JPS62258058A - Method for removing adhered concrete and removal promoter - 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 Application Field] The present invention provides a method for transferring uncured concrete adhering to the surface of a formwork panel for concrete pouring to the poured concrete and removing it from the formwork panel. This invention relates to a removal accelerator used for this purpose.

[Conventional technology]

Concrete placement in construction work, civil engineering work, etc. is generally performed using formwork panels. These formwork panels are made of plywood, metal, plastic, etc., and not only define the shape of the concrete that is poured, but also play the role of maintaining that shape until the concrete has completed its initial hardening and has developed sufficient strength. .

The time from concrete pouring to demolding usually takes one day in summer and about two days in winter, and it is known that under the same conditions, the longer this period is, the better the condition of the concrete will be. It is being However, the buildings being constructed are becoming increasingly taller, and the construction period is lengthening accordingly. Therefore, due to the request to shorten the construction period,
After pouring concrete, the time required for demolding is increased by 1! ! Efforts are being made to keep it to a minimum. Therefore, uncured concrete often remains attached to the surface of the formwork panel that comes into contact with concrete (hereinafter referred to as the panel surface). This is because the hydration hardening of the poured concrete was insufficient, and a very small amount of the surface layer adhered to the panel surface and transferred.

By the way, the use of formwork panels is not limited to just one time.
When constructing high-rise buildings, it is usually used repeatedly several times in a row (this way of using a formwork panel that has been used once for the next pouring is called ``repurposing'' the formwork panel). etc., the formwork is assembled, concrete poured, and formwork dismantled for each floor, and this process is repeated, and the same formwork panels are used repeatedly for these series of operations. Therefore, at the initial stage of use of formwork panels, the adhesion of uncured concrete was a very thin layer like dusting powder, covering a small area, but as the formwork panels are repeatedly used, they grow. , sometimes with a thickness of 1
~1.5 fins can be reached.

When concrete is poured using such contaminated formwork panels, the concrete surface is stained and the adhesion of finishing materials such as exterior tiles and spray paint materials is reduced.

Therefore, once the adhesion of concrete had progressed to a certain extent, the formwork panels were cleaned by cleaning the surface and used for the next concrete pouring. but,
This scraping work was done manually, which required a lot of effort and was inefficient.

Conventionally, therefore, an oil-based mold release agent is applied to the surface of the form panel before pouring to prevent concrete from adhering to the form panel. Alternatively, when the adhering contamination has progressed to a certain extent, a cleaning operation is performed and then an oil-based mold release agent is applied.

This oil-based mold release agent is mainly composed of light oil, single heavy oil, waste oil, or the like. When this is applied to the surface of the formwork panel in advance and concrete is poured, the oil-based mold release agent on the panel surface causes a chemical reaction with the alkali in the poured concrete and turns into metal soap, causing the formwork panel to A release layer is created between the mold and the concrete. This release layer prevents concrete from adhering to the panel surface and facilitates demolding.

[Problem that the invention seeks to solve]

The above oil-based mold release agent is used to prevent uncured concrete from adhering to the surface of the formwork panel, and does not have the effect of removing uncured concrete if it has already adhered to the surface of the formwork panel. If concrete adhered to the surface, a labor-intensive cleaning process was required to remove it, which resulted in extremely poor skewering.

In addition, if oil-based mold release agent accidentally adheres to the surface of installed reinforcing bars, the adhesion between concrete and reinforcing bars will be impaired.
building! There was a risk that the strength of the eye body would be reduced.

Furthermore, when concrete is poured using a formwork panel coated with an oil-based mold release agent, the surface of the concrete after molding is
Chemical reaction products such as metal soap remain. Furthermore, the above-mentioned chemical reaction is not always completed reliably, and unreacted oil may remain on the concrete surface. Therefore, there was a problem that these metal soaps and unreacted oils stain the concrete surface and reduce the adhesive strength of the exterior and materials. [Means for solving the problem] The present inventor has As a result of conducting research on the physical properties of concrete that adheres to formwork panels, we found that even if concrete adheres to the panel surface, if the hydration reaction of the adhering concrete itself progresses, it becomes easy to detach from the formwork panel. We have come to the conclusion that the concrete sets and hardens together with the newly poured concrete and is removed from the panel surface.

Based on this knowledge, the present invention provides a non-oil-based method for removing concrete adhering to formwork panels that does not affect the strength of the building and has excellent workability, as well as a removal accelerator.

The feature of the removal accelerator according to the present invention is that it consists of an aqueous solution containing 45 mHt% or less of calcium chloride.

In addition, to the removal accelerator, if desired, 5% by weight or less of a surfactant, or 1 offl% or less of one or more inorganic salts such as aluminum chloride, sodium sulfate, and magnesium chloride may be added. Good, even mineral oil, animal oil.

It is also possible to emulsify and appropriately blend 30% by weight or less of oil such as vegetable oil. (However, the oil content is
It is expressed as weight % before emulsification. ) To remove adhering concrete from a formwork panel using the removal accelerator, apply the above removal accelerator to the surface of the formwork panel to which uncured concrete has adhered, leave it for a predetermined period of time, and then remove the adhering concrete from the formwork panel. The frame panel is used for the next concrete pouring, and the concrete adhering to the surface of the formwork panel is transferred to the next concrete pouring.

[Effect]

Calcium chloride contained in the removal accelerator according to the present invention absorbs moisture from the air due to its deliquescent property, and maintains the surface of the concrete to which it is attached in a moist state. Therefore, the adhering concrete is prevented from drying and the hydration reaction continues until the next rotation. Calcium chloride also has the effect of promoting the hydration reaction of concrete itself. Therefore, while most of the calcium chloride is diluted and diffused by the poured concrete during placement, some remains on the panel surface and assists in hardening of the newly placed concrete surface layer. The faster the surface layer sets and hardens, the more complete the integration with the deposited concrete and the better the removal ability. The above effect increases as the concentration of calcium chloride increases, but if the concentration exceeds 45% by weight, it becomes difficult to dissolve, impairing workability, and may reduce the strength of concrete. Therefore, it is preferable to use the content within a range of 45% or less.

The surfactant added together with calcium chloride reduces the surface tension, makes it easier for the removal accelerator to penetrate into the adhered concrete, and contributes to promoting the hydration reaction.
It penetrates the interface between the adhered concrete and the formwork panel, increases the adhesive force between the two, and contributes to the removal action. However, if the concentration becomes high, the curing of concrete will be delayed, so it is used at a concentration of 5% by weight or less.

Inorganic salts such as aluminum chloride, sodium sulfate, and magnesium chloride, which are added as desired, have the effect of promoting hydration hardening of concrete, similar to calcium chloride. However, since there is a risk that calcium chloride present at the same time may be precipitated, it is preferable to use a non-alkaline inorganic salt as much as possible, and the amount added is preferably 10% by weight or less.

When emulsified oil is mixed, it penetrates into the bonding interface between the adhered concrete and the formwork panel, reducing the adhesion force.
To further ensure the removal effect. When the oil content increases, it becomes difficult to decompose calcium chloride into /8, so
The content should not exceed 30% by weight. In addition, by emulsifying the oil, it is easily dispersed into the concrete being poured, so even if it accidentally adheres to installed reinforcing bars, the problem of reducing the strength of the building mentioned above does not occur. .

After demolding the form panel, there is an unavoidable waiting time due to construction constraints before the next pouring. During this waiting period, the adhering concrete on the panel surface is exposed to the outside air and quickly dries, inhibiting the progress of the hydration reaction, and as a result, it does not integrate with the next poured concrete. When the aqueous solution containing the hydroxide is applied to the form panel, the uncured concrete on the surface is kept moist and the hydration reaction continues. The strength of concrete increases as the hydration reaction progresses, and the mechanism is that tricalcium silicate, the main component of cement, hydrates to form calcium silicate hydrate and calcium hydroxide. The focus is on reaction. ! f Hydration reaction is a reaction accompanied by volume increase.

Therefore, by leaving the removal accelerator for an appropriate period of time after applying the removal accelerator, the concrete grows as the hydration reaction progresses, and stress is generated at the boundary with the formwork panel due to the increase in volume, giving it peeling activity. This is a major driving force for eliminating adhering concrete from the surface of formwork panels.

When a formwork panel that has been coated with a removal accelerator is used for the next concrete pouring, the newly poured concrete is in a fluid state, so it gets into the gaps between the adhering concrete, and the adhering concrete is maintained in a moist state. Therefore, it has good affinity with newly poured concrete, so it is incorporated into the surface layer of newly poured concrete and is firmly integrated, and together with the peeling activity caused by the increase in volume, During demolding, it is easily removed from the panel surface and transferred to the newly poured concrete surface.

In addition, the removal accelerator applied to areas of the formwork panel to which concrete is not attached promotes hydration hardening of the surface of the concrete that will be placed next time, thereby preventing new adhesion contamination from occurring.

〔Example〕

Table 1 shows the results of an experiment in which the composition and content of the removal accelerator were varied and the degree of tax reduction of adhered concrete was investigated in order to confirm the effects of the present invention.

The experiment was conducted as follows. First, a formwork panel with uncured concrete adhered to its surface cut into 303 squares was prepared as a sample.

Next, for each sample, half of the concrete adhesion area was coated with a removal accelerator with a brush, and the other half was left untreated. After this was left for 3 days, it was used for concrete pouring. After a period of time, remove the mold and observe the extent of adhering concrete removal.

The degree of removal was determined by visually measuring the area where the adhering concrete had fallen off in the area where the removal accelerator was applied, based on the condition of the untreated area.

The surfactant used in the experiment was sodium higher alcohol ethoxy sulfate (manufactured by Teikoku Kako Co., Ltd.).

Additionally, turbine oil was used as the oil to be added. In carrying out the experiment, a stock solution was obtained by diluting turbine oil 3 with thinner 1 and emulsifying it by adding surfactant 2 in terms of volume ratio, and diluting this as appropriate with a calcium chloride solution before use.

As a comparative example, a specimen coated with tap water was used (Fragrance C).

(The following margins continue from Table 1) As shown in Table 1, the fragrance C shown as a comparative example is
Although tap water is simply applied and moistened, adhering concrete is not removed by this method at all.In contrast, the effect of the present invention on removing adhering concrete is remarkable. Perfumes I-1 to I-4 use a removal accelerator containing only calcium chloride, and it can be seen that the removal effect increases as the concentration increases.

The ability to remove adhering concrete is further improved when a surfactant coexists with calcium chloride.

As is clear from the experiments of 11-1 and 11-2, by incorporating a small amount of surfactant, adhering concrete was completely removed by the next pouring, a remarkable result.

The sample used in the above experiment was a formwork panel to which uncured concrete was artificially attached.

Incense-applied ■-1 to 3, formwork panels used in actual construction work and having concrete adhered to their surfaces were used as test specimens. In experiments with perfume 111-1 and 111-2, although the removal effect was superior compared to the conventional one, it was slightly lower than that of perfume 111-2. This is thought to be because the uncured concrete used in actual construction work has a stronger W-walled state. Therefore, an experiment was conducted using a removal accelerator containing emulsified oil as shown in Fragrance 1-3. The results are shown in Table 1
As shown, it is clear that the removal effect is further enhanced by the addition of oil.

As a reference example, the results of an experiment using a 0.6% by weight solution of a surfactant as a removal accelerator are shown (perfume ■). The removal effect was also demonstrated at this time, but when leaving the formwork panel in the open air for a long time after demolding, calcium chloride is added to the removal accelerator to prevent the adhering concrete from drying out. It is preferable to contain.

Table 2 below shows the results of implementing the present invention in actual building construction and investigating the extent to which concrete adhering to the surface of formwork panels was removed.

The example was carried out using the following procedure.

■ Among the formwork panels used for concrete pouring and demolded, 5 were relatively large with concrete adhesion.
Select one.

■ Spray a removal accelerator onto the surface of the selected formwork panel and leave it for 10 days.

■ Perform the next concrete pour using the above form panel and leave it for 48 hours until the initial hardening is completed.

■ Form the formwork panels and observe the state of concrete adhesion on the surface.

This example was carried out during the construction of a 14-story building, and after finishing pouring on the 5th, 8th, and 11th floors, the above operations were performed on the formwork panels, and this was used to perform the following steps. floors, namely the 6th and 9th floors.

The concrete was poured for each of the 12 floors. In this experiment, it was decided that the form panel that had been subjected to the skin removal treatment would not be used in subsequent experiments.

The formwork panel used was a plywood board with a width of 60 cm and a length of 180 cm whose surface was coated with polyethylene.

Generally, formwork panels in which the surface of a plate material is coated with a urethane-based, acrylic-based, or olefin-based resin film are generally used. This prevents the sugar contained in the wood of the panel from leaching out and damaging the concrete.

b. Prevent moisture in the concrete surface layer from being absorbed into the panels and delaying hydration.

C. Prevent the panels from absorbing moisture from the concrete and reducing its strength.

d. Make the panel surface smooth and hydrophobic to make it difficult for concrete to adhere to it.

The purpose is to

This example differs from the experiment shown in Table 1 above in that aluminum chloride or sodium sulfate was added as an inorganic salt to the removal accelerator. However, the surfactant and turbine oil were the same as those used in the experiment shown in Table 1 above. The amount of removal accelerator applied is approximately 50g/r
It is rl.

The numerical values shown in Table 2 are the amount of concrete adhered before treatment and the ratio of the area occupied by concrete adhered to the cast form panel after treatment, respectively, expressed as percentages. In addition, the rate of change is the ratio of the area amount changed by pouring after treatment to the concrete adhesion area before treatment, expressed as a percentage.

(See Table 2 below) As shown in Table 2, most of the adhering concrete is removed from the formwork panel surface by implementing the present invention.

In general, the adhered concrete that remains when high-rise floors are poured has not only a larger adhesion area but also a stronger adhesion because the formwork panels have been reused more times. Nevertheless, according to the present invention, a reliable removal state can be obtained. Additive A leaves some adhering concrete remaining, but if necessary, change the composition of the removal accelerator, such as increasing the content of calcium chloride or surfactant, or changing the type of inorganic salt. This allows for reliable removal.

In particular, if an emulsified oil like Fragrance C is included, the removal effect can be further ensured.

Embodiments of the present invention are not limited to the above. For example, the application of the removal accelerator to the formwork panel may be sufficiently effective not immediately after molding, but after it is left for an appropriate period of time. Can be done. That is, a sufficient removal effect can be obtained by applying a removal accelerator to a formwork panel that has been left for an appropriate period of time after demolding, and then allowing the hydration reaction to proceed for the required period of time. In addition, during particularly dry periods such as summer, apply a removal accelerator for 1 hour between molding and next pouring.
If you apply J, you will get even more effect.

Furthermore, the removal operation does not need to be performed every time the formwork is formed;
A removal accelerator may be applied at appropriate intervals after each predetermined number of pours, or a removal operation may be carried out if it is determined by visual inspection that adhering contamination has progressed again on the formwork panel from which adhering concrete has been removed. is also possible.

Surfactants that can be used in the present invention include the aforementioned Bakaadecatol So-120 and the like ii! In addition to chain-type nonionic surfactants, sodium alkylbenzenesulfonate and the like are also used.

In addition to the above-mentioned aluminum chloride and sodium sulfate, magnesium chloride, potassium carbonate, sodium carbonate, potassium sulfate, and the like can also be used as inorganic salts.

In addition to the above turbine oil, the oil content includes spindle oil,
Mineral oils such as kerosene, liquid paraffin, and petrolatum, vegetable oils such as soybean oil, olive oil, coconut oil, and castor oil, and animal oils such as cow oil and whale oil can be used.

Furthermore, although it is unnecessary to add, it is of course also possible to use the removal accelerator according to the present invention to prevent concrete from adhering by applying the removal accelerator to the surface of the formwork panel before casting. In that case, it exhibits an excellent effect in preventing adhesion of concrete.

(Effects of the Invention) As explained above, according to the present invention, even when uncured concrete is already attached to the panel surface,
This can be integrated with newly placed concrete and easily removed. Moreover, after removing this removal accelerator from the mold,
- With just one application, the hydration reaction of the adhered concrete will continue for a long time until the next pouring! The process required for removal becomes extremely simple.

In addition, no chemical products or unreacted substances remain on the panel surface as in the conventional case. Therefore, the concrete surface will not be roughened or soiled, resulting in a beautiful finished surface and reliable adhesion of spray painting materials, exterior tiles, etc.

Further, unlike conventional oil-based mold release agents, the removal accelerator of the present invention is water-based, so it does not damage the concrete surface, but rather promotes hydration hardening of the concrete surface. In addition, even if it is mistakenly attached to reinforcing bars, etc., there is no risk of poor adhesion to concrete and loss of building strength, so it is extremely easy to work with. Further, since there is no need to perform cleaning work as in the past, the manpower and effort required for this can be omitted.

Claims (1)

[Claims] 1. In a method for removing concrete adhering to the surface of a formwork panel used for concrete pouring, 45% as a main component is added to the surface of the formwork panel after demolding to which concrete has adhered. Applying an adhesion concrete removal accelerator consisting of an aqueous solution containing calcium chloride in a weight percent or less,
A method for removing adhered concrete, characterized in that after leaving it for a required period of time, the formwork panel is used for the next concrete pouring, and the adhered concrete is transferred to the next concrete to be poured. 2. The method for removing adhering concrete according to claim 1, wherein the adhering concrete removal accelerator contains 5% by weight or less of a surfactant. 3. The adhesion concrete removal accelerator according to claim 1 or 2, in which 10% by weight or less of one or more inorganic salts such as sodium sulfate, aluminum chloride, and magnesium chloride is added. How to remove adhered concrete. 4. The adhering concrete removal accelerator contains 30% by weight or less of an oil such as mineral oil, animal oil, or vegetable oil in an emulsified form. Adhesive concrete removal method described in section. 5. An agent for promoting the removal of concrete adhering to the surface of formwork panels used for concrete placement, which is characterized by being composed of an aqueous solution containing 45% by weight or less of calcium chloride as a main component. agent. 6. The adhesion concrete removal accelerator according to claim 5, wherein 5% by weight or less of a surfactant is added. 7. The adhering concrete removal accelerator according to claim 5 or 6, wherein 10% by weight or less of one or more inorganic salts such as aluminum chloride, sodium sulfate, and magnesium chloride are added. 8. Promotion of adhering concrete removal according to claim 5, 6 or 7, in which 30% by weight or less of oil such as mineral oil, animal oil or vegetable oil is added in an emulsified form. agent.