Drying accelerator for cement-based building materials

Abstract

A drying accelerator for a cement-based building material, consisting of an active component that consists to 1 to 100 wt.% of at least one compound selected from the group consisting of alkoxylated natural resins and alkoxylated synthetic resins and 0 to 99 wt.% of at least one plasticizer and optionally 0 to 50 wt.% of at least one defoaming agent, components a), b) and c) adding up to 100 wt.%. The building material additive accelerates extremely, when admixed to the mixing water of the binder or binder blend, the drying of concretes and cement-based binder blends.

Description

[0001] Drying accelerator for cement-based building materials

[0002] The invention relates to drying accelerators for cement-based building materials, wherein the building materials contain at least one substance selected from cement, lime, gypsum, and high-alumina cement. The invention further relates to the use of the drying accelerator and to building materials containing the drying accelerator.

[0003] Such building materials include, in particular, prefabricated concrete elements and precast concrete parts that are manufactured industrially, semi-industrially or manually and delivered to the construction site in finished form and installed there, site concrete, i.e. concrete that is first mixed on the construction site, brought to the installation point and dries and hardens at the installation point and from which, for example, plasters, screeds, backfills, levelling compounds or precast concrete parts are made, and ready-mixed concrete that is produced in a mixing plant and delivered to the construction site in liquid form in a transport mixer.

[0004] Concretes used to make the above-mentioned products are generally based on cement as an inorganic binder. These concretes may contain gypsum, high-alumina cement, and lime as additional binders in varying proportions. Aggregates such as gravel, sand, and crushed stone, as well as by-products such as ash, blast furnace slag, or silica dust, and additives are typically added to the concrete to improve, achieve, or avoid certain properties in the finished concrete or to optimize the mixing process.

[0005] The market demands the fastest possible production and further processing, or manufacture and installation, of these products. This is achieved by achieving the required strength and other technical properties. In addition to the minimum strength, further requirements may include the products remaining below a maximum permissible residual moisture content, as is particularly the case with screed. Residual moisture values ​​are defined for screeds to prevent damage caused by escaping moisture after the screed has been covered with tiles, floorboards, or parquet. A maximum permissible residual moisture content can be achieved more quickly through the use of drying accelerators. At the same time, the usual workflow in product manufacturing should remain unchanged or only slightly altered, and, if possible, the building material should be easier to process and manufacture.

[0006] The production and processing of concrete mixes for screed, precast elements, or ready-mixed concrete for floor slabs or wall elements has not changed fundamentally in recent years. Innovations are more evident in the area of ​​admixtures or additives than in concrete itself. An exception to this are fast-drying solid mixes, which, while also achieving the desired drying targets, are costly and can quickly cause processing problems if site conditions deviate from the processing specifications.

[0007] Surfactants can be used to facilitate processing and make the concrete flow smoothly. The disadvantage of surfactants is that they create air voids, which can reduce the density of, for example, a screed or precast concrete component to such an extent that the required minimum strengths can no longer be achieved. Products made from ready-mixed or site-mixed concrete often fail to achieve the required strengths. Surfactants can also inhibit drying and prevent the desired residual moisture content from being reached.

[0008] In order to achieve faster drying, the water content in cement-based mixtures can be reduced by using superplasticizers, but this can reduce the final strength considerably and during processing and drying, increased cracking and damage due to changes in the shrinkage behavior of the concrete can occur.

[0009] Additionally, laboratory tests have shown that while superplasticizers reduce the water content in the concrete mix, they do not necessarily lead to faster drying. This is because, although there is less water in the concrete, the water content is still above the required residual moisture content and has only a slight tendency to move out of the structure more quickly than a higher water content. When considering screed, superplasticizers require a smaller amount of water, but the water used still remains in the structure for too long, and readiness for covering is either not achieved or only slightly accelerated. As a result, a higher water content does not necessarily lead to shorter drying times and faster readiness for covering. Rather, the water must be encouraged to leave the structure, which is demonstrably achieved by the present invention.

[0010] In general, today's concretes dry faster, and screeds are ready for covering significantly sooner than they were 20 years ago. Under optimal conditions, residual moisture in the screed can reach no more than 3.5% by mass after 28 days or less. The drying time depends, among other things, on the screed's build-up height, the quality of the raw materials used, the amount of water used in production, and the ambient and material temperatures in conjunction with the relative humidity. Deviations from the optimal mixes and production processes, as well as climatic conditions during production, can easily lead to drying times of 90 days or far longer.

[0011] Newer developments promise readiness for flooring after three days under very specific conditions, which in reality are either impossible or only possible with considerable effort. These screeds and concretes must be applied extremely quickly and often with great effort (they can be applied in less than 45 minutes), and these systems are also very expensive. Therefore, they are only used in special cases (approximately 1% of all construction sites).

[0012] If accelerated drying is desired, this means faster drying of any type of concrete product than can currently be achieved under normal construction or production conditions. In the area of ​​screed construction, a readiness for covering under fifteen days is urgently sought. An even earlier readiness for covering after five to ten days would be optimal. At the same time, the costs for admixtures should only slightly increase the overall costs of the project. In the production of precast concrete elements, drying accelerators enable accelerated drying and thus more economical use of the required storage capacity and production facilities. In the area of ​​ready-mixed concrete, there are a very large number of applications, each based on a different recipe for the amount of water, binder, and aggregates.

[0013] The objective of the invention was therefore to develop a drying accelerator that significantly accelerates the drying of building materials. The moisture must be demonstrably released from the concrete and not masked by tolerated elevated measured values ​​or correction factors. Existing moisture must not be masked to the point where it is no longer detectable, as this approach only postpones the escape of moisture and the associated damage. Ideally, the residual moisture test should be performed according to the standard, ensuring that no elevated residual moisture values ​​require approval.

[0014] The drying accelerator should be easy to dose and incorporate into the binder mix. Precast concrete elements should be able to be removed from the formwork, transported, and installed more quickly, screeds should be ready for covering more quickly, and ready-mixed concrete should dry more quickly. The drying accelerator should be suitable for all types of concrete, especially screeds, leveling compounds, all types of backfill, and precast concrete elements.

[0015] The maximum permissible residual moisture content of concrete should be achieved in a shorter time than currently possible. Using a screed as an example, the goal was to reduce the residual moisture content to below 3.2% within 14 days in order to achieve "ready for covering," i.e., the point at which subsequent work on the dried screed can begin. In addition to accelerated drying, the screed must also achieve the flexural strength required by the standard. The remaining residual moisture content should be below 3.2%, the limit for screeds with underfloor heating. If no underfloor heating is installed, the limit is 3.5%.

[0016] Surprisingly, it has been found that a drying accelerator for cement-based building materials comprising an active component which contains the following substances: a) 1 to 100% by weight, in particular 2 to 60% by weight, preferably 10 to 40% by weight, of at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins, b) 0 to 99% by weight, in particular 40 to 98% by weight, preferably 60 to 90% by weight, of at least one superplasticizer and optionally c) 0 to 50% by weight, in particular 0 to 20% by weight, preferably 1 to 15% by weight, of at least one defoamer, the sum of components a), b) and c) being 100% by weight, achieves these objects and, when added to the mixing water of the binder or binder mix, extremely accelerates the drying of concretes and other cement-based binder mixtures depending on the composition.

[0017] The building materials contain at least one substance selected from cement, lime, gypsum, and high-alumina cement. The weight fraction of the drying accelerator in the mixture of building material and drying accelerator is preferably from 0.01 to 4.0 wt.%, in particular from 0.05 to 2.0 wt.%, particularly preferably from 0.1 to 1.0 wt.%.

[0018] In principle, the drying accelerator presented here is suitable for all cement-based building materials, including all ready-mixed concrete applications that contain cement as a binder and for which accelerated drying is desired or required.

[0019] Component a), which is a water-soluble solid, is preferably dissolved beforehand to simplify the preparation of a liquid drying accelerator. Component a) can be combined as a solid with the other components of the drying accelerator, and the mixture can be converted to a liquid state. Particularly preferably, component a) is first converted to the liquid state and then combined with the other ingredients to form the drying accelerator. A particularly preferred concentration is 20%.

[0020] It turns out that the drying effect is achieved in particular by component a). However, component a) tends to form air voids in aqueous solution. Air voids can lead to a reduced density and thus to a reduced strength of the dried concrete. To reduce the negative effect of air voids in the concrete structure, a defoamer can be added to prevent or reduce pore formation. For the same purpose, a superplasticizer can be added, which reduces the tendency towards foam formation. The use of superplasticizers does not necessarily eliminate foam formation, but it can reduce it. Foam formation must be reduced in such a way that the remaining foam does not negatively affect the quality of the end product. The desired residual moisture content and other required properties must be achieved.At the same time, the flow agent used can reduce the water requirement of the overall mixture, which supports the drying process. It is important to note that the flow agent alone does not provide sufficient drying; rather, in combination with component a), it supports its drying-accelerating effect.

[0021] Only component a) alone, components a) and b) or a) and c) together, and the three components a), b), and c) always dry faster than a base sample. However, the drying effect of component a) is the factor that drives the residual moisture content below the desired limit. Component b) allows for reduced water usage, which further reduces the remaining drying time, but component b) alone does not reduce the water content of the concrete mix below the desired limit, as the water used still remains in the system for too long and the desired drying value is not achieved. Otherwise, experiments in the past with the simple addition of a superplasticizer would have been successful, and the issue of accelerating drying would no longer exist. The active component of the drying accelerator therefore preferably contains components a) and b) or components a) and c), particularly preferably all three components a), b), and c).

[0022] In principle, any defoamer is suitable for reducing the foaming tendency of a), however, silicone-based defoamers are less suitable because they reduce concrete strength. Also less suitable, but usable, are defoamers that are only stable within certain temperature ranges, those that are not frost-resistant, or those that require a pH value that differs from the strongly alkaline environment of cement-based binders. Therefore, polymer-based defoamers that possess the aforementioned properties are particularly preferred.

[0023] The term "cement-based building material" means that it is a building material mix, i.e. a mixture of binder, gravel and water, in which the binder consists of at least 50 wt.%, in particular at least 60 wt.% and particularly preferably at least 70 wt.% cement, while other binders such as gypsum, lime or high-alumina cement are present in a total of a maximum of 49 wt.%, in particular a maximum of 40 wt.% and particularly preferably a maximum of 30 wt. The binder particularly preferably has a CEM I according to DIN EN 197, as this more reliably achieves the required strengths. Screeds provided with the drying accelerator according to the invention are ready for covering after five to eighteen days, depending on the formulation of the drying accelerator and the selected concrete or screed.The maximum residual moisture content is sustainably below the maximum, the water is demonstrably released from the system, and no harmful resorption occurs. The addition of additional additives or other aids to achieve accelerated drying is not necessary. It should be noted that local conditions strongly influence the drying process. Drying only occurs when moisture can be released into the ambient air. If this air is saturated and not exchanged, drying ceases until fresh air with sufficient capacity to absorb moisture reaches the concrete surface.

[0024] Concrete treated with the drying accelerator according to the invention, especially screeds and concrete that requires compaction, is often considerably easier to work with. However, this effect depends heavily on the chosen formulation.

[0025] The drying accelerator causes accelerated drying of the binder mixture, during which:

[0026] 1. the mixing water used is demonstrably escaping, but

[0027] 2. at the same time, the amount of water sufficient for hydration remains in the binder mix and

[0028] 3. no harmful absorption occurs.

[0029] Fundamentally, it is important to question whether the amount of water reduced by the drying accelerator is sufficient for hydration, or whether the amount of water required for hydration is not reached, resulting in the resulting concrete not achieving the required strength, thus failing to meet the required minimum strengths. However, the opposite is true. By using the drying accelerator according to the invention, higher strength values ​​can be achieved with the same amount of binder than without the drying accelerator.

[0030] It's also important that the drying accelerator, thanks to its superplasticizer content, reduces the water requirement of a concrete mix. The example of screed demonstrates that the water requirement can be significantly reduced during screed preparation in the screed mixer. With a mixer volume of 200 liters, the water requirement for a CTF4 screed is up to 34 liters. Depending on the type and moisture content of the gravel and cement used, this water requirement can be reduced by 10-75%.

[0031] The present invention has a broad range of applications. The drying accelerator can be used in concrete containing cement as a binder, preferably cement of standard class CEM I or a binder mixture containing cement, lime, gypsum, high-alumina cement, or a mixture thereof. Portland cement is always present in at least 50% by weight, thus making it a cement-based building material. The number of products and their variants that can be produced with accelerated drying using these binders and the drying accelerator according to the invention is wide. Thus, the drying accelerator can be used in the manufacture of all the products mentioned above:

[0032] Such building materials include in particular

[0033] 1. prefabricated precast concrete elements and precast concrete components that are manufactured industrially, semi-industrially or manually and are delivered to the construction site in their finished form and installed there, e.g. prefabricated elements for house construction or sewerage construction, railway sleepers, curbstones, customised or standardised prefabricated elements, and exposed concrete elements, to name just a few;

[0034] 2. Site concrete, i.e. concrete that is first mixed on the construction site, transported to the installation site, and dries and hardens (hydrates) there, e.g. floor slabs, ceiling slabs, formwork fillings, plasters, screeds, backfills, leveling compounds, exposed concrete elements;

[0035] 3. Ready-mixed concrete, which is produced in a mixing plant and delivered to the construction site in liquid form in a transport mixer and from which, for example, the products mentioned under 1. and 2. are manufactured on site;

[0036] 4. Cement-based flow screeds. Concretes used to make the products listed under 1. to 4. are generally based on cement as an inorganic binder. These concretes can, in a particularly suitable manner, contain gypsum, high-alumina cement, and lime in varying proportions as additional binders in the binder mix. Aggregates such as gravel, sand, and crushed stone, by-products such as ash, blast furnace slag, or silica dust, and chemical additives are typically added to the concrete to improve, achieve, or avoid certain properties in the finished concrete, or to optimize the mixing process.

[0037] The drying accelerator according to the invention offers another relevant advantage, particularly for use in screeds. A major problem in screed production is the formation of cracks, as well as what is known as "cupping." Cracks are caused by the shrinkage behavior of concrete / screed. Screed is typically divided into three different shrinkage classes, which provide information about the extent to which the screed shrinks. As is known to those skilled in the art, standard screed shrinks by up to 10 mm per meter. For a screed containing the additive according to the invention, shrinkage is less than 0.5 mm, placing it in shrinkage class 2, "reduced shrinkage."

[0038] The shrinkage behavior can also be used to determine the extent to which a screed is prone to cracking. A screed of shrinkage class 1 should not exhibit any cracking, but cracks cannot be ruled out in screeds of shrinkage classes 2 and 3. Surprisingly, it was found that in concrete treated with the drying accelerator according to the invention, particularly in screeds, significantly fewer cracks form, or cracking can even be completely avoided. This applies not only to screeds of shrinkage class 1, but also to screeds of shrinkage classes 2 and 3. Although cracks usually occur in conventional screeds of shrinkage classes 2 and 3, this is not the case for screeds containing the drying accelerator according to the invention.

[0039] “Bowling” is the term used to describe the problem that arises because screed dries at different speeds across its cross-section, i.e. it is moister at the bottom than at the top during the drying process and drying takes place more slowly near the walls than in the middle of the room. These effects lead to the screed behaving like a “bimetal” and “pulling up” at the corners and walls, which in turn causes the screed to be higher at the edges than in the middle. The resulting appearance resembles a bowl, which is why the upward bending of the screed is referred to as “bowling”. Also surprisingly, it was found that in concrete treated with the drying accelerator according to the invention, especially in screeds, there is a significantly lower tendency to bowling, and that bowling can even be prevented completely.Due to the uniform drying of the screed caused by the drying accelerator according to the invention, upward bending of the screed is avoided.

[0040] Another problem when working with cement-based building materials, particularly screed, is absorption. Even when the screed has reached the desired degree of drying, the water content in the screed may increase again if it is exposed to increased humidity for a certain period of time. This is highly undesirable, as the previously achieved readiness for flooring may subsequently no longer be achieved. This severely limits the time at which a screed can be covered with a floor covering. This, in turn, leads to unnecessary restrictions in work planning on construction sites, as, for example, the date for applying the floor covering cannot simply be postponed for a few days and the screed usually requires extensive drying.Surprisingly, it was found that in concrete treated with the drying accelerator according to the invention, especially in screeds, water absorption in the screed can be significantly reduced or even completely eliminated. Therefore, even a subsequent increase in air humidity in a room with dried screed is unproblematic when using the drying accelerator according to the invention. It not only accelerates drying but also ensures that water absorption is significantly reduced or even eliminated. When using the drying accelerator according to the invention, the natural water absorption due to increased air humidity does not lead to the limit values ​​for maximum residual moisture being exceeded.

[0041] Another relevant factor for the quality of a screed is its strength. After 28 days, an F4 screed must reach a certain standardized strength (> 4 N / mm 2). Surprisingly, it was found that a screed containing the drying accelerator according to the invention regularly exceeds the required strength values ​​of classes F4 to F7 by at least 20% compared to a screed without the drying accelerator. An increase in strength is already achieved by a drying accelerator which only contains component a) as the active component. A strength increase of at least 8% is achieved. The increase in strength is further increased if both component a) and component b) are included as the active component. A strength increase of at least 20% is achieved. Thus, with the drying accelerator according to the invention it is possible for an F4 screed to achieve strength class F5. Comparable increases in strength are also achieved in the other strength classes.

[0042] As component a), alkoxylated natural resins and synthetic resins, propoxylated or, in particular, ethoxylated natural resins and synthetic resins, are particularly preferably used for the drying accelerator according to the invention. Ethoxylated natural resins are very particularly preferred.

[0043] The drying accelerator preferably contains at most 80% by weight, more preferably at most 60% by weight and most preferably at most 40% by weight of at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins.

[0044] Furthermore, the drying accelerator preferably contains at least 20% by weight, further preferably at least 30% by weight, in particular at least 40% by weight, very particularly preferably at least 50% by weight and in particular at least 60% by weight of at least one flow agent.

[0045] The flow agent is preferably at least one compound selected from the group consisting of polycarboxylate ethers, polyaryl ethers, naphthalenesulfonate, ligninsulfonate, and melaminesulfonate, with polycarboxylate ethers and polyaryl ethers being particularly preferred and enabling particularly rapid drying. Polycarboxylate ethers are preferably used as flow agents, particularly variants or mixed forms that reduce water consumption while maintaining the same viscosity. Examples of polycarboxylate ether flow agents that possess these properties are MelFlux 239 from BASF or products from the MasterGlenium series from MASTER BUILDERS SOLUTIONS. The selection of manufacturers and products is extensive.

[0046] Examples of consistency-preserving superplasticizers include products from the MasterEase range from MASTER BUILDERS SOLUTIONS, melamine-based superplasticizers, and the VZ series retarders from SIKA. Here, too, the selection of manufacturers and products is extensive.

[0047] For the at least one defoamer, a proportion of at most 40 wt.%, preferably at most 30 wt.%, particularly preferably at most 20 wt.%, in particular at most 15 wt.% is particularly advantageous. It should be noted that this applies to the concentration of the active ingredient, so that with diluted defoamers, higher application quantities are also possible due to the water content of the active ingredient-water mixture.

[0048] The active component of the drying accelerator particularly preferably contains a) 1 to 60% by weight, in particular 5 to 40% by weight, preferably 10 to 30% by weight, of at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins, b) 40 to 99% by weight, in particular 60 to 95% by weight, preferably 70 to 90% by weight, of at least one flow agent and optionally c) 0 to 50% by weight, in particular 0 to 20% by weight, preferably 1 to 15% by weight of at least one defoamer, the sum of components a), b) and c) being 100% by weight.

[0049] As described above, component b) further reduces the drying time already reduced by component a) and also provides an even further increase in strength.

[0050] Most preferably, the active component of the drying accelerator contains a) 5 to 40% by weight, in particular 10 to 30% by weight, of at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins, and b) 60 to 95% by weight, in particular 70 to 90% by weight, of at least one flow agent, the sum of components a) and b) being 100% by weight.

[0051] It therefore contains only components a) and b). A weight fraction of at least 60 wt.%, preferably at least 70 wt.%, in particular at least 80 wt.% of at least one flow agent is particularly preferred.

[0052] Such a composition ensures particularly rapid drying of the building material. At the same time, good workability is possible if the composition of components a) and b) is chosen accordingly.

[0053] Superplasticizers differ primarily in their effect on concrete. They can either allow a reduction in the amount of water used while maintaining the same viscosity, or they can allow for longer processing of the concrete, thus delaying curing, or they can offer a combination of both properties. All three variants can be used within the scope of this invention. This also applies to mixed forms in which several superplasticizers are used simultaneously. However, the variants that save water are preferred, since a reduced amount of water in combination with component a) further accelerates drying.

[0054] Particularly suitable flow agents in the context of this invention are flow agents based on naphthalenesulfonate, ligninsulfonate, melaminesulfonate, polyarylether (PAE) or polycarboxylateether (PCE).

[0055] Component a) is a natural or synthetic resin that becomes water-soluble through chemical adaptation. For this purpose, the resin is alkoxylated, preferably ethoxylated. Ethoxylation is the addition of ethylene oxide (oxirane) to the resin. The process is well known to those skilled in the art.

[0056] Possible synthetic resins that can be used for the present invention are phenolic resins, epoxy resins, polyester resins, acrylonitrile butadiene styrene resins (ABS resins), polyacrylates, alkyd resins, polyurethane resins, polyamide resins, vinyl ester resins and furan resins.

[0057] Component a) is preferably a natural resin, preferably gum resin, which becomes water-soluble through chemical adaptation. For this purpose, the natural resin is alkoxylated, especially propoxylated or ethoxylated. Ethoxylation is the addition of ethylene oxide (oxirane) to the resin. The process is well known to those skilled in the art. For the purposes of the present invention, the ethoxylated variant is particularly preferred.

[0058] The degree of ethoxylation of the resin varies depending on the resin chosen. For the purposes of this invention, any degree of ethoxylation that makes the selected resin water-soluble is sufficient. Balsam resin with an ethoxylation degree of 30-80 mol, such as the product U-Flakes from LEVACO, is particularly preferred.

[0059] Particularly preferred natural resins are tall oil, wood resin, balsam resin, resins known as rosin, and adducts of maleic acid. Other preferred compounds as component a) are diterpenic and triterpenic acids and their soaps (especially potassium and sodium soaps). Particularly preferred diterpenic acids are abietanes, especially abietic acid, neoabietic acid, levopimaric acid, palustric acid, and dehydroabietic acid, as well as pimarans and isopimarans, especially pimaric acid, sandaracopimaric acid, and podocarpic acid, and labdanes, especially copalic acid, eperueic acid, labdanolic acid, polyalthic acid, and pinifolic acid. Among the triterpenic acids, the following substances are particularly preferred: dammarolic acid, tirucallanes, in particular (iso)-masticadienoic acid, elemolic acid and elemonic acid, oleananes, in particular oleanonic acid, oleanolic acid, moronic acid and α-boswellic acid, llrsanes, in particular ursolic acid, ursonic acid and β-boswellic acid as well as the lupane lupeolic acid.The aromatic acids cinnamic acid and benzoic acid as well as their benzyl and other esters are also particularly suitable.

[0060] Particularly preferred as component a) is the use of ethoxylated balsam resin, such as the product U-Flakes from LEVACO.

[0061] The defoamer (component c) can be selected from a vast array of possible defoamers. Available types of defoamers include silicone, polymer, and mineral oil-based defoamers. Silicone-based defoamers are available as concentrates, emulsions, powders, or solutions. Polymer-based defoamers can be in the form of concentrates, emulsions, or solutions. Mineral oil-based defoamers are available as concentrates or emulsions. In principle, individual variants can also be provided as freeze-dried powders. The vast majority of variants are suitable for the present invention because they eliminate the air voids created by components a and b. Differences are as follows: A- In efficiency:

[0062] In the amount to be used to sufficiently eliminate the air voids created during the mixing process.

[0063] B- In compatibility with the binder:

[0064] Incompatibility is demonstrated by the fact that the 28-day strength of the manufactured test specimens does not reach the required minimum strength and the test specimens have a lower strength than the zero sample.

[0065] C- Temperature sensitivity:

[0066] The drying accelerator produced is not frost-resistant. It either loses its effectiveness completely after exposure to frost or requires extensive heating to reactivate it.

[0067] Silicone-based defoamers weaken the concrete structure and reduce its final strength, as silicone, as experts know, inhibits crystal formation in concrete. The use of silicone-based defoamers is possible, but only makes sense if the required minimum concrete strengths are reliably achieved in the final product. In screeds, this would lead to increased use of cement in the production process, which is why silicone-based defoamers are less suitable. Their use is advisable when the drying accelerator must be added as a powder.

[0068] Newly developed polymer-based defoamers are no longer temperature-sensitive. The previously known disadvantages of these defoamers no longer apply, which is why they are preferable to oil-based defoamers.

[0069] Previous polymer-based defoamers had the following disadvantages: At low temperatures, frost damage can occur, which can necessitate laborious heating of the drying accelerator. Often, frost damage is irreversible; the drying accelerator loses its effectiveness altogether, and the drying accelerator must be disposed of. At excessively high temperatures, the defoamer in the drying accelerator can at least partially lose its effectiveness and must be disposed of at great expense. As mentioned, these disadvantages no longer exist in the latest versions of these defoamers, which is why they are the particularly preferred solution. A good solution for the present invention are mineral oil-based defoamers, which can also be frost-sensitive, but any reduction in effectiveness due to frost is usually reversible. High temperatures (>35 °C) are usually not a problem.

[0070] The following table provides an overview

[0071] Defoamers

[0072] Defoamer variants and their drying effect in conjunction with components a and b compared to the O-sample

[0073] For the purposes of the present invention, polymer-based defoamers are preferred provided they are insensitive to frost and stable to temperatures above 40°C. All tested variants fulfill the purpose and remove the air voids from an aqueous solution of components a and b. One product example of a polymer-based defoamer is ESCA NP01 from KCC BASILDON. Polydimethylsiloxane and silicone mixtures are also suitable as defoamers, although the molecular weight Mw does not appear to play a role here. Product examples are Dispelair 392 from BCD Chemie, Hamburg, or Hoesch FDP from Hoesch Chemie, Düren, which deliver comparable drying results to oil-based defoamers but may exhibit weaknesses in final strengths after 28 days. Tri-n-butyl phosphate and triisobutyl phosphate are also very suitable compounds as defoamers.The substances mentioned are particularly well able to destroy or neutralise the air pores formed by components a) and b) which can impair the stability of the building material.

[0074] The drying acceleration effect is achieved by the composition according to the invention. Therefore, the composition according to the invention preferably contains exclusively components a) to c) as described in claim 1. However, other compounds may also be added to the composition according to the invention without this departing from the scope of the present invention.

[0075] In particular, the active components can be used in conjunction with other building material additives. Thus, a combined product can further contain a salt, a pH adjuster, an antioxidant, and / or a preservative. A combined product can therefore optionally comprise other components commonly used in the field of concrete and screeds, such as salts such as calcium nitrate, pH adjusters, antioxidants, or preservatives. The total proportion of such optional additional components, if present, is preferably no more than 35% by weight, more preferably no more than 10% by weight, of the sum of the weight proportions of the active component and other additives.

[0076] The drying accelerator can be added to the binder mix as a powder without any additional additives. If the drying accelerator is in powder or other dry form, it can be added to the cement powder or any other component of the concrete. A preferred method for producing the drying accelerator as a powder is freeze-drying.

[0077] The drying accelerator is preferably added to the binder mix as a liquid, with the active ingredient dissolved in water as an auxiliary agent, so that it is preferably present as an aqueous liquid drying accelerator. This enables particularly simple dosing. The water content is particularly advantageously 0.1 to 90 wt. %, preferably 15 to 80 wt. %, in particular 30 to 60 wt. %, based on the total drying accelerator. The drying accelerator can therefore be present as a pure (active ingredient) component and thus be highly dosed. The concentration of components a, b, and c can be 100% here, whereby component a) should be dissolved in water beforehand.

[0078] If the drying accelerator is added to the mixing water on the construction site, the concentration of the drying accelerator in the mixing water and thus in the overall mixture is considerably lower. This results in only between 0.1 and 0.4% drying accelerator per liter of water. Depending on the selected water content in the building material, this value can vary considerably. Even at this concentration, the drying accelerator is fully effective, although the drying time may be longer due to the increased water content.

[0079] The liquid drying accelerator can be added to the mixing water or to any component of the concrete. However, it is preferred to add it to the mixing water, as it then disperses more quickly throughout the overall mix.

[0080] The drying accelerator can also be present in intermediate forms that are neither solid nor liquid, i.e. as a gel or viscous mass.

[0081] The drying accelerator can also be produced and used as a dry solid, as a powder, or in any other non-liquid form. This option is not particularly advantageous for practical reasons. For this purpose, the components can be freeze-dried, which advantageously increases water solubility, or solid or powder versions of components a, b, and c can be selected and added as a mixture to the mixing water.

[0082] The drying accelerator is preferably added to the solid mix in the mixing water in such an amount that the total mixture consisting of solid mix and mixing water contains from 0.01 wt.% to 4 wt.%, in particular from 0.05 to 2.0 wt.%, particularly preferably from 0.1 to 1 wt.%. The required amount of drying accelerator should be selected proportionally to the amount of cement used, but is influenced by factors such as cement quality, grinding fineness of the cement as well as the type and quality of the selected aggregates such as gravel and crushed stone and the type and quality of the admixtures in the cement. A further influencing factor is the addition of chemical additives, which, in interaction with the drying accelerator, can have an additional effect on the drying process.

[0083] The amount of water added to a binder mix varies greatly depending on the concrete application, with the addition rate to the binder mix preferably being selected so that the weight ratio of water to cement (w / c) is in the range of 0.2 to 0.8, preferably 0.25 to 0.75, and particularly preferably 0.35 to 0.7. An additional addition of superplasticizers is possible to further reduce the water content or extend the processing time, but is not always advisable, as the additional addition of superplasticizers can have a negative impact on drying, on the overall solid mixture, or on the final product.

[0084] The invention further relates to the use of the drying accelerator to accelerate the drying process in building materials, wherein the building materials contain at least one substance selected from cement, lime, gypsum, and high-alumina cement. The weight fraction of the drying accelerator in the mixture of building material and drying accelerator is in particular from 0.01 wt.% to 4 wt.%, preferably from 0.05 to 2.0 wt.%, particularly preferably from 0.1 to 1 wt.%.

[0085] As described above, one problem with the processing of cement-based building materials, especially screed, is resorption, i.e., the subsequent increase in the water content of the screed when exposed to elevated humidity for a certain period of time. This is, as described, highly undesirable, as the previously achieved readiness for covering may subsequently be lost.

[0086] Surprisingly, it has been found that in concrete provided with the drying accelerator according to the invention, particularly in screeds, the resorption of water into the screed can be significantly reduced or even completely prevented. The present invention therefore also relates to the use of the drying accelerator according to the invention to reduce or prevent the resorption of water into the building material. Even a subsequent increase in air humidity in a room with dried screed is therefore unproblematic if the drying accelerator according to the invention is used. Not only is drying accelerated, but water resorption is also greatly reduced or even eliminated. The natural absorption and release of moisture by the screed or concrete with varying air humidity is maintained.However, with the drying accelerator according to the invention, this does not accumulate to such an extent that the limit values ​​for residual moisture are exceeded again.

[0087] As also described above, another relevant factor for the quality of a screed is its strength. Surprisingly, it was found that a screed containing the drying accelerator according to the invention regularly exceeds the required strength values ​​of classes F4 to F7 by at least 20% compared to a screed without the drying accelerator. The present invention therefore also relates to the use of the drying accelerator according to the invention to increase the strength of the building material. At a given point in time, the strength of a screed containing the drying accelerator according to the invention is approximately 20% higher than that of a screed without the drying accelerator.

[0088] All preferred embodiments described above for the drying accelerator apply individually and in any combination for the uses described.

[0089] The drying accelerator may be used for only one of the uses described above or for any combination of the uses described, including all uses.

[0090] Furthermore, the present invention relates to building materials containing the drying accelerator, wherein the building material contains at least one substance selected from cement, lime, gypsum, and high-alumina cement. The building material is, in particular, a prefabricated precast concrete element, a precast concrete component, a site-mixed concrete, a ready-mixed concrete, a screed, in particular a flowing screed, a plaster, or a backfill.

[0091] In a preferred embodiment, the drying accelerator is contained in the building material as a solid, in particular in powder form. Most preferably, the drying accelerator is contained in freeze-dried form. In another preferred embodiment, the drying accelerator is added to the building material in a pasty or gel-like consistency. The drying accelerator is particularly preferably added to the building material as a liquid, dissolved in water as an auxiliary agent, so that it is preferably present as an aqueous liquid drying accelerator. This enables particularly simple dosing. The water content is particularly advantageously 0.1 to 90 wt. %, preferably 15 to 80 wt. %, in particular 30 to 60 wt. %, based on the total drying accelerator, i.e., the sum of the active ingredient component(s), any additives, and auxiliary agent(s).

[0092] In addition to the components mentioned, the building material may contain other common additives. Examples include corrosion inhibitors, shrinkage reducers, pigments, or other chemical additives to optimize the performance of the final product or processing, but their proportion generally does not exceed 10%.

[0093] All preferred embodiments described above for the drying accelerator also apply to the building material according to the invention.

[0094] The present invention is particularly suitable for screeds, since the drying time, the residual moisture content achieved, the processing effort and the strength development are often particularly important for screeds.

[0095] A process for producing a cement screed comprises the following steps:

[0096] I) mixing all components comprising cement, aggregate, water and the drying accelerator according to the invention to obtain a screed mixture,

[0097] II) distributing the screed mixture into the desired shape / on the application area and

[0098] III) drying / curing of the screed mixture.

[0099] In the first step of the process, components comprising cement, aggregate, water, and the drying accelerator according to the invention are mixed to obtain a screed mixture. To obtain an F4 screed according to the invention (F4 stands for flexural strength after 28 days of at least 4.0 N / mm 2 or more) are per m 3The following quantities are required: 270 kg of cement (preferably Portland cement Cem I), 1705 kg of gravel, 170.1 kg of water, and 1.5 kg of drying accelerator. The amount of water added can vary depending on the moisture content of the gravel. The order in which the components are mixed is arbitrary. However, the drying accelerator is preferably added to the water. The usual mixing instructions for producing such cement mixtures must be followed.

[0100] As is generally known, cement is an inorganic, hydraulic binder. When water is added, hydrates form from the cement clinker phases, binding the water and causing the cement paste to solidify or harden, forming the solid cement paste or cement product. The cement preferably comprises Portland cement. To produce cement, clinker or cement clinker is finely ground, either alone or with other main components and / or up to 5% by weight of minor components. Calcium sulfate (in the form of FGD gypsum and / or anhydrite) is also added to control setting.

[0101] Latently hydraulic and / or pozzolanic and / or inert additives can be added as further main constituents and / or minor constituents for the production of the cement. Examples are ground granulated blast furnace slag, pozzolans such as tempered phonolite or trass, fly ash, burnt oil shale, limestone powder and silica fume. Cements are classified according to their composition. Different, partly country-specific standards exist for this, e.g. DIN EN 197-1, in which the cements are classified according to the proportion of cement clinker and, if present, the type and quantity of other constituents. The additive according to the invention is suitable for all types of cement, in particular for Portland cement and Portland composite cements which, in addition to Portland cement, comprise, for example, at least one other main constituent selected from ground granulated blast furnace slag, silica fume, pozzolans, fly ash, burnt oil shale or limestone. Portland composite cements are preferred for screeds.

[0102] According to the classification in DIN EN 197-1, the preferred cement is CEM I (Portland cement) or CEM II (Portland composite cement). CEM I and CEM II / A or CEM II / B cements with limestone powder of class 42.5 R or 42.5 N are particularly suitable for screeds. Of course, cement types classified according to other standards are also suitable.

[0103] Depending on the application, the binder mix may contain alumina cement.

[0104] Although high-alumina cement is expensive, it aids the curing of Portland cement. This can occur so quickly that the solid mix must be slowed down to remain workable. Portland / high-alumina cement sometimes shrinks significantly. The drying speed and shrinkage make high-alumina cement an unsuitable component of a screed, but other applications may prefer this combination. Even in screeds, the binder mix used can contain small amounts of high-alumina cement, with no more than 5% by weight, preferably no more than 1% by weight, based on the total weight of the binder mix being high-alumina cement, although, as mentioned, this is not preferred.

[0105] Common materials can be used as aggregate, such as round or crushed sand and / or gravel, with aggregates up to 8 mm being preferred. A screed mix, for example, can contain a maximum grain size of up to 4 mm, or a concrete mix up to 8 mm. Screeds are applied to all types of floors to provide a solid, level base. The screed mix is ​​preferably not a self-leveling screed.

[0106] Examples

[0107] Test methods:

[0108] To ensure the determination of the actual residual moisture content, only the two test methods according to DIN EN 18560 Part 1 are used. Especially when using Method 1, this ensures that the actual residual moisture content is determined, provided the drying temperature is set at 105 °C, the drying process is not interrupted prematurely, and is maintained throughout the drying process. A lower temperature leaves moisture in the tested material.

[0109] Test method 1 (humidity measurement):

[0110] Gravimetric moisture measurement according to DIN EN 18560 Part 1 (also known as kiln drying). A sample of the prepared sample mixture is taken and the non-chemically bound moisture is extracted at 105 °C. The difference between the initial weight and the final weight at constant weight is divided by the final weight to determine the residual moisture content in %.

[0111] Test method 2 (humidity measurement):

[0112] Calcium carbide method (CM method). Standardized test kits are available for commercially available CM measurements. These test kits contain all the components required for the test, including the test container in which the calcium carbide is added to the screed to be tested. This container is also colloquially called a CM bottle.

[0113] Procedure for a CM measurement: A screed sample is taken and placed in the test container. Steel balls and glass ampoules filled with calcium carbide are added. The test container is then shaken, releasing the calcium carbide. The residual water in the sample reacts with the calcium carbide and releases a gas. The gas pressure created by the gas is measured, and the residual moisture content is determined from this.

[0114] According to DIN EN 18560, other methods for determining residual moisture are not permitted.

[0115] Test method 3 (measurement of flexural strength):

[0116] To determine strength, the flexural tensile strength is measured. The flexural tensile strength is determined as described in DIN 18560-2:2022-08 and EN 13892-2:2002 (D). The flexural tensile strengths are expressed in N / mm 2 specified.

[0117] Test method 4 (shrinkage / cracking):

[0118] The tendency to crack formation is derived from the shrinkage behavior of a concrete / screed. As experts know, standard screed shrinks by up to 10 mm per meter. Shrinkage is measured in a shrinkage channel according to DIN EN 13892-9. The screed is placed in the channel at a specified length, width, and height, and the shrinkage (shortening in length) is measured over the drying process. For a screed containing an additive according to the invention, shrinkage is less than 0.5 mm, and it falls into the "reduced shrinkage" shrinkage class.

[0119] Drying accelerator (all information per kg)

[0120] Drying accelerator variant 1:

[0121] 4.0% ethoxylated resin (U-Flakes / LEVACO)

[0122] 20% PCE superplasticizer 239 from BASF

[0123] 0% defoamer

[0124] 76.0% water drying accelerator variant 2:

[0125] 4.0% liquefied ethoxylated resin (U-Flakes / LEVACO)

[0126] 20% superplasticizer MasterEase 5452 from Master Builders Solution

[0127] 0% defoamer

[0128] 76.0% water

[0129] Drying accelerator variant 3:

[0130] 6.0% ethoxylated resin (U-Flakes / LEVACO)

[0131] 25.0% PCE superplasticizer Dynamon 1012 from MAPEI

[0132] 1.5% defoamer XiaMeter AF-0400 from DOW Europe

[0133] 67.5% water

[0134] Drying accelerator variant 4:

[0135] 8.0% ethoxylated resin (U-Flakes / LEVACO)

[0136] 30.0% PCE superplasticizer VZ 2 from SIKA

[0137] 6.0% defoamer, DISPELAIR 707 from BCD Chemie

[0138] 56.0% water

[0139] Drying accelerator variant 5:

[0140] 10.0% ethoxylated resin (U-Flakes / LEVACO)

[0141] 0.0% PCE solvent

[0142] 3.0% defoamer Berolan DF-100 from CASEA Deutschland GmbH

[0143] 87.0% water

[0144] Drying accelerator variant 6:

[0145] 12.0% ethoxylated resin (U-Flakes / LEVACO)

[0146] 0.0% PCE solvent

[0147] 0.0% defoamer

[0148] 88.0% water

[0149] Drying accelerator variant 7:

[0150] 4.0% ethoxylated resin (U-Flakes / LEVACO)

[0151] 70.0% PCE superplasticizer 239 & 1012

[0152] 0.0% defoamer

[0153] 26.0% water drying accelerator variant 8:

[0154] 8.0% liquefied ethoxylated resin (U-Flakes / LEVACO)

[0155] 50.0% PCE superplasticizer VZ2 & 239

[0156] 4.0% defoamer

[0157] 38.0% water

[0158] Drying accelerator variant 9:

[0159] 12.0% liquefied ethoxylated resin (U-Flakes / LEVACO)

[0160] 30.0% PCE superplasticizer 988 & 246

[0161] 7.0% defoamer

[0162] 51.0% water

[0163] Examples of concrete mixes

[0164] Example 1 screed:

[0165] Standard screed CTF4 (CTF4 stands for flexural strength after 28 days of at least 4.0 N / mm 2 ):

[0166] A class CTF4 screed consists of cement, water and gravel.

[0167] The following quantities are required per m3:

[0168] • Cement (e.g. CEM I, 42, 5N) 270 kg

[0169] • Gravel 1705 kg

[0170] • Water 170.1 kg

[0171] • Drying accelerator variants 1 to 9: 1.50 kg.

[0172] Mixing is typically done in a screed mixer, which typically has a mixing volume of 200 liters. The mixing sequence is the same, but in practice, the following sequence has become established: 1. Partial amount of gravel, 2. Cement, 3. Water, 4. Remaining amount of gravel. The respective drying accelerator (variants 1 to 9) is added to the water beforehand for better distribution.

[0173] Test execution and review of test results:

[0174] Drying acceleration: To determine the degree of accelerated drying, a binder mix with the various drying accelerator variants and an identical mix without drying accelerator are prepared, and the drying behavior of these two mixtures is compared (test method: gravimetric moisture measurement according to DIN EN 18560 Part 1). Depending on the composition of the binder and the drying accelerator used, differences in the drying behavior of the example mixtures arise. Within the scope of this patent specification, the drying time of the variants with drying accelerator is always shorter than that without drying accelerator, provided both variants are subject to comparable drying conditions.

[0175] For the screed produced according to Example 1 with the drying accelerators according to Variants 1 - 9 and the zero sample (“Variant 10”), the following values ​​for the residual moisture are obtained:

[0176] Drying accelerator

[0177] Efficiency of the drying accelerator

[0178] * Residual moisture determined by gravimetric moisture measurement according to DIN EN 18560 Part 1 in the kiln

[0179] Table 1 - Drying acceleration strength measurement

[0180] The flexural tensile strength of the standard CTF4 screed, produced as described in Example 1, can be significantly increased by adding the drying accelerator according to the invention. The increase in strength is even greater when the drying accelerator contains both components a) and b) than when only component a) is included. The results are recorded in Table 2.

[0181] Drying accelerator

[0182] Flexural tensile strength measurement

[0183] Table 2 - Determination of flexural strength

[0184] Shrinkage behavior / cracking:

[0185] The drying accelerator according to the invention significantly reduces shrinkage to less than 0.5 mm / m. Furthermore, it has been shown that despite the remaining shrinkage tendency, no cracks appear.

[0186] Cracking-shrinkage according to DIN EN 13892-9

[0187] Example 2 Ready-mixed concrete:

[0188] Ready-mixed concrete for floor slabs, strength class C 20 / 25:

[0189] Ready-mixed concrete of this class has a compressive strength of 25 N / mm 2 and consists of cement, water, and gravel. Per m 3 the following quantities are required:

[0190] • Cement (CEM I, 42, 5R) 350 kg,

[0191] • Aggregates (including fine grain and fine sand) up to 800 kg

[0192] • Maximum grain size 16 mm up to a maximum of 30% of the total weight per m 3

[0193] • Water 165 kg,

[0194] • Additives up to 15% of the total weight of the mixture

[0195] • Drying accelerator variant 2: 2.0 kg.

[0196] Mixing is usually done in a ready-mix concrete plant, and delivery to the construction site is made by truck mixer. The mixing sequence for concrete production is the same, but in practice, it has proven effective to add the additives to the mixing water to ensure better distribution throughout the mix.

[0197] Example 3 precast concrete parts:

[0198] Concrete for standard components (e.g. curbs), strength class C 16 / 20:

[0199] A concrete of this class has a compressive strength of 20 N / mm 2 and consists of cement, water, and gravel. Per m 3 the following quantities are required:

[0200] • Cement (CEM I, 42, 5R) 240 kg, • Aggregates (including fine grain and fine sand) up to 750 kg

[0201] • Maximum grain size up to 20% of the total weight per m 3

[0202] • Water 180 kg maximum,

[0203] • Additives up to 15% of the total weight of the mixture

[0204] • Drying accelerator variant 2: 2.0 kg.

[0205] Mixing typically takes place in the precast manufacturer's own mixing facilities. The exact recipe is often a trade secret, especially the type and composition of the additives, as rapid demolding and drying are desired for economic reasons. The mixing sequence for concrete production is the same, but in practice, it has proven effective to add the additives to the mixing water to ensure better distribution throughout the mix.

[0206] Example 4:

[0207] Screed CTF5 (CTF5 stands for flexural strength after 28 days of at least 5.0 N / mm 2 ):

[0208] A class CTF5 screed consists of cement, water and gravel.

[0209] Per m 3 the following quantities are required:

[0210] • Cement (Cem II, 42, 5N) 335 kg

[0211] • Gravel 1,705 kg

[0212] • Water 530 kg

[0213] • Drying accelerator variant 6: 1.75 kg.

[0214] Mixing is typically done in a screed mixer, which typically has a mixing capacity of 200 liters. The mixing sequence is the same, but in practice, the following sequence has become established: 1. Partial amount of gravel, 2. Cement, 3. Water, 4. Remaining amount of gravel. The drying accelerator is added to the water beforehand to ensure optimal distribution in the mixer.

[0215] Example 5: Site concrete for ceilings and wall elements:

[0216] Concrete for wall components, strength class C 25 / 30: Concrete of this class has a compressive strength of 30 N / mm 2 and consists of cement, water, and gravel. Per m 3 the following quantities are required:

[0217] • Cement (CEM I, 42, 5R) 280 kg, • Aggregates (including fine grain and fine sand) up to 750 kg

[0218] • Maximum grain size up to 20% of the total weight per m 3

[0219] • Water 168 kg maximum,

[0220] • Additives up to 15% of the total weight of the mixture

[0221] • Drying accelerator variant 7: 1.5 kg.

[0222] Mixing is usually done in the precast manufacturer's own mixing facilities. The exact recipe is often a trade secret, especially the type and composition of the additives, as rapid demolding and drying of the precast elements are desired for economic reasons. The mixing sequence for concrete production is the same, but in practice, it has proven effective to add the additives to the mixing water to ensure better distribution throughout the mix.

Claims

Patent claims 1. A drying accelerator for a cement-based building material, comprising an active component containing the following substances: a) 1 to 100 wt.%, in particular 2 to 60 wt.%, preferably 10 to 40 wt.%, of at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins; b) 0 to 99 wt.%, in particular 40 to 98 wt.%, preferably 60 to 90 wt.%, of at least one superplasticizer; and optionally c) 0 to 50 wt.%, in particular 0 to 20 wt.%, preferably 1 to 15 wt.%, of at least one defoamer, wherein the sum of components a), b) and c) equals 100 wt.%.

2. Drying accelerator according to claim 1, characterized in that the alkoxylated resins and synthetic resins are propoxylated or, in particular, ethoxylated resins and synthetic resins.

3. Drying accelerator according to claim 1 or 2, characterized in that substance c) is selected from the group consisting of silicone-based, polymer-based and mineral oil-based defoamers as well as defoamers based on vegetable or animal oils, wherein the polymer-based defoamers are preferred.

4. Drying accelerator according to any one of claims 1 to 3, characterized in that the active component a) contains 1 to 60 wt.%, in particular 5 to 40 wt.%, preferably 10 to 30 wt.%, at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins, b) 40 to 99 wt.%, in particular 60 to 95 wt.%, preferably 70 to 90 wt.%, at least one superplasticizer and optionally c) 0 to 50 wt.%, in particular 0 to 20 wt.%, preferably 1 to 15 wt.%, at least one defoamer, wherein the sum of components a), b) and c) yields 100 wt.%.

5. Drying accelerator according to claim 1 or 2, characterized in that the active component a) contains 5 to 40 wt.%, in particular 10 to 30 wt.%, of at least one compound selected from the group consisting of natural alkoxylated resins and alkoxylated synthetic resins, and b) contains 60 to 95 wt.%, in particular 70 to 90 wt.%, of at least one superplasticizer, wherein the sum of components a) and b) results in 100 wt.%.

6. Drying accelerator according to one of claims 1 to 5, characterized in that the resin or synthetic resin of substance a) is selected from at least one compound of the group consisting of tall oil, root resin, balsam resin, rosin and adducts of maleic acid, wherein balsam resin and rosin are particularly preferred.

7. Drying accelerator according to one of claims 1 to 6, characterized in that the mobile phase is at least one compound selected from the group consisting of polycarboxylate ethers, polyaryl ethers, naphthalenesulfonate, lignosulfonate and melaminesulfonate.

8. Drying accelerator according to one of claims 1 to 7, characterized in that it contains no further additives besides the active component.

9. Drying accelerator according to one of claims 1 to 7, characterized in that it contains one or more additives in addition to the active component, wherein the proportion of the additives in the sum of the active component and the additives is preferably at most 35 wt.%, in particular at most 10 wt.%.

10. Drying accelerator according to any one of claims 1 to 9, characterized in that it contains water as an additive, wherein the water content is 0.1 to 90 wt.%, preferably 15 to 80 wt.%, in particular 30 to 60 wt.%, based on the total drying accelerator.

11. Use of the drying accelerator according to any one of claims 1 to 10 as a drying accelerator for cement-based building materials.

12. Use according to claim 11, characterized in that the weight fraction of the drying accelerator in the mixture of building material (binder) and drying accelerator is from 0.01 to 4.0 wt.%‰, in particular from 0.05 to 2.0 wt.%‰, particularly preferably 0.1 to 1.0 wt.%‰.

13. Use according to claim 11 or 12, characterized in that the drying accelerator reduces or prevents the absorption of water into the building material.

14. Use according to one of claims 11 to 13, characterized in that the drying accelerator increases the strength of the building material.

15. Cement-based building material, characterized in that the building material further comprises a drying accelerator according to one of claims 1 to 10.

16. Building material according to claim 15, characterized in that the building material contains drying accelerator in the amount of 0.01 to 4.0 wt.%, in particular 0.05 to 2.0 wt.%, preferably 0.1 to 1.0 wt.%.

17. Building material according to claim 15 or 16, characterized in that the drying accelerator is added to the building material in a liquid, pasty or gel-like consistency.

18. Building material according to one of claims 15 to 17, characterized in that the drying accelerator is contained in the building material as a solid, in particular in powder form, preferably in freeze-dried form.

19. Building material according to one of claims 15 to 18, characterized in that the building material is a concrete mixture from which a prefabricated concrete element, a concrete formwork, site-mixed concrete, ready-mixed concrete or a screed, including a flowable screed, can be produced.

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