JPH01187263A - Inverted lining concreting method - Google Patents

Abstract

PURPOSE:To increase the bonding strength of a construction joint by placing an impregnated sheet with retarder on the upper part of a bottom form, placing reinforced fibrous concrete, washing out the lower part of a form after removing the form and placing another concrete on a fibrous surface to join. CONSTITUTION:An impregnated sheet 2 with retarder in advance is placed on the upper part of a bottom form 1, a proper amount of reinforced fibrous concrete is, first of all, placed into a space made in a specific part of a retaining wall 4 of a side form 5, and it brings into contact with the sheet 2 to cause the retarder of the sheet 2 to elude into water of concrete 6. Normal concrete 7 is placed thereon and is hardened, then the bottom form 1 and the side form 5 are removed to wash out the unhardened surface of the lower part of the reinforced fibrous concrete 6 which is brought into contact with the sheet 2. According to the constitution, a recessed and projected surface of the reinforced fiber is wholly exposed over the lower part, and the bonding strength of a concrete joint can be increased.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to a reverse rolling concrete method in which concrete is poured sequentially from the top to the bottom, and in particular, a method for firmly bonding post-cast concrete to the lower surface of pre-cast concrete. related to the technology of

(Prior art) In the reverse-rolling concrete method, it is difficult to bring the lower post-cast concrete into close contact with the upper pre-cast concrete because of the subsidence. For this reason, in most reverse winding construction methods to date, this has been dealt with by injecting grout into the gap created at the joint after the concrete hardens, or by filling the gap with non-shrinkage mortar. This is a measure to fill in the gaps created at the joints by post-processing.

Recently, various techniques have been proposed to prevent gaps from forming at the joints. For example, it is constructed using expandable concrete, and its expandability prevents gaps from forming at the joints. In addition, the placed post-cast concrete is hardened while being compressed to prevent the post-cast concrete from sinking and to prevent the generation of gaps.

As a technique that can be used in conjunction with the above-mentioned measures to fill in gaps at joints with post-treatment and measures to prevent gaps from forming at joints, roughening the lower surface of pre-cast concrete can make it easier to match post-cast concrete. There is a way to increase the bonding strength of

Methods for roughening the lower surface of pre-cast concrete include: ■ Rub it hard with a wire brush, ■ Wash with water after sandblasting, ■ Apply a setting retarder to the lower surface during pouring, and wash with water after demolding. This method has been known for a long time. The simple method (2) has a significantly poor working efficiency, and the method (2), which uses sand blasting, requires large-scale equipment and significantly deteriorates the working environment. Therefore, method (2) using a setting retarder is considered to be an effective method.

A conventional method for roughening the lower surface of pre-cast concrete using a setting retarder will be described in detail. First, a liquid setting retarder is applied to the upper surface of the outer formwork that partitions the lower surface of the concrete pouring space, and concrete is poured on top of this. When this happens, the setting retarder acts on the lower surface of the poured concrete, delaying the hardening of this area. When the lower surface of the poured concrete is washed with high-pressure water after demolding, the uncured concrete is removed and a rough, uneven concrete surface appears.

(Problems to be Solved by the Invention) As mentioned above, the conventional surface roughening method in which a liquid setting retarder is applied to the upper surface of the bottom form before concrete is poured has the following problems. Ta.

■It is troublesome to apply the setting retarder evenly to the bottom formwork. If the retarder is not applied evenly, the depth at which the retarder reaches its effect will vary greatly.

■When concrete is poured onto a bottom form that has been coated with a retardant, the retardant will be dispersed by the force of the concrete, and even if it is applied evenly, the distribution of the retardant will be extremely uneven. Disturbed.

■The bottom formwork is not installed horizontally, but at an angle with the front elevated. A coagulant is applied on top of this sloping bottom form before concrete is poured, but the liquid retarder collects on the lower side along the slope. As a result, there is insufficient coagulant on the high side and too much retarder on the low side.

As mentioned above, with conventional methods, it is difficult to apply the setting retarder uniformly to the lower surface of the poured concrete, and rough surfaces may not appear due to lack of retarder, or the retarder may work deeper than necessary. During washing with water, a large amount of unhardened concrete was locally washed out, making it impossible to obtain a uniform surface roughening effect.

In addition to the above, there was also the following problem.

- In the reverse-rolling concrete method, ordinary concrete using ordinary aggregates such as sand, gravel, or crushed stone is used. In the case of concrete using such small granular ordinary aggregate, even if the lower surface of the pre-cast concrete is roughened by the above-mentioned method using a setting retarder, the degree of unevenness is not that large and the surface is not roughened. Although the bond strength with the post-cast concrete was higher than when it was not used, the effect was not sufficient to meet expectations.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to firmly bond the lower surface of pre-cast concrete and post-cast concrete with a simple operation.

(Means for Solving the Problems) Therefore, in this invention, a sheet impregnated with a setting retarder is bonded to the top side of the bottom form, and fiber-reinforced concrete is poured at least in the portion in contact with this sheet. After demolding, the lower surface of the fiber-reinforced concrete that the sheet had been in contact with was washed with water to expose the fibers, and the lower concrete to be placed next was bonded to this fiber-exposed surface.

(Function) The above sheet is uniformly impregnated with a setting retarder in advance, and its distribution is completely unaffected by the slope of the bottom formwork or the force of the poured concrete, and the setting retardant is uniformly retarded on the underside of the poured concrete. The effect of the agent is exerted.

Furthermore, since the portions that are roughened by the action of the setting retarder are the fiber-reinforced concrete, fibers are exposed in the roughened portions. Since the post-cast concrete adheres closely to this fiber-exposed surface, the reinforcing effect of the fibers is also exerted at this joint.

(Example) When carrying out the method of the present invention, a sheet made of paper, nonwoven fabric, polymeric water absorbing material, or the like is used, which is impregnated with a setting retarder in advance.

This type of seat is known as "SKP Zervimento" (
Product name) is commercially available.

As shown in FIG. 1, the above-mentioned retardant-impregnated sheet 2 is placed on the upper surface of the bottom formwork 1 and fixed with, for example, a stable metal fitting 3. Next, as shown in FIG. 2, the bottom formwork 1 and side formwork 5 with the sheets 2 attached are installed at predetermined portions of the retaining wall 4, and concrete is poured into the concrete placement space surrounded by these. First, an appropriate amount of fiber-reinforced concrete 6 is poured, and then ordinary concrete 7 is poured. The first poured fiber-reinforced concrete 6 comes into contact with the sheet 2 on the bottom formwork 1, and ordinary concrete 7 is placed on top of this layer of concrete 6. Note that steel fibers, vinylon fibers, polypropylene fibers, carbon fibers, etc. are used as reinforcing fibers for the concrete 6, and steel fibers with high hardness are particularly preferred. Further, the ordinary concrete 7 is concrete using ordinary aggregate such as sand, gravel, or crushed stone.

When the fiber-reinforced concrete 6 comes into contact with the sheet 2 on the bottom formwork 1, the setting retarder impregnated in the sheet 2 is eluted into the concrete 6 by the moisture contained in the concrete 6. As a result, the portion of the fiber-reinforced concrete 6 that is in contact with the sheet 2 hardens later than other portions. After the fiber-reinforced concrete 6 and ordinary concrete 7 have hardened, the bottom form 1 and side form 5 are removed, and as shown in Figure 3, the lower surface of the fiber-reinforced concrete 6 that was in contact with the sheet 2 is washed by spraying water. and wash away uncured surface concrete.

Then, as shown in FIG. 4, the reinforcing fibers 6a are exposed on the lower surface of the concrete 6, and the concrete surface also becomes an uneven and rough surface. Since the action of the setting retarder by the sheet 2 is uniformly applied to the concrete 6, the surface condition of the lower surface of the concrete 6 (the degree of unevenness and the manner in which the reinforcing fibers 6a are exposed) is almost uniform over the entire surface.

After that, post-cast concrete is poured in the same manner under the concrete 6, but when the post-cast concrete is poured onto the uneven lower surface of the pre-cast concrete where the reinforcing fibers 6a are exposed, the reinforcing fibers 6a are exposed. The part penetrates into the post-cast concrete and the cohesiveness of this poured part is extremely high.

Note that if the curing period of the concrete is increased, the hardness of the concrete increases, so it is better to use high-pressure water in the above-mentioned washing process.

In addition, fiber reinforced concrete may be used not only locally but also throughout the area.

(Effects of the Invention) As explained in detail above, in the reverse-wound concrete method according to the present invention, a sheet impregnated with a setting retarder is bonded to the top side of the bottom form, and fiber-reinforced concrete is Since the sheet is cast, the retardant contained in the sheet is uniformly eluted and acts on the lower surface of the poured concrete, and by washing the lower surface of the poured concrete that the sheet was in contact with with water after demolding, the entire lower surface is covered. An uneven surface appears with reinforcing fibers exposed uniformly over the area. Since the post-cast concrete is poured onto the exposed uneven surface of the reinforcing fibers, the bonding force at the poured joint becomes extremely large.

[Brief explanation of the drawing]

FIGS. 1 to 4 are diagrams schematically showing the steps of a reverse-rolling concrete method according to an embodiment of the present invention. 1... Bottom formwork 2... Retardant impregnated sheet 3... Stable fittings 4... Earth retaining wall 5... Side formwork 6... Fiber reinforced concrete

Claims (1)

[Claims] (1) In the reverse roll concrete method, in which concrete is poured sequentially from the top to the bottom, a sheet impregnated with a setting retardant is bonded to the top side of the bottom formwork that partitions the bottom of the concrete placement space. Fiber-reinforced concrete is cast at least in the part that contacts this sheet, and after demolding, the lower surface of the fiber-reinforced concrete that the sheet was in contact with is washed with water to expose the fibers, and the lower part to be poured next on this fiber-exposed surface. A reverse-rolling concrete construction method that is characterized by joining concrete together.