ADDITIVES FOR THE INTERNAL POST-TREATMENT OF MINERAL BINDER COMPOSITIONS

Description

Technical field

[0001] The invention relates to an additive for mineral binder compositions, in particular a post-treatment agent for mineral binder compositions, and its use. The invention further relates to a mineral binder composition containing the additive, molded parts obtainable therefrom, and a method for producing the mineral binder composition. State of the art

[0002] The density of the binder matrix is ​​crucial for the quality and durability of hardened mineral binder compositions, such as concrete or mortar.

[0003] Durable products based on cured mineral binder compositions are distinguished not only by their compressive strength. Even more important is their water resistance, especially in near-surface areas. The lower the porosity and the denser the near-surface areas, the greater the resistance to external influences, stresses, and attacks.

[0004] However, this is only achieved if specific measures are taken to protect freshly mixed binder compositions, e.g., fresh concrete, against: (i) premature drying due to wind, sun, low humidity, (ii) extreme temperatures (cold, heat) and rapid temperature changes, (iii) rain, (iv) thermal and physical shocks, (v) chemical attack, and (vi) mechanical stresses. Such measures are also referred to as "curing".

[0005] In practice, premature drying poses a serious problem, impairing, among other things, the strength development of the hardening mineral binder composition. If no measures are taken in this regard, there is a risk of reduced strength in near-surface areas, a tendency to crumble, increased water permeability, reduced weather resistance, low resistance to chemical attack, the formation of early shrinkage cracks, and an increased risk of subsequent shrinkage cracking.

[0006] To prevent premature drying, freshly mixed binder compositions, such as fresh concrete, are typically subjected to curing. Known curing methods include applying liquid curing compounds (e.g., Sika® < Antisol® < E-20), leaving the concrete in the formwork, covering it with foil, applying water-based coverings, continuously spraying it with water, or underwater storage, as well as combinations of these methods.

[0007] Also known is the use of additives, which are added to the mineral binders when mixed with water to counteract premature drying. This process is referred to as "internal post-treatment" or "internal curing".

[0008] In this context, WO 2015 / 028547 A1 (Cemex Research Group AG) describes, for example, a process in which cement components, an internal curing agent, and surfactants are milled together. The internal curing agent consists of cellulose fibers dispersed by the surfactants. Milling the curing agent together with the cement components is intended to result in more stable and efficient curing behavior.

[0009] However, existing methods and agents for the post-treatment of mineral binder compositions are often complex to manufacture, complicated to apply, or their effectiveness is not entirely convincing. Therefore, there remains a need for new and more advantageous methods and agents for the post-treatment of mineral binder compositions. Description of the invention

[0010] The object of the invention is therefore to overcome the aforementioned disadvantages. In particular, an improved agent for the post-treatment of mineral binder compositions is to be provided. The agent should be suitable for internal post-treatment and should not impair the workability, setting behavior, or strength of the binder compositions as much as possible. Furthermore, advantageous methods, uses, and binder compositions that enable efficient internal post-treatment are to be provided.

[0011] Surprisingly, it was found that the problem according to claim 1 can be solved.

[0012] As demonstrated in trials, the additives according to the invention can be used as efficient and highly effective agents for the internal post-treatment or curing of mineral binder compositions. Trials have shown that the additives positively influence the shrinkage behavior of mineral binder compositions, e.g., concrete compositions, and significantly reduce cracking. This applies both during the setting and hardening period and in the cured state. Undesirable drying of the mineral binder compositions can be effectively prevented. At the same time, the additives according to the invention have little to no effect on the workability, setting, or strength of cured binder compositions. The additives can, for example, be added directly to the mixing water.Prior grinding with cement components is therefore unnecessary, which greatly simplifies its use. Furthermore, it has been shown that the additives are compatible with other typical additives for mineral binder compositions.

[0013] Further aspects of the invention are the subject of further independent claims. Particularly preferred embodiments of the invention are the subject of dependent claims. Ways to implement the invention

[0014] A first aspect of the present invention relates to an additive for mineral binder compositions, in particular an internal post-treatment agent for mineral binder compositions, comprising at least one water-absorbing substance, wherein the water-absorbing substance comprises or consists of at least one starch ether, in particular hydroxyalkyl starch, specifically hydroxypropyl starch, and at least one shrinkage reducer.

[0015] A "mineral binder" is specifically a binder, particularly an inorganic binder, which reacts in the presence of water in a hydration reaction to form solid hydrates or hydrate phases. This can be, for example, a hydraulic binder (e.g., cement or hydraulic lime), a latent hydraulic binder (e.g., slag or blast furnace slag), a pozzolanic binder (e.g., fly ash, trass, or rice husk ash), and / or a non-hydraulic binder (gypsum or quicklime). Mixtures of the various binders are also possible.

[0016] In particular, the mineral binder or binder composition contains a hydraulic binder, preferably cement. A cement with a cement clinker content of ≥ 35 wt.% is particularly preferred. In particular, the cement is of type CEM I, CEM II, CEM III, CEM IV, CEM V (according to standard EN 197-1). Specifically, it is cement of type CEM I and / or CEM II.

[0017] Advantageously, the proportion of the hydraulic binder in the total mineral binder is at least 5 wt.%, in particular at least 20 wt.%, preferably at least 35 wt.%, and specifically at least 65 wt.%. According to a further advantageous embodiment, the mineral binder consists of at least 95 wt.% hydraulic binder, in particular cement.

[0018] However, it can also be advantageous if the binder composition contains other binders in addition to or instead of a hydraulic binder. These are, in particular, latent hydraulic binders and / or pozzolanic binders. Suitable latent hydraulic and / or pozzolanic binders are, for example, slag, fly ash, and / or silica dust. The binder composition can also contain inert substances such as limestone flour, quartz flour, and / or pigments. In an advantageous embodiment, the mineral binder contains 5–95 wt.%, in particular 5–65 wt.%, and specifically 15–35 wt.%, latent hydraulic and / or pozzolanic binders.

[0019] In the present context, a "cementous binder" is understood to mean in particular a binder or a binder composition containing at least 5 wt.%, in particular at least 20 wt.%, preferably at least 35 wt.%, and in particular at least 65 wt.% cement.

[0020] The water-absorbing substance and the shrinkage reducer can, in principle, be present independently of each other, for example in separate containers, as a two- or multi-component additive. However, it is preferred that the water-absorbing substance and the shrinkage reducer are mixed, particularly in a common container. In this case, the additive is a one-component additive.

[0021] The at least one water-absorbing substance and the at least one shrinkage reducer are chemically different.

[0022] Disclosed but not fully claimed water-absorbing substances include at least one representative from the group consisting of superabsorbent polymers, layered silicates, starch, and cellulose. The term "starch" here refers to both unmodified and modified starch. Unmodified starch is a polysaccharide with the formula (C₆H₁₀O₅)n, consisting essentially of α-D-glucose units. The parameter "n" indicates the average number of repeating units. The term "modified starch" is known to those skilled in the art. This refers in particular to starches that have been physically, enzymatically, and / or chemically modified.

[0023] Superabsorbent polymers are also known as superabsorbents. These are preferably polyacrylates or copolymers of acrylic acid and sodium acrylate.

[0024] A manifestation in which the water-absorbing substance comprises or consists of at least one layered silicate is disclosed but not claimed. This is in particular a layered silicate containing magnesium. The layered silicate is especially preferred from the group consisting of vermiculite, palygorskite, and / or sepiolite. Vermiculite is particularly preferred.

[0025] Such compounds, in combination with a shrinkage reducer, have proven to be particularly effective means for internal post-treatment.

[0026] The water-absorbing substance contains or consists of starch ethers, in particular hydroxyalkyl starch. Hydroxypropyl starch is especially advantageous. The starch ether is obtainable, in particular, by the chemical reaction of unmodified starch with an alkylene oxide, especially a propylene oxide. This is known to those skilled in the art. Corresponding starch ethers are also commercially available from various suppliers. In the present context, starch ethers or hydroxyalkyl starch have proven to be particularly preferred.

[0027] In particular, the water-absorbing substance includes vermiculite and starch ethers, especially hydroxyalkyl starch or hydroxypropyl starch.

[0028] According to another advantageous embodiment, the water-absorbing substance comprises both starch ethers, in particular hydroxyalkyl starch or hydroxypropyl starch, and cellulose.

[0029] The shrinkage-reducing substance is advantageously selected from alcohols, monoalcohols, glycols, diols, alkanediols, alkenediols, polyols, alkanolamines and / or polyalkylene oxides. Mixtures of these substances are also possible.

[0030] Polyols, preferably diols, have proven particularly suitable as shrinkage-reducing substances. Polyols or diols with 2–15, preferably 3–10, and especially preferably 4–6 carbon atoms are particularly advantageous. These are preferably alkane polyols or alkane diols. These consist of straight or branched hydrocarbon chains bearing exactly two hydroxyl groups at different positions. However, they contain no other heteroatoms or multiple bonds. Diols are particularly advantageous in each case.

[0031] Particularly preferred shrinkage-reducing substances are ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butyldiglycol, neopentyl glycol, and / or hexylene glycol. Hexylene glycol and / or neopentyl glycol, especially neopentyl glycol, are particularly advantageous.

[0032] The following embodiments of the invention have proven to be particularly advantageous: a) The shrinkage-reducing substance comprises a diol, in particular an alkanediol, and the water-absorbing substance comprises starch ethers. b) The shrinkage-reducing substance comprises hexylene glycol and / or neopentyl glycol, and the water-absorbing substance comprises starch ethers. c) The shrinkage-reducing substance comprises neopentyl glycol, and the water-absorbing substance comprises vermiculite and starch ethers. d) The shrinkage-reducing substance comprises neopentyl glycol, and the water-absorbing substance comprises starch ethers.

[0033] A weight ratio of the shrinkage-reducing substance to the water-absorbing substance is generally advantageously 5:95 - 99:1, preferably 25:75 - 98:2.

[0034] A weight ratio of starch ether, in particular hydroxyalkyl starch, especially hydroxypropyl starch, to the shrinkage-reducing substance is preferably in the range of 1:99 - 50:50, preferably 3:97 - 25:75, in particular 6.5:93.5 - 20:80, in particular 7:93 - 15:85, most preferably 7.5:92.5 - 12.5:87.5.

[0035] The case is disclosed but not claimed in which the water-absorbing substance comprises or consists of a layered silicate, in particular vermiculite, and a weight ratio of the water-absorbing substance to the shrinkage-reducing substance is preferably in the range of 50:50 - 95:5, preferably 55:45 - 80:20, in particular 60:40 - 75:25, and specifically 62:38 - 70:30.

[0036] In general, and based on the total weight of the additive, the shrinkage-reducing substance comprises, in particular, a proportion of 5–99 wt.%, preferably 25–98 wt.%. The water-absorbing substance advantageously comprises a proportion of 1–95 wt.%, preferably 2–75 wt.%.

[0037] The proportion of starch ether, in particular hydroxyalkyl starch, specifically hydroxypropyl starch, based on the total weight of the additive, is advantageously 1 - 50 wt.%, preferably 3 - 25 wt.%, in particular 6.5 - 20 wt.%, in particular 7 - 15 wt.%, most preferably 7.5 - 12.5 wt.%.

[0038] It is disclosed but not claimed that the water-absorbing substance comprises or consists of a layered silicate, in particular vermiculite, and that the proportion of the water-absorbing substance based on the total weight of the additive is advantageously 50 - 95 wt.%, preferably 55 - 80 wt.%, in particular 60 - 75 wt.%, and specifically 62 - 70 wt.%.

[0039] Furthermore, the additive may additionally contain at least one further additive, wherein the further additive is in particular selected from the group comprising defoamers, dyes, preservatives, flow agents, liquefiers, accelerators, retarders, air-entraining agents and / or corrosion inhibitors.

[0040] The additive may also optionally contain a solvent, e.g. water and / or an alcohol.

[0041] Another aspect of the present invention relates to a mineral binder composition, in particular a mortar and / or concrete composition, comprising a mineral binder and an additive as described above. The mineral binder is also defined as described above.

[0042] The mineral binder composition can be either a dry binder composition or a binder composition mixed with water.

[0043] The additive advantageously comprises a proportion of 0.01–10 wt.%, in particular 0.1–8 wt.%, preferably 0.1–5 wt.% or 0.5–3 wt.%, relative to the weight of the mineral binder. Optimal effect of the additive is achieved at such proportions.

[0044] Advantageously, the additive also comprises a superplasticizer, in particular a polycarboxylate ether. If present, the superplasticizer advantageously comprises 0.01–6 wt.%, in particular 0.1–4 wt.%, and more preferably 0.5–3 wt.%, relative to the mineral binder. Due to the combination of the additive according to the invention and the superplasticizer, the workability of the binder composition can be improved, and higher compressive strengths are achieved. As has been shown, the superplasticizer hardly impairs, or does not impair, the effect of the additive.

[0045] Advantageously, the flow agent is a comb polymer comprising a polycarboxylate backbone with polyether side chains attached to it. The side chains are attached to the polycarboxylate backbone primarily via ester, ether, and / or amide groups.

[0046] Corresponding polycarboxylate ethers and manufacturing processes are disclosed, for example, in EP 1 138 697 B1 on page 7, line 20 to page 8, line 50, and in its examples, or in EP 1 061 089 B1 on page 4, line 54 to page 5, line 38, and in its examples. In a variation thereof, as described in EP 1 348 729 A1 on pages 3 to 5 and in its examples, the comb polymer can be produced in the solid state.

[0047] The disclosure of these patent specifications is hereby included, in particular by reference.

[0048] Such comb polymers are also commercially distributed by Sika Schweiz AG under the trade name series ViscoCrete ®<.

[0049] In a further preferred embodiment, the binder composition additionally contains solid aggregates, in particular gravel, sand and / or aggregates. Such binder compositions can be used, for example, as mortar mixes or concrete mixes.

[0050] In particular, the binder composition additionally contains water, wherein the weight ratio of water to mineral binder is preferably in the range of 0.25–0.8, particularly 0.3–0.6, preferably 0.35–0.5. Such binder compositions can be processed directly as mortar or concrete mixes.

[0051] An additional aspect of the present invention relates to a molded body obtainable by curing a binder composition as described above after the addition of water. The molded body thus produced can have virtually any desired shape and, for example, be a component of a structure, such as a building, a wall, or a bridge.

[0052] An additional aspect of the invention relates to the use of at least one water-absorbing substance and at least one shrinkage reducer or additive according to the invention for the internal post-treatment of a mineral binder composition. The at least one water-absorbing substance, the at least one shrinkage reducer, and the mineral binder composition are defined as described above.

[0053] In particular, the additive according to the invention can be used as an agent for the internal post-treatment of a mineral binder composition.

[0054] The additive according to the invention is also suitable for reducing the shrinkage of a mineral binder composition, particularly during the setting and / or hardening period.

[0055] It is also advantageous to use the additive according to the invention to reduce the drying out of a mineral binder composition, especially during the setting and / or hardening period.

[0056] Furthermore, the additive according to the invention is suitable for reducing the formation of cracks, especially during the setting and / or hardening period, in a mineral binder composition.

[0057] The aforementioned setting and / or hardening period includes in particular the first 28 days, especially the first 7 days or the first 2 days, after the mixing of the mineral binder composition.

[0058] The use of the additive according to the invention is also advantageous for improving the chemical resistance and / or the mechanical strength of a surface of a mineral binder composition.

[0059] The mineral binder compositions are defined as described above.

[0060] From the following exemplary embodiments, further advantageous embodiments of the invention will become apparent to the person skilled in the art. Brief description of the drawing

[0061] The figures used to illustrate the exemplary embodiments show: Fig. 1: Left: A cuboid formwork filled with a mortar mixture, with an L-shaped steel rib running centrally and along its entire width; Right: A detail view of the steel rib; Fig. 2: A side view of a crack in the hardened mortar mixture made of Fig. 1 above the steel rib. The arrow marks the position of the crack; Fig. 3: A top view of the crack from Fig. 2 The arrow again marks the position of the crack; Fig. 4: The shrinkage over time of mortar mixtures without (diamonds) and with an additive based on vermiculite or neopentyl glycol (squares or triangles). Examples of implementation 1. Substances used

[0062] The following substances were used for the exemplary implementations: Table 1 Designation substance mS Hydroxypropyl starch (Emset KH 6; Emsland Stärke GmbH, Germany) SSV Vermiculite NPG Neopentyl glycol V1 Conventional external paraffin-based after-treatment agent (Antisol® < E-20, Sika Switzerland AG) V2 Conventional internal post-treatment agent based on cellulose (Hidratium®, Cemex Research Group AG, Switzerland)

[0063] Vermiculite (SSV)and neopentyl glycol (NPG) are commercially available from various suppliers and were used in pure form (purity > 97%). 2. Provision of additional funds

[0064] The additives according to the invention listed below in Table 2 were used. Z1 and Z3 as well as the non-inventive additive Z2 manufactured: Table 2 Designation Water abs. Substance / proportion Shrinkage reducer / proportion Z1 mS / 8.16 wt.% NPG / 91.84 wt.% Z2 SSV / 66.7 wt.% NPG / 33.3 wt.% Z3 mS / 11.7 wt.% NPG / 88.3 wt.%

[0065] In all of the mortar tests described below, a modified polycarboxylate in the form of Sika® ViscoCrete® -3081 S was used as a superplasticizer. Sika® ViscoCrete® -3081 S is a comb polymer with a polycarboxylate backbone and polyalkylene oxide side chains linked via ester groups. The superplasticizer was used at a concentration of 1.0 wt%, based on the binder, and was premixed with the mixing water. 3. Mortar mixtures

[0066] The effectiveness of the additives according to the invention was tested in mortar mixtures. For this purpose, mortars as specified in Table 3 were used. Table 3: Dry composition of the mortar mixtures used Grass grain size 8 mm) ( component Mixture M1 Mixture M2 CEM I 750 g - CEM II A-LL - 750 g Limestone filler 141 g 141 g Sand 0-1 mm 738 g 738 g Sand 1-4 mm 1107 g 1107 g Sand 4-8 mm 1154 g 1154 g

[0067] For mixture M1 Swiss CEM I 42.5 N cement (a mixture of cements from Normo 4 [Siggenthal / Holcim AG], Vigier CEM I 42.5 N [Vigier Ciment AG], and CEM I 42.5 N [Wildegg / Jura cement] in a weight ratio of 1:1:1) with a Blaine fineness of 3,600 cm² / g was used. The sands, limestone filler, and cement were dry-mixed for one minute in a Hobart mixer. Within 30 seconds, the mixing water, containing the superplasticizer (1.0 wt% based on cement) and, if applicable, the admixture, was added. Z1 - Z3 or V2Once dissolved or dispersed, the cement was added and mixed for another 2.5 minutes. The total wet mixing time was 3 minutes in each case. The water-cement ratio (w / c ratio) was in the range of 0.49–0.55 (see Table 4).

[0068] mixture M2 It was produced in the same way, but Swiss CEM II A-LL (Wildegg / Jura cement) was used as the cement. The water / cement ratio (w / c ratio) was 0.58 (see Table 5).

[0069] The proportion of any additive present, based on cement, was 0.17 wt% for additives. V2, 0.5% by weight for the additives Z1 and Z3 as well as 1.35% by weight for the additive Z3. This corresponds to the optimal dosages for the respective additives. 4. Test procedure

[0070] To determine the effect of the additives, a cuboid formwork (31 cm × 16 cm × 4 cm) with an L-shaped steel rib running centrally and along the entire width was provided in laboratory tests (see Fig. 1 The steel rib served as a predetermined breaking point. The formwork was then filled with the freshly mixed mortar and stored in a climate chamber with a wind tunnel under defined conditions. Temperature, relative humidity, and wind speed could all be controlled during storage. After two days, the samples produced in this way were visually inspected for any cracking (see [reference]). Figs. 2 and 3 ).

[0071] Shrinkage behavior was tested according to the Swiss standard SIA 262 / 1 using prisms (120 mm × 120 mm × 360 mm) at 20°C and 65% relative humidity after 1, 2, 3, and 7 days. The observed changes in prism length relative to the baseline sample (value after 1 day) were recorded accordingly in parts per thousand (‰).

[0072] The effect of the additives on the setting behavior of the mortar mixtures was also investigated by measuring the temperature development over time at an ambient temperature of 20°C. Temperature measurements were taken using a thermocouple as a temperature sensor in a known manner. All samples were measured under identical conditions. In this case, the setting time is defined as the time elapsed from mixing the mortar until the temperature maximum is reached after the induction or resting phase.

[0073] Furthermore, the compressive strengths of the mortar mixtures were determined at various times (1, 7, and 28 days) after mixing. The compressive strength test (in N / mm²) was performed on prisms (40 x 40 x 160 mm) according to standards EN 12390-1 to 12390-4.

[0074] The slump (ABM) of each mortar mix was measured immediately after mixing, as well as 30 and 60 minutes later. The slump (ABM) of the mortar was measured according to EN 1015-3.

[0075] The air content was determined immediately after mixing the mortar mixture according to standard EN 1015-7 (air content). 5. Results 5.1 Crack formation

[0076] Table 4 shows the effect of the additives in terms of preventing cracking under different conditions and using mortar mix. M1.It is desirable that no cracks form if possible. The tests were carried out as described above in Chapter 4.

[0077] During the trials A - C and F - G Additives according to the invention were used. For comparison purposes, the reference experiments were also conducted. R1 - R8 The experiments were conducted with or without additives not in the invention. R4 and R5 was the additive V1 They are not added to the mortar mixture, but are used subsequently for external post-treatment as intended by the manufacturer.

[0078] The results in Table 4 clearly show that the additives according to the invention Z1 and Z3 perform at least as well as known external post-treatment products in terms of crack prevention. (V1)or conventional internal aftertreatment agents (V2).

[0079] Table 5 shows the results using mortar mix M2. During the trials J and K Additives according to the invention were used. Reference experiments were conducted for comparison purposes. (R9 - R14) The experiments were conducted with or without additives not in the invention. R11 and R12 was the additive V1 They are not added to the mortar mixture, but are used subsequently for external post-treatment as intended by the manufacturer.

[0080] The data in Table 5 show that the additives according to the invention also function without problems in other types of cement and, in some cases, even perform better than known curing agents. For example, the additive prevents Z3Crack formation is also effective at wind speeds of 3-7 km / h (see test). K). Under the appropriate conditions, the conventional means V2 However, cracks are already present (see test R14). 5.2 Shrinkage behavior

[0081] The shrinkage behavior was measured using a mortar mix of type M2 and using an additive of the type Z2 (not according to the invention) was investigated. The mortar mixtures were produced as described in Chapter 3. Fig. 4 The results are shown. The upper curves with the data points in the form of squares and triangles correspond to two measurement series with additional materials of the type Z2. Out of Fig. 4 It is evident that, compared to a reference sample without additives for post-treatment (curve with data points in the form of diamonds), the shrinkage behavior is positively influenced. 5.3 Workability, strength and setting behavior

[0082] To examine the influence of the additives on workability, strength, and setting behavior, the slump (ABM), air content, temperature maximum time t(TM), and compressive strength were investigated, as described in Chapter 4. Table 6 provides an overview of the tests performed and the results. Mortar mix was used for all tests. M1 used.

[0083] As can be seen from the data in Table 6, the additives according to the invention hardly affect, or do not affect at all, the workability, strength and setting behavior of mortar compositions.

[0084] It has thus been shown in particular that the additives according to the invention are suitable as efficient and highly effective agents for the internal post-treatment or internal curing of mineral binder compositions. Specifically, the shrinkage behavior of the mineral binder compositions is positively influenced, and cracking can be significantly reduced. Undesirable drying of mineral binder compositions can therefore be effectively avoided. At the same time, the additives according to the invention have little to no effect on the workability, setting, or strength of the binder compositions.

[0085] However, the embodiments described above are to be understood merely as illustrative examples, which can be modified as desired within the scope of the invention.

Claims

1. Admixture for mineral binder compositions, in particular an internal after-treatment agent for mineral binder compositions, comprising (i) at least one water-absorbing substance wherein the water-absorbing substance comprises or consists of at least one starch ether, in particular hydroxyalkyl starch, especially hydroxypropyl starch, and (ii) at least one shrinkage reducer.

2. Admixture according to at least one of the preceding claims, characterized in that the shrinkage-reducing substance is selected from among alcohols, monoalcohols, glycols, diols, alkanediols, alkenediols, polyols, alkanolamines and / or polyalkylene oxides.

3. Admixture according to Claim 2, characterized in that the shrinkage-reducing substance is selected from among alkanediols, in particular alkanediols having 2-15, preferably 3-10, particularly preferably 4-6, carbon atoms.

4. Admixture according to Claim 3, characterized in that the shrinkage-reducing substance comprises hexylene glycol and / or neopentyl glycol, in particular neopentyl glycol.

5. Admixture according to at least one of the preceding claims, characterized in that the shrinkage-reducing substance comprises neopentyl glycol and the water-absorbing substance comprises starch ether.

6. Admixture according to at least one of the preceding claims, characterized in that a weight ratio of the shrinkage-reducing substance to the water-absorbing substance is 5:95-99:1, preferably 25:75-98:2.

7. Admixture according to at least one of the preceding claims, characterized in that a further additive is additionally present, with the further additive being selected, in particular, from the group consisting of antifoams, dyes, preservatives, flow improvers, plasticizers, accelerators, retarders, air pore formers and / or corrosion inhibitors.

8. Mineral binder composition, in particular a mortar and / or concrete composition, containing a mineral binder and an admixture according to any of Claims 1-7.

9. Shaped body obtainable by curing a mineral binder composition according to Claim 8 which has been mixed with water.

10. Process for producing a mineral binder composition, in particular a mineral binder composition according to Claim 8, wherein an admixture according to at least one of Claims 1-7 is mixed with a mineral binder.

11. Use of at least one water-absorbing substance and at least one shrinkage reducer or of an admixture according to any of Claims 1-7 for the internal after-treatment of a mineral binder composition.