KR102205003B1 - Shotcrete composition for marine structure - Google Patents

Abstract

The present disclosure provides a shotcrete composition for marine structures, having no steel fibers, and including 25 to 35 wt% of cement, 55 to 65 wt% of sand, 1 to 5 wt% of oyster shell powder, 1 to 5 wt% of metakaolin, 0.1 to 5 wt% of a melamine-based water reducing agent, 1 to 5 wt% of bauxite, 1 to 5 wt% of ocher, and 0.1 to 5 wt% of methylcellulose. The shotcrete composition for marine structures uses metakaolin instead of silica fume for high strength expression, thereby significantly reducing the unit cost of shotcrete.

Description

Shotcrete composition for offshore structures {SHOTCRETE COMPOSITION FOR MARINE STRUCTURE}

The present disclosure relates to a shotcrete composition for offshore structures.

Artificial reef is a fishing facility for the purpose of protecting and cultivating marine life by artificially installing structures on the seabed or underwater. Sofa blocks and tetrapods are installed on the shores of the waves. In order to prevent loss and movement, artificial reefs, sofa blocks, and tetrapods are made of concrete.

Concrete can cause problems in the manufacturing process and delivery process due to its heavy weight, and problems in coloring offshore structures due to its monotonous grayish-white color. Although artificial rock mass has been developed as a lightweight material that can easily manufacture such coloring and molding structures (KR 10-0810746 B1), it has a problem that cannot be used for artificial reefs due to weak compressive strength.

Shotcrete is the most important support member in the construction of tunnels or underground spaces, as it is a temporary support member to stabilize the excavation section immediately after excavation of a tunnel or underground space, and is used as a permanent support material even after completion of a tunnel or underground space. Korean Patent Registration No. 10-0376546 manufactured an artificial reef using the excellent adhesion of shotcrete.

However, the conventional structure made of concrete or shotcrete has a problem in that it cannot create a habitat for marine plants such as seaweed due to the cement poison.

For the high performance of shotcrete, silica fume, a fine powder admixture, is essentially used. However, as the production of silica fume takes a lot of electricity, the price of silica fume is up to 10 times higher than that of cement. Moreover, when a large amount of silica fume is used, the unit quantity increases in order to obtain the same dough concentration, causing problems such as initial cracking, and when silica fume is mixed, bleeding is small, so the amount of water retained increases. As a result, there was a problem in that the amount of high-performance water reducing agent, which has a large drying shrinkage and is also expensive, increases proportionally.

On the other hand, in the case of shotcrete containing steel fibers, there is a problem that agglomeration occurs frequently in the transfer hose due to magnetism between the steel fibers during the transfer of the shotcrete, resulting in poor workability, and rebound occurs during the spraying of the shotcrete, causing the steel fibers to become dark. It can also cause environmental problems because it is discharged with burrs.

On the other hand, oyster shells left on the shore are becoming the main cause of marine environmental pollution, and there is a need to develop technologies that can be recycled by developing their use in an environmentally friendly manner.

The present disclosure was conceived to solve the above problems, and the present disclosure not only significantly reduces the unit cost of shotcrete by using metakaolin instead of silica fume for high strength expression, but also oyster shell powder, metakaolin, melamine-based water reducing agent, An object of the present invention is to provide a shotcrete composition for marine structures capable of promoting the growth of marine plants without impeding the expression of high strength by using bauxite and loess.

In addition, it is an object of the present disclosure to provide a shotcrete composition for offshore structures capable of implementing various patterns and coloring a variety of colors by reducing the amount of rebound without using steel fibers.

According to the first aspect of the present disclosure, the shotcrete composition for offshore structures is 25 to 35% by weight of cement, 55 to 65% by weight of sand, 1 to 5% by weight of oyster shell powder, 1 to 5% by weight of metakaolin, It contains 0.1 to 5% by weight of a melamine-based water reducing agent, 1 to 5% by weight of bauxite, 1 to 5% by weight of loess, and 0.1 to 5% by weight of methylcellulose, and there is no steel fiber.

According to an exemplary embodiment, the particle size of the oyster shell powder is 0.8 mm to 5.0 mm.

According to an exemplary embodiment, the melamine-based water reducing agent is selected from the group consisting of a melamine sulfonic acid formalin condensate, a melamine sulfonate condensate, and a melamine sulfonate polyol condensate.

According to an exemplary embodiment, the bauxite contains calcium aluminate, and is a by-product from smelting aluminum ore.

According to an exemplary embodiment, the shotcrete composition for marine structures further comprises 1 to 5% by weight of gypsum.

According to an exemplary embodiment, the shotcrete composition for offshore structures further comprises 1 to 5% by weight of white cement.

According to the second aspect of the present disclosure, the method of manufacturing an offshore structure includes 25 to 35% by weight of cement, 55 to 65% by weight of sand, 1 to 5% by weight of oyster shell powder, 1 to 5% by weight of metakaolin, A shotcrete composition for marine structures containing 0.1 to 5% by weight of a melamine-based water reducing agent, 1 to 5% by weight of bauxite, 1 to 5% by weight of loess, and 0.1 to 5% by weight of methylcellulose, and without steel fibers Preparing a; Preparing a liquid composition by mixing 40 to 100 parts by weight of water based on 100 parts by weight of the shotcrete composition for offshore structures; And molding the liquid composition by pouring it into a frame for an offshore structure.

According to an exemplary embodiment, the particle size of the oyster shell powder is 0.8 mm to 5.0 mm.

According to an exemplary embodiment, the melamine-based water reducing agent is selected from the group consisting of a melamine sulfonic acid formalin condensate, a melamine sulfonate condensate, and a melamine sulfonate polyol condensate.

According to an exemplary embodiment, the bauxite contains calcium aluminate, and is a by-product from smelting aluminum ore.

According to an exemplary embodiment, the shotcrete composition for marine structures further comprises 1 to 5% by weight of gypsum.

According to an exemplary embodiment, the shotcrete composition for offshore structures further comprises 1 to 5% by weight of white cement.

The shotcrete composition for marine structures according to the present disclosure not only significantly reduces the unit cost of shotcrete by using metakaolin instead of silica fume for high strength expression, but also contains oyster shell powder, metakaolin, melamine-based water reducing agent, bauxite, and loess. By using it, the growth of seaweed can be promoted without impeding the expression of high intensity.

In addition, the shotcrete composition for offshore structures according to the present disclosure can implement various patterns by reducing the amount of rebound without using steel fibers, and various colors can be colored by not using a formwork coating agent.

1A and 1B are photographs of a tetrapod made of shotcrete composition for offshore structures of the present disclosure.

Before describing the present disclosure in more detail, terms or words used in the specification and claims are not to be limited to their usual or dictionary meanings, and the concept of terms will be described in order to explain the present disclosure in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present disclosure based on the principle that it can be properly defined. Therefore, the configuration of the embodiment described in the present specification is only one preferred example of the present disclosure, and does not represent all of the technical spirit of the present disclosure, and various equivalents and modifications that can replace them at the time of application It should be understood that there may be.

Concentrations, amounts, and other numerical data can be expressed in range format. This range format is used only for convenience and brevity, and is to be interpreted flexibly as including the expressly listed numerical values as well as all individual numerical values or sub-ranges encompassed within that range. For example, a numerical range of “about 1 to about 5” should be construed as including the values of about 1 to about 5 explicitly listed, as well as the individual values and sub-ranges within the indicated range. Thus, this numerical range includes individual values such as 2, 3, and 4, subranges such as 1-3, 2-4, 3-5, etc., as well as individually 1, 2, 3, 4, and 5 do.

Hereinafter, preferred embodiments of the present disclosure will be described in detail so that those of ordinary skill in the art to which the present disclosure pertains may easily implement the present disclosure. In addition, in describing the present disclosure, detailed descriptions of related known technologies that may unnecessarily obscure the subject matter of the present disclosure will be omitted.

The marine structures used in the present disclosure are all sculptures including sofa blocks, tetrapods, artificial rocks, etc., installed on the seabed or shore, as well as artificial fish reefs installed for protection and deposition activity of fish and shellfish to increase production of offshore fisheries. It is used as a concept that includes.

In general, when concrete is used as a material for offshore structures, the minimum allowable compressive strength is 180-220 kgf/㎠, so even if an offshore structure is made of other materials, if the undersea artificial structure has a higher strength, it is a suitable material for use as an offshore structure. Can be said.

Hereinafter, each component constituting the shotcrete composition according to the present disclosure will be described in detail.

<cement>

Portland cement is generally used as the cement, and in some cases, when it is necessary to generate strength early after construction or when the curing period cannot be sufficiently taken after construction, crude portland cement, ultrafast cement, etc. may be used.

In one or more embodiments, the content of cement may be 25 to 35% by weight, 25 to 30% by weight, 30 to 35% by weight, or all ranges and subranges therebetween.

If the cement content is less than 25% by weight, it may be difficult to secure sufficient strength. In general, increasing the content of cement increases the strength, but exceeding a certain content can be negative. Since the main strength of shotcrete is due to the sand-sand interaction, an excessive amount of cement exceeding 35% by weight interferes with the sand-sand interaction, and the shotcrete can be easily broken.

<Sand>

When the sand is hardened, it is bonded to each other by the cement component to form the most basic skeleton of the shotcrete structure.

In one or more embodiments, the content of sand can be 55 to 65% by weight, 55 to 60% by weight, 60 to 65% by weight, or all ranges and subranges therebetween.

If the content of sand is less than 55% by weight, the strength may be reduced due to little sand-sand interaction, and if it exceeds 65% by weight, the strength may be lowered due to a relatively insufficient amount of cement to be applied to the surface area of the sand.

<Oyster Shell Powder>

The powder component of the oyster shell may be obtained by pulverizing a shell with a particle size of 5.0 mm or less, 4.0 mm or less, 3.0 mm or less, or 2.0 mm by removing organic matter from oysters produced in nature or artificially grown. Preferably, after washing the shellfish shell, heating and/or firing at 100 to 1,000°C, 200 to 900°C, 300 to 800°C, 400 to 700°C, or 500 to 600°C, the particle size is 0.8 to 5.0 mm, Powder obtained by grinding into 1 to 4 mm, or 2 to 3 mm may be used.

When the heating and/or sintering is processed at a lower temperature than 100° C., it is difficult to pulverize into powder, the processing time is lengthened, and energy consumption may increase accordingly. When the heating and/or firing is processed at a temperature higher than 1,000° C., the inherent properties of the oyster shell may be lost.

On the other hand, when the particle size of the oyster shell is less than 0.8 mm, characteristics as a nature-friendly material may be lost, and when it exceeds 5.0 mm, miscibility may be lowered and thus may not be uniformly distributed in the composition.

Oysters are produced in large quantities for food, but their shells have not yet been used for other purposes and are discarded or simply buried, causing serious marine environmental pollution.

Oyster shell is composed of more than 90% CaO and other Na ₂ O, SiO ₂ , Al ₂ O ₃ , MgO, etc., so it is also compatible with cement made of CaO (more than 50%), SiO ₂ , Al ₂ O ₃ etc. Because of this, it has excellent cohesion with cement when manufacturing shotcrete. Therefore, the shot concrete structure obtained by curing the composition including the powder of the oyster shell may have excellent hardness and strength. Moreover, since the oyster shell itself is a natural natural product and is an important substrate for the attachment of oyster larvae and seaweed, the early attached organisms can grow better by using the oyster shell as a material for marine structures.

If the content of oyster shell powder is increased and the content of fine aggregates such as sand is reduced, the weight is reduced compared to the case of using sand, and marine structures such as artificial reefs may be administered to the soft base.

In one or more embodiments, the content of oyster shell powder is 1% to 5%, 1% to 4%, 1% to 3%, 1% to 2%, or all ranges therebetween. And sub-ranges.

In order to fully utilize the efficacy of the above-described oyster shell component, the content of the oyster shell powder must be 1% by weight or more, but if it is mixed in excess of 5% by weight, the strength of shotcrete may be weakened by lowering the bonding strength of the cement. .

<Metakaolin>

The shotcrete according to the present disclosure uses metakaolin that can prevent the shotcrete from falling off while improving long-term durability as well as securing all mechanical properties such as compressive strength and flexural strength, instead of a silica fume admixture that has been used for high strength.

Metakaolin is an amorphous material that behaves as an artificial pozzolan, and the strength and workability when such metakaolin is used for shotcrete have the following characteristics.

First of all, the content of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) is high, and both components are amorphous and have a large specific surface area, so components such as C ₃ S and C ₂ S of cement are the result of hydration. Calcium Silicate Hydrate (CSH gel), Calcium Aluminate Hydrate (CAH gel), and calcium alumino-silicate hydrate (Calcium Alumino-Silicate) are combined with produced calcium hydroxide (Ca(OH) ₂ ). It forms more hydrates such as Hydrate, making the tissue more dense.

The reaction formula for hydration of calcium hydroxide and metakaolin is as follows.

Ca(OH) ₂ + (SiO ₂ , Al ₂ O ₃ ) = 3CaO·2SiO ₂ ·3H ₂ O /3CaO·Al ₂ O ₃ ·6H ₂ O

Metakaolin, SiO ₂ or Al ₂ O ₃ eluting from itself, causes a secondary pozzolanic reaction over a long period of time with Ca(OH) ₂ , which is the primary hydrate of cement. The reaction of the calcium hydroxide produced in cement and the pozzolanic material to form a calcium silicate hydrate is called a pozzolan reaction. Calcium silicate (CSH) or calcium aluminate (CAH) hydrate produced by this reaction has a denser hydration structure than Ca(OH) _{2, which} is a hydrate of cement itself, and has a capillary pore that is a major path for chloride ions to travel. Due to the dense filling, It improves the penetration resistance to chloride ions.

In addition, the reaction with calcium hydroxide reduces harmful alkalinity and has a better potential for weathering, as well as a distinct watertightness when incorporated into a cement paste formulation. This watertightness can improve strength and reduce water permeability.

As such metakaolin, both products manufactured overseas and products manufactured in Korea can be used. While silica fume used in the past is an industrial by-product, metakaolin is produced under good management and control, so it has the advantage that the change in physical and chemical properties is very small.

Since the composition using metakaolin according to the present disclosure has a relatively large particle size, there is an advantage of using a small amount of a high-performance water reducer than that of conventional Portland cement concrete. That is, at the same water/cement ratio (W/C), metakaolin concrete can reduce the content of high-performance water reducing agent by at least 20% and up to 50% compared to silica fume concrete, and it is less sticky than conventional silica fume compositions. Workability and finish can also be expressed.

According to the present disclosure, since metakaolin can be used to create high-performance shotcrete with high strength/high durability, the shotcrete lining can be used as a permanent support material.

In addition, the present disclosure is an admixture for expressing high strength as described above in a general shotcrete composition composed of cement, water, aggregate, admixture, and quick-setting agent. By using metakaolin instead of the commonly used silica fume, the most of silica fume Overcoming the major drawbacks of high drying shrinkage and the proportional increase in the amount of high-performance water reducing agent that is expensive, it can contribute to the increase of the workability of shotcrete.

In addition, since shotcrete is sprayed, unlike concrete, considerable rebound occurs when it is poured on the tunnel wall or the outer surface of artificial rock.As in the present disclosure, a metakaolin admixture is applied to prevent the shotcrete from falling off. can do.

In one or more embodiments, the content of metakaolin is 1 to 5% by weight, 1 to 4% by weight, 1 to 3% by weight, 1 to 2% by weight, 2 to 5% by weight, 3 to 5% by weight, 4 to 5 % By weight, or all ranges and subranges in between.

If the content of metakaolin is less than 1% by weight, the long-term strength enhancing effect, the initial hydration heat suppression effect, the sulfate-resistant effect, and the effect of lowering the alkalinity are insignificant, and the predetermined performance cannot be exhibited.If the content exceeds 5% by weight, the sulfate-resistant effect, The effect of lowering the alkalinity increases, but the strength may decrease due to the lack of the relative amount of cement in the binder.

<Supervisor>

As used herein, a water reducing agent is an admixture used to even out the small air bubbles in the shotcrete when constructing shotcrete. The water reducing agent is a surfactant with excellent foaming properties and improves freezing and melting resistance, corrosion resistance and durability by evenly generating small bubbles in shotcrete.

In addition, the water reducing agent improves the fluidity of the shotcrete composition to facilitate the pouring operation, lowers the thermal conductivity of the hardened shotcrete, and has secondary effects such as improving watertightness.

In addition, the water reducing agent is to increase the fluidity of shotcrete by dispersing the cement particles, and their use greatly reduces the number of units required to manufacture shotcrete having a desired kneading quality, and as a result, the amount of unit cement can be reduced.

At this time, the water reducing rate of the water reducing agent used in the shotcrete composition is generally about 10 to 15%, but the water reducing rate of which is 20 to 30% is collectively referred to as a high performance water reducing agent in the present disclosure.

Preferred high performance water reducing agents may be selected from the group consisting of naphthalene-based, melamine-based, polycarboxylic acid-based, amino sulfonic acid-based water reducing agents, or mixtures thereof.

As a naphthalene water reducing agent, modified lignin, alkylaryl sulfonic acid and active persistent polymer, polyalkyl isyl sulfonic acid and reactive polymer, alkyl aryl sulfonic acid high condensate, sulfonic acid group carboxyl group-containing polypolymer, alkyl naphthalene sulfonic acid, alkylaryl sulfonic acid modified lignin ball Condensate and modified lignin, lignin derivative and alkylaryl sulfonate, or at least one selected from these.

Examples of the melamine-based water reducing agent include one or more selected from the group consisting of a melamine sulfonic acid formalin condensate, a melamine sulfonate condensate, and a melamine sulfonate polyol condensate.

As an example of a polycarboxylic acid water reducing agent, a copolymer containing an unsaturated carboxylic acid monomer as a single component or a salt thereof, such as poly(alkylene glycol) monoacrylate, poly(alkylene glycol) monomethacrylate, maleic anhydride and styrene Copolymers, copolymers of acrylates and methacrylates, and copolymers derived from monomers copolymerizable with these monomers.

Examples of the amino sulfonic acid water reducing agent include an aromatic amino sulfonic acid polymer compound, an aromatic polymer condensate and a lignin sulfonic acid derivative, or at least one or more mixtures selected from these.

In one or more embodiments, the content of water reducing agent is 0.1 to 5% by weight, 0.1 to 4% by weight, 0.1 to 3% by weight, 0.1 to 2% by weight, 0.1 to 1% by weight, or all ranges or sub-ranges therebetween. Can be If the content of the water reducing agent is less than 0.1% by weight, dispersion stability and fluidity may be deteriorated, and if it exceeds 5% by weight, separation of the material and strength reduction may occur.

<Bauxite>

According to the present disclosure, the bauxite containing calcium aluminate reacts with metakaolin to increase the C ₃ A and C ₃ S components of the cement component, thereby increasing the strength of shotcrete, and also can accelerate the condensation of the shotcrete. have. Therefore, the shotcrete composition according to the present disclosure can exhibit strength in a short time,

In one embodiment, bauxite containing calcium aluminate can be obtained from a by-product that occurs when smelting aluminum ore, and is therefore environmentally friendly.

In another embodiment, calcium aluminate may be obtained by heat treatment, such as firing a mixture of a CaO raw material and an Al ₂ O ₃ raw material in a kiln or melting it with electricity.

The powderiness of the calcium aluminate has a blast specific surface area of 3,000 to 8,000 cm 2 /g, preferably 5,000 to 8,000 cm 2 /g in terms of rapid setting and strength development.

In one or more embodiments, the content of calcium aluminate may be 1 to 5% by weight, 1 to 4% by weight, 1 to 3% by weight, 1 to 2% by weight, or all ranges and subranges therebetween.

If the content of calcium aluminate is less than 1% by weight, the effect of condensation and early strength development of shotcrete may decrease, and if it exceeds 5% by weight, there is a risk of clogging of the pipe in the shotcrete construction equipment, and a lot of dust is generated. Etc. workability may be deteriorated.

<Ocher>

Ocher is yellow or yellowish brown soil made by weathering rocks, and mainly consists of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), and iron oxide (Fe ₂ O ₃ ), potassium oxide (K ₂ O) and quicklime ( It is a mixture containing a trace amount of CaO) and the like. This loess mainly has a particle size of 0.002 to 0.005 mm in diameter and exhibits weak acidity. This loess is not toxic at all, and exhibits weak acidity, so it is possible to solve the problem that marine organisms that occur when strongly alkaline concrete are not used.

In addition, since far-infrared rays are generated from the loess, it sterilizes harmful bacteria in the sea to help propagate marine organisms. In addition, the loess contains four enzymes, catalase, diphenol oxidase, cyclase, and protease, and can play a role in removing toxins.

Therefore, according to the present disclosure, when the shotcrete mixed with loess is applied to an underwater structure such as an artificial fish reef, it increases the habitat of seaweed and fish with the effect of removal of cement poison, far-infrared radiation, adsorption of heavy metals, etc. It has the effect of preventing.

In one or more embodiments, the content of loess may be 1 to 5% by weight, 1 to 4% by weight, 1 to 3% by weight, 1 to 2% by weight, or all ranges and sub-ranges therebetween.

If the loess content is less than 1% by weight, the efficacy of loess may not appear. When loess reacts with water, the volume decreases by about 6% due to agglomeration between particles, which is the main cause of cracking. Therefore, cracks may occur if the loess content exceeds 5% by weight.

If gypsum is additionally added to the addition of loess like this, the gypsum causes a hydration reaction to expand the volume. Therefore, contraction due to loess and expansion due to gypsum are balanced, and cracking can be suppressed.

<Thickener>

The shotcrete composition according to the present disclosure may include a thickener in order to increase the viscosity of the shotcrete composition and improve mixing performance between the compositions. The thickener can reduce the amount and rebound of the rapid setting agent during construction by giving viscosity to the composition. Methyl Cellulose, Welan gum, and Sepiolite can be used as a thickener.

In one or more embodiments, the content of thickener is 0.1 to 5% by weight, 0.1 to 4% by weight, 0.1 to 3% by weight, 0.1 to 2% by weight, 0.1 to 1% by weight, or all ranges or sub-ranges therebetween. Can be

If the content of the thickener is less than 0.1% by weight, the effect of reducing the amount of rapid setting and rebound may be insignificant.As a result of the low viscosity of the shotcrete, the shotcrete composition flows down and does not maintain a certain thickness, so that the function of the shotcrete structure may not be displayed properly. In addition, construction problems may occur.

On the other hand, if it exceeds 5% by weight, the viscosity may be high, resulting in a storage problem and construction may become difficult.

<gypsum>

Examples of gypsum used in one embodiment of the present disclosure include anhydrous gypsum, semihydrated gypsum, and dihydrate gypsum, and chemical gypsum such as natural gypsum, phosphate gypsum, flue gas desulfurization gypsum, and hydrofluoric gypsum, or gypsum obtained by heat treatment thereof. have. Among these, natural anhydride gypsum has a slower dissolution rate than that of semi-hydrated gypsum or dihydrate, and therefore has a suitable reactivity with calcium aluminate powder and is preferable in terms of strength development.

The particle size of this gypsum is generally higher than that used for cement, for example, a specific surface area of 4,000 to 6,000 ㎠/g is preferable. Gypsum, by generating etringite at the initial stage of the hydration of shotcrete, promotes the setting and hardening of the shotcrete, thereby enabling the shotcrete to exhibit coarse stiffness, which has an effective effect on the early strength improvement of the shotcrete.

When the anhydride is mixed, ethringite (3CaO·Al ₂ O ₃ ·3CaSO ₄ ·32H ₂ O) hydrate is initially produced to accelerate condensation and hardening, and accordingly, the shotcrete exhibits crude stiffness.

The content of gypsum may be 1 to 5% by weight, 1 to 4% by weight, 1 to 3% by weight, 1 to 2% by weight, or all ranges and subranges therebetween, based on the total shotcrete composition.

If the gypsum content is less than 1% by weight, the effect of condensation and early strength development of shotcrete decreases, and if it exceeds 5% by weight, it expands for a long time, and after hardening, the shotcrete may cause expansion and failure. As the amount of metakaolin used to improve the durability and durability is reduced, the strength and durability of shotcrete may be adversely affected.

<White cement>

In one embodiment, the shotcrete composition of the present disclosure includes back cement to reduce the amount of rebound when the shotcrete is poured.

The back cement used in the shotcrete composition of the present disclosure is white, compared to the color of the usual Portland cement, and has a characteristic that less harmful components are generated than the conventional general cement. In addition, white cement absorbs excess moisture and shortens drying time by pozzolanic reaction, promotes internal hardening, and also plays a role in enhancing bonding.

The shotcree of the present disclosure does not use gray slag or fly ash. The white cement has a low content of iron oxide and has white color, and can develop various colors by adding a pigment, and can increase early strength.

The content of the back cement may be 1 to 5% by weight, 1 to 4% by weight, 1 to 3% by weight, 1 to 2% by weight, or all ranges and subranges therebetween, based on the total weight of the shot concrete composition.

When the amount of the back cement is less than 1% by weight, the effect of enhancing hardening is significantly reduced and the strength is reduced, and when the content is more than 5% by weight, the curing speed is high and local cracking occurs.

<number of mixtures>

In one or more embodiments, based on 100 parts by weight of the shotcrete composition, 40 to 100 parts by weight, 40 to 90 parts by weight, 40 to 80 parts by weight, 40 to 70 parts by weight, 40 to 60 parts by weight, 40 to 50 parts by weight, Or it is possible to mix all ranges and subranges between them. The blended water may include tap water, sea water, or a combination thereof, but is not limited thereto.

If the number of blending is less than 40 parts by weight, the water binder ratio in the shotcrete blending is low, which has a good effect on the strength development, but the desired kneading quality cannot be obtained, so fluidity cannot be secured. , The water binder ratio may be too high to achieve a predetermined strength.

1A and 1B are photographs of a tetrapod made of a shotcrete composition for offshore structures of the present disclosure. As shown in FIGS. 1A and 1B, the shotcrete composition according to the present disclosure may implement various patterns such as having a natural rock surface.

Example

The present disclosure will be described in more detail through the following examples, but the scope of the present disclosure is not limited to the following examples.

A shotcrete composition having the components shown in Table 1 was prepared. The compressive strength was carried out by KS F 2405 "Concrete Compressive Strength Test Method".

Ingredient (kg)
Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 1 cement
30 30 30 30 30 sand
50 50 50 50 50 Oyster Shell Powder
4 4 4 0 4 Metakaolin
4 4 4 4 0 Melamine superplasticizer
3 3 3 3 3 Bauxite
3 3 3 3 3 ocher
3 3 3 3 3 Methyl cellulose
3 3 3 3 3 gypsum
0 3 3 0 0 White cement
0 0 3 0 0 Compressive strength (Mpa) Age of Age 9 10 12 7 5 Age of Age 27 28 30 25 24 Age of Age 37 40 44 34 33

When the marine structure prepared in Example 3 was administered to seawater, the pH was measured, and as a result of the measurement, a pH of about 8.4 was maintained.

Therefore, while the conventional offshore structure made of cement concrete has a strong alkalinity that creates a strong alkaline state of pH 10 or higher in seawater, the offshore structure manufactured using the shotcrete composition for offshore structures of the present disclosure maintains a pH of about 8.4 in seawater. As a result, it can be seen that it has the advantage of being relatively weakly alkaline, which can reduce the impact on the submarine ecosystem.

<Effect of seaweed>

In order to confirm the difference in epitaxy of seaweed, an artificial fish reef prepared with the composition of Example 3 including oyster shells and an artificial fish reef prepared with Comparative Example 1 not including oyster shells were thrown into seawater at a depth of about 4 m. After that, the emergence of seaweed was confirmed for 5 months in 1 month increments. It was confirmed that microalgae are growing in the artificial fish reef according to Example 3 at a time point 3 months after installation in seawater. On the other hand, in the artificial fishweed according to Comparative Example 1, microalgae formation was confirmed only 5 months after administration.

Therefore, the artificial fish reef prepared with the shotcrete composition according to the present disclosure containing oyster shells compared to the existing artificial reef can increase the rate of infestation of marine organisms.

Although the present disclosure has been described in detail through specific embodiments, this is for explaining the present disclosure in detail, and the present disclosure is not limited thereto, and those having ordinary skill in the art within the technical spirit of the present disclosure It is obvious that it can be modified or improved.

All simple modifications or changes of the present disclosure belong to the scope of the present disclosure, and the specific scope of protection of the present disclosure will be clarified by the following claims.

Claims (12)

25 to 35% by weight of cement,
55 to 65% by weight of sand,
1 to 5% by weight of oyster shell powder,
1 to 5% by weight of metakaolin,
0.1 to 5% by weight of a melamine-based water reducing agent,
1 to 5% by weight of bauxite,
1 to 5% by weight of loess, and
Including 0.1 to 5% by weight of methylcellulose,
No steel fibers,
The bauxite contains calcium aluminate, and is a by-product from smelting aluminum ore, shotcrete composition for offshore structures. The method according to claim 1,
The particle size of the oyster shell powder is 0.8 mm to 5.0 mm shotcrete composition for offshore structures. The method according to claim 1,
The melamine-based water reducing agent is a shotcrete composition for marine structures selected from the group consisting of a melamine sulfonic acid formalin condensate, a melamine sulfonate condensate, and a melamine sulfonate polyol condensate. delete The method according to claim 1,
Shotcrete composition for marine structures further comprising 1 to 5% by weight of gypsum. The method according to claim 1,
Shotcrete composition for offshore structures further comprising 1 to 5% by weight of back cement. 25 to 35% by weight of cement, 55 to 65% by weight of sand, 1 to 5% by weight of oyster shell powder, 1 to 5% by weight of metakaolin, 0.1 to 5% by weight of melamine-based water reducing agent, 1 to 5% by weight Of bauxite, 1 to 5% by weight of loess, and 0.1 to 5% by weight of methylcellulose, and there is no steel fiber, and the bauxite contains calcium aluminate, which is a by-product from smelting aluminum ore. , Preparing a shotcrete composition for offshore structures;
Preparing a liquid composition by mixing 40 to 100 parts by weight of water based on 100 parts by weight of the shotcrete composition for offshore structures; And
A method of manufacturing an offshore structure comprising the step of pouring the liquid composition into a frame for an offshore structure. The method of claim 7,
The particle size of the oyster shell powder is 0.8 mm to 5.0 mm in the manufacturing method of the offshore structure. The method of claim 7,
The melamine-based water reducing agent is a method for producing a marine structure selected from the group consisting of a melamine sulfonic acid formalin condensate, a melamine sulfonate condensate, and a melamine sulfonate polyol condensate. delete The method of claim 7,
The shotcrete composition for offshore structures further comprises 1 to 5% by weight of gypsum. The method of claim 7,
The shotcrete composition for offshore structures further comprises 1 to 5% by weight of back cement.

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