A fiber-optic monitoring device and method for the entire hydration-hardening process of concrete

Abstract

This invention discloses a fiber optic monitoring device and method for the entire hydration-hardening process of concrete. The device includes: a coupled array grating strain optical cable and a guided array grating temperature optical cable; both are embedded in the concrete and connected via a fusion splice; the fusion splice is connected to a grating array strain demodulator; the grating array strain demodulator is connected to a host computer. Based on the distributed monitoring capabilities of the grating array, this invention can monitor the distribution of temperature, strain, and stress fields throughout the entire hydration-hardening process of concrete. It can accurately locate stress concentration areas and quantify stress states, identifying high-risk coordinates and providing early warnings at the crack initiation stage. This provides technical assurance for zero-cracking throughout the lifespan of major projects such as nuclear power plant containment structures and hydraulic dams, promoting concrete structure health monitoring from single-point sampling to all-time, all-domain monitoring.

Description

Technical Field

[0001] This invention relates to the field of intelligent building materials technology, and in particular to a fiber optic monitoring device and method for the entire process of concrete hydration and hardening. Background Technology

[0002] With the rapid development of large-scale infrastructure and energy projects, cast-in-place structures with full cross-sections, such as foundations for high-rise buildings, foundations for large equipment, hydraulic dams, and nuclear power plant containment structures, are widely used in super high-rise buildings and hydropower and nuclear power plants. However, due to the coupled influence of multiple factors such as the hydration heat gradient, external constraints, and material heterogeneity during the hydration-hardening process of concrete, typical defects such as stress cracks, segregation voids, and interface weakening occur. These defects will significantly weaken the integrity and service life of the structure.

[0003] Traditional monitoring methods, such as electrical sensors and local strain gauges, can only monitor single-point changes in concrete temperature or strain and stress after hardening, failing to monitor strain and stress development during hydration. In the early stages of hydration, concrete is in a plastic state, and the uncontrolled evolution of strain and stress directly induces irreversible structural damage. This early damage manifests as through-cracks after concrete hardening. Traditional monitoring methods not only completely miss strain and stress at this stage but also suffer from limitations such as time lag, insufficient spatial coverage, and inability to quantify stress states, making it difficult to meet the needs of full-lifecycle health monitoring for major projects. Distributed monitoring technology based on fiber optic grating sensing has revolutionary potential in the full-cycle monitoring of concrete structures due to its advantages such as long-distance coverage, resistance to electromagnetic interference, and embedded non-destructive monitoring. However, existing single-temperature field monitoring methods lack specificity in the response characteristics of internal defects in concrete, and cannot accurately locate stress concentration areas or quantify stress states based solely on temperature anomalies.

[0004] Therefore, there is an urgent need for a monitoring method that integrates the synchronous sensing of three parameters: temperature, strain, and stress. This method can capture the evolution of temperature and strain fields inside concrete in real time, construct a mechanical mechanism map of defect initiation, and achieve early warning based on dynamic stress field reconstruction. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose an optical fiber monitoring device and method for the entire process of concrete hydration and hardening. This invention solves the technical problem that existing single temperature field monitoring methods lack specificity in their response characteristics to internal defects in concrete, and cannot accurately locate stress concentration areas and quantify stress states based solely on temperature anomalies.

[0006] In a first aspect, the present invention provides an optical fiber monitoring device for the entire process of concrete hydration and hardening, comprising: a coupled array grating strain optical cable, a guided array grating temperature optical cable, a fusion splice, an optical fiber patch cord, a grating array strain demodulator, a network cable, and a host computer; the coupled array grating strain optical cable and the guided array grating temperature optical cable are embedded in the concrete, and are connected by a fusion splice; the fusion splice is connected to the grating array strain demodulator by an optical fiber patch cord; the grating array strain demodulator is connected to the host computer by a network cable.

[0007] Secondly, the present invention provides a fiber optic monitoring method for the entire process of concrete hydration and hardening, comprising the following steps:

[0008] S1, Reference Calibration: Obtain the initial center wavelength information of each strain grating. and the initial center wavelength information of each temperature grating ;

[0009] S2. Synchronous Data Acquisition: Obtain the real-time center wavelength information of each strain grating. and real-time center wavelength information of each temperature grating ;

[0010] S3. Wavelength offset calculation: based on the initial center wavelength information of each strain grating. Initial center wavelength information of each temperature grating Real-time center wavelength information of each strain grating and real-time center wavelength information of each temperature grating Obtain real-time wavelength offset information for each strain grating. Real-time wavelength offset information of each temperature grating ;

[0011] S4. Temperature Compensation and Strain Separation: Based on Real-Time Wavelength Offset Information of Each Temperature Grating Obtain temperature change information at the corresponding location Based on the real-time wavelength offset information of each strain grating Obtain true strain change information ;

[0012] S5. Full-field reconstruction and output: Based on the mapping relationship between raster numbers and spatial coordinates, the internal temperature field distribution of concrete is generated. (x, y, z, t) and strain field distribution (x, y, z, t), real-time output of temperature-time curves and strain-time curves for the entire process of concrete hydration and hardening;

[0013] Where i refers to the strain grating number, 1≤i≤n; j refers to the temperature grating number, 1≤j≤m.

[0014] Compared with the prior art, the beneficial effects of the present invention include:

[0015] Based on the distributed monitoring capabilities of grating arrays, this invention can monitor the distribution of temperature, strain, and stress fields throughout the entire process of concrete hydration and hardening. It can accurately locate stress concentration areas and quantify stress states, and can lock high-risk coordinates and provide early warnings at the crack initiation stage. This provides technical assurance for zero cracking throughout the entire life cycle of major projects such as nuclear power plant containment structures and water conservancy dams, and promotes the health monitoring of concrete structures from single-point sampling to all-time and all-domain monitoring. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of one embodiment of the fiber optic monitoring device for the entire process of concrete hydration and hardening provided by the present invention.

[0017] Figure 1 In the middle, 1. Concrete, 2. Coupling-type array grating strain optical cable, 3. Conducting-type array grating temperature optical cable, 4. Fusion joint, 5. Fiber optic patch cord, 6. Grating array strain demodulator, 7. Network cable, 8. Host computer, 2-1 to 2-n, strain grating, 3-1 to 3-m, temperature grating. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Please see Figure 1 In a first aspect, the present invention provides an optical fiber monitoring device for the entire process of concrete hydration and hardening, comprising: a coupled array grating strain optical cable 2, a guided array grating temperature optical cable 3, a fusion splice 4, an optical fiber patch cord 5, a grating array strain demodulator 6, a network cable 7, and a host computer 8; the coupled array grating strain optical cable 2 and the guided array grating temperature optical cable 3 are embedded in concrete 1, and are connected by the fusion splice 4; the fusion splice 4 is connected to the grating array strain demodulator 6 by the optical fiber patch cord 5; the grating array strain demodulator 6 is connected to the host computer 8 by the network cable 7.

[0020] In this invention, the coupled array grating strain optical cable 2 is used to monitor the settlement strain and stress during the initial stage of concrete hydration and the thermal expansion strain and stress during the hardening period in real time; the guided array grating temperature optical cable 3 is used to monitor the internal temperature changes of concrete from the initial stage of hydration to the final stage of hardening in real time; the fusion joint 4 is used to fuse the ends of the two optical cables into a single output channel, ensuring that the reflection spectrum is transmitted along the same path, eliminating the time scale deviation of the two channels, and making the synchronization error ≤1ms; the grating array strain demodulator 6 is configured to synchronously acquire and demodulate the wavelength information of each marker grating (2-1 to 2-n and 3-1 to 3-m) with the same time reference and sampling frequency, and obtain the strain measurement value and temperature measurement value of the corresponding discrete spatial position point inside the concrete; the host computer 8 is used to receive the synchronous temperature and strain data from the grating array strain demodulator 6, and calculate the stress inside the concrete based on this data, generating curves or spectra that reflect the evolution of the temperature field, strain field and stress field throughout the entire process of concrete hydration and hardening.

[0021] In this embodiment, the surface of the modulated array grating strain optical cable 2 is encapsulated with a modulus-adaptive carbon mineralization encapsulation layer.

[0022] Preferably, the raw materials for the modulus-adaptive carbon mineralization encapsulation layer include: a first carbon mineralization material, a modulus adjuster, and a first silane coupling agent.

[0023] In this invention, the modulus-adaptive carbon mineralization encapsulation layer utilizes the enhanced mineralization of the first carbon mineralization material in an alkaline environment to construct a dense barrier resistant to alkaline corrosion and hydrogen loss; a modulus modulator is used to achieve progressive mechanical adaptation between the encapsulation layer and the concrete and optical fiber, ensuring high-fidelity stress / strain transfer and suppressing microbending loss; a first silane coupling agent is used to establish a stable chemical interface resistant to humid heat and alkaline corrosion, preventing delamination failure; the three work together to ensure the long-term stable and precise service of the optical fiber in the complex chemical-mechanical environment of concrete.

[0024] More preferably, by mass parts, the raw materials of the modulus-adaptive carbon mineralization encapsulation layer include: 75-92 parts of the first carbon mineralization material, 5-15 parts of the modulus adjuster, and 0.8-3 parts of the first silane coupling agent.

[0025] More preferably, the first carbon mineralization material includes one or more of the following: dicalcium silicate γ-type, monocalcium silicate, tricalcium disilicate, steel slag, magnesium slag, etc.

[0026] More preferably, the modulus modulator includes one or more of silica aerogel micropowder, elastomer particles, aramid fibers, etc.

[0027] More preferably, the first silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane.

[0028] Preferably, the thickness of the modulus-adaptive carbon mineralization encapsulation layer is 0.5-2 mm.

[0029] In this embodiment, the method for fabricating a tuned-coupled array grating strain optical cable includes the following steps:

[0030] The first carbon mineralizing material, the modulus regulator, the first silane coupling agent and water are mixed to obtain the first mixture.

[0031] The first mixture is coated onto the surface of the array grating strained optical cable to obtain the first green blank;

[0032] The first green embryo undergoes a first carbon mineralization process to obtain a modulated array grating strain optical cable.

[0033] Preferably, during the mixing process of the first carbon mineralizing material, the modulus regulator, the first silane coupling agent and water, the water-to-solid ratio is 0.15-0.25.

[0034] Preferably, during the first carbon mineralization process, the carbon dioxide pressure is 0.1-0.3 MPa, the temperature is 20-50℃, the relative humidity is 50%-95%, the carbon dioxide concentration is 20%-100%, and the carbon mineralization time is 1-3 hours.

[0035] In this embodiment, the surface of the conductive array grating temperature optical cable 3 is encapsulated with a thermally conductive carbon mineralization encapsulation layer.

[0036] Preferably, the raw materials for the thermally conductive carbon mineralization encapsulation layer include: a second carbon mineralization material, a high thermal conductivity filler, and a second silane coupling agent.

[0037] In this invention, the thermally conductive carbon mineralization encapsulation layer utilizes the enhanced mineralization of a second carbon mineralization material in an alkaline environment to construct a dense barrier resistant to alkaline corrosion and hydrogen loss; a high thermal conductivity filler is used to form a continuous thermally conductive path, ensuring that the optical fiber accurately senses the true temperature of the concrete and simultaneously eliminates the interference of thermal stress on the optical signal; a second silane coupling agent is used to establish a stable chemical interface that resists humid heat and alkaline corrosion, preventing delamination failure and improving the durability of the encapsulation; the three elements work together to ensure high-fidelity, high-synchronization, and high-reliability monitoring of the optical fiber in the complex thermo-mechanical coupling environment of concrete.

[0038] More preferably, by mass parts, the raw materials of the thermally conductive carbon mineralization encapsulation layer include: 80-95 parts of the second carbon mineralization material, 5-15 parts of the high thermal conductivity filler, and 0.5-2 parts of the second silane coupling agent.

[0039] More preferably, the second carbon mineralization material includes one or more of the following: dicalcium silicate γ-type, monocalcium silicate, tricalcium disilicate, steel slag, magnesium slag, etc.

[0040] More preferably, the high thermal conductivity filler includes one or more of expanded graphite, boron nitride, carbon nanotubes, and graphene oxide.

[0041] More preferably, the second silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane.

[0042] Preferably, the thickness of the thermally conductive carbon mineralization encapsulation layer is 0.5-2 mm.

[0043] In this embodiment, the method for fabricating a guided array grating temperature optical cable includes the following steps:

[0044] The second carbon mineralization material, the high thermal conductivity filler, the second silane coupling agent and water are mixed to obtain the second mixture.

[0045] The second mixture is coated onto the surface of the array grating temperature optical cable to obtain the second green blank;

[0046] The second green embryo undergoes a second carbon mineralization process to obtain a conductive array grating temperature optical cable.

[0047] Preferably, during the mixing of the second carbon mineralization material, the high thermal conductivity filler, the second silane coupling agent, and water, the water-to-solid ratio is 0.15-0.25.

[0048] Preferably, during the second carbon mineralization process, the carbon dioxide pressure is 0.1-0.3 MPa, the temperature is 20-50℃, the relative humidity is 50%-95%, the carbon dioxide concentration is 20%-100%, and the carbon mineralization time is 1-3 hours.

[0049] This invention pioneers a distributed dual-optical-cable collaborative sensing and dynamic decoupling technology. By optimizing the heat conduction path and elastic modulus matching of the temperature and strain optical cables enhanced by the encapsulation layer, the sensing sensitivity of the optical cables to the internal temperature and strain of concrete is significantly improved. This enables synchronous reconstruction and millimeter-level spatial analysis of the internal temperature field, strain field, and stress field of concrete throughout its entire service life, from the initial stage of hydration reaction to hardening.

[0050] In this embodiment, the coupled array grating strain optical cable 2 contains n fiber Bragg gratings discretely distributed along its length direction, respectively labeled as strain gratings 2-1, 2-2, ..., 2-n. The grating spacing is adjustable according to the monitoring accuracy requirements, ranging from 10cm to 1m. The guided array grating temperature optical cable 3 contains m fiber Bragg gratings discretely distributed along its length direction, respectively labeled as temperature gratings 3-1, 3-2, ..., 3-m. The grating positions are spatially matched with the strain grating positions. Here, n and m are both positive integers ≥1.

[0051] In this invention, the one-to-one spatial matching of the temperature grating position and the strain grating position means that the temperature grating and the strain grating are axially aligned in the same monitoring area with a deviation of ≤5mm.

[0052] In this embodiment, the coupled array grating strain optical cable 2 and the conductive array grating temperature optical cable 3 are set according to the first optical cable spacing d1 to ensure that the paired gratings are axially aligned with a deviation of ≤5mm, and are embedded in concrete according to the preset three-dimensional mesh structure.

[0053] Preferably, the spacing d1 of the first optical cable is ≤1cm.

[0054] Preferably, in critical areas of concrete (i.e., constraint boundaries, geometric abrupt changes, etc.), the second optical cable spacing (i.e., the embedment spacing) d2 ≤ 10 cm; in non-critical areas of concrete (i.e., large-volume uniform regions), the second optical cable spacing d2 ≤ 50 cm, that is, the spacing in non-critical areas can be relaxed to 10-50 cm.

[0055] In this invention, the constraint boundary refers to the connection interface between the vertical component and the underlying rigid foundation (such as the base plate or pile cap) (such as the wall base or column foot), the joint surface of concrete poured at different times, and the area around rigid embedded parts (reinforcing bars) embedded in the concrete; the geometric abrupt change refers to the part of the structure where the shape and size change abruptly or discontinuously, such as concave corners ("L"-shaped inner wall corners), convex corners, and the junctions where the cross-sectional dimensions change abruptly. Due to the special nature of the structure, the distribution of optical fibers needs to be restricted at the constraint boundary and the geometric abrupt change.

[0056] In this embodiment, the fiber optic monitoring device for the entire process of concrete hydration and hardening also includes an alarm (not shown in the figure), which is connected to the host computer 8 via a network cable.

[0057] Secondly, the present invention provides a fiber optic monitoring method for the entire process of concrete hydration and hardening, comprising the following steps:

[0058] S1, Reference Calibration: Obtain the initial center wavelength information of each strain grating. and the initial center wavelength information of each temperature grating ;

[0059] S2. Synchronous Data Acquisition: Obtain the real-time center wavelength information of each strain grating. and real-time center wavelength information of each temperature grating ;

[0060] S3. Wavelength offset calculation: based on the initial center wavelength information of each strain grating. Initial center wavelength information of each temperature grating Real-time center wavelength information of each strain grating and real-time center wavelength information of each temperature grating Obtain real-time wavelength offset information for each strain grating. Real-time wavelength offset information of each temperature grating ;

[0061] S4. Temperature Compensation and Strain Separation: Based on Real-Time Wavelength Offset Information of Each Temperature Grating Obtain temperature change information at the corresponding location Based on the real-time wavelength offset information of each strain grating Obtain true strain change information ;

[0062] S5. Full-field reconstruction and output: Based on the mapping relationship between raster numbers and spatial coordinates, the internal temperature field distribution of concrete is generated. (x, y, z, t) and strain field distribution (x, y, z, t), real-time output of temperature-time curves and strain-time curves for the entire process of concrete hydration and hardening;

[0063] Where i refers to the strain grating number, 1≤i≤n; j refers to the temperature grating number, 1≤j≤m.

[0064] In this embodiment, step S1 includes:

[0065] S11. After the concrete is poured and before the hardening begins, the grating array strain demodulator 6 performs synchronously at the first preset sampling frequency.

[0066] S12. Transmit broadband light source signals to the coupled array grating strain optical cable 2 and the guided array grating temperature optical cable 3, and receive the reflection spectrum of each grating;

[0067] S13. Analyze the peak values ​​of the reflection spectra of each grating to obtain the initial center wavelength information of each strain grating (2-1, 2-2, ..., 2-n). and the initial center wavelength information of each temperature grating (3-1, 3-2, ..., 3-m) .

[0068] In this embodiment, step S2 includes:

[0069] S21. During the concrete hardening process, the grating array strain demodulator 6 is executed synchronously at the second preset sampling frequency.

[0070] S22. Transmit broadband light source signals to the coupled array grating strain optical cable 2 and the guided array grating temperature optical cable 3, and receive the reflection spectrum of each grating;

[0071] S23. Analyze the peak values ​​of the reflection spectrum of each grating to obtain the real-time center wavelength information of each strain grating. and real-time center wavelength information of each temperature grating .

[0072] In this invention, the first preset sampling frequency and the second preset sampling frequency are the same.

[0073] Preferably, in steps S1 and S2, the sampling time deviation between the spatially matched strain grating and the temperature grating is ≤1ms.

[0074] Preferably, in steps S1 and S2, the wavelength demodulation interval between adjacent gratings is ≤0.1 pm.

[0075] Preferably, in step S3, the real-time wavelength offset of each grating is calculated in real time by the grating array strain demodulator 6.

[0076] Preferably, in step S3, the formula for calculating the real-time wavelength offset of each strain grating (i.e., the total offset of each strain grating) is as follows:

[0077] = - .

[0078] Preferably, in step S3, the calculation formula for the real-time wavelength offset of each temperature grating (i.e., the pure temperature offset of each temperature grating) is as follows:

[0079] = - .

[0080] In this embodiment, in step S4, The calculation formula is as follows:

[0081] ;

[0082] in, The temperature sensitivity coefficient of the temperature grating is expressed in pm / °C.

[0083] Specifically, The calibration method is as follows: A temperature grating in a free state (i.e., without any mechanical constraints) is heated at a first heating rate (1-10℃ / min, including but not limited to 1℃ / min, 2℃ / min, 5℃ / min, 8℃ / min, 10℃ / min, etc.) from a first temperature (15-30℃, including but not limited to 15℃, 20℃, 25℃, 30℃, etc.) to a second temperature (60-100℃, including but not limited to 60℃, 70℃, 80℃, 90℃, 100℃, etc.), and the actual temperature value is recorded. Simultaneously, the real-time center wavelength of the grating is measured using a demodulator. ,right The slope of the linear fit to the relationship curve is... .

[0084] In this embodiment, in step S4, The calculation formula is as follows:

[0085] ;

[0086] Where k is the temperature grating number that matches the spatial position of strain grating i; The temperature-strain cross-sensitivity coefficient of the strain grating (i.e., the coefficient of wavelength change of the strain grating caused by temperature change), unit: pm / °C; The strain sensitivity coefficient of the strain grating, unit: pm / .

[0087] Specifically, The calibration method is as follows: The strain grating, which is in a free state (i.e., without any mechanical constraints and with zero stress), is heated at a second heating rate (1-10℃ / min, including but not limited to 1℃ / min, 2℃ / min, 5℃ / min, 8℃ / min, 10℃ / min, etc.) from a third temperature (15-30℃, including but not limited to 15℃, 20℃, 25℃, 30℃, etc.) to a fourth temperature (60-100℃, including but not limited to 60℃, 70℃, 80℃, 90℃, 100℃, etc.), and the actual temperature values ​​are recorded. Simultaneously, the real-time center wavelength of the grating is measured using a demodulator. ,right The slope of the linear fit to the relationship curve is... Furthermore, the first heating rate is the same as the second heating rate, the first temperature is the same as the third temperature, and the second temperature is the same as the fourth temperature.

[0088] Specifically, The calibration method is as follows: firmly attach the strain grating to the calibration beam, and use the first strain rate (1-10) / s, including but not limited to 1 / s、2 / s、5 / s、8 / s、10 / s etc.) by the first strain (0-100 , including but not limited to 0 10 30 50 70 90 100 (etc.) upgraded to the second strain (100-1000) , including but not limited to 100 200 400 500 800 1000 (etc.), while simultaneously measuring the real-time center wavelength of the grating. ,right The slope of the linear fit to the relationship curve is... .

[0089] In this embodiment, the fiber optic monitoring method for the entire process of concrete hydration and hardening further includes:

[0090] Step S6, Stress field calculation: based on strain change information Temperature change information and the elastic modulus of concrete and coefficient of thermal expansion This generates the stress field distribution in the concrete: ; and optionally,

[0091] Step S7, Risk Alert: If any location point If the concrete tensile strength threshold is exceeded, the host computer triggers a cracking risk alarm and accurately locates the high-risk area based on the mapping relationship between the grating number and spatial coordinates.

[0092] In this invention, the elastic modulus of concrete The elastic modulus was obtained by measuring the elastic modulus of specimens cured under the same conditions at different ages.

[0093] In this invention, the coefficient of thermal expansion of concrete is typically 10. / ℃.

[0094] This invention does not limit the tensile strength threshold; those skilled in the art can select it according to actual conditions. For example, the tensile strength threshold can be continuously adjusted within the range of 1.4 to 2.3 MPa.

[0095] In this invention, the grating array strain demodulator 6 acquires the reflection spectrum via fiber optic patch cord 5, incorporates a high-precision photodetector with a wavelength resolution ≤0.1 pm, and synchronously analyzes the real-time wavelength offset information of each strain grating. and real-time wavelength offset information of each temperature grating The temperature calculation was obtained through signal processing unit analysis: The strain solution is obtained by executing a temperature compensation algorithm in real time: The host computer 8 is connected to the grating array strain demodulator 6 via network cable 7 to realize data fusion and decision-making based on strain and temperature values, and simultaneously based on strain values. and temperature value Combined with the elastic modulus of concrete and coefficient of thermal expansion Generates stress field distribution: If any position point If the concrete tensile strength threshold is exceeded, the host computer triggers a cracking risk alarm and accurately locates the high-risk area based on the mapping relationship between the grating number and spatial coordinates.

[0096] Example 1

[0097] Please see Figure 1 The fiber optic monitoring device for the entire process of concrete hydration and hardening in this embodiment includes: a coupled array grating strain optical cable 2, a guided array grating temperature optical cable 3, a fusion splice 4, an optical fiber patch cord 5, a grating array strain demodulator 6, a network cable 7, and a host computer 8; the coupled array grating strain optical cable 2 and the guided array grating temperature optical cable 3 are embedded in the concrete 1 and connected by the fusion splice 4; the fusion splice 4 is connected to the grating array strain demodulator 6 by the optical fiber patch cord 5, and the grating array strain demodulator 6 is connected to the host computer 8 by the network cable 7.

[0098] Among them, the surface of the modulated array grating strain optical cable 2 is encapsulated with a modulus-adaptive carbon mineralization encapsulation layer with a thickness of 1 mm; the surface of the conductive array grating temperature optical cable 3 is encapsulated with a thermally conductive carbon mineralization encapsulation layer with a thickness of 1 mm. By mass parts, the raw materials of the modulus-adaptive carbon mineralization encapsulation layer include: 18 parts water, 90 parts carbon mineralization material (magnesium slag), 5 parts modulus adjuster (silica aerogel micro powder), and 0.8 parts silane coupling agent (γ-aminopropyltriethoxysilane); by mass parts, the raw materials of the thermally conductive carbon mineralization encapsulation layer include: 17 parts water, 85 parts carbon mineralization material (magnesium slag), 10 parts high thermal conductivity filler (boron nitride), and 1 part silane coupling agent (N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane). The preparation method of the above-mentioned coupled array grating strain optical cable 2 includes the following steps: mixing magnesium slag, silica aerogel powder, γ-aminopropyltriethoxysilane and water to obtain a first mixture; placing the array grating strain optical cable in the middle of the mold, so that the first mixture completely covers the optical cable, pressing it tightly to obtain a first green preform; and carbonizing the first green preform in a carbon dioxide atmosphere, with a carbon dioxide pressure of 0.3 MPa, a temperature of 25°C, a relative humidity of 95%, a carbon dioxide concentration of 99%, and a carbonization time of 2 h to obtain the coupled array grating strain optical cable 2. The preparation method of the above-mentioned guided array grating temperature optical cable 3 includes the following steps: mixing magnesium slag, boron nitride, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane with water to obtain a second mixture; placing the array grating temperature optical cable in the middle of the mold, so that the second mixture completely covers the optical cable, pressing it tightly to obtain a second green preform; and carbonizing the second green preform in a carbon dioxide atmosphere, with a carbon dioxide pressure of 0.3 MPa, a temperature of 25°C, a relative humidity of 95%, a carbon dioxide concentration of 99%, and a carbonization time of 2 h to obtain the guided array grating temperature optical cable 3.

[0099] The adjustable-coupled array grating strain optical cable 2 has a strain grating array discretely distributed along its length, and the conductive array grating temperature optical cable 3 has a temperature grating array discretely distributed along its length. The positions of the gratings are spatially matched with the positions of the strain gratings, and the grating spacing inside the optical cable is 10cm. After the adjustable-coupled array grating strain optical cable 2 and the conductive array grating temperature optical cable 3 are tightly connected and fixed in parallel at a spacing of 1cm, the parallel optical cables are arranged in a three-dimensional grid structure with a horizontal and vertical spacing of 20cm and embedded in concrete with dimensions of 0.8m×0.8m×2m.

[0100] The fiber optic monitoring device used for the entire process of concrete hydration and hardening also includes an alarm, which is connected to the host computer 8 via a network cable.

[0101] The fiber optic monitoring method for the entire hydration-hardening process of concrete in this embodiment includes the following steps:

[0102] (1) Reference calibration: After the concrete pouring is completed and before the hardening begins, the grating array strain demodulator 6 performs synchronous operation at the first preset sampling frequency (0.1Hz); it transmits broadband light source signals to the coupled array grating strain optical cable 2 and the guided array grating temperature optical cable 3, and receives the reflection spectrum of each grating; it analyzes the peak value of the reflection spectrum of each grating and obtains the initial center wavelength information of each strain grating (2-1, 2-2, ..., 2-n). and the initial center wavelength information of each temperature grating (3-1, 3-2, ..., 3-m) ;

[0103] (2) Synchronous data acquisition: During the concrete hardening process, the grating array strain demodulator 6 performs synchronously at the second preset sampling frequency (0.1Hz); it transmits broadband light source signals to the coupled array grating strain optical cable 2 and the guided array grating temperature optical cable 3, and receives the reflection spectrum of each grating; it analyzes the peak value of the reflection spectrum of each grating and obtains the real-time center wavelength information of each strain grating. and real-time center wavelength information of each temperature grating ;

[0104] (3) Wavelength offset calculation: The real-time wavelength offset of each grating is calculated in real time using the grating array strain demodulator 6. The calculation formula includes:

[0105] = - (Total offset of each strain grating).

[0106] = - (Pure temperature offset of each temperature grating);

[0107] (4) Temperature compensation and strain separation: based on the real-time wavelength offset of each temperature grating Calculate the temperature change value at the corresponding location. And from the real-time wavelength offset of each strain grating Separate the true strain change value The calculation formula includes:

[0108] ;

[0109] ;

[0110] in, is the temperature sensitivity coefficient of the temperature grating, in pm / °C; k is the temperature grating number that matches the spatial position of the strain grating i. The temperature-strain cross-sensitivity coefficient of the strain grating (i.e., the coefficient of wavelength change of the strain grating caused by temperature change), unit: pm / °C; The strain sensitivity coefficient of the strain grating, unit: pm / .

[0111] Specifically, The calibration method is as follows: Place the temperature grating in a free state (i.e., without any mechanical constraints) into a high-precision constant temperature chamber, and heat it from 20℃ to 80℃ at a heating rate of 5℃ / min, and record the actual temperature value using a precision thermometer. Simultaneously, the real-time center wavelength of the grating is measured using a demodulator. ,right The slope of the linear fit to the relationship curve is... .

[0112] Specifically, The calibration method is as follows: Place the strain grating in a free state (i.e., without any mechanical constraints) into a high-precision constant temperature chamber, and heat it from 20℃ to 80℃ at a heating rate of 5℃ / min, and record the actual temperature value using a precision thermometer. Simultaneously, the real-time center wavelength of the grating is measured using a demodulator. ,right The slope of the linear fit to the relationship curve is... .

[0113] Specifically, The calibration method is as follows: firmly attach the strain grating to the calibration beam, and then... The rate is 50 / s Increased to 500 Simultaneously, the real-time center wavelength of the grating is measured. ,right The slope of the linear fit to the relationship curve is... .

[0114] (5) Full field reconstruction and output: The host computer 8 generates the internal temperature field distribution of the concrete according to the mapping relationship between the raster number and the spatial coordinates. (x, y, z, t) and strain field distribution (x, y, z, t), and output the temperature-time curve and strain-time curve of the entire process of concrete hydration-hardening in real time;

[0115] (6) Stress field calculation: based on strain change information Temperature change information and the elastic modulus of concrete and coefficient of thermal expansion This generates the stress field distribution in the concrete: ;

[0116] (7) Risk Alert: When any location point is detected When the tensile strength of concrete exceeds the threshold (2.1 MPa for C50 concrete), the host computer triggers a cracking risk alarm. Based on the grating number-spatial coordinate mapping table, the high-risk area can be accurately located and cooled.

[0117] Example 2

[0118] The rest of the contents are the same as in Example 1, except that the amount of high thermal conductivity filler is 12 parts and the amount of modulus modifier is 7 parts.

[0119] Example 3

[0120] The rest of the contents are the same as in Example 1, except that the amount of high thermal conductivity filler is 14 parts and the amount of modulus modifier is 9 parts.

[0121] Comparative Example 1

[0122] The rest of the contents are the same as in Example 1, except that the amount of high thermal conductivity filler is 0 parts and the amount of modulus modifier is 0 parts.

[0123] Comparative Example 2

[0124] The rest of the contents are the same as in Example 1, except that the amount of silane coupling agent in the raw materials of both the modulus-adaptive carbon mineralization encapsulation layer and the thermally conductive carbon mineralization encapsulation layer is 0 parts.

[0125] Comparative Example 3

[0126] The rest of the content is the same as in Example 1, except that the carbon mineralization material is replaced with HR-809 epoxy resin, and the two components A and B are mixed in a weight ratio of 2:1.

[0127] Performance testing

[0128] The performance of the fiber optic monitoring devices in different embodiments and comparative examples was evaluated by measuring temperature and strain accuracy. Lower measurement accuracy values ​​indicate better performance of the fiber optic monitoring device. The test results are shown in Table 1. The formulas for calculating temperature and strain measurement accuracy are as follows:

[0129]

[0130] ;

[0131] Where, ΔT precision With Δε precision These represent the accuracy of temperature measurement and the accuracy of strain measurement, respectively. The value is a fixed value of 0.1 pm, determined by the performance of the demodulator. , Obtained by the calibration method in Example 1 above; (°C) (pm) represent the temperature measurement deviation and strain transmission error between the paired gratings, respectively.

[0132] Specifically, the temperature measurement deviation between paired gratings It is obtained through the following steps:

[0133] (1) Using the method in step (4) of Example 1, obtain the center wavelength of the temperature grating in the guided array grating temperature optical cable at a reference temperature T0 (20°C). and temperature sensitivity coefficient K T (Unit: pm / °C) and the center wavelength of the strain grating in a tuned-coupled array grating strained optical cable under the same reference temperature T0 and zero stress state. Temperature-strain cross-sensitivity coefficient (Unit: pm / °C);

[0134] (2) Place the paired guided array grating temperature optical cable and the tuned-coupled array grating strain optical cable in a uniform temperature field and a zero-stress state. Set the initial temperature field value to 20℃. After the temperature reaches the set value, continue to keep it at that temperature for at least 60 minutes to ensure that the temperature at all points of the grating is completely balanced. Record this point as the stable point i=1. Raise the temperature to the next temperature point 30.0℃. After the temperature is reached, keep it at that temperature for at least 60 minutes. Record this as the stable point i=2. Repeat this process, raising the temperature to 40.0℃, 50.0℃, 60.0℃, 70.0℃, and 80.0℃ in sequence, and record the stable points. When the system reaches stability at the i-th temperature point, synchronously record the current wavelength of the temperature grating. and strain grating current wavelength ;

[0135] (3) For a temperature grating, its sensing temperature The solution can be obtained directly from the following formula:

[0136] ;

[0137] For the strain grating, in this zero-stress experiment, its wavelength change was entirely caused by temperature; therefore, its temperature coefficient should be used. To reverse calculate its sensed temperature :

[0138] ;

[0139] At the same measurement point i, the instantaneous deviation of the temperature sensed by the two gratings for:

[0140] ;

[0141] (4) All the results obtained throughout the temperature change experiment For statistical analysis of a data series, the standard deviation of the series is δT, calculated using the following formula:

[0142] .

[0143] Specifically, strain transmission error It is obtained through the following steps:

[0144] (1) Using the method in step (4) of Example 1, obtain the strain sensitivity coefficient of the strain grating in the tuned-coupled array grating strain optical cable. (Unit: pm / µε);

[0145] (2) The coupled array grating strain cable and the foil resistance strain gauge (with an accuracy of ±0.3 µε) are closely arranged side by side and axially aligned, and firmly attached to the same side surface of the reinforced concrete beam used for testing. The entire device is placed in a constant temperature environment of 20℃ to eliminate the influence of temperature changes. A strain of 100 µε is applied to the beam, and the readings of the foil resistance strain gauge are recorded simultaneously. (Unit: µε) and the current center wavelength of the strain grating (Unit: pm), and the initial center wavelength at 20°C without applied strain. ;

[0146] (3) Using the calibration coefficient of the strain grating The apparent strain it "sensed" was calculated from the change in its wavelength. :

[0147] ;

[0148] (4) Calculate the strain transfer error using the following formula:

[0149] .

[0150] Table 1 Test results of temperature measurement accuracy and strain measurement accuracy

[0151]

[0152] Please refer to Table 1. As can be seen from Table 1, the addition of boron nitride significantly improves the temperature measurement accuracy of the arrayed grating temperature optical cable; the addition of silica aerogel powder significantly improves the strain measurement accuracy of the arrayed grating strain optical cable. This is because boron nitride, through its hexagonal in-plane ultra-high thermal conductivity (300-600 W / (m·K)), constructs an efficient heat transfer network in the temperature optical cable encapsulation layer: the plate-like boron nitride horizontally overlaps in the mineralized matrix to form a permeation path, increasing the thermal conductivity to ≥5.8 W / (m·K), shortening the delay time of concrete temperature change transmission to the fiber core by 62% (from 8.5 s → 3.2 s), and increasing the temperature measurement accuracy by 28.6% (from ±0.07℃ → ±0.05℃), achieving millimeter-level real-time tracking of hydration temperature rise; silica aerogel micropowder, with its nanoporous structure with a porosity greater than 90%, reduces the encapsulation layer modulus from 50 GPa to 3-5 GPa. GPa, precisely matching the fiber coating modulus (1-2 GPa): its pores disperse stress concentration, combined with a silane-reinforced high specific surface area interface (bond strength ≥2.5 MPa), improving strain transfer efficiency to greater than 95% and optimizing strain measurement accuracy by 16.7% (from ±1.2 GPa). →±1 ), accurately analyze the early micro-shrinkage of concrete.

[0153] Compared with the prior art, the beneficial effects of the present invention include:

[0154] (1) This invention uses a dual-optical-cable temperature-strain synchronous decoupling mechanism. By utilizing the collaborative analysis of the total offset of the strain grating and the pure temperature variable of the temperature grating, a thermal expansion mechanical transmission chain is established. The real strain is accurately separated by the compensation algorithm, and the constraint stress is reconstructed in real time by the dynamic stress field, thus realizing the analysis of temperature-induced cracking stress in the entire process of concrete hydration-hardening.

[0155] (2) This invention successfully fabricates conductive array grating temperature optical cables and modulus-adaptive array grating strain optical cables by encapsulating array grating temperature optical cables and array grating strain optical cables with thermally conductive carbon mineralization encapsulation layers and modulus-adaptive carbon mineralization encapsulation layers. By optimizing the thermal conduction path and elastic modulus matching of the temperature optical cable and strain optical cable enhanced by the encapsulation layer, the sensing and measurement accuracy of the optical cable for the internal temperature and strain of concrete is significantly improved, realizing the synchronous reconstruction and millimeter-level spatial analysis of the internal temperature field, strain field and stress field of concrete from the initial stage of hydration reaction to the hardened service life.

[0156] (3) By adjusting the spatial density of the grating and the sampling synchronization accuracy, this invention can adapt to the differentiated monitoring needs from thin-walled components to large-volume concrete. Combined with the spatial mapping relationship of the grating number, strain field monitoring is directly converted into equivalent displacement early warning, realizing in-situ diagnosis of stress evolution under arbitrary constraints (i.e., concrete size, shape, etc.).

[0157] (4) Compared with existing traditional electrical sensor monitoring technologies, this invention improves the early temperature and strain identification accuracy to ±0.05℃ / ±1℃ through temperature-strain dual-field synchronous sensing and dynamic decoupling algorithm. The false alarm rate for crack risk is reduced by 90%; and the all-fiber embedded design does not require an external power supply, making it significantly more user-friendly in terms of construction and cost-effectiveness over the entire life cycle than traditional electrical sensors.

[0158] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An optical fiber monitoring device for the entire process of hydration-hardening of concrete, characterized by, include: The components include: a modulated array grating strain gauge optical cable, a guided array grating temperature optical cable, fusion splices, fiber optic patch cords, a grating array strain demodulator, network cables, and a host computer; among which... The coupled array grating strain optical cable and the conductive array grating temperature optical cable are embedded in concrete, and the coupled array grating strain optical cable and the conductive array grating temperature optical cable are connected through the fusion splice. The fusion splice is connected to the grating array strain demodulator via the fiber optic patch cord; The grating array strain demodulator is connected to the host computer via the network cable; The surface of the coupled array grating strain optical cable is encapsulated with a modulus-adaptive carbon mineralization encapsulation layer. The raw materials of the modulus-adaptive carbon mineralization encapsulation layer include: a first carbon mineralization material, a modulus adjuster, and a first silane coupling agent. By mass, the raw materials of the modulus-adaptive carbon mineralization encapsulation layer include: 75-92 parts of the first carbon mineralization material, 5-15 parts of the modulus adjuster, and 0.8-3 parts of the first silane coupling agent. The first carbon mineralization material includes one or more of dicalcium silicate, monocalcium silicate, tricalcium disilicate, steel slag, and magnesium slag. The modulus adjuster includes one or more of silica aerogel micropowder, elastomer particles, and aramid fiber. The first silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane. The thickness of the modulus-adaptive carbon mineralization encapsulation layer is 0.5-2 mm.

2. The device for monitoring the whole process of hydration-hardening of concrete according to claim 1, characterized in that, The method for preparing the tuned-coupled array grating strain optical cable includes the following steps: mixing a first carbon mineralization material, a modulus adjuster, a first silane coupling agent, and water to obtain a first mixture; coating the surface of the array grating strain optical cable with the first mixture to obtain a first green preform; subjecting the first green preform to a first carbon mineralization treatment to obtain the tuned-coupled array grating strain optical cable; during the mixing of the first carbon mineralization material, the modulus adjuster, the first silane coupling agent, and water, the water-to-solid ratio is 0.15-0.25; during the first carbon mineralization treatment, the carbon dioxide pressure is 0.1-0.3 MPa, the temperature is 20-50℃, the relative humidity is 50%-95%, the carbon dioxide concentration is 20%-100%, and the carbon mineralization time is 1-3 hours.

3. The device for monitoring the whole process of hydration-hardening of concrete according to claim 1, characterized in that, The surface of the guided array grating temperature optical cable is encapsulated with a thermally conductive carbon mineralization encapsulation layer; the raw materials of the thermally conductive carbon mineralization encapsulation layer include: a second carbon mineralization material, a high thermal conductivity filler, and a second silane coupling agent; wherein... By weight, the raw materials of the thermally conductive carbon mineralization encapsulation layer include: 80-95 parts of a second carbon mineralization material, 5-15 parts of a high thermal conductivity filler, and 0.5-2 parts of a second silane coupling agent; and / or, The second carbon mineralization material includes one or more of the following: dicalcium silicate γ-type, monocalcium silicate, tricalcium disilicate, steel slag, and magnesium slag; and / or, The high thermal conductivity filler includes one or more of expanded graphite, boron nitride, carbon nanotubes, and graphene oxide; and / or, The second silane coupling agent comprises one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane; and / or, The thickness of the thermally conductive carbon mineralization encapsulation layer is 0.5-2 mm; and / or, The method for preparing the guided array grating temperature optical cable includes the following steps: mixing a second carbon mineralization material, a high thermal conductivity filler, a second silane coupling agent, and water to obtain a second mixture; coating the surface of the array grating temperature optical cable with the second mixture to obtain a second green preform; subjecting the second green preform to a second carbon mineralization treatment to obtain the guided array grating temperature optical cable; during the mixing of the second carbon mineralization material, the high thermal conductivity filler, the second silane coupling agent, and water, the water-to-solid ratio is 0.15-0.25; during the second carbon mineralization treatment, the carbon dioxide pressure is 0.1-0.3 MPa, the temperature is 20-50℃, the relative humidity is 50%-95%, the carbon dioxide concentration is 20%-100%, and the carbon mineralization time is 1-3 hours.

4. The device for monitoring the whole process of hydration-hardening of concrete according to claim 1, characterized in that, The tuned-coupled arrayed grating strain optical cable contains n fiber Bragg gratings discretely distributed along its length, with a grating spacing of 10cm to 1m; the guided arrayed grating temperature optical cable contains m fiber Bragg gratings discretely distributed along its length, with their grating positions spatially matched one-to-one with the strain grating positions; n and m are both positive integers ≥1; and / or, The coupled array grating strain optical cable and the conductive array grating temperature optical cable are set according to the first optical cable spacing d1 to ensure that the paired gratings are axially aligned with a deviation of ≤5mm, and are embedded in concrete according to a preset three-dimensional mesh structure. The spacing of the first optical cable d1 is ≤1cm; in critical areas of concrete, the spacing of the second optical cable d2 is ≤10cm; in non-critical areas of concrete, the spacing of the second optical cable d2 is ≤50cm.

5. A method for monitoring the entire process of hydration-hardening of concrete by means of optical fibers, characterized in that, Includes the following steps: S1, reference calibration: obtain initial center wavelength information of each strain grating and initial center wavelength information of each temperature grating ; S2. Synchronous Data Acquisition: Obtain the real-time center wavelength information of each strain grating. and real-time center wavelength information of each temperature grating ; S3. Wavelength offset calculation: based on the initial center wavelength information of each strain grating. Initial center wavelength information of each temperature grating Real-time center wavelength information of each strain grating and real-time center wavelength information of each temperature grating Obtain real-time wavelength offset information for each strain grating. Real-time wavelength offset information of each temperature grating ; S4, temperature compensation and strain separation: based on the real-time wavelength shift information of each temperature grating Obtain temperature change value information of the corresponding position , based on the real-time wavelength shift information of each strain grating Obtain real strain change value information ; S5, full field reconstruction and output: based on the mapping relationship between the grating number and the spatial coordinates, the internal temperature field distribution of concrete is generated (x, y, z, t) and strain field distribution (x, y, z, t), real-time output temperature-time curve and strain-time curve of the whole process of concrete hydration-hardening; Where i refers to the strain grating number, 1≤i≤n; j refers to the temperature grating number, 1≤j≤m; The fiber optic monitoring method for the entire process of concrete hydration and hardening is implemented by the fiber optic monitoring device for the entire process of concrete hydration and hardening as described in any one of claims 1-4.

6. The method for monitoring the whole process of concrete hydration-hardening by using optical fiber according to claim 5, characterized in that, Step S1 includes: S11. After the concrete pouring is completed and before the hardening begins, the grating array strain demodulator is synchronously executed at the first preset sampling frequency. S12. Transmit broadband light source signals to the coupled array grating strain optical cable and the guided array grating temperature optical cable, and receive the reflection spectrum of each grating; S13, analyze the peak value of the reflection spectrum of each grating, obtain the initial center wavelength information of each strain grating and the initial center wavelength information of each temperature grating .

7. The method for monitoring the entire process of concrete hydration-hardening by using optical fiber according to claim 5, characterized in that, Step S2 includes: S21. During the concrete hardening process, the grating array strain demodulator is executed synchronously at the second preset sampling frequency. S22. Transmit broadband light source signals to the coupled array grating strain optical cable and the guided array grating temperature optical cable, and receive the reflection spectrum of each grating; S23, analyze the peak value of the reflection spectrum of each grating, obtain the real-time center wavelength information of each strain grating and the real-time center wavelength information of each temperature grating .

8. The fiber optic monitoring method for the entire hydration-hardening process of concrete according to claim 5, characterized in that, In step S3, the formula for calculating the real-time wavelength offset of each strain grating is as follows: = - ； The formulas for calculating the real-time wavelength offset of each temperature grating are as follows: = - 。 9. The method for monitoring the entire process of hydration-hardening of concrete according to claim 5, characterized in that, In step S4, The calculation formula is as follows: ； wherein is the temperature sensitivity coefficient of the temperature grating, in pm / °C; The calculation formula is as follows: ； Where k is the temperature grating number that matches the spatial position of strain grating i; The temperature-strain cross-sensitivity coefficient of the strain grating, in pm / °C; The strain sensitivity coefficient of the strain grating, unit: pm / .

10. The method for monitoring the entire process of hydration-hardening of concrete according to claim 5, characterized in that, Also includes: Step S6, Stress field calculation: based on strain change information Temperature change information and the elastic modulus of concrete and coefficient of thermal expansion This generates the stress field distribution in the concrete: ; Step S7, Risk Alert: If any location point If the concrete tensile strength threshold is exceeded, the host computer triggers a cracking risk alarm and accurately locates the high-risk area based on the mapping relationship between the grating number and spatial coordinates.

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