A long-life self-sensing sandwich concrete pavement for emergency repair and reconstruction and its construction method

Abstract

This invention relates to a long-life, self-sensing sandwich concrete pavement for emergency repair and construction, and its construction method, belonging to the field of composite concrete pavement structures. The pavement consists of a bottom layer, a middle layer, and a top layer from bottom to top. The bottom layer is a long-life, ultra-high-strength tensile layer; the middle layer is a self-sensing compressive and shear-resistant layer; and the top layer is a freeze-thaw resistant, impact-resistant, and wear-resistant layer. The bottom layer has a thickness of 85–120 mm, the middle layer 160–250 mm, and the top layer 35–65 mm. The bottom layer uses ultra-high-performance concrete, the middle layer uses pre-filled intelligent aggregate concrete, and the top layer uses mixed organic fiber reinforced high-performance concrete. This invention enables the pavement to have a self-sensing function. Through a conductive network constructed from intelligent aggregate and conductive mortar within the middle layer, changes in the electrical signals of the sandwich concrete pavement can be monitored in real time, intelligently sensing the pavement's service status and providing data support for traffic monitoring and intelligent maintenance.

Description

Technical Field

[0001] This invention belongs to the field of composite concrete pavement structure, and relates to a long-life self-sensing sandwich concrete pavement for emergency repair and construction, and its construction method. Background Technology

[0002] In road and airport engineering, the surface layer of concrete pavement primarily bears the impact and wear from tires and the effects of adverse environments. Internally, it responds to tire impacts with compressive, tensile, and shear stresses, which are borne by the upper, lower, and overall layers, respectively. Traditional concrete pavements often use dry-hardened concrete, which is difficult to construct, time-consuming, and lacks functional zoning, making it impossible to specifically improve the performance of different parts of the pavement and achieve the concept of long-life design. Furthermore, the testing of concrete pavements uses destructive methods such as core drilling, which cannot provide real-time evaluation of service status and inevitably damages the existing pavement structure to some extent.

[0003] Expanding self-sensing and self-monitoring capabilities is a crucial aspect of the intelligent upgrading of transportation infrastructure, primarily achieved through the embedding of various sensors within the structure. Currently, these sensors generally suffer from complex installation, high maintenance costs, poor compatibility with concrete, and signal attenuation due to environmental interference. Furthermore, sensor-based self-sensing and monitoring are often limited to localized areas and cannot accurately characterize the overall service status of the structure. Summary of the Invention

[0004] The purpose of this invention is to address the limitations of traditional single-layer concrete pavements in road and airport engineering, such as lack of functional zoning, difficulty in local modification, and long construction time. It provides a long-life, self-sensing sandwich concrete pavement for emergency repair and construction, along with its construction method. This pavement is easy to construct, possesses excellent mechanical, durability, and self-sensing properties, enabling long-term healthy service and real-time data collection of traffic flow and structural deformation, providing a basis for traffic control and engineering maintenance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A long-life self-sensing sandwich concrete pavement for emergency repair and construction, wherein the pavement consists of a bottom layer, a middle layer and a top layer from bottom to top; the bottom layer is a long-life ultra-high strength tensile layer, the middle layer is a self-sensing compressive and shear layer, and the top layer is a freeze-thaw resistant, impact resistant and wear-resistant layer.

[0007] Furthermore, the thickness of the bottom layer is 85–120 mm, the thickness of the middle layer is 160–250 mm, and the thickness of the top layer is 35–65 mm.

[0008] Furthermore, the lower layer uses ultra-high performance concrete, the middle layer uses pre-filled smart aggregate concrete, and the upper layer uses hybrid organic fiber reinforced high performance concrete.

[0009] A construction method for the above-mentioned long-life self-sensing sandwich concrete pavement for emergency repair and reconstruction, the method being as follows:

[0010] Step 1: The preparation method of the lower layer is carried out according to the following steps:

[0011] (1) Weigh out the following by mass percentage: 31%–36% cement, 8%–12% fly ash viscosity reducer, 2%–4% slag powder, 4%–6% silica fume, 30%–40% fine aggregate, 1%–3% high-performance water-reducing agent, 0.05%–0.15% retarder, 6%–8% water, and 6%–8% steel fiber.

[0012] (2) Put cement, fly ash viscosity reducer, slag powder, silica fume and fine aggregate into the mixer and dry mix for 2 minutes. Then add mixing water mixed with high performance water reducer and retarder and mix for 4-5 minutes. During the mixing process, evenly sprinkle steel fiber and continue mixing for 2-3 minutes. Pour the evenly mixed high-flowability ultra-high performance concrete into the formwork.

[0013] Step 2: The preparation method of the intermediate layer is carried out according to the following steps:

[0014] (1) After the lower layer is poured, fill the template with smart aggregate with a thickness of 160-200mm and lay metal electrode mesh at 500mm intervals. The metal electrode mesh is made of copper or other metal materials with stable and good conductivity. The height of the copper mesh is 180-220mm and the width of the copper mesh is 75% of the pavement width.

[0015] (2) Weigh out the following by mass percentage: 45%–55% cement, 5%–10% fly ash viscosity reducer, 5%–15% conductive filler, 15%–25% fine aggregate, 10%–13% water, 0.8%–1.2% high-performance water-reducing agent, and 0.05%–0.16% retarder;

[0016] (3) Put cement, fly ash viscosity reducer, conductive filler and fine aggregate into the mixer and mix for 2 minutes. Then add mixing water mixed with high performance water reducer and retarder and mix for 2-3 minutes. Pour the evenly mixed conductive mortar into the template to fill the gaps between the smart aggregates.

[0017] Step 3: The preparation method of the upper layer is carried out according to the following steps:

[0018] (1) Weigh out the following by mass percentage: 18%–25% cement, 2%–5% slag powder, 30%–35% fine aggregate, 35%–40% coarse aggregate, 0.05%–0.14% mixed organic fiber, 5%–7% water, 0.25%–0.3% air-entraining water-reducing agent, and 0.06%–0.08% retarder;

[0019] (2) Put cement, slag powder, fine aggregate and coarse aggregate into the mixer and mix for 3 minutes. During this time, evenly sprinkle mixed organic fibers. Then add mixing water mixed with air-entraining water-reducing agent and retarder and mix for 4-5 minutes. Pour the evenly mixed fiber concrete into the template, vibrate to compact and roughen the surface.

[0020] By curing the sandwich concrete pavement constructed according to the above steps, a long-life, self-sensing sandwich concrete pavement for emergency repair and reconstruction is obtained.

[0021] Further, in step one, the cement used in the lower layer is rapid-hardening cement, such as one of rapid-hardening sulfoaluminate cement and phosphate cement; the average particle size of the fly ash viscosity reducer is 1.5-2.0 μm; the average particle size of the slag powder is 4.5-5.5 μm; the average particle size of the silica fume is 0.15-0.35 μm; the fineness modulus of the fine aggregate is 2.7±0.2; the solid content of the high-performance water-reducing agent is 40%, and the water reduction rate is >50%; the retarder is borax; and the steel fiber is 13 mm long and 0.20 mm in diameter.

[0022] Furthermore, in step two, the preparation method of the smart aggregate used in the intermediate layer is carried out according to the following steps:

[0023] I. Weigh out 65%–75% of the composite calcium-based solidification component, 5%–15% of the conductive filler, 2%–3% of the catalytic solution, and 15%–20% of the water by weight percentage; wherein the composite calcium-based solidification component includes 50%–60% fly ash, 5%–10% calcium boride, 25%–35% cement, 5%–10% silica fume, 2%–5% calcium sulfate whiskers, and 2%–5% calcium carbonate whiskers;

[0024] 2. After mixing the composite calcium curing component and conductive filler in a mixer for 2 minutes, add the catalytic solution and mix for 3-5 minutes to obtain the catalytically modified powder. Then add mixing water and mix for 3-5 minutes. Pour the mixture into a mold and let it solidify and harden at room temperature. After hardening, demold and transfer it into an autoclave for autoclaving at 1.0 MPa and 170-180℃ for 72 hours.

[0025] 3. The blocks obtained by the above steps are crushed and screened to obtain intelligent aggregates of different particle sizes. The intelligent aggregates used in pre-filled aggregate concrete have a particle size > 4.75mm.

[0026] Furthermore, the catalytic solution contains one or two of phosphoric acid, sulfuric acid, and acetic acid, wherein the concentration of phosphoric acid is 14.7 mol / L, the concentration of sulfuric acid is 18.4 mol / L, and the concentration of acetic acid is 6 mol / L.

[0027] Furthermore, the fly ash in the composite calcium-based solidification component is Class I fly ash with an average particle size of 8–20 μm; the calcium boride density is 2.3 g / cm³.3 The average particle size is 1–3 μm; the cement is silicate cement / ordinary silicate cement with a strength grade of 42.5 / 52.5; the average particle size of silica fume is 0.15–0.35 μm; the calcium sulfate whiskers and calcium carbonate whiskers are 30–200 μm long and 0.5–5 μm in diameter; the conductive filler is one or two of nano-graphite, carbon nanotubes, carbon black or chopped carbon fibers, wherein the average particle size of nano-graphite is 20–25 nm, the average particle size of carbon nanotubes is 5–8 μm, the average particle size of carbon black is 15–20 μm, and the average particle size of chopped carbon fibers is 0.5 mm long and 7 μm in diameter.

[0028] Furthermore, in step two, the cement used in the intermediate layer is rapid-hardening cement, such as one of rapid-hardening sulfoaluminate cement and phosphate cement; the fly ash viscosity reducer has an average particle size of 1.5–2.0 μm; the conductive filler is one or two of nano-graphite, carbon nanotubes, and carbon black, wherein the average particle size of nano-graphite is 20–25 nm, the average particle size of carbon nanotubes is 5–8 μm, and the average particle size of carbon black is 15–20 μm; the fine aggregate is 40–80 mesh quartz sand; the high-performance water-reducing agent has a solid content of 40% and a water reduction rate >50%; and the retarder is borax.

[0029] Furthermore, in step three, the cement used in the upper layer is rapid-hardening cement, such as one of rapid-hardening sulfoaluminate cement and phosphate cement; the average particle size of the slag powder is 4.5–5.5 μm; the fineness modulus of the fine aggregate is 2.7 ± 0.2; the particle size range of the coarse aggregate is 5–10 mm; the mixed organic fibers are ultra-high molecular weight polyethylene fibers and polyacrylonitrile fibers in a mass ratio of 1:1, wherein the length of the ultra-high molecular weight polyethylene fibers is 15 mm and the diameter is 25 μm, and the length of the polyacrylonitrile fibers is 15 mm and the diameter is 12–20 μm; the solid content of the air-entraining water-reducing agent is 30%, and the water reduction rate is >10%; the retarder is borax.

[0030] The advantages of this invention over the prior art are as follows:

[0031] (1) This invention makes different parts of the pavement more suitable for actual application scenarios and has a longer service life in complex environments. The invention uses a three-layer sandwich structure design to give the upper layer antifreeze, impact resistance and wear resistance, the middle layer self-sensing compressive and shear resistance, and the lower layer long service life and ultra-high tensile strength.

[0032] (2) Shorten construction time and improve the efficiency of emergency repair and construction. The lower layer uses high-flowability ultra-high performance concrete, which does not require vibration after pouring; the middle layer adopts a construction process of pre-filled intelligent aggregate and conductive mortar for rapid grouting, which greatly shortens the construction time and provides a solution for emergency repair and construction tasks in road and airport projects.

[0033] (3) Enable the pavement to have self-sensing capabilities. Through the conductive network constructed by intelligent aggregates and conductive mortar in the intermediate layer, the changes in electrical signals of the sandwich concrete pavement can be monitored in real time, and the service status of the pavement can be intelligently sensed, providing data support for traffic monitoring and intelligent maintenance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the long-life self-sensing sandwich concrete pavement for emergency repair and construction according to the present invention, wherein 1 is the top layer (freeze-resistant, impact-resistant and wear-resistant layer), 2 is the middle layer (self-sensing compressive and shear-resistant layer), and 3 is the bottom layer (long-life ultra-high strength tensile layer).

[0035] Figure 2 This is a schematic diagram of the self-sensing principle of the middle layer, where 4 is a metal electrode, 5 is smart aggregate, and 6 is conductive mortar. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0037] This invention proposes a novel three-layer sandwich concrete pavement structure to shorten construction time and significantly improve resistance to spalling and cracking. It also endows the pavement with self-sensing and self-monitoring capabilities, enabling it to meet the needs of emergency repairs and construction under special circumstances while ensuring long-term safe and healthy service in freeze-thaw environments. The top layer (formed surface) of this novel sandwich pavement is a freeze-thaw resistant, impact-resistant, and wear-resistant layer, utilizing a hybrid of ultra-high molecular weight polyethylene fiber and polyacrylonitrile fiber to enhance freeze-thaw resistance, impact resistance, and wear resistance. The middle layer (compression zone) is a self-sensing compressive and shear resistant layer, employing pre-filled aggregates to accelerate construction and using intelligent aggregate overlap and conductive mortar filling to strengthen the system's electrical response under load. The bottom layer (tension zone) is a long-life, ultra-high strength tensile layer, using ultra-high performance concrete to improve the structure's flexural strength and durability. The pre-filled intelligent aggregate self-sensing concrete uses a novel intelligent aggregate synthesized through acid-catalyzed surface modification and autoclaving of composite calcium-based curing components and conductive fillers. During construction, aggregates are pre-filled to ensure the smart aggregates overlap and form a framework, followed by the pouring of conductive mortar to fill the gaps in the framework. The smart aggregates and conductive mortar combine to form a continuous and stable conductive network within the intermediate layer. By monitoring the electrical signals of the intermediate layer, the service status of the sandwich concrete pavement structure can be sensed in real time, providing a basis for traffic control and pavement maintenance. The long-life self-sensing sandwich concrete pavement for emergency repair and reconstruction proposed in this invention, from the perspectives of structural functional zoning and material performance design, significantly improves the service life of concrete pavements while expanding its application prospects in emergency repair and reconstruction, intelligent maintenance, and traffic monitoring.

[0038] Example 1

[0039] A type of sandwich concrete pavement for emergency repair and construction has a bottom layer thickness of 110mm, a middle layer thickness of 220mm, and a top layer thickness of 50mm.

[0040] The preparation method of the lower layer of ultra-high performance concrete for sandwich pavement is carried out according to the following steps:

[0041] I. Weigh out the following by weight percentage: 32% cement, 8% fly ash viscosity reducer, 3% slag powder, 5% silica fume, 36% fine aggregate, 1.5% high-performance water-reducing agent, 0.1% retarder, 7.4% water, and 7% steel fiber.

[0042] 2. Add cement, fly ash viscosity reducer, slag powder, silica fume, and fine aggregate to a mixer and dry mix for 2 minutes. Then add mixing water containing high-performance water-reducing agent and retarder and mix for 4-5 minutes. During the mixing process, evenly sprinkle in steel fibers and continue mixing for 2-3 minutes. Pour the uniformly mixed, high-flowability, ultra-high-performance concrete into the formwork. Tests show that the 28-day flexural strength of the lower layer is 21 MPa, and the 28-day compressive strength is 109 MPa.

[0043] The cement used in the lower layer is rapid-hardening sulfoaluminate cement with a strength grade of 42.5. The average particle size of the fly ash viscosity reducer is 1.5-2.0 μm; the average particle size of the slag powder is 4.5-5.5 μm; the average particle size of the silica fume is 0.15-0.35 μm; the fineness modulus of the fine aggregate is 2.7±0.2; the solid content of the high-performance water-reducing agent is 40%, and the water reduction rate is >50%; the retarder is borax; and the steel fiber is 13 mm long and 0.20 mm in diameter.

[0044] The preparation method of the surface layer in pre-filled intelligent aggregate concrete is carried out according to the following steps:

[0045] 1. After the lower layer is poured, fill the inside of the template with smart aggregate, with a thickness of 160-200mm, and arrange metal electrodes at 500mm intervals.

[0046] II. Weigh out the following components by weight percentage: 52% cement, 8% fly ash viscosity reducer, 9% conductive filler, 18% fine aggregate, 11.7% water, 1.2% high-performance water-reducing agent, and 0.1% retarder. The mass ratio of carbon nanotubes to nanographite in the conductive filler is 2:8.

[0047] 3. Add cement, fly ash viscosity reducer, conductive filler, and fine aggregate to a mixer and mix for 2 minutes. Then add mixing water containing high-performance water-reducing agent and retarder and mix for 2-3 minutes. Pour the uniformly mixed conductive mortar into the mold to fill the gaps between the smart aggregates. Tests showed that the 28-day compressive strength of the intermediate layer was 45 MPa; the resistivity was 203 Ω·cm.

[0048] The cement used in the intermediate layer is rapid-hardening sulfoaluminate cement with a strength grade of 42.5. The fly ash viscosity reducer has an average particle size of 1.5–2.0 μm. The conductive filler is carbon nanotubes and nanographite, with an average particle size of 5–8 μm for carbon nanotubes and 20–25 nm for nanographite. The fine aggregate is 40–80 mesh quartz sand. The high-performance water-reducing agent has a solid content of 40% and a water reduction rate of >50%. The retarder is borax.

[0049] The preparation method of the smart aggregate used in the intermediate layer is carried out according to the following steps:

[0050] I. Weigh out the following components by weight percentage: 75% composite calcium-based solidification component, 6% conductive filler, 3% catalytic solution, and 16% water. The composite calcium-based solidification component comprises 50% Grade I fly ash, 10% calcium boride, 30% cement, 5% silica fume, 2% calcium sulfate whiskers, and 3% calcium carbonate whiskers. The mass ratio of carbon nanotubes to nanographite in the conductive filler is 3:7, and the mass ratio of phosphoric acid to acetic acid in the catalytic solution is 1:1.

[0051] 2. Add the composite calcium-based curing component and conductive filler to a mixer and stir for 2 minutes. Then add the catalytic solution and stir for 3-5 minutes to obtain the catalytically modified powder. Add mixing water and stir for 3-5 minutes. Pour the mixture into a mold and allow it to solidify and harden at room temperature. After hardening, demold and transfer the mixture to an autoclave for autoclaving at 1.0 MPa and 170-180℃ for 72 hours.

[0052] 3. The blocks obtained by the above steps are crushed and screened to obtain intelligent aggregates of different particle sizes. The intelligent aggregates used in pre-filled aggregate concrete have a particle size > 4.75mm.

[0053] The composite calcium-based solidification component used in the intelligent aggregate of the intermediate layer includes fly ash, calcium boride, cement, silica fume, calcium sulfate whiskers, and calcium carbonate whiskers. The fly ash is Class I fly ash with an average particle size of 8–20 μm; the calcium boride has a density of 2.3 g / cm³. 3 The average particle size is 1–3 μm; the cement is silicate cement with a strength grade of 42.5; the average particle size of silica fume is 0.15–0.35 μm; the calcium sulfate whiskers and calcium carbonate whiskers are 30–200 μm long and 0.5–5 μm in diameter; the conductive fillers are carbon nanotubes and nanographite, with the average particle size of nanographite being 20–25 nm and the average particle size of carbon nanotubes being 5–8 μm; the catalytic solution is phosphoric acid and acetic acid, with the concentration of phosphoric acid being 14.7 mol / L and the concentration of acetic acid being 6 mol / L.

[0054] The preparation method of the surface layer of hybrid organic fiber reinforced high-performance concrete is carried out according to the following steps:

[0055] I. Weigh out the following components by weight percentage: 22% cement, 3% slag powder, 32% fine aggregate, 37% coarse aggregate, 0.07% mixed organic fiber, 5.6% water, 0.27% air-entraining water-reducing agent, and 0.06% retarder. The mass ratio of ultra-high molecular weight polyethylene fiber to polyacrylonitrile fiber in the mixed organic fiber is 1:1.

[0056] 2. Add cement, slag powder, fine aggregate, and coarse aggregate to a mixer and mix for 3 minutes. During this process, evenly sprinkle in the mixed organic fibers. Then add mixing water containing air-entraining water-reducing agent and retarder and mix for 4-5 minutes. Pour the uniformly mixed fiber-reinforced concrete into the formwork, vibrate to compact it, and roughen the surface. Experiments showed that the 28-day compressive strength of the top layer was 55 MPa; the mass loss after 500 freeze-thaw cycles was 3.8%, and the relative dynamic modulus of elasticity was 86%.

[0057] The cement used in the upper layer is rapid-hardening sulfoaluminate cement with a strength grade of 42.5; the average particle size of the slag powder is 4.5-5.5 μm; the fineness modulus of the fine aggregate is 2.7±0.2; the particle size range of the coarse aggregate is 5-10 mm; the mixed organic fibers are ultra-high molecular weight polyethylene fibers and polyacrylonitrile fibers, wherein the length of the ultra-high molecular weight polyethylene fibers is 15 mm and the diameter is 25 μm, and the length of the polyacrylonitrile fibers is 15 mm and the diameter is 12-20 μm; the solid content of the air-entraining water-reducing agent is 30%, and the water reduction rate is >10%; the retarder is borax.

[0058] Example 2

[0059] The difference between this embodiment and Embodiment 1 lies in the materials and proportions used in preparing the smart aggregate.

[0060] The preparation method of the smart aggregate used in the surface layer in this embodiment is carried out according to the following steps:

[0061] I. Weigh out the following components by weight percentage: 70% composite calcium-based solidification component, 10% conductive filler, 3% catalytic solution, and 17% water. The composite calcium-based solidification component comprises 60% Grade I fly ash, 5% calcium boride, 25% cement, 5% silica fume, 2% calcium sulfate whiskers, and 3% calcium carbonate whiskers. The conductive filler has a mass ratio of nano-graphite to chopped carbon fiber of 9:1, and the catalytic solution has a mass ratio of phosphoric acid to acetic acid of 1:1.

[0062] 2. Add the composite calcium-based curing component and conductive filler to a mixer and stir for 2 minutes. Then add the catalytic solution and stir for 3-5 minutes to obtain the catalytically modified powder. Add mixing water and stir for 3-5 minutes. Pour the mixture into a mold and allow it to solidify and harden at room temperature. After hardening, demold and transfer the mixture to an autoclave for autoclaving at 1.0 MPa and 170-180℃ for 72 hours.

[0063] Third, the blocks obtained by the above steps are crushed and screened to obtain intelligent aggregates of different particle sizes.

[0064] After the lower layer is poured, the smart aggregate obtained in the above preparation steps is filled into the mold to a thickness of 160-200 mm, and metal electrodes are arranged at 500 mm intervals. Following the conductive mortar mix ratio in Example 1, uniformly mixed conductive mortar is poured into the mold to fill the gaps between the smart aggregates. Tests showed that the 28-day compressive strength of the middle layer was 40 MPa, and the resistivity was 125 Ω·m.

[0065] The conductive filler used in the intelligent aggregate of the middle layer is nano-graphite and short-cut carbon fiber. The average particle size of the nano-graphite is 20-25 nm, and the short-cut carbon fiber is 0.5 mm long and 7 μm in diameter.

[0066] Comparative Example 1

[0067] This comparative example uses a single-layer airport concrete pavement with a thickness of 380 mm. The raw materials include silicate cement with a strength grade of 42.5, fine aggregate with a fineness modulus of 2.7, coarse aggregate with a particle size range of 4.75 to 31.5 mm, and an air-entraining water-reducing agent with a solid content of 30% and a water reduction rate of >10%.

[0068] Weigh out the following materials by weight percentage: 14% cement, 24% fine aggregate, 55% coarse aggregate, 6.7% water, and 0.3% air-entraining water-reducing agent. Mix these materials thoroughly, pour the mixture, and compact it. Before pouring, place metal electrodes at 500mm intervals. Tests showed that the pavement had a 28-day flexural strength of 5.4 MPa, a 28-day compressive strength of 46 MPa, a mass loss of 3.2% after 300 freeze-thaw cycles, a relative dynamic modulus of elasticity of 78.5%, and a resistivity of 3.5 × 10⁻⁶. 6 Ω·cm.

[0069] Comparative Example 2

[0070] A type of sandwich concrete pavement has a bottom layer thickness of 110mm, a middle layer thickness of 220mm, and a top layer thickness of 50mm.

[0071] The preparation method of the lower layer of ultra-high performance concrete for sandwich pavement is carried out according to the following steps:

[0072] I. Weigh out the following by weight percentage: 32% cement, 8% fly ash viscosity reducer, 3% slag powder, 5% silica fume, 36% fine aggregate, 1.5% high-performance water-reducing agent, 0.1% retarder, 7.4% water, and 7% steel fiber.

[0073] 2. Add cement, fly ash viscosity reducer, slag powder, silica fume, and fine aggregate to a mixer and dry mix for 2 minutes. Then add mixing water containing high-performance water-reducing agent and retarder and mix for 4-5 minutes. During the mixing process, evenly sprinkle in steel fibers and continue mixing for 2-3 minutes. Pour the uniformly mixed, high-flowability, ultra-high-performance concrete into the formwork. Tests show that the 28-day flexural strength of the lower layer is 21 MPa, and the 28-day compressive strength is 109 MPa.

[0074] The cement used in the lower layer is rapid-hardening sulfoaluminate cement with a strength grade of 42.5. The average particle size of the fly ash viscosity reducer is 1.5-2.0 μm; the average particle size of the slag powder is 4.5-5.5 μm; the average particle size of the silica fume is 0.15-0.35 μm; the fineness modulus of the fine aggregate is 2.7±0.2; the solid content of the high-performance water-reducing agent is 40%, and the water reduction rate is >50%; the retarder is borax; and the steel fiber is 13 mm long and 0.20 mm in diameter.

[0075] The preparation method for the surface layer of pre-filled aggregate concrete is carried out according to the following steps:

[0076] 1. After the lower layer is poured, fill the inside of the template with coarse aggregate to a thickness of 160-200mm, and arrange metal electrodes at 500mm intervals.

[0077] 2. Weigh out the following components by weight percentage: 51% cement, 10% fly ash viscosity reducer, 25% fine aggregate, 12.9% water, 1.0% high-performance water-reducing agent, and 0.1% retarder.

[0078] 3. Add cement, fly ash viscosity reducer, and fine aggregate to a mixer and mix for 2 minutes. Then add mixing water containing high-performance water-reducing agent and retarder and mix for 2-3 minutes. Pour the uniformly mixed mortar into the mold to fill the voids between the coarse aggregate. Tests show that the 28-day compressive strength of the intermediate layer is 55 MPa; the resistivity is 4.3 × 10⁻⁶. 6 Ω·cm.

[0079] The coarse aggregate used in the intermediate layer has a particle size range of 5-10 mm; the cement is rapid-hardening sulfoaluminate cement with a strength grade of 42.5; the fly ash viscosity reducer has an average particle size of 1.5-2.0 μm; the fine aggregate is 40-80 mesh quartz sand; the high-performance water-reducing agent has a solid content of 40% and a water reduction rate of >50%; and the retarder is borax.

[0080] The preparation method of the surface layer of hybrid organic fiber reinforced high-performance concrete is carried out according to the following steps:

[0081] I. Weigh out the following components by weight percentage: 22% cement, 3% slag powder, 32% fine aggregate, 37% coarse aggregate, 0.07% mixed organic fiber, 5.6% water, 0.27% air-entraining water-reducing agent, and 0.06% retarder. The mass ratio of ultra-high molecular weight polyethylene fiber to polyacrylonitrile fiber in the mixed organic fiber is 1:1.

[0082] 2. Add cement, slag powder, fine aggregate, and coarse aggregate to a mixer and mix for 3 minutes. During this process, evenly sprinkle in the mixed organic fibers. Then add mixing water containing air-entraining water-reducing agent and retarder and mix for 4-5 minutes. Pour the uniformly mixed fiber-reinforced concrete into the formwork, vibrate to compact it, and roughen the surface. Experiments showed that the 28-day compressive strength of the top layer was 55 MPa; the mass loss after 500 freeze-thaw cycles was 3.8%, and the relative dynamic modulus of elasticity was 86%.

[0083] The cement used in the upper layer is rapid-hardening sulfoaluminate cement with a strength grade of 42.5; the average particle size of the slag powder is 4.5-5.5 μm; the fineness modulus of the fine aggregate is 2.7±0.2; the particle size range of the coarse aggregate is 5-10 mm; the mixed organic fibers are ultra-high molecular weight polyethylene fibers and polyacrylonitrile fibers, wherein the length of the ultra-high molecular weight polyethylene fibers is 15 mm and the diameter is 25 μm, and the length of the polyacrylonitrile fibers is 15 mm and the diameter is 12-20 μm; the solid content of the air-entraining water-reducing agent is 30%, and the water reduction rate is >10%; the retarder is borax.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Comparative Example 2 is that the intermediate layer uses conductive mortar.

[0086] The preparation method of the surface layer of pre-filled coarse aggregate concrete in this comparative example is carried out according to the following steps:

[0087] 1. After the lower layer is poured, fill the inside of the template with coarse aggregate to a thickness of 160-200mm, and arrange metal electrodes at 500mm intervals.

[0088] II. Weigh out the following components by weight percentage: 52% cement, 8% fly ash viscosity reducer, 9% conductive filler, 18% fine aggregate, 11.7% water, 1.2% high-performance water-reducing agent, and 0.1% retarder. The mass ratio of carbon nanotubes to nanographite in the conductive filler is 2:8. The average particle size of the carbon nanotubes is 5–8 μm, and the average particle size of the nanographite is 20–25 nm.

[0089] 3. Add cement, fly ash viscosity reducer, conductive filler, and fine aggregate to a mixer and mix for 2 minutes. Then add mixing water containing high-performance water-reducing agent and retarder and mix for 2-3 minutes. Pour the uniformly mixed conductive mortar into the mold to fill the gaps between the smart aggregates. Tests showed that the 28-day compressive strength of the intermediate layer was 51 MPa; the resistivity was 1730 Ω·cm.

[0090] The materials and preparation methods of the top layer, middle layer aggregate, and bottom layer are the same as those of Comparative Example 2.

Claims

1. A construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavements, characterized in that: The pavement consists of a bottom layer, a middle layer, and a top layer from bottom to top; the bottom layer is a long-life, ultra-high-strength tensile layer, the middle layer is a self-sensing compressive and shear-resistant layer, and the top layer is a freeze-thaw resistant, impact-resistant, and wear-resistant layer; the method is as follows: Step 1: The preparation method of the lower layer is carried out according to the following steps: (1) Weigh out the following by mass percentage: 31%~36% cement, 8%~12% fly ash viscosity reducer, 2%~4% slag powder, 4%~6% silica fume, 30%~40% fine aggregate, 1%~3% high-performance water-reducing agent, 0.05%~0.15% retarder, 6%~8% water, and 6%~8% steel fiber; (2) Put cement, fly ash viscosity reducer, slag powder, silica fume and fine aggregate into the mixer and dry mix for 2 minutes. Then add mixing water mixed with high performance water reducer and retarder and mix for 4-5 minutes. During the mixing process, evenly sprinkle steel fiber and continue mixing for 2-3 minutes. Pour the evenly mixed high-flowability ultra-high performance concrete into the formwork. Step 2: The preparation method of the intermediate layer is carried out according to the following steps: (1) After the lower layer is poured, fill the template with smart aggregate with a thickness of 160~200mm and lay metal electrode mesh at 500mm intervals. (2) Weigh out the following by mass percentage: 45%~55% cement, 5%~10% fly ash viscosity reducer, 5%~15% conductive filler, 15%~25% fine aggregate, 10%~13% water, 0.8%~1.2% high-performance water-reducing agent, and 0.05%~0.16% retarder; (3) Add cement, fly ash viscosity reducer, conductive filler and fine aggregate into the mixer and mix for 2 minutes. Then add mixing water mixed with high performance water reducer and retarder and mix for 2-3 minutes. Pour the uniformly mixed conductive mortar into the template to fill the gaps between the smart aggregates. In step two, the preparation method of the smart aggregate used in the intermediate layer is carried out according to the following steps: I. Weigh out 65%~75% of the composite calcium-based solidification component, 5%~15% of the conductive filler, 2%~3% of the catalytic solution, and 15%~20% of the water by weight percentage; wherein the composite calcium-based solidification component includes 50%~60% fly ash, 5%~10% calcium boride, 25%~35% cement, 5%~10% silica fume, 2%~5% calcium sulfate whiskers, and 2%~5% calcium carbonate whiskers; 2. After mixing the composite calcium curing component and conductive filler in a mixer for 2 minutes, add the catalytic solution and mix for 3-5 minutes to obtain the catalytically modified powder. Then add mixing water and mix for 3-5 minutes. Pour the mixture into a mold and let it solidify and harden at room temperature. After hardening, demold and transfer it into an autoclave for autoclaving at 1.0 MPa and 170-180℃ for 72 hours.

3. The blocks obtained by the above steps are crushed and screened to obtain intelligent aggregates of different particle sizes; Step 3: The preparation method of the upper layer is carried out according to the following steps: (1) Weigh out the following by mass percentage: 18%~25% cement, 2%~5% slag powder, 30%~35% fine aggregate, 35%~40% coarse aggregate, 0.05%~0.14% mixed organic fiber, 5%~7% water, 0.25%~0.3% air-entraining water-reducing agent, and 0.06%~0.08% retarder; (2) Put cement, slag powder, fine aggregate and coarse aggregate into the mixer and mix for 3 minutes. During this time, evenly sprinkle mixed organic fibers, then add mixing water mixed with air-entraining water-reducing agent and retarder and mix for 4-5 minutes. Pour the evenly mixed fiber concrete into the template, vibrate to compact and roughen the surface. By curing the sandwich concrete pavement constructed according to the above steps, a long-life, self-sensing sandwich concrete pavement for emergency repair and reconstruction is obtained.

2. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: The bottom layer has a thickness of 85~120mm, the middle layer has a thickness of 160~250mm, and the top layer has a thickness of 35~65mm.

3. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: The bottom layer uses ultra-high performance concrete, the middle layer uses pre-filled smart aggregate concrete, and the top layer uses hybrid organic fiber reinforced high performance concrete.

4. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: In step one, the cement used in the lower layer is rapid-hardening cement, such as rapid-hardening sulfoaluminate cement and phosphate cement; the average particle size of the fly ash viscosity reducer is 1.5~2.0μm; the average particle size of the slag powder is 4.5~5.5μm; the average particle size of the silica fume is 0.15~0.35μm; the fineness modulus of the fine aggregate is 2.7±0.2; the solid content of the high-performance water-reducing agent is 40%, and the water reduction rate is >50%; the retarder is borax; and the steel fiber is 13mm long and 0.20mm in diameter.

5. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: The catalytic solution contains one or two of phosphoric acid, sulfuric acid, and acetic acid, wherein the concentration of phosphoric acid is 14.7 mol / L, the concentration of sulfuric acid is 18.4 mol / L, and the concentration of acetic acid is 6 mol / L.

6. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: The fly ash in the composite calcium-based solidification component is Class I fly ash with an average particle size of 8-20 μm; the calcium boride density is 2.3 g / cm³. 3 The average particle size is 1~3μm; The cement is silicate cement / ordinary silicate cement with a strength grade of 42.5 / 52.5; the average particle size of silica fume is 0.15~0.35μm; the calcium sulfate whiskers and calcium carbonate whiskers are 30~200μm long and 0.5~5μm in diameter; the conductive filler is one or two of nano-graphite, carbon nanotubes, carbon black or chopped carbon fibers, wherein the average particle size of nano-graphite is 20~25nm, the average particle size of carbon nanotubes is 5~8μm, the average particle size of carbon black is 15~20μm, and the average particle size of chopped carbon fibers is 0.5mm long and 7μm in diameter.

7. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: In step two, the cement used in the intermediate layer is rapid-hardening cement, such as rapid-hardening sulfoaluminate cement and phosphate cement; the fly ash viscosity reducer has an average particle size of 1.5~2.0μm; the conductive filler is one or two of nano-graphite, carbon nanotubes, and carbon black, wherein the average particle size of nano-graphite is 20~25nm, the average particle size of carbon nanotubes is 5~8μm, and the average particle size of carbon black is 15~20μm; the fine aggregate is 40~80 mesh quartz sand; the high-performance water-reducing agent has a solid content of 40% and a water reduction rate of >50%; and the retarder is borax.

8. The construction method for emergency repair and reconstruction of long-life self-sensing sandwich concrete pavement according to claim 1, characterized in that: In step three, the cement used in the upper layer is rapid-hardening cement, such as rapid-hardening sulfoaluminate cement or phosphate cement; the average particle size of the slag powder is 4.5~5.5μm; the fineness modulus of the fine aggregate is 2.7±0.2; the particle size range of the coarse aggregate is 5~10mm; the mixed organic fibers are ultra-high molecular weight polyethylene fibers and polyacrylonitrile fibers in a mass ratio of 1:1, wherein the length of the ultra-high molecular weight polyethylene fibers is 15mm and the diameter is 25μm, and the length of the polyacrylonitrile fibers is 15mm and the diameter is 12~20μm; the solid content of the air-entraining water-reducing agent is 30%, and the water reduction rate is >10%; the retarder is borax.

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