Steam curing system and method for concrete product

Abstract

To provide a steam curing system capable of producing a concrete product of a constant quality even if an ambient temperature varies.SOLUTION: A steam curing system 1 comprises: a steam supply device 10 that supplies steam to curing chambers 21 to 24; an ambient temperature measurement unit 39t that measures an ambient temperature; a counter 34 that measures an elapsed time JT after the steam is supplied; and a steam supply control unit 35 that measures the ambient temperature regularly during curing, updates a curing time ET predetermined in advance to be varied based on the ambient temperature, and when the elapsed time JT exceeds the curing time ET stops supplying steam to the curing chambers 21 to 24.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a system and method for steam curing, including steam curing, of a concrete product. [Background technology]

[0002] Patent Document 1 describes a method for curing mass concrete that can cure in the shortest possible time while preventing cracks from occurring in response to the outside air temperature that changes between summer and winter when constructing a mass concrete structure such as a dam. It also describes a method for creating an optimal curing temperature pattern for concrete at each different outside air temperature in advance based on temperature history and stress level obtained from a full-scale model experiment, and for constructing a mass concrete structure, selecting a table of curing temperature patterns corresponding to the outside air temperature at that time (when pouring concrete), and curing the poured concrete based on that curing temperature pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-344437 A Summary of the Invention [Problem to be solved by the invention]

[0004] Steam curing is often used to accelerate the hardening of concrete when concrete products such as gutter blocks, rainwater storage infiltration basins, hand holes, oil-water separators, L-shaped retaining walls, and wiring boxes are prefabricated in factories. Cement undergoes a chemical reaction and sets when mixed with water. The main cement hydrates are calcium silicate hydrate (tobermorite), calcium hydroxide, calcium aluminate hydrate, and calcium sulfoaluminate hydrate, and the main hardening agents are alite (tricalcium silicate 13CaO·Si02) and belite tricalcium silicate (2CaO·Si02). Tobermorite acts as a glue to harden the concrete. The hydration reaction of cement is an exothermic reaction, and heat of hydration is generated during the hardening process.

[0005] Curing is the process of allowing concrete to harden sufficiently. Applying heat during the initial curing process activates the molecules, accelerating the hardening rate. Humidity during curing is also important. If the concrete dries out during curing, the hydration reaction will not occur sufficiently, making it difficult to harden and also posing the problem of drying shrinkage. Therefore, curing is preferably carried out in a moist state, and steam curing is used.

[0006] Factory prefabricated concrete products often adopt normal pressure steam curing to improve the turnover rate of the formwork and enable early shipment of the product. In steam curing, a special room called a curing chamber or curing tank is created, and steam generated by a boiler, which is the steam source, is ventilated into the designated curing chamber to heat and humidify the concrete in the formwork, promoting the development of strength. Even when the formwork concrete structure (concrete product) is heated and humidified in the curing chamber, it is not possible to completely block the influence of outside air. In steam curing, reducing the amount of fuel consumed by the boiler that generates the steam is one of the important issues, but if the formwork concrete product after steam curing is not sufficiently hardened to be demolded, there is an increased risk of injury due to the product being broken or falling during the demolding process, and damage to machinery and equipment.

[0007] Therefore, when steam curing concrete products in a curing room, the curing time is shortened in summer and extended in winter, but the setting of the curing time is based only on experience. In particular, since steam curing takes several hours, steam curing is often performed at night, and the setting of the curing time is based only on the outside temperature when the steam supply is started. Therefore, if the outside temperature drops suddenly in winter, the concrete product may not have reached the strength required for demolding the next morning, even after the set curing time has passed. On the other hand, if the curing time is set too long, it is not possible to save fuel consumed by the boiler. In addition, when manufacturing a large amount of concrete products or a wide variety of concrete products, many curing rooms are required, and increasing the boiler equipment to accommodate them has a significant impact on production costs, so measures are needed. [Means for solving the problem]

[0008] One aspect of the present invention is a system for steam curing of concrete products having a steam supply device for supplying steam to a curing chamber that contains a concrete product in a formwork to be cured. The steam curing system further has an outside air temperature measuring unit for measuring the outside air temperature, and a control device for controlling the supply of steam to the curing chamber. The control device includes an elapsed time measuring unit for measuring the elapsed time after steam is supplied to the curing chamber, and a steam supply control unit for periodically updating a curing time that is preset to vary based on the outside air temperature based on the outside air temperature that is periodically measured during the elapsed time, and for stopping the supply of steam to the curing chamber when the elapsed time exceeds the updated curing time.

[0009] In this steam curing system, instead of determining the curing time solely based on the conditions before the start of curing, such as when the concrete is poured into the formwork or when curing begins, the system tracks the change in outside air temperature during curing and determines the timing to stop the supply of steam to the curing room based on the outside air temperature during curing, thereby urging the end of curing. Therefore, if the outside air temperature drops during curing, the end of curing is automatically extended, so there is no need to set the initial curing time to a long time, including a margin for temperature changes at night, and fuel consumed by the boiler can be saved. In addition, even if the outside air temperature drops unexpectedly at night, sufficient curing time is automatically ensured, so it is possible to prevent a situation in which the concrete product in the formwork after steam curing is not sufficiently hardened to be removed from the formwork.

[0010] The steam curing system may further include a room temperature measuring unit that measures the room temperature in the curing chamber, and a room temperature control unit that controls the amount of steam supplied to the curing chamber to control the room temperature to a set temperature based on the elapsed time. When steam curing a concrete product, it becomes possible to control the temperature at multiple stages, such as pre-curing and main curing, and room temperature control can be performed independently of the control of the steam supply.

[0011] The steam supply device may include a path for dividing the multiple curing chambers into multiple groups and supplying steam to the multiple groups, and the control device may include multiple group control units for controlling the supply of steam to each of the multiple groups. Each of the multiple group control units may include an elapsed time measurement unit for each group and a steam supply control unit. That is, each group control unit may include an elapsed time measurement unit for measuring the elapsed time of each of the multiple groups. Furthermore, each group control unit may include a steam supply control unit for controlling the supply of steam to each of the multiple groups based on the elapsed time of each of the multiple groups and the curing time for each group (group unit) that is set in advance for each of the multiple groups to vary based on the outside air temperature and is periodically updated based on the outside air temperature during the elapsed time of each of the multiple groups. The length of the curing time may vary not only depending on the outside air temperature but also depending on the type of concrete product to be cured and the performance (heat retention performance, capacity, etc.) of the curing chamber. Therefore, by dividing into multiple groups and appropriately controlling the curing time, the time to actually supply steam for curing can be further shortened and fuel can be saved.

[0012] The control device may include a first control unit that supplies steam to some of the groups in sequence and / or a second control unit that supplies steam to some of the groups in parallel. After starting the supply of steam to a first group of the groups, the first control unit stops the supply of steam to the first group and starts the supply of steam to a second group of the groups when the elapsed time of the first group exceeds a periodically updated curing time for the first group. The second control unit supplies steam at a timing when the elapsed time of the first group and the elapsed time of the third group overlap.

[0013] In this steam curing system, since the curing time is updated according to the outside air temperature, the preset curing time may be set to the minimum time without any leeway, and control can be performed to supply steam to multiple groups in sequence. For example, when setting a curing time with a leeway for multiple groups, if the time available for curing is limited, such as at night, it is necessary to provide a steam supply device for each of the multiple groups, which may increase not only fuel but also equipment costs such as boilers and piping. In contrast, the steam curing system of the present invention can minimize the preset curing time, making it possible to set a schedule for supplying steam to multiple groups in sequence, and even if the temperature drops at night, the quality of the concrete product can be maintained by simply updating the curing time for the group that is curing (during the elapsed time) at the time the temperature drops, and the extension time can also be minimized. Therefore, even in a steam curing system that handles a large number of curing chambers, not only can fuel be saved, but also an increase in equipment costs such as boilers can be suppressed.

[0014] The steam supply control unit may include functionality for updating the curing time by increasing or decreasing the time for a first curing time preset for a first outside air temperature based on a temperature difference of the periodically measured outside air temperature relative to a first preset outside air temperature.

[0015] Another aspect of the present invention is a control device for a steam supply device that supplies steam to a curing chamber that contains a concrete product in a formwork to be cured. The control device has a steam supply control unit that periodically updates a curing time that is preset to vary based on an outside air temperature based on an outside air temperature measured during the elapsed time after steam is supplied to the curing chamber, and stops the supply of steam to the curing chamber when the elapsed time exceeds the periodically determined curing time.

[0016] Yet another embodiment of the present invention is a method for manufacturing a concrete product, which includes supplying steam to a curing chamber that contains a formworked concrete product to be cured. In this manufacturing method, the step of curing by supplying steam includes measuring the elapsed time after supplying steam to the curing chamber, periodically updating a curing time that is preset to vary based on an outside air temperature based on an outside air temperature that is periodically measured during the elapsed time, and stopping the supply of steam to the curing chamber when the elapsed time exceeds the updated curing time.

[0017] Curing by supplying steam may include controlling the room temperature to a temperature set based on the elapsed time by controlling the amount of steam supplied to the curing chamber. Curing by supplying steam may include dividing the multiple curing chambers into multiple groups and supplying steam to the multiple curing chambers. Dividing the multiple curing chambers into multiple groups and supplying steam to the multiple groups may include measuring the elapsed time of each of the multiple groups, and controlling the supply of steam to each of the multiple groups based on the elapsed time of each of the multiple groups and a curing time for each of the multiple groups that is set in advance for each of the multiple groups to vary based on an outside air temperature and that is periodically updated based on the outside air temperature during the elapsed time of each of the multiple groups. Controlling the supply of steam to each of the multiple groups may include stopping the supply of steam to the first group and starting the supply of steam to a second group of the multiple groups when the elapsed time of the first group exceeds the periodically updated curing time for the first group after starting the supply of steam to a first group of the multiple groups.

[0018] Yet another aspect of the present invention is a method for controlling a steam supply device that supplies steam to a curing chamber that contains a formworked concrete product to be cured. The method includes periodically updating a curing time that is preset to vary based on an outside air temperature based on an outside air temperature measured during an elapsed time after steam is supplied to the curing chamber, and stopping the supply of steam to the curing chamber when the elapsed time exceeds the periodically determined curing time. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a block diagram showing an overview of a steam curing system. [Diagram 2] Graph showing an example of temperature change (temperature control) in a curing chamber. [Diagram 3] FIG. 1 is a diagram showing an example of a steam curing schedule in which a curing chamber is divided into multiple groups. [Figure 4] 1 is a flowchart showing an overview of steam curing control. [Diagram 5] This is an example of a PC screen for selecting a pattern. [Figure 6] This is an example of a PC screen for setting a pattern. [Figure 7] An example of a PC screen for assigning patterns to groups of curing rooms. [Figure 8] An example of a PC screen, showing the operation screen for a steam curing system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1 shows an overview of a steam curing system. This steam curing system 1 is a system that automatically measures the outside air temperature periodically and appropriately fine-tunes the steam curing time. The steam curing system 1 includes a steam supply device (steam supply system) 10 that supplies steam to one or more curing chambers. In this example, the steam supply device 10 includes two boilers 11 and 12, a common steam header 13 connected to these boilers 11 and 12, and a first steam header 15 and a second steam header 16 that receive steam from the common steam header 13. This steam supply device 10 is capable of supplying steam to a plurality of curing chambers divided into a plurality of groups. For example, the first steam header 15 supplies steam to two curing chambers 21 and 22 as a first group G1. The second steam header 16 also supplies steam to two curing chambers 23 and 24 as a group G2. Similarly, the steam supply device 10 can supply steam to a plurality of curing chambers in parallel and / or in sequence, such as the curing chambers of group G3 and the curing chambers of group Gn, within the range that the boilers 11 and 12 can supply steam to.

[0021] Taking the curing chambers 21-24 as an example, each of the curing chambers 21-24 stores a concrete product (concrete structure, concrete product in formwork) 2, which is made by pouring concrete into a formwork, and maintains the concrete product in a hot and humid state for a prescribed period of time (steam curing). After curing, the concrete product in formwork 2 is removed from the curing chambers 21-24, and the formwork 3 and the concrete product 5 are separated (removed from the formwork), and the concrete product is further aged for an appropriate period of time in an indoor or outdoor stockyard, and then shipped. Steam curing is one of the processes for ensuring the strength required for removal from the formwork in a short period of time.

[0022] The steam curing system 1 further includes a boiler control system 14 that controls the on / off and / or output of the boilers 11 and 12 based on the pressure of a pressure gauge (pressure transmitter) 13p attached to the common steam header 13, an outside air temperature measurement unit 39t that measures the outside air temperature, a control device (steam supply control system) 30 that controls the steam supplied to the groups of curing chambers G1 to Gn, and a room temperature control system 40 that controls the room temperature of each of the curing chambers 21 to 24. The room temperature control systems 40 provided in the curing chambers 21 to 24 have a common configuration and include a room temperature measurement unit (thermometer, temperature transmitter) 41 that measures the room temperature RT of each of the chambers 21 to 24, a control valve 42 that controls the supply of steam to each of the chambers 21 to 24, and a room temperature control unit 43 that controls the control valve 42 connected to each of the chambers 21 to 24 so that the room temperature RT measured by the room temperature measurement unit 41 falls within a predetermined range and changes over time according to a predetermined function. The control device 30 may include a group control unit 31 that controls the supply of steam to the groups G1 and G2 to which the first and second steam headers 15 and 16 belong based on the pressure of pressure gauges (pressure transmitters) 15p and 16p attached to the headers 15 and 16, respectively, which are provided in groups.

[0023] FIG. 2 shows an example of controlling the room temperature of each of the chambers 21-24. The curing period (curing time) ET may include a period from the start of steam supply to a temperature Tpt suitable for pre-curing, a pre-curing period in which the temperature is maintained at Tpt, a period in which the temperature is increased to a temperature Ttt for main curing, and a main curing period in which the temperature is maintained at Ttt. The curing time ET may be set after the conditions for pre-curing are met. In pre-curing, the room temperature RT is kept relatively low, for example, at 40°C (±5°C), and in main curing, it is kept relatively high, for example, at 60°C (±5°C) in winter. In summer, the temperature setting for pre-curing and main curing may be the same, but it is preferable that the temperature for main curing does not exceed 65°C, and therefore it is often kept at about 60°C. The room temperature control unit 43 has a function to maintain the room temperature RT at, for example, 40°C (±5°C) during pre-curing, and at, for example, 60°C (±5°C) during main curing in winter. Furthermore, the room temperature control unit 43 has a function to maintain the rate of increase of the room temperature RT at 20°C or less per hour. If the curing start time t0 is the time when steam supply begins, in winter, since the outside air temperature is low, it may take, for example, one hour from boiler startup to reach the curing start time t0, whereas in summer, since the outside air temperature is high, it may take, for example, 0.5 hours from boiler startup to reach the curing start time t0.

[0024] It is possible to determine whether the conditions for pre-curing are met from the room temperature RT. In addition, when the conditions for starting curing are met, the room temperature control unit 43 uses the control valve 42 to throttle the amount of steam supply or turn it on and off, and controls the room temperature RT to be the pre-curing temperature Tpt. This causes the pressure in the first and second steam headers 15 and 16 to rise. Therefore, it can also be determined whether the conditions for starting curing are met by monitoring the pressure in the steam headers 15 and 16 with the pressure gauges 15p and 16p.

[0025] The control device 30 includes a group control unit 31 that controls the pressure of the steam headers 15 and 16 that supply steam to each group. The group control units 31 for each header have a common configuration, and each group control unit 31 includes a control valve 33 that controls the steam supply to the headers (e.g., the header 15) belonging to the respective group, an elapsed time measurement unit (e.g., a counter) 34 that measures the elapsed time JT, a steam supply control unit 35 that compares the elapsed time JT with the curing time ET and turns off (closes) the control valve 33 when the elapsed time JT exceeds the curing time ET, and a valve control unit 36 ​​that controls the opening degree of the control valve 33 or controls the control valve 33 on and off to control the internal pressure of the header 15 to be constant. When a close signal is received from the steam supply control unit 35, the valve control unit 36 ​​closes the control valve 33 and stops the steam supply to the headers (e.g., the header 15) of each group.

[0026] The counter 34 measures the elapsed time JT corresponding to the curing time ET. In this example, the counter 34 measures the elapsed time JT after the supply of steam to the curing chamber 21 is started. If the curing time ET is a period after the pre-curing conditions are met, the counter 34 may start measuring the elapsed time JT, for example, when the pressure of the first steam header 15 exceeds a predetermined value, determining that the curing start conditions are met. The counter 34 may start counting the elapsed time JT by detecting that the temperature of the curing chamber 21 has reached a predetermined temperature (pre-curing temperature) Tpt.

[0027] The steam supply control unit 35 periodically updates the curing time ET, which is preset to vary based on the outside air temperature AT, based on the outside air temperature AT periodically measured during the elapsed time JT, and stops the supply of steam to the curing chamber when the elapsed time JT exceeds the updated curing time ET. The steam supply control unit 35 may include, for example, a curing time register 51 in which the curing time ET is stored, a curing time updating unit 52 that updates the curing time ET based on the outside air temperature AT measured by the outside air temperature measuring unit 39t and sets it in the curing time register 51, and a comparison unit 53 that compares the curing time ET in the curing time register 51 with the elapsed time JT measured (timed) by the counter 34.

[0028] The control device 30 includes a central control unit 32 that controls the steam curing system 1 as a whole via a plurality of group control units 31. The central control unit 32 includes a first control unit 32a that supplies steam to some of the groups G1 to Gn of the curing chambers in sequence via the group control unit 31 to perform curing, a second control unit 32b that supplies steam to some of the groups G1 to Gn of the curing chambers in parallel to perform curing, and an external interface 32c for monitoring start / stop and operating conditions via a personal computer (PC) 37 or the like. The external interface 32c may include a function for performing initial settings including setting the curing time ET of each group.

[0029] The curing time update unit 52 included in the steam supply control unit 35 of each group control unit 31 periodically measures the outside air temperature AT during the elapsed time JT during which the concrete product with formwork is cured in the curing chamber of each group, for example, in 5-minute increments, periodically updates the curing time ET that is preset to vary based on the outside air temperature AT, and sets the curing time ET in the curing time register 51. The curing time update unit 52 can set a reference curing time taking into account the characteristics of the concrete product to be cured and / or conditions such as the season via the PC 37, and conditions for varying the reference curing time depending on whether the outside air temperature rises or falls. For example, a reference first curing time ET1 (for example, 3 hours) is set for a reference first outside air temperature AT1 (for example, 10°C), and can be preset in relation to a temperature difference ΔAT from the reference outside air temperature AT1 and a time difference ΔET per temperature difference ΔAT from the reference curing time ET1, for example, per degree difference. If the temperature difference ΔAT is positive, the time difference ΔET corrected with respect to the standard curing time ET1 is negative, and the curing time ET may decrease when the curing time ET is updated based on the outside air temperature. On the other hand, if the temperature difference ΔAT is negative, the time difference ΔET corrected is positive, and the curing time ET may increase when the curing time ET is updated based on the outside air temperature.

[0030] Therefore, even if the outside air temperature AT is a reference temperature (10°C) at time t0 when the steam supply is started, if the outside air temperature AT becomes 6°C during the elapsed time JT during which the steam supply is continued, the curing time update unit 52 updates the curing time ET stored in the register 51 to a value obtained by adding the time difference ΔET (for example, 6 minutes) set in relation to the temperature difference ΔAT (4°C) to the reference curing time ET1 (for example, 3 hours). Therefore, until the elapsed time JT measured by the counter 34 reaches 3 hours and 6 minutes, steam is supplied to the first steam header 15, and the temperature of the curing chamber 21 is maintained at a temperature suitable for steam curing (main curing). Then, when the elapsed time JT exceeds 3 hours and 6 minutes, the steam supply to the first steam header 15 is stopped, the steam curing is terminated, and the temperature of the curing chamber 21 drops to a temperature maintained by the heat retention function of the curing chamber itself.

[0031] During curing (during the elapsed time), if the outside air temperature AT further becomes 4°C, the curing time update unit 52 updates the curing time ET stored in the register 51 to a value obtained by adding the time difference ΔET (for example, 9 minutes) set in association with the temperature difference ΔAT (6°C) to the reference curing time ET1 (3 hours). Therefore, steam is supplied to the first steam header 15 and the temperature of the curing chamber 21 is maintained at a temperature suitable for steam curing (main curing) until the elapsed time JT measured by the counter 34 reaches (or is less than) 3 hours and 9 minutes. Then, when the elapsed time JT exceeds (or is equal to or greater than) 3 hours and 9 minutes, the supply of steam to the first steam header 15 is stopped and the steam curing is terminated.

[0032] On the other hand, when the outside air temperature AT rises during curing (during the elapsed time), the curing time update unit 52 changes (updates) the curing time ET stored in the register 51 to a shorter value, inversely to the above. In this way, in this steam curing system 1, instead of determining the curing time ET univocally only when the concrete is poured into the formwork, when curing is started, or when the conditions are just before that, the change in the outside air temperature AT during curing is traced, and the curing time ET is updated based on the outside air temperature AT during curing. Therefore, when curing is completed, or at a timing appropriate for the outside air temperature AT in the vicinity of that time, the supply of steam to the curing chamber 21 can be stopped, and curing can be completed. Therefore, if the outside air temperature AT at the start of curing is low, the curing time ET is automatically lengthened, and if the outside air temperature AT further drops during curing, the curing time ET is automatically extended. Also, if the outside air temperature AT at the start of curing is high, the curing time ET is shortened.

[0033] Therefore, by using the steam curing system 1 to steam-cure the concrete product 2 in the formwork and produce the concrete product 5, the temperature and time of the steam curing that affect the concrete product 5 can be automatically managed. Therefore, the quality of the cured concrete product 5 can be kept almost constant regardless of the season. In addition, by automatically measuring the outside air temperature AT and automatically managing the curing time ET, it is possible to avoid using extra boiler fuel and reduce costs. In addition, the life of the boilers 11 and 12 is extended and the maintenance costs are reduced. In particular, in winter, even if the temperature drops suddenly at night, it is possible to prevent problems with demolding of the concrete product due to insufficient curing. In addition, in summer, it is possible to suppress the occurrence of cracks (hair cracks) caused by excessive steam curing.

[0034] Furthermore, it is no longer necessary to set the curing time ET to an excessive (with a margin) value in anticipation of nighttime temperature changes. This saves fuel costs and makes it possible to set a schedule for supplying steam sequentially to some or all of the groups G1 to Gn, or to several groups (combinations), and steam curing can be performed using a common steam supply device 10 for multiple groups. This makes it possible to reduce equipment costs for steam curing.

[0035] Several patterns (schedules) are shown in Fig. 3. As shown in Fig. 3(a), if the basic curing time ET of the first group G1 of the curing chamber is 3 hours, the basic curing time ET of the second group G2 of the curing chamber is 3 hours, and the basic curing time ET of the third group G3 of the curing chamber is 2 hours, if the curing time ET is set to 4 hours in anticipation of a drop in temperature at night, then at most two groups can be supported by one steam supply device during the eight hours at night. In the steam curing system 1 of this example, it is possible to schedule with the basic curing time ET, and as shown in Fig. 3(a), a schedule can be set in the first control unit 32a such that the groups G1, G2, and G3 are steam cured in sequence for eight hours.

[0036] When the outside temperature drops at night, as shown in FIG. 3(b), the curing time ET of group G1 is updated to 3.1 hours, and the curing time ET of group G2 is updated to 3.1 hours, and it may take 8.2 hours to complete the curing of group G3. However, there is no shortage of curing time for each group, and the steam curing process can be completed in the curing chambers of the three groups.

[0037] Furthermore, when the amount of steam consumed in the curing chamber of group G3 is small, for example, as shown in FIG. 3(c), steam curing can be performed by supplying steam in parallel to the third group G3 and the fourth group G4, making it possible to perform steam curing by making the most of the capacity of the steam supply device 1.

[0038] FIG. 4 shows an overview of the process for manufacturing a concrete product using this steam curing system 1. First, in step 61, a pattern is set in which the curing time ET varies with the outside air temperature AT. FIGS. 5 to 7 show an example of an initial setting screen of the PC 37. As shown in FIG. 5, eight patterns can be set in this steam supply control device 30. FIG. 6 shows a screen for setting each pattern. The time difference ΔET from the reference time (reference curing time) with respect to the temperature difference ΔAT from the reference temperature (reference outside air temperature) AT1 can be set in minutes. Furthermore, as shown in FIG. 7, the pattern to be applied and the reference time ET1 can be set for each group of curing chambers.

[0039] Returning to FIG. 4, when the initial settings are completed, in step 62, the boiler is started to start preparation for steam curing. FIG. 8 shows an example of the operation screen of the PC 37. First, the manual / automatic changeover button 81 is set to automatic. Next, the operation on / off button 82 of the curing room (curing group) is operated to turn on the operation button of the curing room to be operated. After that, the automatic start button 83 is operated. The automatic start button 83 operates the control system 14 of the boilers 11 and 12, which automatically controls the boilers 11 and 12. In step 63, measurement of the elapsed time JT of the first selected group, for example, group G1, is started, and in step 64, the room temperature control system 40 of each of the curing rooms 21 and 22 of group G1 is operated to start room temperature control.

[0040] In step 65, the curing time update unit 52 of the supply control unit 35 periodically measures the outside air temperature AT using a thermometer 39t installed outdoors, and in step 66, updates the curing time ET in accordance with the measured outside air temperature AT according to a preset pattern and sets it in the curing time register 51. In step 67, the comparison unit 53 compares the curing time ET set in the curing time register 51 with the elapsed time JT counted by the counter 34, and if the elapsed time JT exceeds the curing time ET, stops the supply of steam to the group G1, and in step 68, checks whether there is a group for which steam curing is scheduled next. For example, if steam curing is scheduled for the group G2, the process returns to step 63 and starts steam curing for the group G2. If there is no group scheduled, in step 69, the comparison unit 53 instructs the valve control unit 36 ​​to stop the steam supply.

[0041] As shown in Fig. 8, the operation screen of PC 37 has, for each curing room (curing group), a display 85 of the current outside air temperature AT, a display 86 of the curing time (set time) ET calculated based on the outside air temperature AT and the set pattern, and a display 87 of the difference (remaining time) between the curing time ET and the elapsed time JT. PC 37 may have a function for storing past curing data, and may have a function for analyzing whether the curing time was sufficient or insufficient for the outside air temperature. PC 37 may also have a function for connecting to the Internet, and may have a function for changing various settings by historical operations from an external terminal.

[0042] As described above, the steam curing system 1 includes a steam supply control system 30, and the group-based control unit 31 includes a counter 34 for measuring the elapsed time JT after the curing start conditions are met (steam supply is started) for the curing chambers belonging to each group, and a steam supply control unit 35 for periodically measuring the outside air temperature AT during curing, updating the curing time ET that is preset to vary based on the outside air temperature AT, and stopping the supply of steam to the curing chambers 21-24 of each group when the elapsed time JT exceeds the periodically updated curing time ET. Therefore, the timing for stopping the supply of steam to the curing chambers 21-24, etc., can be determined based on the outside air temperature AT during curing, and curing can be terminated. Therefore, the setting of the curing time ET is automatically changed according to the fluctuation of the outside air temperature AT during curing, and a curing time suitable for the production of concrete products can be secured regardless of the season, and the curing time can be prevented from being unnecessarily long. Therefore, the quality of the concrete products can be stabilized, and the fuel consumed by the boiler can be saved. Therefore, by performing steam curing using the steam curing system 1 to manufacture a concrete product, a high-quality concrete product can be manufactured at low cost.

[0043] Furthermore, this steam curing system 1 has a room temperature control system 40 that controls the room temperature of each of the curing chambers 21-24, independently of the steam supply control system 30. Therefore, the room temperature of each of the curing chambers 21-24 can be controlled so that pre-curing at a relatively low temperature is performed for a predetermined period of time, regardless of the length of the curing time ET, and then main curing at a high temperature is performed until the end of the curing time ET. This room temperature control system 40 allows room temperature control suitable for steam curing, such as pre-curing and main curing, with a simple configuration, independently of the steam supply control.

[0044] This steam curing system 1 further includes a plurality of steam headers for dividing the plurality of curing chambers 21-24 into a plurality of groups and supplying steam to each of the steam headers, and includes a steam supply control unit 31 for each header (group). Therefore, the steam supply time to each of the plurality of groups of curing chambers can be controlled based on the elapsed time JT and the curing time ET of each group. Therefore, the plurality of curing chambers can be divided into a plurality of groups, and the curing time can be controlled for each group, and the plurality of groups can be steam cured in sequence and / or in parallel. Furthermore, the curing time ET can be set for each group so that the time is adjusted according to a different pattern depending on the outside air temperature AT. Therefore, the length of the curing time ET can be freely set for each group depending not only on the outside air temperature but also on the type of concrete product to be cured and the performance of the curing chamber (heat retention performance, capacity, etc.).

[0045] The number of boilers as the steam generation source is not limited to two, and may be one, or three or more. Furthermore, steam for curing can be obtained from a boiler external to the steam curing system 1. The configuration including the piping routes and instruments shown in the drawings and above is an example, and can be modified in various ways depending on the number of curing chambers, grouping of the curing chambers, the size and layout of the prefabricated factory for concrete products including the steam curing system 1, etc. [Explanation of symbols]

[0046] 1 Steam curing system, 2 Concrete product in formwork 5. Demolded concrete products 21~24 Curing room 30 Steam supply control system 37 Personal Computer (PC) 40 Room Temperature Control System

Claims

1. A steam supply device for supplying steam to a curing chamber that contains a formwork-encased concrete product to be cured; an outside temperature measuring unit for measuring the outside temperature; A control device for controlling the supply of steam to the curing chamber, The control device includes an elapsed time measurement unit that measures the elapsed time after steam is supplied to the curing chamber; a steam supply control unit that periodically updates a curing time that is preset to vary based on the outside air temperature, based on the outside air temperature that is periodically measured during the elapsed time, and stops the supply of steam to the curing chamber when the elapsed time exceeds the updated curing time.

2. In claim 1, A room temperature measuring unit for measuring the room temperature of the curing chamber; and a room temperature control unit configured to control the amount of steam supplied to the curing chamber, thereby controlling the room temperature to a set temperature based on the elapsed time.

3. In claim 1, The steam supply device includes a path for supplying steam to the plurality of curing chambers by dividing the plurality of curing chambers into a plurality of groups, The control device includes a plurality of group control units each controlling a supply of steam for each of the plurality of groups, Each of the plurality of group control units has an elapsed time measurement unit for measuring an elapsed time of each of the plurality of groups; and a steam supply control unit that controls supply of steam to each of the plurality of groups based on the elapsed time of each of the plurality of groups and the curing time for each of the plurality of groups, the curing time being set in advance for each of the plurality of groups to vary based on the outside air temperature, the curing time being periodically updated based on the outside air temperature during the elapsed time of each of the plurality of groups.

4. In claim 3, the control device includes a first control unit that, after starting a supply of steam to a first group among the multiple groups, when the elapsed time of the first group exceeds the curing time that has been periodically updated for the first group, stops the supply of steam to the first group and starts the supply of steam to a second group among the multiple groups.

5. In claim 3 or 4, the control device includes a second control unit that starts supplying steam at a timing when the elapsed time of a first group among the plurality of groups and the elapsed time of a third group among the plurality of groups overlap.

6. In claim 1, the steam supply control unit includes a function of updating the curing time by increasing or decreasing a first curing time preset for the first outside air temperature based on a temperature difference of the periodically measured outside air temperature relative to the first outside air temperature.

7. A control device for a steam supply device that supplies steam to a curing chamber that contains a concrete product in a formwork to be cured, A control device having a steam supply control unit that periodically updates a curing time that is preset to vary based on an outside air temperature based on the outside air temperature measured during an elapsed time after steam is supplied to the curing chamber, and stops the supply of steam to the curing chamber when the elapsed time exceeds the updated curing time.

8. A method for producing a concrete product, comprising: supplying steam to a curing chamber that contains a concrete product in a form to be cured, The supplying of steam to cure includes measuring an elapsed time after supplying steam to the curing chamber; periodically updating a curing time that is preset to vary based on an outside air temperature based on the outside air temperature that is periodically measured during the elapsed time, and stopping the supply of steam to the curing chamber when the elapsed time exceeds the periodically determined curing time.

9. In claim 8, The curing by supplying steam includes controlling an amount of steam supplied to the curing chamber to thereby control a room temperature to a temperature set based on the elapsed time.

10. In claim 8 or 9, The curing by supplying steam includes dividing a plurality of the curing chambers into a plurality of groups and supplying steam to the plurality of curing chambers, Dividing the plurality of curing chambers into a plurality of groups and supplying steam thereto includes measuring an elapsed time for each of the plurality of groups; and controlling a supply of steam to each of the multiple groups based on the elapsed time of each of the multiple groups and the curing time for each of the multiple groups, the curing time being set in advance for each of the multiple groups to vary based on the outside air temperature, and the curing time for each of the multiple groups being periodically updated based on the outside air temperature during the elapsed time of each of the multiple groups.

11. In claim 10, controlling the supply of steam to each of the plurality of groups includes, after starting the supply of steam to a first group among the plurality of groups, when the elapsed time of the first group exceeds the curing time that is periodically updated for the first group, stopping the supply of steam to the first group and starting the supply of steam to a second group among the plurality of groups.

12. A method for controlling a steam supply device that supplies steam to a curing chamber that contains a concrete product in a formwork to be cured, comprising: a curing time that is preset to vary based on an outside air temperature, periodically updating the curing time based on the outside air temperature measured during an elapsed time after steam is supplied to the curing chamber, and stopping the supply of steam to the curing chamber when the elapsed time exceeds the periodically determined curing time.

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