A prestressed duct grouting material for negative temperature applications and its preparation method

Abstract

This invention discloses a prestressed grouting material for negative temperature applications and its preparation method, belonging to the field of building materials technology. The prestressed grouting material for negative temperature applications comprises the following components: cement, slag powder, microsilica powder, nano-silica, water-reducing agent, expanding agent, antifreeze agent, defoamer, and auxiliary heating composition. The prestressed grouting material for negative temperature applications prepared by this invention has good grout flow properties and high strength, making it particularly suitable for prestressed grouting construction in low-temperature environments.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a prestressed grouting material for negative temperature applications and its preparation method. Background Technology

[0002] In recent years, my country's infrastructure system, including highway bridges, has developed rapidly. Post-tensioned prestressed duct grouting material has been widely used in bridge structures due to its unique economic and technical advantages. It has properties such as good fluidity, high strength, and micro-expansion, which can protect prestressing tendons from external ion erosion. When bonded together with prestressing tendons, it can play a synergistic role between the beam concrete and the prestressing tendons, improving the overall safety and stability of the box girder. It can also eliminate fatigue damage to anchorages caused by stress changes under repeated loading of prestressed concrete structures, thereby improving the reliability and durability of components.

[0003] The "Technical Specification for Construction of Highway Bridges and Culverts" (JTG / T F50-2011) stipulates that grouting can be carried out at temperatures above 5°C, but insulation measures must be taken below 5°C. In northern regions, grouting during autumn and winter typically employs steam curing or other insulation methods. This technology not only increases construction costs but also consumes a significant amount of energy, and the construction quality cannot be effectively guaranteed. Chinese patent application CN115432963A discloses a grouting material for prestressed ducts in highway bridges; however, this grouting material cannot be applied normally below 5°C without insulation measures, otherwise problems such as inadequate hardening and reduced strength will occur.

[0004] Therefore, there is an urgent need to develop a prestressed duct grouting material for use in negative temperatures, which would have practical application value in order to avoid the need for other insulation measures during construction in autumn and winter. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a prestressed grouting material suitable for negative temperatures and with good mechanical properties.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A prestressed duct grouting material for negative temperature applications comprises the following components: cement, slag powder, microsilica powder, nano silica, water-reducing agent, expanding agent, antifreeze agent, defoamer, and auxiliary heating composition.

[0008] Preferably, the prestressed grouting material for negative temperature applications comprises, by weight, the following components: 750-850 parts cement, 100-150 parts slag powder, 150-200 parts microsilica powder, 20-50 parts nano silica, 50-100 parts water-reducing agent, 60-80 parts expanding agent, 50-100 parts antifreeze agent, 0.5-1.5 parts defoamer, and 10-20 parts auxiliary heating composition.

[0009] Preferably, the cement is a mixture of ordinary Portland cement and sulfoaluminate cement in a mass ratio of 3-5:1. The ordinary Portland cement is P.O42.5 or P.O525. Cement, as a cementitious material, plays an important role in the performance of grouting materials. Since grouting materials must be able to generate strength under negative temperature conditions, ordinary Portland cement is difficult to meet the requirements. Therefore, this invention selects a mixture of ordinary Portland cement and sulfoaluminate cement.

[0010] Preferably, the slag powder has a specific surface area of ​​400-450 m². 2 / kg, average particle size ≤4μm.

[0011] Preferably, the specific surface area of ​​the microsilica powder is 15,000-18,000 m². 2 / kg; Microsilica can improve the fluidity of cement slurry and fill the pores of hardened cement slurry, thereby improving the strength of the material.

[0012] Preferably, the nano-silica is hydrophilic fumed nano-silica with a specific surface area of ​​200–300 m². 2 The chloride ion content is less than 0.06% between / g; nano silica has a strong pozzolanic effect, which can reduce the slump and spread of the slurry, shorten the setting time of the slurry, and improve the early strength of the material.

[0013] Preferably, the water-reducing agent is any one or a mixture of two or more of naphthalene-based water-reducing agents, fatty acid-based water-reducing agents, and polycarboxylate-based water-reducing agents; more preferably, the water-reducing agent is a polycarboxylate-based water-reducing agent. The water-reducing agent can ensure fluidity while also providing advantages such as reduced water consumption, increased strength, and guaranteed durability.

[0014] Preferably, the expanding agent is a mixture of magnesium oxide and calcium oxide.

[0015] Preferably, the antifreeze is one or a mixture of ethylene glycol, urea, sodium nitrite, sodium acetate, calcium chloride, and potassium carbonate.

[0016] More preferably, the antifreeze is a mixture of ethylene glycol and urea in a mass ratio of 1:1.5-2.5. This mixture of ethylene glycol and urea can lower the freezing point and regulate the freezing time, and can form a protective film on the material surface, thus providing thermal insulation.

[0017] Preferably, the defoamer is a polyether-modified silicone defoamer and / or a dimethyl silicone oil defoamer.

[0018] Preferably, the auxiliary heating composition comprises, by weight, the following components: 5-10 parts zinc powder, 3-5 parts sodium hypochlorite, 2-4 parts montmorillonite, 5-10 parts polyethylene glycol, and 10-20 parts tricalcium aluminate.

[0019] More preferably, the montmorillonite is obtained by acidification followed by the addition of a pore-forming agent and high-temperature calcination. The preparation method is as follows: 1-5 parts by weight of montmorillonite are mixed and reacted with 10-20 parts by weight of 10-20 wt% dilute sulfuric acid, filtered, washed, dried, and then mixed with 0.5-1 parts by weight of sodium dodecyl sulfate. The mixture is calcined at 400-600℃ for 2-4 hours and then reacted with 15-20 parts by weight of γ-aminopropyltriethoxysilane to obtain the montmorillonite.

[0020] The auxiliary heating composition of this invention can provide a large amount of heat in cement paste, causing the temperature to rise rapidly and providing the necessary temperature conditions for cement hydration, thus ensuring the early mechanical properties of the material. Specifically, zinc powder, upon contact with oxygen in the air, undergoes an oxidation reaction catalyzed by water and sodium hypochlorite, releasing a large amount of heat. Montmorillonite and polyethylene glycol can store the heat generated by the auxiliary heating material through phase change, releasing it when the paste temperature falls below a certain threshold, maintaining a reasonable temperature range. Treatment of montmorillonite removes impurities from its surface, and the introduction of a pore-forming agent increases its porosity, allowing for better heat storage. Treatment with γ-aminopropyltriethoxysilane improves its dispersion in the cement paste, thereby improving the hardened cement paste. Sodium lignosulfonate generates bubbles during paste mixing, reducing the thermal conductivity of the paste and maintaining its temperature within a reasonable range. Tricalcium aluminate reacts rapidly with water, accelerating the hydration process while maintaining the continuity of paste hydration, thus ensuring the early strength of the material.

[0021] The present invention also discloses a method for preparing the above-mentioned prestressed duct grouting material for negative temperature, comprising the following steps: weighing each raw material according to the formula, mixing and stirring cement, slag powder, microsilica powder and nano silica evenly, and then adding water-reducing agent, expansion agent, antifreeze agent, defoamer and auxiliary heat composition and stirring and mixing evenly to obtain the prestressed duct grouting material for negative temperature.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The prestressed grouting material for negative temperature applications of the present invention has good grout flow properties and high early strength, and is particularly suitable for construction and use in low temperature environments above -5℃.

[0024] The auxiliary heating composition prepared by this invention can rapidly release a large amount of heat and store the generated heat through phase change, maintaining the temperature of the grout within a reasonable range. The time the grout maintains a positive temperature inside is much longer than its initial setting time, thus ensuring a reduced probability of free water freezing. It can be used at temperatures above -10℃ without any insulation measures. The grout exhibits normal setting at low temperatures, with a long final setting time and a 28-day strength ≥60MPa. Detailed Implementation

[0025] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0026] To avoid unnecessary details, unless otherwise specified, all items used in the following examples are commercially available products, and all methods used are conventional methods unless otherwise specified.

[0027] Example 1

[0028] A method for preparing a prestressed grouting material for negative temperature applications includes the following steps: mixing 750g of cement, 100g of slag powder, 150g of microsilica powder, 20g of nano-silica, and 50g of polycarboxylate superplasticizer until homogeneous; then adding a mixture of 60g of magnesium oxide and calcium oxide, 20g of ethylene glycol, 40g of urea, 1g of dimethyl silicone oil defoamer, and 10g of auxiliary heating composition and mixing until homogeneous to obtain the prestressed grouting material for negative temperature applications.

[0029] The cement is a mixture of P.O42.5 silicate cement and sulfoaluminate cement in a mass ratio of 3:1;

[0030] The mass ratio of magnesium oxide to calcium oxide is 1:2;

[0031] The auxiliary heating composition is a mixture of 2g zinc powder, 1.2g sodium chlorate, 0.8g montmorillonite, 2g polyethylene glycol, and 4g tricalcium aluminate.

[0032] Example 2

[0033] A method for preparing a prestressed duct grout for negative temperature applications is the same as in Example 1, except that:

[0034] The montmorillonite is obtained by acidification followed by the addition of a pore-forming agent and high-temperature calcination. The preparation method is as follows: 50g of montmorillonite is mixed with 1000g of 10% dilute sulfuric acid and heated to 50℃ for 1h. After natural cooling, it is filtered, and the filter cake is washed with water until the pH value is neutral. After drying at 60℃ for 8h, it is mixed evenly with 10g of sodium dodecyl sulfate and then calcined at 500℃ for 3h. After cooling, it is mixed with 150g of γ-aminopropyltriethoxysilane and heated to 40℃ for 2h. The filter cake is collected by filtration and dried at 60℃ for 8h to obtain the montmorillonite.

[0035] Example 3

[0036] A method for preparing a prestressed grouting material for negative temperature applications includes the following steps: mixing 800g of sulfoaluminate cement, 130g of slag powder, 180g of microsilica powder, 40g of nano-silica, and 85g of polycarboxylate superplasticizer until homogeneous; then adding a mixture of 70g of magnesium oxide and calcium oxide, 20g of ethylene glycol, 40g of urea, 0.5g of dimethyl silicone oil defoamer, and 15g of auxiliary heating composition and mixing until homogeneous to obtain the prestressed grouting material for negative temperature applications.

[0037] The cement is a mixture of ordinary silicate cement and sulfoaluminate cement in a mass ratio of 5:1;

[0038] The mass ratio of magnesium oxide to calcium oxide is 2:1;

[0039] The auxiliary heating composition is a mixture of 3g zinc powder, 1.5g sodium chlorate, 1.5g montmorillonite, 3g polyethylene glycol, and 6g tricalcium aluminate.

[0040] Comparative Example 1

[0041] A method for preparing a prestressed duct grouting material for negative temperature is the same as in Example 1, except that the auxiliary heating composition does not contain montmorillonite.

[0042] Comparative Example 2

[0043] The preparation method of a prestressed duct grout for negative temperature is the same as in Example 1, except that the auxiliary heating composition does not contain polyethylene glycol.

[0044] Comparative Example 3

[0045] The preparation method of a prestressed duct grout for negative temperature is the same as in Example 1, except that the auxiliary heating composition does not contain zinc powder.

[0046] Comparative Example 4

[0047] A method for preparing a prestressed duct grout for negative temperature is the same as in Example 1, except that the auxiliary heating composition does not contain sodium chlorate.

[0048] Comparative Example 5

[0049] A method for preparing a prestressed duct grout for negative temperature is the same as in Example 1, except that the auxiliary heating composition does not contain tricalcium aluminate.

[0050] Test Example 1

[0051] Performance testing:

[0052] Test Method: Water was added to the negative-temperature prestressed duct grouting materials prepared in each embodiment and comparative example at a water-cement ratio of 0.28. The prepared grout was tested for various performance indicators and then molded. The mold size was 40mm × 40mm × 160mm. Grout performance tests were conducted at 0℃. Setting time was determined according to the "Standard Consistency Water Requirement, Setting Time and Soundness Test Method for Cement" (GB / T1346); compressive strength and flexural strength were determined according to the "Cement Mortar Strength Test Method (ISO Method)" (GB / T17671); fluidity was determined according to the technical indicators for pressure drop in post-tensioned prestressed concrete beam ducts specified in the "Technical Specification for Construction of Highway Bridges and Culverts" (JTGT / 3650-2020). Performance tests were conducted on the negative-temperature prestressed duct grouting materials prepared in the above embodiments and comparative examples. The test results are shown in Table 1.

[0053] Table 1. Performance test results of prestressed duct grouting material for negative temperature applications

[0054]

[0055] As can be seen from the experimental results in Table 1, the prestressed grouting material for negative temperature applications prepared by this invention can solidify at -10℃, meeting the requirements of the "Technical Specification for Construction of Highway Bridges and Culverts" (JTGT / 3650-2020) regardless of whether it is at room temperature or low temperature. The grouting material provided by this invention has suitable initial and final setting times, high compressive and flexural strengths, stable performance, and is simple and convenient to use.

[0056] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A prestressed duct grouting material for negative temperature applications, characterized in that, By weight, it comprises the following components: 750-850 parts cement, 100-150 parts slag powder, 150-200 parts microsilica powder, 20-50 parts nano silica, 50-100 parts water-reducing agent, 60-80 parts expanding agent, 50-100 parts antifreeze agent, 0.5-1.5 parts defoamer, and 10-20 parts auxiliary heating composition. The cement is a mixture of ordinary silicate cement and sulfoaluminate cement in a mass ratio of 3-5:1; The auxiliary heating composition comprises, by weight, the following components: 5-10 parts zinc powder, 3-5 parts sodium hypochlorite, 2-4 parts montmorillonite, 5-10 parts polyethylene glycol, and 10-20 parts tricalcium aluminate. The montmorillonite is obtained by acidification followed by the addition of a pore-forming agent and high-temperature calcination. The preparation method is as follows: 1-5 parts by weight of montmorillonite are mixed with 10-20 parts by weight of 10-20 wt% dilute sulfuric acid and reacted. After filtration, washing, and drying, the mixture is mixed with 0.5-1 parts by weight of sodium dodecyl sulfate. The mixture is calcined at 400-600℃ for 2-4 hours and then reacted with 15-20 parts by weight of γ-aminopropyltriethoxysilane to obtain the montmorillonite.

2. The prestressed duct grouting material for negative temperature applications according to claim 1, characterized in that: The slag powder has a specific surface area of ​​400-450 m². 2 / kg, average particle size ≤4μm.

3. The prestressed duct grouting material for negative temperature applications according to claim 1, characterized in that: The nano-silica is hydrophilic fumed nano-silica with a specific surface area of ​​200–300 m². 2 The chloride ion content is less than 0.06% per gram.

4. The prestressed duct grouting material for negative temperature applications according to claim 1, characterized in that: The water-reducing agent is any one or a mixture of two or more of the following: naphthalene-based water-reducing agents, fatty acid-based water-reducing agents, and polycarboxylate-based water-reducing agents.

5. The prestressed duct grouting material for negative temperature applications according to claim 1, characterized in that: The antifreeze is one or more of the following: ethylene glycol, urea, sodium nitrite, sodium acetate, calcium chloride, and potassium carbonate.

6. The method for preparing prestressed grouting material for negative temperature applications according to any one of claims 1-5, characterized in that, The process includes the following steps: weighing each raw material according to the formula, mixing and stirring cement, slag powder, microsilica powder, and nano silica evenly, then adding water-reducing agent, expansion agent, antifreeze agent, defoamer, and auxiliary heat composition and stirring and mixing evenly to obtain the prestressed duct grouting material for negative temperature applications.

Images