Cementitious composition having a controlled shrinkage rate and method for controlling shrinkage of cementitious grout

Abstract

1. A method for controlling shrinkage of a cementitious material, the method comprising: (i) providing a cementitious material, (ii) adding aluminum powder to the cementitious material, (iii) adding calcium oxide or magnesium oxide to the cementitious material, and (iv) adding a shrinkage-reducing agent that is an organic molecule to the cementitious material. A cementitious grout comprising aluminum powder, calcium oxide or magnesium oxide, and a shrinkage-reducing agent that is an organic molecule.

Description

[Technical Field]

[0001] The present invention relates to a method for controlling shrinkage of cementitious compositions using a combination of aluminum powder, calcium oxide or magnesium oxide, and a shrinkage-inhibiting agent that is an organic molecule. The present invention also relates to a cementitious grout comprising such a combination of aluminum powder, calcium oxide or magnesium oxide, and a shrinkage-inhibiting agent that is an organic molecule. [Background technology]

[0002] It is well known that cementitious materials, such as concrete or grout, shrink during hardening. Known shrinkage mechanisms can be classified as plastic shrinkage, drying shrinkage, autogenous shrinkage, and carbonation shrinkage. Shrinkage is often problematic because it generates internal stresses within the hardened cementitious material, which can lead to cracking if the stresses are higher than the tensile strength of the material. Furthermore, shrinkage is particularly problematic in the case of cementitious materials for grouting, since grouting materials are typically intended to completely fill a predetermined volume.

[0003] The use of additives for cementitious materials that can suppress or compensate for shrinkage is known to those skilled in the art. For example, gas-generating additives can be used to compensate for shrinkage in cementitious materials. The most frequently used gas-generating additive is aluminum powder. However, literature has shown that the action of aluminum powder can lead to excessive expansion and strength reduction, especially when Portland cement is replaced with ground granulated blast furnace slag (GGBFS) in cementitious materials (J. Kuziak et al., "Influence of the Type of Cement on the Action of the Admixture Containing Aluminum Powder", Materials, 2021, 14, 2927).

[0004] However, replacing Portland cement with pozzolans and / or latent hydraulic materials such as GGBFS is desirable to reduce the CO2 footprint of cementitious materials, especially cementitious grout.

[0005] It is also known from WO 2016 / 185264 (Holcim Technology) that a combination of low-reactivity calcium or magnesium oxide and organic shrinkage-reducing agents can be used to control shrinkage in concrete compositions based on a binder comprising 75% by weight of Portland cement and 25% by weight of GGBFS. Summary of the Invention [Problem to be solved by the invention]

[0006] However, there remains a need for further and improved additives to reduce shrinkage in cementitious materials, especially when there is a high degree of replacement of Portland cement with pozzolans and / or latent hydraulic substances, especially with GGBFS. [Means for solving the problem]

[0007] One object of the present invention is to provide a method for inhibiting shrinkage of cementitious materials, particularly cementitious grouts. Most preferably, the present invention provides a method for inhibiting shrinkage of cementitious materials when cement, particularly Portland cement, is replaced by slag, particularly GGBFS. It is also an object of the present invention to provide a cementitious material for grouting having an inhibited shrinkage rate. In particular, such cementitious grouts have a high replacement rate of cement by slag. The cementitious materials, particularly grouts, of the present invention are useful in many applications, for example in the construction of wind towers.

[0008] The object of the present invention is achieved by the method according to claim 1. Therefore, the core of the present invention is to suppress shrinkage of a cementitious composition by adding aluminum powder and calcium oxide or magnesium oxide to the cementitious composition. The present invention utilizes the finding that aluminum powder and calcium oxide or magnesium oxide act synergistically to suppress shrinkage of cementitious materials (particularly when cement is replaced by slag).

[0009] Further aspects of the invention are the subject of the independent claims. Preferred embodiments of the invention are the subject of the dependent claims. DETAILED DESCRIPTION OF THE INVENTION

[0010] In a first aspect, the present invention relates to a method for controlling shrinkage of a cementitious material, said method comprising the steps of: (i) providing a cementitious material; (ii) adding aluminum powder to the cementitious material; (iii) adding calcium oxide or magnesium oxide to the cementitious material; (iv) adding a shrinkage-reducing agent, which is an organic molecule, to the cementitious material; (where the cementitious material, after hardening, has a strength of 800 kg / m 3 or more, preferably 1800 kg / m 3 (It has a density of more than 10 ...

[0011] A cementitious material, within the context of the present invention, is a material comprising at least one cementitious binder and, optionally, further aggregates, fillers, admixtures, additives, and / or water. Further materials, such as reinforcing fibers, may also be present. The cementitious material of the present invention sets and hardens when mixed with water.

[0012] Within the context of the present invention, a cementitious binder is a binder that reacts with water to form a solid hydrate. Therefore, the cementitious binder can be hardened with water and sets and hardens even when exposed to water. Examples of cementitious binders include cement, particularly Portland cement (as described in standard EN 197-1), aluminate cement (as described in standard EN 14647), and calcium sulfoaluminate cement. The cementitious binder of the present invention may further contain a pozzolan and / or a latent hydraulic substance. Particularly preferred within the context of the present invention are cementitious binders that contain or consist of cement and slag, particularly Portland cement and ground granulated blast furnace slag (GGBFS). Additional pozzolan and / or latent hydraulic substances that can be present in the cementitious binder include fly ash, silica fume, finely divided silica, tass, marl, and clay, particularly calcined clay.

[0013] In an embodiment, the method of the present invention is characterized in that the cementitious material comprises a cementitious binder, said cementitious binder comprising cement and slag, in particular Portland cement and ground granulated blast furnace slag.

[0014] In some embodiments of the method of the invention, the cementitious binder comprises or consists of Portland cement and slag, in particular GGBFS, and the weight ratio of slag to the total dry weight of the cementitious binder is at least 10% by weight, preferably at least 20% by weight, more preferably at least 40% by weight, in particular at least 66% by weight.

[0015] The term "control of shrinkage," within the context of the present invention, relates to the reduction of shrinkage and / or expansion of a cementitious composition compared to a non-inventive composition without the addition of aluminum powder and calcium or magnesium oxide. Therefore, "control" and "reduction" are used interchangeably herein. Shrinkage and / or expansion begins upon the addition of water to the cementitious composition and continues upon setting and hardening. Therefore, within the context of the present invention, shrinkage includes plastic shrinkage as well as autogenous and chemical shrinkage. However, it does not include shrinkage of fully hardened cementitious materials, e.g., due to carbonation. Shrinkage and / or expansion can be measured according to standards EN 12617-4 (dimensional stability), ASTM C827 (expansion of fresh mortar), and ASTM C1698 (autogenous shrinkage).

[0016] In an embodiment of the method of the present invention, aluminum powder, calcium oxide or magnesium oxide, and a shrinkage-reducing agent that is an organic molecule are added to a dry cementitious material, which is a cementitious material as described above, having a water content of 5% by weight or less, preferably 1% by weight or less, based on the total weight of the cementitious material. Such addition is particularly possible when producing a dry mortar or dry grout.

[0017] The method of the present invention may further comprise the step of adding water, in particular mixing water with the cementitious composition. The water is preferably added in an amount to achieve the desired workability of the resulting mixture. Typically, water is added in an amount to achieve a weight ratio of dry cementitious composition to water of between 0.05 and 1.0, preferably between 0.06 and 0.3.

[0018] In the method of the present invention, aluminum powder, calcium oxide or magnesium oxide, and an organic molecule shrinkage-reducing agent can be added to the cementitious material in one or more steps.

[0019] For example, it is possible to add aluminum powder, calcium oxide or magnesium oxide, and the shrinkage inhibitor, which is an organic molecule, all in one step, or the addition in one step may be in the form of a premix of aluminum powder, calcium oxide or magnesium oxide, and the shrinkage inhibitor, which is an organic molecule.

[0020] For example, it is possible to add aluminum powder, calcium oxide or magnesium oxide, and the shrinkage-reducing agent which is an organic molecule in two or more steps. For example, aluminum powder, calcium oxide or magnesium oxide, and the shrinkage-reducing agent which is an organic molecule can be added to the cementitious composition one after the other in any predetermined order.

[0021] In an embodiment, in the method of the present invention, the aluminum powder, calcium oxide or magnesium oxide, and the shrinkage-reducing agent, which is an organic molecule, are added to the dry cementitious material as a premix or are added one after the other in any predetermined order.

[0022] In an embodiment of the method of the present invention, aluminum powder, calcium oxide or magnesium oxide, and / or shrinkage inhibitors that are organic molecules are added with the mixing water.

[0023] The term "density" within the context of the present invention relates to bulk density, which is measured within the context of the present invention in accordance with standard EN 1015-6.

[0024] As is known to those skilled in the art, the density of a cementitious material is highly dependent on the densities of the constituent components of the cementitious material and also on the air content of the hardened cementitious material.

[0025] After hardening, 800kg / m 3 or more, preferably 1800 kg / m 3 To achieve these densities of the cementitious material, it is particularly preferred to limit the amounts of various lightweight components and / or to limit the air content.

[0026] Lightweight components have low density, specifically 1200 kg / m 3 The preferred lightweight aggregates are aggregates or fillers having a density of: Lightweight components include, for example, wood particles, rubber particles, plastic particles, and / or porous particles such as foamed glass, expanded clay, or pumice. It is particularly preferred that the cementitious material of the present invention does not include any lightweight aggregates.

[0027] The air content of the hardened cementitious material should not exceed 14% by volume, preferably not exceed 12% by volume, and in particular not exceed 6% by volume. The air content can be reduced, for example, by adding a suitable defoamer. An example of a defoamer is tributyl phosphate. The air content can also be reduced, for example, by applying a vacuum to the cementitious material after mixing with water. The air content can be measured, for example, as described in standard EN 12350-7:2019.

[0028] Aluminum powder and calcium oxide or magnesium oxide are particulates within the context of the present invention. Particulates can be distinguished by their particle size.

[0029] The particle size, its distribution, or average particle size of aluminum powder and calcium oxide or magnesium oxide can be measured by laser diffraction, preferably according to the standard ISO 13320:2009. Specifically, a Mastersizer 2000 instrument from Malvern Instruments GmbH (Germany) is used, which is equipped with a Hydro 2000G dispersion unit and Mastersizer 2000 software. For example, isopropanol is suitable as a measuring medium. In the context of the present invention, the average particle size specifically corresponds to the D50 value (50% of the particles are smaller than a given value, and correspondingly 50% are larger than it).

[0030] In an embodiment of the method of the present invention, the aluminum powder has a particle size D50 in the range of 0.1 to 45 μm, preferably 0.2 to 20 μm, more preferably 0.5 to 15 μm, even more preferably 1 to 10 μm, and especially 2 to 8 μm.

[0031] In an embodiment of the method of the present invention, the calcium oxide or magnesium oxide has a particle size D50 in the range of 10 to 50 μm.

[0032] Throughout the present invention, calcium oxide and magnesium oxide may be used interchangeably.

[0033] In the method of the present invention, a shrinkage inhibitor is added which is an organic molecule. In an embodiment, the shrinkage inhibitor is selected from the following: glycols, preferably polypropylene glycol, polyethylene glycol, or mixed polypropylene-polyethylene glycol, polyalkylene glycols, especially alkyl ethers of neopentyl glycol, polyols, especially glycerin or erythritol, alkoxylated polyols, especially alkoxylated glycerin or alkoxylated erythritol, alkylated ethanolamines, carboxylic acid esters of polyalkylene glycols, especially fatty acid esters of polyalkylene glycols. A particularly preferred organic shrinkage inhibitor has the chemical structure (I): [ka] During the ceremony, R are each independently a linear or branched, saturated or unsaturated aliphatic, alicyclic or aromatic hydrocarbon residue having 3 to 38 carbon atoms; EO is ethylene oxide and PO is propylene oxide; a=1 to 4, n = 0 to 40, m=0 to 40, Here, the sum of n+m = 4 to 80, Here, EO and PO may be arranged randomly, in blocks, or with a gradient.

[0034] In an embodiment of the method of the present invention, the aluminum powder is added in an amount of 0.0001 to 0.01 wt %, based on the weight of the cementitious binder present in the cementitious material.

[0035] 800kg / m 3 or more, preferably 1800 kg / m 3 To achieve these hardened cementitious material densities, lower amounts of aluminum powder are particularly preferred.

[0036] In an embodiment, the calcium oxide or magnesium oxide is added in an amount of 1 to 5% by weight, based on the weight of cementitious binder present in the cementitious material.

[0037] In an embodiment, the organic molecule shrinkage reducing agent is added in an amount of 0.1 to 2% by weight, based on the weight of the cementitious binder present in the cementitious material.

[0038] In yet another aspect, the present invention relates to a cementitious grout comprising or consisting of (in each case based on the total dry weight of the cementitious grout): a) 10 to 80 wt. % of a cementitious binder, the cementitious binder comprising cement and slag; b) 0.0001 to 0.01 wt. % aluminum powder; c) 0.3 to 2% by weight of calcium oxide or magnesium oxide; d) 0.03 to 1 wt. % of a shrinkage inhibitor that is an organic molecule; e) 10 to 80% by weight, based on the dry weight of the grout, of at least one aggregate and / or filler; f) optionally, 0.001 to 0.1% by weight of azodicarbonamide, and e) optionally further additives.

[0039] In an embodiment, the cementitious grout of the present invention comprises or consists of: a) 10 to 80% by weight of a cementitious binder, based on the cementitious grout, the cementitious binder including cement and slag; b) 0.0001 to 0.01% by weight of aluminum powder, based on the cementitious grout; c) 1 to 5% by weight, based on the cementitious grout, of calcium oxide or magnesium oxide; d) 0.1 to 2% by weight, based on the cementitious grout, of a shrinkage inhibitor which is an organic molecule; e) 10 to 80% by weight, based on the dry weight of the grout, of at least one aggregate and / or filler; f) optionally, 0.001 to 0.1% by weight of azodicarbonamide, and e) optionally further additives.

[0040] All previously mentioned embodiments also relate to this aspect.

[0041] Further additives are additives generally known to be useful in cementitious compositions, in particular concrete or mortar. Such additives are in particular selected from the following: accelerators, retarders, pigments, fibers, biocides, defoamers, air-entrainers, redispersible polymer powders, and viscosity modifiers, in particular thickeners, plasticizers, and / or superplasticizers. These additives are chemically and / or structurally distinct from the shrinkage inhibitors, which are organic molecules as defined above.

[0042] One particularly useful additional additive is azodicarbonamide. In an embodiment of the invention, a method for controlling shrinkage of a cementitious material includes adding azodicarbonamide to the cementitious material.

[0043] The aggregates and / or fillers are inert materials known in the concrete or mortar industry. The aggregates are in particular sand, gravel, recycled plastics, lightweight aggregates such as glass beads, and / or bio-based aggregates. The fillers are in particular fine limestone powder.

[0044] In an embodiment, the cementitious binder in the cementitious grout of the invention comprises or consists of 5 to 95 wt. % Portland cement and 5 to 95 wt. % slag, in particular ground granulated blast furnace slag, in each case based on the dry weight of the cementitious binder.

[0045] In some cases, it may be preferred for the cementitious binder in the cementitious grout of the present invention to further include microsilica, silica fume, and / or calcium hydroxide.

[0046] Thus, preferred cementitious binders may comprise or consist of: i) 5 to 50% by weight of Portland cement; ii) 5 to 50% by weight of slag, in particular ground granulated blast furnace slag; iii) 1 to 5 wt. % silica fume; iv) 0.5 to 3 wt. % microsilica, and v) 0.1 to 1% by weight of calcium hydroxide.

[0047] Highly preferred cementitious grouts of the present invention comprise or consist of: a) 10 to 80% by weight, based on the cementitious grout, of a cementitious binder, the cementitious binder consisting of: i) 5 to 50% by weight of Portland cement; ii) 5 to 50% by weight of slag, in particular ground granulated blast furnace slag; iii) 1 to 5 wt. % silica fume; iv) 0.5 to 3 wt. % microsilica, and v) 0.1 to 1% by weight of calcium hydroxide, b) 0.0001 to 0.01% by weight of aluminum powder, based on the cementitious grout; c) 1 to 5% by weight, based on the cementitious grout, of calcium oxide or magnesium oxide; d) 0.1 to 2% by weight, based on the cementitious grout, of a shrinkage inhibitor which is an organic molecule; e) 10 to 80% by weight, based on the dry weight of the grout, of at least one aggregate and / or filler; f) optionally, 0.001 to 0.1% by weight of azodicarbonamide, and e) optionally further additives.

[0048] The grouts of the present invention have reduced or controlled shrinkage and / or expansion properties and can be used in applications where a non-shrinking grout is required.

[0049] In another aspect, the present invention relates to an additive for a cementitious composition, the additive comprising aluminum powder, calcium oxide or magnesium oxide, and an organic molecule shrinkage suppressant. The additive of the present invention may further comprise azodicarbonamide.

[0050] The additives of the present invention can be used to control shrinkage of cementitious materials.

[0051] All previously mentioned embodiments also relate to this aspect. [Example]

[0052] Example 1 The cementitious grout materials were prepared by thoroughly mixing the raw materials shown in Table 1 below for 3 minutes using a laboratory mixer. The mixture was visually uniform. Examples 1 and 2 are comparative examples not according to the present invention. Examples 3 and 4 are examples according to the present invention.

[0053] [Table 1]

[0054] To prepare the liquid grouts, each powder from Examples 1-4 was gradually added to mixing water in a 3 L Hobart mixer within 3 minutes. Water was used in an amount such that the water to powder weight ratio was 0.075. Mixing was then continued at high speed for 2 minutes. The liquid grout compositions were then used immediately in the following experiments.

[0055] Dimensional stability was tested according to standard EN 12617-4. Fresh mortar expansion was tested according to standard ASTM C827. Autogenous shrinkage was tested according to standard ASTM C1698. All measurements were carried out after the times indicated in Table 2 below.

[0056] Table 2 below summarizes the results.

[0057] [Table 2]

[0058] From the above examples, it can be seen that the compositions of the present invention exhibit improved dimensional stability (see Examples 1 and 2 compared with Example 4). Furthermore, it can be seen that the compositions of the present invention exhibit good expansion properties in the fresh state and low autogenous shrinkage (see Examples 1 and 2 compared with Example 3).

[0059] Example 2 The cementitious grout material was prepared in the same manner as in Example 1 by thoroughly mixing the raw materials listed in Table 3 below in a laboratory mixer for 3 minutes. The mixture was visually uniform. Examples 5-8 are examples of the present invention.

[0060] [Table 3]

[0061] The liquid grouts were prepared in the same manner as in Example 1 using the powders of Examples 5 to 8, respectively.

[0062] Table 4 below summarizes the results.

[0063] [Table 4]

Claims

1. 1. A method for controlling shrinkage of a cementitious material, said method comprising: (i) providing a cementitious material; (ii) adding aluminum powder to the cementitious material; (iii) adding calcium oxide or magnesium oxide to the cementitious material; (iv) adding a shrinkage-reducing agent, which is an organic molecule, to the cementitious material; Including, Here, the cementitious material has a compressive strength of 800 kg / m after hardening. ３ or more, preferably 1800 kg / m ３ The method has a density of at least

2. 2. The method of claim 1, wherein aluminum powder, calcium oxide or magnesium oxide, and a shrinkage-reducing agent which is an organic molecule are added to the dry cementitious material.

3. 2. The method according to claim 1, wherein aluminum powder, calcium oxide or magnesium oxide, and / or a shrinkage inhibitor which is an organic molecule is added together with the mixing water.

4. 4. The method according to any one of claims 1 to 3, characterized in that the cementitious material comprises a cementitious binder, the cementitious binder comprising cement and slag, in particular Portland cement and ground granulated blast furnace slag.

5. 5. The method according to claim 4, characterized in that the weight ratio of slag to the total dry weight of cementitious binder is at least 10% by weight, preferably at least 20% by weight, more preferably at least 40% by weight, in particular at least 66% by weight.

6. 6. The method according to any one of claims 1 to 5, characterized in that the aluminium powder has a particle size D50 in the range of 0.1 to 45 μm, preferably 0.2 to 20 μm, more preferably 0.5 to 15 μm, even more preferably 1 to 10 μm, and especially 2 to 8 μm.

7. 7. The method according to any one of claims 1 to 6, characterized in that the calcium oxide or magnesium oxide has a particle size D50 in the range of 10 to 50 μm.

8. 8. The method according to any one of claims 1 to 7, characterized in that the aluminium powder is added in an amount of 0.0001 to 0.01 wt.% based on the weight of cementitious binder present in the cementitious material.

9. 9. The method according to any one of claims 1 to 8, characterized in that the calcium oxide or magnesium oxide is added in an amount of 1 to 5 wt. %, based on the weight of cementitious binder present in the cementitious material.

10. 10. The method according to any one of claims 1 to 9, characterized in that the organic molecule shrinkage inhibitor is added in an amount of 0.1 to 2 wt%, based on the weight of cementitious binder present in the cementitious material.

11. 11. The method according to claim 1, wherein the shrinkage inhibitor is an organic molecule selected from glycols, preferably polypropylene glycol, polyethylene glycol or mixed polypropylene-polyethylene glycol, polyalkylene glycols, in particular alkyl ethers of neopentyl glycol, polyols, in particular glycerin or erythritol, alkoxylated polyols, in particular alkoxylated glycerin or alkoxylated erythritol, alkylated alkanolamines, carboxylic acid esters of polyalkylene glycols, in particular fatty acid esters of polyalkylene glycols.

12. A cementitious grout comprising: (in each case based on the total dry weight of said cementitious grout) a) 10 to 80 wt. % of a cementitious binder, the cementitious binder comprising cement and slag; b) 0.0001 to 0.01 wt. % aluminum powder; c) 0.3 to 2% by weight of calcium oxide or magnesium oxide; d) 0.03 to 1 wt. % of a shrinkage inhibitor which is an organic molecule; e) 10 to 80 wt. % of at least one aggregate and / or filler, based on the dry weight of the grout; f) optionally 0.001 to 0.1 wt. % azodicarbonamide, and e) optionally further additives A cementitious grout comprising or consisting of:

13. 13. Cementitious grout according to claim 12, characterized in that the cementitious binder comprises or consists of 5 to 95% by weight of Portland cement and 5 to 95% by weight of slag, in particular ground granulated blast furnace slag, in each case based on the dry weight of the cementitious binder.

14. The cementitious binder is (in each case, amounts based on the dry weight of the cementitious binder) i) 5 to 50% by weight of Portland cement; ii) 5 to 50% by weight of slag, in particular ground granulated blast furnace slag; iii) 1 to 5 wt. % of silica fume; iv) 0.5 to 3 wt. % of microsilica, and v) 0.1 to 1% by weight of calcium hydroxide; 14. A cementitious grout according to claim 12 or 13, characterized in that it comprises or consists of:

15. 1. An additive for a cementitious composition, said additive comprising aluminum powder, calcium oxide or magnesium oxide, and a shrinkage-reducing agent that is an organic molecule.

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