CN112979242B

CN112979242B - Concrete for filling hollow square pile, preparation method thereof and hollow square pile filling method

Info

Publication number: CN112979242B
Application number: CN202110211029.4A
Authority: CN
Inventors: 陈家冬; 汪小健; 吴亮; 张亮; 胡世林; 蒋国春; 徐坤
Original assignee: Jiangsu Foundation Engineering Co ltd
Current assignee: Jiangsu Foundation Engineering Co ltd
Priority date: 2021-02-25
Filing date: 2021-02-25
Publication date: 2022-08-26
Anticipated expiration: 2041-02-25
Also published as: CN112979242A

Abstract

The application relates to the field of building pile foundations, and particularly discloses concrete for filling a hollow square pile, a preparation method of the concrete and a filling method of the hollow square pile. The concrete for filling the hollow square pile comprises cement, water, broken stone, sand, kaolin, steel fiber, chopped glass fiber, an expanding agent, a water reducing agent, carbon black and a dispersing agent; the preparation method comprises the following steps: preparing raw materials according to a ratio, and mixing and stirring cement, broken stone, sand, kaolin, steel fiber and chopped glass fiber; adding water, an expanding agent and a water reducing agent, and continuously mixing and stirring; adding carbon black and a dispersing agent, and stirring to obtain the concrete for filling the hollow square pile. The composition of the present application can be used for filling a hollow square pile, which has an advantage of improving the bending strength of concrete for filling the hollow square pile, thereby improving the strength of the hollow square pile.

Description

Concrete for filling hollow square pile, preparation method thereof and hollow square pile filling method

Technical Field

The application relates to the field of building pile foundations, in particular to concrete for filling a hollow square pile, a preparation method of the concrete and a filling method of the hollow square pile.

Background

The hollow square pile is a concrete prefabricated component with a square cross section and a hollow cylinder body, and mainly comprises a cuboid pile body, an end plate, a steel ferrule and the like. The hollow square pile is manufactured by a pre-tensioning method prestress process and a centrifugal forming method, can be prefabricated in a factory, has the advantages of high strength, convenience in construction, short construction period and the like, and is widely applied.

The bending strength of the pile body of the hollow square pile is reduced due to the hollow cylinder body. When the hollow square pile is used as a foundation pile and is driven into a foundation, particularly when the hollow square pile is applied to high-rise buildings, the horizontal resistance of a pile body is reduced due to the defects on the hollow square pile structure, so that the buildings have certain potential safety hazards. Therefore, there is a need for improvements in hollow square piles to increase their bending strength and thereby reduce the safety risk of construction.

In order to improve the bending strength of the hollow square pile, a method of filling concrete may be used. Concrete is poured into the cylinder of the hollow square pile, and after the concrete is hardened, the hardened concrete fills the interior of the hollow square pile to obtain a solid composite pile body, so that the strength of the pile body is improved.

Because the concrete is a brittle material, the toughness is lower, and the concrete is easy to crack, even if the concrete is poured into the hollow square pile, the composite pile body still has the risk of cracking due to the defect of the bending toughness of the concrete. Therefore, it is necessary to further modify the concrete used for filling the hollow square pile so as to improve the bending strength thereof and reduce the possibility of the pile body breaking.

Disclosure of Invention

In order to improve the bending strength of the concrete for filling the hollow square pile and further improve the strength of the hollow square pile, the application provides the concrete for filling the hollow square pile, the preparation method of the concrete and the filling method of the hollow square pile.

In a first aspect, the present application provides a concrete for filling a hollow square pile, which adopts the following technical scheme:

the concrete for filling the hollow square pile is prepared from the following raw materials in parts by mass:

290 portions of cement

110 portions of water

610 portions of gravel and 650 portions of gravel

500 portions of sand and 530 portions

80-100 parts of kaolin

12-20 parts of steel fiber

20-45 parts of chopped glass fiber

1.5 to 2.5 portions of expanding agent

0.5 to 1.5 portions of water reducing agent

9-12 parts of carbon black

1-1.5 parts of a dispersing agent.

By adopting the technical scheme, the chopped glass fiber and silicate substances in cement are subjected to hydration reaction to generate calcium hydroxide, so that the chopped glass fiber and the concrete are combined by chemical bonds; in addition, the chopped glass fibers have strong bonding property with concrete, and the chopped glass fibers are filled in gaps of the concrete, so that the structural strength of the concrete is improved; the chopped glass fiber and the concrete are simultaneously subjected to physical connection and chemical combination, so that the toughness of the concrete is improved, and the bending strength of the concrete is enhanced;

the steel fiber also has the filling effect on the cracks in the concrete, and can block the expansion of the cracks in the concrete and the formation of macro cracks, so that good bending strength is provided for the concrete; the chopped glass fiber and the steel fiber are simultaneously mixed into the concrete, the two fibers are irregularly distributed in the concrete, when the concrete is subjected to horizontal force, a three-dimensional framework formed by the chopped glass fiber and the steel fiber in the concrete plays a role in offsetting stress applied to the concrete, and due to the fact that the steel fiber is physically connected with the concrete, the chopped glass fiber is added, chemical bonds are generated through hydration reaction, pores between the steel fiber and the concrete are filled, and the effect of synergistically strengthening the bending strength of the concrete is achieved;

on one hand, the carbon black is doped to enhance the cohesiveness in the concrete, and when the concrete is subjected to the action of horizontal stress, the physical adsorption effect of the carbon black can offset the impact of partial external force to play a role in reinforcement; on the other hand, the molecular particle size of the carbon black is smaller than the diameters of the chopped glass fiber and the steel fiber, the carbon black can further fill the pores in the concrete, and the bonding force in the concrete is enhanced through physical adsorption, so that the bending strength of the concrete is further improved;

the dispersant is added into the concrete, so that the carbon black is conveniently dispersed in the water phase, the filling effect of the carbon black in the concrete is improved, and the synergistic enhancement effect on the bending strength of the concrete is improved.

Preferably, the mass ratio of the steel fibers to the chopped glass fibers is 1 (1.6-3).

By adopting the technical scheme, under the condition that the content of other raw materials and the preparation process are the same, the steel fibers and the chopped glass fibers are added into the concrete according to the mass ratio range, and the synergistic strengthening effect of the steel fibers and the chopped glass fibers on the bending strength of the concrete is optimal.

Preferably, the mass ratio of the steel fibers to the chopped glass fibers is 1: 2.5.

By adopting the technical scheme, under the condition that the content of other raw materials and the preparation process are the same, the synergistic reinforcement effect of the steel fibers and the chopped glass fibers on the concrete is optimal under the special proportion.

Preferably, the diameter of the steel fiber is 0.55-0.7mm, and the length of the steel fiber is 30-50 mm.

By adopting the technical scheme, when the diameter of the steel fiber is 0.55-0.7mm and the length of the steel fiber is 30-50mm, the crack expansion resisting effect of the steel fiber cannot be reduced due to too small size of the steel fiber, and too large gap between the steel fiber and concrete cannot be caused due to too large size of the steel fiber, so that the steel fiber has the best reinforcing effect on the bending strength of the concrete.

Preferably, the particle size of the carbon black is 300-450 nm.

By adopting the technical scheme, when the particle size of the carbon black is 300-450nm, the carbon black molecules cannot reduce the physical adsorption effect due to too small particle size, and the dispersion effect in the concrete cannot be influenced due to too large particle size, so that the carbon black has the best enhancement effect on the bending strength of the concrete.

Preferably, the expanding agent is an alunite expanding agent.

By adopting the technical scheme, certain shrinkage can be generated during cement hardening to cause cracks to be formed in the concrete, calcium sulphoaluminate clinker in the alunite expanding agent can react with calcium hydroxide in the concrete to generate alunite, so that the solid phase volume is increased, the shrinkage generated during cement hardening is compensated, the possibility of forming cracks in the concrete is reduced, calcium hydroxide consumed by the alunite expanding agent can be obtained by reacting chopped glass fibers with silicate substances in the concrete, and the compensation effect of the alunite expanding agent on the concrete volume is optimal.

Preferably, the water reducing agent is a polycarboxylic acid water reducing agent or a sulfamate water reducing agent.

By adopting the technical scheme, the polycarboxylate water reducer and the sulfamate water reducer are both high-performance water reducers, have excellent water reducing performance and have the best water reducing effect on concrete.

Preferably, the dispersant is an anionic dispersant.

By adopting the technical scheme, the anionic dispersing agent has good compatibility, has the best optimization effect on the dispersibility of the carbon black in the water phase, and is beneficial to improving the reinforcing effect of the carbon black on the bending strength of the concrete.

In a second aspect, the present application provides a method for preparing concrete for filling a hollow square pile, which adopts the following technical scheme: a preparation method of concrete for filling a hollow square pile comprises the following steps:

s1, preparing raw materials according to a ratio, mixing cement, gravel, sand, kaolin, steel fibers and chopped glass fibers, and stirring for 5-8min to obtain a mixture A;

s2, adding water, an expanding agent and a water reducing agent into the mixture A, and stirring for 4-6min to obtain a mixture B;

and S3, adding carbon black and a dispersing agent into the mixture B, and stirring for 2-5min to obtain the concrete for filling the hollow square pile.

By adopting the technical scheme, the raw materials are mixed and stirred for three times, and in the first stirring, the steel fibers and the chopped glass fibers are uniformly distributed in the mixture of cement, gravel, sand and kaolin; during the second stirring, adding water, an expanding agent and a water reducing agent to ensure that the chopped glass fiber and the silicate in the cement are fully subjected to hydration reaction, and simultaneously, the expanding agent is subjected to reaction to ensure that the volume of the concrete is expanded; in the third stirring, the carbon black and the dispersing agent are added, so that the carbon black is fully mixed in the raw materials, the possibility of agglomeration is reduced, the dispersing effect of the carbon black is improved, and the concrete for filling the hollow square pile with high bending strength is obtained.

In a third aspect, the application provides a method for filling a hollow square pile, which adopts the following technical scheme:

a hollow square pile filling method comprises the following steps:

p1, connecting one end of the hollow square pile with an iron plate, wherein the iron plate seals an opening at one end of the hollow square pile;

p2, driving one end of the hollow square pile with the iron plate into the foundation through a pile driver;

and P3, pouring the concrete for filling the hollow square pile into one end of the hollow square pile outside the foundation until the concrete for filling the hollow square pile is filled in the hollow square pile.

By adopting the technical scheme, after one end of the hollow square pile is sealed by the iron plate, the hollow square pile is driven into the foundation, and then the concrete for filling the hollow square pile is poured into the hollow square pile to obtain the solid composite pile body, so that the horizontal resistance of the hollow square pile is improved.

In summary, the present application has the following beneficial effects:

1. because the chopped glass fiber, the steel fiber and the carbon black are added into the concrete, the steel fiber and the chopped glass fiber have a filling effect on cracks in the concrete, and the steel fiber can prevent the expansion of the cracks in the concrete and the formation of macroscopic cracks, so that good bending strength is provided for the concrete; because the steel fiber and the concrete are physically connected, the addition of the chopped glass fiber generates chemical bonds through hydration reaction, thereby filling the pores between the steel fiber and the concrete and playing a role in synergistic enhancement on the bending strength of the concrete; on one hand, the carbon black enhances the cohesiveness inside the concrete, on the other hand, the carbon black further fills the pores in the concrete, and the bonding force inside the concrete is enhanced through physical adsorption, so that the bending strength of the concrete is further improved.

2. According to the preparation method, the raw materials are mixed and stirred for three times, so that the steel fibers and the chopped glass fibers are uniformly distributed in the mixture of cement, broken stone, sand and kaolin, the chopped glass fibers and silicate in the cement fully undergo hydration reaction, and meanwhile, the expanding agent reacts, so that the volume of the concrete expands, the carbon black is fully mixed in the raw materials, the dispersion effect of the carbon black is improved, and the concrete for filling the hollow square pile with high bending strength is obtained.

3. According to the method, after one end of the hollow square pile is sealed through the iron plate, the hollow square pile is driven into the foundation, then concrete for filling the hollow square pile is poured into the hollow square pile, a solid composite pile body is obtained, the horizontal resistance of the hollow square pile is improved, the bending strength of the hollow square pile is enhanced due to the fact that the bending strength of the concrete for filling the hollow square pile is high, and the possibility of damage to the pile body is reduced.

Drawings

Fig. 1 is a schematic structural diagram for showing a positional relationship among a hollow square pile, an iron plate and a foundation in an application example of the present application.

Description of reference numerals: 1. hollow square piles; 2. an iron plate; 3. and (5) foundation construction.

Detailed Description

Source of raw materials

Unless otherwise specified, the specifications and sources of the raw materials in the following examples and comparative examples are shown in Table 1 below.

TABLE 1 raw material specifications and sources

Raw materials	Specification of	Source
			Cement	P.O 42.5	Guizhou Rongsheng building materials Co Ltd
Crushing stone	Particle size range (mm) 10-18	Yunnan Sandy Stone Material Co Ltd
			Sand	GB/T14684-2011 building sand	Tianjin Fuyuan Wantong sandstone sales Limited
Kaolin clay	R005368	Shanghai Ian Chemical Technology Co.,Ltd.
			Steel fibre	Reagent grade	Luoyang Botian chemical Co Ltd
Chopped glass fiber	Class E	WU lake Jun Fa glass fiber trade Co Ltd
			Carbon fiber	C301640	SHANGHAI ALADDIN BIOCHEMICAL TECHNOLOGY Co.,Ltd.
Alunite expanding agent	The purity is 99 percent	Wuhan Mengqi science and technology Co Ltd
			Calcium oxide swelling agent	2020101	Henan Bolang Industrial Co., Ltd.
Polycarboxylic acid water reducing agent	PA96208	GUANGDONG WENGJIANG CHEMICAL REAGENT Co.,Ltd.
			Sulfamate water reducing agent	First stage	Guizhou Huangteng building materials Co., Ltd
Naphthalene water reducing agent	Industrial grade	Nantong Runfeng petrochemical Co., Ltd
			Carbon black	R005968	Shanghai Ian Chemical Technology Co.,Ltd.
Activated carbon	A856762	SHANGHAI MACKLIN BIOCHEMICAL Co.,Ltd.
			Anionic dispersant	Industrial grade	Shandong Xiang Showa New Material Co., Ltd
Nonionic dispersant	Industrial grade	Nantong Yongle chemical Co., Ltd

Examples

Example 1

A preparation method of concrete for filling a hollow square pile comprises the following steps:

s1, weighing 290kg of cement, 120kg of water, 650kg of sandstone, 510kg of sand, 80kg of kaolin, 20kg of steel fiber, 30kg of chopped glass fiber, 1.5kg of calcium oxide expanding agent, 0.5kg of naphthalene water reducing agent, 10kg of carbon black and 1kg of nonionic dispersing agent respectively, wherein the diameter of the steel fiber is 0.5mm, the length of the steel fiber is 25mm, and the particle size of the carbon black is 500 nm;

mixing cement, broken stone, sand, kaolin, steel fiber and chopped glass fiber, and stirring for 5min to obtain a mixture A;

s2, adding water, a calcium oxide expanding agent and a naphthalene water reducing agent into the mixture A, and stirring for 6min to obtain a mixture B;

and S3, adding carbon black and a nonionic dispersing agent into the mixture B, and stirring for 4min to obtain the concrete for filling the hollow square pile.

Example 2

s1, respectively weighing 300kg of cement, 130kg of water, 610kg of sand, 530kg of sand, 90kg of kaolin, 12kg of steel fiber, 45kg of chopped glass fiber, 2kg of calcium oxide expanding agent, 1kg of naphthalene water reducing agent, 9kg of carbon black and 1.2kg of nonionic dispersing agent, wherein the diameter of the steel fiber is 0.9mm, the length of the steel fiber is 60mm, and the particle size of the carbon black is 200 nm;

mixing cement, broken stone, sand, kaolin, steel fiber and chopped glass fiber, and stirring for 6min to obtain a mixture A;

s2, adding water, a calcium oxide expanding agent and a naphthalene water reducing agent into the mixture A, and stirring for 5min to obtain a mixture B;

and S3, adding carbon black and a nonionic dispersing agent into the mixture B, and stirring for 2min to obtain the concrete for filling the hollow square pile.

Example 3

s1, respectively weighing 310kg of cement, 110kg of water, 630kg of sandstone, 500kg of sand, 100kg of kaolin, 18kg of steel fiber, 20kg of chopped glass fiber, 2.5kg of calcium oxide expanding agent, 1.5kg of naphthalene water reducing agent, 12kg of carbon black and 1.5kg of nonionic dispersing agent, wherein the diameter of the steel fiber is 0.7mm, the length of the steel fiber is 55mm, and the particle size of the carbon black is 250 nm;

mixing cement, broken stone, sand, kaolin, steel fiber and chopped glass fiber, and stirring for 8min to obtain a mixture A;

s2, adding water, a calcium oxide expanding agent and a naphthalene water reducing agent into the mixture A, and stirring for 4min to obtain a mixture B;

and S3, adding carbon black and a non-ionic dispersing agent into the mixture B, and stirring for 5min to obtain the concrete for filling the hollow square pile.

Examples 4 to 6

Examples 4-6 differ from example 3 in the amounts of steel and chopped glass used in the raw materials, as specified in the following table:

table 2 examples 4-6

Examples	Steel fiber/kg	Chopped glass fiber/kg
			Example 4	13	39
Example 5	18	28.8
			Example 6	15	37.5

Examples 7 to 9

Examples 7-9 differ from example 6 in the diameter and length of the steel fibres in the feedstock, as specified in the following table:

table 3 examples 7-9

Examples	Diameter of steel fiber/mm	Length of steel fiber/mm
			Example 7	0.6	30
Example 8	0.7	50
			Example 9	0.55	35

Examples 10 to 12

Examples 10-12 differ from example 9 in the particle size of the carbon black in the feedstock, as specified in the following table:

TABLE 4 examples 10 to 12

Examples	Carbon black particle size/nm
		Example 10	300
Example 11	450
		Example 12	400

Example 13

Example 13 differs from example 12 in that an alunite expanding agent of the same mass was selected as the expanding agent instead of the calcium oxide-based expanding agent.

Example 14

Example 14 differs from example 13 in that a polycarboxylic acid water-reducing agent of the same quality was selected as the water-reducing agent instead of the naphthalene water-reducing agent.

Example 15

Example 15 differs from example 13 in that the same quality sulfamate water reducing agent was selected as the water reducing agent instead of the naphthalene water reducing agent.

Example 16

Example 16 differs from example 15 in that the same mass of anionic dispersant is used as the dispersant instead of the nonionic dispersant.

Comparative example

Comparative example 1

Comparative example 1 differs from example 3 in that carbon fibres of the same quality are used instead of steel fibres.

Comparative example 2

Comparative example 2 differs from example 3 in that the same quality of carbon fiber is used instead of chopped glass fiber.

Comparative example 3

Comparative example 3 differs from example 3 in that the same mass of activated carbon was used instead of carbon black.

Comparative example 4

Comparative example 4 differs from example 3 in that no dispersant is included in the feed.

Performance test

Detection method/test method

The concrete for filling the hollow square pile of the examples and the comparative examples was subjected to performance testing, and flexural strength testing was performed: the test was carried out in GB/T50081-2019 using a Z020 model Universal mechanical tester from Zwick, Germany. Wherein, the test piece adopts a standard test piece with the thickness of 150mm multiplied by 600mm, and the maintenance age is 28 d.

The results of the tests of examples 1 to 6 are shown in Table 5.

Table 5 examples 1-6 test results for properties

The results of the tests of examples 7 to 12 are shown in Table 6.

Table 6 results of performance tests of examples 7 to 12

The results of the tests of examples 13 to 16 are shown in Table 7.

TABLE 7 results of testing the properties of examples 13 to 16

Example test items	Example 13	Example 14	Example 15	Example 16
					Flexural strength/MPa	33.5	33.7	33.9	34.3

The results of the tests of comparative examples 1 to 4 are shown in Table 8.

TABLE 8 results of performance testing of comparative examples 1-4

Comparative example test item	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4
					Flexural strength/MPa	25.3	23.1	25.7	26.3

It can be seen by combining examples 1-16 and comparative examples 1-2 with tables 5-8 that when steel fibers and chopped glass fibers are used as raw materials, the bending strength of concrete is greatly improved, which indicates that the steel fibers and chopped glass fibers have the best synergistic enhancement effect on the bending strength of concrete.

It can be seen from the combination of examples 1 to 16 and comparative example 3 and tables 5 to 8 that when carbon black is used as a raw material, the bending strength of concrete is greatly improved, and the strength of concrete is improved by far less than that of carbon black when activated carbon is used as a substance having the same physical adsorption effect, which indicates that the synergistic enhancement effect of carbon black, steel fiber and chopped glass fiber is the best.

It can be seen from the combination of examples 1-16 and comparative example 4 and tables 5-8 that the addition of the dispersant greatly improves the flexural strength of the concrete, which indicates that the improvement of the dispersion effect of the dispersant on the carbon black is beneficial to the enhancement of the flexural strength of the concrete by the carbon black.

In combination with examples 1-6 and Table 5, it can be seen that when the mass ratio of the steel fibers to the chopped glass fibers is in the range of 1 (1.6-3), the flexural strength of the concrete is better, which indicates that in this range, the synergistic enhancement effect of the steel fibers and the chopped glass fibers on the flexural strength of the concrete is better; wherein, when the mass ratio of the steel fiber to the chopped glass fiber is 1:2.5, the bending strength of the concrete is optimal, and the synergistic enhancement effect of the steel fiber and the chopped glass fiber is optimal.

It can be seen from the combination of examples 6-9 and tables 5-6 that the steel fibers and chopped glass fibers have the best synergistic effect and the best reinforcing effect on the flexural strength of concrete when the diameter of the steel fibers is 0.55-0.7mm and the length of the steel fibers is 30-50 mm.

It can be seen from the combination of examples 9-12 and Table 6 that when the particle size of carbon black is in the range of 300-450mm, the dispersion effect of carbon black in concrete is the best, and the reinforcing effect on the flexural strength of concrete is better.

Combining examples 12 and 13 with tables 6-7, it can be seen that the flexural strength of the concrete is higher when an alunite expanding agent is selected as the expanding agent.

It can be seen by combining examples 13-15 with table 7 that when a polycarboxylic acid water reducer or a sulfamate water reducer is selected as the water reducer, the water reducing effect on the concrete is better, and the obtained concrete has higher bending strength.

When the anionic dispersant is selected as the dispersant, it can be seen from the combination of examples 15 and 16 and table 7 that the effect of dispersing carbon black in concrete is the best and the effect of reinforcing the flexural strength of concrete is the best, and example 16 is the most preferred example.

Application example

Referring to fig. 1, a method for filling a hollow square pile includes the steps of:

p1, fixedly connecting one end of the hollow square pile 1 with an iron plate 2, sealing an opening at one end of the hollow square pile 1 by the iron plate 2, and enabling the area of the iron plate 2 to be equal to the cross section of the hollow square pile 1;

p2, driving one end of the hollow square pile 1 with the iron plate 2 into the foundation 3 through a pile driver, wherein the hollow square pile 1 is vertically arranged;

p3, pouring the concrete for filling the hollow square pile in the above embodiment into the end of the hollow square pile 1 outside the foundation 3 until the concrete for filling the hollow square pile fills the hollow square pile 1, and completing the filling of the hollow square pile 1 after the concrete for filling the hollow square pile is hardened.

After one end of the hollow square pile 1 is sealed through the iron plate 2, the hollow square pile 1 is driven into the foundation 3, and then concrete for filling the hollow square pile is poured into the hollow square pile 1 to obtain a solid composite pile body, so that the horizontal resistance of the hollow square pile 1 is improved, the bending strength of the hollow square pile 1 is enhanced due to the high bending strength of the concrete for filling the hollow square pile, and the possibility of damaging the pile body is reduced.

Since the bending strength of the filled hollow square pile 1 is affected by the bending strength of the concrete for filling the hollow square pile, in the above examples, example 16 is the most preferable example, and the concrete for filling the hollow square pile prepared in example 16 has the best bending strength. Therefore, the hollow square pile 1 obtained by filling the concrete for filling a hollow square pile of example 16 was most excellent in bending strength.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The concrete for filling the hollow square pile is characterized by being prepared from the following raw materials in parts by mass:

290 portions of cement and 310 portions

110 portions of water

610 portions of gravel and 650 portions of gravel

500 portions of sand and 530 portions

80-100 parts of kaolin

12-20 parts of steel fiber

20-45 parts of chopped glass fiber

1.5 to 2.5 portions of expanding agent

0.5-1.5 parts of water reducing agent

9-12 parts of carbon black

1-1.5 parts of a dispersing agent,

wherein the mass ratio of the steel fiber to the chopped glass fiber is 1 (1.6-3), and the particle size of the carbon black is 300-450 nm.

2. The concrete for filling a hollow square pile according to claim 1, wherein: the mass ratio of the steel fibers to the chopped glass fibers is 1: 2.5.

3. The concrete for filling a hollow square pile according to claim 1, wherein: the diameter of the steel fiber is 0.55-0.7mm, and the length of the steel fiber is 30-50 mm.

4. The concrete for filling a hollow square pile according to claim 1, wherein: the expanding agent is alunite expanding agent.

5. The concrete for filling a hollow square pile according to claim 1, wherein: the water reducing agent is a polycarboxylic acid water reducing agent or a sulfamate water reducing agent.

6. The concrete for filling a hollow square pile according to claim 1, wherein: the dispersant is an anionic dispersant.

7. The method for preparing concrete for filling a hollow square pile according to claim 1, comprising the steps of:

s1, preparing raw materials according to the proportion, mixing cement, broken stone, sand, kaolin, steel fiber and chopped glass fiber, and stirring for 5-8min to obtain a mixture A;

and S3, adding the carbon black and the dispersing agent into the mixture B, and stirring for 2-5min to obtain the concrete for filling the hollow square pile.

8. A method for filling a hollow square pile is characterized by comprising the following steps:

p1, connecting one end of the hollow square pile (1) with an iron plate (2), wherein the iron plate (2) seals the opening at one end of the hollow square pile (1);

p2, driving one end of the hollow square pile (1) with the iron plate (2) into the foundation (3) through a pile driver;

p3 pouring the concrete for filling the hollow square pile of claim 1 into the end of the hollow square pile (1) located outside the foundation (3) until the concrete for filling the hollow square pile fills the inside of the hollow square pile (1).