Concrete construction method

Abstract

To provide a concrete construction method capable of securing strength required for the concrete and suppressing impact on a concrete surface by a curing sheet.SOLUTION: A concrete construction method comprises: a placing step of pouring concrete into a construction area and leveling the surface; a compacting step of applying vibration to the placed concrete after the placing step; a pressing step of leveling the surface by pressing an iron to the surface after the compacting step; and a curing step of curing the placed concrete after the pressing step. The placing step through the pressing step are executed on a day when the placing step is executed. The curing step has a sprinkling step of sprinkling water on the surface, and a curing film laying step of laying a transparent film preventing water from permeating on the surface. The curing film laying step is executed in the morning or later of the next day of the placing step after leaving the placed concrete without curing during the night.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a concrete construction method, and more particularly to a concrete construction method in an environment where water evaporation is frequent. [Background technology]

[0002] Traditionally, floor slabs in buildings, such as floors in logistics warehouses, are often bare concrete with no surface finish. In bare concrete floors, cracks and strength on the concrete surface directly affect the user's operations. In the construction of concrete in such structures, in order to ensure the required quality of the concrete, such as strength, durability, and watertightness, it is necessary to keep the temperature and humidity necessary for hardening for a certain period of time after pouring the concrete, which is called curing. There are several known methods of concrete curing, including the flooding method, in which water is poured onto the surface of the concrete, the watering method, in which water is sprayed by workers or automatically by sprinklers, the film curing method, in which a film curing agent is sprayed as soon as possible after the surface finishing of the concrete to prevent water evaporation, the moisture retention method, in which the concrete is thoroughly sprayed with water and then covered with a sheet to adhere to the surface, the heat retention method, in which exposed concrete surfaces and openings are covered with sheets, the insulation method, in which an insulation mat is laid on the surface of the concrete or a formwork with insulation material such as urethane foam is used, and a combination of these methods is also known. Wet curing keeps the concrete moist and promotes proper hydration of the concrete, but it is necessary to maintain an appropriate moist state, especially during hot weather, when a lot of water evaporates from the concrete.

[0003] The wet curing of concrete disclosed in Patent Document 1 is a curing method for wet curing concrete poured on site with a concrete curing sheet, the method including a primary water supplying step of supplying water to the concrete curing sheet, a moisture content measuring step of directly measuring the moisture content of the concrete curing sheet after the primary water supplying step, and a secondary water supplying step of supplying a preset amount of water to the concrete curing sheet based on the moisture content of the concrete curing sheet measured in the moisture content measuring step. In other words, the water-absorbed curing sheet is placed in contact with the concrete surface, the moisture content of the sheet is managed, and the temperature of the surface of the concrete base slab is measured to control the timing and amount of water supplied to the concrete surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-163498 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the wet curing method of concrete disclosed in Patent Document 1, a concrete curing sheet is placed on the surface after concrete is poured. Generally, when ordinary Portland cement is used, the wet curing period is set to start "after finishing" or "after the end of setting", and especially during the hot summer months, it is set to "when the bleeding water disappears", and is performed for 5 days or more as a standard service period. If the wet curing is not performed properly, the concrete is not hydrated properly, and the compressive strength of the concrete cannot be properly secured. In addition, if a watertight sheet is laid at the time when the bleeding water disappears from the concrete surface, the wrinkles of the sheet will remain on the concrete. In particular, in the case of an exposed floor without a surface finish, if the sheet is laid at the time when the bleeding water disappears for wet curing, there is a problem that the sheet's traces will remain on the surface due to the influence of the sheet.

[0006] The present invention is made in response to the above-mentioned demand, and has an object to provide a concrete construction method which ensures the necessary strength for concrete and reduces the effect of the curing sheet on the concrete surface. [Means for solving the problem]

[0007] The concrete construction method of the present invention comprises a pouring step of pouring concrete into a construction area and leveling the surface, a compaction step of vibrating the poured concrete after the pouring step, a pressing step of applying a trowel to the surface to level it after the compaction step, and a curing step of curing the poured concrete after the pressing step, wherein the pouring step to the pressing step are carried out on the same day that the pouring step is carried out, and the curing step comprises a watering step of spraying water on the surface, and a curing film laying step of laying a transparent, water-impermeable film on the surface, and the curing film laying step is carried out after the morning of the day after the pouring step is carried out, after the poured concrete has been left overnight without curing. Effect of the Invention

[0008] According to the present invention, by adjusting the timing of the curing process during concrete construction, deformation of concrete caused by the curing sheet can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] 2 is a flowchart of a concrete construction method according to the first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram of a concrete construction method according to the first embodiment and a construction experiment environment of a comparative example. [Diagram 3] 3 is a graph showing the transition of the cumulative amount of water evaporation from the open concrete surface in the experimental environment shown in FIG. 2. [Figure 4] This figure shows the scratch test results for each casting area in the construction experiment. [Diagram 5] This figure shows the results of air permeability tests for each casting area in the construction experiment. [Figure 6] This figure shows the results of compression tests on core concrete in each pouring area of ​​the construction experiment. [Figure 7] FIG. 1 is an explanatory diagram of a test specimen 100 for a curing condition test of a concrete construction method according to the first embodiment and a comparative example thereof. [Figure 8] FIG. 1 is a diagram showing changes in the internal and surface temperatures of a test specimen 100 subjected to a curing condition test, as well as changes in air temperature. [Figure 9] The results of the compressive strength test of each test specimen 100 that underwent the curing test are shown. [Figure 10] The results of the scratch test and the air permeability test of each test specimen 100 that underwent the curing test are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment described below. Each figure is a schematic illustration, and the relative size and plate thickness of each member are not limited to the dimensions shown in the drawings. Also, the size relationship of each component member in the following drawings may differ from the actual one.

[0011] Embodiment 1 The concrete construction method according to the first embodiment is a concrete construction method for constructing a slab that constitutes, for example, the floor or roof of a building. For example, a floor slab may be constructed outdoors, in the heat of the day and under direct sunlight. In such an environment, a large amount of water evaporates from the poured concrete. The amount of water evaporation varies depending on the temperature, humidity, wind speed, and presence or absence of direct sunlight at the location where the concrete is poured. The concrete construction method according to the first embodiment is a concrete construction method that is particularly suitable for use in the heat of the day.

[0012] (Concrete construction method) Fig. 1 is a flow chart of a concrete construction method according to the first embodiment. When constructing a floor slab or the like, the surrounding formwork and the reinforcing bars to be placed inside the concrete are first laid. Then, concrete is poured into the casting area (step S1). The concrete to be poured has a W / C ratio of 38.5% to 61%.

[0013] After pouring the concrete, the surface of the concrete is leveled using a drill or the like (step S2). Steps S1 and S2 are collectively referred to as the concrete pouring process.

[0014] Once the concrete pouring process is complete, a compaction process is carried out in which the concrete is vibrated (step S3). The compaction process can be carried out, for example, by inserting a vibrator into the concrete to apply vibration, by applying vibration from outside the formwork, or by applying vibration to the surface of the floor slab. By applying vibration to the poured concrete, the concrete spreads throughout the gaps in the formwork. The compaction process can be carried out using a ram or other tool as an auxiliary tool if necessary.

[0015] When the compaction process is completed and the concrete has developed a predetermined hardness (for example, when it has hardened enough that a worker wearing snowshoes can stand on it), the pressing process is carried out (step S4). In this process, the concrete surface is finished with a trowel. The concrete surface is pressed down with a manual or mechanical trowel to remove any unevenness that has occurred on the surface.

[0016] The time from the start of pouring concrete to the start of the pressing process is generally set to between 30 minutes and 120 minutes.

[0017] Concurrently with the compaction process, water is supplied to the concrete before it hardens. This process is called the water supply process (step S5). In the water supply process, water is sprayed onto the surface of the concrete depending on the cumulative amount of water that has evaporated since the start of concrete pouring, and the amount of water supplied varies depending on weather conditions and the installation environment of the floor slab. In the concrete construction method according to the first embodiment, water is supplied to the poured concrete in an amount equal to or greater than 10% and equal to or less than 50% of the amount of water that evaporates from the poured concrete. The water supply process in step S5 involves spraying water onto the surface of the concrete before it hardens. The water supply process may be omitted.

[0018] Once the holding down and water supplying steps are complete, the poured concrete is left for a prescribed period of time, and after it has at least begun to harden, the watering step is carried out (step S6). The pouring step, holding down and water supplying steps are completed on the same day that the pouring step is carried out. After the holding down and water supplying steps are completed, the concrete is left overnight, and the watering step is carried out the following morning. This watering is intended to cure the concrete in a moist state.

[0019] Once the water sprinkling process is complete, a curing sheet laying process (step S7) is performed as necessary. Curing is performed by covering the surface of the concrete that has been watered with a transparent, water-impermeable curing sheet. The curing process involves keeping the concrete that has been made moist by water sprinkling in that moist state, and thus maintaining the concrete that has been made moist in the water sprinkling process. Note that steps S7 and S8 are sometimes referred to together as the curing process. Wet curing of concrete prevents the loss of moisture and promotes the hydration of the concrete.

[0020] The condition in which the curing sheet is laid on the concrete surface is maintained for at least 5 days, and preferably for 7 days or more.

[0021] (Details of the water supply process) The water supplying step in the concrete application method according to the first embodiment is carried out in a time period before the concrete hardens. In the flow chart shown in FIG. 1, the water supplying step (step S5) is shown to be carried out after the holding step (step S4), but water may be supplied to the surface of the cast concrete immediately before, immediately after, or simultaneously with the holding step. The amount of water supplied is determined according to the amount of water evaporated from the cast concrete during the time from pouring the concrete to the holding step. In the first embodiment, water is supplied to the cast concrete in an amount of 10% to 50% of the amount of water evaporated. In detail, the appropriate amount of water to be supplied varies depending on the W / C of the cast concrete. When the W / C of the cast concrete is 61% or less, it is desirable to supply water to the surface in an amount of 20% to 50% of the amount of water evaporated from the cast concrete.

[0022] In particular, when the W / C of the cast concrete is 38.5%, it is preferable to set the amount of water supplied to 20% to 50% of the amount of water that evaporates, and more preferably to 20%. On the other hand, when the W / C value of concrete is large, the amount of water contained in the concrete is large and cracks are less likely to occur, so when the W / C value is 38.5% to 61%, the amount of water supplied is effective in suppressing cracks as long as it is 20% to 50% of the amount of water that evaporates. Also, when the W / C of cast concrete is 48% or more, the amount of water supplied may be 10% to 50% of the amount of water that evaporates, and more preferably, it is 10% to 20%.

[0023] When the amount of water supplied is between 20% and 50% of the evaporation amount, the amount of water per unit area of ​​poured concrete is 0.28 L / m 2 More than 0.70L / m 2This is the amount of water to be supplied when the water supply process is carried out between 60 and 120 minutes after the concrete is placed, when the outside temperature is about 38°C, and is set assuming work under direct sunlight in summer, for example. Thus, when the temperature of the environment in which the concrete is placed is 38°C or lower, the water supply amount is at least 0.70 L / m 2 The following water should be supplied. Furthermore, if the W / C of the cast concrete is 48% or more, the water supply amount is 0.14L / m 2 More than 0.70L / m 2 It may be less than 0.14 L / m 2 More than 0.28L / m 2 It is recommended to keep the water supply at 0.14 L / m or less. This is because if the amount of water supplied is too much, the strength of the concrete surface may decrease, and the scratch test results tend to be poor. Also, if the amount of water supplied is too little, cracks are likely to occur on the concrete surface, so the amount of water supplied should be at least 0.14 L / m 2 It is desirable to have more than this.

[0024] When the outside temperature is lower than 38°C, the amount of water evaporated from the concrete is reduced, so it is desirable to reduce the amount of water supplied to less than the amount indicated above, but to a maximum of 0.70 L / m 2 In addition, when the W / C of the cast concrete is 48% or more, the amount of water supplied is preferably 0.28L / m 2 In order to prevent cracks from occurring due to an insufficient water supply, the water supply should be at least 0.14 L / m 2 In an environment where the outside temperature is below 38°C, if the W / C of the poured concrete is 48% or more, the water supply rate should be 0.14L / m 2 More than 0.28L / m 2 By setting the values ​​below, it is possible to prevent cracks in the concrete and ensure the strength of the concrete surface even if there are variations in the humidity, wind speed, and presence or absence of direct sunlight in the concrete pouring environment.

[0025] (Details of the curing process) In the concrete construction method according to the first embodiment, concrete is poured to form a floor slab attached to steel beams, which is an exposed floor without a surface finish, for example in a logistics warehouse. When constructing such a floor slab, the concrete may be subject to the effects of environments such as outdoors where the amount of water evaporation fluctuates. The curing process is to keep the temperature and humidity required for hardening for a certain period of time after pouring the concrete, thereby protecting it from harmful effects.

[0026] Traditionally, JASS5 (Architectural Institute of Japan Standard Specification for Building Construction JASS5 Reinforced Concrete Construction 2022) stipulates that the moist curing period for concrete must be at least 5 days when using ordinary Portland cement and for the standard period of service, and that the start time must be "after finishing" or "after setting is complete," depending on the method, and especially during the hot season, it is stated to be "when the bleeding water has disappeared."

[0027] In the concrete construction method according to the first embodiment, at least the curing sheet laying step is not performed on the day of the casting step, but the cast concrete is left overnight and then performed on the following day or later. However, in the heat of summer, if the concrete is left for a long period without curing, the moist environment of the concrete may not be properly maintained and the quality may deteriorate, so it is preferable to lay the curing sheet on the morning following the day of the concrete casting step. In the concrete construction method according to the first embodiment, even if the condition of "the time when the bleeding water disappears" shown in the above JASS5 is satisfied on the day of the casting step, the curing sheet is not laid on the day of the casting step, but is laid at least 8 hours after the concrete is cast, and more preferably 12 hours after the concrete is cast.

[0028] The curing sheet laying process according to the first embodiment uses a transparent resin film as the curing sheet and lays it over the entire surface of the concrete forming the floor slab. The curing sheet is one that is impermeable to water, is transparent, and allows the surface of the concrete to be visually confirmed from the outside after laying. Even if the curing sheet is laid, the surface of the concrete may dry out, but by using a transparent curing sheet, it is easy to check whether the surface of the concrete is wet or dry. If the surface of the concrete is dry, moisture can be appropriately supplied between the concrete surface and the curing sheet to ensure a wet state. In addition, a resin film of 0.15 mm or more is used as the curing sheet. In the case of a film of 0.15 mm or more but less than 0.2 mm, it is thin and the weight can be suppressed, but on the other hand, it is easy to wrinkle and may be difficult to evenly fit the concrete surface. Therefore, it is preferable to use a resin film of 0.2 mm or more. By using such a film, there is an advantage that the film is less likely to wrinkle, is easy to install along the surface of the concrete, and can be reused. Furthermore, if wrinkles in the curing sheet are significant, the wrinkles may cause deformation of the concrete surface even if the curing sheet is laid at the timing described in embodiment 1. For this reason, it is preferable to use a resin film of 0.2 mm or more as the curing sheet.

[0029] Before laying the curing sheet, water is sprayed onto the surface of the concrete. The water spraying process may be carried out on the day the concrete is poured, or may be carried out the day after pouring before the curing sheet laying process. The water spraying process and the curing sheet laying process in the flowchart of FIG. 1 are collectively referred to as the curing process. In particular, curing in which the water spraying process and the curing sheet laying process according to the first embodiment are carried out together may be referred to as "water supply-film curing".

[0030] In this way, in the concrete construction method according to the first embodiment, the timing of the curing step is controlled so that it is not performed immediately after the step is completed, but rather at a certain interval, thereby preventing deformation of the concrete, such as the transfer of wrinkles from the curing sheet. Also, by performing the curing step on the morning following the concrete pouring step, the compressive strength, surface strength, and denseness of the concrete can be ensured even if the concrete is left for a period of time without being wet cured.

[0031] (About the effect of the water supply process in the concrete construction method) Fig. 2 is an explanatory diagram of the construction experiment environment of the concrete construction method according to the first embodiment and its comparative example. In the construction experiment environment, a 10m square concrete pouring area was constructed to evaluate the concrete construction method according to the first embodiment, and the pouring area was divided into eight areas. Of the eight areas, AE-0, AE-10, AE-20, and AE-50 were poured with concrete having a W / C of 48%, and SP-0, SP-10, SP-20, and SP-50 were poured with concrete having a W / C of 38.5%. Note that W / C is the average value of the concrete per 1m of concrete. 3 is the mass ratio of water to cement contained in the

[0032] Each of the eight pouring areas is 5m x 2.5m in size. Each area is partitioned and configured to allow concrete of different specifications to be poured.

[0033] [Table 1]

[0034] Table 1 above shows the specifications for the concrete poured in the AE and SP regions out of the eight regions. The concrete shown as "30-15-20N" is concrete poured in the AE region. The concrete shown as "42-15-20N" is concrete poured in the SP region. The two types of concrete have different W / C, but are otherwise adjusted to be roughly the same. The two types of concrete differ in compressive strength after hardening, with "30-15-20N" having a compressive strength of 30N / mm 2 The "42-15-20N" has a compressive strength of 42N / mm 2 The above-mentioned measures have been adjusted to achieve the above.

[0035] The "Slump" column in Table 1 above shows the results of the slump test for each type of concrete; the higher the value, the higher the fluidity of the fresh concrete. Fresh concrete was placed into a slump cone, which was then removed to measure how many centimeters the height of the top of the concrete had dropped. Slump tests can be measured using the method specified in JIS A 1101. Additionally, the "Air content" column in Table 1 above shows the amount of air contained in the fresh concrete. Air content tests can be measured using methods specified in JIS A 1116, 1118, 1128, etc.

[0036] The "receiving temperature" in Table 1 above is the temperature of the ready-mixed concrete itself when it was received at the site where the construction test was conducted. In this construction experiment, the receiving temperature was adjusted to be close to the allowable limit of 38°C. Additionally, the outside air temperature is the outside air temperature at the site where the construction test was conducted. These were set on the assumption that concrete construction would be conducted during the hot season.

[0037] In the upper half of the casting area shown in Figure 2, concrete indicated as "30-15-20N" in Table 1 was cast, and in the lower half, concrete indicated as "42-15-20N" in Table 1 was cast. These were cast simultaneously.

[0038] The concrete poured into the eight pouring areas shown in Figure 2 was constructed based on the flow shown in Figure 1. However, the amount of water supplied to each of the eight pouring areas differs during the water supply process. The amount of water supplied to the eight pouring areas is as follows:

[0039] [Table 2]

[0040] Water was sprayed in the casting areas AE-0, AE-10, AE-20, AE-50, SP-0, SP-10, SP-20 and SP-50 so that the ratio of the amount of water supplied to the amount of water evaporated from the concrete was the "target value" shown in Table 2. However, since the amount of water evaporated from the concrete and the amount of water supplied to the concrete vary, the amount of water actually supplied to the concrete was as shown in the "Actual amount of water sprayed relative to the amount of evaporation" column in Table 2. In this experiment, AE-0 and SP-0 are comparative examples in which no water was supplied, and the others are examples in which water was supplied.

[0041] Figure 3 is a graph showing the transition of the cumulative amount of water evaporation from the open surface of the concrete in the experimental environment shown in Figure 2. In this experiment, in order to estimate the amount of water evaporating from the pouring area shown in Figure 2, a 150 mm x 150 mm x 150 mm box was filled with concrete, the weight of the box was measured, and the amount of water evaporated from the open surface of the concrete was measured. The horizontal axis of Figure 3 is the time since the concrete was poured (material age), and the vertical axis is the amount of evaporated water [kg / m 2 The value shown in "Actual amount of water sprayed versus evaporation amount" in Table 2 above was calculated using the median amount of evaporation between the first and second water sprays and the third water spray shown in Figure 3. Specifically, the amount of water evaporated from the concrete was calculated by identifying the evaporation amount at 90 [min] in the graph in Figure 3. The relationship between this value and the amount of water sprayed (L / m 2 The values ​​in the column (above) were used to calculate the "actual amount of water sprayed relative to the amount of evaporation."

[0042] In other words, in this experiment, the ratio of the amount of water supplied in the water supply process to the amount of water evaporation, i.e., the value of "(amount of water supplied to concrete) / (amount of water evaporation from concrete)", is the value shown in "Actual amount of water sprayed relative to amount of evaporation."

[0043] (Evaluation Results) The rightmost column in Table 2 shows the evaluation results of the presence and size of cracks in the concrete poured in each area in this experiment. Cracks occurred in the concrete poured in the AE-0 and SP-0 areas, where no water was supplied during the water supply process. The concrete poured in AE-0 had a W / C of 48%, which means it contained a relatively large amount of water, but when water was not supplied, small cracks measuring 0.06 mm in width occurred. Additionally, the concrete poured in SP-0 had a W / C of 38.5%, which means it contained a lower amount of water, resulting in even larger cracks.

[0044] In the casting area AE-0, cracks were present, although they were very small. In the casting area SP-0, cracks were present with a width of 0.45 mm, and in the casting area SP-10, cracks were present with a width of 0.35 mm. No cracks were present in the other casting areas.

[0045] In addition, the concrete poured into SP-10 cracked even after spraying water, but this concrete had a W / C of 38.5%, meaning that it contained a relatively small amount of water. As shown in Table 2, the amount of water sprayed onto SP-10 was actually 8.8% of the amount that evaporated, and the amount of water that could be supplied was less than 10%. From this, it can be said that for concrete that contains a small amount of water when poured, it is necessary to supply a relatively large amount of water during the water supply process. For concrete with a W / C of 38.5%, supplying at least 20% water can suppress surface cracks.

[0046] The concrete in the casting areas of AE-10, AE-20, and AE-50 did not crack and had a good surface.The concrete in the casting areas of SP-20 and SP-50 did not crack and had a good surface.

[0047] Generally, in summer, when the temperature is high and exposed to wind, water evaporates quickly and the surface shrinks, but since the matrix is ​​rapidly formed by cement hydration, the speed at which the water lost on the surface due to evaporation is supplied from the inside is delayed, and the surface shrinks and cracks occur. However, according to the concrete construction method of the first embodiment, it is possible to suppress cracks by supplying an appropriate amount of water from the direction of the concrete before hardening as described above. In addition, it can be said that cracks are less likely to occur when the W / C value of the concrete is large, that is, when the water content is large to begin with. Therefore, for example, when the W / C is even larger, such as 61%, cracks do not occur at least as in the concretes AE-10 to AE-50 in Table 2 above.

[0048] Figure 4 shows the results of the scratch test for each casting area in the construction experiment. The scratch test was carried out using an evaluation method used by the Architectural Finish Society of Japan, and measures the width of the scratch (seam width) created when the base concrete surface was scratched, thereby gauging the strength of the concrete surface. This makes it easy to determine whether there is a weak layer on the surface that could cause adhesion problems during construction. The results shown in Figure 4 were measured when the concrete was 91 days old.

[0049] The results of the scratch test showed that the surface strength tended to be relatively low in the casting area where a large amount of water was supplied in the water supply process. Specifically, the width of the scratches tended to be large in AE-50 and SP-50. However, the results showed that the concrete surfaces of AE-50 and SP-50 were also at a level that could be judged to be sufficiently strong.

[0050] Figure 5 shows the results of the air permeability test for each casting area in the construction experiment. The air permeability test was performed using the Trent method (RJ Trrent "A two-chamber vacuum cell for measuring the coefficient of permeability to air of the concrete cover on site" Materials and Structures, 1992, 25, 358-365). The air permeability test measures the degree of density of the concrete surface. Concrete with a high air permeability coefficient has a coarse structure near the surface and tends to have low durability. The results shown in Figure 5 were measured when the concrete was 91 days old.

[0051] The results of the air permeability test were generally good, but there was a large variation in the air permeability coefficient in the casting area where the water supply process was not performed. Specifically, only the casting area of ​​SP-0 had a high air permeability coefficient, which raised concerns about the durability of the concrete.

[0052] In addition, in the pouring area where the water supply process was performed, the air permeability coefficient was generally good. However, in the AE-50 and SP-50 areas, the air permeability coefficient tended to be slightly higher.

[0053] Figure 6 shows the results of the compression test of the core concrete in each casting area of ​​the construction experiment. The compression test was conducted according to the JIS A 1108:2018 concrete compressive strength test method. The results shown in Figure 6 were measured when the concrete was 91 days old.

[0054] In the construction experiment, the concrete strength in each casting area was 30 N / mm for the area with W / C=48% concrete. 2 , 42N / mm in the area of ​​concrete with W / C=38.5% 2 The results were satisfactory.

[0055] Conventionally, concrete has been constructed using a construction method that does not supply moisture before hardening, as with the concrete in the pouring regions of Comparative Examples AE-0 and SP-0, and there have been concerns that supplying moisture before hardening may have a negative effect on the quality of the concrete. However, according to the concrete construction method of embodiment 1, the concrete can ensure sufficient strength even if moisture is supplied before hardening, and surface cracks can be suppressed as shown in Table 2.

[0056] On the other hand, concrete that does not undergo a water supply process will develop cracks in the early stages of its life. In particular, the above construction experiment was carried out by simulating outdoor concrete construction in hot weather with an outside temperature of about 38°C, as shown in Table 1. In such an environment, cracks will develop if there is no water supply, but cracks on the concrete surface can be suppressed by carrying out an appropriate water supply process before the concrete hardens.

[0057] (About the effect of the curing process in concrete construction methods) Fig. 7 is an explanatory diagram of a test specimen 100 for a curing condition test of the concrete construction method according to the first embodiment and a comparative example. The test specimen 100 for the curing condition test is a rectangular parallelepiped of length 900 mm x width 900 mm x height 200 mm, and a thermocouple 50 for measuring the surface and internal temperatures is installed in the center. The cylinder indicated by the dashed line in Fig. 7 is an example of a cut-out portion of a test piece 90 for performing a compressive strength test.

[0058] In the concrete construction method according to the first embodiment, as described above, the curing process is not carried out immediately after the pressing and water supplying processes are completed, but is carried out after a certain interval. This method allows the curing sheet to be laid without damaging the aesthetic appearance of the concrete surface, but on the other hand, unlike conventional construction methods, it is necessary to check whether leaving the concrete after the pressing and water supplying processes has any effect on the strength of the concrete. The curing condition test was carried out using multiple test specimens 100 shown in Figure 7, with the properties of the ready-mixed concrete and the curing conditions changed for each. The properties of the ready-mixed concrete are shown in Table 3 below, and the curing conditions are shown in Table 4 below.

[0059] [Table 3]

[0060] [Table 4]

[0061] In Table 4 above, the condition marked "Yes" in the "Direct sunlight" column of "Curing conditions, etc." is one in which a simple roof was placed over the specimen to provide shade after the material was 28 days old. Also, the condition marked "Yes" in the "Finishing spray" column of "Curing conditions, etc." is one in which a water supplying step was carried out to supply 5.5 to 12.0% of the amount of water that had evaporated to each specimen 100 before the pressing step.

[0062] The curing process according to the first embodiment is carried out under the conditions of S-c1, S-c2, and S-c3 in Table 4. In other words, the test specimens 100 placed under the conditions of S-c1, S-c2, and S-c3 were subjected to the pressing process on the day before the curing process, and were then left overnight, and the watering process and the laying of the curing sheet were carried out the following morning. The curing sheet was left in place until the material was 7 days old, after which the curing sheet was removed.

[0063] The test specimen 100 under the condition of St1, which is indicated as "standard curing" in the "moist curing" column of "curing conditions, etc.", is a test piece of a concrete strength test specimen that has been subjected to curing in water maintained at 20±3°C or in a moist state with humidity close to 100%. The test specimen 100 cured under the condition of St1 has smaller temperature change and higher accuracy than curing in air. However, the condition of St1 cannot be implemented in actual floor slab construction, etc. In other words, the test specimen 100 placed under the condition of St1 is placed under ideal curing conditions for concrete, and represents the ideal quality of concrete.

[0064] In other words, by conducting compressive strength tests, scratch tests and air permeability tests on specimens 100 under conditions S-c1, S-c2 and S-c3 in Table 4 above and comparing the test results with those of specimen 100 in St1, it can be confirmed whether the concrete produced by the curing process according to embodiment 1 can ensure practical quality.

[0065] On the other hand, the test specimens 100 tested under the conditions S-d1, S-d2 and S-d3 in Table 4 above were not subjected to any curing process.

[0066] The materials constituting the concrete used in the experiment are shown in Table 5 below. The composition of the ready-mix concrete used to prepare each test specimen 100 is shown in Table 6 below.

[0067] [Table 5]

[0068] [Table 6]

[0069] That is, the curing condition test was carried out by placing the three types of concrete shown in Table 6 above under the conditions of S-c1, S-c2, S-c3, S-d1, S-d2, S-d3 and St1 shown in Table 4. Each test specimen 100 was placed under the conditions shown in Table 4, and evaluated by performing a compressive strength test, a scratch test and an air permeability test at predetermined times up to a material age of 91 days.

[0070] FIG. 8 shows the internal and surface temperatures of the test specimen 100 subjected to the curing condition test, as well as the change in air temperature. The internal and surface temperatures of the test specimen 100 shown are those of a representative test specimen 100 with a W / C of 48% placed under the condition of S-c3. The other test specimens 100 were also placed in the same air temperature environment. The internal and surface temperatures of the test specimen 100 were relatively higher than the air temperature on the day of casting and the day after, but from the third day onwards, they were almost the same as the air temperature. The average outside air temperature was about 30°C until the material was 7 days old, which was a so-called hot weather environment.

[0071] Fig. 9 shows the results of the compressive strength test of each test specimen 100 that underwent the curing test. In general, the results showed that the specimens 100 that were water-supplied and cured with a film (test specimens 100 under conditions S-c1 to S-c3) had higher compressive strength than those that were not cured (test specimens 100 under conditions S-d1 to S-d3). Focusing on the test specimens 100 with a W / C ratio of 48%, S-c3, which was constructed in the shade and cured, had a compressive strength 9 N / mm higher than S-d3, which was not cured. 2 The strength is high, and S-c1, which was installed in the sun and cured, has a strength of 3N / mm 2 The strength is high. S-c2 and S-d1 were made by spraying water during the pressing process in addition to the conditions of S-c1 and S-d1, and similarly, the compressive strength was higher with water supply and film curing than without curing. Also, the compressive strength of test piece 100, which was water supply and film cured, was about the same as that of the control test piece with standard curing performed under the conditions of St1.

[0072] Figure 10 shows the results of the scratch test and air permeability test for each test specimen 100 that underwent the curing test. The scratch test was performed according to the Japan Architectural Finish Association method, and the air permeability test was performed according to the Trent method. The scratch width from the scratch test is shown as the measured value at a pressure of 1.0 kg. At a W / C of 61%, S-d1 and S-d3 had clearly larger scratch widths, while at a W / C of 48% and 38.5%, S-c1 was better than the others. The measured air permeability coefficient from the air permeability test tended to be larger for S-d3 at W / Cs of 61%, 48%, and 38.5%.

[0073] As shown above, when water supply-film curing was used, the compressive strength at 91 days was higher than without curing, the surface strength was also higher, and the surface density was also better.

[0074] Although the present invention has been described above based on the embodiment, the present invention is not limited to the configuration of the above-mentioned embodiment. In short, it should be noted that the gist (technical scope) of the present invention includes various modifications, applications, and uses that a person skilled in the art may make as necessary.

[0075] The concrete construction method described above may include a combination of the features shown in the following Supplementary Notes 1 to 8. The combinations are described below.

[0076] [Appendix 1] The casting process involves pouring concrete into the construction area and leveling the surface. A compaction process of applying vibration to the poured concrete after the pouring process; After the compaction step, a pressing step of pressing a trowel against the surface to level it; A curing process for curing the poured concrete after the pressing process, From the casting process to the pressing process, It is carried out on the day the concrete pouring process is carried out, The curing process includes: A water spraying step of spraying water on the surface; A protective film laying step of laying a transparent, water-impermeable film on the surface, The protective film laying process includes: This concrete construction method comprises leaving the poured concrete overnight without curing, and then carrying out the pouring step on or after the morning of the day following the pouring step. [Appendix 2] The water spraying step includes: 2. A method for constructing concrete according to claim 1, which is carried out on the same day as the casting step. [Appendix 3] The protective film laying process includes: 2. The method of concrete construction according to claim 1, which is carried out after the poured concrete has overcome its initial brittle state. [Appendix 4] The protective film laying process includes: The concrete construction method according to claim 3, which is carried out at least 12 hours after the start of the pouring step. [Appendix 5] The film is 5. The concrete construction method according to any one of claims 1 to 4, wherein the surface is configured to be visible through the concrete construction method. [Appendix 6] The film is The concrete construction method according to any one of appendices 1 to 5, wherein the thickness is 0.15 mm or more. [Appendix 7] The film is The concrete construction method according to any one of appendices 1 to 5, wherein the thickness is 0.20 mm or more. [Appendix 8] The concrete to be poured is 8. The method for constructing concrete according to any one of claims 1 to 7, wherein the W / C is 38.5% or more and 61% or less. [Explanation of symbols]

[0077] 50 thermocouples, 90 specimens, 100 specimens, SP-0 pouring area, St1 control specimen, AE-0 pouring area, AE-10 pouring area, AE-20 pouring area, AE-50 pouring area, SP-0 pouring area, SP-10 pouring area, SP-20 pouring area, SP-50 pouring area.

Claims

1. The casting process involves pouring concrete into the construction area and leveling the surface. A compaction process of applying vibration to the poured concrete after the pouring process; After the compaction step, a pressing step of pressing a trowel against the surface to level it; A curing process for curing the poured concrete after the pressing process, From the casting process to the pressing process, It is carried out on the day the concrete pouring process is carried out, The curing process includes: A water spraying step of spraying water on the surface; A protective film laying step of laying a transparent, water-impermeable film on the surface, The protective film laying process includes: This concrete construction method comprises leaving the poured concrete overnight without curing, and then carrying out the pouring step on or after the morning of the day following the pouring step.

2. The water spraying step includes: The concrete construction method according to claim 1 , which is carried out on the same day as the casting step.

3. The protective film laying process includes: The method of claim 1 , wherein the concrete is placed after the concrete has left its initial brittle state.

4. The protective film laying process includes: The concrete construction method according to claim 3, wherein the concrete construction method is carried out at least 12 hours after the start of the pouring step.

5. The film is The concrete construction method according to any one of claims 1 to 4, wherein the surface is configured to be visible through the concrete construction method.

6. The film is The concrete construction method according to any one of claims 1 to 4, wherein the thickness is 0.15 mm or more.

7. The film is The concrete construction method according to any one of claims 1 to 4, wherein the thickness is 0.20 mm or more.

8. The concrete to be poured is The concrete construction method according to any one of claims 1 to 4, wherein W / C is 38.5% or more and 61% or less.

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