阅读说明：本技术 硬化的水泥基材料的非侵入修复和改造 (Non-invasive repair and modification of hardened cement-based materials ) 是由 C·瓦尔维尔德 R·加西亚 L·格拉尼索 于 2020-05-25 设计创作，主要内容包括：本发明涉及修复和/或密封硬化的水泥基材料,尤其是混凝土结构的水性组合物,该水性组合物包含胶体二氧化硅和聚羧酸。本发明的水性组合物显示开裂的水泥基材料的非常高的渗透深度以及密封能力。(The present invention relates to an aqueous composition for repairing and/or sealing hardened cementitious materials, in particular concrete structures, comprising colloidal silica and a polycarboxylic acid. The aqueous composition of the present invention shows a very high penetration depth and sealing ability of the cracked cement-based material.)

1. An aqueous composition for repairing and/or sealing hardened cementitious materials, especially hardened concrete structures, comprising colloidal silica and at least one polycarboxylic acid, wherein the at least one polycarboxylic acid is not a comb polymer.

2. The aqueous composition according to claim 1, wherein the colloidal silica has a weight average particle size in the range of from 1nm to 150nm, preferably from 2nm to 35nm, more preferably from 5nm to 10 nm.

3. Aqueous composition according to any one of claims 1 to 2, wherein the content of colloidal silica is in the range of from 1 to 50 wt. -%, preferably from 5 to 50 wt. -%, and the content of polycarboxylic acid is in the range of from 1 to 50 wt. -%, preferably from 2 to 50 wt. -%, in particular from 2 to 25 wt. -%, based on the total weight of the aqueous composition.

4. An aqueous composition according to any one of claims 1 to 3, wherein the weight ratio of colloidal silica to polycarboxylic acid is at least 4, preferably at least 4.5 on a dry weight basis.

5. Aqueous composition according to any of the preceding claims, wherein at least one polycarboxylic acid consists of at least 85 mol%, preferably at least 90 mol%, more preferably at least 95 mol%, in particular at least 99 mol%, of monomers, each based on the total composition of the polycarboxylic acid, selected from acrylic acid, methacrylic acid, 3-dimethylacrylic acid, crotonic acid, isocrotonic acid, angelic acid, tiglic acid, maleic acid, fumaric acid, itaconic acid and sorbic acid, preferably selected from acrylic acid and/or methacrylic acid.

6. Aqueous composition according to claim 5, wherein at least one polycarboxylic acid is a homopolymer, preferably a homopolymer of acrylic or methacrylic acid.

7. Aqueous composition according to any of the preceding claims, wherein the total amount of colloidal silica, polycarboxylic acid and water is at least 80 wt. -%, preferably at least 90 wt. -%, based on the total weight of the aqueous composition.

8. Aqueous composition according to any of the preceding claims, wherein the water content is at least 15 wt. -%, preferably at least 25 wt. -%, more preferably at least 40 wt. -%, based on the total weight of the aqueous composition.

9. Method of repairing and/or sealing a hardened cementitious material, comprising the step of applying an aqueous composition according to any one of claims 1 to 8 to the hardened cementitious material or a part thereof to fill any cracks having a width of at most 10 mm.

10. The method according to claim 9, wherein the hardened cement-based material is a hardened concrete structure, in particular a hardened reinforced concrete structure.

11. The method according to any one of claims 9 to 10, wherein the aqueous composition is applied by injection, migration, penetration or application onto the surface of the structure, for example by brushing, spraying or roller.

12. A method according to any one of claims 9 to 11, wherein the hardened cement-based material comprises cracks.

13. A method according to any one of claims 9 to 12, wherein applying the aqueous composition to the hardened cementitious material is non-invasive.

14. A method according to any one of claims 9 to 13, wherein the method comprises at least one additional treatment of the hardened cementitious material selected from the group consisting of protecting the reinforcing material by applying a corrosion inhibitor, crack sealing with a reactive agent, or waterproofing the surface of the hardened cementitious material with a hydrophobic material.

15. Use of an aqueous composition according to any one of claims 1 to 7 for repairing and/or sealing hardened cement-based materials, preferably hardened concrete structures, especially hardened reinforced concrete structures.

Technical Field

The present invention relates to an aqueous composition for repairing and/or sealing hardened cementitious materials, in particular concrete structures, a method for repairing and/or sealing hardened cementitious materials using an aqueous composition and the corresponding use of an aqueous composition.

Background

Modern concrete is a very durable building material and, if proportioned and placed properly, will result in a very long service life under normal conditions. In any case, the hardened cement-based material, in particular concrete structures, are subject to damage, which may be the result of, for example, improper manufacture or deterioration from weathering or other harsh conditions due to mechanical, physical or chemical attack. Therefore, repairing and/or sealing hardened cement-based materials may be necessary to improve the durability of the structure. The need to repair and heal cement-based materials, particularly concrete structures, is becoming increasingly important and will be an important market in the future, as the long life cycle of buildings has ever-increasing potential.

In addition to inorganic binder based concrete repair materials suitable for repairing or restoring damaged structures, there are a range of other materials used for repairing and/or sealing hardened cement-based materials.

For example, pure colloidal silica may be used to repair and seal hardened reinforced concrete structures. However, the effectiveness is low.

EP3053901(Sika AG) teaches an aqueous composition for repairing and/or sealing hardened concrete structures comprising colloidal silica and polycarboxylate ether. However, the depth of penetration of such compositions may be limited.

US 2013/281577(w.r.grace & Co) describes aqueous additive compositions for modifying cementitious compositions comprising colloidal nanoparticles consisting of silica and polycarboxylate ether. However, the use of repairing hardened cementitious materials is not disclosed, and the depth of penetration of such compositions is not subsequently optimized.

EP 2251376(Sika AG) teaches aqueous polymer dispersions comprising, inter alia, from 5 to 15% by weight of comb polymer, from 10 to 30% by weight of fumed or colloidal silica and from 30 to 70% by weight of water in a preferred embodiment. However, the use for repairing hardened cementitious materials is not disclosed, and the penetration depth of such compositions is not subsequently optimized.

JP 2014-177394 describes a repair method of a concrete structure, in which a restoration material is applied to a place where a part of the concrete structure is removed, wherein the restoration material is a mortar composition, particularly comprising cement, a fluidizing agent containing a polycarboxylic acid-based copolymer, and amorphous silica fine powder. However, the solution provided is a mortar that is not able to penetrate deep cracks.

US 2004/0077768(Akzo Nobel) discloses co-dispersions of colloidal silica and organic binders such as poly (acrylic acid). However, these systems are used as coating materials rather than for repairing hardened cement-based materials.

A commercially available example of an admixture for water impermeable and crystalline water resistant concrete is SikaSeries Sika Schweiz AG, which is a crystalline admixture for self-healing concrete resulting in self-healing based on crystallization, reacts with portlandite (calcium hydroxide) to produce water insoluble crystals. Also sold are crystal admixtures for water proofing.

Other examples of agents for repairing and/or sealing concrete structures are bacillus sphaericus, zinc sulfate, alumina coated silica nanoparticles, blast furnace slag or fly ash.

Materials used for repair and/or sealing are often quite expensive or exhibit low performance, especially low permeation depths. Many schemes do not support the self-healing process. Application to cementitious materials can be complex and time consuming.

Summary of The Invention

It is therefore an object of the present invention to provide a composition for repairing and/or sealing hardened cementitious materials, in particular concrete structures and reinforced concrete structures, which overcomes the drawbacks of the prior art approaches discussed above. In particular, the composition should be relatively inexpensive, capable of being applied simply and/or quickly to hardened cementitious materials, and exhibit a high penetration depth. In addition, the composition should exhibit good performance by initiating the healing process of the cement.

Surprisingly, this object is achieved by an aqueous composition comprising a combination of colloidal silica and a polycarboxylic acid.

The present invention therefore relates to an aqueous composition for repairing and/or sealing hardened cementitious materials, especially concrete structures, comprising colloidal silica and a polycarboxylic acid, wherein the polycarboxylic acid according to claim 1 is not a comb polymer.

The main advantages of the composition are the low cost compared to other solutions, and the simplicity and/or rapidity of application. Surprisingly, improved performance is also achieved, since the penetration depth of the composition is very high, preferably at least 10mm, especially at least 20mm or more, and a new growth of hydrated cement product occurs, especially along the sides of the crack, which aids the crack "healing" process.

The aqueous composition enables non-invasive treatment of hardened cement-based materials, especially concrete structures, which effectively interact with existing concrete matrices to form new hydration products during the secondary hydration of cement and/or SCM. SCM is a common abbreviation for supplementing cementitious materials such as fly ash or cinders such as blast furnace slag.

The invention also relates to a method of repairing and/or sealing a hardened cementitious material, in particular a concrete structure, comprising the steps of applying the aqueous composition according to the invention to the hardened cementitious material or a part thereof so as to fill any cracks having a width of at most 10mm, and the use of the aqueous composition for repairing and/or sealing a hardened cementitious material. Preferred embodiments of the invention are set forth in the dependent claims.

Where applicable, the details given below apply equally to the aqueous compositions, methods and uses.

Brief description of the drawings

Fig. 1 is a schematic illustration of a method of applying an aqueous composition according to the invention by migration. In fig. 1, an aqueous composition of the present invention is disposed as a catholyte 3 on one side of a hardened concrete structure 1 to be repaired or sealed. Water, in particular distilled water, is provided on the other side as an anolyte 2. The electrodes 4, 5 are immersed in the anolyte and catholyte, respectively, which are connected to a voltage source 6 (e.g., 12V). For example, the potential may be applied in 3 cycles, i.e., 2 days on and 1 day off.

FIG. 2 is a schematic representation of a cracked test specimen used in the examples.

In fig. 2, a mortar prism 1 has cracks 2 extending to a depth less than the diameter of the prism.

Detailed Description

The aqueous composition comprises colloidal silica. Colloidal silica refers to silica particles dispersed in a colloidal state in a liquid phase, usually water. Colloids are stable dispersions of particles. Stable dispersions or colloids of silica particles are also referred to as silica sols. The colloidal silica is typically amorphous silica. Colloidal silica is commercially available from a number of companies, for example from Nouryon under the trade name Levasil. Commercial products of colloidal silica may vary, for example, in pH, particle size, or concentration. One type of colloidal silica or a mixture of two or more types of colloidal silica differing in particle size, for example, may be used.

The colloidal silica may be an anionic colloidal silica or a cationic colloidal silica. As known to the skilled person, dispersions of colloidal silica typically comprise cations or anions for stabilization. In the case of cationic colloidal silica, the silica particles are typically coated with alumina. The colloidal silica may be a non-surface modified silica or a surface modified silica, e.g. surface modified with a silane or siloxane.

The weight average particle size of the colloidal silica is generally in the range of from 1 to 150nm, preferably in the range of from 2nm to 35nm, more preferably from 5nm to 10 nm. Particularly preferred are small particle size dispersions, for example with a weight average particle size of about 5 nm. The weight average particle size as used herein can be determined by a dynamic light scattering method as described in ISO 22412: 2017.

The aqueous composition further comprises at least one polycarboxylic acid. The aqueous composition may comprise one or more polycarboxylic acids.

Within the context of the present invention, a polycarboxylic acid is a homopolymer or copolymer of at least one ethylenically unsaturated carboxylic or dicarboxylic acid. Suitable ethylenically unsaturated carboxylic or dicarboxylic acids are selected from the following: acrylic acid, methacrylic acid, 3-dimethylacrylic acid, crotonic acid, isocrotonic acid, angelic acid, tiglic acid, maleic acid, fumaric acid, itaconic acid and sorbic acid, preferably selected from acrylic acid and/or methacrylic acid.

The homo-or copolymers of ethylenically unsaturated carboxylic or dicarboxylic acids may contain small amounts of further comonomers such as ethylene, propylene, butadiene, isoprene, styrene, alkyl esters of acrylic and methacrylic acid, acrylonitrile, acrylamide, vinyl esters, preferably vinyl acetate, vinyl chloride and vinyl pyrrolidone. However, it is preferred that the polycarboxylic acids of the invention consist of at least 85 mol%, preferably at least 90 mol%, more preferably at least 95 mol%, in particular at least 99 mol%, of monomers selected from the above list of ethylenically unsaturated carboxylic acids or dicarboxylic acids, each based on the total composition of the polycarboxylic acid.

The above homopolymers or copolymers may be linear or branched, and they may be additionally crosslinked. The copolymer may be random, block copolymer, or have a gradient.

According to an embodiment, the polycarboxylic acid is a homopolymer, preferably a homopolymer of acrylic or methacrylic acid.

The polycarboxylic acids of the invention can be used in their protic form or in their partially or fully neutralized form.

According to a preferred embodiment, at least part of the carboxyl groups of the polycarboxylic acids of the invention are neutralized with oxides or hydroxides of alkali metals or alkaline earth metals or with ammonia.

According to a particularly preferred embodiment, the polycarboxylic acids are polyacrylates or polymethacrylates, in particular in the form of their sodium salts.

Weight average molecular weight (M) of polycarboxylic acid_w) Preferably 1 '000-150' 000g/mol, more preferably 5 '000-100' 000g/mol, especially 5 '000-10' 000 g/mol. The weight average molecular weight can be determined by Gel Permeation Chromatography (GPC).

According to an embodiment, the polycarboxylic acid may be in solid form, preferably with a fine powder having a particle size between 20 and 3000 μm, preferably between 50 and 1000 μm, more preferably between 90 and 850 μm. Particle size distribution can be determined by methods as described in ASTM C136 and ASTM C117.

According to a further embodiment, the polycarboxylic acid may be in the form of an aqueous formulation, in particular a solution or dispersion. The aqueous formulation has a solids content of at least 25 wt.%, preferably at least 30 wt.%, in particular at least 40 wt.%, each based on the total weight of the aqueous formulation.

The polycarboxylic acids of the present invention do not contain any polyoxyalkylene group bonded to the polycarboxylic acid backbone. The polycarboxylic acids of the present invention are therefore not comb polymers, also known as PCE superplasticizers.

According to a most preferred embodiment of the invention, the polycarboxylic acid is a homopolymer of acrylic or methacrylic acid, in particular in the form of their sodium salts, having a weight-average molecular weight M as measured by GPC_wIs 1 '000-150' 000g/mol, preferably 5 '000-100' 000g/mol, in particular 5 '000-10' 000 g/mol.

The aqueous composition of the present invention contains water. As mentioned above, various aqueous formulations of colloidal silica or silica sol, respectively, and polycarboxylic acids are commercially available. Further commercially available polycarboxylic acid products may be mixtures with water. Aqueous compositions can be readily produced by mixing an aqueous dispersion of colloidal silica or silica sol, respectively, with a polycarboxylic acid, for example as an aqueous solution or dispersion. The water content can be adjusted by adding additional water, if necessary. The pH can be adjusted, if necessary, by adding acids or bases.

The aqueous composition is a liquid. The aqueous composition is preferably an aqueous dispersion or sol. The pH of the aqueous composition may vary over a wide range depending on the type of components used and the desired application. According to embodiments, the pH of the aqueous composition may vary between 1 and 13, preferably between 6 and 12, especially between 7.5 and 11.

The content of colloidal silica in the aqueous composition is preferably 1 to 50 wt%, more preferably 5 to 50 wt% or 10 to 50 wt% and still more preferably 5 to 45 wt% or 10 to 45 wt%, based on the total weight of the aqueous composition. As usual, the weight of colloidal silica here refers to SiO₂I.e. without water.

The content of polycarboxylic acid in the aqueous composition is preferably from 1 to 50 wt. -%, more preferably from 2 to 50 wt. -% or from 4 to 50 wt. -% and still more preferably from 2 to 25 wt. -% or from 4 to 25 wt. -%, based on the total weight of the aqueous composition.

In a preferred embodiment, the content of colloidal silica in the aqueous composition is from 10 to 20% by weight, based on the total weight of the aqueous composition, and/or the content of polycarboxylic acid in the aqueous composition is from 2 to 10% by weight, in particular from 2 to 5% by weight, based on the total weight of the aqueous composition.

According to a particularly preferred embodiment, the weight ratio of colloidal silica to polycarboxylic acid is at least 4, preferably at least 4.5 on a dry weight basis.

The amount of water in the aqueous composition is, for example, at least 15 wt.%, preferably at least 25 wt.%, more preferably at least 40 wt.% or at least 60 wt.%, based on the total weight of the aqueous composition.

The aqueous composition may optionally further comprise one or more additives. The additives may be those commonly used in this technical field.

In particular, it is generally suitable that the aqueous composition does not contain a hydraulic mineral binder, such as cement, because the mineral binder has reactivity with water. According to a particularly preferred embodiment, the composition of the invention is free of hydraulic mineral binders, in particular cement.

The total amount of colloidal silica, polycarboxylic acid and water may vary depending on the need, e.g. at least 80 wt. -%, preferably at least 90 wt. -%, more preferably at least 95 wt. -%, based on the total weight of the aqueous composition.

According to an embodiment, the aqueous composition of the invention therefore comprises (in each case based on the total weight of the aqueous composition)

1 to 50% by weight, preferably 5 to 50% by weight, of colloidal silica,

1 to 50% by weight, preferably 2 to 50% by weight, in particular 2 to 25% by weight, of polycarboxylic acid,

-at least 15 wt.%, preferably at least 25 wt.%, more preferably at least 40 wt.% of water,

wherein the weight ratio of colloidal silica to polycarboxylic acid is at least 4, preferably at least 4.5 on a dry weight basis, and wherein the total amount of colloidal silica, polycarboxylic acid and water is at least 80 wt%, preferably at least 90 wt%.

According to a further embodiment, the aqueous composition of the invention consists of (in each case based on the total weight of the aqueous composition)

1 to 50% by weight, preferably 5 to 50% by weight, of colloidal silica,

1 to 50% by weight, preferably 2 to 50% by weight, in particular 2 to 25% by weight, of polycarboxylic acid,

-at least 15 wt.%, preferably at least 25 wt.%, more preferably at least 40 wt.% of water,

wherein the weight ratio of colloidal silica to polycarboxylic acid is at least 4, preferably at least 4.5 on a dry weight basis.

In particular, the aqueous composition of the present invention does not contain a comb polymer or polycarbonate ether (PCE). By free it is meant that the content of such comb polymer or polycarbonate ether (PCE) is below 0.1 wt.%, preferably below 0.01 wt.%.

The aqueous composition according to the invention is suitable for a method of repairing and/or sealing hardened cementitious materials, in particular hardened concrete structures. The concrete structure is preferably a hardened reinforced concrete structure.

The hardened concrete structure or hardened reinforced concrete structure may be, for example, any civil engineering structure or a part thereof. Examples of civil structures are buildings, bridges, pipelines, dams, reservoirs, underground structures such as tunnels, underpasses of livestock and monuments. The hardened concrete structure or hardened reinforced concrete structure may be, for example, a wall, a slab, a beam, a column, a pier, a column, a handrail, a retaining wall, a foundation, a floor, a frame, a curb, a sill, a roof, a cornice, or a corner.

The degree of impermeability of concrete to water is determined by the impermeability of the adhesive matrix. Hardened concrete is a porous material that allows water or other media to pass through the capillary structure. These capillary structures are voids created by excess water in the concrete that is not necessary for the chemical reaction of hardening, known as hydration.

In addition, hardened cement-based materials, particularly concrete structures, may have damage or defects, for example caused by thermal, mechanical, chemical and/or physical attack. Common damage or defects in cementitious materials are, for example, cracks, voids or gaps. Of course, such damage or defects further reduce impermeability.

Cracks having a width of at most a few millimetres, for example cracks having a width of at most 2mm, 5mm or 10mm, can be repaired or sealed by the aqueous composition of the invention. Although cracks having a width of less than 0.4mm or 0.2mm are generally considered to be not problematic for the structural integrity of cementitious materials, especially hardened concrete, such cracks may also be repaired or sealed using the aqueous composition of the present invention, for example in order to improve or restore the aesthetic impression of the concrete surface.

A method of repairing and/or sealing a hardened cementitious material, in particular a hardened concrete structure, comprising the step of applying the aqueous composition of the invention to the hardened cementitious material, in particular the concrete structure or a part thereof. Depending on the purpose, the aqueous composition may be applied to the entire hardened cementitious material or only a portion thereof. For example, the treatment may be performed only on portions of the hardened concrete structure that include damage or defects or may be exposed to more severe conditions than other portions, such as contact with water.

The application of the aqueous composition to the hardened cementitious material, in particular a concrete structure, or a part thereof, may be carried out by conventional means. The aqueous composition may be applied to the surface of the cement-based material or a portion thereof, for example by roller, brush, trowel or by spraying (e.g. by air gun spraying or airless spraying), such that the material may penetrate the surface. Transport is primarily by capillary suction. This may also be considered as infiltration or impregnation.

Alternatively, the aqueous composition may be applied to the hardened cementitious material, in particular the concrete structure, or a part thereof, by injection. Common injection devices such as manual injection devices or syringe pumps may be used. Injection is particularly suitable for filling cracks, but this can also be achieved by the other methods mentioned.

Alternatively, the aqueous composition may be applied by migration to a hardened cementitious material, in particular a concrete structure, or a part thereof (see fig. 1). Migration methods are known to the skilled person, in which the anolyte is located on one side of the hardened concrete structure to be repaired or sealed and the catholyte is located on the other side. An external potential is then applied across the hardened cement-based material so that ions can migrate into the structure. In the migration method according to the invention, the aqueous composition of the invention is used as an electrolyte, preferably as a catholyte. The other electrolyte, preferably the anolyte, is for example water, in particular distilled water. The migration may be performed in one or more cycles of applying the external potential.

Thus, the aqueous composition is preferably applied to the hardened cementitious material, especially the concrete structure, or a part thereof, by injection, migration or capillary suction. Injection and capillary suction are very simple application methods. The migration method is fast and time-saving.

The method of the invention is a non-invasive method. By non-invasive is meant a non-destructive method, i.e. without removing the cement-based material, in particular concrete, to be repaired and/or sealed, for example cracked concrete.

The method of the invention is particularly suitable for hardened concrete structures or hardened reinforced concrete structures comprising cracks.

Sealing the cement-based material refers to protection against ingress, i.e. reducing or preventing ingress of undesirable agents such as water, other fluids, steam, gases, chemicals and biological agents. Sealing is a measure to improve the impermeability of concrete.

The amount of the aqueous composition to be applied to the hardened cementitious material, in particular the concrete structure or a part thereof, is not particularly limited.

The aqueous composition of the present invention is typically applied as one coating, layer or step. However, it is also possible and in some cases preferred to apply the aqueous composition of the invention in a plurality of coatings, layers or steps, for example in two or three coatings, layers or steps, with a waiting period in between after each application. Application in multiple coatings, layers or steps may further enhance the penetration depth of the aqueous composition of the present invention.

The components of the aqueous composition according to the invention can form insoluble materials throughout the pores and capillary structure of the concrete and seal the concrete. Thus, the protection against penetration of water and other fluids may be improved, so that the impermeability is enhanced.

In addition, the aqueous composition may also repair the damage or defects of hardened cementitious materials, particularly concrete structures, by enhancing the self-healing properties of the cementitious material and improving the ability to heal damage or defects, such as cracks.

The components of the aqueous composition, particularly colloidal silica, effectively interact with the existing cement-based matrix of the cement-based material (especially concrete) to form a new hydrated cement product during the secondary hydration of the cement and/or SCM. The growth of new hydrated cement products occurs particularly on the crack side, which is also involved in the crack healing process. Thus, a restoration of the cement-based material may occur.

The aqueous composition of the present invention comprising colloidal silica and a polycarboxylic acid has significantly improved properties, especially improved depth of penetration, compared to the use of colloidal silica by itself or in combination with PCE. Thus, the aqueous composition applied by the method of the invention is able to form new hydration products on both sides of the crack, in some cases with Ca/Si ratios lower than 1.0, which proves the effectiveness of the method. Although the common value of the portland CSH phase in SEM characterization is Ca/Si ═ 1.4-2.0, the new chemical and physical healing is based on a different phase (which is not portlandite) with a Ca/Si ratio of 0.5-1.

The method of the present invention is suitable for sealing hardened cement-based materials, especially concrete structures. The method is particularly suitable for filling cracks having a width of at most 10mm in the hardened cementitious material, in particular concrete. The impermeability of the cement-based material may be improved by such treatment. The method of the invention is therefore suitable for the retrofitting of cement-based materials, in particular concrete structures. The method of the invention is also suitable for repairing hardened cement-based materials, especially concrete structures, as it causes expansion of new hydrated cement products, especially on both sides of cracks, so that healing or restoration can be achieved. Of course, the method is also suitable for simultaneously repairing and sealing hardened cement-based materials, in particular concrete structures.

The process of the present invention may optionally include additional steps. Such further steps are, in particular, the preparation of the surface to be treated, for example cleaning, dusting, drying, wetting and/or the application of a primer.

The method of the present invention may optionally be combined with at least one additional treatment of the cementitious material. The additional treatment may be selected from at least one of the conventional treatments of hardened cement-based materials, especially concrete structures, such as reinforcement (reinformance) for protecting reinforced concrete by applying corrosion inhibitors, crack sealing with reactive agents such as epoxy or polyurethane resins, or waterproofing of the surface of the concrete structure with hydrophobic materials (hydrophobic impregnation).

The aqueous composition of the present invention is therefore suitable for repairing and/or sealing hardened cementitious materials, especially concrete structures, preferably hardened reinforced concrete structures. In particular, the aqueous composition of the invention is suitable for filling in hardened cement-based materials, in particular concrete, having cracks with a width of at most 10 mm.

Examples

Testing of penetration depth and crack filling capability

Table 1: materials used

¹40% by weight aqueous solution of a comb polymer (Mw about 45'000g/mol, polyacrylate backbone and polyethylene glycol side chains, molar ratio of side chains to acrylate: 1.86)

²50% by weight aqueous solution of polyacrylate (Mn:5'000g/mol)

Example 1 is an aqueous composition of the present invention. Reference 1 and reference 2 are reference examples.

The compositions reference 1, reference 2 and example 1 were applied on a 4x4x16cm mortar prism made of a mortar based on ordinary portland cement (CEM I R/SR) and quartz sand, with a cement/sand ratio of 0.33 and a water/cement ratio of 0.5. Adding 600g/m of 12mm length³The monofilament polypropylene fiber of (1). The addition of fibers is necessary to prevent complete cracking of the test specimens upon introduction of cracks. The mortar prisms were fully cured at 21 ℃/95% relative humidity. One crack per mortar prism was then introduced by three-point bending, with a width between 229 and 326 μm.

Application of the compositions reference 1, reference 2 and example 1 was done by a two-step procedure at 21 ℃/60% relative humidity. In a first step, each composition was allowed to freely penetrate the entire area of the crack for 24h, then the surface was allowed to dry for 2 days and then the free penetration was repeated for another 24 h. In a second step, an electric field (12V) is applied to the test specimen for 24 h.

The penetration depth was measured by analyzing the material composition inside the crack along the crack side by energy dispersive X-ray spectroscopy (EDX) and Scanning Electron Microscopy (SEM) in backscatter mode. Determination of SiO along the respective depth of the crack on the cross section of the treated test specimen after curing for 28d at 23 ℃/50% relative humidity₂、CaO、Al₂O₃、K₂O and SO₃Relative abundance of (a). When in useThe applied compositions formed gels of calcium silicate hydrate (CSH-gels) and the CaO/SiO of these gels was subsequently calculated₂The ratio determines the depth of penetration. With CaO/SiO₂Ratio of<The CSH phase of 1 is derived from the CSH-gel of one of the compositions Ref 1, Ref 2, EXAMPLE 1, with CaO/SiO₂Ratio of>The CSH phase of 1 is the surrounding mortar phase.

Table 2 below shows the individual CaO/SiO₂Ratio and thus relative penetration depth. As can be seen, the permeation of the inventive sample, example 1, is significantly higher than any reference.

The crack filling degree was determined visually with the aid of a stereo magnifier. This depends on the growth of new hydrated cement phases.

Table 2 below shows the crack filling levels. It can be seen that the inventive example, example 1, has a higher degree of crack filling close to the surface and up to a depth of 1 mm.

TABLE 2

Depth [ mm ]]	0.5	1	3	10	20	30
							CaO/SiO2Reference 1	n.m.	0.87	1.05	n.m.	n.m.	n.m.
CaO/SiO2Reference 2	0.09	0.26	0.60	1.01	1.47	n.m.
							Crack filling degree reference 2	In part	In part	In part	In part	In part	n.m.
CaO/SiO2Comparative example 1	0.84	0.95	0.95	0.56	0.64	0.64
							Crack filling degree example 1	Is totally produced from	Is totally produced from	In part	In part	In part	In part

n.m. not measurable

Additional tests were performed to show effective filling or healing of the cracks. This test is based on resistivity measurements across the filled crack, which means the resistivity across the repaired mortar. Lower resistivity indicates more effective treatment because the cracks are filled with conductive material.

As can be seen from table 3 below, this resistivity is lower for the inventive example, example 1, compared to reference 2, which means that the repair is more effective using example 1.

TABLE 3

Time after treatment [ d]	1	3	4	7
					Resistivity [ k Ω x cm ]]Reference 2	41.2	42.5	43	40.5
Resistivity [ k Ω x cm ]]Example 1	39.5	39	41	39.5