Concrete pipe pile and concrete pipe pile steam curing method thereof

Abstract

The invention discloses a concrete pipe pile and a concrete pipe pile steam curing method thereof, and relates to the technical field of concrete pipe pile manufacturing. The concrete pipe pile comprises the following components and structures: a, a concrete admixture is prepared from the following components in percentage by weight: 2 to 6 percent of light calcined magnesia, 10 to 15 percent of silica fume, 1 to 3 percent of nano silicon dioxide and the balance of high-silica sand of which the SiO2 content is greater than or equal to 90 percent; and b, a spiral steam guide groove is formed in the inner wall of the pipe pile, the depth of the steam guide groove is 2-3 mm, and the spiral interval is 50-80 mm. According to the invention, a composite admixture system and a multi-stage intelligent maintenance process are synergistically innovated; the micro-expansion effect of light calcined magnesia in the composite admixture and the nano-filling effect of nano-silica are complementary, hydration reaction is accelerated and shrinkage stress is compensated in the initial stage of steam curing, so that the three-day compressive strength of the pipe pile breaks through 50 MPa and is improved by 60% or above compared with that of a traditional process, and the cost is reduced. And meanwhile, a composite structure of the outer wall alkali-resistant glass fiber gridding cloth and the aerogel coating effectively inhibits thermal stress cracks.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete pipe pile manufacturing, and in particular to a concrete pipe pile structure that optimizes the mechanical properties of the pipe pile by using composite mineral admixtures, and a multi-stage steam curing control method based on solar preheating and artificial intelligence algorithms. Background Art

[0002] As a key component in the field of infrastructure construction, the performance of concrete pipe piles is directly related to the safety and durability of the project. Traditional concrete pipe piles mostly use conventional admixtures such as fly ash and mineral powder. Although they can improve some working performance, they are slow to activate their activity in a steam curing environment, resulting in insufficient early strength growth. To shorten the curing cycle, some solutions attempt to achieve strength targets by increasing the amount of cement or raising the steam temperature, but this can easily lead to differences in the hardening rate inside and outside the pipe piles. The large temperature difference between the core and the surface causes microcracks, which seriously affect the impermeability and bearing capacity. In addition, the uniformity of steam penetration inside the pipe piles is highly dependent on the structural design of the curing equipment. The existing technology mostly uses straight-through steam pipes or a single inner wall air distribution method, which makes it difficult to achieve efficient steam diffusion in thick-walled pipe piles. Local over-wetting or drying phenomena occur frequently, which restricts the stability of industrial production.

[0003] At the steam curing process level, existing technologies generally rely on coal-fired boilers or electric heating equipment to provide heat sources, resulting in high energy consumption and prominent carbon emission pressure. Although some studies have introduced solar preheating technology to reduce initial energy consumption, it is still necessary to switch to traditional energy at night or in rainy weather due to fluctuations in lighting conditions and insufficient energy storage technology, and the energy-saving effect is limited. At the same time, temperature and humidity control during the curing process is still mainly based on manual experience or simple PLC programs, lacking a dynamic response to the material properties and environmental parameters of the pipe piles. Temperature fluctuations in the constant temperature stage often exceed ±5°C, resulting in increased discreteness in the strength of the same batch of pipe piles. Especially for the refined curing required for high-strength pipe piles, existing technologies find it difficult to balance the contradiction between the heating rate and the thermal stress of the material. Extending the curing cycle has become a helpless choice to ensure quality, significantly reducing production efficiency.

[0004] The demand for green transformation in the concrete products industry is becoming increasingly urgent. The high water consumption and high emission problems of traditional curing processes have not yet been fundamentally resolved. The direct discharge of large amounts of waste heat steam not only wastes energy, but the residual acidic substances in the condensed water also aggravate equipment corrosion. Although a few schemes have attempted to achieve waste heat recovery through pipeline modification, the heat exchange efficiency of the single-loop design is insufficient, and there is no supporting water quality regulation system, and the recycling rate is less than 50%. In addition, the existing admixture system has weak adaptability to curing conditions and is prone to problems such as slow setting and strength shrinkage in low temperature or dry environments, which limits the application scenarios of pipe pile products. How to achieve a low-carbon and intelligent curing process while improving the performance of pipe piles through collaborative innovation in materials science and energy technology is still a bottleneck that the current technical system urgently needs to break through. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a concrete pipe pile and a steam curing method for the concrete pipe pile, which can solve the problems raised by the above-mentioned background technology.

[0006] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions:.

[0007] 1. Composite admixture concrete pipe pile structure

[0008] Synergistic optimization mechanism of material components

[0009] 1. Activity control of light-burned magnesium oxide:

[0010] The calcination temperature of light-burned magnesium oxide is strictly controlled within a range of 750-850°C (800°C was used in Example 2), stabilizing its activity index at 120-150s (tested according to GB / T 17671). Within this range, the expansion rate of magnesium oxide matches the concrete setting process: during the preheating stage (40-50°C), it begins to expand slightly (expansion rate 0.01%-0.03%) to compensate for the plastic shrinkage of concrete; during the constant temperature stage (75-85°C), it expands faster (expansion rate 0.05%-0.08%) to fill capillary pores and increase the 3D strength by more than 30% (compared to traditional admixtures).

[0011] Critical value basis: when the MgO content is greater than 6%, the expansion rate in the constant temperature stage exceeds 0.1%, resulting in cracks on the surface of the pile (see the data of Comparative Example 1); when it is less than 2%, the expansion compensation is insufficient and the 28d shrinkage rate exceeds the standard (≥0.03%).

[0012] 2. Particle size effect of nano-silica:

[0013] Nano-SiO2 prepared by gas phase method, particle size 10-20nm, specific surface area 380-420m 2Its high surface energy significantly promotes cement hydration reaction. Experiments show that adding 2% nano-SiO2 can advance the C3S hydration exothermic peak by 1.2 hours and increase the 3d compressive strength by 25% (compared with the group without adding nano-materials).

[0014] Dispersion technology: Nano-SiO2 and silica fume are pre-dry mixed in the admixture at a ratio of 1:5, and then dispersed into the concrete using a high-speed mixer (speed 2000rpm) to avoid agglomeration of nanoparticles.

[0015] 3. The skeleton function of high silica sand:

[0016] Natural quartz sand with a SiO2 content of ≥90% and a particle size distribution of 0.15-1.18 mm (the cumulative sieve residue meets the requirements of GB / T 14684 Zone II) is selected to form a "micron-nano" particle gradation with silica fume, and the filling efficiency is increased by 15% compared with ordinary river sand (the porosity is measured by mercury intrusion, and the porosity in Example 1 is reduced to 8.7%).

[0017] Steam duct structure design

[0018] 1. Helix angle optimization:

[0019] The steam guide groove forms an angle of 30-45° (preferably 35°) with the pile axis, allowing steam to penetrate evenly along a spiral path. CFD simulations show that when the angle is less than 30°, steam retention time is too long and local humidity exceeds the standard (>98%); when it is greater than 45°, the steam flow rate is too fast and the penetration depth is insufficient (compared to traditional straight grooves, the steam coverage area of this invention is increased by 40%).

[0020] 2. Catalytic function of porous ceramic particles:

[0021] The CaO-Al2O3-SiO2 catalyst loaded on the surface of ceramic particles was prepared by a sol-gel method with a molar ratio of CaO:Al2O3:SiO2 = 5:2:3. It catalyzed the formation of calcium silicate hydrate (CSH) gel in a steam environment at 75-85°C. XRD analysis showed that the amount of CSH gel produced was 18% higher than that of the uncatalyzed group.

[0022] Thermal stress matching of the outer wall composite layer

[0023] 1. Alkali-resistant glass fiber mesh cloth:

[0024] The mesh is constructed using alkali-resistant glass fiber with a ZrO2 content of 14% or greater, a warp and weft density of 1200 tex, and ultrasonically welded to achieve a shear resistance of 50 N or greater. The mesh is pre-impregnated with epoxy resin (curing agent: polyamide 650, ratio 1:1) to ensure a bond strength of 3 MPa or greater with concrete (according to GB / T 7124).

[0025] 2. Thermal insulation properties of aerogel coating:

[0026] The coating is composed of a composite of silica aerogel (95% porosity) and a polyurethane binder (≥60% solids content), with a thermal conductivity of ≤0.02 W / (m·K). The micro-protrusion structure, with a height of 0.1-0.3 mm, is formed by embossing a PDMS template. This structure disrupts boundary layer airflow and reduces convective heat dissipation by 15% (see thermal imaging data in Example 1).

[0027] 2. Multi-stage intelligent steam maintenance method

[0028] Energy coupling during the warm-up phase

[0029] 1. Solar collector selection:

[0030] Adopting all-glass vacuum tube collector (GB / T 17581 standard), the diameter of single tube is 58mm, the length is 1800mm, the heat collection efficiency is ≥75%. 2 ) under the condition that 200L of water can be heated from 25℃ to 65℃ in 1 hour, meeting the preheating requirements.

[0031] 2. Electric energy complementary logic:

[0032] When the light intensity is less than 200W / m 2 When the power density is 2kW / m 3 Prioritize the use of off-peak electricity (22:00-6:00 electricity price 0.35 yuan / kWh), and preset the heating period through the PLC system to reduce energy consumption costs by 30% (Example 3 operating data).

[0033] Dynamic control of constant temperature stage

[0034] 1. Wireless temperature sensor layout:

[0035] The sensor uses a MEMS thermocouple, housed in a 316L stainless steel housing (3mm diameter, 15mm length), embedded in the steam duct at 50cm intervals. Data is transmitted to the PLC via the LoRaWAN protocol, with a transmission distance of ≥200m and a packet loss rate of <0.1%.

[0036] 2.PLC control algorithm:

[0037] Set the core and surface temperature difference threshold ΔT = 5°C. When ΔT> 5°C, the PLC calculates the steam valve opening increment according to the following formula:

[0038]

[0039] Among them, the proportional coefficient K_p = 0.8, the integral coefficient K_i = 0.05, ensuring the temperature control accuracy of ±1°C.

[0040] Water quality management of waste heat recovery systems

[0041] 1. S-type double-circuit pipeline design:

[0042] The inner stainless steel pipe delivers 120°C fresh steam, while the outer copper pipe recovers 60°C waste heat steam. Fluent simulation optimized the pipe bend radius (twice the pipe diameter) and spacing (15cm), achieving a waste heat recovery efficiency of ≥65% (compared to 45% for traditional single-pipe systems).

[0043] 2. pH adjustment module:

[0044] An online pH meter (accuracy ±0.1) was used to monitor the pH of the condensed water. When the pH was <6.5, 0.1 mol / L NaOH solution (at a flow rate of 0.5 L / min) was automatically added; when the pH was >7.5, citric acid solution (concentration 10%) was added. Data from Example 3 showed that the water quality still met the GB / T 14848 standard after 10 cycles.

[0045] Training and deployment of AI algorithms

[0046] 1. LSTM model construction:

[0047] Input parameters: ambient temperature and humidity, pile geometry (wall thickness, diameter, length), admixture ratio (MgO, silica fume, nano-SiO2 content), and curing kiln volume;

[0048] Output parameters: preheating time (0.5-1h), constant temperature (75-85℃), constant temperature time (2-4h), cooling rate (≤15℃ / h);

[0049] Training data: 1000 sets of historical maintenance records, all from the industrial production lines of Examples 1-3, with a mean square error (MSE) of <0.5 after data cleaning.

[0050] 2. Dynamic optimization case:

[0051] When the MgO content in the admixture increases from 4% to 5%, the model automatically increases the constant temperature from 80°C to 83°C and extends the constant temperature time by 0.5 hours to avoid cracking due to excessive expansion rate (see the 28d strength data of Example 2).

[0052] Supporting Data and Comparisons

[0053] Table 1: Strength comparison of different admixture ratios

[0054]

[0055] Table 2: Comparison of waste heat recovery efficiency

[0056]

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The present invention fundamentally solves the core problems of high energy consumption, slow strength development and poor uniformity in traditional concrete pipe pile steam curing through the collaborative innovation of the composite admixture system and the multi-stage intelligent curing process; the micro-expansion effect of the light-burned magnesia in the composite admixture complements the nano-filling effect of nano-silica, accelerating the hydration reaction and compensating for the shrinkage stress at the initial stage of steam curing, so that the compressive strength of the pipe pile exceeds 50MPa in 3 days, which is more than 60% higher than that of the traditional process. At the same time, the composite structure of the alkali-resistant glass fiber mesh cloth and the aerogel coating on the outer wall effectively inhibits thermal stress cracks, and the surface crack rate is reduced to below 0.2%, which significantly improves the durability of the pipe pile; the catalytic effect of the porous ceramic particles in the steam guide groove further optimizes the steam penetration path, and the strength difference between the core and the surface is controlled within 5%, solving the industry problem of uneven performance inside and outside the thick-walled pipe pile.

[0059] In terms of process energy saving and intelligence, the complementary strategy of solar preheating and valley power generation reduces initial energy consumption by 30%. Combined with the S-shaped double-circuit waste heat recovery system, the overall energy consumption is reduced by 40% compared with the traditional coal-fired boiler process. The water consumption per cubic meter of pipe pile maintenance is reduced from 120L to 45L, and the water saving rate exceeds 60%. The AI algorithm accurately predicts the optimal temperature and humidity curve by dynamically learning historical data. The temperature fluctuation range in the constant temperature stage is reduced from ±5℃ of the traditional process to ±1.5℃, shortening the maintenance cycle by 50% while ensuring strength stability. In addition, the recycling of waste heat steam and the automatic adjustment of the pH value of condensed water have increased the water resource recycling rate to 82%, reduced the equipment corrosion rate by 70%, and significantly extended the life of the maintenance equipment.

[0060] The environmental adaptability and economic advantages of this invention are particularly outstanding. In a low-temperature environment of -10°C, through the combination of dual-source heating and thermal insulation coating, the strength of the pipe pile can still reach 48.7MPa after 3 days, breaking through the bottleneck of traditional processes limited by ambient temperature and expanding the feasibility of pipe pile applications in high-altitude and cold regions. The low-carbon design reduces the carbon emissions per unit product to 12.5kgCO2 / m 3 , reduced by 56% compared with the coal-fired boiler process; in industrial implementation, the cost of admixtures only increases by 5%, but the product can achieve a 15%-20% premium due to its high strength and low defect rate. Combined with the reduction in operating costs brought about by energy saving and consumption reduction, the overall investment return cycle is shortened to less than 2 years, which has significant market competitiveness and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0062] Figure 1It is a structural schematic diagram of the present invention;

[0063] Figure 2 is a cross-sectional view of the present invention;

[0064] Figure 3 It is an exploded view of the present invention. DETAILED DESCRIPTION

[0065] Example 1: Pipe pile preparation and maintenance under standard working conditions

[0066] 1. Pipe pile parameters and material preparation

[0067] Pipe pile specifications: outer diameter 600mm, wall thickness 100mm, length 12m, prestressed steel reinforcement ratio 1.2%.

[0068] Composite admixture ratio (weight percentage):

[0069] Lightly burned magnesium oxide (activity index 135s, specific surface area 410m 2 / kg): 4%

[0070] Silica fume (SiO2 content 92%, average particle size 0.1μm): 12%

[0071] Nano-silicon dioxide (particle size 15nm, specific surface area 400m 2 / g): 2%

[0072] High silica sand (SiO2 content 93%, fineness modulus 2.8): 82%

[0073] Steam guide groove structure: The inner wall spiral groove depth is 2.5mm, the spiral pitch is 60mm, and the groove is filled with porous ceramic particles with a porosity of 65% (loaded with CaO-Al2O3-SiO2 catalyst).

[0074] Outer wall composite layer: alkali-resistant glass fiber mesh cloth (weight 320g / m 2 , tensile strength 2100MPa), coated with 0.3mm thick aerogel insulation coating (thermal conductivity 0.018W / (m·K)).

[0075] 2. Steam curing process

[0076] Warm-up phase:

[0077] A Linoret CPC-20 vacuum tube solar collector (heat collection efficiency 78%) was used to raise the temperature in the curing kiln from 25°C to 45°C and the humidity to 75% in one hour.

[0078] Solar energy accounts for 80% of the energy supply, and electric energy accounts for 20%.

[0079] Constant temperature stage:

[0080] Saturated steam was introduced, and the temperature was raised to 80°C at a rate of 8°C / h, and the humidity was 92%, and maintained for 3 hours.

[0081] The temperature difference between the core and the surface is monitored by a pre-buried LoRa wireless temperature sensor (model SHT35, accuracy ±0.3°C), and the PLC system (Siemens S7-1200) dynamically adjusts the steam valve opening to control the temperature difference at 3-4°C.

[0082] Cooling stage:

[0083] After the steam supply is stopped, the temperature is reduced to 38°C at a rate of 12°C / h, and the waste heat steam is recovered through the S-shaped double-circuit pipeline, with a condensate utilization rate of 85%.

[0084] 3. Performance Testing and Results

[0085]

[0086]

[0087] 4. Key Effect Analysis

[0088] Improved strength: Lightly burned MgO and nano-SiO2 work together to increase 3D strength by 60% compared to traditional processes.

[0089] Energy saving and consumption reduction: Solar preheating + waste heat recovery reduces comprehensive energy consumption by 40%.

[0090] Example 2: Preparation of high-strength pipe piles and verification of limit parameters

[0091] 1. Optimization of pipe pile parameters and materials

[0092] Admixture adjustment:

[0093] Lightly burned magnesium oxide was increased to 5% (activity index 140s), nano-SiO2 was increased to 3%, and silica fume was maintained at 12%.

[0094] Structural reinforcement:

[0095] The spacing between the steam guide grooves is reduced to 50mm, and the porosity of the porous ceramic particles is increased to 70%.

[0096] The thickness of the aerogel coating increased to 0.5 mm, and the micro-bump density increased to 15 / cm 2 .

[0097] 2. Adjustment of steam curing parameters

[0098] Constant temperature stage: temperature rises to 85℃, maintained for 4 hours, humidity 95%.

[0099] Intelligent control:

[0100] The LSTM model predicted that the constant temperature time needed to be extended by 0.5 hours due to the increase in MgO content, but the actual duration was 4.5 hours.

[0101] The PLC system triggered two temperature difference exceeding limit (ΔT=6°C) alarms and automatically increased the steam volume by 8%, restoring the temperature difference to 4°C.

[0102] 3. Performance Testing and Results

[0103]

[0104] 4. Technological breakthroughs

[0105] Strength limit: Through admixture optimization + precise temperature control, the 28d strength exceeds 85MPa, meeting the requirements of high-speed railway bridge pile foundations (national standard ≥80MPa).

[0106] Advantages of AI temperature control: It reduces strength fluctuation by 15% compared with manual temperature control and avoids micro cracks caused by over-curing.

[0107] Example 3: Adaptability Verification in Low Temperature Environment

[0108] 1. Working condition simulation

[0109] Environmental conditions: simulated low temperature workshop at -10℃, humidity 30%, light intensity <100W / m 2 .

[0110] Equipment modification:

[0111] Solar collector with 2kW / m 3 The electric heating modules are connected in parallel and switched to valley electricity (0.35 yuan / kWh) at night.

[0112] The S-type steam pipe is covered with 30mm aluminum silicate insulation cotton (thermal conductivity 0.06W / (m·K)).

[0113] 2. Maintenance process adjustment

[0114] Warm-up phase:

[0115] Solar-assisted electric heating takes 1.5 hours to raise the temperature from -10°C to 40°C.

[0116] Electricity consumption during off-peak hours (22:00-6:00) accounts for 70%, and costs are reduced by 25%.

[0117] Constant temperature stage: temperature 80℃ maintained for 3.5 hours, humidity 90%.

[0118] Waste heat recovery: The pH value of the condensed water is adjusted to 7.0 and then recycled. After 10 cycles, the water quality still meets the GB / T14848-2017 Class III standard.

[0119] 3. Performance Testing and Results

[0120]

[0121] 4. Core advantages

[0122] Low temperature adaptability: stable production is possible even at -10℃, with 100% strength compliance rate.

[0123] Low carbon emission reduction: Solar energy + valley electricity reduces carbon emissions by 56%.

[0124] Experimental design

[0125] 1. Admixture activity test

[0126] Method: Cement mortar specimens were prepared according to GB / T 17671-2021, and the 3d and 28d compressive strengths were tested respectively.

[0127] Control group:

[0128] Control group 1: traditional admixture (fly ash 30% + mineral powder 10%);

[0129] Control group 2: only light-calcined MgO (6%) was added without nano-SiO2.

[0130] 2. Steam permeability uniformity verification

[0131] step:

[0132] Insert 10 humidity sensors into the steam guide groove on the inner wall of the pile (distribution spacing is 1m):

[0133] During the constant temperature stage, humidity values were recorded every 10 min, and the standard deviation (SD) was calculated.

[0134] Results: SD of the present invention is 2.1%, and SD of the traditional straight groove structure is 5.8%.

[0135] 3. AI model training and verification

[0136] Dataset: 1000 sets of data including environmental parameters (temperature -10 to 40°C, humidity 20-95%), pile size (diameter 400-1000mm), and admixture ratio.

[0137] Training results:

[0138] Prediction temperature error: ±1.2℃ (test set);

[0139] Curing time error: ±8 minutes.

[0140] Data summary table:

[0141]

[0142] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the technical field without departing from the scope of the present invention.

Claims

1. A concrete pipe pile, characterized in that: It includes the following components and structures: a. Concrete admixtures are composed of the following components by weight: 2%-6% light-burned magnesia, 10%-15% silica fume, 1%-3% nano-silica, and the balance is high-silica sand with SiO2 content ≥90%; b. The inner wall of the pile is provided with a spiral steam guide groove with a depth of 2-3 mm and a spiral pitch of 50-80 mm. The groove is filled with porous ceramic particles with a pore size of 10-50 μm. c. The outer wall of the pile is compounded with alkali-resistant glass fiber mesh cloth, the weight of the mesh cloth is ≥300g / m 2 The outer surface is coated with an aerogel thermal insulation coating with a coating thickness of 0.2-0.5mm and a thermal conductivity coefficient of ≤0.02W / (m·K).

2. A concrete pipe pile according to claim 1, characterized in that: The light-burned magnesium oxide has an activity index of 120-150s (tested according to GB / T 17671) and a specific surface area of ≥400m 2 / kg, and the loss on ignition after calcination at 800°C is ≤5%; the porosity of the porous ceramic particles is 60-70%, and the surface is loaded with a CaO-Al2O3-SiO2 ternary catalyst, which is coated on the surface of the ceramic particles by a sol-gel method, and the coating layer has a thickness of 5-10 μm.

3. A concrete pipe pile according to claim 2, characterized in that: The aerogel thermal insulation coating is composed of silica aerogel and polyurethane binder in a mass ratio of 3:

1. The surface of the coating is provided with micro-protrusion structures with an interval of 1-2 cm, a protrusion height of 0.1-0.3 mm, a hemispherical protrusion with a diameter of 0.5-1 mm; the warp and weft density of the alkali-resistant glass fiber mesh is 5×5 roots / cm 2 The diameter of the single wire is 10-15μm, the tensile strength is ≥2000MPa, and the mesh cloth is bonded to the concrete matrix through epoxy resin adhesive, and the thickness of the adhesive layer is 0.05-0.1mm.

4. A steam curing method for concrete pipe piles, applicable to the concrete pipe piles according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preheating stage: The curing environment temperature is raised from room temperature to 40-50°C through the solar collector, and the humidity is adjusted to 70-80% for 0.5-1 hour; S2, constant temperature stage: saturated steam is introduced into the curing kiln to raise the temperature to 75-85°C at a rate of 5-10°C / h, and the humidity is maintained at 90-95%. The steam valve opening is dynamically adjusted through the PLC system to keep the temperature difference between the core and the surface of the pile ≤ 5°C; S3, cooling stage: stop the steam supply, cool down to below 40℃ at a rate of ≤15℃ / h, and at the same time recover the waste heat steam to the water storage tank for recycling through condensation.

5. The steam curing method for concrete pipe piles according to claim 4, characterized in that: The temperature control in the constant temperature stage is specifically as follows: When the wall thickness of the pipe pile is ≤100mm, the constant temperature is 75-80℃ and the duration is 2-3 hours; When the wall thickness of the pile is greater than 100mm, the constant temperature is 80-85℃ and the duration is 3-4 hours; The humidity control accuracy is ±2%.

6. The steam curing method for concrete pipe piles according to claim 5, characterized in that: The PLC system receives data from wireless temperature sensors embedded in the piles. The sensors are distributed in a spiral pattern in the steam guide grooves on the inner wall of the piles at a spacing of 50 cm. The data acquisition frequency is ≥ 1 time / minute. The temperature range of the sensors is -20°C to 150°C, and the communication protocol is LoRaWAN. The solar collector is connected in parallel with the electric heating module. When the light intensity is less than 200W / m 2 It automatically switches to grid power supply when the power is turned on, and the switching response time is ≤30 seconds. It also gives priority to using off-peak hours (22:00-6:00) for supplementary heating at night.

7. The steam curing method for concrete pipe piles according to claim 6, characterized in that: The waste heat recovery system comprises: The inner layer of the S-shaped double-circuit steam pipeline is made of 316L stainless steel with a wall thickness of 2-3mm. The fresh steam temperature is ≤120°C. The bending radius of the S-shaped double-circuit steam pipeline is 2-3 times the pipe diameter. The spacing between adjacent pipes is 10-15cm. The outer wall of the pipeline is covered with aluminum silicate insulation cotton with a thickness of 20-30mm. The outer pipe is made of copper pipe with a wall thickness of 1.5-2mm and the temperature of the recovered waste heat steam is 40-60℃; The condensate storage tank is equipped with a pH adjustment module, which stabilizes the pH value of the recovered water at 6.5-7.5 by automatically adding citric acid or 0.1mol / L NaOH solution.

8. The steam curing method for concrete pipe piles according to claim 7, characterized in that: An LSTM neural network model was used to optimize the curing parameters. The input parameters of the model included ambient temperature, pile wall thickness, MgO content in the admixture, and curing kiln volume. The output parameters were the optimal temperature and humidity curves and steam flow rate for each stage. The model training dataset contained 1,000 sets of historical curing records, and the prediction error was ≤±1.5°C.

9. The steam curing method for concrete pipe piles according to claim 8, characterized in that: The LSTM neural network model includes: Input layer: 8 neurons corresponding to ambient temperature, humidity, pile wall thickness, diameter, length, MgO content, silica fume content, and nano-SiO2 content in admixtures; Hidden layer: 3 layers, 128 neurons per layer, activation function is ReLU; Output layer: 4 neurons, corresponding to preheating time, constant temperature, constant temperature time, and cooling rate.

10. The steam curing method for concrete pipe piles according to claim 9, characterized in that: During the constant temperature stage, when the temperature difference between the core and the surface of the pile is detected to be greater than 5°C, the following operations are performed: a. Increase the steam injection volume by 5%-10% and continue for 10-15 minutes; b. If the temperature difference is not reduced to ≤5°C, extend the constant temperature stage for 10-15 minutes; c. Trigger an alarm and record abnormal data to the PLC system log.

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