Method for preparing and use of magnesia vegetal concrete

Abstract

The application provides a preparation method and application of magnesite vegetation concrete and belongs to the field of ecological slope protection. The preparation method comprises the following steps: S1, taking aggregates, light-burned magnesia, magnesium chloride hexahydrate, active admixture, water-resisting agent, alkali ion blocking agent, nutrient matching agent and water according to a certain mass fraction ratio; S2, dissolving the magnesium chloride hexahydrate in water to prepare a MgCl2 solution with a mass fraction of 20wt%-25wt%, and standing for 24 hours; S3, mixing the light-burned magnesia with the MgCl2 solution obtained in S2, stirring for 5 minutes, and then sequentially adding the active admixture, alkali ion blocking agent, water-resisting agent and nutrient matching agent, and continuously stirring until a cementitious slurry is formed; S4, adding the aggregates into the cementitious slurry obtained in S3, and continuously stirring until the surface of the aggregates is covered with uniform cementitious slurry to obtain a slurry to be shaped; and S5, loading the slurry obtained in S4 into a mold, vibrating and compacting to form the magnesite vegetation concrete. The magnesite vegetation concrete prepared by the application has the advantages of low alkali, high water resistance, high strength and good vegetation.

Description

Technical Field

[0001] This invention belongs to the field of ecological slope protection, specifically relating to a low-alkali, highly water-resistant magnesium-based vegetation concrete, its preparation method, and its application. Background Technology

[0002] Vegetated concrete, with its unique porous skeleton structure, ensures engineering stability while possessing ecologically friendly characteristics, and has now become an important material for ecological slope protection, mine restoration, and other projects. It is usually formed by a porous system composed of aggregates and cementitious materials, which can not only perform soil stabilization and slope protection functions, but also provide space for plant growth through internal interconnected pores, achieving long-term ecological restoration through the natural reproduction of plants.

[0003] However, due to material limitations, traditional silicate-based vegetated concrete maintains a highly alkaline environment with a pH of 10-12 within its pores, significantly higher than the pH range of 7-9 required for normal plant growth, resulting in low plant survival rates. While current methods employ acidic additives and mixed mineral materials to adjust the alkalinity, these approaches often suffer from unstable effects, short durations of action, and over-adjustment can interfere with the curing reaction of the cementitious materials, causing a 30%-50% decrease in material strength. Overcoming the technical contradiction between the difficulty in synergistically improving ecological adaptability and structural stability has become a core challenge in promoting the practical application of this technology.

[0004] Existing technologies mostly focus on improving plant growth by regulating pore structure and controlling alkalinity (e.g., patents CN119591361A and CN118978377A) or by incorporating fibers to enhance mechanical properties (e.g., patents CN116283203A and CN118791261A). However, these technologies generally suffer from poor plant viability and low strength. Furthermore, for example, patent CN119912229A improves porosity by adding microsilica, fly ash, and ceramsite aggregate, but does not solve the problem of strength decay in long-term water environment; CN117397552A uses phosphate modification to improve water resistance, but sacrifices the ecological compatibility of vegetation concrete in the pursuit of excessive water resistance; and the magnesium oxychloride cement recycled aggregate concrete structure proposed by CN115677318A improves compressive strength and durability, but its water resistance modification relies on the surface hydrophobic coating, and the interface bonding problem between recycled aggregate and magnesium oxychloride cement is not optimized. In long-term use, it may cause internal stress concentration and other defects due to aggregate water absorption and expansion.

[0005] Therefore, in the face of the common problems of high alkalinity, low strength, poor water resistance and stability of existing vegetation concrete, there is an urgent need to develop a new vegetation concrete technology with characteristics such as low alkali and high water resistance, so as to better meet the new needs of different projects such as ecological slope protection and mine restoration. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing magnesium-based vegetation concrete and its application. Magnesium chloride hexahydrate and lightly calcined magnesium oxide are used as raw materials, and appropriate active admixtures are added for modification. The resulting magnesium-based vegetation concrete has advantages such as low alkali, good water resistance, good vegetation properties, high strength and environmental protection, and is suitable for application in the field of ecological slope protection.

[0007] Specifically, the first aspect of the present invention provides a method for preparing magnesium-based vegetation concrete, comprising the following specific steps: S1: Weighing the preparation materials according to a certain mass ratio, wherein the materials specifically include: aggregate, lightly calcined magnesium oxide, magnesium chloride hexahydrate, active admixture, water-resistant agent, alkali ion blocking agent, nutrient adaptant and water; S2: Dissolving the magnesium chloride hexahydrate in water to prepare a MgCl2 solution with a mass fraction of 20wt%-25wt%, and letting it stand for 24 hours;

[0008] S3: Mix lightly calcined magnesium oxide with the MgCl2 solution obtained in S2, stir for 5 minutes in a high-speed mixer, then add active admixture, alkali ion blocking agent, water-resistant agent and nutrient adaptant in sequence, and continue stirring until a gel slurry is formed; S4: Add aggregate to the gel slurry obtained in S3, and continue stirring until the surface of the aggregate is uniformly covered with the gel slurry to obtain the slurry to be formed; S5: Put the slurry to be formed obtained in S4 into a mold, vibrate and compact it to form magnesium-based planted concrete.

[0009] Optionally, the preparation materials weighed according to a certain mass ratio in S1 specifically include: 150-250 parts of aggregate, 50-60 parts of lightly calcined magnesia, 7-9 parts of magnesium chloride hexahydrate, 15-30 parts of active admixture, 0.5-2 parts of water-resistant agent, 1-4 parts of alkali ion blocking agent, 0.1-1 parts of nutrient adaptant and 9-16 parts of water.

[0010] Optionally, the lightly calcined magnesium oxide is characterized in that: the lightly calcined magnesium oxide is prepared from particles of natural magnesite or brucite that have been crushed and screened through a light calcination process; wherein the calcination temperature is 850±100℃, the calcination time is 4 hours, and the magnesium oxide content is ≥85wt% and the active MgO content is ≥50wt%.

[0011] Optionally, the magnesium chloride hexahydrate is industrial-grade MgCl2·6H2O; the magnesium chloride hexahydrate is obtained from salt lake brine, which is acidified and then vacuum concentrated at 80-100℃, and evaporated to a solution density of 1.3-1.4 g / cm³. 3 The crystals were then cooled to 20-30℃ and crystallized for 2-5 hours. After centrifugation, the crystals were washed with 1-5% dilute hydrochloric acid and dried to obtain magnesium chloride hexahydrate crystals with a purity ≥98wt%.

[0012] Optionally, the aggregate is granite, with a rock parent material compressive strength ≥80MPa, water absorption ≤3%, gradation range of 15-25mm continuous gradation, porosity of 22-35%, crushing value of 12-15%, and mud content ≤0.5wt%.

[0013] Optionally, the active admixture is Grade I fly ash; wherein spherical particles account for ≥70% and have a specific surface area of ​​400-600 m². 2 / kg, density between 2.7-3.0 g / cm³ 3 The water requirement is 87%-92%, and the loss on ignition is less than 2%.

[0014] Optionally, the water-resistant agent is ferrous sulfate monohydrate with a purity ≥99% and a density of 2.7-3.0 g / cm³. 3 The average particle size is ≤50μm; the alkaline ion blocking agent is an aqueous acrylic copolymer emulsion with a solid content of 49-51% and a pH value of 7-9; the nutrient adaptant is phosphoric acid with a concentration ≥85wt% and a density of 1.5-1.7 g / cm³.

[0015] A second aspect of the present invention provides a magnesium-based vegetation concrete prepared according to the preparation method described above.

[0016] A third aspect of the present invention provides an application of the aforementioned magnesium-based vegetation concrete in the field of ecological slope protection.

[0017] The present invention has the following beneficial effects:

[0018] (1) Improved water resistance: The sequential addition of fly ash, ferrous sulfate monohydrate and acrylic copolymer emulsion, through hydration, adsorption and film formation synergy, significantly improves the water resistance of magnesium-based planted concrete.

[0019] (2) Alkalinity reduction: Magnesium cement itself has low alkali properties, which can effectively reduce the alkalinity of concrete as a cementing material. In addition, while reducing alkalinity, the film-forming effect of acrylic emulsion can further inhibit the dissolution of alkali. The addition of phosphoric acid further harmonizes the alkalinity of the pore fluid inside the concrete, thus ensuring the alkalinity stability of the pore fluid.

[0020] (3) Phytoecological properties: The interactions between the various components maintain the pH of the pore slurry within a range suitable for the root growth needs of most plants. Mg added or released through reactions 2+ Fe 3+ These can provide the nutrients needed for plant growth.

[0021] (4) High resource utilization: Solid waste is recycled and industrial by-products magnesium chloride and fly ash are reused, which is in line with the development direction of green building materials, reduces the consumption of natural minerals, and reduces carbon emissions.

[0022] Furthermore, additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the following text, or may be learned by practice of the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures and method steps specifically pointed out in the written description, claims, and drawings.

[0023] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0024] The accompanying drawings, which are provided to further illustrate the invention and form part of this application, are not intended to limit the scope of the invention.

[0025] Figure 1 This is a flowchart illustrating the preparation method of magnesium-based vegetation concrete in this embodiment of the invention.

[0026] Figure 2 This is a SEM image of the water resistance mechanism in Example 1 (without additives) of the present invention;

[0027] Figure 3 This is a SEM image of the water resistance mechanism of Example 2 of the present invention (with the addition of ferrous sulfate monohydrate);

[0028] Figure 4 This is a SEM image of the water resistance mechanism in Example 5 of the present invention (with added acrylic acid);

[0029] Figure 5 This is a diagram illustrating the vegetation effect of magnesium-based vegetation concrete in an embodiment of the present invention.

[0030] Figure 6 This is an illustration of the effect of planting vegetation on ordinary silicate concrete.

[0031] Figure 7 This is a comparison diagram of the durability of magnesium-based vegetation concrete in an embodiment of the present invention.

[0032] Figure 8 This is a comparison diagram showing the durability of ordinary silicate concrete. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention. It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only structures and / or processing steps closely related to the solutions according to the invention are shown in the accompanying drawings, while other details not closely related to the invention are omitted.

[0034] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0035] Combined with appendix Figure 1 As shown, one aspect of the present invention provides a method for preparing magnesium-based vegetation concrete, comprising the following specific steps: S1: Weighing the preparation materials according to a certain mass ratio, wherein the materials specifically include: aggregate, lightly calcined magnesium oxide, magnesium chloride hexahydrate, active admixture, water-resistant agent, alkali ion blocking agent, nutrient adaptant, and water; S2: Dissolving magnesium chloride hexahydrate in water to prepare a MgCl2 solution with a mass fraction of 20wt%-25wt%, and letting it stand for 24 hours; S3: Mixing lightly calcined magnesium oxide with the MgCl2 solution obtained in S2, stirring for 5 minutes in a high-speed mixer, then sequentially adding the active admixture, alkali ion blocking agent, water-resistant agent, and nutrient adaptant, and continuing to stir until a gel slurry is formed; S4: Adding aggregate to the gel slurry obtained in S3, and continuing to stir until the surface of the aggregate is uniformly covered with gel slurry, obtaining a slurry to be formed; S5: Filling the slurry to be formed obtained in S4 into a mold, vibrating and compacting it to obtain magnesium-based vegetation concrete.

[0036] Optionally, the preparation materials weighed in S1 according to a certain mass ratio specifically include: 150-250 parts of aggregate, 50-60 parts of lightly calcined magnesia, 7-9 parts of magnesium chloride hexahydrate, 15-30 parts of active admixture, 0.5-2 parts of water-resistant agent, 1-4 parts of alkali ion blocking agent, 0.1-1 parts of nutrient adaptant and 9-16 parts of water.

[0037] Optionally, the feature is that the lightly calcined magnesium oxide is prepared from crushed and screened particles of natural magnesite or brucite through a light-calcination process; wherein the calcination temperature is 850±100℃, the calcination time is 4 hours, and the magnesium oxide content is ≥85wt% and the active MgO content is ≥50wt%. The magnesium oxychloride cement calcination temperature of 850℃, compared to the high-temperature calcination of silicate cement (1450℃), can significantly reduce energy consumption and natural mineral resource consumption, reflecting the development concept of green building materials.

[0038] Optionally, the magnesium chloride hexahydrate is industrial-grade MgCl2·6H2O; the magnesium chloride hexahydrate is made from salt lake brine, which is acidified and then vacuum concentrated at 80-100℃, and evaporated to a solution density of 1.3-1.4 g / cm³. 3 The crystals were then cooled to 20-30℃ and crystallized for 2-5 hours. After centrifugation, the crystals were washed with 1-5% dilute hydrochloric acid and dried to obtain magnesium chloride hexahydrate crystals with a purity ≥98wt%.

[0039] Optionally, the aggregate is granite, with a compressive strength of the parent rock ≥80MPa, a water absorption rate ≤3%, a gradation range of 15-25mm continuous gradation, a porosity of 22-35%, a crushing value of 12-15%, and a mud content ≤0.5wt%.

[0040] Optionally, the active admixture is Grade I fly ash; wherein spherical particles account for ≥70% and have a specific surface area of ​​400-600 m². 2 / kg, density between 2.7-3.0 g / cm³ 3 The water requirement is 87%-92%, and the loss on ignition is less than 2%. The fly ash in it has good filling effect and pozzolanic properties. Its addition can react with magnesium cement to form water-resistant hydrated magnesium silicate gel (MSH gel). Its micro-aggregate effect can fill the internal pores of concrete, optimize the pore distribution of cement, and improve water resistance.

[0041] Preferably, the fly ash microsphere sphericity rate is above 85% to ensure that the magnesium cement has good fluidity.

[0042] Optionally, the water-resistant agent is ferrous sulfate monohydrate with a purity ≥99% and a density of 2.7-3.0 g / cm³. 3 The average particle size is ≤50μm. Ferrous sulfate contains ≥30.5% iron (Fe), and FeSO4 contains ≥30.5% Fe. 2+ It is oxidized to Fe in the weakly alkaline environment of MOC. 3+ Furthermore, it hydrolyzes to form β-Fe-O(OH) (ferric hydroxy oxide), which forms hydrogen bonds and chemical adsorption with the hydration products of magnesium cement, thereby improving water resistance. Ferrous sulfate monohydrate, through Fe... 2+ Oxidized to Fe in a weakly alkaline environment 3+ Furthermore, it hydrolyzes to generate ferric hydroxide, which forms hydrogen bonds and chemical adsorption with the hydration products of magnesium cement, thereby further improving water resistance. Simultaneously, Fe in ferrous sulfate monohydrate... 3+ It can serve as a source of nutrients needed for plant growth, thus promoting plant growth.

[0043] The alkali ion blocking agent is an aqueous acrylic copolymer emulsion with a solid content of 49-51% and a pH value of 7-9. The acrylic emulsion can reduce the alkalinity of magnesium cement. Simultaneously, through its unique molecular structure, it reacts with magnesium cement to coat the surface of hydration products with a hydrophobic film, preventing water erosion of the hydration products and inhibiting alkali dissolution, further reducing the pH value of the pore fluid.

[0044] The nutrient adaptant is phosphoric acid, with a concentration ≥85wt% and a density of 1.5-1.7 g / cm³. The addition of phosphoric acid reacts with the hydration products of magnesium oxychloride cement (such as Mg(OH)₂) to form magnesium phosphate complexes, further adjusting the alkalinity of the pore fluid inside the concrete, stabilizing the pH value of the pore fluid at 7-9 (more preferably, at 6.0-7.5). Simultaneously, this suitable pH level meets the growth requirements of most plant roots, and phosphate (PO₄²⁻) ions... 3－ ) and Mg released by magnesium cement 2+ It combines to form a slow-release magnesium phosphate precipitate, reducing phosphorus loss while continuously promoting chlorophyll synthesis in plants.

[0045] A second aspect of the present invention provides a magnesium-based vegetation concrete prepared according to a preparation method.

[0046] The third aspect of this invention provides an application of magnesium-based vegetation concrete in the field of ecological slope protection.

[0047] The present invention will be further described in detail below through specific embodiments and related comparative examples. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0048] The materials used in this embodiment are as follows:

[0049] The lightly calcined magnesium oxide has a specific surface area of ​​380 m² / kg, a density of 3.58 g / cm³, and a magnesium oxide (MgO) content of 83%. Hydration analysis revealed that the content of active MgO was 58.21%.

[0050] It contains 98% magnesium chloride hexahydrate, is monoclinic, has a light transmittance of ≥90%, and a heat of solution of -82.3 kJ / mol.

[0051] The specific surface area of ​​fly ash is 540 m². 2 / kg, density is 3.0g / cm³ 3 It requires 89% water, has a loss on ignition of less than 2%, and a median particle size of 10 μm.

[0052] The acrylic emulsion has a solid content of 49%-51%, a pH value of 7.0-9.0, and a viscosity of ≤800 mPa·s (25℃).

[0053] Ferrous sulfate monohydrate has a purity of ≥99.0%, an iron (Fe) content of ≥30.5%, and an average particle size of ≤50μm.

[0054] The phosphoric acid is industrial grade phosphoric acid (H3PO4) with a concentration of 85wt%, a purity of ≥98%, and a Cl⁻ content of ≤0.01wt%.

[0055] Example 1

[0056] The components, by mass parts, are as follows:

[0057] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, and 16 parts water.

[0058] The material preparation process is as follows:

[0059] (1) Weigh out the aggregate, magnesium chloride hexahydrate, magnesium oxide, fly ash, ferrous sulfate monohydrate, acrylic emulsion, phosphoric acid, and water according to the mass fractions. (Note that all components are listed here in general terms, but in the following examples, in order to distinguish the specific effects of different components on the product performance, the composition materials of some examples do not cover all component types. It is easy to understand that components not mentioned should be 0. For example, Example 1 only includes aggregate, magnesium oxide, magnesium chloride hexahydrate, and water, which means that fly ash, ferrous sulfate monohydrate, acrylic emulsion, and phosphoric acid are all 0. Similarly, Examples 2-10 refer to the expression method of Example 1.)

[0060] (2) Dissolve magnesium chloride in water to prepare a MgCl2 solution with a mass concentration of 20-25%. It must be left to stand for 24 hours to avoid the endothermic dissolution process of MgCl2 affecting the reaction.

[0061] (3) Mix the lightly calcined magnesium oxide with the MgCl2 solution, and put it into a high-speed mixer and stir for 5 minutes to make it fully and evenly mixed;

[0062] (4) Add the active admixture, vegetation stabilizer, water-blocking agent, water-resistant agent and nutrient adaptant in sequence, and continue stirring until a gel slurry is formed;

[0063] (5) Add aggregate to the cement paste and continue stirring until the surface of the aggregate is covered with a uniform cement paste.

[0064] (6) After the well-mixed slurry and aggregates are put into the mold, they are vibrated and compacted to form the shape, and then cured to the appropriate age.

[0065] (7) Conduct an alkalinity release test on the concrete. Place the concrete prepared in step (6) into a plastic box, add water until the sample surface is submerged, soak for 24 hours, and then measure the pH value of the aqueous solution using an acid-alkalinity tester. Then replace the water with the same mass and repeat the above operation until the pH value of the water tends to be constant, and stop the measurement.

[0066] (8) The concrete obtained in step (6) is subjected to compressive strength test, and the sample cured for 28 days is subjected to water immersion treatment. After immersion for 28 days, the compressive strength test is performed to test its water resistance.

[0067] Example 2

[0068] Based on parts by mass, its components are as follows:

[0069] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 2 parts ferrous sulfate monohydrate and 16 parts water.

[0070] The material preparation process is as described in Example 1.

[0071] Example 3

[0072] Based on parts by mass, its components are as follows:

[0073] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 0.6 parts phosphoric acid and 16 parts water.

[0074] The material preparation process is as described in Example 1.

[0075] Example 4

[0076] Based on parts by mass, its components are as follows:

[0077] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 30 parts fly ash and 16 parts water.

[0078] The material preparation process is as described in Example 1.

[0079] Example 5

[0080] Based on parts by mass, its components are as follows:

[0081] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 3 parts acrylic emulsion and 16 parts water.

[0082] The material preparation process is as described in Example 1.

[0083] Example 6

[0084] Based on parts by mass, its components are as follows:

[0085] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 2 parts ferrous sulfate monohydrate, 0.6 parts phosphoric acid and 16 parts water.

[0086] The material preparation process is as described in Example 1.

[0087] Example 7

[0088] Based on parts by mass, its components are as follows:

[0089] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 2 parts ferrous sulfate monohydrate, 3 parts acrylic emulsion and 16 parts water.

[0090] The material preparation process is as described in Example 1.

[0091] Example 8

[0092] Based on parts by mass, its components are as follows:

[0093] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 30 parts fly ash, 3 parts acrylic emulsion and 16 parts water.

[0094] The material preparation process is as described in Example 1.

[0095] Example 9

[0096] Based on parts by mass, its components are as follows:

[0097] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 3 parts acrylic emulsion, 0.6 parts phosphoric acid and 16 parts water.

[0098] The material preparation process is as described in Example 1.

[0099] Example 10

[0100] Based on parts by mass, its components are as follows:

[0101] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 30 parts fly ash, 1.5 parts ferrous sulfate monohydrate, 3 parts acrylic emulsion, 0.8 parts phosphoric acid and 16 parts water.

[0102] Example 11

[0103] Based on parts by mass, its components are as follows:

[0104] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 15 parts fly ash, 1.5 parts ferrous sulfate monohydrate, 3 parts acrylic emulsion, 0.8 parts phosphoric acid and 16 parts water.

[0105] Example 12

[0106] Based on parts by mass, its components are as follows:

[0107] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 30 parts fly ash, 1.5 parts ferrous sulfate monohydrate, 1 part acrylic emulsion, 0.8 parts phosphoric acid and 16 parts water.

[0108] Example 13

[0109] Based on parts by mass, its components are as follows:

[0110] 200 parts aggregate, 58 parts magnesium oxide, 8 parts magnesium chloride hexahydrate, 30 parts fly ash, 0.5 parts ferrous sulfate monohydrate, 3 parts acrylic emulsion, 0.8 parts phosphoric acid and 16 parts water.

[0111] Comparative Example 1

[0112] The composition of ordinary commercially available vegetation concrete is as follows:

[0113] 100 parts Taihang brand P.O42.5 slag cement, 250 parts aggregate and 35 parts water.

[0114] The material preparation process is as follows:

[0115] (1) Weigh out the cement, aggregate, and water according to the weight proportions;

[0116] (2) Add the weighed cement, aggregate and water to the mixing pot in sequence and stir. First stir slowly for 150 seconds and then stir quickly for 150 seconds to make the slurry evenly mixed.

[0117] (3) After the well-mixed slurry is poured into the mold, it is vibrated and compacted to form the shape, and then cured to the appropriate age.

[0118] (4) Conduct an alkalinity release test on the concrete. Place the concrete prepared in step (3) into a plastic box, add water until the sample surface is submerged, soak for 24 hours, and then measure the pH value of the aqueous solution using an acid-alkalinity tester. Then replace the water with the same mass and repeat the above operation until the pH value of the water tends to be constant, and stop the measurement.

[0119] (5) The concrete obtained in step (3) is subjected to compressive strength test, and the sample cured for 28 days is subjected to water immersion treatment. After immersion for 28 days, the compressive strength test is performed to test its water resistance.

[0120] To highlight the technological advantages of the cement material of this invention, the performance of the cement material was evaluated using indicators such as mechanical properties, water resistance, pH value, and plant growth height. The performance test results of the magnesium-based vegetation concrete of Examples 1-13 and Comparative Example 1 are shown in Table 1.

[0121] Table 1. Performance test results of magnesium-based vegetation concrete in Examples 1-13 and Comparative Example 1

[0122]

[0123] Analysis of Examples 1-2 and 6-7 revealed that the addition of a water-resistant agent significantly improved water resistance and promoted plant growth. Comparison of Examples 1, 3, 7, and 9 showed that the addition of a nutrient adaptant increased plant height after 28 days, significantly improving the vegetative growth effect. Comparison of Examples 1, 4, and 8 showed that the addition of an active admixture improved the water resistance of concrete and reduced the pH of the pore fluid. Comparison of Examples 1 with Examples 5 and 7-9 showed that the addition of an alkaline ion blocking agent effectively reduced the alkalinity of the pore fluid and also improved the water resistance of concrete.

[0124] Analysis of Examples 10-13 shows that reducing the active admixture component in Examples 10 and 11 leads to a decrease in compressive strength and water resistance; reducing the alkaline ion blocking agent component in Examples 10 and 12 leads to an increase in pore liquid pH and a decrease in water resistance; and reducing the water-resistant agent component in Examples 10 and 13 leads to a significant decrease in water resistance.

[0125] Example 1 is attached. Figure 2 As shown, magnesium cement undergoes hydrolytic fracture of its hydration products upon contact with water, resulting in a significant decrease in strength and thus poor water resistance; Example 2 is attached. Figure 3 As shown, after adding ferrous sulfate monohydrate, Fe 2+ It is oxidized to Fe in the weakly alkaline environment of MOC. 3+ Furthermore, it hydrolyzes to generate ferric hydroxide, which chemically adsorbs with the hydration products of magnesium cement, making the needle-like crystals of the hydration products more densely arranged and enhancing water resistance; Example 5 is attached. Figure 4 As shown, acrylic emulsion reacts with magnesium cement through its unique molecular structure to form a film, which prevents the hydration products from being eroded by water.

[0126] The vegetation effects of Example 10 and Comparative Example 1 are shown in the attached figures. Figure 5 , 6 As shown, the plants in magnesium-based vegetated concrete were taller, denser, and growing well after 28 days; while the plants in ordinary silicate concrete were shorter, sparser, and had yellowing leaves, indicating poorer vegetative growth.

[0127] The durability effects of Example 10 and Comparative Example 1 are shown in the attached figures. Figure 7 , 8 As shown, magnesium-based planted concrete has no obvious defects; ordinary silicate concrete shows cracks at some cementitious joints, accompanied by a decrease in strength and poor durability.

[0128] The synergistic effect of the composite admixtures in the concrete prepared by this invention results in a softening coefficient of over 0.85, which is 60% higher than that of unmodified magnesium oxychloride cement. Through the synergistic effects of hydration, adsorption, and film formation among the components of the composite admixtures, the water resistance of the magnesium-based vegetated concrete is jointly improved. The magnesium-based vegetated concrete modified with an alkali ion blocking agent has low pore slurry alkalinity, which is more conducive to plant growth, solving the problem of low plant survival rates caused by high pore slurry alkalinity in traditional vegetated concrete. The water-resistant agent and nutrient adaptant are optimized to improve the water resistance of the magnesium-based vegetated concrete while providing the necessary elements for plant growth and development. This effectively improves the problems of high alkalinity, low strength, and poor water resistance commonly found in existing vegetated concrete materials.

[0129] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or replacing features of other embodiments. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0130] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing magnesium-based vegetation concrete, characterized in that, The specific steps include the following: S1: Weigh the preparation materials according to a certain mass ratio. The materials specifically include: aggregate, lightly calcined magnesium oxide, magnesium chloride hexahydrate, active admixture, water-resistant agent, alkali ion blocking agent, nutrient adaptant and water. S2: Dissolve magnesium chloride hexahydrate in water to prepare a 20wt%-25wt% MgCl2 solution and let it stand for 24 hours; S3: Mix the lightly calcined magnesium oxide with the MgCl2 solution obtained in S2, stir for 5 minutes with a high-speed mixer, then add the active admixture, alkali ion blocking agent, water-resistant agent and nutrient adaptant in sequence, and continue stirring until a gel slurry is formed. The active admixture is Grade I fly ash, wherein spherical particles account for ≥70% and have a specific surface area of ​​400-600 m². 2 / kg, density between 2.7-3.0 g / cm³ 3 The water requirement is 87%-92%, and the loss on ignition is less than 2%; The alkali ion blocking agent is an aqueous acrylic copolymer emulsion with a solid content of 49-51% and a pH value of 7-9. It not only prevents the hydration products from being eroded by water, but also prevents the dissolution of alkali, further reducing the pH value of the pore fluid. The water-resistant agent is ferrous sulfate monohydrate with a purity ≥99% and a density of 2.7-3.0 g / cm³. 3 With an average particle size of ≤50μm, it not only improves the water resistance of magnesium cement but also serves as a nutrient supply source for plant growth, promoting plant growth. The nutrient adaptor is phosphoric acid, with a concentration ≥85wt% and a density of 1.5-1.7 g / cm³. 3 ; S4: Add aggregate to the gelling paste obtained in S3 and continue stirring until the surface of the aggregate is covered with a uniform gelling paste to obtain the paste to be formed. S5: The slurry to be formed obtained in S4 is put into the mold, vibrated and compacted to form magnesium-based vegetation concrete.

2. The preparation method according to claim 1, characterized in that, The preparation materials weighed according to a certain mass ratio as described in S1 specifically include: 150-250 parts aggregate, 50-60 parts lightly calcined magnesia, 7-9 parts magnesium chloride hexahydrate, 15-30 parts active admixture, 0.5-2 parts water-resistant agent, 1-4 parts alkali ion blocking agent, 0.1-1 parts nutrient adaptant and 9-16 parts water.

3. The preparation method according to claim 2, characterized in that: The lightly calcined magnesium oxide is prepared by lightly calcining particles of natural magnesite or brucite after crushing and screening. The calcination temperature is 850±100℃, the calcination time is 4 hours, and the magnesium oxide content is ≥85wt% and the active MgO content is ≥50wt%.

4. The preparation method according to claim 2, characterized in that: The magnesium chloride hexahydrate is industrial grade MgCl2·6H2O; The magnesium chloride hexahydrate is produced from salt lake brine, which is acidified and then vacuum concentrated at 80-100℃ until the solution density is 1.3-1.4 g / cm³. 3 The crystals were then cooled to 20-30℃ and crystallized for 2-5 hours. After centrifugation, the crystals were washed with 1-5% dilute hydrochloric acid and dried to obtain magnesium chloride hexahydrate crystals with a purity ≥98wt%.

5. The preparation method according to claim 2, characterized in that: The aggregate is granite and the parent rock is granite; The aggregate has a compressive strength ≥80MPa, a water absorption rate ≤3%, a gradation range of 15-25mm continuous gradation, a porosity of 22-35%, a crushing value of 12-15%, and a mud content ≤0.5wt%.

6. A magnesium-based vegetation concrete prepared by the preparation method according to any one of claims 1-5.

7. An application of magnesium-based vegetation concrete according to claim 6 in the field of ecological slope protection.

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