Cement-based sensing material, preparation method therefor, and use thereof

Abstract

Disclosed in the present application are a cement-based sensing material, a preparation method therefor, and the use thereof. The material comprises MXene, DOAS powder and cementing materials, the DOAS powder comprising the following components in percentage by mass: 20%-30% of sodium bis(2-ethylhexyl)sulfosuccinate, 15%-30% of 2-octen-1-yl succinic anhydride, 15%-30% of 3-aminophenylboronic acid and 25%-35% of a surfactant. The material of the present application is applied for measurement of chloride ions in concrete. The present application uses the MXene dispersed in DOAS to construct a conductive network, which has good conductivity and sensitivity, stable properties and good durability, and can serve in concrete constructions for a long time period. The present application uses as main components the cementing materials, such as cement, so that the present application has an expansion coefficient close to that of concrete, and therefore achieves good compatibility and can be applied to various concrete constructions.

Description

[0001] The present disclosure relates to a cement material, and a preparation method and use thereof, and in particular relates to a cement-based sensing material, and a preparation method and use thereof. BACKGROUND

[0002] Concrete, as the most widely used civil engineering material, has the advantages of desirable economy, high fire resistance, and strong composite ability. However, the concrete could suffer from erosion when being exposed to aggressive media contained in the environment. Chloride ion erosion, a common corrosive phenomenon in engineering construction, could not only reduce strength of the concrete but also cause corrosion of steel bars inside the concrete. Therefore, it is of great significance to monitor a chloride ion content in the environment where concrete is located in real-time, thereby providing data support for the safety and service life of concrete structures to ensure the durability and safety of engineering buildings.

[0003] In previous studies, a method of destroying the concrete to collect a powder was used to detect the chloride ion content in concrete. However, this method destroys the structure of concrete and could not achieve real-time monitoring of the concrete. Embedding sensors in the concrete is an important method for monitoring the chloride ion content, and there have been some related studies.

[0004] Patent CN217688687U studies a novel concrete chloride ion sensor that utilizes the redox reaction of metal sheets to allow self-powering. However, voltage stability and power supply time of this self-powering still need further study. Patent CN114264589A discloses a detection device for chloride ion penetration resistance of concrete used in on-site environments, but the device has a relatively complex structure. SUMMARY

[0005] Purpose of the present disclosure:

[0006] A first object of the present disclosure is to provide a cement-based sensing material that could monitor concrete in real-time, and has strong sensitivity and stable performance.

[0007] A second object of the present disclosure is to provide a method for preparing the cement-based sensing material described above.

[0008] A third object of the present disclosure is to provide use of the cement-based sensing material described above in chloride ion detection of a concrete.

[0009] Technical solutions:

[0010] The cement-based sensing material includes the following components: a MXene, a DOAS powder, and a cementitious material; where the DOAS powder includes the following components in mass percentage: 20% to 30% of sodium bis(2-ethylhexyl) sulfosuccinate, 15% to 30% of 2-octen-l-ylsuccinic anhydride, 15% to 30% of 3-aminophenylboronic acid, and 25% to 35% of a surfactant.

[0011] In some embodiments, the DOAS powder accounts for 0.05% to 0.5% of a mass of the MXene. In some embodiments, the MXene accounts for 0.01% to 5% of a mass of the cementitious material.

[0012] In the present disclosure, the DOAS powder is prepared by a process including the steps of

[0013] (1) dispersing the sodium bis(2-ethylhexyl) sulfosuccinate, the 2-octen-l-ylsuccinic anhydride, the 3-aminophenylboronic acid, and the surfactant according to the mass percentage in water to obtain a mixed solution;

[0014] (2) removing oxygen from the mixed solution and conducting reaction under stirring to obtain a reaction mixture; and

[0015] (3) freeze-drying the reaction mixture to obtain the DOAS powder.

[0016] In some embodiments, the MXene is at least one selected from the group consisting of TisC2Tx, Ti2CTx, V2CTX, and Nb2CTx, Tx being at least one selected from the group consisting of a -OH functional group and a -F functional group. The MXene has a large specific surface area and requires more water to be wetted. Moreover, there are Van der Waals' forces between MXene sheets, making aggregation effects and entanglement prone to occur in the solution. Therefore, adding the surfactant to destroy the interlayer force of the MXene is an important method to promote the dispersion of the MXene in water. Meanwhile, the MXene has excellent conductivity. Adding the MXene to the cementitious material could improve the conductivity of the sensing material and form a conductive path inside the sensing material, thus enhancing the sensitivity and conductive stability of the sensing material.

[0017] In some embodiments, the MXene is a two-dimensional single-layer MXene. The two-dimensional single-layer MXene is prepared by a process including: subjecting hydrochloric acid and LiF to reaction and etching a MAX phase or etching a MAX phase with hydrofluoric acid. In some embodiments, the MXene has a particle size of 50 pm to 500 pm, and preferably 300 pm. The MXene has a density of 0.5 g / cm3 to 5.0 g / cm3, and a conductivity of 5,000 S / cm to 20,000 S / cm.

[0018] In some embodiments, the surfactant is at least one selected from the group consisting of sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfonate (SDS), sodium lauryl sulfate (SLS), ammonium lauryl sulfate (ALS), cetyltrimethylammonium bromide (CTAB), sodium octadecyl sulfate, .VA-dimethylformamide (DMF), polysorbate 80, and gum arabic.

[0019] In some embodiments, the cementitious material includes cement and silica fume. In some embodiments, the silica fume has an average particle size of 0.01 pm to 0.5 pm and a specific surface area of 10 g / cm3 to 35 m2 / g. In some embodiments, a mass ratio of the silica fume to the cement is in a range of 0.05 to 0.20, and a water-to-cement ratio is in a range of 0.20 to 0.60.

[0020] In the present disclosure, a method for preparing the cement-based sensing material described above includes the following steps:

[0021] (1) dissolving the MXene in a DOAS dispersion to obtain a solution; and

[0022] (2) adding the cementitious material (being composed of cement and silica fume) to the solution obtained in step (1) to obtain a slurry, and stirring and pouring the slurry into a mold and molding to obtain the cement-based sensing material.

[0023] The present disclosure further provides use of the cement-based sensing material described above in chloride ion detection of a concrete.

[0024] In the present disclosure, the use includes: during preparing the cement-based sensing material, stirring and pouring the slurry into the mold and molding, embedding stainless steel meshes as test electrodes separately at both ends of a longer side of the slurry, welding wires separately to both ends of each of the stainless steel meshes, sealing joints between the wires and the ends with epoxy resin, removing the mold after a test specimen is formed, and subjecting the test specimen to maintenance under standard conditions; and putting a resulting sensing material after the maintenance into a concrete liquid and conducting the chloride ion detection.

[0025] Principle of the present disclosure:

[0026] The cement-based sensing material of the present disclosure uses a novel two-dimensional nanomaterial MXene to construct a conductive network. The cement-based sensing material has desirable conductivity and sensitivity. Moreover, using DOAS dispersion to disperse MXene could not only support the distance between MXene sheets, but also fill the defects in the MXene sheets. In this way, wrinkles and agglomeration of MXene sheets caused by defects are prevented, making the cement-based sensing material stable and durable.

[0027] 2-octen-l-ylsuccinic anhydride in a DOAS powder contains carbon-carbon double bonds and carboxylic acid ligands in the molecule. These bonds and ligands show extremely high chemical reactivity and are prone to a series of reactions such as addition, substitution, and polymerization. In addition, the 2-octen-l-ylsuccinic anhydride molecule has a longer molecular chain and could play a "backbone" role. 3-aminophenylboronic acid in the DOAS powder could be self-assembled to form nanoparticles. The nanoparticles are attached to the molecular chain of 2-octen-l-ylsuccinic anhydride through condensation reaction, thereby supporting a fragile "backbone" part to enhance the stability. On one hand, sodium bis(2-ethylhexyl) sulfosuccinate and a surfactant in the DO AS powder could form a complex with the 2-octen-1 -yl succinic anhydride to become a part of the "backbone". On the other hand, the sodium bis(2-ethylhexyl) sulfosuccinate has a complex molecular chain, which could greatly increase the complexity and stability of the "backbone" when being combined with the 2-octen-1-ylsuccinic anhydride. The four components in the DOAS powder are combined to form complex and stable complexes.

[0028] Compared with dispersants that only add surfactants and other polymers, this complex dispersant destroys the Van der Waals' force between MXene sheets. Moreover, the complex "backbone" could also support the distance between MXene sheets, prevent the MXene sheets from aggregating again, and better promote the dispersion of the sheets. In addition, since some MXene sheets are easily broken or deformed during an ultrasonic process, the "backbone" in the DOAS powder could protect the MXene sheets to prevent their surface from cracking. The components in the complex could also fill defects in the MXene sheet and prevent wrinkles and agglomeration of the MXene sheet caused by these defects.

[0029] Beneficial effects:

[0030] Comparing with the prior art, the present disclosure achieves the following significant effects:

[0031] (1) In the present disclosure, a conductive network is constructed by a DOAS dispersion-dispersed MXene, so that the cement-based sensing material shows desirable conductivity and sensitivity, stable performances, and high durability, and could serve in concrete construction projects for a long time. (2) The cement-based sensing material are mainly composed of the cementitious material such as cement, which exhibits an expansion coefficient close to that of the concrete as well as desirable compatibility, and could be applied to various types of concrete buildings. (3) The sensing material of the present disclosure has low cost and simple preparation process. (4) A sensing element made of the sensing material is embedded in various locations of a concrete structure, and electrical signal changes inside the concrete are transmitted through wires. According to the changes in the electrical signal of the cement-based sensing material, the chloride ions inside the concrete could be monitored, thereby predicting the corrosion degree of the reinforced concrete structure by chloride ions during the service period, and then evaluating a service life of the engineering building. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows an electrochemical impedance spectrum of the cement-based sensing material in Example 1 of the present disclosure in concrete simulation liquids with different chloride ion concentrations;

[0033] FIG. 2 shows an electrochemical impedance spectrum of the cement-based sensing material in Example 2 of the present disclosure in concrete simulation liquids with different chloride ion concentrations;

[0034] FIG. 3 shows an electrochemical impedance spectrum of the cement-based sensing material in Comparative Example 1 of the present disclosure in concrete simulation liquids with different chloride ion concentrations;

[0035] FIG. 4 shows an electrochemical impedance spectrum of the cement-based sensing material in Comparative Example 2 of the present disclosure in concrete simulation liquids with different chloride ion concentrations;

[0036] FIG. 5 shows an electrochemical impedance spectrum of the cement-based sensing material in Comparative Example 3 of the present disclosure in concrete simulation liquids with different chloride ion concentrations;

[0037] FIG. 6 shows an electrochemical impedance spectrum of the cement-based sensing material in Comparative Example 4 of the present disclosure in concrete simulation liquids with different chloride ion concentrations;

[0038] FIG. 7 shows an electrochemical impedance spectrum of the cement-based sensing material in Comparative Example 5 of the present disclosure in concrete simulation liquids with different chloride ion concentrations; and

[0039] FIG. 8 shows a relationship between the impedance and chloride ion concentration of the cement-based sensing material with different MXene doping amounts of the present disclosure in concrete simulation liquids with different chloride ion concentrations. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present disclosure will be further described in details below.

[0041] Example 1

[0042] A DOAS powder consisted of the following components in mass percentage: 20% of sodium bis(2-ethylhexyl) sulfosuccinate, 30% of 2-octen-l-yl succinic anhydride, 15% of 3-aminophenylboronic acid, and 35% of SDBS as a surfactant. The DOAS powder was prepared by the following steps.

[0043] (1.1) At room temperature, the sodium bis(2-ethylhexyl) sulfosuccinate, the 2-octen-l-ylsuccinic anhydride, the 3-aminophenylboronic acid, and the surfactant were dispersed according to the mass percentage in deionized water to obtain a mixed solution.

[0044] (1.2) Nitrogen was introduced into the mixed solution to remove oxygen therein, and the mixed solution was magnetically stirred for 7 h at room temperature to obtain a reaction mixture.

[0045] (1.3) The reaction mixture was freeze-dried to obtain the DOAS powder.

[0046] In this example, a method for preparing a cement-based sensing material was conducted as follows.

[0047] (2.1) The DOAS powder was dispersed in deionized water, and a weighed MXene was added thereto. Where MXene sheets had an average particle size of approximately 300 pm, a density of 2.4 g / cm3, and a conductivity of 10,000 S / cm; the DOS A powder accounted for 0.2% of a mass of the MXene, and the MXene accounted for 1.5% of a mass of a cementitious material. A resulting MXene dispersion was ultrasonically stirred with an ultrasonic machine for 10 min to fully wet the MXene surface with water to obtain a MXene dispersion in which the MXene was evenly dispersed.

[0048] (2.2) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as the cementitious material with a water-to-cement ratio of 0.55, where a mass ratio of the silica fume to the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, while the prepared MXene dispersion was slowly poured into the mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mmxlO mm* 10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends each were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0049] Nyquist spectra of the formed sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0050] Example 2

[0051] A DOAS powder consisted of the following components in mass percentage: 30% of sodium bis(2-ethylhexyl) sulfosuccinate, 15% of 2-octen-l-yl succinic anhydride, 30% of 3-aminophenylboronic acid, and 25% of a surfactant. The DOAS powder was prepared by the following steps.

[0052] (1.1) At room temperature, the sodium bis(2-ethylhexyl) sulfosuccinate, the 2-octen-l-ylsuccinic anhydride, the 3-aminophenylboronic acid, and the surfactant were dispersed according to the mass percentage in deionized water to obtain a mixed solution.

[0053] (1.2) Nitrogen was introduced into the mixed solution to remove oxygen therein, and the mixed solution was magnetically stirred for 7 h at room temperature to obtain a reaction mixture.

[0054] (1.3) The reaction mixture was freeze-dried to obtain the DOAS powder.

[0055] In this example, a method for preparing a the cement-based sensing material was conducted as follows.

[0056] (2.1) The DOAS powder was dispersed in deionized water, and a weighed MXene was added thereto. Where MXene sheets had an average particle size of approximately 300 pm, a density of 2.4 g / cm3, and a conductivity of 10,000 S / cm; the DOSA powder accounted for 0.2% of a mass of the MXene, and the MXene accounted for 1.5% of a mass of a cementitious material. A resulting MXene dispersion was ultrasonically stirred with an ultrasonic machine for 10 min to fully wet the MXene surface with water to obtain a MXene dispersion in which the MXene was evenly dispersed.

[0057] (2.2) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as the cementitious material with a water-to—cement ratio of 0.55, where a mass ratio of the silica fume to the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, while the prepared MXene dispersion was slowly poured into the mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mmxlO mm* 10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0058] Nyquist spectra of the sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0059] Example 3

[0060] This example was conducted similar to Example 1 except that: in step (2.1), the DOAS powder accounted for 0.05% of a mass of the MXene; the MXene accounted for 0.01% of a mass of the cementitious material; and in step (2.2), the mass ratio of the silica fume to the cement was 0.05:1, and the water-to-cement ratio was 0.20.

[0061] Example 4

[0062] This example was conducted similar to Example 1 except that: the DOAS powder accounted for 0.5% of a mass of the MXene; the MXene accounted for 5% of a mass of the cementitious material; and in step (2.2), the mass ratio of the silica fume to the cement was 0.20:1, and the water-to-cement ratio was 0.60.

[0063] Comparative Example 1

[0064] A DOAS powder consisted of the following components in mass percentage: 20% of sodium bis(2-ethylhexyl) sulfosuccinate, 30% of 2-octen-l-yl succinic anhydride, 15% of 3-aminophenylboronic acid, and 35% of SDBS as a surfactant. The DOAS powder was prepared by the following steps.

[0065] (1.1) At room temperature, the sodium bis(2-ethylhexyl) sulfosuccinate, the 2-octen-l-ylsuccinic anhydride, the 3-aminophenylboronic acid, and the surfactant were dispersed according to the mass percentage in deionized water to obtain a mixed solution.

[0066] (1.2) Nitrogen was introduced into the mixed solution to remove oxygen therein, and the mixed solution was magnetically stirred for 7 h at room temperature to obtain a reaction mixture.

[0067] (1.3) The reaction mixture was freeze-dried to obtain the DOAS powder.

[0068] In this example, a method for preparing a cement-based sensing material was conducted as follows.

[0069] (2.1) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as the cementitious material with a water-to-cement ratio of 0.55, where a mass ratio of the silica fume to the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mm* 10 mm* 10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends each were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0070] Nyquist spectra of the formed sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0071] Comparative Example 2

[0072] In this example, a method for preparing a cement-based sensing material was conducted as follows.

[0073] (1.1) A weighed MXene was added to deionized water. Where MXene sheets had an average particle size of approximately 300 pm, a density of 2.4 g / cm3, and a conductivity of 10,000 S / cm; and the MXene accounted for 1.5% of a mass of a cementitious material. A resulting MXene dispersion was ultrasonically stirred with an ultrasonic machine for 10 min to fully wet the MXene surface with water to obtain a MXene dispersion in which the MXene was evenly dispersed.

[0074] (1.2) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as the cementitious material with a water-to-cement ratio of 0.55, where a mass ratio of the silica fume to the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, while the prepared MXene dispersion was slowly poured into the mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mm* 10 mm* 10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends each were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0075] Nyquist spectra of the formed sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0076] Comparative Example 3

[0077] In this example, a method for preparing a cement-based sensing material was conducted as follows.

[0078] (1.1) A surfactant was dispersed in deionized water, and a weighed MXene was added thereto. Where MXene sheets had an average particle size of approximately 300 pm, a density of 2.4 g / cm3, and a conductivity of 10,000 S / cm; the surfactant accounted for 0.2% of a mass of the MXene, and the MXene accounted for 1.5% of a mass of a cementitious material. A resulting MXene dispersion was ultrasonically stirred with an ultrasonic machine for 10 min to fully wet the MXene surface with water to obtain a MXene dispersion in which the MXene was evenly dispersed.

[0079] (1.2) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as the cementitious material with a water-to-cement ratio of 0.55, where a mass ratio of the silica fume and the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, while the prepared MXene dispersion was slowly poured into the mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mm><10 mm* 10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends each were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0080] Nyquist spectra of the formed sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0081] Comparative Example 4

[0082] In this example, a method for preparing a cement-based sensing material was conducted as follows.

[0083] (1.1) A 2-octen-l-ylsuccinic anhydride powder was dispersed in deionized water, and a weighed MXene was added thereto. Where MXene sheets had an average particle size of approximately 300 pm, a density of 2.4 g / cm3, and a conductivity of 10,000 S / cm; the 2-octen-l-ylsuccinic anhydride powder accounted for 0.2% of a mass of the MXene, and the MXene accounted for 1.5% of a mass of a cementitious material. A resulting MXene dispersion was ultrasonically stirred with an ultrasonic machine for 10 min to fully wet the MXene surface with water to obtain a MXene dispersion in which the MXene was evenly dispersed.

[0084] (1.2) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as to obtain the cementitious material with a water-to-cement ratio of 0.55, where a mass ratio of the silica fume to the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, while the prepared MXene dispersion was slowly poured into the mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mm* 10 mm 10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends each were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0085] Nyquist spectra of the formed sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0086] Comparative Example 5

[0087] A DOAS powder consisted of the following components in mass percentage: sodium bis(2-ethylhexyl) sulfosuccinate and 3-aminophenylboronic acid at 4:3, 0% of 2-octen-l-ylsuccinic anhydride, and 0% of a surfactant. The DOAS powder was prepared by the following steps.

[0088] (1.1) At room temperature, the sodium bis(2-ethylhexyl) sulfosuccinate, the 2-octen-l-ylsuccinic anhydride, the 3-aminophenylboronic acid, and the surfactant were dispersed according to the mass percentage in deionized water to obtain a mixed solution.

[0089] (1.2) Nitrogen was introduced into the mixed solution to remove oxygen therein, and the mixed solution was magnetically stirred for 7 h at a room temperature to obtain a reaction mixture.

[0090] (1.3) The reaction mixture was freeze-dried to obtain the DO AS powder.

[0091] In this example, a method for preparing a cement-based sensing material was conducted as follows.

[0092] (2.1) The DOAS powder was dispersed in deionized water, and a weighed MXene was added thereto. Where MXene sheets had an average particle size of approximately 300 pm, a density of 2.4 g / cm3, and a conductivity of 10,000 S / cm; the DOSA powder accounted for 0.2% of a mass of the MXene, and the MXene accounted for 1.5% of a mass of a cementitious material. A resulting MXene dispersion was ultrasonically stirred with an ultrasonic machine for 10 min to fully wet the MXene surface with water to obtain a MXene dispersion in which the MXene was evenly dispersed.

[0093] (2.2) 42.5 N Portland cement and silica fume with an average particle size of 0.3 pm were used as the cementitious material with a water-to-cement ratio of 0.55, where a mass ratio of the silica fume to the cement was 1:9. The weighed cement and silica fume were stirred in a mixer, while the prepared MXene dispersion was slowly poured into the mixer, and stirred for 2 min. A resulting sensing material slurry was poured into a 30 mm><10 mm><10 mm mold and molded. Where the mold was vibrated on a vibrating table for 1 min to eliminate air bubbles in the slurry. Stainless steel meshes as test electrodes were embedded separately at both ends of a longer side of the slurry. Wires were welded separately to both ends of each of the stainless steel meshes. Joints between the wires and the ends each were sealed with epoxy resin. The mold was removed 1 day after a test specimen was formed, and the test specimen was subjected to maintenance under standard conditions.

[0094] Nyquist spectra of the formed sensing material in concrete simulated liquids with chloride ion contents of 0 mol / L, 0.5 mol / L, 1.0 mol / L, and 1.5 mol / L were separately measured by a PARATAT 2273 electrochemical workstation. The measurement was conducted at a sinusoidal potential with an amplitude of 5 mV to 20 mV and a frequency of 0.01 Hz to 1,000 kHz.

[0095] As shown in FIG. 1 and FIG. 2, in concrete simulated liquids with different chloride ion concentrations, the Nyquist spectra of the electrode of the sensing material consists of two parts: a high-frequency area and a low-frequency area. The abscissa corresponding to a turning point of the high-frequency and low-frequency areas in the Nyquist spectra of the electrode of the sensing material is taken as a reference, that is, real part impedance Rdc. It can be seen that under different chloride ion concentrations, the Rdc in the Nyquist spectra of the electrode of the sensing material decreases with the increase in chloride ion concentration. FIG. 3 to FIG. 4 show Nyquist spectra of the sensing materials in Comparative Example 1 and Comparative Example 2. It can be seen that the response signal of the electrode of the sensing material in Comparative Example 1 is messy, its Rdc does not change significantly with the chloride ion concentration, such that monitoring of the chloride ion concentration could not be completed. Although the response signal of the sensing material in Comparative Example 2 fluctuated slightly, the changes in Rdc under different chloride ion concentrations are small, and the monitoring could not be completed. FIG. 5 to FIG. 7 are Nyquist spectra of the sensing materials in Comparative Examples 3 to 5. As the chloride ion concentration increases, the material's Rdc also decreases, but there is a poor correspondence between the material's Rdc and the chloride ion concentration.

[0096] FIG. 8 shows a changing trend of Rdc in the electrode of the sensing material in Examples 1 to 3 and Comparative Examples 3 to 5 with chloride ion concentration. Table 1 shows fitting results of the chloride ion concentration and Z' in FIG. 8. It can be seen that the Rdc in the electrode of the sensing material gradually decreases as the chloride ion concentration in the concrete simulation liquid increases. When the MXene content is 1.5% and the DOAS powder dispersant is added, the sensing material's Rdc shows a desirable linear relationship with the change in chloride ion concentration. Therefore, the chloride ion concentration in the concrete environment could be detected by impedance changes at the intersection of high-frequency and low-frequency areas in the Nyquist spectra of the electrode of the sensing material.

[0097] Table 1 Fitting results of chloride ion concentration and Z' in FIG. 8

[0098] Example Example 1 Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 R2 0.98 0.97 0.89 0.80 0.88

[0099] Although the present disclosure is described in detail in conjunction with the foregoing embodiments, they are only a part of, not all of, the embodiments of the present disclosure. Other embodiments can be obtained based on these embodiments without creative efforts, and all of these embodiments shall fall within the scope of the present disclosure.

Claims

1. A cement-based sensing material, comprising the following components:a MXene, a DOAS powder, and a cementitious material;wherein the DOAS powder comprises the following components in mass percentage: 20% to 30% of sodium bis(2-ethylhexyl) sulfosuccinate, 15% to 30% of 2-octen-l-yl succinic anhydride, 15% to 30% of 3-aminophenylboronic acid, and 25% to 35% of a surfactant.

2. The cement-based sensing material of claim 1, wherein the DOAS powder accounts for 0.05% to 0.5% of a mass of the MXene.

3. The cement-based sensing material of claim 1 or 2, wherein the MXene accounts for 0.01% to 5% of a mass of the cementitious material.

4. The cement-based sensing material of claim 1, wherein the DOAS powder is prepared by a process comprising the steps of(1) dispersing the sodium bis(2-ethylhexyl) sulfosuccinate, the 2-octen-l-ylsuccinic anhydride, the 3-aminophenylboronic acid, and the surfactant according to the mass percentage in water to obtain a mixed solution;(2) removing oxygen from the mixed solution and conducting reaction under stirring to obtain a reaction mixture; and(3) freeze-drying the reaction mixture to obtain the DOAS powder.

5. The cement-based sensing material of claim 1, wherein the MXene is at least one selected from the group consisting of Ti3C2Tx, Ti2CTx, V2CTX, and Nb2CTx, Tx being at least one selected from the group consisting of a -OH functional group and a -F functional group.

6. The cement-based sensing material of claim 5, wherein the MXene is a two-dimensional single-layer MXene.

7. The cement-based sensing material of claim 5 or 6, wherein the MXene has a particle size of 50 pm to 500 pm, a density of 0.5 g / cm3 to 5.0 g / cm3, and a conductivity of 5,000 S / cm to 20,000 S / cm.

8. The cement-based sensing material of claim 1 or 4, wherein the surfactant is at least oneselected from the group consisting of sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfonate (SDS), sodium lauryl sulfate (SLS), ammonium lauryl sulfate (ALS), cetyltrimethylammonium bromide (CTAB), sodium octadecyl sulfate, A^A^-di methyl form am ide (DMF), polysorbate 80, and gum arabic.

9. The cement-based sensing material of claim 1, wherein the cementitious material comprises cement and silica fume.

10. The cement-based sensing material of claim 9, wherein the silica fume has an average particle size of 0.01 pm to 0.5 pm and a specific surface area of 10 m2 / g to 35 m2 / g.

11. The cement-based sensing material of claim 9, wherein a mass ratio of the silica fume to the cement is in a range of 0.05 to 0.20, and a water-to-cement ratio is in a range of 0.20 to 0.60.

12. A method for preparing the cement-based sensing material of claim 1, comprising the following steps:(1) dissolving the MXene in a DOAS dispersion to obtain a solution; and(2) adding the cementitious material to the solution obtained in step (1) to obtain a slurry, and stirring and pouring the slurry into a mold and molding to obtain the cement-based sensing material.

13. The preparation method of claim 12, wherein the cementitious material is composed of cement and silica fume.

14. Use of the cement-based sensing material of any one of claims 1 to 11 or the cement-based sensing material prepared by the method of claim 12 or 13 in chloride ion detection of a concrete.

15. The use of claim 14, comprising:during preparing the cement-based sensing material, stirring and pouring a slurry into a mold and molding, embedding stainless steel meshes as test electrodes separately at both ends of a longer side of the slurry, welding wires separately to both ends of each of the stainless steel meshes, sealing joints between the wires and the ends with epoxy resin, removing the mold after a test specimen is formed, and subjecting the test specimen to maintenance under standard conditions; andputting a resulting sensing material after the maintenance into a concrete liquid and conducting the chloride ion detection.

16. A sensing element, which is prepared by a process comprising the steps of(1) dissolving a MXene in a DOAS dispersion to obtain a solution;(2) adding a cementitious material to the solution in step (1) to obtain a slurry, stirring and pouring the slurry into a mold and molding, embedding stainless steel meshes as test electrodes at both ends of a longer side of the slurry; welding wires to both ends of each of the stainless steel meshes, sealing joints between the wires and the ends with epoxy resin, removing the mold after a test specimen is formed, and subjecting the test specimen to maintenance under standard conditions.

17. A DOAS powder, comprising the following components in mass percentage:20% to 30% of sodium bis(2-ethylhexyl) sulfosuccinate, 15% to 30% of 2-octen-l-ylsuccinic anhydride, 15% to 30% of 3-aminophenylboronic acid, and 25% to 35% of a surfactant.

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