KR101346226B1 - Inorganic mending material for stone cultural heritage - Google Patents

Abstract

The present invention relates to inorganic repair material for stone cultural assets for repairing a damaged part of stone forming stone cultural assets, and more particularly, to inorganic repair material for stone cultural assets, wherein the repair material is manufactured using a magnesium oxide-based inorganic binder having excellent physical properties relating to strength and durability instead of cement usually used as a binder and the repair material includes a filler for more enhancing physical properties and durability of the repair material. Additionally, the present invention can obtain the effects of: not occurring a blackening phenomenon or a whitening phenomenon since the binder of the inorganic repair material for stone cultural assets is formed with the inorganic binder including a magnesium oxide having low possibility of occurring a pollution phenomenon; more enhancing physical properties and durability of the inorganic binder by the filler included along with natural silica sand included in a compounding agent; and, in particular, being eco-friendly since the magnesium oxide-based inorganic binder has cement-like properties through an ion bond of metal-nonmetal ions, not polycondensation reactions such as geopolymer, such that an alkali activator is not additionally needed and pH concentration of the surface thereof is lower compared with the concentration of cement. [Reference numerals] (AA) 7 days; (BB) 14 days; (CC) 28 days; (DD) 56 days; (EE) Cement; (FF) Lime; (GG) Mineral+red clay; (HH) Mineral+fly ash; (II) Mineral+wollastonite; (JJ) Mineral+blast furnace slag; (KK) Mineral+chamotte; (LL) Mineral+silica fume0.1; (MM) Mineral+silica fume0.2

Description

Inorganic mending material for stone cultural heritage

The present invention relates to a stone cultural property mineral repair material for repairing damaged portions of the stone constituting the stone cultural properties, more specifically, in place of the general binder cement cement oxide-based excellent physical properties and durability related to strength The present invention relates to a stone cultural material inorganic repair material that includes a filler that makes a repair material using an inorganic binder and further improves physical properties and durability of the repair material.

In the past, the repair materials used for stone cultural properties include lime and cement. Calcium carbonate or calcium hydroxide formed by the reaction of calcium ions (Ca) or sulfur (S), which are the main components of lime or cement, with carbon or water, is the main cause of bleaching and peeling-off phenomena that reduce the appearance and durability of cultural properties. As a result, it is currently refrained from the field of conservative materials for cultural property. In addition, ignoring various environmental problems caused by cement materials (increasing CO ₂ concentration, rising sea water temperature, increasing seawater pH, etc.), and continuing to use cement as a cultural property repair material is a national character of stone cultural property research. not correct.

In addition, the use of unexamined repair materials of stone cultural properties causes chemical and physical damage to the stone, causing the durability and appearance of the members to be degraded. Cement, gypsum, sulfur, and iron cores, which were used to repair cultural property from the 1960s to 1980s, weaken the strength and durability of the stone at the contact point in the long term, leave green water, and damage the appearance. Therefore, problem solving is urgent.

In addition, such conventional repair materials cause damage to stone cultural properties such as black contaminants or whitening phenomena, the black contaminants are called blackenig or black discoloration, air pollutants, organic matter, iron and manganese There is research that can be generated from the transport and deposition of colored minerals. In addition, the report that investigated the blackening phenomenon of stone cultural properties in Gyeongju, Korea shows that SO ₃ 13.01, 4.29wt.% And CaO content 36.02, 20.88wt.% It is estimated that minerals and salts of calcium carbonate may have formed.

In addition, the whitening phenomenon refers to a phenomenon in which dissolved salt components leaked from a water-soluble salt or a lime-containing water-retaining material, such as rainwater or air, remain as white solid salts when moisture is evaporated by the surface of the stone. The stone cultural properties contain Ca and SO ₃ components in the rock itself, so whitening is easy to occur. Especially, the whitening phenomenon occurring at the repair part of the stone cultural properties is considered to be due to the soluble salts eluted from the inside of the cement hardening material used as the repairing material. .

The following equation shows how Portland cement and water are cured with hydrate CSH gel and Ca (OH) ₂ after hydration.

Here, 60% of the cement is composed of CSH gel and 25% is composed of Ca (OH) ₂ . Dual Ca (OH) ₂ is a soluble salt that meets carbon dioxide to form an insoluble CaCO ₃ salt, or dissolves in water at low temperatures in an ionic state, thus maintaining high pH and helping to compact the tissue of the CSH gel. . Calcium carbonate has a very low chemical reactivity and takes a long time to cause whitening in nature.

However, during the hydration of CSH gel, bleaching may occur depending on the temperature phenomenon. CSH has a chemically strong binding force, so that the hydration reaction is late instead of high strength, so that water containing Ca (OH) ₂ dissolved in the cement remains. As this water is eluted to the cement surface, it meets carbon dioxide and causes whitening by leaving insoluble calcium carbonate by the following equation.

Therefore, at high temperature and dry air temperature, evaporation of water occurs quickly, so that whitening is less likely because soluble components are not derived to the surface by internal evaporation. However, at low temperature and high humidity, the hydration reaction is slowed down, the water is easily transported, and unreacted Ca (OH) ₂ is drawn out of the surface to cause whitening.

In addition, geopolymers, which have recently emerged as repair materials for stone cultural properties, have undergone chemically rapid condensation polymerization reactions under high alkali conditions in which Si and Al minerals have added alkali activators at a suitable temperature or high temperature. It has the principle of expressing strength by forming silicate gel. However, geopolymers are affected by curing temperature and curing time, and the production cost is expensive and difficult because the strength varies according to the Mol concentration of alkali activator.

The following is a representative prior art regarding the mineral cultural relics of stone cultural properties.

Korean Laid-Open Patent No. 10-2010-0137057 relates to a nano composite epoxy adhesive for preservation of stone cultural properties, in a mixture of 40 to 99.99 wt% epoxy resin and 0.01 to 60 wt% of a nanocluster filler having an epoxy group and nano pores. The present invention relates to a nanocomposite epoxy adhesive for preservation of a stone cultural property made by adding a room temperature curing type curing agent at an equivalent ratio of 0.8 to 1.2, and optionally a reactive diluent 0.01 based on the weight of the mixture of the epoxy resin and the filler to reduce the viscosity of the adhesive. It may further comprise ~ 40wt%, and in order to obtain faster and more robust adhesive properties depending on the process environment, characterized in that it further comprises 0.01 ~ 4wt% of the curing accelerator based on the weight of the mixture of the epoxy resin and the filler The present invention relates to a nano composite epoxy adhesive for preserving stone cultural properties.

The prior art is to improve the permeability of water through the nano-pores by mixing a nanocluster filler having an epoxy group and nano-pores in the epoxy resin that is the main component of the adhesive secondary damage due to water condensation caused by the water inside the stone does not escape to the outside And, the epoxy resin using a saturated carbon system without double bonds or triple bonds has the effect of having a color stability that does not cause yellowing due to UV and moisture over time, but includes an organic material such as epoxy resin Therefore, the long-term preservation of stone cultural properties due to the deformation of organic materials is difficult, and the continuous research and development is required to solve this problem.

The present invention has been made to improve the problems according to the prior art of the stone, in particular, the repair material used for the repair or restoration work of the stone cultural property, the conventional stone culture material inorganic repair material is a material such as cement, gypsum, sulfur or iron core It has been configured to weaken the strength and durability of the stone at the contact point in the long term, or to leave a rust, there was a problem that pollution such as blackening or whitening phenomenon occurs;

Insufficient physical properties related to strength, insufficient durability with respect to high water absorption, elution of ions or salts, acid resistance or freeze-thawing resistance, etc., resulting in the problem that the repaired part of the stone cultural property is easily damaged or peeled off. Therefore, the main purpose is to provide a solution to this.

The present invention has been made to solve the above-

100 parts by weight of a compound comprising 150 to 200 parts by weight of natural silica and 5 to 90 parts by weight of filler based on 100 parts by weight of an inorganic binder consisting of magnesium oxide or an inorganic binder (MgO) mainly composed of magnesium oxide Wow; 15-25 parts by weight of water; presents a stone cultural properties mineral repair material, characterized in that the composition is mixed.

The stone cultural properties inorganic repair material according to the present invention as described above is composed of an inorganic binder containing magnesium oxide, the binder of the stone cultural properties inorganic repair material is less likely to cause contamination, it does not cause blackening or whitening phenomenon Can be obtained;

It is possible to obtain an effect of further improving the physical properties and durability of the inorganic binder by the filler included in addition to the natural silica included in the formulation;

In particular, magnesium oxide-based inorganic binders do not require alkali activators because they have properties like cement through ion-bonding of metal-non-metal ions rather than geopolymerization such as geopolymers. Can be obtained;

In addition, the magnesium oxide inorganic binder can express more than 70% of the physical properties within the initial 4 hours with a very fast curing time compared to cement, it is possible to obtain the effect of performing as a repair material in a short time.

1 is a graph showing the compressive strength of the stone cultural properties mineral water-retaining material of the preferred embodiment according to the present invention.
Figure 2 is a graph showing the flexural tensile strength of the stone cultural properties mineral repair material of a preferred embodiment of the present invention.
Figure 3 is a graph showing the change in absorption rate of the stone mineral cultural mineral repair material of the preferred embodiment of the present invention.
Figure 4 is a photograph showing the dissolution test of the stone mineral cultural mineral repair material of a preferred embodiment of the present invention.
Figure 5 is a graph showing the freeze-thawing resistance of the stone mineral cultural mineral repair material of the preferred embodiment of the present invention.
6 to 8 is a graph showing the weight loss rate according to the acidity of the stone cultural properties mineral repair material of a preferred embodiment of the present invention.

The present invention relates to a stone cultural properties inorganic repair material for repairing damaged portions of the stone constituting the stone cultural properties, with respect to 100 parts by weight of inorganic binder (MgO) consisting primarily of magnesium oxide or magnesium oxide 100 parts by weight of a compounding material including 150 to 200 parts by weight of silica sand and 5 to 90 parts by weight of a filler; 15-25 parts by weight of water; relates to a stone cultural properties inorganic water-retaining material characterized in that the mixture is configured.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

Specifically, the compounding material is composed of only magnesium oxide, or an inorganic binder (hereinafter, referred to as 'inorganic binder') containing magnesium oxide as a main component, natural silica and a filler is mixed in a predetermined composition ratio, the inorganic binder It is a configuration for maintaining the shape of the repair portion of the stone cultural properties having a certain strength and adhesive strength, such as conventional cement or lime.

At this time, the inorganic binder of the present invention is composed of only magnesium oxide, or composed of an inorganic material mainly composed of magnesium oxide, conventional cement (Cement) or lime (Lime) is the main component containing calcium oxide (CaO) as a whitening phenomenon The effect of solving the problem that has been caused can be obtained.

That is, magnesium oxide (natural mineral binder), which is an embodiment of the inorganic binder of the present invention, is whitened as shown in Table 1 (chemical composition and physical properties of cement, lime, and natural mineral binder (MB)). Calcium oxide (CaO) components that can cause a phenomenon is almost 5-8%, there is a characteristic of absorbing water and carbon dioxide in the air as a compound of magnesium and oxygen.

In addition, magnesium oxide exists in the form of pericles in nature, and artificially, it can be obtained through calcination (heat treatment) of magnesium carbonate (Magnesite) or magnesium hydroxide (Brucite).

In connection with the above, the inorganic binder according to the present invention can be used having a variety of average particle size according to the judgment of those skilled in the art, it is preferred to use within 20 ~ 60㎛. The general stone culture material is made of stone such as granite, and if the average particle size of the inorganic binder which acts as an adhesive for the repair material is less than 20㎛, the inorganic binder for water to mix the components of the compound material with too small particle size If the dispersion is not easy, and if it exceeds 60㎛, the particle size is so large that the adsorption of the inorganic binder to the pores of the stone constituting the stone cultural properties insufficient adsorption due to the problem that the adhesive strength is falling within the above range It is desirable to have an average particle size.

In addition, magnesium oxide is a very low-molecular molecule at room temperature, and can be separated into ions and combined with other molecules to form salts or hydrates only when a high temperature of 2000 ° C. and a long-term environment are given. Even if it is used, the causative agent which produces salt or hydrate is produced less than the cement containing a large amount of calcium oxide, and the effect which can ensure the outstanding durability of the repair part of a stone cultural property can be obtained.

That is, the correlation between the magnesium contained in the magnesium oxide and the calcium contained in the calcium oxide of the cement is as shown in Table 2 (compare the chemical properties of magnesium and calcium). At this time, magnesium and calcium have the same chemical properties because they correspond to the same group on the periodic table, but the durability of the repair part of the stone cultural properties according to the degree of ionization has a completely different characteristics. Specifically, the distance between ions is also expressed as the distance between atomic numbers, and the shorter the distance between ions, the greater the ionic bonding force, so that the binding force of magnesium oxide (MgO) is greater than that of calcium oxide (CaO), so that the reactivity of magnesium oxide (MgO) is increased. It can be said that it is smaller than the reactivity of this calcium oxide (CaO). In addition, the solubility product constant is the solubility in the solvent, Ksp means the solubility constant by water (H ₂ O). Lower solubility product constants do not ionize in solution.

In addition, natural silica is included in the compound to improve the strength of the repair material, it is included in the general repair material has the same purpose as the natural silica to improve the strength of the repair material. At this time, it will be apparent that the natural silica sand of the present invention can be applied to various kinds according to the type and state of the stone constituting the stone cultural properties to be repaired.

In connection with the above, the average particle size of the natural silica sand according to the present invention is freely applicable according to the judgment of those skilled in the art, but it is preferable to use 5-10 μm. That is, when the average particle size of natural silica sand is less than 5 μm, the particle size is too small, so that it is difficult to easily disperse the inorganic binder and water, and when the average particle size exceeds 10 μm, the particle size is too large and the It is preferable to have an average particle size within the above range because foreign matter on the stone occurs.

In addition, the composition ratio of natural silica is preferably included in the blending material at 150 to 200 parts by weight based on 100 parts by weight of the inorganic binder. If the composition of natural silica is less than 150 parts by weight, the composition of natural silica is insignificant to constitute a stone cultural property. It is difficult to realize the strength of the repair material of a similar level to the stone, and if it exceeds 200 parts by weight, because the composition of natural silica to the inorganic binder is too high, there is a problem that the adhesion by the inorganic binder is insufficient, the above range It is preferable to maintain the composition ratio inside.

In addition, the filler (Filler) is a configuration for further improving the physical properties and durability of the strength of the repair material according to the present invention, it can be smoothly mixed with the inorganic binder and natural silica included in the blend, especially It is a configuration that reinforces the physical strength of natural silica sand and controls the detailed physical characteristics and durability improvement according to various states or types of stone placed in various environments.

That is, the filler may be used as long as it can use the general inorganic material and can reflect the physical and chemical properties of the inorganic material to the repair material, but Hwangto, Fly Ash, wollastonite ( It is preferable to use any one or more of Wollastonite, Blast Furnace Slag, Chamotte or Silica Fume.

Specifically, the hwangto is a mineral belonging to the halosite of the Kaolin group which is the same as kaolin as a mineralogy, and the main components are SiO ₂ and Al ₂ O ₃ Fe ₂ O ₃ . It is known that the concrete admixture and its components are similar to have the properties of natural pozzolanic. In addition, it is preferable to use the ocher of the present invention by calcination to remove moisture.

In addition, fly ash is dust generated when incineration of coal powder, which is used as a raw material of coal, at a high temperature of about 1400 to 1500 ° C. The main components are SiO ₂ , Al ₂ O ₃ , and Fe ₂ O ₃ . It is divided into and belongs to artificial pozzolanic. In addition, since fly ash is spherical in shape, it is mixed and used in a compound, thereby improving workability, such as reducing the amount of water used in the same slump and lowering the heat of hydration. In addition, the fly ash having a large powder also serves to improve durability by filling voids between the inorganic binder particles of the present invention. In addition, the mixing ratio of the fly ash to the compounding material does not have a direct relationship with the compressive strength of the prepared repair material, but it has the effect of improving the long-term strength of the repair material between 3-6 months depending on the mixing of the fly ash. .

In addition, wollastonite suppresses the hydration expansion of the blended material mixed with the prepared water mixed with the blended material of the present invention, increases the plastic strength of the finished repaired material and increases the resistance to thermal shock. In particular, the general material containing wollastonite is a material known to be able to improve the bending strength, also in the present invention has the effect of improving the physical strength of the repair material.

In addition, blast furnace slag (Blast Furnace Slag) is a by-product obtained in the process of manufacturing pig iron in the blast furnace, and is formed by the synthesis of clay and limestone in iron ore, the main components are CaO, SiO ₂ , Al ₂ O ₃ This is similar to Portland Cement. In addition, the blast furnace slag in the present invention is used in the form of fine powder to exhibit the effect of improving the workability when mixing the compounding material and water, which does not exhibit viscosity at the beginning of the mixing because the surface of the blast furnace slag in the form of fine powder is smooth and dense This is because it gives fluidity. In particular, the blast furnace slag according to the present invention enhances the strength of the water-retaining material and reduces the size of the pores between the respective compositions of the compound, thereby reducing the permeability and improving acid resistance.

In addition, chamotte is a powder obtained by sintering clay once and pulverizing it. It is known as a main raw material of general refractory brick or refractory mortar made of main components such as SiO ₂ and Al ₂ O ₂ . In addition, the chamotte of the present invention has an effect of reducing the plastic shrinkage of the water-retaining material when mixed with the other compositions of the blend.

In addition, silica fume is an industrial by-product generated when preparing a metal silicon or silicon alloy, and the main component is SiO ₂ . Specifically, since silica fume is mostly composed of SiO ₂ and is in an ultra fine state, it is rapidly dissolved in an alkaline solution to precipitate a silica gel layer. Therefore, the silica fume used in the present invention, like fly ash, activates the pozzolanic reaction to suppress the heat of hydration, and enhances the long-term strength of the repairing material as well as the short-term strength.

In addition, the filler of the present invention may be mixed in a predetermined composition in the compound as an additive to the compound, and the characteristics according to the type of filler is mixed in one or more types of compound appropriately depending on the type and condition of the stone culture material to be repaired This can be reflected. At this time, the composition ratio of the filler mixed in the compounding material may also be appropriately adjusted according to the judgment of those skilled in the art, but is preferably included in the composition ratio of 5 to 90 parts by weight based on 100 parts by weight of the inorganic binder.

That is, if the composition of the filler is less than 5 parts by weight with respect to 100 parts by weight of the inorganic binder, there is a problem that the composition of the filler is insignificant and the effect of improving the physical properties and durability of the strength of the water-retaining material by the filler is weak. If it exceeds 90 parts by weight, the composition of the filler to the inorganic binder is too high, so that the adhesive force caused by the inorganic binder decreases, so it is preferable to maintain the composition ratio within the above range.

In addition, the compounding material of the above configuration is made of a repair material by mixing a certain amount of water in a state in which the inorganic binder, natural silica and the filler is uniformly mixed.

That is, the compound of the above configuration is made of a water-retaining material having a certain fluidity, such as cement, and the water-retaining material having a certain fluidity is treated to the repaired part of the damaged stone cultural property to serve as a repairing material.

At this time, the mixing ratio of the compounding material and water can be appropriately adjusted by those skilled in the art in consideration of the strength, workability or curing time of the water-retaining material by dilution of the compounding material, but the mixing ratio of water 15 to 25 parts by weight based on 100 parts by weight of the compounding material It is desirable to have. Specifically, when water is mixed at less than 15 parts by weight with respect to 100 parts by weight of the compounding material, there is a problem that the composition of the water is too small and that each composition of the compounding material is not easily mixed. It is preferable to maintain the mixing ratio within the above range because the high strength of the finished repair material is reduced, the work material is too thin, the workability is lowered, and the hardening time of the repaired part is too long.

In connection with the above, the present invention is to maintain the mixing ratio of the compounding material and water as described above, it is generally configured to have a floor test value, which is a value representing the fluidity of the mortar, such as concrete has a range of 160 ~ 180mm. At this time, the floor test value in the above range has an effect of properly securing the fluidity of the repair material according to the present invention to further improve the ease of operation.

The following is a preferred embodiment of making a stone cultural property mineral repair material according to the present invention and a comparative example of making a general repair material. In addition, the test and test results for testing the physical properties and durability of the test piece made by the above Examples and Comparative Examples.

Ⅰ. Test piece production

1. Make mortars (corresponding to repair materials) of Comparative Examples and Examples at the composition ratios and mixing ratios shown in Table 3 below, and introduce the test pieces into the mold.

2. Storage of Test Specimens

The specimens are cured in the air for 1 day after molding, and during the rest of the curing period, the cement mortar (No. 1) is cured under water in a curing tank at 23 ± 2 ° C, lime mortar (No. 2) and inorganic binder. Mortars (No. 3 to No. 9) are cured in a thermo-hygrostat with a temperature of 20 ± 2 ℃ and a relative humidity of 65 ± 10%.

Ⅱ. exam

II-1. Physical property test

1. Compressive strength test

The compressive strength test can evaluate the performance of compressive stress in axial stress. When the compressive stress of the material is greater than the compressive strength of the material, deformation due to local compressive fracture occurs, resulting in deformation of the structure, or in the case of repairing materials, the structure can not bear the weight of the structure.

The compressive strength was measured according to KS L 5101 (Korea Industrial Standard: Test method for compressive strength of cement mortar) .The test specimens were taken after 3, 7, 14, 28 and 56 days of 3 specimens of 50 × 50 × 50mm size for each variable. Measured.

The specimens were placed on a universal testing machine (UTM) platen so that the centerline of the specimen and the test equipment were on the same vertical line and the top of the specimen was in complete parallel with the pressure side of the tester. The pressurization speed is applied at a speed that the maximum load (about 1350 kg) is within 20 seconds to 80 seconds. The compressive strength is obtained from the following equation.

2. Flexural tensile strength test

Common stone and concrete structures are vulnerable to tensile stress. Stresses greater than the flexural strength of the material may cause cracks and dropouts in the structure. The maintenance material for stone cultural properties could also be subjected to tensile stress depending on the location. The test pieces were measured on 28 days of curing in accordance with KS F 4042 (Korea Industrial Standard: Polymer cement mortar for repairing concrete structures).

In the flexural tensile strength test, the distance between the grounds is 100mm and the center of the specimen is loaded at a load speed of 50 ± 10 N per second to find the maximum load. Bending tensile strength is calculated by the following formula and rounded to one decimal place with the average value of three specimens.

II-2. Durability test

1. Water absorption test

Absorption rate is a percentage of the ratio of absorption to the dry weight of an object. At this time, the amount of absorption is the value of subtractive weight minus the weight of the dry condition. Absorption tests show the relative porosity and durability of an object. In particular, in the case of repair materials, if the absorption rate is large, the absorption rate is low because it may be affected by the external environment penetration such as snow and rain.

Absorption test was carried out by drying the test specimens in a dryer at 105 ± 2 ℃ for 24 hours in accordance with KS F 2518 (Korean Standards Association: Test Method for Absorption and Specific Gravity of Stone), and then cooled for 30 minutes to weigh the dry specimen. Immerse in distilled or filtered water at 5 ℃ for 48 hours. After this time, the specimens are removed from the bath at the same time and the surface is wiped with a damp cloth and placed to a precision of 0.1 g. Three specimens were tested for 28 days and 56 days after curing. Absorption was calculated by the following equation and the average value of the three specimens was recorded.

2. Dissolution test

Ion chromatography (ICS-3000 / Dionex) analysis was performed to determine the ions eluted when the water was exposed to moisture (H2O) for a long time. The combination of cement, lime and inorganic binders and fillers is intended to determine the potential for secondary pollutants in the ions that are eluted when rainwater is received, depending on the chemical composition of the material.

In this test, a 28-day cured test piece was cut into 40 × 40 × 15 mm and washed with distilled water to measure the concentration of ions eluted from the same volume of the sample, and 9 pieces of the washed test piece were washed with 500 ml of distilled water for 14 days, 28 days, Soak for 56 days. The aqueous solution obtained at the time point corresponding to each measurement time was extracted with a dropper, and stored in a 20 ml container at low temperature, followed by ion chromatography analysis.

3. Freeze thawing test

Freezing and thawing resistance is a very important factor in repairing stone cultural properties. Most of the stone cultural properties are exposed to the outdoor environment, so weathering is likely to occur. Like the rock, the repair material is composed of aggregates, so when the water in the cracks or voids freezes, tensile stresses occur between the voids or cracks due to volume expansion, causing the cracks to expand and additional microcracks occur. Is generated. In the freeze-thaw repetition process, the difference in thermal expansion rate between minerals due to the temperature change, the weakening of the binding force between particles by water, and the volume expansion due to the freezing of water in the pores are combined. Weathering due to freeze-thawing can cause severe degradation in the durability of repair materials, which can lead to severe damage to cultural properties due to reduced strength and appearance changes.

That is, the test was placed in the air during the freezing step and in the water during the freezing step according to the KS F 2456 B method (Korean Standards Association: Method for Rapid Freezing After Air Freezing) and ASTM C 666. The test pieces were prepared in 5 x 5 x 5 cm for each formulation, and the test was carried out at 28 days of age. One cycle of freezing and thawing was conducted for 3 hours, and the temperature of the test piece was controlled to -18 ° C during freezing and 4 ° C for melting. After lapse of time, the relative dynamic modulus was measured every 100 cycles in order to observe the change in dynamic modulus. At 300 cycles of final freeze thawing, the specimens were taken out of the freeze thaw tester, and the appearance change, weight change, and ultrasonic velocity were measured.

4. Acid resistance test

Acid resistance evaluation for conservative mortar has not yet been standardized in Korea. A 28 day 5 × 5 × 5 cm test piece was immersed in an acid solution to observe the weight change and appearance change of 7 days, 14 days and 28 days.

In the immersion solution, an aqueous solution of sulfuric acid (H ₂ SO ₄ ) having a molecular weight of 98.08, accounting for 84% of the acid ratio, was prepared at pH1, pH3, and pH5. The pH concentration was converted into 0.1 N (2.7%) sulfuric acid aqueous solution = pH 1 to dilute the pH 1 sulfuric acid aqueous solution 100 times in distilled water to dilute pH 3, pH 3 100 times to prepare a pH 5 sulfuric acid aqueous solution.

Since the surface of cement, lime, and inorganic binder mortar is covered with strong basicity before acidic solution immersion, the neutralization rate is very fast during acidic solution immersion. Therefore, during the first two weeks, the concentration was measured every 24 hours to maintain acidity, and the remaining period was changed solution every three days. The formula for calculating the weight reduction rate of the test piece is as follows.

Ⅲ. Test result

III-1. Physical property test results

1. Compressive strength test result

The compressive strength was evaluated by taking an average of three test specimens aged 7, 14, 28 and 56 days for each variable. Table 4 shows the results of the measured compressive strength. KS F 4042 (Korea Industrial Standard: Polymer Cement Mortar Quality Standards) Based on the 28-day strength, six specimens satisfying the 20MPa compressive strength quality criteria were listed in order of high strength cement (No. 1), MB + SF0. 1 (No. 8), MB + CH (No. 7), MB + BFS (No. 6), MB + FA (No. 4), MB + SF 0.2 (No. 9). Overall, cement had the highest strength, and lime (No. 2) had no properties as a repair material. In particular, MB + SF0.1 (No. 8), which has the best strength except cement, has strength equivalent to 82% of cement at 7 days, 87% at 14 days, 75% at 28 days, and 100.1% at 56 days. Came out.

In the comparative graph of compressive strength of FIG. 1, the MB + SF0.1 specimen (No. 8) and the MB + SF0.2 specimen (No. 9) showed high early strength, but increased slowly than other specimens until 28 days. Then, on the 56th, you can see a surge in robbery. This means that silica fume has a positive effect on the long-term strength of magnesium.

2. Result of flexural tensile strength test

The average value of three test pieces for each variable after the 28-day curing test was performed in FIG. 2. KS F 4042 (Korea Industrial Standard: Polymer Cement Mortar Quality Standard) Four specimens satisfying the flexural strength quality criterion of 6 MPa or more, and the best results were obtained in cement (No. 1), similar to compressive strength, and MB + BFS ( No. 6), MB + CH (No. 7), and MB + SF0.1 (No. 8) showed the highest strengths. Contrary to the compressive strength results, it is estimated that a net-shaped hydrate structure was produced in the mortar containing blast furnace slag or chamotte rather than silica fume-added specimens to assist the flexural tensile strength.

III-2. Durability test

1. Absorption test result

Absorption rate of Cement mortar (No. 1) was the lowest for the 28 days and 56 days cured specimens, lime lime (No. 2) was the highest. Among the specimens incorporating the inorganic binder and the filler, MB + SF0.1 (No.8) mortar showed the lowest value as shown in the compressive strength and the flexural strength.

In addition, Figure 3 shows the change in absorption rate at 28 and 56 days of age. The rate of absorption reduction of MB + SF0.1 (No. 8) and MB + SF0.2 (No. 9) test pieces, which exhibited a sharp increase in strength between 28 and 56 days in the compressive strength test, was MB + BFS (No .6), MB + CH (No. 7), MB + FA (No. 4), MB + WS (No. 5), MB + HT (No. 3) It can be seen that significantly higher. This means that silica fume can disperse the initial rapid hydration concentration of inorganic binder mortar with ultrafast diameter performance.

2. Dissolution test result

The eluted ion measurement result values (ppm) and ion concentration change amount of nine test specimens for 14, 28 and 56 days are shown in Tables 6 to 7. In the case of lime mortar, the volume expanded when it was added to distilled water, and the test piece was destroyed. Too much Ca component was eluted, so that an accurate value could not be obtained.

As a result of analysis for each specimen, firstly, in the case of cement mortar, the elution ions were reduced in the ions except K, Ca, and Na, which are highly reactive, because the cement was hydrated in distilled water during the dissolution test. . Nevertheless, the increasing number of Ca ions, which are most active in the hydration process, is due to the soluble Ca (OH) 2 salt. Ca (OH) 2 is a salt that dissolves in water and maintains high pH to help cement hydration. It has been found to cause whitening when this salt flows out of cement.

In addition, the concentration of potassium (K +) ions in inorganic binder mortars (No. 3 to No. 9) was more than 30 times higher than that of cement and lime mortar, which is a hydrate consisting of a combination of K + and Mg 2 + ions in the inorganic binder mortar. That is, chromatography is an apparatus for analyzing components according to the reactivity of a substance. Among elution ions, K, Ca, Na, and Mg tend to have higher ionization tendency (reactivity) toward K (potassium). The greater the distance between two ions in the reactivity sequence, the greater the reaction constant ratio, the faster the reaction rate of the more reactive ions and the less elution of the less reactive ions. In the case of the inorganic binder mortar, hydrates are formed by the combination of K and Mg ions. Since the distance between the two ions is greater than the distance between Ca and K in the order of reaction of K ions and Mg ions, the elution amount of highly reactive K ions becomes extremely active and the amount of elution is relatively low for Mg ions which are relatively reactive. It is reduced.

Although calcium ions are soluble ions, when eluted in the form of Ca (OH) ₂ , they meet with carbon in the air to form CaCO ₃ , an insoluble salt, causing whitening. But potassium is a highly reactive and soluble ion, and all the salts that potassium produces are invisible because they dissolve in water. Therefore, the dissolution of Mg ion inde problems than potassium, Ca (OH) ₂ more than 10 times the solubility of Mg (OH) ₂ is low and the insoluble salt was then little risk of elution. FIG. 4 is a photograph taken on the last day of the dissolution test. In the case of cement and lime mortar, white salt was generated and floated on the surface, but in the case of the inorganic binder mortar, no salt was formed.

3. Freeze thaw test results

Freeze thaw resistance is dependent on the amount of entrained air in the mortar and the spacing of entrained air, and is evaluated by measuring the measured relative dynamic modulus. The relative dynamic modulus of elasticity for each cycle is shown in Table 8. Lime mortar (No. 2) was destroyed in 20 cycles so that the relative dynamic modulus could not be measured. Up to 100 cycles, it takes about 12.5 days, and No.1, No.4, No.6, No.8 (cement, MB + FA, MB + BFS, MB + SF0.1) have relatively high dynamic modulus. Although relatively stable, 300cycle (approximately 37.5 days) No.1 and No.6 (cement, MB + BFS) specimens were 61.6% and 59.9%, respectively, and the dynamic elastic modulus was rapidly lowered compared to 100cycle, resulting in relatively freeze-thawing resistance. Appeared to fall (FIG. 5). Therefore, the mortar added with inorganic binder can be seen to increase the resistance to freezing and thawing in the long term, and showed similar or high dynamic elasticity as compared with cement (NO.1).

4. Acid resistance test result

Table 9 shows the weight change of the specimens by date. Since lime mortar (Np.2) does not have tight pores, the sulfuric acid solution rapidly penetrates into the mortar and expands to form insoluble salts (CaSO ₄ ) inside the test specimen, so that cracking occurs after one day of immersion. It breaks and the weight of salt increases as in pH 1, showing the opposite graph.

6, 7, 8 shows the weight before the immersion and the weight reduction rate after 7 days / 14 days / 28 days immersion in a graph by acidity. It can be seen that the larger the weight loss change, the larger the slope of the graph. The initial weight loss was -2.5 ~ -4% for inorganic binders (No.3 ~ No.9), which was generally larger than cement-1.02%. This is because cement maintains high basicity (pH12 ~ 13) during curing, so it meets acidic solution in the early stage of immersion and actively neutralizes, whereas inorganic binder mortar forms neutral hydrate, K-Struvite, pH8 ~ Because of maintaining 10, the initial weight loss rate was different due to a lot of erosion from the acid solution initially. For similar reasons, the inorganic binder mortar specimens (No. 4, 5, and 6) containing some calcium, such as cement, in the filler, the initial weight loss rate was smaller than those in the NO.7 and NO.8 specimens, but rapidly increased as the number of immersion days passed. appear.

In the case of pH5 shown in Fig. 8, since it is weakly acidic, the effect of erosion is small, and only 0.1g difference greatly affects the weight loss rate. Therefore, the acid resistance test indicates that it is good to evaluate the analysis result assuming long-term damage caused by acid rain (pH5.6) in the extreme environment of pH1 and pH3.

The MB + SF0.1 specimen (No. 8) was shown to receive less sulfuric acid solution penetration than other inorganic binder specimens due to its high durability. This is because other inorganic binder specimens have a large number of voids due to early quenching during casting, because for the MB + SF0.1 specimen, silica fume reduced the voids by delaying the concentration of the initial hydration of magnesium and potassium phosphate.

As a result of acid resistance test, cement shows low weight loss and excellent acid resistance, but for accurate experiment, cement should be compared by air curing like inorganic binder. This is due to the formation of CSH Gel with strong alkaline surface formation and strong bonding power of Si-O-Si by 28 days of underwater curing of cement. However, the actual stone cultural site repair site, unlike the experimental environment, does not create an environment where the cement is sufficiently hydrated for 28 days, so the inorganic binder is more durable than the experimental results.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It is possible to carry out various changes in the present invention.

Claims (3)

delete 100 parts by weight of inorganic binder (MgO) consisting of at least one of magnesium oxide obtained by calcination of Periclese type magnesium oxide, magnesium carbonate (Magnesite) or magnesium oxide obtained by calcination of magnesium hydroxide (Brucite). 100 parts by weight of a compounding material comprising 150 to 200 parts by weight of natural silica and 5 to 90 parts by weight of a filler; 15-25 parts by weight of water; are mixed and configured,
The inorganic binder is composed of having an average particle size within 20 ~ 60㎛,
The filler is a stone culture material mineral repair material, characterized in that composed of any one or more of ocher, wollastonite, blast furnace slag, chamotte or silica fume.
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