Alkali-reducing protective agent for reinforced cement-based cementing material for basalt fiber and application of alkali-reducing protective agent

Abstract

The invention discloses an alkali-reducing protective agent for a reinforced cement-based cementing material for basalt fibers and application of the alkali-reducing protective agent, and belongs to the technical field of building materials. The alkali-reducing protective agent is prepared from the following raw materials in percentage by weight: 20 to 40 weight percent of active silicon dioxide aerogel, 15 to 30 weight percent of metakaolin, 10 to 25 weight percent of lithium slag powder, 5 to 15 weight percent of nano calcium carbonate, 3 to 8 weight percent of redispersible latex powder, 1 to 5 weight percent of water reducing agent and 0.5 to 2 weight percent of retarder. The invention also discloses an application of the alkali-reducing protective agent in a cement cementing material. According to the invention, the alkalinity of a set cement hole solution around the basalt fiber can be efficiently and enduringly reduced, physical and chemical dual protection barriers are formed on the surface of the basalt fiber, the alkali corrosion of the fiber is obviously delayed, and the long-term durability and enhancement efficiency of the basalt fiber are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a basalt fiber reinforced cementitious material alkali-reducing and protective agent and its application. Background Technology

[0002] Basalt fiber (BF) is an inorganic fiber made from natural basalt ore through high-temperature melting and drawing. It has excellent properties such as high strength, high modulus, high temperature resistance, corrosion resistance and environmental friendliness, making it a civil engineering reinforcement material with great application potential.

[0003] However, during long-term service, basalt fibers are exposed to highly alkaline cement-based environments (pore fluid pH can reach 13.5). Their silica-oxygen network structure is susceptible to OH⁻ ion corrosion, leading to fiber surface dissolution, diameter reduction, significant degradation of mechanical properties, and even brittle fracture, thus losing their reinforcing effect. This "alkali corrosion" problem severely restricts the widespread application of basalt fibers in cement-based materials.

[0004] Currently, the main methods to solve this problem include: 1. treating the surface of the fibers with a coating (such as using a coupling agent); 2. reducing the alkalinity of the cement matrix (such as adding a large amount of mineral admixtures). However, the former is complex and costly, and the interfacial compatibility between the coating and the cement matrix is ​​not yet stable; the latter will delay the cement hydration process and affect the early strength development.

[0005] Therefore, developing a specialized alkali-reducing protective agent that can efficiently suppress the alkalinity of pore solutions in cementitious materials, specifically protect basalt fibers from erosion, and not damage the performance of the cement matrix has become a key technological challenge for promoting the development of basalt fiber reinforced cementitious materials. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an alkali-reducing protective agent for basalt fiber-reinforced cementitious materials. This alkali-reducing protective agent can effectively and stably reduce the pH value of the cementitious pore solution and construct a dense protective layer on the fiber surface, thereby significantly delaying the alkali corrosion process and ultimately effectively extending the service life of basalt fibers in the cement matrix, ensuring their long-term reinforcing efficacy.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A basalt fiber reinforced cementitious material alkali-reducing and protective agent, comprising the following raw materials by weight percentage: Active silica aerogel: 20wt%-40wt%; Metakaolin: 15wt%-30wt%; Lithium slag powder: 10wt%-25wt%; Nano calcium carbonate: 5wt%-15wt%; Redispersible latex powder: 3wt%-8wt%; Water-reducing agent: 1wt%-5wt%; Retarder: 0.5wt%-2wt%.

[0008] Furthermore, the specific surface area of ​​the active silica aerogel is ≥600 m² / g.

[0009] The active silica aerogel has extremely high volcanic ash activity and microporous adsorption capacity, which can quickly consume Ca(OH)2 produced by cement hydration and fundamentally reduce alkalinity.

[0010] Furthermore, the metakaolin is calcined kaolin with an activity index of not less than 105%.

[0011] The main function of the metakaolin is to provide active Al2O3 and SiO2, which react with Ca(OH)2 to generate more stable hydrated calcium silicate (CSH) and hydrated calcium aluminate (CAH) gels, refine the pore structure, and block the migration of OH- ions.

[0012] Furthermore, the lithium slag powder is an industrial by-product containing SiO2, Al2O3 and Li2O, with SiO2 content of 20wt%-25wt%, Al2O3 content of 15wt%~25wt%, and Li2O content of 0.18wt%-0.30wt%.

[0013] In addition to the active Al2O3 and SiO2 reacting with Ca(OH)2 to form more stable hydrated calcium silicate (CSH) and hydrated calcium aluminate (CAH) gels, the lithium slag powder also contains Li + Ions can also promote early hydration of cement, forming a denser microstructure, while their pozzolanic effect can continuously consume alkali.

[0014] Furthermore, the particle size distribution of the nano-calcium carbonate satisfies the following condition: D50 is 20nm-100nm.

[0015] The nano-calcium carbonate not only acts as a hydration nucleus, promoting the precipitation of hydrated calcium silicate gel and accelerating microstructure formation, but also reacts with tricalcium aluminate and other substances in cement hydration products to generate aluminocarbonate (single-carbon type hydrated calcium aluminocarbonate). This product expands in volume, effectively compensating for the chemical shrinkage of cement paste, reducing shrinkage microcracks at the source, and thus blocking OH... - Corrosion ions can penetrate through channels.

[0016] Furthermore, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

[0017] The water-reducing agent is used to overcome the problem of increased water demand in the system caused by the addition of multiple components in the protective agent, and ensures the workability and density of the slurry through its water-reducing effect.

[0018] Furthermore, the redispersible latex powder is at least one of ethylene-vinyl acetate or acrylate copolymer.

[0019] The redispersible latex powder can form a film on the fiber surface after emulsification in water, creating a physical barrier that effectively prevents OH- ions from directly contacting the fiber.

[0020] Furthermore, the retarder is at least one of sodium gluconate or sodium citrate.

[0021] The retarder is used to counteract the accelerating effect that lithium slag powder and nano-calcium carbonate may cause, ensuring the workable time for construction.

[0022] The present invention also provides the application of basalt fiber reinforced cementitious material alkali-reducing protective agent in cementitious materials: the dosage of the alkali-reducing protective agent is 2.0wt%~5.0wt% of the total mass of cementitious materials.

[0023] Furthermore, the alkali-reducing protective agent is first dry-mixed with basalt fiber for 1-2 minutes, and then dry-mixed evenly with cementitious materials, aggregates and admixtures before adding water and stirring.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. Preliminary Enrichment During Dry Mixing: The dry mixing process achieves preliminary enrichment of the various components of the alkali-reducing protective agent on the fiber surface ("seeding effect"). During the dry mixing process, components such as lightweight, fine-particle-size redispersible latex powder, nano-calcium carbonate, and active silica aerogel are preferentially adsorbed onto the basalt fiber surface through mechanical force, forming a pre-prepared protective layer. This effect significantly increases the local concentration of functional components around the fiber, laying the foundation for efficient and precise targeted protection during subsequent hydration.

[0025] 2. The interface region becomes the core site for reaction and film formation: After adding water and stirring, the pre-enriched latex powder is rapidly redispersed into polymer emulsion particles; simultaneously, highly active pozzolanic materials (active silica aerogel, metakaolin, lithium slag powder) undergo a vigorous reaction at the fiber-slurry interface region, preferentially and rapidly consuming Ca(OH)2 in this area, forming a localized low-pH environment. This environment not only directly alleviates alkaline corrosion, but more importantly, it induces polymer particle instability and demulsification, condensing in situ on the fiber surface to form a dense and continuous protective film, achieving a synergistic effect of chemical alkali reduction and physical barrier.

[0026] 3. Efficient and continuous source-based alkali reduction: Through the combined pozzolanic effect of active silica aerogel, metakaolin and lithium slag powder, the system can efficiently and continuously consume Ca(OH)2 generated by cement hydration, and stabilize the pH value of the pore solution below 11.5 from the source, providing a long-term safe service environment for basalt fibers.

[0027] 4. Dual Barrier Protection: The synergistic effect of nanomaterials (nano-calcium carbonate) and polymers (redispersible latex powder) constructs an organic-inorganic composite dual protective barrier. Nano-calcium carbonate refines the matrix structure and compensates for shrinkage through nucleation, filling, and the generation of expansive products; the redispersible latex powder physically isolates the corrosive medium. Together, they significantly block OH... - By disrupting the migration channels of harmful ions, it achieves dual protection that combines addressing both the root cause and the symptoms.

[0028] 5. Comprehensive enhancement of cement matrix performance: This alkali-reducing protective agent not only does not damage the matrix performance, but its components can further promote hydration and optimize the pore structure through pozzolanic reaction and micro-filling effect, thereby simultaneously improving the later strength, impermeability and durability of cement-based materials.

[0029] 6. Green and environmentally friendly: It innovatively uses industrial by-products such as lithium slag, realizing the efficient utilization of solid waste resources, reducing production costs, and conforming to the concept of green and sustainable building materials.

[0030] 7. Easy to use: This alkali-reducing protective agent is in dry powder form. Its pre-dry mixing process does not require changes to the existing concrete production process, making it easy to use and promote its application in large-scale projects. Detailed Implementation

[0031] In this invention, unless otherwise stated, the particle size distribution characteristics (such as D50, D90, etc.) are measured using a laser diffraction particle size analyzer according to the ISO 13320:2009 standard. During measurement, water or ethanol is used as the dispersion medium, and the sample is pretreated by ultrasonic dispersion for 3 minutes, for example.

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] In this embodiment of the invention, the specific surface area of ​​the active silica aerogel is ≥600 m² / g.

[0034] In this embodiment of the invention, the metakaolin is calcined kaolin with an activity index of not less than 105%.

[0035] In this embodiment of the invention, the lithium slag powder is an industrial by-product containing SiO2, Al2O3 and Li2O, with the SiO2 content being 20wt%-25wt%, the Al2O3 content being 15wt%~25wt%, and the Li2O content being 0.18wt%-0.30wt%.

[0036] In this embodiment of the invention, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

[0037] In this embodiment of the invention, the particle size distribution of nano-calcium carbonate satisfies: D50 is 20nm-100nm.

[0038] Example 1 As a preferred embodiment of the present invention, the composition of the alkali-reducing protective agent disclosed in this embodiment is shown in Table 1.

[0039] Table 1. Composition of the alkali-reducing and protective agent in Example 1

[0040] In this embodiment, the redispersible latex powder is ethylene-vinyl acetate.

[0041] In this embodiment, the retarder is sodium gluconate.

[0042] Application Example 1 M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2wt%. 3wt% of the alkali-reducing protective agent of this embodiment was added by weight of cement.

[0043] Example 2

[0044] As a preferred embodiment of the present invention, the composition of the alkali-reducing protective agent disclosed in this embodiment is shown in Table 2.

[0045] Table 2. Composition of the alkali-reducing and protective agent in Example 2

[0046] In this embodiment, the redispersible latex powder is an acrylate copolymer.

[0047] In this embodiment, the retarder is sodium gluconate.

[0048] Application Example 2 M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2wt%. 5wt% of the alkali-reducing protective agent of this embodiment was added by weight of cement.

[0049] Example 3

[0050] As a preferred embodiment of the present invention, the composition of the alkali-reducing protective agent disclosed in this embodiment is shown in Table 3.

[0051]

[0052] In this embodiment, the redispersible latex powder is an acrylate copolymer.

[0053] In this embodiment, the retarder is sodium gluconate.

[0054] Application Example 3 M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2wt%. 3wt% of the alkali-reducing protective agent of this embodiment was added by weight of cement.

[0055] Example 4 As a preferred embodiment of the present invention, the composition of the alkali-reducing protective agent disclosed in this embodiment is shown in Table 4.

[0056] Table 4. Composition of the alkali-reducing and protective agent in Example 4

[0057] In this embodiment, the redispersible latex powder is an acrylate copolymer.

[0058] In this embodiment, the retarder is sodium gluconate.

[0059] Application Example 4 M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2wt%. 3wt% of the alkali-reducing protective agent of this embodiment was added by weight of cement.

[0060] Example 5 As a preferred embodiment of the present invention, the composition of the alkali-reducing protective agent disclosed in this embodiment is shown in Table 5.

[0061] Table 5 Composition of the Alkalinity-Reducing Protective Agent in Example 5

[0062] In this embodiment, the redispersible latex powder is an acrylate copolymer.

[0063] In this embodiment, the retarder is sodium gluconate.

[0064] Application Example 5 M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2wt%. 3wt% of the alkali-reducing protective agent of this embodiment was added by weight of cement.

[0065] Comparative Example 1 This comparative example does not incorporate the alkali-reducing protective agent of this invention. M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999, "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2wt%.

[0066] Comparative Example 2 This comparative example does not incorporate the alkali-reducing protective agent of this invention, but instead incorporates 3 wt% silica fume (a single alkali-reducing material) by weight of cement. M40 cement mortar specimens were prepared, and the standard mix proportion (reference group) was determined according to the standard GB / T17671-1999, "Test Method for Strength of Cement Mortar (ISO Method)". Cement:water:standard sand = 450g:225g:1350g; basalt fiber content was 0.2 wt%.

[0067] Cement mortar test blocks were prepared according to the following methods for each application example and comparative example: First, dry mix basalt fiber and protective agent (alkali-reducing protective agent / silica fume) for 2 minutes, then dry mix with cement and standard sand for 2 minutes, then add water and stir for 3 minutes. Prepare standard cement mortar test blocks of 40mm×40mm×160mm according to GB / T17671-1999 "Test Method for Strength of Cement Mortar ISO Method".

[0068] After standard curing of cement mortar test blocks for 28 days, accelerated corrosion tests were conducted using saturated Ca(OH)2 solution at 80℃. The flexural strength retention rate of basalt fibers in the mortar was tested after 28 days and 60 days of curing, and the test results are shown in Table 6.

[0069] Table 6 Test Results

[0070] The results are shown in Table 6: After 60 days of accelerated corrosion, the flexural strength retention rate of all standard cement mortar specimens in the application examples was significantly higher than that of the two comparative examples. This fully demonstrates that the alkali-reducing protective agent of this invention can effectively delay the alkali corrosion of basalt fibers under different formulations and dosages, thereby maintaining the long-term mechanical properties of the mortar specimens.

[0071] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A basalt fiber reinforced cementitious composite alkalinity reducing agent, characterized by, The raw materials include the following in terms of weight percentage: Active silica aerogel: 20wt%-40wt%; Metakaolin: 15wt%-30wt%; Lithium slag powder: 10wt%-25wt%; Nano calcium carbonate: 5wt%-15wt%; Redispersible latex powder: 3wt%-8wt%; Water reducing agent: 1wt%-5wt%; Retarder: 0.5wt%-2wt%.

2. The alkalinity reducing agent for a basalt fiber reinforced cementitious composite material according to claim 1, characterized by, The specific surface area of the active silica aerogel is ≥600 m² / g.

3. The alkali-reducing protective agent for basalt fiber reinforced cementitious composites according to claim 1, characterized in that, The metakaolin is calcined kaolin with an activity index not less than 105%.

4. The alkalinity reducing agent for a basalt fiber reinforced cementitious composite material according to claim 1, characterized by, The lithium slag powder is an industrial by-product containing SiO2, Al2O3 and Li2O, with the content of SiO2 being 20wt%-25wt%, the content of Al2O3 being 15wt%-25wt%, and the content of Li2O being 0.18wt%-0.30wt%.

5. The alkalinity reducing agent for a basalt fiber reinforced cementitious composite material according to claim 1, characterized by, The particle size distribution of the nano calcium carbonate satisfies: D50 is 20nm-100nm.

6. The alkalinity reducing agent for a basalt fiber reinforced cementitious composite material according to claim 1, characterized by, The redispersible latex powder is at least one of ethylene-vinyl acetate or acrylic ester copolymer.

7. The alkalinity reducing agent for a basalt fiber reinforced cementitious composite material according to claim 1, characterized by, The water reducing agent is a polycarboxylic acid high-efficiency water reducing agent.

8. The alkalinity reducing agent for a basalt fiber reinforced cementitious composite material according to claim 1, characterized by, The retarder is at least one of sodium gluconate or sodium citrate.

9. Use of an alkali-reducing admixture according to any one of claims 1 to 8 in a cementitious material, characterized in that, The dosage of the alkali-reducing protective agent is 2.0wt%-5.0wt% of the total mass of the cementitious material.

10. The use of an alkali-reducing admixture in cementitious materials according to claim 9, characterized in that, The alkali-reducing protective agent is first dry-mixed with basalt fiber for 1-2 minutes, and then dry-mixed with the cementitious material, aggregate and admixture, and then water is added for stirring.

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