JPH02217345A - Placing of underwater concrete - Google Patents

Abstract

PURPOSE:To effectively and inexpensively suppress dispersion of concrete materials without influence of dissolved salts, pH, etc., by blending the concrete materials with a polysaccharide of microorganism just before adding the concrete materials into water. CONSTITUTION:In placing underwater concrete, sand is blended with cement, just before adding the blend into water, the concrete materials are blended with a polysaccharide of microorganism as a dispersion inhibitor and added to water. Xanthan gum, etc., an anionic natural polymer substance produced from a saccharide such as glucose as a raw material is preferably used as the concrete example of the polysaccharide of microorganism. Since xanthan gum is bonded to calcium ion and water of cement component and shows high viscosity, the amount of xanthan gum blended is relatively small and is preferably about 0.5-2kg based on 1m<3> concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for placing underwater concrete used for the foundations of structures, etc.

(Prior art) When constructing concrete underwater, it is inevitable that some of the cement will mix with the water in the construction area during pouring and be washed away. Therefore, it is necessary to use concrete with a rich mix. In order to obtain highly viscous concrete with little material separation, the proportion of fine aggregate is relatively high, and the amount of cement used is about twice the normal amount. However, it is difficult to sufficiently suppress the dispersion of cement and fine particles, which inevitably reduces the strength and density of hardened concrete, and also causes fine particles to float in water, causing water pollution.
There were problems such as material loss due to washing away.

In order to solve these problems, methods have recently been proposed in which various thickeners and flocculants are mixed into concrete materials such as sand and cement. Also, as a dispersion inhibitor that can suppress the dispersion of concrete components into water.
Acrylic resins and cellulose ester derivatives are also commercially available.

(Problems to be Solved by the Invention) However, methods for suppressing the dispersion of concrete materials using these flocculants etc. have the following problems: (1) there is a limit to the optimal amount of water to be mixed to be effective as a dispersion inhibitor; The dispersion suppressing effect may not be achieved due to the influence of salts dissolved in the water and the pH of the water, and (3)
) There are problems such as high usage and high costs.

The present invention has been made in view of the above-mentioned problems, and its purpose is to cast underwater concrete to obtain a hardened concrete body with satisfactory strength, etc., without being affected by the amount of mixed water, dissolved salts, pH, etc. It provides a construction method.

(Means for achieving the object and its effect) The inventor
In order to achieve the above objectives, various studies were conducted on microbial polysaccharides, and due to their unique physical properties, the above (1) to (3)
) The present invention is based on these findings, and the present invention is based on these findings, and it is possible to overcome the problems of microbial polysaccharides. This is an underwater concrete casting method characterized by mixing microbial polysaccharides with the material.

In the present invention, the method of pouring concrete into water is as follows:
Although not particularly limited, a concrete pouring method using a tremie is preferred since the microbial polysaccharide is mixed immediately before concrete is poured into water.

As the microbial polysaccharide used, xanthan gum, which is an anionic natural polymer substance produced from glucose saccharide as a raw material, is used. This xanthan gum is soluble in water, has high dispersibility in water, and exhibits high viscosity at low concentrations. Xanthan gum does not show a decrease in viscosity due to changes or the addition of salts.Furthermore, xanthan gum exhibits high viscosity when combined with calcium ions and water (H2O), which are components of cement. Hit 0
．． 5 to 2 kg is appropriate.

Next, in the present invention, the means for mixing xanthan gum, which is a microbial polysaccharide, into the concrete material is not particularly limited, but as mentioned above, it is not preferable to leave it for a long time after mixing due to its strong viscosity and binding force. , it is necessary to mix it immediately before putting it into the water. Therefore, it is desirable to mix the xanthan gum into the concrete material using a suitable mixer and then immediately introduce it into the hopper of the tremie and throw it into the water.

(Example) Each example of the present invention and a conventional example will be described below. In the conventional example, a mixture of sand, cement, and a commercially available dispersion inhibitor is poured into water, and in the present invention, a dispersion inhibitor (xanthan gum) is mixed into the mixture of sand and cement. , immediately poured into water, and the water was adjusted to contain salts equivalent to seawater.

After pouring the concrete into water, the physical properties of the hardened product were measured, and the results shown in Table 1 were obtained.

According to the observation of the underwater concrete according to the embodiment of the present invention from pouring to hardening, the dispersion of the concrete material was almost suppressed.

(Effect of the invention) From the above, this invention brings about the following effects.

(1) Since the xanthan gum used in the present invention exhibits high viscosity and binding strength at low concentrations, it is possible to obtain the effect of suppressing the dispersion of concrete materials without being limited by the amount of water mixed.

(2) The dispersion suppressing effect is not affected by salts dissolved in water or the pH of the water.

(3) A cured product with satisfactory physical properties can be obtained.

(4) Compared to the conventional method, the amount of the agent used is small, so the construction cost is relatively low.

(5) Can be used even in places with flowing water.

Therefore, this invention has great practical value.

Claims (1)

[Claims] A method for placing concrete in water, which comprises adding a microbial polysaccharide to the concrete material immediately before the concrete material is placed in water.