A concrete embedded sacrificial anode structure and its protective shell and preparation method

Abstract

The present invention discloses a concrete embedded sacrificial anode structure, a protective shell and a preparation method thereof, and belongs to the technical field of steel bar protection in concrete structures. The present invention discloses a concrete embedded sacrificial anode protective shell, the protective shell comprises a double-layer composite mortar, wherein the water absorption rate of the shell mortar layer is not less than 30%, the strength is not less than 25MPa, and the water absorption rate of the lining mortar layer is not less than 90%, and the strength is not greater than 5Mpa. The use of the protective shell of the present invention can effectively solve the problem that when the sacrificial anode method is used in the prior art to protect the steel bars in the concrete structure, the volume expansion caused by the rust of the anode metal is easy to cause damage to the concrete entity, and at the same time, the humidity, pH and other environments of the anode metal can be guaranteed, thereby ensuring the anti-rust effect of the steel bars.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel bar protection in concrete structures, and more specifically, relates to a concrete embedded sacrificial anode structure and a gradient composite mortar protective shell thereof and a preparation method thereof. Background Art

[0002] Steel bar corrosion is one of the main diseases affecting the durability of concrete projects. Steel bar corrosion in concrete has become a major issue of concern to the world and is considered to be the primary cause of the durability of concrete structures. Steel bar corrosion has or is causing huge economic losses to the national economy, so preventing steel bar corrosion is particularly important for improving the durability of concrete.

[0003] The corrosion of steel bars in concrete is an electrochemical process that requires the presence of an anode, a cathode, and an electrolyte. The moist concrete matrix is ​​a good electrolyte, and the embedded steel bars provide the anode and cathode. Under certain environmental conditions (such as the presence of oxygen and water), the steel bars begin to corrode, and the corrosion is generally pitting corrosion. Electrons flow between the anode and the cathode, causing iron to be oxidized into Fe(OH)2 or Fe(OH)3, which is 2 to 7 times larger in volume than elemental iron. Due to the increase in volume, ordinary concrete is brittle, which causes irreversible expansion and cracking damage to the concrete. This damage, combined with the failure of the performance of the steel bars after corrosion, will greatly reduce the durability of the concrete structure.

[0004] In order to solve the deterioration and damage of steel bar corrosion to reinforced concrete components, according to the electrochemical principle, two metals with different electrode potentials are placed in an electrolyte system, and the metal with a more negative electrode potential is the anode. The electrode potential difference between the two metals is used as the current source for cathodic protection. This is the basic principle of the sacrificial anode method. The concrete steel bar sacrificial anode method is a method of connecting a metal or alloy with a potential more negative than the steel bar potential in the concrete with the protected steel bar, and relying on the current generated by the continuous corrosion and dissolution of the metal with a more negative potential to protect the steel bars in the concrete. The sacrificial anode method is an electrochemical protection method, which has the advantages of being simple and easy to operate, and does not interfere with nearby facilities. However, the disadvantage of this method is that it cannot solve the problem of expansion caused by corrosion of the anode metal (steel or sacrificial metal).

[0005] Therefore, a protective layer is needed when sacrificial anode metal is embedded in concrete. This protective layer must first be able to absorb the volume expansion of the anode metal during operation and protect the concrete entity from being damaged by the internal volume growth. In other words, in addition to eliminating the corrosion of the steel bars, it is also necessary to solve the damage to the concrete caused by the volume expansion caused by the corrosion of the anode metal. This protective layer can not only protect the anode metal from being damaged during the pouring and vibration process of concrete construction, but also maintain the humidity, pH and other working environments of the anode metal.

[0006] At present, the protective layer of the buried sacrificial anode is generally made of porous, low-strength natural aggregate to configure the protective layer mortar to absorb the volume expansion of the anode metal after corrosion. However, natural aggregate has the disadvantages of uneven strength and uneven pores. The pores cannot be completely connected, so it cannot maintain the working environment of the sacrificial anode metal, nor can it effectively prevent the volume increase of the anode metal after corrosion. At the same time, due to the low strength of the protective mortar, the buried sacrificial anode is very easy to be damaged during on-site concrete pouring and vibration construction. Summary of the invention

[0007] 1. Problem to be solved

[0008] The purpose of the present invention is to provide a concrete embedded sacrificial anode structure, a protective shell and a preparation method thereof, so as to effectively solve the problem that when the sacrificial anode method is used in the prior art to protect the steel bars in the concrete, the volume expansion caused by the corrosion of the anode metal is easy to cause damage to the concrete entity, and at the same time, the humidity, pH and other environments of the anode metal can be guaranteed, thereby ensuring the anti-corrosion effect of the steel bars.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] The invention discloses a concrete embedded sacrificial anode protective shell, which comprises a gradient composite mortar, wherein the water absorption rate of the shell mortar layer is not less than 30%, the strength is not less than 25MPa, and the water absorption rate of the lining mortar layer is not less than 90%, and the strength is not greater than 5Mpa.

[0012] The present invention innovatively arranges a gradient composite mortar as a protective shell on the outside of the sacrificial anode, and designs the water absorption rate and strength parameters of the shell mortar layer and the lining mortar layer, so as to absorb the volume expansion generated by the anode metal during operation and protect the concrete entity from being destroyed by the internal volume growth, and also protect the anode metal from being damaged during the pouring and vibration process of concrete construction, and at the same time effectively ensure the humidity, pH and other environments required for the anode metal to work.

[0013] Specifically, since the water absorption rate of the inner lining mortar layer is high and the strength is low, when the anode metal corrodes and expands in volume, the inner lining mortar layer is destroyed under the action of the bursting force, creating enough space to absorb the volume of the anode metal corrosion expansion, thereby preventing the concrete entity from being damaged; at the same time, since the outer shell mortar layer has sufficient strength and ensures interconnected pores, on the one hand, during on-site concrete pouring and vibration construction, it can effectively protect the sacrificial anode and prevent the sacrificial anode from being damaged; on the other hand, it can allow the ions and liquids required by the anode metal to pass smoothly through the outer shell mortar layer to ensure its working environment.

[0014] Furthermore, the outer shell mortar layer and the inner lining mortar layer are bonded together by means of a gel formed by cement hydration reaction, and the bonding strength thereof is not less than 1Mpa, thereby ensuring that the pores between the inner and outer layers can be effectively connected, thereby further protecting the working environment of the anode metal.

[0015] Furthermore, the thickness ratio of the outer shell mortar layer to the inner lining mortar layer is (2-3):1, which is beneficial to further ensure the effectiveness of the protective layer.

[0016] Furthermore, a foam stabilizer is added to both the outer shell mortar layer and the inner lining mortar layer. The addition of the foam stabilizer can change the surface tension of water, and stabilize the introduced gas inside the mortar under the action of mechanical stirring, thereby ensuring the porosity required for the mortar work and at the same time allowing the pores of the inner and outer mortar layers to be interconnected. It should be noted that the present application does not make specific requirements for the specific material selection of the foam stabilizer, as long as the above effects can be achieved, that is, existing foam stabilizer materials such as alkylphenol ethylene oxide condensate can be directly used, and other foam stabilizer materials can also be used.

[0017] Furthermore, the raw materials of the outer shell mortar layer include the following components in parts by mass: 135-140 parts of cementitious materials, 90-94 parts of composite admixtures, 680-700 parts of expanded clay sand, 1-3 parts of foam stabilizer, 85-95 parts of anode working environment maintaining agent and 140-150 parts of water; the raw materials of the inner lining mortar layer include the following components in parts by mass: 14-16 parts of cementitious materials, 60-65 parts of composite admixtures, 230-235 parts of expanded clay sand, 0.5-1.0 parts of foam stabilizer, 25-35 parts of anode working environment maintaining agent and 30-40 parts of water.

[0018] By optimizing the mass ratio of each component in the raw materials of the inner and outer mortar layers, the different requirements of the inner and outer mortar layers for strength, porosity and other properties can be met. The addition of the anode working environment retainer can effectively ensure the long-term working environment of the anode metal, especially maintain the alkaline and ion environment required for its normal work, and ensure the working activity of the sacrificial anode. The retainer can be selected from inorganic active salt materials such as potassium hydroxide, potassium bromide, potassium nitrate, etc., or other substances that can achieve its function.

[0019] Furthermore, the cementitious material is white silicate cement with a strength grade of 42.5, and the composite admixture is a material obtained by compounding the ground metal mine tailings with silicon powder, and the particle size of the ground metal mine tailings is 300-400 meshes.

[0020] The invention discloses a concrete embedded sacrificial anode structure, comprising a sacrificial anode, which is pre-embedded in concrete and electrically connected to steel bars, and the protective shell of the invention is arranged outside the sacrificial anode.

[0021] The preparation method of the protective shell of the present invention is to cast the inner lining mortar layer and the outer shell mortar layer in layers on the outside of the sacrificial anode according to the raw material ratio. The specific preparation process is as follows:

[0022] (1) Preparation of lining mortar layer

[0023] ① Add foam stabilizer to water and stir evenly;

[0024] ② Mix the cementitious material and aggregate evenly and add them into the water in step ① and stir;

[0025] ③Continue to add anode working environment maintaining agent and stir evenly;

[0026] ④Pouring into mold;

[0027] ⑤After the mortar has finally set, replace it with the outer mortar mold;

[0028] (2) Preparation of shell mortar layer

[0029] ①Mix the foam stabilizer with 50% water and stir evenly;

[0030] ② After mixing the cementitious material and aggregate evenly, add them into the water in step ①, and continue to add the remaining 50% of water and stir evenly;

[0031] ③Continue to add environmental maintenance agent and stir evenly;

[0032] ④Pouring into mold;

[0033] (3) Steam pressure curing.

[0034] In summary, compared with the prior art, the present invention can achieve the following beneficial effects:

[0035] (1) The present invention adopts a double-layer composite mortar protective shell of a concrete-embedded sacrificial anode, thereby effectively solving the problems existing in the existing sacrificial anode metal protective layer, wherein the outer layer has sufficient strength and ensures interconnected pores, thereby protecting the anode metal from external damage and ensuring a working environment in which ions and liquids required by the anode metal can pass smoothly; the strength of the inner layer mortar is designed to be lower than the bursting force of the sacrificial anode metal volume expansion when it is corroded, thereby ensuring that the inner layer mortar is destroyed when the anode metal volume expands, thereby creating sufficient space to absorb the volume expansion of the anode metal due to corrosion.

[0036] (2) The present invention adds a certain amount of foam stabilizer to the outer shell mortar layer and the inner lining mortar layer, thereby forming a certain amount of pores in the outer shell mortar layer and the inner lining mortar layer, and ensuring the uniformity of the pores and the interconnection between the pores. By optimizing the overall raw material composition and ratio of the outer shell mortar layer and the inner lining mortar layer, the different requirements of the outer shell mortar layer and the inner lining mortar layer for strength and porosity can be ensured, thereby ensuring the performance of their efficacy.

[0037] (3) In the present invention, the inner and outer mortars are made of the same type of raw materials in different proportions and are cast in layers. The preparation process is relatively simple and can protect concrete reinforcement in a simple and economical way. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with specific embodiments. It should be noted that the following specific embodiments are only an example of the technical solution of the present application, but are not limited to the solutions of each specific embodiment, such as the specific material selection of the gelling material, the composite admixture, the anode working environment maintaining agent and the foam stabilizer.

[0039] Example 1

[0040] A concrete embedded sacrificial anode structure of this embodiment includes a sacrificial anode, which is pre-embedded in concrete and electrically connected to the steel bars, and a protective shell is provided on the outside of the sacrificial anode. The protective shell of this embodiment includes a double-layer composite mortar, wherein the water absorption rate of the outer shell mortar layer is not less than 30%, the strength is not less than 25MPa, the water absorption rate of the inner lining mortar layer is not less than 90%, the strength is not greater than 5Mpa, the thickness ratio of the outer shell layer to the inner cushion layer is 2:1, and the outer shell mortar layer and the inner lining mortar layer are bonded by gel formed by cement hydration reaction, and the bonding strength is not less than 1Mpa. The protective shell can be a bar cube or a cylinder, and its shape is not limited.

[0041] Among them, the 30% water absorption rate of the outer shell mortar can ensure the porosity of the mortar layer. These pores are interconnected, which is conducive to the passage of water, and the strength is not less than 25MPa, so that the sacrificial anode metal can be effectively protected and prevented from being damaged during the pouring and vibration process of concrete construction. At the same time, it can also resist the damage to the anode metal caused by the stress generated during the concrete hydration reaction, and ensure the buried position of the anode metal. The 90% water absorption rate of the inner cushion mortar can ensure that the mortar layer has sufficient pores. When the sacrificial anode is in working state, the inner cushion mortar uses its own low strength characteristics to be destroyed under the action of the anode metal expansion force, interconnecting the pores to form an effective space to offset the volume expansion of the anode metal reaction, and avoid the damage of the overall volume expansion of the buried sacrificial anode to the concrete entity structure. The gel bonding between the inner and outer mortar layers, which relies on the cement hydration reaction, can ensure the interconnection of the pores of the inner and outer layers, thereby ensuring the working environment of the anode metal.

[0042] Specifically, the raw materials of the outer shell mortar layer in this embodiment include the following components in mass fractions: 138 parts of cementitious material (Portland cement), 92 parts of composite admixture (material obtained by grinding metal mine tailings and compounding with silicon powder), 690 parts of ceramsite sand, 2 parts of foam stabilizer (alkylphenol ethylene oxide condensate is used in this embodiment), 90 parts of anode working environment agent (potassium hydroxide is used in this embodiment) and 143.7 parts of water; the raw materials of the inner lining mortar layer include the following components in mass fractions: 16 parts of cementitious material, 61 parts of composite admixture, 231 parts of ceramsite sand, 0.92 parts of foam stabilizer, 30 parts of anode working environment agent and 35.8 parts of water. The inner lining mortar layer and the outer shell mortar layer can be layered and poured on the outside of the sacrificial anode according to the raw material ratio. The specific preparation process is as follows:

[0043] (1) Preparation of lining mortar layer

[0044] ① Add foam stabilizer to water and stir evenly;

[0045] ② Mix the cementitious material and aggregate evenly and add them into the water in step ① and stir;

[0046] ③Continue to add anode working environment maintaining agent and stir evenly;

[0047] ④Pouring into mold;

[0048] ⑤After the mortar has finally set, replace it with the outer mortar mold;

[0049] (2) Preparation of shell mortar layer

[0050] ①Mix the foam stabilizer with 50% water and stir evenly;

[0051] ② After mixing the cementitious material and aggregate evenly, add them into the water in step ①, and continue to add the remaining 50% of water and stir evenly;

[0052] ③Continue to add environmental maintenance agent and stir evenly;

[0053] ④Pouring into mold;

[0054] (3) Steam pressure curing.

[0055] Example 2

[0056] A concrete embedded sacrificial anode structure of the present embodiment has the same structure as that of Embodiment 1, except that the raw materials of the outer shell mortar layer of the present embodiment include the following components in parts by mass: 135 parts of cementitious material (using white silicate cement with a strength grade of 42.5), 90 parts of composite admixture (a material obtained by grinding metal mine tailings and compounding them with silicon powder), 680 parts of ceramsite sand, 1 part of foam stabilizer (alkylphenol ethylene oxide condensate is used in the present embodiment), 85 parts of anode working environment maintaining agent (potassium bromide is used in the present embodiment) and 140 parts of water; the raw materials of the inner lining mortar layer include the following components in parts by mass: 14 parts of cementitious material, 60 parts of composite admixture, 230 parts of ceramsite sand, 0.5 parts of foam stabilizer, 25 parts of anode working environment maintaining agent and 30 parts of water, and the thickness ratio of the outer shell mortar layer to the inner lining mortar layer is 3:1.

[0057] Example 3

[0058] A concrete embedded sacrificial anode structure of the present embodiment has the same structure as that of Embodiment 1, except that the raw materials of the outer shell mortar layer of the present embodiment include the following components in parts by mass: 140 parts of cementitious material (white silicate cement), 94 parts of composite admixture, 700 parts of ceramsite sand, 3 parts of foam stabilizer (alkylphenol ethylene oxide condensate is used in the present embodiment), 95 parts of anode working environment maintaining agent (potassium nitrate is used in the present embodiment) and 150 parts of water; the raw materials of the inner lining mortar layer include the following components in parts by mass: 15 parts of cementitious material, 65 parts of composite admixture, 235 parts of ceramsite sand, 1.0 part of foam stabilizer, 35 parts of anode working environment maintaining agent and 40 parts of water, and the thickness ratio of the outer shell mortar layer to the inner lining mortar layer is 2.5:1.

[0059] Example 4

[0060] A concrete embedded sacrificial anode structure of the present embodiment has the same structure as that of Embodiment 1, except that the raw materials of the outer shell mortar layer in the present embodiment include the following components in parts by mass: 136 parts of cementitious material, 93 parts of composite admixture, 688 parts of expanded clay sand, 2.5 parts of foam stabilizer, 93 parts of anode working environment maintaining agent (potassium bromide is used in the present embodiment) and 148 parts of water; the raw materials of the inner lining mortar layer include the following components in parts by mass: 14 parts of cementitious material, 63 parts of composite admixture, 233 parts of expanded clay sand, 0.7 parts of foam stabilizer, 28 parts of anode working environment maintaining agent and 38 parts of water.

Claims

1. A concrete embedded sacrificial anode protection housing, characterized in that: The protective shell includes a gradient composite mortar, wherein the water absorption rate of the shell mortar layer is not less than 30%, and the strength is not less than 25MPa, and the water absorption rate of the lining mortar layer is not less than 90%, and the strength is not greater than 5Mpa; the shell mortar layer and the lining mortar layer are bonded by a gel formed by a cement hydration reaction, and the bonding strength is not less than 1Mpa, and a foam stabilizer is added to both the shell mortar layer and the lining mortar layer to ensure that there are interconnected pores between the shell mortar layer and the lining mortar layer.

2. The concrete embedded sacrificial anode protection housing according to claim 1, characterized in that: The thickness ratio of the outer shell mortar layer to the inner lining mortar layer is (2-3):

1.

3. A concrete embedded sacrificial anode protection housing according to claim 1 or 2, characterized in that: The raw materials of the shell mortar layer include the following components in parts by mass: 135-140 parts of cementitious material, 90-94 parts of composite admixture, 680-700 parts of ceramsite sand, 1-3 parts of foam stabilizer, 85-95 parts of anode working environment maintaining agent and 140-150 parts of water.

4. The concrete embedded sacrificial anode protection housing according to claim 3, characterized in that: The raw materials of the lining mortar layer include the following components in parts by mass: 14-16 parts of cementitious material, 60-65 parts of composite admixture, 230-235 parts of ceramsite sand, 0.5-1.0 parts of foam stabilizer, 25-35 parts of anode working environment maintaining agent and 30-40 parts of water.

5. The concrete embedded sacrificial anode protection housing according to claim 4, characterized in that: The cementitious material is white silicate cement with a strength grade of 42.5, and the composite admixture is a material obtained by compounding the ground metal mine tailings with silicon powder. The particle size of the ground metal mine tailings is 300-400 meshes.

6. A concrete embedded sacrificial anode structure, comprising a sacrificial anode, the sacrificial anode is pre-embedded in concrete and electrically connected to a steel bar, characterized in that: The outside of the sacrificial anode is provided with a protective shell according to any one of claims 1-5.

7. A method for preparing a protective shell according to any one of claims 1 to 5, characterized in that: The lining mortar layer and the outer shell mortar layer are poured in layers on the outside of the sacrificial anode according to the raw material ratio.