Alkali-corrosion-resistant self-healing high-ductility concrete and preparation method thereof

Abstract

The invention discloses alkali-corrosion-resistant self-healing high-ductility concrete, which is prepared from the following components in parts by weight: 750 to 800 parts of cement, 100 to 150 parts of silica fume, 500 to 550 parts of coal ash, 550 to 600 parts of fine aggregate, 250 to 300 parts of deionized water and 20 to 30 parts of water reducing agent, and the composite fiber is prepared from the following components in parts by weight: 50 to 800 parts of cement, 100 to 150 parts of silica fume, 500 to 550 parts of coal ash, 550 to 600 parts of fine aggregate, 250 to 300 parts of deionized water and 20 to 30 parts of water reducing agent. The volume mixing amount of the composite fiber is 0.3-2.5% of that of the concrete; the preparation method of the composite fiber specifically comprises the following steps: by taking MXene modified polyethylene fiber as a matrix, implanting a thermal response type microcapsule into the core part of the MXene modified polyethylene fiber, and carrying out fiber surface treatment, so as to prepare the composite fiber.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and in particular relates to a highly ductile concrete that is resistant to alkali corrosion and self-healing, and its preparation method. Background Technology

[0002] Concrete structures serving in harsh alkaline environments face the significant challenge of synergistic damage from alkali corrosion and cracking. While traditional high-ductility concrete (HDC) significantly improves ductility and crack control through fiber toughening, its core component—synthetic fibers—is prone to surface erosion and performance degradation in strongly alkaline media, weakening the toughening effect. Simultaneously, conventional self-healing mechanisms are often inefficient or produce unstable products in continuous alkaline environments, failing to effectively repair cracks and block erosion pathways. Existing technologies such as microbial remediation or pre-embedded microcapsules present challenges. The former struggles to survive in strongly alkaline environments, while the latter often faces bottlenecks such as a weak interface between the capsule and the matrix, uncontrollable release of the repair agent, and insufficient alkali resistance and compatibility of the capsule itself with the matrix, rendering the self-healing function unreliable under complex service conditions. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology. This invention provides a high-ductility concrete that is resistant to alkali corrosion and self-healing, and its preparation method. Through integrated fiber design, this invention organically combines MXene reinforcement, intelligent thermal response repair and nano-level alkali-resistant protection, and simultaneously solves the three core problems of high ductility, efficient self-healing and long-term alkali corrosion resistance. It provides an innovative solution for concrete structures in extreme alkali corrosion environments that combines high toughness, self-healing ability and ultra-long durability.

[0004] To achieve the above-mentioned objectives, the technical solution provided by this invention patent is as follows:

[0005] A self-healing, alkali-resistant, high-ductility concrete comprising cement, silica fume, fly ash, fine aggregate, deionized water, water-reducing agent, and composite fiber, wherein the composition by weight comprises the following components: 750-800 parts cement, 100-150 parts silica fume, 500-550 parts fly ash, 550-600 parts fine aggregate, 250-300 parts deionized water, and 20-30 parts water-reducing agent, wherein the volumetric content of the composite fiber is 0.3-2.5% of the concrete.

[0006] The composite fiber is prepared by using MXene-modified polyethylene fiber as a matrix, implanting thermally responsive microcapsules into the core of the MXene-modified polyethylene fiber, and then performing fiber surface treatment to prepare the composite fiber.

[0007] Furthermore, the fine aggregate is quartz sand fine aggregate with a fineness modulus of 1.8-2.5 and a bulk density of 1600-1800 kg / m³.3 The SiO2 content in the fine aggregate is ≥98%.

[0008] Furthermore, the cement is P·Ⅱ52.5 silicate cement.

[0009] Furthermore, the silica fume contains ≥92% SiO2 and has a specific surface area ≥15000 m². 2 / kg.

[0010] Furthermore, the fly ash is Grade I fly ash, with a loss on ignition ≤5% and a fly ash residue fineness of ≤12% on a 45μm sieve.

[0011] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent.

[0012] Furthermore, the preparation of the MXene-modified polyethylene fiber is specifically as follows: MXene is synthesized by etching with a Ti-LiF / HCl solution, the polyethylene fiber is surface-treated with ozone water to increase interfacial adhesion, and the polyethylene fiber is prepared by immersing it in an MXene dispersion under an atmosphere filled with N2.

[0013] Furthermore, the surface treatment of the MXene-modified polyethylene fiber specifically involves: constructing a protective layer on the surface of the MXene-modified polyethylene fiber. The protective layer on the surface of the MXene-modified polyethylene fiber consists of an interfacial silane coupling layer and a SiO2 nano-encapsulation layer, from the outside to the inside. The thickness of the SiO2 nano-encapsulation layer is 1-10 nm. After the protective layer on the surface of the MXene-modified polyethylene fiber is constructed, the MXene-modified polyethylene fiber is immersed in an environment with pH ≥ 13 to ensure that the conductivity attenuation rate of the MXene-modified polyethylene fiber is ≤ 15%.

[0014] Furthermore, the wall material of the thermally responsive microcapsule is polyurethane, the core material of the thermally responsive microcapsule is a mixture of epoxy resin and latent curing agent, and the rupture temperature of the thermally responsive microcapsule is 50-70℃.

[0015] A method for preparing the alkali-resistant, self-healing, high-ductility concrete as described above, the method specifically includes the following steps:

[0016] S1. Weigh each raw material according to the weight parts, mix cement, silica fume and fly ash evenly, then add composite fiber and mix evenly to obtain dry powder.

[0017] S2, mix the water-reducing agent and water evenly to obtain the liquid material;

[0018] S3. Mix the dry powder and liquid materials evenly to obtain a slurry. Shape and cure the slurry to obtain high-ductility concrete.

[0019] Based on the above technical solution, the alkali-resistant, self-healing, high-ductility concrete and its preparation method of this invention have achieved the following technical effects through practical application:

[0020] 1. The present invention provides a high ductility concrete that is resistant to alkali corrosion and self-healing. This high ductility concrete is based on MXene-modified PE fiber core implanted with thermally responsive microcapsules and constructed with an interfacial silane coupling layer and a surface SiO2 nano-encapsulation layer. Through multi-level structural innovation, it achieves a synergistic leap in performance and simultaneously breaks through the three key performance bottlenecks of high ductility, efficient self-healing and long-term alkali corrosion resistance.

[0021] 2. This invention provides a self-healing, alkali-resistant, high-ductility concrete using MXene (such as Ti3C2T). x The modification of PE fibers by nanosheets significantly improves the fiber's mechanical strength, modulus, and interfacial bonding with the cement matrix. This not only ensures that the material can effectively achieve strain hardening and multi-crack behavior under stress, achieving an ultimate tensile strain far exceeding that of ordinary concrete and excellent crack control, but also significantly enhances the chemical stability of the fiber itself in strongly alkaline environments, resisting OH... - The strength loss and embrittlement caused by erosion ensure the durability of the toughening effect. Detailed Implementation

[0022] To make the objectives, technical solutions, and effects of this invention clearer, specific examples are provided below. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this invention.

[0023] A self-healing, alkali-resistant, high-ductility concrete comprising cement, silica fume, fly ash, fine aggregate, deionized water, water-reducing agent, and composite fiber, wherein the composition by weight comprises the following components: 750-800 parts cement, 100-150 parts silica fume, 500-550 parts fly ash, 550-600 parts fine aggregate, 250-300 parts deionized water, and 20-30 parts water-reducing agent, wherein the volumetric content of the composite fiber is 0.3-2.5% of the concrete.

[0024] The composite fiber is prepared by using MXene-modified polyethylene fiber as a matrix, implanting thermally responsive microcapsules into the core of the MXene-modified polyethylene fiber, and then performing fiber surface treatment to prepare the composite fiber.

[0025] First, MXene (such as Ti3C2T) xThe modification of PE fibers by nanosheets significantly improves the fiber's mechanical strength, modulus, and interfacial bonding with the cement matrix. This not only ensures that the material can effectively achieve strain hardening and multi-crack behavior under stress, achieving ultimate tensile strain far exceeding that of ordinary concrete and excellent crack control capabilities, but also significantly enhances the chemical stability of the fiber body in a strongly alkaline environment, resisting strength loss and embrittlement caused by OH- erosion, and ensuring the durability of the toughening effect.

[0026] Secondly, the thermoresponsive microcapsules implanted in the core endow the material with intelligent self-healing capabilities. Due to the excellent conductivity of MXene, the microcapsule rupture temperature matches the MXene heating temperature (50±5℃), and the repair rate is ≥90% when the crack width is ≤2mm. When a crack occurs, causing local stress concentration or temperature rise, the microcapsule wall material melts and ruptures due to heat, enabling precise and controllable release of the repair agent to the crack tip. It then rapidly solidifies to form a dense sealing layer, effectively blocking the intrusion of corrosive media and restoring structural integrity. This overcomes the shortcomings of traditional self-healing technologies, which rely on insufficient moisture or alkalinity and have unreliable triggering mechanisms.

[0027] Meanwhile, the silane coupling layer constructed on the fiber surface and the dense SiO2 nano-encapsulation layer form a dual protective barrier, creating an organic-inorganic hybrid protective layer. After immersion in a simulated pore solution with pH ≥ 13.5 for 30 days, the conductivity retention rate is ≥ 85%. The silane coupling agent significantly enhances the bond strength and stress transfer efficiency of the fiber-cement matrix interface through chemical bonding, reducing the risk of interfacial debonding; while the SiO2 nano-layer acts as a highly corrosion-resistant physical barrier, effectively blocking external alkaline ions (such as Na+). + K + The penetration and erosion of OH- into the fiber body and core microcapsules significantly delays fiber performance degradation and microcapsule functional failure, substantially extending the service life of the entire fiber reinforcement phase under harsh alkaline corrosion environments. Ultimately, these innovative components work synergistically, enabling the concrete to not only possess excellent deformation capacity and crack resistance in extremely alkaline corrosive environments, but also to actively and rapidly repair damage and maintain long-term stability of its protective and repair functions. This provides a revolutionary solution for critical concrete structures in harsh environments such as chemical plants and coastal saline-alkali areas, offering high toughness, self-healing intelligence, and ultra-long durability.

[0028] The fine aggregate is quartz sand, with a fineness modulus of 1.8-2.5 and a bulk density of 1600-1800 kg / m³. 3 The SiO2 content in the fine aggregate is ≥98%.

[0029] The cement is P·Ⅱ52.5 silicate cement.

[0030] The silica fume contains ≥92% SiO2 and has a specific surface area ≥15000 m². 2 / kg.

[0031] The fly ash is Grade I fly ash, with a loss on ignition ≤5% and a fineness of ≤12% on a 45μm sieve.

[0032] The water-reducing agent is a polycarboxylate water-reducing agent.

[0033] The preparation of MXene-modified polyethylene fiber is as follows: MXene is synthesized by etching with Ti in LiF / HCl solution, polyethylene fiber is surface treated with ozone water to increase interfacial adhesion, and polyethylene fiber is prepared by immersing in MXene dispersion in an atmosphere filled with N2.

[0034] MXene is typically synthesized by selective etching of a Ti-based precursor (such as Ti3AlC2) in an HCl solution (hydrochloric acid solution) containing LiF (lithium fluoride). After etching, the reaction product is diluted with deionized water to terminate the reaction. Then, residual impurities such as LiF, HCl, and AlCl3 are removed by repeated centrifugation and washing until the pH of the supernatant is close to neutral. The washed MXene precipitate can be directly dispersed in deionized water or an organic solvent to obtain an MXene dispersion.

[0035] The surface treatment of the MXene-modified polyethylene fiber specifically involves: constructing a protective layer on the surface of the MXene-modified polyethylene fiber. The protective layer on the surface of the MXene-modified polyethylene fiber consists of an interfacial silane coupling layer and a SiO2 nano-encapsulation layer, from the outside to the inside. The thickness of the SiO2 nano-encapsulation layer is 1-10 nm. After the protective layer on the surface of the MXene-modified polyethylene fiber is constructed, the MXene-modified polyethylene fiber is immersed in an environment with pH ≥ 13 to ensure that the conductivity attenuation rate of the MXene-modified polyethylene fiber is ≤ 15%.

[0036] The formation of the interface layer on the surface of MXene-modified polyethylene fibers is achieved through a two-step process: First, a chemically bonded interface layer is formed on the fiber surface using a silane coupling agent. A 1-3 wt% silane-ethanol solution is reacted with the fiber at 60°C for 2-4 hours, allowing the silane to covalently bond with the functional groups on the fiber surface. After ethanol cleaning and drying at 80°C, a stable interface is formed. Subsequently, a SiO2 encapsulation layer is deposited using the sol-gel method. Tetraethyl orthosilicate and ethanol are mixed at a 1:10 ratio, and ammonia is added as a catalyst to adjust the pH to 9-10, hydrolyzing to form a SiO2 sol. The fiber is immersed in the sol for 10-20 minutes to form a dense SiO2 nanolayer on the fiber surface. This is followed by pre-drying at 60°C and curing at 120°C for 2 hours to complete the preparation. The entire process must be carried out under an inert atmosphere to prevent the oxidation of MXene.

[0037] The wall material of the thermally responsive microcapsule is polyurethane, the core material of the thermally responsive microcapsule is a mixture of epoxy resin and latent curing agent, and the rupture temperature of the thermally responsive microcapsule is 50-70℃.

[0038] A method for preparing the alkali-resistant, self-healing, high-ductility concrete as described above, the method specifically includes the following steps:

[0039] S1. Weigh each raw material according to the weight parts, mix cement, silica fume and fly ash evenly, then add composite fiber and mix evenly to obtain dry powder.

[0040] S2, mix the water-reducing agent and water evenly to obtain the liquid material;

[0041] S3. Mix the dry powder and liquid materials evenly to obtain a slurry. Shape and cure the slurry to obtain high-ductility concrete.

[0042] Since the composite fiber in this invention is made from MXene-modified polyethylene (PE) fiber as the matrix, and MXene material has good conductivity, hydrophilicity, mechanical adjustability and high photothermal conversion efficiency, the concrete prepared by this invention can be applied to intelligent sensing and self-sensing in civil engineering to form a synergistic effect of concrete self-sensing and self-healing. It can also be used in electromagnetic absorption, temperature regulation and heating (de-icing and snow removal) and other fields, with broad application prospects.

[0043] MXene (such as Ti3C2T) xThe modification of PE fibers with nanosheets significantly enhances the mechanical strength and matrix anchoring force of the fibers through their high specific surface area and interfacial interactions. Simultaneously, the implantation of thermoresponsive microcapsules into the fiber core introduces an environmentally friendly active repair mechanism: due to the excellent electrical conductivity of MXene-modified polyethylene (PE) fibers, when cracks occur leading to localized stress concentration or when electricity generates heat, the microcapsules melt and rupture upon heating, precisely releasing the internal repair agent to the crack for rapid sealing. Because MXene materials are prone to oxidation failure under alkaline conditions, to further ensure the long-term stability of the fiber-concrete interface in alkaline corrosion environments and the directional triggering efficiency of the microcapsules, an interfacial silane coupling layer and a surface SiO2 nano-encapsulation layer are constructed on the surface of the MXene-modified PE fibers. The silane coupling agent enhances the chemical bonding and stress transfer between the fiber and the cement matrix; while the dense SiO2 nano-layer acts as a robust physical barrier, greatly delaying the penetration and erosion of alkaline ions into the fiber body and the core microcapsules, ensuring the durability of the fiber toughening effect and the microcapsule function under alkaline corrosion environments.

[0044] Example 1

[0045] In this embodiment, the composition is 780 parts cement, 141 parts silica fume, 495 parts fly ash, 567 parts fine aggregate, 255 parts deionized water, 21.2 parts water-reducing agent, and 1.5% MXene-modified polyethylene (PE) fiber. The MXene-modified polyethylene (PE) fiber is prepared by etching MXene with a Ti-LiF / HCl solution, surface treating the polyethylene (PE) fiber with ozone water to increase interfacial adhesion, and immersing the polyethylene (PE) fiber in an MXene dispersion under a N2 atmosphere.

[0046] The concrete preparation method in this embodiment is as follows:

[0047] 1) Weigh each raw material according to its weight.

[0048] 2) Mix cement, silica fume, and fly ash evenly, then add composite fibers and mix evenly to obtain a dry powder.

[0049] 3) Mix the water-reducing agent and water evenly to obtain a liquid mixture.

[0050] 4) Mix the dry powder and liquid materials evenly to obtain a slurry.

[0051] 5) The slurry is then molded and cured to obtain the final product.

[0052] The flowability of the MXene-modified polyethylene (PE) fiber high-ductility concrete was tested according to JGJ / T70-2009, the compressive strength according to GB / T50081-2019, and the tensile strength and tensile strain according to DBJ61 / T 112-2016. The results showed that the flowability of the MXene-modified polyethylene (PE) fiber high-ductility concrete was 240 mm, the 28-day compressive strength was 118.72 MPa, the 28-day tensile strength was 7.82 MPa, the tensile strain was 9.95%, the average crack width was 1.86 mm, and the average crack width after self-healing was 1.82 mm.

[0053] Comparative Example 1

[0054] In Comparative Example 2 of the alkali-resistant, self-healing, high-ductility concrete used in this invention:

[0055] The proportions of each part in this comparative example are different from those in Example 1. In this example, there are 780 parts of cement, 141 parts of silica fume, 495 parts of fly ash, 567 parts of fine aggregate, 255 parts of deionized water, 21.2 parts of water-reducing agent, and 1.5% of polyethylene (PE) fiber. The polyethylene (PE) fiber is conventional polyethylene (PE) fiber.

[0056] The flowability of the high-ductility concrete with polyethylene (PE) fibers was tested according to JGJ / T70-2009, the compressive strength according to GB / T50081-2019, and the tensile strength and tensile strain according to DBJ61 / T112-2016. The results showed that the flowability of the PE fiber-reinforced high-ductility concrete was 205 mm, the 28-day compressive strength was 101.37 MPa, the 28-day tensile strength was 6.57 MPa, the tensile strain was 5.23%, the average crack width was 3.81 mm, and the average crack width after self-healing was 3.80 mm.

[0057] The concrete preparation method in this embodiment is as follows:

[0058] 1) Weigh each raw material according to its weight.

[0059] 2) Mix cement, silica fume, and fly ash evenly, then add polyethylene fibers and mix evenly to obtain a dry powder.

[0060] 3) Mix the water-reducing agent and water evenly to obtain a liquid mixture.

[0061] 4) Mix the dry powder and liquid materials evenly to obtain a slurry.

[0062] 5) The slurry is then molded and cured to obtain the final product.

[0063] Comparative Examples 1 and 2 show that, compared to MXene-modified polyethylene (PE) fiber, the compressive strength of MXene-modified polyethylene (PE) fiber increased by 17.12%, the tensile strength by 19.02%, and the tensile strain by 90.25%, while the average crack width decreased by 1.95 mm. The healing effect after crack formation was almost nonexistent in both examples. Compared to Examples 1 and 2, the composite fiber showed only slight changes in compressive strength, tensile strength, tensile strain, and average crack width compared to MXene-modified polyethylene (PE) fiber, indicating that crack self-healing was not an issue. Compared to Examples 2 and 3, the improvement is 90%, indicating that the composite fiber formed by implanting thermally responsive microcapsules into the core of MXene-modified polyethylene (PE) fibers and undergoing a special surface treatment process does not affect the mechanical properties of concrete, while ensuring excellent self-healing performance. Therefore, this integrated fiber design organically combines MXene reinforcement, intelligent thermally responsive repair, and nano-level alkali-resistant protection, which can solve the three core problems of high ductility, efficient self-healing, and long-term alkali corrosion resistance. It provides an innovative solution for concrete structures in extreme alkali corrosion environments that combines high toughness, self-healing ability, and ultra-long durability.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A self-healing, alkali-resistant, high-ductility concrete, characterized in that, The concrete comprises cement, silica fume, fly ash, fine aggregate, deionized water, water-reducing agent, and composite fiber. Its composition, by weight, includes the following components: 750-800 parts cement, 100-150 parts silica fume, 500-550 parts fly ash, 550-600 parts fine aggregate, 250-300 parts deionized water, and 20-30 parts water-reducing agent. The volumetric content of the composite fiber is 0.3-2.5% of the concrete. The composite fiber is prepared by using MXene-modified polyethylene fiber as a matrix, implanting thermally responsive microcapsules into the core of the MXene-modified polyethylene fiber, and then performing fiber surface treatment to prepare the composite fiber.

2. The alkali-resistant, self-healing, high-ductility concrete according to claim 1, characterized in that, The fine aggregate is quartz sand, with a fineness modulus of 1.8-2.5 and a bulk density of 1600-1800 kg / m³. 3 The SiO2 content in the fine aggregate is ≥98%.

3. The alkali-resistant, self-healing, high-ductility concrete according to claim 3, is characterized in that, The cement is P·Ⅱ52.5 silicate cement.

4. The alkali-resistant, self-healing, high-ductility concrete according to claim 1, characterized in that, The silica fume contains ≥92% SiO2 and has a specific surface area ≥15000 m². 2 / kg.

5. The alkali-resistant, self-healing, high-ductility concrete according to claim 1, characterized in that, The fly ash is Grade I fly ash, with a loss on ignition ≤5% and a fineness of ≤12% on a 45μm sieve.

6. The alkali-resistant, self-healing, high-ductility concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

7. The alkali-resistant, self-healing, high-ductility concrete according to claim 1, characterized in that, The preparation of MXene-modified polyethylene fiber is as follows: MXene is synthesized by etching with Ti in LiF / HCl solution, polyethylene fiber is surface treated with ozone water to increase interfacial adhesion, and polyethylene fiber is prepared by immersing in MXene dispersion in an atmosphere filled with N2.

8. The alkali-resistant, self-healing, high-ductility concrete according to claim 7, characterized in that, The surface treatment of the MXene-modified polyethylene fiber specifically involves: constructing a protective layer on the surface of the MXene-modified polyethylene fiber. The protective layer on the surface of the MXene-modified polyethylene fiber consists of an interfacial silane coupling layer and a SiO2 nano-encapsulation layer from the outside to the inside. The thickness of the SiO2 nano-encapsulation layer is 1-10 nm. After the protective layer on the surface of the MXene-modified polyethylene fiber is constructed, the MXene-modified polyethylene fiber is immersed in an environment with pH ≥ 13 to make the conductivity attenuation rate of the MXene-modified polyethylene fiber ≤ 15%.

9. The alkali-resistant, self-healing, high-ductility concrete according to claim 1, characterized in that, The wall material of the thermally responsive microcapsule is polyurethane, the core material of the thermally responsive microcapsule is a mixture of epoxy resin and latent curing agent, and the rupture temperature of the thermally responsive microcapsule is 50-70℃.

10. A method for preparing alkali-resistant, self-healing, high-ductility concrete as described in any one of claims 1-9, characterized in that, The preparation method specifically includes the following steps: S1. Weigh each raw material according to the weight parts, mix cement, silica fume and fly ash evenly, then add composite fiber and mix evenly to obtain dry powder. S2, mix the water-reducing agent and water evenly to obtain the liquid material; S3. Mix the dry powder and liquid materials evenly to obtain a slurry. Shape and cure the slurry to obtain high-ductility concrete.