KR0145101B1 - Method of manufacturing high flowing cement - Google Patents

Abstract

Purpose: To provide high flow concrete

Composition: 250 to 280 kg of normal cement, 80 to 110 kg of fly ash, 170 to 185 of water, fine aggregate and 310 to 340 kg of coarse aggregate, and 0.2 to 0.4% of thickener and binder It is mix | blended in the ratio which adds 1.0 to 2.0% of high performance AE reducing agent, and uses 3 to 8% of stone powders of the binder weight ratio.

Description

Manufacturing method of high flow concrete

TECHNICAL FIELD This invention relates to the manufacturing method of high flow concrete especially in the manufacturing method of concrete.

Until now, with the development of construction technology, the demand for new construction technology such as high density and high reinforcement, along with the deterioration of social perception of construction engineers, the avoidance of 3D and the aging of skilled workers have accelerated the development and commercialization of high flow concrete. Is urgently needed.

Of course, the development of high-flow concrete has been made for about 10 years, but the exact information on the mixing method and the physical properties are not provided until now, and the construction performance on the site is also insufficient in Korea and abroad. .

The present invention is excellent in the general strength, considering that the above-mentioned causes are due to problems such as the construction cost is increased due to the use of a large amount of powder such as cements in order to increase the fluidity of the conventional high flow concrete The purpose is to produce a high flow concrete having a. In order to achieve the above object, it is characterized in that it is prepared by adding the stone powder of a single mineral composition consisting of high-quality calcite crystals with low impurities produced in Korea, the intrinsic copper concrete produced in this way is economical and constructability It was confirmed that the durability is excellent.

The above-mentioned stone powder is a powder having a high powder degree that passes through the particle size # 300, and such a powder powder has a feature of ensuring the desired fluidity while improving the filling property by filling the pores of concrete.

High-flow concrete, which does not require compaction for the purpose of improving the reliability of concrete structures, increasing the efficiency of construction, and rationalization, has the flexibility to fill the corners of the formwork without using a vibrator (vibration compaction) in the uncured state. In order to obtain high viscosity concrete to have a material separation resistance that can pass between reinforcing bars without causing closure due to material release during flow) It must follow.

In order to solve the above conditions, the present invention is to be noted that the following points should be noted and solved. In other words,

First, the characteristics of material blendability common to high flow concrete

1) A large amount of powder (cimine, admixture).

2) Low water-powder ratio (W / P).

3) Powders with low powderyness are often used.

4) It uses high performance air entrainer.

As mentioned above, the effect of fine aggregates on the closing of mortar through a narrow gap is such that when the fine aggregate volume concentration (fine aggregate volume ratio) in the mortar is higher than a certain value (close limit fine aggregate concentration), flow closure will occur and thus form In order to be filled with high-flow concrete that can be filled in every corner, the volume of fine aggregate in mortar must be kept below a certain value, and depending on the particle size, water-powder ratio, type of powder, and powder of fine aggregate In order for concrete to flow between reinforcing bars without causing flow closure due to material separation during flow, the mortar must have an appropriate separation resistance (viscosity).

Second, the characteristics of admixtures include the use of a high performance water reducing agent. The high performance water reducing agent requires high fluidity under low water-powder ratio. Thus, naphthalinic acid and polycarboxylic acid are used. It is in use, and there are no examples of ordinary use of Portland cement alone. Since the particle size distribution of portland cement is usually narrow, a lot of water is required to obtain concrete having the same workability, so that the limit of water-cement that can be blended is increased, and general high performance reducing agents are C ₃ A and C ₄ AF in cement. Since the adsorption amount of silicate such as C ₃ S is reduced preferentially, the blast furnace slag fine powder or fly ash, which is well blended with the high performance water reducing agent, to exhibit high fluidity at low water-cement ratio due to the low dispersion force. Etc. are used.

The performance required for such chemically admixtures for high dynamic concrete is as follows.

A) For unhardened concrete

-Excellent fluidization performance

-Maintenance performance of fluidity (including air volume and separation resistance)

-Proper condensation test, bleeding rate

-Good pump pressure

B) in the case of hardened concrete

-Does not adversely affect the mechanical properties (compressive strength, flexural strength, tensile strength, Young's modulus, etc.).

-No negative effects on dry shrinkage or creep.

Excellent durability (freeze resistance, water permeability, resistance to neutralization, etc.).

As the chemical admixture according to the above required performance, a combination of an AE water reducing agent and a high performance water reducing agent or a high performance AE water reducing agent may be used, but a high performance water reducing agent based on polycarboxylic acid may be given in consideration of the setting time.

Third, powder materials include 1) blast furnace slag, 2) fly ash, and 3) limestone powder. As is known, the high temperature generated as a by-product during the production of pig iron during smelting by the blast furnace method is known. The amorphous slag obtained by quenching the blast furnace slag in the molten state (about 1,500 ° C.) with water and crushing it is latent hydraulic which reacts with water in the presence of alkali such as calcium hydroxide. Particularly, the finely ground crushed slag powder has high hydration activity, and thus the latent hydraulic properties of the blast furnace slag fine powder are high, and the rheological properties of the blast furnace slag fine powder with high powder degree are large in powder and the average distance between particles is short. Due to the large viscosity, the separation resistance of the mortar has an advantage, but the blast furnace slag powder produced in Korea has a problem that it is difficult to secure the quality of the constant high-flow concrete due to the severe variation in the quality of the produced product.

Fly ash, which is generated as a by-product from the combustion of fine powder coal in coal-fired power plants, causes pozzolanic reactions that slowly combine with calcium hydroxide produced during hydration at room temperature to form insoluble stable calcium silicate. Since the particles are spherical, the fluidity of concrete is improved by the ball bearing effect, but also fly ash may not be stable in product quality and air volume is difficult to control due to air adsorption of fly ash particles. For the purpose of enhancing the strength of concrete and improving the rheological properties, fine powder, which is an inert mineral such as limestone powder, is used as an additive material, but recently, when high-flow concrete is applied to large structures where temperature cracking is a problem. Mineral fine powder It is noted that use.

Limestone as described above is mainly composed of calcite (hexagonal system), but in some cases, it may be eragonite (cobblestone: 斜 方 晶 系), limestone is chemically calcium carbonate (CaCO ₃ ), the composition is CaO 56.03 %, CO ₂ is 43.97%.

Fourth, in the separation reducing agent (thickener), the separation reducing agent used in the high flow concrete as in the present invention is a cellulose-based water-soluble polymer, a polyacrylamide-based water-soluble polymer, a biopolymer manufactured by fermentation technology. These may be combined with absorbent polymers and special inorganic powders, or include water soluble polymers and water soluble polymers.

The basic characteristics of the separation reducing agent are to increase the viscosity of paste and mortar and to improve the separation resistance of the material, thereby increasing the filling property. However, the type of separation reducing agent differs in the key point mechanism and rheology characteristics (yield value, plastic viscosity). Cellulose, acrylic, and the like have common characteristics such as dissolving in water to increase the viscosity.

Fifth, the blended water is present in the gap between solid particles as a material that is easy to deform and flow among the constituent materials of concrete, and the increase in quantity does not mean an increase of material to facilitate deformation and flow. It is effective to enlarge. The water in the unhardened concrete is confined to the deformation flow, and there is water that is limited to its movement around solid particles other than freely moving water. The latter is solid particles when a relative velocity occurs between them. Water that does not move freely in the gap between solid particles is called restraint water.

In general, concrete having a large number of free water is easy to deform and flow. However, when the amount of free water increases with respect to the amount of powder, the viscosity of the paste decreases, and the frequency of direct contact and collision of particles with large particle diameters increases, thereby increasing deformation and flow by solid particles. In order to impart proper fluidity to the paste (mortar), it is necessary to control the free amount.

Sixth, the high flow concrete in the mixing of materials ensures the material separation resistance by using the separation reducing agent due to the increase of the powder content. The time required for the value to be constant is also long. Therefore, it is necessary to fully examine the type, blending capacity, and blending time of the mixer. In addition, consideration should be given to the selection of the mixer to be used for the compounding, the amount to be mixed, and the mixing time. And it is a problem to consider beforehand also in the input method of a material at the time of compounding. Therefore, in the present invention, a forced biaxial mixer is used, and the compounding amount is about 60-90% of the nominal capacity, and the mixing time is longer than that of the concrete, and in the case of the input of materials, the batch input method and the mortar are mixed first, and then the coarse aggregate is finished. The thickener can also be added directly by hand.

The cement used in the embodiment of the present invention usually used Portland cement, and its chemical and physical properties are shown in Tables 1 and 2 below.

The coarse aggregate used in the embodiment of the present invention used a crushed stone having a maximum dimension of 19 mm, the fine aggregate is to use the Han River mountain sand. The physical properties of the aggregates are shown in Table 3.

Meanwhile, the fly ash used in the embodiment of the present invention uses a fly ash produced in Korea to enhance long-term strength and fluidity due to ball airing effect, and the physical and chemical components of the fly ash are shown in Table 4.

The powder used in the examples of the present invention used a powder of trace ultrafine powder that passed through # 300 sieve for proper workability and bleeding effect, which showed a tendency of bleeding to decrease as the amount of lime added increased. As stone powder was added, bleeding decreased, and as the amount of stone powder was increased, workable concrete could be obtained due to the increase in viscosity due to fine powder. Table 5 shows the chemical properties of the limestone powders used.

In this example, a high performance AE water reducing agent was used to reduce the unit quantity and to control the slump when manufacturing high flow concrete. The characteristics are shown in Table 6.

In order to increase the high fluidity of the embodiments of the present invention, since a material separation is likely to occur, a thickener was used to prevent this. The properties of the thickeners are shown in Table 7.

EXAMPLE

The mixture was added to a blender at the following mixing ratio, followed by dry mixing for 1 minute, mixing with water and admixture, and then mixing for 5 minutes.

250 to 280 kg of normal cement, 80 to 110 kg of fly ash, 170 to 185 of water, 310 to 340 kg of fine aggregate and 0.2 to 0.4% of medium quantity of medium is added per 1.0m3 of high flow concrete. 3 to 8% of stone powder was used as a compounding ratio with the high performance AE water reducing agent of 2.0%.

The high flow concrete obtained according to the above embodiment was manufactured using a mold of 10 × 20 cm according to KSF 2405 to prepare a specimen for compressive strength test, and subjected to a slump test according to KSF 2404 to examine the filling property. For tests not included in KS regulations such as filling test, the results of the most appropriate experiments are shown in the table below with reference to domestic and international research data and thesis. The compressive strength was 283㎏ / ㎠ at 91 days of age.

Table 8. Test results of high flow concrete

As described above, according to the present invention, many problems are caused in the application of large structures by increasing the heat of hydration due to the excessive amount of powder by increasing the fluidity by using a lot of powders such as cement in the conventional manufacturing method of high flow concrete. Compared to the fact that there was a decisive obstacle to practical use due to the increase in unit cost, the present invention manufactures high-flow concrete using ultra-fine grains that pass through # 300 sieve, so that the fluidity and filling of concrete without increasing the amount of powder such as cement It is an economical and industrially useful invention because it is possible to obtain an effect of improving durability by improving the properties and reducing the bleeding and increasing the strength and reducing the heat of hydration by improving the voids.

Claims (2)

250 to 280 kg of ordinary cement, 80 to 110 kg of fly ash, 170 to 185 of water, fine aggregate and 310 to 340 kg of coarse aggregate, and 0.2 to 0.4% of thickener and binder A method for producing a high-flow concrete, characterized in that the addition of 1.0 to 2.0% of the high performance AE reducing agent with 3% to 8% of the binder weight ratio. Claim 1 Claim 1 stone powder according to claim 1 is a method for producing a high-flowing concrete, characterized in that the stone powder is made by interfering with the # 300 sieve or eragonite.