JPS63234085A - Artificial basement material consisting of fly ash - Google Patents

Abstract

PURPOSE:To obtain the titled artificial basement material readily applied, having light specific weight and preferably used for backfill material thrown into a filled ground such as an artificial land and bulkhead, etc., filler, material for reclamation, etc., by blending a fly ash with coarse particle content and water at a specific ratio. CONSTITUTION:The aimed material obtained by blending (A) fly ash which is a main component with (B) 20-80wt.% coarse particle content based on the total dried weight of components (A) and (B) and consisting of sand, volcanic ash, bottom ash, light-weight aggregate, etc., and (C) 20-70wt.% water based on the total weight of components (A) and (B). Further the material contains preferably a surfactant.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention utilizes fly ash, which is suitable for use as backfilling material, filler material, reclaim material, etc., to be put into reclaimed land such as artificial islands, sea walls, etc. Regarding artificial ground materials.

``Conventional technology and its problems'' Conventionally, top sand has been mainly used as such artificial ground material. However, artificial ground using sand has the following problems, and solutions to these problems have been awaited.

■ Landfill sand deposited naturally on reclaimed land or seawalls on artificial islands, etc. has a high specific gravity of 1.8 to 1.85, so if the original ground beneath the artificial ground is soft, it may There is a high risk of major ground subsidence and landslide destruction. Therefore, it will be necessary to perform significant ground improvement on the original ground before adding sand to the landfill.

■ It is virtually impossible to perform compaction and compaction at the time of inputting the reclaimed sand, so the reclaimed sand is left loosely piled on the original ground after being input. Therefore, there is a risk that the artificial ground itself may sink due to various loads acting on the artificial ground after it has been deposited, and there is also a high risk that liquefaction of the ground may occur when a strong external force such as an earthquake is applied. For this reason, it becomes necessary to perform ground improvement on the artificial ground itself formed on the original ground.

■ Because reclaimed sand cannot be expected to harden or improve its self-reliance over time, the thickness of the reclaimed sand that has been put in, that is, the deeper the reclaimed depth, the more difficult it is to prevent the outside of cofferdams, revetments, etc. surrounding the reclaimed sand. The earth pressure acting on the shell wall also increases, and therefore it becomes necessary to construct a very strong outer shell wall. Furthermore, as mentioned in (2) above, when performing ground improvement on artificial ground, the accompanying pressure increase must be taken into account.

``Means for Solving the Problems'' Therefore, this invention uses fly ash as a main component, mixes coarse particles and water to form an artificial ground material made of fly ash, and also uses fly ash and coarse particles as a main component. The dry weight ratio of coarse particles to the total dry weight of particles is 20 to 80.
% and the weight ratio of water to the total dry weight is within the range of 20 to 70%, thereby solving the above problems.

Hereinafter, the artificial ground material made of fly ash of the present invention will be explained in detail. First, fly ash is collected from coal ash generated from coal-fired power plants and other coal-burning plants, and is not particularly limited in its type, properties, etc. This fly ash has pozzolanic activity similar to cement, and has the property of hardening itself by reacting with water. Furthermore, since fly ash has a specific gravity of about 1.55 when hardened by adding water, which is smaller than the reclaimed sand, it is possible to form a lightweight artificial ground.

Here, if fly ash is left for a long time after being discharged from the coal-fired power plant, etc., the water content ratio in fly ash may increase, which may reduce the self-hardening properties of fly ash. There is a possibility that there may be. or,
Due to construction conditions or other reasons, there may be cases where it is necessary to make the formed artificial ground develop a predetermined strength in a short period of time. In such cases, it is preferable to add an appropriate amount of a curing aid such as cement or gypsum. For example, in the case of cement, the greater the amount of this hardening aid added, the greater the strength.However, considering the versatility of the artificial ground material of this invention, we have determined that it has sufficient strength as an artificial ground (normal material age). 3kg/cm in 28 days
In order to obtain a compressive strength of 2 to 4% by weight based on the total dry weight of fly ash and coarse particles, it is sufficient.

Then, water and coarse particles are added to this fly ash to produce a slurry-like artificial ground material. That is, fly ash alone is a powder, and as it is, it is difficult to compact and compact it underwater. Therefore, by using fly ash as a slurry-like artificial ground material, the self-hardening properties of fly ash eliminate the need for operations such as compaction, and also facilitate operations such as transportation.

As this water, in addition to clean water such as ordinary tap water and well water, natural water such as lake water and seawater can be used.

Among these waters, seawater is preferable because it is easily available at construction sites or mainly in coastal areas.

The amount of water mixed is 20 to 70%, preferably 40% by weight, based on the total dry weight of fly ash and coarse particles (this weight is also added if the hardening aid is added).
It is within the range of ~60%. If the weight ratio of water is less than 20%, the slump value approaches O, fluidity deteriorates, and construction becomes difficult. Similarly, if the weight ratio of water exceeds 80%, the slump value increases, leading to material separation, resulting in a decrease in the strength of the artificial ground and an increase in the shrinkage rate.

In addition, the water may contain ligninsulfonic acid, if necessary.
Surfactants such as hydroxy acid salts and their derivatives, polyols and their derivatives are added. By adding this surfactant, the fluidity of the slurry-like artificial ground material can be improved and a uniform slurry reclaimed ground can be constructed.

Further, as the coarse particles, sand, volcanic ash, bottom ash (the remainder after fly ash is collected from coal ash), lightweight aggregate, etc. are used. This coarse particles are fly ash,
It is mixed for the purpose of uniformly kneading water, etc., increasing the amount of slurry-like artificial ground material, or adjusting the specific gravity of artificial ground material. In other words, if a slurry-like artificial ground material is produced by kneading only fly ash and water, the fly ash and water will not be mixed uniformly, and the fly ash will aggregate into lumps, resulting in so-called "clumps". Form. Therefore, by mixing coarse particles with these fly ash and water, the formation of the "clumps" due to the coarse particles is suppressed and uniform kneading is promoted. In addition, considering the amount of fly ash produced and the distance from the production site to the construction site, it is uneconomical to construct an artificial ground material in the form of a slurry with only fly ash and water, so it is necessary to replace it with fly ash. It is preferable to appropriately mix a moisturizing filler. In particular, the volcanic ash is preferable as a fly ash replacement material because it has a relatively high pozzolanic activity, although it is not as good as that of fly ash.

Furthermore, when building a tunnel using the shield construction method on the artificial ground of this invention, if the specific gravity of the ground around the shield excavator, including the artificial ground, is too light, it will be difficult to suppress the buoyancy of the tunnel by the weight of the upper ground. There is a concern that this could impede excavation or cause the tunnel to collapse. In this way, it is preferable to adjust the specific gravity of the artificial ground material as appropriate by mixing coarse particles in accordance with its use. The amount of the coarse particles mixed is 20 to 80%, preferably 30 to 60%, in dry weight ratio of the coarse particles to the total dry weight of fly ash and coarse particles.

If the dry weight ratio of the coarse particles is less than 20%, the specific gravity of the artificial ground will be too light and there is a risk that it will have an adverse effect on the surrounding area during or after construction. In addition, the dry weight ratio of coarse particles h<so
If it exceeds %, the strength required for the artificial ground will not be achieved because the fly ash will be reduced by that amount.

In this way, a predetermined amount of water and coarse particles are mixed with the fly ash, and if necessary, curing aids and surfactants are added, and this mixture is kneaded with a normal mixing machine such as a forced mixer. , it becomes the desired slurry-like artificial ground material. Then, this artificial ground material is used for reclamation by being put into the seabed or seawall that is the planned reclamation site through a transfer pipe, or it is placed on the ground as backfill soil or embankment to form an artificial ground. .

The artificial ground formed in this way has sufficient compressive strength of 3 kgr/cm" or more, so there is no need to consider ground subsidence or liquefaction of the artificial ground itself. Therefore, ground improvement work on artificial ground becomes unnecessary.

Along with this, since the artificial ground material has self-hardening properties,
There is no need to make the outer shell wall surrounding it strong,
Construction becomes easier. Furthermore, since the specific gravity of the hardened artificial ground is lighter than the specific gravity of reclaimed sand, which is the conventional artificial ground material, there is no fear of subsidence or landslide destruction of the original ground, and there is no need for ground improvement work on the original ground.

In particular, artificial ground materials contain coarse particles such as volcanic ash,
This makes it possible to uniformly mix the mixture of fly ash, water, etc., and also allows the specific gravity of the artificial ground to be adjusted to match the construction conditions. Furthermore, when the coarse particles are volcanic ash, this volcanic ash has the same pozzolanic activity as fly ash, so it can be mixed as a fly ash replacement material.

"Example" Hereinafter, the artificial ground material made of fly ash of the present invention will be explained in more detail with reference to Examples, but the artificial ground material made of fly ash of the present invention is not limited to the examples shown below.

(Experiment example) By mixing fly ash, volcanic ash, cement and water,
An artificial ground material made of the fly ash of this invention was manufactured. The fly ash was discharged in a wet state from a coal-fired power plant and was used without drying after being left for one week to one month. The physical properties of fly ash are shown in Table 1.

Below is the margin of this page Table 1 These fly ash are made from coal produced in Hokkaido, and have a high calcium content of about 6%. Therefore, if it is discharged and stored in a dry state, it is presumed that due to the self-hardening properties of fly ash, it will develop a compressive strength of approximately kgf/c+a'' upon mixing with water.

Volcanic ash is mixed as an extender for artificial ground material made of fly ash, and is produced from central Hokkaido.
After removing 2III11 or more particles, it was used in a wet state. The natural moisture content of the volcanic ash used in the experiment was 22.
．． 8%, average particle size is 290 μm, and specific gravity is 2.59.

Portland cement is commonly used as a hardening agent for artificial ground because of the above-mentioned self-hardening properties of fly ash, which may be degraded by wet conditions, and the need to obtain a certain level of strength within a short period of time. The additives were added within a range of several percent. As water for mixing fly ash, volcanic ash, and cement, seawater collected from Tokyo Bay was filtered and used.

A slurry-like artificial ground material was prepared by kneading each of the above materials in a 3e Hobart mixer for 5 minutes. The rotational speed of the Hobart mixer is 60 rpm with planetary motion and 14 Orpm with rotational motion.

The fluidity, specific gravity, and material separation of the slurry-like artificial ground material thus obtained were investigated.

The fluidity of the artificial ground material was measured using a special slump cone for mortar and plaster that has the same shape as a normal slump cone for concrete and a height of 15 cm. In addition, the specific gravity of the artificial ground material was measured using a mud balance, which is used to measure the density of drilling mud. Furthermore, material separation of the artificial ground material was measured using a 100 ml measuring cylinder.

Next, after measuring each characteristic of these artificial ground materials, this artificial ground material was filled into a vinyl chloride mold with a diameter of 5 cm and a height of 1'0 cm, and the upper surface was closed with a polyethylene film. It was cured in seawater whose temperature was maintained at ℃. The strength characteristics of the artificial ground material thus hardened were then measured. The strength characteristics were mainly measured using a uniaxial compression test (strain rate: 0°8%/min).

In the following experimental results, terms indicating the composition of fly ash, volcanic ash, and cement are defined as follows.

・Volcanic ash content (As): fly ash, weight ratio of dry volcanic ash to the total dry weight of volcanic ash ・Cement addition rate (Ac): weight ratio of cement to the total dry weight of fly ash, volcanic ash ・Blended water content ratio (Wp) : Weight ratio of total moisture to total dry weight of dry fly ash, dry volcanic ash, and cement Figure 1 shows the weight ratio of cement as a hardening aid when volcanic ash is not mixed in the artificial ground material (As = 0%). FIG. 3 is a diagram showing the relationship between the added amount of and the compressive strength of artificial ground. Other conditions are shown in the figure.

The fly ash used in this experiment contains about 6% calcium as shown in the table above, and therefore,
If it is discharged and stored in a dry state, it is estimated that it will develop a compressive strength of several kgf/am.
If this fly ash is stored in a dry state, it is considered unnecessary to add cement as a hardening aid. However, since this fly ash was left in a wet state for one month after being discharged, it is thought that the self-hardening properties that it should originally have had deteriorated. However, even with such fly ash, strength can be expected to increase by adding a small amount of cement.

FIG. 2 is a diagram showing the relationship between the amount of volcanic ash added and the compressive strength of artificial ground. Other conditions are shown in the figure. Although volcanic ash alone cannot provide sufficient compressive strength, it is understood that if it is used in combination with fly ash, sufficient strength will be developed as a material for artificial ground. In this case, within the range of volcanic ash content of 37% to 63%,
No significant difference was observed in the strength development of the artificial ground.

FIG. 3 is a diagram showing the relationship between the wet density of the artificial ground after hardening and the volcanic ash content. As shown in the figure, it is possible to adjust the specific gravity of the artificial ground formed by adjusting the amount of volcanic ash mixed appropriately. This result shows that volcanic ash,
This is due to the fact that the specific gravity of volcanic ash is greater than that of fly ash, but it is also thought to be due to the fact that material separation and shrinkage become greater due to the addition of volcanic ash. In other words, Figure 4 is a diagram showing the relationship between the breathing rate and contraction rate of artificial ground and the volcanic ash content.As shown in Figure 4, as the volcanic ash content increases, the breathing rate and contraction rate also increase. In other words, the material separation of the slurry-like artificial ground material increases, and the volcanic ash content increases to 60 to 7.
It has peaked at around 5%. This result is because the particle size of volcanic ash is larger than the particle size of fly ash, so fly ash fills the gaps between volcanic ash without any gaps, which increases the apparent specific gravity of the mixture due to the so-called particle size adjustment effect. However, it can be interpreted that this is because free water was generated.

FIG. 5 is a diagram showing the relationship between the wet density of the artificial ground after hardening and the mixed gold/water ratio. As in Figure 3, it can be seen that the specific gravity of the artificial ground can be adjusted by increasing or decreasing the volcanic ash content. Similarly, it is also possible to adjust the specific gravity of the artificial ground to some extent by increasing or decreasing the mixed metal/water ratio.

Figure 6 shows 1. It is a figure which shows the relationship between the slump value which shows the fluidity of a slurry-like artificial ground material, and a compound water ratio. Although it depends on the amount of volcanic ash mixed, the fluidity of the artificial ground material also improves as the gold-water ratio increases. Similarly, FIG. 7 is a diagram showing the relationship between the slump value and volcanic ash content of artificial ground materials. A similar trend to the results shown in FIG. 4 is shown.

Based on the experimental results shown above, we will discuss the blending ratio of each mixture suitable as an artificial ground material. Considering the versatility of artificial ground materials, the required performance values are as follows.

- Axial compressive strength: 3 kgr/am at 28 days old
■Wet density: 1.7 g/am' or less ■Breathing rate: 3% or less ■Fluidity Varnish lamp value 12 cm or less The compounding ratio that satisfies these performances is as shown in Table 2 below.

Table 2 "Effects of the Invention" As explained in detail above, the artificial ground material made of fly ash of the present invention has fly ash as its main component, mixed with coarse particles and water, and The dry weight ratio of the coarse particles to the total dry weight of fly ash and coarse particles was within the range of 20 to 80%, and the weight ratio of water to the total dry weight was within the range of 20 to 70%. Because it is a concrete material, it hardens on its own after being poured into a planned landfill site, etc., and has sufficient strength as an artificial ground, so there is no need to consider ground subsidence or liquefaction of the artificial ground itself. Therefore, there is no need for ground improvement work on the artificial ground, and there is no need to strengthen the outer shell wall surrounding the artificial ground, making construction easier. Furthermore, since the specific gravity of the hardened artificial ground is lighter than the specific gravity of reclaimed sand, which is the conventional artificial ground material, there is no risk of subsidence or landslide destruction of the original ground, and there is no need for ground improvement work on the original ground. . Coarse particles such as volcanic ash are mixed into the artificial ground material of this invention, which makes it possible to uniformly mix the mixture of fly ash, water, etc. The specific gravity can be adjusted.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of cement added and the compressive strength of the artificial ground, Figure 2 shows the relationship between the amount of volcanic ash added and the compressive strength of the artificial ground, and Figure 3 shows the relationship between the amount of cement added and the compressive strength of the artificial ground. Figure 4 shows the relationship between the wet density of the ground and the volcanic ash content. Figure 4 shows the relationship between the breathing rate and shrinkage rate of the artificial ground and the volcanic ash content. Figure 5 shows the wet density of the artificial ground after hardening. Figure 6 is a diagram showing the relationship between the slump value of the artificial ground material and the mixed gold-water ratio, and Figure 7 is the relationship between the slump value of the artificial ground material and the volcanic ash content2. FIG.

Claims (4)

[Claims] (1) An artificial ground material consisting mainly of fly ash, mixed with coarse particles and water, in which the dry weight ratio of the coarse particles to the total dry weight of fly ash and coarse particles is An artificial ground material made of fly ash, characterized in that the weight ratio of water to the total dry weight is within the range of 20 to 80%, and the weight ratio of water to the total dry weight is within the range of 20 to 70%. (2) The artificial ground material made of fly ash according to claim 1, wherein the coarse particles are volcanic ash. (3) An artificial ground material made of fly ash according to claim 1 or 2, characterized in that a hardening aid is added. (4) An artificial ground material made of fly ash according to claim 1, 2 or 3, characterized in that a surfactant is added thereto.