JPH0532969A - Soil-solidifying agent - Google Patents

Abstract

PURPOSE:To provide a soil-solidifying agent comprising an alumina cement and a polyacrylic acid having in ion-exchanged-water absorbing ability and a neutralization degree using a specific alkali hydroxide and ammonia. and having excellent safety and remarkable activity to increase the solidification rate and solidification strength of soil. CONSTITUTION:The objective soil-solidifying agent comprises (A) a highly water- absorbing polymer comprising a polyacrylic acid having a neutralization degree of 30-80mol.% using an alkali hydroxide (e.g. sodium hydroxide) and/or ammonia and an ion-exchanged-water absorbing ability of 300-1200 times volume and (B) an alumina cement having a composition comprising 40% of alumina, 40% of calcium oxide, 10% of silicon oxide and approximately 10% of ferric (III) oxide. The agent is useful for the reinforcement of soils such as the effective solidification of water-containing soils, e.g. sand soil, sludges, highly organic substance-containing soils and silts, and the large solidifying reinforcement of the ground.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention effectively solidifies hydrated soils such as highly hydrated cohesive soils, sandy soils, sludges, highly organic soils, sludges and silts, or imparts great solidification strength to the ground. The present invention relates to a soil solidifying agent useful for soil reinforcement.

[0002]

[Prior Art] The earth and sand generated during civil engineering work are
Since it contains a large amount of water and is highly fluid, it is extremely difficult to handle, and particularly makes it difficult to carry it out using a belt conveyor or a dump truck. Further, since such soil is used for landfilling, it is necessary to have a compressive strength that allows vehicles such as trucks to pass through. For this reason, various methods for solidifying and stabilizing a water-containing soil have been conventionally investigated. For example, in (a) JP-A-58-187485, a method of mixing a water-absorbent soil with a super absorbent polymer to reduce free water in the soil. (B) Japanese Patent Laid-Open No. 64-81886 proposes a method of using a water-containing soil solidifying agent composed of a (meth) acrylamide (co) polymer and gypsum.

[0003]

However, in (a), although a great effect is exhibited by drastically reducing the water content of the soil, it is difficult to say that the solidification strength is always satisfactory. There are drawbacks such that water is separated due to vibration during transportation by means such as water, and when it comes into contact with water again due to rainfall or the like, it collapses and becomes weak again. In (b), the acrylamide monomer is extremely toxic and is easily absorbed through the skin, so that there is a great risk in producing such a polymer, and the polymerization reaction of acrylamide is insufficient. , Monomer remains and causes poisoning. Furthermore, when polyacrylamide is mixed with soil, there is still concern about the safety after decomposition in the natural world, which is an extremely serious problem. However, if it is possible to find a solidifying agent that solidifies the water-containing soil very quickly to enable immediate removal and exhibits sufficient solidifying strength and is highly safe, its significance will be extremely significant.

[0004]

[Means for Solving the Problems] As a result of intensive studies to solve such problems, it was found that "neutralization degree with caustic alkali and / or ammonia is 30 to 80 mol% and water absorption capacity of ion-exchanged water is 300 to 1200. The present invention has been completed by finding that "a superabsorbent polymer made of acrylic acid and a soil-solidifying agent made of alumina cement, which is double the number of times", meet the purpose. That is, the present invention has the effect of promoting the solidification rate and solidification strength of hydrous soil by using a solidifying agent consisting of a superabsorbent polymer made of acrylic acid and an alumina cement showing a specific range of neutralization degree and the ability to absorb ion-exchanged water. It appears prominently. Furthermore, since both acrylic acid and alumina cement have low toxicity, they can be said to be excellent solidifying agents in terms of safety.

The present invention will be described in detail below. The superabsorbent polymer in the present invention is obtained by partially neutralizing acrylic acid with an alkali and polymerizing it. A suitable degree of neutralization is 30 to 80 mol%, preferably 40 to 75 mol%. When the neutralization degree is less than 30 mol%, the dissociation degree of acrylic acid is low and the water absorption ability is lowered, so that the effect of the present invention cannot be exhibited when mixed with alumina cement. When the degree of neutralization exceeds 80 mol%, such a polymer exhibits alkalinity, which requires careful handling and is not preferable. As the neutralizing agent for acrylic acid, caustic alkali such as sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide and ammonia are used alone or in combination of two or more kinds, but industrially, sodium hydroxide, water are used. Potassium oxide, especially sodium hydroxide is preferable in view of economy.

The method for polymerizing acrylic acid in the present invention is not particularly limited, and any method such as bulk polymerization, aqueous solution polymerization, spray polymerization, reverse phase emulsion polymerization and reverse phase suspension polymerization may be used. The polymer thus obtained has an ion exchange water absorption capacity of 300 to
1200 times, preferably 500 to 1000 times is suitable, and when it is less than 300 times, the solidifying ability is lowered and immediate curability is not particularly obtained. On the other hand, when it exceeds 1,200 times, the solidification rate can be obtained, but since the initial solidification force of the solidified body is weak, when the solidified product is vibrated, the solidifying agent does not show an excellent effect as a solidifying agent which separates water.

The alumina cement used in the present invention is produced by mixing a raw material containing a large amount of alumina such as bauxite with limestone and melting or firing it in a rotary kiln or the like. Generally, its chemical composition is 40% alumina, 40% calcium oxide, 10% silicon oxide and iron (III) oxide.
It is said to be close to 10%, and is characterized in that the hydration reaction is much quicker and faster than that of ordinary cement (Portland cement). In the solidifying agent of the present invention, the weight ratio of such superabsorbent polymer and alumina cement is usually 5: 9.
Preference is given to 5 to 90:10, preferably 15:85 to 60:40. If the weight ratio of the superabsorbent polymer is high, the compressive strength of the solidified product tends to be insufficient. On the other hand, if the weight ratio is low, the solidification speed decreases, which may hinder the transportation work.

When using the solidifying agent of the present invention, it is possible to optionally use an optional component such as an inorganic powder such as silicon dioxide, silica, activated clay, silica sand, diatomaceous earth, pearlite or bentonite. .. The water-containing soil using the solidifying agent of the present invention can be used for any of high water-content specific clay, sandy soil, sludge, high organic soil, sludge, silt, and any other soil requiring solidification treatment. The addition amount of the solidifying agent in the present invention varies depending on the water content ratio and the properties of the water-containing soil, but is usually 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of the solid content of the water-containing soil. is there.

The method of adding the solidifying agent in the present invention is not limited at all, and for example, a method of premixing the components (a) and (b) and adding to the soil, a method of adding the components (a) and (b) Examples include a method of separately adding to soil. Further, the solidifying agent of the present invention can be added all at once or divided into several times.

[0010]

[Operation] The soil-solidifying agent of the present invention has excellent safety and solidifies water-containing soil very quickly, enables immediate transportation, and imparts strength to the ground in the construction of soft ground. It is an excellent solidifying agent.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples. Examples 1 to 6 Acrylic acid / sodium acrylate copolymer and Lumnite (alumina cement, manufactured by Alcoa Kasei Co., Ltd.) were added to 100 parts by weight of sandy soil having a water content of 40% (as solid content).
The solidification rate of the hydrous soil and the compressive strength of the solidified soil were measured by mixing at the mixing ratio shown in. The results are summarized in Table 3. ○ Measurement method of solidification rate A predetermined amount of water-containing soil was charged into a universal mixing stirrer for mortar, and then a predetermined amount of solidifying agent was added while stirring. After the addition, the time required for the soil to show no fluidity or a water-free aggregated state was measured as the setting time. ○ Method for measuring the compressive strength of solidified soil The solidified soil is filled in a mold and solidified,
A columnar type specimen having a diameter of 100 mm and a height of 200 mm, which was not subjected to lateral pressure, was applied to a uniaxial compression tester, and its maximum stress was divided by the cross-sectional area to obtain uniaxial compression strength.

[0012]

[Table 1]

Comparative Examples 1 to 6 Using the solidifying agents shown in Table 2, the solidifying rate of the hydrous soil and the compressive strength of the solidified soil were measured according to Example 1. The results are summarized in Table 3.

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Effect] The solidifying agent of the present invention is excellent in safety and solidifies the water-containing soil very quickly, enables immediate unloading, and exhibits a remarkable effect of retaining a large strength in the soil.

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[Procedure amendment]

[Submission date] August 31, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

[0015]

[Table 3]

Claims (1)

Claims: 1. A neutralization degree with caustic alkali and / or ammonia is 30 to 80 mol%, and an ability to absorb ion-exchanged water is 300.
~ 1200 times super absorbent polymer made of polyacrylic acid and soil solidifying agent made of alumina cement