Adjunct admixture for cementitious compositions, and cementitious compositions containing the same.

Abstract

The present invention relates to cementitious compositions having a binder that is a source of aluminates and / or sulfoaluminates, and more particularly to accelerators for cementitious compositions, the accelerators comprising a source of alkali metal carbonates, metal sulfates, alkali metal hydroxides, and optionally alkali metal bicarbonates, alkaline earth metal hydroxides, or alkaline earth metal oxides. The present invention also relates to cementitious compositions having a binder that is a source of aluminates and / or sulfoaluminates and the accelerator of the present invention.

Description

Technical Field

[0001] The present invention relates to an accelerating admixture for cementitious compositions, and a cementitious composition comprising the same, particularly to a cementitious composition having a cementitious binder that is a source of aluminate and / or sulfoaluminate. Background Art

[0002] In the field of special mortars, for example cementitious tile adhesives, it is known to use aluminate cement as the cementitious binder. Aluminate cements are recognized for their rapid strength development. Aluminate cements can be used alone or in a mixture with Portland cement.

[0003] However, the use of aluminate cement as a binder in cementitious compositions typically requires the addition of a setting accelerator. Currently, the most typical setting accelerator is lithium carbonate. The effect of lithium carbonate has been studied, for example, in the paper "The influence of lithium carbonate on phase composition of calcium aluminate cement paste" by M. Niziurska et al., published in Procedia Engineering, 108 (2015), 363-370.

[0004] Similarly, lithium carbonate is used for accelerating the setting and hardening of sulfoaluminate cement. Calcium sulfoaluminate cement is known as an alternative material to Portland cement for reducing the environmental footprint of cementitious compositions.

[0005] However, the use of lithium carbonate in cementitious compositions based on aluminate cement or sulfoaluminate cement presents new problems. In particular, the availability of lithium carbonate for the construction industry has significantly decreased, mainly because lithium salts, in particular, are required for battery manufacturing and electromobility.

[0006] Therefore, it is desirable that a substitute for lithium carbonate be provided to promote the setting and hardening of cementitious compositions based on aluminate cement or sulfoaluminate cement. [Overview of the project] [Problems that the invention aims to solve]

[0007] One object of the present invention is to provide a cementitious composition having a cementitious binder that is a source of aluminates and / or sulfoaluminates, which has accelerated setting and / or hardening. Another object of the present invention is to provide admixtures for accelerating the setting and / or hardening of cementitious compositions, in particular cementitious compositions having a cementitious binder that is a source of aluminates and / or sulfoaluminates. [Means for solving the problem]

[0008] Surprisingly, combinations of alkali metal carbonates, metal sulfates, alkali metal hydroxides, and optionally sources of alkali metal bicarbonates, alkaline earth metal hydroxides, or alkaline earth metal oxides have been found to be effective accelerators for cementitious compositions, particularly for cementitious compositions having a cementitious binder that is a source of aluminates and / or sulfoaluminates.

[0009] Therefore, the object of the present invention is achieved by the subject matter of claim 1. Further aspects of the present invention are the subject matter of the independent claim. Preferred embodiments are the subject matter of the dependent claim. [Modes for carrying out the invention]

[0010] Detailed method In a first embodiment, the present invention relates to a cementitious composition, a) At least one cementitious binder that is a source of aluminates and / or sulfoaluminates, b) A promoter, (1) Alkali metal carbonate, preferably sodium carbonate, (2) A metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (3) Alkali metal hydroxides, (4) Depending on the circumstances, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide, preferably a source of calcium hydroxide or calcium oxide, Accelerators containing, This relates to cementitious compositions containing [specific components].

[0011] In this context, the cementitious composition is a composition comprising at least one cementitious binder, an accelerator, and optionally one or more admixtures chemically distinct from aggregates, fillers, accelerators, and water, which are sources of aluminates and / or sulfoaluminates.

[0012] Cementaceous binders react in the presence of water to form insoluble hydrates. This reaction is called a hydration reaction, and it is through this process that strength is achieved.

[0013] In this context, aluminates are inorganic phases containing aluminum oxides. In particular, aluminates include CA6, CA2, CA, C3A, and C 12 A7 (where C: CaO; A: Al2O3). In this context, the sulfoaluminate is an inorganic phase containing oxides of aluminum, sulfur, and optionally silicon or iron. In particular, the sulfoaluminate is C4(A 3-x F x)$(where C:CaO; A:Al2O3; F:Fe2O3; $:SO3), and x is an integer from 0 to 3. According to the embodiment, the cementitious binder that is the source of aluminates and / or sulfoaluminates is a high-alumina cement having an aluminum content of at least 30% by weight, particularly at least 35% by weight, particularly 35-58% by weight, as measured as Al2O3. Preferably, the cementitious binder that is the source of aluminates is calcium aluminate cement (CAC) or alumina cement in accordance with the standard EN 14647:2006-01. Other terms often used for types of high-alumina cement are ciment fondu, Tonerdeschmelzzement, or alumina molten cement.

[0014] According to the embodiment, the cementitious binder, which is a source of aluminates and / or sulfoaluminates, is C4(A 3-x F x The present invention relates to calcium sulfoaluminate cement (CSA) containing a clinker containing )$(C:CaO;A:Al2O3;F:Fe2O3;$:SO3) (where x is an integer from 0 to 3). The CSA of the present invention is typically an aluminate (CA, C3A, C 12 The CSA comprises a further phase selected from A7 (where C:CaO; A:Al2O3)), belite (C2S (where C:CaO, S:SiO2)), ferrite (C2F, C2AF, C4AF (where C:CaO; A:Al2O3; F:Fe2O3)), ternesite (C5S2 (where C:CaO, S:SiO2; $:SO3)), and anhydrous gypsum. According to one embodiment, the CSA of the present invention comprises 15-75% by weight of C4A3, 0-10% by weight of aluminate, 0-70% by weight of belite, 0-35% by weight of ferrite, 0-20% by weight of ternesite, and 0-20% by weight of anhydrous gypsum, based on the total dry weight of the CSA cement.

[0015] Preferably, at least one cementitious binder is selected from calcium aluminate cement and / or calcium sulfoaluminate cement.

[0016] The cementitious binder of the present invention may also include a mixture of alumina cement, particularly calcium aluminate cement, and calcium sulfoaluminate cement.

[0017] The cementitious binder of the present invention may include a further cementitious binder in addition to at least one cementitious binder that is a source of aluminates and / or sulfoaluminates. The further cementitious binder can be selected from Portland cement, in particular CEM I, CEM II, CEM III, CEM IV, or CEM V in accordance with the standard EN 197-1:2011, pozzolanes, and latent hydraulic binders. Pozzolanes and latent hydraulic binders are natural pozzolanes such as slag, in particular blast furnace slag or basic oxygen slag, clay, calcined clay, in particular metakaolin, kiln dust, microsilica, fly ash, pyrolysis silica, precipitated silica, silica fume, zeolite, rice husk ash, calcined oil shale, and pumice and truss.

[0018] The cementitious binder of the present invention may further contain calcium sulfate. Calcium sulfate may be present in the form of calcium sulfate hemihydrate, calcium sulfate dihydrate, and / or anhydrous gypsum. According to embodiments, at least one cementitious binder of the present invention is a mixture of Portland cement and one of calcium aluminate cement or calcium sulfoaluminate cement.

[0019] The weight ratio of Portland cement to calcium aluminate cement or calcium sulfoaluminate cement in the cementaceous composition of the present invention can vary over a wide range. The weight ratio of Portland cement to one of calcium aluminate cement or calcium sulfoaluminate cement may preferably be between 10:1 and 1:1, more preferably between 3:1 and 1:1.

[0020] When the ratio is based on the total weight of at least one cementitious binder, this criterion means the sum of all cementitious binders present.

[0021] According to an embodiment, the cementitious composition comprises at least one cementitious binder that is a source of aluminate and / or sulfoaluminate, further comprises Portland cement, pozzolan, and / or latent hydraulic binder, and the content of aluminate and / or sulfoaluminate is 2 to 30 wt%, preferably 5 to 25 wt%, particularly between 6 to 10 wt%, based on the total dry weight of the cementitious binder.

[0022] According to an embodiment, the cementitious composition is a) comprises at least one cementitious binder that is a source of aluminate and / or sulfoaluminate, further comprises Portland cement, pozzolan, and / or latent hydraulic binder, and the content of aluminate and / or sulfoaluminate is 2 to 30 wt%, preferably 5 to 25 wt%, particularly between 6 to 10 wt%, based on the total dry weight of the cementitious binder, b) an accelerator, (1) an alkali metal carbonate, preferably sodium carbonate, and (2) a metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, and (3) an alkali metal hydroxide, and (4) optionally, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide, preferably a source of calcium hydroxide or calcium oxide, and comprises an accelerator including the above components.

[0023] In this context, the accelerator is a material or mixture of materials that can accelerate the setting and / or hardening of a cementitious composition. Acceleration of setting can be measured as a reduction in setting time relative to a reference. Acceleration of hardening can be measured as an increase in strength after a specific hardening time relative to a reference, particularly compressive strength and / or flexural strength. The terms solidification and hardening can be used synonymously in this context. Setting time can be measured as described in the standard EN 196-3:2016. Compressive strength and flexural strength can be measured in accordance with the standards EN 1015-11:2019 or EN 12390-3:2019-10.

[0024] The accelerator of the present invention comprises an alkali metal carbonate, a metal sulfate, an alkali metal hydroxide, and optionally a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide. According to a preferred embodiment, the accelerator of the present invention comprises an alkali metal carbonate, a metal sulfate, an alkali metal hydroxide, and optionally a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide.

[0025] Alkali metal carbonates are particularly lithium carbonate, sodium carbonate, and potassium carbonate. Preferably, the alkali metal carbonate is sodium carbonate. It is generally preferable that the cementitious composition of the present invention does not contain lithium carbonate.

[0026] The metal sulfate is very preferably selected from sodium sulfate, potassium sulfate, or aluminum sulfate. Aluminum sulfate is particularly preferred. The term "aluminum sulfate" includes aluminum sulfate hydrate, for example, Al2(SO4)3·14H2O.

[0027] The alkali metal hydroxide is preferably selected from sodium hydroxide or potassium hydroxide.

[0028] Preferably, the source of alkaline earth metal hydroxide is selected from slaked lime, and the source of alkaline earth metal hydroxide is selected from natural hydraulic lime, blended lime, hydraulic lime, and air-hardened lime. When used in the context of the present invention, natural hydraulic lime, blended lime, hydraulic lime, and air-hardened lime mean the materials described in the standard EN 459-1:2015.

[0029] The preferred alkali metal bicarbonate is sodium bicarbonate.

[0030] According to a preferred embodiment, the cementitious composition of the present invention (in each case, based on the total dry mass of at least one cementitious binder) (i) 0.01 to 2.0% by weight, preferably 0.1 to 1.5% by weight, more preferably 0.2 to 0.8% by weight of an alkali metal carbonate, preferably sodium carbonate, (ii) 0.01 to 1% by weight, preferably 0.1 to 0.5% by weight of a metal sulfate, more preferably 0.1 to 0.3% by weight of sodium sulfate, potassium sulfate, or aluminum sulfate, (iii) 0.01 to 1% by weight, preferably 0.05 to 0.25% by weight, more preferably 0.02 to 0.1% by weight of an alkali metal hydroxide, (iv) A source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide in an amount of 0.4 to 5% by weight, preferably a source of calcium hydroxide or calcium oxide, Includes.

[0031] The cementitious composition of the present invention may further contain one or more admixtures chemically distinct from aggregates, fillers, accelerators, and water. In particular, the cementitious composition of the present invention is a construction material, such as mortar, especially dry mortar, grout, or concrete.

[0032] The aggregate may be any material that is non-reactive in the hydration reaction of the cementitious binder. The aggregate may be any aggregate typically used in construction materials. Typical aggregates include, for example, rock, crushed stone, gravel, sand, especially quartz sand, river sand, and / or crushed sand. However, the aggregate may also be selected from bio-derived materials, such as flex, hemp, straw, rapeseed, or sunflower. The aggregate may also be crushed and recycled construction materials, especially concrete.

[0033] The term "filler" refers to calcareous or siliceous material with fine particle sizes. One very typical filler is crushed limestone. The particle size of fillers is smaller than that of aggregates. For example, fillers can have particle sizes of less than 0.063 mm. In particular, 90% of fillers have particle sizes of less than 0.063 mm.

[0034] Further admixtures are admixtures that are chemically different from the accelerators of the present invention. According to embodiments, further admixtures are selected from the group consisting of plasticizers, fluidizers, shrinkage reducers, air entrainers, deaeration agents, stabilizers, viscosity modifiers, thickeners, water reducers, retarders, water resistant agents, fibers, foaming agents, defoaming agents, redispersible polymer powders, dust suppressants, chromate reducers, pigments, biocides, rust inhibitors, and steel passivators. Further accelerators, particularly organic accelerator additives, nitrates, nitrites, thiocyanates, and / or silicates may also be present, but are not preferred.

[0035] In another embodiment, the present invention relates to a hardened object, preferably a part of a structure, which can be obtained by mixing the aforementioned cementitious composition with water and subsequently hardening the mixture.

[0036] According to the embodiment, the cementitious composition is mixed with water at a weight ratio of water to cement between 0.1 and 0.8, preferably between 0.2 and 0.6. The mixing method itself is well known to those skilled in the art. The curing of the mixture of water and cementitious composition is preferably carried out at a temperature between 5 and 50°C and a pressure of about 1 atmosphere. However, the mixture can also be cured at higher temperatures and / or higher pressures, for example, by steam curing or autoclave curing. Typically, the cured object is formed by molding the mixture of water and cementitious composition, which is still wet and fluid. Molding can be done, for example, by spraying, troweling, rolling, or brushing onto a solid support, by injecting into molds, formwork, or gaps, or by coating in a free form.

[0037] In particular, the cementitious composition of the present invention can be used as a cementitious tile adhesive, grouting material, self-leveling underlayment, self-leveling overlayment, primer, repair mortar, masonry thin joint mortar or concrete, screed, indoor and outdoor wall leveler, non-shrinking grout, thin joint mortar, waterproof mortar, or anchoring mortar. The cementitious tile adhesive conforms particularly to standard EN 12004-1. The grouting material conforms particularly to standard EN 13888. The self-leveling underlayment or self-leveling overlay conforms particularly to standard EN 13813. The primer conforms particularly to standard EN 998-1. The repair mortar conforms particularly to standard EN 1504-3. The masonry mortar or concrete conforms particularly to standards EN 998-2 and EN 206-1. Screed conforms specifically to standard EN 13813. Non-shrinkage grout conforms specifically to standard EN 1504-6. Syn-joint mortar conforms specifically to standard EN 998-2. Waterproof mortar conforms specifically to standard EN 1504-2. Anchoring mortar conforms specifically to standard EN 1504-6.

[0038] The cementitious composition of the present invention may be concrete.

[0039] In another aspect, the present invention relates to a method for accelerating the setting and / or hardening of a cementitious composition. (1) Alkali metal carbonate, preferably sodium carbonate, (2) A metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (3) Alkali metal hydroxides, (4) Depending on the circumstances, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide, preferably a source of calcium hydroxide or calcium oxide, Regarding the use of admixtures including the above.

[0040] All of the embodiments described above also apply to this embodiment.

[0041] The admixtures are, (1) Alkali metal carbonate, preferably sodium carbonate, (2) A metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (3) Alkali metal hydroxides, (4) Depending on the circumstances, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide, preferably a source of calcium hydroxide or calcium oxide, It can consist of

[0042] The admixture may be in the form of a one-component composition. In a one-component composition, all components are contained within a single compartment. One-component compositions have the advantage of simpler usage and reduced likelihood of problems due to incorrect usage. In this context, the admixture is preferably a one-component composition comprising an alkali metal carbonate, a metal sulfate, an alkali metal hydroxide, and optionally a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide.

[0043] The admixture may be in the form of a two-component or multi-component composition. A two-component or multi-component composition contains individual components in two or more spatially separated containers. A two-component or multi-component composition may have the advantage of improved shelf life and allow for easier adjustment of the amount of individual components used.

[0044] The admixture or any of its components may be in the form of a free-flowing powder, granular pellets, flakes, or compressed material. The admixture or any of its components may also be in the form of a slurry or solution in water.

[0045] Accelerated setting can be measured as a reduction in setting time for various references. The reference is a cementitious composition that does not contain at least one component of the accelerator. Setting time can be measured as described in the standard EN 196-3:2016.

[0046] The acceleration of hardening can be measured as an increase in strength, particularly compressive and / or flexural strength, after a specific hardening time relative to a reference. The reference is a cementitious composition that does not contain at least one component of the accelerator. Compressive and flexural strengths can be measured in accordance with the standards EN 1015-11:2019 or EN 12390-3:2019-10.

[0047] The admixtures of the present invention can be used to promote the setting and / or hardening of compositions containing any of the aforementioned cementitious binders. For example, the admixtures of the present invention can be used to promote the setting and / or hardening of compositions containing only Portland cement and not high-alumina cement or sulfoaluminate cement. It is preferable to use the admixtures of the present invention to promote the setting and / or hardening of cementitious compositions containing at least one cementitious binder that is a source of aluminate and / or sulfoaluminate. A mixture of Portland cement, at least one cementitious binder that is a source of aluminate and / or sulfoaluminate, and optionally calcium sulfate can be used.

[0048] According to the embodiments, the admixture of the present invention (in each case, based on the total weight of the admixture) (1) 10 to 80% by weight, preferably 15 to 50% by weight of alkali metal carbonate, preferably sodium carbonate, (2) 1 to 50% by weight, preferably 2 to 20% by weight of a metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (3) 1 to 50% by weight, preferably 1 to 10% by weight of an alkali metal hydroxide, (4) Depending on the circumstances, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide in an amount of 1 to 80% by weight, preferably a source of calcium hydroxide or calcium oxide, It includes or consists of.

[0049] In particular, in the admixture of the present invention, the alkali metal hydroxide is sodium hydroxide, the source of the alkali metal bicarbonate is selected from sodium bicarbonate, the source of the alkaline earth metal hydroxide is selected from slaked lime, and the source of the alkaline earth metal oxide is selected from natural hydraulic lime, blended lime, hydraulic lime, and air-hardened lime.

[0050] In particular, in the admixture of the present invention, the weight ratio of alkali metal carbonate to alkali metal hydroxide is between 20:1 and 10:1.

[0051] In particular, in the admixture of the present invention, the weight ratio of metal sulfate to alkali metal hydroxide is between 10:1 and 1:1.

[0052] The aforementioned admixture can be used in the aforementioned cementitious composition. The admixture of the present invention can be used as an accelerator in the cementitious composition of the present invention.

[0053] Further details of the present invention will be shown to those skilled in the art by the following embodiments, which are not intended to limit the invention in any way. [Examples]

[0054] Table 1 below shows the raw materials used in the examples.

[0055] [Table 1]

[0056] The cementitious composition was prepared by mixing all the components in the amounts shown in Tables 2 and 3 below on a Hobart mixer until substantially homogeneous. Next, water was added in an amount that resulted in a water-to-powder weight ratio of 0.21, and mixing was continued for 3 minutes.

[0057] The setting time was measured as specified in the standard EN 196-3:2016.

[0058] Compressive strength (CS) and flexural strength (FS) were measured in accordance with the standard EN 1015-11:2019 after the times shown in the table below.

[0059] [Table 2]

[0060] The results in Table 2 above show that curing is accelerated by the combined use of sodium carbonate, sodium hydroxide, and aluminum sulfate (see the strength over all periods in Example 1 compared to the reference example). When one of the accelerator components is removed, slower strength development is observed (see Reference Examples 1-3). Therefore, the use of a combination of sodium carbonate, sodium hydroxide, and aluminum sulfate yields particularly good curing acceleration.

[0061] [Table 3]

[0062] The results in Table 3 above show that curing is accelerated by the combined use of sodium carbonate, sodium hydroxide, and aluminum sulfate (see the strength over all periods in Example 2 compared to the reference example). When one of the accelerator components is removed, slower strength development is observed (see Reference Examples 4-6). Therefore, particularly good curing acceleration is obtained by using a combination of sodium carbonate, sodium hydroxide, and aluminum sulfate. Setting is also particularly improved when a combination of sodium carbonate, sodium hydroxide, and aluminum sulfate is used (see Example 2).

[0063] [Table 4]

[0064] Reference Example 8 shows that, even in the presence of the same accelerating admixture, a purely Portland cement-based cementitious binder does not achieve the same early strength as a composition having the cementitious binder of the present invention (see Example 1). Examples 3 and 4 show that hardening is accelerated in the presence of smaller amounts of aluminates and / or sulfoaluminates.

[0065] [Table 5]

[0066] Examples 5 and 6 show that the effect is further enhanced by the use of calcium hydroxide. Examples 6-10 show the effects of different amounts of sodium carbonate, sodium hydroxide, and aluminum sulfate used.

Claims

1. A cementitious composition, a) At least one cementitious binder that is a source of aluminates and / or sulfoaluminates, b) A promoter, (1) Alkali metal carbonate, preferably sodium carbonate, (2) A metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (3) Alkali metal hydroxides, (4) Depending on the circumstances, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide, preferably a source of calcium hydroxide or calcium oxide, Accelerators containing, A cementitious composition containing the following:

2. The cementitious composition according to claim 1, characterized in that the at least one cementitious binder is selected from calcium aluminate cement and / or calcium sulfoaluminate cement.

3. The cementitious composition according to claim 1 or 2, characterized in that the at least one cementitious binder is a mixture of Portland cement and one of calcium aluminate cement or calcium sulfoaluminate cement.

4. The cementitious composition according to claim 3, characterized in that the weight ratio of Portland cement to calcium aluminate cement or calcium sulfoaluminate cement is between 10:1 and 1:1, preferably between 3:1 and 1:

1.

5. The cementitious composition according to at least one of claims 1 to 4, characterized in that the alkali metal hydroxide is selected from sodium hydroxide or potassium hydroxide.

6. The cementitious composition according to at least one of claims 1 to 5, characterized in that the source of the alkaline earth metal hydroxide or alkaline earth metal oxide is selected from slaked lime, natural hydraulic lime, blended lime, hydraulic lime, and air-hardened lime.

7. A cementitious composition, (in each case, based on the total dry mass of the at least one cementitious binder) (i) 0.01 to 2.0% by weight, preferably 0.1 to 1.5% by weight, more preferably 0.2 to 0.8% by weight of an alkali metal carbonate, preferably sodium carbonate, (ii) 0.01 to 1% by weight, preferably 0.1 to 0.5% by weight, more preferably 0.1 to 0.3% by weight of a metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (iii) 0.01 to 1% by weight, preferably 0.02 to 0.25% by weight, more preferably 0.02 to 0.1% by weight of an alkali metal hydroxide, (iv) Depending on the case, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide in an amount of 0.4 to 5% by weight, preferably a source of calcium hydroxide or calcium oxide, A cementitious composition according to at least one of claims 1 to 6, characterized by containing the following:

8. A cementitious composition according to at least one of claims 1 to 7, characterized in that it does not contain lithium carbonate.

9. A hardened object, preferably a part of a structure, which can be obtained by mixing a cementitious composition according to at least one of claims 1 to 8 with water, and then hardening the mixture.

10. For promoting the setting and / or hardening of cementitious compositions, (1) Alkali metal carbonate, preferably sodium carbonate, (2) Metal sulfate, preferably sodium sulfate, potassium sulfate or aluminum sulfate, (3) Alkali metal hydroxides, (4) Depending on the circumstances, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide, preferably a source of calcium hydroxide or calcium oxide, Use of admixtures containing the above.

11. The use according to claim 10, characterized in that the cementitious composition comprises at least one cementitious binder which is a source of aluminates and / or sulfoaluminates.

12. Admixture (based on the total weight of the admixture in each case), (1) 10 to 80% by weight, preferably 15 to 50% by weight of an alkali metal carbonate, preferably sodium carbonate, (2) 1 to 50% by weight, preferably 2 to 20% by weight of a metal sulfate, preferably sodium sulfate, potassium sulfate, or aluminum sulfate, (3) 1 to 50% by weight, preferably 1 to 10% by weight of an alkali metal hydroxide, (4) Depending on the case, a source of alkali metal bicarbonate, alkaline earth metal hydroxide, or alkaline earth metal oxide in an amount of 1 to 80% by weight, preferably a source of calcium hydroxide or calcium oxide, Admixture containing or consisting of.

13. The admixture according to claim 12, characterized in that the alkali metal hydroxide is sodium hydroxide, the source of the alkali metal bicarbonate is selected from sodium bicarbonate, the source of the alkaline earth metal hydroxide is selected from slaked lime, and the source of the alkaline earth metal oxide is selected from natural hydraulic lime, blended lime, hydraulic lime, and air-hardened lime.

14. The admixture according to at least one of claim 12 or 13, characterized in that the weight ratio of alkali metal carbonate to alkali metal hydroxide is between 20:1 and 10:

1.

15. The admixture according to at least one of claims 12 to 14, characterized in that the weight ratio of the metal sulfate to the alkali metal hydroxide is between 10:1 and 1:1.

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