A shotcrete erosion-resistant material and its preparation method and application

Abstract

The application provides a kind of shotcrete erosion-resistant material and its preparation method and application, shotcrete erosion-resistant material includes the following weight parts of raw materials: silicate 50-300 parts, organic silicon powder 20-50 parts, calcium oxalate 50-100 parts, nanometer material 10-60 parts, silica ash 100-300 parts, polyacrylamide 5-20 parts;Anti-sulfate erosion shotcrete includes: cement, mineral admixture, coarse aggregate, fine aggregate, steel fiber, accelerator, water reducing agent, water, erosion-resistant material.Erosion-resistant material can effectively improve the medium erosion resistance of shotcrete and the compactness of concrete matrix, can effectively improve the strength of shotcrete, reduce the erosion rate of sulfate ion;Protect shotcrete from sulfate erosion damage, avoid damage to shotcrete due to external environmental erosion, leading to surface spalling and strength reduction, can be widely used in the construction of underground structures such as tunnel in erosion environment, to ensure the safety of structure service.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a sprayed concrete anti-erosion material, its preparation method, and its application. Background Technology

[0002] The mining method is a commonly used construction method in tunnel construction, and shotcrete is an indispensable component of this method. Shotcrete is a special type of concrete that uses spraying machinery and compressed air or other power to propel a mixture at high speed onto a target surface, automatically compacting it and rapidly developing strength. Shotcrete is characterized by its short setting time and high early strength. However, as the use of shotcrete has gradually increased, its durability issues have become increasingly apparent and are attracting growing attention.

[0003] Shotcrete, influenced by accelerators and the spraying process, exhibits significant differences in its hydration process and hydration product composition compared to ordinary concrete, resulting in notable variations in microstructure, mechanical properties, and permeability. Furthermore, shotcrete is in direct contact with the external environment, making it more susceptible to sulfate ion intrusion, leading to sulfate attack. Sulfate attack in shotcrete causes spalling, powdering, and even cracking, severely threatening the durability and service life of tunnel structures. Therefore, improving the sulfate resistance of shotcrete is crucial for reducing subsequent maintenance and extending structural lifespan.

[0004] Patent CN114656184B discloses an anti-sulfate concrete admixture, its preparation method, and concrete thereof. The anti-sulfate concrete admixture includes barium carbonate, barium hydroxide, hydrotalcite, fly ash, and mineral powder. Barium salts can react with SO4. 2- The formation of stable BaSO4 precipitates can be used to address sulfate attack in concrete. However, because its addition to cement leads to rapid setting of cementitious materials, barium salts are not suitable for directly consuming the SO4 that has penetrated into concrete. 2- .

[0005] Patent CN115180867B discloses a targeted anti-sulfate corrosion agent with a spherical shell structure, its preparation method, and its application. The corrosion agent of this invention is obtained by cross-linking and curing a sodium carboxylate emulsion containing nano-silica in a barium salt solution and then curing it in the barium salt solution. This avoids the direct reaction between the barium salt and the gypsum in the cement during the initial hydration stage, which would affect the workability of the shotcrete. However, the use of a large amount of nano-silica in shotcrete can affect the workability of the concrete and thus affect the shotcrete spraying process.

[0006] Patent CN113735489A discloses an anti-sulfate corrosion agent, shotcrete, and its preparation method. The anti-sulfate corrosion agent is prepared by using a certain proportion of mineral admixtures, silica fume, calcium powder, expansion agent, graphene oxide, gypsum, and dispersant. Shotcrete is then prepared using the anti-sulfate corrosion agent. The invention states that the anti-sulfate corrosion agent improves the anti-sulfate corrosion performance of shotcrete and reduces the rebound rate of concrete to below 10%. However, the use of graphene oxide in concrete cannot be applied on a large scale at present.

[0007] Patent CN107986671A proposes a low-resilience, corrosion-resistant composite admixture for shotcrete. This admixture is made by mixing water-reducing agents, thickeners, air-entraining agents, defoamers, retarders, and mineral admixtures in a certain mass ratio. It increases the corrosion resistance coefficient of shotcrete to over 90%. However, the high proportion of mineral admixtures and retarders in the admixture is not conducive to increasing the early strength of shotcrete. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a shotcrete anti-erosion material, its preparation method, and its application. The anti-erosion material contains multiple components that work together to effectively improve the shotcrete's resistance to media erosion and the compactness of the concrete matrix. The combined effect of these two factors can effectively increase the strength of the shotcrete and reduce the erosion rate of sulfate ions. This sulfate-resistant shotcrete can be applied to the initial support construction of tunnels. Through the synergistic effect between the components, it accelerates the early hydration of concrete and improves the early strength of the shotcrete.

[0009] A sprayed concrete anti-erosion material, comprising the following raw materials in parts by weight:

[0010]

[0011] The aforementioned silicates are one or more of sodium silicate, sodium metasilicate, calcium silicate, and magnesium silicate. Silicates can accelerate the early hydration of concrete, increase the density of the concrete matrix, and help improve the early strength of shotcrete, meeting the need for rapid increase in the early strength of shotcrete.

[0012] The aforementioned organosilicon powder is a silane-based organosilicon powder with a particle size of less than 500 micrometers. Organosilicon powder has hydrophobic properties, which can inhibit the transport of moisture within concrete, thereby reducing the water absorption rate of shotcrete and the migration and diffusion of sulfate ions, delaying the reaction of sulfate ions with concrete hydration products, and reducing sulfate erosion damage to shotcrete.

[0013] Calcium oxalate is a white crystalline powder. It acts as a catalyst in the hardening reaction, accelerating the reaction between cement and water to form CSH gel and the hardening product Ca(OH)₂. This catalytic effect improves the early strength and crack resistance of concrete. Furthermore, calcium oxalate promotes the hydration of compounds such as Al₂O₃ and Fe₂O₃ in cement clinker, increasing the reactivity of the clinker and enhancing the strength and durability of concrete.

[0014] The aforementioned nanomaterials are one or more of nano-silica, nano-iron dioxide, nano-calcium carbonate, and nano-titanium dioxide, in combination. By using nanomaterials, the cement hydration reaction is accelerated, which helps increase the early strength of shotcrete; simultaneously, it improves the density of concrete, reduces the migration and diffusion of sulfate ions in shotcrete, and enhances the sulfate attack resistance of shotcrete.

[0015] The specific surface area of ​​the aforementioned silica fume is greater than 18000 m². 2 The silica content is not less than 85% and the concentration is per kg. When silica fume is added to concrete, it reacts with Ca(OH)₂ during the setting and hardening process of cement to form hydrated calcium silicate (CSH) gel, thereby increasing the density of the concrete matrix. In addition, the calcium silicate hydrate formed by the silica fume reaction has a low calcium-to-silica ratio and strong polymerization effect, further improving the erosion resistance of shotcrete. At the same time, the pozzolanic reaction of silica fume consumes the Ca(OH)₂ content in the hydration products, reducing the Ca(OH)₂ content that can react with sulfate ions to form gypsum, further improving the erosion resistance of concrete.

[0016] The aforementioned polyacrylamide has a molecular weight greater than 4 million. Polyacrylamide has thickening and water-retaining properties, which can improve the workability of shotcrete, while inhibiting water evaporation and reducing the bleeding channels formed by water evaporation.

[0017] By combining silicates and nanomaterials, the early hydration process of concrete is accelerated, increasing its density. Simultaneously, calcium oxalate accelerates the cement hydration reaction, further enhancing the early strength of shotcrete. Silica fume further fills the voids in the concrete matrix, increasing its density through pozzolanic reaction. The water-retaining properties of polyacrylamide and the hydrophobic properties of organosilicon powder reduce bleeding channels and pores in the concrete matrix, while simultaneously creating a hydrophobic effect within existing voids, thereby reducing the erosion by corrosive ions.

[0018] A method for preparing a shotcrete anti-erosion material includes the following steps: (1) First, silicate, organosilicon powder and silica fume are added to a mixer and stirred for 15-20 minutes; (2) Then, calcium oxalate, nanomaterials and polyacrylamide are added and stirred for 10-15 minutes to obtain the anti-erosion material.

[0019] A sulfate-resistant shotcrete comprises the following raw materials in parts by weight: cement: 350-600 parts; mineral admixtures: 50-200 parts; coarse aggregate: 700-900 parts; fine aggregate: 700-900 parts; steel fiber: 5-30 parts; accelerator: 20-50 parts; water-reducing agent: 4-10 parts; water: 200-400 parts; and the above-mentioned anti-corrosion material: 20-80 parts.

[0020] The cement mentioned above is silicate cement with a strength grade greater than or equal to 42.5; the coarse aggregate mentioned above is continuously graded crushed stone with a particle size between 5-16mm; the fine aggregate mentioned above is river sand or manufactured sand with a fineness modulus between 2.4-3.2; the water-reducing agent mentioned above is a polycarboxylate water-reducing agent; the steel fiber mentioned above is any one of hooked steel fiber, corrugated steel fiber, or straight steel fiber, with a fiber length of 15-50mm and an aspect ratio greater than 45. Steel fibers in shotcrete can reduce the rebound of shotcrete, while improving the crack resistance of concrete and reducing cracks caused by shotcrete shrinkage. The accelerator mentioned above is an alkali-free accelerator. Traditional alkali-based accelerators easily cause later-stage strength loss in concrete and are also highly corrosive. The water mentioned above meets the requirements of relevant standards for concrete mixing water.

[0021] A method for preparing sulfate-resistant shotcrete includes the following steps: First, aggregates, cement, mineral admixtures, and anti-corrosion materials are mixed and stirred at room temperature for 60±5s; then, fibers are added and stirred for 30±5s; then, mixing water and water-reducing agent are added and stirred for 90±5s to obtain a mixture; the mixture and alkali-free quick-setting agent are mixed and sprayed through a wet concrete spraying machine to obtain sulfate-resistant shotcrete.

[0022] The present invention has the following advantages over the prior art:

[0023] (1) The anti-corrosion material of this application can effectively improve the resistance of shotcrete to media erosion and the compactness of the concrete matrix. Under the combined effect of the two effects, it can effectively improve the strength of shotcrete and reduce the erosion rate of sulfate ions. This application protects shotcrete from sulfate erosion and avoids damage to shotcrete caused by external environmental erosion, resulting in surface spalling and strength reduction. It can be widely used in the construction of underground structures such as tunnels in erosive environments to ensure the safe service of the structure.

[0024] (2) Sulphate-resistant shotcrete can be applied to the initial support construction of tunnels. Through the synergistic effect between the components, it can accelerate the early hydration of concrete and improve the early strength of shotcrete. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] The specific weight proportions of the anti-corrosion materials used in each embodiment and comparative example of this application are shown in Table 1, and the specific preparation methods are as follows:

[0027] (1) First, add silicate, organosilicon powder and silica fume into the mixer and stir for 15 minutes;

[0028] (2) Then add calcium oxalate, nanomaterials, and polyacrylamide and continue stirring for 10 minutes to obtain the anti-corrosion material.

[0029] Table 1

[0030] silicates Organosilicon powder Calcium oxalate Nanomaterials silica ash Polyacrylamide S1 125 35 85 40 155 16 S2 170 50 60 30 275 20 S3 50 50 85 60 260 8 S4 300 26 92 43 105 6 S5 245 40 90 53 100 10 S6 180 44 89 33 220 10 S7 220 34 68 35 220 12 D1 - - - - - - D2 - 50 60 30 200 10 D3 220 - 80 45 150 15 D4 90 50 80 50 - 20 D5 130 40 - 30 120 - D6 200 30 75 - 230 8

[0031] The preparation method of sulfate-resistant shotcrete in the embodiments and comparative examples of this application includes the following steps: First, aggregates, cement, mineral admixtures, and anti-corrosion materials are mixed and stirred at room temperature for 60 seconds; then, fibers are added and stirred for 30 seconds; next, mixing water and water-reducing agent are added, and the mixture is stirred for 90 seconds. The concrete is then poured out of the mixer, an accelerator is added, and the concrete is manually mixed until uniform. Concrete test blocks are then formed. The resulting mixture is then mixed with an alkali-free accelerator using a wet shotcrete machine and sprayed to obtain sulfate-resistant shotcrete.

[0032] The component ratios of sulfate-resistant shotcrete in various embodiments and comparative examples of this application are shown in Table 2 below:

[0033] Table 2

[0034]

[0035]

[0036] Test Example 1: Concrete Compressive Strength Test

[0037] After the concrete was formed, the compressive strength of different groups of concrete was measured at 1 day, 7 days and 28 days. The test results are shown in Table 3.

[0038] Table 3 Results of concrete compressive strength test

[0039]

[0040] The data in Table 3 show that in Examples 1-7 using the anti-erosion material, the compressive strength of the shotcrete at 1 day was greater than 20 MPa, while the compressive strength of Comparative Examples 1-6 decreased to varying degrees and was less than 20 MPa. At 7 days, the maximum compressive strength of the comparative concrete was 26.6 MPa. After using the anti-erosion material, the strength of the shotcrete steadily increased, reaching a maximum of 35.5 MPa in the examples. With increasing age, the strength of the shotcrete gradually increased. The comparative shotcrete strength ranged from 30 to 34 MPa, while the compressive strength of the shotcrete in the examples was greater than 35 MPa, reaching a strength grade of C35. This is due to the synergistic effect of the components of the anti-erosion material in this application, which accelerates early hydration of concrete, improves concrete density, and effectively increases the mechanical properties of concrete at different ages, thereby reducing the risk of erosion of the shotcrete.

[0041] Test Example 2: Concrete Resistance to Sulfate Attack Experiment

[0042] After demolding, the concrete specimens underwent standard curing. After curing to the specified age, a sulfate wet-dry cycle test was conducted using a sulfate wet-dry cycle tester according to GB / T50082 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The compressive strength changes of the concrete specimens after 60, 90, and 120 sulfate wet-dry cycles were measured, and the sulfate resistance coefficient of the concrete was calculated. The test results are shown in Table 4.

[0043] Table 4. Concrete resistance to sulfate attack coefficient

[0044]

[0045] The test results show that the sulfate resistance coefficient KS of the comparative shotcrete was less than 100 after 60 wet-dry cycles, indicating that the concrete had already suffered sulfate attack damage, resulting in surface spalling and cracking, and a decrease in compressive strength. As the number of wet-dry cycles increased, the sulfate attack damage of the comparative shotcrete was further aggravated. After 120 wet-dry cycles, the sulfate resistance coefficient KS of the comparative shotcrete was only 52, and the mechanical properties of the concrete decreased by nearly 50%.

[0046] For the shotcrete in the embodiments, due to the use of anti-corrosion materials, the concrete exhibits excellent resistance to sulfate attack. Even after 120 sulfate wet-dry cycles, the sulfate attack resistance coefficient KS of the concrete is greater than 100, indicating that the shotcrete is not affected by sulfate attack under the sulfate wet-dry cycle environment, and its mechanical properties are not lost. This is because the anti-corrosion material of this application can effectively improve the resistance of shotcrete to media erosion and the compactness of the concrete matrix. Under the combined effect of the two effects, the erosion rate of sulfate ions is reduced, and the shotcrete does not suffer significant damage after erosion. By using the anti-corrosion material and the sulfate-resistant shotcrete prepared by this application, the sulfate attack resistance of shotcrete can be effectively improved, and it can be protected from sulfate attack damage. It can be widely used in the construction of underground structures such as tunnels in corrosive environments to ensure the safe service of the structure.

[0047] Test Example 3: Rebound Rate Test

[0048] The test method refers to JGJ / T 372-2016 "Technical Specification for Application of Shotcrete". The rebound rate of concrete in different embodiments and comparative proportions was tested, and the test results are shown in Table 5 below.

[0049] Table 5. Concrete resistance to sulfate attack coefficient

[0050] serial number Rebound rate of shotcrete (%) Example 1 15.6 Example 2 14.5 Example 3 16.3 Example 4 13.9 Example 5 14.7 Example 6 16.2 Example 7 15.9 Comparative Example 1 25.3 Comparative Example 2 22.4 Comparative Example 3 21.6 Comparative Example 4 22.6 Comparative Example 5 23.6 Comparative Example 6 21.2

[0051] According to the rebound rate test results above, the rebound rate of the concrete in the examples was all below 17%, while the rebound rate of the concrete in the comparative examples was all above 21%, with a maximum of 25.3%. This proves that using the anti-erosion material of this application also has a certain effect on reducing the rebound rate of concrete. This is because the anti-erosion material of this application can effectively improve the compactness and early strength of the shotcrete matrix, thus increasing the cohesiveness of the concrete and reducing the rebound rate.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A sprayed concrete anti-erosion material, characterized in that, The ingredients include the following parts by weight: 50-300 parts of silicate 20-50 parts of organosilicon powder 50-100 parts of calcium oxalate 10-60 parts of nanomaterials 100-300 parts silica fume 5-20 parts of polyacrylamide.

2. The anti-corrosion material for shotcrete according to claim 1, characterized in that: The silicate is one or more of sodium silicate, sodium metasilicate, calcium silicate, and magnesium silicate.

3. The anti-corrosion material for shotcrete according to claim 1, characterized in that: The organosilicon powder is a silane-based organosilicon powder with a particle size of less than 500 micrometers.

4. The anti-corrosion material for shotcrete according to claim 1, characterized in that: The nanomaterial is one or more of nano-silica, nano-iron dioxide, nano-calcium carbonate, and nano-titanium dioxide.

5. The anti-corrosion material for shotcrete according to claim 1, characterized in that: The specific surface area of ​​the silica fume is greater than 18000 m². 2 / kg and the silica content is not less than 85%.

6. The anti-corrosion material for shotcrete according to claim 1, characterized in that: The polyacrylamide has a molecular weight greater than 4 million.

7. A method for preparing a shotcrete anti-erosion material according to any one of claims 1-6, characterized in that, The process includes the following steps: (1) First, add silicate, organosilicon powder and silica fume into a mixer and stir for 15-20 minutes; (2) Then add calcium oxalate, nanomaterials and polyacrylamide and continue stirring for 10-15 minutes to obtain the anti-corrosion material.

8. A type of sulfate-resistant shotcrete, characterized in that, The concrete comprises the following raw materials in parts by weight: Cement: 350-600 parts; Mineral admixtures: 50-200 parts; Coarse aggregate: 700-900 parts; Fine aggregate: 700-900 parts; Steel fiber: 5-30 parts; 20-50 parts quick-setting agent; 4-10 parts water-reducing agent; Water 200-400 parts; anti-erosion material: 20-80 parts; the anti-erosion material is the anti-erosion material for shotcrete as described in claim 1.

9. The sulfate-resistant shotcrete according to claim 8, characterized in that: The cement is silicate cement; the coarse aggregate is continuously graded crushed stone with a particle size between 5-16 mm; the fine aggregate is river sand or manufactured sand with a fineness modulus between 2.4 and 3.2; the water-reducing agent is polycarboxylate water-reducing agent; the steel fiber is any one of hooked steel fiber, corrugated steel fiber, or straight steel fiber, with a fiber length of 15-50 mm and an aspect ratio greater than 45; the accelerator is an alkali-free accelerator.

10. The method for preparing sulfate-resistant shotcrete according to claim 8, characterized in that: The process includes the following steps: First, mix aggregates, cement, mineral admixtures, and anti-corrosion materials at room temperature for 60±5 seconds; then add steel fibers and mix for 30±5 seconds; then add mixing water and water-reducing agent, and mix for 90±5 seconds to obtain a mixture. After mixing the mixture and quick-setting agent with a concrete wet spraying machine, spray it out to obtain sulfate-resistant sprayed concrete.

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