JP7411319B1 - Soil cement manufacturing method - Google Patents

Abstract

The present invention provides a method for producing soil cement that has high deformation followability, is easy to re-excavate, and can expand its uses and applications. The present invention is a method for producing soil cement, which includes at least the following steps (A) to (D). (A) Mixture preparation step of adding at least 50 to 400 kg of solidifying agent per 1 m3 of soil cement to soil cement to prepare a mixture. (B) Temporarily storing the mixture for a period when the mixture can be crushed. (C) Temporary curing step of the mixture, in which the mixture after the temporary curing is crushed to a particle size of 200 mm or less to obtain a crushed product (D) The crushed product Compaction process of crushed material to obtain soil cement [Selected diagram] Figure 1

Description

The present invention is a method for producing soil cement that has high deformation followability, is easy to re-excavate, and can expand its uses and applications.

Soil cement, in a broad sense, refers to a mixture (fresh state) of earth and sand mixed with a solidifying agent, water, etc., and a solidified body that is hardened by hydration of the solidifying agent.
Nowadays, due to environmental concerns, soil cement, which is made from earth and sand generated during various types of construction work, is often used. This allows the generated soil to be effectively used at the same site as the construction site or at a different construction site, extending the life of the soil disposal site and reducing the costs of transporting, disposing, and procuring the soil, as well as noise and vibration when transporting the soil. Environmental problems such as these can be suppressed. Therefore, soil cement has the advantage of being economical and less likely to cause the above-mentioned environmental problems.

Conventionally, in the production of soil cement, there are two methods for adding a solidifying agent to soil and sand: a one-time addition method in which the entire amount of the solidifying agent is added to the soil at once (Patent Document 1, Patent Document 2), and a method in which the solidifying agent is added twice. There is a divided addition method (Patent Document 3) in which primary and secondary additions are made to soil and sand separately.
However, in the case of the bulk addition method, when the soil is difficult to solidify such as volcanic ash clay and organic soil, or highly viscous soil such as heavy clay, the amount of solidified material required to achieve the target strength is It is more abundant than other soils such as coarse-grained soil and low moisture content soil.

In addition, the split addition method has the advantage that the same strength as the batch addition method can be obtained with a smaller amount of solidifying agent added than the batch addition method, but since the strength is relatively high, In construction work that requires re-excavation, such as backfilling underground pipes, re-excavation may become difficult, so it was not suitable for the application. Furthermore, soil cement produced by the divided addition method has the disadvantage of having a small fracture strain and poor followability to strain (deformation) caused by earthquakes and the like.
Therefore, with the divided addition method, applications and applications are limited, and it is difficult to optimize the amount of solidifying agent added, which may result in excess or shortage of solidifying agent in soil cement.

JP 2019-15022 Publication JP 2018-21303 Publication Patent No. 704216

Therefore, an object of the present invention is to provide a method for producing soil cement that has high deformation followability, is easy to re-excavate, and can expand its uses and applications.

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that the method for producing soil cement having the following configuration can achieve the above object, and have completed the present invention.

[1] A method for producing soil cement, which includes at least the following steps (A) to (D).
(A) A process for producing a mixture, in which at least 50 to 400 kg of a solidifying agent is added to soil cement per 1 m ³ of soil cement and mixed to produce a mixture. However, the solidifying agent is added only once (first addition only), and no second addition is performed.
(B) Temporary curing step of the mixture, in which the mixture is temporarily placed and cured for a period in which the compressive strength of the mixture becomes 0.03 to 1.5 N/mm ² (C) The temporary curing is carried out. Crushing the finished mixture to obtain a crushed product with a particle size of 200 mm or less, (D) crushing step of the mixture, rolling and molding the crushed product,
(d1) The compressive strength after 28 days of molding is 0.04 to 0.45 N/mm ² for the 3-day-old crushed material, and 0.07 to 0 for the 7-day-old crushed material. .55 N/mm ² , 0.07 to 0.66 N/mm ² for a 28-day-old crushed material , and 0.12 to 0.44 N/mm for a 365-day-old crushed material ² ,
(d2) The compressive strength after 91 days of molding is 0.07 to 0.56 N/mm ² for the 3-day-old crushed material, and 0.11 to 0 for the 7-day-old crushed material. .78 N/mm ² , 0.18 to 1.09 N/mm ² for a 28-day-old crushed material , and 0.18 to 0.69 N/mm for a 365-day-old crushed material ² ,
Compression step of crushed material to obtain soil cement [2] The method for producing soil cement according to the above [1], wherein in the step (C), the crushed material is stored until used.
[3] The method for producing soil cement according to [1] or [2] above, wherein in the step (D), the compacted soil cement is further cured.

The soil cement produced according to the present invention has high deformation followability and is strong enough to be re-excavated.
In addition, since the mixture prepared in step (A) is temporarily cured for a certain period of time, and the crushed material crushed in step (C) is stored until it is used, a long period of use can be ensured. The applications and uses of cement can be expanded.

(C) Photographs showing the state of the mixture after temporary curing in the process. The left photograph shows a state in which the mixture is too strong to be crushed, and the center photograph shows a state in which it is easy to crush and has been crushed. The photo on the right shows a state in which it has become muddy and cannot be crushed.

As described above, the present invention provides a soil soil that includes at least (A) a step of preparing a mixture, (B) a step of temporarily curing the mixture, (C) a step of crushing the mixture, and (D) a step of compacting the crushed material. This is a method of manufacturing cement.
Hereinafter, the present invention will be explained in detail by dividing into the steps (A) to (D).

(A) Step of Preparing a Mixture The step (A) is a step of adding and mixing at least a solidifying agent to earth and sand to prepare a mixture. Next, the earth and sand, solidification material, mixing device, and water addition will be explained in this order.
(i) Earth and sand Earth and sand includes earth and sand generated from construction sites such as buildings and road construction sites, leftover soil, waste soil, etc., earth and sand generated at construction sites such as excavation, and earth and sand collected near construction sites. One or more types selected from the soil and sand that can be used can be mentioned. The type of soil is not particularly limited, and is selected from coarse-grained soil, fine-grained soil, volcanic ash clay soil, organic soil, soil that is difficult to solidify such as highly organic soil, and highly viscous soil such as clay. One or more types may be mentioned.

(ii) Solidification material The solidification material is one or more selected from blast furnace cement type B, blast furnace cement type A, blast furnace cement type C, Portland cement, silica cement, fly ash cement, ecocement, and cementitious solidification materials. be. Here, the cement-based solidification material is a composite material with cement as a base material, and is suitable for solidification purposes such as general soft soil, special soil (general purpose type), and high organic content soil, and the conditions at the solidification site. You should decide accordingly.
As an example of commercially available cement-based solidifying materials, the general-purpose type is Geoset 200 (registered trademark, manufactured by Taiheiyo Cement Co., Ltd.), and the one for high organic soil is Geoset 225 (registered trademark, manufactured by Taiheiyo Cement Co., Ltd.). (manufactured by), etc. In addition, in consideration of low cost and high solidification performance, the solidification material is preferably blast furnace cement type B and a cement-based solidification material.

The amount of the solidifying agent added is 50 to 400 kg per 1 m ³ of the soil cement. If the amount added is less than 50 kg per ¹ m3 of soil cement, the strength of the soil cement will not be sufficient, as shown in Comparative Example 1 in Table 1 and Comparative Example 10 in Table 3 below, and if it exceeds 400 kg, the soil cement will not have sufficient strength. As shown in Comparative Example 6 in Table 1 and Comparative Example 13 in Table 3, the strength of soil cement becomes excessive, and it may not be easy to crush it in the step (C). The amount of the solidifying agent added is preferably 80 to 300 kg per 1 m ³ of soil cement. Further, the appropriate amount to be added may be determined in advance by an indoor mixing test or the like.

(iii) Mixing device The device for mixing the earth and sand and the solidifying material is not particularly limited, and may be a mixer generally used for mixing concrete or mortar, such as a tilting mixer, a forced mixing mixer, a drum mixer, Examples include gravity mixers and hand mixers. Further, at construction sites and the like, examples of the mixing device include a backhoe, a bucket mixer, a batch type or continuous type mixer exclusively for soil cement, and the like.
By the way, the following points can be cited as the effects produced by adding a solidifying agent to earth and sand.
(a) The apparent water content ratio decreases.
(b) The soil properties are improved because the soil particles in the soil aggregate.
(c) Workability such as compaction is improved.
(d) Calcium ions in the solidification material react with corrosive acids such as humic acid in the soil to fix the corrosive acids that inhibit solidification of soil cement, thereby further promoting the solidification reaction.

(iv) Addition of water In the step (A), there are cases where it is difficult or impossible to stir and mix the solidification material due to the high viscosity of the soil, or where the moisture content of the soil is low and the water required for hydration of the solidification material is insufficient. If the amount is insufficient, it is preferable to add water when kneading the mixture.
Here, the case where it is difficult or impossible to stir and mix the solidification material due to the high viscosity of the earth and sand cannot be unambiguously stated because the stirring and mixing depends on the performance of the mixing device, but for example, This refers to cases where stirring/mixing is not possible, or when the mixture is not uniform.
Moreover, the water used for the addition of water includes tap water, river water, lake water, seawater, treated sewage water, and the like. Note that the amount of water to be added is preferably determined by actually preparing a mixture using the water to be used. When using water other than tap water, it is preferable to confirm in advance that it will not adversely affect solidification performance.

(B) Step of temporary curing of mixture The step (B) is a step of temporarily curing the mixture for a period during which the mixture can be crushed.
The above-mentioned "period during which crushing is possible" depends on the performance of the instruments and equipment used for crushing, but for example, in terms of compressive strength of the mixture, it is a period during which the compressive strength of the mixture is 0.03 to 1.5 N/mm ² . be. If the compressive strength is less than 0.03 N/mm ² , the strength of the mixture will not reach the strength ^that can be crushed, and it may turn into mud when force is applied. It may not be easy to crush or it may be difficult to compact the material after crushing. Note that the compressive strength is preferably 0.08 to 1.0 N/mm ² . Incidentally, based on Tables 1 to 3 below, the period of temporary curing is within the range of 3 to 365 days.
As a general rule, the greater the amount of solidified material and the longer the curing period, the greater the strength and therefore the difficulty of crushing. However, even if the amount of solidified material is large, if the curing period is short, crushing may be easy because the increase in strength is small. On the other hand, even if the amount of solidified material is small, if the curing period is long, the degree of increase in strength will be large, which may make crushing difficult. In other words, since [strength (mainly dependent on the amount of solidified material)/curing period/difficulty of crushing] are interrelated, it is important to determine each in consideration of the purpose and place of use. Therefore, it is preferable to conduct a preliminary mixing test using actual soil.
Further, the method of temporary curing is not particularly limited, and examples include sheeting, sealed curing, and sealed curing.

(C) Step of crushing the mixture This step is a step of crushing the mixture that has been temporarily cured into particles having a particle size of 200 mm or less to obtain a crushed product. If the particle size exceeds 200 mm, rolling may become difficult. The particle size is preferably 150 mm or less, more preferably 100 mm or less, even more preferably 50 mm or less, and still more preferably 10 mm or less.
Further, the crushing method used in the present invention is not particularly limited, but includes a method of crushing the mixture after the temporary curing using a crusher equipped with a sieve, a method of crushing the mixture with a backhoe bucket or a caterpillar, etc. can be mentioned.

In addition, if the compressive strength of the mixture at the time of crushing exceeds 1.0 N/ ^mm2 , the strength of soil cement will be improved by increasing the compaction property (filling property) of the crushed material, so add water to the crushed material. It is preferable to do so.
The water used for the water addition can be tap water, river water, lake water, seawater, treated sewage water, or the like. Note that the amount of water to be added is preferably determined by actually preparing a mixture using the water to be used. At that time, when using water other than tap water, it is preferable to confirm that it does not adversely affect solidification performance.
It is convenient to store the crushed material until it is used. By using the stored crushed material through compaction, etc. in a timely manner, it is possible to expand the uses and uses of soil cement in the future.

(D) Step of rolling the crushed material This step is a step of rolling the crushed material to obtain soil cement.
The rolling method used in the present invention is not particularly limited, and examples include rolling using a vibrating roller or a vibration damper. In addition, for applications requiring higher strength, it is preferable to add a solidifying agent to the crushed material and compact it.
Moreover, when the strength of soil cement is insufficient, soil cement can also be obtained by adding a solidifying agent to the crushed material in the compaction step.
In this step, curing is preferably performed to prevent freezing after construction in the winter and to prevent drying of the pouring surface after construction in the summer. The curing includes the use of curing sheets and curing mats, and the combination of these curing with watering and endothermic curing.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples.
1. Materials used (1) Sample soil The sample soils used were soil from Kanagawa Prefecture (Table 1), soil from Shizuoka Prefecture (A in Table 2), soil from Hiroshima Prefecture (B in Table 2), and soil from Hokkaido. soil from Kumamoto prefecture (C in Table 2), and soil from Kumamoto prefecture (Table 3).

(2) Solidifying material The solidifying materials used were Geoset 225 [registered trademark, manufactured by Taiheiyo Cement Co., Ltd.] (Tables 1 and 3) and Blast Furnace Cement B type [manufactured by Taiheiyo Cement Co., Ltd.] (Table 2).

2. Determination of Difficulty of Crushing According to the formulations shown in Tables 1 to 3, the sample soil and the solidification material for primary addition were kneaded using a Hobart mixer to prepare a mixture. However, if kneading was difficult, water was added until kneading was possible.
Next, the mixture is placed in a plastic bag, and the mixture is sealed and cured temporarily until the compressive strength of the mixture becomes 0.02 (Comparative Example 1, etc.) to 2.07 (Comparative Example 6) N/ ^mm2 . After that, the mixtures having the ages listed in Tables 1 to 3 were crushed by passing through a sieve with an opening of 9.5 mm.
The difficulty level of crushing was determined based on the conditions at the time of crushing each mixture. In addition, in Comparative Example 10, in which the strength at the time of crushing is 0.01 N/mm ² , and Comparative Examples 1 and 11, in which the strength at the time of crushing is 0.02 N/mm ² , when pressure is applied to pass through the sieve, It turned into mud and could not be crushed.

3. Preparation of Specimen Next, the crushed material alone (Example) or the crushed material and a solidifying material for secondary addition (Comparative Example) were kneaded using a Hobart mixer according to the formulations shown in Tables 1 to 3. The kneaded material was compacted into a mold with an inner diameter of 50 mm and a height of 100 mm according to the Japan Cement Association Standard Test Method (JCAS L-01) to prepare specimens for Examples and Comparative Examples.
Further, the test specimens of Reference Examples 1 to 3 were produced only by compaction without adding a solidifying agent.

4. Water Resistance Test The water resistance of the above-mentioned specimen (described as solidified material in Tables 1 to 3) was determined by visually observing whether or not the specimen turned into mud or collapsed, in order to evaluate the water resistance of soil cement due to rainfall, etc. The water resistance was determined to be good or bad. In addition, in Tables 1 and 2, the water resistance of the solidified material is determined by using a test specimen 28 days after molding, which was prepared by compacting a crushed material obtained by crushing a 7-day-old mixture. Moreover, in Table 3, a test piece after 28 days of molding was used, which was prepared by rolling a crushed material obtained by crushing a mixture of 28 days old.

5. Compressive strength test and fracture strain test Compressive strength of the specimen (expressed as "strength" in the table), and fracture strain of the specimen 28 days after molding using the crushed material of the 7-day-old mixture was measured in accordance with JIS A 1216 "Unconfined compression test method for soil".
In addition, in Comparative Example 13 in Table 3, the compacting material was molded immediately after the primary addition of the solidifying material, and the compaction of the molded product (specimen used for normal compressive strength tests) was performed 28 days after molding and 91 days after molding. Strength, fracture strain, and water resistance were measured. Furthermore, the difficulty of crushing in Comparative Example 13 was determined based on the measured strength.
The above results are shown in Tables 1 to 3, and we will mainly compare examples and comparative examples in which the type of soil (production area) and the type and amount of solidification agent, which affect the physical properties of soil cement, are the same. , the evaluation of the test results is discussed below.

(1) Regarding Table 1 (i) Comparison of Example 5 and Comparative Examples 2 and 3 Even though the (total) amount of solidifying agent added was the same as 250 kg/ ^m3 , after 28 days and 91 days of molding, The strength ratios (numbers in parentheses) of Example 5/Comparative Example 2 and Example 5/Comparative Example 3 are 0.10 to 0.20 for the 7-day-old material and the 28-day-old material. It was low. Note that the numerical value in parentheses in Table 1, for example, "0.20" of the 7-day-old crushed material of Comparative Example 2 indicates the strength ratio of Example 5/Comparative Example 2. The same applies to the others in Table 1.
In addition, the fracture strain of Example 5 was about 4 times higher than that of Comparative Examples 2 and 3 for both the 7-day-old and 28-day-old pieces, indicating excellent deformation followability. Furthermore, the water resistance of the Examples and Comparative Examples was good.

(ii) Comparison of Example 7 and Comparative Examples 4 and 5 Even though the (total) amount of solidifying agent added was the same as 350 kg/ ^m3 , Example 7/Comparative Example 28 days and 91 days after molding The strength ratios (numerical values in parentheses) of Example 4 and Example 7/Comparative Example 5 were as low as 0.11 to 0.22 in the 7-day-old and 28-day-old pieces.
In addition, the fracture strain of Example 7 was about 5 times higher than that of Comparative Examples 4 and 5 for both the 7-day-old and 28-day-old pieces, indicating excellent deformation followability. Furthermore, the water resistance of the Examples and Comparative Examples was good.
In addition, although both the compressive strength and fracture strain of Reference Example 1 (no solidifying agent added) were comparable to those of Comparative Example 1 (with solidifying agent added) using the same earth and sand, it was not modified with a solidifying agent. The water resistance was poor.

(iii) Regarding Comparative Example 1 In Comparative Example 1, since the amount of solidifying agent added per 1 m ³ of soil cement was as small as 40 kg/m ³ , it turned into mud during crushing, making crushing difficult. Therefore, in the present invention, if the amount of solidifying agent added is less than 50 kg/m ³ per 1 m ³ of soil cement in order to lower the strength, crushing becomes difficult.

(3) Regarding Table 2 Comparison of Example 11 and Comparative Example 7 Despite the (total) addition amount of solidifying agent being the same as 240 kg/ ^m3 , the strength ratio of Example 11/Comparative Example 7 (in parentheses) ) was as low as 0.43 to 0.86 in the 7-day-old and 28-day-old materials. Note that the numerical value in parentheses in Table 2, for example, "0.86" for the 7-day-old crushed material of Example 11 indicates the strength ratio of Example 11/Comparative Example 7. The same applies to the others in Table 2.
Further, the fracture strain was approximately 1.3 times higher in Example 11 than in Comparative Example 7, and the deformation followability was excellent. Furthermore, both Example 11 and Comparative Example 7 had good water resistance.
Moreover, even if the type of soil changes, such as when the sample soil is from Hiroshima (Example 12, Comparative Example 8) or from Hokkaido (Example 13, Comparative Example 9), the sample soil is from Shizuoka (Example 11, Comparative Example 7). The same thing can be said.
In addition, although both the compressive strength and fracture strain of Reference Example 2 (no solidifying agent added) were comparable to those of Example 9 (with solidifying agent added) using the same earth and sand, it was not modified with a solidifying agent. The water resistance was poor.

(4) About Table 3 (i) Comparison of Example 14 and Comparative Example 11 Despite the (total) addition amount of solidifying agent being the same as 150 kg/ ^m3 , the strength ratio of Example 14/Comparative Example 11 (Numbers in parentheses) were low at 0.38 to 0.76 for the 28-day-old material and the 365-day-old material. Note that the numerical value in parentheses in Table 3, for example, "0.76" of the 28-day-old crushed material of Example 14 indicates the strength ratio of Example 14/Comparative Example 11. The same applies to the others in Table 3.
Moreover, the fracture strain in Example 14 is about 1.1 times higher than that in Comparative Example 11, and the deformation followability is high. Furthermore, both Example 14 and Comparative Example 11 had good water resistance.
From these results, it can be seen that even if the crushed material is used for a temporary curing period of 365 days, it is possible to produce soil cement that has appropriate strength, has high deformation followability, and is highly water resistant.
Although both the compressive strength and fracture strain of Reference Example 3 (no solidifying agent added) were comparable to those of Comparative Example 10 (with solidifying agent added) using the same earth and sand, it was not modified with a solidifying agent. The water resistance was poor.

(ii) Comparison of Example 16 and Comparative Example 12 Even though the (total) amount of solidifying agent added is the same as 250 kg/ ^m3 , the strength ratio of Example 16/Comparative Example 12 (value in parentheses) was as low as 0.34 to 0.88 in the 28-day-old and 365-day-old materials.
Further, the fracture strain in Example 16 is 1.8 times higher than that in Comparative Example 12, and the deformation followability is excellent. Furthermore, both Example 16 and Comparative Example 12 had good water resistance.
From these results, it can be seen that even if the crushed material is used for a temporary curing period of 365 days, it is possible to produce soil cement that has appropriate strength, has high deformation followability, and is highly water resistant.
(iii) Regarding Comparative Example 10 In Comparative Example 10, since the amount of solidifying agent added per 1 m ³ of soil cement was as small as 30 kg/m ³ , it turned into mud during crushing, making crushing difficult.
(iv) Regarding Comparative Example 13 As mentioned above, Comparative Example 13 is a compact molded by compaction immediately after the primary addition of the solidifying material (a specimen used in a normal compressive strength test). Compared to soil cement, it has a high compressive strength and is difficult to crush, and its fracture strain is low, so it is inferior in deformation followability.

Claims (3)

A method for producing soil cement, comprising at least the following steps (A) to (D).
(A) A process for producing a mixture, in which at least 50 to 400 kg of a solidifying agent is added to soil cement per 1 m ³ of soil cement and mixed to produce a mixture. However, the solidifying agent is added only once (first addition only), and no second addition is performed.
(B) Temporary curing step of the mixture, in which the mixture is temporarily placed and cured for a period in which the compressive strength of the mixture becomes 0.03 to 1.5 N/mm ² (C) The temporary curing is carried out. Crushing the finished mixture to obtain a crushed product with a particle size of 200 mm or less, (D) crushing step of the mixture, rolling and molding the crushed product,
(d1) The compressive strength after 28 days of molding is 0.04 to 0.45 N/mm ² for the 3-day-old crushed material, and 0.07 to 0 for the 7-day-old crushed material. .55 N/mm ² , 0.07 to 0.66 N/mm ² for a 28-day-old crushed material , and 0.12 to 0.44 N/mm for a 365-day-old crushed material ² ,
(d2) The compressive strength after 91 days of molding is 0.07 to 0.56 N/mm ² for the 3-day-old crushed material, and 0.11 to 0 for the 7-day-old crushed material. .78 N/mm ² , 0.18 to 1.09 N/mm ² for a 28-day-old crushed material , and 0.18 to 0.69 N/mm for a 365-day-old crushed material ² ,
Compaction process of crushed material to obtain soil cement The method for producing soil cement according to claim 1, wherein in the step (C), the crushed material is stored until used. The method for producing soil cement according to claim 1 or 2, wherein in the step (D), the compacted soil cement is further cured.

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