JPS6130088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel fiber concrete construction method, and is used, for example, in a ground improvement method.

Steel fiber concrete is a mixture of concrete and steel fibers in order to suppress dry cracking, increase tensile and bending strength, and improve durability, impact resistance, and abrasion resistance.
Current applications include paving concrete, tunnel lining concrete, and factory products. However, it is said that the effect on compressive strength is small.

When constructing steel fiber concrete, the problem is that the slump decreases, so in order to maintain the specified workability, the fine aggregate ratio,
There are problems with workability, such as the need to increase the amount of cement per unit, and the need for a special dispersion machine because the steel fibers become entangled to form fiber balls during mixing.

The steel fiber concrete construction method of this invention was developed based on the above-mentioned circumstances, and involves dry kneading steel fibers with a cement hardening material and fine aggregate, that is, in a dry state without using water. The cement-based hardening material is filled or laid in the ground, and underground water permeates through it, thereby hardening the cement-based hardening material to form steel fiber concrete. Here, the cementitious hardening material includes, for example, ordinary Portland cement, early-strength Portland cement, blast furnace cement, and other cements. (Hereinafter, simply referred to as cement.) Therefore, in this invention, by dry kneading steel fibers with cement and fine aggregate, fiber balls are not formed, so kneading is easy, and it is possible to mix steel fibers with cement and fine aggregate. can be delivered to the site.

In general, soil improvement materials do not need to have a strength of 150 to 300 Kgf/cm ² like regular concrete, but only need about 1.0 Kgf/cm ² , and can be injected directly into the ground or by creating voids. If the cement is hardened by taking in ground water by filling, it will be possible to obtain the necessary strength as shown in Figure 1.

However, since the strength of the steel fiber is low, the adhesion strength is reduced, so it is better to make the length of the steel fiber longer.

Currently, steel fiber is only considered for use in concrete, so the length of the fiber is
The thickness is about 20 to 30 mm, because the strength of concrete can be expected to be about 200 kgf/cm ² or more. According to experimental research, cases of 100 kgf/cm ² or less have been confirmed frequently, so it was confirmed that the conventional fiber length needs to be about 30 mm or more, and 50 mm or less is appropriate from the construction point of view. .

Figure 1 is a graph showing the relationship between material age and unconfined compressive strength, and the specimen was made by placing filter paper 2 in a cylindrical mold 1 with a height of 100 mm and an inner diameter of 50 mm as shown in Figure 2. did. The blend is blast furnace B cement:
0.5, hemihydrate gypsum: 0.5, river sand: 5, A in the figure is rd
(Specific gravity of fine aggregate in dry state) = 1.4, B is rd
= 1.5, C is for rd = 1.6, and D is for rd = 1.7.

Next, an example of ground improvement will be explained.

When an embankment is constructed, an arcuate collapse as shown in Figure 3 will occur due to the rising water level within the embankment and site restrictions due to the attempt to raise the legal slope (3 in the figure indicates the collapse surface). To prevent this, it is possible to install permeable materials and reinforcing materials within the embankment. Conventional methods include using a drain sheet and a wire mesh, and using a wire mesh inside a layer of hardened powder material, but in these cases, the process of providing the water-permeable material and reinforcing material is time-consuming.

On the other hand, when steel fiber is mixed with cement and dry fine aggregate, the work is simple, as all you have to do is repeat the steps of rolling out the embankment material, rolling it, rolling out the dry mix material, and rolling it. , the air-filled material plays the role of both a reinforcing material and a permeable material. That is, as a water permeable material, a water permeability coefficient of 10 ^-2 to ^{10 -3} cm/sec has been obtained, and as a reinforcing material, it is generally known that steel fiber improves tensile resistance.

FIG. 4 shows an embodiment in which the present invention is applied to the ground improvement of embankment, in which the dry mix material 4 and the embankment material 5 are laid in layers as described above. After being laid, the cement hardens due to the underground water that seeps into it, allowing it to exhibit the aforementioned effects as steel fiber concrete.

Note that during embankment, this empty kneaded material 4 has not yet hardened, so even if the upper embankment material 5 is compacted by heavy machinery, the reinforcing material will not be destroyed. There is also no need to worry about rust, as the steel fiber is covered with cement.

As described above, according to the method of the present invention, steel fibers are mixed with cement-based hardening material and fine aggregate and then filled or laid in the ground, so construction is easy and fiber balls occur. Work efficiency can be greatly improved, such as by preventing In addition, regarding the adhesion between concrete and steel fiber, the length of the steel fiber is 30%.
Good results can be obtained by setting it to ~50 mm.
Furthermore, air-mixed materials such as cement-based hardening materials and fine aggregates serve as both reinforcement materials and permeable materials (water permeability coefficient of approximately 10 ^-2 to ^{10 -3} cm/sec), thereby consolidating the surrounding ground. can be promoted.

[Brief explanation of the drawing]

Figure 1 is a graph showing the results of the uniaxial compression test, Figure 2 is a perspective view showing how the supply body for the test was prepared, Figure 3 is a cross-sectional view showing how the embankment collapses, and Figure 4 is the graph showing the results of the uniaxial compression test. It is a sectional view when the invention is applied to ground improvement in an embankment. 1...mold, 2...filter paper, 3...disintegration surface,
4... Dried material, 5... Embankment material.

Claims (1)

[Claims] 1 Steel fibers having a length of 30 mm to 50 mm are dry mixed with cement hardening material and fine aggregate without using water, and then filled or laid in the ground. A method for constructing steel fiber concrete, characterized in that the cement-based hardening material is hardened by infiltration of gray water to form steel fiber concrete. 2. The steel fiber concrete construction method according to claim 1, wherein the steel fiber concrete is laid in the ground in layers.