JPH0214308B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to the improvement of a neutral solidifying agent whose main ingredients are blast furnace water slag and expelled gypsum, and its production method, and is used for improving soft ground, solidifying sludge, and as an admixture for cement. It is mainly used as a substitute for cement. (Conventional technology) To improve soft ground and solidify sludge, blast furnace water slag has traditionally been dried and crushed, and a small amount of hydraulic inorganic material is mixed in to activate the hydraulic properties of the blast furnace water slag. A solidification agent manufactured by the above-mentioned method is widely used, and the solidification treatment is performed by mixing a mixture of the solidification agent and cement milk into soft soil or sludge and stirring the mixture. The solidifying agent is produced by the reaction between lime glass in blast furnace water slag and hydroxide lime in mortar, etc., to produce lime silicate and lime aluminate, which are similar to the main compounds of Portland cement, and improve hydraulic properties. At the same time, it forms a dense hydrated structure and increases the solidification strength. However, the solidifying agent produced from the blast furnace water slag usually needs to be mixed with cement milk at a ratio of about 1:1, and if the mixing ratio of cement milk is reduced, a sufficient solidifying effect cannot be obtained. Therefore, in actual use, a large amount of cement is required, leading to high costs for ground improvement and sludge treatment. Furthermore, the solidifying agent requires a considerable curing period to complete solidifying, and has the disadvantage that the compressive strength of the solidified product is not sufficiently increased. For example, for 1 m ² of silty clay with a combined water ratio of 120% and a specific gravity of 1.45 g/cm ³ ,
When 120 kg of mixed milk with a 1:1 ratio of solidification agent and cement milk is mixed, the indoor axial compressive strength after 30 days is about 2 to 3 kg/cm ² (15 to 17 kg/cm ² if 300 kg is mixed) In order to increase the solidification strength, a long curing period and a large amount of solidification agent and cement milk are required. On the other hand, it has been known that blast furnace water slag undergoes a hydration reaction with gypsum in the presence of an alkaline stimulant and has the effect of solidifying soft soil and the like. That is,
The alumina component in the blast furnace water slag undergoes a hydration reaction with gypsum due to the action of alkaline reaction accelerators such as cement and slaked lime, producing so-called hardened ettringite, which solidifies soft soil and the like. However, with solidifying agents manufactured using cement or slaked lime as stimulants, even if the amount of stimulant is increased (15 to 20% by weight), the hydration reaction between alumina and gypsum is extremely slow, and solidification takes a considerable amount of time. Moreover, there are disadvantages in that the solidified product exhibits strong alkalinity and the compressive strength of the solidified product is extremely low. In addition, in order to increase the rate of hydration reaction between alumina and gypsum, a method for producing a solidifying agent is being developed that uses strong alkaline substances such as potassium hydroxide (KOH) and sodium hydroxide (NaOH) as stimulants.
However, even in this case, 15 to 20
% by weight of a strong alkaline stimulant is required (the reaction rate will be saturated even if more is added), and as a result, the alkalinity of the solidified product will be about 10 to 11 in terms of PH value, which will prevent alkaline contamination of soil and ground. In addition, in the case of processing sludge, etc., there is a risk of secondary pollution due to the disposal of solidified sludge. Furthermore, the solidifying agent manufactured by the above-mentioned method has a low compressive strength, and there is a risk of cracking due to the reaction with the alkali aggregate, making it completely impossible to use it in construction as a substitute for cement. (Problems to be Solved by the Invention) The present invention solves the above-mentioned problems with conventional solidifying agents mainly composed of blast furnace water slag, namely, the solidifying time is quite long and the compressive strength of the solidified product is relatively low. This is an attempt to solve problems such as the solidified material is strongly alkaline, causing environmental pollution, and the solidified material is strongly alkaline and has low mechanical strength, making it unsuitable for use as a cement substitute. It is an object of the present invention to provide a method for producing a solidifying agent that has a fast solidifying rate, is weakly alkaline, does not cause environmental pollution, and has sufficient mechanical strength as a solidified product, and can be used as a substitute for cement. This is the purpose. (Means for Solving the Problems) In order to solve the above-mentioned problems, the inventors of the present application have developed a method for achieving strong hydration with a smaller amount of alkaline stimulants by adding other substance components to the alkaline stimulants. To neutralize the solidified product by obtaining a reaction promoting effect and adding a substance component that exhibits a neutralizing effect as the solidification progresses;
The idea was to increase the sensitivity to irritants and promote the hydration reaction by activating the blast furnace water slag and expelled gypsum itself. In addition to conducting numerous solidification tests using the mixing ratio of these and the mixing ratio of blast furnace water slag and de-exhausted gypsum as parameters, we also conducted various tests on the activation treatment of blast furnace water slag and de-exhaust gypsum using ozone. Ta. The present invention was created based on the above idea and various tests based on the idea, and the solidifying agent according to the first invention of the present application contains 1 to 4% by weight of magnesium and 1 to 5% by weight of calcium chloride. and either or both of 1 to 5% by weight of cement and 0.1 to 0.5% by weight of calcium hydroxide, and either or both of 1.5% by weight or less of aluminum sulfate and 0.3% by weight or less of citric acid, The basic composition is 20 to 50% by weight of flue gas desulfurization gypsum and the remainder is blast furnace water slag. In addition, the second invention of the present application provides fine powder of flue gas desulfurization gypsum, which is obtained by exposing fine powder of blast furnace water slag and flue gas desulfurization stone bone in an ozone atmosphere for a certain period of time, and then treating it with 20 to 50% by weight of ozone. , 1 to 4% by weight of magnesium, 1 to 5% by weight of calcium chloride, and 1 to 5% by weight of magnesium.
% by weight of cement and 0.1 to 0.5% by weight of calcium hydroxide or both, 1.5% by weight or less of aluminum sulfate and 0.3% by weight of citric acid or both, and the balance of the above. The basic structure of the invention is to mix it with fine powder of blast furnace water slag that has been treated with ozone. (Function) In the solidifying agent according to the present invention, basically, the hydration reaction between the alumina component in the water slag and gypsum is promoted by the alkaline stimulant to produce a hardened ettringite product. It is assumed that a solidifying effect is exerted. At this time, by adding a small amount of magnesium and calcium chloride to an alkaline stimulant such as cement or calcium hydroxide, the stimulant is activated and the ability to promote the hydration reaction is greatly improved. As a result, the hardened ettringite product is rapidly produced, the solidification time is shortened, and the solidification strength of the solidified product is significantly improved. In addition, when the solidifying agent of the present invention is mixed with cement, etc., the lime-rich glass in the water slag reacts with the lime hydroxide in the cement, producing silicic acid similar to the main compound of Portland cement. Lime and aluminate lime are produced, and the resulting hydraulic action is superimposed on the solidification action. Furthermore, it is assumed that the added aluminum sulfate and citric acid exert a neutralizing effect as solidification progresses, and neutralization of the solidified product is achieved. In addition, by exposing the main components, the removed gypsum and blast furnace water slag, to an ozone atmosphere, the alumina components in the gypsum and water slag are activated.
It is assumed that, in conjunction with the action of the stimulant, the production of ettringite is further promoted and a denser hydrated structure is formed, thereby achieving a significant improvement in the mechanical strength of the solidified product. Ru. (Example) Hereinafter, the present invention will be explained in detail based on an example of the present invention. Blast furnace slag is produced by rapidly cooling molten blast furnace slag discharged from a blast furnace with fresh water or seawater, drying it, and pulverizing it (particle size: 5 to 30 μm). The pulverized blast furnace water slag is subsequently introduced into an ozone generator, where it is exposed to an ozone atmosphere for a certain period of time. The ozone exposure treatment is carried out by dropping fine slag powder along a zigzag chute from top to bottom inside the ozone generator, and the residence time of the fine powder in the ozone atmosphere is 10 minutes. ~20 seconds, the power of the ozone generator light source is 2KW x 10 units, and the processing capacity of slag fine powder is 10-15Kg/min. It is preferable to use molten blast furnace slag quenched with fresh water as the blast furnace water slag, and for exposure treatment in an ozone atmosphere, as mentioned above, the power of the ozone generator light source is 2KW.
In the case of ×10 groups, retention for about 10 to 20 seconds is sufficient, and even if the ozone treatment is further strengthened, no significant change in the increase in mechanical strength of the solidified product is observed. Table 1 shows the chemical components of the blast furnace slag used in this example.

[Table] On the other hand, flue gas desulfurization gypsum is produced by drying and finely pulverizing (particle size 5 to 20μ
m) and has the chemical components as shown in Table 2. Further, as in the case of blast furnace water slag, the removed gypsum is subjected to a bleaching treatment in an ozone atmosphere after drying and pulverization, and the ozone treatment conditions are the same as in the case of the blast furnace water slag.

[Table] Tables 3 and 4 show the mixing ratio of each component of the solidifying agent produced in this example.

【table】

[Table] Cement and calcium hydroxide constitute the main stimulants, and when cement is used alone, it is necessary to add 1 to 5 Wt%. If the cement content is less than 1 Wt%, the hydration reaction between the alumina and gypsum in the blast furnace water slag will not be promoted, and the cement
If it exceeds 5 Wt%, not only will the alkalinity of the solidified product increase, but the effect of promoting the hydration reaction will be saturated, and a mixing ratio of 1 to 3 Wt% is most suitable. The same is true when using calcium hydroxide as the main stimulant; below 0.1 Wt%, the hydration reaction is too slow, and above 0.5 Wt%, the alkalinity of the solidified product increases and the reaction rate increases. This is because the improvement is not so great in this case, and a mixing ratio of 0.1 to 0.2 Wt% is the optimum value. Although cement and calcium hydroxide are used alone in this example, it is also possible to use both together, for example, 1Wt% of cement and 0.1Wt% of calcium hydroxide. Of course. Magnesium and calcium chloride serve a supplementary function to the main stimulant, activate the main stimulant, and significantly promote the hydration reaction by acting synergistically with the main stimulant. In addition, in order to promote the hydration reaction, metallic magnesium or magnesium oxide must be added at 1 to 4 Wt% (the optimal value is 1 to 2 Wt%).
%), calcium chloride 1-5% (optimal value is 1-5%)
3 Wt%), and if either falls below its minimum value, the promoting effect decreases. In addition, the amount of magnesium and calcium chloride is 4 and 5 Wt%, respectively.
If it exceeds this, the effect of promoting the hydration reaction will be saturated. Therefore, the amounts added should be 4 and 5 Wt% or less, respectively. When aluminum sulfate is added in an amount of 1.5% by weight or more, the expansion rate of the solidified product becomes too large and cracks are likely to occur in the solidified product. As a result, the amount added should be less than 1.5% by weight, and 0.8
A range of ~1.2% by weight is most desirable. When citric acid is added in an amount of 0.3% by weight or more,
The solidifying time of the solidifying agent is significantly delayed, causing various problems in practical use. Therefore, when using a solidifying agent at high temperatures, it is desirable to add it in an amount of 0.3% by weight or less. Depleted gypsum and blast furnace water slag (or blast furnace water slag treated with ozone) are the basic components of the solidifying agent, and the ratio of the two (blast furnace water slag/depleted gypsum) is approximately 1 to 4. The position is appropriate, preferably
A value of 1.2 to 2.0 is optimal. Insufficient amount of plaster
Even if it is less than 20Wt% or the amount of gypsum is 50Wt%
Conversely, even if the blast furnace water slag becomes insufficient, the solidifying performance and solidifying strength of the solidifying agent will decrease. Therefore,
In this embodiment, the amount of removed gypsum is 20 to 50 Wt%, and the remainder after removing the stimulant and activator is blast furnace water slag. Although the ratio of the amount of blast furnace water slag to the amount of gypsum includes a value considerably larger than the theoretical value, the reactivity of the alumina component in the blast furnace water slag to removed gypsum (dihydrate gypsum) is due to the reactivity of gypsum. Because it is related to solubility, etc., it has been confirmed that extremely good solidification properties can be obtained even if the amount of gypsum is considerably less than the theoretical value. Figure 1A shows the solidification test results of the solidifying agent according to the first invention of the present application listed in Table 3 above, when the mixing ratio of the solidifying agent and water (solidifying agent/water) was 1.7. is the value of In the case of this solidifying agent, the compressive strength was 150 Kg/cm ² after 7 days and 270 Kg/cm ² after 14 days, 28
The solidification rate and solidification strength are approximately 390Kg/cm ² per day, which is approximately close to that of Portland cement (compressive strength after 7 days of approximately 190Kg/cm ² when the cement/water mixing ratio is 1.7). In addition, the alkalinity of the solidified product by the solidification agent is PH7.7 to 7.8, which is slightly alkaline and close to neutral, and has a higher alkalinity than the conventional cement-based hardening agent whose main ingredient is blast furnace water slag. becomes significantly lower. Furthermore, using the solidifying agent according to the present invention, the water content ratio is 120.
%, when 1 m ² of silty clay with a specific gravity of 1.45 Kg/cm ² is mixed with 120 kg of molten milk of the solidifying agent, the indoor-axial compressive strength after 30 days during natural solidification at atmospheric temperature (average 18°C) becomes 4~5Kg/ ^cm2 ,
Compared to the conventional cement-based solidifying agent based on blast furnace water slag, the compressive strength of the solidified product is improved by 20 to 30%, and the solidifying time is also significantly shortened. Table 5 below shows data when the solidifying agent according to the first invention of the present application was used at a landslide site (Constructed by Nippon Koei Co., Ltd., Uchiyama landslide site, January 30, 1985) ).

【table】

Claims (1)

[Scope of Claims] 1 1 to 4% by weight of magnesium, 1 to 5% by weight of calcium chloride, 1 to 5% by weight of cement, and either or both of 0.1 to 0.5% by weight of calcium hydroxide. , 1.5% by weight or less of aluminum sulfate and 0.3% by weight or less of citric acid, or both, 20 to 50% by weight of flue gas desulfurization gypsum, and the balance consisting of blast furnace water slag. 2. The fine powder of blast furnace water slag and the fine powder of flue gas desulfurization gypsum are exposed in an ozone atmosphere for a certain period of time, and then
20-50% by weight of fine powder of ozonated flue gas desulfurization gypsum, 1-4% by weight of magnesium, and 1-4% by weight of magnesium.
5% by weight of calcium chloride, 1 to 5% by weight of cement and/or 0.1 to 0.5% of calcium hydroxide, 1.5% by weight or less of aluminum sulfate, and 0.3% by weight or less of citric acid. A method for producing a neutral solidifying agent, which comprises mixing one or both of the above and the remaining part with a fine powder of the blast furnace slag subjected to the ozone treatment.