KR20100068642A - Pre-mix composition for shotcrete of wet method and repair method using the same - Google Patents

Abstract

PURPOSE: A wet shotcrete premix composition of high performance is provided to ensure excellent strength and rapid forming ability. CONSTITUTION: A shotcrete premix composition of high performance contains cement and 440-460kg/m^3 of silica fume, 9-12 weight parts of silica fume, and 0.1-0.3 weight parts of synthetic fiber. The water-binder ratio is 41-43.5. The maximum value of the thick aggregate is 10mm. A method for reinforcing and repairing wet shotcrete comprises: a step of examining deterioration part and selecting an object to be repaired and reinforced; a step of removing the deterioration part by hydrodemolition; a step of producing the premix composition; and a step of finishing installed surface.

Description

High-performance wet shotcrete premix composition and wet shotcrete repair and reinforcement method using the same {PRE-MIX COMPOSITION FOR SHOTCRETE OF WET METHOD AND REPAIR METHOD USING THE SAME}

TECHNICAL FIELD The present invention relates to the field of construction, and in particular, to a premix composition used in a wet shotcrete process.

WET METHOD Shotcrete is a concept that is different from DRY METHOD. It refers to concrete that adds water to the injector when water is mixed and supplies it to the injector. Pressure type, screw and piston pump pressure type method is roughly divided (Fig. 1).

This method has been in use for about 50 years, and the development of the equipment and materials was particularly active in the 1970s and 1980s (ACI 506R-05).

Wet shotcrete has the advantage of easy quality control and less rebound and dust generation than dry shotcrete because it sprays the pre-blended materials at a constant mixing ratio.

In addition, the construction volume is larger than dry shotcrete, which is suitable for mass construction.

On the other hand, the equipment is large and constrained by the materials used, and the transport distance is shorter than dry shotcrete.

Recently, with the development of maintenance wet shotcrete, research on the reduction of equipment capacity and size and the application of small diameter hoses is also in progress.

However, the necessity of research on the premix composition for increasing the performance of the conventional wet shotcrete to be used in various applications has been highlighted, and the reason is as follows.

First, the conventional shotcrete is too narrow in its range of use.

This shotcrete method can serve as a structure in a short time, and can be freely constructed from extremely thin to very thick structures without using formwork, so that weathering, peeling, or peeling of sand, vertical shafts, slopes or walls is eliminated. It can be applied to the maintenance of slopes and curved structures dams, harbors and bridges and sub-structures, sewer pipes, road pavements, etc. It can be applied to various purposes.

However, most of domestic wet shotcrete is used as primary support material after excavation of new tunnel, and it is rarely used for maintenance or construction of curved structures like overseas.

Most of the materials for domestic wet shotcrete repair applications are mortar, which is used for surface repair of surface deterioration rather than repair reinforcement.

For this reason, the air pressure is also about 1 bar, usually shotcrete air pressure is injected at a very small pressure compared to 6 ~ 10bar.

Therefore, there has been a need for a high performance wet shotcrete capable of expanding the application range of the wet shotcrete.

Second, the conventional shotcrete is difficult to control quality, the frequent cases of the poor.

Recently, in the tunnel design criteria (Ministry of Construction, 2007), the standard strength of general shotcrete and high-strength shotcrete has been defined as 21, 35 MPa, but the quality control of shotcrete in Korea is very poor.

As a result of confirming the compressive strength of shotcrete in the tunnel under construction in Korea, the difference in strength is very large, about 10 ~ 33MPa, and there have been cases where it has fallen below the standard strength.

In other words, the management of quality maintenance with shotcrete quality is also very important.

Accordingly, the need for high performance wet shotcrete and premixed shotcrete has also increased for quality improvement and quality control of wet shotcrete.

Third, the amount of quick payments should be reduced.

Since shotcrete is constructed by spraying, it is necessary to quickly cure it, so it is often mixed with a fastener. However, when the filler is excessively added above the standard addition amount, the shotcrete has a fatal effect on the long-term strength or durability of the shotcrete. .

In addition, since the fastener contains a high concentration of alkali, care must be taken in regard to environmental problems and worker safety.

Therefore, it is necessary to develop high performance wet shotcrete for the development of wet shotcrete without using a fastener.

Fourth, it is urgent to develop a material having excellent workability (pumping property and shorting property).

Wet shotcrete is constructed in such a way that the blended material is transported along the hose due to its properties, and the workability (pumpability) varies depending on the pump equipment, the fluidity of the material, the type of material used and the mixing ratio.

In particular, even the same equipment and slump conditions can be pumped depending on the materials used.

In addition, the shorting property, which is an important factor of the performance of shotcrete, is determined by the thickness of rebounding and shortening during shoting.

This shortening property depends on various factors such as the target structure, the equipment, the skill of the nozzle man, and the material used.

Since wet shotcrete differs in pumping property and shotability due to various factors, it is necessary to develop a shotcrete material having excellent pumping property and shotability in order to obtain a concrete solidified body of a certain quality.

Fifth, it is necessary to develop a material that can exhibit strength without using steel fibers.

Steel fiber generally uses a bundle type, which is well dispersed in concrete, but due to the composition and performance of the adhesive, fiber balling occurs, which is inadequate for mixing with wet shotcrete. .

Therefore, it is necessary to develop a material capable of increasing strength by being mixed with shotcrete instead of steel fiber.

The present invention has been derived to solve the above problems, it is possible to expand the scope of application, easy quality control, can exhibit the quick setting performance even without using a fastener, workability (pumping and shorting) It is an object of the present invention to propose a high performance wet shotcrete premix composition and a wet shotcrete repair and reinforcement method using the same, which are excellent and can exhibit excellent strength without using steel fibers.

The present invention, in order to achieve the object as described above, cement and silica fume 440 ~ 460 kg / ㎥ is included, when it is called 100 parts by weight, the silica fume 9 ~ 12 parts by weight; 0.1 to 0.3 parts by weight of synthetic fibers; including, the aggregate aggregate (S / a) is 65 to 70 parts by weight, the water-binder ratio (W / B) is 41 to 43.5 parts by weight, the maximum coarse aggregate is 10mm A high performance wet shotcrete premix composition is provided.

It is preferable to further include 3 to 4 parts by weight of the polymer.

It is preferable to further comprise 0.1 to 0.2 parts by weight of a high performance water reducing agent.

It is preferable that the said high performance sensitizer is a polycarboxylic acid type.

It is preferable to further contain 0.2-0.3 weight part of thickeners.

It is preferable to further include 0.005 to 0.01 part by weight of AE agent.

The present invention provides a wet shotcrete method using the premix composition, the method comprising: examining a deterioration unit and selecting a repair and reinforcement target; Removing the deterioration portion by using hydrodemolition; Producing and deploying the premix composition in situ; We present a wet shotcrete repair and reinforcement method including a; finishing the laid surface.

The present invention can expand the scope of application, easy quality control, can exhibit the fastening performance even without using a fastener, excellent workability (pumping and shorting), excellent strength without using steel fibers A high performance wet shotcrete premix composition and a wet shotcrete repair and reinforcement method using the same are presented.

Hereinafter, embodiments of the present invention will be described in detail.

The high performance wet shotcrete premix composition according to the present invention basically includes cement and silica fume 440-460 kg / m 3, and when it is 100 parts by weight, silica fume 9-12 parts by weight; 0.1 to 0.3 parts by weight of synthetic fibers; including, the aggregate aggregate (S / a) is 65 to 70 parts by weight, the water-binder ratio (W / B) is 41 to 43.5 parts by weight, the maximum coarse aggregate is 10mm It features.

Silica fume increases pumpability and shorting property, improves workability, and plays a role of increasing watertightness and durability.

Synthetic fiber is a component that replaces the steel fiber incorporated in the conventional shotcrete, and exhibits excellent bending toughness, crack resistance, and adhesion, but does not generate fiber balling like the conventional steel fiber. Improve at the same time.

The water-binder ratio (W / B) is 41 to 43.5 parts by weight, which is the result of the maximum reduction within the range that does not impair the pumping property to obtain high strength shotcrete.

The maximum coarse aggregate size of 10mm is good in terms of minimizing rebound to prevent waste of materials.

In this case, when the premix composition for wet shotcrete is formed, it is possible to obtain a sufficiently tight and faithful solidified body by simply spraying and spraying with air pressure, and by adding silica fume, high strength and high durability concrete can be obtained. High quality bar and shotcrete can be achieved.

In terms of construction, the mixing of the admixture as described above lowers the viscosity of the material and ensures fluidity, so that the pumping property can be increased, and the shorting property can be improved by reducing the rebound after the shortening and increasing the thickness of the paste.

In addition, all materials can be powdered and commercialized in the form of a premix, which adds an effect of improving construction performance.

The use of such high performance materials allows for long-term commonality without requiring refurbishment and ultimately economical construction.

Wet shotcrete repair and reinforcement method using the premix composition is made by the following process.

After investigating the deterioration of the concrete structure, such as the inclined portion, and selecting the repair and reinforcement (Fig. 2), using the hydrodemolition, etc. to remove the deterioration (Fig. 3).

The above premix composition is produced and laid in situ (FIGS. 4, 5) and finishes the laid surface (FIG. 6).

When 3 to 4 parts by weight of the polymer is further included in the formulation of the above-described premix composition, the shorting property, the adhesion property and the bending toughness increase, and the effect of suppressing the crack and increasing the watertightness and durability can be obtained.

In order to secure the fluidity for the shotcreability, the use of a high-performance water reducing agent requires appropriate control. Experimental results show that the use of 0.1-0.2 parts by weight is appropriate, and polycarboxylic acid-based materials are best applied.

If the above formulation further comprises 0.2 to 0.3 parts by weight of thickener, the effect of reducing the rebound of the material to minimize the loss of material is added.

If the above formulation further comprises 0.005 to 0.01 parts by weight of AE, the effect of obtaining high strength and high durability solidified body is added.

Hereinafter, the test result for examining the performance of the composition by this invention is demonstrated.

Table 1 is a compounding table of one embodiment of the composition according to the present invention, Table 2 is a compressive strength and bending strength test results of the shotcrete solidified body according to the above compounding table, Table 3 shows the permeability characteristics according to the chlorine ion permeation test.

Compared to the general wet shotcrete solidified body, the 7-day compressive strength is about 15 to 20 MPa, and the 28-day compressive strength is about 21 to 30 MPa, whereas the shotcrete solidified body according to the embodiment of the present invention has a considerably superior compressive strength. It can be seen.

In addition, it can be seen that the 7-day bending strength of the general wet shotcrete solidified body is about 3 MPa, and the 28-day compressive strength is about 4.5 MPa, in the case of the shotcrete solidified body according to the embodiment of the present invention has a relatively excellent bending strength. .

Since the permeation resistance of the general wet shotcrete solidified body is about 2000 ~ 4000 C, it can be seen that the shotcrete solidified body according to the embodiment of the present invention has excellent performance in terms of permeability resistance.

In addition, referring to Table 3, it can be seen that the permeability characteristics according to the chlorine ion permeation test is also excellent.

Since the above has been described only with respect to some of the preferred embodiments that can be implemented by the present invention, the scope of the present invention, as is well known, should not be construed as limited to the above embodiments, the present invention described above It will be said that both the technical idea and the technical idea which together with the base are included in the scope of the present invention.

1 is a conceptual diagram of a conventional wet shotcrete method.

2 to 6 are photographs showing the construction process of the shotcrete method according to the present invention.

Claims (7)

Cement and silica fume 440 ~ 460 kg / ㎥ is included, when 100 parts by weight, 9-12 parts by weight of the silica fume; 0.1 to 0.3 parts by weight of synthetic fibers; including, Fine aggregate ratio (S / a) is 65 to 70 parts by weight, water-binder ratio (W / B) is 41 to 43.5 parts by weight, coarse aggregate maximum dimension is high performance wet shotcrete premix composition. The method of claim 1, High performance wet shotcrete premix composition, characterized in that it further comprises 3 to 4 parts by weight of polymer. The method of claim 2, A high performance wet shotcrete premix composition, further comprising 0.1 to 0.2 parts by weight of a high performance water reducing agent. The method of claim 3, The high performance sensitizer is a high performance wet shotcrete premix composition, characterized in that the polycarboxylic acid-based. The method of claim 4, wherein A high performance wet shotcrete premix composition, further comprising 0.2 to 0.3 parts by weight of a thickener. The method of claim 5, A high performance wet shotcrete premix composition, characterized in that it further comprises 0.005 to 0.01 parts by weight of AE. As a wet shotcrete method using the premix composition according to any one of claims 1 to 6, Examining the deterioration unit and selecting a repair and reinforcement object; Removing the deterioration portion by using hydrodemolition; Producing and deploying the premix composition in situ; Finishing the laid surface; Including wet shotcrete repair and reinforcement methods.

Images