Process for the production of calcium silicate-containing stone blanks useful in constructing building walls

Abstract

A process and apparatus is provided for the production of calcium silicate-containing stone blanks which are useful in constructing building walls. A crude mixture, of a granulated silicate-containing material, lime, water, a cement and a foaming agent, is subjected to no more than a minimum application of external pressure and is subsequently hardened in an autoclave. The cement produces the necessary strength for the blank, so that the latter becomes transportable while the final strength is achieved by reaction of the silicate-containing material during the autoclave treatment. In order to arrive at acceptable molding times and in order to achieve a simplified process with slight fragment bulk density and optimal head damping characteristics, the crude mixture is rendered pourable, is filled into molds in a quantity corresponding to the fragment volume of the stone blank, and the crude mixture in the mold is heated essentially uniformly to a temperature between 45°C and 90°C until achieving the desired blank-strength.

The production of the blanks is carried out in molds, which are equipped with a heating system for heating the crude mixture in the molds, whereby the heating takes place by means of an electric high frequency field and/or indirectly via the molds and possibly via mold spikes, which are individually heatable and serve for the development of a pattern of holes in the stone.

Description

g/cm³ g/liter.

The resulting crude mixture had a temperature of 15°C and was filled into a mold, the box of which was heated to a temperature of 75°C and the spikes of which were heated to a temperature of top of 76°C and on the bottom of 82°C Prior to shaping, the mold and the spikes were treated with a release agent. After a molding time of 80 seconds, the stove blank was removed from the mold. The degree of excess filling of the mold amounted to 12%.

The crude mixture had a bulk density of 1150 kg/m³, the blank had a fragment bulk density of 1285 kg/m³ and a blank strength of more than 0.12 m.kg/sec² /mm².

Claims

1. A method for producing stones on calcium silicate-basis, which are useful in constructing building walls, the method comprising the following steps:

a. forming a crude mixture of granulated comprising a silicate-containing material, lime, water, cement and a foaming agent, using such an amount of water that the crude mixture is pourable selected from the group consisting of quartz sand, pumice, alumina, quartz powder, boiler slag, and fly ash; a calcium containing material selected from the group consisting of calcium oxide, partially hydrated lime and calcium hydroxide and in addition to the silicate containing material and calcium containing material a cement, said cement acting as a binder, a foaming agent and water, said water added in an amount sufficient to render the crude mixture pourable and by using a cement composition starting with strength-forming reactions substantially at elevated temperatures,

b. pouring the crude mixture of step (a) into molds,

c. heating the crude mixture in the molds to a temperature of between 45°C and 90°C--substantially without compacting the crude mixture to start the strength-forming reactions of the cement,

d. subjecting the crude mixture in the molds to the elevated temperature for 10 seconds to 5 minutes until the stone blanks formed in the molds from the crude mixture by heating to the elevated temperature achieves the desired blank strength necessary for removing the blanks from the molds,

e. removing the blanks from the molds and transporting the blanks to an autoclave, and

f. steam hardening the stone blanks in the autoclave.

2. The process as defined in claim 1, wherein an accelerating agent and/or a retarding agent are added to the mixture in step (a) for accelerating or retarding the cement reaction.

3. The process as defined in claim 1, wherein the crude mixture in the molds is subjected to the elevated temperature of 45°C to 90°C for 30 seconds to 1 minute, the heating of the crude mixture being carried out by contact heating of the molds.

4. The process as defined in claim 1, wherein the crude mixture in the molds is subjected to the elevated temperatures of 45°C to 90°C for 10 to 60 seconds, the heating of the crude mixture being carried out by applying a high frequency voltage to the molds.

5. The process as defined in claim 1, including the step of gravimetrically measuring the volume of crude mixture added to the molds and thereafter controlling the amount of water and foam added in step (a).

6. The process as defined in claim 1, including slightly compressing the crude mixture poured into the molds in step (b) to achieve its intended volume.

7. The process as defined in claim 1, wherein the foaming agent added in step (a) has a bulk density of from about 50 to 100 g/l.

8. The process as defined in claim 7, wherein the foaming agent is a sulfated fatty alcohol.

9. The process is defined in claim 1, wherein the foaming agent contains CO₂.

10. The process as defined in claim 1, wherein the lime and water are added in the form in step (a).

11. The process as defined in claim 1, wherein said lime is slaked lime.

12. The process as defined in claim 1, including forming holes in the crude mixture while in the molds in step (c) simultaneously with the heating of the crude mixture.

13. The process as defined in claim 2, wherein the accelerating agent and/or a retarding agent are added to the mixture in step (a) at the same elevated temperatures to which the crude mixture is subjected.

14. The process as defined in claim 13, wherein the temperature of the accelerating agent and/or retarding agent and the crude mixture are maintained constant. 15. A method for producing stones in constructing building walls, said method comprising the steps of:

(a) forming a pourable crude mixture including a foam, said crude mixture having a temperature wherein the temperature does not exceed the instability temperature of the foam, and which mixture is hardenable by chemical reaction of its ingredients to a final strength state, suitable for a construction stone, by a curing process, said crude mixture including water and foam and also including a cement adjusted by at least one agent so that strength forming reactions of the cement are initiated at an elevated temperatures of between 45°C and 90°C,

(b) pouring the crude mixture of step (a) into mold means,

(c) heating the crude mixture in the mold means to a temperature of between 45°C and 90°C--substantially without compacting the crude mixture--to start the strength forming reactions of the cement,

(d) subjecting the crude mixture in the mold means to said temperature of between 45°C and 90°C for 10 seconds to 5 minutes until the mixture in the mold means achieves a blank strength, due to strength forming reactions of said cement, substantially less than that of said final strength state but sufficient for the material to be removed from the mold means as blanks which retain the shape of the mold means after removal,

(e) removing the blanks from the mold means, and

(f) then curing the blanks to said final strength state. 16. The method defined in claim 15 wherein said at least one agent is an accelerating agent and/or a retarding agent for accelerating and/or

retarding said cement strength forming reactions. 17. The process defined in claim 15 wherein said crude mixture after being poured into said mold means is subjected to the elevated temperature of 45°C to 90°C for thirty seconds to one minute, the heating of the crude mixture being carried out by contact heating of the mold means. 18. The method defined in claim 15, wherein said crude mixture after being poured into said mold means is subjected to the elevated temperature of 45°C to 90°C for ten to sixty seconds, the heating of the crude mixture being carried out by applying a high frequency voltage to the molds. 19. The method defined in claim 15, including the step of gravimetrically measuring the volume of crude mixture added to the mold means and thereafter controlling the amount of water and foam added in step (a). 20. The method defined in claim 15, including slightly compressing said crude mixture after it is poured into said mold means in step (b) to achieve its intended volume. 21. The method defined in claim 15, wherein the foam included in said crude mixture in

step (a) has a bulk density of from 50 to 100 g/l. 22. The method defined in claim 21, wherein said foam is produced from a sulfated fatty alcohol. 23. The method defined in claim 15, wherein said foam contains CO₂. 24. The method defined in claim 16 wherein the accelerating agent and/or retarding agent are added to said crude mixture in step (a) depending upon the temperature of said crude mixture. 25. The method defined in claim 16 wherein the temperature of said crude mixture and of said accelerating agent and/or retarding agent added to said crude mixture is maintained constant.