A preservative against sulphate attack and a method for its preparation

Abstract

The present application relates to a kind of anti-sulphate erosion preservatives and its preparation method, a kind of anti-sulphate erosion preservatives, preparation raw materials of the anti-sulphate erosion preservatives include: dense component 25-55 parts;Expanding agent 15-40 parts;Ion curing agent 5-10 parts;Preservative adjuvant 10-20 parts;And inhibitor 3-10 parts.The anti-sulphate erosion preservatives prepared in the present application has super strong anti-sulphate erosion performance, after adding the anti-erosion agent in concrete, dense structure can be formed in the interior of concrete, reduce concrete cracking.The present application is lower than traditional method using anti-sulphate cement single concrete cost, anti-sulphate erosion capacity and anti-chloride ion penetration capacity are significantly improved, with higher economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to an anti-sulfate corrosion agent and its preparation method. Background Technology

[0002] Cement-based composite materials, represented by concrete, are frequently damaged in practical engineering applications due to insufficient concrete durability, including freeze-thaw corrosion, chloride ion corrosion, sulfate corrosion, and carbonation. These damages generally involve multiple mechanisms, including chemical reactions, microstructural changes, and mechanical failure, and in some harsh environments, they can even involve a combination of factors. Among the many corrosion problems, sulfate corrosion has received widespread attention due to its complex mechanisms and forms. Generally, sulfate corrosion of concrete includes physical crystallization damage caused by sulfates and chemical damage resulting from the formation of corrosive products through chemical reactions. Corrosive products leading to chemical damage include ettringite, gypsum, and calcium carbonate; these diverse corrosive products significantly increase the difficulty of studying sulfate corrosion.

[0003] my country has a long coastline and many saline-alkali and salt lake areas, where sulfate content is generally high. Sulfate corrosion is particularly severe in concrete structures. Many power plants, dams, tunnels, highways, seaports, and airports have suffered damage such as expansion, cracking, and failure before reaching their expected design service life. Furthermore, concrete structures and components are subjected to other environmental factors during their service life, such as ambient temperature, relative humidity, wet-dry cycles, various loads, and freeze-thaw cycles. These factors may act one or more cumulatively on concrete, easily causing significant erosion of the foundation and the concrete components at the base of buildings, affecting the stability and safety of concrete structures, and threatening personal and property safety.

[0004] Improving the sulfate resistance of cement concrete has become an important aspect of concrete durability design. Currently, the sulfate resistance of cement concrete can be considered from the following directions:

[0005] 1) Rationally design the concrete mix proportions and adopt appropriate curing techniques. However, a drawback is its poor resistance to sulfate attack.

[0006] 2) Use special cement – ​​sulfate-resistant cement. Although cement concrete prepared with sulfate-resistant cement has good resistance to sulfate attack, there are few manufacturers of sulfate-resistant cement, the supply is tight, and the transportation costs are high, resulting in high project costs;

[0007] 3) Apply a protective coating to areas of concrete susceptible to sulfate corrosion. The disadvantages of this method are high cost and the fact that most coatings are organic compounds with poor UV resistance and aging resistance, making them prone to peeling and failing to achieve the intended protective purpose.

[0008] In recent years, a small number of products similar to concrete corrosion inhibitors have appeared on the market. Some of them have a lot of material composition, complex manufacturing process, and harsh usage conditions, resulting in high cost; others have good early resistance to sulfate corrosion, but the later effect does not meet the requirements. Summary of the Invention

[0009] Therefore, it is necessary to provide a preservative with excellent resistance to sulfate attack and its preparation method.

[0010] To achieve the above objectives, the present invention provides a technical solution:

[0011] A sulfate-resistant preservative, wherein the raw materials for preparing the sulfate-resistant preservative, by weight, include:

[0012]

[0013] Furthermore, the raw materials for preparing the inhibitor include polyethylene glycol phosphate and sorbitol.

[0014] Furthermore, the raw materials for preparing the inhibitor, by weight, include:

[0015]

[0016] Furthermore, the steps for preparing the inhibitor include:

[0017] The polyethylene glycol phosphate, sorbitol, and polymerization inhibitor are heated to 50-60°C to obtain a mixture.

[0018] An unsaturated carboxylic acid and a catalyst are added to the mixture, and the temperature is raised to 90–140°C to carry out an esterification reaction for 4–6 hours. After the reaction is completed, the inhibitor is obtained.

[0019] Furthermore, the unsaturated carboxylic acids include acrylic acid and methacrylic acid.

[0020] Furthermore, the dense component includes at least one of mineral powder, fly ash, and silica fume.

[0021] Furthermore, the expanding agent includes a sulfoaluminate micro-expanding agent.

[0022] Furthermore, the ionic curing agent includes a barium salt.

[0023] Furthermore, the preservative includes calcium nitrite.

[0024] This invention also provides a method for preparing a sulfate-resistant preservative, comprising the following steps:

[0025] The sulfate-resistant preservative is obtained by compounding the compacting component, the expanding agent, the ion curing agent, the preservative additive, and the inhibitor.

[0026] The beneficial effects of this invention are:

[0027] The sulfate-resistant corrosion inhibitor prepared by this invention exhibits superior resistance to sulfate attack. When added to concrete, this inhibitor creates a dense internal structure, reducing concrete cracking. Compared to traditional methods using sulfate-resistant cement, this invention offers lower per-cubic-meter concrete costs and significantly improved resistance to sulfate attack and chloride ion penetration, resulting in substantial economic and social benefits.

[0028] This invention modifies sorbitol and polyethylene glycol phosphate to prepare inhibitors with carboxylic acid groups and methyl groups, thereby dispersing the initially generated ettringite and sulfate crystal particles and preventing them from agglomerating. It also prevents expansion and damage by inhibiting the growth of corrosion product lattices through the occupancy of metal cations.

[0029] This invention combines chemical and physical methods to prepare a high-performance sulfate-resistant corrosion inhibitor. From a chemical reaction perspective, it can effectively inhibit the formation of crystalline corrosion products, greatly improving the corrosion resistance of concrete. From a physical perspective, it can form a passivation film, preventing the corrosion of steel bars and improving the density of concrete, thereby enhancing the concrete's resistance to the intrusion of harmful substances. Detailed Implementation

[0030] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0031] In the embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0032] A sulfate-resistant preservative, wherein the raw materials for preparing the sulfate-resistant preservative, by weight, include:

[0033]

[0034] In one embodiment, the compacted component includes at least one of mineral powder, fly ash, and silica fume.

[0035] The specific surface area of ​​the dense components is ≥400m². 2 / kg, when the dense component is added to concrete, it can form a composite cementitious system with good micro-gradation with cement, and fill each other during the hydration process, which reduces the porosity of concrete and greatly improves its density, thereby improving the concrete's resistance to the intrusion of harmful substances.

[0036] In one embodiment, the expanding agent comprises a sulfoaluminate microexpanding agent.

[0037] The expansive agent participates in the cement hydration process and produces a certain amount of expansive hydration products. During the process of concrete strength growth, the concrete undergoes a certain volume expansion, which compensates for the shrinkage caused by the loss of water due to drying, increases the volume stability of the concrete, prevents shrinkage cracks, and improves the crack resistance and waterproofing of the concrete.

[0038] In one embodiment, the ionic curing agent includes barium salts, specifically Ba(OH)2 and BaCO3.

[0039] Barium carbonate (BaCO3) can decompose ettringite before sulfate ions invade, thereby reducing the risk of accelerated formation of calcareous carboxylic acid due to ettringite; while barium hydroxide can react with sulfate ions to form barium sulfate, and the barium sulfate crystals formed can block the surrounding channels, reduce the invasion rate of sulfate ions, and consume the invading sulfate ions.

[0040] In one embodiment, the preservative agent includes calcium nitrite.

[0041] Calcium nitrite can form a passivation film on the surface of steel bars, preventing corrosion and also increasing the strength of concrete.

[0042] In one embodiment, the raw materials for preparing the inhibitor include polyethylene glycol phosphate and sorbitol.

[0043] The polyethylene glycol phosphate can inhibit the formation of ettringite, and the inhibitory effect of sorbitol can effectively prevent the nucleation of calcareous carbosulfanite. The six hydroxyl groups in sorbitol can replace or enter the sulfate group in ettringite and calcareous carbosulfanite, thereby inhibiting the formation of ettringite and calcareous carbosulfanite.

[0044] Polyethylene glycol phosphate reacts with sorbitol to form an esterification product. The esterification product can be hydrolyzed under alkaline conditions, providing carboxylic acid and methyl groups to disperse the initially formed ettringite and sulfate crystal particles and prevent them from agglomerating. It also prevents the growth of corrosion product lattices by occupying metal cations, thus preventing expansion and damage.

[0045] Furthermore, the raw materials for preparing the inhibitor, by weight, include:

[0046]

[0047] Furthermore, the steps for preparing the inhibitor include:

[0048] The polyethylene glycol phosphate, sorbitol, and polymerization inhibitor are heated to 50-60°C to obtain a mixture.

[0049] Under nitrogen protection, unsaturated carboxylic acid and catalyst are added to the mixture, and the temperature is raised to 90-140°C for esterification reaction for 4-6 hours. After the reaction is completed, the inhibitor is obtained.

[0050] In one embodiment, the unsaturated carboxylic acid includes acrylic acid and methacrylic acid, wherein the mass ratio of acrylic acid to methacrylic acid is (1-4):1.

[0051] In one embodiment, the polyethylene glycol phosphate is a polyethylene glycol (molecular weight 600-1200) phosphate.

[0052] This invention also provides a method for preparing a sulfate-resistant preservative, comprising the following steps:

[0053] The sulfate-resistant preservative is obtained by compounding the compacting component, the expanding agent, the ion curing agent, the preservative additive, and the inhibitor.

[0054] Example

[0055] 1. Preparation of inhibitors

[0056] 300g of polyethylene glycol phosphate (polyethylene glycol molecular weight 800), 100g of sorbitol, and 2.1g of hydroquinone as a polymerization inhibitor were added to a reaction vessel and heated to 60°C. Under nitrogen protection, 24.5g of acrylic acid, 71.0g of methacrylic acid, and 2.6g of p-toluenesulfonic acid as a catalyst were added. Then, the temperature was slowly raised to 90-140°C for esterification reaction for 4 hours. After the reaction was completed, the inhibitor was obtained by cooling.

[0057] 2. Preparation of preservatives resistant to sulfate attack

[0058] The sulfate-resistant preservative is obtained by compounding the compacting component, the expanding agent, the ion curing agent, the preservative additive, and the inhibitor prepared in step 1 above.

[0059] The raw materials and their amounts in each embodiment are shown in Table 1.

[0060] Table 1. Raw materials and their quantities in each embodiment.

[0061]

[0062] To verify the performance of the sulfate-resistant corrosion inhibitor of the present invention, the applicant conducted performance tests on the corrosion inhibitors obtained in Examples 1-3 and Comparative Examples 1-6, with a test dosage of 6% of the cementitious material. The corrosion resistance of the sulfate-resistant corrosion inhibitors obtained in Examples 1-3 was tested according to standard JC / T1011-2006 "Sulfate-resistant Corrosion Inhibitors for Concrete," specifically the corrosion resistance coefficient K, expansion coefficient E, and chloride ion penetration resistance. The compressive strength and corrosion resistance coefficient Kf of the sulfate-resistant corrosion inhibitors in each example were tested after 150 wet-dry cycles according to standard GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete." The test results are shown in Table 2 below.

[0063] Table 2 Performance Test Results

[0064]

[0065]

[0066] According to the standard JC / T1011-2011 regarding the corrosion resistance performance requirements of sulfate-resistant preservatives, the corrosion resistance coefficient K≥0.90, the expansion coefficient E≤1.50, and the 28-day chloride ion diffusion coefficient ratio≤0.85. As can be seen from the test results in Table 1 above, the corrosion resistance performance of the sulfate-resistant preservative of the present invention meets the requirements. In addition, after 150 dry-wet cycles (KS150), the compressive strength corrosion resistance coefficient Kf of the sulfate-resistant preservatives in each embodiment is greater than 75%, thus indicating that the sulfate-resistant preservatives in each embodiment have excellent sulfate resistance performance.

[0067] It should be noted that the specific parameters or reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A preservative resistant to sulfate attack, characterized in that, The raw materials for preparing the sulfate-resistant preservative, by weight, include: 25-55 parts of dense component; 15-40 parts of expanding agent; 5-10 parts of ion curing agent; 10-20 parts of preservative additive; and Inhibitor 3-10 parts; The raw materials for preparing the inhibitor, by weight, include: 2-3.5 parts of polyethylene glycol phosphate; 3-4.5 parts of unsaturated acid; 1 part sorbitol; Polymerization inhibitor 0.01~0.1 parts; and Catalyst: 0.01~0.1 parts; The steps for preparing inhibitors include: The polyethylene glycol phosphate, sorbitol, and polymerization inhibitor are heated to 50-60°C to obtain a mixture. An unsaturated acid and a catalyst are added to the mixture, and the temperature is raised to the reaction temperature to carry out an esterification reaction for 4-6 hours. After the reaction is completed, the inhibitor is obtained. The dense component includes at least one of mineral powder, fly ash, and silica fume; The ion curing agent includes a barium salt; The preservative agent includes calcium nitrite.

2. The sulfate-resistant preservative according to claim 1, characterized in that, The unsaturated acids include acrylic acid and methacrylic acid.

3. The preservative against sulfate attack according to claim 1, characterized in that, The expanding agent includes a sulfoaluminate micro-expanding agent.

4. A method for preparing a sulfate-resistant preservative as described in any one of claims 1 to 3, characterized in that, Including the following steps: The sulfate-resistant preservative is obtained by compounding the compacting component, the expanding agent, the ion curing agent, the preservative additive, and the inhibitor.

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