CN112160443B - Summer crack resistance construction method for underground side wall structure concrete - Google Patents
Summer crack resistance construction method for underground side wall structure concrete Download PDFInfo
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- CN112160443B CN112160443B CN202010986603.9A CN202010986603A CN112160443B CN 112160443 B CN112160443 B CN 112160443B CN 202010986603 A CN202010986603 A CN 202010986603A CN 112160443 B CN112160443 B CN 112160443B
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- C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
- C04B22/06—Oxides, Hydroxides
- C04B22/066—Magnesia; Magnesium hydroxide
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- E04G21/02—Conveying or working-up concrete or similar masses able to be heaped or cast
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- E04G9/00—Forming or shuttering elements for general use
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Abstract
The invention discloses a summer crack resistance construction method for underground side wall structure concrete. According to the anti-cracking construction method, the side wall structure concrete is divided into segmented structures which are sequentially distributed in a range of 8-10 m and a range of 2-5m, reinforcing mesh is bound in segments, temperature control water pipes are distributed in the 2-5m segmented reinforcing mesh, stressors are buried in all the reinforcing mesh, concrete doped with different expansion agents is poured in different segmented reinforcing mesh, a temperature control template replaces a traditional side wall structure concrete template, the tensile stress in the concrete is adjusted through the segmented design of the reinforcing mesh, the concrete with different expansion performances and a temperature control maintenance mode, and crack control on the side wall structure concrete is achieved based on the measured stress. The crack-resistant technical method has higher requirement on technical controllability, but has better crack-resistant effect, and especially has better guiding significance on crack resistance of the concrete of the super-long side wall which is continuously poured during summer construction.
Description
Technical Field
The invention relates to the technical field of concrete crack resistance, in particular to a summer crack resistance construction method for underground side wall structure concrete.
Background
The underground side wall structure concrete is represented by urban underground rail transit subway stations and lake bottom tunnels, the cracking of the underground side wall structure concrete is very common in the solid engineering structure, and is also a problem which is very difficult to solve and overcome in the field of concrete engineering.
At present, the method for reducing the cracking of the underground side wall is mainly started from the concrete angle and the construction design angle, and the concrete angle mainly relates to the addition of additives with expansion and contraction compensation performance and the control of the mold-entering temperature and the temperature development process of the concrete, so that the contraction and the temperature stress of the concrete are reduced; the construction design angle mainly relates to the one-time pouring length of the concrete with the side wall structure, so that the cracking risk is reduced. At present, the two means are effective means for solving the cracking problem of the side wall concrete, the cracking degree can be greatly relieved, even the generation of visible cracks on the appearance of the side wall can be thoroughly avoided under the condition that the two means are combined with each other, but published research data show that the once pouring length of the side wall structure concrete without cracking is ensured to be 5m under the condition that temperature control and expansion materials are not adopted in actual engineering by taking summer as an example, the hidden danger of water leakage can be generated at the position of a construction joint, even under the condition that the expansion materials are used, the pouring length with controllable cracking is not more than 20m, and therefore, the existing technology for cracking resistance of the side wall structure concrete still needs to be further developed.
In order to solve the cracking problem of the concrete of the underground or underwater side wall structure under the condition of ultralong continuous pouring, concrete materials and a construction process are necessary to be combined, and the invention provides a process method for avoiding cracking of the concrete of the side wall structure, which can solve the problem of self shrinkage of the concrete from the aspect of materials and solve the problem of cracking caused by overlarge shrinkage tensile stress of the concrete from the aspect of processes, thereby technically greatly reducing the cracking risk of the concrete of the side wall structure.
Disclosure of Invention
The invention provides a summer crack-resistant construction method for underground side wall structure concrete, aiming at solving the problem that the underground side wall structure concrete is easy to crack during ultralong continuous casting in summer construction in the prior art.
The invention provides a summer crack resistance construction method for underground side wall structure concrete, which specifically comprises the following steps:
(1) binding a reinforcing mesh of a side wall structure on the upper part of a hardened bottom plate concrete structure, binding the reinforcing mesh of the side wall structure in sections, dividing the side wall structure into sectional structures which are sequentially distributed in the range of 8-10 m, 2-5m, 8-10 m and 2-5m … … by the reinforcing mesh, distributing temperature control water pipes in all the 2-5m sectional reinforcing meshes, and arranging movable partition plates between the 2-5m sectional reinforcing meshes and the 8-10 m sectional reinforcing meshes, wherein the movable partition plates are perpendicular to the bottom plate concrete structure;
(2) before the concrete pouring construction of the side wall structure, pre-burying a stress meter in the center of all segmented steel bar nets, wherein the stress meter is connected with an online monitoring device through a cable, the online monitoring device collects stress and temperature data of the stress meter and presents the data online in a network form, the stress meter is used for monitoring the stress development inside the concrete in real time from the beginning of the concrete pouring by utilizing the online monitoring device, and the stress meter has a temperature compensation function and can simultaneously test the temperature of the concrete;
(3) replacing a traditional concrete formwork with a temperature control formwork, connecting hollow structures of the temperature control formwork of the whole side wall structure in series by using connecting pipes, determining the operation reliability of the concrete formwork by checking the air tightness of the temperature control formwork and a temperature control water pipe, and respectively pouring concrete doped with different expanding agents in a 2-5m segmented reinforcing mesh and a 8-10 m segmented reinforcing mesh, wherein a magnesium oxide expanding agent is doped in the 2-5m segmented concrete, and a calcium-magnesium composite expanding agent is doped in the 8-10 m segmented concrete;
(4) the method comprises the steps that cold air is introduced into a temperature control template from the side wall structure concrete pouring, the maximum temperature difference between the temperature of the cold air and the central temperature of 8-10 sections of concrete is not more than 25 ℃, the side wall structure concrete is integrally cooled, meanwhile, cold water is introduced into a temperature control water pipe, the 2-5m sections of concrete are further cooled, and along with the increase of the concrete pouring height, a movable partition plate is gradually lifted upwards, so that the 2-5m sections of concrete and the 8-10 m sections of concrete are connected into a whole;
(5) after concrete pouring is finished, gradually releasing hydration heat along with the concrete hydration, stopping running of the temperature control water pipe when the temperature of the concrete in the 2-5m section reaches a temperature peak, and adjusting the temperature of cold air in the temperature control template to enable the temperature of the cold air in the temperature control template to be lower than the central temperature of the concrete in the 8-10 m section and the temperature difference to be not more than 10 ℃; the temperature history theories of all 2-5m sectional concrete or 8-10 m sectional concrete are the same, and the measured maximum data are used as reference, wherein the temperature histories actually have small differences;
(6) in the concrete temperature reduction stage, due to superposition of temperature reduction shrinkage and self-shrinkage, the internal stress of the concrete is gradually changed from compressive stress to tensile stress, when the actual tensile stress in the concrete in the section of 8-10 m is greater than 1.5MPa, hot water is introduced into a temperature control water pipe to heat the concrete in the section of 2-5m, the expansion reaction of a magnesium oxide expanding agent of the concrete in the section of 2-5m is further promoted, and meanwhile, the concrete in the section of 8-10 m is extruded through thermal expansion of the structure, so that the tensile stress is reduced, and the actual tensile stress in the concrete in the section of 8-10 m is ensured to be not greater than 2.0 MPa;
(7) when the actually measured tensile stress in the 8-10 m segmented concrete is less than 1.5MPa or the tensile stress is more than 1.5MPa but the growth rate is less than 0.1MPa/d, reducing the temperature of hot water in the temperature-controlled water pipe at the rate of 0.5 ℃/h, and stopping introducing hot water when the difference between the temperature of the hot water and the temperature of the 8-10 m segmented concrete is less than 5 ℃;
(8) after the temperature control of the temperature control water pipe is stopped, the internal stress of the concrete is continuously changed along with the development of self-shrinkage and temperature drop shrinkage of the concrete, at the moment, the temperature difference between the gas temperature in the temperature control template and the central temperature of the concrete in the section of 8-10 m is adjusted to be-10 ℃, the temperature effect of expansion with heat and contraction with cold of the concrete is realized by refrigerating or heating the concrete, so that the actually measured stress in the concrete in the section of 8-10 m is not more than 2.0MPa, and when the internal tensile stress of the concrete in the section of 8-10 m tends to be stable or gradually reduced within the range of less than 2.0MPa, the temperature control of the temperature control template is stopped, and the temperature control template is dismantled;
(9) and filling the temperature control water pipe with expansion mortar to complete the anti-cracking construction process.
And (2) in the step (1), the distance between every two sections of reinforcing meshes is 5-10 cm.
And (2) the height of the movable partition plate in the step (1) is not less than that of the reinforcing mesh.
In the step (1), the temperature control water pipes are circulating water pipes and are arranged in a snake shape in the 2-5m segmented reinforcing mesh, and when cold water or hot water is introduced into the temperature control water pipes, the temperature fields of the temperature control water pipes are evenly distributed in the 2-5m segmented concrete.
In the step (3), the magnesium oxide expanding agent is formed by mixing magnesium oxide with the activity of 80s, 120s, 180s and 240s according to the mass ratio of 10-25: 30-50: 15-30; the calcium-magnesium composite expanding agent is prepared from calcium oxide and magnesium oxide according to the weight ratio of 30-50: 50-70, wherein the activity of the magnesium oxide is one or two of 80s and 120 s. The calcium-magnesium composite expanding agent can effectively compensate early shrinkage of concrete with the section of 8-10 m, the magnesium oxide expanding agent is low in reactivity, and can continuously generate an expansion reaction under the condition of heating of a temperature control water pipe to generate effective expansion energy.
The temperature difference between the cold water temperature of the temperature control water pipe and the temperature of the 2-5m segmented concrete core in the step (4) is not more than 25 ℃, and the temperature difference between the hot water temperature of the temperature control water pipe and the temperature of the 8-10 m segmented concrete core in the step (6) is not more than 30 ℃.
The temperature control template in the step (3) is of an internal hollow structure, the temperature control template comprises a steel plate structure, a heat insulation material plate and a reinforcing plate, the steel plate structure is a concrete contact surface, the steel plate structure and the heat insulation material plate form a hollow structure, the reinforcing plate covers the heat insulation material plate, the reinforcing plate and the steel plate structure are fixedly connected through bolts, ventilation interfaces are arranged on the double-layer structure of the reinforcing plate and the heat insulation material plate, the ventilation interfaces are communicated with the hollow structure, and the ventilation interfaces of adjacent temperature control templates can be connected through connecting pipes so that the hollow structures of the adjacent temperature control templates are communicated; different temperature control templates can be communicated with each other, and air flow can flow in the internal hollow structure.
The invention has the following beneficial effects:
(1) the anti-cracking method can continuously pour the concrete of the underground side wall structure for a super long time, ensure the integrity of the structure and avoid cracking and water seepage;
(2) the anti-cracking technical means of the invention is based on tensile stress regulation and control, and the concrete crack is effectively avoided by real-time stress monitoring;
(3) the long wall structure is segmented, but the segments are integrated after pouring, the structural integrity is not influenced, the 8-10 m and 2-5m segmented concrete has different expansion regulation and control performances, and the internal tensile stress of the concrete is effectively regulated and controlled by combining temperature control measures.
(4) In summer, the temperature of the concrete entering a mold is higher and extremely difficult to control, so that the cracking risk of the concrete is greatly improved compared with other seasons.
Drawings
Fig. 1 is a structural diagram of sectional binding and stress monitoring arrangement of a reinforcing mesh of a side wall structure.
Fig. 2 is a structural view before concrete pouring construction of the side wall structure.
Fig. 3 is a structural view in a side wall structure concrete pouring construction process.
FIG. 4 is a top view of the side wall structure after concrete pouring but without filling the temperature-controlled water pipes.
Fig. 5 is a front view of the side wall structure concrete after the temperature-controlled water pipe is filled.
Fig. 6 is a structural view of a concrete temperature control template with a side-tipping structure.
The labels in FIGS. 1-6 are: 1 is 8~10m segmentation reinforcing bar net, 2 is 2~5m segmentation reinforcing bar net, 3 is the movable partition, 4 is the stressometer, 5 is on-line monitoring equipment, 6 is accuse temperature water pipe, 7 cables, 8 is 2~5m segmentation concrete, 9 is 8~10m segmentation concrete, 10 is accuse temperature template, 11 is the bottom plate concrete, 12 is the steel sheet structure, 13 is insulation board, 14 is the reinforcing plate, 15 is hollow structure, 16 is the interface of ventilating, 17 is the bolt.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
The invention provides a summer crack resistance construction method for underground side wall structure concrete, which specifically comprises the following steps:
(1) binding a steel bar mesh of a side wall structure on the upper part of a hardened bottom plate concrete structure, binding the steel bar mesh of the side wall structure in sections, dividing the side wall structure into sectional structures which are sequentially distributed in the ranges of 8-10 m, 2-5m, 8-10 m and 2-5m … … by the steel bar mesh, distributing temperature control water pipes 6 in all the 2-5m sectional steel bar meshes 2, and arranging movable partition plates 3 between the 2-5m sectional steel bar meshes 2 and the 8-10 m sectional steel bar meshes 1 and perpendicular to the bottom plate concrete structure;
(2) before side wall structure concrete pouring construction, pre-burying a stress meter 4 in the center of all segmented steel bar nets, wherein the stress meter 4 is connected with an online monitoring device 5 through a cable 7, the online monitoring device 5 collects stress and temperature data of the stress meter and presents the data online in a network form, and the stress meter has a temperature compensation function and can simultaneously test the temperature of concrete by utilizing the online monitoring device to monitor the stress development in the concrete in real time from the beginning of concrete pouring;
(3) replacing a traditional concrete formwork with a temperature control formwork 10, connecting hollow structures 15 of the temperature control formwork 10 of the whole side wall structure in series by using connecting pipes, determining the operation reliability of the concrete formwork by checking the air tightness of the temperature control formwork and a temperature control water pipe, and respectively pouring concrete doped with different expanding agents in a 2-5m segmented reinforcing mesh and a 8-10 m segmented reinforcing mesh, wherein a magnesium oxide expanding agent is doped in the 2-5m segmented concrete 8, and a calcium-magnesium composite expanding agent is doped in the 8-10 m segmented concrete 9;
(4) the method comprises the steps that cold air is introduced into a temperature control template from the side wall structure concrete pouring, the maximum temperature difference between the temperature of the cold air and the central temperature of 8-10 sections of concrete is not more than 25 ℃, the side wall structure concrete is integrally cooled, meanwhile, cold water is introduced into a temperature control water pipe, the 2-5m sections of concrete are further cooled, and along with the increase of the concrete pouring height, a movable partition plate is gradually lifted upwards, so that the 2-5m sections of concrete and the 8-10 m sections of concrete are connected into a whole;
(5) after concrete pouring is finished, gradually releasing hydration heat along with the concrete hydration, stopping running of the temperature control water pipe when the temperature of the concrete in the 2-5m section reaches a temperature peak, and adjusting the temperature of cold air in the temperature control template to enable the temperature of the cold air in the temperature control template to be lower than the central temperature of the concrete in the 8-10 m section and the temperature difference to be not more than 10 ℃; the temperature history theories of all 2-5m sectional concrete or 8-10 m sectional concrete are the same, and the measured maximum data are used as reference, wherein the temperature histories actually have small differences;
(6) in the concrete temperature reduction stage, due to superposition of temperature reduction shrinkage and self-shrinkage, the internal stress of the concrete is gradually changed from compressive stress to tensile stress, when the actual tensile stress in the concrete in the section of 8-10 m is greater than 1.5MPa, hot water is introduced into a temperature control water pipe to heat the concrete in the section of 2-5m, the expansion reaction of a magnesium oxide expanding agent of the concrete in the section of 2-5m is further promoted, and meanwhile, the concrete in the section of 8-10 m is extruded through thermal expansion of the structure, so that the tensile stress is reduced, and the actual tensile stress in the concrete in the section of 8-10 m is ensured to be not greater than 2.0 MPa;
(7) when the actually measured tensile stress in the 8-10 m segmented concrete is less than 1.5MPa or the tensile stress is more than 1.5MPa but the growth rate is less than 0.1MPa/d, reducing the temperature of hot water in the temperature-controlled water pipe at the rate of 0.5 ℃/h, and stopping introducing hot water when the difference between the temperature of the hot water and the temperature of the 8-10 m segmented concrete is less than 5 ℃;
(8) after the temperature control of the temperature control water pipe is stopped, the internal stress of the concrete is continuously changed along with the development of self-shrinkage and temperature drop shrinkage of the concrete, at the moment, the temperature difference between the gas temperature in the temperature control template and the central temperature of the concrete in the section of 8-10 m is adjusted to be-10 ℃, the temperature effect of expansion with heat and contraction with cold of the concrete is realized by refrigerating or heating the concrete, so that the actually measured stress in the concrete in the section of 8-10 m is not more than 2.0MPa, and when the internal tensile stress of the concrete in the section of 8-10 m tends to be stable or gradually reduced within the range of less than 2.0MPa, the temperature control of the temperature control template is stopped, and the temperature control template is dismantled;
(9) and filling the temperature control water pipe with expansion mortar to complete the anti-cracking construction process.
And (2) in the step (1), the distance between every two sections of reinforcing meshes is 5-10 cm.
And (2) the height of the movable partition plate in the step (1) is not less than that of the reinforcing mesh.
In the step (1), the temperature control water pipes are circulating water pipes and are arranged in a snake shape in the 2-5m segmented reinforcing mesh, and when cold water or hot water is introduced into the temperature control water pipes, the temperature fields of the temperature control water pipes are evenly distributed in the 2-5m segmented concrete.
In the step (3), the magnesium oxide expanding agent is formed by mixing magnesium oxide with the activity of 80s, 120s, 180s and 240s according to the mass ratio of 10-25: 30-50: 15-30; the calcium-magnesium composite expanding agent is prepared from calcium oxide and magnesium oxide according to the weight ratio of 30-50: 50-70, wherein the activity of the magnesium oxide is one or two of 80s and 120 s. The calcium-magnesium composite expanding agent can effectively compensate early shrinkage of concrete with the section of 8-10 m, the magnesium oxide expanding agent is low in reactivity, and can continuously generate an expansion reaction under the condition of heating of a temperature control water pipe to generate effective expansion energy.
The temperature difference between the cold water temperature of the temperature control water pipe and the temperature of the 2-5m segmented concrete core in the step (4) is not more than 25 ℃, and the temperature difference between the hot water temperature of the temperature control water pipe and the temperature of the 8-10 m segmented concrete core in the step (6) is not more than 30 ℃.
The temperature control template in the step (3) is of an internal hollow structure, the temperature control template comprises a steel plate structure 12, a heat insulation material plate 13 and a reinforcing plate 14, the steel plate structure 12 is a concrete contact surface, the steel plate structure 12 and the heat insulation material plate 13 form a hollow structure 15, the reinforcing plate 14 covers the heat insulation material plate 13, the reinforcing plate 14 and the steel plate structure 12 are fixedly connected through bolts 17, a ventilation interface 16 is arranged on a double-layer structure of the reinforcing plate and the heat insulation material plate and is communicated with the hollow structure, and ventilation interfaces of adjacent temperature control templates can be connected through connecting pipes to enable the hollow structures of the adjacent temperature control templates to be communicated; different temperature control templates can be communicated with each other, and air flow can flow in the internal hollow structure.
Example 1
And carrying out concrete construction on the side wall structure of a certain underground engineering, wherein the one-time pouring length of the side wall structure is 36m, the thickness of the side wall is 0.7m, the height of the side wall is 5.6m, and the construction design divides the side wall structure into five sections, namely 8m, 4m, 10m, 4m and 10 m.
In the construction preparation stage, a reinforcing mesh is bound in each section, the distance between two adjacent reinforcing meshes is 5cm, a movable partition plate is arranged between the adjacent reinforcing meshes, and a temperature control water pipe is arranged in a 4m section reinforcing mesh;
before concrete pouring construction, a stress meter is embedded in a structural reinforcing mesh in advance, from the beginning of concrete pouring, the stress development in the concrete is monitored in real time by utilizing online monitoring equipment, the stress meter has a temperature compensation function and can be used for simultaneously testing the temperature of the concrete, and the strain meter is connected with the online monitoring equipment through a cable;
replacing a traditional concrete template with a temperature control template, installing the temperature control template, checking the operation reliability of the temperature control template and a temperature control water pipe, and respectively pouring different concretes in a 4m segmented reinforcing mesh and 8m and 10m segmented reinforcing meshes, wherein a magnesium oxide expanding agent is doped in the 4m segmented concrete and is formed by mixing magnesium oxides with activity values of 80s, 120s, 180s and 240s according to the mass ratio of 20:20:40:20, a calcium magnesium composite expanding agent is doped in the 8m and 10m segmented concrete, the mass ratio of calcium oxide to magnesium oxide is 40:60, and the magnesium oxide is magnesium oxide with an activity value of 120 s;
when the concrete pouring is started, testing the mold-entering temperature to be 30 ℃, introducing cold air of 8 ℃ into the temperature control template, integrally cooling the concrete of the side wall structure, introducing cold water of 5 ℃ into the temperature control water pipe, further cooling and controlling the temperature of the concrete of 4m sections, and simultaneously gradually lifting up the movable partition plate along with the increase of the pouring height of the concrete so as to connect the concrete of 4m sections with the concrete of 8m and 10m sections into a whole;
after concrete pouring is finished, the hydration heat is gradually released along with the concrete hydration, the temperature of the concrete is gradually increased, and in the process, the difference between the temperature control template and the central temperature of the concrete with the sections of 8m and 10m is not more than 25 ℃, and the difference between the cold water temperature of the temperature control water pipe and the central temperature of the concrete with the sections of 4m is not more than 25 ℃;
after concrete is poured for 26 hours, the temperature of the concrete is increased from 30 ℃ to 62 ℃, the temperature begins to show a descending trend, the temperature is changed from 62 ℃ to 61.5 ℃, at the moment, the temperature of cold water in the temperature control water pipe is 38 ℃, cold water circulation of the temperature control water pipe is stopped, and meanwhile, the temperature of cold air in the temperature control template is adjusted to keep the temperature of the cold air in the temperature control template between 8 ℃ and 10 ℃ below the central temperature of the concrete in sections of 8m and 10 m;
in the temperature reduction stage of the concrete, due to superposition of temperature reduction shrinkage and self-shrinkage, the internal stress of the concrete is gradually changed from compressive stress to tensile stress, when the maximum tensile stress in the 8m and 10m concrete is greater than 1.5MPa, hot water is introduced into a temperature control water pipe to heat the 4m segmented concrete, the expansion reaction of a magnesium oxide expanding agent of the 4m segmented concrete is further promoted, and meanwhile, the 8m and 10m segmented concrete is extruded through thermal expansion of the structure, so that the tensile stress is reduced, and the internal tensile stress of the 8m and 10m segmented concrete is ensured to be not greater than 2.0 MPa;
when the internal tensile stress of the concrete in the sections of 8m and 10m is less than 1.5MPa, reducing the temperature of hot water in the temperature-controlled water pipe at the speed of 0.5 ℃/h, and stopping introducing the hot water when the difference between the temperature of the hot water and the temperature of the concrete in the sections of 8m and 10m is less than 5 ℃;
after the temperature control of the temperature control water pipe is stopped, the internal stress of the concrete is continuously changed along with the development of self-shrinkage and temperature drop shrinkage of the concrete, at the moment, the temperature difference between the temperature of the air flow of the temperature control template and the central temperature of the concrete in the sections of 8m and 10m is adjusted to be-10 ℃, the internal stress of the concrete in the sections of 8m and 10m is not more than 2.0MPa, when the internal tensile stress of the concrete in the sections of 8m and 10m is gradually reduced within the range of less than 2.0MPa, the temperature control of the temperature control template is stopped, the temperature control template is dismantled, the temperature control water pipe is filled with expansion mortar, and the anti-crack construction process is completed.
When the age of the concrete reaches 30 days, carrying out crack observation on the concrete of the side wall structure, wherein the result shows that no penetrating shrinkage crack is found, no water seepage and water leakage condition exists, and the engineering effect is good.
Example 2
The concrete construction of the side wall structure of a certain underground engineering is carried out, the concrete is marked as C40P10, the one-time pouring length of the side wall structure is 40m, the thickness of the side wall is 1.0m, and the height of the side wall is 4.8 m.
In the construction preparation stage, a reinforcing mesh is bound in each section, the distance between two adjacent reinforcing meshes is 6cm, a movable partition plate is arranged between the adjacent reinforcing meshes, and a temperature control water pipe is arranged in a 4m section reinforcing mesh;
before concrete pouring construction, a stress meter is embedded in a structural reinforcing mesh in advance;
replacing a traditional concrete template with a temperature control template, installing the temperature control template, checking the operation reliability of the temperature control template and a temperature control water pipe, and respectively pouring different concretes in a 4m segmented reinforcing mesh and a 8m segmented reinforcing mesh, wherein the 4m segmented concrete is doped with a magnesium oxide expanding agent which is formed by mixing magnesium oxides with activity values of 80s, 120s, 180s and 240s according to the mass ratio of 20:20:30:30, the 8m and 10m segmented concrete is doped with a calcium magnesium composite expanding agent, the mass ratio of calcium oxide to magnesium oxide is 30:70, and the magnesium oxide is magnesium oxide with an activity value of 120 s;
when the concrete pouring is started, testing the mold-entering temperature to be 33 ℃, introducing 8 ℃ cold air into the temperature control template, integrally cooling the concrete of the side wall structure, introducing 5 ℃ cold water into the temperature control water pipe, further cooling and controlling the temperature of the 4m segmented concrete, and simultaneously, gradually lifting the movable partition plate upwards along with the increase of the pouring height of the concrete so as to connect the 4m segmented concrete and the 8m segmented concrete into a whole;
after concrete pouring is finished, the hydration heat is gradually released along with the concrete hydration, the temperature of the concrete gradually rises, and in the process, the difference between the temperature control template and the central temperature of the 8m segmented concrete is not more than 25 ℃, and the difference between the cold water temperature of the temperature control water pipe and the central temperature of the 4m segmented concrete is not more than 25 ℃;
after the concrete is poured for 32 hours, the temperature of the concrete reaches 71 ℃ of the temperature peak, the temperature begins to show a descending trend, the cold water circulation of the temperature control water pipe is stopped, and meanwhile, the cold air temperature in the temperature control template is adjusted to keep the cold air temperature of the temperature control template between 8 ℃ and 10 ℃ lower than the central temperature of the segmented concrete of 8 m;
in the temperature reduction stage of concrete, due to superposition of temperature reduction shrinkage and self-shrinkage, the internal stress of the concrete is gradually changed from compressive stress to tensile stress, when the maximum tensile stress in the concrete with the length of 8m is greater than 1.5MPa, hot water is introduced into a temperature control water pipe to heat the concrete with the length of 4m, the expansion reaction of a magnesium oxide expanding agent of the concrete with the length of 4m is further promoted, and meanwhile, the concrete with the length of 8m is extruded through thermal expansion of a structure, so that the tensile stress is reduced, and the internal tensile stress of the concrete with the length of 8m is ensured to be not greater than 2.0 MPa;
when the internal tensile stress of the 8m segmented concrete is less than 1.5MPa, reducing the temperature of hot water in the temperature control water pipe at the speed of 0.5 ℃/h, and stopping introducing the hot water when the difference between the temperature of the hot water and the temperature of the 8m segmented concrete is less than 5 ℃;
after the temperature control of the temperature control water pipe is stopped, the internal stress of the concrete is continuously changed along with the development of self-shrinkage and temperature drop shrinkage of the concrete, at the moment, the temperature difference between the temperature of the air flow of the temperature control template and the central temperature of the 8m segmented concrete is adjusted to be-10 ℃, the internal stress of the 8m segmented concrete is not more than 2.0MPa, when the internal tensile stress of the 8m segmented concrete is gradually reduced within the range of less than 2.0MPa, the temperature control of the temperature control template is stopped, the temperature control template is removed, the temperature control water pipe is filled with expansion mortar, and the anti-cracking construction process is completed.
When the age of the concrete reaches 30 days, the internal stress value of the concrete is within the range of 0.1-0.5 MPa, the internal stress of the structure is compressive stress, which indicates that the whole structure is in an expansion compression state, and when the age reaches 60 days, the internal compressive stress of the concrete structure is within the range of 0.3-0.6 MPa and is relatively stable, which indicates that the whole concrete is maintained in a micro-expansion state under the good temperature control in the previous period and the continuous compensation contraction action of the later-stage expanding agent. Through carrying out crack observation on the concrete of the side wall structure, no penetrating shrinkage crack is found, the water seepage and leakage conditions are avoided, and the engineering effect is good.
Comparative example 1
In the project in embodiment 2, the construction is carried out in a conventional manner at the same time, the length of one-time pouring is 40m, the traditional steel formwork is used as a construction formwork, the concrete is conventional concrete, the 4 th day after pouring is demolded, geotextile is used for hanging and covering after demolding, and watering and maintenance are carried out regularly.
Actual engineering effects show that when the age of concrete reaches 7d, namely 3d after form removal, part of concrete cracks are found, the cracks are vertically distributed, when the age of concrete reaches 10d, the number of the concrete cracks is obviously increased, about 2-3 m cracks are formed, the regularity is high, when the age of concrete reaches 20d, 30% of cracks are found to have water leakage, and when the age of concrete reaches 50d, 45% of cracks are found to have water leakage in different degrees.
As can be seen from the crack resistance effects of the example 2 and the comparative example 1, the technical method of the present invention has a significant effect on crack resistance and water resistance in summer.
Claims (7)
1. The summer crack resistance construction method for the underground side wall structure concrete is characterized by comprising the following steps of:
(1) binding a reinforcing mesh of a side wall structure on the upper part of a hardened bottom plate concrete (11) structure, binding the reinforcing mesh of the side wall structure in sections, dividing the side wall structure into sectional structures which are sequentially distributed in the ranges of 8-10 m, 2-5m, 8-10 m and 2-5m … … by the reinforcing mesh, arranging temperature control water pipes (6) in all the 2-5m sectional reinforcing meshes (2), and arranging movable partition plates (3) between the 2-5m sectional reinforcing meshes (2) and the 8-10 m sectional reinforcing meshes (1) and perpendicular to the bottom plate concrete (11) structure;
(2) before the concrete pouring construction of the side wall structure, pre-burying a stress meter (4) in the center of all segmented steel bar nets, wherein the stress meter (4) is connected with an online monitoring device (5) through a cable (7), the stress development inside the concrete is monitored in real time by using the online monitoring device (5) from the beginning of the concrete pouring, and the stress meter (4) has a temperature compensation function and can simultaneously test the temperature of the concrete;
(3) replacing a traditional concrete formwork with a temperature control formwork, connecting hollow structures (15) of the temperature control formwork (10) of the whole side wall structure in series by using connecting pipes, installing the hollow structures, determining the operation reliability of the hollow structures by checking the air tightness of the temperature control formwork (10) and a temperature control water pipe (6), and respectively pouring concrete doped with different expanding agents in a 2-5m segmented reinforcing mesh (2) and an 8-10 m segmented reinforcing mesh (1), wherein a magnesium oxide expanding agent is doped in the 2-5m segmented concrete (8), and a calcium-magnesium composite expanding agent is doped in the 8-10 m segmented concrete (9);
the temperature control template is of an internal hollow structure and comprises a steel plate structure (12), a heat insulation plate (13) and a reinforcing plate (14), the steel plate structure (12) is a concrete contact surface, the steel plate structure (12) and the heat insulation plate (13) form a hollow structure (15), and the reinforcing plate (14) covers the heat insulation plate (13);
(4) introducing cold air into the temperature control template (10) from the beginning of side wall structure concrete pouring, wherein the maximum temperature difference between the temperature of the cold air and the central temperature of 8-10 sections of concrete (9) is not more than 25 ℃, simultaneously introducing cold water into the temperature control water pipe, and gradually lifting the movable partition plate (3) upwards along with the increase of the concrete pouring height to enable 2-5m sections of concrete (8) and 8-10 m sections of concrete (9) to be connected into a whole;
(5) after concrete pouring is finished, gradually releasing hydration heat along with the concrete hydration, stopping running of the temperature control water pipe (6) when the temperature of the 2-5m sectional concrete (8) reaches a temperature peak, and adjusting the temperature of cold air in the temperature control template (10) to ensure that the temperature of the cold air in the temperature control template (10) is lower than the central temperature of the 8-10 m sectional concrete (9) and the temperature difference is not more than 10 ℃;
(6) in the concrete temperature reduction stage, when the actually measured tensile stress in the 8-10 m segmented concrete (9) is larger than 1.5MPa, hot water is introduced into the temperature control water pipe (6) to heat the 2-5m segmented concrete (8), so that the actually measured tensile stress in the 8-10 m segmented concrete (9) is not larger than 2.0 MPa;
(7) when the actually measured tensile stress in the 8-10 m segmented concrete (9) is less than 1.5MPa or the tensile stress is more than 1.5MPa but the growth rate is less than 0.1MPa/d, reducing the temperature of hot water in the temperature-controlled water pipe (6) at the rate of 0.5 ℃/h, and stopping introducing hot water when the difference between the temperature of the hot water and the temperature of the 8-10 m segmented concrete (9) is less than 5 ℃;
(8) after the temperature control of the temperature control water pipe (6) is stopped, adjusting the temperature difference between the gas temperature in the temperature control template and the central temperature of the segmented concrete of 8-10 m to be-10 ℃, so as to ensure that the actually measured stress in the segmented concrete of 8-10 m is not more than 2.0MPa, and when the tensile stress in the segmented concrete of 8-10 m tends to be stable or gradually reduced within the range of less than 2.0MPa, stopping the temperature control of the temperature control template, and dismantling the temperature control template;
(9) and (3) filling the temperature-controlled water pipe (6) with expansion mortar to finish the anti-crack construction process.
2. The method for constructing concrete crack resistance of an underground side wall structure in summer according to claim 1, wherein the distance between the reinforcing meshes of each section in the step (1) is 5-10 cm.
3. The summer crack resistance construction method of concrete for an underground side wall structure according to claim 1, wherein the height of the movable partition in step (1) is not lower than that of the reinforcing mesh.
4. The summer crack resistance construction method for the underground side wall structure concrete according to claim 1, characterized in that in the step (1), the temperature control water pipes are circulating water pipes and are arranged in a serpentine shape in 2-5m segmented reinforcing mesh, and when cold water or hot water is introduced into the temperature control water pipes, the temperature fields of the temperature control water pipes are uniformly distributed in the 2-5m segmented concrete.
5. The construction method for cracking-resistant underground side wall structure concrete in summer according to claim 1, characterized in that in the step (3), the magnesium oxide expanding agent is a mixture of magnesium oxide with activity of 80s, 120s, 180s and 240s according to a mass ratio of 10-25: 30-50: 15-30; the calcium-magnesium composite expanding agent is prepared from calcium oxide and magnesium oxide according to the weight ratio of 30-50: 50-70, wherein the activity of the magnesium oxide is one or two of 80s and 120 s.
6. The construction method for cracking-resistant underground side wall structure concrete in summer according to claim 1, wherein the temperature difference between the cold water temperature of the temperature control water pipe in the step (4) and the temperature of the 2-5m sectional concrete core is not more than 25 ℃, and the temperature difference between the hot water temperature of the temperature control water pipe in the step (6) and the temperature of the 8-10 m sectional concrete core is not more than 30 ℃.
7. The construction method for cracking resistance of underground side wall structure concrete in summer according to claim 1, characterized in that the reinforcing plate (14) and the steel plate structure (12) of the temperature control formwork in step (3) are fixedly connected through bolts (17), the double-layer structure of the reinforcing plate (14) and the heat insulation plate (13) is provided with ventilation interfaces (16), the ventilation interfaces (16) are communicated with the hollow structure (15), and the ventilation interfaces of adjacent temperature control formworks are connected through connecting pipes to communicate the hollow structures of the adjacent temperature control formworks.
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