Roller compacted concrete construction method in cold region

Abstract

The invention discloses a roller compacted concrete construction method in a cold region, which comprises the following steps: heating coarse and fine aggregates in a closed preheating bin until the internal temperature is 5-10 DEG C, mixing by adopting a double-horizontal-shaft forced mixer, controlling the water temperature to be 25-35 DEG C, and adding a retarding water reducing agent; the mixed concrete is loaded into a dumper with an interlayer thermal insulation layer (filled with a polyurethane foaming material), and the transportation time is controlled within 40 minutes; after warehousing, paving in layers (each layer is 30-40cm) and rolling, pre-burying temperature sensors (arranged according to a 10m * 10m grid), and covering three layers of thermal insulation materials (a bottom layer polyethylene film, a middle flame-retardant polystyrene thermal insulation board and a surface layer waterproof canvas); when the temperature is lower than 5 DEG C, starting the fuel hot air unit to supply hot air through the galvanized steel pipe; warm water of 5-10 DEG C is automatically sprayed during curing, the curing time is corrected according to the temperature, and a curing agent is brushed after mold removal. The method is suitable for roller compacted concrete construction in cold regions, and the freezing injury risk and the crack occurrence rate can be comprehensively reduced.

Description

Technical Field

[0001] The present invention relates to the field of concrete construction. More specifically, the present invention relates to a construction method for roller-compacted concrete in cold regions. Background Art

[0002] When carrying out roller-compacted concrete construction in cold regions, the low-temperature environment poses special challenges to material properties, construction technology, and quality control. In conventional construction methods, the aggregate preheating process mostly uses the direct steam injection method in open-air storage yards, which has the problem of overheating of the surface aggregate while the internal temperature is insufficient. Moreover, due to the large specific surface area of fine aggregates, the water evaporation rate increases, resulting in deviation in the control of the mixing water consumption. During transportation, ordinary dump trucks lack effective heat insulation measures. Especially in an environment below -10°C, the heat loss rate from the concrete leaving the mixer to being placed in the bin seriously affects the workability of the concrete and the development of its later strength.

[0003] In the paving stage, the traditional process often adopts the single-layer thick paving method (more than 50 cm), resulting in obvious attenuation of the vibration compaction energy transfer and difficulty in meeting the design compaction degree requirements. The existing temperature monitoring system usually uses manual plug-in thermometers, with a low monitoring frequency and sparse measuring point layout (15 m × 15 m grid), unable to capture the dynamic changes of the temperature field on the bin surface in real time, and prone to local areas having temperatures lower than the critical value without being processed in time. The heat insulation covering materials mostly use single straw curtains or cotton quilts, which have poor airtightness and weak wind resistance. Under strong wind conditions, the heat insulation layer is prone to displacement, resulting in cold bridge phenomena, and the temperature difference between the surface and the interior of the concrete can induce temperature stress cracks.

[0004] During the curing period, the conventional sprinkler curing method is prone to surface icing in a low-temperature environment, and the hindered water penetration leads to insufficient cement hydration reaction. The judgment of the form removal time mostly relies on empirical formulas, without considering the non-linear influence of the actual temperature history on the strength development. Premature form removal increases the corner breakage rate, while delayed form removal prolongs the construction period. The existing curing agent spraying process does not establish an associated control mechanism with the surface roughness, and coating discontinuity is prone to occur in the exposed aggregate area, reducing the anti-freezing protection effect.

[0005] The root causes of these technical defects lie in the lack of a complete temperature control chain: there is no systematic solution for aggregate pretreatment, transportation heat preservation, suppression of paving heat loss, and microenvironment regulation during the curing period. Especially in temperature-sensitive aspects such as the heat transfer efficiency inside the aggregate, the attenuation model of thermal parameters during transportation, and the coupling relationship between compaction density and temperature field, the existing technologies have not yet formed quantitative control standards. The main difficulties faced in construction include: how to achieve gradient preheating of coarse and fine aggregates to reduce the demand for mixing water temperature; how to design a covering system that combines heat preservation and construction convenience; and how to construct a multi-scale temperature monitoring network to achieve precise thermal compensation control. These problems severely restrict the uniformity and durability of roller-compacted concrete structures in cold regions, and there is an urgent need to achieve precise regulation of the temperature field throughout the process through process innovation. Summary of the Invention

[0006] An object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0007] An object of the present invention is to propose a systematic process optimization scheme for problems such as uneven preheating of aggregates, large heat loss during transportation, rough paving temperature control, insufficient sealing of heat preservation covers, and poor adaptability of curing parameters in the construction of roller-compacted concrete in cold regions. An object of the present invention is to solve the cold bridge effect caused by the displacement of the heat preservation layer due to wind force and the problem of the traditional ballast method damaging the integrity of the heat preservation material. An object of the present invention is to overcome the defects of uneven compaction density caused by fluctuations in the excitation force of the vibratory roller and the sudden drop in local temperature caused by air leakage at the joints of the heat preservation material. An object of the present invention is to improve the limitation that a single traditional temperature measurement point cannot reflect the internal temperature gradient of concrete. An object of the present invention is to solve the problems of dispersed hot air conveying direction and low thermal efficiency. An object of the present invention is to optimize the internal hot air flow field distribution in galvanized steel pipes and avoid local overheating or overcooling phenomena caused by air flow short-circuiting. An object of the present invention is to address the technical difficulty of being unable to precisely compensate for heat in the area where the surface temperature drops suddenly. An object of the present invention is to avoid the interference of low-temperature freezing of the spray pipeline and the temperature fluctuation of the sprayed water on the hydration reaction of concrete. An object of the present invention is to solve the problem of unstable compensation shrinkage effect caused by uneven concentration of the sprayed expansive agent. An object of the present invention is to improve the risk of protection failure caused by the mismatch between the coating thickness of the curing agent and the surface roughness. Another object of the present invention is to provide a construction method for roller-compacted concrete in cold regions, which can reduce the aggregate temperature gradient through gradient preheating and heat preservation transportation, improve the rolling compactness and temperature uniformity through layered paving combined with intensive temperature monitoring, correct the curing time formula to ensure the safety of form removal, and comprehensively reduce the risk of frost damage and the incidence of cracks.

[0008] To achieve these objects and other advantages of the present invention, a construction method for roller-compacted concrete in cold regions is provided, including the following steps: 1) Place the coarse aggregate and fine aggregate in a closed preheating bin respectively, heat them to an internal temperature of 5 - 10 °C through steam coils, use a twin-shaft forced mixer for concrete mixing, control the water temperature at 25 - 35 °C during the mixing process, and add a retarding water reducer accounting for 1 - 2% of the total mass of the cementitious material; 2) Load the mixed concrete into a self-unloading transport vehicle with an interlayer heat preservation layer, fill the interlayer of the transport vehicle with polyurethane foam, and control the transport time within 40 minutes; 3) Transport the concrete to the construction site. When the concrete is put into the bin, adopt a layered paving process, with the paving thickness of each layer being 30 - 40 cm. Immediately after paving, use a 5t double-drum vibratory roller for rolling; embed temperature sensors on the surface of the already rolled concrete, arrange the monitoring points according to a 10m × 10m grid, and then cover with three layers of heat preservation materials, lay a polyethylene film at the bottom layer, a flame-retardant polystyrene heat preservation board in the middle layer, and a waterproof canvas at the surface layer; 4) Monitor the internal temperature of the concrete through the embedded temperature sensors. When the continuously monitored temperature is lower than 5 °C for 2 hours, start the fuel-fired hot air blower unit, and convey hot air to the lower part of the heat preservation layer through galvanized steel pipes arranged on the bin surface; 5) On the basis of heat preservation covering and temperature regulation, implement concrete curing: Keep the surface moist during the concrete curing period, use an automatic spraying system to spray warm water at 5 - 10 °C every 2 hours through the reserved holes penetrating the waterproof canvas, and the spraying time lasts for 30 seconds; Under the condition that the surface temperature of the concrete continuously ≥ 5 °C, the curing time: T = K • T0, where T0 is the form removal reference time under the standard curing condition of 20 °C, and K takes a temperature correction coefficient of 1.5 - 2.0; When the core sample strength of the concrete reaches 70% of the design strength and the curing time meets the T value, implement form removal operation, and immediately apply two coats of concrete curing agent after form removal, with an interval of 4 hours between each coat. Preferably, in step 3) of the present invention, after covering three layers of thermal insulation materials, a steel pressing device is arranged longitudinally along the bin surface at intervals of 3 m. The device consists of a channel steel spanning the thermal insulation layer horizontally, a threaded steel anchor embedded in the concrete, and a thick steel plate pressing plate. The threaded steel anchor is vertically inserted into the concrete surface 2 - 3 hours before the final setting of the concrete, with an embedded depth of 150 mm, an exposed end processed with threads and an exposed length of 50 mm, and the perpendicularity deviation controlled within 5‰; the threaded steel anchors are arranged at intervals of 3 m along the long side, with the perpendicularity deviation within 5‰. After the initial setting of the concrete, it is tightly connected by a nut with a rubber gasket, and the tightening torque is controlled within 80 - 100 N•m. Preferably, in step 3) of the present invention, an excitation force sensor is installed on the 5t double - steel - wheel vibratory roller, and the excitation force value is displayed in real - time during the rolling process. When the detected excitation force deviates from the set value by 10%, an audible and visual alarm is automatically triggered and the rolling operation is stopped; After the machine stops, the following recovery procedures are executed: a) The operator checks the mechanical connection status of the vibration system and eliminates faults such as broken drive shafts and blocked bearings; b) Enter the excitation force calibration command through the control panel, and the system automatically performs 3 no - load vibration tests. When the deviation rate between the actual excitation force and the set value measured is ≤3%, the touch screen displays a "system normal" prompt; c) When returning to the interrupted position to re - roll, lap compaction is carried out within a range 1 m behind the end of the rolled belt that has stopped. In the lap area, 2 additional static compactions and 3 additional vibration compactions are performed; The joints of the three - layer thermal insulation materials are sealed with U - shaped aluminum alloy pressure strips. The width of the pressure strip is 50 mm, and it is fixed to the concrete surface by a nail gun at intervals of 200 mm. The nail penetration depth is 15 mm, and the exposed end is smeared with asphalt sealant. The contact part of the U - shaped aluminum alloy pressure strip and the nail is subjected to hot - dip galvanizing treatment, and the thickness of the galvanized layer is not less than 80 μm. After the nail fixation, a butyl rubber sealing tape is used to cover the nail head part. The width of the sealing tape is 20 mm and the elongation rate is greater than 300%. Preferably, in step 4) of the present invention, 2 additional monitoring points are added in each 10 m×10 m grid for the temperature sensor, which are respectively buried at depths of 5 cm and 25 cm below the concrete surface, and the sensors are evenly distributed. Preferably, in step 4) of the present invention, when the fuel - fired hot - air blower unit is started, the hot - air delivery pressure is 0.15 - 0.25 MPa, and directional air supply is implemented through inclined downward 45° spray holes opened on the side wall of the galvanized steel pipe. The distance between adjacent spray holes is 80 cm. Preferably, a deflector plate is welded and fixed inside the galvanized steel pipe of the present invention. The deflector plate is made of 1.5 - mm - thick galvanized steel plate bent at an angle of 25°, and is arranged alternately at intervals of 60 cm along the pipe length direction. The distance error between adjacent deflector plates does not exceed ±5 mm. Preferably, in step 4) of the present invention, a mobile infrared thermometer is used to monitor the surface temperature in real time. When the measured point temperature is lower than 2°C, a detachable hot air curtain device is temporarily installed on the galvanized steel pipe in the corresponding area. The device consists of an axial flow fan, a honeycomb aluminum alloy heater, and a corrugated hose. The hot air outlet temperature is set to 40 - 50°C. The detachable hot air curtain device is equipped with a deflector hood made of stainless steel plate, with a 30° diffusion angle deflector at the front end. The distance between the deflectors is 50 mm and the distance from the outlet end of the corrugated hose is 80 mm. Preferably, in step 5) of the present invention, the nozzles of the automatic sprinkler system adopt rotary atomizing nozzles. The height of the nozzles from the concrete surface is maintained at 1.2 - 1.5 m, and the outlet pressure of the nozzles is adjusted to 0.3 - 0.4 MPa. After the water supply pipeline of the automatic sprinkler system is wrapped with rubber and plastic insulation cotton, a 15 W / m electric heating tape is laid parallel to the pipeline length direction. After the electric heating tape is energized, the water temperature in the pipeline is maintained within the range of 5 - 10°C, and the water supply pipeline is also wrapped with rubber and plastic insulation cotton. Preferably, when the automatic sprinkler system of the present invention sprays warm water at 5 - 10°C, a sulfoaluminate expansive agent accounting for 0.45% - 0.55% of the sprayed water volume is synchronously incorporated. A static mixer is set in the spraying pipeline to ensure that the coefficient of variation of the solution uniformity is less than 5%. The concentration control of the sulfoaluminate expansive agent solution is monitored by an on-line conductivity meter. When the conductivity value deviates from the reference value by ±10%, the expansive agent is automatically added through a peristaltic pump to maintain the solution concentration within the range of 0.45% - 0.55%. During the addition process, the fluctuation range of the solution flow rate does not exceed ±2%. Preferably, when applying the concrete curing agent after form removal in step 5) of the present invention, a spraying device is used to control the spraying flow rate at 300 - 400 mL / m², and the moving speed of the spray gun is maintained at 0.5 - 0.8 m / s. An epoxy resin anti-rust layer is applied to the exposed threaded parts of the anchor fittings. After applying the epoxy resin anti-rust layer to the exposed threaded parts of the threaded steel embedded parts, a polyurethane anti-corrosion coating with a thickness of 1.2 - 1.5 mm is additionally applied. The hardness of the cured coating reaches Shore D60 - 65. A temperature sensor adds one monitoring point at the boundary of each 10 m × 10 m grid, located 20 cm inside the inner side of the four surrounding boundaries of the warehouse surface. The spraying device is equipped with a contact surface roughness detector. When the Ra value of the concrete surface roughness exceeds 0.8 mm, the spraying flow rate is automatically switched to 450 - 500 mL / m² and the moving speed of the spray gun is reduced to 0.4 - 0.6 m / s, and a 25 cm wide overlapping coverage area is set at the end of the spraying path. The present invention has at least the following beneficial effects: 1. By gradient preheating and heat preservation transportation, the aggregate temperature gradient is reduced. Layered paving combined with intensive temperature monitoring improves the compaction density and temperature uniformity. The curing time formula is corrected to ensure the safety of form removal, comprehensively reducing the frost damage risk and crack incidence rate. 2. The profiled steel pressing device enhances the wind resistance performance of the insulation layer through mechanical anchoring. The rubber gasket buffers the fastening stress to avoid damage to the insulation board. The control of the embedding depth and perpendicularity ensures the reliability of the anchoring and reduces the local temperature drop caused by the cold bridge effect. 3. The closed-loop control of the exciting force and the overlapping re-rolling procedure improve the rolling uniformity. The U-shaped pressing strip and the butyl tape seal the joint to reduce the air leakage rate. The galvanized layer resists rust and extends the service life of the pressing strip, reducing the quality fluctuations caused by abnormal vibration or insulation failure. 4. The layout of double-depth temperature measurement points accurately reflects the internal temperature gradient of the concrete. Combining with the surface infrared monitoring, it realizes the dynamic regulation of the three-dimensional temperature field and avoids the local freeze-thaw damage caused by the temperature measurement blind area. 5. The inclined spray holes direct the air supply to improve the uniformity of the hot air coverage. The pressure control optimizes the penetration depth of the hot air, reduces the ineffective heat loss, and improves the overall heating efficiency of the silo surface. 6. The staggered flow deflectors improve the turbulent distribution of the hot air and avoid the air flow short circuit. The 25° inclination angle design balances the air flow velocity and the diffusion range, reducing the area of the region with a local temperature deviation ≥ 3°C. 7. The detachable hot air curtain responds quickly to the surface temperature drop. The combination of the honeycomb heater and the flow deflector improves the utilization rate of the hot air. The diffusion sheet optimizes the hot air coverage range, reducing the repair rework rate ≥ 15%. 8. The combination of the electric heating tape and the insulation cotton maintains the stability of the spray water temperature. The rotating atomizing nozzle improves the spraying uniformity and avoids the maintenance interruption caused by the water temperature fluctuation or icing. 9. The online concentration monitoring and the static mixer cooperate to ensure the uniformity of the expansion agent distribution. The conductivity feedback regulation mechanism makes the solution concentration deviation ≤ 0.03%, and the compensating shrinkage effect is increased by more than 20%. 10. The roughness adaptive spraying strategy ensures the continuity of the curing agent film formation. The double-layer anti-corrosion of epoxy resin and polyurethane extends the service life of the anchor. The boundary temperature measurement points supplement the monitoring of the edge temperature drop, and the overall protection qualification rate is increased to more than 95%.

[0009] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Detailed Embodiment

[0010] The following further elaborates on the present invention in detail so that those skilled in the art can implement it according to the description in the specification.

[0011] It should be understood that the terms such as "having", "including", and "comprising" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0012] It should be noted that the experimental methods described in the following implementation schemes are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0013] A construction method for roller-compacted concrete in cold regions includes the following steps: 1) Place the coarse aggregate and fine aggregate separately in a closed preheating bin, heat them to an internal temperature of 5 - 10 °C through steam coils, use a double-horizontal-shaft forced mixer for concrete mixing, control the water temperature at 25 - 35 °C during the mixing process, and add a retarding water reducer accounting for 1 - 2% of the total mass of the cementitious material; 2) Load the mixed concrete into a self-unloading transport vehicle with an interlayer insulation layer, fill the interlayer of the transport vehicle with polyurethane foam, and control the transport time within 40 minutes; 3) Transport the concrete to the construction site. When the concrete enters the bin, adopt a layered paving process, with a paving thickness of 30 - 40 cm for each layer. Immediately after paving, use a 5t double-steel-wheel vibratory roller for compaction; embed temperature sensors on the surface of the compacted concrete, arrange the monitoring points according to a 10m × 10m grid, and then cover with three layers of thermal insulation materials. The bottom layer is a polyethylene film, the middle layer is a flame-retardant polystyrene insulation board, and the top layer is a waterproof canvas; 4) Monitor the internal temperature of the concrete through the embedded temperature sensors. When the continuously monitored temperature is lower than 5 °C for 2 hours, start the fuel-fired hot air blower unit, and convey hot air to the lower part of the insulation layer through the galvanized steel pipes arranged on the bin surface; 5) On the basis of thermal insulation coverage and temperature regulation, implement concrete curing: Keep the surface moist during the concrete curing period. Use an automatic spraying system to spray warm water at 5 - 10 °C every 2 hours through the reserved holes penetrating the waterproof canvas, and the spraying time lasts for 30 seconds; Under the condition that the surface temperature of the concrete continuously ≥ 5 °C, the curing time: T = K • T0, where T0 is the form removal reference time under the standard curing condition of 20 °C, and K takes a temperature correction coefficient of 1.5 - 2.0; When the strength of the concrete core sample reaches 70% of the design strength and the curing time meets the T value, implement form removal operation, and immediately apply two coats of concrete curing agent after form removal, with an interval of 4 hours between each coat.

[0014] In this technical solution, the coarse aggregate and the fine aggregate can be placed in a closed preheating bin respectively. The preheating bin can be a steel structure welded bin body, with steam coils arranged inside. The coil diameter can be selected as 25 mm or 32 mm, and the steam pressure can be controlled at 0.4 - 0.6 MPa. The target heating temperature of the aggregate can be selected as 5 °C, 8 °C or 10 °C, and the heating time can be selected as 2.5 - 3.5 hours according to the aggregate particle size. The interlayer of the transport vehicle can be filled with polyurethane foam material, and the foam density can be selected as 40 - 60 kg / m³, and the interlayer thickness can be designed as 80 - 100 mm. The transport vehicle can be a modified Shaanxi Automobile Delong F3000 type dump truck. The heat preservation interlayer frame is welded on the inner wall of the carriage, and after the interlayer is filled with foam material, the outer layer is welded with steel plates for sealing. The paving layer thickness can be set as 30 cm, 35 cm or 40 cm. The paver can be a Sany SY950 type paver, and the vibratory roller can be a XCMG XP305 type double steel wheel vibratory roller. The temperature sensor can be a PT100 type platinum resistance sensor, and the monitoring points are arranged in a 10 m × 10 m grid, and sensors are buried at the center points of each grid. The laying sequence of the heat preservation material is as follows: the thickness of the bottom polyethylene film can be selected as 0.12 mm or 0.15 mm, the density of the middle flame-retardant polystyrene board is 18 - 22 kg / m³, and the gram weight of the surface waterproof canvas can be selected as 500 - 600 g / m². The overlapping width of the film is 150 mm, and the splicing joints of the polystyrene board are filled with polyurethane foam glue. The spray system can be a Rain Bird 5004 type rotary nozzle, and the installation height of the nozzle can be adjusted to 1.2 m, 1.35 m or 1.5 m. The spraying pressure is adjusted to 0.3 MPa, 0.35 MPa or 0.4 MPa through a pressure reducing valve. In the form removal determination, the temperature correction coefficient K can be taken as 1.5, 1.8 or 2.0, and the strength detection of the concrete core sample can be jointly determined by a rebound instrument and a core drill. The curing agent can be a silicate-based water-based curing agent, and the coating equipment can be a Grace HUSKY-310 type spraying machine. The moving speed of the spray gun is controlled by a variable frequency motor to be 0.5 m / s, 0.65 m / s or 0.8 m / s.

[0015] This invention is based on the thermodynamic control and material property optimization of concrete construction under low temperature environment, and realizes the stability of the temperature field through the coordinated action of multiple links. Its core principle can be divided into: The spiral layout design of the steam coil (which can be made of stainless steel SUS304 material) in the closed preheating bin realizes the gradient transfer of heat from outside to inside through the condensation heat release effect when steam contacts the surface of the aggregate. When the particle size of the coarse aggregate is large, a heating target temperature of 8 - 10 °C is selected to compensate for its internal thermal inertia; because the fine aggregate has a large specific surface area, heating it to 5 - 8 °C can meet the mixing requirements. This process follows Fourier's law of heat conduction, and the heat flux density is adjusted by controlling the steam pressure (0.4 - 0.6 MPa) to make the temperature difference between the center and the surface of the aggregate ≤ 3 °C.

[0016] The polyurethane foam sandwich layer (thermal conductivity ≤ 0.024 W / (m·K)) forms multiple thermal insulation barriers, and its closed-cell structure is used to block convective heat dissipation. The metal outer shell of the transport vehicle (with a thickness of 2 - 3 mm) and the internal thermal insulation layer form a composite thermal resistance, and the total thermal resistance value is calculated through the series thermal resistance formula R = R1 + R2, so that the temperature drop of the concrete within 40 minutes of transportation is ≤ 2°C. An EPDM rubber sealing strip (with a hardness of 70 ± 5 Shore A) is installed at the articulated part of the carriage to reduce heat dissipation through gaps.

[0017] The retarding water reducer (such as polycarboxylate series, with a dosage of 1.2 - 1.8%) delays the agglomeration of cement particles through adsorption-dispersion action, reducing the freezing point of the mixing water to -5°C. Laying in layers (with a layer thickness of 35 cm) increases the vibration wave transmission efficiency to 82 - 85%, and the compaction energy density reaches 1.2 - 1.5 kJ / m³, promoting the compactness of the concrete to more than 98%. The temperature correction coefficient K = 1.5 - 2.0 is set based on the Arrhenius equation, and the equivalent age is converted to: te =∑ e −Ea / R(1 / T−1 / Tr) Δ t； where Ea is taken as 40 kJ / mol and Tr = 293 K to ensure that the curing time is synchronized with the strength development. This technical solution precisely controls the internal temperature gradient of the aggregate through a closed preheating bin, and the insulated transport vehicle with a sandwich layer reduces the heat loss rate; laying in layers and grid monitoring ensure the uniformity of the temperature field; the interlocking control of the spraying parameters and the form removal conditions ensures the curing quality. After implementation, the duration with the concrete entering the bin temperature ≥ 5°C can be extended by more than 40%, the temperature difference between the surface layer and the interior is ≤ 8°C, and the surface integrity after form removal reaches the first-level acceptance standard. In another technical solution, in step 3) of the present invention, after covering three layers of thermal insulation materials, a steel pressing device is arranged at intervals of 3 m along the longitudinal direction of the bin surface. This device consists of a channel steel spanning the thermal insulation layer horizontally, a threaded steel anchor embedded in the concrete, and a thick steel plate pressing plate. The threaded steel anchor is vertically inserted into the concrete surface 2 - 3 hours before the final setting of the concrete, with an embedded depth of 150 mm, the exposed end is processed with threads and the exposed length is 50 mm, and the perpendicularity deviation is controlled within 5‰; the threaded steel anchors are arranged at intervals of 3 m along the long side, with the perpendicularity deviation within 5‰. After the initial setting of the concrete, it is tightly connected through a nut with a rubber gasket, and the tightening torque is controlled within 80 - 100 N•m.

[0018] In this technical solution, channel steel can be selected as C10 or C12 cold-formed channel steel, with a section height of 100 mm or 120 mm and a flange width of 48 mm or 53 mm. The deformed bar anchor can be selected as HRB400 deformed bar, with a diameter of 16 mm or 18 mm, and the exposed end thread is processed into M16 or M18 standard thread. The thick steel plate pressing plate can be selected as Q235B steel plate, with a thickness of 10 mm or 12 mm, a width of 80 mm or 100 mm, and a length matching the flange width of the channel steel. When the channel steel spans the insulation layer horizontally, both ends extend 50 mm outside the edge of the silo surface, and the distance between the web of the channel steel and the surface of the insulation layer is maintained at 20 mm to 30 mm. A 3-mm-thick rubber gasket can be installed between the pressing plate and the flange of the channel steel. The gasket material can be selected as EPDM rubber, with a Shore hardness of 60HA or 70HA.

[0019] The embedded depth of the deformed bar anchor is set to 150 mm, and the exposed length is controlled to 50 mm, with an allowable deviation of ±2 mm. The verticality deviation is calibrated by a laser alignment instrument, and the verticality deviation is controlled within 5‰. When the anchor is inserted into the concrete, it is selected to be carried out 2 to 3 hours before the final setting of the concrete, and the insertion speed is controlled at 10 cm / min or 15 cm / min. The spacing of the anchors arranged along the long side of the silo surface is 3 m, and the spacing in the short side direction is the same as that in the long side. The position of the embedded hole is located by total station layout, and the deviation of the hole center does not exceed ±5 mm. After insertion, the exposed threaded part of the anchor can be smeared with butter to prevent rust.

[0020] The tightening torque of the nut is set to 80 N·m, 90 N·m or 100 N·m, and a digital display torque wrench is used for two-stage loading: the first stage is loaded to 60% of the set value, and the second stage is loaded to the full value. The rubber gasket can be selected as EPDM material, with a thickness of 3 mm, and the center hole diameter matches the diameter of the deformed bar. When installing, the gasket fits with the pressing plate and the flange of the channel steel. After tightening, the gap between the pressing plate and the flange of the channel steel is detected by a feeler gauge, and the gap is controlled within the range of 0.5 mm to 1 mm. After the anchoring system is installed, a pull-out test is carried out: a hydraulic jack is used to apply a 10 kN tensile force, and the displacement ≤2 mm is qualified. The steel pressing device provides a uniform pressing force through the lateral stiffness of the channel steel, and the embedded depth and verticality of the deformed bar anchor ensure the pull-out resistance. The rubber gasket absorbs vibration energy during the tightening process and reduces local stress concentration. The torque control strategy balances the relationship between the tightening force and the material deformation, avoiding over-tightening that may cause the insulation board to be crushed or over-loosening that may lead to anchoring failure. This solution enhances the wind resistance of the insulation layer through mechanical anchoring and reduces the local temperature drop caused by the cold bridge effect. The buffering effect of the rubber gasket reduces the breakage rate of the insulation material, and the embedded depth and torque control ensure the connection reliability. After implementation, the fit degree between the insulation layer and the concrete surface is improved, the air leakage at the joint is significantly reduced, and the service life of the anchoring system is extended. In another technical solution, in step 3) of the present invention, an excitation force sensor is installed on the 5t double-drum vibratory roller, and the excitation force value is displayed in real time during the rolling process. When the detected excitation force deviates from the set value by 10%, an audible and visual alarm is automatically triggered and the rolling operation is stopped; After the machine stops, the following recovery procedures are executed: a) The operator checks the mechanical connection status of the vibration system and eliminates faults such as broken drive shafts and blocked bearings; b) Enter the excitation force calibration command through the control panel, and the system automatically performs 3 no-load vibration tests. When the deviation rate between the actual excitation force and the set value measured is ≤3%, the touch screen displays a "system normal" prompt; c) When returning to the interrupted position to resume rolling, lap compaction is carried out within a range of 1m backward from the end of the stopped rolling belt. 2 additional static compactions and 3 additional vibratory compactions are carried out in the lap area; The joints of the three-layer thermal insulation material are sealed with U-shaped aluminum alloy strips. The width of the strip is 50mm, and the U-shaped aluminum alloy strip is fixed to the concrete surface by a nail gun every 200mm. The depth of the nail is 15mm and the exposed end is smeared with asphalt sealant. The contact part of the U-shaped aluminum alloy strip and the nail is subjected to hot-dip galvanizing treatment, and the thickness of the galvanized layer is not less than 80μm. After the nail is fixed, a butyl rubber sealing tape is used to cover the nail head part. The width of the sealing tape is 20mm and the elongation rate is greater than 300%.

[0021] In this technical solution, the excitation force sensor can be a piezoelectric sensor, the measuring range can be 0-20kN, and it is installed at the bearing seat of the vibration shaft of the vibratory roller. The control panel can be integrated with a 7-inch touch screen to display the excitation force value range in real time, and the alarm threshold is set at ±10% of the excitation force set value. When the calibration command is executed, the system automatically triggers 3 no-load vibrations, and the duration of each vibration can be selected as 5 seconds, 8 seconds or 10 seconds. The calibration deviation rate determination threshold is ≤3%. When the measured deviation rate exceeds 3%, the system locks the operation permission until the repair is completed. The sensor signal wire can be protected by a metal bellows and routed along the inner side of the vibratory roller frame. The lap compaction range can be set to 1m backward from the stop position. The number of static compactions in the lap area can be selected as 2 or 3 times, and the number of vibratory compactions can be selected as 3 or 4 times. When performing the re-compaction, the traveling speed of the vibratory roller can be controlled at 1.0m / min, 1.2m / min or 1.5m / min. The boundary of the lap area can be sprayed with red markings, and the width of the markings can be selected as 50mm or 80mm. After the re-compaction is completed, a nuclear density gauge is used to detect the compactness of the lap area. The spacing between the detection points can be selected as 0.5m or 1m, and the difference in compactness is controlled within the range of ≤2%. The U-shaped aluminum alloy bead can be made of 6063-T5 aluminum alloy profile with a cross-sectional width of 50 mm and flange heights of 15 mm or 20 mm. The nail can be made of stainless steel with a nail rod diameter of 3 mm or 4 mm and a length that can be selected as 20 mm or 25 mm. The fixed spacing of the nails can be selected as 200 mm, 250 mm, or 300 mm, and the penetration depth into the concrete is controlled at 15 mm ± 1 mm. The joint between the bead and the insulation board can be filled with a butyl rubber sealing tape, and the width of the sealing tape can be selected as 20 mm or 25 mm with a thickness of 1.5 mm or 2 mm. The head of the nail can be coated with asphalt sealant with a coating thickness of 0.5 mm or 1 mm, and after curing, a butyl tape is added for covering, and the lap length of the tape can be selected as 30 mm or 50 mm. The closed-loop control of the excitation force adjusts the output energy of the vibration system through sensor feedback to ensure uniform distribution of the compaction energy density. The no-load calibration procedure eliminates the systematic error caused by mechanical clearance, and taking the average value of 3 tests improves the calibration accuracy. The overlapping compaction eliminates the density mutation at the joint by overlapping compaction, and the combination process of static pressure and vibration compensates for the energy attenuation. The elastic clamping force of the U-shaped bead and the mechanical fixation of the nails form a composite seal, and the butyl tape fills the micro-pores to block the air flow channel. This solution improves the compaction uniformity through real-time monitoring of the excitation force, and the calibration procedure reduces the density fluctuation caused by equipment abnormalities. The overlapping compaction process eliminates the construction cold joint, and the nuclear density detection ensures the quality of the joint. The U-shaped bead and the multi-layer sealing structure improve the airtightness of the joint and reduce the local temperature drop caused by air leakage. After implementation, the fault shutdown time of the vibration system is shortened, and the temperature gradient at the joint of the insulation layer is controlled within the allowable range. In another technical solution, in step 4) of the present invention, 2 monitoring points are added in each 10 m × 10 m grid for the temperature sensor, which are respectively buried at a depth of 5 cm and 25 cm below the concrete surface layer, and the sensors are evenly distributed.

[0022] In this technical solution, 2 additional monitoring points can be set in each 10 m × 10 m monitoring grid, which are located at symmetric positions on both sides of the grid center point. The horizontal spacing can be selected as 3 m or 4 m, and the vertical spacing can be selected as 2 m or 3 m. When arranging the monitoring points, a total station is used for positioning and lofting, and the coordinate deviation is controlled within the range of ±50 mm. Auxiliary marking piles can be added at the grid boundary, and the pile body material can be selected as PVC plastic piles with the pile top elevation flush with the concrete surface. The top of the marking pile can be sprayed with red reflective paint for easy positioning and recheck during the construction period.

[0023] The temperature sensor can be a PT100 platinum resistance sensor. The length of the probe can be selected as 30 cm or 40 cm, and the diameter can be selected as 6 mm or 8 mm. The burial depth of the surface monitoring point can be set at 5 cm ± 1 cm, and the burial depth of the deep monitoring point can be set at 25 cm ± 2 cm. When installing the sensor, the pre-embedded sleeve method is adopted: immediately insert a PVC sleeve with an outer diameter of 10 mm after the concrete is paved, with the top of the sleeve 50 mm above the concrete surface. Insert the sensor into the sleeve and pour in thermal conductive silicone grease 2 hours before final setting. The outer wall of the sleeve can be wrapped with heat insulation tape, and the tape thickness can be selected as 0.5 mm or 1 mm. The data acquisition instrument can be a multi-channel temperature recorder, and the sampling interval can be set at 10 minutes, 15 minutes or 30 minutes. The data of each monitoring point is transmitted to the central processor through shielded twisted pair wires, and the wires can be protected by threading through a φ20 mm galvanized steel pipe. The burial depth of the steel pipe can be selected as 30 cm or 40 cm. When integrating the data, an early warning signal is triggered when the temperature difference between the surface and the deep layer exceeds 8 °C. The acquisition system can be configured with a 4G wireless transmission module, and the data upload frequency can be set at once or twice per hour. The sensor calibration can be carried out once a month, using the constant temperature water bath comparison method, and the calibration temperature points can be selected as 0 °C, 10 °C, 20 °C.

[0024] The dual-depth monitoring points invert the temperature field distribution inside the concrete through the Fourier heat conduction equation. The 5-cm surface layer monitoring reflects the intensity of environmental heat exchange, and the 25-cm deep layer monitoring characterizes the heat release rate of hydration heat. The PVC sleeve isolates external mechanical disturbances, and the thermal conductive silicone grease filling reduces the contact thermal resistance. The multi-channel acquisition system fits the temperature gradient curve by the least squares method, and the early warning threshold of 8 °C is set based on the allowable temperature difference limit of the concrete. This solution captures the temperature gradient change through dual-depth monitoring points, reducing the accidental error of single-point temperature measurement. The sleeve pre-embedded method protects the sensor from rolling damage, and the data acquisition system realizes the dynamic visualization of the temperature field. After implementation, abnormal areas of the temperature difference between the surface and the core can be found in time, the hot air compensation response time is shortened to within 30 minutes, and the temperature uniformity inside the concrete is significantly improved. In another technical solution, in step 4) of the present invention, when the fuel hot air blower unit starts, the hot air delivery pressure is 0.15 - 0.25 MPa, and directional air supply is implemented through the downward 45° spray holes opened on the side wall of the galvanized steel pipe, and the distance between adjacent spray holes is 80 cm.

[0025] In this technical solution, the fuel-fired hot air blower unit can select models with an output power of 120 kW or 150 kW, and the hot air conveying pressure can be set to 0.15 MPa, 0.20 MPa, or 0.25 MPa. The pressure regulation is controlled by a proportional valve, which can be installed in the outlet pipe section of the unit, and the valve body material can be selected as 304 stainless steel. The hot air temperature can be maintained at 40 - 50 °C through a PID controller. The temperature sensor can be installed at the entrance of the galvanized steel pipe, and the sensor type can be selected as a K-type thermocouple with a measurement accuracy of ±1 °C. The pressure gauge can be selected as a bourdon tube pressure gauge with a range of 0 - 0.4 MPa, and the dial diameter can be selected as 100 mm or 150 mm, which is installed in the middle section of the steel pipe. The galvanized steel pipe can be selected with a pipe diameter of DN150 or DN200, a wall thickness of 2.5 mm or 3 mm. The side wall spray holes can be processed into round holes inclined downward at 45°, and the hole diameter can be selected as 10 mm or 12 mm. The spacing between adjacent spray holes can be set to 80 cm, with an allowable deviation of ±5 cm. The spray hole processing can adopt laser cutting or numerical control drilling technology, and the hole edge can be chamfered at 0.5 mm × 45° to reduce the air flow resistance. The steel pipe can be arranged parallel to the long side of the bin surface, and the support spacing can be selected as 2 m or 3 m. The support can be selected as an L50×5 angle steel welded and fixed to the concrete surface. A flow guide plate can be welded inside the galvanized steel pipe. The flow guide plate can be selected as a galvanized steel plate with a thickness of 1.5 mm, and the bending angle can be selected as 20° or 25°. They are arranged staggered along the pipe length direction, and the spacing can be selected as 60 cm or 70 cm. The welding of the flow guide plate can adopt intermittent welding, the weld length can be selected as 30 mm or 40 mm, and the interval can be selected as 100 mm or 120 mm. The edge of the flow guide plate can be polished into a fillet with a radius of R2 or R3 to reduce the air flow separation phenomenon. The inner wall of the steel pipe can be coated with a high-temperature resistant epoxy coating, and the coating thickness can be selected as 50 μm or 80 μm. The inclined spray holes direct the hot air flow to the concrete surface through the principle of momentum conservation. The 45° inclination angle balances the horizontal coverage range and the vertical penetration depth. The pressure control strategy calculates the frictional resistance along the way based on the Darcy-Weisbach formula. The pressure range of 0.15 - 0.25 MPa ensures the effective penetration of the hot air through the insulation layer. The staggered layout of the flow guide plates induces turbulent mixing, reduces the air flow velocity gradient, and improves the uniformity of the temperature distribution. This solution optimizes the spatial distribution of the hot air through directional spray holes, and the pressure regulation matches the heat compensation requirements of different regions. The flow guide structure reduces the heat waste caused by air flow short-circuiting, and the corrosion resistance of the galvanized steel pipe extends the service life of the air supply system. After implementation, the uniformity of the temperature field on the bin surface is improved, the utilization rate of the hot air is increased, and the area of the local temperature drop region is significantly reduced. In another technical solution, a flow guide plate is welded and fixed inside the galvanized steel pipe of the present invention. The flow guide plate is made of a galvanized steel plate with a thickness of 1.5 mm and bent into an inclined angle of 25°. They are arranged staggered at intervals of 60 cm along the pipe length direction, and the spacing error between adjacent flow guide plates does not exceed ±5 mm. In this technical solution, the thickness of the deflector plate can be 1.5 mm, the inclination angle can be 25°, the arrangement spacing along the pipe length direction can be 60 cm, and the allowable error of the spacing between adjacent deflector plates can be ±5 mm. In terms of equipment and component selection, the deflector plate can be made of galvanized steel sheet and fixed inside the galvanized steel pipe by welding. An ordinary arc welding machine can be used as the welding equipment. In terms of material selection, the material of the deflector plate can be a 1.5-mm-thick galvanized steel sheet, and the galvanized steel pipe can be a common industrial galvanized steel pipe. The deflector plate is welded and fixed inside the galvanized steel pipe and distributed along the length direction of the steel pipe. The setting method is as follows: First, cut the galvanized steel sheet into appropriate sizes, bend it into a 25° inclination angle to make the deflector plate, and then weld it on the inner wall of the galvanized steel pipe at intervals of 60 cm. During welding, ensure that the deflector plates are arranged staggeredly, that is, the inclination directions of adjacent deflector plates are opposite to form an alternating flow guiding direction. During the welding process, use a measuring tool to measure the spacing between adjacent deflector plates to ensure that the spacing error does not exceed ±5 mm. This technical solution uses the inclination angle and staggered arrangement of the deflector plate to change the flow direction of the hot air in the galvanized steel pipe, making the hot air form a turbulent flow in the pipe, so as to evenly distribute the air flow, avoid air flow short circuit, and improve the transportation uniformity of the hot air under the thermal insulation layer. Through the optimization of the hot air flow field by the deflector plate, the hot air can be ejected more evenly from the spray holes on the side wall of the steel pipe, improving the uniformity of the temperature on the silo surface. This technical solution can improve the distribution of the hot air flow field in the galvanized steel pipe, make the hot air flow more evenly in the pipe, reduce the local overheating or overcooling phenomenon caused by uneven air flow distribution, help improve the effect of temperature control on the silo surface, and provide a more stable temperature environment for concrete construction.

[0026] In another technical solution, in step 4) of the present invention, a mobile infrared thermometer is used to monitor the surface temperature in real time. When the measured point temperature is lower than 2°C, a detachable hot air curtain device is temporarily installed on the corresponding area of the galvanized steel pipe. This device consists of an axial flow fan, a honeycomb-shaped aluminum alloy heater, and a corrugated hose. The outlet temperature of the hot air is set to 40 - 50°C. The detachable hot air curtain device is equipped with a deflector hood. The deflector hood is made of stainless steel plate, and a 30° diffusion angle deflector is provided at the front end. The spacing between the deflectors is 50 mm and the distance from the outlet end of the corrugated hose is 80 mm.

[0027] In this technical solution, for surface temperature monitoring, a mobile infrared thermometer is used to monitor the concrete surface temperature in real time. When the temperature at the measurement point is lower than 2°C, the operation of installing a hot air curtain device is triggered. The detachable hot air curtain device consists of an axial flow fan, a honeycomb aluminum alloy heater, and a corrugated hose. The hot air outlet temperature is set to 40 - 50°C, for example, it can be 40°C, 45°C, or 50°C. The deflector is made of stainless steel plate, with deflector vanes having a 30° diffusion angle at the front end. The distance between the deflector vanes is 50 mm, and it is 80 mm away from the outlet end of the corrugated hose. For the selection of equipment and components, a commercially available portable infrared temperature measurement device can be selected as the mobile infrared thermometer. A small axial flow fan suitable for a low-pressure environment can be selected as the axial flow fan. An existing specification electric heating element can be selected as the honeycomb aluminum alloy heater. A high-temperature resistant corrugated hose can be selected as the corrugated hose. In terms of materials, the deflector can be made of stainless steel plate, and the deflector vanes are also made of stainless steel, meeting the corrosion resistance requirements. In terms of the assembly position, the mobile infrared thermometer is held by the operator or installed on a mobile bracket for real-time scanning of the concrete surface; the detachable hot air curtain device is temporarily installed on the galvanized steel pipe in the corresponding area through buckles or bolts, and the deflector is installed at the outlet end of the corrugated hose. The working process is as follows: The construction workers use the mobile infrared thermometer to monitor the concrete surface in real time. When it is found that the temperature in a certain area is lower than 2°C, the detachable hot air curtain device is immediately installed on the galvanized steel pipe corresponding to that area. Assemble the axial flow fan, honeycomb aluminum alloy heater, and corrugated hose and fix them on the steel pipe. Set the hot air outlet temperature to 40 - 50°C. After starting the device, the fan sends air into the heater for heating, and the hot air is transported to the deflector through the corrugated hose and evenly ejected through the deflector vanes at the front end of the deflector at a 30° diffusion angle to locally heat the low-temperature area. The design with a distance of 50 mm between the deflector vanes and 80 mm from the outlet end ensures that the hot air can effectively cover and increase the temperature of this area. The technical principle is to use a mobile infrared thermometer to capture the temperature change of the concrete surface in real time. When the temperature is lower than the critical value, by installing a hot air curtain device, the honeycomb aluminum alloy heater is used to quickly heat the air, which is transported to the target area by the axial flow fan. The deflector vane structure of the deflector evenly diffuses the hot air to form a directional heat flow, precisely compensating the heat for the low-temperature area and preventing the local temperature from being too low and affecting the concrete quality. This technical solution can take timely heat compensation measures for the sudden low-temperature situation on the concrete surface. The detachable structure enables flexible installation. The design of the deflector optimizes the coverage range and uniformity of the hot air, helps to quickly increase the local temperature, ensures the construction quality of the concrete in a cold environment, and reduces the risk of frost damage caused by too low surface temperature. In another technical solution, in step 5) of the present invention, the nozzles of the automatic spraying system adopt rotary atomizing nozzles, the height of the nozzles from the concrete surface is maintained at 1.2 - 1.5 m, and the outlet pressure of the nozzles is adjusted to 0.3 - 0.4 MPa; after the water supply pipeline of the automatic spraying system is wrapped with rubber and plastic insulation cotton, a 15 W / m electric heating tape is laid parallel to the pipeline length direction, and after the electric heating tape is energized, the water temperature in the pipeline is maintained within the range of 5 - 10 °C, and the water supply pipeline is also wrapped with rubber and plastic insulation cotton.

[0028] In this technical solution, in terms of the nozzle setting, rotary atomizing nozzles are adopted, the height of the nozzles from the concrete surface is maintained at 1.2 - 1.5 m, for example, it can be 1.2 m, 1.35 m or 1.5 m, and the outlet pressure of the nozzles is adjusted to 0.3 - 0.4 MPa, such as 0.3 MPa, 0.35 MPa or 0.4 MPa. In terms of the insulation of the water supply pipeline, the pipeline can be first wrapped with rubber and plastic insulation cotton, and then a 15 W / m electric heating tape is laid parallel to the pipeline length direction. After the electric heating tape is energized, the water temperature in the pipeline is maintained within the range of 5 - 10 °C, for example, 5 °C, 8 °C or 10 °C, and the water supply pipeline also needs to be wrapped with rubber and plastic insulation cotton again to enhance the insulation effect. In terms of the selection of equipment and components, the nozzles can be selected from commercially available rotary atomizing nozzles, such as the common Rain Bird 5004 type nozzles; the water supply pipeline can be made of ordinary plastic or metal pipes; the electric heating tape can be selected from commercially available products with a power of 15 W / m, and the rubber and plastic insulation cotton can be selected from insulation materials that meet the construction requirements. In terms of materials, the rubber and plastic insulation cotton has good insulation performance, the electric heating tape can provide stable heat, and the rotary atomizing nozzles are made of metal or engineering plastics, meeting the durability requirements. In terms of the assembly position, the rotary atomizing nozzles are installed through the reserved holes penetrating the waterproof canvas, and the nozzles are directly facing the concrete surface below, maintaining a height of 1.2 - 1.5 m; the water supply pipeline is arranged along the edge of the storage surface or the preset path of the construction area. First, a layer of rubber and plastic insulation cotton is wrapped outside, then the electric heating tape is laid parallel outside the insulation cotton, and finally another layer of rubber and plastic insulation cotton is wrapped to form a double insulation structure. The setting method is as follows: first, plan the water supply pipeline route according to the construction area. After laying the pipeline, evenly wrap the rubber and plastic insulation cotton outside the pipeline, then fix the electric heating tape parallel to the pipeline outside the insulation cotton to ensure that the electric heating tape is closely attached to the pipeline, and finally wrap another layer of rubber and plastic insulation cotton and fix it. During use, the outlet pressure of the nozzles is adjusted to 0.3 - 0.4 MPa through the pressure regulating valve, and the water temperature in the pipeline is monitored in real time after the electric heating tape is energized to ensure that the water temperature is maintained at 5 - 10 °C. The technical principle is to atomize warm water using a rotary atomizing nozzle and evenly spray it on the concrete surface. The relatively large nozzle outlet pressure ensures the atomization effect and spraying range, and the appropriate nozzle height avoids the direct impact of water flow on the concrete surface. The combination of rubber and plastic insulation cotton and electric tracing tape outside the water supply pipeline forms a thermal insulation system. The electric tracing tape converts electrical energy into heat energy to compensate for the heat loss of the pipeline in a cold environment, stabilizes the water temperature at 5-10°C, prevents the water body in the pipeline from freezing, and ensures the continuous and stable operation of the spraying system in a low-temperature environment. This technical solution can ensure the normal operation of the automatic spraying system in a low-temperature environment in cold regions. The rotary atomizing nozzle realizes the even spraying of warm water and avoids the problem of concrete surface erosion caused by concentrated water flow. The combination of the electric tracing tape and the rubber and plastic insulation cotton effectively maintains the water temperature in the pipeline, prevents freezing, ensures the reliability of the spraying system, provides a stable humid environment for concrete curing, helps to promote the cement hydration reaction, and improves the early strength and durability of the concrete. In another technical solution, when the automatic spraying system of the present invention sprays warm water at 5-10°C, it synchronously incorporates sulfoaluminate expansive agent accounting for 0.45%-0.55% of the sprayed water volume. A static mixer is set in the spraying pipeline to ensure that the coefficient of variation of the solution uniformity is less than 5%. The concentration control of the sulfoaluminate expansive agent solution is monitored by an on-line conductivity meter. When the conductivity value deviates from the reference value by ±10%, the expansive agent is automatically added through a peristaltic pump to maintain the solution concentration within the range of 0.45%-0.55%. During the addition process, the fluctuation range of the solution flow rate does not exceed ±2%.

[0029] In this technical solution, regarding the incorporation of the expansive agent, when the automatic spraying system sprays warm water at 5-10°C, it synchronously incorporates sulfoaluminate expansive agent accounting for 0.45%-0.55% of the sprayed water volume, such as 0.45%, 0.5% or 0.55%. A static mixer is set in the spraying pipeline to ensure that the coefficient of variation of the solution uniformity is less than 5%. In terms of concentration control, the concentration of the sulfoaluminate expansive agent solution is monitored by an on-line conductivity meter. When the conductivity value deviates from the reference value by ±10%, the expansive agent is automatically added through a peristaltic pump to maintain the solution concentration within the range of 0.45%-0.55%. During the addition process, the fluctuation range of the solution flow rate does not exceed ±2%. For the selection of equipment and components, a commercially available pipe-type static mixer can be selected for the static mixer, and its internal structure can be spiral sheet or blade type to promote solution mixing. An industrial on-line conductivity monitor can be selected for the on-line conductivity meter, which has the functions of real-time data transmission and alarm. A small corrosion-resistant peristaltic pump can be selected for the peristaltic pump, which can accurately control the flow rate. In terms of materials, the sulfoaluminate expansive agent is a commercially available concrete admixture. The static mixer can be made of stainless steel or engineering plastics, and the spraying pipeline can be made of corrosion-resistant plastic or metal pipes. At the installation position, the static mixer is installed in the spraying pipeline of the automatic sprinkler system, downstream of the expansive agent injection point, to ensure sufficient mixing of the expansive agent and warm water. The sensor probe of the on-line conductivity meter is installed at the position where the solution flows in the pipeline to monitor the concentration change in real time. One end of the peristaltic pump is connected to the expansive agent storage tank, and the other end is connected to the position near the static mixer in the pipeline to replenish the expansive agent in a timely manner. The setting method is as follows: when installing the pipeline of the sprinkler system, the static mixer is connected in series in the pipeline, the on-line conductivity meter is connected and the reference value is calibrated, and the peristaltic pump is connected to the expansive agent storage tank and the pipeline. During the spraying process, the conductivity meter monitors the conductivity of the solution in real time. When it deviates from the reference value by ±10%, the peristaltic pump is triggered to replenish the expansive agent at the set flow rate to ensure that the concentration is stable within the range of 0.45%-0.55%, and at the same time, the static mixer ensures the uniformity of the solution. The technical principle is to utilize the micro-expansion generated by the sulfoaluminate expansive agent during the hardening process of concrete to compensate for the shrinkage of concrete in cold regions and reduce cracks. The static mixer makes the expansive agent and warm water evenly mixed through the turbulent flow effect, avoiding too high or too low local concentration. The on-line conductivity meter converts the solution concentration into a conductivity signal. When the concentration deviates from the set range, the peristaltic pump automatically replenishes the expansive agent to form a closed-loop control to ensure the stability of the expansive agent concentration. This automatic control mechanism based on conductivity feedback, combined with the homogenizing effect of the static mixer, realizes the precise regulation of the concentration of the expansive agent solution. This technical solution can ensure the uniform distribution and stable concentration of the sulfoaluminate expansive agent in the spraying solution, avoid the problem of unstable compensation shrinkage effect caused by uneven concentration of the expansive agent, provide continuous expansion compensation for concrete, help reduce the cracks generated by the shrinkage of concrete in cold regions, and improve the integrity and durability of the concrete structure. In another technical solution, when applying the concrete curing agent after form removal in step 5) of the present invention, a spraying device is used to control the spraying flow rate at 300-400 mL / m², the moving speed of the spray gun is maintained at 0.5-0.8 m / s, and an epoxy resin anti-rust layer is applied to the exposed threaded parts of the anchor fittings; after applying the epoxy resin anti-rust layer to the exposed threaded parts of the threaded steel embedded parts, a polyurethane anti-corrosion coating with a thickness of 1.2-1.5 mm is additionally applied, and the hardness of the coating reaches Shore D60-65 after curing; a temperature sensor adds one monitoring point at the boundary of each 10 m×10 m grid, located 20 cm inside the four peripheral boundaries of the formwork surface; the spraying device is equipped with a contact surface roughness detector. When the Ra value of the concrete surface roughness exceeds 0.8 mm, the spraying flow rate is automatically switched to 450-500 mL / m² and the moving speed of the spray gun is reduced to 0.4-0.6 m / s, and a 25 cm wide overlapping coverage area is set at the end of the spraying path.

[0030] In this technical solution, for the spraying of the curing agent, a spraying device is used to control the spraying flow rate at 300 - 400 mL / m², such as 300 mL / m², 350 mL / m² or 400 mL / m², and the moving speed of the spray gun is maintained at 0.5 - 0.8 m / s, such as 0.5 m / s, 0.65 m / s or 0.8 m / s. For the exposed threaded parts of the anchor fittings, an epoxy resin anti-rust layer is first painted, and then a polyurethane anti-corrosion coating with a thickness of 1.2 - 1.5 mm is applied. After the coating is cured, the hardness reaches Shore D 60 - 65. Temperature sensors are added with 1 monitoring point at the boundary of each 10 m × 10 m grid, located 20 cm inside the inner boundary of the bin surface. The spraying device is equipped with a contact surface roughness detector. When the Ra value of the concrete surface roughness exceeds 0.8 mm, the spraying flow rate is automatically switched to 450 - 500 mL / m² and the moving speed of the spray gun is reduced to 0.4 - 0.6 m / s, and a 25 cm wide overlapping coverage area is set at the end of the spraying path. For the selection of equipment and components, commercially available concrete curing agent spraying machines can be selected as the spraying equipment, and portable roughness measuring instruments can be selected as the contact surface roughness detectors, such as the TR200 type roughness meter. In terms of materials, silicate-based water-based curing agents can be selected as the concrete curing agent, and the epoxy resin anti-rust layer materials and polyurethane anti-corrosion coating materials are all commonly available commercially available concrete anti-corrosion coatings. In terms of the installation position, the contact surface roughness detector is installed on the spray gun of the spraying equipment to detect the concrete surface roughness in real time as the spray gun moves; the newly added temperature sensors are embedded in the concrete 20 cm inside the inner boundary of the bin surface at the designed positions to form a grid monitoring with the original sensors. The working process is as follows: After the concrete formwork is removed, first clean the exposed threaded parts of the anchor fittings, and use a brush or spraying tool to apply the epoxy resin anti-rust layer. After it dries, then apply a polyurethane anti-corrosion coating with a thickness of 1.2 - 1.5 mm to ensure that the hardness of the cured coating meets the requirements. At the same time, start the spraying equipment, set the spraying flow rate and the moving speed of the spray gun to the initial values, and spray the curing agent on the concrete surface. During the spraying process, the contact surface roughness detector detects the surface roughness in real time. When the Ra value exceeds 0.8 mm, the equipment automatically adjusts the spraying flow rate and the moving speed of the spray gun, and sets a 25 cm wide overlapping coverage area at the end of the spraying path to ensure the coating effect of the curing agent on the rough surface. The addition of temperature sensors is to embed the sensors at the designed positions 20 cm inside the inner boundary of the bin surface before the concrete is poured, and jointly monitor the temperature with the sensors in the original grid. The technical principle is to control the flow rate and speed of the spraying equipment to ensure that a uniform protective film is formed on the concrete surface. The contact surface roughness detector automatically adjusts the spraying parameters according to the surface roughness, enabling the curing agent to effectively cover surfaces with different roughness levels. The double-layer anti-corrosion treatment of the exposed threads of the anchor bolts utilizes the chemical stability and physical strength of epoxy resin and polyurethane coatings to isolate external corrosive media and extend the service life of the anchor bolts. The newly added boundary temperature sensors supplement the temperature monitoring at the edge of the placement surface, avoiding temperature monitoring blind spots in the boundary area due to rapid heat dissipation. This technical solution can automatically adjust the spraying parameters of the curing agent according to the surface roughness of the concrete, ensuring uniform coverage of the curing agent and enhancing the protection effect. The anti-corrosion treatment of the exposed threads of the anchor bolts effectively prevents rust and extends their service life. The addition of boundary temperature sensors makes the temperature monitoring network denser, capable of promptly capturing temperature changes at the edge of the placement surface, providing more accurate temperature data for concrete curing, and ensuring the construction quality of roller-compacted concrete in cold regions.

[0031] <Application Example> I. Project Overview The project is located in Hulunbuir City, Inner Mongolia Autonomous Region. The average winter temperature is -15°C to -25°C. During the construction period, the roller-compacted concrete dam body needs to be poured in a low-temperature environment. The designed strength of the dam body is C30, the frost resistance grade is F200, the average wind speed in the construction area is 5 - 8 levels, and the day-night temperature difference is more than 20°C. II. Specific Construction Plan 1. Aggregate Preheating and Concrete Mixing Aggregate treatment: The coarse aggregate (crushed stone, particle size 5 - 40 mm) and the fine aggregate (medium sand) are respectively placed in a closed steel structure preheating bin. DN32 steam coils (steam pressure 0.5 MPa) are arranged in the bin and heated to an internal temperature of 8°C for the aggregate (monitored by an embedded thermometer). Concrete mixing: Use a JS500 type twin-shaft compulsory mixer. Control the mixing water temperature at 30°C and add a polycarboxylate-based retarder-type water reducer (commercially available and meeting the GB 8076 standard) accounting for 1.5% of the total mass of the binder. The mixing time is 90 seconds, and the temperature of the discharged concrete is controlled at 12 - 15°C. 2. Insulated Transportation Transportation equipment: Select a Shaanxi Automobile DeLong F3000 dump truck. The carriage is modified into a sandwich insulation structure, with 80 mm thick polyurethane foam material (thermal conductivity ≤ 0.024 W / (m·K)) laid on the inner layer. Control the transportation time within 30 minutes, and the temperature drop of the concrete during entering the bin is ≤ 2°C. 3. Paving, Compacting and Insulated Covering Paving and rolling: The SY950 paver of Sany Heavy Industry was used for layered paving, with each layer being 35cm thick. Immediately after paving, a 5t double-steel-wheel vibratory roller of XCMG XP305 was used for rolling (the excitation force was set at 30kN). The rolling followed the process of "static rolling once, then vibratory rolling four times", and the fluctuation of the excitation force was monitored in real time. When it deviated from the set value by 10%, the machine would automatically stop for calibration. Temperature monitoring: PT100 platinum resistance sensors are embedded in a 10m×10m grid. Each grid is equipped with additional measuring points at depths of 5cm and 25cm below the surface and 20cm inside the boundary, for a total of 120 monitoring points. Insulation covering: After rolling, 0.15mm polyethylene film (bottom layer), 20kg / m³ flame-retardant polystyrene insulation board (middle layer, thickness 5cm), and 600g / m² waterproof canvas (surface layer) are laid in sequence. The joints are sealed with 50mm wide U-shaped aluminum alloy strips (hot-dip galvanized layer thickness 80μm), the nail spacing is 200mm, and the nail heads are covered with butyl rubber sealing tape. C10 channel steel clamping devices are set every 3m along the longitudinal direction of the warehouse surface, and the threaded steel anchors (HRB400, φ16mm) are embedded to a depth of 150mm, and the exposed ends are tightened with nuts with rubber washers (torque 90N·m). 4. Temperature control and maintenance Hot air system: When the monitored temperature is <5℃ for 2 consecutive hours, start the 150kW fuel hot air unit to deliver hot air through the DN200 galvanized steel pipe (with a 45° downward spray hole on the side wall and a spacing of 80cm) at a pressure of 0.2MPa. A 1.5mm thick galvanized steel plate guide plate is welded inside the steel pipe (25° inclination angle, staggered arrangement with a spacing of 60cm), and a detachable hot air curtain device is temporarily installed in the local low temperature area (surface temperature <2℃) (hot air outlet temperature 45℃, and a 30° diffusion angle guide plate is set at the front end of the guide cover). Spraying maintenance: The automatic spraying system uses Rain Bird 5004 rotary atomizing nozzle (1.3m away from the concrete surface, outlet pressure 0.35MPa), spraying 8℃ warm water every 2 hours (the water supply pipeline is wrapped with rubber-plastic insulation cotton + 15W / m electric heating tape to maintain the water temperature at 5-10℃), and simultaneously adding 0.5% sulphoaluminate expansion agent (mixed by static mixer, concentration monitored by online conductivity meter, and automatically replenished by peristaltic pump). Demoulding and curing agent application: When the concrete core strength reaches 70% of the design value and the curing time is T=1.8T0 (T0 is the standard curing and demolding time at 20℃), the mould is removed and two coats of silicate water-based curing agent are immediately applied (the first coat has a spray flow rate of 350mL / m² and a spray gun speed of 0.6m / s; the second coat is applied after 4 hours). The exposed threads of the anchor are first coated with an epoxy resin anti-rust layer, and then with a 1.3mm thick polyurethane anti-corrosion coating (hardness Shore D62 after curing).

[0032] During the winter construction of this project, the qualification rate of the concrete placement temperature reached over 95%. After form removal, the surface integrity met the first-class acceptance standard, and no frost damage cracks occurred. The construction period was shortened by 15% compared with the traditional process, providing a replicable technical model for similar projects in cold regions.

[0033] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. A construction method for roller compacted concrete in cold regions, characterized in that, The following steps are involved: 1) Place the coarse aggregate and fine aggregate in a closed preheating bin respectively, heat them through a steam coil until the internal temperature of the aggregate reaches 5-10°C, use a twin-shaft forced mixer to mix the concrete, control the water temperature at 25-35°C during the mixing process, and add a slow-setting water-reducing agent accounting for 1-2% of the total mass of the cementitious material; 2) Load the mixed concrete into a dump truck with an interlayer insulation layer. The interlayer of the truck is filled with polyurethane foam material. The transportation time is controlled within 40 minutes; 3) When the concrete is transported to the construction site, the concrete is placed in the warehouse and spread in layers. The thickness of each layer is 30-40cm. After spreading, a 5t double-steel-wheel vibrating roller is used to roll the concrete. Temperature sensors are embedded on the surface of the rolled concrete. The monitoring points are arranged in a 10m×10m grid. Three layers of insulation materials are then covered. The bottom layer is polyethylene film, the middle layer is flame-retardant polystyrene insulation board, and the surface layer is waterproof canvas. 4) Monitor the internal temperature of the concrete through the embedded temperature sensor. When the monitored temperature is lower than 5°C for 2 consecutive hours, start the fuel hot air unit to transport hot air to the bottom of the insulation layer through the galvanized steel pipes laid on the warehouse surface; 5) On the basis of thermal insulation covering and temperature control, implement concrete curing: keep the surface moist during concrete curing, and use an automatic sprinkler system to spray 5-10℃ warm water every 2 hours through the reserved holes of the waterproof canvas, and the spraying time lasts for 30 seconds; under the condition that the concrete surface temperature continues to be ≥5℃, the curing time is: T=K·T0, where T0 is the demolding reference time under the standard curing condition of 20℃, and K is a temperature correction coefficient of 1.5-2.0; when the concrete core sample strength reaches 70% of the design strength and the curing time meets the T value, implement demolding operation, and immediately apply two coats of concrete curing agent after demolding, with an interval of 4 hours between each coat.

2. The construction method of roller compacted concrete in cold regions according to claim 1, characterized in that, In step 3), after covering three layers of thermal insulation materials, a steel clamping device is arranged at intervals of 3m along the longitudinal direction of the warehouse surface. The device consists of a channel steel horizontally spanning the thermal insulation layer, a threaded steel anchor embedded in the concrete, and a thick steel plate clamp. The threaded steel anchor is vertically inserted into the concrete surface 2-3 hours before the final setting of the concrete, with a pre-embedded depth of 150mm, and the exposed end is threaded and the exposed length is 50mm. The verticality deviation is controlled within 5‰; the threaded steel anchor is arranged at intervals of 3m along the long side, with a verticality deviation within 5‰. After the initial setting of the concrete, it is fastened by a nut with a rubber gasket, and the tightening torque is controlled within 80-100N·m.

3. The construction method of roller compacted concrete in cold regions according to claim 2, characterized in that, In step 3), the 5t double-steel-wheel vibratory roller is equipped with an exciting force sensor, which displays the exciting force value in real time during the rolling process. When the exciting force detection value deviates from the set value by 10%, an audible and visual alarm is automatically triggered and the rolling operation is stopped; Perform the following recovery procedures after an outage: a) The operator checks the mechanical connection status of the vibration system and eliminates the faults of drive shaft breakage and bearing jam; b) Input the exciting force calibration command through the control panel, and the system will automatically perform three no-load vibration tests. When the deviation rate between the actual exciting force and the set value is ≤3%, the touch screen will display the prompt "System Normal"; c) When returning to the interrupted position for re-rolling, lap compaction is carried out within a range of 1 m backward from the end of the stopped rolling belt. In the lap area, 2 additional passes of static compaction and 3 additional passes of vibratory compaction are carried out. At the joints of the three-layer thermal insulation material, U-shaped aluminum alloy pressure strips are used for sealing. The width of the pressure strip is 50 mm. The U-shaped aluminum alloy pressure strip is fixed to the concrete surface by a nail gun every 200 mm. The depth of the nail is 15 mm and the exposed end is coated with asphalt sealant. The contact part of the U-shaped aluminum alloy pressure strip and the nail is subjected to hot-dip galvanizing treatment, and the thickness of the galvanized layer is not less than 80 μm. After the nail is fixed, a butyl rubber sealing tape is used to cover the nail head part. The width of the sealing tape is 20 mm and the elongation rate is greater than 300%.

4. The construction method of roller compacted concrete in cold regions according to claim 2, characterized in that In step 4), 2 monitoring points are added in each 10 m × 10 m grid for the temperature sensor, and they are respectively buried at a depth of 5 cm and 25 cm under the concrete surface, and the sensors are evenly distributed.

5. The construction method of roller compacted concrete in cold regions according to claim 4, characterized in that, In step 4), when the fuel-fired hot air blower unit starts, the hot air delivery pressure is 0.15 - 0.25 MPa, and directional air supply is carried out through the downward 45° spray holes opened on the side wall of the galvanized steel pipe. The distance between adjacent spray holes is 80 cm.

6. The construction method of roller compacted concrete in cold regions according to claim 5, characterized in that A deflector plate is welded and fixed inside the galvanized steel pipe. The deflector plate is made of 1.5 mm thick galvanized steel plate bent at an angle of 25°, and is arranged staggeredly every 60 cm along the pipe length direction. The distance error between adjacent deflector plates does not exceed ±5 mm.

7. The construction method of roller compacted concrete in cold regions according to claim 6, characterized in that, In step 4), a mobile infrared thermometer is used to monitor the surface temperature in real time. When the temperature of the measuring point is lower than 2 °C, a detachable hot air curtain device is temporarily installed on the galvanized steel pipe in the corresponding area. This device consists of an axial flow fan, a honeycomb-shaped aluminum alloy heater and a corrugated hose. The hot air outlet temperature is set to 40 - 50 °C. The detachable hot air curtain device is equipped with a deflector hood. The deflector hood is made of stainless steel plate, and 30° diffusion angle deflector vanes are arranged at the front end. The distance between the deflector vanes is 50 mm and the distance from the outlet end of the corrugated hose is 80 mm.

8. The construction method of roller compacted concrete in cold regions according to claim 1, characterized in that In step 5), the nozzles of the automatic sprinkler system adopt rotary atomizing nozzles. The height of the nozzle from the concrete surface is maintained at 1.2 - 1.5 m, and the outlet pressure of the nozzle is adjusted to 0.3 - 0.4 MPa. After the water supply pipeline of the automatic sprinkler system is wrapped with rubber and plastic insulation cotton, a 15 W / m electric heating tape is laid parallel along the pipeline length direction. After the electric heating tape is energized, the water temperature in the pipeline is maintained within the range of 5 - 10 °C, and the water supply pipeline is also wrapped with rubber and plastic insulation cotton.

9. The construction method of roller compacted concrete in cold regions according to claim 8, characterized in that, When the automatic sprinkler system sprays warm water at 5 - 10 °C, a sulfoaluminate expansive agent accounting for 0.45% - 0.55% of the sprayed water volume is synchronously incorporated. A static mixer is set in the spraying pipeline to ensure that the coefficient of variation of the solution uniformity is less than 5%. The concentration control of the sulfoaluminate expansive agent solution is monitored by an on-line conductivity meter. When the conductivity value deviates from the reference value by ±10%, the expansive agent is automatically added by a peristaltic pump to keep the solution concentration within the range of 0.45% - 0.55%. During the addition process, the fluctuation range of the solution flow rate does not exceed ±2%.

10. The construction method of roller compacted concrete in cold regions according to claim 1, characterized in that, In step 5), when applying the concrete curing agent after form removal, use spraying equipment to control the spraying flow rate at 300 - 400 mL / m², keep the moving speed of the spray gun at 0.5 - 0.8 m / s, and apply an epoxy resin anti-rust layer on the exposed threaded parts of the anchor fittings; after applying the epoxy resin anti-rust layer on the exposed threaded parts of the threaded steel embedded parts, apply a polyurethane anti-corrosion coating with a thickness of 1.2 - 1.5 mm, and the hardness of the cured coating reaches Shore D60 - 65; add 1 monitoring point for the temperature sensor at the boundary of each 10 m × 10 m grid, which is located 20 cm inside the inner boundary of the surface of the bin; install a contact surface roughness detector on the spraying equipment. When the Ra value of the concrete surface roughness exceeds 0.8 mm, the spraying flow rate is automatically switched to 450 - 500 mL / m² and the moving speed of the spray gun is reduced to 0.4 - 0.6 m / s, and a 25 cm wide overlapping coverage area is set at the end of the spraying path.