Winter small-volume concrete construction heating maintenance method

Abstract

The invention relates to a winter small-volume concrete construction heating curing method. The method comprises the following steps: firstly, mounting a bracket in a secondary concrete range; a resistance wire is wound on the mounting bracket, and the end of the resistance wire is reserved outside the concrete; the resistance wire is electrified after being connected with a power supply, and concrete is heated by heat of the resistance wire to cooperate with concrete curing. The maintenance device for heating the small-size concrete in winter construction is designed, the resistance wire is pre-buried in the shear-resistant groove of the small-size concrete, the resistance wire is heated before concrete pouring and within the required maintenance time, it is effectively guaranteed that the strength of the small-size concrete in winter construction is improved, and the freezing injury problem is avoided.

Description

Technical Field

[0001] The invention relates to the field of building construction, and in particular to a heating and curing method for small-volume concrete construction in winter. Background Art

[0002] In the process of construction, winter construction will be carried out due to tight construction schedule. For winter construction, how to ensure that the concrete does not suffer from freezing damage due to low temperature is the key goal to be controlled during construction.

[0003] Construction concrete involves equipment foundations, walls, columns and other large structures. There are also some bonding surface concrete used to bond structures such as beams and columns. The volume of bonding surface concrete is small and is usually called small volume concrete.

[0004] For larger volumes of concrete, such as raft foundations, integral wall columns, beams, slabs and stairs of floors, comprehensive heat storage methods, greenhouse methods and other measures are generally used to maintain the concrete, which can basically avoid the occurrence of concrete freezing damage.

[0005] For small-volume concrete with relatively small volume, its own reaction releases little heat, and the comprehensive heat storage method alone cannot achieve the insulation and maintenance effect, which will cause serious frost damage and cause serious construction quality problems. The conventional insulation and maintenance method for small-volume concrete in the existing technology is the greenhouse method, but since the foundations of steel structure factories are distributed far apart, multiple greenhouses need to be set up, and each greenhouse needs to be equipped with a separate hot air blower for heating. The temperature in the greenhouse will also be transferred to the outside by the steel columns, resulting in poor constant temperature effect of the greenhouse, which greatly increases the construction cost. Summary of the invention

[0006] The technical problem to be solved by the present invention is that there is currently a lack of effective heating and curing equipment for small-volume concrete, which leads to the problem that small-volume concrete often suffers from freezing damage.

[0007] The present invention solves the above-mentioned problem by adopting the following technical solution: A heating and curing method for small-volume concrete construction in winter. The first step is to calculate the heating power of the buried resistance wire per unit volume or area according to the construction temperature, the surface coefficient of the heated concrete, the technical indicators of the insulation materials and the heating rate. Then, according to the total engineering volume of each construction section, the number of equipment, cables and resistance wires invested, and the layout spacing of the resistance wires are calculated. The second step is to design and manufacture a mounting bracket according to the arrangement spacing of the resistance wires, and to arrange the mounting bracket in the concrete; The third step is to wind the resistance wire on the mounting bracket, and leave the end of the resistance wire outside the concrete; Step 4: Connect the resistance wire to the power supply; The fifth step is to energize the resistance wire and use the heat from the resistance wire to heat the concrete to assist in the maintenance of the concrete.

[0008] Compared with the prior art, the present invention adopting the above structure has the following beneficial effects: The present invention designs a curing device that can be used for heating small-volume concrete during winter construction. By pre-embedding a resistance wire in the shear groove of the small-volume concrete, the resistance wire is heated before concrete pouring and within the required curing time, thereby effectively ensuring that the strength of the small-volume concrete during winter construction is improved and avoiding frost damage.

[0009] Preferably, the power supply is installed in a distribution box, which is also provided with a transformer, the transformer is connected to a main cable, the main cable is connected to a resistance wire through a branch line, and the transformer outputs currents of three voltage levels: low voltage, medium voltage and high voltage.

[0010] Optionally, the mounting bracket is composed of transverse steel bars, longitudinal steel bars and vertical bars, the vertical bars are vertically arranged in a small volume of concrete, the transverse steel bars and longitudinal steel bars are arranged in a transverse and longitudinal grid, the intersection points are fixed to the vertical bars, and the spacing between the transverse steel bars and the longitudinal steel bars and the ends of the vertical bars is equal to the thickness of the concrete protective layer of the resistance wire.

[0011] Optionally, the resistance wire is spirally wound on the surface of the transverse steel bars and the longitudinal steel bars.

[0012] Optionally, the lower end of the vertical reinforcement at the reserved hole position falls on the bottom of the reserved hole, and the resistance wire is spirally coiled on the surface of the vertical reinforcement.

[0013] Preferably, the resistance wire is a single iron core insulated resistance wire with a length of 25 m and a diameter of 1.2 mm.

[0014] Preferably, the process of controlling the temperature of concrete by energizing the resistor is: S1, heating starts, using low voltage to heat the concrete at a rate of 5℃ / h. When the concrete temperature reaches 10℃, it stabilizes for 1 hour; S2, after stabilizing the low voltage for 1 hour, adjust to medium voltage and heat the concrete at a rate lower than 10℃ / h. When the concrete temperature reaches 23℃~27℃, heat it intermittently at this level to keep the concrete in this temperature range. S3, due to the stratification of the hardened and liquid parts of the concrete, the resistance of the resistance wire will gradually decrease, so when the concrete is finally set, the power supply voltage of the resistance wire is adjusted to a high voltage, and the concrete is heated at a rate of 10℃ / h. When the concrete temperature reaches 40℃, the heating is stopped; S4, the concrete surface is covered with windproof and heat-insulating measures, and the concrete temperature is controlled to be cooled at a rate lower than 5°C / h by the thickness of the windproof and heat-insulating measures; S5, when the concrete temperature is lower than 25°C, repeat step S3; when the concrete reaches 600°C, the small volume concrete curing is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall circuit layout of the present invention; Figure 2 It is a small volume concrete structure of the column foundation; Figure 3 It is a small volume concrete solid structure of the column foundation; Figure 4 It is a schematic diagram of a first embodiment of the mounting frame structure in a small volume concrete of the bonding surface of the present invention; Figure 5 This is a schematic diagram of an embodiment of the mounting frame structure in a small volume concrete of the present invention. Figure 6 It is a schematic diagram of the resistance wire of the present invention being wound on a mounting frame; In the figure: 1. Resistance wire; 2. Small volume concrete; 3. Branch line; 4. Main cable; 5. Distribution box; 6. Transformer; 7. Mounting bracket; 701. Horizontal steel bar; 702. Longitudinal steel bar; 703. Vertical steel bar; 8. Foundation; 801. Reserved opening; 9. Steel column. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with embodiments, the purpose of which is only to provide a better understanding of the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0017] The present invention is directed to a secondary poured concrete bonding layer between a steel column foundation concrete and a steel plate at the bottom of a steel column 9 in a steel structure workshop.

[0018] According to the conventional indicators of concrete, when the structural surface coefficient of concrete mixed with silicate cement is less than 6, the curing temperature is controlled at 25℃ and the maximum shall not exceed 40℃.

[0019] The measured resistivity of the 1.2mm2 diameter iron core resistance wire 1 is 0.18Ω / m. When the concrete temperature rises at 5℃ / h, the heat required per square meter is 3000kJ. The ambient temperature is -25℃, the temperature rise is 25℃, and the concrete surface is covered with a layer of plastic film for insulation and insulation quilt to prevent snow. It is calculated that the heat loss per hour is about 174.9kJ, the hydration heat of silicate cement is 650kJ / kg, the temperature rise coefficient is 0.013℃ / h, and the cement consumption per cubic meter of B50 concrete is 450kg. When the temperature rises, the concrete hydration heat dissipates 950.6KJ / h per cubic meter. Therefore, the number of resistance wires 1 is calculated according to the corresponding parts.

[0020] See also Figures 1 to 6The heating and curing method for small-volume concrete construction in winter provided by the present invention is carried out according to the following steps: The first step is to calculate the heating power of the buried resistance wire per unit volume or area according to the construction temperature, the surface coefficient of the heated concrete, the technical indicators of the insulation materials, the heating rate, etc., and then calculate the number of equipment, cables, and resistance wires invested according to the total project volume of each construction section, calculate the layout spacing of the resistance wires, and plan the layout of the resistance wires and equipment.

[0021] The second step is to design and manufacture the mounting bracket 7 according to the arrangement spacing of the resistance wire 1, and arrange the mounting bracket 7 in the concrete. As shown in the figure, the mounting bracket 7 is composed of a horizontal steel bar 701, a longitudinal steel bar 702 and a vertical steel bar 703. The vertical steel bar 703 is vertically arranged in the small volume concrete 2. The horizontal steel bars 701 and the longitudinal steel bars 702 are arranged in a horizontal and vertical mesh, and the intersection is fixed to the vertical steel bar 703. The spacing between the horizontal steel bars 701 and the longitudinal steel bars 702 and the end of the vertical steel bar 703 is equal to the thickness of the concrete protective layer of the resistance wire 1.

[0022] The third step is to wind the resistance wire 1 on the mounting bracket 7, and leave the end of the resistance wire 1 outside the concrete. The resistance wire 1 can be one or more. In a small volume of concrete 2, multiple resistance wires 1 should be connected together, and a terminal should be left outside the concrete. Optionally, the resistance wire 1 is spirally wound on the surface of the horizontal reinforcement 701 and the longitudinal reinforcement 702. If the steel column 9 fixed foundation 8 is a concrete foundation with a reserved opening 801, the vertical reinforcement 703 at the position of the reserved opening 801 has its lower end placed at the bottom of the reserved opening 801, and the resistance wire 1 is spirally wound on the surface of the vertical reinforcement 703.

[0023] In the fourth step, the resistance wire 1 is connected to the power supply for power supply. The power supply is installed in the distribution box 5, and the distribution box 5 is also provided with a transformer 6. The transformer 6 is connected to the main cable 4, and the main cable 4 is connected to the resistance wire 1 through the branch line 3. The transformer 6 outputs currents of three voltage levels: low voltage, medium voltage and high voltage. According to the actual situation of the project site, a 380V power supply can be selected, and the three output voltages of low, medium and high can be selected as 45V, 55V and 75V. The three output voltages can be a common interface set on the distribution box 5, or three interfaces can be set separately, and each interface is connected to at least one resistance wire 1.

[0024] The fifth step is to energize the resistance wire 1 and use the heat of the resistance wire 1 to heat the concrete to assist in the curing of the concrete.

[0025] At the construction site, the steel columns 9 are generally arranged in multiple rows and columns. Therefore, when setting up the circuit, the concrete heating resistors 1 on the joint surfaces of each steel column 9 should be uniformly connected to a power distribution cabinet for heating control management. Specifically, a 95mm2 aluminum core main cable 4 is connected from the transformer 6 and passed through the middle of the two rows of foundations 8. A 6mm2 single-core aluminum wire (branch line 3) is connected from the main cable 4 and extended to the vicinity of the foundation 8 and connected to the resistor 1.

[0026] The layout of transformer 6 and distribution box 5. According to the calculation results, the resistance wire 1 is arranged in groups and the power switch and transformer 6 are arranged respectively. After the concrete pouring is completed and covered with water-retaining and heat-insulating materials, heating begins.

[0027] Layout of cables and resistance wires 1. The main cable 4 is connected to each resistance wire 1 with a 6mm2 wire, and the joints are tightly wrapped with insulating tape to prevent contact with metal objects; the buried resistance wire 1 is 5-10cm away from the concrete surface to prevent the insulation layer from melting; the length and layout spacing of each resistance wire 1 should be consistent to ensure uniform heating; after the maintenance expires, the exposed part of the branch line 3 is cut off from the concrete surface for next use, and the connecting wires and cables can be reused many times.

[0028] The resistance wire 1 adopts a single iron core insulated resistance wire 1 with a length of 25m and a diameter of 1.2mm.

[0029] To prevent cracking due to too fast or too high a heating rate, the heating rate is controlled at 5℃ / h and the maximum temperature is controlled at 40℃. When the above temperature is reached, the power should be turned off and the heating should be stopped in time. When the temperature drops to 25℃, the power can be continued for heating.

[0030] Specifically, when the temperature rise of concrete is controlled by the resistance wire 1, the specific control method is: S1, heating starts, using low voltage to heat the concrete at a rate of 5℃ / h. When the concrete temperature reaches 10℃, it stabilizes for 1 hour; S2, after stabilizing the low voltage for 1 hour, adjust to medium voltage and heat the concrete at a rate lower than 10℃ / h. When the concrete temperature reaches 23℃~27℃, heat it intermittently at this level to keep the concrete in this temperature range. S3, due to the stratification of the hardened and liquid parts of the concrete, the resistance of the resistance wire 1 will gradually decrease, so when the concrete is finally set, the power supply voltage of the resistance wire 1 is adjusted to a high voltage, and the concrete is heated at a rate of 10°C / h. When the concrete temperature reaches 40°C, the heating is stopped; S4, the concrete surface is covered with windproof and heat-insulating measures, and the concrete temperature is controlled to be cooled at a rate lower than 5°C / h by the thickness of the windproof and heat-insulating measures; S5, when the concrete temperature is lower than 25°C, repeat step S3; when the concrete reaches the age of 600°C, the curing of the small volume concrete 2 is completed.

[0031] Specifically, the insulation measure is to cover the concrete surface with plastic film and quilt.

[0032] After the concrete is compacted, it should be covered tightly in time and then powered on to start heating and curing. The concrete temperature should be measured within 3 days after the start of heating. Within the first hour, the temperature should be tested every 15 to 20 minutes. If the temperature increases too quickly, the voltage should be lowered, and if it increases too slowly, the voltage should be increased. In the subsequent period, check at least twice an hour.

[0033] The present invention is a curing device for heating small-volume concrete during winter construction. A resistance wire is pre-embedded in a shear groove of the small-volume concrete, and the resistance wire is heated before concrete pouring and within the required curing time. This solution ensures the construction quality of the small-volume concrete at the junction of the steel column and the concrete foundation during winter construction, and avoids concrete freezing damage caused by low temperature.

[0034] The above description is only a preferred feasible embodiment of the present invention, and does not limit the scope of rights of the present invention. All equivalent changes made using the contents of the present specification and its drawings are included in the scope of rights of the present invention.

Claims

1. A heating and curing method for small-volume concrete construction in winter, characterized by: The first step is to calculate the heating power of the buried resistance wire (1) per unit volume or area according to the construction temperature, the surface coefficient of the heated concrete, the technical indicators of the insulation material and the heating rate, and then calculate the number of equipment, cables and resistance wires (1) invested according to the total engineering volume of each construction section, and calculate the layout spacing of the resistance wires (1); The second step is to design and manufacture a mounting bracket (7) according to the arrangement spacing of the resistance wires (1), and to arrange the mounting bracket (7) in the concrete; The third step is to wind the resistance wire (1) on the mounting bracket (7), and the end of the resistance wire (1) is left outside the concrete; Step 4: Connect the resistor wire (1) to the power supply; The fifth step is to energize the resistance wire (1) and utilize the heat of the resistance wire (1) to heat the concrete, thereby cooperating with the curing of the concrete.

2. The heating and curing method for small-volume concrete construction in winter according to claim 1 is characterized in that: The power supply is installed in a distribution box (5), and a transformer (6) is also provided in the distribution box (5). The transformer (6) is connected to the main cable (4), and the main cable (4) is connected to the resistance wire (1) through a branch line (3). The transformer (6) outputs currents of three voltage levels: low voltage, medium voltage and high voltage.

3. The heating and curing method for small-volume concrete construction in winter according to claim 1 is characterized in that: The mounting bracket (7) is composed of transverse steel bars (701), longitudinal steel bars (702) and vertical steel bars (703); the vertical steel bars (703) are vertically arranged in the small-volume concrete (2); the transverse steel bars (701) and the longitudinal steel bars (702) are arranged in a transverse and longitudinal grid pattern; the intersections are fixed to the vertical steel bars (703); the spacing between the transverse steel bars (701) and the longitudinal steel bars (702) and the ends of the vertical steel bars (703) is equal to the thickness of the concrete protective layer of the resistance wire (1).

4. The heating and curing method for small-volume concrete construction in winter according to claim 3 is characterized in that: The resistance wire (1) is spirally wound on the surface of the transverse steel bar (701) and the longitudinal steel bar (702).

5. The heating and curing method for small-volume concrete construction in winter according to claim 3 is characterized in that: The lower end of the vertical rib (703) located at the reserved hole (801) falls on the bottom of the reserved hole (801), and the resistance wire (1) is spirally wound on the surface of the vertical rib (703).

6. The heating and curing method for small-volume concrete construction in winter according to claim 1 is characterized in that: The resistance wire (1) is a single iron core insulated resistance wire (1) with a length of 25 m and a diameter of 1.2 mm.

7. The heating and curing method for small-volume concrete construction in winter according to claim 1 is characterized in that: The process of controlling the temperature of concrete by energizing the resistor is as follows: S1, heating starts, using low voltage to heat the concrete at a rate of 5℃ / h. When the concrete temperature reaches 10℃, it stabilizes for 1 hour; S2, after stabilizing the low voltage for 1 hour, adjust to medium voltage and heat the concrete at a rate lower than 10℃ / h. When the concrete temperature reaches 23℃~27℃, heat it intermittently at this level to keep the concrete in this temperature range. S3, due to the stratification of the hardened and liquid parts of the concrete, the resistance of the resistance wire (1) will gradually decrease, so when the concrete is finally set, the power supply voltage of the resistance wire (1) is adjusted to a high voltage, and the concrete is heated at a rate of 10°C / h. When the concrete temperature reaches 40°C, the heating is stopped; S4, the concrete surface is covered with windproof and heat-insulating measures, and the concrete temperature is controlled to be cooled at a rate lower than 5°C / h by the thickness of the windproof and heat-insulating measures; S5, when the concrete temperature is lower than 25°C, repeat step S3; when the concrete reaches 600°C, the curing of the small volume concrete (2) is completed.

8. The heating and curing method for small-volume concrete construction in winter according to claim 7 is characterized in that: The thermal insulation measure is to cover the concrete surface with plastic film and quilt.

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