Post-tensioning prestressed duct grouting material and preparation method thereof

Abstract

The application belongs to the technical field of building materials, and particularly relates to a post-tensioning prestress duct grouting material and a preparation method thereof. The grouting material comprises the following components in mass fractions: cement 60-70 parts, slag powder 10-15 parts, silica fume 2-5 parts, rheological component 16-24 parts, stabilizing component 1-2 parts, dry component 3-5 parts, expanding agent 0.01-0.03 parts, defoaming agent 0-0.02 parts, and water reducing agent 0.15-0.3 parts. The cement, slag powder, silica fume, rheological component, stabilizing component and dry component are weighed and uniformly mixed, and then the expanding agent, defoaming agent and water reducing agent are added and uniformly stirred. Mixing water is weighed according to a water-binder ratio of 0.28, and rapid stirring is performed to obtain the grouting material with high homogeneity and low water sensitivity, so that good flow performance can be achieved, water bleeding and stratification of the slurry caused by excessive water consumption or external water can be reduced, the tensile strength of the cement slurry can be improved, and the toughness and crack resistance of the slurry can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a post-tensioning prestressed duct grouting material and a preparation method thereof. BACKGROUND

[0002] Prestressed concrete duct grouting is a key process in bridge construction. On the one hand, it protects the prestressed steel from being exposed to avoid or slow corrosion, ensuring the safety of the prestressed concrete structure. On the other hand, it ensures the good combination of the prestressed steel and the concrete, ensuring the effective transmission of the prestress and improving the reliability and durability of the structure.

[0003] The grouting material on the market often excessively pursues high fluidity and ignores the problems of bleeding or stratification. In the prestressed duct grouting construction, the problems such as excessive bleeding of the grouting material itself, the entry of curing water into the corrugated pipe during curing, the insufficient control of the water-binder ratio during mixing, and the insufficient mixing time leading to uneven grout, are all likely to cause the grout in the prestressed duct to be not dense or even contain free water. In the winter season in the northern region, the dilute grout or free water in the duct expands due to ice formation, leading to cracking along the corrugated pipe and accelerating the corrosion and fracture of the prestressed steel.

[0004] Patent CN116120004 A discloses a duct grouting material with low fluidity loss and a preparation method thereof. The setting time adjusting component is composed of one or more of lithium carbonate, lithium sulfate and lithium chloride, the rheological component is a sinker, the high fluidity and low fluidity loss of the grouting material are achieved, and the lithium slag is used to replace cement to realize the utilization of solid waste. Patent CN114804762 A discloses a new prestressed duct grouting material and a preparation method thereof, which solves the problems of large shrinkage and early strength of the grout, and reasonably utilizes rock debris, phosphorus slag powder and coal gangue powder to realize the recycling of solid waste.

[0005] The existing patents mainly focus on the fluidity, mechanical properties and shrinkage properties of the grouting material, and use industrial waste to prepare the grouting material, thereby ignoring the uniformity and stability of the grout itself, the adverse effects of industrial waste on the uniformity of the grout, and the effects of external water on the performance of the grout. The duct grouting material product pursues high fluidity, and although the water-binder ratio is low, the uniformity is poor, the water sensitivity is high, and the problems of bleeding, segregation and stratification are likely to occur. The prestressed duct grouting material has slow setting and hardening, and the degree of grouting saturation is difficult to guarantee. Therefore, it is necessary to develop a post-tensioning prestressed duct grouting material with high uniformity and low water sensitivity. SUMMARY

[0006] The technical problem solved by the present application is to provide a post-tensioning prestressed duct grouting material and a preparation method thereof.

[0007] The technical scheme adopted is as follows:

[0008] The post-tensioning prestressed duct grouting material comprises the following components in mass fraction: cement 60-70 parts, slag powder 10-15 parts, silica fume 2-5 parts, rheological component 16-24 parts, stabilizing component 1-2 parts, drying component 3-5 parts, expanding agent 0.01-0.03 parts, defoaming agent 0-0.02 parts, and water reducing agent 0.15-0.3 parts.

[0009] Preferably, the cement is 42.5 or 52.5 ordinary Portland cement, the density of which is not less than 3.05 g / cm 3 , and the specific surface area of which is not less than 300 m 2 / kg.

[0010] Preferably, the slag powder is S95 grade granulated blast furnace slag powder, the density of which is not less than 2.85 g / cm 3 , the specific surface area of which is not less than 440 m 2 / kg, and the fluidity ratio of which is not less than 100.

[0011] Preferably, the silica fume is non-encrypted silica fume, the specific surface area of which is 18000-25000 m 2 / kg, and the silicon dioxide content of which is ≥95%.

[0012] Preferably, the rheological component is uniformly mixed by 40-60 parts of 1000-mesh fly ash, 10-20 parts of 2500-mesh fly ash, and 30-50 parts of microbeads, and is mixed uniformly by using a high-speed shearing stirrer at a speed of 2000 r / min for 10 min. The 1000-mesh and 2500-mesh fly ash is obtained by air classification of the original fly ash from a power plant, and the best mixing ratio of the 1000-mesh fly ash, the 2500-mesh fly ash, and the microbeads is determined according to the theory of the closest packing of particles. That is, the best particle size distribution of each fly ash is calculated according to formula (1).

[0013]

[0014] In the formula, P(D) is the percentage content of the particle size D in the admixture; D max is the maximum particle size in the admixture; D min is the minimum particle size in the admixture; and q is the distribution modulus.

[0015] The percentage of different mesh fly ash composition is determined, and the specific implementation is as follows:

[0016] The particle cumulative size distribution of different mesh fly ash and microbeads is obtained by using a particle size analyzer, a target function is established in MATLAB software by formula (1), the residual sum of squares (RSS) is used to represent the packing density of the composite fly ash admixture, and the RSS formula is shown in formula (2):

[0017]

[0018] In the formula, RSS is the residual sum of squares, P mix and P tar are the target grading curve and the actual packing curve respectively;

[0019] The mass percentage of different mesh fly ash is adjusted, when the RSS is the minimum, the particle size distribution curve of the admixture is closest to the target function curve, and the particle packing of the admixture is the most compact, at this time, the proportion of the three different mesh fly ash is the best composition ratio.

[0020] Preferably, the stabilizing component is a mixture of polysilicic acid flocculants and tackifiers; wherein the mass fraction of polysilicic acid flocculants is 97-100 parts, and the mass fraction of tackifiers is 0-3 parts.

[0021] Preferably, the polysilicic acid flocculants are inorganic high molecular flocculants, metal ions are embedded in the polysilicic acid molecular chain, and are one or a combination of polysilicic acid iron, polysilicic acid aluminum, polysilicic acid iron aluminum, polysilicic acid iron zinc, and polysilicic acid aluminum zinc, and polysilicic acid iron aluminum or polysilicic acid iron zinc is preferably selected.

[0022] The tackifier is a redispersible latex powder or a cellulose ether; the cellulose ether is one or a combination of carboxymethyl cellulose ether, hydroxyethyl cellulose ether, and carboxymethyl hydroxyethyl cellulose ether.

[0023] Preferably, the drying component is a silicon gel composite desiccant modified by graphene oxide, wherein the lateral particle size of the graphene oxide is 1-10 μm, the number of layers is less than 5, and the oxygen content is 30-40%.

[0024] The silicon gel composite desiccant is composed of 50-60 parts of mesoporous silica gel and 40-50 parts of fine pore silica gel; the specific surface area of the mesoporous silica gel is 400-600 m 2 / g, and the particle size is not greater than 150 μm; the specific surface area of the fine pore silica gel is 600-800 m 2 / g, and the particle size is not greater than 75 μm.

[0025] The preparation method of the silicon gel composite desiccant is as follows:

[0026] A certain mass of graphene oxide is added into anhydrous ethanol solution, ultrasonic dispersion is carried out until the graphene oxide is uniformly dispersed in the ethanol solution; a certain mass of mesoporous silica gel and fine pore silica gel is dried at 110 DEG C for 2h, and after cooling to room temperature, is added into the graphene oxide ethanol solution to soak for 48h; ultrasonic treatment is carried out on the solution during the soaking, the ultrasonic power is not less than 360W, and the ultrasonic time is not less than 1h; then, the mixed solution is placed in a 60 DEG C vacuum drying oven to dry, and the dried mixture is placed in a 110 DEG C drying oven to dry for 2-3h, to obtain a graphene oxide modified silica gel composite desiccant;

[0027] The mass ratio of graphene oxide to silica gel in the anhydrous ethanol solution is (0.05-0.1):1.

[0028] Preferably, the expanding agent is a plastic expanding agent; the defoaming agent is one of a silicone defoaming agent, a polyether defoaming agent or a silicone modified polyether defoaming agent; and the water reducing agent is a polycarboxylic acid high-efficiency powder water reducing agent.

[0029] The preparation method of the post-tensioning method prestressed duct grouting material comprises the following steps:

[0030] Step one: the cement, slag powder, silica fume, rheological component, stabilizing component and drying component are weighed according to the mass fraction, then are moved into a high-speed shearing mixer, the mixer is started to stir at high speed for 10min, the mixer rotates at 2000r / min, and the materials are uniformly mixed;

[0031] Step two: the expanding agent, defoaming agent and water reducing agent are weighed according to the mass percentage, are put into the mixer in step one, and high-speed stirring is continuously carried out for 5min, to obtain the prestressed duct grouting material;

[0032] Step three: a certain mass of mixing water is weighed according to the water-binder ratio 0.28, is slowly poured into the grouting material in step two, is slowly stirred for 3min first, and then is quickly stirred for 5min, to obtain the uniformly mixed low water sensitivity prestressed duct grouting material; the mixer rotates at 1500-2000r / min, and the linear velocity is greater than 10m / s.

[0033] Compared with the prior art, the application has the beneficial effects that:

[0034] 1) Different mesh fly ashes are mixed according to certain proportions to obtain fly ashes with more reasonable gradation, improve the early activity of the fly ash and the flow assisting effect of the fly ash on the cement-based material; the composite of the fly ash and microbeads is used as the rheological component, to realize the good flow performance of the duct grouting material;

[0035] 2) Poly-silicic acid flocculants as a stabilizing component, with strong bridging and adsorption properties, can achieve uniform and stable cement slurry, and at the same time, can decompose silicate and polymeric metal ions in weak alkaline solution, generate C-S-H and AFt gel, and play a "nucleus effect" to accelerate the formation of hydration products, thereby improving the hydration reaction rate of cement-based composite cementitious materials; the addition of redispersible latex powder or cellulose ether further promotes the stabilizing effect of the flocculant and reduces the risk of slurry bleeding and stratification caused by excessive water or external water;

[0036] 3) Silica gel-based composite desiccant as a drying component, combined with the porous surface properties of silica gel, further absorbs excess moisture, reduces the humidity inside the pore channel, and locks the excess moisture inside the porous silica gel, as internal curing moisture after the hardening of the grout, reducing the risk of serious grout bleeding caused by improper construction, thereby ensuring the quality of the hole grouting;

[0037] 4) Using graphene oxide modified silica gel can further improve the specific surface area and adsorption properties of silica gel desiccant, improving the water absorption capacity of the drying component; at the same time, it can also take advantage of the excellent mechanical properties of graphene oxide to improve the tensile strength of the cement paste and significantly improve the toughness and crack resistance of the paste. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A comparison chart of the sensitivity of a post-tensioned prestressed hole grouting material prepared for the examples and comparative examples to water consumption. DETAILED DESCRIPTION

[0039] The accompanying drawings are for illustrative purposes only; some well-known common knowledge and its description in the examples may be omitted for those skilled in the art, therefore, cannot be understood as a limitation on the present application.

[0040] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application will be further described in detail below in conjunction with the examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0041] Example 1:

[0042] The post-tensioning method is that a hollow pipe is placed when pouring concrete, and then prestressed steel bars are placed after the concrete has strength, and the hollow pipe is filled with grouting material. The embodiment of the application provides a post-tensioning prestressed hole grouting material, and the specific composition is as follows: cement 60 parts, slag powder 10 parts, silica fume 3 parts, rheological component 22 parts (1000 mesh fly ash, mass ratio of 2500 mesh fly ash to microbead is 5:2:3), stabilizing component 2 parts (mass ratio of polysilicic acid iron aluminum flocculant to carboxymethyl cellulose ether is 1:0.05), dry component 3 parts (mass ratio of mesoporous silica gel, fine pore silica gel to graphene oxide is 5.2:4:0.8), expanding agent 0.02 parts, defoaming agent 0.01 parts and water reducing agent 0.2 parts.

[0043] Embodiment 2

[0044] The embodiment of the application provides a post-tensioning prestressed hole grouting material, and the specific composition is as follows:

[0045] Cement 65 parts, slag powder 10 parts, silica fume 2 parts, rheological component 18 parts (1000 mesh fly ash, mass ratio of 2500 mesh fly ash to microbead is 5:2:3), stabilizing component 1 part (mass ratio of polysilicic acid iron aluminum flocculant to carboxymethyl cellulose ether is 1:0.05), dry component 4 parts (mass ratio of mesoporous silica gel, fine pore silica gel to graphene oxide is 5.2:4:0.8), expanding agent 0.02 parts, defoaming agent 0.02 parts and water reducing agent 0.25 parts.

[0046] Embodiment 3

[0047] The embodiment of the application provides a post-tensioning prestressed hole grouting material, and the specific composition is as follows:

[0048] Cement 68 parts, slag powder 10 parts, silica fume 2 parts, rheological component 16 parts (1000 mesh fly ash, mass ratio of 2500 mesh fly ash to microbead is 5:2:3), stabilizing component 1 part (mass ratio of polysilicic acid iron aluminum flocculant to carboxymethyl cellulose ether is 1:0.05), dry component 3 parts (mass ratio of mesoporous silica gel, fine pore silica gel to graphene oxide is 6:4:0.8), expanding agent 0.02 parts, defoaming agent 0.02 parts and water reducing agent 0.3 parts.

[0049] The preparation method of the post-tensioning prestressed hole grouting material in embodiments 1-3 comprises the following steps:

[0050] Step one: 1000 mesh fly ash, 2500 mesh fly ash and microbead are weighed according to the above mass percentage, and the three materials are uniformly mixed by using a high-speed shearing stirrer to obtain a rheological component;

[0051] Step two: polysilicic acid iron aluminum flocculant and carboxymethyl cellulose ether are weighed according to the above mass percentage, and are uniformly mixed to obtain a stabilizing component;

[0052] Step three: take the mesoporous silica gel, fine pore silica gel, graphene oxide according to the above mass percentage. Disperse the graphene oxide in anhydrous ethanol and ultrasonically disperse for 30 min; dry the mesoporous silica gel and fine pore silica gel at 110℃ for 2 h, and then add them to the graphene oxide ethanol solution after cooling to room temperature, and immerse them while ultrasonically treating for 1 h, and then immerse them for 48 h; then, place the mixed solution in a 60℃ vacuum drying oven for drying, and place the dried mixture in a 110℃ drying oven for drying for 2-3 h to obtain the dried components.

[0053] Step four: take the cement, slag powder, silica fume, rheological component, stabilizing component, and dried component according to the above mass percentage, and then move them into a high-speed shearing mixer, start the mixer to stir at high speed for 10 min, and stir the materials uniformly at a mixer speed of 2000 r / min; take the expanding agent, defoaming agent, and water reducing agent according to the above mass percentage, and then place them in the mixer, continue to stir at high speed for 5 min to obtain a low water sensitivity post-tensioning prestressed duct grouting material.

[0054] Comparative Example 1

[0055] The same cement, slag powder, silica fume, microbeads, expanding agent, water reducing agent, and defoaming agent as in the example are used, and the fly ash is F-class I-grade ash that meets GB / T 1596 “Fly Ash for Use in Cement and Concrete”, and a prestressed duct grouting material includes the following mass components: cement 65 parts, slag powder 15 parts, silica fume 5 parts, fly ash 10 parts, microbeads 5 parts, expanding agent 0.02 parts, water reducing agent 0.25 parts, and defoaming agent 0.01 parts.

[0056] The above mass percentage of each type of raw material is used, and then the materials are moved into a high-speed shearing mixer, the mixer is started to stir at high speed for 10 min, and the materials are stirred uniformly at a mixer speed of 2000 r / min to obtain a post-tensioning prestressed duct grouting material.

[0057] Comparative Example 2

[0058] The same cement, slag powder, silica fume, microbeads, expanding agent, water reducing agent, and defoaming agent as in the example are used, and the fly ash is F-class I-grade ash that meets GB / T 1596 “Fly Ash for Use in Cement and Concrete”, and a prestressed duct grouting material includes the following mass components: cement 70 parts, slag powder 15 parts, silica fume 3 parts, fly ash 10 parts, microbeads 2 parts, expanding agent 0.015 parts, water reducing agent 0.3 parts, and defoaming agent 0.015 parts.

[0059] The above mass percentage of each type of raw material is used, and then the materials are moved into a high-speed shearing mixer, the mixer is started to stir at high speed for 10 min, and the materials are stirred uniformly at a mixer speed of 2000 r / min to obtain a post-tensioning prestressed duct grouting material.

[0060] Performance Test

[0061] The prestressed duct grouting materials prepared according to Examples 1-3 and Comparative Examples 1-2 were mixed with water at a water-cement ratio of 0.28, and various properties of the grouting materials were tested. The mixing and performance testing were carried out in accordance with the provisions of JTG / T 3650-2020 "Technical Specifications for Highway Bridge and Culvert Construction". The specific results are shown in Table 1.

[0062] Table 1 compares the performance of post-tensioned prestressed duct grouting materials prepared in the examples and comparative examples.

[0063]

[0064] As shown in Table 1, the bleeding rate and pressure bleeding rate of the grouting materials in Examples 1, 2, and 3 were all 0, while the grouting materials in Comparative Examples 1 and 2 exhibited a certain degree of free bleeding rate, and the pressure bleeding rate was relatively high. The presence of the stabilizing and drying components significantly improved the bleeding problem of the grouting materials, ensuring that the grout did not separate or bleed. All the grouting materials in these examples showed good uniformity. The setting time of the grouting materials in Examples 1, 2, and 3 was shorter than that in Comparative Examples 1 and 2, indicating a shorter setting time, which is beneficial for improving grouting efficiency.

[0065] The prestressed grouting materials prepared according to Examples 1-3 and Comparative Examples 1-2 were mixed with different water-cement ratios, and the 3-hour inter-wire bleeding rate of all grouts was tested. The selected water-cement ratios were 0.28, 0.30, 0.35, 0.40, and 0.50. The specific results are as follows: Figure 1 As shown. From Figure 1 As can be seen, when the water-cement ratio is below 0.35, the 3-hour bleeding rate between steel wires of the grouting slurry in Examples 1, 2, and 3 is 0. However, the 3-hour bleeding rate between steel wires of the grouting slurry in Comparative Examples 1 and 2 increases continuously with the increase of the water-cement ratio, and the rate of increase also gradually increases. The grouting slurry in these examples exhibits lower water sensitivity and more stable slurry properties.

[0066] The raw materials used in the embodiments 1-3 of the present application are classified and collected to obtain fly ash of different mesh, and the particle size distribution of the fly ash is improved by using the theory of close packing of particles; the flowability of the pressure grouting slurry is significantly improved by using the "ball rolling effect" of fly ash and microbeads; the uniformity of the slurry is improved and the ability of the slurry to resist bleeding and delamination caused by external moisture is improved by compounding the polysilicic acid flocculant with latex powder or cellulose ether; the silica gel composite desiccant can efficiently absorb the excess moisture around the slurry, and the more the moisture, the faster the absorption, and the less the moisture, the slower the absorption, and the moisture is stored in the porous silica gel to form internal curing effect, which reduces the water sensitivity of the slurry, improves the hydration reaction environment in the later stage, and improves the later strength; the spherical particles of silica gel can improve the flowability of the slurry, and limiting the particle size of silica gel can reduce the requirements on the pressure grouting equipment and ensure the smoothness of pressure grouting; graphene oxide can significantly improve the water adsorption performance of silica gel and significantly improve the toughness and crack resistance of the slurry; the use of polysilicic acid flocculant can preferentially form a gel similar to the hydration product of cement as a "crystal nucleus" to induce the formation of the hydration product of the cementitious material, accelerate the coagulation and hardening of the pressure grouting material, and further improve the efficiency of the post-pressure grouting pipe removal.

[0067] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples, and the changes, modifications, additions or replacements made by the person skilled in the art within the essential scope of the present application shall also belong to the protection scope of the present application.

Claims

1. A post-tensioned prestressed duct grouting material, characterized in that, The components include the following parts by weight: 60-70 parts cement, 10-15 parts slag powder, 2-5 parts silica fume, 16-24 parts rheology modifier, 1-2 parts stabilizing component, 3-5 parts drying component, 0.01-0.03 parts expansive agent, 0-0.02 parts defoamer, and 0.15-0.3 parts water-reducing agent; The slag powder is S95 grade granulated blast furnace slag powder, with a density of not less than 2.85 g / cm³. 3 Specific surface area not less than 440m² 2 / kg, flowability ratio not less than 100; The silica fume is unrefined silica fume with a specific surface area of ​​18,000–25,000 m². 2 / kg, silica content ≥95%; The drying component is a graphene oxide-modified silica gel composite desiccant, wherein the graphene oxide has a transverse particle size of 1-10 μm, fewer than 5 layers, and an oxygen content of 30-40%. The silica gel composite desiccant is composed of 50-60 parts of mesoporous silica gel and 40-50 parts of fine-porous silica gel; the mesoporous silica gel has a specific surface area of ​​400-600 m². 2 / g, particle size not greater than 150μm; the specific surface area of ​​the fine-pored silica gel is 600-800m². 2 / g, particle size not greater than 75μm; The preparation method of the silica gel composite desiccant is as follows: A certain mass of graphene oxide was added to anhydrous ethanol solution and ultrasonically dispersed until the graphene oxide was uniformly dispersed in the ethanol solution. A certain mass of mesoporous silica gel and microporous silica gel were dried at 110℃ for 2 hours, cooled to room temperature, and then added to the graphene oxide ethanol solution for soaking for 48 hours. During the soaking period, the solution was ultrasonically treated with an ultrasonic power of not less than 360W and an ultrasonic time of not less than 1 hour. Then, the mixed solution was placed in a vacuum drying oven at 60℃ to dry, and the dried mixture was placed in a drying oven at 110℃ to dry for 2-3 hours to obtain a graphene oxide modified silica gel composite desiccant. The mass ratio of graphene oxide to silica gel in the anhydrous ethanol solution is (0.05-0.1):

1.

2. The post-tensioned prestressed duct grouting material according to claim 1, characterized in that, The cement is ordinary Portland cement with a density of not less than 3.05 g / cm³. 3 Specific surface area not less than 300m² 2 / kg.

3. The post-tensioned prestressed duct grouting material according to claim 1, characterized in that, The rheological component is composed of 40-60 parts of 1000-mesh fly ash, 10-20 parts of 2500-mesh fly ash, and 30-50 parts of microspheres, which are uniformly mixed using a high-speed shear mixer at a speed of 2000 r / min for 10 min until uniformly mixed.

4. The post-tensioned prestressed duct grouting material according to claim 1, characterized in that, The stabilizing component is a mixture of polysilicic acid flocculant and thickener; wherein, the mass fraction of polysilicic acid flocculant is 97-100 parts and the mass fraction of thickener is 0-3 parts.

5. The post-tensioned prestressed duct grouting material according to claim 4, characterized in that, The polysilicic acid flocculant is an inorganic polymeric flocculant that embeds metal ions into the polysilicic acid molecular chain, and is one or a combination of several of the following: polyferric silicate, polyaluminum silicate, polyferric aluminum silicate, polyferric zinc silicate, and polyaluminum zinc silicate. The thickener is a redispersible latex powder or a cellulose ether; the cellulose ether is one or a combination of several of carboxymethyl cellulose ether, hydroxyethyl cellulose ether, and carboxymethyl hydroxyethyl cellulose ether.

6. The post-tensioned prestressed duct grouting material according to claim 1, characterized in that, The expanding agent is a plastic expanding agent; the defoamer is one of an organosilicon defoamer, a polyether defoamer, or an organosilicon-modified polyether defoamer; and the water-reducing agent is a polycarboxylate high-efficiency powder water-reducing agent.

7. A method for preparing post-tensioned prestressed duct grouting material as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Weigh out the cement, slag powder, silica fume, rheology component, stabilizing component, and drying component according to the mass proportions, then transfer them into a high-speed shear mixer. Turn on the mixer and mix at high speed for 10 minutes at a speed of 2000 r / min until the materials are evenly mixed. Step 2: Weigh out the expansion agent, defoamer, and water-reducing agent by mass percentage, put them into the mixer from Step 1, and continue to mix at high speed for 5 minutes to obtain the prestressed duct grouting material; Step 3: Weigh a certain amount of mixing water according to a water-cement ratio of 0.28, and slowly pour it into the grouting material from Step 2. Stir slowly for 3 minutes, then stir quickly for 5 minutes to obtain a uniformly mixed low-water-sensitive prestressed duct grouting material; the mixer speed is 1500-2000 r / min and the linear velocity is greater than 10 m / s.

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