JPH03243681A - Delayed static crushing agent and method for treating head of concrete pile hammered at position with the same - Google Patents

Abstract

PURPOSE:To provide the subject crushing agent attached to a reinforcing steel cage before the application of concrete to facilitate an excessive concrete- removing work by mixing calcined lime, etc., with at least one of a saccharide, an alkali silicofluoride and a specific hydraulic setting material. CONSTITUTION:Calcined lime and/or calcined dolomite are mixed with a combi nation of at least one kind selected from (A) 0.05-5 wt.% (preferably 0.1-2 wt.%)of a saccharide, a polyhydric alcohol and an organic acid (salt), (B) 0.05-10 wt.% (preferably).1-5 wt.%) of an alkali silicofluoride and (C) 1-50 wt.% (prefer ably 5-30 wt.%) of a hydraulic setting material comprising (i) a hydraulic setting material containing 11CaO.7Al2O3.CaF2, (ii) hydraulic setting material containing 12CaO.7Al2O3 and (iii) a hydraulic setting material containing 3CaO.3 Al2O3.CaSO4 to provide the objective crushing agent.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a slow-acting static crushing agent that utilizes the water expansion of calcium oxide, and to the construction of cast-in-place concrete piles using this slow-acting static crushing agent. This article relates to a bed head treatment method that involves systematically crushing the head portion.

(Prior Art) In recent years, a method using a so-called static crushing agent has been widely used as a pile cap treatment method for cast-in-place piles.

In this construction method, after the concrete has hardened, the expansion pressure of a static crushing agent is developed to cause cracks in the excess concrete and to systematically crush the pile cap. Specifically, a sheathed pipe filled with a static crushing agent mixed at a predetermined water ratio is installed on the planned fracture line of the reinforcing bar corner, and after this reinforcing bar cage is sunk into the pile hole, concrete is placed and static crushing is carried out. The material is crushed by the expansion pressure of the target crushing agent.

(Problems to be Solved by the Invention) By the way, the above-mentioned conventional static crushing agents have significantly higher water reactivity than slow-acting crushing agents, and it is necessary to apply the static crushing agent before sinking the reinforcing bar cage into the pile hole. If the slurry is prepared, expansion pressure will develop before the concrete has sufficiently hardened, resulting in problems such as insufficient cracking of the concrete and the inability to control the direction of the cracks.

Therefore, the technical problem of the present invention is to provide a delayed effect to the reaction of a static crushing agent to delay the development of expansion pressure, and to maintain appropriate fluidity and hardening properties of the slurry, thereby enabling planned crushing of excess concrete. It aims to make it possible.

The present inventors have found that when using alkali fluorosilicides, there is a particularly slow-acting effect. The present invention was developed based on the discovery that a slow-acting static crushing agent blended with quicklime in combination with the following is optimal for planned pile cap treatment of cast-in-place concrete piles.

(Means for Solving the Problems) In order to solve the above technical problems, the present invention first provides hard calcined quicklime and/or calcined dolomite with a first group of sugars,
Polyhydric alcohol, organic acid, organic acid salt, Group 2: Alkali fluorosilicide, Group 3: 11CaO"7Al2O3"
Hydraulic material containing CaF2, 12Ca0・7Al2O3
Hydraulic material containing 3CaO・3AI203・CaSO
Using a static crushing agent mixed with a combination of at least one selected from each of the three groups consisting of hydraulic materials including No. 4, Second, before sinking the reinforcing steel cage into the pile hole, A container such as a spiral sheath pipe is attached to the pile head treatment part of the reinforcing bar cage, a slurry-like static crushing agent is poured into this container, and after waiting for it to harden, the reinforcing bar cage is sunk, concrete is poured and cured, and the concrete is poured. The method used is a pile cap treatment method for cast-in-place concrete piles, in which the expansion pressure of a static crushing agent is developed to cause cracks in the pile cap after hardening, and the pile cap excess concrete is crushed.

Addition of the first group of sugars, polyhydric alcohols, *organic acids, and organic acid salts is effective in improving fluidity. Addition amount is 0.0 for internal cutting.
It is 5 to 5% by weight, preferably 0.1 to 2% by weight. 5
If the weight percentage is exceeded, the effect reaches a plateau and the fluidity is not improved any further, and depending on the additive, the delayed effect of the water utilization reaction may be significantly reduced. If the amount is less than 0.05% by weight, the fluidity will not be improved. Examples of polyhydric alcohols include sorbitol, mannitol, and xylitol; examples of organic acids include citric acid and gluconic acid; and examples of organic acid salts include sodium borate, potassium borate, and calcium borate.

Addition of the second group of alkali fluorosilicides is effective in delaying the hydration reaction when combined with the first group, and is effective in imparting curability when combined with the third group. The amount added is 0.05 to 10% by weight, preferably 0.1 to 5% by weight for internal cutting.
It is. If it exceeds 10% by weight, the slow-acting properties will decrease. Moreover, if it is less than 0.05% by weight, the effects in terms of both slow-acting properties and imparting curability will be insufficient. Examples of alkali silicofluorides include sodium silicofluoride and potassium silicofluoride.

Addition of the third group of hydraulic materials containing 11CaO'7ALaO:+''CaF2, hydraulic materials containing 12Ca0.7Al□03, and hydraulic materials containing 3CaO.3A1.03.CaSO4 imparts hardening properties and improves water utilization. It is effective in retarding the process.The amount added is 1 to 50% by weight for internal cutting.
Preferably it is 5 to 30% by weight. If it exceeds 50% by weight, crushing performance will be reduced. Further, if it is less than 1% by weight, curability cannot be sufficiently imparted. Examples of these hydraulic materials include calcium fluoroalkunate and calcium fluoroalkunate.

The static crushing agent constructed in this way has a large retardation effect, and even when water is added to form a slurry, a rapid reaction does not occur and the hydration reaction proceeds gradually, so there is a delay in the time until expansion pressure is developed. This means that the period can be extended. Note that the fluidity of the slurry is ensured, and the quicklime is also sufficiently hardened.

Next, a pile cap treatment method for cast-in-place concrete piles according to the present invention will be explained based on FIG. 1. First, a container is attached to the head treated portion of the reinforcing bar cage (processing step 100). For example, a flat or round spiral sheath tube (about 40 mm in diameter and 50 cm in length) is used for this container. A plurality of these are arranged and connected to the main reinforcement with binding wires.

Next, the static crushing agent in the spiral sheath tube is prepared into a slurry (processing step 101). There are various methods for making this adjustment.For example, the spiral sheath pipe is filled with powdered static crushing agent in advance and water is poured into it to make a slurry, or the spiral sheath pipe is first filled with reinforcing steel. A method is to attach the static crushing agent to the cage and fill the inside of the pipe with a static crushing agent prepared in the form of a slurry.Furthermore, to fill the spiral sheath pipe with a static crushing agent in the form of a slurry before installing it in the reinforcing steel cage,
Here's how to attach this to a rebar cage.

Next, the reinforcing cage with the spiral sheathed pipe attached thereto is placed in a previously excavated pile hole, and concrete is poured (processing step 102). Concrete is placed above the location where the spiral sheath pipe is placed, and the concrete is cured and hardened in this state (processing step 103).

Since static crushing agents have slow-acting properties, they gradually cause a hydration reaction when water is added, and after the concrete has finished curing, that is, after it has sufficiently hardened, it develops expansion pressure, rupturing the spiral sheath pipe and breaking the concrete pile. Cracks are generated in the excess head portion (processing step 104).

Thereafter, the worker can easily and systematically process the pile cap by removing the cracked pile cap excess concrete block by block (processing step 105).

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 The slow-acting effect of a static crushing agent was tested when various chemicals were added to quicklime.

In this test, hard-burned quicklime was used as the quicklime. Its chemical composition is shown in Table 1, and its particle size structure is shown in Table 2.

Table 1 Chemical composition of hard-burned quicklime (wt , potassium fluorosilicide, sodium hydroxide, potassium carbonate, and a third
"Material A", "Material B" and "Material C" were used as groups, respectively. Here, “material A” is 11CaO・7Al
A hydraulic material containing 2O3・CaF2 (abbreviated as C1□A7・CaF2), “Material B” is 12CaO”7A1゜03 (
Hydraulic material containing (abbreviated as Ct2Ay), "Material C" is 3
CaO”3A1z03”Ca504 (abbreviation C3A3Ca
The compound composition and fineness of each material are shown in Table 3, Table 49, and Table 5, respectively.

Next, the results of the delayed effect of various crushing agents to which the above-mentioned chemicals were added are shown in Table 6 together with comparative examples.

Table 6 Test results of various crushing agents (notes) Nos. 11 to 4 are examples, Nos. 5 to 8 are comparative examples Experimental conditions: Water/crushing agent ratio is 30%, after kneading at a temperature of 20°C,
Curing test method in a constant-temperature water tank at 35°C: Improved Crushing Agent Committee method using thick-walled steel pipes with a bottom plate Judging from the test results above, concrete hardens sufficiently within a 7-day curing period. Therefore, the development pattern of the expansion pressure of the static crushing agent is 50 kg on the first day of the water use reaction.
It is preferable to suppress it to about f/cm2 or less and increase it as much as possible on the 7th day. Static crushing agent of this example (No. 1 to 4)
) were below 50 Kgf/cm2 on the first day, and had increased to over 500 Kgf/cm2 on the seventh day, so they were on target from the perspective of the inflation pressure pattern.

On the other hand, in the comparative examples (Nos. 5 to 8), although the expansion pressure was sufficiently developed on the 7th day, the expansion pressure on the 1st day was too large, so the concrete did not fully harden. It will manifest itself.

In addition to not being able to sufficiently generate cracks, there is also no suppressing effect in controlling the direction of cracks, and cracks occur quickly.

Example 2 A test was conducted on the directionality of cracks in concrete using the samples No. 1 to 8 above.

This test method is as shown in Figures 2 and 3.
Set the planned fracture line 2 in the horizontal direction in the middle of the formwork 1 of 60 x H120 x H60 (cm), and
Above are flat spiral sheath tubes 3a and 3b with a diameter of 40 m/m.
Set two pieces, pour concrete into formwork 1, and
After curing in a constant temperature bath at 5°C, the degree of cracking caused by static crushing agent and the direction of cracking were examined.

The test results are shown in Table 6 above.

According to this, in the cases of Examples (Nos. 1 to 4), large cracks were generated on the planned fracture line 2, indicating good planned fracture properties. However, in the case of Comparative Examples (Nos. 5 to 8), the cracks were not large enough, and the cracks also deviated significantly from the planned fracture line 2, making it impossible to control the direction of the cracks. , the planned crushing was poor.

Example 3 Using the sample No. 1 in Table 6 above, an on-site experiment was conducted on pile cap treatment of cast-in-place concrete.

As shown in FIGS. 4 and 5, the diameter d of the pile hole 10
= 1400mm (The diameter of the hoop muscle is approximately 700mm,
The cover thickness is approximately 150 mm, the diameter of the main reinforcement is 25 mm, the diameter of the hoop reinforcement is 10 mm), and the height of the excess portion h = 1000
mm. φ 10cm above the planned break line 2 of the pile cap
A flat spiral sheath tube 5 with a diameter of 50'' was installed at 400 mm and 700 mm above the planned break line 2, round spiral sheath tubes 6a and 6b with a diameter of 401 mm were installed along the inside of the main reinforcement 7. Each spiral sheath tube 5,6a.

6b is not attached directly to the main reinforcement 7, but a main reinforcement edge cutting material 8 made of foamed polyethylene is attached in advance to the main reinforcement 7 of the pile head so that no racks are formed, and the binding wire 9 is attached from above. Connect with.

On the other hand, ordinary concrete with a nominal strength of 300 kgf/cm", a slump of 12 cm, and a maximum aggregate diameter of 20 mm was poured and cured.

Based on the above test results, first the flat spiral sheath tube 5
A crack was formed on the planned break line 2, and the width of the crack expanded over time, and then a crack caused by the round spiral sheath tube 6 appeared above it.

The crack caused by the flat spiral sheath pipe 5 occurs in the state of root cutting in the horizontal direction, and is ±5% from the planned fracture position.
The width was within cm. From this, it was found that in the flat spiral sheath tube 5, planned fracture with directionality of cracks is possible. On the other hand, cracks caused by the round spiral sheath tube 6 occur in the excess portion above the cracks caused by the flat spiral sheath tube 5. Since the cracks caused by the flat spiral sheath tube 5 first occur in the horizontal direction, the cracks caused by the round spiral sheath tube 6 that occur after that occur in the flat spiral sheath tube 5.
It does not reach the pile body below the crack.

〔effect〕

As explained above, according to the slow-acting static crushing agent of the present invention, sugar or *
By adding hydraulic materials containing organic acids, alkali silicofluorides, and calcium aluminate minerals,
It is now possible to delay the onset of expansion pressure of the crushing agent.

Further, according to the pile cap treatment method for cast-in-place concrete piles using the above-mentioned static crushing material, the static crushing agent can be attached before concrete is placed, making the work easier.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the work process of the pile cap processing method according to the present invention, Fig. 2 is a side view of a concrete formwork in which a spiral sheath pipe is installed, Fig. 3 is a plan view of the concrete formwork, and Fig. 4 The figure is a side view of the pile head of the reinforcing bar cage, and FIG. 5 is a plan view of the pile head of the reinforcing bar corner. 2...Planned break lines 3a, 3b...Spiral sheath pipe 5...Flat spiral sheath pipe 6a, 6b Round spiral sheath pipe 7...Main reinforcement 10...Pile hole Figure 1 Figure 2

Claims (2)

[Claims] (1) Hydraulic material containing quicklime and/or calcined dolomite: 1st group: sugars, polyhydric alcohols, organic acids, organic acid salts 2nd group: alkali silicofluorides 3rd group: 11CaO・7Al_2O_3・CaF_2 12CaO - Hydraulic material containing 7Al_2O_3 A static crushing agent characterized by combining and mixing at least one kind selected from each of the three groups of hydraulic materials containing 3CaO, 3Al_2O_3, and CaSO_4. (2) Before sinking the reinforcing bar cage into the pile hole, attach a container to the pile cap treatment area of the reinforcing bar cage, fill the container with a slurry-like static crushing agent, and after confirming hardening, sink the reinforcing bar cage. death,
Pile cap treatment for cast-in-place concrete piles involves pouring and curing the concrete, causing expansion of the static crushing agent during the weakening phase of the concrete to generate cracks in the pile cap, and crushing the pile cap excess concrete. Construction method.