CN118666595A - Cement-based hydrophobic breathable coating for protecting railway bridge concrete structure - Google Patents

Abstract

A cement-based hydrophobic breathable coating for protecting a railway bridge concrete structure relates to the field of railway bridge concrete structure protective coatings. The concrete structure is designed for mainly solving the problem that the coating of the existing railway bridge concrete structure is easy to crack or fall off. The powder material comprises the following raw materials in parts by weight: 400-500 parts of high belite sulphoaluminate cement, 20-100 parts of quick hardening components, 20-35 parts of expanding agents, 0.5-2 parts of stabilizing agents, 1-2 parts of defoaming agents, 4-6 parts of thixotropic lubricants, 10-20 parts of modifying agents and 350-450 parts of fillers; mixing the above materials uniformly to obtain powder material. Before coating, the powder material and a proper amount of water are stirred into slurry, and then the slurry is fully ground and uniformly mixed into refined slurry. And cleaning the surface of the concrete structure matrix, and spraying refined slurry after the surface is dried. And (5) brushing hydrophobic emulsion after the surface of the refined slurry coating is dried. The method has the advantage of improving the durability of the concrete structure of the railway bridge.

Description

A cement-based hydrophobic breathable coating for protecting railway bridge concrete structures

Technical field:

The invention relates to the field of protective coatings for railway bridge concrete structures, and in particular to a water-repellent and breathable coating modified based on cement-based materials.

Background technology:

Water is a carrier for various corrosive media to enter the concrete matrix and cause damage, so it is necessary to block the water in the environment. In order to improve the durability of reinforced concrete structures, high molecular epoxy resin protective coatings or exterior wall coatings are generally used to provide decorative protection for reinforced concrete structures, forming a closed coating or film to play a decorative role and prevent water from entering the concrete matrix. However, it will cause the water in the matrix to vaporize and cannot be removed, causing the pressure to increase, resulting in cracking or falling off of the coating. Especially for railway bridge concrete structures, the waterproof layer of the bridge deck is more easily damaged under strong dynamic loads. Due to the large amount of ballast accumulated on the ballasted track subgrade and the track system, it is difficult to repair the waterproof layer of the bridge deck in time after it is damaged. When rain or snow exists and drainage is not smooth, some water will enter the concrete matrix; if the side facade of the bridge body adopts a closed coating, the water entering the matrix from the bridge deck will not be removed, which will cause frost heave in winter and vaporization in summer will damage the coating.

The most effective way to protect concrete structures is to prevent concrete from absorbing moisture. High-belite sulphoaluminate cement-based coatings have low alkalinity, which can prevent the degradation of isooctylsilane in a strong alkaline environment. At the same time, the silicon-oxygen bonds formed have high activity, which is conducive to forming stable covalent bonds with silane.

Summary of the invention:

The technical problem to be solved by the present invention is to provide a cement-based hydrophobic and breathable coating for protecting railway bridge concrete structures, which can improve the hydrophobicity of the cement-based coating and is breathable.

The object of the present invention is achieved in that:

The cement-based hydrophobic breathable coating includes: mixing powder material with an appropriate amount of water into a slurry, applying it on the surface of the concrete structure matrix, and then applying a special hydrophobic emulsion after solidification.

Among them, the powder material includes the following raw materials in parts by weight: 400-500 parts of white (or ordinary) high-belite sulphoaluminate cement, 20-100 parts of fast-hardening components, 20-35 parts of expanders, 0.5-2 parts of stabilizers, 1-2 parts of defoamers, 4-6 parts of thixotropic lubricants, 10-20 parts of modifiers, and 350-450 parts of fillers; the amount of powder material used is 100-300g/㎡.

You can also add 2 parts of dispersant, 1 part of water repellent, 1 part of lime, 2 parts of pigment, and 0.2 parts of pigment synergist.

The model of the high-belite sulphoaluminate cement is BS-WCFR 42.5;

The rapid hardening component uses amorphous glassy high-activity high-calcium calcium aluminate;

The expansion agent is anhydrous gypsum powder;

The dispersant used is polycarboxylate water reducer, model SD-600P-S02;

The stabilizer is hydroxypropyl methylcellulose, model number is HPMC30000;

The model of defoamer is P803;

The thixotropic lubricant is made of wood fiber, model B00;

The modifier is a dispersible latex powder, model number is Wacker 5010;

The water repellent agent is silane-siloxane emulsion;

The filler is 400-mesh heavy calcium;

The pigment enhancer is made of high-purity barium sulfate;

The remaining raw materials are common commercial products and are of industrial grade.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before coating, the reserved dry powder material is stirred with an appropriate amount of water into a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1: (0.6-1).

Before painting, clean the surface of the concrete structure substrate from dust and grind it, rinse it with high-pressure water, and after the surface is dry, repair the defective part with cement-based repair mortar, and then use cement-based putty to prime and smooth it. After drying, spray, roll or brush the refined slurry.

After the surface of the cement-based refined slurry coating is dry, apply the hydrophobic emulsion. The hydrophobic emulsion is prepared using commercially available water-based silane-siloxane emulsion, such as BS4004 from Wacker of Germany, and is prepared with water at a ratio of 1:5 (mass ratio). Apply the hydrophobic emulsion twice using wet-on-wet (wet-on-wet means applying it again when the first coat is not dry) to ensure that there is no omission or liquid accumulation.

The dosage of hydrophobic emulsion is 200-300g/㎡. Hydrophobic emulsion is a colorless and transparent solution, and its hydrophobic component is silane-siloxane; it has the advantages of improving the hydrophobic properties of cement-based coatings and making them breathable.

The advantages of the present invention are: on the one hand, the coating can be used for decorative coating of the side facades of newly built railway concrete bridges, reduce the basicity of the matrix, prevent the degradation of hydrophobic components, and slow down the carbonization speed and carbonization depth of silicate cement-based concrete structures.

In order to obtain suitable construction properties, the amount of water used in mixing cement-based coatings is usually much greater than its theoretical water requirement (when the hydration reaction between cement and water is completely carried out, the water-cement ratio is between 0.16-0.25 depending on the type of cement), and the excess water will escape from the system, leaving many open pores in the cement-based structure. In addition, various pore structures are formed due to various other reasons such as construction. In short, cement-based materials are porous. Due to the porous structure of the cement-based coating and the formation of a discontinuous hydrophobic coating between silane-siloxane and the silicate hydration product of the coating matrix, the waterproof and breathable function of the coating is guaranteed.

On the other hand, in addition to achieving the above functions for old concrete structures, the silicate hydration products of the fresh coating matrix introduced by the cement-based coating are highly active, which is conducive to forming stable covalent bonds with silane-siloxane, thus providing a guarantee for the hydrophobic and breathable functions.

The long-term and stable service of the hydrophobic and breathable function is beneficial to the anti-fouling, anti-corrosion and decorative protection of concrete structures, and improves the durability of concrete structures of railway bridges.

Specific implementation method:

The cement-based hydrophobic breathable coating includes: mixing powder material with an appropriate amount of water into a slurry, applying it on the surface of the concrete structure matrix, and then applying a special hydrophobic emulsion after solidification.

Among them, the powder material includes the following raw materials in parts by weight: 400-500 parts of white (or ordinary) high-belite sulphoaluminate cement, 20-100 parts of fast-hardening components, 20-35 parts of expanders, 0.5-2 parts of stabilizers, 1-2 parts of defoamers, 4-6 parts of thixotropic lubricants, 10-20 parts of modifiers, and 350-450 parts of fillers; the amount of powder material used is 100-300g/㎡.

You can also add 2 parts of dispersant, 1 part of water repellent, 1 part of lime, 2 parts of pigment, and 0.2 parts of pigment synergist.

The model of the high-belite sulphoaluminate cement is BS-WCFR 42.5;

The rapid hardening component uses amorphous glassy high-activity high-calcium calcium aluminate;

The expansion agent is anhydrous gypsum powder;

The dispersant used is polycarboxylate water reducer, model SD-600P-S02;

The stabilizer is hydroxypropyl methylcellulose, model number is HPMC30000;

The model of defoamer is P803;

The thixotropic lubricant is made of wood fiber, model B00;

The modifier is a dispersible latex powder, model number is Wacker 5010;

The water repellent agent is silane-siloxane emulsion;

The filler is 400-mesh heavy calcium;

The pigment enhancer is made of high-purity barium sulfate;

The remaining raw materials are common commercial products and are of industrial grade.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before coating, the reserved dry powder material is stirred with an appropriate amount of water into a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1: (0.6-1).

Before painting, clean the surface of the concrete structure substrate from dust and grind it, rinse it with high-pressure water, and after the surface is dry, repair the defective part with cement-based repair mortar, and then use cement-based putty to prime and smooth it. After drying, spray, roll or brush the refined slurry.

After the surface of the cement-based refined slurry coating is dry, apply the hydrophobic emulsion. The hydrophobic emulsion is prepared using commercially available water-based silane-siloxane emulsion, such as BS4004 from Wacker of Germany, and is prepared with water at a ratio of 1:5 (mass ratio). Apply the hydrophobic emulsion twice using wet-on-wet (wet-on-wet means applying it again when the first coat is not dry) to ensure that there is no omission or liquid accumulation.

The dosage of hydrophobic emulsion is 200-300g/㎡. Hydrophobic emulsion is a colorless and transparent solution, and its hydrophobic component is silane-siloxane; it has the advantages of improving the hydrophobic properties of cement-based coatings and making them breathable.

Embodiment 1;

The powder material includes the following raw materials in parts by weight: 400 parts of white high-belite sulphoaluminate cement, 60 parts of fast-hardening components, 35 parts of expanders, 0.9 parts of stabilizers, 1 part of defoamers, 5 parts of thixotropic lubricants, 14 parts of modifiers, and 380 parts of fillers.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before painting, the reserved dry powder material is stirred with an appropriate amount of water into a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1:0.6.

The refined slurry is sprayed, rolled or brushed on the surface of the concrete structure matrix, and after the cement-based refined slurry coating is dry, the hydrophobic emulsion is then brushed.

Embodiment 2;

The powder material includes the following raw materials in parts by weight: 440 parts of ordinary high-belite sulphoaluminate cement, 30 parts of fast-hardening components, 20 parts of expanders, 1.3 parts of stabilizers, 1.5 parts of defoamers, 6 parts of thixotropic lubricants, 20 parts of modifiers, and 410 parts of fillers.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before painting, the reserved dry powder material is mixed with an appropriate amount of water to form a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1:1.

The refined slurry is sprayed, rolled or brushed on the surface of the concrete structure matrix, and after the cement-based refined slurry coating is dry, the hydrophobic emulsion is then brushed.

Embodiment 3;

The powder material includes the following raw materials in parts by weight: 500 parts of white high-belite sulphoaluminate cement, 100 parts of fast-hardening components, 28 parts of expanders, 1.8 parts of stabilizers, 2 parts of defoamers, 4 parts of thixotropic lubricants, 10 parts of modifiers, and 350 parts of fillers; the amount of the powder material is 100-300g/㎡.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before painting, the reserved dry powder material is stirred with an appropriate amount of water into a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1:0.8.

The refined slurry is sprayed, rolled or brushed on the surface of the concrete structure matrix, and after the cement-based refined slurry coating is dry, the hydrophobic emulsion is then brushed.

Embodiment 4;

The powder material includes the following raw materials in parts by weight: 470 parts of white high-belite sulphoaluminate cement, 20 parts of fast-hardening components, 32 parts of expanders, 2 parts of stabilizers, 2 parts of defoamers, 4 parts of thixotropic lubricants, 18 parts of modifiers, 450 parts of fillers, 2 parts of dispersants, 1 part of hydrophobic agents, 1 part of lime, 2 parts of pigments, and 0.2 parts of pigment enhancers.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before painting, the reserved dry powder material is mixed with an appropriate amount of water to form a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1:0.9.

The refined slurry is sprayed, rolled or brushed on the surface of the concrete structure matrix, and after the cement-based refined slurry coating is dry, the hydrophobic emulsion is then brushed.

Embodiment 5;

The powder material includes the following raw materials in parts by weight: 400 parts of white high-belite sulphoaluminate cement, 80 parts of fast-hardening components, 20 parts of expanders, 0.5 parts of stabilizers, 1.3 parts of defoamers, 6 parts of thixotropic lubricants, 16 parts of modifiers, 440 parts of fillers, 2 parts of dispersants, 1 part of hydrophobic agents, 1 part of lime, 2 parts of pigments, and 0.2 parts of pigment enhancers.

The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use.

Before painting, the reserved dry powder material is stirred with an appropriate amount of water into a slurry, and then fully ground and mixed into a refined slurry using a colloid mill. The mass ratio of the powder material to water is 1:0.6.

The refined slurry is sprayed, rolled or brushed on the surface of the concrete structure matrix, and after the cement-based refined slurry coating is dry, the hydrophobic emulsion is then brushed.

According to the test, the coating of the present invention has the following excellent properties in addition to the basic technical properties of ordinary inorganic dry powder exterior wall coatings such as protection and decoration:

(1) Water vapor transmission rate V/g(㎡·d)＞150, equivalent air layer thickness Sd _/ m＜0.14, reaching the Ⅰ (high) level of this indicator.

(2) Static contact angle θ ≥ 150°, advancing contact angle ≥ 120°.

The surface tension of the concrete structure is reduced, and the water repellency of the concrete structure can reach more than 98%.

(3) Water absorption ratio: ≤10% in chloride environment; ≤20% in general environment. The water absorption ratio remains unchanged after 1000h of ultraviolet irradiation and 21d of alkaline treatment by immersion in 0.1M KOH (aq).

(4) Anti-fouling ≤ 15%.

The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims (4)

1. A cement-based hydrophobic breathable coating for protecting railway bridge concrete structures, characterized in that: a powder material is mixed with an appropriate amount of water to form a slurry, which is applied to the surface of the concrete structure matrix and then hardened, and then a hydrophobic emulsion is applied; The powder material includes the following raw materials in parts by weight: 400-500 parts of high belite sulphoaluminate cement, 20-100 parts of rapid hardening component, 20-35 parts of expansion agent, 0.5-2 parts of stabilizer, 1-2 parts of defoamer, 4-6 parts of thixotropic lubricant, 10-20 parts of modifier, and 350-450 parts of filler; The above raw materials are fully mixed in the above weight proportions to form a dry powder material for later use; Before coating, stir the reserved dry powder material with water to form a slurry, and then grind it into a refined slurry with a colloid mill. The mass ratio of the powder material to water is 1: (0.6-1); Before painting, the surface of the concrete structure substrate is cleaned of dust and polished, rinsed and, after the surface is dry, the defective part is repaired with cement-based repair mortar, and then the cement-based putty is used for primer and leveling. After drying, the refined slurry is sprayed, rolled or brushed; After the cement-based refined slurry coating is dry, apply the hydrophobic emulsion. 2. The cement-based hydrophobic and breathable coating for protecting railway bridge concrete structures according to claim 1 is characterized in that: 2 parts of dispersant, 1 part of hydrophobic agent, 1 part of lime, 2 parts of pigment, and 0.2 parts of pigment enhancer can also be added to the powder material. 3. The cement-based hydrophobic breathable coating for protecting railway bridge concrete structures according to claim 1 or 2, characterized in that the hydrophobic emulsion is applied twice. 4. The cement-based hydrophobic breathable coating for protecting railway bridge concrete structures according to claim 1 or 2, characterized in that the amount of powder material is 100-300 g/m2, and the amount of hydrophobic emulsion is 200-300 g/m2.