JP2020050579A - Coarse aggregate for concrete - Google Patents

Abstract

To provide a coarse aggregate which can improve not only the compressive strength but also the tensile strength of concrete and can be obtained with good productivity at low cost.SOLUTION: A coarse aggregate for concrete 10A is made of metal, and metal droplets formed from melted metal are deposited on its surface. The coarse aggregate preferably has a shape of a column having a predetermined length with both ends crushed and the thickness of the column increases from each end toward its central area. The coarse aggregate can be of substantially tetrahedron shape 10A or of the shape 10D in which tetrahedrons are joined by sides 13a. It can be in a shape where two or more recesses that dent towards the center and projections that face the dents are formed with regard to its contour of its plan view; it can also be in shape 10E which has two or more projections 16 that protrude from the central area 14 toward the contour L1 and the tops of projections 16 are on the same plane, and the thickness of the central area 14 is larger than that of the edge of recesses 15 and or than that of the tops of projections 16.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coarse aggregate for concrete, a method for producing the same, and concrete using the same.

  Concrete is usually prepared by mixing water, coarse aggregate (crushed stone or gravel) and fine aggregate (sand) in cement, and mixing the mixture (so-called ready-mixed concrete) based on the hydration reaction between water and cement. It has the advantage of exhibiting a very high compressive strength as a building material, but has a tensile strength of 1/10 to 1/13 of the compressive strength, which is extremely lower than the compressive strength. Has disadvantages.

  In order to compensate for such a drawback, it is common to arrange reinforcing bars assembled in a matrix in a vertical and horizontal matrix in concrete, but recently, propylene fibers (Patent Document 1), organic fibers and irregular Including reinforcing fibers such as steel fibers (Patent Literature 2), using coarse aggregates manufactured in a rugged chestnut shape (Patent Literature 3), three-dimensionally radially projecting coarse aggregates (Patent Document 4) and the like have been proposed.

JP 2017-178755 A JP 2001-220201 A U.S. Pat. No. 3,846,085 JP 2006-527175 A

  However, when reinforcing fibers are mixed into ready-mixed concrete, the reinforcing fibers may not be uniformly dispersed throughout and may agglomerate, and various strengths of the concrete structure may vary from place to place. There is a problem that stress is concentrated on the concrete and cracks are easily generated in the concrete. In addition, since reinforcing fibers are not a common essential component of conventional concrete, there is a concern that the use of the reinforcing fibers makes it difficult to adjust the composition of the essential components of concrete and to adjust the properties of concrete.

  Therefore, instead of reinforcing with fibers other than the essential components of concrete, a coarse aggregate, which is one of the essential components of concrete, is required to be capable of improving not only the compressive strength but also the tensile strength of concrete. Have been.

  On the other hand, since coarse aggregate accounts for about 35 to 45 vol% of the compounding component of concrete, it is necessary to obtain it with good productivity and low cost as a building material. Coarse aggregate having a chestnut shape or a shape in which legs are projected three-dimensionally radially takes time and effort to manufacture, resulting in poor productivity and cannot be obtained at low cost.

  An object of the present invention is to provide a coarse aggregate capable of improving not only the compressive strength but also the tensile strength of concrete at a high productivity and at a low cost with respect to the above-mentioned problems of the conventional technology.

  The present inventor has found that a metal coarse aggregate having a size similar to that of a conventional coarse aggregate can achieve the above-mentioned object by adhering molten metal droplets to the surface thereof, and completed the present invention. It led to.

  That is, the present invention provides a coarse aggregate for metal concrete, which provides a coarse aggregate in which metal particles are welded to the surface by molten metal droplets, in particular, an embodiment in which the coarse aggregate is a ferromagnetic material. The present invention provides an aspect in which the coarse aggregate has a shape in which both ends of a columnar body having a predetermined length are crushed, and the thickness increases from each of the both ends toward the center.

  The present invention also relates to a method for producing a coarse aggregate for concrete made of metal, wherein molten metal droplets generated from the electrode by performing arc discharge using an electrode on the surface of the metal constituting the coarse aggregate. Is provided.

  In addition, the present invention provides a concrete containing at least cement, fine aggregate, and coarse aggregate for concrete as described above.

  Further, the present invention provides a method for transporting a precast concrete product containing the coarse aggregate, wherein the coarse aggregate for concrete is a magnetic material having the above-mentioned shape, wherein the electromagnet is actuated. The present invention provides a method for transporting a precast concrete product to a predetermined location by releasing the electromagnet and transporting the precast concrete product to a predetermined location.

  Since the metal coarse aggregate for concrete of the present invention has molten metal droplets adhered to the surface, the tensile strength of concrete is lower than that of coarse aggregate of the same shape having no molten metal droplets adhered to the surface. Dramatically improved. The molten metal droplet on the surface of the coarse aggregate can be efficiently and inexpensively formed on the surface of the metal constituting the coarse aggregate by performing arc discharge using an electrode.

  In particular, when this coarse aggregate has a shape in which both ends of a columnar body of a predetermined length are crushed and the thickness increases from each of the both ends toward the center, an anchor portion is provided at both ends or the center. Since it functions, the coarse aggregate is less likely to move with respect to the tensile force applied to the concrete, and it is possible to suppress the occurrence of microcracks at the interface between the coarse aggregate and the mortar. For this reason, the tensile strength of concrete can be remarkably improved as compared with the conventional coarse aggregate such as crushed stone and gravel.

  The coarse aggregate having such a shape can be easily and inexpensively manufactured by pressing a metal.

  Furthermore, when the coarse aggregate for concrete of the present invention is a magnetic material, a precast concrete product containing the coarse aggregate can be easily transported using an electromagnet, and can be easily installed in a building or the like. Become.

  Since the coarse aggregate for concrete of the present invention can be formed in the same size as the conventional coarse aggregate, it can be pumped from a concrete mixer to a casting place when mixed with ready-mixed concrete.

FIG. 1 is a perspective view of a coarse aggregate for concrete 10A of the present invention. FIG. 2 is a top view of the coarse aggregate for concrete 10A of the present invention. FIG. 3 is a side view of the coarse aggregate for concrete 10A of the present invention. FIG. 4 is a perspective view of the coarse aggregate for concrete 10B of the present invention. FIG. 5 is a perspective view of the coarse aggregate for concrete 10C of the present invention. FIG. 6 is a perspective view of the coarse aggregate for concrete 10D of the present invention. FIG. 7A is a perspective view of a concrete coarse aggregate 10E of the present invention. FIG. 7B is a plan view of the coarse aggregate for concrete 10E of the present invention. FIG. 7C is a side view of the coarse aggregate for concrete 10E of the present invention. FIG. 8 is a perspective view of the coarse aggregate for concrete 10F of the present invention. FIG. 9A is a perspective view of a coarse aggregate for concrete 10G of the present invention. FIG. 9B is a plan view of the coarse aggregate for concrete 10G of the present invention. FIG. 9C is a side view (A arrow view) of the coarse aggregate for concrete 10G of the present invention. FIG. 9D is a side view (B arrow view) of the coarse aggregate for concrete 10G of the present invention. Drawing 10 is a manufacturing process figure of coarse aggregate 10G for concrete of the present invention. FIG. 11 is a perspective view of the coarse aggregate for concrete 10H of the present invention. FIG. 12A is a perspective view of the coarse aggregate for concrete 10I of the present invention. FIG. 12B is a side view of the coarse aggregate for concrete 10I of the present invention. FIG. 13A is a perspective view of the coarse aggregate for concrete 10J of the present invention. FIG. 13B is a side view of the coarse aggregate for concrete 10J of the present invention. FIG. 14A is a perspective view of a coarse aggregate for concrete 10K of the present invention. FIG. 14B is a side view of the concrete coarse aggregate 10K of the present invention. FIG. 15 is a drawing substitute photograph of the coarse aggregate for concrete of the present invention, the surface of which is roughened by metal particles due to molten metal droplets. FIG. 16 is a drawing substitute photograph of the coarse aggregate used in Example 1. FIG. 17 is a drawing substitute photograph of the coarse aggregate used in Example 2. FIG. 18 is a drawing substitute photograph of the coarse aggregate used in Example 3. FIG. 19 is an explanatory diagram of a method of attaching a molten metal droplet to the metal constituting the coarse aggregate.

    Hereinafter, the coarse aggregate for concrete of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or equivalent components.

(Overview of coarse aggregate)
This is a coarse aggregate for metal made of concrete, characterized in that metal particles due to molten metal droplets are deposited on the surface, whereby the tensile strength of concrete using the coarse aggregate is significantly improved. The effect of improving the tensile strength of concrete by welding metal particles to the surface of the coarse aggregate can be obtained regardless of the shape of the coarse aggregate, but preferably, the shape itself of the coarse aggregate also improves the tensile strength. I do.

Examples of such a shape of the coarse aggregate include a shape in which both ends of a columnar body having a predetermined length are crushed, and the thickness increases from each of the both ends toward the center. In this case, the compressive strength of the concrete is equal to or higher than that of the conventional coarse aggregate such as crushed stone and gravel, and the tensile strength can be significantly improved as compared with the conventional coarse aggregate. That is, the compressive strength (JIS A 1108) of a concrete of a normal mix design used for civil engineering and building construction is 20 to 30 N / mm ² , and the split tensile strength (JIS A 1113) is 1/10 to 1/10 of the compressive strength. It is as low as about 1/13, and the ratio is further reduced in the case of high-strength concrete. However, according to the concrete coarse aggregate of the present invention, the split tensile strength can be made larger than 1/10 of the compressive strength, In the case of a usual blending design, the tensile strength can be made larger than 3 N / mm ² , preferably larger than 4 N / mm ² .

(Size of coarse aggregate)
The size of the coarse aggregate can be as large as the conventional coarse aggregate, such as gravel or crushed stone, to enable pumping of the ready-mixed concrete into which it is blended. Specifically, it is preferable that the particle size and the particle size are in the range specified in JIS A 5308. Usually, the particle diameter is in the range of 5 mm to 25 mm, and the length in the longitudinal direction is about 20 to 50 mm. preferable.

(Coarse aggregate shape)
In the present invention, the shape of the coarse aggregate is not particularly limited, because the effect of improving the tensile strength of concrete by welding the metal particles to the surface of the coarse aggregate can be obtained regardless of the shape of the coarse aggregate. However, since the shape of the coarse aggregate is also preferable to improve the tensile strength of the concrete, the shape of the coarse aggregate is, for example, such that both ends of a columnar body having a predetermined length are crushed, and a center is formed from each of the both ends. The shape is such that the thickness increases toward the part. With this shape, the end portion or the center portion of the coarse aggregate can function as an anchor portion. Here, the pillar may be hollow or solid, and the outer shape of the pillar may be a prism or a cylinder.

  As an example of the coarse aggregate having such a shape, for example, there is a coarse aggregate for concrete 10A shown in FIG. In the coarse aggregate for concrete 10A, both ends 11a and 11b of the cylindrical body are alternately closed, and the thickness of the coarse aggregate gradually increases from the ends 11a and 11b toward the center of the coarse aggregate. And the entire coarse aggregate has a substantially tetrahedral shape. In the coarse aggregate 10A, the ends 11a and 11b function as anchors A1 and A2. That is, as shown in FIG. 2, when a tensile force is applied in the dotted arrow direction B1 in such a shape, the anchor portion A1 is wider than the other end in a top view, The coarse aggregate for concrete 10A is unlikely to be displaced in the direction of the dotted arrow B1, and the occurrence of cracks in the concrete can be suppressed (anchor effect). Also, as shown in FIG. 3, when a tensile force is generated in the direction indicated by the dotted arrow B2, the anchor portion A2 is wider than the other end in a side view. B2 is hardly displaced, and it is possible to suppress the occurrence of cracks in concrete.

  In FIGS. 1 to 3, the case where a tensile force is applied in the longitudinal direction of the coarse aggregate for concrete 10A of the present invention has been described, but the tensile force is applied not only in the longitudinal direction but also in a direction intersecting the longitudinal direction. A similar anchoring effect occurs when this is done.

  In FIG. 1, the side 13a connecting the substantially tetrahedral anchor portions A1 and A2 of the concrete coarse aggregate 10A is represented as a fold, but the coarse aggregate for concrete shown in FIG. The side surface 18 may be configured as a continuous curved surface as in 10B.

  Such coarse aggregates for concrete 10A and 10B are simpler in shape than conventional coarse aggregates in which legs are protruded three-dimensionally in a rugged chestnut shape or three-dimensionally, and are solid and long metal. The columnar body or the hollow and long pipe-shaped metal columnar body is plastically deformed and pressed off by press working to obtain a predetermined length, so that it can be manufactured with good productivity and at low cost.

  The coarse aggregate for concrete of the present invention preferably has a hollow portion. When the hollow portion exists, the specific gravity of the coarse aggregate for concrete can be reduced, so that the weight of the concrete can be reduced. Further, the specific gravity can be adjusted by adjusting the volume ratio of the hollow portion of the coarse aggregate for concrete, and the dispersibility of the coarse aggregate for concrete in the ready-mixed concrete can be improved. Therefore, in terms of specific gravity adjustment, a pipe-shaped metal aggregate is used rather than a solid coarse aggregate formed of a solid rod-shaped metal columnar body for the concrete coarse aggregate 10B having the outer shape shown in FIG. It is preferable to use a coarse aggregate having a hollow portion formed from a columnar body. Further, when the coarse aggregate for concrete 10B is formed from a pipe-shaped metal columnar body, the inside of the coarse aggregate may be completely blocked from the outside at the crushed portions of both end portions 11a and 11b, The inside and the outside of the coarse aggregate may communicate with each other. As a mode in which the inside and the outside of the hollow coarse aggregate communicate with each other, a hole 12 may be provided on a side surface of the hollow coarse aggregate 10C as shown in FIG. The size of the hole 12 is preferably such that mortar slightly penetrates into the hollow portion from the outside of the coarse aggregate 10C. Mortar penetrating into the hollow part also exerts an anchor effect.

  On the other hand, by making the coarse aggregate solid, the compressive strength can be improved, which is preferable as a coarse aggregate for high-strength and ultra-high-strength concrete.

  The outer shape of the coarse aggregate for concrete of the present invention may be a shape in which substantially tetrahedrons are connected to each other by one side 13b as in a coarse aggregate 10D shown in FIG. In the coarse aggregate 10D, the anchor portion A3 is formed at the center in the longitudinal direction, and it is expected that the anchor effect of the coarse aggregate 10D for concrete is further enhanced. When the tetrahedrons on both sides of the anchor part A3 are hollow, these hollow parts may communicate with each other at the anchor part A3 or may be blocked.

  As shown in a coarse aggregate 10E shown in FIGS. 7A and 7B, two or more recesses 15 recessed from the outer line L1 toward the central portion 14 in plan view and a convex portion 16 corresponding to the concave portion 15 or an outer shape from the central portion 14. It has two or more protrusions 16 protruding toward the line, the tips of these protrusions 16 are on the same plane, and the thickness of the central portion 14 is the thickness of the end of the recess 15 or the end of the protrusion 16. The shape may be thicker than that. More specifically, the coarse aggregate 10E for concrete includes a total of four convex portions 16 radially arranged and a total of four convex portions 16 formed between adjacent convex portions 16 in a plan view shown in FIG. 7B. It has a recess 15. Here, the contour line L1 refers to a contour line formed by sequentially connecting the convex portions 16 or the vertices of the convex angles.

  7C, the coarse aggregate 10E has a thickness T1 of the central portion 14 at the end portions 15a on both sides of the concave portion 15, as shown in a side view seen from the concave portion 15 side. It is thicker than the thickness T2 of the end 16a of the convex portion 16. More specifically, the thickness is gradually reduced from the central portion 14 to both ends 15a of the concave portion 15 (that is, from the end portion 16a of the convex portion 16). Therefore, even if a force is applied to move the coarse aggregate 10E in the direction of the thin end portions 15a and 16a (the upward or downward arrow direction in FIG. 7C) in the concrete, the thick central portion 14 is anchored. It functions as a part and hinders movement of the coarse aggregate 10E. Therefore, the adhesive force between the mortar portion of the concrete and the coarse aggregate is increased, cracks are hardly formed in the concrete, and the tensile strength and the bending strength are improved.

  Also in the embodiment shown in FIG. 7A, the coarse aggregate for concrete may be hollow or solid as described above.

  The method for manufacturing the coarse aggregate for concrete 10E shown in FIG. 7A can be selected according to the forming material. For example, when formed from a metal material such as steel, a metal such as a plate, a rod, or a pipe is used. It is possible to give press work to cut off and shape the material.

  The coarse aggregate for concrete 10F shown in FIG. 8 is formed between a total of four convex portions 16 arranged radially and the adjacent convex portions 16 like the coarse aggregate for concrete 10E shown in FIG. 7A. The central portion 14 is thicker than the end portions 15a on both sides of the concave portion 15 or the end portions 16a of the convex portions 16, and functions as an anchor portion. The thickness of the central portion 14 is thicker than the coarse aggregate 10E for concrete shown in FIG. 7A, and the central portion 14 is formed hollow. Further, ribs 17 are formed radially from the central portion 14 to the tip portion 16a of the convex portion. The formation of the ribs 17 can increase the strength of the coarse aggregate 10F against compression and deformation.

  The coarse aggregate 10F for concrete shown in FIG. 8 can be manufactured by press-forming and joining two metal plates. Therefore, the coarse aggregate 10F has a joint L2 of these press-formed products.

  The coarse aggregate for concrete 10G shown in FIGS. 9A to 9D is also formed between a total of four convex portions 16 arranged radially and the adjacent convex portions 16 similarly to the coarse aggregates 10E and 10F described above. The central portion 14 is thicker than the end portions 15 a on both sides of the concave portion 15 or the end portions 16 a of the convex portions 16. The coarse aggregate 10G is formed hollow.

  As shown in FIG. 10, the concrete coarse aggregate 10G is formed by pressing the metal pipe 1 at predetermined intervals by pressing to form rectangular small pieces 3 with openings 2 at both ends of the metal pipe 1 closed. Is pressed in from four sides to form the concave portion 15.

  The concrete of the present invention in which the tips of the plurality of projections 16 are on the same plane in a plan view and the thickness of the central portion 14 is thicker than the thickness of the end of the recess 15 or the tip of the projection 16. The coarse aggregate for use can further take various shapes, and the number thereof is not particularly limited as long as it has a plurality of convex portions or concave portions. For example, as in a coarse aggregate for concrete 10H shown in FIG. 11, five concave portions 15 and five convex portions 16 may be provided, and the number of the convex portions 16 or the concave portions 15 may be increased.

  On the other hand, a coarse aggregate for concrete 10I shown in FIGS. 12A and 12B may have a shape having two concave portions 3 and four convex portions 4 in plan view, and may be a coarse aggregate for concrete shown in FIGS. 13A and 13B. A shape having two projections 16 in plan view, such as 10J, may be used. When the number of the concave portions 15 or the convex portions 16 is reduced in this manner, the direction in which the individual coarse aggregate for concrete is difficult to move in the concrete is limited, but a large number of coarse aggregates for concrete are randomly dispersed in the concrete. In this case, the strength such as the tensile strength is improved in any direction.

  Also in the coarse aggregates 10E to 10J shown in FIGS. 7A to 13B, the inside may be hollow or solid, and if hollow, the adhesion between the coarse aggregate and the mortar is improved. For this purpose, for example, a hole 12 for communicating the surface with the hollow interior may be provided like a coarse aggregate for concrete 10K shown in FIGS. 14A and 14B. Such a coarse aggregate having a plurality of holes 12 can be easily manufactured using, for example, a punching mesh.

(Coarse aggregate forming material)
The coarse aggregate for concrete of the present invention can be formed from various metal materials, for example, iron, aluminum, titanium, copper, stainless steel and the like. Also, in order to improve the corrosion resistance of the coarse metal aggregate, a coating film of various plastics may be formed on the surface and, if necessary, the inner surface of the hollow portion, and an oxide film of the metal material may be formed. You may. These can be formed by a known method.

  In particular, the coarse aggregate for concrete of the present invention is preferably formed from a magnetic material such as iron. Thereby, the coarse aggregate for concrete itself and various concrete products including the coarse aggregate for concrete can be transported using the electromagnet. Further, at the time of manufacturing various types of concrete products, the position of the coarse aggregate for concrete in the concrete can be controlled by using an electromagnet. For example, the amount of the coarse aggregate for concrete can be increased in a region exhibiting low bending strength as compared with other regions.

(Welding of metal particles on the surface of coarse aggregate)
In the present invention, in any of the above-mentioned shapes, in order to improve the adhesion between the coarse aggregate and the mortar, a part or all of the surface thereof, and preferably, a molten metal droplet generated by a spattering phenomenon of various weldings is attached. Then, a sputtering method or the like in which the surface is roughened by metal particles deposited on the surface can be employed.

  Above all, it is preferable to perform a sputtering method in which an arc discharge is performed by using an electrode on a surface of a metal constituting the coarse aggregate to cause a molten metal droplet generated from the electrode to adhere. As a result, a large number of metal particles Q are deposited on the entire surface of the coarse aggregate due to adhesion of molten metal droplets, as shown in FIG. And the concrete using the coarse aggregate in which the metal particles Q are welded to the entire surface as described above has a remarkably improved tensile strength. In addition, welding such metal particles Q to the surface of the coarse aggregate by arc discharge can be performed at high productivity and at low cost.

  As a specific method of attaching a molten metal droplet to the surface of the coarse aggregate by a sputtering method of performing an arc discharge, before performing the arc discharge, a metal constituting the coarse aggregate is manufactured in a predetermined shape in advance, Thereafter, a method of performing arc discharge can be adopted. Examples of the predetermined shape in this case include the above-described hollow tetrahedron shape or a shape in which the tetrahedrons are joined together on one side, and the metal constituting the coarse aggregate is manufactured in a predetermined shape in advance. In the step of forming, substantially tetrahedrons or substantially tetrahedrons are joined together on one side by performing plastic deformation or press-cutting by pressing on metal pipes at predetermined intervals (for example, 20 to 50 mm) from mutually displaced directions. A step of producing a shaped shape. Here, it is preferable that the directions of the press-processed portions at predetermined intervals are shifted from 45 degrees to 90 degrees.

  In this case, for example, as shown in FIG. 19, a negative electrode is connected to a wall of a furnace 31 having a U-shaped cross section, a negative electrode is also connected to an upper electrode plate 32, and a positive electrode is internally provided. A rod 33 is installed, the metal 30 constituting the coarse aggregate is put in the furnace 31, and the furnace 31 is swung as indicated by an arrow, and sparks are generated by the electrode rod 33 and the electrode plate 32. 34 is performed by adhering to the metal 30 constituting the coarse aggregate. At this time, it is preferable to heat the furnace 31. Further, a cylindrical rotary furnace was used in place of the furnace 31 having a U-shaped cross section, and the electrode rod and the negative electrode were similarly sparked in the furnace while rotating the rotary furnace to form coarse aggregate in the furnace. Molten metal droplets may adhere to the metal to be formed.

  In addition, as a specific method for attaching molten metal droplets to the surface of the coarse aggregate by a sputtering method that performs arc discharge, a plurality of metal pillars are juxtaposed in a plane and the metal pillars are brought into contact with each other. The body is rotated, and molten metal droplets generated from the electrodes by the arc discharge adhere to the entire surface thereof, thereby forming a metal column having metal particles adhered to the surface, and forming a predetermined interval between the metal columns. Opening may be performed to form the coarse aggregate into a predetermined shape. In this case, the process of manufacturing the coarse aggregate into a predetermined shape can be performed in the same manner as described above. For example, a metal pipe to which metal particles are adhered by molten metal droplets is pressed at a predetermined interval from directions shifted from each other. By performing plastic deformation or press-cutting in step (a), a step of producing a coarse aggregate into a shape in which substantially tetrahedrons or substantially tetrahedrons are joined together on one side can be mentioned.

  If necessary, metal particles that have weakly adhered to the surface of the coarse aggregate for concrete may be removed, and the surface may be smoothed as long as the amount of adhesion is not impaired.

  The size of these projections or depressions is not particularly limited, but is preferably a size that does not hinder the pumping of the ready-mixed concrete.

  The coarse aggregate for concrete of the present invention can be replaced by a part or all of the coarse aggregate in the conventional concrete composition. The coarse aggregate for concrete of the present invention can also be applied to reinforced concrete. Hereinafter, concrete using the coarse aggregate for concrete of the present invention will be described.

  The concrete of the present invention contains at least cement, fine aggregate, and the above-described coarse aggregate for concrete of the present invention. As the cement, JIS R5210 “Portland cement”, JIS R5211 “Blast furnace cement”, JIS R5212 “Silica cement”, JIS R5213 “Fly ash cement”, JIS R5214 “Eco cement” and the like can be applied as appropriate.

  The fine aggregate is classified according to JIS A 1102. Specifically, the fine aggregate is an aggregate that passes through a 10 mm net sieve and passes at least 85% by mass of a 5 mm net sieve, and usually has a size of 2 mm or less. It is an aggregate having a particle size.

  The mass ratio of the main material in the concrete mixture is generally cement: fine aggregate: coarse aggregate = 1: 2 to 3: 4 to 6, but varies depending on the use of the concrete. Furthermore, water, a thickener, a water reducing agent, a setting accelerator and the like used in the production of general concrete and mortar can be appropriately contained.

  Preferred examples of application of the coarse aggregate for concrete of the present invention include concrete precast products, such as conventional foam-type or lightweight aggregate-type lightweight reinforced concrete plates which are vulnerable to compression and bending. Strong lightweight reinforced concrete plates. Further, the present invention can be preferably applied to a concrete structure that does not use a reinforcing bar (for example, a dam wall, a road directly laid on the ground, a solid foundation of a building, a pavement square, and the like). As a special application example, the present invention can be preferably applied to a reinforced concrete slab of a highway installed at a position away from the ground.

  Precast concrete products, such as lightweight reinforced concrete plates and reinforced concrete floor slabs, to which the coarse aggregate for concrete of the present invention is applied are formed into panels of a predetermined size, and are transported and installed in panel units. It will also be removed on a panel basis to repair walls and roads. For this reason, when the coarse aggregate for concrete of the present invention is made of a magnetic material, the panel can be attracted to the electromagnet, transported, installed, and removed, thereby improving workability.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Comparative Example 1
Concrete was prepared with the following composition, kneaded (5.5 L) with a mixer, molded using a formwork of φ10 × 20 cm and a formwork of 10 × 10 × 40 cm. Specimens are prepared by curing in water for up to 28 days, and the compressive strength and split tensile strength are calculated according to JIS A 1108 (test method for compressive strength of concrete) and JIS A 1113 (test method for splitting tensile strength of concrete). did. As a result, the compression strength was 28.33 N / mm ² , the tensile strength was 2.23 N / mm ² , and the ratio between the tensile strength and the compressive strength was 0.08.

[Formulation]
Cement: 111 L / m ³ (350 kg / m ³ )
Water: 175 L / m ³ (175 kg / m ³ )
Fine aggregate: 287 L / m ³ (746 kg / m ³ )
Coarse aggregate (crushed stone): 407 L / m ³ (1079 kg / m ³ )

Comparative Example 2
As a coarse aggregate, an iron pipe (diameter: 15 mm) was pressed into a length of 30 mm from alternate directions by press working to produce a tetrahedral hollow iron coarse aggregate. Concrete was prepared with the following composition in the same manner as in Comparative Example 1 except that this iron coarse aggregate was used as a coarse aggregate, a specimen was prepared, and a compressive strength test and a split tensile strength test were performed. As a result, although the compressive strength was equivalent to that of Comparative Example 1, the ratio of the tensile strength to the compressive strength was 0.16, and the ratio of the tensile strength to the compressive strength was improved.

[Formulation]
Cement: 111 L / m ³ (350 kg / m ³ )
Water: 175 L / m ³ (175 kg / m ³ )
Fine aggregate: 296 L / m ³ (770 kg / m ³ )
Coarse aggregate (coarse aggregate of Example 1): 398 L / m ³ (1898 kg / m ³ )

Example 1
Arc discharge was performed on the tetrahedral coarse iron aggregate of Comparative Example 2 using an iron electrode, and molten metal droplets were adhered to the entire surface of the coarse iron aggregate to deposit metal particles. This photograph is shown in FIG. A concrete was prepared with the following composition in the same manner as in Comparative Example 1 except that the welded metal particles were used as a coarse aggregate, a specimen was prepared, and a compression strength test and a split tensile strength test were performed. . As a result, the compression strength was almost the same as that of Comparative Example 2, but the tensile strength was improved to 2.63 N / mm ² .

[Formulation]
Cement: 111 L / m ³ (350 kg / m ³ )
Water: 175 L / m ³ (175 kg / m ³ )
Fine aggregate: 353 L / m ³ (918 kg / m ³ )
Coarse aggregate (coarse aggregate of Example 2): 341 L / m ³ (1545 kg / m ³ )

Example 2
Metal grains were welded in the same manner as in Example 1 except that the iron pipe used as the material for forming the coarse aggregate and the length of the coarse aggregate were larger than the coarse aggregate obtained by welding the metal grains of Example 1. Coarse aggregate was produced. This photograph is shown in FIG. Each photograph shown in the examples was taken under the same photographing conditions.

Using this as a coarse aggregate, a concrete was prepared with the following composition in the same manner as in Comparative Example 1 except that the kneading amount was changed to 3.5 L, a specimen was prepared, and a compression strength test and a split tensile strength test were performed. went. As a result, the tensile strength was improved to 3.08 N / mm ² .

[Formulation]
Cement: 111 L / m ³ (350 kg / m ³ )
Water: 175 L / m ³ (175 kg / m ³ )
Fine aggregate: 167 L / m ³ (453 kg / m ³ )
Coarse aggregate (coarse aggregate of Example 3): 360 L / m ³ (1550 kg / m ³ )

Example 3
For the coarse aggregate to which the metal particles of Example 2 were welded, the length of the coarse aggregate was further increased by using an iron pipe having the same diameter, and a press mark was formed on the surface by pressing, and thereafter, By performing arc discharge, a coarse aggregate to which metal particles were welded was produced. This photograph is shown in FIG.

Except for using this as a coarse aggregate, a concrete was prepared with the following composition in the same manner as in Example 2, a specimen was prepared, and a compressive strength test and a split tensile strength test were performed. As a result, compressive strength 31.91N / mm ^2, the tensile strength was improved significantly with 3.93N / mm ^2.

  The coarse aggregate for concrete of the present invention can remarkably increase the tensile strength of concrete and the compressive strength can be made equal to or more than conventional coarse aggregates such as crushed stone and gravel. Aggregate is useful as a building material because it can be obtained at high productivity and at low cost.

DESCRIPTION OF SYMBOLS 1 Metal pipe or iron pipe 2 Opening 3 Small pieces 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10I, 10J, 10K Coarse aggregate for concrete 11a, 11b End 12 Hole 13a, 13b Side 14 Center Part 15 Concave part 16 Convex part 17 Rib 18 Side surface 30 Metal 31 constituting coarse aggregate Furnace 32 Electrode plate 33 Electrode rod 34 Molten metal droplet L1 Outer line L2 Joint A1, A2, A3 Anchor part B1, B2 Tensile direction Q Metal Grain T1 Thickness at center T2 Thickness at end

Claims (18)

  Coarse aggregate for metal concrete, the surface of which is coated with metal particles by molten metal droplets.   The coarse aggregate for concrete according to claim 1, wherein the coarse aggregate is a ferromagnetic material.   The coarse aggregate for concrete according to claim 2, wherein the ferromagnetic material is iron.   The coarse aggregate for concrete according to any one of claims 1 to 3, wherein the coarse aggregate has a shape in which both ends of a columnar body having a predetermined length are crushed, and the thickness increases from each of the both ends toward the center. aggregate.   The coarse aggregate for concrete according to any one of claims 1 to 4, wherein the coarse aggregate has a shape in which both ends of the cylindrical body are alternately closed.   The coarse aggregate for concrete according to claim 4, wherein the coarse aggregate has a substantially tetrahedral shape.   The coarse aggregate for concrete according to any one of claims 1 to 4, wherein the coarse aggregate has a shape in which substantially tetrahedrons are joined at one side.   Coarse aggregate has two or more recesses recessed from the outer line toward the central portion in plan view and a convex portion corresponding to the concave portion, or two or more convex portions projecting from the central portion toward the outer line, and The concrete according to any one of claims 1 to 4, wherein the tip of the projection is in the same plane, and the thickness of the center is thicker than the thickness of the edge of the recess or the edge of the projection. For coarse aggregate.   The coarse aggregate for concrete according to claim 8, wherein the thickness gradually decreases from the center to the end of the projection.   A method for producing a coarse aggregate for metal concrete, wherein a molten metal droplet generated from the electrode is caused to adhere to a surface of a metal constituting the coarse aggregate by performing arc discharge using an electrode. Manufacturing method.   The method for producing a coarse aggregate for concrete according to claim 10, wherein a metal constituting the coarse aggregate is formed into a predetermined shape before arc discharge is performed.   The method for producing a coarse aggregate for concrete according to claim 11, wherein in a step of manufacturing a metal constituting the coarse aggregate into a predetermined shape, the metal pipes are pressed at predetermined intervals from directions shifted from each other. A method for producing a shape in which substantially tetrahedrons or substantially tetrahedrons are joined together on one side by performing plastic deformation or press-cutting.   13. The method for producing a coarse aggregate for concrete according to claim 12, wherein, in the step of manufacturing the metal constituting the coarse aggregate into a predetermined shape, the metal pipe is formed from a direction shifted by about 90 degrees at predetermined intervals. A method of producing a metal constituting a coarse aggregate into a substantially tetrahedral shape by cutting off while deforming.   The method for producing a coarse aggregate for concrete according to claim 10, wherein the metal constituting the coarse aggregate is subjected to arc discharge to cause molten metal droplets to adhere to the metal, and then the metal is formed into a predetermined shape. how to.   The method for producing a coarse aggregate for concrete according to claim 14, wherein a plurality of metal pillars are juxtaposed, and the metal pillars are rotated while being in contact with each other. The molten metal droplets generated from the above are adhered, thereby forming a metal column having metal particles adhered to the surface, and pressing the metal column at predetermined intervals to form the coarse aggregate into a predetermined shape. How to make.   The method for producing a coarse aggregate for concrete according to claim 15, wherein a metal pipe is used as the metal column, and the metal pipes to which the metal particles are attached by the molten metal droplets are separated from each other at a predetermined interval. A method of producing a coarse aggregate for concrete having a shape in which substantially tetrahedrons or substantially tetrahedrons are joined together on one side by performing plastic deformation or push-cutting by press working.   Concrete containing at least cement, fine aggregate, and coarse aggregate for concrete according to any one of claims 1 to 9.   A method for transporting a precast concrete product containing coarse aggregate for concrete according to claims 2 to 9, wherein the electromagnet is actuated to attract the precast concrete product, transported to a predetermined place as it is, and release the electromagnet to release the precast concrete product. A method of transporting concrete products at a predetermined location.