KR100465483B1 - Admixture of Ready Mixed Concrete Using Limestone Powder - Google Patents

Abstract

PURPOSE: Provided is ready-mixed concrete admixture which is improved in flowability, the resistance against the separation of materials, the inhibition of bleeding and the reduction of hydration caloric value and is reduced in manufacturing cost. CONSTITUTION: The ready-mixed concrete admixture comprises a lime stone fine powder which has a chemical composition comprising 92.5 wt% or more of CaCO3, 5 wt% or less of MgO, 0.5 wt% or less of SO3, 1.0 wt% or less of Al2O3 and 1.0 wt% or less of wet powder, and has a Blaine specific surface area of 2,000-6,000 cm2/g. Preferably the ready-mixed concrete admixture comprises 100 parts by weight of a lime stone fine powder; 0.01-0.20 parts by weight of a grinding aid; and/or 0.05-1.0 parts by weight of a strength enhancer.

Description

Mixture of Ready Mixed Concrete Using Limestone Powder

The present invention relates to a ready-mixed concrete mixture using a limestone fine powder, and more particularly, to a ready-mixed concrete mixed material using a limestone fine powder to improve the quality of the ready-mixed concrete using limestone fine powder as a mixture of ready-mixed concrete will be.

The domestic ready mixed concrete market is constantly improving, and the cement industry tends to reduce production costs while maintaining production. The difference is the ready mixed concrete market.

Currently, the mixed materials mainly used in Korea include fly ash, blast furnace slag powder, and the like, and their powder degree is 3,000 to 4,500 cm 2 / g. Among them, fly ash is a waste from thermal power plants, and has a merit of low cost. However, when the fly ash is applied to the product, there is a problem that the cement replacement amount of the fly ash is limited to about 10% by weight of the cement. This is due to the reactivity of fly ash is significantly lower than that of cement, and the initial strength of concrete is lowered when it is used more than 10% by weight. In addition, for the same reason, the blast furnace slag powder is also limited in its cement replacement amount to about 20% by weight when applied to the product.

Nevertheless, blast furnace slag powder and fly ash are currently used by ready-to-use ready-mixed concrete makers due to cost-cutting efforts and quality improvement efforts, and shortages appear in the peak season in the domestic mixed material market. Necessity is emerging.

The present invention is to solve the problems as described above, while ensuring the basic quality of the ready-mixed concrete itself to improve the fluidity, improved material separation resistance, bleeding suppression, suppression of hydration heat generation, limestone fine powder that can reduce the manufacturing cost of ready-mixed concrete The purpose is to provide a ready-mixed concrete mixture.

1 is a graph showing the particle size distribution of the limestone fine powder of the ready-mixed concrete mixture according to the present invention.

Figure 2 is a graph showing the change in the substitution rate of the ready-mixed concrete mixture according to the invention and the amount of AE water reducing agent used.

Figure 3 is a graph showing the amount and bleeding rate of the ready-mixed concrete mixture according to the present invention.

Figure 4 is a graph showing the setting time of concrete by the ready-mixed concrete mixture according to the present invention.

5 is a graph comparing the compressive strength of the ready-mixed concrete ready to mix according to the sample of the ready-mixed concrete mixed concrete according to the present invention.

Figure 6 is a graph showing the thermal insulation temperature increase of the ready-mixed concrete ready-mixed concrete according to the invention.

The ready-mixed concrete mixture using limestone fine powder according to the present invention has a chemical composition of at least 92.5% by weight of CaCO ₃ , at most 5% by weight of MgO, at most 0.5% by weight of SO ₃ , at most 1.0% by weight of Al ₂ O _3, and the like. It is characterized by consisting of fine limestone powder of 1.0% by weight or less of moisture.

In addition, the ready-mixed concrete mixture according to the present invention may be added at least one of a grinding aid, strength enhancer.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. Prior to this, the terms or words used in the present specification and claims are defined in the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concept of the term in order to explain his invention in the best way. It must be interpreted to mean meanings and concepts.

The ready-mixed concrete mixture using limestone fine powder according to the present invention is a limestone, and its chemical composition is composed of calcium oxide (CaO), magnesium oxide (MgO), sulfur trioxide (SO ₃ ), aluminum oxide (Al ₂ O ₃ ), and moisture.

In the present invention, in order to achieve the above object, selection of the quality of limestone is important. If the limestone is low in quality, it is often difficult to adjust the particle size and control the shape of the limestone fine powder.

The chemical composition of the limestone raw material is shown in Table 1.

As shown in Table 1, the chemical composition of limestone is 52.6% by weight of calcium oxide (CaO) and 43.79% of carbon dioxide (CO ₂ ), but because it is a natural substance, Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ as some impurities And components such as MgO and the like.

TABLE 1

That is, the ready-mixed concrete mixture using the limestone fine powder according to the present invention, calcium carbonate (CaCO ₃ ) 92.5% by weight or more, magnesium oxide (MgO) 5% by weight or less, sulfur trioxide (SO ₃ ) 0.5% by weight or less, aluminum oxide (Al ₂ O ₃ ) 1.0% by weight or less, moisture content 1.0% by weight or less, and is ground to a fine powder.

In the present invention, when preparing the limestone fine powder, a strength enhancer and a grinding aid may be further added to enable adjustment of particle size distribution, particle shape, components, and the like.

Grinding aid (eg, Di-Ethylene-Glycol, DEG) may be added in an amount of 0.01 to 0.20% by weight based on 100% by weight of limestone fine powder. It can be adjusted according to the quality of the limestone, and if the addition amount is too small, the desired purpose as the mixed concrete mixture cannot be achieved, and if it is 0.20% by weight or more, it causes the ball coating, which causes the particle size distribution and the shape heterogeneity. It is preferable to use within 0.01 to 0.20 weight%.

Strength enhancers (e.g., Tri-Iso-Propanol-Amine (TIPA) may be added to 0.05 to 1.0% by weight, mixed and pulverized, where the lime specific surface area of the limestone fine powder is 2,000 to 6,000 cm ² / to g, are provided, will be the usual increase in the amount of limestone powder for the cement according to the addition of the strength enhancer. the grinding aids where consuming grinding preparation of 2000cm ² is less than / g excess amount, 6000cm ² / g If it exceeds this, stirring is difficult.

1 is a graph showing the particle size distribution of fine limestone powder having a specific surface area of 4,050 cm ² / g.

The particle size distribution of the limestone fine powder according to the present invention is slightly smaller than the average portland cement, and is composed of finer particles. Therefore, when the ready-mixed powder is added to the ready-mixed concrete mixture according to the present invention, the workability and It is excellent in chargeability and durability is improved.

Accordingly, by using 5 to 30% by weight of the limestone fine powder to portland cement, the flowability of concrete, the improvement of material separation resistance, the bleeding suppression, the suppression of hydration heat generation, and the production cost of ready-mixed concrete are reduced.

Hereinafter, an Example is given and this invention is demonstrated in detail.

<Example 1>

5.0% by weight of strength enhancer (TIPA) and 0.1% by weight of grinding aid (DEG) were added to limestone having a chemical composition as shown in Table 1, and then ground in a ball mill to prepare a limestone fine powder having a brain specific surface area of 4,050 cm ² / g.

Grinding limestone powder prepared by pulverization was usually substituted by 20% by weight of Portland cement to carry out the compressive strength of mortar in accordance with KS L 5105 (Test method for compressive strength of hydraulic cement mortar). The results are shown in Table 2.

TABLE 2

As a result, the specific gravity and the specific surface area were not significantly different from the general limestone fine powder as a comparative example, but the compressive strength expression rate was shown to be improved along with the improvement of the physical filling property.

<Example 2>

Limestone fine powder was prepared in the same manner as in Example 1, and the physical properties of the uncured and hardened concrete were measured.

Table 3 shows the concrete mix design table of the mixture of 12% by weight of ordinary Portland cement (OPC) and fly ash (FA), which is an embodiment and comparative example of the present invention.

TABLE 3

division G _max (mm) Target workability W / C (%) S / a (%) W (kg / ㎥) Unit material amount (㎏ / ㎥) Slump (cm) Air volume (%) C FA Mixed material S G Comparative example OPC 25 15 ± 2.5 5 ± 1.5 55.2 49.5 166 300.7 - - 892 959 12% FA 264.6 36.0 - 885 952 Example 12% 264.6 - 36.0 889 967 15% 255.6 - 45.1 889 956

The slump of concrete is increased when the ready-mixed concrete mixture according to the present invention is substituted for the amount of binder, and the flow rate is also increased in the high fluidity concrete. Especially in the case of concrete with a large amount of binder, the effect of improving flowability and deformation is great.

In addition, since the adsorption amount of the admixture is relatively small, the amount of admixture required to obtain the same workability is smaller than that of the case where the portland cement is used alone, resulting in a unit quantity reduction effect as shown in FIG. 2. In other words, the amount of admixtures can be reduced by about 10% for AE water reducers and 20% for high performance AE water reducers than in Portland cement alone.

The concrete using the ready-mixed concrete mixture according to the present invention suppresses the moving speed of the bleeding water, so that the amount of bleeding is reduced and the bleeding speed is also smaller than that of the concrete which is not used as shown in FIG. 3.

In addition, the condensation of the concrete has a characteristic that the initial and termination is slightly delayed than when used in the ordinary portland cement alone as shown in FIG.

The compressive strength of the hardened concrete was carried out, and the results are shown in FIG. 5. As a result, it showed that the strength expression was equal to or higher than that of the fly ash, and the strength expression was superior to that of the case of using ordinary limestone fine powder. That is, the substitution of ordinary limestone fine powder tends to increase the water-binding ratio and naturally decreases the strength. In the present invention, the strength increaser and the physical filling effect, and the reaction with various calcium aluminates, such as fly ash, react with pozzolanic. It showed similar intensity expression.

In addition, as shown in Figure 6, the amount of heat of hydration is reduced, the final heat rise temperature is affected by the type and amount of the binder, but because of the effect of reducing the heat of hydration as much as the amount of the ready-mixed concrete mixture according to the invention of the binder, usually Portland cement It shows a lower heat insulation temperature rise and can suppress the occurrence of cracking due to the reduction of heat of hydration.

As described above, according to the ready-mixed concrete mixture using the limestone fine powder according to the present invention, by using only 10 to 30% by weight of the concrete binder, there is an effect of improving the fluidity, bleeding suppression and heat of hydration, and when used as a fine aggregate replacement It is to improve workability.

In addition, when the mixed material of the present invention is partially substituted for large-size mass concrete structures such as bridge piers, LNG tank bottom and side walls, underground continuous walls, and building foundations, high-flow concrete, and high-strength concrete, it is possible to suppress the occurrence of temperature cracking due to heat of cement hydration. effective.

High-flow concrete is a new concept concrete that can be placed on a structure without any compaction by significantly improving fluidity while maintaining material separation resistance. In order to satisfy the above properties, the amount of powder is required to be higher than that of general concrete. . However, using only the present invention as part of the binder without the use of expensive thickeners can greatly improve the required fluidity and durability while suppressing the generation of heat of hydration.

When the ready-mixed concrete mixture according to the present invention is used as a filler for high-strength concrete, strength may be increased by void filling effect, dispersion of binder, reduction of internal defects due to bleeding inhibition, and the like.

Thus, by using as a binder of the high-flow concrete of the factory product, it is possible to suppress the temperature separation caused by the material separation resistance and the heat of hydration.

While the invention has been described and illustrated in connection with a preferred embodiment for illustrating the principles of the invention, the invention is not limited to the configuration and operation as such is shown and described. Rather, it will be apparent to those skilled in the art that many changes and modifications to the present invention are possible without departing from the spirit and scope of the appended claims. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

Claims (5)

In a ready-mixed concrete mixture using a limestone fine powder mixed with a grinding aid and a strength enhancer, The chemical composition is 92.5 wt% or more of CaCO ₃ , 5 wt% or less of MgO, 0.5 wt% or less of SO ₃ , 1.0 wt% or less of Al ₂ O _{3 and} 1.0 wt% or less of moisture, and the specific surface area of the rain is 2,000 to 6,000. A ready-mixed concrete mixture using limestone fine powder, characterized in that the limestone fine powder is cm 2 / g. delete 2. The ready-mixed concrete mixture using limestone fine powder according to claim 1, wherein the grinding aid is added in an amount of 0.01 to 0.20% by weight based on 100% by weight of the fine limestone powder. 4. The ready-mixed concrete mixture using limestone fine powder according to claim 1 or 3, wherein the strength enhancer is added in an amount of 0.05 to 1.0% by weight based on 100% by weight of the limestone fine powder. delete