KR100908675B1 - Concrete composition for revealing high early strength - Google Patents

Abstract

A concrete composition is provided to secure excellent early strength at low temperature even with the small amount of cement used and to lower the viscosity of the concrete composition. A concrete composition includes Portland cement and cement binder. The concrete composition is composed of 1-40 parts of quicklime, 1-40 parts of limestone powder and 0.1-5 parts of high-functional air entaining agent on a basis of 100 parts of mixture of Portland cement and cement binder. The degree of particle size of quicklime is 500~8000cm^2/g and limestone powder is 500~8000cm^2/g. The cement binder is one or two kinds of materials selected from the group consisting of blast furnace slag, fly ash and silica fume. The amount of Portland cement and cement binder used is 250~450kg/m^3.

Description

[0001] CONCRETE COMPOSITION FOR REVEALING HIGH EARLY STRENGTH [0002]

More particularly, the present invention relates to a low-temperature early strength concrete composition, and more particularly, to a method of replacing part of portland cement and cement binders, which are concrete compositions, with quicklime and limestone fine powder to cause heat generation by reacting the quicklime with water contained in concrete So that the temperature of the concrete is kept elevated, and the limestone fine powder improves the fluidity.

In the concrete frame construction, if the concrete quality is met after the concrete is placed in the strength, etc., the mold will be dismantled and the subsequent process will proceed. Therefore, in order to satisfy the quality standards and shorten the time required for the entire process, it is required to develop an early strength concrete composition capable of shortening the period of reaching a predetermined reference strength after pouring concrete.

The standard specification of concrete specifies that the minimum strength standard for dismantling formwork in concrete frame construction is 5 MPa (50 kgf / ㎠) for vertical members, 2/3 or more of the design reference strength for horizontal members, or 14 MPa Kgf / cm < 2 >). These regulations

It plays an important role not only in the strength standard for demolishing formwork in concrete frame construction but also in securing quality to prevent initial East Sea damage in Hanchong construction.

The concrete used in the construction site generally has a strength level of 21 ~ 35 MPa (210 ~ 350 ㎏f / ㎠) in design strength. In case of the conventional technique, f / ㎠) should be at least 2 days after concrete pouring.

However, in practice, in order to shorten the air of the construction work, the form of the structure is indiscreetly removed before the strength of the concrete reaches the reference strength of the formwork disassembly, thereby causing deterioration of the quality of the concrete structure.

In addition, in case of pouring concrete during the winter season, concrete is put in order to shorten the construction period, and it is desired to heat cure at 13 ~ 15 ℃ to dismantle the mold in 18 hours. However, in the case of cement, hydration starts immediately after reacting with water. In general, the lower the temperature than the standard curing temperature, the longer the setting time becomes. If the curing temperature is 20 ° C, the curing time is about 10 to 11 hours. If the curing temperature is lowered to 15 ° C, the curing time is increased to about 15 to 20 hours. If the curing temperature is lowered to 10 ° C, It also slows down to almost 22 to 25 hours. Therefore, it was very difficult to obtain early strength at low temperatures.

Therefore, a large amount of Portland cement and cement binder is required to maintain the compressive strength of 5 MPa in 18 hours as described above. It is necessary to maintain a low water-cement ratio and to prevent the deterioration of the cementing time of the Portland cement. Should be used.

However, when such a low water-cement ratio is used, the viscosity of the cement mixture increases due to a low water-cement ratio, and it is difficult to practically put the product on the site in consideration of the slump loss occurring during the transportation time to the site. If the workability of the concrete is not ensured at the construction site, voids due to the protrusion of gravel and insufficient filling are generated, the material of the concrete is separated due to excessive compaction, and joint parts such as call joint are generated There are many problems in the construction and cause a lot of problems in the safety of the structure.

Also, in case of increasing the temperature of the concrete by heating the temperature of the used water to more than 40 ℃ in order to secure the early strength in the winter period, the energy required to heat the water and the excessive cost such as the boiler and the hot water storage tank In addition to increasing the temperature of the concrete in the actual construction site, there is a limit to increase the temperature of the whole concrete. In case of raising the water temperature to a higher temperature in order to produce a higher temperature concrete, And the like.

Also, even if hot water is used as the water cement ratio and cement amount as described above, if the curing air temperature of the poured concrete is maintained at 13 ° C, the compressive strength after 18 hours of casting becomes difficult to express 5Mpa. Therefore, the curing air temperature should be controlled higher than 13 ℃ after concrete pouring, and when the temperature of a large site is raised, the expense increases exponentially and the purpose of the construction cost reduction due to the construction period shortened by the construction company disappears.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-mentioned problems of the conventional method of expressing the early strength of concrete, and it is an object of the present invention to provide a method of manufacturing a cement- The present invention provides a low temperature early strength concrete composition in which the initial temperature of concrete is maintained to be maintained as the quicklime reacts with water contained in the concrete to cause heat generation, and the flowability is improved by the limestone fine powder.

In order to accomplish the above object, the present invention provides a concrete composition comprising a Portland cement and a cement binder,

1 to 40 parts by weight of quicklime, 1 to 40 parts by weight of a limestone fine powder, and 0.1 to 5 parts by weight of a polyether-based (PE-based) high-performance AE water reducing agent (crude steel) with respect to 100 parts by weight of the Portland cement and the cement- .

According to the present invention, the low-temperature early strength can be secured with a small amount of cement concrete, the viscosity of the concrete composition can be remarkably reduced, and the low-temperature early strength can be secured even at a high water-cement ratio, It is possible to shorten the period of pouring the concrete and to secure the early strength even at a low curing temperature, thereby reducing the cost of curing the site and lowering the viscosity of the cement mixture, And the like.

Hereinafter, the present invention will be described in detail.

First, the concrete composition according to the present invention comprises Portland cement and a cement binder.

Since the portland cement is generally used, description thereof will be omitted. The above Portland cement can be selectively used depending on the purpose of use, for example, one kind of ordinary Portland cement, two kinds of heat portland cement, three kinds of crude steel portland cement, four kinds of low heat portland cement and five kinds of sulphate portland cement. Not limited.

The blast furnace slag may be one or more selected from the group consisting of blast furnace slag, fly ash and silica fume. The blast furnace slag may be a crucible, Which is not self-hydraulically and is a potential hydraulic oil that hardens by reaction with a cement compound. The blast furnace slag is filled with voids between the cement particles to delay the operation of hydration of cement. Therefore, it has a low resistance to freezing and thawing, low initial strength and long-term strength, and has excellent resistance to seawater and chemical resistance.

The fly ash is a by-product, which is a by-product recovered by a dust collector in a combustion boiler such as a thermal power plant, and is an admixture representing a Poezolite trimer whose particle size is significantly lower than that of cement particles. Fly ash, which is a spherical fine particle, acts like a ball bearing in the case of dilute concrete, thereby lowering the unit yield and reducing the bleeding phenomenon of the concrete. The hardness of the hardened concrete at the initial age is low, It is an admixture material that has an effect on application to scalpels and so on and has excellent resistance to sulfate by reducing hydration heat.

In addition, the silica fume is an admixture obtained by electrostatic precipitator of the silicon by-product of ultrafine particles generated in the production of silicon. In the well mixed concrete, the silica fume is filled with void spaces between the cement particles to form a high strength, Concrete can be implemented.

The weight part used as a blending ratio used in the following is based on the use amount of the Portland cement and the cement binder (100 parts by weight).

In the present invention, the portland cement and the cement binder are mixed with the quicklime and the limestone fine powder, and a certain amount of the Portland cement and the cement binder is replaced with the quicklime and the limestone fine powder. This is because when the quicklime reacts with water in the concrete, 15.2 kcal heat is generated, so that when the concrete is poured, the temperature of the concrete rises and the concrete is maintained until the form is disassembled. The chemical reaction formula for the quicklime is as follows.

CaO + H ₂ O -> Ca (OH) ₂ + 15.2 kcal

The portland cement exhibits a better hydration reaction when partially substituted by quicklime.

In this case, the quicklime is mixed in an amount of 1 to 40 parts by weight based on 100 parts by weight of the sum of the Portland cement and the cement binder. If the amount of the quicklime is less than 1 part by weight, the effect of mixing is insufficient, The amount of the cement is excessively reduced and the compounding ratio of the cement is reduced, so that there is a possibility that the physical properties as concrete may be lowered.

If the powdery degree is less than 500 cm 2 / g, the size of the quicklime powder is too large to be suitable for concrete, and when the powdery degree is more than 8000 cm 2 / g, This is because the increase in cost is not economical.

In the present invention, 1 to 40 parts by weight, based on 100 parts by weight of the sum of Portland cement and cement binder, is mixed with the calcium oxide and the limestone fine powder. When the amount of the limestone powder is less than 1 part by weight, If the improvement effect is not sufficiently exhibited and if the limestone fine powder is mixed in an amount exceeding 40 parts by weight, it becomes excessive, which may affect the development of low-temperature early strength for the purpose of the present invention, thereby deteriorating the physical properties of the concrete.

If the powdery degree is less than 500 cm < 2 > / g, the size of the limestone powder is too large to be suitable for concrete, and if it exceeds 8000 cm < 2 & This is because the cost of crushing is increased, which is not economical.

In the present invention, the PE-based high-performance AE water reducing agent (crude steel type) is mixed together with the quicklime and the limestone fine powder, which is also referred to as a highly water-reducing admixture. The high-performance AE water reducing agent has a high water reducing rate and a low slump loss which can reduce the unit water by 15 to 20%, and significantly reduces the water-taking action during the air entraining operation, the coagulation delay adjusting operation, and the water- It is an admixture with excellent fluidity and slump retention ability. The present invention uses a polyether-based early strength type and is characterized by having a molecular structure having a shorter main chain length and a longer side chain length than conventional PC based high performance AE water reducing agents. And the strength is expressed early without delaying hydration. When the amount of the high performance AE water reducing agent is less than 0.1 parts by weight, the effect becomes insignificant. When the amount of the high performance AE water reducing agent is more than 5 parts by weight, the admixture becomes excessive, so that the mixing ratio of the high performance AE water reducing agent is 0.1 to 5 parts by weight do.

Although the amount of the Portland cement and the cement binder is 100 parts by weight, it is preferable that the amount of the concrete is 250 to 450 kg / m 3. If it exceeds 450kg / m3, it is a high-strength concrete and has a high self-hydration heat, which may cause slump loss and cracks.

In the present invention, the concrete composition includes Portland cement and a cement binder. However, it is a matter of course that the aggregate (fine aggregate, coarse aggregate) and water are included, so that a detailed description thereof is omitted.

It goes without saying that a fluidizing agent, an accelerator, a quick-setting agent, etc. may be mixed and used in addition to the high-performance AE water reducing agent as an admixture.

The test was carried out under the following conditions, and the concrete temperature change was measured by KS F 4009 for 24 hours after the general strength test. Also, the strength at 18 hours early temperature and 28 days at low temperature were measured.

The most important quality characteristic in concrete is compressive strength. Even if low early strength is secured, it may not be meaningful when the strength of the concrete is lower than 28 days. Therefore, the compressive strength of existing concrete and long- .

The mixing ratios of the respective Examples and Comparative Examples were as follows.

In Examples 1 to 3, 5% by weight, 10% by weight and 15% by weight of quicklime were added to Portland cement and cement binder, respectively. In Examples 4 to 6, the test was performed by adding 5% by weight, 10% by weight and 15% by weight of quicklime to the internal weight of the Portland cement and cement binder, respectively.

The temperature changes of Comparative Example 1 and Examples 1 to 6 were measured, and the measurement results are shown in Table 2 below.

As the admixture, Binder X 0.5% was applied to all formulations of the AE water reducing agent standard in all of the comparative examples and the examples.

As shown in the above Comparative Examples and Examples, it was found that the temperature of the concrete was increased in all of the Examples in which the quicklime was substituted, and the rise temperature of the concrete was also increased proportionally as the addition ratio was increased. I could.

1 is a graph showing the hydration heat of a concrete using a hydration heat meter, and a graph of red color (CH2 of hydration heat meter) is a result of a concrete using a cement alone (Comparative Example 1) (CH3) is the result of replacing the concrete with 10% of the fresh lime (Example 5), and the graph of purple (CH1 of hydration heat meter) shows the outside temperature of the laboratory.

The vertical axis in FIG. 1 represents the temperature, and the horizontal axis represents the elapsed time, in which six pieces of data are displayed at intervals of 5 hours. That is, the red color 2: 10.0 means that the hydration heat of the channel 2 is 10 ° C, and it can be confirmed that the black color graph shows higher hydration heat than the red color graph as shown in FIG.

Since it was confirmed from Examples 1 to 6 that the temperature of the concrete is increased when the quicklime having a predetermined powder or more is used, the compressive strength with time at the curing temperature of 13 ° C is measured, Experiments were conducted. The blending ratios of the respective examples and comparative examples are shown in Table 3.

In order to determine whether the strength of ⁵ N / mm ² or more was obtained by curing at an ambient temperature of 13 캜, 0.5% of Binder X was used as a standard type of AE water reducing agent in Comparative Examples 2 to 4, And 0%, 10% and 10%, respectively, of cement binder were used.

In Comparative Examples 5 to 7, 1.0% of Binder X was used as a standard type of PC-based high performance AE water reducing agent, and 0%, 10% and 10% of the amount of Portland cement and cement binder were respectively used.

In Comparative Examples 8 and 7 to 8, Binder X 1.0% was used as a standard type of PE-based high-performance AE water reducing agent, and 0%, 10% and 10% of the amount of Portland cement and cement binder were respectively used.

The results of the compressive strength measurement in the short-term and long-term ages of Comparative Examples 2 to 8 and Examples 7 to 8 are shown in Table 4, and the expression values of the compressive strength by temperature were measured and shown in Table 5.

As can be seen from the test results of Comparative Examples 2 to 8 and Examples 7 to 8, the compressive strengths of 3 days and 7 days of 28 days were no problem for all of the Examples, Values, indicating that the compression strengths of Examples were higher than those of Comparative Examples.

Table 5 shows the results of evaluating the low-temperature early compression strengths of Comparative Examples 2 to 8 and Examples 7 to 8.

From the above test results, it was found that, in order to obtain a compressive strength of at least 5 N / mm ² , 36 hours at 15 ° C and 18 hours at 20 ° C were required in the case of using the AE water reducer standard type without addition of quicklime (Comparative Example 2) In the case of using the AE water reducing agent (Comparative Example 5), it required 36 hours at 13 占 폚, 24 hours at 15 占 폚 and 18 hours at 20 占 폚. Also in the case of the PE-based high-performance AE water reducing agent (Comparative Example 8), a compressive strength of not less than 5 N / mm ² was exhibited at 13 ° C for 24 hours and at 15 ° C and 20 ° C for less than 18 hours.

 However, in case of using 10% of Portland cement and cement binder as excipient and internal mortar, the compression strength was increased in all formulations, but the compressive strength was increased to 5N / mm2 within 13 hours at 13 ℃ It can be seen that the present invention is very useful because it is understood that the present invention is limited to the case where the PE-based high-performance AE water reducing agent is used.

 However, in both of the comparative examples and the examples thus far, when the amount of quicklime is added as a part of the amount of Portland cement and cement binder, the initial slump value tends to decrease with an increase in the amount of quicklime Respectively. In order to compensate for this, it was concluded that the increase of the unit quantity of concrete may be difficult to manifest the low temperature early strength and the increase of the compressive strength in the long term age. In order to overcome this problem, the use of limestone powder, which is known to be effective in improving the fluidity of concrete, is mixed with Portland cement and cement And 1 to 40 parts by weight based on 100 parts by weight of the total of the binder and the binder to improve the fluidity, thereby achieving the object of the present invention more effectively and economically.

Table 6 below shows the blending ratio of concrete added with quicklime and limestone fine powder.

The results of the above mixing test are shown in Table 7.

As shown in the test results of Comparative Examples 9 to 15 and Examples 9 to 10, when the limestone fine powder having a specific particle size was used as the mortar and mortar in an amount of 10% of the amount of the Portland cement and the cement binder, the fluidity tended to increase in all formulations And the compressive strength of 3 days and 7 days of 28 days in all of the examples were equal to or higher than those of the comparative examples without any problem and the compressive strength values were higher than those of the comparative examples. Respectively. Since the limestone powder does not have its own hydraulic properties, the compressive strength is expected to decrease when the Portland cement and cement binder are partially substituted. However, when the limestone powder is used with the quicklime, the compressive strength is not significantly decreased. The compressive strength of the concrete was increased by the addition of the limestone fine powder to the pores of the internal structure of the concrete.

Table 8 shows the results of tests carried out in Comparative Examples 9 to 15 and Examples 9 to 10 to determine the low-temperature early compression strength.

Example 9, the compressive strength of more than 5N / mm ² without changing the initial slump value less than the case of 10 13 ℃ 18 times expressed invention than with the open from the test results the addition of calcium oxide and limestone powder simultaneously PE-based high-performance AE water-reducing agent It was possible to achieve the predetermined purpose pursued.

The above-mentioned low-temperature early strength concrete composition of the present invention can be used directly as a foundation for building structures at construction sites, as well as for vibration products such as remicon and steam curing products (water pipe, PC panel, etc.), centrifugal products PHC files, etc.), and the use thereof is not limited. The present invention has been described above with reference to the embodiments, but the present invention is not limited thereto, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

FIG. 1 is a graph showing the heat of hydration of low-temperature early strength concrete according to the present invention. FIG.

Claims (6)

A concrete composition comprising a Portland cement and a cementitious binder, Wherein the quicklime has a powdery degree of from 500 to 8000, and the amount of the quicklime is from 1 to 40 parts by weight, the limestone fine powder is from 1 to 40 parts by weight, and the high-performance AE water reducing agent is from 0.1 to 5 parts by weight based on 100 parts by weight of the Portland cement and cement- Cm 2 / g, and the limestone powder has a particle size of 500 to 8000 cm 2 / g. The cement binder is one or more selected from blast furnace slag, fly ash and silica fume, and the amount of the Portland cement and cement binder Lt; RTI ID = 0.0 > kg / m3. ≪ / RTI > delete delete delete delete The method according to claim 1, Wherein the concrete composition comprises aggregate and water.

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