KR20150068101A - Cement composition for pretentioned spun high strength concrete pile and concrete composition including the same - Google Patents

Abstract

In the present invention, disclosed is a concrete composition, which is allowed to manufacture an optimal cement mixture for high strong PHC pile and high strong PHC pile without a curing process under high pressure and temperature by using a first type Portland cement, industrial byproducts and fine powder binders wherein the cement mixture for prestressed concrete (PHC) comprises 20-50 wt% of the first type Portland cement; 40-65 wt% of granulated blast furnace slag; and 5-15 wt% of fine powder binders wherein the concrete for the PHC comprises 540-650 kg/m^3 of the cement mixture; 110-130 kg/m^3 of water; 563-800 kg/m^3 of fine aggregates; 1,020-1,296 kg/m^3 of thick aggregates; and 6.5-16.3 kg/m^3 of chemical admixture.

Description

TECHNICAL FIELD The present invention relates to a cement composition for a high-strength prestressed concrete pile and a concrete composition containing the cement composition for a high strength prestressed concrete pile,

The present invention relates to a cement admixture for producing a high strength prestressed concrete pile and a concrete composition containing the same, and more particularly, to a cement admixture containing an industrial byproduct and a high-strength binder for producing an ultrahigh-strength prestressed concrete pile of 120 MPa And a concrete composition containing the same.

The design reference strength of a pretensioned spun high strength concrete pile (hereinafter referred to as "PHC file" for convenience) which is widely used in construction sites is 78.5 N / mm 2, and the existing precast file ") Is 49.1 N / mm < 2 >.

In addition, since the long-term permissible stress of the PHC file is about 1.5 times the long-term allowable stress of the PC file, the design bearing capacity can be greatly improved and it is advantageous to extend the design range.

In addition, the concrete used in the manufacture of PHC pile has high impact strength, excellent impact resistance, excellent microstructure inside the pile, excellent resistance to freezing and thawing and chemical resistance to chemical agents, and resistance to fracture bending moment It has strong characteristics.

However, recently, as the construction of civil engineering structures is becoming more popular, and the application range of civil engineering buildings is widening and the construction technology is greatly developed, the demand for PHC files having higher end bearing capacity than conventional products is increasing. Due to such changes in the market environment, ultra high strength PHC files of 100 MPa or more have been commercialized.

A method of manufacturing a high strength PHC file is disclosed in Japanese Patent Laid-Open No. 10-1247400 (hereinafter referred to as "prior art 1") and a 10- 1172635 (Ultra High Strength Concrete Composition for Centrifugal Formed PEI Pile; hereinafter referred to as "Prior Art 2").

While the compressive strength of a typical PHC file is at the level of 80 MPa, the concrete composition disclosed in the above prior arts 1 and 2 has a very high compressive strength of 120 MPa.

Prior art 1 is a method for curing a steel sheet at a temperature of 65 to 85 ° C for 1 to 3 hours and then curing at a high temperature and a high temperature for a period of 3 to 4 hours from 180 to 190 ° C, A secondary holding step of curing for a period of time, and a slow cooling step) to produce a concrete composition. However, this manufacturing method has a limitation that it is possible to manufacture an ultra-high-strength PHC pile only when a high-temperature high-pressure curing facility is provided.

Unlike Prior Art 1, Prior Art 2 is characterized in that ultra high strength PHC pile of 120 MPa can be manufactured by only steam curing without high temperature high pressure curing process, but ultra high strength PHC pile is manufactured using three kinds of crude steel portland cement. The three kinds of crude steel portland cement are advantageous for securing early strength, but they are inferior in economic efficiency and quality control compared with one kind of ordinary portland cement.

It is an object of the present invention to provide an ultrahigh strength cement mixture and a concrete composition containing the same to produce an ultra-high strength PHC pile having a strength of 120 MPa or more only by a steam curing process.

In particular, the present invention provides a concrete composition capable of producing an ultrahigh strength PHC pile without a cement mixture and a high-temperature and high-pressure curing process optimized for an ultra-high strength PHC pile using one kind of ordinary Portland cement, industrial by- There is a purpose.

In order to accomplish the above object, the present invention provides a cement mixture for a prestressed concrete (PHC) pile comprising 20 to 50% by weight of one kind of ordinary Portland cement; 40 to 65% by weight of blast furnace slag fine powder; And 5 to 15% by weight of a high-strength binder.

Preferably, the content of the one kind of ordinary Portland cement is 35 to 45% by weight, and the blast furnace slag fine powder contains 5 to 15% by weight of natural anhydrous gypsum, flue gas desulfurization gypsum or phosphate by-product, / g or more.

Preferably, the blast furnace slag fine powder has a powder degree of 5,000 cm 2 / g or more, and the amount of natural anhydrite and flue gas desulfurization gypsum or by-product phosphate by weight is 5 to 15% by weight.

In addition, the high-strength binder is preferably a mixture of fine-grained cement, meta-kaolin or diatomaceous earth in an amount of 0.5 to 15% by weight, and the amount of the high-strength binder in the mixture is 8 to 12% by weight desirable.

The concrete for a PHC pile according to the present invention is a cement mixture of 540 to 650 kg / m 3, which is defined above. Water of 110 to 130 kg / m 3, fine aggregate of 563 to 800 kg / m 3; Coarse aggregate of 1,020 ~ 1,296 kg / m3; And a chemical admixture of 6.5 to 16.3 kg / m < 3 >.

Here, the strength of the coarse aggregate is 150 MPa or more, and the ratio of the fine aggregate (fine aggregate ratio; S / a) in the whole aggregate is preferably 32 to 42 wt%.

The cement admixture according to the present invention has an excellent strength development characteristic under the steam curing condition, and is suitable for the manufacture of super high strength PHC pile.

In addition, since it contains a large amount of industrial byproducts and non-plastic binders, it is effective in reducing the environmental burden through recycling of resources. As the amount of cement used decreases, carbon dioxide (produced in the production of one ton of cement, To reduce emissions and reduce energy consumption.

In addition, the concrete composition for an ultra-high strength PHC pile according to the present invention can secure a concrete having a high compressive strength of 120 MPa or more by using only the steam curing process without the high temperature high pressure curing process using the above cement mixture, The present invention is advantageous in that it can secure economical efficiency because it contains one kind of ordinary portland cement which is most widely used as general cement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between temperature and time during the curing of a concrete composition for preparing an ultra-high strength PHC pile according to an embodiment of the present invention. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of a mixed cement for producing an ultrahigh strength PHC pile according to the present invention and a concrete composition containing the same will be described in detail. Although the present invention has been described in detail by way of the illustrated embodiments, the present invention is not limited by these embodiments.

1. Cement mixture

The cement admixture for ultra high strength PHC pile according to the present invention is characterized by containing industrial by-products and non-plastic binders. Specifically, 20 to 50 wt% of one kind of ordinary Portland cement, 40 to 65 wt% of blast furnace slag fine powder, And 5 to 15% by weight of a high-strength binder.

The blast furnace slag fine powder is obtained by quenching the blast furnace slag in a hot molten state generated as a by-product during the smelting of pig iron, and is a material obtained by vitrifying the blast furnace slag by quenching. The reactivity is high and the blast furnace slag, blend for cement and concrete It is used as a material. Such blast furnace slag fine powders are known to be cured (latent hydraulic) by alkali, though they are hard to cure themselves, and hardening is accelerated by the action of calcium hydroxide and sulphate, which are hydration products of cement.

In the present invention, blast furnace slag fine powders having such characteristics are used as a material of the cement mixture. Particularly, blast furnace slag fine powders contain 5 ~ 15% of natural anhydrous gypsum, flue gas desulfurization or phosphate by-product, / g. < / RTI >

The high-strength binder used in the cement admixture according to the present invention comprises 0.5 to 15% by weight of fine-particle cement, meta-kaolin or diatomaceous earth, and a limestone fine powder having a powder degree of 12,000 cm2 / g or more.

The components and the proportions of the cement mixture according to the present invention are shown in Table 1 below.

Components and proportions of the cement admixture
Composition ratio (% by weight)

Characteristic
cement

20 to 50
1 species ordinary Portland cement
Blast furnace slag
Fine powder

40 to 65
The powder has a natural anhydrous gypsum of more than 4,500㎠ / g
5 to 15% by weight of flue gas desulfurization or phosphate by-product
High powder binder

5 to 15 A limestone fine powder having a powder degree of 12,000 cm < 2 > / g or more,
0.5 to 15% by weight of cement or meta kaolin or diatomaceous earth

1 species ordinary Portland cement

As the cement constituting the cement admixture according to the present invention, one kind of ordinary Portland cement is used and the amount thereof is 20 to 50% by weight, preferably 35 to 45% by weight.

When the amount of the first type Portland cement is less than 20% by weight, the reactivity of the blast furnace slag fine powder and the high-strength binder is low. When the amount is more than 50% by weight, sufficient strength can not be secured in the steam curing.

blast furnace pull Slag Fine powder

The blast furnace slag fine powder has a powder degree of not less than 4,500 cm2 / g, preferably a blast furnace slag fine powder having a powder degree of not less than 5,000 cm2 / g.

The blast furnace slag fine powder is a latent hydraulic material and has a property of curing in the presence of calcium hydroxide produced through the hydration reaction of cement. Therefore, the blast furnace slag fine powder has a smaller contribution to the initial strength than the cement at normal temperature conditions, but the reactivity is greatly improved as the temperature rises, thus contributing to the initial strength more than the cement in the steam curing condition.

The blast furnace slag fine powder contains 5 to 15% by weight of fountain gypsum, desulfurization gypsum or phosphate by-product, and the amount used in the cement mixture is 40 to 65% by weight, preferably 45 to 58% by weight.

When the blast furnace slag fine powder is used in an amount of 40 wt% or less, sufficient strength is not exhibited during the steam curing process. When the blast furnace slag powder is used in an amount of 65 wt% or more, the calcium hydroxide produced by the hydration reaction of the cement is insufficient.

The gypsum has a characteristic of making the internal structure of the concrete hardened by the reaction of hydration of the cement and the blast furnace slag. When the amount of the gypsum used is too small, the compactness of the structure becomes insufficient. When the amount of the gypsum is exceeded, Lt; RTI ID = 0.0 > dense < / RTI >

In the present invention, a desulfurized gypsum or a phosphate by-product is used to prevent the deterioration of workability which may occur when natural anhydrous gypsum alone is used and to secure a stable quality. Also, the gypsum was pulverized together with the blast furnace slag to distribute the gypsum particles and the slag fine powder particles evenly, thereby improving the reactivity.

High powder Binders

The high-strength binder material constituting the cement mixture according to the present invention comprises 0.5 to 15% by weight of fine-particle cement, meta kaolin or diatomaceous earth in a limestone fine powder having a powder degree of 12,000 cm2 / g or more.

The high-strength binder has an average particle diameter of 5 μm or less and is used as a binder and a filler for modifying a weak region (transition region) formed at the interface between the cement particles and the aggregate, thereby contributing to the improvement of strength and durability.

The amount of the high-strength binder used is 5 to 15% by weight, preferably 8 to 12% by weight. When the high-strength binder is not more than 5 wt% or not less than 15 wt%, the filler effect is reduced or the effect of modifying the transition region is decreased, so that it is difficult to contribute to the strength enhancement.

Hereinafter, a concrete composition for ultra high strength PHC pile according to the present invention, which is made of the above cement composition, will be described.

2. Concrete  Composition

The concrete composition for ultra high strength PHC pile according to the present invention includes 540 to 650 kg / m 3 of cement mixture, 110 to 130 kg / m 3 of water, 563 to 800 kg / m 3 of fine aggregate, and 1,020 to 1,296 kg / m 3 of coarse aggregate , And a chemical admixture for concrete (6.5 to 16.3 kg / m3) for reducing the quantity of concrete and ensuring workability.

The composition ratios of these concrete compositions are shown in the following table.

W / B
(weight %)

S / a
(weight %)
Unit material amount (kg / m3)

Water (W)
Cement mixture
(B)
Fine aggregate
(S)
Coarse aggregate
(G)
Admixture
(AD)
17-24

32 ~ 42
95 ~ 130
540 to 650
563 to 800
1,020 ~ 1,296
6.5 to 16.3

water( Mixed water )

The mixing water is most preferably in the range of 110 to 130 kg / m3. When the mixing water is 110 kg / m 3 or less, the defective workability of the concrete tends to cause defective molding and the productivity deteriorates. Also, when the mixing water is more than 130㎏ / ㎥, the flowability of the concrete increases and the internal diameter of the pile becomes uneven and the compressive strength decreases.

Fine aggregate rate (S / a)

The fine aggregate ratio (S / a) is a volume ratio of the fine aggregate in the total aggregate, which greatly affects the formability of the ultra high strength concrete for PHC piles.

In view of this, the fine aggregate content in the concrete composition according to the present invention is 32 to 42%, preferably 35 to 39% by weight.

When the fine aggregate content is less than 32% by weight, the cement paste or mortar can not sufficiently fill the gap between the coarse aggregate and the coarse aggregate, resulting in reduced formability and liability of filling failure. Also, when the fine aggregate content is 42% by weight or more, the formability is improved but the compressive strength can be reduced.

Amount of fine aggregate (S) and bold Aggregate amount (G)

Considering the above-mentioned fine aggregate ratio, the amount of binder and the amount of water, the amount of fine aggregate is preferably in the range of 563 to 800 kg / m3.

Also, for the concrete composition of the present invention, a high strength aggregate having a maximum dimension of 25 mm or less and a strength of 150 MPa is used, and the coarse aggregate amount is preferably 1,020 to 1,296 kg / m3.

When the strength of the coarse aggregate is 150 MPa or less, even if the binder has sufficient compressive strength, the coarse aggregate is damaged and it is difficult to stably secure the compressive strength of 120 MPa or more.

Mixed material ( AD )

The concrete composition according to the present invention contains a chemical admixture in the range of 6.5 to 16.3 kg / m < 3 > so that sufficient formability is ensured and cement and binder particles are evenly distributed and can effectively contribute to the improvement of compressive strength.

As the chemical admixture, it is preferable to use a polycarboxylate-based high-performance water reducing agent containing a large amount of a preservative agent in order to ensure excellent water reducing effect and ensure moldability.

Hereinafter, preferred embodiments of the concrete composition including the cement admixture according to the present invention will be described.

The composition ratios of the components constituting the cement mixture contained in the concrete composition according to Example 1 are as shown in the following Table.

cement
mixture

1 species Common Portland
cement
Blast furnace slag fine powder (43% by weight)

The high-strength binder (12% by weight)
Slag

Natural anhydrous
Desulfurization plaster
Limestone
Fine cement
45 wt%

32 wt%
9 wt%
2 wt%
11.5 wt%
0.5 wt%

The concrete composition according to Example 1 including the cement admixture according to Table 3 and the concrete composition according to Comparative Example 1 made of one kind of ordinary Portland cement and high strength admixture are shown in Table 4 below.

W / B
(weight%)
S / a
(weight%)
Unit material amount (kg / m3)
Water (W) The cement admixture (B) C A Fine aggregate
(S) Coarse aggregate
(G) Admixture
(AD)
Comparative Example 1

21
37
106
540
60
667
1197

10.2
Example 1

21
37
106
600
687
1197
9.0

In Table 4 above, "A" is a high strength blend and "C" is a type 1 ordinary Portland cement.

The concrete composition according to Example 1 and the concrete composition according to Comparative Example 1 were cured under the following curing conditions (i.e., curing conditions shown in FIG. 1).

Post-molding transposition: 2 hours

Temperature rise time to 85 ° C: 2 hours

85 캜 Holding time: 5 hours

Natural cooling

The compressive strength of the concrete according to Example 1 cured under the above conditions and the concrete according to Comparative Example 1 were measured after 24 hours (after 1 day) and 168 hours (after 7 days), respectively. Are shown in Table 5 below.

Compressive strength (MPa) after 24 hours

Compressive strength (MPa) after 168 hours
Comparative Example 1
91.2

101.2
Example 1
112.3

121.1

As can be seen from the above Table 5, the concrete manufactured using the one kind ordinary portland cement and the high strength mixed material had a compressive strength of about 100 MPa after 7 days, but the concrete according to Example 1 of the present invention had 7 days And a compressive strength of 121 MPa was exhibited.

The composition ratios of the components constituting the cement mixture contained in the concrete composition according to Example 2 are as shown in the following Table.

cement
mixture

1 species Common Portland
cement
Blast furnace slag fine powder (52% by weight)

The high-strength binder (10% by weight)
Slag

Natural anhydrous
Desulfurization plaster
Limestone
Fine cement
38 wt%

42 wt%
8.5 wt%
1.5 wt%
9.0 wt%
1.0 wt%

The concrete composition according to Example 2 including the cement admixture according to Table 6, and the concrete composition according to Comparative Example 2 composed of the one kind ordinary portland cement and the high strength admixture are shown in Table 7 below.

W / B
(weight%)
S / a
(weight%)
Unit material amount (kg / m3)

Water (W) cement
The mixture (B)
C
A Fine aggregate
(S) Coarse aggregate
(G) Admixture
(AD)
Comparative Example 2

21
37

112
558
62
675

1176
12.0

Example 2

21

37

102
580
697

1214
9.0

In Table 7 above, "A" is a high strength mixed material and "C"

The concrete compositions according to Comparative Examples 2 and 2 were each cured under the same curing conditions as the curing conditions in Example 1 (i.e., the curing conditions shown in FIG. 1), and the cured concrete according to Example 2 and Comparative Example 2 were measured for compressive strength after 24 hours (after 1 day) and 168 hours (after 7 days), respectively.

The measurement results of the compressive strength are shown in Table 8 below.

Compressive strength (MPa) after 24 hours

Compressive strength (MPa) after 168 hours
Comparative Example 2
92.1

104.5
Example 2
109.3

122.3

As can be seen from the above Table 8, the concrete of Comparative Example 2, which was produced by using one kind of ordinary Portland cement and a high strength mixed material, had a compressive strength of about 104 MPa after 7 days, The compressive strength of the concrete was 122 MPa after 7 days.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention.

Claims (10)

In a cement admixture for prestressed concrete piles,
20 to 50% by weight of one kind of ordinary Portland cement;
40 to 65% by weight of blast furnace slag fine powder; And
5 to 15% by weight of a high-strength binder. The cement admixture according to claim 1, wherein the content of the one kind of ordinary Portland cement is 35 to 45% by weight. The cement admixture according to claim 1, wherein the blast furnace slag fine powder contains 5 to 15% by weight of natural anhydrous and flue gas desulfurization or by-product phosphate by-product, and the powder degree is 4,500 cm 2 / g or more. 4. The cement admixture according to claim 3, wherein the blast furnace slag fine powder has a powder degree of 5,000 cm < 2 > / g or more, and the amount of natural anhydrite and flue gas desulfurization gypsum or by-product phosphate is 5-15 wt%. The cement admixture according to claim 1, wherein the high-strength binder is a mixture of fine-grained cement or meta-kaolin or diatomaceous earth in an amount of 0.5 to 15 wt.% In a limestone fine powder having a powder degree of 12,000 cm 2 / g or more. The cement admixture according to claim 5, wherein the amount of the high-strength binder used is 8 to 12 wt%. A cement admixture according to any one of claims 1 to 6 of 540 to 650 kg / m 3;
Fine aggregate of 563 to 800 kg / m3;
Coarse aggregate of 1,020 ~ 1,296 kg / m3; And
A concrete composition for prestressed concrete piles comprising a chemical admixture of 6.5 to 16.3 kg / m3. The concrete composition for a prestressed concrete pile according to claim 7, wherein the coarse aggregate has a strength of 150 MPa or more. The concrete composition for prestressed concrete piles according to claim 7, wherein the fine aggregate (fine aggregate) ratio (S / a) in the total aggregate is 32 to 42 wt%. The concrete composition for prestressed concrete piles according to claim 9, wherein the ratio of fine aggregate in the total aggregate is 35 to 39 wt%.

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