DE19704066C2 - Use of a dry mix to produce a mortar compatible with waste material - Google Patents

Description

The invention relates to a dry mixture for producing an altmateri non-compatible mortar, preferably for use in the area of monument conservation and when renovating historic buildings, consisting of a binder and min at least a surcharge.

It is known from the results of various studies on historical mortars that that plaster mortar in the various building eras since the Middle Ages in Germany has also been used outdoors. The reason for its use is partly due to its favorable mortar properties. So z. B. no Delete or swamp required. Gypsum mortar is characterized by fast setting development, low shrinkage and the ability to recrystallize. Be ne use was also suggested by its occurrence. Where gypsum or anhydrite in large quantities, they are also as masonry, mortar means and mortar surcharge have been used, of which numerous objects in the southern Harz and testify in the Thuringian area. Some of these are historical, original Medieval mortar, including plasters, masonry mortar and core mortar, still in use today very good condition.

When renovating this gypsum-containing historical building structure, there are always problems that arise from the formation of propellant mineral (ettringite and / or thaumasite) when cement or hydraulic lime are used as renovation building materials. Because of this danger of driving, it is not permitted to bring hydraulic binders into contact with sulfate binders; In these cases, the use of conventional hydraulic binders with Al ₂ O ₃ contents <1% is ruled out for building renovation in the area of monument conservation and / or for the renovation of historic buildings.

This has not always been taken into account and was often recognized too late. So are recent Past mistakes in construction technology have been made, which resulted had that the lifespan of historic buildings had not been increased as intended on the contrary, through the use of highly hydraulic mortar in ignorance the decay of these buildings was accelerated. The cause of this misconduct is more or less in the general reservations of the Experts against the use of gypsum or anhydrite as a building material.

It is Z. B. known, screed gypsum and anhydrite binder from anhydrous anhydrite through Grinding or mixing with exciters, e.g. B. to produce quicklime. The Reservations against the use of these building materials may result. a. from the fact that plaster as Hardening product in contrast to cement or hydraulically hardening lime is soluble, d. H. it does not show the weather resistance of one outdoors highly hydraulic mortar. This also gave rise to the structural requirement, An hydritbinder not to be used on components that have a long-term effect are or may be exposed to moisture.

So the problem is, on the one hand, to find a building material that matches the histori building structure is compatible, but on the other hand it is sufficiently high Resistance to aging, so that the preservation of historical buildings in the long term is possible and economically justifiable.

US Pat. No. 3,954,492 describes a calcium sulfate anhydrite mortar. where the particle size of anhydrite in terms of feeding mechanical Energy is optimized. This ensures that the anhydrite particles in the mortar position activated under the influence of mechanical forces. The so made Among other things, mortar also has an improved general minimum durability on, but may be related to the preservation of historical buildings not sufficiently meet the requirements to be made.

DE 37 30 067 A1 describes a mortar mixture, the finely ground anhydrite and coarse-grained synthetic anhydrite and their outstanding properties is to level itself under the influence of gravity that before or after the mixture has hardened, no further action is taken Making a horizontal surface are required. So this is mortar well suited for the production of floors or similar flat surfaces. Dage Its use as exterior plastering mortar for the renovation of historic buildings is not sufficient  possible because mortar for the outdoor area wet or dry on vertical walls let spray on and stick there. Also the mortar described here in terms of its composition, not specifically related to the connection with a histori built structure.

In DD-PS 20 04 641 it is proposed in connection with the production of Anhydrite floating screed contains the component natural sand in whole or in part through crushed sand or to replace crushed sand or other crushed products. Hereby the The goal pursued, for example, the waste products of the crushed stone chippings industry a sensible len recycling. An improvement in durability when used in This does not result in a connection with historical buildings.

DD 269 295 A3 also describes a "process for the production of highly stressed, decorative screed floors and gypsum-based slabs " is a material in which hard plaster, i.e. commercially available plaster binder, as Binder is used. Take other mortars on the mortar described here Publications related, for example M. Steinbrecher: "Historical gypsum screed Flooring ", magazine architecture No. 6/90, publishing house for building and M. Steinbrecher "Gypsum screed and mortar: reviving old techniques", trade magazine for builders attitude, publisher P. Meininger, issue 10/1992, 8th year.

The mortar described here is primarily for the renovation of historic old buildings substance provided. With this mixture, the intention is to create historical mortar immediately understand. Since this mortar is based on hard-form plaster, are disadvantageous additives such. B. sodium citrate, required the hardening of the hard plaster of Paris retards what is involved in machine processing (dry or spray wet) is absolutely necessary.

The object of the invention is to provide a dry mix for producing a waste material compatible mortar, preferably for use in the area of monument conservation and in the renovation of historical buildings, which is the material basis of the Corresponds to the original building fabric and at least the weather resistance achieved that have the historical building materials.

According to the invention the object is achieved in that 1 part by weight of anhydrite binder and 0.5 to 3 parts by weight of pure gypsum / anhydrite crushed sand as an additive or 0.5 to 3 parts by weight of a mixture of gypsum / anhydrite crushed sand and quartz sand are provided as an additive as components of the dry mixture , the proportion of quartz sand in the batch being up to 60%. This creates an anhydrite-bonded mortar for outdoor use that is compatible with the historical building fabric and also has properties that are characterized by good workability (measured as a slump) and a favorable solidification behavior (measured as workability time). In addition, sufficiently high strength values (compressive, bending tensile and tensile strength) can be achieved after 28 days of storage in a normal climate, e.g. B. a compressive strength of <= 2 N / mm ² it is sufficient and also a favorable dynamic modulus of elasticity and a hy gric elongation in the range of 0.2 to 2 mm / m. If this mortar is protected from driving rain during processing and is not exposed to direct moistening in the plinth area or on the crowns of the walls, it will at least reach the service life of the historic building material to which it is connected during the renovation measure and also guarantees a durable and permanent connection the historical building material.

The dry mix is in the composition shown 1 part by weight of anhydrite binder and 0.5 to 3 parts by weight of the mentioned additives for application in dry spray suitable if the water binder value is 0.3, d. H. provided 1 kg the dry mortar component is mixed with 300 ml of water. When dry spraying process, the mortar components are dry (pneumatic) until spraying nozzle promoted. The water is added to the spray nozzle to the extent that one optimal sprayability guaranteed. In connection with the dry application spraying offers the dry mix proposed in this way the advantage of an increased Weather resistance.

An advantageous embodiment of the invention, in particular for the production of Au ßputzmörtel for wet spraying, is that as components of the Troc Mix 1 part by weight of anhydrite binder and 0.5 to 2 parts by weight of pure Gypsum / anhydrite crushed sand as an aggregate or 0.5 to 2 parts by mass of a mixture Gypsum / anhydrite crushed sand and quartz sand are provided as a supplement, the Share of quartz sand in the batch is up to 60%. This exterior plastering mortar is especially suitable for wet spray application. The mortar in a mortar mixer and mixed with the mixing water then using a pump on a spray nozzle with the addition of compressed air applied the wall. The water binder value in this application should be approx. 0.35.  

There is also a preferred embodiment of the invention in that 1 part by mass as components of the dry mixture Anhydrite binder and 1 to 3 parts by mass of pure gypsum / anhydrite crushed sand as Surcharge or 1 to 3 parts by weight of a mixture of gypsum / anhydrite crushed sand and Quartz sand is provided as a supplement, the proportion of quartz sand in the Ge amount is up to 60%. The water / binder ratio should be 0.5 in this case up to 0.55. This amount of water to be added corresponds approximately to a spread dimension of a = 12 cm.

The gypsum / anhydrite crushed sand should advantageously be in fractions from 0.25 mm to 4 mm should be provided, the sieve passages with a sieve hole width of 4 mm approx. 100%, with a screen hole width of 2 mm approx. 62%, with a screen hole width of 1 mm approx. 35% and with a screen hole size of 0.5 mm approx. 12%, each with a tole margin of ± 5% and based on the total weight of the plaster / Anhydrite crushed sand.

Furthermore, it is advantageous if the quartz sand provided in the surcharge is selected structural sand is provided in fractions of 0.125 mm to 4 mm, the Sieve passes with a sieve hole width of 4 mm approx. 100%, with a sieve hole width of 2 mm approx. 92%, with a sieve hole width of 1 mm approx. 80%, with a sieve hole width of 0.5 mm approx. 40%, and with a sieve hole size of 0.25 mm approx. 10%, each Weil with a tolerance of ± 5% and each based on the total weight of the ge washing construction sand.

The object of the invention is further achieved in that for the dry media as components 1 part by mass of anhydrite bandage medium and 1 to 3 parts by weight of gypsum / anhydrite chippings are provided as a supplement. Here this gives the advantage of further adaptation to the monument conservation requirements requirements and good compatibility with old materials. The gypsum / anhydrite grit should be provided with grain sizes of 0.2 mm to 8 mm.

The gypsum / anhydrite chips should be provided in fractions from 0.25 mm to 8 mm be, the sieve passes with a sieve hole size of 8 mm approx. 100%, with a Sieve hole width of 4 mm approx. 60%, with a sieve hole width of 2 mm approx. 38%, with a Sieve hole width of 1 mm approx. 20%, and with a sieve hole width of 0.5 mm approx. 8% conditions, each with a tolerance of ± 5% and based on the total weight of gypsum / anhydrite chips.  

From an economic point of view, it is advantageous if REA gypsum which has been thermally treated and provided with at least one exciter is used as the anhydrite binder. REA gypsum is to be understood as the gypsum that is formed during flue gas desulfurization. The thermal treatment of the REA gypsum takes place between 600 ° C and 700 ° C in rotary tube or fluidized bed furnaces. The anhydrite binder can be prepared from the anhydrous anhydrite by grinding or mixing with a salt-like exciter, such as K ₂ SO ₄ , or a basic exciter, such as Ca (OH) ₂ , or else with mixed exciters. The proportions of the exciters should be within the limits that are commonly used. The average chemical composition of the anhydrite binder should correspond to proportions of <92% CaSO ₄ , <2% SiO ₂ , <1% CaO _(free) and <0.01% Cl. By selecting the stimulators according to type and quantity, the time of bracing and early hardening can be influenced.

The invention will be explained in more detail below using an exemplary embodiment become. So be z. B. used to build the tower of a church gypsum / anhydrite rock and been connected with gypsum-containing grout. The original one Exterior plaster is weathered and it is necessary to further decay of the tower to prevent renovation of the masonry including the application of a make new exterior plaster.

The dry mix to be used for the plaster consists, for example, of 1 mass part of anhydrite binder, 1 part by weight of broken plaster / anhydrite sand and 0.5 Ma parts of quartz sand. The gypsum / anhydrite crushed sand in grain sizes of 0.2 mm to 4 mm and the quartz sand as washed construction sand with grain sizes of 0 mm admixed up to 2 mm.

The gypsum / anhydrite crushed sand is provided in fractions from 0.25 mm to 4 mm, with a sieve opening of 4 mm approx. 100%, with a Sieve hole width of 2 mm approx. 62%, with a sieve hole width of 1 mm approx. 35% and at one, sieve hole width of 0.5 mm is approx. 12%. The percentages are in each case based on the total weight of the gypsum / anhydrite crushed sand.

The quartz sand provided in the surcharge is a washed construction sand in fractions from 0.125 mm to 4 mm is provided, with the sieve passages in a sieve hole of 4 mm approx. 100%, with a sieve hole width of 2 mm approx. 92%, with a Sieve hole width of 1 mm approx. 80%, with a sieve hole width of 0.5 mm approx. 40%, and at  a sieve hole size of 0.25 mm is approximately 10%. The percentages are in each case based on the total weight of the washed construction sand. The percentage points of the individual sieve passes should neither for the gypsum / anhydrite crushed sand nor for the washed construction sand should not exceed a tolerance of ± 5%.

The plaster to be made from this is very good for application in the wet spray process suitable, provided that the aforementioned dry mix per 1 kg of dry mortar 350 ml of water can be added. The plaster applied in this way is very good compatible with the historical building fabric and shows at least the weather conditions durability of this old building substance.

Claims (5)

1. Use a dry mixture of 1 part by mass of anhydrite binder and

• a) 0.5 to 2 parts by weight of pure gypsum crushing sand and / or anhydrite crushing sand as a supplement or
• b) 0.5 to 2 parts by mass of a mixture of plaster crushed sand and / or anhy third crushed sand and up to 60% by weight quartz sand, based on the amount, as a surcharge

for the production of exterior plaster mortar for historical buildings. 2. Use of a dry mix according to claim 1, in which a gypsum crushing sand and / or anhydrite crushed sand used in fractions from 0.25 mm to 4 mm whose / its sieve passages with a sieve opening of 4 mm 100%, at a screen hole width of 2 mm 62%, with a screen hole width of 1 mm 35% and with a sieve hole width of 0.5 mm amount to 12%, each with a tolerance of ± 5% and in each case based on the total weight of the gypsum and / or anhydrite crushed sand. 3. Use of a dry mixture according to claim 1 or 2, in which a gewa shear construction sand used as quartz sand in fractions from 0.125 mm to 4 mm whose sieve passes with a sieve opening of 4 mm 100%, with a Sieve hole width of 2 mm 92%, with a sieve hole width of 1 mm 80%, with a Sieve hole width of 0.5 mm 40% and 10% for a sieve hole width of 0.25 mm wear, each with a tolerance of ± 5% and each based on the Ge total weight of the washed construction sand. 4. Use of a dry mixture according to one of the preceding claims, in which an anhydrite binder obtained by thermal treatment of an FGD gypsum is used, the at least one exciter in the form of a salt, such as K ₂ SO ₄ , and / or basic exciter, such as Ca. (OH) _{2 were} added. 5. Use of a dry mixture according to claim 4, in which an anhydrite binder is used, the average chemical composition of which is <92% CaSO ₄ , <2% SiO ₂ , <1% CaO _free and <0.01% Cl.