Highly anti-segregation nanocomposite slurry and preparation method thereof

Abstract

The application discloses a kind of high anti-decomposition nano composite pressure slurry and preparation method thereof, the pressure slurry includes silicate cement 40-60 parts by mass, silica 10-15 parts, nano alumina 1-3 parts, perovskite nano titanium dioxide 0.5-1 part, xanthan gum 0.02-0.05 parts, hydroxypropyl methyl cellulose ether 0.1-0.3 parts, calcium sulfoaluminate 3-5 parts, calcined magnesium oxide 2-3 parts, polycarboxylic acid water reducing agent 0.5-1.2 parts and water, the mass of water is determined by water-binder ratio, and water-binder ratio is 0.26-0.30.The application is suitable for low temperature construction environment, has high anti-decomposition, good flow degree retention, can improve early strength prestressed duct pressure slurry, and supporting its low temperature preparation method, ensure slurry homogeneity and low temperature adaptability, suitable for severe cold area prestressed engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a high anti-segregation nano-composite pressure grouting material and a preparation method thereof. BACKGROUND

[0002] The pressure grouting material is a key material for filling the post-tensioning prestressed duct, and its functions include protecting the prestressed tendon, transmitting the prestress and improving the structural durability. However, the existing technology has the following significant defects:

[0003] Poor anti-segregation property: the traditional water reducing agent (such as naphthalene and polycarboxylic acid) is difficult to stabilize the slurry of the pressure grouting material at a high water-binder ratio (>0.30), resulting in stratification and a bleeding rate of >3%. The segregation of the slurry reduces the duct density and weakens the prestress transmission efficiency, and even causes structural safety hazards.

[0004] Insufficient low-temperature performance: in a low-temperature (<5℃) environment, the cement hydration speed is greatly reduced, the setting time is prolonged to more than 12 hours, and the 3-day strength is <10MPa. The insufficient early strength easily leads to duct deformation, and the low-temperature shrinkage intensifies the risk of cracks, affecting the construction progress and structural reliability.

[0005] Environmental defects: the traditional aluminum powder expander releases hydrogen gas when encountering water, polluting the environment and causing abnormal local pressure in the duct. At the same time, the alkali content (Na2O equivalent >0.6%) in the pressure grouting material easily causes alkali-aggregate reaction, causing concrete expansion and cracking, and shortening the service life of the structure.

[0006] Insufficient durability: the existing pressure grouting material has a strength loss rate of >20% after 200 freeze-thaw cycles, and a 28-day dry shrinkage rate of >400×10 -6 Long-term shrinkage and freeze-thaw deterioration accelerate the cracking of the duct, weaken the protection of the prestressed tendon, and threaten the long-term stability of the structure.

[0007] In summary, the deficiencies of the existing pressure grouting material in anti-segregation property, low-temperature adaptability, environmental protection and durability seriously restrict its application in complex environmental engineering. Therefore, it is urgent to develop a new pressure grouting material that takes into account the flowability, strength, environmental protection and durability to meet the high-standard requirements of modern prestressed structures. SUMMARY

[0008] The purpose of the present application is to provide a pressure grouting material with high anti-segregation property, low-temperature rapid hardening, low shrinkage and environmental protection characteristics, and to solve the defects in the prior art.

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

[0010] In one aspect, a high anti-segregation nanocomposite pressure slurry is provided, comprising the following components in parts by mass: Portland cement 40-60 parts, silica fume 10-15 parts, nano-alumina 1-3 parts, perovskite nano-titanium dioxide 0.5-1 part, xanthan gum 0.02-0.05 part, hydroxypropyl methyl cellulose ether 0.1-0.3 part, calcium sulfoaluminate 3-5 parts, calcined magnesium oxide 2-3 parts, polycarboxylic acid water reducer 0.5-1.2 parts, and water;

[0011] The silica fume, nano-alumina, and perovskite nano-titanium dioxide constitute a composite nanometer mineral admixture, the xanthan gum and hydroxypropyl methyl cellulose ether constitute a bio-based thickening agent, the calcium sulfoaluminate and calcined magnesium oxide constitute a double expansion source, and the mass of the water is determined by a water-binder ratio, the water-binder ratio being 0.26-0.30.

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

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

[0014] Further, the perovskite nano-titanium dioxide is prepared by the following method:

[0015] Sa1, tetrabutyl titanate and lanthanum nitrate in a molar ratio of 1:0.05 are dissolved in anhydrous ethanol, mixed and stirred to form a uniform solution, wherein the mass of the anhydrous ethanol is 3-5 times the mass of the tetrabutyl titanate; concentrated ammonia is added to the solution to adjust the pH value of the solution to 9-10, and the solution is transferred to a high-pressure reaction kettle, and reacted at 80-90°C for 12-15h to obtain a reaction product;

[0016] Sa2, the reaction product is high-speed centrifuged for 10-15min, and the precipitate is washed with deionized water and anhydrous ethanol for 3-5 times respectively; the washed solid is dried at 60-80°C under a vacuum degree of -0.09 to -0.1MPa for 12-24h to obtain a precursor powder;

[0017] Sa3, the precursor powder is placed in a muffle furnace, heated to 500°C under nitrogen protection, then kept warm for 2-3h, and naturally cooled to obtain the perovskite nano-titanium dioxide.

[0018] Further, in Sa1, the stirring speed is 300-500r / min, and the time is 30-60min; in Sa2, the high-speed centrifugation speed is 8000-10000r / min; in Sa3, the heating rate is 2-5°C / min.

[0019] Further, the surface hydroxyl density of the perovskite type nano-titanium dioxide is 2.5-3.8 / nm 2 .

[0020] Further, the perovskite type nano-titanium dioxide and the carboxyl groups of xanthan gum form a hydrogen bond crosslinking network, and the dynamic viscoelastic modulus of the hydrogen bond crosslinking network is 3.5-4.2.

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

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

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

[0024] In another aspect, a preparation method of high anti-segregation nano-composite pressure slurry is provided, comprising the following steps:

[0025] S1, mixing silicate cement, composite nano-mineral admixture and double expansion source to form aggregate and preheating to 40±2℃;

[0026] S2, dividing water into two parts, the mass ratio of the first part of water to the second part of water is 4:1; under the stirring speed of 60±5rpm, the first part of water and polycarboxylic acid water reducer are added to the aggregate and stirred for 2min, then the second part of water and bio-based thickening agent continue to stir for 3min, to obtain the high anti-segregation nano-composite pressure slurry, and the out-machine temperature of the pressure slurry is ≥15℃.

[0027] Preferably, in S2, the first part of water and polycarboxylic acid water reducer form a mixed solution, and then the mixed solution is stirred and added to the aggregate for stirring for 2min.

[0028] The prepared high anti-segregation nano-composite pressure slurry is immediately subjected to pressure grouting construction, so that it is ensured to be used up within 1h without additional water and powder during the process.

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

[0030] 1、The composite nanomineral admixture of the present application is silica fume, nanometer alumina and perovskite nanometer titanium dioxide, which form a multi-level nanofilling network, the surface hydroxyl groups (-OH) of which form hydrogen bond crosslinking with the polar groups (-COOH, -OH) of the bio-based thickening agent (xanthan gum, hydroxypropyl methyl cellulose ether), forming a dynamic shear thinning structure, reducing viscosity fluctuation (the viscosity standard deviation is reduced from ±50 mPa·s of the traditional formula to ±10 mPa·s), and effectively improving the out-machine flow performance of the grouting material.

[0031] 2、The present application uses the oxygen vacancies (O-vacancy) of perovskite nanometer titanium dioxide as an electron donor to accelerate the early hydration reaction of calcium sulfoaluminate (CSA), and the heat release amount of the hydration reaction in 3 hours is increased by 40% (compared with the control group without perovskite nanometer titanium dioxide), so that the early strength of the grouting material in a low-temperature environment is significantly improved.

[0032] 3、The present application adopts double expansion source synergistic regulation and magnesium oxide surface coating, and the perovskite nanometer titanium dioxide particles form a nanometer coating layer on the surface of the calcined magnesium oxide through electrostatic adsorption, delaying the hydration expansion time (from 1-3 days of the conventional to 3-7 days), and complementing the early expansion of calcium sulfoaluminate, with a difference in expansion rate Δε≤0.02%.

[0033] 4、The present application ensures the initial hydration activity in a low-temperature construction environment through preheating and mixing treatment of the aggregate; a stepwise water injection process is adopted to fully wet the cementitious material and form a uniform slurry matrix under the condition of low-speed stirring at 60±5 rpm; the remaining 20% water and bio-based thickening agent are injected in the second stage, and the stirring is continued for 3 minutes, which effectively avoids the local aggregation of the thickening agent, and at the same time, the molecular chain of the thickening agent is fully stretched through shear force regulation. The whole stirring process is strictly maintained at low speed (60±5 rpm), which not only ensures the uniform dispersion of the material, but also avoids the introduction of too many air bubbles by high-speed stirring. The slurry temperature out of the machine is stably ≥15℃, which realizes the construction adaptability in a low-temperature environment (-5℃), and at the same time, the initial fluidity of the grouting material is ≤17s, the 60min fluidity retention rate is ≥85%, and the bleeding rate is ≤1.5%, forming a high-quality slurry with high rheological stability and low-temperature early strength characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The figure is the comparison curve of the heat release amount of the calcium sulfoaluminate hydration reaction of Example 1 and Comparative Example 4 of the present application. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] In the embodiments of the present application, the used nano-aluminum oxide is in a granular form, the used perovskite nano-titanium dioxide is in a granular form, the used xanthan gum is in a powder form, and the used polycarboxylic acid water reducing agent is in a powder form.

[0037] Embodiment 1

[0038] As a preferred embodiment of the present application, the components of the high anti-segregation nano-composite pressure slurry in this embodiment are shown in Table 1.

[0039] Table 1 Component composition of the high anti-segregation nano-composite pressure slurry in Embodiment 1

[0040]

[0041]

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

[0043] Embodiment 2

[0044] As a preferred embodiment of the present application, the components of the high anti-segregation nano-composite pressure slurry in this embodiment are shown in Table 2.

[0045] Table 2 Component composition of the high anti-segregation nano-composite pressure slurry in Embodiment 2

[0046] Components Mass parts (parts) Silicate cement 40 Silica fume 10 Nano-alumina 1 Perovskite nano-titanium dioxide 0.5 Xanthan gum 0.02 Hydroxypropyl methyl cellulose ether 0.1 Calcium sulfoaluminate 3 Calcined magnesium oxide 2 Polycarboxylic acid water reducer 0.5

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

[0048] Embodiment 3

[0049] As a preferred embodiment of the present application, the components of the high anti-segregation nano-composite pressure slurry in this embodiment are shown in Table 3.

[0050] Table 3 Component composition of the high anti-segregation nano-composite pressure slurry in Embodiment 3

[0051]

[0052]

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

[0054] Comparative Example 1

[0055] The difference between the present comparative example and Example 1 is that the present comparative example uses a commercially available conventional formulation instead of the formulation of the present application, the commercially available conventional formulation does not include the composite nanomineral admixture and the bio-based thickening agent, and uses aluminum powder expander instead of the dual-expansion source, uses a naphthalene-based water reducing agent instead of the polycarboxylic acid water reducing agent, and the water-binder ratio is increased to 0.35.

[0056] Comparative Example 2

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

[0058] Comparative Example 3

[0059] The difference between the present comparative example and Example 1 is that the present comparative example uses polyacrylamide instead of the bio-based thickening agent (xanthan gum and hydroxypropyl methyl cellulose ether), and the remaining components are consistent with Example 1.

[0060] Comparative Example 4

[0061] The difference between the present comparative example and Example 1 is that the present comparative example uses ordinary nanometer SiO2 instead of perovskite type nanometer titanium dioxide, and the remaining components are consistent with Example 1.

[0062] Comparative Example 5

[0063] The difference between the present comparative example and Example 1 is that the present comparative example uses aluminum powder expander instead of the dual-expansion source (calcium sulphoaluminate and calcined magnesium oxide), and the remaining components are consistent with Example 1.

[0064] Comparative Example 6

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

[0066] Test Example 1

[0067] The performance of the press slurry of Examples 1-3 and Comparative Examples 1-6 was tested, and the test results are shown in Tables 4, 5 and 6.

[0068] Table 4 Performance test results of the press slurry of Examples and Comparative Examples 1

[0069]

[0070] Table 5 Performance test results of the press slurry of Examples and Comparative Examples 2

[0071]

[0072]

[0073] Table 6 Performance test results of the grouting material of the examples and the comparative examples 3

[0074]

[0075] According to the data in Tables 4-6, the examples 1-3 of the present application are superior to the comparative examples in terms of flowability (initial ≤ 18 s, 60 min ≤ 25 s), low-temperature strength (-5℃ / 3d ≥ 18 MPa, 28d ≥ 50 MPa), durability (200 times of freeze-thaw strength loss rate ≤ 10%, shrinkage rate ≤ 300 × 10 -6 ) and environmental protection (no hydrogen, alkali content ≤ 0.3%) and the like. The comparative example 1 (conventional formula) has problems such as large flowability loss (60 min 34.5 s), low low-temperature strength (-5℃ / 3d only 5.2 MPa) and high shrinkage rate (420 × 10 -6 ) and the like; the comparative examples 2-6 show that the removal of nano-alumina, the replacement of thickening agent or expansion source, the adjustment of water-binder ratio and the like result in significant performance decline (such as the freeze-thaw loss rate of comparative example 4 increases to 15.4%, the shrinkage rate of comparative example 6 reaches 465 × 10 -6 ), proving that the composite nano-mineral admixture, the bio-based thickening system and the double 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 harsh engineering requirements and be suitable for prestressed engineering in severe cold regions.

[0076] Test Example 2

[0077] The heat release amount of the calcium sulfoaluminate hydration reaction in the examples 1 and the comparative example 4 was tested, and the test results are shown in Table 7. The data in Table 7 were fitted into a curve comparison chart, i.e. Figure 1 .

[0078] Table 7 Heat release amount data of calcium sulfoaluminate hydration of the examples 1 and the comparative example 4

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

[0080] According to Tables 7 and Figure 1It can be seen that the calcium sulphoaluminate hydration exothermic peak of Example 1 (perovskite type nano-titanium dioxide) is advanced to 6 hours (220 J / g), and the total exothermic quantity is 770 J / g, which is significantly improved compared with 10 hours (150 J / g) and 555 J / g (+38.7%) of Comparative Example 4 (ordinary nano-SiO2). The data show that the perovskite type nano-titanium dioxide has a synergistic effect with the bio-based thickening agent and the double expansion source: catalyzing the early hydration of calcium sulphoaluminate, accelerating the formation of ettringite, and releasing the expansion stress in advance; enhancing the hydration reaction activity, promoting the increase of the total exothermic quantity, and realizing more sufficient volume compensation; forming a dynamic synergy with other components in the system, such as Figure 1 As shown, the exothermic rate is fast, the peak value is high, and the decay is gentle.

[0081] Finally, it should be noted that: the above examples are only the preferred embodiments of the present application to illustrate the technical solutions of the present application, but not limit it, of course, nor limit the patent scope of the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement to part or all of the technical features; and 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 application; that is to say, any modification or polishing without substantial significance in the main design idea and spirit of the present application, and the technical problems solved are still consistent with the present application, which should be included in the protection scope of the present application; in addition, the technical solutions of the present application are directly or indirectly applied to other related technical fields, which are also included in the patent protection scope of the present application.

Claims

1. A high green strength nanocomposite slurry, characterized in that, The following components are included by mass fraction: Portland cement 40-60 parts, silica fume 10-15 parts, nano-alumina 1-3 parts, perovskite nano-titanium dioxide 0.5-1 part, xanthan gum 0.02-0.05 part, hydroxypropyl methylcellulose ether 0.1-0.3 part, calcium sulfoaluminate 3-5 parts, calcined magnesium oxide 2-3 parts, polycarboxylic acid water reducer 0.5-1.2 parts, and water; The silica fume, nano-alumina, and perovskite nano-titanium dioxide constitute a composite nano-mineral admixture, the xanthan gum and hydroxypropyl methylcellulose ether constitute a bio-based thickening agent, the calcium sulfoaluminate and calcined magnesium oxide constitute a dual expansion source, and the mass of the water is determined by a water-binder ratio of 0.26-0.

30.

2. The high anti-segregation nanocomposite green compact material of claim 1, wherein, The specific surface area of the perovskite nano-titanium dioxide is ≥150 m² / g.

3. The high anti-segregation nanocomposite green compact of claim 1, wherein, The perovskite nano-titanium dioxide is prepared by the following method: Sa1, dissolve tetrabutyl titanate and lanthanum nitrate in a molar ratio of 1:0.05 in anhydrous ethanol, mix and stir to form a uniform solution, wherein the mass of the anhydrous ethanol is 3-5 times the mass of the tetrabutyl titanate; add concentrated ammonia water to the solution to adjust the pH value of the solution to 9-10, and transfer the solution to a high-pressure reaction kettle, and react at 80-90°C for 12-15 hours to obtain a reaction product; Sa2, centrifuge the reaction product at high speed for 10-15 minutes, and wash the precipitate with deionized water and anhydrous ethanol for 3-5 times respectively; dry the washed solid at 60-80°C under a vacuum degree of -0.09 to -0.1 MPa for 12-24 hours to obtain a precursor powder; Sa3, place the precursor powder in a muffle furnace, heat to 500°C under nitrogen protection, then keep warm for 2-3 hours, and naturally cool down to obtain the perovskite nano-titanium dioxide.

4. The high anti-segregation nanocomposite green compact material of claim 3, wherein the nanometer-sized particles are selected from the group consisting of SiC, Si3N4, Al2O3, TiO2, ZrO2, and combinations thereof. In the Sa1, the stirring speed is 300-500 r / min for 30-60 min; in the Sa2, the high-speed centrifugation speed is 8000-10000 r / min; in the Sa3, the heating rate is 2-5°C / min.

5. The high anti-segregation nanocomposite green compact of claim 1, wherein, The surface hydroxyl group density of the perovskite nano-titanium dioxide is 2.5-3.8 / nm².

6. The high anti-segregation nanocomposite green compact of claim 1, wherein, The carboxylic acid groups of the perovskite nano-titanium dioxide form a hydrogen bond cross-linking network with the xanthan gum.

7. The high anti-segregation nanocomposite green compact material of claim 1, wherein, The perovskite nano-titanium dioxide catalyzes the hydration reaction of calcium sulfoaluminate through oxygen vacancies, the heat release of the hydration reaction for 6 hours is ≥220 J / g, and the surface coating layer thickness of the calcined magnesium oxide after the hydration reaction is 5-15 nm.

8. The high anti-segregation nanocomposite green compact of claim 1, wherein, The MgO content in the calcined magnesium oxide is ≥95wt%, and the D90 of the calcined magnesium oxide is ≤10 μm.

9. The high anti-segregation nanocomposite green compact of claim 1, wherein, The mass ratio of the calcined magnesium oxide to the calcium sulfoaluminate is 1:1.5-1:

2.

10. The method according to any one of claims 1 to 9, characterized in that, The following steps are included: S1, pre-mix Portland cement, composite nano-mineral admixture, and dual expansion source to form aggregate and preheat to 40±2°C; S2, divide the water into two parts, the mass ratio of the first part of water to the second part of water is 4:1; under the stirring speed of 60±5 rpm, the first part of water and the polycarboxylate superplasticizer are added into the aggregate and stirred for 2 min, then the second part of water and the bio-based thickening agent continue to be stirred for 3 min, to obtain the high anti-segregation nano-composite pressure slurry, and the temperature of the pressure slurry out of the machine is greater than or equal to 15 DEG C.

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