CN114907077A

CN114907077A - Fiber woven mesh reinforced nanometer cement-based composite material and preparation method thereof

Info

Publication number: CN114907077A
Application number: CN202210637232.2A
Authority: CN
Inventors: 刘彬; 王激扬; 万成霖; 陈氏凤; 王志萍
Original assignee: Zhejiang University ZJU; Zhejiang College of Construction
Current assignee: Zhejiang University ZJU; Zhejiang College of Construction
Priority date: 2022-06-07
Filing date: 2022-06-07
Publication date: 2022-08-16

Abstract

The invention belongs to the technical field of engineering materials, and particularly relates to a high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite material and a preparation method thereof, wherein the preparation method comprises the following steps: (1) dissolving the dispersion liquid, adding the nano material, stirring and performing ultrasonic treatment to obtain a nano material dispersion liquid; (2) mixing water and the nano material dispersion liquid, and stirring; (3) adding cement mortar, stirring, then placing into a mold, and vibrating on a vibrating table at high frequency; (4) and (4) placing the prepared fiber woven mesh in a template, pouring the concrete slurry prepared in the step (3), and demolding and maintaining after hardening. The invention reduces the interface porosity, improves the bonding capacity of the fiber woven mesh and the matrix, improves the utilization rate of the fiber mesh in the common fiber woven mesh reinforced concrete, improves the tensile property under the condition of ensuring the compression resistance and the folding resistance, further improves the structure seismic resistance, and has great significance and practical benefits on the technological innovation, the economic development, the natural environment and the social progress of China.

Description

Fiber woven mesh reinforced nanometer cement-based composite material and preparation method thereof

Technical Field

The invention belongs to the technical field of engineering materials, and particularly relates to a high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite material and a preparation method thereof.

Background

Under the environment that extreme natural disasters frequently occur, the structural safety problem that the existing building structure of long-term service arouses because bearing capacity is not enough is increasingly outstanding, needs to seek a novel material that can carry out reinforcement economically, high-efficiently. The prior fiber woven mesh reinforced concrete (TRC) is a novel reinforced building material formed by uniformly mixing cement paste, mortar or concrete as a base material and a proper amount of discontinuous short fibers or continuous long fibers as a reinforcing material in concrete.

At present, when a TRC material is prepared, a cut fiber net is generally placed in a wood mould uniformly after being tightened according to actual requirements, a batten with certain thickness is used for fixing (according to the thickness of actual requirements of components), and stressed fiber bundles of different layers of fiber nets are aligned with each other; and then directly pouring the stirred fine concrete into a mould, then placing the mould on a vibration table for slight vibration, leveling the surface and folding, curing at room temperature for 24 hours, then removing the mould, and carrying out standard curing to 28 days of age, thus finishing the manufacture of the TRC material or the member. However, the method has certain technical defects, and the existing fiber woven mesh reinforced concrete has the problems that the fiber bundle is not uniformly stressed due to the problems of poor interface performance between fibers and a concrete matrix, more interface pores, bonding and the like, so that the utilization rate of the fiber woven mesh is not high, and further improvement is still needed.

Disclosure of Invention

Based on the above disadvantages and shortcomings of the prior art, an object of the present invention is to solve at least one or more of the above problems of the prior art, in other words, an object of the present invention is to provide a high strength and high toughness fiber woven mesh reinforced nano cement-based composite material and a method for preparing the same, which satisfies one or more of the above requirements, by uniformly dispersing nano materials (multi-walled carbon nanotubes, multi-layered graphene, etc.) in a carboxyl solution to form a mixed solution, and preparing a fiber woven mesh reinforced concrete (TRC) matrix together with cement, sand, slag, water, additives, etc., so that the matrix can be combined with different types of fiber woven meshes to form the high strength and high toughness TRC composite material, especially solving the problems of low porosity of matrix cement, interface bonding capability with fiber bundles, and low utilization rate of fiber mesh in common TRC.

In order to achieve the purpose, the invention adopts the following technical scheme:

a high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite board comprises concrete slurry and a fiber woven mesh.

Preferably, the concrete slurry comprises 550-705 parts by weight of cement, 300-455 parts by weight of fly ash, 25-45 parts by weight of metakaolin, 70-80 parts by weight of silica fume, 4.5-6.0 parts by weight of a water reducing agent, 830-950 parts by weight of fine sand and 500-700 parts by weight of a carboxyl nano material.

As a preferable scheme, the carboxyl nanomaterial comprises one or more of nano silicon dioxide, a multi-walled carbon nanotube, a carbon nanofiber and a graphene nanosheet.

A preparation method of a high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite board comprises the following steps:

(1) dissolving and heating the dispersion liquid, and adding the nano material to obtain a nano material dispersion liquid;

(2) adding fine cement mortar to obtain concrete slurry;

(3) pouring or spraying the concrete slurry prepared in the step (2) into the fiber woven mesh, and demolding and curing after hardening.

Preferably, the dispersion liquid in the step (1) is a dispersion liquid in which a nanomaterial is disposed using a carboxyl dispersant.

Preferably, the heating temperature in the step (1) is not more than 68-70 ℃ of the cloud point temperature.

Preferably, the fine cement mortar in the step (2) comprises cement, fly ash, metakaolin, silica fume, purified water, a water reducing agent and fine sand.

Preferably, the fiber woven mesh in step (3) includes one of a basalt fiber woven mesh, a carbon fiber woven mesh, an aramid fiber woven mesh, an alkali-resistant glass fiber woven mesh, or a fiber hybrid woven mesh.

Preferably, in the step (3), the mesh size of the fiber woven mesh is 25mm by 25mm, 1-4 layers are arranged, the distance between each layer of woven mesh is 3mm, and the protective layer is 5 mm.

Preferably, the curing in the step (3) is performed for 24 hours at room temperature, then the mold is removed, and standard curing is performed to the age of 28 days.

Compared with the prior art, the invention has the beneficial effects that:

(1) the novel TRC composite material reduces the interfacial porosity by doping the nano material dispersion liquid, improves the bonding capability of the fiber woven mesh and the matrix, and ensures the cooperative working capability of the fiber woven mesh and the matrix, thereby improving the utilization rate of the fiber mesh in the common TRC.

(2) The invention greatly improves the ultimate tensile property under the condition of ensuring the compression resistance and the bending resistance, can further improve the seismic resistance of the structure, reduces the possibility and the degree of the structure to be damaged in rare earthquakes, reduces the repair cost, saves the relevant cost of urban construction, and has great significance and practical benefit on the technological innovation, the economic development, the natural environment and the social progress of China.

Drawings

FIG. 1 is a flow chart of the preparation of the matrix of the nano cement-based composite material of example 1 of the present invention

FIG. 2 is a flow chart of manufacturing a cement-based composite board reinforced with a fiber woven mesh according to example 1 of the present invention

FIG. 3 is a schematic view of dispersion of graphene nanosheets and silica fume in a composite cement matrix in example 1 of the present invention

FIG. 4 is a scanning electron microscope image of a graphene nanosheet-silica fume-cement-based composite material in example 1 of the present invention during a 28-day age period

FIG. 5 is a diagram showing an aperture distribution map and a cumulative aperture distribution map in example 1 of the present invention

Detailed Description

In order to more clearly illustrate the embodiments of the present invention, some embodiments of the present invention are described below. It will be obvious to those skilled in the art that other embodiments may be alternatively obtained from these embodiments without inventive effort.

According to the invention, through doping of nano materials (multi-walled carbon nanotubes, multi-layer graphene nanosheets and the like), not only is the compactness of the material improved, but also the porosity is reduced; the expansion of micro-nano cracks is solved through the bridging action of the nano materials, so that the toughness of the base material is improved; through the combination optimization of the metakaolin and the silicon powder, the bonding performance of the fiber and the matrix in a static state is improved, the fluidity in a dynamic state is improved, the infiltration effect on the fiber woven mesh is improved, and the utilization rate (average stress level) of the fiber woven mesh in a stressed state is obviously improved; the dispersing agent is used for preparing the nano material dispersion liquid, so that the uniform dispersion of the nano material in the cement alkaline environment is realized, the excellent mechanical property of the nano material is fully exerted, the micro crack expansion is hindered, the crack is bridged, the hydration reaction is promoted, and the mechanical property of the composite material is improved; through the regulation and control modification of the metakaolin and the silicon powder, the dynamic fluidity and the static bonding property of a cement matrix are greatly improved, the pouring is convenient, the infiltration of the fiber woven mesh is promoted, the holes of the woven mesh interface are reduced, the interface bonding force is increased, and the toughness of the composite material is improved; after the silica fume is doped, the silica fume can fill part of gaps due to the nanometer size of the silica fume and can generate hydration reaction in the gaps, so that the interface action between graphene nanosheets and the interface action between the graphene nanosheets and the cement matrix are increased.

Namely, the problem of the dispersibility of the nano material is solved by preparing a dispersion liquid through a carboxyl dispersant; through the combined action of the silica fume and the nano material, the problem of porosity is solved, a compact structure is achieved, and the strength is up to more than 200 MPa; through the common regulation and control action of the silica fume and the metakaolin, the problems of the pouring fluidity and the infiltration of the woven mesh are solved, the woven mesh and the cement matrix are enabled to work cooperatively, strain hardening and high toughness are formed under high stress, and the ultimate tensile strain can be stabilized to be more than 10%.

The cement in the embodiment of the invention adopts PII 52.5 cement; the sand adopts fine sand with the maximum size of 653 mu m; mixing water is common tap water; the dispersing agent is a Pasteur polycarboxylic acid water reducing agent; the defoaming agent is DEFEN 157 type; the carbon nano-tube is a multi-wall carbon nano-tube containing carboxyl functional groups developed by Chinese academy of sciences, and relevant technical indexes are shown in table 1.

TABLE 1 related technical indices of carbon nanotubes

A full-flow preparation process of a high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite material is characterized in that a carboxyl nanometer material dispersion liquid is a dispersion mixed liquid of nanometer materials accounting for 0.1% of the weight of cement, carbon-glass fiber mixed woven meshes are adopted, the mesh size of the fiber woven meshes is 25mm by 25mm, the mixing ratio is shown in Table 2, the water consumption of a comparative example is the same as that of an example, the comparative example is 200kg of purified water, and the example is 200kg of purified water plus the dispersion liquid, because the dispersion liquid is carboxyl-bearing and has the water reducing effect, 0.5kg of water reducing agent is less used in the comparative example. The 0.5kg water reducing agent added in the comparative example is used for ensuring the fluidity of the composite material, so that the composite material is soaked and attached to the fiber woven mesh, and the concrete is shown in table 3.

TABLE 2 TRC mix ratio (unit kg/m) ³ )

Example 1

S1: adding water and a polycarboxylic acid dispersant into a container, stirring by using a glass rod until the dispersant is completely dissolved, adding a weighed nano material (multi-walled carbon nanotubes (MWCNTs) or multi-layer graphene (MLGs)), and performing ultrasonic vibration in a water bath by using an ultrasonic instrument for 60 minutes to obtain a nano material dispersion solution;

s2: cleaning a stirrer, wiping or draining the stirrer for later use, and weighing the use amounts of various raw materials such as fine sand, cement, water, silica fume, metakaolin, a water reducing agent, a defoaming agent and the like;

s3: selecting a fiber woven mesh with proper type and mesh size;

s4: making a mould with certain size (length, width and thickness), and respectively tightening and fixing the fiber woven mesh in the mould in a layering way according to a certain height; the distance of each layer of the woven mesh can be set to be 3mm, and the distance of each protective layer is set to be 5 mm;

s5: pouring the weighed cement and sand into a stirring pot for uniform stirring;

s6: pouring the uniformly dispersed nano material dispersion liquid into a stirring pot, cleaning a suspension vessel by the residual extra water, then pouring into the stirring pot, and adding a defoaming agent;

s7: firstly, uniformly stirring by hand, slowly stirring for 3 minutes by adopting a machine, and then quickly stirring for 2 minutes to obtain a TRC matrix material;

s8: pouring a TRC base material into a mould, placing the mould on a vibration table, vibrating to compact and smoothening the surface;

s9: curing at room temperature for 24 hours, then removing the mold, and carrying out standard curing to 28-day age to finish the preparation;

s10: compressive Strength test A cement matrix is poured into a standard 160mm by 40mm mould. An external vibrator is used to facilitate compaction and reduce the number of bubbles. And demolding all the samples after 24 hours, and curing for 2 days in a natural curing mode under the conditions that the temperature is 20 +/-2 ℃ and the relative humidity is more than or equal to 95 percent for at least 28 days.

As shown in fig. 1 and 2, in example S1, the dispersant is a polycarboxylic acid water reducing agent, and the carbon nanotube dispersion solution is prepared using an ultrasonic instrument model jiekang PS-20, wherein the temperature is increased by ultrasonic vibration for a long time during the ultrasonic process, and the dispersion of the nanocarbon material is affected by flocculation and aggregation of the dispersant when the temperature exceeds 45 ℃.

In S2, the stirring pot is cleaned and wiped to make the inner surface of the pot moist and free of open water, and the used stirrer is a J-550 type cement mortar stirrer.

In S6, since the nanomaterial dispersion solution contains a certain amount of water (less than 50%), the water-cement ratio must be controlled by removing the water in the required amount of water; cleaning the vessel with the remaining extra water required in the mixing ratio and adding the water into the stirring pot; the used defoamer is a DENGFENG 613 type defoamer, and the dosage of the defoamer is 2 percent of the cement content;

by adopting the technical scheme, the ultrasonic instrument is utilized to prepare the uniform dispersion liquid of the nano material, so that the uniform dispersion liquid is uniformly dispersed in the cement aggregate to play roles of filling micro-nano pores and nucleating to promote hydration, after silica fume is doped, the silica fume can fill part of the pores due to the nano size of the silica fume and generates hydration reaction in the pores, the interface effect between graphene nanosheet layers and between the graphene nanosheets and the cement matrix is further increased as shown in figure 3, the metakaolin is utilized to promote the dynamic fluidity and fully infiltrate the fiber woven mesh, and finally the high-strength high-toughness TRC composite material can be prepared as shown in figure 4.

Example 2

The TRC production method described in example 2 was substantially the same as in example 1, except that the formulation conditions described in table 2 were used.

Example 3

The TRC production method described in example 3 was substantially the same as in example 1, except that the formulation conditions described in table 2 were used.

Comparative example 1

Comparative example 1 the TRC was prepared in the same manner as in example 1 except that the formulation conditions shown in table 2 were used.

Comparative example 2

Comparative example 2 the TRC was prepared in the same manner as in example 2 except that the formulation conditions shown in table 2 were used.

Comparative example 3

Comparative example 3 the TRC was prepared in the same manner as in example 3 except that the formulation conditions described in table 2 were used.

The strength and direct tensile property tests of the fiber woven mesh reinforced cement-based composite materials obtained in examples 1 to 3 and comparative examples 1 to 3 were carried out after curing for 28 days as shown in Table 3. The test instrument adopts 25T and 100T high-performance fatigue testing machines (Instron) to test the flexural strength, the compressive strength and the ultimate tensile strain of the thin plate of the test piece, and the loading rates of the flexural test and the compressive test are respectively 3kN/min and 144kN/min according to Chinese specifications JTG 3420-2020. The mechanical properties of the cement mortar are operated according to the relevant regulations of the test method standard of the mechanical properties of common cement mortar (GB 50081-2002) and the test and evaluation standard of the strength of the cement mortar (GB 50107-2010).

Table 3 results of performance testing of TRC articles obtained in examples and comparative examples

Table 4 TRC matrix pore structure test results obtained in examples and comparative examples

Number of	Porosity (%)	Average pore diameter (nm)	Critical pore diameter (nm)
				Comparative examples 1, 2 and 3	13.30	16.3	26.3
Example 1	12.77	14.8	21.1
				Example 2	11.83	10.1	12.3
Example 3	12.6	7.8	5.17

In fact, a fiber bundle consisting of hundreds or thousands of fiber monofilaments with a diameter of several microns is generally not completely penetrated by the fine concrete matrix with larger particle size, and the edge filaments are well bonded to the matrix. During loading, the edge filaments are susceptible to brittle fracture from stresses imparted by the matrix, resulting in a reduction in the cross-sectional area of the fiber bundle. Thus, a coefficient k is defined as the ratio of the tensile load capacity of the TRC composite to that of an equivalent amount of web to characterize the utilization of the web in the TRC (table 3). In addition, the porosities, average pore diameters and critical pore diameters of the example and comparative example substrates were obtained by mercury intrusion test (table 4 and fig. 5). The increase of the mechanical property can be obtained that the fiber woven mesh material is not changed, and the tensile property is greatly improved along with the change of the matrix, which means that the bonding property is improved.

The results show that the novel high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite material obtained by the invention ensures the mechanical property, greatly improves the tensile strain property, improves the compactness of the material, reduces the interface porosity, improves the toughness of the matrix material, improves the bonding capacity of the fiber woven mesh and the matrix, ensures the cooperative working capacity of the fiber woven mesh and the matrix, particularly obviously improves the utilization rate of the fiber mesh in common fiber woven mesh reinforced concrete, improves the tensile property under the condition of ensuring compression resistance and folding resistance, further improves the structure seismic resistance, and has great significance and practical benefits on the progress of scientific and technological innovation, economic development, natural environment and society in China.

The foregoing has described only the preferred embodiments and principles of the present invention in detail, and it will be apparent to those skilled in the art that variations may be applied to the embodiments based on the technical concept provided by the present invention, and such variations should be considered as within the scope of the present invention.

Claims

1. The high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite board is characterized by comprising concrete slurry and a fiber woven mesh.

2. The high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite material as claimed in claim 1, wherein the concrete grout comprises 550-705 parts by weight of cement, 300-455 parts by weight of fly ash, 25-45 parts by weight of metakaolin, 70-80 parts by weight of silica fume, 4.5-6.0 parts by weight of water reducing agent, 830-950 parts by weight of fine sand and 500-700 parts by weight of carboxyl nanometer material.

3. The high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite material as claimed in claim 2, wherein the carboxyl nanometer material comprises one or more of nanometer silica, multi-wall carbon nanotubes, carbon nanofibers and graphene nanosheets.

4. The preparation method of the high-strength high-toughness fiber woven mesh reinforced nanometer cement-based composite board is characterized by comprising the following steps of:

(2) adding fine cement mortar to obtain concrete slurry;

5. The method according to claim 4, wherein the nanomaterial dispersion liquid in the step (1) is a dispersion liquid in which a nanomaterial is disposed using a carboxyl dispersant.

6. The method according to claim 4, wherein the heating temperature in the step (1) is not more than 68 to 70 ℃ higher than the cloud point temperature.

7. The method as claimed in claim 4, wherein the fine cement mortar in the step (2) comprises cement, fly ash, metakaolin, silica fume, purified water, water reducing agent, fine sand.

8. The method according to claim 4, wherein the woven fiber mesh of step (3) comprises one of a woven basalt fiber mesh, a woven carbon fiber mesh, a woven aramid fiber mesh, a woven alkali-resistant glass fiber mesh, or a woven hybrid fiber mesh.

9. The method according to claim 4, wherein the mesh size of the fiber woven mesh in the step (3) is 25mm by 25mm, 1 to 4 layers are provided, the distance between each layer of the woven mesh is 3mm, and the protective layer is 5 mm.

10. The method according to claim 4, wherein the curing in step (3) is performed after 24 hours at room temperature, and then the mold is removed, and standard curing is performed to 28 days of age.