KR102603775B1 - Geo-polymer Mortar for Concrete Surface Repair And Concrete Section Recovery And Method for Concrete Surface Repair And Concrete Section Recovery Using the Same - Google Patents

Abstract

The present invention improves economic efficiency by promoting the creation of hydrotalcite in the cement matrix through the incorporation of magnesium oxide and aluminum oxide without adding separate hydrotalcite, and compresses even if a large amount of magnesium oxide and aluminum oxide are mixed. It relates to a geopolymer mortar composition for salt-resistant concrete surface repair and cross-section restoration using the promotion of hydrotalcite formation without reduction in strength and chlorine ion penetration resistance, and a method for concrete surface repair and cross-section restoration using the same, salt-resistant salt according to the present invention. The geopolymer mortar composition for surface repair and cross-sectional restoration of decomposed concrete includes a binder including calcium aluminate cement, fly ash, and slag fine powder; And, based on 100 parts by weight of the binder, 10 to 20 parts by weight of magnesium oxide (MgO) powder, 5 to 10 parts by weight of aluminum oxide (Al ₂ O ₃ ) powder, 40 to 40 parts by weight of a three-component alkaline activator consisting of sodium hydroxide, water glass and water. Hydrotalcite is produced by the reaction of the magnesium oxide (MgO) powder and the aluminum oxide (Al ₂ O ₃ ) powder, including 60 parts by weight, 0.3 to 1.0 parts by weight of a setting retardant, and 10 to 20 parts by weight of a filler. It is characterized by

Description

Geopolymer mortar composition for salt-resistant concrete surface repair and section recovery using the promotion of hydrotalcite formation, and method for concrete surface repair and section recovery using the same {Geo-polymer Mortar for Concrete Surface Repair And Concrete Section Recovery And Method for Concrete Surface Repair And Concrete Section Recovery Using the Same}

The present invention relates to a geopolymer mortar composition used for concrete surface repair and cross-sectional reinforcement. More specifically, it uses fly ash and slag, which are industrial by-products, as a binder, and aluminum oxide (Al ₂ O). ₃ ), Geopolymer mortar for surface repair and cross-section restoration of salt-resistant concrete with high salt resistance by promoting the creation of hydrotalcite with a Mg-Al bonding structure inside the concrete matrix by mixing magnesium oxide (MgO). It relates to a composition and a method for concrete surface repair and cross-section restoration using the same.

In general, it has been recognized that concrete structures can be used semi-permanently due to their high durability, but recently, as a result of many researches and surveys of existing structures, concrete structures also cannot avoid the aging phenomenon, especially as the age deteriorates. There are often cases where it loses its original function before it lasts more than ten years.

As mentioned above, there are various deterioration phenomena that shorten the lifespan of concrete, but in particular, the effect of corrosion of reinforcing bars due to chloride intruding from outside, such as when concrete was manufactured using sea sand from which salt has not been removed, or when used in winter, such as melting agents or snow removal materials. As a result, damage to concrete structures is being investigated as being serious.

Conventionally, when trying to repair a structure that has suffered deterioration due to chlorine ions, an anti-corrosion method using acrylic or epoxy-based surface covering materials, a rebar corrosion method using a nitrite-based corrosion inhibitor, and a corrosion inhibitor and silicate-based impregnation agent were used. The rebar corrosion inhibition method was mainly used. However, the anti-corrosion method using the acrylic or epoxy-based surface coating material is effective in fundamentally blocking chlorine ions and carbon dioxide penetrating from the outside by forming a coating film by applying the coating material to the surface of concrete or mortar, but due to physical and chemical heterogeneity with the matrix. As a result, performance deterioration such as peeling and falling off over time cannot be avoided, and there is a problem in that the corrosion rate increases when chlorine ions or the like invade afterwards.

In addition, the reinforcing bar corrosion method using the nitrous acid-based corrosion inhibitor has a clear effect on reinforcing bar corrosion inhibition, but the amount added to obtain the reinforcing bar corrosion-inhibiting effect is excessive, and there is a high risk of affecting the initial characteristics of the mortar, such as causing rapid setting, and nitrous acid-based corrosion. Inhibitors are added to mortar or applied directly to reinforcing bars, but they do not directly fix chlorine ions and are only involved in forming a passive film on the reinforcing bars, so there is a limit to corrosion inhibition.

The reinforcing bar corrosion inhibition method using the corrosion inhibitor and silicate-based impregnation agent increases the alkalinity around the reinforcing bar in addition to the existing corrosion inhibitor reinforcing bar corrosion inhibition technology, thereby slowing down the corrosion rate to that extent, thereby obtaining a more effective reinforcing bar corrosion inhibition effect. However, the use of silicate-based minerals When applying a penetrant to the surface of concrete, it is realistically difficult to penetrate along the capillaries in the concrete, and since the penetrant is applied only to the surface, it is very unclear whether the alkalinity in the overall concrete increases. In the case of inorganic penetrants, it depends on the moisture distribution on the surface of the matrix. Because constructability was affected, there were problems with construction.

To solve this problem, Republic of Korea Patent No. 10-0515948 states that after base treatment to remove foreign substances in the concrete structure, 20 to 40 wt% of cement, 1 to 5 wt% of alumina cement, and high powder are added to the base treated concrete structure. For cross-sectional restoration consisting of 5 to 20 wt% of filler, 1 to 5 wt% of powdered polymer, 005 to 02 wt% of water reducing agent, 001 to 01 wt% of reinforcing fiber, 1 to 2 wt% of nitrite-based hydrotalcite or nitrite-based hydrocalumite, and silica sand. A method of forming a multi-stage barrier capable of blocking and delaying salt pollutants is disclosed by mixing mortar with mixing water and restoring the cross section through continuous spraying or hand plastering.

However, the conventional cement composition for surface repair and cross-section restoration containing hydrotalcite, including the repair method using the mortar composition for cross-section restoration of the registered patent described above, involves restoring the cross-section by mixing pre-prepared nitrite-based hydrotalcite into cement. Because the mortar composition is manufactured, the economic efficiency is significantly reduced, and as the amount of nitrite-based hydrotalcite increases, the compressive strength and chlorine ion penetration resistance decrease.

Republic of Korea Patent No. 10-0515948

The present invention is intended to solve the above-described problem, and the purpose of the present invention is to improve economic efficiency by promoting the production of hydrotalcite in the cement matrix through the incorporation of magnesium oxide and aluminum oxide without adding separate hydrotalcite. A geopolymer mortar composition for salt-resistant concrete surface repair and cross-section restoration using the promotion of hydrotalcite production, which improves the compressive strength and chlorine ion penetration resistance even when large amounts of magnesium oxide and aluminum oxide are mixed, and the concrete surface using the same It provides repair and cross-sectional restoration methods.

The geopolymer mortar composition for salt-resistant concrete surface repair and cross-section restoration according to the present invention for achieving the above object includes a binder containing calcium aluminate cement, fly ash, and slag fine powder; And, based on 100 parts by weight of the binder, 10 to 20 parts by weight of magnesium oxide (MgO) powder, 5 to 10 parts by weight of aluminum oxide (Al ₂ O ₃ ) powder, 40 to 40 parts by weight of a three-component alkaline activator consisting of sodium hydroxide, water glass and water. Hydrotalcite is produced by the reaction of the magnesium oxide (MgO) powder and the aluminum oxide (Al ₂ O ₃ ) powder, including 60 parts by weight, 0.3 to 1.0 parts by weight of a setting retardant, and 10 to 20 parts by weight of a filler. It is characterized by

The magnesium oxide (MgO) powder is preferably pretreated by firing at a temperature of 700 to 1000°C before being mixed with the binder.

In addition, the filler is preferably a mixture of zirconium silicate (ZrSiO ₄ ) powder and oyster shell powder in a weight ratio of 70:30 to 60:40.

In the geopolymer mortar composition of the present invention, 10 to 15 parts by weight of seaweed fibers obtained by immersing the fibers in an aqueous metal salt solution containing aluminum ions are added in an amount of 10 to 15 parts by weight based on 100 parts by weight of the binder, and 1 to 15 parts by weight of sodium carbonate is added to 100 parts by weight of the binder. By adding an additional 2 parts by weight, hydrotalcite can be created and coated on the surface of the seaweed fiber.

The method of surface repair and cross-section restoration of a concrete structure using the geopolymer mortar composition according to the present invention as described above is,

Cleaning the substrate through chipping and high-pressure water washing;

Steps of removing rebar rust and applying a rebar rust preventive agent while the background surface is prepared;

Applying a primer to the surface on which the reinforcing bar rust preventive agent is applied; and

Applying the above-described geopolymer mortar composition to the surface on which the primer is applied;

may include.

The geopolymer mortar composition for concrete surface repair and cross-section restoration of the present invention produces Mg- in the geopolymer mortar by the reaction of magnesium oxide (MgO) and aluminum oxide (Al ₂ O ₃ ) mixed with a binder and an alkali activator. The production of hydrotalcite, which has an Al bonded structure, can be promoted, and the ion exchange effect of hydrotalcite produced in the mortar provides the effect of effectively suppressing chloride penetration.

In addition, since there is no need to prepare hydrotalcite in advance, there is an economic advantage in terms of time and price.

Additionally, by mixing magnesium oxide (MgO) powder at 10-20% of the total weight of the binder, harmful phase transition of calcium aluminate cement (CAC) to stable hydrate is suppressed, and hydrotalcite is generated by reacting with metastable hydrate to form internal There is an advantage in preventing weakening of porous microstructure and strength due to shrinkage.

By mixing fillers made of zirconium silicate (ZrSiO ₄ ) powder and oyster shell powder together at a predetermined mixing ratio, geopolymer mortar can have high compressive strength in a room temperature environment, and can be used as an injection and filling method for crack repair or cross-section restoration of concrete. When applied to , the effect of increasing pot life and improving injectability and filling properties can be obtained.

Figure 1 is a graph showing XRD results for examples and comparative examples of geopolymer mortar compositions for salt-resistant concrete surface repair and cross-section restoration according to the present invention.
Figure 2 is a graph showing TD/DTG results for examples and comparative examples of geopolymer mortar compositions for salt-resistant concrete surface repair and cross-section restoration according to the present invention.

The geopolymer mortar composition for salt-resistant concrete surface repair and cross-section restoration according to the present invention contains magnesium oxide (MgO) that generates hydrotalcite in a binder containing calcium aluminate cement, fly ash, and slag fine powder. ) powder and aluminum oxide (Al ₂ O ₃ ) powder are mixed, and fillers including an alkali activator, a setting retardant, zirconium silicate (ZrSiO ₄ ) powder, and oyster shell powder are mixed to form the magnesium oxide. This is to promote the production of hydrotalcite in cement morlat by the reaction of (MgO) powder and aluminum oxide (Al ₂ O ₃ ) powder.

Preferably, the geopolymer mortar composition for concrete surface repair and cross-section restoration includes magnesium oxide (MgO) powder relative to 100 parts by weight of the binder containing calcium aluminate cement, fly ash, and slag fine powder. 10 to 20 parts by weight, 5 to 10 parts by weight of aluminum oxide (Al ₂ O ₃ ) powder, 40 to 60 parts by weight of a three-component alkaline activator composed of sodium hydroxide, water glass and water, and 0.3 to 1.0 parts by weight of a setting retardant. , the filler may be composed of a mixture of 10 to 20 parts by weight.

Fly ash and slag react with an alkali activator to produce a geopolymer mortar composition with excellent mechanical/physical properties. Geopolymer generates N-A-S-H through the following hydration reaction, and this N-A-S-H is superior to C-S-H gel in terms of durability.

SiO ₂ , Al ₂ O ₃ + alkali metal ion → condensation reaction → Alumino-silicate gel (NASH)

Alkaline-activated geopolymer using fly ash and slag has a very fast initial reaction rate, which can cause shrinkage and cracking as well as lower strength, so calcium aluminate cement (CAC) is used together with fly ash and slag. It is mixed in a predetermined weight ratio and used as a binder. The mixing ratio of calcium aluminate cement (CAC) and fly ash and slag fine powder is preferably 30:30:40 or 20:30:50 by weight. It is desirable to use slag fine powder with a Blaine value of 5000 or more.

Calcium aluminate cement (CAC) has the advantage of not only superior compressive and adhesion strength compared to ordinary Portland cement (OPC), but also superior chlorine ion penetration resistance. However, when calcium aluminate cement (CAC) is exposed to high temperatures and humidity, there is a detrimental conversion of metastable hexagonal aluminate hydrate to stable cubic calcium aluminate hydrate. Stable cubic hydrate has a higher density than metastable hexagonal hydrate, so internal shrinkage occurs, and this internal shrinkage can cause porous microstructure and weakening of strength. These harmful conversions can make calcium aluminate cement (CAC) susceptible to chloride attack and other durability problems such as carbonation.

This harmful phase transformation of calcium aluminate cement (CAC) can be suppressed by magnesium oxide (MgO) powder. Magnesium oxide (MgO) powder inhibits the phase transition of calcium aluminate cement (CAC) into stable hydrate and reacts with metastable hydrate to produce hydrotalcite. It was confirmed that the mixing ratio of magnesium oxide (MgO) powder to suppress harmful phase transition of calcium aluminate cement (CAC) and generate hydrotalcite is preferably 10 to 20 parts by weight per 100 parts by weight of binder.

Hydrotalcite with a Mg-Al bond structure created inside the cement mortar by mixing magnesium oxide (MgO) and aluminum oxide (Al ₂ O ₃ ) reduces the diffusion of chlorine ions inside the mortar due to the ion exchange effect, thereby reducing the concrete It provides the effect of increasing safety by preventing corrosion of steel bars in structures.

In order to further increase the reactivity of the magnesium oxide (MgO) powder, it is preferable to pre-treat the magnesium oxide (MgO) powder by firing it at a temperature of 700 to 1000°C before mixing it with the binder. Magnesium oxide (MgO) powder calcined at a temperature of 700~1000℃ is more reactive than magnesium oxide (MgO) powder calcined at a high temperature exceeding 1000℃, so it causes the hydrotalcite formation reaction more actively and has the effect of reducing shrinkage. It was confirmed that there is.

Aluminum oxide (Al ₂ O ₃ ) powder with a purity of 95% or more is suitable.

The alkaline activator is mixed with the binder to create geopolymer mortar. The alkaline activator can be a three-component alkaline activator consisting of sodium hydroxide, water glass, and water, and can be mixed in an amount of 40 to 60 parts by weight for 100 parts by weight of the binder. You can.

As a setting retardant, commonly used tartaric acid, citric acid, sodium gluconate, etc. can be used, and can be used in an amount of 0.3 to 1.0 parts by weight per 100 parts by weight of the binder. As the content of magnesium oxide increases, the hydration reaction becomes faster, so the setting speed is adjusted by adding a setting retardant.

The filler may be a mixture of zirconium silicate (ZrSiO ₄ ) powder and oyster shell powder in a weight ratio of 70:30 to 60:40.

Zirconium silicate (ZrSiO ₄ ) has a low thermal expansion coefficient, and the elastic modulus and refractive tension in the sintered body are the best among silicate ceramics.

Oyster shell shell consists mainly of crystals and organic media substances secreted from the mantle, and is typically composed of a very thin, single-layer periostracum, a prismatic layer composed of calcareous material, and a tiered nacreous layer. It is known to be mainly in the form of calcite, with a ratio of organic and inorganic materials of 3 to 5%: 95 to 97%, and that it is mostly inorganic calcium carbonate.

In this way, the filler consisting of zirconium silicate (ZrSiO ₄ ) powder and oyster shell powder is mixed with a binder and an alkali activator to ensure that the geopolymer mortar has high compressive strength in a room temperature environment, and is used as an injection method for crack repair or cross-section restoration of concrete. When applied to the filling method, it increases the pot life and improves injectability and fillability.

Additionally, geopolymer mortar compositions can use reinforcing fibers as reinforcing materials, and seaweed fibers can be used as reinforcing fibers. Seaweed fiber is composed of fructose and cellulose as main ingredients, does not melt easily with heat, and has a thickness of 1 to 10 ㎛ and a length of tens to thousands of ㎛.

These seaweed fibers can be used as is, but since seaweed fibers mainly consist of fructose and cellulose, the seaweed fibers are immersed in an aqueous metal salt solution containing aluminum ions and an aluminum ion layer is coated on the surface of the seaweed fibers. The aluminum ion layer reacts with magnesium oxide and an alkali activator in the mortar composition to promote hydrotalcite production on the surface of the algae fibers, making it possible to obtain seaweed fiber reinforcement coated or attached with hydrotalcite. At this time, it is desirable to add sodium carbonate along with the seaweed fibers to the geopolymer mortar composition so that aluminum ions react more actively with magnesium oxide on the surface of the seaweed fibers to smoothly generate hydrotalcite.

The seaweed fiber coated with the aluminum ion layer may be added in an amount of 10 to 15 parts by weight based on 100 parts by weight of the binder, and 1 to 2 parts by weight of sodium carbonate may be added per 100 parts by weight of the binder.

The method of surface repair and cross-sectional restoration of a concrete structure using the geopolymer mortar composition described above can proceed as follows.

First, the surface is cleaned through chipping and high-pressure water washing. Then, with the base surface cleaned, remove the rust from the reinforcing bars and apply a rust preventive to the reinforcing bars, and then apply a primer to the surface where the rust preventive to the reinforcing bars has been applied.

Next, the geopolymer mortar composition described above is applied to the surface on which the primer is applied.

The geopolymer mortar composition for concrete surface repair and cross-section restoration of the present invention produces Mg in the geopolymer mortar by the reaction of magnesium oxide (MgO) and aluminum oxide (Al ₂ O ₃ ) mixed with a binder and an alkali activator. -The production of hydrotalcite, which has an Al bonded structure, can be promoted, and chloride penetration can be effectively suppressed through the ion exchange effect of hydrotalcite produced in the mortar.

In particular, magnesium oxide (MgO) powder is mixed at 10-20% of the total weight of the binder to suppress harmful phase transition to stable hydrate of calcium aluminate cement (CAC) and reacts with metastable hydrate to generate hydrotalcite There is an advantage in preventing weakening of porous microstructure and strength due to shrinkage.

Example

CAC
(g) Fly Ash (g) slag
Powder (g) Magnesium oxide (g) Aluminum oxide (g) Filler (g) Alkaline activator (g) Set retardant (g)
Example 1 300 300 400 100 100 100 550 5 Example 2 300 300 400 200 100 100 550 5 Comparative Example 1 300 300 400 0 0 100 550 5

After mixing the geopolymer mortar composition in the mixing amount (g) as shown in Table 1, the geopolymer mortar composition was poured into a mold and cured at room temperature to prepare a specimen. The magnesium oxide used in Table 1 was pretreated by firing at 700°C.

Figures 1 and 2 show the XRD and TD/DTG results for Examples 1 and 2 and Comparative Example 1, respectively. The amount of hydrotalcite produced in Examples 1 and 2 in which magnesium oxide and aluminum oxide were mixed together. You can see that this has increased significantly.

In addition, as shown in Table 2 below, the compressive strength and chlorine ion permeability test results showed that Examples 1 and 2 had increased compressive strength and significantly improved chlorine ion penetration resistance compared to Comparative Example 1.

division Compressive strength (MPa) Chlorine ion penetration resistance (Coulomb) Example 1 58.8 192 Example 2 59.3 228 Comparative Example 1 56.4 955

In the above, the present invention has been described in detail with reference to examples, but those skilled in the art will be able to make various substitutions, additions, and modifications without departing from the technical spirit described above. It is natural, and such modified embodiments should also be understood as falling within the scope of protection of the present invention as defined by the patent claims attached below.

Claims (5)

A binder containing calcium aluminate cement, fly ash, and slag fine powder; and,
Based on 100 parts by weight of the binder, 10 to 20 parts by weight of magnesium oxide (MgO) powder, 5 to 10 parts by weight of aluminum oxide (Al ₂ O ₃ ) powder, and 40 to 60 parts by weight of a three-component alkaline activator consisting of sodium hydroxide, water glass, and water. hydrotalcite is produced by the reaction of the magnesium oxide (MgO) powder and the aluminum oxide (Al ₂ O ₃ ) powder, including 0.3 to 1.0 parts by weight of a setting retardant, and 10 to 20 parts by weight of a filler,
A geopolymer mortar composition for salt-resistant concrete surface repair and cross-section restoration, wherein the magnesium oxide (MgO) powder is pretreated by firing at a temperature of 700 to 1000°C before being mixed with the binder. delete The geopolymer mortar composition for salt-resistant concrete surface repair and cross-section restoration according to claim 1, wherein the filler is a mixture of zirconium silicate (ZrSiO ₄ ) powder and oyster shell powder in a weight ratio of 70:30 to 60:40. The method of claim 1, wherein 10 to 15 parts by weight of seaweed fibers in which the fibers are immersed in an aqueous metal salt solution containing aluminum ions are further added to 100 parts by weight of the binder, and 1 to 2 parts by weight of sodium carbonate is added to 100 parts by weight of the binder. In addition, a geopolymer mortar composition for surface repair and cross-section restoration of salt-resistant concrete coated with hydrotalcite generated on the surface of the seaweed fiber. Cleaning the substrate through chipping and high-pressure water washing;
Steps of removing rebar rust and applying a rebar rust preventive agent while the background surface is prepared;
Applying a primer to the surface on which the reinforcing bar rust preventive agent is applied; and
Applying the geopolymer mortar composition according to claim 1 on the surface to which the primer has been applied;
Salt-resistant concrete surface repair and cross-section restoration method including.