KR102547030B1 - High Strength Concrete Composition for Polygons Shaped Precast Concrete - Google Patents

Abstract

The present invention relates to a concrete composition for ultra-high-strength prismatic PC members produced by centrifugal molding, and more specifically, unlike the existing PHC pile mixture produced by centrifugal molding, unhardened concrete secures a slump to minimize voids in unhardened concrete By injecting a large amount of concrete into the mold, it is possible to increase the amount of concrete input into the mold for centrifugal molding by lowering the hollowness in the final product, so that the efficiency of the member is increased by enlarging the cross section of the rectangular PC member, and the rectangular shape with a large cross section It relates to a concrete composition for ultra-high-strength prismatic PC members manufactured by centrifugal molding to secure ultra-high strength of concrete without applying silica fume while being able to manufacture PC members by centrifugal molding.
A preferred embodiment of the present invention is a concrete composition composed of a binder, fine aggregate, coarse aggregate, and water, wherein the unit binder contains 60 to 80 wt% cement, 5 to 15 wt% blast furnace slag (S/P), and 15 to 25 wt% strength mixture. %, and 1.0 to 1.4 wt% of the polycarboxylic acid-based centrifugally molded PC member admixture is additionally mixed with the unit binder.

Description

Concrete composition for ultra-high strength prismatic PC member produced by centrifugal molding {High Strength Concrete Composition for Polygons Shaped Precast Concrete}

The present invention relates to a concrete composition for ultra-high-strength prismatic PC members produced by centrifugal molding, and more specifically, unlike the existing PHC pile mixture produced by centrifugal molding, unhardened concrete secures a slump to minimize voids in unhardened concrete By injecting a large amount of concrete into the mold, it is possible to increase the amount of concrete input into the mold for centrifugal molding by lowering the hollowness in the final product, so that the efficiency of the member is increased by enlarging the cross section of the rectangular PC member, and the rectangular shape with a large cross section It relates to a concrete composition for ultra-high-strength prismatic PC members manufactured by centrifugal molding to secure ultra-high strength of concrete without applying silica fume while being able to manufacture PC members by centrifugal molding.

Concrete manufactured by the centrifugal molding method is representative of PHC PILE, hume pipe, etc. Since this centrifugal molding method produces the shape of a structure with a physical method using centrifugal and centripetal force, As the amount of water used can be reduced, the high strength of concrete can be achieved.

For prismatic members such as rectangular beams produced by ultra-high-strength centrifugal molding, steel rods or strands for introducing prestress are arranged to secure target bending stiffness, and hollowness must be limited to at least 10% or less to secure cross-sectional stiffness. In the existing composition for producing such a centrifugal molded member, there is almost no slump of unhardened concrete by minimizing the unit quantity, and due to this, the gap between the unhardened concrete materials is large, making it difficult to put a large amount of concrete into the closed cross-section mold, and a large amount of concrete Due to the impossibility of injection, the porosity of the cross section of a general centrifugal formed member was 46% to 55%, and the stress on the load of the member acted greatly, which had limitations in maximizing the efficiency of the member.

As a background technology of the present invention, there is Korean Patent Registration No. 1654651 "mixture of high-strength concrete" (Patent Document 1). In the background art, 'in the mixed material of high-strength concrete containing blast furnace slag powder and having a compressive strength of 80 MPa or more, it is made by mixing 95 to 99% of blast furnace slag powder and 1 to 5% of inorganic additives for viscosity control, and the inorganic material for viscosity control A mixed material for high-strength concrete in which Na2CO3 is 40 to 60% and CaCO3 is 40 to 60% is proposed as an additive. Viscosity control and strength expression are possible so that the performance of the blast furnace slag can be maintained and the strength can be improved at the same time.

However, the background art also has almost no slump, and due to this, the gap between the unhardened concrete materials is large, making it difficult to input a large amount of concrete into the closed cross-section mold, and the porosity of the cross section of a general centrifugal molded member is 46% to 55% due to the inability to input a large amount of concrete. There was a problem that the efficiency of the member could not be maximized due to the large stress on the load of the member in %.

Korean Patent Registration No. 1654651 "Mixed material for high-strength concrete"

The present invention is to solve the above problems, unlike the existing PHC PILE mixture, the unhardened concrete secures a slump to minimize the voids in the unhardened concrete and inject a large amount of concrete into the mold to increase the hollowness in the final product. It is possible to increase the amount of concrete input into the mold for centrifugal molding by increasing the cross-section of the prismatic PC member to increase the efficiency of the member, and it is possible to manufacture the prismatic PC member with a large cross section by centrifugal molding, and concrete without applying silica fume The purpose is to provide a concrete composition for prismatic PC members to secure ultra-high strength.

The present invention is a concrete composition composed of a combination of binder, fine aggregate, coarse aggregate and water, wherein the unit binder is composed of 60 to 80 wt% of cement, 5 to 15 wt% of blast furnace slag (S/P), and 15 to 25 wt% of strength mixture, Cement is a mixture of two types of cement (C1, C2) with different fineness, but C1 ( MgO 3.5%, SO ₃ 3.1%, fineness 3,830 cm ² /g ) and C2 ( MgO 2.2%, SO ₃ 3.2%). , powder degree 4,370cm ² /g), C1: C2 is mixed within the range of 1: 1.5 to 1: 3.5 in weight ratio, and 100 parts by weight of the unit binder, polycarboxylic acid-based dispersing agent and polycarboxylic acid-based retaining agent are mixed in a cellulose-based 1.0 to 1.4 parts by weight of an admixture for polycarboxylic acid-based centrifugal molding PC members additionally composed of a liquid thickener and an antifoaming agent are additionally mixed, and the slump is 150 mm or more and the hollow rate is 10% or less. It is intended to provide a concrete composition for PC members.

In addition, unit binder amount 540 ~ 660kg / m ³ , unit quantity 113 ~ 138kg / m ³ , fine aggregate 650 ~ 794kg / m ³ , coarse aggregate 989 ~ 1209kg / m ³ Candle produced by centrifugal molding, characterized in that it is mixed It is intended to provide a concrete composition for high-strength prismatic PC members.

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In addition, it is intended to provide a concrete composition for ultra-high strength prismatic PC members produced by centrifugal molding, characterized in that the fine aggregate ratio (S / a) is 35 to 45 wt%.

The concrete composition for ultra-high-strength prismatic PC members produced by centrifugal molding of the present invention, unlike the existing PHC PILE mixture, secures a slump in unhardened concrete to minimize voids in unhardened concrete and injects a large amount of concrete into the mold to obtain the final product It is possible to increase the amount of concrete injected into the mold for centrifugal molding by lowering the hollowness, so that the efficiency of the member is increased by enlarging the cross section of the prismatic PC member. There is a very useful effect of securing ultra-high strength of concrete without applying it.

The following drawings attached to this specification illustrate a preferred embodiment of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention is limited to those described in the accompanying drawings. It should not be construed as limiting.
1 is a graph showing the mixing ratio of the binder of one embodiment of the ultra-high strength prismatic PC member concrete composition of the present invention and the comparative example.
Figure 2 is a diagram showing the results of slump experiments of one embodiment and comparative example of the concrete composition for ultra-high strength prismatic PC member of the present invention.
3 is a diagram showing the hollowness test results of an embodiment of the concrete composition for ultra-high strength prismatic PC member of the present invention and a comparative example.
Figure 4 is a diagram showing the results of compressive strength test of one embodiment and comparative example of the concrete composition for ultra-high strength prismatic PC member of the present invention.
5 is a diagram illustrating a dispersion and slump maintenance model of a compatibilizer for a centrifugally molded PC member.

Below, the present invention will be described in detail with reference to the embodiments presented in the accompanying drawings, but the presented embodiments are illustrative for a clear understanding of the present invention, and the present invention is not limited thereto.

Hereinafter, the technical configuration of the present invention according to a preferred embodiment will be described in detail.

In general, high-strength concrete requires a large amount of cement compared to general concrete, and experiments show that W/C decreases and compressive strength increases as the unit cement amount increases below 500 kg/ ^m3 . [ Korea Concrete Institute, Concrete Engineering] However, in general precast concrete, there is a limit to increasing the amount of cement per unit to develop concrete compressive strength of 100 MPa, so silica fume (95.1%), the main component of which is a large amount of SiO ₂ , is used as a mixture. used to increase concrete strength.

It is extremely rare to apply expensive silica fume unless it is a high-strength concrete structure for on-site casting. In the case of high-strength precast concrete, despite advantages such as weight reduction and simplified on-site heavy equipment, etc., and securing economic feasibility, product price competitiveness is low. The use amount is limited in terms of economic feasibility, and accordingly, in the present invention, a mixing ratio for enhancing the strength of concrete was derived by applying the centrifugal molding method, which is a high-strength concrete manufacturing technology.

In the present invention, the unit amount of binder was increased compared to the PHC PILE mixing ratio to improve strength, and the fine aggregate ratio (S/a) was increased for fine aggregate and coarse aggregate to secure workability, and admixture (AD) performance The blending ratio was derived by minimizing the amount of unit binder according to.

When the unit amount of binder is less than 540 kg/m ³ , there is no strength enhancement effect, and when mixing in excess of 660 kg/m ³ , economical efficiency is reduced, so it is preferable to mix 540 to 660 kg/m ³ .

In the present invention, the strength is increased by reducing the unit quantity, and the lack of workability due to the decrease in the unit quantity is secured by applying an admixture containing a large amount of an AE agent, which is a bubble stabilizer for evenly inserting small air bubbles in concrete. , In the present invention, in order to prevent an increase in concrete volume due to a large amount of air bubbles, fluidity was secured by increasing the content of the polycarboxylic acid-based dispersant without using an AE agent. In addition, it is a centrifugal molded PC member that can secure workability by adding a cellulose-based liquid thickener to secure the retention time of concrete properties through the use of an appropriate amount of polycarboxylic acid-based retaining agent and prevent material separation of concrete due to the increase in dispersant content. Apply a solvent admixture to secure workability (slump).

When the unit quantity is less than 113kg/m ³ and mixed, workability is lacking, and when mixed in excess of 138kg/m ³ , a decrease in strength may occur, so it is preferable to mix 113 to 138kg/m ³ .

Improvement of workability through unit quantity and fine aggregate ratio can be equally applied to general concrete, but as in the present invention, it is difficult to derive an appropriate mixing ratio for each material in high-strength concrete of 100 MPa, and an increase in fine aggregate ratio reduces strength, It can cause separation, etc., and slump can be increased by increasing the unit quantity, but this causes a decrease in strength, and when applied to centrifugal molding, sludge flows down in the hollow part after centrifugal molding, resulting in thick layers or poor internal holes. .

Therefore ^, in the present invention ^, when the fine aggregate ratio is increased, phenomena such as strength reduction or material separation occur, and when the fine aggregate ratio is lowered, workability is deteriorated. Therefore, the fine aggregate (S/a) of fine aggregate and coarse aggregate was increased to about 35 to 45 wt% to secure workability and strength.

For general concrete mixing, the final mixing ratio is derived after mixing research by trial and error method according to the concrete mixing design. The mixing ratio was derived by trial and error method.

However, in the present invention, unlike the existing PHC PILE mixture, the unhardened concrete secures a slump and minimizes the voids in the unhardened concrete to inject a large amount of concrete into the mold to derive a mixing ratio that lowers the hollowness in the final product.

Therefore, in the present invention, the amount of unit binder for strength enhancement compared to the PHC PILE mixing ratio was increased, and the fine aggregate and coarse aggregate increased S/a to secure workability, and also, the unit according to the admixture (AD) performance The mixing ratio was derived by minimizing the amount of binder.

The unit binder is composed of cement 60~80wt%, blast furnace slag (S/P) 5~15wt%, and strength mixture 15~25wt%.

When cement hardens through a hydration reaction, it starts to harden from the surface. The finer the cement, the wider the surface area, so the reaction rate is faster and the early strength is higher. Therefore, the fineness of the cement is preferably 3,000 cm ² /g or more.

In particular, although one product with a constant powder degree can be used for cement, two types of cement (C1, C2) with different powder degrees are used because the strength is affected by the workability and filling effect according to the use of cement with different powder degrees. It is preferable to mix and use C1 (MgO 3.5%, SO ₃ 3.1%, fineness 3,830cm ² /g) and C2 (MgO 2.2%, SO ₃ 3.2%, fineness 4,370cm ² /g) The product is used, and C1:C2 is preferably mixed in a weight ratio of 1:1.5 to 1:3.5.

It is known that 50 wt% of blast furnace slag can be applied to concrete, and a large amount of material is used to reduce the heat of hydration in concrete applied to foundations and dams with large scalpels. However, general concrete, especially precast concrete manufactured in factories, is limitedly used for reasons such as workability (viscosity), rough finishing treatment, and repair.

For the strength mixture, the mixture used in the production of general centrifugal molding PHC PILE was used. The strength mixture for centrifugal molding has a higher dispersion and higher gypsum-based material content than the PC strength mixture, so it is more effective in forming concrete and developing strength during centrifugal molding. am.

The reason for presenting 5 to 15% of blast furnace slag and 15 to 25 wt% of the strength mixture is to set the amount of blast furnace slag to 40 wt% or less by combining the amount of the strength mixture with the amount of strength mixture because the blast furnace slag is mixed in the strength mixture. For example, when the strength mixture and the blast furnace slag exceed 40wt%, the concrete mixture becomes viscous, so the rate at which concrete is introduced from the mixer to the mold decreases, and a small amount tends to stick and harden in the mixer hopper.

The admixture for the centrifugal molded PC member is further mixed with 1.0 to 1.4 parts by weight of 100 parts by weight of the above-mentioned unit binder.

The admixture for centrifugal molding PC members is a compound having a functional group called -COOH (carboxylic acid) or -COONa (carboxylate) in the polymer structure. Admixtures with high solid content are used to ensure required concrete properties through admixtures.

Apply precast concrete product to existing concrete mixture --> pouring --> steam curing --> mixing from demolding --> casting --> steam curing --> centrifugal molding --> centrifugal molding added by demoulding In order to achieve this, it is necessary to use the optimal mixture and admixture suitable for the characteristics of concrete. (Steam curing: Maintain for 4 to 6 hours at the maximum temperature of 75℃ ~ 85℃)

In particular, in the present invention, by using a polycarboxylic acid-based admixture for centrifugal molding PC members, the content of the polycarboxylic acid-based dispersant is increased instead of the air entraining agent (AE agent), and cellulose is used to prevent material separation that may occur due to an increase in the amount of the dispersant. Fluidity was secured by using a polycarboxylic acid-based admixture for centrifugally molded PC members, an admixture that controls the amount of air by applying a liquid thickener and applying a small amount of antifoaming agent.

The admixture for centrifugally molded PC members is an admixture composed of 55 to 65% polycarboxylic acid dispersant, 100 parts by weight of polycarboxylic acid based retaining agent 35 to 45%, 1 to 3 parts by weight of cellulose liquid type thickener, and 0.05 to 0.15% by weight of antifoaming agent. As a result, the polycarboxylic acid dispersant accelerates the dispersion of particles due to rapid adsorption during concrete mixing, increases the surface area, and has the characteristics of rapid hydration and loss of fluidity after the maximum fluidity is expressed after mixing.

Polycarboxylic acid-based retaining agents have characteristics such that particle dispersion is slow due to slow adsorption, fluidity maintenance section exists due to competition between particle dispersion and hydration, and hydration continues even after concrete mixing.

When mixed in less than 1.0 parts by weight, workability deteriorates, and when mixed in excess of 1.4 parts by weight, economical efficiency decreases, so it is preferable to mix 1.0 to 1.4 parts by weight.

5 is a diagram illustrating a dispersion and slump maintenance model of a compatibilizer for a centrifugally molded PC member.

As shown in FIG. 5, the admixture for centrifugally molded PC members expresses fluidity through dispersion between cement particles and prevents secondary aggregation to express retention performance.

<Experimental example>

Slump, hollowness and compressive strength were tested according to Comparative Examples and Examples.

1. Mixing Ratio

1 is a graph showing the mixing ratio of the binder of one embodiment of the ultra-high strength prismatic PC member concrete composition of the present invention and the comparative example.

division W/B
(%) S/a
(%) Unit amount (kg/m ³ ) AD
(%) W C1 C2 S/P H/M SF Comparative Example 1 20.6 42 165 - 400 280 - 120 1.8(S) Comparative Example 2 19.2 35 100 416 - - 104 - 1.3(B) Example 20.8 40 125 120 330 30 120 - 1.2(A)

1) Comparative Example 1 (PC), Comparative Example 2 (PHC PILE), Example (this application)

- Comparative Example 1 is the mixing ratio for producing 100 MPa class concrete by the general precast concrete method (Slump 180mm, hollow rate 0%: closed section, binder amount 800kg/m ³ )

- Comparative Example 2 is the mixing ratio for producing 78.5 MPa class concrete by centrifugal molding method (Slump 0mm, hollowness 36.0 ~ 46.2%, binder amount 520kg/m ³ )

- Example is the mixing ratio for producing 100 MPa class concrete by centrifugal molding method (Slump 180mm, hollow rate 10% or less, binder amount 600kg/m ³ )

- In Comparative Example 2 (78.5MPa), which is the mixing ratio of centrifugal molded concrete, the amount of strength mixture containing 21.4% of cement (C2) with a higher powder fineness of 540 cm ² /g and SO ₃ was increased to increase the strength (21.5MPa ↑) Sikkim.

- Liquidity is increased by increasing unit quantity and fine aggregate (S/a) to increase slump.

- Blast furnace slag increases long-term strength, has a concrete filling effect, and is used as a substitute for cement, thereby reducing carbon and recycling through the use of industrial by-products.

The amount of binder is the sum of all cement (C1, C2), blast furnace slag (S/P), and strength mixture, and the concrete compressive strength is 100MPa by increasing the amount of cement (C1 + C2) and strength mixture in the example mixing ratio to enhance strength. It is possible to derive the above compounding ratio, and the amount of each material is flexible due to the difference in characteristics according to the origin of the material, so the compounding ratio has variability. In addition, in areas where the quality of each material is good, the mixing cost can be reduced by increasing the content of blast furnace slag, so setting the range for each material is inevitable, so the binder amount, fine aggregate, and coarse aggregate are ± 10% of the embodiment, cement, blast furnace slag, The intensity mixture was set to ± 5% in the examples.

2) Material characteristics

Cement was a mixture of cements with different fineness, C1 (MgO 3.5%, SO ₃ 3.1%, fineness 3,830cm ² /g) and C2 (MgO 2.2%, SO ₃ 3.2%, fineness 4,370cm ² /g) Same as

SF: SiO ₂ 95.1%, SO ₃ 0.7%, fineness 23.4m ² /g

S/P : MgO 3.4%, SO ₃ 0.5%, fineness 4,610 cm ² /g

H/M: SO ₃ 21.4%, fineness 5,380 cm ² /g

Admixture (S): Improved dispersion performance compared to general PC admixture

Admixture (A): Increase solid content and add cellulose-based liquid thickener component to the admixture used for PHC PILE

Admixture (B): Polycarboxylic acid-based admixture mainly used for PHC PILE production

2. Slump, hollow rate experiment

Set slump & hollow ratio

Figure 2 is a diagram showing the slump test results of an embodiment of the concrete composition for ultra-high strength prismatic PC members of the present invention and a comparative example, Figure 3 is a comparison with one embodiment of the ultra-high strength concrete composition for prismatic PC members of the present invention It is a diagram showing the hollowness test results of an example.

The slump and hollowness of Examples and Comparative Examples were tested, and the results were shown in Table 2 and FIGS. 2 and 3.

division slump
(mm) hollow specimen note mm % Comparative Example 1 180 - - - Comparative Example 2 15 95 28.6 - Example 210 60 9.0 -

The currently used concrete slump for centrifugal molding is about 15mm, and it is necessary to secure a slump of 150mm or more, which is the slump of general precast concrete, in order to put a large amount of concrete into a mold of a limited size.

As shown in Table 2, the slump of 150 mm or more was Comparative Example 1 and Example, and the hollowness was 28.6% in Comparative Example 2 and 9.0% in Example.

3. Compressive strength test

Figure 4 is a diagram showing the results of compressive strength test of one embodiment and comparative example of the concrete composition for ultra-high strength prismatic PC member of the present invention.

The compressive strength was tested on the 1st, 7th, 14th and 28th days of Examples and Comparative Examples, and the results were shown in Table 3 and FIG.

division Compressive strength (MPa) target 1 day 7 days 14 days 28 days Comparative Example 1 - 85.5 93.7 105.2 100 MPa Comparative Example 2 76.2 84.3 - - 78.5 MPa Example 100.7 104.4 - - 100 MPa

As shown in Table 3 and FIG. 4, despite the high amount of binder material of 800 kg / m ³ despite the use of expensive silica fume in general PC mixing ratio, it takes 28 days of curing period to develop the target strength, whereas the mixing ratio of Example In the furnace, more than 100MPa is secured in demoulding strength with 600kg/m ³ binding material, and it is possible to secure additional strength of about 4% or more in the 7-day strength, which is the curing period of general centrifugal molding products.

Unlike the PHC PILE mixture produced by conventional centrifugal molding, the concrete composition for ultra-high-strength prismatic PC members produced by centrifugal molding of the present invention as described above secures a slump in unhardened concrete to minimize voids in unhardened concrete, so that many molds are formed. It is possible to increase the amount of concrete injected into the mold for centrifugal molding by lowering the hollowness of the final product by injecting a large amount of concrete, so that the efficiency of the member is increased by enlarging the cross section of the rectangular PC member, and the rectangular PC member having a large cross section is centrifugally formed. Although it can be manufactured by molding, it has a very useful effect of securing ultra-high strength of concrete without applying silica fume.

So far, the present invention has been described in detail with reference to the presented embodiments, but those skilled in the art can make various modifications and variations without departing from the technical spirit of the present invention with reference to the presented embodiments. will be. The present invention is not limited by these variations and modifications, but is limited only by the claims appended below.

Claims (5)

A concrete composition composed of a combination of binder, fine aggregate, coarse aggregate and water,
The unit binder is composed of cement 60~80wt%, blast furnace slag (S/P) 5~15wt%, strength mixture 15~25wt%,
Cement is a mixture of two types of cement (C1, C2) with different fineness, but C1 ( MgO 3.5%, SO ₃ 3.1%, fineness 3,830 cm ² /g ) and C2 ( MgO 2.2%, SO ₃ 3.2%). , the powder degree is 4,370 cm ² /g), and C1: C2 is mixed within the range of 1: 1.5 to 1: 3.5 in weight ratio,
In 100 parts by weight of the unit binder, 1.0 to 1.4 parts by weight of a polycarboxylic acid-based admixture for centrifugal molded PC member, which is additionally composed of a cellulose-based liquid thickener and an antifoaming agent in a polycarboxylic acid-based dispersing agent and a polycarboxylic acid-based retaining agent, is further mixed.
A concrete composition for ultra-high strength prismatic PC members produced by centrifugal molding, characterized in that the slump is 150 mm or more and the hollow rate is 10% or less. The method of claim 1,
Unit bonding material 540~660kg/m ³ ,
Unit quantity 113~138kg/m ³ ,
Fine aggregate 650~794kg/m ³ ,
Coarse aggregate 989 ~ 1209kg / m ³ Concrete composition for ultra-high strength prismatic PC member produced by centrifugal molding, characterized in that blended. delete delete The method of claim 2,
Fine aggregate ratio (S / a) is a concrete composition for ultra-high strength prismatic PC member produced by centrifugal molding, characterized in that 35 ~ 45wt%.

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