CN115124302A - Low-temperature-rise anti-cracking corrosion-resistant large-volume concrete preparation technology and cooling-pipe-free construction method - Google Patents
Low-temperature-rise anti-cracking corrosion-resistant large-volume concrete preparation technology and cooling-pipe-free construction method Download PDFInfo
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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
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- C04B28/04—Portland cements
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D21/00—Methods or apparatus specially adapted for erecting or assembling bridges
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
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Abstract
The invention discloses a preparation technology of low-temperature-rise anti-cracking corrosion-resistant large-volume concrete and a construction method without cooling water pipes; comprises the following steps: a low temperature rise and low shrinkage mass concrete preparation technology; b: the anti-cracking performance of the mass concrete is improved; c: the corrosion resistance of the mass concrete is improved; d: the special crack control technology for the mass concrete construction quality. By adopting the high-doped mineral admixture mixing proportion optimization design based on the theory of dense accumulation theory, the ultra-dispersed, high-efficiency water reducing, slump retaining, slow setting and shrinkage inhibiting composite admixture is developed, the hydration temperature rise inhibitor is doped to inhibit the temperature rise, and the modified polypropylene temperature rise shrinkage type fiber is used for improving the crack resistance, so that the low-temperature-rise crack-resistant corrosion-resistant mass concrete which adopts the common cement to replace the medium and low hydration heat special cement can be prepared, and the low-temperature-rise crack-resistant mass concrete has the characteristics of good plasticity and toughness, low cement consumption, controllable temperature rise range, high crack resistance safety coefficient, excellent durability and the like.
Description
Technical Field
The invention relates to a low-temperature-rise anti-cracking and corrosion-resistant large-volume concrete, in particular to a preparation technology of the low-temperature-rise anti-cracking and corrosion-resistant large-volume concrete and a construction method without cooling water pipes.
Background
With the rapid development of social and economic construction, the gravity center of the construction of China gradually emphasizes remote mountain areas, western dangerous mountain areas, turbulent rivers, lakes and seas and other severe environments, the requirements on concrete materials are continuously improved, and the sizes of the members are continuously increased, so that the large-volume concrete members are widely applied to engineering construction, such as bridge bearing platforms and anchorages, arch bridge arch supports and arch rings, tower column solid sections, high-rise building bottom plates, large-scale conversion beams, ultra-thick wall bodies and other large-volume concrete structures. However, the concrete material has poor heat-conducting property and large concrete size, heat released by hydration of cement in the early stage of pouring is not accumulated and is not dispersed, the internal temperature is higher than the surface temperature of the concrete to generate temperature difference stress, and when the temperature difference stress is higher than the tensile strength of the concrete, cracks are generated to influence the bearing capacity and the durability of the structure. With the increasing requirement for the service life of bridges, the tighter the crack control, the more important the temperature control is to the large volume of concrete.
At present, the commonly used temperature crack control technical measures for large-volume concrete at home and abroad mainly comprise:
(1) method for reducing heat insulation temperature rise of large volume concrete by adopting medium and low heat cement
By adopting the special cement with low hydration heat release, medium and low hydration heat, and adding the mineral admixture and the retarding water reducing agent, the hydration temperature rise of the concrete with large volume can be reduced, the temperature difference between the inside and the outside can be reduced, and the concrete cracking caused by temperature stress can be prevented. However, medium and low hydration heat cements belong to non-universal portland cements, and require adjustment of production processes in cement plants for special production, so that the production cost is high. The daily required cement amount is large, the construction period is short, the operation time is centralized in large-scale water conservancy and hydropower engineering, the special customized production can be realized, the large-volume concrete engineering amount in bridge engineering is less, the construction period is long, the operation time is dispersed, the daily required cement amount is less, the customized production is not convenient, and the purchase is difficult. Therefore, the cost for preparing the large-volume concrete for bridge engineering by adopting the medium and low hydration heat cement and the mineral admixture is high, and the realization difficulty is large.
(2) Control the temperature of the mould and pre-embed the cooling water pipe
The main technical measures for controlling the concrete temperature in the construction and pouring process comprise controlling the mold-entering temperature and pre-burying a cooling water pipe. However, there are the following problems:
firstly, a water mixing and ice adding measure is mostly adopted for controlling the mold-entering temperature, but the ice making difficulty is high in remote mountainous areas, the ice adding efficiency is low, partial concrete bleeding and segregation are easily caused by ice block melting, meanwhile, the arrangement cost of the cooling water pipe embedding technology is high, cooling water is easy to leak, the concrete quality is influenced, and the phenomenon of slurry pressing incompact exists;
secondly, water resources are generally deficient in high altitude areas, and cooling by introducing cooling water is difficult to realize: even if water sources exist, most of the water is mountain snow melting ice water, the water temperature is low, heating and temperature adjusting equipment needs to be additionally arranged when the water is used as cooling water, so that the difference between the temperature of water entering a cooling water pipe and the maximum temperature of the mass concrete is not more than 25 ℃, the temperature difference of water inlet and outlet is less than 10 ℃, the water temperature control difficulty is high, the cost is high, and the mass concrete is easy to crack when the water is not controlled;
the lack of fresh water in the corrosion environment of ocean, bittern and sulfate causes corrosion of a cooling water pipe by adopting a local water source, and the fresh water needs to be remotely conveyed, so that the implementation of reducing temperature rise by fresh water cooling is difficult and the cost is higher;
(3) by using phase-change energy-storage concrete
The phase-change material has the advantages of large energy storage density, small volume expansion rate, approximate isothermy maintenance in the heat absorption or heat release process, and the like. The phase-change energy storage concrete prepared by the phase-change material can effectively reduce the internal temperature rise rate of the concrete and delay the occurrence time of a temperature peak. At present, the phase change energy storage concrete technology mainly adopts a paraffin phase change system, bentonite and decanoic acid phase change aggregates, an alkanoic acid phase change microcapsule material and the like. However, the phase change energy storage concrete has high technical cost, complex preparation process, reduced mechanical properties, fewer standard specifications of related construction control and great difficulty in popularization and application.
Aiming at the defects of common temperature crack control technical measures for mass concrete at home and abroad, the inventor develops the following four key technologies through research and a large amount of engineering application for more than 20 years: A. the control standard and the preparation technology of the raw materials of the low-temperature-rise low-shrinkage large-volume concrete; B. the anti-crack performance of mass concrete is improved; C. the corrosion resistance of the mass concrete is improved; D. the large volume concrete has no cooling water pipe and is applied in crack control.
The invention integrates the technologies, and forms a preparation method of low-temperature-rise anti-cracking and corrosion-resistant large-volume concrete and a construction method without cooling water pipes. Compared with the traditional large-volume concrete with cooling water pipes, the large-volume concrete can be prepared by replacing special cement with medium and low hydration heat with common cement, so that the large-volume concrete for bridge engineering has low temperature rise, high crack resistance and excellent durability, the cracking risk is reduced under the condition of canceling the cooling water pipes, temperature cracks are avoided, the durability of the large-volume concrete engineering is improved, the construction period is shortened, and the construction cost is reduced. The method solves the technical problems that large-volume concrete is difficult to arrange cooling water pipes and the durability is poor in severe environments such as large temperature difference, water shortage, high erosion and the like in western mountain areas, is successfully applied to multiple engineering examples, and has important engineering practical significance.
Disclosure of Invention
Therefore, in order to solve the above-mentioned disadvantages, the present invention provides a method for preparing a low-temperature-rise low-shrinkage bulk concrete and a method for controlling cracking without cooling water pipe construction. The invention aims to: aiming at the technical problems of large temperature difference, water shortage, high erosion and the like in western mountainous areas, difficulty in arrangement of cooling water pipes in large-volume concrete, poor durability and the like in other severe environments in the prior art, the invention provides a preparation method of low-temperature-rise anti-cracking and anti-corrosion large-volume concrete and a construction method of a cooling-water-free pipe thereof.
The invention is realized in this way, construct a low temperature rise low shrinkage large volume concrete preparation method, characterized by, mainly by compounding of the compound admixture, mix proportion design method, optimization method, hydration temperature rise inhibit the technology to make up of mix proportion parameter of the high mineral admixture;
the composite additive is a special additive for large-volume concrete, which is prepared by introducing a high-quality air entraining agent, a defoaming agent, a viscosity modifier, a polyether shrinkage-reducing additive, a glue reducer and other water reducer additives into a super-dispersing, high-water-reducing and slow-release slump-retaining polycarboxylic superplasticizer;
the design method of the mixing proportion of the high mineral admixture is designed by adopting a maximum dense estimated accumulation method, and the dosage of concrete cement and the adiabatic temperature rise are reduced to the maximum extent under the condition of ensuring that the concrete has excellent workability, mechanical property, volume stability and hot blood performance;
the optimization method of the mix proportion parameters is that on the basis of the design of the mix proportion of the mineral-doped admixture, a design test optimizes and adjusts the mix proportion parameters such as the concrete water-cement ratio, the sand rate, the grain size and the gradation of coarse and fine aggregates, the using amount of cementing materials, the admixture mixing amount and the like, and the concrete mix proportion with the minimum cement using amount, low adiabatic temperature rise and guaranteed strength is preferably selected by combining test data;
the hydration temperature rise inhibition technology is that 1-3 recommended mixing ratios are optimized on the basis of the mixing ratio design, and a hydration temperature rise inhibitor with the use amount of 0.1-0.3% of a cementing material is added to further reduce the hydration temperature rise.
The method for preparing low temperature-rising low shrinkage mass concrete according to claim 1, wherein 1 to 5kg/m can be added to C50 and above mass concrete with higher hydration heat or special crack-resistant parts with higher requirement for crack-resistant performance 3 The temperature rise shrinkage type fiber reinforced concrete has the advantages of crack resistance and durability.
The method for preparing low temperature-rising low shrinkage large-volume concrete according to claims 1-2, characterized in that for the large-volume concrete in western, ocean and environments containing chloride ions, sulfate ions and other aggressive ions, besides the above technical measures, 3% -8% of the amount of cementitious material used for the corrosive ion transmission inhibitor (hydrophobic compound pore plug) can be added to improve the corrosion resistance and mechanical properties of the large-volume concrete in the environments of corrosive and ocean service.
The method for preparing low temperature rise low shrinkage large volume concrete according to claims 1-3, wherein common 42.5 grade cement can be used for replacing cement with medium and low hydration heat for the large volume concrete.
A method for controlling crack of a cooling-water-free pipe in construction by using the large-volume concrete as claimed in any one of claims 1 to 3, which is characterized by mainly comprising a raw material control standard, a construction temperature control standard, a construction quality control method, construction pouring quality and warm and wet maintenance measures;
the raw material control standard is as follows: (1) cement: the fineness of the cement is preferably less than 0.04 mm; the use temperature is less than or equal to 60 ℃; mineral admixture is adopted to replace cement; the grade of the cement can be improved to reduce the consumption of the cement; the later 60d or 90d age intensity can be used to replace the design intensity of the 28d age;
(2) mineral admixture: the use temperature is less than or equal to 40 ℃;
(3) coarse aggregate: the coarse aggregate adopts continuous graded broken stone, and the maximum grain size is less than or equal to 31.5 mm; the apparent density of the coarse aggregate is more than or equal to 2600kg/m 3 The mud content is less than or equal to 1.0 percent, and the crushing value is less than or equal to 10 percent; the using temperature is 5 ℃ lower than the ambient temperature;
(4) fine aggregate: medium sand is adopted, the mud content is less than or equal to 1 percent, and the fineness modulus is 2.6-3.0; the using temperature is 5 ℃ lower than the ambient temperature; other indexes need to meet the specification;
(5) additive: the use temperature is less than or equal to 30 ℃;
the construction temperature control standard is as follows: the concrete pouring temperature is preferably 10-32 ℃; the temperature rise of the concrete is less than or equal to 50 ℃; the internal temperature of the concrete is less than or equal to 70 ℃; the temperature difference between the inside and the outside of the concrete is less than or equal to 25 ℃; the cooling rate of the concrete is less than or equal to 2.0 ℃/d; the temperature difference between the newly poured concrete and the connected hardened concrete surface or rock is less than or equal to 25 ℃; the temperature of curing water sprayed and injected on the surface of the concrete is lower than the temperature difference of the surface of the concrete and is less than or equal to 15 ℃; the difference between the average temperature of the concrete section and the ambient temperature during the concrete construction of the post-cast strip is less than or equal to 15 ℃; when the large-volume concrete is constructed in layers, the construction interval is generally 7 d;
the construction quality control method comprises the following steps: the storage capacity and the crushing capacity of the ice blocks are improved; monitoring of aggregate moisture content is enhanced, mixing water consumption is adjusted in time, and water-cement ratio and slump are controlled to avoid segregation to generate floating slurry; the mixing capability of concrete is increased, and the mixing amount is kept to be more than or equal to 150m 3 Finishing pouring within 45 hours; when concrete is poured in a layered mode for the last 50cm, the initial setting time of the concrete is shortened to be within 10h, and therefore the concrete can be conveniently chiseled early to store water; accumulated water in the tank car is drained in advance; the charging of the concrete tank car is not lower than 6m 3 ；
The construction pouring quality and warm and wet maintenance measures are as follows: during concrete pouring, the material is forbidden to be distributed from the center to the edge, slurry is prevented from being driven to the edge, the material is distributed by a pump truck at the edge and is tightly close to the template, and the concrete is poured in a segmented and layered mode; reinforcing corners and vibrating; preferably, an aqueous release agent or a release paint is used; the mixing time of the temperature rise shrinkage fiber is prolonged by 40 to 60 seconds; spraying and cooling the bin surface; and early water storage and maintenance.
The invention has the following advantages:
(1) low temperature rise and low shrinkage: based on the design principle that a dense accumulation body is formed by a cementing material and coarse and fine aggregates so as to improve the mechanical property and the durability of the concrete, the admixture with composite functions of ultra-dispersed cement particles, high-efficiency water reduction, slump retention and retardation, shrinkage reduction and the like and raw materials of 42.5-grade common cement, fly ash, mineral powder, machine-made sand, broken stone and the like are adopted, and the prepared C30-C50 large-volume concrete reduces the cement consumption by more than 10 percent on the premise of meeting the mechanical property and the durability of the design requirement, thereby realizing the low-temperature-rise and low-shrinkage performance of the concrete; aiming at the large-volume concrete with C60 and above or the part with special crack resistance requirement, hydration temperature rise inhibitor can be doped, the hydration rate of cement can be effectively inhibited, the peak value of the hydration heat release rate is reduced by more than 50%, and the early hydration heat release process is effectively regulated and controlled.
(2) High crack resistance: the construction method realizes the performances of low volume shrinkage, strong crack resistance, high toughness and the like of the mass concrete by doping the temperature-rising shrinkage type fibers, thereby obviously reducing the difficulty of crack control in the construction process and reducing the cracking risk of the mass concrete.
(3) Excellent resistance to seawater and bittern erosion: for the large-volume concrete under high erosion and other severe environments, besides the technical measures of combining the design of high-doped mineral admixture, adopting a water-reducing shrinkage-reducing additive, doping temperature-rising shrinkage fibers, a hydration temperature-rising inhibitor and the like, the micro structure of the large-volume concrete can be regulated and controlled by adopting an aggressive ion transmission inhibitor, so that the corrosion resistance of the large-volume concrete is greatly improved.
(4) Constructing concrete with the large volume of C30-C60 without cooling water pipes: the low-temperature-rise low-shrinkage high-crack-resistance high-toughness large-volume concrete prepared by the method combines the technical measures of construction quality control of the large-volume concrete prepared by the method, so that the tensile strength in the concrete is greater than the temperature difference stress, the crack-resistance safety coefficient is high, the hydration temperature rise range is controllable, and the C30-C60 large-volume concrete is not arranged with cooling water pipes.
(5) High-quality and quick construction: the large-volume concrete prepared by the method has the characteristics of low hydration temperature rise, low volume shrinkage, excellent anti-cracking capability, good toughness and the like, the conventional construction equipment and quality control technology are adopted together with effective temperature control technical measures, the anti-cracking and temperature control capabilities of the large-volume concrete component are improved, the conditions of delayed maintenance measures, unfavorable construction control and the like are prevented, the high fault tolerance rate is realized, and meanwhile, the arrangement of cooling water pipes can be cancelled, so that the high-quality and quick construction of the large-volume concrete is ensured.
(6) The economic benefit is remarkable: the construction method directly reduces the cost of large-volume concrete cement, the cost of arranging cooling water pipes, the construction period and the like, also improves the plasticity and the toughness of the concrete, obviously improves the fatigue resistance and the durability of the concrete, finally prolongs the service life of the structure, saves the reinforcing and maintaining cost within the service life, and simultaneously improves the safety of the structure.
(7) And (3) improving ecological benefits: the method relates to the technical measures of greatly reducing the consumption of cement, eliminating cooling water pipes and the like, reduces the environmental pollution caused by producing materials such as cement, steel and the like and laying the cooling water pipes during construction, does not need to exploit cooling water sources, and improves the ecological benefits of engineering.
Drawings
FIG. 1 example 1 volume stability comparison test of low temperature rising volume concrete and ordinary volume concrete
FIG. 2 example 2 volume stability comparison test of low temperature rise crack resistance mass concrete and low temperature rise mass concrete
FIG. 3 example 3 volume stability comparison test of low temperature rise corrosion resistant mass concrete and ordinary mass concrete FIG. 4-FIG. 5 are schematic operation flow diagrams.
Detailed Description
The present invention will be described in detail with reference to fig. 1 to 5, and the technical solutions in the embodiments of the present invention will be clearly and completely described, 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.
The invention provides a preparation method of low-temperature-rise anti-cracking and anti-corrosion large-volume concrete and a construction method of a cooling-water-pipe-free concrete through improvement, the low-temperature-rise anti-cracking and anti-corrosion large-volume concrete can be prepared by adopting common cement to replace special cement with medium and low hydration heat without arranging cooling water pipes, and the low-temperature-rise anti-cracking and anti-corrosion large-volume concrete meets the application requirements of good plasticity and toughness, low cement consumption, controllable temperature rise range, high anti-cracking safety coefficient and excellent durability.
In order to achieve the purpose, the invention adopts the technical scheme that:
A. low temperature rise and shrinkage large volume concrete preparation technology
(1) The invention provides a preparation requirement of a low-temperature-rise large-volume concrete composite additive, which is characterized by comprising the following steps of:
the method comprises the steps of preparing a super-dispersed cement particle, a high-efficiency water-reducing, shrinkage-inhibiting and slow-release slump-retaining additive by adopting a super-dispersed, high-water-reducing and slow-release slump-retaining polycarboxylate superplasticizer, introducing a high-quality air entraining agent, a defoaming agent and a viscosity modifier for viscosity control, and assisting polyether shrinkage-reducing additives for compensating shrinkage; the cement dosage can be further reduced by compounding the gel reducer for the large-volume concrete with high hydration temperature.
(2) The invention provides a mix proportion design method of a large-volume concrete high-mineral admixture, which is characterized by comprising the following steps of:
the mix proportion design method adopts a maximum dense framework stacking method, adjusts the mixing amount of mineral admixtures such as fly ash, mineral powder, active stone powder, silica fume and the like, takes the working performance, the mechanical property and the thermal property of the concrete required by design as evaluation indexes, and optimally selects the concrete mix proportion with the minimum cement consumption, low adiabatic temperature rise and ensured strength by combining test data.
(3) The invention provides a method for optimizing the mix proportion parameters of mass concrete, which is characterized by comprising the following steps: on the basis of the design of the mix proportion of the high-mineral-doped admixture, the mix proportion parameters such as the concrete water-cement ratio, the sand rate, the grain size and gradation of coarse and fine aggregates, the use amount of a cementing material, the admixture mixing amount and the like are optimized and adjusted by taking the concrete working performance, the mechanical property and the thermal property required by the design as evaluation indexes, and the mix proportion of the concrete with the minimum cement use amount, low adiabatic temperature rise and guaranteed strength is preferably selected by combining with test data.
(4) The invention provides a method for inhibiting hydration temperature rise by mass concrete, which comprises the following steps: for high-grade concrete with higher hydration heat or special anti-cracking parts with higher anti-cracking performance requirements, 1-3 recommended mixing ratios can be optimized on the basis of the design of the mixing ratio, and a hydration temperature rise inhibitor with the use amount of 0.1-0.3% of the cementing material is added to further reduce the hydration temperature rise.
B. The technology for improving the crack resistance of the mass concrete comprises the following steps: furthermore, 1-5 kg/m can be mixed into the concrete with high hydration heat of C50 and above large volume or special anti-cracking parts with high anti-cracking performance requirement 3 The temperature rise shrinkage type fiber reinforced concrete has the advantages of crack resistance and durability.
C. The technology for improving the corrosion resistance of the mass concrete comprises the following steps: furthermore, for the mass concrete in western parts, oceans and environments containing chloride ions, sulfate ions and other aggressive ions, in addition to the technical measures, 3% -8% of the amount of cementing materials of aggressive ion transmission inhibitors (hydrophobic compound pore plugs) can be added, so that the corrosion resistance and the mechanical property of the mass concrete in the aggressive and marine service environments are improved, and the technical index is referred to concrete anti-erosion inhibitors (JCT 2553-2019).
D. The no-cooling water pipe construction crack control technology for the low temperature rise crack-resistant corrosion-resistant large-volume concrete construction is characterized in that the control standard of raw materials in the construction is as follows:
(1) cement: the cement can adopt common 42.5 grade cement to replace cement with medium and low hydration heat; in order to improve the early strength of the concrete, the fineness of the cement is preferably less than 0.04 mm; preparing materials in advance, prolonging the storage time, covering a tank body with spray cold water, and ensuring that the use temperature is less than or equal to 60 ℃; mineral admixture is adopted to replace cement; the grade of the cement can be improved to reduce the consumption of the cement; the late 60d or 90d age intensity may be used instead of the design intensity for the 28d age.
(2) Mineral admixture: the quality of the mineral admixture meets the regulations of mineral admixture application technical Specifications (GB/T51003-2014), the materials are prepared in advance, the storage time is prolonged, a tank body is covered by spraying cold water, and the use temperature is less than or equal to 40 ℃.
(3) Coarse aggregate: the coarse aggregate should adopt continuous graded broken stone, the maximum grain size should not exceed 31.5 mm; the apparent density of the coarse aggregate is not less than 2600kg/m 3 The mud content is not more than 1.0 percent, and the crushing value is not more than 10 percent; the materials are put in a storage yard in advance, put in a warehouse for storage, put on a shed for shading, sprayed with ice water for cooling, and the use temperature is lower than the ambient temperature by 5 ℃.
(4) Fine aggregate: medium sand is adopted, the mud content is less than or equal to 1 percent, and the fineness modulus is 2.6-3.0; the materials are put in a field and stored in a warehouse in advance, the material field is covered by a shed for shading, and the using temperature is 5 ℃ lower than the ambient temperature; other indicators must meet the specifications.
(5) Additive: the admixture adopts an ultra-dispersed slump-retaining composite admixture compounded with foam homogenizing and stabilizing components; the use temperature is less than or equal to 30 ℃.
The no-cooling water pipe construction crack control technology for the low temperature rise crack resistance and corrosion resistance large volume concrete construction is characterized in that the temperature control standard in the construction is as follows:
(1) the concrete pouring temperature is not lower than 10 ℃ or higher than 32 ℃;
(2) the temperature rise of the concrete is not more than 50 ℃;
(3) the internal temperature of the concrete is not more than 70 ℃;
(4) the temperature difference between the inside and the outside of the concrete does not exceed 25 ℃;
(5) the concrete cooling rate is not more than 2.0 ℃/d;
(6) the temperature difference between the newly poured concrete and the connected hardened concrete surface or rock is not more than 25 ℃;
(7) the temperature of curing water sprayed and injected on the surface of the concrete is lower than the temperature difference of the surface of the concrete and is not more than 15 ℃;
(8) the difference between the average temperature of the concrete section and the ambient temperature is less than 15 ℃ during the concrete construction of the post-cast strip;
(9) when the large-volume concrete is constructed in layers, the construction interval is generally 7 d.
A technology for controlling crack of a cooling water pipe-free construction constructed by the low-temperature-rise anti-cracking and corrosion-resistant mass concrete is characterized in that the construction quality control method comprises the following steps:
(1) the water tank is enlarged, the amount of stored ice water is increased, the crushing capacity of ice blocks is improved, and the water temperature is reduced and controlled;
(2) monitoring of aggregate moisture content is enhanced, mixing water consumption is adjusted in time, and water-cement ratio and slump are controlled to avoid segregation to generate floating slurry;
(3) the mixing capability of the concrete is increased, and the mixing amount is kept to be more than or equal to 150m 3 Finishing pouring within 45 hours;
(4) when the concrete is poured in a layered mode for the last 50cm, the initial setting time of the concrete is shortened to be within 10h, and therefore the concrete can be conveniently chiseled early to store water.
(5) Accumulated water in the tank truck is drained in advance. The working fluctuation of the concrete caused by human factors is prevented;
(6) the charging of the concrete tank car is not lower than 6m 3 . When the ambient temperature is high and the sunlight is strong, the temperature in the tank car is high, the concrete and the air of the tank car generate heat exchange during transportation and stirring, the water evaporation rate of the concrete is accelerated, the water-cement ratio of the concrete in the tank is easy to reduce, the slump loss is easy to cause, and the transportation capacity is preferably increased to reduce errors.
A no cooling water pipe construction crack control technology of the above-mentioned low temperature rise anti-crack corrosion-resistant large volume concrete construction, pouring quality and warm and humid maintenance measure are in the construction:
(1) optimizing a concrete distribution mode: when concrete is poured, the material is forbidden to be distributed from the center to the edge, so that the phenomenon that slurry is driven to the edge part to cause large shrinkage is avoided, and the risk of concrete cracking is increased. The edge part is distributed by a pump truck and is close to the template, and the concrete is poured in a layered way in sections, so that the good homogeneity of the concrete is ensured;
(2) reinforcing vibration at corners: uniformly distributing concrete, controlling the slump of the bottom layer according to design requirements, and reducing the slump to 16-18 cm when the bearing platform is poured to the last 50cm, so as to avoid floating;
(3) the release agent is preferably an aqueous release agent: the aqueous release agent can form an isolation film on the surface of the template, completely isolates the concrete from directly contacting the template, and air bubbles on the contact surface can quickly overflow to improve the appearance quality of the concrete; an oily release agent is not suitable, the viscosity and the consistency are high, bubbles are not easy to discharge, and the appearance quality is easy to reduce;
(4) considering fiber homogeneity: the mixing of the temperature-rise shrinkage type fiber is prolonged by 40-60 s to fully disperse the anti-crack fiber;
(5) concrete bin surface spraying: when pouring concrete, spraying on the surface of the bin, reducing the temperature of the bin surface, and preventing plastic shrinkage cracks and cold seams caused by water evaporation of the concrete;
(6) early water storage and maintenance: the problem that if water is not stored on the surface of the concrete or the water is not stored sufficiently and rainfall occurs in the concrete curing process is avoided, the phenomenon that the supercooled rainwater is directly poured on the surface of the concrete to cause great internal and external temperature difference is avoided, and the risk of cracking of the large-volume concrete is increased;
(7) when the large-volume concrete is poured to about the last 50cm, the concrete slump is reduced by 2cm, and the retarding time is adjusted to 8-9 h; and (3) chiseling in time after the top concrete is poured, chiseling the periphery of the bearing platform firstly, carrying out regional water storage maintenance on chiseled concrete slag, spraying a retarder on the surface after the concrete is poured, and after the top concrete is finally set to be 5-10 mm away from the concrete surface, using a high-pressure water gun to blast.
Due to the adoption of the technical scheme, the invention has the beneficial effects that:
(1) low temperature rise and low shrinkage: based on the design principle that a dense accumulation body is formed by a cementing material and coarse and fine aggregates so as to improve the mechanical property and the durability of the concrete, the admixture with composite functions of ultra-dispersed cement particles, high-efficiency water reduction, slump retention and retardation, shrinkage reduction and the like and raw materials of 42.5-grade common cement, fly ash, mineral powder, machine-made sand, broken stone and the like are adopted, and the prepared C30-C50 large-volume concrete reduces the cement consumption by more than 10 percent on the premise of meeting the mechanical property and the durability of the design requirement, thereby realizing the low-temperature-rise and low-shrinkage performance of the concrete; aiming at the large-volume concrete with C60 and above or the part with special crack resistance requirement, a hydration temperature rise inhibitor can be doped, the cement hydration rate can be effectively inhibited, the peak value of the hydration heat release rate is reduced by more than 50 percent, and the early hydration heat release process is effectively regulated and controlled.
(2) High crack resistance: according to the construction method, the temperature-rising shrinkage fibers are doped, so that the performances of low volume shrinkage, high crack resistance, high toughness and the like of the mass concrete are realized, the crack control difficulty in the construction process is obviously reduced, and the cracking risk of the mass concrete is reduced.
(3) Excellent resistance to seawater and bittern erosion: for the large-volume concrete under high erosion and other severe environments, besides the technical measures of combining the design of high-doped mineral admixture, adopting a water-reducing shrinkage-reducing additive, doping temperature-rising shrinkage fibers, a hydration temperature-rising inhibitor and the like, the micro structure of the large-volume concrete can be regulated and controlled by adopting an aggressive ion transmission inhibitor, so that the corrosion resistance of the large-volume concrete is greatly improved.
(4) Constructing concrete with the large volume of C30-C60 without cooling water pipes: the low-temperature-rise low-shrinkage high-crack-resistance high-toughness large-volume concrete prepared by the method combines the technical measures of construction quality control of the large-volume concrete prepared by the method, so that the tensile strength in the concrete is greater than the temperature difference stress, the crack-resistance safety coefficient is high, the hydration temperature rise range is controllable, and the C30-C60 large-volume concrete is not arranged with cooling water pipes.
(5) High-quality and quick construction: the large-volume concrete prepared by the method has the characteristics of low hydration temperature rise, low volume shrinkage, excellent anti-cracking capability, good toughness and the like, the conventional construction equipment and quality control technology are adopted, and effective temperature control technical measures are adopted, so that the anti-cracking and temperature control capabilities of large-volume concrete components are improved, the conditions of delayed maintenance measures, unfavorable construction control and the like are prevented, the high fault tolerance rate is realized, meanwhile, the arrangement of cooling water pipes can be cancelled, and the high-quality and quick construction of the large-volume concrete is ensured.
(6) The economic benefit is remarkable: the construction method directly reduces the cost of concrete cement, the cost of arranging cooling water pipes, the construction period and the like of the large-volume concrete, improves the plasticity and the toughness of the concrete, obviously improves the fatigue resistance and the durability of the concrete, finally prolongs the service life of the structure, saves the reinforcing and maintaining cost within the service life, and simultaneously improves the safety of the structure.
(7) And (3) improving ecological benefits: the method relates to the technical measures of greatly reducing the consumption of cement, eliminating cooling water pipes and the like, reduces the environmental pollution caused by producing materials such as cement, steel and the like and laying the cooling water pipes during construction, does not need to exploit cooling water sources, and improves the ecological benefits of engineering.
The invention is described in detail below with reference to the accompanying drawings:
firstly, selecting raw materials:
(1) cement: preparing the P.O 42.5 cement in advance, prolonging the storage time, covering a tank body with spray cold water, and ensuring that the use temperature is less than or equal to 60 ℃;
TABLE 1 technical indices of cement
(2) Fly ash: 4.10 percent of loss on ignition and 88 percent of water requirement of the grade I fly ash; the ignition loss of the second-grade fly ash is 4.97 percent, and the water demand ratio is 101 percent; preparing materials in advance, prolonging the storage time, covering the tank body with spray cold water, and enabling the use temperature to be less than or equal to 40 ℃.
(3) Mineral powder: the S95-grade mineral powder is prepared in advance, the storage time is prolonged, and the tank body is covered with cold water for spraying, and the using temperature is less than or equal to 40 ℃.
TABLE 2 technical indices of mineral powder
(4) Coarse aggregate: 5-26.5 mm continuous graded broken stone, the mud content is 0.3%, and the crushing value is 10%; the materials are put in a storage yard in advance, put in a warehouse for storage, put on a shed for shading, sprayed with ice water for cooling, and the use temperature is lower than the ambient temperature by 5 ℃.
(5) Fine aggregate: medium sand with fineness modulus of 2.7, materials are put into a field and put in a warehouse for storage in advance, and a shed is built in a stock ground for shading, and the using temperature is lower than the ambient temperature by 5 ℃.
(6) Additive: the admixture adopts a super-dispersion slow-release slump-retaining composite admixture compounded with uniform-foam and foam-stabilizing components, and the use temperature is less than or equal to 30 ℃.
Example 1
Second, research on preparation of low-temperature-rise low-shrinkage bulk concrete
The raw materials are utilized, the ultra-dispersed cement particles, the high-efficiency water reducing, shrinkage inhibiting and slow-release slump retaining composite admixture are adopted, the mix proportion of the high-mineral admixture of the mass concrete is optimally designed based on the theory of dense accumulation, the low-temperature-rise shrinkage mass concrete is prepared, and the low-temperature-rise shrinkage mass concrete is compared with the mass concrete prepared by a common mix proportion design method.
TABLE 3C 40 concrete mixing ratio (kg/m) 3 )
TABLE 4 concrete Performance index
As can be seen from FIG. 3 and Table 4, group A2 adopts the optimized design of the mix proportion of the high mineral admixture based on the theory of dense packing and the composite admixture of the compound hydration temperature rise inhibitor is doped, and the low temperature rise and low shrinkage large volume concrete is prepared under the application requirements of meeting the working performance and the mechanical performance. Compared with the common large-volume concrete (A1), the water consumption of the A2 group concrete is reduced by 14.4 percent, the cement consumption is reduced by 56.0 percent, the 28d drying shrinkage rate is reduced by 22.5 percent, the adiabatic temperature rise is reduced by 28.1 percent (14.2 ℃), and the chlorine ion permeability resistance and the early crack resistance are both better improved.
The composite additive and the high-mineral-doped admixture are designed to further reduce the cement consumption and water demand of the concrete, enhance the compactness of the concrete under dense stacking and improve the thermal property and durability of the concrete; the hydration temperature rise inhibitor can reduce the peak value of hydration heat release rate, regulate and control the early hydration heat release process and reduce the early internal highest temperature of the concrete.
Example 2
Third, research for improving crack resistance of large-volume concrete
On the basis of low-temperature-rise low-shrinkage large-volume concrete, 1kg/m of concrete is doped 3 The temperature rise shrinkage type organic anti-crack fiber (called 'temperature shrinkage fiber' for short) is used for preparing low-temperature rise anti-crack large-volume concrete, and is compared with the low-temperature rise low-shrinkage large-volume concrete.
TABLE 6 concrete Performance index
As can be seen from FIG. 5 and Table 6, under the condition of satisfying the working performance requirement of the design requirement, 1kg/m is blended 3 Compared with low-temperature-rise low-shrinkage bulk concrete (B1 group), the low-temperature-rise crack-resistant bulk concrete (B2 group) with the temperature-shrinkage fibers is beneficial to the development of mechanical properties, the splitting tensile strength of 7d and 28d is respectively improved by 30.3 percent and 22.5 percent, the drying shrinkage of 28d is reduced by 22.0 percent, and the early crack resistance is improved from L-IV to L-V.
The temperature rise shrinkage type fiber not only has the functions of toughening, crack resistance and strengthening of the conventional crack resistance fiber, but also can reversely shrink when the concrete is heated and expanded, the retraction force of the fiber is transmitted to the hardened slurry through interface bonding, micro pre-compression stress is applied to the gelled slurry on a micro-microscopic scale, and the tensile stress generated by the large-volume concrete due to the internal and external temperature difference is partially or completely offset, so that the crack resistance of the concrete at the temperature rise/fall stage is improved.
Example 3
Four, the improvement research of the corrosion resistance of the mass concrete
On the basis of low-temperature-rise low-shrinkage mass concrete, and under the condition of meeting the working performance requirement of design requirement, an aggressive ion transmission inhibitor with the dosage of 5% of cementing material is doped to prepare the low-temperature-rise corrosion-resistant mass concrete, which is compared with the common mass concrete.
TABLE 7C 40 concrete mixing ratio (kg/m) 3 )
TABLE 8 concrete Performance index
As can be seen from FIG. 7 and Table 8, under the condition of meeting the working performance and mechanical performance requirements of the design requirements, compared with the common large-volume concrete (C1), the low-temperature-rise corrosion-resistant large-volume concrete (C2) which is doped with the aggressive ion transport inhibitor with the usage of 5% of the cementing material has the advantages that the electric flux at 28d is reduced by 53.4%, the drying shrinkage at 28d is reduced by 28.6%, the adiabatic temperature rise is reduced by 18.2% (9.2 ℃), and the early-stage crack resistance is improved from L-III to L-V.
The aggressive ion transmission inhibitor (hydrophobic compound pore plug) can form hydrophobic property on the concrete surface and can also react with Ca 2+ Complex reaction is generated, and a water-insoluble complex is separated out to block capillary pores, prevent water and erosion ions from entering, enhance the compactness of the concrete and improve the durability and mechanical property of the concrete.
Example 4
Fifthly, construction of large-volume concrete without cooling water pipes
The concrete mixing ratio adopted in the embodiment 4 is the same as that provided in the embodiments 1 to 3.
(1) The concrete slump meets 160-250 mm, the expansion degree meets 500-660 mm, the stirring time of the concrete doped with the anti-crack fibers is prolonged by 40-60 s, and the pouring temperature is preferably 10-32 ℃;
(2) pouring: firstly, the concrete tank truck can drain accumulated water in advance, and the transportation capacity of the tank truck is more than or equal to 6m 3 ；
Secondly, arranging chute tubes to perform slow descending material distribution operation, distributing materials from the edge to the center, distributing materials at the edge by using a pump truck, abutting against a template, and pouring in a segmented and layered manner to ensure good homogeneity of concrete;
thirdly, when the concrete is poured in a layered mode for the last 50cm, the slump of the concrete is reduced to 16-18 cm so as to avoid floating slurry, the initial setting time is shortened to be within 10h, and the concrete is convenient to scabble and store water as early as possible;
(3) warm and wet maintenance measures: firstly, a template is preferably made of water-based release agent or release paint, a heat-insulating film is immediately covered after concrete pouring is finished, steam curing is adopted inside the template, water storage and curing are carried out as soon as possible after top surface concrete is finally solidified, and the water storage depth is more than or equal to 20 cm;
secondly, the surface of the template is cooled by spraying, the temperature rise of the concrete is less than or equal to 50 ℃, the internal temperature is less than or equal to 70 ℃, the internal and external temperature difference is less than or equal to 25 ℃, the cooling rate is less than or equal to 2.0 ℃/d, the layered construction interval is generally 7d, and the template can be disassembled after being maintained with the template for more than 4 d.
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 (5)
1. A low temperature rise crack-resistant corrosion-resistant large-volume concrete preparation technology is characterized by mainly comprising the preparation of a composite additive, a mix proportion design method of a high-doped mineral admixture, an optimization method of mix proportion parameters and a hydration temperature rise inhibition technology;
the composite additive is a special additive for large-volume concrete, which is prepared by introducing a high-quality air entraining agent, a defoaming agent, a viscosity modifier, a polyether shrinkage-reducing additive, a glue reducer and other water reducer additives into a super-dispersing, high-water-reducing and slow-release slump-retaining polycarboxylic superplasticizer;
the mix proportion design method of the high-mineral-doped admixture is designed by adopting a maximum dense estimated accumulation method, and the dosage of concrete cement and adiabatic temperature rise are reduced to the maximum extent under the condition of ensuring that the concrete has excellent workability, mechanical property, volume stability and hot blood performance;
the optimization method of the mix proportion parameters is that on the basis of the design of the mix proportion of the mineral-doped admixture, a design test optimizes and adjusts the mix proportion parameters such as the concrete water-cement ratio, the sand rate, the grain size and the gradation of coarse and fine aggregates, the using amount of cementing materials, the admixture mixing amount and the like, and the concrete mix proportion with the minimum cement using amount, low adiabatic temperature rise and guaranteed strength is preferably selected by combining test data;
the hydration temperature rise inhibition technology is that 1-3 recommended mixing ratios are optimized on the basis of the mixing ratio design, and a hydration temperature rise inhibitor with the use amount of 0.1-0.3% of a cementing material is added to further reduce the hydration temperature rise.
2. The technology for preparing the low temperature-rising, anti-cracking and anti-corrosion large-volume concrete according to claim 1, wherein 1-5 kg/m can be doped into C50 with higher hydration heat and above large-volume concrete or special anti-cracking parts with higher requirement on anti-cracking performance 3 The temperature rise shrinkage type fiber reinforced concrete has the advantages of crack resistance and durability.
3. The technology for preparing the low-temperature-rise crack-resistant corrosion-resistant large-volume concrete according to claims 1-2, characterized in that for the large-volume concrete in western regions, oceans and environments containing chloride ions, sulfate ions and other aggressive ions, besides the technical measures, 3% -8% of the amount of the cementing material of the aggressive ion transmission inhibitor (hydrophobic combined pore plug) can be added to improve the corrosion resistance and mechanical properties of the large-volume concrete in the service environment of the oceans and the aggressive ion transmission inhibitor.
4. The technology for preparing the low-temperature-rise crack-resistant corrosion-resistant large-volume concrete according to claims 1 to 3, wherein common 42.5-grade cement can be used for replacing cement with medium and low hydration heat in the large-volume concrete.
5. A method for controlling crack of a cooling-water-free pipe without cooling water construction by using low-temperature-rise anti-crack and corrosion-resistant large-volume concrete is characterized by mainly comprising a raw material control standard, a construction temperature control standard, a construction quality control method, construction pouring quality and warm-wet maintenance measures;
the raw material control standard is as follows: (1) cement: the fineness of the cement is preferably less than 0.04 mm; the use temperature is less than or equal to 60 ℃; mineral admixture is adopted to replace cement; the grade of the cement can be improved to reduce the consumption of the cement; the later 60d or 90d age intensity can be used to replace the design intensity of the 28d age;
(2) mineral admixture: the use temperature is less than or equal to 40 ℃;
(3) coarse aggregate: the coarse aggregate adopts continuous graded broken stone, and the maximum grain size is less than or equal to 31.5 mm; the apparent density of the coarse aggregate is more than or equal to 2600kg/m 3 The mud content is less than or equal to 1.0 percent, and the crushing value is less than or equal to 10 percent; the using temperature is 5 ℃ lower than the ambient temperature;
(4) fine aggregate: medium sand is adopted, the mud content is less than or equal to 1 percent, and the fineness modulus is 2.6-3.0; the using temperature is 5 ℃ lower than the ambient temperature; other indexes need to meet the specification;
(5) additive: the use temperature is less than or equal to 30 ℃;
the construction temperature control standard is as follows: the concrete pouring temperature is preferably 10-32 ℃; the temperature rise of the concrete is less than or equal to 50 ℃; the internal temperature of the concrete is less than or equal to 70 ℃; the temperature difference between the inside and the outside of the concrete is less than or equal to 25 ℃; the concrete cooling rate should be less than or equal to 2.0 ℃/d; the temperature difference between the newly poured concrete and the connected hardened concrete surface or rock is less than or equal to 25 ℃; the temperature difference of curing water sprayed and injected on the surface of the concrete is less than or equal to 15 ℃ when being lower than the temperature difference of the surface of the concrete; the difference between the average temperature of the concrete section and the ambient temperature during the concrete construction of the post-cast strip is less than or equal to 15 ℃; when the large-volume concrete is constructed in layers, the construction interval is generally 7 d;
the construction quality control method comprises the following steps: the storage capacity and the crushing capacity of the ice blocks are improved; monitoring of aggregate moisture content is enhanced, mixing water consumption is adjusted in time, and water-cement ratio and slump are controlled to avoid segregation and floating slurry generation; the mixing capability of the concrete is increased, and the mixing amount is kept to be more than or equal to 150m 3 Finishing pouring within 45 hours; when concrete is poured in a layered mode for the last 50cm, the initial setting time of the concrete is shortened to be within 10h, and therefore the concrete can be conveniently chiseled early to store water; accumulated water in the tank car is drained in advance; the charging of the concrete tank car is not lower than 6m 3 ；
The construction pouring quality and warm and wet maintenance measures are as follows: during concrete pouring, the material is forbidden to be distributed from the center to the edge, slurry is prevented from being driven to the edge, the material is distributed by a pump truck at the edge and is tightly close to the template, and the concrete is poured in a segmented and layered mode; reinforcing corners and vibrating; preferably, an aqueous release agent or a release paint is used; the mixing time of the temperature-rise shrinkage type fiber is prolonged by 40 to 60 seconds; spraying and cooling the bin surface; early water storage and maintenance.
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| CN115124302B (en) | 2023-05-23 |
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