JP2001200525A - Method for improving physical properties of material of structure by using microorganism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for intentionally changing physical properties of materials forming a structure, including both of natural ground materials such as earth and rock masses, and artificial construction materials such as concrete, in the fields of civil engineering, construction, resources, and environmental engineering, or in the field of archeology. SOLUTION: First, to microorganisms inhabiting the materials of the structure, chemical components including hydrogen ions, oxygen, moisture, organic matters, and salinity, for instance, are given, to thereby control the viable cell count of specific microorganisms. Then, to the microorganisms inhabiting the materials of the structure, physical factors including temperature, ultrasonic waves, current, vibrations, pressure, light, radioactivity, a magnetic field, for instance, are given, to thereby control the viable cell count of the specific microorganisms.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to civil engineering, architecture, resources,
In the fields of environmental engineering and archeology, etc., we aim at structural materials including both natural ground materials such as soil or rock and artificial construction materials such as concrete, A method for changing.

[0002]

2. Description of the Related Art In the field of engineering, for example, in the field of civil engineering and architectural engineering, when constructing a structure, the ground (soil or bedrock) of the foundation on which the structure is supported must be uniform and uniform. It is preferable in terms of design and construction. However, the ground in nature is never uniform, complex, and often heterogeneous. Therefore, a part or the whole of the target ground is often improved according to the purpose (for example, increase in strength). For example, when a large structure such as a nuclear power plant or a dam is targeted, seismic reinforcement and foundation improvement are applied to protect the structure from natural disasters such as earthquakes in view of the importance of the structure.

[0003] In the case of soil ground, various methods are generally employed for soil reinforcement in terms of strength and deformation characteristics, such as compacting the ground dynamically or statically or injecting a chemical solution. On the other hand, rock bolts and anchors are often installed on rock, but when there is a partially weathered part, this problem is dealt with by replacing the weakened part that has weathered with a harder material. Is the current situation.

[0004]

The ground materials (rock, earth, etc.) and construction materials (metals, concrete, etc.) used as structural materials have been subjected to possible corrosion countermeasures in advance, but have been completed. No further processing is done, and it is therefore often left to the existing natural environment. In the case of a structure installed on the ground, it is strongly affected by the ecology of microorganisms in the ground.

[0005] When the structural material is bedrock For example, in the case of sedimentary rock, a carbonate mineral (CaCO ₃ ), which is a typical cementation substance, is dissolved by acids such as hydrochloric acid and sulfuric acid. When the cementation effect decreases or disappears, a weathering phenomenon occurs in the ground material. As a result, for example, the strength of the ground decreases in terms of mechanical characteristics.

When the structural material is soil The microorganisms in the soil secrete various adhesive substances and have a strong tendency to aggregate with clay particles. An example is a filamentous fungus such as Fusarium that forms spores wrapped in a sticky substance. It is an established fact that such effects are a major factor in determining soil strength. On the other hand, if the distribution of microorganisms exceeds the limit and becomes coarse, the strength of the soil may decrease. This is because the habitat of the microorganisms deteriorates, and as a result, the microorganisms die and the number of viable bacteria decreases.

When the structural material is metal Deterioration of the metal material is related to metal corrosion. For metal corrosion to occur, the presence of suitable water and a reduction reaction that consumes electrons are required. Microorganisms in the soil meet these two conditions in various ways and promote corrosion. Typically, there are sulfur oxidizing bacteria, sulfate reducing bacteria, iron oxidizing bacteria, and the like.

When the structural material is concrete Sulfate ions in gypsum (calcium sulfate) contained in concrete are reduced by sulfate-reducing bacteria to elemental sulfur and hydrogen sulfide, which causes deterioration of concrete.

On the other hand, sulfides and sulfur contained in the concrete material or produced by the sulfate-reducing bacteria are oxidized by the sulfur-oxidizing bacteria to form strongly acidic sulfuric acid, which further accelerates the deterioration of concrete.

As described above, the property change of the structural material related to microorganisms is left to the natural environment, and as a result, unintended deterioration of strength, acceleration of deformation, deterioration of durability, etc. occur in artificial construction materials, Further, even in the case of a natural ground material, problems such as unintended deterioration of strength, acceleration of deformation, deterioration of durability, and deterioration of water permeability occur.

[0011] Furthermore, the injection of a chemical solution, which is carried out as one method of ground improvement, has a very serious living environment problem such that the chemical component penetrates over a wide area in the ground, which is a major factor causing local environmental pollution.

[0012]

Means for Solving the Problems The present invention specifies microorganisms that already inhabit structural materials including both artificial construction materials and natural ground materials, and administers chemical and physical components to the microorganisms. The number of viable bacteria was controlled by manipulating the habitat.

[0013]

[Action] Identify the natural ground materials among the structural materials, for example, those microorganisms already inhabiting the ground such as soil and bedrock that affect the properties of the materials. Is administered to control the number of viable bacteria.

This makes it possible to control the amount of microorganisms that react with the natural ground material, that is, the variable mass of the natural ground material.

Among the structural materials, microorganisms which already exist on the surface of an artificial construction material such as a metal or concrete structure or on the surrounding ground are specified, and those which affect the properties of the material are specified. The number of viable bacteria is controlled by administering chemical or physical components that are growth / suppression / killing factors.

This makes it possible to control the amount of microorganisms reacting with the artificial construction material, that is, the variable mass of the construction material.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment, it is assumed that the rock is intentionally softened in the ground material in order to improve the efficiency of excavation work. Rocks are roughly divided into sedimentary rocks, igneous rocks and metamorphic rocks. Among them, for example, in the case of sedimentary rocks, mudstone, sandstone, rock, tuff and the like correspond. Each of these rocks was formed by depositing clay, sand, rubble, and volcanic ash on the bottom of the water or on the ground surface, and then consolidated under the pressure of the ground. What is needed for consolidation is, for example, in the case of sandstone, a material for bonding between sand particles, that is, a cementation material.

The most typical cementation material is calcite (CaCO ₃ ), a carbonate mineral.
There is. This calcite (CaCO ₃ ) is generally used as a cementation material for sedimentary rocks.

Therefore, for example, after drilling a hole in the sedimentary rock, the above-mentioned sulfur oxidizing bacteria are mixed. The strong sulfuric acid secreted by the sulfur oxidizing bacteria causes calcite (CaC), a cementation substance that fills the space between rock particles.
O ₃ ) is dissolved, the bonding force between the particles is weakened, and softening of the rock consolidated as sedimentary rock occurs.

Next, a second embodiment of the present invention will be described. Here, of the structural materials, an example in which the properties of the soil soil, which is a natural material, is changed is adopted.

A method for improving the properties of the soil ground with higher strength will be described.

As described above, a major factor for maintaining the strength of the soil soil is the distribution environment of microorganisms that secrete adhesive substances. Therefore, for example, the ecological environment of the filamentous fungi forming the adhesive substance is externally controlled.

[0023] Filamentous fungi are generally considered to have sufficient aeration and moisture conditions, as well as replenishment such as organic matter content, as living conditions. Therefore, components such as oxygen, water, and organic substances are administered (injection of oxygen, injection of water, burying of organic substances) to activate the ecology of the microorganisms and to proliferate.

The filamentous fungus thus identified is actively multiplied, a large amount of sticky substance is obtained, and the aggregate structure of the ground is further strengthened. Therefore, the ground strength is improved.

Next, as a third embodiment, a description will be given of a method of making the foundation of a concrete structure having a foundation buried in the ground more durable.

As described above, a major factor that causes deterioration of concrete structures is that sulfate ions contained in concrete are reduced by sulfate reducing bacteria that inhabit the ground to become elemental sulfur and hydrogen hydride, thereby causing deterioration of concrete.

Further, sulfides and sulfur contained in concrete or produced by sulfate-reducing bacteria are oxidized by sulfur-oxidizing bacteria to form strongly acidic sulfuric acid, which further accelerates the deterioration of concrete.

Next, the ecology of the sulfur oxidizing bacteria and the sulfate-reducing bacteria is examined. The sulfur oxidizing bacteria are classified as chemoautotrophic bacteria, use reduced inorganic compounds as an energy source, and use carbon dioxide as a carbon source. Is a microorganism that utilizes The growth pH has a property of 0.5 to 5.5 and the growth temperature has a property of 10 to 37 ° C.

[0029] Sulfate-reducing bacteria are a typical type of anaerobic bacteria.

These

[0028]

Thus, components such as hydrogen ions, temperature, and oxygen are appropriately administered to the ground (eg, injection of an alkaline solution, injection of high-pressure steam, injection of oxygen, etc.) to destroy the ecological environment of the microorganism. Means include burying, mixing, spraying, and pouring.

In this way, the sulfate-reducing bacteria and the sulfur-oxidizing bacteria can be positively killed, and it is possible to prevent the deterioration of the concrete structure to which these react naturally.

As an application of the first to third embodiments, for example, in the case of geological disposal technology for radioactive waste, microorganisms living in very small voids existing in natural barriers and artificial barriers are specified. Similarly, by controlling the habitat environment, when various waste products such as microorganism products and feces or microorganisms die, the voids are filled with dead bodies of the microorganisms themselves. Thereby, the permeability of the natural barrier and the artificial barrier can be improved.

Other factors controlling the ecological environment of various microorganisms include chemical components such as hydrogen ions, oxygen, water, and organic substances, as well as various nutrients and salts, and physical components include the above-described temperature. And ultrasonic, current, vibration, pressure, light, radioactivity, magnetic field, etc.

In the first embodiment, the acceleration of rock mass deterioration and the second
In the embodiment, reinforcement of soil was described, and in the third embodiment, prevention of deterioration of concrete structures was described. The same can be applied for conflicting purposes such as strengthening of rock, weakening of soil and active deterioration of concrete structures. Further, artificial construction materials are not limited to concrete, and various other materials such as metal and wood can be used.

[0035]

[Effect] Among microorganisms already inhabiting structural materials including both artificial construction materials and natural ground materials, microorganisms having ecological functions related to material properties are specified. The habitat is changed by administering chemical and physical components.

[0036] Thus, it is possible to intentionally kill / suppress / proliferate the specific microorganism and control the viable cell count.

In other words, the properties of the structural material can be intentionally varied by utilizing the ecology of the microorganism.

Therefore, there is no environmental pollution associated with the ground improvement as in the past, and the physical properties such as strength characteristics (hardening / softening), deformation characteristics, durability characteristics, and water permeability of the structural material can be freely controlled safely and at low cost. It has an excellent practical effect of being able to do so.

Claims (2)

[Claims] 1. A structure material made of microorganisms, wherein a chemical component is administered to microorganisms inhabiting a structure material including a ground material and a construction material so as to control the viable count of a specific microorganism. Method of improving physical properties of 2. A structural material based on a microorganism, wherein a physical component is administered to a microorganism living in a structural material including a ground material and a construction material to control the viable count of a specific microorganism. Method of improving physical properties of