JPS621671B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to muddy water used in muddy water construction methods such as underground wall construction method and muddy water shield construction method. Bentonite mud, which is mainly composed of bentonite, has been known as mud water used in underground wall construction methods and the like. This bentonite mud water is made by dispersing 6 to 8% bentonite (weight ratio, the same applies hereinafter) in tap water, and has excellent wall-building properties.
We have many achievements. However, this bentonite muddy water has ion exchange ability or base substitution ability, which is one of the characteristics of bentonite.
It has the disadvantage that it deteriorates due to the influence of various ions (especially ions from metal salts, etc.) leached from soil, groundwater, seawater, cement, etc. In particular, the contamination of seawater and cement significantly reduces the stability of bentonite mud. For this reason, as a measure to prevent stability deterioration due to contamination with seawater or cement, thickeners such as carboxymethyl cellulose (CMC) and dispersants such as lignin sulfonic acid compounds and polyphosphates are added at approximately 0.05 to 0.3% each. Sometimes. Thickeners have the effect of maintaining the viscosity of muddy water and reducing the amount of water dewatered, while dispersants prevent deterioration due to salt contamination, settle mixed soil, and reduce the specific gravity of muddy water.
It has the effect of preventing an increase in viscosity. However, the effects of these thickeners and dispersants are not sufficient, with salt water (NaCl) at 0.5-0.7% and cement components at 0.5-0.
If it is mixed in at a concentration of 1% or more, it becomes unusable. However, at construction sites, seawater often mixes in at 1% or more, and when concrete is poured, up to 5 to 7% of cement components may mix in. Adding the above-mentioned thickeners and dispersants is not effective as a countermeasure against deterioration. It was insufficient. For this reason, polymer slurry based on CMC, which does not deteriorate even when mixed with seawater or cement components, is being used. However, this polymer muddy water has the disadvantage that the CMC rots and deteriorates during the summer and loses its function. In addition, when applying the rotary excavation method using an excavation pit to the excavation method,
CMC is separated together with mixed soil and CMC
must be constantly replenished, making it uneconomical in terms of cost.Therefore, polymer slurry is also by no means satisfactory as slurry for muddy construction methods. Furthermore, bentonite mud must be manufactured using high-quality clean water that does not contain Cl ions or Ca ions, but it is becoming increasingly impossible to obtain such high-quality clean water at construction sites. . This invention was made in view of the above circumstances, and is stable, does not gel even when seawater components or cement components are mixed in at high concentrations, and is stable.
The purpose of the present invention is to provide muddy water for muddy construction methods that can sufficiently maintain its functions and can be produced using low-quality water such as river water, groundwater, well water, etc., without requiring high-quality clean water. The muddy water of the present invention has at least bentonite, a water-soluble vinyl acetate polymer, and a polyacrylate, and the content of the water-soluble vinyl acetate polymer is 0.05 to 5% by weight, and the polyacrylic acid The complexing power of the salt for Ca ions is 300 mg/g or more, and the blending amount of the polyacrylate is 0.1 to
The content is 3% by weight. The bentonite used in this invention is
Examples include particles having a particle size of about 200 to 350 mesh, which have been conventionally used for bentonite mud, but are not particularly limited. The amount of bentonite to be mixed is 1 to 18% by weight of the muddy water, and usually preferably about 4 to 8%. In addition, polyacrylates that have complexing power for Ca ions include sodium salts, potassium salts, ammonium salts of polyacrylic acid, and amine salts such as monoethanolamine, diethanolamine, triethanolamine, pyridine, piperidine, and mopholine. 300 mg/g or more is used. Here, the complexing power for Ca ions was determined by titration of an aqueous calcium acetate solution. Polyacrylates with complexing power have the effect of preventing gelation due to the mixing of seawater components and cement components into muddy water and maintaining stability. It also has the effect of strengthening the thickening effect of the water-soluble vinyl acetate polymer described below. The blending amount of this polyacrylate is 0.1 to 3 in weight ratio to muddy water.
%, preferably 0.2-0.6%. If it is less than 0.1%, the above-mentioned stabilizing effect cannot be obtained sufficiently, and if it exceeds 3%, the viscosity of the mud becomes too high, making kneading impossible and exhibiting agglomeration, which is disadvantageous. The water-soluble vinyl acetate polymer is, for example, a water-soluble polymer obtained by polymerization or copolymerization reaction, saponification, etc. using vinyl acetate as a main component. This water-soluble vinyl acetate polymer is added as a thickener and is resistant to bacteria, so even if it is used under relatively high water temperatures such as in the summer, it will not rot or deteriorate due to bacteria. There is no. The blending amount of this water-soluble vinyl acetate polymer is 0.05 to 5% by weight based on the muddy water. Furthermore, the water used for the muddy water of the present invention is not limited to high-quality water such as tap water, but also low-quality water that is easy to procure at low cost, such as groundwater, river water, and industrial water that contain various ions. be able to. This is because various ions contained in water are complexed by using the polyacrylate having the ability to complex Ca ions, and their reaction with bentonite is inhibited. The muddy water of this invention fully exhibits its functions with bentonite, the above-mentioned polyacrylate and water-soluble vinyl acetate polymer, but if necessary, a thickening agent such as known CMC or a humate salt may be added. , a ligurin sulfonic acid compound, a hexametaphosphate, a tripolyphosphate, and the like may be added. The amount of the thickener added is 0.05 to 0.3 wt% with respect to the muddy water, and the amount of the dispersant added is also 0.05 to 0.3 wt%. Furthermore, when using under conditions where the water temperature is 20°C or higher, the addition of CMC should be avoided. Next, a more specific explanation will be given by showing an experimental example. [Experiment example] Eleven muddy water samples No. 1 to No. 11 were prepared using two types of bentonite with different swelling properties, a dispersant, and a thickener under the formulation conditions shown in Table 1. The properties and salt tolerance were measured. As a dispersant,
Among the polyacrylates according to the present invention, sodium polyacrylate and sodium hexametaphosphate, lignin sulfonate, and sodium humate were used as comparative examples. As the thickener, water-soluble vinyl acetate polymer according to the present invention and comparative example
CMC was used. All mixed water used was tap water. For adjustment, mix with a mixer for 5 minutes, then stir with a propeller type stirrer for 15 to 30 minutes.
I left it for another day and tried it again. No. 1 to 11 shown in the table
To each sample, cement or sodium chloride was added as a salt to a predetermined concentration shown in the table, and the properties of the sample were measured. Measurement is 20±
The experiment was carried out at a temperature of 0.5°C. Note that the symbols in the evaluation column in the table represent the following evaluations. ◎: Good ○: Usable ×: Unusable

[Table] Note 1 Tap water was used as the mixed water, and the amount added represents the weight percentage based on 1 part of water. 2 A and B each represent two types of bentonite with different swelling properties. 3 PANa is sodium polyacrylate,
HPNa is sodium hexametaphosphate, LSS
represents lignin sulfonate, and FNa represents sodium humate. 4 PVA represents a water-soluble vinyl acetate polymer. 5 FV represents the flow time of 500 ml (unit: seconds) by Funnel viscometer. 6C represents cement. 7 A supernatant was produced. 8 It turned into a gel. Nos. 1 and 4 in Table 1 above are properties of bentonite alone. In this case, it can be seen that the mixture of 1% cement causes complete deterioration. Although not shown in the table, other tests have shown that muddy water made only of bentonite deteriorates when 0.1% cement is mixed in.
It has been confirmed that mixing with 0.5% NaCl causes deterioration. Nos. 7 and 8 show the properties of muddy water containing bentonite and water-soluble vinyl acetate polymer PVA as a thickener. In these cases, although the bentonite concentration was lower than in Nos. 1 and 4, the viscosity (FV) was higher, confirming the effectiveness of PVA as a thickener. However, when cement and NaCl are mixed in, deterioration cannot be prevented and the stability of the muddy water is found to be insufficient. Nos. 2 and 5 show the properties of muddy water containing bentonite and sodium polyacrylate as a dispersant. The change in viscosity (FV) compared to No. 1 and 4 is as follows:
Although it is rarely seen, it is stable against cement contamination, confirming the effectiveness of sodium polyacrylate as a salt-resistant agent. Note that in order to adjust the viscosity of muddy water, it is necessary to separately add a thickener. Nos. 3 to 3-5 and Nos. 6 to 6-5 show the properties of muddy water according to the present invention. Performance differs slightly depending on the type of bentonite (in this case, A and B have different swelling properties), but bentonite A can be used with up to 5% cement and 1% NaCl, while bentonite B can be used with 2% cement and 1% NaCl. %
It can be seen that it can be used even if it is mixed with. Nos. 9 to 11 show the properties of muddy water mixed with conventionally used CMC. It can be seen that these conventional muddy waters degrade and become unusable when just 1% cement or 1% NaCl is mixed in. These conventional Nos. 9 to 11 and Nos. 3 to 1 according to the present invention
Comparing No. 3-5 and No. 6 to 6-5, CMC
The mud of the present invention, which contains PVA and PANa without using CMC, not only has excellent resistance to rot and deterioration, but also has cement resistance and salt resistance comparable to conventional mud that contains CMC. It was found to have excellent stability. Also, No. 1, 2, 3, 7 or No. 4 in Table 1,
Comparing the FV of 5, 6, and 8 after leaving them for a day and night,
It can be confirmed that when a combination of PVA and PANa is added to bentonite mud, the thickening effect of PVA is significantly enhanced. As is clear from the results in Table 1, the muddy water of the present invention is a stable muddy water that does not deteriorate even if cement or salts such as NaCl are mixed in. In this way, being able to impart salt resistance has a great practical effect.
In other words, in actual construction, it is impossible to avoid contact between muddy water and concrete during concrete pouring, and in the conventional muddying process, muddy water within 10 meters of the concrete pouring surface was disposed of. Since the muddy water of the invention has excellent cement resistance, there is very little deterioration due to cement and there is no need to dispose of it, and the muddy water that was conventionally discarded can be recovered and used. In addition, the above-mentioned salt tolerance is exhibited even when the production water used for muddy water preparation contains some salts, which causes low-quality water (groundwater, river water, drilling mud separation water, etc.)
It is also possible to make muddy water using it. As explained above, the muddy water for the muddy construction method of the present invention contains at least bentonite, a polyacrylate, and a water-soluble vinyl acetate polymer. Due to the water-soluble vinyl acetate polymer, which has high salt resistance and is resistant to bacterial decomposition, it can be used in relatively high-temperature environments. Therefore, muddy water that was conventionally discarded during concrete placement can be effectively reused, disposal costs are reduced, and processing equipment can be downsized. In addition, since it has salt resistance, it is possible to use low-cost and easily procured underground water, river water, separated drilling mud water, etc. as production water.
Furthermore, it can be installed in areas with high salt content, such as coastal landfills, without any problems. Furthermore, unlike polymer slurry made mainly of CMC, it does not rot due to bacteria, etc., so it maintains a specified viscosity even under conditions of high water temperature, such as in the summer, and can be successfully applied. In addition, it is possible to create concentrated mud water and dilute it using separated drilling mud water generated on-site, which allows for effective use of separated water and the use of high-quality water such as expensive tap water. You can save money. Furthermore, since gelation of muddy water does not occur, deterioration in the quality of poured concrete due to gelation of muddy water is prevented. Moreover, since the muddy water of the present invention uses a combination of a water-soluble vinyl acetate polymer and a polyacrylate, the thickening effect of the water-soluble vinyl acetate polymer is highly exhibited. Therefore, in the muddy water of the present invention, the amount of expensive water-soluble vinyl acetate polymer used can be reduced, and the cost of the muddy water can be reduced, which is extremely effective in practical terms.

Claims (1)

[Claims] 1. Consists of at least bentonite, a water-soluble vinyl acetate polymer, and a polyacrylate, and the blending amount of the water-soluble vinyl acetate polymer is 0.05.
~5% by weight, for use in muddy water construction methods, characterized in that the polyacrylate has a complexing power for Ca ions of 300 mg/g or more, and the amount of the polyacrylate is 0.1 to 3% by weight. muddy water.