Methods to improve the workability of a mineral binder composition comprising at least one mineral binder and additionally recycled powder, mineral binder composition and hardened mineral binder composition

Abstract

The present invention relates to a method for improving the workability of a mineral binder composition comprising at least one mineral binder and additionally recycled powder, the method comprising the steps of: a) providing at least one mineral binder, b) mixing recycled powder, c) mixing at least one workability improver selected from the group consisting of polycarboxylates, lignin sulfonates, glycolic acids, sugars, or mixtures thereof, and d) mixing with water.

Description

Technical Field

[0001] This invention relates to the recycling of mineral binder materials. In particular, it relates to materials and methods for improving the workability of mineral binder compositions comprising at least one mineral binder and additionally recycled powder. The recycled powder can be obtained from the recycling of waste building materials such as demolition waste, substandard building materials, or surplus building materials. [] Prior Technology

[0002] To date, a significant amount of discarded building materials (such as hardened concrete or mortar from demolition or substandard production) or surplus building materials are dumped in landfills. Only a small portion is partially reused as raw materials for low-tech applications within the construction industry.

[0003] Furthermore, current practice involves crushing waste building materials, especially demolition debris, and reusing only the coarse-grained fraction, typically discarding the finer-grained fraction. This is because reusing the finer-grained fraction could affect the properties of the newly hardened concrete. Therefore, current practice can only be considered incomplete.

[0004] Infrastructure in many parts of the world is aging and in dire need of reconstruction, at least in parts. Therefore, a large amount of waste building materials from the demolition of structures such as concrete buildings are available and will continue to be available in the coming years. However, due to new regulations, waste disposal has become increasingly expensive and difficult in some regions and countries. Furthermore, waste building materials contain valuable materials, such as binders with cementing properties and aggregates that can often be reused to produce new building materials. Therefore, the recycling of waste building materials is a crucial issue.

[0005] Both EP 2 978 724 and EP 2 708 520 describe methods for obtaining aggregates and / or carbonated binders from demolition waste or waste building materials. These methods include carbonation and pulverization steps. EP 2 978 724 also teaches that, compared to cement grout or mortar without such powdered mineral materials, the initial spreadability of cement grout or mortar containing powdered mineral materials (i.e., substantially carbonated binders), except for the mineral binder, is not significantly altered. However, EP 2 978 724 does not provide any methods to improve the initial flowability and / or long-term workability of such mineral binder compositions.

[0006] Therefore, there is a need for materials and methods that improve the workability of mineral binder compositions comprising at least one mineral binder and additionally recycled powder. Summary of the Invention

[0007] The object of this invention is to improve the workability of mineral binder compositions comprising at least one mineral binder and additionally recycled powder. In particular, the object of this invention is to increase initial flow and / or prolong the time for maintaining a certain flow in a mineral binder composition comprising at least one mineral binder and additionally recycled powder. In the context of this invention, the flow of the mineral binder composition refers to slump flow as measured according to standard EN 1015-3.

[0008] Another object of the present invention is to provide mineral binder compositions, particularly mortar or concrete compositions, comprising at least one mineral binder and additional recycled powder and having improved workability. In this context, improved workability means an increase in initial flow and / or an extension of the time required to maintain a certain flow in a mineral binder composition comprising at least one mineral binder and additionally recycled powder.

[0009] It has been unexpectedly discovered that the object of the present invention can be achieved by mixing workability improvers selected from the group consisting of polycarboxylates, lignin sulfonates, glycoacids, sugars, or mixtures thereof.

[0010] For example, compared to the same mineral binder composition without the at least one workability improver, the mineral binder composition produced according to the method of the present invention exhibits an initial slump spread, as measured according to EN 1015-3, that is increased by at least 20%, preferably at least 30%, more preferably at least 45%, and especially at least 50%. Simultaneously, the slump spread remains at a high level over an extended period, for example, at least 30 minutes, preferably at least 60 minutes, more preferably at least 90 minutes, and especially at least 120 minutes. The slump spread is maintained for the given time if the slump spread value measured after mixing, after a given time, changes by no more than 35%, preferably no more than 30%, and especially no more than 25% relative to the initial slump spread measured directly after mixing. Furthermore, the setting time is extended to a value still acceptable for most practical applications.

[0011] Therefore, the object of the present invention is achieved by the method and composition as claimed in the independent claim. Preferred embodiments of the invention are the subject of the dependent claim. Simple Explanation of the Diagram

[0012] none Implementation

[0013] In a first aspect, the present invention relates to a method for improving the workability of a mineral binder composition comprising at least one mineral binder and additionally recycled powder, the method comprising the following steps: a) Provide at least one mineral binder, b) Mix the recycled powder. c) Mixing at least one workability improver selected from the group consisting of polycarboxylates, lignin sulfonates, glycoacids, sugars, or mixtures thereof, and d) Mix the water.

[0014] In this context, the improvement in workability of a mineral binder composition relates to an increase in initial slump spread and / or an extension of the time during which a certain slump spread is maintained. Slump spread can be measured according to standard EN 1015-3. Therefore, in the method of the present invention, compared with the initial slump spread and / or the change in slump spread over time of the same mineral binder composition not containing at least one workability improver of the present invention, the initial slump spread of a mineral binder composition containing at least one mineral binder and additionally recycled powder and at least one workability improver is increased and / or the maintenance of a certain slump spread of such a mineral binder composition over time is extended.

[0015] According to an embodiment, in the method of the present invention, the initial slump expansion, as measured according to EN 1015-3, is increased by at least 20%, preferably at least 30%, more preferably at least 45%, and especially at least 50%, compared to the same mineral binder composition without the at least one workability improver.

[0016] In this context, mineral binders are preferably selected from cement, gypsum, lime, magnesium oxide, alumina, geopolymers, potential hydraulic binders, and / or volcanic ash.

[0017] Cement can specifically be Portland cement of the CEM I, CEM II, CEM III, CEM IV and CEM V types as described in standard EN 197-1, calcium aluminate cement as described in standard EN 14647, and / or calcium sulfoaluminate cement. The term "gypsum" refers to all forms of CaSO4, particularly anhydrous CaSO4, CaSO4 α- and β-hemihydrates, and CaSO4 dihydrate. The term "lime" refers to natural hydraulic lime, blended lime, hydraulic lime, and air lime as described in standard EN 459-1:2015. The term "alumina" represents alumina, aluminum hydroxide, and / or alumina such as gibbsite and boehmite, calcined or rapidly calcined alumina, alumina obtained by the Bayer process, and hydrated alumina such as amorphous mesophase alumina and p-phase alumina. Volcanic ash and potential hydraulic materials are preferably selected from the following groups of components: slag, clay, calcined clay (especially metakaolin), kiln ash, microsilica powder, fly ash, fumed silica, precipitated silica, silica powder, zeolite, rice husk ash, burning oil shale, and natural volcanic ash (such as pumice, volcanic soil, and finely ground limestone).

[0018] According to the embodiments, the at least one mineral binder is selected from the group consisting of: Portland cement (especially Portland cement of the CEM I type), calcium aluminate cement, calcium sulfoaluminate cement, gypsum, hydraulic lime, air lime, geopolymer, slag, clay, finely ground limestone, and mixtures thereof.

[0019] In this context, the term "recycled powder" refers to mineral powder that has been recovered from waste building materials. Methods for recovering or recycling powder from waste building materials include mechanical methods, particularly crushing and / or grinding the waste building materials. According to embodiments, recycled powder is recovered from waste building materials by mechanical methods, particularly crushing and / or grinding, and subsequently separated from aggregates, for example, by separation by size or weight. Recycled powder can be partially or fully hydrated. It can also be partially or fully carbonated, for example, by natural carbonation that occurs when using mineral binders. However, it is also possible for recycled powder to not be carbonated.

[0020] In addition to mechanical methods, chemical methods may be used as needed. Chemical methods for recovering recycled powders include, for example, carbonation, acid treatment, and / or dissolution / precipitation of waste building materials. A particularly preferred method for recovering recycled powders from waste building materials is the chemomechanical method, in which mechanical and chemical treatments are combined to recover the recycled powders. The mechanical and chemical treatments can be carried out sequentially, simultaneously, or in multiple steps.

[0021] According to an embodiment of the present invention, recycled powder is recovered from waste building materials by the following steps: first, the waste building material blocks are carbonated in a CO2 atmosphere, and then the carbonated material is ground to separate the recycled powder from the aggregate.

[0022] According to a particularly preferred embodiment of the invention, recycled powder is recovered from waste building materials by crushing and / or grinding while simultaneously carbonizing the waste building materials. Such methods are described, for example, in EP 2 978 724 and EP 2 708 520.

[0023] Preferably, the recycled powder of this invention is separated from aggregates, fibers, metals, and wood present in waste building materials. Specifically, the recycled powder contains no aggregates. Aggregates are defined below.

[0024] There are no particular limitations on the waste building materials that can be used as a source of recycled powder. Preferred sources of waste building materials include, for example, demolition waste and substandard materials or surplus materials from production. Particularly preferred sources are waste concrete or mortar, such as from the demolition of concrete structures, substandard concrete or mortar, and surplus concrete, such as surplus concrete from premixed equipment. However, other waste building materials such as bricks or plaster, such as plaster base coat, plasterboard, plaster mortar undercoat, can also be used as a source of recycled powder. In particular, mixed waste building materials can be used to recycle the recycled powder according to the invention. The mixed waste building materials contain two or more different mineral binders. The mixed waste building materials can be generated, for example, from the demolition of infrastructure in which more than one binder material has been used, such as cementitious masonry with plaster plaster, brickwork with cemented mortar and / or base coat. Mixed waste building materials can also be produced from formulations of concrete or mortar containing more than one binder, such as Portland cement and slag, Portland cement and gypsum, Portland cement and aluminate cement, and combinations of gypsum, Portland cement and clay, and limestone as needed. Mixed waste building materials can also contain composite cements, such as CEM II, CEM III, CEM IV, or CEM V as described in standard EN 197-1. Of course, mixed waste building materials can also contain materials other than mineral binders that are common to building materials systems. Such other materials include aggregates, fibers, glass, metals, wood, and organic polymers as defined below.

[0025] The chemical composition of the recycled powder of this invention depends on the chemical composition of the mineral binder or mineral binder composition present in the waste building materials. Depending on the elemental oxide composition of the recycled powder, it can be used for various purposes. For example, when the elemental oxide composition is similar to that of a hydraulic mineral binder, the recycled powder can be used as a filler or supplementary cementitious material in concrete or mortar. For example, when it contains additional calcium sulfate, the recycled powder can be used for the sulfation of mineral binders. The recycled powder has a particle size ranging from nanometers to several micrometers. Typically, the particle size of the recycled powder is in the range of 0–0.250 mm, preferably 0.001–0.200 mm, and especially 0.01–0.125 mm, as determined by sieve analysis as described in standard EN 933-1. This facilitates the separation of the recycled powder from the aggregate during recycling.

[0026] According to a preferred embodiment, the recycled powder of the present invention comprises at least one cement clinker, particularly Portland cement clinker, or is composed of at least one cement clinker, particularly Portland cement clinker.

[0027] Particularly preferred is that the recycled powder of the present invention is carbonated recycled powder. Carbonated recycled powder can be recovered from mineral binders or mineral binder compositions that have undergone natural carbonation, especially mortar or concrete. However, it is preferable that the carbonated recycled powder is mineral powder or mineral powder composition that has already been treated in a carbonation process. Suitable carbonation methods are described, for example, in EP 2 978 724, EP 2 708 520 and WO 2015 / 123769.

[0028] According to some embodiments, the carbonated recycled powder is a carbonated product of a mixture of two or more mineral binders. This is especially true in cases where mixed waste building materials are subjected to carbonation to form carbonated recycled powder.

[0029] In this context, the term "carbonation" refers to the combination of carbon dioxide in a compound or the chemical reaction of carbon dioxide with the starting material. Carbonation of mineral binders or mineral binder compositions (e.g., cement, mortar, or concrete) occurs to some extent naturally. However, the term "carbonation" is preferred here to refer to a process in which carbonation is intentionally enhanced or accelerated compared to the natural process. This can be achieved by providing an excess of carbon dioxide. Therefore, "carbonation" specifically includes the treatment of the starting material with carbon dioxide.

[0030] Regarding mineral binders, "carbonation" refers to a process essentially the reverse of the chemical process of calcination, such as that carried out in a cement kiln. For example, hardened mineral binders in the form of hydraulic cement, which are essentially composed of calcium, silicates, and aluminum hydrates, can react with carbon dioxide to form the corresponding carbonates. Carbonated mineral binders, especially carbonated Portland cement, typically have a lower pH compared to uncarbonated materials. Therefore, the progressive carbonation of mineral binders, especially hardened mineral binders, can be measured by a decrease in pH. For example, the progressive carbonation of concrete can be detected by spraying the concrete surface with an ethanol phenolphthalein solution. Colorless areas indicate carbonated concrete, and purple areas indicate uncarbonated concrete.

[0031] Therefore, the carbonated recycled powder in this context is a mineral binder that has already been carbonated. Preferably, the carbonated recycled powder in this context is carbonated recycled Portland cement.

[0032] The carbonated recycled powder of the present invention, preferably carbonated recycled Portland cement, may be partially or fully carbonated, preferably fully carbonated. According to embodiments, the recycled powder comprises fully carbonated cement, preferably fully carbonated Portland cement, or is substantially composed of fully carbonated cement, preferably fully carbonated Portland cement.

[0033] The progress of carbonation can be determined, for example, by measuring the partial pressure of CO2 during the process of exposing the mineral binder or mineral binder composition to a CO2 atmosphere. If the partial pressure of CO2 decreases, carbonation occurs. If the partial pressure of CO2 does not decrease further, carbonation can be considered essentially complete. Alternatively, the progress of carbonation can also be determined by measuring the pH value of the mineral binder or mineral binder composition. If the pH value of the pore solution of the Portland cement-based mineral binder composition or the Portland cement or Portland cement-based mineral binder composition slurry is between 12.5 and 14, carbonation has essentially not occurred. Once its pH drops to a value between 7 and 9, carbonation is essentially complete.

[0034] According to embodiments, in the method of the present invention, the weight ratio between the at least one mineral binder and the recycled powder is between 99:1 and 5:95, preferably between 94:6 and 45:55, and more preferably between 94:6 and 65:35.

[0035] In the method of the present invention, at least one workability improver selected from the group consisting of polycarboxylate, lignin sulfonate, glycoacid, sugar, or mixtures thereof is mixed.

[0036] In this context, the term "polycarboxylate" refers to polycarboxylic acid, polycarboxylate ether, and polycarboxylate ester. Preferred in this context are polycarboxylate ether and polycarboxylate ester (both abbreviated as PCE). Therefore, a particularly preferred type of workability improver is PCE.

[0037] The PCE of this invention comprises or consists of the following. (i) The repeating unit A of the general structure (I), (I) as well as (ii) Repeating unit B of general structure (II), (II) in Each Ru independently represents either hydrogen or methyl. Each Rv independently represents hydrogen or COOM, where M is independently H, an alkali metal, or an alkaline earth metal. m = 0, 1, 2 or 3, p = 0 or 1, Each R1 is independently -(CH2)z-[YO]nR4, where Y is a C2 to C4 alkyl group and R4 is a H, C1 to C20 alkyl group, -cyclohexyl, -alkylaryl, or -N(-Ri)j-[(CH2)z-PO3M]3-j, z = 0, 1, 2, 3 or 4, n = 2 - 350, j = 0, 1 or 2, Ri represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and M represents a hydrogen atom, an alkali metal, an alkaline earth metal or an ammonium ion. Furthermore, the repeating units A and B in the PCE have a molar ratio of A:B in the range of 10:90 to 90:10.

[0038] According to a preferred embodiment, the side chain R1 of the PCE of the present invention is -(CH2)z-[YO]nR4, wherein z = 0, Y is a C2 alkyl group, n = 11-350, preferably 22-250, and R4 is H or methyl.

[0039] According to another preferred embodiment, the molar ratio A:B of the PCE of the present invention is 10:90-60:30.

[0040] According to a particularly preferred embodiment, in the polycarboxylate ethers and / or polycarboxylate esters of the present invention, the side chain R1 is -(CH2)z-[YO]nR4, where z = 0, Y is C2 alkyl, n = 11-350, preferably 22-250, and R4 is H or methyl, and the molar ratio of A:B is 10:90-60:30.

[0041] The PCE of this invention preferably has an average molecular weight Mw in the range of 1,000 - 1,000,000, more preferably 1,500 - 500,000, most preferably 2,000 - 100,000, and particularly 3,000 - 75,000 or 3,000 - 50,000 g / mol. The molar mass Mw is determined by gel permeation chromatography (GPC) using polyethylene glycol (PEG) as a standard. This technique is known to those skilled in the art.

[0042] The PCE according to the present invention can be a random or non-random copolymer. Non-random copolymers are in particular alternating copolymers, block copolymers, gradient copolymers, or mixtures thereof.

[0043] According to the present invention, the PCE can be prepared by free radical polymerization of a mixture comprising: at least one olefinically unsaturated carboxylic acid monomer of general formula (Ia). (Ia) and at least one olefinic unsaturated monomer of general formula (IIa) (IIa) Ru, Rv, m, p, and R1 have the meanings given above, and the ring bond represents both cis- and trans-double bond isomers or a mixture thereof.

[0044] Suitable conditions for carrying out free radical polymerization are known to those skilled in the art and are described, for example, in EP 1 103 570.

[0045] The PCE according to the present invention can also be prepared by polymer analog reaction. In particular, the PCE according to the present invention can be prepared by esterification of a homopolymer or copolymer containing repeating units of general formula (I) with a polyalkylene glycol of general formula (III). (III), R1 is defined above.

[0046] Suitable methods for preparing the PCE according to the invention by esterification are known to those skilled in the art and are described, for example, in EP 1138697 (Sika AG).

[0047] In addition to at least one olefinically unsaturated carboxylic acid monomer of general formula (Ia) and at least one olefinically unsaturated macromonomer of general formula (IIa), the PCE according to the present invention may contain one or more other monomers. [M]. These other monomers [M] may be selected from styrene, ethylene, propylene, butene, butadiene, isoprene, vinyl acetate, vinyl chloride, acrylonitrile, N-vinylpyrrolidone and / or (meth)acrylate hydroxyalkyl esters.

[0048] Preferably, in each case, the one or more additional monomers, relative to all the monomers constituting the PCE, The molar fraction of [M] is equal to or less than 66 mol%, preferably equal to or less than 50 mol%, more preferably equal to or less than 25 mol%, particularly preferably equal to or less than 10 mol%, especially equal to or less than 5 mol%. In a very particularly preferred embodiment, the PCE is substantially free of additional monomer units. [M].

[0049] As used herein, the term "lignin sulfonate" refers to a salt consisting of a lignin sulfonate anion and a suitable cation, and particularly includes substances such as sodium lignin sulfonate (CAS No. 8061-51-6), magnesium lignin sulfonate (CAS No. 8061-54-9), and calcium lignin sulfonate (CAS No. 8061-52-7). The cation does not play a role in the efficacy of this invention. Lignosulfonates are prepared from lignin, which is produced in plants, especially woody plants.

[0050] Lignin is a three-dimensional amorphous polymer, unlike most other biopolymers, it does not possess regularly ordered or repeating units. For this reason, although various models have been proposed for the "average" structure, a definitive lignin structure cannot be named. Those skilled in the art are familiar with the heterogeneity of lignin between different plant taxa and between different tissues, cells, and cell wall layers within each species.

[0051] Lignosulfonates are formed as a byproduct of pulp production under the influence of sulfurous acid, leading to sulfonation and some degree of demethylation of lignin. Similar to lignin, they exhibit a wide variety of structures and compositions. They are soluble in water across the entire pH range but insoluble in ethanol, acetone, and other common organic solvents.

[0052] The methods used for separating and purifying lignin sulfonates are familiar to those skilled in the art. In the Howard method, calcium lignin sulfonate is precipitated by adding excess lime to the waste sulfite leachate. Lignosulfonates can also be separated by forming insoluble quaternary ammonium salts with long-chain amines. On an industrial scale, ultrafiltration and ion exchange chromatography can be used to purify lignin sulfonates.

[0053] The lignin sulfonates available according to the present invention are commercially available under various trade names, such as Ameri-Bond, Borresperse, Dynasperse, Kelig, Lignosol, Marasperse, Norlig, Lignosite, Reax, Wafolin, Wafex, Wargotan, Wanin, Wargonin, Vanillex, and others. Paper), Vanisperse, Vanicell, Ultrazine, Ufoxane (Bolliger Company), Serla-Bondex, Serla-Con, Serla-Pon, Serla-Sol (Serlachius), Collex, Zewa (Wadhof-Holmes Company), Raylig (ITT Rayonier Company).

[0054] Of course, mixtures of different lignin sulfonates can also be used. Furthermore, lignin sulfonates can be in both liquid and solid forms.

[0055] In the context of this invention, "glycolic acid" refers to a monosaccharide having a carboxyl group. It can belong to any class of aldonic acids, ursonic acids, uronic acids, or glycolic acids. Preferably, it is an aldonic acid. Examples of glycolic acids usable with respect to this invention include, but are not limited to, gluconic acid, ascorbic acid, neuraminic acid, glucuronic acid, galacturonic acid, iduronic acid, mucilic acid, and glycolic acid. Glucolic acids can be in the form of free acids or salts. According to embodiments, salts of glycolic acids can be salts of metals from Groups Ia, IIa, Ib, IIb, IVb, and VIIIb of the periodic table. Preferred salts of glycolic acids are salts of alkali metals, alkaline earth metals, iron, cobalt, copper, or zinc. Salts of sodium, potassium, and calcium are particularly preferred. D-form and L-form glycolic acids are also preferred. Particularly preferred glycolic acids are gluconic acid and its salts, especially sodium gluconate.

[0056] According to a preferred embodiment of the present invention, the at least one workability improver is sodium gluconate.

[0057] In the context of this invention, "sugar" refers to a carbohydrate having an aldehyde or acetal moiety. In a particularly preferred embodiment, the sugar belongs to the group of monosaccharides or disaccharides. Examples of sugars include, but are not limited to, glyceraldehyde, thioalose, erythrose, xylose, lysolose, ribose, arabinose, allose, azoose, glucose, mannose, gulose, idole, galactose, tarose, fructose, sorbitol, lactose, maltose, sucrose, lactulose, trehalose, cellobiose, chitobiose, isomaltose, paraginose, mannobiose, raffinose, and xylobiose. Sugars can also be used in the form of dextrin, distiller's grains, or molasses. D-form and L-form sugars are also preferred. Particularly preferred sugars are fructose, mannose, maltose, glucose, galactose, dextrin, distiller's grains, and molasses. The term "sugar" in this context should be understood to also include hydrogenated sugars. Hydrogenated sugars are especially hydrogenated starch hydrolysates or hydrogenated glucose syrups. Hydrogenated sugars are produced by the partial hydrolysis of oligosaccharides and polysaccharides, followed by hydrogenation. The result is a mixture of sugar alcohols.

[0058] Of course, in this context, two or more, such as a mixture of three or four workability improvers, can be used in combination. The advantage of this is that it can achieve certain synergistic effects in improving workability.

[0059] For example, a mixture of two different polycarboxylates can be used. Two different polycarboxylates mean that the polycarboxylates differ in their chemical and / or structural composition. The difference can be, for example, different repeating units A and / or B or different molar ratios A:B, where A and B are as described above. The difference can also be a random structure compared to a non-random polycarboxylate, such as a block structure. Furthermore, a mixture of a polycarboxylate and a sugar acid, preferably sodium gluconate, can be used. A mixture of sugar and sodium gluconate can also be used. A mixture of polycarboxylate, sugar, and sugar acid (preferably sodium gluconate) can also be used.

[0060] According to the embodiments, the at least one workability improver is therefore selected from a mixture of two different polycarboxylates, or from a mixture of a polycarboxylate and a sugar acid, preferably sodium gluconate, or from a mixture of sugar and sodium gluconate.

[0061] According to another embodiment, the at least one workability improver is therefore a mixture of polycarboxylate, sugar, and sugar acid (preferably sodium gluconate).

[0062] In the method of this invention, the mixing of recycled powder, at least one workability improver, and water with at least one mineral binder can be carried out by any suitable method known to those skilled in the art. Suitable mixers include, for example, horizontal single-shaft mixers, twin-shaft paddle mixers, vertical shaft mixers, belt mixers, track mixers, tank changer mixers, tumbling containers, vertical mixing chambers, or air-mixing operations. Mixing can be continuous or batch-mixed.

[0063] According to an embodiment, before mixing with water, at least one workability improver is mixed into a mixture of at least one mineral binder and recycled powder.

[0064] According to another embodiment, at least one workability improver is mixed with mixed water into a mixture of at least one mineral binder and recycled powder.

[0065] According to another embodiment, at least one workability improver is first mixed with at least one mineral binder, then a carbonate binder is mixed into the mixture, followed by the mixing of water.

[0066] At least one of the workability improvers of the present invention can be mixed in its liquid or solid pure chemical form. Similarly, at least one of the workability improvers of the present invention can be mixed as a liquid solution or dispersion. Preferred solutions or dispersions are aqueous solutions or dispersions. At least one workability improver can also be mixed in a dry form, for example, adsorbed onto a drying carrier or as a spray-dried powder.

[0067] According to embodiments, in the method of the present invention, the at least one workability improver is selected from polycarboxylate salts, and in each case, the weight of the mixed polycarboxylate salt relative to the dry weight of the present recycled powder is between 0.1 and 3.0 w%, preferably 0.20 to 1.125 w%, and more preferably from 0.40 to 0.85 w%. In such cases, the weight of the polycarboxylate salt refers to the total dry weight of all the polycarboxylate salts present. That is, if a mixture of two or more different polycarboxylate salts is present, the weight refers to the combined dry weight of such polycarboxylate salts.

[0068] According to another embodiment, in the method of the present invention, the at least one workability improver is selected from lignin sulfonate, and in each case, the weight of the mixed lignin sulfonate is between 1.0 and 6.0 w%, preferably 3.5 to 5.5 w%, and more preferably 4.0 to 5.0 w%, relative to the dry weight of the recycled powder present.

[0069] According to another embodiment, in the method of the present invention, the at least one workability improver is selected from glycolic acid, especially sodium gluconate, and in each case, the weight of the mixed glycolic acid, especially sodium gluconate, is between 0.025 and 1.0 w%, preferably 0.3 to 0.9 w, relative to the dry weight of the recycled powder present.

[0070] According to another embodiment, in the method of the present invention, the at least one workability improver is selected from sugar, and in each case, the weight of the mixed sugar is between 0.5 and 2.0 w%, preferably 0.7 to 1.5 w, relative to the dry weight of the recycled powder present.

[0071] According to another embodiment, in the method of the present invention, the at least one workability improver is selected from a mixture of polycarboxylate and glycolic acid, preferably sodium gluconate. In each case, the weight of the mixed polycarboxylate is between 0.20 and 1.125 w%, preferably 0.25 and 0.85 w%, relative to the dry weight of the recycled powder present, and the weight of the mixed glycolic acid, preferably sodium gluconate, is between 0.025 and 1.0 w%, preferably 0.28 and 0.5 w%.

[0072] According to another embodiment, in the method of the present invention, the at least one workability improver is selected from a mixture of sugar and sugar acid, preferably sodium gluconate. In each case, the weight of the mixed sugar is between 0.5 and 2.0 w% relative to the dry weight of the recycled powder present, and the weight of the mixed sugar acid, preferably sodium gluconate, is between 0.025 and 1.0 w%, preferably 0.10 and 0.50 w%.

[0073] According to another embodiment, in the method of the present invention, the at least one workability improver is selected from a mixture of polycarboxylates, sugars and sugar acids, preferably sodium gluconate. In each case, relative to the dry weight of the recycled powder present, the weight of the mixed polycarboxylates is between 0.1 and 3.0 w%, preferably 0.1 to 1.125 w%, the weight of the mixed sugars is between 0.1 and 2.0 w%, preferably 0.2 to 1.2 w%, and the weight of the mixed sugar acids, preferably sodium gluconate, is between 0.025 and 1.0 w%, preferably 0.07 to 0.50 w%.

[0074] The method of the present invention may further include the step of adjusting the dosage of at least one workability improver, which is selected from the group consisting of polycarboxylates, lignin sulfonates, glycoacids, sugars, or mixtures thereof. Preferably, the dosage is adjusted in such a manner that the workability of the mineral binder composition containing recycled powder is substantially the same as that of the same mineral binder composition without recycled powder. In particular, the mineral binder composition without recycled powder contains an additional amount of mineral binder to compensate for the omitted recycled powder. In other words, the recycled powder can be considered as a substitute for, and especially a partial substitute for, the mineral binder.

[0075] Therefore, the present invention also relates to a method for determining the optimal dosage of at least one workability improver for a mineral binder composition comprising at least one mineral binder and recycled powder, the method comprising the following steps: a) Provide a mixture comprising at least one mineral binder and recycled powder, b) Mix the first amount of at least one workability improver selected from the group consisting of polycarboxylates, lignin sulfonates, glycolic acids, sugars, or mixtures thereof. c) Mix the water, d) Measure the workability of the mixture obtained according to step c). e) Compare the workability measured in step e) with the target workability. f) If the comparison in step e) deviates beyond a predetermined threshold, adjust the amount of at least one workability improver mixed in step b), and g) Repeat steps a) - f) until the comparison in step e) does not deviate more than the predetermined threshold.

[0076] According to a preferred embodiment, the target workability used in step e) is the same as that provided in step a) but without the addition of any recycled powder. According to another preferred embodiment, the target workability used in step e) is the same as that of the mixture provided in step a), but with an additional amount of mineral binder to compensate for the amount of unmixed recycled powder. The predetermined thresholds used in steps f) and g) can be, for example, no more than 50%, preferably no more than 25%, and especially no more than 10%. All other definitions and embodiments described in this invention also apply to this method.

[0077] In a second aspect, the present invention relates to a mineral binder composition, particularly concrete or mortar, comprising... a) At least one mineral binder and recycled powder in a weight ratio of 99:1 to 5:95, preferably 94:6 to 45:55, and even more preferably 94:6 to 65:35. b) At least one performance improver, c) At least one type of aggregate, d) Additional additives as needed, and e) Water as needed.

[0078] The at least one mineral binder, the recycled powder, and the at least one workability improver are as described above.

[0079] Aggregates can be any material that is non-reactive in the hydration reaction of the binder. Aggregates can be any aggregate typically used in building materials. Typical aggregate systems include, for example, rock, crushed stone, gravel, sand, especially quartz sand, river sand and / or artificial sand, slag, recycled concrete, glass, expanded glass, hollow glass beads, glass ceramics, volcanic rock, pumice, perlite, vermiculite, quarry waste, raw, fired or molten soil or clay, porcelain, electrofused or sintered abrasives, sintered carriers, and silica dry gel. Aggregates can also be bio-based aggregates, such as, for example, hemp fiber. Aggregates used in this invention can have any shape and size typically common to such aggregates. Particularly preferred aggregate systems are sand. Sand is a naturally occurring granular material consisting of finely crushed rock or mineral particles. It is available in various forms and sizes. Examples of suitable sand are quartz sand, limestone sand, river sand, or crushed aggregate. Suitable sands are described, for example, in standards such as ASTM C778 or EN 196-1. Of course, aggregate mixtures are also acceptable.

[0080] Other additives can be any additives commonly used in the mortar and concrete industry, except for lignin sulfonates, saccharides, sugars, and polycarboxylates (including PCE). In particular, other additives can be selected from plasticizers, shrinkage reducers, air-entraining agents, degassing agents, stabilizers, viscosity modifiers, thickeners, water-reducing agents, retardants, accelerators, water-resistant agents, fibers, foaming agents, defoamers, redispersible polymer powders, dust removers, chromate reducing agents, pigments, biocides, corrosion inhibitors, and steel passivators.

[0081] In each case, relative to the total dry weight of the composition, the combined amount of at least one mineral binder and carbonate binder in the mineral binder composition of the present invention can be between 10-79 w%, preferably 15-60 w.

[0082] In each case, relative to the total dry weight of the composition, the amount of at least one workability improver in the mineral binder composition of the present invention can be between 0.025 and 6.0 w%, preferably 0.1 to 4.5 w%, and more preferably 0.2 to 1.5 w.

[0083] In each case, the amount of the at least one aggregate in the mineral binder composition of the present invention can be between 15 and 84 w%, preferably 34 to 79 w, relative to the total dry weight of the composition.

[0084] In each case, the combined amount of additional additives (if present) may be from 0.1 to 10 w relative to the total dry weight of the composition.

[0085] The amount of water (if present) can be such that the water-to-adhesive ratio is between 0.1 and 0.8, preferably 0.2 to 0.6, and especially 0.25 to 0.4.

[0086] According to embodiments, the mineral binder composition of the present invention, especially mortar or concrete, therefore comprises or consists of the following (in each case, relative to the total dry weight of the composition). a) 10-79 wt%, preferably 15-60 wt%, of at least one mineral binder and carbonate binder. b) At least one workability improver at 0.025-6.0 wt%, preferably 0.1-4.5 wt%, and more preferably 0.2-1.5 wt%. c) At least one aggregate, preferably 15-84 wt%, or more preferably 35.5-80.5 wt%. d) Additional additives of 0.1-10 w% as needed, and e) The amount of water required should be adjusted to achieve a water-to-adhesive ratio between 0.1 and 0.8, preferably 0.2 to 0.6, and especially 0.25 to 0.4.

[0087] Therefore, the mineral binder composition of the present invention, especially mortar or concrete, can be a dry or wet composition.

[0088] The mineral binder composition of this invention can be concrete, especially crane and bucket concrete, pumped concrete, precast concrete, ready-mixed concrete, shotcrete, slipform concrete, high-performance concrete, ultra-high-performance concrete, self-compacting concrete, roller-compacted concrete, lightweight concrete, heavy concrete, rotary pile concrete, underwater concrete, or mass concrete. The mineral binder composition of this invention can also be a cementitious tile adhesive, grouting material, self-leveling lining, self-leveling overlay, base coat, repair mortar, thin-layer brick / stone bonding mortar or concrete, mortar underlayer, wall leveling agent for internal or external use, anti-shrinkage mortar, thin-joint mortar, waterproof mortar, or anchoring mortar.

[0089] Concrete, especially according to standard EN 206. Cemented tile adhesive, especially according to standard EN 12004-1. Grouting materials, especially according to standard EN 13888. Self-leveling underlayment or self-leveling topcoat, especially according to standard EN 13813. Primer, especially according to standard EN 998-1. Repair mortar, especially according to standard EN 1504-3. Masonry mortar or concrete, especially according to standards EN 998-2 and EN 206-1. Mortar underlayment, especially according to standard EN 13813. Non-shrink mortar, especially according to standard EN 1504-6. Thin joint mortar, especially according to standard EN 998-2. Waterproof mortar, especially according to standard EN 1504-2. Anchoring mortar, especially according to standard EN 1504-6.

[0090] In another aspect, the present invention also relates to an admixture for improving the workability of mineral binder compositions comprising recycled powder, said admixture comprising or consisting of the following: a) At least one workability improver selected from polycarboxylates, lignin sulfonates, glyco acids, sugars, or mixtures thereof, and b) Water as needed.

[0091] Mineral binders, recycled powders, polycarboxylates, lignin sulfonates, glycoacids, and sugars are as described above.

[0092] The amount of water in the blend of the present invention can vary in a wide range. Preferably, in each case, the amount of water (if present) relative to the total weight of the blend is between 1-90 w%, more preferably 10-66 w%, and even more preferably 15-50 w%.

[0093] The blends of this invention may further comprise other additives commonly used in the mortar and concrete industries, in addition to lignin sulfonates, saccharides, sugars, and polycarboxylates (including PCE). In particular, the additional additives may be selected from plasticizers, shrinkage reducers, air-entraining agents, degassing agents, stabilizers, viscosity modifiers, thickeners, water-reducing agents, retardants, accelerators, water-resistant agents, fibers, foaming agents, defoamers, redispersible polymer powders, dust removers, chromate reducing agents, pigments, biocides, corrosion inhibitors, and steel passivators.

[0094] According to the embodiment, compared with the same mineral binder composition that does not contain at least one workability improver, the mineral binder composition as described above and which contains water has an increase of at least 20%, preferably at least 30%, more preferably at least 45%, and especially at least 50% in initial slump expansion as measured according to EN 1015-3.

[0095] In a final aspect, the present invention relates to a hardened mineral adhesive composition, preferably as part of a building, which is obtained by curing a mineral adhesive composition as described above, and wherein water is present.

[0096] Preferably, curing is carried out at a temperature between 5°C and 40°C and at atmospheric pressure. In principle, the mineral binder composition can also be cured at higher temperatures and / or increased pressures, such as in an autoclave.

[0097] The following examples will provide alternative implementations for those skilled in the art. They are not intended to limit the invention. [] [Example] []

[0098] [Material]: - CEM I 42.5 N, CEM II / A-LL 42.5 N and CEM II / B-LL 42.5 N are supplied by Vigier in accordance with standard EN 197-1. - Recycled powder is obtained as follows: CEM I 42.5 N was suspended in water at 23°C until completely hardened. The hardened product was dried at 80°C, conditioned at 20°C / 65% relative humidity until constant weight was achieved, and then ground in a needle mill to a particle size < 0.063 mm. The powdered material was stored in a reactor at 23°C / 65% relative humidity, with the powder gently stirred and a continuous gaseous flow of CO2 passing through the reactor. Following the carbonation process, the amount of carbonate was measured by thermogravimetric analysis (TGA). Carbonate was determined by TGA based on mass loss over a temperature range of 500°C–800°C. Sufficient carbonation was considered achieved if the TGA indicated the presence of 55–60 w% carbonate. - PCE-1 series co-(polyacrylate-polymethacrylate), having Mn = 5000 g / mol and methoxy-terminated polyethylene oxide side chains (Mn = 3000 g / mol); with the following molar ratios: Carboxylate:side chain = 4.5 - PCE-2 series co-(polyacrylate-polymethacrylate), having Mn = 5000 g / mol and methoxy-terminated polyethylene oxide side chains (Mn = 1000 g / mol); with the following molar ratios: Carboxylate:side chain = 1.6 - PCE-3 is a copolymer of polyethylene oxide (Mn = 2400 g / mol), acrylic acid, and 2-hydroxyacrylate, starting with methyl allyl alcohol in a molar ratio of 0.625 : 0.416 : 2.80. - PCE-4 series co-(polyacrylate-polymethacrylate), having Mn = 5000 g / mol and methoxy-terminated polyethylene oxide side chains (Mn = 1000 g / mol); with the following molar ratios: Carboxylate:side chain = 0.8 - PCE-5 series co-(polyacrylate-polymethacrylate), having Mn = 5000 g / mol and methoxy-terminated polyethylene oxide side chains (Mn = 500 g / mol); with the following molar ratios: Carboxylate:side chain = 1.0 - Ligno: Sodium lignosulfonate from LignoStar group BV - Gluco: Sodium gluconate (>99%) from Sigma-Aldrich. - Melasse: Untreated melasse from sugarcane used in sugar production (solids content approximately 80 Gew.-%; pH = 5.5) - Polysorb: Hydrogenated glucose syrup, 12 w% sorbitol content (Polysorb 70 / 12)

[0099] [Measurement]: - At the time following the completion of the mixing method shown in the table below, the slump spread is determined using a cone with a volume of 39 cm³ according to EN 1015-3. Slump spread < 60 mm is not measured and is indicated as "< 60" in any case in the table below. - The onset of solidification was determined using isothermal conduction calorimetry according to ASTM C1702-17. For this purpose, the heat of hydration was recorded using a CAL 8000 apparatus from Calumetrix. The onset of solidification corresponds to a point on the curve of heat flux over time, at which the first local minimum was measured. Example 1

[0100] In Example 1, the effects of various workability improvers used alone on cement paste were evaluated. CEM I 42.5 N was used as the mineral binder and dry-mixed with recycled powder until visually homogeneous. The weight mixing ratio of mineral binder to recycled powder was 82:18. The mixture of mineral binder and recycled powder was mixed with a certain amount of water to obtain a water:binder weight ratio of 0.45. Mixing was performed for 2 min using a propeller mixer at a speed of 2.5–5.5 m / s. The corresponding workability improvers were added along with the mixed water in the amounts shown in Table 1 below.

[0101] Table 1 below provides an overview of the results. Example 1-1 is a comparative example and is not based on the invention. Examples 1-2-1-22 are based on the invention. [Table 1]: Example 1-1-1-22; Dosage is given as w% relative to the combined dry weight of mineral binder and recycled powder. Example Performance improver dose Collapse spread [mm] Initial solidification [min] 3 min 30 min 60 min 90 min 120 min 1-1 none 0 79 68 < 60 < 60 < 60 75 1-2 PCE-1 0.05 117 102 84 74 < 60 n.m. 1-3 PCE-1 0.1 140 116 98 82 67 n.m. 1-4 PCE-2 0.075 120 116 112 103 86 120 1-5 PCE-2 0.1 120 127 124 116 108 150 1-6 PCE-3 0.1 102 114 152 126 120 120 1-7 PCE-3 0.15 111 123 144 148 142 150 1-8 PCE-3 0.2 104 132 153 159 166 180 1-9 PCE-4 0.1 104 113 116 114 102 120 1-10 PCE-4 0.15 113 121 123 123 118 150 1-11 PCE-4 0.2 115 125 124 127 123 180 1-12 PCE-5 0.1 114 108 96 84 81 120 1-13 PCE-5 0.15 118 121 113 106 100 150 1-14 PCE-5 0.2 121 128 130 123 116 150 1-15 Ligno 0.6 106 98 93 79 <60 300 1-16 Ligno 0.8 113 105 98 96 81 420 1-17 Ligno 1.0 118 113 106 97 84 540 1-18 Gluco 0.05 119 100 95 88 79 150 1-19 Gluco 0.1 128 110 102 98 93 300 1-20 Gluco 0.15 133 111 108 103 97 420 1-21 Melasse 0.2 131 106 102 98 85 480 1-22 Melasse 0.4 142 118 110 106 101 540 nm: Not measured

[0102] As can be seen from Table 1 above, compared with compositions containing the same mineral binder and recycled powder but without workability improvers, all tested workability improvers significantly increased the initial slump spread and were able to maintain the slump for a longer period of time. In fact, in most cases, when using the workability improver according to the present invention, the initial slump spread and slump spread retention rate were improved relative to the slump spread performance of cement paste based on CEM II / A-LL with a water-to-cement ratio of 0.45.

[0103] For most practical applications, the measured setting time remains within an acceptable range. In the case of ready-mixed concrete, an increased setting time may even be beneficial. Example 2

[0104] Example 2 was carried out in the same manner as Example 1, except that the weight mixing ratio of mineral binder to recycled powder was 65:35.

[0105] Table 2 below provides an overview of the results. Example 2-1 is a comparative example and is not based on the invention. Examples 2-2 to 2-7 are based on the invention. [Table 2]: Examples 2-1 - 2-7; Dosage is given as w% relative to the combined dry weight of the mineral binder and recycled powder. Example additive dose Collapse spread [mm] Initial solidification [min] 3 min 30 min 60 min 90 min 120 min 2-1 none 0 < 60 < 60 < 60 < 60 < 60 60 2-2 PCE-1 0.1 116 83 < 60 < 60 < 60 nm 2-3 PCE-2 0.075 96 63 < 60 < 60 < 60 75 2-4 PCE-2 0.1 101 74 < 60 < 60 < 60 75 2-5 PCE-2 0.2 135 128 116 95 74 90 2-6 PCE-4 0.25 88 116 125 126 110 180 2-7 PCE-4 0.4 110 138 146 145 143 270 nm: Not measured

[0106] As shown in Table 2 above, compared with compositions containing the same mineral binder and recycled powder but without workability improvers, all tested workability improvers significantly increased the initial slump spread and were able to maintain the slump for a longer period. In fact, for Examples 2-2, 2-5, and 2-7, the initial slump spread was even greater than that of the CEM II / B-LL-based cement paste with a water-to-cement ratio of 0.45. Furthermore, for Examples 2-5, 2-6, and 2-7, the initial slump spread retention rate was improved compared to the CEM II / B-LL-based cement paste with a water-to-cement ratio of 0.45.

[0107] For most practical applications, the measured setting time remains within an acceptable range. In the case of ready-mixed concrete, an increased setting time may even be beneficial. Example 3

[0108] In Example 3, the effects of various workability improvers used in combination on cement paste were evaluated. Example 3 was conducted in the same manner as Example 1, except that a combination of workability improvers was used.

[0109] Table 3 below provides an overview of the results. Examples 3-1 to 3-23 are based on the present invention. [Table 3]: Example 31-3-23; Dosage is given as w% relative to the combined dry weight of the mineral binder and recycled powder. Example additive Powder amount Depth of drop [mm] Initial coagulation [min] 3 min 30 min 60 min 90 min 120 min 3-1 PCE-1 PCE-2 0.025 0.05 129 118 107 91 81 120 3-2 PCE-1 PCE-4 0.04 0.04 118 113 110 109 98 150 3-3 PCE-1 PCE-3 0.05 0.075 121 126 128 one two three 116 180 3-4 PCE-1 PCE-4 0.05 0.05 126 139 136 129 110 150 3-5 PCE-2 Gluco 0.15 0.025 103 112 113 78 63 180 3-6 PCE-2 Gluco 0.15 0.05 109 130 126 107 92 240 3-7 PCE-2 Gluco 0.15 0.075 115 124 125 118 106 300 3-8 PCE-2 Polysorb 0.15 0.025 125 108 106 90 78 180 3-9 PCE-2 Polysorb 0.15 0.05 126 121 117 90 86 240 3-10 PCE-2 Polysorb 0.15 0.075 128 134 128 104 94 300 3-11 PCE-2 Gluco Polysorb 0.15 0.05 0.025 124 136 132 115 101 210 3-12 PCE-2 Gluco Polysorb 0.15 0.05 0.05 127 138 129 113 92 240 3-13 PCE-2 Gluco Polysorb 0.15 0.025 0.075 125 128 121 87 83 240 3-14 PCE-3 Gluco 0.05 0.05 118 118 114 116 112 210 3-15 PCE-3 Gluco 0.075 0.05 121 124 128 131 130 240 3-16 PCE-3 Polysorb 0.05 0.05 117 118 121 118 114 150 3-17 PCE-3 Polysorb 0.075 0.05 124 127 130 132 128 210 3-18 PCE-4 Gluco 0.1 0.025 123 126 124 120 117 150 3-19 PCE-4 Polysorb 0.1 0.05 131 127 125 122 120 120 3 - 20 PCE-5 Gluco 0.1 0.05 116 115 113 109 107 150 3 - 21 PCE-5 Gluco 0.1 0.025 112 109 106 98 90 120 3 - 22 PCE-5 Polysorb 0.1 0.05 132 126 121 114 106 150 3 - 23 Molasses Gluco 0.1 0.025 133 117 107 103 91 360

[0110] As can be seen from Table 3 above, compared with compositions containing the same mineral binder and recycled powder but without workability improvers, all combinations of the tested workability improvers significantly increased the initial slump expansion and were able to maintain the slump for a longer period of time.

[0111] For most practical applications, the measured setting time remains within an acceptable range. In the case of ready-mixed concrete, an increased setting time may even be beneficial. Example 4

[0112] Example 4 was carried out in the same manner as Example 3, except that the weight mixing ratio of mineral binder to recycled powder was 65:35.

[0113] Table 4 below provides an overview of the results. Examples 4-1 to 4-12 are based on the present invention. [Table 4]: Examples 4-1 to 4-12; Dosage is given as w% relative to the combined dry weight of the mineral binder and recycled powder. Example additive dose Collapse spread [mm] Initial solidification [min] 3 min 30 min 60 min 90 min 120 min 4-1 PCE-1 PCE-2 0.025 0.05 129 118 107 91 81 120 4-2 PCE-1 PCE-3 0.08 0.08 126 120 118 112 88 120 4-3 PCE-1 PCE-3 0.075 0.125 110 123 110 95 78 120 4-4 PCE-1 PCE-4 0.1 0.1 138 132 126 118 112 180 4-5 PCE-1 PCE-4 Gluco 0.05 0.15 0.025 117 120 116 98 80 180 4-6 PCE-2 Gluco 0.15 0.075 126 128 122 93 78 150 4-7 PCE-2 Gluco 0.1 0.15 108 127 124 122 108 240 4-8 Molasses PCE-2 0.2 0.075 112 110 110 95 90 300 4-9 PCE-3 Gluco 0.1 0.1 104 110 114 112 96 270 4-10 PCE-3 Molasses 0.05 0.4 114 121 118 115 110 120 4-11 PCE-3 Molasses 0.075 0.4 115 120 126 124 112 150 4-12 PCE-3 Molasses Gluco 0.05 0.4 0.025 107 118 130 116 110 180

[0114] As shown in Table 4 above, compared to compositions containing the same mineral binder and recycled powder but without workability improvers, all combinations of the tested workability improvers significantly increased the initial slump spread and were able to maintain the slump for an extended period. For most practical applications, the measured setting times remained within acceptable limits. In the case of ready-mixed concrete, the increased setting time may even be beneficial. Example 5

[0115] Example 5 was carried out in the same manner as Example 3, except that the weight mixing ratio of mineral binder to recycled powder was 70:30, and a water:binder weight ratio of 0.50 was used.

[0116] Table 5 below provides an overview of the results. Examples 5-2 to 5-8 are based on the present invention. [Table 5]: Examples 5-1 - 5-8; Dosage is given as w% relative to the combined dry weight of the mineral binder and recycled powder. Example additive dose Collapse spread [mm] 3 min 30 min 60 min 90 min 120 min 5-1 none 135 nm nm nm nm 5-2 PCE-1 PCE-2 0.12 0.12 197 168 140 n.m. n.m. 5-3 PCE-1 PCE-2 0.09 0.15 187 172 148 n.m. n.m. 5-4 PCE-1 PCE-2 0.12 0.15 200 179 152 n.m. n.m. 5-5 PCE-1 PCE-2 0.09 0.18 208 186 163 145 n.m. 5-6 PCE-1 PCE-2 0.03 0.24 197 183 163 147 n.m. 5-7 PCE-1 PCE-2 0.12 0.30 225 224 211 190 176 5-8 PCE-1 PCE-2 0.06 0.36 227 225 208 194 181 nm: Not measured

[0117] As can be seen from the results in Table 5, the initial slump spread was significantly increased by the tested workability modifiers. It can also be seen that, at a given total dosage of workability modifiers, the slump spread retention rate increased at a lower ratio of PCE-1 to PCE-2.

[0118] none

[0119] none

Claims

1. A method for improving the workability of a mineral binder composition comprising at least one mineral binder and additionally recycled powder, the method comprising the steps of: a) providing at least one mineral binder, b) mixing the recycled powder, c) mixing at least one workability improver selected from a mixture of two different polycarboxylates, or a mixture of a polycarboxylate and a sugar acid, or a mixture of a sugar and sodium gluconate, and d) mixing with water.

2. The method as described in claim 1, characterized in that the recycled powder comprises fully carbonized cement.

3. The method as described in claim 1, characterized in that the recycled powder consists of fully carbonized cement.

4. The method as described in claim 1, characterized in that the recycled powder comprises fully carbonized Portland cement.

5. The method as described in claim 1, characterized in that the recycled powder consists of fully carbonized Portland cement.

6. The method as claimed in claim 1, characterized in that the weight ratio between the at least one mineral binder and the recycled powder is between 99:1 and 5:

95.

7. The method according to any one of claims 1 to 3, characterized in that the at least one workability improver is a mixture of two different polycarboxylates, or a mixture of a polycarboxylate and a glycolic acid, wherein the polycarboxylate comprises: a) a repeating unit A of general formula (I), and b) a repeating unit B of general formula (II), wherein each Ru independently represents hydrogen or methyl, each Rv independently represents hydrogen or COOM, wherein M is independently H, an alkali metal, or an alkaline earth metal, m = 0, 1, 2, or 3, p = 0 or 1, each R1 is independently -(CH2)z-[YO]n-R4, wherein Y is a C2 to C4 alkyl group and R4 is H, C1 to C20 alkyl group, -cyclohexyl, -alkylaryl, or -N(-Ri)j-[(CH2)z-PO3M]3-j, z = 0, 1, 2, 3, or 4, n = 2 - 350, j = 0, 1, or 2, Ri represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and M represents a hydrogen atom, an alkali metal, an alkaline earth metal, or an ammonium ion, and wherein repeating units A and B in the polycarboxylate have a molar ratio of A to B in the range of 10:90 to 90:

10.

8. The method according to any one of claims 1 to 3, characterized in that the at least one workability improver is selected from a mixture of polycarboxylate and sodium gluconate.

9. The method according to any one of claims 1 to 3, characterized in that the at least one mineral binder is selected from the group consisting of: Portland cement, calcium aluminate cement, calcium sulfoaluminate cement, gypsum, hydraulic lime, air lime, geopolymer, slag, clay, finely ground limestone, and mixtures thereof.

10. The method according to any one of claims 1 to 3, characterized in that the at least one workability improver is selected from a mixture of polycarboxylate and glycoacid, and in each case, the weight of the mixed polycarboxylate is between 0.20 and 1.125 w% relative to the dry weight of the recycled powder present, and the weight of the mixed glycoacid is between 0.025 and 1.0 w%.

11. A mineral binder composition comprising a) at least one mineral binder and recycled powder in a weight ratio of 99:1 to 5:95, b) at least one workability improver selected from a mixture of two different polycarboxylates, or a mixture of a polycarboxylate and a sugar acid, or a mixture of sugar and sodium gluconate, and c) at least one aggregate.

12. The mineral binder composition as claimed in claim 11, characterized in that it contains water and has an initial slump flow that is increased by at least 20% as measured according to EN 1015-3 compared to the same mineral binder composition that does not contain the at least one workability improver.

13. A hardened mineral adhesive composition obtained by curing a mineral adhesive composition as described in claim 11, wherein water is present, or obtained by curing a mineral adhesive composition as described in claim 12.