KR102318755B1 - Repair and reinforcement shotcrete composition containing VAE polymer and hemp fiber - Google Patents

Abstract

The present invention relates to a shotcrete composition for repairing and reinforcing containing a VAE polymer and hemp fibers, which can be used to precisely repair a concrete structure when durability of the concrete structure is reduced by a deicing agent and various environmental factors such as salt damage, neutralization, and freezing and thawing and when the concrete structure is deteriorated and damaged along with corrosion of rebar. The present invention is characterized by comprising, in the unit volume of shotcrete, 150-250 kg/m^3 of water, 300-400 kg/m^3 of cement, 1,000-12,000 kg/m^3 of fine aggregate, 450-550 kg/m^3 of coarse aggregate, 70-120 kg/m^3 of fine powder of blast furnace slag, 20-30 kg/m^3 of a VAE polymer, 15-30 kg/m^3 of a blowing agent, 4-5 kg/m^3 of a water reducing agent, 20-30 kg/m^3 of silica fume, 4-5 kg/m^3 of a shrinkage reducing agent, and 0.5-2 kg/m^3 of jute fibers or kenaf having the length of 5-15 mm.

Description

Repair and reinforcement shotcrete composition containing VAE polymer and hemp fiber

The present invention provides a VAE polymer capable of precisely repairing concrete structures whose durability is deteriorated due to salt damage, neutralization, freeze-thaw, etc. caused by deicing agents and various environmental factors, and deteriorated and damaged along with corrosion of reinforcing bars, and It relates to a shotcrete composition for repair and reinforcement containing hemp fibers.

In recent years, concrete structures have been used in various fields such as houses, roads, bridges, skyscrapers, dams, and the like.

The durability of these concrete structures decreases due to cracks, water leakage, slab sag, freeze damage, neutralization over time, and the use of salt-containing aggregate due to external loads, drying shrinkage, etc. this can result

In particular, in the case of bridges, it is expected that it will take more than 20 years to reach grades D and E, which require reinforcement due to major member defects or are prohibited from use because of a risk to the safety of the bridge and reinforcement or remodeling. .

For maintenance of such a concrete structure, the damaged area is crushed using a breaker, etc., and after removing the crushed residue, new concrete is poured on the crushed surface and cured. However, there is a problem in that the concrete flows down in the process of repairing the damaged area.

Accordingly, there is an urgent need for the development of shotcrete capable of precisely repairing concrete structures.

As for the background of the present invention, Patent Registration No. 10-1313084 is published in the Korean Intellectual Property Office.

The problem to be solved by the present invention is to precisely repair a concrete structure that deteriorates due to salt damage, neutralization, freeze and thaw, etc., and deteriorates and breaks along with corrosion of reinforcing bars due to snow removal agents and various environmental factors. An object of the present invention is to provide a shotcrete composition for repair and reinforcement containing a VAE polymer and abrasive fibers that can be used.

The shotcrete composition for repair and reinforcement containing the VAE polymer and hemp fibers according to an embodiment of the present invention is water 150kg/m3 to 250kg/m3, cement 300kg/m3 to 400kg/m3, fine aggregate 1,000kg/m3 to 1,2000kg /㎥, coarse aggregate 450kg/㎥ ∼ 550kg/㎥, blast furnace slag fine powder 70kg/㎥ ∼ 120kg/㎥, VAE polymer 20kg/㎥ ∼ 30kg/㎥, expanding agent 15kg/㎥ ∼ 30kg/㎥, water reducing agent 4kg/㎥ ∼ 5kg/ m3, silica fume 20kg/m3 ~ 30kg/m3, shrinkage reducing agent 4kg/m3 ~ 5kg/m3, jute fiber or sheep hemp fiber 0.5kg/m3 ~ 2kg/m3 having a length of 5 ~ 15mm.

Preferably, per unit volume, water 184kg/m3, cement 322kg/m3, fine aggregate 1,125kg/m3, coarse aggregate 491kg/m3, fine blast furnace slag powder 92kg/m3, VAE polymer 23kg/m3, expanding agent 23kg/m3, water reducing agent 4.6kg /m3, silica fume 23kg/m3, shrinkage reducing agent 23kg/m3, jute fiber or sheep hemp fiber 1kg/m3 having a length of 5 to 15mm.

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The present invention, by containing VAE polymer, shrinkage reducing agent, and hemp fiber together, the shotcrete composition for repair and reinforcement satisfies all the test results evaluation criteria of slump, air volume, compressive strength, salt penetration resistance, chlorine ion diffusion coefficient, and crack resistance. , has the advantage of being able to precisely repair concrete structures that deteriorate due to causes such as neutralization over time, use of salt-containing aggregates, etc., corrosion of rebar, and deterioration and damage of structures.

In addition, the present invention has the advantage of having good workability, low material loss, and construction with a large thickness even when shorting an existing concrete structure with a shorting device.

1 is a photograph of test results for crack resistance (ring test) of Examples and Comparative Examples of the present invention.
2 is a photograph of test results obtained by shorting the shotcrete composition of Example 2 of the present invention with a concrete shorting device.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The shotcrete composition for repair and reinforcement containing the VAE polymer and hemp fiber according to the present invention is based on 100 parts by weight of water 150kg/m3 to 250kg/m3 per unit volume of cement 300kg/m3 to 400kg/m3, fine aggregate 1,000kg/m3 ∼ 1,2000kg/㎥, coarse aggregate 450kg/㎥ ∼ 550kg/㎥, blast furnace slag fine powder 70kg/㎥ ∼ 120kg/㎥, VAE polymer 20kg/㎥ ∼ 30kg/㎥, expanding agent 15kg/㎥ ∼ 30kg/㎥, water reducing agent 4kg/ ㎥ ∼ 5kg/㎥, silica fume 20kg/㎥ ∼ 30kg/㎥, shrinkage reducing agent 4kg/㎥ ∼ 5kg/㎥, hemp fiber 0.5kg/㎥ ∼ 2kg/㎥.

In particular, the present invention is water 184kg/m3, cement 322kg/m3, fine aggregate 1,125kg/m3, coarse aggregate 491kg/m3, blast furnace slag fine powder 92kg/m3, VAE polymer 23kg/m3, expanding agent 23kg/m3, water reducing agent 4.6kg/m3 , It is preferable to consist of silica fume 23kg/m3, shrinkage reducing agent 23kg/m3, hemp fiber 1kg/m3.

Conventional Portland cement is mainly used as the cement of the present invention. The cement is preferably contained in an amount of 300 kg/m 3 to 400 kg/m 3 per unit volume of shotcrete.

Fine aggregates are those with a particle diameter of 5 mm or less, and coarse aggregates are classified as those with a particle diameter of 5 mm to 15 mm. At this time, it is preferable that the fine aggregate ratio is 70% or more. It is preferable that the fine aggregate contains 1,000kg/m3 to 1,2000kg/m3 and coarse aggregate 450kg/m3 to 550kg/m3 per unit volume of shotcrete.

Blast furnace slag fine powder is a latent hydraulic material, and it increases the chemical resistance and durability by making the hydration structure of concrete dense. The fine powder of blast furnace slag preferably contains 70 kg/m 3 to 120 kg/m 3 per unit volume of shotcrete.

VAE polymer increases the viscosity when mixed with cement and has excellent adhesion by self-watering reaction, reduces rebound (concrete splashing phenomenon), and improves watertightness and crack resistance. The VAE polymer has the structure of Formula 1, and preferably contains 20 kg/m 3 to 30 kg/m 3 per unit volume of shotcrete. At this time, when a small amount of VAE polymer is added, the viscosity is lowered, the rebound excess and adhesion performance are lowered, the crack resistance and watertightness are lowered. There is a problem that the compressive strength is severely reduced.

[Formula 1]

The expanding agent can improve durability and chemical resistance by inhibiting initial cracking due to hydration reaction during material mixing and construction, and minimize shrinkage cracking in the initial stage. The expanding agent uses a CSA expanding agent, and it is preferable to include 15 kg/m 3 to 30 kg/m 3 per unit volume of shotcrete. If the amount of intumescent material used is too large, it may induce the expansion of concrete and cause cracks and cross-section loss.

The water-reducing agent is for improving strength by reducing the water-cement ratio, and it is preferable to use polycarboxylic acid. The water reducing agent is preferably contained in an amount of 4 kg/m 3 to 5 kg/m 3 per unit volume of shotcrete. If the amount of water reducing agent used is small, the water reducing effect is insufficient, and if the amount used is large, concrete will flow down and workability will be deteriorated.

Silica fume, combined with VAE polymer, has excellent salt damage blocking effect, improves water tightness by filling between cement particles, and reduces the amount of ground by improving the adhesion of shotcrete. Silica fume is preferably contained in an amount of 20 kg/m 3 to 30 kg/m 3 per unit volume of shotcrete.

The shrinkage reducing agent can prevent the phenomenon of cracking due to shrinkage as the concrete dries. It is preferable to use liquid SCA-30 powder Peraminⓡ SRA 10 as the shrinkage reducing agent. The shrinkage reducing agent is preferably included in an amount of 4 kg/m 3 to 5 kg/m 3 per unit volume of shotcrete.

The hemp fibers absorb water and are formed integrally with each other during concrete curing, so that there is no gap between the hemp fibers and the concrete and a strong stress is generated. These hemp fibers use jute fibers and sheep hemp fibers, and preferably have a length of 5 to 15 mm. The hemp fiber is preferably contained in an amount of 0.5 kg/m 3 to 2 kg/m 3 per unit volume of shotcrete. At this time, if the hemp fiber is less than 5mm, the stress action is low and the crack resistance is lowered.

Hereinafter, examples of the shotcrete composition for repair and reinforcement containing the VAE polymer and hemp fibers of the present invention will be presented in more detail, and the present invention is not limited by the examples presented below.

<Production of shotcrete composition for repair and reinforcement>

As shown in Table 1 below, 184 kg, cement 322 kg, fine aggregate 1,125 kg, coarse aggregate 491 kg, admixture 92 kg, polymer 23 kg, expanding agent 23 kg, water reducing agent 4.6 kg, silica fume 23 kg, shrinkage reducing agent 23 kg, and , using 1 kg of 10 mm long hemp fibers, mixing them with VAE polymer, a shrinkage reducing agent, and hemp fibers. The shotcrete compositions for repair and reinforcement of Comparative Examples 1 to 3 in which only the polymer was mixed were prepared (the mixing unit was based on kg/m 3 ).

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 Comparative Example 3
(liquid) W/C (%) 40 40 40 40 40 Fine aggregate rate (%) 70 70 70 70 70 water 184 184 184 184 184 cement 299 299 322 322 322 fine aggregate rate 1,119 1,119 1,125 1,125 1,125 coarse aggregate 489 489 491 491 491 blast furnace slag
fine powder 92 92 92 92 92 VAE Polymer 23 23 23 23 46 inflatable 23 23 23 23 23 water reducing agent 4.6 4.6 4.6 4.6 4.6 Silica fume 23 23 - - - shrinkage agent
(liquid, powder) 2.3 2.3 - - - Hemp fiber (10mm) 1.0 1.0 - - -

<Test Example 1>

The shotcrete compositions for repair and reinforcement prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a slump test (degree of kneading) according to the method specified in KS F 2402, and are shown in Table 2. The slump test tests the toughness of the dough, such as the softness and consistency of concrete, and the higher the number, the better the workability, that is, the workability when pouring concrete.

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 Comparative Example 3
(liquid) Slump (mm) 90 85 90 100 110

As can be seen in Table 2, the shotcrete compositions for repair and reinforcement of Examples 1 and 2 and Comparative Examples 1 to 3 all satisfied the slump standard of 80 to 120 mm.

<Test Example 2>

The shotcrete compositions for repair and reinforcement prepared in Examples 1 and 2 and Comparative Examples 1 and 3 were subjected to an air quantity test according to the method specified in KS F 2421, and are shown in Table 3.

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 Comparative Example 3
(liquid) Air volume (%) 3.5 5.2 7.4 6.0 7.0

As can be seen in Table 3, Examples 1 and 2 satisfied the air amount standard of 3 to 6%, but Comparative Examples 1 and 3 did not satisfy the air amount standard, and only Comparative Examples 2 and 4 The air quantity standard was satisfied. In particular, it was found that the quality of the shotcrete composition for repair and reinforcement of the present invention was significantly lower than that of the comparative example, and thus the quality was very good. In addition, it can be seen that when the liquid shrinkage reducing agent is used, the amount of air is lower than that of the spray-type shrinkage reducing agent, so that the quality of the shotcrete can be maintained more excellently.

<Test Example 3>

The shotcrete compositions for repair and reinforcement prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a compressive strength test according to the method specified in KS F 2405, and are shown in Table 3.

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 Comparative Example 3
(liquid) Compressive strength (MPa)
(28 days) 43.5 42.9 37.9 37.2 36.2

As can be seen in Table 4, Examples 1, 2, and Comparative Examples 1 to 3 all satisfied the compressive strength of 35 MPa or more. In particular, the shotcrete composition for repair and reinforcement of the present invention exhibits compressive strengths of 43.5, MPa, and 42.9 MPa than Comparative Examples 1, 2, and 3, indicating that the quality of the shotcrete is very excellent.

<Test Example 4>

The shotcrete compositions for repair and reinforcement prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a salt penetration resistance test according to the method specified in KS F 2711, and are shown in Table 5.

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 Comparative Example 3
(liquid) RCPT (Coulombs)
(56 days) 833 792 763 1,359 1,467

As can be seen in Table 5, Examples 1 and 2 satisfied the salt penetration resistance criterion of 1,000 or less (Coulombs), but Comparative Examples 2 and 3 did not satisfy the salt penetration resistance criterion and Comparative Example 1 Only the salt penetration resistance standards were satisfied.

<Test Example 5>

The shotcrete compositions for repair and reinforcement prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a chlorine ion diffusion coefficient test according to the method specified in NT Build 492, and are shown in Table 6.

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 Comparative Example 3
(liquid) Chloride ion diffusion coefficient
(*10 ^-12 m ² /sec) 2.83 2.73 3.24 3.74 3.91 Endurance (years)
(KCI code) 103 107 89 77 73

As can be seen in Table 6, Examples 1 and 2 exhibited very excellent results with durability exceeding 100, but Comparative Example 2, Comparative Example 2, and Comparative Example 3 had low durability of 90 or less.

<Test Example 6>

The shotcrete compositions prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to a crack resistance (ring test) test according to the method specified in ASTM C 1581, and are shown in Table 7 and FIG. 1 .

Example 1
(liquid) Example 2
(minute) Comparative Example 1 Comparative Example 2 crack resistance
(ring test) age 77 days age 74 days age 29 days age 36 days

As can be seen in Table 7, Examples 1 and 2 showed very excellent results because cracks did not occur until 77 days and 74 days, but Comparative Examples 2 and 2 were confirmed to be as low as 36 days or less. . In addition, as shown in FIG. 1 , it was confirmed that the size and depth of cracks were also significantly smaller in Examples 1 and 2.

As can be seen from the experimental examples, the shotcrete composition for repair and reinforcement containing the VAE polymer of the present invention together with a shrinkage reducing agent and hemp fiber has slump, air volume, compressive strength, salt penetration resistance, chlorine ion diffusion coefficient, and crack resistance. It can be seen that all of the evaluation criteria were satisfied as a result of the experiment, and in particular, it was very excellent in uniform resistance, which was superior to that of the comparative example.

<Test Example 7> Mock-up test

The shorting test was conducted using a concrete pump machine (water jet pump pressure 2500 bar, flow rate 40 L/min) for spraying the shotcrete composition prepared according to Example 2 of the present invention, and the quality test was confirmed and shown in Table 8. In addition, a photograph of the pasting thickness is shown in FIG. 2 .

Evaluation items target Assessment Methods result Compressive strength (MPa) 35 or more KS F 2405 59.5 / 60.2 Salt penetration resistance (Coulombs) 1,000 or less KS F 2711 477 / 345 Chloride ion diffusion coefficient (*10 ^-12 m ² /sec) 3.0 or less NT Build 492 1.22 / 1.11 crack resistance No cracks up to 56 days ASTM C 1581 no cracks Check the adhesive thickness (mm) over 100 - 200 Rebound Rate (%) 15 or less - 9.8

As a result of the experiment, the rebound rate obtained a total value of 9.8%. It shows better workability and less material loss than general spray-on concrete. The maximum construction thickness was measured to be 200mm, and it is judged that it is possible to construct more than that.

Those skilled in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and their All changes or modifications derived from the concept of equivalents should be construed as being included in the scope of the present invention.

Claims (4)

Water 150kg/㎥ ∼ 250kg/㎥ per unit volume, cement 300kg/㎥ ∼ 400kg/㎥, fine aggregate 1,000kg/㎥ ∼ 1,2000kg/㎥, coarse aggregate 450kg/㎥ ∼ 550kg/㎥, fine powder of blast furnace slag 70kg/㎥ ∼ 120kg/㎥, VAE polymer 20kg/㎥ ∼ 30kg/㎥, expanding agent 15kg/㎥ ∼ 30kg/㎥, water reducing agent 4kg/㎥ ∼ 5kg/㎥, silica fume 20kg/㎥ ∼ 30kg/㎥, shrinkage reducing agent 4kg/㎥ ∼ 5kg /m3, including jute fiber or sheep hemp fiber 0.5kg/m3 to 2kg/m3 having a length of 5 to 15mm, the chemical formula of the VAE polymer is

This is a concrete pump machine that sprays phosphorus shotcrete composition. At one time of pouring, the thickness is 100mm or more, the air volume is 3~6%, the compressive strength is 35Mpa or more, the salt penetration resistance is 1,000 Coulombs or less, the chlorine ion diffusion coefficient 3*10 ^-12 m ² / A shotcrete composition for repair and reinforcement containing a VAE polymer and hemp fibers, characterized in that the sec or less, the rebound rate is 15% or less.
The method according to claim 1, Water 184kg/m3, cement 322kg/m3, fine aggregate 1,125kg/m3, coarse aggregate 491kg/m3, fine blast furnace slag powder 92kg/m3, VAE polymer 23kg/m3, expanding agent 23kg/m3, water reducing agent 4.6kg/m3 , Silica fume 23kg / ㎥, shrinkage reducing agent 23kg / ㎥, jute fiber or sheep hemp fiber 1kg / ㎥ having a length of 5 ~ 15mm A shotcrete composition for reinforcing repair and reinforcement containing a VAE polymer and hemp fibers. delete delete

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