JP2844211B2 - Kneading method of ultra-high-strength concrete hardened body and ultra-high-strength concrete compound - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for kneading an ultra-high-strength concrete hardened product in a precast concrete product such as a PC pile, a PC pole, a PC girder and a concrete compound thereof. .

"Conventional technology and problems to be solved by the invention" Conventionally, high-strength concrete using expensive high-strength cement or special aggregate has a compressive strength of 800 kg / cm ² -100
Various types of about 0 kg / cm ² have been developed, but recently
There is an increasing demand for practical use of ultra-high-strength concrete exceeding 000 kg / cm ² .

Therefore, in recent years, by combining silica fume and a high performance water reducing agent as industrial by-products, 1000 kg / cm ²
Although it has been reported that an ultra-high-strength concrete exceeding 100% can be obtained, it is not yet at a practically usable stage.

"Means for solving the problem" As a result of repeated research and experiments in order to solve the above-mentioned conventional problems, the present invention is practical in terms of economy and workability, and furthermore, to obtain ultra-high strength. Concrete is not always uniquely determined by the large amount of its composition,
By kneading ordinary Portland cement, high-purity silica fume, high-performance water reducing agent, fine aggregate, water, etc. at a predetermined mixing ratio with a predetermined kneading method, it is super-dense, high-viscosity, easy to handle, and 1200 kg / The present inventors have found that ultra-high-strength concrete exceeding cm ² can be economically obtained, and have completed the present invention.

That is, the first invention is usually Portland cement 400-6
To 00Kg / m ^3, 15~50% of high-purity silica fume (cement outside split), 2% to 8% high performance water reducing agent (cement ratio), blended with 30 to 55 percent fine aggregate, cement, water After molding with a compound kneaded at a ratio of 2.2 to 6.0, the mixture is subjected to autoclave curing so as to reliably obtain an ultra-high-strength concrete cured product having the above characteristics.

In addition, the second invention is an ordinary Portland cement 400
The ~600Kg / m ^3, 15~50% of high-purity silica fume (cement outside split) were kneaded by adding fine aggregate (30-55%) and coarse aggregate primary water blended, high performance The water-reducing agent is mixed with 2 to 8 (cement ratio) and the secondary water is added to make the cement / water ratio 2.
This is a method of kneading a concrete compound by kneading a mixture of 2 to 6.0 so as to reliably obtain an ultra-high-strength concrete having the above characteristics.

High-purity silica fume of the present invention, SiO ₂ is 90% or more, preferably using silica fume of 94% or more.

As the fine aggregate and the coarse aggregate, commonly available ordinary aggregates can be used.

"Examples" Hereinafter, the present invention will be described in more detail based on specific examples (experimental examples), but the present invention is not limited to these examples.

Experiment I In this experiment, the relationship between the mixing ratio of silica fume and the compressive strength of concrete with respect to the unit cement amount was examined by a two-way arrangement method based on the factors and levels listed in Table 1.
In the experiment, silica fume SF was a powder having a SiO ₂ concentration of 94%, cement C was ordinary Portland cement, and the water cement ratio and the binder water ratio were as shown in Table 2.

In addition, as common conditions of Experiment I other than the above, the experiment was performed as shown in Table 3.

Here, G is coarse aggregate, S is fine aggregate, W is water, and AD is a high-performance water reducing agent (trade name: Mighty 150).

Autoclave curing holding time is 10 atmospheres (normal pressure)
Means the steam curing time held at a temperature of 180 ° C,
The kneading method of the compounding materials is the method A shown in Table 4, that is, the cement C, the silica fume CF, the fine aggregate S and the coarse aggregate G are mixed, the primary water W is added, and the mixture is kneaded for 1 minute. Agent
A method of adding AD and secondary water W and kneading for 3 minutes was used.

Then, using the concrete kneaded as described above, two types of cylindrical and cylindrical specimens P ₁ and P ₂ each as a concrete hardened body were changed to three pieces each while changing the mixing ratio of silica fume and the unit cement amount. Each was manufactured and the compressive strength of each was examined.

Cylindrical specimen P ₁ is 10cm diameter by vibration compaction molding, the height
Formed in 20cm cylindrical, cylindrical specimens P ₂ is formed by centrifugal force forming by high-speed rotation (35G) outside diameter 20cm, the height 30cm cylindrical.

 The results (estimated values) of the experiment I are shown in FIG. 1 and FIG.

From these results, it can be seen that when the mixing ratio of silica fume exceeds 10%, the compressive strength rapidly increases, and when it becomes about 15% or more, an ultra-high strength of 1000 kg / cm ² or more can be obtained.

Also, it can be seen that when the unit cement amount exceeds about 400 kg / cm ³ , an ultra-high strength with a compressive strength of 1000 kg / cm ² or more can be obtained.

Comparing the cylindrical specimen P ₁ and a cylindrical specimen P _2, but the former is a tendency that compressive strength than the latter is grossly up seen, which upon centrifugal molding of high-speed rotation in the latter It is considered that silica fume is separated and hardly leads to an increase in strength.

This also results of observation of the finished state of the inner surface of the cylindrical specimen P _2, from becoming worse as mixing rate of silica fume is higher, float on the inner surface fine components such as silica fume is separated It is thought that it comes out.

Furthermore, although investigate the relationship of the cylindrical specimen P ₂ of Young's modulus and strength and strain, despite compression strength 1000 Kg / cm ² or more ultra-high strength, concrete much different 800 Kg / cm ² in Young's Modulus No, and the relationship between strength and strain (by destructive test)
Can be seen to extend linearly until destruction, leading to destruction,
It turned out to be low elasticity in spite of the ultra high strength.

Experiment II Compressive strength 1500Kg
It was found that an ultra-high strength of at least / cm ² was obtained, but in this experiment, the L16 orthogonal table (6
Factor, 2.4 level), in addition to the silica fume mixing rate and unit cement amount, further change the mixing rate of high-performance water reducing agent, silica fume kneading conditions, centrifugal molding conditions, and autoclave holding time to achieve ultra-high strength An experiment was conducted to select the factors for obtaining the results.

In this experiment II, other conditions were performed as shown in Table 3.

As the kneading method, in addition to the above-mentioned A method, S method shown in Table 4, that is, after mixing cement C, fine aggregate S and coarse aggregate G, adding primary water W and kneading for 3 minutes, silica fume CF, A method of adding a silica fume slurry kneaded with the high-performance water reducing agent AD and the secondary water W and kneading for 3 minutes was used. According to the experimental conditions, the same cylindrical specimen P ₁ and cylindrical specimen P ₂ as in Experiment I were used. Were created.

 The results (estimated values) of Experiment II are shown in FIGS.

From this result, it can be seen that when the mixing ratio of silica fume exceeds 30%, the compressive strength gradually decreases, and when it exceeds about 50%, the compressive strength further decreases.
% Is considered optimal.

Also, as with Experiment I, it can be seen that the compressive strength increases in the range of 350 to 400 kg / cm ³ as the amount of cement increases, as in Experiment I.

For high performance water reducing agents, increase the amount of
It can be seen that the compressive strength increases in the range of 5%, but it is approximately 2 to 8% in relation to the mixing ratio with silica fume.
It can be predicted from other experimental results that high-strength concrete can be obtained.

The relationship between the cement water ratio and the compressive strength is correlated as shown in FIGS. 5 to 7, and it can be seen that the strength tends to increase as the cement water ratio increases (as the water cement ratio decreases). At this level, there was almost no significant difference between the AC curing time and the centrifugal rotation condition.

As for the kneading method, it was found that the compressive strength was higher when silica fume was used as the powder.

This is presumably because when used in the form of a slurry, the silica fume particles sufficiently retain water and require a large amount of unit water, resulting in a decrease in the cement water ratio.

In addition, through experiments, it was found that silica fume concrete had a high viscosity and did not separate even in water, and that when centrifugal molding could be performed, the slurry did not come out.

Experiment III In this experiment, based on the factors and levels listed in Table 6, the unit cement amount, fine aggregate ratio (S / a%) and kneading method were further changed using the L9 orthogonal table (3 factors, 3 levels). An experiment was conducted to select factors for obtaining high strength.

Other common conditions of Experiment III were as shown in Table 3.

The results (estimated values) of Experiment III are shown in FIG. 2 and FIG.

From this result, it was found that when the unit cement amount was in the range of 500 kg / m ³ or more, the increase did not necessarily contribute to the increase in compressive strength.

Also, in the kneading method, the method B shows a slight decrease in strength, and when silica fume is used in the slurry after all, even if the charging order of the slurry is changed from that in the method S, the water retention in the particles is similarly caused and the cement water ratio is reduced. Is considered to be a factor.

The fine aggregate ratio did not show any significant difference at this level.

Experiment V In this experiment, based on the factors and levels listed in Table 7, the two-way layout method was used to select the mixing ratio of the high-performance water-reducing agent and other factors for obtaining ultra-high strength by changing the slump value. Was done.

As common conditions of Experiment V other than the above, the experiment was performed as shown in Table 8.

FIG. 3 shows the results (estimated values) of Experiment V.

From these results, the high performance water reducing agent showed almost the same tendency as in Experiment II when the mixing ratio was in the range of 3 to 5%, but when the silica fume mixing ratio was 30%, the addition ratio was 5%.
In the above, it was found that the compressive strength almost reached a plateau.

The slump value did not show any significant difference at this level.

Experiment VI In this experiment, based on the factors and levels listed in Table 9, the one-way layout method was used to change the fine aggregate ratio (S / a%) and select other factors for obtaining even higher strength. went.

Other common conditions of Experiment V were as shown in Table 10.

Results of experiments V, the cylindrical specimens P ₂ due to centrifugal force molding has been found that finished clean inner surface higher fine aggregate ratio, see little effect as shown in FIG. 8 in compressive strength It is not, who cylindrical specimen P ₁ by vibration compaction than cylindrical specimens P ₂ it was found that variations in the strength is small.

[Effects of the Invention] As described above, according to the present invention, a practically usable ultra-high-strength concrete hardened body and a kneading method thereof can be reliably obtained.

[Brief description of the drawings]

1 to 8 are diagrams showing the experimental results of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-43726 (JP, A) JP-A-58-219013 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 28 / 04,22 / 06

Claims (2)

(57) [Claims] [Claim 1] Normal Portland cement 400-600Kg / m ³
In addition, 15-50% of high purity silica fume (cement ratio), 2-8% of high performance water reducing agent (ratio of cement) and 30-55% of fine aggregate are mixed, and cement / water ratio of 2.2-6.0 %, Which is molded using a kneaded mixture and then cured in an autoclave to have a compressive strength of 1200 kgf / cm ² or more. 2. An ordinary Portland cement of 400 to 600 kg / m ^3.
Then, high-purity silica fume is mixed with 15-50% (cement ratio), fine aggregate (30-55%) and coarse aggregate, and the primary water is added and kneaded. 8% (cement ratio) and secondary water is added to make cement / water ratio 2.2 ~
By kneading as 6.0%, the compressive strength is 1200 kgf / cm ²
A method of kneading an ultra-high-strength concrete compound, characterized in that the above-mentioned ultra-high-strength concrete hardened body is obtained.