Multifunctional seawater and sea sand ecc materials based on ion reconstitution and endogenous and exogenous synergistic regulation and preparation method thereof

Abstract

The application relates to a multifunctional seawater and sea sand ECC material based on ion reformation and endogenous and exogenous synergistic regulation and a preparation method thereof, and belongs to the technical field of building materials. The base body comprises cement 0.6-0.8 parts by mass, silica ash 0.2-0.4 parts by mass, quartz powder 0-0.2 parts by mass, expanding agent 0.03-0.09 parts by mass, seawater 0.15-0.23 parts by mass, sea sand 0.31-0.46 parts by mass, polycarboxylic acid water reducing agent 0.02-0.03 parts by mass and silane coupling agent 0.001-0.002 parts by mass, and the content of polyethylene fiber is 2%-2.5% of the volume of the base body. The shrinkage performance is regulated by endogenous and exogenous expansion factors, the endogenous expansion factor refers to Cl ‑ and SO4 2‑ in the seawater and sea sand participate in the hydration reaction to not only produce AFt and Friedel's salt with expansibility but also realize ion solidification, the exogenous expansion factor refers to the fact that the externally added expanding agent participates in the hydration reaction to produce expansible substances, and the strength, ductility and shrinkage are high.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a multifunctional seawater sand ECC material and its preparation method based on ion reconstruction and synergistic regulation of internal and external sources. Background Technology

[0002] In recent years, marine infrastructure construction has developed rapidly, including major infrastructure projects such as submarine tunnels, offshore platforms, and islands and reefs. Currently, there are many types of materials used in marine infrastructure, among which concrete has become the most widely used material due to its abundant raw material sources, simple preparation process, low production cost, and stable performance.

[0003] Freshwater and river sand are currently the most widely used raw materials for concrete. However, the overuse of freshwater and river sand resources is detrimental to ecological protection. Therefore, for marine infrastructure construction, it is necessary to use marine materials (seawater and sea sand) with wider availability as raw materials to prepare concrete. With the development of marine engineering infrastructure, compared with traditional concrete materials, the design of next-generation marine concrete materials has put forward requirements for ultra-high strength, ultra-high toughness, long service life, and multi-functionality. Since high-ductility cement-based composite materials can not only overcome the problems of low toughness and easy cracking of traditional concrete, but also have excellent crack width control capabilities, it is necessary to prepare ultra-high strength and ultra-high ductility cement-based composite materials using seawater and sea sand as raw materials, based on the micromechanical design theory of high-ductility cement-based composite materials.

[0004] Due to the characteristics of ultra-high strength and ultra-high ductility cement-based composites, such as large cementitious material content, small aggregate particle size, and low water-cement ratio, the shrinkage strain of ultra-high strength and ultra-high ductility cement-based composites is approximately twice that of traditional concrete. Although ultra-high strength and ultra-high ductility cement-based composites possess ultra-high strength and good crack control capabilities, their poor volume stability limits their further application in practical engineering. (The last sentence appears to be unrelated and possibly a fragment: "mixing seawater corrosive ions (Cl...") - and SO4 2- It will participate in and accelerate the hydration reaction, generating expansive substances such as Friedel's salt and ettringite (AFt), which is beneficial to the development of mechanical properties, durability and volume stability of cement-based materials.

[0005] Currently, there is a large body of technical literature on using AFt as an exogenous expansion factor, while there is relatively little literature on using Friedel's salt as an exogenous expansion factor. Research revealed that Chinese invention patent CN102167536B, entitled "Secondary Ethausenite-type Expansive Agent and its Preparation Method and Application," describes how, after incorporating a secondary ettringite-type expansive agent into cement concrete, the monosulfide-type hydrated calcium sulfoaluminate (AFm) in the expansive agent undergoes a rehydration reaction under sufficient gypsum conditions, forming ettringite (C3A·3CaSO4·32H2O) expanding crystals in the hardened cement concrete. This generates a pre-stress of 0.2-0.7 MPa within the concrete and maintains a micro-expansion state of 0-100 με, thus improving... The internal stress state of concrete improves the crack resistance of concrete structures. Meanwhile, the Chinese invention patent CN112194404B, entitled "A Low-Shrinkage and Low-Creep Concrete Composite Additive Suitable for Early-Age Prestressed Tensioning," utilizes the hydration reaction of anhydrous calcium sulfoaluminate and calcium sulfate to provide AFt crystals. By leveraging the seeding effect of silica fume and the early-strength effects of lithium carbonate and triisopropanolamine, the formation rate of AFt in the hydration products is accelerated, achieving the goals of micro-expansion, early strength, low shrinkage, and low creep. This is also a commonly used method currently employing AFt as an exogenous expansion factor.

[0006] However, no technical solutions have yet been found regarding the use of Friedel's salt and AFt as intrinsic swelling factors. The inventors' research has found that using Friedel's salt and AFt as intrinsic swelling factors can not only achieve the effect of controlling erosion ions (Cl...) - and SO4 2- Functional reconstruction can also suppress the shrinkage of cement-based materials. The shrinkage of cement-based materials occurs throughout their entire life cycle. Based on the hydration reaction mechanism of the intrinsic expansion factors Friedel's salt and AFt, from the perspective of the time dimension of cement-based material shrinkage, relying solely on Friedel's salt and AFt as intrinsic expansion factors is insufficient to suppress the shrinkage. Therefore, it is necessary to introduce extrinsic expansion factors to form a gradient response with the intrinsic expansion factors over time. Currently, there is a considerable amount of technical literature on the time-dimensional regulation of cement-based materials by extrinsic expansion factors, but no technical literature on the synergistic regulation of cement-based materials by intrinsic and extrinsic expansion factors over time has been found.

[0007] In summary, considering the shrinkage characteristics of ultra-high strength and ultra-high ductility cement-based composite materials made from seawater and sea sand, and based on the hydration reaction characteristics of the intrinsic expansion factors (Friedel's salt and AFt), and taking into account the synergistic compensation of the shrinkage gradient response between different extrinsic expansion factors and the intrinsic expansion factors in the time dimension, a low-shrinkage ultra-high strength and ultra-high ductility cement-based composite material made from seawater and sea sand was prepared, which is of great significance for marine infrastructure construction. Summary of the Invention

[0008] To address the shortcomings of the prior art, this invention provides a multifunctional seawater sand ECC material and its preparation method based on ion reconstruction and synergistic regulation of endogenous and exogenous expansion factors. The shrinkage performance is regulated by endogenous and exogenous expansion factors, where the endogenous expansion factor refers to the Cl- content in the seawater sand. - and SO4 2- The hydration reaction not only produces expansive AFt and Friedel's salt, but also achieves ion solidification. The exogenous expansion factor refers to the expansive substances produced by the externally added expansion agent in the hydration reaction, which makes the material have the characteristics of high strength, high ductility and low shrinkage.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A multifunctional seawater and marine sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources is proposed. The ECC material is composed of a matrix and polyethylene fibers. The matrix comprises the following components by mass: 0.6-0.8 parts cement, 0.2-0.4 parts silica fume, 0-0.2 parts quartz powder, 0.03-0.09 parts expanding agent, 0.15-0.23 parts seawater, 0.31-0.46 parts marine sand, 0.02-0.03 parts polycarboxylate superplasticizer, and 0.001-0.002 parts silane coupling agent. The content of polyethylene fibers is 2%-2.5% of the matrix volume.

[0011] Furthermore, the cement is general-purpose silicate cement or special cement, and has a compressive strength greater than 52.5 MPa at 28 days.

[0012] Furthermore, the silica fume has a SiO2 content of greater than 98%, and the quartz powder has a SiO2 content of greater than 99%.

[0013] Furthermore, the expanding agent is a sulfoaluminate expanding agent, a calcium oxide expanding agent, a magnesium oxide expanding agent, or a composite expanding agent.

[0014] Furthermore, the chloride ion concentration in the seawater is 10000 mg / L to 22000 mg / L.

[0015] Furthermore, the maximum particle size of the sea sand does not exceed 600 μm.

[0016] Furthermore, the polycarboxylate superplasticizer has a water reduction rate of 16% to 22% and a solid content of 50%.

[0017] Furthermore, the silane coupling agent is of type KH551, KH602, KH791, KH792 or KH902.

[0018] Furthermore, the polyethylene fiber has a length of not less than 6 mm, a diameter of not less than 12 μm, and a tensile strength of not less than 1950 MPa.

[0019] A method for preparing multifunctional seawater sand ECC materials based on ion reconstruction and synergistic regulation of endogenous and exogenous sources includes the following steps:

[0020] Step 1: Hydrolyze the silane coupling agent in seawater to obtain an aqueous solution, and then stir the aqueous solution and silica fume in a mixer until they are evenly dispersed and free of agglomeration;

[0021] Step 2: First, add polycarboxylate superplasticizer and mix thoroughly. If quartz powder is available, add quartz powder, cement, expansion agent, and sea sand in sequence. If quartz powder is unavailable, add cement, expansion agent, and sea sand in sequence. Then, mix at 140 r / min for 1-2 minutes, followed by 285 r / min for 1-2 minutes. Next, add polyethylene fiber and mix at 140 r / min for 1-2 minutes, followed by 285 r / min for 3-5 minutes. Finally, pour the mixture into a mold and vibrate it on a standard vibrating table for 120 seconds. Then, seal the mold and demold within 48 hours. After demolding, cure in an environment with a temperature of 80-90℃ for 9 days, and then continue curing in an environment with a temperature of 20±2℃ and a relative humidity of ≥90% for 5 days.

[0022] Compared with the prior art, the beneficial effects of the present invention are: the present invention regulates the shrinkage properties of cement-based composite materials through endogenous and exogenous expansion factors, wherein the endogenous expansion factor refers to the Cl in seawater and sea sand. - and SO4 2- The hydration reaction not only produces expansive AFt and Friedel's salt, but also achieves ion solidification. Exogenous expansion factors refer to externally added expansion agents that participate in the hydration reaction and produce expansive substances, such as AFt, Mg(OH)2, and Ca(OH)2. These substances not only have the characteristics of high strength, high ductility, and low shrinkage, but also can be sourced locally for marine infrastructure construction, realizing the utilization of marine resources and having good economic and environmental benefits. The prepared seawater sand ECC material has great prospects for marine engineering applications, especially for marine engineering infrastructure in extreme environments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the mechanism of combined regulation of shrinkage by internal and external expansion factors in the ECC material of this invention.

[0024] Figure 2 This is a tensile stress-strain curve of the material obtained in Example 1;

[0025] Figure 3 This is a tensile stress-strain curve of the material obtained in Example 2;

[0026] Figure 4 This is a tensile stress-strain curve of the material obtained in Example 3;

[0027] Figure 5 This is a tensile stress-strain curve of the material obtained in Example 4. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] A multifunctional seawater and marine sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources is composed of a matrix and polyethylene fibers. The matrix comprises the following components by mass: 0.6-0.8 parts cement, 0.2-0.4 parts silica fume, 0-0.2 parts quartz powder, 0.03-0.09 parts expansion agent, 0.15-0.23 parts seawater, 0.31-0.46 parts marine sand, 0.02-0.03 parts polycarboxylate superplasticizer, and 0.001-0.002 parts silane coupling agent. The content of polyethylene fibers is 2%-2.5% of the matrix volume.

[0030] All the above raw materials are commercially available finished products. The cement is either general-purpose Portland cement (Portland cement and ordinary Portland cement) or special cement (medium-heat Portland cement, sulfate-resistant Portland cement, oil well cement, etc.), and has a 28-day compressive strength greater than 52.5 MPa. The cementitious material, composed of silica fume and cement matrix, has a SiO2 content greater than 98%. The quartz powder has a SiO2 content greater than 99%. The expanding agent is a sulfoaluminate expanding agent, a calcium oxide expanding agent, etc. Magnesium oxide-based or composite expanding agents; chloride ion concentration in seawater of 10000 mg / L to 22000 mg / L; maximum particle size of sea sand not exceeding 600 μm; water reduction rate of polycarboxylate superplasticizer of 16% to 22%, solid content of 50%; silane coupling agent of type KH551, KH602, KH791, KH792 or KH902; polyethylene fiber length not less than 6 mm, diameter not less than 12 μm, tensile strength not less than 1950 MPa.

[0031] A method for preparing multifunctional seawater sand ECC materials based on ion reconstruction and synergistic regulation of endogenous and exogenous sources includes the following steps:

[0032] S1. The silane coupling agent is fully hydrolyzed in seawater to obtain an aqueous solution. Then, the aqueous solution and silica fume are stirred in a mixer until they are evenly dispersed and free of agglomeration.

[0033] S2. First, add polycarboxylate superplasticizer and mix thoroughly. Then, add quartz powder (if applicable), cement, expansion agent, and sea sand in sequence, and stir at 140 r / min for 1-2 minutes, then at 285 r / min for 1-2 minutes. Next, add polyethylene fiber and stir at 140 r / min for 1-2 minutes, then at 285 r / min for 3-5 minutes. Finally, pour the mixture into a mold and vibrate it on a standard vibrating table for 120 seconds. Then, seal it with a film and demold within 48 hours. After demolding, cure it in an environment with a temperature of 80-90℃ for 9 days, and then continue to cure it in an environment with a temperature of 20±2℃ and a relative humidity of ≥90% for 5 days.

[0034] The ECC material prepared by this invention, combined with Figure 1 As shown, it is based on the principle of hydration thermodynamics, through the action of corrosive ions (Cl... - and SO4 2- The targeted transformation of Cl was achieved. - and SO4 2- Functional reconstruction established a multi-field coupled contraction control mechanism for ion diffusion, chemical reaction, and crystal growth. - and SO4 2- Functional restructuring is mainly reflected in two aspects, one of which is Cl - and SO4 2- Immobilized within the crystals of Friedel's salt and ettringite (AFt), an intrinsic shrinkage compensation mechanism is formed, where Friedel's salt and AFt compensate for shrinkage through lattice expansion and intercalation expansion, respectively. Furthermore, Friedel's salt and AFt form a 3D interlocking network with the CSH gel, improving the toughness of the CSH gel framework and enhancing its volumetric stability. Based on Cl... - and SO4 2- To compensate for shrinkage characteristics over time and achieve a dynamic equilibrium state of shrinkage stress throughout the lifespan of cement-based composite materials, a time-varying gradient compensation shrinkage mechanism was established based on the hydration kinetics of exogenous expansion factors (magnesium oxide (MgO), calcium oxide (CaO), sulfoaluminate, etc.) and considering the temporal differences in chemical reactions between exogenous and exogenous expansion factors. This mechanism compensates for shrinkage in stages and forms a gradient response with the endogenous expansion factors over time.

[0035] Example 1

[0036] The matrix comprises the following components by weight: 0.6 parts cement, 0.4 parts silica fume, 0.03 parts expansion agent, 0.15 parts seawater, 0.31 parts sea sand, 0.03 parts polycarboxylate superplasticizer, and 0.002 parts silane coupling agent. The polyethylene fiber content is 2% of the matrix volume. The tensile stress-strain curve of the ECC material prepared accordingly is combined with... Figure 2 As shown.

[0037] Example 2

[0038] The matrix comprises the following components by weight: 0.8 parts cement, 0.2 parts silica fume, 0.2 parts quartz powder, 0.03 parts expansion agent, 0.15 parts seawater, 0.31 parts sea sand, 0.03 parts polycarboxylate superplasticizer, and 0.001 parts silane coupling agent. The content of polyethylene fiber is 2% of the matrix volume. The tensile stress-strain curve of the ECC material prepared accordingly is combined with... Figure 3 As shown.

[0039] Example 3

[0040] The matrix comprises the following components by weight: 0.7 parts cement, 0.3 parts silica fume, 0.1 parts quartz powder, 0.06 parts expansion agent, 0.19 parts seawater, 0.36 parts sea sand, 0.025 parts polycarboxylate superplasticizer, and 0.0015 parts silane coupling agent. The content of polyethylene fiber is 2.25% of the matrix volume. The tensile stress-strain curve of the ECC material prepared accordingly is combined with... Figure 4 As shown.

[0041] Example 4

[0042] The matrix comprises the following components by weight: 0.7 parts cement, 0.3 parts silica fume, 0.1 parts quartz powder, 0.09 parts expansion agent, 0.23 parts seawater, 0.46 parts sea sand, 0.02 parts polycarboxylate superplasticizer, and 0.0015 parts silane coupling agent. The content of polyethylene fiber is 2.5% of the matrix volume. The tensile stress-strain curve of the ECC material prepared accordingly is combined with... Figure 5 As shown.

[0043] The ECC materials prepared according to the method of the present invention through the above four embodiments have the following mechanical and shrinkage performance indicators, which are shown in Table 1:

[0044] Table 1. Relevant mechanical and shrinkage performance technical indicators for Examples 1-4

[0045]

[0046] The compressive strength test was conducted according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)"; the tensile property test was conducted according to JC / T 2461-2018 "Test Method for Mechanical Properties of High-Ductility Fiber Reinforced Cement-Based Composite Materials"; and the shrinkage property test was conducted according to JTG 3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering".

[0047] By comparing the mechanical and shrinkage performance indicators of Example 1 and ordinary high-ductility cement-based composite materials, seawater sand not only reduced the shrinkage strain of cement-based composite materials by approximately 10%, but also improved the initial crack strength, ultimate tensile strength, and ultimate tensile strain. Comparing the mechanical and shrinkage performance indicators of Example 1 and Example 3 in Table 1, it was found that with the increase of the expansive agent dosage, the compressive strength decreased by approximately 13%, but remained greater than 120 MPa, meeting the compressive strength requirements of ultra-high performance concrete; the initial crack strength did not change significantly; the ultimate tensile strain increased by approximately 2% and exhibited saturated cracking; and the shrinkage strain was effectively reduced by approximately 24%.

[0048] It is evident that the ECC material prepared by this invention, through the combined regulation of internal and external expansion factors to control shrinkage performance, can effectively reduce the shrinkage strain of cement-based composite materials, promote multi-crack development and increase ultimate tensile strain while meeting mechanical performance requirements. Moreover, it can be sourced locally, which helps to reduce raw material costs and has certain economic and environmental benefits. The prepared ECC material can simultaneously meet the requirements of compressive strength greater than 120 MPa, ultimate tensile strain greater than 7%, and shrinkage strain less than 900 με.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing multifunctional seawater sand ECC materials based on ion reconstruction and synergistic regulation of internal and external sources, characterized in that: The ECC material is composed of a matrix and polyethylene fibers. The matrix comprises the following components by weight: 0.6-0.8 parts cement, 0.2-0.4 parts silica fume, 0-0.2 parts quartz powder, 0.03-0.09 parts expanding agent, 0.15-0.23 parts seawater, 0.31-0.46 parts sea sand, 0.02-0.03 parts polycarboxylate superplasticizer, and 0.001-0.002 parts silane coupling agent. The polyethylene fiber content is 2%-2.5% of the matrix volume. Its preparation method includes the following steps: Step 1: Hydrolyze the silane coupling agent in seawater to obtain an aqueous solution, and then stir the aqueous solution and silica fume in a mixer until they are evenly dispersed and free of agglomeration; Step 2: First, add polycarboxylate superplasticizer and mix thoroughly. If quartz powder is available, add quartz powder, cement, expansion agent, and sea sand in sequence. If quartz powder is unavailable, add cement, expansion agent, and sea sand in sequence. Then, mix at 140 rpm for 1-2 minutes, followed by 285 rpm for 1-2 minutes. Next, add polyethylene fiber and mix at 140 rpm for 1-2 minutes, followed by 285 rpm for 3-5 minutes. Finally, pour the mixture into a mold and vibrate it on a standard vibrating table for 120 seconds. Then, seal the mold and demold within 48 hours. After demolding, cure in an environment with a temperature of 80-90℃ for 9 days, and then continue curing in an environment with a temperature of 20±2℃ and a relative humidity of ≥90% for 5 days.

2. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources according to claim 1, characterized in that: The cement is general-purpose silicate cement or special cement, and its compressive strength at 28 days is greater than 52.5 MPa.

3. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of endogenous and exogenous sources according to claim 1, characterized in that: The silica fume has an SiO2 content greater than 98%, and the quartz powder has an SiO2 content greater than 99%.

4. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources according to claim 1, characterized in that: The expanding agent is a sulfoaluminate expanding agent, a calcium oxide expanding agent, a magnesium oxide expanding agent, or a composite expanding agent.

5. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources according to claim 1, characterized in that: The chloride ion concentration in the seawater is 10000 mg / L to 22000 mg / L.

6. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of endogenous and exogenous sources according to claim 1, characterized in that: The maximum particle size of the sea sand shall not exceed 600 μm.

7. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources according to claim 1, characterized in that: The polycarboxylate superplasticizer has a water reduction rate of 16% to 22% and a solid content of 50%.

8. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of endogenous and exogenous sources according to claim 1, characterized in that: The silane coupling agent is of model number KH551, KH602, KH791, KH792 or KH902.

9. The preparation method of multifunctional seawater sand ECC material based on ion reconstruction and synergistic regulation of internal and external sources according to claim 1, characterized in that: The polyethylene fiber has a length of not less than 6 mm, a diameter of not less than 12 μm, and a tensile strength of not less than 1950 MPa.

Images