JP5799509B2 - Soil improving material and soil improving method - Google Patents

Description

  The present invention relates to a soil improvement material using a crushed material obtained by crushing concrete, and a soil improvement method.

  In the construction industry, unnecessary concrete is generated in various forms. For example, return concrete is generated at a rate of about 1% of the shipment amount in the ready-mix factory as well as the demolition glass at the demolition site, and residual concrete that is not placed at the construction site is generated. At present, most of these are treated as waste. Recently, however, it has been studied to reuse these concretes as resources by applying predetermined treatments.

  As an example of the material to be reused, for example, recycled fine powder can be mentioned. That is, when reclaimed fine powder (waste cement fine powder, etc.) is produced as a by-product when producing recycled aggregate by crushing concrete waste and removing aggregate from the waste, the recycled fine powder is used as a soil improvement material. Use is under consideration. And as a water absorption material which absorbs the water | moisture content in soil, it can be used effectively. However, because of its low hydraulic property (the property of curing by reacting with moisture in the soil, etc., which is also called self-hardening), there is a problem in the use of the solidified material for soil improvement.

  Here, Patent Document 1 discloses heating the regenerated fine powder to 500 ° C. or higher as a method for increasing the hydraulic property of the regenerated fine powder. It is also conceivable to mix cement as a method for increasing the hydraulic properties of the regenerated fine powder.

JP-A-2005-320201

  However, when the regenerated fine powder is heated to 500 ° C. or higher, hydraulic properties are imparted, but the action of the heated regenerated fine powder may increase the pH and electrical conductivity of the soil in which the regenerated fine powder is mixed. Along with this, there are concerns about the diffusion of high alkali components into the environment and the adverse effects on vegetation caused by high electrical conductivity. Moreover, when mixing cement, there exists a possibility that pH may become too high similarly.

  Furthermore, when hydraulic properties are not required, unheated regenerated fine powder may be used as a soil conditioner, but at this time, when the regenerated fine powder is by-produced from young concrete waste material. Due to its high alkalinity, there was a risk of excessively increasing the pH and electrical conductivity of the soil even when unheated.

  Furthermore, the problem of excessive increase in soil pH and electrical conductivity due to the use of the above-mentioned young concrete waste material is not limited to recycled fine powder, that is, aggregate formed by crushing such concrete waste material. It was a problem that could occur when the crushed concrete in a state of containing was reused as a soil conditioner.

  The present invention has been made in view of the conventional problems as described above, and an object thereof is a soil improvement material using a crushed material such as regenerated fine powder obtained by crushing concrete, It aims at providing the soil improvement material which can suppress the excessive raise of the pH of the soil at the time of mixing, and an electrical conductivity, and the soil improvement method using the same.

In order to achieve this object, the invention shown in claim 1
A soil conditioner,
Crushing material obtained by crushing concrete;
With superphosphate lime,
And a blast furnace slag .
According to the first aspect of the present invention, the soil improvement material has a crushed material obtained by crushing concrete and lime superphosphate. Therefore, when the soil improving material is mixed with the soil to be improved, the pH and electrical conductivity of the soil may increase due to the action of the former crushing material. Exerts a neutralizing action to lower the pH and electrical conductivity of the soil. Accordingly, it is possible to suppress an excessive increase in the pH and electrical conductivity of the soil when mixed in the soil.
Moreover, since it has a blast furnace slag, the elution to the soil of the hexavalent chromium in the crushed material can be suppressed.

The invention shown in claim 2
Crushing material obtained by crushing concrete;
Lime superphosphate,
The age of the concrete is within 2 years,
Furthermore, it is a soil improvement material characterized by having blast furnace slag .
According to the second aspect of the present invention, the soil conditioner has a crushed material of concrete whose age is less than 2 years and a blast furnace slag, and in the case of the combination, the intervention of water As a result, the crushed material and the blast furnace slag react to develop hydraulic properties. Therefore, hydraulic property can be imparted to the soil improvement material without heat-treating the crushed material. As a result, it is possible to suppress an increase in environmental load and cost increase related to CO ₂ emissions.

The invention shown in claim 3
Crushing material obtained by crushing concrete;
Lime superphosphate,
The electrical conductivity of the suspension obtained by adding the crushed material to demineralized water with a liquid-solid ratio of 10 is 200 (mS / m) or more,
Furthermore, it is a soil improvement material characterized by having blast furnace slag .
According to the invention described in claim 3 above , the soil conditioner has the crushed material having an electric conductivity of the suspension of 200 (mS / m) and the blast furnace slag, and in the case of the combination The crushed material and blast furnace slag react with each other due to the presence of water, and hydraulic properties are developed. Therefore, hydraulic property can be imparted to the soil improvement material without heat-treating the crushed material. As a result, it is possible to suppress an increase in environmental load and cost increase related to CO ₂ emissions.

Invention of Claim 4 is the soil improvement material of Claim 2 or 3 ,
The crushed material is a regenerated fine powder that is generated when the aggregate is taken out of the concrete,
The blast furnace slag is mixed with the regenerated fine powder so that a weight ratio of the blast furnace slag to a total weight of the regenerated fine powder and the blast furnace slag is 0.2 or more and 0.8 or less.
According to the fourth aspect of the invention, the hydraulic property of the hydraulic material using the regenerated fine powder as the crushed material can be effectively increased. In addition, if it is set to 0.5 or more especially in 0.2-0.8, hydraulic property can be maximized substantially.

The invention shown in claim 5
Crushing material obtained by crushing concrete;
Lime superphosphate,
The crushed material is a regenerated fine powder that is generated when the aggregate is taken out of the concrete,
The regenerated fine powder is heated.
According to the fifth aspect of the present invention, it is possible to enjoy the effect of lowering the pH and electrical conductivity of the soil that can be achieved by lime superphosphate.

The invention described in claim 6
Crushing material obtained by crushing concrete;
Lime superphosphate,
The crushed material is a soil-improving material, which is a regenerated fine powder generated when an aggregate is taken out from the concrete .
According to the sixth aspect of the present invention, since the crushed material is a regenerated fine powder, the effects of the first to fourth aspects can be reliably achieved.

Invention shown in claim 7, a soil improvement material according to any one of claims 1 to 3,
The crushed material is crushed concrete containing aggregates, which is obtained by crushing the concrete.
According to the seventh aspect of the present invention, the crushed material can be used as a soil improving material while containing the aggregate obtained by crushing the concrete.

The invention shown in claim 8
A soil improvement method comprising mixing the soil improvement material according to any one of claims 1 to 7 with soil to be improved.
According to the eighth aspect of the present invention, the above-described effects can be achieved.

  According to the present invention, it is a soil improvement material using a crushed material such as regenerated fine powder obtained by crushing concrete, and can suppress an excessive increase in pH and electrical conductivity of the soil when mixed in the soil. A soil improvement material and a soil improvement method using the same can be provided.

FIG. 1A shows the compressive strength of the specimen of regenerated fine powder A as an example of the crushed material, and FIG. 1B shows the compressive strength of the specimen of regenerated fine powder B. It is the compressive strength of the specimen of crushed concrete as an example of the crushed material.

=== First Embodiment ===
The soil improvement material of 1st Embodiment is mixed with soil by being sown in the soil of improvement object. And after this mixing, it shows the hydraulic property which is the property which hardens | cures and hardens | cures by reacting with the water | moisture content in soil, etc., thereby solidifying the soft ground etc. of improvement object and improving the soil quality.

  This soil improvement material has the crushing material obtained by crushing concrete, and a superphosphate lime, In this 1st Embodiment, the regenerated fine powder is used as an example of said crushing material. And these both are mixed by the compounding ratio (weight ratio) of 0.975: 0.025-0.90: 0.10, for example, are bag-packed as a soil improvement material, and are carried on-site.

Recycled fine powder is by-produced in the process of extracting coarse aggregate such as gravel and fine aggregate such as sand as recycled aggregate from concrete waste. The particle size is, for example, 200 microns or less, and the specific surface area is, for example, 2000 to 10000 (cm ² / g). In addition, as a method of taking out the recycled aggregate from the concrete waste material, for example, a heated grinding method or the like can be cited.

  Here, generally, if it remains in the state taken out from the above-mentioned concrete waste material, the regenerated fine powder has low hydraulic properties and is hard to be hardened (solidified) even when mixed in soil. For this reason, in this 1st Embodiment, after the above-mentioned taking-out process, it heat-processes and the hydraulic property of the reproduction | regeneration fine powder is improved.

  The heat treatment is performed in a heating furnace, and the heat treatment is performed so that the temperature of the regenerated fine powder is 500 ° C. or higher, preferably 600 ° C. or higher, and more preferably 700 ° C. or higher. As a heating furnace, the structure which has the screw conveyor and the combustion burner in the furnace is mentioned, for example. And while the regenerated fine powder is conveyed in the furnace by the screw conveyor, the regenerated fine powder is heated to the above-mentioned target temperature by the combustion burner.

On the other hand, superphosphate lime is also a granular material. Superphosphate lime is intended to suppress a significant increase in the pH and electrical conductivity of the soil after spraying the soil conditioner. That is, when the above-described heat treatment is performed on the regenerated fine powder, the pH and electrical conductivity in the soil may become too high due to the action of the regenerated fine powder mixed in the soil. Ingredients may diffuse into the soil, or the soil's electrical conductivity may increase and adversely affect vegetation. For this reason, lime superphosphate is mixed in advance as part of the soil amendment material, so that after mixing the soil amendment material with the soil, the high alkali component is contained by the following neutralization reaction with lime superphosphate. As a result, diffusion of highly alkaline components into the soil and increase in the electrical conductivity of the soil are suppressed.
Ca (H ₂ PO ₄ ) ₂ + 2Ca (OH) ₂ → Ca ₃ (PO ₄ ) ₂ + 4H ₂ O

  Here, it is desirable that the soil conditioner further has blast furnace slag. If it does so, it will also suppress that hexavalent chromium in reproduction | regeneration fine powder elutes in soil. Details are as follows. Since blast furnace slag is produced in a reduced state when producing cast iron, iron or the like contained in a small amount in the blast furnace slag is reduced and has a reducing power. Therefore, by the reducing power of the blast furnace slag, hexavalent chromium in the regenerated fine powder is reduced to trivalent chromium and insolubilized, thereby suppressing elution of hexavalent chromium into the soil. In addition, it is considered that the incorporation of hexavalent chromium when the alkali content of the regenerated fine powder reacts with the blast furnace slag to produce hydrated minerals also contributes to suppression of elution.

  By the way, although the soil improvement material of the above-mentioned 1st Embodiment was what mixed superphosphate lime with the heated reproduction | regeneration fine powder, when hydraulicity is not requested | required, for example, only water absorption is required. For example, unheated regenerated fine powder may be used as a soil improvement material. However, at this time, depending on the regenerated fine powder, there is a concern that the pH and electrical conductivity of the soil may be excessively increased. In this case, a mixture of superphosphate lime may be used as the soil improving material. Hereinafter, this is referred to as a soil improvement material according to a modification of the first embodiment. In particular, regenerated fine powder that is relatively young as regenerated fine powder, for example, regenerated fine powder with an age of 2 years or less has high activity (mainly high alkalinity). The rate becomes excessively high and, depending on the soil, it exceeds the allowable upper limit. Therefore, in that case, it is necessary to mix lime superphosphate even with non-heated regenerated fine powder.

The suppression effect of pH and electrical conductivity of the soil improvement material of the first embodiment described above and its modification has been confirmed by experiments. In addition, the effect of suppressing hexavalent chromium by blast furnace slag has also been confirmed. Tables 1 and 2 below show the experimental conditions and experimental results. In addition, each numerical value of the regenerated fine powder, the blast furnace slag, the superphosphate lime, and the standard sand in Table 1 and Table 2 indicates the blending ratio (weight ratio), and the “−” mark indicates that the material is not mixed. It means that there is.

Here, the experimental method will be described with reference to Tables 1 and 2.
First, two types of regenerated fine powders having a material age of 1 year and a material age of 24 years were prepared. Table 1 shows the case when the material age is 1 year, and Table 2 shows the case when the material age is 24 years. In addition, in the case of a material age of 1 year, both a non-heated thing and the thing heated to 300 degreeC were prepared as reproduction | regeneration fine powder. In the case of a material age of 24 years, both a non-heated material and a material heated to 700 ° C. were prepared.

And in the mixing ratio of each experimental level T1 to T6 in Table 1 and the mixing ratio of each experimental level U1 to U8 in Table 2, regenerated fine powder, standard sand, superphosphate lime, and blast furnace slag are mixed, thereby Samples corresponding to each experimental level were made. In both Tables 1 and 2, the even number of the sample number is an example according to the first embodiment in which superphosphate lime is mixed or a modification thereof, and the odd number is that of superphosphate lime. It is a comparative example of mixing.
And after mixing by such a mixing | blending, pH of each sample, electrical conductivity, and the elution amount of hexavalent chromium were measured.

The measurement of pH was performed according to the following procedure in accordance with the soil test pH test method of the soil engineering society standard (JIG021-2000) for soil.
(1) Remove particles having a particle size of 10 mm or more from the sample.
(2) Put 10 g of sample in 50 mL of demineralized water and suspend with a stirring rod.
(3) A sample liquid for measurement is allowed to stand for 30 minutes to 3 hours.
(4) After stirring the sample solution, the electrode of the pH meter is immersed in the sample solution.
(5) After the reading of the pH meter has stabilized, read the pH.

Moreover, the electrical conductivity was measured according to the following procedure in accordance with the method for testing the electrical conductivity of the soil suspension in accordance with the Geotechnical Society Standard JIG021-2000.
(1) Remove particles having a particle size of 10 mm or more from the sample.
(2) Put 10 g of sample in 100 mL of demineralized water and suspend with a stirring rod.
(3) A sample liquid for measurement is allowed to stand for 30 minutes to 3 hours.
(4) The platinum electrode portion of the conductivity meter is immersed in the sample solution while stirring the sample solution.
(5) After the indicated value of the electric conductivity meter is stabilized, the electric conductivity values (S / m, mS / m) are read.
Furthermore, the elution amount of hexavalent chromium was measured by the dissolution test of the Ministry of the Environment Notification No. 18 on March 6, 2003 (August 23, 1991 Environment Agency Notification No. 46).

  The experimental results will be described. When the experimental results on the right side of Table 1 and Table 2 are referred to by comparing the even number and odd number of the sample numbers, the pH and electrical conductivity can be increased by mixing lime superphosphate regardless of the age of the sample and the presence or absence of heating. It can be seen that the rate is decreasing. Thereby, according to the soil improvement material of 1st Embodiment which has a superphosphate lime, and its modification, it is demonstrated that the excessive raise of the pH of a soil at the time of mixing in soil and an electrical conductivity can be suppressed. It was done.

  Further, in particular, by comparing the samples U1 and U5, it can be seen that heating the regenerated fine powder having a material age of 24 years at 500 ° C. or higher (700 ° C.) increases the pH and electrical conductivity. And U6, it was confirmed that the above-mentioned increased pH and electrical conductivity can be lowered by the incorporation of lime superphosphate.

  Furthermore, comparison between samples T3 and T5, comparison between samples T4 and T6, comparison between samples U1 and U3, comparison between samples U2 and U4, comparison between samples U5 and U7, comparison between samples U6 and U8 From this, it can also be seen that the elution amount of hexavalent chromium is reduced by mixing blast furnace slag. Therefore, it was also demonstrated that further mixing of blast furnace slag can suppress elution of hexavalent chromium in the regenerated fine powder into the soil.

=== Second Embodiment ===
In the first embodiment described above, hydraulic property is imparted to the soil improvement material by heating the regenerated fine powder, but when the activity of the regenerated fine powder is high, blast furnace slag is mixed without heat treatment. It is possible to impart hydraulic properties only by this. The activity referred to here is mainly the high reactivity with the blast furnace slag.
Therefore, the soil improvement material of this 2nd Embodiment has regenerated fine powder and blast furnace slag with high activity by the compounding ratio (weight ratio) of 0.8: 0.2-0.2: 0.8. And it has what mixed regenerated fine powder and blast-furnace slag, and a superphosphate lime with the compounding ratio (weight ratio) of 0.9: 0.1-0.975: 0.025.

And, according to such a soil improvement material, since the heat treatment of the regenerated fine powder can be omitted in the production process, there is no increase in the environmental load related to CO ₂ emission of the heat treatment and no cost increase related to the heating cost. As a result, the cost of soil improvement materials can be greatly reduced.
The activity (alkaline height) of the regenerated fine powder is determined based on the age of the concrete waste material or the electrical conductivity of the regenerated fine powder suspension.

When the determination index is the former material age, if the material age is within 2 years, it is determined that the activity is high. Here, the age is the number of years elapsed from the date of manufacture of the concrete. In other words, the date for calculating the age of ages is the day when the manufacture of concrete is started (the day when cement, water, and aggregate are mixed). It may be the year of completion of the building. The end date of the calculation is the date on which recycled fine powder is by-produced from concrete waste. In addition, the reason why the activity can be determined by the age is that if the age is long, the period of exposure to CO ₂ in the atmosphere is long and neutralization is also progressing, and the alkalinity is also low. It is possible. In addition, if the material age is within 2 years, it has been confirmed by a number of measurement cases that the electrical conductivity described later has an activity corresponding to 200 (mS / m) or more.
On the other hand, when the determination index is electrical conductivity (hereinafter also referred to as EC), the activity is high if the electrical conductivity of the suspension of the regenerated fine powder to be measured is 200 (mS / m) or more. Is determined.

The measurement of the electrical conductivity is performed in accordance with the method for testing the electrical conductivity of the soil suspension according to the Geotechnical Society Standard JIG021-2000. That is, it is measured by the following procedures (1) to (5). However, in the above test method of JIG021-2000, the liquid-solid ratio (ratio of the weight of the sample to the weight of water) is set to 5, but here, the liquid conductivity is considered in consideration of the high electrical conductivity of the regenerated fine powder. The solid ratio is 10.
(1) A sample obtained by removing regenerated fine powder having a particle size of 10 mm or more is used as a sample.
(2) 10 g of regenerated fine powder is put into 100 mL of demineralized water and suspended with a stirring rod.
(3) A sample liquid for measurement is allowed to stand for 30 minutes to 3 hours.
(4) The platinum electrode portion of the conductivity meter is immersed in the sample solution while stirring the sample solution.
(5) After the indicated value of the electric conductivity meter is stabilized, the electric conductivity values (S / m, mS / m) are read.

  By the way, just mixing blast furnace slag with such highly active regenerated fine powder does not cure yet because it is in a substantially dry state with almost no water intervening. That is, hydraulic properties are not expressed. However, when the soil improving material is mixed in the soil to be improved, the soil improving material reacts with moisture in the soil and hardens (that is, develops hydraulic properties).

  The hypothesis is why water sclerosis becomes high when blast furnace slag is mixed with regenerated fine powder with high activity (that is, regenerated fine powder with high electrical conductivity or young age). However, it can be explained as follows.

First, the regenerated fine powder contains calcium silicate hydrate (nCaO · SiO ₂ ) and calcium hydroxide (Ca (OH) ₂ ), which are hydrated products of cement.
On the other hand, blast furnace slag is an aluminosilicate based on CaO and MgO, in which four components of SiO ₂ , Al ₂ O ₃ , CaO, and MgO occupy about 97%. When this blast furnace slag comes into contact with water, a thin and dense hydrate containing silicate as a main component is generated on the particle surface, which becomes a film. Basically, no further hydration reaction proceeds. . However, in an alkaline solution such as Ca (OH) ₂ , this coating is broken, and SiO ₂ , Al ₂ O ₃ , CaO, and MgO in the blast furnace slag are eluted, and as a result, like a cement clinker. The hydration reaction begins and a hydrated product is formed and cured. This is called the latent hydraulic property of the slag. Here, among the regenerated fine powders, the higher the electrical conductivity or the younger the material, the higher the alkalinity. Therefore, these regenerated fine powders are sources of Ca ²⁺ and OH ⁻ . Thus, it is considered that the hydraulic property of the blast furnace slag is effectively increased, thereby improving the hydraulic property of the entire soil improvement material.

  As described above, the qualitative reason why hydraulic property can be imparted by mixing blast furnace slag when the activity of the regenerated fine powder is high has been described, but since a confirmation experiment is actually performed, the experiment will be described below.

Table 3 shows the materials used in the experiment. Table 4 shows the experimental conditions. In addition, each numerical value which concerns on the water in Table 4, regenerated fine powder, blast furnace slag, lime superphosphate, and cement has shown the compounding ratio (weight ratio).

  As described above, in this experiment, first, the effect of the presence or absence of addition of blast furnace slag on the hydraulic properties of the two types of recycled fine powders A and B produced as a by-product when the recycled aggregate is manufactured is examined. That is, as shown in Table 3, regenerated fine powder A having a material age of 1 year is prepared as a regenerated fine powder having high activity, and regenerated fine powder B having a material age of 24 years is prepared as a regenerated fine powder having low activity. ing.

  We are also investigating the effect of blending amount of blast furnace slag on hydraulic properties. That is, as shown in K0 to K3 of Table 4, the ratio of the regenerated fine powder and the blast furnace slag is changed while keeping the total weight of the regenerated fine powder and the blast furnace slag (hereinafter also referred to as the weight of the base material) constant. ing. Specifically, the weight ratio of the blast furnace slag to the weight of the base material (regenerated fine powder and blast furnace slag) is changed at four levels of 0, 0.25, 0.5, and 0.75.

  Furthermore, about the reproduction | regeneration fine powder A with high activity, the influence on the hydraulic property of the presence or absence of superphosphate lime is also investigated. Incidentally, the experimental level of K4 in which superphosphate lime is mixed corresponds to the soil conditioner of the second embodiment.

The hydraulic property is evaluated by the compressive strength of a specimen that simulates soil. The specimens are prepared as follows for each experimental level of K0 to Q4 in Table 3.
First, regenerated fine powder, blast furnace slag, and standard sand as a simulated soil material are blended at a blending ratio shown in Table 3, and depending on the experimental level, superphosphate lime is also blended. Basically, the blending ratio of water, soil improvement material (regenerated fine powder, blast furnace slag, and superphosphate lime) and standard sand is set to 0.7: 1: 3. Further, the weight ratio of the blast furnace slag to the base material (regenerated fine powder and blast furnace slag) is changed at the above-mentioned four levels (0, 0.25, 0.5, 0.75).

  As mixing, empty kneading is performed for 10 seconds, low-speed kneading for 20 seconds with the amount of water shown in Table 4, and high-speed kneading for 40 seconds. Then, this kneaded material is put into a tubular steel mold having a diameter of 50 mm and a height of 100 mm, and after curing, it is cured at 20 ° C. until the strength test material age. The strength test material age is, for example, 7 days.

  If it does so, it will demold from a cylindrical steel formwork, will take out a test body, this test body will be set to a compression tester, and a uniaxial compression test will be performed. And the value which divided the maximum load until destruction by the cross-sectional area of 50 mm in diameter is made into the compressive strength of the specimen.

  In addition, in this experiment, in order to make the improvement level of the hydraulic property by the cement mixing of the conventional method a comparison object, a specimen obtained by mixing the cement of Table 3 with the regenerated fine powder instead of the blast furnace slag is prepared as a comparative example. . These comparative examples are K5 and Q4 in Table 4.

  FIG. 1A shows the experimental result of the regenerated fine powder A, and FIG. 1B shows the experimental result of the regenerated fine powder B. In addition, each percentage (0%, 25%, 50%, 75%) concerning Sg in FIG. 1A and FIG. 1B is the weight ratio of the blast furnace slag to the base material (regenerated fine powder and blast furnace slag).

  From FIG. 1A and FIG. 1B, when the blast furnace slag is mixed with the regenerated fine powder A having a high activity, the compressive strength is greatly improved as a whole, but even if the regenerated fine powder B having a low activity is mixed with the blast furnace slag, the compressive strength is increased. It can be seen that does not improve. Therefore, it has also been experimentally confirmed that the hydraulic properties are improved only by mixing blast furnace slag with the regenerated fine powder A having high activity.

In addition, while the compressive strength of the cement-mixed specimens K5 and Q4, which is a conventional method, is about 1 (N / mm ² ), the weight of the blast furnace slag is 0.25 weight on the recycled fine powder A (material age 1 year). Specimen K1 blended in a ratio has a compressive strength of 2.1 (N / mm ² ), and thus has a hydraulic property equal to or higher than that of the conventional method. From this, in the case of recycled fine powder whose age of the concrete waste is within 2 years (at least within 1 year), the weight ratio of the blast furnace slag to the total weight of the base material (regenerated fine powder and blast furnace slag) is 0.25. In this way, it is considered that the hydraulic property can be ensured more than the conventional cement mixing method.

  Moreover, it turns out that hydraulic property does not improve so much even if the weight ratio of the blast furnace slag with respect to the total weight of a base material is made larger than 0.5 from the comparison of the test bodies K1, K2, and K3. Therefore, from the viewpoint of efficiently improving hydraulic properties, when the age of the concrete waste is regenerated fine powder within one year, the weight ratio of the blast furnace slag may be 0.5 or more and 0.75 or less. it is conceivable that.

=== Third Embodiment ===
In the soil improvement material of the first embodiment and the second embodiment described above, “regenerated fine powder” is exemplified as an example of the “crushed material” as the material, but in the third embodiment described below, “crushed material” "Is mainly different in that it uses" crushed concrete containing aggregates in which concrete waste is crushed ". That is, the soil improvement material of the third embodiment is a mixture of aggregate-containing crushed concrete and lime superphosphate.

  For crushed concrete, return concrete that has been returned as it is after shipment from the ready-mix factory or remaining concrete that has not been placed at the construction site is left to stand for the next day to several months, for example. Generated.

Therefore, this crushed concrete contains cement and aggregate. Here, in general, aggregate refers to coarse aggregate such as gravel and fine aggregate such as sand. In this example, crushed concrete includes these coarse aggregate and fine aggregate. Only one of them may be included, or both may be included.
For example, by removing crushed concrete through a sieve or the like, and removing particles with a particle size exceeding 5 mm, the aggregate may contain only particles with a particle size of 5 mm or less, or without sieving. In addition, various particle sizes may be mixed and adjusted.

  Then, the crushed concrete thus formed is also mixed with lime superphosphate at a predetermined blending ratio in the same manner as in the case of the above-mentioned regenerated fine powder. Sent to.

  Here, the crushed concrete is generated from return concrete or residual concrete. Therefore, the age of the concrete waste material, which is the elapsed time from the start of concrete production, is extremely short, for example, the next day to the third day, and therefore the alkalinity of the cement components contained therein is high. Therefore, if such crushed concrete is mixed into the soil as it is, this highly alkaline component may diffuse into the soil or the soil's electrical conductivity may increase based on the same component, which may adversely affect vegetation. .

  About this point, in the soil improvement material of this 3rd Embodiment, the superphosphate lime is also contained as mentioned above. Therefore, after mixing the soil amendment material into the soil, the high alkaline component derived from the crushed concrete is neutralized by the neutralization reaction of lime superphosphate, so that adverse effects on the vegetation are effectively suppressed. .

  In addition, when the alkalinity of the crushed concrete is high, that is, when the activity is high, the blast furnace slag is mixed into the crushed concrete as in the case of the above-mentioned recycled fine powder, so that its hydraulic property is reduced. Can be increased.

  The activity at that time can be evaluated by the age of the concrete waste material or the electrical conductivity of the crushed concrete suspension, as in the case of the recycled fine powder. For example, the age of the material is within 2 years, or the electrical conductivity is If it is 200 (mS / m) or more, the improvement of hydraulic property by provision of blast furnace slag can be expected. This is because this crushed concrete also has the same component of cement as so-called regenerated fine powder, that is, it can be said that this crushed concrete contains regenerated fine powder.

  The method for calculating the age is almost the same as in the case of recycled fine powder. That is, the production start date of the concrete for the waste material is set as the start date, and the end date is the day when the crushed concrete is crushed and generated from the concrete waste material.

Also, the method of measuring the electrical conductivity is almost the same as that of the above-mentioned regenerated fine powder. That is, the liquid-solid ratio (ratio of the weight of the sample to the weight of water) of the suspension used for the test is set to 10 as in the above-described test method for regenerated fine powder, and the following procedures (1) to (5) It is measured by.
(1) A sample obtained by removing crushed concrete having a particle size of 10 mm or more is used.
(2) 10 g of crushed concrete as a sample is put into 100 mL of demineralized water and suspended with a stirring rod.
(3) A sample liquid for measurement is allowed to stand for 30 minutes to 3 hours.
(4) The platinum electrode portion of the conductivity meter is immersed in the sample solution while stirring the sample solution.
(5) After the indicated value of the electric conductivity meter is stabilized, the electric conductivity values (S / m, mS / m) are read.

  In addition, the mixing of blast furnace slag suppresses the elution of hexavalent chromium contained in the crushed concrete into the soil, as in the case of recycled fine powder.

  And according to the soil improvement material of this 3rd Embodiment, the following effects can also be show | played. That is, the crushed concrete is used as a soil improvement material in an aggregate-containing state obtained by crushing concrete waste. As a result, effective use of concrete waste is promoted.

  By the way, the improvement effect of hydraulic property and the suppression effect of hexavalent chromium by the application of blast furnace slag to the highly crushed concrete have been confirmed by experiments, and will be described below.

As the concrete waste material, the returned concrete returned to the ready-mix factory was used. That is, after this return concrete was hardened, it was crushed with a crusher, and sieved to take out particles having a particle size of 5 mm or less, and this was used as crushed concrete. Hereinafter, this crushed concrete is also referred to as “recycled sand”. Table 5 shows the experimental conditions. In addition, each numerical value related to water, recycled sand, and blast furnace slag in Table 5 indicates a blending ratio (weight ratio). The mixing ratio (weight ratio) of cement and aggregate in the recycled sand is 1: 3, the age of the concrete waste material related to the recycled sand is about half a year, and its electrical conductivity is 474 (mS / m) and the pH was 12.6.

Initially, the experiment which concerns on the influence on the hydraulic property of the compounding quantity of blast furnace slag is demonstrated. Here, hydraulic properties are evaluated by the compressive strength of the specimen.
That is, first, as shown in C1 to C4 in Table 5, while maintaining the ratio of recycled sand and blast furnace slag to a constant total weight of recycled sand and blast furnace slag (hereinafter also referred to as the weight of the base material). By changing at four levels, a four-level specimen is created.
Next, each specimen blended at each blending ratio is kneaded, and is subjected to empty kneading for 10 seconds, low speed kneading for 20 seconds with the amount of water shown in Table 5, and high speed kneading for 40 seconds. Then, this kneaded material is put into a tubular steel mold having a diameter of 50 mm and a height of 100 mm, and after curing, it is cured at 20 ° C. until the strength test material age. The strength test material age is, for example, 7 days.
Finally, the specimen is removed from the cylindrical steel mold, and the specimen is set on a compression tester to perform a uniaxial compression test. And the value which divided the maximum load until destruction by the cross-sectional area of 50 mm in diameter is made into the compressive strength of the specimen.

FIG. 2 shows the experimental results. As can be seen with reference to FIG. 2, the specimen C1 unmixed with blast furnace slag has a compressive strength as low as 0.1 (N / mm ² ), whereas specimens C2 and C3 mixed with blast furnace slag. , C4, the compressive strength is greatly improved, such as 2.8, 7.0, and 9.8 (N / mm ² ), respectively. Therefore, it can be seen that, even if recycled sand, that is, crushed concrete, is used regardless of recycled fine powder, the compression strength is greatly improved by mixing blast furnace slag when the age is young. And it was proved that this improves the hydraulic property only by mixing blast furnace slag with high activity crushed concrete. Moreover, hydraulic properties could be secured even when using superphosphate lime.

Moreover, FIG. 2 also shows that hydraulic property becomes high as the mixing ratio of blast furnace slag becomes high.
Furthermore, it can be seen from the comparison with the cement mixing specimens K5 and Q4 that are the conventional method of FIGS. 1A and 1B that the hydraulic property equal to or higher than that of the conventional method can be imparted by mixing the blast furnace slag. That is, while the compressive strength of the cement-mixed specimens K5 and Q4 of the conventional method shown in FIGS. 1A and 1B is about 1 (N / mm ² ), the specimen C2 in which blast furnace slag is blended with crushed concrete. , C3, and C4 have a compressive strength larger than that, and can impart hydraulic properties equal to or higher than those of conventional methods.

  For the measurement of hexavalent chromium elution amount, the experiment shown in Table 5 was conducted in accordance with the dissolution test of Ministry of the Environment Notification No. 18 (August 23, 1991, Environment Agency Notification No. 46) on March 6, 2003. This is done for each level.

  Table 5 shows the results. From the comparison between the specimen C1 and the specimens C2 to C4 in Table 5, it can be seen that the elution of hexavalent chromium is suppressed by mixing the blast furnace slag. Therefore, it was proved that elution of hexavalent chromium was suppressed by mixing blast furnace slag even with recycled sand, that is, crushed concrete, regardless of recycled fine powder.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A deformation | transformation and improvement are possible in the range which does not deviate from the summary. In other words, it goes without saying that the equivalents of the present invention are also included in the scope of the present invention.

Claims (8)

Crushing material obtained by crushing concrete;
With superphosphate lime,
And a blast furnace slag . Crushing material obtained by crushing concrete;
Lime superphosphate,
The age of the concrete is within 2 years,
Furthermore, the soil improvement material characterized by having a blast furnace slag. Crushing material obtained by crushing concrete;
Lime superphosphate,
The electrical conductivity of the suspension obtained by adding the crushed material to demineralized water with a liquid-solid ratio of 10 is 200 (mS / m) or more,
Furthermore, the soil improvement material characterized by having a blast furnace slag. The soil improvement material according to claim 2 or 3 ,
The crushed material is a regenerated fine powder that is generated when the aggregate is taken out of the concrete,
The soil characterized in that the blast furnace slag is mixed with the regenerated fine powder so that the weight ratio of the blast furnace slag to the total weight of the regenerated fine powder and the blast furnace slag is 0.2 or more and 0.8 or less. Improvement material. Crushing material obtained by crushing concrete;
Lime superphosphate,
The crushed material is a regenerated fine powder that is generated when the aggregate is taken out of the concrete,
The regenerated fine powder is a heated soil improving material. Crushing material obtained by crushing concrete;
Lime superphosphate,
The soil-improving material, wherein the crushed material is a regenerated fine powder produced when an aggregate is taken out from the concrete. It is a soil improvement material in any one of Claims 1 thru | or 3 ,
The soil-improving material, wherein the crushed material is crushed concrete containing aggregates, which is obtained by crushing the concrete. The soil improvement method characterized by mixing the soil improvement material in any one of Claims 1 thru | or 7 with the soil of improvement object.