Highly durable erosion resistant concrete for substation foundation construction and method of construction thereof

Abstract

This application relates to the field of concrete technology, specifically disclosing a high-durability, corrosion-resistant concrete for substation foundation construction and its construction method. The high-durability, corrosion-resistant concrete mix comprises the following components by weight: 1040-1080 parts coarse aggregate, 780-800 parts fine aggregate, 280-300 parts silicate cement, 60-80 parts mineral admixtures, 30-50 parts modified basalt fiber, 3.4-3.8 parts polycarboxylate superplasticizer, and 122-126 parts water. The modified basalt fiber is basalt fiber with acrylic polymer grafted onto its surface. Compared with ordinary concrete, the high-durability, corrosion-resistant concrete of this application provides better protection against chloride ion penetration in the presence of stray currents, which is beneficial to the long-term service life of substation foundations.

Description

Technical Field

[0001] This application relates to the field of concrete technology, and more specifically, to a high-durability, erosion-resistant concrete for substation foundation construction and a construction method thereof. Background Technology

[0002] Substations, as transformer and distribution hubs in the power system, are a crucial component of the national power grid. With the expansion of the power grid, the number of substations is also gradually increasing. Currently, most substation foundations are constructed of reinforced concrete and are exposed to the natural environment for extended periods after commissioning, making them susceptible to erosion and damage. Therefore, improving the durability and erosion resistance of concrete is of great significance for extending the service life of substations.

[0003] One type of substation foundation concrete in the related technology comprises the following components by weight: 1040 parts coarse aggregate, 780 parts fine aggregate, 280 parts silicate cement, 60 parts mineral admixture, 3.4 parts polycarboxylate superplasticizer, and 122 parts water.

[0004] Regarding the aforementioned technologies, the inventors believe that when the substation foundation concrete is located in a stratum rich in chloride salts, stray currents leaking into the soil during substation operation will promote the penetration of chloride ions into the concrete through electric field force. The penetration of chloride ions will exacerbate the corrosion of steel bars, which is not conducive to the long-term service of the substation foundation. Summary of the Invention

[0005] In related technologies, when the substation foundation concrete is located in a chloride-rich stratum, stray currents promote the penetration of chloride ions into the concrete, which is detrimental to the long-term service life of the substation foundation. To improve this defect, this application provides a high-durability, corrosion-resistant concrete for substation foundation construction and its construction method.

[0006] In a first aspect, this application provides a high-durability, corrosion-resistant concrete for substation foundation construction, employing the following technical solution:

[0007] A high-durability, corrosion-resistant concrete for substation foundation construction, wherein the mixture comprises the following components in parts by weight: 1040-1080 parts coarse aggregate, 780-800 parts fine aggregate, 280-300 parts silicate cement, 60-80 parts mineral admixtures, 30-50 parts modified basalt fiber, 3.4-3.8 parts polycarboxylate superplasticizer, and 122-126 parts water, wherein the modified basalt fiber is basalt fiber with acrylic polymer grafted onto its surface.

[0008] By adopting the above technical solution, compared with related technologies, this application applies basalt fibers with acrylic polymer introduced on the surface to concrete mixes, resulting in highly durable and erosion-resistant concrete.

[0009] When stray currents pass through the concrete foundation of a substation in related technologies, calcium hydroxide and calcium silicate gel in the cement hydration products will decompose and release calcium ions. Driven by stray currents, calcium ions migrate and are lost, leading to an increase in the porosity of the concrete and making it easier for chloride ions to penetrate into the concrete.

[0010] In the high-durability, corrosion-resistant concrete of this application, the acrylic polymer on the surface of the modified basalt fiber exists in the form of anionic polymer, thus generating electrostatic attraction for calcium ions. The modified basalt fiber's migration is hindered by aggregates and cement paste in hardened concrete, and the matrix of the modified basalt fiber (basalt fiber) also has good insulation properties. Therefore, stray currents are unlikely to cause the calcium ions adsorbed by the modified basalt fiber to migrate, thereby reducing porosity increase caused by calcium ion diffusion and loss. Because porosity increase is limited, the high-durability, corrosion-resistant concrete of this application can provide better protection against chloride ion penetration even in the presence of stray currents, which is beneficial for the long-term service of substation foundations.

[0011] Preferably, the mineral admixture includes finely ground slag.

[0012] By adopting the above technical solution, ground granulated blast furnace slag can transform calcium hydroxide crystals into hydrated calcium silicate gel through a pozzolanic reaction. The hydrated calcium silicate gel produced by the pozzolanic reaction can fill the capillary pores inside the concrete caused by water evaporation, thereby increasing the density of the concrete. At the same time, the hydration products of ground granulated blast furnace slag can also combine with chloride ions to form hydrated calcium chloroaluminate (Friedel salt). This chemical adsorption achieves the fixation of chloride ions. Therefore, using ground granulated blast furnace slag as a mineral admixture helps to hinder the penetration of chloride ions.

[0013] Preferably, the mineral admixture also includes basalt powder.

[0014] While the hydration products of ground ore slag can fix chloride ions by combining with them to form calcium chloroaluminate hydrate, the continuous action of stray currents causes the calcium chloroaluminate hydrate to electrolyze, releasing some chloride ions. This results in a dynamic equilibrium between the formation and electrolysis of the calcium chloroaluminate hydrate, which is not conducive to the complete fixation of chloride ions. However, when basalt powder and ground ore slag are used together as mineral admixtures, the components of the basalt powder that have not participated in the pozzolanic reaction have good insulating properties. This can hinder the conduction of stray currents around the hydration products of the ground ore slag, thereby inhibiting the electrolysis of calcium chloroaluminate hydrate and helping to improve the chloride ion fixation effect of the ground ore slag.

[0015] Preferably, the modified basalt fiber is prepared according to the following method:

[0016] (1) Soak and wash the basalt fiber with detergent, and then dry it for later use; mix ethanol, water and silane coupling agent, and heat at 60-70℃ for 20-30 min to obtain silane modified liquid; in this step, the silane coupling agent molecule contains vinyl groups;

[0017] (2) The dried basalt fiber is mixed with silane modification liquid, stirred for 50-70 minutes, and then the basalt fiber is taken out and dried to obtain silanized basalt fiber.

[0018] (3) Mix silanized basalt fiber, acrylic acid, water-soluble azo initiator and water to obtain a reaction solution. Stir and heat the reaction solution at 75-85℃ for 1-2 hours. Then filter the reaction solution and dry the filtrate to obtain modified basalt fiber.

[0019] By adopting the above technical solution, this application grafts vinyl-containing siloxane groups onto the surface of basalt fibers through treatment with silane-modified liquid, thereby obtaining silanized basalt fibers. Then, this application further polymerizes acrylic acid and vinyl groups under the action of an initiator, ultimately introducing the acrylic acid polymer onto the surface of the silanized basalt fibers through the siloxane groups as a medium, thus obtaining modified basalt fibers.

[0020] Preferably, sodium hydroxide solution is used as the detergent during soaking and washing.

[0021] By adopting the above technical solution, sodium hydroxide solution can break the silicon-oxygen bonds on the surface of basalt fibers, increase the surface roughness and total amount of silanol groups, provide more grafting sites for siloxane groups from silane coupling agents, and help increase the total amount of carboxyl groups on the surface of modified basalt fibers.

[0022] Preferably, in step (2) of preparing the modified basalt fiber, nano-silica is mixed together with the dried basalt fiber and silane modification liquid.

[0023] By employing the above-mentioned technical solution, the silanol groups of nano-silica can condense with the silanol groups on the surface of basalt fibers to form new siloxane bonds, thereby bonding with the basalt fibers. The nano-silica bonded to the surface of basalt fibers increases the surface roughness of the basalt fibers and can also provide grafting sites for siloxane groups from silane coupling agents, thus helping to increase the total amount of carboxyl groups on the surface of modified basalt fibers.

[0024] Preferably, the amount of nano-silica used is 1.6-2.8% of the weight of basalt fiber.

[0025] By adopting the above technical solution, the amount of nano-silica used is optimized, which helps to fully increase the total amount of carboxyl groups on the surface of modified basalt fibers while saving nano-silica, thereby improving the protective effect against chloride ion penetration.

[0026] Preferably, the mixture of the high-durability and corrosion-resistant concrete also includes PVA dispersible latex powder.

[0027] By adopting the above technical solution, as the concrete hardens, the particles of PVA dispersible latex powder will gradually aggregate into a film, thereby restricting the migration of various ions in the concrete. This not only reduces the outflow of calcium ions but also hinders the invasion of chloride ions. At the same time, it can also improve the overall resistivity of the concrete. In the presence of stray current, it can provide better protection against chloride ion penetration, which is beneficial to the long-term service of the substation foundation.

[0028] Preferably, the amount of PVA dispersible latex powder used is 5-10% of the sum of the weights of silicate cement and mineral admixtures.

[0029] By adopting the above technical solution, the optimal amount of PVA dispersible latex powder is selected, which helps to improve the protection effect against chloride ion penetration as much as possible while saving PVA dispersible latex powder.

[0030] Secondly, this application provides a construction method for high-durability, corrosion-resistant concrete used in substation foundation construction, employing the following technical solution.

[0031] A construction method for high-durability, corrosion-resistant concrete used in substation foundation construction includes the following steps:

[0032] (1) Mix the concrete mixture as described above, pour the concrete mixture into the formwork, and then cure it.

[0033] (2) After the curing reaches the specified age, the formwork is removed to obtain the concrete foundation. Epoxy resin anti-corrosion coating is applied to the surface of the concrete foundation. After the coating has cured, the construction of high-durability and corrosion-resistant concrete can be completed.

[0034] By adopting the above technical solution, after the construction of high-durability and corrosion-resistant concrete is completed in the manner described above, the high-durability and corrosion-resistant concrete can play a certain protective role against chloride ion penetration in the presence of stray current, while the epoxy resin anti-corrosion coating reduces the area of ​​direct contact between the high-durability and corrosion-resistant concrete and the soil, which is beneficial to the long-term service of the substation foundation.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. This application applies basalt fibers with acrylic polymer introduced on their surface to concrete mixes, which reduces the increase in porosity caused by the diffusion and loss of calcium ions. Therefore, it can provide better protection against chloride ion penetration in the presence of stray current, which is beneficial to the long-term service of substation foundations.

[0037] 2. In this application, basalt powder and ground slag are used together as mineral admixtures. The components of basalt powder that have not participated in the pozzolanic reaction have good insulation properties, which can hinder the conduction of current around the hydration products of ground slag, thereby inhibiting the electrolysis of hydrated calcium chloroaluminate and helping to improve the fixation effect of ground slag on chloride ions.

[0038] 3. The construction method of this application reduces the direct contact area between the high-durability and corrosion-resistant concrete and the soil through epoxy resin anti-corrosion coating, and improves the protective effect of the high-durability and corrosion-resistant concrete against chloride ion penetration in the presence of stray current, which is beneficial to the long-term service of the substation foundation. Detailed Implementation

[0039] The present application will be further described in detail below with reference to the embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0040] Preparation example of modified basalt fiber

[0041] The following explanation uses Preparation Example 1 as an example.

[0042] Preparation Example 1

[0043] In this preparation example, the modified basalt fiber was prepared according to the following method:

[0044] (1) Soak and wash the basalt fiber with detergent for 30 minutes and then dry it for later use; mix ethanol, water and silane coupling agent and heat at 65°C for 25 minutes to obtain silane modified solution; in this step, the weight ratio of ethanol to water is 7:3, the mass fraction of silane coupling agent in silane modified solution is 4%, the silane coupling agent is vinyltriethoxysilane, and the detergent is water;

[0045] (2) The dried basalt fiber is mixed with silane modification liquid, so that the silane modification liquid completely immerses the basalt fiber. After stirring for 60 minutes, the basalt fiber is taken out and dried to obtain silanized basalt fiber.

[0046] (3) Silanized basalt fiber, acrylic acid, water-soluble azo initiator and water are mixed to obtain a reaction solution. The reaction solution is stirred and heated at 80°C for 2 hours. Then the reaction solution is filtered and the filtrate is dried in an oven at 105°C to obtain modified basalt fiber. In this step, the weight ratio of silanized basalt fiber to water is 1:5, the mass fraction of acrylic acid in the reaction solution is 15%, the mass fraction of water-soluble azo initiator is 1.2%, and the water-soluble azo initiator is azobisisobutyramidine hydrochloride.

[0047] Preparation Example 2

[0048] The difference between this preparation example and Preparation Example 1 is that the detergent used during soaking and washing is a 10 g / L sodium hydroxide solution.

[0049] Preparation Example 3

[0050] The difference between this preparation example and example 2 is that in step (2) of preparing modified basalt fiber, nano-silica is mixed together with dried basalt fiber and silane modification liquid, and the amount of nano-silica is 1.2% of the weight of basalt fiber.

[0051] As shown in Table 1, the difference between Preparation Examples 3-7 lies in the percentage of nano-silica used relative to the weight of basalt fibers (hereinafter referred to as nano-silica percentage).

[0052] Table 1. Proportion of Nano-Silica

[0053] sample Preparation Example 3 Preparation Example 4 Preparation Example 5 Preparation Example 6 Preparation Example 7 Nano silica percentage 1.2 1.6 2.2 2.8 3.2

[0054] Example

[0055] Examples 1-5

[0056] The following description uses Example 1 as an example.

[0057] Example 1

[0058] This embodiment provides a high-durability, corrosion-resistant concrete for substation foundation construction. The mixture of the high-durability, corrosion-resistant concrete includes the following components: 1040 kg of coarse aggregate, 780 kg of fine aggregate, 280 kg of silicate cement, 60 kg of mineral admixtures, 30 kg of modified basalt fiber, 3.4 kg of polycarboxylate superplasticizer, and 122 kg of water. The coarse aggregate is 5-31.5 mm continuously graded crushed stone, the fine aggregate is natural medium sand, the silicate cement specification is P.O42.5, the mineral admixture is Grade I ground blast furnace slag, and the water reduction rate of the polycarboxylate superplasticizer is 27%.

[0059] This embodiment also provides a construction method for high-durability, corrosion-resistant concrete used in substation foundation construction, including the following steps:

[0060] (1) Prepare concrete mix according to the formula, pour the concrete mix into the formwork, and then cure it;

[0061] (2) After the curing reaches the specified age, the formwork is removed to obtain the concrete foundation. Epoxy resin anti-corrosion coating is applied to the surface of the concrete foundation. After the coating has cured, the construction of high-durability and corrosion-resistant concrete can be completed.

[0062] As shown in Table 2, the main difference between Examples 1-5 lies in the different raw material ratios of the concrete mix.

[0063] Table 2 Raw material proportions for concrete mix

[0064]

[0065] Example 6

[0066] The difference between this embodiment and embodiment 5 is that the mineral admixture is made by mixing finely ground slag and basalt powder in a weight ratio of 2:1.

[0067] Examples 7-12

[0068] As shown in Table 3, the difference between Examples 7-12 and Example 6 is that the preparation methods of the modified basalt fibers are different.

[0069] Table 3 Examples of preparation of modified basalt fibers

[0070] sample Preparation example of modified basalt fiber Example 6 Preparation Example 1 Example 7 Preparation Example 2 Example 8 Preparation Example 3 Example 9 Preparation Example 4 Example 10 Preparation Example 5 Example 11 Preparation Example 6 Example 12 Preparation Example 7

[0071] Example 13

[0072] The difference between this embodiment and Embodiment 12 is that the mixture of the high-durability and erosion-resistant concrete also includes PVA dispersible latex powder, and the amount of PVA dispersible latex powder is 3% of the sum of the weights of silicate cement and mineral admixtures.

[0073] As shown in Table 4, the difference between Examples 13-17 is that the percentage of PVA dispersible latex powder used relative to the total weight of silicate cement and mineral admixtures (hereinafter referred to as the PVA powder percentage) is different.

[0074] Table 4. Proportion of PVA Powder

[0075] sample Example 13 Example 14 Example 15 Example 16 Example 17 PVA powder percentage / % 3 5 7 10 12

[0076] Comparative Example

[0077] Comparative Example 1

[0078] The difference between this comparative example and Example 1 is that the mixture of the high-durability and erosion-resistant concrete does not contain modified basalt fibers.

[0079] Comparative Example 2

[0080] The difference between this comparative example and Example 1 is that the modified basalt fiber in the mixture of high-durability and erosion-resistant concrete is replaced with basalt fiber by mass.

[0081] Performance testing methods

[0082] In the following testing methods, each concrete mix ratio includes a test group and a control group. The test group and the control group are formed in the same way and cured under the same conditions. Each test group and each control group includes three specimens.

[0083] Test steps:

[0084] Concrete mixtures were prepared according to the formulations of the various embodiments and comparative examples. The concrete mixtures were then formed into 100mm × 100mm × 100mm cubic specimens. A φ12 HRB335 threaded steel bar was inserted perpendicularly to the center of the exposed surface of the specimen (the side not in contact with the inner wall of the mold). The exposed length of the threaded steel bar was 20mm, and the insertion depth was 60mm. The threaded steel bar was pre-treated by removing the oxide layer and rust with sandpaper and then degreased by washing with anhydrous ethanol and acetone. A wire was welded to one end of the threaded steel bar, and the weld was sealed with epoxy resin.

[0085] After the threaded steel bars are installed, the specimens are cured for 28 days. Then, the side adjacent to the exposed surface is designated as the permeable surface. Epoxy resin is applied to the five sides of the specimen, excluding the permeable surface, to seal them. The specimens are then immersed in an 8% sodium chloride solution for 180 days.

[0086] After soaking for 180 days, the specimens of the control group were sliced, and the maximum penetration depth of chloride ions was measured using a micrometer according to the silver nitrate colorimetric method. The test result was taken as the average value of the three specimens and recorded as d1.

[0087] While treating the control group specimens, a DC electric field of 4V / cm was applied to the surface of the test group specimens via a wire (the negative terminal of the power supply was connected to the plate, and the positive terminal was connected to the wire welded to the steel bar; both the plate and the specimens were immersed in sodium chloride solution). After 168 hours of loading, the test group specimens were sliced, and the maximum penetration depth of chloride ions was measured using a micrometer according to the silver nitrate colorimetric method. The test result was taken as the average value of the three specimens and recorded as d2.

[0088] Calculate the difference between d2 and d1, and then calculate the ratio R of this difference to d1. The calculation results of R are shown in Table 5.

[0089] Table 5

[0090]

[0091]

[0092] Combining Examples 1-5 and Comparative Example 1 with Table 5, it can be seen that the R values ​​measured in Examples 1-5 are all less than those in Comparative Example 1, indicating that the modified basalt fiber adsorbs calcium ions, reduces the porosity increase caused by the diffusion and loss of calcium ions, and provides better protection against chloride ion penetration in the presence of stray current.

[0093] Combining Example 1 and Comparative Example 2 with Table 5, it can be seen that the R value measured in Example 1 is less than that in Comparative Example 2, indicating that in the presence of stray current, the insulation properties of basalt fiber alone cannot sufficiently prevent the penetration of chloride ions.

[0094] Combining Examples 5 and 6 with Table 5, it can be seen that the R value measured in Example 6 is less than that in Example 5. This indicates that when basalt powder and ground slag are used together as mineral admixtures, the components in the basalt powder that have not participated in the pozzolanic reaction have good insulation properties, which can hinder the conduction of stray currents around the hydration products of ground slag, thereby inhibiting the electrolysis of hydrated calcium chloroaluminate and helping to improve the fixation effect of ground slag on chloride ions.

[0095] Combining Examples 6 and 7 with Table 5, it can be seen that the R value measured in Example 7 is less than that in Example 6. This indicates that the sodium hydroxide solution can break the silicon-oxygen bonds on the surface of basalt fibers, increase the surface roughness and the total amount of silanol groups, provide more grafting sites for siloxane groups from silane coupling agents, help increase the total amount of carboxyl groups on the surface of modified basalt fibers, and thus improve the adsorption effect of modified basalt fibers on calcium ions.

[0096] Combining Examples 7, 8-12, and Table 5, it can be seen that the R values ​​measured in Examples 8-12 are lower than those in Example 7. This indicates that nano-silica provides more grafting sites for the siloxane groups from the silane coupling agent, which helps to increase the total amount of carboxyl groups on the surface of the modified basalt fiber, thereby improving the adsorption effect of the modified basalt fiber on calcium ions. Among Examples 8-12, Example 8 has the highest R value. Although the R value of Example 12 is the lowest, it is close to the R value of Example 11, and Example 12 uses the largest amount of nano-silica. Therefore, in order to improve the protection effect against chloride ion penetration as much as possible while conserving nano-silica, the preferred amount of nano-silica should be 1.6-2.8% of the weight of the basalt fiber.

[0097] Combining Examples 12, 13-17, and Table 5, it can be seen that the R values ​​of Examples 13-17 are all lower than that of Example 12. This indicates that after the PVA dispersible latex powder forms a film in the concrete, it restricts the migration of ions in the concrete. This not only reduces the outflow of calcium ions but also hinders the invasion of chloride ions, while simultaneously increasing the overall resistivity of the concrete. In the presence of stray currents, it provides better protection against chloride ion penetration, which is beneficial for the long-term service of the substation foundation. Among Examples 13-17, Example 13 has the highest R value. While Example 17 has the lowest R value, it is close to that of Example 16, and Example 17 uses the largest amount of PVA dispersible latex powder. Therefore, to improve the protection against chloride ion penetration as much as possible while conserving PVA dispersible latex powder, the preferred amount of PVA dispersible latex powder should be 5-10% of the sum of the weights of silicate cement and mineral admixtures.

[0098] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-durability, corrosion-resistant concrete for substation foundation construction, characterized in that, The high-durability and corrosion-resistant concrete mix comprises the following components in parts by weight: 1040-1080 parts coarse aggregate, 780-800 parts fine aggregate, 280-300 parts silicate cement, 60-80 parts mineral admixture, 30-50 parts modified basalt fiber, 3.4-3.8 parts polycarboxylate superplasticizer, and 122-126 parts water. The modified basalt fiber is basalt fiber with acrylic polymer grafted onto its surface. The modified basalt fiber is prepared according to the following method: (1) Soak and wash the basalt fiber with detergent, and then dry it for later use; mix ethanol, water and silane coupling agent, and heat at 60-70℃ for 20-30 min to obtain silane modified liquid; in this step, the silane coupling agent molecule contains vinyl groups; (2) The dried basalt fiber is mixed with silane modification liquid, stirred for 50-70 min, and then the basalt fiber is taken out and dried to obtain silanized basalt fiber; (3) Mix silanized basalt fiber, acrylic acid, water-soluble azo initiator and water to obtain a reaction solution. Stir and heat the reaction solution at 75-85℃ for 1-2 hours. Then filter the reaction solution and dry the filtrate to obtain modified basalt fiber.

2. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 1, characterized in that, The mineral admixture includes finely ground slag.

3. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 2, characterized in that, The mineral admixture also includes basalt powder.

4. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 1, characterized in that, The detergent used during soaking and washing is a sodium hydroxide solution.

5. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 4, characterized in that, In step (2) of preparing the modified basalt fiber, nano-silica is mixed with the dried basalt fiber and silane modification liquid.

6. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 5, characterized in that, The amount of nano-silica used is 1.6-2.8% of the weight of basalt fiber.

7. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 1, characterized in that, The mixture of the high-durability and corrosion-resistant concrete also includes PVA dispersible latex powder.

8. The high-durability, corrosion-resistant concrete for substation foundation construction according to claim 7, characterized in that, The amount of PVA dispersible latex powder used is 5-10% of the sum of the weights of silicate cement and mineral admixtures.

9. A construction method for high-durability, corrosion-resistant concrete used in substation foundation construction, characterized in that, Includes the following steps: (1) Mix the high-durability and corrosion-resistant concrete as described in any one of claims 1-8, pour the high-durability and corrosion-resistant concrete into the formwork, and then cure it; (2) After the curing reaches the specified age, the formwork is removed to obtain the concrete foundation. Epoxy resin anti-corrosion coating is applied to the surface of the concrete foundation. After the coating has cured, the construction of high-durability and corrosion-resistant concrete can be completed.

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