JP2006077433A - Concrete surface finishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete surface finishing method which enables early poured flooring by shortening a curing period, while ensuring abrasion resistance and peel strength of a coating material for a surface. <P>SOLUTION: Concrete is laid, and a concrete surface is covered with a mat for vacuum treatment in a state of a bleeding ratio of 70-90%, so that vacuum dewatering treatment can be performed. After that, the concrete is cured. This enables the early poured flooring by shortening the curing period. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a concrete surface finishing method using a vacuum concrete method for vacuum dehydrating a cast concrete surface in the case of flat cast concrete work in the field of building civil engineering.

  A normal method for finishing a concrete floor surface is to place concrete or mortar smoothly (hereinafter referred to simply as “concrete”, including mortar in this specification), and after the concrete is tightened by a hydration reaction. The surface of the concrete is finished by pressing down the surface with rivets.

  The surface of the floor concrete has the disadvantage that it is weak due to the influence of breathing water and latency, and it is easy to wear and dust, so that the surface strength can be improved and the surface aesthetics has been improved. It has been used as a dustproof floor and a painted floor by applying a synthetic resin type coating material on the surface. This coating material was applied and finished after about 2 to 4 weeks or more when the strength of the concrete became stable and the surface moisture decreased, and the aesthetic finish was performed.

  However, in order to shorten the curing period, if the coating surface is applied with the concrete surface remaining fragile, there is no problem with the floor where people can walk, but there is no problem with the floor for industrial use, especially in factories and warehouses. There are the following problems on floors where forklifts and transport vehicles such as backyards frequently pass and where loads are concentrated locally. That is, the concrete surface layer in contact with the coating material collapses due to repeated loads or impacts, and as a result, the coating material peels off from the concrete surface, and this part quickly wears down to a step, For this reason, there has been a problem that peeling further proceeds, the floor becomes uneven, and the function and aesthetics of the floor are significantly impaired.

On the other hand, a vacuum concrete method is widely known as a method for strengthening the surface layer of concrete, but this method involves covering the concrete surface with a vacuum treatment mat immediately after placing the concrete, and lowering the bottom surface of the mat. This is a method in which excess water in the surface layer of the concrete is sucked and removed while the pressure is reduced by a vacuum pump and held for a certain time (for example, Patent Document 1). According to this method, high surface strength can be obtained with concrete alone, so in the field of civil engineering, it is used in places where there is significant load on slopes, roads, etc., where wear is significant, non-slip applications, and freeze-thaw applications. .
Japanese Patent Laid-Open No. 02-74759

  However, in order to remove surplus water as much as possible by the vacuum concrete method and strengthen the concrete surface layer, when implementing immediately after placing concrete, in the case of a Japanese building floor, you must ride on the placed concrete. There is a problem of not becoming. Furthermore, since a pressure reduction time of 1.5 minutes or more per 1 cm thickness of the concrete surface layer is required, a processing time of 25 to 30 minutes per place is required for a concrete surface layer of 15 cm thickness, and is applicable to building floor concrete. There was a problem that was difficult.

  Therefore, the present invention provides a concrete surface that can work on the placed concrete, shorten the curing period and enable early coating while ensuring the wear resistance and peel strength of the coating material on the surface. The purpose was to provide a finishing method.

  In order to solve the above problems, the present inventors have completed the present invention by finding that the curing period can be further shortened by performing vacuum dehydration after the breathing rate reaches 70 to 90%. . That is, in the concrete surface finishing method of the present invention, concrete is placed, and after the breathing rate reaches 70 to 90%, the vacuum treatment mat is coated on the concrete surface, vacuum dehydration treatment is performed, and curing is then performed. It is characterized by.

  In building floor concrete, since the concrete is placed continuously in the construction area, the worker must work on the placed concrete in finishing work. However, if the breathing rate is 70 to 90%, the worker can work while wearing “net clogs” and riding on the concrete. Moreover, when the breathing rate is 70 to 90%, a large amount of breathing water is present on the surface of the cast concrete, and as a result, excess water can be removed by short-time vacuum dehydration. In addition, an effect of smoothing the finish can be obtained. On the other hand, if the breathing rate is less than 70%, the concrete is soft and the worker cannot get on it. In addition, since the breathing water is not concentrated on the surface layer, it takes a long time to dewater the surplus water. In addition, the trace of the vacuum processing mat and the footprint of the worker are easily attached, and the finish is not smooth. On the other hand, if the breathing rate is greater than 90%, it is easy to work on the concrete, but the hydration reaction proceeds and the concrete surface becomes hard, resulting in unevenness and the vacuum processing mat does not adhere. Therefore, air enters from the surroundings and the degree of vacuum does not increase, making it difficult to dehydrate. Also, if the breathing rate is greater than 90%, the hydration reaction is exponentially faster and exceeds the speed of the dehydration process. Therefore, when dehydrating a large area, the dehydration process is impossible, and as a result It may not be possible to obtain the characteristics.

  In the present invention, the vacuum dehydration process can be performed while applying vibration to the vacuum processing mat by the vibration generating means. As a result, the adhesion of the vacuum processing mat to the concrete surface is improved and a stable degree of vacuum is obtained. As a result, the amount of dewatering can be increased and the concrete surface can be evenly dewatered.

  Further, in the present invention, prior to curing, a resin concrete layer having a finished surface can be formed by spraying a synthetic resin emulsion on the surface of uncured concrete and performing tacking. Since the resin concrete layer has a function of blocking the concrete from the outside air, the inside of the concrete can be retained and cured, and the cement hydration reaction proceeds sufficiently. Thereby, it is considered that high strength can be obtained in a shorter period of time. In addition, since the concrete is shielded from the outside air by the resin concrete layer, drying shrinkage is suppressed and no cracking occurs.

  Further, in the present invention, the breathing rate of the placed concrete can be directly measured, but the penetration resistance value obtained by a proctor penetration resistance test can be used instead of the measurement of the breathing rate. That is, the relationship between the breathing rate and the penetration resistance value is obtained in advance, and the breathing rate is estimated from the penetration resistance value actually measured by the proctor penetration resistance test. Since it is not necessary to directly measure the breathing rate of the placed concrete, the work becomes simple and skill is not required.

According to the present invention, the inside of concrete can be water-retaining, and high strength can be obtained in a shorter period of time. In particular, the vacuum dehydration process removes excess water from the surface layer of the concrete and reduces it, and at the same time, it is consolidated at an atmospheric pressure of 6 to 8 t / m ^2. The pores involved are reduced to become a dense structure and strengthened, and the compressive strength and wear resistance strength are increased. Therefore, buckling, crushing or peeling of the concrete surface layer itself due to impact or repeated load is unlikely to occur. In addition, since the coating material is applied to the concrete surface that has been vacuum dehydrated and becomes dense and strong, the adhesion between the coating film and the concrete surface is large, and in combination with the strengthening of the concrete surface layer, the coating material is applied. Peeling of the film is difficult to occur, and the durability of the coating material coating film is increased. Furthermore, since the voids that are the cause of blistering when the coating material is applied are significantly reduced, the occurrence of blistering can be suppressed. In addition, since excess water remaining in the concrete is removed by vacuum dehydration, the influence of moisture that hinders adhesion of the coating material can be eliminated without drying for a long period of time as in the prior art.

Hereinafter, embodiments of the present invention will be described.
In the present invention, after concrete pouring, vacuum dehydration is performed after the breathing rate reaches 70 to 90%. Here, the breathing rate refers to the ratio of the amount of free water that has floated on the concrete surface after a predetermined time has elapsed after being placed in concrete, and is defined by (breathing water amount / mixed water amount) × 100 (%). The The breathing rate of 70 to 90% indicates a cured state that allows a person to work on the breathing rate. The breathing rate is more preferably 75 to 90%.

  Further, in the present invention, it is possible to use a method of measuring the degree of hardening of the placed concrete by a proctor penetration resistance test and estimating the breathing rate based on the relationship between the previously determined breathing rate and the penetration resistance value. . Here, the Procter penetration resistance test is a method for measuring the setting time of concrete defined in ANSI / ASTMC 403-77. Proctor penetration resistance test is usually performed by attaching a penetration part (needle head) for measuring the degree of hardening of a predetermined size to a penetration resistance measuring device (spring type or hydraulic type), and gradually inserting the penetration part into the concrete to be measured. Further, it penetrates to a depth of 1 inch at a constant speed (for example, 1 inch / 10 seconds). The load required for the penetration of the penetration portion is divided by the tip end area of the penetration portion to obtain the penetration resistance value. However, in the measurement, since the mortar from which the gravel (coarse aggregate) is removed from the blended concrete is tested, the work is complicated and skill is required.

  On the other hand, in this invention, the improved proctor penetration test apparatus which has a disk-shaped penetration part fixed to the single side | surface of the plate for fixation is used. In this improved apparatus, the load required to penetrate only the thickness of the penetration portion is measured. However, when the penetration portion penetrates only the thickness of the penetration portion, the fixing plate hits the concrete surface. Since it is not necessary to visually confirm the penetration depth of the penetration portion, the measurement is simple. Moreover, since the placed concrete itself is used as a measurement target, it is not necessary to remove gravel from the mixed concrete, so that it is not necessary to prepare a measurement sample and can be carried out in a short time. In addition, the diameter of an intrusion part can be selected with the magnitude | size of the gravel used for concrete.

  For example, using a modified Proctor penetration test apparatus equipped with a 50 mm diameter penetration plate, the results of determining the relationship between the breathing rate and the penetration resistance value for the concrete to be placed are shown in Table 1 and based on the results. The breathing rate-penetration resistance value curve is shown in FIG. The horizontal axis represents the breathing rate, the vertical axis represents the penetration resistance value, and the solid line and the wavy line indicate cases where the slump is 15 cm and 18 cm, respectively. The penetration resistance value tended to increase monotonously with the increase in the breathing rate, but the increase rate increased when the breathing rate exceeded 70%. A penetration resistance value of about 200 to about 700 N corresponds to a breathing rate of 70 to 100%. Specifically, the breathing rate-penetration resistance value curve of FIG. 1 is prepared in advance for the concrete to be placed, and the breathing rate corresponding to the penetration resistance value measured in the field is read from this curve. This makes it possible to estimate the breathing rate without directly measuring the breathing rate for the cast concrete on site.

Table 1.

  After the concrete is placed, vacuum dehydration is performed in a state where the breathing rate is 70 to 90%. Specifically, a vacuum processing mat is put on the concrete surface, and the lower surface of the mat is decompressed by a vacuum pump. The mat includes an airtight cover having an upper surface connected to a vacuum pipe and a filter medium on the lower surface of the airtight cover, and the vacuum pipe is connected to a vacuum pump and a water separator. In use, the lower surface side of the mat is covered with the concrete surface, and the gap between the lower surface of the mat and the concrete surface is reduced by a vacuum pump. The degree of vacuum is 50 to 85%, more preferably 60 to 85%. Moreover, processing time is 1 to 15 minutes, More preferably, it is 3 to 10 minutes irrespective of the thickness of concrete.

  The mat is used with a filter medium attached thereto. For this filter medium, for example, a cement particle impervious high-density fabric woven with thermoplastic fibers described in Japanese Patent No. 3254079 is used. It is preferable to use it. In particular, a high-density fabric woven with thermoplastic fibers and thermocompression-bonded on at least one side thereof, or this high-density fabric as a filter layer, and a non-woven fabric as a water-permeable layer with an adhesive on the back side for easy water flow and ventilation It is preferable to use a laminated fabric bonded together as a filter medium.

  The vacuum dehydration process is preferably performed while applying vibration to the vacuum processing mat by the vibration generating means. As a result of improving the adhesion of the vacuum processing mat to the concrete surface and obtaining a stable degree of vacuum, it is possible to increase the amount of dewatering and to uniformly dewater the concrete surface. When there are variations in concrete properties such as construction sites (for example, solar radiation after placing, tightening of concrete due to wind, etc., variation in surface dryness, variation in slumps from batch to batch, etc.) The degree of adhesion may be insufficient. However, by applying vibration to the vacuum processing mat, the vacuum processing mat can be brought into close contact with the concrete regardless of variations in the properties of the concrete.

  Here, the vibration generating means is not particularly limited as long as it can apply vibration from the upper part of the vacuum processing mat, but it is preferable to use a vibrator float. Vibrator float is a float attached to a float that is used to flatten the surface of the concrete. By moving this to the front, back, left, and right, vibration is applied to the concrete so that the mat for vacuum treatment adheres to the concrete. Can do. A frequency of 1000 to 15000 times / minute can be used. Since the breathing rate is 70 to 90% and used under vacuum dehydration, the concrete is not softened by vibration of the vibrator float.

  Since the vacuum dehydration process is performed after surplus water floats and accumulates on the surface layer after placing the concrete, the dehydration process for suction drainage can be performed efficiently in a short time. And since the excess water has been removed by this vacuum dehydration treatment, when applying the coating material, the swelling of the coating film due to the residual moisture of the concrete, and the pinholes and dents of the coating film due to large internal bubbles are reduced, A smooth and excellent surface coating can be formed.

  As the synthetic resin emulsion sprayed on the concrete surface after the vacuum dehydration treatment, emulsions such as acrylic, styrene butadiene rubber, ethylene vinyl acetate, vinyl acetate vinyl chloride, epoxy, and urethane can be used. This synthetic resin emulsion forms a resin concrete layer on the concrete surface and shields the concrete surface layer from the outside air, thereby enabling water curing of the concrete surface layer. Moreover, the adhesive force with the coating material coated on the surface is increased.

The amount of the synthetic resin emulsion sprayed is suitably about ²⁰ to 150 g / m ² in terms of resin solids. When the resin solid content is less than 20 g / m ² , the resin content of the resin concrete layer is insufficient, so that the water retention effect cannot be obtained and the strength of the surface layer is lowered. If the resin solid content is more than 150 g / m ² , as a result, the water in the emulsion increases to the concrete surface layer, and the resin-containing concrete layer is soft and difficult to dry, resulting in poor finished appearance and workability. Incurs a decline.

  After spraying the synthetic resin emulsion, apply the coating material. The coating material is a coating liquid in which a non-solvent, solvent-based, water-based or emulsion-based room temperature curable resin is used as a base material, and an appropriate pigment or dye is blended therewith. Illustratively, coating materials such as epoxy, acrylic, polyester, acrylic solvent, aqueous acrylic, and vinyl chloride can be used. Moreover, it is preferable to apply a primer prior to the coating material. The adhesive strength / peeling strength and abrasion resistance of the coating film can be further improved. As the primer, a diluted solution obtained by appropriately diluting the coating solution for the coating material can be used.

  According to this embodiment, the concrete subjected to vacuum dehydration has a rapid onset of strength, and the concrete surface and the surface layer, which are the bonding interface, are low-moisture and densified. Even during construction, for example, within 2 weeks, strong adhesion and a beautiful appearance can be obtained.

The concrete used in the following examples and comparative examples is cement 285 kg / m ³ , water 185 kg / m ³ , fine aggregate 914 kg / m ³ , coarse aggregate 918 kg / m ³ and AE agent 0.914 kg / m ³ ( The mixture was formulated with a water cement ratio of 65% and a nominal strength of 20 MPa and a slump of 18 cm.

[Example 1]
After placing the above concrete to a thickness of 15 cm, compacting with a vibrator, leveling with a mallet, and after the breathing rate reaches 75%, a vacuum processing mat is placed on the concrete surface and a vacuum pump is used. The bottom surface of the mat was depressurized and held under reduced pressure for 5 minutes. The dehydration rate was 14.9%. Here, the value estimated from the penetration resistance value measured by the penetration resistance test and the breathing rate-penetration resistance value curve is used for the breathing rate, and the results are shown in Table 2. Immediately after the vacuum dehydration treatment, an acrylic emulsion (BF coat, manufactured by Meiko Kensho) was sprayed at a solid content of 100 g / cm ² , and then the surface layer was made into resin concrete using a wooden mallet and a hammer to smooth the surface. .

  Next, this concrete was cured for 7 days under indoor drying curing conditions, and then each synthetic resin coating material was applied to the surface. As the synthetic resin coating material, epoxy-based, acrylic solvent-based and acrylic water-based coating materials were selected.

Epoxy-based paint is applied with 150g / m ^{2 of} epoxy primer (Daido Paint Co., Ltd., product name Yucacrete impregnated primer) on the concrete surface after curing and curing, and paint material (Daido Paint Co., Ltd.) 3 hours later. Product name Yucacrete tile 70) was applied to a thickness of 2 mm and allowed to dry naturally.

Similarly, the acrylic solvent-based coating material is 200 g / m ² , using as a primer a diluent obtained by adding 30 parts by weight of a predetermined thinner to 100 parts by weight of an acrylic solvent-based paint (manufactured by Daido Paint Co., Ltd., product name: BOJIN COAT). 5 hours later, a coating material prepared by adding 10 parts by weight of the thinner to 100 parts by weight of the paint was applied at 250 g / m ² and allowed to dry naturally.

The acrylic water-based coating material was applied at 100 g / m ² with 100 parts by weight of an acrylic water-based paint (manufactured by Daido Paint Co., Ltd., product name water-based Bojin Coat) as a primer, with a diluted solution of 50 parts by weight of tap water, After 5 hours, 350 g / m ^{2 of the} paint was applied as a coating material and allowed to dry naturally.

[Example 2]
The test was performed under the same conditions as in Example 1 except that the vacuum dehydration process was performed after the breathing rate reached 90%. The dehydration rate was 14.3%. The results of the penetration resistance test are shown in Table 2.

Example 3
The test was performed under the same conditions as in Example 1 except that the vacuum dehydration process was performed while applying vibration to the vacuum processing mat using a vibrator float. The dehydration rate was 15.2%. The results of the penetration resistance test are shown in Table 2.

[Comparative Example 1]
The test was performed under the same conditions as in Example 1 except that the vacuum dehydration process was performed after the breathing rate reached 100%. The dehydration rate was 2.3%. The results of the penetration resistance test are shown in Table 2.

[Comparative Example 2]
When the breathing rate is less than 70%, it is impossible to work on the cast concrete. The test was performed under the same conditions as in Example 1 except that the penetration resistance test and vacuum dehydration were not performed.

ここで、脱水率は、（排水量／練り混ぜ水）×１００（％）で規定される。 Table 2.

Here, the dehydration rate is defined by (drainage / mixed water) × 100 (%).

  The concrete on which the surface coating film was formed as described above was measured for adhesive strength and impact strength 14 days after the coating material was applied. The bond strength test method is as follows. Concrete is cut into a grid of 4 x 4 cm to the depth that reaches the concrete, including the coating material, and a test jig is attached to the coating material in the grid. This was carried out in the manner of measuring the vertical tensile strength using a polishing type adhesion tester. The impact strength test was carried out by dropping a 1 kg formed weight onto a painted concrete surface from a height of 1.5 m in accordance with the test method of JIS A5403.

  The adhesive strength test results are shown in Table 3. In Examples 1, 2 and 3, a higher adhesive force was obtained on the concrete surface than Comparative Examples 1 and 2. The finishing method of the comparative example has a low adhesive strength of the paint film, but this is because the strength of the concrete surface layer is low because the breathing water on the concrete surface is not removed.

Table 3.

  The impact strength test results are shown in Table 4. It can be seen that the dent depth due to the impact of the coating film formed by the finishing method of Example 1 is greatly improved as compared with the comparative example. In the case of using acrylic water-based paint, there was a part that caused interface fracture in the adhesive strength test. This is because some paint was filtered and the adhesive strength was secured to the inside of the concrete. It is thought that there is not. Even in this case, the pulverization phenomenon was not recognized in the concrete surface layer part on the back surface of the peeled coating film.

Table 4.

  In the method of the comparative example, floating was observed in the coating film of all the coating materials due to impact, and a powdered cement mixture due to buckling collapse of the concrete surface layer portion was observed on the back side of the floating coating film, and the dent depth was The diameter of the recess was also larger than that of the example.

  As described above, according to the present invention, since the vacuum dehydration treatment is performed after the breathing rate reaches 70 to 90%, and then the curing is performed, the strength is obtained in a shorter period of time, for example, within two weeks. It is done. Thereby, the coating material can be applied at an early stage, and the construction period can be shortened. In addition, the coating material maintains a stable adhesive force for a long period of time, can eliminate surface peeling and collapse phenomenon due to impact, etc., and can form a beautiful and durable floor surface with high quality. . Thereby, the period during which the wear resistance of the coating material coating film can be maintained becomes the maintenance period for the floor as it is, and this maintenance period can be further extended by selecting a coating material with good wear resistance.

It is an example of the graph which shows the relationship between a breathing rate and penetration resistance value used for estimation of a breathing rate in this invention.

Claims (4)

  A concrete surface finishing method in which concrete is cast, a vacuum treatment mat is coated on the concrete surface after the breathing rate reaches 70 to 90%, vacuum dehydration treatment is performed, and curing is then performed.   The concrete surface finishing method according to claim 1, wherein the vacuum dehydration process is performed while applying vibration to the vacuum processing mat by a vibration generating means.   Prior to the curing, the concrete surface finishing method according to claim 1 or 2, wherein a synthetic resin emulsion is sprayed on the surface of the uncured concrete to form a resin concrete layer that has been surface-finished by pressing. The degree of hardening of the cast concrete is measured by a proctor penetration resistance test, and the breathing rate is estimated based on the relationship between the breathing rate and the penetration resistance value obtained in advance. Concrete surface finishing method.

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