Building material additive for cement-based building materials

Description

[0001] The invention relates to building material additives for cement-based building materials, wherein the building materials contain at least one substance selected from cement, lime, gypsum, and alumina cement. The invention further relates to the use of the building material additive and to building materials containing the building material additive.

[0002] Such building materials include, in particular, prefabricated concrete elements and precast concrete parts, which are manufactured industrially, semi-industrially or manually and are delivered to the construction site in finished form and installed there; site-mixed concrete, i.e., concrete that is mixed on the construction site, transported to the point of use and dries and hardens at the point of use, and from which, for example, plasters, screeds, fillings, leveling compounds, and precast concrete parts are produced; and ready-mix concrete, which is produced in the mixing plant and delivered to the construction site in a transport mixer in an unhardened form.

[0003] The concretes used to manufacture the aforementioned products are generally based on cement as an inorganic binder. These concretes may contain gypsum, alumina cement, and lime as additional binders in varying proportions within the binder mix. The binder mix is ​​then blended with water. Typically, aggregates such as gravel, sand, and crushed stone, as well as admixtures like ash, blast furnace slag, or silica dust, and chemical additives are added to the concrete to improve, achieve, or prevent specific properties in the finished concrete or to optimize the mixing process.

[0004] The market demands the fastest possible production, processing, and installation of these products. This is achieved through accelerated drying while simultaneously attaining the required strength and other necessary technical properties. The goal, therefore, can be to reach, maintain, and even fall below the maximum permissible residual moisture content or minimum strength of these products as quickly as possible. At the same time, this should be accompanied by improved, easier processing during the product's manufacture and application, and, if possible, the established workflow for product production should remain unchanged or be altered only minimally.

[0005] The production and processing of concrete mixes for screed, precast elements, or ready-mix concrete for floor slabs or wall elements has not fundamentally changed in recent years. Innovations are more readily observed in the area of ​​admixtures or additives than in the concrete itself.

[0006] To achieve faster drying, the water content in cement-based mixes can be reduced by using superplasticizers. However, this often makes the concrete more difficult to work with, and the final strength is sometimes significantly reduced. Surfactants are commonly used to facilitate workability and make the concrete easier to handle. The disadvantage of surfactants is that they create air voids, which can reduce the density of, for example, a screed or a precast concrete element to such an extent that the required minimum strengths are no longer achieved. Products made from ready-mix concrete or site-mixed concrete often fail to reach the required strengths as a result.

[0007] While plasticizers reduce the water content in the concrete mix, they don't necessarily lead to faster drying. Although there is less water in the concrete, this water doesn't migrate out of the structure more quickly. Similarly, in screed, plasticizers do result in less water being used, but because the remaining water doesn't migrate out of the structure any faster, no accelerated drying time is achieved. Therefore, a lower water content in a concrete mix doesn't automatically lead to shorter drying times or faster drying.

[0008] US 4126470 A concerns a cementitious composition which includes inter alia polyethylene glycol and addresses the amount of mixing water in relation to setting and hardening times.

[0009] Generally speaking, today's concrete dries faster and screeds are ready for covering much sooner than 20 years ago. Under optimal conditions, residual moisture in the screed can be no more than 3.1% by mass after 14 to 28 days, although the drying time depends on factors such as the screed thickness, the quality of the raw materials used, and the amount of water used in production. Small deviations from the optimal mixes and production processes can easily lead to drying times of more than 90 days.

[0010] Newer developments promise a readiness for covering after three days under very specific conditions, which are either not achieved in reality or only with considerable effort. For example, the processing time is less than 45 minutes, meaning the process must be completed within 45 minutes, and these systems are also very expensive. Therefore, they are only used in special cases (max. 1% of all construction sites).

[0011] The market demands early drying of all types of concrete products under normal construction site or manufacturing conditions. In screed construction, a readiness for covering after seven days is urgently required. Ideally, this would be achieved even earlier, after three days. At the same time, the costs for additives should only marginally increase the overall costs of the project. In the production of precast concrete elements, drying accelerators allow for faster demolding and thus more economical use of the production equipment. Ready-mix concrete has a very large number of applications, each based on a different formulation of binders and aggregates.

[0012] The object of the invention was therefore to develop a building material additive that significantly accelerates the drying of building materials. The moisture must demonstrably leave the concrete and not merely be "encapsulated" or rendered "invisible" to measuring devices. Existing moisture must not be masked to the point of being undetectable, as such a procedure only postpones the escape of moisture and the associated damage. Ideally, the residual moisture test should be carried out according to standards, ensuring that no elevated residual moisture values ​​need to be approved.

[0013] Another task was to ensure that, despite improved drying properties, the strength was not adversely affected, but rather – on the contrary – increased strength and early strength (flexural and / or compressive strength) could be achieved.

[0014] Furthermore, improved workability of the concrete was desirable, as this would significantly simplify handling on the construction site.

[0015] Ultimately, the task was to reduce the amount of water that needs to be added to the concrete during production, because the less water is present in the concrete at the beginning, the less water needs to be released from the concrete later to achieve the desired residual moisture.

[0016] The building material additive should be easy to dose and incorporate into the binder mix. It should enable faster demolding, transport, and installation of precast concrete elements, faster drying of screeds, and faster drying of ready-mix concrete. The additive should be suitable for all types of concrete, and especially for screeds, leveling compounds, all types of backfill, and precast concrete elements.

[0017] The maximum permissible residual moisture content of concrete and gypsum mixtures should be reached in a shorter time than is currently possible. Using screed as an example, the goal was to reduce the residual moisture to below 3.1% within three days to achieve "readiness for covering," meaning the point at which subsequent trades, building upon the dried screed, can begin their work. In addition to accelerated drying, the screed must also achieve the flexural strength required by standards.

[0018] Surprisingly, it was found that a building material additive for cement-based building materials consists of an active component made up of the following substances: a) 35 to 95 wt.%, in particular 50 to 90 wt.%, of at least one polyethylene glycol, b) 5 to 45 wt.%, in particular 10 to 40 wt.%, of at least one compound selected from the group consisting of natural ethoxylated resins and ethoxylated synthetic resins, and c) 0 to 40 wt.%, in particular 0.1 to 35 wt.%, of at least one defoamer, where the sum of components a), b) and c) equals 100 wt.%, solves these problems and, when added to the mixing water of the binder or binder mix, extremely accelerates the drying of concretes and cement-based binder mixtures.

[0019] It should be noted that components a and b already accelerate the drying process, but the combination of the three components a), b), and c) is preferable in its effect. Furthermore, the building material additive according to the invention ensures that less water needs to be added for the mixing process. At the same time, the resulting concrete exhibits higher strength compared to conventionally produced concrete. Finally, the building material additive according to the invention significantly improves the workability of the concrete.

[0020] 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 most preferably at least 70 wt.% cement, while other binders, such as gypsum, lime, or alumina cement, are present in total in a maximum of 49 wt.%, in particular at a maximum of 40 wt.%, and most preferably at a maximum of 30 wt.%. The binder is particularly preferably a CEM I according to DIN EN 197, as this more reliably achieves the required strengths.

[0021] Screeds treated with the building material additive according to the invention are ready for covering after three to seven days. The maximum residual moisture content is consistently below the limit, the water is demonstrably released from the system, and no harmful absorption occurs. The addition of further additives or other aids to achieve accelerated drying is not necessary.

[0022] Concrete, including screeds and concretes that need to be compacted, provided with the building material additive according to the invention can be processed considerably more easily.

[0023] The building material additive causes accelerated drying of the binder mixture, during which: 1. the mixing water used demonstrably escapes, but 2. at the same time the amount of water sufficient for hydration remains in the binder mix and 3. no damaging absorption takes place.

[0024] The fundamental question is whether the reduced amount of available water for hydration, due to the building material additive, hinders crystallization of the concrete structure to such an extent and weakens it to such a degree that the required minimum strengths can no longer be achieved. However, the opposite is true. Higher strength values ​​can be achieved with the use of the building material additive according to the invention than without the additive.

[0025] Furthermore, it is important that the building material additive reduces the water requirement of a concrete mix, thus acting as a plasticizer. The example of screed demonstrates that the water requirement decreases significantly during screed production in the screed mixer. With a mixer volume of 200 liters, the water requirement for a CTF4 screed is 34 liters. Depending on the type and moisture content of the aggregate and the binder used, this water requirement is reduced by 10-25%.

[0026] The present invention has broad applicability. The building material additive 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, alumina cement, or a mixture thereof, wherein cement is present in each case at a minimum of 50% by weight, i.e., it is a cement-based building material. The number of products and their variants that can be produced with these binders and the building material additive according to the invention, with accelerated drying, is extensive. The building material additive can be used in the production of all the aforementioned products. Such building materials include, in particular, 1. Prefabricated concrete elements and precast concrete components, manufactured industrially, semi-industrially, or manually, and delivered to the construction site in their finished form for installation, e.g., prefabricated elements for house construction or sewer construction, railway sleepers, curbs, individual or standardized prefabricated elements, and exposed concrete elements, to name just a few; 2. Site-mixed concrete, i.e., concrete that is mixed on-site, transported to the point of use, and dries and hardens (hydrates) there, e.g., floor slabs, ceiling slabs, formwork infill, plaster, screed, fillers, leveling compounds, and exposed concrete elements; 3. Ready-mix concrete, produced in a mixing plant and delivered to the construction site in liquid form by a truck mixer, from which, for example, the products mentioned under 1. and 2. are manufactured on-site; 4. Cement-based self-leveling screeds; 5.Aerated concretes are available in two main categories: those that are autoclaved and those that are not, but instead require an alternative foaming process, such as the use of a foaming agent or pore-forming agent. Aerated concretes can be prefabricated industrially or produced and installed on-site.

[0027] The concretes used to manufacture the products listed under points 1 to 5 are generally based on cement as an inorganic binder. These concretes can be particularly well-suited to containing gypsum, alumina cement, and lime in varying proportions as additional binders in the binder mix. Aggregates such as gravel, sand, and crushed stone, as well as admixtures like ash, blast furnace slag, or silica dust, and chemical additives are typically added to the concrete to improve, achieve, or prevent specific properties in the finished concrete or to optimize the mixing process.

[0028] The proportion of component a) is particularly preferably at least 40 wt.%, in particular at least 50 wt.%, preferably at least 55 wt.%, particularly preferably at least 60 wt.%, in particular at least 65 wt.%. The maximum proportion of component a) is preferably at most 90 wt.%, in particular at most 85 wt.%, more preferably at most 80 wt.%. A particularly preferred range for component a) is from 50 to 90 wt.%, more preferably 55 to 85 wt.%, and more preferably from 65 to 80 wt.%.

[0029] The proportion of component b) is particularly preferably at least 10 wt.%, in particular at least 12 wt.%, and preferably at least 15 wt.%. The maximum proportion of component b) is preferably at most 40 wt.%, in particular at most 35 wt.%, and particularly preferably at most 30 wt.%. A particularly preferred range for component b) is from 10 to 40 wt.%, preferably 12 to 35 wt.%, and more preferably from 15 to 30 wt.%.

[0030] The proportion of component c) is particularly preferably at least 0.1 wt.%, in particular at least 0.5 wt.%, more preferably at least 1 wt.%, further preferably at least 2 wt.%, even more preferably at least 5 wt.%, in particular at least 7 wt.%. The maximum proportion of component c) is preferably at most 35 wt.%, in particular at most 30 wt.%, in particular at most 25 wt.%. A particularly preferred range for component c) is from 0.1 to 35 wt.%, more preferably 2 to 30 wt.%, in particular from 4 to 25 wt.%.

[0031] In a further particularly preferred embodiment of the present invention, the active component of the building material additive consists of a) 55 to 85 wt.%, in particular 65 to 80 wt.%, of at least one polyethylene glycol, b) 12 to 35 wt.%, in particular 15 to 30 wt.%, of at least one compound selected from the group consisting of natural ethoxylated resins and ethoxylated synthetic resins, and c) 2 to 30 wt.%, in particular 4 to 25 wt.%, of at least one defoamer.

[0032] Such a composition results in particularly fast drying while simultaneously ensuring good workability of the building material.

[0033] It is evident that the drying effect is achieved by components a and b. However, components a and b tend to form air voids in aqueous solution. Air voids lead to a reduction in the weight of the concrete and thus to a reduced strength of the dried concrete. To minimize this effect, it is therefore particularly advantageous to add a defoamer, component c. In principle, any defoamer is suitable. However, silicone-based defoamers are less suitable because they reduce the concrete's 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 specific pH value that differs from that of the binder dissolved in water.

[0034] The polyethylene glycol (PEG), also known as macrogol, used preferably has a molecular weight Mw of at least 200 g / mol, particularly at least 500 g / mol, preferably at least 1,000 g / mol, and most preferably at least 1,500 g / mol. More preferably, the PEG used has a molecular weight of up to 20,000 g / mol, preferably up to 10,000 g / mol, and most preferably up to 8,000 g / mol. The molecular weight of the polyethylene glycol is preferably from 200 to 20,000 g / mol, particularly from 500 to 15,000 g / mol, most preferably from 1,000 to 10,000 g / mol, and most preferably from 1,500 to 8,000 g / mol.

[0035] In addition to simple, i.e., unsubstituted, PEG, a preferred embodiment may also use methoxy polyethylene glycol (MPEG), i.e., methylated polyethylene glycol, or a mixture of one or more PEGs and / or one or more MPEGs as component a). The MPEG used preferably has a molecular weight Mw of at least 200 g / mol, in particular at least 500 g / mol, and preferably at least 750 g / mol. Furthermore, the PEG used preferably has a molecular weight of up to 20,000 g / mol, preferably up to 10,000 g / mol, and particularly preferably up to 5,000 g / mol, and in particular up to 2,000 g / mol. The use of MPEG positively influences the overall drying rate by limiting the time delay caused by the drying process, since the drying process is linear.

[0036] Component b) is a natural or synthetic resin that becomes water-soluble through chemical modification. This is achieved by ethoxylating the resin. Ethoxylating is the addition of ethylene oxide (oxirane) to the resin. The process is well known to those skilled in the art.

[0037] 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.

[0038] Natural resins are particularly preferred for the present invention.

[0039] Natural resins particularly preferred include tall oil, root resin, balsam resin, resins referred to as rosin, and other amber-based resins and adducts of maleic acid; rosin, in particular, is a preferred natural resin. Further preferred compounds as component b) are diterpenic acids and triterpenic acids and their soaps (especially potassium and sodium soaps). Particularly preferred among the 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, polyalthiic acid, and pinifolic acid.The following triterpenic acids are particularly preferred: dammarolic acid, tirucallanes, especially (iso)masticadienonic acid, elemolic acid and elemonic acid, oleananes, especially oleanonic acid, oleanolic acid, moronic acid and α-boswellic acid, ursanes, especially ursolic acid, ursonic acid and β-boswellic acid, as well as lupane lupeolic acid. The aromatic acids cinnamic acid and benzoic acid, as well as their benzyl and other esters, are also particularly suitable.

[0040] 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 also be supplied as concentrates, emulsions, or solutions. Particularly preferred polymer-based defoamers are those based on polyalkylene glycol ethers. Mineral oil-based defoamers are available as concentrates or emulsions. In principle, all variants can be supplied as freeze-dried powders. The vast majority of these variants are suitable for the present invention because they eliminate the air voids generated by components a) and b). Differences are as follows: A- Efficiency: The quantity required to adequately eliminate air voids created during the mixing process. B- Compatibility with the binder: Incompatibility is indicated by the 28-day strength of the produced test specimens not reaching the required minimum strength, and the test specimens exhibiting lower strength than the control sample. C- Temperature sensitivity: The produced building material additive is not frost-resistant. It either loses its effectiveness completely after exposure to frost or must be reactivated by costly heating.

[0041] Silicone-based defoamers weaken the concrete structure and reduce the final strength of concrete because, as experts know, silicone inhibits crystal formation in concrete. The use of silicone-based defoamers is possible, but only advisable if the required minimum concrete strengths are achieved. In screed, this would lead to an increased use of cement in the production process, which is why silicone-based defoamers are less suitable. Their use is only advisable when the additive must be added in powder form.

[0042] Polymer-based defoamers are temperature-sensitive. At low temperatures, frost damage can occur, necessitating laborious warming of the building material additive. Frost damage is often irreversible; the building material additive loses its effectiveness completely and must be disposed of. At excessively high temperatures, the defoamer in the building material additive can at least partially lose its effectiveness and requires costly disposal.

[0043] Mineral oil-based defoamers are particularly preferred for the present invention, although they can also be sensitive to frost; however, any reduction in effectiveness due to frost is usually reversible. High temperatures (>35°C) are generally not a problem.

[0044] The following Table 1 provides an overview: Defoamer

[0045] Defoamer variants and their drying effect in conjunction with components a and b compared to the 0 sample Table 1: Defoamers Designation supplier type Drying effect in conjunction with components a) and b) compared to 0-sample Disadvantage Dispelair 262 BCD Chemie, Hamburg Oil-based strongly accelerating - Dispelair 268 BCD Chemie, Hamburg Oil-based strongly accelerating - Dispelair 707 BCD Chemie, Hamburg Polymer-based strongly accelerating not frost-resistant, temperature-sensitive Hoesch LVW Hoesch Chemie, Düren Polymer-based strongly accelerating Not frost-resistant, temperature-sensitive Foam Clear Esca-NP Basildon Chemicals, Abington, UK Polymer-based strongly accelerating KCC BC 2670 Basildon Chemicals, Abington, UK Polymer-based strongly accelerating Xiameter AFE 0400 BCD Chemie, Hamburg silicone-based strongly accelerating Strength-reducing Xiameter ACP 1266 BCD Chemie, Hamburg silicone-based strongly accelerating Strength-reducing Hoesch FDP Hoesch Chemie, Düren silicone-based strongly accelerating Strength-reducing ViaPort 9010 CASEA Gips, Ellrich Silicone-based powder accelerating Strength-reducing, high application rate Berolan DF-100 CASEA Gips, Ellrich Silicone-based powder accelerating Strength-reducing, high application rate CliqSmart CM 110 CASEA Gips, Ellrich Silicone-based powder accelerating Strength-reducing, high application rate

[0046] Within the scope of the present invention, polymer-based defoamers, mineral oil-based defoamers, or defoamers based on vegetable or animal oils are preferred, with polymer-based and mineral oil-based defoamers being particularly preferred. Particularly preferred polymer-based defoamers are those based on polyalkylene glycol ethers. Oil-based defoamers can be in the form of an emulsion or a concentrate. All tested variants fulfill their purpose and remove air pores from an aqueous solution of components a) and b). A product example of a mineral oil-based defoamer is Dispelair 268 from BCD Chemie, Hamburg, or BC2370 from Hoesch Chemie, Düren. Vegetable oils are preferably in the form of a combination of mono- or diglycerides of a fatty acid. An example is the emulsifier E471, which is used in the food industry in bread and baked goods.

[0047] Polydimethylsiloxane and silicone compounds are also suitable as defoamers, with the molecular weight (Mw) appearing to be irrelevant. Product examples include Dispelair 392 from BCD Chemie, Hamburg, and Hoesch FDP from Hoesch Chemie, Düren, which deliver comparable drying results to oil-based defoamers, but may exhibit weaknesses in final strength after 28 days. Trin-butyl phosphate and triisobutyl phosphate are also very suitable defoamers. These substances are particularly effective at destroying or neutralizing the air pores formed by the polyethylene glycol and the ethoxylated natural resin or the ethoxylated synthetic resin (components a) and b)), which can impair the stability of the building material. This prevents the formation of foam bubbles and results in an exceptionally favorable packing structure of the building material, leading to improved and simplified processing of the concrete.The amount of labor required to produce a screed is thus reduced by at least 10%.

[0048] In addition to the active ingredient, the building material additive may contain an additional component that imparts further beneficial properties to the building material. Suitable additional components include a salt, a pH adjuster, an antioxidant, a processing aid, a liquefier, a colorant, and / or a preservative. Examples of such additional components commonly used in concrete and gypsum are salts like calcium nitrate, pH adjusters, antioxidants, or preservatives. The proportion of such optional additional components, if present, is preferably lower than that of the active ingredient and is preferably a maximum of 70% by weight, and particularly preferably not more than 20% by weight of the active ingredient.

[0049] The building material additive can be added to the binder mix as a powder without any further additives. If the additive is in powder or other dry form, it can be added to the cement powder or any other component of the concrete. One method of producing the additive as a powder is freeze-drying.

[0050] In a preferred embodiment, the construction additive can thus be produced and used as a dry solid, as a powder, or in any other non-liquid form. For this purpose, the components or the construction additive as a whole can be freeze-dried, and / or solid or powdered variants of components a, b, and / or c are selected and added as a mixture either to the dry components of the concrete or to the mixing water. In a preferred embodiment, the construction additive, initially in liquid form, is freeze-dried as a whole and added to the binder mix or the entire construction mix, i.e., the mixture of the binder mix and the other solids such as aggregates, admixtures, and / or additives. A finished binder mix or construction mix including the construction additive is obtained, so that only water needs to be added.

[0051] Preferably, the building material additive is added to the binder mix as a liquid, dissolved in water as an auxiliary agent, so that it is preferably present as an aqueous liquid building material additive. The water content is particularly advantageously 0.1 to 95 wt.%, preferably 15 to 90 wt.%, particularly 25 to 85 wt.%, and most preferably 35 to 80 wt.%, based on the total building material additive-water solution.

[0052] The building material additive can therefore be present as pure active ingredient components and thus be highly concentrated. The concentration of active ingredient components a, b, and c can be 100% by weight if no other substance / additional component is added to the building material additive, which is preferred.

[0053] The building material additive can also be present in a diluted aqueous solution and added as a liquid. The latter allows for particularly easy dosing. A preferred water-to-active-ingredient ratio is between 20:80 and 80:20. Such concentrations enable precise dosing to ensure the desired amount of active ingredient is present in the final product.

[0054] If the building material additive is added to the mixing water on the construction site, the concentration of the additive in the mixing water, and therefore in the overall mixture, is considerably lower. The concentration is then in the per mille range. Preferably, between 0.3 and 7 wt.‰, and especially between 0.5 and 3 wt.‰, of building material additive is added to 1 liter of mixing water. Despite this seemingly low concentration, the building material additive is fully effective. The moisture content of the gravel must be taken into account when determining the amount of mixing water.

[0055] Assuming a typical screed mix containing 34 liters of water per 200 liters of mix, the building material additive is preferably present in the finished screed mix at a concentration of 0.05 to 1 wt.‰, and particularly 0.1 to 0.5 wt.‰. The required amount of the building material additive should be proportional to the amount of cement used, but is influenced by factors such as cement quality, cement fineness, cement particle size distribution, and impurities in the cement.

[0056] The liquid building material additive can be added to the mixing water or to any component of the concrete. However, addition to the mixing water is preferred.

[0057] The building material additive can also exist in intermediate forms, neither solid nor liquid, i.e. as a gel or viscous mass.

[0058] The invention further relates to the use of the building material additive as a drying accelerator to accelerate the drying process of cement-based building materials. As already described above, the building material additive according to the invention exhibits excellent drying-accelerating properties and enables the residual moisture contents required by the relevant standards to be achieved within a shorter time than is the case with conventional cement-based building materials without the building material additive according to the invention.

[0059] As explained above, 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 most preferably at least 70 wt.% cement, while other binders, such as gypsum and lime, are present in total at a maximum of 49 wt.%, in particular at a maximum of 40 wt.%, and most preferably at a maximum of 30 wt.%. The binder is particularly preferably a CEM I according to DIN EN 197, as this more reliably achieves the required strengths.

[0060] The weight fraction of the building material additive in the mixture of building material and building material additive is preferably from 0.05 to 1 wt.-‰, in particular from 0.1 to 0.5 wt.-‰.

[0061] As already explained above, the question arises whether the reduced amount of available water for hydration, due to the building material additive, hinders crystallization of the concrete structure to such an extent and weakens it to such a degree that the required minimum strengths can no longer be achieved. However, the opposite is evident. The use of the building material additive according to the invention results in higher strength values ​​than without the additive, which thus also acts as a strength enhancer for concrete and concrete products. Therefore, the present invention also relates to the use of the building material additive according to the invention as a strength enhancer for concrete and concrete products. Concrete with the building material additive according to the invention exhibits increased strength and early strength (flexural and / or compressive strength).

[0062] Furthermore, the building material additive according to the invention reduces the water requirement of a concrete mix; the additive thus acts as a plasticizer. Using screed as an example, it is evident that the water requirement for screed production in the screed mixer decreases considerably. With a mixer volume of 200 liters, the water requirement for a conventional CTF4 screed is 34 liters. Depending on the type and moisture content of the gravel and cement used, this water requirement is reduced by 10-25% when using the building material additive according to the invention. The present invention therefore also relates to the use of the building material additive according to the invention as a processing aid for concrete.

[0063] The building material additive according to the invention preferably exhibits all of the effects simultaneously, i.e., it acts as a drying accelerator, a processing aid, a plasticizer, and a strength enhancer for cement-based concrete. Thus, the building material additive according to the invention significantly improves and simplifies concrete processing in many respects.

[0064] Furthermore, the present invention relates to cement-based building materials containing the building material additive according to the invention. The building material is, in particular, a prefabricated concrete element, a concrete formwork, site-mixed concrete, ready-mix concrete, or a screed, especially a self-leveling screed.

[0065] Preferably, the binder mix or the entire building material mix—that is, the mixture of the binder mix and other solids such as aggregates, additives, and / or other materials—contains the building material additive in freeze-dried form. For this purpose, the building material additive, initially produced as a liquid, is freeze-dried as a whole and then added to the binder mix or the building material mix. This results in a ready-to-use binder mix or building material mix including the building material additive, so that only water needs to be added. In this way, rapid-setting cement or rapid-setting concrete is produced.

[0066] All preferred embodiments described above for the building material additive also apply to the use and the building material according to the invention.

[0067] In addition to the components mentioned, the building material may contain other common additives. Examples include corrosion inhibitors, plasticizers, shrinkage reducers, or pigments.

[0068] The present invention is particularly suitable for screeds, since the drying time, the processing effort, the initial water requirement and the strength development are often of particular importance for screeds, as the readiness for covering is an important factor and the fastest possible drying of a screed in construction is highly desirable.

[0069] A process for producing a cement screed includes the following steps: a) mixing components comprising cement, aggregate, water and the building material additive according to the invention as described above to obtain a screed mixture, b) distributing the screed mixture into the desired shape / on the application surface and c) drying / curing the screed mixture.

[0070] In the first step of the process, components comprising cement, aggregate, water, and the inventive building material additive are mixed to obtain a screed mixture. To obtain a CTF4 screed according to the invention (F4 stands for a flexural strength after 28 days of at least 4.0 N / mm² or more), the following quantities are required per m³: cement (preferably Portland cement Cem I) 270 kg, gravel 1705 kg, water 170.1 kg, and 0.75 liters of the inventive building material additive of variant 1 (su). The order in which the components are mixed is arbitrary. However, it is preferable to add the building material additive to the water. The usual mixing instructions for the production of such cement mixtures must be followed.

[0071] As is generally known, cement is an inorganic, hydraulic binder. Upon the addition of water, hydrates form from the cement clinker phases, binding the water and causing the cement paste to solidify and harden, forming the cement stone or cement product. 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 wt.% of minor components. Calcium sulfate (gypsum and / or anhydrite) is also added as a minor component to regulate the setting process.

[0072] Other main and / or minor components for the production of cement can include latent hydraulic and / or pozzolanic and / or inert additives. Examples include granulated blast furnace slag, pozzolans such as tempered phonolite or trass, fly ash, burnt oil shale, limestone flour, and silica fume. Cements are classified according to their composition. Various standards exist for this purpose, some of which are country-specific, e.g., DIN EN 197-1, which classifies cements according to the proportion of cement clinker and, if present, the type and quantity of other components. 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 component selected from granulated blast furnace slag, silica fume, pozzolans, fly ash, burnt oil shale, or limestone. Portland composite cements are preferred for screeds.

[0073] According to the classification in the standard DIN EN 197-1, the preferred cement is therefore CEM I (Portland cement) or CEM II (Portland composite cement). CEM I and CEM II / A or CEM II / B cements with limestone flour 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.

[0074] Depending on the application, the binder mix may contain alumina cement. While alumina cement is expensive, it aids the hardening of Portland cement. This hardening can occur so rapidly that the solids mix must be slowed down to remain workable. Portland / alumina cement shrinks considerably. The drying rate and shrinkage make alumina cement an impractical component of screed, although other applications may favor this combination. Even in screed, the binder mix used may contain small amounts of 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. However, as mentioned, this is not preferred.

[0075] The usual aggregate materials can be used, such as rounded aggregate or crushed sand and / or gravel, with an aggregate size of up to 8 mm being preferred. A screed mix can contain, for example, a maximum aggregate size of up to 4 mm, or concrete 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. Example of building material additives (all values ​​per kg) Building material additive variant 1:

[0076] 20.0 wt% PEG 4000 (molecular weight 4,000 g / mol) 2.5 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 2.0 wt% defoamer, Antifoam LVW from Julius Hoesch AG 75.5 wt% water Building material additive variant 2:

[0077] 5.0 wt% PEG 8000 (molecular weight 8,000 g / mol) 20.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 1.5 wt% defoamer XiaMeter AF-0400 from DOW Europe 73.5 wt% water Building material additive variant 3:

[0078] 1.5 wt% PEG 6000 (molecular weight 6,000 g / mol) 2.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 1.5 wt% defoamer DISPELAIR 707 from BCD Chemie 95.0 wt% water Building material additive variant 4:

[0079] 30 wt% PEG 500 (molecular weight 500 g / mol) 3.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 15.0 wt% defoamer Berolan DF-100 from CASEA Deutschland GmbH 52.0 wt% water Building material additive variant 5:

[0080] 10 wt% PEG 1000 (molecular weight 1,000 g / mol) 4.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 4.0 wt% defoamer Dispelair 268, BCD Chemie, Hamburg 77.0 wt% water Building material additive variant 6:

[0081] 27.5 wt% PEG 2000 (molecular weight 2,000 g / mol) 12.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 15.0 wt% defoamer Xiameter AFE 1266 45.5 wt% water Building material additive variant 7:

[0082] 6.0 wt% PEG 10000 (molecular weight 10,000 g / mol) 0.5 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 1.0 wt% defoamer Hoesch FDP from Hoesch Chemie 92.5 wt% water Building material additive variant 8:

[0083] 5.0 wt% PEG 12000 (molecular weight 12,000 g / mol) 5.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 4.0 wt% defoamer Hoesch LVW from Hoesch Chemie 86.0 wt% water Building material additive variant 9:

[0084] 10.0 wt% PEG 1500 (molecular weight 1,500 g / mol) 3.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 0.7 wt% defoamer KCC Basildon BC 2370 from Basildon Chemicals 86.3 wt% water Building material additive variant 10:

[0085] 15.0 wt% PEG 2000 (molecular weight 2,000 g / mol) 6.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 1.2 wt% defoamer KCC Basildon Foam Clear Esca-NP from Basildon Chemicals 77.8 wt% water Building material additive variant 11:

[0086] 15.0 wt% MPEG 750 (molecular weight 750 g / mol) 6.0 wt% ethoxylated natural resin (molecular weight of ethoxylation 50 g / mol) - UFlakes from Levaco 0.1 wt% defoamer KCC Basildon Foam Clear Esca-NP from Basildon Chemicals 78.9 wt% water Examples of concrete mixes Example 1: Screed CTF4 with flexural strength after 28 days > 4.0 N / mm²<

[0087] A screed of class CTF4 consists of cement, water, and gravel. The following quantities are required per m³: Cement (e.g. Cem I, 42.5N) 270 kg, gravel 1705 kg, water 170.1 kg, a building material additive of variants 1 to 11 in a quantity of 0.35 kg.

[0088] The mixing is usually done in a screed mixer, which typically has a mixing volume of 200 to 220 liters. The mixing sequence is arbitrary, but the following order has become established in practice: 1. Partial quantity of gravel, 2. Cement, 3. Water, 4. Remaining quantity of gravel. The building material additive is added to the water beforehand to ensure better distribution in the mixer. Example 2: Ready-mix concrete for floor slabs, strength class C 2025:

[0089] Ready-mix concrete of class C2025 consists of the components cement, water, aggregates and additives.

[0090] The following quantities are required per m³: Cement (Cem I, 52.5R) 350 kg, aggregates (including flour and fine sand) 600 kg, maximum aggregate size 410 kg, water 165 kg, additives: polypropylene fiber 20 mm, 2.0 kg, building material additive variant 3, 0.5 kg

[0091] The mixing usually takes place at the ready-mix concrete plant, and delivery to the construction site is made by truck mixer. The mixing sequence is arbitrary during concrete production; however, in practice, it has proven beneficial to add the additives to the mixing water to ensure better distribution within the mix. Example 3: Precast concrete elements, wall elements, strength class C 2025:

[0092] A concrete of class C2025 consists of the components cement, water, aggregates and additives.

[0093] The following quantities are required per m³: Cement (Cem I, 52.5R) 350 kg, aggregates (including flour and fine sand) 600 kg, maximum aggregate size 405 kg, water 165 kg, additives: polypropylene fiber 10 mm, 2.0 kg, superplasticizer MasterGlenium SKY 688 from BASF, 2.5 kg, construction material additive variant 6, 0.5 kg Example 4: Screed CTF5, flexural strength after 28 days > 5.0 N / mm2):

[0094] A screed of class CTF5 consists of cement, water, and gravel. The following quantities are required per m³: Cement (Cem II, 42.5N) 335 kg Gravel 1705kg, water 210kg, building material additive variant 2, 0.5kg.

[0095] The mixing is usually done in a screed mixer, which typically has a mixing volume of 200-220 liters. The mixing sequence is the same, but the following order has become established in practice: 1. Partial quantity of gravel, 2. Cement, 3. Water, 4. Remaining quantity of gravel. The building material additive is added to the water beforehand so that it is better distributed in the mixer. Example 5: On-site concrete for wall elements: Concrete mix for precast concrete elements

[0096] Ready-mix concrete of class C2025 consists of cement, water, and gravel. The following quantities are required per m³: Cement (Cem I, 42.5R) 350 kg, aggregates (including flour and fine sand) 700 kg, maximum aggregate size 22 mm, 310 kg, water 165 kg, additives not required (up to 15% of the total weight of the mixture is permitted), building material additive variant 7, 0.75 kg

[0097] The mixture is prepared directly on the construction site. The mixing order for the concrete is arbitrary, however, in practice it has proven beneficial to add the additives to the mixing water so that they are better distributed throughout the mixture. Testing methods:

[0098] To avoid any influence from increased residual moisture, only the two test methods according to standard DIN EN 18560 Part 1 are used. Test method 1: Gravimetric moisture measurement (also drying in a kiln)

[0099] Here, a sample of the prepared example mixture is taken and the non-chemically bound moisture is extracted at 105°C. The weight difference between the initial and final weights, assuming constant weight, is divided by the final weight to determine the residual moisture content in %. Test method 2: Calcium carbide method.

[0100] Here, a sample is taken and placed in a bottle (a "CM bottle"). Steel balls and glass ampoules filled with calcium carbide are added. The CM bottle is then shaken, releasing the calcium carbide. The remaining water in the sample reacts with the calcium carbide, producing a gas. The resulting gas pressure is measured, and the residual moisture content is determined from this measurement.

[0101] Other methods for determining residual moisture are not permitted according to DIN EN 18560.

[0102] Analysis of the test results of the standard screed with building material additives 1 to 11 and without building material additives: To compare the drying properties of cements with the building material additives of variants 1 to 11 and without building material additives, i.e., to determine the degree of accelerated drying, a CTF4 screed according to Example 1 was produced with the various building material additives and without building material additives, and the drying behavior of these screeds was compared. The residual moisture was determined according to test method 1 (gravimetric moisture measurement in a drying oven). The results are shown in Table 2 below: building material additive Efficiency of the building material additive

[0103] Table 2: Residual moisture content when using various building material additives CTF4 screed accelerator variant Component a Component b Component c Residual moisture after 3 days* Residual moisture 7 days* 1 PEG 4000 U Flakes Antifoam LVW 4,38% 3,24% 2 PEG 8000 U Flakes Xiameter AF-0400 4,70% 3,18% 3 PEG 6000 U Flakes Dispelair 707 3,05% 3,12% 4 PEG 500 U Flakes Berolan DF-100 4,65% 3,43% 5 PEG 1000 U Flakes Dispelair 268 3,41% 2,97% 6 PEG 2000 U Flakes Xiameter AFE-1266 3,11% 2,89% 7 PEG 10000 U Flakes Hoesch FDP 3,67% 3,07% 8 PEG 12000 U Flakes Hoesch LVW 4,22% 3,16% 9 PEG 1500 U Flakes KCC BC 2670 3,10% 2,86% 10 PEG 2000 U Flakes KCC Foam-Clear Esca-NP 3,27% 2,96% 11 MPEG 750 U Flakes KCC Foam-Clear Esca-NP 3,08% 2,76% 12 0-Sample, no supplement TB 5,43% 3,69% * Residual moisture determined by gravimetric moisture measurement according to DIN EN 18560 Part 1 in a drying oven

[0104] Depending on the composition of the binder and the building material additive used, the drying behavior of the example mixtures differs, with the drying time of the variants with building material additive always being shorter than that without building material additive within the scope of this patent specification.

Claims

1. A building material additive for a cement-based building material, consisting of an active component which consists of the following substances: a) 35 to 95% by weight, in particular 50 to 90% by weight, of at least one polyethylene glycol, b) 5 to 45% by weight, in particular 10 to 40% by weight, of at least one compound selected from the group consisting of natural ethoxylated resins and ethoxylated synthetic resins, and c) 0 to 40% by weight, in particular 0.1 to 35% by weight, of at least one defoamer, wherein the sum of components a), b) and c) is 100% by weight.

2. The building material additive according to claim 1, characterized in that the active component consists of: a) 55 to 85% by weight of at least one polyethylene glycol, b) 12 to 35% by weight of at least one compound selected from the group consisting of natural ethoxylated resins and ethoxylated synthetic resins, and c) 2 to 30% by weight of at least one defoamer.

3. The building material additive according to claim 2, characterized in that the active component consists of: a) 65 to 80% by weight of at least one polyethylene glycol, b) 15 to 30% by weight of a compound selected from the group consisting of natural ethoxylated resins and ethoxylated synthetic resins, and c) 4 to 25% by weight of at least one defoamer.

4. The building material additive according to any one of claims 1 to 3, characterized in that substance b) is selected from at least one compound of the group consisting of tall oil, wood rosin, balsam resin, colophony and adducts of maleic acid, wherein colophony is particularly preferred.

5. The building material additive according to any one of claims 1 to 4, characterized in that the building material additive, in addition to the active component, further contains a salt, an agent for adjusting the pH value, an antioxidant, a processing aid, a plasticizer and / or a preservative.

6. The building material additive according to any one of claims 1 to 5, 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 and the mineral-oil-based defoamers are preferred.

7. The building material additive according to any one of claims 1 to 6, characterized in that it contains water as an auxiliary agent, wherein the water content is 0.1 to 90% by weight, preferably 30 to 85% by weight, in particular 40 to 75% by weight, based on the total building material additive.

8. Use of the building material additive according to any one of claims 1 to 7 as a drying accelerator for cement-based building materials.

9. Use of the building material additive according to any one of claims 1 to 7 as a strength enhancer for concrete and concrete products.

10. Use of the building material additive according to any one of claims 1 to 7 as a processing aid for concrete.

11. Use according to any one of claims 8 to 10, characterized in that the weight proportion of the building material additive in the mixture of building material and building material additive is from 0.05 to 1 ‰ by weight, in particular from 0.1 to 0.5 ‰ by weight.

12. A cement-based building material, characterized in that the building material further contains a building material additive according to any one of claims 1 to 7.

13. The building material according to claim 12, characterized in that the building material contains from 0.05 to 1 ‰ by weight, preferably 0.1 to 0.5 ‰ by weight, of the building material additive.

14. The building material according to claim 12 or 13, characterized in that the building material additive is contained in freeze-dried form.

15. The building material according to any one of claims 12 to 14, characterized in that the building material is a prefabricated concrete element, a concrete molded part, a site-mixed concrete, a ready-mixed concrete or a screed, in particular a flowing screed.