Anti-corrosion admixture for sprayed concrete as well as preparation method and application of anti-corrosion admixture

Abstract

The invention relates to the field of concrete, and particularly discloses an anti-corrosion additive for sprayed concrete and a preparation method and application thereof, the anti-corrosion additive comprises the following raw materials by weight: 10-20 parts of silica fume, 15-30 parts of fly ash, 3-8 parts of polypropylene fiber, 4-8 parts of chitosan oligosaccharide and 6-18 parts of porous silicon dioxide loaded with phosphate; the preparation method comprises the following steps: mixing the silica fume, the fly ash, the chitosan oligosaccharide and the phosphate-loaded porous silicon dioxide, adding the polypropylene fiber, and mixing to prepare the corrosion-resistant admixture; the invention also discloses an application of the anti-corrosion admixture in sprayed concrete. The method has the characteristics that the corrosion resistance of the sprayed concrete is improved, and the mechanical property of the sprayed concrete is improved.

Description

Technical Field

[0001] The present application relates to the field of concrete, and more specifically, to an anti-corrosion admixture for shotcrete and a preparation method and application thereof. Background Art

[0002] With the rapid development of infrastructure construction, tunnel engineering, as an important channel connecting cities and villages, mountainous areas and plains, has been widely used in transportation, water conservancy, mining and other fields, especially in mountainous and hilly areas, where tunnels are important channels connecting the two places. As a supporting structure for tunnels, shotcrete mainly uses spraying equipment to mix cement, aggregates and accelerators in a certain proportion, and then sprays them onto the surface of the tunnel surrounding rock through a high-pressure nozzle, so that the concrete quickly solidifies to form a high-density, high-strength supporting structure, which has the advantages of timely support, good quality, simple and flexible operation, etc. Under the geological conditions of weak surrounding rocks, the use of shotcrete, steel arch and anchor composite support can better highlight the advantages of shotcrete.

[0003] Under the background of rapid development of infrastructure, tunnel engineering has made great progress in basic research, design theory and construction technology, and the research results are remarkable. In the process of tunnel construction and use, a kind of difficult problem is often encountered. In the soft water and seepage environment, calcium ions in concrete are continuously dissolved and released with the infiltration water, forming a concentration gradient. Under the action of the concentration gradient, calcium ions in concrete are continuously dissolved, and calcium dissolution occurs. Calcium dissolution leads to increased porosity of concrete and gradual deterioration of microstructure, affecting its mechanical properties; and when karst water is rich in bicarbonate ions, it combines with dissolved calcium ions to form calcium bicarbonate. When it encounters carbon dioxide in the air during the flow process, it will further react to form water-insoluble calcium carbonate, which will gradually precipitate in the drainage system of the tunnel, causing blockage. Ultimately, the above-mentioned effects have an adverse effect on the structural safety and service life of the tunnel.

[0004] Therefore, it is of great significance to study the calcium dissolution resistance of shotcrete. Summary of the invention

[0005] In order to improve the corrosion resistance of shotcrete and improve its mechanical properties, the present application provides an anti-corrosion admixture for shotcrete and a preparation method and application thereof.

[0006] In the first aspect, the present application provides an anti-corrosion admixture for shotcrete, which adopts the following technical solution: An anti-corrosion admixture for shotcrete comprises the following raw materials in parts by weight: 10-20 parts of silica fume, 15-30 parts of fly ash, 3-8 parts of polypropylene fiber, 4-8 parts of chitosan oligosaccharide and 6-18 parts of porous silica loaded with phosphate.

[0007] By adopting the above technical scheme, the anti-corrosion admixture in the present application is based on silica fume and fly ash as mineral admixtures. The addition of silica fume reacts with calcium hydroxide in concrete through volcanic ash reaction to form a denser CSH (calcium silicate hydrate) gel, which can improve the density and impermeability of concrete and improve the anti-corrosion performance of concrete; and the fly ash has high activity and can react with calcium hydroxide in concrete to generate more hydration products to fill the pores inside the concrete, thereby improving the density and strength of the concrete. At the same time, the active ingredients in the fly ash can chemically react with other components in the concrete to form more stable compounds, further improving the anti-corrosion performance of the concrete.

[0008] In the present application, porous silica loaded with phosphate is added to the above-mentioned mineral admixtures. The porous silica can slowly release phosphate ions, react with free calcium ions in concrete, form stable calcium phosphate compounds, fill the pores and cracks inside the concrete, and reduce the migration of calcium ions, thereby improving the compactness and anti-corrosion properties of the concrete. In addition, the porous silica is added in the form of being loaded in the pore structure of silica. On the one hand, more phosphates can be loaded to play a greater role in calcium fixation and reduce the migration of calcium ions. On the other hand, the pore structure of the porous silica acts as a physical barrier, further reducing the migration of calcium ions and the penetration and erosion of external water, thereby further improving the anti-corrosion properties.

[0009] The chitosan oligosaccharide in the present application has the characteristics of alkalinity and can neutralize acidic substances. When encountering the neutral and acidic environment of dissolving water, it helps to effectively lock calcium ions and prevent the calcium ions from forming insoluble compounds due to encountering acidic substances and being lost, thereby slowing down the calcium dissolution phenomenon and improving the anti-corrosion performance of concrete.

[0010] Optionally, the polypropylene fiber is added after being modified, and the specific operation is as follows: 1) Mix trimethylolpropane triglycidyl ether and N,N-dimethylformamide to prepare a crosslinking agent solution, and then add a peroxide initiator, benzophenone and maleic anhydride to prepare a modifier solution; 2) The polypropylene fiber is immersed in the prepared modifier solution, and then dried and irradiated and cross-linked in an ultraviolet environment with a wavelength of 254-365 nm. The irradiation time is 10-20 minutes and the total radiation amount is 10 kGy.

[0011] By adopting the above technical scheme, in the present application, trimethylolpropane triglycidyl ether is used as a crosslinking agent, maleic anhydride is used as a modifier, and under the action of a peroxide initiator, free radicals are generated on the surface of the polypropylene fiber, which can form a crosslinking structure with maleic anhydride to introduce a carboxyl functional group, and benzophenone is used as a photosensitizer to improve the crosslinking effect during subsequent ultraviolet radiation crosslinking. At the same time, the epoxy groups in the trimethylolpropane triglycidyl ether crosslinking agent form a chemical crosslinking structure with the active sites on the surface of the polypropylene fiber, so that when the polypropylene fiber forms a more complex three-dimensional network structure in the concrete, the formation of the above crosslinking structure can improve the fiber The bonding strength with the concrete matrix enhances the anchoring effect of the modified polypropylene fiber in the concrete, helps to enhance the mechanical bite force between the fiber and the aggregate, and can be better anchored in the concrete. At the same time, the carboxyl functional groups in the polypropylene fiber can also form chemical bonds with functional groups such as hydroxyl groups in chitosan oligosaccharides and porous silica, and the carboxyl functional groups can also form complexes with calcium ions to form stable complexes, thereby firmly locking the calcium ions through chemical bonding and reducing their loss rate, thereby firmly anchoring the above-mentioned solid calcium components in the concrete matrix, further reducing the calcium loss phenomenon and improving the anti-corrosion performance of the concrete.

[0012] Optionally, in the modification process of the polypropylene fiber, the mass ratio of trimethylolpropane triglycidyl ether to N,N-dimethylformamide in step 1) is 1:(5-6), the amount of peroxide initiator added is 1-3wt% of the amount of trimethylolpropane triglycidyl ether added, the amount of benzophenone added is 0.5-0.8wt% of trimethylolpropane triglycidyl ether, the mass ratio of maleic anhydride to trimethylolpropane triglycidyl ether is 1:(2-3), and the mass ratio of trimethylolpropane triglycidyl ether to polypropylene fiber is 1:(4-6).

[0013] Optionally, during the modification treatment of the polypropylene fiber, the immersion time in step 2) is 30-40 minutes and the immersion temperature is 55-65°C.

[0014] Optionally, the peroxide initiator is one or both of dibenzoyl peroxide and dicumyl peroxide.

[0015] By adopting the above technical solution and controlling the above parameters to modify the polypropylene fiber and add it into concrete, the anti-corrosion performance and mechanical properties of the concrete can be improved better.

[0016] Optionally, the porous silica loaded with phosphate is prepared by the following method: The porous silica is first immersed in a phosphate solution with a mass concentration of 3-5wt% at normal pressure for 10-20min, then filtered, centrifuged and washed to obtain primary porous silica; Then the primary modified porous silica is immersed in a phosphate solution with a mass concentration of 5-10wt% for 10-20min at a pressure of 0.2-0.3MPa, and then filtered, centrifuged, and washed to obtain the secondary modified porous silica; The obtained second-modified porous silica is immersed in a phosphate solution with a mass concentration of 20-30wt% at normal pressure for 15-25min, and then filtered, centrifuged and washed to obtain the third-modified porous silica; The prepared triple-modified porous silica is immersed in a phosphate solution with a mass concentration of 25-30wt% at normal pressure for 5-15 minutes, and then filtered, centrifuged, washed and dried to obtain porous silica loaded with phosphoric acid.

[0017] By adopting the above technical scheme, in the present application, porous silica is immersed in a phosphate solution for loading to achieve phosphate loading, and multiple loadings are performed with gradually increasing concentrations. In this way, since phosphate diffusion needs to overcome the resistance of the pores to enter the interior of the porous silica, as the number of immersion times increases and the phosphate concentration increases, the phosphate loading in the external pores gradually increases, while the loading in the internal pores is relatively small, thereby achieving a gradient loading structure of the porous silica with more phosphate inside and outside and less phosphate inside.

[0018] In such a structure, the phosphates in the initial internal and external pores combine with calcium ions to form a complex. The phosphates loaded in the external pores are more likely to contact and react with the calcium ions in the concrete to form more calcium phosphate protective layers, thereby forming a calcium phosphate protective layer on the concrete surface. This can effectively alleviate the penetration of the external dissolution environment and thus slow down the calcium dissolution phenomenon.

[0019] Optionally, the phosphate is selected from one or more of trisodium phosphate, ammonium phosphate, and sodium tripolyphosphate.

[0020] By adopting the above technical solution, the above phosphate can be selected to form a stable complex with calcium, play a better role in calcium fixation, and thus improve the anti-corrosion performance of concrete.

[0021] Optionally, the anti-corrosion additive further includes 8-15 parts of silicone-modified acrylic resin and 3-5 parts of silane coupling agent.

[0022] By adopting the above technical scheme, the present application also adds a silicone modified acrylic resin, which contains both a hydrophilic acrylic ester segment and a hydrophobic silicone segment, which work together to form a hydration layer that can absorb water and a composite protective layer that can repel water. The hydration layer can play a certain buffering role to reduce the impact of water on concrete, and can also maintain the internal moisture balance of concrete to a certain extent, reduce the dissolution and erosion of external moisture on the internal chemical components of concrete, and can also prevent excessive erosion of external moisture, which has a positive effect on anti-corrosion performance. The addition of silane coupling agent helps to improve its compatibility with mineral admixtures and porous silica, etc., and play a better role.

[0023] In a second aspect, the present application provides a method for preparing an anti-corrosion admixture for shotcrete, using the following technical solution: A method for preparing an anti-corrosion admixture for shotcrete comprises the following steps: The anti-corrosion admixture is prepared by mixing silica fume, fly ash, chitosan oligosaccharide and porous silica loaded with phosphate and then adding polypropylene fiber.

[0024] By adopting the above technical solution, the method provided by the present application is simple, convenient and easy to realize industrialization.

[0025] Optionally, the anti-corrosion admixture also includes 8-15 parts of silicone-modified acrylic resin and 3-5 parts of silane coupling agent, and the mixture of silicone-modified acrylic resin and silane coupling agent is used as component A, and the mixture of silica ash, fly ash, chitosan oligosaccharide, porous silica loaded with phosphate and polypropylene fiber is used as component B, the mass ratio of component A to component B is 1:(8-10), and they are packaged separately.

[0026] By adopting the above technical solution, the organosilicon-modified acrylic resin and the mineral admixture are packaged separately and added to the concrete for mixing at the same time when used, which facilitates storage and transportation without affecting use.

[0027] In a third aspect, the present application provides an application of an anti-corrosion admixture for shotcrete, using the following technical solution: The invention discloses an application of an anti-corrosion admixture for shotcrete in shotcrete.

[0028] By adopting the above technical scheme, when the anti-corrosion admixture prepared in the present application is applied to shotcrete, the dissolution of calcium hydroxide can be reduced, and the anti-calcium corrosion performance of shotcrete can be greatly improved. It can not only avoid the blockage of the drainage system due to calcium dissolution, but also alleviate the reduction of the mechanical properties of concrete due to calcium dissolution.

[0029] In summary, this application has the following beneficial effects: 1. In the present application, porous silica loaded with phosphate is added to the above-mentioned mineral admixtures. The porous silica can slowly release phosphate ions, react with free calcium ions in concrete, form stable calcium phosphate compounds, fill the pores and cracks inside the concrete, and reduce calcium ion migration, thereby improving the compactness and corrosion resistance of the concrete. In addition, the porous silica is added in the form of being loaded in the pore structure of silica. On the one hand, more phosphate can be loaded to play a more calcium-fixing role and reduce calcium ion migration. On the other hand, the pore structure of the porous silica acts as a physical barrier, further reducing the migration of calcium ions and the penetration and erosion of external water, thereby further improving the corrosion resistance. 2. The chitosan oligosaccharide in the present application has the characteristics of alkalinity, which can neutralize acidic substances. When encountering the neutral and acidic environment of the dissolving water, it helps to effectively lock the calcium ions and prevent the calcium ions from forming insoluble compounds due to encountering acidic substances and being lost, thereby slowing down the calcium dissolution phenomenon and improving the anti-dissolution performance of the concrete; 3. In the present application, after the polypropylene fiber is cross-linked with trimethylolpropane triglycidyl ether and modified with maleic anhydride, carboxyl functional groups are introduced, so that the polypropylene fiber forms a more complex three-dimensional network structure in the concrete. The formation of the above-mentioned cross-linked structure can improve the bonding strength between the fiber and the concrete matrix, and enhance the anchoring effect of the modified polypropylene fiber in the concrete. At the same time, the carboxyl functional groups in the polypropylene fiber can also form chemical bonds with functional groups such as hydroxyl groups in chitosan oligosaccharides and porous silica, and the carboxyl functional groups can also form complexes with calcium ions to form stable complexes, thereby firmly locking the calcium ions through chemical bonding and reducing their loss rate, thereby firmly anchoring the above-mentioned solid calcium components in the concrete matrix, further reducing the calcium loss phenomenon, and improving the anti-corrosion performance of the concrete. DETAILED DESCRIPTION

[0030] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0031] In the following preparation examples and embodiments, the organosilicon-modified acrylic resin is an organosilicon-modified acrylic resin model 2029 produced by Green Union (Jining) Chemical Technology Co., Ltd.

[0032] The porous silica uses mesoporous silica with a pore size of 5-20 nm, and more specifically, uses mesoporous silica model XD-S05J produced by Qinghe Chaotai Metal Materials Co., Ltd.

[0033] The following preparation example is an example of the preparation of porous silica loaded with phosphate Preparation Example 1 A method for preparing porous silica loaded with phosphate comprises the following steps: S1. The porous silica is first immersed in a phosphate solution with a mass concentration of 4 wt% at normal pressure for 15 min, then filtered, centrifuged and washed to obtain primary porous silica; S2, then immersing the primary modified porous silica in a phosphate solution with a mass concentration of 8wt% for 15min at an immersion pressure of 0.2MPa, and then filtering, centrifuging, and washing to obtain the secondary modified porous silica; S3, immersing the obtained second-modified porous silica in a phosphate solution with a mass concentration of 25wt% at normal pressure for 20min, then filtering, centrifuging and washing to obtain the third-modified porous silica; S4, immersing the obtained three-modified porous silica in a phosphate solution with a mass concentration of 28 wt% at normal pressure for 10 minutes, then filtering, centrifuging, washing and drying to obtain porous silica loaded with phosphoric acid. The above phosphate solution is specifically selected from ammonium phosphate solution.

[0034] Preparation Example 2 A method for preparing porous silica loaded with phosphate comprises the following steps: S1. The porous silica is first immersed in a phosphate solution (a mixed solution of phosphate and water) with a mass concentration of 3 wt% at normal pressure for 20 min, and then filtered, centrifuged and washed to obtain a primary porous silica; S2, then immersing the primary modified porous silica in a phosphate solution with a mass concentration of 5wt% for 20min at an immersion pressure of 0.2MPa, and then filtering, centrifuging, and washing to obtain the secondary modified porous silica; S3, immersing the obtained second-modified porous silica in a phosphate solution with a mass concentration of 20wt% at normal pressure for 25min, then filtering, centrifuging and washing to obtain the third-modified porous silica; S4, immersing the obtained three-modified porous silica in a phosphate solution with a mass concentration of 25wt% at normal pressure for 15min, then filtering, centrifuging, washing and drying to obtain porous silica loaded with phosphoric acid. The above phosphate solution is specifically selected from sodium tripolyphosphate solution.

[0035] Preparation Example 3 A method for preparing porous silica loaded with phosphate comprises the following steps: S1. The porous silica is first immersed in a phosphate solution with a mass concentration of 5 wt% at normal pressure for 10 min, then filtered, centrifuged and washed to obtain primary porous silica; S2, then immersing the primary modified porous silica in a phosphate solution with a mass concentration of 10wt% for 10min at an immersion pressure of 0.3MPa, and then filtering, centrifuging, and washing to obtain the secondary modified porous silica; S3, immersing the obtained second-modified porous silica in a phosphate solution with a mass concentration of 30wt% at normal pressure for 15min, then filtering, centrifuging and washing to obtain the third-modified porous silica; S4, immersing the obtained three-modified porous silica in a phosphate solution with a mass concentration of 30wt% at normal pressure for 5min, then filtering, centrifuging, washing and drying to obtain porous silica loaded with phosphoric acid. The above phosphate solution is specifically selected from trisodium solution.

[0036] Preparation Example 4 A method for preparing porous silica loaded with phosphate is carried out according to the method in Preparation Example 1, except that step S2 is carried out under normal pressure.

[0037] Preparation Example 5 A method for preparing porous silica loaded with phosphate is carried out according to the method in Preparation Example 1, except that the porous silica is directly immersed in an ammonium phosphate solution with a mass concentration of 10wt% at normal pressure for 60min, and then filtered, centrifuged and washed to obtain the porous silica loaded with phosphate.

[0038] Example 1 A method for preparing an anti-corrosion admixture for shotcrete comprises the following steps: 15 kg of silica fume, 22 kg of fly ash, 6 kg of chitosan oligosaccharide and 12 kg of porous silica loaded with phosphate prepared in Preparation Example 1 were mixed, and then 5 kg of polypropylene fiber was added to mix, so as to prepare an anti-corrosion admixture.

[0039] Example 2 A method for preparing an anti-corrosion admixture for shotcrete comprises the following steps: 10 kg of silica fume, 15 kg of fly ash, 4 kg of chitosan oligosaccharide and 6 kg of porous silica loaded with phosphate prepared in Preparation Example 2 were mixed, and then 3 kg of polypropylene fiber was added to mix, so as to prepare an anti-corrosion admixture.

[0040] Example 3 A method for preparing an anti-corrosion admixture for shotcrete comprises the following steps: 20 kg of silica fume, 30 kg of fly ash, 8 kg of chitosan oligosaccharide and 18 kg of porous silica loaded with phosphate prepared in Preparation Example 3 were mixed, and then 8 kg of polypropylene fiber was added to mix, thereby preparing an anti-corrosion admixture.

[0041] Embodiment 4-5 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the porous silica loaded with phosphate is the porous silica loaded with phosphate prepared in Preparation Example 4 and Preparation Example 5, respectively.

[0042] Example 6 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the anti-corrosion admixture includes independently packaged component A and component B, wherein component A is mixed by the method in Example 1, and component B is mixed by 12 kg of silicone-modified acrylic resin and 4 kg of silane coupling agent KH-550, and the mass ratio of component A to component B is 1:9.

[0043] Example 7 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the anti-corrosion admixture includes independently packaged component A and component B, wherein component A is mixed by the method in Example 1, and component B is mixed by 8 kg of silicone-modified acrylic resin and 3 kg of silane coupling agent KH-550, and the mass ratio of component A to component B is 1:8.

[0044] Example 8 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the anti-corrosion admixture comprises independently packaged component A and component B, wherein component A is mixed by the method in Example 1, and component B is mixed by 15 kg of silicone-modified acrylic resin and 5 kg of silane coupling agent KH-550, and the mass ratio of component A to component B is 1:10.

[0045] Example 9 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the polypropylene fiber is added after being modified. The specific operation is as follows: 1) Mix trimethylolpropane triglycidyl ether and N,N-dimethylformamide in a mass ratio of 1:5 to prepare a crosslinking agent solution, and then add a peroxide initiator, benzophenone and maleic anhydride to prepare a modifier solution; The peroxide initiator is selected from one or both of dibenzoyl peroxide and diisopropylbenzene peroxide, the added amount of the peroxide initiator is 1-3wt% of the added amount of trimethylolpropane triglycidyl ether, the added amount of benzophenone is 0.6wt% of the added amount of trimethylolpropane triglycidyl ether, the added mass ratio of maleic anhydride to trimethylolpropane triglycidyl ether is 1:2.5, and the added mass ratio of trimethylolpropane triglycidyl ether to polypropylene fiber is 1:5; 2) The polypropylene fiber was immersed in the prepared modifier solution for 35 minutes at a temperature of 60°C. After the immersion, the fiber was dried and then irradiated and cross-linked in an ultraviolet environment with a wavelength of 365 nm. The irradiation time was 15 minutes and the total amount of radiation was 10 kGy. Finally, the fiber was washed and dried to obtain the modified polypropylene fiber.

[0046] Example 10 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the polypropylene fiber is added after being modified. The specific operation is as follows: 1) Mix trimethylolpropane triglycidyl ether and N,N-dimethylformamide in a mass ratio of 1:5 to prepare a crosslinking agent solution, and then add a peroxide initiator, benzophenone and maleic anhydride to prepare a modifier solution; The peroxide initiator is selected from one or both of dibenzoyl peroxide and diisopropylbenzene peroxide, the added amount of the peroxide initiator is 1-3wt% of the added amount of trimethylolpropane triglycidyl ether, the added amount of benzophenone is 0.5wt% of the added amount of trimethylolpropane triglycidyl ether, the added mass ratio of maleic anhydride to trimethylolpropane triglycidyl ether is 1:2, and the added mass ratio of trimethylolpropane triglycidyl ether to polypropylene fiber is 1:4; 2) The polypropylene fiber is immersed in the prepared modifier solution for 30 minutes at a temperature of 65°C. After the immersion, it is dried and then radiated and cross-linked in an ultraviolet environment with a wavelength of 254 nm. The irradiation time is 10 minutes and the total radiation amount is 8 kGy. Finally, it is washed and dried to obtain the modified polypropylene fiber.

[0047] Embodiment 11 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the polypropylene fiber is added after being modified. The specific operation is as follows: 1) Mix trimethylolpropane triglycidyl ether and N,N-dimethylformamide in a mass ratio of 1:6 to prepare a crosslinking agent solution, and then add a peroxide initiator, benzophenone and maleic anhydride to prepare a modifier solution; The peroxide initiator is selected from one or both of dibenzoyl peroxide and diisopropylbenzene peroxide, the added amount of the peroxide initiator is 1-3wt% of the added amount of trimethylolpropane triglycidyl ether, the added amount of benzophenone is 0.8wt% of the added amount of trimethylolpropane triglycidyl ether, the added mass ratio of maleic anhydride to trimethylolpropane triglycidyl ether is 1:3, and the added mass ratio of trimethylolpropane triglycidyl ether to polypropylene fiber is 1:6; 2) The polypropylene fiber is immersed in the prepared modifier solution for 40 minutes at a temperature of 55°C. After the immersion, it is dried and then irradiated and cross-linked in an ultraviolet environment with a wavelength of 365nm. The irradiation time is 20 minutes and the total radiation amount is 12kGy. Finally, it is washed and dried to obtain the modified polypropylene fiber.

[0048] Comparative Example 1 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that chitosan oligosaccharide is not added.

[0049] Comparative Example 2 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that the porous silica loaded with phosphate is replaced by an equal amount of a mixture of sodium phosphate and porous silica, and the added mass ratio of sodium phosphate to porous silica is 1:4, that is, the sodium phosphate is not loaded on the porous silica, but the sodium phosphate, porous silica and silica fume are directly mixed and added.

[0050] Comparative Example 3 A method for preparing an anti-corrosion admixture for shotcrete is carried out according to the method in Example 1, except that an equal amount of porous silica loaded with phosphate is replaced by sodium phosphate.

[0051] Application Examples The anti-corrosion admixtures prepared in the above examples and comparative examples are applied to the preparation of concrete. More specifically, the method for preparing concrete using the anti-corrosion admixture comprises the following steps: 300 kg of cement (42.5 grade ordinary Portland cement) is mixed with 950 kg of coarse aggregate (crushed stone with a continuous particle size of 5-20 mm) and 680 kg of fine aggregate (sand with a fineness modulus of 3.3-3.5) to prepare a primary mixture, and then 3 kg of a water reducer (polycarboxylate water reducer) is mixed with 145 kg of water, and 8 kg of the above-mentioned anti-corrosion admixture is added, stirred and mixed, and then the primary mixture is added, and stirred and mixed to prepare shotcrete.

[0052] Performance Testing The concrete prepared by using the anti-corrosion admixtures in the above examples and comparative examples was made into concrete specimens and then immersed in deionized water after standard curing for 28 days. After immersion for 7 days, the Ca content in the immersion solution was detected. 2+ Concentration, at the same time, concrete specimens without anti-corrosion admixture were selected as the control group and the above operation was also carried out. The Ca 2+ The test results are shown in Table 1 below.

[0053] Table 1: With reference to the test results of the embodiment and the control group in Table 1 above, it can be seen that when the anti-corrosion admixture prepared in the embodiment is added to the concrete, the calcium ion dissolution of the concrete can be effectively reduced. With reference to the test results of Example 1 and Example 4, when porous silica is loaded with phosphate, when multi-gradient impregnation treatment is performed, no pressurization treatment is performed during low-concentration impregnation treatment, and the final calcium ion dissolution phenomenon is increased. Low-concentration pressurized impregnation treatment is more conducive to the penetration of phosphate, which helps to fix calcium. Combined with the test results of Example 5, when porous silica is loaded with phosphate, a single concentration is used for penetration, and its load is more uniform, and its anti-corrosion performance is significantly reduced. The gradient impregnation in Example 1 helps to form a gradient load, and thus the calcium fixation effect can be better exerted.

[0054] Referring to the test results of Example 1 and Examples 6-8, when the anti-corrosion admixture is also added with silicone-modified acrylic resin and silane coupling agent, its anti-corrosion performance is further improved. Combined with the test results of Examples 9-11, the anti-corrosion performance of the polypropylene fiber is greatly improved after the modification. The formation of the cross-linked structure on the polypropylene fiber and the introduction of the carboxylic acid functional group are more conducive to forming chemical bonds with chitosan oligosaccharides and porous silica, which is more conducive to the fixation of calcium and the prevention of migration, thereby improving its anti-corrosion performance. Combined with the test results of Example 1 and Comparative Example 1, when chitosan oligosaccharides are not added in Comparative Example 1, its anti-corrosion effect is reduced. Combined with the test results of Comparative Examples 2 and 3, when phosphate and porous silica are directly added without loading or only sodium phosphate is added, its anti-corrosion effect is significantly reduced.

[0055] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An anti-corrosion admixture for shotcrete, characterized in that: It includes the following raw materials in parts by weight: 10-20 parts of silica fume, 15-30 parts of fly ash, 3-8 parts of polypropylene fiber, 4-8 parts of chitosan oligosaccharide and 6-18 parts of porous silica loaded with phosphate.

2. The anti-corrosion admixture for shotcrete according to claim 1, characterized in that: The polypropylene fiber is added after being modified, and the specific operation is as follows: 1) Mix trimethylolpropane triglycidyl ether and N,N-dimethylformamide to prepare a crosslinking agent solution, and then add a peroxide initiator, benzophenone and maleic anhydride to prepare a modifier solution; 2) The polypropylene fiber is immersed in the prepared modifier solution, and then after drying, it is irradiated and cross-linked in an ultraviolet environment with a wavelength of 254-365nm. The irradiation time is 10-20min, and the total radiation amount is 8-12kGy. Finally, it is washed and dried to obtain the modified polypropylene fiber.

3. The anti-corrosion admixture for shotcrete according to claim 2, characterized in that: In the polypropylene fiber modification process, the mass ratio of trimethylolpropane triglycidyl ether to N,N-dimethylformamide added in step 1) is 1:(5-6); The added amount of the peroxide initiator is 1-3wt% of the added amount of trimethylolpropane triglycidyl ether, the added amount of benzophenone is 0.5-0.8wt% of the trimethylolpropane triglycidyl ether, the added mass ratio of maleic anhydride to trimethylolpropane triglycidyl ether is 1:(2-3), and the added mass ratio of trimethylolpropane triglycidyl ether to polypropylene fiber is 1:(4-6).

4. The anti-corrosion admixture for shotcrete according to claim 2, characterized in that: When the polypropylene fiber is modified, the immersion time in step 2) is 30-40 minutes and the immersion temperature is 55-65°C.

5. The anti-corrosion admixture for shotcrete according to claim 2, characterized in that: The peroxide initiator is selected from one or both of dibenzoyl peroxide and dicumyl peroxide.

6. The anti-corrosion admixture for shotcrete according to claim 1, characterized in that: The porous silica loaded with phosphate is prepared by the following method: The porous silica is first immersed in a phosphate solution with a mass concentration of 3-5wt% at normal pressure for 10-20min, then filtered, centrifuged and washed to obtain primary porous silica; Then the primary modified porous silica is immersed in a phosphate solution with a mass concentration of 5-10wt% for 10-20min at a pressure of 0.2-0.3MPa, and then filtered, centrifuged, and washed to obtain the secondary modified porous silica; The obtained second-modified porous silica is immersed in a phosphate solution with a mass concentration of 20-30wt% at normal pressure for 15-25min, and then filtered, centrifuged and washed to obtain the third-modified porous silica; The prepared triple-modified porous silica is immersed in a phosphate solution with a mass concentration of 25-30wt% at normal pressure for 5-15 minutes, and then filtered, centrifuged, washed and dried to obtain porous silica loaded with phosphoric acid.

7. The anti-corrosion admixture for shotcrete according to claim 1, characterized in that: The phosphate is selected from one or more of trisodium phosphate, ammonium phosphate, and sodium tripolyphosphate.

8. The anti-corrosion admixture for shotcrete according to claim 1, characterized in that: The anti-corrosion additive also contains 8-15 parts of organosilicon-modified acrylic resin and 3-5 parts of silane coupling agent.

9. A method for preparing the anti-corrosion admixture for shotcrete as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: The anti-corrosion admixture is prepared by mixing silica fume, fly ash, chitosan oligosaccharide and porous silica loaded with phosphate and then adding polypropylene fiber.

10. Use of the anti-corrosion admixture for shotcrete as claimed in any one of claims 1 to 8 in shotcrete.

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