Concrete structure for water treatment having self-healing and waterproofing properties by using inorganic self-healing mixture

Abstract

The present invention relates to a concrete structure for water treatment having self-healing and waterproofing properties by using an inorganic self-healing mixture, the structure comprising cement and the inorganic self-healing mixture which includes blast furnace slag, fly ash, a smectite clay mineral, and gypsum powder.

Description

Concrete water treatment structure with self-healing and waterproofing performance using inorganic self-healing mixture

[0001] The present invention relates to a concrete water treatment structure including a mixture that can improve physical properties such as crack reduction, self-healing performance, increased compressive strength, improved chemical resistance, reduced permeability, and increased salt damage resistance.

[0002] Ready-mixed concrete used on-site can develop cracks due to various factors arising during the production and construction processes. Concrete water treatment structures, where these unavoidable defects occur, require waterproofing treatment.

[0003] Traditionally, waterproofing by coating has been relatively widely used for waterproofing water treatment structures. This is because the coating, such as urethane, sheet, or FRP, is installed on the outside of the concrete. Therefore, in the early stages of construction, the water inside the tank does not come into direct contact with the concrete, so even if there are defects in the concrete matrix, the waterproofing performance can be exhibited due to the water-proofing effect.

[0004] However, most of these waterproofing coating materials are organic, making them difficult to integrate with inorganic concrete. Furthermore, they can become damaged over time. Therefore, concrete structures with long service lives require ongoing maintenance to maintain their waterproofing performance.

[0005] However, it is difficult to repair structures buried underground or water treatment structures using the waterproofing method mentioned above because moisture continuously exists.

[0006] To address this, some concrete waterproofing agents are used in conjunction with the concrete matrix to provide waterproofing properties. However, concrete waterproofing agents are unlikely to be effective in cases where cracks, joints, or other defects occur within the concrete matrix. Furthermore, if moisture penetrates the concrete matrix, its durability can deteriorate more quickly than expected.

[0007] Especially for water treatment structures that can cause chemical corrosion, such as wastewater, measures must be taken to enhance durability.

[0008] Meanwhile, although Portland cement has the property of autogenous healing, it is known that the crack healing performance by autogenous healing is so low that it is less than 0.1 mm, so it is not possible to effectively heal cracks in concrete with only the performance of the cement itself.

[0009] As an example of existing technology, Korean Patent Registration No. 2187932 discloses self-healing concrete in which an inorganic self-healing material is mixed with ordinary Portland cement, wherein the inorganic self-healing material is nano-calcite, and the nano-calcite is mixed in an amount of 0.5 to 0.9 wt%, thereby ensuring self-healing performance for a crack width of 0.25 mm or more.

[0010] However, even if the above technology has some degree of self-healing potential, it has the problem that it cannot sufficiently provide properties such as crack resistance and chemical resistance.

[0011] Accordingly, the present invention aims to provide a concrete water treatment structure including a mixture that can reduce the occurrence of cracks, allow cracks that occur over time to heal, and improve physical properties such as compressive strength and chemical resistance in order to solve the above problems.

[0012] In order to achieve the above purpose, a concrete water treatment structure having self-healing and waterproofing performance using the inorganic self-healing mixture of the present invention (hereinafter referred to as the “structure of the present invention”) is characterized by including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, smectite clay mineral, and gypsum powder.

[0013] As an example, the above gypsum powder is characterized by having a coating layer applied to the outer surface.

[0014] As an example, the coating layer is characterized by comprising an outer layer composed of a low-melting-point thermoplastic resin and an inner layer containing hydroxypropyl methylcellulose phthalate, acetic acid, magnesium salt, and hydrogenated polyterpene.

[0015] As an example, the inner layer is characterized by further addition of raffinose.

[0016] As described above, the structure of the present invention can exhibit crack resistance and self-healing performance when cracks occur afterward, and has the advantage of extending the durability life by improving physical properties such as chemical resistance, compressive strength, and water tightness.

[0017] Figure 1 is a graph showing the results of compressive strength tests of comparative examples and examples.

[0018] Figure 2 is a graph showing the results of measuring the length change of a comparative example and an example.

[0019] Figure 3 is a graph showing the experimental results for the 0.3 mm crack healing rate.

[0020] Hereinafter, the present invention will be described in detail with reference to the attached drawings.

[0021] Since the embodiments of the present invention can be modified in many different forms, the scope of the present invention is not limited to the embodiments described below, as they do not specify or imply the limits of the present invention, but rather describe general methods that can be utilized through the present invention.

[0022] The structure of the present invention is characterized by including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, smectite clay mineral, and gypsum powder. That is, the structure of the present invention is a structure constructed with a composition including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, smectite clay mineral, and gypsum powder; wherein the type of the water treatment structure is not limited.

[0023] The composition applied to the present invention naturally includes water in addition to the above compositions, and the type of water is not limited, but it is preferable to use water that is purified cleanly and free of impurities.

[0024] In addition, water and binder (W / B) are values ​​that determine the strength and durability of concrete, such as design standard strength and mixing strength, and it is desirable to have W / B of 20 to 30 weight% so that drying shrinkage of concrete and material separation do not occur.

[0025] In addition, the composition applied to the present invention further includes aggregates in addition to the above compositions, and the aggregates include coarse aggregates and fine aggregates.

[0026] The above coarse aggregate is generally referred to as gravel, and is not limited to any type as long as it is commonly used in the industry. It is recommended to use crushed aggregate or natural aggregate as the above coarse aggregate, and it is preferably recommended to use one that satisfies KS F 2502 or KS F 2527.

[0027] The above fine aggregate is generally referred to as sand, and both fine and coarse aggregates can be used. The fine aggregate should preferably pass almost completely through a No. 4 sieve (ASTM C125, 4.75 mm), and silica sand, etc. are recommended.

[0028] The above coarse aggregate is preferably a material remaining mainly in the No. 4 sieve (ASTM C125, 4.75 mm), such as silica sand, quartz, marble, granite, limestone, calcite, feldspar, alluvial sand, other sands, or other durable aggregates or mixtures thereof.

[0029] In addition, in the present invention, in order to determine the fluidity of concrete, it is good for the fine aggregate ratio (S / a) to be 20 to 40 volume%, which can be calculated as the volume ratio of sand (S) to the total aggregate volume (sand + gravel, a).

[0030] The above mixture is characterized in that it includes blast furnace slag, fly ash, smectite clay mineral, and gypsum powder.

[0031] Preferably, it is characterized in that 50 to 150 parts by weight of fly ash, 50 to 150 parts by weight of smectite clay mineral, and 30 to 80 parts by weight of gypsum powder are included for 100 parts by weight of blast furnace slag.

[0032] The above-mentioned blast furnace slag does not react directly when in contact with water, but has latent hydraulic properties that harden when in contact with hydroxyl ions and sulfates. Previously, chemical activators were added to induce reactions in the blast furnace slag, but the excessive use of these chemical activators led to problems of secondary contamination.

[0033] Accordingly, in the present invention, gypsum powder is added instead of a chemical activator, and since the gypsum powder is added as a stimulant, it is advantageous in terms of environmental friendliness.

[0034] The above plaster powder has a fineness of 2500 to 4000 cm 2 / g, and it is reasonable to apply a sulfate series with 20 to 80% CaO and 25 to 50% SO3.

[0035] The above smectite clay minerals are clay minerals whose main component is smectite, and bentonite is a representative example. For example, calcium-based bentonite can be applied. These smectite clay minerals have the property of absorbing / swelling moisture, so even without continuous contact with moisture, the absorbed moisture helps to secure the characteristic of calcium ion dissolution, which is effective for self-healing.

[0036] The above gypsum powder is Ca 2 + Wow SO4 2- Dissolved in SO4 2- It heals cracks by forming ettringite, a needle-like hydrate, and monosulfate, a plate-like hydrate, and Ca 2 + is CO3 2- It reacts with calcium carbonate (CaCO3) to heal cracks.

[0037] In addition, in the present invention, a coating layer is applied to the outer surface of the gypsum powder. This is to control the problem that the gypsum powder reacts with moisture during the storage and mixing process, making it impossible to expect the self-healing ability to be exhibited later.

[0038] In particular, the coating layer is characterized by comprising an outer layer composed of a low-melting-point thermoplastic resin and an inner layer containing hydroxypropyl methylcellulose phthalate, acetic acid, hydrogenated polyterpene, and magnesium salt.

[0039] The low-melting-point thermoplastic resin constituting the outer layer exposed to the outside can be formed using various known materials, for example, by a composition containing polyol or organic diisocyanate. It is preferable that the outer layer melts at a temperature of 50 to 90°C, which is the range of heat of hydration.

[0040] The composition of this outer layer completely blocks the moisture exposure of the gypsum powder during the storage process, and the outer layer is removed by the heat of hydration during the mixing process.

[0041] It is preferable that the inner layer in contact with the outer edge of the gypsum be mixed with 20 to 100 parts by weight of acetic acid, 20 to 100 parts by weight of magnesium salt, and 5 to 10 parts by weight of hydrogenated polyterpene, per 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0042] The above hydroxypropyl methylcellulose phthalate (HPMCP) functions as a film forming agent and is a cellulose-based polymer with HPMC as its core structure.

[0043] The above acetic acid corresponds to a composition for improving adhesion to a surface, and the above magnesium salt functions as a stabilizer.

[0044] This inner layer is intended to delay the gypsum powder from contacting moisture after the outer layer is melted and removed during the mixing process, thereby controlling the pre-reaction of the gypsum powder during the mixing process, etc., and thereby multiplying the expression of the self-healing effect when cracks occur later.

[0045] In particular, the above-mentioned magnesium salt functions as a stabilizer, but when it comes into contact with moisture due to crack formation, it creates brucite as an expandable hydrate, thereby doubling the crack healing effect of gypsum. In other words, it enables more dense filling of the crack area.

[0046] In addition, hydrogenated polyterpene is further added to the inner layer, and the addition of hydrogenated polyterpene enables early curing, thereby enabling early self-healing. In other words, the self-healing speed is increased.

[0047] However, when hydrogenated polyterpenes are added in this way, drying shrinkage cracks may occur at the interface of the crack healing portion due to moisture evaporation due to early curing. Therefore, an example is presented in which raffinose is further included in the inner layer, and raffinose functions as a moisturizer to improve resistance to cracks at the interface caused by drying shrinkage, etc. as mentioned above.

[0048] It is appropriate to mix 1 to 5 parts by weight of raffinose per 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0049] The following describes embodiments of the present invention through experimental examples.

[0050] As shown in Table 1 below, each sample was prepared, and the mixture was prepared to contain 50 parts by weight of fly ash, 50 parts by weight of smectite clay mineral, and 30 parts by weight of gypsum powder for 100 parts by weight of blast furnace slag, and the results of the compressive strength test for each sample are shown in Table 2.

[0051] Mixing type, binder ratio (weight %), cement mixture, comparative example 100-S1964S29010S38020

[0052] Mixing type 28-day compressive strength (MPa) Comparative example 42.2S 149.3S 251.2S 350.9

[0053] As can be seen from the above experimental results, S2 has the best compressive strength. Below, experiments are conducted with a binder of 10 wt% mixed material for 90 wt% cement.

[0054] [Example 1]

[0055] A sample was prepared by mixing 100 parts by weight of blast furnace slag with 50 parts by weight of fly ash, 50 parts by weight of smectite clay mineral, and 30 parts by weight of gypsum powder.

[0056] [Example 2]

[0057] The mixture was mixed to include 50 parts by weight of fly ash, 50 parts by weight of smectite clay mineral, and 30 parts by weight of gypsum powder for 100 parts by weight of blast furnace slag, and the gypsum powder was applied as a coating layer including an outer layer composed of a low-melting-point thermoplastic resin (polyol) and an inner layer composed of 50 parts by weight of acetic acid and 30 parts by weight of magnesium salt for 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0058] [Example 3]

[0059] The mixture was mixed to include 50 parts by weight of fly ash, 50 parts by weight of smectite clay mineral, and 30 parts by weight of gypsum powder for 100 parts by weight of blast furnace slag, and the gypsum powder was applied with an outer layer composed of a low-melting-point thermoplastic resin (polyol) and a coating layer containing 50 parts by weight of acetic acid, 30 parts by weight of magnesium salt, and 5 parts by weight of hydrogenated polyterpene for 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0060] [Example 4]

[0061] The mixture was mixed to include 50 parts by weight of fly ash, 50 parts by weight of smectite clay mineral, and 30 parts by weight of gypsum powder for 100 parts by weight of blast furnace slag, and the gypsum powder was applied to an outer layer composed of a low-melting-point thermoplastic resin (polyol) and a coating layer containing 50 parts by weight of acetic acid, 30 parts by weight of magnesium salt, 5 parts by weight of hydrogenated polyterpene, and 1 part by weight of raffinose for 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0062] First, a 28-day compressive strength test was performed on Example 1 (SHC) and Comparative Example (Plain), and the results are shown in Fig. 1. As seen in Fig. 1, SHC exhibits a 19.6% strength enhancement effect compared to Plain.

[0063] Self-healing mixed materials contain expandable materials, which are effective in increasing strength. However, if the strength increase is large, the self-healing performance may decrease. Therefore, it is desirable to adjust the amount used so that the strength increase effect is not high and the compressive strength increase rate at 28 days is 15-30% compared to Plain.

[0064] Next, a chloride ion diffusion coefficient test was performed for the comparative example and Example 1. The results are shown in Table 3 below. As shown in Table 3, the chloride ion diffusion coefficient test results for Example 1 (SHC) and the comparative example (Plain) at 28 days of curing show that SHC shows a 62.5% decrease in chloride ion diffusion coefficient compared to Plain. Due to the characteristics of the material, SHC has the effect of reducing pores in the concrete matrix and healing microcracks, thereby increasing resistance to salt damage.

[0065] Chloride ion diffusion coefficient (10 -12 m 2 / sec)Reduction rate (%)Comparative example 14.4-Example 15.462.5

[0066] Next, the experimental results for the length change rate for the comparative example (Plain) and Example 1 (SHC) are shown in Fig. 2. As seen in Fig. 2, the shrinkage of SHC at 28 days is 502 με, and that of Plain is 768 με, showing that the shrinkage of SHC is reduced by 34.6% compared to that of Plain.

[0067] In addition, crack healing rate experiments were performed for comparative examples and examples, and the results are shown in Fig. 3.

[0068] Crack healing rate refers to the extent to which the amount of water flowing out through the crack surface is reduced according to the age through the constant-level permeability test. Figure 3 shows the crack healing rate after 7 to 28 days (healing age 7 to 28 days) from the time of crack occurrence for a crack width of 0.3 mm. The examples show that the healing rate after 7 days from crack occurrence is 78.6 to 86.4%, and after 14 days, the healing rate is 85.9 to 94.2%. In addition, it can be seen that the standard of a healing rate of 90% or more is satisfied at a healing age of 28 days.

[0069] Next, when comparing the examples, it can be seen that the case of Example 2 exhibits a more advantageous effect than Example 1. This is because, in the case of Example 1, there may be a problem in that the gypsum powder reacts with moisture during the storage and mixing process, making it impossible to expect the self-healing ability to be exhibited afterwards, and this problem is solved by applying a coating layer to the gypsum powder as in Example 2.

[0070] In addition, it can be seen that the case of Example 3 exhibits a more advantageous effect on self-healing ability than the case of Example 2. This is because the case of Example 3 increases the self-healing speed by adding more hydrogenated polyterpene to the inner layer, and the case of Example 4 exhibits the most advantageous effect. It is believed that the case of Example 4 exhibits a more advantageous effect because the inner layer includes more raffinose, which improves the resistance to cracking at the crack healing interface.

Claims

1. A concrete water treatment structure having self-healing and waterproofing performance using an inorganic self-healing mixture, characterized by including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, smectite clay mineral, and gypsum powder.

2. In paragraph 1, The above gypsum powder, A concrete water treatment structure having self-healing and waterproofing performance using an inorganic self-healing mixture characterized by a coating layer applied to the outer surface.

3. In paragraph 2, The above coating layer is, A concrete water treatment structure having self-healing and waterproofing performance using an inorganic self-healing mixture characterized by comprising an outer layer composed of a low-melting-point thermoplastic resin and an inner layer containing hydroxypropyl methylcellulose phthalate, acetic acid, magnesium salt, and hydrogenated polyterpene.

4. In paragraph 3, A concrete water treatment structure having self-healing and waterproofing performance using an inorganic self-healing mixture characterized in that raffinose is further added to the inner layer.

Images