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

Abstract

The present invention relates to a precast concrete structure for water treatment having self-healing and waterproofing performance by using an inorganic self-healing mixture, which is constituted by assembling concrete panels manufactured by precasting, wherein the concrete panel is manufactured by a composition comprising: cement; and an inorganic self-healing mixture containing blast furnace slag, fly ash, an expanding agent, and gypsum powder.

Description

Precast concrete water treatment structure with self-healing and waterproofing performance using inorganic self-healing admixture

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

[0002] 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.

[0003] 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.

[0004] However, it is difficult to repair structures buried underground or water treatment structures using the waterproofing method mentioned above because moisture continuously exists.

[0005] To compensate for this, there are cases where a concrete waterproofing agent with waterproofing properties is used in parallel with the concrete matrix, but it is difficult to expect effective waterproofing properties from the concrete waterproofing agent if defects such as cracks or construction joints occur in the concrete matrix.

[0006] Furthermore, if moisture penetrates the concrete matrix in this way, the concrete's durability can deteriorate more quickly than expected. This is especially true for water treatment structures prone to chemical attack, such as wastewater and sewage, requiring measures to enhance durability.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] Accordingly, the present invention aims to provide a water treatment structure constructed by assembling precast concrete panels containing 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.

[0011] In order to achieve the above purpose, a precast concrete water treatment structure (hereinafter referred to as “structure of the present invention”) having self-healing and waterproofing performance using an inorganic self-healing mixture of the present invention is constructed by assembling concrete panels manufactured by precasting, and the concrete panels are characterized in that they are manufactured using a composition including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, an expanding agent, gypsum powder, and magcarbon.

[0012] As an example, the above gypsum powder is characterized by having a coating layer applied to the outer surface.

[0013] 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.

[0014] As an example, the inner layer is characterized by further addition of raffinose.

[0015] The present invention is a technology applicable to water treatment structures using a single / double wall method, and has the advantage of shortening the construction period and reducing construction costs because the precast concrete panel has waterproofing properties of its own, so the waterproofing process can be omitted.

[0016] In addition, by introducing self-healing technology, it can heal cracks and construction joints that occur in the concrete matrix on its own, so it has the advantage of improving durability by preventing erosion from various harmful factors coming in from the outside as well as waterproofing.

[0017] In addition, since it is capable of self-healing from the moment a crack appears in the concrete, it can overcome the disadvantage of existing waterproofing methods in which the waterproofing performance varies greatly depending on the quality of the materials used and the construction skills of the worker. It also has the advantage of being able to repair underground structures and water treatment structures in use that are difficult to repair in the future.

[0018] Figure 1 is a graph showing the results of compressive strength tests of comparative examples and examples.

[0019] Figure 2 is a graph showing the results of measuring the length change of a comparative example and an example.

[0020] Figure 3 is a graph showing the experimental results for the 0.3 mm crack healing rate.

[0021] Hereinafter, the present invention will be described in detail with reference to the attached drawings.

[0022] 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.

[0023] The structure of the present invention is composed by assembling concrete panels manufactured by precasting, and the concrete panels are characterized in that they are manufactured by a composition including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, expandable material, gypsum powder, and magcarbon.

[0024] The structure of the present invention relates to a water treatment structure constructed by assembling precast concrete panels. Various known technologies exist for constructing such a water treatment structure by assembling precast concrete panels, examples of which include double-wall and single-wall construction methods.

[0025] In particular, the structure of the present invention is characterized in that the concrete panel is manufactured by precasting using a composition including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, expandable material, gypsum powder, and magcarbon.

[0026] The composition applied to the present invention naturally includes water in addition to the above components, and the type of water is not limited, but it is preferable to use water that is purified cleanly and free of impurities.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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).

[0033] The above mixture is characterized in that it includes blast furnace slag, fly ash, expandable material, and gypsum powder.

[0034] Preferably, it is characterized in that it contains 50 to 150 parts by weight of fly ash, 50 to 150 parts by weight of expandable material, 30 to 80 parts by weight of gypsum powder, and 10 to 30 parts by weight of magcarbon for 100 parts by weight of blast furnace slag.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The above-mentioned expansion agent is not limited in type and is intended to control cracks, etc. caused during the hardening process. For example, a calcium sulfo-aluminate reactive inorganic material containing 50 to 80% CaO, 10 to 20% Al2O3, and 1 to 7% SO3, or an inorganic material that has undergone a calcination and refining process containing 30 to 40% SiO2, 1 to 5% free CaO, and 5 to 20% reactive CaO, etc. can be used.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The above hydroxypropyl methylcellulose phthalate (HPMCP) functions as a film forming agent and is a cellulose-based polymer with HPMC as its core structure.

[0046] The above acetic acid corresponds to a composition for improving adhesion to a surface, and the above magnesium salt functions as a stabilizer.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] It is appropriate to mix 1 to 5 parts by weight of raffinose per 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0052] The above magnecarbon (MgO-C) is a material that forms sheets (seeds) of a self-healing composite and has the function of forming a highly active multi-lamellar structure by physical energy and chemical energy in the MC process.

[0053] The following describes embodiments of the present invention through experimental examples.

[0054] As shown in Table 1 below, each sample was manufactured, and the mixture was manufactured to contain 50 parts by weight of fly ash, 50 parts by weight of calcium sulfoaluminate, 30 parts by weight of gypsum powder, and 10 parts by weight of magnesia carbon 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.

[0055] Mixing type, binder ratio (weight %), cement mixture, comparative example 100-S1982S2955S39010

[0056] Mixing type 28-day compressive strength (MPa) Comparative example 43.1S 155.2S 259.3S 357.1

[0057] As can be seen from the above experimental results, S2 has the best compressive strength. Below, experiments are conducted with a binder of 5 wt% mixed material for 95 wt% cement.

[0058] [Example 1]

[0059] 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 calcium sulfoaluminate, 30 parts by weight of gypsum powder, and 10 parts by weight of magnesia carbon.

[0060] [Example 2]

[0061] The mixture was mixed to include 50 parts by weight of fly ash, 50 parts by weight of calcium sulfoaluminate, 30 parts by weight of gypsum powder, and 10 parts by weight of magnesium carbon for 100 parts by weight of blast furnace slag. 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.

[0062] [Example 3]

[0063] The mixture was mixed to include 50 parts by weight of fly ash, 50 parts by weight of calcium sulfoaluminate, 30 parts by weight of gypsum powder, and 10 parts by weight of magnesia carbon for 100 parts by weight of blast furnace slag. 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, and 5 parts by weight of hydrogenated polyterpene for 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0064] [Example 4]

[0065] The mixture was mixed to include 50 parts by weight of fly ash, 50 parts by weight of calcium sulfoaluminate, 30 parts by weight of gypsum powder, and 10 parts by weight of magnesia carbon for 100 parts by weight of blast furnace slag. 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.

[0066] First, a pitching ratio experiment was conducted for the comparative example and Example 1, and the results are shown in Table 3 below. As can be seen in Table 3, Example 1 yields more advantageous results in pitching ratio than the comparative example.

[0067] Classification Absorption (g) Comparison of permeability ratio Example 5.33 - Example 13.220.605

[0068] In addition, compressive strength tests were performed on the comparative example (Plain) and the example 1 (SHm) for 1 day and 7 days, and the compressive strength tests were performed based on the curing temperature standards applied when producing precast products, with a maximum temperature of 60°C and a maximum temperature maintenance time of 4 hours, and the compressive strength was measured on 1 day and 7 days.

[0069] As shown in Fig. 1, the compressive strength at 1 day, which is the demoulding strength, increased by 28.9% for SHm compared to Plain, and also increased by 17.5% at 7 days. In general, in the case of a binder containing an intumescent material, cracks may occur due to excessive expansion effect under high-temperature curing conditions applied during precast production, but the self-healing concrete waterproofing agent of the present invention uses an intumescent material of the MgO series, and thus has the characteristic of not causing expansion cracks even during high-temperature curing.

[0070] Additionally, the experimental results for the length change rate for the comparative example (Plain) and Example 1 (SHm) are shown in Fig. 2.

[0071] The length change rate test results for SHm and Plain can be used to evaluate the shrinkage rate of concrete over time. SHm contains an expansive agent, which can compensate for initial concrete shrinkage.

[0072] And at 28 days of age, the shrinkage of SHm is 311με, and that of Plain is 562με, showing that the shrinkage of SHm is reduced by 44.6% compared to that of Plain.

[0073] Additionally, crack healing rate experiments were conducted for comparative examples and examples. The crack healing rate experiments showed the healing rate at 7 days (healing time) and 14 days (healing time of 14 days) from the time of crack initiation for a crack width of 0.3 mm. The results are presented in Fig. 3.

[0074] As seen in Fig. 3, in the case of the examples, the healing rate is 70.4 to 83.0% after 7 days from the occurrence of cracks, as shown in the graph, and the healing rate is 85.4 to 98.1% after 14 days, showing a healing rate of over 90% at the 14-day healing period.

[0075] 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.

[0076] 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 precast concrete water treatment structure having self-healing and waterproofing performance using an inorganic self-healing mixture, characterized in that the precast concrete panel is manufactured by assembling concrete panels, wherein the concrete panel is manufactured by a composition including cement; and an inorganic self-healing mixture including blast furnace slag, fly ash, expandable material, gypsum powder, and magcarbon.

2. In paragraph 1, The above gypsum powder, A precast 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. A precast 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 precast 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.

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