JPH07136693A - Sludge solidification agent - Google Patents

Abstract

PURPOSE:To absorb water from sludge early and solidify it promptly by mixing a compound comprising fly ash and cement with a compound comprising aluminum sulfate, calcium salt, alkali metal carbonate, and silica. CONSTITUTION:In a solidification agent useful for the improvement of weak ground, and the containment of organic sludge and harmful industrial waste, etc., 10-30 pts.wt. of a compound (A) comprising 5-30 pts.wt. of aluminum sulfate, 10-50 pts.wt. of calcium salt, 0.1-10 pts.wt. of alkali metal carbonate, 10-20 pts.wt. of silica or silica fume, and, if necessary, 3-15 pts.wt. of titanium oxide is incorporated with 80-90 pts.wt. of a compound (B) comprising 40-90 pts.wt. of fly ash or PS ash and 10-60 pts.wt. of cement. By using the solidification agent, water is adsorbed and at the same time organic substance are mixed; thereafter, with the progress of solidification by cement, a pozzolana reaction is induced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidifying agent which can be used for improving soft ground and containing organic sludge such as sludge or toxic industrial waste.

[0002]

2. Description of the Related Art Currently, the mainstream of solidifying agents is cement-based, and lime-based solidifying agents are used for organic soil and other special purposes, but they are not generally used because problems such as alkali outflow have not been solved. Is the current situation.

[0003]

[Problems to be Solved] The present invention can be applied not only to inorganic soils but also to organic soils, and moreover, it can rapidly absorb moisture in the soil, increase the strength of an object to be solidified with a rapid hardening reaction, and be lightweight. An inexpensive powdery treatment agent is provided. Further, the present invention provides a solidifying agent that does not significantly change the pH of treated soil.

[0004]

The present invention utilizes the self-hardening property of fly ash (coal ash) or incineration ash (PS ash) of papermaking pulp discharged from a papermaking process that does not use a chlorine-based bleaching agent, and uses ettringite by a solidification reaction. And aluminum oxide, calcium compound, alkali metal carbonate, silica fume, etc., as a reaction aid for producing CSH (calcium silicate hydrate), and titanium oxide, and contact with soil At the same time as absorbing water in the initial stage of the hydration reaction, the organic matter is taken in, and thereafter the solidification by the cement component proceeds to eventually lead to the pozzolanic reaction. The solidifying agent of the present invention is 5 to 30 parts by weight of aluminum sulfate, 10 to 50 parts by weight of calcium salt, 0.1 to 10 parts by weight of alkali metal carbonate, silica or silica fume 1.
8 to 10 parts by weight of compound (A1) consisting of 0 to 20 parts by weight of compound (B) consisting of 40 to 90 parts by weight of fly ash or PS ash and 10 to 60 parts by weight of cement.
The mixture is mixed in an amount of 0 to 90 parts by weight, and the solidification reaction is caused by being sprayed on the treated area or added to the object to be solidified and stirred. Further, the use of the compound (A2) in which 3 to 15 parts by weight of titanium oxide is added to the compound (A1) has the effect of enhancing the removal of harmful substances in the soil.

When sprayed or agitated on soil or the like, in the solidifying agent of the present invention, fly ash and PS ash rapidly absorb moisture in the soil by the porous surface and also contain gypsum component, aluminum oxide, oxide contained in itself. Cure is accelerated by silicon or the like. The calcium compound added in the present invention is to further enhance the hardening reaction inherently possessed by the fly ash and the like, and the addition amount of the compound is experimentally determined within the above range. Silica-based components are also mixed for the same purpose, but not only supplement the lack of curing components, but also contribute to the formation of curing reaction products, ethrin guide and CSH (calcium silicate hydrate). It is a thing. Ettringite is 3
As shown in the chemical formula CaO.Al ₂ O ₃ .3CaSO ₄ .32H ₂ O, a large amount of water is consumed by the hydration reaction in the formation thereof. CSH also consumes a large amount of water. At the same time, the surrounding organic substances are taken in by these hydration reactions. Since these formation reactions proceed even in the presence of organic matter, the solidifying agent of the present invention effectively acts on both organic soil and inorganic soil. Further, since silica fume is amorphous, it crystallizes violently at the same time when the reaction starts. At this time, the cement-based hardening reaction product produced from the cement that is present at the same time interacts with each other in an interfering manner to form a siliceous strong hardness crystal. In the process of hydrolyzing aluminum sulfate to form a colloid of aluminum hydroxide, polycondensation ions of aluminum are produced as a polymer and are condensed while adsorbing soil particles. This coagulation action, together with the physical water absorption action of each additive and the fly ash, contributes to the development of early strength and early age strength of the present drug. Further, aluminum sulfate has the effect of causing the solidification reaction, which proceeds as an alkali reaction as a whole, to proceed even in the non-alkali region, and to prevent the target soil from becoming alkaline. Further, the alkali carbonate participates in the solidification reaction by promoting the elution of the reactive ions Si ⁴⁺ and Al ³⁺ from the siliceous material forming a part of the ash component. Each of the above-mentioned agents is diversified and complicatedly related to each other to form various solidification reactants, and the cement acts as a solidifying material for these solidification reactants. The cement is preferably Portland cement or early strength cement. In addition to this, titanium oxide and silica oxide added at the same time are substances contained in fly ash and the like, but the addition of titanium oxide causes decomposition of heavy metals, organic matter, agriculture, etc. in the target soil. It has been confirmed that removal is facilitated. Although the details of this reaction mechanism are not clear, it is presumed that the catalytic action caused by the irradiation of sunlight is involved.

[0006]

【Example】

Formulation (A1) Aluminum sulfate 10 parts by weight Calcium sulfate 10 parts by weight Sodium carbonate 0.1 parts by weight Silica fume 10 parts by weight Formulation (B) PS ash 70 parts by weight Early strength cement 20 parts by weight 90 parts by weight of the compound (B) was mixed with 10 parts by weight of A1) to prepare the mixture. Table 1 shows the results of component analysis of the entire formulation at the above ratio.

[0007]

[Table 1] The analytical values of arsenic, lead, cadmium, hexavalent chromium and other heavy metals were all below the analytical detection limit.

[0008]

[Test Example 1] Shinkawa sludge uniaxial compression test for soil improvement (sludge collected from Shinkawa, Hamamatsu City, Shizuoka Prefecture) Specimen creation date: March 19, 1993 Test date: March 26, 1993 (7 days curing ) Testing organization: Matsuura Construction Office Co., Ltd. Testing method: Shinkawa river bottom sediment sludge, which is organic sludge 2
A uniaxial compression test was carried out by collecting 00 g and preparing a test sample in which the same amounts by weight of the stabilizing treatment mixture of Examples ((A1) and (B)) and the stabilizing treatment mixture with the cement-based solidifying agent were mixed for comparison. It was Although mixed in the same amount (100 g), with respect to the solidifying agents of Examples, those having different compounding ratios (E1), (E2),
Three types of (E3) were prepared (Table 2), and for the cement type, solidifying agents of different manufacturers were used as K1, K2 and K3 (Table 3). K1: High-organic cement-based solidifying agent manufactured by M company K2: Cement-based solidifying agent manufactured by M company K3: Cement-based solidifying agent manufactured by O company

[0009]

[Table 2] Example Uniaxial compression test of stabilized products Sludge 200 g

[0010]

[Table 3] Uniaxial compression test for cement stabilized products Sludge 200g

[0011]

[Discussion] The solidifying agent of the present invention is (E1), (E2), (E3)
Both exhibit sufficient strength. Usually, in the case of the treatment of organic sludge, most of them are required to be carried out promptly, and the strength of the above test results is not required, so it can be understood that the amount used is smaller than the amount used for the cement-based solidifying agent. This time, apart from cement-based K2 and K3, which were not able to even prepare specimens, of the specimens that had reached the crushing test, even the specimen of the lowest strength (E2), the target soil was dredged. Considering that the organic sludge is discharged at that time, the strength of about 1/3 of the expression strength is sufficient. Moreover, if the ranking is made in order of low cost among these, (E2), (E
1), (E3), and K1. From the target strength for ordinary organic sludge treatment, 50% for (E2), 40% for (E1), relative to the amount added in this test,
In the case of (E3), the target strength is sufficiently achieved with an addition amount of about 30%. In the above experiment, (E3) is likely to be judged to be the cheapest, but it can be said that (E2) is optimal in terms of total cost in the field where immediate effect is actually required. Although K1 is a cement type, it exhibits sufficient strength, which is a natural result because it is a special solidifying agent for high organic matter. The solidifying agent (E3) of the present invention has higher strength than K1 for high organic matter. (E1), (E
(E3) of 2) and (E3) obtained the highest strength because it was due to the test piece crushing test by 7-day curing, and the generation of ettringite and CSH was just completed, and the medium-term strength was controlled. It is considered that this is because it is in the strength reaction area of cement hydrate.

[0012]

Test Example 2 As a solidifying agent, a compound (A2) obtained by adding 10 parts by weight of titanium oxide to the compound (A1) of the example was used. Sludge burial surface surface improvement test Test place: Eniwa City, Hokkaido Tamagawa-gumi Sludge burial site Test date: May 8, 1993: Plate loading test May 12
Daily field situation: When a boring test was conducted at three arbitrary sites, the N value was zero up to the shallowest 9 m and the deepest 13 m. Test method: 5 m x 10 m is partitioned on site and a depth of 1.5 m is modified from the surface. The solidifying agent content is 3.
5% by weight. The machine used is a normal Yumbo machine, and a bucket stabilizer is used as a special attachment to perform kneading evenly. A flat plate loading test was carried out at two locations within the construction range as collected data (Tables 4 and 5).

[0013]

[Table 4] Plate loading test results Measurement location: No. 1 Date of measurement: May 12, 1993 Measurer: Tsutomu Matsuo (Tamagawa Gumi Laboratory) Loading plate diameter 30 cm Loading plate area 706.5 cm ² Soil improvement Construction on May 8, 1993 Completed 18:00

[0014]

[Table 5] Measurement location: No. 2 Date of measurement: May 12, 1993 Measurer: Tsutomu Matsuo Loading plate diameter 30 cm Loading plate area 706.5 cm ²

The relationship between the subsidence amount and the total load in Tables 4 and 5 is graphed as shown in FIGS. 1 and 2.

[0016]

[Discussion] The construction site was a sled burial site with a length of 9 m or more, and the site condition was a bottomless swamp. Before the treatment, it was a place where it was unlikely that heavy machinery would invade, but a 17 ton weight Yumbo was able to proceed while spraying and stirring the solidifying agent of the present invention.
After excavating a part of it 4 days after the completion of rolling compaction,
The solidified state could be confirmed up to around 2 m to 2.5 m at the solidified location at a depth of 1.5 m. It is considered that this is because the fly ash absorbed water and at the same time, the water in the lower part absorbed and solidified due to a capillary phenomenon. At the same time, it seems that an amorphous component such as silica fume actively contributes to the progress of solidification. The “plate loading test data” obtained by the solidification treatment was a result that exceeded the roadbed strength of a first-class national highway.

[0017]

[Effect] Since the solidifying agent of the present invention produces ettringite and CSH, which are hardly affected by the presence of organic matter, as hardening reaction products, the solidification agent is sufficiently solidified not only on inorganic soil but also on organic soil. Exert a reaction. In addition, since the organic and inorganic components of the soil are hardly affected, the required amount will not dramatically increase due to the presence of organic matter more than expected during the soft ground improvement work like the conventional cement type. As long as the water content ratio is fixed, there is no risk of exceeding the required amount calculated at the time of construction planning. Furthermore, since the amount of cement contained in the present solidifying agent is relatively small, and aluminum sulfate and the like act as a solidification reaction auxiliary agent and at the same time also function as a PH adjusting agent, the soil PH value after stabilization is adjusted to a neutral range. It can be maintained at a high level, which is extremely desirable for environmental protection. Coal ash, paper ash, and the like in the solidifying agent of the present invention are a type of industrial waste, and therefore they can be solved together with their processing problems, are effective as waste recycling, and are inexpensive. In addition, ash, which is the main component, absorbs water contained in the target soil rapidly, which has immediate effect on the reaction, and requires less amount of time and amount of input to reach the target strength and target water content ratio. There are advantages. Generally, most of odors and harmful substances contained in the sludge to be treated exist in a state of being dissolved in water in the sludge. However, since various conventional solidifying agents have a form of taking in water by a chemical reaction or a form of producing water, they are ineffective against the original bad odor of sludge, or worse, they generate a strange odor. However, according to the solidification mechanism of the solidifying agent, the water content is absorbed by the porous surface of the ash, and the surface is coated with the hardening reaction products such as ettringite and CSH. Therefore, the odor is reduced with the progress of the solidification reaction, and becomes completely odorless at the end of the solidification reaction. Similarly, harmful substances such as heavy metal ions are also contained inside the ash component and do not elute again. In addition, the conventional products have a specific gravity of 1 or more as a whole, but the solidifying agent of the present invention has a light specific gravity because it contains a large amount of ash and silica fume. In particular, dredging sludge and the like are required to be quickly carried out, but since the solidifying agent of the present invention has a low specific gravity, it can also help reduce the weight of the carried-out soil after admixture and reduce costs.

[Brief description of drawings]

1 is a flat plate loading test No. 2 in Test Example 2. FIG. The graph which shows the amount of subsidence of 1 and the load strength.

2 is a flat plate loading test No. 2 in Test Example 2. FIG. The graph which shows the amount of subsidence of 2 and the relationship of load intensity.

[Explanation of symbols]

 None

Claims (2)

[Claims] 1. Aluminum sulfate 5 to 30 parts by weight, calcium salt 10 to 50 parts by weight, alkali metal carbonate 0.1.
-10 parts by weight, and 10 to 30 parts by weight of the compound (A1) consisting of 10 to 20 parts by weight of silica or silica fume,
A sludge solidifying agent containing 80 to 90 parts by weight of the compound (B) consisting of 40 to 90 parts by weight of fly ash or PS ash and 10 to 60 parts by weight of cement. 2. An aluminum sulfate of 5 to 30 parts by weight, a calcium salt of 10 to 50 parts by weight, and an alkali metal carbonate of 0.1.
-10 parts by weight, 10 to 20 parts by weight of silica or silica fume, and 3 to 15 parts by weight of titanium oxide (A
2) 10 to 30 parts by weight of fly ash or PS
A sludge solidifying agent containing 80 to 90 parts by weight of the mixture (B) consisting of 40 to 90 parts by weight of ash and 10 to 60 parts by weight of cement.