Manufacturing a binder with high β belite content

Abstract

The present invention relates to a method for manufacturing a binder with high β belite content comprising the steps: a) providing a starting material by selecting one raw material having a Ca/Si molar ratio of 1.5 to 2.5 or by mixing two or more raw materials to obtain a starting material with the Ca/Si molar ratio of 1.5 to 2.5; b) hydrothermal treatment of the starting material produced in step a) in an autoclave at a temperature of 100 to 300° C. and a retention time of 0.1 to 24 h, wherein the water/solids ratio is from 0.1 to 100 to provide an intermediate product; c) annealing the intermediate product obtained in step b) in a flash calciner at 620 to 630° C., wherein the retention time is 1-30 seconds.

Claims

1. A method for manufacturing a binder with β belite content of at least 20% by weight comprising the steps: a) providing a starting material by selecting one raw material having a Ca/Si molar ratio of 1.5 to 2.5 or by mixing two or more raw materials to obtain a starting material with the Ca/Si molar ratio of 1.5 to 2.5; b) hydrothermal treatment of the starting material produced in step a) in an autoclave at a temperature of 100 to 300° C. and a retention time of 0.1 to 24 h, wherein the water/solid ratio is from 0.1 to 100 to provide an intermediate product; c) annealing the intermediate product obtained in step b) in a flash calciner at 620 to 630° C., wherein the retention time is 1-30 seconds.

2. The method according to claim 1, wherein the molar ratio of calcium to silicon in the starting material is 2±10%.

3. The method according to claim 1, wherein primary and/or secondary raw materials are used to provide the starting material, the primary and/or secondary raw materials being selected from the group consisting of quartz, sand, gravel, limestone, portlandite (Ca(OH).sub.2), burnt lime, unburnt lime, silicious fly ash, calcareous fly ash, and grain fractions from the reprocessing of cement-containing binders in building materials, and mixtures thereof.

4. The method according to claim 1, wherein the raw material(s) is(are) are optimised with respect to particle size and particle size distribution by mechanical or thermal treatment.

5. The method according to claim 1, wherein additional elements, also in the form of compounds, are added in an amount from 0.1 to 30% by weight to the raw material or during the mixing of the raw materials, for hydrothermal treatment or for annealing.

6. The method according to claim 1, wherein the starting material is seeded with 0.01-30% by weight of seed nuclei containing at least one calcium silicate hydrate.

7. The method according to claim 1, wherein one or more of the raw materials or the starting material is burnt at temperatures of 400 to 1400° C.

8. The method according to claim 1, wherein hydrothermal treatment occurs at a temperature of 150° C. to 250° C., with a water/solids ratio of 2 to 20, and retention times of 1 to 16 hours.

9. The method according to claim 1, wherein the intermediate product is annealed at a temperature of 625° C.±2° C. with a retention time of 1 to 3 seconds.

10. The method according to claim 2, wherein primary and/or secondary raw materials are used to provide the starting material, the primary and/or secondary raw materials being selected from the group consisting of quartz, sand, gravel, limestone, portlandite (Ca(OH).sub.2), burnt lime, unburnt lime, silicious fly ash, calcareous fly ash, grain fractions from the reprocessing of cement-containing binders in building materials, and mixtures thereof.

11. The method according to claim 2, wherein the raw material(s) is(are) optimised with respect to particle size and particle size distribution by mechanical or thermal treatment.

12. The method according to claim 10, wherein the raw material(s) is(are) optimised with respect to particle size and particle size distribution by mechanical or thermal treatment.

13. The method according to claim 5, wherein the additional elements are selected from the group consisting of sodium, potassium, boron, sulphur, phosphorous and combinations thereof.

14. The method according to claim 6, wherein the calcium silicate hydrate is one or more of α-C.sub.2SH, afwillite, calcio-chondrodite.

15. The method according to claim 7, wherein the starting material is burnt at temperatures of 750 to 1100° C.

16. The method according to claim 4, wherein additional elements, also in the form of compounds, are added in an amount from 0.1 to 30% by weight to the raw material or during the mixing of the raw materials, for hydrothermal treatment or for annealing.

17. The method according to claim 4, wherein hydrothermal treatment occurs at a temperature of 150° C. to 250° C., with a water/solids ratio of 2 to 20, and retention times of 1 to 16 hours.

18. The method according to claim 17, wherein the intermediate product is annealed at a temperature of 625° C.±2° C. with a retention time of 1 to 3 seconds.

19. The method according to claim 3, wherein additional elements, also in the form of compounds, are added in an amount from 0.1 to 30% by weight to the raw material or during the mixing of the raw materials, for hydrothermal treatment or for annealing.

20. The method according to claim 3, wherein the intermediate product is annealed at a temperature of 625° C.±2° C. with a retention time of 1 to 3 seconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows incremental heat flow and FIG. 1b shows cumulative heat flow as measured by heat release measurements of pastes prepared according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) The invention will be illustrated further with reference to the examples that follow, without restricting the scope to the specific embodiments described. If not otherwise specified any amount in % or parts is by weight and in the case of doubt referring to the total weight of the composition/mixture concerned.

(3) The invention further includes all combinations of described and especially of preferred features that do not exclude each other. A characterization as “approximately”, “around” and similar expression in relation to a numerical value means that up to 10% higher and lower values are included, preferably up to 5% higher and lower values, and in any case at least up to 1% higher and lower values, the exact value being the most preferred value or limit.

(4) The term “substantially free” means that a particular material is not purposefully added to a composition, and is only present in trace amounts or as an impurity. As used herein, unless indicated otherwise, the term “free from” means that a composition does not comprise a particular material, i.e. the composition comprises 0 weight percent of such material.

Example 1

(5) A starting material mixture was made from 41.93 kg Portlandite, 18.07 kg micro-silica and 1.2 kg α-C.sub.2SH seeds. The oxide composition of the raw materials is presented in table 1.

(6) TABLE-US-00001 TABLE 1 Component Portlandite Micro-silica SiO.sub.2 94.05% Al.sub.2O.sub.3 0.61% CaO 75.67% 0.31% MgO 0.59% K.sub.2O 1.12% Fe.sub.2O.sub.3 0.4% Na.sub.2O 0.21% P.sub.2O.sub.5 0.04% Loss on ignition (1050° C.) 24.33% 2.73%

(7) The finely ground raw materials were mixed with each other and with water in a water/solids ratio of 1 and placed into an autoclave at 190° C. for 375 minutes. An intermediate product was obtained, which contained 65% α-C.sub.2SH and had a maximum particle size of 200 μm. The intermediate product could be used as such for tempering as it contained very little water. 5 kg were fed into a flash calciner (FLSmidth, DK) having vertical cylindrical design with fuel combustion in intimate contact with the feed, a setup of 6 m and a further 3 m insulated piping before quench air is introduced before an uninsulated steel pipe that leads to the bag filter. The inlet temperature was set to 675° C. resulting in an average temperature in the calciner of 625° C. The retention time was adjusted to 1.29 seconds. The average temperature inside the insulated pipe was 455° C. and passage took 0.18 seconds. Herein, it was assumed that gas and particles have the same retention time, gases were calculated as ideal gases and the temperature was calculated as simple average for each part of the calciner. A nearly complete conversion of the intermediate product was observed, the composition of the obtained product is summarized in table 2.

(8) TABLE-US-00002 TABLE 2 Phase formula amount [% by weight] C.sub.2SH-alpha Ca.sub.2(SiO.sub.4)(H.sub.2O) 0.5 γ-Belite, C.sub.2S Ca.sub.2SiO.sub.4 4.7 α-Belite, C2S 8.2 χ-Belite, C.sub.2S 5.1 β-Belite, C.sub.2S 43.4 Σ Belite 61.4 Dellaite Ca.sub.6(Si.sub.2O.sub.7)(SiO.sub.4)(OH).sub.2 not detected Calcite CaCO.sub.3 7.2 Portlandite Ca(OH).sub.2 1.0 Quartz SiO.sub.2 0.2 amorphous content 28.7 Total 100.0

(9) The results in table 2 show that a high amount of β belite is obtained according to the invention, while x belite and γ belite are only formed in low amounts. The amount of highly reactive X ray amorphous phase is also quite high. Reactivity was proven by calorimetry. Heat release measurements of pastes prepared with water-to-solid of 1 were recorded over 7 days by an isothermal calorimeter (TAM Air, TA Instruments, Sweden). The incremental heat flow as well as the cumulative heat flow are shown in FIGS. 1 a and b, respectively.