JP5711896B2 - Wet curing method for concrete structures - Google Patents

Description

  The present invention relates to a concrete placement work for a wall-like structure in civil engineering / architectural work, and provides a curing method from concrete placement to hardening.

  It is recommended that the concrete be driven into the formwork and remain wet until the formwork is removed, and a method of laying water or a wet mat on the exposed surface of the concrete is used. Although these methods can be used to spray water manually, depending on the level and timing of water spraying, the concrete surface cannot always be kept wet. Moreover, in the case of sprinkling with a hose, the water may be temporarily excessively sprinkled and the water may be wasted. Thus, it is necessary to maintain a moderately moist state without depending on human hands and within the curing period. Furthermore, it is also important to reduce labor costs and eliminate water waste by automatically spraying water.

  In addition, curing is usually completed in about 7 days after casting, which is the time when the mold is removed, due to cost and construction problems. However, at around 7 days of age, the concrete is in the middle of hydration, and if exposed to the outside air at this point, drying may proceed from the concrete surface and the subsequent hydration of the cement may be inhibited. In particular, since the member is thin in the wall-like structure, drying of the entire cross section proceeds. If the hydration is thus inhibited, the durability of the cover concrete is impaired. Focusing on the fine void structure results in a relatively coarse void due to hydration inhibition by drying, resulting in a decrease in mass transfer resistance that affects durability, resulting in a low durability concrete. For this reason, it is desirable to keep the wet state as much as possible after demolding and to continue the hydration.

  For example, patents relating to the curing method include JP2009-10169A and JP2009-84981, which are proposed as curing methods for reducing temperature cracks that occur when mass concrete members are formed, This is mainly performed for the purpose of cooling and keeping the inside and outside of the member. Moreover, although the wet curing method is proposed by Unexamined-Japanese-Patent No. 2009-30246, Unexamined-Japanese-Patent No. 2004-375673, and Unexamined-Japanese-Patent No. 2010-24785, it is the curing method only by a sheet | seat.

JP 2009-101568 A JP 2009-84981 A JP 2009-30246 A JP 2004-375673 A JP 2010-24785 A

Formwork is used for placing concrete, and curing may be performed after removing the formwork for the reasons described above. However, as an initial curing, it is important to perform a wet / thermal curing during the period from immediately after driving to the removal of the mold. However, it is often difficult to perform heat insulation / wet curing at the stage where the mold is installed, and to continue heat insulation / humidity after the mold is removed. In addition, curing is performed by watering, but the wet state is not partial, and it is also necessary to uniformly wet the concrete surface.
The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a curing method of a concrete structure that can achieve good strength expression, densify the concrete surface, and improve durability. There is.

In order to achieve the above object, the present invention arranges a curing sheet so as to surround the entire circumference of the placement site including the mold immediately after the concrete is placed in the mold, and from above the placement site. Sprinkle water to maintain the atmospheric humidity in the curing sheet within a preset range, perform curing, perform demolding work in the curing sheet, and after demolding, place an air sheet on the entire side of the concrete. Winding and curing are continued while continuing the watering.

In the present invention, first, wet curing with watering is performed for the purpose of promoting hydration in the initial stage before demolding and ensuring the initial strength. Water spray does not require a large amount of water, and a mist-like one that keeps the atmospheric humidity in the curing sheet high is sufficient. A curing sheet is used in combination to maintain the curing atmosphere temperature and high humidity. Furthermore, at the time of demolding, demolding work is carried out in the curing sheet for the purpose of preventing extreme drying and temperature changes. Furthermore, after demolding, wind the air sheet immediately and continue the curing (sealing curing instead of the air curing) while continuing watering.
According to the present invention, it is possible to promote the hydration of cement, which is the most important as the initial curing of concrete, to increase the humidity of the atmosphere around the mold and to provide a stable curing temperature that eliminates daily changes in the outside temperature. That is. Hydration of cement, which is the most important for the initial curing of concrete, can be promoted, good strength can be developed, the concrete surface can be densified, and durability can be improved.
The object of the present invention can be applied to all concrete works in civil engineering and construction work, but the effect is particularly great in column members and wall members having a relatively high difference in the height of the concrete member.

It is a figure which shows the example of application in the reinforced concrete of an existing bridge pier, and an outer-winding seismic reinforcement construction. (A) is the conceptual diagram of watering sheet curing, (B) is the top view. (A) is a conceptual diagram of a measurement part, (B) is explanatory drawing of a measurement position. It is explanatory drawing which shows the difference in concrete temperature by the presence or absence of a curing sheet. It is a figure which shows the measurement result of the atmospheric temperature inside and outside a curing sheet. It is a figure which shows the relative humidity inside and outside a curing sheet. It is a figure which shows the relationship between a space | gap diameter and an integrating | accumulating space | gap amount. It is a figure which shows the relationship between a space | gap diameter and a LOG differential space | gap amount.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the present embodiment, the present invention is applied to the case where the existing concrete pier 10 is reinforced by placing externally wound concrete 12 on the outside of the existing pier 10.
As shown in FIGS. 1A to 1E, the outer-wrapped concrete 12 that reinforces the concrete structure has a large height, and the placing of the concrete is performed in a plurality of times.
That is, after removing the formwork of the concrete structure located below from the first concrete structure 12A located at the lowest position to the second concrete structure 12B and the third concrete structure 12C above it. The formwork for constructing the concrete structure above it will be installed and concrete will be placed.

First, when constructing the first concrete structure 12A, a mold is assembled around the existing pier 10 and concrete is placed in the mold.
Then, immediately after the placement, the vinyl curing sheet 14 is arranged so as to surround the entire side periphery of the placement location including the mold.
As shown in FIG. 1 (D), this curing sheet 14 is used by rolling out a sheet having a length corresponding to the height of the existing pier 10 and pulling it out.
Moreover, it waters from the upper part of a placement location, and it cures by maintaining the atmospheric humidity in the curing sheet 14 in the preset range.
The humidity in this case is preferably 80% to 100%, for example.
For example, as shown in FIG. 2, the watering is performed by installing a pipe 16 having a large number of holes above the placement site, supplying water from the irrigation channel, tap water, etc. to the pipe 16 by a pump 18. This is done by spraying in a mist from the hole.
In this case, a water storage unit 20 that can store water is provided in the lower part of the curing sheet 14, and the water storage unit 20 receives the sprinkled water, and when the received water is pumped up and sprinkled, The water supply path can be shortened, which is advantageous for cost reduction.

After elapse of a predetermined curing period, a demolding operation is performed in the curing sheet 14, and after demolding, the air sheet 22 is wound around the entire side surface of the first concrete structure 12A.
At the same time, a formwork for constructing the second concrete structure 12B is assembled around the existing pier 10 and concrete is placed in the formwork.
Then, immediately after the placement, the curing sheet 14 rolled up so as to surround the entire circumference of the placement location including the mold and the entire circumference of the first concrete structure 12A is lifted, and the curing sheet 14 is pulled out downward.
Moreover, it waters from the upper part of a placement location, and it cures by maintaining the atmospheric humidity in the curing sheet 14 in the preset range.

Further, after a predetermined curing period has elapsed, demolding work is performed in the curing sheet 14, and after demolding, the air sheet 22 is wound around the entire side surface of the second concrete structure 12B.
At the same time, a formwork for constructing the third concrete structure 12C is assembled around the existing pier 10 and concrete is placed in the formwork.
Then, immediately after placing, the curing sheet 14 that is rounded to surround the entire circumference of the placement location including the mold and the entire circumferences of the first and second concrete structures 12A, 12B is lifted, and the curing sheet 14 Pull out downward.
Moreover, it waters from the upper part of a placement location, and it cures by maintaining the atmospheric humidity in the curing sheet 14 in the preset range.

  Thus, it is preferable to continue the curing of the first, second, and third concrete structures 12A, 12B, and 12C to at least about 28 days of age while continuing to spray water.

Thus, in the present embodiment, wet curing with watering is performed for the purpose of promoting hydration in the initial stage before demolding and ensuring the initial strength. This is because initial curing after placing (especially moisture and temperature necessary for hydration of cement) is important in order to improve crack resistance. This is because, in particular, construction during winter requires measures to promote hardening and strength of concrete.
Water spray does not require a large amount of water, and a mist-like one that keeps the atmospheric humidity in the seat high is sufficient.
Further, the curing sheet 14 maintains the temperature and high humidity of the curing atmosphere.
Furthermore, the demolding operation is performed in the curing sheet 14 in the form of a curtain for the purpose of preventing extreme drying and temperature changes.
It is preferable to continue the curing (sealing curing instead of air curing) until the material age is about 28 days while wrapping the air sheet 22 promptly after demolding and continuing watering.

The temperature of the concrete wall member and the atmosphere temperature / humidity of curing when the curing method according to the present embodiment was applied and when the curing was carried out as standard were measured.
3A and 3B show a conceptual diagram of an application example and a concept of temperature measurement.
FIG. 4 shows the measurement result of the concrete temperature, and FIG. 5 shows the measurement result of the ambient temperature inside and outside the curing sheet 14.
4 and 5, it can be seen that the installation of the curing sheet 14 shows a high distribution of the concrete temperature. Moreover, it turns out that the high temperature is shown in the curing sheet 14. FIG. It can be seen that the installation of the curing sheet 14 can prevent a change in the atmospheric temperature, in particular, a temperature decrease due to the influence of the outside air temperature.

FIG. 6 shows the measurement results of the relative humidity inside and outside the curing sheet 14.
It can be seen that high humidity is maintained inside the curing sheet 14 by watering. It can be seen that the same curing is continuously carried out at the time of demolding and after demolding, and a high humidity atmosphere is maintained for a long time. This promotes hydration without drying the concrete surface, promotes good strength development and densification of the concrete surface, leading to improved durability.

FIG. 7 and FIG. 8 show the case in which the curing with the wet curing sheet 14 was stopped at the age of 1, 3, 7, and 28 days after the concrete was placed, and the case exposed to the air was 91 days after the placing. The result of examining the fine void structure is shown.
FIG. 7 shows the relationship between the void diameter and the accumulated void amount, and FIG. 8 shows the relationship between the void diameter and the LOG differential void amount.
For the void structure, a mercury intrusion porosimeter was used and it was carried out on a specimen separately collected from concrete. Also. We are investigating the void structure in the paste where the aggregate is removed from the concrete. Note that. As a comparison, a case where wet curing is carried out until the age of 91 days is also shown.
7 and 8, it can be seen that the earlier the age of starting exposure in the air, the larger the void amount peak in the coarse void diameter, and the larger the void amount. The effect of such void structure on durability is a future issue, but it is known that the durability of concrete has an effect on the amount of capillary voids and coarse voids from 3 nm to 50 μm. It is considered that the durability of concrete is improved by performing wet curing for as long as possible.

10 …… Existing bridge pier 12 …… Externally wound concrete 12A, 12B, 12C …… Concrete structure 14 …… Curing sheet 16 …… Sprinkling pipe 22 …… Air sheet

Claims (4)

Immediately after placing the concrete into the mold, a curing sheet is arranged so as to surround the entire circumference of the side of the placement including the mold,
Water is sprinkled from the top of the placement site and the ambient humidity in the curing sheet is maintained within a preset range for curing,
Perform demolding work in the curing sheet,
After demolding, wrap the air sheet around the entire side of the concrete,
Continue curing while continuing the watering,
A method for curing a concrete structure characterized by the above. The concrete structure has a large height, and the placing of the concrete is performed in a plurality of times. The first concrete structure located at the lowest position, the second concrete structure thereon, and the third concrete are provided. After placing the formwork for constructing the upper concrete structure into the Nth concrete structure after removing the formwork of the concrete structure located below, put the concrete into the Nth concrete structure Go,
The placement of the curing sheet, watering, and winding of the air sheet are performed for each construction of each concrete structure from the first concrete structure located at the lowermost position to the Nth concrete structure located at the uppermost position.
The method for curing a concrete structure according to claim 1. The bottom of the front Symbol curing sheet, provided the possibility and water reserving portion of the reservoir of water,
The watering is performed by receiving the sprinkled water in the water reservoir and pumping up the received water.
The method for curing a concrete structure according to claim 1 or 2, wherein the concrete structure is cured. Curing of while performing the watering, to continue until at least the age of 28 days,
The method for curing a concrete structure according to any one of claims 1 to 3, wherein the concrete structure is cured.

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