DE1646962A1 - Process for the production of hydrothermally hardened sand-lime moldings - Google Patents

Description

Process for the production of hydrothermally hardened sand-lime moldings. -The invention relates to a process for the production of hydrothermally hardened lime sand moldings from a mixture of hydrated lime and silica-rich sand as well as water and optionally inorganic and / or organic fibers and a subsequent hydrothermal hardening under a saturated steam pressure of about '(0-20 atmospheres corresponding to temperatures of about "I'75 to 210 0 C.

Various methods are already known, sand-lime moldings by hydrothermal hardening of an intimate mixture of hydrated lime and / or cement and to produce sand and water. The general procedure here is that Lime hydrate and silicic acid-containing components together with large amounts of water intensively mixed and processed into a thin paste, which is then put into molds cast steam-hardened. Using window-grain sands and application of particularly intensive processing methods are fine-pored on this whiteness Light stones with densities of 0.3 to 1.2 g / cm3 and relatively high strengths have been produced, which are limited due to the porosity.

It has also been proposed to produce high-strength lime sand moldings from finely divided quartz, lime and possibly coarser aggregates through intensive mixing and subsequent compaction of the mixture by pressing, tamping or the like and hydrothermal hardening. The after. Moldings produced by this process have considerable strengths at densities of approximately: 1.9 to 2.1 g / cm3, namely. more than 2000 kp / cm2. Such strengths can only be achieved with high lime contents, and so the amount of calcium oxide used is about 25 to 30 j, based on the finely divided quartz sand. The setting of a specific volume weight takes place in the case of the lightweight moldings by varying the amount of water to be added, and in the case of the high-strength moldings by varying the amount of water used. Press pressure. In general, moldings with densities of up to 1.6 g / cm3 can be produced by varying the amount of water to be added and, if necessary, shaking or vibrating, while pressing or tamping is necessary to achieve higher densities. Surprisingly, it was found that sand-lime moldings with high strengths of 550 kp / cm2 up to 1200 kp / cm2 with densities of 1.0 to 1.65 g / cm3 can be produced by adding part of a mixture of hydrated lime and finely divided silica-containing Component as well as plenty of water wet-mechanically processed up to a significant increase in viscosity and another part of a dry-mechanically produced mixture of lime :. hydrate, finely divided silicic acid-containing component and optionally coarser aggregates is added in a precisely defined amount depending on the desired density of the final molded body and both parts are subjected to a further mixing process.

It has been shown to be: beneficial when the amount of Galcium :. Oxide in the wet-mechanically prepared mixture is about 45 percent by weight, based on the finely divided, silicic acid-containing component, and the amount of calcium oxide in the dry-mechanically-produced mixture is about 10-15 percent by weight, based on the finely divided, silicic acid-containing component, without taking into account coarser aggregates.

It is also advantageous to use 5-14 percent by weight of a coarserbu Additives, based on the finely divided, mechanically produced silicic acid Add mixture. The: designation "dry mechanically produced Mixture "does not exclude a certain, small addition of water. This should however, do not exceed 5 percent by weight, based on the total solids. -The total water content of the wet-mechanically and dry-mechanically produced Mixtures is advantageously about 20-45 percent by weight, based on the total Solids. Higher water contents lead to the formation of cracks in the hardened moldings. The setting of a specific volume weight is particularly advantageous in the following way: - First, through intensive mixing, a mixture of Lime hydrate and finely divided silica-containing components as well as water By changing the water content in this mixture, density can be between 0.3 and 1.2 g / cm3 can be set as desired, with the ratio of hydrated lime to finely divided, silicic acid-containing component is essentially constant and the weights per unit area relate to the moldings which are cured in an autoclave are obtained: A certain part of the wet-mechanically processed component is now a "dry mechanically" produced mixture of hydrated lime, sand, Pebbles (broken grain size 2 -? Mm) and water are added and with this-again mixed, the weight ratios of the individual components of this mixture be kept constant. From the amount of added, wet-mechanically processed Mixture and its water content can, within certain limits, depend on the density of the final molded body produced after the autoclave hardening. Details go from Example 1 and the .empirical up. put table. emerged.

Example Adjustment of a molding to a density of 1.6 @ g / cm3. White lime hydrate is intensively mixed with fine sand with a grain size of 0-00Ju and water for about 5 minutes in such a way that there is a "significant increase in viscosity. A centrifugal faceplate mixer with 1450 rpm was used, the peripheral speed of which was about 35 m / sec. fraud.

For the production of such a wet-mechanically processed. mixture 19'I g of fine sand, 200 g of white lime hydrate and 369 g of H2O are used in the manner indicated mixed. This mixture would be poured into molds and in a known manner Subjected to autoclave curing, moldings with a density of 0.8 g / cm3 result. At the same time, the following mixture is made in a conventional, low-speed mixer produced: 64 g fine sand _ 225 g white lime hydrate-893 g river sand 0 - 1 mm grain size 128 g broken pebbles 2 -? mm grain size 57 g water. The stirring time for this Mixing process took 5 minutes.

Now-35 percent by weight, based on both mixtures, will be intense Wet mechanically processed component with 65 percent by weight of the "dry mechanically" mixed component again a mixing process of 5 minutes duration in the low speed 1Vlischvorrichtung subjected.

The final mixture obtained in this way is used to cast moldings measuring 4 x 4 x 16 cm without shaking, tamping,: pressing or the like, which are cured directly in the autoclave at 20,000 corresponding to a saturated steam pressure of 15 atmospheres for 4 1/2 hours.

Prior storage or preheating is not necessary. Both the heating-up time and the blowing-off speed of the autoclave are 70 ° C./minute. The shaped bodies then removed from the autoclave are then dried in a drying cabinet at 105 ° C. for 4 hours. The density of the dried moldings was 1.58 g / cm3. The compressive strength and flexural strength were carried out 24 hours after the moldings had completely cooled down. The mean value from 6 tests resulted in a value of 984 kp / cm2 for the compressive strength and a value of 93 kp / cm2 for the flexural strength. DU determination of the compressive and flexural tensile strength was carried out in accordance with the standard specification in accordance with DIN 'I' (64.

The table below shows the setting of the density of the moldings obtained from the mixture produced by wet-mechanical and dry-mechanical means. The amount of wet mechanical mixture (A) which was added to the "dry mechanical" mixture (B) was in all "cases 35 percent by weight, based on both mixtures.

Despite the coarse aggregates contained therein, the molded bodies have an extraordinarily homogeneous structure that is free of cracks or visible forums is. The high strength of the moldings at the densities determined is likely on a very even distribution of the wet-mechanically processed components large specific surface in the dry mechanically produced mixture.

Of course, it is possible within the scope of the invention to type and Change the amount of the individual components of both mixtures. For example, can Grain size and grain structure of the finely divided, silica-containing sands used, Lime content, type and amount of the coarser aggregate, autoclave conditions, etc. to be changed.

In particular, it is also possible to carry out the wet technical processing in the complete absence of the finely dispersed, silicic acid-containing component. Furthermore, quicklime can also be used in place of hydrate, for example in the form of fine white lime, in the production of the wet mechanical mixture, whereby the additional water requirement for the extinguishing process must be taken into account accordingly of inorganic or organic fiber materials such as asbestos, glass fibers, cellulose fibers or the like. Advantageously Example 2 Adjustment of a molded grain to a density of 1.2 g / cm3: To produce the wet-mechanically processed mixture, 19% of fine sand, 200 g White lime hydrate and 930 g of H20 in the same way as in Example 1 mixed intensively. After curing in the autoclave, this mixture would result in moldings with a hem weight of 0.4 g / cm3.

At the same time, the same mixture as "in Example 1 was dry-mechanically and continue as in Example 1. The density of the dried Molded body was 1.22 g / cm3. The mean value from 6 tests resulted for the Compressive strength a value of 510 kp / cm2 and: a value for the flexural tensile strength of 49 kp / cm2.

Claims (9)

Claims: 1. Process: for the production of hydrothermally hardened lime sand moldings from a mixture of hydrated lime and silica-rich sand as well as water and optionally inorganic and / or organic fibers and a subsequent hydrothermal hardening under a steam pressure of: about 10-20 atmospheres, corresponding to = Temperatures of about 175 to 210 ° G, because chgeken: n -zeichn: e 't that part of a mixture of hydrated lime and finely divided, silica-containing component as well as plenty of water is wet-mechanically processed up to a significant increase in the viscosity of the mixture and another, Dry-mechanically produced mixture of hydrated lime, finely divided silicic acid-containing component and optionally, coarser additives in a precisely defined amount depending on the desired density of the final molded body is added - and both mixtures are subjected to a further mixing process. 2. The method according to claim 1, d a d u r c h, g- e: k e n n. = Z e i c h n e t that the amount of gallium oxide in the wet-mechanically processed mixture between 40 and 50 percent by weight, based on the finely divided silicic acid Component ,: is:. 3. The method according to claim 1 ', dadurchge k_ enn z. ei ch net that the amount of calcium oxide in the dry mechanically produced mixture is 6-20 percent by weight based on the finely divided, silicic acid-containing component 4. Procedure according to the. Claims 1 to 3, characterized in that the dry-mechanically produced mixture of 0-50% by weight of coarser aggregates, based on the finely divided, silicic acid-containing component, is added. 5. The method according to the preceding claims, since you rchgekennze ic hnet that the dry mechanically produced mixture 0 - 5 percent by weight of water, based on on total solids. . 6. Procedure according to the preceding Claims that the dry mechanical .Manufactured mixture mixed with inorganic and / or organic fibers will. 7. The method according to the preceding claims, d a d u r c h. g e k e n n z ei c h e t that the water content of the entire mixture is 15 - 45 percent by weight, based on the total solids, amounts to: 8 .. Method according to the preceding Claims that the peripheral speed of the mixer for wet mechanical processing is 20 - 40 m / sec: 9. Procedure after the previous. Claims. d a d u r c h e k e n n n z e i. c h n e t that the setting of the density of the finished sand-lime moldings at im essentially constant composition of the dry mechanically produced mixture by changing the water content in the wet mechanically processed mixture takes place: 10: Method according to the preceding claims, .d a d u r c h, g e k E n n n n e n g e n e t that: the wet mechanical treatment in the absence of the finely divided, Silica-containing component takes place. 11 ': method according to the preceding claims, D a d u r c h e k e n n n z e i c h n e t that in the wet mechanical treatment Quicklime, preferably white fine lime, is used.