Application method of limestone powder in plateau concrete construction

Abstract

The invention discloses an application method of limestone powder in plateau concrete construction, which comprises the following steps: taking concrete sand, stone, cement, an additive and water as base materials, and simultaneously adding a limestone powder mineral admixture to prepare concrete used on the plateau. According to the invention, field application of tunnel injection, secondary lining, pier body, inverted arch, inverted arch filling layer and prefabricated part full-hole slag concrete can be realized, and the concrete with high mechanical property, low hydration temperature rise and small strain fluctuation is prepared, so that high-quality utilization of tunnel hole slag is realized, the construction cost is reduced, the construction quality is improved, and the construction cost is reduced. The application of the plateau harsh environment concrete in a field entity structure is powerfully supported.

Description

Technical Field

[0001] The invention relates to the technical field of concrete construction, and in particular to an application method of limestone powder in plateau concrete construction. Background Art

[0002] Plateau concrete refers to concrete used in plateau areas, and its performance and application are affected by the special climatic conditions of the plateau. There are some quality problems with sand and gravel raw materials in plateau areas, such as coarse sand, high mud content, poor coarse aggregate shape, and high crushing index values. These factors will affect the workability, mechanical properties and durability of concrete. In addition, the plateau has a dry climate and a large temperature difference between day and night, which makes concrete prone to surface cracking. The low pressure and low humidity environment in the plateau have a certain impact on the strength and durability of concrete. Especially in the construction of plateau tunnels, the high-quality utilization rate of tunnel slag is low, the price of fly ash is high, the performance fluctuates greatly, and it has the outstanding characteristics of harsh application environment conditions such as severe cold, strong winds and large temperature differences on the plateau. Concrete faces severe challenges in preparation, construction and application. At present, there is no good solution to the problem of concrete construction in plateau environments. Summary of the invention

[0003] In order to solve the above problems existing in the prior art, a method for applying limestone powder in plateau concrete construction is provided.

[0004] The technical solution adopted by the present invention to solve its technical problem is: The present invention provides a method for applying limestone powder in plateau concrete construction, comprising: The method comprises: taking concrete sand, stone, cement, admixture and water as base materials, and adding stone powder mineral admixture to prepare concrete for plateau use.

[0005] Preferably, the admixtures in the invert and base plate concrete include a water reducing agent, and the ratio of cement: stone powder mineral admixture: concrete sand: crushed stone: water reducing agent: water = 1.00: 0.25: 2.46: 3.53: 0.0125: 0.45.

[0006] Preferably, the admixtures in the secondary lining concrete include water reducing agent and air entraining agent. Cement: stone powder mineral admixture: concrete sand: crushed stone: water reducer: air entraining agent: water is = 1.00:0.25:2.25:3.51:0.0125:0.0063:0.41.

[0007] Preferably, the initial support shotcrete includes a water reducer and an accelerator, and the ratio of cement: stone powder mineral admixture: sand: crushed stone: water reducer: accelerator: water = 1.00: 0.11: 1.88: 1.74: 0.0111: 0.0889: 0.39.

[0008] Preferably, the admixtures in the shotcrete include a water reducing agent and an accelerating setting agent, and the shotcrete construction process includes the following steps: Construction preparation: shotcrete is mixed centrally at the mixing station, and the operation is carried out by a wet spraying manipulator. After that, the base surface is treated by high-pressure air, and the base surface is leveled at uneven places. The sprayed concrete is sprayed in sections, parts and blocks, first on the wall and then on the arch, from bottom to top. The nozzle makes a uniform clockwise spiral rotation on the sprayed rock surface, and moves horizontally for half a circle per circle. The spiral diameter is 20 to 30 cm, or it can be moved back and forth in an S-shaped manner. Leveling: When the thickness of the sprayed concrete is flush with the outer edge of the steel frame, the wet spraying manipulator uses a scraper to scrape off the sprayed concrete on the surface of the steel frame, and finally sprays 3cm of concrete on the entire surface. After the concrete spraying is completed, use a ruler to measure the depth of the two adjacent convex surfaces of the initial support base surface, and then measure the distance between the two adjacent convex surfaces of the initial support base surface; During the spraying process, the rebound rate of concrete is tested, and strong, tear-resistant plastic sheeting is laid in the hole in advance. The concrete is collected and weighed after each part is completed. The rebound volume of the left and right side walls and the arch is calculated separately, and the relevant spraying start and end times are recorded. After the sprayed concrete has finally set, maintenance is carried out.

[0009] Preferably, the secondary lining concrete construction process includes the following steps: Construction preparation: The secondary lining concrete is centrally mixed at a mixing station. Before the secondary lining construction, temperature strain sensors are installed inside the secondary lining formwork. The installation locations include the secondary lining arch top, the secondary lining arch waist and the secondary lining arch wall. Second lining concrete pouring, the second lining concrete is centrally mixed by the mixing station, the second lining concrete mixing uses the mixing station to centrally mix, adopts the secondary or multiple feeding method, the concrete mixing starts from the time all materials are loaded into the mixer and starts to mix until the unloading starts; Concrete pouring: Concrete is poured from the formwork window from bottom to top, symmetrically and layer by layer. The temperature of concrete entering the mold is between 10 and 30 degrees Celsius. The top of the arch is punched twice. After the thick slurry flows out evenly from the longitudinal overflow holes, the overflow holes are blocked, and then all the pneumatic vibrators of the arch are opened and then pressure is applied to the trolley for additional pouring. Concrete vibration is carried out by using an attached vibrator and then an inserted vibrator for vertical vibration, with fast insertion and slow withdrawal. After the concrete strength and curing time meet the requirements, the formwork is removed and after the secondary lining concrete is demolded, moisture-retaining curing is carried out.

[0010] Preferably, the inverted arch concrete construction process comprises the following steps: Construction preparation: the concrete of the invert arch is mixed centrally at a mixing station, the invert arch is excavated, the soil surrounding rock is excavated mechanically, and the stone surrounding rock is drilled with a pneumatic drill. After loosening blasting, the rock is transported out of the cave mechanically. After excavation, the ground loose ballast and silt of this section are cleaned up; Steel bar installation construction, steel bar processing, steel bar installation, measurement and layout are carried out before construction to determine the steel bar installation position, and the erection bars are installed first. Short steel bars are used to support each row of steel bars, and the mechanical connectors of the steel bars are staggered; The inverted arch end formwork and water stop are installed. The inverted arch end steel formwork consists of upper and lower L-shaped arc formworks. The embedded steel edge rubber water stop is clamped and fixed by the upper and lower L-shaped steel formworks. The gap near the shotcrete side is fixed with wooden boards. After the inverted arch reinforcement is installed, the tunnel bottom annular back-attached rubber water stop is installed first. After the installation is completed, the lower part of the inverted arch end formwork L-shaped formwork is installed, and then the embedded steel edge rubber water stop is installed. The inverted arch is constructed using a self-propelled hydraulic trestle with an arc formwork. The bottom of the inverted arch arc formwork uses a horizontal paving formwork, equipped with an automatic material distribution chute. The low side wall uses a fixed formwork equipped with a longitudinal embedded waterstop clamp, and the end is equipped with a waterstop positioning steel end formwork. The invert concrete is poured, the concrete is poured, the concrete is poured in layers, and then the concrete is vibrated and the invert filling layer is constructed. After the invert lining concrete has finally set, the invert filling concrete construction is carried out, the top surface of the invert filling is finished and leveled, and then the concrete is cured.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The present invention makes full use of stone powder mineral admixtures to prepare working performance maintaining materials suitable for full-slag concrete of different lithologies, prepares full-slag concrete for structures such as primary support, secondary lining, invert and invert filling layer, invert prefabricated block, bridge cast-in-place pile, abutment, pier body, etc. in the harsh plateau environment, improves the production quality of concrete by clarifying construction processes such as feeding sequence, mixing time, vibration parameters and maintenance measures, casts full-slag pier body and invert prefabricated block concrete of full size of different lithologies, can realize the on-site application of full-slag concrete for tunnel spraying, secondary lining, pier body, invert and invert filling layer, and prefabricated components, prepares concrete with high mechanical properties, low hydration temperature rise and small strain fluctuation, thereby realizing high-quality utilization of tunnel slag, reducing engineering cost, improving engineering quality, and strongly supporting the application of concrete in on-site physical structures in the harsh plateau environment. DETAILED DESCRIPTION

[0012] The following embodiments of the present invention are described in detail. The following embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0013] This embodiment proposes a method for applying limestone powder in plateau concrete construction, comprising: It includes: using concrete sand, stone, cement, admixture and water as the base material, and adding stone powder mineral admixture to prepare concrete for plateau use, the stone powder mineral admixture is limestone, the concrete sand is medium sand, and the crushed stone specification is 5~31.5mm.

[0014] The admixtures in the concrete of the invert and base plate include water reducer, cement: stone powder mineral admixture: concrete sand: crushed stone: water reducer: water = 1.00:0.25:2.46:3.53:0.0125:0.45. The water reducer is a polycarboxylic acid high-performance water reducer, specifically, cement, stone powder mineral admixture, fine aggregate, coarse aggregate (5-10mm, 10-20mm, 16-31.5mm in the ratio of 20%:50%:30%), water reducer, water.

[0015] The admixtures in the secondary lining concrete include water reducing agent and air entraining agent. Cement: stone powder mineral admixture: concrete sand: crushed stone: water reducer: air entraining agent: water is = 1.00:0.25:2.25:3.51:0.0125:0.0063:0.41.

[0016] The water reducer is a polycarboxylic acid high-performance water reducer, and the air entraining agent is a ZTW-1 air entraining agent. Specifically, the ingredients include cement, stone powder mineral admixture, fine aggregate, coarse aggregate (5-10mm, 10-20mm, 16-31.5mm in a ratio of 20%:50%:30%), water reducer, air entraining agent, and water.

[0017] Initial support shotcrete includes water reducer and accelerator, cement: stone powder mineral admixture: sand: crushed stone: water reducer: accelerator: water = 1.00: 0.11: 1.88: 1.74: 0.0111: 0.0889: 0.39. The water reducer is a polycarboxylic acid high-performance water reducer, and the accelerator is a liquid accelerator, specifically, cement, stone powder mineral admixture, fine aggregate, coarse aggregate (5-10mm), water reducer, accelerator, water.

[0018] The full-slag shotcrete uses stone powder mineral admixtures to completely replace fly ash. The aggregates used are all produced from lithological slag parent rock. The fine aggregate specifications are medium sand. The admixtures in the shotcrete include water reducers and accelerators. The shotcrete construction process includes the following steps: Construction preparation: the raw materials of shotcrete must be inspected and qualified before use. The accelerator should be properly stored to prevent moisture and deterioration. The water-cement ratio of the mixture should be strictly controlled. The working condition of the accelerator injection ring should be checked frequently. Shotcrete is mixed centrally at the mixing station and operated by a wet spraying manipulator. After that, the base surface is treated. The mixing time should not be less than 1.5 minutes, and the parking time of the concrete mixture should not be more than 30 minutes. The slump of the initial support concrete of the wet spraying tunnel should not be greater than 180cm.

[0019] Then the base surface is treated by using high-pressure air to level the uneven areas. Shotcrete is sprayed in sections, parts and blocks, from bottom to top, first on the wall and then on the arch. The nozzle makes a uniform clockwise spiral rotation on the sprayed rock surface, and moves horizontally for half a circle for one circle, with a spiral diameter of 20 to 30 cm; or an S-shaped reciprocating movement is used. During spraying, the section length should not exceed 6 m, and the section should be first from bottom to top, with a block size of 2 m×2 m.

[0020] Spraying thickness: the thickness of the sprayed concrete on the side wall is controlled at 7-12cm, and the thickness of the arch is controlled at 4-7cm, and the thickness of the sprayed layer is kept uniform. Spraying distance, wind pressure, and angle: the spraying distance is 1.2-1.5m, the wind pressure on the side wall is 0.3-0.5MPa, and the wind pressure on the arch is 0.4-0.65MPa. The normal spraying angle is 90±3°. When there are embedded parts, the spraying angle needs to be inclined.

[0021] Leveling: When the thickness of the shotcrete is flush with the outer edge of the steel frame, the wet shotcrete robot uses a scraper to scrape off the shotcrete on the surface of the steel frame. Finally, the entire surface is sprayed with 3 cm of concrete to ensure that the shotcrete surface is flat as a whole. After the concrete is sprayed, use a ruler to measure the depth D of the two adjacent convex surfaces of the initial support base, and then measure the distance L between the two adjacent convex surfaces of the initial support base (not more than 1m). The depth-to-length ratio (D / L) between the two protrusions should not be greater than 1 / 20.

[0022] During the spraying process, the rebound rate of concrete is tested. The tank truck enters and exits the mixing station and passes the weighing scale to confirm the total amount m1 of sprayed anchor concrete used on site. Strong and tear-resistant plastic sheeting is laid in the hole in advance. After each part is completed, m2 is collected and weighed. The rebound amount is calculated separately for the left and right side walls and the arch. The calculation formula is: rebound rate = m2 / m1. The relevant spraying start and end time is recorded. After the sprayed concrete has finally set, maintenance is carried out.

[0023] The secondary lining concrete construction process includes the following steps: Construction preparation: The secondary lining concrete is centrally mixed at a mixing station. Before the secondary lining construction, a total of 12 temperature strain sensors are installed inside the secondary lining formwork, including 3 temperature strain sensors installed at the secondary lining arch top, 3 temperature strain sensors installed at the secondary lining arch waist, and 6 temperature strain sensors installed at the secondary lining arch wall (installed on two plates and two linings, 3 on each plate); The trolley is in place and the formwork is installed. The formwork lining trolley is designed and manufactured according to the tunnel clearance size and uses an integral steel formwork; Before pouring the secondary lining concrete, the water content of coarse and fine aggregates needs to be measured and the construction mix ratio needs to be adjusted in time. The secondary lining concrete is centrally mixed by a mixing station. The secondary lining concrete is centrally mixed by a mixing station and adopts a secondary or multiple feeding method. The concrete mixing starts from the time all materials are loaded into the mixer and starts to be mixed until the unloading starts. Measures should be taken to prevent segregation, leakage, severe bleeding and slump loss during the transportation of concrete. When the concrete is transported by a concrete mixer truck, it needs to be stirred slowly during the transportation. When the mixer truck arrives at the pouring site, it rotates at high speed for 120 seconds before feeding the concrete mixture into the hopper of the pump truck. Concrete pouring: Concrete is poured from the formwork window from bottom to top, symmetrically and layer by layer. The temperature of concrete entering the mold is between 10 and 30 degrees Celsius. The top of the arch is punched twice. After the thick slurry flows out evenly from the longitudinal overflow holes, the overflow holes are blocked, and then all the pneumatic vibrators of the arch are opened and then pressure is applied to the trolley for additional pouring. Concrete vibration, use attached vibrator to vibrate, single point vibrate for 5 to 10 seconds, then use inserted vibrator to vibrate vertically, insert quickly and pull out slowly, each vibration point consolidation time is 10 to 30 seconds, until no bubbles appear on the concrete surface, to prevent over-vibration and missed vibration. When vibrating, keep the vibrator 10 to 20 cm away from the template surface.

[0024] The demolding time of the secondary lining can be determined after laboratory testing. It can only be removed when the concrete strength reaches more than 10MPa and the curing time with the mold is not less than 60h, and the difference between the surface temperature and the ambient temperature is not greater than 15℃. After the trolley loosens the mold, it will immediately move and follow the steam curing trolley and the spray curing stand for curing. It is strictly forbidden to stop and wait after loosening the mold. Keep records at the same time. After the tunnel secondary lining concrete is demolded, moisturizing curing must be carried out within 2h. The difference between the curing water temperature and the concrete surface temperature shall not be greater than 15℃, and the total curing time shall not be less than 14 days. Keep relevant records at the same time.

[0025] The invert concrete construction process includes the following steps: Construction preparation: the concrete of the invert arch is mixed centrally at a mixing station, the invert arch is excavated, the soil surrounding rock is excavated mechanically, and the stone surrounding rock is drilled with a pneumatic drill. After loosening blasting, the rock is transported out of the cave mechanically. After excavation, the ground loose ballast and silt of this section are cleaned up; Rebar installation construction, rebar processing, rebar installation, inverted arch rebar is installed manually. To ensure accurate rebar installation, lines are drawn on the side walls of the inverted arch according to the design elevation to ensure accurate rebar installation. Measurement and setting out are carried out before construction to determine the rebar installation position. Standoff rebar is installed first. Short rebars are used to support each row of rebars, and the rebar mechanical connectors are staggered. The inverted arch end formwork and waterstop are installed. The waterstop is positioned by using the self-made positioning fixtures installed on the top of the side formwork on both sides of the hydraulic trestle to position the embedded steel plate waterstop. After the inverted arch side formwork is positioned, the top surface of the side formwork is the top surface of the concrete; the embedded steel plate waterstop has its center line marked in advance. During installation, the positioning fixture is directly clamped at the center line to ensure the position and height of the steel plate waterstop.

[0026] There is also another installation method. The steel formwork at the end of the inverted arch is composed of upper and lower L-shaped arc formworks. The embedded steel-edge rubber waterstop is clamped and fixed by the upper and lower L-shaped steel formworks. The gap close to the shotcrete (back-sticked rubber waterstop) side is fixed with wooden boards to ensure that the caulking material is in close contact with the surface of the shotcrete to prevent leakage. After the installation of the inverted arch steel bars is completed, the annular back-sticked rubber waterstop at the bottom of the tunnel is installed first. After the installation is completed, the lower part of the L-shaped formwork of the inverted arch end formwork is installed, and then the embedded steel-edge rubber waterstop is installed.

[0027] The inverted arch construction adopts a self-propelled hydraulic trestle with an arc formwork. The bottom of the inverted arch arc formwork adopts a horizontal paving formwork and is equipped with an automatic material distribution chute to reduce the labor intensity of workers. The concrete is evenly distributed and has a large vibration range, which can achieve no dead angle vibration with an inserted vibrator. The low side wall adopts a fixed formwork equipped with a longitudinal embedded waterstop clamp, and the end is equipped with a waterstop positioning steel end formwork to ensure the quality and efficiency of concrete and waterstop construction. The invert concrete is poured, the concrete is poured, the concrete is poured in layers, and then the concrete is vibrated and the invert filling layer is constructed. After the invert lining concrete has finally set, the invert filling concrete construction is carried out, the top surface of the invert filling is finished and leveled, and then the concrete is cured.

[0028] After pouring, the concrete shall be kept moist and maintained. The time for concrete watering and curing shall comply with the regulations (not less than 14 days), and the number of watering times shall be sufficient to keep the concrete moist. The water used for concrete curing shall be the same as the water used for mixing, and the difference between the water temperature and the concrete surface temperature shall not be greater than 15°C. Before the concrete strength reaches 5MPa, the formwork and bracket shall not be installed on it. The formwork shall not be removed if the strength does not reach 70% of the design value, and the use of machinery is strictly prohibited if the strength does not reach 100% of the design value. Watering is prohibited when the ambient temperature is below 5°C. Moisturizing and heat preservation measures shall be taken on the surface. After demoulding, the contact surface of the small side wall concrete construction shall be roughened. The concrete strength shall not be less than 10MPa during roughening. The depth of the roughening groove shall be 1 to 2cm. The roughening is based on the removal of the concrete surface slurry, the half-embedded and half-exposed gravel, and the exposure of 75% of the fresh aggregate. The longitudinal spacing is 10cm. After roughening, the loose slag on the surface shall be washed clean with high-pressure water.

[0029] The construction process of the full-hole slag pier body concrete includes the following steps: Construction preparation: The concrete of the whole slag pier body should be mixed centrally in a mixing station. In order to better monitor the concrete temperature and strain changes of the test pier, a total of 7 temperature strain collectors are installed inside the pier body formwork before the pier body construction. Temperature strain sensors are arranged at the center of the test pier, 1 / 4 position and 4~6cm away from the surface to monitor the temperature of the concrete core and surface. A total of 7 temperature strain sensors are arranged for each test pier.

[0030] Before installing the formwork and assembling the formwork, first use a polisher to level the surface, clean it, and apply the preferred coating agent. The formwork installation should meet the construction design requirements, and the installation should be stable and reliable. The formwork joints should be tight and should not leak. The pier body formwork is assembled and formed by manual cooperation with a car crane. Each time a section of the formwork is hoisted, the verticality and geometric shape of the formwork are checked. Only after it is correct can the next layer be assembled. After the formwork is installed, bolts are added immediately to tighten it. The exposed part is locked with double nuts. The bolts are firmly connected and there should be no misalignment. The contact surface between the formwork and the concrete should be cleaned and coated with an isolation agent. Before pouring concrete, the accumulated water and debris in the formwork should be cleaned.

[0031] Before pouring and mixing concrete, the moisture content of coarse and fine aggregates needs to be measured and the construction mix ratio needs to be adjusted in time. Concrete mixing is carried out by centralized mixing in a mixing station, with two or more feeding methods. The mixing time of concrete is not less than 180s from the time all materials are loaded into the mixer to the start of unloading. After adding the water reducer, the concrete mixture continues to be stirred in the mixer, and the slump of concrete is controlled at 160-200mm.

[0032] Measures should be taken to prevent segregation, leakage, severe bleeding and slump loss during the transportation of concrete. When concrete is transported by a concrete mixer truck, it needs to be stirred slowly during the journey; when the mixer truck arrives at the pouring site, it rotates at high speed for 120 seconds before feeding the concrete mixture into the hopper of the pump truck.

[0033] Before pouring concrete, check the bracket, formwork, steel bars and embedded parts, clean up the debris, water and dirt on the steel bars in the formwork, and fill the gaps of the formwork tightly. Concrete pouring adopts pumping method, layered spreading, layered pouring and layered vibration. The thickness of pumped concrete is about 50cm. When pouring new concrete on the newly poured lower concrete, the upper concrete is poured before the lower concrete begins to set.

[0034] Concrete vibration: During the concrete pouring process, the concrete should be vibrated at any time to make it uniform and dense. Vibration is performed using an inserted vibrator for vertical point vibration. When the concrete slump is small, the distribution of vibration points needs to be increased. During the concrete vibration process, repeated vibration should be avoided to prevent over-vibration. The stability of the formwork support and the tightness of the joints need to be checked to prevent leakage during the concrete vibration process.

[0035] When vibrating, follow the principle of fast insertion and slow pulling, vibrate from all sides to the middle, the distance between vibration points should not be greater than 1.5 times the effective radius of the vibrating rod, keep a distance of 5 to 10 cm from the template, and insert 5 to 10 cm into the lower layer of concrete until the concrete stops sinking, no bubbles appear, and the surface is slurry. After the concrete is vibrated, promptly trim and smooth the exposed surface of the concrete, and apply a second coat and press it after the slurry is set; it is strictly forbidden to sprinkle water when smoothing the surface.

[0036] The curing time of the pier body concrete with formwork shall not be less than 4 days, and the curing time of the pier body concrete with formwork shall not be less than 5 days. The formwork removal shall be carried out in a time-controlled, temperature-controlled and packaged-as-it-is removed manner. In addition to the concrete strength at the time of demolding, the concrete surface temperature (caused by hydration heat) shall not be too high at the time of demolding. The difference between the concrete surface temperature and the ambient temperature shall not be greater than 15°C, so as to avoid the concrete from cooling too quickly and cracking when it contacts the air. It is even more forbidden to pour cold water for curing at this time. The formwork shall not be removed before the temperature inside the concrete begins to drop and when the temperature inside the concrete is the highest. The demolding should be carried out in the reverse order of the formwork erection, without damaging the concrete and reducing the damage of the formwork. The formwork can only be removed and hoisted after the formwork is separated from the concrete.

[0037] After the concrete curing, steam curing or spray curing of the pier body is completed, "plastic film / water-saving and moisturizing curing film + thick geotextile" should be used for long-term wrapping and curing in time, and ensure that the wrapping is not damaged or leaking. The wrapping material shall not be disassembled at will unless there are special circumstances.

[0038] The precast concrete construction process includes the following steps: The full-hole slag concrete solid structure of the invert precast block mainly includes construction preparation, mold inspection and adjustment, concrete pouring, concrete curing, and formwork removal.

[0039] Mould inspection: Clean the mould carefully before mould assembly. After cleaning, there should be no residual debris or floating rust on any part of the inner surface of the mould. Use a mould release agent with stable quality, suitable for spraying and good demoulding effect. Steel bar skeleton and embedded parts are strictly prohibited from contacting the mould release agent. Use a clean rag to apply evenly, thinly and evenly. Do not miss or accumulate at the corner of the mould. If there is any, clean it with cotton yarn to ensure that the mould joints do not leak.

[0040] Concrete should be poured and formed continuously. When pouring, pay attention to make the concrete uniform in the mold. The concrete vibration adopts the automatic vibration of the attached pneumatic vibrator of the mold and the manual vibration of the inserted vibrator. No vibration or over-vibration is allowed. To ensure the quality of product vibration, the construction method of vibrating while pouring is adopted. In actual operation, the vibration time is controlled according to the fluidity of concrete. When pouring concrete, test blocks with the same conditions should be retained, and the test blocks made should be representative.

[0041] After the formwork is removed and the inverted arch precast blocks are cooled to a temperature difference of no more than 20°C from the outside environment and the strength of the test pieces in the laboratory is checked to reach 20MPa, the demoulding and lifting can be notified. The inverted arch precast blocks are cured in a water curing tank. The demoulded precast blocks are first placed in a static curing area by a turning machine for curing. When the temperature difference between the precast blocks and the water curing tank is no more than 15°C, the precast blocks are then hoisted into the water curing tank for curing for 5 to 7 days by a turning machine. The precast blocks should be lifted and lowered slowly during lifting. It is strictly forbidden to collide with the static curing tank, the wall of the water curing tank and other inverted arch precast blocks. The precast blocks must be completely immersed in water The solid structure of small-scale component full-hole slag concrete mainly includes construction preparation, steel bar processing, formwork construction, concrete pouring, finished product maintenance and demoulding. Among them, the process flow of steel bar processing: steel bar straightening, cutting, bending, tying and stacking.

[0042] During formwork construction, cable trenches, cover plates and other small components are formed using hard plastic formwork. To facilitate demolding, demolding should be done when the temperature is highest on the day. Be careful during demolding to ensure that there is no edge gnawing, corner drop or bumping. After demolding, some concrete residue will inevitably stick to the formwork. The hard plastic formwork should be soaked in 26% hydrochloric acid for 2 to 3 minutes, and then the concrete residue should be scraped off with a bamboo knife wrapped in cotton cloth, and then rinsed with clean water. After the above procedures, the hard plastic formwork is as bright as new.

[0043] Before using hard plastic formwork and steel formwork, use a clean towel to clean the dust and impurities in the mold, and apply clean edible salad oil for isolation. Then stack the cleaned molds neatly. The templates should be checked and repaired regularly. For those that cannot be repaired and unqualified, they should be removed from the market in time and replaced with new qualified templates.

[0044] Concrete is poured. After the concrete is transported to the site, its performance is tested to see if it meets the requirements. The concrete tank truck transports the concrete to the mold placement area through the on-site transportation road, directly feeds the concrete into the mold through the chute, and starts the light vibration table to vibrate the concrete. The vibration time is 1-2 minutes, until the bubbles in the concrete are completely dispersed and the concrete surface is flat, then stop vibrating. Move the poured concrete components to the curing area, and after the finished products reach the demolding strength through automatic spray curing, use a forklift to transfer the finished products to the curing area for curing for 14 days before transferring them to the storage area.

[0045] The curing and demoulding of finished products, and the curing of small components such as cable trenches and cover plates are concentrated in the curing area. Premature curing will cause the concrete surface to fall off, while late curing will cause strength reduction and cracks. The specific curing time should be after the initial setting of the concrete. In order to avoid discoloration of the covering and contamination of the concrete surface, non-woven geotextiles are used for spray covering and curing, and the curing time is not less than 14 days.

[0046] The product maintenance process is: semi-finished product static curing, demoulding, spray curing, transportation and stacking, and natural curing. Static curing: After the components are formed on the vibration table, they are transported to the static curing area for static curing. The components must be placed flat during static curing. After the concrete is initially set, it is cured by automatic spraying.

[0047] Demolding: When the strength of the product reaches 50% of the requirement, it can be demoulded. After demoulding, take protective measures for the product, sandwich the product with geotextiles, and slow down when transporting with a forklift to prevent bumps. Curing: After transporting to the curing area, cover with non-woven geotextiles and perform curing through an automatic spraying system. The curing time should not be less than 14 days.

[0048] The present application makes full use of stone powder mineral admixtures to prepare a material for maintaining the working performance of full-slag concrete suitable for different rock types, and prepares full-slag concrete for tunnel primary support, secondary lining, invert and invert filling layer, invert precast block and bridge cast-in-place piles, abutments, pier bodies and other structures under the harsh environment of the plateau. The production quality of concrete is improved by clarifying the construction processes such as feeding sequence, mixing time, vibration parameters and maintenance measures, and cast full-slag pier bodies and invert precast block concrete of sufficient size with different rock types, which can realize the on-site application of full-slag concrete for tunnel spraying, secondary lining, pier body, invert and invert filling layer, and prefabricated components, and prepares concrete with high mechanical properties, low hydration temperature rise and small strain fluctuation, thereby realizing high-quality utilization of tunnel slag, reducing project costs, improving project quality, and strongly supporting the application of concrete in on-site physical structures in harsh plateau environments.

[0049] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for applying limestone powder in plateau concrete construction, characterized in that: include: Concrete for plateau use is prepared with concrete sand, stone, cement, admixtures and water as the base material and stone powder mineral admixtures added.

2. The method for applying limestone powder in plateau concrete construction according to claim 1, characterized in that: The admixtures in the concrete of the invert and base plate include water reducer, cement: stone powder mineral admixture: concrete sand: crushed stone: water reducer: water = 1.00:0.25:2.46:3.53:0.0125:0.

45.

3. The method for applying limestone powder in plateau concrete construction according to claim 1, characterized in that: The admixtures in the second lining concrete include water reducer and air entraining agent. The ratio of cement: stone powder mineral admixture: concrete sand: crushed stone: water reducer: air entraining agent: water is = 1.00:0.25:2.25:3.51:0.0125:0.0063:0.

41.

4. The method for applying limestone powder in plateau concrete construction according to claim 1, characterized in that: The initial support shotcrete includes water reducer and accelerator, cement: stone powder mineral admixture: sand: crushed stone: water reducer: accelerator: water = 1.00: 0.11: 1.88: 1.74: 0.0111: 0.0889: 0.

39.

5. The method for applying limestone powder in plateau concrete construction according to claim 1, characterized in that: The admixtures in shotcrete include water reducers and accelerators. The construction process of shotcrete includes the following steps: Construction preparation: shotcrete is mixed centrally at the mixing station, and the operation is carried out by a wet spraying manipulator. After that, the base surface is treated by high-pressure air, and the base surface is leveled at uneven places. The sprayed concrete is sprayed in sections, parts and blocks, first on the wall and then on the arch, from bottom to top. The nozzle makes a uniform clockwise spiral rotation on the sprayed rock surface, and moves horizontally for half a circle per circle. The spiral diameter is 20 to 30 cm, or it can be moved back and forth in an S-shaped manner. Leveling: When the thickness of the sprayed concrete is flush with the outer edge of the steel frame, the wet spraying manipulator uses a scraper to scrape off the sprayed concrete on the surface of the steel frame, and finally sprays 3cm of concrete on the entire surface. After the concrete spraying is completed, use a ruler to measure the depth of the two adjacent convex surfaces of the initial support base surface, and then measure the distance between the two adjacent convex surfaces of the initial support base surface; During the spraying process, the rebound rate of concrete is tested, and strong, tear-resistant plastic sheeting is laid in the hole in advance. The concrete is collected and weighed after each part is completed. The rebound volume of the left and right side walls and the arch is calculated separately, and the relevant spraying start and end times are recorded. After the sprayed concrete has finally set, maintenance is carried out.

6. The method for applying limestone powder in plateau concrete construction according to claim 1, characterized in that: The secondary lining concrete construction process includes the following steps: Construction preparation: The secondary lining concrete is centrally mixed at a mixing station. Before the secondary lining construction, temperature strain sensors are installed inside the secondary lining formwork. The installation locations include the secondary lining arch top, the secondary lining arch waist and the secondary lining arch wall. Second lining concrete pouring, the second lining concrete is centrally mixed by the mixing station, the second lining concrete mixing uses the mixing station to centrally mix, adopts the secondary or multiple feeding method, the concrete mixing starts from the time all materials are loaded into the mixer and starts to mix until the unloading starts; Concrete pouring: Concrete is poured from the formwork window from bottom to top, symmetrically and layer by layer. The temperature of concrete entering the mold is between 10 and 30 degrees Celsius. The top of the arch is punched twice. After the thick slurry flows out evenly from the longitudinal overflow holes, the overflow holes are blocked, and then all the pneumatic vibrators of the arch are opened and then pressure is applied to the trolley for additional pouring. Concrete vibration is carried out by using an attached vibrator and then an inserted vibrator for vertical vibration, with fast insertion and slow withdrawal. After the concrete strength and curing time meet the requirements, the formwork is removed and after the secondary lining concrete is demolded, moisture-retaining curing is carried out.

7. The method for applying limestone powder in plateau concrete construction according to claim 1, characterized in that: The invert concrete construction process includes the following steps: Construction preparation: the concrete of the invert arch is mixed centrally at a mixing station, the invert arch is excavated, the soil surrounding rock is excavated mechanically, and the stone surrounding rock is drilled with a pneumatic drill. After loosening blasting, the rock is transported out of the cave mechanically. After excavation, the ground loose ballast and silt of this section are cleaned up; Steel bar installation construction, steel bar processing, steel bar installation, measurement and layout are carried out before construction to determine the steel bar installation position, and the erection bars are installed first. Short steel bars are used to support each row of steel bars, and the mechanical connectors of the steel bars are staggered; The inverted arch end formwork and water stop are installed. The inverted arch end steel formwork consists of upper and lower L-shaped arc formworks. The embedded steel edge rubber water stop is clamped and fixed by the upper and lower L-shaped steel formworks. The gap near the shotcrete side is fixed with wooden boards. After the inverted arch reinforcement is installed, the tunnel bottom annular back-attached rubber water stop is installed first. After the installation is completed, the lower part of the inverted arch end formwork L-shaped formwork is installed, and then the embedded steel edge rubber water stop is installed. The inverted arch is constructed using a self-propelled hydraulic trestle with an arc formwork. The bottom of the inverted arch arc formwork uses a horizontal paving formwork, equipped with an automatic material distribution chute. The low side wall uses a fixed formwork equipped with a longitudinal embedded waterstop clamp, and the end is equipped with a waterstop positioning steel end formwork. The invert concrete is poured, the concrete is poured, the concrete is poured in layers, and then the concrete is vibrated and the invert filling layer is constructed. After the invert lining concrete has finally set, the invert filling concrete construction is carried out, the top surface of the invert filling is finished and leveled, and then the concrete is cured.