Self-repairing lightweight aggregate concrete and preparation method thereof

Abstract

The invention discloses self-repairing lightweight aggregate concrete and a preparation method thereof. The self-repairing lightweight aggregate concrete comprises the following components in percentage by mass: 20-30% of cement; 40-50% of standard sand; 15 to 25 percent of packaging ceramsite; 8-12% of water; the encapsulated ceramsite comprises 30-35% of ceramsite, 30-35% of a repairing agent sodium silicate aqueous solution, 10-12% of an encapsulating material and 23-25% of a dispersing material. Performance tests show that the self-repairing lightweight aggregate concrete provided by the invention has very strong self-repairing capability.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a self-healing lightweight aggregate concrete and its preparation method. Background Technology

[0002] Lightweight aggregate concrete is widely used in high-rise buildings and bridge projects due to its lightweight, excellent thermal insulation, and seismic performance. However, its porous structure easily leads to problems such as low tensile strength and susceptibility to cracking. Traditional repair methods are mostly passive, costly, and have limited effectiveness. Among existing self-healing technologies, microencapsulation and microbial methods suffer from poor stability of repair agents and insufficient environmental adaptability. Therefore, developing a highly efficient and stable self-healing lightweight aggregate concrete material is of great significance. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a self-healing lightweight aggregate concrete and its preparation method. Based on sodium silicate-loaded ceramsite, this lightweight aggregate concrete self-healing material significantly improves the self-healing performance and durability of concrete by optimizing the ceramsite adsorption and encapsulation process.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] In a first aspect, the present invention provides a self-healing lightweight aggregate concrete, comprising the following components and mass percentages: cement 20-30%; standard sand 40-50%; encapsulated ceramsite 15-25%; water 8-12%; water-reducing agent 0.5-1%, wherein the encapsulated ceramsite comprises ceramsite 30-35%, a repair agent sodium silicate aqueous solution 30-35%, encapsulating material 10-12%, and dispersing material 23-25%.

[0006] Furthermore, the cement is any one or a combination of PI 52.5, PO 52.5 and PO 42.5.

[0007] Furthermore, the particle size of the ceramsite is 2.36–9.5 mm.

[0008] Furthermore, the concentration of the repair agent is 20-40%; the dispersing material is any one or a combination of PI52.5, PO52.5 and PO42.5.

[0009] Furthermore, the encapsulation material comprises epoxy resin E44 and curing agent polyamide resin.

[0010] Secondly, the present invention provides a method for preparing self-healing lightweight aggregate concrete, comprising the following steps:

[0011] (1) Pretreatment of ceramsite: After drying the ceramsite, the remediation agent is adsorbed under vacuum conditions to obtain ceramsite with saturated adsorption.

[0012] (2) Coating and encapsulation: The saturated adsorbed ceramic particles are immersed in the encapsulation material, stirred and then mixed and dispersed with the dispersion material, and solidified to form encapsulated ceramic particles;

[0013] (3) Concrete preparation: Cement, standard sand and encapsulated ceramsite are dry-mixed according to the proportion, water-reducing agent and water are added and stirred into shape, and then cast into specimens. After curing, self-healing lightweight aggregate concrete is obtained.

[0014] Further, in step (1), the adsorption parameters are vacuum degree -0.1 to -0.09 MPa, duration 30 to 40 min, and then stand at room temperature and normal pressure for 48 to 72 h.

[0015] Furthermore, in step (1), the pretreatment of ceramsite also includes filtering out excess repair agent and transferring the saturated ceramsite to a towel to rub dry until the surface is free of water.

[0016] Furthermore, in step (3), the curing conditions are as follows: in a standard curing room, the curing temperature is maintained within the range of 20±2℃, and the relative humidity needs to reach more than 95%.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention is rationally designed and has a simple preparation method, and has the following advantages:

[0019] (1) The self-healing lightweight aggregate concrete provided by this invention optimizes the formulation of lightweight aggregate (ceramsite) loaded with sodium silicate, uses ceramsite that has adsorbed the repair agent (sodium silicate solution), and pre-prepared into encapsulated ceramsite, which can release the repair agent to repair the concrete when there are cracks. The mechanism is as follows: When the self-healing lightweight aggregate concrete is not affected by the external environment, load or deformation, the encapsulated ceramsite is well preserved. When it is damaged by the external environment and the matrix cracks, the encapsulated ceramsite breaks and releases the internal sodium silicate solution during the crack propagation process. Then the sodium silicate solution dissolves in the water in the crack to form SiO3- and reacts with Ca(OH)2 in the cement matrix to generate CSH gel, which finally seals the crack. The reaction equation is Na2SiO3+Ca(OH)2=x(CaO·SiO2)H2O+Na2O. In addition to the reaction of sodium silicate with Ca(OH), the self-healing process at the crack also involves the formation of calcium carbonate. The main process involves CO in the environment dissolving in the moisture within the cracks to form CO32- ions. These ions react with Ca(OH)2 to form CaCO3 precipitate, as shown in the equation Ca(OH)2 + CO2 = CaCO3 + H2O. These precipitates fill and block the cracks. As the cracks are gradually filled by the healing products, the broken specimen achieves self-healing.

[0020] (2) This invention also investigated the key factors of adsorption treatment through experiments, and determined the optimal combination of adsorption and encapsulation. This formulation significantly improved the loading efficiency of the repair agent (adsorption rate increased by 111.7%) and the encapsulation stability, providing reliable technical support for the industrial application of lightweight aggregate (ceramsite) self-healing systems.

[0021] (2) A repair efficiency optimization strategy based on the control of ceramsite particle size was proposed.

[0022] Larger-sized ceramsite, with its greater internal porosity, can adsorb more sodium silicate solution and release more silicate ions, thus generating more healing products. Its crack closure rate is significantly better than that of the smaller-sized group. Conversely, when using smaller-sized ceramsite, these encapsulated particles form finer pores in the cement matrix, exhibiting a better filling effect. This optimizes the pore structure, effectively increasing the density between the encapsulated particles and the matrix, while reducing ion transport paths. Consequently, specimens with smaller-sized ceramsite show better repair performance in terms of ultrasonic wave velocity and strength compared to those with larger-sized particles. This finding provides a new approach to improving self-healing performance through lightweight aggregate particle size design, overcoming the limitation of traditional repair agent carriers that only focus on chemical compatibility.

[0023] (3) The dynamic response mechanism of sodium silicate remediation agent under different maintenance environments was revealed.

[0024] By comparing three curing environments—outdoor curing, curing chamber curing, and calcium hydroxide solution curing—the optimal repair effect was found in the calcium hydroxide environment. This study elucidated the synergistic repair mechanism of sodium silicate reacting with Ca(OH)₂ at cracks to form CSH gel and calcium carbonate, providing a theoretical basis for the design of environmentally adaptable self-healing concrete. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the specimen prepared in Example 1 of the present invention;

[0026] Figure 2 This is a diagram showing the distribution of encapsulated ceramic particles at the cross-section of the specimen prepared in Example 1 of the present invention;

[0027] Figure 3 This is a diagram of a specimen with cracks prepared in Example 1 of the present invention;

[0028] Figure 4 The crack closure rate of Comparative Example 1, Example 1, and Example 2 of the present invention after 28 days of curing in three different environments;

[0029] Figure 5 The strength restoration rate of Comparative Example 1, Example 1, and Example 2 after 28 days of curing in three different environments is shown.

[0030] Figure 6 The capillary water absorption coefficient reduction rate of Comparative Example 1, Example 1, and Example 2 of the present invention after 28 days of curing in three different environments;

[0031] Figure 7 The reduction rate of chloride ion diffusion coefficient after 28 days of curing in three different environments is compared with Comparative Example 1 and Examples 1 and 2 of the present invention. Detailed Implementation

[0032] Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations as sequential processes, many of these operations can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but may also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subroutine, etc.

[0033] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] This invention provides a method for preparing a bilayer composite membrane, comprising the following steps:

[0035] (1) Pretreatment of ceramsite: After drying the ceramsite, the remediation agent is adsorbed under vacuum conditions to obtain ceramsite with saturated adsorption.

[0036] (2) Coating and encapsulation: The saturated adsorbed ceramic particles are immersed in the encapsulation material, stirred and then mixed and dispersed with the dispersion material, and solidified to form encapsulated ceramic particles;

[0037] (3) Concrete preparation: Cement, standard sand and encapsulated ceramsite are dry-mixed according to the proportion, water-reducing agent and water are added and mixed into molds, and self-healing lightweight aggregate concrete is obtained after curing.

[0038] Example 1

[0039] (1) Pretreatment of ceramsite: Select ceramsite samples with a particle size range of 4.75-9.5mm, dry them at a constant temperature to a constant weight, weigh 100g, and place them in a vacuum dish; then add 100g of 30% sodium silicate solution to the vacuum dish, ensuring that the liquid surface completely covers the ceramsite, and seal all joints with Vaseline to ensure airtightness; then connect the vacuum dish to the water pump, and continuously evacuate the vacuum under -0.1MPa conditions until no bubbles are released, continue for 30min, and then turn off the water pump; after the negative pressure disappears, transfer the ceramsite and solution to another container, and let it stand at room temperature for 72h to ensure that the ceramsite reaches a saturated adsorption state; finally filter out the excess solution, transfer the saturated adsorbed ceramsite to a towel and rub it dry until the surface is water-free, weigh it to obtain 211.7g, and the adsorption rate (mass of adsorbed solution / mass of dried ceramsite) is 111.7%;

[0040] (2) Coating and encapsulation: Add the ceramsite treated in step (1) to a beaker, then add 20g of epoxy resin E44 and 12g of curing agent polyamide resin to the beaker, let stand for 1 minute to allow the resin to contact the ceramsite, and then stir to make the ceramsite evenly coated with resin; to avoid the ceramsite sticking together, add 70g of PI52.5 cement, mix and shake to disperse; finally, sieve out the excess cement, dry for 24 hours to obtain the coated and encapsulated ceramsite, and seal and store it.

[0041] (3) Concrete preparation: 500g of PI52.5 cement, 1000g of standard sand, 300g of encapsulated ceramsite, 175g of water, and 4g of polycarboxylate superplasticizer were mixed, poured, and molded to obtain specimens. After curing, self-healing lightweight aggregate concrete was obtained. Images of the specimens are shown below. Figure 1 As shown, after the specimen was cut, the cross-section was inspected, as follows: Figure 2 As shown, the concrete encapsulated ceramsite prepared in this embodiment is uniformly dispersed, avoiding the situation where unevenly dispersed encapsulated ceramsite leads to uneven stress on the test block and ceramsite agglomeration affects the performance of the test block.

[0042] The specimen size used in step (3) is 40mm×40mm×160mm, and the specific preparation process is as follows:

[0043] First, mix cement and standard sand evenly, then add encapsulated ceramsite and continue stirring until homogeneous. After the mixture is fully mixed, add an appropriate amount of water-reducing agent and continue stirring. Next, add a measured amount of water and stir until a uniform slurry is formed. Pour the prepared slurry into a 40mm×40mm×160mm triple mold in two layers: after pouring the first layer to half the height of the mold, precisely lay pre-cut wire mesh; after pouring the second layer, place it on a vibrating table and vibrate to ensure the specimen is compacted. Immediately after molding, the mold is transferred to a standard curing room for 1 day before demolding. To ensure smooth demolding, the inner surface of the mold needs to be pre-oiled. For each pour, three sets of specimens are prepared for both the experimental and control groups; the preparation of all subsequent specimens strictly follows this standard.

[0044] Example 2

[0045] (1) Pretreatment of ceramsite: Select ceramsite samples with a particle size range of 2.36-4.75mm, dry them at a constant temperature to a constant weight, weigh 100g, and place them in a vacuum dish; then add 110g of 30% sodium silicate solution to the vacuum dish, ensuring that the liquid surface completely covers the ceramsite, and seal all joints with Vaseline to ensure airtightness; then connect the vacuum dish to the water pump, and continuously evacuate the vacuum at -0.098MPa until no bubbles are released, for 30min, and then turn off the water pump; after the negative pressure disappears, transfer the ceramsite and solution to another container, and let it stand at room temperature for 72h to ensure that the ceramsite reaches a saturated adsorption state; finally filter out the excess solution, transfer the saturated adsorbed ceramsite to a towel and rub it dry until the surface is water-free, weigh it to obtain 221.9g, and the adsorption rate (mass of adsorbed solution / mass of dried ceramsite) is 121.9%;

[0046] (2) Coating and encapsulation: Add the ceramsite treated in step (1) to a beaker, then add 22g of epoxy resin E442 and 11g of curing agent polyamide resin to the beaker, let stand for 1 minute to allow the resin to contact the ceramsite, and then stir to make the ceramsite evenly coated with resin; to avoid the ceramsite sticking together, add 70g of PO52.5 cement, mix and shake to disperse; finally, sieve out the excess cement, dry for 24 hours to obtain the coated and encapsulated ceramsite, and seal and store it.

[0047] (3) Concrete preparation: Mix 500g of PO52.5 cement, 1000g of standard sand, 300g of encapsulated ceramsite, 175g of water, and 4g of polycarboxylate superplasticizer according to the proportion, and pour the mixture into a specimen according to the method in Example 1. After curing, self-healing lightweight aggregate concrete is obtained.

[0048] Comparative Example 1

[0049] (1) Pretreatment of ceramsite: Select ceramsite samples with a particle size range of 4.75-9.5mm, dry them at a constant temperature to a constant weight, weigh 100g, and place them in a vacuum dish; then add 110g of deionized water to the vacuum dish to ensure that the liquid surface completely covers the ceramsite, and seal all interfaces with Vaseline to ensure airtightness; then connect the vacuum dish to the water pump, and continuously evacuate the vacuum at -0.098MPa until no bubbles are released, for 30min, and then turn off the water pump; after the negative pressure disappears, transfer the ceramsite and solution to another container, and let it stand at room temperature for 72h to ensure that the ceramsite reaches a saturated adsorption state; finally filter out the excess solution, transfer the saturated adsorbed ceramsite to a towel and rub it dry until the surface is water-free, weigh it to obtain 205.8g, and the adsorption rate (mass of adsorbed solution / mass of dried ceramsite) is 105.8%;

[0050] (2) Coating and encapsulation: Add the ceramsite treated in step (1) to a beaker, then add 22g of epoxy resin E442 and 11g of curing agent polyamide resin to the beaker, let stand for 1 minute to allow the resin to contact the ceramsite, and then stir to make the ceramsite evenly coated with resin; to avoid the ceramsite sticking together, add 70g of PO52.5 cement, mix and shake to disperse; finally, sieve out the excess cement, dry for 24 hours to obtain the coated and encapsulated ceramsite, and seal and store it.

[0051] (3) Concrete preparation: Mix 500g of PO52.5 cement, 1000g of standard sand, 300g of encapsulated ceramsite, 175g of water, and 4g of polycarboxylate superplasticizer according to the proportion, and pour the mixture into a specimen according to the method in Example 1. After curing, self-healing lightweight aggregate concrete is obtained.

[0052] Table 1 shows the mix proportions of cement-based materials for Comparative Examples 1, 1, and 2.

[0053] Table 1. Mix proportions of cement-based materials

[0054]

[0055] Performance testing:

[0056] To verify the performance of the self-healing material described in this invention, a series of tests were conducted on the specimens prepared in Comparative Example 1, Example 1, and Example 2, including indicators such as crack repair effect, mechanical property repair, and durability.

[0057] 1. Crack Repair Effectiveness Test

[0058] Test method: Cracks were pre-induced using the three-point bending method, wherein the cracked specimen prepared in Example 1 is as follows. Figure 3 As shown, the ZBL-F130 crack observation instrument was used to measure the change in crack width on the specimen surface and to calculate the crack closure rate.

[0059] Test conditions: The specimens were cured for 28 days in outdoor environment, standard curing room (20±2℃, RH≥95%), and saturated calcium hydroxide solution (other conditions are the same as standard curing room).

[0060] Test Results: Table 2 shows the crack closure rates of Comparative Example 1, Example 1, and Example 2 under different curing conditions.

[0061] Table 2 Crack Closure Rate under Different Maintenance Environments

[0062] Specimen Environmental maintenance Crack closure rate (%) Comparative Example 1 outdoor 9.72 Comparative Example 1 Cultivation Room 21.73 Comparative Example 1 calcium hydroxide 26.48 Example 1 outdoor 15.07 Example 1 Cultivation Room 28.61 Example 1 calcium hydroxide 42.78 Example 2 outdoor 15.05 Example 2 Cultivation Room 26.20 Example 2 calcium hydroxide 29.21

[0063] in conclusion:

[0064] The repair effect was best under calcium hydroxide curing conditions, with the highest crack closure rate (42.78% in Example 1). Large-diameter ceramsite (4.75-9.5mm) performed better in crack width repair, while small-diameter ceramsite (2.36-4.75mm) was more advantageous in strength repair. The data in Table 2 are plotted as a bar chart, as shown below. Figure 4 As shown.

[0065] 2. Mechanical property repair test

[0066] Test method: The initial strength (f1) and the strength after repair (f2) of the specimen were determined by compressive strength test.

[0067] The formula for calculating the strength repair rate is:

[0068] Test results: Table 3 shows the strength restoration rate of Comparative Example 1, Example 1 and Example 2 under different maintenance environments.

[0069] Table 3 Strength restoration rate under different maintenance conditions

[0070]

[0071]

[0072] in conclusion:

[0073] After 28 days, the strength repair rate of specimens in both Example 1 and Example 2 exceeded 30%, indicating that the self-healing material can effectively repair mechanical properties. The strength repair rate of small-diameter ceramsite (Example 2) was even higher, indicating that it is more conducive to the repair of mechanical properties. The data in Table 3 are plotted as a bar chart, as shown below. Figure 5As shown, calcium hydroxide provides the best curing and repair effect. When specimens are cured in calcium hydroxide, the stable alkaline environment is extremely beneficial for the hardening process after the initial setting of concrete, ensuring sufficient hydration reaction and thus improving the strength and durability of the concrete. Secondly, this environment accelerates the hydration reaction of cement, promoting the formation of products such as hydrated calcium silicate, making the concrete structure denser and stronger.

[0074] 3. Durability Testing

[0075] (1) Capillary water absorption rate test

[0076] Test Method: The capillary water absorption coefficient of the specimens under different curing conditions was measured according to ASTM C1585-13. Test Results: Table 4 shows the reduction rate of capillary water absorption coefficient of Comparative Example 1, Example 1, and Example 2 after 28 days of curing under different conditions.

[0077] Table 4. Reduction rate of capillary water absorption coefficient under different maintenance conditions

[0078]

[0079]

[0080] in conclusion:

[0081] The self-healing material significantly reduces capillary water absorption, with large-particle ceramsite (Example 1) showing an even higher reduction rate (35.2%). The data in Table 4 are plotted as a bar chart, as shown below. Figure 6 As shown.

[0082] (2) Chloride ion permeability test

[0083] Test method: The chloride ion diffusion coefficient was determined by the RCM method (GB / T 50082-2009).

[0084] Test results: Table 5 shows the reduction rate of chloride ion diffusion coefficient between Comparative Example 1 and Examples 1 and 2 after 28 days of curing under different curing conditions.

[0085] Table 5. Reduction rate of chloride ion diffusion coefficient under different maintenance conditions

[0086]

[0087]

[0088] in conclusion:

[0089] Small-diameter ceramsite (Example 2) exhibits stronger resistance to chloride ion penetration, with a chloride ion diffusion coefficient reduced by 29.69%, which is superior to large-diameter ceramsite (24.32%). The data in Table 5 are plotted as a bar chart, as shown below. Figure 7 As shown.

[0090] Overall Conclusion

[0091] 1. Under calcium hydroxide curing conditions, the self-healing effect is the best (crack closure rate 42.78%, strength repair rate 65.79%).

[0092] 2. Large-diameter ceramsite (4.75-9.5mm) is more suitable for repairing crack width, while small-diameter ceramsite (2.36-4.75mm) is more conducive to mechanical property repair and impermeability improvement.

[0093] 3. The material of this invention can significantly improve the self-healing ability, durability and long-term service performance of concrete, and is suitable for engineering fields such as high-rise buildings and bridges.

[0094] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, based on the guidance provided in this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A self-healing lightweight aggregate concrete, characterized in that, The product comprises the following components and their mass percentages: cement 20-30%; standard sand 40-50%; encapsulating ceramsite 15-25%; water 8-12%; and water-reducing agent 0.5-1%. The encapsulating ceramsite includes ceramsite 30-35%, sodium silicate aqueous solution as a repair agent 30-35%, encapsulating material 10-12%, and dispersing material 23-25%.

2. The self-healing lightweight aggregate concrete according to claim 1, characterized in that, The cement is any one or a combination of PI 52.5, PO 52.5 and PO 42.

5.

3. The self-healing lightweight aggregate concrete according to claim 1, characterized in that, The particle size of the ceramsite is 2.36–9.5 mm.

4. The self-healing lightweight aggregate concrete according to claim 1, characterized in that, The sodium silicate aqueous solution has a concentration of 20-40%; the dispersing material is any one or a combination of PI52.5, PO52.5 and PO42.

5.

5. The self-healing lightweight aggregate concrete according to claim 1, characterized in that, The encapsulation material comprises epoxy resin E44 and curing agent polyamide resin, with a mass ratio of 1:1 to 2.

6. A method for preparing self-healing lightweight aggregate concrete according to claims 1 to 5, comprising the following steps: (1) Pretreatment of ceramsite: After drying the ceramsite, the remediation agent is adsorbed under vacuum conditions to obtain ceramsite with saturated adsorption. (2) Coating and encapsulation: The saturated adsorbed ceramic particles are immersed in the encapsulation material, stirred and then mixed and dispersed with the dispersion material, and solidified to form encapsulated ceramic particles; (3) Concrete preparation: Cement, standard sand and encapsulated ceramsite are dry-mixed according to the proportion, water-reducing agent and water are added and stirred into shape, and then cast into specimens. After curing, self-healing lightweight aggregate concrete is obtained.

7. The method for preparing self-repairing lightweight aggregate concrete according to claim 6, characterized in that, In step (1), the adsorption parameters are vacuum degree -0.1 to -0.09 MPa, duration 30 to 40 min, and then stand at room temperature and normal pressure for 48 to 72 h.

8. The method for preparing self-repairing lightweight aggregate concrete according to claim 6, characterized in that, In step (1), the pretreatment of ceramsite also includes filtering out excess repair agent and transferring the saturated ceramsite to a towel to rub dry until the surface is free of water.

9. The method for preparing self-repairing lightweight aggregate concrete according to claim 6, characterized in that, In step (3), the curing conditions are as follows: in a standard curing room, the curing temperature is maintained within the range of 20±2℃, and the relative humidity needs to reach more than 95%.

Images