Concrete construction method for raft plate of heat absorption tower foundation of photo-thermal power station

Abstract

The invention provides a concrete construction method for a foundation raft of a heat absorption tower of a photo-thermal power station, which comprises the following steps of: laying a circulating cooling water system in a raft foundation through a water supply pipe, and uniformly arranging a plurality of temperature monitoring points in the longitude and latitude directions of the foundation raft; before concrete is poured, a cooling water pipe is filled with cooling water in advance, pouring is conducted through an inclined plane layering method, the thickness of each layer is 400 mm, and the layers are vibrated compactly; after concrete pouring is completed, the surface of concrete is covered with a layer of plastic film and then covered with a layer of cotton felt or regenerated blanket for heat preservation and maintenance, the internal and external temperatures of the concrete are measured regularly, the internal and external temperature difference of the concrete does not exceed 25 DEG C through water cooling, the internal temperature of the concrete is not larger than 70 DEG C, and the cooling speed of the concrete is controlled to be smaller than or equal to 2.0 DEG C / d. According to the method, concrete cracks caused by uneven heat dissipation inside and outside the concrete in the construction process are remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete construction, and in particular relates to a concrete construction method for a foundation raft slab of a heat absorbing tower in a solar thermal power station. Background Art

[0002] The heat absorption tower is the most important structure in the concentrated solar thermal system of a tower-type solar thermal power station. It is also the tallest structure in a solar thermal power station. The total height of the structure is generally more than 150m. The common structure of a heat absorption tower is a concrete structure system or a steel structure system, and the main structure is made of a single material. The foundation of the heat absorption tower consists of three parts: the base plate, the ring wall, and the stairs and elevator foundation. The base plate is a plate structure with a radius of about 20 meters, a plate thickness of about 3 meters, and a cross-sectional size greater than 1m. It belongs to large-volume concrete construction. The main characteristics of large-volume concrete construction are large volume, relatively small surface coefficient, relatively concentrated heat release of cement hydration, and relatively fast internal temperature rise. When the temperature difference between the inside and outside of the concrete is large, temperature cracks will occur in the concrete, affecting the structural safety and normal use. Summary of the invention

[0003] In order to solve the technical problem that cracks are prone to occur during the construction of a foundation raft slab of a heat absorbing tower in a solar thermal power station, the present invention provides a concrete construction method for a foundation raft slab of a heat absorbing tower in a solar thermal power station.

[0004] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is:

[0005] A method for concrete construction of a raft slab for a heat absorbing tower foundation of a solar thermal power station, characterized in that it comprises the following steps:

[0006] A. Arrangement of temperature control system

[0007] A circulating cooling water system is laid in the raft foundation through a water supply pipe, and multiple temperature monitoring points are evenly arranged in the longitude and latitude directions of the foundation raft. Each temperature monitoring point is evenly distributed with multiple temperature probes in the height direction. The temperature probes are connected to an electronic thermometer outside the concrete to measure the internal temperature of the concrete;

[0008] B. Concrete pouring

[0009] Before pouring concrete, fill the cooling water pipe with cooling water in advance, and pour concrete by inclined layering method. Measure the concrete entering mold temperature, ambient temperature and slump at any time during the pouring process. After pouring, use a flat vibrator to level the concrete surface, press once for wooden molds and twice for steel molds. After pouring concrete for 4 to 6 hours, use a second press to eliminate surface cracks.

[0010] C. Concrete maintenance

[0011] After the concrete is poured, cover the surface of the concrete with a layer of plastic film, and then cover it with a layer of cotton felt or recycled blanket for insulation and maintenance. Measure the temperature inside and outside the concrete regularly, and use water cooling to ensure that the temperature difference between the inside and outside of the concrete does not exceed 25°C, and the internal temperature of the concrete is not more than 70°C. The cooling rate of the concrete is controlled at ≤2.0°C / d. When the requirements cannot be met, add insulation measures and the maintenance time should be no less than 14 days.

[0012] Control the cooling rate of large-volume concrete at ≤2.0℃ / d to prevent cracks caused by temperature stress and shrinkage differences. Once cracks occur, harmful media such as external water, chloride ions, carbon dioxide, etc. can easily invade the concrete, corrode the steel bars, destroy the internal structure of the concrete, and reduce durability.

[0013] The distance between the temperature monitoring points of the present invention is 2-3m, the distance between the temperature measuring probes is 600-800mm, and the temperature measuring probes at the upper and lower ends are 50mm away from the concrete top and the ground respectively.

[0014] Due to the large volume of concrete, the hydration heat accumulated during the construction process is large, the internal and external heat dissipation is uneven, and the internal and external constraints are inconsistent, which causes large temperature stress inside the concrete, resulting in cracks and burying serious quality risks. Therefore, the present invention sets a circulating cooling water pipe in the large volume concrete, which is the main key measure for cooling the large volume concrete.

[0015] The circulating cooling water system of the present invention comprises a cold water tank, a return water tank, a left cold water pipe group and a right cold water pipe group. The water inlet of the cold water tank is connected to the water outlet of the return water tank, and the return water tank is connected to a cooling pool; the water outlet of the cold water tank is connected to the water inlets of the left cold water pipe group and the right cold water pipe group through an inlet pipe, and the water inlet of the return water tank is connected to the water outlets of the left cold water pipe group and the right cold water pipe group through an outlet pipe. The left cold water pipe group is laid on the left side of the raft, and the right cold water pipe group is laid on the right side of the raft. The left cold water pipe group and the right cold water pipe group each comprise three cooling water pipes and are arranged in three layers, namely, upper, middle and lower layers. The cooling water pipes are coiled in a "bow" shape and cover the raft of that layer.

[0016] The present invention adopts a three-layer water cooling system according to the thickness of the raft of the heat absorption tower of the solar thermal power station, and evenly lays cooling water pipes on each layer to ensure that the concrete can dissipate heat evenly. Preferably, the cooling water pipes of the upper layer are 600mm away from the top of the raft, the cooling water pipes of the lower layer are 800mm away from the bottom of the raft, and the cooling water pipes of the middle layer are arranged 800mm above the cooling water pipes of the lower layer; the outermost row of cooling water pipes on the side are 600mm away from the edge of the concrete, and the "bow"-shaped pipe spacing of the cooling water pipes is 2000mm; the water inlets of the left cold water pipe group and the right cold water pipe group are each provided with a solenoid valve, and the solenoid valve is 400mm away from the raft.

[0017] In step C of the present invention, after the concrete is poured, temperature monitoring is started at the time of initial setting, and temperature measurement records are filled in and a temperature curve is drawn, and moisture retention and heat preservation maintenance measures are adjusted in time according to the temperature control index; the temperature monitoring frequency is: on the 1st to 3rd day, the temperature is measured once every 2 hours; on the 4th to 7th day, the temperature is measured once every 4 hours; on the 7th to 21st day, the temperature is measured once every 8 hours; on the 21st to 30th day, the temperature is measured once every 12 hours.

[0018] The present invention suspends the water cooling operation when the difference between the maximum temperature of concrete and the surface temperature is not greater than 15°C; restarts the water cooling system when the difference between the maximum temperature of concrete and the surface temperature is close to 25°C; after the water cooling is completed, the cooling water pipe is promptly grout-grouted and blocked with cement slurry; when the difference between the surface temperature and the ambient temperature is less than 20°C, the side formwork is removed, and soil is promptly backfilled to retain moisture and keep heat.

[0019] In step B of the present invention, three pump trucks are used for simultaneous pouring, each pump truck covers 1 / 3 of the area, and pouring is performed from outside to inside in the same direction. The concrete pouring speed is 0.1m / h to avoid excessive concentration of hydration heat and the occurrence of cold joints.

[0020] Due to the large pouring range, the pump truck has a limited length of pump pipe, and the maximum coverage area is 1 / 3; pouring from the outside to the inside can make the outside form a certain shape of the structure first, providing operating space for construction workers, and construction workers stand on the poured part to vibrate the inside to ensure the quality of vibration. The three pump trucks pour in a clockwise or counterclockwise direction.

[0021] The concrete of the present invention comprises, by mass, 300-400 parts of sulfate-resistant cement, 700-800 parts of medium sand, 1000-1100 parts of crushed stone, 35-50 parts of fly ash, 50-70 parts of mineral powder, 75-95 parts of admixture and 130-150 parts of water; the admixture comprises 5-8 parts of slow-setting pumping agent, 0.8-1 part of polypropylene fiber, 10-15 parts of polycarboxylic acid water-reducing agent, 0.07-0.1 part of air-entraining agent, 1.5-2 parts of early strength antifreeze agent, 25-30 parts of low-alkali expansion agent and 32-38 parts of sulfate-resistant admixture.

[0022] Preferably, the concrete is composed of the following by mass: 360 parts of sulfate-resistant cement, 760 parts of medium sand, 1050 parts of crushed stone, 40 parts of fly ash, 60 parts of mineral powder, 140 parts of water, 6 parts of slow-setting pumping agent, 0.9 parts of polypropylene fiber, 12.85 parts of polycarboxylic acid water-reducing agent, 0.072 parts of air-entraining agent, 1.8 parts of early strength antifreeze agent, 28.8 parts of low-alkali expansion agent and 36 parts of sulfate-resistant admixture.

[0023] Controlling the water-cement ratio of concrete to 14:36 ​​and using a lower water-cement ratio can effectively reduce shrinkage and reduce the tensile stress caused by shrinkage, thereby preventing cracks. At the same time, it can make the concrete more compact, reduce porosity, and make it more difficult for harmful media from the outside (such as chloride ions, carbon dioxide, etc.) to penetrate, reducing the risk of cracking caused by steel corrosion, concrete carbonization, etc. At the same time, cement will not generate a large amount of hydration heat during the hardening process of concrete due to excessive use. Especially in large-volume concrete, excessive hydration heat will cause the internal temperature to rise too quickly, forming a large temperature difference with the outside, generating temperature stress and causing cracks.

[0024] Preferably, the crushed stone is composed of small stones of 5-20 mm and medium stones of 20-40 mm, the mud content of the small stones and medium stones is 0.4%, and the ratio of small stones to medium stones is 1.5:1.3.

[0025] In concrete, the selection of crushed stones is crucial to preventing cracks. Selecting crushed stones with appropriate particle sizes can make the internal structure of concrete denser, reduce porosity, and improve crack resistance. The ratio of small stones to medium stones is controlled at 1.5:1.3. Good grading allows for reasonable matching of crushed stones of different particle sizes, which can minimize the gaps between crushed stones. This can reduce the amount of cement slurry used, reduce the shrinkage of concrete, and prevent cracks.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention arranges a circulating cooling water pipe and a temperature monitoring system in the mass concrete to monitor the temperature inside and outside the concrete in real time, and controls the temperature difference between the inside and outside of the concrete to not exceed 25°C through water cooling, and the internal temperature of the concrete to not exceed 70°C. In the concrete curing stage, the cooling rate of the concrete is controlled to ≤2.0°C / d, and the insulation work is done effectively, which significantly reduces the problem of uneven heat dissipation inside and outside the concrete during the construction process, and the large temperature difference between the inside and outside causes concrete cracks.

[0028] 2. The temperature monitoring points of the present invention are evenly distributed throughout the entire foundation raft. The circulating cooling water system adopts two groups of cold water pipes on the left and right, and each group is divided into three layers of cooling water pipes, namely, upper, middle and lower layers, to ensure that the cooling water pipes are evenly distributed throughout the entire foundation raft. The spacing between the monitoring points and the spacing between the cooling water pipes are strictly controlled to achieve the purpose of accurate temperature measurement and rapid and uniform cooling.

[0029] 3. When preparing concrete, the present invention strictly controls the water-cement ratio and cement dosage, adds polypropylene fiber, low-alkali expansion agent and anti-sulfate admixture for synergistic effect, enhances the anti-cracking effect, and selects well-graded stones to further prevent concrete cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the arrangement of temperature monitoring points of the raft plate of the heat absorption tower foundation of the present invention.

[0031] Figure 2 It is a schematic diagram of the arrangement of temperature probes of the raft plate of the heat absorption tower foundation of the present invention.

[0032] Figure 3 It is a schematic diagram of the circulating cooling water system of the cross section of the raft plate of the heat absorption tower foundation of the present invention.

[0033] Figure numerals: 1, cold water tank; 2, return water tank; 3, cooling pool; 4, left cold water pipe group; 5, right cold water pipe group; 6, water inlet pipe; 7, water outlet pipe; 8, cooling water pipe; 9, solenoid valve; 10, valve plate. DETAILED DESCRIPTION

[0034] In order to more clearly and in detail illustrate the technical solution of the present invention, the present invention is further described below through relevant embodiments. The following embodiments are only for specific explanation of the implementation method of the present invention, and do not limit the protection scope of the present invention.

[0035] Example 1

[0036] A method for concrete construction of a raft slab for a heat absorbing tower foundation of a solar thermal power station comprises the following steps:

[0037] A. Arrangement of temperature control system

[0038] like Figure 1 and Figure 2 As shown, a circulating cooling water system is laid in the raft foundation through a water supply pipe, 9 temperature monitoring points are evenly arranged in the longitude and latitude directions of the foundation raft, and each temperature monitoring point is evenly distributed with 5 temperature probes in the height direction. The temperature probes are connected to the electronic thermometer outside the concrete to measure the internal temperature of the concrete;

[0039] B. Concrete pouring

[0040] Before pouring concrete, fill the cooling water pipe with cooling water in advance, and pour concrete in layers using the inclined surface method. Each layer is 400 mm thick and is vibrated and compacted layer by layer. During the pouring process, measure the concrete's mold temperature, ambient temperature and slump at any time. After pouring, use a flat vibrator to level the concrete surface, apply pressure once on the wooden mold and twice on the steel mold. After pouring for 4 to 6 hours, apply pressure a second time to eliminate surface cracks.

[0041] C. Concrete maintenance

[0042] After the concrete is poured, cover the surface of the concrete with a layer of plastic film, and then cover it with a layer of cotton felt or recycled blanket for insulation and maintenance. Measure the temperature inside and outside the concrete regularly, and use water cooling to ensure that the temperature difference between the inside and outside of the concrete does not exceed 25°C, and the internal temperature of the concrete is not more than 70°C. The cooling rate of the concrete is controlled at ≤2.0°C / d. When the requirements cannot be met, add insulation measures and the maintenance time should be no less than 14 days.

[0043] Example 2

[0044] This embodiment is based on embodiment 1:

[0045] The distance between the temperature monitoring points is 2-3m, the distance between the temperature measuring probes is 600-800mm, and the temperature measuring probes at the upper and lower ends are 50mm away from the concrete top and the ground respectively.

[0046] Example 3

[0047] This embodiment is based on embodiment 1:

[0048] like Figure 3 As shown, the circulating cooling water system includes a cold water tank 1, a return water tank 2, a left cold water pipe group 4 and a right cold water pipe group 5. The water inlet of the cold water tank 1 is connected to the water outlet of the return water tank 2, and the return water tank 2 is connected to the cooling pool 3; the water outlet of the cold water tank 1 is connected to the water inlets of the left cold water pipe group 4 and the right cold water pipe group 5 through an inlet pipe 6, and the water inlet of the return water tank 2 is connected to the water outlets of the left cold water pipe group 4 and the right cold water pipe group 5 through an outlet pipe 7. The left cold water pipe group 4 is laid on the left side of the raft 10, and the right cold water pipe group 5 is laid on the right side of the raft 10. The left cold water pipe group 4 and the right cold water pipe group 5 each include three cooling water pipes 8 and are arranged in three layers of upper, middle and lower layers. The cooling water pipes 8 are coiled in a "bow" shape and cover the raft 10 of this layer.

[0049] Due to the large volume of concrete, the large amount of hydration heat accumulated during the construction process, the uneven heat dissipation inside and outside, and the inconsistent constraints inside and outside, cause large temperature stress inside the concrete, resulting in cracks, which posed serious quality risks. Therefore, three layers of DN32 galvanized steel pipes are set in the large volume of concrete as circulating cooling water pipes. Before pouring concrete, the cooling water pipes should be pre-filled with cooling water. During the cooling process, the cooling pool continuously injects low-temperature water into the return water tank, neutralizes and cools the high-temperature water recovered in the return water tank, and then sends the cooled cold water into the cold water tank, and then sends it to the left cold water pipe group and the right cold water pipe group through the water inlet pipe for circulating cooling.

[0050] The cooling water pipes on the upper layer are 600mm away from the top of the raft slab, the cooling water pipes on the lower layer are 800mm away from the bottom of the raft slab, and the cooling water pipes on the middle layer are arranged 800mm above the cooling water pipes on the lower layer; the cooling water pipes on the outermost row on the side are 600mm away from the edge of the concrete, and the "bow"-shaped pipe spacing of the cooling water pipes is 2000mm; the water inlets of the left cold water pipe group and the right cold water pipe group are each provided with a solenoid valve, and the solenoid valve is 400mm away from the raft slab.

[0051] Example 4

[0052] This embodiment is based on embodiment 1:

[0053] In the step C described above, after the concrete is poured, temperature monitoring is started at the time of initial setting, and temperature measurement records are filled in and temperature curves are drawn, and moisture retention and heat preservation maintenance measures are adjusted in time according to temperature control indicators; the frequency of temperature monitoring is: on the 1st to 3rd day, the temperature is measured once every 2 hours; on the 4th to 7th day, the temperature is measured once every 4 hours; on the 7th to 21st day, the temperature is measured once every 8 hours; on the 21st to 30th day, the temperature is measured once every 12 hours.

[0054] When the difference between the maximum temperature of concrete and the surface temperature is no more than 15°C, suspend the water cooling operation; when the difference between the maximum temperature of concrete and the surface temperature is close to 25°C, restart the water cooling system; after the water cooling is completed, promptly use cement slurry to grout and seal the cooling water pipe; when the difference between the surface temperature and the ambient temperature is less than 20°C, remove the side formwork and backfill the soil in time to retain moisture and keep warm.

[0055] Example 5

[0056] This embodiment is based on embodiment 1:

[0057] In the step B, three pump trucks are used for simultaneous pouring, each pump truck covers 1 / 3 of the area, and pouring is performed from outside to inside in the same direction. The concrete pouring speed is 0.1 m / h.

[0058] Example 6

[0059] The present invention uses P.MSR 42.5 sulfate-resistant cement with low alkali, low hydration heat and long setting time. The concrete mix design complies with the relevant provisions of the current national standard "Ordinary Concrete Mix Design Specification" JGJ55, and at the same time considers factors such as actual structure and large-volume concrete construction technology. On the basis of satisfying construction performance, mechanical properties and durability, the mix and admixture are optimized in accordance with the principle of low cement dosage and high-efficiency crack resistance. Concrete with different weight mix ratios is shown in Table 1.

[0060] The air entraining agent in the admixture may be a rosin resin type air entraining agent, and the pumping agent may be any conventional retarding pumping agent such as lignin sulfonate, hydroxycarboxylic acid and its salts, sugar and carbohydrate.

[0061] Table 1 Concrete with different weight mix ratios

[0062]

[0063]

[0064] Performance tests were carried out on 12 groups of concrete. The working performance of the concrete in the example was tested in accordance with the provisions of GB / T50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures"; the mechanical properties of the concrete were tested in accordance with GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Ordinary Concrete"; the "crack-resistant flat plate test" was used to determine the early crack resistance of the concrete, and the test results were expressed as the calculated total crack area per unit area. The smaller the value, the better the crack resistance.

[0065] Table 2 Concrete performance test results

[0066]

[0067]

[0068] It can be seen from Table 2 that the slump and compressive strength of concrete in groups 3, 4, 5, 7 and 8 meet the construction requirements, and the crack area is small. On the basis of the concrete in group 5, anti-cracking admixtures are added to further optimize the anti-cracking performance.

[0069] Table 3 Performance test results of concrete

[0070]

[0071] The addition of low-alkali expansive agent is used to compensate for the shrinkage of concrete and reduce the occurrence of cracks in concrete structures; the anti-sulfate admixture reacts with aluminate in cement to generate stable substances, preventing it from reacting with sulfate to generate expansive products. At the same time, it can fill the pores of concrete, prevent sulfate from entering the interior, and extend the service life of the concrete structure. As can be seen from Table 3, the synergistic effect of polypropylene fiber, low-alkali expansive agent and anti-sulfate admixture has the best anti-cracking performance of concrete.

[0072] In concrete, the selection of crushed stone is crucial to preventing cracks. Selecting crushed stone with the right particle size can make the internal structure of concrete denser, reduce porosity, and improve crack resistance. Further, based on the 21st group of concrete, 5-20mm small stones and 20-40mm medium stones were selected, with a mud content of 0.4%. By changing the ratio of small stones to medium stones, the performance test results showed the best crushed stone ratio.

[0073] Table 4 Performance test results of concrete

[0074]

[0075] It can be seen from Table 4 that when the mass ratio of small stone: medium stone is 1.5:1.3, the cracking area is the smallest and the concrete crack resistance is the best.

[0076] Example 7

[0077] This embodiment is based on embodiment 1:

[0078] The concrete comprises, by mass, 360 parts of anti-sulfate cement, 800 parts of medium sand, 1050 parts of crushed stone, 50 parts of fly ash, 40 parts of mineral powder, 95 parts of admixtures and 140 parts of water; the admixtures include 6 parts of slow-setting pumping agent, 1 part of polypropylene fiber, 15 parts of polycarboxylic acid water reducer, 0.1 parts of air entraining agent, 2 parts of early strength antifreeze agent, 30 parts of low-alkali expansion agent and 38 parts of anti-sulfate admixture. Small stones of 5-20 mm and medium stones of 20-40 mm are selected, with a mud content of 0.4%, and the mass ratio of small stones to medium stones is 1.5:1.3. The total cracking area per unit area of ​​the obtained concrete is 30 mm 2 / m 2 .

[0079] Example 8

[0080] This embodiment is based on embodiment 1:

[0081] The concrete comprises, by mass, 365 parts of anti-sulfate cement, 750 parts of medium sand, 1060 parts of crushed stone, 40 parts of fly ash, 60 parts of mineral powder, 75 parts of admixtures and 145 parts of water; the admixtures include 8 parts of slow-setting pumping agent, 0.8 parts of polypropylene fiber, 10 parts of polycarboxylic acid water reducer, 0.075 parts of air entraining agent, 1.5 parts of early strength antifreeze agent, 25 parts of low-alkali expansion agent and 32 parts of anti-sulfate admixture. Small stones of 5-20 mm and medium stones of 20-40 mm are selected, with a mud content of 0.4%, and the mass ratio of small stones to medium stones is 1.5:1.3. The total cracking area per unit area of ​​the obtained concrete is 28 mm 2 / m 2 .

[0082] Example 9

[0083] The construction method of the present invention is promoted and applied in the heat absorption tower of the Xinhua Power Generation Jinghe 100,000-kilowatt solar thermal project. The heat absorption tower foundation is buried at a depth of 7.8m, and the foundation type is a raft foundation. The foundation consists of three parts: the bottom plate, the ring wall, and the stairs and elevator foundation. The foundation bottom plate is a plate structure with a radius of 20.3m and a plate thickness of 2.8m; the cross-sectional shape of the foundation ring wall is a right-angled trapezoid with a height of 4.70m, an upper width of 1.15m, and a lower width of 7.95m. The foundation bottom plate is poured with concrete for about 3623m 3 , cone concrete about 1500m 3 . Three pump trucks poured in a counterclockwise direction.

[0084] The concrete used is composed of the following by mass: 360 parts of anti-sulfate cement, 760 parts of medium sand, 1050 parts of crushed stone, 40 parts of fly ash, 60 parts of mineral powder, 140 parts of water, 6 parts of slow-setting pumping agent, 0.9 parts of polypropylene fiber, 12.85 parts of polycarboxylic acid water reducer, 0.072 parts of air entraining agent, 1.8 parts of early strength antifreeze agent, 28.8 parts of low-alkali expansion agent and 36 parts of anti-sulfate admixture. The crushed stone is composed of small stones of 5-20 mm and medium stones of 20-40 mm, the mud content of the small stones and medium stones is 0.4%, and the ratio of small stones to medium stones is 1.5:1.3. The total cracking area per unit area of ​​the obtained concrete is 25 mm 2 / m 2 .

[0085] It took only 20 days from construction to pouring, which saved one month compared with the same type of large-volume concrete construction. All data indicators met the requirements of the design technical standards and regulations, and the construction process was smooth. By using this construction method, the construction period was shortened, the construction quality of the foundation was guaranteed, the consumables and energy consumption were reduced during the construction process, and environmental pollution was reduced.

[0086] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A concrete construction method for the foundation raft of a solar thermal power station heat absorption tower, characterized in that: The following steps are involved: A. Arrangement of temperature control system A circulating cooling water system is laid in the raft foundation through a water supply pipe, and multiple temperature monitoring points are evenly arranged in the longitude and latitude directions of the foundation raft. Each temperature monitoring point is evenly distributed with multiple temperature probes in the height direction. The temperature probes are connected to an electronic thermometer outside the concrete to measure the internal temperature of the concrete; B. Concrete pouring Before pouring concrete, fill the cooling water pipe with cooling water in advance, and pour concrete by inclined layering method. Measure the concrete entering mold temperature, ambient temperature and slump at any time during the pouring process. After pouring, use a flat vibrator to level the concrete surface, press once for wooden molds and twice for steel molds. After pouring concrete for 4 to 6 hours, use a second press to eliminate surface cracks. C. Concrete maintenance After the concrete is poured, cover the surface of the concrete with a layer of plastic film, and then cover it with a layer of cotton felt or recycled blanket for insulation and maintenance. Measure the temperature inside and outside the concrete regularly, and use water cooling to ensure that the temperature difference between the inside and outside of the concrete does not exceed 25°C, and the internal temperature of the concrete is not more than 70°C. The cooling rate of the concrete is controlled at ≤2.0°C / d. When the requirements cannot be met, add insulation measures and the maintenance time should be no less than 14 days.

2. The concrete construction method for the foundation raft of the heat absorbing tower of a solar thermal power station according to claim 1 is characterized in that: The distance between the temperature monitoring points is 2-3m, the distance between the temperature measuring probes is 600-800mm, and the temperature measuring probes at the upper and lower ends are 50mm away from the concrete top and the ground respectively.

3. The concrete construction method for the foundation raft of the heat absorbing tower of a solar thermal power station according to claim 1 is characterized in that: The circulating cooling water system includes a cold water tank, a return water tank, a left cold water pipe group and a right cold water pipe group. The water inlet of the cold water tank is connected to the water outlet of the return water tank, and the return water tank is connected to the cooling pool; the water outlet of the cold water tank is connected to the water inlets of the left cold water pipe group and the right cold water pipe group through an inlet pipe, and the water inlet of the return water tank is connected to the water outlets of the left cold water pipe group and the right cold water pipe group through an outlet pipe. The left cold water pipe group is laid on the left side of the raft, and the right cold water pipe group is laid on the right side of the raft. The left cold water pipe group and the right cold water pipe group each include three cooling water pipes and are arranged in three layers of upper, middle and lower layers. The cooling water pipes are coiled in a "bow" shape and cover the raft of that layer.

4. The concrete construction method for the foundation raft of the heat absorbing tower of a solar thermal power station according to claim 3 is characterized in that: The cooling water pipes on the upper layer are 600mm away from the top of the raft slab, the cooling water pipes on the lower layer are 800mm away from the bottom of the raft slab, and the cooling water pipes on the middle layer are arranged 800mm above the cooling water pipes on the lower layer; the cooling water pipes on the outermost row on the side are 600mm away from the edge of the concrete, and the "bow"-shaped pipe spacing of the cooling water pipes is 2000mm; the water inlets of the left and right cold water pipe groups are each provided with a solenoid valve, and the solenoid valve is 400mm away from the raft slab.

5. The concrete construction method for the foundation raft of the heat absorbing tower of a solar thermal power station according to claim 1 is characterized in that: In the step C described above, after the concrete is poured, temperature monitoring is started at the time of initial setting, and temperature measurement records are filled in and temperature curves are drawn, and moisture retention and heat preservation maintenance measures are adjusted in time according to temperature control indicators; the frequency of temperature monitoring is: on the 1st to 3rd day, the temperature is measured once every 2 hours; on the 4th to 7th day, the temperature is measured once every 4 hours; on the 7th to 21st day, the temperature is measured once every 8 hours; on the 21st to 30th day, the temperature is measured once every 12 hours.

6. The method for concrete construction of the foundation raft slab of the heat absorbing tower of a solar thermal power station according to claim 1, characterized in that: When the difference between the maximum temperature of concrete and the surface temperature is no more than 15°C, suspend the water cooling operation; when the difference between the maximum temperature of concrete and the surface temperature is close to 25°C, restart the water cooling system; after the water cooling is completed, promptly use cement slurry to grout and seal the cooling water pipe; when the difference between the surface temperature and the ambient temperature is less than 20°C, remove the side formwork and backfill the soil in time to retain moisture and keep warm.

7. The concrete construction method for the foundation raft of the heat absorbing tower of a solar thermal power station according to claim 1, characterized in that: In the step B, three pump trucks are used for simultaneous pouring, each pump truck covers 1 / 3 of the area, and pouring is performed from outside to inside in the same direction. The concrete pouring speed is 0.1 m / h.

8. The method for concrete construction of the foundation raft slab of the heat absorbing tower of a solar thermal power station according to claim 1, characterized in that: The concrete comprises, by mass, 300-400 parts of sulfate-resistant cement, 700-800 parts of medium sand, 1000-1100 parts of crushed stone, 35-50 parts of fly ash, 50-70 parts of mineral powder, 75-95 parts of admixtures and 130-150 parts of water; the admixtures comprise 5-8 parts of retarding pumping agent, 0.8-1 part of polypropylene fiber, 10-15 parts of polycarboxylic acid water reducer, 0.07-0.1 parts of air entraining agent, 1.5-2 parts of early strength antifreeze agent, 25-30 parts of low-alkali expansion agent and 32-38 parts of sulfate-resistant admixture.

9. The method for concrete construction of the foundation raft slab of the heat absorbing tower of a solar thermal power station according to claim 8, characterized in that: The concrete is composed of 360 parts of sulfate-resistant cement, 760 parts of medium sand, 1050 parts of crushed stone, 40 parts of fly ash, 60 parts of mineral powder, 140 parts of water, 6 parts of slow-setting pumping agent, 0.9 parts of polypropylene fiber, 12.85 parts of polycarboxylic acid water-reducing agent, 0.072 parts of air-entraining agent, 1.8 parts of early-strength antifreeze agent, 28.8 parts of low-alkali expansive agent and 36 parts of sulfate-resistant admixture.

10. The method for concrete construction of the foundation raft slab of the heat absorbing tower of a solar thermal power station according to claim 8, characterized in that: The crushed stones are composed of small stones of 5-20 mm and medium stones of 20-40 mm, the mud content of the small stones and the medium stones is 0.4%, and the ratio of the small stones to the medium stones is 1.5:1.3.

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