, trass, brick-dust, artificial glasses, waste glass, silica fume, burned organic matter residues rich in silica such as rice husk ash, carbonated recycled concrete fines, natural pozzolans other than hyaloclastite, and mixtures of two or more thereof.

[0121] Embodiment 20: Use of a composition comprising [0122] a hyaloclastite as pozzolan containing 45-62 wt.-% SiO.sub.2, 10-20 wt.-% Al.sub.2O.sub.3, 6-15 wt.-% Fe.sub.2O.sub.3, 7-15 wt.-% CaO, 7-15 wt.-% MgO, 1.5-4 wt.-% (Na.sub.2O+K.sub.2O), and having 0-5 wt.-% loss on ignition at 950° C. and ≥50 wt.-% X-ray amorphous phase, and [0123] a carbonate filler with an at least bimodal particle size distribution as mineral addition for composite cements comprising a hydraulic cement or a caustic activator.