JPH0989736A - Condensation delaying sheet for surface treatment of test piece for concrete-compressive strength test - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the condensation delaying sheet for surface treatment of the test piece for a concrete-compressive-strength test, which can improve the workability and the reliability of the surface washing work that is performed as the pretreatment of capping when the test piece for the compression strength test of the concrete is formed, and can thereby manufacture the test piece having high quality efficiently. SOLUTION: The condensation delaying sheet, which is formed by applying or impregnating a concrete-condensation delaying agent into a sheet-shaped base material, is molded into the shape approximately corresponding to the upper-surface shape of a formwork for manufacturing the test piece for the concrete-compressive-strength test. At the same time, a plurality of through holes 3 are provided in the sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a set retardation sheet used for surface treatment when preparing a specimen for concrete compressive strength test.

[0002]

2. Description of the Related Art In preparing a specimen for concrete compressive strength test, the upper surface is usually finished by capping. That is, JIS
A 1132 stipulates how to make such specimens,
According to the same standard, the capping is done by placing a concrete sample (fresh concrete) in a specified bottomed cylindrical formwork, washing the upper surface with water at an appropriate time to remove the leitance, and then wiping the water and removing the cement paste. It is placed and pressed uniformly to the top surface of the mold with a pressing plate made of polished glass.

[0003]

However, the work associated with such a series of cappings is by no means easy, and above all, the work of washing the upper surface with water to remove the leitance is limited to a short time before the concrete is completely hardened. Due to the restriction of the work period, which requires processing at a certain time, even a person with considerable skill had a limit to the processing capacity. Moreover, the surface roughening is not sufficient only by removing the reitance, and the hardened layer of the capped cement paste may peel off. Therefore, in practice, a wire brush or the like is used to remove the leitance and to roughen the surface, which requires considerable labor.

Therefore, recently, a concrete set retarder is directly sprinkled on the surface of the cast concrete, or a suitable sheet such as paper or cloth is applied to the surface of the concrete, and the concrete set retarder is applied from above. Methods have been proposed for spreading and delaying the hardening of concrete surfaces.

However, even with such a method, it is difficult to uniformly disperse the set retarder over a large number of specimens, and it takes time to prepare the set retarder before the work. In terms of sex and reliability, it was not yet sufficient.

The present invention has been made to address the above-mentioned problems of the prior art, and the workability and reliability of the surface washing operation performed as a pretreatment for capping when preparing a concrete compressive strength test specimen. Therefore, it is an object of the present invention to provide a set retardation sheet for surface treatment of a concrete compressive strength test specimen that enables efficient production of a high quality specimen.

[0007]

A set retardation sheet for surface treatment of a concrete compressive strength test specimen of the present invention is a set retardation sheet obtained by coating or impregnating a sheet-like base material with a concrete set retarder and drying. It is characterized in that it is formed into a shape that substantially corresponds to the shape of the upper surface of the mold for producing a specimen for concrete compressive strength test, and that the sheet is provided with a plurality of through holes.

In such a set retardation sheet for surface treatment of the concrete compressive strength test specimen, the concrete compressive strength test specimen is easily and closely contacted with the surface of the concrete placed in the mold for producing the concrete compressive strength test specimen. It can be placed and the set retarder can act sufficiently and uniformly on the concrete surface to form a set retarder layer of uniform desired thickness. Also, it is easy to peel off after that,
In most cases, the set retardation layer after being stripped off can be easily washed out only by high pressure water washing without using a wire brush or the like, and a uniformly thin and sufficiently roughened surface can be formed. Further, when the wire brush is used, the labor is greatly reduced. Therefore, workability is improved, and a sufficiently roughened surface has
Since it is possible to provide a thin and firmly bonded capping layer, it is possible to produce a high-quality sample with high productivity.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of an embodiment of a set retardation sheet for surface treatment of a concrete compressive strength test specimen of the present invention.

As shown in FIG. 1, the set retardation sheet for surface treatment of the concrete compressive strength test specimen is a set retardation sheet obtained by coating or impregnating a sheet-like base material with a concrete set retarder and drying. Becomes the diameter of 2
A circular part 1 formed in a circular shape having the same diameter as or slightly smaller than the inner diameter of the bottom end cylindrical concrete compressive strength test specimen forming frame having a cylindrical hollow portion having a double height,
The circular portion 1 has an ear portion 2 integrally provided on the outer periphery thereof. The circular portion 1 is provided with a plurality of through holes 3 which vertically pass through the circular portion 1. The through holes 3 are for venting air when the setting retardation sheet is placed in contact with the surface of the concrete cast in the formwork and for discharging the bleeding water leaching to the concrete surface to the outside. The adhesion between the set retardation sheet and concrete can be improved. In addition, it is desirable that the through holes 3 have a diameter of about 5 mm or less and that they are provided substantially evenly at a rate of about 1 per 1 to 10 cm ^2. There is also
If the number is too large or if they are non-uniformly provided, there is a possibility that the retarding effect of the setting retarder may be insufficient or there may be variations.

Examples of the sheet-like base material which constitutes the set retardation sheet include paper, plastic film, cloth, and a laminate of these. Among these, paper and plastic film are water-resistant adhesive. It is suitable to use adhesives, or paper or plastic film that has been waterproofed with a waterproof material such as silicone resin, urethane resin, or asphalt. Especially, two pieces of kraft paper are used asphalt or atactic polypropylene. It is desirable to use tarpaulin paper that is integrally laminated via.

As the concrete setting retarder to be coated or impregnated on such a base material, various conventionally known ones can be used. Among them, oxycarboxylic acids and saccharides as described below can be used. It is preferable to use as a main component because the setting retardation layer has excellent uniformity and the depth thereof can be easily adjusted. That is, gluconic acid, arabonic acid, glucoheptonic acid, 2-ketogluconic acid, 5-ketogluconic acid, citric acid, malic acid, tartaric acid, pyruvic acid and oxycarboxylic acids such as salts thereof, and saccharose, maltose,
Sugars such as raffinose, lactose, glucose, fructose, mantose and arabinose in a weight ratio.
A mixture of 5:95 and 95: 5 is suitable, and a mixture of sodium gluconate and sucrose is particularly suitable. The setting retarder may contain a thickener, an anti-sticking agent, a dispersant, water and the like which are usually added.

As the setting retardation sheet, it is possible to use a commercially available setting retardation paper for washing out the concrete surface, such as makeup on the concrete surface or roughening of the concrete joint.

In such a set retardation sheet for surface treatment of a concrete compressive strength test specimen, the circular portion 1 can be easily brought into contact with the surface of the concrete placed in the mold by holding the ear 2 easily. Since it is possible to dispose the air bubbles and bleeding water generated between the concrete and the plurality of through holes 3 provided in the circular portion 1, it is possible to form a non-adhesive portion and to prevent adhesion. The decrease can be prevented, and the active ingredient of the set retarder can be uniformly and sufficiently acted on the concrete surface. Hereinafter, the procedure for producing a concrete compressive strength test specimen using such a set retardation sheet will be described.

First, uncured concrete sampled or prepared by the method specified in JIS A 1115 or JIS A 1138 is cast into a predetermined concrete compressive strength test specimen forming form according to JIS A 1132. Set and fill.
Next, the set retardation sheet is placed on the surface of the cast concrete, and the surface of the concrete is lightly pressed to be adhered thereto. At this time, the setting retarder should be in contact with the concrete. After the concrete is cured and cured for a predetermined time as it is, the set retardation paper is peeled off by holding the ears, and the set retardation layer including the laitance layer on the concrete is washed out with water. After this, wipe off the water, put the cement paste,
Press the plate evenly to the top of the form and let it stand. When the cement paste has hardened, demold,
Then, the specimen is completed by curing for a predetermined time.

In the process of preparing the specimen, the work of washing out the surface prior to the capping with the cement paste is extremely easy due to the action of the set retardation sheet, and does not require a wire brush or the like and requires skill. Instead, it can be washed out simply by washing with water. Also, because of this, restrictions on processing time are reduced,
Further, since the set retardation sheet can be easily attached and detached, the processing efficiency is significantly improved, and the productivity of the specimen can be increased. Moreover, since the concrete surface can be sufficiently roughened, the adhesive strength of the cement paste is increased, and it becomes possible to produce a good quality specimen.

As described above, by using the set retardation sheet, it is possible to enhance the treatment efficiency and the treatment performance of the surface treatment at the time of preparation of the specimen, and thus to greatly improve the quality and productivity of the specimen. it can.

The set retardation sheet is formed into a circular shape that fits substantially inside the mold for producing a concrete compressive strength test specimen, but the present invention is not limited to such a shape. The shape may be circular or polygonal, which is larger than the form. However,
In this case, it is desirable to use a setting retardation sheet material having flexibility so that the setting retardation sheet can be brought into contact with at least almost the entire surface of the cast concrete.

[0020]

EXAMPLES Next, the embodiments of the present invention will be described more specifically by way of examples.

Example 1 15 parts by weight of sodium gluconate and 15 parts by weight of saccharose and 1 part by weight of sodium salt of carboxyalkyl ether starch were formed on one surface of tarpaulin paper obtained by integrally bonding two pieces of kraft paper via homotype atactic polypropylene. , A set retarder consisting of 12 parts by weight of calcined diatomaceous earth and 67 parts by weight of water was applied and dried to a dry weight of 4.7 g / m ^2, and the set retardation paper was cut with a cutter and the diameter of 1
mm through holes were evenly provided to prepare a set retardation paper for surface treatment of a concrete compressive strength test specimen (circular diameter 98 mm, 25 through holes) as shown in FIG.

Example 2 A set retardation paper for surface treatment of a concrete compressive strength test specimen was prepared in the same manner as in Example 1 except that the number of through holes was 13.

Example 3 A set retardation paper for surface treatment of a concrete compressive strength test specimen was prepared in the same manner as in Example 1 except that the diameter of the circular portion was 95 mm.

Then, in order to evaluate the performance of the setting retardation paper obtained in each of the above-mentioned examples, an attempt was made to prepare a test piece using these. That is, first, 300 parts by weight of ordinary Portland cement (specific gravity: 3.16 g / cm ³ ) was added to a mold for creating a concrete compressive strength test specimen with a diameter of 100 mm and a height of 200 mm.
Water 165 parts by weight, river sand (specific gravity 2.62 g / cm ³ ) 820 parts by weight, crushed stone as coarse aggregate (specific gravity 2.71 g / cm ³ , maximum size 20 mm) 1035
Part by weight and fresh concrete mixed with 0.6 part by weight of AE water reducing agent (water cement ratio 55%, slump 15 cm, air volume
4.5%) is poured and filled, and the surface of the sheet is covered with a set retardation paper and lightly pressed to make it adhere. Then, at a temperature of 30 ° C and a humidity of 60%, 1 ~
Air dried for 4 days. After placement 1, 2, 3, and 4
After each day, peel off the set retardation paper covered with the ears, wash the concrete surface with pressured water, wipe off the water, put the cement paste on it, and press the plate to the top of the formwork. Press uniformly and let it stand to harden the cement paste.
The test piece was completed by demolding and curing in water.

Table 1 shows the characteristics of the specimens thus obtained, that is, the adhesiveness of cement paste, the ease of surface washing treatment (latance removal treatment) in the preparation process, and the peeling of set retardation paper. And the degree of adhesion of the retarded setting paper to concrete.

The adhesion of the cement paste, the easiness of surface washing treatment, and the peeling property of the set retardation paper were evaluated as follows: easy ◎, slightly easy ○, slightly difficult Δ, difficult ×, very difficult. The difficulty is shown as XX.

In addition, in Table 1, for comparison, an example using the setting retardation paper without the through holes and the ears of Example 1, Example 1
In Comparative Example 1 and Comparative Example 2, an example of using a setting retardation paper in which no through hole is provided and only an ear portion is used, and a case of producing a sample without using the setting retardation paper, respectively.
And as Comparative Example 3.

[0028]

[Table 1] From Table 1, according to the setting retardation paper of the example, the surface treatment at the time of making a specimen can be performed very easily and satisfactorily, and restrictions on the treatment time are also reduced, so that the specimen of good quality can be obtained. It is clear that can be produced with high productivity.

[0029]

As described above, the set retardation sheet for surface treatment of the concrete compressive strength test specimen of the present invention can be easily placed on the concrete surface placed in the specimen making frame to delay settling. Since the agent can be effectively acted on and the subsequent peeling off can be easily performed, the workability and reliability of the surface treatment at the time of preparing the specimen can be significantly improved. Therefore, the quality and productivity of the specimen can be improved.

[Brief description of drawings]

FIG. 1 is a top view showing an example of a set retardation sheet for surface treatment of a concrete compressive strength test specimen of the present invention.

[Explanation of symbols]

 1 ………… Circular part 2 ………… Ear part 3 ……… Through hole

Claims (4)

[Claims] 1. A setting retardation sheet obtained by applying or impregnating a sheet-like base material with a concrete setting retarder and drying it into a shape substantially corresponding to the top surface shape of a concrete compressive strength test specimen making formwork. In addition, a set retardation sheet for surface treatment of a concrete compressive strength test specimen, characterized in that the sheet is provided with a plurality of through holes. 2. The set retardation sheet for surface treatment of a concrete compressive strength test specimen according to claim 1, wherein the set retardation sheet substantially fits inside a formwork for forming a concrete compressive strength test specimen. A set retardation sheet for surface treatment of concrete compressive strength test specimens, which is characterized by being shaped. 3. The set retardation sheet for surface treatment of a concrete compressive strength test specimen according to claim 1 or 2, wherein a stripping ear portion is provided on an outer edge portion of the set retardation sheet. A set retardation sheet for surface treatment of concrete specimens for compressive strength tests. 4. The set retardation sheet for surface treatment of a concrete compressive strength test specimen according to claim 1, wherein the set retardation sheet is formed by integrating two pieces of kraft paper with atactic polypropylene interposed therebetween. The surface of the specimen for concrete compressive strength test, characterized in that it is obtained by applying and drying a concrete set retarder containing oxycarboxylic acids and saccharides as set retarding components on one side of tarpaulin paper laminated on Set delay sheet for processing.