KR100464184B1 - Cement Mineral Based Set Accelerator for Shotcrete and the manufacturing method thereof - Google Patents

Abstract

The present invention relates to a cement mineral quickener for shotcrete, comprising 50 to 90 parts by weight of calcium aluminate amorphous powder, 4 to 30 parts by weight of sodium carbonate, and 0.1 to 20 parts by weight of anhydrous gypsum in a uniform mixed state. 0.1 to 10 parts by weight of sodium aluminate, 0.1 to 20 parts by weight of hydrated lime, and 0.1 to 0.5 parts by weight of a thickener may be further included.

The fastener is prepared by using a preparative mixer such as a paddle mixer, a ribbon mixer, a drum mixer, or by putting it in a ball mill or a vibrating mill and grinding it in a short time so as to obtain a uniform mixing state.

The present invention for shotcrete fasteners are low alkalinity, less toxic to the human body and can minimize environmental pollution, and provide strength similar to or higher than the compressive strength of concrete. In addition, the amount of rebound material is greatly reduced, providing a reduction in construction cost and a synergistic effect on construction quality.It is suitable for both dry and wet construction, and it has the effect of increasing the compressive strength and also provides strong fastening force in the water part where groundwater seeps out. Indicates.

Description

Cement Mineral Based Set Accelerator for Shotcrete and the manufacturing method

The present invention relates to a concrete fastener, and more particularly to a cement mineral quickener for shotcrete and a method of manufacturing the same.

In tunnel construction, dam construction or underground structure construction, shotcrete is used as a work for preventing collapse by reinforcing a crack in a rock or ground. Such shotcrete is used in a manner of curing by spraying through the ready-mixed concrete, a pump, a nozzle, etc. on the ceiling or wall of the construction site, the fastener for fastening the property is essential.

As a fastener which has been used conventionally, there are the following.

First, an inorganic salt quickener can be mentioned. It is a fastener mainly composed of sodium aluminate powder and sodium carbonate. It is applied only to the dry construction method of mixing dry concrete and fastener, and then kneading with water at a nozzle. The fastness is excellent but strong alkaline. It burns the worker's skin and causes environmental pollution, and the 28-day compressive strength is reduced by about 20% to 30% compared to the original concrete, and has a problem of long-term strength reduction.

Second, there are water glass-based liquid quickeners. It is widely used as a wet construction method in which the ready-mixed concrete is transferred to compressed air by using a large automated equipment to knead and spray the liquid fastener at the nozzle part. However, due to its weak fastening power, an excess of 10% of the ready-mixed concrete should be used. Because of this, the long-term strength appears low, and even after the concrete is cured, the water glass component melts in the leachate, which has a problem of polluting the environment.

Third, there is a sodium aluminate-based liquid quickener. Since it is used in a small amount compared to the water glass system, it is somewhat advantageous to the long-term strength characteristics, but as a strong alkaline substance, its toxicity is severe, which is harmful to the human body of the worker and adversely affects the environment.

It is an object of the present invention to provide an improved quickener containing calcium aluminate and a method for producing the same which can solve the problems of the conventional quickener as described above.

More specifically, an object of the present invention is to provide a fastening agent and a method of manufacturing the same, which can reduce the construction cost, reduce the construction cost, and are suitable for both dry and wet construction.

In order to achieve the above object, the present invention is characterized in that it comprises 50 to 90 parts by weight of calcium aluminate amorphous powder, 4 to 30 parts by weight of sodium carbonate, and 0.1 to 20 parts by weight of anhydrous gypsum in a uniform mixed state.

In addition, the present invention may further include 0.1 to 10 parts by weight of sodium aluminate in the mixture, and may further include 0.1 to 20 parts by weight of calcined lime and 0.1 to 0.5 parts by weight of a thickener.

In general, the thickener is used as the main component of carboxylated styrene butadiene of 0.5% or less in order to reduce dust and rebound amount in the construction site.

The method for preparing the shotcrete fastener may be uniformly mixed using a powder mixer such as a paddle mixer, a ribbon mixer, a drum mixer, or the like by mixing the constituents, or put into a ball mill and a vibration mill and pulverized for a short time. It is characterized by making a state.

Hereinafter, the embodiment according to the present invention will be described in more detail together with the properties and the manufacturing method of each component.

Preparation of Calcium Aluminate Minerals

The calcium aluminate mineral that is the main component of the fastener according to the present invention is a mineral consisting of CaO and Al ₂ O ₃ . This mineral forms a continuous solid solution of C ₃ AC ₁₂ A ₇ -CA-CA ₂ , depending on the molar ratio of the two components, and when mixed with Ca (OH) ₂ or Portland cement, CAH ₁₀ , C ₂ AH ₈ , C _It has a characteristic of forming a hydrate such as ₃ AH ₆ and curing it rapidly. The rapidity of the minerals themselves is increased to C ₃ A, which is a high content of CaO, but when added to Portland cement, there is a problem in that physical properties are difficult to control, and quenched amorphous rather than crystalline shows much higher quickness. In order to improve the formation, the raw material containing 80% or more of CaO and 45 to 60 parts by weight of the raw material containing 70% or more of Al ₂ O ₃ are combined to be melted in an electric furnace and melted in an electric furnace, and then 3 to 10 in a rotary cooler. Amorphous C12A7 beads prepared by injecting 10-50 kg / min of water into the high pressure air stream sprayed at a pressure of kgf / cm2 to have a glass phase of 10 mm or less have a specific surface area of 5000 cm / g as a ble inch. Pulverized as much as possible.

Among the calcium aluminate minerals, the best properties are expressed in minerals having a composition of C ₁₂ A ₇ . Therefore, in order to obtain a fastening force that can be used as a fastener, the specific surface area must be pulverized so that the bleinch is 5000 cm 2 / g or more. When calcium aluminate is used at less than 50 parts by weight, the initial quenching power is significantly lowered, and there is a problem that the irritation becomes worse because the compounding amount of alkaline substances is relatively increased to supplement the physical properties. Since the compounding quantity of the alkaline substance which can improve the quickening power became extremely small, the initial fastening power was reduced. Therefore, calcium aluminate is preferably used 50 to 90 parts by weight when the total weight of the fastener to 100, preferably it was confirmed that the best physical properties in the range of 60 to 80 parts by weight.

Slaked lime

Slaked lime increases the concentration of Ca (OH) ₂ during the initial hydration reaction, thereby accelerating the production rate of calcium aluminate hydrate. When the amount of lime is more than 20 parts by weight, the initial contact with water generates rapid gas condensation and interferes with the aggregation of the shotcrete, which causes the shotcrete to fail to adhere to the construction site.

Anhydrous gypsum

Anhydrous gypsum has the effect of improving the late curing rate and compressive strength. Sulfur trioxide ions, a component of gypsum, react with calcium aluminate hydrate during initial hydration to produce acicular crystals called ethrinzite. It grows over time and serves to strengthen the binding of hydration tissue.

Although gypsum has half-hydrated gypsum, dihydrated gypsum and anhydrous gypsum, depending on the bonding state of crystallized water, gypsum has been confirmed to have the best physical properties when anhydrous gypsum is added. It is preferable to use gypsum within 20 parts by weight, and when excessively added, cracking occurs in the construction site due to abnormal expansion of the hardened body or causes a problem of weakening of initial fastening force.

Sodium carbonate

Sodium carbonate enhances the post-cure rate and initial strength, relieves gastric condensation of shotcrete and secures the fluidity of shotcrete to enhance the adhesion of shotcrete.

Sodium aluminate

Calcium aluminate minerals show rapid hardening after a few minutes, but very few reactions occur within the first minute, so initial dropout is likely to occur. To compensate for this drawback, the present invention adds a small amount of sodium aluminate to promote reactivity within the first minute. Sodium aluminate is preferably added at 10 parts by weight or less. In case of excessive addition, the initial quenching is excessive and the adhesion of shotcrete is weakened, and the alkalinity is increased, so that the irritation is severe. According to the experience of the present inventors, it was confirmed that when added within 5 parts by weight, the best physical properties.

Thickener

The most problematic problem during shotcrete construction is that the sprayed shotcrete does not adhere to dust and rebounds. In the present invention, in order to alleviate these problems, a powder prepared by spray-drying highly carboxylated styrene butadiene copolymer latex as a thickener for increasing the viscosity of shotcrete is added within 0.5 part by weight based on the total weight of the fastener. Adding 0.5 parts by weight or more is not recommended because it leads to a weakening of quickness and an increase in cost.

The following is an experimental result comparing and measuring the physical properties of concrete using fasteners having different composition ratios.

Experimental Example 1

50 parts by weight of powdery amorphous calcium aluminate having a composition of C ₁₂ A ₇ prepared by grinding in a ball mill so that the bleinch is 6000 cm 2 / g is mixed with sodium carbonate, slaked lime and sodium aluminate as shown in Table 1. To prepare a fastener. Unit% represents weight%.

The measurement test of penetration resistance is usually carried out by leaving dry mortar containing Portland cement (one type), steel sand containing FM 2.7 and 5% water so that the ratio of cement and sand is 1: 3, for 10 minutes. 5% of the fastener was mixed for the amount of cement, 40% of the water was added to the cement weight, and rapidly mixed for about 20 seconds, and the mold was filled. The coagulation characteristics of the coagulation properties were measured for each time zone by the cogwheel penetration resistance according to ASTM C 403-65T (proctor penetration resistance method), and the results are shown in Table 2.

In this case, mixing cement and aggregate and leaving it for 10 minutes is intended to give conditions close to site conditions. In actual construction sites, it takes at least 10 minutes to mix and aggregate aggregate and cement to transport equipment. Moisture of the aggregate and the water reacts to form a hydrate film on the cement particles, which causes a phenomenon that the fastening force is significantly lowered than when the dry mortar is mixed immediately. This phenomenon becomes worse as the time left after mixing, and the existing test method can not reflect the decrease in fastening power in the field because the existing test method is evaluated by immediately testing the mixing of dry mortar. Therefore, in the present invention, the dry mortar was mixed, and then left to stand for 10 minutes to measure the fastening force that can be exhibited in the field. The test was carried out in a thermostat controlled at 23 ° C.

In addition, in order to test the compressive strength characteristics, cement, sand and crushed stone less than 15mm were mixed according to Table 3 to make a dry concrete. Rapid mixing for a second, filled in a cylindrical concrete mold 100mm in diameter, 200mm in height to cure 24 hours in a room controlled at 23 ℃. After 24 hours, the mold was dismantled and the specimens were placed in a water bath adjusted to 23 ° C. to continue curing. Table 3 shows the mixing ratio of each material to prepare a test specimen for compressive strength.

A quick payment C ₁₂ A ₇ Sodium carbonate Anhydrous gypsum Slaked lime Sodium aluminate Thickener One 50 30 15 - 5 - 2 50 30 - 15 5 - 3 50 20 15 15 - - 4 50 20 10 15 5 - 5 50 20 10 14.9 5 0.1

A quick payment Penetration Resistance (kgf / cm ² ) Compressive strength (kgf / cm ² ) 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 1 day 3 days 7 days 28 days One 20 76 120 150 192 134 220 262 289 2 32 106 120 132 164 134 199 233 270 3 18 72 160 192 240 123 230 270 302 4 36 108 120 140 170 140 238 275 292 5 24 80 172 200 240 139 230 280 289

Maximum coarse aggregate (mm) Water, cement ratio (%) Aggregate aggregate rate (%) Unit weight (kg / m ³ ) cement sand Pebble water A quick payment 15 45 60 400 1080 730 180 20

Experimental Example 2

Table 4 shows the mixing ratio of the fastener, and Table 5 shows the penetration resistance accordingly. Experimental environment and method are the same as in Experimental Example 1.

A quick payment C ₁₂ A ₇ Sodium carbonate Anhydrous gypsum Slaked lime Sodium aluminate Thickener 6 70 20 5 - 5 - 7 70 20 - 5 5 - 8 70 20 5 5 - - 9 70 15 5 5 5 - 10 70 15 4.9 5 5 0.1 11 90 5 2 - 3 - 12 90 5 - 2 3 - 13 90 5 2 3 - - 14 90 5 One 2 2 - 15 90 4.9 One 2 2 0.1

A quick payment Penetration Resistance (kgf / cm ² ) Compressive strength (kgf / cm ² ) 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 1 day 3 days 7 days 28 days 6 48 112 172 194 260 156 225 251 276 7 56 100 140 148 180 113 197 243 265 8 36 152 248 284 320 137 207 250 290 9 56 120 180 232 260 149 210 252 271 10 44 120 160 188 200 146 210 247 272 11 36 140 260 344 368 29 189 245 309 12 28 120 180 220 260 54 197 222 258 13 10 120 238 280 320 39 202 265 321 14 20 120 188 220 240 50 187 280 302 15 20 92 160 208 240 46 183 268 306

Experimental Example 3

The following experiment is to compare the fastener currently commercially available with the fastener produced by the present invention, which is typically measured and compared the penetration resistance. Here 'Quick Payment A' is an inorganic salt product widely used in Korea, and 'Quick Payment B' is 'Denka-T5' manufactured and sold by Electrochemical Industry Co., Ltd. (Japan) as a mineral class payment. 'Quickener C' refers to the rapidener prepared by the present invention.

The experiment was carried out through dry and wet experiments to measure the difference of physical properties according to the construction method of the fastener. In the dry experiment, the experimental environment and method were the same as in Experimental Example 1, and the fastener was blended with 5% of the cement, and the results are shown in Table 6. In the wet experiment, we extended the measurement object and added liquid silicate and liquid aluminate system, which are widely used in wet construction, to the comparative object, and the experimental conditions and blending were according to Experimental Example 1 and the mixing order of the materials reflected the wet construction conditions. Water was added to the blended dry mortar, left to mix for 10 minutes, and then a fastener was added thereto. The amount of the fastener was tested by mixing 12% of the liquid silicate and 6% of the liquid aluminate as the standard usage of the construction site.For the quickeners B and F, the mineral filler was 5 % And 7% were measured separately. The compressive strength test was performed by mixing cement, sand, crushed gravel, water, and a glidant used in Experimental Example 1 according to Table 8, mixing for 3 minutes, and rapidly mixing for about 20 seconds by adding a fastener. It was put in a cylindrical concrete mold and the curing and compressive strength was measured according to Experimental Example 1 and the results are shown in Table 7.

A quick payment Penetration Resistance (kgf / cm ² ) Compressive strength (kgf / cm ² ) 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 1 day 3 days 7 days 28 days Quick Payment A 20 48 60 88 128 118 169 210 226 Quick payment B 16 44 80 116 154 120 189 216 254 Quick payment C 40 120 168 200 228 137 216 274 310

A quick payment Penetration Resistance (kgf / cm ² ) Compressive strength (kgf / cm ² ) 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 1 day 3 days 7 days 28 days Liquid silicate 10 32 36 54 76 111 135 167 224 Liquid Aluminate 0 8 64 100 160 104 173 202 240 Quick Payment A 6 24 56 80 100 127 164 208 254 Quick payment B (5%) 6 28 68 84 100 139 230 265 312 Quick payment C (5%) 8 68 100 124 160 156 258 311 368 Quick payment B (7%) 14 40 76 100 134 146 229 268 308 Quick payment C (7%) 20 92 126 150 180 168 264 309 362

Maximum coarse aggregate (mm) Water, cement ratio (%) Aggregate aggregate rate (%) Slump (cm) Unit weight (kg / m ³ ) cement sand Pebble Glidants water A quick payment 15 42 60 12 460 1030 683 4.6 207 23

From the above experiment results, it can be confirmed that the penetration resistance of the shotcrete in which the fastener C according to the present invention is blended is excellent in both dry and wet.

The fastener according to the present invention is made of calcium aluminate, a cement-based mineral, and has a low alkalinity by adding a very small amount of strong alkaline substances such as sodium aluminate. It is less toxic and minimizes environmental pollution, and in the long term, it forms a hydrated mineral called ethrinzite, which makes the hydrated structure of the concrete hardened structure more dense, resulting in a strength similar to or higher than that of the original concrete. .

In addition, the calcium aluminate-based fasteners according to the prior art generally have a weaker fastening power than the inorganic salt-based powdery fasteners, so that the construction cost is increased because the mixing amount should be about 10% to 15%, which is about twice as fast. According to the present invention, even with the addition amount of 5% to 7%, which is similar to the inorganic salt-based fastener, it exhibits excellent physical properties and significantly reduces the amount of rebound material, which is the main cause of material loss in tunnel construction, thereby reducing construction cost and synergistic effect of construction quality. Is provided.

According to the present condition of the use of the domestic fastener, the powder quickener is used only for dry construction, and the liquid quickener is used only for wet construction. However, according to the present invention, it is suitable for both constructions and can be applied as it is to conventional dry construction. In addition, by attaching the powder supply system to the wet construction apparatus has the advantage that can be applied to wet construction.

In particular, in the wet application using the liquid quickener, the water content of the liquid quickener is about 50%, and the more the liquid quickener is added, the higher the water ratio of the ready-mixed concrete becomes. It is easy to cause problems, and it is always suffering from instability of construction quality because fluidizing agent is used to minimize water cost of ready-mixed concrete and careful management of slump is required. However, the fasteners according to the present invention are powdery and cement minerals, so there is no problem of quality instability due to excessive water ratio, even if they are added in an appropriate range, and the added fasteners themselves are cured to form hydrates. Therefore, it shows strong fastening force in the water part where groundwater seeps out.

Claims (13)

CaO raw materials 45 to 60 parts by weight of Al ₂ O ₃ 70% contain material 40 to 55 parts by weight of CaO is 40 to which more than 55 parts by weight containing at least 80%, and mixed to Al ₂ O ₃ is added to 40 to 50 wt. By melting the mixture in an electric furnace, and then spraying together 10 to 50 kg / min water into a high-pressure air stream sprayed at a pressure of 3 to 10 kgf / cm2 in a rotary cooler so that the melt becomes a glass phase of 10 mm or less. 4 to 30 parts by weight of sodium carbonate, 1 to 20 parts by weight of hydrated lime, 1 to 20 parts by weight of anhydrous gypsum, in 50 to 90 parts by weight of the pulverized powder of amorphous C ₁₂ A ₇ beads having a specific surface area of 5000 cm 2 / g or more as a ble inch Cement mineral filler for shotcrete, characterized in that for mixing. delete delete delete delete delete CaO raw materials 45 to 60 parts by weight of Al ₂ O ₃ 70% contain material 40 to 55 parts by weight of CaO is 40 to which more than 55 parts by weight containing at least 80%, and mixed to Al ₂ O ₃ is added to 40 to 50 wt. By melting the mixture in an electric furnace, and then spraying together 10 to 50 kg / min water into a high-pressure air stream sprayed at a pressure of 3 to 10 kgf / cm2 in a rotary cooler so that the melt becomes a glass phase of 10 mm or less. 4 to 30 parts by weight of sodium carbonate, 1 to 20 parts by weight of hydrated lime, 1 to 20 parts by weight of anhydrous gypsum, in 50 to 90 parts by weight of the pulverized powder of amorphous C ₁₂ A ₇ beads having a specific surface area of 5000 cm 2 / g or more as a ble inch Method for producing a cement mineral quickener for shotcrete, characterized in that for mixing. delete delete delete delete delete delete