High-segregation-resistance nano-composite grouting material and preparation method thereof

Abstract

The invention discloses a nano composite grouting material with high segregation resistance and a preparation method thereof, and the grouting material comprises the following components in parts by mass: 40-60 parts of Portland cement, 10-15 parts of silica fume, 1-3 parts of nano aluminum oxide, 0.5-1 part of perovskite type nano titanium dioxide, 0.02-0.05 part of xanthan gum, 0.1-0.3 part of hydroxypropyl methyl cellulose ether, 3-5 parts of calcium sulphoaluminate, 2-3 parts of calcined magnesium oxide, 0.5-1.2 parts of a polycarboxylate superplasticizer and water. The mass of the water is determined according to a water-binder ratio, and the water-binder ratio is 0.26-0.30. The prestressed duct grouting material is suitable for a low-temperature construction environment, has high segregation resistance and good fluidity retentivity, can improve the early strength, is matched with the low-temperature preparation method of the prestressed duct grouting material, ensures the homogeneity and low-temperature adaptability of the grouting material, and is suitable for prestressed engineering in severe cold areas.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a high-segregation-resistant nano-composite grouting material and a preparation method thereof. Background Art

[0002] Grouting material is a key material for filling post-tensioned prestressed ducts. Its functions include protecting prestressed tendons, transferring prestress, and improving structural durability. However, the existing technology has the following significant defects:

[0003] Poor resistance to segregation: Traditional water-reducing agents (such as naphthalene and polycarboxylic acid) are difficult to stabilize the slurry of grouting materials at high water-binder ratios (>0.30), resulting in stratification and water seepage rate >3%. Slurry segregation will reduce the density of the pores, weaken the efficiency of prestressing transmission, and even cause structural safety hazards.

[0004] Insufficient low-temperature performance: In low-temperature environments (<5°C), the cement hydration rate is greatly reduced, the setting time is extended to more than 12 hours, and the 3-day strength is <10MPa. Insufficient early strength can easily lead to pore deformation, and low-temperature shrinkage increases the risk of cracks, affecting construction progress and structural reliability.

[0005] Environmental defects: Traditional aluminum powder expansion agent releases hydrogen when in contact with water, polluting the environment and causing abnormal local pressure in the pores. 2 O equivalent>0.6%) can easily induce alkali-aggregate reaction, causing concrete expansion and cracking, shortening the life of the structure.

[0006] Insufficient durability: The existing grouting material has a strength loss rate of >20% after 200 freeze-thaw cycles, and a drying shrinkage rate of >400×10 -6 Long-term shrinkage and freeze-thaw deterioration accelerate pore cracking, weaken the protection of prestressed tendons, and threaten the long-term stability of the structure.

[0007] In summary, the shortcomings of existing grouting materials in terms of anti-segregation, low temperature adaptability, environmental protection and durability seriously restrict their application in complex environmental engineering. Therefore, it is urgent to develop a new type of grouting material that takes into account fluidity, strength, environmental protection and durability to meet the high standards of modern prestressed structures. Summary of the invention

[0008] The purpose of the present invention is to provide a grouting material with high segregation resistance, low temperature rapid hardening, low shrinkage and environmental protection characteristics, and to match it with a low temperature construction process to solve the defects in the prior art.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] On the one hand, a high-segregation-resistant nano-composite grouting material is provided, which comprises the following components by weight: 40-60 parts of silicate cement, 10-15 parts of silica fume, 1-3 parts of nano-alumina, 0.5-1 parts of perovskite-type nano-titanium dioxide, 0.02-0.05 parts of xanthan gum, 0.1-0.3 parts of hydroxypropyl methylcellulose ether, 3-5 parts of calcium sulfoaluminate, 2-3 parts of calcined magnesium oxide, 0.5-1.2 parts of polycarboxylic acid water reducer and water;

[0011] Silica fume, nano-alumina and perovskite-type nano-titanium dioxide constitute a composite nano-mineral admixture, xanthan gum and hydroxypropyl methylcellulose ether constitute a bio-based thickener, calcium sulfoaluminate and calcined magnesium oxide constitute a dual expansion source, and the quality of water is determined by the water-binder ratio, which is 0.26-0.30.

[0012] The water-cement ratio is the mass ratio of water to cementitious material, and the cementitious material is composed of silicate cement, silica fume, nano-alumina and perovskite-type nano-titanium dioxide.

[0013] Furthermore, the specific surface area of ​​the perovskite nano-titanium dioxide is ≥150m 2 / g.

[0014] Furthermore, the preparation method of the perovskite nano titanium dioxide is as follows:

[0015] Sa 1 , dissolving tetrabutyl titanate and lanthanum nitrate in anhydrous ethanol at a molar ratio of 1:0.05, mixing and stirring to form a uniform solution, wherein the mass of anhydrous ethanol is 3 to 5 times the mass of tetrabutyl titanate; adding concentrated ammonia water to the solution to adjust the pH value of the solution to 9 to 10, transferring the solution with a pH value of 9 to 10 to a high-pressure reactor, reacting at 80 to 90° C. for 12 to 15 hours to obtain a reaction product;

[0016] Sa 2 , centrifuging the reaction product at high speed for 10 to 15 minutes, washing the centrifuged precipitate 3 to 5 times with deionized water and anhydrous ethanol respectively; drying the washed solid at 60 to 80° C. and vacuum degree of -0.09 to -0.1 MPa for 12 to 24 hours to obtain a precursor powder;

[0017] Sa 3 , placing the precursor powder in a muffle furnace, heating it to 500° C. under nitrogen protection, then keeping it warm for 2 to 3 hours and then cooling it naturally to obtain the perovskite-type nano-titanium dioxide.

[0018] Furthermore, the Sa 1 The mixing speed is 300 to 500 r / min and the time is 30 to 60 min; 2 The speed of the high-speed centrifuge is 8000-10000 r / min;3 The heating rate is 2-5°C / min.

[0019] Furthermore, the surface hydroxyl density of the perovskite nano-titanium dioxide is 2.5 to 3.8 per nm. 2 .

[0020] Furthermore, the perovskite-type nano-titanium dioxide forms a hydrogen bond cross-linking network with the carboxylic acid groups of xanthan gum, and the dynamic viscoelastic modulus of the hydrogen bond cross-linking network is 3.5 to 4.2.

[0021] Furthermore, the perovskite-type nano-titanium dioxide catalyzes the hydration reaction of calcium sulfoaluminate through oxygen vacancies, the heat released by the hydration reaction for 6 hours is ≥220 J / g, and the thickness of the surface coating layer of the calcined magnesium oxide after the hydration reaction is 5 to 15 nm.

[0022] Furthermore, the MgO content in the calcined magnesium oxide is ≥95wt%, and the D90 of the calcined magnesium oxide is ≤10μm.

[0023] Furthermore, the mass ratio of the calcined magnesium oxide to the calcium sulphoaluminate is 1:1.5 to 1:2.

[0024] On the other hand, a method for preparing a highly anti-segregation nanocomposite grouting material is provided, comprising the following steps:

[0025] S1. Premixing silicate cement, composite nano-mineral admixture and dual expansion source to form aggregate and preheating to 40±2°C;

[0026] S2. Divide the water into two parts, with the mass ratio of the first part of water to the second part of water being 4:1; add the first part of water and the polycarboxylate water reducer to the aggregate at a stirring speed of 60±5rpm and stir for 2min, then continue to stir the second part of water and the bio-based thickener for 3min to obtain the highly segregation-resistant nano-composite grouting material, the outlet temperature of the grouting material being ≥15°C.

[0027] Preferably, in S2, the first portion of water and the polycarboxylate water-reducing agent are mixed to form a mixed solution, and the mixed solution is then added to the aggregate with stirring for 2 minutes.

[0028] The high-segregation-resistant nano-composite grouting material prepared by the present invention is immediately put into grouting construction to ensure that it is used up within 1 hour without adding additional water and powder in the middle.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The composite nano-mineral admixture of the present invention is silica fume, nano-alumina and perovskite-type nano-titanium dioxide, which form a multi-level nano-filling network. The surface hydroxyl groups (-OH) thereof are hydrogen-bonded with the polar groups (-COOH, -OH) of the bio-based thickener (xanthan gum, hydroxypropyl methylcellulose ether) to form a dynamic shear-thinning structure, thereby reducing viscosity fluctuations (the viscosity standard deviation is reduced from ±50 mPa·s of the traditional formula to ±10 mPa·s), and effectively improving the flowability of the grouting material out of the machine.

[0031] 2. The present invention uses oxygen vacancies (O-vacancy) of perovskite nano-titanium dioxide as electron donors to accelerate the early hydration reaction of calcium sulfoaluminate (CSA). The heat release of the hydration reaction for 3 hours is increased by 40% (compared with the control group without perovskite nano-titanium dioxide), which significantly improves the early strength of the grouting material in a low temperature environment.

[0032] 3. The present invention adopts dual expansion source coordinated regulation and magnesium oxide surface coating. The perovskite-type nano titanium dioxide particles form a nano-scale coating layer on the surface of calcined magnesium oxide through electrostatic adsorption, delaying the hydration expansion time (extended from the conventional 1-3 days to 3-7 days), and complementing the early expansion of calcium sulfoaluminate, and the expansion rate difference Δε≤0.02%.

[0033] 4. The present invention ensures the initial hydration activity in a low-temperature construction environment by preheating and mixing the aggregate; adopts a step-by-step water addition process, and fully wets the cementitious material and forms a uniform slurry matrix under the low-speed stirring condition of 60±5rpm; in the second stage, the remaining 20% ​​of water and bio-based thickener are injected, and stirring is continued for 3 minutes. The step-by-step feeding mechanism effectively avoids local agglomeration of the thickener, and at the same time, the thickener molecular chain is fully extended through shear force regulation. The entire stirring process strictly maintains a low speed (60±5rpm), which not only ensures uniform dispersion of the material but also avoids the introduction of too many bubbles by high-speed stirring. The slurry outlet temperature is stable at ≥15℃. While achieving construction adaptability in a low-temperature environment (-5℃), the initial fluidity of the grouting material is ≤17s, the 60min fluidity retention rate is ≥85%, and the water bleeding rate is ≤1.5%, forming a high-quality slurry with both high rheological stability and low-temperature early strength characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a comparative curve diagram of the heat release of the calcium sulphoaluminate hydration reaction of Example 1 of the present invention and Comparative Example 4. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In the embodiments of the present invention, the nano-alumina used is in granular form, the perovskite-type nano-titanium dioxide used is in granular form, the xanthan gum used is in powder form, and the polycarboxylate water-reducing agent used is in powder form.

[0037] Example 1

[0038] As a preferred embodiment of the present invention, the components of a highly anti-segregation nano-composite grouting material of this embodiment are shown in Table 1.

[0039] Table 1 Components of the high anti-segregation nanocomposite press grouting material of Example 1

[0040]

[0041]

[0042] In this embodiment, the quality of water is determined by a water-to-binder ratio of 0.28.

[0043] Example 2

[0044] As a preferred embodiment of the present invention, the components of a highly anti-segregation nano-composite grouting material of this embodiment are shown in Table 2.

[0045] Table 2 Components of the high anti-segregation nanocomposite grouting material of Example 2

[0046] Components Mass parts (parts) Portland cement 40 Silica Fume 10 Nano Alumina 1 Perovskite nano-titanium dioxide 0.5 Xanthan gum 0.02 Hydroxypropyl methyl cellulose 0.1 Calcium sulphoaluminate 3 Calcined Magnesium Oxide 2 Polycarboxylate water reducer 0.5

[0047] In this embodiment, the quality of water is determined by a water-to-binder ratio of 0.26.

[0048] Example 3

[0049] As a preferred embodiment of the present invention, the components of a highly anti-segregation nano-composite grouting material of this embodiment are shown in Table 3.

[0050] Table 3 Components of the high anti-segregation nanocomposite grouting material of Example 3

[0051]

[0052]

[0053] In this embodiment, the quality of water is determined by a water-to-binder ratio of 0.30.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that this comparative example adopts a commercially available conventional formula to replace the formula of the present invention, the commercially available conventional formula does not include a composite nano-mineral admixture and a bio-based thickener, and an aluminum powder expansion agent is used to replace the dual expansion source, and a naphthalene-based water reducer is used to replace the polycarboxylic acid water reducer, and the water-to-binder ratio is increased to 0.35.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that this comparative example uses silica fume instead of nano alumina, and the other components are consistent with Example 1.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that polyacrylamide is used in this comparative example to replace the bio-based thickener (xanthan gum and hydroxypropyl methylcellulose ether), and the other components are consistent with Example 1.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that this comparative example uses ordinary nano-SiO 2 The perovskite nano-titanium dioxide was replaced, and the other components were consistent with those in Example 1.

[0062] Comparative Example 5

[0063] The difference between this comparative example and Example 1 is that this comparative example uses aluminum powder expansion agent to replace the dual expansion sources (calcium sulfoaluminate and calcined magnesium oxide), and the other components are consistent with Example 1.

[0064] Comparative Example 6

[0065] The difference between this comparative example and Example 1 is that the water-binder ratio of this comparative example is increased from 0.28 to 0.32, and the other components are consistent with Example 1.

[0066] Test Example 1

[0067] The performance tests were conducted on the grouting materials of Examples 1 to 3 and Comparative Examples 1 to 3, and the test results are shown in Tables 4, 5 and 6.

[0068] Table 4 Performance test results of grouting materials of embodiments and comparative examples 1

[0069]

[0070] Table 5 Performance test results of grouting materials of embodiments and comparative examples 2

[0071]

[0072]

[0073] Table 6 Performance test results of grouting materials of embodiments and comparative examples 3

[0074]

[0075] According to the data in Tables 4 to 6, Examples 1 to 3 of the present invention have good fluidity (initial ≤18s, 60min≤25s), low temperature strength (-5°C / 3d≥18MPa, 28d≥50MPa), durability (200 freeze-thaw strength loss rate≤10%, shrinkage rate≤300×10 -6 ) and environmental protection (no hydrogen, alkali content ≤ 0.3%) are better than the comparative example. Comparative Example 1 (conventional formula) has large fluidity loss (60min 34.5s), low low temperature strength (-5℃ / 3d only 5.2MPa) and high shrinkage (420×10 -6 ) and other problems; Comparative Examples 2 to 6 show that the removal of nano-alumina, replacement of thickeners or expansion sources, and adjustment of water-binder ratios all lead to significant performance declines (e.g., the freeze-thaw loss rate of Comparative Example 4 increased to 15.4%, and the shrinkage rate of Comparative Example 6 reached 465×10 -6 ), which proves that the composite nano-mineral admixture, bio-based thickening system and dual expansion source have a synergistic effect, which can simultaneously solve the problems of anti-segregation, low-temperature hydration, shrinkage compensation and environmental protection, meet the stringent engineering needs, and are suitable for prestressed engineering in severe cold areas.

[0076] Test Example 2

[0077] The heat release of the calcium sulphoaluminate hydration reaction in Example 1 and Comparative Example 4 was tested, and the test results are shown in Table 7. The data in Table 7 are fitted into a curve comparison chart, that is, Figure 1 .

[0078] Table 7 Calcium sulphoaluminate hydration heat release data of Example 1 and Comparative Example 4

[0079] Time (h) Example 1 Heat release (J / g) Comparative Example 4 Heat Release (J / g) 0 0 0 2 25 10 4 80 35 6 220 (peak) 90 8 180 120 10 130 150(peak) 12 95 110 24 60 70 48 40 45 72 20 25 Total heat release 770 555

[0080] According to Table 7 and Figure 1 It can be seen that the exothermic peak of calcium sulfoaluminate hydration in Example 1 (perovskite-type nano-titanium dioxide) is advanced to 6 hours (220 J / g), and the total heat release is 770 J / g, which is much higher than that in Comparative Example 4 (ordinary nano-SiO 2) in 10 hours (150 J / g) and 555 J / g (+38.7%) were significantly improved. The data show that perovskite nano-titanium dioxide has a synergistic effect with bio-based thickeners and dual expansion sources: catalyzing the early hydration of calcium sulfoaluminate, accelerating the formation of calcium sulfate aluminate, and releasing expansion stress in advance; enhancing the activity of hydration reaction, increasing the total heat release, and achieving more sufficient volume compensation; forming dynamic synergy with other components of the system, such as Figure 1 As shown, the heat release rate is fast, the peak value is high and the decay is gentle.

[0081] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

Claims

1. A highly anti-segregation nanocomposite grouting material, characterized in that: The following components are included by mass: 40-60 parts of silicate cement, 10-15 parts of silica fume, 1-3 parts of nano-alumina, 0.5-1 parts of perovskite-type nano-titanium dioxide, 0.02-0.05 parts of xanthan gum, 0.1-0.3 parts of hydroxypropyl methylcellulose ether, 3-5 parts of calcium sulfoaluminate, 2-3 parts of calcined magnesium oxide, 0.5-1.2 parts of polycarboxylic acid water reducer and water; Silica fume, nano-alumina and perovskite-type nano-titanium dioxide constitute a composite nano-mineral admixture, xanthan gum and hydroxypropyl methylcellulose ether constitute a bio-based thickener, calcium sulfoaluminate and calcined magnesium oxide constitute a dual expansion source, and the quality of water is determined by the water-binder ratio, which is 0.26-0.

30.

2. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The specific surface area of ​​the perovskite nano-titanium dioxide is ≥150m 2 / g.

3. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The preparation method of the perovskite nano titanium dioxide is as follows: Sa1, dissolving tetrabutyl titanate and lanthanum nitrate in anhydrous ethanol at a molar ratio of 1:0.05, mixing and stirring to form a uniform solution, wherein the mass of anhydrous ethanol is 3 to 5 times the mass of tetrabutyl titanate; adding concentrated ammonia water to the solution to adjust the pH value of the solution to 9 to 10, transferring the solution with a pH value of 9 to 10 to a high-pressure reactor, and reacting at 80 to 90° C. for 12 to 15 hours to obtain a reaction product; Sa2, centrifuge the reaction product at high speed for 10 to 15 minutes, wash the centrifuged precipitate 3 to 5 times with deionized water and anhydrous ethanol respectively; dry the washed solid at 60 to 80° C. and vacuum degree of -0.09 to -0.1 MPa for 12 to 24 hours to obtain a precursor powder; Sa3. Place the precursor powder in a muffle furnace, heat it to 500° C. under nitrogen protection, then keep it warm for 2 to 3 hours and cool it naturally to obtain the perovskite nano-titanium dioxide.

4. The highly segregation-resistant nanocomposite grouting material according to claim 3, characterized in that: In the Sa1, the mixing and stirring speed is 300-500 r / min, and the time is 30-60 min; in the Sa2, the high-speed centrifugal speed is 8000-10000 r / min; in the Sa3, the heating rate is 2-5°C / min.

5. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The surface hydroxyl density of the perovskite nano-titanium dioxide is 2.5 to 3.8 per nm. 2 .

6. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The perovskite-type nano-titanium dioxide and the carboxylic acid groups of xanthan gum form a hydrogen bond cross-linking network, and the dynamic viscoelastic modulus of the hydrogen bond cross-linking network is 3.5-4.

2.

7. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The perovskite nano titanium dioxide catalyzes the hydration reaction of calcium sulfoaluminate through oxygen vacancies, the heat released by the hydration reaction for 6 hours is ≥220 J / g, and the thickness of the surface coating layer of the calcined magnesium oxide after the hydration reaction is 5-15 nm.

8. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The MgO content in the calcined magnesium oxide is ≥95wt%, and the D90 of the calcined magnesium oxide is ≤10μm.

9. The highly segregation-resistant nanocomposite grouting material according to claim 1, characterized in that: The mass ratio of the calcined magnesium oxide to the calcium sulphoaluminate is 1:1.5 to 1:

2.

10. The method for preparing a highly segregation-resistant nanocomposite grouting material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Premixing silicate cement, composite nano-mineral admixture and dual expansion source to form aggregate and preheating to 40±2°C; S2. Divide the water into two parts, with the mass ratio of the first part of water to the second part of water being 4:1; add the first part of water and the polycarboxylate water reducer to the aggregate at a stirring speed of 60±5rpm and stir for 2min, then continue to stir the second part of water and the bio-based thickener for 3min to obtain the highly segregation-resistant nano-composite grouting material, the outlet temperature of the grouting material being ≥15°C.

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