Super-strong high-toughness PHC pipe pile top concrete and construction method

Abstract

The water-binder ratio of the concrete is 0.18-0.20, the total use amount of a cementing material is not larger than 660 kg / m < 3 >, the cementing material comprises Portland cement, granulated blast-furnace slag powder and silica fume, the granulated blast-furnace slag powder accounts for 20-30% of the cementing material, the silica fume accounts for 5-10% of the cementing material, namely, the water-binder ratio of the concrete is 0.18-0.20, and the total use amount of the cementing material is not larger than 660 kg / m < 3 >. Each cubic meter of the concrete comprises the following materials: 400-500 kg of Portland cement; 100 to 150 kg of granulated blast furnace slag powder; 40 to 80 kg of silica fume; 700 to 800 kg of sand; the weight of the crushed stones is 1000 to 1150 kg; 13.0 to 18.0 kg of a water reducing agent; the water consumption is 110 to 125 kg; and 40 to 60 kg of steel fiber. The invention further discloses a construction method of the super-strong high-toughness PHC pipe pile top concrete. The anti-hammering capacity of the pile top is improved, and the breakage rate of the pile top is reduced.

Description

Technical Field

[0001] The present invention relates to a super-strong and high-toughness PHC pipe pile top concrete and a construction method thereof. Background Art

[0002] During the pile driving process of PHC pipe piles, the pile top is always in the state of maximum stress and maximum strain. When the load exceeds a certain value, the concrete compressive ultimate strength decreases significantly. The instantaneous stress generated by the hammer energy at the pile top exceeds the strength that the C80 concrete pile body can withstand, causing the concrete strain at the pile top to exceed its ultimate strain and resulting in cracking and damage of the pile head. The damaged pile head needs to be repaired, which not only increases costs but also affects the construction progress.

[0003] The concrete at the top of the PHC pipe pile is the same as the concrete of the pile body, with a strength grade of C80, and the compressive strength of the 7-day cube specimen is above 80 MPa, and the splitting tensile strength is above 4.0 MPa. According to the theory of dynamic compressive damage of concrete based on the load history, it is necessary to improve the compressive strength of the pile top concrete and enhance the ability to resist the ultimate strain.

[0004] Currently, the C80 concrete used in PHC pipe piles uses conventional materials such as cement, blast furnace slag powder, natural medium sand, 5-25 mm gravel, polycarboxylate superplasticizer, and steam curing.

[0005] Therefore, in combination with the current production situation, considering raising the concrete strength grade to above C100 within the range of 3 m from the pile top and at the same time reducing the difficulty of concrete pouring into the mold, a super-strong and high-toughness PHC pipe pile top concrete and a construction method thereof are proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a super-strong and high-toughness PHC pipe pile top concrete and a construction method thereof to overcome the existing defects, improve the anti-hammering ability of the pile top, and reduce the pile top breakage rate.

[0007] The technical solution to achieve the above purpose is as follows:

[0008] A super-strong and high-toughness PHC pipe pile top concrete, with a water-binder ratio of 0.18 - 0.20, and the total amount of binder materials not exceeding 660 kg / m 3 , and the binder materials include Portland cement, granulated blast furnace slag powder, and silica fume. Among them, the granulated blast furnace slag powder accounts for 20 - 30% of the binder materials, and the silica fume accounts for 5 - 10% of the binder materials. That is, the composition of each material in every cubic meter of concrete is as follows:

[0009] Portland cement: 400 - 500 kg;

[0010] Granulated blast furnace slag powder: 100 - 150 kg;

[0011] Silica fume: 40 - 80 kg;

[0012] Sand: 700 - 800 kg;

[0013] Crushed stone: 1000 - 1150 kg;

[0014] Water reducing agent: 13.0 - 18.0 kg;

[0015] Water consumption: 110 - 125 kg;

[0016] Steel fiber: 40 - 60 kg.

[0017] Preferably, the variety and specification of Portland cement is P·II 52.5, the specific surface area is 350 - 380 m 2 / kg, the C3A content is < 8.0%, the alkali content is < 0.60%, and the standard consistency water consumption is ≤ 28.0%;

[0018] The fluidity of the neat cement of Portland cement and admixture is ≥ 260 mm;

[0019] The flexural strength of Portland cement at 3 days is ≥ 5.5 MPa, the compressive strength at 3 days is ≥ 30.0 MPa, the flexural strength at 28 days is ≥ 7.7 MPa, and the compressive strength at 28 days is ≥ 57.8 MPa.

[0020] Preferably, the variety and specification of granulated blast furnace slag powder is S95 grade, and the raw material is granulated blast furnace slag produced by large steel mills;

[0021] The 7-day activity index of granulated blast furnace slag powder should be greater than 75%, the 28-day activity index should be greater than 100%, and the fluidity ratio should be greater than 95%;

[0022] The main component of silica fume is silicon dioxide SiO 2 , and its total content is not less than 90%, and the specific surface area is 20000 - 25000 m 2 / kg.

[0023] Preferably, the sand is hard natural sand, the fineness modulus of the sand is 2.4 - 3.0, and the total mud content is ≤ 1.0%;

[0024] The pebbles in the sand: the content of particles with a particle size ≥ 10 mm is ≤ 5.0%, and the content of particles with a particle size ≥ 5 mm is ≤ 10.0%;

[0025] The mica content in the sand is ≤ 1.0%, the light substance content is ≤ 1.0%, the sulfide and sulfate content is ≤ 0.5%, and the chloride content is ≤ 0.01%.

[0026] Preferably, the varieties of crushed stone include but are not limited to basalt and sandstone;

[0027] The particle size distribution of crushed stone is 16 - 25 mm and 5 - 16 mm;

[0028] The total mud content of the crushed stone shall be ≤0.5%, the crushing index value shall be ≤8.0%, the saturated water cube compressive strength of the crushed stone shall be ≥120 MPa, the content of needle-like and flaky particles shall be ≤5.0%, the apparent density shall be ≥2700 kg, the loose bulk density shall be ≥1450 kg, the water absorption rate shall be ≤1.0%, the soundness shall be ≤5.0%, and the sulfides and sulfates shall be ≤0.5%.

[0029] Preferably, the water reducing agent adopts a polycarboxylate superplasticizer, and the chloride ion content is not more than 0.02%;

[0030] Tap water is used for water; when other water sources are used, the water does not contain harmful impurities or oils that affect the normal setting and hardening of cement and the later-stage performance of concrete;

[0031] The tensile strength Rm of the steel fiber: 1000 < Rm ≤ 1300 MPa;

[0032] The shape of the steel fiber is end-hooked;

[0033] The length of the steel fiber is 30 ± 3 mm, the equivalent diameter is 0.7 ± 0.02 mm, and the aspect ratio is 45 ± 15%.

[0034] Preferably, according to the parameter ranges, different combined mix ratio designs are carried out, and the compressive strength, splitting tensile strength, flexural strength, and impact resistance of concrete at different ages are detected. Finally, the composition of each material per cubic meter of concrete is as follows:

[0035] Water-binder ratio: 0.19, water consumption: 115 kg, binder dosage: 605 kg, among which, the dosage of Portland cement: 424 kg, the dosage of slag powder: 121 kg, the dosage of silica fume: 60 kg, the dosage of water reducing agent: 15.1 kg, the dosage of sand: 760 kg, the dosage of crushed stone: 1050 kg, among which, the dosage of crushed stone with a particle size distribution of 5 - 16 mm is 315 kg, the dosage of crushed stone with a particle size distribution of 16 - 25 mm is 735 kg, and the dosage of steel fiber: 40 kg.

[0036] A construction method for the concrete at the top of a super-strong and high-toughness PHC pipe pile according to the second aspect of the present invention includes:

[0037] Step S1, the operator of the mixing plant inputs the dosage of each material per cubic meter of concrete according to the concrete batching notice provided by the test personnel. After confirmation, batching is carried out;

[0038] Step S2, calculate the mixing volume in advance according to the pile type. First, put the sand, crushed stone, steel fiber, half of the water, and steel fiber into the mixer and stir for 20 s;

[0039] Step S3, then add the binder and stir for 20 s. Finally, add the remaining water and water reducing agent into the mixer and stir for more than 180 s. After the concrete mixture is uniform and stable, then start discharging;

[0040] In step S4, after transporting the concrete to the designated position by the ash transport trolley, the concrete is then distributed by the fully automatic intelligent concrete distributor.

[0041] In step S5, after the concrete distribution is completed, the entire manufacturing process is completed through the processes of mold closing, tensioning, centrifugation, steam curing, and demolding.

[0042] Preferably, in the said step S2, the mixing volume is 1.0 - 1.5 m 3 , and the steel fibers are added manually;

[0043] In the said step S4, during the concrete distribution process, the trolley travels back and forth and distributes the concrete in layers.

[0044] Preferably, in the said step S5, the centrifugation process is divided into four stages: low speed, low-medium speed, medium speed, and high speed, with a total time of 20 - 25 minutes and a centrifugal acceleration of 36g - 42g;

[0045] The steam curing process is divided into four stages: static stop, heating up, constant temperature, and cooling down, with a total time of 10 - 12 hours. The maximum steam curing temperature is not more than 75°C, the steam saturation is not less than 90%, and the heating rate is not more than 15°C / h;

[0046] When demolding and relaxation, the controlled value of the compressive strength of the pile concrete under normal pressure steam curing reaches 70 MPa.

[0047] The beneficial effects of the present invention are:

[0048] After the finished pile of the present invention goes through processes such as batching, mixing, transporting, distributing, centrifuging, steam curing, and demolding, the inner wall and appearance quality of the pile top are inspected. At the same time, through experimental studies on the compressive strength, splitting tensile strength, flexural strength, impact resistance, etc. of concrete at different ages, the construction mix ratio and production process of the pile top concrete of the pipe pile are determined. Through on-site pile driving verification, finally, the breakage rate of the pile top of the pipe pile is achieved to be lower than 0.5%;

[0049] In terms of concrete distribution, the present invention adopts a fully automatic intelligent concrete distributor, which also has mixing and vibration functions, effectively ensuring the uniformity of the concrete and that the slump meets the requirements, avoiding the phenomenon of enlarged slump due to the high viscosity of the concrete, and effectively guaranteeing the quality of the concrete;

[0050] The present invention improves the performance of the pile top concrete of the PHC pipe pile, enhances the hammer resistance of the pile top, reduces the breakage rate of the pile top, reduces the construction cost, speeds up the project progress, further enhances the product popularity, and escorts the enterprise brand products. Description of the Drawings

[0051] Figure 1 It is a flow chart of a construction method for the pile top concrete of a super-strong and high-toughness PHC pipe pile of the present invention. Detailed Embodiments

[0052] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0053] The present invention will be further described below in conjunction with the accompanying drawings.

[0054] A super-strong and high-toughness PHC pipe pile top concrete, with a water-binder ratio of 0.18 - 0.20, and the total binder material dosage not exceeding 660 kg / m 3 , and the binder material includes Portland cement, granulated blast furnace slag powder, and silica fume. Among them, the granulated blast furnace slag powder accounts for 20 - 30% of the binder material, and the silica fume accounts for 5 - 10% of the binder material. That is, the composition of each material in every cubic meter of concrete is as follows:

[0055] Portland cement: 400 - 500 kg;

[0056] Granulated blast furnace slag powder: 100 - 150 kg;

[0057] Silica fume: 40 - 80 kg;

[0058] Sand: 700 - 800 kg;

[0059] Crushed stone: 1000 - 1150 kg;

[0060] Water reducing agent: 13.0 - 18.0 kg;

[0061] Water consumption: 110 - 125 kg;

[0062] Steel fiber: 40 - 60 kg.

[0063] In the embodiment, the variety and specification of the Portland cement is P·I I52.5, the specific surface area is 350 - 380 m 2 / kg, the C3A content < 8.0%, the alkali content < 0.60%, and the standard consistency water consumption ≤ 28.0%;

[0064] The net paste fluidity of the Portland cement and the admixture ≥ 260 mm;

[0065] The flexural strength of Portland cement at 3 days is ≥5.5 MPa, the compressive strength at 3 days is ≥30.0 MPa, the flexural strength at 28 days is ≥7.7 MPa, and the compressive strength at 28 days is ≥57.8 MPa.

[0066] In the examples, the granulated blast-furnace slag powder is of the S95 grade, and the raw material is granulated blast-furnace slag produced by large steel mills;

[0067] The 7-day activity index of the granulated blast-furnace slag powder should be greater than 75%, the 28-day activity index should be greater than 100%, and the fluidity ratio should be greater than 95%.

[0068] In the examples, the main component of silica fume is silicon dioxide SiO 2 , and its total content is not less than 90%, and the specific surface area is 20000 - 25000 m 2 / kg.

[0069] In the examples, the sand is hard natural sand, the fineness modulus of the sand is 2.4 - 3.0, and the total mud content ≤1.0%;

[0070] In the sand, the content of pebbles with a particle size ≥10 mm is ≤5.0%, and the content of pebbles with a particle size ≥5 mm is ≤10.0%;

[0071] The mica content in the sand is ≤1.0%, the light substance content is ≤1.0%, the sulfides and sulfates are ≤0.5%, and the chlorides are ≤0.01%.

[0072] In the examples, the types of crushed stones include but are not limited to basalt and sandstone;

[0073] The particle size distribution of the crushed stones is 16 - 25 mm and 5 - 16 mm;

[0074] The total mud content of the crushed stones is ≤0.5%, the crushing index value is ≤8.0%, the saturated cubic compressive strength of the crushed stones is ≥120 MPa, the needle-like and flaky content is ≤5.0%, the apparent density is ≥2700 kg, the loose bulk density is ≥1450 kg, the water absorption rate is ≤1.0%, the soundness is ≤5.0%, and the sulfides and sulfates are ≤0.5%.

[0075] In the examples, the water-reducing agent uses a polycarboxylate superplasticizer, and the chloride ion content is not more than 0.02%.

[0076] In the examples, tap water is used as the water; when using other water sources, the water does not contain harmful impurities or oils that affect the normal setting and hardening of the cement and the later performance of the concrete.

[0077] In the examples, the tensile strength Rm of the steel fiber: 1000 < Rm ≤ 1300 MPa;

[0078] The shape of the steel fiber is end-hooked;

[0079] The length of the steel fiber is 30 ± 3 mm, the equivalent diameter is 0.7 ± 0.02 mm, and the length-diameter ratio is 45 ± 15%.

[0080] In the embodiments, according to the ranges of various parameters, different combined mix designs are carried out, and the compressive strength, splitting tensile strength, flexural strength, and impact resistance of the concrete at different ages are detected. Finally, the composition of each material in every cubic meter of concrete is as follows:

[0081] Water-binder ratio: 0.19, water consumption: 115 kg, binder material consumption: 605 kg, among which, the consumption of Portland cement: 424 kg, the consumption of slag powder: 121 kg, the consumption of silica fume: 60 kg, the consumption of water reducer: 15.1 kg, sand ratio: 40%, sand consumption: 760 kg, crushed stone consumption: 1050 kg, among which, the crushed stone with a particle size distribution of 5 - 16 mm has a consumption of 315 kg, and the crushed stone with a particle size distribution of 16 - 25 mm has a consumption of 735 kg, steel fiber consumption: 40 kg.

[0082] As Figure 1 shown, a construction method for the concrete at the top of a super-strong and high-toughness PHC pipe pile includes:

[0083] Step S1, the operator in the mixing plant inputs the consumption of each material in every cubic meter of concrete according to the concrete batching notice provided by the test personnel. After confirmation, batching is carried out.

[0084] In step S2, C100 concrete is used in the normal 3 - m range at the pile top. According to the pile type, the mixing volume is calculated in advance. First, the sand, crushed stone, steel fiber, half of the water, and the steel fiber are put into the mixer together and stirred for 20 s.

[0085] In the embodiments, the mixing volume is 1.0 - 1.5 m 3 , and the steel fiber is added manually.

[0086] In step S3, the binder material is added and stirred for 20 s, and finally the remaining water and water reducer are added to the mixer and stirred for more than 180 s. After the concrete mixture is uniform and stable, the discharging starts.

[0087] In the embodiments, the water reducer is added to the water weighing bucket in advance.

[0088] In step S4, after the concrete is transported to the designated position by the ash transport trolley, it is then distributed by the fully automatic intelligent distributing machine. The fully automatic intelligent distributing machine itself has functions of stirring and vibration, thus solving the problems of high viscosity and difficult distribution of the super-strong and high-toughness concrete at the pile top.

[0089] In the embodiments, during the distribution process, the trolley walks back and forth and distributes the material in layers to ensure uniform distribution.

[0090] Step S5: After the concrete placement is completed, the entire manufacturing process is finished through the processes of mold closing, tensioning, centrifugation, steam curing, and demolding.

[0091] In the embodiment, the centrifugation process is divided into four stages: low speed, low-medium speed, medium speed, and high speed. The total time is 20 - 25 minutes, and the centrifugal acceleration is 36g - 42g.

[0092] The steam curing process is divided into four stages: static stop, temperature rise, constant temperature, and temperature drop. The total time is 10 - 12 hours. The maximum steam curing temperature is not greater than 75°C, the steam saturation is not less than 90%, and the temperature rise rate is not greater than 15°C / h.

[0093] When demolding and relaxation, the control value of the compressive strength of the normal pressure steam cured pile concrete reaches 70MPa.

[0094] In the present invention, relevant tests are carried out by selecting different raw materials, the varieties, specifications, and technical quality indicators of the raw materials are proposed, and then different mix ratio designs and trial mixes are carried out. The properties of the concrete mixture, as well as the compressive strength, splitting tensile strength, impact resistance, etc. are detected, and then the concrete mix ratio is determined and applied to the pile top of the PHC pipe pile.

[0095] The super-strong and high-toughness concrete mix ratio is used on the pipe pile production line. After processes such as batching, mixing, transporting, placing, centrifuging, steam curing, and demolding, the inner wall and appearance quality of the pile top are inspected. At the same time, through test studies on the compressive strength, splitting tensile strength, flexural strength, impact resistance, etc. of the concrete at different ages, the construction mix ratio and production process of the pipe pile pile top concrete are determined. Through on-site pile driving verification, the breakage rate of the pipe pile pile top is finally reduced to less than 0.5%.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A super strong and high toughness PHC pipe pile top concrete, characterized in that: The water-cement ratio of concrete is 0.18-0.20, and the total cementitious material dosage is not more than 660kg / m 3 The cementitious materials include silicate cement, granulated blast furnace slag powder and silica fume, wherein the granulated blast furnace slag powder accounts for 20-30% of the cementitious materials and the silica fume accounts for 5-10% of the cementitious materials. That is, the composition of each material in each cubic meter of concrete is as follows: Portland cement: 400-500kg; Granulated blast furnace slag powder: 100-150kg; Silica fume: 40-80kg; Sand: 700-800kg; Crushed stone: 1000-1150kg; Water reducing agent: 13.0-18.0kg; Water consumption: 110-125kg; Steel fiber: 40-60kg.

2. The ultra-strong and high-toughness PHC pipe pile top concrete according to claim 1, characterized in that: The specification of silicate cement is P·II52.5, with a specific surface area of ​​350~380m 2 / kg, C3A content <8.0%, alkali content <0.60%, standard consistency water consumption ≤28.0%; The fluidity of the pure paste of Portland cement and admixtures is ≥260mm; The 3-day flexural strength of silicate cement is ≥5.5MPa, the 3-day compressive strength is ≥30.0MPa, the 28-day flexural strength is ≥7.7MPa, and the 28-day compressive strength is ≥57.8MPa.

3. The ultra-strong and high-toughness PHC pipe pile top concrete according to claim 1, characterized in that: The specification of granulated blast furnace slag powder is S95 grade, and the raw material is granulated blast furnace slag produced by large steel mills; The 7-day activity index of granulated blast furnace slag powder should be greater than 75%, the 28-day activity index should be greater than 100%, and the fluidity ratio should be greater than 95%; The main component of silica ash is silicon dioxide SiO2, the total content of which is not less than 90%, and the specific surface area is 20000-25000m 2 / kg.

4. The ultra-strong and high-toughness PHC pipe pile top concrete according to claim 1, characterized in that: The sand is hard natural sand, the fineness modulus of the sand is 2.4-3.0, and the total mud content is ≤1.0%; Pebbles in sand: content of particles with a diameter of ≥10 mm is ≤5.0%, content of particles with a diameter of ≥5 mm is ≤10.0%; The mica content in the sand is ≤1.0%, the light matter content is ≤1.0%, the sulfide and sulfate content is ≤0.5%, and the chloride content is ≤0.01%.

5. The ultra-strong and high-toughness PHC pipe pile top concrete according to claim 1, characterized in that: Crushed stone varieties include, but are not limited to, basalt and sandstone; The crushed stone particle size is 16-25 mm and 5-16 mm; The total mud content of crushed stone is ≤0.5%, the crushing index value is ≤8.0%, the compressive strength of saturated cube of crushed stone is ≥120MPa, the needle-like content is ≤5.0%, the apparent density is ≥2700kg, the loose bulk density is ≥1450kg, the water absorption rate is ≤1.0%, the firmness is ≤5.0%, and the sulfide and sulfate are ≤0.5%.

6. The ultra-strong and high-toughness PHC pipe pile top concrete according to claim 1, characterized in that: The water reducer adopts polycarboxylic acid high-performance water reducer, and the chloride ion content is not more than 0.02%; Tap water is used; when other water sources are used, the water does not contain harmful impurities or oils that may affect the normal coagulation and hardening of cement and the later performance of concrete; Steel fiber tensile strength Rm: 1000<Rm≤1300MPa; The shape of the steel fiber is end hook type; The steel fiber length is 30±3mm, the equivalent diameter is 0.7±0.02mm, and the aspect ratio is 45±15%.

7. The ultra-strong and high-toughness PHC pipe pile top concrete according to claim 1, characterized in that: According to the range of each parameter, different combination mix ratios are designed, and the compressive strength, splitting tensile strength, flexural strength and impact resistance of concrete at different ages are tested. Finally, the composition of each material in each cubic meter of concrete is as follows: Water-cement ratio: 0.19, water consumption: 115kg, cementitious material consumption: 605kg, including: Portland cement consumption: 424kg, slag powder consumption: 121kg, silica fume consumption: 60kg, water reducer consumption: 15.1kg, sand consumption: 760kg, gravel consumption: 1050kg, including: 315kg of gravel with particle grading of 5-16mm, 735kg of gravel with particle grading of 16-25mm, and 40kg of steel fiber consumption.

8. A method for constructing ultra-strong and high-toughness PHC pipe pile top concrete, characterized in that: include: Step S1, the operator of the mixing plant inputs the amount of each material per cubic meter of concrete according to the concrete batching notice provided by the test personnel, and after confirming that it is correct, the batching is carried out; Step S2, calculate the mixing volume in advance according to the pile type, first put sand, crushed stone steel fiber, half of the water and steel fiber into the mixer, and mix for 20 seconds; Step S3, add the cementitious material and stir for 20 seconds, and finally add the remaining water and water reducing agent into the mixer and stir for more than 180 seconds. After the concrete mixture is uniform and stable, start feeding; Step S4, transporting concrete to the designated location by a concrete transport vehicle, and then placing concrete by a fully automatic intelligent concrete placing machine; Step S5, after the concrete is placed, the entire production process is completed through mold closing, tensioning, centrifugation, steaming, and demolding.

9. A super-strong and high-toughness PHC pipe pile top concrete construction method according to claim 8, characterized in that: In step S2, the stirring volume is 1.0-1.5m 3 , steel fibers are added artificially; In step S4, the material laying process uses a vehicle to move back and forth and lay materials in layers.

10. The method for constructing super-strong and high-toughness PHC pipe pile top concrete according to claim 8, characterized in that: In step S5, the centrifugation process is divided into four stages: low speed, low-medium speed, medium speed, and high speed, with a total time of 20 to 25 minutes and a centrifugal acceleration of 36 g to 42 g; The steaming process is divided into four stages: static stop, heating, constant temperature and cooling. The total time is 10 to 12 hours. The highest temperature of steaming is not more than 75°C, the steam saturation is not less than 90%, and the heating rate is not more than 15°C / h. When the formwork is removed and tension is released, the control value of the compressive strength of the atmospheric pressure steam-cured pile concrete reaches 70MPa.

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