JPH0372590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a floating concrete material with a specific gravity of 1.0 or less and a method for manufacturing an underwater floating structure using the material.

Due to their economic efficiency and importance, various types of underwater floating structures such as floating fish reefs, floating wave-dissipating structures, floating bridges, and artificial floating islands have attracted increasing public interest as marine development has developed in recent years. However, in order to enable the construction of the above-mentioned structure, this invention uses a floating concrete material that floats sufficiently in water, has a low water absorption rate, and has a large pressure resistance depth. The present invention provides a method for manufacturing a submerged floating reinforced concrete structure.

By the way, as well as conventional aerated concrete, ultra-lightweight concrete in which hollow bodies such as natural pumice, expanded polystyrene, perlite, and shirasu balloons are mixed and solidified with cement is known as concrete with a specific gravity of 1.0 or less. Because hollow products were used as they were, they all absorbed water, broke, and settled when immersed in water. In addition, in conventional syntactic foam, hollow bodies such as glass balloons and pressure-resistant glass bulbs are filled and solidified in resin.
The formulation is limited to a single product or two products, and the particle size distribution is
It has been difficult to obtain lighter-than-water composites using heavy cement binders because they are discontinuous, confined to narrow areas, and have certain limitations on filling rates. Floating concrete that floats underwater and can be used safely has not yet been known.

The present invention will be described in detail below. The present invention relates to a cement composite material in which a hollow body as a buoyancy material is filled into a cement-based binder and solidified.

Using cement as a binder has many advantages such as being cheap, harmless, and easy to handle. However, for example, when the water-cement ratio is 50%, the specific gravity of cement paste is around 1.82. Because it was too heavy, it was extremely difficult to use it as a floating body.

However, the inventor of the present application has focused on the fact that most of the properties of a composite material are determined by the properties and proportions of both the binder and the filler. , regarding the hollow body of the filler,
By selecting materials, sorting products, and adjusting particle size, cement composites can be made to float in water.

The material for the hollow body must have a strong and stable bond with cement, high compressive strength, and low true density. Products such as micro hollow spheres, hollow multivesicular bodies, and granular foam glass made from substances are generally available.

Among these products, the hollow body to be filled as a buoyancy material must have a completely sealed surface shell wall so as not to absorb water into the internal space, and have a sufficiently small apparent specific gravity so as to have a large surplus buoyancy. And at the same time,
In order to avoid destruction by water pressure, those with a maximum pressure resistance depth that is greater than the diving depth used are selected, and the particle size of these selected items is adjusted and used so that the filling rate is sufficiently large. .

However, the relationship between obtaining a large maximum pressure depth with a small apparent specific gravity is contradictory to each other, and the relationship between particles having different particle sizes is still unclear.

By elucidating the relationship between buoyancy performance and mechanical strength when the particle size and material of the hollow body are different, the present invention is capable of determining the required apparent specific gravity and maximum withstand pressure even when the particle size and material are different. It has been found that a product that satisfies both depths can be obtained, so by combining these methods, the particle size can be adjusted to have a continuous distribution over a wide range, and the filling rate can be further improved. This allows the cement composite to float in water.

In other words, Figure 1 shows a hollow sphere with two particles having the same thickness and diameter ratio of the surface shell wall and different particle sizes.
The surface area is inversely proportional to the diameter. Similarly, when they are made of the same material, their mechanical properties such as apparent specific gravity and maximum withstand pressure are the same. Furthermore, when these similar hollow spheres with different particle sizes are arranged in the same manner (for example, in a cubic arrangement), the buoyancy properties such as the excess buoyancy per unit volume in seawater and the maximum pressure resistance depth become the same. Therefore, it can be seen that in the case of a composite obtained by solidifying each of these with a binder, the filling ratio is the same, so the specific gravity, pressure resistance, and material strength due to the content of the binder are all the same. .

In other words, among similar hollow spheres made of the same material, large and small diameter particles differ only in surface area, but have the same buoyancy and mechanical properties. Therefore, hollow bodies are created by selecting a group of similar bodies whose similarity ratio, which is the ratio of shell wall thickness to diameter, is within a certain range in order to satisfy the desired apparent specific gravity and maximum pressure depth. As a result, safety as a buoyancy material can be ensured.

Therefore, the method for selecting buoyant materials from among the hollow products is to first remove those with damage or small holes on the surface shell wall, and sedimentation components such as clay, by using a water gutter method or the like. We aim to improve quality by removing water and selecting those that do not absorb water into the internal space. Next, a group of similar hollow bodies is obtained by a pressure-resistant residual method using a pressurized liquid in a pressure vessel, a flotation method using a specific gravity liquid, etc. so as to obtain the desired apparent specific gravity and required maximum pressure-resistant depth. This makes them buoyant materials that can be safely used underwater.

Furthermore, for various hollow bodies of different materials and manufacturing methods, the range of the above-mentioned similarity ratio differs depending on the true density and compressive strength of the material. By selecting and using particles that meet the maximum pressure resistance depth, it becomes possible to obtain particles of various sizes in a wide range of sizes. Therefore, if these fine particles to coarse particles are mixed to have an appropriate particle size distribution, the filling rate of the hollow body will be increased in the same way as the mixing method for ordinary concrete, and at the same time, the mixability and fluidity will be good. You will be able to make it happen.

That is, by adjusting the particle size of the buoyant material, for example, by using micro hollow spheres as fine particles, flotation separation when mixed with the cement binder hardly occurs, and dispersion and mixing properties are also improved. Furthermore, if hollow polyvesicular bodies having a small to coarse particle size are added to the above-mentioned fine particle fraction as a coarse particle fraction, the overall volume performance rate of the buoyancy material will be improved. In addition, by adjusting the overall particle size distribution of these fine particles to coarse particles, fluidity and workability are improved, so molding can be easily performed by pouring into a mold, and molding can be easily performed by pouring into a mold. After molding, a product with uniform specific gravity and strength can be obtained.

The cement composite thus obtained becomes sufficiently buoyant in water as the filling rate of the hollow body increases, but its strength decreases as the amount of binder decreases. . Therefore, in order to obtain a cement composite having the desired strength, specific gravity, and pressure resistance, it is recommended to first determine the relationship between the filling rate and the strength of the composite for each type of hollow product through experiments. Since the filling ratio, apparent specific gravity, and maximum pressure-resisting depth of the hollow body required for this are given, the selection range of the group of analogues that satisfies these is also automatically determined.

In order to obtain a composite with excellent buoyancy performance and material strength, as mentioned above, for the hollow body, a material with high compressive strength and low true density is used,
By narrowing the selection range of similar groups, we carefully select those with excellent quality, and at the same time, we also carefully select the type of binder, the addition of admixtures, and the application of various processing methods. By arranging technical means,
This is also possible by increasing the bonding strength.

As detailed above, the present invention solves the above-mentioned difficulties by elucidating the relationship between buoyancy properties and mechanical properties when the particle size and material of the hollow body are different. The hollow body to be filled is
After selecting a group of analogues that satisfy the desired apparent specific gravity and maximum pressure resistance depth, blending from fine particles to coarse particles is carried out over a wide range to obtain the desired filling rate, mixability, and fluidity. By continuously adjusting the particle size distribution, we have succeeded in providing a floating concrete material that can be safely used underwater.

In order to manufacture an underwater floating structure using the above-mentioned floating concrete material, a reinforcing steel structure is enclosed inside to compensate for the necessary strength of the structure. In other words, the manufacturing method for underwater floating structures involves determining the strength, specific gravity, and pressure resistance of the floating concrete material to be used based on the structure's shape, size, underwater resistance, diving depth, desired buoyancy, underwater weight, etc. , the reinforcing structure required for structural calculations is assembled, placed in a mold, and then integrally formed by pouring the above-mentioned materials into the mold.

The underwater floating reinforced concrete structure manufactured in this way is a rigid body with homogeneous specific gravity and strength as a whole, so when it is floating and moored underwater,
Even when shaken by waves, the center of buoyancy and center of gravity do not shift, making it stable, sturdy, and highly durable. Of course, it is made of a material with a large pressure resistance depth and low water absorption, and has the necessary buoyancy and safe strength, so it is safe for long-term underwater mooring. It is also effective as a base for seaweed to adhere to, so if it is adjusted to have an appropriate underwater weight and placed on the seabed, it is possible to create a seaweed bed even on a soft floating muddy seabed.

As described above, the underwater floating concrete structure of the present invention has excellent underwater buoyancy performance, is inexpensive, and can be mass-produced, so it can be widely used as various marine structures, such as: It is expected that it will have great effects if used for constructing ocean farms that make use of the ocean three-dimensionally.

<Example> The buoyancy materials are micro hollow spheres with a fine particle size (a mixture of two types) with a bulk volume of 1.2 and an air dry weight of 188 g, a hollow multivesicular body with a small particle size (a mixture of three types) of 1.6 and 500 g, and a hollow multivesicular body with a coarse particle size. 1.6, 265g was used. These buoyant materials have previously had surface shell wall defects removed, and the particle size has been adjusted to provide good workability and sufficient volume performance.

Ordinary Portland cement is used as a binding material.
A cement paste consisting of 800 g, 150 g of watertightening material (fine particle size activated silica), 15 g of high performance water reducer, and 242 c.c. of water was used. When this paste alone was solidified, the specific gravity C was 2.017. The water-tight binding material reduces water absorption and is effective in preventing corrosion of reinforcing steel due to seawater intrusion into the concrete molded body.

When the above buoyant material and engagement material are mixed and mixed with 293 c.c. of water and mixed and cast, the volume V = 2975 c.c. and the weight W =
Floating concrete with an excess buoyancy of 2362 g, an excess buoyancy Q ₂ of 612 g, and a specific gravity J of 0.794 was obtained.

Here, assuming that only the 293 c.c. of additional mixed water was used as water adsorbed on the surface of the buoyancy material, and no voids were formed, the apparent specific gravity Z of the entire buoyancy material is 0.478, and the filling rate g is Calculated as 0.799. Therefore, even though the density of the binder C=2.017 is very large, since Z≪1.0 and g≫0.524, the specific gravity of floating concrete, J=Z×g+C*(1−g)
= 0.794, it floats underwater and has sufficient underwater buoyancy even as a reinforced concrete structure.

As a trial, the compressive fracture strength of this floating concrete was σ ₃₃ =46.3 Kg/cm ² on the 33rd day after pouring.

Also, from the 13th day after pouring this floating concrete,
It was continuously immersed in water at a depth of 0.20 m until the 28th day, and at a depth of 2.20 m from the 28th to the 210th day, and the measured specific gravity values on each day were 0.806, 0.808, and 0.813, so it was found that approximately Even after 200 days of immersion in water, the specific gravity does not increase.
The water absorption was only 0.007, and the water absorption was extremely small.

From the above examples, it has become clear that this invention actually makes it possible to produce a completely new floating concrete and is useful. These are in no way intended to indicate the scope or limits of the properties of floating concrete. Similarly, depending on changes in the type and properties of the binder or buoyant material, molding method, etc., it is of course possible to construct optimal technical means other than the above embodiments.

[Brief explanation of drawings]

FIG. 1 shows a comparison of the buoyancy and mechanical properties of two similar hollow spheres, one with a large particle size and one with a small particle size, and the various properties of the composite.

Claims (1)

[Claims] 1. A cement composite material made by uniformly mixing and solidifying a binding material mainly made of cement and a hollow body made of a material that has a strong and stable bonding force with the binding material. In this process, the hollow body is selected as a buoyancy material whose surface shell wall is completely sealed and which satisfies both the desired apparent specific gravity and maximum pressure resistance depth, and the buoyancy material is A floating concrete material that is characterized by being able to float in water, by blending the material's particle size from fine to coarse and adjusting the particle size to obtain the desired filling rate and fluidity. 2. In a cement composite material, which is made by uniformly mixing and solidifying a binding material mainly composed of cement and a hollow body made of a material that has a strong bonding force with the binding material and is stable, the hollow body The body is selected as a buoyant material whose surface shell wall is completely sealed and which satisfies both the desired apparent specific gravity and maximum pressure resistance depth, and the particle size of the buoyant material is reduced. The floating concrete material, which is characterized by its ability to float in water, is made by blending everything from particles to coarse particles and adjusting the particle size to obtain the desired filling rate and fluidity. Adjust the specific gravity and pressure resistance to be obtained, assemble the reinforcing structure necessary for the design of the structure, and cast the above material into the installed formwork to integrally form it. Method for manufacturing underwater floating reinforced concrete structures.