CN114776008A - One-time pouring construction method for C50 high-strength concrete super-large-volume bottom plate - Google Patents
One-time pouring construction method for C50 high-strength concrete super-large-volume bottom plate Download PDFInfo
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- 238000010276 construction Methods 0.000 title claims abstract description 25
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 80
- 239000004568 cement Substances 0.000 claims abstract description 21
- 239000002985 plastic film Substances 0.000 claims abstract description 20
- 229920006255 plastic film Polymers 0.000 claims abstract description 20
- 239000000498 cooling water Substances 0.000 claims abstract description 19
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- 239000010881 fly ash Substances 0.000 claims abstract description 16
- 239000004575 stone Substances 0.000 claims abstract description 15
- 239000000843 powder Substances 0.000 claims abstract description 14
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 11
- 239000002994 raw material Substances 0.000 claims abstract description 11
- 229910052500 inorganic mineral Inorganic materials 0.000 claims abstract description 9
- 239000011707 mineral Substances 0.000 claims abstract description 9
- 235000019738 Limestone Nutrition 0.000 claims abstract description 8
- 239000006028 limestone Substances 0.000 claims abstract description 8
- 238000003780 insertion Methods 0.000 claims abstract description 7
- 230000037431 insertion Effects 0.000 claims abstract description 7
- 230000003020 moisturizing effect Effects 0.000 claims abstract description 5
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims abstract description 3
- 239000010410 layer Substances 0.000 claims description 16
- 238000001816 cooling Methods 0.000 claims description 15
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- 229910000831 Steel Inorganic materials 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- 239000010959 steel Substances 0.000 claims description 9
- 239000002893 slag Substances 0.000 claims description 8
- 230000001276 controlling effect Effects 0.000 claims description 7
- 238000012423 maintenance Methods 0.000 claims description 7
- 238000012544 monitoring process Methods 0.000 claims description 7
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- 239000003795 chemical substances by application Substances 0.000 claims description 6
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- 238000001035 drying Methods 0.000 claims description 3
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/02—Conveying or working-up concrete or similar masses able to be heaped or cast
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/24—Safety or protective measures preventing damage to building parts or finishing work during construction
- E04G21/246—Safety or protective measures preventing damage to building parts or finishing work during construction specially adapted for curing concrete in situ, e.g. by covering it with protective sheets
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The invention relates to a one-time pouring construction method for a C50 high-strength concrete super-large-volume bottom plate, which comprises the steps of mixing raw materials including ordinary silicate 42.5 cement, mineral powder, fly ash, limestone machine-made sand, limestone broken stones, water and a water reducing agent to obtain C50 high-strength concrete; the concrete mold-entering temperature is controlled to be 10-25 ℃, the insertion points of the vibrating rods are uniformly arranged, the vibrating time and the insertion depth are reasonably controlled, the surface of the bottom plate is timely plastered to eliminate the risk of stress concentration, three layers of cooling water pipe networks are arranged on the central plane of the thickness of the bottom plate, the water inflow and outflow water temperature of the cooling water pipes is strictly controlled, the water flow speed and the water flow size ensure that the water temperature difference of an inlet and an outlet is less than or equal to 10 degrees, the water flow is adjusted according to the temperature condition, and the temperature change rate is not more than 2 degrees/day. The plastic film for moisturizing and curing is a recyclable film with a relatively thick thickness, and the curing time is not less than 14 days. The invention can effectively control the temperature of the central concrete of the super-large-volume bottom plate and prevent the temperature crack of the member caused by overlarge temperature stress.
Description
Technical Field
The invention belongs to the technical field of concrete construction control, and particularly relates to a one-time pouring construction method for a C50 high-strength concrete super-large-volume bottom plate.
Background
After the large-volume concrete is poured, the hydration heat of cement can cause the temperature inside the concrete to rise remarkably, the highest temperature can reach 60-80 ℃ generally, and even can be higher, the heat dissipation of the surface of the concrete is relatively fast, so that the concrete forms internal and external temperature difference, the compression stress is generated inside the concrete, the tensile stress is generated outside the concrete, and the early elastic modulus and the tensile strength of the concrete are both very low, so that cracks are easily generated on the surface of the concrete. During the curing and cooling period, the internal temperature of the concrete is reduced to generate shrinkage deformation, but the deformation is subjected to the action of foundation or other constraints to generate internal cracks.
In the process of mass concrete construction, in order to prevent the generation of temperature cracks or reduce the probability of the generation of the temperature cracks of the concrete, a temperature control method which can reduce the highest hydration temperature of the concrete and reduce the internal and external temperature difference of the concrete is required to be adopted.
The common concrete temperature control technology is a cooling water pipe method, which utilizes cold water to absorb hydration heat of concrete and control the highest temperature of concrete. When the volume of the concrete pouring block is small, the temperature stress is small, and the temperature stress of the concrete block can be effectively controlled by utilizing the cooling water pipe. However, as the volume of the concrete cast block increases, the cooling water pipe has a reduced ability to control the temperature rise of the concrete, and a large temperature difference of the concrete is caused around the cooling water pipe, resulting in a large amount of cold-shrinkage microcracks.
The temperature control measures of doping the phase change material into mass concrete are researched by the students by utilizing the characteristics that the phase change material has high energy storage density, can absorb or release a large amount of heat from the outside in the phase change process and is isothermal or approximately isothermal.
In conclusion, the cooling water pipe is used as the most common cooling method for mass concrete, and a large amount of cold shrinkage micro cracks are generated around the cooling water pipe; the phase-change material has more problems as a new research direction for temperature control of mass concrete.
The moisture preservation and the heat preservation maintenance of the mass concrete are important measures for ensuring the construction quality of the foundation slab concrete. According to similar engineering experience, the large-volume concrete of the engineering bottom plate is maintained by water storage, the surface temperature of the large-volume concrete in a maintenance period is higher (generally 30-60 ℃), and if the moisture-preserving maintenance measures are improper or the coverage is not tight, the water dispersion on the surface of the concrete is quicker, and the dry shrinkage crack is easily generated, so that the quality defect of the surface of the concrete is easily caused.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the bottom plate is super thick, the concrete strength level is high, and the concrete belongs to typical large-volume concrete engineering. In the face of one-off pouring, the thickness of the cast steel plate exceeds 10000m3The ordinary portland cement has high hydration heat, but the low hydration heat cement has high price and is uneconomical, so that under the condition of adopting the ordinary portland cement, the ultra-large-volume bottom plate of the concrete can effectively control the hydration temperature rise of the concrete, delay the cooling rate, reduce the concrete shrinkage, improve the ultimate tensile strength of the concrete, improve the constraint condition, design structure and the like, and further effectively inhibit the occurrence and development of harmful cracks of the large-volume concrete.
In order to achieve the purpose, the invention provides the following technical scheme:
preparing C50P 10 high-strength concrete: uniformly stirring and mixing raw materials including 260-300 parts by weight of cement, 90-120 parts by weight of slag powder, 100-120 parts by weight of fly ash, 40-60 parts by weight of expanding agent, 750-780 parts by weight of sand, 940-960 parts by weight of broken stone, 150-160 parts by weight of water and 7-10 parts by weight of water reducing agent to obtain C50P 10 high-strength concrete; wherein, the cement is ordinary portland cement PO42.5, and the materials of the sand and the crushed stone are limestone;
concrete conveying: the pouring amount per hour is about 45 square according to the vehicle pump, and the full-load pouring speed is estimated to be 360 square/hour according to the calculation of 60 square per hour by the chute. By combining the transport distance conditions of a site and a mixing plant, 14 vehicles need to be pressed on the site during the peak period, and 57-71 tank trucks need to be ensured to ensure that the condition of material break does not exist on the site by combining the above considerations.
Pouring concrete: strictly controlling raw materials, allowing cement to enter a field and stand for more than 7 days, and allowing fly ash to stand for more than 3 days, so that the temperature of a cement and mineral admixture is not more than 20 ℃, covering a sandstone yard to avoid insolation, and if the temperature of the sandstone is too high, adopting cold water for spraying and cooling. When each section of concrete is poured, the slump and the temperature of concrete mixtures in 5 concrete tanks are continuously measured from the moment that the first concrete tank truck arrives at a pouring place, the workability is observed, the phenomena of segregation, bleeding, layering and the like cannot exist, and the unqualified concrete is checked to be firmly rejected. When the measured consistency and temperature of the concrete mixture are stable, the measurement should be performed every 2 hours. The concrete mold-entering temperature is controlled within 25 ℃, in order to control the mold-entering temperature, the stirring time of a mixer truck is reduced, pouring is started after the concrete is on the spot, and the waiting time is reduced;
concrete vibrating: because the concrete slump is large, the concrete slope is relatively long to pave, the concrete must be vibrated towards the slope along the slope foot and the slope top of the fixed line simultaneously during vibration, and the vibrating rod must be inserted into the poured layer for 50-100 mm, so that no cold seam is formed between layers, and the layers are tightly combined to form a whole. The inserting points of the vibrating rods need to be uniformly arranged, the vibrating rods need to be inserted regularly in sequence, and the vibrating rods can move in an arrangement mode and a staggered mode, so that the concrete leakage vibration is avoided as much as possible. The vibration time of each plug point needs to be controlled well, generally within 15-20 seconds, and the vibration cannot be carried out, so that the segregation phenomenon of concrete is avoided. Generally, the vibration time at each point is preferably determined by that the concrete surface is horizontal and does not obviously sink any more, bubbles are not generated any more, and mortar is spread on the surface. When raft lower floor concrete vibrates, the hand that vibrates should be gone down to the interior concrete that vibrates of foundation slab, closely vibrates the concrete, is favorable to the insertion point to target in place, vibrates the closely knit condition and controls easily, is difficult for leaking the vibration.
Treating the surface of the bottom plate: the coarse steel bar part of the bottom plate surface is easy to have early plastic crack-settlement crack after vibration and before initial setting, and must be eliminated by controlling blanking and secondary vibration, so as to avoid the defect of concrete, which causes stress concentration and influences the prevention and treatment effect of temperature shrinkage crack. The surface has thick steel bar parts, and after vibration and before initial setting, shrinkage cracks are easy to appear on the concrete surface, and the cracks are eliminated by manual three-time pressing and smearing in time. After the treatment, in order to prevent the concrete surface from drying and shrinking due to the continuous evaporation of water, the surface should be covered, moisturized and maintained immediately.
Concrete temperature control measures: three layers of cooling water pipe nets are arranged on the central plane of the thickness of the bottom plate. When meeting the water collecting pit, the cooling water pipe downwardly rounds the center of the thickness of the bottom plate of the water collecting pit. According to 1500mm intervals in the inside vertical direction of concrete, the horizontal direction is arranged (is matchd with shaped steel stand modulus, and the installation of being convenient for is fixed) according to 3000mm intervals three-layer diameter for the water heat pipe of 30mm with thin wall iron pipe preparation, and the temperature of intaking of water pump is regulated and control in real time according to the inside detection temperature data of bottom plate to the warm water is given first place to, send water through the water pump and progressively take out the inside heat of concrete, reduce the inside and outside difference in temperature. The cooling circulation system is divided into 5 single-layer loops and 15 total loops, and the total length of each water pipe is controlled to be 150-200 m. The cooling circulation system is shown in figure 1.
Monitoring the temperature of concrete: when the temperature difference between the inside and the outside of the concrete reaches 18 ℃, the early warning is carried out on site responsible personnel, leveling personnel are added, and the calendering speed is accelerated. The alarm should be given immediately when the temperature difference reaches 22 ℃. The water inlet and outlet flow of the cooling water pipe is strictly tested, the water temperature difference of the inlet and the outlet is ensured to be less than or equal to 10 degrees through the speed and the size of the water flow, the temperature measurement record is monitored, the water flow is adjusted according to the temperature condition, and the temperature change rate is enabled to be not more than 2 degrees/day.
And (3) maintaining after pouring: the plastic film for moisturizing and curing is preferably a recyclable film with a relatively thick thickness, the joint of two adjacent plastic films needs to be lapped, the lapping width is not less than 200mm so as to ensure that air does not leak, the plastic films are required to be tightly attached to the surface of concrete, and corners and the lapping position are firmly pressed by battens or reinforcing steel bars. The plastic film which protrudes out of the positions of the embedded parts, the position of the water collecting pit, the corners of the bottom plate and the like is carefully covered tightly and is airtight. When the plastic film is used for covering, if water on the surface of the concrete is dispersed and whitened, the surface of the concrete is always in a wet state in a curing period, condensed water beads are always contained in the plastic film, and if parts which are not tightly covered and are air-leaked are found, the thickness covered by the plastic film is increased. The concrete moisture-retention curing time is not less than 14 days, the cooling rate of the concrete is controlled not to exceed the standard requirement, and when the maximum temperature difference between the surface temperature of the concrete and the atmosphere is less than 20 ℃, the heat-insulation material can be completely removed.
Through adopting above-mentioned technical scheme, this patent starts from the raw and other materials selection of concrete, mix proportion design, the pouring of concrete, the vibration, temperature control, temperature monitoring and control factors such as later stage maintenance, carries out omnidirectional control to the work progress of bulky concrete, ensures that the super large volume bottom plate is once only pour smoothly to the ten thousand cubic concretes, and the result shows, can effectively control the inside highest temperature of concrete, concrete internal surface difference in temperature and surface restraint to effectively prevent the formation and the development of temperature crack.
According to the invention, the C50P 10 high-strength concrete is prepared by uniformly stirring and mixing raw materials including 260-300 parts by weight of cement, 90-120 parts by weight of slag powder, 100-120 parts by weight of fly ash, 40-60 parts by weight of expanding agent, 750-780 parts by weight of sand, 940-960 parts by weight of broken stone, 150-160 parts by weight of water and 7-10 parts by weight of water reducer to obtain C50P 10 high-strength concrete;
in the invention, the ordinary silicate is P.O type silicate cement with the strength of 42.5 grade.
In the invention, the fly ash is F II type fly ash which accords with GBT1596-2017 fly ash for cement and concrete.
In the invention, the mineral powder is S95 grade mineral powder which accords with GBT 18046 and 2017 granulated blast furnace slag powder used in cement, mortar and concrete.
In the invention, the crushed stone is II-type limestone crushed stone which meets GBT14685-2011 construction pebble and crushed stone, and the particle sizes of the crushed stone are respectively 5-25 mm in continuous gradation.
In the invention, the machine-made sand is medium sand which accords with GB-T14684-2011 construction sand, the parent rock is limestone, and the parent rock belongs to the II area in a graded manner.
In the invention, the water reducing agent is a high-performance polycarboxylic acid water reducing agent, the water reducing rate is 25%, and the solid content is more than 12%.
In the invention, the water is used for mixing common concrete.
The invention has the beneficial effects that:
(1) the construction method starts with the control factors of raw material selection, mix proportion design, transportation, pouring, vibration, temperature control, temperature monitoring and maintenance of the concrete, carries out all-around control on the construction process of the large-volume concrete, can smoothly ensure one-time continuous pouring of the concrete super-large-volume bottom plate exceeding 10000 ten thousand cubic meters, and has the advantages of effectively controlling the highest temperature inside the concrete, the temperature difference inside the concrete and surface constraint, thereby effectively preventing the formation and development of temperature cracks;
(2) the invention starts with the temperature control of the concrete raw material, the temperature of the cast-in mould and the temperature after casting, and is beneficial to further ensuring the inner surface temperature control of the concrete;
(3) the concrete processing scheme is provided in concrete pouring mode, use of the vibrating rod, bottom plate surface treatment, layout of cooling water pipes in temperature control measures, maintenance and the like, and is favorable for further guaranteeing control of temperature and cracks during large-volume concrete construction.
Drawings
FIG. 1 is a circulation regulation diagram of a cooling water system.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Example 1
One-time pouring construction method for C50 high-strength concrete super-large-volume bottom plate, wherein the thickness of the super-large-volume bottom plate is 3.5m-5m, the local thickness is 5.85m, and the pouring area of the concrete is 3100m2The one-time continuous pouring amount 18000 method comprises the following steps and operations:
preparing C50P 10 high-strength concrete: uniformly stirring and mixing raw materials including 300 parts of cement, 90 parts of slag powder, 100 parts of fly ash, 49 parts of expanding agent, 760 parts of sand, 957 parts of crushed stone, 160 parts of water and 8.8 parts of water reducing agent according to parts by weight to obtain C50P 10 high-strength concrete, wherein the total hydration heat of the cementing material is 322.93 kJ/kg;
concrete conveying: the pouring amount per hour is about 45 square according to the vehicle pump, and the full-load pouring speed is estimated to be 360 square/hour according to the calculation of 60 square per hour by the chute. By combining the transport distance conditions of a site and a mixing plant, 14 vehicles need to be pressed on the site during the peak period, and 60 tank cars are ensured to ensure that the condition of material break does not exist on the site by combining the above considerations.
Pouring concrete: strictly controlling raw materials, standing cement for more than 7 days when entering a field, and fly ash for more than 3 days to ensure that the temperature of cement and mineral blended materials is not more than 20 ℃, covering a sandstone stock yard to avoid insolation, and adopting cold water for spraying and cooling if the temperature of the sandstone is overhigh. When each section of concrete is poured, the slump and the temperature of concrete mixtures in 5 concrete tanks are continuously measured from the moment that the first concrete tank truck arrives at a pouring place, the workability is observed, the phenomena of segregation, bleeding, layering and the like cannot exist, and the unqualified concrete is checked to be firmly rejected. When the measured consistency and temperature of the concrete mixture had stabilized, the measurements should be made every 2 h. The temperature of the concrete to the mold is controlled within 25 ℃, in order to control the mold-entering temperature, the stirring time of a mixer truck is reduced, pouring is started after the concrete arrives, and the waiting time is reduced;
concrete vibrating: because the concrete slump is large, the concrete slope is relatively long to pave, the concrete must be vibrated towards the slope along the slope foot and the slope top of the fixed line simultaneously during vibration, and the vibrating rod must be inserted into the poured layer for 50-100 mm, so that no cold seam is formed between layers, and the layers are tightly combined to form a whole. The insertion points of the vibrating rods need to be uniformly arranged, the vibrating rods need to be inserted regularly in sequence, and the vibrating rods can move in an arrangement mode and a staggered mode to avoid concrete leakage vibration as much as possible. The vibration time of each plug point needs to be controlled well, generally within 15-20 seconds, and the vibration cannot be carried out, so that the segregation phenomenon of concrete is avoided. Generally, the vibration time at each point is preferably determined by that the concrete surface is horizontal and does not obviously sink any more, bubbles are not generated any more, and mortar is spread on the surface. When the concrete on the lower layer of the raft board is vibrated, the vibrating hand is required to vibrate the concrete in the foundation slab, the concrete is vibrated in a close range, the insertion point is facilitated to be in place, the vibrating and compacting condition is easy to control, and vibration leakage is not easy to occur.
Treating the surface of the bottom plate: the thick steel bar part of the bottom plate surface is easy to have early plastic crack-settlement crack after vibration and before initial setting, and must be eliminated by controlling blanking and secondary vibration, so as to avoid the defect of concrete, which causes stress concentration and influences the prevention and treatment effect of temperature shrinkage crack. The surface has thick steel bar parts, and after vibration and before initial setting, shrinkage cracks are easy to appear on the concrete surface, and the cracks are eliminated by manual three-time pressing and smearing in time. After the treatment, in order to prevent the concrete surface from drying and shrinking due to the continuous evaporation of water, the surface should be covered, moisturized and maintained immediately.
Concrete temperature control measures: three layers of cooling water pipe nets are arranged on the central plane of the thickness of the bottom plate. When meeting the water collecting pit, the cooling water pipe downwardly rounds the center of the thickness of the bottom plate of the water collecting pit. According to 1500mm intervals in the inside vertical direction of concrete, the horizontal direction is arranged (is matchd with shaped steel stand modulus, and the installation of being convenient for is fixed) according to 3000mm intervals three-layer diameter for the hydrothermal pipe of 30mm with thin wall iron pipe preparation, and the temperature of intaking of water pump is regulated and control in real time according to the inside detection temperature data of bottom plate to warm water is given first place to, send water through the water pump and progressively take out the inside heat of concrete, reduces the inside and outside difference in temperature. The cooling circulation system is divided into 5 single-layer loops and 15 total loops, and the total length of each water pipe is controlled to be 150-200 m.
Monitoring the temperature of concrete: when the temperature difference between the inside and the outside of the concrete reaches 18 ℃, the early warning is carried out on site responsible personnel, leveling personnel are added, and the calendering speed is accelerated. And immediately alarming when the temperature difference reaches 22 ℃. The water inlet and outlet flow of the cooling water pipe is strictly tested, the water temperature difference of the inlet and the outlet is ensured to be less than or equal to 10 degrees through the speed and the size of the water flow, the temperature measurement record is monitored, the water flow is adjusted according to the temperature condition, and the temperature change rate is enabled to be not more than 2 degrees/day.
And (3) maintaining after pouring: the plastic film for moisturizing and curing is preferably a recyclable film with a relatively thick thickness, the joint of two adjacent plastic films needs to be lapped, the lapping width is not less than 200mm so as to ensure that air does not leak, the plastic films are required to be tightly attached to the surface of concrete, and corners and the lapping position are firmly pressed by battens or reinforcing steel bars. The plastic film which protrudes out of the positions of the embedded parts, the position of the water collecting pit, the corners of the bottom plate and the like is carefully covered tightly and is airtight. When the plastic film is used for covering, if water on the surface of the concrete is dispersed and whitened, the surface of the concrete is always in a wet state in a curing period, condensed water beads are always contained in the plastic film, and if parts which are not tightly covered and are air-leaked are found, the thickness covered by the plastic film is increased. The concrete moisture-retention curing time is not less than 14 days, the cooling rate of the concrete is controlled not to exceed the standard requirement, and when the maximum temperature difference between the surface temperature of the concrete and the atmosphere is less than 20 ℃, the heat-insulation material can be completely removed.
The monitoring result of the concrete temperature of the base plate with the ultra-large volume is as follows: the maximum temperature of the central concrete occurs at 61.0 ℃ in 33h, the temperature begins to decrease after 36h, the temperature decreases to 50 ℃ in 85h, decreases to below 45 ℃ after 116h, and decreases to 42.0 ℃ after 142 h. The maximum temperature of the lateral surface concrete is 45.9 ℃ when the time is 19 hours, and the environmental temperature is 25.6-36.9 ℃. After the concrete is poured, the maximum value of the temperature difference between the center and the side surface is 36 hours, the maximum value is 16.6 ℃, the temperature difference between the inner surface and the side surface does not exceed 25 ℃ in the whole process from the concrete pouring heating to the cooling, the requirement that the specification is not more than 25 ℃ is met, and no obvious crack exists on the surface of the bottom plate.
Example 2
This example differs from example 1 in the preparation of high strength concrete of C50P 10.
Preparing C50P 10 high-strength concrete: uniformly stirring and mixing raw materials including 260 parts of cement, 120 parts of slag powder, 120 parts of fly ash, 50 parts of expanding agent, 763 parts of sand, 942 parts of crushed stone, 165 parts of water and 10 parts of water reducing agent according to parts by weight to obtain C50P 10 high-strength concrete, wherein the total hydration heat of the cementing material is 311.90 kJ/kg;
the construction result of the floor concrete with the ultra-large volume is as follows: the maximum temperature of the central concrete is 57.4 ℃ after 41h, the temperature is reduced after 42h, the temperature is reduced to below 50 ℃ after 100h, the temperature is reduced to below 45 ℃ after 134h, and the temperature is reduced to 42.9 ℃ after 162 h. The maximum temperature of the lateral surface concrete is 42.1 ℃ when the time is 48 hours, and the environmental temperature is 26.9-40.0 ℃. After the concrete is poured, the maximum value of the temperature difference between the center and the side surface is 42h and 13.1 ℃, the temperature difference between the inner surface and the side surface does not exceed 25 ℃ in the whole process from the concrete pouring heating to the cooling, the temperature difference between the inner surface and the side surface meets the requirement of being lower than 25 ℃, and no obvious crack exists on the surface of the bottom plate.
Claims (9)
1. A one-time pouring construction method for a C50 high-strength concrete super-large-volume bottom plate is characterized by comprising the following specific steps: :
(1) preparing C50P 10 high-strength concrete: the raw materials are cement, slag powder, fly ash, an expanding agent, sand, ore, water and a water reducing agent, 260-300 parts by weight of cement, 90-120 parts by weight of slag powder, 100-120 parts by weight of fly ash, 40-60 parts by weight of the expanding agent, 750-780 parts by weight of sand, 940-960 parts by weight of broken stone, 150-160 parts by weight of water and 7-10 parts by weight of the water reducing agent are stirred and mixed uniformly to obtain C50P 10 high-strength concrete; wherein: the cement is ordinary portland cement PO42.5, and the aggregate mother rock materials of sand and gravel are limestone;
(2) concrete conveying: pouring the concrete by a vehicle pump in a volume of 42-48 square meters per hour, and calculating the chute by 60 square meters per hour, wherein the estimated full-load pouring speed is 360 square meters per hour; by combining the transport distance conditions of a site and a mixing plant, 14 vehicles are required to be pressed on the site during the peak period, and 57-71 tank trucks are required to be ensured to avoid the situation of material breakage on the site by combining the consideration;
(3) pouring concrete: strictly controlling raw materials, entering cement and standing for 3-7 days, entering fly ash and mineral powder and standing for 3-5 days, keeping the temperature of cement and mineral blended materials at 10-20 ℃, covering a sand and gravel material yard to avoid insolation, and if the temperature of the sand and gravel materials is higher than 3 ℃ of the environment, adopting cold water for spraying and cooling; when each section of concrete is poured, continuously measuring the slump and the temperature of concrete mixtures in 5 vehicles from the moment that a first concrete tank vehicle arrives at a pouring place, observing the workability, avoiding the phenomena of segregation, bleeding, layering and the like, and firmly settling the unqualified concrete after checking; when the consistency and the temperature of the measured concrete mixture are stable, the measurement is carried out once every 2 hours, the mold-entering temperature of the concrete is controlled to be 10-25 ℃, in order to control the mold-entering temperature, the stirring time of a mixer truck is reduced, pouring is started after the concrete mixture arrives, and the waiting time is reduced;
(4) vibrating concrete: when concrete is vibrated, the slope toe and the slope top are vibrated towards the slope simultaneously along a fixing line, and a vibrating rod is inserted into a poured layer for 50-100 mm, so that cold seams are not formed between layers, and the concrete and the poured layer are tightly combined into a whole; the inserting points of the vibrating rods need to be uniformly arranged, the vibrating rods need to be regularly inserted in sequence, and the vibrating rods can move in an arrangement mode and a staggered mode, so that the concrete leakage vibration is avoided as much as possible; the vibration time of each insertion point is 15-20 seconds, excessive vibration cannot be caused, and the segregation phenomenon of concrete is avoided; the vibration time at each point is preferably determined by that the concrete surface is horizontal and does not obviously sink any more, bubbles do not appear any more and mortar is spread on the surface; when the concrete on the lower layer of the raft is vibrated, the vibrating hand is required to descend into the foundation slab to vibrate the concrete, and the concrete is vibrated at a short distance, so that the insertion point is favorably positioned, the vibration compaction condition is easy to control, and the vibration leakage is not easy to occur;
(5) treating the surface of the bottom plate: the position of a plate surface coarse steel bar on the plate surface of the bottom plate, which is easy to have an early plastic crack-settlement crack after vibration and before initial setting, must be eliminated by controlling blanking and secondary vibration; the surface is provided with thick steel bar parts, and after vibration and before initial setting, shrinkage cracks are easy to appear on the surface of concrete, and the cracks are eliminated by manual three-time pressing and smearing in time; after treatment, in order to prevent the concrete surface from drying and shrinking due to continuous evaporation of water, surface covering, moisturizing, heat preserving and curing are carried out immediately;
(6) concrete temperature control measures: three layers of cooling water pipe networks are arranged on the central plane of the thickness of the bottom plate; when meeting the water collecting pit, the cooling water pipe downwardly rounds the center of the thickness of the lower bottom plate of the water collecting pit; the water inlet temperature of a water pump is regulated and controlled in real time according to the detected temperature data in the bottom plate, the warm water is taken as the main water, the heat in the concrete is gradually taken out by the water pump to reduce the internal and external temperature difference; the cooling circulation system is divided into 5 single-layer loops and 15 total loops, and the total length of each water pipe is controlled to be 150-200 m;
(7) monitoring the temperature of concrete: when the temperature difference between the inside and the outside of the concrete reaches 18 ℃, early warning is carried out on site responsible personnel, leveling personnel are added, and the calendering speed is accelerated; when the temperature difference reaches 22 ℃, an alarm is given immediately; strictly testing the water inlet and outlet amount of the cooling water pipe, ensuring that the water temperature difference of an inlet and an outlet is less than or equal to 10 degrees through the speed and the size of water flow, monitoring temperature measurement records, and adjusting the water flow according to the temperature condition to ensure that the temperature change rate is not more than 2 degrees/day;
(8) and (3) curing after pouring: the joint of two adjacent plastic films needs to be lapped, the lapping width is not less than 200mm, so as to ensure no air leakage, the plastic films are required to be tightly attached to the surface of concrete, and the corners and the lapping positions are firmly pressed by battens or steel bars; when the plastic film is used for covering, if the water on the concrete surface is dispersed and lost more and whitened, the concrete surface is always in a wet state in a maintenance period, condensed water drops are always contained in the plastic film, and if parts which are not tightly covered and leak air are found, the thickness covered by the plastic film is increased; the concrete moisturizing and curing time is not less than 14 days, the cooling rate of the concrete is controlled not to exceed the standard requirement, and when the maximum temperature difference between the surface temperature of the concrete and the atmosphere is less than 20 ℃, the heat-insulating material can be completely removed.
2. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the ordinary silicate is P.O type silicate cement with the strength of 42.5 grade.
3. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the fly ash is F II type fly ash which accords with GBT1596-2017 fly ash for cement and concrete.
4. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the mineral powder is S95 grade mineral powder which meets GBT 18046-2017 granulated blast furnace slag powder used in cement, mortar and concrete.
5. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the polymer emulsion is milky liquid prepared by blending, compounding and crosslinking polyethylene-vinyl acetate and acrylic emulsion, and has the solid content of 44-50% and the density of 1.05-1.10g/cm3The pH value is 5.
6. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the crushed stone is II-type limestone crushed stone which meets GBT14685-2011 construction pebble and crushed stone, and the particle sizes of the crushed stone are respectively 5-25 mm continuous gradation.
7. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the machine-made sand is medium sand which accords with GB-T14684-2011 construction sand, the parent rock is limestone, and the parent rock belongs to a II area in a graded manner.
8. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the water reducing agent is a high-performance polycarboxylic acid water reducing agent, the water reducing rate is 25%, and the solid content is more than 12%.
9. The one-time pouring construction method for the C50 high-strength concrete super-large-volume bottom plate according to claim 1, characterized in that: the water is used for mixing common concrete.
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