Intelligent sensing and active regulation concrete super large plate anti-cracking system and construction method

Abstract

The application discloses an intelligent sensing and active regulation concrete super-large plate anti-cracking system and a construction method thereof. The system comprises phase change temperature control concrete material, intelligent stress guiding structure, optical fiber sensing monitoring network, self-adaptive intelligent maintenance system and central control decision platform. The phase change temperature control concrete material is poured to form a concrete super-large plate. The intelligent stress guiding structure and the optical fiber sensing monitoring network are arranged in the concrete super-large plate. The self-adaptive intelligent maintenance system is arranged inside and above the concrete super-large plate. The central control decision platform is connected with the optical fiber sensing monitoring network and the self-adaptive intelligent maintenance system. The application relates to the technical field of building construction and can solve the technical problems in the prior art.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to an intelligent sensing and active control system and construction method for crack-resistant ultra-large concrete slabs. Background Technology

[0002] With urban development extending into underground spaces, the construction of large-scale basements after deep foundation pit excavation has become commonplace. These basement structures typically feature oversized floor slabs, side walls, and roof slabs, with large volumes poured in a single operation. During the hardening process, concrete generates significant heat of hydration, causing a rapid increase in internal temperature. Subsequently, during the cooling phase, the strong constraints from the foundation, external wall soil, or previously poured components limit thermal shrinkage and drying shrinkage, leading to substantial tensile stress within the concrete. When this tensile stress exceeds its early tensile strength, harmful cracks develop. These cracks not only compromise the structure's integrity and waterproofing, reducing its durability, but their random and unpredictable distribution also poses significant challenges to quality control and subsequent repairs, severely restricting the safety and long-term service performance of ultra-large volume concrete structures.

[0003] Currently, several conventional technical measures have been developed to address crack resistance in concrete structures: At the material level, methods such as optimizing mix proportions, using low-heat cement, or adding expansion agents are commonly employed to reduce the heat of hydration or compensate for some shrinkage at the source. At the structural level, common practices include adding temperature-controlled reinforcing steel to disperse cracks or installing post-cast strips to release early shrinkage stress. Regarding monitoring, traditional methods mainly rely on pre-embedded point sensors, such as thermocouples and vibrating wire strain gauges, to sample and measure temperature and strain at key points. For curing, surface curing methods such as regular watering and covering with insulation materials are frequently used to control surface humidity and temperature.

[0004] However, existing technologies have revealed many shortcomings in practice, making it difficult to effectively solve the crack resistance problem of ultra-large plate structures:

[0005] (1) Existing material technologies have limited and passive capabilities to regulate temperature stress. Although optimizing the mix proportion and using low-heat cement can reduce the temperature rise to a certain extent, the effect is limited. The effect of the expansion agent is greatly affected by the conditions and lacks stability. In particular, it cannot dynamically and actively intervene in the peak heat of hydration, which means that the root cause of temperature stress has not been fundamentally solved.

[0006] (2) Existing structural measures are passive in concept and cannot actively guide cracks. Adding steel bars can only disperse the crack width to a limited extent, but cannot prevent the cracks from being generated. In fact, it may even exacerbate the cracking risk by increasing the constraint. Post-cast strips are complicated to construct and have a long construction period. Moreover, the joints are easy to become weak points in waterproofing. Both lack the ability to transform disordered cracks into ordered and controllable cracks.

[0007] (3) Existing monitoring technologies have blind spots and cannot support accurate decision-making. Relying on point sensors cannot achieve full-domain, continuous, and real-time perception of the three-dimensional temperature and strain fields of the entire concrete body. The data obtained is discrete and incomplete, with a large number of monitoring blind spots, and cannot provide a comprehensive and reliable data foundation for early warning and control.

[0008] (4) Existing curing methods are crude and inefficient, and lack linkage with the internal condition. Traditional surface curing mainly relies on experience and timed operation, and cannot be dynamically adjusted according to the actual thermal state of the concrete. Its control effect on the internal core temperature is weak, and it is difficult to accurately control the temperature difference between the inside and outside. The timeliness and accuracy of curing are insufficient.

[0009] (5) The various anti-cracking links in the existing technology are isolated from each other and lack system-level coordination. The measures such as materials, structure, monitoring and maintenance are often designed and implemented independently, failing to form a closed-loop intelligent system of "perception-decision-execution". As a result, the anti-cracking process relies on human experience judgment and passive response, resulting in low overall efficiency.

[0010] Therefore, there is a need to provide an intelligent sensing and active control system and construction method for crack resistance of large concrete slabs, which can solve the above-mentioned technical problems. Summary of the Invention

[0011] The purpose of this invention is to provide an intelligent sensing and active control system for crack resistance of large concrete slabs and a construction method that can solve the above-mentioned technical problems.

[0012] This invention is implemented as follows:

[0013] A smart sensing and active control system for crack resistance of large-scale concrete slabs includes phase change temperature-controlled concrete material, intelligent stress guiding structure, fiber optic sensing and monitoring network, adaptive intelligent curing system, and central control decision platform. The phase change temperature-controlled concrete material is poured to form large-scale concrete slabs, and the intelligent stress guiding structure and fiber optic sensing and monitoring network are both arranged inside the large-scale concrete slabs. The adaptive intelligent curing system is set inside and above the large-scale concrete slabs, and the central control decision platform is connected to the fiber optic sensing and monitoring network and the adaptive intelligent curing system.

[0014] The intelligent stress-guiding structure includes a low-friction slip layer, a time-varying bonded steel mesh layer, and a pre-designed foam stress concentration element. The low-friction slip layer is laid on the basement contact layer. Several layers of time-varying bonded steel mesh are laid at intervals along the thickness direction of the large concrete slab and aligned with several layers of fiber optic sensing monitoring network. The time-varying bonded steel mesh layer is located above the low-friction slip layer. The pre-designed foam stress concentration element is located in the first time-varying bonded steel mesh layer above the low-friction slip layer.

[0015] The fiber optic sensing and monitoring network of several layers is laid at intervals along the thickness direction of the super-large concrete slab and aligned with several layers of time-varying bonded steel mesh of the intelligent stress-guided structure; each layer of fiber optic sensing and monitoring network includes distributed temperature sensing fiber and distributed strain sensing fiber, both of which are connected to the central control decision platform.

[0016] The adaptive intelligent curing system includes an internal cooling subsystem and a surface curing subsystem. The internal cooling subsystem includes cooling water pipes, a manifold, and a circulating water pump. The cooling water pipes are arranged in a rectangular pattern, continuously and uninterruptedly surrounding the bottom and middle of the large concrete slab, forming two independent loops: a bottom loop and a middle loop. The inlet and outlet pipes of both loops are led out of the surface of the large concrete slab and connected to the manifold. A circulating water pump is installed on both loops and is connected to the central control decision platform. The surface curing subsystem includes several zone-controlled intelligent curing shed units. Each intelligent curing shed unit includes an insulation blanket and a spray device consisting of atomizing nozzles controlled by solenoid valves. The solenoid valves are connected to the central control decision platform.

[0017] The intelligent sensing and active control system for crack resistance of large concrete slabs also includes an UAV infrared-assisted monitoring subsystem, which includes a UAV and an infrared thermal imager mounted on the UAV. The infrared thermal imager is connected to the central control decision system.

[0018] A construction method for an intelligent sensing and active control system for crack-resistant ultra-large concrete slabs includes the following steps:

[0019] S1. Based on finite element software, temperature and stress fields are simulated throughout the construction process. The mix proportion and gradient distribution scheme of phase change temperature-controlled concrete material, the optimal layout of intelligent stress-guided structure, and the optimal layout of fiber optic sensing monitoring network are determined by calculation.

[0020] S2. Prepare phase change temperature-controlled concrete material for large concrete slabs according to the mix proportion designed in step S1.

[0021] S3. Install the intelligent stress guiding structure at the layout position designed in step S1.

[0022] S4. Install the fiber optic sensing and monitoring network according to the layout designed in step S1.

[0023] S5: Install an adaptive intelligent maintenance system;

[0024] S6. Phase change temperature-controlled concrete material is poured and cured to form super-large concrete slabs;

[0025] S7. After the phase change temperature-controlled concrete material has set, the central control decision platform starts and collects the monitoring data of the fiber optic sensor monitoring network, and controls the adaptive intelligent curing system to carry out intelligent curing of the large concrete slab.

[0026] S8. Proactive guidance and follow-up handling.

[0027] Step S2 includes the following sub-steps:

[0028] Step S21: Raw material selection and pretreatment;

[0029] Paraffin-based PCM with a phase transition temperature of 45±2℃ and a latent heat ≥120kJ / kg was used as the core. PCM microcapsules were formed by oil-water emulsification and in-situ polymerization of the PCM using a polymethyl methacrylate / silica hybrid shell. The particle size was 10~50μm and the shell thickness was 1~5μm. Microcapsules with an open porosity of 25%~40% and an apparent density of 600~900kg / m³ were selected. 3 Porous ceramic aggregate PCA was dried at 105℃ for 2-4 hours until the quality was constant.

[0030] In step S21, the selection parameters for PCM microcapsules and porous ceramic aggregate PCA are categorized according to the target equivalent PCM content as follows:

[0031] a) PCM content 8%, i.e. low grade: PCM microcapsules D50 particle size is 10~20μm, shell thickness is 1~2μm; porous ceramic aggregate PCA open porosity is 25~30%, pore throat D50 is 30~50μm;

[0032] b) PCM content 10%, i.e. medium to low grade: PCM microcapsules D50 particle size is 15~30μm, shell thickness is 1~3μm; porous ceramic aggregate PCA open porosity is 28~35%, pore throat D50 is 40~60μm;

[0033] c) PCM content 12%, i.e. medium to high grade: PCM microcapsules D50 particle size is 20~40μm, shell thickness is 2~4μm; porous ceramic aggregate PCA open porosity is 30~38%, pore throat D50 is 50~70μm;

[0034] d) PCM content 15%, i.e. high grade: PCM microcapsules D50 particle size is 20~50μm, shell thickness is 3~5μm; porous ceramic aggregate PCA open porosity is 35~40%, pore throat D50 is 60~80μm;

[0035] S22. Preparation of functional load-bearing aggregates;

[0036] The dried porous ceramic aggregate PCA was placed in a vacuum chamber and degassed to -0.08 to -0.095 MPa for 10 to 20 minutes. Under vacuum, an aqueous dispersion of PCM microcapsules was injected, wherein the dispersion contained C... s Defined as the mass fraction of "microcapsule dry weight / total dispersion weight", and set and prepared according to the target adsorption mass fraction η and the expected single loading efficiency ξ using the following formula:

[0037]

[0038] In the formula, C s η is the solid content of the dispersion; η is the target adsorption mass fraction, taken as 10%~20%; ξ is the expected single loading efficiency, taken as 0.6~0.8; M1 is the dry mass of porous ceramic aggregate PCA before loading; M2 is the total mass of the dispersion to be injected in one operation.

[0039] The pressure was then maintained at -0.08 to -0.095 MPa for 30 to 60 minutes, followed by return to atmospheric pressure and standing for 20 to 40 minutes. This allowed the microcapsules to enter and remain in the open channels of the porous ceramic aggregate PCA under the action of capillary action and pressure difference, forming a supported functional aggregate. After loading, the aggregate was dried at a low temperature of 35 to 40°C to constant weight. The actual target adsorption mass fraction η was then checked to see if it fell within 10% to 20%. If it was insufficient, the solid content C of the dispersion was increased. s Alternatively, a short-term load can be added to correct the situation;

[0040] S23, Secondary sealing and surface densification;

[0041] Functional load-bearing aggregates were subjected to sol-gel SiO2 sealing treatment and cured at 60℃ for 2~6 hours to obtain impermeable functional aggregates.

[0042] Step S23 includes the following sub-steps:

[0043] S231, Solution preparation: Select tetraethoxysilane, anhydrous ethanol, deionized water and hydrochloric acid as raw materials, mix them in a molar ratio of 1:6:4:0.01, stir magnetically for 30~45 min to obtain a transparent sol, and then age it in an environment of 25℃ for 30 min.

[0044] S232, Pre-wetting: Place the loaded functional aggregate in ethanol and quickly wet it for 30-60 seconds, then drain it for 1 minute.

[0045] S233, Immersion-Lifting: Immerse the pre-wetted load-bearing functional aggregate in the basket into the transparent sol obtained in step S231 for 60~120s, and lift it vertically at a speed of 1~3mm / s. Then let it stand at room temperature with ventilation for 10~15min to complete one coating.

[0046] S234, Cyclic coating; Repeat steps S232 and S233 2 to 4 times until the target film thickness is reached;

[0047] S235, Curing; Place the cyclically coated loaded functional aggregate in a 60℃ hot air oven for 2~6 hours to complete condensation and densification, and obtain the anti-leakage functional aggregate, then cool it to room temperature for later use.

[0048] S24. Mixing;

[0049] The impermeable functional aggregate is used to replace the conventional coarse aggregate of the same gradation in the mixing process. No free PCM or microcapsules should be added during the mixing stage. When the target equivalent PCM content is 8%, 10%, 12%, and 15%, the corresponding replacement ratio of impermeable functional aggregate is 20~25%, 25~35%, 30~45%, and 40~55%, respectively.

[0050] Mixing sequence and time: First, dry mix the conventional coarse aggregate with 50% of the mixing water for 15 seconds. Then, add the cement and admixtures and wet mix for 45-60 seconds. Finally, add the anti-seepage functional aggregate and the remaining 50% of the mixing water according to the substitution ratio and mix at low speed for 45 seconds. The total mixing time is ≤2.5 minutes to obtain phase change temperature control concrete material.

[0051] Step S3 includes the following sub-steps:

[0052] S31, Low-friction slip layer laying;

[0053] The low-friction slip layer uses PTFE strips. A continuous ring of PTFE strips is laid around the perimeter of the large concrete slab, with a distance w between the edges of the slab, as a peripheral slow-release zone. The width of the peripheral slow-release zone is d, where 150mm≤w≤200mm and 200mm≤d≤400mm. Inside the large concrete slab, PTFE strips are laid in orthogonal directions to form a grid. The PTFE strips are parallel to the edges of the large concrete slab and extend across its entire length / width. The center-to-center distance between two parallel adjacent PTFE strips is w', where 5.0m≤w'≤7.5m.

[0054] S32. Installation of time-varying bonded steel mesh layer;

[0055] According to the design requirements of step S1, steel bars with a surface coated with a hydrolyzable polymer are laid out, wherein the first layer of time-varying bonded steel mesh layer is 50~60mm away from the upper surface of the PTFE strip;

[0056] The hydrolyzable polymer coating on the surface of the steel bar is a polyester film formed by single spraying. The polyester film is made of polylactic acid or polylactic acid-glycolic acid copolymer or polycaprolactone, and the dry film thickness is 5~30μm.

[0057] S33, Installation of pre-formed foam stress concentration elements;

[0058] The preformed foam stress concentration element is made of closed-cell cross-linked polyethylene foam with a density of 30~80 kg / m³. 3 The preformed foam stress concentration element has a compression modulus of 3~15MPa and a closed-cell rate of ≥90%. The preformed foam stress concentration element has a strip structure with a width of 30~60mm and a thickness of 10~20mm. After the lower time-varying bonded steel mesh layer is installed, the preformed foam stress concentration element is laid and tied to the first time-varying bonded steel mesh layer.

[0059] Step S5 includes the following sub-steps:

[0060] S51. After the reinforcement is tied and before the phase change temperature-controlled concrete is poured, the cooling water pipe of the adaptive intelligent curing system is fixed above the time-varying bonded reinforcement mesh layer of the lower layer. The outlet and inlet of the cooling water pipe extend to the outside of the concrete super-large slab and are connected to the manifold to form a bottom loop.

[0061] S52. The cooling water pipe of the adaptive intelligent maintenance system is fixed below the time-varying bonded steel mesh layer in the middle layer. The outlet and inlet of the cooling water pipe extend to the outside of the concrete super-large slab and are connected to the manifold to form a middle loop.

[0062] In steps S51 and S52, the horizontal spacing between adjacent cooling water pipes arranged in a rectangular, continuous pattern is S1, 1.5m≤S1≤2.0m, and the distance from the perimeter of the large concrete slab is S2, S2≥0.2m.

[0063] S53. Install circulating water pumps on the bottom loop and the middle loop respectively, and connect the circulating water pumps to the central control decision platform;

[0064] S54. Install several intelligent curing shed units in sections above the large concrete slab, and connect the intelligent curing shed units to the central control decision platform.

[0065] In step S6, when pouring the phase change temperature controlled concrete (PCM) material, the PCM content in the PCM formula is designed with a gradient distribution to inherently enhance crack resistance: the upper limit of 15% PCM content is used in the PCM formula for the bottom area of ​​the slab; the lower limit of 8% PCM content is used in the PCM formula for the top area of ​​the slab; and for the middle area, the PCM content in the PCM formula for the basement side walls and bottom is 10%, and the PCM content in the PCM formula for the top of the basement is 12%.

[0066] In step S7, the operation of the central control decision platform is as follows: the platform continuously receives real-time temperature and strain data uploaded from the fiber optic sensor monitoring network, and triggers specific decision-making logic and execution actions based on the following mechanism:

[0067] When the highest temperature in any area inside the super-large concrete slab exceeds 60°C, the "internal cooling" command is triggered, and the internal cooling subsystem of that area is activated.

[0068] When the temperature difference between the inside and outside of any area of ​​the large concrete slab is detected to be greater than 25°C, the "surface insulation" command is triggered, the surface curing subsystem of that area is started, and the insulation blanket of that area is automatically covered.

[0069] When the tensile stress in any area of ​​the super-large concrete slab exceeds 0.8 times the tensile strength of the concrete in the same period, the "Comprehensive Control and Early Warning" command is triggered, and the "Internal Cooling" and "Surface Insulation" commands for that area are also triggered. The internal cooling subsystem and surface curing subsystem for that area are activated, and an alarm is issued to the management personnel.

[0070] In step S8, during system operation, stress is allowed and monitored to be concentrated and released at the intelligent stress-guided structure; after the phase change temperature-controlled concrete material shrinks and stabilizes, pressure grouting is used to seal the regular cracks generated by the intelligent stress-guided structure to restore its integrity and waterproofness.

[0071] During the construction of the super-large concrete slab, the UAV infrared-assisted monitoring subsystem is activated. The UAV, equipped with an infrared thermal imager, regularly performs full-area flight scanning of the surface of the super-large concrete slab. The infrared thermal imager detects the intensity of infrared radiation radiated from the surface of the super-large concrete slab, generates a high-resolution surface temperature field distribution map, and sends the surface temperature field distribution map to the central control decision platform for cross-validation and calibration with the monitoring data of the fiber optic sensor monitoring network.

[0072] Compared with the prior art, the present invention has the following advantages:

[0073] 1. This invention achieves active temperature control at the material level by introducing a phase change temperature-controlled concrete material with dynamic heat absorption and release capabilities, enabling proactive intervention and precise management of the hydration heat process in concrete. This phase change temperature-controlled concrete material can absorb a large amount of latent heat through phase change when the temperature rises, effectively suppressing internal temperature peaks; and release heat during cooling, buffering the cooling rate. This minimizes temperature deformation and temperature stress at the source, overcoming the shortcomings of traditional material technologies that can only passively reduce hydration heat without dynamically controlling the temperature field.

[0074] 2. This invention integrates a low-friction slip layer, pre-formed stress concentration elements, and time-varying bonded steel bars to form an intelligent stress-guided structural system. This system can actively guide and control crack morphology. Through a time-varying synergistic mechanism that partially releases constraints in the early stage, guides cracks to generate along a predetermined path in the middle stage, and restores bonding in the later stage to ensure overall integrity, it actively induces originally unpredictable and randomly distributed harmful cracks to be concentrated at preset and continuous physical weak surfaces. This transforms disordered micro-cracks into single, regular macro-cracks, realizing the transformation of cracks from uncontrollable to guideable and manageable, overcoming the limitations of traditional structural measures that passively deal with cracks.

[0075] 3. This invention constructs a sensing system capable of synchronously and continuously acquiring three-dimensional temperature and strain field data inside concrete by deploying an optical fiber sensing and monitoring network based on the principles of Raman and Brillouin scattering. This system can achieve full-domain, real-time, and accurate perception of the internal state of large concrete slabs, overcoming the monitoring blind spots of point sensors. It provides a full-domain, high-precision data foundation for subsequent intelligent decision-making and can coordinate with the central control decision platform based on specific monitoring data to achieve dynamic control of the temperature and humidity fields of concrete.

[0076] 4. This invention constructs an adaptive intelligent curing system through an internal cooling subsystem and a surface curing subsystem, establishing an adaptive curing mechanism that can dynamically respond based on real-time monitoring data. This enables the regulation of the temperature and humidity fields of the large concrete slab, that is, based on the actual thermal state inside the large concrete slab, it automatically triggers internal water cooling or surface heat preservation and moisture retention, changing the situation of traditional curing methods being extensive, inefficient, and disconnected from the internal state.

[0077] 5. This invention integrates phase change temperature-controlled concrete materials, intelligent stress-guiding structures, fiber optic sensing monitoring networks, and adaptive intelligent curing systems into a collaborative intelligent whole through a central control decision platform. By executing closed-loop control logic of data perception, stress prediction, risk assessment, and command generation, it coordinates the intelligent operation of the entire system, shifting from passive waterproofing to proactive crack prevention. Through controlled guidance, it transforms uncontrollable crack problems into predictable and manageable technical processes, ultimately achieving full-cycle management of proactive crack prevention, controlled guidance, and post-cracking repair. This solves the key problem of fragmented processes and lack of system-level collaboration in existing technologies, achieving an intelligent upgrade of crack resistance technology for large concrete slabs. Attached Figure Description

[0078] Figure 1 This is a structural layout plan of the intelligent sensing and active control concrete super-large slab crack-resistant system of the present invention;

[0079] Figure 2 This is a cross-sectional view of the structural layout of the intelligent sensing and active control concrete super-large slab crack-resistant system of the present invention.

[0080] Figure 3 yes Figure 2 Enlarged view of point A in the middle;

[0081] Figure 4 This is a schematic diagram of the cooling water pipe laying in the intelligent sensing and active control system for crack resistance of large concrete slabs according to the present invention.

[0082] In the figure, 1 is a large concrete slab, 2 is a low-friction slip layer, 3 is a pre-formed foam stress concentration element, 4 is a time-varying bonded steel mesh layer, 5 is a fiber optic sensing monitoring network, and 6 is a cooling water pipe. Detailed Implementation

[0083] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0084] Please see the appendix Figure 1 and attached Figure 2 A smart sensing and active control system for crack resistance of large concrete slabs includes phase change temperature-controlled concrete material, intelligent stress guiding structure, fiber optic sensing and monitoring network 5, adaptive intelligent curing system, and central control decision platform. The phase change temperature-controlled concrete material is poured to form a large concrete slab 1. The intelligent stress guiding structure and fiber optic sensing and monitoring network 5 are both arranged inside the large concrete slab 1. The adaptive intelligent curing system is set inside and above the large concrete slab 1. The central control decision platform is connected to the fiber optic sensing and monitoring network 5 and the adaptive intelligent curing system.

[0085] The concrete super-large slab crack-resistant system of the present invention achieves proactive prevention, controlled guidance and post-cracking repair of cracks through the synergistic effect of materials, structure, monitoring, execution and decision-making.

[0086] Among them, the phase change temperature-controlled concrete material layer dynamically regulates the heat of hydration of concrete and reduces temperature stress through the physical process of the internal composite phase change material absorbing or releasing latent heat at the phase change point.

[0087] The intelligent stress-guided structure releases constraints through a pre-set low-friction interface and guides the concentrated release of shrinkage stress through artificially set weak surfaces, thereby transforming random cracks into manageable cracks with predetermined paths.

[0088] The fiber optic sensing and monitoring network 5, based on the physical effects of Raman and Brillouin scattering in optical fibers, can sense the temperature and strain fields in the three-dimensional space inside concrete in real time, providing a data basis for decision-making.

[0089] Based on monitoring data, the adaptive intelligent curing system uses an active heat exchange mechanism of internal water cooling and surface insulation to precisely regulate the temperature and humidity fields of concrete in both directions.

[0090] The central control decision platform sequentially executes closed-loop control logic of data perception, stress prediction, risk assessment, and instruction generation to coordinate the intelligent operation of the entire system.

[0091] Please see the appendix Figure 1 and attached Figure 2 The intelligent stress-guiding structure includes a low-friction slip layer 2, a time-varying bonded steel mesh layer 4, and a pre-designed stress concentration element. The low-friction slip layer 2 is laid on the basement contact layer (for the basement bottom, this contact layer is the leveled foundation surface; for the basement sidewall, this contact layer is the outer formwork on the side adjacent to the foundation pit; for the basement roof slab, this contact layer is the inner formwork adjacent to the interior of the basement). Several layers of time-varying bonded steel mesh layer 4 are laid at intervals along the thickness direction of the concrete super-large slab 1 within the concrete super-large slab 1 and aligned with several layers of fiber optic sensing monitoring network 5. The time-varying bonded steel mesh layer 4 is located above the low-friction slip layer 2. The pre-designed stress concentration element is located within the first layer of time-varying bonded steel mesh layer 4 above the low-friction slip layer 2.

[0092] Please see the appendix Figure 2 The fiber optic sensing and monitoring network 5, consisting of several layers, is laid at intervals along the thickness direction of the super-large concrete slab 1 within the super-large concrete slab 1 and is aligned with several layers of time-varying bonded steel mesh 4 of the intelligent stress-guided structure. Each layer of the fiber optic sensing and monitoring network 5 includes distributed temperature sensing fibers and distributed strain sensing fibers, both of which are connected to the central control decision platform.

[0093] Preferably, the distributed temperature sensing fiber and the distributed strain sensing fiber can be the OSD-1 distributed fiber temperature and strain monitoring system produced by Guangzhou Oumeidai Instrument Equipment Co., Ltd.

[0094] Preferably, the fiber optic sensing monitoring network 5 is configured in three layers. The three layers of fiber optic sensing monitoring network 5 are located at depths of 0.1h, 0.5h and 0.9h (h is the slab thickness for the bottom and top of the basement; h is the slab height for the basement sidewalls) from the bottom of the concrete super-large slab 1, respectively, and are mainly deployed around the columns, the edges of the slab and the laying area of ​​the intelligent stress guiding structure.

[0095] The working principle of distributed temperature sensing fiber optic cable is as follows: based on the Raman scattering effect, the intensity of the Anti-Stokes light generated when the laser propagates in the fiber is sensitive to temperature. By measuring the intensity ratio of the Anti-Stokes light to the Anti-Stokes light using a demodulator, the temperature value at any point along the fiber can be calculated. Compared with traditional point sensors, the measured temperature data is more comprehensive and complete.

[0096] The working principle of distributed strain sensing fiber is as follows: based on the Brillouin scattering effect, when the fiber is affected by strain or temperature, the frequency of the backscattered light from the Brillouin will drift. By accurately measuring the amount of this frequency drift, the strain value at any point along the fiber can be calculated. Compared with traditional point sensors, the measured strain data is more comprehensive and complete.

[0097] Please see the appendix Figure 4 The adaptive intelligent curing system includes an internal cooling subsystem and a surface curing subsystem. The internal cooling subsystem includes cooling water pipes 6, a manifold, and a circulating water pump. The cooling water pipes 6 are arranged in a rectangular pattern, continuously and uninterruptedly surrounding the bottom and middle of the large concrete slab 1, forming two independent loops: a bottom loop and a middle loop. The inlet and outlet of both loops are led out of the surface of the large concrete slab 1 and connected to the manifold. A circulating water pump is installed on both loops, and the circulating water pump is connected to the central control decision platform. The surface curing subsystem includes several zone-controlled intelligent curing shed units. Each intelligent curing shed unit includes an insulation blanket and a spray device consisting of atomizing nozzles controlled by solenoid valves. The solenoid valves are connected to the central control decision platform.

[0098] When the central control decision platform issues a cooling command, the circulating water pump starts, pumping cooling water through the manifold into the designated area's loop (bottom loop and / or middle loop) for circulation. This process is based on the principle of forced convection heat transfer, where the flowing cooling water exchanges heat efficiently with the interior of the high-strength concrete. Through water convection, the heat of hydration accumulated inside the concrete is continuously carried away, achieving active cooling from within the structure and thus reducing the peak temperature inside the concrete.

[0099] Preferably, the cooling water pipe 6 can be a flexible cooling water pipe made of high-density polyethylene, with a diameter of 25~32mm and a wall thickness of 2.0~2.5mm.

[0100] Preferably, the insulation blanket can be covered and uncovered using an automated rolling mechanism based on existing technology, which is controlled by a central control decision platform. After the automated rolling mechanism lays the insulation blanket on the large concrete slab 1 under the control of the central control decision platform, the insulation blanket forms a physical insulation layer on the surface of the large concrete slab 1, which slows down the convection and radiation heat dissipation between the surface of the large concrete slab 1 and the air, thereby reducing the internal and external temperature difference and suppressing the generation of surface tensile stress.

[0101] The water supply lines and insulation blankets for the spray system are divided into zones, and the spray system in each zone is independently controlled by its corresponding solenoid valve. When the central control decision platform issues a command, the insulation blanket in the corresponding zone is automatically covered or uncovered, and the atomizing nozzles of the spray system open and close intermittently or continuously according to the set program.

[0102] After the spraying device is activated, the water mist absorbs a large amount of latent heat of vaporization as it evaporates on the surface of the large concrete slab 1, which can reduce the surface temperature of the large concrete slab 1. At the same time, this process provides moisture to the surface of the large concrete slab 1, inhibiting plastic shrinkage and drying shrinkage caused by excessively rapid evaporation of moisture.

[0103] The intelligent sensing and active control system for crack resistance of large concrete slabs also includes an UAV infrared-assisted monitoring subsystem, which includes a UAV and an infrared thermal imager mounted on the UAV. The infrared thermal imager is connected to the central control decision system.

[0104] Please see the appendix Figure 1 and attached Figure 2 A construction method for an intelligent sensing and active control system for crack-resistant ultra-large concrete slabs includes the following steps:

[0105] S1. Based on finite element software, temperature and stress fields are simulated throughout the construction process. The mix proportion and gradient distribution scheme of phase change temperature-controlled concrete material, the optimal layout of intelligent stress-guided structure, and the optimal layout of fiber optic sensing monitoring network 5 are determined by calculation, so as to achieve accurate design of simulation first and construction later.

[0106] S2. Prepare phase change temperature-controlled concrete material for the super-large concrete slab 1 according to the mix proportion designed in step S1.

[0107] Phase change temperature-controlled concrete material is composed of a paraffin phase change material PCM core, an organic / inorganic hybrid shell, porous ceramic aggregate channels for physical support, and an outer sealing membrane composite structure.

[0108] Step S2 includes the following sub-steps:

[0109] Step S21: Raw material selection and pretreatment.

[0110] Paraffin-based PCM with a phase transition temperature of 45±2℃ and a latent heat ≥120kJ / kg was used as the core. PCM microcapsules were formed by oil-water emulsification and in-situ polymerization of the PCM using a polymethyl methacrylate / silica (PMMA / SiO2) hybrid shell. The microcapsules had a particle size of 10~50μm and a shell thickness of 1~5μm. The microcapsules used had an open porosity of 25%~40% and an apparent density of 600~900kg / m³. 3 Porous ceramic aggregate PCA was dried at 105℃ for 2-4 hours until the quality was constant.

[0111] In step S21, the selection parameters for PCM microcapsules and porous ceramic aggregate PCA are categorized according to the target equivalent PCM content as follows:

[0112] a) PCM content 8% (low grade): PCM microcapsules D50 particle size is 10~20μm and shell thickness is 1~2μm; porous ceramic aggregate PCA open porosity is 25~30% and pore throat D50 is 30~50μm.

[0113] b) PCM content 10% (medium to low grade): PCM microcapsules D50 particle size is 15~30μm and shell thickness is 1~3μm; porous ceramic aggregate PCA open porosity is 28~35% and pore throat D50 is 40~60μm.

[0114] c) PCM content 12% (medium to high grade): PCM microcapsules D50 particle size is 20~40μm, shell thickness is 2~4μm; porous ceramic aggregate PCA open porosity is 30~38%, pore throat D50 is 50~70μm.

[0115] d) PCM content 15% (high grade): PCM microcapsules D50 particle size is 20~50μm, shell thickness is 3~5μm; porous ceramic aggregate PCA open porosity is 35~40%, pore throat D50 is 60~80μm.

[0116] The higher the PCM content, the greater the number / volume fraction of microcapsules per unit volume, and the higher the risks of mixing and pumping shear, pore retention and leakage. Therefore, it is necessary to appropriately thicken the shell, increase the pore throat and raise the open porosity of porous ceramic aggregate PCA to ensure smooth loading and controllable subsequent pore sealing without sacrificing its durability.

[0117] S22. Preparation of functional load-bearing aggregates.

[0118] The dried porous ceramic aggregate PCA was placed in a vacuum chamber and degassed to -0.08 to -0.095 MPa for 10 to 20 minutes. Under vacuum, a PCM microcapsule aqueous dispersion was slowly injected, wherein the dispersion contained C... s Defined as the mass fraction of "microcapsule dry weight / total dispersion mass", and set and prepared according to the target adsorption mass fraction η (i.e., the dry weight of microcapsules in the channels after loading / the dry weight of porous ceramic aggregate PCA before loading, taken as 10%~20%) and the expected single loading efficiency ξ (i.e., the dry weight of microcapsules remaining in the channels after one cycle / the dry weight of microcapsules in the injected dispersion, taken as 0.6~0.8) using the following formula:

[0119]

[0120] In the formula, C sη is the solid content of the dispersion (mass fraction, dry mass of microcapsules / total mass of dispersion); η is the target adsorption mass fraction (dry mass of microcapsules in the channels after loading / dry mass of porous ceramic aggregate PCA before loading, taken as 10%~20%); ξ is the expected single loading efficiency (dry mass of microcapsules remaining in the channels after one cycle / dry mass of microcapsules in the dispersion injected this time, taken as 0.6~0.8); M1 is the dry mass of porous ceramic aggregate PCA before loading, and M2 is the planned total mass of dispersion injected in one cycle.

[0121] The pressure was then maintained at -0.08 to -0.095 MPa for 30 to 60 minutes, followed by a slow return to atmospheric pressure and standing for 20 to 40 minutes. This allowed the microcapsules to enter and remain in the open channels of the porous ceramic aggregate PCA under the influence of capillary action and pressure difference, forming a supported functional aggregate. After loading, the aggregate was dried at a low temperature of 35 to 40°C to constant weight. The actual target adsorption mass fraction η was then checked to see if it fell within 10% to 20%. If it was insufficient, the solid content C of the dispersion was increased. s Alternatively, a short-term load can be added for correction.

[0122] S23, Secondary sealing and surface densification.

[0123] Functional load-bearing aggregates were subjected to sol-gel SiO2 sealing treatment (film thickness 10~30μm) and cured at 60℃ for 2~6h to obtain impermeable functional aggregates.

[0124] Step S23 includes the following sub-steps:

[0125] S231, Solution preparation.

[0126] Tetraethoxysilane, anhydrous ethanol, deionized water, and hydrochloric acid (1 mol / L) were selected as raw materials and mixed in a molar ratio of 1:6:4:0.01. The mixture was magnetically stirred for 30-45 minutes to obtain a transparent sol, which was then aged at 25°C for 30 minutes.

[0127] S232, Prewetting.

[0128] The loaded functional aggregate is rapidly immersed in ethanol for 30-60 seconds, and then drained for 1 minute (to facilitate the entry of the sol into the pores).

[0129] S233, Impregnation-lifting.

[0130] The pre-wetted load-bearing functional aggregate is immersed in the transparent sol obtained in step S231 for 60-120 seconds and then vertically lifted at a speed of 1-3 mm / s. After that, it is left to stand at room temperature with ventilation for 10-15 minutes to complete one coating.

[0131] S234, cyclic coating.

[0132] Repeat steps S232 and S233 2 to 4 times until the target film thickness is reached (approximately 5 to 10 μm per time).

[0133] S235, Curing.

[0134] The cyclically coated loaded functional aggregate is placed in a 60℃ hot air oven for 2~6 hours to complete condensation and densification, and then cooled to room temperature for use.

[0135] S24. Mixing.

[0136] The same quality of anti-permeability functional aggregate is used to replace conventional coarse aggregate of the same gradation in the mixing process. No free PCM or microcapsules shall be added during the mixing stage. When the target equivalent PCM content is 8%, 10%, 12%, and 15%, the corresponding replacement ratio of anti-permeability functional aggregate is 20~25%, 25~35%, 30~45%, and 40~55%, respectively.

[0137] Mixing sequence and time: First, dry mix the conventional coarse aggregate with 50% of the mixing water for 15 seconds. Then, add the cement and admixtures and wet mix for 45-60 seconds. Finally, add the anti-seepage functional aggregate and the remaining 50% of the mixing water according to the substitution ratio and mix at low speed for 45 seconds. The total mixing time is ≤2.5 minutes to obtain phase change temperature control concrete material.

[0138] The same grade of conventional coarse aggregate and admixtures are conventional mixing materials for concrete, and their specific components will not be described in detail here.

[0139] S3. Install the intelligent stress-guiding structure at the layout position designed in step S1.

[0140] Step S3 includes the following sub-steps:

[0141] S31, Low-friction slip layer 2 is laid.

[0142] Preferably, the low-friction slip layer 2 can be made of strip-shaped polytetrafluoroethylene (PTFE) strips with a thickness of 0.8~1.5mm.

[0143] The dynamic friction coefficient and static friction coefficient between the low-friction slip layer 2 and the contact layer of the basement (for the bottom of the basement, the contact layer is the leveled foundation surface; for the side walls of the basement, the contact layer is the outer formwork on the side adjacent to the foundation pit; for the top slab of the basement, the contact layer is the inner formwork adjacent to the interior of the basement) are ≤0.08.

[0144] A continuous ring of PTFE strips is laid around the perimeter of the large concrete slab 1, with an inward distance w (150mm≤w≤200mm) along the edge of the slab. The width of the peripheral slow-release strip is d (200mm≤d≤400mm). Inside the large concrete slab 1, PTFE strips are laid in orthogonal directions to form a grid. The PTFE strips are parallel to the edge of the large concrete slab 1 and extend through the entire length / width. The center-to-center distance between two parallel adjacent PTFE strips is w', 5.0m≤w'≤7.5m.

[0145] The peripheral slow-release zone and the grid-like PTFE strips together constitute the low-friction slip layer 2. The low-friction slip layer 2 partially relieves the external constraints between the slab and the external environment by forming a low-friction interface around and inside the large concrete slab 1. When the concrete shrinks, the low-friction interface allows the slab to produce small, controllable relative displacements, thereby directly releasing some of the tensile stress generated by complete constraint.

[0146] S32, Time-varying bonded steel mesh layer 4 installation.

[0147] According to the design requirements of step S1, steel bars with a surface coated with a hydrolyzable polymer are laid out, wherein the first layer of time-varying bonded steel mesh layer 4 is 50~60mm away from the upper surface of the PTFE strip.

[0148] In the early stages of concrete hardening (approximately 0-7 days), the surface is coated with a hydrolyzable polymer layer, forming an isolation layer between the reinforcing steel and the phase change temperature-controlled concrete. This significantly reduces the bond strength, minimizing the restraining effect of the reinforcing steel on the shrinkage of the phase change temperature-controlled concrete. At this time, the pre-formed foam stress concentration element 3 can effectively guide crack propagation. As time progresses (approximately 7-14 days), the hydrolyzable polymer coating hydrolyzes and fails in the alkaline environment of the cement, and the bond strength between the reinforcing steel and the phase change temperature-controlled concrete returns to normal levels, regaining its structural restraining effect and ensuring that the crack width is controlled and the overall integrity of the structure is guaranteed in the later stages.

[0149] The steel bars are constructed using conventional tying techniques to form a steel mesh layer; the construction process will not be described in detail here.

[0150] The hydrolyzable polymer coating on the surface of the steel bars in the time-varying bonded steel mesh layer 4 is a polyester film formed by single spraying. The polyester film is selected from polylactic acid (PLA), polylactic acid-glycolic acid copolymer (PLGA), or polycaprolactone (PCL), and the dry film thickness is 5~30μm.

[0151] The hydrolyzable polymer coating undergoes ester bond hydrolysis in the alkaline pore liquid (pH > 12.5) generated during cement hydration and gradually dissolves and fails within 7–14 days of age. This results in a controllable time-varying bond strength at the steel-concrete interface: the bond bearing capacity 0–7 days after pouring is 0.3–0.5 times that of steel bars of the same specification without the hydrolyzable polymer coating, recovers to ≥0.8 times during 7–14 days, and then tends to be similar to that of conventional steel bars. This achieves a smooth transition from low constraint in the early stage to high constraint in the later stage, taking into account both early stress release and structural integrity in the later stage. This time-varying characteristic solves the contradiction between the need to release stress in the early stage and the need to ensure integrity in the later stage.

[0152] S33, Installation of pre-formed foam stress concentration element 3.

[0153] Preferably, the preformed foam stress concentration element 3 is made of closed-cell cross-linked polyethylene foam with a density of 30~80 kg / m³. 3 The pre-formed foam stress concentration element 3 has a compression modulus of 3~15MPa and a closed-cell rate of ≥90%. It is a strip structure with a width of 30~60mm and a thickness of 10~20mm. After the lower time-varying bonded steel mesh layer 4 is installed, the pre-formed foam stress concentration element 3 is laid and tied onto the first time-varying bonded steel mesh layer 4, with the laying method and position consistent with the PTFE strip.

[0154] The preformed foam stress concentration element 3 is fixed in the time-varying bonded steel mesh layer 4 above the low-friction slip layer 2, i.e. the lower time-varying bonded steel mesh layer 4. It artificially creates a continuous physical weak surface inside the concrete with mechanical properties much lower than the surrounding concrete. Under load or deformation, the stress will preferentially increase significantly at the weakest point of the component. The preformed foam stress concentration element 3 forces the remaining shrinkage tensile stress that has not been released by the low-friction slip layer 2 to be highly concentrated on this physical weak surface. When it exceeds the early tensile strength of the concrete, it will induce cracks to preferentially generate and penetrate at this predetermined location.

[0155] The intelligent stress-guiding structure is a composite system pre-installed within the large concrete slab 1 to actively control the morphology of shrinkage cracks. Its function is to transform uncontrollable, randomly distributed surface cracks or through cracks into single, regular cracks that develop along a predetermined path and are easy to manage later, through a collaborative mechanism. The low-friction slip layer 2, the pre-designed foam stress concentration element, and the time-varying bonded steel mesh layer 4 together constitute a time-varying system, sequentially achieving a complete process of partial stress release, guiding cracks along a predetermined path, and controlling cracks while ensuring overall integrity, thus achieving the core objective of intelligent crack guidance.

[0156] S4. Install the fiber optic sensing and monitoring network according to the layout designed in step S1.

[0157] Specifically, in step S32, during the reinforcement binding stage of installing the time-varying bonded steel mesh layer 4, distributed temperature sensing optical fibers and distributed strain sensing optical fibers are laid in three layers inside the large concrete slab 1 and aligned with the three-layer time-varying bonded steel mesh layer.

[0158] S5: Install an adaptive intelligent maintenance system.

[0159] Step S5 includes the following sub-steps:

[0160] S51. After the reinforcement binding is completed and before the phase change temperature-controlled concrete is poured, fix the cooling water pipe 6 of the adaptive intelligent curing system 20-40mm above the lower time-varying bonded steel mesh layer 4 (i.e., the first time-varying bonded steel mesh layer 4), as shown in the attached figure. Figure 2 and attached Figure 3 As shown, the outlet and inlet of the cooling water pipe 6 extend to the outside of the large concrete slab 1 and connect to the manifold, forming a bottom loop, as shown in the attached diagram. Figure 4 As shown.

[0161] S52. Fix the cooling water pipe 6 of the adaptive intelligent maintenance system 20-40mm below the time-varying bonded steel mesh layer 4 in the middle layer (i.e., the time-varying bonded steel mesh layer 4 located in the middle of the large concrete slab 1), as shown in the attached diagram. Figure 2 and attached Figure 3 As shown, the outlet and inlet of the cooling water pipe 6 extend to the outside of the large concrete slab 1 and are connected to the manifold to form a central loop.

[0162] Preferably, in steps S51 and S52, the horizontal spacing between adjacent cooling water pipes 6 arranged in a rectangular, continuous pattern is S1, 1.5m≤S1≤2.0m, and the distance from the perimeter of the large concrete slab 1 is S2, S2≥0.2m.

[0163] S53. Install circulating water pumps on the bottom loop and the middle loop respectively, and connect the circulating water pumps to the central control decision platform.

[0164] S54. Install several intelligent curing shed units in sections above the large concrete slab 1, and connect the intelligent curing shed units to the central control decision platform.

[0165] S6. Phase change temperature-controlled concrete material is poured and cured to form a super-large concrete slab 1.

[0166] In step S6, when pouring the phase change temperature controlled concrete (PCM) material, the PCM content in the PCM formula is designed with a gradient distribution to inherently enhance crack resistance: For the bottom area of ​​the slab (divided according to the pouring sequence, within a pouring height of 0.2~0.3h, where h is the slab thickness for the top and bottom of the basement, and h is the slab height for the side walls), the PCM content is capped at 15%; for the top area of ​​the slab (divided according to the pouring sequence, within a pouring height of 0.7~1h), the PCM content is capped at 15%. Within a height of 0.0h, for the top and bottom of the basement (where h is the slab thickness) and for the side walls (where h is the slab height), the phase change temperature-controlled concrete formula adopts a lower limit of 8% PCM admixture. For the intermediate area (divided according to the pouring sequence, within a pouring height of 0.3~0.7h, for the top and bottom of the basement (where h is the slab thickness) and for the side walls (where h is the slab height), the phase change temperature-controlled concrete formula for the basement side walls and bottom adopts a 10% PCM admixture, and the phase change temperature-controlled concrete formula for the basement top adopts a 12% PCM admixture.

[0167] By using the phase change temperature-controlled concrete formula PCM dosage designed with this gradient distribution, the bottom of the super-large concrete slab 1 is closer to the peak hydration heat region, and the higher PCM dosage can more effectively absorb the core heat; the higher PCM dosage in the stress concentration region can provide additional crack resistance reserve, realizing the optimized configuration and precise delivery of material properties.

[0168] The phase change temperature-controlled concrete material prepared in step S2 has the following characteristics after pouring: when the phase change temperature-controlled concrete hydrates and heats up to the phase change point, the phase change temperature-controlled concrete material changes from solid to liquid, absorbs a large amount of latent heat, and effectively suppresses the temperature peak; during the cooling stage of the phase change temperature-controlled concrete, the phase change material re-solidifies from liquid to solid, releases latent heat, buffers the cooling rate, and thus reduces temperature deformation and stress from the source.

[0169] Compared with ordinary concrete, phase change temperature-controlled concrete after curing retains ≥95% of its 28-day compressive strength, reduces the probability of crack formation by more than 70%, and improves its impermeability by more than 40%. Curing is a routine procedure in concrete construction and will not be elaborated here.

[0170] S7. After the phase change temperature-controlled concrete material has set, the central control decision platform starts and collects the monitoring data of the fiber optic sensing monitoring network 5, and controls the adaptive intelligent curing system to carry out intelligent curing of the concrete super-large slab 1.

[0171] In step S7, the operation of the central control decision platform is as follows: the platform continuously receives real-time temperature and strain data uploaded by the fiber optic sensing monitoring network 5, and triggers specific decision-making logic and execution actions based on the following mechanism:

[0172] When the highest temperature in any area inside the super-large concrete slab 1 is detected to be >60℃, the "internal cooling" command is triggered, and the internal cooling subsystem of that area is activated. The circulating cooling water prevents the concrete performance from being damaged by excessively high absolute temperatures and generating huge compressive stress.

[0173] When the temperature difference between the inside and outside of any area of ​​the large concrete slab 1 is detected to be greater than 25°C, the "surface insulation" command is triggered, the surface curing subsystem of that area is started, and the insulation blanket of that area is automatically covered to suppress the surface tensile stress caused by the excessive temperature difference.

[0174] When the tensile stress in any area of ​​the super-large concrete slab 1 exceeds 0.8 times the tensile strength of the concrete in the same period, the "Comprehensive Control and Early Warning" command is triggered, and the "Internal Cooling" and "Surface Insulation" commands for that area are also triggered. The internal cooling subsystem and surface curing subsystem for that area are activated, and an alarm is issued to the management personnel.

[0175] S8. Proactive guidance and follow-up handling.

[0176] During system operation, stress is allowed to be concentrated and released at the intelligent stress-guided structure; after the phase change temperature-controlled concrete material shrinks and stabilizes (usually after 60 days), the regular cracks generated by the intelligent stress-guided structure are sealed by pressure grouting to restore its integrity and waterproofness.

[0177] During the construction of the large concrete slab 1, the UAV infrared-assisted monitoring subsystem was activated. The UAV, equipped with an infrared thermal imager, regularly performed a full-area flight scan of the surface of the large concrete slab 1. The infrared thermal imager detected the intensity of infrared radiation radiated from the surface of the large concrete slab 1, generating a high-resolution surface temperature field distribution map. The surface temperature field distribution map was then sent to the central control decision platform for cross-validation and calibration with the monitoring data of the fiber optic sensor monitoring network 5. This ensured the full coverage and accuracy of the monitoring data and made up for the lack of spatial coverage density of fixed sensors.

[0178] Generating high-resolution surface temperature field distribution maps based on infrared thermal imaging technology is a standard practice in this field, and its specific execution process will not be elaborated here.

[0179] The central control decision platform can perform cross-validation and calibration of the surface temperature field distribution map and the temperature data of the fiber optic sensing monitoring network 5 through software programs. This is a common data processing method in the field, and its specific execution process will not be described in detail here.

[0180] This invention integrates materials, construction, monitoring, and maintenance into a novel crack-resistant system with full-cycle intelligent sensing and proactive control capabilities. It fundamentally solves the cracking problem of large concrete slabs, significantly improving the controllability and economy of the project while ensuring the structural performance of these slabs. The intelligent stress-guided structure transforms random cracks into regular cracks, greatly reducing the difficulty and cost of subsequent detection and treatment. Meanwhile, the precise control of phase-change temperature-controlled concrete materials and curing improves the physical quality of the concrete from the source, reduces the risk of leakage, and extends the structural lifespan.

[0181] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A smart sensing and active control system for crack resistance in large concrete slabs, characterized by: It includes phase change temperature-controlled concrete material, intelligent stress guidance structure, fiber optic sensing and monitoring network (5), adaptive intelligent curing system and central control decision platform; the phase change temperature-controlled concrete material is poured to form a large concrete slab (1), the intelligent stress guidance structure and fiber optic sensing and monitoring network (5) are arranged in the large concrete slab (1); the adaptive intelligent curing system is set inside and above the large concrete slab (1), and the central control decision platform is connected to the fiber optic sensing and monitoring network (5) and the adaptive intelligent curing system; The intelligent stress guiding structure includes a low-friction slip layer (2), a time-varying bonded steel mesh layer (4), and a pre-formed foam stress concentration element (3); the low-friction slip layer (2) is laid on the basement contact layer; several layers of time-varying bonded steel mesh layer (4) are laid at intervals along the thickness direction of the concrete super-large slab (1) and aligned with several layers of fiber optic sensing monitoring network (5); the time-varying bonded steel mesh layer (4) is located above the low-friction slip layer (2), and the surface of the time-varying bonded steel mesh layer (4) is covered with a hydrolyzable polymer coating; the pre-formed foam stress concentration element (3) is located in the first layer of time-varying bonded steel mesh layer (4) above the low-friction slip layer (2).

2. The intelligent sensing and active control concrete super-large slab crack-resistant system according to claim 1, characterized in that: Several layers of fiber optic sensing and monitoring networks (5) are laid at intervals along the thickness direction of the concrete super-large slab (1) and aligned with several layers of time-varying bonded steel mesh layers (4) of the intelligent stress-guided structure; each layer of fiber optic sensing and monitoring network (5) includes distributed temperature sensing fiber and distributed strain sensing fiber, and both distributed temperature sensing fiber and distributed strain sensing fiber are connected to the central control decision platform.

3. The intelligent sensing and active control concrete super-large slab crack-resistant system according to claim 1, characterized in that: The adaptive intelligent curing system includes an internal cooling subsystem and a surface curing subsystem. The internal cooling subsystem includes cooling water pipes (6), a manifold, and a circulating water pump. The cooling water pipes (6) are arranged in a rectangular shape around the bottom and middle of the large concrete slab (1) to form two independent loops, namely the bottom loop and the middle loop. The inlet and outlet of the two loops are led out of the surface of the large concrete slab (1) and connected to the manifold. A circulating water pump is installed on both loops and is connected to the central control decision platform. The surface curing subsystem includes several intelligent curing shed units with zone control. Each intelligent curing shed unit includes a heat insulation blanket and a spray device consisting of atomizing nozzles controlled by electromagnetic valves. The electromagnetic valves are connected to the central control decision platform.

4. The intelligent sensing and active control system for crack resistance of large concrete slabs according to claim 1, characterized in that: The intelligent sensing and active control system for crack resistance of large concrete slabs also includes an UAV infrared-assisted monitoring subsystem, which includes a UAV and an infrared thermal imager mounted on the UAV. The infrared thermal imager is connected to the central control decision system.

5. A construction method for the intelligent sensing and active control concrete super-large slab crack-resistant system as described in claim 1, characterized in that: Includes the following steps: S1. Based on the finite element software, the temperature field and stress field of the entire construction process are simulated. The mix proportion and gradient distribution scheme of the phase change temperature control concrete material, the optimal layout of the intelligent stress guidance structure and the optimal layout of the fiber optic sensing monitoring network (5) are determined by calculation. S2. Prepare phase change temperature-controlled concrete material for the super-large concrete slab (1) according to the mix proportion designed in step S1. S3. Install the intelligent stress guiding structure at the layout position designed in step S1. S4. Install the fiber optic sensing and monitoring network according to the layout designed in step S1 (5). S5: Install an adaptive intelligent maintenance system; S6. Phase change temperature-controlled concrete material is poured and cured to form a super-large concrete slab (1). S7. After the phase change temperature-controlled concrete material has set, the central control decision platform starts and collects the monitoring data of the fiber optic sensing monitoring network (5), and controls the adaptive intelligent curing system to carry out intelligent curing of the concrete super-large slab (1). S8. Proactive guidance and follow-up handling.

6. The construction method according to claim 5, characterized in that: Step S2 includes the following sub-steps: Step S21: Raw material selection and pretreatment; Paraffin-based PCM with a phase transition temperature of 45±2℃ and a latent heat ≥120kJ / kg was used as the core. PCM microcapsules were formed by oil-water emulsification and in-situ polymerization of the PCM using a polymethyl methacrylate / silica hybrid shell. The particle size was 10~50μm and the shell thickness was 1~5μm. Microcapsules with an open porosity of 25%~40% and an apparent density of 600~900kg / m³ were selected. 3 Porous ceramic aggregate PCA was dried at 105℃ for 2-4 hours until the quality was constant. S22. Preparation of functional load-bearing aggregates; The dried porous ceramic aggregate PCA was placed in a vacuum chamber and evacuated to -0.08 to -0.095 MPa for 10 to 20 minutes to degas it; PCM microcapsule aqueous dispersion was injected under vacuum. Then, continue to maintain the pressure at -0.08~-0.095MPa for 30~60min, then return to normal pressure and let stand for 20~40min, so that the microcapsules enter and remain in the open channels of the porous ceramic aggregate PCA under the action of capillary and pressure difference, forming a loaded functional aggregate. After loading, the product is dried at a low temperature of 35~40℃ until constant weight. S23, Secondary sealing and surface densification; Functional load-bearing aggregates were subjected to sol-gel SiO2 sealing treatment and cured at 60℃ for 2~6 hours to obtain impermeable functional aggregates. S24. Mixing; Mixing sequence and time: First, dry mix the conventional coarse aggregate with 50% of the mixing water for 15 seconds. Then, add the cement and admixtures and wet mix for 45-60 seconds. Finally, add the anti-seepage functional aggregate and the remaining 50% of the mixing water and mix at low speed for 45 seconds. The total mixing time is ≤2.5 minutes to obtain phase change temperature control concrete material.

7. The construction method according to claim 5, characterized in that: Step S3 includes the following sub-steps: S31, Low-friction slip layer (2) is laid; The low-friction slip layer (2) uses PTFE strips. A ring of PTFE strips is continuously laid around the perimeter of the concrete super-large slab (1) along the inward distance of the slab edge as a peripheral slow-release zone. PTFE strips are laid inside the concrete super-large slab (1) in a longitudinal and transverse orthogonal direction to form a grid. S32, Installation of time-varying bonded steel mesh layer (4); According to the design requirements of step S1, steel bars with a surface coated with a hydrolyzable polymer are laid out; The hydrolyzable polymer coating on the surface of the steel bar is a polyester film formed by a single spraying process; S33, Installation of preformed foam stress concentration element (3); The preformed foam stress concentration element (3) is made of closed-cell cross-linked polyethylene foam and has a strip structure. After the lower time-varying bonded steel mesh layer (4) is installed, the preformed foam stress concentration element (3) is laid and tied to the first time-varying bonded steel mesh layer (4).

8. The construction method according to claim 5, characterized in that: Step S5 includes the following sub-steps: S51. After the reinforcement is tied and before the phase change temperature control concrete is poured, the cooling water pipe (6) of the adaptive intelligent curing system is fixed above the time-varying bonded steel mesh layer (4) of the lower layer. The outlet and inlet of the cooling water pipe (6) extend to the outside of the concrete super-large slab (1) and are connected to the manifold to form a bottom loop. S52. The cooling water pipe (6) of the adaptive intelligent maintenance system is fixed below the time-varying bonded steel mesh layer (4) in the middle layer. The outlet and inlet of the cooling water pipe (6) extend to the outside of the concrete super-large slab (1) and are connected to the manifold to form a middle loop. S53. Install circulating water pumps on the bottom loop and the middle loop respectively, and connect the circulating water pumps to the central control decision platform; S54. Install several intelligent curing shed units in sections above the super-large concrete slab (1) and connect the intelligent curing shed units to the central control decision platform.

9. The construction method according to claim 5, characterized in that: In step S7, the operation of the central control decision platform is as follows: the platform continuously receives real-time temperature and strain data uploaded by the fiber optic sensing monitoring network (5), and triggers specific decision-making logic and execution actions based on the following mechanism: When the highest temperature in any area inside the super-large concrete slab (1) is detected to be >60℃, the "internal cooling" command is triggered, and the internal cooling subsystem of that area is started. When the temperature difference between the inside and outside of any area of ​​the super-large concrete slab (1) is detected to be >25℃, the "surface insulation" command is triggered, the surface curing subsystem of that area is started, and the insulation blanket of that area is automatically covered. When the tensile stress in any area of ​​the super-large concrete slab (1) is greater than 0.8 times the tensile strength of the concrete in the same period, the "Comprehensive Control and Early Warning" command is triggered, and the "Internal Cooling" and "Surface Insulation" commands for that area are triggered at the same time. The internal cooling subsystem and surface curing subsystem of that area are started, and an alarm is issued to the management personnel. During the construction of the large concrete slab (1), the UAV infrared auxiliary monitoring subsystem is activated. The UAV is equipped with an infrared thermal imager to perform full-area flight scanning of the surface of the large concrete slab (1) regularly. The infrared thermal imager detects the infrared intensity radiated on the surface of the large concrete slab (1), generates a high-resolution surface temperature field distribution map, and sends the surface temperature field distribution map to the central control decision platform for cross-validation and calibration with the monitoring data of the fiber optic sensing monitoring network (5).

Images