JP5416504B2 - High toughness concrete tread, method for producing concrete tread - Google Patents

Description

  The present invention relates to a tough concrete tread that is optimal for a wide stair tread and can be easily manufactured using a normal gravity kneaded cement mixer without using a forced kneaded cement mixer, and a method for manufacturing the same. . Further, the present invention is not limited to a stair tread, and can be applied to a general-purpose high-toughness concrete molded plate and a method for manufacturing the same for the same purpose.

  When both ends of PCa treads (cement molded product) arranged in a staircase shape are sandwiched between steel girders, the staircase width (the width of the treads) is generally about 1.0 m from the viewpoint of bending strength. It was. In a wide type of staircase, when it is desired to use a footboard of 1.8 m to 3.0 m, a conventional footboard cannot be used.

(1) Conventional technology 1
In Patent Document 1, a steel plate is placed in a mold corresponding to the width of a plurality of treads, and stress is introduced to realize a tread plate having a length of 1.8 m to 3.0 m. In this case, the long concave portion is divided by a partition plate to form a mold corresponding to the width of a plurality of treads, a PC steel rod is disposed through the partition plate, and the concave portion is filled with concrete. It was.

  In this case, in order to introduce prestress (tensile force), a dedicated facility is required, the manufacturing factory is limited, and it cannot be easily applied. Moreover, in order to exhibit a desired strength performance, appropriate prestress management was necessary. Moreover, in order to produce economically, it is necessary to manufacture a large amount of treads at a time, and it is not suitable for small-scale production (for example, production of about 100 pieces. A surface treatment process is also required, and production was not easy.

(2) Conventional technology 2
Conventionally, vinylon sharpened reinforced concrete blended as shown in Table 1 below has also been used as a fiber reinforced concrete tread. In this case, the vinylon fiber has a diameter = 0.66 mm, a length = 30 mm, and a volume = 0.010 cm ³ / piece. The fiber mixing rate is the number of fibers in 1 m ³ of concrete. When the fiber mixing rate is 0.6%, the number of fibers is about 585,000.

  The conventional concrete tread using vinylon has a low bending toughness (stickiness), and when cracks are concentrated and cracks are generated, the crack width becomes conspicuous. This is considered to be because the number of fibers that can be mixed into the concrete cannot be increased because the fiber shape of the vinylon fiber is thick and long.

(3) Conventional technology 3
In addition, proposals have been made to improve bending strength, fracture energy and toughness with a hydraulic plastic material having a diameter of 0.005 to 1.0 mm and a length of 2 to 30 mm of organic or inorganic fibers such as vinylon fibers. (Patent Document 2). In this proposal, there is a description that there is a possibility that a compressive strength of 130 Mpa or more and a bending strength of 20 Mpa or more can be achieved (Patent Document 2, Paragraph 0009).

  In addition, a high strength mortar having a diameter of 0.01 to 1.0 mm and a length of 2 to 30 mm of an organic fiber such as vinylon fiber has been proposed (Patent Document 3). In this proposal, it is described that there is a possibility that the compressive strength is 200 Mpa or more and the ratio of bending strength / compressive strength can be set to 1/4 to 1/7 (Patent Document 3, paragraph number 0019).

Japanese Patent Laid-Open No. 11-264222 JP 2001-181004 A JP 2002-193655 A

  Therefore, in the prior arts 1 to 3, it was not possible to easily produce a small amount using a gravity cement mixer, and it was not possible to ensure sufficient bending strength and strength to withstand impact.

  In the present invention, the amount of cement is increased, and fibers having a sufficiently smaller thickness and a sufficiently shorter length than the vinylon fibers conventionally used in concrete molded products are introduced in large quantities. Solved the problem.

That is, the present invention includes 2 vinylon resin fibers having a diameter of 0.1 mm and a length of 12 mm, including water, cement of 800 kg / m ³ or more, fine aggregate, admixture, without using a thickener. 0.0 Vol.% / M ³
Knead the material with added gravity with a gravity mixer,
A tread manufactured by forming pre-stress without forming a fiber ball on the surface,
The tread is composed of a tread base and an upward convex portion.
A connecting rebar is arranged in the width direction of the tread base, and a nut is fixed to each end of the connecting rebar to form a mounting screw hole; and
It is a high toughness concrete tread characterized by arranging reinforcing bars in the width direction of the upper convex part .

Furthermore, it is the manufacturing method of the tough concrete tread characterized by manufacturing in the following procedures.
(1) The tread comprises a tread base and an upward convex part,
A connecting rebar is arranged in the width direction of the tread base, a nut is fixed to each end of the connecting rebar, a mounting screw hole is formed, and a reinforcing bar is arranged in the width direction of the upper convex part. Configure the formwork.
(2) Water, cement of 800 kg / m ³ or more, fine aggregate, admixture, cement is prepared without using a thickener, and a concrete material is constructed.
(3) Next, the concrete material is put into a gravity mixer to form a stirred concrete material.
(4) Next, while agitating the concrete material, 2.0 Vol.% / M ³ of vinylon resin fiber having a diameter of 0.1 mm and a length of 12 mm is gradually added.
(5) Next, the agitated concrete material is filled into the mold,
(6) Next, without prestressing and forming so as not to produce fiber balls on the surface, the surface is troweled, subjected to predetermined curing, and demolded .

  The cement in the above refers to a hydraulic material used for a normal mold-molded product.

  Further, in the above, the diameter of the vinylon fiber is 0.08 to 0.2 mm, but the strength of the fiber is insufficient when it is 0.08 mm or less, and the fiber reinforcement is compared with the input amount of fiber when it is 0.2 mm or more. I cannot expect the effect.

  Moreover, although the length of the vinylon fiber was 10-15 mm, if it is 10 mm or less, the fiber connection effect cannot be expected, and if it is 10 mm or more, a fiber ball is likely to occur and a problem occurs during production.

Further, the blending ratio of the vinylon fiber is 0.5 to 3.0 Vol.% / M ³ , but the reinforcing effect cannot be obtained at 0.5 or less, and the fiber is not mixed at 3.0 or more, About 2% is considered optimal.

  In addition, a high-toughness concrete molded board is most suitable for a stair tread, but it can also be applied to a saddle girder. In particular, it is effective for applications in which bending or impact occurs due to external force.

  Since this invention made the vinylon fiber thinner and shorter and increased the mixing ratio compared to the prior art, the bending toughness of the concrete molded plate was increased without introducing prestress, and a product resistant to cracking was obtained. Can be configured. That is, even if cracks that do not affect the strength are generated, the initial cracks are dispersed and the crack width can be reduced, so that the cracks can be made inconspicuous. Therefore, it is possible to construct a concrete molded plate that is optimal for a wide stair tread.

In the tread of the embodiment of the present invention, (a) is a plan view, (b) is a front view, and (c) is a side view. A part of steel step using the tread of the embodiment of the present invention is shown. The assembly of the steel frame staircase using the tread of the Example of this invention is represented. The test body of a bending test is represented, (a) is a front view of this application tread, (b) is a side view, (c) is a front view of the prestressed concrete tread of a comparative example, (d) is also a side view. . It is a figure explaining the test method of a bending test. It is a load-deflection graph showing the result of a bending test. It is a load-deflection graph showing the result of a bending test. The test body of an impact test is represented, (a) is a front view, (b) is a side view. The method of an impact test is represented, (a) is a front view, (b) is a side view.

(1) “Cement 800kg / m ³ or more”, “Diameter 0.08-0.2mm, length 10-15mm vinylon resin fiber 0.5-3Vol.% / M ³ ”, fine aggregate, blending Add water to the agent to make up the concrete material.
(2) Put the concrete material into the gravity mixer (not the forced mixer) to form the agitated concrete material.
(3) Next, agitated concrete material is filled into a mold that matches the product to be manufactured.
(4) At this time, the agitated concrete material is solidified by predetermined curing without introducing prestress. Demolding to produce the concrete product of this invention.
(5) This concrete product has high toughness and is effective for products that are required to have impact and bending resistance.

Next, examples will be described.

1. Formulation

(1) Vinylon fiber (Kuraray “RECS100 × 12”)
Diameter = 0.1. mm, length = 12 mm, volume = 0.000094247 m ³ / piece The fiber mixing rate is the number of fibers in 1 m ³ of concrete, and the number of fibers when the fiber mixing rate is 2.0% is about 212,208,000. Become. Therefore, the number is 363 times that of the prior art 2.

(2) Mixing of concrete (cement) is according to Table 2 below.

2. Production method

(1) A mold for manufacturing a tread has a shape capable of forming a tread 10 including a tread base 1 and an upper projection 2. The tread base 1 is formed with a tread width = 2500 mm, a tread thickness = 80 mm, and a tread size = 300 mm, and the upper convex part 2 is a tread base 1 from the top surface of the tread to the kick side = 80 mm, depth = 40 mm. It is formed with.
In the mold, the insert nut 4 is disposed over the entire length in the width direction at the tread base portion forming portion. The insert nut 4 is configured by fixing nuts 6 to both ends of the connecting reinforcing bar 5, and the connecting reinforcing bar 5 is a round bar having a diameter of 19 mm. Moreover, the deformed reinforcing bar 8 of D10 is arrange | positioned in the width direction in the upper convex part formation part of a formwork (FIG. 1).

(2) in a cement mixer heavy force type, placed cement, water, fine aggregate, a predetermined stirring. After an appropriate time has elapsed, the vinylon fibers are gradually introduced into the cement mixer while stirring.

  An admixture is appropriately put into a cement mixer and further kneaded to complete a stirred concrete material.

(3) Subsequently, the cement mixer is operated to fill the formwork with the stirred concrete material. After the predetermined curing, the mold is removed to complete the concrete tread 10 (FIG. 1).

3. Use of tread board 10

  The treads 10 and 10 are arranged in a step-like manner in the same manner as the conventional treads, and both ends are sandwiched between steel plate girder 12 and 12, and bolts are inserted from the side of the girder 12 to the nut 6 of the insert nut 4 of the tread plate 10. The steel staircase 20 is configured by tightly connecting 14 and 14 (FIGS. 2 and 3). In FIG. 3, 17 is a baseboard, and 16 is a landing, which is constructed by placing reinforcement on a landing deck plate and placing concrete.

4). Performance comparison experiment A (formulation)

(1) Change the blending contents as shown in Table 3 and Table 4, and blend NO. 1-5, the preparation of the present Example of the preparation of Table 2 above, and the preparation of the conventional technique 2 were compared.

(2) As shown in Tables 5 and 6, the blending of the present example is good with no defects during production. In particular, the kneadability due to the difference in blending and the trowel finish will be considered.

  In order to uniformly disperse the thin vinylon fiber, which is a feature of the present application, in the concrete, it is necessary to make the mortar (water and cement) serving as a base material viscous. If there is no viscosity, the vinylon fibers are entangled with each other to form a ball (so-called “fiber ball”), and the properties of fiber reinforced concrete cannot be obtained.

In this case, it is necessary to devise the following in order to obtain viscosity.
(a) Reduce material particles. For example, fine-grained sand and fine admixture materials such as fly ash and silica fume are used.
(b) Add a thickener. In this case, the material cost increases and the productivity decreases due to an increase in material types.

On the other hand, when the viscosity comes out, the following new problems arise.
(a) Cannot be kneaded with a tilting barrel mixer (gravity mixer) or concrete mixer truck (gravity mixer), which has a high penetration rate. This is because fiber balls are generated unless forced stirring is performed. Therefore, it is necessary to provide a forced stirring type mixer, and the production factory is limited.
(b) When finishing the concrete casting surface with a trowel, if the viscosity is high, it will not finish cleanly. Accordingly, the appearance quality is deteriorated, a new process for finishing the surface (placed surface) is generated, and the finishing time is increased.

  Therefore, in the present invention, it was possible to realize a formulation having both kneadability and iron finish.

In other words, fiber balls cannot be produced, and the casting surface can be easily finished by trowel finishing, has little effect on the process, and does not require the addition of new materials such as new additives and additives. Realized a viscosity of. In addition, the fine aggregate was “natural sand” that can be obtained at any manufacturing plant, and the amount of unit cement was increased to make the mortar more viscous. The concrete material itself realized an epoch-making effect, similar to the material used in the second prior art (Table 2).

5. Performance comparison B (bending strength)

(1) As shown in FIG. 4, a test body (FIGS. 4A and 4B) of the present invention having the same outer shape (FIGS. 4A and 4B) and a conventional prestressed concrete tread 30 (FIGS. 4C and 4D) are used. Compare. Each test body 10 and 30 is formed with a step width of 2500 mm.
The test body 10 of the tread board 10 of the present invention has the same structure as that of the above embodiment.
The test body 30 of the prestressed concrete tread 30 used a φ16 deformed reinforcing bar (in the present invention, a φ19 round bar) as an insert nut. Moreover, the test body 30 is different from the test body 10 in that a welded wire net made of φ3.2 reinforcing bars is embedded in the tread body and the upward convex portion. The test body 30 was prestressed by embedding a PC strand of φ2.9 (FIGS. 4C and 4D).

(2) As shown in FIG. 5, a fulcrum beam 33 is placed on the center part of both test bodies 10 and 30 fixed to the support side plates 32 and 32 at both ends, and a load of 10 t is applied to the center of the fulcrum beam 33. The deflection at the center of the test bodies 10 and 30 was measured with a displacement meter.

(3) “Load (kg) -deflection (cm) curve” of both test bodies 10 is shown in FIG.

(4) Compared to the case of the prestressed concrete tread, the specimen 10 (tread 10 of the present invention) is inferior in the initial crack initiation load, but the bending toughness after the occurrence of crack (crack) is not inferior, and the maximum load to be destroyed Then it exceeded the prestressed concrete tread.

(5) In the test body 10, the staircase width is 2500 mm (the connecting rebar 5 is φ19), but the same applies to the staircase width is 2500 mm (the connecting rebar 5 is φ16) and the staircase width is 1200 mm (the connecting rebar 5 is φ19). A bending strength test was performed. The load-deflection curve at that time is shown in FIG. 7 together with the case of 2500 mm (the connecting reinforcing bar 5 is φ19).
Stores and movie theaters assuming a bending strength value of 2900 N / m ² and a width of 2500 mm for office staircases assumed to have a width of 1200 mm with regard to the loading capacity of staircase steps from the provisions of the Building Standards Law Enforcement Ordinance When calculated from the value of the staircase of 3500 N / m ² , etc., each resulted in a safety factor of 2.4 times or more even when the initial crack occurred. Furthermore, when calculated at the maximum load, it was found that the safety factor was 8.6 times or more and sufficient proof stress was retained (Table 7).
Moreover, even if it is a 2500 mm wide tread with the preparation of the test body 10 of the present invention, it has a proof stress that can sufficiently satisfy the load of the Building Standard Law.

6). Performance comparison C (impact resistance)

(1) An impact test by the weight drop method was performed on the treads prepared according to the above-described example, and the impact resistance performance was verified.

(2) Specimen

The tread 10 of the present invention has the shape shown in FIG. 8 with the composition of the above embodiment, the effective width is 1200 mm, and side plates 35 and 35 made of steel plates with a thickness of 9 mm are fixed at both ends. In addition, when the effective width is 1200 mm, the deformed reinforcing bar 8 of the upper convex portion is omitted.
Comparative Example 1 is a second conventional vinylon fiber tread having the composition shown in Table 1, and has the same shape as the test body 10 of the tread 10 of the present invention (see FIG. 8).
Comparative Example 2 is the same concrete blend as in the above example, except that it is a plain blend excluding vinylon fibers. The shape is the same as the test body 10 of the tread board 10 of the present invention (see FIG. 8).

(3) Test method

  The test was an impact test by a weight drop method, and a mold weight having a weight of 10 kg was freely dropped at the center of the test body 10 as shown in FIG. The height at which the initial crack and initial crack were generated was examined by gradually increasing the drop height to 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 100 cm, and 2 m. After 2 m, without increasing the fall height, the number of times the weight was dropped was increased, and the fall was repeated until the specimen was repeatedly destroyed.

(4) A 10 kg iron weight was dropped on the test piece (tread), and the height at which the initial crack was generated was compared with the number of times the tread was destroyed by repeating the drop from a height of 2 m (Table 8). . According to Table 8, in comparison between the tread 10 of the present invention and the test body of Comparative Example 1 (tread of Conventional Example 2), both the initial crack generation height and the number of drops until failure exceeded that of Comparative Example 1.
In the test body 10 according to the composition of the present invention, the effect of dispersing cracks was recognized when the tread was impacted. It was found that the structure was maintained even when subjected to several degrees of impact, and that the function of the tread board could be fully achieved even when the step was damaged by falling objects.

1 Tread base 2 Upper convex part 4 Insert nut 5 Connecting rebar (insert nut)
6 Nut (insert nut)
8 Deformed bar 10 Tread (test body)
12 Sasara girders 14 Bolts 20 Steel staircase 30 Comparative example tread (test body)

Claims (2)

Water, 800 kg / m ³ or more cement, fine aggregate, admixture , no thickener, 0.1 mm diameter , 12 mm long vinylon resin fiber 2.0 Vol. % / M ³
Knead the material with added gravity with a gravity mixer,
A tread manufactured by forming pre-stress without forming a fiber ball on the surface,
The tread is composed of a tread base and an upward convex portion.
A connecting rebar is arranged in the width direction of the tread base, and a nut is fixed to each end of the connecting rebar to form a mounting screw hole; and
A high toughness concrete tread , wherein reinforcing bars are arranged in the width direction of the upper convex portion . A method for producing a high-toughness concrete tread characterized by the following steps.
(1) The tread comprises a tread base and an upward convex part,
A connecting reinforcing bar is arranged in the width direction of the tread base, a nut is fixed to each end of the connecting reinforcing bar, a screw hole for mounting is formed, and a reinforcing bar is arranged in the width direction of the upper convex part. Configure the formwork.
(2) water, 800 kg / m ³ or more cement, without the use of thickeners include fine aggregate, admixtures, formulated cement, constituting the concrete material.
(3) Next, the concrete material is put into a gravity mixer to form a stirred concrete material.
(4) Next, while stirring the concrete material , 2.0 Vol.% / M ³ of vinylon resin fiber having a diameter of 0.1 mm and a length of 12 mm is gradually added.
(5) Next, in the mold, the stirred concrete material is filled,
(6) Next, a pre-stress is not introduced and a fiber ball is not formed on the surface, the surface is troweled, subjected to a predetermined curing, and demolded.

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