A concrete sulfate-resistant admixture and a method for preparing the same

Abstract

The application discloses a concrete anti-sulfate erosion admixture and a preparation method thereof, and relates to the technical field of concrete admixtures. The admixture comprises the following components in mass fractions: an anti-erosion component 40-60 parts and mineral powder 100 parts. The anti-erosion component is prepared by mixing sodium oxide, silicon oxide and calcium oxide, and then grinding the mixture into an additive powder after high-temperature calcination. The concrete anti-sulfate erosion admixture and the preparation method thereof have the advantages that the raw materials are easy to obtain, the admixture is composed of only two components, the preparation process is simple, and each component can be put into use after mechanical mixing. The internal alkalinity of the pore solution of the concrete is improved by adding the anti-erosion component, the generation of sulfate erosion products such as ettringite is inhibited, the risk of sulfate erosion of the concrete is fundamentally reduced, and the glassy high-alkaline substance is gradually released into the pore solution of the concrete along with the hydration reaction, thereby having little influence on the mechanical properties of the concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, specifically to a concrete admixture for resisting sulfate attack and its preparation method. Background Technology

[0002] Sulfate attack on concrete refers to the physicochemical changes that occur when concrete is exposed to external sulfates in environments containing soluble sulfates, such as lakes and seawater, leading to expansion, cracking, and even softening. Essentially, sulfate attack occurs when sulfate ions from the external environment penetrate the pores of the cementitious material, reacting with ions or hydrates in the pore solution to form expansive products such as gypsum or ettringite. This damages the microstructure of the concrete, causing performance degradation. Sulfate attack is a common problem in concrete structures in the eastern coastal areas and western saline-alkali and salt lake regions of my country, resulting in a service life far shorter than designed. Therefore, effectively addressing sulfate attack in concrete structures is crucial for improving concrete durability and service life.

[0003] Currently, measures to inhibit sulfate attack on concrete mainly focus on two aspects: first, increasing the density of concrete to prevent sulfate ions from penetrating into the concrete interior; and second, inhibiting the physicochemical reactions that generate sulfate products, thereby fundamentally reducing the risk of sulfate attack on concrete. Therefore, in engineering, commonly used methods to inhibit sulfate attack include incorporating mineral admixtures such as fly ash, silica fume, and mineral powder; and adding chemical admixtures such as barium carbonate or barium hydroxide. While using mineral admixtures alone can delay the formation of sulfate attack products to some extent, there is still a risk of deterioration under long-term corrosion. Furthermore, this method requires a large dosage to achieve the desired anti-sulfur attack effect, resulting in high costs and significant impacts on concrete mechanics at higher dosages. On the other hand, chemical admixtures such as barium salts are expensive, have a short effective period, and can easily affect the workability of fresh concrete, making them difficult to promote in engineering applications.

[0004] The alkalinity of the pore solution in cement-based materials is a crucial factor influencing the formation of sulfate attack products. Researchers such as Zheng Keren, studying the mechanism of glass powder's resistance to sulfate attack in silicate cement, discovered that after adding sodium-calcium glass powder, its alkaline components are gradually released into the pore solution of the cement-based material as the glass powder dissolves, resulting in a significant increase in the alkalinity of the pore solution. This highly alkaline pore solution environment fundamentally inhibits the formation of sulfate attack products in concrete, such as ettringite, thereby reducing the risk of sulfate attack on concrete. However, due to the low reactivity of the glass powder (only about 35% at 120 days), the glass powder dosage needs to reach approximately 30%, leading to other problems in concrete, such as a decrease in mechanical properties.

[0005] In view of this, we propose a concrete sulfate-resistant admixture and its preparation method. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a concrete sulfate-resistant admixture and its preparation method, thus solving the problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: a concrete sulfate-resistant admixture, the admixture comprising the following components in parts by mass: 40-60 parts of anti-corrosion component and 100 parts of mineral powder, wherein the anti-corrosion component is formed by mixing sodium oxide, silicon oxide and calcium oxide, and then grinding them into additive powder after high-temperature calcination.

[0008] Optionally, the specific surface area of ​​the additive powder is greater than 600 m² / kg.

[0009] Optionally, the chemical composition of the corrosion-resistant components, in parts by mass, is as follows:

[0010] Sodium oxide 15-45 parts;

[0011] 70-45 parts of silicon dioxide;

[0012] Calcium oxide 5-20 parts.

[0013] Optionally, the sodium oxide raw material is one of analytical grade sodium carbonate, soda ash, sodium hydroxide, and table salt; the silicon oxide raw material is one of analytical grade silicon dioxide, quartz sand, sandstone, quartzite, and gangue rock; and the calcium oxide raw material is one of analytical grade calcium carbonate, calcite, limestone, and chalk.

[0014] Optionally, the concrete sulfate-resistant admixture may replace the concrete cementitious material by mass, with the replacement amount being 10% to 15% of the total mass of the cementitious material.

[0015] Optionally, the alkali content of the corrosion-resistant component is 15% to 45%.

[0016] A method for preparing a concrete sulfate-resistant admixture, the method comprising the following steps:

[0017] Step S1: Prepare the raw materials for the anti-corrosion component and mix them together.

[0018] Step S2: After mixing evenly, calcine at 1100℃~1300℃;

[0019] Step S3: After calcination, the solid is rapidly cooled at room temperature. The rapidly cooled block solid is crushed by a crusher and then ground into powder by a ball mill to obtain additive powder.

[0020] Step S4: Package and store the additive powder from step S3.

[0021] Optionally, a dry powder mixer may be used for the mixing process.

[0022] This invention provides a concrete admixture for resisting sulfate attack and its preparation method. It possesses the following characteristics:

[0023] Beneficial effects:

[0024] 1. The concrete sulfate-resistant admixture and its preparation method use readily available raw materials, consisting of only two components. The preparation process is simple, and the components can be put into use after mechanical mixing. By adding the anti-corrosion component, the alkalinity inside the concrete pore solution is increased, inhibiting the formation of sulfate erosion products such as ettringite, thus fundamentally reducing the risk of concrete being eroded by sulfate. At the same time, the glassy, ​​highly alkaline substances will be gradually released into the concrete pore solution as the hydration reaction proceeds, with minimal impact on the mechanical properties of the concrete.

[0025] 2. The concrete sulfate-resistant admixture and its preparation method utilize the strong alkalinity of high-alkalinity glass to enhance the hydration activity of mineral powder and increase the density of concrete. This improves the concrete's sulfate resistance from the outside while having little impact on its mechanical properties. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] This invention provides a technical solution: a concrete admixture for resisting sulfate attack, comprising the following components in parts by weight: 50 parts of an anti-corrosion component and 100 parts of mineral powder. The anti-corrosion component is formed by mixing sodium oxide, silicon dioxide, and calcium oxide, followed by high-temperature calcination and grinding into an additive powder. The specific surface area of ​​the additive powder is greater than 600 m² / kg. The alkali content of the anti-corrosion component is 15%–45%.

[0029] The chemical composition of the corrosion-resistant components, by mass, is as follows: sodium oxide 35 parts; silicon oxide 45 parts; calcium oxide 20 parts.

[0030] The sodium oxide raw material is one of analytical grade sodium carbonate, soda ash, sodium hydroxide, or table salt; the silicon oxide raw material is one of analytical grade silicon dioxide, quartz sand, sandstone, quartzite, or gangue rock; the calcium oxide raw material is one of analytical grade calcium carbonate, calcite, limestone, or chalk. The concrete sulfate-resistant admixture replaces 10% to 15% of the total mass of concrete cementitious materials.

[0031] Step S1: Prepare the raw materials for the anti-corrosion component and mix them using a dry powder mixer.

[0032] Step S2: After mixing evenly, calcine at 1100℃~1300℃;

[0033] Step S3: After calcination, the solid is rapidly cooled at room temperature. The rapidly cooled block solid is crushed by a crusher and then ground into powder by a ball mill to obtain additive powder.

[0034] Step S4: Package and store the additive powder from step S3.

[0035] Example 2

[0036] The concrete sulfate-resistant admixture containing corrosion-resistant components provided in this embodiment is prepared using the same method as in Example 1, except that the chemical composition of the corrosion-resistant components, sodium oxide, silicon oxide, and calcium oxide, is in a mass ratio of 25:60:15.

[0037] Example 3

[0038] The concrete sulfate-resistant admixture containing corrosion-resistant components provided in this embodiment is prepared using the same method as in Example 1, except that the chemical composition of the corrosion-resistant components, sodium oxide, silicon oxide, and calcium oxide, is in a mass ratio of 45:45:10.

[0039] Example 4

[0040] The concrete sulfate-resistant admixture containing corrosion-resistant components provided in this embodiment is prepared using the same method as in Example 1, except that the chemical composition of the corrosion-resistant components, sodium oxide, silicon oxide, and calcium oxide, is in a mass ratio of 15:70:15.

[0041] Comparative Example 1.1

[0042] The concrete sulfate-resistant admixture containing corrosion-resistant components provided in this embodiment is prepared using the same method as in Example 1, except that the chemical composition of the corrosion-resistant components, sodium oxide, silicon oxide, and calcium oxide, is in a mass ratio of 55:42:3.

[0043] Comparative Example 1.2

[0044] The difference from Example 1 is that, according to the chemical composition of the corrosion-resistant component in Example 1, uncalcined sodium oxide, silicon oxide and calcium oxide mixed powder are directly added to a unit mass of concrete in the same amount.

[0045] Comparative Example 1.3

[0046] The difference from Example 1 is that this comparative example is a baseline group without the concrete sulfate-resistant admixture provided by the present invention.

[0047] It is worth noting that the performance tests of the concrete sulfate-resistant admixtures in Examples 1-4 and Comparative Examples 1.1-1.3 were conducted in accordance with the standard "Concrete Anti-corrosion Agents" (JC / T 1011-2021). Two types of specimens were prepared: one was a mortar specimen with a fixed water-cement ratio of 0.5, used to test the mortar's fluidity and strength; the other was a cement paste specimen with a fixed water-cement ratio of 0.4, used to test the coefficient of thermal expansion. All other test details were performed according to the standard. The cement used was silicate-based cement, the sand and gravel were standard sand, and the water was deionized water. During the tests, the amount of the concrete sulfate-resistant admixture accounted for 12% of the cement content. The experimental results are as follows:

[0048]

[0049]

[0050] The addition of the concrete sulfate-resistant admixture provided by this invention has little effect on the compressive strength and fluidity of concrete; at the same time, the expansion coefficient is less than 1.5, which has a good anti-sulfate attack effect.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A concrete admixture for resisting sulfate attack, characterized in that: The additive comprises the following components in parts by weight: 40-60 parts of corrosion-resistant component and 100 parts of mineral powder. The corrosion-resistant component is made by mixing sodium oxide, silicon oxide, and calcium oxide, calcining at high temperature, and then grinding into additive powder. The chemical composition of the corrosion-resistant components, in parts by mass, is as follows: Sodium oxide 15-45 parts; 70-45 parts of silicon dioxide; 5-20 parts of calcium oxide; The admixture is prepared by the following steps: Step S1: Prepare the raw materials for the anti-corrosion component and mix them together. Step S2: After mixing evenly, calcine at 1100℃~1300℃; Step S3: After calcination, the solid is rapidly cooled at room temperature. The rapidly cooled block solid is crushed by a crusher and then ground into powder by a ball mill to obtain additive powder. Step S4: Package and store the additive powder from step S3.

2. The concrete sulfate-resistant admixture according to claim 1, characterized in that: The specific surface area of ​​the additive powder is greater than 600 m² / kg.

3. The concrete sulfate-resistant admixture according to claim 1, characterized in that: The alkali content of the corrosion-resistant component is 15% to 45%.

4. The concrete sulfate-resistant admixture according to claim 3, characterized in that: The mixing process uses a dry powder mixer.

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