CN114685140A - An ecological protective layer for improving concrete durability, preparation method and application thereof - Google Patents

Abstract

The invention discloses an ecological protection layer for improving concrete durability, a preparation method and application thereof, and relates to the technical field of anti-corrosion materials. The raw material includes the following components in parts by weight: 500-600 parts of magnesium oxide, 200-300 parts of magnesium chloride, 900-1000 parts of fine aggregate, 200-260 parts of water, 10-20 parts of water reducing agent, and 3-20 parts of water-resisting agent. 8 parts, admixtures 25-150 parts. The invention further improves the mechanical and water resistance properties of magnesium oxychloride cement by adding highland barley straw ash on the basis of adding water-resistant agent as phosphoric acid to the magnesium oxychloride cement mortar, and effectively solves the problem of water resistance of the magnesium oxychloride cement mortar in a water-immersed environment. It also improves the interface bonding performance with ordinary concrete, and ensures the reliability of magnesium oxychloride cement mortar and ordinary concrete working together in salt lakes and saline soil areas.

Description

An ecological protective layer for improving concrete durability, preparation method and application thereof

technical field

The invention relates to the technical field of anti-corrosion materials, in particular to an ecological protection layer for improving the durability of concrete, a preparation method and an application thereof.

Background technique

Salt lakes and saline soil areas contain a large amount of corrosive salts, and the chloride ion concentration in some areas is as high as 300g/L. The service life of ordinary concrete under these conditions is less than 10 years, and some structures have been seriously damaged in 2-3 years. . At present, high-performance concrete and external protection technology are mainly used to improve the durability of concrete in salt lakes and saline soil areas. However, high-performance concrete requires better curing conditions, and it is difficult to achieve the expected performance in the harsh salt lake environment. Secondly, the application of high-performance concrete has greatly increased the project cost, resulting in additional expenditure on resources such as human and financial resources. External protection technology mainly uses functional coatings for protection or uses organic materials such as glass fiber reinforced plastics for protection. However, the effect of paint protection is not obvious. With the increase of exposure time, the paint gradually cracks and falls off in the harsh salt lake environment, which requires frequent and repeated brushing. The use of glass fiber reinforced plastics and other protective technologies will greatly increase the difficulty of construction, increase the construction cost, and prolong the construction period of the project. At present, the durability improvement technology of concrete in the harsh climate environment of salt lakes and saline soil areas has shown obvious drawbacks, and has not achieved breakthrough results, and there is no widely recognized or accepted technical means.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the problems in the prior art, and to provide an ecological protective layer for improving the durability of concrete, a preparation method and an application thereof. The protective layer further improves the mechanical and water resistance properties of magnesium oxychloride cement by adding water-resistant agent as phosphoric acid to magnesium oxychloride cement mortar, and effectively solves the problem of water resistance of magnesium oxychloride cement mortar under water immersion environment. The problem of insufficient performance is improved, and the interface bonding performance with ordinary concrete is improved to ensure the reliability of magnesium oxychloride cement mortar and ordinary concrete working together in salt lakes and saline soil areas.

The first object of the present invention is to provide an ecological protective layer for improving the durability of concrete, the raw materials of which include the following components by weight: 500-600 parts by weight of magnesium oxide, 200-300 parts of magnesium chloride, and 900-1000 parts of fine aggregate , 200-260 parts of water, 10-20 parts of water reducing agent, 3-8 parts of water-resistant agent, and 25-150 parts of admixture; wherein, the admixture is highland barley straw ash (HBSA).

Preferably, the raw materials include the following components by weight: 583.44 parts of magnesium oxide, 221.72 parts of magnesium chloride, 937.5 parts of fine aggregates, 220.04 parts of water, 16.02 parts of water reducing agent, 6.87 parts of water resistant agent, and 29.17 to 145.86 parts of admixtures. share.

More preferably, the highland barley straw ash is prepared according to the following steps:

The highland barley straw is naturally incinerated to ash powder, the incinerated ash powder is calcined at 600° C. for 2 hours, and then the calcined ash powder is mechanically ground for 2-4 hours to obtain the highland barley straw ash.

More preferably, the particle size of the highland barley straw ash is 6-10 μm, and the specific surface area is 2050-2100 kg/m ² .

Preferably, the fine aggregate is river sand with a fineness modulus of 2.5-2.7; the water-reducing agent is a polycarboxylic acid-based superplasticizer; and the water-resisting agent is phosphoric acid.

The second object of the present invention is to provide a kind of preparation method of the ecological protective layer that improves concrete durability, comprises the following steps:

The raw materials are mixed and mixed to form mortar, and then the obtained mortar is smeared or sprayed on the concrete surface for natural curing, that is, the ecological protection layer is obtained on the concrete surface.

Preferably, when the smearing method is adopted, smear is performed according to the bottom layer, the middle layer and the surface layer in sequence, the smearing thickness of each layer is 5-7mm, and the total smearing thickness is 15-20mm.

Preferably, when the spraying method is adopted, the mixed mortar is sprayed onto the concrete surface at one time, and its thickness is 15-20 mm.

Preferably, the concrete surface is also coated with an interface agent before applying or spraying the mortar.

The third object of the present invention is to provide an application of an ecological protective layer in improving the durability of concrete.

Compared with the prior art, the beneficial effects of the present invention are:

The ecological protective layer for improving the durability of concrete provided by the present invention is based on adding a water-resistant agent as phosphoric acid to the magnesium oxychloride cement mortar, and adding highland barley straw ash to improve the mechanical and water resistance properties of the magnesium oxychloride cement; The active admixture of ash, used in combination with phosphoric acid, can improve the water resistance of magnesium oxychloride cement mortar to 87.68%, effectively solve the problem of insufficient water resistance of magnesium oxychloride cement mortar in a water-immersed environment, and ensure magnesium oxychloride cement mortar. The long-term nature of the mortar and ordinary concrete working together. Magnesium oxychloride cement does not need to be cured under standard conditions, and can have high strength under natural conditions, which is not available in other functional cement mortars and coatings, ensuring the synergy between magnesium oxychloride cement mortar and ordinary concrete suitability for work.

The magnesium oxychloride cement used in the invention has high resistance to salt and brine erosion, and as the outer protective layer of ordinary concrete, it can effectively resist the corrosion of ordinary concrete in salt lake and saline soil environments, so that the durability of ordinary concrete can be improved. 30%, to ensure the effectiveness of the protective layer and ordinary concrete working together;

The magnesium oxychloride cement used in the present invention has good bonding performance and can be well bonded with the interface of ordinary concrete. The 14d interface bonding strength of magnesium oxychloride cement mortar and ordinary concrete can reach 1.46Mpa, which ensures the protective layer. Reliability to work with ordinary concrete.

Description of drawings

Fig. 1 is the preparation process flow of HBSA;

Fig. 2 is the XRD pattern of HBSA;

Fig. 3 is a histogram of the bond strength of the ecological protective layer provided in Example 1 with ordinary concrete with different thicknesses;

4 is a bar graph of the compressive strength of the ecological protective layers provided in Examples 1 to 5 and Comparative Example 1 in dry and saturated states;

Fig. 5 is the softening coefficient curve of the ecological protective layer provided by Examples 1-5 and Comparative Example 1;

Fig. 6 is the SEM image of the ecological protection layer provided by Example 1 and Comparative Example 1, wherein Fig. 6a is the SEM image of the ecological protection layer provided by Example 1, and Fig. 6b is the SEM image of the ecological protection layer provided by Comparative Example 1;

7 is a bar graph of the concrete compressive strength of the concrete protected by the ecological protective layer provided by Example 1 and the concrete protected by the protective layer provided by Comparative Example 1;

Fig. 8 is the concrete ultrasonic velocity bar graph of the concrete protected by the ecological protective layer provided by Example 1 and the protective layer protected by the comparative example 1;

9 is a bar graph of the compressive strength of concrete and ordinary concrete protected by the ecological protective layer provided in Example 1;

Fig. 10 is the concrete and ordinary concrete ultrasonic velocity histogram that the ecological protective layer protection provided by embodiment 1 provides;

11 is a bar graph of the corrosion current density of steel bars in the reinforced concrete and ordinary reinforced concrete protected by the ecological protective layer provided in Example 1.

Detailed ways

In order to enable those skilled in the art to better understand that the technical solutions of the present invention can be implemented, the present invention will be further described below with reference to specific embodiments, but the embodiments are not intended to limit the present invention.

The applicable objects of the present invention are ordinary concrete structures below C50 in salt lakes and saline soil areas, and C40 concrete is used in the basic test of the following examples, and the mixing ratio design is shown in Table 1.

Table 1C40 concrete mix ratio design (kg/m ³ )

cement sand stone water water reducer 432 558 1242 168 6.48

The admixture used in the following examples is highland barley straw ash (HBSA), and HBSA is a self-prepared active admixture suitable for magnesium oxychloride cement mortar. The specific preparation method is as follows: the highland barley straw is naturally incinerated outdoors until the ash powder is completely cooled, and the incinerated ash powder is calcined twice in a muffle furnace at a calcination temperature of 600°C and a calcination time of 2h. After the calcination is completed, the completely cooled ash powder is sieved in an automatic shaker with a mesh size of 0.6 mm to remove solid impurities such as soil and sand. Then, the sieved ash powder was ground in a roller ball mill, and the grinding time was 2h. The ash powder obtained after grinding is HBSA mixed in magnesium oxychloride cement mortar, and the preparation process of HBSA is shown in Figure 1.

The main components of the prepared HBSA are shown in Table 2, and the XRD test results are shown in Figure 2. Among them, the content of SiO ₂ in HBSA is 61.75%, the content of SO ₃ is 1.75%, and the loss on ignition (LOI) is 4.55%. The SO ₃ content meets the requirements of the national standard GB/T2847-2005 "Pozzolanic Mixtures for Cement", which requires no more than 3.5%, and the loss on ignition meets the standard requirements and no more than 10%. By testing the XRD pattern of HBSA and calculating its crystallinity, it can be found that the content of active SiO ₂ in HBSA is 48.45%, which makes HBSA have a higher active effect. In addition, the average particle size of HBSA after 2h grinding was 8.6 μm and the specific surface area was 2088kg/m ² . The smaller particle size and larger specific surface area promoted the active effect of HBSA.

Chemical composition of table 2HBSA (%)

The magnesium oxide adopted in the following examples is light-burning magnesium oxide, and the magnesium chloride is industrial magnesium chloride; the fine aggregate adopted is the fineness modulus 2.6, and the particle diameter is less than the river sand of 4.75mm; the water-reducing agent adopts the water-reducing efficiency as 21% polycarboxylate superplasticizer, and phosphoric acid is used for water resistance.

Example 1

An ecological protective layer for improving the durability of concrete, the raw material of which comprises the following components: magnesium oxide 583.44kg/m ³ , magnesium chloride 221.72kg/m ³ , fine aggregate 937.5kg/m ³ , water 220.04kg/m ³ , reduced Water agent 16.02kg/m ³ , water resistant agent 6.87kg/m ³ , admixture 58.34kg/m ³ . Wherein, the dosage of admixture is 10% of the dosage of magnesium oxide.

The above-mentioned preparation method of the ecological protective layer of improving concrete durability, comprises the following steps:

On-site mixing should be carried out according to the above-mentioned raw material ratio and requirements. The mixed mortar should be used up within 2 hours. After more than 2 hours, it should be mixed again. Before the ecological protection layer is applied to the outer surface of the concrete, the concrete surface should be simply cleaned and the surface soil should be washed away. There is no need for chisel treatment; then the interface agent is painted on the concrete surface, and the interface agent can be YJ-302 concrete interface treatment agent used in the construction of new and old concrete, which is an organic polymer emulsion; the interface agent is painted in two times. For the first time, apply the interface agent evenly on the outer surface of the concrete, and then apply the interface agent for the second time after the interface agent is basically solidified; , that is, the ecological protection layer can be obtained on the concrete surface;

The ecological protection layer is applied manually, and the construction can be carried out according to the construction method of plastering mortar. The plastering should be carried out in three layers, the bottom layer, the middle layer and the surface layer. The thickness is 18mm; the bonding strength between the ecological protective layer and ordinary concrete can reach 1.46Mpa in 14d and 1.56Mpa in 28d, which fully meets the interface bonding strength requirements of plastering mortar.

Example 2

Same as Example 1, the difference is,

The raw material includes the following components: magnesium oxide 583.44kg/m ³ , magnesium chloride 221.72kg/m ³ , fine aggregate 937.5kg/m ³ , water 220.04kg/m ³ , water reducing agent 16.02kg/m ³ , water resistant agent 6.87 kg/m ³ , admixture 29.17kg/m ³ .

Wherein, the dosage of admixture is 5% of the dosage of magnesium oxide.

Example 3

Same as Example 1, the difference is,

The raw material includes the following components: magnesium oxide 583.44kg/m ³ , magnesium chloride 221.72kg/m ³ , fine aggregate 937.5kg/m ³ , water 220.04kg/m ³ , water reducing agent 16.02kg/m ³ , water resistant agent 6.87 kg/m ³ , admixture 87.52kg/m ³ .

Among them, the dosage of admixture is 15% of the dosage of magnesium oxide.

Example 4

Same as Example 1, the difference is,

The raw material includes the following components: magnesium oxide 583.44kg/m ³ , magnesium chloride 221.72kg/m ³ , fine aggregate 937.5kg/m ³ , water 220.04kg/m ³ , water reducing agent 16.02kg/m ³ , water resistant agent 6.87 kg/m ³ , admixture 116.69kg/m ³ .

Wherein, the dosage of admixture is 20% of the dosage of magnesium oxide.

Example 5

Same as Example 1, the difference is,

The raw material includes the following components: magnesium oxide 583.44kg/m ³ , magnesium chloride 221.72kg/m ³ , fine aggregate 937.5kg/m ³ , water 220.04kg/m ³ , water reducing agent 16.02kg/m ³ , water resistant agent 6.87 kg/m ³ , admixture 145.86kg/m ³ .

Among them, the dosage of admixture is 25% of the dosage of magnesium oxide.

Example 6

The same as Example 1, the difference is that in the process of preparing the ecological protective layer for improving the durability of concrete, the ecological protective layer is constructed by spraying, and the mixed mortar can be sprayed and constructed at one time. The optimal thickness of ecological protection should be about 18mm.

Example 7

Same as Example 1, the difference is,

The raw material includes the following components: magnesium oxide 500kg/m ³ , magnesium chloride 200kg/m ³ , fine aggregate 900kg/m ³ , water 200kg/m ³ , water reducing agent 10kg/m ³ , water resistance agent 3kg/m ³ , mixed with Mixed material 25kg/m ³ .

Example 8

Same as Example 1, the difference is,

The raw material includes the following components: magnesium oxide 600kg/m ³ , magnesium chloride 300kg/m ³ , fine aggregate 1000kg/m ³ , water 260kg/m ³ , water reducing agent 20kg/m ³ , water resistant agent 8kg/m ³ , mixed with Mixed material 150kg/m ³ .

Compare file 1

The same as Example 1, the difference is that no admixture is added to the raw material.

In order to illustrate the relevant performance of the ecological protection layer provided by the present invention, Examples 1 to 5 and Comparative Example 1 were tested.

In order to illustrate the bond strength between the ecological protection layer and ordinary concrete, the ecological protection layer provided in Example 1 was constructed on the surface of ordinary concrete with a thickness of 6mm, 12mm, 18mm and 24mm. , as shown in Figure 3, the histogram of the bond strength between the ecological protection layer of different thicknesses and ordinary concrete; it can be seen from Figure 3 that the ecological protection layer with a thickness of 18mm adheres to the surface of ordinary concrete, and its 14d can reach 1.46Mpa, 28d can reach 1.56Mpa, which fully meets the interface bonding strength requirements of plastering mortar.

(1) Incorporation of HBSA can significantly improve the mechanical and water resistance of the protective layer.

The compressive strength of magnesium oxychloride cement mortar with different HBSA content in dry and saturated state was tested, as shown in Figure 4;

4 is a bar graph of the compressive strength of the ecological protective layers provided in Examples 1 to 5 and Comparative Example 1 in dry and saturated states;

It can be seen from Figure 4 that when the content of HBSA is 5%, the compressive strength of the ecological protective layer in both dry and saturated states reaches the maximum value, and the mechanical properties are the highest.

Figure 5 is the softening coefficient curve of the ecological protective layer provided by Examples 1 to 5 and Comparative Example 1. When the dosage of HBSA is 10%, the softening coefficient of the ecological protective layer is the largest, indicating that the ecological protective layer under this dosage is under the condition of immersion in water. with minimal loss of compressive strength. When the content of HBSA is 10%, the softening coefficient of the ecological protective layer reaches 87.68%, which is 6.79% higher than that without HBSA. Therefore, the incorporation of 10% HBSA can significantly improve the water resistance and mechanical properties of the ecological protective layer, effectively solving the problem of poor water resistance of the ecological protective layer.

Fig. 6 is the SEM image of the ecological protection layer provided by Example 1 and Comparative Example 1, wherein Fig. 6a is the SEM image of the ecological protection layer provided by Example 1, and Fig. 6b is the SEM image of the ecological protection layer provided by Comparative Example 1;

It can be seen from Figure 6 that more magnesium silicate hydrate (M-S-H) is generated in the microscopic morphology of the ecological protective layer doped with HBSA, which optimizes the pore structure, enhances the compactness of the structure, and improves the mechanical and water resistance properties.

(2) Incorporation of HBSA can significantly improve the corrosion resistance of the protective layer

The concrete protected by the ecological protective layer provided in Example 1 and the concrete protected by the protective layer provided in Comparative Example 1 were subjected to anti-corrosion tests. Wherein, the concrete specimen protected by the ecological protective layer provided in Example 1 is denoted as HBSA-MOCM, and the concrete specimen protected by the protective layer provided in Comparative Example 1 is denoted as N-MOCM.

The Chaka Salt Lake brine was used as the corrosive medium, and the HBSA-MOCM and N-MOCM specimens were immersed in the salt lake brine for 60 d, and the durability indicators such as strength and ultrasonic velocity were tested respectively. The test results are shown in Figures 7-8. Figure 7 is a bar graph of concrete compressive strength of the concrete protected by the ecological protective layer provided by Example 1 and the protective layer protected by Comparative Example 1; Histogram of ultrasonic velocity of concrete protected by protective layer;

It can be seen from Figures 7-8 that the compressive strength and ultrasonic velocity of the HBSA-MOCM specimen before and after erosion are higher than those of the N-MOCM specimen. After being eroded by salt lake brine, the strength retention rate of HBSA-MOCM specimen is 77.76%, and the strength retention rate of N-MOCM specimen is 74.65%. The ultrasonic velocity retention rate of the HBSA-MOCM specimen was 90.54%, and the ultrasonic velocity loss rate of the N-MOCM specimen was 87.24%. The strength of HBSA-MOCM specimens increased by 14.01% and the ultrasonic velocity increased by 4.86% compared with N-MOCM specimens after being eroded by salt lake brine.

(3) The durability of concrete protected by ecological protective layer is significantly improved than that of ordinary concrete

The concrete (MOCM-OPC) and the ordinary concrete (OPC) test piece protected by the ecological protective layer provided in Example 1 will all be subjected to a long-term immersion test in the salt lake brine, and the concrete test piece before and after 360d salt lake brine erosion is compressive The intensity and ultrasonic velocity change, as shown in Figure 8.

Fig. 9 is the concrete (MOCM-OPC) and ordinary concrete (N-OPC) compressive strength bar chart that the ecological protective layer protection provided by embodiment 1 provides; Fig. 10 is the ecological protective layer protective concrete and ordinary concrete that embodiment 1 provides Ultrasonic velocity histogram;

It can be seen from Figures 9 to 10 that the loss rate of compressive strength of MOCM-OPC specimens is 6.01% lower than that of N-OPC specimens, and the loss rate of ultrasonic velocity is reduced by 13%. After being corroded by salt lake brine, the compressive strength of MOCM-OPC is 29.36% higher than that of N-OPC, and the ultrasonic velocity is 17.59% higher than that of N-OPC.

The reinforced concrete (MOCM-OPC) and ordinary reinforced concrete (N-OPC) specimens protected by the ecological protective layer provided in Example 1 are all carried out in the salt lake brine to carry out a constant current electrification accelerated corrosion test. When the theoretical mass loss rate of the steel bar reaches 6% means that after 1236h accelerated test, the test results of corrosion current density of steel bars are shown in Figure 11.

11 is a bar graph of the corrosion current density of steel bars in the reinforced concrete and ordinary reinforced concrete protected by the ecological protective layer provided in Example 1. It can be seen from Fig. 9 that after the accelerated corrosion test, the corrosion current density of steel bars in the concrete protected by the ecological protective layer provided in Example 1 is reduced by 32.5% compared with ordinary concrete. Therefore, using the ecological protection layer protection provided in Example 1 as the protection layer of ordinary concrete can effectively improve the durability of concrete, and the improvement efficiency is more than 30%. According to the service life of general-purpose concrete structures of 50 years, the service life of concrete structures in the salt lake area can be extended for at least 15 years.

To sum up, the ecological protection layer for improving the durability of concrete provided by the present invention is to add highland barley straw ash on the basis of magnesium oxychloride cement mortar to improve the corrosion resistance; It can effectively improve the water resistance of magnesium oxychloride cement. When used in combination with phosphoric acid, the water resistance of magnesium oxychloride cement mortar can be increased to 87.68%, which effectively solves the problem of insufficient water resistance of magnesium oxychloride cement mortar in a water-immersed environment. Long-term performance of magnesium oxychloride cement mortar working with ordinary concrete. Magnesium oxychloride cement does not need to be cured under standard conditions, and can have high strength under natural conditions, which is not available in other functional cement mortars and coatings, ensuring the synergy between magnesium oxychloride cement mortar and ordinary concrete suitability for work.

The magnesium oxychloride cement used in the present invention has high resistance to salt and brine corrosion, and as the outer protective layer of ordinary concrete, it can effectively resist the corrosion received by ordinary concrete in the environment of salt lake and saline soil, so that the durability of ordinary concrete can be improved. Increase by 30% to ensure the effectiveness of the protective layer and ordinary concrete working together;

The magnesium oxychloride cement used in the present invention has good bonding performance and can be well bonded with the interface of ordinary concrete. The 14d interface bonding strength of magnesium oxychloride cement mortar and ordinary concrete can reach 1.46Mpa, which ensures the protective layer. Reliability to work with ordinary concrete.

The present invention describes preferred embodiments and their effects. However, once those skilled in the art are aware of the basic inventive concepts, additional changes and modifications may be made to these embodiments. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of the present invention.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. The ecological protective layer for improving the durability of concrete is characterized by comprising the following raw materials in parts by weight: 500-600 parts of magnesium oxide, 200-300 parts of magnesium chloride, 900-1000 parts of fine aggregate, 200-260 parts of water, 10-20 parts of water reducing agent, 3-8 parts of water-resistant agent and 25-150 parts of admixture;

wherein the admixture is highland barley straw ash.

2. The ecological protective layer for improving the durability of concrete according to claim 1, wherein the raw materials comprise the following components in parts by weight: 583.44 parts of magnesium oxide, 221.72 parts of magnesium chloride, 937.5 parts of fine aggregate, 220.04 parts of water, 16.02 parts of water reducing agent, 6.87 parts of water resisting agent and 29.17-145.86 parts of admixture.

3. The ecological protective layer for improving the durability of concrete according to claim 2, wherein the highland barley straw ash is prepared by the following steps:

naturally burning the highland barley straws into ash powder, calcining the burned ash powder at 600 ℃ for 2h, and mechanically grinding the calcined ash powder for 2-4 h to obtain the highland barley straw ash.

4. The ecological protective layer for improving the durability of concrete according to claim 3, wherein the particle size of the highland barley straw ash is 6-10 μm, and the specific surface area is 2050-2100 kg/m²。

5. The ecological protective layer for improving the durability of concrete according to claim 1, wherein the fine aggregate is river sand with a fineness modulus of 2.5-2.7; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent; the water-resistant agent is phosphoric acid.

6. The method for preparing the ecological protection layer for improving the durability of concrete according to claim 1, comprising the following steps:

mixing and stirring the raw materials to form mortar, then smearing or spraying the obtained mortar on the surface of concrete, and naturally curing, namely obtaining the ecological protection layer on the surface of the concrete.

7. The method for preparing the ecological protective layer for improving the durability of the concrete according to claim 6, wherein when the coating method is adopted, the coating is sequentially carried out according to the bottom layer, the middle layer and the surface layer, the coating thickness of each layer is 5-7mm, and the total coating thickness is less than or equal to 20 mm.

8. The method for preparing the ecological protection layer for improving the durability of the concrete according to claim 6, wherein when a spraying mode is adopted, the mixed mortar is sprayed to the surface of the concrete at one time, and the thickness of the mixed mortar is 15-20 mm.

9. The method for preparing the ecological protection layer for improving the durability of concrete according to claim 6, wherein the surface of concrete is coated with an interface agent before being coated or sprayed with mortar.

10. Use of the ecological protective layer according to claim 1 for improving the durability of concrete.

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