JPH0242779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a construction method for economically constructing a homogeneous concrete structure by pouring a concrete mixture into water that causes separation of cement components and aggregate components that are washed away by water. Regarding the law.

The construction method of pouring concrete underwater using tremie pipes and concrete pumps is well known. However, conventional underwater concrete requires a fairly rich mix of 370 kg or more of cement ^per cubic meter, which poses problems in terms of fluidity and economic efficiency of the concrete mixture. In addition, underwater concrete, which is thickened by adding a water-soluble nonionic polymer compound to prevent the cement and aggregate components from separating during falling into water, is well-known, but it is used in large quantities. If so, there are still economic problems.

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

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 objects, is capable of casting a concrete mixture in water that causes separation of cement and aggregate components when washed with water, at a rate of 2 to 7 kg/m2. The specific gravity containing dissolved water-soluble nonionic polymer compound of ³ is
A mortar layer of 2.0 or less is poured into the bottom of the pouring section under the water surface, and before this mortar layer sets and hardens, the above-mentioned concrete mix is supplied to the underside of the mortar layer, and the concrete mix is supplied to the bottom of the concrete mix. It is characterized by raising the water level while covering the pouring surface with the mortar layer (water barrier layer).

The attached drawings are all schematic vertical cross-sectional side views for explaining the underwater concrete construction method according to the present invention, and FIG. 1 shows the formation of a water barrier layer at the initial stage of construction, and FIG. , shows a construction situation in which a concrete mix is placed below the water barrier layer formed in the initial stage, and the concrete mixture itself causes separation of cement and aggregate components when washed with water, and the third The figure shows the situation at the completion stage of construction.

The method of the invention is advantageously 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 sometimes simply referred to as ordinary concrete mix) is poured into a water surface through a pouring pipe 1. The water barrier layer 3 is poured at a predetermined location below 2, but before pouring the ordinary concrete mixture, a specific mortar is poured in the area where the ordinary concrete mixture is to be poured to form the water barrier layer 3. do. 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 pour mortar until the tip of the pouring pipe 1 is buried in the mortar. Needless to say (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/m ³ 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, as well as methylcellulose, ethylcellulose, hydroxyethylcellulose and hydroxypropyl. There are cellulose derivatives such as cellulose. Additions of more than about 7 Kg/m ³ of such water-soluble nonionic polymeric compounds are not necessary in most cases.

Additionally, 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 this purpose, the specific gravity must be between that of water and that of ordinary concrete mix. Since mortar generally satisfies this requirement, mortar is used to form the water barrier layer in the present invention, but for safe construction, the specific gravity of mortar is preferably 2.0 or less. If desired, the specific gravity of the unset mortar can be reduced to substantially less than 2.0 through the use of blowing agents, blowing agents and/or lightweight aggregates.

It is also desirable that the water barrier layer mortar has good flexibility and can be deformed according to the shape of the raised surface of the ordinary concrete to be cast underneath. For this purpose, it is possible to improve the fluidity of the mortar by replacing a portion of the cement component in the mortar layer (for example, approximately 50% or less) with fly ash, to the extent that the strength of the mortar is not affected. can. Additionally, an appropriate fluidizing agent may be added to the mortar.

In the method of the present invention, before setting and hardening the mortar layer,
A regular concrete mixture is placed underneath.
In other words, the water barrier mortar must not set and harden until the pouring of the ordinary concrete mix is complete. If necessary, suitable super-retarders or retarded dispersants can be incorporated into the mortar to retard the setting and hardening of the mortar.

In addition, even if ordinary concrete entrains mortar, it is desirable to design the composition of mortar so that the entrained mortar does not become a defective part, so that the hardened mortar has the same strength as hardened ordinary concrete. , needless to say. Designing mortar components as described above according to a given specific ordinary concrete
This can be easily done by a person skilled in the art.

A predetermined water barrier layer 3 is formed by pouring a sufficient amount of mortar (Fig. 1), and before the water barrier layer 3 sets and hardens, an ordinary concrete mixture 4 is poured under it (Fig. 1). Figure 2). Water barrier layer 3
After the ordinary concrete mixture placed on the lower side 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, which has not hardened yet, also rises, and the ordinary concrete is constantly poured. 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 has a small amount of cement per 1 m ³ and requires expensive additives (water-soluble nonionic polymer compounds to prevent components from separating in water). And it can be cheap. The ordinary 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 the method of the present invention, the contact with water is cut off by the water barrier layer mortar, so the quality of the poured ordinary concrete is stable, and there are no local defects and the quality of the concrete is uniform and reliable. washes up on a highly sensitive structure. In addition, since there is no outflow of cement due to the washing action of water, it is not only economically advantageous to be able to reduce the amount of cement per unit of the ordinary concrete mixture to be poured, but also because the reduction in the amount of cement improves hydration. Since the amount of heat generated is reduced, there is the benefit of preventing or reducing the occurrence of defects such as temperature cracks.
Furthermore, the highly fluid ordinary concrete mix that is applied underwater by the method of the present invention fills every corner of the structure and wraps the buried metal objects such as reinforcing bars in a suitable manner. The result is a concrete structure with excellent integrity.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal 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 driving, 2
...Water surface, 3...Water barrier layer of mortar, 4...Ordinary concrete.

Claims (1)

[Claims] 1 When pouring a concrete mixture in water that causes separation of cement and aggregate components when washed with water, a specific gravity containing a dissolved water-soluble nonionic polymer compound of 2 to 7 Kg/ ^m3 is required. A layer of mortar with a value of 2.0 or less is poured into the bottom of the pouring area below the water surface.
Before this mortar layer sets and hardens, the concrete mix is supplied to the underside of the mortar layer, and as the concrete mix is supplied, the concrete mix is raised in water while covering the pouring surface with the mortar layer. This underwater concrete construction method is characterized by: