Carbonized polymer point modified hydrated calcium silicate film for humidity monitoring and preparation method and application of carbonized polymer point modified hydrated calcium silicate film

Abstract

The invention relates to a carbonized polymer point modified calcium silicate hydrate film for humidity monitoring and a preparation method and application thereof. The carbonized polymer point modified calcium silicate hydrate film takes a calcium silicate hydrate film as a matrix, and carbonized polymer points are uniformly dispersed in the calcium silicate hydrate film. The preparation method comprises the following steps: preparing carbonized polymer dot powder; uniformly mixing the carbonized polymer dot powder, water, a calcareous material and a siliceous material to obtain turbid liquid; regulating the pH value of the turbid liquid by using a pH regulator, and uniformly mixing; stirring and reacting under water bath heating; and after the reaction is completed, carrying out suction filtration and drying to obtain the carbonized polymer point modified hydrated calcium silicate film. Compared with the prior art, by introducing the carbonized polymer points, the electronic conductivity of the C-S-H material is improved, and the prepared film can be applied to concrete humidity monitoring and is sensitive in detection.

Description

Technical Field

[0001] The invention relates to the field of concrete structure damage monitoring, and in particular to a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring, and a preparation method and application thereof. Background Art

[0002] Concrete is currently the world's most important building material and is widely used in various engineering structures. However, in a complex and changeable service environment, concrete is susceptible to a variety of factors such as salt-alkali corrosion, freeze-thaw damage, fatigue loads, and steel corrosion. These external environmental effects will gradually cause the concrete structure to deform and crack, especially the internal damage is difficult to detect directly from the outside, posing a serious threat to the service life and safety of the structure. Among them, the most direct impact is the intrusion of water. Therefore, the development of efficient monitoring technology for the depth of external water intrusion into concrete has become one of the key issues that need to be urgently addressed in the current field of building materials research.

[0003] At present, the concrete structure damage monitoring technology mainly introduces conductive fillers into the cement matrix to improve the conductivity of the material and realize real-time perception of damage. Common sensor types include piezoelectric, piezoresistive and magnetoresistive sensors. For example, Chinese patent CN115165971A discloses a concrete structure mechanics and corrosion damage detection and evaluation method based on sensitive materials. The method installs the sensitive material sensor unit at the stress or corrosion risk position of the concrete structure, detects the voltage and current, obtains the resistance value of the sensitive material sensor unit, and realizes the rapid detection of internal damage of the concrete structure. Chinese patent CN108818882A discloses a concrete smart aggregate and its preparation method. By setting a humidity sensor module and a fiber resistor, in the case of failure of the piezoelectric ceramic sensing module, the humidity sensor module and the fiber resistor can also be used to compensate for the failure of the signal acquisition function of the smart aggregate, which is conducive to reducing the possibility of accidents caused by damage to the concrete building structure.

[0004] However, these technologies still have significant bottlenecks, such as poor signal stability (low signal-to-noise ratio and difficult-to-control volatility), agglomeration effect of conductive fillers, rheological properties of slurries, and ion polarization phenomena, which further restrict the improvement of monitoring performance. Summary of the invention

[0005] The purpose of the present invention is to provide a carbonized polymer dot modified calcium silicate hydrate film for humidity monitoring and a preparation method and application thereof. The prepared film can be applied to concrete humidity monitoring and has sensitive detection.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] One of the objectives of the present invention is to provide a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring. The film is based on a calcium silicate hydrate film, and carbonized polymer dots are uniformly dispersed in the calcium silicate hydrate film.

[0008] Preferably, the size of the carbonized polymer dots is 2 nm - 100 nm, and the loading amount of the carbonized polymer dots in the carbonized polymer dot-modified calcium silicate hydrate film is 40 wt% - 80 wt%.

[0009] Preferably,

[0010] The raw materials of the carbonized polymer dots include the following components in parts by mass:

[0011]

[0012] Preferably, the raw materials of the calcium silicate hydrate film include the following components in parts by mass:

[0013]

[0014] Among them, the mass ratio of the calcareous material to the siliceous material is 0.5 - 2.

[0015] More preferably, the mass ratio of the calcareous material to the siliceous material is 2.

[0016] Preferably, the polymer monomer is selected from any one or more of acrylamide and acrylic acid.

[0017] Preferably, the calcareous material is selected from any one or more of calcium chloride, calcium nitrate, quicklime, and calcium hydroxide.

[0018] Preferably, the siliceous material is selected from any one or more of silica fume, rice husk ash, and sodium silicate.

[0019] Preferably, the pH regulator is selected from one or both of sodium hydroxide and dilute hydrochloric acid.

[0020] Another objective of the present invention is to provide a preparation method of the carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring, including the following steps:

[0021] S1: Prepare carbonized polymer dot powder;

[0022] S2: Mix the carbonized polymer dot powder, water, calcareous material, and siliceous material evenly to obtain a suspension;

[0023] S3: Use a pH regulator to adjust the pH value of the suspension and mix evenly;

[0024] S4: Stir and react under water bath heating;

[0025] S5: After the reaction is completed, carry out suction filtration and drying to obtain the carbonized polymer dot-modified hydrated calcium silicate film.

[0026] Preferably, in step S1, the preparation of the carbonized polymer dot powder includes the following steps:

[0027] S1.1: Mix the polymer monomer and water evenly by mass, and then add ammonium persulfate and N,N'-methylenebisacrylamide and mix evenly to obtain a mixed solution;

[0028] S1.2: Carry out a hydrothermal reaction on the mixed solution;

[0029] S1.3: After the hydrothermal reaction is completed, carry out dialysis and rotary evaporation treatment to obtain the carbonized polymer dot powder.

[0030] More preferably, in step S1.1, the "mix evenly" means ultrasonic treatment for 8 - 12 min with an ultrasonic power of 20 W / L - 30 W / L.

[0031] More preferably, in step S1.2, the temperature of the hydrothermal reaction is 160 - 200 °C, the time is 6 - 10 h, and the hydrothermal reaction is carried out in a hydrothermal reaction kettle.

[0032] Even more preferably, in step S1.2, the temperature of the hydrothermal reaction is 180 °C and the time is 8 h.

[0033] More preferably, in step S1.3, the "dialysis" means using a dialysis bag with a pore size of 0.1 - 0.3 μm to screen out macromolecular impurities, and even more preferably using a 0.22 - μm dialysis bag to screen out macromolecular impurities.

[0034] More preferably, in step S1.3, the "rotary evaporation" is used to remove the liquid solvent, and the parameters of the rotary evaporation include a temperature range of 50 - 80 °C and a rotary evaporation time of 1 - 4 h.

[0035] Preferably, in step S2, the "mix evenly" means ultrasonic treatment for 1 - 5 min with an ultrasonic power of 20 W / L - 30 W / L.

[0036] Preferably, in step S3, the pH value of the adjusted suspension is 7 - 9, and more preferably 7 - 8.

[0037] Preferably, in step S3, the "mix evenly" means ultrasonic treatment for 1 - 5 min with an ultrasonic power of 20 W / L - 30 W / L.

[0038] Preferably, in step S4, the temperature of the water bath heating is 30 - 50 °C, the rotation speed of the stirring reaction is 300 rpm - 600 rpm, and the time is 12 h - 24 h.

[0039] Further preferably, in step S4, the temperature of the water bath heating is 40°C, the rotation speed of the stirring reaction is 600 rpm, and the time is 24 h.

[0040] Preferably Further preferably, in step S5, the temperature of the drying is 45°C and the time is 24 h.

[0041] Preferably, the method for preparing the carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring includes the following steps:

[0042] First, mix the polymer monomer and water in proportion by mass, and ultrasonicate for 10 min to obtain a uniform solution A. Then add ammonium persulfate and N,N'-methylenebisacrylamide to solution A in proportion, and ultrasonicate for 10 min to obtain a uniform solution B. Immediately afterwards, pour solution B into a hydrothermal reaction kettle and react at 180°C for 8 h to obtain a yellow transparent solution C. Use a 0.22-μm dialysis bag to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, obtain carbonized polymer dot powder D. Prepare a suspension by mixing the synthesized carbonized polymer dot powder D, water, calcareous material, and siliceous material, and ultrasonicate for 3 min to mix evenly. Use a pH regulator to adjust the pH value of the solution to an appropriate range, and ultrasonicate for 3 min. Then, under a 40-degree water bath, stir and react for 24 h to obtain a suspension E. Filter the suspension E to form a film, and place it in a 45°C vacuum oven to dry for 24 h to obtain a carbonized polymer dot-modified calcium silicate hydrate film F.

[0043] The third object of the present invention is to provide an application of the carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring.

[0044] Preferably, the carbonized polymer dot-modified calcium silicate hydrate film is used for environmental humidity monitoring.

[0045] Preferably, the carbonized polymer dot-modified calcium silicate hydrate film is used for monitoring the internal humidity of cement concrete, including the following steps:

[0046] A: Prepare the carbonized polymer dot-modified calcium silicate hydrate film into a suitable size according to the size of the cement concrete to be monitored;

[0047] B: During the concrete pouring process, bury the carbonized polymer dot-modified calcium silicate hydrate film of a suitable size into the interior of the cement concrete and connect it to an external current detection device;

[0048] C: By observing the change of current, realize the monitoring of the internal humidity of the cement concrete and use it to judge the risk of damage to the cement concrete structure.

[0049] Further preferably, when the internal humidity of the cement concrete is relatively high, it indicates that the cement concrete structure has a certain damage risk; when the internal humidity of the cement concrete is relatively low, it indicates that the amount of external environment intrusion is small and the damage risk of the cement concrete structure is low.

[0050] The present invention proposes a hydrated calcium silicate film (C-S-H) material modified by carbonized polymer dots, which can significantly improve the humidity monitoring performance. As a new type of nanomaterial, carbonized polymer dots have excellent electrical conductivity, high specific surface area, and abundant surface functional groups (such as carbon-oxygen bonds and carbon-nitrogen bonds). By introducing carbonized polymer dots into the C-S-H matrix, not only can its electrical conductivity be significantly improved, but also a sensitive response to humidity scenarios can be achieved, providing a new research path for the development of high-performance humidity monitoring functional materials. In addition, this material has the advantages of simple preparation process, good dispersibility, and excellent compatibility with the matrix. The present invention provides an efficient and reliable new solution for the real-time monitoring, intelligent diagnosis, and multifunctional application of concrete structures, and has important engineering application value and broad industrialization prospects.

[0051] As Figure 1 shown, the present invention improves the electrical conductivity of the composite material by intercalating carbonized polymer dots into the layer spacing of hydrated calcium silicate (C-S-H). During the composite process, due to its nanoscale size, the carbonized polymer dots can effectively insert into the interlayer structure of the C-S-H material, thereby expanding the layer spacing, reducing the interlayer charge shielding effect, and providing more channels for electron migration. At the same time, the nitrogen and oxygen functional groups on the surface of the carbonized polymer dots can form an interfacial bond with the Ca-OH and Si-OH functional groups in the C-S-H, forming a stable bonding effect, and further improving the conduction efficiency of electrons in the composite system.

[0052] The intercalation effect of the carbonized polymer dots not only improves the structural order of the C-S-H interlayer, but also constructs an efficient electron conduction network spanning the interlayer, enabling electrons to quickly pass through the C-S-H interlayer region. During this process, the abundant surface functional groups (such as nitrogen bonds and oxygen bonds) of the carbonized polymer dots form coordination bonds with the calcium ions in the C-S-H interlayer, further stabilizing the intercalation structure and enhancing the continuity of electron conduction. In addition, the uniform distribution of the carbonized polymer dots in the interlayer avoids the phenomenon of uneven local performance caused by poor dispersibility of traditional conductive modified materials.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) The present invention provides a carbonized polymer dot-modified hydrated calcium silicate film for humidity monitoring. The film is modified by introducing carbonized polymer dots into the hydrated calcium silicate film, and successfully endows the hydrated calcium silicate material with a unique humidity-induced electrical conductivity transition ability, having a humidity monitoring function.

[0055] (2) By introducing carbonized polymer dots, the present invention forms a synergistic effect with the Ca-OH and Si-OH functional groups in the C-S-H matrix to construct an efficient electron conduction network, significantly improving the electron conductivity of the C-S-H material and providing the possibility for its application in the fields of energy storage, sensors, and multifunctional materials.

[0056] (3) The carbonized polymer dots in the present invention can be uniformly dispersed in the C-S-H material system, forming a stable interfacial interaction with the matrix, and solving the problems of poor dispersibility and insufficient compatibility of traditional modified materials.

[0057] (4) The present invention adopts a green and environmentally friendly preparation process, avoiding the high energy consumption and complex operations in traditional modification technologies, not only reducing costs but also meeting the requirements for the development of environmentally friendly materials.

[0058] (5) The carbonized polymer dot-modified C-S-H material of the present invention has good tensile strength.

[0059] (6) The carbonized polymer dot-modified C-S-H material in the present invention has good cost advantages, can be prepared on a large scale, and meets the actual needs of the multifunctional material field. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a schematic diagram of the interaction between the carbonized polymer dots and the C-S-H structure of the present invention;

[0061] Figure 2 are the resistance values of the carbonized polymer dot-modified C-S-H (Example 1), pure C-S-H (Comparative Example 1), and nano-carbon black-modified C-S-H (Comparative Example 2) of the present invention;

[0062] Figure 3 is the magnitude of the current value of the carbonized polymer dot-modified C-S-H (Example 1) of the present invention at different humidities. DETAILED DESCRIPTION OF THE INVENTION

[0063] This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0064] Unless otherwise specified, the reagents, methods, instruments, and equipment used in the present invention are conventional reagents, methods, instruments, and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0065] A carbonized polymer dot modified calcium silicate hydrate film for humidity monitoring, the film is based on a calcium silicate hydrate film, and carbonized polymer dots are uniformly dispersed in the calcium silicate hydrate film. The size of the carbonized polymer dots is 2nm - 100nm, and the loading amount of the carbonized polymer dots in the carbonized polymer dot modified calcium silicate hydrate film is 40wt% - 80wt%.

[0066] Among them, the raw materials of the carbonized polymer dots include the following components in parts by mass:

[0067]

[0068] Preferably, the raw materials of the calcium silicate hydrate film include the following components in parts by mass:

[0069]

[0070] Among them, the mass ratio of the calcareous material to the siliceous material is 0.5 - 2.

[0071] Its preparation method is as follows:

[0072] First, mix the polymer monomer and water in proportion by mass, and ultrasonicate for 10 min to obtain a uniform solution A. Then add ammonium persulfate and N,N'-methylenebisacrylamide to solution A in proportion, and ultrasonicate for 10 min to obtain a uniform solution B. Immediately afterwards, pour solution B into a hydrothermal reaction kettle and react at 180 °C for 8 h to obtain a yellow transparent solution C. Use a 0.22 μm dialysis bag to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, obtain carbonized polymer dot powder D. Prepare a suspension of the synthesized carbonized polymer dot powder D, water, calcareous material and siliceous material, and ultrasonicate for 3 min to mix evenly. Use a pH regulator to adjust the pH value of the solution to the appropriate range, and ultrasonicate for 3 min. Then, under a 40 °C water bath, stir and react for 24 h to obtain a suspension E. Filter the suspension E to make a film, and place it in a 45 °C vacuum oven to dry for 24 h to obtain a carbonized polymer dot modified calcium silicate hydrate film F.

[0073] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0074] Example 1:

[0075] A carbonized polymer dot modified calcium silicate hydrate film for humidity monitoring, the raw materials include the following components in parts by mass:

[0076]

[0077] In this embodiment, the composition of the calcium material is as follows: calcium chloride 50wt%, calcium nitrate 20wt%, quicklime 10wt%, calcium hydroxide 20wt%; the composition of the silicon material is as follows: silica fume 30wt%, rice husk ash 10wt%, sodium silicate 60wt%; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0078] First, 10 parts of polymer monomers and 100 parts of water are mixed in proportion and ultrasonicated for 10 min to obtain a uniform solution A. Then, 1 part of ammonium persulfate and 1 part of N,N'-methylenebisacrylamide are added to solution A in proportion and ultrasonicated for 10 min to obtain a uniform solution B. Immediately afterwards, solution B is poured into a hydrothermal reaction kettle and reacted at 180 °C for 8 h to obtain a yellow transparent solution C. The macromolecular impurities in solution C are sieved out using a 0.22 μm dialysis bag, and after rotary evaporation treatment, carbonized polymer dot powder D is obtained. The synthesized carbonized polymer dot powder D, 100 parts of water, 30 parts of calcium material and 20 parts of silicon material are formulated into a suspension, and ultrasonicated for 3 min to mix evenly. The pH value of the solution is adjusted to 8 using 2 parts of pH regulator and ultrasonicated for 3 min, and then stirred and reacted at 40 °C in a water bath for 24 h to obtain a suspension E. The suspension E is filtered to form a film, and placed in a vacuum oven at 45 °C and dried for 24 h to obtain a carbonized polymer dot modified calcium silicate hydrate film F.

[0079] Example 2:

[0080] A carbonized polymer dot modified calcium silicate hydrate film for humidity monitoring, the raw materials including the following components in parts by mass:

[0081]

[0082] In this embodiment, the composition of the calcium material is as follows: calcium chloride 50wt%, calcium nitrate 20wt%, quicklime 10wt%, calcium hydroxide 20wt%; the composition of the silicon material is as follows: silica fume 30wt%, rice husk ash 10wt%, sodium silicate 60wt%; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0083] First, 30 parts of polymer monomers and 100 parts of water were mixed in proportion and ultrasonicated for 10 min to obtain a uniform solution A. Then, 5 parts of ammonium persulfate and 10 parts of N,N'-methylenebisacrylamide were added to solution A in proportion and ultrasonicated for 10 min to obtain a uniform solution B. Immediately afterwards, solution B was poured into a hydrothermal reaction kettle and reacted at 180 °C for 8 h to obtain a yellow transparent solution C. A 0.22 μm dialysis bag was used to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, a carbonized polymer dot powder D was obtained. The synthesized carbonized polymer dot powder D, 200 parts of water, 80 parts of calcareous material and 40 parts of siliceous material were formulated into a suspension, and ultrasonicated for 3 min to mix evenly. 5 parts of pH regulator was used to adjust the pH value of the solution to 8, and ultrasonicated for 3 min. Then, under a 40 °C water bath, it was stirred and reacted for 24 h to obtain a suspension E. The suspension E was filtered to form a film, and placed in a 45 °C vacuum oven to dry for 24 h to obtain a carbonized polymer dot modified calcium silicate hydrate film F.

[0084] Example 3:

[0085] A carbonized polymer dot modified calcium silicate hydrate film for humidity monitoring, the raw materials comprising the following components in parts by mass:

[0086]

[0087] In this example, the composition of the calcareous material is as follows: 50 wt% calcium chloride, 20 wt% calcium nitrate, 10 wt% quicklime, 20 wt% calcium hydroxide; the composition of the siliceous material is as follows: 30 wt% silica fume, 10 wt% rice husk ash, 60 wt% sodium silicate; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0088] First, 50 parts of polymer monomers and 100 parts of water were mixed in proportion and ultrasonicated for 10 min to obtain a uniform solution A. Then, 10 parts of ammonium persulfate and 10 parts of N,N'-methylenebisacrylamide were added to solution A in proportion and ultrasonicated for 10 min to obtain a uniform solution B. Immediately afterwards, solution B was poured into a hydrothermal reaction kettle and reacted at 180 °C for 8 h to obtain a yellow transparent solution C. A 0.22 μm dialysis bag was used to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, a carbonized polymer dot powder D was obtained. The synthesized carbonized polymer dot powder D, 200 parts of water, 100 parts of calcareous material and 50 parts of siliceous material were formulated into a suspension, and ultrasonicated for 3 min to mix evenly. 5 parts of pH regulator was used to adjust the pH value of the solution to 8, and ultrasonicated for 3 min. Then, under a 40 °C water bath, it was stirred and reacted for 24 h to obtain a suspension E. The suspension E was filtered to form a film, and placed in a 45 °C vacuum oven to dry for 24 h to obtain a carbonized polymer dot modified calcium silicate hydrate film F.

[0089] Comparative Example 1

[0090] Different from Example 1, carbonized polymer dots are not used for modification.

[0091] A hydrated calcium silicate film, the raw materials comprising the following components in parts by mass:

[0092]

[0093] In this embodiment, the composition of the calcareous material is as follows: calcium chloride 50 wt%, calcium nitrate 20 wt%, quicklime 10 wt%, calcium hydroxide 20 wt%; the composition of the siliceous material is as follows: silica fume 30 wt%, rice husk ash 10 wt%, sodium silicate 60 wt%; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0094] 100 parts of water, 30 parts of calcareous material and 20 parts of siliceous material are formulated into a suspension, and ultrasonically mixed for 3 min to be uniformly mixed. 2 parts of pH regulator are used to adjust the pH value of the solution to 8, and ultrasonically treated for 3 min, and then stirred and reacted at 40 °C in a water bath for 24 h to obtain suspension E. The suspension E is placed in a vacuum oven at 45 °C and dried for 24 h to obtain hydrated calcium silicate powder.

[0095] Comparative Example 2

[0096] Different from Example 1, carbonized polymer dots are not used for modification, and an equal mass of nano-carbon black is used for modification. The nano-carbon black is purchased from Ketjenblack EC-300J, with a specific surface area of 800 m 2 / g.

[0097] A nano-carbon black modified hydrated calcium silicate film, the raw materials comprising the following components in parts by mass:

[0098]

[0099]

[0100] In this embodiment, the composition of the calcareous material is as follows: calcium chloride 50 wt%, calcium nitrate 20 wt%, quicklime 10 wt%, calcium hydroxide 20 wt%; the composition of the siliceous material is as follows: silica fume 30 wt%, rice husk ash 10 wt%, sodium silicate 60 wt%; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0101] First, 10 parts of nano carbon black and 100 parts of water were mixed in proportion and ultrasonicated for 10 min to obtain a uniform suspension A. The suspension A, 100 parts of water, 30 parts of calcareous material and 20 parts of siliceous material were formulated into a suspension, and ultrasonicated for 3 min to mix evenly. 2 parts of pH regulator were used to adjust the pH value of the solution to 8, and ultrasonicated for 3 min. Then, under a water bath at 40 °C, it was stirred and reacted for 24 h to obtain a suspension B. The suspension B was filtered to form a film, and placed in a vacuum oven at 45 °C and dried for 24 h to obtain a nano carbon black modified calcium silicate hydrate film F.

[0102] Comparative Example 3

[0103] Different from Example 2, the dosage of calcareous material was changed to 60 parts, and the dosage of siliceous material was changed to 60 parts.

[0104] A calcium silicate hydrate film, the raw materials include the following components in parts by mass:

[0105]

[0106] In this example, the composition of the calcareous material was as follows: 50 wt% calcium chloride, 20 wt% calcium nitrate, 10 wt% quicklime, 20 wt% calcium hydroxide; the composition of the siliceous material was as follows: 30 wt% silica fume, 10 wt% rice husk ash, 60 wt% sodium silicate; the pH regulator was sodium hydroxide and dilute hydrochloric acid.

[0107] First, 30 parts of polymer monomer and 100 parts of water were mixed in proportion and ultrasonicated for 10 min to obtain a uniform solution A. Then, 5 parts of ammonium persulfate and 10 parts of N,N'-methylenebisacrylamide were added to solution A in proportion and ultrasonicated for 10 min to obtain a uniform solution B. Immediately afterwards, solution B was poured into a hydrothermal reaction kettle and reacted at 180 °C for 8 h to obtain a yellow transparent solution C. A 0.22 μm dialysis bag was used to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, a carbonized polymer dot powder D was obtained. The synthesized carbonized polymer dot powder D, 200 parts of water, 60 parts of calcareous material and 60 parts of siliceous material were formulated into a suspension, and ultrasonicated for 3 min to mix evenly. 5 parts of pH regulator were used to adjust the pH value of the solution to 8, and ultrasonicated for 3 min. Then, under a water bath at 40 °C, it was stirred and reacted for 24 h to obtain a suspension E. The suspension E was filtered to form a film, and placed in a vacuum oven at 45 °C and dried for 24 h to obtain a carbonized polymer dot modified calcium silicate hydrate film F.

[0108] Comparative Example 4

[0109] Different from Comparative Example 2, the dosage of calcareous material was changed to 40 parts, and the dosage of siliceous material was changed to 80 parts.

[0110] A nano carbon black modified calcium silicate hydrate film, the raw materials include the following components in parts by mass:

[0111]

[0112] In this comparative example, the composition of the calcium material is as follows: calcium chloride 50 wt%, calcium nitrate 20 wt%, quicklime 10 wt%, calcium hydroxide 20 wt%; the composition of the silica material is as follows: silica fume 30 wt%, rice husk ash 10 wt%, sodium silicate 60 wt%; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0113] First, 10 parts of nano carbon black and 100 parts of water are mixed in proportion and ultrasonicated for 10 min to obtain a uniform suspension A. The suspension A, 100 parts of water, 40 parts of calcium material and 80 parts of silica material are formulated into a suspension, and ultrasonicated for 3 min to mix evenly. 2 parts of pH regulator are used to adjust the pH value of the solution to 8, and ultrasonicated for 3 min. Then, under a water bath at 40 °C, it is stirred and reacted for 24 h to obtain a suspension B. The suspension B is filtered to form a film, and placed in a vacuum oven at 45 °C and dried for 24 h to obtain a nano carbon black modified calcium silicate hydrate film F.

[0114] Comparative Example 5

[0115] Different from Comparative Example 3, the hydrothermal reaction temperature is changed to 160 °C.

[0116] A calcium silicate hydrate film, comprising the following components in parts by mass:

[0117]

[0118] In this comparative example, the composition of the calcium material is as follows: calcium chloride 50 wt%, calcium nitrate 20 wt%, quicklime 10 wt%, calcium hydroxide 20 wt%; the composition of the silica material is as follows: silica fume 30 wt%, rice husk ash 10 wt%, sodium silicate 60 wt%; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0119] First, 30 parts of polymer monomers and 100 parts of water were mixed in proportion and ultrasonicated for 10 min to obtain a uniform solution A. Then, 5 parts of ammonium persulfate and 10 parts of N,N'-methylenebisacrylamide were added to solution A in proportion and ultrasonicated for 10 min to obtain a uniform solution B. Immediately afterwards, solution B was poured into a hydrothermal reaction kettle and reacted at 160 °C for 8 h to obtain a yellow transparent solution C. A 0.22-μm dialysis bag was used to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, a carbonized polymer dot powder D was obtained. The synthesized carbonized polymer dot powder D, 200 parts of water, 60 parts of calcareous material, and 60 parts of siliceous material were formulated into a suspension and ultrasonicated for 3 min to mix evenly. 5 parts of pH regulator were used to adjust the pH value of the solution to 8 and ultrasonicated for 3 min. Then, under a 40-degree water bath, the mixture was stirred and reacted for 24 h to obtain a suspension E. The suspension E was filtered to form a film and placed in a 45 °C vacuum oven to dry for 24 h to obtain a calcium silicate hydrate film F.

[0120] Comparative Example 6

[0121] Different from Comparative Example 3, the hydrothermal reaction temperature was changed to 200 °C.

[0122] A calcium silicate hydrate film, the raw materials include the following components in parts by mass:

[0123]

[0124] In this comparative example, the composition of the calcareous material is as follows: 50 wt% calcium chloride, 20 wt% calcium nitrate, 10 wt% quicklime, 20 wt% calcium hydroxide; the composition of the siliceous material is as follows: 30 wt% silica fume, 10 wt% rice husk ash, 60 wt% sodium silicate; the pH regulator is sodium hydroxide and dilute hydrochloric acid.

[0125] First, 30 parts of polymer monomers and 100 parts of water were mixed in proportion and ultrasonicated for 10 min to obtain a uniform solution A. Then, 5 parts of ammonium persulfate and 10 parts of N,N'-methylenebisacrylamide were added to solution A in proportion and ultrasonicated for 10 min to obtain a uniform solution B. Immediately afterwards, solution B was poured into a hydrothermal reaction kettle and reacted at 200 °C for 8 h to obtain a yellow transparent solution C. A 0.22-μm dialysis bag was used to screen out the macromolecular impurities in solution C, and after rotary evaporation treatment, a carbonized polymer dot powder D was obtained. The synthesized carbonized polymer dot powder D, 200 parts of water, 60 parts of calcareous material, and 60 parts of siliceous material were formulated into a suspension and ultrasonicated for 3 min to mix evenly. 5 parts of pH regulator were used to adjust the pH value of the solution to 8 and ultrasonicated for 3 min. Then, under a 40-degree water bath, the mixture was stirred and reacted for 24 h to obtain a suspension E. The suspension E was filtered to form a film and placed in a 45 °C vacuum oven to dry for 24 h to obtain a calcium silicate hydrate film F.

[0126] The calcium silicate hydrate film for monitoring needs to have a certain tensile strength inside the concrete to ensure that the material itself is not damaged under the action of force. Therefore, its tensile performance is evaluated. Referring to the national standard "Textiles - Tensile properties of fabrics - Part 1: Determination of breaking force and elongation at break (strip method)" (GB / T 3923.1-2013), the calcium silicate hydrate films prepared in Examples 1-3 and Comparative Examples 1-6 above are used. The test instrument is an electronic universal testing machine.

[0127] Table 1 Physical properties of calcium silicate hydrate films in Examples 1-3 and Comparative Examples 1-6.

[0128]

[0129] Table 1 shows the physical properties of carbonized polymer dot-modified calcium silicate hydrate films in Examples 1-3 and Comparative Examples 1-6. Examples 1, 1 and 2 evaluated the effect of carbonized polymer dot modification on the tensile strength of calcium silicate hydrate films. The results show that unmodified or carbon black-modified calcium silicate hydrate films have no tensile strength, and the modification with carbonized polymer dots can significantly enhance the tensile ability of calcium silicate hydrate films.

[0130] Examples 2, 3 and 4 evaluated the effect of the theoretical calcium-silicon ratio on the tensile properties of carbonized polymer dot-modified calcium silicate hydrate films. The results show that when the theoretical calcium-silicon ratio (mass fraction ratio of calcareous material to siliceous material) is 2:1, the tensile strength of the calcium silicate hydrate film is optimal.

[0131] Examples 3, 5 and 6 evaluated the effect of the synthesis temperature of carbonized polymer dots on the tensile properties of modified calcium silicate hydrate films. The results show that the tensile properties of the calcium silicate hydrate film obtained by modifying with carbonized polymer dots synthesized at 180 degrees are optimal.

[0132] Two stainless steel meshes are respectively placed on the upper and lower sides of each sample (each calcium silicate hydrate film) prepared in Example 1 and Comparative Examples 1-2, and pressed into the same size of the sample to be tested under 10 MPa. The DC direct current technology is used to measure the resistance of the sample.

[0133] Figure 2Shows the apparent resistivity of carbonized polymer dots modified C-S-H (Example 1), pure C-S-H (Comparative Example 1), and carbon black modified C-S-H (Comparative Example 2). The results show that the modification with carbonized polymer dots reduces the resistance of C-S-H by about two orders of magnitude, and the resistance of the carbon black modified sample is relatively low. Under the condition of 60% external humidity, no obvious change in the resistance value occurs for both the pure C-S-H sample and the carbon black modified sample. However, due to the unique conduction mechanism, the carbonized polymer dots modified C-S-H exhibits a large change in the resistance value under the influence of humidity, with a decrease amplitude reaching about one order of magnitude, showing sensitivity to humidity.

[0134] Figure 3 Shows the difference in current values exhibited by the carbonized polymer dots modified C-S-H of Example 1 in different humidity environments. It can be seen that as the humidity increases, the resistance value of the carbonized polymer dots modified C-S-H film decreases, thereby leading to an increasing trend in the monitored current value. Further, we can utilize this unique conduction mechanism to realize a hydrated calcium silicate film with humidity sensitivity, which can be used for environmental humidity monitoring and further for fields such as intelligent monitoring of cement concrete.

[0135] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A carbonized polymer dot modified calcium silicate hydrate film for humidity monitoring, characterized in that: The calcium silicate hydrate film is used as a matrix, and carbonized polymer dots are uniformly dispersed in the calcium silicate hydrate film.

2. The carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to claim 1, characterized in that: The size of the carbonized polymer dots is 2nm-100nm, and the loading amount of the carbonized polymer dots in the carbonized polymer dot-modified calcium silicate hydrate film is 40wt%-80wt%.

3. The carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to claim 1, characterized in that: The raw materials of the carbonized polymer dots include the following components in parts by weight: The raw materials of the calcium silicate hydrate film include the following components in parts by mass: Wherein, the mass ratio of the calcareous material to the siliceous material is 0.5-2.

4. The carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to claim 3, characterized in that: The polymer monomer is selected from any one or more of acrylamide and acrylic acid; the calcareous material is selected from any one or more of calcium chloride, calcium nitrate, quicklime, and calcium hydroxide; the siliceous material is selected from any one or more of silica ash, rice husk ash, and sodium silicate; and the pH adjuster is selected from one or both of sodium hydroxide and dilute hydrochloric acid.

5. A method for preparing a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Preparation of carbonized polymer dot powder; S2: mixing carbonized polymer dot powder, water, calcium material and silicon material uniformly to obtain a suspension; S3: Use a pH adjuster to adjust the pH value of the suspension and mix well; S4: Stir the reaction under water bath heating; S5: After the reaction is completed, the reaction is filtered and dried to obtain the carbonized polymer dot-modified calcium silicate hydrate film.

6. The method for preparing a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to claim 5, characterized in that: In step S1, the preparation of carbonized polymer dot powder includes the following steps: S1.1: Mix the polymer monomer and water evenly according to the mass fraction, then add ammonium persulfate and N,N'-methylenebispropionamide and mix evenly to obtain a mixed solution; S1.2: subjecting the mixed solution to a hydrothermal reaction; S1.3: After the hydrothermal reaction is completed, dialysis and rotary evaporation are performed to obtain the carbonized polymer dot powder.

7. The method for preparing a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to claim 6, characterized in that: In step S1.2, the temperature of the hydrothermal reaction is 160-200°C and the time is 6-10h; In step S1.3, the dialysis refers to using a 0.1-0.3 μm dialysis bag to screen out macromolecular impurities.

8. The method for preparing a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring according to claim 5, characterized in that: In step S3, the pH value of the suspension after adjustment is 7-9; In step S4, the water bath heating temperature is 30-50°C, the stirring reaction speed is 300rpm-600rpm, and the time is 12h-24h; In step S5, the drying temperature is 40-50°C and the drying time is 20-28 hours.

9. An application of a carbonized polymer dot-modified calcium silicate hydrate film for humidity monitoring as claimed in any one of claims 1 to 4, characterized in that: The carbonized polymer dot-modified calcium silicate hydrate film is used for environmental humidity monitoring.

10. The use of carbonized polymer dots modified calcium silicate hydrate film for humidity monitoring according to claim 9, characterized in that: The carbonized polymer dot-modified calcium silicate hydrate film is used for monitoring the internal humidity of cement concrete, comprising the following steps: A: According to the size of the monitored cement concrete, the carbonized polymer dots modified calcium silicate hydrate film is prepared into a suitable size; B: During the concrete pouring process, a carbonized polymer dot-modified calcium silicate hydrate film with a suitable size is buried inside the cement concrete and connected to an external current detection device; C: By observing the changes in electric current, the internal humidity of cement concrete can be monitored and used to determine the risk of damage to the cement concrete structure.

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