Anti-crack high-performance concrete and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and discloses an anti-crack high-performance concrete and a preparation method thereof, the anti-crack high-performance concrete comprises an energy synergistic long-acting micro-expanding agent formed by light calcined magnesia modified by a nano copper oxide catalyst; the multi-signal response type self-repairing agent is composed of anhydrous metastable state aluminosilicate glass body powder and slow release type fluoride salt particles. The preparation method comprises the following steps: mechanically co-grinding the two functional components and a part of the cementing material to obtain a functional master batch, and mixing the functional master batch with the remaining materials. Through the synergistic effect of the functional components and the unique preparation process, the drying shrinkage of the concrete is effectively inhibited, and the mechanical property is improved. When cracks are generated, the self-repairing system can be triggered by signals such as moisture to react with the micro-expansive agent in a synergistic manner, and a compact product is generated to effectively block the cracks, so that the durability and reliability of the concrete are remarkably improved, and the technical problem of cracking of concrete materials is solved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a crack-resistant high-performance concrete and its preparation method. Background Technology

[0002] As a core structural material in engineering, the long-term durability and structural safety of concrete are largely constrained by cracking. Due to its own hydration reaction and changes in environmental humidity, concrete undergoes self-shrinkage and drying shrinkage. This volumetric instability is the fundamental cause of the formation of internal microcracks and even macroscopic cracks.

[0003] On the one hand, to solve this technical problem, existing technologies typically employ the addition of expansive agents to compensate for concrete shrinkage. However, traditional expansive agents often suffer from problems such as excessively rapid early expansion rates, overly concentrated release of expansion energy, and mismatch with the concrete shrinkage process, and their later compensation capacity is generally insufficient. For the increasingly used lightly calcined magnesium oxide expansive agents, the differences in raw material sources and calcination processes make it difficult to precisely control their hydration rate, resulting in significant instability in their expansion effect in concrete.

[0004] On the other hand, existing technologies have explored various approaches to endow concrete with self-repair capabilities after damage. However, the healing ability of ordinary concrete matrices is very limited, exhibiting only a certain degree of self-closing effect on cracks with extremely small widths. Furthermore, externally applied repair agent systems generally suffer from insufficient repair product generation, a simplistic response and repair mechanism, and poor adaptability to complex crack environment changes, resulting in low overall repair efficiency. In addition, when multiple functional admixtures are used together, conventional mixing processes struggle to ensure uniform dispersion of each component at the microscale within the concrete matrix, easily leading to agglomeration and hindering the full utilization of their activity, thus limiting the improvement of the overall crack resistance and repair performance of concrete. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a crack-resistant high-performance concrete and its preparation method. It solves the problems of existing technologies where ordinary expansion agents mainly work in the early stages and have limited compensation effects on later and long-term shrinkage; and some self-healing technologies have problems such as single repair signals, slow response speed, insufficient amount of repair products generated, or poor compatibility with the matrix, resulting in low repair efficiency and failing to fundamentally solve the problem of long-term crack resistance and durability of concrete.

[0006] To achieve the above objectives, the present invention provides a crack-resistant high-performance concrete and a method for preparing the same.

[0007] The first aspect of this invention provides a crack-resistant high-performance concrete, made from the following raw materials in parts by weight: Cementitious material: 400-550 parts; Fine aggregate: 600-800 parts; Coarse aggregate: 900-1100 parts; Water: 140-180 servings.

[0008] The cementitious material is composed of cement, mineral admixtures, multi-signal responsive self-healing agent, and energy-synergistic long-lasting micro-expansion agent; The dosage of the multi-signal responsive self-healing agent is 5%-10% of the total mass of the cementitious material, the dosage of the energy-synergistic long-lasting micro-expansion agent is 4%-8% of the total mass of the cementitious material, and the remainder is cement and mineral admixtures. The multi-signal responsive self-healing agent is composed of anhydrous metastable aluminosilicate glass powder and slow-release fluoride salt microparticles. The energy-synergistic long-acting micro-expansion agent is a highly active periclase containing a nanoscale energetic catalyst.

[0009] In a further technical solution, the anhydrous metastable aluminosilicate glass powder in the multi-signal responsive self-healing agent is obtained by melting SiO2, Al2O3 and CaO at 1450-1550℃ for 1.5-2.5 hours and then quenching with water, and the molar ratio of the three is (1.8-2.2):1:(2.8-3.2); The slow-release fluoride salt microparticles are calcium fluoride microparticles with a polysiloxane hydrophobic film with a thickness of 50-100 nanometers coated on their surface.

[0010] The polysiloxane hydrophobic film is formed by curing a coating solution. The coating solution is prepared by dissolving polydimethylsiloxane in an organic solvent to form a solution with a mass fraction of 5%-15%, then adding a silane coupling agent at a mass fraction of 0.5%-1.5% of the polydimethylsiloxane to the solution, and stirring until homogeneous. The organic solvent is toluene, xylene, or ethyl acetate.

[0011] In a further technical solution, the energy-synergistic long-lasting micro-expansion agent is prepared by calcining magnesite powder containing 0.5%-2.0% nano-sized energetic catalyst at a constant temperature of 800-900℃ for 1.5-2.5 hours. The nanoscale energetic catalyst is one of nano-ferric oxide or nano-copper oxide.

[0012] In a further technical solution, in the multi-signal responsive self-healing agent, the mass ratio of the anhydrous metastable aluminosilicate glass powder to the slow-release fluoride salt particles is (9.0-9.5):(0.5-1.0).

[0013] In a further technical solution, the energy-synergistic long-acting micro-expansion agent is prepared in a raw material where the mass ratio of the nano-sized energetic catalyst to the magnesite powder is (98.0-99.5):(0.5-2.0).

[0014] A second aspect of the present invention provides a method for preparing the above-mentioned crack-resistant high-performance concrete, comprising the following steps: S1. Preparation of functional masterbatch: Take the full amount of the multi-signal response self-healing agent and the energy synergistic long-acting micro-expansion agent, and then take 25%-35% of the total amount of cement and 45%-55% of the total amount of mineral admixtures. Mechanically co-grind and activate the aforementioned materials for 30-60 minutes to prepare functional masterbatch. S2. Mixing: Initially mix all aggregates, the remaining cement and mineral admixtures with 65%-75% of the total water, then add the functional masterbatch prepared in step S1 and mix, and finally add the remaining mixing water and water-reducing agent for final mixing. S3. Curing: After the concrete mixture obtained in step S2 is formed, it is subjected to 14 days of initial standard wet curing and 2-3 rounds of intermediate dry-wet cycle curing.

[0015] In a further technical solution, the mechanical co-milling activation described in step S1 is carried out in a high-energy ball mill, with the ball mill speed set to 200-300 rpm.

[0016] In a further technical solution, the intermediate dry-wet cycle curing described in step S3 includes drying for 5-7 days in an environment with a relative humidity of 60±5%, followed by saturation in water for 2 days.

[0017] In a further technical solution, the specific operation of the initial stirring in step S2 is as follows: Dry mix all aggregates, the remaining cement and mineral admixtures for 120-150 seconds, then add 65%-75% of the total water and wet mix for 120-150 seconds.

[0018] In a further technical solution, the method further includes a step of preparing the sustained-release fluoride salt microparticles before step S1, wherein the step is as follows: Calcium fluoride microparticles are placed in a fluidized bed and coated with a coating solution prepared by polydimethylsiloxane. The coating is then dried and cured at a temperature of 60-80°C to form a polysiloxane hydrophobic film on the surface of the calcium fluoride microparticles.

[0019] This invention provides a crack-resistant high-performance concrete and its preparation method. It has the following beneficial effects: 1. This invention utilizes an energy-synergistic long-lasting micro-expansion agent prepared by co-calcining nano-sized energetic catalysts with magnesite powder. By leveraging the continuous and stable micro-expansion stress generated by the agent throughout the entire lifespan of concrete, it effectively compensates for the long-term shrinkage of the material, achieving the beneficial effect of actively inhibiting the initiation and development of cracks from the source.

[0020] 2. This invention constructs a self-healing agent composed of anhydrous metastable aluminosilicate glass powder and slow-release fluoride salt microparticles coated with a hydrophobic polysiloxane film. This agent can respond to chemical signals (environmental alkalinity) and physical signals (crack propagation). Once triggered, it releases active substances to generate repair products, achieving efficient self-repair of microcracks and improving the long-term durability of materials.

[0021] 3. By setting a step in the preparation method to mechanically co-grind and activate two functional additives with a portion of cementitious materials, the present invention pre-prepares functional masterbatch, ensuring highly uniform dispersion of functional components in the concrete matrix and enhancing their reactivity, thereby achieving the beneficial effects of avoiding local performance failure and ensuring stable and uniform overall crack resistance and self-healing effect. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Test materials: The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0024] Water-reducing agent, CAS No.: 8068-05-1; Magnesium carbonate, CAS No.: 546-93-0; Nano-ferric oxide, CAS No.: 1309-37-1; Nano copper oxide, CAS No.: 1317-38-0; Silicon dioxide, CAS No.: 14808-60-7; Aluminum oxide, CAS No.: 1344-28-1; Calcium oxide, CAS No.: 1305-78-8; Calcium fluoride, CAS No.: 7789-75-5; Polydimethylsiloxane, CAS No.: 9016-00-6; Silane coupling agent: chemical name is 3-aminopropyltriethoxysilane, CAS number: 919-30-2.

[0025] Preparation of an energy-synergistic long-lasting micro-expanding agent (Preparation Example A): Preparation Example A1: Nano-ferric oxide and magnesite powder were weighed at a mass ratio of 0.5:99.5 and mechanically mixed in a mixer until homogeneous. The homogeneous powder was placed in a high-temperature calcination furnace, heated to 800℃, and calcined at a constant temperature for 1.5 hours. After calcination, the mixture was cooled to room temperature with the furnace. The resulting blocky product was ground and passed through a 200-mesh sieve to obtain the energy-synergistic long-acting micro-expansion agent, denoted as product A1.

[0026] Preparation Example A2: Nano-copper oxide and magnesite powder were weighed at a mass ratio of 1.25:98.75 and mechanically mixed in a mixer until homogeneous. The homogeneous powder was placed in a high-temperature calcining furnace, heated to 850℃, and calcined at a constant temperature for 2.0 hours. After calcination, the mixture was cooled to room temperature with the furnace. The resulting blocky product was ground and passed through a 200-mesh sieve to obtain the energy-synergistic long-lasting micro-expansion agent, denoted as product A2.

[0027] Preparation Example A3: Nano-ferric oxide and magnesite powder were weighed at a mass ratio of 2.0:98.0 and mechanically mixed in a mixer until homogeneous. The homogeneous powder was placed in a high-temperature calcining furnace, heated to 900℃, and calcined at a constant temperature for 2.5 hours. After calcination, the mixture was cooled to room temperature with the furnace. The resulting blocky product was ground and passed through a 200-mesh sieve to obtain the energy-synergistic long-acting micro-expansion agent, denoted as product A3.

[0028] Preparation of a multi-signal responsive self-healing agent (Preparation Example B): Step 1: Preparation of anhydrous metastable aluminosilicate glass powder (B-1) Weigh the raw materials according to the molar ratio of SiO2:Al2O3:CaO = 2:1:3 and mix them evenly in a mixer. Place the mixture in a high-temperature melting furnace, heat it to 1500℃, and melt it at this temperature for 2 hours. After melting, quickly pour the melt into room temperature water for water quenching. Collect the obtained glass fragments, dry them in an oven at 105℃ for 4 hours, then grind them and pass them through a 325-mesh sieve. The resulting powder is the anhydrous metastable aluminosilicate glass powder, denoted as B-1.

[0029] Step 2: Preparation of slow-release fluoride salt microparticles (B-2) This step includes the preparation of the coating solution and the coating process.

[0030] First, prepare the coating solution: Dissolve polydimethylsiloxane in toluene and mechanically stir until completely dissolved to prepare a 10% (w / w) solution. Then, add 1.0% (w / w) of silane coupling agent (by mass of polydimethylsiloxane) to the solution and continue stirring for 30 minutes to ensure uniform dispersion, thus obtaining the coating solution, denoted as B-2-Sol (coating solution of B-2).

[0031] Next, the coating process is carried out: micron-sized calcium fluoride powder is placed in a fluidized bed coating machine. The fluidized bed is started, and after the powder reaches a stable fluidized state, the coating solution B-2-Sol is atomized and sprayed into the bed through a nozzle at the bottom. The bed temperature is set to 70℃, and spraying and drying / curing operations are performed. After spraying, hot air is continuously circulated for drying for 15 minutes until the solvent completely evaporates. The resulting product is a slow-release fluoride salt microparticle with a uniformly coated surface of a polysiloxane hydrophobic film, denoted as B-2.

[0032] Step 3: Preparation of the self-healing agent finished product (Preparation Example B) Weigh the anhydrous metastable aluminosilicate glass powder (B-1) prepared in step 1 and the slow-release fluoride salt microparticles (B-2) prepared in step 2 according to a mass ratio of 9.25:0.75. Place both in a three-dimensional mixer and mix at low speed for 20 minutes to ensure uniform mixing and avoid physical damage to the coating film of the microparticles. The resulting powder is the multi-signal responsive self-healing agent, denoted as product B.

[0033] Examples 1-3: Example 1: This embodiment provides a method for preparing crack-resistant high-performance concrete, the specific steps of which are as follows: S1. Preparation of Functional Masterbatch: Weigh out the total amount of multi-signal responsive self-healing agent (Product B, 22.5 parts) and energy-synergistic long-acting micro-expansion agent (Product A1, 18 parts), and then weigh out 25% (71.75 parts) of the total cement content and 45% (55.125 parts) of the total mineral admixture content. Put the above four materials into a high-energy planetary ball mill, set the ball mill speed to 200 rpm, and perform mechanical co-milling activation for 30 minutes to prepare the functional masterbatch.

[0034] S2. Mixing: Add all the required amounts of fine aggregate (700 parts), coarse aggregate (1000 parts), remaining cement (215.25 parts), and mineral admixtures (67.375 parts) to a forced concrete mixer and dry mix for 120 seconds. Then add 65% (104 parts) of the total water and wet mix for 120 seconds. Add all the functional masterbatch prepared in step S1 to the mixer and continue mixing for 120 seconds to ensure uniform dispersion. Finally, pre-mix the remaining 35% water (56 parts) with the total amount of water-reducing agent (4.5 parts) and add this mixture to the mixer, then final mix for 120 seconds to obtain the concrete mixture.

[0035] S3. Curing: The concrete mixture obtained in step S2 is poured into specimens of the required size. The specimens undergo initial standard wet curing for 14 days in a standard curing room (temperature 20℃, relative humidity 95%). Afterwards, two rounds of intermediate wet-dry cycle curing are performed. The specific operation for each cycle is as follows: the specimen is placed in a constant temperature and humidity chamber and dried for 5 days in an environment with a relative humidity of 60%, and then saturated in water at 20℃ for 2 days.

[0036] Example 2: This embodiment provides a method for preparing crack-resistant high-performance concrete, the specific steps of which are as follows: S1. Preparation of Functional Masterbatch: Weigh out the total amount of multi-signal responsive self-healing agent (Product B, 22.5 parts) and energy-synergistic long-acting micro-expansion agent (Product A2, 36 parts), and then weigh out 30% (83.7 parts) of the total cement content and 50% (59.75 parts) of the total mineral admixture content. Put the above four materials into a high-energy planetary ball mill, set the ball mill speed to 250 rpm, and perform mechanical co-milling activation for 45 minutes to prepare the functional masterbatch.

[0037] S2. Mixing: Add all the required amounts of fine aggregate (700 parts), coarse aggregate (1000 parts), remaining cement (195.3 parts), and mineral admixtures (59.75 parts) to a forced concrete mixer and dry mix for 120 seconds. Then add 65% (104 parts) of the total water and wet mix for 120 seconds. Add all the functional masterbatch prepared in step S1 to the mixer and continue mixing for 120 seconds to ensure uniform dispersion. Finally, pre-mix the remaining 35% water (56 parts) with the total amount of water-reducing agent (4.5 parts) and add this mixture to the mixer, then final mix for 120 seconds to obtain the concrete mixture.

[0038] S3. Curing: The concrete mixture obtained in step S2 is poured into specimens of the required size. The specimens undergo initial standard wet curing for 14 days in a standard curing room (temperature 20℃, relative humidity 95%). Afterwards, two rounds of intermediate wet-dry cycle curing are performed. The specific operation for each cycle is as follows: the specimen is placed in a constant temperature and humidity chamber and dried for 6 days in an environment with a relative humidity of 60%, and then saturated in water at 20℃ for 2 days.

[0039] Example 3: This embodiment provides a method for preparing crack-resistant high-performance concrete, the specific steps of which are as follows: S1. Preparation of Functional Masterbatch: Weigh out the total amount of multi-signal responsive self-healing agent (Product B, 22.5 parts) and energy-synergistic long-acting micro-expansion agent (Product A3, 44 parts), and then weigh out 35% (94.85 parts) of the total cement content and 55% (63.525 parts) of the total mineral admixture content. Put the above four materials into a high-energy planetary ball mill, set the ball mill speed to 300 rpm, and perform mechanical co-milling activation for 60 minutes to prepare the functional masterbatch.

[0040] S2. Mixing: Add all the required amounts of fine aggregate (700 parts), coarse aggregate (1000 parts), remaining cement (176.15 parts), and mineral admixtures (51.975 parts) to a forced concrete mixer and dry mix for 120 seconds. Then add 65% (104 parts) of the total water and wet mix for 120 seconds. Add all the functional masterbatch prepared in step S1 to the mixer and continue mixing for 120 seconds to ensure uniform dispersion. Finally, pre-mix the remaining 35% water (56 parts) with the total amount of water-reducing agent (4.5 parts) and add this mixture to the mixer, then final mix for 120 seconds to obtain the concrete mixture.

[0041] S3. Curing: The concrete mixture obtained in step S2 is poured into specimens of the required size. The specimens undergo initial standard wet curing for 14 days in a standard curing room (temperature 20℃, relative humidity 95%). Afterwards, three rounds of intermediate wet-dry cycle curing are performed. The specific operation for each cycle is as follows: the specimen is placed in a constant temperature and humidity chamber and dried for 7 days in an environment with a relative humidity of 60%, and then saturated in water at 20℃ for 2 days.

[0042] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that this comparative example is ordinary concrete, without the addition of energy-synergistic long-lasting micro-expansion agent and multi-signal responsive self-healing agent, and without the preparation steps of functional masterbatch, but otherwise the same.

[0043] Comparative Example 2: Compared with Example 2, the difference is that the micro-expansion agent used in this comparative example is ordinary light-burned magnesium oxide, which is prepared by calcining magnesite powder at 850°C for 2.0 hours without adding nano-copper oxide catalyst. All other aspects are the same.

[0044] Comparative Example 3: Compared with Example 2, the difference is that: this comparative example does not add a multi-signal responsive self-healing agent, its mass is replaced by an equal amount of cement, and everything else is the same.

[0045] Comparative Example 4: Compared with Example 2, the difference is that the self-healing agent used in this comparative example does not contain slow-release fluoride salt particles (B-2), that is, the self-healing agent is composed only of anhydrous metastable aluminosilicate glass powder (B-1), and all other aspects are the same.

[0046] Comparative Example 5: Compared with Example 2, the difference is that this comparative example does not use the S1 step of preparing functional masterbatch, but directly mixes the energy-synergistic long-acting micro-expansion agent, the multi-signal responsive self-healing agent and other powder components, while the rest are the same.

[0047] Test Example 1-3: Test Example 1: Compressive Strength Test Test method: This test aims to determine the cubic compressive strength of the concrete prepared in Examples 1-3 and Comparative Examples 1-5.

[0048] The tests were conducted in accordance with GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". 150mm×150mm×150mm cubic specimens prepared and cured according to the aforementioned method were removed at 7 days, 28 days, and 90 days of curing.

[0049] The testing steps are as follows: S1. Remove the specimen from the curing environment, wipe its surface with a damp cloth, and check the appearance of the specimen to ensure that there are no obvious defects.

[0050] S2. Place the specimen at the center of the lower pressure plate of the microcomputer-controlled electro-hydraulic servo pressure testing machine. The pressure-bearing surface of the specimen should be the side surface during molding.

[0051] S3. Start the testing machine and adjust the upper pressure plate to contact the specimen. Apply the load continuously and uniformly at a loading rate of 0.6 MPa / s until the specimen fails.

[0052] S4. Record the maximum load value P (unit: kN) when the specimen fails.

[0053] S5, compressive strength value fcu Through formula Calculation, where A is the bearing area of ​​the specimen (22500mm²). 2 Three specimens were tested for each mix proportion, and the arithmetic mean of the three measurements was taken as the compressive strength value of that mix proportion at that age.

[0054] Test results: Table 1: Test results of compressive strength of concrete in each group (MPa) Component Name 7 days 28 days 90 days Example 1 48.2 65.1 78.4 Example 2 51.5 72.8 85.3 Example 3 53.1 76.4 89.2 Comparative Example 1 38.7 55.2 60.1 Comparative Example 2 43.6 61.3 68.5 Comparative Example 3 50.1 68.7 75.1 Comparative Example 4 50.8 70.2 80.9 Comparative Example 5 44.3 63.9 71.6 Results analysis: As shown in Table 1, the concrete prepared according to Examples 1-3 exhibits higher compressive strengths at 7 days, 28 days, and 90 days than the concrete in Comparative Examples 1-5. This result indicates that by combining a specifically prepared energy-synergistic long-lasting micro-expansion agent with a multi-signal responsive self-healing agent and employing a functional masterbatch preparation process, the density and mechanical properties of the concrete matrix can be effectively improved. The preparation step of the functional masterbatch involves high-energy mechanical co-grinding activation, which increases the specific surface area of ​​each functional component and introduces lattice defects, thereby enhancing its chemical reactivity. Simultaneously, this step ensures a uniform distribution of each component at the microscale, laying a structural foundation for its function within the cement matrix.

[0055] A comparison of Example 2 and Comparative Example 2 shows that the application of the energy-synergistic long-lasting micro-expansion agent (product A2) significantly increased the strength of concrete. The mechanism lies in the fact that during the high-temperature calcination of magnesite, nano-copper oxide altered the microcrystalline structure of the lightly calcined magnesia product and refined the grains, resulting in a smoother and more continuous hydration process within the concrete. This controlled micro-expansion effect effectively compensates for the chemical shrinkage and drying shrinkage of concrete during hardening, inhibits the generation and development of internal microcracks, and forms a denser microstructure, thereby improving macroscopic compressive strength. This effect is particularly pronounced at 90 days of age, confirming its long-lasting effect.

[0056] By comparing the results of Example 2 with those of Comparative Examples 3, 4, and 5, the roles of each component and process step can be further clarified. The anhydrous metastable aluminosilicate glass powder (B-1) in the multi-signal responsive self-healing agent exhibits late-stage pozzolanic activity; its slowly reacting products can fill the capillary pores in the matrix, which is one reason why the strength of Example 2 is higher than that of Comparative Example 3 without this agent. The slowly released fluoride salt microparticles (B-2) promote the hydration of the silicate system, resulting in a better late-stage strength enhancement effect in Example 2 compared to Comparative Example 4 without these microparticles. The strength difference between Example 2 and Comparative Example 5 confirms the necessity of the functional masterbatch preparation step. Direct incorporation of functional components without mechanical co-milling activation results in lower dispersibility and reactivity, weakening their optimization effect on the matrix structure and ultimately leading to a decrease in compressive strength.

[0057] Test Example 2: Drying Shrinkage Rate Test Test method: This test aims to determine the shrinkage deformation of each group of concrete prepared in Examples 1-3 and Comparative Examples 1-5 under dry conditions.

[0058] The tests were conducted in accordance with GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Prismatic specimens measuring 100mm × 100mm × 515mm were used for the tests.

[0059] The testing steps are as follows: S1. The concrete mixture prepared according to the aforementioned method is poured into a prism mold, and probes are pre-embedded at both ends of the specimen.

[0060] S2. After curing the specimens in the mold for 24 hours, remove them from the mold, number them, and immediately measure their initial length L0. Use a vertical concrete shrinkage meter to take the reading, accurate to 0.001 mm.

[0061] S3. After demolding, the specimens are transferred to a constant temperature and humidity chamber (temperature 20℃, relative humidity 60%) for drying and curing.

[0062] S4. Measure the length L of each specimen at 3 days, 7 days, 14 days, 28 days, 60 days, and 90 days of age. t .

[0063] S5, Drying shrinkage rate ε at different ages st Through formula Calculate, where L b Using a reference length of 500 mm, the results are expressed as micro-strain (με). Three specimens were tested for each mix design, and the arithmetic mean of the three measurements was taken as the drying shrinkage rate of that mix design at that age.

[0064] Test results: Table 2: Results of concrete drying shrinkage rate test (με) for each group Component Name 3 days 7 days 14 days 28 days 60 days 90 days Example 1 68 131 184 243 289 312 Example 2 55 108 157 211 254 273 Example 3 47 94 138 185 223 241 Comparative Example 1 115 224 341 478 582 627 Comparative Example 2 92 179 268 381 465 508 Comparative Example 3 61 123 175 239 291 318 Comparative Example 4 58 116 169 224 277 295 Comparative Example 5 83 161 235 324 398 437 Results analysis: Table 2 shows that the concrete prepared in Examples 1-3 exhibited lower drying shrinkage rates throughout the entire 3-90 day period compared to Comparative Examples 1-5. This result indicates that combining an energy-synergistic long-lasting micro-expansion agent with a multi-signal-responsive self-healing agent and introducing it into concrete through a functional masterbatch preparation step can effectively suppress volume shrinkage caused by moisture migration. The functional masterbatch preparation step, through mechanical co-grinding, ensured uniform micro-dispersion of each functional component, providing a prerequisite for achieving homogeneous shrinkage compensation throughout the entire concrete matrix.

[0065] The comparison results between Example 2 and Comparative Examples 1 and 2 reveal the effect of the energy-synergistic long-acting micro-expansion agent (Product A2) in inhibiting shrinkage. Comparative Example 1, which does not contain this agent, has the highest shrinkage rate. Comparative Example 2, using ordinary light-burned magnesium oxide, has a lower shrinkage rate but is still higher than that of Example 2. The mechanism is that the hydration reaction rate of the light-burned magnesium oxide in Product A2, due to the catalytic modification by nano-copper oxide, is effectively controlled to produce magnesium hydroxide. This continuous and gradual hydration reaction generates a solid product with a certain crystallization pressure in the concrete pore network. The volume of this product is larger than that of the reactants, thereby producing a micro-expansion effect inside. This effect can directly offset part of the shrinkage stress caused by capillary water loss, significantly reducing the macroscopic drying shrinkage value of concrete.

[0066] Comparative analysis of Example 2 with Comparative Examples 3, 4, and 5 further confirmed the synergistic effect of the self-healing agent components and the preparation process. Compared with Comparative Example 3, which did not contain the self-healing agent, Example 2 showed a lower shrinkage rate. This is because the anhydrous metastable aluminosilicate glass powder (B-1) in the self-healing agent underwent a late-stage hydration reaction, and the resulting hydrated calcium silicate gel and other products filled and refined the capillary pores, increasing the resistance to water migration. Meanwhile, compared with Comparative Example 4, which did not contain slow-release fluoride salt particles (B-2), Example 2 showed a further reduction in shrinkage rate, indicating that the fluoride ions released by B-2 promoted the hydration degree of the cementitious material, forming a denser matrix structure. The data differences between Example 2 and Comparative Example 5 indicate that the components not treated by the functional masterbatch process are unevenly dispersed in the matrix and have low activity, leading to reduced efficiency in their expansion compensation and pore structure optimization effects, ultimately resulting in a higher drying shrinkage rate.

[0067] Test Example 3: Quantitative Evaluation of Crack Repair Effectiveness Test method: This test aims to quantitatively evaluate the repair capabilities of the concrete groups prepared in Examples 1-3 and Comparative Examples 1-5 for precast cracks after undergoing dry-wet cycle curing.

[0068] The test used a prism specimen with dimensions of 100mm×100mm×400mm.

[0069] The testing steps are as follows: S1. Curing each group of specimens in a standard curing room (temperature 20℃, relative humidity 95%) for 28 days.

[0070] S2. Place the specimen on a computer-controlled electro-hydraulic servo pressure testing machine and perform pre-cracking treatment using a three-point bending loading method. By controlling the loading with displacement, create a macroscopic crack with a through width of approximately 0.2 mm at the bottom mid-span of the specimen. Immediately after loading, measure and record the initial crack width W0 using a crack width observation instrument.

[0071] S3. Place the pre-cracked specimen in a specific repair environment for 28 days of wet-dry cycle curing. The specific operation for each cycle is as follows: immerse the specimen in water at 20℃ for 2 days, and then transfer it to a constant temperature and humidity chamber (temperature 20℃, relative humidity 60%) for 5 days to dry. A total of 4 cycles are performed.

[0072] S4. After the repair period, remove the specimen from the environment and measure the residual crack width W after repair at the same location as the initial measurement using the same crack width observation instrument. f .

[0073] S5, Surface crack repair rate η is obtained through the formula Calculation. Three specimens were tested for each mix design, and the arithmetic mean of the three measurements was taken as the final crack repair rate for that mix design.

[0074] Test results: Table 3: Test results of concrete crack repair rate for each group Results analysis: The test results in Table 3 show that the concrete prepared in Examples 1-3 exhibited a significantly higher surface crack repair rate than all comparative examples. This result confirms that the composite system of energy-synergistic long-acting micro-expansion agent and multi-signal-responsive self-healing agent, after being introduced into concrete through the functional masterbatch preparation process, can effectively repair cracks in the matrix. The mechanical co-grinding activation step of the functional masterbatch enables the two functional admixtures to achieve uniform compounding and dispersion at the microscale, providing a structural basis for subsequent efficient and synergistic chemical and physical interactions at the crack interface.

[0075] The crack repair process is triggered by multiple signals. Once a crack forms, external moisture and air (containing carbon dioxide) penetrate the concrete matrix along the crack channel, triggering a chemical reaction. The core component of the multi-signal responsive self-healing agent, anhydrous metastable aluminosilicate glass powder (B-1), upon contact with moisture and a high-pH pore solution, undergoes glass structure instability and hydration, as well as a pozzolanic reaction, generating products such as hydrated calcium silicate (CSH) gel. These products can fill and seal the cracks. Comparing the results of Example 2 and Comparative Example 4, the presence of slow-release fluoride salt microparticles (B-2) improved the repair rate. The mechanism is that when the coating layer breaks at the crack due to stress or environmental changes, the slowly released fluoride ions promote the hydration reaction process of the silicate system, accelerating the generation of repair products and thus achieving more complete crack closure.

[0076] Energy-synergistic long-acting micro-expansion agent also plays a role in this repair process. Newly exposed, incompletely hydrated lightly calcined magnesium oxide particles in the crack area continue to undergo hydration upon contact with moisture, generating larger magnesium hydroxide crystals. This produces localized expansion stress within the crack, which reduces the crack width and provides a substrate for the chemical products generated by the self-healing agent. The difference in repair rates between Example 2 and Comparative Example 5 clarifies the necessity of the functional masterbatch preparation process. Unactivated functional components exist in agglomerated or coarse-particle form, resulting in uneven distribution in the matrix. When cracks occur, it is impossible to guarantee a sufficient number of active repair units at the interface, thus significantly reducing repair efficiency. This technical solution achieves efficient repair of concrete cracks through the combination of component compounding and preparation process.

Claims

1. A crack-resistant high-performance concrete, characterized in that, Made from the following raw materials in parts by weight: Cementitious material: 400-550 parts; Fine aggregate: 600-800 parts; Coarse aggregate: 900-1100 parts; Water: 140-180 parts; The cementitious material is composed of cement, mineral admixtures, multi-signal responsive self-healing agent, and energy-synergistic long-lasting micro-expansion agent; The dosage of the multi-signal responsive self-healing agent is 5%-10% of the total mass of the cementitious material, the dosage of the energy-synergistic long-lasting micro-expansion agent is 4%-8% of the total mass of the cementitious material, and the remainder is cement and mineral admixtures. The multi-signal responsive self-healing agent is composed of anhydrous metastable aluminosilicate glass powder and slow-release fluoride salt microparticles. The energy-synergistic long-acting micro-expansion agent is a highly active periclase containing a nanoscale energetic catalyst.

2. The crack-resistant high-performance concrete according to claim 1, characterized in that, In the aforementioned multi-signal responsive self-healing agent: The anhydrous metastable aluminosilicate glass powder is prepared by melting SiO2, Al2O3 and CaO at 1450-1550℃ for 1.5-2.5 hours and then quenching with water, and the molar ratio of the three is (1.8-2.2):1:(2.8-3.2). The slow-release fluoride salt particles are calcium fluoride particles with a polysiloxane hydrophobic film with a thickness of 50-100 nanometers coated on their surface.

3. The crack-resistant high-performance concrete according to claim 1, characterized in that, In the energy-synergistic long-acting micro-expanding agent: The energy-synergistic long-acting micro-expansion agent is prepared by calcining magnesite powder containing 0.5%-2.0% nano-sized energetic catalyst at a constant temperature of 800-900℃ for 1.5-2.5 hours. The nanoscale energetic catalyst is either nano-ferric oxide or nano-copper oxide.

4. The crack-resistant high-performance concrete according to claim 1, characterized in that, In the multi-signal responsive self-healing agent, the mass ratio of the anhydrous metastable aluminosilicate glass powder to the slow-release fluoride salt particles is (9.0-9.5):(0.5-1.0).

5. The crack-resistant high-performance concrete according to claim 1, characterized in that, In the energy-synergistic long-acting micro-expansion agent, the mass ratio of the highly active periclase to the nanoscale energetic catalyst is (98.0-99.5):(0.5-2.0).

6. A method for preparing the crack-resistant high-performance concrete according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of functional masterbatch: Take the full amount of the multi-signal response self-healing agent and the energy synergistic long-acting micro-expansion agent, and then take 25%-35% of the total amount of cement and 45%-55% of the total amount of mineral admixtures. Mechanically co-grind and activate the aforementioned materials for 30-60 minutes to prepare functional masterbatch. S2. Mixing: Initially mix all aggregates, the remaining cement and mineral admixtures with 65%-75% of the total water, then add the functional masterbatch prepared in step S1 and mix, and finally add the remaining mixing water and water-reducing agent for final mixing. S3. Curing: After the concrete mixture obtained in step S2 is formed, it is subjected to 14 days of initial standard wet curing and 2-3 rounds of intermediate dry-wet cycle curing.

7. The method for preparing crack-resistant high-performance concrete according to claim 6, characterized in that, The mechanical co-milling activation described in step S1 is carried out in a high-energy ball mill, with the ball mill speed set to 200-300 rpm.

8. The method for preparing crack-resistant high-performance concrete according to claim 6, characterized in that, The intermediate dry-wet cycle curing described in step S3 involves drying for 5-7 days in an environment with a relative humidity of 60±5%, followed by saturation in water for 2 days.

9. The method for preparing crack-resistant high-performance concrete according to claim 6, characterized in that, The specific operation of the initial stirring in step S2 is as follows: Dry mix all aggregates, the remaining cement and mineral admixtures for 120-150 seconds, then add 65%-75% of the total water and wet mix for 120-150 seconds.

10. The method for preparing crack-resistant high-performance concrete according to claim 6, characterized in that, The method further includes a step of preparing the sustained-release fluoride salt microparticles before step S1, wherein the step is as follows: Calcium fluoride microparticles are placed in a fluidized bed and coated with a coating solution prepared by polydimethylsiloxane. The coating is then dried and cured at a temperature of 60-80°C to form a polysiloxane hydrophobic film on the surface of the calcium fluoride microparticles.

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