JPS625198B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for solidifying muddy, sludge-like or powdery waste or soft ground. In recent years, the amount of industrial waste and the sludge caused by it has been increasing, and these often contain harmful substances that harm the health of humans and animals and the growth of plants, and their treatment is extremely important. It has become a serious problem. In addition, improvement of soft ground is desired in order to make effective use of it. Cement solidification treatment has been known as one of these countermeasures. However, these waste materials generally contain substances that interfere with the solidification of cement. Therefore, unless a particularly large amount of cement is used, it is difficult to achieve the target strength by simply using cement. However, using a large amount of cement increases the amount of work and is uneconomical, so as a means to put cement solidification into practical use, a method of adding inorganic chemicals containing sulfate radicals in addition to cement (patent No.
730891, JP-A-50-57070), Method of adding chlorides of alkali metals and alkaline earth metals (JP-A-51
-28344) or a method of adding an alkali metal carbonate (Japanese Patent Application Laid-Open No. 51-95426) has been proposed. However, methods using these solidifying agents require mixing for a long time until they are sufficiently uniform in order to be effective, which requires more expensive dispersants and powerful mixing equipment. It was not always advantageous from an economic and work standpoint. As a result of various studies in order to develop a solidifying agent that overcomes these conventional drawbacks, the present inventors have found that a hydraulic cement composition and an acidic alkali metal composition can be used for muddy, sludge-like or powdery waste or soft ground. It has been found that the addition of carbonate and/or sesquicarbonate provides good workability, excellent effects, and is economical, and has already been proposed in Japanese Patent Application No. 52-129231. However, the solidifying agent consisting of a hydraulic cement composition and an acidic carbonate or/and a sesquicarbonate of an alkali metal emphasizes short-term strength rather than long-term strength as a strength promoting effect. Of course, it is important to promote short-term strength, but in cases where the nature of civil engineering work is strong, long-term strength is more required because the foundation ground is often used for semi-permanent structures. For this reason, the present inventors have conducted repeated research on solidifying agents that ensure good workability and satisfy not only short-term strength but also long-term strength. The inventors have discovered that the objective can be achieved by adding an alkali metal sulfate to a system consisting of a sesquicarbonate and a sesquicarbonate, and have proposed the present invention. In the present invention, short-term strength refers to strength developed within 7 days, and long-term strength refers to strength developed within 20 days or more. The present invention provides a method for applying (A) a hydraulic cement composition to muddy, sludge-like or powdery waste or soft ground.
100 parts by weight, (B) 5 to 25 parts by weight of an acidic carbonate or/and sesquicarbonate of an alkali metal, and (C) 5 to 25 parts by weight of an alkali metal or alkaline earth metal sulfate.
25 parts by weight, the weight ratio of (B) acidic carbonate or/and sesquicarbonate of alkali metal and (C) sulfate of alkali metal or alkaline earth metal is 80/20.
This is a method for solidifying waste or soft ground, which is characterized in that it is added at a ratio of ~20/80. The objects to be treated in the present invention include sludge, waste mud from muddy water works in urban civil engineering works, red mud generated from aluminum smelting, crushed stone mud, and other mud; sludge, such as water supply and sewage sludge, and industrial wastewater treatment sludge; municipal garbage; Industrial waste such as incineration ash from incineration of water treatment sludge, powdered dust collected by electrostatic precipitators, etc., or soft soil such as loam soil, masa soil, peat layer, whitebait or sludge. It is the ground. The hydraulic cement composition that is the first component of the solidifying agent used in the present invention is ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement, moderate-heat Portland cement, blast furnace cement, fly-ash cement, silica cement, and ultra-rapid-hardening Portland cement. A hydraulic cement composition made by mixing one or more selected from cement and alumina cement, and further adding and mixing one or more of slag, lime, gypsum, fly ash, white clay, etc. as appropriate. It can also be used successfully.
When adding slag, lime, gypsum, fly ash, white clay, etc., the amount should be determined based on the properties of the object to be solidified and the amount of acidic carbonates of alkali metals used in the present invention. However, it is generally preferred that the content is 5% by weight or more and 50% by weight or less based on the base hydraulic cement composition. Further, the acidic carbonate of the alkali metal which is the second component of the solidifying agent used in the present invention is not particularly limited, but acidic sodium carbonate and acidic potassium carbonate are particularly effective, and others such as lithium salt, rubidium salt, cesium salt, etc. , or a mixture thereof can be effectively used. Furthermore, as the alkali metal sesquicarbonate, industrially produced sesquicarbonate or naturally occurring sesquicarbonate can be effectively used. In the present invention, in addition to the hydraulic cement composition - a system consisting of acidic carbonates and/or sesquicarbonates of alkali metals, at least one alkali metal sulfate such as sodium sulfate or potassium sulfate is added as a third component. Its feature is that it can be used. As the third component, it is more effective to use an alkali metal sulfate than an alkaline earth metal sulfate. Figure 1 shows the amount of the second component (anhydrous acidic sodium carbonate) and the third component (anhydrous sodium sulfate), each alone, and a mixture of both added to the hydraulic cement composition of the first component. Fig. 2 shows the influence on the short-term (7 days old) unconfined compressive strength, and Fig. 2 shows the influence on the long-term (28 days old) uniaxial compressive strength. As can be seen from FIGS. 1 and 2, when the strength promoting effect is compared between the addition of the second component and the third component alone, the effect of adding the second component alone is higher regardless of long-term or short-term use. However, when the third component is used in combination, the increase is higher than when the second component is added alone, and the ratio is larger in the long term. This shows that a synergistic effect is exerted by the addition of the third component in the long term. Although the reason for the synergistic effect caused by the addition of the third component is not clear, the addition of the third component further promotes the production of ettringite from sulfate and carbonate groups, and also improves the flow of acidic carbonates of alkali metals. This is thought to be due to the solidification effect making a large contribution and mixing with the waste to be solidified sufficiently homogeneous. In the present invention, the preferable range of the proportion of the second and third components used as solidification aids varies depending on the type and properties of the waste to be solidified, the desired degree of solidification, etc. In the present invention, the first
It is essential to use 5 to 25 parts by weight of the second component, the acidic carbonate and/or sesquicarbonate of the alkali metal, per 100 parts by weight of the component hydraulic cement composition. Furthermore, it is essential that the third component, an alkali metal sulfate, be used in an amount of 5 to 25 parts by weight per 100 parts by weight of the hydraulic cement composition. If the upper limits of both the second and third components exceed the above-mentioned upper limit, especially 50 parts by weight, not only will the cost be high, but the long-term strength after solidification will not be sufficiently increased. In addition, the second component and the third component
The mixing ratio of the components is 80:20 to 20:80 by weight in order to take advantage of the fluidity improving effect of the second component.
More preferably, the ratio is selected within the range of 60:40 to 40:60. Furthermore, the addition ratio of the solidifying agent consisting of the first to third components to be added to the waste etc. to be solidified cannot be determined unconditionally, but in general, it is 1 to 50 parts by weight,
More preferably, it is added in an amount of 5 to 30 parts by weight. In the present invention, the method of adding and mixing the solidifying agent is not limited at all, and there is a method of mixing the first to third components in advance and adding and mixing this to waste etc., and a method of adding and mixing the first to third components separately. Other methods include adding and mixing them to waste materials, etc., either simultaneously or sequentially. The solidifying agent comprising the first to third components of the present invention has a large effect of promoting strength, especially medium- and long-term strength, and has appropriate fluidity, so it has the effect of improving workability. . The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. Example 1 100 parts by weight of ordinary Portland cement was mixed with 100 parts by weight of sludge deposited in Tokuyama Bay with a moisture content of 250% (silty clay, containing 5% humins, flow value 130 mm) as shown in Table 1. Add and mix 2 parts by weight of anhydrous acidic sodium carbonate and anhydrous sodium sulfate as solidification aids in different ratios, and
Pour into a cylindrical formwork of 50mm and height 100mm, and
The solidified material was cured and fixed in a humid atmosphere at 20° C. and 90% humidity, and the uniaxial compressive strength of this solidified material was measured on 1st, 7th, and 28th days. The results are shown in Table 1.

[Table] Example 2 The sludge deposited in Osaka Bay with a moisture content of 280% (silty clay, containing 5% humins, flow value 150mm) was added to 100 parts by weight of wet standard and 6 parts by weight of ordinary Portland cement. A solidified product was prepared in the same manner as in Example 1 by mixing the additives in varying amounts, and the unconfined compressive strength was measured at 7 days and 28 days. Cases in which anhydrous acidic sodium carbonate and anhydrous sodium sulfate (mixing ratio 60:40), anhydrous acidic sodium carbonate alone, and anhydrous sodium sulfate alone are used as solidification aids are sequentially shown as codes 1, 2, and 3, respectively. Figure 1 shows the 1-day compressive strength, and Figure 2 shows the 28-day compressive strength. However, Figures 1 and 2
In the figure, the horizontal axis is ordinary Portland cement.
Parts by weight of solidification aid are shown based on 100 parts by weight. Example 3 Using the same sludge as used in Example 2, 10 parts by weight of wet basis, 10 parts by weight of ordinary Portland cement and anhydrous acidic sodium carbonate-anhydrous sodium sulfate mixture (mixing ratio:
60:40) were added and mixed to prepare a solidified body in the same manner as in Example 1, and the uniaxial compressive strength was measured. The same procedure was also carried out for a mixture of anhydrous acidic potassium carbonate and potassium sulfate (mixing ratio 60:40). Furthermore,
Anhydrous acidic sodium carbonate, anhydrous sodium sulfate,
The same procedure was carried out for a mixture of two parts of each of anhydrous acidic potassium carbonate and potassium sulfate. Table 2 shows the 7-day aged uniaxial compressive strength and the 28-day aged uniaxial compressive strength.

[Table] Example 4 Using the same sludge as used in Example 2, 10 parts by weight of ordinary Portland cement and 2 parts of a mixture of sodium sesquicarbonate and anhydrous sodium sulfate (mixing ratio 60:40) per 100 parts by weight on a wet basis. were added and mixed to create a solidified body in the same manner as in Example 1,
Uniaxial compressive strength was measured. The same procedure was also carried out for a mixture of two parts of sodium sesquicarbonate alone. The results of unconfined compressive strength measurements on the 7th and 28th days are shown in Table 3.

【table】 [Brief explanation of the drawing]

Figure 1 is a diagram showing the uniaxial compressive strength at 7-day age when anhydrous acidic sodium carbonate, anhydrous sodium sulfate, and a mixture of the two are added to hydraulic cement in varying amounts. Figure 2 also shows the uniaxial compressive strength at 28 days old.

Claims (1)

[Claims] 1. Adding (A) 100 parts by weight of a hydraulic cement composition, (B) 5 to 25 parts by weight of an acidic carbonate or/and sesquicarbonate of an alkali metal to muddy, sludge-like or powdery waste or soft ground. Addition of (C) 5 to 25 parts by weight of alkali metal sulfate to (B) acidic carbonate or/and sesquicarbonate of alkali metal and (C) alkali metal sulfate in a weight ratio of 80/20 to 20/ 80. A method for solidifying waste or soft ground, which is characterized by adding it to a concentration of 80%.