Preparation method of PCCP pipe core concrete special anti-cracking self-repairing agent

Abstract

The application discloses a preparation method of a PCCP pipe core concrete special anti-cracking self-repairing agent, and comprises the following steps: crushing dolomite into two particle sizes of 5mm-10mm and 80mm-150mm, uniformly mixing, fully calcining in a high-temperature furnace at 900-1200 DEG C, then naturally cooling to room temperature, finely grinding to pass through a 75-micron sieve, taking as an A component; uniformly mixing one or more of calcium sulphoaluminate, nano calcium carbonate and calcium aluminate, taking as a B component; mixing the A component 4-8 parts and the B component 2-6 parts, placing in a granulator, uniformly spraying anhydrous ethanol in the rotating process of the granulator, after the spraying is completed, rotating and granulating for 110-120s, continuously spraying an ethanol solution of rosin acid or boric acid, rotating and granulating for 110-120s, and the PCCP pipe core concrete special anti-cracking self-repairing agent can be obtained. The PCCP pipe core concrete special anti-cracking self-repairing agent is suitable for water conveying PCCP pipe core concrete, the mixing amount is 3-10%, the cost is low, the self-healing of cracks below 0.5mm can be realized, and the mechanical properties of the concrete are not obviously affected.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology and relates to a method for preparing a special crack-resistant self-healing agent for PCCP core concrete. Background Technology

[0002] PCCP (prestressed concrete cylinder pipe) is widely used in water supply, drainage, and oil transportation projects. Its structural performance and durability directly affect the long-term safe operation of the pipeline system. However, during service, the concrete core of PCCP is prone to micro-cracks due to factors such as drying shrinkage, temperature changes, internal and external water pressure, and chemical corrosion. These cracks not only reduce the impermeability of the concrete, allowing corrosive media to penetrate and accelerate the corrosion of the steel cylinder, but may also lead to localized stress concentration, thus affecting the overall structural stability of the pipeline. Under long-term operating conditions, the propagation of cracks may even cause the steel wires to break, ultimately leading to pipeline failure. Therefore, improving the crack resistance of the PCCP core concrete and enabling it to self-heal after cracks appear is crucial for improving the durability and service life of PCCP pipelines.

[0003] Currently, the main methods for improving the crack resistance of concrete include optimizing the mix proportion, adding fiber materials, and using expansive agents. However, these methods still have certain limitations in PCCP core concrete. For example, fiber-reinforced concrete has a certain effect on crack resistance, but adding fibers may affect the fluidity of the concrete and increase the difficulty of construction. Although expansive agents can compensate for shrinkage, if the expansion rate does not match the concrete hardening process, it may lead to insufficient expansion effect or later expansion cracking. In addition, traditional crack repair methods mainly rely on manual intervention, such as surface coating repair and grouting repair, which have problems such as high maintenance costs, low repair efficiency, and difficulty in repairing internal micro-cracks, making it difficult to meet the requirements of long-term service of PCCP pipelines.

[0004] WO2015074343A1 discloses a microencapsulation method for a water-based concrete repair agent. This invention achieves efficient encapsulation of the repair agent through a controllable emulsion process, with superior microcapsule stability and release controllability. However, its preparation steps are complex, making it difficult to control the release amount of the microcapsule repair agent, which can easily lead to insufficient local repair of concrete. CN110255948A discloses a self-healing concrete crack-resistant agent, its preparation method, and crack-resistant self-healing concrete. This invention's product can be directly added during concrete processing and mixing without affecting normal operation, making it highly practical. However, the dispersibility of nano-sized carbon black in this patent may affect the repair effect, offering limited improvement to the long-term durability of concrete. CN120757324A discloses a self-healing concrete crack-resistant agent and its preparation method. The self-healing concrete crack-resistant agent provided by this invention is mainly used for intelligent identification and self-repair of concrete cracks, achieving efficient repair through a synergistic mechanism of microbial mineralization, calcium ion slow release, and magnetothermal response. Its preparation process is complex, and the long-term survival rate and repair stability of microorganisms in the alkaline environment of concrete still need to be investigated. CN115010440A discloses a crack-resistant self-healing concrete and its preparation method, which has the advantages of improving the repair effect and timeliness of concrete cracks, but its preparation process is relatively complex. CN110357519A discloses a method for preparing crack-resistant self-healing reinforced concrete. The crack-resistant self-healing reinforced concrete prepared by this invention has excellent crack resistance, can self-repair after micro-cracks occur, and has strong mechanical properties, but it has many raw material components and the process is relatively complex.

[0005] Therefore, developing a crack-resistant self-healing agent specifically for PCCP pipe core concrete, enabling the concrete to not only possess excellent crack resistance during service but also spontaneously repair cracks after they form, is of great significance for improving the structural safety and durability of PCCP pipelines. This repair agent should automatically activate when micro-cracks appear inside the concrete, filling the cracks, preventing crack propagation, and also possessing characteristics such as impermeability, high durability, and wide environmental adaptability. This will extend the pipeline's service life, reduce maintenance costs, and ensure the long-term stable operation of the pipeline system. Summary of the Invention

[0006] The thin concrete core of PCCP pipes, coupled with their pressurized service environment and long-term water flow, presents both a key challenge and a significant difficulty: ensuring the long-term retention and effectiveness of self-healing agents for PCCP pipe core concrete while maintaining economic viability. Current methods for improving the crack resistance of concrete have limitations when applied to PCCP pipe core concrete. To address these technical challenges, this invention develops a specialized crack-resistant self-healing agent for PCCP pipe core concrete. This agent is low-cost, requires a dosage of 3% to 10% in concrete, is suitable for water conveyance PCCP pipe core concrete, and can achieve self-healing of cracks up to 0.5 mm, while having no significant impact on the workability and mechanical properties of the concrete.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a crack-resistant self-healing agent for PCCP core concrete includes the following steps:

[0009] 1) Crush dolomite into two particle sizes: 5mm~10mm and 80mm~150mm. Mix them evenly in a mass ratio of 1:1. Place them in a high-temperature furnace at 900℃~1200℃ for full calcination. Then, let them cool naturally to room temperature and grind them into fine powder using a ball mill until they all pass through a 75μm sieve. This powder is used as component A.

[0010] 2) Mix one or more of calcium sulfoaluminate, nano calcium carbonate, and calcium aluminate evenly as component B;

[0011] 3) Mix 4-8 parts of component A and 2-6 parts of component B to obtain component C; place 10 parts of component C in a granulator, and spray 1 part of anhydrous ethanol evenly during the rotation of the granulator. After spraying, rotate and granulate for 110-120 seconds, and continue to spray 2 parts of ethanol solution of rosin resin acid or boric acid, and rotate and granulate for 110-120 seconds.

[0012] 4) Dry the prepared granules thoroughly in an oven at 40℃~50℃, and sieve out particles smaller than 0.315mm and particles larger than 1mm to obtain the special crack-resistant self-healing agent for PCCP pipe core concrete.

[0013] The purity of the dolomite mentioned in step 1) is greater than 97%.

[0014] In step 3), the rosin resin acid ethanol solution contains 30% to 50% rosin resin acid, and the boric acid ethanol solution contains 3% to 5% boric acid. The reason for using either rosin resin acid ethanol solution or boric acid ethanol solution is that after the ethanol evaporates, a dense solidified film can be formed on the surface of the repair agent particles, achieving a coating effect.

[0015] The dosage of the special anti-cracking self-healing agent for PCCP core concrete is 3% to 10% of the total amount of cementitious materials, and it is added internally.

[0016] In this invention, dolomite is crushed into two particle sizes: 5mm~10mm and 80mm~150mm. The main components of calcined dolomite are calcium oxide and magnesium oxide. Different particle sizes result in different degrees of sintering of magnesium oxide and calcium oxide after calcination. A lower degree of sintering leads to a faster reaction. Combinations of different reaction times maintain the long-lasting repair effect. Simultaneously, an alkaline environment is formed, reacting with unhydrated cement.

[0017] The granulation process consists of two steps. First, anhydrous ethanol is sprayed evenly to complete the initial granulation. Then, a rosin resin acid ethanol solution or a boric acid ethanol solution is sprayed to complete the final granulation. The initial ethanol spraying causes the powder to form granules; the subsequent spraying of the rosin resin acid ethanol solution or boric acid ethanol solution forms a solidified film on the particle surface. After the ethanol evaporates, it coats the particle surface, preventing reaction failure. After cracks form, the particles rupture, and the internal calcium oxide and magnesium oxide react to form products such as hydrated calcium silicate to repair the cracks.

[0018] This invention is low in cost, with a self-healing crack-resistant agent dosage of 3%~10%, and is suitable for concrete cores of PCCP pipes used for water conveyance and regulation. It can achieve self-healing of cracks smaller than 0.5mm and has no significant impact on the mechanical properties of concrete.

[0019] Beneficial effects: After incorporating the special crack-resistant self-healing agent for PCCP core concrete of this invention, the self-healing agent will not crack or be lost during the concrete mixing and pouring process, and can exist in the concrete for a long time. When cracks smaller than 0.5mm appear in the core concrete, under water-flow conditions, the self-healing agent gradually releases cement hydration activating components and calcareous materials at the cracks, filling the cracks and enabling the concrete cracks to self-heal. This invention is low in cost, the crack-resistant self-healing agent dosage is 3%~10%, it is suitable for PCCP core concrete, and has no significant impact on the workability and mechanical properties of the concrete. Detailed Implementation

[0020] The present invention will be further illustrated below with reference to examples. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0021] Example 1

[0022] A method for preparing a special crack-resistant self-healing agent for PCCP core concrete:

[0023] (1) Crush dolomite with a purity greater than 97% into two particle sizes of 5mm~10mm and 80mm~150mm, mix them evenly at a mass ratio of 1:1, place them in a high-temperature furnace at 900℃~1200℃ for full calcination, then cool them naturally to room temperature, and grind them finely with a ball mill until they all pass through a 75μm sieve, which is used as component A.

[0024] (2) Mix calcium sulfoaluminate, nano calcium carbonate and calcium aluminate in a ratio of 1:1:1 to form component B;

[0025] (3) Mix 5 parts of component A and 5 parts of component B to obtain component C;

[0026] (4) Place 10 parts of component C in a granulator. While the granulator is rotating, spray 1 part of anhydrous ethanol evenly. After spraying, rotate and granulate for 120 seconds. Then, spray 2 parts of ethanol solution of rosin resin acid and rotate and granulate for another 120 seconds. Dry the granulated particles thoroughly in an oven at 40℃~50℃. Sieve out particles smaller than 0.315mm and larger than 1mm to obtain the special crack-resistant self-healing agent for PCCP pipe core concrete.

[0027] Example 2

[0028] A method for preparing a special crack-resistant self-healing agent for PCCP core concrete:

[0029] (1) Crush dolomite with a purity greater than 97% into two particle sizes of 5mm~10mm and 80mm~150mm, mix them evenly at a mass ratio of 1:1, place them in a high-temperature furnace at 900℃~1200℃ for full calcination, then cool them naturally to room temperature, and grind them finely with a ball mill until they all pass through a 75μm sieve, which is used as component A.

[0030] (2) Mix calcium sulfoaluminate, nano calcium carbonate and calcium aluminate in a ratio of 1:1:1 to form component B;

[0031] (3) Mix 5 parts of component A and 5 parts of component B to obtain component C;

[0032] (4) Place 10 parts of component C in a granulator, and spray 1 part of anhydrous ethanol evenly during the rotation of the granulator. After spraying, rotate and granulate for 120 seconds to obtain the special crack-resistant self-healing agent for PCCP core concrete.

[0033] Example 3

[0034] A method for preparing a special crack-resistant self-healing agent for PCCP core concrete:

[0035] (1) Crush dolomite with a purity greater than 97% into particles with a diameter of 5 mm to 10 mm, place it in a high-temperature furnace at 900℃ to 1200℃ for full calcination, then cool it naturally to room temperature, and grind it with a ball mill until it all passes through a 75 μm sieve, as component A;

[0036] (2) Mix calcium sulfoaluminate, nano calcium carbonate and calcium aluminate in a ratio of 1:1:1 to obtain component B; (3) Mix 5 parts of component A and 5 parts of component B to obtain component C;

[0037] (4) Place 10 parts of component C in a granulator. While the granulator is rotating, spray 1 part of anhydrous ethanol evenly. After spraying, rotate and granulate for 120 seconds. Then, spray 2 parts of ethanol solution of rosin resin acid and rotate and granulate for another 120 seconds. Dry the granulated particles thoroughly in an oven at 40℃~50℃. Sieve out particles smaller than 0.315mm and larger than 1mm to obtain the special crack-resistant self-healing agent for PCCP pipe core concrete.

[0038] Example 4

[0039] The dosage of the special crack-resistant self-healing agent for PCCP core concrete is 0%.

[0040] The dosages of the special crack-resistant self-healing agent for PCCP core concrete prepared in Examples 1, 2, and 3 were 4%, 6%, and 8%, respectively. The 28-day compressive strength of the concrete was tested. Cracks were prepared by preloading specimens with 90% of the compressive strength, and then the concrete was cured in water for 3 days and 28 days. The compressive strength recovery rate was tested, and the results are shown in Table 1.

[0041] Table 1 Results of concrete compressive strength and compressive strength recovery rate

[0042]

[0043] Comparing Example 1 and Example 4: (1) After standard curing for 28 days, the compressive strength of Example 1 with self-healing agent and Example 4 without self-healing agent is basically the same ("28-day compressive strength" column), indicating that the self-healing agent described in Example 1 has no significant effect on the compressive strength of the concrete itself; (2) With the addition of 4% to 8% of the anti-cracking self-healing agent prepared in this invention (Example 1), the compressive strength recovery rate of concrete cured in water for 3 days is 60.9% to 74.5%, and the compressive strength recovery rate of concrete cured in water for 28 days is 75.6% to 92.8%, while the compressive strength recovery rate of concrete cured in water for 3 days and 28 days without self-healing agent in Example 4 is 25.8% and 28.7% respectively, and the self-healing agent significantly improves the strength recovery rate; (3) The compressive strength recovery rate is improved when the dosage of anti-cracking self-healing agent in Example 1 changes from 4% to 8%.

[0044] Comparing Examples 2 and 4: In Example 2, the recovery rate of concrete compressive strength was similar to that without the crack-resistant self-healing agent (Example 1). Comparing Examples 2 and 1, without the crack-resistant self-healing agent, the recovery rate of concrete compressive strength after 3 days and 28 days of water curing (Example 2) was significantly reduced, indicating that coating is crucial in the preparation of the crack-resistant self-healing agent.

[0045] Comparing Example 3 and Example 1: Under the same dosage conditions, the compressive strength recovery rate of Example 3 is lower than that of Example 1. In Example 3, the dolomite is composed of a single particle size, while in Example 1, the dolomite is composed of two particle sizes. Under the same calcination temperature and time conditions, the sintering degree of dolomite with different particle sizes is different, resulting in different properties of the generated products, thus affecting the repair effect of the crack-resistant self-healing agent.

[0046] After soaking the concrete specimen formed in Example 1 in water for 90 days, it was cut open, and complete self-healing agent particles could be seen on the concrete interface, indicating that the self-healing agent can exist in the specimen for a long time and be well preserved.

Claims

1. A method for preparing a special crack-resistant self-healing agent for PCCP core concrete, characterized in that: Includes the following steps: 1) Crush the dolomite, calcine it fully in a high-temperature furnace at 900℃~1200℃, then cool it naturally to room temperature, and grind it finely with a ball mill until it all passes through a 75μm sieve, which is used as component A; 2) Mix one or more of calcium sulfoaluminate, nano calcium carbonate, and calcium aluminate evenly as component B; 3) Mix 4-8 parts of component A and 2-6 parts of component B to obtain component C; 4) Place 10 parts of component C in a granulator. While the granulator is rotating, spray 1 part of anhydrous ethanol evenly. After spraying, rotate and granulate for 110s~120s. Then spray 2 parts of rosin resin acid ethanol solution or boric acid ethanol solution and rotate and granulate for 110s~120s. 5) After the prepared particles are thoroughly dried, the particles smaller than 0.315mm and larger than 1mm are sieved out to obtain the special crack-resistant self-healing agent for PCCP core concrete.

2. The preparation method of a special crack-resistant self-healing agent for PCCP core concrete according to claim 1, characterized in that, The dolomite is crushed into two particle sizes: 5mm~10mm and 80mm~150mm, and then mixed evenly at a mass ratio of 1:

1.

3. The preparation method of a special crack-resistant self-healing agent for PCCP core concrete according to claim 1, characterized in that, The rosin resin acid ethanol solution contains 30% to 50% rosin resin acid; the boric acid ethanol solution contains 3% to 5% boric acid.

4. The special anti-crack self-healing agent for PCCP core concrete is prepared by the preparation method according to claims 1 to 3.

5. The PCCP core concrete-specific crack-resistant self-healing agent according to claim 4, characterized in that, The particle size of the crack-resistant self-healing agent is 0.315mm~1mm.

6. The application of the special crack-resistant self-healing agent for PCCP core concrete as described in claim 4 in the preparation of crack-resistant self-healing PCCP core concrete.

7. The application according to claim 6, characterized in that, The dosage of the PCCP core concrete-specific crack-resistant self-healing agent in concrete is 3% to 10%.

Images