WO2020200170A1

WO2020200170A1 - Method for preparing damage-self-reporting concrete

Info

Publication number: WO2020200170A1
Application number: PCT/CN2020/082085
Authority: WO
Inventors: 王清; 李耀; 郑旭; 王宁
Original assignee: 山东科技大学
Priority date: 2019-04-04
Filing date: 2020-03-30
Publication date: 2020-10-08
Also published as: CN110002809A; CN110002809B

Abstract

Disclosed is a method for preparing a damage-self-reporting concrete, comprising the steps of dissolving PMMA in chloroform; dissolving CVL in phenyl acetate; then placing same in a vortex mixer for vortex mixing, so as to obtain an oil phase; adding a silica sol to distilled water as a continuous phase, and then subjecting the continuous phase and the oil phase to vortex mixing so as to obtain a pre-emulsion; adding a 1 M HCl solution to the pre-emulsion, and adjusting the pH of the pre-emulsion to 8.0; then subjecting same to an ultrasonic bath under ice bath cooling conditions to form an oil-in-water emulsion; stirring the resulting emulsion in a pre-heated oil bath at 40ºC to evaporate the chloroform, so as to obtain a suspension; cooling the resulting suspension to room temperature, and subjecting same to vacuum filtration to obtain a microcapsule; and adding a dispersion system of the microcapsules to a concrete slurry and stirring same, and casting same so as to obtain the damage-self-reporting concrete. The method combines visual sensing and concrete damage monitoring, that is to say, a color change means that a crack appears, which is intuitional and clear, and same has a high sensitivity and can reduce construction difficulties.

Description

Method for preparing self-reporting damage concrete

Technical field

The invention relates to the field of concrete structure health monitoring, in particular to a method for preparing self-reporting damage concrete.

Background technique

With the continuous development of the construction industry, a large number of engineering constructions are carried out in various places, but often due to various defects in the design and construction quality, the buildings or structures are strained during the trial period. If the strain is developed too large, it will affect the structure Safety and durability. Therefore, it is particularly important to monitor the health of the structure.

At present, the structural health monitoring of buildings is mainly for strain monitoring, relying on strain sensors, such as distributed optical fiber sensors. However, the traditional distributed optical fiber sensor, due to the various shortcomings of the optical fiber itself, causes the optical fiber sensor to also have disadvantages such as high cost, large error, difficult construction, and limited monitoring parts. And because of its high cost and large limitations, it cannot be widely used in building structural health monitoring. A more detailed description is given below:

There are usually three ways for the existing distributed optical fiber sensor to be embedded in the internal structure of the concrete: ordinary burying, supplementary burying, and paste burying. Ordinary burying means using steel bars to fix the optical fiber, finally pouring concrete, and monitoring with fiber grating sensor after completion. The filling type is to slot in the designated inspection position, and then backfill the concrete. Pasting and burying is to use pasting materials to paste the fiber grating sensor on the concrete surface for detection, cut a groove on the concrete surface, lay the distributed optical fiber in the groove, and encapsulate it with epoxy resin.

The working principle of the distributed optical fiber sensor is roughly as follows: the optical fiber sensor is embedded in the concrete structure to be measured. When the concrete structure is strained, the optical fiber structure will also produce corresponding strain. The strain can be detected by detecting the strain of the optical fiber. Strain information of concrete members. When the strain of concrete structure is too large, cracks will occur. Since the strain of the optical fiber follows the change of the concrete being detected, the theoretical strain value of the optical fiber at the crack will have a peak value. This is how the distributed optical fiber sensor detects the crack.

technical problem

The existing distributed optical fiber sensor has the following technical disadvantages:

(1) The distributed optical fiber will slip relative to the concrete when the concrete crack occurs, resulting in inaccurate measurement results;

(2) It is necessary to dig trenches on the concrete surface during construction, which will damage the integrity of the concrete surface and increase the difficulty of construction;

(3) The crack can only be detected when the optical fiber penetrates the crack. If the crack does not intersect the optical fiber, it cannot be detected;

(4) The optical fiber sensor can only detect cracks, but cannot detect scratches, crushes and other damages on concrete.

Technical solutions

In order to solve the above technical problems, one of the objectives of the present invention is to provide a microcapsule dispersion system or a capsule-type visual strain sensor, which is applied to the structural health monitoring of concrete structures and can perform real-time in-situ monitoring. , The effect is intuitive and obvious, and the sensitivity is high, so as to solve the problems of the existing strain sensor's complex process, the inability of real-time in-situ detection, poor accuracy, and large detection position limitations.

The microcapsule dispersion is prepared by the following method:

(1) Dissolve 500 mg of polymethyl methacrylate (PMMA) in 5 g of chloroform to obtain solution one;

... (2) In another container, dissolve 100 mg of crystal violet lactone (CVL) in 1 g of phenyl acetate to obtain solution two;

(3) Put solution 1 and solution 2 into a vortex mixer for vortex mixing to obtain an oil phase;

(4) Add 3.2g of HS-30 silica sol as an emulsion stabilizer into 16.8g of distilled water as the continuous phase, then add the continuous phase to the vortex mixer and vortex the oil phase for 2 minutes to obtain a pre-emulsion ；

... (5) Add 1M to the pre-emulsion HCl solution, adjust the pH value of the pre-emulsion to 8.0;

(6) The pre-emulsion after adjusting the pH value is cooled in an ice bath using an ultrasonic bath to form an oil-in-water emulsion. The amplitude of the ultrasonic wave is 30% to 50%, with a 30-second pulse and a 10-second pause for 3 minutes. ；

(7) Stir the obtained emulsion in a preheated oil bath at 40°C (stirring speed is 1000 rpm, stirring time is 16 hours) to evaporate the chloroform to obtain a suspension;

(8) Cool the obtained suspension to room temperature, and use vacuum filtration to obtain microcapsules, and wash the microcapsules several times with water and ethanol to obtain a microcapsule dispersion.

The microcapsule dispersion system can be applied to concrete structures to realize the self-reporting damage function of concrete structures.

The second objective of the present invention is to provide a self-reporting damage concrete, which is made by mixing conventional raw material cement, fly ash, medium sand, gravel, water, and visual strain sensors, ie, a microcapsule dispersion system. Conventional raw material cement: fly ash: medium sand: crushed stone: water=1: 0.4: 2.29: 2.29: 0.47, calculated by mass ratio; in addition, the mass ratio of cement and microcapsule dispersion is 1: 0.1, cement The mass ratio of water reducing agent is 1: 0.024. The above ratio can be adjusted according to actual working conditions or required concrete strength.

The third purpose of the present invention is to propose a method for preparing self-reporting damage concrete. The concrete prepared by this method combines visual sensing and concrete damage monitoring, which can perform real-time in-situ monitoring, with obvious visual effects and sensitivity. Higher merit.

The technical solution adopted by the present invention is:

A method for preparing self-reportable damage concrete includes the following steps:

... (1) Dissolve polymethyl methacrylate in chloroform to obtain solution one;

... (2) Dissolving crystal violet lactone in phenyl acetate to obtain solution two;

(4) Add a silica sol of model HS-30 as an emulsion stabilizer to distilled water as a continuous phase, and then add the continuous phase to a vortex mixer to vortex and mix with the oil phase to obtain a pre-emulsion;

(6) Make the pre-emulsion after adjusting the pH value into an oil-in-water emulsion using an ultrasonic bath under ice cooling;

(7) Stir the obtained emulsion in a preheated oil bath at 40°C to evaporate the chloroform to obtain a suspension;

(8) Cool the obtained suspension to room temperature, and use vacuum filtration to obtain microcapsules, and wash the microcapsules several times with water and ethanol to obtain a microcapsule dispersion;

(9) Mix cement, fly ash, medium sand, crushed stone and water, and stir for 1-2 minutes to obtain slurry;

(10) Add the microcapsule dispersion to the slurry and stir for 1-2 minutes;

(11) Then add water reducing agent to the slurry and stir for 2-3 minutes, then pour;

(12) After curing and removing the mold, a layer of microcapsule dispersion is coated on the surface of the concrete to obtain concrete with self-reported damage.

Preferably, in step (1): the mass ratio of polymethyl methacrylate to chloroform is 1:10.

Preferably, in step (2): the mass ratio of crystal violet lactone to phenyl acetate is 1:10.

Preferably, in step (4): the mass ratio of silica sol to distilled water is 1:5-6; the vortex mixing time of the continuous phase and the oil phase is 2 minutes.

Preferably, in step (6): the amplitude of the ultrasonic wave is 30% to 50%, and it is continuously performed for 3 minutes at a time sequence of 30 seconds pulse and 10 seconds pause.

Preferably, in step (7): the stirring speed is 1000 rpm, and the stirring time is 16 hours.

Preferably, in step (10), the microcapsule dispersion is added to the slurry with a mass ratio of cement: microcapsule dispersion=1:0.1-0.3.

Beneficial effect

(1) The traditional distributed optical fiber sensor will produce inaccurate results due to relative slippage with concrete when cracks occur in concrete. Microcapsules have high sensitivity, that is, they are mixed in concrete and directly cover the surface of concrete. Produce slippage and dislocation;

(2) The traditional distributed optical fiber sensor needs to dig trenches on the concrete surface during construction, which destroys the integrity of the concrete surface, but also increases the difficulty of construction; this method is simple to construct and the microcapsule part can be prefabricated without damage to the original structure;

(3) The traditional distributed optical fiber sensor can only detect the crack when the optical fiber penetrates through the crack. If the crack does not intersect the optical fiber, it cannot be detected; while the microcapsule sensor has a large monitoring range and can be performed as long as there are microcapsules distributed. Strain monitoring.

Description of the drawings

The present invention will be further explained below in conjunction with the drawings and specific embodiments:

Figure 1 is a schematic diagram of the structural principle of the self-reporting damage concrete prepared by the present invention;

Figure 2 is a schematic diagram of the principle of the present invention after cracks appear in the concrete.

In the picture: 11 is the microcapsule layer on the concrete surface, 12 is the concrete structure layer, 21 is the crack of the concrete structure, 22 is the activated microcapsule in the microcapsule layer on the concrete surface, 23 is the unactivated microcapsule layer on the concrete surface 24 is the activated microcapsule in the concrete structure layer.

The ratio in the figure is just for easy understanding. The actual size of the microcapsules is nanometers and is evenly distributed throughout the structure. It is colorless before being activated, and appears blue after activation.

Embodiments of the invention

The principle content involved in the present invention is introduced as follows:

In the present invention, polymethyl methacrylate (PMMA) is first dissolved in chloroform to make it liquid, and the amount of PMMA determines the thickness of the shell of the microcapsule; crystal violet lactone (CVL) is used as the core material of the microcapsule, and CVL is solid Powder, dissolved in phenyl acetate to become liquid, the amount of crystal violet lactone should not be too much, otherwise it may cause incomplete coating. The HS-30 type silica sol added in the present invention is used as an emulsifier to help form an emulsion; the pH value is adjusted by adding 1M HCl solution to help the formation of microcapsules.

The method for preparing microcapsules in the present invention is a solvent evaporation method. An oil-in-water emulsion (O/W type emulsion) has been formed from step (6) of the preparation method, and the emulsion droplets contain the core material (CVL) and the capsule Wall material (PMMA) and volatile solvent (chloroform). When the oil bath is heated in step (7), chloroform is gradually removed from the emulsion droplets, and the PMMA in the droplets undergoes phase separation due to the volatilization of chloroform (PMMA It is a solid, dissolved in chloroform, called liquid), and then migrates to the surface of the CVL oil droplet, and is enriched on the surface; when the chloroform is completely evaporated, an oil core/polymer shell with CVL as the core and PMMA as the outer shell is obtained. Microcapsules.

The CVL used in the present invention is a leuco dye, which is usually colorless, and silica is its developer. After the microcapsule is ruptured, the core material CVL flows out, and the silicon dioxide on the shell of the microcapsule appears blue. Therefore, as long as the microcapsules are broken, they will appear blue. The silica comes from the silica sol added in step (4) and remains on the surface of the microcapsule shell after the microcapsule coating is completed.

The main purpose of the ice bath conditions used in the preparation step (6) of the present invention is to lower the temperature and prevent the chloroform from evaporating in advance.

It is also necessary to clarify that in the process of mixing the microcapsule dispersion system with cement to prepare concrete, the present invention only requires slight stirring (the stirring speed is generally about 1000 rpm, which is not much different from the stirring speed in the preparation process of the microcapsule dispersion system) The concrete can be obtained by self-compacting evenly, without vibrating, so the microcapsule dispersion system will not break during the preparation process.

The present invention not only mixes the concrete with the microcapsule dispersion system, but also coats the concrete surface with a layer of microcapsule dispersion system. This is mainly because most of the cracks in the concrete structure develop from the surface, so the final coating on the surface is Strengthen the monitoring of the surface (to prevent the uneven distribution of microcapsules on the surface of the concrete during the setting and hardening process of the concrete), and the specific coating method is to lightly brush.

With reference to the drawings, the present invention proposes a method for preparing self-reporting damage concrete. This method combines visual sensing and concrete damage monitoring. Cracks appear when the color changes, which is intuitive (especially when monitoring structures that do not allow cracks. It is more convenient); and to reduce the difficulty of construction, the optical fiber sensor needs to be grooved on the surface of the concrete, and the self-reported damage concrete based on the microcapsule technology introduced in the present invention is simple to prepare and can be completed before pouring, and some steps can be prefabricated; High sensitivity, as long as the concrete is damaged, it can be triggered regardless of cracking, abrasion, or crushing. The microcapsules are evenly distributed throughout the structure, and all parts of the structure can be monitored in real time.

The present invention selects the following materials in the preparation of self-reporting damage concrete:

Polymethyl methacrylate (PMMA), chloroform, violet crystal lactone (CVL), phenyl acetate, silica sol (model HS-30), HCL (concentration 1mol/L), cement (model P.O42) .5R), fly ash, medium sand, crushed stone (particle size 10-20mm), superplasticizer (Subbot PCA-1 superplasticizer).

(1) Dissolve 500 mg of polymethyl methacrylate (PMMA) in 5 g of chloroform to obtain solution one.

(2) Dissolve 100 mg of crystal violet lactone (CVL) in 1 g of phenyl acetate in another container to obtain solution 2.

(3) Mix Solution 1 and Solution 2 in a container as the oil phase.

(4) Add 3.2g of silica sol (the type of silica sol is HS-30) as an emulsion stabilizer into 16.8g of distilled water as the continuous phase, and combine the oil phase and the continuous phase in a vortex mixer, and vortex for 2 minutes , Get a pre-emulsion.

(5) Adjust the pH value of the pre-emulsion to 8.0 by adding 1M HCl solution to the pre-emulsion.

(6) Use an ultrasonic bath to form an oil-in-water emulsion under ice cooling (ultrasonic conditions: 30% to 50% amplitude; 30 seconds pulse, 10 seconds pause; continuous for 3 minutes).

(7) Quickly transfer the obtained emulsion in a preheated oil bath at 40°C (transfer the emulsion from an ultrasonic cleaner to a stirring device), and stir at 1000 rpm for 16 hours to evaporate the chloroform to obtain a suspension.

(8) Cool the resulting suspension to room temperature and filter the microcapsules using vacuum. The microcapsules are washed several times with water and ethanol to obtain a microcapsule dispersion.

(9) The above-mentioned raw materials are mixed and stirred for 1-2 minutes in a mass mixing ratio of cement: fly ash: medium sand: crushed stone: water=1:0.4:2.29:2.29:0.47 to obtain a slurry.

(10) Add the microcapsule dispersion to the slurry according to the mass ratio of cement: microcapsules=1:0.1 and stir for 1-2 minutes.

(11) Add the high efficiency water reducing agent according to the mass ratio of cement: water reducing agent=1:0.024 and mixing for 2-3 minutes before pouring.

The parts not mentioned in the above methods can be realized by adopting or learning from existing technologies.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. And variants, the protection scope of the present invention is defined by the appended claims and their equivalents.

Claims

A method for preparing self-reportable damage concrete, which is characterized by comprising the following steps:

(1) Dissolve polymethyl methacrylate in chloroform to obtain solution one;

(2) Dissolve crystal violet lactone in phenyl acetate to obtain solution two;

(3) Put solution 1 and solution 2 into a vortex mixer for vortex mixing to obtain an oil phase;

(4) Add a silica sol of model HS-30 as an emulsion stabilizer to distilled water as a continuous phase, and then add the continuous phase to a vortex mixer to vortex and mix with the oil phase to obtain a pre-emulsion;

(5) Add 1M HCl solution to the pre-emulsion and adjust the pH value of the pre-emulsion to 8.0;

(6) Make the pre-emulsion after adjusting the pH value into an oil-in-water emulsion using an ultrasonic bath under ice cooling;

(7) Stir the obtained emulsion in a preheated oil bath at 40°C to evaporate the chloroform to obtain a suspension;

(8) Cool the obtained suspension to room temperature, and use vacuum filtration to obtain microcapsules, and wash the microcapsules several times with water and ethanol to obtain a microcapsule dispersion;

(9) Mix cement, fly ash, medium sand, crushed stone and water, and stir for 1-2 minutes to obtain slurry;

(10) Add the microcapsule dispersion to the slurry and stir for 1-2 minutes;

(11) Then add water reducing agent to the slurry and stir for 2-3 minutes, then pour;

(12) After curing and removing the mold, a layer of microcapsule dispersion is coated on the surface of the concrete to obtain concrete that can report damage.
The method for preparing self-reportable damage concrete according to claim 1, wherein in step (1): the mass ratio of polymethyl methacrylate to chloroform is 1:10.
The method for preparing self-reportable damage concrete according to claim 1, wherein in step (2): the mass ratio of crystal violet lactone to phenyl acetate is 1:10.
The method for preparing self-reportable damage concrete according to claim 1, wherein in step (4): the mass ratio of silica sol to distilled water is 1:5-6; the vortex of continuous phase and oil phase Spin mixing time is 2 minutes.
The method for preparing self-reportable damage concrete according to claim 1, characterized in that, in step (6): the amplitude of the ultrasonic wave is 30% to 50%, according to the time sequence of 30 second pulse and 10 second pause, Continue for 3 minutes.
The method for preparing self-reportable damage concrete according to claim 1, characterized in that in step (7): the stirring speed is 1000 rpm, and the stirring time is 16 hours.
The method for preparing self-reportable damage concrete according to claim 1, wherein in step (10): a mass ratio of cement: microcapsule dispersion = 1:0.1-0.3 is added to the slurry Add microcapsule dispersion system.