CN111533512A - Preparation method of ductility delayed coagulation fine aggregate concrete with initial setting time of 48-72 h - Google Patents

Preparation method of ductility delayed coagulation fine aggregate concrete with initial setting time of 48-72 h Download PDF

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CN111533512A
CN111533512A CN202010381934.XA CN202010381934A CN111533512A CN 111533512 A CN111533512 A CN 111533512A CN 202010381934 A CN202010381934 A CN 202010381934A CN 111533512 A CN111533512 A CN 111533512A
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concrete
cement
fly ash
slag powder
agent
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CN111533512B (en
Inventor
朱炳喜
高文达
黄根民
蒋一波
尚超军
周阜军
肖强
陈远兵
王学刚
尚志清
陈南
王小勇
袁尧
陈艳丽
夏祥林
张良群
朱维
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Jiangsu Huaiyin Water Conservancy Construction Co ltd
Jiangsu Hydraulic Engineering Construction Co ltd
Jiangsu Yancheng Water Conservancy Construction Co ltd
Nanjing Water Conservancy Construction Engineering Co ltd
Yangzhou Water Conservancy Construction Engineering Co ltd
JIANGSU WATER CONSERVANCY SCIENTIFIC RESEARCH INSTITUTE
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Jiangsu Huaiyin Water Conservancy Construction Co ltd
Jiangsu Hydraulic Engineering Construction Co ltd
Jiangsu Yancheng Water Conservancy Construction Co ltd
Nanjing Water Conservancy Construction Engineering Co ltd
Yangzhou Water Conservancy Construction Engineering Co ltd
JIANGSU WATER CONSERVANCY SCIENTIFIC RESEARCH INSTITUTE
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    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02Compositions 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
    • C04B28/04Portland cements
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • C04B2111/2038Resistance against physical degradation
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • C04B2111/22Carbonation resistance

Abstract

A preparation method of ductility retarding fine aggregate concrete with initial setting time of 48-72 hours belongs to the technical field of building construction, and particularly relates to a preparation technology of ductility retarding fine aggregate concrete. The cement, the fly ash, the slag powder and the reinforcing compacting agent are adopted to form a cementing material, and the fly ash, the slag powder and the reinforcing compacting agent improve the performance of a concrete mixture, and also can improve the early or later strength of concrete, improve a pore structure and improve the compactness of the concrete; meanwhile, the effects of saving resources and protecting the environment are achieved. The method is suitable for pier wall reinforced concrete structures in the fields of construction engineering, hydraulic engineering, traffic engineering, water transportation engineering and the like, a layer of ductility slow setting concrete is poured at the root of the pier wall, and the method is also suitable for underground secant piles and structural construction joint parts needing pouring in different times.

Description

Preparation method of ductility delayed coagulation fine aggregate concrete with initial setting time of 48-72 h
Technical Field
The invention belongs to the technical field of building construction, and particularly relates to a preparation technology of ductile delayed coagulation fine aggregate concrete.
Background
At present, the cracking problem of the pier wall in the reinforced concrete building in the fields of construction engineering, hydraulic engineering, traffic engineering, water transport engineering and the like is prominent, because the deformation of the pier wall concrete caused by temperature shrinkage, self-shrinkage, plastic shrinkage, drying shrinkage and the like in the setting and hardening stage generates temperature stress when being restrained by a lower structure. The common concrete has high compressive strength but low tensile strength which is only 1/8-1/13 of the compressive strength, high elastic modulus and low ductility; when the temperature stress of the concrete exceeds the tensile strength, the concrete will crack. In order to solve the problem of temperature cracks of the pier wall concrete, the technical measures generally adopted in engineering comprise: the anti-crack reinforcing steel bars are arranged, the reinforcing strips and the post-pouring strips are arranged, the structural size of one-time pouring is reduced, the cement using amount is reduced, mineral admixture, anti-crack fibers and an expanding agent are used, the warehousing temperature of concrete is reduced, water cooling is conducted, heat preservation, moisture preservation, maintenance and the like are conducted, however, temperature cracks still occur in a large number of pier wall structures, and some structural cracks are serious. Harmful cracks generated in the concrete structure not only affect the appearance of the structure, but also accelerate the durability failure of the concrete structure, so that the internal steel bars are corroded in advance, the appearance quality of the building is seriously affected, and the feeling of insecurity in mind is brought to people. If a layer of ductility retarding concrete is poured at the root of the pier wall, the setting time of the ductility retarding concrete is 36-60 hours later than that of common concrete at the upper part of the pier wall, and after the concrete at the upper part is set and hardened and most of shrinkage deformation is finished, the ductility retarding concrete at the root of the pier wall begins to be set and hardened, so that the constraint of the bottom plate on the temperature deformation of the pier wall is relieved, the temperature stress of the pier wall is reduced, and the risk of generating cracks of the pier wall is reduced.
The wall body with the height of more than 10m needs long pouring time, and if the pouring process is suspended due to reasons, a construction cold joint can be formed. If a layer of ductility retarding concrete is poured before the pause, the construction cold joint can be avoided.
Disclosure of Invention
Aiming at the defects of the prior art and the requirements of the construction process, the invention aims to provide a preparation method of ductility delayed coagulation fine aggregate concrete with initial setting time of 48-72 h.
The technical scheme of the invention is as follows: firstly, mixing fine aggregate, rubber fine particles, coarse aggregate and fibers for 10-30 seconds, then adding cement, fly ash, slag powder, a reinforcing compacting agent, a magnesium oxide expanding agent and a first part of mixing water, mixing for 10-30 seconds, then adding a second part of mixing water, a water reducing agent, an air entraining agent and a retarder, and mixing uniformly to obtain ductility retarding fine aggregate concrete with the initial setting time of 48-72 hours;
the total amount of the cement, the fly ash, the slag powder and the reinforcing compacting agent accounts for 420-480 kg/m of the total mass of the concrete3
The total amount of the fly ash, the slag powder and the reinforcing compacting agent accounts for 30-50% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the fly ash accounts for 10-20% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the slag powder accounts for 15-20% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the reinforcing compacting agent accounts for 5-10% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the magnesium oxide expanding agent accounts for 3-6% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the water accounts for 40-48% of the total mass of the cement, the fly ash, the slag powder, the reinforcing compacting agent and the magnesium oxide expanding agent;
the water reducing agent accounts for 0.6-1.6% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent,
the water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is 25-30%;
the air entraining agent accounts for 0.03-0.05% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the retarder accounts for 0.8-1.8% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the rubber fine particles account for 3-6% of the total mass of the fine aggregates and the rubber fine particles;
the sum of the mass of the fine aggregate and the rubber fine particle accounts for 36 to 45 percent of the total mass of the fine aggregate, the rubber fine particle and the coarse aggregate;
the fiber accounts for 2.0kg/m of the total weight of the concrete3~4.0kg/m3
The mass ratio of the first part of mixing water to the second part of mixing water is 30-50: 70-50.
The initial setting time test of the ductile delayed coagulation fine aggregate concrete with the initial setting time of 48-72 hours refers to data tested at the curing temperature of 17-23 ℃ according to the Hydraulic concrete test Specification (SL 352-2006).
The cement, the fly ash, the slag powder and the reinforcing compacting agent are adopted to form the cementing material, and the fly ash, the slag powder and the reinforcing compacting agent improve the performance of a concrete mixture, improve the early or later strength of the concrete, improve the pore structure and improve the compacting performance of the concrete; meanwhile, the effects of saving resources and protecting the environment are achieved.
The invention is suitable for pier wall reinforced concrete structures in the fields of construction engineering, hydraulic engineering, traffic engineering, water transportation engineering and the like, a layer of ductility delayed coagulation concrete is poured at the root part of the pier wall, and the invention is also suitable for underground secant piles and structural construction joint parts needing pouring in different times.
The invention is doped with fine rubber particles and fibers, thereby improving the stress-strain relationship of the concrete and improving the ductility, the toughness and the crack resistance of the concrete. The rubber fine particles are one of 40 mesh, 50 mesh or 80 mesh. The fiber is dispersed in the concrete, so that the early shrinkage rate of the concrete is reduced, the distribution of hardened concrete cracks can be dispersed, the width of crack development is reduced, harmful cracks are prevented, and the toughness of the concrete can be improved. The fiber is one of polypropylene fiber and polyacrylonitrile fiber.
The concrete is mixed with a reinforcing compacting agent, such as one of ultrafine fly ash, ultrafine slag powder or silica powder. The particle composition of the cementing material can be improved, the capillary pores of the cementing material can be filled, the compacting and filling effects can be exerted, and the compactness of the concrete can be improved. The ultrafine fly ash, the ultrafine slag powder and the silica powder can also play a role in higher volcanic ash activity, and particularly, the silica powder is a high-activity mineral admixture. The reinforcing compacting agent can play a role in improving the strength, durability and the like of the concrete in the early or later period. The reinforced compacting agent accounts for 5-10% of the total mass of the cement, the fly ash, the slag powder and the reinforced compacting agent.
The water reducing agent is selected to reduce the cement consumption and the cementing material consumption of the concrete, improve the pore structure of the concrete and improve the compactness of the concrete, and the shrinkage rate of the concrete prepared by adopting the polycarboxylic acid high-performance water reducing agent is generally lower than that of other water reducing agents; for preparing ductility retarding fine aggregate concrete, a polycarboxylic acid high-performance water reducing agent is selected, and the water reducing rate of the water reducing agent is 25-30%; the polycarboxylic acid high-performance water reducing agent accounts for 0.6-1.6% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent.
The retarder is selected to prolong the setting time of the concrete, the retarder is tested according to the standard of concrete admixture (GB 8076-2008), and the initial setting time of the concrete doped with the retarder is more than 72 hours when the doping amount of the concrete accounts for 1.8 percent of the mass of the cement.
In order to improve the frost resistance of concrete, improve the workability of fresh concrete mixture and prevent the fresh concrete mixture from segregation, bleeding and hardening, an air entraining agent is doped into the concrete. The air entraining agent accounts for 0.03-0.05% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent.
In order to prevent the fibers from aggregating into lumps in the concrete stirring process and improve the dispersion uniformity of the fibers and the rubber fine particles, the fine aggregate, the rubber fine particles, the coarse aggregate and the fibers are stirred together.
In order to improve the compatibility of the water reducing agent, the air entraining agent and the retarder to cement, fly ash, slag powder, a reinforcing compacting agent and a magnesium oxide expanding agent and reduce the adsorbability, the cement, the fly ash, the slag powder, the reinforcing compacting agent, the magnesium oxide expanding agent, the first part of mixing water and the stirred fine aggregate, the rubber fine particles, the coarse aggregate and the fibers are stirred together.
And finally, stirring the second part of mixing water, a water reducing agent, an air entraining agent and a retarder together with the stirred cement, the fly ash, the slag powder, the reinforcing compacting agent, the magnesium oxide expanding agent, the first part of mixing water, the fine aggregate, the rubber fine particles, the coarse aggregate and the fibers until the mixture is uniformly mixed.
In a word, the concrete formed by adopting the proportion of the invention can prolong the setting time of the concrete and improve the compactness, durability, toughness and ductility of the hardened concrete.
Further, the cement of the invention is one of 42.5 ordinary portland cement, 42.5 portland cement, 52.5 ordinary portland cement or 52.5 portland cement in strength grade; meanwhile, the specific surface area of the cement is required to be not more than 350m2The water consumption for the standard consistency is not more than 28 percent, because the water consumption for the standard consistency of the cement is increased by 5-8 kg/m when the water consumption for the standard consistency of the cement is increased by 1 percent and the water consumption for the concrete is increased by 5-8 kg/m3The invention selects the cement with standard consistency and lower water consumption, which is beneficial to reducing the water consumption of the concrete.
The fly ash and the slag powder are added into the concrete, so that the workability and pumpability of the concrete can be improved, the later strength is improved, the porosity of the concrete is reduced, the compactness of the concrete is improved, and the hydration heat of the concrete is reduced. The fly ash is F-class I or II fly ash which meets the standard requirements of fly ash for cement and concrete (GB/T1596-2017).
The larger the specific surface area of the slag powder is, the higher the activity is, the early hydration heat and self-shrinkage of the concrete are increased along with the increase of the specific surface area of the slag powder, therefore, the slag powder is S95-grade granulated blast furnace slag powder which meets the standard requirement of granulated blast furnace slag powder (GB/T18046-2017) used in cement and concrete, and the specific surface area is not more than 450m2/kg。
The concrete can generate volume shrinkage after being solidified and hardened, and the magnesium oxide expanding agent is doped into the concrete and reacts with water to generate hydration reaction to form magnesium hydroxide, so that the concrete generates delayed volume expansion and can compensate the volume shrinkage of the concrete. The concrete can obtain better expansion performance by doping light-burned magnesium oxide with the active reaction time of 100-200 s. Therefore, the magnesium oxide expanding agent is a magnesium oxide expanding agent for medium and medium-speed concrete in the standard of magnesium oxide expanding agent for concrete (CBMF 19-2017).
According to the invention, the rubber fine particles are doped into the concrete, so that the ductility, toughness and fracture energy of the concrete can be improved, and the ultimate elongation after fracture is improved; the elastic modulus of the rubber fine particles is low, the rubber fine particles are similar to a spring unit, various internal forces existing in a concrete test piece can be eliminated or slowed down, stress concentration is reduced, extension and expansion of micro cracks can be effectively inhibited and delayed, the micro cracks cannot be connected and communicated with one another, the time of visible macro cracks appearing in the concrete is delayed, and therefore the toughness of the concrete can be improved; however, the rubber fine particles have hydrophobicity, are weakly bonded with the interface of cement paste, have low elastic modulus, and cause strength reduction when being doped into concrete; the finer the rubber fine particles are, the more the water consumption of the concrete is increased, and the energy consumption required for processing the rubber fine particles is also increased; the coarser the rubber fine particles, the lower the bond strength with cement paste, and the lower the elastic modulus, the lower the concrete strength. Therefore, the fineness of the rubber fine particles is 40 mesh, 50 mesh or 80 mesh.
The finer the fine aggregate, the larger the surface area, the larger the water consumption for concrete, and the coarser the fine aggregate, the higher the concrete sand ratio and the higher the concrete shrinkage. Therefore, the fineness modulus of the selected fine aggregate is 2.4-3.1; the mud, mud blocks and mica in the fine aggregate can increase the shrinkage of the concrete and reduce the frost resistance. Therefore, the content of mud in the fine aggregate is less than or equal to 1 wt%, the content of mud blocks is 0, and the content of mica is less than or equal to 0.5 wt%.
The larger the particle size of the coarse aggregate is, the lower the bonding strength with cement mortar is, the lower the ductility of concrete is, and meanwhile, the larger the particle size of the coarse aggregate is, the possibility of segregation of concrete mixtures is increased, and the construction defects of honeycombing, water seepage, scenting tide and the like are easily generated at the root of a pier wall, so that the coarse aggregate is continuously graded by 5-15 mm. In addition, the larger the mud content and the mud block content of the coarse aggregate, the larger the concrete shrinkage, and the frost resistance is also reduced; if the content of the needle-shaped particles is high, the quality of the concrete mixture is reduced, and the water consumption of the concrete is increased; the crushing value greatly reduces the strength of concrete; when the water absorption rate is high, the slump loss of concrete is accelerated, and the water consumption for concrete mixing can be increased, so that the coarse aggregate is 5-16 mm continuous particle size and clean broken stones or pebbles, the mud content of the coarse aggregate is less than or equal to 0.5 wt%, the mud block content is 0, the needle-shaped particle content is less than or equal to 8%, the crushing value is less than or equal to 10%, and the water absorption rate is less than or equal to 1%.
The addition of fine rubber particles into concrete can reduce the early strength and the later strength of the concrete, the addition of retarder can reduce the early strength of the concrete, and the addition of too much retarder can reduce the later strength of the concrete. To compensate for the loss of strength, reinforcing compactants are incorporated into the concrete. The reinforcing compacting agent is one of ultrafine fly ash, ultrafine slag powder or silicon powder.
The fiber is polypropylene fiber or polyacrylonitrile fiber in the standard of synthetic fiber for cement concrete and mortar (GB/T21120-2018), the breaking strength is more than or equal to 500MPa, and the initial modulus is more than or equal to 5 × 103MPa, and the elongation of the cross section is more than or equal to 30 percent.
Compared with the common concrete, the ductile delayed coagulation fine aggregate concrete with the initial setting time of 48-72 hours has the following characteristics:
1) the initial setting time of the concrete is 48-72 h.
2) The bending elastic modulus is reduced by more than 20 percent, the bending ultimate tensile value is improved by more than 50 percent, and the crack resistance of the concrete is improved.
3) The anti-abrasion performance is more than 1.5 times of that of common concrete, and the anti-carbonization performance and the anti-chloride ion permeability are higher than those of the common concrete.
4) The waste tire fine particles and the industrial waste residues such as the fly ash and the slag powder are used as functional materials for improving the performance of the concrete, so that the problems of land occupation and environmental pollution of the waste tires, the fly ash and the slag powder are solved, and the purposes of protecting the environment, changing waste into valuable and recycling resources are achieved.
Detailed Description
Firstly, engineering target:
a water gate project is a general environment hydraulic building of an inland river, has 5 holes and a net width of a single hole of 10m, and is divided into 2 bottom plates, wherein one bottom plate is a two-hole one-connection structure, and the other bottom plate is a three-hole one-connection structure. The gate pier has the length of 30m, the height of 12m, the thickness of the middle pier of 1.8m, and the thickness of the side pier and the seam pier of 1.2 m. The concrete design strength grade of the structural parts such as the bottom plate, the gate pier and the like is C30, the frost resistance grade is F50 and the impermeability grade is W6.
In order to prevent temperature cracks from being generated in the gate pier construction process, when the gate pier is poured, a layer of C30 ductility delayed coagulation fine-stone concrete with the thickness of 20cm is poured at the root of the gate pier, and the initial setting time of the concrete is 60-70 h.
Secondly, preparing concrete:
1. preparing raw materials:
(1) and (3) cement.
42.5 the common Portland cement, the cement strength of which conforms to the regulation of the Standard of general Portland cement (GB 175-2007). The specific surface area of the cement is 330 m2Water consumption at standard consistency 27.2% per kg.
(2) Coarse aggregate.
The coarse aggregate 1 is a continuous and clean crushed stone with nominal size fraction of 5-16 mm, the content of mud is 0.36 wt%, the content of mud blocks is 0, the content of needle-shaped particles is 5.5 wt%, the crushing value is 7.2%, and the water absorption rate is 0.8%.
The coarse aggregate 2 is clean crushed stone with nominal size fraction of 16-31.5 mm, mud content of 0.40 wt%, needle-shaped particle content of 6.5 wt%, crushing value of 7.8% and water absorption of 0.6%.
(3) Fine aggregate.
The method adopts the Yangtze river medium sand with the fineness modulus of 2.56, the mud content is 0.72 wt%, the mud block content is 0 wt%, and the mica content is 0.45 wt%.
(4) Fly ash.
Class F class II fly ash meeting the specifications of fly ash used in cement and concrete (GB/T1596-2017) has a loss on ignition of 1.6%.
(5) Slag powder.
Granulated blast furnace slag powder for use in Cement and concrete (GB/T18046-2017) Standard S95 granulated blast furnace slag powder having a specific surface area of 395 m2/kg。
(6) And (4) reinforcing a compacting agent.
Adopts superfine slag powder with specific surface area of 960m2/kg。
Ultrafine fly ash or silica powder can also be used.
(7) A water reducing agent.
The water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is 30% when the mixing amount is 1.5% according to the water reducing rate tested by concrete admixture (GB 8076-2008).
(8) An air entraining agent.
The mixing amount is 0.05 percent of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent in the concrete.
(9) A retarder.
Is an ultra retarder, and the mixing amount of the ultra retarder is 1.2 percent of the total amount of cement, fly ash, slag powder and reinforcing compacting agent in concrete.
(10) Fine particles of rubber.
The fineness is 50 meshes.
(11) A crack resistant fiber.
The artificial synthetic polyacrylonitrile fiber is in accordance with cementThe polyacrylonitrile fiber in the synthetic fiber (GB/T21120-2018) standard for concrete and mortar has the requirements of breaking strength of 620MPa and initial modulus of more than or equal to 5.23 × 103MPa, and the elongation of the cross section is more than or equal to 32.3 percent.
(12) A magnesium oxide expanding agent.
Magnesium oxide expanding agent for concrete (CBMF 19-2017) standard medium-and-medium-speed type magnesium oxide expanding agent for concrete.
(13) And water was mixed.
Tap water.
2. Weighing:
the mixing ratio is 1: 280kg of cement, 70kg of fly ash, 70kg of slag powder, 30kg of superfine slag powder, 688kg of fine aggregate, 30kg of rubber fine particles, 1002kg of coarse aggregate 1, 5.4kg of polycarboxylic acid high-performance water reducing agent, 0.225kg of air entraining agent, 5.4kg of retarder, 190kg of tap water, 22kg of magnesium oxide expanding agent and 2.0kg of polyacrylonitrile fiber are respectively weighed for the root delayed coagulation fine-aggregate concrete.
The mixing ratio is 2: 210kg of cement, 75kg of fly ash, 75kg of slag powder, 699kg of fine aggregate, 298kg of coarse aggregate 1, 893kg of coarse aggregate 2, 4.3kg of polycarboxylic acid high-performance water reducing agent, 1.08kg of air entraining agent, 145kg of tap water and 1.0kg of polyacrylonitrile fiber are respectively weighed for the common concrete with the root part above.
3. Mixing:
mixing with a double-horizontal-shaft forced mixer.
(1) Delayed coagulation fine aggregate concrete at the root of the gate pier: adding fine aggregate, rubber fine particles, coarse aggregate 1 and fibers into a mixer according to the mixture ratio of 1, and mixing for 30 seconds; then 40 percent of cement, fly ash, slag powder, superfine slag powder, magnesium oxide expanding agent and mixing water are added into the mixer and mixed for 30 seconds; and finally, adding 60 percent of mixing water, a water reducing agent, an air entraining agent and a retarder, and mixing for 90 seconds to form the concrete.
The slump of the formed concrete is 160mm through detection, and the air content is 3.2%.
Can be used in this engineering.
(2) Common concrete above the root of the gate pier: the concrete is prepared by adding cement, fly ash, slag powder, fine aggregate, coarse aggregate 1, coarse aggregate 2, water reducing agent, air entraining agent and fiber into a mixer according to the mixing proportion of 2, and mixing for 60 seconds.
The slump of the formed concrete is 170mm through detection, and the air content is 3.3%.
Can be used in this engineering.
Thirdly, an application process:
1. and (3) steel bar installation:
the steel bars are manufactured and installed according to the design requirements, and the manufacturing and installation quality of the steel bars is in accordance with the regulations of Water Gate construction Specifications (SL 27-2014).
2. Installing a template:
the average daily temperature of the gate pier concrete after pouring is more than 10 ℃, and the strength of the ductility delayed coagulation fine aggregate concrete at the root part meets the requirement of form removal when the form removal is carried out for 12 days on the gate pier, so that the template at the root part of the gate pier and the templates above the root part are not separately manufactured and installed.
The gate pier template and the support are designed according to the water gate construction specification (SL 27-2014), and the manufacturing and installation quality of the gate pier template and the support meets the water gate construction specification (SL 27-2014) and the design requirements.
3. Pouring:
and after the gate pier steel bars and the templates are installed, roughening and cleaning the joint surface of the bottom plate and the gate pier, spraying water to moisten the joint surface before pouring, removing accumulated water on the surface, and entering a pouring stage.
In addition to meeting the specifications of the water gate construction code (SL 27-2014) and the hydraulic concrete construction code (SL 677-2014) and design documents, the concrete pouring needs to pay attention to the following operation points:
before pouring, a guide pipe is arranged in the inner cavity of the gate pier template, and the distance from a discharge port of the guide pipe to the surface of the bottom plate is controlled to be 0.8-1.0 m.
Conveying the ductile delayed coagulation fine stone concrete with the mix proportion of 1 into a bin by using a concrete pump truck, controlling the thickness to be about 20cm, manually flattening the concrete, adopting a medium-frequency vibrator to vibrate and compact, wherein the vibration frequency of the vibrator is not higher than 6000 times/min, and preventing the gas content of the concrete from being reduced.
After the ductile delayed coagulation fine stone concrete is poured, pouring the gate pier common concrete with the mix proportion of 2 continuously, enabling the gate pier common concrete to reach 50-60 cm below the top layer steel bars of the gate pier, standing for 50-60 min, waiting for the concrete to be primarily sunk, and performing secondary compaction before pouring the concrete continuously.
4. Smearing:
the top surface of the gate pier structure is plastered for at least 2 times, and secondary plastering is carried out before the concrete is initially set.
5. And (5) maintenance:
after the concrete is poured, the temperature is above 10 ℃, and the template counter-pulling screw rods which are upwards arranged from the bottom plate and above the 3 rd row are loosened 6 days after the concrete is poured, wherein the temperature is 11: 00 supplying the maintenance water from the top of the gate pier for 1 time. The removal of the formwork was started 12 days.
Before the gate pier template begins to be dismantled, a spraying device is arranged to spray towards the surface direction of the structural concrete, and the spraying maintenance time is 14 days.
6. The concrete construction quality is as follows:
(1) the initial setting time of the ductility delayed coagulation fine aggregate concrete at the root part of the gate pier is 65.4 hours.
(2) The ductility slow-setting fine aggregate concrete strength of the gate pier root: the strength of a 28-day concrete standard curing test piece is 36.8MPa, the estimated value of the concrete resilience strength of the brake pier root structure is 33.3MPa when the equivalent curing time reaches 600 ℃ d, the frost resistance reaches the F50 requirement, and the impermeability grade reaches the W6 requirement.
(3) The strength of the common concrete poured above the root of the gate pier is as follows: the 28-day concrete standard curing test pieces are tested in 3 groups, the compressive strength is 37.2MPa, 36.3MPa and 35.4MPa respectively, and the estimated value of the resilience strength of the structural concrete is 36.8MPa when the equivalent curing time reaches 600 ℃ d.
(4) The frost resistance of the common concrete poured above the root of the gate pier reaches the requirement of F50, and the impermeability grade reaches the requirement of W6.
7. The implementation effect is as follows:
the gate pier was found to have no vertical temperature cracks.

Claims (10)

1. The preparation method of the ductility delayed coagulation fine aggregate concrete with the initial setting time of 48-72 hours is characterized by comprising the following steps:
firstly, mixing fine aggregate, rubber fine particles, coarse aggregate and fibers for 10-30 seconds, then adding cement, fly ash, slag powder, a reinforcing compacting agent, a magnesium oxide expanding agent and a first part of mixing water, mixing for 10-30 seconds, then adding a second part of mixing water, a water reducing agent, an air entraining agent and a retarder, and mixing uniformly to obtain ductility retarding fine aggregate concrete with the initial setting time of 48-72 hours;
the total amount of the cement, the fly ash, the slag powder and the reinforcing compacting agent accounts for 420-480 kg/m of the total mass of the concrete3
The total amount of the fly ash, the slag powder and the reinforcing compacting agent accounts for 30-50% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the fly ash accounts for 10-20% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the slag powder accounts for 15-20% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the reinforcing compacting agent accounts for 5-10% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the magnesium oxide expanding agent accounts for 3-6% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the water accounts for 40-48% of the total mass of the cement, the fly ash, the slag powder, the reinforcing compacting agent and the magnesium oxide expanding agent;
the water reducing agent accounts for 0.6-1.6% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent,
the water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is 25-30%;
the retarder accounts for 0.8-1.8% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the air entraining agent accounts for 0.03-0.06% of the total mass of the cement, the fly ash, the slag powder and the reinforcing compacting agent;
the rubber fine particles account for 3-6% of the total mass of the fine aggregates and the rubber fine particles;
the sum of the mass of the fine aggregate and the rubber fine particle accounts for 36 to 45 percent of the total mass of the fine aggregate, the rubber fine particle and the coarse aggregate;
the fiber accounts for 2.0kg/m of the total weight of the concrete3~4.0kg/m3
The mass ratio of the first part of mixing water to the second part of mixing water is 30-50: 70-50.
2. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the cement is one of 42.5 ordinary portland cement, 42.5 portland cement, 52.5 ordinary portland cement or 52.5 portland cement in the standard of general portland cement (GB 175-2007), and the specific surface area is not more than 350m2Per kg, water consumption at standard consistency is not more than 28%.
3. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the fly ash is class F I or class II fly ash in the standard of fly ash for cement and concrete (GB/T1596-2017).
4. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the slag powder is S95 level granulated blast furnace slag powder in the standard of granulated blast furnace slag powder (GB/T18046-2017) used in cement and concrete, and the specific surface area is not more than 450m2/kg。
5. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the magnesium oxide expanding agent is a magnesium oxide expanding agent for medium and medium speed type concrete in the standard of magnesium oxide expanding agent for concrete (CBMF 19-2017).
6. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the fineness of the rubber fine particles is 40 meshes, 50 meshes or 80 meshes.
7. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the fine aggregate is natural river sand or machine-made sand, the fineness modulus is 2.5-3.1, the content of mud in the fine aggregate is less than or equal to 1 wt%, the content of mud blocks is 0, and the content of mica is less than or equal to 0.5 wt%.
8. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the coarse aggregate is clean broken stone or pebble with continuous particle size of 5-16 mm, the mud content of the coarse aggregate is less than or equal to 0.5 wt%, the mud block content is 0, the content of needle-shaped particles is less than or equal to 8%, the crushing value is less than or equal to 10%, and the water absorption rate is less than or equal to 1%.
9. The preparation method of the ductility retarding fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, which is characterized in that: the reinforcing compacting agent is one of ultrafine fly ash, ultrafine slag powder or silicon powder.
10. The preparation method of the ductile delayed coagulation fine aggregate concrete with the initial setting time of 48-72 h according to claim 1, wherein the fiber is polypropylene fiber or polyacrylonitrile fiber in the standard of synthetic fiber (GB/T21120-2018) for cement concrete and mortar, the breaking strength is more than or equal to 500MPa, and the initial modulus is more than or equal to 5 × 103MPa, and the elongation of the cross section is more than or equal to 30 percent.
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