Concrete composition for water treatment structures having self-healing and waterproofing performance by using self-healing mixture, and concrete water treatment structure using same

Abstract

The present invention relates to a concrete composition for water treatment structures having self-healing and waterproofing performance by using a self-healing mixture, and a concrete water treatment structure using same, wherein the concrete composition comprises: cement; and a self-healing mixture containing blast furnace slag, fly ash, an expanding material, and gypsum powder.

Description

Concrete composition for water treatment structures possessing self-healing and waterproofing performance using a self-healing admixture, and a concrete water treatment structure using the same

[0001] The present invention relates to a concrete composition for water treatment structures containing an admixture capable of improving physical properties such as increased compressive strength, improved chemical resistance, reduced permeability ratio, and increased resistance to salt damage while exhibiting crack reduction and self-healing performance, and to a concrete water treatment structure using the same.

[0002] Concrete used on-site can crack due to various factors arising during the production and construction processes. Waterproofing methods are essential for concrete water treatment structures where such unavoidable defects occur.

[0003] Traditionally, membrane waterproofing has been relatively widely used for the waterproofing of water treatment structures. Since membranes such as urethane, sheets, or FRP are installed on the exterior of the concrete, the water inside the tank does not come into direct contact with the concrete during the initial construction phase. This allows for waterproofing performance due to the water-blocking effect, even if there are defects in the concrete matrix. However, as most of these water-blocking membrane materials are organic, integrated construction with inorganic concrete is difficult, and problems such as membrane deterioration occur over time. Therefore, for concrete structures with a long service life, continuous maintenance is required to maintain waterproofing performance.

[0004] However, due to the continuous presence of moisture in underground structures or water treatment facilities, it is difficult to repair them using the waterproofing methods mentioned above. To compensate for this, there are cases where concrete waterproofing agents are applied in parallel to the concrete matrix; however, effective waterproofing performance cannot be expected from concrete waterproofing agents when defects such as cracks or construction joints occur in the concrete matrix.

[0005] Furthermore, if moisture penetrates the concrete matrix in this way, the durability of the concrete can deteriorate faster than expected. In particular, for water treatment structures susceptible to chemical erosion, such as sewage and wastewater, measures to reinforce durability must be implemented.

[0006] Meanwhile, ordinary Portland cement has the characteristic of self-healing cracks, but it is known that the crack healing performance by self-healing is insufficient at less than 0.1 mm, so the cement itself alone cannot effectively heal cracks that occur in concrete.

[0007] As an example of existing technology, Korean Patent Registration No. 2187932 presents self-healing concrete in which an inorganic self-healing material is mixed with ordinary Portland cement, wherein the inorganic self-healing material is nanocalcite and the nanocalcite is mixed in an amount of 0.5 to 0.9 weight percent, thereby ensuring self-healing performance in crack widths of 0.25 mm or more.

[0008] However, even if the above technology is expected to have some degree of self-healing, there is a problem in that it cannot sufficiently provide physical properties such as crack resistance and chemical resistance.

[0009] Accordingly, the present invention aims to provide a concrete composition for water treatment structures and a concrete water treatment structure using the same, which includes a mixture capable of reducing the occurrence of cracks and allowing cracks to heal over time while simultaneously improving physical properties such as compressive strength and chemical resistance, in order to solve the above-mentioned problems.

[0010] To achieve the above objective, a concrete composition for a water treatment structure having self-healing and waterproofing performance using the self-healing admixture of the present invention (hereinafter referred to as the "composition of the present invention") is characterized by comprising cement; and a self-healing admixture comprising blast furnace slag, fly ash, an expansive agent, and gypsum powder.

[0011] Here, the water treatment structure is a structure constructed using the composition of the present invention, and its type is not limited.

[0012] In addition, the present invention discloses a concrete water treatment structure using the composition of the present invention.

[0013] As explained above, the composition of the present invention can exhibit crack resistance and self-healing performance in the event of subsequent crack occurrence, and has the advantage of extending the durability life by improving physical properties such as chemical resistance, compressive strength, and watertightness.

[0014] FIG. 1 is a graph showing the compressive strength test values ​​for the examples.

[0015] Figure 2 is a graph showing flow test values ​​for the examples.

[0016] FIG. 3 is a graph showing experimental values ​​of the rate of change of length for the examples.

[0017] Figure 4 is a graph showing the salt resistance test values ​​for the examples.

[0018] Figure 5 is a graph showing the experimental results for a 0.3mm crack healing rate.

[0019] Since embodiments of the present invention can be modified in various different forms, the scope of the present invention is not limited to the embodiments described below, as it describes general methods that can be utilized through the present invention rather than specifying or implying the limitations of the present invention.

[0020] The composition of the present invention is characterized by comprising cement; and a self-healing mixture comprising blast furnace slag, fly ash, an expansive agent, and gypsum powder.

[0021] In addition to the above compositions, the composition applied to the present invention naturally includes water. Although the type of water is not limited, it is preferable to use cleanly purified water free of impurities.

[0022] In addition, water and binder (W / B) is a value that determines the strength and durability of concrete, such as design standard strength and mix strength, and it is desirable to have a W / B ratio of 20 to 30 weight percent so that drying shrinkage and material segregation of the concrete do not occur.

[0023] In addition, the composition applied to the present invention further includes aggregate in addition to the above compositions, and the aggregate includes coarse aggregate and fine aggregate.

[0024] The above coarse aggregate is generally also called gravel, and is not limited to any specific type as long as it is commonly used in the industry. It is preferable to use crushed aggregate or natural aggregate for the above coarse aggregate, and preferably, it is preferable to use one that satisfies KS F 2502 or KS F 2527.

[0025] The above fine aggregate is generally referred to as sand, and both fine aggregate and coarse aggregate can be used. The above fine aggregate should be a material that passes almost completely through a No. 4 sieve (ASTM C125, 4.75 mm), and it is recommended to use silica sand, etc.

[0026] The above coarse aggregate is preferably a material that remains mainly on a 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.

[0027] In addition, in order to determine the fluidity of the concrete, it is preferable that the fine aggregate ratio (S / a) be 20 to 40 volume%, which can be calculated as the volume ratio of sand (S) to the volume of total aggregate (sand + gravel, a).

[0028] The above mixture is characterized by including blast furnace slag, fly ash, an expansive agent, and gypsum powder.

[0029] Preferably, it is characterized by including 50 to 150 parts by weight of fly ash, 5 to 30 parts by weight of an expansive agent, and 5 to 30 parts by weight of gypsum powder per 100 parts by weight of blast furnace slag.

[0030] The above 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 a reaction of the blast furnace slag, but there was a problem of secondary pollution due to the excessive use of such chemical activators.

[0031] Accordingly, in this invention, gypsum powder is added instead of a chemical activator, and since the gypsum powder is added as an activator, it is advantageous in terms of being environmentally friendly.

[0032] The above gypsum powder has a fineness of 2500 to 4000 cm⁻¹ 2 It is appropriate to apply a sulfate series with 20 to 80% CaO and 25 to 50% SO3, with a value of / g.

[0033] The above gypsum powder is Ca 2 + and SO4 2- Dissolved into SO4 2- It heals cracks by forming acicular hydrate Ettringite and platy hydrate monosulfate, and Ca 2 + CO3 2- It reacts with to form calcium carbonate (CaCO3) and heals the crack.

[0034] In addition, the present invention applies a coating layer to the outer edge of the gypsum powder. This is intended to control the problem where the gypsum powder reacts with moisture during storage and mixing processes, making it impossible to expect the subsequent manifestation of self-healing ability.

[0035] In particular, the coating layer is characterized by being composed of an outer layer made of a low-melting-point thermoplastic resin and an inner layer containing hydroxypropyl methylcellulose phthalate, acetic acid, hydrogenated polyterpene, and magnesium salt.

[0036] The low-melting point thermoplastic resin constituting the outer layer exposed to the outside can be made of various known materials, and, for example, can be formed by a composition containing polyols or organic diisocyanates. It is preferable that the outer layer melts at a hydration heat range of 50 to 90°C.

[0037] The composition of this outer layer completely prevents the gypsum powder from being exposed to moisture during storage, and allows the outer layer to be removed by the heat of hydration during the mixing process.

[0038] The inner layer in contact with the outer edge of the gypsum is preferably composed of 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 polyterpenes, per 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0039] The above hydroxypropyl methylcellulose phthalate (HPMCP) functions as a film-forming agent and is a cellulose-based polymer with HPMC as its core structure.

[0040] The above acetic acid corresponds to a composition for improving adhesion to the surface, and the above magnesium salt functions as a stabilizer.

[0041] This inner layer is designed to delay contact between the gypsum powder and moisture when the aforementioned outer layer is melted and removed during the mixing process, thereby controlling the pre-reaction of the gypsum powder during the mixing process and doubling the manifestation of self-healing efficacy in the event of subsequent crack formation.

[0042] In particular, the above magnesium salt functions as a stabilizer, but when it comes into contact with moisture due to cracking, it forms brucite as an expansive hydrate, thereby doubling the crack healing efficacy of the gypsum. In other words, it enables more dense filling of the cracked area.

[0043] In addition, hydrogenated polyterpenes are further added to the inner layer, and early self-healing is enabled by causing early curing through the addition of hydrogenated polyterpenes. In other words, the speed of self-healing is enhanced.

[0044] However, when hydrogenated polyterpenes are added in this manner, premature curing can lead to moisture evaporation, which may induce drying shrinkage cracks at the interface of the crack healing area. Accordingly, an example is presented in which raffinose is further included in the inner layer; raffinose is designed to function as a humectant to improve resistance to cracks at the interface caused by the aforementioned drying shrinkage.

[0045] It is appropriate to mix 1 to 5 parts by weight of raffinose with respect to 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0046] In addition, the present invention provides an example in which mag-carbon is further included in the self-healing mixture. The mag-carbon (MgO-C) is a material that functions to form a highly active multi-lamellar structure by physical and chemical energy in the MC process while serving as a seed for the self-healing mixture.

[0047] Preferably, it is reasonable to mix 1 to 10 parts by weight of magcarbon with respect to 100 parts by weight of blast furnace slag.

[0048] In addition, the present invention provides an example in which a smectite clay mineral is applied as the expansion agent. The smectite clay mineral is a clay mineral with smectite as its main component, and bentonite is a representative example.

[0049] These smectite clay minerals have the property of absorbing and swelling moisture, which helps ensure the release of calcium ions effective for self-healing through the absorbed moisture, even without continuous contact with water.

[0050] In addition, the present invention provides an example in which a polyanionic polymer is applied as the expansion agent.

[0051] Alginate can be applied to these polyanionic polymers.

[0052] When the above smectite clay mineral is added as an expansive agent, both cations and anions are adsorbed during the water absorption process. In this case, OH-, which is required to produce calcium hydroxide in the cement hydration reaction, is adsorbed, which can inhibit the hydration reaction. Therefore, in the present invention, a polyanionic polymer is added so that only cations, such as calcium ions, are selectively adsorbed during water absorption as well as during expansion, thereby controlling problems such as strength reduction.

[0053] Meanwhile, in the present invention, there may be a problem of reduced workability due to the addition of gypsum, and as previously mentioned, while self-healing ability is exhibited by the gypsum, there may also be a problem of drying cracks due to premature hardening.

[0054] Accordingly, the present invention further presents an example in which polyaspartate is additionally included in the mixture to complement the workability resulting from the addition of gypsum while simultaneously improving resistance to drying cracks.

[0055] In other words, the addition of polyaspartate improves dispersibility to complement workability, and enhances resistance to drying cracks through moisturization.

[0056] However, when only polyaspartate is added, there is a problem where a decrease in strength is caused by material separation, etc.

[0057] Accordingly, the present invention provides an example in which abietic acid is further included in addition to polyaspartate.

[0058] The addition of abietic acid controls the reduction in strength while additionally improving resistance to corrosion.

[0059] Preferably, 1 to 5 parts by weight of a mixture of polyaspartate and abietic acid are blended with 100 parts by weight of blast furnace slag, and polyaspartate and abietic acid are blended in a weight ratio of (7:3) to (9:1).

[0060] An embodiment of the present invention is described below through experimental examples.

[0061] As shown in Table 1 below, each sample was prepared, and the mixture was prepared to contain 50 parts by weight of fly ash, 10 parts by weight of alginate, and 10 parts by weight of gypsum powder for every 100 parts by weight of blast furnace slag, and the results of the compressive strength test for each sample are shown in Table 2.

[0062] Mix Type Binder Ratio (Weight%) Cement Mixture Comparative Example 100-S1964S29010S38020

[0063] Mix Type 28-Day Compressive Strength MPa Comparative Example 4 2.2S 15 0.8S 25 2.6S 35 2.0

[0064] As can be seen from the experimental results above, S2 has the best compressive strength. Accordingly, tests for compressive strength, flow, change in length, salt resistance, and crack healing rate were conducted using 90% by weight of cement and 10% by weight of the admixture as the binder, and the results are presented in Table 3 and Figures 1 to 5 below.

[0065] [Example 1]

[0066] A sample was prepared by mixing 50 parts by weight of fly ash, 10 parts by weight of alginate, and 10 parts by weight of gypsum powder for every 100 parts by weight of blast furnace slag.

[0067] [Example 2]

[0068] A sample was prepared by mixing 50 parts by weight of fly ash, 10 parts by weight of alginate, 10 parts by weight of gypsum powder, and 2 parts by weight of magnesium carbon for every 100 parts by weight of blast furnace slag.

[0069] [Example 3]

[0070] The mixture was formulated in the same manner as in Example 1, but the gypsum powder was applied such that the coating layer included 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 every 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0071] [Example 4]

[0072] The mixture was formulated in the same manner as in Example 3, but the gypsum powder was applied such that an outer layer composed of a low-melting point thermoplastic resin (polyol) and a coating layer comprising 50 parts by weight of acetic acid, 30 parts by weight of magnesium salt, and 5 parts by weight of hydrogenated polyterpenes were applied to 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0073] [Example 5]

[0074] The mixture was formulated in the same manner as in Example 4, but the gypsum powder was applied such that an outer layer composed of a low-melting point thermoplastic resin (polyol) and a coating layer comprising 50 parts by weight of acetic acid, 30 parts by weight of magnesium salt, 5 parts by weight of hydrogenated polyterpenes, and 1 part by weight of raffinose were applied for every 100 parts by weight of hydroxypropyl methylcellulose phthalate.

[0075] [Example 6]

[0076] The formulation was prepared in the same manner as in Example 1, but smectite clay mineral was added as an expansive agent instead of alginate.

[0077] [Example 7]

[0078] The mixture was formulated in the same manner as in Example 1, but with an additional 1 part by weight of polyaspartate per 100 parts by weight of blast furnace slag in the mixture.

[0079] [Example 8]

[0080] The mixture was formulated in the same manner as in Example 1, but with an additional 1 part by weight of polyaspartate and abietic acid (weight ratio of 9:1) per 100 parts by weight of blast furnace slag in the mixture.

[0081] Test Item Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Test Standard Compressive Strength (28 days) MPa 5 2.6 5 3.2 5 2.9 5 3.1 5 2.4 4 5.7 4 6.5 5 0.9 KS F240 5 Flow mm 185 180 180 180 185 180 195 195 Length Change Rate (%) 0.1 9 0.0 9 4 0.0 4 10.0 2 3 0.0 4 7 0.2 1 0.0 16 0.0 1 KS F242 4 Chloride Ion Diffusion Coefficient (10 -12 m 2 / sec)5.42.554.212.831.575.673.132.52ASTM C267

[0082] Looking at the compressive strength of Table 3 and Figure 1 above, it can be seen that Example 6 is smaller than Example 1. This is believed to be due to the addition of smectite clay mineral as an expansion agent in Example 6, which causes OH- to be adsorbed during the water absorption process, thereby inhibiting the hydration reaction.

[0083] In contrast, it can be seen that Example 1 is more advantageous than Example 6 in terms of compressive strength, which is attributed to the addition of alginate as an expansion agent, which causes only cations to be absorbed during the moisture absorption process.

[0084] In addition, it can be seen that the compressive strength in Example 7 is lower than in Example 1, which is attributed to material separation and other factors resulting from the addition of polyaspartate to improve workability and resistance to drying cracks. To compensate for this, in Example 8, it is determined that the problem of strength reduction is resolved by the addition of abietic acid in addition to polyaspartate.

[0085] Looking at the workability in Table 3 and Figure 2 above, it can be seen that Examples 7 and 8 are the most excellent, which is attributed to the addition of more polyaspartate to improve dispersibility.

[0086] Looking at the crack resistance and salt resistance aspects in Table 3, Figure 3, and Figure 4 above, it can be seen that the case of Example 2 exhibits more favorable effects than Example 1, which is attributed to the improvement in self-healing ability due to the addition of more magcarbon to Example 2.

[0087] In addition, regarding crack resistance and salt resistance, it can be seen that Example 3 exhibits more favorable effects than Example 1. This is because, in the case of Example 1, there may be a problem where the gypsum powder reacts with moisture during storage and mixing processes, making it impossible to expect the self-healing ability to manifest afterward; therefore, it is believed that this problem is resolved by applying a coating layer to the gypsum powder as in Example 3.

[0088] In addition, it can be seen that the case of Example 4 exhibits more favorable effects in terms of crack resistance and salt damage resistance than the case of Example 3, which is attributed to the fact that the self-healing speed is enhanced by adding more hydrogenated polyterpenes to the inner layer in the case of Example 4, and the case of Example 5 exhibits more favorable effects than the case of Example 4, which is attributed to the fact that the resistance to cracks at the crack healing interface is improved by including more raffinose in the inner layer in the case of Example 5.

[0089] In addition, it can be seen that the cases of Examples 7 and 8 yield more favorable effects than Example 1, which is attributed to the improvement in crack resistance as mentioned above. In this case as well, it is believed that the additional addition of polyaspartate in Example 7 improves resistance to drying cracks, and in particular, the case of Example 8 shows even better effects, which is attributed to the addition of abietic acid in addition to polyaspartate, which improves the durability of the paste.

[0090] In addition, crack healing rate experiments were performed on comparative examples and embodiments, and the results are shown in Fig. 5.

[0091] The crack healing rate refers to the degree to which the amount of water flowing out through the crack surface decreases with age through a constant head permeability test. Figure 5 shows the crack healing rate for a crack width of 0.3 mm after 7 to 28 days (healing age 7 to 28 days) from the time the crack occurred.

[0092] The examples show a healing rate of 79.5–84.1% after 7 days have passed since the crack occurred, and a healing rate of 82.6–93.7% after 14 days. 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.

[0093] When comparing the following examples, it can be seen that Example 2 exhibits a more favorable effect than Example 1, which is attributed to the inclusion of more magcarbon in the mixture.

[0094] It can be seen that the effect of Example 3 is more favorable than that of Example 1. This is because, in the case of Example 1, there may be a problem where the gypsum powder reacts with moisture during storage and mixing processes, making it impossible to expect the self-healing ability to manifest afterward; therefore, it is believed that this problem is resolved by applying a coating layer to the gypsum powder as in Example 3.

[0095] In addition, it can be seen that the case of Example 4 exhibits a more favorable effect on self-healing ability than the case of Example 3, which is attributed to the fact that the self-healing speed is enhanced by adding more hydrogenated polyterpenes to the inner layer in the case of Example 4, and the case of Example 5 exhibits the most favorable effect, which is attributed to the fact that the resistance to cracks at the crack healing interface is improved by including more raffinose in the inner layer in the case of Example 5.

[0096] Meanwhile, the present invention also discloses concrete water treatment structures, and relates to water treatment structures constructed using the composition of the present invention mentioned above.

[0097] Such concrete water treatment structures include a water treatment structure constructed by assembling precast concrete panels using the composition of the present invention mentioned above. Various known technologies exist for structures formed by assembling such precast concrete panels, such as double-wall or single-wall construction methods.

Claims

1. Cement; and A concrete composition for a water treatment structure having self-healing and waterproofing performance using a self-healing mixture characterized by comprising a self-healing mixture comprising blast furnace slag, fly ash, an expansive agent, and gypsum powder.

2. In Paragraph 1, A concrete composition for water treatment structures having self-healing and waterproofing performance using a self-healing admixture characterized by further including magcarbon in the self-healing admixture.

3. In Paragraph 1, A concrete composition for water treatment having self-healing and waterproofing performance using a self-healing mixture characterized in that the above gypsum powder has a coating layer applied to its outer edge, and the coating layer consists of an outer layer composed of a low-melting point thermoplastic resin and an inner layer comprising hydroxypropyl methylcellulose phthalate, acetic acid, magnesium salt, and hydrogenated polyterpene.

4. In Paragraph 3, A concrete composition for water treatment having self-healing and waterproofing performance using a self-healing mixture characterized by the addition of raffinose to the inner layer.

5. In Paragraph 1, A concrete composition for water treatment having self-healing and waterproofing performance using a self-healing admixture characterized in that the expansive agent is a smectite clay mineral.

6. In Paragraph 1, A concrete composition for water treatment having self-healing and waterproofing performance using a self-healing admixture characterized in that the expansive agent is a polyanionic polymer.

7. In Paragraph 1, A concrete composition for water treatment having self-healing and waterproofing performance using a self-healing admixture characterized by further including polyaspartate.

8. In Paragraph 7, A concrete composition for water treatment having self-healing and waterproofing performance using a self-healing admixture characterized by further including abietic acid.

9. A concrete water treatment structure using a concrete composition for a water treatment structure having self-healing and waterproofing performance by using a self-healing admixture according to any one of claims 1 to 8.

10. In Paragraph 9, A concrete water treatment structure characterized by being constructed by assembling precast concrete panels using a concrete composition for water treatment structures that possesses self-healing and waterproofing performance using the above-mentioned self-healing mixture.

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