Island reef modified coral aggregate UHPC, preparation method thereof and island reef prefabricated member

Abstract

The invention discloses island reef modified coral aggregate UHPC, a preparation method thereof and an island reef prefabricated part. The modified coral aggregate UHPC is prepared by mixing the following raw materials in parts by mass: 30 to 50 parts of cement, 5 to 15 parts of ion migration inhibitor, 40 to 60 parts of modified coral aggregate, 3 to 7 parts of stainless steel fiber, 0.4 to 0.8 part of indented polyethylene fiber, 0.3 to 0.7 part of water reducing agent, 0.5 to 1.5 parts of rubber powder, 0.05 to 0.15 part of defoaming agent, 1 to 3 parts of combined expanding agent, 0.5 to 1.5 parts of early strength agent, 0.1 to 0.2 part of carbon fiber, 0.05 to 0.1 part of carbon nano tube and 9 to 12 parts of mixing water. The prepared modified coral aggregate UHPC has the advantages of self-compaction, high strength, high toughness, high durability and high electromagnetic shielding property, local materials can be used, island prefabricated members such as fish reefs and offshore platforms can be prepared from the modified coral aggregate UHPC, and the requirements of island engineering construction and use are met.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering materials, in particular to marine engineering materials, and specifically to an island-reef modified coral aggregate UHPC and a preparation method thereof, and an island-reef prefabricated part. Background Art

[0002] There are abundant coral aggregate resources in tropical marine areas, which are low in mining cost and are potential natural building materials. Using coral aggregate to prepare concrete can not only reduce construction costs, but also make full use of local natural resources and promote the sustainable development of the construction industry.

[0003] At present, relatively few UHPC prefabricated parts are prepared using coral as aggregate. Chinese invention patent application CN118184200A discloses a high-performance cement-based UHPC, which uses polymer matrix, fiber material, carbon black nanomaterial, antioxidant, water, coupling agent, dispersant, and catalyst as raw materials to prepare cement-based UHPC. However, the aggregate in the invention is selected as ordinary sand, and long-term use is not conducive to the sustainable development of ecological environment and resource utilization; at the same time, for island and reef areas, the use of land sand as aggregate has certain challenges in transportation. Chinese invention patent application CN112551974A discloses a seawater coral sand ultra-high performance concrete and its preparation method, which uses coral sand but does not modify the coral sand, and cannot enhance the coral aggregate body. The focus is on the self-shrinkage problem of ultra-high performance concrete, and at the same time uses modified kaolin to improve the erosion resistance to seawater, and cannot meet the use requirements of tropical islands and reefs in many aspects such as self-compacting, strength, toughness, durability and electromagnetic shielding.

[0004] Tropical islands and reefs are close to the equator and face harsh natural environments such as high temperature, high humidity, high salinity and high radiation all year round. Therefore, it is urgent to prepare coral aggregate UHPC with high strength and high durability that can effectively resist external environmental erosion, and through further technological innovation and reasonable design, the material can have electromagnetic shielding properties, improve the anti-detection capabilities of important island and reef facilities, and bring more significant social and economic benefits.

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

[0006] In order to solve the above problems, the first aspect of the present invention discloses an island reef modified coral aggregate UHPC, which has self-compacting, high strength, high toughness, high durability and high electromagnetic shielding properties.

[0007] The second aspect of the present invention discloses a method for preparing island and reef modified coral aggregate UHPC, which can obtain local materials and is easy to implement.

[0008] The third aspect of the present invention discloses an island and reef 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 achieved in this way:

[0010] The present invention first provides an island reef modified coral aggregate UHPC, which is mixed with the following raw materials by 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] Scored 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] Rubber powder, 0.5~1.5 parts;

[0020] Defoaming agent, 0.05~0.15 parts;

[0021] Combined expansion agent, 1 to 3 parts;

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

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

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

[0025] Preferably, the cement is one or more of Portland cement, ordinary Portland cement, sulphoaluminate 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 roofs 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 microbeads, and hydrophobically modified silica fume.

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

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

[0030] The specific surface area of ​​the hydrophobically modified silica fume is 20000-30000m 2 / kg.

[0031] Preferably, the raw material of the modified coral aggregate is obtained by crushing, ball milling and screening coral reef discs, and its maximum particle size is 1.25 mm. The mass proportion of each particle size range is: 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 prepared 0.04 mm to 1.25 mm continuously graded coral aggregate is modified, including:

[0033] (1) Put the continuously graded coral aggregate, cement, ion migration inhibitor and mixing water into a 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 turned off, stirring at a low speed of 960 to 1200 r / h for 1 to 2 minutes and at a high speed of 7200 to 12000 r / h for 2 to 3 minutes. Stop stirring when the mixture is fully mixed;

[0035] (3) Turn on the vacuum pump and evacuate the device to 5% to 10% of atmospheric pressure. Stir at a high speed of 7200 to 12000 r / h for 3 to 5 minutes. When the surface of the coral aggregate is fully coated by the cement slurry and relatively regular spherical particles are formed, stop stirring.

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

[0037] (5) The dried mixture is screened with a sieve to obtain the target coral aggregate with a particle size range of 0.04 mm to 1.25 mm, which is the prepared modified coral aggregate.

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

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

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

[0041] Preferably, the combined expansion agent is one or more of a plastic expansion agent, a calcium oxide expansion agent, a calcium sulfoaluminate expansion agent, a magnesium oxide expansion agent, and a calcium oxide-calcium sulfoaluminate composite expansion 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 scored polyethylene fiber has a diameter of 24 μm, a length of 12 mm, and a longitudinal score on the surface;

[0045] Preferably, the carbon fiber is 6mm chopped 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 not exceeding 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 the island-reef modified coral aggregate UHPC, comprising:

[0048] (1) All components of UHPC, except mixing water, stainless steel fiber, scored polyethylene fiber, carbon fiber and carbon nanotubes, are mixed uniformly according to the mass ratio;

[0049] (2) Add mixing water and continue to stir evenly to obtain UHPC slurry;

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

[0051] The present invention also provides an island reef prefabricated component based on the island reef modified coral aggregate UHPC, and the island reef prefabricated component includes a fish reef and an offshore platform.

[0052] The beneficial effects of the present invention compared with the prior art include at least:

[0053] (1) Self-compacting. First, the present invention first modifies the coral aggregate according to its loose, porous and easy to absorb water characteristics. Using the negative pressure environment formed by the vacuum mixer, the slurry formed by mixing cement, ion migration inhibitor and mixing water is filled into the pores of the coral aggregate and evenly wrapped on the surface of the coral aggregate to form relatively regular spherical particles to obtain modified coral aggregate, so as to reduce the absorption of mixing water by the coral aggregate during the mixing process and reduce the decrease in fluidity caused by the irregular shape of the coral aggregate; secondly, in the preparation process, by wrapping the surface of the modified coral aggregate with a hydrophobic clean slurry film, its effect on the fluidity of UHPC is further reduced; thirdly, among the ion migration inhibitors used in the present invention, the hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microspheres and hydrophobically modified silica fume are all treated with hydrophobic modification, the water demand is reduced, and the fluidity of UHPC is further improved; fourthly, the present invention uses a high-efficiency polycarboxylic acid water reducer with a water reduction rate of more than 40%, and the fluidity of UHPC is further improved.

[0054] (2) High strength. First, by modifying the coral aggregate, the slurry is filled into the pores of the coral aggregate and then continues to hydrate and harden, so that the strength of UHPC is greatly enhanced. The grading is designed, the stacking is tight, and the aggregate support effect is strong. Secondly, the present invention uses a mixture of stainless steel fiber, notched polyethylene fiber and carbon fiber, which can effectively improve the mechanical properties of UHPC. Thirdly, the ion migration inhibitor used in the present invention improves the strength after hardening through the principle of the most dense stacking, and the ion migration inhibitor has a secondary hydration effect. The hydration product gradually fills the internal pores of UHPC, further improving the long-term strength of UHPC.

[0055] (3) High toughness. The stainless steel fiber, ultra-high molecular weight notched polyethylene fiber and carbon fiber used in the present 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 performance. The ultra-high molecular weight notched 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 rubber powder is dissolved in the mixing water can improve the UHPC microstructure at the nano level, further improving the toughness of UHPC.

[0056] (4) High durability. First, the ion migration inhibitor used in the present invention can inhibit Cl - , SO4 2- ,Mg + Harmful ions migrate and Al is dissolved during the UHPC hardening process. 3+ions, avoiding the dissolution of hydration products in the UHPC matrix, and the secondary hydration of the ion migration inhibitor makes the UHPC matrix more compact and improves durability; secondly, the present invention uses modified coral aggregates, which greatly improves the compactness of the UHPC matrix after hardening, and at the same time can block the infiltration of harmful ions in the coral aggregates, thereby improving durability; thirdly, the cement used in the present invention can effectively prevent the corrosion of harmful substances such as acids and alkalis by reasonably compounding aluminate cement, sulphoaluminate cement, and ferroaluminate cement, thereby improving durability. For example, the hydration of C3A (tricalcium aluminate) and C4A (tetracalcium aluminate) in aluminate cement can form stable compounds to resist sulfate corrosion; fourthly, the present invention uses a combined expansion agent to keep UHPC in a micro-expansion state at all times, effectively preventing its shrinkage and cracking, avoiding the formation of channels for harmful ions to enter the matrix, and further improving the durability of UHPC.

[0057] (5) High electromagnetic shielding. First, the UHPC prepared by the present invention has a dense base material structure, and the core part of the coral aggregate retains some pores. It has excellent mechanical properties and enhanced impedance matching, which is conducive to the incidence of electromagnetic waves. The internal attenuation path of electromagnetic waves increases, and the electromagnetic shielding is higher than that of ordinary ultra-high performance concrete. Second, the present invention uses stainless steel fiber, carbon fiber hybrid and carbon nanotubes, which have the effect of double 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 utilization rate. The present invention combines the current situation of island and reef engineering construction, and uses local materials to crush and screen coral reef plates to obtain coral aggregates instead of traditional aggregates such as quartz sand and river sand. Seawater can be used for mixing, which saves transportation and raw material costs, saves economic costs, and can effectively 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 multiple or all of the above-mentioned beneficial effects must be possessed or achieved at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0061] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment in size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0062] Figure 1 A schematic diagram of a coral aggregate raw material modification process of the present invention is shown as an example;

[0063] Figure 2 The following is an exemplary illustration of the microscopic morphology comparison of the scoring of a polyethylene fiber of the present invention, wherein: (a) is an unscored polyethylene fiber, and (b) is a scored polyethylene fiber;

[0064] Figure 3 The schematic diagram of the process of preparing a modified coral aggregate UHPC of the present invention is shown as an example;

[0065] Figure 4 The schematic diagram of the overall structure of a modified coral aggregate UHPC preform (fish reef) of the present invention is exemplified;

[0066] Figure 4A Exemplary illustration Figure 4 The main view of

[0067] Figure 4B Exemplary illustration Figure 4 Side view of

[0068] Figure 4C Exemplary illustration Figure 4 A top view of

[0069] Figure 5 A schematic diagram of a modified coral aggregate UHPC preform (offshore platform) of the present invention is shown as an example;

[0070] Figure 5A Exemplary illustration Figure 5 Side view of

[0071] Figure 5B Exemplary illustration Figure 5 Top view of the .

[0072] In the various drawings, the same or corresponding reference numerals represent the same or corresponding parts. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with the embodiments and drawings. Here, the illustrative embodiments of the present invention and their description are used to explain the present invention, but are not intended to limit the present invention.

[0074] It should be understood that the terms "include / comprise", "consist of..." or any other variations are intended to cover non-exclusive inclusion, so that a product, device, process or method that includes a series of elements includes not only those elements, but also may include other elements not explicitly listed when necessary, or also includes elements inherent to such product, device, process or method. In the absence of more restrictions, the elements defined by the sentence "include / comprise...", "consist of..." do not exclude the presence of other identical elements in the product, device, process or method that includes the elements.

[0075] The specific implementation and preferred scheme of the island and reef modified coral aggregate UHPC proposed by the present invention are described in detail below.

[0076] The present invention first provides a reef modified coral aggregate UHPC, which is mixed with the following raw materials by mass ratio: 30-50 parts of cement, 5-15 parts of ion migration inhibitor, 40-60 parts of modified coral aggregate, 3-7 parts of stainless steel fiber, 0.4-0.8 parts of scored polyethylene fiber, 0.3-0.7 parts of water reducer, 0.5-1.5 parts of rubber powder, 0.05-0.15 parts of defoamer, 1-3 parts of combined expansion agent, 0.5-1.5 parts of early strength agent, 0.1-0.2 parts of carbon fiber, 0.05-0.1 parts of carbon nanotubes, and 9-12 parts of mixing water. The UHPC prepared by the present invention is made of local materials, has self-compacting, high strength, high toughness, high durability, and high electromagnetic shielding. The UHPC prefabricated fish reefs and offshore platforms prepared thereby meet the construction and use requirements of reef engineering.

[0077] In some embodiments, the cement is preferably one or more combinations of Portland cement, ordinary Portland cement, sulphoaluminate cement, ferroaluminate cement and aluminate cement. The cement used in the present invention can effectively prevent corrosion by harmful substances such as acids and alkalis and improve durability by reasonably compounding aluminate cement, sulphoaluminate cement and ferroaluminate cement. For example, C3A (tricalcium aluminate) and C4A (tetracalcium aluminate) in aluminate cement can form stable compounds after hydration to resist sulfate corrosion.

[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 m 2 / kg, Al2O3 content is greater than 15%; the specific surface area of ​​hydrophobic modified glass microspheres is 3000~6000m 2 / kg, Al2O3 content is greater than 40%; the specific surface area of ​​hydrophobic modified silica fume is 20000~30000m 2 / kg, SiO2 content is greater than 95%.

[0080] The hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microbeads and hydrophobically modified silica fume in the present invention are all treated with hydrophobic modification, so that the water demand is reduced and the fluidity of UHPC is further improved.

[0081] Furthermore, the ion migration inhibitor of the present invention inhibits Cl - , SO4 2- ,Mg 2 + Harmful ions migrate and Al is dissolved during the UHPC hardening process. 3+ Ions avoid the dissolution of hydration products in the UHPC matrix. The secondary hydration of the ion migration inhibitor makes the UHPC matrix denser and more durable. In addition, through the principle of the closest stacking, the strength of UHPC is improved after hardening, and the ion migration inhibitor has a secondary hydration effect. The hydration products gradually fill the internal pores of UHPC, further improving the long-term strength of UHPC.

[0082] In some embodiments, the raw material of the modified coral aggregate is obtained by crushing, ball milling and screening coral reef discs, and its maximum particle size is 1.25 mm. The mass proportion of each particle size range is: 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, the present invention first modifies the coral aggregate raw material before material preparation, that is, the prepared continuous graded coral aggregate raw material with a particle size of 0.04 mm to 1.25 mm is modified. This is a pre-process for material preparation. Figure 1 As shown, the modification method 100 includes the following steps:

[0084] In block 101, cement, ion migration inhibitor and mixing water are separately taken, and the continuously graded coral aggregate raw material, cement, ion migration inhibitor and mixing water are added into a 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 taken at this time have nothing to do with the main material of the prepared material, and are materials taken separately for the modification needs, and the specific amount taken is based on the coral aggregate raw material and added in proportion;

[0085] In block 102, the vacuum mixer is turned on, and the mixture is stirred for 3 to 5 minutes with the vacuum pump turned off, wherein the low-speed stirring (960 to 1200 r / h) is for 1 to 2 minutes, and the high-speed stirring (7200 to 12000 r / h) is for 2 to 3 minutes. When the mixture is fully stirred, the stirring is stopped;

[0086] In block 103, the vacuum pump is turned on to evacuate the inside of the device to 5% to 10% of the atmospheric pressure, and high-speed stirring (7200 to 12000 r / h) is performed for 3 to 5 minutes. When the surface of the coral aggregate is fully coated by the cement slurry and relatively regular spherical particles are formed, stirring is stopped;

[0087] In block 104, the mixed material is taken out and evenly spread and air-dried for 24 hours, during which the mixed material is periodically vibrated using a high-frequency vibration table to prevent adhesion and affect the uniformity of the modified coral aggregate;

[0088] In block 105, the dried mixed material is taken and sieved with a sieve, and the target coral aggregate with a particle size range of 0.04 mm to 1.25 mm is the prepared modified coral aggregate.

[0089] The present invention first modifies the coral aggregates for their looseness, porosity and easy water absorption. The principle of the modification method is to use negative pressure to absorb cement paste, which is different from ordinary immersion or granulation, so that the cement paste hardens and strengthens. Specifically, a negative pressure environment is formed by using a vacuum mixer to fill the slurry made by mixing cement, ion migration inhibitor and mixing water into the pores of the coral aggregates, and evenly wrap it on the surface of the coral aggregates to form relatively regular spherical particles, so as to reduce the absorption of mixing water by the coral aggregates during the mixing process, and reduce the decrease in fluidity caused by the irregular shape of the coral aggregates. Secondly, during the preparation process, by wrapping a hydrophobic net slurry film on the surface of the modified coral aggregate, its effect on the fluidity of UHPC is further reduced, thereby obtaining a large flow state. Moreover, after the slurry is filled into the pores of the coral aggregates, it continues to hydrate and harden, and the strength of the coral aggregates is greatly enhanced. The grading is designed, the stacking is tight, and the aggregate support effect is strong, thereby obtaining high strength. In addition, through the modification of the coral aggregates, the density of the matrix after hardening of the UHPC is greatly improved, and the durability is improved.

[0090] In some embodiments, the water reducer is an early-strength high-efficiency polycarboxylic acid water reducer with a water reduction rate greater than 40%, which can further improve the fluidity of UHPC.

[0091] In some embodiments, the rubber powder is one or both of vinyl acetate and ethylene copolymer. The rubber powder is dissolved in the mixing water to form a nanoemulsion, which can improve the microstructure of UHPC at the nano level and increase the flexural strength of UHPC, thereby obtaining high strength.

[0092] In some embodiments, the defoamer is one or both of a powdered silicone defoamer and a polyether defoamer. The defoamer can effectively reduce the introduction of bubbles during the mixing process of high-performance cement-based UHPC preparation, making the UHPC denser after hardening, and further effectively improving the strength.

[0093] It should be noted that the present invention uses a combined expansion agent to keep UHPC in a micro-expanded state at all times, effectively preventing its shrinkage and cracking, avoiding the formation of channels for harmful ions to enter the interior of the matrix, and further improving the durability of UHPC.

[0094] In some embodiments, stainless steel fiber is added, with a diameter of 0.22 mm and a length of 12 mm; notched polyethylene fiber is added, with a diameter of 24 μm, a length of 12 mm, and longitudinal notches on the surface; carbon fiber is added as 6 mm short-cut carbon fiber with a tensile strength of not less than 3 GPa; and carbon nanotubes are added as multi-walled carbon nanotubes with an outer diameter of no more than 8 nm, an inner diameter of 2 to 5 nm, and a length of 0.5 to 2 μm. First, the use of stainless steel fiber, notched polyethylene fiber and carbon fiber mixed can effectively improve the mechanical properties of coral aggregate UHPC, such as Figure 2 As shown in the figure, the comparison of microscopic pictures shows that the notch increases the surface area of ​​the polyethylene fiber, which has stronger adhesion to the cement stone and better strengthening and toughening effect; secondly, the stainless steel fiber, ultra-high molecular weight notched polyethylene fiber and carbon fiber can play a positive synergistic role after being mixed. The stainless steel fiber has extremely high strength and stiffness, which can improve the compressive performance. The ultra-high molecular weight notched polyethylene fiber has high strength properties and can significantly improve the crack resistance of concrete; and the use of stainless steel fiber, carbon fiber hybrid and carbon nanotube mixture 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.

[0095] In some embodiments, the mixing water is one or more of seawater, desalinated seawater, fresh water, and rainwater naturally collected from the roof of island and reef buildings. In the present invention, the mixing water is obtained locally, saving the cost of transportation and raw materials.

[0096] Example 1

[0097] 40 parts of cement, 10 parts of ion migration inhibitor, 50 parts of modified coral aggregate, 5 parts of stainless steel fiber, 0.6 parts of scored polyethylene fiber, 0.15 parts of carbon fiber, 0.1 parts of carbon nanotubes, 0.5 parts of water reducer, 1 part of rubber powder, 0.1 parts of defoamer, 2 parts of combined expansion agent, 1 part of early strength agent, and 10 parts of 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; the combined expansive agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansive agent and 50% magnesium oxide expansive agent.

[0099] Example 2

[0100] 30 parts of cement, 10 parts of ion migration inhibitor, 60 parts of modified coral aggregate, 3 parts of stainless steel fiber, 0.4 parts of scored polyethylene fiber, 0.1 parts of carbon fiber, 0.07 parts of carbon nanotubes, 0.3 parts of water reducer, 1 part of rubber powder, 0.1 parts of defoamer, 1.5 parts of combined expansion agent, 1 part of early strength agent, and 9 parts of 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; the combined expansive agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansive agent and 50% magnesium oxide expansive agent.

[0102] Example 3

[0103] 50 parts of cement, 10 parts of ion migration inhibitor, 40 parts of modified coral aggregate, 7 parts of stainless steel fiber, 0.8 parts of scored polyethylene fiber, 0.2 parts of carbon fiber, 0.1 parts of carbon nanotubes, 0.7 parts of water reducer, 1 part of rubber powder, 0.12 parts of defoamer, 2.5 parts of combined expansion agent, 1 part of early strength agent, and 12 parts of 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; the combined expansive agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansive agent and 50% magnesium oxide expansive agent.

[0105] Comparative Example 1

[0106] 40 parts of cement, 10 parts of ion migration inhibitor, 50 parts of coral aggregate, 5 parts of stainless steel fiber, 0.6 parts of scored polyethylene fiber, 0.15 parts of carbon fiber, 0.1 parts of carbon nanotubes, 0.5 parts of water reducer, 1 part of rubber powder, 0.1 parts of defoamer, 2 parts of combined expansion agent, 1 part of early strength agent, and 10 parts of 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; the combined expansive agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansive agent and 50% magnesium oxide expansive agent.

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

[0109] Comparative Example 2

[0110] 40 parts of cement, 10 parts of ion migration inhibitor, 50 parts of modified coral aggregate, 5 parts of stainless steel fiber, 0.6 parts of scored polyethylene fiber, 0.5 parts of water reducer, 1 part of rubber powder, 0.1 parts of defoamer, 2 parts of combined expansion agent, 1 part of early strength agent, and 10 parts of 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; the combined expansive agent consists of 50% calcium oxide-calcium sulfoaluminate composite expansive agent and 50% magnesium oxide expansive agent.

[0112] The difference between this comparative example and the present invention is that no carbon fiber and carbon nanotube are used.

[0113] After testing, the properties of modified coral aggregate UHPC are shown in Table 1.

[0114] Table 1 UHPC performance of each case

[0115]

[0116] Note: The electromagnetic shielding effectiveness refers to the provisions of GJB 6190-2008 "Test Method for Shielding Effectiveness of Electromagnetic Shielding Materials" and uses the shielding room window method. The test frequency is 2GHz.

[0117] As can be seen from Table 1, the modified coral aggregate UHPC for islands and reefs provided by the present invention has excellent mechanical properties, a 28d compressive strength of more than 125MPa, a 28d flexural strength of more than 20MPa, and high strength and high toughness characteristics; the expansion is not less than 700mm, and it has high self-compacting characteristics; the electric flux basically does not exceed 70C, the sulfate corrosion resistance is not less than KS120, the impermeability is not less than P30, and it has high durability characteristics. From the electric flux of comparative example 1 of 231.6C, it can be seen that the unmodified coral aggregate leads to increased internal pores, large ion permeability, and very poor durability; the electromagnetic shielding effectiveness is all above 40dB, and it has high electromagnetic shielding properties, indicating that the modified coral aggregate UHPC provided by the present invention meets the strength requirements while having the characteristics of self-compacting, high durability and high electromagnetic shielding properties, and can be made from local materials, and is suitable for island and reef engineering construction.

[0118] The present invention also provides a method for preparing modified coral aggregate UHPC, such as Figure 3 As shown, including:

[0119] In block 201, firstly, the powder is mixed, that is, each component of UHPC, except mixing water, stainless steel fiber, scored polyethylene fiber, carbon fiber and carbon nanotube is mixed uniformly according to the mass ratio;

[0120] In block 202, water is then added to prepare a slurry, i.e., mixing water is added and continued to be stirred evenly to obtain a UHPC slurry;

[0121] In frame 203, various fibers are finally added, namely, stainless steel fibers, scored polyethylene fibers, carbon fibers and carbon nanotubes, and stirring is continued until the fibers are evenly dispersed, thus obtaining modified coral aggregate UHPC.

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

[0123] like Figure 4 , 4A , 4B, 4C, and Figure 5 , 5AAs shown in Figure 5B, a UHPC prefabricated part made of the modified coral aggregate UHPC provided by the present invention is shown. Taking fish reefs and offshore platforms as examples, the main structure of the fish reef is composed of prefabricated UHPC panels and prefabricated UHPC bottom plates. The fish reef is triangular in shape from the side, which can improve the stability of the structure, and the diamond holes on the panel can effectively reduce the impact force of water. Since the fish reef is in a seawater environment, this prefabricated fish reef is designed to have high durability, high strength, high toughness, high electromagnetic shielding, and high local material rate by adjusting the properties of raw materials in response to the corrosiveness of seawater. The fish reef prefabricated part can serve for a long time in my country's tropical island and reef environment. The offshore platform is mainly composed of a deck, a buoy, and an anchor cable. The deck is composed of a certain amount of modified coral aggregate UHPC prefabricated panels spliced ​​together by steel bars or bolts. A hole of a certain size should be reserved at the bottom of the deck to facilitate connection with the buoy. The buoy provides support by storing seawater inside, but because the buoy is light and easily pushed away by waves, anchor cables are added around the buoy to secure it.

[0124] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

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

Claims

1. A reef modified coral aggregate UHPC, characterized in that: The following raw materials are mixed according to mass ratio: Cement, 30-50 parts; Modified coral aggregate, 40-60 parts; Ion migration inhibitor, 5-15 parts; Stainless steel fiber, 3-7 parts; Scored 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; Defoaming agent, 0.05~0.15 parts; Combined expansion agent, 1 to 3 parts; Early strength agent, 0.5~1.5 parts; Mix with water, 9~12 parts.

2. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that: The cement is one or more of Portland cement, ordinary Portland cement, sulphoaluminate cement, ferroaluminate cement and aluminate cement; The mixing water is one or more of seawater, desalinated seawater, fresh water, and rainwater naturally collected from the roofs of island and reef buildings.

3. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that: The ion migration inhibitor is one or more of hydrophobically modified ultrafine high-alumina slag powder, hydrophobically modified glass microbeads, and hydrophobically modified silica fume.

4. The island and reef modified coral aggregate UHPC according to claim 3, characterized in that: The specific surface area of ​​the hydrophobically modified ultrafine high-alumina slag powder is 1000-2500m 2 / kg; The specific surface area of ​​the hydrophobically modified glass microspheres is 3000-6000 m 2 / kg; The specific surface area of ​​the hydrophobically modified silica fume is 20000-30000m 2 / kg.

5. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that: The raw materials of the modified coral aggregate are obtained by crushing, ball milling and screening coral reef discs, and the maximum particle size is 1.25 mm. The mass proportion of each particle size range is: 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%.

6. The island and reef modified coral aggregate UHPC according to claim 5, characterized in that: The obtained continuously graded coral aggregate raw material with a particle size of 0.04 mm to 1.25 mm is modified as follows: (1) Separately take cement, ion migration inhibitor and mixing water, and put the continuously 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 turned off, stirring at a low speed of 960 to 1200 r / h for 1 to 2 minutes and at a high speed of 7200 to 12000 r / h for 2 to 3 minutes. Stop stirring when the mixture is fully mixed; (3) Turn on the vacuum pump and evacuate the device to 5% to 10% of atmospheric pressure. Stir at a high speed of 7200 to 12000 r / h for 3 to 5 minutes. When the surface of the coral aggregate is fully coated by the cement slurry and relatively regular spherical particles are formed, stop stirring. (4) Take out the mixture and spread it evenly and dry it in the sun for 24 hours. During this period, use a high-frequency vibration table to vibrate the mixture regularly to prevent it from sticking and affecting the uniformity of the modified coral aggregate; (5) The dried mixture is screened with a sieve to obtain the target coral aggregate with a particle size range of 0.04 mm to 1.25 mm, which is the prepared modified coral aggregate.

7. The island and reef modified coral aggregate UHPC according to claim 1, characterized in that: The water reducer is an early strength high efficiency polycarboxylate water reducer; The rubber powder is one or two of vinyl acetate and ethylene copolymer; The defoamer is one or both of a powdered silicone defoamer and a polyether defoamer; The combined expansion agent is one or more of a plastic expansion agent, a calcium oxide expansion agent, a calcium sulfoaluminate expansion agent, a magnesium oxide expansion agent, and a calcium oxide-calcium sulfoaluminate composite expansion agent; The early strength agent is one or more of calcium formate, sodium aluminate, anhydrous sodium sulfate and sodium carbonate.

8. 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; The scored polyethylene fiber has a diameter of 24 μm, a length of 12 mm, and a longitudinal score on the surface; The carbon fiber is 6mm short chopped carbon fiber with a tensile strength of not less than 3GPa; 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.

9. A method for preparing the island-reef modified coral aggregate UHPC according to any one of claims 1 to 8, comprising: (1) All components of UHPC, except mixing water, stainless steel fiber, scored polyethylene fiber, carbon fiber and carbon nanotubes, are mixed uniformly according to the mass ratio; (2) Add mixing water and continue to stir evenly to obtain UHPC slurry; (3) Finally, stainless steel fiber, notched polyethylene fiber, carbon fiber and carbon nanotube are added, and stirring is continued until the fibers are evenly dispersed, thereby obtaining the modified coral aggregate UHPC.

10. An island reef prefabricated component of the island reef modified coral aggregate UHPC according to any one of claims 1 to 8, wherein the island reef prefabricated component comprises a fish reef and an offshore platform.

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