A pipe pile admixture and its preparation process

Abstract

The present invention provides a pipe pile admixture and a preparation process thereof, and relates to the technical field of concrete processing. The pipe pile admixture is prepared by mixing ethylene glycol, glycerol ether, polycarboxylic acid water reducer, hydroxypropyl methylcellulose / chitosan modified material, modified xanthan gum, cocoyl diethanolamine, and polycaprolactone microspheres. The present invention overcomes the shortcomings of the prior art, and the prepared pipe pile admixture mixed pipe pile concrete can effectively improve the pumping effect of concrete, while improving the early strength performance of concrete, and comprehensively improving the mechanical properties of pipe pile concrete.

Description

Technical Field

[0001] The invention relates to the technical field of concrete processing, and in particular to a pipe pile admixture and a preparation process thereof. Background Art

[0002] Pipe piles are a type of pile foundation and are an indispensable building material for industrial and construction industries made of concrete. As a prefabricated pile, pipe piles are widely used in industrial and civil construction, municipal administration, transportation, water conservancy, railways and other fields. Existing pipe piles are divided into prestressed concrete pipe piles (PC pipe piles), prestressed concrete thin-walled pipe piles (PTC pipe piles) and prestressed high-strength concrete pipe piles (PHC pipe piles) according to concrete strength grade and wall thickness.

[0003] PHC piles have the advantages of reliable quality, convenient pile planting, fast construction speed, and good pile foundation seismic performance. The traditional PHC pile production process includes batching and metering, concrete mixing, pouring into molds, steel bar tensioning, centrifugal forming, steaming in pools, releasing and demoulding, autoclave high-pressure curing, finished product inspection, and finished product stacking. This process also includes processes such as mold cleaning and cage loading. Among them, pool curing and autoclave high-pressure curing have the greatest impact on the performance of PHC piles. According to traditional construction experience, whether the hammer method or static pressure method is used, the higher the strength grade of the concrete, the lower the actual damage degree of the pile. High-strength prestressed concrete piles require that the strength of the pile concrete must reach C80 or above.

[0004] In view of the high energy consumption of autoclave curing and the poor durability of concrete in the production process of PHC pipe piles, existing research mainly improves the early strength function of pipe piles by adding polycarboxylic acid water reducers. Compared with the pipe pile concrete prepared by the existing autoclave process, the durability of the pipe pile concrete with the addition of polycarboxylic acid water reducers has been greatly improved. However, the workability of pipe pile concrete is difficult to control, and polycarboxylic acid admixtures are more sensitive to the workability of low water-cement ratio concrete and semi-dry hard concrete, resulting in uneven operability or pumpability. The autoclave-free process must use polycarboxylic acid admixtures, so at this stage, research on admixtures for pipe piles has begun. It is crucial to improve the comprehensive performance of pipe pile concrete by adding admixtures with different components and different proportions. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a pipe pile admixture and a preparation process thereof. The admixture mixed with pipe pile concrete can effectively improve the pumping effect of concrete, while improving the early strength performance of concrete, thereby comprehensively improving the performance of pipe pile concrete.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions:

[0007] A pipe pile admixture comprises the following raw materials in parts by weight: 12-18 parts of ethylene glycol, 4-8 parts of glycerol ether, 8-12 parts of polycarboxylic acid water reducer, 4-6 parts of hydroxypropyl methylcellulose / chitosan modified material, 2-6 parts of modified xanthan gum, 1-4 parts of cocoyl diethanolamine, and 2-4 parts of polycaprolactone microspheres; wherein the hydroxypropyl methylcellulose / chitosan modified material is prepared by dissolving cellulose and chitosan in trifluoroacetic acid, mechanically stirring and mixing, drying, cleaning, and then crushing; and the modified xanthan gum is prepared by esterifying xanthan gum with maleic anhydride.

[0008] Preferably, the preparation method of hydroxypropyl methylcellulose / chitosan modified material comprises the following steps:

[0009] S1-1, vacuum drying hydroxypropyl methylcellulose and chitosan at 110° C. for 1-2 h to obtain dried hydroxypropyl methylcellulose and chitosan for later use;

[0010] S1-2, mixing the dried hydroxypropyl methylcellulose and chitosan in a mass ratio of 1:2, dissolving the mixture in trifluoroacetic acid, mechanically stirring to obtain a mixed solution, and drying the mixed solution to obtain a mixed material;

[0011] S1-3. The mixture is repeatedly washed with a sodium hydroxide solution having a pH of 8.5 for 2-6 hours, and then washed with clean water for 2-6 hours. The mixture is then taken out, dried, and crushed to obtain a hydroxypropyl methylcellulose / chitosan modified material.

[0012] Preferably, the rotation speed of the mechanical stirring in step S1-2 is 400-600 r / min, and the stirring time is 15-20 min.

[0013] Preferably, the drying method in step S1-2 is drying in a fume hood at room temperature for 24-48 hours, and the drying method in step S1-3 is constant temperature drying at 60-70° C. to constant weight.

[0014] Preferably, the preparation method of modified xanthan gum comprises the following steps:

[0015] S2-1, dissolving maleic anhydride in tetrahydrofuran, then adding xanthan gum, and swelling treatment at room temperature for 2 hours to obtain a mixed solution;

[0016] S2-2, heating the mixed solution in a water bath at 60-70°C and condensing and refluxing for 4-6 hours, then filtering to remove the solvent, and obtaining a mixture for use;

[0017] S2-3. The above mixture is mixed evenly with 90% ethanol and then centrifuged. The precipitate is collected and vacuum dried at 35-45°C to obtain modified xanthan gum.

[0018] Preferably, the molar ratio of maleic anhydride and xanthan gum in step S2-1 is 8:1.

[0019] Preferably, the amount of the pipe pile admixture added to the concrete is 0.5%-2% of the total mass of cement.

[0020] The preparation method of the pipe pile admixture comprises the following steps:

[0021] (1) Mixing hydroxypropyl methylcellulose / chitosan modified material, modified xanthan gum and polycaprolactone microspheres, and then drying to obtain a premix for later use;

[0022] (2) Mix ethylene glycol, glycerol ether and polycarboxylic acid water reducer and stir them evenly, then add coconut oil diethanolamine to obtain a mixed solution for use;

[0023] (3) Add the premix into the mixed solution, heat and stir evenly to obtain the pipe pile admixture.

[0024] Preferably, the rotation speed for fully stirring in step (2) is 200-400 r / min, and the stirring time is 10-15 min.

[0025] Preferably, the heating and stirring temperature in step (3) is 40-50° C., the stirring speed is 60-80 r / min, and the stirring time is 40-60 min.

[0026] The present invention provides a pipe pile admixture and a preparation process thereof, which has the following advantages compared with the prior art:

[0027] The present invention adopts polycarboxylic acid water-reducing agent mixed with hydroxypropyl methylcellulose / chitosan modified material, modified xanthan gum and polycaprolactone microspheres to be dispersed together as an admixture for pipe pile concrete, which can effectively improve the water retention performance of concrete, further optimize the fluidity of concrete, shorten the setting time of concrete, improve the early strength of concrete, and comprehensively improve the compressive strength of concrete. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The concrete formula of the pipe pile used in the following examples is as shown in Table 1:

[0030] Table 1

[0031]

[0032] The cement is P·Ⅰ52.5 grade cement with a specific surface area of ​​368m 2 / kg, 3d compressive strength is 29.7MPa, 28d compressive strength is 61.5Mpa;

[0033] The average particle size of ultrafine fly ash is 3 μm, and the activity index is 92%;

[0034] The mineral powder is S95 grade mineral powder produced by Nanjing Nangang Jiahua New Building Materials Co., Ltd.;

[0035] The content of silicon dioxide in silica ash is ≥95%;

[0036] The fineness modulus of river sand is 2.7;

[0037] The water-cement ratio of the pipe pile concrete is 0.28.

[0038] The polycarboxylate water reducer used below is TD- JSS2 polycarboxylate water reducer.

[0039] Example 1 1. Preparation of hydroxypropyl methylcellulose / chitosan modified material:

[0040] (1) Drying hydroxypropyl methylcellulose and chitosan in vacuum at 110°C for 1.5 h to obtain dry cellulose and chitosan for later use;

[0041] (2) Mixing the dried hydroxypropyl methylcellulose and chitosan in a mass ratio of 1:2, dissolving in trifluoroacetic acid, and mechanically stirring at a speed of 500 r / min for 15 min to obtain a mixed solution, and drying the mixed solution in a fume hood at room temperature for 30 h to obtain a mixed material;

[0042] (3) The mixture was repeatedly rinsed with a sodium hydroxide solution with a pH of 8.5 for 4 h, and then rinsed with clean water for 4 h. The mixture was then taken out and dried at a constant temperature of 65°C to a constant weight to obtain a hydroxypropyl methylcellulose / chitosan modified material.

[0043] 2. Preparation of modified xanthan gum:

[0044] (1) Dissolve maleic anhydride in 20 volumes of tetrahydrofuran, then add xanthan gum in a molar ratio of maleic anhydride to xanthan gum of 8:1, and perform swelling treatment at room temperature for 2 hours to obtain a mixed solution;

[0045] (2) The mixed solution was heated in a water bath at 65°C and condensed under reflux for 5 h, and then filtered to remove the solvent to obtain a mixture for use;

[0046] (3) The above mixture was mixed evenly with 90% ethanol and then centrifuged. The precipitate was collected and vacuum dried at 40°C for 2 h to obtain modified xanthan gum.

[0047] 3. Preparation of polycaprolactone microspheres:

[0048] (1) dissolving polycaprolactone with a molecular weight of 4000 in dichloromethane to prepare a 12% polycaprolactone solution;

[0049] (2) The polycaprolactone solution was added to 3 times the volume of 0.5% PVA aqueous solution, stirred at 6000 r / min for 10 min, and then the solvent was removed by rotary evaporation and dried to obtain polycaprolactone microspheres.

[0050] Example 2: Preparation of pipe pile admixture:

[0051] (1) Prepare the materials according to the following weight proportions:

[0052] 12 parts of ethylene glycol, 4 parts of glycerol ether, 8 parts of polycarboxylic acid water reducer, 4 parts of hydroxypropyl methylcellulose / chitosan modified material, 2 parts of modified xanthan gum, 1 part of cocoyl diethanolamine, and 2 parts of polycaprolactone microspheres;

[0053] (2) Mix the hydroxypropyl methylcellulose / chitosan modified material, modified xanthan gum and polycaprolactone microspheres, and dry them at 60° C. to constant weight to obtain a premix for later use;

[0054] (3) Ethylene glycol, glycerol ether and polycarboxylic acid water reducer are mixed and stirred at a speed of 300 r / min for 15 min, and then coconut oil diethanolamine is added to obtain a mixed solution for use;

[0055] (4) Add the premix into the mixed solution and stir at 45°C and 70 r / min for 50 min to obtain pipe pile admixture A.

[0056] Example 3: Preparation of pipe pile admixture:

[0057] (1) Prepare the materials according to the following weight proportions:

[0058] 18 parts of ethylene glycol, 8 parts of glycerol ether, 12 parts of polycarboxylic acid water reducer, 6 parts of hydroxypropyl methylcellulose / chitosan modified material, 6 parts of modified xanthan gum, 4 parts of cocoyl diethanolamine, and 4 parts of polycaprolactone microspheres;

[0059] (2) Mix the hydroxypropyl methylcellulose / chitosan modified material, modified xanthan gum and polycaprolactone microspheres, and dry them at 60° C. to constant weight to obtain a premix for later use;

[0060] (3) Ethylene glycol, glycerol ether and polycarboxylic acid water reducer are mixed and stirred at a speed of 300 r / min for 15 min, and then coconut oil diethanolamine is added to obtain a mixed solution for use;

[0061] (4) Add the premix into the mixed solution and stir at 45°C and 70 r / min for 50 min to obtain pipe pile admixture B.

[0062] Comparative Example 1: Preparation of pipe pile admixture:

[0063] (1) Prepare the materials according to the following weight proportions:

[0064] 12 parts of ethylene glycol, 4 parts of glycerol ether, 8 parts of polycarboxylic acid water reducer, 1.4 parts of hydroxypropyl methylcellulose, 2.6 parts of chitosan, 2 parts of modified xanthan gum, 1 part of cocoyl diethanolamine, and 2 parts of polycaprolactone microspheres;

[0065] (2) Mix hydroxypropyl methylcellulose, chitosan, modified xanthan gum and polycaprolactone microspheres, and dry them at 60°C to constant weight to obtain a premix for later use;

[0066] (3) Ethylene glycol, glycerol ether and polycarboxylic acid water reducer are mixed and stirred at a speed of 300 r / min for 15 min, and then coconut oil diethanolamine is added to obtain a mixed solution for use;

[0067] (4) Add the premix into the mixed solution and stir at 45°C and 70 r / min for 50 min to obtain pipe pile admixture C.

[0068] Comparative Example 2: Preparation of pipe pile admixture:

[0069] (1) Prepare the materials according to the following weight proportions:

[0070] 12 parts of ethylene glycol, 4 parts of glycerol ether, 8 parts of polycarboxylic acid water reducer, 4 parts of hydroxypropyl methylcellulose / chitosan modified material, 2 parts of xanthan gum, 1 part of cocoyl diethanolamine, and 2 parts of polycaprolactone microspheres;

[0071] (2) Mix the hydroxypropyl methylcellulose / chitosan modified material, xanthan gum and polycaprolactone microspheres, and dry them at 60°C to constant weight to obtain a premix for later use;

[0072] (3) Ethylene glycol, glycerol ether and polycarboxylic acid water reducer are mixed and stirred at a speed of 300 r / min for 15 min, and then coconut oil diethanolamine is added to obtain a mixed solution for use;

[0073] (4) Add the premix into the mixed solution and stir at 45°C and 70 r / min for 50 min to obtain pipe pile admixture D.

[0074] Comparative Example 3: Preparation of pipe pile admixture:

[0075] (1) Prepare the materials according to the following weight proportions:

[0076] 12 parts of ethylene glycol, 4 parts of glycerol ether, 8 parts of polycarboxylic acid water reducer, 4 parts of hydroxypropyl methylcellulose / chitosan modified material, 2 parts of modified xanthan gum, 1 part of cocoyl diethanolamine;

[0077] (2) Mix the hydroxypropyl methylcellulose / chitosan modified material and the modified xanthan gum, and dry them at 60°C to constant weight to obtain a premix for later use;

[0078] (3) Ethylene glycol, glycerol ether and polycarboxylic acid water reducer are mixed and stirred at a speed of 300 r / min for 15 min, and then coconut oil diethanolamine is added to obtain a mixed solution for use;

[0079] (4) Add the premix into the mixed solution and stir at 45°C and 70 r / min for 50 min to obtain pipe pile admixture E.

[0080] Test: Add the pipe pile admixture according to Table 2 below to the pipe pile concrete, stir at a speed of 100r / min for 30min after adding the pipe pile admixture, control the water-binder ratio to 0.28, and obtain each group of sample pipe pile concrete.

[0081] Table 2

[0082]

[0083] 1. The expansion of each group of sample pile concrete was tested according to the requirements of GB / T50080-2002 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The expansion of each group of samples is shown in Table 3 below:

[0084] Table 3

[0085]

[0086] It can be seen from the above table that experimental groups 1-3 all have good expansion, that is, the concrete has good fluidity, which is convenient for subsequent pumping and construction.

[0087] 2. Test the setting time of each group of sample pile concrete in accordance with GB / T50080-2002 "Standard for Test Methods of Ordinary Concrete Mixture Performance". The specific test results are shown in Table 4 below:

[0088] Table 4

[0089]

[0090] It can be seen from the above table that experimental groups 1-3 can all complete final setting in a relatively short time.

[0091] 3. The mechanical properties of the concrete of each group of sample pipe piles were tested. The specific testing process was carried out in accordance with the provisions of GB / T 50081-2019 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete". The compressive strength of the concrete was tested after curing for 1d, 3d and 28d. The specific results are shown in Table 5 below:

[0092] Table 5

[0093]

[0094] It can be seen from the above table that the pipe pile concrete prepared in experimental groups 1-3 has higher compressive strength in both the early and late stages of curing.

[0095] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pipe pile admixture, characterized in that: The pipe pile admixture comprises the following raw materials in parts by weight: 12-18 parts of ethylene glycol, 4-8 parts of glycerol ether, 8-12 parts of polycarboxylic acid water reducer, 4-6 parts of hydroxypropyl methylcellulose / chitosan modified material, 2-6 parts of modified xanthan gum, 1-4 parts of cocoyl diethanolamine, and 2-4 parts of polycaprolactone microspheres; The hydroxypropyl methylcellulose / chitosan modified material is prepared by dissolving cellulose and chitosan in trifluoroacetic acid, mechanically stirring and mixing, drying, cleaning and then crushing, and the specific preparation method includes the following steps: S1-1, vacuum drying hydroxypropyl methylcellulose and chitosan at 110° C. for 1-2 h to obtain dried hydroxypropyl methylcellulose and chitosan for later use; S1-2, mixing the dried hydroxypropyl methylcellulose and chitosan in a mass ratio of 1:2, dissolving the mixture in trifluoroacetic acid, mechanically stirring to obtain a mixed solution, and drying the mixed solution to obtain a mixed material; S1-3, the mixture is repeatedly washed with a sodium hydroxide solution with a pH of 8.5 for 2-6 hours, and then washed with clean water for 2-6 hours, and then taken out, dried and crushed to obtain a hydroxypropyl methylcellulose / chitosan modified material; The modified xanthan gum is prepared by esterifying xanthan gum with maleic anhydride, and the specific preparation method comprises the following steps: S2-1, dissolving maleic anhydride in tetrahydrofuran, then adding xanthan gum, and swelling treatment at room temperature for 2 hours to obtain a mixed solution; S2-2, heating the mixed solution in a water bath at 60-70°C and condensing and refluxing for 4-6 hours, then filtering to remove the solvent, and obtaining a mixture for use; S2-3. The above mixture is mixed evenly with 90% ethanol and then centrifuged. The precipitate is collected and vacuum dried at 35-45°C to obtain modified xanthan gum.

2. A pipe pile admixture according to claim 1, characterized in that: The rotation speed of the mechanical stirring in step S1-2 is 400-600 r / min, and the stirring time is 15-20 min.

3. A pipe pile admixture according to claim 1, characterized in that: The drying method of step S1-2 is to dry in a fume hood at room temperature for 24-48 hours, and the drying method of step S1-3 is to dry at a constant temperature of 60-70° C. to a constant weight.

4. A pipe pile admixture according to claim 1, characterized in that: In the step S2-1, the molar ratio of maleic anhydride to xanthan gum is 8:

1.

5. The pipe pile admixture according to any one of claims 1 to 4, characterized in that: The amount of the pipe pile admixture added to concrete is 0.5%-2% of the total mass of cement.

6. A method for preparing the pipe pile admixture according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Mixing hydroxypropyl methylcellulose / chitosan modified material, modified xanthan gum and polycaprolactone microspheres, and then drying to obtain a premix for use; (2) Mix ethylene glycol, glycerol ether and polycarboxylic acid water reducer and stir them evenly, then add coconut oil diethanolamine to obtain a mixed solution for use; (3) Add the premix into the mixed solution, heat and stir evenly to obtain the pipe pile admixture.

7. The preparation method according to claim 6, characterized in that: The rotation speed for fully stirring in step (2) is 200-400 r / min, and the stirring time is 10-15 min.

8. The preparation method according to claim 6, characterized in that: The heating and stirring temperature in step (3) is 40-50° C., the stirring speed is 60-80 r / min, and the stirring time is 40-60 min.

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