CN115108785A

CN115108785A - Ultra-high-ductility double-doped fiber concrete and preparation method thereof

Info

Publication number: CN115108785A
Application number: CN202210839768.2A
Authority: CN
Inventors: 于国军; 郭世购
Original assignee: Jiangsu University
Current assignee: Suzhou Peilinchang Electric Technology Co.,Ltd.
Priority date: 2022-07-18
Filing date: 2022-07-18
Publication date: 2022-09-27

Abstract

The invention discloses ultra-high ductility double-doped fiber concrete and a preparation method thereof, wherein the ultra-high ductility double-doped fiber concrete comprises 250 parts by weight of fine river sand 200-; the preparation steps are as follows: weighing fine river sand and cement according to a metered proportion, uniformly stirring, adding fly ash and a water reducing agent, uniformly mixing and stirring, adding weighed water, stirring, and finally adding PVA (polyvinyl alcohol) and PE (polyethylene) fibers into the mixture after uniformly mixing until uniformly stirring to obtain the concrete. The affinity of PVA fiber and concrete is better, and the ductility of PE fiber, intensity are better, so the tensile strength of the concrete that adds PVA fiber and PE fiber simultaneously can show and promote to the ductility and the toughness of concrete also have showing and promote, can effectively prevent the concrete fracture. And the strength of the concrete is improved, and the workability of the concrete is obviously improved by adding the high-efficiency water reducing agent.

Description

Ultra-high-ductility double-doped fiber concrete and preparation method thereof

Technical Field

The invention relates to the technical field of concrete, and relates to ultra-high ductility double-doped fiber concrete and a preparation method thereof.

Background

Concrete structure's fragility is big, and is easy to split, and in long-term use, because the complicated environment around, can make the structure surface produce tiny crack, although tiny crack can not influence the holistic bearing capacity of structure, durability and normal use function, when the structure appears the broad crack, harmful gas passes through inside the crack gets into the structure, makes concrete carbonization, and the reinforcing bar corrodes, influences the bearing capacity and the durability of structure. The early failure of the concrete structure occurs occasionally, which not only causes great economic loss, but also causes a great deal of casualties;

the high-ductility fiber reinforced cement-based composite material is high-ductility ductile concrete, has great capacity of absorbing energy, can obviously improve the seismic performance and the crack resistance of a concrete structure, can improve the overall mechanical performance and the durability of the material by adding the PVA fiber, and has good engineering application prospect. The modes of incorporation of fibers are mainly divided into mono-component and multi-component, and the incorporation of a single fiber has certain disadvantages.

In the current domestic patents, many fibers are applied to concrete. The construction method for the basalt fiber concrete reinforced masonry structure house disclosed in the Chinese patent CN202110567250.3 can retain the advantages of high compressive strength of concrete and the like, and simultaneously increases the tensile property, the wear resistance, the impact resistance and the like of the concrete, but the tensile property and the impact resistance of the concrete are limited due to the single fiber. The 'composite fiber concrete pavement structure' disclosed by Chinese patent CN201721524539.2 solves the problems of fragility, ductility and poor anti-seismic performance of the existing pavement, but because the added fibers are layered, the bonding effect with concrete is limited, and the composite fiber concrete pavement structure is easy to fall off.

Disclosure of Invention

Compared with the existing high-ductility fiber concrete, the concrete prepared by the invention has reasonable material selection and optimized proportion, adopts the mixture of PVA and PE fibers, adjusts the fiber proportion, and better promotes the tensile property of the concrete by utilizing the affinity of the PVA fibers and the concrete and the high strength of the PE fibers, thereby promoting the ductility and the toughness of the concrete, leading the concrete not to generate cracks easily and prolonging the service life of the concrete.

The present invention achieves the above-described object by the following technical means.

The ultra-high ductility double-doped fiber concrete comprises the following raw materials in parts by weight: 250 portions of fine river sand, 320 portions of cement, 320 portions of fly ash, 10-20 portions of water reducing agent, 33-47 portions of PE fiber, 17-23 portions of PVA fiber and 200 portions of water 150.

In the scheme, the ultra-high ductility double-doped fiber concrete comprises the following raw materials: 220 parts of fine river sand, 303 parts of cement, 303 parts of fly ash, 15 parts of a water reducing agent, 180 parts of water, 21 parts of PVA fiber and 42 parts of PE fiber.

In the scheme, the fine river sand is fine sand with the particle size of 1-2 mm.

In the scheme, the cement is ordinary portland cement with the model number of 42.5R.

In the scheme, the water reducing agent is a naphthalene-based high-efficiency water reducing agent.

In the scheme, the fly ash is first-grade fly ash.

In the above scheme, the PVA fibers are polyvinyl alcohol fibers.

In the above scheme, the PE fiber is an ultra-high molecular weight polyethylene fiber.

A preparation method of ultra-high ductility double-doped fiber concrete comprises the following preparation steps: weighing fine river sand and cement according to a metered proportion, uniformly stirring for 1-2min to obtain a mixture A, adding fly ash and a water reducing agent, uniformly mixing and stirring for 2min to obtain a mixture B, adding weighed water, stirring for 2-3min, finally, uniformly mixing two fibers of PVA and PE, adding the mixture, and continuously stirring for 3-5min until the mixture is uniformly stirred to obtain the concrete.

Compared with the prior art, the invention has the following advantages:

1. the ultra-high ductility double-doped fiber concrete adopts a proper amount of PE fibers, the fibers have high modulus and high strength, the comprehensive performance is more suitable for being added into concrete casting materials compared with other fibers, and the ductility and toughness of the fiber concrete can be better improved by adopting the proper amount of PE fibers.

2. The ultra-high ductility double-doped fiber concrete adopts a proper amount of PVA fiber, the PVA fiber has good affinity and binding property with base materials such as cement, gypsum and the like, and can be better combined with cement and stone sand, the integrity of the concrete is greatly improved, and cracks are not easy to generate.

3. The invention uses a proper amount of PVA and PE fiber to mix, can complement the disadvantages of each other, is more beneficial to improving the ductility and toughness of the concrete, and can improve the durability of the concrete to a certain extent and prolong the service life of the concrete because the two fibers have the performances of wear resistance and corrosion resistance.

Drawings

FIG. 1 is a schematic view of a concrete of example 1 of the present invention before a tensile test;

FIG. 2 is a schematic view showing the concrete of example 1 after the tensile test;

FIG. 3 is a stress-strain curve of the tensile test of the concrete in example 1 and comparative example 6;

FIG. 4 is a schematic view of a concrete of example 1 of the present invention before bending test;

FIG. 5 is a schematic view showing the concrete of example 1 after bending resistance test;

FIG. 6 is a graph showing the load displacement curves of the bending resistance tests of the concrete in example 1 and comparative example 6 according to the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

Example 1

The formula of the ultra-high ductility double-doped fiber concrete and the preparation method thereof are shown in the table 1.

TABLE 1 proportioning table of concrete raw materials

Principal Components	Proportioning per part	Mass fraction/%	Particle size/mm	Remarks to note
					Fine river sand	220	21.5	1
Cement	303	29.7	Powder body	42.5R
					Fly ash	303	29.7	Powder body	First stage
Water reducing agent	15	1.5	\	Naphthalene series high efficiency water reducing agent
					PVA fiber	21	/	0.039	Length 12mm
PE fiber	42	/	0.024	Length 9mm
					Water (W)	180	17.6	/

The refractory concrete of this example was prepared as follows:

(1) mixing and stirring the weighed fine river sand particles and cement for 1-2min to obtain a mixture A;

(2) then adding the fly ash and the water reducing agent, mixing and stirring for 2min uniformly to obtain a mixture B, then adding the weighed water, stirring for 2-3min,

(3) and finally, uniformly mixing the two fibers, adding the mixture into the mixture, and continuously stirring for 3-5min until the mixture is uniformly stirred to obtain the concrete, wherein the concrete is shown in figure 1.

FIG. 2 is a schematic diagram of the prepared concrete after tensile test, in example 1, a very small crack occurs in the test piece, the load is extremely reduced, then the crack is slowly increased, the crack is reduced after being increased to a certain degree, then the crack is increased again, the process is repeated until the load is increased to the maximum load, the crack is reduced again, then the process is repeated until the test piece is broken, in the process, a new crack occurs in each decrease or the original crack width is increased, and the crack at the position where the test piece width is changed develops into a main crack along with the increase of the load until the fracture is broken. The test piece of example 1 did not break suddenly after cracking but slowly broken slowly with increasing load, which is ductile failure. Therefore, the tensile property and the ductility of the ultra-high ductility fiber concrete are greatly improved, and the concrete can be effectively prevented from cracking.

FIG. 3 is a stress-strain curve of a tensile test of the concrete prepared in example 1 and comparative example 6, and sample one, sample two and sample three are concrete samples prepared in example 1; as can be seen by combining the test piece of the comparative example 6 in the attached figure 3, the test piece of the comparative example 6 can not bear the tensile force directly after the crack appears, and the load is reduced. The load of the first test piece, the second test piece and the third test piece in the embodiment 1 is temporarily reduced after the crack occurs, and then the load is continuously increased due to the action of the fiber until the load is continuously reduced after the test pieces completely lose the bearing capacity. It can be seen that the tensile strength of the test piece is significantly improved due to the action of the fibers;

meanwhile, as can be seen from fig. 3, the tensile strength of the test piece in example 1 is significantly improved after the test piece is doped with the PVA and PE fibers, the maximum tensile strength can reach 4.57Mpa, the maximum strain can reach 0.81, and the ductility and toughness of the test piece are significantly improved compared with those of the conventional double-doped fiber concrete and single-doped fiber concrete.

Referring to FIG. 4, the figure shows the pre-experimental bending resistance test piece of ultra-high ductility double-doped fiber concrete, in which the fibers are uniformly distributed and the surface is slightly rough due to the fibers.

With reference to fig. 5, fig. 5 is a diagram of the ultra-high ductility double-doped fiber concrete bending-resistant test piece after the test, and it can be seen that, for the test piece in example 1, as the load is continuously increased, a first crack appears in the pure bending section, the load-deflection curve is deviated or a first peak point appears, and then the curve continuously rises and exceeds the first peak point; with the increase of the load, the second crack and the third crack appear successively according to the conditions, then a plurality of fine cracks appear successively on the pure bending section of the test piece, the cracks develop slowly, and the load-deflection curve presents a plurality of peak points. When the deflection of the test piece is increased to a certain degree, one main crack appears in a plurality of fine cracks and continuously expands towards the pressed area, and the bearing capacity begins to decline after the test piece reaches the peak load. It can be seen that the incorporation of fibers greatly improves the toughness and ductility of the concrete.

With reference to fig. 6, fig. 6 is a load-displacement curve of the bending test of the ultra-high ductility double-doped fiber concrete test piece, and with reference to fig. 6, it can be seen that when the test piece 6 bears the bending load, the displacement is very small, and after cracks appear, the load reaches the maximum value, and the test piece is damaged. The test piece of embodiment 1 load continues to rise after appearing first crack, and the test piece appears many slight cracks, and when along with load increase, the test piece middle part crack develops for the main crack gradually, and later the test piece loses bearing capacity. Therefore, the bending resistance of the test piece is obviously improved due to the action of the fibers.

Meanwhile, as can be seen from fig. 6, the bending strength of the first, second and third test pieces in the embodiment is significantly improved after PVA and PE fibers are doped in the first, second and third test pieces, and the brittleness damage of the concrete is overcome, the maximum bending strength can reach 11.32Mpa, the maximum displacement can reach 1.54mm, and the concrete is still connected together when being damaged due to the action of the fibers and is not completely damaged, so that the toughness and ductility of the concrete are improved to a great extent.

Example 2

The formula of the ultra-high ductility double-doped fiber concrete and the preparation method thereof are shown in the table 2.

TABLE 2 proportioning table of concrete raw materials

The preparation steps are as follows:

(2) then adding the fly ash and the water reducing agent, mixing and stirring for 2min to obtain a mixture B, then adding the weighed water, stirring for 2-3min,

(3) and finally, uniformly mixing the two fibers, adding the mixture into the mixture, and continuously stirring for 3-5min until the mixture is uniformly stirred to obtain the concrete.

Example 3

The raw material formulation of the ultra-high ductility double-doped fiber concrete and the preparation method thereof is shown in Table 3.

TABLE 3 proportioning table of concrete raw materials

Principal Components	Proportioning per part	Mass fraction/%	Particle size/mm	Remarks for note
					Fine river sand	220	21.5	1
Cement	303	29.7	Powder body	42.5R
					Fly ash	303	29.7	Powder body	First stage
Water reducing agent	15	1.5	\	Naphthalene series high efficiency water reducing agent
					PVA fiber	23	/	0.039	Length 12mm
PE fiber	47	/	0.024	Length 9mm
					Water (W)	180	17.6	/

The concrete is prepared by the following steps: :

(3) and finally, uniformly mixing the two fibers, adding the mixture into the mixture, and continuously stirring for 3-5min until the mixture is uniformly stirred to obtain the concrete. Comparative example 4:

the raw material formulation of the ultra-high ductility double-doped fiber concrete and the preparation method thereof is shown in Table 4.

TABLE 4 proportioning table of concrete raw materials

The concrete is prepared by the following steps: :

(3) finally, uniformly mixing the two fibers, adding the mixture into the mixture, and continuously stirring for 3-5min until the mixture is uniformly stirred to obtain concrete;

the raw materials in this experiment were: the fly ash is first-grade fly ash, the water reducing agent is a naphthalene-based high-efficiency water reducing agent, the PVA fiber is polyvinyl alcohol fiber, the PE fiber is ultra-high molecular weight polyethylene fiber, and the cement is ordinary portland cement with the model number of 42.5R.

Comparative example 5:

the raw material formulation of the ultra-high ductility double-doped fiber concrete and the preparation method thereof is shown in Table 5.

TABLE 5 concrete raw material proportioning table

Principal Components	Proportioning per part	Mass fraction/%	Particle size/mm	Remarks to note
					Fine river sand	220	21.5	1
Cement	303	29.7	Powder body	42.5R
					Fly ash	303	29.7	Powder body	First stage
Water reducing agent	15	1.5	\	Naphthalene series high efficiency water reducing agent
					PVA fiber	40	/	0.039	Length 12mm
PE fiber	20	/	0.024	Length 9mm
					Water (W)	180	17.6	/

The concrete is prepared by the following steps: :

the raw materials in this experiment were: the fly ash is first-grade fly ash, the water reducing agent is a naphthalene-based high-efficiency water reducing agent, the PVA fiber is polyvinyl alcohol fiber, the PE fiber is ultra-high molecular weight polyethylene fiber, and the cement is ordinary portland cement with the model number of 42.5R. Comparative example 6:

the formula of a common concrete and a preparation method thereof are shown in Table 6.

TABLE 6 proportioning table of concrete raw materials

Principal Components	Proportioning per part	Mass fraction/%	Particle size/mm	Remarks for note
					Fine river sand	220	21.5	1
Cement	303	29.7	Powder body	42.5R
					Fly ash	303	29.7	Powder body	First stage
Water reducing agent	15	1.5	\	Naphthalene series high efficiency water reducing agent
					Water (W)	180	17.6	/

The refractory concrete of this example was prepared as follows:

(3) finally pouring the mixture into a mould to obtain concrete;

the raw materials in this experiment were: the fly ash is first-grade fly ash, the water reducing agent is a naphthalene-based high-efficiency water reducing agent, and the cement is ordinary portland cement with the model number of 42.5R.

The main properties of the examples and comparative examples are shown in table 7.

TABLE 7 Main Performance tables

Examples	Peak strain	Peak intensity/Mpa	Ultimate displacement/mm	Ultimate Strength/N
					Example 1	0.081	4.569	1.51	13.32
Example 2	0.074	4.110	1.54	11.40
					Example 3	0.068	3.825	1.24	12.52
Comparative example 4	0.049	3.079	0.91	9.02
					Comparative example 5	0.043	3.232	0.88	9.19
Comparative example 6	0.033	1.233	0.74	7.04

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.

Claims

1. The ultra-high ductility double-fiber-doped concrete is characterized by comprising, by weight, 200-250 parts of fine river sand, 300-320 parts of cement, 300-320 parts of fly ash, 10-20 parts of a water reducing agent, 33-47 parts of PE (polyethylene) fibers, 17-23 parts of PVA (polyvinyl alcohol) fibers and 150-200 parts of water.

2. The ultra-high ductility double-doped fiber concrete as claimed in claim 1, wherein the concrete comprises 220 parts by weight of fine river sand, 303 parts by weight of cement, 303 parts by weight of fly ash, 15 parts by weight of water reducing agent, 180 parts by weight of water, 21 parts by weight of PVA fiber and 42 parts by weight of PE fiber.

3. The ultra-high ductility double-doped fiber concrete as claimed in claim 1, wherein the fine river sand has a particle size of 1 to 2 mm.

4. The ultra-high ductility double-blended fiber concrete according to claim 1, wherein the cement is portland cement 42.5R.

5. The ultra-high ductility double fiber-doped concrete according to claim 1, wherein the fly ash is a primary fly ash.

6. The ultra-high ductility double-doped fiber concrete as claimed in claim 1, wherein the water reducing agent is a naphthalene-based superplasticizer with a water reducing rate of 25%.

7. The ultra-high ductility double-fiber-blended concrete according to claim 1, wherein the PE fibers are ultra-high molecular weight polyethylene fibers.

8. The ultra-high ductility double-doped fiber concrete according to claim 1, wherein the PVA fiber is a polyvinyl alcohol fiber.

9. The method for preparing ultra-high ductility double-doped fiber concrete according to any one of claims 1 to 8, characterized by comprising the steps of:

weighing fine river sand and cement according to a metered ratio, uniformly stirring for 1-2min to obtain a mixture A, adding fly ash and a water reducing agent, uniformly mixing and stirring for 2min to obtain a mixture B, adding weighed water, stirring for 2-3min, finally, uniformly mixing two fibers of PVA and PE, adding the mixture into the mixture, and continuously stirring for 3-5min until the mixture is uniformly stirred to obtain the concrete.