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CN112521094A - C35 steam-free curing concrete for fabricated building and preparation method thereof - Google Patents

C35 steam-free curing concrete for fabricated building and preparation method thereof Download PDF

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Publication number
CN112521094A
CN112521094A CN202011436701.1A CN202011436701A CN112521094A CN 112521094 A CN112521094 A CN 112521094A CN 202011436701 A CN202011436701 A CN 202011436701A CN 112521094 A CN112521094 A CN 112521094A
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concrete
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王鹏刚
付华
崔东波
金祖权
孙晓光
赵铁军
高嵩
熊传胜
孙培旺
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Mountain Jingbo Environmental Protection Materials Co ltd
Qingdao University of Technology
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Mountain Jingbo Environmental Protection Materials Co ltd
Qingdao University of Technology
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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
    • 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
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • 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
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/76—Use at unusual temperatures, e.g. sub-zero
    • 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
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention relates to the technical field of concrete, in particular to C35 steam-free curing concrete for an assembly type building and a preparation method thereof. In the concrete, the preparation raw materials of each cubic meter of the concrete comprise the following components: cement, 220-400 kg; 0-180kg of fly ash; 0-180kg of mineral powder; 725.8-754kg of sand; 1086-1114.2kg of stones; 16kg of nano C-S-H-PCE; 0.4-4.8kg of water reducing agent; 115.2-192kg of water. The nano C-S-H-PCE early strength agent is adopted to regulate the early hydration process of cement, accelerate the generation of early hydration products of the cement and the formation of microstructures, further optimize the concrete mixing ratio, prepare the non-autoclaved concrete product with low energy consumption and high durability, effectively avoid the heat damage inside the product and the generation of structural defects in the damp-heat curing process, improve the overall performance of the concrete product and reduce the later maintenance cost of the concrete product.

Description

C35 steam-free curing concrete for fabricated building and preparation method thereof
Technical Field
The invention relates to the technical field of concrete, in particular to C35 steam-free curing concrete for an assembly type building and a preparation method thereof.
Background
In recent years, as "housing industrialization and building industrialization" are gradually implemented, the proportion of the prefabricated buildings in new buildings is increasing. The application of precast concrete components in fabricated buildings is increasingly widespread, and the precast concrete components become an important way for realizing green construction and low-carbon economy. In the fabricated building, the concrete strength grades of the precast concrete members are mostly C30 and C35. However, the early strength of the precast concrete is low at present, and the turnover of the mold is slow, so that the cost of the precast concrete is high. Precast concrete component is mainly through steam curing mode preparation simultaneously, and steam curing can cause adverse effect to the inside pore structure of concrete, causes the concrete swelling to warp easily, delays the ettringite inflation, influences the volume stability who evaporates the concrete to there is the run-down in the later stage of evaporating the concrete, the fracture risk grow scheduling problem. In addition, along with the acceleration of industrialization and urbanization processes, the amount of raw waste garbage is increased, and according to the annual newspaper for preventing and treating the pollution environment of solid wastes of China and cities in 2020 published by the ministry of ecological environment, the annual output of industrial solid wastes in China is up to 13.1 hundred million t in 2019, and the annual output of fly ash is up to 4.9 hundred million t in China. Although the solid waste is now comprehensively utilized by various industries, the accumulation amount of the fly ash is as high as 20 hundred million t, and the solid waste is easily landfilled or stockpiled in the open air without any treatment, thereby wasting land and resources and polluting the environment.
The design strength requirement of the fabricated building concrete is not lower than C35, and the slump of the fabricated building concrete needs to be controlled within the range of 160-200 mm in consideration of the pumping construction requirement. According to the production flow of the concrete product, the strength of the assembled concrete product for the building in 24 hours is not lower than 20 MPa. According to the relevant regulations of GB/T50476 and 2019 'design Specification for durability of concrete structure', under the condition of general environmental class B environmental action level, a building (structure) with the service life of 50 years is designed, and the maximum water-cement ratio of the adopted concrete is 0.5; (ii) a The minimum dosage of the cementing material is 300 kg; the minimum protective layer thickness should be more than or equal to 20mm, so the carbonization depth of the concrete in the carbonization box for accelerating carbonization 28d is less than 20 mm; (ii) a If the concrete structure is used in a light chlorine salt environment, the 28d chloride ion diffusion coefficient should be less than or equal to 10 multiplied by 10-12m2S; if the structure is in service in a micro-freezing area, the adopted concrete has certain frost resistance, and the loss of the dynamic elastic modulus after 250 times of freeze-thaw cycle is less than 20 percent; in addition, the concrete should have a certain volume stability, and 80d self-shrinkage of less than 350X 10-6。
In order to solve the problems and requirements, researchers at home and abroad currently carry out systematic research on the heat damage mechanism of the steam-cured concrete, the mechanical property evolution in the steam-cured process and the deterioration mechanism of the steam-cured concrete, and the performances of the steam-cured concrete are improved by changing the water-cement ratio, the mineral admixture mixing amount, the steam-curing system and the like. But the problems of heat damage, high energy consumption, concrete durability damage caused by steam curing and the like caused by steam curing cannot be fundamentally solved. Therefore, many researchers have prepared the C35 non-autoclaved concrete by controlling raw materials and optimizing the mixing proportion of the concrete and various types of early strength agents. The early strength of concrete can be improved by using various types of early strength agents to prepare the non-autoclaved concrete, but many early strength agents have the problems of complex use, influence on the durability of the concrete, high cost and the like.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides C35 steam-free curing concrete for an assembly type building and a preparation method thereof, the early hydration process of cement is regulated and controlled by adopting a nano C-S-H-PCE early strength agent, the generation of early hydration products of the cement and the formation of a microstructure are accelerated, further, the concrete mixing ratio is optimized, a low-energy-consumption and high-durability steam-free curing concrete product is prepared, the heat damage and the structural defect inside the product in the damp-heat curing process are effectively avoided, the integral performance of the concrete product is improved, and the later maintenance cost of the concrete product is reduced.
The technical scheme of the invention is as follows: the C35 non-steam curing concrete for the fabricated building, wherein, in the concrete, the preparation raw materials of each cubic meter of the concrete comprise the following components:
cement, 220-400 kg;
0-180kg of fly ash;
0-180kg of mineral powder;
725.8-754kg of sand;
1086-1114.2kg of stones;
16kg of nano C-S-H-PCE;
0.4-4.8kg of water reducing agent;
115.2-192kg of water.
The cement of the invention is P.I 52.5 Portland cement, and the specific surface area is less than or equal to 400m2Per kg, initial setting time is more than or equal to 45min, final setting time is less than or equal to 390min, MgO content is less than or equal to 5 percent, C3The content of A is less than or equal to 8 percent, the content of chloride ions is less than or equal to 0.06 percent, and the loss on ignition is less than or equal to 3 percent. The fly ash is I-grade low-calcium fly ash, the screen residue of a square hole with the diameter of 45 mu m is less than or equal to 12 percent, the water demand ratio is less than or equal to 95 percent, the ignition loss is less than or equal to 5 percent, and SO3The content is less than or equal to 3.5 percent, the content of free CaO is less than or equal to 1 percent, and the radioactivity is qualified; the mineral powder is S95 grade mineral powder, the fluidity ratio is more than or equal to 95 percent, the ignition loss is less than or equal to 3 percent, and the SO3The content is less than or equal to 4 percent, the content of chloride ions is less than or equal to 0.06 percent, the content of glass bodies is more than or equal to 85 percent, and the radioactivity is qualified.
The stone adopted by the invention adopts basalt broken stone with 5-20mm continuous gradation, the content of needle-shaped particles in the stone is less than or equal to 10 percent, the crushing value is less than or equal to 12 percent, the mud content is less than or equal to 1 percent, the mud block content is less than or equal to 0.5 percent, the water absorption rate is less than or equal to 1.0 percent, and the content of sulfides and sulfates is less than or equal to 0.5 percent. The sand is river sand with fineness modulus of 2.4-2.9, the mud content of the river sand is less than or equal to 1.5%, the mud block content is less than or equal to 0.8%, the sulfide and sulfate content is less than or equal to 0.5%, the chloride ion content is less than or equal to 0.02%, the fine particle content below 0.315mm is more than or equal to 10%, and the fine powder content below 0.15mm is more than or equal to 3%.
The nanometer C-S-H-PCE early strength agent adopted by the invention is a milk white liquid, the particle size is 50-100nm, the water reducing rate is not less than 25%, and the mixing amount is 2% -4% of the total mass of cement, fly ash and mineral powder.
The invention further optimizes the mixing proportion of the C35 non-autoclaved concrete in the aspects of workability, strength, durability, shrinkage rate and the like of the concrete, the water-gel ratio of the optimized concrete is 0.288-0.480, and the dosage of the cementing material (the sum of cement, fly ash and mineral powder) is not more than 400kg/m3The sand rate is 40-45%.
The invention also discloses a preparation method of the C35 steam-free curing concrete for the fabricated building, which comprises the following steps:
s1, providing 400kg of cement, 0-180kg of fly ash, 0-180kg of mineral powder, 725.8-754kg of sand, 1086-1114.2kg of stones, 16-18kg of nano C-S-H-PCE early strength agent and 115.2-192kg of water;
s2, stirring and dry-mixing the sand, the stones, the cement, the fly ash and the mineral powder to obtain a mixed base material;
s3, adding the nano C-S-H-PCE early strength agent into water, and uniformly mixing to obtain a mixed solution;
and S4, adding the mixed solution into the mixed base material, and stirring and mixing to obtain the C35 steam-free curing concrete for the fabricated building.
Pouring the concrete obtained by stirring in the step S4 into an assembly type building mould, vibrating and compacting through a vibrating table and an inserted vibrating rod, pulling out a core rod before entering a concrete product curing kiln after the assembly type member is subjected to overall surface folding, carrying out secondary surface folding after the concrete surface is subjected to water folding, and then conveying the mould to the curing kiln for normal temperature curing, wherein the curing temperature is 20 +/-3 ℃, and the relative humidity is more than or equal to 95%.
And after the concrete is cured for 24 hours, pushing the mold out of the curing kiln, removing the mold, hoisting the concrete after the mold removal into a curing pool, and curing for at least 7 days in water, wherein the temperature T of the curing pool is 20 +/-3 ℃, then hoisting out the concrete member, and stacking the concrete member in a concrete product stacking place.
The fabricated building C35 non-autoclaved concrete prepared by the invention meets the 20MPa form removal requirement for 24h, and the chloride ion permeability resistance, the carbonization resistance, the frost resistance and the shrinkage performance respectively meet the requirement that the chloride ion diffusion coefficient is less than or equal to 10 multiplied by 10 in 28 days-12m2The carbonization depth of 28d is less than 20mm, the loss of the dynamic elastic modulus after 250 freeze-thaw cycles is less than 20 percent, and the self-shrinkage of 80d is less than 350 multiplied by 10-6And (4) requiring.
The invention has the beneficial effects that:
(1) the method solves the problems of non-durability, high energy consumption, large shrinkage and easy cracking in the development of the concrete product industry, and adopts the nano C-S-H-PCE early strength agent to regulate the early hydration process of the cement, so as to accelerate the generation of early hydration products of the cement and the formation of microstructures; further, by optimizing the concrete mixing proportion, the non-autoclaved concrete product with low energy consumption and high durability is prepared, the heat damage and the structural defect in the product in the damp and hot curing process are effectively avoided, the overall performance of the concrete product is improved, and the later maintenance cost of the concrete product is reduced;
(2) the present application proposes a C35 curing-free concrete for fabricated buildings. The nanometer C-S-H-PCE can improve the 24H strength of C35 concrete, and when the blending amount of the fly ash is 45%, the 24H strength of the concrete is improved by 67%. The nano C-S-H-PCE can obviously improve the early strength of the C35 concrete doped with the mineral admixture without influencing the later strength; the nanometer C-S-H-PCE can cause the reduction of the chlorine ion permeation resistance of C35 concrete, but the diffusion coefficients of the chlorine ions of the concrete except for a pure cement group and FA-15% -4% are less than 10 multiplied by 10-12m2S; the incorporation of the nano C-S-H-PCE can improve the carbonization resistance of the C35 concrete 28 d; nano C-S-H-PCE can reduce dynamic elastic modulus of C35 concreteLoss of mass; the self-shrinkage of C35 concrete can be reduced by the incorporation of the nano C-S-H-PCE; according to the obtained mechanical property, durability and shrinkage property of the C35 concrete, selecting C35 non-autoclaved concrete meeting the conditions for matching and carrying out cost analysis, wherein the cost of the C35 non-autoclaved concrete is reduced to 21-34.5 yuan/m compared with the cost of the autoclaved concrete3。
Drawings
FIG. 1(a) is the effect of a nano C-S-H-PCE early strength agent on the strength of C35 fly ash concrete at 0-90 d;
FIG. 1(b) is the effect of the nano C-S-H-PCE early strength agent on the strength of C35 mineral powder concrete at 0-90 d;
FIG. 1(C) is the effect of the nano C-S-H-PCE early strength agent on the strength of C35 complex blended fly ash mineral powder concrete at 0-90 d;
FIG. 2(a) is the effect of a nano C-S-H-PCE early strength agent on the freezing resistance of C35 fly ash concrete;
FIG. 2(b) is the effect of the nano C-S-H-PCE early strength agent on the freezing resistance of C35 fine ore concrete;
FIG. 2(C) is the effect of the nano C-S-H-PCE early strength agent on the frost resistance of C35 complex fly ash-doped mineral powder concrete;
FIG. 3(a) is the effect of a nano C-S-H-PCE early strength agent on the self-shrinkage of C35 fly ash concrete;
FIG. 3(b) is the effect of nano C-S-H-PCE early strength agent on self-shrinkage of C35 fine ore concrete;
FIG. 3(C) is the effect of the nano C-S-H-PCE early strength agent on the self-shrinkage of C35 complex fly ash mineral powder concrete;
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The invention can be implemented in a number of ways different from those described herein and similar generalizations can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
The invention discloses C35 steam-free curing concrete for an assembly type building, wherein the preparation raw materials of each cubic meter of concrete in the concrete comprise the following components:
cement, 220-400 kg;
0-180kg of fly ash;
0-180kg of mineral powder;
725.8-754kg of sand;
1086-1114.2kg of stones;
16kg of nano C-S-H-PCE;
0.4-4.8kg of water reducing agent;
115.2-192kg of water.
The cement of the invention adopts P.I 52.5 Portland cement, and the specific surface area is less than or equal to 400m2Per kg, initial setting time is more than or equal to 45min, final setting time is less than or equal to 390min, MgO content is less than or equal to 5 percent, C3The content of A is less than or equal to 8 percent, the content of chloride ions is less than or equal to 0.06 percent, and the loss on ignition is less than or equal to 3 percent.
The fly ash in the invention adopts I-grade low-calcium fly ash, the screen residue of a square hole with the diameter of 45 mu m is less than or equal to 12 percent, the water requirement ratio is less than or equal to 95 percent, the ignition loss is less than or equal to 5 percent, and SO3The content is less than or equal to 3.5 percent, the content of free CaO is less than or equal to 1 percent, and the radioactivity is qualified. Fly ash is a fine solid particulate matter captured from flue gas generated in the coal burning process, and does not include ash discharged from a hearth of a coal burning facility. The fly ash is mainly from the production and supply industries of electric power and heat and other industries using coal burning facilities, and along with the development of the electric power industry, the discharge amount of the fly ash becomes one of the industrial waste residues with larger discharge amount in China. After the fly ash is doped into cement, the fly ash is dissolved in an alkaline environment, and can perform secondary reaction with calcium hydroxide generated by cement hydration to generate hydrated calcium silicate with development strength. The activity depends on the fineness of the fly ash particles. The fly ash contains a large amount of spherical glass microspheres, and after the fly ash is mixed into concrete, the fluidity of fresh concrete can be improved, the density of the fly ash is generally lower than that of cement, and under the condition of the same mass, the volume of gelled slurry in the concrete can be increased, and the working performance of the concrete can be improved. Meanwhile, the fly ash contains a large amount of fine particles, so that a water seepage channel in concrete can be cut off, and the impermeability of the concrete is improvedCan be used.
The mineral powder in the invention adopts S95 grade mineral powder, the mineral powder adopts S95 grade mineral powder, the fluidity ratio is more than or equal to 95 percent, the ignition loss is less than or equal to 3 percent, and the SO3The content is less than or equal to 4 percent, the content of chloride ions is less than or equal to 0.06 percent, the content of glass bodies is more than or equal to 85 percent, and the radioactivity is qualified. The mineral powder is a high-fineness and high-activity powder obtained by treating a fused mass mainly containing calcium aluminosilicate obtained by blast furnace ironmaking through processes of drying, grinding and the like, and is a high-quality concrete admixture and cement mixing material. Along with the improvement of the process, the fineness of the mineral powder is continuously improved, so that the activity of the mineral powder is greatly improved, and the manufacturing cost of the mineral powder is only half of that of common portland cement, so that the mineral powder can replace cement to save a large amount of cement, save energy and realize green sustainable development. The mineral powder is used as a mineral admixture in the concrete, so that the later strength is improved, the bleeding performance of the concrete is improved, and the cohesiveness of the concrete is improved.
The stone in the invention adopts basalt broken stone with 5-20mm of continuous gradation, the content of needle-shaped particles in the stone is less than or equal to 10 percent, the crushing value is less than or equal to 12 percent, the mud content is less than or equal to 1 percent, the mud block content is less than or equal to 0.5 percent, the water absorption rate is less than or equal to 1.0 percent, and the content of sulfide and sulfate is less than or equal to 0.5 percent. The sand is river sand with fineness modulus of 2.4-2.9, the mud content of the river sand is less than or equal to 1.5%, the mud block content is less than or equal to 0.8%, the sulfide and sulfate content is less than or equal to 0.5%, the chloride ion content is less than or equal to 0.02%, the fine particle content below 0.315mm is more than or equal to 10%, and the fine powder content below 0.15mm is more than or equal to 3%.
The nanometer C-S-H-PCE early strength agent adopted by the invention is milky liquid, the particle size is 50-100nm, and the water reducing rate is 25%. The doping amount of the nano C-S-H-PCE early strength agent is 2-4% of the total mass of the cement, the fly ash and the mineral powder.
The invention further comprehensively considers the aspects of workability, strength, durability, shrinkage rate and the like of the concrete, provides the preferable water-cement ratio of the concrete, and the water-cement ratio is 0.288-0.480; the dosage of the cementing material is not more than 400kg/m3(ii) a The sand rate is controlled to be about 40 percent, and is generally 40 to 45 percent.
The fabricated building C35 non-autoclaved concrete prepared according to the requirements of the invention meets the 20MPa form removal requirement for 24h and has chloride ion resistanceThe permeability, the carbonization resistance, the freezing resistance and the shrinkage performance respectively meet the condition that the chloride ion diffusion coefficient is less than or equal to 10 multiplied by 10 in 28 days-12m2The carbonization depth of 28d is less than 20mm, the loss of the dynamic elastic modulus after 250 freeze-thaw cycles is less than 20 percent, and the self-shrinkage of 80d is less than 350 multiplied by 10-6And (4) requiring.
The invention also discloses a preparation method of the C35 steam-free curing concrete for the fabricated building, which comprises the following steps.
Firstly, 400kg of cement, 0-180kg of fly ash, 0-180kg of mineral powder, 725.8-754kg of sand, 1086-1114.2kg of stones, 16-18kg of nano C-S-H-PCE and 115.2-192kg of water are provided.
And secondly, mixing the sand, the pebbles, the cement, the fly ash and the mineral powder, and stirring and dry-mixing to obtain a mixed base material. Firstly, placing sand and stones into a stirrer to be uniformly stirred, then placing a gel material comprising cement, fly ash and mineral powder into the uniformly stirred sand and stones to be fully stirred, and obtaining a mixed base material after the materials are dry-mixed.
And step three, adding the nano C-S-H-PCE early strength agent into water, and uniformly mixing to obtain a mixed solution.
Fourthly, adding the mixed base material of the mixing solution into the mixed base material, and stirring and mixing to obtain the C35 non-steam curing concrete for the prefabricated building.
Next, concrete which is stirred completely is poured into the mould, the concrete is vibrated compactly through a vibrating table and an inserted vibrating rod, and in the vibrating process, air bubbles discharged from a top cover part of the mould are wiped open by an ash knife so as to be beneficial to smoothly discharging the air bubbles in the mould. In the whole vibrating process, the conditions of fastening bolts, screws and other embedded parts of the die are observed, and if the die deforms or shifts, the vibrating is stopped immediately for repairing. After the vibration is finished, the mould is pushed away from the position of the vibration table, and the whole surface is folded, so that the surface of the concrete is flat and smooth. And then, conveying the die to a curing kiln for normal-temperature curing, wherein the curing temperature is 20 +/-3 ℃, and the relative humidity is more than or equal to 95%.
And after the concrete is cured for 24 hours, pushing the mold out of the curing kiln, removing the mold, hoisting the concrete after the mold removal into a curing pool, and curing for at least 7 days in water, wherein the temperature T of the curing pool is 20 +/-3 ℃, then hoisting out the concrete member, and stacking the concrete member in a concrete product stacking place.
Example 1
In the embodiment, the mix proportion of the C35 concrete of the prefabricated building is designed according to JGJ55-2011 'design rule for mix proportion of common concrete', and when the total amount of the cementing material is 400kg/m3When the fly ash, the single-blended fly ash of the mineral powder and the complex blending of the mineral powder respectively account for 15 percent, 30 percent and 45 percent of the total amount of the cementing material. When the fly ash and the mineral powder are mixed, the mixing amount ratio is 1: 2. The recommended formula of the assembly type building C35 non-autoclaved concrete is shown in Table 1 by comprehensively considering the factors of workability, 24-hour form removal strength, mechanical property, chloride ion corrosion resistance, carbonization resistance, frost resistance, shrinkage performance, material cost and the like. As can be seen from Table 1, the cost of non-autoclaved concrete is reduced to 21-34.5 yuan/m compared to autoclaved concrete3。
TABLE 1 recommended mix proportion of C35 non-autoclaved concrete for fabricated building
Figure BDA0002829298410000071
Example 2
The cement of this example was P.I 52.5 portland cement, the total amount of cement materials being 400kg/m3The sand rate is uniformly 40%, the doping amount of the nano C-S-H-PCE early strength agent (hereinafter abbreviated as n-C-S-H-PCE) is 4%, and the influence of adding the n-C-S-H-PCE on the C35 non-autoclaved concrete for the fabricated building for 24H is shown in Table 2.
TABLE 2 influence of n-C-S-H-PCE on the 24H compressive strength (MPa) of the fabricated building C35 non-autoclaved concrete
Figure BDA0002829298410000072
As shown in Table 2, the strength of the C35 concrete increased and then decreased for 24h as the amount of fly ash added increased. After the n-C-S-H-PCE is doped, when the mixing amount of the fly ash is 15%, 30% and 45%, the strength of the concrete for 24 hours is respectively improved by 18%, 1% and 67%, and when the mixing amount of the fly ash is 45%, the strength of the C35 concrete is improved to the highest extent; the strength change of the C35 concrete for 24H is small along with the increase of the mixing amount of the mineral powder, after the n-C-S-H-PCE is mixed, when the mixing amount of the mineral powder is 15%, 30% and 45% respectively, the strength of the concrete for 24H is improved by 10.4%, 18.5% and 25.1%, and the strength of the concrete for 24H is improved by the n-C-S-H-PCE along with the increase of the mixing amount of the mineral powder; with the increase of the mixing amount of the fly ash and the mineral powder, the strength of the C35 concrete is reduced for 24 hours, and the fly ash mainly plays a main role. After the n-C-S-H-PCE is doped, when the doping amount is 15%, 30% and 45%, the strength of the concrete is increased by 27.9%, 19.0% and 20.0% respectively after 24 hours. The above results show that n-C-S-H-PCE can significantly improve the 24H strength of C35 concrete doped with mineral admixtures.
As can be seen from fig. 1(a) to 1(C), when no n-C-S-H-PCE is added, the compressive strength of the concrete 1d is the greatest at a fly ash content of 30%, and the compressive strengths of the concretes 3d, 7d, 28d, and 90d increase with increasing fly ash content as the age increases. When the mixing amount of the fly ash is 45%, the early strength is improved relatively high; when the mixing amount of the mineral powder is 15%, the strength of the concrete at the 1d age and the 3d age is increased, and when the mixing amount is 30% and 45%, the strength of the concrete at the 1d age and the 3d age is reduced, so that excessive mineral powder replaces cement, the pozzolanic effect of the mineral powder is relatively slow, and the early strength of the concrete is reduced. After the mineral powder is doped into the concrete from the age of 7d to the age of 90d, the strength of the concrete is improved; when the fly ash and the mineral powder are mixed, the strength of the concrete 1d and 3d is reduced, because the early fly ash and the mineral powder only play a role in filling. From 7d, the strength of the concrete is continuously increased along with the increase of the mixing amount and the age, mainly because the later hydration of the fly ash and the mineral powder is more sufficient, and the later strength of the concrete is improved. After the n-C-S-H-PCE is doped, the strength of 1d, 3d and 7d of the mineral concrete can be obviously improved, and the later strength of the mineral concrete is not influenced.
Example 3
The cement of this example was P.I 52.5 Portland cement, the total amount of the cementing material being400kg/m3The sand rate is uniformly 40%, the doping amount of n-C-S-H-PCE is 4%, and the influence of the addition of n-C-S-H-PCE on the C35 non-curing concrete chloride ion diffusion system for the fabricated building is shown in Table 3.
TABLE 3 chloride ion diffusion coefficient (10) of n-C-S-H-PCE for fabricated building C35 non-autoclaved concrete-12m2Influence of/s)
Figure BDA0002829298410000081
As shown in Table 3, the permeability coefficient of chloride ions of C35 concrete is decreased with the increase of the amount of fly ash, and the resistance to chloride ion penetration of concrete is gradually improved, which indicates that the impermeability of concrete is improved by the addition of fly ash. Compared with cement, the fly ash has smaller particle size, so that the compactness of the powder can be improved by doping the fly ash, and the cement can fully react to generate a hydration product by the water-cement ratio of 0.48, so that the structure of the set cement is more compact. With the increase of the mixing amount of the mineral powder, the chloride ion permeability coefficient of the C35 concrete is reduced, and the chloride ion permeation resistance of the concrete is enhanced. The reason is that the mineral powder can be hydrated with the Ca (OH) formed when the cement is hydrated2Reaction, consumption of Ca (OH)2Can promote the cement to be further hydrated to generate more C-S-H gel, so that Ca (OH)2The crystal grains become small, the microstructure of the concrete is improved, the concrete is more compact, and the chloride ion permeability resistance of the concrete is improved. In addition, compared with the non-doped mineral admixture, the permeability coefficient of the concrete chloride ions of the double-doped fly ash and the mineral powder is smaller, which shows that the doped fly ash and the mineral powder are also beneficial to improving the permeability resistance of the concrete chloride ions, and the reason is that the fly ash and the mineral powder exert different volcanic ash effects, so that the internal pores of the concrete are reduced, and the permeability resistance of the concrete is improved.
After the n-C-S-H-PCE is doped, the chloride ion diffusion coefficient of the C35 concrete is increased, so that the chloride ion permeation resistance of the concrete is reduced. Mainly because the n-C-S-H-PCE can promote the early hydration of the cement to form a compact structure, and because the water-gel ratio of the C35 concrete is higher, free water occupies the waterThe formation of compact spaces results in large porosity and reduced resistance to chloride ion penetration. However, the concrete chlorine ion diffusion coefficients except for the pure cement group and the FA-15% -4% group were all less than 10X 10-12m2/s。
Example 4
The cement of this example was P.I 52.5 portland cement, the total amount of cement materials being 400kg/m3The sand rate is uniformly 40%, and the doping amount of n-C-S-H-PCE is 4%. The effect of n-C-S-H-PCE on the carbonation depth of the fabricated building C35 non-autoclaved concrete 28d is shown in Table 4.
TABLE 4 influence of n-C-S-H-PCE on the carbonation depth (mm) of the fabricated building C35 non-autoclaved concrete 28d
Figure BDA0002829298410000091
As shown in Table 4, the addition of n-C-S-H-PCE in the same water-cement ratio reduced the carbonation depth of the 28d concrete, increased the anti-carbonation capability, with the extent of the carbonation depth reduction being 3% -11%, which is mainly due to the increase of the content of the C-S-H gel of the carbonizable material.
When the doping amount of the n-C-S-H-PCE is the same, the carbonization depth is gradually increased along with the increase of the doping amount of the mineral admixture, and the carbonization resistance is reduced. For example, after the n-C-S-H-PCE is added, the carbonization depth of 30 percent of the mineral powder at 28d is 4.96mm, and the carbonization depth of 45 percent of the mineral powder at 28d is 5.48 mm. This is because, when the mineral admixture replaces cement, the cement quality is reduced, and the cement hydrates to produce carbonizable substances Ca (OH)2The content is reduced, and the content of the C-S-H gel of the carbonizable substances generated by the secondary hydration reaction of the mineral substances is also reduced, finally resulting in the reduction of the anti-carbonization capability of the concrete. Meanwhile, the carbonization depth of the concrete with different mixing ratios is continuously increased along with the increase of the age. In addition, the influence of the three minerals on the carbonization performance of the concrete is analyzed, so that the carbonization depth of the concrete is the lowest when the mineral powder is added, namely the carbonization resistance is the best.
Example 5
Freeze-thaw damage is an important index for evaluating the durability of concrete, and the fabricated building C35 non-autoclaved concrete must have good durability while satisfying early strength.
The cement of this example was P.I 52.5 portland cement, the total amount of cement materials being 400kg/m3The sand rate is uniformly 40%, and the doping amount of n-C-S-H-PCE is 4%. The effect of n-C-S-H-PCE on the relative dynamic elastic modulus of fabricated building C35 non-autoclaved concrete after 250 freeze-thaw cycles is shown in FIGS. 2(a) to 2 (C).
When the doping amount of the n-C-S-H-PCE is 0%, the relative dynamic elastic modulus of the concrete with the doping amount of the fly ash of 30% is reduced most rapidly, and the faster the dynamic elastic modulus is reduced along with the increase of the doping amount of the fly ash, the worse the frost resistance of the concrete is. When the n-C-S-H-PCE is doped, the relative dynamic elastic modulus of the concrete with the 30 percent of fly ash content becomes relatively flat, and the relative dynamic elastic modulus loss of the concrete with the 15 percent of fly ash content is relatively reduced. When the number of freeze-thaw cycles reaches 100, the relative dynamic elastic modulus of the fly ash with the doping amount of 15 percent and 30 percent is respectively improved by 10.8 percent and 50.0 percent compared with the condition without adding n-C-S-H-PCE. The results show that the frost resistance of the concrete doped with the fly ash can be improved by doping the n-C-S-H-PCE.
When the doping amount of the n-C-S-H-PCE is 0%, the relative dynamic elastic modulus of the concrete with the 30% of mineral powder doping amount is changed more smoothly than that of the concrete with the 15% of mineral powder doping amount along with the increase of the number of freeze-thaw cycles. After the n-C-S-H-PCE is doped, when the number of freeze-thaw cycles is 250, the dynamic elastic modulus of the concrete doped with 15% and 30% of the mineral powder is 85.17% and 90.2% respectively, and the concrete is obviously improved compared with the concrete not doped with the n-C-S-H-PCE. The n-C-S-H-PCE can promote the hydration of the mineral powder and improve the compactness of the concrete, and the secondary hydration of the mineral powder can also improve the compactness and the frost resistance of the concrete.
When the doping amount of the n-C-S-H-PCE is 0%, the relative dynamic elastic modulus curve with the doping amount of 30% is slowly reduced compared with the 15% doping amount along with the increase of the number of freeze-thaw cycles. After the n-C-S-H-PCE is added, the dynamic elastic modulus curve of the concrete becomes more gentle, and when the number of freeze-thaw cycles is 250, the frost resistance of the concrete can be obviously improved by adding the nano C-S-H-PCE.
Example 6
The cement of this example was P.I 52.5 portland cement, the total amount of cement materials being 400kg/m3The sand rate is uniformly 40%, and the doping amount of n-C-S-H-PCE is 4%. The performance of the n-C-S-H-PCE on the self-shrinkage performance of the fabricated building C35 non-autoclaved concrete is shown in FIGS. 3(a) to 3 (b).
As can be seen, the self-shrinkage of the concrete is reduced after the n-C-S-H-PCE is doped. This is because the addition of n-C-S-H-PCE promotes the hydration of cement in the concrete, especially promotes the hydration of the cementing material within 24 hours, the framework is formed earlier, and the elastic modulus of the concrete is relatively large. With the progress of hydration of the cementing material, the water consumption of the concrete doped with the n-C-S-H-PCE is less than that of the concrete not doped with the n-C-S-H-PCE, the reduction of the relative humidity in the concrete is slower, and the shrinkage driving force is relatively smaller according to the Kelvin law. In conclusion, the concrete doped with the n-C-S-H-PCE has small contraction driving force compared with the concrete of a comparison group, but has larger elastic modulus, so the self-contraction is smaller.
In view of the above, it is desirable to provide,
(1) the n-C-S-H-PCE can improve the 24H strength of the C35 concrete, and when the blending amount of the fly ash is 45%, the strength of the C35 concrete is improved to the highest extent in 24H. The n-C-S-H-PCE can improve the strength of the fly ash concrete 1d, 3d and 7 d. The n-C-S-H-PCE can improve the early strength of the ore powder concrete; when the compound doping amount is 15%, 30% and 45%, the strength of the concrete for 24h is increased by 27.9%, 19.0% and 20.0% respectively. The n-C-S-H-PCE can obviously improve the early strength of the C35 concrete mixed with the mineral admixture and does not influence the later strength thereof.
(2) The n-C-S-H-PCE can cause the reduction of the chlorine ion penetration resistance of C35 concrete, but the diffusion coefficients of the chlorine ions of the concrete except for the pure cement group and the FA-15% -4% group are less than 10 multiplied by 10-12m2S; the incorporation of the n-C-S-H-PCE can reduce the total carbonation depth of the C35 concrete 28 d; the n-C-S-H-PCE can reduce the loss of the dynamic elastic modulus of C35 concrete, and the relative dynamic elastic modulus of 15% and 30% fly ash concrete is improved by 10.85% and 50.06% when the freeze-thaw cycle is performed for 100 times.When the number of freeze-thaw cycles is 250, the dynamic elastic modulus of 15% and 30% of the fine concrete is 85.2% and 90.2%, respectively.
(3) The incorporation of n-C-S-H-PCE can reduce the self-shrinkage of C35 concrete.
(4) According to the obtained mechanical property, durability and shrinkage property of the C35 concrete, selecting C35 non-autoclaved concrete meeting the conditions for matching and carrying out cost analysis, wherein the cost of the C35 non-autoclaved concrete is reduced to 21-34.5 yuan/m compared with the cost of the autoclaved concrete3。
The steam-free curing C35 concrete for the fabricated building and the preparation method thereof provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (6)

1. The C35 non-steam curing concrete for the fabricated building is characterized in that the concrete is prepared from the following raw materials per cubic meter:
cement, 220-400 kg;
0-180kg of fly ash;
0-180kg of mineral powder;
725.8-754kg of sand;
1086-1114.2kg of stones;
16kg of nano C-S-H-PCE;
0.4-4.8kg of water reducing agent;
115.2-192kg of water.
2. The C35 steam-free curing concrete for fabricated buildings according to claim 1, wherein the cement is P.I 52.5 Portland cement with specific surface area of 400m or less2Per kg, initial setting time is more than or equal to 45min, final setting time is less than or equal to 390min, MgO content is less than or equal to 5 percent, C3The content of A is less than or equal to 8 percent, the content of chloride ions is less than or equal to 0.06 percent, and the ignition loss is less than or equal to 3 percent; the coal ash is I-grade low-calcium fly ash, the screen residue of a square hole with the diameter of 45 mu m is less than or equal to 12 percent, the water demand ratio is less than or equal to 95 percent, the loss on ignition is less than or equal to 5 percent, and SO3The content is less than or equal to 3.5 percent, and the content of free CaO is less than or equal to 1 percent; the mineral powder is S95 grade mineral powder, the fluidity ratio is more than or equal to 95 percent, the ignition loss is less than or equal to 3 percent, and the SO3The content is less than or equal to 4 percent, the content of chloride ions is less than or equal to 0.06 percent, and the content of glass bodies is more than or equal to 85 percent;
the stone adopts basalt broken stone with 5-20mm of continuous gradation, the content of needle-shaped flaky particles in the stone is less than or equal to 10 percent, the crushing value is less than or equal to 12 percent, the mud content is less than or equal to 1 percent, the mud block content is less than or equal to 0.5 percent, the water absorption rate is less than or equal to 1.0 percent, and the content of sulfide and sulfate is less than or equal to 0.5 percent; the sand is river sand with fineness modulus of 2.4-2.9, the mud content of the river sand is less than or equal to 1.5%, the mud block content is less than or equal to 0.8%, the sulfide and sulfate content is less than or equal to 0.5%, the chloride ion content is less than or equal to 0.02%, the fine particle content below 0.315mm is more than or equal to 10%, and the fine powder content below 0.15mm is more than or equal to 3%.
3. The coastal subway segment C50 steam-free curing concrete as claimed in claim 1, wherein said nano C-S-H-PCE early strength agent is milk white liquid, particle size is 50-100nm, water reducing rate is not less than 25%, and the mixing amount of nano C-S-H-PCE early strength agent is 2% -4% of the total mass of cement, fly ash and mineral powder.
4. The C35 steam-free curing concrete for fabricated building as claimed in claim 1, wherein the water-to-cement ratio of the concrete is at most 0.48, and the total amount of cement, fly ash and mineral powder is not more than 400kg/m3Sand ratio of40％-45％。
5. A method for preparing C35 non-steam curing concrete for prefabricated buildings according to any one of claims 1 to 4, wherein the method comprises the following steps:
s1, providing 400kg of cement, 0-180kg of fly ash, 0-180kg of mineral powder, 725.8-754kg of sand, 1086-1114.2kg of stones, 16-18kg of nano C-S-H-PCE and 115.2-192kg of water;
s2, mixing sand, pebbles, cement, fly ash and mineral powder, and stirring for dry mixing to obtain a mixed base material;
s3, adding the nano C-S-H-PCE into water, and uniformly mixing to obtain an additive;
and S4, adding the mixed base material into the additive, and stirring and mixing to obtain the C35 steam-free curing concrete for the fabricated building.
6. The method as claimed in claim 5, wherein the concrete obtained by stirring in step S4 is poured into a mold, compacted by vibration of a vibration table and an inserted vibrating rod, after the whole surface of the assembled member is finished, the core rod is pulled out before the assembled member enters the curing kiln for the concrete product, after the surface of the concrete is hydrated, the surface is secondarily finished, and then the mold is conveyed to the curing kiln for normal temperature curing, wherein the curing temperature is 20 +/-3 ℃, and the relative humidity is more than or equal to 95%;
and after the concrete is cured for 24 hours, pushing the mold out of the curing kiln, removing the mold, hoisting the concrete member after the mold is removed into a curing pool, and curing for at least 7 days in water, wherein the temperature T of the curing pool is 20 +/-3 ℃, then hoisting the concrete member out, and stacking the concrete member in a concrete product stacking place.
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