A concrete admixture resistant to acid rain erosion and preparation method thereof

Abstract

The present invention belongs to the technical field of building materials, and specifically relates to a concrete admixture resistant to acid rain erosion and a preparation method thereof. In the present invention, slag ore, a waste material generated during tunnel excavation, is selected as a raw material, the ratio of quartz and feldspar is regulated by a neutral flotation solution, and dimethylacetamide is used in an alkaline environment to react with feldspar microcrystals attached to the quartz surface on the surface of the slag powder, thereby forming an organic coating on the surface of the slag powder. The organic coating can block the pores of the slag powder and produce a protective effect against acidic chemical erosion media, thereby making the slag powder have higher impermeability and chemical corrosion resistance. At the same time, borax is also added in the present invention. Borax hinders the agglomeration of impurities such as ettringite around the concrete skeleton under microscopic conditions, effectively improving the fluidity of the concrete and effectively preventing the reduction of the mechanical properties of the concrete structure.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a concrete admixture resistant to acid rain erosion and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] The performance of concrete structures exposed to acid rain corrosion environment for a long time deteriorates rapidly. The damage of acid rain to concrete structures is mainly due to the chemical corrosive medium (H + , SO4 2- Acid rain (such as carbon monoxide, carbon monoxide, and chlorine) penetrates the pores of concrete, reacting chemically with certain components and causing the CSH gel to decompose. This degrades the concrete's strength and adhesion, impacting its performance. Furthermore, acid rain entering concrete structures accelerates the corrosion of rebar. Consequently, the aging of concrete structures and the resulting economic losses caused by acid rain are becoming increasingly serious.

[0004] The use of mineral admixtures, as the sixth component of concrete, in concrete is currently receiving increasing attention. However, since the raw materials for preparing mineral admixtures are derived from ores in the natural environment, they themselves contain a large amount of chemically corrosive media and are also prone to acid rain corrosion of concrete. At the same time, some low-cost concrete admixtures will cause the formation of impurities such as ettringite around the concrete skeleton, and there is also a risk of reducing the strength of concrete. In addition, some concrete admixtures will cause local agglomeration and stress concentration in the concrete after use. Therefore, how to solve the problems of improving concrete strength, acid rain corrosion resistance, and good dispersion in concrete after adding concrete admixtures is one of the important development directions of concrete admixtures. Summary of the Invention

[0005] To overcome the above-mentioned problems, the present invention provides a concrete admixture resistant to acid rain erosion and a preparation method thereof. The present invention uses slag ore, a waste material generated during tunnel excavation, as a raw material. The ratio of quartz to feldspar is regulated using a neutral flotation solution. Dimethylacetamide reacts with feldspar crystallites attached to the quartz surface of the slag powder in an alkaline environment, thereby forming an organic coating on the surface of the slag powder. This organic coating can block the pores of the slag powder and provide protection against acidic chemical erosion media, thereby imparting higher impermeability and chemical corrosion resistance to the slag powder. Furthermore, borax is added to the present invention. Borax, under microscopic conditions, inhibits the aggregation of impurities such as ettringite around the concrete skeleton, effectively improving the fluidity of the concrete and preventing degradation of the mechanical properties of the concrete structure.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a method for preparing a concrete admixture resistant to acid rain erosion, the method comprising the following steps:

[0008] (1) Crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation; then crushing the slag ore after flotation, washing and drying it to obtain pre-stone powder;

[0009] (2) adding the pre-stone powder obtained in step (1) to a dimethylacetamide solution, adjusting the pH value of the solution to alkaline, and heating to fully react to obtain organic fossil powder;

[0010] (3) placing the organic fossil powder obtained in step (2) in an organic solution of borax, stirring the mixture evenly, filtering to remove the solvent, and drying the mixture to obtain a concrete admixture resistant to acid rain erosion.

[0011] The second aspect of the present invention provides a concrete admixture resistant to acid rain corrosion prepared by the above preparation method.

[0012] The beneficial effects of the present invention are:

[0013] (1) The present invention uses slag ore, a waste material generated during the tunnel excavation process, as a raw material, and controls the ratio of quartz to feldspar by means of a neutral flotation solution. Dimethylacetamide is used in an alkaline environment to react with feldspar microcrystals attached to the quartz surface of the slag powder, thereby forming an organic coating on the surface of the slag powder. The organic coating can block the pores of the slag powder and produce a protective effect against acidic chemical corrosion media, thereby making the slag powder have higher impermeability and chemical corrosion resistance.

[0014] (2) In the present invention, the slag ore after flotation is crushed to obtain ultrafine slag stone powder with a particle size of ≤80μm, medium-fine slag stone powder with a particle size of 80-200μm, and coarse slag stone powder with a particle size of 0.2-1.0mm. The ultrafine slag stone powder improves the density and durability of cement, the medium-fine slag stone powder can make the equilibrium torque and the torque integral area tend to be balanced, so as to achieve the stability of the performance of the admixture of the present invention, and the coarse slag stone powder can improve the stirring and dispersing effect when the admixture of the present invention is mixed with concrete, so that the admixture can be effectively dispersed in the concrete.

[0015] (3) In the present invention, the addition of coarse slag stone powder and borax can improve the stirring and dispersing effect when the admixture of the present invention is mixed with concrete, prevent the occurrence of local agglomeration and stress concentration in the concrete, effectively improve the fluidity of the concrete, and effectively prevent the reduction of the mechanical properties of the concrete structure. DETAILED DESCRIPTION

[0016] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0018] A first typical embodiment of the present invention provides a method for preparing a concrete admixture resistant to acid rain erosion, the method comprising the following steps:

[0019] (1) Crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation; then crushing the slag ore after flotation, washing and drying it to obtain pre-stone powder;

[0020] (2) adding the pre-stone powder obtained in step (1) to a dimethylacetamide solution, adjusting the pH value of the solution to alkaline, and heating to fully react to obtain organic fossil powder;

[0021] (3) placing the organic fossil powder obtained in step (2) in an organic solution of borax, stirring the mixture evenly, filtering to remove the solvent, and drying the mixture to obtain a concrete admixture resistant to acid rain erosion.

[0022] In one or more embodiments, in step (1), the slag ore is quartz slag ore; slag ore, a waste material generated during tunnel excavation, can be directly selected. Such slag ore mainly contains quartz and feldspar. Preferably, the feldspar content in the slag ore is ≥10 wt%.

[0023] In one or more embodiments, in step (1), the method for preparing the neutral flotation liquid comprises: dissolving chloroacetic acid in a 2 wt % sodium hydroxide alcohol aqueous solution to prepare a 4 mol / L chloroacetic acid solution, and then slowly adding oxalic acid to adjust the pH value to 6.8-7.2, thereby obtaining the neutral flotation liquid; wherein the volume ratio of ethanol to water in the 2 wt % sodium hydroxide alcohol aqueous solution is 2:8.

[0024] When the neutral flotation liquid is used, the upper oil layer needs to be separated and removed, and sodium hexametaphosphate is added as an inhibitor at a ratio of 2 wt%.

[0025] In one or more embodiments, in step (1), the feldspar content of the slag ore after flotation is 8-10 wt %. The neutral flotation liquid is added to adjust the ratio of quartz to feldspar.

[0026] In one or more embodiments, in step (1), the slag ore after flotation is crushed to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80-200 μm, and coarse slag powder with a particle size of 0.2-1.0 mm.

[0027] Furthermore, the mass ratio of the ultrafine slag stone powder, the medium-fine slag stone powder and the coarse slag stone powder is 1: (0.7-0.8): (0.2-0.3).

[0028] Ultrafine slag stone powder can be considered quartz microspheres, which act as fillers in cement. Cement systems treated with quartz microspheres exhibit higher viscosities than untreated systems. Furthermore, the inventors' research has found that the quartz microsphere content also affects cement performance. An appropriate amount of quartz microspheres can improve cement performance, replacing some cementitious materials and enhancing cement density and durability. This is because quartz microspheres exhibit a ball bearing effect, and cement systems with a high quartz microsphere content exhibit greater shear sensitivity. With increasing quartz microsphere content, the apparent viscosity of the cement material first increases and then decreases. However, the apparent viscosity is not significantly related to quartz microsphere particle size. The maximum torque first increases and then decreases with increasing quartz microsphere content, while the energy consumption versus time curves, represented by the equilibrium torque and torque integrated area, show a generally increasing trend. As the particle size of the slag stone powder increases, the addition of medium-fine slag stone powder can balance the equilibrium torque and torque integrated area, thereby achieving the stability of the performance of the admixture of the present invention. The final addition of coarse slag powder ensures the effectiveness of the overall admixture. Overly fine admixtures can produce water-based agglomerates during use, resulting in poor dispersibility. However, admixtures made with a small amount of coarse slag powder can improve the mixing and dispersion effect when subsequently mixed with concrete, allowing the admixture to be effectively dispersed in the concrete.

[0029] In one or more embodiments, in step (2), the solvent in the dimethylacetamide solution is a mixed solution of alcohol and water, preferably a mixed solution of ethanol and water, and further preferably, the volume ratio of ethanol to water is 0.6-0.8:0.4-0.2, preferably 0.7:0.3;

[0030] The concentration of dimethylacetamide in the dimethylacetamide solution is 1-3 mol / L.

[0031] In one or more embodiments, in step (2), the mass ratio of dimethylacetamide to pre-stone powder is 87-261:200.

[0032] In one or more embodiments, in step (2), triethylamine is added to adjust the pH value to 9-11 to form the alkaline condition.

[0033] In one or more embodiments, in step (2), the temperature of the heating reaction is 55 to 65° C., preferably 60° C.; the time of the heating reaction is 30 to 60 minutes, preferably 45 minutes.

[0034] There are two main reasons for treating slag ore in an alkaline environment: first, the acidic chemical corrosion medium remaining in the slag powder can be neutralized under alkaline conditions; second, dimethylacetamide reacts with the feldspar microcrystals attached to the quartz surface on the surface of the slag powder in an alkaline environment, thereby forming an organic coating on the surface of the slag powder. This organic coating can seal the pores of the slag powder and produce a protective effect against acidic chemical corrosion media, making the slag powder have higher impermeability and resistance to chemical corrosion. It is worth noting that compared with the preparation method of mixing high-purity quartz sand and silicate and then reacting with dimethylacetamide, the effect of directly using slag powder for reaction is better. This is because quartz and feldspar are highly combined under natural conditions in slag powder, which is also a disadvantage of the difficulty of flotation separation of common slag ores. However, for the present invention, the high combination of quartz and feldspar under natural conditions can ensure that the organic coating formed by dimethylacetamide can effectively coat and protect the quartz microbeads at the same time. After high-purity quartz sand and silicate are treated in the same way, the quartz sand and silicate are still in a separated state, and the organic coating is difficult to effectively protect the quartz sand, thereby affecting the acid rain corrosion resistance.

[0035] In one or more embodiments, in the step (3), the solvent in the organic solution of borax is a mixed solution of alcohol and water, preferably a mixed solution of ethanol and water. Further preferably, the volume ratio of ethanol to water is 0.6-0.8:0.4-0.2, preferably 0.7:0.3.

[0036] In one or more embodiments, in step (3), the amount of borax used is 0.8 to 1.2 wt% of the mass of the organic fossil powder.

[0037] The introduction of borax inhibits the aggregation of impurities such as ettringite around the concrete skeleton at a microscopic level, effectively improving the concrete's fluidity and preventing a reduction in the mechanical properties of the concrete structure. The addition of borax to the organic solvent also prevents the agglomeration of the slag powder in the aqueous system, ensuring that the resulting slag powder is fine and has good doping properties.

[0038] In one or more embodiments, a method for preparing a concrete admixture resistant to acid rain erosion comprises the following steps:

[0039] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, and placing the gravel in a neutral flotation solution for flotation; then crushing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80 to 200 μm, and coarse slag powder with a particle size of 0.2 to 1.0 mm, washing and drying the ultrafine slag powder, medium-fine slag powder, and coarse slag powder, respectively, and mixing them in a mass ratio of 1: (0.7 to 0.8): (0.2 to 0.3) to obtain pre-stone powder;

[0040] (2) adding the pre-stone powder obtained in step (1) to a 1-3 mol / L dimethylacetamide alcohol aqueous solution, adjusting the pH value of the solution to 9-11, and heating at 55-65° C. for 30-60 minutes to fully react, thereby obtaining organic fossil powder;

[0041] (3) placing the organic fossil powder obtained in step (2) in an alcohol-water solution of borax, stirring the mixture evenly, filtering to remove the solvent, and drying the mixture to obtain a concrete admixture resistant to acid rain erosion.

[0042] A second typical embodiment of the present invention provides a concrete admixture resistant to acid rain corrosion prepared by the above preparation method.

[0043] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0044] Prepare a neutral flotation fluid: Dissolve chloroacetic acid in a 2wt% sodium hydroxide-alcoholic aqueous solution to create a 4 mol / L chloroacetic acid solution. Slowly add oxalic acid to adjust the pH to 6.8-7.2. The 2wt% sodium hydroxide-alcoholic aqueous solution contains a volume ratio of ethanol to water of 2:8. Remove the upper oil layer and add 2wt% sodium hexametaphosphate as a suppressant.

[0045] Example 1

[0046] Preparation of concrete admixtures resistant to acid rain erosion:

[0047] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation, adjusting the amount of feldspar, and then pulverizing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80 to 200 μm, and coarse slag powder with a particle size of 0.2 to 1.0 mm, washing and drying the ultrafine slag powder, medium-fine slag powder, and coarse slag powder, respectively, and mixing them in a mass ratio of 1:0.75:0.25 to obtain pre-stone powder; characterization shows that the feldspar content in the pre-stone powder is about 8.6 wt%, the quartz content is about 91.3 wt%, and the remainder is a small amount of inevitable impurities;

[0048] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylacetamide was added to prepare a 2 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylacetamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylacetamide solution, and heated at 60°C for 45 minutes to fully react to obtain organic fossil powder;

[0049] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0050] Example 2

[0051] Preparation of concrete admixtures resistant to acid rain erosion:

[0052] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation, adjusting the amount of feldspar, and then pulverizing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80 to 200 μm, and coarse slag powder with a particle size of 0.2 to 1.0 mm, washing and drying the ultrafine slag powder, medium-fine slag powder, and coarse slag powder, respectively, and mixing them in a mass ratio of 1:0.7:0.3 to obtain pre-stone powder; characterization shows that the feldspar content in the pre-stone powder is about 8.8wt%, the quartz content is about 91.2wt%, and the remainder is a small amount of inevitable impurities;

[0053] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylacetamide was added to prepare a 1.5 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylacetamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylacetamide solution, and heated at 60°C for 45 minutes to fully react, thereby obtaining organic fossil powder;

[0054] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0055] Example 3

[0056] Preparation of concrete admixtures resistant to acid rain erosion:

[0057] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation, adjusting the amount of feldspar, and then pulverizing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80 to 200 μm, and coarse slag powder with a particle size of 0.2 to 1.0 mm, washing and drying the ultrafine slag powder, medium-fine slag powder, and coarse slag powder, respectively, and mixing them in a mass ratio of 1:0.8:0.2 to obtain pre-stone powder; characterization shows that the feldspar content in the pre-stone powder is about 8.7 wt%, the quartz content is about 91.2 wt%, and the remainder is a small amount of inevitable impurities;

[0058] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylacetamide was added to prepare a 3 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylacetamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylacetamide solution, and heated at 60°C for 45 minutes to fully react, thereby obtaining organic fossil powder;

[0059] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0060] Experimental Example 1

[0061] A base material was prepared by mixing a reference cement and the acid rain-resistant concrete admixture prepared in Examples 1 to 3 in a mass ratio of 7:3, wherein the reference cement was commercially available Portland cement. The base material and kaolin were mixed in a conventional 1:1 mass ratio, and water was added to control the water-cement ratio to 0.6, followed by stirring to prepare concrete. Furthermore, the same concrete was prepared using the reference cement without the acid rain-resistant concrete admixture as the base material for comparison and testing. The tests included compressive strength testing, salt spray aging testing, and acid corrosion testing. The compressive strength test results are shown in Table 1 below, and the salt spray aging and acid corrosion test results are shown in Table 2.

[0062] The salt spray aging test is a neutral salt spray aging test. The concrete sample is placed in a salt spray chamber and subjected to a neutral salt spray test. The test temperature is selected to be 35°C. The pH value is adjusted to 6.5-7.2, and the salt spray sedimentation rate is 1-3mL / 80cm 2 h, and the sedimentation volume is 1-2 mL / 80 cm 2 The salt spray test lasted for 14 days. The mass loss rate before and after the test was calculated.

[0063] In the acid corrosion test, the concrete specimens were placed in an acidic solution with a pH of 3.5. After 28 days, the specimens were weighed and the mass loss rate before and after the test was calculated.

[0064] Table 1 Compressive strength test results

[0065] serial number 3-day intensity 7-day strength 28-day strength Benchmark comparison 6.8MPa 27.1MPa 38.9MPa Example 1 7.2MPa 29.3MPa 41.2MPa Example 2 7.0MPa 29.2MPa 41.2MPa Example 3 7.3MPa 29.3MPa 41.0MPa

[0066] Table 2 Results of salt spray aging test and acid corrosion test

[0067]

[0068] It can be seen from the compressive strength test results in Table 1 that the addition of the acid rain resistant concrete admixture of the present invention can slightly improve the compressive strength of the concrete.

[0069] The salt spray aging test and acid corrosion test results in Table 2 show that the addition of the acid rain-resistant concrete admixture of the present invention significantly improves the corrosion resistance of concrete. In particular, in the acid corrosion test, under strong acidic conditions, the mass loss rate decreased by approximately 77.6% to 78.6% after 28 days compared to the baseline, demonstrating a significant improvement in acid corrosion resistance.

[0070] Comparative Example 1

[0071] Preparation of concrete admixtures:

[0072] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a commercially available alkaline flotation solution (purchased from Xinhai Mining Technology Equipment Co., Ltd.), and then pulverizing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80 to 200 μm, and coarse slag powder with a particle size of 0.2 to 1.0 mm. The ultrafine slag powder, medium-fine slag powder, and coarse slag powder are washed and dried respectively, and mixed in a mass ratio of 1:0.75:0.25 to obtain pre-stone powder; characterization shows that the feldspar content in the pre-stone powder is about 2.9 wt%, the quartz content is about 97.0 wt%, and the remainder is a small amount of inevitable impurities;

[0073] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylacetamide was added to prepare a 2 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylacetamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylacetamide solution, and heated at 60°C for 45 minutes to fully react to obtain organic fossil powder;

[0074] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0075] Comparative Example 2

[0076] Preparation of concrete admixtures:

[0077] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation, adjusting the amount of feldspar, and then crushing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm and medium-fine slag powder with a particle size of 80 to 200 μm. The ultrafine slag powder and the medium-fine slag powder are washed and dried respectively, and mixed in a mass ratio of 1:0.75 to obtain pre-stone powder; characterization shows that the feldspar content in the pre-stone powder is about 8.7wt%, the quartz content is about 91.3wt%, and the remainder is a small amount of inevitable impurities;

[0078] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylacetamide was added to prepare a 2 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylacetamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylacetamide solution, and heated at 60°C for 45 minutes to fully react to obtain organic fossil powder;

[0079] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0080] Comparative Example 3

[0081] Preparation of concrete admixtures:

[0082] (1) crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation, adjusting the amount of feldspar, and then pulverizing the slag ore after flotation to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80 to 200 μm, and coarse slag powder with a particle size of 0.2 to 1.0 mm, washing and drying the ultrafine slag powder, medium-fine slag powder, and coarse slag powder, respectively, and mixing them in a mass ratio of 1:0.75:0.25 to obtain pre-stone powder; characterization shows that the feldspar content in the pre-stone powder is about 8.6 wt%, the quartz content is about 91.3 wt%, and the remainder is a small amount of inevitable impurities;

[0083] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylformamide was added to prepare a 2 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylformamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylformamide solution, and heated at 60°C for 45 minutes to fully react, thereby obtaining organic fossil powder;

[0084] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0085] Experimental Example 2

[0086] The base cement, the concrete admixtures prepared in Example 1 and Comparative Examples 1 to 3 were mixed in a mass ratio of 7:3 to prepare a base material, wherein the base cement was commercially available Portland cement. The base material and kaolin were mixed in a conventional mass ratio of 1:1, and water was added to control the water-cement ratio to 0.6, and concrete was prepared after stirring. In addition, the same concrete preparation was carried out using the base cement without the addition of the acid rain erosion resistant concrete admixture as the base material as a benchmark comparison and test. The test included a compressive strength test, a salt spray aging test and an acid corrosion test. The compressive strength test results are shown in Table 3 below, and the salt spray aging test and acid corrosion test results are shown in Table 4. The salt spray aging test and the acid corrosion test are the same as those in Experimental Example 1.

[0087] Table 3 Compressive strength test results

[0088] serial number 3-day intensity 7-day strength 28-day strength Benchmark comparison 6.8MPa 27.1MPa 38.9MPa Example 1 7.2MPa 29.3MPa 41.2MPa Comparative Example 1 7.5MPa 29.7MPa 43.1MPa Comparative Example 2 6.5MPa 25.8MPa 38.0MPa Comparative Example 3 7.3MPa 29.1MPa 41.1MPa

[0089] Table 4 Results of salt spray aging test and acid corrosion test

[0090]

[0091] From the compressive strength test results in Table 3, it can be seen that the addition of the acid rain resistant concrete admixture of the present invention can slightly improve the compressive strength of the concrete.

[0092] Compared with Example 1, Comparative Example 1, which employed alkaline flotation to increase the quartz content in the slag powder, did improve the mechanical properties of the concrete, but exhibited some degradation in corrosion resistance, particularly in the acid corrosion test, far inferior to Example 1. This suggests that retaining a certain amount of feldspar in the slag powder significantly improves the performance of the admixture. Furthermore, horizontal comparative tests were conducted using different process controls to control the feldspar content of the slag powder to approximately 3.7wt%, 5.9wt%, 8.1wt%, 9.8wt%, 10.9wt%, and 11.6wt%, with all other impurities ≤0.1wt%. The results showed that to achieve good corrosion resistance (neutral salt spray aging test mass loss ≤0.65% and acid corrosion test mass loss ≤3.5%), a feldspar content of 8.1-9.8wt% was required. Excessive feldspar content slightly weakened the corrosion resistance and significantly decreased the mechanical properties.

[0093] Compared with Example 1, Comparative Example 2 did not use coarse slag powder, and a certain amount of agglomeration was found during the preparation process, which resulted in a decrease in mechanical properties and a significant decrease in corrosion resistance.

[0094] Compared with Example 1, Comparative Example 3, which uses dimethylformamide instead of dimethylacetamide, also exhibits a significant decrease in corrosion resistance. This is because the organic coating formed by the reaction of dimethylformamide with feldspar is relatively weaker than that of dimethylacetamide.

[0095] Comparative Example 4

[0096] Preparation of concrete admixtures:

[0097] (1) Ultrafine quartz powder with a particle size of ≤80 μm and ultrafine feldspar powder with a particle size of ≤80 μm are selected and mixed in a mass ratio of 8.5:91.5 to form an ultrafine mixed powder; medium-fine quartz powder with a particle size of 80-200 μm and medium-fine feldspar powder with a particle size of 80-200 μm are selected and mixed in a mass ratio of 8.5:91.5 to form a medium-fine mixed powder; coarse quartz powder with a particle size of 0.2-1.0 mm and coarse feldspar powder with a particle size of 0.2-1.0 mm are selected and mixed in a mass ratio of 8.5:91.5 to form a coarse mixed powder; the ultrafine mixed powder, medium-fine mixed powder and coarse mixed powder are mixed in a mass ratio of 1:0.75:0.25 to form a pre-stone powder, wherein the quartz powder and feldspar powder are both commercially available products with a purity of ≥99.0%;

[0098] (2) Ethanol and water were mixed in a volume ratio of 7:3 as a solvent, dimethylacetamide was added to prepare a 2 mol / L dimethylacetamide solution, and the pH value was adjusted to 10.5 with triethylamine. The pre-stone powder was added to the dimethylacetamide solution at a ratio of 200 g of pre-stone powder per liter of dimethylacetamide solution, and heated at 60°C for 45 minutes to fully react to obtain organic fossil powder;

[0099] (3) Ethanol and water are mixed in a volume ratio of 7:3 as a solvent, 1 wt% of the mass of organic fossil powder (commercially available 80 mesh borax) is dispersed in the solvent, and then the organic petrochemical powder is added to ensure that the organic fossil powder is completely immersed and then stirred and mixed. After filtering to remove the solvent and drying, a concrete admixture resistant to acid rain erosion is obtained.

[0100] Experimental Example 3

[0101] The base material was prepared by mixing the reference cement, the concrete admixtures prepared in Example 1 and Comparative Example 4 in a mass ratio of 7:3, wherein the reference cement was commercially available Portland cement. The base material and kaolin were mixed in a conventional mass ratio of 1:1, and water was added to control the water-cement ratio to 0.6, and concrete was prepared after stirring. In addition, the same concrete preparation was carried out using the reference cement without the acid rain erosion resistant concrete admixture as the base material as a benchmark comparison and test. The test included a compressive strength test, a salt spray aging test and an acid corrosion test. The compressive strength test results are shown in Table 5 below, and the salt spray aging test and acid corrosion test results are shown in Table 6. The salt spray aging test and acid corrosion test were the same as those in Experimental Example 1.

[0102] Table 5 Compressive strength test results

[0103] serial number 3-day intensity 7-day strength 28-day strength Benchmark comparison 6.8MPa 27.1MPa 38.9MPa Example 1 7.2MPa 29.3MPa 41.2MPa Comparative Example 4 7.9MPa 30.2MPa 43.9MPa

[0104] Table 6 Results of salt spray aging test and acid corrosion test

[0105]

[0106] From the above test results, it can be seen that the mechanical properties of the admixture prepared by directly using high-purity quartz powder and feldspar powder as raw materials are significantly improved compared with Example 1, which shows that quartz powder does have a strong ability to improve the mechanical properties of concrete. However, from the corrosion resistance test, it can be seen that the corrosion resistance of concrete prepared by using the mixed powder obtained by mixing quartz powder and feldspar powder as pre-stone powder is significantly lower than that of Example 1 in which slag stone powder is directly used for preparation. This is because when slag stone powder is directly used for preparation, the actual remaining feldspar after controlling the feldspar content is very firmly combined with quartz. During the treatment process of step (2), feldspar actually plays the role of a "connector" to achieve an effective combination of quartz, feldspar and organic modifier, which is difficult to achieve in the treatment of step (2) in Comparative Example 4. Under natural conditions, the high degree of bonding between quartz and feldspar ensures that the organic coating formed by dimethylacetamide can effectively protect the quartz microbeads. However, when high-purity quartz sand and silicate are treated in the same manner, the quartz sand and silicate remain separated, making it difficult for the organic coating to effectively protect the quartz sand, thereby affecting its resistance to acid rain corrosion. This also indirectly proves that simply mixing quartz and feldspar does not produce the desired effect. Instead, it is necessary to directly use slag powder, which forms a very strong bond under natural conditions, as the raw material to achieve the desired effect.

[0107] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a concrete admixture resistant to acid rain erosion, characterized in that: The preparation method comprises the following steps: (1) Crushing the slag ore to obtain gravel with a particle size of 5 to 20 mm, placing the gravel in a neutral flotation solution for flotation; then crushing the slag ore after flotation, washing and drying it to obtain pre-stone powder; (2) adding the pre-stone powder obtained in step (1) to a dimethylacetamide solution, adjusting the pH value of the solution to alkaline, and heating to fully react to obtain organic fossil powder; (3) placing the organic fossil powder obtained in step (2) in an organic solution of borax, stirring evenly, filtering to remove the solvent, and drying to obtain a concrete admixture resistant to acid rain erosion; In the step (1), the slag ore is quartz slag ore, and the feldspar ratio in the quartz slag ore is ≥10wt%; the feldspar content of the slag ore after flotation is 8-10wt%; In the step (1), the slag ore after flotation is crushed to obtain ultrafine slag powder with a particle size of ≤80 μm, medium-fine slag powder with a particle size of 80-200 μm, and coarse slag powder with a particle size of 0.2-1.0 mm; the mass ratio of the ultrafine slag powder, medium-fine slag powder, and coarse slag powder is 1:(0.7-0.8):(0.2-0.3); In the step (2), the concentration of dimethylacetamide in the dimethylacetamide solution is 1 to 3 mol / L; In the step (3), the amount of borax used is 0.8 to 1.2 wt% of the mass of the organic fossil powder.

2. The preparation method according to claim 1, wherein In step (1), the preparation method of the neutral flotation liquid comprises: dissolving chloroacetic acid in a 2wt% sodium hydroxide alcohol aqueous solution to prepare a 4 mol / L chloroacetic acid solution, and then slowly adding oxalic acid to adjust the pH value to 6.8-7.2, thereby obtaining the neutral flotation liquid; wherein the volume ratio of ethanol to water in the 2wt% sodium hydroxide alcohol aqueous solution is 2:

8.

3. The preparation method according to claim 1, wherein In the step (2), the solvent in the dimethylacetamide solution is a mixed solution of alcohol and water.

4. The preparation method according to claim 3, wherein In the step (2), the solvent in the dimethylacetamide solution is a mixed solution of ethanol and water.

5. The preparation method according to claim 4, wherein The volume ratio of ethanol to water is 0.6-0.8:0.4-0.

2.

6. The preparation method according to claim 5, wherein The volume ratio of ethanol to water is 0.7:0.

3.

7. The preparation method according to claim 1, wherein In the step (2), the mass ratio of dimethylacetamide to pre-stone powder is 87-261:200; Alternatively, in step (2), triethylamine is added to adjust the pH value to 9-11 to form the alkaline condition.

8. The preparation method according to claim 1, wherein In the step (2), the temperature of the heating reaction is 55 to 65° C.; and the time of the heating reaction is 30 to 60 minutes.

9. The preparation method according to claim 8, wherein In the step (2), the temperature of the heating reaction is 60° C.; the time of the heating reaction is 45 minutes.

10. The preparation method according to claim 1, wherein In the step (3), the solvent in the organic solution of borax is a mixed solution of alcohol and water.

11. The preparation method according to claim 10, characterized in that In the step (3), the solvent in the organic solution of borax is a mixed solution of ethanol and water.

12. The preparation method according to claim 11, characterized in that The volume ratio of ethanol to water is 0.6-0.8:0.4-0.

2.

13. The preparation method according to claim 12, wherein The volume ratio of ethanol to water is 0.7:0.

3.

14. A concrete admixture resistant to acid rain corrosion prepared by the preparation method according to any one of claims 1 to 13.

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