JPH0559363A - Hydrous soil improver - Google Patents

Abstract

(57) [Summary] [Structure] A hydrated soil improver comprising fly ash, lime and / or gypsum, and a water-soluble polymer. [Effect] The soil quality of construction residual soil with a high water content can be improved and reused for backfilling. It can also be used as fly ash.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agent for improving water-containing soil, and in particular, it improves soil quality of construction residual soil (hereinafter referred to as "remaining soil") generated by construction and civil engineering work and reuses it as a resource. The present invention relates to a water-containing soil improving agent suitable for.

[0002]

2. Description of the Related Art Conventionally, most of the remaining soil generated in various places cannot be reused and is either disposed of in landfill or taken out to other places, but there is considerable illegal dumping, which is an important issue for environmental destruction. Is increasing. This is because the amount of residual soil is increasing rapidly due to active redevelopment projects, while land reclamation work is decreasing, making it difficult to secure a place for receiving residual soil.

In the case of road construction, it is legally required to use sand to backfill the dug up site. Therefore, in general, it is necessary to bring the sand and sand to the backfill from other places, and the problem of environmental destruction is also occurring here. Regarding the reuse of the residual soil generated in such a situation, there is an example of operating a test plant for the residual soil treatment using quicklime.

On the other hand, the amount of coal ash "fly ash" generated in domestic coal-fired power plants is estimated at 5 million tons in 1990. Although its usage has been studied for many years, it is only used as a raw material for fly ash cement, and most of it is disposed of at the time of sea landfill. However, since the amount of processing is huge, there are concerns about environmental problems in the ocean.

[0005]

The method of the test plant described above is intended to improve only the residual soil of good quality, and is intended for the residual soil that is sun-dried and has a low water content because the site is vast. On the other hand, when considering an ordinary improvement plant, the site cannot be large, so the residual soil with a high water content generated at the site must be improved as it is without drying in the sun. It is highly sticky and adheres to mixers, etc., making it difficult to operate and not processing. In addition, there is a problem in that the strength of soil cannot be expected to improve even if treated.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the problems of the prior art and obtain an excellent improving agent for reusing the residual soil, and as a result, use fly ash and specific components in combination. As a result, they have found that water-containing soil such as residual soil can be reused for backfilling, and have reached the present invention. That is, the gist of the present invention lies in a hydrated soil conditioner comprising fly ash, lime and / or gypsum, and a water-soluble polymer.

The present invention will be described in detail below. The improvement of the water-containing soil in the present invention is to reuse the water-containing soil having high softness or high stickiness for backfilling or the like, so as to improve the strength and impart fluidity like sand, and to prevent swelling in water. It is to solidify. Therefore, the improvement of the water-containing soil in the present invention simply solidifies and solidifies the water-containing soil,
It does not leave liquidity lost.

The fly ash used in the present invention is an ash which is generally defined and which is extracted from smoke-bearing gas of a pulverized coal combustion boiler. Used. The composition of fly ash varies slightly depending on the raw material coal, but the constituent components are usually 50 to 70% by weight of SiO ₂ and 1 of Al ₂ O _3.
0-40% by weight, and also contains Fe ₂ O ₃ , CaO, MgO and the like.

[0009] As a form of using fly ash,
Usually, 10 to 30% by weight of fly ash is mixed with Pordland cement to prepare a fly ash cement, and this fly ash cement can also be used as the fly ash of the present invention. The lime used in the present invention is preferably quick lime, but slaked lime can also be used. The quicklime may be one that is usually sold on the market. It can also be used.

The gypsum used in the present invention is preferably anhydrous gypsum, but hemihydrate gypsum can also be used.
The weight ratio of fly ash to lime and / or gypsum is usually 1: 0.01 to 50, preferably 1: 0.05.
-20, more preferably 1: 0.01-10.

The water-soluble polymer used in the present invention is usually a polymer which is dissolved in at least 1 g or more in 100 ml of water, and is generally a (meth) acrylamide homopolymer or a copolymer thereof. It is illustrated. The copolymer preferably has a carboxyl group as a hydrophilic group, and in particular, of all monomers constituting the polymer, the monomer having a carboxyl group is usually 1 to 80 mol%, It is preferably contained in an amount of 5 to 60 mol%.
In addition, the carboxyl group may be present in either free acid or salt form.

Examples of the salt include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, ammonium salts, amine salts such as alkylamines having 1 to 18 carbon atoms and alkanolamines. , And a mixture of two or more of them, but an alkali metal salt is preferable.

As the water-soluble polymer having a carboxyl group, a (meth) acrylamide-based polymer containing (meth) acrylic acid or a salt thereof, a copolymer of maleic acid or a salt thereof with vinyl acetate, and itaconic acid. Further, there are copolymers of salts thereof with (meth) acrylamide, etc., but (meth) acrylamide polymers containing (meth) acrylic acid or salts thereof are preferable. (Meta)
Examples of the acrylamide polymer containing acrylic acid or a salt thereof include those obtained by copolymerizing (meth) acrylic acid or a salt thereof with (meth) acrylamide, and (meth)
It may be a partially hydrolyzed product of acrylamide. Further, a copolymer obtained by combining the above-mentioned monomers may be used.

Further, in the above polymer, a monomer containing a sulfonic acid group as a hydrophilic group, such as vinyl sulfonic acid,
It may be a copolymer including allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and salts thereof. Further, a hydrophobic monomer such as an olefin, an acrylic ester, or a vinyl ester may be contained as long as it does not impair the water solubility.

The molecular weight of the water-soluble polymer used in the present invention is usually 1,000,000 or more, preferably 5,000,000 or more. Although the production method is not particularly limited, it is generally a radical polymerization method, and solution polymerization using water or a lower alcohol as a solvent is adopted. The concentration of the monomer is usually 10% by weight or more, preferably 15 to 60% by weight.

When a polymerization initiator is polymerized in an aqueous solvent, peroxides such as potassium persulfate and ammonium persulfate, and redox type initiators using them, N, N'-azobis- (2-amidinopropane). Dihydrochloride, 4,4 '
A water-soluble radical polymerization initiator such as -azobis- (4-cyanovaleric acid) -2-sodium is preferable. The amount of the radical polymerization initiator used is usually 0.005 to 5% by weight, preferably 0.1% to the weight of the copolymerizable monomer mixture.
It is from 05 to 0.5% by weight.

The polymerization method is not particularly limited, but if an aqueous solution polymerization is exemplified, a method of polymerization with stirring, a method of polymerization in an adiabatic state by standing in a container, a method of polymerization while removing heat in a sheet form, an oil A method of polymerizing in a water-in-water emulsion or dispersion state is exemplified. As a method of standing and polymerizing, after removing oxygen through a predetermined monomer aqueous solution through nitrogen gas, a predetermined temperature and no radical polymerization initiator are added and uniformly mixed, and then a nitrogen gas stream is generated and a predetermined temperature is set. A holding method is exemplified. The polymerization temperature is usually selected in the range of 10 to 150 ° C according to the molecular weight of the desired polymer, but is preferably 40 to 80 ° C.

The polymer thus obtained is directly dried in a drier or treated with a dehydrating agent, dried and pulverized before being used as a sample. The mixing weight ratio of the water-soluble polymer and lime or gypsum is usually 1: 1 to 1: 500, preferably 1: 2.
˜1: 250.

The soil to which the present invention is applied is usually a soil having a water content ratio of 20 or more. In particular, the use of the improving agent of the present invention can be expected to have a water content ratio of 40 to 200%, and further a water content ratio of 5%.
It is a soil with a high water content ratio of 0 to 150%, and specifically, it is the residual soil that is generated by general civil engineering and construction work such as water and sewer construction, road construction, and residential land development. The water content ratio is a value representing the ratio of the mass of soil water lost by oven drying at 110 ° C to the oven dry mass of soil in percentage, and is measured by JISA1203 (water content test method). It is a value.

The soil includes the Kanto loam layer, gravel, sand and the like, which is usually a mixture of these, but concrete fragments may be mixed depending on the site of occurrence. Since the water content depends on the soil type, it depends largely on the site where the water is generated. The one having a high water content ratio is, for example, the Kanto loam layer, which usually has a water content ratio of about 80 to 120% and has a high tackiness, but it is solidified and granulated by using the improving agent of the present invention so that it is fluidized. Property is imparted, the adhesiveness and the swelling property in water are eliminated, and the ground supporting force is improved, and the backfilling can be reused.

The addition amount of the improving agent of the present invention is not particularly limited because it depends on the water content of the treated soil, but the addition amount of lime and / or gypsum is 0.2 to 2 with respect to the remaining soil.
It is 0% by weight, preferably 0.5 to 10% by weight, and the amount of fly ash added is usually 0.5 to 50% by weight, preferably 1 to 30% by weight. The water-soluble polymer content is 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight, based on the residual soil.

The method of adding the improver of the present invention is not particularly limited, but preferably a method of adding lime and / or gypsum after adding and mixing the water-soluble polymer and fly ash, but adding and mixing or premixing at the same time. There is nothing wrong with using it. The mixing with the soil is carried out by an ordinary method, for example, a method of spraying the improving agent on the water-containing soil on a belt conveyor and mixing with a backhoe. Fly ash, lime, gypsum are usually added as powder, but the water-soluble polymer is in powder form,
You may add as an aqueous solution.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Examples 1 to 3 and Comparative Examples 1 to 9 Using the Kanto loam layer having a water content ratio of 80%, which is difficult to treat among the water-containing soils, as a raw material soil, an improvement test was conducted. Also,
The fly ash was obtained from a coal-fired power plant at the Yokkaichi Plant of Mitsubishi Kasei Co., Ltd., and its composition was 59% SiO ₂ , 30% Al ₂ O ₃ , and 5% Fe ₂ O _3. Met. Further, as a water-soluble polymer, a copolymer of acrylamide: sodium acrylate = 80: 20 (molar ratio) (intrinsic viscosity [η] = 23.2) was used.

The raw material soil was subdivided into polyethylene bags of 7 kg each and subjected to an improvement treatment. The improvement treatment is as follows: Mix 7g of water-soluble polymer powder in each bag, and mix with fly ash 420g (6% of soil), 630g.
(9%) and 1,400 g (20%), respectively, and further 2
10 g of quicklime powder was added and stirred. Immediately sealed to prevent water from splashing. After 6 days of sealed curing, JI
SA1210 (Soil compaction test method by tamping)
According to the above, the improved soil was divided into three layers in a mold having an inner diameter of 15 cm, and each of them was tamped 92 times with a 4.5 kg rammer to perform a tamping test.

Next, according to JISA1211 (CBR test method), preparation for a water immersion expansion test was performed, and the expansion amount was traced by immersing in a water tank for 4 days. Further, after taking out from the water tank to remove water and performing a predetermined measurement after 15 minutes, C
BR (California Bearing Rati)
o) A load-penetration amount curve was obtained using a tester. The load at a penetration amount of 2.5 mm (hereinafter, abbreviated as penetration strength) was read and CBR was calculated by the following formula. The standard load in the formula was 1,370 kg, which is the standard load for 2.5 mm penetration defined by JIS. The larger the CBR value, the higher the strength.

[0026]

Further, the condition of the improved soil was visually observed. The results of the above tests are shown in Table 1 (FA in the table indicates fly ash). In addition, the expansion ratios determined from the expansion amounts after 4 days of water immersion measured at the same time were all good at 1% or less.

Comparative Examples 1 to 3 use fly ash and quick lime alone, Comparative Example 4 use quick lime alone, Comparative Examples 5 and 6 use quick lime and water-soluble polymer in combination, and Comparative Examples 7 and 8 are the cases where fly ash was used alone. Further, Comparative Example 9 is the result of the test of the raw material soil, and it was tamped by hand because it had a large tackiness and could not be tampered with by the tamping tester.

[0029]

[Table 1]

Examples 4 and 5 and Comparative Examples 10 to 12 The same treatments and tests as in Example 1 were carried out except that anhydrous gypsum powder was used instead of quicklime. The results are shown in Table 2. In Comparative Examples 10 and 11, when fly ash and anhydrous gypsum were used together, Comparative Example 12 was used alone, and in Comparative Example 13, anhydrous gypsum and water-soluble polymer were used together. This is the case. The water-soluble polymer here is a 30 mol% partial hydrolyzate of polyacrylamide (extreme clay [η] = 19.5).

[0031]

[Table 2]

[0032]

EFFECTS OF THE INVENTION The residual soil having a high water content ratio, which has been conventionally difficult to use and has been subject to illegal dumping, can be improved in a plant without being directly dried in the sun by using the water-containing soil improving agent of the present invention. The fly ash, which is currently in trouble, cannot be reused as a resource for backfilling, and can be used as a resource. In this way, it is possible to prevent the environmental destruction due to illegal dumping of the residual soil and the extraction of sand for backfilling, and to reduce the environmental pollution due to the landfill of fly ash, which greatly contributes to the local community.

Claims (1)

[Claims] 1. A hydrated soil improver comprising fly ash, lime and / or gypsum, and a water-soluble polymer.