Concrete with high salt corrosion resistance based on chloride ion chemical fixation and preparation method thereof

Abstract

The invention discloses high salt corrosion resistant concrete based on chloride ion chemical fixation and a preparation method thereof. The concrete is prepared from the following components in parts by weight: 270 to 400 parts of cement, 50 to 100 parts of mineral admixture, 3 to 15 parts of styrene-acrylic emulsion, 600 to 800 parts of fine aggregate, 1000 to 1200 parts of coarse aggregate, 5 to 10 parts of composite admixture, 12 to 15 parts of salt corrosion resistant agent and 150 to 180 parts of water, the mineral admixture is composed of 1000-mesh fly ash, 2000-mesh fly ash and fly ash microbeads, the addition amount of the 1000-mesh fly ash accounts for 45-55% of the total mass of the mineral admixture, the addition amount of the 2000-mesh fly ash accounts for 15-25% of the total mass of the mineral admixture, and the addition amount of the fly ash microbeads accounts for 25-35% of the total mass of the mineral admixture; the composite admixture is composed of a polycarboxylic acid type high-efficiency water reducing agent and an air entraining agent, the addition amount of the polycarboxylic acid type high-efficiency water reducing agent accounts for 80-90% of the total mass of the composite admixture, and the addition amount of the air entraining agent accounts for 10-20% of the total mass of the composite admixture. All the components of the concrete have a synergistic effect, so that the strength and the durability can be ensured on the basis of improving the salt corrosion resistance of the concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete preparation technology, specifically to a highly salt-resistant concrete based on chloride ion chemical fixation and its preparation method. Background Technology

[0002] In coastal areas, saline-alkali zones, and cold regions where de-icing salt is used, concrete structures are exposed to high-salt environments for extended periods, making them susceptible to salt corrosion. Chloride salts, in particular, easily cause steel reinforcement corrosion, leading to a decrease in concrete strength and consequently affecting the durability and safety of buildings. Traditional concrete has poor resistance to salt corrosion, making it difficult to meet the engineering requirements of these special environments. Therefore, developing highly salt-resistant concrete with solidified chloride ions and a simple preparation process is of great significance. Although there has been considerable research on highly salt-resistant concrete, the technology and processes are complex, requiring the coordination of various admixtures in the concrete formulation, resulting in high raw material costs. Furthermore, the simultaneous balance between strength and durability is not always achieved, thus limiting the application of highly salt-resistant concrete. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a high salt-erosion-resistant concrete based on chloride ion chemical fixation and its preparation method. The components work synergistically to improve the concrete's salt-erosion resistance while simultaneously ensuring strength and durability.

[0004] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a high salt-erosion resistant concrete based on chloride ion chemical fixation, comprising the following components in parts by weight: 270-400 parts cement, 50-100 parts mineral admixture, 3-15 parts styrene-acrylic emulsion, 600-800 parts fine aggregate, 1000-1200 parts coarse aggregate, 5-10 parts composite admixture, 12-15 parts salt-erosion resistant agent, and 150-180 parts water; The mineral admixture is composed of 1000-mesh fly ash, 2000-mesh fly ash, and fly ash microspheres. The amount of 1000-mesh fly ash added accounts for 45-55% of the total mass of the mineral admixture, the amount of 2000-mesh fly ash added accounts for 15-25% of the total mass of the mineral admixture, and the amount of fly ash microspheres added accounts for 25-35% of the total mass of the mineral admixture. The composite admixture consists of a polycarboxylate superplasticizer and an air-entraining agent, with the polycarboxylate superplasticizer accounting for 80-90% of the total mass of the composite admixture and the air-entraining agent accounting for 10-20% of the total mass of the composite admixture.

[0005] Furthermore, the cement is 42.5 or 52.5 ordinary Portland cement, and the cement density is not less than 3.05 g / cm³. 3 Specific surface area not less than 300m² 2 / kg.

[0006] Furthermore, the average particle size of the mineral admixture is not greater than 6 μm, the D90 is not greater than 12 μm, and the specific surface area is not less than 5 m². 2 / g.

[0007] Furthermore, the styrene-acrylic emulsion has a solid content of more than 50%, a pH of 4-6, and a viscosity of less than 3000 mPa·s.

[0008] Furthermore, the fine aggregate is quartz sand or manufactured sand with a fineness modulus of 2 to 2.5, and the coarse aggregate is crushed stone or pebbles with a particle size of 5 to 20 mm.

[0009] Furthermore, the salt-resistant agent is composed of phosphogypsum and magnesite, with the amount of phosphogypsum accounting for 65-75% of the total weight of the salt-resistant agent and the amount of magnesite accounting for 25-35% of the total weight of the salt-resistant agent.

[0010] Furthermore, the salt-resistant agent is prepared by a grinding process, and its specific surface area after grinding is not less than 400 m². 2 / kg.

[0011] Secondly, the present invention also provides a method for preparing highly salt-resistant concrete based on chloride ion chemical fixation, comprising the following steps: (1) Weigh out cement, mineral admixtures, fine aggregates and coarse aggregates according to the proportions, and mix them evenly using a mixer to obtain a mixed dry material; (2) Weigh the compound admixture and water according to the proportion, dissolve the compound admixture in water, and stir evenly to obtain a compound admixture solution; (3) Mix the dry mixture obtained in step (1) with the composite admixture solution obtained in step (2), then add styrene-acrylic solution and stir evenly, and finally add salt erosion resistant agent and continue stirring until evenly mixed to obtain concrete paste.

[0012] The beneficial effects of this invention are as follows: (1) This invention provides a high salt-resistant concrete based on chloride ion chemical fixation, which adds a mineral admixture composed of 1000-mesh fly ash, 2000-mesh fly ash and fly ash microspheres. By selecting and controlling the fly ash particles, the cementitious material system and aggregate gradation are optimized, ensuring high salt resistance while giving the concrete good mechanical strength to meet structural load-bearing requirements. The mineral admixture added in this invention (average particle size ≤6μm, D90≤12μm) has a micro-aggregate filling effect and pozzolanic effect, making the internal structure of the concrete more compact and effectively blocking the intrusion channels of the corrosive medium. Moreover, the larger fly ash particles have a hollow structure and a complex internal specific surface area, which helps to resist the chloride ion in the cement paste. -It has physical adsorption and solidification effects. The fly ash (providing active Al2O3) and the salt corrosion resistant agent (creating a reaction environment) work together to provide a better and more durable aluminum source and reaction site for the generation of F salt or other solidified chloride ion products. (2) The high salt-resistant concrete of the present invention also contains styrene-acrylic emulsion, which can promote cement hydration, resulting in the production of more CSH gel to bind Cl. - This improves the cement colloid's ability to react with Cl. - It has good physical curing ability; at the same time, styrene-acrylic emulsion promotes chemical reaction with hydration products to generate more F salt and K salt, which improves chemical curing ability; at the same time, styrene-acrylic emulsion forms a physical barrier in the pores of concrete, which delays the erosion of the concrete interior by external solutions. (3) The high salt erosion resistant concrete of the present invention also contains composite admixtures, wherein the polycarboxylate high-efficiency water-reducing agent ensures that the concrete mixture still has excellent fluidity and pumpability after the addition of high salt erosion resistant components, making it easy to construct and pour; the introduction of air-entraining agent stably introduces an appropriate amount of small, closed air bubbles, further improving the freeze-thaw resistance of the concrete. (4) The high salt erosion resistant concrete of the present invention also contains a salt erosion resistant agent, which is made by grinding phosphogypsum and magnesite in a specific ratio. This component can react synergistically with cement hydration products, effectively refine the pore structure, reduce porosity, and generate an expansive sulfoaluminate phase, which significantly inhibits the penetration and diffusion of harmful substances such as chloride ions and sulfate ions, thereby greatly improving the long-term durability and service life of concrete in harsh environments such as saline-alkali land, coastal areas, and de-icing salt. (5) The main raw material of the salt erosion resistant agent in the high salt erosion resistant concrete of the present invention, phosphogypsum, is an industrial by-product. Its effective utilization not only reduces the cost of the concrete, but also provides a high-value-added resource utilization path for the large amount of accumulated phosphogypsum, which meets the requirements of green and sustainable development. The mineral admixture is mainly derived from the deep processing of industrial waste fly ash, which reduces the dependence on traditional expensive anti-corrosion additives or higher grade cement, and optimizes the cost of raw materials while ensuring high performance. Moreover, the preparation method is simple and reduces the operation difficulty in the production process.

[0013] (6) This invention introduces a styrene-acrylic emulsion with specific components into a high salt-erosion resistant concrete system, which produces a significant synergistic effect with ultrafine mineral admixtures and salt-erosion resistant agents: the continuous hydrophobic polymer film formed by the styrene-acrylic emulsion effectively blocks the intrusion of external corrosive media (chloride ions, water) (manifested as an extremely low capillary water absorption rate), creating a stable reaction environment for the internal chemical salt-resistant system; while the matrix microstructure optimized by ultrafine mineral admixtures and further compacted by salt-erosion resistant agents provides a dense and firm adhesion substrate for the polymer film, making the film more complete and the mechanical properties better; the three work together to achieve a deep coupling between "physical barrier" and "chemical curing", so that the concrete achieves excellent results in key durability indicators such as electrical flux, chloride ion diffusion coefficient, and salt-freezing spalling resistance, which far exceed the simple superposition of the performance of each component, and is especially suitable for harsh salt-freezing and marine environments. Detailed Implementation

[0014] This invention provides a highly salt-resistant concrete based on chloride ion chemical fixation and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0015] Example 1 This embodiment provides a highly salt-resistant concrete based on chloride ion chemical fixation, comprising the following components in parts by weight: 52.5 Ordinary Portland cement 270 parts, mineral admixture 50 parts (composed of 1000 mesh fly ash, 2000 mesh fly ash and fly ash microspheres, with a mass ratio of 50%, 20% and 30% respectively), styrene-acrylic emulsion 6 parts, fine aggregate (quartz sand) 750 parts, coarse aggregate (crushed stone) 1070 parts, composite admixture 6 parts (composed of polycarboxylate type high-efficiency water-reducing agent and air-entraining agent, with a mass ratio of 80% and 20% respectively), salt erosion resistant agent 12 parts (composed of phosphogypsum and magnesite, with a mass ratio of 70% and 30% respectively), water 160 parts.

[0016] The density of the above-mentioned ordinary Portland cement is 3.2 g / cm³. 3 Specific surface area is 325m² 2 / kg; The above-mentioned mineral admixtures have an average particle size of 5 μm, a D90 of 11 μm, and a specific surface area of ​​8 m². 2 / g; The solid content of the above-mentioned styrene-acrylic emulsion is 55%, and its pH is 5 and viscosity is 2050 mPa·s; The fineness modulus of the above-mentioned quartz sand is 2.1, and the particle size of the above-mentioned crushed stone is 10 mm; The above-mentioned anti-salt corrosion agent is prepared by a grinding process, and its specific surface area after grinding is 465m². 2 / kg.

[0017] Based on the above proportions, weigh out each component material, first use a mixer to mix cement, mineral admixture, fine aggregate, and coarse aggregate evenly to obtain a mixed dry material; then dissolve the composite admixture in water and stir evenly to obtain a composite admixture solution; finally mix the mixed dry material with the composite admixture solution, add styrene-acrylic solution and stir evenly, then add anti-salt erosion agent and continue stirring until uniform to obtain concrete paste.

[0018] Example 2 This embodiment provides a highly salt-resistant concrete based on chloride ion chemical fixation, comprising the following components in parts by weight: 42.5 Ordinary Portland cement 340 parts, mineral admixture 60 parts (composed of 1000 mesh fly ash, 2000 mesh fly ash and fly ash microspheres, with a mass ratio of 53%, 16% and 31% respectively), styrene-acrylic emulsion 12 parts, fine aggregate (quartz sand) 720 parts, coarse aggregate (crushed stone) 1100 parts, composite admixture 8 parts (composed of polycarboxylate type high-efficiency water-reducing agent and air-entraining agent, with a mass ratio of 83% and 17% respectively), salt erosion resistant agent 12 parts (composed of phosphogypsum and magnesite, with a mass ratio of 75% and 25% respectively), water 160 parts.

[0019] The density of the above-mentioned ordinary Portland cement is 3.35 g / cm³. 3 Specific surface area is 342m² 2 / kg; The above-mentioned mineral admixtures have an average particle size of 5.2 μm, a D90 of 11 μm, and a specific surface area of ​​8 m². 2 / g; The solid content of the above styrene-acrylic emulsion is 58%, and its pH is 5 and viscosity is 2210 mPa·s; The fineness modulus of the above-mentioned quartz sand is 2.1, and the particle size of the above-mentioned crushed stone is 10 mm; The above-mentioned anti-salt corrosion agent is prepared by a grinding process, and its specific surface area after grinding is 474 m². 2 / kg.

[0020] Based on the above proportions, weigh out each component material, first use a mixer to mix cement, mineral admixture, fine aggregate, and coarse aggregate evenly to obtain a mixed dry material; then dissolve the composite admixture in water and stir evenly to obtain a composite admixture solution; finally mix the mixed dry material with the composite admixture solution, add styrene-acrylic solution and stir evenly, then add anti-salt erosion agent and continue stirring until uniform to obtain concrete paste.

[0021] Example 3 This embodiment provides a highly salt-resistant concrete based on chloride ion chemical fixation, comprising the following components in parts by weight: 42.5 Ordinary Portland cement 400 parts, mineral admixture 70 parts (composed of 1000 mesh fly ash, 2000 mesh fly ash and fly ash microspheres, with a mass ratio of 47%, 20% and 33% respectively), styrene-acrylic emulsion 15 parts, fine aggregate (quartz sand) 700 parts, coarse aggregate (crushed stone) 1070 parts, composite admixture 9 parts (composed of polycarboxylate type high-efficiency water-reducing agent and air-entraining agent, with a mass ratio of 78% and 22% respectively), salt erosion resistant agent 15 parts (composed of phosphogypsum and magnesite, with a mass ratio of 68% and 32% respectively), water 160 parts.

[0022] The density of the above-mentioned ordinary Portland cement is 3.35 g / cm³. 3 Specific surface area is 342m² 2 / kg; The above-mentioned mineral admixtures have an average particle size of 5.2 μm, a D90 of 11 μm, and a specific surface area of ​​8 m². 2 / g; The solid content of the above styrene-acrylic emulsion is 58%, and its pH is 5 and viscosity is 2210 mPa·s; The fineness modulus of the above-mentioned quartz sand is 2.1, and the particle size of the above-mentioned crushed stone is 10 mm; The above-mentioned anti-salt corrosion agent is prepared by a grinding process, and its specific surface area after grinding is 474 m². 2 / kg.

[0023] Based on the above proportions, weigh out each component material, first use a mixer to mix cement, mineral admixture, fine aggregate, and coarse aggregate evenly to obtain a mixed dry material; then dissolve the composite admixture in water and stir evenly to obtain a composite admixture solution; finally mix the mixed dry material with the composite admixture solution, add styrene-acrylic solution and stir evenly, then add anti-salt erosion agent and continue stirring until uniform to obtain concrete paste.

[0024] Comparative Example 1 The difference between this comparative example and Example 1 is that the mineral admixture in this comparative example is fly ash, which meets the Class F, Grade I ash standard of GB / T1596 "Fly Ash for Cement and Concrete". All other aspects are the same.

[0025] Comparative Example 2 The difference between this comparative example and Example 1 is that no phenylpropanol solution was added in this comparative example; all other aspects are the same.

[0026] Comparative Example 3 The difference between this comparative example and Example 1 is that the mineral admixture in this comparative example is fly ash, which meets the Class F, Grade I ash standard of GB / T1596 "Fly Ash for Cement and Concrete", and no styrene-acrylic solution is added. All other aspects are the same.

[0027] Comparative Example 4 The difference between this comparative example and Example 1 is that no anti-salt corrosion agent was added in this comparative example; all other aspects are the same.

[0028] Comparative Example 5 The difference between this comparative example and Example 1 is that no anti-salt corrosion agent or styrene-acrylic solution was added in this comparative example; all other aspects are the same.

[0029] The concrete prepared according to Examples 1-3 and Comparative Examples 1-5 were subjected to various performance tests. The workability and air content of the mixtures were tested according to the provisions of GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The various durability performance tests of the hardened concrete were conducted according to the provisions of GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete". The chloride ion content was determined according to the method in JTS / T236-2019 "Technical Specification for Testing and Inspection of Concrete in Water Transport Engineering". The specific results are shown in Table 1. Table 1. Concrete performance test results The data in the table show that the high salt-erosion resistant concrete prepared in Examples 1-3 of this invention exhibits comprehensive advantages in all aspects of performance compared with Comparative Examples 1-5, and the materials show a synergistic effect, specifically manifested as follows: Workability: The initial slump and slump of Examples 1-3 remained high (200mm / 190mm) after 1 hour, with minimal loss over time, which was significantly better than Comparative Examples 1 and 3 using conventional materials. This proves that the composite cementitious system and admixture of the present invention can effectively ensure the good workability of concrete. Resistance to chloride ion attack: In the electrical flux test and chloride ion diffusion coefficient test, the values ​​of Examples 1-3 at 28d and 56d were much lower than those of Comparative Examples 1-5. Among them, the electrical flux of Example 3 at 56d was as low as 540C, which has reached an extremely high level of impermeability. In the chloride ion curing rate test, the curing efficiency of Examples 1-3 (35-46%) was significantly higher than that of Comparative Examples 1-5 (18-33%). Freeze-thaw resistance and salt-freeze resistance: The freeze-thaw durability index of Examples 1-3 is generally higher than 90%, which is far superior to Comparative Examples 1-5. In the salt-freeze resistance test, the spalling amount per unit area of ​​Examples 1-3 (minimum 280g / cm²) is much lower than that of Comparative Examples 1-5 (maximum 1196g / cm²), which proves that the concrete of the present invention can not only resist the freeze-thaw of pure water, but also effectively resist the accelerated freeze-thaw damage caused by salt solutions such as de-icing salt. Synergistic effect of mineral admixtures / salt erosion resistant agents and styrene-acrylic emulsion: Compared with Comparative Examples 1-5, the concrete performance of Example 1 is better, which shows that the "physical barrier (emulsion)" and "chemical curing / densification (mineral admixtures / salt erosion resistant agents)" produce a "1+1>2" synergistic effect. The styrene-acrylic emulsion protects the internal chemical system, while the optimized internal structure provides a better substrate for the polymer film.

[0030] In addition, the performance of Example 3 is better than that of Examples 1 and 2, mainly because Example 3 has a low water-cement ratio, a high total cementitious material (cement + mineral admixture) content, and a high content of styrene-acrylic emulsion, salt erosion resistant agent and other additives.

[0031] Based on the above analysis, the high salt erosion resistant concrete provided by this invention achieves a comprehensive balance of high workability, high later strength, extremely high chloride ion penetration resistance, and excellent freeze / salt freeze resistance through the specific selection and optimized combination of each key component. It is especially suitable for harsh engineering environments such as coastal areas, saline-alkali lands, and areas where de-icing salt is used, and has significant engineering application value.

[0032] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0033] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A highly salt-resistant concrete based on chloride ion chemical fixation, characterized in that, It includes the following components by weight: 270-400 parts cement, 50-100 parts mineral admixture, 3-15 parts styrene-acrylic emulsion, 600-800 parts fine aggregate, 1000-1200 parts coarse aggregate, 5-10 parts composite admixture, 12-15 parts salt erosion resistant agent, and 150-180 parts water; The mineral admixture is composed of 1000-mesh fly ash, 2000-mesh fly ash, and fly ash microspheres. The amount of 1000-mesh fly ash added accounts for 45-55% of the total mass of the mineral admixture, the amount of 2000-mesh fly ash added accounts for 15-25% of the total mass of the mineral admixture, and the amount of fly ash microspheres added accounts for 25-35% of the total mass of the mineral admixture. The composite admixture consists of a polycarboxylate superplasticizer and an air-entraining agent, with the polycarboxylate superplasticizer accounting for 80-90% of the total mass of the composite admixture and the air-entraining agent accounting for 10-20% of the total mass of the composite admixture.

2. The high salt-erosion-resistant concrete based on chloride ion chemical fixation according to claim 1, characterized in that, The cement is ordinary Portland cement, and its density is not less than 3.05 g / cm³. 3 Specific surface area not less than 300m² 2 / kg.

3. The high salt-erosion-resistant concrete based on chloride ion chemical fixation according to claim 1, characterized in that, The mineral admixture has an average particle size of no more than 6 μm, a D90 of no more than 12 μm, and a specific surface area of ​​no less than 5 m². 2 / g.

4. The high salt-erosion-resistant concrete based on chloride ion chemical fixation according to claim 1, characterized in that, The styrene-acrylic emulsion has a solid content greater than 50%, a pH of 4-6, and a viscosity of less than 3000 mPa·s.

5. The high salt-erosion-resistant concrete based on chloride ion chemical fixation according to claim 1, characterized in that, The fine aggregate is quartz sand or manufactured sand with a fineness modulus of 2 to 2.5, and the coarse aggregate is crushed stone or pebbles with a particle size of 5 to 20 mm.

6. The high salt-erosion-resistant concrete based on chloride ion chemical fixation according to claim 1, characterized in that, The salt-resistant agent is composed of phosphogypsum and magnesite, with the amount of phosphogypsum accounting for 65-75% of the total weight of the salt-resistant agent and the amount of magnesite accounting for 25-35% of the total weight of the salt-resistant agent.

7. A highly salt-resistant concrete based on chloride ion chemical fixation according to claim 6, characterized in that, The salt corrosion resistant agent is prepared by a grinding process, and its specific surface area after grinding is not less than 400 m². 2 / kg.

8. A method for preparing highly salt-resistant concrete based on chloride ion chemical fixation as described in any one of claims 1-7, characterized in that, Including the following steps: (1) Weigh out cement, mineral admixtures, fine aggregates and coarse aggregates according to the proportions, and mix them evenly using a mixer to obtain a mixed dry material; (2) Weigh the compound admixture and water according to the proportion, dissolve the compound admixture in water, and stir evenly to obtain a compound admixture solution; (3) Mix the dry mixture obtained in step (1) with the composite admixture solution obtained in step (2), then add styrene-acrylic solution and stir evenly, and finally add salt erosion resistant agent and continue stirring until evenly mixed to obtain concrete paste.

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