JPH0688427A - Method of absorbing excessive water from concrete - Google Patents

Abstract

PURPOSE:To carry out drying and finishing of concrete in a short time by laying an water-absorptive sheet in which high water-absorptive polymer is interposed between two water-permeable sheets, on a base layer before placing of concrete. CONSTITUTION:High water-absorptive polymer (b) or a high water-absorptive polymer composite b' is interposed between two water-permeable sheets so as to obtain a high water-absorptive sheet (c). Then, the sheet (c) is laid on a base layer (a), and then, concrete (e) is placed. Excessive water in the concrete (e) is absorbed by the sheet (c) so that the drying and finishing of the concrete (e) may be made in a short time. The water once absorbed in the sheet (c) will be suitably fed to the concrete (e) over a long time, thereby it is possible to alleviate the lowering of the strength of the concrete (e) and the neutralization thereof.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for absorbing concrete surplus water. More specifically, the present invention relates to a method of absorbing excess water, promoting early strength development of concrete, and reducing surface breathing water, suppressing generation of surface layer reitance, and preventing shrinkage and shrinkage cracking of concrete. It is a thing. The present invention also relates to an invention that can contribute to the prevention of dryout and neutralization of concrete for a long period of time by the internal water retention function.

[0002]

2. Description of the Related Art Generally, breathing water is generated on the surface layer of concrete at a very early stage after it is poured. This breathing water is so-called surplus water, which is the amount of water required for the hydration reaction of cement removed. When concrete is mixed or poured, a large water ratio is generally used to improve workability, but this becomes surplus water (and breathing water) later.

Conventionally, breathing water is usually left to stand and naturally dried. During this time, the temperature is high in the summer, so the breathing water evaporates quickly, and it does not take a long time to finish the concrete surface, so it can be completed relatively quickly. The finishing time depends on the construction contents, but in the summer, it is generally 7 to 10 after placing concrete.
Although it is thought that it will finish in about an hour, the hydration exothermic reaction of cement is slow due to the low temperature in winter, and depending on the work contents, hardening gradually starts from about 12 to 13 hours and 18 to 19 for slow ones. Some take nearly 24 hours.

[0004] In this way, it takes time to finish the concrete because not only the effect of temperature but also the breathing water which is the surplus water has a great influence.

Regarding the treatment of breathing water, which is excess water for concrete, recently, there is also a product for laying a water-absorbent sheet using a water-absorbing polymer on the surface of the concrete after placing the concrete to absorb the breathing water. .

However, the method of laying a water absorbent sheet on the surface layer of concrete after casting has the following problems. The technician or specialist must judge the time and amount of breathing water to be spread depending on the amount of breathing water, the weather, and the work contents that differ from site to site. The absorbed sheet must be collected and disposed of. The water-absorbent polymer that has absorbed water from the water-absorbent sheet may partially leak and adhere to the surface of the concrete structure, which must be cleaned.

In addition to the above problems, it is said that such a conventional method has a problem in workability due to the adjustment of work time allocation and its complexity, and that the finished surface is also satisfactory. hard.

[0008]

The present invention seeks to provide a solution to the above problems found in the prior art methods.

[0009]

[Means for Solving the Problems]

[Summary of the Invention] <Summary> The present invention is to simply and easily reduce excess water by laying a water-absorbent sheet on a foundation layer and absorbing excess water before pouring concrete, and a water-absorbent sheet. The present invention is intended to provide a method that can save the extra trouble of collecting.

Therefore, according to the method of absorbing excess concrete water according to the present invention, a water-absorbent sheet obtained by sandwiching a super-water-absorbent polymer between two water-permeable sheets is laid on a foundation layer before concrete is poured, The water-absorbent sheet is made to absorb excess water in the concrete.

<Effect> According to the present invention, it is possible to reduce the amount of surplus water that has conventionally floated as breathing water on the surface of concrete after it has been cast. Therefore, it is possible to dry concrete and finish it in a short time. Further, since it is not necessary to collect the water absorbing sheet and to process the water absorbing sheet, the degree of freedom in the construction work is increased, and thus the construction period can be significantly shortened.

Further, according to the present invention, the excess water once absorbed by the water absorbent sheet is appropriately supplied to the concrete for a long period of time, so that the concrete is not excessively dried. Therefore, it is possible to considerably prevent the strength of the concrete from being lowered and the carbonization thereof.

[Detailed Description of the Invention] <Water Absorbent Sheet> The water absorbent sheet used in the present invention comprises a super absorbent polymer sandwiched between two water permeable sheets.

As the super absorbent polymer, various conventionally known polymers can be used. In the present invention, for example, a water-insoluble superabsorbent resin, for example, starch-acrylate-graft polymer cross-linked product, polyacrylate cross-linked product, acrylate-acrylic acid ester copolymer cross-linked product, acrylic acid ester and One or more selected from the group consisting of a saponified product of a vinyl acetate copolymer cross-linked product, an acrylic acid salt-acrylamide copolymer cross-linked product, and a hydrolyzate of a polyacrylonitrile cross-linked product can be used.

Since the absorption of excess water is greatly affected by the initial water absorption rate, it is preferable to use a water-absorbing polymer having a high water absorption rate.

The above-mentioned superabsorbent polymer is often in the form of powder, but the superabsorbent polymer in the present invention does not need to be in the form of powder, and its shape, size, etc. are arbitrary. .

As the water-permeable sheet sandwiching the water-absorbent polymer, any one can be used as long as the required strength and water permeability can be obtained. In the present invention, for example,
Paper, a plastic sheet, a non-woven sheet, and a laminate of a plurality of these sheets can be used.

The combination of two water-permeable sheets sandwiching the superabsorbent polymer is also optional, and the superabsorbent polymer can be sandwiched between the same or different water-permeable sheets. Typical examples of the water-absorbent sheet in the present invention include a water-absorbent polymer sandwiched between two water-permeable papers, and generally a plastic with one surface laminated with a thin film such as polyethylene. A laminated sheet and a cover sheet with a water-absorbent polymer sandwiched between them, a non-woven fabric is used in combination with the paper sheet instead of the paper sheet, and a non-woven fabric is used between the non-woven fabric and the non-woven fabric. Something is sandwiched, etc.

The basis weight of the water-absorbent polymer is 0.01 Kg / m
^{2 to} 0.3 Kg / m ² , preferably 0.05 Kg / m ^{2 to} 0.1
It is 5 Kg / m ² . 0.01 kg / m water absorbability is deteriorated less than ^2, whereas protrusion water absorption sheet is broken resin optionally in that it 0.3 Kg / m ² exceeds too much water absorption, may become an obstacle depending work Yes, it is also uneconomical.

The water-absorbent sheet of the present invention absorbs excess water of cast concrete, but the water-absorbent sheet that absorbs excess water supplies water to the concrete structure in an appropriate and long-term manner. It prevents the poured concrete from being excessively dried.

Concrete weight 350 Kg / m ² (w / c =
55 excess water is about 15%, as an example those i.e. about 4~5Kg / m ^2), the wetback (water return amount) water was applied absorbed water-absorbing sheet (water absorption) measurement of the diaper Rating After confirming the return, the following will occur (however, the return of water occurs due to a capillary phenomenon, and it is assumed that the water in the concrete has dried considerably over the years).

First, 1 g of the water-absorbing polymer is put into an alkaline aqueous solution of calcium hydroxide having a pH of 12 (pseudo-concrete surplus water), and the alkaline aqueous solution is slowly absorbed by the water-absorbing polymer. Put the absorbed polymer in a nylon tea bag and seal it, then 100 x 100 mm
Square filter paper (standard filter paper (example) Advantic ^# 24) 1
Prepare 0 sheets and weigh to the last 4 digits. Then, the polymer in a nylon bag is sandwiched between prepared filter papers. 1
A load of SUS 100 x 100 mm square and 4.5 kg weight is placed on the filter paper and measured for 5 minutes. After the measurement, the load is removed, the polymer bag is removed, the filter paper weight is measured, and the return water absorption is determined. The amount of water returned from the weighing is about 3 g, which is about 0.3 kg / m ² , but this amount of water does not have any adverse effect on the concrete and is sufficient to prevent excessive drying of the concrete. Considered to be quantity.

<Concrete Construction Process> The construction process by which the effects of the present invention can be satisfactorily obtained will be described below with reference to the drawings as necessary.

It is preferable that the underlayer a, on which concrete is to be cast, be well preliminarily solidified, smoothed, and adjusted for easy walking. The water-absorbent sheet c is laid on the water-absorbent sheet c, but it is sometimes preferable that the powdery water-absorbent polymer b and the composite thereof are optionally sprayed in an appropriate amount before the water-absorbent sheet is laid. This is to perform appropriate spraying for absorbing excess water in excess of the planned absorption amount in the water-absorbent sheet c, or for removing excess water earlier than the scheduled time.

Here, the composite of water-absorbent polymer means, specifically, various water-absorbent resin powders using a binder of a water-soluble polymer, such as soil, sand, bentonite, activated carbon, carbon. Granulated by adhering to an inorganic substance such as, and known as a water-absorbing agent. Since this composite of water-absorbent polymer is obtained as relatively large particles (2 to 10 mm), it does not easily scatter during on-site construction work, is easy to handle even when mixed with other powder materials, and is on wet ground. In the case of spraying to, it is preferable because it is unlikely to be in a mamako state.

The water absorbent sheet is preferably laid evenly. When the water absorbent sheet has been laid, concrete is poured. This concrete can be poured in exactly the same way as usual. INDUSTRIAL APPLICABILITY The present invention can be applied to general conventional concrete in general (that is, including cement mixtures such as cement and cement mortar), and the effect is uniformly recognized when applied. Is.

It is also possible to use a method of directly spraying the superabsorbent polymer or a composite thereof directly into the concrete being poured to absorb excess water. At this time, the desirable amount of the water-absorbent polymer and the composite thereof is (when the underlayer before laying the water-absorbent sheet has already been applied with the total amount thereof), 0.
It is 1% to 3%, preferably about 0.5% to 2.0%.

After the concrete has been cast, a regular wood leveling iron trowel retainer and a mechanical trowel retainer can be used in the usual steps to complete the final finish.

[0029]

The following examples and the accompanying drawings will more specifically illustrate the present invention.

<Example-1> A water absorbing sheet c was carefully laid on the entire surface of the underlayer (floor road surface). As the water absorbent sheet c, a water absorbent polymer having a weight per unit area of 0.1 kg / m ² was used. After laying the water-absorbing sheet, concrete prepared with a water / cement ratio of 55%, a unit cement amount of about 318 Kg / m ² , and an aggregate amount of about 1800 Kg / m ³ was poured to a thickness of about 20 cm. After pouring, the rise of breathing water was a little less than the pouring of ordinary concrete, and the effect was confirmed. The surface leveling and pressing time was about 1.0 to 2.5 hours earlier than the normal one. In addition, the surface latance is not conspicuous even after one month of casting at present, and it is considered that the surface latance is sufficiently effective as compared with ordinary concrete. This is because the water-absorbent sheet in the base layer sequentially absorbs excess water in the concrete, so there is initial breathing water, but the hardening as a whole is accelerated and the surface strength is developed quickly. It is estimated that

The concrete water absorption amount of the water absorbing sheet is
Theoretically, assuming that the basis weight of the water-absorbing polymer is 0.1 kg / m ² , it absorbs about 200 times in tap water, and if it is assumed that the alkaline aqueous solution of pH 11-12 absorbs 1/5 of tap water, it absorbs about 40-5.
It becomes 0 to 4 kg- ⁵ kg / m ² , while the concrete excess water is considered to be about 4 kg / m ^{2 under} these conditions, so that the absorbent sheet has a sufficient capacity to absorb the concrete excess water.

On the other hand, the water absorbed by the water absorbent sheet is replenished with water from the inside when the surface layer concrete is in a dry region. Therefore, by backing up water from the side of the water absorbing sheet, it is useful for preventing dryout of concrete and for preventing neutralization.

<Example-2> 1.0 kg / m ^{2 of the} water-absorbent polymer b was previously sprayed. In this case, the weight per unit area of the water-absorbent polymer is 0.05 kg / m ^{2 to} 3.0 kg / m ^2.
2 , preferably 0.5 Kg / m ^{2 to} 2.0 Kg / m ² is a suitable amount, and a composite thereof is 0.5 Kg / m ^{2 to} 5.0 Kg / m ² , preferably 1.0 Kg / m ^{2 to} 3 A suitable amount is 0.0 Kg / m ² . Next, water-absorbent sheet (weight of water-absorbent polymer 0.1 kg /
m ² ) was laid all over. Thereafter, as in Example-1, a water / cement ratio of 55%, a unit cement amount of about 318 kg / m ³ ,
Concrete e prepared by mixing and preparing an aggregate amount of 1800 Kg / m ³ was similarly poured in a thickness of 20 cm. Regarding the breathing water and the concrete press-finishing state after placing concrete, no difference was observed after one month of placing as compared with Example-1.

<Example-3> 2 kg / m ^{2 of the} water-absorbent polymer composite b'was previously sprayed. Then, the water absorbing sheet c was laid all over. Furthermore, 2 kg of water-absorbent polymer composite b '
/ m ² while being sprayed, the following examples 1,2 and similar water / cement ratio of 55%, the unit cement content of about 318Kg / m ^3, the aggregate amount of 1800 kg / m concrete e about 20 formulated preparation of ³
It was placed with a thickness of cm. The breathing water after placing concrete is felt to be quite small, and the effect can be seen. The concrete surface leveling time and the surface finish state were not significantly different between Examples 1, 2, and 3 after one month.

[0035]

EFFECTS OF THE INVENTION According to the present invention, the generation of breathing water of concrete after pouring is suppressed, the work of treating breathing water is unnecessary, and its drying can be performed in a short time, and the strength of concrete can be increased. The ability to prevent deterioration and neutralization is as described above in the section "Means for solving the problem".

[Brief description of drawings]

FIG. 1 is a plan view showing a construction process according to the present invention in a stepwise manner.

FIG. 2 is a diagram showing a cross section of the layer structure obtained in the construction process of FIG.

[Explanation of symbols]

 a Base layer (floor surface, road surface layer such as ground stone) b Water-absorbent polymer b'Water-absorbent polymer composite c Water-absorbent sheet d Reinforcing bar e Concrete

Front page continuation (72) Inventor Koji Kato 1 Toho-cho, Yokkaichi-shi, Mie Prefecture Yokkaichi Research Institute, Mitsubishi Petrochemical Co., Ltd.

Claims (1)

[Claims] 1. A water-absorbent sheet comprising a super-water-absorbent polymer sandwiched between two water-permeable sheets is laid on a foundation layer before concrete is cast, and the water-absorbent sheet becomes excess water in concrete. A method for absorbing concrete surplus water, which comprises absorbing water.