JPH0811909B2 - Static crushing method - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a static crushing method for concrete. INDUSTRIAL APPLICABILITY When the static crushing method of the present invention is applied to the pile head treatment of cast-in-place foundation piles, it is possible to solidify concrete and cut the pile heads.

[Prior art]

As is well known, in-situ foundation piles for construction work are prepared by placing a basket of reinforcing steel in a hole provided in the soil and filling with concrete from the bottom of the hole to solidify it. Since the strength of the part is not sufficient due to the mixture of the collapsed soil in the hole, it is extremely necessary to remove the pile head. For the pile head treatment, there is a method in which a hole is punched after placing and a so-called static crushing material such as a quick lime slurry is filled and crushed, but it is difficult to cut it from a desired place cleanly. In addition, this work requires a great deal of labor for drilling and filling.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a static crushing method capable of solidifying a concrete cast body represented by a cast-in-place foundation pile and simultaneously cutting the cast body from a desired place.

[Means for Solving the Problems]

The static crushing method of the present invention comprises particles of a hydration expandable substance enclosed in a water-permeable tube, which absorbs water from the surroundings to expand the static crushable material in an unsolidified state. It is embedded in the concrete pouring body in and the water in the fresh concrete permeates through the water-permeable tube and enters the inside, and the hydrated expansive substance in the statically crushed material hydrates and expands due to the entered water. It consists in crushing the concrete that is solidifying. The hydrated expansive substance is selected from commonly used substances such as quick lime, calcined dolomite or ettringite. The quick lime may be produced by lightly burning limestone to about 900 to 1200 ° C, produced by hard baking to about 1200 to 1800 ° C, or produced by electrofusion.
In addition, dolomite that is lightly baked at 700 to 1200 ° C., and those that are manufactured by baking at a higher temperature than that can be selectively used. As the water permeable tube, for example, a plastic tube such as polyvinyl chloride (PVC) in which holes are formed by a roll having many needles may be used. It is advisable to add sand or sand and gravel to the hydrated expansive substance, and then enclose it in the above water-permeable tube. When storing this crushed material, moisture in the air, CO ₂
Means necessary for preventing weathering due to, for example, vacuum packaging may be used. Hydration may be promoted by mixing an appropriate amount of bentonite or a polymer absorbent in the crushed material. If necessary, a hydration inhibitor or retarder, a fluidizing agent, etc. are added.

[Work]

The static crushing of the present invention will be described with reference to the drawings by taking an example of placing a concrete pile in the ground. As shown in FIGS. 1 and 2, the reinforcing bar 2 is placed in the hole provided in the soil.
When dropping the basket and filling the fresh concrete, the tube of the static crushing material 1 is wound around the reinforcing bar at the position where the pile head is to be cut. When the surroundings of the static crushed material 1 are filled with ready-mixed concrete 3, there is sufficient water in the surroundings, so the water enters through the needle holes of the tube, and as a result of hydration expansion, the static crushed material gradually Increase its volume. At this time, if there is sand or a mixture of sand and gravel, they facilitate the penetration of water into the interior. The static crushing material 1 continues to expand even after the surrounding green concrete 3 is solidified, and the static crushing material 1 exerts an expansion pressure in the vertical and radial directions thereof. As a result, the solidified concrete is vertically cut at the position where the static crushing material 1 was wound. The concrete head 4 shown in FIG. 3 remains when the cut head is pulled out upwards or broken into pieces. There are various modes of using the static crushing material other than the above. First, as shown in FIG. 1 and FIG. 2, it is obvious that static crushing material may be wound around the outside of the reinforcing bar and fixed, or fixed inside the reinforcing bar, if necessary. It goes without saying that it may be used both inside and outside. In the case of a relatively large pile, naturally the rebar is also large, and the tube of static crushing material to be fixed to it is also large and long, so the fixing work is troublesome, and it is necessary to fix it to the rebar made by welding in the horizontal position. When the artificial crushing material is fixed and hoisted by a crane and put into a hole in the soil, the position may shift. Therefore, as shown in FIG. 4 and FIG.
It is recommended to prepare a basket 5 for accommodating the statically crushed material in advance and attach it to the reinforcing bar. The basket may be made of iron wire or aluminum wire of appropriate thickness,
A plastic molded product may be used. This basket is also attached only to the inside of the reinforcing bar in the illustrated example, but it is needless to say that it should be used on both inside and outside of the reinforcing bar as required. In another important aspect, the concrete is once poured and then the static shredder is pushed into place therein. The action of this static crushing material by utilizing the water in the surrounding fresh concrete is no different from the above. Normal ready-mixed concrete does not harden for 20 to 30 minutes after it is filled into the holes to drive the piles, so if you work immediately after placing it, you can position the static crushing material at the desired part. it can. In the above-mentioned embodiment, the band of the static crushing material is wound on the outer side and / or the inner side of the reinforcing bar so that the tremie pipe whose central part is used for filling the ready-mixed concrete comes in and goes out, so that it does not interfere with it. It was to do. If the static crushed material is pushed in after the pouring of fresh concrete as described above, there is no need to consider the entry and exit of the tremie pipe. Therefore, for example, as shown in FIG. 6 and FIG.
It is possible to make a dedicated basket 5 that spreads over the entire inside of the reinforcing bar, put static crushing material in it, and push it into fresh concrete. On the other hand, the pile head portion to be removed is easier to handle if it is divided as small as possible. Therefore, it is better to disperse the static crushed material not only on the surface to be cut but also in the ready-mixed concrete located above it. That is,
As shown in the figure, the basket is provided with a plurality of shelves, and static crushing materials are put into each of the shelves and pushed into the fresh concrete of the pile head portion.

Example 1 A PVC tube having an outer diameter of 24 mm and a length of about 3 m was perforated with a roll having a large number of needles, and then a mixture of quicklime particles and sand and gravel was mixed with a ratio of 1: 1 or 2: 1. A static fracturing material was made by filling in a ratio and sealing both ends of the tube by heat sealing. When constructing a cast-in-place pile with a diameter of 1000 mm,
A tube of PVC was put on 1 m, and the tube of this statically crushed material was wound and fixed at the position where the pile head of the reinforcing bar was to be cut. Concrete was poured and crushed materials were buried. About 15 hours later, when the head of the pile was pulled up, it could be easily separated, and the cross section was at the planned position and was flat.

Example 2 Construction of a cast-in-place pile having a diameter of 1300 mm was performed using a reinforcing bar having a diameter of 1100 mm. Separately, prepare a cylindrical basket with a diameter of 1000 mm and a height of 750 mm, partition it into 250 mm by 3 stages, and use static crushed material made by using PVC tubes with an outer diameter of 21 mm for each.
The product was cut into a desired length and heat-sealed at both ends, and 10 pieces were arranged in a grid pattern in length and width. Two of these baskets were piled up and down and pushed into the pile head concrete immediately after placing. After the solidification of the concrete, the pile head part was divided into many pieces and could be easily removed.

【The invention's effect】

When cutting the pile head of a cast-in-place concrete foundation pile, when using the conventional static crushing technique, there was a concern that it could not always be cut completely at a desired position, but according to the present invention, This is resolved. Since the cutting is performed at the same time as the solidification of the concrete, the conventional work of removing the pile head after solidification is avoided, and the working time is short.

[Brief description of drawings]

The drawings explain the present invention by taking a pile head treatment, which is a typical application example thereof, as an example. FIG. 1 is a longitudinal section showing a static crushed material embedded in a concrete pouring body. FIG. 2 is a plan view, FIG. 2 is a transverse cross-sectional view taken along the line AA of FIG. 1, and FIG. 3 is a vertical cross-sectional view showing a state where the cut pile heads are removed. FIG. 4 is a longitudinal sectional view corresponding to FIG. 1, showing another embodiment in which a static crushing material is embedded in a concrete pouring body, and FIG. 5 is a transverse cross section in the BB direction of FIG. It is a side view. FIG. 6 is a longitudinal sectional view showing still another embodiment in which the statically crushed material is embedded in a concrete pouring body, which is also a vertical sectional view corresponding to FIG. 1, and FIG. 7 is a CC direction of FIG. FIG. 1 …… Static crushed material 2 …… Reinforcing bar 3 …… Green concrete 4 …… Concrete pile 5 …… Cage

Claims (7)

[Claims] 1. A static crushing material, which is made by encapsulating particles of a hydration expandable substance inside a water-permeable tube and is capable of absorbing water from the surroundings and expanding, is a concrete casting in an unsolidified state. It is buried in the structure and allows the water in the fresh concrete to pass through the water-permeable tube and enter the inside, and the hydrated expansive substance in the statically crushed material hydrates and expands due to the entering water. Then, a static crushing method comprising crushing the solidifying concrete. 2. When pouring concrete into a cast-in-place foundation pile, a static crushing material in which particles of a hydration expandable substance are enclosed inside a water-permeable sieve is fixed to an appropriate portion of the reinforcing bar, and the concrete The static crushing method according to claim 1, which comprises cutting the pile head portion together with solidification of concrete by expanding the hydration-expandable substance with the water content. 3. The static crushing method according to claim 2, wherein a basket for static crushing material attached to the reinforcing bar is used to fix the static crushing material at a suitable position on the reinforcing bar. 4. When concrete is cast on a cast-in-place foundation pile, a static crushing material in which particles of a hydration-expandable substance are enclosed inside a water-permeable tube is placed in an unsolidified concrete cast body after casting. The static crushing method according to claim 1, which comprises cutting the pile head portion together with solidification of concrete by pushing it into a position and expanding the hydration expandable substance with the water content of the fresh concrete. 5. A static hydrate according to claim 1, wherein a hydrated expansive substance selected from quicklime, calcined dolomite or ettringite is used and bentonite or a polymeric water absorbing agent is added. Crushing method. 6. A plastic tube having a large number of needle holes as a water permeable tube.
Static crushing method of paragraph. 7. The static crushing method according to claim 1, wherein sand or a mixture of sand and gravel is enclosed together with particles of the hydration expandable substance in a water-permeable tube for use.