JP2009242118A - Steel fiber-reinforced mortar with fiber oriented - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method to efficiently perform the orientation of short fibers in short fiber-reinforced mortar, and to provide the mortar with the short fibers oriented obtained by the method. <P>SOLUTION: Steel fibers in the mortar are oriented by reciprocating a magnet in a fixed direction at the neighborhood of the surface of the mortar after placing steel-fiber reinforced mortar. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forming a steel fiber reinforced mortar in which fibers are oriented by magnetic force, and a steel fiber reinforced mortar structure formed by this method.

  Conventionally, short fiber reinforced mortar has been used for the purpose of improving brittle fracture, preventing cracking and increasing tensile strength. This is because the short fibers are mixed and kneaded into the mortar and the short fibers are three-dimensionally randomly oriented, thereby improving the mechanical properties of the mortar such as bending strength, tensile strength, bending toughness and impact resistance. Examples of the short fibers to be mixed include inorganic fibers such as glass fibers and carbon fibers, short fibers of organic fibers such as vinylon fibers, polypropylene fibers, and aramid fibers, and short fibers of metal fibers such as steel fibers (for example, Patent Documents 1 to 3) is known. By applying this to outer shell precast concrete products, outer wall repair mortar, etc., it is expected to improve the durability and earthquake resistance of concrete structures. However, the method of mixing short fibers has a problem that variation in mechanical characteristics increases when the mixed state of the mixed short fibers becomes non-uniform.

Japanese Unexamined Patent Publication No. 6-115988 Japanese National Patent Publication No. 9-500352 JP-A-11-246255

  As described above, mortar is widely used as an outer shell precast concrete product, an outer wall repair material, and the like, but cracks generated in the mortar tend to occur in a specific direction in a specific part of the building. For this reason, the location where mortar cracks are likely to occur and the direction of cracks at those locations can be predicted to some extent from the structure of the building. To cope with this, when short fiber reinforced mortar is used as a wall material, etc., the short fibers are oriented at right angles to the direction where cracks are expected to occur at the places where cracks are expected to occur. Do it. Conventionally, when short fibers are mixed in mortar or the like, it is difficult to uniformly disperse and mix the short fibers in the mortar, and there is a problem that fluidity is reduced due to the mixing of the short fibers. Various technologies have been developed, but there are few studies on the directionality of mixed short fibers. Until now, as a method for orienting short fibers, a method has been attempted in which parallel partition plates are densely arranged, short fiber reinforced concrete is poured into this gap and oriented by applying vibration or centrifugal force. . The present inventors have also examined such vibrations and pouring directions, but have not obtained sufficiently satisfactory results. If the orientation of the short fibers can be performed in any predetermined direction, the mortar can be efficiently prevented from cracking, and the durability and earthquake resistance of the mortar structure can be improved.

  Accordingly, an object of the present invention is to provide a method for efficiently orienting short fibers in a short fiber reinforced mortar and an oriented mortar of the short fibers obtained thereby.

  The present inventors have intensively studied to solve these problems. As a result, steel fibers are used as short fibers, mixed with mortar, kneaded, and coated with mortar mixed with steel fibers. Or after pouring into the mold, reciprocating the magnet in a certain direction in the vicinity of the mortar surface, it is possible to orient the steel fibers in the vicinity of the surface that is more tensioned in the mortar. It was found that the strength of the steel was maintained and the toughness was improved. The present invention has been made based on such findings.

  That is, the present invention relates to a method of forming a steel fiber reinforced mortar containing oriented steel fibers, wherein a steel fiber reinforced mortar is placed and then a magnet is reciprocated in a certain direction near the surface of the mortar. .

  The present invention also relates to a steel fiber reinforced mortar structure including oriented steel fibers formed by the above method.

  In the method, the placing includes application of steel fiber mortar, spraying, and pouring into a mold. Further, the method for forming a steel fiber reinforced mortar containing oriented steel fibers of the present invention and the steel fiber reinforced mortar material used in the steel fiber reinforced mortar structure formed by this method are well known or known methods and materials. It may be formed using. That is, the cement, fine aggregate, compounding agent, and the like used may be any conventionally known one, and the compounding amount and water compounding amount may be any as long as they are within the conventionally known range. Things may be used. The length, width or diameter, shape, and material of the steel fiber may be any as long as they are within a conventionally known range. For example, as a conventional steel fiber, one having a length of 20 to 80 mm and a nominal diameter of about 0.3 to 0.8 mm is generally used. Further, the placement method may be the same as the conventional method.

  In the present invention, a magnet is used to orient the steel fibers, but any magnet may be used as long as it can apply a magnetic force to the steel fibers in the mortar material such as a permanent magnet and an electromagnet. The stronger the magnetic force applied to the steel fibers, the stronger the tendency of orientation, but if it is too strong, depending on the viscosity of the mortar, the mixed steel fibers are attracted in the direction of the magnet and aggregate to cause orientation and dispersibility. Since it tends to decrease, the maximum magnetic flux density on the mortar surface is preferably about 60 mT. Furthermore, the degree of orientation is also affected by the moving speed of the magnet and the number of reciprocations. The slower the moving speed of the magnet, the stronger the tendency of the steel fibers to be oriented. However, when the magnet speed is too slow, the mixed steel fibers are attracted in the direction of the magnets, and the tendency of the orientation to deteriorate due to aggregation. If the moving speed is increased too much, the steel fibers will not be oriented. For this reason, although the moving speed of a normal magnet changes with magnetic force of a magnet, ie, the magnetic flux density of the mortar surface, and other conditions, it is usually preferable to set it as about 5-10 cm / s. On the other hand, if the number of reciprocations of the magnet is small, the orientation is difficult, but if it is increased, the degree of orientation does not improve as much as the number of times is increased. The number of reciprocations of the magnet is also affected by the magnetic force of the magnet, but is generally preferably about 4 to 8 times. Furthermore, the orientation of the steel fibers in the mortar is also affected by the viscosity of the mortar in which the steel fibers are mixed and the amount of the steel fibers mixed. When the viscosity of the mortar mixed with the steel fibers is low, the orientation tendency increases, but the tendency of the steel fibers to be attracted by the magnet also increases. On the other hand, when the viscosity is high, the orientation of the steel fibers becomes difficult. Therefore, the viscosity of the mortar is usually preferably about 0.085 to 0.161 Pa · s, and the mixing amount of steel fibers is preferably about 0.5 to 1.5%. In addition, the fiber length is somewhat affected. Thus, the orientation of the steel fiber is influenced by the magnitude of the magnetic force, the moving speed of the magnet, the number of reciprocations of the magnet, the mortar viscosity, the mixing amount of the steel fiber, and the like. Therefore, the orientation of the steel fiber reinforced mortar of the present invention may be possible because the orientation of the steel fiber may be possible depending on other conditions. The preferable range of the above conditions in the forming method is not necessarily limited to the above specific conditions.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described more specifically below.
In the present invention, even if steel fibers are mixed in the mortar and the steel fibers are oriented by reciprocating the magnet, it is possible to directly confirm how the steel fibers behave and are oriented in the mortar. difficult. For this reason, first, a model experiment using a transparent pseudo mortar was conducted to examine the effects of various conditions such as the strength of the magnetic force, the moving speed of the magnet, the number of reciprocations, the viscosity of the mortar, and the amount of steel fibers mixed on the orientation of the steel fibers. confirmed. Hereinafter, the model experiment will be specifically described by the following [Experiment 1] and [Experiment 2]. In [Experiment 1], the orientation of one steel fiber is confirmed, and based on this experiment, [Experiment 2] Then, the orientation was confirmed with a normal steel fiber mixing amount.

[Experiment 1]
In Experiment 1, the materials shown in Table 1 below were used.

  In Table 1, as the superabsorbent resin, Sunfresh ST-500MPS (manufactured by Sanyo Chemical Industries, Ltd.) was used. The viscosity of the aqueous resin solution is approximately linearly proportional to the concentration. The magnet is a ferrite magnet having a size of 40 mm × 40 mm × 10 mm, the attraction force is 2 kg, and the maximum magnetic flux density is 130 mT.

  The experiment was performed using the apparatus shown in FIG. In the apparatus of FIG. 1, a magnet is fixed on a belt conveyor, and the bottom surface of the transparent case is disposed at a position 10 mm from the upper end surface of the magnet. FIG. 2 is an explanatory view for explaining a method of measuring the angle of the steel fiber disposed in the resin, FIG. 3 is a cross-sectional view of the transparent case portion where the steel fiber is disposed, and FIG. 4 is a plan view of the transparent case portion. FIG.

  In this experiment, first, a superabsorbent resin was placed in a transparent case, and hot water was poured into the transparent case to dissolve the superabsorbent resin, thereby preparing a liquid plastic viscosity: η = 0.16. And as shown in FIG. 1, the transparent case which arrange | positions a magnet on a belt conveyor and accommodates a superabsorbent resin solution in the position which maintained this magnet and the fixed distance (distance between a case internal bottom face and a magnet: 10 mm). Arranged. In the resin of the transparent case, as shown in FIG. 3, two steel fibers (length 30 mm, with hooks on both ends) are placed at a height of 0, 10, 20, and 30 mm from the bottom of the transparent case, parallel to the bottom. In addition, the steel fibers were arranged at two levels of 45 ° and 90 ° with respect to the moving direction of the magnet. In this state, the magnet was reciprocated five times at various speeds by moving the belt conveyor, and the change in the angle of the fiber was evaluated. The experiment was performed by changing the maximum magnetic flux density of the magnet, the moving speed of the magnet, the distance between the magnet fibers, the initial fiber angle, and the number of reciprocations of the magnet as shown in Table 2 (level) below. After performing the orientation treatment by magnetic force, the angle formed by the magnet traveling direction and the steel fiber was measured to obtain a measurement angle. Therefore, the measurement angle is not the change angle of the steel fiber. The measurement angle was the average value of the measurement angles of the two steel fibers under the same conditions. Note that the maximum magnetic flux density (B = 183, 203, 224, 232) of the magnetism imparting surface of the magnet was changed by changing the number of magnets used to 1 to 4. At this time, the maximum magnetic flux density on the pseudo mortar surface (bottom surface) was about 52 mT, respectively.

  The result of the experiment (result after reciprocating the magnet 5 times) is shown in FIG. FIG. 5 is a diagram showing the measurement angle of the steel fiber with respect to the moving speed (cm / s) of the magnet for each magnetic flux density of the magnet. When the measuring angle becomes zero, the steel fiber is oriented in the moving direction of the magnet. It shows that. FIG. 5 (a) shows the orientation effect when the maximum magnetic flux density is 183 mT, but no change in angle was observed for magnet-fiber distances of 20, 30, and 40 mm (ie, no orientation occurred). ) When the moving speed of the magnet was increased, the measurement angle was a value close to the original angle or the original angle even in the case of 10 mm, and the orientation effect was inferior. FIG. 5B shows the experimental results when the maximum magnetic flux density is 203 mT. From FIG. 5B, when the initial angle is 90 °, the magnet fiber distance is 40 mm. Although no change in angle is observed regardless of the moving speed, when the initial angle is 45 °, the change in angle is observed depending on the moving speed of the magnet when the distance between the magnet fibers is 30 mm or less. When it is 10 mm, it can be seen that the steel fibers are substantially oriented in the magnet moving direction, regardless of the initial angle and the moving speed of the magnet. Further, from FIGS. 5 (c) and 5 (d), it can be seen that the orientation tendency of this steel fiber becomes larger as the maximum magnetic flux density further increases.

  From the results of this experiment, it was confirmed that the fiber was more easily oriented in the direction of travel of the magnet as the magnetic force was higher and the moving speed was slower. Furthermore, in this experiment, it was confirmed that when the traveling direction and the fiber were almost parallel, the resistance to the pseudo mortar was greatly reduced, attracted by magnetic attraction, and started moving not only in the angle change but also in the magnet traveling direction. It was done. The greater the angle formed by the magnet traveling direction and the steel fiber, the greater the resistance when orienting in the traveling direction. In particular, in the case of 90 °, the rotational direction of the angle change is not determined and the resistance is considerably large. For this reason, the initial angle of 45 ° is easier to align than the initial angle of 90 °. Even in the experiment of the initial angle of 90 °, the resistance decreases and the amount of change in the angle increases when the initial orientation begins in the magnet traveling direction. For this reason, it can be understood that the orientation is further improved as the number of reciprocations increases. Further, the orientation effect was higher as the moving speed of the magnet was slower. However, in the case of being too slow, for example, at 5 cm / s, it is considered that the fiber loses dispersibility and aggregates. For this reason, the application rate of magnetic force is suitably about 5 cm / s or more and about 20 cm / s, and more preferably about 10 cm / s.

[Experiment 2]
In the experiment 1, an experiment using only two steel fibers was performed at each of the distances of 10, 20, 30, and 40 mm between the magnet fibers, and it was confirmed that the steel fibers could be oriented. In an actual short fiber reinforced mortar, In general, about 1% or 2% of fibers are mixed. Therefore, an experiment in which steel fibers are further mixed with 0.5%, 1.0%, and 1.5% of the superabsorbent resin using the apparatus shown in FIG. The effect of the amount of steel fibers mixed was investigated. In this experiment, the liquid plastic viscosity was 0.06 in addition to 0.16, and the moving speed of the magnet was 10 cm / s and 20 cm / s. The effect of the number of reciprocations of the magnet was also observed. Furthermore, the maximum magnetic flux density of the magnet was 232 mT. From this experiment, when the fiber amount is 1.5%, since the fiber amount is large, the fibers are sterically constrained even in the 16th reciprocation and hardly oriented, and the low viscosity created within the viscosity range of the mortar. In the pseudo mortar (η = 0.06), the fibers sunk and aggregated to deteriorate the orientation. When the fiber amount was 0.5%, the fibers were likely to sink, but they were more easily oriented than 1.0% and 1.5%, and were oriented substantially in the direction of travel with the application of a magnetic force at the fourth round.

  From the above experiments 1 and 2, since it was confirmed that the steel fibers could be oriented by the magnetic force in the steel fiber reinforced mortar, the orientation of the steel fibers in the mortar and the effect thereof were further confirmed. Table 3 shows materials used in Experiment 3.

[Experiment 3]
A mortar specimen (40 mm × 40 mm × 160 mm) was prepared under the conditions shown in the formulation table shown in Table 4 below, and then the basic mechanical properties were evaluated using the three-point one-point loading bending test apparatus shown in FIG. The test specimens were 9 specimens each including 3 specimens with no fiber orientation, a specimen with a fiber amount of 0.5% and no fiber orientation, and a specimen with a fiber orientation of 0.5% and a fiber orientation. Produced. The curing was a sealed curing in 7 days.

The mortar was kneaded in the following order and time.
Dispose kneading cement and fine aggregate and knead 1 minute Add water with admixture and knead 4.5 minutes Further kneading (mixed here if fiber is present) 2 minutes

  Placed after completion of mixing. For orientation, magnetism was applied after casting. The flow measurement was performed at the same time as the placement, and the test specimen containing the fiber was measured immediately before the fiber was mixed. Further, in order to prevent unintended fiber settlement, the test was not performed including the test piece without fiber mixing, and tapping was performed 12 times, 5 times from the lateral side surface and 1 time from the axial side surface. Viscosity was measured with plain mortar without fiber mixing at the casting stage.

  The test body mold was made of an acrylic mold having a thickness of 10 mm, the speed was adjusted by a belt conveyor from the lower surface, the side of the magnet was brought into contact with acrylic, and magnetism was imparted horizontally to the mold. From Experiments 1 and 2, the conditions relating to magnetism were set such that the moving speed was 10 [cm / s], the maximum magnetic flux density on the applied surface was 232 mT, and the number of reciprocations was 4. The moving speed was set to 10 cm / s to prevent a decrease in dispersibility, and the number of reciprocations was about 4 in Experiment 1, and no significant difference was observed in the orientation effect. Four round trips were made to minimize the difference. The magnetism was applied early after kneading, and was set within 20 minutes.

  In addition, in the experiment with a fiber amount of 0.5%, a specimen with a small number of fibers on the fractured surface was found, and the number of fibers on the cut surface was highly variable, so the fiber amount was set to clarify the effect of steel fibers. A specimen with 1.0% was also produced under the same conditions as the fiber amount of 0.5%. Table 5 shows the composition of a test specimen having a fiber amount of 1.0%. Considering that it is difficult to orient due to the large amount of fibers, the number of reciprocations was set to eight.

  The flow characteristics of the test specimen were measured using a flow table. The measurement results are shown in Table 5 (the number in the table is the flow table vibration frequency). Moreover, the bending test of the test body was performed by a three-point type one-point loading using the apparatus shown in FIG. At that time, while measuring the load and the deflection with a data logger, it was measured at main timing such as when the load was greatly reduced, and at intervals of 5 seconds. The results of the bending test are shown in FIG. 7 (fiber amount 0.5%) and FIG. 8 (fiber amount 1.0%).

  From the measurement results of the load deformation curve by the bending test at the age of 7 days in FIGS. 7 and 8, the influence of the presence or absence of fibers and the presence or absence of orientation is not seen until the occurrence of bending cracks, and the history of the load deformation curve is almost Although it overlaps, after that, the influence by the presence or absence of a fiber and the presence or absence of an orientation comes out. From FIG. 7 and FIG. 8, it was confirmed that the strength with the maximum load transfer was maintained as compared with the case where the orientation was not present, and it was confirmed that the toughness was improved by the fiber orientation due to the magnetic force.

[The invention's effect]
As is clear from the above, the orientation of the steel fibers in the steel fiber reinforced mortar can be performed by reciprocating the magnet in a predetermined direction, thereby enhancing the toughness against cracking of the mortar, and the mortar structure Can improve durability and earthquake resistance.

It is a schematic diagram of an orientation experiment apparatus. It is a figure which shows the angle measuring method of steel fiber. It is sectional drawing of the case part of the experimental apparatus of FIG. It is a top view of the case part of the experimental apparatus of FIG. It is a figure which shows the magnetic orientation processing result in a pseudo mortar. It is a schematic diagram of the bending test apparatus of a test body. It is a graph which shows the result of the bending test of the test body of fiber mixing amount 0.5%. It is a graph which shows the result of the bending test of the test body of 1% of fiber mixing amount.

Claims (8)

  A method of forming a steel fiber reinforced mortar containing oriented steel fibers, wherein the steel fiber reinforced mortar is cast and then a magnet is reciprocated in a certain direction near the surface of the mortar.   The method for forming a steel fiber reinforced mortar containing oriented steel fibers according to claim 1, wherein the placing includes applying, spraying or pouring steel fiber mortar into a formwork.   The method of forming a steel fiber reinforced mortar containing oriented steel fibers according to claim 1 or 2, wherein the magnetic force by the magnet is about 60 mT at the maximum on the mortar surface.   The method for forming a steel fiber reinforced mortar containing oriented steel fibers according to any one of claims 1 to 3, wherein the moving speed of the magnet is 5 to 10 cm / s.   The method for forming a steel fiber reinforced mortar containing oriented steel fibers according to any one of claims 1 to 4, wherein the number of reciprocations of the magnet is 4 to 8.   The steel fiber reinforced mortar containing oriented steel fibers according to any one of claims 1 to 5, wherein a viscosity of the mortar mixed with the steel fibers is 0.085 to 0.161 Pa · s. how to.   The method for forming a steel fiber reinforced mortar containing oriented steel fibers according to any one of claims 1 to 6, wherein the mixing amount of the steel fibers is 0.5 to 1.5%.   A steel fiber reinforced mortar structure comprising oriented steel fibers formed by the method according to claim 1.

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