JPS61286416A - Underwater concreting - Google Patents

Abstract

PURPOSE:To cast concrete-kneaded substance in small cement quantity under water, by setting mortar layer dissolving and including water-soluble nonionic high-molecular compound with the specific gravity of a specified value or less, and by casting concrete-kneaded substance before it is set and hardened. CONSTITUTION:Water-shielding layer 3 is formed by driving mortar dissolving and including water-soluble nonionic high-molecular compound of 2-7kg/m<3> with the specific gravity of 2.0 or less. After that, before the water-shielding layer 3 is set and hardened, normal-concrete-kneaded substance 4 is driven under the layer 3. As the set surface of the normal-concrete-kneaded substance 4 gets risen, the water-shielding layer 3 which is not yet hardened is also risen and the normal concrete 4 is always shielded from water. As the result, the concrete is not arranged to come in contact with water, and the quality of the cast normal concrete is stabilized, and without forming partial defects, the homogeneous structure of high reliability can be obtained.

Description

[Detailed Description of the Invention] The present invention economically constructs a homogeneous concrete structure by placing a concrete mixture in water that causes separation of cement and aggregate components when washed with water. Regarding construction methods.

The construction method of pouring concrete underwater using tremie pipes and concrete pumps is well known. However, conventional underwater concrete is specified to have a fairly rich blend of 370 kg or more of cement per lnf, which is problematic in terms of fluidity and economic efficiency of the concrete mixture. In addition, there is also underwater concrete whose viscosity is thickened by adding a water-soluble nonionic polymer compound to prevent the cement and aggregate components from separating during falling into water. When used, there are still economic problems.

Accordingly, one object of the present invention is to provide a new underwater concrete construction method that can be implemented economically.

Another object of the present invention is to provide a novel underwater concrete construction method that can safely cast a concrete mix with a low cement content and high fluidity underwater.

Another object of the present invention is to provide a new underwater concrete construction method that uses as little water-soluble nonionic polymer compound as possible.

The underwater concrete construction method of the present invention, which achieves the above-mentioned objectives, uses a concrete mix of 2 to 7 kg/m3 when pouring into water a concrete mix that causes separation of cement components and bone phase components when washed with water. A mortar layer containing a dissolved water-soluble nonionic polymer compound and having a specific gravity of 2.0 or less is cast, and then the mortar layer is used as a water barrier layer, and before the mortar sets and hardens, the concrete mixture is poured into the mortar. It is characterized by pouring on the underside of the layer.

The attached drawings are both schematic vertical cross-sectional side views for explaining the underwater concrete construction method according to the present invention, and the first
The figure shows the formation of the water barrier layer at the initial stage of construction, and Figure 2 shows the formation of the water barrier layer at the initial stage. Fig. 3 shows the construction situation in which a concrete mix that causes separation is placed, and Fig. 3 shows the situation at the completion stage of the construction.

The method of the invention is conveniently carried out using construction equipment such as tremie pipes and concrete pumps. In the method of the present invention, a concrete mix that causes separation of cement components and aggregate components when washed with water (hereinafter simply referred to as ordinary concrete mix) is transported through a pouring pipe 1 to a water surface 2. Before pouring the ordinary concrete mixture, a specific mortar is poured at the place where the ordinary concrete mixture is to be poured to form the water barrier layer 3. . In order for the poured mortar layer to function as a water barrier layer for the ordinary concrete that will be poured afterwards, it is necessary to wait until the tip of the pouring pipe 1 is buried in the mortar to be poured.
Needless to say, mortar must be placed (see Figure 1).

Mortar for this purpose must not cause component separation even when washed with water. In most cases, this requirement can be met by incorporating about 2 kg/n1 or more of a water-soluble nonionic polymer compound dissolved in the mortar. Examples of suitable water-soluble nonionic polymeric compounds include:
Synthetic polymeric compounds such as polyvinyl alcohol, water-soluble partially saponified polyvinyl acetate, polyacrylamide and polyethylene oxide, and methylcellulose.

There are cellulose derivatives such as ethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose. Approximately 7 kg/r+ of such a water-soluble nonionic polymer compound? Additions in excess of 10% are not necessary in most cases.

In addition, in order for the mortar to function effectively as a water barrier layer during the pouring of the ordinary concrete mixture, it is necessary to maintain a stable position between the water and the ordinary concrete mixture. for.

Generally speaking, mortar satisfies this requirement, so the specific gravity must be between that of water and that of ordinary concrete mix.2 In the present invention, mortar is used to form the water barrier layer, but there are some concerns regarding safe construction. In order to achieve this, the specific gravity of the mortar should be lower than 2.0; if desired, the specific gravity of the unhardened mortar can be reduced substantially below 2.0 by the use of a blowing agent and/or lightweight aggregate. can be lowered.

It is also desirable that the water barrier layer mortar can be flexibly deformed depending on the shape of the raised surface of the ordinary concrete to be cast underneath.

For this purpose, a portion of the cement component of one mortar (for example, about 50%) must be
The fluidity of the mortar can be improved by replacing it with, for example, fly ash. Further, a suitable fluidizing agent may be added to one mortar.

In the method of the invention, before setting and hardening of one mortar layer.

A regular concrete mixture is placed underneath.

In other words, the water barrier layer mortar must not set and harden until the pouring of the normal concrete mix is complete; if necessary, a slip that retards the setting and hardening of the mortar;
A super-retarder or retardant dispersant may be incorporated into the mortar.

Also, even if normal concrete gets wrapped up in mortar, the part where it gets rolled up 5 times will not become a defective part.

Needless to say, it is desirable to design the components of mortar so that the hardened mortar has the same strength as hardened ordinary concrete.

It is within the skill of those skilled in the art to design the components of the mortar as described above depending on the particular concrete used.

After a predetermined water barrier layer 3 is formed by pouring a sufficient amount of mortar (Fig. 1), before the water barrier layer 3 sets and hardens, an ordinary concrete mixture 4 is poured under it (Fig. 2). ), after the ordinary concrete mixture poured under the water barrier layer 3 reaches the tip of the pouring pipe 1, as the surface on which the ordinary concrete mixture is poured rises, the water barrier layer 3 that has not hardened yet also rises. It rises and always shields the ordinary concrete 4 from water. Figure 3 shows the situation at the completion stage of construction.

The ordinary concrete mix that can be constructed underwater by the method of the present invention is inexpensive, has a small amount of cement per lnl, and does not require expensive additives (water-soluble nonionic polymer compounds to prevent components from separating in water). can be something. The plain concrete mix can also be highly fluid with the addition of fly ash, superplasticizers and/or super-retarders. When such a concrete mixture itself is washed with water, the cement component and the aggregate component separate. However, in one method of the present invention,
Since contact with water is cut off by the water barrier layer mortar, the quality of the poured ordinary concrete is stable and there are no local defects.

Launch into a homogeneous high performance structure. Also.

There is no leakage of cement due to the washing action of water.

Being able to reduce the amount of cement per unit of the ordinary concrete mixture to be cast is not only economically advantageous, but also because the reduction in the amount of cement reduces the calorific value of hydration.
This has the advantage of preventing or reducing the occurrence of defects such as temperature cracks. moreover.

The highly fluid ordinary concrete mix that is applied underwater by the method of the present invention fills every corner of the structure and suitably wraps the buried metal objects such as reinforcing bars, so it has excellent adhesion and integrity with the buried metal objects. The result is a good quality concrete structure.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional side view showing the formation of a water barrier layer in the initial stage of construction according to the method of the present invention. Figure 2 is a similar diagram showing the construction situation in which ordinary concrete mix is poured under the water barrier layer formed at the initial stage, and Figure 3 is a similar diagram showing the situation at the completion stage of construction. . 1. Piping for pouring, 2. Water surface, 3. Mortar water barrier layer, 4. Ordinary concrete.

Claims (1)

[Claims] When pouring a concrete mixture into water that causes separation of cement and aggregate components when washed with water, it is necessary to use a specific gravity compound containing a dissolved water-soluble nonionic polymer compound of 2 to 7 kg/m^3. is characterized by casting a mortar layer having a water barrier of 2.0 or less, and then using the mortar layer as a water barrier layer to cast the concrete mixture below the mortar layer before setting and hardening of the mortar. Underwater concrete construction method.