CN112961267A

CN112961267A - Acrylic resin repairing material for repairing concrete micro-cracks

Info

Publication number: CN112961267A
Application number: CN202110161096.XA
Authority: CN
Inventors: 王涛; 韩健; 郭泽萌; 徐玲玲; 邓敏; 黄晓军; 黄蓓; 莫立武
Original assignee: Nanjing Tech University
Current assignee: Nanjing Tech University
Priority date: 2021-02-05
Filing date: 2021-02-05
Publication date: 2021-06-15
Anticipated expiration: 2041-02-05
Also published as: CN112961267B

Abstract

The invention relates to an acrylic resin repairing material for repairing concrete micro-cracks, which is prepared from the following components in parts by weight: 60-85 parts of methyl methacrylate resin monomer, 0.4-0.8 part of initiator, 10-30 parts of plasticizer and 0.4-0.8 part of accelerator. The invention takes methyl methacrylate monomer as raw material, adopts bulk polymerization reaction to prepare the patching material, and adds auxiliary agent to promote the reaction if necessary. The repair material has the advantages of low viscosity and good fluidity, and can meet the repair requirement of ultra-small microcracks with the width of 0.05 mm. The material has high mechanical strength and toughness, and good chemical erosion resistance, ultraviolet aging resistance and frost resistance. The strength can be reached within 2-4h at normal temperature, and the pavement and wall concrete can be allowed to be used and passed in a short time after the repair is finished.

Description

Acrylic resin repairing material for repairing concrete micro-cracks

Technical Field

The invention belongs to the technical field of concrete, and particularly relates to an acrylic resin repairing material for repairing concrete micro-cracks.

Background

Concrete is the most common building material in China, but is easily corroded by self factors and surrounding environment, and diseases such as cracks, peeling and peeling can occur, wherein the cracks are the most important form. The wall surface cracks are caused by various reasons, firstly, the wall surface cracks are caused by external loads, and the most common reason is that the wall surface cracks are caused by external loads; secondly, the crack caused by the secondary stress of the structure is caused by the difference between the actual working state of the structure and the calculation hypothesis model; finally, cracks due to deformation stresses, including structural deformations caused by shrinkage, expansion, temperature and uneven settlement, are produced when the deformation is constrained, and when the stress exceeds the tensile strength of the concrete, cracks are produced.

Compared with pavement cracks, the width of the wall cracks is smaller, usually 0.1-0.8 mm, and the width of individual cracks is larger than 0.8mm or smaller than 0.1 mm. When concrete cracks, if the concrete is not treated in time, the anti-permeability capability of a building is reduced, the using function of the building is influenced, the corrosion of reinforcing steel bars and the carbonization of the concrete are caused, the durability of the material is reduced, further structural damage is easily caused, and huge loss is caused economically.

At present, various concrete repair materials are developed at home and abroad, but all have certain defects, for example, inorganic repair materials such as common portland cement have the defects that the repair interface is broken due to high shrinkage rate during hydration, the setting time is long, and concrete facilities cannot be put into use in a short time after being repaired; for example, the magnesium phosphate cement has extremely high hardening speed, difficult adjustment of setting time and large hydration heat; among the organic repair materials, epoxy resin materials also have many disadvantages, including a high viscosity, difficulty in filling when the crack width is small, high cost, and poor ductility and high brittleness, and are prone to fracture.

Disclosure of Invention

The invention aims to solve the defects of the prior art and provides an acrylic resin repairing material for repairing concrete micro cracks, which has low viscosity and good fluidity, can be used for repairing the micro cracks with the width less than 0.6mm on a concrete wall surface, and has the characteristics of good bonding effect, high mechanical strength, good durability and simple construction mode.

Another object of the present invention is to provide a method for producing the above polyacrylic resin type repair material.

Technical scheme

An acrylic resin repairing material for repairing concrete micro-cracks is prepared from the following components in parts by weight: 60-85 parts of methyl methacrylate resin monomer, 0.4-0.8 part of initiator, 10-30 parts of plasticizer and 0.4-0.8 part of accelerator.

The initiator is organic peroxide initiator, such as any one of benzoyl peroxide, methyl ethyl ketone peroxide or tert-butyl peroxybenzoate.

The plasticizer is phthalate, such as any one of dioctyl phthalate, dibutyl phthalate or diisodecyl phthalate.

The promoter is tertiary amine and its salt promoter, such as N, N-dimethylaniline or dimethylethanolamine.

The preparation method of the polyacrylic resin repair material comprises the following steps:

1) stirring and reacting a methyl methacrylate resin monomer, an initiator and a plasticizer at 60-100 ℃, stopping heating when the viscosity of a system reaches 20-40 mPa & s, and stopping reaction to obtain a prepolymer;

2) and (4) placing the prepolymer into cold water for cooling, and adding an accelerant to obtain the prepolymer.

Further, in the step (1), before the methyl methacrylate resin monomer is used, the methyl methacrylate resin monomer is pretreated in a water bath condition at the temperature of 20-80 ℃ or washed by NaOH solution and distilled water to remove a small amount of polymerization inhibitor added in the storage process of the methyl methacrylate resin monomer.

The construction method of the polyacrylic resin repair material is a grouting method, and the repair material is injected into the deep part of the crack to achieve the purpose of restoring the structural integrity, the durability and the waterproofness. The method comprises the steps of embedding grouting nozzles, sealing joints, preparing a repairing material to perform grouting, closing after filling one grouting nozzle, opening the next grouting nozzle, maintaining for 24 hours after finishing the grouting, leveling the grouting nozzles, and finally grinding the sealing material by a grinder.

The invention has the beneficial effects that: compared with other existing repairing materials, the repairing material has the characteristics of low viscosity and good fluidity, can flow into ultra-small microcracks with the width of 0.05mm for repairing, has higher mechanical strength (such as bonding strength, bending strength and tensile strength) and can reach certain strength in the early stage, for example, pavement and wall surfaces can be allowed to use and pass in a shorter time after the repairing is completed, and has better durability such as chemical erosion resistance, ultraviolet aging resistance and frost resistance.

Drawings

FIG. 1 shows the results of the adhesion strength test of the polyacrylic resin type repair materials obtained in examples 1 to 3;

FIG. 2 shows the results of the flexural strength test of the polyacrylic resin repair materials obtained in examples 1 to 3;

FIG. 3 shows the UV aging resistance test results of the polyacrylic resin repair materials prepared in examples 1 to 3;

FIG. 4 is a diagram illustrating grouting effect during actual crack repair;

FIG. 5 is a microscopic view showing a crack in a core sample.

Detailed Description

In order that the objects and advantages of the invention will be more clearly understood, the following description is given in conjunction with the accompanying examples. It is to be understood that the following text is merely illustrative of one or more specific embodiments of the invention and does not strictly limit the scope of the invention as specifically claimed.

Example 1

An acrylic resin repairing material for repairing concrete micro-cracks is prepared from the following components in parts by weight: 76 parts of methyl methacrylate resin monomer, 0.56 part of initiator (benzoyl peroxide), 22.88 parts of plasticizer (dioctyl phthalate) and 0.56 part of accelerator (N, N-dimethylaniline).

1) stirring and reacting methyl methacrylate resin monomer, initiator and plasticizer at 80 ℃ for 22min to obtain a system viscosity of 20.3mPa & s, stopping heating, and stopping reaction to obtain a prepolymer;

Example 2

An acrylic resin repairing material for repairing concrete micro-cracks is prepared from the following components in parts by weight: 76 parts of methyl methacrylate resin monomer, 0.56 part of initiator (methyl ethyl ketone peroxide), 22.88 parts of plasticizer (dibutyl phthalate) and 0.56 part of accelerator (dimethylethanolamine).

1) stirring and reacting methyl methacrylate resin monomer, initiator and plasticizer at 80 ℃ for 24min to obtain a system viscosity of 27.5mPa & s, stopping heating, and stopping reaction to obtain a prepolymer;

Example 3

An acrylic resin repairing material for repairing concrete micro-cracks is prepared from the following components in parts by weight: 77 parts of methyl methacrylate resin monomer, 0.57 part of initiator (benzoyl peroxide), 21.86 parts of plasticizer (dioctyl phthalate) and 0.57 part of accelerator (N, N-dimethylaniline).

1) stirring and reacting a methyl methacrylate resin monomer, an initiator and a plasticizer at 80 ℃ for 24min to obtain a system viscosity of 23.1mPa & s, stopping heating, and stopping reaction to obtain a prepolymer;

Performance testing

1. Viscosity measurement

The prepolymers of examples 1-3 were tested for viscosity change with reaction time and the results are shown in Table 1:

TABLE 1

As can be seen from Table 1, the viscosity of the polyacrylic resin repair material can be controlled, the viscosity is generally 20-40 mPa & s in the actual repair engineering, the gelling time is 22-26 min, the material can be used for repairing under a rapid emergency condition, and in addition, the low viscosity can cause better fluidity and can be used for repairing fine microcracks with the width less than 0.6 mm.

2. Bond Strength test

Breaking a 40mm multiplied by 160mm mortar test piece on an anti-bending machine, keeping a 3-5 mm gap between two sections, sealing by using an adhesive tape, injecting the repairing material of the embodiment 1-3 into the gap, and measuring the anti-bending strength of the repairing material after curing for 3d, 7d and 28d at normal temperature to be used as the bonding strength. The results are shown in FIG. 1.

As can be seen from FIG. 1, the repair material prepared by the embodiment of the invention has higher bonding strength and meets the requirements of application engineering on the repair material.

3. Flexural Strength test

The prepolymer of the polyacrylic resin repair material prepared in example 1-3 was poured into a self-made mold of 120mm × 20mm × 20mm to test the bending resistance, and the bending strength of the repair material was calculated according to formula (1).

Wherein:

r-bending ultimate Strength of the Material, MPa

F-maximum load in flexural failure of the material, N

L-distance between two points of material under load, m

b-width of cross section of the material specimen, m

h-height of the section of the material specimen, m

The results of the bending strength test are shown in fig. 2, and it can be seen from fig. 2 that the repair material prepared by the example of the present invention has excellent bending strength.

4. Chemical resistance test

The prepolymer of the polyacrylic resin repair material prepared in example 1-3 was poured into a self-made mold of 120mm × 20mm × 20mm, and after 10 days, the material was completely cured and soaked in clean water, 5% NaCl and 5% MgSO₄In the solution, the sample was taken out after 90d to test the bending strength, and compared with a blank sample to calculate the retention rate of the bending strength. The results are shown in Table 2:

TABLE 2

As can be seen from Table 2, after 90 days of soaking in different solutions, the repair materials prepared by the embodiment of the invention have the bending strength retention rate of more than 95%, and have excellent chemical erosion resistance.

5. Ultraviolet aging resistance test

The prepolymer of the polyacrylic resin repair material prepared in example 1-3 was poured into a self-made mold of 120mm × 20mm × 20mm, and after curing was completed for 10 days, the cured product was placed in an ultraviolet box, and taken out and tested for flexural strength at different times, and the flexural strength retention rate was calculated by comparing the tensile strength with a blank sample without being placed in an ultraviolet box, and the results are shown in fig. 3.

As can be seen from FIG. 3, the repair material prepared by the embodiment of the invention has good ultraviolet aging resistance, and the bending strength retention rate can still reach about 80% under the ultraviolet irradiation condition of 1440h for a long time.

6. Test for Freeze resistance

Pouring the prepolymer of the polyacrylic resin repair material prepared in the embodiment 1-3 into a self-made mold with the thickness of 120mm multiplied by 20mm, curing for 10 days, performing a freeze-thaw cycle experiment, wherein the freeze-thaw temperature is-20 ℃, the freeze-thaw time is 4 h/time, the bending strength is tested after 200 cycles, and the strength retention rate is obtained by comparing with a blank sample without freeze-thaw cycle. The results are shown in Table 3:

TABLE 3

As can be seen from Table 3, the repair material prepared by the embodiment of the invention has the bending strength retention rate of 96-98% after 200 freeze-thaw cycles, and has excellent freezing resistance.

Engineering application test:

the method is characterized in that crack repair is carried out at an airport in Zhejiang in 2020 and 10/15 to 2020 and 12/20, the polyacrylic resin repair material of the embodiment 1 is adopted for repair, and the repair process flow is as follows:

surface treatment → embedding grouting nozzle → sealing seam → preparing repairing slurry → grouting → dismantling glue injector → dismantling grouting nozzle → sealing and smoothing → checking and accepting

1. Surface treatment

And cleaning dust on the surface of the concrete by using a brush and a steel wire ball, removing floating skins and hollow plasters which are easy to fall off around the crack, cleaning the parts about 25mm away from the two sides of the crack by using a cleaning cloth and a sponge, and keeping the parts dry.

2. Embedded grouting nozzle

The distance between the positions of the grouting nozzles is 350mm, and when the grouting nozzles are embedded, a layer of joint sealing glue with the thickness of about 2mm is firstly smeared on a chassis of the grouting nozzles to paste the junction of the grouting inlet on a standard position.

4. Sealing seams

And sealing the gap after the grouting nozzle is fixed, smearing a layer of gap sealing glue with the thickness of 4mm and the width of about 25mm on two sides of the gap, and starting grouting after the gap sealing glue is smeared for 6 hours and reaches a certain hardening degree.

5. Grouting agent

Screwing the glue injector absorbing 50mL of repair liquid on the grouting nozzle base, sequentially opening the glue injectors from bottom to top for injection, stopping the injection of the current glue injector when the next grouting nozzle discharges the grout, plugging the glue injector by a plug, and opening the next glue injector until the crack is fully filled, as shown in fig. 4.

6. Demolish the glue injection device

And after grouting is finished, removing the glue injector, detaching the embedded grouting nozzle when slurry in the joint is initially set but does not flow outwards, and sealing and troweling the grouting opening by using joint sealing cement.

7. Inspection acceptance

After grouting, the reinforcement effect and quality should be checked.

FIG. 4 is a view showing grouting effect during actual crack repair, and it can be seen that the grouting effect is good; after repairing, core drilling and sampling are carried out on the cracks of the wall surface, the picture of the core sample is shown in figure 5, figure 5 is an observation picture of the cracks of the core sample after being magnified by a microscope, and as can be seen from the figure, the cracks are basically filled with the repairing material, which shows that the grouting repairing effect is good, and in addition, the wall surface condition is good so far, and no durability problem exists.

Claims

1. The acrylic resin repairing material for repairing the micro cracks of the concrete is characterized by being prepared from the following components in parts by weight: 60-85 parts of methyl methacrylate resin monomer, 0.4-0.8 part of initiator, 10-30 parts of plasticizer and 0.4-0.8 part of accelerator.

2. The acrylic resin-based repair material for repairing a fine crack of concrete according to claim 1, wherein the initiator is an organic peroxide-based initiator, such as any one of benzoyl peroxide, methyl ethyl ketone peroxide or tert-butyl peroxybenzoate.

3. The acrylic resin based patching material for repairing concrete micro cracks according to claim 1, wherein the plasticizer is any one of phthalate esters, such as dioctyl phthalate, dibutyl phthalate or diisodecyl phthalate.

4. The acrylic resin based patching material for repairing concrete microcracks according to claim 1, 2 or 3, characterized in that the accelerator is a tertiary amine and its salt accelerator, such as N, N-dimethylaniline or dimethylethanolamine.

5. The method for preparing the acrylic resin based patching material for repairing concrete microcracks according to any one of claims 1 to 4, comprising the following steps:

6. The method for preparing a polyacrylic resin based patching material of claim 5, wherein in the step (1), the methyl methacrylate resin monomer is pretreated in a water bath condition of 20-80 ℃ or washed with NaOH solution and distilled water before being used.