CN115124302B - Low-temperature-rise anti-cracking corrosion-resistant large-volume concrete preparation technology and cooling-water-pipe-free construction method - Google Patents
Low-temperature-rise anti-cracking corrosion-resistant large-volume concrete preparation technology and cooling-water-pipe-free construction method Download PDFInfo
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Abstract
The invention discloses a low-temperature rising anti-cracking corrosion-resistant large-volume concrete preparation technology and a cooling water pipe-free construction method; comprising, A: a low-temperature rise low-shrinkage large-volume concrete preparation technology; b: a technique for improving the crack resistance of a large-volume concrete; c: a technique for improving corrosion resistance of mass concrete; d: the special crack controlling technology for large-volume concrete construction quality. The high-doped mineral admixture based on the theory of compact stacking is optimally designed, the composite admixture with super-dispersion, high-efficiency water reduction, slump retaining retarding and shrinkage inhibition is developed, the hydration temperature rise inhibitor is doped to inhibit temperature rise, and the modified polypropylene temperature rise shrinkage fiber is used to improve the cracking resistance, so that the low-temperature rise cracking resistance and corrosion resistance large-volume concrete which adopts ordinary cement to replace the medium-low hydration heat special cement can be prepared, and the concrete has the characteristics of good plasticity and toughness, low cement consumption, controllable temperature rise range, high cracking resistance safety coefficient, excellent durability and the like.
Description
Technical Field
The invention relates to a low-temperature-rise anti-cracking anti-corrosion large-volume concrete, in particular to a low-temperature-rise anti-cracking anti-corrosion large-volume concrete preparation technology and a cooling water pipe-free construction method thereof.
Background
Along with the rapid development of social and economic construction, the center of gravity of the construction of China gradually focuses on remote mountain areas, the requirements of building structures under severe environments such as western dangerous mountain areas, turbulent rivers, lakes and seas and the like on concrete materials are continuously improved, and the sizes of components are continuously increased, so that large-volume concrete components are widely applied to engineering construction, such as large-volume concrete structures such as bridge bearing platforms and anchorage, arch bridge arches and archrings, solid sections of tower columns, high-rise building bottom plates, large-scale conversion beams, ultra-thick walls and the like. But the concrete material has poor heat conducting performance, large volume and larger concrete size, heat accumulation of hydration heat release of the cement in early pouring 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 durability of the structure. Along with the improvement of the service life requirement of the bridge, the more severe the crack control is, the more important the temperature control is for the mass concrete.
At present, the common temperature crack control technical measures for the mass concrete at home and abroad mainly comprise:
(1) Reducing the adiabatic temp. rise of large-volume concrete by using middle-low-temp. cement
The special cement with low hydration heat and mineral admixture and the slow setting water reducing agent are adopted, so that the hydration temperature rise of the mass concrete can be reduced, the internal and external temperature difference is reduced, and the concrete cracking caused by temperature stress is prevented. However, the middle-low hydration cement belongs to non-universal silicate cement, and the cement factory is required to adjust the production process to carry out special production, so that the production cost is high. The large-scale hydraulic and hydroelectric engineering has the advantages of large daily cement consumption, short construction period and concentrated operation time, and can be specially customized for production, while the bridge engineering has the advantages of small large-volume concrete engineering amount, long construction period and dispersed operation time, small daily cement consumption, inconvenient customized production and difficult purchase. Therefore, the cost for preparing the bridge engineering large-volume concrete by adopting the middle-low hydration hot cement and the mineral admixture is high, and the realization difficulty is high.
(2) Control the temperature of entering the mould and pre-buried cooling water pipe
The main technical measure for controlling the concrete temperature in the construction pouring process is to control the mold-in temperature and pre-embed the cooling water pipe. But has the following problems:
(1) the method has the advantages that the mold-entering temperature is controlled by adopting a measure of adding ice by mixing water, but the ice making difficulty in remote mountain areas is high, the ice adding efficiency is low, partial concrete bleeding segregation is easily caused by ice melting, meanwhile, the technical layout cost of the embedded cooling water pipe is high, the quality of the concrete is easily influenced by leakage of the cooling water, and the phenomenon of non-compaction of grouting exists;
(2) the water resources are usually deficient in high-altitude areas, and cooling by cooling water is difficult to realize: even if a water source exists, most of the water sources are mountain snow melting ice water, the water temperature is low, heating temperature regulating equipment is needed to be additionally arranged for taking the water sources as cooling water, so that the difference between the temperature of water entering a cooling water pipe and the highest temperature of the mass concrete is not more than 25 ℃, the difference between water inlet and outlet temperatures 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 temperature is controlled improperly;
(3) the lack of fresh water in the sea, bittern and sulfate erosion environment causes the corrosion of cooling water pipes by adopting local water sources, and fresh water needs to be conveyed remotely, so that the cooling of fresh water is adopted to reduce the implementation difficulty of temperature rise and the cost is higher;
(3) Concrete using phase change energy storage
The phase change material has the advantages of high energy storage density, small volume expansion rate, and the like, and can keep approximate isothermal in the heat absorption or heat release process. The phase-change energy storage concrete prepared by adopting the phase-change material can effectively reduce the internal temperature rise rate of the concrete and delay the occurrence time of temperature peaks. The current technology for realizing the phase-change energy storage concrete mainly adopts a paraffin phase-change system, bentonite and capric acid phase-change aggregate, an alkanoic acid phase-change microcapsule material and the like. But the phase-change energy storage concrete has high technical cost, complex preparation process, reduced mechanical property, less standard specification of related construction control and great popularization and application difficulty.
Aiming at the defect of the common temperature crack control technical measures of the large-volume concrete at home and abroad, the inventor develops the following four key technologies through more than 20 years of research and a large number of engineering applications: A. low temperature raising, low shrinkage and large volume concrete material controlling standard and preparing technology; B. a technique for improving the crack resistance of a large-volume concrete; C. a technique for improving corrosion resistance of mass concrete; D. the crack controlling technology for large-volume concrete cooling-free water pipe construction.
The invention integrates the technology, and forms a low-temperature rising anti-cracking corrosion-resistant large-volume concrete preparation method and a cooling water pipe-free construction method. Compared with the traditional large-volume concrete cooled by arranging the cooling water pipe, the ordinary cement can be adopted to replace the special cement with medium and low hydration heat to prepare the large-volume concrete, so that the bridge engineering large-volume concrete has low temperature rise, high crack resistance and excellent durability, and under the condition of canceling the cooling water pipe, the cracking risk is reduced, the temperature crack is avoided, the durability of the large-volume concrete engineering is improved, the construction period is shortened, and the engineering cost is reduced. The method solves the technical problems that the large-volume concrete is difficult to arrange cooling water pipes and has poor durability in the severe environments of large temperature difference, water shortage, high erosion and other severe environments in the western mountain areas, is successfully applied to a plurality of engineering examples, and has important engineering practical significance.
Disclosure of Invention
Therefore, in order to solve the defects, the invention provides a preparation method of low-temperature rise low-shrinkage large-volume concrete and a construction crack control method of a cooling water pipe. The invention aims at: aiming at the technical problems that the temperature difference in western mountain areas is large, water is deficient, high erosion and other severe environments are difficult to arrange cooling water pipes, the durability is poor and the like in large-volume concrete, the invention provides a preparation method of low-temperature rise anti-cracking corrosion-resistant large-volume concrete and a cooling water pipe-free construction method thereof.
The invention is realized in such a way, and constructs a low temperature rise low shrinkage large volume concrete preparation method, which is characterized by mainly comprising a compound admixture preparation, a high-doped mineral admixture mix proportion design method, a mix proportion parameter optimization method and a hydration temperature rise suppression technology;
the composite additive is a special additive for large-volume concrete, which is compounded by adopting super-dispersion, high-water-reduction and slow-release slump-retaining polycarboxylic superplasticizer, and introducing high-quality air entraining agent, defoaming agent, viscosity modifier, polyether shrinkage-reducing additive, reducing agent and other water reducer auxiliary agents;
the mixing proportion design method of the highly doped mineral admixture is designed by adopting a maximum compaction estimation stacking method, so that the concrete cement consumption and the adiabatic temperature rise are reduced to the greatest extent under the condition of ensuring that each working property, mechanical property, volume stability and hot blood performance of the concrete are excellent;
the optimization method of the mixing proportion parameters is that on the basis of the design of the mixing proportion of the mineral-doped admixture, the design test is used for optimizing and adjusting the mixing proportion parameters such as the water cement proportion, the sand ratio, the grain size and gradation of coarse and fine aggregates, the consumption of cementing materials, the mixing amount of additives and the like, and the concrete mixing proportion with the least consumption of cement, low adiabatic temperature rise and ensured strength is optimized according to test data;
the hydration temperature rise inhibition technology is that on the basis of the design of the above-mentioned proportion, 1-3 recommended proportion is optimized, and the hydration temperature rise inhibitor with the dosage of 0.1% -0.3% of the cementing material is doped to further reduce the hydration temperature rise.
The method for preparing a low-temperature-rise low-shrinkage large-volume concrete according to claim 1, wherein the concrete with high C50 and above hydration heat or special crack resistance parts with high crack resistance performance requirements can be mixed with 1-5 kg/m 3 Temperature rise shrinkage type fiber reinforced concrete crack resistance and durability.
The method for preparing the low-temperature-rise low-shrinkage large-volume concrete according to claim 1-2, wherein the method is characterized in that for the large-volume concrete in the environments of western parts, oceans and aggressive ions containing chloride ions, sulfate ions and the like, besides adopting the technical measures, an aggressive ion transmission inhibitor (hydrophobic compound pore plug) accounting for 3% -8% of the dosage of a cementing material can be doped, so that the corrosion resistance and mechanical properties of the large-volume concrete in the aggressive and oceanic service environments are improved.
The method for preparing the low-temperature-rise low-shrinkage large-volume concrete according to claim 1-3, wherein the large-volume concrete and the cement can adopt common 42.5-grade cement to replace the cement with medium and low hydration heat.
A method for controlling crack of a large-volume concrete cooling-free water pipe construction by using the large-volume concrete according to any one of claims 1 to 3, which is characterized by mainly comprising raw material control standards, construction temperature control standards, construction quality control methods, construction pouring quality and temperature and humidity maintenance measures;
the raw material control standard is: (1) cement: the fineness of the cement is preferably less than 0.04mm; the use temperature is less than or equal to 60 ℃; mineral admixture should be used to replace cement; the cement mark can be improved to reduce the cement consumption; the design strength of the 28d age can be replaced by the strength of the later 60d or 90d 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 diameter is less than or equal to 31.5mm; the apparent density of 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 use temperature should be 5 ℃ lower than the ambient temperature;
(4) Fine aggregate: adopting medium sand, wherein the mud content is less than or equal to 1 percent, and the fineness modulus is 2.6 to 3.0; the use temperature should be 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 surface or rock of the connected hardened concrete is less than or equal to 25 ℃; the temperature of curing water sprayed on the concrete surface is lower than the temperature difference of the concrete surface by 15 ℃; the average temperature of the concrete section and the ambient temperature difference are less than or equal to 15 ℃ during post-cast strip concrete construction; when large-volume concrete is subjected to layered construction, the construction interval is generally 7d;
the construction quality control method comprises the following steps: the storage capacity and the crushing capacity of ice cubes are improved; the monitoring of the water content of the aggregate is enhanced, the mixing water consumption is timely adjusted, the water-cement ratio and slump are controlled, and the generation of slurry by segregation is avoided; increase the mixing capacity of concrete and keep the mixing amount more than or equal to 150m 3 And/h, finishing pouring within 45 h; when the concrete is poured in layers for the last 50cm, the initial setting time of the concrete is shortened to be within 10 hours, so that the concrete can be conveniently and early roughened for water storage; the tank truck is drained by accumulated water in advance; the concrete tank truck is not suitable for being charged with less than 6m 3 ；
The construction pouring quality and the temperature and humidity maintenance measures are as follows: during concrete pouring, material distribution from the center to the edge is forbidden, slurry is prevented from being removed to the edge, and the edge adopts pump truck material distribution and close to a template for sectional and layered pouring; reinforcing vibration at corners; aqueous release agents or release paints are preferably used; the mixing time of the temperature-rising shrinkage type fiber is prolonged by 40 to 60 seconds; spraying and cooling the bin surface; and (5) early water storage and maintenance.
The invention has the following advantages:
(1) Low temperature rise and low shrinkage: based on the design principle that the cementing material and coarse and fine aggregates form a compact stack body so as to improve the mechanical property and durability of the concrete, the cement consumption is reduced by more than 10 percent on the premise that the mechanical property and durability of the design requirements are met, and the low-temperature rise and low-shrinkage performance of the prepared C30-C50 mass concrete are realized by adopting an additive with composite functions of ultra-dispersed cement particles, efficient water reduction, slump retaining and retarding, shrinkage reduction and the like, 42.5 grade ordinary cement and raw materials such as fly ash, mineral powder, machine-made sand and crushed stone; aiming at the mass concrete with C60 and above or the parts with special cracking resistance requirements, the hydration temperature rise inhibitor can be doped, so that 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 can be effectively regulated and controlled.
(2) High crack resistance: the method realizes the performances of low volume shrinkage, strong crack resistance, high toughness and the like of the large-volume concrete by adopting the temperature rise shrinkage type fiber, thereby obviously reducing the crack control difficulty in the construction process and reducing the crack risk of the large-volume concrete.
(3) The seawater and bittern corrosion resistance is excellent: for the large-volume concrete under high erosion and other severe environments, besides the technical measures of combining the design of the high-doped mineral admixture, adopting the water-reducing and shrinkage-reducing admixture, doping the temperature-rising and shrinkage-reducing fiber, the hydration temperature-rising inhibitor and the like, the micro-structure of the concrete can be regulated and controlled by adopting the erosive ion transmission inhibitor, so that the corrosion resistance of the concrete is greatly improved.
(4) C30-C60 large-volume concrete for construction 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 the construction quality control of the large volume concrete by the method, so that the internal tensile strength of the concrete is larger 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 arranged without cooling water pipes.
(5) High-quality rapid construction: the large-volume concrete prepared by the construction method has the characteristics of low hydration temperature rise, low volume shrinkage, excellent crack resistance, good toughness and the like, and adopts conventional construction equipment and quality control technology to assist in effective temperature control technical measures, so that the crack resistance and temperature control capability of the large-volume concrete member are improved, the conditions of hysteresis of maintenance measures, unfavorable construction control and the like are prevented, the high fault tolerance is realized, the arrangement of cooling water pipes can be canceled, and the high-quality and rapid construction of the large-volume concrete is ensured.
(6) Obvious economic benefit: the construction method directly reduces the cost of mass concrete cement, the cost of cooling water pipe layout, the construction period and the like, improves the plasticity and toughness of the concrete, obviously improves the fatigue resistance and durability of the concrete, finally prolongs the service life of the structure, saves the reinforcing and maintaining cost in the service life, and improves the safety of the structure.
(7) Improving ecological benefits: the construction method relates to the technical measures of greatly reducing the cement consumption, eliminating the cooling water pipe and the like, reducing the environmental pollution caused by cement, steel and other materials and construction and arrangement of the cooling water pipe, avoiding exploitation of cooling water sources and improving engineering ecological benefits.
Drawings
FIG. 1 example 1 comparative test of volume stability of temperature-rising high volume concrete and ordinary high volume concrete
FIG. 2 example 2 comparative test of volume stability of temperature-rising crack-resistant high-volume concrete
Fig. 3 example 3 comparative test of the volume stability of temperature rise corrosion resistant high volume concrete and normal high volume concrete fig. 4-5 are schematic operation flow diagrams.
Detailed Description
The following detailed description of the present invention will provide clear and complete description of the technical solutions of the embodiments of the present invention, with reference to fig. 1-5, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a preparation method of low-temperature rise anti-cracking corrosion-resistant large-volume concrete and a cooling water pipe-free construction method thereof by improving the preparation method, and the low-temperature rise anti-cracking corrosion-resistant large-volume concrete can be prepared by adopting common cement to replace medium-low hydration heat special cement without arranging cooling water pipes for construction, and can meet 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 above purpose, the invention adopts the following technical scheme:
A. preparation technology of low-temperature-rise low-shrinkage large-volume concrete
(1) The invention provides the preparation requirement of a low temperature rise large-volume concrete composite additive, which is characterized in that:
super-dispersed, high-water-reducing and slow-release slump-retaining polycarboxylic superplasticizer is adopted, high-quality air entraining agent, defoaming agent and viscosity modifier are introduced to carry out viscosity regulation and control, polyether shrinkage-reducing additive is used for compensating shrinkage, and super-dispersed cement particles, high-efficiency water-reducing, shrinkage-inhibiting and slow-release slump-retaining additive is prepared; the cement consumption can be further reduced by compounding the gel reducing agent for the mass concrete with raised hydration temperature.
(2) The invention provides a mix proportion design method of a large-volume concrete high-doped mineral admixture, which is characterized by comprising the following steps of:
the mixing proportion design method adopts a maximum compact skeleton 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, mechanical performance and thermal performance of the concrete required by design as assessment indexes, and combines test data to preferably select the concrete mixing proportion with minimum cement consumption, low adiabatic temperature rise and ensured strength.
(3) The invention provides an optimization method of a large-volume concrete mixing proportion parameter, which is characterized by comprising the following steps of: on the basis of the design of the high-doped mineral admixture blending ratio, the working performance, mechanical performance and thermal performance of the concrete required by the design are taken as assessment indexes, the blending ratio parameters such as the concrete water-cement ratio, sand ratio, coarse and fine aggregate particle size and grading, the consumption of cementing materials, the admixture blending amount and the like are optimally adjusted, and the concrete blending ratio with the least cement consumption, low adiabatic temperature rise and ensured strength is optimized by combining test data.
(4) The invention provides a method for inhibiting hydration temperature rise of a large-volume concrete, which comprises the following steps: for high-grade concrete with higher hydration heat or special anti-cracking parts with higher requirements on anti-cracking performance, 1-3 recommended mixing ratios can be optimized on the basis of the design of the mixing ratios, and the hydration temperature rise inhibitor with the dosage of 0.1% -0.3% of the cementing material is doped to further reduce the hydration temperature rise.
B. The technology for improving the cracking resistance of the mass concrete comprises the following steps: furthermore, for the concrete with high C50 and above of hydration heat or special crack resistance position with high requirement of crack resistance, 1-5 kg/m of the concrete can be mixed 3 Temperature rise shrinkage type fiber reinforced concrete crack resistance and durability.
C. The technology for improving the corrosion resistance of the large-volume concrete comprises the following steps: furthermore, for large-volume concrete in western, ocean and aggressive ion environments containing chloride ions, sulfate ions and the like, besides adopting the technical measures, aggressive ion transmission inhibitors (hydrophobic compound pore plug materials) with the dosage of 3-8% of the cementing materials can be doped, so that the corrosion resistance and mechanical properties of the large-volume concrete in aggressive and ocean service environments are improved, and the technical index requirements refer to the concrete anti-erosion inhibitors (JCT 2553-2019).
D. The cooling water pipe-free construction crack control technology for constructing the low-temperature-rise crack-resistant corrosion-resistant large-volume concrete is characterized in that the control standard of raw materials in construction is as follows:
(1) And (3) 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 smaller than 0.04mm; the material preparation is carried out in advance, the storage time is prolonged, the tank body is covered with spray cold water, and the use temperature is ensured to be less than or equal to 60 ℃; mineral admixture should be used to replace cement; the cement mark can be improved to reduce the cement consumption; the later 60d or 90d age strength may be used instead of the 28d age design strength.
(2) Mineral admixture: the quality of the mineral admixture meets the specification of mineral admixture application technical specification (GB/T51003-2014), the material preparation is carried out in advance, the storage time is prolonged, the tank body is covered with spray cold water, and 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 not more than 31.5mm; the apparent density of the coarse aggregate is not less than 2600kg/m 3 The mud content is not more than 1.0%, and the crushing value is not more than 10%; the materials are advanced to enter a yard, stored in a warehouse, covered by a shed for sunshade, sprayed with ice water for cooling, and the use temperature is 5 ℃ lower than the environment temperature.
(4) Fine aggregate: adopting medium sand, wherein the mud content is less than or equal to 1 percent, and the fineness modulus is 2.6 to 3.0; the materials are advanced to enter a field, stored in a warehouse, and the material field is covered with a awning for shading, and the use temperature is lower than the environment temperature by 5 ℃; other indexes are required to meet the specification.
(5) Additive: the additive is an ultra-dispersed slump retaining type composite additive of a compound foam stabilizing component; the use temperature is less than or equal to 30 ℃.
The cooling water pipe-free construction crack control technology for constructing the low-temperature-rise anti-crack corrosion-resistant large-volume concrete is characterized in that the temperature control standard in construction is as follows:
(1) The concrete pouring temperature is not suitable to be lower than 10 ℃ and 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 is not more than 25 ℃;
(5) The cooling rate of the concrete is not more than 2.0 ℃/d;
(6) The temperature difference between the newly poured concrete and the surface or rock of the connected hardened concrete is not more than 25 ℃;
(7) The temperature of curing water sprayed on the concrete surface is lower than the temperature difference of the concrete surface by not more than 15 ℃;
(8) The average temperature of the concrete section and the environmental temperature difference are less than 15 ℃ during the construction of the post-cast strip concrete;
(9) When large-volume concrete is layered, the construction interval is generally 7d.
The cooling water pipe-free construction crack control technology for constructing the low-temperature-rise anti-crack corrosion-resistant large-volume concrete is characterized by comprising the following steps of:
(1) The pool is enlarged, the ice water storage amount is increased, the breaking capacity of ice cubes is improved, and the water temperature is reduced and controlled;
(2) The monitoring of the water content of the aggregate is enhanced, the mixing water consumption is timely adjusted, the water-cement ratio and slump are controlled, and the generation of slurry by segregation is avoided;
(3) Increase the mixing capacity of concrete and keep the mixing amount more than or equal to 150m 3 And/h, finishing pouring within 45 h;
(4) When the concrete is poured in layers and is finally 50cm, the initial setting time of the concrete is shortened to be within 10 hours, and the concrete can be conveniently and early roughened to store water.
(5) The tank truck should accumulate water in advance for draining and cleaning. The concrete workability fluctuation caused by human factors is prevented;
(6) The concrete tank truck is not suitable for being charged with less than 6m 3 . When the ambient temperature is high and the sunlight is strong, the temperature in the tank truck is higher, and the concrete and the air in the tank truck generate heat exchange during transportation and stirring, so that the water evaporation rate of the concrete is accelerated, the collapse loss is easily caused by the decrease of the water-cement ratio of the concrete in the tank, and the transportation quantity is preferably improved to reduce errors.
A cooling water pipe construction crack control technology for constructing the low temperature rise crack resistant corrosion resistant large-volume concrete comprises the following pouring quality and temperature and humidity maintenance measures:
(1) Optimizing concrete distribution mode: and when the concrete is poured, the material is prevented from being distributed from the center to the edge, slurry is prevented from being driven to the edge, larger shrinkage is generated, and the risk of concrete cracking is increased. The edges are distributed by a pump truck and are abutted against the templates, and the concrete is poured in a segmented and layered manner, so that good uniformity of the concrete is ensured;
(2) Strengthen corner vibration: the concrete is uniformly distributed, the slump of the bottom layer is controlled according to the design requirement, and when the bearing platform is poured to the last 50cm, the slump is reduced to 16-18 cm, so that the floating slurry is avoided;
(3) The release agent is preferably an aqueous release agent: the water-based release agent can form an isolating film on the surface of the template, so that the concrete is completely isolated from being in direct contact with the template, and bubbles on the contact surface can rapidly overflow, thereby improving the appearance quality of the concrete; oily release agent is not suitable, the viscosity and the consistency are higher, bubbles are not easy to discharge, and the appearance quality is easy to be reduced;
(4) Consider fiber homogeneity: adding temperature-rising shrinkage type fiber, and prolonging the stirring time by 40-60 s to fully disperse the anti-cracking fiber;
(5) Spraying concrete bin surface: when pouring concrete, spraying the bin surface, cooling 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 maintenance: the phenomenon that water is not stored on the concrete surface or is insufficient is avoided, if rainfall occurs in the concrete curing process, the supercooled rainwater is prevented from directly pouring on the concrete surface, so that the great internal and external temperature difference is caused, and the cracking risk of the large-volume concrete is increased;
(7) When the concrete with large volume is poured to about 50cm at last, the slump of the concrete is reduced by 2cm, and the retarding time is adjusted to 8-9 h; and after the top surface concrete is poured, roughening is carried out in time after initial setting, wherein the four peripheral parts of the bearing platform are firstly chiseled during roughening, and the roughened concrete slag is subjected to regional water storage maintenance, or retarder is sprayed on the surface after the concrete pouring is finished, and after final setting is carried out under the condition of being 5-10 mm away from the concrete surface, the roughening is carried out by adopting a high-pressure water gun.
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 the cementing material and coarse and fine aggregates form a compact stack body so as to improve the mechanical property and durability of the concrete, the cement consumption is reduced by more than 10 percent on the premise that the mechanical property and durability of the design requirements are met, and the low-temperature rise and low-shrinkage performance of the prepared C30-C50 mass concrete are realized by adopting an additive with composite functions of ultra-dispersed cement particles, efficient water reduction, slump retaining and retarding, shrinkage reduction and the like, 42.5 grade ordinary cement and raw materials such as fly ash, mineral powder, machine-made sand and crushed stone; aiming at the mass concrete with C60 and above or the parts with special cracking resistance requirements, the hydration temperature rise inhibitor can be doped, so that 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 can be effectively regulated and controlled.
(2) High crack resistance: the method realizes the performances of low volume shrinkage, strong crack resistance, high toughness and the like of the large-volume concrete by adopting the temperature rise shrinkage type fiber, thereby obviously reducing the crack control difficulty in the construction process and reducing the crack risk of the large-volume concrete.
(3) The seawater and bittern corrosion resistance is excellent: for the large-volume concrete under high erosion and other severe environments, besides the technical measures of combining the design of the high-doped mineral admixture, adopting the water-reducing and shrinkage-reducing admixture, doping the temperature-rising and shrinkage-reducing fiber, the hydration temperature-rising inhibitor and the like, the micro-structure of the concrete can be regulated and controlled by adopting the erosive ion transmission inhibitor, so that the corrosion resistance of the concrete is greatly improved.
(4) C30-C60 large-volume concrete for construction 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 the construction quality control of the large volume concrete by the method, so that the internal tensile strength of the concrete is larger 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 arranged without cooling water pipes.
(5) High-quality rapid construction: the large-volume concrete prepared by the construction method has the characteristics of low hydration temperature rise, low volume shrinkage, excellent crack resistance, good toughness and the like, and adopts conventional construction equipment and quality control technology to assist in effective temperature control technical measures, so that the crack resistance and temperature control capability of the large-volume concrete member are improved, the conditions of hysteresis of maintenance measures, unfavorable construction control and the like are prevented, the high fault tolerance is realized, the arrangement of cooling water pipes can be canceled, and the high-quality and rapid construction of the large-volume concrete is ensured.
(6) Obvious economic benefit: the construction method directly reduces the cost of mass concrete cement, the cost of cooling water pipe layout, the construction period and the like, improves the plasticity and toughness of the concrete, obviously improves the fatigue resistance and durability of the concrete, finally prolongs the service life of the structure, saves the reinforcing and maintaining cost in the service life, and improves the safety of the structure.
(7) Improving ecological benefits: the construction method relates to the technical measures of greatly reducing the cement consumption, eliminating the cooling water pipe and the like, reducing the environmental pollution caused by cement, steel and other materials and construction and arrangement of the cooling water pipe, avoiding exploitation of cooling water sources and improving engineering ecological benefits.
The invention is described in detail below with reference to the attached drawings:
1. raw material selection:
(1) And (3) cement: P.O42.5 cement, which is prepared in advance, the storage time is prolonged, the tank body is covered with spray cold water, and the use temperature is ensured to be less than or equal to 60 ℃;
table 1 cement specifications
(2) Fly ash: class I fly ash has a loss on ignition of 4.10% and a water demand ratio of 88%; class II fly ash has a loss on ignition of 4.97% and a water demand ratio of 101%; the material preparation is carried out in advance, the storage time is prolonged, the tank body is covered with spray cold water, and the use temperature is less than or equal to 40 ℃.
(3) Mineral powder: s95 grade mineral powder is prepared in advance, the storage time is prolonged, the tank body is covered with spray cold water, and the use temperature is less than or equal to 40 ℃.
Table 2 mineral powder technical index
(4) Coarse aggregate: 5-26.5 mm continuous graded broken stone, 0.3% of mud content and 10% of crushing value; the materials are advanced to enter a yard, stored in a warehouse, covered by a shed for sunshade, sprayed with ice water for cooling, and the use temperature is 5 ℃ lower than the environment temperature.
(5) Fine aggregate: the fineness modulus of the medium sand is 2.7, the materials are advanced, put in storage and stored, the material yard is covered with a awning, and the use temperature is lower than the environment temperature by 5 ℃.
(6) Additive: the additive is an ultra-dispersed slow-release slump retaining type composite additive compounded with foam stabilizing components, and the use temperature is less than or equal to 30 ℃.
Example 1
2. Study on preparation of low-temperature-rise low-shrinkage large-volume concrete
By utilizing the raw materials, the ultra-dispersed cement particles, the high-efficiency water reducing, shrinkage inhibiting and slow-release slump retaining type composite additive is adopted, the optimization design of the mixing proportion of the high-volume concrete and the high-doped mineral admixture is carried out based on the theory of compact stacking, the low-temperature rise low-shrinkage large-volume concrete is prepared, and the low-temperature rise low-shrinkage large-volume concrete is compared with the large-volume concrete prepared by the common mixing proportion design method.
TABLE 3 C40 concrete mix (kg/m) 3 )
TABLE 4 concrete Performance index
As can be seen from FIG. 3 and Table 4, the A2 group adopts the optimal design of the mixing proportion of the high-doped mineral admixture based on the theory of dense accumulation, and the composite admixture for compounding the hydration temperature rise inhibitor is doped, so that the low-temperature rise low-shrinkage large-volume concrete is prepared under the condition of meeting the application requirements of working performance and mechanical performance. Compared with the common large-volume concrete (A1 group), the water consumption of the A2 group concrete is reduced by 14.4%, the cement consumption is reduced by 56.0%, the 28d drying shrinkage is reduced by 22.5%, the heat insulation temperature rise is reduced by 28.1% (14.2 ℃), and the anti-chloride ion permeability and early crack resistance are both better improved.
The design of the composite additive and the highly-doped mineral admixture can further reduce the cement consumption and the water demand of the concrete, strengthen the compactness of the concrete under dense accumulation, and improve the thermal property and the durability of the concrete; the hydration temperature rise inhibitor can reduce the peak value of hydration heat release rate, regulate and control the progress of early hydration heat release and reduce the highest temperature of the early interior of concrete.
Example 2
3. Research on improvement of crack resistance of large-volume concrete
On the basis of low-temperature rise low-shrinkage large-volume concrete, 1kg/m of concrete is mixed 3 The temperature-rising shrinkage type organic anti-cracking fiber (called as temperature shrinkage fiber for short) is used for preparing the low-temperature-rising anti-cracking large-volume concrete, and the low-temperature-rising low-shrinkage large-volume concrete is compared with the low-temperature-rising low-shrinkage large-volume concrete.
TABLE 5 C50 concrete mix (kg/m) 3 )
TABLE 6 concrete Performance index
As can be seen from FIG. 5 and Table 6, the blending amount is 1kg/m under the working performance requirement satisfying the design requirement 3 Compared with the low-temperature-rise low-shrinkage large-volume concrete (B1 group), the low-temperature-rise anti-cracking large-volume concrete (B2 group) of the temperature-shrinkage fiber has the advantages of low temperature rise and crack resistanceThe fiber is favorable for the development of mechanical properties, the split tensile strength of 7d and 28d is respectively improved by 30.3 percent, 22.5 percent, the drying shrinkage rate of 28d is reduced by 22.0 percent, and the early cracking resistance is improved from L-IV to L-V.
Besides the toughening, crack resistance and strengthening functions of the conventional anti-cracking fiber, the temperature-rising shrinkage fiber can also reversely shrink when the concrete is heated and expanded, the retractive force of the fiber is transferred to the hardened slurry through interface bonding, and micro-pre-compression stress is applied to the gelled slurry on a micro-micro scale, so that the tensile stress of the mass concrete due to internal and external temperature difference is partially or completely counteracted, and the anti-cracking performance of the concrete in the temperature rising/reducing stage is improved.
Example 3
4. Research on corrosion resistance improvement of large-volume concrete
On the basis of low-temperature rise low-shrinkage large-volume concrete, under the working performance requirement meeting the design requirement, the corrosive ion transmission inhibitor with the dosage of 5% of the cementing material is doped to prepare the low-temperature rise corrosion-resistant large-volume concrete, and the low-temperature rise corrosion-resistant large-volume concrete is compared with the common large-volume concrete.
TABLE 7 C40 concrete mix (kg/m) 3 )
TABLE 8 concrete Performance index
As can be seen from tables 7 and 8, under the condition of meeting the working performance and mechanical performance requirements of the design requirements, the low temperature rise corrosion-resistant large-volume concrete (C2 group) doped with the aggressive ion transmission inhibitor, the dosage of which is 5 percent, has the advantages that the 28d electric flux is reduced by 53.4 percent, the 28d drying shrinkage rate is reduced by 28.6 percent, the adiabatic temperature rise is reduced by 18.2 percent (9.2 ℃), and the early cracking resistance is improved from L-III to L-V compared with the common large-volume concrete (C1 group).
Aggressive ion transport inhibitors (hydrophobically bound pore plugs) can form concrete surfacesHydrophobic character, and also can be matched with Ca 2+ And a complex reaction is generated, and a water-insoluble complex is separated out to block capillary holes, so that entry of moisture and erosion ions is prevented, the compactness of the concrete is enhanced, and the durability and mechanical properties of the concrete are improved.
Example 4
5. Large-volume concrete construction without cooling water pipe
The concrete mix adopted in example 4 was the same as that provided in examples 1 to 3.
(1) The slump of the concrete is 160-250mm, the expansion degree is 500-660mm, the stirring time of the concrete doped with the anti-cracking fiber is prolonged by 40-60 s, and the pouring temperature is preferably 10-32 ℃;
(2) Pouring: (1) the concrete tank truck drains off accumulated water in advance, and the transportation capacity of the tank truck is more than or equal to 6m 3 ；
(2) The chute serial barrels are arranged for slowly descending and distributing, the edges are distributed from the edges to the center, the edges are distributed by adopting a pump truck and abutted against the templates, and the chute serial barrels are cast in a segmented and layered manner, so that good uniformity of concrete is ensured;
(3) when the concrete is poured in layers 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 10 hours, and the concrete is convenient for roughening and storing water early;
(3) And (3) a warm-wet maintenance measure: (1) the template is preferably water-based release agent or release paint, the heat-insulating film is covered immediately after concrete pouring is finished, steam curing is adopted in the template, and water is stored and cured early after the top surface concrete is finally cured, wherein the water storage depth is more than or equal to 20cm;
(2) the surface of the template is sprayed and cooled, the temperature rise of concrete is less than or equal to 50 ℃, the internal temperature is less than or equal to 70 ℃, the internal-external temperature difference is less than or equal to 25 ℃, the cooling rate is less than or equal to 2.0 ℃/d, the layering construction interval is generally 7d, and the template is suitable to be maintained for more than 4d with the template and can be disassembled.
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 (3)
1. A method for preparing low-temperature-rise anti-cracking corrosion-resistant large-volume concrete is characterized in that,
the raw material control standard of the low temperature rise anti-cracking corrosion-resistant mass concrete is as follows:
(1) And (3) cement: p. 042.5 cement, the use temperature is less than or equal to 60 ℃;
(2) Fly ash: class II fly ash has a loss on ignition of 4.97% and a water demand ratio of 101%; the use temperature is less than or equal to 40 ℃;
(3) Mineral powder: s95 grade mineral powder, the use temperature is less than or equal to 40 ℃;
(4) Coarse aggregate: 5-26.5 mm continuous graded broken stone, 0.3% of mud content and 10% of crushing value; the use temperature is 5 ℃ lower than the ambient temperature;
(5) Fine aggregate: middle sand with fineness modulus of 2.7 and using temperature lower than 5 ℃ of environment temperature;
(6) Additive: the additive adopts an ultra-dispersed slow-release slump-retaining composite additive of a compound foam-homogenizing and stabilizing component, and the use temperature is less than or equal to 30 ℃;
the raw material mixing ratio of the low temperature rise anti-cracking corrosion-resistant mass concrete is as follows:
cement 140kg/m 3 : class II fly ash 140kg/m 3 : 120kg/m of mineral powder 3 : 751kg/m of sand 3 : 1050kg/m of crushed stone 3 : 143kg/m of water 3 : composite admixture 4.4 kg/m 3 : hydration temperature rise inhibitor 0.6kg/m 3 ；
The construction process of the low temperature rise anti-cracking corrosion-resistant mass concrete comprises the following steps of;
(1) The slump of the concrete is 160-250mm, and the expansion degree is 500-660mm;
(2) Pouring: (1) the concrete tank truck drains off accumulated water in advance, and the transportation capacity of the tank truck is more than or equal to 6m 3 The method comprises the steps of carrying out a first treatment on the surface of the (2) The chute serial barrels are arranged for slowly descending and distributing, the edges are distributed from the edges to the center, the edges are distributed by adopting a pump truck and abutted against the templates, and the chute serial barrels are cast in a segmented and layered manner, so that good uniformity of concrete is ensuredThe method comprises the steps of carrying out a first treatment on the surface of the (3) When the concrete is poured in layers 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 10 hours, and the concrete is convenient for roughening and storing water early;
(3) And (3) a warm-wet maintenance measure: (1) the template is preferably water-based release agent or release paint, the heat-insulating film is covered immediately after concrete pouring is finished, steam curing is adopted in the template, and water is stored and cured early after the top surface concrete is finally cured, wherein the water storage depth is more than or equal to 20cm; (2) the surface of the template is sprayed and cooled, the temperature rise of 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 layering construction interval is generally 7d, and the template can be disassembled above 4d of template curing.
2. A method for preparing low-temperature-rise anti-cracking corrosion-resistant large-volume concrete is characterized in that,
the raw material control standard of the low temperature rise anti-cracking corrosion-resistant mass concrete is as follows:
(1) And (3) cement: p. 042.5 cement, the use temperature is less than or equal to 60 ℃;
(2) Fly ash: class I fly ash has a loss on ignition of 4.10% and a water demand ratio of 88%; the use temperature is less than or equal to 40 ℃;
(3) Mineral powder: s95 grade mineral powder, the use temperature is less than or equal to 40 ℃;
(4) Coarse aggregate: 5-26.5 mm continuous graded broken stone, 0.3% of mud content and 10% of crushing value; the use temperature is 5 ℃ lower than the ambient temperature;
(5) Fine aggregate: middle sand with fineness modulus of 2.7 and using temperature lower than 5 ℃ of environment temperature;
(6) Additive: the additive adopts an ultra-dispersed slow-release slump-retaining composite additive of a compound foam-homogenizing and stabilizing component, and the use temperature is less than or equal to 30 ℃;
the raw material mixing ratio of the low temperature rise anti-cracking corrosion-resistant mass concrete is as follows:
235kg/m cement 3 : class I fly ash 132kg/m 3 : 108kg/m of mineral powder 3 : sand 677kg/m 3 : 1106kg/m of crushed stone 3 : 142kg/m of water 3 : 8kg/m of composite additive and hydration temperature rise inhibitor 3 : thermal shrinkage fiber 1.0kg/m 3 ；
The construction process of the low temperature rise anti-cracking corrosion-resistant mass concrete comprises the following steps of;
(1) The slump of the concrete meets 160-250mm, the expansion degree meets 500-660mm, the stirring time of the concrete doped with the anti-crack fibers is prolonged by 40-60 s, and the pouring temperature is 10-32 ℃;
(2) Pouring: (1) the concrete tank truck drains off accumulated water in advance, and the transportation capacity of the tank truck is more than or equal to 6m 3 The method comprises the steps of carrying out a first treatment on the surface of the (2) The chute serial barrels are arranged for slowly descending and distributing, the edges are distributed from the edges to the center, the edges are distributed by adopting a pump truck and abutted against the templates, and the chute serial barrels are cast in a segmented and layered manner, so that good uniformity of concrete is ensured; (3) when the concrete is poured in layers 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 10 hours, and the concrete is convenient for roughening and storing water early;
(3) And (3) a warm-wet maintenance measure: (1) the template is preferably water-based release agent or release paint, the heat-insulating film is covered immediately after concrete pouring is finished, steam curing is adopted in the template, and water is stored and cured early after the top surface concrete is finally cured, wherein the water storage depth is more than or equal to 20cm; (2) the surface of the template is sprayed and cooled, the temperature rise of 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 layering construction interval is generally 7d, and the template can be disassembled above 4d of template curing.
3. A method for preparing low-temperature-rise anti-cracking corrosion-resistant large-volume concrete is characterized in that,
the raw material control standard of the low temperature rise anti-cracking corrosion-resistant mass concrete is as follows:
(1) And (3) cement: p. 042.5 cement, the use temperature is less than or equal to 60 ℃;
(2) Fly ash: class II fly ash has a loss on ignition of 4.97% and a water demand ratio of 101%; the use temperature is less than or equal to 40 ℃;
(3) Mineral powder: s95 grade mineral powder, the use temperature is less than or equal to 40 ℃;
(4) Coarse aggregate: 5-26.5 mm continuous graded broken stone, 0.3% of mud content and 10% of crushing value; the use temperature is 5 ℃ lower than the ambient temperature;
(5) Fine aggregate: middle sand with fineness modulus of 2.7 and using temperature lower than 5 ℃ of environment temperature;
(6) Additive: the additive adopts an ultra-dispersed slow-release slump-retaining composite additive of a compound foam-homogenizing and stabilizing component, and the use temperature is less than or equal to 30 ℃;
the raw material mixing ratio of the low temperature rise anti-cracking corrosion-resistant mass concrete is as follows:
150kg/m of cement 3 : class II fly ash 147kg/m 3 : 103kg/m of mineral powder 3 : 751kg/m of sand 3 : 1080kg/m of crushed stone 3 : 126kg/m of water 3 : composite admixture 5kg/m 3 : aggressive ion transport inhibitor 20kg/m 3 ；
The construction process of the low temperature rise anti-cracking corrosion-resistant mass concrete comprises the following steps of;
(1) The slump of the concrete is 160-250mm, and the expansion degree is 500-660mm;
(2) Pouring: (1) the concrete tank truck drains off accumulated water in advance, and the transportation capacity of the tank truck is more than or equal to 6m 3 The method comprises the steps of carrying out a first treatment on the surface of the (2) The chute serial barrels are arranged for slowly descending and distributing, the edges are distributed from the edges to the center, the edges are distributed by adopting a pump truck and abutted against the templates, and the chute serial barrels are cast in a segmented and layered manner, so that good uniformity of concrete is ensured; (3) when the concrete is poured in layers 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 10 hours, and the concrete is convenient for roughening and storing water early;
(3) And (3) a warm-wet maintenance measure: (1) the template is preferably water-based release agent or release paint, the heat-insulating film is covered immediately after concrete pouring is finished, steam curing is adopted in the template, and water is stored and cured early after the top surface concrete is finally cured, wherein the water storage depth is more than or equal to 20cm; (2) the surface of the template is sprayed and cooled, the temperature rise of 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 layering construction interval is generally 7d, and the template can be disassembled above 4d of template curing.
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| CN106587831A (en) * | 2016-12-13 | 2017-04-26 | 武汉理工大学 | Super-elevation pumping marine concrete and preparation method thereof |
| CN114622563A (en) * | 2022-03-28 | 2022-06-14 | 上海市建筑科学研究院有限公司 | Crack-free mass concrete construction method |
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| CN105298133A (en) * | 2015-10-13 | 2016-02-03 | 悉地（苏州）勘察设计顾问有限公司 | Construction method to strengthen crack resistance of large-volume concrete baseplate |
| CN106587831A (en) * | 2016-12-13 | 2017-04-26 | 武汉理工大学 | Super-elevation pumping marine concrete and preparation method thereof |
| CN114622563A (en) * | 2022-03-28 | 2022-06-14 | 上海市建筑科学研究院有限公司 | Crack-free mass concrete construction method |
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