JPH0262158B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a soil stabilizer composition for soft ground,
Specifically, the present invention provides a soil stabilizer composition having stable setting retarding properties. BACKGROUND ART Ground improvement methods have been widely used in the past to mix soil stabilizers into soft ground to harden and strengthen it. In addition, in recent years, from the viewpoint of preserving the natural environment and preventing pollution, there has been a deep mixing method that improves soft ground such as seabeds and lakes by fixing and stabilizing it in its current location. In such construction methods, a mixing machine with stirring blades is generally inserted into the soft ground, and a soil stabilizing material in the form of slurry is injected from the tip of the shaft of the machine and mixed. It adheres to the ground layer and hardens to improve the ground. Furthermore, by carrying out the above-mentioned constructions adjacently and consecutively, an integrated improved ground in the form of a wall, lattice, block, etc. can be obtained by sequentially overlapping and joining. However, when forming an integrated improved ground through continuous construction as described above, it is necessary for the soil stabilizing material injected in the overlapped areas to be mixed well one after another and then hardened. There is a need for a soil stabilizing material that has sufficient setting retardation properties and then quickly develops hardening strength. In view of the above objectives, the present inventors have already developed cement,
We have proposed a composition containing lime and oxycarboxylic acid or its salt as constituent components, and a composition composed of cement, calcium dihydrogen phosphate, and oxycarboxylic acid or its salt, but we have developed an even better soil stabilizing material. We carried out intensive research on the subject.
As a result, a slurry prepared by adding water to a composition consisting of cement, a water-soluble phosphate, and an oxycarboxylic acid or its salt exhibits an extremely good setting retarding effect after being mixed into soft ground. Since the slurry viscosity is lower than that of plain,
The present invention was completed based on the discovery that it is easy to handle and has high workability, and that it can be mixed uniformly with clay, so it always exhibits a stable setting retardation effect. That is, the present invention is a soil stabilizer composition containing 0.004 to 0.070 mol of water-soluble phosphate and 0.002 to 0.030 mol of oxycarboxylic acid or its salt per 100 parts by weight of cement. The cement used in the present invention is not particularly limited, but generally includes ordinary Portland cement, special cement such as early strength or moderate heat Portland cement, mixed cement such as blast furnace cement or fly ash cement, and these may be used alone or in combination. can do. In the soil stabilizer composition of the present invention, the combination of the hydroxycarboxylic acid or its salt described later by incorporating a water-soluble phosphate as one of the constituent components can produce a soil stabilizer composition that has a good setting retarding effect. It is extremely important to maintain the viscosity of the slurry obtained by adding water to the composition at a low level and to improve the miscibility with the viscosity in order to stably exhibit the setting retarding effect. As the water-soluble phosphate, those having a solubility in water of 0.5 mol/or more are preferably used. Specifically, alkali metal salts of orthophosphate such as potassium phosphate dipotassium phosphate, tripotassium phosphate, sodium phosphate, disodium phosphate, trisodium phosphate, ammonium phosphate, dibasic phosphate, etc. Ammonium orthophosphate such as triammonium phosphate; acidic pyrophosphates such as potassium acidic pyrophosphate and sodium acidic pyrophosphate; polyphosphates such as sodium tripolyphosphate; metaphosphates such as potassium trimetaphosphate and sodium trimetaphosphate. Potassium phosphate is particularly recommended. Further, even if two or more of the phosphates are blended, the setting retardation property will not be impaired in any way. In the soil stabilizer composition of the present invention, cement 100
It is desirable to mix 0.004 to 0.070 mol, preferably 0.010 to 0.040 mol, of the water-soluble phosphate per part by weight. If the blended amount of phosphate is less than the above 0.004 mol, setting retardation will decrease and
When the amount exceeds 0.070 mol, the setting time tends to become abnormally long and the hardening strength tends to decrease. Next, in the soil stabilizer composition of the present invention, oxycarboxylic acid or its salt may be blended as another component, which has good setting retarding properties due to a synergistic effect with the water-soluble phosphate described above. , is extremely important in order to obtain a soil stabilizer composition that has a low viscosity when made into a slurry. Examples of the oxycarboxylic acid include acids such as acharitic acid, citric acid, malic acid, and gluconic acid, and their alkali metal salts such as sodium and potassium salts, and calcium salts. One of these days,
Malic acid and gluconic acid or their salts are recommended, especially the sodium salt. The amount of oxycarboxylic acid or salt thereof is generally 0.002 to 0.030 mol, preferably 0.004 to 0.004 mol, per 100 parts by weight of cement.
It is 0.020 mole. That is, if the amount of oxycarboxylic acid or its salt is less than the above range,
The viscosity of the cement slurry increases, preventing uniform mixing with the viscosity, and a stable setting retardation effect cannot be expected. Moreover, when the above range is exceeded, not only the setting delay time becomes extremely long, but also the curing strength becomes insufficient. In addition, if a slurry prepared with cement and water-soluble phosphate alone is left as is,
Because it solidifies within a day, it will solidify in the slurry tank, piping, etc. and cause problems during construction the next day. However, if oxycarboxylic acid or its salt is added above the above range, The composition of the present invention also has storage stability such that no caking occurs even if it is left as is. The composition of the present invention is mixed with a predetermined amount of water depending on the purpose and used in the form of a slurry to improve soft ground. After being poured into soft ground, the slurry stably exhibits a sufficient setting retarding effect. can do. Moreover, it is possible to develop rapid curing strength thereafter. Although the mechanism by which the composition of the present invention exerts the above effects is not clear, the present inventors estimate as follows. That is, calcium hydroxide produced by hydration from cement particles in the slurry reacts with a water-soluble phosphate and an oxycarboxylic acid or its salt to produce an insoluble compound, which covers the surface of the cement particles. At that time, the reactivity of the water-soluble phosphate with the calcium hydroxide and the surface active action of the oxycarboxylic acid or its salt act synergistically, and the cement particles are uniformly covered with the insoluble compound, Furthermore, since the viscosity of the slurry is lowered, it is possible to mix the slurry and clay uniformly, and it is estimated that there is no partial hardening at the start of setting, and a stable setting retardation effect is exhibited. The method for preparing the soil stabilizer composition of the present invention is not particularly limited as long as it has the above composition when water is added to form a slurry. For example, cement,
A method of blending a phosphate, an oxycarboxylic acid or a salt thereof to form a composition and adding water thereto, a method of adding cement to an aqueous solution of a phosphate and an oxycarboxylic acid or a salt thereof to form a composition, etc. is suitable. It should be noted that the soil stabilizer composition of the present invention may be mixed with other known cement additives, such as other setting retarders, if necessary, without any particular limitation. The soil stabilizer composition of the present invention is generally adjusted to a slurry with a water to soil stabilizer composition ratio of 50 to 150%, and is used for the above-mentioned continuous construction on soft ground, for example, in the form of an integrated wall. Improved ground can be obtained. EXAMPLES Examples and comparative examples of the present invention will be described below, but the present invention is not limited thereto. In Examples and Comparative Examples, the reproducibility of setting time and the hardening state at the start of setting were measured by the following method. In addition, the measured values indicate average values. Γ reproducibility: Using a sample with the same composition, the soil is treated in the same manner every 5 times, and then the setting time and hardening strength are measured, and the difference between the highest value and the lowest value is calculated based on the lowest value. Those with a ratio of less than 10% are considered good.
Items of 10% or more were evaluated as defective. Cured state at the start of Γ setting: Of the specimens after uniaxial compressive strength testing, the presence or absence of partial hardening was judged with a finger before and after the start of setting. Uniformly cured...... Partially cured......× Example 1 Natural water content collected from the seabed of Yokohama Daikoku Pier: 90
To 100 parts by weight of clay, 10.7 parts by weight of a soil stabilizer composition prepared by mixing potassium phosphate and sodium gluconate with respect to cement in the proportions shown in Table 1 was added to 100 parts by weight of clay at a water/soil stabilizer composition ratio of 60%. It was injected as a cement slurry, stirred and mixed for a certain period of time, and the treatment setting time and unconfined compressive strength were measured. In addition, the viscosity of the cement slurry, the state of the slurry after being left for 24 hours, the reproducibility of the setting time of the treated soil, and the hardening state at the start of setting were also measured. The results are shown in Table 1. Note that Nos. 1, 2, 4, 11, and 12 in Table 1 correspond to comparative examples.

【table】

[Table] × mark... 〃 〃 〃 Coagulation.
Example 2 Natural water content 90 collected from the seabed of Yokohama Daikoku Pier
The experiment was carried out in the same manner as in Example 1 using 10.7 parts by weight of a soil stabilizer composition prepared by mixing 100 parts by weight of clay with 10.7 parts by weight of phosphate and oxycarboxylic acid or its salt in the proportions shown in Table 2 based on cement. did. The results are shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1. Water-soluble phosphate based on 100 parts by weight of cement.
A soil stabilizer composition containing 0.004 to 0.070 mol and 0.002 to 0.030 mol of an oxycarboxylic acid or its salt. 2. The soil stabilizer composition according to claim 1, wherein the cement is ordinary Portland cement, early strength Portland cement, moderate heat Portland cement, blast furnace cement, or fly ash cement. 3. The soil stabilizer composition according to claim 1, wherein the water-soluble phosphate is an alkali metal salt or ammonium salt of orthophosphoric acid, pyrophosphoric acid, or polymetaphosphoric acid. 4 Claim 1 in which the oxycarboxylic acid is malic acid, tartaric acid, citric acid or gluconic acid
Soil stabilizing material composition described in . 5. The soil stabilizer composition according to claim 1, wherein the oxycarboxylic acid salt is a sodium salt.