A modified coral aggregate (UHPC) for islands and reefs, its preparation method, and island and reef prefabricated components.

Abstract

This invention discloses a modified coral aggregate UHPC for islands and reefs, its preparation method, and prefabricated island and reef components. The modified coral aggregate UHPC, by mass ratio, is composed of the following raw materials: cement, 30-50 parts; ion migration inhibitor, 5-15 parts; modified coral aggregate, 40-60 parts; stainless steel fiber, 3-7 parts; notched polyethylene fiber, 0.4-0.8 parts; water-reducing agent, 0.3-0.7 parts; adhesive powder, 0.5-1.5 parts; defoamer, 0.05-0.15 parts; combined expansion agent, 1-3 parts; early strength agent, 0.5-1.5 parts; carbon fiber, 0.1-0.2 parts; carbon nanotubes, 0.05-0.1 parts; and mixing water, 9-12 parts. The modified coral aggregate UHPC prepared by this invention has self-compacting properties, high strength, high toughness, high durability and high electromagnetic shielding, and can be sourced locally. It can be used to manufacture prefabricated island and reef components such as artificial reefs and offshore platforms, meeting the needs of island and reef engineering construction and use.

Description

Technical Field

[0001] This invention relates to the field of civil engineering materials technology, especially marine engineering materials, specifically to a modified coral aggregate UHPC for islands and reefs, its preparation method, and prefabricated island and reef components. Background Technology

[0002] Tropical marine regions possess abundant coral aggregate resources, which are inexpensive to extract and represent a potential natural building material. Using coral aggregate to prepare concrete can not only reduce construction costs but also make full use of local natural resources, promoting the sustainable development of the construction industry.

[0003] Currently, there are relatively few UHPC precast components prepared using coral as aggregate. Chinese invention patent application CN118184200A discloses a high-performance cement-based UHPC, which uses a polymer matrix, fiber materials, carbon black nanomaterials, antioxidants, water, coupling agents, dispersants, and catalysts as raw materials. However, this invention uses ordinary sand as aggregate, which is not conducive to the sustainable development of the ecological environment and resource utilization in the long term. Furthermore, for island and reef areas, using terrestrial sand as aggregate presents certain challenges in transportation. Chinese invention patent application CN112551974A discloses a seawater coral sand ultra-high performance concrete and its preparation method. It uses coral sand but does not modify it, thus failing to strengthen the coral aggregate itself. Its main focus is on the self-shrinkage problem of ultra-high performance concrete. It also uses modified metakaolin to improve seawater erosion resistance, but it cannot meet the requirements of tropical islands and reefs in terms of self-compacting properties, strength, toughness, durability, and electromagnetic shielding.

[0004] Tropical island and reef regions, due to their proximity to the equator, face harsh natural environments year-round, including high temperatures, high humidity, high salinity, and high radiation. Therefore, there is an urgent need to develop high-strength, high-durability coral aggregates (UHPC) that can effectively resist external environmental erosion. Furthermore, through technological innovation and rational design, the material should be equipped with electromagnetic shielding properties to enhance the anti-detection capabilities of critical island and reef facilities, leading to more significant socio-economic benefits.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] To address the aforementioned problems, the first aspect of this invention discloses a modified coral aggregate UHPC for islands and reefs, which possesses self-compacting properties, high strength, high toughness, high durability, and high electromagnetic shielding.

[0007] The second aspect of this invention discloses a method for preparing island and reef modified coral aggregate UHPC, which can utilize locally sourced materials and is easy to implement.

[0008] The third aspect of this invention discloses a prefabricated component of island and reef modified coral aggregate UHPC, which meets the needs of island and reef engineering construction and use.

[0009] The above aspects of the present invention are implemented as follows:

[0010] This invention first provides a modified coral aggregate (UHPC) for islands and reefs, which is composed of the following raw materials in a specific mass ratio:

[0011] Cement, 30-50 parts;

[0012] Modified coral aggregate, 40-60 parts;

[0013] Ion migration inhibitor, 5-15 parts;

[0014] Stainless steel fiber, 3-7 parts;

[0015] Scoring polyethylene fiber, 0.4~0.8 parts;

[0016] Carbon fiber, 0.1~0.2 parts;

[0017] Carbon nanotubes, 0.05~0.1 parts;

[0018] Water-reducing agent, 0.3~0.7 parts;

[0019] Adhesive powder, 0.5~1.5 parts;

[0020] Defoamer, 0.05~0.15 parts;

[0021] Combined expanding agent, 1-3 parts;

[0022] Early-strength agent, 0.5~1.5 parts;

[0023] Mix with water, 9-12 parts.

[0024] This invention uses modified coral aggregate, combined with ion migration inhibitors, special fibers, and necessary additives, to obtain a UHPC material with self-compacting properties, high strength, high toughness, high durability, and high electromagnetic shielding.

[0025] Preferably, the cement is one or more of silicate cement, ordinary silicate cement, sulfoaluminate cement, ferroaluminate cement, and aluminate cement;

[0026] Preferably, the mixing water is one or more of seawater, desalinated seawater, fresh water, and rainwater naturally collected from the rooftops of island and reef buildings.

[0027] Preferably, the ion migration inhibitor is one or more of hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microspheres, and hydrophobically modified silica fume.

[0028] Preferably, the specific surface area of ​​the hydrophobically modified ultrafine high-alumina slag powder is 1000~2500 m². 2 / kg;

[0029] The specific surface area of ​​the hydrophobically modified glass microspheres is 3000~6000 m². 2 / kg;

[0030] The specific surface area of ​​the hydrophobically modified silica fume is 20,000~30,000 m². 2 / kg.

[0031] Preferably, the modified coral aggregate is obtained from coral reef plates through crushing, ball milling, and screening, with a maximum particle size of 1.25 mm. The mass percentage of each particle size range is as follows: 0.04 mm < particle size ≤ 0.16 mm accounts for 5-20%, 0.16 mm < particle size ≤ 0.315 mm accounts for 5-20%, 0.315 mm < particle size ≤ 0.63 mm accounts for 40-50%, and 0.63 mm < particle size ≤ 1.25 mm accounts for 30-40%.

[0032] Preferably, the obtained 0.04mm~1.25mm continuously graded coral aggregate is modified, including:

[0033] (1) The continuously graded coral aggregate, cement, ion migration inhibitor, and mixing water are added to the vacuum mixer in a mass ratio of 1:0.9:0.1:0.4;

[0034] (2) Turn on the vacuum mixer and stir for 3 to 5 minutes with the vacuum pump off, including 1 to 2 minutes of low speed stirring at 960 to 1200 r / h and 2 to 3 minutes of high speed stirring at 7200 to 12000 r / h. Stop stirring when the mixture is fully mixed.

[0035] (3) Turn on the vacuum pump and evacuate to 5%~10% atmospheric pressure inside the device. Stir at 7200~12000r / h for 3~5min until the surface of the coral aggregate is fully coated with cement slurry and forms relatively regular spherical particles. Stop stirring.

[0036] (4) Take out the mixture, spread it evenly, and let it dry for 24 hours. During this period, use a high-frequency vibration table to vibrate the mixture regularly to prevent adhesion and affect the uniformity of the modified coral aggregate.

[0037] (5) Take the dried mixture and sieve it with a sieve. The target coral skeleton with a particle size range of 0.04mm to 1.25mm is the modified coral skeleton.

[0038] Preferably, the water-reducing agent is an early-strength, high-efficiency polycarboxylate water-reducing agent;

[0039] Preferably, the adhesive powder is one or two of vinyl acetate and ethylene copolymer;

[0040] Preferably, the defoamer is one or both of powdered silicone defoamer and polyether defoamer;

[0041] Preferably, the combined expanding agent is one or more of the following: plastic expanding agent, calcium oxide type expanding agent, calcium sulfoaluminate type expanding agent, magnesium oxide type expanding agent, and calcium oxide-calcium sulfoaluminate composite expanding agent;

[0042] Preferably, the early strength agent is one or more of calcium formate, sodium aluminate, anhydrous sodium sulfate, and sodium carbonate.

[0043] Preferably, the stainless steel fiber has a diameter of 0.22 mm and a length of 12 mm;

[0044] Preferably, the notched polyethylene fiber has a diameter of 24 μm and a length of 12 mm, with longitudinal notches on its surface;

[0045] Preferably, the carbon fiber is a 6mm short-cut carbon fiber with a tensile strength of not less than 3GPa;

[0046] Preferably, the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of no more than 8 nm, an inner diameter of 2-5 nm, and a length of 0.5-2 μm.

[0047] The present invention also provides a method for preparing UHPC (Ultra-High Polymerized Coral) based on the aforementioned island and reef modified coral aggregate, comprising:

[0048] (1) Mix all components in UHPC, except for mixing water, stainless steel fiber, and notched polyethylene fiber, carbon fiber and carbon nanotubes, according to the mass ratio.

[0049] (2) Add mixing water and continue stirring until homogeneous to obtain UHPC slurry;

[0050] (3) Finally, stainless steel fiber, indented polyethylene fiber, carbon fiber and carbon nanotube are added, and stirring is continued until the fibers are evenly dispersed to obtain the modified coral aggregate UHPC.

[0051] The present invention also provides an island and reef prefabrication based on the island and reef modified coral aggregate UHPC, the island and reef prefabrication including artificial reefs and offshore platforms.

[0052] The advantages of this invention over the prior art include at least the following:

[0053] (1) Self-compacting. First, this invention modifies the loose, porous, and easily absorbent characteristics of coral aggregate. Using a vacuum mixer to create a negative pressure environment, a slurry made of cement, ion migration inhibitors, and mixing water is filled into the pores of the coral aggregate and evenly coated on the surface of the coral aggregate, forming relatively regular spherical particles, thus obtaining modified coral aggregate. This reduces the absorption of mixing water by the coral aggregate during the mixing process and reduces the decrease in fluidity caused by the irregular shape of the coral aggregate. Second, during the preparation process, a hydrophobic slurry film is coated on the surface of the modified coral aggregate to further reduce its impact on the fluidity of UHPC. Third, the ion migration inhibitors used in this invention, including hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microspheres, and hydrophobically modified silica fume, have all undergone hydrophobic modification treatment, reducing water demand and further improving the fluidity of UHPC. Fourth, this invention uses a high-efficiency polycarboxylate superplasticizer with a water reduction rate of more than 40%, further improving the fluidity of UHPC.

[0054] (2) High strength. First, by modifying the coral aggregate, the slurry fills the pores of the coral aggregate and continues to hydrate and harden, the strength of UHPC is greatly enhanced. The gradation is designed and the packing is dense, resulting in strong aggregate support. Second, the present invention uses a mixture of stainless steel fiber, indented polyethylene fiber and carbon fiber, which can effectively improve the mechanical properties of UHPC. Third, the ion migration inhibitor used in the present invention improves the strength after hardening through the principle of the closest packing. Moreover, the ion migration inhibitor has a secondary hydration effect, and the hydration products fill the internal pores of UHPC step by step, further improving the long-term strength of UHPC.

[0055] (3) High toughness. The stainless steel fiber, ultra-high molecular weight indented polyethylene fiber and carbon fiber used in this invention can play a positive synergistic role after being mixed. The stainless steel fiber has extremely high strength and stiffness, which can improve the compressive strength. The ultra-high molecular weight indented polyethylene fiber and carbon fiber have high strength properties, which can significantly improve the crack resistance of concrete. In addition, the nanoemulsion formed after the adhesive powder is dissolved in the mixing water can improve the microstructure of UHPC at the nanoscale, further improving the toughness of UHPC.

[0056] (4) High durability. First, the ion migration inhibitor used in this invention can inhibit Cl through physicochemical adsorption. - SO4 2- Mg + Harmful ions migrate and Al is dissolved during the UHPC hardening process. 3+First, the invention employs modified coral aggregate, which significantly improves the density of the hardened UHPC matrix and inhibits the secondary hydration of harmful ions from the coral aggregate, thus enhancing durability. Second, the cement used in this invention, through the rational blending of aluminate cement, sulfoaluminate cement, and ferroaluminate cement, effectively prevents corrosion from harmful substances such as acids and alkalis, improving durability. For example, the hydration of C3A (tricalcium aluminate) and C4A (tetracalcium aluminate) in aluminate cement can form stable compounds that resist sulfate attack. Third, the invention uses a combination of expansion agents to keep the UHPC in a state of micro-expansion, effectively preventing shrinkage and cracking, and avoiding the formation of channels for harmful ions to enter the matrix, further improving the durability of the UHPC.

[0057] (5) High electromagnetic shielding. First, the UHPC prepared by this invention has a dense substrate structure, while the core of the coral aggregate retains some pores. It has both excellent mechanical properties and enhanced impedance matching, which is conducive to the incidence of electromagnetic waves and increases the internal attenuation path of electromagnetic waves. The electromagnetic shielding is higher than that of ordinary ultra-high performance concrete. Second, this invention uses a mixture of stainless steel fiber, carbon fiber and carbon nanotubes, which has the effect of dual loss of resistance loss and magnetic loss. At the same time, the conductivity of UHPC is enhanced, and the electromagnetic shielding effect is further enhanced.

[0058] (6) High local material sourcing rate. In combination with the current situation of island and reef engineering construction, the present invention uses coral aggregate obtained by crushing and screening coral reefs to replace traditional aggregates such as quartz sand and river sand. Seawater can be used for mixing, saving transportation and raw material costs, saving economic costs, and can strongly promote the sustainable development of island and reef construction.

[0059] It should be understood that the implementation of any embodiment of the present invention does not mean that it will simultaneously possess or achieve multiple or all of the above-mentioned beneficial effects. Attached Figure Description

[0060] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0061] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0062] Figure 1 An exemplary schematic diagram of a method for modifying coral aggregate raw materials according to the present invention is shown.

[0063] Figure 2 The present invention provides an exemplary comparison of the microstructure of a polyethylene fiber with notches, wherein: (a) is an unnotched polyethylene fiber, and (b) is a notched polyethylene fiber;

[0064] Figure 3 An exemplary schematic diagram of the process for preparing modified coral aggregate UHPC according to the present invention is shown;

[0065] Figure 4 An exemplary schematic diagram of the overall structure of a modified coral aggregate UHPC prefabricated component (artificial reef) according to the present invention is shown;

[0066] Figure 4A Example shown Figure 4 The main view;

[0067] Figure 4B Example shown Figure 4 Side view;

[0068] Figure 4C Example shown Figure 4 Top view;

[0069] Figure 5 An exemplary schematic diagram of a modified coral aggregate UHPC prefabricated component (offshore platform) according to the present invention is shown.

[0070] Figure 5A Example shown Figure 5 Side view;

[0071] Figure 5B Example shown Figure 5 Top view.

[0072] In the various figures, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0074] It should be understood that the terms "comprising / including," "consisting of," or any other variations are intended to cover non-exclusive inclusion, such that a product, apparatus, process, or method that comprises a list of elements includes not only those elements but may also include, where necessary, other elements not expressly listed, or elements inherent to such a product, apparatus, process, or method. Without further limitation, an element defined by the phrases "comprising / including," "consisting of," does not exclude the presence of additional identical elements in the product, apparatus, process, or method that includes said element.

[0075] The following is a detailed description of the specific implementation and preferred embodiment of the island and reef modified coral aggregate UHPC proposed in this invention.

[0076] This invention first provides a modified coral aggregate (UHPC) for islands and reefs, which, by mass ratio, is composed of the following raw materials: 30-50 parts cement, 5-15 parts ion migration inhibitor, 40-60 parts modified coral aggregate, 3-7 parts stainless steel fiber, 0.4-0.8 parts notched polyethylene fiber, 0.3-0.7 parts water-reducing agent, 0.5-1.5 parts adhesive powder, 0.05-0.15 parts defoamer, 1-3 parts combined expansion agent, 0.5-1.5 parts early strength agent, 0.1-0.2 parts carbon fiber, 0.05-0.1 parts carbon nanotubes, and 9-12 parts mixing water. The UHPC produced by this invention utilizes locally sourced materials and possesses self-compacting properties, high strength, high toughness, high durability, and high electromagnetic shielding. Furthermore, UHPC prefabricated artificial reefs and offshore platforms can be manufactured using this material, meeting the needs of island and reef engineering construction and use.

[0077] In some embodiments, the cement is preferably one or a combination of silicate cement, ordinary silicate cement, sulfoaluminate cement, ferroaluminate cement, and aluminate cement. The cement used in this invention, through the reasonable blending of aluminate cement, sulfoaluminate cement, and ferroaluminate cement, can effectively prevent corrosion from harmful substances such as acids and alkalis, and improve durability. For example, the hydration of C3A (tricalcium aluminate) and C4A (tetracalcium aluminate) in aluminate cement can form stable compounds that resist sulfate attack.

[0078] In some embodiments, the ion migration inhibitor is one or more of hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microspheres, and hydrophobically modified silica fume.

[0079] In some specific embodiments, the specific surface area of ​​the hydrophobically modified ultrafine high-alumina slag powder is 1000~2500 m². 2 / kg, Al2O3 content greater than 15%; specific surface area of ​​hydrophobically modified glass microspheres is 3000~6000 m² / kg. 2 / kg, Al2O3 content greater than 40%; specific surface area of ​​hydrophobically modified silica fume is 20000~30000 m² / kg. 2 / kg, SiO2 content greater than 95%.

[0080] The hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microspheres, and hydrophobically modified silica fume in this invention have all undergone hydrophobic modification treatment, which reduces water demand and further improves the flowability of UHPC.

[0081] Furthermore, the ion migration inhibitor in this invention inhibits Cl through physicochemical adsorption. - SO4 2- Mg 2 + Harmful ions migrate and Al is dissolved during the UHPC hardening process. 3+ The ion migration inhibitor prevents the dissolution of hydration products in the UHPC matrix. The secondary hydration of the ion migration inhibitor makes the UHPC matrix more compact and improves its durability. In addition, through the principle of closest packing, the strength of UHPC after hardening is improved. Moreover, the ion migration inhibitor has a secondary hydration effect, and the hydration products fill the internal pores of UHPC step by step, further improving the long-term strength of UHPC.

[0082] In some embodiments, the modified coral aggregate is obtained from coral reef plates through crushing, ball milling, and screening. Its maximum particle size is 1.25 mm, and the mass percentage of each particle size range is as follows: 0.04 mm < particle size ≤ 0.16 mm accounts for 5-20%, 0.16 mm < particle size ≤ 0.315 mm accounts for 5-20%, 0.315 mm < particle size ≤ 0.63 mm accounts for 40-50%, and 0.63 mm < particle size ≤ 1.25 mm accounts for 30-40%. The apparent density is 2350-2450 kg / m³, and the bulk density is 1005-1065 kg / m³.

[0083] Furthermore, before material preparation, this invention first modifies the coral aggregate raw material, specifically modifying the continuously graded coral aggregate raw material with a particle size of 0.04 mm to 1.25 mm. This is a preliminary procedure for material preparation. Figure 1 As shown, the modification treatment method 100 includes the following steps:

[0084] In box 101, cement, ion migration inhibitor, and mixing water are added separately. The continuously graded coral aggregate raw material, cement, ion migration inhibitor, and mixing water are added to the vacuum mixer in a mass ratio of 1:0.9:0.1:0.4. It is easy to understand that the cement, ion migration inhibitor, and mixing water added at this time are not related to the main material of the prepared material. They are materials added separately for the purpose of modification. The specific amount added is based on the coral aggregate raw material and is added in proportion.

[0085] In box 102, turn on the vacuum mixer and stir for 3-5 minutes with the vacuum pump off, including 1-2 minutes of low-speed stirring (960-1200 rpm) and 2-3 minutes of high-speed stirring (7200-12000 rpm). Stop stirring once the mixture is fully homogenized.

[0086] In frame 103, turn on the vacuum pump and evacuate to 5%~10% atmospheric pressure inside the device. Stir at high speed (7200~12000r / h) for 3~5 minutes until the surface of the coral aggregate is fully coated with cement slurry and forms relatively regular spherical particles. Then stop stirring.

[0087] In frame 104, the mixture is taken out, spread evenly, and dried for 24 hours. During this period, a high-frequency vibration table is used to vibrate the mixture regularly to prevent adhesion and affect the uniformity of the modified coral aggregate.

[0088] In frame 105, the dried mixture is taken and sieved using a sieve. The target coral aggregate with a particle size range of 0.04 mm to 1.25 mm is the modified coral aggregate obtained.

[0089] This invention first addresses the loose, porous, and easily absorbent characteristics of coral aggregate by modifying it. The modification method utilizes negative pressure to draw in cement slurry, unlike ordinary soaking or granulation, resulting in enhanced hardening of the cement slurry. Specifically, a vacuum mixer creates a negative pressure environment to fill the pores of the coral aggregate with a slurry made of cement, ion migration inhibitors, and mixing water, uniformly coating the surface of the coral aggregate to form relatively regular spherical particles. This reduces the absorption of mixing water during mixing and minimizes the decrease in fluidity caused by the irregular shape of the coral aggregate. Secondly, during the preparation process, a hydrophobic slurry film is coated onto the surface of the modified coral aggregate to further reduce its impact on the fluidity of UHPC, thereby achieving a high fluidity. Furthermore, after the slurry fills the pores of the coral aggregate, it continues to hydrate and harden, significantly enhancing the strength of the coral aggregate. The gradation is designed for dense packing and strong aggregate support, resulting in high strength. Additionally, the modification of the coral aggregate significantly improves the density and durability of the hardened UHPC matrix.

[0090] In some embodiments, the water-reducing agent is an early-strength, high-efficiency polycarboxylate water-reducing agent with a water reduction rate of more than 40%, which can further improve the flowability of UHPC.

[0091] In some embodiments, the adhesive powder is one or both of vinyl acetate and ethylene copolymers. After the adhesive powder dissolves in the mixing water, it forms a nanoemulsion, which can improve the microstructure of UHPC at the nanoscale, thereby increasing the flexural strength of UHPC and achieving high strength.

[0092] In some embodiments, the defoamer is one or both of powdered silicone defoamer and polyether defoamer. The defoamer can effectively reduce the introduction of air bubbles during the mixing process in the preparation of high-performance cement-based UHPC, making the hardened UHPC more dense and further improving its strength.

[0093] It should be noted that the present invention uses a combination of expansion agents to keep UHPC in a state of micro-expansion, effectively preventing it from shrinking and cracking, avoiding the formation of channels for harmful ions to enter the matrix, and further improving the durability of UHPC.

[0094] In some embodiments, stainless steel fibers with a diameter of 0.22 mm and a length of 12 mm are incorporated; as well as notched polyethylene fibers with a diameter of 24 μm and a length of 12 mm, with longitudinal notches on the surface; 6 mm short-cut carbon fibers with a tensile strength of not less than 3 GPa are incorporated; and multi-walled carbon nanotubes with an outer diameter not exceeding 8 nm, an inner diameter of 2-5 nm, and a length of 0.5-2 μm are incorporated. Firstly, using a mixture of stainless steel fibers, notched polyethylene fibers, and carbon fibers can effectively improve the mechanical properties of coral aggregate UHPC, such as... Figure 2 As shown in the microscopic image comparison, the scoring increases the surface area of ​​polyethylene fibers, resulting in stronger adhesion to cement stone and better reinforcement and toughening effects. Secondly, the blending of stainless steel fibers, ultra-high molecular weight scored polyethylene fibers, and carbon fibers exhibits a positive synergistic effect. Stainless steel fibers possess extremely high strength and stiffness, which can improve compressive strength, while ultra-high molecular weight scored polyethylene fibers have high strength properties, which can significantly improve the crack resistance of concrete. Furthermore, the use of a blend of stainless steel fibers, carbon fibers, and carbon nanotubes has the effect of reducing both resistive and magnetic losses, while the conductivity of UHPC is enhanced, further strengthening the electromagnetic shielding effect.

[0095] In some embodiments, the mixing water is one or more of seawater, desalinated seawater, fresh water, and rainwater naturally collected from the rooftops of island and reef buildings. In this invention, the mixing water is sourced locally, saving on transportation and raw material costs.

[0096] Example 1

[0097] 40 parts cement, 10 parts ion migration inhibitor, 50 parts modified coral aggregate, 5 parts stainless steel fiber, 0.6 parts notched polyethylene fiber, 0.15 parts carbon fiber, 0.1 parts carbon nanotube, 0.5 parts water-reducing agent, 1 part adhesive powder, 0.1 parts defoamer, 2 parts combined expansion agent, 1 part early strength agent, and 10 parts mixing water.

[0098] The cement consists of 80% P·II 52.5 grade silicate cement, 10% ferroaluminate cement and 10% aluminate cement; the ion migration inhibitor consists of 40% hydrophobically modified ultrafine high-alumina slag powder, 40% hydrophobically modified glass microspheres and 20% hydrophobically modified silica fume; the early strength agent consists of 50% sodium carbonate and 50% calcium formate; and the combined expansion agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansion agent and 50% magnesium oxide expansion agent.

[0099] Example 2

[0100] 30 parts cement, 10 parts ion migration inhibitor, 60 parts modified coral aggregate, 3 parts stainless steel fiber, 0.4 parts notched polyethylene fiber, 0.1 parts carbon fiber, 0.07 parts carbon nanotubes, 0.3 parts water-reducing agent, 1 part adhesive powder, 0.1 parts defoamer, 1.5 parts combined expansion agent, 1 part early strength agent, and 9 parts mixing water.

[0101] The cement consists of 80% P·II 52.5 grade silicate cement, 10% ferroaluminate cement and 10% aluminate cement; the ion migration inhibitor consists of 40% hydrophobically modified ultrafine high-alumina slag powder, 40% hydrophobically modified glass microspheres and 20% hydrophobically modified silica fume; the early strength agent consists of 50% sodium carbonate and 50% calcium formate; and the combined expansion agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansion agent and 50% magnesium oxide expansion agent.

[0102] Example 3

[0103] 50 parts cement, 10 parts ion migration inhibitor, 40 parts modified coral aggregate, 7 parts stainless steel fiber, 0.8 parts notched polyethylene fiber, 0.2 parts carbon fiber, 0.1 parts carbon nanotubes, 0.7 parts water-reducing agent, 1 part adhesive powder, 0.12 parts defoamer, 2.5 parts combined expansion agent, 1 part early strength agent, and 12 parts mixing water.

[0104] The cement consists of 80% P·II 52.5 grade silicate cement, 10% ferroaluminate cement and 10% aluminate cement; the ion migration inhibitor consists of 40% hydrophobically modified ultrafine high-alumina slag powder, 40% hydrophobically modified glass microspheres and 20% hydrophobically modified silica fume; the early strength agent consists of 50% sodium carbonate and 50% calcium formate; and the combined expansion agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansion agent and 50% magnesium oxide expansion agent.

[0105] Comparative Example 1

[0106] 40 parts cement, 10 parts ion migration inhibitor, 50 parts coral aggregate, 5 parts stainless steel fiber, 0.6 parts notched polyethylene fiber, 0.15 parts carbon fiber, 0.1 parts carbon nanotubes, 0.5 parts water-reducing agent, 1 part adhesive powder, 0.1 part defoamer, 2 parts combined expansion agent, 1 part early strength agent, and 10 parts mixing water.

[0107] The cement consists of 80% P·II 52.5 grade silicate cement, 10% ferroaluminate cement and 10% aluminate cement; the ion migration inhibitor consists of 40% hydrophobically modified ultrafine high-alumina slag powder, 40% hydrophobically modified glass microspheres and 20% hydrophobically modified silica fume; the early strength agent consists of 50% sodium carbonate and 50% calcium formate; and the combined expansion agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansion agent and 50% magnesium oxide expansion agent.

[0108] The difference in this comparative example is that the coral aggregate was not modified.

[0109] Comparative Example 2

[0110] 40 parts cement, 10 parts ion migration inhibitor, 50 parts modified coral aggregate, 5 parts stainless steel fiber, 0.6 parts notched polyethylene fiber, 0.5 parts water-reducing agent, 1 part adhesive powder, 0.1 parts defoamer, 2 parts combined expansion agent, 1 part early strength agent, and 10 parts mixing water.

[0111] The cement consists of 80% P·II 52.5 grade silicate cement, 10% ferroaluminate cement and 10% aluminate cement; the ion migration inhibitor consists of 40% hydrophobically modified ultrafine high-alumina slag powder, 40% hydrophobically modified glass microspheres and 20% hydrophobically modified silica fume; the early strength agent consists of 50% sodium carbonate and 50% calcium formate; and the combined expansion agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansion agent and 50% magnesium oxide expansion agent.

[0112] The difference between this comparative example and the one using carbon fiber and carbon nanotubes is that carbon fiber and carbon nanotubes were not used.

[0113] The performance of the modified coral aggregate UHPC is shown in Table 1 after testing.

[0114] Table 1 UHPC Performance of Each Case

[0115]

[0116] Note: Electromagnetic shielding effectiveness is tested using the shielded room window method as specified in GJB 6190-2008 "Test Method for Shielding Effectiveness of Electromagnetic Shielding Materials" at a frequency of 2GHz.

[0117] As shown in Table 1, the modified coral aggregate UHPC provided by this invention exhibits excellent mechanical properties, with a 28-day compressive strength exceeding 125 MPa and a 28-day flexural strength exceeding 20 MPa, demonstrating high strength and high toughness. Its spread is not less than 700 mm, indicating high self-compacting properties. Its electrical flux is generally no more than 70 C, its sulfate resistance is not less than KS120, and its impermeability is not less than P30, demonstrating high durability. Furthermore, as shown by the electrical flux of 231.6 C in Comparative Example 1, the unmodified coral aggregate results in increased internal porosity, high ion permeability, and very poor durability. Its electromagnetic shielding effectiveness is above 40 dB, indicating high electromagnetic shielding performance. This demonstrates that the modified coral aggregate UHPC provided by this invention meets strength requirements while also possessing self-compacting, high durability, and high electromagnetic shielding properties. Moreover, it can be sourced locally, making it suitable for island and reef engineering construction.

[0118] This invention also provides a method for preparing modified coral aggregate UHPC, such as... Figure 3 As shown, it includes:

[0119] In frame 201, the powder is first mixed evenly, that is, the components of UHPC, except for mixing water, stainless steel fiber, and notched polyethylene fiber, carbon fiber and carbon nanotube are mixed evenly according to the mass ratio.

[0120] In frame 202, water is added to prepare the slurry, that is, mixing water is added and the mixture is stirred evenly to obtain UHPC slurry;

[0121] In frame 203, various fibers are added last, namely stainless steel fibers, indented polyethylene fibers, carbon fibers and carbon nanotubes, and stirring is continued until the fibers are evenly dispersed to obtain modified coral aggregate UHPC.

[0122] The preparation method follows the process of dry material mixing → slurry preparation → fiber dispersion, which is simple and easy to implement, and the material quality can be guaranteed.

[0123] like Figure 4 , 4A 4B, 4C, and Figure 5 , 5AFigure 5B shows a UHPC prefabricated component made using the modified coral aggregate UHPC provided by this invention. Taking artificial reefs and offshore platforms as examples, the main structure of the artificial reef consists of prefabricated UHPC panels and prefabricated UHPC base plates. The artificial reef has a triangular shape when viewed from the side, which improves the stability of the structure, and the diamond-shaped holes on the panels can effectively reduce the impact force of water. Since the artificial reef is in a seawater environment, this prefabricated artificial reef is designed to address seawater corrosion by adjusting the properties of raw materials, resulting in a prefabricated artificial reef component with high durability, high strength, high toughness, high electromagnetic shielding, and high local sourcing rate, enabling it to serve for a long time in the tropical island and reef environment of my country. The offshore platform mainly consists of a deck, pontoons, and anchor cables. The deck is composed of a certain amount of modified coral aggregate UHPC prefabricated panels spliced ​​together by means of steel bars or bolts. A hole of a certain size should be reserved at the bottom of the deck to facilitate connection with the pontoons. The buoys provide support by storing seawater inside, but because they are light, they are easily pushed away by waves. Therefore, anchor cables are added around the buoys for fixation.

[0124] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0125] While several specific implementation details are included in the foregoing discussion, these should not be construed as limiting the scope of the invention. Certain features described in the context of individual embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations.

Claims

1. A modified coral aggregate (UHPC) for islands and reefs, characterized in that, By mass ratio, it is composed of the following raw materials: Cement, 30-50 parts; modified coral aggregate, 40-60 parts; ion migration inhibitor, 5-15 parts; Stainless steel fiber, 3-7 parts; The composition of the following components is as follows: notched polyethylene fiber, 0.4-0.8 parts; carbon fiber, 0.1-0.2 parts; carbon nanotubes, 0.05-0.1 parts; water-reducing agent, 0.3-0.7 parts; rubber powder, 0.5-1.5 parts; defoamer, 0.05-0.15 parts; combined expanding agent, 1-3 parts; early strength agent, 0.5-1.5 parts; mixing water, 9-12 parts. The ion migration inhibitor is one or more of the following: hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microspheres, and hydrophobically modified silica fume. The raw materials for the modified coral aggregate undergo modification treatment, specifically: (1) Take cement, ion migration inhibitor and mixing water separately, and put the continuous graded coral aggregate raw materials, cement, ion migration inhibitor and mixing water into a vacuum mixer in a mass ratio of 1:0.9:0.1:0.4; (2) Turn on the vacuum mixer and stir for 3 to 5 minutes with the vacuum pump off, including 1 to 2 minutes of low speed stirring at 960 to 1200 r / h and 2 to 3 minutes of high speed stirring at 7200 to 12000 r / h. Stop stirring when the mixture is fully mixed. (3) Turn on the vacuum pump and evacuate the device to 5%~10% atmospheric pressure. Stir at 7200~12000r / h for 3~5min until the surface of the coral aggregate is fully coated with cement slurry and forms relatively regular spherical particles. Stop stirring. (4) Take out the mixture, spread it evenly, and let it dry for 24 hours. During this period, use a high-frequency vibration table to vibrate the mixture regularly to prevent adhesion and affect the uniformity of the modified coral aggregate. (5) Take the dried mixture and sieve it with a sieve. The target coral skeleton with a particle size range of 0.04mm to 1.25mm is the modified coral skeleton.

2. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The cement is one or more of silicate cement, ordinary silicate cement, sulfoaluminate cement, ferroaluminate cement, and aluminate cement.

3. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The mixing water is one or more of the following: seawater, desalinated seawater, fresh water, and rainwater naturally collected from the rooftops of island and reef buildings.

4. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The specific surface area of ​​the hydrophobically modified ultrafine high-alumina slag powder is 1000~2500 m². 2 / kg.

5. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The specific surface area of ​​the hydrophobically modified glass microspheres is 3000~6000 m². 2 / kg.

6. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The specific surface area of ​​the hydrophobically modified silica fume is 20,000~30,000 m². 2 / kg.

7. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The modified coral aggregate is made from coral reef material through crushing, ball milling, and screening. Its maximum particle size is 1.25 mm, and the mass percentage of each particle size range is as follows: 0.04 mm < particle size ≤ 0.16 mm accounts for 5-20%, 0.16 mm < particle size ≤ 0.315 mm accounts for 5-20%, 0.315 mm < particle size ≤ 0.63 mm accounts for 40-50%, and 0.63 mm < particle size ≤ 1.25 mm accounts for 30-40%.

8. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The water-reducing agent is an early-strength, high-efficiency polycarboxylate water-reducing agent.

9. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The adhesive powder is one or both of vinyl acetate and ethylene copolymer.

10. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The defoamer is one or both of powdered silicone defoamer and polyether defoamer.

11. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The combined expanding agent is two or more of the following: plastic expanding agent, calcium oxide type expanding agent, calcium sulfoaluminate type expanding agent, magnesium oxide type expanding agent, and calcium oxide-calcium sulfoaluminate composite expanding agent.

12. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The early strength agent is one or more of calcium formate, sodium aluminate, anhydrous sodium sulfate, and sodium carbonate.

13. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The stainless steel fiber has a diameter of 0.22 mm and a length of 12 mm.

14. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The scored polyethylene fiber has a diameter of 24 μm and a length of 12 mm, with longitudinal scoring on its surface.

15. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The carbon fiber is a 6mm short-cut carbon fiber with a tensile strength of not less than 3GPa.

16. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that, The carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of no more than 8 nm, an inner diameter of 2-5 nm, and a length of 0.5-2 μm.

17. A method for preparing island and reef modified coral aggregate UHPC according to any one of claims 1 to 16, comprising: (1) Mix all components in UHPC, except for mixing water, stainless steel fiber, notched polyethylene fiber, carbon fiber and carbon nanotube, according to the mass ratio. (2) Add mixing water and continue stirring until homogeneous to obtain UHPC slurry; (3) Finally, stainless steel fiber, indented polyethylene fiber, carbon fiber and carbon nanotube are added, and stirring is continued until the fibers are evenly dispersed to obtain the modified coral aggregate UHPC.

18. A reef prefabrication of reef modified coral aggregate UHPC according to any one of claims 1 to 16, the reef prefabrication comprising artificial reefs and offshore platforms.

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