JPS6065755A - Underwater concrete composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater concrete composition with excellent seawater resistance.

When pouring pre-mixed concrete into water, the concrete may separate due to contact with water.
The poured concrete becomes uneven and it is difficult to ensure the specified mechanical properties and watertight properties. Therefore, special equipment is used to avoid contact with water, such as tremie pipes, concrete pumps, and packets, but in reality, various factors can cause concrete to be washed with water, separated, and hardened. Underwater construction of concrete has been a difficult technique because it may not work or its strength may be significantly reduced.

As a method for easily constructing underwater concrete by improving these points, it is already known to add a water-soluble polymer and allow the concrete to fall freely in water to cast concrete (DE2326647).

However, when the above method is used in places that come into contact with seawater, such as offshore structures or seawall structures, the seawater resistance of concrete becomes a problem. In addition, in order to secure the specified strength and self-leveling property, the unit water volume must be increased significantly, for example by 50 kg/m', and in order to obtain the normal strength with this unit water volume, 100 to 9/m m'
There is a drawback that the amount of cement per unit must be increased by a large amount.

The present invention has excellent separation resistance such that separation does not occur even when it comes into contact with water, and can increase the water-cement ratio and improve fluidity while satisfying a predetermined strength. The purpose of the present invention is to provide an underwater concrete composition having high seawater resistance.

That is, the present invention is an underwater concrete composition with excellent seawater resistance, which is made by adding a water-soluble polymer, an antifoaming agent, an anhydrous ceracola-containing material, and/or a calcining filler.

The water-soluble polymer used as an additive in the present invention is a substance that imparts adhesion to concrete and increases its resistance to separation in water, such as polyacrylamide, polyethibine oxide, polyvinyl alcohol, and These include cellulose ethers such as methylhydroxyethylcellulose, hydroxyethylcellulose, methylcellulose, and hydroxypropylcellulose.

The amount of water-soluble polymer added varies depending on the type, molecular weight, degree of substitution, etc. of the water-soluble polymer, and also depending on the intended casting environment conditions, but generally it is 5% by weight or less based on the cement. It is. Similarly, water-soluble polymers may be used singly or in combination of two or more, but hydroxyethylcellulose and methylcellulose are preferred because of their improved solubility from the standpoint of kneading.

Antifoaming agents reduce the amount of air in concrete, which increases significantly due to the addition of water bathing polymers, and suppress the decline in compressive strength. Product name: “Anti-Floss F”
, Toshiba Silicone ■Product name rTsA-732'', San Nopco ■Product name r SN-Defoamer 14HP.

24HPJ, etc., and powder-based ones are preferable from the standpoint of kneading. The amount of antifoaming agent added varies depending on the type of antifoaming agent, but is 0.3 to 10% by weight based on the water-soluble polymer.

The anhydrous ceracola-containing material may be anhydrous ceracola alone, but it is one that has anhydrous ceracola as its main component and mixed with fine powder such as silica flower or activated clay. ■Items commercially available under the trade name "Athanose-Permix" or the like may also be used. A similar effect can be expected even if a calcination interval is used. However, since it is difficult to control coagulation, it is preferable to use a product containing anhydrous ceracola.

The amount of anhydrous ceracola-containing material and/or calcination buffer is as follows:
From the viewpoint of seawater resistance, it is preferable that the amount is 3% by weight or less, preferably 0.5 to 2% by weight, calculated as SO3 based on the cement.

The cause of seawater resistant white balls due to the addition of anhydrous Ceracola-containing materials and/or calcination intermediates is due to Ca in C3A, C, and AF.
It is thought that the reason for the increase in strength is that the pore structure of the hardened material shifts to a smaller size due to the formation of ettringite at the initial stage of the material, and the structure becomes denser. .

The above-mentioned additives may be added at the time of mixing concrete or separately to pre-mixed concrete, or they may be added at the same time. However, considering convenience during kneading and mixing, it is preferable to add all powders at once.

Similarly, when mixing the underwater concrete of the present invention, the mixing conditions for concrete materials such as cement and aggregate may be the usual mixing conditions, and the unit cement amount is 320 to 5 oz.
o It is preferable that the unit water amount is 170 Kg/m'' or more at a Ky/quiet level.

Normally, concrete is compacted after it is poured, but in underwater construction, compaction work is often difficult, unlike in normal cases. However, since the underwater concrete of the present invention (hereinafter simply referred to as concrete) has excellent separation resistance, it is possible to secure a sufficient amount of water per unit of water in the concrete, thereby increasing self-leveling properties and filling the concrete with its own weight. I come to do it. Further, in the present invention, the water-cement ratio can be increased while satisfying a predetermined strength due to the effect of the anhydrous Ceracola-containing material and/or the calcination interval, which is more preferable in terms of self-leveling properties.

It is also possible to use chemical admixtures such as retardants, AE agents, and water reducing agents, which are commonly used, and pozzolans. Furthermore, the present invention is not limited to use in seawater;
It can be used even in fresh water.

As explained above, the underwater concrete composition of the present invention has high separation resistance and excellent seawater resistance, so it can be placed by directly free-falling concrete into seawater, especially in the ocean. Furthermore, structures near the coast that are in contact with the sea surface can be easily constructed or repaired. Further, if the underwater concrete composition of the present invention is used, there is no need to take special consideration when placing concrete underwater, which is very preferable from the viewpoint of shortening the construction period and reducing construction costs.

The present invention will be further explained below with reference to Examples.

Example 1) As shown in Experiments 1 to 4 in Table 1, a water-soluble polymer, an antifoaming agent, and an anhydrous Ceracola-containing material were added and mixed with concrete to prepare in-air and underwater specimens. Specimens made in the air were made by pouring concrete into a mold in the air and pounded with a mallet, and specimens made underwater were made by pouring concrete into a form that had been submerged in water beforehand and then tapping it with a hammer. .

Judging the self-leveling property of Ko7ri'V-to.

Therefore, a liquidity test was conducted. That is, the slump and flow were measured when the slump cone was slowly pulled up. In addition, in order to examine the properties of the cured product, the compressive strength of the specimens produced in water and in the air, and the seawater resistance of the specimens produced in water were measured. The seawater resistance test was conducted using a 5% Mg5O solution. The results are shown in Table-2 and Table-3.

Table 1 shows the mixture, Table 2 shows the properties of fresh concrete and compressive strength of the hardened concrete, and Table 3 shows the results of 5
% MgSO4 solution for a given age.

Comparative Example Experiments were conducted in the same manner as in Example 1) by blending the test plates 6 to 8 in Table 1. The results are shown in Table-2 and Table-3.

Example 2) The same procedure as in Example 1) was carried out except that in the formulation of experimental plate 5 in Table 1, a calcination spacing was used instead of the anhydrous ceracola-containing material.

Materials used> Antifoaming agent: Sanno Pro Co., Ltd. trade name r14HPJ Calcined Alum: Showa Mining Co., Ltd. trade name “Guimix” fine aggregate (S)
: Natural sand produced for Sagami 5 k (w) : 7 and 4 heads - 1 *1) SOs equivalent vs. cement weight % War) vs. cement weight % *3) Calcined masonry SO8 equivalent vs. cement weight Uochi Table-2 Table-3

Claims (1)

[Claims] An underwater concrete composition having excellent seawater resistance and containing a water-soluble polymer, an antifoaming agent, an anhydrous ceracola-containing material, and/or a calcining filler.