KR20180107708A - HIGH STRENGTH GROUTING COMPOSITION FOR SlAB REINFORCEMENT OF DUPLEX TUNNELS - Google Patents

Abstract

The present invention relates to a grouting composition, comprising: cement; aggregates; additives; and water. The present invention relates to a high strength grouting composition for slab reinforcement of a multi-layered tunnel, wherein the additive comprises an EthyleneVinyl acetate-based polymer.

Description

TECHNICAL FIELD [0001] The present invention relates to a high strength grouting composition for slab reinforcement in a multi-

The present invention relates to a high strength grouting composition for slab reinforcement in a multi-layer tunnel.

Grouting refers to penetration of a grouting composition with special properties into the ground by means of a pump or the like for integration of the joints of the structure in order to improve the geotechnical properties to meet the purpose.

As a typical method of grouting, there is a chemical solution injection method. A waterglass grouting composition is used as the main component of the chemical solution injection method. The durability of the grouting using the waterglass based grouting composition is determined by the adhesion of the soil and waterglass grouting composition. However, as the flow rate of the groundwater increases, dilution and loss of the chemical solution become worse, and the durability and the strength of the chemical solution decrease due to the decrease of the adhesive force and the elution of the chemical solution.

As described above, the waterglass-based method can be used for the purpose of the present invention due to problems such as durability, strength and elution, and permanent ground reinforcement is impossible due to syneresis phenomenon. In addition, the area where the particles are thick and can be injected is very limited.

In particular, the grout for reinforcement of slabs in a multi-layer tunnel is required to exhibit high strength and excellent durability, and the water glass method is not suitable for slab reinforcement of layer tunnels.

Therefore, it is necessary to study a high-strength grouting composition for slab reinforcement of a multi-layer tunnel.

It is an object of the present invention to provide a high-strength grouting composition for slab reinforcement of a multi-layer tunnel which can simultaneously satisfy high fluidity and high strength.

According to an aspect of the present invention, there is provided a grouting composition comprising a cement, a fine aggregate, an additive, and water, wherein the additive is selected from the group consisting of ethylene vinyl acetate (EVA) Based polymer.

In one embodiment, the additive may further comprise a thickening agent.

In one embodiment, the thickener may be any one selected from the group consisting of a cellulose-based thickener, a starch-based thickener, a solidifying agent, a cellulose fiber and asbestos, or a combination thereof.

The high-strength grouting composition for reinforcing a slab of a multi-layer tunnel according to an embodiment of the present invention can satisfy both high fluidity and high strength by using an ethylene vinyl acetate (PTFE) polymer as a polymer for an admixture.

On the other hand, even if the effects are not explicitly mentioned here, the effect described in the following specification, which is expected by the technical features of the present invention, and its potential effects are treated as described in the specification of the present invention.

Fig. 1 is a view of a foreground in which a submerged test is conducted.
Fig. 2 (a) is a photograph of a flow table, and Fig. 2 (b) is a photograph of a state in which the degree of flow is measured.
3 is a photograph of a compressive strength tester using a compressive strength test.
4 shows the compressive strength test results of Comparative Example and Examples 1 and 2.
Figs. 5 to 7 show the change rates of the lengths of the comparative examples, the first and second embodiments in order of age.
* The accompanying drawings illustrate examples of the present invention in order to facilitate understanding of the technical idea of the present invention, and thus the scope of the present invention is not limited thereto.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.

The present invention relates to a high strength grouting composition for slab reinforcement in a multi-layer tunnel. However, the present invention is not limited to a slab reinforcement of a multi-layer tunnel, and can be used for repairing an underground structure.

The grouting composition used for the maintenance of the ground structure, that is, the slab reinforcement of the multi-layer tunnel, should satisfy both the high fluidity and the high strength.

To this end, in the grouting composition comprising the cement, the fine aggregate, the additive and the water of the present invention, the additive may include ethylene vinyl acetate (ethylene vinyl acetate) polymer.

The materials used in the present invention are as follows.

Cement is usually Portland cement. Portland cement (KS L 5201) is obtained by mixing raw materials including silica, aluminum, iron oxide and lime as main components in an appropriate ratio, firing the mixture, and adding the appropriate amount of gypsum to the obtained clinker. The types of portland cement are divided into one kind of ordinary Portland cement, two kinds of thermal portland cement, three kinds of crude steel portland cement, four kinds of low temperature portland cement and five kinds of sulphate portland cement. In the present invention, All cements can be applied.

 Silica was used as fine aggregate. Silica sand having a particle diameter of 0.6 mm or less, a density of about 2.62 g / cm 3, and a water absorption rate of 0.3% or less was used.

Additives may include promoters, fillers, high strength materials, flow fires and polymers.

The accelerator may enhance the initial strength, and an amine strength promoter or an aluminum condensation accelerator may be used. The amine-based strength promoter for increasing the strength is a compound in which the hydrogen atom of ammonia (NH3) is substituted with 1 to 3 hydrocarbon groups (R), and monoethanolamine (MEA), diethanolamine (DEA) At least one of triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), and triisopropanolamine (TIPA) is mixed. An aluminum-promoting accelerator may be additionally used for the initial strength development. At least one of sodium aluminate (NaAlO ₂ ), aluminum sulfate (Al ₂ (SO ₄ ) _3, aluminum sulfate) may be used as the aluminum conversion promoter.

Amorphous calcium aluminate (Amorphous 12CaO · 7Al ₂ O ₃ ; C12A7), CSA (3CaO · 3Al ₂ O ₃ · CaSO _4, C4A3S) may be used as a filler. Amorphous calcium aluminate is an amorphous mineral produced by burning bauxite and limestone in an electric furnace and quenching in the form of small granules with a diameter of 1 to 2 mm or less. Powder is also produced by pulverizing the powder to 50 μm / g or more , Preferably 50 to 70 mu m / g. It reacts with cement hydrate, Ca (OH) ₂ and type II natural anhydrous gypsum, rapidly forming ettringite and hardening cement. However, when the amount is high, the initial excessively large ettringite is rapidly formed, so that the condensation is very short and the strength is not expressed.

In the present invention, precipitated silica is used as a high strength material. Silica fume and type II anhydrous gypsum can also be used together.

The precipitated silica is a particle having a BET specific surface area of about 220 to 350 cm2 / g. The precipitated silica is produced by reacting an alkali silicate aqueous solution with an acid. The precipitated silica is very small in particle size and thus has an excellent effect of filling the finer voids of concrete. It also exhibits a higher level of reactivity than silica fume in the chemical changes of the microparticles. However, there is a possibility that the compounding number may increase due to the property of absorbing water on the surface of the particles.

The "BET specific surface area" Bruno Le, Phi. H. Emmet, Lee. By S. Brunaure, P. H. Emmett, E.Teller. Chem. Soc., 60, 309 (1938), which is considered to be equivalent to the average primary particle diameter of silica. For example, if the primary particles are assumed to be spherical, as described in "Powder Engineering of Modified Powder Properties" (1985), it is preferable that the ratio of the specific surface area to the average diameter of the primary particles satisfy the following formula 1), and the larger the specific surface area, the smaller the average primary particle size becomes.

D = 6 / (S? Rho) (1)

(Where D is the average primary particle size, S is the specific surface area, and rho is the density of the particles)

Silica fume is a generic term of byproducts generated by floating in the exhaust gas when a silicon alloy such as silicon or ferrosilicon is produced in an electric arc furnace. As a raw material of the silicon alloy, silica fume is used as a reducing agent such as silica, coal, And put into an electric furnace to produce ferrosilicon at a high temperature of about 2,000 ° C. At this time, the intermediate product SiO is gasified, which is oxidized by air and converted into SiO2, which is again condensed to form ultra-fine particles. The resulting ultrafine particles are recovered by using an electric dust collector to obtain silica fume. The silica fume is amorphous with 90% or more spherical shape and has a particle diameter of 1 μm or less, an average particle size of about 0.1 μm, a specific surface area of about 20 m 2 / g, and a specific gravity of about 2.1 to 2.2. ) ₂ ) and pozzolanic reaction to form concrete micropores and generate hydrates, thereby exhibiting high strength.

Type II anhydrous gypsum is obtained by pulverizing natural gypsum with a fine powder at a rate of 50 m2 / g or more through a pulverizer. It has a crystal structure and is reactive in an alkali environment. It reacts with calcium silicate hydrate (CSH) and A12O3 It is possible to express Ettringite which is the crystal of the needle bed in the concrete pore and to densify the structure to express high strength.

The fluidizing agent can increase the fluidity of the grouting composition of the present invention, and can reduce the water mixing amount while maintaining the same workability. The effect of reducing the water mixing amount can reduce the void volume in the grouting composition, thereby improving the strength and reducing the shrinkage due to drying. The fluidizing agent is not particularly limited, and may include at least one of a polycarboxylic acid-based dispersant, a lignin sulfonate-based dispersant, a polynaphthalene sulfonate-based dispersant, and a polymelamine sulfonate-based dispersant. If the amount of the fluidizing agent is small, sufficient fluidity can not be secured, and in case of excessive amount, the material separation phenomenon may occur.

In the present invention, ethylene vinyl acetate (ethylene vinyl acetate) polymer is used as the polymer. The most significant feature of the present invention is to use an ethylene vinyl acetate polymer as a polymer, thereby improving the cracking resistance and strength of the grouting composition.

Meanwhile, the present invention may further include a thickener as an additive. The thickening agent can prevent sedimentation and separation of the material, impart water retention to the drying and curing material, and improve lubricity, adhesion and cohesion. The thickener may be any one selected from the group consisting of cellulose-based thickener, starch-based thickener, solidifying agent, cellulose fiber and asbestos, or a combination thereof.

The grouting composition of various examples was prepared using the above-mentioned materials to conduct the dropping time test, the flow test, the bleeding test, the compressive strength test, and the length change test.

Table 1 shows the blending ratios of the comparative example and the example 1 and the example 2, in which the water-mortar ratio is increased to 12%, 15%, 18% and 21%. Example 1 is characterized in that the additive material further comprises an ethylene vinyl acetate (ethylene vinyl acetate) polymer and a thickener as compared with the comparative example, and Example 2 is characterized in that the additive comprises an ethylene vinyl acetate (PTFE) .

The specimens were weighed in accordance with the formulation ratio shown in Table 1, and then mixed in a high-half period, and then poured into molds for curing.

The dropping time test is for evaluating the flowability of the grouting composition, and the viscosity and flowability were measured by measuring the time and flow rate as shown in Fig. 1 by KS F 2432 " Consistency Test Method of Injection Mortar ".

The flow test was carried out in accordance with KS L 5111 " Flow Table for Cement Test " as shown in Fig. 2 (a) to evaluate the fluidity of the grouting composition. The diameters of the two points intersecting the flow of the grouting composition without striking the table (see Fig. 2 (b)) were measured. In order to increase the accuracy of the test, each experiment was conducted three times for each subject, and the average was calculated as the maximum value.

On the other hand, in the bleeding test, the bleeding rate of the grout was measured in accordance with the domestic regulation KS F 2433 "Test method for bleeding rate and expansion rate of injected mortar". The test was performed by filling a 1000 ml cylinder with 800 ml of a certain amount of grout and measuring the amount of bleeding that changed with time.

Table 2 shows the results of the dropping time experiment, the flow test and the bleeding test.

First, the dropping time tended to decrease with increasing water-mortar ratio (W / M) as a result of the drop test. In Examples 1 and 2, .

Flow test results show that the flow value of the big sample is 150 ~ 255mm, and the flow value increases proportionally as the W / M ratio increases. The flow value of Example 1 was in the range of 230 to 310 mm according to the W / M ratio, and it was found that the flowability was better than that of Comparative Example. However, the flow value of Example 1 increased with increasing W / M, but the increase rate after 15% was decreased. The flow value of Example 2 exhibited the greatest flow value in the grout at W / M 21% and the flow value in the range of 195 to 320 mm according to the increase in W / M. As compared with Comparative Example, It was good.

As a result of the bleeding test, the bleeding in the comparative example occurred in the range of 2 to 4%, but in Examples 1 and 2, the bleeding did not occur regardless of the W / M.

Next, the compressive strength test method was used as a test method for measuring the compressive strength of the test specimen, and the test was conducted by the method of KS F 2314 "Unconfined compressive test method of soil" using a compressive strength tester shown in FIG. The specimens used for the measurement of compressive strength were fabricated using 5 × 5 × 5 cm molds, and 3 days, 7 days, 28 days, and 56 days of rapid development were recorded at 1 day, 3 days, 7 days, 28 days, and 56 days The strength was measured and the compressive strength test was carried out at a rate of 1.0 mm / min. Figure 4 shows the result.

Referring to FIG. 4, in the test results, in Examples 1 and 2, the strength per day of 21 MPa, which is the strength standard for a multi-layer tunnel, was satisfied. In the comparative example, the strength increase width was larger at the initial age (1 day to 7 days), but the strength increase width decreased with age. The strength with W / M ratio tended to decrease in all compounding conditions.

Each test specimen was subjected to a longitudinal change test according to the age at a temperature of 23 ± 3 ° C and a relative humidity of 60 ± 5%. The rate of change in length by age was measured and evaluated on the basis of the initial test body. The results are the same as in Figs. 5 to 7 (in the order of Comparative Example, Examples 1 and 2). Test results In Examples 1 and 2, the rate of change of length was lower than that of Comparative Example, so that the deformation was small. It is considered that the deformation of the test specimen becomes smaller as the internal matrixes of Examples 1 and 2 are tight and the strength is increased.

As a result of the above-mentioned experimental results, it can be understood that the fluidity and the strength are remarkably increased in Examples 1 and 2 as compared with Comparative Examples. It is considered that the additive includes ethylene vinyl acetate (ethylene vinyl acetate) polymer. Particularly, in Example 1 including a thickener, the fluidity was better than that in Example 2, and it was confirmed that Example 2 had higher strength than Example 1.

The scope of protection of the present invention is not limited to the description and the expression of the embodiments explicitly described in the foregoing. It is again to be understood that the present invention is not limited by the modifications or substitutions that are obvious to those skilled in the art.

Claims (3)

A grouting composition comprising cement, fine aggregates, additives and water,
Wherein the additive comprises an ethylene vinyl acetate (PTFE) polymer. The slab reinforcement according to claim 1, wherein the additive comprises ethylene vinyl acetate (PTFE).
The method according to claim 1,
Wherein the additive further comprises a thickener. ≪ RTI ID = 0.0 > 8. < / RTI >
3. The method of claim 2,
Wherein the thickener is any one selected from the group consisting of a cellulose-based thickener, a starch-based thickener, a solidifying agent, a cellulose fiber and an asbestos, or a combination thereof. Composition.

Images