Reinforced concrete gradient anticorrosion structure and preparation method thereof

Abstract

This invention discloses a reinforced concrete gradient anti-corrosion structure and its preparation method. The reinforced concrete gradient anti-corrosion structure comprises, from the inside out, at least one layer of rust inhibitor-intercalated hydrotalcite mortar and at least one layer of calcined hydrotalcite mortar. The thickness of the calcined hydrotalcite mortar layer is greater than that of the rust inhibitor-intercalated hydrotalcite mortar layer. In the innermost rust inhibitor-intercalated hydrotalcite mortar layer, the amount of rust inhibitor-intercalated hydrotalcite in the mortar is 0.4-0.6%. With each outermost layer, the amount of hydrotalcite in the mortar increases by 0.8-1.2 times. In the outermost calcined hydrotalcite mortar layer, the amount of calcined hydrotalcite in the mortar is 3-8%. This invention significantly reduces the amount of hydrotalcite materials added without reducing the anti-corrosion performance of the mortar layer, thereby significantly saving economic costs.

Description

Technical Field

[0001] This invention relates to the field of steel reinforcement corrosion protection technology, and in particular to a reinforced concrete gradient corrosion protection structure and its preparation method. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Reinforced concrete is a crucial component of various civil engineering and hydraulic structures, possessing excellent mechanical properties and economic efficiency, and is widely used in engineering projects worldwide. However, due to issues such as chloride ion corrosion, the reinforcing steel in concrete undergoes varying degrees of corrosion after prolonged service. This further deteriorates the entire reinforced concrete structure, causing significant economic losses and safety hazards.

[0004] Adding anti-corrosion materials to concrete is a common method for protecting reinforced concrete from corrosion. Among them, hydrotalcite, due to its unique ion exchange properties and layered nanostructure, can solidify chloride ions and block their transport, thus exhibiting excellent anti-corrosion effects on steel bars and becoming a highly sought-after new anti-corrosion material.

[0005] However, in existing technologies, hydrotalcite rust inhibitors are often directly incorporated into mortar to prepare a single-layer steel reinforcement anti-corrosion layer. For example, patent CN 114933322A (publication date: August 23, 2022) discloses a calcium-aluminum type hydrotalcite with intercalated rust inhibitor, its preparation method, and its application. The method involves adding the prepared intercalated hydrotalcite rust inhibitor to cement mortar at 10 wt% of the cement content to prepare a pure mortar test block coated with carbon steel.

[0006] Patent CN 115124270B (authorization announcement date: May 2, 2023) discloses a layered adsorption-type hydrotalcite mortar rust-inhibiting layer, its preparation method, and its application. The method involves coating cement mortar onto the surface of reinforcing steel as a rust-inhibiting layer. After each layer of mortar is applied, a layer of hydrotalcite-loaded rust-inhibiting particles is adsorbed onto the mortar surface. After a period of curing, the above steps are repeated to obtain the layered adsorption-type hydrotalcite mortar rust-inhibiting layer. Although this patent uses a layered application of hydrotalcite-loaded rust-inhibiting agent, the process is cumbersome, requiring the application of mortar first, followed by the application of hydrotalcite-loaded rust-inhibiting agent, and repeated multiple times. Furthermore, the rust-inhibiting agent forms a separate rust-inhibiting layer rather than being uniformly distributed within the mortar, which can prolong its diffusion time within the mortar layer.

[0007] Furthermore, existing technologies do not employ different anti-corrosion solutions tailored to the varying anti-corrosion requirements of reinforced concrete in different locations, resulting in a lack of rigor in anti-corrosion measures. Summary of the Invention

[0008] In view of this, the present invention provides a reinforced concrete gradient anti-corrosion structure and its preparation method, which significantly reduces the amount of hydrotalcite added while ensuring anti-corrosion performance, and has good economic benefits.

[0009] In a first aspect, the present invention provides a reinforced concrete gradient anti-corrosion structure, comprising, from the inside out, at least one layer of rust inhibitor-intercalated hydrotalcite mortar and at least one layer of calcined hydrotalcite mortar.

[0010] The thickness of the calcined hydrotalcite mortar layer is greater than that of the rust inhibitor intercalated hydrotalcite mortar layer. In the innermost rust inhibitor intercalated hydrotalcite mortar layer, the amount of rust inhibitor intercalated hydrotalcite in the mortar is 0.4-0.6%. With each outermost layer, the amount of hydrotalcite in the mortar increases by 0.8-1.2 times. In the outermost calcined hydrotalcite mortar layer, the amount of calcined hydrotalcite in the mortar is 3-6%.

[0011] Preferably, the rust inhibitor intercalation layer of hydrotalcite mortar consists of 1 to 3 layers, and more preferably 2 layers.

[0012] Preferably, the calcined hydrotalcite mortar layer consists of 1 to 3 layers, and more preferably 2 layers.

[0013] Preferably, the rust inhibitor intercalated hydrotalcite is selected from one or more of pyridoxine intercalated calcium aluminum hydrotalcite, benzotriazole intercalated calcium aluminum hydrotalcite, vitamin B3 intercalated hydrotalcite, or calcium nitrite intercalated hydrotalcite.

[0014] Preferably, the calcined hydrotalcite is selected from calcined magnesium aluminum hydrotalcite or calcium aluminum hydrotalcite, with a calcination temperature of 400-600℃ and a calcination time of 2-6 hours.

[0015] Preferably, the rust inhibitor intercalated hydrotalcite mortar layer and the calcined hydrotalcite mortar layer further contain an anti-cracking agent and a water-retaining agent; preferably, the anti-cracking agent is added at a dosage of 1-2% in the mortar, and the water-retaining agent is added at a dosage of 0.5-1.5% in the mortar. More preferably, the anti-cracking agent is selected from magnesium oxide, calcium oxide, acrylate polymers, acrylic polymers, or hydroxypropyl methylcellulose, and the water-retaining agent is selected from polyacrylamide, polyethylene glycol, polyether polyol, glycerol, carboxymethyl cellulose, xanthan gum, or maltodextrin.

[0016] Preferably, the thickness of the rust inhibitor intercalated hydrotalcite mortar layer is 3-5 mm, and the thickness of the calcined hydrotalcite mortar layer is 6-10 mm.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned reinforced concrete gradient anti-corrosion structure, comprising the following steps:

[0018] Prepare cement mortar containing 0.4-0.6% rust inhibitor intercalated hydrotalcite, pour in steel reinforcement, and after molding, form the innermost layer of rust inhibitor intercalated hydrotalcite mortar.

[0019] Prepare subsequent cement mortars containing rust inhibitors and cement mortars containing calcined hydrotalcite by increasing the amount of hydrotalcite in the mortar by 0.8 to 1.2 times, and then pour and shape them layer by layer to obtain the final product.

[0020] Preferably, the curing conditions after each layer of cement mortar is poured are: curing in a curing chamber at 20-30℃ and 90-98% humidity for 20-30 hours.

[0021] Preferably, after the outermost layer of cement mortar containing calcined hydrotalcite is poured, it is cured in a curing chamber at 20-30℃ and 90-98% humidity for 20-30 days.

[0022] Preferably, the cement mortar comprises cement, natural river sand, and water, and the water-cement ratio of the cement mortar is 0.4–0.6, and the cement-sand ratio is 0.4–0.5. The cement is of type PO42.5.

[0023] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0024] (1) This invention firmly grasps the fact that the chloride ion concentration in concrete decreases from the surface to the interior, and proposes the idea of ​​"distribution on demand". The mortar is poured in layers according to the concentration gradient of hydrotalcite, so that the amount of hydrotalcite in the mortar covering the outer layer of steel bars decreases layer by layer, which significantly reduces the amount of hydrotalcite.

[0025] (2) This invention addresses the different corrosion protection requirements of concrete near and far from the reinforcing bars. Specifically, the need for solid chlorine is greater in the outer layer of reinforced concrete, while the need for slow-release rust inhibitors is greater in the inner layer of reinforced concrete. Therefore, this invention adds calcined hydrotalcite to the outer layer and rust inhibitor intercalated hydrotalcite to the inner layer, and sets the outer mortar thickness to be greater than the inner mortar thickness. Under the premise of ensuring that the corrosion protection performance of the mortar layer is not reduced, the amount of hydrotalcite materials added is greatly reduced, thereby significantly saving economic costs. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] As pointed out in the background section, in the prior art, when adding hydrotalcite to reinforced concrete for corrosion protection, the hydrotalcite dosage in a single-layer corrosion protection structure is often relatively high, which leads to higher costs; the layered strategy is cumbersome and can easily lead to slow diffusion of the rust inhibitor hydrotalcite; moreover, the prior art does not adopt different corrosion protection schemes for the different corrosion protection needs of reinforced concrete in different locations, resulting in blind spots in corrosion protection.

[0028] In view of this, the present invention provides a reinforced concrete gradient anti-corrosion structure, which consists of at least one layer of rust inhibitor intercalated hydrotalcite mortar and at least one layer of calcined hydrotalcite mortar, from the inside out.

[0029] The thickness of the calcined hydrotalcite mortar layer is greater than that of the rust inhibitor intercalated hydrotalcite mortar layer. In the innermost rust inhibitor intercalated hydrotalcite mortar layer, the amount of rust inhibitor intercalated hydrotalcite in the mortar is 0.4-0.6%. With each outermost layer, the amount of hydrotalcite in the mortar increases by 0.8-1.2 times. In the outermost calcined hydrotalcite mortar layer, the amount of calcined hydrotalcite in the mortar is 3-6%.

[0030] In reinforced concrete, chloride ion corrosion penetrates from the concrete surface into the interior, eventually reaching the surface of the reinforcing steel. The chloride ion concentration inside the concrete gradually decreases from the outside in; in other words, the required chloride-fixing capacity decreases as the concrete extends from the surface into the interior. Furthermore, the protective efficiency of corrosion inhibitors for reinforcing steel varies in different areas of the concrete. In fact, the concrete outside the reinforcing steel can be divided into a near-reinforcing steel zone (the concrete near the reinforcing steel) and a far-reinforcing steel zone (the outer layer of concrete). In reinforced concrete, in the near-reinforcing steel zone, the added corrosion inhibitor can more easily migrate to the surface of the reinforcing steel and protect it; while in the far-reinforcing steel zone, the corrosion inhibitor has difficulty reaching the surface. Therefore, the near-reinforcing steel zone requires a greater demand for slow-release corrosion inhibitors, while the far-reinforcing steel zone requires a greater demand for chloride fixation. This invention, based on actual corrosion protection requirements, divides the concrete outside the reinforcing steel into an inner and outer layer. Based on these two characteristics of reinforced concrete, this invention involves pouring mortar in layers outside the reinforcing bars. By using different mortar layers, the type, dosage, and thickness of the hydrotalcite material can be varied. This achieves a significant reduction in the amount of hydrotalcite used while ensuring sufficient corrosion and chlorine-fixing capabilities, thereby greatly improving its economic benefits.

[0031] This invention addresses two key characteristics of reinforced concrete corrosion: firstly, the chloride ion concentration decreases with increasing depth; and secondly, the corrosion protection requirements differ between areas near and far from the reinforcing bars. It creatively modifies the composition and structure of the mortar layer surrounding the reinforcing bars. The method involves incorporating hydrotalcite (TLC) according to chloride ion content and the specific concentration gradient between the near and far reinforcing bars, achieving "on-demand distribution." Specifically, the mortar layer surrounding the reinforcing bars is poured in multiple layers with varying LTC concentrations, increasing the LTC content layer by layer from the innermost to the outermost. Different types of LTC are added to the inner and outer layers based on corrosion protection requirements. Simultaneously, the outer mortar layer is made thicker than the inner layer. This gradient corrosion-resistant mortar effectively saves on LTC dosage without compromising corrosion protection, making it significant for widespread application.

[0032] The chloride fixation mechanism of calcined hydrotalcite mainly includes charge adsorption solidification and chemical solidification. Hydrotalcite is a layered mineral composed of positively charged main layers and interlayer anions assembled through non-covalent interactions. It possesses the characteristic of exchangeable interlayer anions, allowing it to adsorb chloride ions into the interlayer space in the presence of chloride ions and solidify through charge adsorption. High-temperature calcined hydrotalcite exhibits relatively high activity.

[0033] Corrosion inhibitor intercalated hydrotalcite, compared to calcined hydrotalcite, involves intercalating the corrosion inhibitor between the layers of calcined hydrotalcite through a chemical co-precipitation method. It possesses the same properties as hydrotalcite, namely the ion exchange characteristics between the layers. In a chloride salt environment, it can adsorb and solidify ions through the exchange between corrosion inhibitor molecules and chloride ions, while simultaneously releasing corrosion inhibitor molecules into the concrete to achieve the purpose of rust prevention for steel reinforcement. It has a dual function of chloride fixation and corrosion inhibition.

[0034] The rust inhibitor intercalated hydrotalcite mortar layer of the present invention is preferably 1 to 3 layers, more preferably 2 layers; the calcined hydrotalcite mortar layer is 1 to 3 layers, more preferably 2 layers. Too few layers make it difficult to fully exert the anti-corrosion effect, while too many layers do not significantly improve the anti-corrosion performance but instead increase the amount of pouring work.

[0035] This invention does not impose any special restrictions on the type of rust inhibitor intercalated hydrotalcite; commonly used rust inhibitor intercalated hydrotalcites in the art can be used. Preferably, the rust inhibitor intercalated hydrotalcite of this invention is selected from one or more of pyridoxine-intercalated calcium aluminum hydrotalcite, benzotriazole-intercalated calcium aluminum hydrotalcite, vitamin B3-intercalated hydrotalcite, or calcium nitrite-intercalated hydrotalcite.

[0036] The calcined hydrotalcite of this invention is calcined magnesium aluminum hydrotalcite or calcium aluminum hydrotalcite, with a calcination temperature of 400–600°C and a calcination time of 2–6 hours. The aluminum phase in the calcined hydrotalcite can react to a certain extent with chloride ions entering the plate to produce F salts. The F salts are stable and not easily decomposed, thereby achieving the effect of chemical solidification.

[0037] The rust inhibitor intercalated layer and the calcined hydrotalcite mortar layer of this invention also contain an anti-cracking agent and a water-retaining agent. This invention does not impose special restrictions on the type and amount of the anti-cracking agent and water-retaining agent; commonly used types and amounts in the art can be used. The preferred dosage of the anti-cracking agent in the mortar is 1-2%, and the preferred dosage of the water-retaining agent in the mortar is 0.5-1.5%. The preferred anti-cracking agent of this invention is magnesium oxide, calcium oxide, acrylate polymers, acrylic polymers, or hydroxypropyl methylcellulose; the preferred water-retaining agent is polyacrylamide, polyethylene glycol, polyether polyol, glycerol, carboxymethyl cellulose, xanthan gum, or maltodextrin.

[0038] The thickness of the rust inhibitor intercalated hydrotalcite mortar layer in this invention is preferably 3-5 mm, and the thickness of the calcined hydrotalcite mortar layer is preferably 6-10 mm. Since the outer layer of reinforced concrete is more susceptible to chloride ion corrosion, the outer calcined hydrotalcite mortar layer is thicker to effectively fix chloride. The chloride ion concentration in the inner layer is significantly reduced; to minimize costs while meeting corrosion protection requirements, the thickness of the inner rust inhibitor intercalated hydrotalcite mortar layer is thinner.

[0039] In another embodiment of the present invention, a method for preparing the above-mentioned reinforced concrete gradient anti-corrosion structure is provided, comprising the following steps:

[0040] Prepare cement mortar containing 0.4-0.6% rust inhibitor intercalated hydrotalcite, pour in steel reinforcement, and after molding, form the innermost layer of rust inhibitor intercalated hydrotalcite mortar.

[0041] Prepare subsequent cement mortars containing rust inhibitors and cement mortars containing calcined hydrotalcite by increasing the amount of hydrotalcite in the mortar by 0.8 to 1.2 times, and then pour and shape them layer by layer to obtain the final product.

[0042] The curing conditions after each layer of cement mortar is poured are as follows: curing in a curing chamber at 20-30℃ and 90-98% humidity for 20-30 hours. After the outermost layer of cement mortar containing calcined hydrotalcite is poured, it is cured in a curing chamber at 20-30℃ and 90-98% humidity for 20-30 days.

[0043] The cement mortar of the present invention comprises cement, natural river sand, and water, wherein the water-cement ratio of the cement mortar is 0.4-0.6, and the cement-sand ratio is 0.4-0.5. The preferred cement type is PO42.5, and the preferred water is tap water.

[0044] Before being poured with mortar, the reinforcing bars of this invention undergo a washing and cleaning process. The washing process is as follows: the reinforcing bars are placed in anhydrous ethanol and ultrasonically cleaned for 3 to 10 minutes, then removed and dried with a hair dryer. This process is repeated 2 to 4 times.

[0045] In this invention, each layer of cement mortar is poured using a PVC pipe of the corresponding size. The cement mortar is poured into the PVC pipe, and the PVC pipe is removed after the cement mortar has cured.

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0047] Example 1

[0048] The process involves pouring cylindrical mortar in four layers outside the reinforcing steel, with each layer containing a different amount of hydrotalcite. Each layer of mortar is poured into a PVC pipe of the corresponding size, and the mortar is then poured into the PVC pipe. The PVC pipe is removed after the mortar has cured.

[0049] The four-layer mortar pouring process is as follows: First, prepare cement mortar containing 0.5% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the first layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the second layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar, pouring the second layer of reinforcing mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of After the SJ-2 reinforced mortar hardens, a cement mortar containing 2% calcined magnesium aluminum hydrotalcite is prepared and poured as the third layer of mortar on the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 hardens, a cement mortar containing 4% calcined magnesium aluminum hydrotalcite is prepared and poured as the fourth layer of mortar on the outer layer of SJ-3. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0050] The curing conditions for the first three layers of mortar after pouring and hardening were as follows: curing for 24 hours in a curing chamber at 25℃ and 95% humidity. After the fourth layer of mortar was poured, curing continued for 28 days under the same conditions to obtain a gradient anti-corrosion mortar. The water-cement ratio of the mortar was 0.5, and the cement-sand ratio was 0.45. The thickness of the first and second mortar layers was 0.3cm, and the thickness of the third and fourth mortar layers was 0.6cm. The diameter of the reinforcing steel was 1cm, and the reinforcing steel underwent a washing and cleaning process before being poured into the mortar. The washing process involved placing the reinforcing steel in anhydrous ethanol and ultrasonically cleaning it for 5 minutes, then removing it and drying it with a hair dryer. This process was repeated 3 times. Crack-resistant agent and water-retaining agent were added to the mortar. The crack-resistant agent was magnesium oxide at a dosage of 1%, and the water-retaining agent was acrylamide at a dosage of 0.5%. The calcination temperature of the magnesium-aluminum hydrotalcite was 400℃, and the calcination time was 6 hours.

[0051] Example 2

[0052] The process involves pouring cylindrical mortar in four layers outside the reinforcing steel, with each layer containing a different amount of hydrotalcite. Each layer of mortar is poured into a PVC pipe of the corresponding size, and the mortar is then poured into the PVC pipe. The PVC pipe is removed after the mortar has cured.

[0053] The four-layer mortar pouring process is as follows: First, prepare cement mortar containing 0.5% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the first layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the second layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar, pouring the second layer of reinforcing mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of After the SJ-2 reinforced mortar hardens, a cement mortar containing 2% calcined magnesium aluminum hydrotalcite is prepared and poured as the third layer of mortar on the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 hardens, a cement mortar containing 4% calcined magnesium aluminum hydrotalcite is prepared and poured as the fourth layer of mortar on the outer layer of SJ-3. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0054] The curing conditions for the first three layers of mortar after pouring and hardening were as follows: curing for 24 hours in a curing chamber at 25℃ and 95% humidity. After the fourth layer of mortar was poured, curing continued for 28 days under the same conditions to obtain a gradient anti-corrosion mortar. The water-cement ratio of the mortar was 0.5, and the cement-sand ratio was 0.45. The thickness of the first and second mortar layers was 0.4cm, and the thickness of the third and fourth mortar layers was 0.7cm. The diameter of the reinforcing steel was 1cm, and the reinforcing steel underwent a washing and cleaning process before being poured into the mortar. The washing process was as follows: the reinforcing steel was placed in anhydrous ethanol and ultrasonically cleaned for 5 minutes, then removed and dried with a hair dryer. This process was repeated 3 times. Crack-resistant agent and water-retaining agent were added to the mortar. The crack-resistant agent was magnesium oxide at a dosage of 1.5%, and the water-retaining agent was acrylamide at a dosage of 1%. The calcination temperature of the magnesium-aluminum hydrotalcite was 500℃, and the calcination time was 3 hours.

[0055] Example 3

[0056] The process involves pouring cylindrical mortar in four layers outside the reinforcing steel, with each layer containing a different amount of hydrotalcite. Each layer of mortar is poured into a PVC pipe of the corresponding size, and the mortar is then poured into the PVC pipe. The PVC pipe is removed after the mortar has cured.

[0057] The four-layer mortar pouring process is as follows: First, prepare cement mortar containing 0.5% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the first layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the second layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar, pouring the second layer of reinforcing mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of After the SJ-2 reinforced mortar hardens, a cement mortar containing 2% calcined magnesium aluminum hydrotalcite is prepared and poured as the third layer of mortar on the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 hardens, a cement mortar containing 4% calcined magnesium aluminum hydrotalcite is prepared and poured as the fourth layer of mortar on the outer layer of SJ-3. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0058] The curing conditions for the first three layers of mortar after pouring and hardening were as follows: curing for 24 hours in a curing chamber at 25℃ and 95% humidity. After the fourth layer of mortar was poured, curing continued for 28 days under the same conditions to obtain a gradient anti-corrosion mortar. The water-cement ratio of the mortar was 0.5, and the cement-sand ratio was 0.45. The thickness of the first and second mortar layers was 0.5cm, and the thickness of the third and fourth mortar layers was 1cm. The diameter of the reinforcing steel was 1cm, and the reinforcing steel underwent a washing and cleaning process before being poured into the mortar. The washing process involved placing the reinforcing steel in anhydrous ethanol and ultrasonically cleaning it for 5 minutes, then removing it and drying it with a hair dryer. This process was repeated 3 times. Crack-resistant agent and water-retaining agent were added to the mortar. The crack-resistant agent was magnesium oxide at a dosage of 2%, and the water-retaining agent was acrylamide at a dosage of 1.5%. The calcium aluminum hydrotalcite was calcined at 600℃ for 2 hours.

[0059] Example 4

[0060] The process involves pouring cylindrical mortar in four layers outside the reinforcing steel, with each layer containing a different amount of hydrotalcite. Each layer of mortar is poured into a PVC pipe of the corresponding size, and the mortar is then poured into the PVC pipe. The PVC pipe is removed after the mortar has cured.

[0061] The four-layer mortar pouring process is as follows: First, prepare cement mortar containing 0.5% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the first layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the formed reinforcing mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the second layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the second layer of mortar, pouring the second layer of reinforcing mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar, forming a cylindrical reinforcing mortar SJ-2; after the hardening of the third layer of mortar SJ-2, prepare cement mortar containing 1% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of After the SJ-2 reinforced mortar hardens, a cement mortar containing 2% calcined magnesium aluminum hydrotalcite is prepared and poured as the third layer of mortar on the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 hardens, a cement mortar containing 4% calcined magnesium aluminum hydrotalcite is prepared and poured as the fourth layer of mortar on the outer layer of SJ-3. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0062] The curing conditions for the first three layers of mortar after pouring and hardening were as follows: curing for 24 hours in a curing chamber at 25℃ and 95% humidity. After the fourth layer of mortar was poured, curing continued for 28 days under the same conditions to obtain a gradient anti-corrosion mortar. The water-cement ratio of the mortar was 0.5, and the cement-sand ratio was 0.45. The thickness of the first and second mortar layers was 0.4cm, and the thickness of the third and fourth mortar layers was 0.8cm. The diameter of the reinforcing steel was 1cm, and the reinforcing steel underwent a washing and cleaning process before being poured into the mortar. The washing process was as follows: the reinforcing steel was placed in anhydrous ethanol and ultrasonically cleaned for 5 minutes, then removed and dried with a hair dryer. This process was repeated 3 times. Crack-resistant agent and water-retaining agent were added to the mortar. The crack-resistant agent was magnesium oxide at a dosage of 1.5%, and the water-retaining agent was acrylamide at a dosage of 1%. The calcium aluminum hydrotalcite was calcined at 500℃ for 5 hours.

[0063] Example 5

[0064] The difference compared to Example 1 is as follows:

[0065] The four-layer mortar pouring process is as follows: First, prepare a cement mortar containing 0.4% pyridoxine-intercalated calcium aluminum hydrotalcite, and use this as the first layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare a cement mortar containing 0.72% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour this as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the formed reinforcing mortar SJ-2 has hardened, prepare a cement mortar containing 1.3% pyridoxine-intercalated calcium aluminum hydrotalcite, and... The third layer of mortar is poured onto the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 has hardened, a cement mortar containing 2.4% calcined magnesium aluminum hydrotalcite is prepared and poured onto the outer layer of SJ-3 as the fourth layer of mortar to form a cylindrical reinforced mortar SJ-4. After the formed reinforced mortar SJ-4 has hardened, a cement mortar containing 4.2% calcined magnesium aluminum hydrotalcite is prepared and poured onto the outer layer of SJ-4 as the fifth layer of mortar. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0066] The thickness of the first, second, and third mortar layers is 0.3cm, and the thickness of the fourth and fifth mortar layers is 0.6cm.

[0067] Example 6

[0068] The difference compared to Example 1 is as follows:

[0069] The four-layer mortar pouring process is as follows: First, prepare cement mortar containing 0.4% pyridoxine-intercalated calcium aluminum hydrotalcite, and use it as the first layer of mortar for pouring reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare cement mortar containing 0.88% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour it as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the formed... After the reinforced mortar SJ-2 hardens, a cement mortar containing 1.9% calcined magnesium aluminum hydrotalcite is prepared and poured as the third layer of mortar on the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 hardens, a cement mortar containing 4.1% calcined magnesium aluminum hydrotalcite is prepared and poured as the fourth layer of mortar on the outer layer of SJ-3. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0070] Example 7

[0071] The difference compared to Example 1 is as follows:

[0072] The four-layer mortar pouring process is as follows: First, prepare cement mortar containing 0.6% pyridoxine-intercalated calcium aluminum hydrotalcite, and use it as the first layer of mortar for pouring the reinforcing bars, forming a cylindrical reinforcing mortar SJ-1; after the formed reinforcing mortar SJ-1 has hardened, prepare cement mortar containing 1.2% pyridoxine-intercalated calcium aluminum hydrotalcite, and pour it as the second layer of mortar on the outer layer of SJ-1, forming a cylindrical reinforcing mortar SJ-2; after the formed... After the reinforced mortar SJ-2 hardens, a cement mortar containing 2.6% calcined magnesium aluminum hydrotalcite is prepared and poured as the third layer of mortar on the outer layer of SJ-2 to form a cylindrical reinforced mortar SJ-3. After the formed reinforced mortar SJ-3 hardens, a cement mortar containing 5.5% calcined magnesium aluminum hydrotalcite is prepared and poured as the fourth layer of mortar on the outer layer of SJ-3. After forming and curing, the desired gradient anti-corrosion reinforced mortar is obtained.

[0073] Example 8

[0074] The difference from Example 1 is that benzotriazole-intercalated calcium aluminum hydrotalcite is used instead of pyridoxine-intercalated calcium aluminum hydrotalcite.

[0075] Comparative Example 1

[0076] Compared to Example 1, Comparative Example 1 did not add hydrotalcite in a gradient layering manner. Instead, 4% calcined magnesium aluminum hydrotalcite was directly added to the mortar using the traditional method, followed by a one-time casting process. The mortar thickness in this comparative example is the sum of the thicknesses of the four mortar layers in Example 1, i.e., a total thickness of 1.8 cm. Except for the contents described above, the other experimental parts are consistent with Example 1.

[0077] Comparative Example 2

[0078] Compared to Example 3, Comparative Example 2 did not add hydrotalcite in a gradient layering manner. Instead, it directly added 4% pyridoxine-intercalated calcium-aluminum hydrotalcite to the mortar using the traditional method, and then cast it in one go. The mortar thickness in this comparative example is the sum of the thicknesses of the four mortar layers in Example 3, i.e., the total thickness is 3 cm. Except for the contents described above, the other experimental parts are the same as in Example 3.

[0079] Comparative Example 3

[0080] Compared with Example 1, the difference is that in the process of pouring the four layers of mortar, the four layers of mortar in Comparative Example 3 are all cement mortar containing pyridoxine-intercalated calcium aluminum hydrotalcite.

[0081] Comparative Example 4

[0082] Compared with Example 1, the difference is that in the process of pouring the four layers of mortar, the four layers of mortar in Comparative Example 4 are all cement mortar containing calcined magnesium aluminum hydrotalcite.

[0083] Comparative Example 5

[0084] Compared with Example 1, the difference is that in the pouring process of the four-layer mortar, the first and second layers of Comparative Example 5 are cement mortar containing calcined magnesium aluminum hydrotalcite, and the third and fourth layers are cement mortar containing pyridoxine intercalated calcium aluminum hydrotalcite.

[0085] Comparative Example 6

[0086] Compared with Example 1, the difference is that the thickness of the first, second, third and fourth mortar layers is 0.3cm.

[0087] Test case

[0088] Corrosion resistance test:

[0089] The corrosion resistance performance of the gradient corrosion-resistant steel mortars obtained in the examples and comparative examples was tested. Specifically, the prepared steel-mortar was subjected to wet-dry cycle corrosion, and the electrochemical performance of the samples was tested using an electrochemical method to calculate the corrosion resistance efficiency. The corrosion solution was a 3% NaCl solution. One wet-dry cycle consisted of: immersion in the corrosion solution for 15 hours, followed by drying in an oven at 80°C for 5 hours, and then air-drying at 25±1°C for 4 hours. Open circuit potential and polarization resistance data are shown in Tables 1 and 2.

[0090] Table 1. Open-circuit potentials (unit: V) for different cycle numbers in Examples 1-4 and Comparative Examples 1-6.

[0091] Comparative Examples / Examples 10 times 30 times 60 times 90 times Comparative Example 1 -0.35 -0.46 -0.54 -0.61 Comparative Example 2 -0.29 -0.33 -0.41 -0.44 Comparative Example 3 -0.31 -0.36 -0.42 -0.56 Comparative Example 4 -0.39 -0.49 -0.55 -0.68 Comparative Example 5 -0.36 -0.48 -0.53 -0.57 Comparative Example 6 -0.40 -0.50 -0.57 -0.72 Example 1 -0.37 -0.45 -0.52 -0.63 Example 2 -0.34 -0.39 -0.45 -0.51 Example 3 -0.27 -0.32 -0.39 -0.43 Example 4 -0.33 -0.37 -0.42 -0.49

[0092] Table 2 Corrosion protection efficiency (unit: %) of Examples 1-4 and Comparative Examples 1-6 at different cycle numbers

[0093]

[0094]

[0095] The cost of Example 1 was set at 50. The cost of the rust inhibitor hydrotalcite was calculated as twice as that of the calcined hydrotalcite. The cost data in Table 3 is obtained.

[0096] Table 3 Cost accounting for Examples 1-4 and Comparative Examples 1-6

[0097] Comparative Serial Number Cost accounting Example sequence number Cost accounting Comparative Example 1 216 Example 1 50 Comparative Example 2 360 Example 2 60 Comparative Example 3 122 Example 3 83 Comparative Example 4 72 Example 4 66 Comparative Example 5 113 Comparative Example 6 32

[0098] Based on the open circuit potential data in Table 1, the corrosion resistance efficiency data in Table 2, and the cost accounting in Table 3, the analysis is as follows:

[0099] The comparison between Comparative Example 1 and Example 1 shows that the anti-corrosion performance of the gradient anti-corrosion mortar of this invention is no weaker than that of mortar with hydrotalcite incorporated in the traditional method. However, the hydrotalcite content in this invention is reduced from 4% in the outermost layer to 0.5% in the innermost layer, significantly reducing the amount of hydrotalcite and lowering the cost by about 77%, resulting in significant economic benefits. Comparative Example 2 demonstrates that increasing the thickness of the anti-corrosion mortar layer can significantly improve the protection efficiency of the reinforcing steel, but the cost will increase significantly, resulting in poor economic benefits. The comparison between Comparative Example 3 and Example 1 shows that using rust inhibitor-intercalated hydrotalcite instead of calcined hydrotalcite for reinforcing steel corrosion protection can improve the protection efficiency of the reinforcing steel to a certain extent, but the increase in effect is not significant, and the cost increases. The four layers of mortar in Comparative Example 4 are all cement mortar containing calcined magnesium aluminum hydrotalcite. It can be seen that its anti-corrosion effect is worse than that of Comparative Example 1, indicating that the inner layer of cement mortar containing pyridoxine-intercalated calcium aluminum hydrotalcite has better anti-corrosion performance. Comparative Example 5 demonstrates that cement mortar containing pyridoxine-intercalated calcium aluminum hydrotalcite, as an outer protective layer, can inhibit chloride ion diffusion and transport. However, using cement mortar containing calcined magnesium aluminum hydrotalcite as an inner layer fails to release rust inhibitors to protect the reinforcing bars, resulting in low overall reinforcing bar protection efficiency and high cost. Comparative Example 6 demonstrates that reducing the thickness of the cement mortar layer containing calcined magnesium aluminum hydrotalcite significantly reduces costs, but this reduction in thickness leads to a substantial decrease in the protection efficiency for the reinforcing bars, making it difficult to achieve a good anti-corrosion effect.

[0100] The solutions in Embodiments 1 to 4 of the present invention ensure the anti-corrosion effect of the anti-corrosion mortar on the reinforcing steel while reducing the cost by 60% to 80%. After 100 cycles, the anti-corrosion efficiency is still higher than 60%.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A reinforced concrete gradient anti-corrosion structure, characterized in that, From the inside out, it includes at least one layer of rust inhibitor intercalated hydrotalcite mortar and at least one layer of calcined hydrotalcite mortar. The thickness of the calcined hydrotalcite mortar layer is greater than that of the rust inhibitor intercalated hydrotalcite mortar layer; in the innermost rust inhibitor intercalated hydrotalcite mortar layer, the amount of rust inhibitor intercalated hydrotalcite in the mortar is 0.4~0.6%, and with each outermost layer, the amount of hydrotalcite in the mortar increases by 0.8~1.2 times; in the outermost calcined hydrotalcite mortar layer, the amount of calcined hydrotalcite in the mortar is 3~6%. The thickness of the rust inhibitor intercalated hydrotalcite mortar layer is 3~5mm, and the thickness of the calcined hydrotalcite mortar layer is 6~10mm.

2. The reinforced concrete gradient anti-corrosion structure as described in claim 1, characterized in that, The rust inhibitor intercalation layer of hydrotalcite mortar consists of 1 to 3 layers; the calcined hydrotalcite mortar layer consists of 1 to 3 layers.

3. The reinforced concrete gradient anti-corrosion structure as described in claim 2, characterized in that, The rust inhibitor intercalation layer of hydrotalcite mortar consists of two layers; the calcined hydrotalcite mortar layer consists of two layers.

4. The reinforced concrete gradient anti-corrosion structure as described in claim 1, characterized in that, The rust inhibitor intercalated hydrotalcite is selected from one or more of pyridoxine intercalated calcium aluminum hydrotalcite, benzotriazole intercalated calcium aluminum hydrotalcite, vitamin B3 intercalated hydrotalcite, or calcium nitrite intercalated hydrotalcite.

5. The reinforced concrete gradient anti-corrosion structure as described in claim 1, characterized in that, The calcined hydrotalcite is selected from calcined magnesium aluminum hydrotalcite or calcium aluminum hydrotalcite, with a calcination temperature of 400~600℃ and a calcination time of 2~6 hours.

6. The reinforced concrete gradient anti-corrosion structure as described in claim 1, characterized in that, The rust inhibitor intercalated hydrotalcite mortar layer and the calcined hydrotalcite mortar layer also contain crack-resistant agents and water-retaining agents.

7. The reinforced concrete gradient anti-corrosion structure as described in claim 6, characterized in that, The crack-resistant agent is added to the mortar at a dosage of 1-2%, and the water-retaining agent is added to the mortar at a dosage of 0.5-1.5%. The crack-resistant agent is selected from magnesium oxide, calcium oxide, acrylate polymers, acrylic polymers, or hydroxypropyl methylcellulose, and the water-retaining agent is selected from polyacrylamide, polyethylene glycol, polyether polyol, glycerol, carboxymethyl cellulose, xanthan gum, and maltodextrin.

8. The method for preparing a reinforced concrete gradient anti-corrosion structure according to any one of claims 1 to 7, characterized in that, Includes the following steps: Prepare cement mortar containing 0.4~0.6% rust inhibitor intercalated hydrotalcite, pour in steel reinforcement, and after molding, form the innermost layer of rust inhibitor intercalated hydrotalcite mortar. Prepare subsequent cement mortars containing rust inhibitors and cement mortars containing calcined hydrotalcite by increasing the amount of hydrotalcite in the mortar by 0.8 to 1.2 times, and pour and shape them layer by layer to obtain the final product.

9. The preparation method according to claim 8, characterized in that, The curing conditions after each layer of cement mortar is poured are as follows: curing in a curing chamber at 20~30℃ and 90~98% humidity for 20~30 hours; after the outermost layer of cement mortar containing calcined hydrotalcite is poured, curing is carried out in a curing chamber at 20~30℃ and 90~98% humidity for 20~30 days.

10. The preparation method according to claim 8, characterized in that, The cement mortar includes cement, natural river sand and water, and the water-cement ratio of the cement mortar is 0.4~0.6 and the cement-sand ratio is 0.4~0.5.

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