JP2009263583A - Soil modifying composition and soil modifying method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil modifying composition consisting of one component for allowing efficient soil modifying facilities/work, giving a homogeneously mixed component to prevent deterioration in functions of respective materials due to mixing, and keeping stable quality through transportation and after storage. <P>SOLUTION: The soil modifying composition is composed of one component material consisting of (A) 100 pts.mass of burnt gypsum with a mean particle size of 10-100 μm and (B) 0.1-5 pts.mass of a polymer coagulant of fine particles with a mean particle size of 30-180 μm, and the constituents (A) and (B) are added and mixed so that a ratio of the mean particle size of the constituent (B) to that of the constituent (A) ranges from 0.5 to 5. The soil modifying method using the soil modifying composition is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a soil modification composition and a soil modification method using the same.

  Cement-based solidification materials are mainly used for soil improvement such as construction surplus soil and dredged sludge, but there is a risk of secondary contamination due to high alkali. For this reason, from the consideration of the environment, neutral soil reforming that does not hinder the generation of plants is desired, and the use of gypsum-based soil modifying materials is expected as one means.

  However, in actual soil improvement work, especially when the moisture content of the target soil is high, such as construction sludge and dredged sludge, using only calcined gypsum for reforming increases the amount of addition and makes it economical. There was a problem that it was not right. In order to cope with this problem, it has been proposed to use calcined gypsum and a polymer flocculant such as poly (meth) acrylic acid in combination (for example, see Patent Document 1). In this case, a general method is a two-stage treatment in which the polymer flocculant is first mixed with the target soil to aggregate the soil particles, and then the moisture content is reduced by coating with calcined gypsum.

JP-A-10-279940

  However, in the method of treating in two steps, it is necessary to install two systems of addition equipment for calcined gypsum and for the polymer flocculant, and there is a problem that the soil modification work becomes complicated. For soil improvement such as construction residue and dredged sludge, where economic treatment is the top priority, these are extremely serious problems. To deal with this problem, it is conceivable that two types of materials for calcined gypsum and a polymer flocculant are integrated (premixed), but in this case, there are the following problems. In other words, it is difficult to uniformly mix calcined gypsum and polymer flocculant, and even if they are combined into one material, the material will be separated during transportation and pumping, resulting in unstable quality. There was also a problem. In addition, since the polymer flocculant itself is easily affected by moisture, there is a problem that it is difficult to maintain a stable quality when it is made into one material. Furthermore, the conventional soil modification compositions have a substantially constant soil solidification time, making it difficult to adjust the working time, and there is room for improvement in this respect as well.

  Therefore, the object of the present invention is to enable soil reforming equipment and work to be efficiently performed by integrating the composition for soil reforming into one material, and the components are uniformly mixed and mixed. An object of the present invention is to provide a soil modifying composition that does not deteriorate the function of each material and that maintains stable quality even after transportation and storage. Another object of the present invention is to provide an economical soil reforming method with good work efficiency by using the above-described excellent soil reforming composition. Furthermore, the objective of this invention is providing the more economical soil reforming method excellent in work efficiency and processing efficiency which can adjust the solidification time of soil suitably.

  The above object is achieved by the present invention described below. That is, according to the present invention, (A) 100 parts by mass of calcined gypsum having an average particle diameter of 10 to 100 μm, and (B) 0.1 to 5 parts by mass of fine polymer flocculant having an average particle diameter of 30 to 180 μm. It is contained in a range, and it is made into one material with a material that is added and mixed so that the ratio of the average particle size of (B) / (A) average particle size is in the range of 0.5-5. A soil modification composition, and a soil modification method using the soil modification composition.

  As a preferred form of the present invention, (C) a setting time adjusting agent is added and mixed in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of (A) calcined gypsum, A composition for soil improvement in which the setting time is adjusted can be mentioned.

  More specifically, the (C) setting time adjusting agent is at least one component selected from metal salts, carboxylic acids and carboxylates, and (C) at least one setting time adjusting agent. One component is a metal salt selected from potassium sulfate, aluminum sulfate and magnesium oxide. (C) At least one component of a setting time regulator is citric acid, sodium gluconate, L- Examples thereof include a soil modifying composition which is a carboxylic acid selected from tartaric acid or a carboxylate thereof.

  According to the present invention, when the composition for soil improvement is made into one material, the components are uniformly mixed, there is no deterioration in the function of each material due to the mixing, and stable quality even after transportation and storage. A retained soil modification composition is provided. In addition, according to the present invention, by using the above-described excellent soil reforming composition, an efficient and economical soil reforming method capable of efficiently performing soil reforming equipment and work is provided. Is possible. According to the preferable form of this invention, the composition for soil improvement which can adjust a working time easily, is easy to use, and can perform a more efficient process is provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. In order to solve the above-described problems of the prior art, the present inventors have heretofore been unable to obtain a uniform product or to stabilize the quality when the calcined gypsum and the polymer flocculant are combined. A detailed study was conducted. As a result, the polymer flocculants conventionally used for soil modification are rough and coarse in particle size (200-700 μm), which makes it difficult to uniformly mix with calcined gypsum. Even if it is used as a soil modification composition, if it is subjected to vibrations during transportation, the coarse particles (polymer flocculant) segregate and the materials are separated during transportation and pumping, resulting in unstable quality. It turns out that there is a problem of becoming. Further, as described above, the polymer flocculant itself is easily affected by moisture, and this has also been found to be a major cause of difficulty in maintaining stable quality.

  As a result of further detailed examination based on the above-described findings, the inventors of the present invention have a specific particle size of calcined gypsum and a polymer flocculant and a specific blend, thereby improving soil. The present invention has been found out that the composition can be made into one material in a uniform state without problems such as segregation. In particular, it has been found that by setting the particle size of a polymer flocculant, which has been coarse and rough in the past, to a specific particle size range, calcined gypsum and the polymer flocculant can be made uniform. It was.

  Since the two types of materials, calcined gypsum and polymer flocculant, are unified into a uniform state, the soil modifying composition of the present invention requires two conventional steps. The soil modification work that has been performed can be omitted in one step, and work efficiency can be significantly improved.

  Moreover, the composition for soil improvement of the present invention is in a state in which fine polymer flocculant is uniformly mixed in calcined gypsum having moisture absorption performance. According to the study by the present inventors, since it is in the above-described state, the two types of materials, calcined gypsum and polymer flocculant, do not interfere with each other's function, but rather change due to moisture absorption. Since the quality of the polymer flocculant which is easy to do is stabilized, it is considered that the quality of the composition for soil modification of the present invention is maintained stably as a result. As a result of further investigation, by adding a setting time adjusting agent to the soil reforming composition of the present invention that has been integrated into one material as described above, the solidification time of the improved soil, which has been almost constant until now, is appropriately set. It has been found that it is possible to adjust.

Hereinafter, each material which comprises the composition for soil improvement of this invention is demonstrated.
(Calcined gypsum)
The calcined gypsum constituting the composition for soil modification of the present invention is an important component that imparts solidification performance to the composition for soil modification. Examples of calcined gypsum include β-type hemihydrate gypsum, α-type hemihydrate gypsum, type III anhydrous gypsum, or a mixture thereof. The raw gypsum may be any of natural products, by-product gypsum, or waste gypsum, but it is more preferable to use waste gypsum in consideration of economy. The particle size of the calcined gypsum constituting the composition for soil modification of the present invention varies somewhat depending on the raw material gypsum used and the degree of pulverization, but the average particle size is 10 to 100 μm, more preferably 20 to 80 μm, still more preferably, A thing about 30-60 micrometers is used. In addition, since the workability in manufacturing and use is particularly bad when the average particle size is less than 10 μm, the large average particle size exceeding 100 μm is limited to special applications. It is rarely used because it is not targeted.

(Polymer flocculant)
The polymer flocculant constituting the soil modification composition of the present invention is a component that lowers the moisture content of the soil by absorbing the moisture of the soil, such as construction residual soil, construction sludge and dredged sludge to be treated. As the polymer flocculant to be blended in the soil modifying composition of the present invention, the particle size is made finer than that of conventional products, and the average particle size is 30 to 180 μm, more preferably 50 to 150 μm, still more preferably, A thing of about 70-120 micrometers is used. Those having an average particle size of less than 30 μm are still difficult to obtain, and those having an average particle size of more than 180 μm are not suitable for one material. Furthermore, according to the study by the present inventors, it was found that the particle size of the polymer flocculant is preferably equal to or slightly larger than the particle size of calcined gypsum. More specifically, the average particle size of the polymer flocculant / average particle size of calcined gypsum = 0.5 to 5.0, more preferably 0.8 to 3.0, and most preferably 1.0 to 2. It is preferably about 0.

  Any polymer flocculant conventionally used as a soil conditioner can be used. Specifically, any of anionic, nonionic, and cationic polymer flocculants can be used, and among them, anionic or nonionic polymer flocculants are preferably used. In particular, any of those used for coagulation and precipitation of industrial wastewater can be used. More specifically, those made of polyacrylamide or acrylamide / sodium acrylate copolymer are preferred. As described above, the feature of the present invention is that these polymer flocculants are mixed with calcined gypsum in the form of fine particles having an average particle diameter of 30 to 180 μm.

  The composition for soil modification of the present invention is 0.1 to 5 parts by mass, more preferably 1 to 3 parts by mass of the fine particle polymer flocculant described above with respect to 100 parts by mass of the above-mentioned calcined gypsum. A material obtained by adding and mixing in a range is made into one material. In addition, a mixture of less than 0.1 parts by mass of a fine polymer flocculant with 100 parts by mass of calcined gypsum is not sufficient in the aggregation effect of the polymer flocculant, while a mixture of more than 5 parts by mass. Is not economical due to high material costs.

(Setting time adjusting agent)
Furthermore, an appropriate amount of a setting time adjusting agent can be added to the soil modifying composition of the present invention. By comprising in this way, it becomes possible to adjust suitably the solidification time of the improved soil which was almost constant until now. By comprising in this way, the composition for soil improvement variously designed so that solidification time may differ is obtained. Therefore, if the composition for soil modification having the above-described configuration is used, the solidification time of the target soil can be promoted as compared with the conventional one, and conversely, it can be delayed. This is because the composition for soil modification of the present invention having a solidification time according to the work process can be selected, so that the work process is determined in comparison with the conventional work process determined by the solidification time of the composition for soil modification. It is very useful in terms of efficiency.

  Examples of the setting time adjusting agent that can be used in the present invention include at least one component selected from metal salts, carboxylic acids, and carboxylates. Examples of the metal salt include potassium sulfate, aluminum sulfate, and magnesium oxide. Examples of the carboxylic acid and the carboxylate include a carboxylic acid selected from citric acid, sodium gluconate, and L-tartaric acid, or a carboxylate thereof. As these addition amounts, the setting time adjusting agent may be added and mixed in the range of 0.01 to 20 parts by mass, more preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of calcined gypsum. Moreover, what is necessary is just to add with solid and the particle size should just be the same grade as a polymer flocculent.

  The composition for soil improvement of the present invention is formed by uniformly mixing the above-described components into one material, and examples of the method for forming the material include the following methods. First, the raw gypsum is fired, pulverized to a predetermined particle size, and then stored in a calcined gypsum storage tank. Further, the polymer flocculant and the setting time adjusting agent are each stored in an auto feeder. The three kinds of materials prepared as described above are put into a paddle mixer by a predetermined amount. For example, a batch of about 1.2 t in a paddle mixer is mixed for 5 minutes to form a single material, and then stored in a product tank.

  Next, an Example and a comparative example are given and this invention is demonstrated concretely. In the following description, “parts” and “%” are based on mass unless otherwise specified.

[Examples and Comparative Examples]
The following calcined gypsum and the polymer flocculant were kneaded and then combined into one material by the method described above to prepare soil reforming compositions of Examples and Comparative Examples. As the calcined gypsum, waste gypsum was pulverized and fired, and then crushed and adjusted to a predetermined particle size. The main component of the polymer flocculant is an acrylamide / sodium acrylate copolymer (anion amount: 30 to 35 mol%, anion degree: 3.6 to 3.8 meq / gr, molecular weight: about 9 million). And those adjusted to a predetermined particle size were used.

  Four types of calcined gypsum having an average particle size adjusted to 10 μm, 30 μm, 50 μm, and 100 μm were used. Further, four types of polymer flocculants having an average particle size adjusted to 30 μm, 90 μm, 180 μm, and 200 μm were used. And combining these, each composition for soil improvement of the composition of Table 1 was produced. As described above, it is not practical that calcined gypsum has an average particle size of more than 100 μm, and polymer flocculants having an average particle size of less than 30 μm are hardly available. Therefore, it was omitted from the subject of consideration.

<Evaluation>
A soil modification (solidification) operation was performed on the mud soil with a water content of 77% using the respective soil modification compositions of Examples and Comparative Examples shown in Table 1. That is, with respect to 1 m ³ of the mud to be reformed, 300 kg of each soil reforming composition was added and kneaded and then the reforming operation was performed. Moreover, the soil after modification | reformation was observed visually and the condition of the modification | reformation was evaluated on the following reference | standard. The obtained results are shown in Table 1.
(Evaluation criteria)
A: Solidified in a completely uniform state.
○: Solidified in an almost uniform state.
Δ: Gypsum pieces in which only calcined gypsum was hydrated were also observed.
X: Gypsum pieces in which only calcined gypsum was hydrated were also observed.

[Comparative Example 3]
The soil modification (solidification) is performed by performing the following two steps on 1 m ³ of mud with a moisture content of 77% similar to that used in the previous evaluation. Evaluation was performed in the same manner as in the case where the reforming operation was performed using the composition. First, 6 kg of the fine particle polymer flocculant (average particle size: 90 μm) used in the examples was added to the mud and kneaded to prepare an aggregate. Thereafter, 294 kg of calcined gypsum (average particle size: 50 μm) was added and kneaded to perform a modification (solidification) operation. The same polymer flocculant as that used in the examples was used.

  As a result, although the mud was improved, the appearance of the kneaded material was in a state in which the periphery of the aggregate by the polymer flocculant was solidified by calcined gypsum, and a gypsum piece in which only calcined gypsum was hydrated was also observed. It was done. On the other hand, when the reforming operation was carried out using the soil reforming composition of the previous example, the mud was uniformly solidified and clearly had different properties. In the case of the soil reforming composition of the example in which calcined gypsum and the polymer flocculant are mixed and uniformly made into a single material, when contacting the mud, the polymer flocculant is first instantaneously contained in the mud. It was speculated that it was solidified in a uniform state by reacting with moisture and reacting with the remaining moisture after a little delay.

[Comparative Example 4]
6 kg of a granular polymer flocculant having an average particle size of 200 μm or more is mixed with 294 kg of calcined gypsum having an average particle size of 50 μm, and the mixture is made into one material in the same manner as in the examples, and the composition for soil modification A product was made.

  As a result, it was confirmed by visual observation that the polymer flocculant having coarse particles as compared with calcined gypsum cannot be uniformly dispersed in the composition for soil modification. In particular, it was confirmed that the materials were easily separated when the same vibration was applied as in the case of transporting the obtained composition in a container or when pneumatic transportation was performed. In addition, when the mud soil reforming operation was performed using such a material-separated composition for soil reforming, the solidified state fluctuated and a stable reforming operation could not be performed. In addition, in the case of the soil improvement composition of the Example demonstrated previously formed by mix | blending the fine particle polymer flocculent close | similar to calcined gypsum, it confirmed that material separation did not occur during transport.

[Reference test example]
Soil obtained by sufficiently mixing 1 g of the above polymer flocculant with 50 g of fine particle polymer flocculant having an average particle diameter of 90 μm used in the previous example and 49 g of calcined gypsum having an average particle diameter of 50 μm used in the previous example. Each of the reforming compositions was thinly spread on a watch glass and left in a constant temperature and humidity chamber (temperature 30 ° C., relative humidity 90%) set to a high humidity state for 24 hours for comparison. The fine polymer flocculant alone absorbed the moisture in the air and swelled, but the sample dispersed and mixed in the calcined gypsum was stable because the calcined gypsum absorbed moisture, and the polymer flocculant did not swell. .

[Examples 6 and 7]
6 kg of fine particle polymer flocculant (average particle size: 90 μm) used in the previous example was added to 294 kg of calcined gypsum (average particle size: 50 μm) calcined from the waste gypsum board pulverized product, A predetermined amount of each of the setting time adjusting agents shown in Table 2 was added and mixed thoroughly with a mixer to prepare each soil modifying composition. Specifically, in Example 6, potassium sulfate was added as an accelerator for accelerating the coagulation reaction, and in Example 7, citric acid was added in an amount shown in Table 2 to retard the coagulation reaction. Next, using the same mud with a water content of 77% as used in the evaluation, 300 kg of each obtained composition for soil modification was added to 1 m ³ of the mud, and the soil solidification performance after kneading was compared. did. The obtained results are also shown in Table 2. As a result, it was confirmed that the solidification time (working time) of the mud can be adjusted depending on the situation at the site where the soil is reformed by appropriately selecting a setting time adjusting agent to be blended in the soil reforming composition. Depending on the composition and moisture content of the target soil, the solidification time, which was about 1 hour in the past, can be shortened to about 30 minutes, or 3 hours or more. It has been found that the efficiency of can be greatly improved.

Claims (6)

  (A) To 100 parts by mass of calcined gypsum having an average particle size of 10 to 100 μm, (B) a fine particle polymer aggregating agent having an average particle size of 30 to 180 μm is contained in a range of 0.1 to 5 parts by mass, and Soil reforming characterized in that it is a single material made of a material that is added and mixed so that the ratio of (B) average particle size / (A) average particle size is in the range of 0.5 to 5 Composition.   Further, in the material, (C) the setting time adjusting agent is added and mixed in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the calcined gypsum of (A), and the solidification time is adjusted. The composition for soil improvement according to claim 1.   (C) The composition for soil reforming according to claim 2, wherein the setting time adjusting agent is at least one component selected from metal salts, carboxylic acids and carboxylates.   (C) The composition for soil improvement of Claim 3 whose at least 1 component of a setting time regulator is a metal salt chosen from potassium sulfate, aluminum sulfate, and magnesium oxide.   (C) The composition for soil reforming according to claim 3, wherein at least one component of the setting time adjusting agent is a carboxylic acid selected from citric acid, sodium gluconate, and L-tartaric acid, or a carboxylate thereof.   A soil reforming method using the composition for soil reforming according to claim 1.