JPS60234808A - Manufacture of high-strength concrete beam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a high-strength concrete girder incorporating high glare stress.

[Conventional technology]

Precast (PC) concrete girders, which are often used for bridge girders, have the advantage of being able to significantly increase the bending strength in terms of design theory and making the bridge girder low-strength. Pour into the formwork containing the PC steel.

While molding, 140-160kg/cm of PO4
” r) Prestressed and then cured.

[Problem that the invention seeks to solve]

With the above formulation and manufacturing method, even if steam curing is performed, the concrete strength will not exceed JIS (Japanese Industrial Standards).
It was difficult and rare to achieve a value of 500 kg/c+w'' or more, which is specified in the above.

Recently, however, relatively small concrete piles, etc., have been cured in an autoclave to achieve a
kg/CM? PHC piles with a certain level of concrete strength have been manufactured and are commercially available as "PHC piles" as standardized by JIS standards.Also, attempts have also been made to obtain similar high-strength piles by using special admixtures.Concrete bridge girder For large products such as 1000 kg/c, large equipment is required for autoclave curing, and commercially available special admixtures are expensive and difficult to handle.
1+I? It was not possible to obtain a PC bridge girder with a concrete strength higher than that using a practical manufacturing method.

[Means for solving problems]

The present invention aims to solve the above-mentioned problems in manufacturing technology and provide a manufacturing method that can obtain high-strength concrete girders with specifications that are advantageous in terms of design theory and soil acid. P mixed with appropriate amounts of cement, sand, and coarse aggregate
During the concrete placement for C girder, the outer edge of the cement was 10~
Add 30% silica hume and 3-10% dividing agent, mix in a mixer for 3-5 minutes, and pour this into a formwork with an appropriate number of prestressed steel materials arranged in its cross section.

After molding and demolding, steam curing is performed, and 200 kg/
The gist is to introduce a prestress of cm'' or more.

An example of the concrete mix for the above PC girder is shown in Table 1.

Table 1 The above silica hume is an ultrafine particle with a particle size of approximately α1 micron that is produced as a by-product in the production process of ferrosilicon, metal silicon, etc., and is called "silica fume", "silica dust", "silica flower J, etc." An example of the chemical composition of commercially available products is shown in Table 2.

flA name MICROPOZ
2 In the present invention, 10 to 30% of the silica fume (outer side) of the cement is added to the concrete mixture, but if it is less than 10%, the concrete strength will not increase sufficiently, and if it is added in excess of 30%, it will cause special problems. If steam curing is applied to the steel, the strength will actually decrease, so considering economic efficiency, the
0% is the best.

For example, a high-performance water reducing agent with excellent dispersibility such as an alkylallylsulfonic acid type is recommended as a dispersant.
Mighty 150” etc.

In the present invention, 3 to 10% (preferably 4 to 8%) of cement is dissolved in water and added to the concrete mixture.

For mixing (mixing), coarse aggregate, sand, the silica hume, and cement are supplied to the mixer in this order, and the "Mighty 1"
50'' dissolved in water was added last and kneaded for 3 to 5 minutes.

Concrete can be placed and shaped using the usual vibration compaction method, and demolding can be done in the same way as usual.

Steam curing is performed at a heating rate of 20° C./hour and a maximum temperature of about 80° C., which is maintained for about 6 hours and then naturally cooled.

The maximum temperature mentioned above may be around 65℃, but the holding time is 12
This requires approximately twice as much time, which is not practical in terms of cooling time.

According to the method of the present invention as described above, concrete strength is approximately 2 to 3 times that of JIS, 1000 kg/c111t to 150
0 can be easily obtained without any special equipment.

Next, we will discuss the introduction of high glare stress.

As a method for introducing prestress, a pretension method or a post tension method is usually adopted, but in the present invention, either method is suitable.

In the method of the present invention, it is possible to dramatically increase the glare stress in accordance with the above-mentioned performance of the concrete itself, and it is possible to manufacture a girder with excellent bending performance. By combining, it becomes a highly dense structure, so the elastic modulus is 30 ~
This is 60% larger, reducing stress loss due to elastic deformation, which is more advantageous for introducing high glare stress. To explain this in detail, first, the bending performance of a prestressed concrete girder (10 digits) is expressed as a resistance bending moment, that is, a 6-crack bending moment.
MC: Resistance bending moment determined by the cracks of the lower edge of the material member σce: W effect gress-de-gres stress: Bending tensile strength of concrete, Ze; Determined by effective prestress, bending tensile strength and section modulus.

Among these, the tensile strength of the concrete curve does not change due to fit (and the section modulus only increases slightly even if the PC steel material doubles, so the effective prestress is the largest element after all.Therefore, the effective prestress is When examined in detail, (1) the initial total tension load PI of the PC steel material is expressed as follows.

Pl-σp:・Ap Here, σpi: Allowable stress level of PC steel material, Ap: Cross-sectional area of PC steel material. (2) Tensile stress degree σpt of PC steel material immediately after introducing prestress is expressed as follows.Here, Ro ; Stress loss until stress is introduced (relaxation due to steam curing, etc.) nl; Elastic modulus ratio AC at the time of stress introduction; Concrete area (3 At this time, the initial prestress σct introduced to the concrete cross section is (4 ) P due to creep and drying shrinkage of concrete
Here, the stress loss Δσpψ of C steel material is n: elastic modulus of concrete, ψ: creep coefficient of concrete, εS: dry state shrinkage of concrete, Es: elastic modulus of PC steel material (5 Also, PC after applying prestress Stress loss Δσpr due to relaxation of steel material is Δσprtsu(R-Ro) σρt where R; Stress loss due to relaxation of PC steel material (6) Effective tensile stress degree σpe of PC steel material is σpeI
Iwσpt-(Δδptp+Δapr>(7) The effective tensile force pe of the PC steel material is ρe-σpe-Ap. Therefore, m here is the number of PC steel materials.

The stress loss RO until stress introduction in the above equation is determined by the stress loss of the PC steel material due to steam curing, but if autoclave curing is performed, the value of this Ro will be 30~
It will be 40%, which is very disadvantageous.

This is one of the reasons why autoclave curing is not performed in the method of the present invention.

In addition, the elastic modulus n' of concrete in the formula is 25 to 0 x 10" kVcI in 2 days for a normal PC girder.
IP (compression strength [350-400kg/c+w') l
ii y teruruka, or according to the present invention, this t' 4
0×10”kgβ, and it is possible to considerably prevent losses here.

In the above equation (3), the initial prestress σct introduced into the concrete cross section is β to 145 for a compressive strength (at the time of stress introduction) of 400 kg/cI++”, for example, according to the Japan Society of Civil Engineers Prestressed Concrete Specifications.
Same sookgA+' K vs. i7okg/cd Teh
'), even if nl is large, it is said to be less than 1/1.7 of the compressive strength, so this is the PC digit strength target of 1.000 of the present invention.
If applied to ~1.500 kg/C-, theoretically σ
ct is 588-882kg/cxl, compressive strength 600
Even in the case of kg/cd, it is 283 to 42 skv, so the effective prestress becomes a very large value and its contribution to the bending performance of the PC girder further increases. However, the PC
It is also uneconomical in terms of equipment to obtain high-strength concrete walls without any restriction due to the number of diameters of PC steel materials for the cross-sectional shape of the girder.

Therefore, in the present invention, the concrete strength is 1.000.
~1.500kgN was determined.

〔Example〕

In order to obtain the PC bridge girders shown in Figures 1 and 2, the blended materials shown in Table 3 were put into a mixer in the order of coarse aggregate, sand, silica hume, and cement, and after being evacuated for 1 minute,
Mighty 150 was added to water and dissolved by stirring for 30 seconds, then kneaded for 4 minutes.
As shown in the figure, two pieces of PC steel (small diameter) 1 and nine pieces of PC steel (large diameter) 2 are placed one above the other, held together by star lugs 3, in a frame. Officials installed the
Perform vibration compaction.

After removing the disk as usual, cover the sheet and set the temperature increase rate to 2.
The temperature was maintained at 0° C./hour for 6 hours at the maximum temperature of 80° C., and then allowed to cool naturally.

Prestress was introduced after curing, but from the bending moment calculation, by adding a tensile force of 9 & 800 kgf/piece for small diameter PCC steel material, Table 3 kg/cxl effective prestress for concrete 45kv at the upper edge of the girder
2. Lower edge 270kg/cd (!: fx, 6 C
Tokayo 1111 was sold out. (Cracked load x 9.500
kgf, breaking load 17.60 kgf) In the test, as shown in Fig. 3, a PC girder was supported at both ends with spans &000, the load of the span 100 was placed in the center, and a load p was applied to the center.

As a result, the cracking load and breaking load were as shown in Table 4, and the effective prestress was as shown in Table 5.

Table 4 Table 5 The effective prestress (actually measured value) in Table 5 was determined by the following formula. That is, σas −Md/Zc where K, Md: Moment at the time of reopening crack MCw=
(aO @ + σtlt) Regarding prestress,
In Examples 1, 2, and 3, we not only obtained measured values that satisfied the design values, but also obtained values that were much higher than those of the PC digit obtained by the conventional method. [Effects of the Invention] According to the present invention as described above, the following Feel the effect.

1) Concrete girders with a concrete strength of 1000 C or higher can be easily obtained by steam curing alone.

2) Only steam curing is required, so there is no need for expensive or large-scale equipment.

3) Special admixtures that are expensive and difficult to handle become unnecessary.

4) By increasing the strength of concrete, high prestress can be introduced into the prestressing steel material, which can dramatically increase the bending strength. 5) The mixture of silica fume creates a dense structure, which prevents water from penetrating inside. This has the effect of preventing damage caused by freezing or salt damage in the 20s, which has become a problem recently.

[Brief explanation of drawings]

FIG. 1 is a half-cut front view of a 20-digit machine according to the present invention, FIG. 2 is a cross-sectional view of the same, and FIG. 3 is a test state diagram. 1.2--pc @ material, 3-- stirrup. Patent applicant Maeda Seikan Co., Ltd. Figure 1 Figure 2 and Figure 3 Procedural amendment 1, Indication of the case Patent application No. 91504 of 1982 2, Name of the invention Method for constructing high-strength concrete girders 3, Amendment Relationship with the case involving a patent applicant Address Name Maeda Seikan Co., Ltd. 4, Agent 6 Number of inventions increased by amendment (1) Details! tJlt! Table 4 on page 13 is corrected as follows. Table 4 and above

Claims (1)

[Claims] 1. In the concrete mix for PC girders, which is a mixture of appropriate amounts of cement, sand, and coarse aggregate, 10 to 30% of the cement content is added.
The silica hume and the same 3-10% dispersant were added and kneaded in a mixer for 3-5 minutes, and poured into a mold in which an appropriate number of PC@ materials were placed. After molding and demolding, steam curing is performed, and 200 kg/
A method for manufacturing a high-strength concrete girder, characterized by introducing prestress of cr or higher.