A basic magnesium sulfate cement coral concrete for island and reef engineering and its preparation process

Abstract

The application discloses an atoll engineering alkali magnesium sulfate cement coral concrete and a preparation process thereof, and belongs to the technical field of building engineering materials. The concrete formula comprises, in parts by mass, cementing material 560-1085 parts, coral sand fine aggregate 380-1060 parts, coral coarse aggregate 163-454 parts, mixing water 186-307 parts and naphthalene-based high-efficiency water reducing agent 11-28 parts. The cementing material is made of light-burned magnesia, magnesium sulfate pentahydrate, additive and active mineral admixture. The active mineral admixture is a mixture of coral micro powder and granulated blast furnace slag micro powder or fly ash. The application has the advantages of effectively reducing construction cost and engineering period, fast hardening and early strength, good mechanical property, low steel corrosion rate, zero expansion and zero shrinkage, and low cracking probability.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and relates to a concrete material, particularly to a basic magnesium sulfate cement coral concrete for island and reef engineering and its preparation process. Background Technology

[0002] The South China Sea is rich in marine resources. In the construction of island and reef projects, developed countries such as France, the Netherlands and Japan have developed special cement-based materials for marine engineering by using mineral materials such as high-volume slag and fly ash. In recent years, my country has also carried out a lot of research on cementitious materials for marine engineering. Most of them are prepared by composite methods of silicate cement clinker with high-volume slag powder, fly ash, bottom slag and a small amount of silica fume and modified metakaolin.

[0003] Basic magnesium sulfate cement is a novel magnesium-based cementitious material developed based on research into magnesium oxychloride cement and magnesium oxysulfate cement. Its hydration product, the 517 crystal phase structure, endows it with the advantages of magnesium oxychloride cement (lightweight, rapid setting, low alkali, and wear resistance) and magnesium oxysulfate cement (non-hygroscopic and efflorescence-resistant, and less prone to corroding reinforcing steel). Furthermore, basic magnesium sulfate cement is a high-strength, high-performance cement material with durability and reinforcement protection comparable to ordinary Portland cement, demonstrating promising application prospects.

[0004] However, in practical engineering applications, the islands and reefs in the South China Sea are far from the mainland and lack conventional building materials. If these materials are transported by ship from the distant mainland, transportation costs will increase significantly. Moreover, the sea transport process is also affected by natural conditions such as typhoons and waves, making it difficult to control the construction period. How to solve the problem of sourcing building materials and controlling construction costs are urgent issues that need to be addressed in the construction of islands and reefs in the South China Sea. The performance of concrete directly affects the durability and service life of concrete structures in marine environments. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a basic magnesium sulfate cement coral concrete for island and reef engineering and its preparation process. This basic magnesium sulfate cement coral concrete for island and reef engineering uses coral reef sand, which is abundant on islands and reefs in the South China Sea, as the main raw material. This not only expands the land space of islands and reefs in the South China Sea and saves the cost of marine construction materials, but also produces a basic magnesium sulfate cement coral concrete suitable for atmospheric island and reef engineering. This will help promote its application in the field of island and reef engineering in the South China Sea and is in line with the engineering background of using local materials in island and reef engineering in the South China Sea.

[0006] To achieve the above objectives, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, characterized in that its formula comprises, by mass parts: 560-1085 parts of cementitious material, 380-1060 parts of coral sand fine aggregate, 163-454 parts of coral coarse aggregate, 186-307 parts of mixing water, and 11-28 parts of naphthalene-based high-efficiency water-reducing agent; the cementitious material is made of lightly calcined magnesium oxide, magnesium sulfate pentahydrate (MgSO4·5H2O), admixtures, and active mineral admixtures, wherein the active mineral admixtures are a mixture of coral micro powder and granulated blast furnace slag micro powder or fly ash.

[0007] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following feature: wherein the admixture in the cementitious material is aminotrimethylene phosphonic acid (ATMP).

[0008] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein the proportions of each component of the cementitious material are: 230-620 parts of lightly calcined magnesium oxide, 78-181 parts of magnesium sulfate pentahydrate, 2-15 parts of admixture, 60-345 parts of coral powder, 60-210 parts of granulated blast furnace slag powder or 120-350 parts of fly ash.

[0009] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein, in the cementitious material, the light-burned magnesium oxide is one or both of magnesite light-burned powder and dolomite light-burned powder, wherein the mass proportion of active MgO is not less than 50%; the magnesium sulfate pentahydrate is of industrial grade purity (more than 98%); and the admixture aminotrimethylene phosphonic acid has a purity of more than 90%.

[0010] Furthermore, this invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein, in the active mineral admixture of the cementitious material, the coral micropowder is made from coral reef sand through mechanical crushing and grinding, and the specific surface area of ​​the coral micropowder is ≥350m². 2 / kg, preferably ≥400m 2 / kg; Granulated blast furnace slag powder is S95 grade or higher, made from granulated blast furnace slag through mechanical crushing and grinding, with a specific surface area ≥350m². 2 / kg, preferably ≥400m 2 / kg; fly ash is grade II or above, dry-discharged fly ash or made from fly ash slag through mechanical crushing and grinding, and the specific surface area of ​​fly ash is ≥350m². 2 / kg, preferably ≥400m 2 / kg.

[0011] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein the preparation method of the cementitious material is as follows: first, each component is ground and prepared, then lightly calcined magnesium oxide and magnesium sulfate pentahydrate are mixed, and then coral micro powder, granulated blast furnace slag micro powder or fly ash and admixtures are added in sequence to obtain the cementitious material.

[0012] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein the pentahydrate magnesium sulfate is individually ground using a cold grinding process, and the material temperature is controlled not to exceed 45°C during the grinding process.

[0013] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein the particle size of the coral coarse aggregate is 5-20mm; the coral sand fine aggregate and the coral coarse aggregate are pre-absorbed with water before use, and the pre-absorption rate is 5%.

[0014] Furthermore, the present invention provides a basic magnesium sulfate cement coral concrete for island and reef engineering, which may also have the following characteristics: wherein the mixing water is fresh water or desalinated seawater with a chloride ion content of <0.5g / L.

[0015] This invention also provides a preparation process for basic magnesium sulfate cement coral concrete for island and reef engineering, characterized by the following steps: Step 1, adding coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stirring for 1 minute to make them evenly mixed; Step 2, adding mixing water and water-reducing agent, stirring for 3 minutes to obtain the basic magnesium sulfate cement coral concrete for island and reef engineering.

[0016] The beneficial effects of this invention are as follows:

[0017] I. This invention adopts the principle of "using local materials" and uses coral powder as a mixture to prepare island and reef cement without damaging the ecological environment of the islands and reefs. Using it to prepare basic magnesium sulfate cement coral concrete can not only solve the problem of raw material source, but also effectively reduce construction costs and project cycle, accelerate the development process of islands and reefs in the South China Sea, and is of great significance to the construction and repair of concrete projects and military protection projects on islands and reefs.

[0018] II. The basic magnesium sulfate cement coral concrete for island and reef engineering prepared by this invention has the characteristics of rapid hardening and early strength. Specifically, the main components of basic magnesium sulfate cement are magnesium oxide and magnesium sulfate heptahydrate. Compared with the silicate components in ordinary cement, it reacts more easily with water, has a shorter hydration time, and can promote the rapid hardening of concrete. Coral micropowder is used to replace part of the cementitious materials, providing nucleation sites for hydration products. The hydration products generate a 5·1·7 crystal phase, which grows interlocked and has stable properties, giving the concrete better mechanical properties.

[0019] III. The basic magnesium sulfate cement coral concrete for island and reef engineering prepared by this invention can effectively reduce the corrosion rate of reinforcing steel and improve structural durability, thereby ensuring long-term engineering quality. Specifically, the chemical and filling effects of coral micropowder in basic magnesium sulfate cement coral concrete can optimize the pore structure and reduce the gas content in the concrete at a low replacement level (5%). The composition of coral micropowder is similar to that of limestone, and it dissolves in water to produce hydroxide ions, which helps maintain the alkaline environment of the concrete. The corrosion rate of reinforcing steel is usually affected by the pH value of the concrete, and a higher pH value helps to slow down the corrosion process of the reinforcing steel. The hydration products in the concrete contain magnesium sulfate, and these compounds can react chemically with the surface of the reinforcing steel to form a protective magnesium oxide film. This film helps to prevent oxygen and water from further contacting the reinforcing steel, thereby inhibiting further corrosion of the reinforcing steel.

[0020] IV. The basic magnesium sulfate cement coral concrete for island and reef engineering prepared by this invention has the characteristics of early shrinkage, slight expansion after seven days, and stability after 14 days, with zero overall expansion and zero shrinkage, and is not prone to cracking. Specifically, basic magnesium sulfate cement has a relatively low heat of hydration during the reaction. High-temperature hydration reaction may cause the concrete to expand rapidly in the early stage, resulting in large shrinkage. Low-temperature hydration helps to reduce the early shrinkage of concrete. The hydration products of basic magnesium sulfate cement have a small volume and stable properties, and are not prone to volume change, thereby reducing shrinkage caused by volume change of hydration products. Using coral micropowder to replace part of the cementitious material can reduce the water-cement ratio and the number of internal pores in the concrete. At the same time, it forms a continuous particle size distribution together with coral sand fine aggregate and coral coarse aggregate, ensuring the stability of the concrete volume. Attached Figure Description

[0021] Figure 1 This is the XRD pattern of coral micropowder;

[0022] Figure 2 It is the XRD pattern of granulated blast furnace slag;

[0023] Figure 3 It is the XRD pattern of fly ash;

[0024] Figure 4 It is a chromatogram of the hydration products of cementitious materials;

[0025] Figure 5 It has a 517 whisker-reinforced structure;

[0026] Figure 6 It is the development of compressive strength of basic magnesium sulfate cement coral concrete (mixed with granulated blast furnace slag and coral powder) for island and reef engineering;

[0027] Figure 7It is the development of compressive strength of basic magnesium sulfate cement coral concrete (mixed with fly ash and coral powder) for island and reef engineering;

[0028] Figure 8 The graph shows the corrosion current density test results of concrete prepared with different contents of coral powder (comparative examples and examples 3, 5, and 7). Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] Example 1

[0031] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add fresh water and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0032] The cementitious material is composed of 230 parts lightly calcined magnesia, 105 parts magnesium sulfate pentahydrate, 5 parts aminotrimethylenephosphonic acid, 70 parts coral reef powder, and 150 parts granulated blast furnace slag powder. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and granulated blast furnace slag separately to achieve a specific surface area ≥400 m². 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, and the material temperature is controlled not to exceed 45℃ during the grinding process; the ground light calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and granulated blast furnace slag micro powder containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0033] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used for island and reef engineering, mixed and cured with fresh water, are as follows:

[0034] Table 1. Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C30

[0035]

[0036]

[0037] Example 2

[0038] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add fresh water and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0039] The cementitious material is composed of 460 parts of lightly calcined magnesia, 114 parts of magnesium sulfate pentahydrate, 6 parts of aminotrimethylenephosphonic acid, 120 parts of coral reef powder, and 60 parts of granulated blast furnace slag powder. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and granulated blast furnace slag separately to achieve a specific surface area of ​​420 m². 2 / kg and 380m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, and the material temperature is controlled not to exceed 45℃ during the grinding process; the ground light calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and granulated blast furnace slag micro powder containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0040] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used for island and reef engineering, mixed and cured with fresh water, are as follows:

[0041] Table 2. Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C55

[0042]

[0043] Example 3

[0044] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add desalinated seawater (chloride ion content <0.5g / L) and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0045] The cementitious material is composed of 620 parts of lightly calcined magnesia, 165 parts of magnesium sulfate pentahydrate, 5 parts of aminotrimethylenephosphonic acid, 120 parts of coral reef powder, and 90 parts of granulated blast furnace slag powder. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and granulated blast furnace slag to obtain a specific surface area of ​​390 m². 2 / kg and 430m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, and the material temperature is controlled not to exceed 45℃ during the grinding process; the ground light calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and granulated blast furnace slag micro powder containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0046] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used in island and reef engineering, mixed and cured with desalinated seawater, are as follows:

[0047] Table 3 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C50

[0048]

[0049] Example 4

[0050] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add desalinated seawater (chloride ion content <0.5g / L) and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0051] The cementitious material is composed of 490 parts lightly calcined magnesia, 155 parts magnesium sulfate pentahydrate, 15 parts aminotrimethylenephosphonic acid, 180 parts coral reef powder, and 90 parts granulated blast furnace slag powder. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and granulated blast furnace slag separately to achieve a specific surface area of ​​400 m². 2 / kg and 440m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, and the material temperature is controlled not to exceed 45℃ during the grinding process; the ground light calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and granulated blast furnace slag micro powder containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0052] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used in island and reef engineering, mixed and cured with desalinated seawater, are as follows:

[0053] Table 4. Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C60

[0054]

[0055] Example 5

[0056] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add fresh water and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0057] The cementitious material is composed of 580 parts of lightly calcined magnesia, 181 parts of magnesium sulfate pentahydrate, 9 parts of aminotrimethylenephosphonic acid, 105 parts of coral reef powder, and 210 parts of granulated blast furnace slag powder. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and granulated blast furnace slag separately to achieve a specific surface area ≥400 m². 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, and the material temperature is controlled not to exceed 45℃ during the grinding process; the ground light calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and granulated blast furnace slag micro powder containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0058] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used for island and reef engineering, mixed and cured with fresh water, are as follows:

[0059] Table 5 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C40

[0060]

[0061] Example 6

[0062] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add fresh water and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0063] The cementitious material is composed of 550 parts lightly calcined magnesium oxide, 146 parts magnesium sulfate pentahydrate, 4 parts aminotrimethylenephosphonic acid, 150 parts coral micropowder, and 150 parts fly ash. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and fly ash to achieve a specific surface area of ​​410 m². 2 / kg and 440m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, controlling the material temperature to not exceed 45℃ during the grinding process; the ground lightly calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and fly ash containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0064] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used for island and reef engineering, mixed and cured with fresh water, are as follows:

[0065] Table 6 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C40

[0066]

[0067] Example 7

[0068] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add desalinated seawater (chloride ion content <0.5g / L) and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0069] The cementitious material is composed of 370 parts lightly calcined magnesium oxide, 174 parts magnesium sulfate pentahydrate, 4 parts aminotrimethylenephosphonic acid, 345 parts coral micropowder, and 105 parts fly ash. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and fly ash to achieve a specific surface area of ​​385 m². 2 / kg and 450m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, controlling the material temperature to not exceed 45℃ during the grinding process; the ground lightly calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and fly ash containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0070] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used in island and reef engineering, mixed and cured with desalinated seawater, are as follows:

[0071] Table 7 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C30

[0072]

[0073] Example 8

[0074] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add fresh water and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0075] The cementitious material is composed of 360 parts lightly calcined magnesium oxide, 136 parts magnesium sulfate pentahydrate, 4 parts aminotrimethylenephosphonic acid, 200 parts coral micropowder, and 300 parts fly ash. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and fly ash to achieve a specific surface area of ​​460 m². 2 / kg and 380m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, controlling the material temperature to not exceed 45℃ during the grinding process; the ground lightly calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and fly ash containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0076] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used for island and reef engineering, mixed and cured with fresh water, are as follows:

[0077] Table 8 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C30

[0078]

[0079] Example 9

[0080] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add desalinated seawater (chloride ion content <0.5g / L) and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0081] The cementitious material is composed of 330 parts lightly calcined magnesium oxide, 78 parts magnesium sulfate pentahydrate, 2 parts aminotrimethylenephosphonic acid, 200 parts coral micropowder, and 350 parts fly ash. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and fly ash to achieve a specific surface area of ​​490 m². 2 / kg and 420m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, controlling the material temperature to not exceed 45℃ during the grinding process; the ground lightly calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and fly ash containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0082] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used in island and reef engineering, mixed and cured with desalinated seawater, are as follows:

[0083] Table 9 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C40

[0084]

[0085]

[0086] Example 10

[0087] This embodiment provides a basic magnesium sulfate cement coral concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add desalinated seawater (chloride ion content <0.5g / L) and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes to obtain basic magnesium sulfate cement coral concrete for island and reef engineering.

[0088] The cementitious material is composed of 415 parts lightly calcined magnesium oxide, 120 parts magnesium sulfate pentahydrate, 5 parts aminotrimethylenephosphonic acid, 60 parts coral micropowder, and 120 parts fly ash. The preparation method involves crushing and grinding coral reef sand mixed with aminotrimethylenephosphonic acid and fly ash to achieve a specific surface area of ​​490 m². 2 / kg and 420m 2 / kg of micro powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, controlling the material temperature to not exceed 45℃ during the grinding process; the ground lightly calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then coral micro powder and fly ash containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0089] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used in island and reef engineering, mixed and cured with desalinated seawater, are as follows:

[0090] Table 10 Performance of Basic Magnesium Sulfate Cement Coral Concrete for Island and Reef Engineering with Strength Grade C50

[0091]

[0092] Comparative Example

[0093] This comparative example provides a basic magnesium sulfate cement concrete for island and reef engineering. The preparation process includes the following steps: Step 1: Add pre-absorbed coral sand fine aggregate, coral coarse aggregate and cementing material to a mixing pot and stir for 1 minute to make them evenly mixed; Step 2: Add desalinated seawater (chloride ion content <0.5g / L) and naphthalene-based high-efficiency water-reducing agent, stir for 3 minutes, and the basic magnesium sulfate cement concrete for island and reef engineering is obtained.

[0094] The cementitious material is composed of 450 parts lightly calcined magnesia, 120 parts magnesium sulfate pentahydrate, 5 parts aminotrimethylenephosphonic acid, 120 parts granulated blast furnace slag, and 120 parts fly ash. The preparation method involves crushing and grinding the granulated blast furnace slag and fly ash (with aminotrimethylenephosphonic acid added) to achieve a specific surface area of ​​430 m². 2 / kg and 400m 2 / kg of fine powder; then, magnesium sulfate pentahydrate is ground separately using a cold grinding process, controlling the material temperature to not exceed 45℃ during the grinding process; the ground lightly calcined magnesium oxide is mixed with magnesium sulfate pentahydrate, and then granulated blast furnace slag and fly ash containing aminotrimethylene phosphonic acid are added in sequence according to the formula ratio to obtain the cementitious material.

[0095] The physical and mechanical properties of basic magnesium sulfate cement coral concrete used in island and reef engineering, mixed and cured with desalinated seawater, are as follows:

[0096] Table 11 Performance of Basic Magnesium Sulfate Cement Concrete for Island and Reef Engineering with Strength Grade C40

[0097]

[0098] A comparison of the various embodiments shows that, after using coral powder, coral sand, and coral to prepare basic magnesium sulfate cement coral concrete for island and reef engineering, the strength grade can reach C30 and above. The concrete exhibits optimal mechanical properties when the coral powder content is 120-180 parts, meeting the technical requirements for strength grade in GB / T 50433-2014 "Technical Specification for Marine Engineering Concrete". Furthermore, this method makes significant use of the coral reef sand resources of the South China Sea islands and reefs, reducing overall raw material transportation costs and resulting in substantial economic benefits.

[0099] Furthermore, the current density is caused by the corrosion reaction of the steel reinforcement. Corrosion current density tests were conducted on concrete prepared with different contents of coral powder (comparative examples and Examples 3, 5, and 7), and the results are as follows: Figure 8 As shown, when the coral powder content is 5% (Example 3), the corrosion current density is the lowest, indicating that an appropriate amount of coral powder can effectively prevent the corrosion of steel bars in concrete.

[0100] The basic magnesium sulfate cement coral concrete for island and reef engineering prepared by this invention adopts the principle of "local material sourcing". It uses coral micro powder with calcium carbonate as the main component to replace part of the cementitious materials, and uses coral sand and coral as coarse and fine aggregates. It does not damage the island and reef ecological environment. While ensuring the original performance of the concrete, it solves the problem of the difficulty in the source of raw materials in the construction of ocean island and reef projects. Moreover, it can effectively reduce construction costs and project cycle, and accelerate the development process of ocean islands and reefs. It is of great significance for the construction and repair of concrete projects for island and reef projects, as well as military protection projects.

[0101] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0102] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An atoll engineering magnesium oxide hydroxide sulfate cement coral concrete, characterized in that: the formula comprises, in mass parts: cementing material 560-1085 parts, coral sand fine aggregate 380-1060 parts, coral coarse aggregate 163-454 parts, mixing water 186-307 parts, and naphthalene-based superplasticizer 11-28 parts; the cementing material is made of light-burned magnesia, magnesium sulfate pentahydrate, admixture, and active mineral admixture, the active mineral admixture is a mixture of coral micro-powder and granulated blast furnace slag micro-powder or fly ash, the admixture is amino-trimethylene phosphonic acid; the preparation method of the cementing material is: first, grinding each component to prepare, then mixing the light-burned magnesia with the magnesium sulfate pentahydrate, and then adding the coral micro-powder, the granulated blast furnace slag micro-powder or the fly ash, and the admixture in sequence to obtain the cementing material; the magnesium sulfate pentahydrate is finely ground by a cold grinding process, and the material temperature in the grinding process is controlled to be not more than 45 DEG C; the coral sand fine aggregate and the coral coarse aggregate are pre-absorbed before use, and the pre-absorption rate is 5%; the preparation process of the concrete comprises the following steps: step one, adding the coral sand fine aggregate, the coral coarse aggregate, and the cementing material into a mixing pot and stirring for 1 minute to make them uniformly mixed; step two, adding the mixing water and the superplasticizer and stirring for 3 minutes to obtain the atoll engineering magnesium oxide hydroxide sulfate cement coral concrete; the parts of each component of the cementing material are: light-burned magnesia 230-620 parts, magnesium sulfate pentahydrate 78-181 parts, admixture 2-15 parts, coral micro-powder 60-345 parts, granulated blast furnace slag micro-powder 60-210 parts, or fly ash 120-350 parts.

2. The atoll engineering magnesium oxide hydroxide sulfate cement coral concrete according to claim 1, characterized in that: in the cementing material, the light-burned magnesia is one or both of magnesite light-burned powder and dolomite light-burned powder, and the mass percentage of active MgO is not less than 50%; the magnesium sulfate pentahydrate is of industrial grade purity; and the purity of the admixture amino-trimethylene phosphonic acid is more than 90%.

3. The atoll engineering magnesium oxide hydroxide sulfate cement coral concrete according to claim 1, characterized in that:

4. The atoll engineering magnesium oxide hydroxide sulfate cement coral concrete according to claim 1, characterized in that: the particle size of the coral coarse aggregate is 5-20 mm.

5. The atoll engineering magnesium oxide hydroxide sulfate cement coral concrete according to claim 1, characterized in that: the mixing water is fresh water or desalinated seawater with a chloride ion content of <0.5 g / L. wherein ​ ​ ​ ​ wherein The coral micro powder is made from coral sand as raw material through mechanical crushing and grinding, and the specific surface area of the coral micro powder is ≥350 m 2 / kg. The granulated blast furnace slag micro-powder is S95 grade and above, which is made of granulated blast furnace slag through mechanical crushing and grinding, and the specific surface area of the granulated blast furnace slag micro-powder is ≥350 m 2 / kg. The fly ash is of the second level or above, dry fly ash or fly ash slag mechanically crushed and ground, the specific surface area of the fly ash is ≥350 m 2 / kg. ​ wherein ​ ​ wherein ​

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