Modified marine concrete and method for producing the same

Abstract

The application provides a modified marine concrete and a preparation method thereof, wherein metakaolin, nano-TiO2, graphene and fungal mycelium are used as admixtures, and the seawater and sea sand concrete is modified, so that the modified marine concrete can be used for marine structures. The application can be used for components susceptible to seawater corrosion in marine engineering, such as wave protection dikes, wall bodies and support structures of seaports and wharfs, and bridge piers of cross-sea bridges.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of concrete preparation, and particularly relates to a modified marine concrete and a preparation method thereof. BACKGROUND

[0002] River sand is a key raw material for preparing traditional concrete, but the overexploitation caused by large-scale infrastructure construction in the past few decades has led to the gradual depletion of river sand resources and the destruction of river ecosystems. At the same time, the scarcity of freshwater resources has become a global problem, especially in arid and semi-arid regions.

[0003] China has a long coastline and offshore territory, and seawater and sea sand, as abundant natural resources, can be "taken nearby", so they have potential applications in the preparation of concrete for marine construction (such as port, wharf and island structure). However, because seawater contains a large amount of salt ions (such as chloride, sulfate, sodium, potassium, calcium, magnesium, etc.) and organic matter, and sea sand also contains chloride ions and other impurities (such as feldspar, calcium, magnesium, mica, etc.), direct use will affect the durability and strength of marine concrete, especially increasing the alkali aggregate reaction and corroding the steel bars in the concrete. For example, the post-strength of concrete prepared directly using seawater and sea sand will decrease, because the salt ions such as chloride ions (Cl - ) and sulfate ions (SO4²⁻) in seawater will react with the hydration products of cement to generate expansive substances, and cause steel bar corrosion and expansion, leading to cracking of concrete. Although it promotes the development of early strength of concrete, it will reduce the strength and durability of concrete in the long run.

[0004] In addition, as a cement-based material, concrete has weak cracking resistance, seawater erosion resistance and wave impact resistance, which shortens the service life of marine concrete structures. Therefore, it is particularly important to modify the concrete prepared from seawater and sea sand to obtain a modified concrete that can be effectively used for marine structures.

[0005] Currently, the modification of seawater-sea sand concrete is mainly through the use of fly ash, silica fume or slag and other mineral admixtures to partially replace cement to generate additional hydration products to fill the pores, thereby improving the density of the concrete. Among them, fly ash has been widely used in concrete engineering, but the prepared concrete has low early strength and large drying shrinkage. Silica fume can fill the capillary pores in the concrete, thereby improving the density, impermeability and strength of the concrete, and improving the durability of the concrete. However, silica fume does not have the crystallization ability of cement, and there is a silica powder aggregation phenomenon in the cement slurry. At the same time, the addition of silica fume increases the water consumption and early shrinkage of the concrete. Slag is an industrial byproduct, and the use of slag in the preparation of concrete helps to reduce waste emissions and reduce dependence on natural resources. However, the early strength development of traditional slag concrete is slow, which is a limiting factor in engineering projects that require rapid construction or early demolding. In addition, traditional mineral admixtures such as fly ash have gradually reduced stock due to industrial upgrading. Finally, the above-mentioned traditional mineral admixtures have no obvious inhibitory effect on marine microbial corrosion. SUMMARY

[0006] The application provides a modified marine concrete and a preparation method thereof, which uses metakaolin, nano-TiO2, graphene and fungal mycelium (aspergillus, yeast, alternaria alternata and fusarium) as admixtures, and modifies seawater-sea sand concrete to prepare a modified marine concrete that can be used for marine structures.

[0007] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0008] A modified marine concrete, the mixing ratio of which is composed of the following raw materials in parts by weight: cement 460-600 parts, metakaolin 20-60 parts, nano-TiO2 2-6 parts, graphene 0.46-1 part, fungal mycelium encapsulated sodium alginate gel macro-spheres 0.46-1 part, sea sand 500-600 parts, crushed stone 1000-1200 parts, and seawater 235-245 parts.

[0009] The cement type is P.O 42.5-52.5, the density is 3100-3250 kg / m³, and the quality index must meet the requirements of “General Portland Cement (GB 175-2007)”; the metakaolin is a micron-sized powder, the main components of which are SiO2 and Al2O3, the contents of which are 52%-57% and 43%-48% respectively, and the metakaolin has high pozzolanic activity; the nano-TiO2 has a particle size of 10 nm, an anatase phase, a specific surface area of 75-95 m 2 / g, and a density of 3.8-4.2 g / cm 3; the mycelium is selected from one of Aspergillus, Saccharomycete, Alternaria alternata and Fusarium, to ensure the health and good activity of the mycelium; the graphene is single-layer graphene, with purity > 99%, thickness < 1 nm and particle size of 5-8 μm; the coarse aggregate is broken stone with size of 5-20 mm, continuous gradation, apparent density of 2600-2800 kg / m³ and crushing index of 3-6%; and the fine aggregate is sea sand, with fineness modulus of 2.3-3.0 and good gradation.

[0010] The application belongs to the technical field of building materials, and the preparation method process is shown in Figure 1 . The main steps are as follows:

[0011] 1. Preparation of fungus mycelium encapsulated sodium alginate gel big ball

[0012] First, healthy mycelium is prepared, and a 2wt% sodium alginate solution and a 0.2M calcium chloride solution are configured. Then, the mycelium is uniformly mixed with the sodium alginate solution to ensure that the mycelium is fully dispersed. The mixed solution is added dropwise into the calcium chloride solution using a syringe or dropper. The sodium alginate will quickly crosslink with calcium ions to form a gel ball, which encapsulates the mycelium. Finally, the gel ball is soaked in the calcium chloride solution for a period of time to allow it to fully crosslink, then it is rinsed with clean water to remove residual calcium chloride, and finally it is naturally dried in a cool and ventilated place.

[0013] 2. Preparation of nanomaterial mixed seawater

[0014] Nano-TiO2 and graphene are added to seawater, and the nano-TiO2 and graphene in the seawater are fully dispersed by ultrasonic waves.

[0015] 3. Mixing of cementitious materials

[0016] The fungus mycelium encapsulated sodium alginate gel big ball, cement and metakaolin are fully stirred and mixed to obtain mixed cementitious materials.

[0017] 4. Mixer bowl

[0018] Before starting to stir, the mixed cementitious materials, sea sand, nanomaterial mixed seawater and a small amount of broken stone are added to the mixer in the proportion of the formula for premixing to cover the inner wall of the mixer and discharge excess mortar. This step ensures that the mixing ratio of the mixture is not affected during formal stirring.

[0019] 5. Addition of coarse and fine aggregates

[0020] The broken stone and sea sand are added according to the designed mixing ratio, and the mixer is started to stir for 0.5-1 min to fully mix the aggregates.

[0021] 6. Addition of 70% of the total water amount of nanomaterial mixed seawater

[0022] The remaining 30% of the nano material mixed seawater is evenly poured into the mixer and mixed for 3-4 minutes.

[0023] 7. Adding mixed cementitious materials

[0024] After the aggregate is evenly stirred, the mixed cementitious materials are immediately added and stirred for 1-2 minutes.

[0025] 8. Adding the remaining nano material mixed seawater

[0026] The remaining 30% of the nano material mixed seawater is evenly poured into the mixer and mixed for 3-4 minutes.

[0027] 9. Determining the workability of the freshly mixed marine concrete, such as the slump, and if it meets the requirements, it is molded, if not, the mix ratio is adjusted and steps 2-6 are repeated.

[0028] The advantages of the present application are:

[0029] Calcined kaolin, i.e., metakaolin, can be used as a mineral admixture for seawater and sea sand concrete, replacing part of the cement. With a small amount of addition, it can enhance the resistance of concrete to sulfate attack, reduce alkali-aggregate reaction, and play a beneficial role in prolonging the service life of seawater and sea sand concrete structures. In addition, metakaolin can have a secondary reaction with Ca(OH)2, refining the microstructure of the concrete by reducing the amount of Ca(OH)2 in the paste, improving the impermeability and freeze-thaw resistance of the concrete, and significantly enhancing the early and final compressive strength of the concrete.

[0030] Nano-TiO2 has photocatalytic properties, which can decompose organic pollutants attached to the surface of the concrete, giving the concrete certain self-cleaning function, which is suitable for marine concrete under seawater immersion. In addition, the antibacterial properties of nano-TiO2 can reduce the growth of microorganisms, effectively prevent marine organisms from attaching to the surface of the concrete, reduce the corrosion of microorganisms to the concrete, and thus prolong the service life of marine concrete.

[0031] The addition of graphene acts as a "nanoscale armor" for marine concrete, significantly improving the strength and toughness of the concrete, effectively resisting the erosion and impact of the marine environment. At the same time, it can also reduce the shrinkage and cracking of the concrete, block the intrusion of seawater and harmful ions, prolong the service life of the structure, and improve the safety and sustainability of marine engineering construction.

[0032] Fungal mycelium as a bio-based material brings many advantages to marine concrete. It can enhance the durability of concrete, resist chloride ion erosion and sulfate erosion, and inhibit marine biofilm attachment. Mycelium can also improve the mechanical properties of concrete, increase compressive strength and toughness, and make it more resistant to external damage such as wave impact. Some mycelium can also secrete minerals to repair microcracks, giving concrete self-repairing ability. Fungal mycelium shows great potential in improving the performance and life of marine concrete, and is expected to become an important material for future marine construction. In order to ensure the activity of mycelium during mixing and early hydration of concrete, the mycelium is wrapped in a decomposable sodium alginate gel ball.

[0033] Although the mycelium is wrapped inside the gel ball during the production of concrete, the mycelium can still secrete extracellular polymeric substance (EPS). These EPS can penetrate out of the gel ball and adsorb on the surface of graphene, forming a protective layer and further increasing the spatial distance between graphene, preventing their mutual attraction and agglomeration. As the cement hydration process progresses, the gel ball will slowly decompose and release the mycelium. The large specific surface area of graphene can provide attachment sites for mycelium, which is conducive to the spread and network construction of mycelium. Mycelium can act as a "bridge" to connect different graphene layers, forming a three-dimensional network structure, which improves the compressive strength, toughness and durability of concrete.

[0034] The present application can be used in marine engineering components susceptible to seawater corrosion, such as wave protection dikes, walls and support structures of harbors and wharfs, and bridge piers across the sea. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Flow chart for preparing modified marine concrete. DETAILED DESCRIPTION

[0036] To make the above features and advantages of the present application more obvious and easy to understand, the following examples are described in detail. The methods of the present application are conventional methods in the art unless otherwise specified.

[0037] Preparation of fungal mycelium encapsulated sodium alginate gel balls in Examples 1 and 2:

[0038] First, prepare a healthy Aspergillus mycelium suspension of 2.5 L with a concentration of 10 8The concentration of the mycelium is 0.5 g / mL, and the concentration of the sodium alginate solution is 2 wt%, and the concentration of the calcium chloride solution is 0.2 M. Then, the mycelium is mixed with the sodium alginate solution to ensure that the mycelium is fully dispersed. The mixed solution is added dropwise into the calcium chloride solution using a syringe or dropper. The sodium alginate will quickly cross-link with the calcium ions to form a gel ball, which encapsulates the mycelium. The gel ball is removed and rinsed with water to remove residual calcium chloride. Finally, the gel ball is naturally dried in a cool and ventilated place.

[0039] Example 1 (the strength of the base concrete is C40):

[0040] A modified marine concrete and a preparation method thereof, which are composed of the following raw materials in parts by weight: P.O 42.5 cement: 495.18 parts; metakaolin: 26.2 parts; nano-TiO2: 2.62 parts; graphene: 0.5 parts; fungal mycelium-encapsulated sodium alginate gel large ball: 0.5 parts; sea sand: 548 parts; crushed stone: 1113 parts; seawater: 240 parts.

[0041] The parameter indicators of various materials are as follows:

[0042] The metakaolin has a mesh size of 8000, and the content of SiO2 is 54.53 wt%, and the content of Al2O3 is 43.92 wt%.

[0043] The nano-TiO2 has a particle size of 10 nm, an anatase phase, a specific surface area of 75-95 m 2 / g, and a density of 3.8-4.2 g / cm 3 .

[0044] The graphene is single-layer graphene, with a purity of >99%, a thickness of <1 nm, and a particle size of 5-8 μm.

[0045] The crushed stone has a particle size range of 5 mm-20 mm, a continuous gradation, an apparent density of 2650 kg / m³, and a crushing index of 5%.

[0046] The sand is sea sand, and the sand has a fineness modulus of 2.6 and a gradation zone of 2.

[0047] The cement is P.O 42.5, with a density of 3150 kg / m³, and the quality indicators meet the requirements of “General Portland Cement (GB 175-2007)”.

[0048] The preparation process includes the following steps:

[0049] (1) The fungal mycelium-encapsulated sodium alginate gel large ball is prepared.

[0050] (2) The fungal mycelium-encapsulated sodium alginate gel large ball, cement, and metakaolin are fully stirred to prepare a mixed cementitious material.

[0051] (3) Add nano-TiO2 and graphene into seawater, and prepare nano-material mixed seawater by fully dispersing nano-TiO2 and graphene in seawater through ultrasonic method. Then, according to the mixing ratio, add mixed cementitious material, sea sand, nano-material mixed seawater and crushed stone, and perform scouring in a stirrer. After that, pour out the excess mortar, so that the cement mortar adheres to the cylinder wall of the stirrer, to avoid affecting the mixing ratio of the mixture during formal stirring;

[0052] (4) According to the design mixing ratio, add crushed stone and sea sand, and start the stirrer to stir for 30 s;

[0053] (5) After the aggregate is uniformly stirred, 70% of the total amount of nano-material mixed seawater is immediately added, and stirred for 30 s;

[0054] (6) The mixed cementitious material is uniformly scattered into the stirrer, and stirred for 1 min;

[0055] (7) The remaining 30% of the nano-material mixed seawater is poured into the stirrer, and stirred for 3 min;

[0056] (8) According to the experimental specification, the workability of the freshly mixed marine concrete such as slump is measured, and the requirements are met to form a mold.

[0057] Comparative Example 1

[0058] According to the setting of Example 1, a group of Comparative Example 1 is set. The difference between Comparative Example 1 and Example 1 is that only seawater, sea sand, stone and cement are stirred in the concrete of Comparative Example 1, and no modified material is added.

[0059] The mechanical properties of the concrete obtained in Example 1 and Comparative Example 1 are as follows:

[0060]

[0061] Example 2 (the strength of the base concrete is C50):

[0062] A modified marine concrete and a preparation method thereof are composed of the following raw materials in parts by weight: P.O 52.5 cement: 468.98 parts; metakaolin: 52.4 parts; nano-TiO2: 2.62 parts; graphene: 0.47 parts; fungus mycelium encapsulated sodium alginate gel macro-spheres: 0.47 parts; sea sand: 548 parts; crushed stone: 1113 parts; and seawater: 240 parts.

[0063] The parameter indexes of various materials are as follows:

[0064] The metakaolin is 8000 mesh, wherein the content of SiO2 is 54.53wt%, and the content of Al2O3 is 43.92wt%.

[0065] The nano-TiO2 has a particle size of 10 nm, an anatase phase, and a specific surface area of 75-95 m2 / g, density 3.8-4.2 g / cm 3 .

[0066] Graphene is single-layer graphene, purity > 99%, thickness < 1 nm, particle size 5-8 μm.

[0067] The size range of the crushed stone is 5-20 mm, continuous gradation, apparent density 2650 kg / m³, crushing index 5%.

[0068] The fine aggregate is sea sand, medium sand, fineness modulus 2.6, and the gradation zone belongs to zone 2.

[0069] The cement is P.O 52.5, density 3150 kg / m³, and the quality index meets the requirements of “General Portland Cement (GB 175-2007)”.

[0070] The preparation process comprises the following steps:

[0071] (1) Making the fungus mycelium encapsulated sodium alginate gel large ball.

[0072] (2) Fully stirring the fungus mycelium encapsulated sodium alginate gel large ball, cement and metakaolin to prepare a mixed cementitious material.

[0073] (3) Adding nano-TiO2 and graphene into seawater, preparing nano-material mixed seawater by fully dispersing nano-TiO2 and graphene in seawater through ultrasonic method, and then adding the mixed cementitious material, sea sand and nano-material mixed seawater and crushed stone according to the mixing ratio, and carrying out the rinsing in the stirring machine, and then pouring out the excess mortar, so that the cement mortar adheres to the cylinder wall of the stirring machine, so as to avoid affecting the mixing ratio of the mixture during formal stirring;

[0074] (4) Adding the crushed stone and sea sand according to the designed mixing ratio, and starting the stirring machine to stir for 30 s;

[0075] (5) After the aggregate is uniformly stirred, 70% of the total amount of nano-material mixed seawater is immediately added, and stirred for 30 s;

[0076] (6) The mixed cementitious material is uniformly scattered into the stirring machine, and stirred for 1 min;

[0077] (7) The remaining 30% of the nano-material mixed seawater is poured into the stirring machine, and mixed for 3 min;

[0078] (8) The workability of the freshly mixed marine concrete such as the slump degree is measured according to the experimental specification, and the requirements are met to form the mold.

[0079] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A modified marine concrete, characterized in that: The raw materials include, by weight: 460-600 parts of cement, 20-60 parts of metakaolin, 2-6 parts of nano-TiO2, 0.46-1 part of graphene, 0.46-1 part of fungal mycelium encapsulated sodium alginate gel balls, 500-600 parts of sea sand, 1000-1200 parts of crushed stone, and 235-245 parts of seawater. The preparation method of fungal mycelium-encapsulated sodium alginate gel spheres includes the following steps: first, healthy mycelium is prepared, and a 2wt% sodium alginate solution and a 0.2M calcium chloride solution are prepared; then, the mycelium and the sodium alginate solution are evenly mixed to ensure that the mycelium is fully dispersed; a syringe or dropper is used to add the mixture dropwise into the calcium chloride solution; sodium alginate rapidly cross-links upon encountering calcium ions to form gel spheres, which encapsulate the mycelium; the gel spheres are removed, rinsed with clean water to remove residual calcium chloride, and finally allowed to dry naturally in a cool and ventilated place.

2. The modified marine concrete according to claim 1, characterized in that: The cement type is PO 42.5-52.5, with a density of 3100-3250 kg / m 3 .

3. The modified marine concrete according to claim 1, characterized in that: The metakaolin is in the form of micron-sized powder, and its main components are SiO2 and Al2O3, with contents of 52wt%-57wt% and 43wt%-48wt% respectively.

4. The modified marine concrete according to claim 1, characterized in that: Nano-TiO2 particle size is 10nm, anatase phase, specific surface area is 75-95m 2 / g, density is 3.8-4.2g / cm 3 .

5. The modified marine concrete according to claim 1, characterized in that: The mycelium is selected from one of Aspergillus, yeast, Alternaria alternifolia and Fusarium.

6. The modified marine concrete according to claim 1, characterized in that: The graphene is single-layer graphene with a purity greater than 99%, a thickness less than 1 nm, and a particle size of 5-8 μm.

7. The modified marine concrete according to claim 1, characterized in that: The crushed stone particle size is 5-20mm, with continuous grading, apparent density 2600-2800kg / m³, and crushing index 3-6%.

8. The modified marine concrete according to claim 1, characterized in that: The fineness modulus of sea sand is 2.3-3.0, and the gradation is good.

9. The method for preparing modified marine concrete according to claim 1, characterized in that: The following steps are involved: (1) Preparation of nanomaterials mixed with seawater: Add nano-TiO2 and graphene into seawater, and fully disperse the nano-TiO2 and graphene in the seawater by ultrasonic wave; (2) Preparation of mixed cementitious material: fungal mycelium encapsulated sodium alginate gel balls, cement and metakaolin are fully stirred and mixed to obtain a mixed cementitious material; (3) Before starting to mix, add the mixed cementitious materials, sea sand, nanomaterials, seawater and gravel into the mixer according to the formula ratio for pre-mixing to cover the inner wall of the mixer and discharge the excess mortar. This step ensures that the mixture ratio is not affected during the formal mixing; (4) Add coarse and fine aggregates: Add crushed stone and sea sand according to the designed mix ratio, start the mixer and stir for 0.5-1 minute to fully mix the aggregates; (5) Add the nanomaterial mixed with seawater prepared in step (1) to wet the aggregate, with the amount of nanomaterial mixed with seawater accounting for 70% of the total amount, and then stir for 30 seconds; (6) Immediately add the mixed gelling material and stir for 1-2 minutes; (7) Pour the remaining 30% of the nanomaterial mixed with seawater evenly into the blender and stir for 3-4 minutes; (8) Injection molding.

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