Ultra-high performance fiber reinforced grout

Abstract

A dry cementitious composition comprising, based on the total dry weight of the cementitious composition, a) 4 to 80 wt. % of a cementitious binder, preferably ordinary Portland cement; b) 5 to 95 wt. % of aggregate, the aggregate having a particle size in the range of 0.001 mm to 8 mm; and c) 0.005 to 5 wt. % of carbon fibers, the carbon fibers being provided with a sizing, preferably a polymer sizing, and / or in the form of carbon fiber reinforced polymer lamellae. A preferred application of the cementitious composition is the grouting of offshore or onshore wind turbine towers. The present invention also relates to the use of carbon fibers for the preparation of ultra high performance fiber reinforced grout (UHPFRG) or ultra high performance fiber reinforced concrete (UHPFRC).

Description

[Technical Field]

[0001] The present invention relates to a dry cementitious composition comprising a cementitious binder, an aggregate and specific carbon fibers, the dry cementitious composition being suitable for the preparation of ultra high performance fiber reinforced grout (UHPFRG) or ultra high performance fiber reinforced concrete (UHPFRC). The present invention also relates to the use of the specific carbon fibers as reinforcement for UHPFRG or UHPFRC. [Background technology]

[0002] Cementitious materials are commonly used in concrete or grout, which usually also contain aggregates and additives. When used, the cementitious composition is mixed with water, causing a reaction between the cement and the water, commonly referred to as hydration. After hydration, the cement hardens to form a solid building material.

[0003] In recent years, special concretes such as high performance concrete (HPC) and ultra high performance concrete (UHPC) as well as high performance and ultra high performance grouts (UHPG) have been introduced to the market.

[0004] These special concretes and mortars typically contain a high proportion of inorganic binder and a high proportion of finely graded aggregate, the high proportion of fines providing good uniformity in the material and the high proportion of inorganic binder providing high strength.

[0005] High-strength concrete and grout also contain small to very small amounts of water because evaporation of water not needed for cement hydration leaves pores that reduce strength. For ordinary concrete, the w / c ratio, or the ratio of water to cement by mass, is typically between 0.45 and 0.60. For HPC and UHPC, the w / c ratio is much lower, less than 0.40 and often less than 0.30 or even 0.25.

[0006] However, UHPG and UHPC also exhibit certain disadvantages, such as low tensile strength and low resistance to crack initiation and propagation. To meet these challenges, fiber-reinforced systems called Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) and Ultra-High Performance Fiber-Reinforced Grout (UHPFRG), respectively, have been developed.

[0007] Steel fibers are a commonly used fiber in these systems, which provide greater peak loads and ductile behavior under compressive loads. However, the incorporation of steel fibers has several drawbacks, such as high corrosion potential and high density. Furthermore, UHPFRG and UHPFRC with steel fibers exhibit low fluidity and poor self-compaction.

[0008] Other types of fibers are also used for fiber reinforcement, but the properties achieved are often inadequate. Summary of the Invention [Problem to be solved by the invention]

[0009] It is an object of the present invention to provide a dry cementitious composition suitable for UHPFRC and UHPFRG that overcomes the drawbacks of the prior art. In particular, it is an object of the present invention to provide a dry cementitious composition suitable for UHPFRC and UHPFRG that exhibits high ultimate flexural and compressive strength and improved fatigue behavior and modulus of elasticity, while at the same time reducing the weight of fibers used therein. [Means for solving the problem]

[0010] Surprisingly, this objective could be achieved by a dry cementitious composition comprising a specific aggregate together with a specific carbon fiber.

[0011] The present invention therefore provides a dry cementitious composition comprising, relative to the total dry weight of the cementitious composition: a) 4 to 80% by weight, preferably 10 to 60% by weight, particularly preferably 15 to 50% by weight of a cementitious binder, preferably ordinary Portland cement; b) 5 to 95% by weight, preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight, of aggregates having a particle size in the range of 0.001 mm to 8 mm, determined by sieve analysis in accordance with EN 12192-1:2002 or EN 933-1:2012; c) 0.005 to 5% by weight, preferably 0.01 to 4% by weight, particularly preferably 0.1 to 3% by weight, of carbon fibers, which are provided with a sizing, preferably a polymer sizing, and / or are in the form of carbon fiber-reinforced polymer lamellae. The present invention relates to a dry cementitious composition comprising:

[0012] It has surprisingly been found that the dry cementitious compositions of the present invention can result in cements or grouts having high flexural / compressive strengths, compressive moduli and improved fatigue behaviour.

[0013] Therefore, the use of certain carbon fibers, especially micro carbon fibers, in the compositions of the present invention improves the ultimate strength, modulus of elasticity and fatigue resistance of ultra-high performance fiber reinforced grout (UHP-FRG) or ultra-high performance fiber reinforced concrete (UHP-FRC).

[0014] Further advantages of the present invention are the low tendency to self-shrink, good flowability and self-compacting properties of the compositions of the present invention during processing.

[0015] At the same time, the low density of carbon fibers allows for lower dead load and limited corrosion compared to steel fibers, which improves resistance to harsh conditions such as seawater or environments with high chloride concentrations.

[0016] Further embodiments of the invention are defined in the further independent claims. Preferred embodiments of the invention are defined in the dependent claims. DETAILED DESCRIPTION OF THE INVENTION

[0017] In a first aspect, the present invention provides a dry cementitious composition comprising, relative to the total dry weight of the cementitious composition: a) 4 to 80% by weight of a cementitious binder, in particular ordinary Portland cement; b) 5 to 95% by weight of aggregates having a particle size in the range of 0.001 mm to 8 mm, as determined by sieve analysis in accordance with EN 12192-1:2002 or EN 933-1:2012; c) 0.005 to 5% by weight of carbon fibers provided with a sizing, preferably a polymer sizing, and / or in the form of carbon fiber-reinforced polymer lamellae. The present invention relates to a dry cementitious composition comprising:

[0018] According to an embodiment, the dry cementitious composition comprises, relative to the total dry weight of the cementitious composition: a) 4 to 80 wt. %, preferably 10 to 60 wt. %, more preferably 15 to 50 wt. % of a cementitious binder, preferably ordinary Portland cement; b) 5 to 95% by weight, preferably 20 to 80% by weight, more preferably 30 to 70% by weight of aggregates having a particle size in the range of 0.001 mm to 8 mm, as determined by sieve analysis according to EN 12192-1:2002 or EN 933-1:2012; c) 0.005 to 5% by weight, preferably 0.01 to 4% by weight, more preferably 0.1 to 3% by weight of carbon fibers, provided with a sizing, preferably a polymer sizing, and / or in the form of carbon fiber-reinforced polymer lamellae; and / or Carbon fibers having an average length in the range of 0.001 to 35 mm, preferably 0.001 to 25 mm, more preferably 0.1 to 20 mm, even more preferably 4 to 15 mm, and most preferably 6 to 12 mm. Includes:

[0019] In one preferred embodiment, the dry cementitious composition comprises, based on the total dry weight of the cementitious composition: a) 10 to 60 wt. %, preferably 15 to 50 wt. % of a cementitious binder; b) 20 to 80% by weight, preferably 30 to 70% by weight, of aggregate; c) 0.01 to 4% by weight, preferably 0.1 to 3% by weight, of carbon fiber; Includes:

[0020] The dry cementitious composition of the present invention comprises a cementitious binder, which may be a combination of different cementitious binders. The cementitious binder is in particular a material that reacts in the presence of water by hydration to form a solid hydrate or hydrate phase. It may be a hydraulic binder, in particular cement, that can harden in water and with water, or a latent hydraulic binder that sets with water, in particular granulated blast furnace slag and calcined clay, or a pozzolanic binder, in particular fly ash, silica fume, microsilica or mixtures thereof.

[0021] In this regard, the cementitious composition of the present invention preferably does not contain any reactive polymers or polymeric resins, in particular the cementitious composition preferably does not contain epoxy resins.

[0022] The dry cementitious composition typically has a water content of less than or equal to 10% by weight, preferably less than or equal to 3% by weight, in particular less than or equal to 1% by weight, in each case relative to the total weight of the dry cementitious composition. The dry cementitious composition is usually a powdered cementitious composition.

[0023] The cementitious binder of the dry cementitious composition of the present invention preferably comprises or is ordinary portland cement (OPC).

[0024] In a preferred embodiment, the content of OPC in the cementitious composition of the invention is in the range of 4 to 80% by weight, preferably 26 to 75% by weight, in particular 30 to 66% by weight, in each case relative to the total dry weight of the cementitious composition.

[0025] A suitable OPC is, for example, classified as CEM I in standard DIN 197-1. However, other OPCs, for example, classified in the relevant ASTM, JIS or Chinese standards, are also suitable.

[0026] Instead of OPC, blended cements such as Portland composite cements (CEM II), blast-furnace cements (CEM III), pozzolanic cements (CEM IV) and composite cements (CEM V) according to DIN 197-1 can also be used as cementitious binders.

[0027] Furthermore, in addition to OPC as a cementitious binder, it is possible to use special cements such as calcium sulfoaluminate cement, calcium aluminate cement or mixtures thereof.

[0028] In a preferred embodiment, the OPC is CEM I. According to a further embodiment, the OPC is a white cement. White cement may be preferred in this context due to the reduced water requirement. According to a preferred embodiment, the cementitious binder, in particular the OPC, has a low content of tricalcium aluminate (C3A). A low content means that the content of C3A in the cementitious binder of the present invention is preferably <10 wt. %, more preferably <5 wt. %, based on the total dry weight of the cementitious binder.

[0029] The cementitious binder of the dry cementitious composition of the invention may also comprise a latent hydraulic binder and / or a pozzolanic binder. Suitable latent hydraulic and / or pozzolanic binders are in particular granulated blast furnace slag, calcined clay, fly ash, silica fume and / or microsilica.

[0030] According to an embodiment, the cementitious binder comprises latent hydraulic and / or pozzolanic binders in the range of 1 to 65% by weight, preferably 5 to 35% by weight, more preferably 10 to 20% by weight, in each case relative to the total dry weight of the cementitious binder. Advantageous latent hydraulic and / or pozzolanic binders are granulated blast furnace slag, calcined clay, fly ash, silica fume and / or microsilica.

[0031] In one preferred embodiment, the cementitious binder consists of 100% by weight ordinary Portland cement.

[0032] Suitable cementitious binders should contain in each case, based on the total dry weight of the cementitious binder: a) at least 35% by weight, preferably at least 65% by weight and most preferably at least 80% by weight of ordinary Portland cement; b) 1 to 65% by weight, preferably 5 to 35% by weight, more preferably 10 to 20% by weight of at least one latent hydraulic and / or pozzolanic binder It may comprise or consist of:

[0033] The at least one latent hydraulic and / or pozzolanic binder is preferably selected from granulated blast furnace slag, calcined clay, fly ash, silica fume and / or microsilica.

[0034] The dry cementitious composition according to the invention comprises 4 to 80 wt. %, preferably 10 to 60 wt. %, more preferably 15 to 50 wt. % of cementitious binder relative to the total dry weight of the cementitious composition.

[0035] The dry cementitious composition according to the invention further comprises aggregates, which have a particle size in the range of 0.001 mm to 8 mm, determined by sieve analysis according to EN 12192-1:2002 and / or EN 933-1:2012.

[0036] The aggregate is preferably selected from at least one of limestone, granite, basalt, olivine, aluminium oxide, sand or combinations thereof, preferably sand and / or aluminium oxide.

[0037] The dry cementitious composition comprises 5 to 95% by weight, preferably 20 to 80% by weight, preferably 30 to 70% by weight of aggregates relative to the total dry weight of the cementitious composition, and these aggregates are preferably selected from at least one of limestone, granite, basalt, olivine, aluminium oxide and sand, preferably aluminium oxide and / or sand.

[0038] According to the present invention, the aggregate is used as a powder. Therefore, the aggregate can be characterized by its particle size distribution. The particle size can be analyzed, for example, by sieve analysis as described in EN 12192-1:2002 or EN 933-1:2012. In this method, fine particles are separated from coarser particles by passing the material through multiple sieves with different mesh sizes. The material to be analyzed is vibrated through a series of successively smaller sieves using one or a combination of horizontal, vertical, or rotary motions. For particles with a particle size of less than 75 μm, the wet method of EN 933-1:2012 is used.

[0039] The lower end of the particle size distribution can then be determined by the mesh size of the sieve that retains 100% of the particles, and the upper end can be determined by the smallest mesh size of the sieve through which 100% of the particles will still pass. In the following, mesh sizes, and therefore the lower and upper ends of the particle size distribution, are given in mm.

[0040] The aggregate, preferably selected from at least one of limestone, granite, basalt, olivine, aluminum oxide and sand, preferably has a particle size in the range of 0.036 mm to 7 mm, preferably 0.125 mm to 6 mm, more preferably 0.25 mm to 3 mm, determined by sieve analysis according to EN 12192-1:2002 or EN 933-1:2012.

[0041] Common aggregates are described, for example, in EN 12620:2008-07 and EN 13139:2015-07.

[0042] Sand is a natural granular material composed of finely ground rock or mineral particles. Examples of sand are river sand and / or crushed sand, for example, granite or limestone, or mixtures thereof. The sand is preferably silica sand or quartz sand. Suitable sands are described in the standards ASTM C778 or EN 196-1.

[0043] In this context, aluminum oxide refers to a material having an Al2O3 content of at least 5% by weight, preferably at least 50% by weight, more preferably at least 75% by weight, even more preferably at least 85% by weight, and in particular at least 90% by weight, in each case based on the total dry weight of the material. The aluminum oxide of the present invention typically further comprises SiO2, Fe2O3, TiO2 and / or oxides of alkali metals and alkaline earth metals. Preferred aluminum oxides are aluminas, in particular α-alumina, which may be calcined. A further preferred material is calcined bauxite.

[0044] In this context, aluminum oxide does not relate to aluminates or alumosilicates. Therefore, aluminum oxide is not an aluminate cement or any aluminosilicate. In this context, aluminum oxide does not relate to fibrous alumina. In this context, aluminum oxide preferably does not relate to aluminum oxide-based nanomaterials.

[0045] When aluminum oxide is used as an aggregate, it is particularly preferred that the aluminum oxide has a bimodal particle size distribution. Such a bimodal particle size distribution can be obtained by mixing two types of aluminum oxide with different particle size distributions. Therefore, it is preferred that the aluminum oxide used in the cementitious composition of the present invention is a mixture of two aluminum oxides with different particle size distributions.

[0046] Without wishing to be bound by theory, it is believed that aluminum oxide has a porous structure that allows it to absorb water from the cement paste. The absorbed water is maintained within the aluminum oxide during cement hydration, thus significantly reducing autogenous shrinkage over the hydration period. The free water maintained within the aluminum oxide eventually diffuses into the cement matrix and reacts with unreacted cement after final setting, resulting in a stronger bond of the aluminum oxide to the cement matrix.

[0047] The dry cementitious composition further comprises carbon fibers, which are provided with a sizing, preferably a polymer sizing, and / or are carbon fibers in the form of carbon fiber reinforced polymer lamellae. The sizing is also beneficial in that it improves the flowability of the wet mixture.

[0048] The amount of carbon fibres provided with a sizing, preferably a polymer sizing, and / or in the form of carbon fibre reinforced polymer lamellae in the dry cementitious composition according to the invention ranges from 0.005 to 5% by weight, preferably from 0.1 to 4% by weight, more preferably from 0.1 to 3% by weight, in each case relative to the total dry weight of the dry cementitious composition. The amounts indicated refer to the carbon fibres provided with a sizing, preferably a polymer sizing, and / or in the form of carbon fibre reinforced polymer lamellae, i.e. including any polymeric material contained therein.

[0049] Carbon fibers provided with a sizing, preferably a polymer sizing, carbon fibers in the form of carbon fiber reinforced polymer lamellae, or combinations thereof can be used.

[0050] Such carbon fibers are well known to those skilled in the art and are commercially available. For example, carbon fibers provided with polymer sizing are available in various sizes and modifications from Teijin under the trade name Tenax® or from Toray under the trade name Zoltek®. Carbon fibers in the form of carbon fiber reinforced polymer lamellae are available in various sizes and modifications from Sika under the trade name CarboDur®.

[0051] In one embodiment, the carbon fibers are provided with a sizing, preferably a polymer sizing. A sizing or polymer sizing is usually a thin coating applied to the surface of the fiber. In one embodiment, the carbon fibers are in the form of carbon fiber reinforced polymer lamellae. In these lamellae, bundles of carbon fibers are embedded or bonded in a polymer matrix. Lamellae usually refer to plate-like structures. Lamellae are typically obtained by pultrusion (pultruded carbon fiber reinforced polymer lamellae).

[0052] The following notations regarding suitable embodiments of carbon fibers apply both to carbon fibers provided with a sizing, preferably a polymer sizing, and to carbon fibers in the form of carbon fiber-reinforced polymer lamellae.

[0053] In a particularly preferred embodiment, the carbon fibers are microcarbon fibers. The term microcarbon fibers is generally used for carbon fibers having a diameter of less than 0.3 mm. It is particularly preferred that the carbon fibers have a diameter in the range of 1 to 100 μm.

[0054] The carbon fibers, especially the microfibers, preferably have an average length in the range of 0.001 to 35 mm, preferably 0.001 to 25 mm, more preferably 0.1 to 20 mm, more preferably 4 to 15 mm, and most preferably 6 to 12 mm. In the case of chopped carbon fibers, the average length usually corresponds to the cut length. In the context of this application, average length means the number average length.

[0055] Carbon fibers, especially micro carbon fibers, preferably have an aspect ratio in the range of 1 to 15000, preferably 20 to 15000, more preferably 1000 to 5000. The aspect ratio is defined as the length of a fiber divided by its diameter.

[0056] Carbon fiber aspect ratios within the above preferred ranges result in improved performance, particularly improved crack performance. Without wishing to be bound by any theory, it is believed that the preferred aspect ratios result in a higher amount of carbon fiber in the crack plane, thereby improving crack propagation behavior.

[0057] The carbon fibers are preferably chopped carbon fibers. Chopped and crushed carbon fibers can also be used. Chopped carbon fibers of the desired length can be obtained, for example, by cutting carbon fiber filament yarns provided with sizing, preferably polymer sizing, or by cutting carbon fiber-reinforced polymer lamellae, which are usually provided in rolls. One advantage of chopped carbon fibers is that the carbon fibers are very uniform in length. In another embodiment, chopped and crushed carbon fibers are used.

[0058] The sizing is preferably a polymer sizing or an organic polymer sizing, respectively. The amount of sizing, preferably polymer sizing, in the sized carbon fiber is preferably in the range of 0.1 to 10 wt. %, preferably 0.5 to 5 wt. %, based on the weight of the fiber.

[0059] The amount of polymer in the carbon fiber reinforced polymer lamella is preferably in the range of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, based on the weight of the fiber.

[0060] Examples of suitable materials, particularly polymers, for the sizing, preferably the polymer sizing and / or the reinforcing polymer, are polyvinyl alcohol, polyvinylpyrrolidone (PVP), polyamide (PA), polyacrylate, polydopamine (PDA), 4,4'-diaminodiphenylmethane (MDA), carbon nanotubes, poly(thioarylenephosphine oxide) (PTPO), N-(404-diaminodiphenylmethane)-2-hydroxypropyl methacrylate (DMHM), (3-glycidyloxypropyl)trimethoxysilane (GPTMS), phenoxy polyhydroxyether, polypropylene, polyethylene, epoxy resins, particularly epoxy vinyl esters, carboxymethyl cellulose, polyurethanes, vinyl ester resins, or combinations thereof. Preferred polymers are polyvinyl alcohol, polypropylene, polyethylene, epoxy resins, particularly epoxy vinyl esters, carboxymethyl cellulose, polyurethanes, vinyl ester resins, or combinations thereof. A particularly useful sizing can be obtained from a non-ionic aqueous dispersion of solid bisphenol A epoxy resin having a molecular weight of 100 to 10,000 per epoxide.

[0061] The chopped carbon fibers may have a bulk density in the range of 200 to 800 g / L, preferably 300 to 500 g / L.

[0062] One advantage of the present invention is that carbon fibers weigh much less than the steel fibers conventionally used in UHPFRG and UHPFRC, which makes them easier to handle. Furthermore, carbon fibers are more suitable in terms of safety aspects.

[0063] UHPFRG and UHPFRC with steel fibers exhibit poor fluidity and weak self-compaction. In contrast, UHPFRG and UHPFRC prepared using dry cementitious compositions containing specified carbon fibers showed adequate fluidity and self-compaction properties.

[0064] The use of carbon fibers in combination with aggregate, provided with a sizing, preferably a polymer sizing, or in the form of carbon fiber reinforced polymer lamellae, also ensures concrete or mortar with a particularly high compressive strength.

[0065] The dry cementitious composition of the present invention preferably further comprises a fine filler that is non-reactive in the hydration reaction of the cementitious binder and has a particle size that primarily passes through a 0.125 mm sieve, preferably a 0.063 mm sieve. Typical fillers include finely ground rock dust.

[0066] Preferably, fillers of different particle sizes are mixed to optimally adjust the properties of the cementitious composition. Such mixtures are well known to those skilled in the art.

[0067] The cementitious compositions of the invention advantageously further comprise additives common in the mortar and / or concrete industry, such as plasticizers and / or superplasticizers, redispersible polymers, accelerators, retarders, air entrainers, stabilizers, viscosity modifiers, thickeners, water reducers, accelerators, retarders, water resistance additives, strength enhancing additives, foaming agents, pigments, rust inhibitors, etc. It may be advantageous to combine two or more of the above additives in one cementitious composition.

[0068] According to a suitable embodiment, the dry cementitious composition of the present invention comprises, relative to the total dry weight of the cementitious composition: a) 4 to 80% by weight, preferably 10 to 60% by weight, particularly preferably 15 to 50% by weight of a cementitious binder, preferably ordinary Portland cement; b) 5 to 95% by weight, preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight, of aggregates having a particle size in the range of 0.001 mm to 8 mm, preferably 0.036 mm to 7 mm, more preferably 0.125 mm to 6 mm, even more preferably 0.25 mm to 3 mm, determined by sieve analysis in accordance with EN 12192-1:2002 or EN 933-1:2012; c) 0.005 to 5% by weight, preferably 0.01 to 4% by weight, particularly preferably 0.1 to 3% by weight of carbon fibers, preferably microcarbon fibers, which are provided with a sizing, preferably a polymer sizing, or are in the form of carbon fiber-reinforced polymer lamellae; d) optionally further fine aggregate or filler; e) optionally further additives Includes:

[0069] The dry cementitious composition according to the invention is preferably a grout composition or a concrete composition, in particular a grout composition. In a preferred embodiment, the dry cementitious composition according to the invention is a cementitious composition suitable for ultra high performance fibre reinforced grout (UHPFRG) or ultra high performance fibre reinforced concrete (UHPFRC), in particular for UHPFRG.

[0070] A further aspect of the present invention is the use of carbon fibers, in particular micro carbon fibers, provided with a sizing, preferably a polymer sizing, or in the form of carbon fiber reinforced polymer lamellae, as fiber reinforcement for grout or concrete, in particular Ultra High Performance Fiber Reinforced Grout (UHPFRG) or Ultra High Performance Fiber Reinforced Concrete (UHPFRC).

[0071] A further aspect of the present invention is the use of the dry cementitious composition of the present invention as described above for the preparation of ultra high performance fibre reinforced grout (UHPFRG) or ultra high performance fibre reinforced concrete (UHPFRC), in particular for the purpose of grouting offshore or onshore wind turbine towers or as a repair mortar. The dry cementitious composition of the present invention is particularly suitable for the purpose of grouting offshore or onshore wind turbine towers.

[0072] A further aspect of the present invention is the use of the dry cementitious composition of the present invention as described above in a system according to principles 3, 4 and 7 of EN 1504-3:2006, or in a system according to EN 1504-6:2006, or as a high strength grout according to DAfStb guideline VeBMR:2019, or as a class A, B, C non-shrinkage grout according to ASTM C1107:2020.

[0073] All aspects, proportions and embodiments described above with respect to the dry cementitious compositions of the invention, e.g. with respect to the carbon fibres, aggregate and cementitious binder, also apply to these inventive uses as mentioned therein.

[0074] DIN EN 1504-3:2006 describes products and systems for the protection and repair of concrete structures. Principle 3 relates to the repair of concrete, principle 4 to structural strengthening and principle 7 to the preservation of passive repair.

[0075] The dry cementitious compositions according to the invention are therefore particularly suitable for use as mortars for repair and for structural reinforcement in mortars, concretes or concretes as crack fillers and for increasing the cover on reinforcing bars or replacing neutralized concrete.

[0076] EN 1504-6:2006 relates to products and systems used for anchoring reinforcing steel bars. The cementitious compositions of the present invention are therefore suitable for use for anchoring reinforcing steel bars.

[0077] The DAfStb guideline VeBMR:2019 relates to grouting materials with high early strength and compressive strength class C50 / 60 or higher. The cementitious composition of the present invention is therefore suitable for use as auxiliary concrete material in thin layers and cement mortars, for example for the grouting of joints or for use in column concrete in sleeve foundations.

[0078] A further aspect of the present invention is a method for preparing a hardened cementitious body, comprising the steps of: - mixing said dry cementitious composition according to the invention with water to obtain a wet cementitious composition; - shaping or molding the wet cementitious composition; - hardening the molded or casted wet cementitious composition; The method includes:

[0079] All aspects, proportions and embodiments described above with respect to the dry cementitious compositions of the invention, e.g. with respect to the carbon fibers, aggregate and cementitious binder, also apply to these inventive methods as mentioned therein.

[0080] The present invention is also directed to a cementitious composition comprising the dry cementitious composition of the invention and water, the amount of water being in each case 5 to 50% by weight, preferably 5 to 40% by weight, more preferably 6 to 30% by weight, even more preferably 6 to 20% by weight and most preferably 7 to 10% by weight relative to the total weight of the dry cementitious composition.

[0081] In a preferred embodiment, the cementitious composition is an ultra high performance fiber reinforced grout (UHPFRG) or an ultra high performance fiber reinforced concrete (UHPFRC).

[0082] The water can be any available water, such as distilled water, purified water, tap water, mineral water, spring water, and well water. The use of wastewater is only possible if the composition of such wastewater is known and if the impurities contained therein do not add to the function of any other component of the composition of the present invention. Saltwater cannot be used due to its high chloride content and the associated risk of corrosion of steel reinforcement.

[0083] Methods and equipment for mixing the dry cementitious composition with water are well known to those skilled in the art. The mixing of the dry cementitious composition with water can be carried out, for example, by a handheld agitator, a Hobart mixer, a portable concrete mixer, a mixer truck, a mixing bucket, a paddle mixer, a jet mixer, a screw mixer, an auger mixer, a horizontal single-shaft mixer, a twin-shaft paddle mixer, a vertical shaft mixer, a ribbon blender, an orbital mixer, a change can mixer, a tumbling vessel, a vertical stirring chamber, or an air stirring operation. Mixing can be continuous, semi-continuous, or batchwise. Continuous mixing offers the advantage of high production rates.

[0084] The water used for mixing the dry cementitious composition may contain at least one additive common in the concrete and / or grout industry, particularly preferably a plasticizer or superplasticizer.

[0085] Shaping or molding of the wet cementitious composition is then carried out by conventional procedures well known to those skilled in the art. Upon mixing with water, hardening of the dry cementitious composition begins to occur, resulting in a hardened cementitious body.

[0086] A further aspect of the present invention is a hardened cementitious body obtainable by the method of the present invention described above.

[0087] In a preferred embodiment, the resulting hardened cementitious body has a compressive strength after 28 days of at least 120 MPa, preferably at least 140 MPa, measured according to EN 12190:1998.

[0088] The cementitious hardened body is preferably a mortar or concrete composition, in particular a self-compacting concrete, a high-strength or ultra-high-strength concrete or a high-strength or ultra-high-strength mortar.

[0089] The cementitious hardened body is particularly preferably an ultra-high performance fiber reinforced grout (UHPFRG) or an ultra-high performance fiber reinforced concrete (UHPFRC), in particular UHPFRC. UHPFRG and UHPFRC can be considered as grout or concrete having a compressive strength of at least 120 MPa, preferably at least 140 MPa or even at least 150 MPa after 28 days, measured in accordance with EN 12190:1998.

[0090] Despite the absence of steel fibers that are typically used in UHPFRG or UHPFRC, the hardened cementitious body that can be obtained with the dry cement composition according to the invention ensures relatively good compressive strength as well as improved corrosion protection and a relatively low weight, which is achieved by utilizing the particularly easy-to-handle and versatile dry cement composition according to the invention. [Example]

[0091] Table 1 below provides an overview of the materials used.

[0092] [Table 1]

[0093] Powder grout compositions were prepared using compositions according to Table 2 below.

[0094] [Table 2]

[0095] The examples were prepared by mixing the powder grout composition with fibers in a bag using the procedure of EN 13395-1:2002 (Hobart 3' slow speed + 2' fast speed) before mixing with water to obtain a grout composition containing fibers. The fibers used are shown in Tables 3 and 4 below, which also show the weight ratios and properties of the fibers (see below). The lengths given refer to cut lengths.

[0096] The examples shown in Table 3 compare the Table 2 grout compositions with various fibers (materials, lengths, sizing) from Table 1. Example 1 was run without added fibers as a reference example. Examples 11 and 12, which include carbon fibers, are examples of the present invention. The other examples are comparative examples.

[0097] The examples shown in Table 4 compare the grout compositions of Table 2 with carbon fibers having two types of sizing (PU and epoxy vinyl ester) and different fiber lengths (12, 24, and 34 mm). Example 14 was run without added fiber as a reference sample.

[0098] Mass refers to the mass of fiber used.

[0099] Fraction refers to the weight ratio of the fibers to the total weight of the grout composition including the fibers.

[0100] Density fiber refers to the density of the fiber.

[0101] Volumetric fiber refers to the volume of fiber used.

[0102] To the fiber-containing grout composition, water was added in an amount sufficient to provide 7.5% by weight of the total weight of the dry fiber-containing grout composition.

[0103] The wet composition thus obtained was measured according to the following procedure.

[0104] Testing was carried out in accordance with EN 12190:1998.

[0105] Slump flow: tested according to EN 13391:2004 FS28: Flexural strength tested according to EN 12190:1998 CS28: Compressive strength measured according to EN 12190:1998 on 40 x 40 x 160 mm prisms after curing in water after 28 days EMC28: Elastic modulus tested under compression according to EN 13412:2006 Number of cycles to failure N: fatigue resistance

[0106] [Table 3]

[0107] [Table 4]

Claims

1. A dry cementitious composition comprising, relative to the total dry weight of the cementitious composition: a) 4 to 80 wt. %, preferably 10 to 60 wt. %, more preferably 15 to 50 wt. % of a cementitious binder, preferably ordinary Portland cement; b) 5 to 95% by weight, preferably 20 to 80% by weight, more preferably 30 to 70% by weight of aggregates having a particle size in the range of 0.001 mm to 8 mm, as determined by sieve analysis according to EN 12192-1:2002 or EN 933-1:2012; c) 0.005 to 5 wt. %, preferably 0.01 to 4 wt. %, more preferably 0.1 to 3 wt. % of carbon fibers, provided with a sizing, preferably a polymer sizing, and / or in the form of carbon fiber-reinforced polymer lamellae. A dry cementitious composition comprising:

2. the carbon fibers have an aspect ratio in the range of 1 to 15,000, preferably 20 to 15,000, more preferably 1,000 to 5,000; and / or the carbon fibers are micro carbon fibers having a diameter of less than 0.3 mm; and / or 2. The dry cementitious composition of claim 1, wherein the carbon fibers are chopped carbon fibers or chopped and crushed carbon fibers.

3. 3. The dry cementitious composition according to claim 1 or 2, wherein the aggregate is selected from at least one of limestone, granite, basalt, olivine, aluminium oxide, sand or combinations thereof, preferably sand and / or aluminium oxide.

4. the carbon fibers have an average length in the range of 0.001 to 35 mm, preferably 0.001 to 25 mm, more preferably 0.1 to 20 mm, even more preferably 4 to 15 mm, and most preferably 6 to 12 mm; and / or 4. The dry cementitious composition according to any one of claims 1 to 3, wherein the carbon fibres have a diameter in the range of 1 to 100 μm.

5. the amount of sizing, preferably polymeric sizing, in the sized carbon fibers is in the range of 0.1 to 10 wt. %, preferably 0.5 to 5 wt. %, based on the weight of the carbon fibers; and / or 5. The dry cementitious composition according to any one of claims 1 to 4, wherein the amount of polymer in the carbon fibre reinforced polymer lamellae ranges from 0.1 to 10 wt.%, preferably from 0.1 to 5 wt.%, based on the weight of the carbon fibres.

6. 6. The dry cementitious composition according to any one of claims 1 to 5, wherein the sizing, preferably the polymer of the polymer sizing and / or the reinforcing polymer is selected from polyvinyl alcohol, polyvinylpyrrolidone (PVP), polyamide (PA), polyacrylate, polydopamine (PDA), 4,4'-diaminodiphenylmethane (MDA), carbon nanotubes, poly(thioarylenephosphine oxide) (PTPO), N-(404-diaminodiphenylmethane)-2-hydroxypropyl methacrylate (DMHM), (3-glycidyloxypropyl)trimethoxysilane (GPTMS), phenoxy polyhydroxyether, polypropylene, polyethylene, epoxy resin, in particular epoxy vinyl ester, carboxymethyl cellulose, polyurethane, vinyl ester resin or combinations thereof.

7. 7. A dry cementitious composition according to any one of the preceding claims, wherein the aggregate has a particle size in the range of 0.036mm to 7mm, preferably 0.125mm to 6mm, more preferably 0.25mm to 3mm.

8. 8. A dry cementitious composition and water according to any one of claims 1 to 7, wherein the amount of water is in each case 5 to 50 wt.-%, preferably 5 to 40 wt.-%, more preferably 6 to 30 wt.-%, even more preferably 6 to 20 wt.-%, in particular 7 to 10 wt.-%, relative to the total weight of the dry cementitious composition.

9. 1. Use of carbon fibers, in particular micro carbon fibers, as fiber reinforcement for grout or concrete, in particular for ultra high performance fiber reinforced grout (UHPFRG) or ultra high performance fiber reinforced concrete (UHPFRC), wherein said carbon fibers are provided with a sizing, preferably a polymer sizing, or are in the form of carbon fiber reinforced polymer lamellae.

10. 9. Use of a dry cementitious composition according to any one of claims 1 to 8 for the preparation of an ultra high performance fibre reinforced grout (UHPFRG) or ultra high performance fibre reinforced concrete (UHPFRC), in particular for the purposes of grouting offshore or onshore wind turbine towers, or as a repair mortar.

11. 9. Use of the dry cementitious composition according to any one of claims 1 to 8 in a system according to principles 3, 4 and 7 of EN 1504-3:2006, or in a system according to EN 1504-6:2006, or as a high strength grout according to DAfStb guideline VeBMR:2019, or as a class A, B, C non-shrinkage grout according to ASTM C1107:2020.

12. A method for preparing a hardened cementitious material, comprising: - mixing a dry cementitious composition according to any one of claims 1 to 7 with water to obtain a wet cementitious composition; - shaping or molding the wet cementitious composition; - hardening the formed or molded wet cementitious composition; A method comprising:

13. 13. The method according to claim 12, wherein the amount of water is 5 to 50% by weight, preferably 5 to 40% by weight, more preferably 6 to 30% by weight, even more preferably 6 to 20% by weight, in particular 7 to 10% by weight, in each case relative to the total weight of the dry cementitious composition.

14. A hardened cementitious material obtainable by the method according to claim 12 or 13.

15. 15. The hardened cementitious body according to claim 14, having a compressive strength after 28 days of at least 120 MPa, preferably at least 140 MPa according to EN 12190:1998.

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